用于厚大ADI铸件的分级淬火工艺

Step Iso-Thermal Quenching Process Used to Obtain Heavy Section ADI Casting

为消除厚大球铁件等温淬火时出现的珠光体组织,试验了'预淬火+等温淬火'的分级淬火工艺,预淬火冷却介质为过饱和硝酸盐水溶液.预淬火时间为28 s,使厚壁部位在650～500℃高温区加速冷却.试验结果表明:工件的基体金相组织为针状铁素体+高碳块状奥氏体,力学性能达到了技术要求.

In order to eliminate the pearlite appearing in iso-thermally quenched heavy section ductile iron castings, a step quenching process consisting of previous quenching+iso-thermal quenching was tried. The supersaturated aqueous solution of nitrate salt was taken as the cooling medium for the pre-quenching, and the pre-quenching time was of 28 s to accelerate the cooling of the heavy section in the high temperature range of 650~500 ℃. The test result showed that the matrix structure of the casting was consisted of acicular ferrite+ blocky- shaped high carbon austenite, and its mechanical properties met the technical requirements.