热输入对2205双相不锈钢MIG焊接接头组织及力学性能的影响

Influence of heat input on microstructure and mechanical properties of 2205 DSS metal inert-gas welding joints

采用MIG焊接方法,对2205双相不锈钢进行了不同热输入条件下的焊接试验,对焊接接头的显微组织进行了观察与分析,并对其力学性能进行了测试.结果表明:不完全重结晶区中带状奥氏体边缘起伏随热输入的增大逐渐增强,宽度逐渐增大;焊缝中心的奥氏体大多为等轴状的块状奥氏体,而靠近熔合线则主要为魏氏奥氏体,随着热输入的增大,魏氏奥氏体逐渐减少,而块状奥氏体逐渐增多;随着热输入的增大,焊接接头的抗拉、屈服强度均有轻微降低,而断后延伸率略有升高;焊接接头的显微硬度从母材到焊缝金属先升高后降低,热影响区的显微硬度最高,硬度的变化与焊接接头各区域中奥氏体体积分数有关,随着热输入的增大,各区域中奥氏体体积分数逐渐升高,显微硬度则相应有所降低.

2205 duplex stainless steel plates with a thickness of 3 mm were welded by MIG welding under different heat inputs. Microstructures and properties of the welding joints were tested and analyzed in detail. The results are as follows： the edge fluctuation of the banded austenite in the incomplete recrystallization zone increases and the width of austenite band increases gradually with increase of the heat input. Austenites in the weld center are mostly blocky austenite while widmanstatten austenite dominates in the weld metal near the fusion line. W idmanstatten austenite decreases and the blocky austenite increases with increase of the heat input. The tensile strength and yield strength of the welding joints decreases mildly with increase of the heat input while the elongation increases slightly. The microhardness of the welding joints from the parent metal to the weld metal first increases and then decreases,while the highest microhardness appears in the heat affected zone. Change of the microhardness is related to the volume fraction of austenite in different regions of the welding joints： the volume fraction of austenite in each region increases gradually with increase of the heat input which leads to reduction of the microhardness.