KR20110075263A - Method for extending the life of ceramic roller - Google Patents

Abstract

PURPOSE: A durability extension method of ceramic roll is provided to prevent the deposition of Al-Si system melt by preventing the inflow of Al-Si-based molten material. CONSTITUTION: A water-soluble alumina-based coating solution is manufactured(S110). The water-soluble alumina-based coating solution is coated on a ceramic roll(S120). A coated ceramic roll is dried(S130). The dried ceramic roll is sintered in a low temperature(S140). The water-soluble alumina-based coating solution is manufactured by mixing alumina-based powder, water and hydrochloric acid. An average grain size of the alumina type powder over is over than 10nm less than 40nm .

Description

Method for extending the life of ceramic rollers

The present invention relates to a method for extending the life of a ceramic roll.

Recently, in order to manufacture high-performance automotive steel sheets, automobile steel sheet processing companies are adopting a hot press forming (HPF) process.

The HPF process adopts a heat treatment process that heats the steel sheet to a certain temperature as a preliminary step for processing the steel sheet at a high temperature. The heat treatment process mainly adopts the roller-heath kiln (RHK) method, which is highly thermally efficient while maintaining continuity of work. have. The rollers used for conveying the steel plate in the RHK line are made of metal or ceramic materials. However, since the RHK temperature is 900 ℃ or higher, the rollers made of ceramic materials are more stable than the metal materials. have. Ceramic rollers adopted by RHK line can be made of various materials, but in general, in terms of cost and thermal shock stability, mullite materials having a relative density of 88-92% and silicon carbide or dense molten alumina Mainly adopt ceramic roller.

In the HPF process, the steel sheet is preliminarily heated to a high temperature of 900 ° C. or higher, so that surface oxidation occurs at a high temperature on a general steel surface, and Fe-based oxide remains on the surface of the steel sheet. There is a risk of damaging the surface of the press mold when subjected to subsequent pressing processes. Therefore, in the case of the RHK line, a lot of efforts are made to maintain the atmosphere in the RHK without oxidation to prevent oxidation of the steel sheet conveyed for heat treatment, but complete surface oxidation prevention is difficult. Therefore, in order to prevent oxidation of the steel sheet surface more actively, a steel sheet having an Al-Si-based plating layer is often adopted as a material for processing. In the case of Al-Si plated steel sheet, it forms a liquid phase during the RHK process and protects the surface of the steel sheet from oxidation while forming a liquid phase. As a steel sheet for automobile, it has the advantage of guaranteeing long-term weather resistance. Recently, many Al-Si plated steel sheet is adopted as the automotive steel sheet material for HPF.

However, Al-Si-based plated steel sheet having such advantages has a low melting point Al-Si layer plated on the surface of the steel sheet during the initial high temperature heating in the RHK heat treatment process, and the liquid phase is present on the surface of the steel sheet. At this time, the Al-Si-based liquid generated in contact with the ceramic roller which is responsible for the transfer of the steel sheet reacts with and partially adheres to the surface of the ceramic roller. At this time, the pores of the roller surface lead to physical adsorption. The adhered Al-Si-based liquid compound adheres strongly to the surface of the ceramic roller and does not easily fall off, and as the operation continues, the amount of adhesion gradually increases, which hinders the normal transfer of the steel sheet, and as a result, prevents efficient RHK operation. Done. In the field, the operation must be stopped from time to time in order to remove Al-Si compound stuck on the surface of these ceramic rollers. Such frequent stoppages result in repeated heating and lowering of the furnace body, adding thermal fatigue to the ceramic rollers. In addition, the removal process of artificial ceramic roller surface deposits such as mechanical polishing causes stress concentration inside the ceramic roller, which causes synergy and thermal shock fatigue accumulated in the roller, thereby facilitating roller breakage, resulting in shortening of roller life and small roller replacement. This results in deterioration of productivity.

The present invention is to provide a method for extending the life of the ceramic roll.

Method for extending the life of the ceramic roll according to an embodiment of the present invention, preparing a water-soluble alumina-based coating liquid, coating the water-soluble alumina-based coating liquid on a ceramic roll, drying the coated ceramic roll and the drying Firing the ceramic roll at a low temperature.

The water-soluble alumina-based coating solution may be prepared by mixing alumina-based powder, water and hydrochloric acid. The water content may be 60 wt% or more and 90 wt% or less with respect to the alumina powder. Meanwhile, the average particle size of the alumina powder may be 10 nm or more and 40 nm or less. PH of the water-soluble alumina-based coating solution may be 3 or more and 7 or less.

In the firing step, the firing temperature may be 800 ° C. or higher.

One embodiment of the present invention provides a method for extending the life of a ceramic roll.

Hereinafter, with reference to the accompanying drawings, it will be described an embodiment of the present invention in detail so that those skilled in the art can easily carry out. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In order to clearly describe the present invention, parts irrelevant to the description are omitted in the drawings, and like reference numerals designate like parts throughout the specification.

1 is a schematic process diagram illustrating a method of extending the life of a ceramic roll according to an embodiment of the present invention.

Referring to Figure 1, the method for extending the life of the ceramic roll according to an embodiment of the present invention, the step of preparing a water-soluble alumina-based coating liquid (S110), coating the water-soluble alumina-based coating liquid on a ceramic roll (S120), Drying the coated ceramic roll (S130) and firing the dried ceramic roll at a low temperature (S140).

Preparing a water-soluble alumina coating solution ( S110 )

The water-soluble alumina-based coating solution is prepared by mixing alumina-based powder (AlO (OH)), water and hydrochloric acid. Water is added to the alumina powder and dispersed using a stirrer for a predetermined time.

The average particle size of the alumina powder is 10 nm or more and 40 nm or less, and preferably 20 nm or more and 30 nm or less. The water content may be 60 wt% or more and 90 wt% or less with respect to the alumina powder.

If the water content is less than 60wt%, it is difficult to obtain a uniform coating layer due to poor dispersion. On the other hand, if the water content exceeds 90wt%, the coating efficiency is lowered.

Hydrochloric acid (HCl) is added to increase the dispersion stability of the water-soluble alumina-based coating solution. Final pH may be 3 or more and 7 or less.

Coating a water-soluble alumina coating solution on a ceramic roll ( S120 )

The dispersion stabilized water-soluble alumina coating liquid is coated on a ceramic roll with a brush or a spray. In this case, impregnation may be used.

Drying the ceramic roll ( S130 )

The coated ceramic roll is dried at room temperature for at least 24 hours.

Ceramic rolls Plastic  step( S140 )

The dried ceramic roll is fired at a firing temperature of 800 ° C. or higher to completely remove moisture. In this case, the OH groups present in the alumina-based coating layer are completely removed and stable Al 2 O 3 is produced at high temperature.

The surface pores of the coated ceramic roll are filled with fine alumina particles. As a result, the surface of the ceramic roll becomes smooth. Such a smooth surface of the ceramic roll prevents the penetration of the Al-Si-based melt at the high temperature to prevent the deposition of the Al-Si-based melt. As a result, the lifespan of the coated ceramic rolls according to the embodiment of the present invention can be extended and the operating productivity can be increased.

Experimental Example

1000 g of alumina powder having an average particle size of about 30 nm was weighed, and 8000 g of water was added to the powder, followed by stirring for 1 hour or more using a rotary stirrer. 10 g of concentrated hydrochloric acid was added to the stirred alumina dispersion and stirred for 30 minutes or more to obtain a water-soluble alumina coating liquid in which fine alumina powder was uniformly dispersed in water.

This water-soluble alumina coating liquid was applied to a ceramic roll using a brush or a spray. The coated ceramic roller was dried at room temperature for 2 days or more, and then heated to about 110 ° C. and maintained for 1 hour or more.

A fully dried ceramic roll was charged to RHK and heat treated at about 800 ° C. for at least 5 hours to completely remove moisture while forming a firm Al 2 O 3 coating layer.

After the heat treatment of the ceramic roller was raised to the RHK working temperature, normal operation was performed. Compared with the case where the ceramic roll was not coated, the adhesion amount of the Al-Si melt was reduced by 30% or more and 40% or less.

Although the embodiments of the present invention have been described above, the scope of the present invention is not limited thereto, and various modifications and changes can be made within the scope of the claims and the detailed description of the invention and the accompanying drawings. Naturally, it is within the scope of the present invention.

1 is a schematic process diagram illustrating a method of extending the life of a ceramic roll according to an embodiment of the present invention.

Claims (6)

Preparing a water-soluble alumina coating solution, Coating the water-soluble alumina coating liquid on a ceramic roll, Drying the coated ceramic roll and Firing the dried ceramic roll at a low temperature Life extension method of the ceramic roll comprising a. In claim 1, The water-soluble alumina-based coating solution is a method of extending the life of the ceramic roll is prepared by mixing alumina-based powder, water and hydrochloric acid. 3. The method of claim 2, The water content is a method of extending the life of the ceramic roll is 60wt% or more and 90wt% or less with respect to the alumina-based powder. 3. The method of claim 2, The average particle size of the alumina-based powder is a method of extending the life of the ceramic roll 10nm to 40nm. The method according to any one of claims 1 to 4, The pH of the water-soluble alumina-based coating solution is 3 to 7 or less life of the ceramic roll. The method of claim 5, In the firing step The life extension method of the ceramic roll whose baking temperature is 800 degreeC or more.

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