JPS6043220B2 - Casting method of steel ingot for rolling - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for casting chikon ingots, particularly for rolling, and its purpose is to reduce splash adhesion scratches, hot water wrinkles, double skin, etc., and eliminate non-metallic inclusions and air bubbles on the surface of chikon. The object of the present invention is to provide a casting method that can produce a small number of high-quality steel ingots, extend the life of the mold, omit the use of cylindrical iron plates, omit the need for steel work, and improve yield.

Generally, when molten steel is poured into a mold to manufacture a chikon, deposits and entangled slabs caused by the molten steel climbing up (splash box) and scattering (splash) remain on the chikon surface, so the surface of the chikon generally has unevenness and scratches. There are many, uniform heating,
It is common knowledge that surface flaw grinding is necessary after blooming into slabs, blooms, etc.

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 requiem without the above-mentioned unevenness and surface defects commonly referred to as cracks and sagging defects. Over time, casting methods that use various mold paints have been developed and put into practical use because they are easy to implement and inexpensive, but none of them have been found to make the skin of the soul a beautiful product and improve the yield. This is the current situation. That is, conventional casting methods using mold paints include substances containing a large amount of carbon such as anhydrous tar, pitch, coal, mineral oil, animal and vegetable oils, and molasses, and fluorides such as hydrofluoric acid, fluorosilicic acid, or fluoroboric acid. There are many casting methods that use a mold paint prepared by appropriately selecting sodium, potassium, and calcium salts, oxygen supplying agents, such as alkali salts such as nitric acid, carbonic acid, and perchloric acid, and adding a binder, etc. These release CO at high temperatures.

It has been considered an effective technique because it generates gas, halogen gas, etc., and prevents splash from adhering to the inner wall of the mold or from forming creases. The mold paint used in the above-mentioned casting method not only generates black smoke and explosive gas when pouring molten steel, but also sometimes poses a fire hazard due to the combustion flames, which poses problems for work efficiency and the work environment. Moreover, as mentioned above, the usability effect is not sufficient, and the obtained steel ingots often have rough skin.

The present invention solves the various drawbacks of these conventional casting methods and provides a method for casting steel ingots without surface defects caused by splash-induced scratches, hot water wrinkles, double skin, or entrained slag. That is.

The gist of the present invention is to apply a mold paint consisting of a heated melt, powder, or water solution of a water-soluble resin; or a water-soluble resin mixed with either a water-emulsifiable resin or a water-dispersible resin, or both. 20 as a solid after drying on the wall
A method for casting a steel ingot for rolling, characterized in that the steel ingot is coated at a voltage of 1000 V/7T1, and after the film is formed, the steel ingot is cast by a top pouring or bottom pouring method.

The present invention will be explained in detail below.

The water-soluble resin used in the casting method 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, Alcohol-based polymers such as polyhydroxypropyl methacrylate, polypropylene glycol monoacrylate, polyvinyl alcohol, polyacrylamide, polymethacrylamide,
In addition to amides such as polyisopropylacrylamide and polyallylamine, amine polymers, and modified cellulose systems such as hydroxyethyl cellulose and carboxymethyl cellulose, there are aldehyde polymers, ether polymers, alkyd types, and phenol types.
Furthermore, water-soluble copolymer type styrene-acrylamide,
Also included in the invention are styrene-maleic anhydride, polyvinylpyrrolidone-methyl vinyl ether, and polyethylene oxide.

Furthermore, water-emulsifiable resin refers to resins that are made by enveloping a finely powdered resin that does not dissolve in water with a surfactant and emulsifying it in water. These water-emulsifiable resins are broadly classified into synthetic emulsions obtained by emulsion polymerization and synthetic latexes; the former includes vinyl acetate resin emulsions and acrylic resin emulsions, and the latter include water dispersions of styrene-butadiene emulsion copolymers. There is a system. Furthermore, water-dispersed resin refers to a resin that is made by cutting a solid resin that does not dissolve in water and suspending it in water. Dispersed into a white emulsion, for example. Next, the reason for mixing and adding a water-emulsifiable resin or a water-dispersible resin to a water-soluble resin will be explained. Water-emulsifiable resins or water-dispersible resins are solid resins that are emulsified or dispersed in water. Compared to water-soluble resins, these resins have better heat resistance when applied to molds and when pouring into molten steel, and they also have better heat resistance when applied to molds and when pouring into molten steel. Some have good adhesive properties. Therefore, when using a water-soluble resin alone,
If the resin is inferior in performance, such as paintability to molds or drying properties, there is a limit to which a water-emulsifiable resin or water-dispersible resin with superior performance can be mixed and added to achieve the full performance. This can be improved even more. When a water-soluble resin containing these resins is used, a steel ingot with fewer flaws can be produced than when a water-soluble resin is used alone. As mentioned above, the present invention provides a mold paint consisting of a heated melt, a powder, or an aqueous solution of a water-soluble resin, a water-emulsifiable resin or a water-dispersible resin added to the water-soluble resin, or a mixture of both. By applying it to the inner wall of the mold using methods such as spraying, brushing, roller, and dipping, and then injecting molten steel after drying to produce a steel ingot, we were able to successfully obtain a steel ingot with an unprecedentedly beautiful surface. This is what I did.

The resin begins to decompose at temperatures above about 200°C, and after about 7
It is thought that it burns completely at temperatures between 00°C and 800°C, generates a moderate amount of CO2 gas, and prevents the formation of splash boxes and splashes, as well as prevents wrinkles and cleanses molten steel. It will be done. It is also believed that it prevents welding of molten steel and steel ingots to the mold, and further prevents decarburization of the mold. Next, the procedure for applying the mold paint in the method of the present invention will be described in detail.

Spray the resin according to the present invention into a solution by adding it to water,
When applying by a coating method such as brush coating, roller coating, or dipping, there is a suitable 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. The present inventors applied the above-mentioned paint as a heated melt or powder to the inner wall surface of the mold and achieved the effect, but the method of applying it as an aqueous solution also has better workability and eliminates mold treatment and residue after manufacturing. Cleaning, maintenance, and operation of the coating equipment were all easy and effective.

Good results can be obtained if the coating amount of the mold paint used in the method of the present invention is in the range of 20 to 1000'/l based on the solid matter after drying. If the coating amount is less than 20y/Rt, the coating amount will be small and 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, and if the coating is more than 1000y/Rt, the workability of coating and drying will be poor and the effect has become saturated and is less economical.

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 to be used, it is necessary to preheat the mold or mold paint, or to dry it after application. In any case, the paint film must be thoroughly dried. The aforementioned molds include flat, corrugated, and flute molds, and any of these molds can be used.

Next, embodiments of the present invention will be described in detail.

Example 1 The inner wall of a mold for a 100k9 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, both steel ingots manufactured without using mold paint, that is, uncoated, 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 casting method 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 according to the present invention were used at mold inner temperature of 500C to 250C at 100 and 150y/oi (
After producing 10-ton and 16-ton steel ingots, the ingots were poured into molds sprayed with solids (solid content), and then subjected to a blooming rolling process and cooled without any heat treatment. The results are shown in Table 2.

Table 2 shows that the mold paint according to 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 with scratches, and improve the yield.

Furthermore, it has been confirmed that the amount of hot flaw maintenance during direct hot rolling, so-called direct rolling, can be significantly reduced without heating after blooming. Example 3 The inner wall of the mold for 4 blocks of 100k9W was heated to 100°C with a gas burner.
After heating to ~200'C, no mold paint or commercially available mold paint was applied to the inner surface 112, and the mold paint according to the present invention was applied to the other 112 surfaces by brushing, and after drying, the mold paint was melted in a 300k9 atmospheric melting furnace. After a small amount of molten steel was injected into the mold, the injection was immediately stopped, and after solidification, the height of the molten steel creeping up on the mold wall, that is, the height of the splash box, was investigated. Table 3 shows the results.

Table 3 shows that in the method of the present invention, the height of the splash box is extremely small compared to when no coating is applied 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. As explained in detail above, the method of the present invention makes it possible to produce a steel ingot with an extremely good skin when casting a steel ingot, and the steel ingot with the excellent skin has a high yield because it is free of defects. Furthermore, the method of the present invention has extremely significant practical effects, as it enables the production of defect-free final products, that is, high-quality strip steel plates and long steel products, and also enables the omission of cylindrical iron plates.

The method of the present invention can be expected to produce excellent results when used not only for casting ordinary rolled steel ingots, but also for casting special steel and non-ferrous metals. Note that explanatory views of the surface of the steel ingot according to the present invention are shown in FIGS. 1 to 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 also shows the conventional product at 100f/i (solid content)
An explanatory diagram of the surface of a 100k9 steel ingot when coated is superior to 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 surface of a steel ingot when 100 I1/d of polyacrylic acid according to the present invention is applied as a solid content, and is beautiful and has no scratches caused by splashing, which has never been achieved with this type of cast steel ingot. Has skin without hot water wrinkles. Further, in the present invention, an appropriate amount of a pH adjuster may be added so that the pH of the mold paint becomes a value of 5.8 to 8.6. If the mold paint is acidic, add alkaline substances such as sodium hydroxide, potassium hydroxide, calcium hydroxide, calcium oxalate, sodium tartrate, potassium tartrate, and alkaline polymers such as sodium polyacrylate to the pH adjuster. On the other hand, if the mold paint is alkaline, it is preferable to add a carboxylic acid or polycarboxylic acid such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, etc. to the pH adjusting agent, and an acidic substance such as the above-mentioned acid-based polymer. That is, in the present invention, it is permissible to add very small amounts of the above-mentioned additives, etc., within a range that does not deviate from the purpose.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the surface of a steel ingot cast without coating, Fig. 2 is an explanatory diagram of the surface of a steel ingot cast using a mold paint (conventional product) according to a well-known method, and Fig. 3 is an explanatory diagram of the surface of a steel ingot cast according to the present invention. FIG. 2 is an explanatory diagram of the surface of a steel ingot cast using mold paint. 1... Surface flaws, 2... Hot water lines.

Claims (1)

[Claims] 1 Water-soluble resin; or a mold paint consisting of a heated melt or powder or water solution of a water-soluble resin and either a water-emulsifiable resin or a water-dispersible resin, or a mixture of both, is applied to the inner wall surface of the mold after drying. 20-1000g as solid matter
/m^2, and after forming a film, pouring molten steel and casting a steel ingot.