KR810000573B1 - Method of producing ingots of unalloyed and alloyed steels - Google Patents

Abstract

Large ingots with improved structure are cast in molds contg. a slag topping bath elec. heated to >= 120kwh/ton ingot during soldification. Slag is prevented from enterng the gap formed during solidification between the mold wall and shrinking ingot. A 43-ton ingot was produced from degassed steel in a mold topped with a slag-contg. fixture having peripheral cooling. The slag was prevented from entering into shell-to ingot shrinkage gap while being heated to liq. for 23h.

Description

Ingot manufacturing method of steel and alloy steel

1-5 are vertical cross-sectional views of various embodiments for carrying out the method of the present invention.

The present invention relates to a process for producing ingots of reduced ingot segregation and non-metallic pure and alloy steels in an improved initial crystallization process. Here, as described in German Patent Publication No. 1,182,102, molten steel is first poured into a mold, and then a slag mixture is fed thereon, so that the slag mixture is energized during the solidification process of the steel in the mold. Energy is advantageous at least 120 kw / hrs per tonne of metryl of the ingot mold.

Such a mold is suitably cooled in the atmosphere. That is, it is not cooled by a special method such as liquid. In carrying out this method, it is possible to use a device with an inclined cooling wall at the upper medium inlet.

When producing large ingots using the method described above, it may be difficult to continue to supply the high energy required for the slag for the entire solidification period. Ingot shrinkage occurs when steel is solidified and the external skin is solidified, thereby reducing the diameter of the ingot. This creates a gap between the wall of the mold and the skin of the solidified ingot, which causes the liquid slag to flow from top to bottom. As a result, the height of the slag jaw located at the top decreases, reducing the electrical resistance used for the discharge of joule heat to generate less joule heat, and the process proceeds through an unstable path to form a pipe on the ingot head. In addition to causing ingot segregation.

It is an object of the present invention to provide an obstacle or seal that prevents the liquid slag on the top of overcoming the above-mentioned drawbacks and challenges from entering the gap formed between the mold wall and the ingot skin when the ingot shrinks. The height of the slag jaw and the electrical resistance of the working slag located on top of the mold are kept substantially constant. Not only does the diameter of the ingot change during solidification, but also shrinks in the vertical direction, causing a particular problem, but this is solved by the present invention.

The present invention solves the problem of electricity by cooling the upper boundary region of the molten steel bordering the slag phase.

According to one embodiment of the invention, the steel is poured on top to fill the area of the upper cooling wall of the mold of steel. That is, slightly above the opening of the mold. The steel boundary area immediately solidifies at the contact area with the upper cooled sidewall. If a gap is formed between the epidermis and the upper sidewall during contraction of the solidified ingot, slag enters into it and solidifies, forming a sealing plug at the inlet of the gap to prevent further entry of the slag. . The resulting annular sealed slag never disturbs the process of metallurgical reaction in the region of the liquid slug, which allows it to keep at a high temperature.

The method according to the invention can be carried out without pouring molten steel to the top. That is, by using an upper part located on the mold to have an annular or generally conical contour that reaches below the level of steel flowing into the mold.

이며, 경사는 tgα를 갖는다. 여기에서 dm은 주형의 직경이고, h는 주형의 높이이다.If the projection has a conical contour, the conical surface of the projection contacting the inner wall of the mold should be at least

And the slope has tgα. Where dm is the diameter of the mold and h is the height of the mold.

The method according to the invention also advantageously uses an apparatus having an upper part fixed to the edge of the mold by a detachable connection method. The connection method can be designed with a crank mechanism. This embodiment can separate the detachable connection as soon as the ingot skin is sufficiently strong, after which the ingot top is carried by its surface.

The apparatus according to the invention is used to pour the molten steel into a mold and then hold it down until the top is impregnated in the molten steel until the ingot skin carrying the top is formed. The advantage of this device is that it consists of an upper part that holds factors such as a drawing anchor on the government, and its end, such as a hammer-head, is suitable for stretching below the steel level in the mold.

Finally, the upper part is made of metal, and it is possible to use an upper part whose bottom is extended into the molten steel. The metal structure may be partially lined with refractory material. When using such a device, cooling in the impregnated annular zone can be carried out with heat absorbing metal structures.

The method according to the invention and the apparatus for carrying out the method will be explained in more detail by means of the following embodiments and the accompanying drawings.

The mold 2 of the steel-manufacturing plant, which forms a water-cooled top 3 on its upper opening in FIG. 1, is placed on the bottom plate 1. The mold was filled with molten steel 4 and further steel was poured into the mold until the level 5 of steel reached the cooling inner wall region of the upper part 3, ie slightly above the mold opening 6. . The produced liquid slag 7 was then introduced from the top, and the electrode 8 connected to the power source 9 was immersed in a slag bath.

The slag was heated using resistance heat. Strong cooling takes place at the contact area between the edge of the steel and the cooled inner wall of the upper part 3, which extends from point A to point B. The ingot contracts and the ingot epidermis cooled between the points A and B is transferred to the points A and B due to shrinkage. The slag solidifies at the entrance of the gap forming the sealing ring 10 for the slag that enters and approaches the annular gap thus formed. The height of the slag jaw at the top 3 is not affected by this plug formation, and the electrical engineering conditions for forming the joule rows do not change. Thus, the required energy supply and the dependent metallurgical effect can be kept constant for a long time.

에 달하는 것이 유익하다.In the specific embodiment shown in FIG. 2, the cooled top 3 is placed on the mold 2, which has an annular projection 11 extending downward, which is below the steel level after filling the mold with steel. Extend to This annular projection is conical and it is preferable that the conical surface 12 has a certain inclination angle. The conical surface 12 of the ring 11 has a vertical line and an angle α, which is made from the height of the ingot and its upper diameter. The slope of this angle α is at least

It is beneficial to reach.

After placing the upper part 3 on the upper edge of the mold 2, the molten steel is filled in the mold so that the protrusion 11 is impregnated in the boundary region of the molten steel. Initial cooling occurs along line AC. The outer band of the ingot head changes position due to shrinkage during solidification of the ingot. After completion of solidification, point C is shifted downward to C ¹ . The outer head of the ingot described as point C during solidification will always move near the cooled upper conical surface, ie, between the retracting ingot skin and the conical surface 12 and no expansion cap will be formed. The slag flows into the small gap 13 and then solidifies to form the sealing plug 10.

In the embodiment shown in FIG. 3, the cooled upper portion 14 is placed on the upper opening of the mold, and an annular downward protrusion 15 is placed on the upper portion, which is below the steel level after filling the molten steel in the mold. To extend. In this embodiment, the upper part is fixed to the circumference of the mold by the detachable connecting means, and the electrical connecting means is preferably designed with a crank mechanism.

The upper portion 14 described in FIG. 3 can be lowered with the apparatus until it can be immersed in the molten steel even after pouring the molten steel into the mold.

When the ingot skin 17 is sufficiently strong, the contact means 16 are separated and the upper portion 14 is transported by the ingot skin itself, resulting in a height reduction of the ingot that solidifies automatically during shrinkage. Thus only a small gap can be formed between the casting ingot and the top on the ingot, where the top is also pressured from the ingot by weight or other device. In contrast, in the same manner as in the embodiment shown in FIG. 2, a structural function, i.e., a gap created between the top exit ring surface and the surface of the ingot head immediately after formation of the ingot skin, is sealed by the slag plug.

In the embodiment shown in FIG. 4 an upper portion 14 can be used, which is fixed to the mold 2 by a detachable connecting means 16 or carried by some mechanism, filling the mold 2 or An annular protrusion 15 is shown which extends below the steel level after lowering the top 14. The top 14 of this embodiment is connected to the joined draw anchor 18, the bottom 14 of which is designed like a hammer-head. These bottoms extend below the steel level and settle therein as soon as the ingot skin 17 solidifies. Then, the connecting means 16 is separated. Thus, a device 14, such as a cooled top, is carried by the ingot cuticle 17 to move the ingot head that shrinks. In this embodiment, the sealing is formed in the same manner as shown in FIG.

The specific embodiment shown in FIG. 5 uses an upper part which can be secured to the mold by the detachable connecting means 16 until a sufficient conveyance of the ingot skin 17 is obtained. This upper portion is composed of a metal structure 20, the inner portion of which is composed of a refractory material (21). The lining has an insulating effect, at least resistant to the chemical action of the slag during solidification of the ingot, and can prevent complete dissolution of the lining and injury to the metal structure by hot slag. The mold was filled with molten steel until the bottom of the annular insert extended into the molten steel. Thickening of the ingot epidermis 17 on the impregnated annular surface of the metal structure 20 occurs due to the endothermic force of the metal confinement. After sufficient conveying effect of the ingot cuticle 17 is achieved, the connecting means 16 to the mold 2 are separated so that the upper part can reduce its height during solidification of the ingot without any interference.

The method according to the invention will be described in more detail by the examples described below.

Example 1

Forging grade ingots of 19.5 metrics were prepared using the apparatus shown in FIG. The molds were designed with polygons, the minimum diameter of 1,305mm at the upper end, and the maximum internal diameter of 1,455mm.

Ingot introduced floor stocking. After the molten steel was filled into the molds used in the steelmaking plant, the molten steel was filled again until the steel level rose to 100 mm from the upper cooling wall area. As a result, the cooled annular ring (because the mold is polygonal) had a maximum thickness of 370 mm and a minimum thickness of 290 mm, with a median diameter of 1,100 mm. Liquid slag was poured on top of the mold. The height of the slag jaw was 18 cm. The slag bath was energized at more than 120 kw / hrs per metric ton for more than 11 hours.

The cooled top was then removed, and the diameter of the ingot was found to be reduced by 48 mm during solidification and 67 mm in height compared to the mold. The cooled area along the upper A-B line and the cooling along the A-B line before the ingot evacuated prevented slag from entering the gap between the mold and the ingot skin.

Example 2

Ingots of 43 metric tons were made with the apparatus shown in FIG. The annular conical surface of the protrusion had an inclination angle α of about 22 ° with respect to the vertical axis of the ingot. The upper diameter of the polygonal mold was at most 1,960 cm, at least 1,725 mm, and the height was 2,400 mm. The top cooled at the height of the slag jaw had a diameter of 1360 mm and the overall height was 800 mm. Filling the entire mold, the ingot was poured into the mold by degassing steel until the annular cone face of the protrusion entered the molten steel. Slag was introduced into the cooled top and the slag was maintained at a temperature above the liquidus temperature of the steel bath by energy supply by the electrode. The heating process was maintained for 23 hours, then the slag was removed and the cooled top lifted up. It can be seen that the upper edge of the ingot was reduced by 85 mm in proportion to the height of the mold (point C ^{1 in} FIG. 2) and the diameter was reduced by 68 mm. It was observed that no slag entered the gap between the mold and the ingot epidermis.

Example 3

The cooled top as described in Figure 3 was placed on the mold. The diameter of the cooled top was 1300 mm for the slag jaw and the overall height of the top was 800 mm. The mold for producing a 43 metric ton ingot was designed with polygons and the maximum diameter was 1960 mm and the minimum diameter 1725 mm at its upper edge. This is placed so that the larger diameter is on the upper side. The overall height of the mold was 2400 mm. The steel was poured into the mold until the steel level reached the entire slope of the top, which was directed to the bottom plate. The slag was poured into the cooled top and the slag was powered over 23 hours. After 45 minutes the connection between the top and the mold was dissociated so that the cooled top was carried by the solidified ingot cuticle alone. During solidification, the ingot shrinked 83 proportional to the mold, and no slag entered between the mold and the ingot cuticle.

Example 4

As shown in FIG. 4, the upper part was fixed to a mold bonded to a cast 85 metric ton ingot, and the upper part was provided with a detachable moving member having a hammer-head type at its lower end to connect with the ingot. At its upper end, the polygonal mold had a maximum diameter of 2,350 mm and a minimum diameter of 2,100 mm. The filling height of the mold was 2,800 mm. The diameter of the cooled top at the height of the slag level was 1420 mm and the overall height of the top was 900 mm. The ingot was cast into a degassed melt to a height where the top surface was inclined downward to contact the substrate and soaked into the melt as a whole. In addition, parts such as hammer-head are immersed in the steel bath by about 60 mm. After casting the ingot, the slag was poured into the cooled top and powered to maintain the temperature above the liquidus temperature of the steel. The electrode length was 2,500 mm and the electrodes were used interchangeably. Sixty minutes after the end of casting of the ingot, the connecting means supporting the cooled top of the mold was separated and the top was transported to the ingot cuticle formed simultaneously. Drawing anchors were used to create a tension of 3,000 kp between the hammer-head-like member cast into the ingot and the top of the mold. The electrode was removed and slag removed after 38 hours of ingot treatment under energy supply. . The draw anchor was then removed and the cooled top lifted up. When manufacturing the ingot with this device, a 75 mm diameter reduction and 94 mm ingot height reduction was observed during solidification of the ingot without slag entering the annular gap between the mold wall and the ingot skin.

Claims (1)

Molten steel is poured into the mold with the top open and a slag mixture is fed over the molten steel in the mold and the molten steel has an upper edge band adjacent to the slag mixture and the steel solidifies in the mold. An improvement in the ingot manufacturing method of steel and alloy steel, which comprises the step of supplying energy to the slag mixture, in which the initial crystallization process is improved, the ingot of the ingot and the content of the contained nonmetallic substance are reduced. Cooling the upper edge of the molten steel along the annular portion projecting into the outer circumferential surface of the mold opening by contacting the cooled upper metal portion, and providing an annular space between the upper portion and the cooled upper edge The edge band is separated from the upper part by the contraction of the ingot. Fabricating an ingot of a steel and alloy steel characterized by weaving, and introducing a portion of the slag mixture into the annular space and solidifying the portion of the slag mixture to form a seal between the mold and the ingot. Way.

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