鉄筋コンクリート用棒鋼のテルミット溶接に関する研究(第1報)

Abstract

For field welding of reinforcing bars, requirements for a process are as follows :1) The operation requires no great skill ; inexperienced men can be trained easily and quickly to do the work.2) No heavy, expensive equipment of any kind is needed.3) All weld joint have tensile strength equal to the ultimate strength of the bar. However, the welding methods in common use have not always fulfiled the above requirements. Judging from the above fact, author has developed a new process of self-preheating thermit welding.This process provides a high speed means for producing sound welds of uniform high quality with less expense.In the first report, author has investigated the thermit mixtures used for this process in regard to workability of them and mechanical properties of weld.The results are of follows ;1) Effective factor to thermit reaction is the homogeneity of mixtures. The homogeneity of mixtures depends upon the constitution of particle size and accordingly the void ratio. The best result is obtained in about 50 percent void ratio. Moreover, the smaller the difference in particle size, the more smoothly thermit reaction goes.2) The ratio of iron oxide/aluminum plays the most important role on soundness of steel. Al-content giving the best ratio is higher by 2 percent than stoichiometric quantity. But Al-content should be decreased according to their deoxidizing power when other deoxidizers coexist in thermit mixture.3) The effect of alloying elemeat on mechanical properties of thermit steel is evident.From the results, author has established a new idea for carbon equivalent applicable to thermit steel.On the baisis of this idea, we shall obtain a thermit mixture with a desirable property.