Abstract：With the improvement of pipeline steel grade, the difficulty in fracture toughness control of girth weld is also increasing. The components of weld are the mixture of base material and filling metals. Therefore, the alloying elements of base material have an important influence on the microstructure and properties of the final weld. Ten types of X80 pipeline steels with different contents of alloying elements were designed, and the welding experiments with same process specifications were conducted for the simulation of girth welding on site. The microstructure of the girth welded joints of the experimental steels with different alloying elements was characterized by scanning electron microscopy (SEM). Meanwhile, the impact toughness of the corresponding welds was also measured. The effects of Mn, Cr and V on the microstructure and properties of the girth welded joints of X80 pipeline steel were investigated. The results showed that partial Mn would be melt into the molten pool during the girth welding process of X80 pipeline steel, but its influence on the weld was limited. The dilution rate of Cr was very unstable. The higher the content of the Cr in base metal, the lower of the dilution rate. The overall dilution rate of Cr was ranged from 25% to 50%. The dilution rate of V was also relatively low with the average of 17%. The Mn dissolved into the weld in the steel plate only accounted for a very small part of the total Mn content, which had a little influence on the microstructure of the weld. Therefore, the weld impact toughness was not affected. Cr element expanded the formation range of granular bainite during the cooling phase transformation process, resulting in a large number of granular bainite structure in the weld. As a result, the number of martensite/austenite (M/A) and the particle size increased, thus reducing the impact toughness of weld. A small amount of V dissolved into the weld in the base steel plate could promote the transformation of bainitic ferrite and avoid the appearance of the coarse M/A particles in weld. However, its influence on the weld impact toughness was not obvious.
侯宇. 合金元素对X80管线钢环焊接头组织和性能的影响[J]. 冶金分析, 2023, 43(4): 24-33.
HOU Yu. Effect of alloying element on microstructure and properties of girth welded joints of X80 pipeline steel. , 2023, 43(4): 24-33.
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