2943 転造ボルトの機械的性質に及ぼす加工順序の影響(S58-2 ねじ(2),S58 機械要素の設計・製造・応用技術)

抄録

In ISO/DIS 898-1: 2006, the tensile testing for full-size bolts has been introduced for cold forged bolts, by which the yield strength, the tensile strength and the elongation after fracture can be obtained using load/elongation curve. However, it is difficult to specify the values corresponding to the material property since the mechanical property of cold-forging bolts is not perfectly clarified. This paper aims to clarify the effect of the manufacturing procedures on the tensile property of full-size bolts. The bolts to be tested were manufactured in the same batch and/or the same conditions except the manufacturing sequence, i.e, thread rolling before heat treatment or thread rolling after heat treatment. The results show that the tensile properties for cold-forged bolts can not simulated by the bolts thread-rolled after heat-treated, but by the bolts preloaded, in which higher level of compressive residual stress exists at the thread root.