EH40船板钢大热输入埋弧焊接头韧化机理研究

Study on the Toughening Mechanism of Joint of EH40 Ship Plate Steel with High Heat Input Submerged Arc Welding

对EH40船板钢进行大热输入(103 kJ/cm)埋弧焊接,通过拉伸、冲击试验,利用金相显微镜、扫描电镜、透射电镜和电子背散射衍射技术分析焊接接头的组织和力学性能。结果表明,焊缝金属组织为大量针状铁素体、少量先共析铁素体和少量M-A组元。大量晶内针状铁素体的生成分割了原奥氏体晶粒,焊缝有效晶粒尺寸为3.2μm。焊缝分析区域内大角度晶界比例为78.6%,大角度晶界主要分布在50°～60°,对焊缝冲击韧度非常有利。M-A组元尺寸较小,数量较少且均匀分布,不会对焊缝金属的韧性产生不利影响。焊接热影响区粗晶区的组织为贝氏体、针状铁素体和先共析铁素体。高熔点颗粒状析出相(TiO、Al2O3、MgO、TiN)的存在抑制粗晶区晶粒的长大,促进针状铁素体的形成,改善了该区域的冲击性能。力学性能试验结果表明焊接接头的强度高于母材,强韧性匹配良好,与组织分析结果一致。

The EH40 ship plate steel is welded with submerged arc welding process, and the microstructure and mechanical property of welded joint are analyzed. The results show that the main microstructures of weld metal are acicular ferrite, a few proeutectoid ferrite and small area of M-A. Acicular ferrite dividing the original austenitic grain, effective grain size of weld metal is 3.2 p.m. Large angle grain boundaries account for 78.6% of the grain boundaries in the analysis area of weld metal, and large angle grain boundaries mainly distribute between 50 degree and 60 degree, which are good for the impact toughness of weld metal. Few evenly distributed M-A with small size is not harmful to the toughness of weld metal. The microstructures of the coarse grained heat affected zone （CGHAZ） consist bainite, acicular ferrite and proeutectoid ferrite. The toughness in the CGHAZ is improved for the existing high melting point granule precipitated phases （TiO, A1203, MgO, TIN）, which prohibit the growing of grain and promote the formation of acicular ferrite. The results of mechanical property show that good property joint is obtained, which is consistent with the results of microstructures.