Ti对低合金高强钢大热输入焊缝夹杂物的影响

Effects of Titanium on Inclusion in High Heat Input Welds of High Strength Low Alloy Steel

对不同Ti质量分数的低合金高强钢气电立焊焊缝夹杂物进行对比分析，并研究焊缝夹杂物数量、分布、类型对焊缝组织的影响。结果表明，当Ti质量分数由0增加至0．028％～0．038％范围内时，夹杂物得到有效细化，尺寸小于2μm的夹杂物比例大幅度提高，促进了针状铁素的形核。当Ti过量时，小于2μm的夹杂物比例迅速降低，贝氏体转变成为主导。夹杂物中心以氧化物为主，外层包裹物为MnS。随着Ti质量分数的增加，夹杂物中Mn、Si等元素减少，Al、Ti、0质量分数增加，夹杂物中心的氧化物以MnO、Si02、Al20，、MgO的次序逐渐转移至边缘，最终被TixOy取代。此过程中，夹杂物由Mn-Si-O转变为Ti-Mn-Al-O，最后转变为Ti-Al-O，并且对于针状铁素体形核而言，完成了无效夹杂物一有效夹杂物一无效夹杂物的转变。

Different non-metallic inclusions in electrogas welds containing various titanium contents are compared and the effects of their number, distribution and type are investigated as well for high strength low alloy（HSLA）steel. The results indicate that the inclusions are effectively refined with the titanium contents ranged in 0.028%-0.038%, and aeicular ferrite in the welds is obviously promoted owing to the significantly increased percentage of the inclusions with a size smaller than 2 μm. However, the percentage of the inclusions with a size smaller than 2 μm is dramatically decreased with the excessive addition of titanium in the welds and it results in bainite transformation. It is also confirmed that the inclusions in the weld metals mainly consists of oxides in the core and MnS coated outside. Manganese and silicon levels are decreased, whereas aluminum, titanium and oxygen are increased in the inclusions with titanium addition. As a result, oxides in the core are expelled to the edges in an order of MnO, SiO2, Al2O3, MgO, and finally replaced by TixOy. Therefore, the inclusion types are transformed from Mn-Si-O without titanium to Ti-Mn-Al-O and finally to Ti-Al-O with excessive titanium addition. The inclusions are suffering the processing from ineffective to effective and then to ineffective with increasing the titanium content.