C含量对2.25Cr-1Mo-0.25V埋弧焊焊缝金属性能的影响

Effect of carbon content on mechanical properties of 2.25Cr-1Mo-0.25V weld metalby SAW

系统研究了C对2.25Cr-1Mo-0.25V埋弧焊焊缝金属常规力学性能及高温持久性能的影响,揭示了碳化物对高温持久性能的关键作用。盘圆的热处理脱碳过程能够使焊丝及熔敷金属的C含量降低约20%,而其他合金元素未发生改变。C含量降低,2.25Cr-1Mo-0.25V埋弧焊焊缝金属表现出强度降低,塑韧性提高、回火脆化倾向减小的特点。在540℃试验温度和210 MPa持久应力下,低C焊缝金属的高温持久断裂时间仅为587 h,比正常焊缝的939 h缩短了30%,不能满足≥900 h的技术要求。低C焊缝中碳化物的析出密度、尺寸均显著低于正常焊缝。碳化物作为高温持久试验过程中阻止晶界滑移和位错迁移的钉扎物,是保证焊缝的高温持久性能的关键。在2.25Cr-1Mo-0.25V埋弧焊焊材进行设计以及产品检验过程中,需重点监控焊丝及熔敷金属C含量,避免出现C含量过低。

Effect of C on the conventional mechanical properties and high temperature rupture life of 2.25 CR-1MO-0.25 V weld metal by submerged arc welding(SAW)was systematically studied,and the key role of carbide on high temperature rupture life was revealed.The heat treatment decarburization process of wire rods could reduce the C content of the welding wire and deposited metal by about 20%,while other alloy elements remained unchanged.With the decrease of C content,2.25 Cr-1Mo-0.25V weld metal by SAW showed characteristics of reduced strength,increased plastic toughness and reduced tendency of tempering embrittlement.Under the test temperature of 540℃and the lasting stress of 210 MPa,the high temperature rupture time of low C weld metal was only 587 h,which was 30%shorter than 939 h of normal weld metal,which could not meet the technical requirements of≥900 h.The precipitation density and size of carbide in low C welds were significantly lower than that of normal welds.The carbides played a key role of pinning effect to prevent migration of grain boundary sliding and dislocation,which could improve the high temperature rupture life of welds.During the design and product inspection of 2.25Cr-1Mo-0.25V SAW materials,it was necessary to monitor the carbon content of welding wire and weld metal to avoid low C content.