生产实践证明,对于湿型铸铁件,由于砂型的导热性好而刚度差、铁水降温快而收缩量较为集中,因而如不加强液态补缩就容易产生收缩缺陷。若片面加大冒口尺寸,以图强化补缩,往往不是效果不佳,就是适得其反。实际上,产生铸件收缩缺陷的因素很多。就冒口而言,不仅取决于冒口尺寸恰当与否,还与冒口的选择和安放位置有很大的关系。后者往往易于被人忽视。由于铸造生产的复杂性,许多工艺条件不能趋于稳定状态, Production practice shows that, for wet cast iron parts, due to the good thermal conductivity of sand and poor rigidity, rapid cooling of molten iron and shrinkage is more concentrated, so if not strengthen the liquid shrinkage is prone to shrinkage defects. If one-sided increase riser size, in order to strengthen the shrink, often not ineffective, is counterproductive. In fact, casting shrinkage defects caused by many factors. In terms of riser, not only depends on the size of riser properly or not, but also with the choice of riser and placement has a great relationship. The latter tend to be easily overlooked. Due to the complexity of casting production, many process conditions can not be stabilized,