Welding stainless steel to carbon steel 8

[apetr26542]

I apologize if this is a redundant post, but I need to specify the proper electrode for welding a 3/4" diameter stainless steel rod (304) to a schedule 40 steel pipe. This will be done in the field and is part of a life line attachment.

 

[pipewelder1999]

A welding procedure should first be qualified by testing to an owner approved code of fabrication . This would be the normal practice for any critical welding. There are other variables besides filler metal that if not controlled could lead to a poor weld.

Filler metals that have been used in other circumstances to weld low carbon steel to 300 series stainles include 309, 310, ENiCrFe and other nickel based alloys.

Before proceeding with any welding on fall protection equipment I would check with a competent person responsible for the design.


Gerald Austin
Iuka, Mississippi

http://www.weldinginspectionsvcs.com

 

[apetr26542]

Thanks for your post, I am the person responsible for its design, E.O.R., it is part of a much larger project. When specifying carbon steel welding I use E70xx, would specifying 309 electrodes or 310 be the proper terminology?

 

[pipewelder1999]

Another option would be to refer to an applicable code or standard.
If you are restricting the process to SMAW then the an example would be E309-xx .
That method, used often on engineering drawings still today is one that theoretically restricts the process to shielded metal arc welding when often FCAW/GMAW or GTAW are being used. All of the previous listed process would have different designators.
Another option is to just refer to the filler metal type as E309-XX or equivelant type for other processes.

Hope that helps.

Gerald Austin .

Gerald Austin
Iuka, Mississippi

http://www.weldinginspectionsvcs.com

 

[GRoberts]

As Gerald mentioned, specifying E70XX ties the fabricator to the SMAW process. If this is not what is intended, the specification could be such as: 70XX, E7XT-X, or ER7XS-X, which would allow the SMAW, FCAW, GMAW, GTAW, SAW, and other processes using 70 KSI minimum tensile strength filler metal. If for instance, you wanted to specify 309 type filler metal, you could specify: 309-XX, E309TX-X, or ER309. The "L" grades of stailess filler metal would be ok to use as well.

 

[apetr26542]

Thanks! You all have been much help. This welding is on the roof of a building, a stainless steel bar needs to be welded to an in place steel pipe. I imagine it will be stick (SMAW). What is the difference between 309, E309T and ER309. Does it matter if the stainless steel is 316 or 304, in this case it is 304. I have alot of questions as I've rarely required this welding and never had to specify the filler for this type of welding. Is 309 the common electrode used, I've seen all sorts of stuff trying to research this, different fillers for chemical environments, marine etc. I don't require this much corrosion resistance.

 

[pipewelder1999]

The format of the number indicates what type of filler metal it is The E prefix indicates electrode . ER Indicates electrode or rod . The "T" indicates a tubular electrode as in the case of flux cored arc welding.

There may be a welder or welding foreman in your organization that could give you some information on this subject and may be a good resource for future questions. Though I do enjoy running off at the fingers

Have a nice day

Gerald Austin
Iuka, Mississippi

http://www.weldinginspectionsvcs.com

 

[metengr]

To add to pipewelder's post, I would suggest using the following for welding;

1. Make sure the carbon steel pipe surface you are welding to is clean of rust, scale or paint and is above 50 deg F.

2. Use the SMAW process with SFA 5.9 E309 welding electrodes.

3. After the completion of welding, perform a Liquid Penetrant inspection of weld and surrounding base metal.

As mentioned previously, and I want to stress that you should make sure that the weld design is adequate for a life line attachment. If necessary, have a registered, Professional Engineer review your design detail - the cost will be well worth the investment.

 

[apetr26542]

Thanks, that is a very helpful post, so you know I am a Registered P.E. in the state of NY. This project is a retrofit for an existing building, we are responsible for the lifeline anchorages to the building roof structure. This is part of an ongoing project where we have just about completed the retrofit for the addition of davit pedestals for window washing equipment.

 

[btrueblood]

This whole thread is worrisome to me -- this is life-critical equipment you are talking about. Have you thought of the corrosion issues regarding welding stainless to plain carbon steel? How will you ensure that the weld joint won't crack through in 20 years? It seems like using a slightly thicker bar of carbon steel would make more sense.

My $.02

 

[apetr26542]

The bent rod is stainless steel, bent into a "U" shape. It is 3/4" round. It is being welding to a 4" sched. 40 galvanized pipe. The welder is instructed to grind off the galvanizing in the vacinity of the weld, weld the "U" bar, and to touch up the ground areas with cold galvanizing compound. Don't worry, I am very familar with lifeline systems, usually they are prefabricated with the hook already welded to the galv pipe and are certified for 5000 lb ultimate load. In this case we have to do a little retrofit.

Finally, all anchorages will be tested to 2500 lbs. Lifeline systems as well as window wasing equipment must also have annual inspections.

 

[pipewelder1999]

DO NOT WELD STAINLESS TO ANY GALVANIZED. Excuse the shouting but this is VERY important. The low melting point zinc WILL cause cracking that is not visible to the naked eye. Just a small amount left after grinding can cause this.

If it has been done before, I can be very confident that there are small cracks along the toe of the SS weld metal adjacent to the stainless.

I have seen this on numerous occasions where welders attached the wrong type pipe doubler for a support on a SS pipe. It has always cracked.

Forgive me for seeming a bit forward but I suggest consulting with a welding engineer even if you are the PE.

I am just a welder/inspector but there seems to be some basic items you could use some help with. I have a tremendous respect for the the many things an engineer must know and I have always enjoyed picking the brain of the ones I have had the priviledge of working with.

In this case here is some of my brain. If I am wrong about this I'm sure someone will straighten me out.


Gerald Austin
Iuka, Mississippi

http://www.weldinginspectionsvcs.com

 

[apetr26542]

I appreciate your input, I am going to call the supplier, it is very common to supply galvanized steel pipes with these bent rods already attached. I am ultimately responsible for the anchorage of the steel pipes to the building structure. They are certifying the safety "devices".

 

[apetr26542]

Let me thank everyone again for their input, I do not mind at all, I've contact the supplier as they produce thousands of these, I've left them a message regarding their procedure and how they address this issue. I will keep you all posted.

 

[Rich2001]

I agree with pipewelder1999.

Grinding will not remove all the galvanizing a thin layer will be smeared over the surface. After grinding heat the surface with a neutral torch to 600F, the steel will turn brown in color and any zinc on the surface will be silver in color.

Consult a PE Welding Engineer, granted there are very few of them, since Ohio is the only state that gives the PE Welding Engineering Exam.

On another note- After any welding you need to perform NDE looking for cracking beneath the galvanized coating in any areas that has reached 280F. An eutectic of tin, and/or bismuth (galvanizing alloys) and zinc can form that can penetrate the grain boundaries of the steel cause them to unzip, i.e. crack.

Still more information- Galvanized pipe is NDE inspected, usually with eddy current, prior to galvanizing, however no inspection is done after galvanizing. Galvanizing is not a coating like paint by a metallurgical coating that can affect the mechanical properties of the steel. Since this application is for lifeline anchorages think about more NDE inspection.

 

[EdStainless]

The systems like this that I have seen were all carbon steel and hot dipped after the hooks were welded. This is also how most highway sign bridges are made.
When I have done spot work welding SS to galv we always required a chemical (acid) cleaning to remove the Zn residue.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[apetr26542]

The supplier told me the exact same thing Edstainless. I think we will find an alternate method of lifeline attachement given the difficulties and issues with the galvanizing. There are other locations available, they will have to brace and reinforce the beams anchoring these devices. This has been a very interesting discussion.

Edstainless, just curious though, is the chemical cleaning reliable? To answer a previous post, regarding NDE, the job has independant monitoring and inspection as well as load testing on every single piece of equipment.

 

[Capntom]

Acid strip is the way to go. Otherwise the zinc, which is soft, will definately get "smeared" into the base steel. The process that Rich2001 is talking about is called "heat tinting". It works very well on surfaces that have a high affinity for oxygen. The aerospace industry uses it quite extensively to detect the presence of coatings.

 

[EdStainless]

apetr,
You can use pickling acid to strip Zn, and almost anything else. If you have to do spot work a grind and then using a pickling paste might get you by. Actually I would first grind, then heat with a torch to oxidize remaining Zn, grind or sand with fresh abrasive, then pickle clean.

I know that it sounds like overkill, but I have seen what trace amounts of Zn and Cu can do to SS welds.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[JLGIII]

I am a structural engineer working for a contractor. Years ago we got contract documents to provide a stainless slug between two galvanized plates and weld using stainless rod. What I understood at the time was that was an invitation to cracking, just as the posters here have said. I called a professor at LeTourneau University, who wrote a basic welding book I have. He told me that as long as the welder whips his rod to burn the zinc off ahead of the cooling pool it would be OK. We have used this process (though never with a WPS) on many projects ever since and have had no difficulty. We have not been called back because welds failed, either.