微量钛对控轧微合金钢焊接HAZ的组织和韧性的影响

EFFECT OF Ti ON STRUCTURE AND TOUGHNESSOF HAZ OF V-Ti-N STEEL

通过模拟焊接热循环，在ＧＬｅｅｂ－１５００装置上模拟了ｖ－Ｔｉ－Ｎ和Ｖ－Ｎ钢焊接热影响区粗晶区（ＧＣ－ＨＡＺ）的组织，并用示波冲击法测定了不同△（从８００℃到５００℃的冷却时间）试样的Ａｋｖ值、解理裂纹形核功（Ｅｉ）和扩展功（Ｅｐ）。用光学显微镜、ＳＥＭ和ＴＥＭ对这两种钢高温奥氏体的晶粒尺寸、过冷奥氏体转变产物和各△条件下的冲击断口进行了定量分析和观察，探讨了加微量钛对焊接ＧＣ－ＨＡＺ的组织和韧性的影响。试验结果表明，与Ｖ－Ｎ钢相比，Ｖ－Ｔｉ－Ｎ钢由于含有适量的钛，使奥氏体晶粒及其转变产物显著细化，并且奥氏体转变产物的形态和分布也得到改善，这使Ｖ－Ｔｉ－Ｎ钢ＧＣ－ＨＡＺ的韧性显著高于Ｖ－Ｎ钢。

The microstructure of HAZ of V-Ti-N and V-N steel were obtained through simulation of thermal cycle by using Gleeb-1500 apparatus, and the CVN values as well as the energy of crack initiation and propagation of the simulated HAZ were measured on Charpy V-notch specimens and instrumented imlpact machine. The prior austenite grain size, the products transformed from cold austenite and the fracture morphology at various △ were observed and analyzed quantitatively through photomicroscope and SEM for studying the effect of Ti addition on microstructure .and toughness of HAZ. The results show that, comparing with V-N steel, the austenitic grain size and products transformed from austenite of V-Ti-N steel is refined effectively and it is the reason why the toughness of V-Ti-N steel is higher than that of V-N steel.