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Question
Hello Mr. Sharma
I would like to clarify the level of Cr that you recommend.
Your comments stated 0.25% - 0.30%
Is this correct or should it be 0.025% - 0.030%?
My level are 0.040% - 0.055%.

Thank you
John Tucker

Answer
Dear John,

Really sorry, please add a zero after decimal point in case of chromium wherever I mentioned it during our discussion.


In general, entrapment of the sludge into the mold cavity has a harmful effect on the mechanical and  physical properties of the casting part which dependent on the alloy’s chemistry, melting and holding temperatures, and time. sludge factor (SF) for Al– Si– Cu alloys. It is useful to determine Fe, Mn, and Cr contents to prevent sludge formation. This factor is calculated from the formula mentioned below:

Sludge Factor (SF) =(1 × wt.%Fe)+(2 × wt.%Mn)+(3 ×wt.%Cr).
It is obvious that Cr is the most deleterious element for the formation of sludge and also changing the morphology of hard inter-metallic compounds.

Alone or in combination, manganese (Mn) and/or chromium (Cr)change the morphology of the iron-rich Al5FeSi phase from its typical platelet/acicular form to a more cubic Al15(MnFe)3Si2 form that is less harmful to ductility.

Thus, on an average; keeping a balance, Chromium > 0.035% give rise to sluge formation as well as brittle inter-metallic compound.You chromium contents are almost double than what it need to be.

Hope, the matter is more clear now.

Best Regards,
R.P.Sharma  

Metallurgy

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RAJINDER PRASAD SHARMA

Expertise

Questions that i can answer:- 1-sand casting of cast iron,S.G. iron,steel and aluminium alloys 2-Gravity die casting of aluminium 3-Low pressure die casting of aluminium 4-High pressure die casting of aluminium 5-Failure analysis of ferrous and non-ferrous castings Questions that i can`t answer:- 1-testing of iron and steel 2-Problem related to welding 3-Problems related to corrosion 4-Amorphous metals,rubbers,nylon,plastics and plastic moulding

Experience

1-Sand casting and ferrous and non-ferrous alloys 2-Gravity die casting,low pressure die casting,high pressure die casting of aluminium alloys.With a specialisation in auto-mobile components castings. 3-Alloy steel making on arc furnace,AOD,VOD,Con-cast root of alloy steel making. I have been working as Foundry man since last 27 years.

Organizations
Hindustan motors Ltd.

Education/Credentials
I am a Metallurgical Engineer graduated from National institute of Technology,warangal(India) in 1984 and in 1991 i completed my masters degree in business administration(M.B.A.) from Institute of Management Technology,Ghaziabad(India).

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