不同冷速下Q1100高強鋼焊接熱影響區(qū)粗晶區(qū)的組織轉(zhuǎn)變特征

不同冷速下Q1100高強鋼焊接熱影響區(qū)粗晶區(qū)的組織轉(zhuǎn)變特征Microstructure Transformation Characteristic of CGHAZ of Q1100 High-Strength Steel at Different Cooling Rates

利用Gleeble-3500型熱模擬試驗機對Q1100高強鋼的焊接過程進行模擬，采用熱膨脹法結(jié)合顯微組織與硬度測試，繪制了該鋼的模擬熱影響區(qū)連續(xù)冷卻轉(zhuǎn)變曲線（SHCCT曲線），研究了不同冷卻速率下焊接熱影響區(qū)粗晶區(qū)的組織轉(zhuǎn)變特征和硬度變化規(guī)律。結(jié)果表明：在模擬焊接條件下，該鋼的奧氏體化溫度明顯高于平衡狀態(tài)下的奧氏體化溫度；當冷卻速率低于2℃·s-1時，熱影響區(qū)粗晶區(qū)為全貝氏體組織；當冷卻速率為2~12℃·s-1時，熱影響區(qū)粗晶區(qū)為貝氏體和馬氏體的混合組織；當冷卻速率超過12℃·s-1時，熱影響區(qū)粗晶區(qū)得到全馬氏體組織；隨著冷卻速率增加，焊接熱影響區(qū)粗晶區(qū)的硬度逐漸增大。

The welding process of Q1100 high-strength steel was simulated with Gleeble-3500 thermal simulator, and then SHCCT(simulated HAZ continuous cooling transformation) diagram of the steel was obtained by using thermal expansion measurement combined with microstructure analysis and hardness testing. The microstructure transformation characteristics and hardness change rule of coarse-grained heat-affected zone (CGHAZ) were studied at different cooling rates. The results show that, the austenitizing temperature of the steel in simulated welding condition was significantly higher than that in the equilibrium state. The CGHAZ was full bainite when the cooling rate was under 2℃·s-1, a mixed microstructure of bainite and martensite was obtained when the cooling rate was 2-12℃·s-1, and the CGHAZ was full martensite when the cooling rate was over 12℃·s-1. The hardness of CGHAZ increased gradually with the increase of cooling rate.