CN118360553B - 9.8-Grade hot-rolled carbon non-cold-heading steel wire rod and manufacturing method thereof - Google Patents
9.8-Grade hot-rolled carbon non-cold-heading steel wire rod and manufacturing method thereof Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 116
- 239000010959 steel Substances 0.000 title claims abstract description 116
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 60
- 229910052799 carbon Inorganic materials 0.000 title claims abstract description 46
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 45
- 150000003839 salts Chemical class 0.000 claims abstract description 110
- 229910001562 pearlite Inorganic materials 0.000 claims abstract description 88
- 238000001816 cooling Methods 0.000 claims abstract description 54
- 238000005496 tempering Methods 0.000 claims abstract description 38
- 238000005098 hot rolling Methods 0.000 claims abstract description 22
- 238000009987 spinning Methods 0.000 claims abstract description 21
- 229910001566 austenite Inorganic materials 0.000 claims abstract description 15
- 238000005096 rolling process Methods 0.000 claims description 50
- 238000000034 method Methods 0.000 claims description 49
- 238000010583 slow cooling Methods 0.000 claims description 32
- 238000004321 preservation Methods 0.000 claims description 15
- 239000000126 substance Substances 0.000 claims description 13
- 230000009467 reduction Effects 0.000 claims description 10
- 239000012535 impurity Substances 0.000 claims description 7
- 229910052698 phosphorus Inorganic materials 0.000 claims description 7
- 229910052717 sulfur Inorganic materials 0.000 claims description 7
- 238000010273 cold forging Methods 0.000 claims description 3
- 239000000203 mixture Substances 0.000 claims description 3
- 238000005242 forging Methods 0.000 claims 1
- 230000001105 regulatory effect Effects 0.000 abstract description 22
- 229910000975 Carbon steel Inorganic materials 0.000 abstract description 12
- 239000010962 carbon steel Substances 0.000 abstract description 12
- 239000011159 matrix material Substances 0.000 abstract description 12
- 229910006639 Si—Mn Inorganic materials 0.000 abstract description 4
- 230000008569 process Effects 0.000 description 23
- 229910000859 α-Fe Inorganic materials 0.000 description 20
- 230000000694 effects Effects 0.000 description 17
- 230000000052 comparative effect Effects 0.000 description 15
- 230000001276 controlling effect Effects 0.000 description 15
- 230000002159 abnormal effect Effects 0.000 description 13
- 238000010438 heat treatment Methods 0.000 description 11
- 229910001563 bainite Inorganic materials 0.000 description 9
- 238000005299 abrasion Methods 0.000 description 8
- 229910045601 alloy Inorganic materials 0.000 description 8
- 239000000956 alloy Substances 0.000 description 8
- 230000003111 delayed effect Effects 0.000 description 8
- 230000035945 sensitivity Effects 0.000 description 8
- 238000005728 strengthening Methods 0.000 description 8
- 238000010586 diagram Methods 0.000 description 7
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- 238000005336 cracking Methods 0.000 description 5
- 230000009466 transformation Effects 0.000 description 5
- 229910052720 vanadium Inorganic materials 0.000 description 5
- 238000000137 annealing Methods 0.000 description 4
- 229910052804 chromium Inorganic materials 0.000 description 4
- 238000007599 discharging Methods 0.000 description 4
- 238000005265 energy consumption Methods 0.000 description 4
- 239000011572 manganese Substances 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 238000004806 packaging method and process Methods 0.000 description 4
- 238000001556 precipitation Methods 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 3
- 239000013078 crystal Substances 0.000 description 3
- 238000001514 detection method Methods 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 238000009413 insulation Methods 0.000 description 3
- 229910000734 martensite Inorganic materials 0.000 description 3
- 238000002360 preparation method Methods 0.000 description 3
- 238000005482 strain hardening Methods 0.000 description 3
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 2
- 238000003723 Smelting Methods 0.000 description 2
- 238000005275 alloying Methods 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 238000007670 refining Methods 0.000 description 2
- 238000005204 segregation Methods 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- 238000009864 tensile test Methods 0.000 description 2
- 208000010392 Bone Fractures Diseases 0.000 description 1
- 206010017076 Fracture Diseases 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 229910001035 Soft ferrite Inorganic materials 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 206010057040 Temperature intolerance Diseases 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 230000009471 action Effects 0.000 description 1
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- 238000005266 casting Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 238000009749 continuous casting Methods 0.000 description 1
- 238000005261 decarburization Methods 0.000 description 1
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- 230000009395 genetic defect Effects 0.000 description 1
- 230000008543 heat sensitivity Effects 0.000 description 1
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- 238000011081 inoculation Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
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- 229910052751 metal Inorganic materials 0.000 description 1
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- 239000011593 sulfur Substances 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
Classifications
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
- C21D8/065—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires of ferrous alloys
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/009—Pearlite
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Manufacturing & Machinery (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Heat Treatment Of Strip Materials And Filament Materials (AREA)
- Heat Treatment Of Steel (AREA)
Abstract
The invention relates to a 9.8-grade hot-rolled carbon non-regulated cold heading steel wire rod and a manufacturing method thereof, wherein the wire rod is produced by hot rolling based on C-Si-Mn carbon steel components, the wire rod is spun into the wire rod according to the spinning temperature of more than or equal to 935 ℃, the wire rod is subjected to strong isothermal treatment in an online salt bath, so that the wire rod is cooled to the molten salt temperature according to the cooling speed of more than or equal to 33 ℃/s, the high-temperature austenite in the wire rod structure is converted into a complex phase structure consisting of pearlite and Wittig body to provide matrix strength, the pearlite and Wittig body are subjected to tempering and toughening through isothermal promotion, and finally, the cold heading steel wire rod is slowly cooled through a roller way, and the micro-structure comprises a mixed structure consisting of tempered pearlite and a small amount of tempered Wittig body, so that the tensile strength is 820-850 MPa, the section shrinkage rate is 58-62%, the strong plastic matching of the cold heading steel wire rod is realized, the wire rod is used for manufacturing 9.8-grade non-regulated high strength fastener bolts and other application fields, and the wire rod has good industrial adaptability and application prospect.
Description
Technical Field
The invention belongs to the technical field of carbon hot-rolled wire rods, and particularly relates to a 9.8-grade hot-rolled carbon non-cold-heading steel wire rod and a manufacturing method thereof.
Background
The cold heading performance is an important processing performance index of cold heading steel, the production capacity of the fastener is seriously affected, and when the 9.8-grade and above high-strength fastener is produced, hot rolled wire rods are required to be subjected to spheroidizing annealing for a plurality of times at the temperature of more than 740 ℃ for a long time, so that spherical or granular carbide tissues are uniformly distributed on a matrix to improve cold plastic deformability, the risks of drawing broken wires and cold heading cracking are reduced, so that after drawing, cold heading is directly performed, and meanwhile, after cold heading forming, the corresponding strength grade can be achieved through tempering heat treatment, and the plurality of spheroidizing annealing and tempering heat treatment are not in accordance with the green production requirement, and have high energy consumption, high production cost and low efficiency, so that the 9.8-grade non-tempering cold heading steel wire rods are developed, and have important significance in realizing the efficient green production of the 9.8-grade high-strength fastener.
At present, in order to meet the requirements of non-quenched and tempered service performance such as high strength and high plasticity of high strength fasteners, cold heading steel wire rods for 9.8 grade high strength fasteners in China are generally designed by adding Cr, V, ti, A, B, mo and other alloy elements on the basis of common carbon steel components, and a stelmor air cooling process after hot rolling and wire spinning is combined, for example: according to the MnV-based non-quenched and tempered cold heading steel wire rod for 9.8-grade fasteners and the production method thereof disclosed in the patent CN115261727B, a C-Si-Mn-V-Ti-Cr-Al component design, a low-temperature wire-laying and slow cooling process are adopted to obtain a ferrite and pearlite structure, the tensile strength is 750-800 MPa, the area reduction rate is more than or equal to 50%, but on one hand, the addition of alloy elements increases the material cost, the alloying strengthening effect is limited and can lead the wire rod to generate certain plastic loss, and the aim of reducing the cost is to omit the alloy elements and obviously reduce the strength of the wire rod and change the phase transition temperature, on the other hand, the addition of the alloy elements increases the hardenability of the material, the martensite and bainite hard and brittle phase defects are easily precipitated under the cooling speed of a Sitermo air cooling line, the plasticity of the wire rod is obviously reduced, the soft phase ferrite proportion in the structure is also increased in the prior art, and the strength of the wire rod is improved by matching with fine grain strengthening, for example: the patent CN117327979A discloses a large-scale non-quenched and tempered cold heading steel, a production method thereof and a fastener prepared by the same and a preparation method thereof, wherein the C-Si-Mn-Al-Nb-Cr-Mg-Pr component design is adopted, and a low-temperature wire-laying and low-speed cooling process is combined to obtain an ultrafine grain ferrite and pearlite structure, so that Rm is 740-780 MPa, Z is more than or equal to 67%, the plasticity is improved, but only the structure consisting of ferrite and pearlite soft phases is obtained, the improvement effect of microalloy and fine grain action on strength is limited, the strength is insufficient, deep drawing and surface reduction are required to be enhanced under the condition of quenching and tempering-free treatment, the plastic loss is large in the process, and the drawing wire breakage and cracking risk are aggravated; meanwhile, the low-temperature rolling can increase abrasion of a rolling line and affect rolling efficiency.
At present, the technical difficulty and the cause that the 9.8-grade hot-rolled carbon cold heading steel wire rod is difficult to meet the non-adjustment requirement compared with the alloyed steel wire rod are that: (1) Compared with alloyed steel, the carbon steel has the advantages of simple smelting, but after the steel does not contain Cr, V, ti, A, B, mo and other strengthening alloy elements, the carbon content of the strengthening elements is relatively high, the strength of the steel is obviously increased, but the plasticity is obviously reduced, simultaneously, the sensitivity is greatly increased, austenite grains are easy to grow, the early cooling speed of air cooling is too fast, abnormal structures such as Wipe body, bainite and martensite are caused, wherein the Wipe body is accompanied with coarse grains, the Wipe body is left in a final structure in the continuous cooling process, coarse crystals can be formed, the mechanical property of the steel is reduced, the dislocation density of the Wipe body is larger, the plastic toughness and impact performance of the steel are reduced particularly, in order to avoid the abnormal structure and prolong the high-temperature transformation time, slow cooling or delayed slow cooling technology after low-temperature rolling and wire laying is adopted for the carbon steel wire rods, but small amount of incompletely transformed high-temperature austenite structures are remained after continuous cooling, and the sensitivity of the ferrite and pearlite is still enabled to be converted into the ultra-low-temperature austenite structures at the low cooling speed of a medium-temperature interval, and the non-transformed high-temperature austenite structures are still difficult to be regulated and controlled into the ultra-low-temperature structures, so that the ultra-low-temperature structures are difficult to be hard to be easily converted into the ultra-low-temperature structures, and have the ultra-low temperature and have the hardness.
(2) Because the stelmor air-cooled wire has a limited length, even if certain production efficiency is lost, the cooling is slowly or delayed after rolling, so that the duty ratio of ferrite in a tissue is increased, the plasticity of the wire rod can be improved to a certain extent, but the incubation time of pearlite in the continuous cooling process is shorter, the high-temperature softening is difficult to maintain after the pearlite is obtained, the plasticity of a matrix tissue is limited to be improved, and cold heading cracking is caused in the annealing-free and tempering-free processes due to work hardening.
Disclosure of Invention
The invention aims to solve at least one of the technical problems to a certain extent, and provides a 9.8-grade hot-rolled carbon non-tempering cold heading steel wire rod and a manufacturing method thereof, wherein the structure and performance of the wire rod can be regulated and controlled, thereby being beneficial to realizing the tempering-free high-efficiency green production of 9.8-grade high-strength fasteners, reducing the production cost of the whole process and improving the production efficiency.
The technical scheme adopted for solving the technical problems is as follows:
A9.8-grade hot-rolled carbon non-cold heading steel wire rod comprises the following chemical components in percentage by mass: c:0.39% -0.44%, si:0.15% -0.35%, mn: 0.3-0.5%, P is less than or equal to 0.020%, S is less than or equal to 0.020%, and the balance is Fe and unavoidable impurities; the microstructure includes a mixed structure composed of tempered pearlite as main and a small amount of tempered Wittig body.
The design basis of the chemical components and the mass percentage of the cold heading steel wire rod comprises:
(1) Carbon: c is the most effective and economic strengthening element in steel, and can obviously improve the tensile strength of the steel along with the increase of the carbon content, but can lead to the reduction of the plasticity and cold workability of the steel and increase the delayed fracture risk of the fastener, and simultaneously the heat sensitivity is increased, so that the mass percent of C is controlled to be 0.39% -0.44% on the basis of not adding Cr, V, ti, A, B, mo and other strengthening alloy elements for the purpose of reducing the material cost and properly improving the carbon content on the basis of ensuring the final strength grade of the 9.8-grade non-adjusting fastener.
(2) Silicon: si element is a good reducing agent and deoxidizer and can be dissolved in austenite to improve the strength of steel, but excessive silicon promotes columnar crystal growth in a casting blank, increases surface decarburization tendency, improves the cold work hardening degree of steel and reduces the cold plastic deformation and toughness of steel, so that the mass percentage of Si is controlled to be 0.15% -0.35%.
(3) Manganese: mn element is a good deoxidizer and desulfurizer, the strength grade and hardenability of the wire rod can be improved through solid solution strengthening effect, the austenite area is enlarged, the transformation temperature of martensite and bainite is reduced, the method is favorable for refining pearlite, but the excessive Mn content can aggravate the segregation of steel, the overheat sensitivity and tempering brittleness tendency of steel are increased, the plasticity and structure control of steel are both adversely affected, and in order to achieve the strength, structure control and cold workability of steel, the Mn content is properly reduced, so that the mass percentage of Mn is controlled to be 0.3% -0.5%.
(4) Phosphorus, sulfur: the P element and the S element belong to impurity elements, and the segregation at the grain boundary can reduce the toughness of the steel, and the lower the toughness is, the better, so that the P is controlled to be less than or equal to 0.020 percent, and the S is controlled to be less than or equal to 0.020 percent.
On the basis of the components of the C-Si-Mn carbon steel, the hot rolled cold heading steel wire rod abandons the microstructure of the traditional ferrite and pearlite, and is manufactured into a mixed structure which mainly uses tempered pearlite and has a small amount of tempered Wittig body tissue, the tempered pearlite in the mixed structure has the characteristics of higher strength and hardness than the ferrite structure and moderate strength and plasticity of lamellar pearlite tissue with higher plasticity than bainite tissue, and compared with the existing cold heading steel wire rod, the cold heading steel wire rod improves the plasticity of the wire rod by increasing the ferrite ratio, and on the basis of excluding soft ferrite and hard brittle phase bainite, the cold heading steel wire rod further eliminates the internal stress of the pearlite tissue by using the tempered structure to toughen, so that the tempered pearlite tissue obtains obviously improved plasticity and toughness compared with the pearlite tissue, and the plastic loss caused by carburetion is compensated; compared with the existing cold heading steel wire rod, the Wehner body structure is regarded as an overheat abnormal structure for reducing the steel impact performance, tempered Wehner bodies in the mixed structure utilize the strength characteristics of needle-shaped Wehner body structures which extend from crystal boundaries to the inside and are formed and separated according to a shearing mechanism and have strength higher than pearlite, the dislocation density of the Wehner body structure is further reduced by tempering to realize toughening, and the tempered Wehner body structure which is strong and tough is obtained, so that the genetic defect caused by the Wehner body structure is avoided, the strength loss caused by strengthening alloy elements such as Cr, V, ti, A, B, mo and the like is not increased, further the hot rolled cold heading steel wire rod strong plasticity matching is realized on the basis of low-cost component design, and the 9.8-grade non-tempering cold heading fastening piece is facilitated, and the drawing broken wire and the cold heading cracking risk under the non-spheroidizing annealing and non-tempering processes are reduced.
Preferably, the volume percentage of the tempered pearlite is 80% -89%, the volume percentage of the tempered Width body is 11% -20%, the strength and the plasticity of the cold heading steel wire rod are reduced as the tempered pearlite is higher, and the strength and the plasticity of the cold heading steel wire rod are reduced as the tempered Width body is higher, so that the ratio of the tempered pearlite to the tempered Width body structure can be regulated, and the strong-plasticity matching of the cold heading steel wire rod can be regulated.
Preferably, the lamellar spacing of the tempered pearlite is 150-180 nm, the strength and the plasticity of the cold heading steel wire rod are improved when the lamellar spacing is lower, and the strength and the plasticity of the cold heading steel wire rod are improved when the lamellar spacing is higher, so that the lamellar spacing of the tempered pearlite can be further controlled, and the strong-plasticity matching of the cold heading steel wire rod can be further regulated and controlled.
Preferably, the cold heading steel wire rod has the specification of 8.0-18.0 mm, the tensile strength of 820-850 MPa and the reduction of area of 58-62%, and compared with the existing hot rolled carbon cold heading steel wire rod, the cold heading steel wire rod has the advantages that the tensile strength is improved on the basis of not adding reinforced alloy elements, the work hardening and the plastic loss are reduced in a non-hardening and tempering process, meanwhile, the cold heading steel wire rod plasticity which is not input into the existing ferrite and pearlite mixed structure is realized, and the drawing broken wire and the cold heading cracking risk are reduced in the non-hardening and tempering manufacturing process of the 9.8-level cold heading fastener.
The application of the 9.8-grade hot-rolled carbon non-tempering cold heading steel wire rod comprises the step of producing a 9.8-grade cold heading fastener under the annealing-free and tempering-free conditions.
The manufacturing method of the 9.8-grade hot-rolled carbon non-cold-heading steel wire rod comprises the following steps: based on the chemical component hot rolling production wire rod of the 9.8-grade hot rolled carbon non-cold heading steel wire rod, the wire rod is spun into the wire rod according to the spinning temperature of more than or equal to 935 ℃, the wire rod is subjected to on-line salt bath strong isothermal treatment, the wire rod is cooled to the molten salt temperature according to the cooling speed of more than or equal to 33 ℃/s, the high-temperature austenite in the wire rod structure is converted into a complex phase structure consisting of pearlite and Wittig body, isothermal tempering is carried out, and finally the complex phase structure is slowly cooled by a roller way, so that the cold heading steel wire rod with a microstructure comprising a mixed structure consisting of tempered pearlite and a small amount of tempered Wittig body is manufactured.
Compared with the prior art, the method has the advantages that the risk of abnormal structure is reduced and the inoculation time of ferrite and pearlite is increased by low-temperature wire-laying on the basis of the C-Si-Mn carbon steel components, the method directly carries out on-line strong isothermal treatment of salt bath after wire-laying, enables pearlite to be fully transformed and tempered with Winter body tissues, so that the limitation of the Winter body tissues on the low-temperature wire-laying requirement can be broken, the wire-laying temperature is improved, elements such as TI, V, nb, mo and the like which prevent austenite grains from growing are not added, and the high-temperature wire-laying is combined, so that small part of coarse high-temperature austenite after wire-laying can be strongly cooled through on-line salt bath at the cooling speed of more than or equal to 33 ℃/s, the pre-eutectoid phase in steel is mixed with lamellar pearlite in a needle-shaped form, and the proportion of tempered Winter body in the mixed tissues is larger as the wire-laying temperature is higher; on the other hand, the limitation of low-temperature spinning on low-temperature rolling can be broken, the abrasion in the rolling line and the spinning process is reduced, and the production efficiency is improved.
The wire rod after wire spinning is directly subjected to online salt bath, compared with air cooling, the wire rod has a faster cooling speed, the contact type high heat exchange capability of molten salt is utilized, particularly when the wire rod with larger specification is manufactured, compared with air cooling, the temperature difference between the surface and the core of the wire rod can be reduced, the fluctuation of mechanical properties is reduced, the phase transition temperature interval of ferrite can be quickly skipped at the faster cooling speed, the high-temperature austenitic structure is fully converted into a complex-phase structure mainly comprising pearlite and a small amount of Winter, compared with the slow cooling or delayed cooling process after wire spinning, the temperature of the salt bath can be kept at the molten salt temperature for a long time of high-temperature isothermal time, the wire rod not only can fully inoculate pearlite and Winter body structure, provide matrix strength, but also can be tempered at a longer time of high temperature isothermal temperature, promote the tempering of pearlite and tempered Winter body structure to form a tempered pearlite and a tempered Winter body, regulate the sheet spacing of the tempered pearlite structure, and further regulate and control the wire rod structure, and avoid the problem that the conventional slow cooling bainite structure is not completely caused by the slow cooling process of the high-temperature austenitic structure due to higher carbon content transformation.
The wire rod is kept in a high-temperature state after being subjected to strong isothermal in an online salt bath, isothermal time is prolonged by slow cooling through a roller way, and on the basis of avoiding excessive reduction of lamellar spacing of tempered pearlite and increase of energy consumption, the softening effect in the later stage of strong isothermal treatment in the online salt bath can be exerted by utilizing the high-temperature state, so that further toughening of tempered pearlite and tempered Wifollowing body is promoted, the softening effect of a wire rod matrix structure is improved, the production cost of the whole process of material, hot rolling and controlled cooling is further reduced, and the wire rod structure and performance are regulated and controlled by combining the strong isothermal in the online salt bath and the slow cooling technology through carbon chemical component design.
Preferably, the final rolling temperature is controlled to be more than or equal to 950 ℃ in hot rolling production, the grain size of the rolled wire rod is less than or equal to 9 grades, on one hand, the higher final rolling temperature can be adopted for higher wire-laying temperature, so that the abrasion of a rolling line is reduced, the rolling efficiency is improved, on the other hand, the improvement of the rolling temperature is accompanied with coarsening of the grain size, and the tempering is beneficial to the generation of a small amount of Wittig body tissue at the corresponding wire-laying temperature.
Preferably, the spinning temperature is lower than 960 ℃, the rolling temperature is lower, the grain size is finer, the grain size grade is higher, the spinning temperature is lower, and the tempered Wittig body ratio is smaller, so that the spinning temperature can be further controlled to regulate and control the ratio of tempered pearlite to tempered Wittig body.
Preferably, the molten salt temperature of the online salt bath strong isothermal treatment is 560-590 ℃, and the isothermal time is 370-650 s; after the wire rod subjected to wire spinning is directly subjected to online salt bath strong isothermal treatment, the wire rod can be subjected to rapid reduction of the wire spinning temperature to the molten salt temperature, the higher the molten salt temperature is, the longer the isothermal time is, the larger the lamellar spacing of a tempered pearlite structure is, the tempering softening and toughening effect is obvious, the strength of the cold heading steel wire rod is reduced, the plasticity is increased, the ferrite structure can appear when the molten salt temperature is too high, the excessively long isothermal time can cause the energy consumption to be too high, and the wire rod strength loss is large, otherwise, the lower the molten salt temperature is, the shorter the isothermal time is, the lamellar spacing of the tempered pearlite structure is smaller, the strength of the cold heading steel wire rod is increased, the plasticity is reduced, the abnormal bainite structure can appear when the molten salt temperature is too low, the pearlite and the Width body structure are insufficiently tempered, the toughening effect is reduced, and the plastic loss is large, so that the molten salt temperature and isothermal time of online salt bath strong isothermal treatment can be further controlled, the lamellar spacing of the cold heading steel wire rod, the pearlite structure and the toughening effect can be further regulated, and the plasticity of the wire rod can be further regulated, and matched.
Preferably, the circulation amount of molten salt for the strong isothermal treatment of the online salt bath is controlled to be 320-450 t/h, the temperature rise of the molten salt is less than or equal to 9 ℃, and the treatment precision of the strong isothermal treatment of the online salt bath and the consistency of cold heading steel wire rods can be further controlled by reducing the temperature rise of the molten salt through regulating the circulation amount of the molten salt.
Preferably, the roller way slow cooling adopts a roller way speed of 0.1-0.3 m/s to convey the wire rod into a heat insulation cover, after cooling to 410-440 ℃ for 5-15 min, the roller way speed is increased to 0.7-1.2 m/s until collecting the coil, the roller way is adopted to convey the wire rod into the heat insulation cover for roller way slow cooling treatment, the roller way speed is controlled to continue the high temperature state of the wire rod after salt bath by using a lower cooling speed to further toughen tempered pearlite and tempered Weishi body, meanwhile, when the wire rod is reduced to below 410 ℃, the softening effect is reduced, and in order to avoid product accumulation caused by the excessively low roller way speed, the roller way speed can be properly increased to maintain high-efficiency production.
Compared with the prior art, the invention has the beneficial effects that:
(1) Aiming at the problems that the existing 9.8-grade high-strength fastener cold heading steel wire rod is usually subjected to alloying design to meet the service performance requirement of a high-strength fastener, and multiple spheroidizing annealing and tempering heat treatment are still needed, the production energy consumption is high, the cost is high and the efficiency is low, the invention successfully develops the 9.8-grade high-strength fastener cold heading steel wire rod, adopts the carbon chemical composition design, abandons the microstructure of the traditional ferrite and pearlite, and the microstructure type comprises a mixed structure mainly comprising tempered pearlite and a small amount of Wilstonian, so that the tensile strength is 820-850 MPa, the reduction of area is 58-62%, the strong plastic matching of the cold heading steel wire rod is realized, and the cold heading steel wire rod is used for manufacturing 9.8-grade non-tempering high-strength fastener bolts and other application fields and has good industrial applicability and application prospect.
(2) Aiming at the problems of low efficiency, high abrasion, abnormal structure and insufficient plasticity of the cold heading steel wire rod caused by adopting low-temperature wire-laying and slow cooling or delayed cooling processes of the existing hot-rolled carbon cold heading steel wire rod, the invention successfully develops a manufacturing method of the 9.8-grade hot-rolled carbon non-modulated cold heading steel wire rod, through the design of carbon chemical components, the combination of high-temperature wire-laying, on-line salt bath strong isothermal and roller way slow cooling technology, the high-temperature austenite is enabled to be fully converted into a complex phase structure consisting of pearlite and a small amount of Wittig body by using strong cooling, the matrix strength is provided, long-time tempering is carried out, the tempering pearlite and the tempered Wittig body are promoted to be further toughened, the wire rod structure and performance are regulated and controlled, and the manufacturing method is used for green production of 9.8-grade high-strength fasteners, so that the whole flow production cost is reduced, the production efficiency is improved, and the method has good industrial applicability and application prospect.
Drawings
The foregoing and/or additional aspects and advantages of the invention will become apparent and may be better understood from the following description of embodiments taken in conjunction with the accompanying drawings in which:
FIG. 1 is a metallographic structure diagram of example 1 of the present invention;
FIG. 2 is a metallographic structure diagram of comparative example 1 of the present invention;
FIG. 3 is a metallographic structure diagram of example 2 of the present invention;
FIG. 4 is a metallographic structure of example 3 of the present invention.
Detailed Description
The embodiments described below are exemplary only and are not intended to limit the description of the features and characteristics of the invention, in order to set forth the best mode of carrying out the invention, intended to illustrate it and to enable those skilled in the art to practice it, without any limitation to its scope, which is defined solely by the claims appended hereto.
Example 1:
The preferred embodiment of the manufacturing method of the 9.8-grade hot-rolled carbon non-modulated cold heading steel wire rod comprises the following chemical components in percentage by mass: c:0.43%, si:0.33%, mn:0.46%, P:0.018%, S:0.02% of Fe and the balance of unavoidable impurities; the manufacturing method comprises the following steps of hot rolling, wire laying, on-line salt bath strong isothermal treatment, roller way slow cooling and coil collecting, and specifically comprises the following steps of:
The hot rolling procedure is used for heating a billet with the specification of 220mm multiplied by 220mm through a heating furnace to obtain a high-temperature billet with rolling plasticity, rapidly rolling the billet into a wire rod with the specification of 16mm at high temperature through a rolling line, reducing the abrasion of a rolling mill of the rolling line, improving the rolling efficiency, regulating and controlling the grain size of a structure, preparing a small amount of Wittig bodies for subsequent precipitation on the structure through properly coarsened grains, and specifically: controlling the final rolling temperature to 955 ℃, wherein the grain size of the rolled wire rod is less than or equal to 9 grades; the wire rod of rolling line is used for wire rod through the wire rod machine of throwing, and control wire rod temperature to be 940 ℃, austenitizing be follow-up on-line salt bath strong isothermal treatment, and the preparation on the control pearlite and Wittig body tissue ratio is made on the tissue, and the wire rod spreads on the roll table and is transported along the roll table.
The online salt bath strong isothermal treatment adopts a salt bath tank with molten salt arranged therein, is used for conveying wire rods after spinning to pass through the molten salt of the salt bath tank through a roller way, reduces the cooling speed of the wire rods to the temperature of the molten salt, quickly skips the phase transition temperature interval of ferrite at a higher cooling speed, fully converts high-temperature austenitic tissues in the wire rods into complex phase tissues mainly composed of pearlite and a small amount of Wittig bodies, simultaneously tempers at high temperature for a long time, promotes the tempering of the pearlite to form tempered pearlite, regulates the lamellar spacing of the tempered pearlite, and further toughens the Wittig bodies to form tempered Wittig bodies, and is also used for avoiding the occurrence of abnormal bainitic tissues in the roller way slow cooling process due to higher sensitivity of carbon steel, and is specific: the molten salt temperature is 569 ℃, the isothermal time is 455s, the molten salt circulation amount is 410t/h, and the molten salt temperature rise is less than or equal to 9 ℃.
The roller way slow cooling procedure is to convey the wire rods coming out of the salt bath into a heat preservation cover for slow cooling treatment by using a roller way, and the high temperature state of the wire rods after the on-line strong isothermal treatment of the salt bath is utilized to promote the tempering pearlite and the tempering Wittig body to be further toughened, so that the softening effect of the wire rod matrix structure is improved, and the method is specific: conveying the wire rods from the salt bath into a heat preservation cover at a roller way speed of 0.2m/s, cooling to 420 ℃ for 12min, and then increasing the roller way speed to 1m/s until the wire rods are conveyed to a coil collecting station; the coil collecting procedure is used for collecting and coiling the wire rods into coils through a coil collecting drum, and obtaining cold heading steel wire rod finished products after packaging and warehousing, and a metallographic structure diagram of the cold heading steel wire rod finished products is shown in figure 1.
Comparative example 1:
A manufacturing method of a hot-rolled carbon cold heading steel wire rod is different from example 1 in that: the manufacturing method comprises the following steps of hot rolling, spinning, delayed cooling and coil collecting, and specifically comprises the following steps of: the final rolling temperature of the hot rolling process is 802 ℃, the grain size of the rolled wire rod is 11 grade, the wire laying temperature of the wire laying process is 785 ℃, the delayed cooling is achieved by conveying the wire rod subjected to wire laying into a heat insulation cover through a roller way, phase transformation is completed in the cover at a cooling speed of 0.6 ℃/s, and the cold heading steel wire rod is obtained after coil collection and wire laying, and a metallographic structure diagram of the cold heading steel wire rod is shown in figure 2.
Comparative example 2:
A manufacturing method of a hot-rolled carbon cold heading steel wire rod is different from example 1 in that: the manufacturing method comprises the following steps of hot rolling, spinning, quick air cooling of stelmor, heat preservation cooling and coil collection, and specifically comprises the following steps of: the method comprises the steps of starting a 1-4 # fan according to 50% of the Steyr rapid air cooling, controlling a wire rod to cool to 745 ℃ at a speed of 4.9 ℃/s, closing a heat preservation cover by the fan, conveying the wire rod into the heat preservation cover at a roller way speed of 0.2m/s, and operating the wire rod in the cover at a cooling speed of 0.2 ℃/s until the wire rod is collected, and obtaining the cold heading steel wire rod after the wire rod is collected and taken off.
Example 2:
The preferred embodiment of the manufacturing method of the 9.8-grade hot-rolled carbon non-modulated cold heading steel wire rod comprises the following chemical components in percentage by mass: c:0.39%, si:0.26%, mn:0.5%, P:0.02%, S:0.017%, the balance being Fe and unavoidable impurities; the manufacturing method comprises the following steps of hot rolling, wire laying, on-line salt bath strong isothermal treatment, roller way slow cooling and coil collecting, and specifically comprises the following steps of:
the hot rolling procedure is used for heating a billet with the specification of 160mm multiplied by 160mm through a heating furnace to obtain a high-temperature billet with rolling plasticity, rapidly rolling the billet into a wire with the specification of 8mm at high temperature through a rolling line, reducing the abrasion of a rolling mill of the rolling line, improving the rolling efficiency, regulating and controlling the grain size of a structure, preparing a small amount of Wittig bodies for subsequent precipitation on the structure through properly coarsened grains, and specifically: controlling the final rolling temperature to 974 ℃, wherein the grain size of the rolled wire rod is less than or equal to 9 grades; the wire rod of rolling line is used for wire rod through the wire rod machine of throwing, and the wire rod is transported along the roll table on the roll table by regulating and controlling pearlite and Wittig body tissue ratio when the wire rod is treated by austenitizing to be in the subsequent online salt bath strong isothermal treatment at 958 ℃.
The online salt bath strong isothermal treatment adopts a salt bath tank with molten salt arranged therein, is used for conveying wire rods after spinning to pass through the molten salt of the salt bath tank through a roller way, reduces the cooling speed of the wire rods to the temperature of the molten salt, quickly skips the phase transition temperature interval of ferrite at a higher cooling speed, fully converts high-temperature austenitic tissues in the wire rods into complex phase tissues mainly composed of pearlite and a small amount of Wittig bodies, simultaneously tempers at high temperature for a long time, promotes the tempering of the pearlite to form tempered pearlite, regulates the lamellar spacing of the tempered pearlite, and further toughens the Wittig bodies to form tempered Wittig bodies, and is also used for avoiding the occurrence of abnormal bainitic tissues in the roller way slow cooling process due to higher sensitivity of carbon steel, and is specific: the molten salt temperature is 560 ℃, the isothermal time is 370s, the molten salt circulation quantity is 450t/h, and the molten salt temperature rise is less than or equal to 9 ℃.
The roller way slow cooling procedure is to convey the wire rods coming out of the salt bath into a heat preservation cover for slow cooling treatment by using a roller way, and the high temperature state of the wire rods after the on-line strong isothermal treatment of the salt bath is utilized to promote the tempering pearlite and the tempering Wittig body to be further toughened, so that the softening effect of the wire rod matrix structure is improved, and the method is specific: conveying the wire rods from the salt bath into a heat preservation cover at a roller way speed of 0.1m/s, cooling to 440 ℃ for 15min, and then increasing the roller way speed to 1.2m/s until the wire rods are conveyed to a coil collecting station; the coil collecting procedure is used for collecting and coiling the wire rods into coils through a coil collecting drum, and obtaining cold heading steel wire rod finished products after packaging and warehousing, and a metallographic structure diagram of the cold heading steel wire rod finished products is shown in figure 3.
Comparative example 3:
a manufacturing method of a hot-rolled carbon cold heading steel wire rod, which is different from example 2 in that: the final rolling temperature is controlled to be 947 ℃, the grain size of the rolled wire rod is controlled to be 10 grade, the wire laying temperature is controlled to be 930 ℃, and the cold heading steel wire rod is obtained after coil collecting and coil discharging.
Comparative example 4:
a manufacturing method of a hot-rolled carbon cold heading steel wire rod, which is different from example 2 in that: and controlling the temperature of molten salt to be 482 ℃, and obtaining the cold heading steel wire rod after coil collecting and coil discharging.
Example 3:
The preferred embodiment of the manufacturing method of the 9.8-grade hot-rolled carbon non-modulated cold heading steel wire rod comprises the following chemical components in percentage by mass: c:0.41%, si:0.35%, mn:0.3%, P:0.018%, S:0.015% of Fe and the balance of unavoidable impurities; the manufacturing method comprises the following steps of hot rolling, wire laying, on-line salt bath strong isothermal treatment, roller way slow cooling and coil collecting, and specifically comprises the following steps of:
The hot rolling procedure is used for heating a billet with the specification of 220mm multiplied by 220mm through a heating furnace to obtain a high-temperature billet with rolling plasticity, rapidly rolling the billet into a wire with the specification of 11mm at high temperature through a rolling line, reducing the abrasion of a rolling mill of the rolling line, improving the rolling efficiency, regulating and controlling the grain size of a structure, preparing a small amount of Wittig bodies for subsequent precipitation on the structure through properly coarsened grains, and specifically: controlling the final rolling temperature to 965 ℃, wherein the grain size of the rolled wire rod is less than or equal to 9 grades; the wire rod of rolling line is used for wire rod through the wire rod machine of throwing, and the wire rod is transported along the roll table on the roll table by regulating and controlling pearlite and Wittig body tissue ratio when the wire rod is treated by austenitizing to be in the subsequent online salt bath strong isothermal treatment at 949 ℃.
The online salt bath strong isothermal treatment adopts a salt bath tank with molten salt arranged therein, is used for conveying wire rods after spinning to pass through the molten salt of the salt bath tank through a roller way, reduces the cooling speed of the wire rods to the temperature of the molten salt, quickly skips the phase transition temperature interval of ferrite at a higher cooling speed, fully converts high-temperature austenitic tissues in the wire rods into complex phase tissues mainly composed of pearlite and a small amount of Wittig bodies, simultaneously tempers at high temperature for a long time, promotes the tempering of the pearlite to form tempered pearlite, regulates the lamellar spacing of the tempered pearlite, and further toughens the Wittig bodies to form tempered Wittig bodies, and is also used for avoiding the occurrence of abnormal bainitic tissues in the roller way slow cooling process due to higher sensitivity of carbon steel, and is specific: the temperature of the molten salt is 584 ℃, the isothermal time is 591s, the circulation quantity of the molten salt is 395t/h, and the temperature rise of the molten salt is less than or equal to 9 ℃.
The roller way slow cooling procedure is to convey the wire rods coming out of the salt bath into a heat preservation cover for slow cooling treatment by using a roller way, and the high temperature state of the wire rods after the on-line strong isothermal treatment of the salt bath is utilized to promote the tempering pearlite and the tempering Wittig body to be further toughened, so that the softening effect of the wire rod matrix structure is improved, and the method is specific: conveying the wire rods from the salt bath into a heat preservation cover at a roller way speed of 0.25m/s, cooling to 416 ℃ for 8min, and then increasing the roller way speed to 0.9m/s until the wire rods are conveyed to a coil collecting station; the coil collecting procedure is used for collecting and coiling the wire rods into coils through a coil collecting drum, and obtaining a cold heading steel wire rod finished product after packaging and warehousing, and a metallographic structure diagram of the cold heading steel wire rod finished product is shown in fig. 4.
Comparative example 5:
A manufacturing method of a hot-rolled carbon cold heading steel wire rod, which is different from example 3 in that: controlling the molten salt temperature to be 625 ℃, the isothermal time to be 700s, and obtaining the cold heading steel wire rod after coil collection and offline.
Comparative example 6:
A manufacturing method of a hot-rolled carbon cold heading steel wire rod, which is different from example 3 in that: and controlling the molten salt temperature to be 550 ℃ and the isothermal time to be 350s, and obtaining the cold heading steel wire rod after coil collection and coil discharging.
Example 4:
The preferred embodiment of the manufacturing method of the 9.8-grade hot-rolled carbon non-modulated cold heading steel wire rod comprises the following chemical components in percentage by mass: c:0.44%, si:0.15%, mn:0.38%, P:0.017%, S:0.016 percent of Fe and the balance of unavoidable impurities; the manufacturing method comprises the following steps of hot rolling, wire laying, on-line salt bath strong isothermal treatment, roller way slow cooling and coil collecting, and specifically comprises the following steps of:
The hot rolling procedure is used for heating a billet with the specification of 220mm multiplied by 220mm through a heating furnace to obtain a high-temperature billet with rolling plasticity, rapidly rolling the billet into a wire with the specification of 18mm at high temperature through a rolling line, reducing the abrasion of a rolling mill of the rolling line, improving the rolling efficiency, regulating and controlling the grain size of a structure, preparing a small amount of Wittig bodies for subsequent precipitation on the structure through properly coarsened grains, and specifically: controlling the final rolling temperature to 950 ℃ and controlling the grain size of the rolled wire rod to be less than or equal to 9 grades; the wire rod of rolling line is used for wire rod through the wire rod machine of throwing, and the wire rod is controlled to be at 935 ℃ in the wire rod throwing process, and when austenitizing is carried out in the subsequent online salt bath strong isothermal treatment, the preparation on the structure of pearlite and Wittig body structure is regulated and controlled, and the wire rod is scattered on a roller way and conveyed along the roller way.
The online salt bath strong isothermal treatment adopts a salt bath tank with molten salt arranged therein, is used for conveying wire rods after spinning to pass through the molten salt of the salt bath tank through a roller way, reduces the cooling speed of the wire rods to the temperature of the molten salt, quickly skips the phase transition temperature interval of ferrite at a higher cooling speed, fully converts high-temperature austenitic tissues in the wire rods into complex phase tissues mainly composed of pearlite and a small amount of Wittig bodies, simultaneously tempers at high temperature for a long time, promotes the tempering of the pearlite to form tempered pearlite, regulates the lamellar spacing of the tempered pearlite, and further toughens the Wittig bodies to form tempered Wittig bodies, and is also used for avoiding the occurrence of abnormal bainitic tissues in the roller way slow cooling process due to higher sensitivity of carbon steel, and is specific: the molten salt temperature is 590 ℃, the isothermal time is 650s, the molten salt circulation quantity is 320t/h, and the molten salt temperature rise is less than or equal to 9 ℃.
The roller way slow cooling procedure is to convey the wire rods coming out of the salt bath into a heat preservation cover for slow cooling treatment by using a roller way, and the high temperature state of the wire rods after the on-line strong isothermal treatment of the salt bath is utilized to promote the tempering pearlite and the tempering Wittig body to be further toughened, so that the softening effect of the wire rod matrix structure is improved, and the method is specific: conveying the wire rods from the salt bath into a heat preservation cover at a roller way speed of 0.3m/s, cooling to 410 ℃ for 6min, and then increasing the roller way speed to 0.7m/s until the wire rods are conveyed to a coil collecting station; the coil collecting procedure is used for collecting and winding the coil rod into coils through the coil collecting drum, and obtaining a cold heading steel coil rod finished product after packaging and warehousing.
Comparative example 7:
A manufacturing method of a hot-rolled carbon cold heading steel wire rod, which is different from example 4 in that: the manufacturing method comprises the steps of hot rolling, wire laying, on-line strong isothermal treatment in salt bath, air cooling and coil collecting, wherein the air cooling is realized by adopting the steps of closing a fan, opening a heat preservation cover, conveying at a roller way speed of 0.95m/s, and obtaining the cold heading steel coil after coil collecting and coil discharging, wherein the cooling speed of the coil is 2.3 ℃/s.
The cold heading steel wire rods obtained in the examples and the comparative examples are subjected to structure and performance detection: tensile testing was performed using the metal material tensile test section 1 of GB-T228.1-2021: room temperature test method, to obtain tensile strength and reduction of area, and to perform tissue detection according to the metal microstructure detection method of GB/T13298 standard, the comparison results obtained are shown in table 1 below:
TABLE 1 comparison of the composition of the steel wire rods of the different Cold heading and the properties of the wire rod structure of the manufacturing method
Compared with the existing low-temperature wire laying and delayed cooling processes, the method still can separate out abnormal structures at the tail end of a stelmor air cooling line to obviously lower the plasticity of cold heading steel wire rods, on the basis of the C-Si-Mn carbon steel components, coarse high-temperature austenite after high Wen Tu wires passes through online salt bath, the transformation temperature interval of ferrite can be quickly skipped at a higher cooling speed, the austenite is transformed into a complex phase structure with a needle-shaped morphology and a small amount of pre-eutectoid phase mixed with lamellar pearlite to form a Winter body structure, and the problem that the existing bainite abnormal structure occurs due to the increase of the sensitivity of the carbon steel is avoided; as can be seen from the comparison results of examples 1-4 and comparative example 2, compared with the existing high-temperature wire laying process adopting rapid air cooling and heat preservation cooling, the invention not only can fully inoculate pearlite and Wittig body tissues and provide matrix strength, but also can temper at high temperature for a longer time, promote tempering of pearlite and Wittig body tissues to form tempered pearlite and tempered Wittig body and further toughen, adjust the lamellar spacing of the tempered pearlite tissues, the lamellar spacing of the tempered pearlite is 150-180 nm after roller way slow cooling, the cold forging steel wire rod can achieve the tensile strength of 820-850 MPa and the reduction of area of 58-62%, the strong plastic matching of the cold forging steel wire rod is realized, and the invention is used for manufacturing 9.8-grade non-tempering high strength fastener bolts and other application fields and has good industrial applicability and application prospects.
As can be seen from the comparison results of examples 1-4 and comparative example 3, the higher the spinning temperature is, the larger the proportion of tempered Wittig bodies in the mixed structure is, and the higher the proportion of tempered Wittig bodies is, the strength of the cold heading steel wire rod is increased, and the plasticity is reduced, so that the proportion of tempered pearlite and tempered Wittig bodies can be further regulated, and the strong-plasticity matching of the cold heading steel wire rod can be further regulated; as is clear from the comparison between the example 2 and the comparative example 4, the bainite abnormal structure occurs when the molten salt temperature is too low, which is disadvantageous to the wire rod plasticity.
As can be seen from the comparison result of the embodiment 3 and the comparative example 5, ferrite can appear when the molten salt temperature is too high, the temperature of the molten salt is too high, the isothermal time is too long, the lamellar spacing of the tempered pearlite structure is too large, the tempering softening and toughening effects are more obvious, and the strength and plasticity of the cold heading steel wire rod are reduced; as can be seen from the comparison result of the embodiment 3 and the comparative example 6, the molten salt temperature is too low and the isothermal time is too short, the lamellar spacing in the tempered pearlite structure is too small, and the strength and plasticity of the cold heading steel wire rod are increased, so that the molten salt temperature and isothermal time of the on-line salt bath strong isothermal treatment can be further controlled, and the mixed structure of the cold heading steel wire rod, the lamellar spacing of the tempered pearlite structure and the tempering toughening effect can be further regulated.
As is apparent from the comparison between the results of example 4 and comparative example 7, the softening effect in the late stage of the strong isothermal treatment in the online salt bath can be exerted by the roller way slow cooling, the further toughening of tempered pearlite and tempered Wittig body can be promoted, and the softening effect of the wire rod matrix structure can be improved.
The above list of detailed descriptions is only specific to practical embodiments of the present invention, and they are not intended to limit the scope of the present invention, for example: the billet before hot rolling can be produced by adopting the process flows of converter smelting, refining and continuous casting, and all equivalent embodiments or changes which do not depart from the technical spirit of the invention are included in the protection scope of the invention.
Claims (10)
1. The 9.8-grade hot-rolled carbon non-cold heading steel wire rod is characterized by comprising the following chemical components in percentage by mass: c:0.39% -0.44%, si:0.15% -0.35%, mn: 0.3-0.5%, P is less than or equal to 0.020%, S is less than or equal to 0.020%, and the balance is Fe and unavoidable impurities; the microstructure comprises a mixed structure composed of 80-89% by volume of tempered pearlite and 11-20% by volume of tempered Wittig body; the manufacturing method comprises the following steps:
Based on the chemical composition hot rolling production wire rod of the 9.8-grade hot rolled carbon non-cold heading steel wire rod, wire rod is spun into wire rod according to spinning temperature of more than or equal to 935 ℃, the wire rod is subjected to on-line salt bath strong isothermal treatment, so that the wire rod is cooled to molten salt temperature according to cooling speed of more than or equal to 33 ℃/s, high-temperature austenite in the wire rod structure is converted into a complex phase structure consisting of pearlite and Wittig body, isothermal tempering is carried out, and finally, the wire rod is slowly cooled by a roller way, so that the cold heading steel wire rod with a microstructure comprising a mixed structure consisting of tempered pearlite as main component and a small amount of tempered Wittig body is manufactured;
The final rolling temperature is controlled to be more than or equal to 950 ℃ in hot rolling production, the grain size of the rolled wire rod is less than or equal to 9 levels, the molten salt temperature of the on-line salt bath strong isothermal treatment is 560-590 ℃, the isothermal time is 370-650 s, the roller way slow cooling adopts the roller way speed of 0.1-0.3 m/s to convey the wire rod into a heat preservation cover, and after the wire rod is cooled to 410-440 ℃ for 5-15 min, the roller way speed is increased to 0.7-1.2 m/s until coil collection.
2. The 9.8-grade hot rolled carbon non-cold heading steel wire rod according to claim 1, wherein the lamellar spacing of the tempered pearlite is 150-180 nm.
3. The 9.8-grade hot rolled carbon non-modulated cold heading steel wire rod of claim 1, wherein the cold heading steel wire rod has a specification of 8.0-18.0 mm, a tensile strength of 820-850 mpa and a reduction of area of 58-62%.
4. Use of a 9.8 grade hot rolled carbon non-temper forging steel wire rod as claimed in claim 1, comprising for producing a 9.8 grade cold forging fastener in an annealing-free and tempering-free condition.
5. The manufacturing method of the 9.8-grade hot-rolled carbon non-cold heading steel wire rod is characterized by comprising the following steps of:
The 9.8-grade hot-rolled carbon non-cold heading steel wire rod based on the chemical component hot rolling production wire rod, wherein the wire rod is spun into the wire rod according to the spinning temperature of more than or equal to 935 ℃, the wire rod is subjected to on-line salt bath strong isothermal treatment, so that the wire rod is cooled to the molten salt temperature according to the cooling speed of more than or equal to 33 ℃/s, the high-temperature austenite in the wire rod structure is converted into a complex phase structure consisting of pearlite and Wittig body, isothermal tempering is carried out, and finally the complex phase structure is slowly cooled by a roller way, so that the cold heading steel wire rod with a microstructure comprising a mixed structure consisting of tempered pearlite as main and a small amount of tempered Wittig body is prepared.
6. The method for manufacturing a 9.8-grade hot rolled carbon non-cold heading steel wire rod according to claim 5, wherein the hot rolling production is performed at a controlled finish rolling temperature of not less than 950 ℃ and the grain size of the wire rod after rolling is not more than 9 grade.
7. The method of producing a 9.8-grade hot rolled carbon non-cold heading steel wire rod as defined in claim 6, wherein the wire laying temperature is < 960 ℃.
8. The method for manufacturing a 9.8-grade hot rolled carbon non-cold heading steel wire rod according to any one of claims 5 to 7, wherein the molten salt temperature of the on-line salt bath strong isothermal treatment is 560 to 590 ℃, and the isothermal time is 370 to 650s.
9. The manufacturing method of the 9.8-grade hot rolled carbon non-cold heading steel wire rod, which is characterized by controlling the molten salt circulation amount of the online salt bath strong isothermal treatment to be 320-450 t/h and the molten salt temperature rise to be less than or equal to 9 ℃.
10. The method for manufacturing the 9.8-grade hot-rolled carbon non-cold heading steel wire rod, which is characterized in that the roller way slow cooling is carried into a heat preservation cover at a roller way speed of 0.1-0.3 m/s, after cooling to 410-440 ℃ for 5-15 min, the roller way speed is increased to 0.7-1.2 m/s until coil collection.
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| CN118186310B (en) * | 2024-05-17 | 2024-08-30 | 江苏永钢集团有限公司 | 12.9-Grade quenching-free high-hardenability hot-rolled multiphase cold heading steel wire rod and manufacturing method thereof |
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| CN107326161A (en) * | 2017-05-26 | 2017-11-07 | 邢台钢铁有限责任公司 | A kind of control method of medium carbon cold heading steel wire rod Widmannstatten structure |
| CN118166189A (en) * | 2024-05-16 | 2024-06-11 | 江苏永钢集团有限公司 | 12.9-Grade annealing-free hot-rolled complex-phase cold heading steel wire rod and manufacturing method thereof |
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