Help: ZG27-5 quenching and tempering of cast steel

the so-called grade steel generally refers to the steel whose mechanical properties and chemical composition meet the standards of American Railway Association () and grade steel. Since 2, all couplers of freight trains approved in the United States have adopted grade steel. In order to meet the demand of high-speed and heavy-load railway transportation, grade steel is gradually replacing the traditional ordinary carbon cast steel and becoming the leading material of railway freight car couplers in China. A high-strength, fine-grained medium-and low-carbon alloy steel involved in American patent consists of cast steel with the following components: , , , , , and impurities as the balance. Proper quenching and tempering temperatures can improve the strength and plasticity of the steel.