供机械性能试验用的灰铸铁试样毛坯,一般都附在铸件上从同一个浇口中浇注的。但是,由于铸造工艺的改进,有些铸造方法很难带浇试样。例如,柴油机的汽缸套是用金属型离心浇注法铸造的,这样就不可能再带上同样条件的试样毛坯。另外,用砂箱浇注的铸件,虽然可以带上条件相同的试样,但用比例法求出来的试样壁厚,往往与铸件的实际壁厚相差很大。例如,柴油机机身上的壁厚,薄的只有6毫米,厚的地方却有几十毫米,而随附的试样直径为30毫米。由于冷却条件的不同,这样的试样所得的试验结果很难说是具有代表性的。为了避免这种现象,几年来我们在一 Gray cast iron sample blanks for mechanical properties tests are typically cast on castings from the same gate. However, due to the improvement of the casting process, some casting methods are difficult to bring with the sample. For example, the cylinder liner of a diesel engine is cast using a metal centrifugal casting method, so that it is impossible to bring a sample blank of the same condition. In addition, castings cast with sand boxes, although the same conditions can be brought with the sample, but the sample wall thickness calculated using the proportion method, often with the actual wall thickness of castings vary widely. For example, the wall thickness of a diesel engine body is only 6mm thin and tens of millimeters thick where the sample diameter is 30mm. Due to the different cooling conditions, the test results obtained from such a sample are hardly representative. In order to avoid this phenomenon, we are in a few years