Welding Issue?
Welding Issue?
(OP)
Hi All,
Recently, two rectangle hollow bar which was welded together was detached from each other after years of operation. Kindly see attached.
I would like to seek professional advise here on what could be the possible reasons for such failure?
It seem to me this was probably due to poor welding (the welded area seem to be lifted off from the base material) and hence, it could not take the operation load.
On the side note, the shiny portion seem to be brittle failure and the left side suffered quite a bit of deformation.
Kindly advise.
Thanks,
JHWC
Recently, two rectangle hollow bar which was welded together was detached from each other after years of operation. Kindly see attached.
I would like to seek professional advise here on what could be the possible reasons for such failure?
It seem to me this was probably due to poor welding (the welded area seem to be lifted off from the base material) and hence, it could not take the operation load.
On the side note, the shiny portion seem to be brittle failure and the left side suffered quite a bit of deformation.
Kindly advise.
Thanks,
JHWC





RE: Welding Issue?
RE: Welding Issue?
Just curious, usually under sem or high resolution microscopy, what are the things to look up for if there is underbead cracking?
Thanks.
RE: Welding Issue?
RE: Welding Issue?
RE: Welding Issue?
RE: Welding Issue?
"Recently, ............after years of operation."
So, despite the poor welding, a pretty long service life was attained?
Could you PLEASE provide information on the rest of the structure, environment, and expected loading?
Even Higher quality welding is not going to compensate for the basic limitations of that style joint if loading is significant.
A welded square tube light pole fails like this in a windy environment -
https://www.hobartwelders.com/weldtalk/attachment....
The crack initiation points are the corners. Higher nominal stress, plus the concentrated stress at the toe of the welds make it so.
The welds in the middle of the flat faces are on vacation until the very end, when cracks have slowly propagated well in from the corners, and they are all that is left.
Sometimes triangular gussets are proudly added to the middle of the tube faces to "beef up" the joint.
The late, great Omer Blodgett explains why that is not a real good idea.
http://weldingdesign.com/processes/using-gussets-a...
2 down, 18 to go.
RE: Welding Issue?
Dik
RE: Welding Issue?
Let me provide you with more information:
(a) It acts as a support bracket for a bar which weighs around 100 kg.
(b) There will be 2 support brackets to support the bar.
(c) The maximum distance apart between 2 bracket is 5m (max)
(d) The whole system is out in the open environment
(e) The bracket is made of mild steel, with tensile strength around 280 MPa.
I suspect why it can last so long is probably due to the compressive forces acting against the crack propagation.
Could you please further elaborate what do you mean by
- The crack initation are the corners - which corner specifically? the left or right?
- What do you mean by the toe of the weld?
RE: Welding Issue?
Could you explain little further on "inside angle of the connection?"
Thanks.
RE: Welding Issue?
Need to add on the bracket.
1. The supporting bracket is made of mild steel, welded at 49 degree
2. The supporting bracket is coated with galvanising zinc (hot-dipped)
3. The supporting bracket is able to hold at least 100 kg in weight.
Thanks.
RE: Welding Issue?
RE: Welding Issue?
How about those darker in colour?
I attached one file here for better viewing.
RE: Welding Issue?
RE: Welding Issue?
Last question, do you reckon any discolouration from the surface since it is dipcoat with galvanising zinc.
Thanks.
RE: Welding Issue?
RE: Welding Issue?