Structure and properties of welded joints of low-alloy thermomechanically processed (09G2FB) and quenched and tempered shipbuilding steels (10XN2MD, 08XN3MD, and 12XN3MF), welded with manual metal arc welding (MMA) and submerged arc welding (SAW), were studied. Effects of specific energy input on the microstructure, mechanical properties, and impact energy of the heat-affected zone (HAZ) have been investigated, and probable reasons for crack formation in welded joints have been found. It was found that welding heat input increase leads to a significant increase in grain size near the fusion boundary and the formation of martensite with high hardness. Therefore, the heat input is recommended to be limited to 2.5–3.5 kJ/mm for these specific steel grades. The study indicates that microalloying elements can be used to limit the grain growth when the steel is subjected to high temperatures during welding thermal cycle. Carbon content and alloying level reduction tend to increase the steel ductility and lower the HAZ toughness.

中文翻译：

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高强度耐寒造船用钢对电弧焊热循环敏感性的研究

研究了通过手工金属电弧焊（MMA）和埋弧焊（SAW）焊接的低合金热机械加工（09G2FB）和调质的造船钢（10XN2MD，08XN3MD和12XN3MF）的焊接接头的结构和性能。研究了比能输入对热影响区（HAZ）的组织，力学性能和冲击能的影响，并发现了焊接接头中形成裂纹的可能原因。已经发现，焊接热输入的增加导致熔合边界附近的晶粒尺寸显着增加并且形成具有高硬度的马氏体。因此，对于这些特定的钢种，建议将热量输入限制为2.5-3.5 kJ / mm。研究表明，当钢在焊接热循环中经受高温时，微合金元素可用于限制晶粒长大。碳含量和合金化程度的降低往往会增加钢的延展性并降低HAZ韧性。