| 摘要 |
PURPOSE:To improve strength characteristics, and to reduce the cost by heating and hardening a cold-formed material, and thereafter, executing a warm heading formation at a tempering temperature, and subsequently, executing warm trim forming and warm rolling. CONSTITUTION:A material which has been brought to preliminary forming by cold working in processes I, II and III is bought to hardening in a process IV, also brought to quick heating in the next process V and heated to a tempering temperature, and a warm heading formation is executed. Subsequently, thereafter, before the remaining heat of the V-th process is cooled, warm trim forming of a process VI is executed. Also, after a heating process VII, warm rolling is executed in the VIII-th process, and a reinforced bold is obtained. According to this method, a reinforced bolt in which strength of the neck part and the threaded part is well-balanced is obtained, and also since an inexpensive and low grade material is used, the cost can be reduced. |
