JPH0662888B2 - High temperature antioxidant paint for steel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention is applied to the surface of a steel material, particularly a billet slab, to prevent its high temperature oxidation, and also to generate scale in a high temperature oxidizing atmosphere in a heating furnace. The present invention relates to a high-temperature antioxidant paint for steel materials, which can prevent peeling and can be easily peeled off before rolling, and in particular prevent damage to the coating film due to dew droplets caused by the temperature difference between the steel material and heated air near the inlet of a continuous heating furnace. .

[Prior Art] As is well known, billet slabs are heated to 11050 in a heating furnace or soaking furnace.
It is heated at a temperature of ~ 1200 ℃ and rolled into a product. When the billet slab is a steel material at the level of ordinary steel, the scale is less likely to be generated in the heating furnace, and the descaling is relatively easy. However, when this billet slab is of high-grade steel quality, a large amount of oxide scale is generated due to the furnace time and temperature, descaling is also difficult, and productivity due to reduced yield, resource saving and product finishing Is a problem from the perspective of.

Conventionally, many high temperature anti-oxidation agents have been studied and developed in order to prevent the slab slab from being oxidized and the scale from being generated under high temperature. Many paints contain silica-based refractories, magsia-based refractories, low-melting metal or inorganic salts, but they are called Cu, Ni, Cr-containing slab steel type, continuous type or batch type heating furnace. Due to the difference in operating methods, there are drawbacks such as oxidation prevention, scale generation prevention, and insufficient peelability. Therefore, at present, a high-grade steel slab is covered with a thin iron plate protective cover to cover the surface of the steel material and sent to a heating furnace to prevent the surface of the steel material from being exposed to an oxidizing atmosphere as much as possible to prevent the generation of slab scale. However, this thin iron plate protective cover requires a great deal of labor for mounting on a steel material, and since it indirectly heats, it also becomes a factor of deteriorating the basic unit of heating furnace fuel.

High-temperature antioxidant paint is easy to peel off with anti-oxidation and scale prevention, and even if scale is generated, the scale is easily peeled off with high pressure water before rolling with the paint, that is, descaling is easy. Is required. If scale and paint remain during rolling, the surface of the product will be scratched.

Therefore, the inventors of the present invention have proposed a high-temperature antioxidant coating satisfying these requirements in Japanese Patent Publication No. 63-58886 (Japanese Patent Application No. 59-106526).
No.), Japanese Patent Publication No. 63-58887 (Japanese Patent Application No. 59-106527) and Japanese Patent Publication No. 63-58888 (Japanese Patent Application No. 59-183838). Among these applications, the high temperature antioxidant coating of Japanese Patent Application Laid-Open No. 63-58888 (Japanese Patent Application No. 59-183838) showing particularly good effect has the following composition: a) As a ceramic substrate At least one selected from the group consisting of silicon carbide, silicon nitride, stabilized zircon, and mica; 20 to 50% by weight; and b) the following three aluminas as ceramic aids: 25
-50% by weight, Alumina (1): Flat fine alumina with large α crystal and small sintering shrinkage, Alumina (2): Flat with high α conversion and stable firing shrinkage, average particle size of 100μ or less Granular Alumina and Alumina (3): Medium Soda Grade Easy-to-burn Crystalline Ultrafine Alumina with a Low Water Content, c) At least one selected from the group consisting of neutral aminium phosphate as a binder, colloidal silica, and alumina sol; 1
0-40% by weight, d) at least one member of the group of Fe, Cu, Ni and Cr powders;
10% by weight, e) Sodium carbonate as a ceramic sintering accelerator; 5 to
30% by weight, and f) Aqueous emulsion or aqueous solution of polymer and / or copolymer forming a water resistant coating: 2.5 to 15% by weight (solid content) (however, the total of components a) to f) is , 100% by weight. ) When applying this paint on steel material, an additional 10 to 10
It has been found that coating workability is improved when 15% by weight (relative to the total amount of the composition) of water is mixed in the composition.

[Problems to be Solved by the Invention] However, since the steel material is transferred on a metal roll before being operated into the heating furnace, when the coating material is applied to the steel material, There is a problem that a part is peeled off due to a physical impact by a metal roll and a scale is generated in the peeled part in the heating furnace. It is possible to dry the paint before entering the heating furnace in order to avoid the generation of the scale, but even if it does, there is a problem that productivity is lowered and economic efficiency is deteriorated.

[Means for Solving Problems] The high temperature antioxidant coating according to the present invention is disclosed in Japanese Examined Patent Publication No. 63-58888.
No. 59-183838 (Japanese Patent Application No. 59-183838), by further mixing 3 to 15% by weight of potassium titanate fiber (g) component having a diameter of 10 to 30 μ and a length of 100 to 500 μ with the high temperature antioxidant paint. This is a solution to the above problems.

That is, the inventors of the present invention have proposed Japanese Patent Publication No. 63-58888 (Japanese Patent Application No.
No. 183838) The diameter of the high temperature anti-oxidant paint according to the application is 10-30
By mixing potassium titanate fiber with a length of 100 μm to 500 μm, the fiber acts as an aggregate to increase the strength of engagement between coatings, preventing the penetration of high-temperature oxidizing gas and physical impact. It has been found that the strength is increased.

Here, the amount of the potassium titanate fiber, which is the component g), is set to the range of 3 to 15% by weight because the effect as an aggregate is small when the amount of potassium titanate fiber is less than 3% by weight, and 15% by weight is selected. When it exceeds the above range, the fibers project to the surface of the coating film and a coating film having a uniform composition cannot be obtained. However, in the range of 3 to 15% by weight, the strength of the coating film can be increased without causing such an inconvenience. Is.

The potassium titanate fiber used as component g) has the composition: K ₂ Ti ₄ O ₉ and / or K ₂ Ti ₆ O.
Plate-like fibers having a large contact area with a tunnel crystal structure having a diameter of _{10 to 30} μm and a length of 100 to 500 μm are preferable.

The ceramics [a) component as a base material is preferably one having high heat resistance (for example, 2200 ° C. for silicon carbide), and the amount used is as follows: components a), b), c), d) and e) (hereinafter, It is necessary to be in the range of 20 to 50% by weight of the total of all components).
If the content of component a) is less than 20% by weight, the coating film will not be densely formed,
The permeation amount of the oxidizing atmosphere gas increases, the desired antioxidant effect cannot be obtained, and if it exceeds 50% by weight, the thermal conductivity decreases,
The consumption of heating energy increases and the energy loss increases.

Alumina [b) component] as a ceramic auxiliary material is a combination of flat particles having a high alpha conversion [alumina (1) and (2)] and easily sinterable ultrafine particles [alumina (3)]. is there.

Alumina (1) has a large α crystal, a small sintering shrinkage rate, especially 5% or less (1600 ° C., 3 hours), and a flat-shaped hiding power, especially fine particles of 1 to 10 μm. Is.

Alumina (2) has stable calcination shrinkage, and in particular has a shrinkage ratio of 10% or less (1600 ° C, 3 hours), a high α-formation rate, an average particle size of 100μ or less, especially 20μ or less, especially 30-60μ
It is a flat particle with excellent hiding power.

Alumina (3) has a low water content, especially Na ₂ O.
Medium soda grade containing 0.2 to 0.3% by weight, and easy-sinterable ultrafine particles having an average particle size of 1 μm or less.

Alumina [component (b)] as a ceramic auxiliary material has a film thickness
If it is 100 μ or less, a dense coating film with sufficient hiding power cannot be obtained at 25 wt% or less, and at 50 wt% or more,
The peelability of the coating film becomes poor.

Alumina (1), (2) and (3) are mutually (1.5 ~
It has been found that advantageous results are obtained when used in a weight ratio of 3) :( 0.5-2) :( 1-3).

Neutral aluminum phosphate used as a binder,
At least one of the group consisting of colloidal silica and alumina sol [component (c)] is used to stabilize the bond of the ceramic base material which is the component a) and to enhance the adhesion with the steel material. The amount used of all ingredients
It should be in the range of 10-40% by weight. When the content of this binder is 10% by weight or less, the mixed and kneaded product is hard and adhesion to the steel surface cannot be obtained, and when it is 40% by weight or more, the effect as a binder does not increase.

The metal powder [d) component consisting of at least one of the group of Fe, Cu, Ni and Cr powders has a oxidative atmosphere (generally O ₂ in exhaust gas: 1 to 2%) in the heating furnace. The reducing atmosphere is maintained in order to avoid contact with the surface of the steel material, or to minimize it. If the metal powder is less than 5% by weight, the surface of the steel material becomes an oxidizing atmosphere, and if it exceeds 10% by weight, the metal powder reacts with or welds to the steel material at a high temperature to change the properties of the steel material surface, so-called product surface, and adversely affect it. Bring

The ceramic sintering accelerator [component (e)] accelerates the sintering of the ceramic base material and the binder at 300 to 800 ° C., hardens the mixed kneaded material of the paint, and enhances the adhesion strength to the steel surface, It plays the role of making the coating film dense.

The lower limit is 5% by weight to maintain an appropriate sintering rate.
If it is less than 5% by weight, the sintering state is poor (weak), the strength between the coating films in the mixed kneaded product is reduced, and the surface of the steel material deteriorates as an erosion area of the oxidizing atmosphere. If it exceeds 30% by weight. The coating film is not densely formed and deviates from the initial purpose.

The amount of the component (f) used is preferably 2.5 to 15% by weight (based on the total amount of the coating material), particularly 2.5 to 13% by weight, as the solid content. If the amount is less than 2.5% by weight, no practical result can be obtained. If the amount is more than 15% by weight, gas is generated due to combustion of this component in the continuous heating furnace, which may cause blistering and peeling of the coating film.

In the case of the coating material of the present invention, in order to improve coating workability,
In addition to the water contained in the component (f), water may be mixed in an appropriate amount. The water content in the paint is preferably about 10 to 15% by weight (including the amount contained in the component f) (based on the whole paint).

[Examples] Hereinafter, the present invention will be described in more detail with reference to Examples.

Example-1 Silicon carbide 10% by weight Silicon nitride 7 〃 Stabilized zircon oxide 7 〃 Alumina (1) 20 〃 〃 (2) 5 〃 〃 (3) 5 〃 Neutral aluminum phosphate 12 〃 Fe powder 3 〃 Copper powder 3 〃 Sodium carbonate 5 〃 Vinyl acetate-ethylene copolymer emulsion (solid content 50% by weight) 8 〃 Potassium titanate fiber 15 〃 Water In addition to a proper amount, shrinkage rate (1600 ℃, 3 hours ) 5%
The following flat high-alpha aruna {This corresponds to alumina (1), hereinafter abbreviated as alumina 1} 20% by weight, average particle size
45μ, Shrinkage rate 10% or less (1600 ℃, 3 hours) Alpha conversion rate 100
% Flat alumina {this corresponds to alumina (2),
Hereinafter, abbreviated as alumina 2} 5 wt% and 0.25 wt% Na
₂ O content average particle size 0.4μ and particle size distribution 0.1-1.5μ
A mixture containing 5% by weight of medium soda grade alumina {which corresponds to alumina (3), hereinafter abbreviated as alumina 3} and an appropriate amount of water is prepared.

This paint is applied to unheated steel for plate steels, ultra high strength steel, high strength steel and ordinary steel, with coating thicknesses of 50μ and 100μ, respectively, to obtain impact resistance, scale generation and peelability. Examined. The measurement results are shown in Table 1.

Example-2 Example-1 is repeated but using the following ingredients.

Silicon carbide 5% by weight Silicon nitride 10 〃 Mica 5 〃 Alumina 1 15 〃 〃 2 5 〃 〃 3 10 〃 Neutral aluminum phosphate 10 〃 Colloidal silica 6 〃 Fe powder 2 〃 Cu powder 5 〃 Ni powder 2 5 〃 〃 Vinyl acetate-ethylene copolymer emulsion (solid content 50% by weight) 10 〃 Potassium titanate fiber 10 〃 Water Appropriate amount Table 1 shows the test results.

Example-3 Example-1 is repeated but using the following ingredients.

Silicon nitride 5% by weight Stabilized zircon 18 〃 Mica 3 〃 Alumina 1 4 〃 〃 2 18 〃 〃 3 8 〃 Colloidal silica 15 〃 Fe powder 2 〃 Cr powder 5 〃 Sodium carbonate 8 〃 Vinyl acetate vinyl acetate-ethylene Combined emulsion (solid content 50% by weight) 8〃 potassium titanate fiber 6〃 water proper amount test results are shown in Table 1.

Example-4 Example-1 is repeated except that the following ingredients are used:

Silicon carbide 18 wt% Stabilized zircon oxide 5 〃 Alumina 1 10 〃 2 10 〃 〃 3 5 〃 Colloidal silica 3 〃 Alumina sol 10 〃 Cu powder 3 〃 Ni powder 4 〃 Sodium carbonate 17 〃 Vinyl acetate-ethylene- Polymer emulsion (solid content 50% by weight) 7 〃 Potassium titanate fiber 8 〃 Water Appropriate amount Table 1 shows the test results.

Example-5 Example-1 is repeated except that the following ingredients are used:

Silicon carbide 15% by weight Silicon nitride 3 〃 Mica 5 〃 Alumina 1 5 〃 〃 2 5 〃 〃 3 15 〃 Colloidal silica 18 〃 Alumina sol 2 〃 Fe powder 1 〃 Cu powder 2 〃 Ni powder 4 sodium 〃 Carbonate 〃 Ethylene-vinyl chloride copolymer emulsion (solid content 50% by weight) 6 〃 Potassium titanate fiber 12 〃 Water Appropriate amount Test results are shown in Table 1.

Comparative Example-1 Example-1 is repeated except that the following components are used.

Silicon carbide 25% by weight Silicon nitride 5 〃 Alumina 1 10 〃 〃 2 10 〃 〃 3 10 〃 Neutral aluminum phosphate 19 〃 Cu powder 5 〃 Ni powder 2 〃 Sodium carbonate 7 〃 Vinyl acetate-ethylene copolymer emulsion (solid Content 50% by weight) 7 〃 Water Appropriate amount Table 1 shows the test results.

Comparative Example-2 Example-1 is repeated except that the following components are used.

Silicon carbide 15% by weight Stabilized zircon oxide 20 〃 Alumina 1 15 〃 〃 2 5 〃 〃 3 15 〃 Colloidal silica 3 〃 Alumina sol 10 〃 Fe powder 3 〃 Cu powder 3 〃 Sodium carbonate 3 〃 Vinyl acetate-ethylene- Polymer emulsion (solid content 50% by weight) 5 〃 water Appropriate amount Table 1 shows the test results.

As can be seen from Table 1, the high temperature antioxidant coating of the present invention has excellent impact resistance, and the excellent properties relating to scale generation and peelability are due to such excellent impact resistance during transportation of metal rollers. One reason is that peeling of the coating film does not occur. Comparative Examples -1 and -2 in which the components except the component g) are the same as those of the coating composition of the present invention (Japanese Examined Patent Publication No. 63-58888).
No. 59/183838) has a problem in impact resistance, and some continuous exfoliation furnaces and batch furnaces are peeled off before operation and scale is observed.

The coating material of the present invention enhances the inter-coating strength using ceramic as a base material and the adhesion strength to the steel surface as described above, and it is a neutral and thin coating film, and the thermal conductivity does not decrease. In addition to achieving many achievements such as improvement of properties, energy saving, and improvement of environmental atmosphere, it has also achieved the prevention of damage to the coating film due to condensation droplets near the inlet of the continuous heating furnace.

The coating material of the present invention exhibits a sufficient antioxidant effect even with a thin coating film of about 50 μm, and prevents and suppresses the generation of scale.
These effects are also exhibited for special and high-grade steel materials (containing Cu, Ni, Cr). However, if it exceeds 200 μ, the heat transfer is deteriorated, the heat pattern of the furnace operation is changed, and the extension of the heating time also has an unavoidable adverse effect, which is not preferable.

[Effects of the Invention] The coating material of the present invention comprises potassium titanate fibers mixed with the conventional high temperature antioxidant coating material, so that the fibers act as an aggregate of the coating film to increase the inter-coating engaging strength, There is an effect that the penetration of the high temperature oxidizing gas is prevented, the altitude is increased against physical impact, and the peeling of the coating film is prevented by following the thermal expansion of the steel material.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshikatsu Ishizu No. 3 Hikari, Kashima-cho, Kashima-gun, Kashima-gun, Ibaraki Sumitomo Metal Industries, Ltd. Kashima Steel Works (72) Inventor Nobuhiko Terada 1-1-1, Hama, Amagasaki-shi, Hyogo No. Kubota Iron Works Co., Ltd. Technology Development Laboratory (72) Inventor Isao Makito 1-1-1, Hama, Amagasaki City, Hyogo Prefecture Kubota Iron Works Co., Ltd. Technology Development Laboratory (72) Inventor Yoichi Nakamura 2 Higashiueno, Taito-ku, Tokyo Chome 18-7 Sanmaru Kasei Kogyo Co., Ltd. (72) Inventor Norimasa Miyagi 2-18-7 Higashiueno, Taito-ku, Tokyo Sanmaru Kasei Kogyo Co., Ltd.

Claims (5)

[Claims] 1. At least one of a) a group of silicon carbide, silicon nitride, stabilized zircon and mica as a ceramic substrate.
Seeds; 20-50% by weight, b) the following three aluminas as ceramic aids: 25
-50% by weight, Alumina (1): Flat fine alumina with large α crystals and small sintering shrinkage, Alumina (2): Flat granules with a high α conversion and stable firing shrinkage with an average particle size of 100μ or less Alumina, Alumina (3): Medium soda grade easily sinterable ultrafine alumina with low water content, c) At least one of the group of neutral aluminum phosphate, colloidal silica and alumina sol as a binder.
Seeds; 10-40% by weight, d) at least one member of the group of Fe, Cu, Ni and Cr powders;
10% by weight, e) Sodium carbonate as a ceramic sintering promoter; 5 to
30% by weight, f) Aqueous emulsion or aqueous solution of polymer and / or copolymer forming a water resistant coating; 2.5-15% by weight
(Solid content), and g) Diameter 10 which acts as an aggregate and enhances the bond strength between coatings.
~ 30μ, 100-500μ long potassium titanate tabular fiber; 3
~ 15% by weight, except that the total of components a) to g) is 100% by weight
High temperature anti-oxidant paint for steel. 2. The alumina (1) has an average particle size of 1 to 10
μ, sintering shrinkage: 5% or less (1600 ° C., 3 hours) of flat fine particles, the alumina (2) has a firing shrinkage of 10% or less (1600
Flat particles having an average particle size of 20 μ or more, particularly 30 to 60 μ, and the alumina (3) is a particle having a Na ₂ O content of 0.2 to 0.3% by weight and an average particle size of 1 μ or less. The high temperature antioxidant paint according to claim 1, which is characterized. 3. The alumina (1), (2) and (3)
[Component (b)] is (1.5 to 3): (0.5 to 2): (1 to 3)
The high temperature antioxidant paint according to claim 1 or 2, wherein the high temperature antioxidant paint is contained in a weight ratio of. 4. The component f) is a vinyl acetate homopolymer, a vinyl acetate copolymer, a vinyl chloride homopolymer or a vinyl chloride copolymer. The high temperature antioxidant paint according to any one of items 1 to 3. 5. The composition according to claim 1, wherein the component (f) is polyvinyl chloride, vinyl acetate / ethylene-copolymer or vinyl acetate / ethylene vinyl chloride-terpolymer. ~ The high temperature antioxidant coating composition according to any one of 4 above.