Cracked mitre joint.

[Mick B]

This will be the 1st of many questions I will have for you all.
I made some handles out of 20mm x 1.8mm RHS and mitred the corners. I clamped it down on the bench and welded one side and within a minute I turned it over and did the other side before I welded the external and internal corners. When I finished smoothing the joint off with a flap disc in the angle grinder I noticed a very fine hairline crack so had to run another bead.

It's just a thought, but could this crack have happened because I didn't let it cool down enough before I smoothed it off ?

 

[oilcooled :)]

Id say you ground all you weld away with the grinder not really a crack more of a fusion issue. Common enough on outside corners.

 

[Mick B]

I guess you are right oilcooled even though the crack was on the face and not on the outside corner.
Is it OK to start grinding as soon as you have finished the weld, or should you really wait until it cools ? Patience is not one of my virtues !

Mick.

 

[Welderpaul]

It is rare for mild steel to crack, as others have said it is likely the weld has just been sat on the surface and you have ground it away.

The weld doesn't need to be cold before grinding.

 

[Mick B]

Thanks Welderpaul. Gee is that a picture of you !

 

[Welderpaul]

Yep, that's me.

Welcome to the forum.

 

[TechnicAl]

A crack will be a meandering line..........lack of fusion will be a very straight line..............usually

In 40 odd years I have been called out to see hundreds of cracks that were LOFs...........people dont like to be told "its not cracked you've never welded it"