采用BNi-2钎料真空钎焊0Cr18Ni9不锈钢管材

Vacuum brazing 0Cr18Ni9 stainless steel pipe to itself with BNi-2 filler alloy

摘要:

针对实际应用中常需要获得异型接头这一目的，采用BNi82CrSiB（BNi-2）钎料钎焊套接0Cr18Ni9不锈钢管材，研究了冷却方式、钎焊温度、保温时间和装配间隙对接头组织结构和力学性能的影响.结果表明：管材套接的特殊结构，填缝间隙对接头影响较大，当间隙过小为5~10 μm时，易出现填缝不足导致无法形成完整接头，接头强度下降；但间隙过大为250~300μm，钎缝中形成大量脆性相并产生微裂纹；冷却方式对组织影响较小，但15℃/min的冷却速度所得接头强度较低；钎焊温度升高或保温时间延长，最大间隙值增大，母材出现溶蚀，性能影响较小.钎焊温度为1 050℃，保温时间为10 min，装配间隙为20~50 μm，随炉冷却所得钎焊接头显微组织结构中未出现共晶组织和金属间化合物，接头性能最高.

Abstract:

Focused on the application of special-shaped joints, 0Cr18Ni9 stainless steel pipes were brazed using BNi82CrSiB (BNi-2) as filler alloy to form a bell and spigot joint. Influences of cooling-down velocity, brazing temperature, holding time and fit-up gap on the microstructure and mechanical property of joints were investigated. Results indicated that the fit-up gap had a great effect on the joints due to the special structure of pipe joints, when the width of gap is only 5~10 μm, it is difficult to fill the lap to form a complete joint and the strength of joints is low, but if the gap is too large up to 250~300 μm, large amounts of brittle phases formed in the brazing seam as well as micro-cracks. Cooling velocity almost made no difference on the microstructure, while the joints cooled at 15℃/min present lower strength than that furnace cooled. Increasing brazing temperature or prolonging holding time, the maximum gap increases and erosion of the matrix can be observed, but both parameters have few effects on mechanical property. When the two pipes with the fit-up gap of 20~50 μm were brazed at 1 050℃ for 10 min and furnace cooled, no eutectic phases and intermetallics appeared in the seam, and the strength of the joint reached the maximum.