We reheat and then soak a specilty steel for 3 hr at a temperature about 100C below austenitizing temperature, and then quench in a water spray tub. It is coil strip with a thickness of .1''.
The material is breaking during re-coiling at the take up reel. SEM anaysis of fracture surface showed coarse cleavage facets that appeared to occur during an intergranular fracture. LOM image showed the presence of blown grains and cleavage cracks. The blown grains were as large as ASTM 1 but only at or near failure cracks. I attached a picture for your review.
It seems clear the cause of failure is related to large grain surface structure. But my questions are 1. what caused the coarse grains at the very surfaces? 2. could re-quench bring back fine grains (need samller than astm 6).
Any inputs, no matter if or not making common sense, are appreciated!
The material is breaking during re-coiling at the take up reel. SEM anaysis of fracture surface showed coarse cleavage facets that appeared to occur during an intergranular fracture. LOM image showed the presence of blown grains and cleavage cracks. The blown grains were as large as ASTM 1 but only at or near failure cracks. I attached a picture for your review.
It seems clear the cause of failure is related to large grain surface structure. But my questions are 1. what caused the coarse grains at the very surfaces? 2. could re-quench bring back fine grains (need samller than astm 6).
Any inputs, no matter if or not making common sense, are appreciated!
