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High Nickel Cast Iron

5K views 15 replies 8 participants last post by  MidLifeIdiot 
#1 ·
I did a search but I cannot find the thread. There was a metallurgist that I believe was debunking the myth of the nickel making blocks and cylinder heads "harder" and even harder to machine, rather the nickel content had nothing to do with the hardness but simply was for flexibility in the cast iron. Was wanting some more expert input on this, thanks.
 
#3 ·
No idea man, don't shoot the inquirer... lol I have always heard the nickel=hard statement too and never thought anything about till I saw an actual metallurgist say it was one of the biggest incorrect myths out there and that nickel content gave the cast iron matrix flexibility and tensile strength not its "hardness." And attributed "hardness" of the matrix to other elements.
 
#4 ·
Was still searching for that thread and came across this comment in a chinese vs dart block thread made by another member/metallurgist: wideopen : "I dont mean to be a party pooper and im not saying anything positive about the chinese shit. But the statement about Nickel, moly and copper giving strength is not a true statement. As a metalurgist I can tell you that the higher the number of these materials the softer the iron is and makes it less likely to crack. The lower the numbers the stronger the iron is, making it more brittle. In metal you have to define your understanding of strength. The more alloy's that you put in iron takes away strength and adds the ability for the moliculas to stretch and then regain the shape. The less alloys in iron make it harder and more brittle, then when it stretchs it will not regain its shape and will eventually fail. A lot of strength depends on how pure the pig iron is that the melt to start with. The number provided will not give you a far comparision of the blocks in question. If anyone has a broke peice from each block I could analysis it and give a very thouough report on which has better chemistry's, yields, tensile and ductility.
 
#10 ·
#9 ·
Regal, he was a metallurgist at a foundry is all I can remember.

With that being said I have found two guys now that actually do metallurgy and both are saying the same thing, High Nickel does not mean harder, but I guess can be thiught of as making it stronger, in terms of tensile strength.
 
#12 ·
So, what makes some castings harder to machine? Is there some actual correlation between the nickel content and machining practices? Does the higher nickel content/ better tensile strength add difficulty and do the lower nickel/ "harder" but more brittle castings make them more machine practice friendly?
 
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