合金元素对大线能量焊接用钢组织性能的影响

Effect of alloying elements on microstructure and properties of high heat input welding steel

为阐明钢中常用合金元素对大线能量焊接热影响区粗晶区（CGHAZ）的影响规律,设计了不同合金质量分数的试验钢,并进行氧化物冶金工艺处理,考察了各试验钢模拟焊接CGHAZ冲击韧性和组织特征。结果表明,低碳高锰有利于韧性的改善,但存在合适的碳质量分数范围,极低碳时需抑制晶界铁素体生成;添加质量分数为0.01%的铌时可保持较高的CGHAZ韧性,但过量的铌促进贝氏体生成而导致韧性恶化;添加质量分数为0.05%的钒时能提高基体强度并保持优良CGHAZ韧性,更高质量分数时因碳化物大量析出导致韧性下降;在一定范围内提高镍和铜质量分数可综合改善钢板强度和CGHAZ韧性;铬和钼的添加可抑制晶界转变产物,促进微细针状铁素体组织生成,但在试验钢成分下较多的M/A使得CGHAZ韧性未得到有效改善。

In order to clarify the influence of common alloying elements on high heat input welding coarse-grained heat affected zone（CGHAZ）in steel,experimental steels containing different alloy mass percent were designed and treated by oxide metallurgy process. Impact toughness and microstructural characteristics of simulated welding CGHAZ of each steel were researched. Results showed that low C and high Mn is in favor of toughness improvement,but there exists a proper range of C mass percent. Grain boundary ferrite needs to be inhibited when C mass percent is ultra low. Relatively high CGHAZ toughness could be obtained with 0.01% Nb addition. However,excessive Nb will cause bainite formation and toughness deterioration. A percentage of 0.05% of V addition could increase matrix strength and keep good CGHAZ toughness,while a larger amount will impair toughness because of carbide precipitation. Increase of Ni-Cu mass percent in a proper range can improve combined properties of strength and CGHAZ toughness. Addition of Cr and Mo can prohibit grain boundary transforming product and promote the formation of fine acicular ferrite. However,CGHAZ toughness had not been improved effectively because of a large amount of M/A formation for the present steel composition.