Development of Mushy-state Forging Method Using Resistance Heating

为了开发一种利用电阻加热进行糊状锻造的方法，通过实验和有限元模拟，研究了A357铝合金坯料的电阻加热特性，并找出了坯料加热稳定、均匀的措施。在该方法中，插入耐热，低导热奥氏体不锈钢SUS304盘之间的铜电极和钢坯作为热绝缘体的设计，以提高钢坯加热的效率。在原计划中，计划使用SUS304不锈钢复合电极，但研究是在插入热绝缘体的模式下进行的，以便于实验操作。在电阻加热中，需要在电极和坯料之间施加接触压力以确保它们的电接触。同时，强烈希望在加热中尽可能地抑制坯料的变形。有可能 ...更多信息 通过减小所施加的接触压力来减小变形，但过度减小会导致坯料和绝热体之间产生火花并停止锻造操作。然后，首先，研究了与电流密度相关的接触压力对火花发生的条件，并明确了这一点。在此基础上，研究了均匀坯料加热所需的绝热层厚度与电流密度和接触压力的关系。在此基础上，对铝合金齿轮进行了实态锻造实验，研究了输入电能和锻造压力对锻造条件的影响。结果表明，糊状锻造法是可行的，但其金相组织受绝热材料厚度的影响较大。因此，在实际应用中，与每个单独的情况相对应地适当调节绝热体厚度是必要的。通过本研究获得的结果已在以下参考文献中公布。少

With an aim of developing a method for mushy-state forging using resistance heating, experiments and finite element simulations were carried out to clarify the resistance heating characteristics of A357 aluminum alloy billet and find out measures for stable and homogeneous billet heating. In the method, insertion of heat resistant, low thermal conductive austenitic stainless steel SUS304 discs between the copper electrodes and billet as thermal insulators was devised to improve the efficiency of the billet heating. In the original plan, using SUS304 stainless steel clad electrodes was planned, but the research was carried out in the mode of inserting the thermal insulators for easy operation of the experiments. In the resistance heating, it is necessary to apply a contact pressure between the electrodes and billet for ensuring their electric contacts. In the meanwhile, it is strongly desired to suppress the deformation of the billet as much as possible in the heating. It is possible to … More reduce the deformation by decreasing the applied contact pressure, but the excessive decrease causes sparking between the billet and thermal insulators and stops the forging operation. Then, first of all, the condition of the contact pressure on the spark occurrence was investigated in relation to the current density and it was made clear. And then, the thickness of the thermal insulators required for homogeneous billet heating was investigated in relations to both the current density and the contact pressure. Based on the findings through the investigations, experimental mushy-state forging of the aluminum alloy into a gear was made to investigate the influence on the forging condition of the operational conditions of the input electric energy and forging pressure. The results indicated that the mushy-state forging method is highly feasible but the metallurgical structure is strongly influenced by the thickness of the thermal insulators used. Therefore, proper adjustment of the thermal insulator thickness corresponding to each individual case is essential in the practical application. The findings obtained through this study were publicized as listed in the REFERENCES below. Less