摘要
本研究通过对HQ—70钢连续冷却转变(CCT)图的测定、组织状态分析、系列温度下切口试样冲击性能试验以及断裂特性考察,阐明了该钢冷脆机制及显微组织控制因素。结果指出:与回火索氏体状态相比,粒状贝氏体的出现使该钢的冷脆倾向性加剧,仅约20％(体积)的粒贝组织就使塑-脆转折临界温度T_(ce)大幅度提高,粒贝含量继续增加时T_(ce)的升值趋于饱和。粒贝组织致脆机制系由低温下的解理断裂特性决定。最后确定了改善冷脆抗力、避免粒贝形成所应保证的最低冷却速度ν_e=40℃/s。
Measuring of continuously cooling transformation diagram, analysis of microstructure, impact test at different temperatures using slot-notched specimen, and observation of fracture morphology were conducted for a HSLA steel HQ-70 in order to clarify the mechanism of low-temperature brittleness and the microstructural aspects controlling the brittleness. The results show that the presence of granular bainite (GB) intensifies the low-temperature. brittleness of the steel in comparison with the case of full tempered sorbite. The critical temperature for the ductile/brittle transition, T_(ce), is elevated substantially with approximately only 20 vol.% and more of GB present. The elevation of T_(ce) tends to be saturated with further increase of GB. An approach to the fractography suggests that the cleavage crack initiation across the massive ferrite grain on which GB based contributes to the cleavage fracture propagated with low energy at low temperatures. As heat-treatment is concerned, a minimum cooling speed of v_c=40℃/s is to be obtained to avoid the formation of GB in the steel.
出处
《钢铁》
CAS
CSCD
北大核心
1992年第4期51-54,共4页
Iron and Steel
