1982年1月20日哈尔滨机务段前进型238号机车发生切轴事故。事故发生前,该段曾多次进行超声波探伤,发现轴上裂纹的深度一直在2.5毫米左右。到事故发生前50天进行的第十次探伤时,裂纹深度测定为2.8毫米。而切轴后检查旧痕竟达80％。为了解产生这一差异的原因,对路内广泛采用的煤水车轴镶入部超声波探伤的方法,作了一些试验,以期深入探讨。一、用小角度探头探内侧裂纹的问题我厂从六十年代后期开始,试验用小角 January 20, 1982 Harbin locomotive forward section 238 locomotive accident occurred. Before the accident, the section had repeatedly conducted ultrasonic flaw detection and found that the depth of the crack on the shaft has been about 2.5 mm. At the tenth flaw detection 50 days prior to the accident, the depth of crack was measured at 2.8 mm. The cut after the inspection of the old mark as much as 80%. In order to understand the reason of the difference, some experiments were carried out on the ultrasonic flaw detection method of the shaft of coal water shaft widely used in the road, in order to probe deeply. First, with a small angle probe to detect the problem of the inner crack I plant from the late sixties, the test with a small angle