Did we significantly alter the strength of this part?
Did we significantly alter the strength of this part?
(OP)
Part is a thin-walled (approx 1/8" avg) 4130 casting, finished machined and "heat treated" - to what extent, I do not know at this time - supplier is investigating - probably an "average" heat treat. The part after we received it was painted with a bake-on system that required it to be cycled as follows: 350 F 30 min, 30 min air cool, 500 F 30 min, air cool. It was re-painted again later and has gone through the same cycle again. So to total: 2 30 min 350 F cycles and 2 500 F 30 min cycles. Other much smaller steel parts of various types were also hanging in this oven and I observed varying color changes from dark blue to straw/gold on unpainted areas of these. The main larger part I am discussing here is totally coated flat black with the paint system and I cannot tell surface coloration on it. Question: did this temp cycling temper and toughen or anneal and weaken. There could be a safety issue here for the handler if the part is significantly weakened. I feel we are OK from reading other docs (such as pg 7 of http://www.carreramini.com/TensileTestNotes-II.pdf ). Would like to know general consensus. Any feedback will be greatly appreciated.





RE: Did we significantly alter the strength of this part?
We have thousands of 4140 parts that are tempered at 900F-1000F that have undergone thousands of temperature cycles of 70F to 600F to 70F to 900F and back again. The cycles times vary from hours to days and some even years with no problems.
RE: Did we significantly alter the strength of this part?
RE: Did we significantly alter the strength of this part?
RE: Did we significantly alter the strength of this part?
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Plymouth Tube
RE: Did we significantly alter the strength of this part?