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熔核的一次结晶是点缝焊接头形成过程中的重要环节之一.熔核一次结晶的组织形态主要受其合金本身的因素(K、m、C_0、D)和工艺因素(G、R)的影响,并且对其接头的机械性能有着很大的影响。本文通过对中碳钢板点缝焊接头形成进行金相观察及其分析、研究,认为中碳钢板点缝焊熔核一次结晶的组织形态为“四周的树枝晶和心部的等轴晶”,并用“成分过冷”的理论初步进行了解释,提出了促进等轴晶发展的途径.同时,还对中碳钢板点缝焊接头进行了大量的拉剪试验,从规范的角度论述了保证接头质量的关键问题是:焊接过程中的热平衡问题。
The primary crystallization of the nugget is one of the most important steps in the formation of the point welded joint.The morphology of the primary crystallization of the nugget is mainly affected by the factors (K, m, C_0, D) and the technological factors (G, R) The impact, and the mechanical properties of its joints have a great impact. In this paper, through the metallographic observation of the formation of spot welded joints of medium carbon steel and its analysis and study, it is considered that the primary morphology of midrib weld nugget of medium carbon steel is “the surrounding dendrites and equiaxed grains of the heart” And the theory of “overcooling” was initially explained, and the way to promote the development of equiaxed grains was put forward.At the same time, a large amount of tensile shear tests were carried out on the spot welded joints of medium carbon steel plates, The key question of quality is: Heat balance problem during welding.