退火是将金属在其临界温度范围缓慢冷却而使铸铁软化的一种热处理工艺。在该过程中,基体的碳含量或结合的碳由于缓慢慢冷却可减至为零,以至仅有铁素体和石墨保留在显微组织中。各种形式的退火提供了达到最大软度和最好机加工性能或保持一定强度的部分软化作用的控制方法。下面概述各种退火处理获得的结果和每种退火处理的程序及应用情况。高温退火铸件加热到临界温度范围以上,即1650～1750°F,会引起一次碳化物或显微组织中游离 Annealing is a heat treatment process that softens cast iron by slowly cooling the metal over its critical temperature range. During this process, the carbon content of the matrix or bound carbon can be reduced to zero due to slow slow cooling, so that only ferrite and graphite remain in the microstructure. Various forms of annealing provide a control of partial softening to achieve maximum softness and best machinability or to maintain a certain strength. The following is a summary of the results obtained for various annealing treatments and the procedures and applications for each annealing treatment. High-temperature annealed castings heated above the critical temperature range, 1650 to 1750 ° F, can cause a carbides or microstructural dissociation