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Lechler Ltd
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Sheffield, S9 2TP, England
Tel: +44(0)114 249 2020
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Descaling

The most exacting demands placed on the surface quality of rolled steel material combined with a further  reduction in the amount of energy used can only be met by using state-of-the-art descaling nozzles.


For more than 60 years Lechler descaling nozzles have played an indispensable roll when it comes to efficient scale removal in hot rolling. An important mile stone was 1992 when the first Lechler Scalemaster was introduced followed shortly by its smaller version the MiniScalemaster. With this nozzle it was possible for the first time to reduce spray heights below 100mm / 4 inch. As a result the descaling water volumes could be reduced by up to 50% and so was the undesired cooling of the slab.  At the same time the impact of the descaling water was increased, a breakthrough especially in thin slab rolling.

The MicroScalemaster has been designed for applications where the spray heights are extremely low and where the space is very limited such as for rail and profile descaling in when it comes to descaling of forged products.

The  Scalemaster HP (High performance) and the MiniScalemaster HP with their optimized internal geometries and the extended stabilizer-filter units, this conventional nozzle design was taken to its maximum in terms of impact performance. A “Long Life” version was also added for highest durability.

The Lechler Scalemaster WSV (Water Stop Valve) stops the undesired flow of low pressure water onto the rolled surface when the descaling system is on bypass or standby mode. This prevents uncontrolled surface cooling, especially important in all plate mills producing pipeline and other high quality plate steel grades.

The Scalemaster Superior is the latest step in the evolution of Lechler descaling nozzles.  Right from the beginning new technologies in product development and in manufacturing have been applied such as CFD (Computational Fluid Dynamics) and MIM (Metal Injection Molding). With these innovative technologies the uniformity of the impact distribution, the impact itself and the service life could be taken to new levels. These factors contribute to open up additional potentials for product quality improvements and for reducing the energy consumption further. 

Hydro-mechanical Descaling Process

Descaling is the process of removing iron oxide scale layers from the hot steel surface by the means of high pressure water jets (see illustration 1).

The jets are formed by special descaling nozzles which are arranged on spray headers in a so called descaling box (or mill descalers) through which the * product travels. Working pressure range from 80 to 450 bar.
* Slab, strip, billet, bloom, beam blanket, etc.
 
LechlerUS-Shop:/images/02_produkte/umwelttechnik/content/Descaling_ContentC1.jpg LechlerUS-Shop:/images/02_produkte/umwelttechnik/content/Descaling_ContentC2.jpg
Illustration 1: High pressure descaling of a 
steel slab
Illustration 2: High pressure descaling of steel

LechlerUK-Shop:/images/pfeil_rechts.png Click here for more information on Descaling Nozzles


Because the interface bond between the scale and the steel surface can be very different a proper descaling nozzle setup is of major importance to reach best descaling results. The setup of a descaling system includes nozzle parameters and the nozzle arrangement. Both have a major influence on the descaling factors, hence the descaling performances (illustration 2). The impact with which the descaling water impinges on the surface is the main criteria to measure the efficiency of a descaling nozzle; this is given in N/mm2.

LechlerUK-Shop:/images/lg.gif Download Brochure "Desclaling: Nozzles and Technology