転造ねじの衝撃引張強度について

抄録

In order to study some characteristics of the impact tensile strength of rolled screw bolts, especially the aging effects after rolling, we have conducted impact tensile tests of 1"/4 and 3"/8 rolled screw bolts made of ordinary and high tension steels, at test temperatures from -190°C to +100°C.
The results obtained are as follows:
(I) The impact tensile strength of rolled screw bolts gets a little larger as test temperatures become lower than +100°C, and shows the maximum value between 0°C and -50°C, while the impact strength gets rapidly small within the temperature below -50°C, and screw bolts show brittle fracture. And the transition temperatures at which ductile fracture is changed into brittle one are below -60°C.
(II) Though the impact tensile strength of cut screw bolts is smaller than that of rolled screw bolts, the effects of test temperatures on the impact tensile strength have nearly the same tendency with the case of rolled screw bolts. However, on cut screw bolts made of heat treated Cr-V alloy steel, the transition temperature seems to move toward lower temperature.
(III) The effect of aging after rolling on the impact tensile strength of rolled screw bolts is recognized at low temperature as for ordinary steels. It makes the impact strength decrease and the transition temperature rise by about 10∼30°C. Therefore, we must be careful, in the use of rolled screw bolts in low temperature. But this effect does not appear in the rolled screw bolts made of heat-treated Cr-V steel and cut screw bolts.