Qi Huan, Pang Qihang, Li Weijuan, Bian Shouyuan
School of Materials and Metallurgy, University of Science and Technology Liaoning, Anshan, 114051, Liaoning, China.
Sci Rep. 2024 Aug 21;14(1):19459. doi: 10.1038/s41598-024-70562-9.
In the present study, the welding thermal cycle of magnesium-treated EH36 steel was simulated by a thermal simulation experiment machine. The effects of welding heat input on the microstructure and low temperature toughness of the welded joint were studied, and the mechanism of acicular ferrite nucleation induced by inclusion was revealed. The results showed that, when the welding heat input of 150 kJ/cm, 250 kJ/cm and 350 kJ/cm was utilized, the microstructure of heat affected zone in the experimental EH36 steel consisted of grain boundary ferrite, acicular ferrite, granular bainite, and a small amount of pearlite, but the volume fraction and grain size of each independent microstructure were different. With the increase of welding heat input, the content of acicular ferrite and granular bainite decreased, the content of grain boundary ferrite increased, and the average grain size increased, whereas the low temperature toughness of the experimental EH36 steel welded joint reduced from 174 to 67 J. Furthermore, inclusions can induce acicular ferrite nucleation, whereas the nucleation mechanism is a combination of low lattice mismatch and low interfacial energy.
在本研究中，采用热模拟实验机模拟了镁处理EH36钢的焊接热循环。研究了焊接热输入对焊接接头组织和低温韧性的影响，揭示了夹杂物诱发针状铁素体形核的机制。结果表明，当采用150 kJ/cm、250 kJ/cm和350 kJ/cm的焊接热输入时，试验用EH36钢热影响区的组织由晶界铁素体、针状铁素体、粒状贝氏体和少量珠光体组成，但各独立组织的体积分数和晶粒尺寸不同。随着焊接热输入的增加，针状铁素体和粒状贝氏体的含量减少，晶界铁素体的含量增加，平均晶粒尺寸增大，而试验用EH36钢焊接接头的低温韧性从174 J降至67 J。此外，夹杂物可诱发针状铁素体形核，其形核机制为低晶格错配和低界面能的组合。
