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一般认为,磷是加剧铸件热裂倾向(特别是对铸钢件和球铁件)的有害元素,因此生产中要尽量降低铸铁的含磷量。我厂生产的ZQ500减速机壳体(HT20—40)易出现裂纹。裂纹表面呈氧化色,成簇出现,曲折而不规则,导致铸件废品率高达70～80％。为解决热裂问题,采取了各种措施:如浇注工艺和造型工艺的改进,开箱时间以及碳、硫、锰含量的控制等,但都没有彻底解决问题。最后通过加入磷铁,使铸铁含磷量由原来的0.05～0.07％增加到0.10～0.15％,才消除了热裂。该铸件经常产生热裂的部位如图1所示。
It is generally believed that phosphorus is a harmful element that aggravates the tendency of hot cracking of castings, especially cast steel and ductile iron pieces. Therefore, it is necessary to minimize the phosphorus content of cast iron in production. I plant the ZQ500 reducer housing (HT20-40) prone to cracks. Crack surface was oxidized, clusters appear, tortuous and irregular, resulting in casting scrap rate as high as 70 to 80%. In order to solve the problem of hot cracking, various measures have been taken: such as the improvement of pouring process and molding process, opening time and the control of carbon, sulfur and manganese contents, etc., all of which have not completely solved the problem. Finally by adding phosphorus iron, phosphorus content of cast iron from the original 0.05 to 0.07% increased to 0.10 to 0.15%, to eliminate the thermal cracking. The casting often produce hot cracking site shown in Figure 1.