Valmet Paper Machinery Inc.

Valmet Oy

Veijo Miihkinen

Jukka Salo

Jorma Leino

Jorma Laapotti

Antti I Ilmarinen

Ari Telama

Ari Talama

The present invention concerns a roll used in the manufacture of paper, for example a central roll in a press or a calender roll, with which the web is in direct contact and from which the web is detached. A coating has been formed onto a cylinder mantle of the roll, the coating being partly made of metal and also including a ceramic material. An outer face of the coating is formed of carbide-rich areas and of matrix areas placed between the carbide-rich areas. The present invention also concerns a method for manufacturing such a roll.

Method for manufacturing a roll directly contacting a web

Roll for directly contacting a web

A synthetic press roll for use in paper machines includes a cylindrical mantle to which a surface layer is applied, the surface layer comprising a mixture of a first powder of metallic material and a second powder of an inorganic material. The metallic material of the first powder includes copper, bronze, stainless steel, nickel, chromium and/or a titanium alloy. The inorganic material of the second powder comprises quartz, feldspar, Al.sub.2 O.sub.3, ZrO.sub.2, TiO.sub.2, TiC, SiC, MgO, Si.sub.3 N.sub.4, Cr.sub.2 O.sub.3, WC, NbC, VC, Cr.sub.7 C.sub.3, or other corresponding ceramic material, or mixtures of the same. The surface layer may be produced by thermal spraying, casting, by winding a sintered or rolled band of the mixture around the mantle, or by forming a flexible mat pre-coating in which the desired mixture is bound by a binder, such as PTFE, and by fixing the precoating to the roll mantle by melting it by means of induction or laser heating. A press roll in accordance with the invention provides a controlled detachment of the paper web from the roll and is more resistant to variations in temperature and to mechanical strains than conventional press rolls.

Synthetic press roll for paper machines and method for manufacturing the

Control of detachment of a web from a roll, such as a paper web from a press roll in a paper machine, in particular a so-called closed press section provided with a smooth-faced press roll. The temperature of the surface of the smooth-faced press roll is adjusted, so that adhesion between the roll surface and the paper web to be detached is influenced or affected. Thereby, the detaching angle and/or the detaching tension of the paper web, is set within an optimal range. Temperature profile of the smooth-faced press roll in the axial direction thereof, can also be adjusted with a view to controlling the detaching of the web.

Control of detachment of a paper web from a roll using heat

A press roll for a paper machine includes a cylindrical mantle formed of metal providing the roll with mechanical strength. A coating is provided on the roll mantle, the coating being partially or entirely metallic. The metallic coating is preferably formed of stainless steel containing chromium and provides for a controlled detachment of the paper web from the roll coating as well as durability, i.e., ability to withstand various strains to which the roll surface is subjected. In addition to the metallic component, the roll coating may also include a component or components of ceramic material.

Press roll

A press roll for a paper machine suitable for use as a substitute for a granite roll includes an inner roll body having a metallic cylindrical exterior to which a coating is applied formed either only of a metallic component or of a mixture of metallic and ceramic components. Where the coating material includes only a metallic component, such a metallic component is chosen so that a separate ceramic component precipitates during the alloying of the material. The coating material is formulated to obtain a surface energy and polarity component thereof which provide the roll surface with suitable web release properties for particular pulp qualities.

Press roll for paper making machines

A press roll for a paper machine includes a cylindrical mantle formed of metal providing the roll with mechanical strength. A coating is provided on the roll mantle, the coating being partially or entirely metallic. The metallic coating is preferably formed of stainless steel containing chromium and provides for a controlled detachment of the paper web from the roll coating as well as durability, i.e., ability to withstand various strains to which the roll surface is subjected. In addition to the metallic component, the roll coating may also include a component or components of ceramic material. A method for manufacturing such a press roll includes the application of the coating to the surface of the cylindrical mantle by band welding wherein the welding admixture band is preferably in the range of between about 30 to 150 mm wide and about 0.5 mm thick. In the band welding, a ceramic admixture may be included in the welding band or, alternatively, the ceramic admixture may be alloyed into the molten weld by means of a shield powder.

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Jyvaskyla, Finland

Veijo Miihkinen