Preheat of base metals in ASME? 2

[m3brunof]

According to AWS D1.1 5.6 one of the paragraphs states "This preheat and all subsequent minimum interpass temperatures shall be maintained during the welding operation for a distance at least equal to the thickness of the thickest welded part( but not less than 3" in all directions from the point of welding".

Where can I find this in ASME?

 

[jte]

What type of equipment are you working with? There are more than one ASME standard or code. Can you tell us which ASME standard or code you are working to?

jt

 

[DVWE]

I don't believe there is a similar statement in ASME. The only guide that I'm aware of is a non-mandatory appendix, Appendix R.

 

[m3brunof]

jte I'm working with section IX. Our welders are certified with ASME section IX and our procedures have a preheat temperature to be met. The problem is that a welder could try to preheat a whole large part as opposed to the statement I wrote above.

I'm trying to find it in writing so I can show it to our welders how large of an area is necessary to preheat.
DVWE I'll look into the appendix R.

Thanks

 

[DVWE]

I'm pretty sure you will have to borrow that statement from an alternate source, such as AWS or even API. API RP582 spells it out exactly the same and makes reference to ASME requirements. The beauty of ASME is that they allow you to determine if something like this should be required or not.

 

[Kiwi2671]

m3brunhof,
It is governed by the applicable fabrication code you are working to, not to ASME IX.
For example ASME B31.3 Clause 330.1.4 Preheat Zone states "The preheat zone shall extend at least 25 mm (1 in) beyond each edge of the weld."
What code are you working to ?
What is minimum preheat temperature of WPS ?
What is average ambient temperature in your area ?
What materials are you welding ?
A bit more info and we may be able to assist further,
Regards,
Kiwi

 

[m3brunof]

Great stuff so far guys.
Kiwi I'm welding P6 CA6NM with GTAW and preheat of 200 degrees.
Ambient temp is 70 degrees.
I'm not sure what fabrication code I'm working to. Where do I find - ASME B31.3 Clause 330.1.4 Preheat Zone states "The preheat zone shall extend at least 25 mm (1 in) beyond each edge of the weld."

 

[metengr]

ASME Codes and Standards have their own set of requirements regarding preheat recommendations.

If you are unsure about what Code or Standard you are working to I would use AWS preheat requirements as you stated above. Otherwise, you can cherry pick preheat recommendations from numerous sources.

Where do I find - ASME B31.3 Clause 330.1.4 Preheat Zone states "The preheat zone shall extend at least 25 mm (1 in) beyond each edge of the weld."

If you have a copy, in ASME B31.3.

 

[Guest102023]

If welders are challenging you to come up with 'proof' for the extent of preheat, I would question their attitude. Preheating only at the point of welding on anything massive is not very effective.
I don't know where the 3" rule originated, but I have seen it specified many times and in many documents. Greater extent of preheat also helps mitigate distortion. ASME only gives 'recommended' preheat values in non-mandatory appendices, but it would be prudent to treat them as 'mandatory' minimums. Any lawyer certainly would ...

 

[stanweld]

Since CA6NM castings are commonly used for pump casings and or impellers and valves, are you repairing them? Preheating, from localized to full (whole casting preheated), will depend on the complexity of the casting shape, thickness and the extent of the repair.

 

[m3brunof]

Stanweld,
This welding was done on a diffusor for a pump and the welder preheated the whole part. It was a minor weld repair, only needed localized preheat. Because the whole part was preheated, warpage occurred. So I'm trying to explain to the welders that in some cases it is not necessary to preheat the whole part. But I'm trying to gather written proof from ASME.
Thanks for all the help everyone!

 

[stanweld]

You will not find such information in ASME Codes. Manufacturing and Welding Engineers need to address repair methodologies based on condition of casting; e.g; heat treat condition, finsh machined condition, casting complexity, nature of repair, etc.

 

[metengr]

Because the whole part was preheated, warpage occurred. So I'm trying to explain to the welders that in some cases it is not necessary to preheat the whole part.

No way. I would bet what little savings I have it was the weld repair itself that caused the warpage.

 

[Kiwi2671]

Brimstoner / Stanweld,
All the ASME codes list both required and/or recommended minimum preheat temperatures dependent on the material.
For example,in B31.3 P numbers 1,3,6,7,8,9 have recommended minimum preheat and P numbers 4,5,10 & 11 have required minimum preheat.
For CA6NM (P 6)the following requirements / recommendations are listed for minimum preheat.

ASME B31.3
300 degrees F / 149 degrees C - Recommended.
Minimum of 1" from weld edge - Required.

ASME B31.1
400 degrees F / 200 C - Required
Minimum of 3" or 1.5 times base metal thickness (whichever is greater) - Required

ASME VIII Div 1
400 degrees F / 204 degrees C - Recommended

Hope that helps regards,
Kiwi

 

[stanweld]

Kiwi2671,
I am fully aware of ASME Boiler & Pressure Vessel and Piping Codes' preheat requirements/recommendations. They do not address how to preheat a casting to affect a repair that will not cause distortion. Left unsupervised without proper direction, I have seen welders over heat, under heat, and otherwise misuse torch preheating, especially when using oxy-fuel gas cutting torches as rosebuds, or when applying rosebud heating and leaving it on, directed in one location on the part while taking a break.

Also Code requirements may be inadequate. I once recommended to a major vessel manufacturer to increase its preheat temperature on some 4" wall Manganese-Molybdenum vessels. They did not heed my recommendation initially, claiming all they had to do was follow Code. They had to repair two full circumferential seams in the 10 ft diameter vessel shell after both fully cracked during a weekend shutdown; they preheated as I recommended thereafter - curiously, no more cracking.

 

[Kiwi2671]

stanweld,
Sincere apologies for misinterpreting your post.
Any thoughts on the OPs preheat of 200 degrees which is 100 - 200 degrees below ASME requirements / recommendations ?
Regards,
Kiwi

 

[stanweld]

200 F preheats have been used to successfully repair CA6NM castings depending on the actual chemistry of the casting, welding process used, weld filler metal used, geometry of part and geometry of repair. I cannot comment as to the adequacy of the preheat temp employed without knowledge of the above. It is noted that the repair was essentially unsuccessful; preheat may well have been inadequate.

 

[Duwe6]

The type, temperature and duration of preheat required is supposed to be addressed in the WPS - welding procedure. If it is there, enforce it. There should be an inspector of some sort 'prowling' the weld shop. If you don't care enough to check preheats, fitups, and roots, how can you expect the welders to care?

If proper preheat requirements do not exist in the WPS, put them in. I recommend uniform heating of the casting - put it in an old, household electric oven for an hour or so.

 

[Guest102023]

I am intimately familiar with CA-6NM, and it can be welded with lower preheat in thinner sections and with very low hydrogen consumables and practice. The use of austenitic fillers also mitigates the need for preheat. With this alloy the weld zone is hardest and most prone to cold cracking (with matching filler).