AISI 4130 Pipe Welding Issue 5

[sw23cyp]

We are experiencing differences in the weldability and weld quality between two different sizes of 4130 pipe. The welding procedure requires a 400F preheat with 650F max interpass temp. The root is E6010 with E10018-D2 H4R for fill and cap. Welds made in the NPS 2 pipe were as expected but NPS 4 were not. The welder complained of the E10018 being "watery" and having trouble with tie ins. The same welder and electrodes were used for both. MTRs for the pipes are attached. Why would there be such a difference in welding?

 

[metengr]

This is probably a technique issue versus material based on the information you provided.

 

[racookpe1978]

Try two other pipes: 2x 2 inch diameter - from a different "box" or crib or melt. Look at the numbers on the pipe. and 2x more 4 inch pipes. Use a different welder on two of the pair.

 

[sw23cyp]

Thank you metengr & racookepe1978 for your help with this. We will get some pipe from a different melt and fab more samples. Short of getting a chemical analysis, is there a way to tell if the NPS 4 was stenciled incorrectly and not actually 4130? The reason I ask, this morning while inspecting welds and checking numbers, I noticed the bevels on the drop from the NPS 4 were not clean relative to other 4130 pipe on the rack. When I asked the welder what had happened. He said he felt like he was trying to cut stainless steel pipe.

 

[Lyrl]

You can check for magnetism. All non-stainless steels and some stainless steels are magnetic. If a magnet won't stick, that's a sure indication it is stainless.

If the pipe is magnetic, then you'd need to do a chem analysis to determine for sure what it is.

 

[sw23cyp]

Thank you for your help, Lyrl.

 

[metengr]

Based on current information above I would now run a check on chemistry for the NPS 4 pipe.It is cheap insurance to verify material.

 

[sw23cyp]

Thank you all for your help. A sample has been sent for analysis and mechanical testing.

 

[sw23cyp]

The analysis confirmed that the XXH, NPS 4 pipe is 4130. Samples for a procedure qualification were welded and sent for testing using an E6010 root and E10018-D2 H4R fill and cap. Unfortunately, the tensile/yield results were unacceptable. Results are attached. We used a 400F preheat with a maximum interpass temperature of 650F. After welding, the sample was wrapped with insulation and cooled to ambient. The sample received PWHT in an oven at 1175F; soaking for three hours. Against our contract metallurgist’s recommendation, we were unable to start the PWHT immediately after welding. Are the low tensile/yield strength due to not immediately putting the sample in the oven or do we have other issues?

 

[gtaw]

Why are you using 6010 for the root pass? The pipe is 1%chrome, 0.5% moly, why wouldn't you select a filler metal with matching chemistry?

I'm not surprised the tensile test results are what they are. I'm surprised they are as high as they are unless you removed all the 6010 when the samples were machined.

The PWHT sounds fairly long for the thickness of the pipe wall.

Consider using a filler metal with a better chemical match.

Best regards - Al

 

[sw23cyp]

Thank you for your feedback, gtaw. I'm having trouble finding a SMAW electrode with matching chemistry. The E7016 H4 electrode was recommended by a Lincoln applications engineer but the chemistry does not match. Is there a more suitable electrode for the root?

 

[gtaw]

E8018-B2 or E8018-B2L comes to mind. There are several companies that can supply it.

Best regards - Al

 

[thebuckstopshere]

I agree with gtaw, E8018-B2 is commonly used for low chromes similar to 4130. Root pass can be difficult with SMAW using low-hydrogen electrodes. Technique is very different from cellulose type electrodes. GTAW process is more commonly used for root pass on piping using ER80S-B2 filler material.

 

[sw23cyp]

gtaw & thebuckstopshere, thank you so much for your guidance.