中锰低温钢富氩混合气体保护焊工艺研究

Study on Argon-rich Mixed Gas Shielded Welding Process of Medium-Mn Low-temperature Steel

较高的锰含量给中锰低温钢焊接带来了挑战,这在一定程度上限制了中锰低温钢在工业生产中的应用。采用富氩混合气体保护焊对中锰低温钢进行焊接试验,研究不同焊接热输入条件下,焊接接头显微组织和力学性能的变化规律。结果表明:除焊缝及母材外,焊接接头各区域均为局部硬化区,且硬化程度随热输入的增加而增大;当热输入由12 kJ/cm增加到22 kJ/cm时,焊接接头的屈服强度由820 MPa降至775 MPa,抗拉强度由983 MPa降至925 MPa;当热输入为12 kJ/cm和16.8 kJ/cm时,其焊接接头在-40℃条件下均有着良好的冲击韧性,且后者焊接接头各区域冲击吸收功较为均匀,在45 J左右;焊缝区细小的夹杂物及针状铁素体提供了高密度的大角度晶界,减缓了裂纹扩展速率。热影响区稳定性较低的残余奥氏体在受到冲击载荷作用时发生相变诱导塑性(TRIP)效应,提高了焊接接头的低温冲击韧性。

The high Mn content poses challenges for the welding of medium-Mn low-temperature steel,which to some extent limits its application in industrial production.Welding experiments were conducted on medium-Mn low-temperature steel using argon-rich mixed gas shielded welding to study the changes in microstructure and mechanical properties of welded joints under different heat input conditions.The results show that,except for the weld and base metal,all areas of the welded joint are localized hardening zones,and the degree of hardening increases with the increase of heat input;When the heat input increases from 12 kJ/cm to 22 kJ/cm,the yield strength of the welded joint decreases from 820 MPa to 775 MPa,and the tensile strength decreases from 983 MPa to 925 MPa;When the heat input is 12 kJ/cm and 16.8 kJ/cm,the welded joint has excellent impact toughness under-40℃conditions,and the impact absorption energy in each area of the welded joint is relatively uniform,around 45 J;The small inclusions and acicular ferrite in the weld zone provide a large number of high-angle grain boundaries(HAGBs)slow down the crack propagation rate.The residual austenite with low stability in the heat-affected zone(HAZ)undergoes transformation-induced plasticity(TRIP)effect under impact load,which improves the low-temperature impact toughness of welded joints.