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Welding Chinese Steel to Australian Steel

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Newtheory

Newtheory

Mechanical
Sep 30, 2011
1
Hi

We need to weld thick mild steel plates from china and with Australian thin ones using australian filler material.
The Chinese Steel Q235B has a different composition and contains C0. 12 ~ 0.20% Mn 0.30 ~ 0.670 Si = 0.30 S = 0.045 P = 0.045. I have attached the page from the Australian standard AS3678 for grade 250 plate showing its composition and differences.


It will be a fillet weld 6 to 10 throat thickness. No fatigue involved and maximum stress would be 40 Mpa.

Does anybody think this might cause a problem and what kind of test can be done to make sure all is OK , NDT for example?
Do we need to change our welding procedures?

Thanks for your help
 
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The slightly higher sulfur content permitted in the Chinese steel may give some problems with welding if you are running a fast welding process, otherwise the two steels appear fairly equivalent. Keep in mind that while the standard permits certain upper bounds of each element it is unlikely that all of the elements are at their top ranges. The 0.45% sulfur is not inconsistent with many of the ASTM standards.
 
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Too much sulphur in steel causes 'cold' shortness, I believe.

Dik
 
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Just because ASTM standards permit up to 0.05% S does not make that a good idea (if you plan to weld at least). Their philosphy appears to me to be not to cut out too many manufacturers or older technologies.

The Mn:S ratio is extremely low. Personally I would not touch this stuff with a 10 foot welding rod, although I'm sure your purchasing agent is promoting it so he can show cost savings. Just remember that repair and rework costs always trump material cost savings, by as much as an order of magnitude. That does not cover what it does to your shop scheduling and your own unpaid overtime processing NCRs.
 
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I agree with Brimstoner. The S and P are too high and Mn: S ratio too low and this will affect weld toughness. I would recommend performing a OES (not PMI!)and evaluate the composition. The material is a permitted range and not an actual product analysis. I would not trust the analysis provided by the manufacturer as Chinese steel certification is usually suspect. Do your own testing. Irrespective of its source of manufacturer, I would reject any steel containing more than 0.030 S and 0.03 P if welding is involved.

 
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Agree that you should base your decision on your own analysis, and predict that the numbers will be worse than those certified.
 
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The S & P are maximum allowables and not atypical of the maximum for same elements on A-283. They are not indicative of resulfurized steels where hot shortness would occur. A 7:1 Mn to S ratio is required to effectively tie up S as complex manganese-ferrosulphide inclusions. At the worst case the Mn:S ratio could be less than 7:1. What are the actual values?

Suggest welding with E7018 electrodes.

 
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