KR100457235B1 - Casting Method for Large Stainless Steel Ingot - Google Patents

Abstract

The present invention relates to a method for casting a large ingot, in particular, injecting molten steel into the ingot mold, in consideration of the solidification characteristics of the stainless steel ingot during the solidification process of the ingot provides a large stainless steel ingot casting method with less casting defects in the ingot For the purpose of

The large-scale stainless steel ingot casting method of the present invention is a molten steel filled with a heat generating thermal insulation material supplied to the surface of the steel ingot, a porous heat insulating material mixed with a metal aluminum powder to produce a mixed heating thermal insulation material, and then prepared mixed heating thermal insulation material in the mold It is then applied to the surface of the coating, and then a porous heat insulating material is applied, and the mixed heat insulating material is applied again, and then the porous heat insulating material is finally applied to extend the exothermic and warming effects of the mixed heat generating heat insulating material.

By extending the exothermic and thermal insulation effect of the mixed heating insulation material by the large-scale stainless steel ingot casting method of the present invention as described above, the internal defects of the large stainless steel ingot can be reduced to improve the casting quality of the large stainless steel ingot.

Description

Casting Method for Large Stainless Steel Ingot

In the process of casting a large stainless steel ingot, the present invention prevents solidification defects caused by inadequate solidification conditions such as solidification cracks or pores in the center of the ingot which are more frequent and severely generated than other steel grades, thereby preventing the ingots having excellent quality. In more detail, the present invention relates to a casting method, and more particularly, by injecting molten steel into a steel ingot mold and effectively insulating the hot water part in consideration of the solidification characteristics of the stainless steel ingot during the solidification of the steel ingot, thereby reducing the casting defects in the steel ingot. It relates to a stainless steel ingot casting method.

Currently, the continuous casting process technology has been developed, most structural stainless alloy steel is produced in the form of plate, bar or square, but large machinery parts, large mold ship parts, etc. are forced to rely on large ingots traditionally manufactured.

Recently, as the quality level required in such a large part and the use rate of the ingot increases, there is a need for a casting method for uniformly improving the quality of the entire manufactured ingot.

In particular, stainless steel alloys require less than 20-50% longer solidification time than other steel grades because the thermal diffusion coefficient of the ingot itself is low when molten steel is injected and solidified, compared to other steel grades. As a result, there is a lack of time to perform the performance of the existing hot water, and the tendency of the solidification residual stress and solidification cracks are generated in the center of the ingot due to the large difference in density compared to other steel types at the end of solidification.

Due to this phenomenon, the defects are predicted by computer simulation before the actual casting process, and the cause of the defect is analyzed and the problems are solved. The conditions for the casting process are being improved but this is also true.

In the casting process of steel ingots, various casting defects occur, which are caused by various casting defects such as ingot segregation, nonmetallic inclusions and residues, solidification shrinkage, solidification cracks, and pores, and the loss is largely increased as the occurrence frequency increases. .

In addition, it is not easy to inspect and determine defects inherent in large ingots when casting defects are generated, which results in a large loss of process cost due to cracking during the forging process and defect detection in the final product.

Most of these internal defects of steel ingots are due to inadequate casting conditions, that is, defects in solidification models, in particular due to intrusion of stainless steel.

In general, when molten steel is injected in the casting of large ingots, the hot water injector adds a high temperature heating material containing metal aluminum to the surface of the molten steel in order to generate heat and keep warm. Although the temperature has been maintained, in many cases of low ingot ratio or large alloy ingot of special alloy, the induction performance is low, leading to casting defect.

In order to solve the problems caused by the poor performance of the ingot and to improve the quality of the ingot, US Patent No. 4,134,433 has installed a graphite electrode rod in the ingot of a large ingot. This is because the molten steel is filled into the mold and intermittently supplies current to the graphite electrode while the molten steel is solidified to control the solidification of the ingot, in particular, the molten portion, and generates an arc at the surface of the molten portion to change the temperature of the molten portion. It is a method of solidifying by increasing the temperature of the steel ingot, and compensating the temperature of the upper part of the steel to keep the temperature high, thereby preventing the floating separation of nonmetallic inclusions, gas removal, shrinkage hole and solidification cracking which may exist in molten steel. Seeking.

In addition to the method described above, a method of maintaining a high temperature of the hot water part by installing a cover in the hot water part to minimize heat dissipation, or by installing an induction coil in a hot top part to measure the temperature of molten steel and intermittently heating the device And a method, or a method of applying heat insulation band having excellent heat insulation to the ingot portion of the steel ingot and the like.

However, the above methods are made up of means for additional temperature compensation or temperature maintenance based on the primordial state in which the temperature of molten steel injected into the ingot mold and the resulting non-uniform temperature distribution, in particular, the temperature of the upper inlet is lowered. .

As described in US Pat. No. 4,134,433, the method of installing and heating a graphite electrode at the ingot in the ingot is advantageous in terms of artificially managing the temperature of the ingot ingot by controlling the current and time supplied to the electrode. In case of prolonged arcing by the electrode, the graphite electrode is eroded by the molten steel surface, and the eroded graphite is mixed in the ingot, and as a result, there is a high possibility of causing problems due to unwanted carbon and other impurities (oxides). There is a problem. In addition, there is a problem that the space consumption rate is high due to securing the installation space of the graphite electrode, there is a problem that the facility investment cost, such as the cradle of the graphite electrode rod is increased.

In addition, there is a method of installing an induction heating coil in the ingot mold ingot to supply an electric current intermittently as the ingot solidifies, thereby precisely controlling the temperature of the ingot without mixing impurities, and improving the casting quality of the ingot. It has the advantage of accurate control of external input condition and pollution of impurity of molten steel and the reduction of equipment investment cost compared to the graphite electrode heating method, but it is somewhat due to the use of induction heating device and the resulting power consumption. The increase in equipment investment cost and the cost due to the power consumption is inevitable.

Hereinafter, a brief description of a large ingot casting apparatus generally used with reference to the accompanying drawings.

As the molten steel is supplied through the injection tube 4 formed in the lower part of the mold 1 and filled in the mold, ingots in the mold are formed. Specifically, the ingot may be divided into a ingot body 2 and a ingot press 3. The steel ingot hot water is formed by supplying extra molten steel to improve the quality of the steel ingot and absorbs casting defects such as solidification shrinkage that may occur in the steel ingot. Stainless steel ingot has a low thermal diffusion rate in the ingot material, and when the ingot and the induction heating material used for general steel are applied, the ingot and the body solidify simultaneously before the ingot body is solidified or the ingot solidifies first. Casting defects such as solidification shrinkage and solidification cracking occur in the body. Therefore, stainless steel ingots are required to extend the working time of the hot water heating material.

SUMMARY OF THE INVENTION The present invention has been made to improve the above-mentioned conventional problems and conditions for prolonging the working time of a hot water heating material, and is free from impurities in the hot water heating method. The elimination of additional costs due to the power consumed to maintain and the continuous consumption of subsidiary materials, the requirement of the hot water of the solidification characteristics of stainless steel ingots, rather than the action of the intermittent hot water heating material for a certain period of time, the effect of the hot water heating and heating effect It is an object of the present invention to provide a large stainless steel ingot casting method that can produce castings having low solidification defects in steel ingots by improving the solidification characteristics of ingots.

Figure 1 is a schematic diagram showing the application of the large stainless steel ingot casting method of the present invention to a general large ingot casting apparatus

<Description of the symbols for the main parts of the drawings>

1: Mold 2: Ingot Body

3: ingot crusher 4: infusion tube

5: surface plate 6: pressure sleeve

7: hot water case 8: mixed heat insulation

9: porous insulating material 10: surface mirroring material

As a means for achieving the above object, the large-scale stainless steel ingot casting method of the present invention, after mixing the heat insulating material supplied to the surface of the ingot molten metal with a porous heat insulating material mixed with metal aluminum powder to produce a mixed heating heat insulating material, and then produced The exothermic insulating material is applied to the surface of the molten steel filled in the mold, and then the porous insulating material is applied again, and then the mixed exothermic insulating material is applied again, and finally the porous insulating material is applied to extend the exothermic and thermal effects of the mixed exothermic thermal material in time. It can be characterized by.

In addition, in the large stainless steel ingot casting method of the present invention, the particles of the metal aluminum powder has a size of 0.5-2mm or less, and the porous heat insulating material constituting the mixed heating insulation material has a mixing ratio of 10-30% by weight , Mixed exothermic insulation and porous insulation is characterized in that the lamination alternately 2-3 times.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In the casting process of the stainless steel ingot, the molten steel is filled in the mold 1, and then the manufacturing method and application method of the hot water heating insulation 8 applied to the steel ingot crushing apparatus 3 will be described in detail.

First, the size of the metal aluminum powder as the heating source is adjusted to be 0.5-2mm, and the mixed heat generating insulation 8 is mixed with the metal aluminum powder having its size adjusted by mixing the rice hull which is the heat insulating material and the porous heat insulating material 9 as the heat insulating material. Manufacture. Subsequently, after the molten steel is filled, the mixed exothermic insulating material 8 thus prepared is first dispersed and coated on the surface of the molten steel, followed by dispersing and coating the chaff, which is the porous insulator 9, and then the mixed exothermic insulating material 8. The coating is dispersed again, and finally, the rice hull which is the porous insulating material 9 is dispersed and applied to increase the heat insulating effect (the chaff serves as a heat insulating material, a heat insulating material and a weak but heat generating material). At this time, the amount of the mixed exothermic heat insulating material required here is determined by the weight fraction according to the weight of the steel ingot and uses a certain amount.

The size of the metal aluminum powder as a heating source in the method of applying the hot-mixed heating exothermic insulation material is 2 mm or less, when the heating material is applied as the metal aluminum powder penetrates into the pores of the chaff when mixed with chaff. The powder is surrounded by the husk husk to have the effect of delaying the combustion.

In addition, setting the size of the metal aluminum powder to 0.5 mm or more is such that as the size of the powder decreases, it is not protected by the husk husk and is instantaneously ignited in direct contact with molten steel to emit heat. It is.

Further, there is an effect of delaying the exothermic action of the mixed exothermic insulating material by alternately stacking the mixed exothermic thermal insulation material and chaff.

As a result, it is possible to extend the exothermic thermal insulation effect of the steel ingot squeeze 3 as a result.

When the delayed combustion condition of the hot-mixed heat-generating insulation is applied to large ingot casting, it is not suitable for the ingot casting of low carbon structural steel with high thermal diffusion coefficient, and the solidification time of the ingot is increased because the thermal diffusion coefficient of the ingot is low like the stainless steel ingot. It is suitable for the casting process of steel ingots.

In the accompanying drawings, reference numeral 2 denotes a steel ingot body, 4 an injection tube, 5 a platen, 6 a presser sleeve, 7 a presser case, and 10 a surface mirror member.

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

(Example 1)

Injecting molten steel with a temperature of 1502 ° C at a rate of 1.2 tons / minute into a mold having a capacity of 5 tons capable of casting SUS316 alloy steel, and 45% by weight of the metal aluminum powder having an average particle size of 0.7-1.0 mm according to the conventional method. The amount of the heating material contained in about 2kg / ton at the completion of filling the molten steel at the completion of filling the molten steel, the mixed heating material made by mixing the chaff of about 10-50% by weight with the conventional heating material in the same manner as described above It was put into a steel ingot hot water part and evaluated.

Moreover, the comparative evaluation also evaluated the case where the mixed heating material which mixed 30 weight% chaff was laminated | stacked alternately with the pure rice hull | bubble part in a steel ingot.

Among the comparative evaluation conditions, the total amount of the heating material input from the same size ingot, and more particularly, the total amount of the metal aluminum powder was the same.

Thus, the results obtained by qualitatively comparing and evaluating the casting internal defects and the quality of the cast steel in accordance with the heating material application conditions of the stainless steel ingot crushed portion is shown in Table 1 below.

For reference, in the conventional large-scale ingot casting process, after the molten steel is filled, the heating material made by mixing the metal aluminum, aluminum slag and ash on the surface of the hot water is applied in a certain amount by weight fraction according to the size of the ingot, and heat insulation such as rice hulls is used. A method of keeping warm with powders has been used.

Chaff ratio Alternating stacking number Shrinkage (%) Fever retention time Internal coagulation crack Crack location Ingot Quality 0 One 8 15 minutes plenty Ingot × 5 One 7 17 minutes plenty Ingot × 10 One 5 20 minutes slightly Ingot ↓ 15 One 3 30 minutes slightly Ingot top ↓ 20 One 0.1 35 minutes Less Ingot top ○ 30 One 0.2 40 minutes Less Ingot top ○ 40 One 0.7 40 minutes slightly Ingot top ↓ 50 One 2.5 40 minutes Plenty Ingot × 60 One 4 45 minutes plenty Ingot × 10 2 3 35 minutes slightly Ingot ↓ 10 3 2 30 minutes slightly Ingot ↓ 10 4 2 30 minutes slightly Ingot ↓ 20 2 0.04 45 minutes none Ingot top ◎ 20 3 0.04 40 minutes none Ingot top ◎ 20 4 0.05 40 minutes none Ingot top ◎ 30 2 0.07 45 minutes Less Ingot top ○ 30 3 0.05 40 minutes none Ingot top ○ 30 4 0.05 40 minutes Less Ingot ○ 40 2 0.6 45 minutes slightly Ingot ↓ 40 3 0.6 40 minutes slightly Ingot ↓ 40 4 0.7 40 minutes slightly Ingot ↓

※ Excellent: ◎,: Good: ○, Normal: △, Under: ↓

[Table 1] is a comparison table comparing the internal quality of the ingot according to the application conditions of the 5 ton SUS316 steel ingot induction heating material, as shown in the table is 20% by weight of the chaff in the conventional heating material, and the chaff It can be seen that the quality of the ingot is the best when the number of layers of mixed heating material and rice husk is 2-4 times.

As described above, by delaying the ignition and exothermic performance of the heating material by the large stainless steel ingot casting method of the present invention to increase the exothermic thermal action time of the hot water, the internal defect of the solidified large stainless steel ingot is reduced to Casting quality can be improved.

Claims (4)

In the casting of a large stainless steel ingot, the exothermic thermal insulation material supplied to the surface of the ingot molten metal after the molten steel is filled in the mold is manufactured as a mixed exothermic thermal insulation material by mixing a porous thermal insulator with the metal aluminum powder as the exothermic supply source, and the mixed exothermic thermal insulation material prepared is It is applied to the surface of the molten steel filled in the mold, and then the porous heat insulating material is applied, and then the mixed heat insulating material is applied again, and finally the porous heat insulating material is applied to the heat generating and the heat insulating effect of the mixed heat insulating material in time A large stainless steel ingot casting method, characterized in that it can be extended. The method of claim 1, wherein the metal aluminum powder particles have a size within 0.5-2 mm. The method of claim 1, wherein the porous heat insulating material constituting the mixed heating insulation material has a mixing ratio within 10-30% by weight . The method of claim 1, wherein the mixed heating insulation material and the porous heat insulating material are alternately laminated three times .