Effect of Multiple heat treatment on CA15 / 410SS
Effect of Multiple heat treatment on CA15 / 410SS
(OP)
I am having difficulty hardening a CA15 casting. The chemistry is within the ASTM spec including the trace elements. The heat treatment I have been running has worked on different lots with similar composition. 1850F - 3h Fan cool usually results in close to 400BHN hardness. On this lot the hardness the first time around was 280BHN, after running the same cycle it dropped to 250 BHN and after running the same cycle third time it dropped down to 200BHN.
I am trying to understand the reason for the hardness to drop after consecutive normalize cycles.
Also is there any way I can regain the 400BHN hardness on this casting?
Please comment.
Thank you
Mahadhatu
I am trying to understand the reason for the hardness to drop after consecutive normalize cycles.
Also is there any way I can regain the 400BHN hardness on this casting?
Please comment.
Thank you
Mahadhatu





RE: Effect of Multiple heat treatment on CA15 / 410SS
Have you attempted oil quenching. perhaps this will be a better option for you to get 400 BHN uniformly and conaistently in your castings.
RE: Effect of Multiple heat treatment on CA15 / 410SS
Are you using a portable (Equotip) teseter to check the hardness? Based on the hardness results that you got, it appears to me that the cooling was not fast enough to get 400 HBW. Have you looked at the microstructure?
Rao Yallapragada
RE: Effect of Multiple heat treatment on CA15 / 410SS
Oil quenching is an option but I would consider it as a last resort.
What I am trying to understand is the reason for the decrease in hardness after multiple normalizing cycles.
Thank you
RE: Effect of Multiple heat treatment on CA15 / 410SS
The chemistry was measured using a SpectroMAX Spectrometer when the I poured the heat. The hardness was measured using a KING Brinnel hardness tester.
I have not yet looked at the microstructure.
Thank you for your input.
RE: Effect of Multiple heat treatment on CA15 / 410SS
RE: Effect of Multiple heat treatment on CA15 / 410SS
I use a protective coating on 410/CA15 and other scale prone alloys. This coating completely eliminates any scaling and peels off after the austenitizing cycle. It is benificial in maintaing wall thicknesses after heat treatment.
Today, I am going to try increasing the austenitizing temperature to 1025C as u suggested and oil quench to see if I can prevent any retained austenite or ferrite.
Thank you for your suggestions and comments. I will post my findings.
RE: Effect of Multiple heat treatment on CA15 / 410SS
RE: Effect of Multiple heat treatment on CA15 / 410SS
Perhaps this might be a rather simple question, but did you check your thermocouples on the gas fired furnace or did you verify the actual austenitizing temperature of the batch before removing from the furnace?
RE: Effect of Multiple heat treatment on CA15 / 410SS
Thanks for the valuable tip. I ground a spot on the castings about 1/8" deep on from the surface and checked the harndess and wallah !! The hardness was 350BHN consistant on all the castings. Multiple austenitizing heat treatments had de carburized the surface to almost 1/8" deep. I am glad we had enough machining stock on all surfaces. That saved a valuable recast and a lot of time!!!!
I appreciate the input from all the Gurus out here. It sure helps when we look at the problem from 10 different point of views as opposed to one.
--------------------------------------
There is always some thing better out there...
Mahadhatu