JPH0250167B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hearth roll for a metal heat treatment furnace.

Conventional hearth rolls are made of a heat-resistant alloy, have a heat-resistant alloy roll body with ceramic materials such as alumina or zirconia sprayed on the surface, have a ceramic sleeve fitted to the roll body, or have an asbestos laminate as the roll shaft. Various rolls have been used, including wrapped ones.

However, none of them has been available that is stable and can withstand long-term use. In other words, scale from the metal strip adheres to the roll surface, forming so-called roll build-up (hard spots), which causes scratches on the surface of the metal strip, lowering the quality of the product, and causing defective products. It had drawbacks.

This was the same even when the ceramic was coated as described above. That is, a large number of micropores exist on the ceramic surface, into which metal scale penetrates, eventually causing the roll build-up phenomenon.

For this reason, a method of sintering ceramic materials at high temperatures has been considered in order to make them porous, but sintering causes large dimensional shrinkage and is extremely difficult to obtain in order to obtain large integrated rolls with good dimensions and precision. It had the disadvantage of being an expensive material.

The present invention can be applied to silicon steel plates etc. at temperatures of 500 to 1200℃.
The present invention relates to a hearth roll for a heat treatment furnace that can be used in a wide temperature range, and is intended to supply a hearth roll that has high mechanical strength and does not cause roll build-up. That is, it has been found that a hearth roll made of SiC ceramic containing 5 to 25% by weight of metallic Si and having an open porosity of 0.5% or less satisfies the above objectives.

Hearth rolls used for heat treating thin sheets such as silicon steel plates do not react with the metal strip at the processing temperature, are heat resistant and have high mechanical strength.
It is required to have good thermal conductivity, a sufficient temperature uniformity range, and excellent abrasion resistance, but above all, as mentioned above, it must not cause scratches on the surface of the product due to roll build-up. It has been demanded.

SiC-based materials are thought to be suitable as such materials, but conventional SiC-based materials, such as silicon carbide reconsolidated or clay sintered materials, have a high wear resistance, but many There are pores, and scale enters into these pores, causing build-up, and in the end, it is not recognized as a good hearth roll.

The present invention makes use of such wear-resistant silicon carbide and applies the bonding force of metal silicon when bonding and molding it, thereby creating a structure with almost no pores and no extreme unevenness on the surface.
It is made of SiC material.

In this case, if the amount of metallic silicon is too large, it will not only reduce the strength of the hearth roll as a whole, but also affect the wear resistance and oxidation resistance, and if it is too small, the pores will not be filled, resulting in a decrease in strength. This results in disadvantages such as the build-up is more likely to occur.

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, a roll body 1 is a hollow roll made of a heat-resistant alloy, and is integrated with a rotating shaft 2. As shown in FIG.

A sleeve 8 made of the SiC-Si material of the present invention is fixed to the roll body 1 with a fixing ring 4.
The metal strip S moves over the sleeve 3 perpendicular to the plane.

The following manufacturing method was used to mold the sleeve made of SiC-Si material.

A mixed powder of silicon carbide and graphite powder was formed into a pipe shape using phenol resin as a binder, and the cured product was brought into contact with molten metal silicon at a temperature of 1600°C or higher in an inert gas atmosphere.

Metallic silicon is produced by silicifying the graphite in the molded body, and the final product is SiC- containing 18% by weight of metallic silicon.
The product was made of Si. This product is obtained as a product with no open pores, and is used as a roll for a heat treatment furnace at 950℃ under a forming gas atmosphere.
A silicon steel plate was annealed continuously for 2000 hours, and the wear status of the rolls and the properties of the silicon steel plate were investigated. As a result, the amount of wear was less than 0.5 mm, and the surface remained smooth, and no scratches, crevices, etc. were observed on the silicon steel plate.

As a comparative example, a recrystallized silicon carbide hearth roll was formed in the same manner as in the example, and a silicon steel plate was heat-treated under the same conditions. After about 50 hours of use, scratches began to appear on the surface of the silicon steel plate, and after 70 hours, After a period of time, the quality deteriorated significantly and the operation was stopped. The apparent porosity of this silicon carbide molded article was initially 16%, but after use, all the pores existing on the surface were found to have been invaded by scale.

In this way, in the present invention, the metal silicon is 5
Since it is made of silicon carbide containing ~25% by weight, it has silicon bonding strength and moderate lubrication, and has an open porosity of 0.5% or less,
The surface is extremely smooth, no roll build-up due to scale adhesion occurs, and the silicon carbide itself has excellent wear resistance, resulting in an excellent hearth roll.

[Brief explanation of drawings]

FIG. 1 is a schematic longitudinal sectional front view showing one embodiment of the present invention. 1...Roll body, 2...Rotating shaft, 3...Sleeve, 4...Fixing ring, S...Metal strip.

Claims (1)

[Claims] 1. A hearth roll for a metal heat treatment furnace, characterized in that it is made of SiC ceramic containing 5 to 25% by weight of metallic Si and having an open porosity of 0.5% or less.