曲轴是柴油机重要部件之一。除要求机械性能、金相结构等合格外,还必须保证曲轴内部的缺陷不超过技术规范,以确保柴油机运转的绝对安全。我厂要求探伤的207E 型球墨铸铁曲轴有两种:一种是十缸2000匹马力的,外形如图1所示,长4280毫米,净重1.3吨;另一种是六缸1000匹马力的,外形如图2所示,长2642毫米,净重0.9吨。由于曲轴形状复杂,各处厚度相差也很大,因而在浇注过程中,铁水冷却速度就不一样。在壁厚变化比较大的地方,容易产生缩孔和疏松之类的缺陷。几年来,在探伤工作中所发现的缺陷,大都出现在 Crankshaft is one of the important parts of diesel engine. In addition to requiring mechanical properties, metallurgical structure and other qualified, but also must ensure that the internal defects of the crankshaft does not exceed the technical specifications to ensure the absolute safety of diesel engine operation. Our factory requires testing of 207E ductile iron crankshaft in two ways: one is the ten-cylinder 2000 horsepower, the shape shown in Figure 1, 4280 mm long, net weight of 1.3 tons; the other is a six-cylinder 1000 horsepower, Shape shown in Figure 2, length 2642 mm, net weight of 0.9 tons. Due to the complex shape of the crankshaft, the thickness of the difference between the various parts is also very large, so in the pouring process, molten iron cooling rate is not the same. Changes in the wall thickness is relatively large, prone to shrinkage and loose defects. In recent years, flaws discovered during the inspection work have mostly appeared