JPS60251218A - High-temperature anti-oxidant paint for steel material - Google Patents

Abstract

PURPOSE:To provide a high-temp. anti-oxidant paint for a steel material, which prevents oxidation and scale formation of the steel material and has good removability by compounding respectively specified ceramic base material, binder, metallic powder and ceramic sintering accelerator at specific ratios. CONSTITUTION:The paint is prepd. which consists of the compsn. contg. 20- 50wt% ceramic base material of at least one kind in the group consisting of silicon carbide, alumina, stabilized zircon and mica, 10-40wt% binder of at least one kind in the group consisting of neutral aluminum phosphate, colloidal silica and alumina sol, 5-10wt% metallic powder of at least one kind in the group consisting of Fe, Cu, Ni and Cr and 5-30wt% sodium carbonate as a ceramic sintering accelerator and in which the total of the components is 100wt%. Such paint is coated after mixing about 10-15wt% water therewith and the thickness of the coated film is made about 100-150mu.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention prevents oxidation by coating the surface of steel materials, especially steel billet slabs, and prevents scale formation in the high-temperature oxidizing atmosphere in a heating furnace. This invention relates to a high-temperature antioxidant coating for steel materials that can be peeled off and easily descaled if scale occurs.

As is well known, steel billet slabs are heated in a heating furnace or soaking furnace.
It is heated at a temperature of 0 to 1200°C and rolled into a product. However, in the case of steel materials on the level of ordinary steel in a heating furnace, there is little scale formation and descaling is relatively easy, but in the case of high-grade steel quality materials, oxidation scales may vary depending on the furnace time and temperature. This is a problem from the viewpoints of productivity, resource saving, and product finishing due to a decrease in yield due to the fact that a large amount of descaling occurs and descaling is difficult.

Conventionally, many high-temperature oxidation-inhibiting paints have been researched and developed in order to prevent oxidation and scale generation of steel billet slabs under high temperatures. Many paints contain silica-based, magnesia-based refractories, low-melting point metals, or inorganic salts, but depending on the steel type of the slab containing Ou, Ml, Or, etc., or the operation of continuous or batch heating furnaces. Due to differences in methods, there are drawbacks such as cracking due to insufficient prevention of oxidation and scale generation and peelability. Therefore, at present, a high-grade steel slab is covered with a protective cover made of a thin iron plate so that the surface of the steel material is sent into a heating furnace to prevent the formation of an oxidizing atmosphere on the surface of the steel material as much as possible, thereby preventing the occurrence of slab scale. However, this thin iron plate protective cover requires a great deal of labor to attach to the steel material, and is also a factor in deteriorating the fuel consumption rate of the heating furnace due to indirect heating.

High-temperature anti-oxidation paint not only prevents oxidation and scale generation, but also easily peels off, and even if scale occurs, the scale can be easily peeled off together with the paint by high-pressure water before rolling, in other words, descaling is easy. This is required. If scale and paint remain during rolling, scratches will occur on the surface of the product.

Therefore, the object of the present invention is to provide a high-temperature oxidation-preventing paint that prevents steel oxidation and scale generation, has good peelability, and even if scale is generated, it can be peeled off together with the scale during the general descaling process using high-pressure water. It is to develop.

As a result of research, this problem can be solved by a high-temperature anti-oxidation paint for steel with the following composition. At least one species from the group of
b) 10 to 40% by weight of at least one member from the group of neutral aluminum phosphate, colloidal silica, alumina sol as binder; C) 5 to 10% by weight of 'fre.
+, Ou +, Ni- and Or powders and a) S ~ 30% by weight of sodium carbonate as ceramic sintering accelerator.

However, the total of components a) to d) is 100% by weight.

When the composition of the present invention is applied onto steel materials, coating workability is improved when approximately 10 to 15% by weight (based on the total amount of the composition) of water is additionally mixed into the composition. It turned out that.

Ceramics as the base material for a) component have high heat resistance (
For example, silicon carbide is used at a temperature of 2200°C), and the amount used is component a
) It must be in the range of 20 to 50% by weight of the total of b) c) and d) (hereinafter referred to as all components). If it is less than 20% by weight, a dense coating film cannot be formed,
The steel material comes into contact with the oxidizing atmosphere gas more often, and the desired oxidation prevention effect cannot be obtained. When the amount exceeds 50% by weight, thermal conductivity decreases, heating energy consumption increases, and energy loss occurs.

The binder of component b) stabilizes the bonding of the ceramic base material of component a) and increases the adhesion with the steel material, and its usage amount must be in the range of 10 to 40% by weight of the total components. .

If the binder is less than 10% by weight, the mixed mixture will be hard and will not be able to adhere to the surface of the steel material. Even if the amount is 40% by weight or more, the binder effect remains unchanged.

The metal powder of component C) is placed in a reducing atmosphere in order to avoid or minimize contact of the oxidizing atmosphere (generally 1 to 2 chloride of O in the exhaust gas) with the steel surface in the heating furnace. It is intended to hold the following.

5% by weight is the minimum value for creating an oxidizing atmosphere on the steel surface.
If it exceeds 10% by weight, it reacts with or welds to the steel material at high temperatures, changing the properties of the steel material surface, so-called product surface, and causing adverse effects.

The temperature of the ceramic sintering accelerator of component d) is 300 to 800°C.
It promotes the sintering of the ceramic base material and binder that are sintered in the process, and serves to make the paint mixing and kneading area hard and increase the adhesion strength to the steel surface, resulting in a dense coating film.

5% by weight is the lower limit to maintain proper sintering rates.

If it is less than that, the sintering condition will be poor (weak), the strength of the coating film in the mixed and kneaded product will decrease, and the surface of the steel material will deteriorate due to the formation of an oxidized atmosphere erosion zone. However, if it exceeds 30% by weight, a tight coating film will not be formed on the ceramic substrate, which will deviate from the initial purpose.

As mentioned above, the paint of the present invention increases the strength of the coating film based on ceramic and the adhesion strength to the surface of metal materials, and
Because it is a neutral and thin coating that does not reduce thermal conductivity, it achieves many results such as resource savings, workability, energy savings, and improved environmental atmosphere.

To explain the coating film thickness here, if it is less than 50 μm, the effect of preventing and suppressing scale generation due to oxidation of steel materials during heating in a heating furnace is low, and special high-grade steel materials (Ou Ni
(containing Or), a strongly adhered scale with very poor removability is generated. On the other hand, if it exceeds 200μ, heat transfer deteriorates, the heat pattern of the furnace operation changes, and the extension of the heating time causes unavoidable adverse effects, which is not preferable. For this reason, a preferable range is 100 to 150μ.

The invention will be explained in more detail by the following examples.

Example 1゜ Ingredients below Silicon carbide 50% by weight Alumina 18% by weight Neutral aluminum phosphate 20% by weight F. Flour 7% by weight Sodium carbonate 25% by weight Water appropriate amount Mix.

This paint is applied to ultra-high tensile strength steel, high tensile strength steel, and ordinary steel in an unheated state to a film thickness of 50 μ to 250 μ, and after air drying for 24 hours, the steel materials are coated as described below. The material is heated and rolled under the furnace time and furnace temperature shown in Table 1.

Table 1 shows the measurement results regarding the scale generation status and the peelability of the antioxidant paint from the scale.

Example 2゜ Example 1 can be repeated except using the following ingredients: Silicon carbide 45% by weight Neutral aluminum phosphate 15% by weight Colloidal silica 12% by weight Fe powder 5 weight Ou powder 3% by weight Sodium carbonate 20% by weight Water appropriate amount The results are shown in Table 1.

Example& Example 1 is repeated except using the following ingredients: Hydrocarbon 14% by weight Silicon nitride 50% by weight Neutral aluminum phosphate 20% by weight Alumina sol 15 weight F. Flour 3 weight - N1 powder 3% by weight Sodium carbonate 15% by weight Water appropriate amount The results are shown in Table 1.

Example (4) Example 1 is repeated except using the following ingredients: Silicon nitride 20% by weight Alumina 15% by weight Mica 8% by weight Neutral aluminum phosphate 15% by weight Colloidal silica 18 weight r・Powder 3% by weight N Oni powder 2% by weight Or powder 2% by weight Sodium carbonate 17% by weight Water appropriate amount The results are shown in Table 1.

Example (5) Example 1 is repeated except that the following components are used and light is shielded.

Silicon carbide 10% by weight Alumina 10 weight- Stabilized zircon 5% by weight Colloidal silica 20% by weight Alumina sol 18% by weight Fe powder 3% by weight Ou powder 4 weight Ni powder 2% by weight Sodium carbonate 28% by weight Water appropriate amount The results are shown in Table 1.

Comparative Example Example 1 was repeated using Scale Guard (trademark) 1000 manufactured by Shinto Paint Co., Ltd. as a conventional high-temperature oxidation-preventing paint. The results are shown in Table 1.

Δ5~20chi: △40~69chi I×20chi or more
: ×40 inches or less As can be seen from Table 1, at coating thicknesses of 100/J or more,
Unlike the comparative example, in the case of the present invention, scale generation was not observed in any case, regardless of the type of steel material and the type of furnace.

Moreover, even at this coating thickness, the coating of the present invention can be completely peeled off by descaling with high-pressure water, but the coating of the comparative example is difficult to peel off. As a result, when the comparative example book was used, there were scratches on the steel plate after rolling, but when the paint of the present invention was used, there were no scratches at all.

When comparing the paint of the present invention with that of a comparative example when the coating film thickness is 50 μm or 80 μm, scale formation was observed in some of the tests using the paint of the present invention. However, in any case, the paint of the present invention is clearly superior, including the removability of the antioxidant paint.

Agent Mitsuyoshi Ezaki Agent: Hikaru Esaki Continuation of page 1 0 shots by Hiroshi Nakamura - Chiyo Company, Tokyo 0

Claims (1)

[Scope of Claims] a) 20 to 50% by weight of at least one member from the group of silicon carbide, silicon nitride, alumina, stabilized zircon, mica as a ceramic substrate; b) 10 to 40% by weight , at least one member from the group consisting of neutral aluminum phosphate, colloidal silica, and alumina sol as a binder, C)5
~10% by weight of at least one of the group of Ire-, Ou-, Nl- and Or powders and a) ~30% by weight of sodium carbonate as a ceramic sintering accelerator, provided that a) ~d) A high-temperature oxidation-preventing paint for steel materials in which the total content of the components is 100% by weight.