Abstract
With carbon steel wire-rods of JIS S35C and 545C which are used for cold formed bolts of medium strength, a study was made on the influence of the annealing treatment under various conditions referring to the structure, mechanical properties and crack occurrence under compression tests utilizing an Amsler universal testing machine or a crankpress.
The purpose of this study is to obtain a fundamental data for spheroidizing annealing of wire-rods in factories.
From the results of this experiments, it is confirmed that pretreatments (cooling in oil, air or furnacee) and annealing conditions (temperature and time) give a correlative influence on the spheroidizing annealing of these wire-rods for cold forming; that there are adequate ranges in the aforementioned temperature and time; that the occurrence of cracks in cold forming is more related to the contraction value than to the elongation; and that, by an oilcooling pretreatment of wire rods, higher-strength bolt blanks can be obtained which are very resistant to occurrence of cracks on cold forming in spite of an annealing at a relatively low temperature and in a relatively short time.
