JPS60141819A - Roll for heat treatment furnace - Google Patents

Abstract

PURPOSE:To manufacture a hearth roll having superior wear resistance and build-up resistance by coating the surface of a hearth roll with a cermet layer consisting of silicon carbide or nitride and a heat-resistant metal by spraying. CONSTITUTION:A coating layer is formed on the surface of a hearth roll for transferring a steel plate used in an oxidizing or reducing atmosphere at 600- 1,000 deg.C high temp. by spraying cermet consisting of 30-70% SiC or Si3N4 having <=1% metallic Si content and the balance heat-resistant metal such as Co, Cr, Mo, Ni, Al, W or Y. The cermet coating layer has high adhesive strength to the roll base, superior wear resistance and build-up resistance, so a hearth roll not damaging a steel plate to be transferred and withstanding long-period use is manufactured.

Description

Detailed Description of the Invention (Field of Application of the Invention) The present invention relates to a roll disposed in a heat treatment furnace for conveying materials to be heat treated, which is particularly suitable for heat treatment with excellent wear resistance and preventing build-up. This relates to a furnace roll (hereinafter referred to as a roll).

(Prior art) For example, when continuously annealing a steel plate, the temperature is 600 to 1000°C.
The steel sheets are passed through an oxidizing or reducing atmosphere, but the no-throttle rolls used to transport the steel sheets are used continuously for long periods of time, so their surfaces are subject to wear and conversely, the steel sheets are Adhering oxides or iron powder are deposited on the surface of the roll, forming so-called build-up. When such wear and build-up occur, the surface of the steel plate is damaged while it is being conveyed on the rolls, causing deterioration of the quality of the steel plate, and sometimes
Immediately the production operation was stopped and the surface of the thrall was ground and cleaned.

For this reason, we have changed the material of hearth rolls,
Alternatively, as described in Japanese Patent Publication No. 57-29549, attempts have been made to thermally spray coat the roll surface with zirconia, alumina, or the like.

However, many of these known attempts have not been fully satisfactory in terms of hot wear resistance or prevention of build-up.

(Objective of the Invention) The present inventors have developed a coating material with excellent wear resistance and good build-up resistance that can be applied to hearth rolls used in these oxidizing or reducing atmospheres.

After experimenting with various coating methods, we have discovered a coated roll that has excellent adhesion to the hearth roll substrate, does not peel off, and has excellent high-temperature strength, and has completed the present invention.

That is, the present invention provides a hearth roll for conveying heat-treated materials, which has a coating layer formed on its surface that has excellent wear resistance and build-up resistance when installed and used in an oxidizing or reducing atmosphere. It was made for that purpose.

(Structure and operation of the invention) The present invention will be described in detail below.

The base of the bar is made of heat-resistant steel. These substrates are coated with 30 to 70% of silicon carbide, silicon nitride, or a mixture thereof with a minimal amount of metallic silicon on the surface.
% by weight (hereinafter abbreviated as %) is formed by thermal spraying. First, the influence of silicon metal in silicon carbide, silicon nitride, or a mixture thereof will be described.

Normally, when producing silicon carbide or silicon nitride, when metal silicon is carbonized or nitrided as a starting material, unreacted metal silicon may remain. Further, when performing reduction carbonization using silicon oxide as a starting material, metallic silicon may be generated.

...-If metallic silicon is present in silicon carbide, silicon nitride, or a mixture thereof in the cermet layer of the throttle, iron powder adhering to the steel plate will adhere and accumulate at high temperatures, making it easy to cause build-up.

Iron powder was placed on a fired body of silicon carbide and silicon nitride containing different amounts of metallic silicon, and in a non-oxidizing atmosphere at 900°C,
By pressing with a half-moon roll and rubbing for 4 hours,
The adhesion and deposition properties of iron powder were investigated.

As shown in Figure 1, the results show that when the metallic silicon content is 1% or more, the adhesion area of iron powder increases rapidly, which is inappropriate, but when the metallic silicon content is 1% or less, extremely excellent build-up resistance is achieved. shows. High-purity silicon carbide and silicon nitride have poor resistance to corrosion due to the fact that it is difficult to form a reaction product with Fe + Fe oxide at temperatures below 1000°C, and because they are covalently bound substances and are stable, they have poor reactivity at high temperatures. In addition to having excellent radial up properties,
Since it is a hard material, it also has excellent wear resistance.

Next, the amounts of silicon carbide, silicon nitride, and mixtures thereof added as cermets will be described. It is extremely difficult to thermally spray high-purity silicon carbide and silicon nitride as they are, so Co+Cr+ Mo+ Ni+ is used as a binder.
It is necessary to create a thermal spray coating with high strength and strong adhesion by forming a matrix using a heat-resistant metal such as A7+W+Y.

Regarding build-up resistance, the higher the content of silicon carbide and silicon nitride, the better the properties, and if the content is less than 30%, sufficient build-up resistance cannot be maintained for practical use. Further, even if the build-up resistance is excellent, it is meaningless if the thermal spray coating peels off from the heat-resistant steel of the roll base, and adhesion strength sufficient to prevent this peeling is required. In order to ensure this adhesion, the greater the content of a heat-resistant metal such as Co+Cr+Mo+Nj+A7+W+Y contained in the cermet layer, the better the adhesion and peeling resistance will be. In order to prevent the thermal spray coating from peeling off, the amount of metal as a binder must be at least 30%.
5- It was confirmed that.

In this way, in order to ensure build-up resistance and peeling resistance, and to perform as a throttle,
The appropriate amount of silicon carbide, silicon nitride, or a mixture thereof is 30 to 70%, and preferably the upper limit is 60%.
It is.

Example ■ 07% silicon metal, 25% silicon carbide, 75% Co-Cr based alloy was thermally sprayed to a thickness of 400μ... - Thrall ■ 0.7% silicon metal, 35% silicon carbide, Co-Cr alloy A hearth roll coated with 65% alloy by thermal spraying to a thickness of 360μ ■ A hearth roll coated by thermal spraying of 50% silicon carbide with 0.7% metal silicon and 50% Co-Cr alloy to a thickness of 420μ ■ Metallic silicon 0.7% silicon carbide 65%, Co-Cr alloy 35% spray coated with a thickness of 390μ...-Throll■ Metallic silicon 07% silicon carbide 78%, Co-Cr 6
- Sprayed coating of 22% of alloy based on metal to a thickness of 350μ...-Throll■ Sprayed coating of 63% silicon carbide of 16% metal silicon and 37% of Co-Cr alloy to a thickness of 410μ...-Throll■ 20% silicon nitride containing 0.8% metallic silicon and 80% Co-Cr alloy were thermally sprayed to a thickness of 450μ...-Sroll ■ Silicon carbide containing 0.8% metallic silicon and silicon nitride (17:8
3) mixture of 60% and Co-Cr alloy 40%.
Thermal spray coated with a thickness of 0μ...-Throll■ Thermal spray coated with 0.8% silicon metal, 81% silicon nitride, and 19% Co-Cr alloy to a thickness of 390μ...-Throll [phase] Heat-resistant steel Using 5CH22...-Throl Each of the above...-Throl in a non-oxidizing atmosphere, using atmosphere temperature 7
A long-term root test was conducted at 50°C.

The results are shown in Table 1.

As shown in Table 1, the rolls of the present invention ■, ■, ■.

(2) indicates excellent build-up resistance and durability, while in other tests, test products L7 were prone to build-up or peeling of the solvent layer.

Furthermore, the same materials as in (1) to (2) were thermally sprayed onto the heat-resistant steel surface of ]-0001000 m, heated to 800 DEG C. for 1 hour, and then cooled with water. The number of times until peeling was repeated is shown in FIG. 2 as a peeling index.

It was confirmed that peeling resistance decreased as the amount of metal decreased, and it was found that the amount of metal as a metal binding material was required to be 30% or more, preferably 40% or more.

(Effects of the Invention) As shown in the above examples, the roll of the present invention has extremely excellent build-up resistance and greatly contributes to extending the life of the roll.

[Brief explanation of the drawing]

Figure 1 is a graph of the relationship between the adhesion of various samples to iron powder and the amount of metal silicon contained in the sample, and Figure 2 is the relationship between the peeling index of various samples and the amount of metal added as a binder. This is a diagram. −】〇 − Tochisan〇su Ounerei no Mikoto procedural amendment (voluntary) January 25, 1985 Manabu Shiga, Commissioner of the Patent Office 1, Indication of the case 1985 Patent Application No. 24-410 2
Title of the invention Roll for heat treatment furnace 3, person making the amendment Relationship to the case Patent applicant Place
2-6 Otemachi, Chiyoda-ku, Tokyo March name (665)
) Nippon Steel Co., Ltd. food coloring representative Takeshi 1) Yutaka 4th generation Osamu Address 3-3-3 Nihonbashi, Chuo-ku, Tokyo 6 Number of inventions increased due to amendment 7 Subject of amendment Patents in the specification, l claims Contents of amendments to each column 8 of the scope and detailed description of the invention (1) The scope of claims is amended as shown in the attached sheet. (2) "In the specification, page 5, line 5 and page 5, line 17,"
The heat-resistant metal j is corrected as V alone or a mixture or alloy of two extensions or alloys-1. (above) Claims: Gold scrap silicon content: silicon carbide, silicon nitride, or a mixture thereof with a maximum content of 30 to 70% by weight, the balance being C
1. A roll for a heat treatment furnace, characterized in that a cermet layer consisting of a single substance or a mixture or alloy of Cr, Mo, Ni, ACIW, and Y is thermally sprayed on a base of the no-throttle roll.

Claims (1)

[Claims] Contains 30 to 70% by weight of silicon carbide, silicon nitride, or a mixture thereof with a metal silicon content of 1% by weight or less, and the balance is C.
o+ Cr+ Mo+ Nil All w+ A thermal spray coating of a cermet layer made of a heat-resistant metal such as Y is...-
A roll for a heat treatment furnace, characterized in that the roll is provided on a base of the roll.