This page particularly concerns the "jobbing mills", i.e. rolling mills having to roll many programs,
large range of thickness, several grade and final aspects.

 

There is a significant difference with, for example, an annealing and pickling line. In this case, all
parameters (strip speed, furnace temperature, bath compositions …) are imposed by the material to
be treated, the furnace power, bath lengths … and entirely given by the equipment supplier.
The main role of the user is to strictly follow the recommendations. The operators are supervisors.

 

Rolling is a complex operation, a lot of parameters intervene, each of them having not the same
influence according to the rolling case. If the strip shape is not totally under control, the rolling speed
is reduced, rolling incidents can occur, quality aspect can be compromised … But the flatness also
depends on a lot of parameters, roll profiles, rolling force …

The equipment is generally very sophisticated, the material to be rolled is changing from pass
to pass; from one grade to another one the behavior during rolling is variable. Consequently,
optimization for every rolling program is a hard problem.

 

Around the world, many mills are not properly used, low speed, low rolling force (then many passes).
So there is no standard practice, the initiative of the operators is very large, they don’t use the same
pass schedules, not the same tensions, ... Obviously the results are variable.

 

For the above reasons, cold rolling is often the bottle neck of the plant.

 

The quality of the final products depends very much on the rolling operation. Keep in mind the non
quality is very costly (cost of the reject material, waste of time, the delivery time is compromised, the
programs of the subsequent machines is disturbed, deviation of the concerned strips …)
The result can be disturbed by a detail, for example the roll roughness … Many surface defects are
difficult to be avoided (chatter marks, scratches …) Flatness is generally the major problem.

 

Rolling can be compared with car race: the strip is the road, the mill is the car and the operator is the
driver. These three factors being under control, the result is mathematically good.
Everything, even a small detail, must not be neglected. If no, it is hopeless to get performances.
All precautions must be taken a priori; during rolling it is too late!

 

The most modern rolling mills run in fully automatic mode, thanks to mathematic model, perfect
optimization of all parameters, perfect and reliable maintenance and roll grinding … In these
conditions the output target is reached, quality is got at the lowest price - ideal solution-
Concerning the operators, it is an error to think because of automatic running anybody can operate!
The modern planes can fly, land … in automatic mode. But not a single company reduces the pilot
training; on the contrary it is reinforced.
The operator must be able to detect any trouble, decide the required action (quick stop, finishing
of the pass …) and properly inform the hierarchy. The hierarchy has to take the best decision (quick
repair, or program change, or waiting up to the next preventive maintenance …)

 

What ever is your actual situation, we can help you.