KR20060123304A - Edge-provided tool and method for the manufacture thereof - Google Patents

Abstract

The invention relates to an edge- provided tool, such as a doctor blade, for use as wiping tool in the production of pulp and/or paper in different stages of the production process. It consists of an edge-provided strip of steel, the edge portion of which has been provided with a wear-resistant coating applied by means of laser technique, so that metallurgical binding is present between said coating and the steel strip, whereby a level of surface hardness of more than 850 HV being attained. Thereby, wear-resistant doctor blades having a long service life have been obtained.

Description

EDGE-PROVIDED TOOL AND METHOD FOR THE MANUFACTURE THEREOF}

Scrapers or cleaning blades, so-called "doctor blades", are widely used in the paper and pulp industry for a variety of purposes, but in most cases they are used to remove raw materials or debris from the surface of rotary rollers. Has the function of cleaning or removing. This doctor blade is used for the purpose of scraping the cylinder surface to separate the paper web from the hard and dry cylinder.

Paper pulp contains fillers for abrasion of doctor blades such as silicon dioxide, great particles and paper fibers, and wear occurs fairly evenly along the edges, and the wear rate of these blades is greater than the corrosion rate. . In addition, Dr. Blade is recognized as a consumable with a very short lifespan, which is usually less than one day. In many cases, they should be replaced immediately after about 5 hours of use. Usually the doctor blade is not regrind and discarded after consumption.

Although there are various principles of paper mills for the use of doctor blades, doctor blades are generally wear-in at first to form blades. Once the doctor blade is formed, its wear is relatively even. Proper "in-situ" -grinding-in is believed to affect the quality of the paper produced. If doctorblade is used later in the paper production process, it is a very important factor because doctorblade affects the quality and surface structure of the paper. The doctor blade may vary in length from about 1 to 10 m.

Therefore, since the doctor blade is exposed to a wide range of wear, various techniques are used, such as adding an antiwear agent to the portion where the blade contacts the cylinder to increase the service life. As an example of reinforcing the top or blade surface of a blade, ceramic hard coating is currently used as a practical solution to reduce the wear of the blade. Such ceramic coatings are usually formed on doctor blades made of hardened and annealed carbon steel, which can be formed by thermal spraying, such as plasma spraying or plasma deposition.

Examples of techniques for forming such wear resistant coatings on doctor blade type cleaning or scraper blades can be found in GB-1-978 988, GB-A-1 289 609 and BG-A-2 130 924. The purpose of all of these known arts is to provide a wear resistant coating on the portion of the blade in contact with the surface of the rotary cylinder.

According to the known art, in order to affect the quality of paper by improving the characteristics and service life of a tool provided with a blade, a thermal (hot) thermal spraying method by HVOF ("high-speed oxygen fuel") is used among various methods. In this method, the additive is sintered and so-called diffusion bonds at about 1000 ° C. Problems of this coating method include cracks, pores, weak bonding, adhesion problems, and the like. Current spray material Al ₂ O ₃ Ceramics, such as this, are used.

The object of the present invention in view of such a situation is to provide a tool provided with a blade such as a doctor blade provided with a coating having improved adhesion than those known to date. At the same time, the deformation of the tool, which can otherwise occur, should be minimized, and the realization of the desired fine evenness of the finished paper product and the absence of scratches should be possible. Furthermore, the influence of the supply of energy or heat to the substrate during the surface treatment should be minimized as much as possible.

It is a further object of the present invention to provide basically a doctorblade-type scraper and / or cleaning blade which provides a paper with a long service life and a smooth and fine surface without scratches and other defects in the manufacture of the paper.

This and further objects are achieved by the provision of a tool having the features described in the independent claims. Preferred embodiments of the invention are described in the dependent claims.

The invention will be explained in more detail with reference to the accompanying drawings.

1 is a perspective view of a doctor blade used directly connected to a roller for the removal of paper pulp during paper production.

2 is an explanatory view of a doctor blade treated with a blade according to the present invention.

Figure 3 is an explanatory view of the coated doctor blade blade according to the present invention from the side.

Figure 4 is an explanatory view of the laser-impregnated doctor blade blade according to the present invention from the side.

5 is an explanatory view showing a laser coating of the doctor blade according to the present invention.

Accordingly, the present invention relates to a tool with a blade and a method of manufacturing the same. More specifically, the present invention is a so-called "doctor blade" and is a type of wiping, scraper and / or cleaning tool used to obtain smooth and fine paper products free from scratches and other defects in paper making, etc. Relates to the tool. In the present invention, not only a tool commonly referred to as a coater blade, but also tools referring to a general knife are included. However, to facilitate the description of the present invention, the subject of the present invention will be hereinafter referred to as "doctor blade", and the concept includes other names.

Thus, the doctor blade 1 is shown in FIG. 1, which is in contact with the roller 2, for example, to remove pulp from the roller 2. As an example of the preferred material known to be able to coat the blade of the material with laser technology according to the invention, a grade of steel having a hardness of at least 450 HV or higher has been selected. Examples of such steels are 0.8 to 1.2% C (by weight%), preferably about 1% C, 0.20 to 0.35% Si, 0.35 to 0.50% Mn, up to 0.02% P, up to 0.01% S And carbon steels having a composition of 0.5% or less of iron as a residual and other additive elements on the periodic table.

In Figures 2 and 3 a steel strip 3 is shown, on which the blade 4 is formed with a coating 4 by laser technology in accordance with the invention. Because of this, the wear resistance increases considerably. The coating consists of, for example, aluminum oxide, stellite (eg stellite 12). Such laser technology is well known to those skilled in the art and is shown in FIG. 5. In laser coating, atomic bonds (also called metallurgical bonds) to steel substrates, which are a feature of the present invention, are obtained, which is shown in FIG. 3.

4 shows a cross section of the doctor blade, which is coated with TiC or the like according to the present invention. Laser impregnation technique is disclosed in patent WO 99/56906. "5" represents the steel band and "6" represents the impregnation by laser technology. Also in this figure the penetration of particles / carbide into the steel substrate has been visualized for the carbides, so that the boundary between the two is significantly removed. The coating consists of, for example, aluminum oxide or stellite, as shown in FIGS. 2 and 3, and the impregnation consists of suitable carbides and / or nitrides.

According to Fig. 5, the surface strengthening portion of the blade portion formed in the strip-shaped doctor blade is provided in the following manner, that is, the coating provided by the powder material 7 is applied to the base material of the doctor blade by laser technology. The powder was provided to the blades with a heat supply to fusion, resulting in the formation of atomic and metallurgical bonds. The heat supply is made by a laser gun 8 and a coating 9 is provided on the substrate. The material supplied to the flowable powder 7 is suitably comprised of refractory materials, such as aluminum oxide. Alternatively, a material such as stellite may be used. An important point with respect to the coating 9 provided on the doctor blade is that the material can be quenched, thereby obtaining the desired microstructure. This microstructure is characterized by toughness and hardness, and more particularly, hardness values corresponding to 850-1300 HV. In this way, high bearing strength is obtained at the same time in the surface layer, while at the same time low friction requirements and desired corrosion resistance are satisfied.

As mentioned above, the coating may consist essentially of aluminum oxide or stellite. However, the coating may also comprise or consist of metal oxides, metal silicates, metal carbides, metal borides, metal nitrides and mixtures thereof. Particularly preferred ceramic materials are selected from aluminum oxide, chromium oxide, zirconium oxide, tungsten carbide, chromium carbide, zirconium carbide, tantalum carbide, titanium carbide, titanium nitride, niobium carbide, and borides.

As mentioned above, laser impregnation occurs by the addition of carbides and nitrides such as TiC, NbC and TiN to the surface of the base material during laser treatment. The particles are sprayed and added under high gas pressure, and at the same time the laser beam locally dissolves the surface layer of the material, thereby allowing the wear resistant particles to penetrate into the substrate. Furthermore, laser coating can be carried out several times, in which case multiple layers are obtained. The strip then has a very strong wear resistant surface.

The thickness of the steel strip is the general thickness of the doctor blade used in the paper industry, with 0.2 to 3 mm and 0.305 to 1.27 mm being suitable. The thickness of the coating or impregnation may be 5 to 15% of the strip thickness.

Claims (12)

Especially as doctor blades or coater blades used as wiping, scraper, and / or cleaning tools in the production of paper pulp and / or paper at various stages of the production process. In the doctor blade or coater blade made of the provided steel, the blade portion is provided with a wear-resistant coating, The blade portion of the blade is formed with a surface hardening coating provided by laser technology, there is a metallurgical bond between the wear-resistant coating and the steel strip, the blade portion is characterized in that the doctor blade or coater blade having a hardness of at least 1000 HV . The doctor blade or coater blade of claim 1, wherein the wear resistant coating has a surface hardness of at least 850 HV. The doctor blade or coater blade according to claim 1, wherein the blade portion of the blade has a surface layer formed by laser coating, the thickness of which is 5 to 15% of the blade thickness. The doctor blade or coater blade according to claim 1, wherein the blade portion of the blade has a surface hardened portion formed by laser coating or laser impregnation, wherein the thickness of the surface hardened portion is 5 to 15% of the blade thickness. The steel according to claim 1, wherein the steel has a composition by weight of 0.8 to 1.2% C, preferably about 1% C, 0.20 to 0.35% Si, 0.35 to 0.50% Doctor blade or cotterblade characterized by Mn, at most 0.02% P, at most 0.01% S, iron as residue and other additive elements on the periodic table of not more than 0.5%. 6. A method for producing a doctorblade or cotterblade according to any one of claims 1 to 5, wherein the material made from steel is first rolled and bladed to have a blade portion formed along one of the blades. The blade portion is provided with a surface hardening layer formed by laser technology such that a metallurgical bond is formed between the layer and the adjacent steel substrate, whereby the blade treatment is performed by forming a powdered steel substrate while forming atomic / metallurgical bonds. A method for producing a doctor blade or coater blade, characterized in that the steel substrate is subjected to laser treatment during powder supply while heat supplying to be fused. A method for producing a doctor blade or cotterblade according to any one of claims 1 to 5, wherein the material made from steel is first rolled and treated with blades to have a blade portion formed along one of the blades, The blade portion is then provided with a surface hardening layer formed by laser technology such that a metallurgical bond is formed between the layer and the adjacent steel substrate, whereby the blade treatment is applied to the laser while an atomic / metallurgical bond is formed. And impregnating and restoring the steel substrate with a laser so as to permeate the particles of the ceramic material into the surface melt. 8. A method for producing a doctor blade or cotter blade according to claim 6 or 7, wherein the powder to be supplied basically comprises aluminum oxide. 8. A method as claimed in claim 6 or 7, wherein the material supplied comprises essentially stellite. 10. The method according to any one of claims 7 to 9, wherein impregnation occurs by supplying carbide and nitride such as TiC, NbC and / or TiN to the steel substrate. The chemical composition of any of claims 6 to 10, wherein the chemical composition of the steel is 0.8% to 1.2% C, preferably about 1% C, 0.20 to 0.35% Si, 0.35 to 0.50% Mn by weight. , Up to 0.02% P, up to 0.01% S, iron as remainder, and other additive elements on the periodic table of 0.5% or less. 12. The method of claim 6, wherein the wear resistant coating has a surface hardness of at least 850 HV.

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