JPS60251219A - 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 by compounding respectively specified ceramic base material, ceramic assistant, binder, metallic powder and sintering accelerator at specific ratios. CONSTITUTION:20-50wt% Ceramic base material of at least one kind among silicon carbide, silicon nitride, stabilized zirconium and mica, 25-50wt% ceramic assistant, 10-40wt% binder of at least one kind among neutral aluminum phosphate, colloidal silica and alumina sol, 5-10wt% metallic powder of at least one kind among Fe, Cu, Ni and Cr and 5-30wt% sodium carbonate which is the ceramic accelerator are so compounded to attain 100wt% in total. The ceramic assistant is constituted of flat pulverous alumina having a large alpha crystal and small shrinkage rate on sintering, flat granular alumina having stable shrinkage on sintering, <=100mu average grain size and a high rate of alpha crystal and easily sinterable ultra-fine alumina of a middle soda grade having a low moisture content.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is applied to the surface of steel materials, especially steel billet slabs, to prevent oxidation, to prevent scale formation in a high-temperature oxidizing atmosphere in a heating furnace, and to easily peel off before rolling. Regarding high-temperature anti-oxidation paints for steel materials.

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 at the level of ordinary steel in a heating furnace, K
The occurrence of Fi scale is small and descaling is relatively easy, but in the case of high-grade steel quality, a lot of oxide scale is generated due to the influence of furnace time and temperature, and descaling is difficult, so the yield is reduced. This has become a problem from the viewpoint of productivity, resource saving, and product finishing due to the decline.

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, magcia-based refractories, low-melting point metals, or inorganic salts, but depending on the steel type of the slab containing Ou, Ni, Or, etc., and the operation of continuous or batch heating furnaces, Due to differences in methods, there are drawbacks such as insufficient oxidation and scale generation prevention and removability. Therefore, at present, high-grade steel slabs are covered with protective covers made of thin iron plates to cover the surface of the steel before being sent to the heating furnace, thereby preventing the formation of an oxidizing atmosphere on the surface of the steel as much as possible to prevent 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 antioxidant coating for steel with the following composition: a) 20 to 50% by weight of silicon carbide, silicon nitride, zircon stabilized as a ceramic substrate; At least one member of the group of mica,
b) 25 to 50% by weight of the following three types of alumina as a ceramic auxiliary material Alumina t1): A flat fine grain alumina with large a-crystals and a low sintering shrinkage rate, Alumina (2): Stable sintering shrinkage Flat granular alumina and alumina with a high pregelatinization rate and an average particle size of 100μ or less (3): Medium soda grade easily sinterable ultrafine alumina with low moisture content c) Medium as a binder with an average particle size of 10 to 40% by weight at least one member from the group consisting of polyaluminum phosphate, colloidal silica, and alumina sol, d) 5 to 10% by weight of F6, Ou
%lii and Or powder and e) 5 to 30% by weight of sodium carbonate as a ceramic sintering accelerator, provided that the sum of components LL) to e) is 100% by weight. be.

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

Cerabax as a base material for component a) has high heat resistance (
For example, silicon carbide is heated to 2200℃) The amount used is component a)
, b), C), d) and θ) C (hereinafter referred to as all components)
It needs to be in the range of 20 to 50% by weight of the total amount. 2
If the zero weight is too low, a dense coating film cannot be formed, and the desired oxidation prevention effect cannot be obtained because the steel material comes into contact with the oxidizing atmosphere gas frequently. If it exceeds 500% by weight, the thermal conductivity decreases, and heating energy consumption increases, resulting in energy loss.

Alumina as a ceramic auxiliary agent of component b) is a combination of flat particles with a high gelatinization rate [alumina (1) and (2)] and easily sinterable ultrafine particles [alumina (3)]. .

Alumina (1) has a large alpha crystal, a small sintering shrinkage rate of 5% or less (xboo℃, 3 hours), and has excellent flat hiding power, especially fine particles of 1 to 10μ. It is.

Alumina (2) has stable firing shrinkage, especially a shrinkage rate of 10μ or less (1tSOO℃, 3 hours), and a high α
average particle size of 100μ or less, especially 20μ or more, especially 3
The particles have a particle size of 0 to 60μ and are excellent in flattened particles.

Alumina (3) has a low moisture content, especially (L2~
[LA3wt%M&! Easily sinterable ultrafine particles with an average particle size of 1μ or less and of medium soda grade content.

Component b) cannot provide a dense coating film with sufficient hidden baker under a 25-weight plate in the case of a coating film of 100 μm or less. On the other hand, if the amount is 50% by weight or more, the peelability of the coating film is poor.

Alumina (1), (2) and (3) are mutually 1,5
~3:[L5~2: It has been found that advantageous results are obtained when used in a weight ratio of 1 to 30.

The binder component (c) stabilizes the bonding of the ceramic base material in a) above and improves the adhesion to the steel material, and the amount used must be in the range of 10 to 40% by weight of the total components. . If this binder is under 10 weight, the mixed mixture will be hard and will not be able to adhere to the surface of the steel material. 4
Even if the amount is increased to 0.00% by weight or more, the binder effect remains unchanged.

d) Component metal powder is prepared in a reducing atmosphere in order to avoid or minimize the oxidizing atmosphere (generally 02 = 1 to 2 in the exhaust gas) from coming into contact with the steel surface in the heating furnace. It is something to keep. 5% by weight is the minimum amount that creates an oxidizing atmosphere on the surface of the steel material, and if it exceeds 100% by weight, it will react with or weld to the copper material at high temperatures, changing the properties of the surface of the steel material, the so-called product surface, and causing negative effects. It will bring about.

θ) Component ceramic sintering accelerator is heated at 500 to 800°C.
It promotes sintering of the ceramic base material and binder to be sintered in the process, and serves to make the paint mixture hard and reduce the adhesion strength to the steel surface, resulting in a dense coating film.

Fi, 5% by weight is the lower limit to maintain a proper sintering rate. If it is less than this, the sintering state will be poor (weak), the strength of the coating film in the mixed kneaded product will be reduced, and the surface of the steel material will deteriorate due to the formation of an oxidizing atmosphere erosion zone. However, if it exceeds 30% by weight, a dense coating film on the ceramic substrate will not be formed, which will deviate from the initial purpose.

As mentioned above, the paint of the present invention uses ceramic as a base material to increase the strength of the coating film and the adhesion strength to the surface of steel materials, and because it is neutral and has a thin coating that does not reduce thermal conductivity, it saves resources and labor. Achieve many results such as performance, energy saving, and environmental atmosphere improvement.

The paint of the present invention exhibits a sufficient antioxidant effect even in a thin coating film of about 50 μm, and prevents and suppresses the formation of scale. Special/high-grade steel materials (Ou.

These effects are also shown for N1, Or input. However, if it exceeds 200μ, the heating transmission will deteriorate,
Changing the heat pattern of the furnace operation and extending the heating time is also undesirable because it causes unavoidable adverse effects.

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

Example 1 In addition to the following ingredients: Silicon carbide: 26% by weight Silicon nitride: 8% by weight Neutral aluminum phosphate: 15% by weight Fe powder: 4% by weight Sodium carbonate: 17% by weight. time)
Flat high α-crystal alumina (this is alumina (
1), hereinafter abbreviated as alumina 1) 15 weight section,
Average particle size 45μ, shrinkage rate (1/100℃, 3 hours) 10
Flat alumina with a pregelatinization rate of 100 qb (this corresponds to alumina (2), hereinafter abbreviated as alumina 2) with a nano content of 5 weight factor and 0.25 weight factor, and an average particle size α4 μ and particle size distribution A mixture containing 10 parts by weight of medium soda grade alumina (corresponding to alumina (3), hereinafter abbreviated as alumina 3) of 0.1 to 1.5 microns and a suitable amount of water is prepared.

Apply this paint to 50μ and 100μ of unheated thick plate steel, ultra-high tensile steel, high tensile steel, and ordinary steel, respectively.
After applying the coating to a coating thickness of 24 hours and air drying for 24 hours, the steel material is heated and rolled under the furnace time and furnace temperature shown in Table 1 below.

Table 1 shows the measurement results regarding the scale generation and the removability of the antioxidant paint.

Example 2 Example 1 is repeated except with the following ingredients: Silicon carbide 15 layers i’chi Silicon nitride 7 Stabilized zircon 5N Alumina 1 10 1 2 6tt I 3 15* Neutral aluminum phosphate 10 '3r3 Idal Silica 10 νe powder 4 Ou powder 3 Sodium carbide 15 tt Water appropriate amount The results are shown in Table 1.

Example 3 Repeat Example 1 except using the following ingredients; Silicon carbide 15 weight Cloud mother 10l Alumina 1 20N 〃　2　7　l #3 10# Colloidal Silica 12 I Alumina sol 15 tt N1 powder 3I Or powder 31 Sodium carbonate 51 Water appropriate amount The results are shown in Table 1.

Example 4 Example 1 is repeated except using the following ingredients: Silicon nitride 15% by weight Stabilized zircon 5N Cloud mother 1 lo l Alumina 1 12 # #2 5# Alumina 3 15 weight section Neutral aluminum phosphate 15 Alponazol 7 IFe powder 51 Or powder 3N Sodium carbonate 8 # Water appropriate amount The results are shown in Table 1.

Example 5 Example 1t - Repeat except using the following ingredients: Silicon carbide 32 weight Child Lumina 1 12 N 1 2 5z ＃　5　8＃ Neutral aluminum phosphate 18 l Ou powder 51 Sodium carbonate 2 (l) Water appropriate amount The results are shown in Table 1.

Comparative Example 1 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.

Comparative example 2 Example 1 can be repeated except using the following ingredients: Silicon carbide 3D weight superior Alumina 1 18 Neutral aluminum phosphate 20 Fθ powder 7 Sodium carbonate 25 Water appropriate amount The results are shown in Table 1.

(Note) The following symbols are used to evaluate the degree of scale generation and the removability of the antioxidant paint (including the removability of scale if scale is generated): ○ No generation 0100 Regretful peeling @ 5% or less 070 to 99%〃 △ 5 to 20 excellent △ 40 to 69 qbtt No occurrence of this was observed. This is compared to the case of Comparative Example 2, in which only Alumina 1 was used as the alumina and the other components were the same as the paint of the present invention, in which scale was observed even with a coating thickness of 100μ. It is also outstanding.

Furthermore, the paint of the present invention can be completely removed by descaling with high-pressure water even at a film thickness of 50 μm, and is significantly superior to Comparative Example 1, which is a conventionally known paint, in this respect as well. In addition, when the paint of Comparative Example 1 was used, scratches were observed on the steel plate after rolling, but no scratches were observed with the paint of the present invention.

Agent Hikaru Esaki Agent: Hikaru Esaki

Claims (1)

Claims: j) a) 20-50% by weight of at least one member from the group of silicon carbide, silicon nitride, stabilized zircon, mica as a ceramic substrate; b) 25-50% by weight of ceramic The following three types of alumina can be used as auxiliary materials: Alumina (1): Flat fine grain alumina with large ff crystals and low sintering shrinkage rate, Alumina (2): High average particle size of 100μ or less with stable sintering shrinkage. A flat granular alumina and alumina (3): low moisture content, medium soda grade, easily sinterable ultrafine alumina C) 10-40% by weight of neutral aluminum phosphate, colloidal silica as a binder , at least one member from the group of alumina sol, d) 5-10% by weight of Fe, Ou, Ni and O
For steel materials composed of at least one member of the group r powder and e) 5 to 30% by weight of sodium carbonate as a ceramic sintering accelerator, provided that the sum of components a) to e) is over 100% by weight High temperature anti-oxidation paint. 2) Alumina (1) is flat fine particles having an average particle size of 1 to 10μ and a sintering shrinkage rate of 5 or less (1600°C, 3 hours), and alumina (2) has a sintering shrinkage rate of 10 μm or less.
(1600℃, 3 hours) with an average particle size of 20μ or more, especially 30 to 60μ, reed and alumina (3 hours).
) is [12-0.5 wt% Nano content and 1
The antioxidant paint according to claim 1, which is fine particles having an average particle size of μ or less. 3) alumina (1) as a ceramic auxiliary agent of component b);
The antioxidant paint according to claim 1 or 2, which contains (2) and (3) in a weight ratio of 1.5 to 3:15 to 2:1 to 3.