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CN-121992302-A - Fine-grain reinforced ultralow-carbon cold forging steel and preparation process thereof

CN121992302ACN 121992302 ACN121992302 ACN 121992302ACN-121992302-A

Abstract

The invention relates to the technical field of cold forging steel, and provides fine-grain reinforced ultralow-carbon cold forging steel and a preparation process thereof. The fine-grain reinforced ultralow-carbon cold heading steel comprises the following raw materials in percentage by weight: less than or equal to 0.02 percent of C, 0.45 to 0.66 percent of Mn, 0.08 to 0.12 percent of Si, less than or equal to 0.02 percent of P, less than or equal to 0.008 percent of S, 0.025 to 0.045 percent of Als, 0.018 to 0.020 percent of Nb, 0.015 to 0.020 percent of V, 0.012 to 0.015 percent of Ti, and the balance of Fe and unavoidable impurities, wherein Mn/(Nb+V+Ti) =10 to 12. Through the technical scheme, the problem of insufficient strength of the ultralow-carbon cold heading steel in the related technology is solved.

Inventors

  • SONG XIN
  • WANG HUIBIN
  • MAO GUOHUI
  • LIAN XINTONG
  • DI LIN
  • JI WEI
  • LIU YUN
  • ZHANG WEIJUN
  • LIU HAIJUN
  • DONG JIANSHENG

Assignees

  • 秦皇岛佰工钢铁有限公司

Dates

Publication Date
20260508
Application Date
20260227

Claims (10)

  1. 1. The fine-grain reinforced ultralow-carbon cold heading steel is characterized by comprising the following raw materials in percentage by weight ：C≤0.02%、Mn 0.45%~0.66%、Si 0.08%~0.12%、P≤0.02%、S≤0.008%、Als 0.025%~0.045%、Nb 0.018%~0.020%、V 0.015%~0.020%、Ti 0.012%~0.015%, and the balance of Fe and unavoidable impurities, wherein Mn/(Nb+V+Ti) =10-12.
  2. 2. The fine grain reinforced ultra-low carbon cold forging steel of claim 1, wherein v=1 to 1.2:1.
  3. 3. A method for preparing fine-grain reinforced ultra-low carbon cold forging steel, which is used for preparing the fine-grain reinforced ultra-low carbon cold forging steel according to any one of claims 1-2, and is characterized by comprising the following steps: S1, mixing materials according to the components, smelting, refining and continuously casting to obtain a casting blank; And S2, heating the casting blank to 1180-1250 ℃, carrying out rough rolling, finish rolling and cooling to room temperature after heat preservation, and collecting rolls to obtain the fine-grain reinforced ultra-low carbon cold forging steel.
  4. 4. The method for preparing the fine-grain reinforced ultralow-carbon cold forging steel according to claim 3, wherein the initial rolling temperature of the rough rolling is 1120-1160 ℃, and the final rolling temperature of the rough rolling is 1020-1050 ℃.
  5. 5. The method for preparing fine-grain reinforced ultralow-carbon cold-forging steel according to claim 3, wherein the initial rolling temperature of the finish rolling is 950-990 ℃, and the final rolling temperature of the finish rolling is 860-890 ℃.
  6. 6. The method for preparing the fine-grain reinforced ultralow-carbon cold heading steel is characterized by comprising the following steps of firstly performing first-stage cooling to 600-650 ℃, then performing second-stage cooling to 400-450 ℃, then performing third-stage cooling to 200-220 ℃ and finally cooling to room temperature, wherein the cooling rates of the first-stage cooling, the second-stage cooling and the third-stage cooling are different.
  7. 7. The method for producing a fine-grain reinforced ultra-low carbon cold-forging steel according to claim 6, wherein the cooling rate of the first-stage cooling is greater than the cooling rate of the second-stage cooling by more than the cooling rate of the third-stage cooling.
  8. 8. The method for preparing the fine-grain reinforced ultralow-carbon cold heading steel according to claim 6, wherein the cooling rate of the first section cooling is 12-15 ℃ per second, the cooling rate of the second section cooling is 5-8 ℃ per second, and the cooling rate of the third section cooling is 1-3 ℃ per second.
  9. 9. The method for preparing fine-grain reinforced ultra-low carbon cold forging steel according to claim 3, wherein the casting blank is a square blank, and the cross-sectional dimension of the square blank is 150mm×150mm.
  10. 10. The method for preparing the fine-grain reinforced ultralow-carbon cold forging steel according to claim 3, wherein the heat preservation time is 100-120 min.

Description

Fine-grain reinforced ultralow-carbon cold forging steel and preparation process thereof Technical Field The invention relates to the technical field of cold forging steel, in particular to fine-grain reinforced ultralow-carbon cold forging steel and a preparation process thereof. Background The ultra-low carbon cold heading steel is a structural steel specially designed for a cold heading forming process, is widely applied to the fields of automobile manufacturing, mechanical equipment, constructional engineering, aerospace and the like by virtue of excellent plastic deformation capability, cold working formability and low cost, and is mainly used for producing various fasteners such as bolts, nuts, rivets, pins and the like. The fastener is used as a core component for mechanical connection, and needs to meet the high plasticity requirement in cold heading processing and the enough strength, fatigue resistance and structural stability in actual service, and the performance of the fastener directly determines the connection reliability and service life of the terminal product. However, in the prior art, in order to ensure cold heading formability, the carbon content of the ultra-low carbon cold heading steel is generally controlled below 0.02%, and the carbon is used as an important strengthening element in the steel, and the solid solution strengthening effect of a matrix is greatly weakened due to the reduction of the carbon content, so that the strength of the steel is insufficient. The cold heading steel has insufficient strength to cause some harm, and in the connection scene of core power and bearing parts such as an automobile chassis, an engine cylinder body, a gearbox and the like, the fastener with insufficient strength is influenced by long-term alternating load, vibration and temperature fluctuation, is easy to generate plastic deformation, fatigue wear and even fracture in advance, directly leads to part connection failure, power transmission interruption, causes accidents such as automobile anchoring, braking failure and the like, endangers the safety of drivers and passengers, and in the field of large-scale engineering equipment such as a building steel structure, a bridge bracket, a tower crane and the like, the low-strength fastener cannot bear the dead weight of the structure, external load and environmental corrosion, is easy to generate connection looseness and slippage, and has potential safety hazards. Therefore, it is necessary to develop a high-strength ultra-low carbon cold forging steel. Disclosure of Invention The invention provides fine-grain reinforced ultra-low carbon cold forging steel and a preparation process thereof, and solves the problem of insufficient strength of the ultra-low carbon cold forging steel in the related technology. The invention provides fine-grain reinforced ultralow-carbon cold forging steel, which comprises the following raw materials in percentage by weight ：C≤0.02%、Mn 0.45%~0.66%、Si 0.08%~0.12%、P≤0.02%、S≤0.008%、Als 0.025%~0.045%、Nb 0.018%~0.020%、V 0.015%~0.020%、Ti 0.012%~0.015%, and the balance of Fe and unavoidable impurities, wherein Mn/(Nb+V+Ti) =10-12. As a further technical scheme, the ratio of Nb to V=1-1.2:1. In the fine-grain reinforced ultralow-carbon cold heading steel, nb is V=1-1.2:1, and is taken as a core element for fine-grain reinforcement, so that the formed precipitated phase has high stability, can effectively pin an austenite grain boundary, inhibit coarsening of austenite grains in the rolling and cooling processes, and lay a foundation for forming fine ferrite grains through subsequent phase transformation. The precipitated phases formed by V can be dispersed and distributed in a ferrite matrix, dislocation slip is prevented, precipitation strengthening effect is supplemented, when Nb is satisfied by V=1-1.2:1, the Nb content is slightly higher than V, the sufficient pinning effect of the grain boundary at high temperature can be ensured, incomplete grain refinement caused by insufficient Nb is avoided, and the dominant position of fine grain strengthening is ensured. The consumption of V can avoid V excessive to cause precipitation phase agglomeration coarsening, can ensure that the precipitation phase quantity is sufficient, and the two are adapted, so that the strength of the ultralow-carbon cold forging steel is effectively improved. The invention also provides a preparation method of the fine-grain reinforced ultra-low carbon cold forging steel, which is used for preparing the fine-grain reinforced ultra-low carbon cold forging steel and comprises the following steps of: S1, mixing materials according to the components, smelting, refining and continuously casting to obtain a casting blank; And S2, heating the casting blank to 1180-1250 ℃, carrying out rough rolling, finish rolling and cooling to room temperature after heat preservation, and collecting rolls to obtain the fine-grain reinforced ultra-low carbon cold forging