CN112795854A - High-strength fastener bolt steel and production method thereof - Google Patents
High-strength fastener bolt steel and production method thereof Download PDFInfo
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
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- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
- C21C5/28—Manufacture of steel in the converter
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/076—Use of slags or fluxes as treating agents
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/10—Handling in a vacuum
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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
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
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- 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
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
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Abstract
The invention discloses a high-strength fastener bolt steel and a production method thereof, wherein the high-strength fastener bolt steel comprises the following chemical components in percentage by mass: 0.24-0.34% of C, 0.17-0.37% of Si, 0.80-1.10% of Mn, 1.10-1.20% of Cr, 0.20-0.30% of Mo, 0.04-0.10% of Ti, 0.20-0.30% of Ni, 0.020-0.040% of Al, 0.01-0.04% of Nb, less than or equal to 0.020% of P, less than or equal to 0.020% of S, and the balance of Fe and inevitable impurities. By adding microalloy elements Nb, Ti and the like, the elongation A of the steel is not lower than 14%, the reduction of area Z is not lower than 60%, the impact energy Aku is not lower than 70J at normal temperature, the production cost is lower, the steel has good delayed fracture resistance, and the requirements of automobiles and aviation on high-strength bolts are completely met under the conditions that the tensile strength is not lower than 1600MPa and the addition of expensive elements is relatively less. The method has the advantages of low production cost, good industrial stability, high economy and good delayed fracture resistance of the product.
Description
Technical Field
The invention belongs to the technical field of metallurgy, and particularly relates to high-strength fastener bolt steel and a production method thereof.
Background
With the development of industries such as wind power, high-end automobiles, large machinery, aerospace and the like, the requirements on various performances of raw materials of various bolts for fasteners applied to the industries are higher and higher. For example, high performance and light weight of parts are required for high-speed development of automobiles, large specification of the wind power industry, high reinforcement and high temperature resistance of the aviation industry and the like, higher requirements are put forward on high stress and light weight of bolts with high strength and high toughness as fasteners, and the requirements of the automobile manufacturing industry are the strongest in this respect; the conventional automotive fasteners and the like have been difficult to satisfy the requirement of high stress of automobiles.
At present, the steel for high-strength fastener bolts in China is mainly carbon alloy steel such as 40Cr, 35CrMo, 42CrMo and the like, the strength grade is mainly 8.8-12.9 grade, and the requirement of the high-strength fastener bolts with the requirement of 12.9 grade on the industries such as automobiles, aviation and the like cannot be met.
The foreign high-strength fastener bolt steel is prepared by adding a proper amount of V and Nb elements on the basis of Cr-Mo steel. The steel has high Mo content, can properly increase the tempering temperature, and has good delayed fracture resistance, but has high notch sensitivity and limited application range due to high contents of C, Cr and Mo.
Disclosure of Invention
The invention aims to provide the high-strength fastener bolt steel with good mechanical property; the invention also provides a production method of the high-strength fastener bolt steel.
In order to solve the technical problems, the invention comprises the following chemical components in percentage by mass: 0.24-0.34% of C, 0.17-0.37% of Si, 0.80-1.10% of Mn, 1.10-1.20% of Cr, 0.20-0.30% of Mo, 0.04-0.10% of Ti, 0.20-0.30% of Ni, 0.020-0.040% of Al, 0.01-0.04% of Nb, less than or equal to 0.020% of P, less than or equal to 0.020% of S, and the balance of Fe and inevitable impurities.
The action mechanism of each chemical component is as follows:
c: the main elements for improving the hardness and the strength of the steel; the C content is too low, the strength of the material after heat treatment is too low, and the strength requirement of the wind power steel cannot be met; too high C content is easy to reduce the plasticity and toughness of the material.
Si: ferrite is obviously strengthened and is an essential element for ensuring the strength; too low strength is insufficient; too high causes the ferrite matrix to become brittle and the toughness to decrease.
Mn: the pearlite forming element can reduce the phase transition temperature and has good effect on both strength and toughness; however, if the Mn content is too high, bainite is easily formed, and the uniformity of the structure and hardness of the material is reduced.
Cr: alloying elements that lower the pearlite transformation temperature; in the invention, Cr and Mn are added simultaneously, thus effectively reducing the pearlite lamellar spacing and improving the strength and toughness of steel; however, if the Cr content is too high, bainite is easily formed, and the uniformity of the steel structure and hardness is reduced.
Al: the crystal grains are refined by combining with N, so that the toughness is improved; however, too high Al content easily causes poor fluidity during continuous casting, and the continuous casting slab is easy to crack, thereby increasing the smelting difficulty of steel.
S: too high control of the elements may reduce the cleanliness of the steel and deteriorate the properties of the steel.
P: the brittleness of steel is increased, and the impact performance is reduced; the content of the P element is controlled to be not more than 0.015 percent, so that the comprehensive performance of the steel can be prevented from being reduced.
Ni: not only can improve the strength of the steel, but also can improve the plasticity and toughness of the steel; ni does not form carbide in steel, can only be dissolved in austenite and ferrite in a solid manner, and plays roles in refining grains, strengthening ferrite, improving toughness, and particularly improving low-temperature impact toughness performance; meanwhile, the hardenability of steel can be increased, and the large-section wind power high-strength bolt which has higher requirement on mechanical property and is uniform is particularly useful.
Ti: besides the functions of grain refinement, precipitation strengthening and fixation N, S, the TiC dispersed and precipitated is a hydrogen trap with the highest trap energy in the steel, and can trap hydrogen to be uniformly dispersed in the crystal, so that the diffusion of the hydrogen is inhibited, and the delayed fracture resistance of the steel is improved.
Nb: the crystal grains are refined, and the toughness of the steel is improved; the above effect is not obtained when the content is less than 0.01%, but the surface quality of the slab is easily affected when the content exceeds 0.05%.
Mo: the hardenability can be controlled, the sensitivity of the steel to the temper brittleness is reduced, the temper brittleness of the steel after high-temperature tempering is prevented, the tensile strength under the high-temperature tempering condition is greatly improved, and the delayed fracture performance of the bolt can be damaged due to the excessively high content of the steel.
The method comprises the working procedures of heating, rolling and heat treatment; the chemical composition and the mass percentage of the steel are as described above.
In the heating procedure of the method, the temperature of a casting blank heating section is 1100-1180 ℃, and the temperature of a soaking section is 1090-1150 ℃.
The rolling process of the method comprises the steps of rolling at the beginning temperature of 1080-1140 ℃, rolling at the end temperature of 900-950 ℃, collecting at the temperature of 550-600 ℃ and slowly cooling steel for 24-36 hours.
The heat treatment process of the method adopts quenching and tempering processes; quenching at 800-900 ℃ and quenching medium quenching oil; the tempering temperature is 200-300 ℃.
Adopt the produced beneficial effect of above-mentioned technical scheme to lie in: by adding microalloy elements Nb, Ti and the like, the elongation A of the steel is not lower than 14%, the reduction of area Z is not lower than 60%, the impact energy Aku at normal temperature is not lower than 70J under the condition of ensuring that the tensile strength is not lower than 1600MPa and adding relatively few expensive elements, the production cost is lower, the delayed fracture resistance is good, and the requirements of automobiles and aviation on high-strength bolts are completely met.
According to the method, the high strength and the high toughness of the steel for the fastener are ensured by adding microalloy elements such as Nb and Ti and optimizing the production process; the mechanical properties of the obtained steel are as follows: rm 1600-1700 MPa, A14-20%, Z60-80% and AKu 70-100J. The method has the advantages of low production cost, good industrial stability and high economy, and the product has good delayed fracture resistance and can completely meet the requirements of automobiles and aviation on high-strength bolts.
Detailed Description
The present invention will be described in further detail with reference to specific embodiments.
Examples 1 to 8: the production method of the high-strength fastener bolt steel comprises the working procedures of smelting, continuous casting, heating, rolling and heat treatment; the respective process steps are as follows.
(1) Smelting: converter smelting, LF refining and VD refining processes are adopted. The end point carbon of the converter smelting is 0.10-0.15 wt%, and the end point phosphorus is less than or equal to 0.015 wt%; the slag discharge in the tapping process is controlled, and the slag discharge amount is controlled to be less than or equal to 3 kg/ton steel. The white slag retention time of LF refining is 30-45 minutes, and CaO-SiO is adopted as refining slag2-Al2O3MgO slag system, the alkalinity R of refining slag is 4.0 to 6.0. The vacuum degree of VD refining is 67Pa or less, and the pure degassing time15-18 min, soft blowing time 15-20 min, and standing time 10-15 min. The process parameters of the smelting process described in the examples are shown in Table 1.
Table 1: process parameters of smelting process
(2) And (3) continuous casting process: the whole process is protected and poured, the long nozzle of the ladle is protected by argon seal, the tundish is emptied by argon, and the crystallizer uses low-carbon covering slag; the electric stirring is controlled to be 180-220A and 2.0-2.5 Hz, and the terminal stirring is controlled to be 110-150A and 6-10 Hz; the superheat degree of the tundish is controlled to be 15-25 ℃, and the continuous casting billet is slowly cooled for 36-48 hours. The process parameters for the continuous casting process described in the examples are shown in Table 2.
(3) A heating procedure: the temperature of the heating section of the casting blank ranges from 1100 ℃ to 1180 ℃, and the temperature of the soaking section ranges from 1090 ℃ to 1150 ℃. The process parameters for the heating sequence described in the examples are shown in Table 2.
Table 2: technological parameters of continuous casting and heating process
(4) A rolling procedure: the initial rolling temperature is 1080-1140 ℃, the final rolling temperature is 900-950 ℃, the collecting temperature is 550-600 ℃, and the steel is slowly cooled for 24-36 hours. The process parameters of the rolling sequence described in the examples are shown in table 2.
(5) A heat treatment process, which adopts an integral heat treatment process and adopts a quenching and tempering process; quenching at 800-900 ℃ and quenching medium quenching oil; the tempering temperature is 200-300 ℃. And (4) performing heat treatment to obtain the bolt steel. The process parameters of the heat treatment procedure described in the examples are shown in table 2.
Table 3: process parameters of rolling and heat treatment process
(6) The steel product standard for the bolt is referred to GB/T3098.1-2010; the product performance detection method is in standard reference GB/T2975-2018. The chemical components and the contents of the steel product for the bolt obtained in each example are shown in Table 4; the mechanical properties of the steel for bolt obtained in each example are shown in Table 5.
Table 4: chemical components and content (wt%) of steel product for bolt
In table 4, the balance of chemical components is Fe and inevitable impurities.
Table 5: mechanical property of obtained steel product for bolt
Claims (5)
1. The production method of the high-strength fastener bolt steel is characterized by comprising the following chemical components in percentage by mass: 0.24-0.34% of C, 0.17-0.37% of Si, 0.80-1.10% of Mn, 1.10-1.20% of Cr, 0.20-0.30% of Mo, 0.04-0.10% of Ti, 0.20-0.30% of Ni, 0.020-0.040% of Al, 0.01-0.04% of Nb, less than or equal to 0.020% of P, less than or equal to 0.020% of S, and the balance of Fe and inevitable impurities.
2. A production method of high-strength fastener bolt steel is characterized by comprising the following steps: the method comprises the working procedures of heating, rolling and heat treatment; the steel comprises the following chemical components in percentage by mass: 0.24-0.34% of C, 0.17-0.37% of Si, 0.80-1.10% of Mn, 1.10-1.20% of Cr, 0.20-0.30% of Mo, 0.04-0.10% of Ti, 0.20-0.30% of Ni, 0.020-0.040% of Al, 0.01-0.04% of Nb, less than or equal to 0.020% of P, less than or equal to 0.020% of S, and the balance of Fe and inevitable impurities.
3. The method for producing a steel for high-strength fastener bolts according to claim 2, characterized in that: in the heating process, the temperature of a casting blank heating section ranges from 1100 ℃ to 1180 ℃, and the temperature of a soaking section ranges from 1090 ℃ to 1150 ℃.
4. The method for producing a steel for high-strength fastener bolts according to claim 2, characterized in that: in the rolling procedure, the initial rolling temperature is 1080-1140 ℃, the final rolling temperature is 900-950 ℃, the collecting temperature is 550-600 ℃, and the steel is slowly cooled for 24-36 hours.
5. The production method for a steel for high-strength fastener bolts according to claim 2, 3 or 4, characterized in that: the heat treatment process adopts a quenching and tempering process; quenching at 800-900 ℃ and quenching medium quenching oil; the tempering temperature is 200-300 ℃.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202011544443.9A CN112795854A (en) | 2020-12-23 | 2020-12-23 | High-strength fastener bolt steel and production method thereof |
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| CN202011544443.9A CN112795854A (en) | 2020-12-23 | 2020-12-23 | High-strength fastener bolt steel and production method thereof |
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Application publication date: 20210514 |