Posted by: A N BALAJI
03/28/2003, 03:34:01
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We are facing severe problems in SS 420 heat treatment.The hardness after hardening and tempering results a very wide variations from 28 - 55 Rc. As per the standard the SS 420 can be tempered as follows:(1) temper between 300 - 375 c to get high hardness range 45 - 55 Rc(2) temper between 570 - 600 C to get low hardness range around 28 RcThe material shall not be tempered between 400 and 550 C because it will result in poor impact properties.Though we keep the tempering cycle as per the recommendations we many times get hardness in the range 30 to 40 Rc. Every time we find it difficult to take gaurd and do impact testing and accept based on impact results.The SS 420 material are checked by us for chemical properties and only those conform to standard requiremtns are taken for machining and heat treatment.Any way this problem can be solved.
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