Peening for stress relief

Date 04-16-2001 10:03

Peening is used to help a weld joint stretch as it cools by relieving internal stresses. Peen lightly with the round end of a ball peen hammer. Too much hammering will add stresses to the weld or cause the weld to work-harden and become brittle.

By Dirk

Date 04-18-2001 03:09

Why are you stress relieving??

Service conditions ?? distortion???

Peening is a "grass root " approach and not without risk as previously advised

Dirk

By pipewelder_1999 (****)

Date 04-20-2001 06:20

Peening does not relieve stress. It redistributes it and changes some from tensile to compressive and the direction. The peening process is not done lightly with a ball peen. Some dents need to be made on the surface of the weld.

When I make a weld the weld metal solidifies and during cooling it contracts in all directions. If the joint is restrained then the stress in the weld goes up. If the joint is unrestrained the stress reduces but the distortion goes up. After the bead is made the joint stress is usually tension and peening the weld causes the weld metal to expand in one direction (The one in tension) and to compress (The peening direction). The subsequent passes will soften some of the work hardened metal.

As with all welding processes, any subsequent processing that could affect the final structure should be closely looked at and tested by competent people.

Good Day
G. Austin

http://www.geocities.com/pipewelder_1999/

By Ted.Chungli (*)

Date 04-20-2001 20:10

Thanks for all the replies, specially the pipewelder.
My metal subject to peening is "Hadfield" including 1.2%C and 14%Mn.
In AWS welding handbook Vol.4 has been indicated that "Peening" will decrease residual stresses in weld metal and cause of being useful "Peening" method for sensitives metal to crack this is recommended.But I am not sure to use this method for Hadfield steel, in addition I dont know how much hammering is enough?
Thanks again
Ted.Chungli

By - Date 04-22-2001 19:13

At the best of times peening is less than satisfactory, because there is so little control that one has over the process. (Possibly if one peens with steel shot, a small degree of repeatability can be assured.) Often, peening produces more problems than solutions.

Also, I think that with Hadfield manganese steel, you will be working against yourself, because of the extrememy high work hardening rate of this steel. These steels are generally used where abrasion impact conditions are present. In the as-welded condition the deposits are not very hard, but as it experiences impacts it tends to harden substantially. If you therefore want to reduce stresses in your Hadfield weld, you should not expose it to any cold deformation. (e.g. Peening)

Why do you want to reduce the weld stresses in any case? You may have other problems that are not related to weld residual stresses! (This we could obviously not know.)

Regards
Niekie