軟鋼のろう付強度におよぼす表面状態の影響(第6報)

主として粗さと残留応力の関係について

抄録

According to the researches already carried out, it is clear that brazed joint strength of specimen with coarse brazing surface is greater than that of ones with smooth brazing surface. It is considered that these phenomena depends on the effect of the following factors:
1) Actual contact area of brazed joint.
2) Residual stress of brazed joint.
3) Hardness distribution of brazed joint.
This paper presents some experimental evidence of residual stress measured by X-ray stress maesuring process and hardness distribution measured by micro-Vickers hardness tester. To obtain smoe experimental data, 10 × 32 × 2.6/m/m mild steel as the base metal and BAg-8 as a filler metal were prepared, and the abutting surfaces of base metals were Polished with various emery papers (No. 60, 120, 240, 400, 600mesh) to set up various roughnesses on the brazing surface. These specimens were brazed with BAg-8 filler metal in the 35 kW resistance furnace operated in hydrogen atmosphere. Residual stress measuremtnt was carried out by means of an X-ray Rstess measurement diffractometer manufactured by Tokyo Shibaura Electric Co.
These examinations gave the results as follows:
1) Residual stress of brazed joint with coarse surface was larger than that of ones with smooth brazing surface.
2) Eesidual stress of y directio n (Fig. 7, 8) was larger than that of x direction; it is considered that these phenomena were caused by soliditic shrinkage of filler metal at the brazed joint.
3) Most of these residual stresses were tension stresses, their max value being 4.5kg/mm² and their min, value being 0.1kg/mm².