Joint strength and microstructures of brazed joints of stainless steel with Fe-based filler

For thermal conversion parts of electrical equipment which are required high corrosion resistance, stainless steel is often used. The joining of such materials is generally conducted with brazing with Ni-based filler. Since Ni is a rare and high-cost material, the substitute filler material which is low-Ni or Ni-free is expected to be developed. Fe-based filler has been developed as one candidate. In this study, joint strength and the microstructure of stainless steel type 304 brazed joint with Fe-based filler were investigated. As the results, it was clarified that shear strength of the joint with Fe-based filler is the almost same level as that with conventional Ni-based filler. Moreover, the effect of joint clearance on the joint strength and the microstructure was also investigated. When joint clearance is more than 50 μm, the final solidified area which consists of Fe-Cr-Ni-Si phases and P-rich phases forms in the center of the brazed joint. The formation of P-rich phases causes the joint strength reduction.