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CN-121976118-A - Low-alloy high-strength steel for easy-to-weld drawing-resistant seat torsion bar and production method

CN121976118ACN 121976118 ACN121976118 ACN 121976118ACN-121976118-A

Abstract

A low alloy high strength steel for a seat torsion bar which is easy to weld and resistant to drawing and a production method thereof belong to the technical field of cold-rolled sheet and strip production in the metallurgical industry. The chemical composition of the alloy is C：0.045～0.070%,Si：0.35～0.45%,Mn：1.2～1.5%,P≤0.010%,S≤0.001%,Als：0.02～0.05%,Nb：0.015～0.035%,Ti：0.08～0.10%, percent by weight, the balance is Fe and unavoidable impurities, and the carbon equivalent CE=0.245-0.320. According to the invention, through component design, hot rolling, acid rolling and continuous annealing processes are matched to obtain a ferrite matrix and a fine aging precipitated phase, so that the yield strength of the high-strength steel reaches 600-760 MPa, the hardness of a welded joint after high-frequency welding is less than 300HV 0.5 , and the welded joint is ensured not to crack in reaming, flattening and special-shaped drawing of a welded pipe.

Inventors

  • CAO XIAOEN
  • JIA YAFEI
  • LI SHOUHUA
  • CHEN XIAOHU
  • JIA LIYING
  • LIU HONGYAN
  • WANG JUNFENG
  • Hou Zhongshi
  • LIU PENG
  • MA ZIYANG

Assignees

  • 邯郸钢铁集团有限责任公司
  • 河钢股份有限公司邯郸分公司

Dates

Publication Date
20260505
Application Date
20260106

Claims (10)

  1. 1. A low-alloy high-strength steel for a torsion bar of a seat, which is easy to weld and resistant to drawing, is characterized by comprising the following chemical components in percentage by weight, wherein the chemical components are ：C：0.045～0.070%,Si：0.35～0.45%,Mn：1.2～1.5%,P≤0.010%,S≤0.001%,Als：0.02～0.05%,Nb：0.015～0.035%,Ti：0.08～0.10%, and the balance of Fe and unavoidable impurities, and the carbon equivalent CE=0.245-0.320.
  2. 2. The low alloy high strength steel for a torsion bar of a seat which is easy to weld and resistant to drawing according to claim 1, wherein the microstructure of the high strength steel is a ferrite matrix, a small amount of carbide and a trace amount of second phase precipitate.
  3. 3. The low-alloy high-strength steel for the easy-welding and drawing-resistant seat torsion bar, which is based on claim 2, is characterized in that the rolling direction yield strength of the high-strength steel is 600-760 MPa, the tensile strength is more than or equal to 650MPa, and the elongation after break A 80mm is more than or equal to 10%.
  4. 4. The low alloy, high strength steel for a torsion bar for a seat which is easy to weld and resistant to drawing according to claim 3, wherein the vickers hardness of the weld heat affected zone of the high strength steel after high frequency welding is less than 300 HV 0.5 .
  5. 5. The method for producing a low alloy, high strength steel for a torsion bar for a seat which is easy to weld and resistant to drawing according to any one of claims 1 to 4, comprising the steps of: (1) Steelmaking and continuous casting processes, namely adopting molten iron desulfurization pretreatment, a top-bottom combined blown converter, LF refining and continuous casting processes; (2) The hot rolling process comprises the steps of heating a plate blank to 1260-1280 ℃, descaling, rough rolling and finish rolling, controlling the initial rolling temperature of finish rolling to 1020-1100 ℃ and the final rolling temperature to 890-930 ℃, adopting laminar cooling after rolling, adopting a U-shaped cooling mode to compensate the head part of strip steel by 100 ℃ and the tail part of the strip steel by not compensating, and performing cooling according to the front section 1/2, and controlling the coiling temperature to 500-520 ℃; (3) An acid rolling procedure, namely cold rolling after pickling the hot rolled coil to obtain chilled strip steel; (4) A continuous annealing procedure, namely sequentially passing the chilled strip steel through a preheating section, a heating section I, a heating section II, a soaking section II, a slow cooling section, a fast cooling section, an overaging section and a leveling treatment; The soaking temperature is 750-770 ℃, the temperature is kept for 130-180 seconds, then the temperature is slowly cooled to 630-650 ℃ at the speed of 2-3 ℃ per second, then the temperature is rapidly cooled to 400-420 ℃ at the speed of 25-40 ℃ per second, then the temperature is subjected to overaging treatment at 420-370 ℃ for 250-350 seconds, and finally the temperature is cooled to room temperature.
  6. 6. The method for producing a low alloy high strength steel for a torsion bar of a seat, which is easy to weld and resistant to drawing, according to claim 5, wherein the steel making and continuous casting process is controlled so that the S content in the steel is less than or equal to 0.001wt% and the C content is 0.045 to 0.070wt%.
  7. 7. The method for producing the low-alloy high-strength steel for the easy-to-weld and drawing-resistant seat torsion bar, which is characterized in that the thickness of a hot rolled steel coil is 2.0-4.0 mm in the hot rolling process, and the steel coil is slowly cooled in a single-layer stacking mode after being taken off, so that forced cooling of a fan is avoided.
  8. 8. The method for producing a low alloy high strength steel for a torsion bar of a seat, which is easy to weld and resistant to drawing, according to claim 5, wherein the reduction ratio is 45 to 60%.
  9. 9. The method for producing a low-alloy high-strength steel for a torsion bar of a seat, which is easy to weld and resistant to drawing, according to claim 5, wherein the continuous annealing process is carried out at a preheating section temperature of 240-260 ℃, a heating section temperature of 630-650 ℃ and a total heating time of 320-480 s.
  10. 10. The method for producing a low-alloy high-strength steel for a torsion bar for a seat, which is easy to weld and resistant to drawing, according to claim 5, wherein the continuous annealing step has a temper rolling force of 6000 to 8000kn with a temper elongation of 0.4 to 0.6%.

Description

Low-alloy high-strength steel for easy-to-weld drawing-resistant seat torsion bar and production method Technical Field The invention belongs to the technical field of production of cold-rolled sheet strips in the metallurgical industry, and particularly relates to low-alloy high-strength steel for a seat torsion bar which is easy to weld and resistant to drawing and a production method thereof. Background The torsion bar of the automobile seat is an important part of the seat assembly, and is matched with the seat angle adjuster to realize the angle adjustment of the seat back. The main processing technology comprises the steps of steel coil longitudinal cutting, longitudinal strip cutting, rolling into round tubes, high-frequency tube welding, fixed-length cutting, round tube detection (reaming, positive pressure/side pressure), special-shaped drawing, fixed-length cutting and torsion detection. In the process, the material needs to be subjected to high-frequency welding and cold forming drawing, and extremely high requirements are placed on the welding performance and the forming performance of the material. The torsion bar of the automobile seat is mainly produced by adopting low-alloy high-strength steel, comprehensively considers the performance requirements of long service cycle, fatigue resistance and the like, and requires that the yield strength of the original base material is more than or equal to 600MPa, and has good welding performance and drawing performance. Only a few steel mills can produce in China, but the quality difference is large, and the problems of reaming weld cracking, positive pressure/side pressure weld cracking, special-shaped drawing weld cracking and the like often occur. The prior art CN202510232416.4 discloses a production method of low-cost cold-rolled low-alloy high-strength steel, but the produced low-alloy high-strength steel cannot meet the strength requirement of a torsion bar of an automobile seat, and meanwhile, production practice shows that the C, P, S content cannot meet the welding-related detection requirement. CN202310147636.8 discloses a 500-800 Mpa-level multi-stage cold-rolled low-alloy high-strength steel strip, but the problems of downstream industrial chain welding and related detection and special-shaped drawing are not considered, and the C, P, S content does not meet the welding requirement, so that the hardness of a weld heat affected zone cannot be ensured. CN202111189125.X discloses a preparation method of 800MPa grade cold-rolled low-alloy high-strength steel with excellent reaming performance, although the excellent reaming performance is mentioned, the C content is designed to be too high (0.11-0.14%), and the C content contains noble alloys Nb and Mo, so that the cost is high, and the requirement of no cracking in drawing a torsion bar welded pipe still cannot be met. Therefore, there is a need to develop a low-alloy high-strength steel with excellent welding performance and good welded pipe drawing performance at low cost so as to meet the manufacturing requirements of high quality and high reliability of the torsion bar of the automobile seat. Disclosure of Invention In order to solve the technical problems, the invention provides a low alloy high strength steel for a torsion bar of a seat which is easy to weld and resistant to drawing and a production method thereof, and the technical scheme adopted by the invention is as follows: The low alloy high strength steel for the easy-to-weld and drawing-resistant seat torsion bar comprises the following chemical components in percentage by weight of ：C：0.045～0.070%,Si：0.35～0.45%,Mn：1.2～1.5%,P≤0.010%,S≤0.001%,Als：0.02～0.05%,Nb：0.015～0.035%,Ti：0.08～0.10%,, wherein the balance of Fe and unavoidable impurities, and the carbon equivalent CE=0.245-0.320. The microstructure of the high-strength steel is a ferrite matrix, a small amount of carbide and a trace amount of second phase precipitated phase. The rolling direction yield strength of the high-strength steel is 600-760 MPa, the tensile strength is more than or equal to 650MPa, and the elongation after fracture A 80mm is more than or equal to 10%. After the high-strength steel is subjected to high-frequency welding, the Vickers hardness of a welding seam heat affected zone of the high-strength steel is less than 300 HV 0.5. The invention also provides a production method of the low-alloy high-strength steel for the easy-to-weld drawing-resistant seat torsion bar, which comprises the following steps of: (1) Steelmaking and continuous casting processes, namely adopting molten iron desulfurization pretreatment, a top-bottom combined blown converter, LF refining and continuous casting processes; (2) The hot rolling process comprises the steps of heating a plate blank to 1260-1280 ℃, descaling, rough rolling and finish rolling, controlling the initial rolling temperature of finish rolling to 1020-1100 ℃ and the final rolling temperature to 890-930 ℃, adop