Analysis on Crack Defects and Process Control of Valve Steel Casting
The reason that causes cracks of valve castings was analyzed,the measures to prevent and eliminate cracks was proposed.The following points were emphasized: the hollow structure of core can improve yieldability and reduce the shrinkage stress;the chemical composition should be controlled strictly,particular sulfur,phosphorus which can easily form low-melting eutectic;Adding RE can refine grains,purify liquid steel and enhance crack resistance;Using iron chill,increasing pouring temperature and weakening progressive solidification under the premise of ensuring good feeding,can realize casting regional simultaneous solidification,thus reduce the thermal stress.