Welding to Existing Annealed Steel Casting

[mattpalermo]

Hello:
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

 

[unclesyd]

Has the structure in question be welded on previously?
I would try to ascertain the material if possible as it could be several steels or irons that could cause problems while welding.
I would take the time to conduct a little weld test. Take a 2"x2" 1/4" thick tab of the material you will weld to the gate and weld the tab to a cleaned area of the piece in question with a full 1/8" fillet weld one side. I would use 6010 rod. Try to break it off by hitting the opposite side from the weld and see how it come off. The weld should bend. If the base metal tears out you have a little problem.
When you do the test make sure the metals are above 60°F.


Come back with the type of weld needed.
Any type of welding is probably going to require preheat and slow cool afterwards.

 

[mattpalermo]

Thank you for your reply. The annealed casting has not been welded on previously. I would be welding a 5/16" fillet weld on it. We are primarly concerned that he heat from the welding would damage the annealed steel. We would prefer not to conduct a field test if possible, but you find that is the best approach?

Thanks
Matt Palermo

 

[unclesyd]

I always like to try this test on an inconspicious place on any unknown material especially a casting as old as yours. Find a place that if a small chunk comes out it want cause any problem. You can cut the tab down to 1"x1" if that will help. You just don't want the parent metal to breakout. Try to test in a cleaned area. One can also checkout the preheat and cooling procedure with this test by preheating the test area to 350°F and welding then covering the area with insulation and then testing.

If the material is weldable we can look at a preheat and a cooling curve for the weld area. As you stated this material has been annealed there is some concern as to why it was annealed in the first place. This helps with the welding but can cause problems on cooling unless controlled.

There are several methods to help once we know it is a weldable material. There is another test, Navy, that we could use to determine weldability but I prefer the tab as it determines if the weld will hold under stress.

Nearly all castings of your age were welded by thermite welding and some times the composition and structure is not amendable to stick welding.

Will the weld be in position or can you have it on a table?

 

[mattpalermo]

The casting is large (approx 2’x2’x1’), in place on a dam in a river and cannot be placed on a table. Is it common procedure to preheat 1918 vintage annealed steel prior to welding? And is 350 degrees a similar temperature that would be recommended in preheating the casting prior to welding so that the tab test would be a good model of what would be performed pending a successful test? Also, where would I find a heating/cooling curve for this condition of welding? Do you think it would be a good idea to calculate the Carbon Equivalent (CE) by performing a chemical composition test to determine the preheat temperature? Removing a tab of the steel could prove very difficult in our complex situation.

Also after I had replied to you, I had realized 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?

In addition, could you please provide me with your background in this type of work?

Thanks again,
Matt Palermo

 

[unclesyd]

With a previous weld and it being in good condition is a very good sign. This somewhat mitigates the tab test, though I would still do one close to the area of interest for the new weld. I would do a non-destructive test, either dye penetrant or magnetic particle, on the previous weld. Your welder might be able to help you with what type welding procedure or rod was used on the previous weld.
Prior to any welding make sure you have sound metal, after you achieve sound metal you could do a dye penetrant test of the area to see if there is any thing that hinder accomplishing a sound weld.
Your welder will get the small tab off as this is very common in fitting and welding.

Knowing the chemical composition of a material is always beneficial but is not entirely necessary as in your case as there has been a successful weld made. The chemistry of the metal can help determine the preheat temperature but other factors like thickness and constraint of the parts also enter into the picture. I chose 350°F as a temperature based on experience when welding somewhat of an unknown. Covering the weld to allow slower cooling is just a precaution and good practice to account for the material and mass effect.

As for background, I have a total of 45 years in materials and metallurgy with a world class valve company(3) and a large synthetic fiber plant and chemical plant(42).

 

[unclesyd]

mattpalermo,
If you are still monitoring this and your other post let us know how the welding went.

This type information would be greatly appreciated by all and a great help if a similar situation comes about.

thanks

unclesyd