Welding procedure for white cast iron on pump impeller. Is it possible?

[Mech5656]

Hello,

We have a pump impeller that is made from white cast iron material. We need to repair it by welding but I found some resource online that says this material is not weldable. Can we weld it using 13% chrome material weld procedure? Any other similar material weld procedure that can be used to weld it? I appreciate your feedback. Thanks

 

[EdStainless]

Do you know the real chemistry? There are a bunch of grades.
You could try it, after you buy the replacement part.
It would take a lot of pre-heat, and then without cooling go into the stress relief furnace, ramp up to SR temp, hold, and then slow cool.
I would give it a 30% chance of working.

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P.E. Metallurgy, consulting work welcomed

 

[Mech5656]

Thank you for answering. Yes, we will pre-heat, weld and then cool it slowly in oven (not at room temp to avoid thermal shock) and then send it for post weld heat treat.

 

[EdStainless]

I would suggest that if you can't do it next to the stress relief furnace you chance of success will drop to 10%.
We used to cast white Cr CI and we shook them out of the molds and went straight into SR without allowing cooling.

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P.E. Metallurgy, consulting work welcomed

 

[TugboatEng]

Cast iron has a very brittle fracture. This means the broken pieces will fit back together with nearly perfect geometry and no gaps. This situation is perfect for brazing with an alloy that has strong wetting/capillary action. Look in to a brazing alloy called AWS BAg3 or 50N. It's commonly used to attach carbide inserts to tool holders. Silicon bronze is a less expensive alternative but it will require some gouging or grinding of the fracture surface because it penetrates less (make sure you leave some of the as fractured surface for alignment).

 

[Mech5656]

Thanks all. I will post composition of material tomorrow and that way we will know exactly what grade it is. Thanks

 

If it is in fact white iron, do not even try.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[weldstan]

Agree with Ed. Get the replacement part before experimenting with repair welding because the repair will more than likely totally destroy the part.

 

[Tmoose]

"REPAIR" is way too open-ended.
It could be adding weld overlay to areas worn less than 10& of the metal thickness.
Or, the worn areas might have turned the vanes into lace.
It could be re-attaching a chunk busted off a vane.
It could be attempting to build up a wallowed out mounting bore and keyway.
Or, a bunch of other things I hadn't thought of in 2 minutes.

As others said, Welding white iron and ASTM A 532 Abrasion resistant Cast Irons is looking for trouble.
Heck, many foundries can't grind off the casting sprues and risers without causing plenty scary heat "checks"/cracks.

 

[arunmrao]

Repair welding of high chrome iron parts is a big NO NO. I would suggest replacing it fast. As a stop-gap, recently for 2 dredger pump castings , I offered Hardox 500. This gave them some breathing time and keep the machines working.

The replacement by Hardox 500 does not include impeller or pump casing.

 

[Mech5656]

Thanks all for replying. Material is white cast iron with 20% chrome.

 

[dik]

Concur with everyone... white cast with high chrome is about as bad as you can get. Best to order the part.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[EdStainless]

At that Cr level I wouldn't touch it.
If it is a small crack you could try to furnace braze it to hold it together, but anything else is out of the question.
Getting these parts out of the molds is hard enough.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[Mech5656]

Thank you all for your responses especially Edstainless. We have decided to scrap the impeller and buy a new one. Thank you again!

 

[0707]

White Iron? Impossible to weld up to know.

luis