CN118166191B - Manufacturing method of 9.8-grade non-cold-heading steel high-strength hot-rolled wire rod - Google Patents

Manufacturing method of 9.8-grade non-cold-heading steel high-strength hot-rolled wire rod Download PDF

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Publication number
CN118166191B
CN118166191B CN202410607550.3A CN202410607550A CN118166191B CN 118166191 B CN118166191 B CN 118166191B CN 202410607550 A CN202410607550 A CN 202410607550A CN 118166191 B CN118166191 B CN 118166191B
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wire rod
molten salt
strength
bainite
rolled wire
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CN118166191A (en
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彭梦都
时彤彤
于同仁
余超
李成斌
张叶飞
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Jiangsu Yonggang Group Co Ltd
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Jiangsu Yonggang Group Co Ltd
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    • 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
    • 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
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • 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
    • C21D2211/002—Bainite
    • 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
    • C21D2211/004—Dispersions; Precipitations
    • 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
    • C21D2211/005—Ferrite
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical 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 manufacturing method of a 9.8-grade non-cold heading steel high-strength hot rolled wire rod, which adopts a C-Si-Mn-Mo component design, wherein Mo is used for effectively inhibiting coarsening of carbide in the early stage of online molten salt controlled cooling, the wire rod after hot rolling and wire spinning is subjected to online molten salt controlled cooling, the molten salt temperature is 570-640 ℃, the isothermal time is 350-700 s, the wire rod is quenched into quenched bainite at a cooling speed of more than or equal to 30 ℃/s, the quenched bainite is promoted to be softened into tempered bainite through isothermal tempering, and then the tempered bainite is slowly cooled through a roller way, so that the hot rolled wire rod with a structure comprising a mixed structure of tempered bainite, a small amount of ferrite and quasi-spheroidized carbide can be manufactured at the same time, the high-strength and plastic matching of the wire rod can be realized, the tensile strength of 830-860 MPa and the section shrinkage rate of 61-67% can be achieved, and the green efficient production requirements of 9.8-grade non-high-strength fastener bolts and other application fields are met.

Description

Manufacturing method of 9.8-grade non-cold-heading steel high-strength hot-rolled wire rod
Technical Field
The invention belongs to the technical field of cold heading steel hot rolled wire rods, and particularly relates to a manufacturing method of a 9.8-grade non-adjustable cold heading steel high-strength hot rolled wire rod.
Background
The production and manufacture of the fastener often need to be subjected to multiple heat treatments, especially the production and manufacture of the 9.8-grade and above high-strength fastener often can reach the corresponding performance grade requirement through multiple spheroidizing annealing and quenching and tempering heat treatment after cold heading forming, but the production efficiency is low, the energy consumption is high, the cost is high and the like. Along with the development of new energy automobile industry and market use demands, the common problems of multiple processing procedures, long period, high energy consumption of multiple heat treatment and high-cost and low-efficiency production of the high-strength fastener bolt are continuously revealed, and the 9.8-grade non-cold heading steel high-strength hot rolled wire rod is developed so as to avoid annealing and quenching and tempering treatment, and the green and high-efficiency production of the 9.8-grade fastener is realized only after drawing and cold heading, so that the problem to be solved is urgently needed at present.
In order to omit the annealing and tempering processes, the hot rolled wire rod of the non-tempering upsetting steel is required to have a component system with higher strength so as to ensure that the 9.8-grade performance grade can be achieved after aging treatment, so that compared with the hot rolled wire rod of the 8.8-grade non-tempering upsetting steel, the hot rolled wire rod of the 9.8-grade non-tempering upsetting steel has higher plastic lifting difficulty on the basis of component design, and meanwhile, the wire rod is required to have higher strength and plastic matching so as to avoid cracking in the drawing and cold upsetting processes. The 9.8-grade non-cold heading steel hot rolled wire rod in the prior art generally adopts a stelmor cooling control process design after rolling and wire laying, 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-Cr-Al component design is adopted, a low-temperature rolling and a Sitelmor slow cooling process are combined to obtain a wire rod structure with the F+P proportion of more than or equal to 99%, the tensile strength is 750-800 MPa, the reduction of area is more than or equal to 50%, on one hand, the content of Mn, V and Cr is reduced for the purpose of reducing the wire rod cost, the strength of the wire rod is seriously reduced, on the other hand, the rolling temperature is increased for the purpose of reducing the wire rod abrasion, the rolling speed and the rolling efficiency, the maximum cooling capacity of the Sitelmor cooling is limited, the online time of the wire rod in the Sitelmor wire rod is obviously prolonged, and even if the low-temperature rolling is adopted, the wire rod can only be cooled to a soft phase transition temperature interval of ferrite and pearlite, the wire rod strength is insufficient, the wire rod can only be maintained in a high-temperature state in a continuous slow cooling process due to the limited cooling capacity of the Sitelmor cooling, and the low-temperature carbonization state of the wire rod cannot be further subjected to the short-time plastic carbonization after the wire rod is inoculated.
Although the prior art discloses the use of a post-laying salt bath treatment to improve the restriction of strengthening and microalloying elements to non-quenched and tempered steel wire rods, for example: according to the non-quenched and tempered steel wire rod and the production method thereof disclosed in the patent CN117327883B, a C-Si-Mn-Ti-Al component design is adopted, and after spinning, a salt bath treatment is carried out at 400-500 ℃ for 180-250 seconds, so that a metallographic structure with the bainite content of more than or equal to 85% and the ferrite content of less than 15% is obtained, other abnormal structures such as pearlite and martensite are avoided, the tensile strength is 620-725 MPa, the reduction of area is 75-85%, on one hand, the purpose of improving the plasticity of the wire rod is to reduce the carbon content, the strength of the wire rod is reduced, the lower tensile strength is required to meet the 9.8-grade strength grade requirement due to the large drawing deformation and cold deformation strengthening strength, and the loss of plasticity is greater in the process, and the risk of cold heading cracking is aggravated; on the other hand, carbon is used as a more economic strengthening element, so that the medium carbon steel content is kept for the purposes of improving the strength of the wire rod, reducing the cost of the wire rod and meeting the requirements of a 9.8-level non-cold heading steel component system, the risks of coarsening and growing up of carbide in the salt bath process are aggravated, the spheroidization of the carbide in the isothermal process is inhibited, and the plasticity of the wire rod is improved to a limited extent.
Disclosure of Invention
The invention aims to solve at least one of the technical problems to a certain extent, and provides a manufacturing method of a 9.8-grade non-adjustable cold heading steel high-strength hot-rolled wire rod, which can give consideration to manufacturing cost, realize high-strength and plastic matching of the wire rod and meet the green and high-efficiency production requirements of 9.8-grade non-adjustable high-strength fastener bolts and other application fields.
The technical scheme adopted for solving the technical problems is as follows:
The manufacturing method of the 9.8-grade non-cold heading steel high-strength hot rolled wire rod is characterized by comprising the following chemical components in percentage by mass: c:0.30% -0.38%, si:0.20% -0.40%, mn:0.65% -0.85%, P is less than or equal to 0.020%, S is less than or equal to 0.020%, mo:0.15% -0.30%, and the balance of Fe and unavoidable impurities; the manufacturing method comprises the following steps: the wire rod after hot rolling and wire spinning is subjected to online molten salt controlled cooling, so that the wire rod is quenched into quenched bainite at a cooling speed of more than or equal to 30 ℃/s, the quenched bainite is promoted to be isothermally tempered and softened into tempered bainite, and then the tempered bainite is slowly cooled by a roller way, so that the hot rolled wire rod with a structure comprising a mixed structure of tempered bainite, a small amount of ferrite and quasi-spheroidized carbide is manufactured.
The design basis of the chemical components and the mass percentages of the hot rolled 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, is favorable for promoting the transformation from austenite to quenched bainite through improving the hardenability, but can lead to the reduction of the plasticity of the steel, increases the decarburization sensitivity and the coarsening risk of carbide, and ensures the high plasticity and the cold working performance of the steel and the final strength level of a 9.8-level non-adjustable fastener, so that the mass percentage of C is controlled to be 0.30% -0.38%.
(2) Silicon: si is a ferrite forming element, can be used as a solid solution hardening element to help the strength to be improved, and can inhibit the coarsening of crystal grains in an online molten salt cooling control stage, so as to inhibit the formation of cementite and the coarsening of carbide, and is beneficial to the spheroidization transformation of carbide, so that the matrix structure is softened by isothermal tempering; however, excessive silicon is unfavorable for cold plastic deformation of steel, so that smelting is difficult and inclusions are easy to form, and therefore, the mass percentage of Si is controlled to be 0.20% -0.40%.
(3) Manganese: mn element can improve the strength grade of the wire rod through solid solution strengthening effect, so that the hardenability of steel is obviously improved, but too high Mn content can increase the overheat sensitivity and coarse grain risk of the steel, and has adverse effects on plasticity and structure control of the steel, so that the mass percent of Mn is controlled to be 0.65% -0.85% in order to achieve both the strength and cold processing performance of the steel.
(4) Molybdenum: mo can obviously improve the hardenability in steel and the tempering stability of the wire rod, so that the transformation from austenite to pearlite in the phase transformation process is inhibited, the bainitic structure is easier to obtain, the coarsening of carbide in the early stage of online molten salt controlled cooling can be effectively inhibited, the growth of carbide in the steel is inhibited, the spheroidization of carbide of tempered bainite in the tempering isothermal process is further promoted, the structure state of the wire rod is favorably regulated and controlled, but the production cost of the wire rod is improved due to the excessively high Mo content, and therefore, the mass percentage of Mo is controlled to be 0.15% -0.30%.
(5) Phosphorus, sulfur: the lower the P element and the S element are, the better, so that the P is less than or equal to 0.020% and the S is less than or equal to 0.020%.
In summary, in order to ensure that the performance grade of the 9.8-grade fastener can be obtained after non-thermal refining, the C-Si-Mn-Mo component design is adopted; on the basis, on-line molten salt controlled cooling is performed by adopting the wire rod direct molten salt treatment after spinning, on one hand, compared with the existing stelmor air cooling process, the cooling speed of the wire rod can be obviously improved, soft-phase pearlite structure is avoided, austenite structure in the wire rod structure after spinning is promoted to be rapidly quenched into quenched bainite, compared with the existing salt bath treatment process, the quenched bainite structure is tempered and softened into tempered bainite structure in a further molten salt isothermal process, the characteristic of high strength of quenched bainite is reserved, the strength loss caused by elements such as Cr and V with higher cost is overcome, the strength of the final wire rod is obviously enhanced, and the plasticity of quenched bainite is improved through tempering, so that the tempered bainite structure with higher plasticity is obtained.
On the other hand, the wire rod can be quickly reduced to the molten salt temperature through the molten salt, compared with a stelmor air cooling process, the wire rod can keep a high-temperature isothermal state for a longer time rather than slow cooling, can enable a small amount of austenitic structure to be converted into a ferrite structure with higher plasticity, is favorable for promoting the isothermal tempering softening of quenched bainite into tempered bainite, and the finer and easier spheroidization of a slice after the quenched bainite is converted into tempered bainite, compared with the existing salt bath treatment process, by the design of the chemical composition containing Mo, the coarsening of carbide in the early stage of online molten salt controlled cooling can be effectively inhibited, the carbide growth in steel can be inhibited, the tempered bainite structure with long high temperature and finer length can be realized, the tempering bainite transformation to quasi-spheroidized carbide can be facilitated, the tempering bainite regulation and control wire rod structure is further softened, the final plasticity of the wire rod is improved, then the tempering bainite regulation and control wire rod structure is slowly cooled through the roller way, the tempering softening effect of the wire rod in the later stage of online molten salt control cooling can be continued by utilizing the wire rod to be in a high temperature state after online salt bath control cooling, the tempering bainite fusing spheroidization and further toughening are promoted, the softening effect of the wire rod matrix structure is improved, compared with the online molten salt control cooling time is prolonged, the roller way slow cooling can avoid the strength loss caused by excessive softening, the energy consumption is lower and more economical, thereby finally realizing the structure regulation and control on the basis of component design, realizing the high-strength and plastic matching of the wire rod, and having good industrial adaptability.
Preferably, the hot rolling process controls the final rolling temperature to be more than or equal to 920 ℃, compared with the prior stelmor air cooling process, the online molten salt controlled cooling has higher cooling speed, can be cooled to a bainite transformation temperature interval more stably, can avoid martensite brittleness defect caused by stelmor forced cooling and temper softening in a longer high-temperature state, and can break the manufacturing limit of low-temperature rolling on 9.8-grade non-cold heading high hot rolled wire rods, reduce the abrasion on a rolling mill at a relatively higher final rolling temperature, and improve the rolling speed and efficiency.
Preferably, the spinning process controls the spinning temperature to be more than or equal to 880 ℃, so that the wire rod tissue can be completely austenitized, and a foundation is provided for the subsequent tissue transformation.
Preferably, the molten salt temperature of the online molten salt cooling control process is 570-640 ℃, and the isothermal time is 350-700 s; in the molten salt temperature interval, the lower the temperature is, the higher the tempered bainite content is, the strength of the wire rod is obviously increased, but the lower the temperature is, the tempered martensite is generated, and the plasticity of the wire rod is obviously reduced; conversely, the higher the temperature is, the ferrite content in the structure is increased, and the plasticity of the ferrite is higher than that of tempered bainite, but the strength is obviously reduced, so that the plasticity of the wire rod is improved and the strength is obviously reduced; the shorter the isothermal time is, the softening effect of tempered bainite is reduced, the content of quasi-spheroidized carbide is reduced, plastic loss is caused, the isothermal time is too short, the incomplete tempering transformation of quenched bainite can obviously reduce the plasticity of a wire rod, and the excessively long isothermal time increases the energy consumption and the manufacturing cost and is accompanied by a certain degree of strength loss; therefore, by further controlling the molten salt temperature and the isothermal time, the tissue proportion in the mixed tissue can be regulated and controlled on the basis of considering the manufacturing cost, and the wire rod strong plasticity matching is realized.
Preferably, the online molten salt cooling control procedure controls the molten salt temperature rise to be less than or equal to 10 ℃, and the molten salt temperature rise can be further controlled by controlling the molten salt circulation quantity, so that the tissue regulation precision is improved, and the fluctuation of the mechanical property of the wire rod is reduced.
Preferably, the roller way slow cooling procedure controls the cooling speed of the wire rod to be 0.3-1.5 ℃/s, the wire rod can be conveyed by the roller way to enter the heat insulation cover, slow running slow cooling is performed at Wen Zhaona, the time that the wire rod is in a high-temperature state is shortened, the high-temperature softening effect of the roller way slow cooling is reduced, the phenomenon that the conveying speed of the roller way is too low and the production efficiency is influenced due to the fact that the cooling speed of the wire rod is too low is avoided, and therefore the cooling speed of the wire rod is further controlled, and the device has proper matrix tissue softening effect on the basis of considering the production efficiency.
Preferably, the volume percentage of tempered bainite in the structure of the hot rolled wire rod is 80% -84%, and the volume percentage of ferrite is 15% -19%; the tempered bainite retains the strength characteristics of the tempered bainite, the strength is obviously higher than that of ferrite, meanwhile, the plastic defect of a quenched structure is obviously improved, the plasticity is lower than that of ferrite but obviously higher than that of the quenched bainite, and therefore, the wire rod strong plasticity matching can be further regulated and controlled by further regulating and controlling the proportions of the tempered bainite, the ferrite and the quasi-spheroidized carbide.
A 9.8-grade non-cold heading steel high-strength hot-rolled wire rod obtained according to the manufacturing method of any one of the 9.8-grade non-cold heading steel high-strength hot-rolled wire rods.
Preferably, the diameter of the hot rolled wire rod is 6.5-16.0 mm, the tensile strength is 830-860 MPa, the reduction of area is 61-67%, compared with the 9.8-grade non-tempering cold heading steel hot rolled wire rod obtained by the prior stelmor air cooling process, the hot rolled wire rod has obviously improved plasticity, higher reduction of area, obviously improved tensile strength and higher basic strength, compared with the non-tempering steel hot rolled wire rod obtained by the prior forced cooling after rolling, the hot rolled wire rod has the advantages that the hot rolled wire rod does not need large drawing deformation, the cold deformation strengthening strength can reach the 9.8-grade strength grade requirement after short-time effective treatment, the cold heading cracking problem caused by the large drawing deformation is avoided, and the hot rolled wire rod has good market application prospect.
The 9.8-grade non-cold-forging steel high-strength hot-rolled wire rod is used for manufacturing a 9.8-grade non-cold-forging steel fastener.
Compared with the prior art, the invention has the beneficial effects that:
(1) Aiming at the current situation that the strength of the existing 9.8-grade non-tempering cold heading steel hot rolled wire rod is improved and meanwhile the manufacturing cost is higher, and the strength and the plasticity are insufficient, the manufacturing method of the 9.8-grade non-tempering cold heading steel high-strength hot rolled wire rod adopts the C-Si-Mn-Mo component design, utilizes the online control cooling and roller way slow cooling technology process design of high heat exchange capability of molten salt, on one hand, rapidly quenches the wire rod into quenched bainite, and promotes the isothermal tempering of the quenched bainite into tempered bainite, so that the strength loss caused by elements such as Cr, V and the like which are not added with higher cost is compensated, the final wire rod strength is obviously enhanced, on the other hand, the coarsening of online molten salt controlled cooling early-stage carbide is effectively inhibited through the design of chemical components containing Mo, and the online molten salt controlled cooling and the roller way slow cooling long-time high-temperature state are combined, the tempered bainite is promoted to be further toughened to the quasi-spheroidized carbide, the softening effect of the wire rod matrix structure is improved, and the wire rod structure regulation, the high strength and the plasticity are matched, and the industrial applicability is good.
(2) Aiming at the limitation of low-temperature rolling on the existing 9.8-grade non-cold heading steel hot rolled wire rod, the manufacturing method of the invention can reduce the abrasion to the rolling mill at a relatively high finishing temperature and improve the rolling speed and efficiency.
(3) Aiming at the current situations that the existing 9.8-level high-strength fastener bolt is multiple in processing procedures, long in period, high in energy consumption of repeated heat treatment and low in cost and production, the invention successfully develops the 9.8-level non-tempering cold heading steel high-strength hot rolled wire rod, the tensile strength of the product is 830-860 MPa, the reduction of area is 61-67%, the wire rod is used for manufacturing the 9.8-level high-strength fastener bolt and other application fields, the annealing and tempering procedures can be omitted, the performance grade of the 9.8-level fastener is achieved through ageing treatment, and the wire rod has good market 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 example 2 of the present invention;
FIG. 3 is a metallographic structure of example 4 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 invention relates to a preferred embodiment of a manufacturing method of a 9.8-grade non-cold heading steel high-strength hot rolled wire rod, which comprises the following chemical components in percentage by mass: c:0.35%, si:0.31%, mn:0.67%, P:0.02%, S:0.018%, mo:0.3% of Fe and the balance of unavoidable impurities; the manufacturing method comprises the following steps of hot rolling, spinning, online molten salt controlled cooling, 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 12mm at high temperature through a rolling line, reducing the abrasion of a rolling mill of the rolling line, and improving the rolling efficiency, and is specific: controlling the final rolling temperature to be 930 ℃; the wire rod of rolling line is used for being wire rod through the wire rod machine of throwing, and the temperature of controlling the wire rod to be 910 ℃ is the austenitizing and is the preparation on the follow-up online fused salt accuse cooling work organization, and the wire rod is scattered on the roll table and is carried along the roll table.
The online molten salt controlled cooling adopts a salt bath tank with molten salt arranged therein, and is used for conveying wire rods after spinning through the molten salt of the salt bath tank through a roller way, so that the wire rods are quenched at a cooling speed of 37 ℃/s, pearlite and quenched martensite structures are prevented from being generated, most of austenite structures are converted into quenched bainite, the quenched bainite is caused to be converted into tempered bainite through isothermal tempering, the tempered bainite is caused to be converted into spheroidized and softened, quasi-spheroidized carbide is formed, a small amount of residual austenite structures are converted into ferrite structures, and the online molten salt controlled cooling is specifically: the molten salt temperature is 596 ℃, the isothermal time is 605s, control by molten salt circulation the temperature rise of the molten salt is less than or equal to 10 ℃.
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 online molten salt controlled cooling is utilized to promote the fusing spheroidization of tempered bainite, and further toughening is specific: controlling the cooling speed of the wire rod to be 1.1 ℃/s until the wire rod is transported to a coil collecting station; the coil collecting procedure is used for collecting the coil rod into coils through a coil collecting drum, and obtaining a hot rolled coil rod finished product after packaging and warehousing, and the metallographic structure diagram of the hot rolled coil rod finished product is shown in figure 1.
Comparative example 1:
A manufacturing method of 9.8-grade cold heading steel hot rolled wire rod, which is different from example 1 in that: the manufacturing method comprises the following steps of low-temperature hot rolling, spinning, stelmor air cooling, heat preservation and cooling and coil collection, and specifically comprises the following steps of: the control finishing temperature of the low-temperature hot rolling process is 825 ℃; the spinning process controls the spinning temperature to be 795 ℃; the stelmor air-cooled heat preservation cooling adopts the steps that wire rods after spinning are conveyed into a heat preservation cover through a roller way, phase change is completed in the cover at a cooling speed of 0.5 ℃/s, and hot-rolled wire rods are obtained after coil collection and coil discharging.
Example 2:
The invention relates to a preferred embodiment of a manufacturing method of a 9.8-grade non-cold heading steel high-strength hot rolled wire rod, which comprises the following chemical components in percentage by mass: c:0.33%, si:0.2%, mn:0.85%, P:0.016%, S:0.019%, mo:0.24% of Fe and the balance of unavoidable impurities; the manufacturing method comprises the following steps of hot rolling, spinning, online molten salt controlled cooling, 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 rod with the specification of 8mm at high temperature through a rolling line, reducing the abrasion of a rolling mill of the rolling line, and improving the rolling efficiency, and is specific: the final rolling temperature is controlled to be 940 ℃; the wire rod of rolling line is used for being wire rod through the wire rod machine of throwing, and the temperature of controlling the wire rod to be 915 ℃ is thrown to the austenitizing and is in preparation on the follow-up online fused salt controlled cooling structure, and the wire rod is scattered on the roller way and is conveyed along the roller way.
The online molten salt controlled cooling adopts a salt bath tank with molten salt arranged therein, and is used for conveying wire rods after spinning through the molten salt of the salt bath tank through a roller way, so that the wire rods are quenched at a cooling speed of 35 ℃/s, pearlite and quenched martensite structures are prevented from being generated, most of austenite structures are converted into quenched bainite, the quenched bainite is caused to be converted into tempered bainite through isothermal tempering, the tempered bainite is caused to be converted into spheroidized and softened, quasi-spheroidized carbide is formed, a small amount of residual austenite structures are converted into ferrite structures, and the online molten salt controlled cooling is specifically: the molten salt temperature is 640 ℃, the isothermal time is 700s, and the molten salt temperature rise is controlled to be less than or equal to 10 ℃ by using the molten salt circulation quantity.
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 online molten salt controlled cooling is utilized to promote the fusing spheroidization of tempered bainite, and further toughening is specific: controlling the cooling speed of the wire rod to be 1.5 ℃/s until the wire rod is transported to a coil collecting station; the coil collecting procedure is used for collecting the coil rod into coils through a coil collecting drum, and obtaining a hot rolled coil rod finished product after packaging and warehousing, and the metallographic structure diagram of the hot rolled coil rod finished product is shown in figure 2.
Comparative example 2:
A manufacturing method of 9.8-grade cold heading steel hot rolled wire rod, which is different from example 2 in that: and the temperature of the molten salt is 680 ℃, so that the hot rolled wire rod is obtained.
Comparative example 3:
A manufacturing method of 9.8-grade cold heading steel hot rolled wire rod, which is different from example 2 in that: and the temperature of the molten salt is 550 ℃, and the hot rolled wire rod is obtained.
Example 3:
The invention relates to a preferred embodiment of a manufacturing method of a 9.8-grade non-cold heading steel high-strength hot rolled wire rod, which comprises the following chemical components in percentage by mass: c:0.38%, si:0.27%, mn:0.77%, P:0.02%, S:0.02%, mo:0.27% of Fe and the balance of unavoidable impurities; the manufacturing method comprises the following steps of hot rolling, spinning, online molten salt controlled cooling, 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, and improving the rolling efficiency, and is specific: controlling the final rolling temperature to be 920 ℃; the wire rod of rolling line is used for being wire rod through the wire rod machine of throwing, and the wire rod temperature is controlled to 895 ℃, austenitizing is the preparation on the follow-up online fused salt accuse cold work tissue, and the wire rod spreads on the roll table and is carried along the roll table.
The online molten salt controlled cooling adopts a salt bath tank with molten salt arranged therein, and is used for conveying wire rods after spinning through the molten salt of the salt bath tank through a roller way, so that the wire rods are quenched at a cooling speed of 35 ℃/s, pearlite and quenched martensite structures are prevented from being generated, most of austenite structures are converted into quenched bainite, the quenched bainite is caused to be converted into tempered bainite through isothermal tempering, the tempered bainite is caused to be converted into spheroidized and softened, quasi-spheroidized carbide is formed, a small amount of residual austenite structures are converted into ferrite structures, and the online molten salt controlled cooling is specifically: the molten salt temperature is 622 ℃, the isothermal time is 473s, and the molten salt temperature rise is controlled to be less than or equal to 10 ℃ by using the molten salt circulation quantity.
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 online molten salt controlled cooling is utilized to promote the fusing spheroidization of tempered bainite, and further toughening is specific: controlling the cooling speed of the wire rod to be 0.6 ℃/s until the wire rod is transported to a coil collecting station; the coil collecting procedure is used for collecting the coil rod into coils through the coil collecting drum, and obtaining a hot rolled coil rod finished product after packaging and warehousing.
Comparative example 4:
A manufacturing method of 9.8-grade cold heading steel hot rolled wire rod, which is different from example 3 in that: the isothermal time is 330s, and a hot rolled wire rod is obtained.
Comparative example 5:
A manufacturing method of 9.8-grade cold heading steel hot rolled wire rod, which is different from example 3 in that: the isothermal time is 180s, and the hot rolled wire rod is obtained.
Example 4:
The invention relates to a preferred embodiment of a manufacturing method of a 9.8-grade non-cold heading steel high-strength hot rolled wire rod, which comprises the following chemical components in percentage by mass: c:0.31%, si:0.4%, mn:0.65%, P:0.019%, S:0.016%, mo:0.15% of Fe and the balance of unavoidable impurities; the manufacturing method comprises the following steps of hot rolling, spinning, online molten salt controlled cooling, 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 rod with the specification of 6.5mm at high temperature through a rolling line, reducing the abrasion of a rolling mill of the rolling line, and improving the rolling efficiency, and is specific: controlling the final rolling temperature to 950 ℃; the wire rod of rolling line is used for being wire rod through the wire rod machine of throwing, and the wire rod temperature is controlled to 932 ℃, austenitizing is the preparation on the follow-up online fused salt accuse cooling work organization, and the wire rod is scattered on the roll table and is transported along the roll table.
The online molten salt controlled cooling adopts a salt bath tank with molten salt arranged therein, and is used for conveying wire rods after spinning through the molten salt of the salt bath tank through a roller way, so that the wire rods are quenched at a cooling speed of 39 ℃/s, pearlite and quenched martensite structures are prevented from being generated, most of austenite structures are converted into quenched bainite, the quenched bainite is caused to be converted into tempered bainite through isothermal tempering, the tempered bainite is caused to be converted into spheroidized and softened, quasi-spheroidized carbide is formed, a small amount of residual austenite structures are converted into ferrite structures, and the online molten salt controlled cooling is specifically: the molten salt temperature is 571 ℃, the isothermal time is 350s, and the molten salt circulation quantity is used for controlling the molten salt temperature rise to be less than or equal to 10 ℃.
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 online molten salt controlled cooling is utilized to promote the fusing spheroidization of tempered bainite, and further toughening is specific: controlling the cooling speed of the wire rod to be 0.3 ℃/s until the wire rod is transported to a coil collecting station; the coil collecting procedure is used for collecting the coil rod into coils through the coil collecting drum, and obtaining a hot rolled coil rod finished product after packaging and warehousing, and a metallographic structure diagram of the hot rolled coil rod finished product is shown in figure 3.
Comparative example 6:
A manufacturing method of 9.8-grade cold heading steel hot rolled wire rod, which is different from example 4 in that: the manufacturing method comprises the steps of hot rolling, wire laying, online molten salt controlled cooling, air cooling and coil collecting, wherein the air cooling process conveys the coil from a salt bath to a coil collecting station by a roller way until the coil is transported to a coil collecting station, and the cooling speed of the coil is 3.5 ℃/s, so as to obtain the hot rolled coil.
The hot rolled wire rods obtained in the above examples and comparative examples were subjected to structure and property 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 hot rolled wire rods with the properties of the wire rod structure of the manufacturing process
As can be seen from the comparison results of examples 1-4 and comparative example 1, the invention combines the technical process design of the online controlled cooling and roller way slow cooling of the high heat exchange capability of molten salt on the basis of adopting the structural design of C-Si-Mn-Mo, compared with the prior art of the Steyr air cooling process, can obviously improve the cooling speed of the wire rod, avoid the occurrence of soft phase pearlite structure, rapidly quench the austenitic structure into quenched bainite, promote the isothermal tempering softening of the quenched bainite into tempered bainite, not only keep the characteristic of the high strength of the quenched bainite, compensate the strength loss caused by elements such as Cr, V and the like without higher cost, obviously strengthen the final wire rod strength, improve the plasticity of the quenched bainite through tempering, effectively inhibit the coarsening of online molten salt controlled cooling early-stage carbide through the structural design of Mo-containing chemical component, combine the online molten salt controlled cooling and slow cooling long-time high temperature state, promote the tempering bainite to transform further to the aligned carbide, can consider the manufacturing cost to improve the softening effect of the wire rod matrix structure, realize the regulation of the wire rod structure, the wire rod strength and the plastic matching, can keep the tensile section of the quenched bainite to 830-86MPa, can compensate the tensile section of the product strength, can reach the high strength, the rolling efficiency of the quenching forging screw is higher than 61.67%, the rolling mill has the high rolling efficiency and the rolling mill has the application speed of high rolling quality of the quenching screw is higher than 8.67, the rolling grade and the rolling grade is relatively high, the rolling grade is suitable for the rolling grade has the application to the high temperature is high grade and the rolling grade is 8, and has the relative low, and the rolling grade is suitable to the rolling grade is low, and has the relative has the rolling grade is 8 and the high and the rolling grade is suitable to the low.
From the comparison of examples 1 to 4, the comparison of example 2 and comparative example 2 shows that the higher the temperature is, the ferrite content in the structure is increased, and the higher the ferrite plasticity is than that of tempered bainite but the strength is obviously reduced, so that the plasticity of the wire rod is improved and the strength is obviously reduced; as can be seen from the comparison of example 2 and comparative example 3, too low a temperature causes tempered martensite to be generated, and increases the difficulty of softening the tempered bainite by transformation into spheroidized form, which causes a significant decrease in wire rod plasticity; from the comparison of examples 1 to 4, the comparison of example 3 with comparative example 4 shows that the shorter the isothermal time is, the lower the softening effect of tempered bainite is, the lower the content of quasi-spheroidized carbide is, and the plastic loss is caused; the isothermal time is too short, and the plasticity of the wire rod can be obviously reduced by incomplete tempering transformation of quenched bainite, so that the structure proportion in a mixed structure can be regulated and controlled on the basis of considering the manufacturing cost by further controlling the molten salt temperature and the isothermal time, and the strong plasticity matching of the wire rod is realized.
As can be seen from the comparison result of the embodiment 4 and the comparative example 6, the wire rod can be in a high-temperature state after being subjected to online salt bath controlled cooling by the roller way slow cooling, the tempering softening effect in the later stage of online molten salt controlled cooling is continued, the tempering bainite fusing spheroidization and further toughening are promoted, and the softening effect of the wire rod matrix structure is improved.
The above-listed series of detailed descriptions are merely specific illustrations of viable embodiments of the present invention, for example: the coil rod can reach the phase transition temperature zone of bainite with a faster cooling speed after being subjected to salt bath, and is converted into quenched bainite in a short time, and the isothermal time is longer, so that the quenching tempering and softening effects can be achieved simultaneously only by carrying out high-temperature long-time isothermal in one salt bath, and the coil rod is not used for limiting the protection scope of the invention, for example: the billet can be obtained by converter smelting, refining and continuous casting in turn, and all equivalent embodiments or modifications which do not depart from the spirit of the present invention should be included in the protection scope of the present invention.

Claims (7)

1. The manufacturing method of the 9.8-grade non-cold heading steel high-strength hot rolled wire rod is characterized by comprising the following chemical components in percentage by mass: c:0.30% -0.38%, si:0.20% -0.40%, mn:0.65% -0.85%, P is less than or equal to 0.020%, S is less than or equal to 0.020%, mo:0.15% -0.30%, and the balance of Fe and unavoidable impurities; the manufacturing method comprises the following steps: quenching the wire rod after hot rolling and wire spinning at a cooling speed of more than or equal to 30 ℃/s to obtain quenched bainite through online molten salt controlled cooling, enabling the quenched bainite to be isothermally tempered and softened to obtain tempered bainite, and slowly cooling through a roller way to obtain a hot rolled wire rod with a structure comprising a mixed structure of tempered bainite, a small amount of ferrite and quasi-spheroidized carbide;
The molten salt temperature of the online molten salt cooling control process is 570-640 ℃, the isothermal time is 350-700 s, the cooling speed of the wire rod is controlled to be 0.3-1.5 ℃/s by the roller way slow cooling process, the volume percentage of tempered bainite in the structure of the hot rolled wire rod is 80-84%, and the volume percentage of ferrite is 15-19%.
2. The method for manufacturing a 9.8-grade non-cold heading steel high-strength hot-rolled wire rod according to claim 1, wherein the hot rolling process controls the final rolling temperature to be equal to or higher than 920 ℃.
3. The method for manufacturing a 9.8-grade non-cold heading steel high-strength hot-rolled wire rod according to claim 2, wherein the wire laying process controls the wire laying temperature to be equal to or higher than 880 ℃.
4. The method for manufacturing the 9.8-grade non-cold heading steel high-strength hot rolled wire rod according to claim 1, wherein the online molten salt cooling control procedure controls the molten salt temperature rise to be less than or equal to 10 ℃.
5. A 9.8-grade non-cold-heading steel high-strength hot-rolled wire rod, characterized in that the hot-rolled wire rod is obtained according to the manufacturing method of the 9.8-grade non-cold-heading steel high-strength hot-rolled wire rod as claimed in any one of claims 1 to 4.
6. The 9.8-grade non-cold heading steel high-strength hot-rolled wire rod according to claim 5, wherein the diameter of the hot-rolled wire rod is 6.5-16.0 mm, the tensile strength is 830-860 mpa, and the reduction of area is 61-67%.
7. Use of a 9.8 grade non-cold-heading steel high strength hot rolled wire rod according to claim 5 for manufacturing a 9.8 grade non-cold-heading steel fastener.
CN202410607550.3A 2024-05-16 2024-05-16 Manufacturing method of 9.8-grade non-cold-heading steel high-strength hot-rolled wire rod Active CN118166191B (en)

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CN117888034B (en) * 2024-03-15 2024-06-07 江苏永钢集团有限公司 2000 MPa-grade vanadium-containing 55SiCr spring steel hot-rolled wire rod and production process thereof
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CN118007033A (en) * 2024-04-09 2024-05-10 江苏永钢集团有限公司 1100 MPa-level Si-Cr spring steel wire rod and rolling and cooling control method thereof

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