Improve quench medium raises ferrule of GCrl5 steeliness bearing to quench quali
From;    Author:Stand originally
My company is at the beginning of 90 time will azotic radical can accuse furnace of atmosphere casting catenary automatic product line applies at temper by dipping in water of ferrule of GCr15 steeliness bearing, temper. Quench medium basically uses N32 mechanical oil. As the accretion of ferrule dimension, appear sometimes quench hardness all is not mixed badly the problem such as distortion, use today after additive of fast quenching oil of Y15T of the reputed founder of the Ix Dynasty undertakes to N32 mechanical oil modified is handled, solved ferrule hardness not all, controlled distortion effectively.

Product line of furnace of catenary of my company casting from 1993 put into production comes at the beginning of 1999 already accumulative total quenchs workpiece 7000 more than T, product quality stabilizes control to be in limits of standard of JB / T1255-1991, quench medium is given priority to with N32 mechanical oil, winter also complements partly N15 machinery is oily, outside controlling moisture content strictly to quenching medium is divided, did not adopt other detect method, will also did not give manage to quench for years quality problem. At the beginning of 1999, because of old oily ageing, brightness of the surface after workpiece quenchs drops, the lampblack when production is bigger, quench casting catenary furnace oil groove rectifies groove to change then with new N32 machinery oil, discover ferrule of large wall large size namely before long ever since (external diameter > 100mm, effective wall is large > after 10mm) quenchs ferrule of easy occurrence part (occupy hardness of surface of 5%-20%) thick end panel about inhomogenous, local hardness is unqualified, appear 6 class (JB / T1255-1991 the 2nd level pursues) above quenchs organization. If graph 1a place is shown, the hardness profile that if graph 1b place is shown,individual ferrule appears.

Organization of metallographic of area of qualification of the hardness in the graph is 2 class, the quantity suits rudimental carbide, but grain is thicker; Hardness rejection area basically is 6 class, 8 class, see occasionally > 8 class, troostite appearance is lump, chunk shape, lump troostite is mid and visible rudimental carbide grain.

1 quality problem is analysed

Uniformity of 1.1 primitive organizations is poorer it is generation quenchs one of reasons of unqualified organization

According to checking, during afore-mentioned problems appear, the ball changes annealing temperature to exceed 820 ℃ , anneal organization grade is 4 class (JB / T1255-1991) of figure of the first level, although belong to qualification, but because partial carbide grain is thicker and distributing not all, cause it is difficult to quench craft is adjusted. Undertook corrective instantly for working procedure of this pair of anneal, but the anneal base of the production before this already hard do poorly done work over again.

1.2 quench temperature whether on the low side
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