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锻钢制的轴类零件存在横向裂纹,往往会在使用过程中突然断裂;有时轴在热处理过程中,或作为备件在库存期间,也会突然象刀削一样整齐地断为两截,其原因部分是由于轴内隐伏着横向裂纹及内应力较大的缘故。横向裂纹对安全生产将会带来严重危害,是钢中不容许存在的缺陷,因此在检验产品质量时,必须严格剔除。采用超声波探伤法能把轴内隐伏着的横向裂纹可靠地检验出来,有助于提高产品质量和改进热加工工艺。一、横向裂纹存在的形式横向裂纹是一种钢中的内裂纹。在超声波探伤中,这种横向裂纹是一种比较常见的宏观缺陷。在轴内,横向裂纹的延伸方向与轴的中心线相垂直,这种缺陷在轴内存在的几何形状多为片状(图1),也有呈腔穴状(图2)。横向裂纹常单独存在,有时在一根轴内同时存在两个以上的横向裂纹,多见于台阶轴的棱台拐角处。
Forged steel shaft parts horizontal cracks, often in the process of sudden rupture; sometimes shaft heat treatment process, or as spare parts in the inventory, it will suddenly cut like a knife neatly cut into two parts, the reason Partly due to the hidden horizontal cracks in the shaft and the larger internal stress. Horizontal cracks on the safety of production will bring serious harm, is not allowed to exist in the steel defects, therefore, in the inspection of product quality, must be strictly excluded. The use of ultrasonic flaw detection method can reliably detect transverse cracks hidden in the shaft, helping to improve product quality and improve thermal processing technology. First, the existence of horizontal cracks in the form of transverse cracks is a kind of steel in the crack. In ultrasonic flaw detection, this transverse crack is a more common macroscopic defect. In the shaft, the transverse crack extends perpendicular to the centerline of the shaft. Most of the defects present in the shaft are flaky (Figure 1) and cavities (Figure 2). Horizontal cracks often exist alone, and sometimes more than two transverse cracks exist in one axis at a time, more common in the step axis of the edge of the pyramid.