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Ted Mooney, P.E. RET
Pine Beach, NJ
The authoritative public forum
for Metal Finishing since 1989
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Is hard chrome plating suitable for leveler/straightener rolls handling hot rolled steel?
adv.
Q. We are in sheet metal processing and mainly deal with slitting and shearing of cold rolled and hot rolled steel. We have to use "straighteners" and "levelers" to remove defects in flatness in the mother coils coming from the rolling mills.
My question: Is hard chrome plating suitable to withstand the abrasive action of hot rolled steel sheets/plates when used on the straightener or leveler rolls? (The roll load may be as high as 100 tonnes in straightening thick steel plates of about 16 mm.)
If suitable, what should be the layer thickness and hardness?
Steel service centre - Calcutta, West Bengal, India
2007
A. Not more than 0.0010-0.0015" (25-38 microns), otherwise it may spall off. Surface preparation must be very carful for high carbon heat treated steel requires a smut removal step. Hardness will be the common 66-69 Rc. Better if fluoride or mixed catalyst baths are used.
Guillermo MarrufoMonterrey, NL, Mexico
2007
Q. Dear Mr. Marrufo,
Thanks for your valued opinion. In our case, the rolls are of ordinary carbon steel of EN-9 grade (average carbon content 0.55%). We are planning to undertake surface hardening of the rolls by flame or induction hardening prior to hard chrome plating. It is difficult to achieve more than HRC 48-50 here. Is this hardness o.k for the durability of Hard chrome plating?
Sincerely,
- Calcutta, West Bengal, India
2007
A. It will depend on your particular situation, but in my opinion, 48-50Rc is rather soft. So, even if the chrome remains there, the whole roll surface may experience deformation. A surface hardness of 58-60Rc would be much better to provide a proper backing to chrome and get full advantage of it. Bearing quality steels such as SAE-52100 (1.00% C) are common for chromed rolls.
Guillermo MarrufoMonterrey, NL, Mexico
2007
A. Dear Sir,
In your case it is possible to deposit tungsten carbide over the roller for an built up hardness of 70-72 Rc which has an excellent mechanical impact resistance compared to hardchrome plating by detonation gun which is an advanced version of thermal spraying, this can give a thickness of 100-300 microns.
- Chennai, Tamilnadu, India
2007
adv.
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