JP2006118026A - Material for surface coating and roll for heat treatment furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a material for surface coating having excellent durability and carburization resistance, and to provide a roll for a heat treatment furnace having excellent carburization resistance. <P>SOLUTION: The surface of a member used at the inside of a heat treatment furnace is coated with a material for surface coating having a composition comprising, by mass, >13 to 30% Al, and the balance substantially Ni. In this way, the carburization resistance and durability of the member improve. Particularly, by using a roll made of carbon obtained by inserting a sleeve made of carbon into a metal core material in which a film for carburization prevention is formed on the surface using the material for surface coating having the above composition as the one for a heat treatment furnace, the durability of the roll improves, and the productivity in a heat treatment furnace operation remarkably improves. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  TECHNICAL FIELD The present invention relates to a surface coating material for coating a member surface to improve carburization resistance, and particularly suitable for improving the carburization resistance of a heat treatment furnace roll used in a heat treatment furnace for heat treating various metal plates. The present invention relates to a coating material and a heat treatment furnace roll which is surface-coated using the coating material.

  Conventionally, when heat-treating a metal plate such as a steel plate in a heat treatment furnace, a roll for carrying in, transporting and unloading is installed in the heat treatment furnace, and the metal plate is moved on the roll to perform heat treatment on the metal plate. ing. As the roll for the heat treatment furnace, for example, a heat-resistant cast steel roll whose surface is sprayed with a ceramic such as aluminum oxide or zirconium oxide has been used. However, the heat-resistant cast steel roll sprayed with ceramic on the surface is liable to adhere to the roll surface due to the metal plate that is the material to be treated during heat treatment, and the adhered foreign material pushes the metal plate that is the material to be treated. There was a problem that wrinkles, rubbing wrinkles, etc. were generated and the product value was remarkably lowered.

Recently, a heat treatment furnace roll (hereinafter also referred to as a carbon roll) in which a carbon sleeve is fitted to an iron core (metal core material) has been used to deal with such problems. This carbon roll is said to be excellent in heat resistance and foreign matter adhesion.
However, in this carbon roll, when the temperature becomes high during use, a carburization phenomenon occurs in which carbon enters the iron core (metal core material) from the carbon sleeve, and the strength of the iron core (metal core material) is lowered and bent. That is, distortion occurs. Therefore, it is difficult to secure a predetermined amount of clearance between the iron core (metal core material) and the sleeve, the roll is easily damaged, and the durability is insufficient. If an accident that the roll breaks in the heat treatment furnace occurs, a sudden work of stopping the line, extracting the damaged roll, and replacing it with a new roll is required, and the productivity is significantly reduced. For this reason, the roll for heat processing furnaces excellent in durability has been desired.

In response to such a demand, for example, Patent Document 1 proposes a carbon roll in which a polycarbosilane film having an average molecular weight of 500 to 2500 is formed on the surface of a metal core (iron core) by surface treatment by baking. ing. According to the technique described in Patent Document 1, the diffusion of carbon from the carbon sleeve to the metal core (iron core) can be prevented by the polycarbosilane film formed on the surface of the metal core (iron core).
Japanese Patent Laid-Open No. 11-50136

However, in the roll for a heat treatment furnace manufactured by the technique described in Patent Document 1, the film component formed on the surface of the metal core (iron core) sublimates and the film disappears early, so that the durability is insufficient. However, there is a problem that long-term use becomes difficult.
The present invention advantageously solves the problems of the prior art, covers the surface of a member such as a roll for a heat treatment furnace used in a heat treatment furnace, and improves the carburization resistance of the member over a long period of time. An object of the present invention is to provide a surface coating material excellent in heat resistance and a heat treatment furnace roll excellent in carburization resistance.

  In order to achieve the above-described problems, the present inventors have made Ni as a material that covers the surface of a member used in a heat treatment furnace and has a heat resistance and does not easily form carbides in a carburizing heat treatment furnace in a reducing atmosphere. Attention was paid to various factors affecting carburization resistance. As a result, the present inventors have found that adding 13 to 30 mass% Al to Ni provides sufficient carburization resistance and heat resistance as a surface coating material for heat treatment furnace members.

The present invention has been completed based on the above findings and further studies. That is, the gist of the present invention is as follows.
(1) A material for surface coating that covers the surface of a member used in a heat treatment furnace, comprising Al in excess of 13 mass% and not more than 30 mass%, with the balance being substantially composed of Ni Surface coating material with excellent carburization resistance.
(2) A roll for a heat treatment furnace formed by fitting a carbon sleeve to a metal core, wherein the metal core contains Al in a surface of more than 13 mass% and not more than 30 mass%, and the balance is substantially made of Ni. A roll for a heat treatment furnace excellent in carburization resistance, characterized by having a film of the composition

  According to the present invention, the carburization resistance and durability of a member such as a roll for a heat treatment furnace used in a heat treatment furnace are improved, so that the member can be used for a long period of time, and sudden work such as line stop and roll replacement is possible. As a result, the productivity of the heat treatment furnace is improved and a remarkable industrial effect is achieved.

The surface coating material of the present invention is a material that covers the surface of a member such as a roll used in a heat treatment furnace, prevents carburization, and improves the carburization resistance of the member. The surface coating material of the present invention preferably covers the surface of a member by spraying, vapor deposition, plating, or the like to prevent carburization from the outside to the member. In addition, the coating method to a member is not limited to these methods.
The material for surface coating of the present invention is an Al-Ni alloy, and contains Al in excess of 13 mass% to 30 mass%, with the balance being substantially Ni. Ni has a high melting point and excellent heat resistance, but by itself, the carburizing gas diffuses and penetrates and is oxidized and peeled off by a small amount of oxygen in the heat treatment furnace. It is inferior in property and cannot prevent carburization of the member. Therefore, in the present invention, Ni is contained in an amount of more than 13 mass% and not more than 30 mass% to improve carburization resistance. By adding Al to Ni, a dense oxide film is formed on the surface of the film by a small amount of oxygen in the heat treatment furnace when it is formed into a film. This oxide film can prevent the carburizing gas from entering the inside of the film and also prevent the film from being oxidized, thereby improving the carburization resistance of the film.

When the Al content is 13 mass% or less, it is difficult to form a dense oxide film, and the exothermic reaction between Ni and Al is insufficient, resulting in a decrease in metallurgical bonding force and adhesion to the substrate (film adhesion). ) Decreases. On the other hand, when Al is contained exceeding 30 mass%, the toughness of the film is lowered. For this reason, Al content was limited to more than 13mass% and below 30mass%. In addition, Preferably it is 15-20 mass%.
The balance other than the above components is substantially Ni. Here, “substantially Ni” means that an impurity element is inevitably included in addition to Ni. As unavoidable impurities, Fe: 1 mass% or less, Co: 1 mass% or less, Mn: 0.5 mass% or less, Si: 0.5 mass% or less, Cr: 1 mass% or less, Ti: 0.5 mass% or less, C: 0.8 mass% The following are acceptable.

  Further, in the present invention, the surface coating material having the above composition is applied to a heat treatment furnace roll. A heat treatment furnace roll 1 to which the surface coating material of the present invention is applied is a heat treatment furnace roll formed by fitting a carbon sleeve 2 to a metal core material 3, and has the above composition on the surface of the metal core material 3. A carburizing prevention coating 4 made of the surface coating material is formed. FIG. 1 schematically shows a cross-sectional structure of the heat treatment furnace roll of the present invention.

The metal core material used in the roll for heat treatment furnace of the present invention is not particularly limited as long as it is a metal material having a predetermined strength. However, the core material made of steel such as austenitic heat-resistant cast steel having excellent heat resistance. (Iron core) is more preferable for a heat treatment furnace.
In the present invention, as described above, a film having a composition containing Al of more than 13 mass% and not more than 30 mass% and substantially consisting of Ni is formed on the surface of the metal core. The method for forming the film is not particularly limited, but it is preferable to use conventional means such as thermal spraying, vapor deposition, plating, etc. Among them, it is preferable to use thermal spraying from the viewpoint of workability of film formation and film formation speed. As the thermal spraying, vapor deposition, and plating methods, plasma spraying, flame spraying, explosive spraying, arc spraying, PVD, CVD, or electroplating can be applied to any known method, and there is no particular limitation. What is necessary is just to adjust conditions so that a desired film thickness can be ensured.

In addition, although the film thickness of the film to be formed varies depending on the film forming method, for example, in the case of thermal spraying, it is preferably 20 to 100 μm. If the film thickness is less than 20 μm, the expected effect cannot be expected. On the other hand, if the thickness exceeds 1000 μm, peeling occurs due to hot internal stress. For this reason, it is more preferable that the film thickness of the film formed on the surface of the metal core is 50 to 200 μm.
In the present invention, a carbon sleeve is fitted to the metal core material on which the coating film having the composition described above is formed to form a heat treatment furnace roll. Thereby, the carburization resistance of the roll for heat treatment furnace improves, and the durability as a roll for heat treatment furnace is remarkably improved.

  Hereinafter, the present invention will be described in more detail based on examples.

A surface coating material having the composition shown in Table 1 was sprayed on the surface of the heat-resistant cast steel metal core (iron core) to form a film having a thickness shown in Table 1. A cylindrical carbon sleeve was fitted into this metal core material to obtain a heat treatment furnace roll of the present invention. The case where no film was formed on the surface of the metal core material was taken as a comparative example (roll No. 11).
The obtained roll was incorporated into an annealing furnace for thin steel sheets and used for one year. In addition, the atmosphere of the annealing furnace for thin steel plates was temperature: 1000 ° C. and atmosphere: nitrogen gas. After use, a specimen was taken from the roll cross section, and the carburization depth was determined by structural observation and elemental analysis by EPMA. Moreover, the amount of distortion (bending amount) generated in the metal core material was measured on the lathe using a dial gauge. The amount of strain was evaluated as ○: less than 1 mm per meter, Δ: 1 mm or more and less than 2 mm per meter, and x: 2 mm or more per meter.

  The obtained results are shown in Table 1.

  In all of the examples of the present invention, carburization is not observed on the surface of the metal core (iron core), and distortion of the metal core (iron core) is hardly generated. On the other hand, in the comparative example that is outside the scope of the present invention, carburization occurs from the surface to a depth of 3.0 mm, and the iron core distortion also occurs 2 mm or more per meter, which cannot be used as a heat treatment furnace roll any more. It was. The example of the present invention in which the film thickness falls outside the preferred range of the present invention has low carburization resistance and leads to carburization.

It is sectional drawing of the roll for heat processing furnaces of this invention.

Explanation of symbols

1 Heat Treatment Furnace Roll 2 Carbon Sleeve 3 Metal Core 4 Carburizing Prevention Film

Claims (2)

  A surface coating material for covering the surface of a member used in a heat treatment furnace, comprising Al in excess of 13 mass% to 30 mass% and having a composition consisting essentially of Ni. Surface coating material with excellent carburizing properties.   A roll for heat treatment furnace in which a carbon sleeve is fitted to a metal core material, and the metal core material has Al on its surface more than 13 mass% and not more than 30 mass%, and the balance is substantially made of Ni. A roll for a heat treatment furnace excellent in carburization resistance, characterized by having a film having a composition.