10B38含硼冷镦钢的研制与开发

Research and Development of 10B38 Boron Containing Cold Heading Steel

采用高温拉伸试验方法,研究了不同高温条件下10B38含硼冷镦钢的强度和塑性。试验结果表明,在热强性方面,700~950℃时抗拉强度由124.8 MPa大幅下降到22.9 MPa;950~1150℃时抗拉强度为12.7~25.5 MPa。在热塑性方面,700~750℃时试验钢的断面收缩率为56%~72%;800~1050℃时,试验钢的断面收缩率≥75%;1050~1150℃时,断面收缩率>65%。根据以上试验数据,将连铸二次冷却水强度由比水量1.35 L/kg优化为1.25 L/kg,优化后连铸坯裂纹指标有明显降低。测定了10B38含硼冷镦钢的过冷奥氏体连续冷却转变曲线,试验结果表明,当冷却速率为0.2~1℃/s,试验钢以较软的铁素体组织为主;当冷却速率为3~10℃/s,试验钢以珠光体组织为主;当冷却速率为20、30℃/s时,试验钢为板条马氏体+珠光体组织;当冷却速率为50℃/s时,室温时形成完全马氏体组织。试验及生产试制结果表明,降低冷却速率到0.5~2℃/s,能获得理想的铁素体和珠光体热轧组织。

The strength and plasticity of 10B38 boron containing cold heading steel under different high temperature conditions were studied using high-temperature tensile testing method.The results showed that the tensile strength decreased significantly from 124.8 MPa to 22.9 MPa at temperatures ranging from 700 to 950℃;At 950 to 1150℃,the tensile strength was 12.7 to 25.5 MPa.In terms of thermoplastic properties,the cross-sectional shrinkage rate at 700-750℃was 56%-72%;When the temperature was between 800 and 1050℃,the cross-sectional shrinkage rate was≥75%;When the temperature was between 1050 and 1150℃,the cross-sectional shrinkage rate was greater than 65%.Based on the above experimental data,the strength of the secondary cooling water in continuous casting was optimized from a specific water content of 1.35 L/kg to a specific water content of 1.25 L/kg.After optimization,the crack index of the continuous casting slab was significantly reduced.The dynamic CCT curves of 10B38 boron containing cold heading steel were measured,The experimental results showed that when the cooling rate was 0.2-1℃/s,the test steel was mainly composed of softer ferrite structure;When the cooling rate was 3-10℃/s,the experimental steel was mainly composed of pearlite structure;When the cooling rate was 20℃/s and 30℃/s,the structure of the test steel was flat noodles martensite+pearlite;When the cooling rate was 50℃/s,a complete martensitic structure was formed at room temperature.The experimental results showed that by reducing the cooling rate to 0.5-2℃/s,ideal ferrite and pearlite hot-rolled structures can be obtained.