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Failure of hardchrome coating on workrolls

We operate an aluminium rolling mill and use chrome plated steel rolls in our rolling mills. The current problem is on our two stand hotmill where we are experiencing patchy loss of chrome coating. It is a 6-8 thousandths hardchrome coating. We have observed equivalent to chicken wire cracking in the coating of faulty rolls as they are returned from coater which correlates to low roll coating life. The roll life has varied from 8 coils to 400 coils of aluminium. The rolls barrel length is 80 inches, diameter is 24 inches. The rolls are ground in our inhouse rollshop and crack tested.

We would like to understand the issues to review with the supplier.

Ross Bennett
- Geelong, Victoria, Australia
2004

Try with chrome thickness of around 0.002". Increasing thickness is a common mistake when trying to increase roll's life. What you need is to wear the chrome plate not to take it off in chunks.

Guillermo Marrufo
Monterrey, NL, Mexico
2004

As stated, a thiner coating of .002" will be better. Although your problem might be coming from one of two things. One is when you have a larger buildup of plating and there is deflection in the rod or roll,etc. you will see these fish scale like cracking and the coating will flake off. Second, when grinding a part of this dia. your speed,feed,travel, and part rotation is crutial. If any of these are off the plating will heat up an cause peeling. When incertain, slower is better.

Jason Gauthier
- Sudbury, Ont., Canada
2004