超高强马氏体钢抗氢致延迟开裂性能的研究

Research on Hydrogen-Induced Delayed Cracking Resistance of Ultra-high Strength Martensitic Steel

超高强马氏体钢易氢致开裂。通过渗氢试验、热脱附试验及动态低应变速率拉伸试验等,研究了具有不同组织的冷轧马氏体钢1号、2号试样的抗氢致延迟开裂性能。1号试样组织为马氏体+铁素体+渗碳体,平均晶粒尺寸为7.0μm;2号试样组织为回火马氏体+渗碳体,平均晶粒尺寸为6.1μm。结果表明:1号试样的表观扩散系数Dap为7.081×10^(-7) cm^(2)/s,2号试样的为4.670×10^(-7) cm^(2)/s;1号试样的可扩散氢含量为0.1923μg/g,明显小于2号试样的0.2605μg/g;2号试样对氢的敏感性大于1号试样;随着充氢电流密度的提高,拉伸试验时1号试样从韧性断裂变为准解理断裂,2号试样则从韧脆性断裂变为穿晶脆性断裂;与1号试样相比,2号试样的氢表观扩散系数和可扩散氢含量均更大;对于超高强钢,除了有效氢陷阱外,减小局部应力也能显著改善抗氢致延迟开裂性能。

Ultra-high strength martensitic steel is easy of hydrogen-induced cracking.The resistance of cold-rolled martensitic steel specimens No.1 and 2 having different microstructures to hydrogen-induced delayed cracking was investigated by means of hydrogen infiltration test,thermal desorption test and dynamic tensile test performed at low strain rate,and the microstructure consisted of martensite,ferrite and cementite,average grain size was 7.0μm for the specimen No.1,and consisted of tempered martensite and cementite,average grain size was 6.1μm for the specimen No.2.The results showed that(a)the apparent diffusion coefficient Dap was 7.081×10^(-7) cm^(2)/s for the specimen No.1,and 4.670×10^(-7) cm^(2)/s for the specimen No.2;(b)the content of diffusible hydrogen in the specimen No.1 was 0.1923μg/g,which was significantly less than 0.2605μg/g in the specimen No.2;(c)the specimen No.2 was more sensitive to hydrogen than the specimen No.1;(d)as the hydrogenating current density increased,the specimen No.1 changed from ductile fracture to quasi-cleavage fracture,whereas the specimen No.2 changed from ductile-brittle fracture to transgranular brittle fracture during tensile test;(e)compared with the specimen No.1,the specimen No.2 exhibited larger apparent diffusion coefficient of hydrogen and larger content of diffusible hydrogen;and(f)as to ultra-high strength steels,the decrease in local stress,in addition to the effective hydrogen trap,also was likely to significantly improve the resistance to hydrogen-induced delayed cracking.