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Mainstrip Twin Roll Casting Design Features

Mainstrip Twin Roll Casting

Mainstrip

Efficient Twin Roll Casting
Low Cost, Low Energy, Low CO2

Casting Floor

The Mainstrip concept ensures optimal availability of the plant. It thus uses two casting heads, which allow quick change of the casting heads and maximum usage of the inline rolling mill and discharge, the expensive part of an installation.

Mainstrip Design Features, Casting Floor

Each casting head is a fully autonomous unit, which can move from the preparation area to the casting position. The cover can be displaced automatically to the side, to give access to the various machine groups.

Quick Change Casting Head

The maximum realistic potential output depends on the cast strip thickness and roll diameter.

Mainstrip Design Features, Quick Change Casting Head

Each independent casting head consists of the complete equipment for casting the strip. To have high availability of the equipment, it is a must to have this quick change solution. Mainstrip can replace the unit like a tundish change. Whilst one casting head is in operation, the second unit can be cleaned and if needed, the rolls are resurfaced or changed at the preparation area. A quick change casting head contains the casting rolls, side dams with adjustment and changing device on each side, roll cleaning, casting rolls and positioning, drives, primary and secondary inertisation containment and the required control and measuring equipment.

Metal Delivery

Substantial development has gone into the development of metal delivery. 

1:1 Water Model

Mainstrip Design Features, Metal Delivery

For this, a 1:1 water model has been built and tested. In parallel, serious CFD modelling has been carried out at the Lucerne University of Applied Science. Main and the university were supported by the Swiss government with 2 KTI / CTI projects (Commission for Technology and Innovation).

Tube Nozzle During Filling

Mainstrip Design Features, Tube Nozzle During Filling.jpg

Various solutions for metal delivery have been developed to ensure a flat bath. The tube nozzle has been created, where the liquid metal is supplied from the centre outwards in the horizontal tube on the lower side and distributed evenly upwards over the width towards the start of the crystallization front and towards the side dams. This solution offers a practically flat meniscus surface. The picture shows the simulation of filling the SEN after 0,98s.

Ball Type Submerged Entry

Mainstrip Design Features, Ball Type Submerged Entry

Substantial CFD water modelling and hot testing have been carried out with a ball-type submerged entry nozzle, to have an efficient, low-cost solution for a width of up to 1300 mm.

Casting Roll

An important Mainstrip innovative invention is the casting roll with the static axle, which is positioned in the casting frame with self-sealing water plates. The sleeve is tensioned in position and is driven by the torque motor, sitting on the axle.

Mainstrip Design Features, Casting Roll

The profile of the casting roll is controlled by Active Profile Control APC-elements, supported on the static axle.

The design contains a future overwidth configuration of up to 3 m and over. 

Depending on quality requirements and productivity, the respective surface is selected. Cleaning and surface preparation (including machining of coat) is done in the casting head preparation area. The rolls with the automatically removed cover, are freely accessible and can be turned, surfaced and machined, driven by the onboard drives.

For more information please contact Main Switzerland.

Roll Cleaning

In casting position, it is vital to keep the roll surface at constant conditions. For this, continuous roll surface cleaning and monitoring are important. It further is to be ensured, that the surface of the rolls enters into the top sealed inert zone, without any contamination. The picture shows the Mainstrip solution, cleaning the roll surface with scratchers, brushes, laser-, and gas barriers. It also includes roll crack monitoring and surface and cracks detection.

For more information please contact Main Switzerland.

Side Dams

Mainstrip Design Features, Side Dams

The Mainstrip concept allows changing the side dam below the casting floor. In this way, the casting floor is free of side dam manipulators or robots, which could be damaged by steel splashes and male operation. 

Side Dam Configurations

Various side dam configurations have been developed, from the established Bor-Nitride solution to reusable side dams in order to keep operating costs down.

Long casting sequences of 8—20 h are more than desirable, to keep the cost on tundish-, metal delivery-, roll surface-, side dams- and inline rolling mill rolls down. For the side dam plates, therefore, recuperable side dams must remain a possibility. Our target is to use a combination of high-temperature alloy material, working against the roll neck and coated refractory inserts on the liquid steel side. The goal is to minimise wear against the roll neck and achieve continuous, consistent operation with the long casting sequences.

For more information please contact Main Switzerland.

Side Dam Oscillation

Mainstrip Design Features, Side Dam Oscillation

Oscillation of side dams can improve the strip edges. In our solution, a slight movement in the direction of the roll circumference and back is simply achieved. A small oscillation drive moves the side dams. With these measures, the strip edge can be improved and possible burrs, respectively tears of the edges, can be avoided.

Inertisation

Essential is a complete sealing of the metal delivery and liquid surface area. The shielded volume is fed by Argon- or an Argon Nitrogen mixture, which also allows influencing the heat extraction of the rolls. The Mainstrip concept ensures, that the rolls are kept inertized on the complete circumference.

From the point, where the formed strip is leaving the casting rolls, called the kissing point, it is guided through the inertisation room, to the horizontally driven insulated pinch rolls, and further to the front pinch of the first inline 4-high rolling mill stand. The horizontal part of the inertisation box can be exchanged sideways, by an induction reheating / respective cooling box.

For more information please contact Main Switzerland.

Inline Rolling

For a wider range and the possibility to change working rolls, two inline 4-high rolling mill stands may be used.

Mainstrip Design Features, Inertisation

Casting head with inertisation room and horizontal position, with hot transport pinch.

Thermomechanical Rolling and Discharge

The cast strip is led by the inline pinch roll to the first rolling mill stand. After the rolling mill stand(s) the respective water strip cooling and the guiding rolls to the edgers, shear and the two coilers forming the plant to the end of the process.

Existing twin roll casting machines, typically employ a single inline 4-high rolling mill stand. Depending on the product- and operating cycle range, a double 4-high rolling mill stand will give advantages in terms of the temperature profile, product thickness, rolling mill roll change during casting and costs.

Mainstrip Design Features, Inline Rolling

Thermomechanical treatment

Depending on the configuration, holding, heating, or cooling may be applied. Setting the inline rolling mill stand(s) in its optimum position and achieving an appropriate cooling strategy, ensures the correct thermo-mechanical treatment.

For mor information please contact Main Switzerland.

Plant Layout

The layout section of a Mainstrip plant shows, that the length from the ladle turret to the discharge end in this case is around 90m.

The section shows a Mainstrip casting installation with two inline rolling mill stands.

A green field mini mill Mainstrip plant with a small workforce requirement has been worked out.

The layout contains a common Main control room for the EAF, LF, VD / VOD and the Mainstrip Caster.

For mor information please contact Main Switzerland.

Mainstrip Design Features, Plant Layout