焊后热处理对CB2耐热钢焊接头组织及力学性能的影响

Effect of post welding heat treatment on microstructure and mechanical properties of CB2 heat resistant steel joints

采用BNi-2非晶薄片作为连接中间层,分别在温度为1060℃,1100℃和1140℃,保温时间为1800 s的条件下,对CB2耐热钢进行瞬时液相焊接,并对接头进行焊后热处理。采用扫描电镜（SEM）和能谱仪（EDS）对接头显微组织和元素分布进行分析,并对接头的力学性能进行测试。结果表明,在焊接过程中,中间层和基体发生明显相互扩散。在1060℃的焊接温度下,接头中心处形成了非等温凝固区,其组成主要为富Cr硼化物。随着连接温度的增加,非等温凝固区消失,形成完全等温凝固区。在接头的扩散影响区,有Cr硼化合物的出现,在温度为1100℃时,其数量达到最大值,而后随温度增加而减少。接头的抗拉强度在1140℃达到最大值为920 MPa,而伸长率低于7%,拉伸断裂发生在接头。在经过焊后热处理后,接头的等温凝固区域宽度增加,而扩散影响区中的Cr硼化物减少,拉伸断裂以韧性断裂方式发生在母材,强度降低为723 MPa,但断后伸长率明显提升至19%,达到原始母材的性能,因此焊后热处理可以优化接头的力学性能。

Transient liquid phase bonding and post bonding heat treatment of CB2 heat resistance steel were performed with BNi-2 amorphous foil as interlayer when bonding at 1060 ℃ , 1100 ℃ and 114-0 ℃ for 1800 s, respectively. Microstructure and composition distribution of the joints were analyzed by means of SEM and EDS, and mechanical properties of the joints were tested. The results show that obvious interdiffnsion of interlayer and base metal occurred during TLP bonding. When bonding at 1060 ℃ , athermal solidified zfme which was mainly consisted of Cr-rich borides formed in the joint centerline area. The athermal solidified zone diminished and isothermally solidified zone formed when increasing the bonding temperature. Cr-rich borides formed in diffusion affected zone of joints, and its amount reach the maximum when bonding at 1100 ℃, but it decreased with the fttrther increase of bonding telnperature. The maximum tensile strcngfll 920 MPa was achieved when bonding at 1140 ℃, but the elongation was less than 7% , meanwhile, tensile fracture occurs at the joint. After post b, mdiug heat treatment, the width of isothermally solidified zone increased, but the amount of Cr-rich borides of diflhsit,n aftcted zone decreased. Tensile fracture located in base metal and tensile strength declined to 723 MPa, but the elongation was improved to 19% , whic, h was comparable with that of base metal. So it can be conclude that post bonding heal trealment can improve the mechanical properties of the ioints.