Stress Relieving Weldment

[jpwazz]

After modifying my back blade I need to make a new bracket for the top link. I'm using
1/4" steel for the weldment and wondering if I should try to stress relieve it at all? If I use a torch to bring it to a "blue temperature" and let it cool, it should be ok, right?? JP.

 

[jenkinsph]

If you are welding mild steel and the tabs are only a few inches long I wouldn't bother. If I was welding long strips together it may be needed.


Steve

 

[kayco53]

Wouldn't worry about it on thin material like that.Just mild steel. On higher grades of steel
and thicker material it is done more often.

 

[oughtsix]

My welding teacher in highschool always told me to beat it with a hammer!

I have seen pneumatic shot peaning devices for stress relieving and I have also seen expensive sonic resonate frequency stress relievers that you attach to the piece while you are welding for 1in + material.

I just beat it with a hammer which I know for a fact relieves stress but I don't know if it actually helps the weld at all?

 

[SPYDERLK]

I use a needle scaler to peen the weld and adjacent metal.
larry

 

[gpflepsen]

Isn't the purpose of peening, hitting with a hammer, etc to induce stress- compressive stress, so the component is less likely to fail from fatigue? Compressive stresses do not facilitate cracking and thus failure.

I would think the important advice here would be not to quick quench and to not overheat.

 

[alltoys]

After modifying my back blade I need to make a new bracket for the top link. I'm using
1/4" steel for the weldment and wondering if I should try to stress relieve it at all? If I use a torch to bring it to a "blue temperature" and let it cool, it should be ok, right?? JP.

Ordinary steel to ordinary steel, NO stress relieving needed. Just line it up and have at it.

Only higher carbon steels involved in repeated hot cold operations like a boiler will have heat treatment.

 

[SPYDERLK]

Isn't the purpose of peening, hitting with a hammer, etc to induce stress- compressive stress, so the component is less likely to fail from fatigue? Compressive stresses do not facilitate cracking and thus failure.

I would think the important advice here would be not to quick quench and to not overheat.

That is good advice, and your thots on peening are true as well. That is why smacking the cooling/cooled surface with media having non discontinuity in shape is so valuable. Welding is pretty intense and by its nature causes extremely rapid expansion that [with the heat] plastically deform/crush adjacent metal. Due to this, on cooling, virtually the whole area is left in tensile stress. Cracks start and progagate from tensile stress combined with a discontiuity in the strength of the material. These latter occur at all external surfaces and at any void surfaces within the material. Peening transforms, to some depth, any surface you can reach from a tensily to compressively stressed area. It also smooths discontinuous [sharp or highly curved] surface features, effectively moderating stress risers. I would call it the most effective tool you have to instantly make a welded area more durable. Combined with a little grinding to smoothly radius transitions before peening and youve done all the easy stuff you can do. Valuable steps -- not difficult.
larry

 

[Lazy]

Using a hammer will only relieve stress in the person doing the welding, after they see how bad the weld looks.

 

[westcliffe01]

Sand/shot blasting can relieve surface stresses. If it was thicker / heavily loaded material it should be pre-heated, interpass temperature maintained while welding and post heat treated. All of these steps are designed to reduce stress build up, reduce risk of hydrogen enbrittlement (sank the liberty ships in WW2) and permit full load carrying capacity of the material.