Zhu Zhengyu, Ran Maoyang, Li Xuyang, Ma Pichang, Liu Shubin, Wang Jiayou
Provincial Key Lab of Advanced Welding Technology, School of Materials Science and Engineering, Jiangsu University of Science and Technology, 666 Changhui Road, Zhenjiang 212100, China.
Jiangsu Province Marine Equipment Intelligent Engineering Technology Research and Development Center, Jiangsu Maritime Institute, 309 Gezhi Road, Nanjing 211170, China.
Materials (Basel). 2024 May 13;17(10):2310. doi: 10.3390/ma17102310.
Hot-rolled backup rolls are widely used in steel rolling and usually need to be repaired by arc hardfacing after becoming worn. However, a corrugated-groove defect commonly occurs on the roll surface due to the uneven hardness distribution in the hardfacing layers, affecting the proper usage of the roll. Accordingly, a new swing-arc submerged arc welding (SA-SAW) process is proposed to attempt to solve this drawback. The microstructure and hardness are then investigated experimentally for both SAW and SA-SAW hardfacing layers. It is revealed that a self-tempering effect occurs in the welding pass bottom and the welding pass side neighboring the former pass for both processes, refining the grain in the two areas. In all the zones, including the self-tempering zone (STZ), heat-affected zone (HAZ), and not-heat-affected zone in the welding pass, both SAW and SA-SAW passes crystallize in a type of columnar grain, where the grains are the finest in STZ and the coarsest in HAZ. In addition, the arc swing improves the microstructure homogeneity of the hardfacing layers by obviously lowering the tempering degree in HAZ while promoting the even distribution of the arc heat. Accordingly, the hardness of the SA-SAW bead overall increases and distributes more uniformly with a maximum difference of < 80 HV along the horizontal direction of the bead. This hardness difference in SA-SAW is accordingly decreased by ~38.5% compared to that of the SAW bead, further indicating the practicability of the new process.
热轧支承辊在轧钢生产中应用广泛，磨损后通常需采用电弧堆焊修复。然而，由于堆焊层硬度分布不均，辊面常出现波纹状沟槽缺陷，影响轧辊的正常使用。为此，提出一种新型摆动电弧埋弧焊（SA - SAW）工艺以解决这一问题。随后对SAW和SA - SAW堆焊层的组织和硬度进行了实验研究。结果表明，两种工艺在焊道底部及相邻焊道侧均出现自回火效应，细化了这两个区域的晶粒。在包括自回火区（STZ）、热影响区（HAZ）和焊道非热影响区在内的所有区域，SAW和SA - SAW焊道均以柱状晶形式结晶，其中STZ晶粒最细，HAZ晶粒最粗。此外，电弧摆动明显降低了HAZ的回火程度，促进了电弧热的均匀分布，从而改善了堆焊层的组织均匀性。因此，SA - SAW焊道的硬度总体提高，沿焊道水平方向的最大差值<80 HV，硬度分布更均匀。与SAW焊道相比，SA - SAW焊道的硬度差相应降低了约38.5%，进一步表明了新工艺的实用性。
