我厂在生产中有一批45钢的套(见图),经淬火后内孔涨大或椭圆,使得磨量不够甚至没有磨量了。我们将此零件在860～870℃(也可稍低一些)加热7～10分钟,然后在油中冷却,反复二、三次可使内孔磨量达0.26～0.65毫米。反复加热冷却的次数由所需磨量来定,效果比较满意。最后热处理工艺为:盐浴炉中加热800～810℃,6～8分钟,在30～50℃的硝盐水溶液(硝酸钠25％,亚硝酸钠20％,硝酸钾20％,水35％, I plant in the production of a group of 45 sets of steel (see photo), the hole after quenching rose or oval, making the amount of grinding is not enough or not the amount of grinding. We will heat the parts at 860 ~ 870 ℃ (also slightly lower) for 7 ~ 10 minutes, and then cooled in oil. The inner hole can be milled 0.26 ~ 0.65 mm after repeated two or three times. The number of repeated heating and cooling by the required amount of wear to be set, the effect is more satisfactory. The final heat treatment process is: salt bath furnace heating 800 ~ 810 ℃, 6 ~ 8 minutes, 30 ~ 50 ℃ in the nitrate solution (sodium nitrate 25%, sodium nitrite 20%, potassium nitrate 20%, water 35%