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WALZEN IRLE Materials - Overview
Food Industry
The following listed roll materials represent the special WALZEN IRLE material index of rolls designed for the Food-Industry.
Regarding stability, surface hardness and wear resistance properties all following roll materials can be adjusted to the customers specific mill conditions.
WALZEN IRLE Material "OCC®"
Microstructure and main properties
Compound poured OCC® rolls consist of a hardened layer of white cast graphite free cementite (ledeburit) and the metallic matrix. The surface hardness and wear resistance is defined by the amount of cemintite in the matrix and the formation of the metallic matrix.
A perlitic, bainitic or martensitic matrix can be obtained using special alloying elements. An increase in the hardness and wear resistance will cause a decrease in the thermal and mechanical capability.
The quality grade OCC®30 describes the proportion of cementite in the microstructure.
The thickness of the wear resistant coating on the compound rolls can be adjusted according to the degree of utilization . The core and journal material of the compound roll can consist of grey cast iron (G) or nodular iron (S).
The strength and bending strength of the roll can be adjusted according to the different operating conditions.
WALZEN IRLE Material "OCE®"
Microstructure and main properties
The essential feature of the OCE® roll is a microstructure which is aimed from the roll surface towards the roll core.
The microstructural components cementite and graphite are arranged in a cellular way vertically to the roll surface.
The graphite proportion continuously increases from the barrel surface to the barrel core and the proportion of free cementite decreases in the same direction.
The metallic basic matrix of OCE® rolls is formed perlitic or bainitic in the hardness range of 340-540 HV. Due to the special matrix and the continuous decrease of hardness from the barrel surface towards the core, OCE® rolls with a surface hardness of up to about 540 HV are suitable for indenting of deep calibres.
OCE® rolls of up to 540 HV are mainly applied as single poured rolls.
In case they are exposed to high wear and mechanical or thermal loads they can also be manufactured as statically poured or centrifugally cast compound rolls with grey cast iron- or nodular iron cores.
WALZEN IRLE Material "OCR®"
Microstructure and main properties
The microstructure of the wear resistant chrome cast alloys consists of chromium rich eutectic carbides of the M7C3 or M23C6 type, in a matrix of pearlite or martensite with finely dispersed secondary carbides.
Due to the special structures of the CR-carbides the chrome cast materials have far superior mechanical strength and higher ductility in comparison to other carbide materials.
Further positive properties are high pressure and thermal resistance. The amount of Cr-carbides in the OCR®-material is variable in a wide range. Increasing amounts of Cr-carbides increase the wear resistance and on the other hand ductility and mechanical strength decreases. The quality grade OCR®25 describes the proportional amount of eutectic Cr-carbides in the microstructure. By using heat treatment and depending upon the amount of Cr-carbides, surface hardness of up to 700 HV can be reached. The decrease in hardness in the usable shell layer is very low.
WALZEN IRLE Material "ORT®"
Microstructure and main properties
In ORT® rolls the graphite has a nodular function which causes significant increase of the material in mechanical strength and ductility compared to lamella cast iron types. Apart from the nodular graphite ORT® rolls can contain different amounts of cementite within the matrix depending on the required wear resistance. The amount of cementite decreases continuously from the roll surface to the barrel core and with a simultaneously increasing amount of nodular graphite.
The metallic matrix of the ORT® rolls is formed perlitically within a hardness range of 380 - 480 HV.
Using a special melting procedure a finely ground matrix is achieved for the ORT®-rolls, whereby the stability and toughness are additionally increased. ORT®-rolls prove to have a very even wear over the entire roll barrel. Hereby pitting or micro indentations to the roll barrel or larger indentations and cracks on the roll edges are largely avoided.
Due to the high elasticity modules ORT® haa good bending strength.
Depending upon the mechanical loads ORT® rolls can be delivered in the following specifications:
- as single poured rolls with cast journals
- as multi-part roll, by which the wear resistant ORT®-shell is fixed to a forged steel axis or two forged steel journals.
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