一种新型2 GPa级低合金超高强度钢及热处理工艺

novel 2 GPa grade low alloy ultra-high strength steel and heat treatment process

在35CrMnSiA钢基础上适当增加Si含量,并添加少量Mo开发出新的2 GPa级40CrMnSi2Mo低合金超高强度钢,并系统地研究淬火温度(875~950℃)、回火温度200~300℃对40CrMnSi2Mo钢力学性能的影响。结果表明,较高的马氏体开始转变温度会降低马氏体内形成孪晶亚结构的倾向,是40CrMnSi2Mo钢韧性较高的主要原因。添加少量Mo能有效抑制回火脆性,300℃回火冲击吸收能量仅降低7.7%。但是,275℃和300℃回火降低残留奥氏体量使断裂韧性下降。新型40CrMnSi2Mo低合金钢于950℃淬火后,在200℃和225℃回火得到的试样强度高于2 GPa,断裂韧性在85 MPa·m^(1/2)以上,其强韧性配合明显优于AISI 4340钢和300M钢,而且低成本的优势使其具有较大的应用前景。

A novel low alloy ultra-high strength steel 40CrMnSi2Mo with a 2 GPa grade tensile strength was developed by adding Si and small amount of Mo in the traditional 35CrMnSiA steel.The effects of quenching temperature(875-975℃)and tempering temperature(200-300℃)on the mechanical properties of the 40CrMnSi2Mo steel were systematically investigated.The results show a higher martensite starting temperature(Ms)decreases the formation tendency of twinning martensite structures,which benefits the toughness of the 40CrMnSi2Mo steel.A small amount of Mo can effectively inhibit the temper brittleness,which makes the impact absorbed energy of the steel tempered at 300℃only decrease 7.7%,while tempering at 275℃and 300℃reduces the retained austenite quantity which leads to the decrease of fracture toughness.In general,a well combination of tensile strength(over 2 GPa)and fracture toughness(over 85 MPa·m~(1/2))of the 40CrMnSi2Mo steel can be obtained when the studied steel quenched at 950℃and tempered at 200℃and 225℃,which outperform that of AISI 4340 steel and 300M steel.It is expected that this novel low-cost steel has a significant application prospect.