JPS62188724A - Roll for heat treating furnace - Google Patents

Abstract

PURPOSE:To obtain a roll having wear resistance at high temp. and superior build-up resistance by coating a roll for a heater treating furnace with boron nitride ceramics. CONSTITUTION:A boron nitride ceramic coating is formed on the surface of the body of a heat resistant cast steel roll for a heat treating furnace by spraying, dipping, brush coating or other method to obtain a roll for a heat treating furnace having superior wear resistance at high temp. and preventing build-up. The resulting roll has a long service life.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention is a roll disposed in a continuous heat treatment furnace for annealing and conveying steel plates, and is particularly excellent in high-temperature wear resistance and build-up prevention. The present invention relates to a heat treatment furnace roll (hereinafter referred to as a hearth roll).

(Prior art) The number of hearth rolls installed in the heat treatment furnace is 600 to 130.
The material to be heat treated is annealed continuously for a long time at an oxidizing or reducing atmosphere temperature of 0℃, and the surface is subject to abrasion due to being transported, and oxides and iron powder from the material to be heat treated may be deposited on the roll surface. It adheres and accumulates to form what is called a buildup.

When such unevenness due to wear and build-up occurs on the hearth roll, the steel plate that is the material to be heat treated is scratched while being transported, causing a decrease in quality. In order to prevent such deterioration in the quality of steel sheets, operations are periodically interrupted to cool down the inside of the heat treatment furnace, and then workers enter the furnace to perform grinding and maintenance on the surface of the hearth rolls. They even replace the roll itself.

For this reason, the material of hearth rolls has traditionally been improved to heat-resistant alloys containing flat chromium or high nickel, or
As described in Japanese Patent No. 7-29549, etc., the roll surface has been coated with ceramics such as zirconia or alumina by thermal spraying.

(Problem to be solved by the invention) However, even improvements in heat-resistant alloys have little effect on preventing build-up caused by adhesive deposits, and thermally sprayed coatings of zirconia and alumina have poor interparticle strength in high-temperature atmospheres. Due to the drawback of deterioration and peeling of the film itself, high temperature resistance 1
7. It is not fully satisfactory in terms of wear resistance and prevention of pill-adsorption.

As a result of various studies, the present inventors have discovered coating materials and coating methods that have excellent high-temperature abrasion resistance and are highly effective in preventing build-up and that should be applied to these hearth rolls used in oxidizing or reducing atmospheres. A coating that has excellent adhesion to the hearth roll base and does not peel off (and has excellent high-temperature strength).
Discovered a ring roll and completed the present invention.

That is, the present invention has been made for the purpose of providing a hearth roll having a coating layer formed on the roll surface that has excellent high-temperature wear resistance and a large build-up prevention effect when used in an oxidizing or reducing atmosphere. It is something that

(Means for Solving the Problems) The gist of the present invention is a roll for a heat treatment furnace having a ceramic coating made of boron nitride.

The present invention will be described in detail below.

The base of the hearth roll is made of heat-resistant cast steel.

A ceramic coating made of boron nitride is applied to the surface of these substrates by spraying, dipping, brushing, or the like. Alternatively, after the surface of the hearth roll is thermally sprayed with various ceramics in advance, a coating made of boron nitride is applied by the method described above.

In the present invention, boron nitride is used as the coating raw material because boron nitride has a crystal structure similar to that of graphite, so it is effective as a solid lubricant and reduces the hot friction force between the steel plate and the roll. This is because we thought that by doing so, we could prevent build-up from the steel plate. Furthermore, boron nitride has excellent corrosion resistance and abrasion resistance among ceramics, has a high melting point of approximately 3000°C, has excellent heat resistance, and has high thermal conductivity, so it can be used to coat metal substrates or ceramic sprayed coatings. This is because it was presumed that it would exhibit high durability even after repeated rapid heating and rapid cooling of the order of 1000°C.

The present inventors conducted the following experiment to investigate the occurrence of buildup in a continuous annealing furnace.

Made of 5US310S, diameter 260 mm, body length 350 mm.
Two Dragon test rolls were made, and both were coated with boron nitride from the center of the roll surface to the drive side (D, S side). An endless cold thin steel plate was wound around these two rolls, and a rotating contact test was conducted. Steel plate is 1.2 **thickness x 1
801 width x 3000 length was welded into an endless piece. Incidentally, FIGS. 1A and 1B are schematic diagrams of the evaluation apparatus used in the test, and FIG. 2 shows the atmosphere and temperature pattern in which the test was conducted.

Further, detailed test conditions are shown below.

In Fig. 1, 1 is an N11l roll, 1a is a boron nitride coated part, 2 is a fish roll, 2a is a boron nitride coated part, 3 is a silicon carbide heating element, 4 is a 1 motor, 5 is a 1Vk12 motor, 6 indicates a balance weight, and 7 indicates an endless cold thin steel plate.

Example Zhang crab 0.15kg/Ryu 2 Rotation speed: 10-roll 80r, p, m N1120-roll 40r, p, m (slip occurred on both rolls) Atmosphere: After heating in 100% N2, N2- 5%I'l
z Switched to reducing atmosphere. (See Figure 2) The oxygen concentration was about 15 ppm.

Temperature: 850℃ Main test time: 20 minutes Roll: Drive side (D,
The S side) was coated with boron nitride by a spray method. (The thickness of the coating is approximately 0.051 mm) After the test, the build-up occurrence in the body length direction of the hearth roll described above was evaluated based on the number of occurrences and the adhesion area ratio. The results are shown in Figure 3.

Figure 3 shows that the number of build-up occurrences and the adhesion area ratio are lower on the drive side coated with boron nitride than on the work side, indicating that boron nitride is superior in preventing build-up occurrence. It was found to be effective.

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

[Brief explanation of drawings]

Figure 1 is a schematic diagram of the 20-roll type build-up performance evaluation device used in this test, where (A) is an overall side view, (B) is a plan view of the roll portion, and Figure 2 is the temperature pattern used in the test. FIG. 3 is a diagram showing the occurrence of build-up after the test. 2nd floor 10-ru, 1llh 20-ru, 3: silicon carbide heating element, 4: 1st motor, 5: 2nd floor motor, 6: balance weight, 7: endless cold thin steel plate. Figure 1: C day) Figure 2: Honsha 6 Okinobun Hitanma (minutes)

Claims (1)

[Claims] A roll for heat treatment furnaces in continuous annealing furnaces that has a ceramic coating made of boron nitride and has excellent high-temperature wear resistance and build-up prevention.