By expand principle of graphitization and using inner riser,the expund of ballizer is carried out in the model and cast of fine and close intexture form.

• 根据球墨铸铁球化时石墨化膨胀原理,利用暗冒口使球化膨胀只能在型内膨胀,从而形成组织致密的铸件;