1988 Volume 6 Issue 2 Pages 267-272
The joint strength of brazed SUS 304 stainless steel has been investigated in relations to silver brazing filler metal composition and test temperatures. The strength was found to depend on the microstructure of silver filler metals. Joints brazed by β-phase type filler metals (with much β-phase) showed high tensile strength at low temperature (-196°C), the a-phase type filler metals, mainly consisted of solid solutions and their eutectic, exhibited medium strength, whereas the AgZn phase type filler metals with AgZn phase has low strength. The a-phase type filler metals showed the highest strength among these three types at higher temperatures. Above all the addition of nickel improved the high temperature strength. The relation between the joint strength at 400°C and zinc equivalence of silver filler metals showed aproximately negative linear relation, increase in zinc equivalence decreased the strength at 400°C. Nickel bearing copper base metal brazed with nickel free filler metals showed high strength at 400°C. The results of creep rupture test at 300°C were similar to the results of tensile test at high temperature. Joints brazed with high zinc equivalence (β-phase type) has inferior creep rupture resistance and a-phase type and nickel bearing filler metals offered longer rupture time.
