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本文利用扫描电镜对65Mn弹簧钢带多点脉冲焊的优质接头和缺陷接头(未加热处理脉冲时)的断口形貌进行了较为系统的观察和研究。揭示了该熔核的一次结晶组织——粗大柱状晶(作者命名)是由更精细的柱状晶所构成,它们的位向基本一致,相互紧密结成一束,外面襄以液膜。每条柱状晶又由脆状树技晶和树枝状晶两种亚晶形态所组成。用浓度过冷结晶理论初步论述了柱状晶中的平面晶和脆晶形态在本文中不能得到的理由。本文还给出了65Mn钢点焊优质接头横断面熔核一次结晶断口的形貌特征。
In this paper, scanning electron microscopy (SEM) was used to systematically observe and study the fracture morphology of high-quality joints and defective joints of 65Mn spring steel multi-point pulse welding (without heat treatment pulse). Reveals that the primary crystal structure of the nugget, the coarse columnar crystals (named by the authors), is composed of finer columnar crystals. Their orientation is basically the same, forming a bundle with each other closely, and the outer surface is covered with a liquid film. Each columnar crystal again by brittle tree technology and dendrite crystal two sub-crystalline form. The theory of concentration supercooling crystallization was used to discuss the reasons why the plane and brittle crystal morphology in columnar crystals can not be obtained in this paper. This article also gives the topography of the primary crystallization fracture of the cross-section nugget of 65Mn steel spot welded joint.