Ti-Ca处理对DH36钢板焊接热影响区组织性能影响的研究

Study on the Microstructures and Properties of the Welding Heat Affected Zone of DH36 Steel Plate with Ti-Ca Treatment

摘要:

利用热力学计算软件和扫描电镜分析Ti-Ca处理DH36钢的夹杂物特征，运用Thermecmaster-100kN热力模拟实验机模拟热输入250—400 kJ?cm^-1的焊接热循环，利用光学显微镜、扫描电镜和激光共聚焦显微镜分析焊接热影响区的显微组织，利用冲击试验机测试了低温韧性。结果表明：DH36钢中的典型夹杂物为Al₂O₃，还存在Al-Ca-Ti-O-Mn-S复合夹杂物，该夹杂物可有效地抑制高温下的奥氏体晶界迁移，促进晶内针状铁素体形成；热输入为250—400 kJ?cm^-1时，热影响区的显微组织由针状铁素体、珠光体和铁素体组成，随着热输入的增大，珠光体和铁素体含量随之增多；在1/2厚度位置模拟250—400 kJ?cm^-1热输入时，在-20 ℃下热影响区的冲击韧性均能充分满足国家规定的行业使用标准要求。

Abstract:

The inclusion characteristics of Ti-Ca treated DH36 steel were analyzed by thermodynamic calculation software and scanning electron microscope. The welding thermal cycle with heat input of 250—400 kJ?cm^-1 was simulated by Thermomaster-100kN thermal simulation machine. The microstructure of the welding heat affected zone was analyzed by optical microscope， scanning electron microscope and laser confocal microscope. The low-temperature toughness was tested by impact testing machine. The results show that the typical inclusion in the steel is Al₂O₃， and there are also Al-Ca-Ti-O-Mn-S composite inclusions， which effectively inhibit the migration of austenite grain boundaries at high temperatures and promote the formation of intragranular acicular ferrite. When the heat input is 250—400 kJ?cm^-1， the microstructure of the heat affected zone is composed of acicular ferrite， pearlite and ferrite. With the increase of heat input， the content of pearlite and ferrite increases. The impact toughness of heat affected zone （HAZ） at -20 ℃ at the 1/2 thickness position simulating 250—400 kJ?cm^-1 heat input can fully meet the industry standard specified by the state.