稀土对700 MPa级大焊接热输入用钢的组织和性能影响

Effects of RE on Microstructure and Properties of 700 MPa Grade Large Heat Input Welding Steel

面向700 MPa级大焊接热输入用钢的迫切需求,通过加稀土(RE)改进制备钢板,基于Gleeble试验模拟焊接热影响区,并开展力学性能测试,以及显微组织和断口分析,结果显示,钢板具有优良的强韧性匹配和抗大焊接热输入性能,母材屈服强度R_(eL)≥600 MPa,抗拉强度R_m≥700~850 MPa,断后伸长率A≥16%,-40℃下冲击吸收能量KV_2≥47 J、焊接热影响区的冲击吸收能量KV2≥34 J,满足相关技术要求。分析发现,添加RE可明显改善钢板母材和焊接热影响区的低温韧性,主要由于细小含RE复合氧化物作为针状铁素体的形核核心,促使焊接热影响区内形成针状铁素体,明显改善了焊接热影响区的韧性。

The RE have been addressed on the improvement in steel making of the 700 MPa grade large heat input welding steel, and microstructure and properties of and its HAZ were investigated by the scanning electron microscopy, metallography, mechanical testing and welding thermal simulation. The results showed that the test steel containing RE had good match between strength, toughness and anti-large heat input welding, and the mechanical properties of the test steel containing RE meet the technical requirements, namely the yield strength ReL≥600 MPa, the tensile strength Rm≥ 700 - 850 MPa, the elongation A ≥ 16%, the -40℃ impact energy KV2 ≥47 J and the -40℃ impact energy of HAZ KV2≥34 J. The toughness of base metal and HAZ of test steel had been improved owing to RE addition. The small dispersed to the RE composite inclusions,which promoted the formation of acicular ferrite in HAZ, were beneficial improvement of HAZ toughness.