Welding to Annealed Steel 2

[mattpalermo]

A Tainter gate (structural steel radial gate at a hydro project in the USA), circa 1918, is being modified to withstand Federal Energy Regulatory Commission (FERC) mandated seismic loadings.

Part of the modification work requires welding to the existing trunnion (pivot point support) that was manufactured as a steel casting and annealed.

After review, the American Welding Society (AWS) D1.1 Structural Design Code does not appear to address this condition.

Are there any special precautions and/or procedures that should be placed on the Contractor prior to and/or after welding to this trunnion?

Please advise.
Thanks,
Matt Palermo

 

[metengr]

I would confirm or determine the chemical composition of the steel casting, and if possible, calculate carbon equivalent (CE). The preheat temperature should be selected based on CE and thickness of the base material (the thicker of the two base materials you are joining). The fact that the trunion is annealed is in your favor. Prior to welding, clean the area and perform a wet fluorescent MT just to be sure no surface defects are in the cast base material.

The welding should be performed with low hydrogen electrodes. Follow AWS guidelines for PWHT. After the completion of welding, I would recommend a wet fluorescent MT of the weld and 1" of surrounding base material.

 

[mattpalermo]

Hello:
thank you for your reply. How do you mean that the fact that it is annealed is in my favor? The heat will not damage the annealed steel? Also, could you please expain what is a wet flourescent MT and how it would help me?

And would this have to be slowly cooled post welding?

Thanks again

 

[metengr]

mattpalermo;
The annealed condition typically signifies the material has been reheated after it has been cast to provide for a relatively residual stress free state, with the lowest strength but increased ductility and toughness (in most cases), which is good for welding purposes.

The heat from welding will locally affect the base metal microstructure and properties of the casting so that is why you need to give careful consideration to preheat, interpass temperature and post weld heat treatment. By the nature of your question, I would suggest you contact a welding engineer or metallurgical engineer to review your specific application in detail, if you are not comfortable.

Wet fluorescent magnetic particle testing (wet MT) is a nondestructive test (NDT) that is commonly used to detect surface flaws that could adversely affect the performance of the weld and base metal. I prefer to use NDT to assure some level of quality weld repair. You can search the internet for various types of nondestructive tests to obtain more background information.

 

[metman]

metengr

It would seem likely that this device might be somewhat massive and therefore possibly awkward for magnetic testing but please correct me if I am way off on this.

Would not dye penetrant testing suffice or would it not meet the AWS code?

I have had better results in identifying cracks with dye-pen vs mag particle in some intances.

Jesus is THE life,
Leonard

 

[metengr]

Metman;
Either NDT method works, depends on a number of factors.

 

[arunmrao]

Normally carbon steel castings are supplied in normalised or normalised and tempered condition. Carbon steel castings being used in annealed condition is rare as the maximum mechanical properties will not be used. As metengr has rightly suggested the chemistry of the casting must be ascertained before preparing the welding plan.

If it is annealed perhaps it may be a low alloy steel(only my guess). Perhaps the source that revealed that the casting is annealed might also furnish the chemical composition.

 

[mattpalermo]

Thank you for all of your replies. The chemical composition is unknown. If I were to perform a chemical composition test to find the CE, once I have the results, where would I look to determine the proper welding procedures including preheating and cooling. Is a chemical composition test performed on site, or does a piece of the casting have to be removed to test off site? We would prefer not to remove a tab as that could prove very difficult in our complex situation.

Do you feel that it would be beneficial to take a 1” x 1” tab to weld it to another piece of steel and bend it to be sure the weld will bend as opposed to tearing the steel? This was suggested to me, but I would prefer to avoid field testing to this degree as I would not like to remove any steel.

Also, I had neglected to mention that a portion of this casting has been welded in 1959 (a 3/8” fillet weld connecting a 3/8” thick steel beam onto the existing 1” thick annealed section). A visual inspection of the weld shows it is in good condition (not cracked). I don't know the welding procedures used during that weld. Could the condition of this existing weld prove helpful in this effort?


Thanks again,
Matt Palermo

 

[arunmrao]

Portable spectrometers are available with testing labs. There is no need to destroy the casting for sample removal.

 

[metengr]

The present 3/8" fillet weld has no bearing on development of your specific welding procedure. I agree with arunmrao, you probably can get by without a removal of base material.
If you hire a lab testing service that has a portable spectrometer have them obtain some field hardness readings of the casting using an Equo-Tip portable hardness tester. The field hardness data can be useful to confirm the condition of the base metal.

 

[nickt1960]

Gents, I would just like to add one more point. MT is the prefered NDT method to PT on castings due to the porous nature of castings versus other forms of manufactured steel. The other weakness with PT is that it can only detect defects that are physically open to the surface, wheras MT will also detect defects that are slightly sub-surface, or those that may have been closed over due to blasting/peening, etc.

You will probably find that the company that provides the portable spectrometer service (otherwise known as PMI - Positive Material Identification) can also perform the NDT for you. Very often these labs also employ metallurgists who may be able to advise on the correct weld procedure thereafter.