【作者】 王海东；

【导师】 路文江； 俞伟元；

【作者基本信息】 兰州理工大学 ， 材料加工工程， 2011， 硕士

【摘要】 瞬时液相扩散焊连接技术由于具有焊接温度低、连接构件的尺寸精度高、残余应力小、接头强度高等优点,在新材料的制备、连接、修复等方面有很大的潜力。但是,瞬时液相扩散焊技术也有美中不足之处,比如降熔元素扩散需要的时间较长,因此在大气环境中焊接时,需要保护焊接接头区域不被氧化的时间也长,成本较高;而且瞬时液相扩散焊对焊接端面的粗糙度要求严格,这些缺点一直制约着TLP焊接技术在钢管焊接方面的广泛应用。本文试图通过改变压力来解决TLP焊接过程中存在的问题,为此进行了以下研究工作:通过正交试验确定出电站锅炉常用钢管12Cr1MoV的最佳焊接工艺参数,在最佳焊接温度和保温时间的条件下,单独研究压力对接头组织和性能的影响规律,并对不同压力下接头的力学性能进行了分析测试,得出随着压力的增加,接头的抗拉强度不断增大,只是压力增大到一定的范围后对强度的影响较小,过大的压力反而降低了强度。比较了12Cr1MoV在TLP和TIG两种不同焊接工艺下接头的显微硬度,发现在TLP焊接条件下接头各区域的综合力学性能均优于TIG。计算了降熔元素Si在不同压力下的扩散系数,比较了不同压力下元素扩散所需的时间。计算结果表明,增加压力可增大扩散距离,从而减少扩散所需要的时间,能提高TLP的焊接效率,并且总结出了压力在整个TLP焊接过程中所起的作用。最后,采用有限元分析软件ABAQUS模拟TLP焊接接头区域温度场和应力场的变化规律,探讨焊后接头的残余应力分布情况。更多还原

【Abstract】 Transient Liquid Phase Bonding with the advantages of low temperature, the size of connected components with high precision, the little residual stress, the strong joint strength etc, has great potential in the preparation of new materials, connectivity, restoration. However, TLP has some disadvantages, such as the Melting Point Depressant element diffusion requires long time. Therefore, when welding in atmosphere, it needs longer time to protect the weld joint area preventing from oxided, and much cost; TLP strictly requires the roughness of welding surface, These shortcomings have been restricted the broader applications of TLP technology in steel pipe welding. This article attempts to solve the problems during TLP process by changing the pressure, so did the following researches:We determine the optimal welding parameters of the common 12Cr1MoV steel in boiler by orthogonal test, in the best conditions of welding temperature and holding time, separately study influence of law of pressure on the joint microstructure and properties, and analysis the mechanical properties of joint in different pressure, we discover that as the pressure increases, increasing the tensile strength of joints, but, when the pressure increases to a certain extent , its influence gradually smaller on the tensile strength, on the contrary, too much pressure reduces the tensile strength. We compare the joint microhardness of 12Cr1MoV under two different welding technology, TLP and TIG., and discover the integrated mechanical properties of joint of each region under the TLP conditions are superior to TIG.We calculate the diffusion coefficient of MPD Si under the different pressures, and compare the time required for elements diffusion under the different pressure. The results show that, increase pressure can increase the diffusion distance, thereby, reduce the time required for diffusion, and improve the TLP welding efficiency, and summed up what roles the pressure play in the entire TLP process.Finally, we simulate the variation of temperature and stress of TLP joint field by the finite element analysis software ABAQUS, and discuss the distribution of residual stress of joint after welding.更多还原