CARBIDE SOLUTION TREATMENT ON ASTM A193 B8M

[rknjs]

Hi ,We have tried some solution annealing of 316 forged bolts to meet the requirements as per ASTM A193 B8M CL.1. Observed hardness before solution treatment was 38HRC .Parts has heated to 1050Deg for 1 hour and water cooled.Hardness has dropped to 125HBW after treatment. We will perform a tension test and corrosion test on these now.Now the concern is hardness has dropped and achieving a minimum tensile of 515MPa as per ASTM A193 B8M with this hardness seems to be very difficult.We expect to get a hardness above 150HBW . Is there anything we can do on the current solution treatment process to achieve this hardness- like changing time /temperature or an aging will work on this ?

Thanks

 

[metengr]

Why did you soak for 1 hour at 1050 deg C? Seems like you stayed at the solution treatment temperature too long.

 

[TVP]

Depending on the size and number of bolts, one hour at temperature is way too long, as metengr noted. The bolts just need to achieve the set temperature and then can be water quenched. Also, you are aware that the solution treatment applies to bar, wire, or the finished fastener, meaning you can just solution treat the bar or wire, and then form/machine + thread.

 

[rknjs]

Thanks for the comments@metenger -Total no of bolts were 900 and the size was 5/8" ,for that reason to achieve the temperature evenly for all the parts we hold for 1 hour.@TVP-if we perform solution treatment on bars and head forming after that normally the head portion will be in strained condition.Hardness on that area will be much more than what required as per standard..We will try with small batches for a soaking period of 15 minutes , 20 minutes and 30 minutes.