t_(8/5)对低合金奥-贝球铁焊接热影响区组织和力学性能的影响

Effect of t 8/5 on Microstructure and Mechanical Properties of HAZ of Low-alloy Austempered Ductile Iron Welding

利用Ｇｌｅｅｂｌｅ－１５００焊接热模拟试验机，在固定的加热速度（１５０℃／ｓ），峰值温度（１０５０℃）及峰值温度保持时间（７ｓ）条件下，研究了８００～５００℃冷却时间（ｔ８／５）对奥氏体－贝氏体球墨铸铁焊接热影响区的组织及力学性能的影响。研究结果表明，当ｔ８／５＝９～１５ｓ时，高碳马氏体占基体组织的９５％以上，σｂ与αＫ值显著下降，当ｔ８／５＝２０～３０ｓ时，马氏体与屈氏体共存，随屈氏体量的增加，σｂ及αＫ值上升；当ｔ８／５＝４０ｓ时，马氏体消除，屈氏体占基体组织的９７％，其σｂ＝６２９ＭＰａ；δ＝４．５％；αＫ＝２８．５Ｊ／ｃｍ２，进一步提高ｔ８／５到１００～２００ｓ，出现一些索氏体及铁素体，σｂ及αＫ稍有下降。

Using Gleeble-1500 welding thermal simulation test machine, the effect of cooling time from 800～500℃ ( t 8/5 ) on the microstructure and mechanical properties of HAZ of low-alloy austempered ductile iron welding has been studied under the fixed heating rate (150℃/s), peak temperature (1050℃) and peak temperature holding time (7s). The experimental results show that when t 8/5 =9～15s, the amount of high carbon martensite is more than 95% in the matrix structure. The tensile strength (σ b) and impact toughness (α K) sharply decrease. When t 8/5 =20～30s, the martensite and troosite coexist. With the increasing troosite amount, the σ b and α K increase. When t 8/5 =40s, martensite disappeared and the matrix is consisted of 97% troosite, its σ s=629 MPa, δ =4.5% and α K=28.5 J/cm 2. Further increasing t 8/5 up to 100～200s, some sorbite and ferrite appear, the σ b and α K slightly decrease.