Multistrand Rolling-Slitting (MRS) is a Non-Conventional Technology of Rebars and Merachnt Bars Production

The MRS technology was developed by RPC «Donix» in cooperation with the specialists of Dotetsk State Technical University and a number of Ukrainian metallurgical works as an alternative for the prevalent «slitting process».

The «slitting-process», developed by «Co-Steel International Company» and improved by «Nippon Kokan Company», consists in forming the multistrand stock from a square or rectangular billet. The multistrand stock consosts of «false round» sections coupled by the 0,75 - 1 mm thick bridge. The stock slitting is carried out by means of breaking the bridge by the wedge-shaped rolls of a special device, installed at the exit from the working rolls, under the action of the expulsive force created by the rolls. After the stock has been slit, the «false round»sections are rolled concurrently into the finished sections, usually in two passes.

The process has a number of essential drawbacks, namely:

The neck which appears after the bridge breaking at the point of slitting and deteriorates the quality of the finished rolled stock.
Low durability of the forming pass.
Slitting device of elaborate design.
Low durability of the slitting wedge-shaped rolls.
Low longitudinal stability of the stock before the slitting device.
Complexity of control over the entry roll guides.

The multistrand (double-strand) rolling-slitting technology is based on fundamentally new patterns of stock slitting: slitting by means of controlled break, shear, mutual shift in sloping passes etc.

The double-strand rolling-slitting technology consist in forming the stock, composed of several billets with cross sections of any shape, coupled along one of the axles by a relatively thick bridge, in multi-groove passes of the working rolls. Slitting of this multistrand stock is carried out immediately in the slitting pass, while the ridges of this pass ensure the double-strand stock centering.

Application of the double-strand rolling-slitting technology requires:

Special roll pass design.
Special equipment roll guides and transfer devices.
Special double-strand devices for thermo-strengthening the rebars.

In comparison with the "slitting-process" the MRS technology has a number of indisputable advantages:

No burrs at the point of the stock slitting, which ensures a better finished surface condition
A higher durability of the forming pass.
A higher specific durability of the working rolls.
No additional devices for the stock slitting and therefore no infrastructure for their maintenance.

The MRS technology allows:

to use billets with enlarged sections for the production of the existing rolled stock range.
to increase the rolling mill yield by 20 - 80%.
to reduce the energy consumption for heating and rolling.
to increase the existing range of products towards the production of light cross sections.

The MRS technology has successfully passed a number of patent, laboratory and industrial tests on the roughing-billet and section mills of different types.

Double-strand rolling-slitting technology was implemented:

in 1995, light-section mill 250-3 of KRSIMMW "Кrivorozhstal" - for reinforcing steel #10 rolling.
in 1996, light-section mill 250-4 of KRSIMMW 'Кrivorozhstal" - for reinforcing steel #12 rolling.
in 1998, light-section mill 250-1 of KRSIMMW "Кrivorozhstal" - for reinforcing steel #8 rolling.
in 1999, linear mill 280 of JSC "Enakievo Metallurgical Works" - for reinforcing steel #10 rolling.
in 2005, 350-2 mill of Makeevka Metallurgical Works.

The author's rights of the technology creators are confirmed by more than 40 inventor's certificates and patents of the USSR, Ukraine, Great Britain and Canada.

More than 30 inventor's certificates and patents are implemented on rolling mills of Donetsk Metallurgical Works, Makeevka Metallurgical Works, "Krivorozhstal" and JSC "Enakievo Metallurgical Works".

At present RPC "Donix" is developing the three-strand rolling-slitting (TRS) technology for continuous casting processing with the separation of the segregation zone into the middle strand.

The MRS technology can be efficiently used on section mills, first of all for the production of die-rolled sections and rounds.

The technology is implemented at:

Integrated Metallurgical Works "Krivorozhstal"

Donetsk Metallurgical Works

Enakievo Metallurgical Works

Makeevka Metallurgical Works