A694 Material Quenching process

[Forrest79]

Dear heat treatment Specialist,

I have a question about the quenching process of the A694 series material.
1. we have experience that for these kind of material, better quenching as soon as posible after moving from furnace to quenching pool.
2. one of our engineer did a test, when move the forgings from the furnace, he let the forgings cool in air first to about 750 degree C, then put into water untile the end. when doing test piece, everything is good, but when batch production, result not good. but this method is theoretically resonable.

any comments about it?

 

[redpicker]

This practice is not recommended because, as you have discovered, it will not produce consistent results. The reason is the cooling rate is important. With the test piece, your engineer probably had a fairly good cooling rate to the 750C but, with the production load, the cooling rate to 750 was probably slow. In production, 750 is too low to begin quenching.

rp