Seek advice on Ni Resist casting
Seek advice on Ni Resist casting
(OP)
I am planning to cast a ASTM A436 Type 2 ( 20% Ni, flake graphite type), Ni resist casting. This is an impeller bowl casting for a single stage vertical lift pump in sea water. The lifting pump is used as circulating water pump in Thermal power station.
The approximate weight of this casting is 2500 kilos.
My concern is about degassing practice to be adopted for this alloy. I have cast smaller weight castings in shorter melt times and did not experience any Hydrogen gas related issue. This is my first, with this weight of casting.
I shall welcome any advice from experts here in helping me produce a sound casting.
Thanks in anticipation.
The approximate weight of this casting is 2500 kilos.
My concern is about degassing practice to be adopted for this alloy. I have cast smaller weight castings in shorter melt times and did not experience any Hydrogen gas related issue. This is my first, with this weight of casting.
I shall welcome any advice from experts here in helping me produce a sound casting.
Thanks in anticipation.
"Even,if you are a minority of one, truth is the truth."
Mahatma Gandhi.





RE: Seek advice on Ni Resist casting
I have never cast NiR2 in anything over about 500kg. We used very standard degassing, but we also made sure that all feedstock was baked out to assure that it was dry.
The biggest issue that I see is related to the wide freezing range and time for full solidification.
The other thing is that we did stress relive all castings, this helps greatly with holding dimensions and resisting SCC.
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P.E. Metallurgy, Plymouth Tube
RE: Seek advice on Ni Resist casting
RE: Seek advice on Ni Resist casting
New age pumps use Duplex S.S castings for this application. However, this replacement part has been in service for over 30 years and is now being replaced. Thus, you still find the Ni Resist 2 specification.
I have been considering using metallic chills, but will it cause any white iron formation in those regions? I don't know.
I shall be adopting degassing practice, using Argon gas and Nickel oxide as cover flux.
Stress relieving after rough machining at 600C will be done.
Thanks once again.
"Even,if you are a minority of one, truth is the truth."
Mahatma Gandhi.