JPS63100169A - Heat treatment furnace hearth roll having excellent build-up resistance - Google Patents

Abstract

PURPOSE:To obtain a heat treatment furnace hearth roll having excellent build-up resistance by subjecting a thermally sprayed film layer on a roll surface to a sealing treatment by using a colloidal soln. of silicic acid anhydride having high heat resistance. CONSTITUTION:The thermally sprayed film layer of the thermally sprayed roll to be used as the heat treatment furnace hearth roll is subjected to the sealing treatment by using the colloidal soln. of the silicic acid anhydride. The above-mentioned colloidal soln. which is prepd. by dispersing the ultrafine particulate silicic acid anhydride into water readily infilters the pores and fine cracks on the surface layer of the thermally sprayed film without bubbling. About 1-20% alcohol is preferably added to said colloidal soln. to additionally enhance the permeability and about 1-10% amines are preferably added thereto the stabilize the colloid. The thermally sprayed roll sealed by said colloidal soln. is precipitated with the silicic acid anhydride crystal having the stable and high heat resistance and is improved in the build-up resistance after the evporation of the dispersion medium.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a heat treatment furnace hearth roll.

(Prior art and problems) When a thermal spray roll is used as a heat treatment furnace hearth roll, pores on the surface of the thermal spray coating and scale that has penetrated or adhered to the fine rack are reduced in the atmosphere and become metal, which grows and causes the so-called It causes build-up and damages the product. The shape of the build-up varies from slug-like single grain to foil-like, and is not constant. Sealing treatment is effective to prevent this build-up, but since it is used in a heat treatment furnace, Sodium silicate and aluminum phosphate are conventionally thought of as sealing agents that must be able to withstand high temperatures, but these may foam when heated or cause the thermal spray coating to crack or peel. This may result in incomplete sealing. As a result of various experiments with these points in mind, the present invention was completed.

(Means for Solving the Problems) The gist of the present invention is to provide a build-up resistant product characterized in that the thermal spray coating layer on the surface of the roll is sealed using a colloidal solution of silicic anhydride. The heat treatment furnace is located in a hearth roll with excellent properties.

The colloidal solution of silicic anhydride used in the present invention is obtained by dispersing silicic anhydride into ultrafine particles in water, and there is no foaming due to chemical reactions.Since water is used as the dispersoid, capillary action occurs within the sprayed coating. penetrates easily. Furthermore, to increase the permeability, it is sufficient to add 1 to 20% alcohol to the dispersoid.If more than 20% alcohol is added, the solvated silicic anhydride colloid will have an ionic bond with the dispersoid that will bond with the alcohol. silicic anhydride salts out.

It is effective to add 1 to 10% of amines such as formamide, ethylamine, and ethanolamine to stabilize the colloid. However, if it is added in an amount of 10% or more, salting out tends to occur.

In a thermal spray roll whose pores have been sealed with a colloidal solution of silicic anhydride, after the dispersoid has vaporized, the silicic anhydride remains in the form of crystals in the pores and fine particles within the thermal sprayed coating. Silicic anhydride is chemically stable and will not be oxidized or reduced even at high temperatures, and will not lose its sealing effect. Therefore, the film will not foam or crack or separate when heated.
When vaporizing the dispersoid, if it is naturally vaporized at room temperature, the concentration of the colloidal solution will gradually increase, and when it is precipitated, it will form large crystals, which will improve the sealing effect.

As described above, by performing a sealing treatment using the colloidal solution of silicic anhydride of the present invention, a heat treatment furnace hearth roll having excellent build-amp resistance can be replaced.

Examples will be described below.

(Example) The sealing agent was 0 using a colloidal solution of 20% silicic anhydride.
Next, the sealing process is (a) applying to the thermal spray coating at room temperature, (b) leaving it to dry naturally for 30 minutes, (c) repeating the above (a) and (b) 10 times, (d) surface finishing polishing, It consists of the following steps: (e) repeating the above (a) to (c); and (f) removing excess silicic acid adhering to the surface of the sprayed coating using sandpaper 11240.

The results of applying the above sealing treatment to an actual machine are shown in Table 1.The rolls sealed with silicic anhydride of the present invention are more susceptible to scale intrusion and physical adsorption than rolls that are not sealed. Because there is no such thing, build-up resistance has been significantly improved, and the continuous use period of the roll has been significantly extended.

Claims (1)

[Claims] A heat treatment furnace hearth roll with excellent build-up resistance, characterized in that the thermal spray coating layer on the roll surface is sealed using a colloidal solution of silicic anhydride.