Ti对大线能量焊接焊缝组织和性能的影响

对不同Ti含量的气电立焊焊缝组织及力学性能进行了对比研究。结果表明,Ti的质量分数在0.028%~0.038%范围内时,焊缝中获得大量细小的针状铁素体,焊缝组织及低温韧性得以明显改善。当Ti过量时,焊缝中的针状铁素体减少,组织以贝氏体为主,低温韧性相应下降。焊缝组织中观察到块状和条状的M-A组元,随着焊缝Ti含量增加,其总量增加。焊缝夹杂物多为以氧化物为核心,外层包裹着MnS的复合夹杂物,并随夹杂物Ti含量的增加,由Mn-Si-Al-O型向Ti-Mn-Al-O型转变,有利于促进针状铁素体形成。而当焊缝中Ti过量时,主要夹杂物又转变为对针状铁素体形核无效的Ti-Al-O型,促进了贝氏体转变。

Effect of Titanium on Microstructure and Mechanical Properties in High Heat Input Welds

The microstructure and mechanical properties were investigated for the electrogas welds containing different titanium contents. The result indicates that the mechanical properties and microstructure of the weld metal are obviously improved due to large amount of fine acicular ferrite when the titanium content is in the range of 0. 028%-0. 038% (mass fraction). However, the impact toughness severely decreases owing to lots of bainite formed in the weld metal as the titanium content further increases. Both blocky and string like M-A constituents are observed in the weld metal, and the amount of M-A constitutes increases with increasing the titanium content. The inclusions in the weld metal are mainly oxides coated by MnS. The inclusions transform from Mn-Si-Al-O type without titanium addition to Ti-Mn-Al-O type with optimum titanium addition, which is effective for acicular ferrite nucleation, and finally to Ti-Al-O type which is ineffective for acicular ferrite nucleation with excessive titanium addition, which promotes bainite transformation.