JPS6043219B2 - Mold paint for steel ingot casting - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mold paint that is applied to a mold during ingot casting, and its purpose is to reduce splash adhesion scratches, hot water wrinkles, double skin, etc., and to reduce non-metallic inclusions on the surface of the ingot. The purpose of the present invention is to provide a casting/mold paint that not only produces a high-quality steel ingot with few particles and bubbles, but also extends the life of the mold, eliminates the need for cylindrical iron plates, eliminates the need for steel work, and improves yield.

Generally, when molten steel is injected into a mold to produce an ingot, deposits and entangled slabs caused by the molten steel creeping up (splash box) and scattering (splash) remain on the requiem surface, so the requiem surface is generally It is common knowledge that there are many irregularities and defects, and that it is necessary to grind the surface after it has been made into slabs, blooms, etc. through soaking and fractional rolling.

The larger and deeper the flaw, the greater the amount of grinding and the worse the yield.

Therefore, various methods have been devised for the purpose of obtaining a steel ingot free from the above-mentioned irregularities and surface defects commonly referred to as cracks and sludge marks. Various types of mold paints have been developed and put into practical use because they are easy to implement and inexpensive, but at present no mold paints have been found that can make the skin of the steel ingot beautiful and improve the yield. That is,
Conventional mold paints include substances containing large amounts of carbon such as anhydrous tar, pitch, coal, mineral oil, animal and vegetable oils, molasses, and fluorides.
For example, appropriately select hydrofluoric acid, fluorosilicic acid, fluoroboric acid, sodium, potassium, and calcium salts, oxygen supplying agents, such as alkali salts such as nitric acid, carbonic acid, perchloric acid, etc., and add a binder, etc. Many of them are prepared using
These generate CO2 gas, halogen gas, etc. at high temperatures, and are thought to prevent splash from adhering to the inner wall of the mold or from forming hot water wrinkles. However, the above-mentioned mold paint not only generates black smoke and irritating gas when pouring molten steel, but also sometimes poses a risk of fire due to the combustion flames, which poses problems in terms of work efficiency and work environment, and furthermore, there are problems with the effectiveness of use. As mentioned above, there are various drawbacks such as not being sufficient and many of the obtained steel ingots having rough skin. The present invention aims to solve the various drawbacks of these conventional mold paints and to provide a steel ingot free of surface defects caused by scratches and hot water lines caused by splash, double skin, or entrained slag. The gist of this is a mold coating for casting steel ingots that consists only of water-soluble resin. The present invention will be explained in detail below.

The water-soluble resin according to the present invention refers to resins that are soluble in water, and the main ones include water-soluble polymers.

This water-soluble resin includes acidic polymers such as polyacrylic acid, polymethacrylic acid, polyvinyl acetic acid, polycrotonic acid, polyitaconic acid, and polymaleic acid; polyacrylic alcohol, polycrotyl alcohol, polymethylbutynol, polyallyl carbinol, and Alcohol-based polymers such as hydroxypropyl methacrylate, polypropylene glycol monoacrylate, and polyvinyl alcohol. Amide or amine polymers such as polyacrylamide, polymethacrylamide, polyisopropylacrylamide, polyallylamine, modified celluloses such as hydroxyethyl cellulose and carboxymethyl cellulose, aldehyde polymers, ether polymers, alkyd polymers, and phenols. system polymer,
and ester polymers.

Furthermore, water-soluble copolymer type styrene-acrylamide,
Also included in the invention are styrene-maleic anhydride, polyvinylpyrrolidone-methyl vinyl ether, and polyethylene oxide.

The present invention also includes, for example, sodium polyacrylate and aluminum polyacrylate, in which a metal such as sodium or aluminum is bonded to the carboxyl group of an acidic polymer.

The water-soluble resin described above was applied as a heated melt, powder, or water solution to the inner wall of the mold by spraying, brushing, dipping, etc., and after drying, molten steel was poured into it to produce a steel ingot. We succeeded in obtaining a steel ingot with a beautiful surface never seen before.

However, the above-mentioned resin begins to decompose at a temperature of about 200°C or higher, completely burns at about 700°C to 800°C, and produces a moderate amount of CO2.
It is thought that it not only generates gas and prevents the formation of a splash box and the generation of splash, but also has the effect of preventing water wrinkles and cleaning the molten steel.

It is also believed that it prevents welding of molten steel and steel ingots to the mold, and further prevents decarburization of the mold. On the other hand, it is also possible to omit the cylindrical iron plate. Next, the procedure for applying the mold paint of the present invention will be described in detail. Dissolving the resin according to the present invention in water to form an aqueous solution, spraying, brushing, roller coating,
When coating using a coating method such as dipping, there is an appropriate viscosity depending on the coating method, so it is preferable to adjust the viscosity to an appropriate value depending on which coating method is used. In the present invention, the material may be made into a powder and may be powder coated, or may be melted at a temperature higher than the softening point, that is, a heated melt may be applied. Good results can be obtained when the coating amount of the mold paint of the present invention is in the range of 20 to 1000 y/wl as a solid after drying. If the coating amount is less than 20y/a, it will be difficult to apply it uniformly to the mold wall, and the surface texture of the cast steel ingot will be slightly inferior.
If the coating is applied in excess of 1, the workability of coating and drying will be poor, the effect will be saturated, and the economy will be poor.

In addition, in general, in mass production processes such as integrated pig steel plants, molds are used repeatedly and therefore remain relatively high temperature, and even when mold paint is applied before pouring molten steel, the temperature remains at about 3.
The temperature may be maintained at around 00°C. If the mold temperature is 50 to 300°C, the paint film will dry in a relatively short time when applying with a solution, so preheating the mold or drying after applying the paint can be done by other means such as gas heating, electric heating, or infrared rays. There is no need to raise the temperature using heating means such as heating, and the work can be performed more economically. However, if the mold has been cooled to near room temperature or if a new mold is used, it is necessary to preheat the mold or mold paint, or to dry it after applying the paint. In any case, it is preferable to dry the coating film sufficiently. Next, embodiments of the present invention will be described in detail.
Example 1 The inner wall of a mold for a 100 kg steel ingot was heated to approximately 100°C to 200°C using a gas burner, then the mold paint was applied by brushing with varying amounts, and after drying was melted in a 300k9 atmospheric melting furnace. Injecting molten low carbon steel into the mold,
After solidification, the steel ingot was cut out, and the surface of the steel ingot was visually inspected to determine surface flaws, hot water wrinkles, etc. caused by splash.
Shown in the table.

In Table 1, steel ingots manufactured using mold paint (that is, no paint) and steel ingots manufactured using commercially available mold paint had many surface defects and hot water wrinkles caused by splashing on the surface of the steel ingots. There is. Compared to these, when the mold paint of the present invention is used, the surface texture of the steel ingot is extremely good. Example 2 Low carbon rimmed steel was melted in a 160 ton pure oxygen top-blown converter,
Commercially available mold paints and mold paints of the present invention were used at 100 and 150 y/bo (solid content) at a mold inner temperature of 50°C to 250°C.
10 tons and 16 tons.
Table 2 shows the results of determining the percentage of repaired area due to sludge defects after manufacturing a ton of steel ingot, going through a blooming rolling process, and cooling it without any heat treatment.

Table 2 shows that the mold paint of the present invention can make the surface of the actual steel ingot beautiful, reduce the number of scratches, significantly reduce the area to be treated for scratches, and improve the yield.

Furthermore, it has been confirmed that the amount of hot flaw maintenance can be significantly reduced when directly hot rolling, so-called direct rolling, is performed without heating after blooming. Example 3 The inner wall of the mold for 100k9 steel ingot was heated to 1000C using a gas burner.
After heating to ~200'C, apply no mold paint or commercially available mold paint to the inner surface 112, apply the mold paint of the present invention to the other 11 parts by brushing, and after drying, melt the molten steel in a 300K9 atmospheric melting furnace. Immediately stop the injection after pouring a small amount into the mold,
Table 3 shows the results of an investigation of the height of the molten steel crawling up on the mold wall after solidification, that is, the height of the splash box.

Table 3 shows that the mold paint of the present invention has an extremely small height of the splash box compared to when it is uncoated and when a commercially available mold paint is applied, and almost no splash box is formed, so there is almost no double skin formation. It can be seen that surface defects are less likely to occur.

From the above, it is thought that it is possible to omit the cylindrical iron plate conventionally used to prevent the formation of a splash box. The present invention is a mold paint made of a water-soluble resin that has never been considered to be used alone in high-temperature metal casting, and it has extremely excellent effects in terms of cost, ease of use, and safety. The present invention is extremely novel in the technical field.

In particular, when used as an aqueous solution, it is easy to apply and dry, and is also environmentally friendly, improving industrial applicability.

As explained in detail above, the mold paint of the present invention enables the production of steel ingots with extremely good skin when casting steel ingots, and the steel ingots with excellent skin have a high yield rate since they are free of defects. The coating material of the present invention has extremely significant practical effects as it enables the production of good quality and defect-free final products, that is, high-quality strip steel plates and long steel products, and also makes it possible to omit the use of cylindrical steel plates.

The mold paint of the present invention can be expected to give excellent results not only in the casting of ordinary steel ingots, but also in the casting of special steel and non-ferrous metals. Note that the surface explanatory diagram of the steel ingot according to the present invention is shown in the first
- Shown in Figure 3.

Figure 1 shows the mold produced without using the mold paint shown in Table 1.
In other words, in the explanatory diagram of the surface of the 100k9 steel ingot without coating, there are many surface flaws 1 and hot water wrinkles 2 caused by splashing. Figure 2 shows the conventional product at 100 y/d (solid content).
An explanatory diagram of the surface of a 100 kg steel ingot with the coating applied is better than the case without coating, but there are quite a few surface scratches 1 and hot water wrinkles 2 caused by splashing. Figure 3 is an explanatory view of the steel ingot surface when the polyacrylic acid according to the present invention is coated at a solid content of 100 Da/d, and shows beautiful and splash-induced scratches that have not been previously achieved with this type of cast steel ingot. The skin has no wrinkles or wrinkles.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the surface of an uncoated cast steel ingot, Figure 2 is an explanatory diagram of the surface of a steel ingot cast using a well-known mold paint (conventional product), and Figure 3 is an explanatory diagram of the surface of a steel ingot cast using the mold paint of the present invention. FIG. 2 is an explanatory view of the surface of a steel ingot cast by 1... Surface flaws, 2... Hot water lines.

Claims (1)

[Scope of Claims] 1. A mold paint for casting steel ingots, characterized by comprising only a water-soluble resin. 2 Claim 1 in which the water-soluble resin is a heated melt
Mold paint for casting steel ingots as described in . 3. A mold paint for casting steel ingots according to claim 1, wherein the water-soluble resin is a powder. 4 Claim 1 consisting of a water-soluble resin as a water solution
Mold paint for casting steel ingots as described in . 5. The mold paint for casting steel ingots according to claim 1, wherein the water-soluble resin is an acidic polymer. 6. The mold paint for casting steel ingots according to claim 1, wherein the water-soluble resin is an alcohol-based polymer. 7. The mold paint for casting steel ingots according to claim 1, wherein the water-soluble resin is an amide polymer. 8. The mold paint for casting steel ingots according to claim 1, wherein the water-soluble resin is an amine polymer. 9. The mold paint for casting steel ingots according to claim 1, wherein the water-soluble resin is a modified cellulose polymer. 10. The mold paint for casting steel ingots according to claim 1, wherein the water-soluble resin is an aldehyde polymer. 11. The mold paint for casting steel ingots according to claim 1, wherein the water-soluble resin is an ether polymer. 12. The mold paint for casting steel ingots according to claim 1, wherein the water-soluble resin is an alkyd polymer. 13. The mold paint for casting steel ingots according to claim 1, wherein the water-soluble resin is a phenolic polymer. 14. The mold paint for casting steel ingots according to claim 1, wherein the water-soluble resin is an ester polymer. 15. The mold paint for casting steel ingots according to claim 1, wherein the water-soluble resin is a copolymer. 16. The mold paint for casting steel ingots according to claim 1, wherein the water-soluble resin is polyacrylic acid or a metal salt thereof.