The slitting technology as applied to continuous bar mills enables the production of two or more strands from one billet. Depending on plant configuration the slitting process can be adapted to rolling mills with a minimum of four final stands in continuous installation.
The process gives the following profits:
Substantial increase in production rates
Reduction in the number of rolling stands
Reduction in operation costs
The slit rolling process differs from conventional continuous rolling by the use of special roll passes and guides to prepare, shape and longitudinally separate the incoming billet into two or more individual strands for further rolling into the finished size.
In principal this process is achieved as follows:
Reducing the billet conventionally through the roughing
and intermediate rolling mill to produce an acceptable
section for the first special shaping pass at the
Precise guidance of this stock to the forming stand
where it is reduced and shaped to form a symmetrical
Further close guidance and control of the "dog bone“ through
the separating stand, were the stock is reduced and shaped
into a "slit pass“, designed to be easily separated
into two equal sections of false round.
A special guide on the delivery side of the separating stand
ensures a clean slitting of the bar and now delivers multiple
strand of equal sections to their respective finishing lines.
For the effective continuous operating of the slit rolling process it is important that all mill equipment is in good order. Particular care and attention must be directed to the condition of the rolling mill. For multiple strand rolling the power availability of the finishing train is of great importance and need to be sufficiently calculated.
The leader sectons for the multiple slit rolling process, e.g. square, rectangular or round have to be of very close tolerance.
Correct pass profile in the rolls
Correct roll gap to ensure no overfill
Correct pass alignment between top and bottom rolls
Sound roll neck bearings and positive roll location to avoid axial
Stiff rolling mill stands providing rigid screwdown and roll
Sound roll quality and good pass conditions
Uniform stock temperature
The guiding of the leader section to the forming pass and on to the separating pass in the separating stand is critical in order to guarantee equally balanced strands.
Desired guiding features are listed as follows:
Sound and robust guides
Precise guide equipment
Positive, adjustable and secure alignment
Guiding of bar close to the stand
Correctly set up and maintained guides in
absolutely good conditions
Besides this a good control throughout the finishing mill is required.