冷間引抜せる鋼管中の残留応力(II)

抄録

Following the previous report of some studies on residual stress measurements, the author studied in this report the sinking and plug drawing of wall thickness, outside diameter ratio, about 10% steel tubings, and investigated on the relations between residual stress and two drawing conditions, namely die contour and reduction.
The results clarified were summarized as follows.
a) In case of sinking (Fig. 6 & Fig. 7)
a. 1) Residual stress increased with the increase of outside diameter reduction.
a. 2) The larger the die angle, within limit of about 10% reduction of olltside diameter, the residual stress of sunk steel tubings were greater.
a. 3) On the other hand, when in excess of 15% reduction of outside diameter, the residual stress of suhk steel tubings with smaller die angle became greater.
a. 4) Within 10-15% reduction of outside diameter, almost no influence of die angle could be observed.
b) In case of plug drawing (Fig. 8 & Fig. 9)
b. 1) By reduction of the wall thickness the residual stress decreased remarkably with the increase of reduction of wall thickness.
b. 2) In case of about 10% reduction of the wall thickness, the residual stress generally increased with. the increase of the outside diameter reduction and the die angle.
b. 3) In case of about 20% reduction of wall thickness, when reduction of the outside diameter and die apgle were smaller, considerable negative stress remained on outer surface, but they decreased with the increase of the die angle. In case of larger reduction of the outside diameter, this phenomenon could not be observed and a comparatively smaller positive residual stress occurred regardless of the die angle.
b. 4) In conclusion, wheh cold-working steel tubing, a moderate reduction of outside diameter and a sufficient reduction of wall thickness are required for the manufacture of cold-drawn steel tubing with smaller residual stress.