40Cr precision steel quenching, precision steel plant in Shandong http: //www.sdlggg.com precision steel
Cr to increase steel hardenability, improve the strength and stability of steel tempering, with excellent mechanical properties. Large cross-sectional dimension or significant quenching of the workpiece, Cr steel should be used. But there is a second class Cr steel temper brittleness .
40Cr quenching and tempering of quenched and tempered precision steel workpiece; various parameters have predetermined process card; we understand in practice are:
(A) 40Cr workpiece after quenching should use oil cooling, 40Cr steel hardenability better cooling can be hardened in oil, and deformation of the workpiece, cracking tendency of small, but small businesses in the oil supply under stressful circumstances, the shape is not complicated workpieces can be quenched in water, they found no cracking, but the operator must strictly control their experience into the water, the water temperature.
(B) after the workpiece precision steel 40Cr quenched hardness is still high, the second tempering temperature will increase 20 ~ 50 ℃, otherwise, hardness decreased difficult.
(C) 40Cr precision steel workpiece after tempering, complex shape in oil cooling, simply cooled in water in order to avoid the impact of the second temper brittleness. Workpiece rapid cooling after tempering, if necessary, Zaishi to eliminate the stress treatment.
Effect of quenching the workpiece quality; the operator level is an important factor; at the same time; and equipment; materials and many other reasons before quenching processing; we think:
(A) of the workpiece is transferred from the furnace to a cooling tank slowly, the workpiece into the water temperature has dropped below the critical point Ar3, resulting partially decomposed, the workpiece is not completely get hardened structure, reach hardness. So small parts coolant to pay attention to speed, large parts to the cold time to master.
(B) of the workpiece installed furnace capacity to be reasonable, appropriate level of 1 to 2, resulting in uneven heating of the workpiece overlap, resulting in uneven hardness.
(C) of the workpiece into the water arrangement should maintain a certain distance, too dense vapor membrane rupture near the workpiece is blocked, causing the workpiece near the lower surface hardness.
(D) quenching furnace, quenching can not breath finish, depending on the oven temperature should be the extent of decline, halfway closed furnace re-warming, for consistent hardness after quenching the workpiece.
(V) to pay attention to the temperature of the cooling liquid, 10% higher than the brine temperature such as 60 ℃, it can not be used. Coolant can not have oil, mud and other impurities, otherwise, there will be insufficient hardness or uniformity.
(Vi) unprocessed rough quenched hardness is not uniform, if you want to get good quality quenched and tempered, rough should roughing, rods to forged.
(Vii) strict quality control, low hardness after quenching from 1 to 3 units, tempering temperature can be adjusted to achieve the hardness, but low hardness after quenching the workpiece, some even only HRC25 ~ 35, must weight
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