How to roll AISI 304 Stainless Steel

[glp86]

We were asked in our Manufacturing Processes class to design a process for the manufacture of AISI 304 stainless steel sheet. Starting with hot rolled sheet 9 gauge (U.S.G.) in thickness and 32” wide. The final product is required to be 30 gauge (U.S.G.) in thickness and 32”. Our design needs to be based on a commercial-practice, tandem rolling operation, achieving the total reduction by progressive rolling without intermediate annealing, unless required.

We need to consider: roll gap geometries, i.e., diameter, lengths, ect., reduction/ pass schedule, lubricant, rolling velocities, etc. also the: residual stresses, strengths, defect, etc. on the final product.

Do any of you guys have any experience with something like this? We could really use some guidance, because most of the information we seem to find is theoretical which is tough to understand and apply.

An explanation of how to do achieve this would be great, including things such as what to make the rollers out of etc. would help a lot.

Thanks!

 

[Dr.D]

I used to work for Bethlehem Steel Co (now gone under), and worked in cold rolling. This is a really ambitious project for a student problem.

There are many combinations of speed, roll diameters, interstand tensions, number of mill stands, etc that will give the required result. When all is said and done, it is largely based on the experience of the head roller (foreman). I'm not clear how you can hope to do this for a classroom project.

 

[jim mcnamara]

As a side note:
This question was asked 11+ years ago... and the OP has not been seen since then.

 

[jrmichler]

But, it is a legitimate question, and I did not find any other threads about rolling.

most of the information we seem to find is theoretical which is tough to understand and apply

And that information is probably the simplest answer you will find. A complete solution is beyond what can be expected from a senior design project. You have two choices:

1) Try to negotiate a simpler project.
or
2) Give it your best effort, and hand in what you have when you run out of time. Recognize that the teacher might be doing this deliberately to separate the students that get started early and put in sincere effort from those that wait until the last minute to put together a last minute rush effort.

Start at the end - the exact thickness and mechanical properties. From that, you use the strain hardening coefficient to find the thickness that needs to be annealed. The roll diameters and hardness at the last stage are calculated from the final sheet mechanical properties and thickness. The rolling forces and sheet width allow you to calculate whether the rolling mill needs to be two high, four high, six high, or cluster (Sendzimer) mills.

You may find that the starting material thickness requires larger diameter rolls. In that case, you will need at least two different rolling mills.

Rolling mill rolls undergo elastic deflection under rolling loads. That elastic deflection means that any given pair of rolls can roll a given material to a minimum thickness, and no thinner. Rolling thin material, such as aluminum foil, requires small diameter rolls made of hard material with high modulus of elasticity. I remember reading of 1/4" diameter rolls made of tungsten carbide.

My old copy of Manufacturing Processes for Engineering Materials, by Kalpakjian has a good section on rolling. That book is still in print, and is a very good general resource.