FI73739B - FOERFARANDE FOER MINIMERING AV SLAGGMEDFOERING. - Google Patents

Description

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The present invention relates to a method for minimizing slag entrainment in the calculation of molten metal from a furnace and to a device used in the method.

In order to improve the utilization of the ingot addition and the control of oxygen removal in steelmaking, it is desirable to minimize the transport of slag with the molten metal when it is lowered in the furnace. Various plug devices have been used to block the down hole of the BOP and Q-BOP furnaces to prevent slag leakage at the beginning of the down when the furnace is first tilted down to discharge the metal. However, most of the slag enters the ladle due to the fact that it enters the impeller formed by the metal, which is formed at the inlet of the counter hole when the rest of the metal is discharged from the furnace.

Two different approaches have been used to solve this latter problem. A device located outside the second furnace is physically started to shut off the flow when slag begins to drain out of the counter hole. Another approach has been to place a floating plug in the furnace that floats on the slag-metal partition surface and clings to the drain hole. However, these floating plugs have the disadvantage that they tend to weld to the wall of the landing hole of the weld-25 and are difficult to remove when it requires combustion with an oxygen flame. This also increases the wear of the counter hole itself. Examples of prior floating plugs are disclosed in Stahl und Eisen, Volume 90, pages 257-263 and Japanese Patent Application 30 47-20803.

The present invention relates to a method for minimizing the entrainment of slag on the surface of molten metal flowing from the furnace through a counter hole, in which a body having a density between the density of molten metal and slag in the furnace is dropped on the surface of the molten slag and metal in the furnace. the cross-section of the smallest dimension is greater than the largest cross-section of the orifice, the molten metal is drained from the furnace through the orifice and then shut off through the orifice to prevent slag from passing over the already molten metal from the furnace. generally planar surfaces, the joints of which are adapted to engage the downhole so that the body blocks 10 to 20-80% of the downhole opening when the body adheres to the downhole, and to monitor the state of flow from the downhole so as to detect current expansion of the door as the body engages the counter hole, thereby shutting off the flow through the counter hole.

The invention further relates to a means for minimizing the entrainment of slag on the surface of molten metal flowing from the furnace through a counting hole, which means is a body having a density between the densities of molten metal and slag in the furnace and having a minimum cross-section greater than the largest cross-sectional opening. , characterized in that the device has equilateral, generally planar surfaces, the joints of which are adapted to engage the counting hole so that the body blocks 20-80% of the counting hole opening when the body 25 engages the counting hole opening.

3 pieces with a density of 3320-6090 kg / m are preferred for use in steelmaking. The body is a material that is substantially insoluble in molten metal and slag.

The body has a maximum dimension of 13-30 cm in any direction and is adapted to close 20-80% of a circular downhole opening with a diameter of 10-25 cm when the intersection of the body surfaces is centrally adhered thereto. Thus, as the last portion of the metal 35 begins to flow out of the furnace, the body tends to adhere to the counting hole, causing the flow to spread, 3 73739 because the hole is only partially blocked. The expanding flow serves as a signal to the furnace operator that slag will soon begin to flow. Thus, the operator can shut off the flow, preventing the slag from entraining the surface of the metal in the ladle. The main advantage of a polygonal body is that it does not permanently adhere to the counter hole and does not require combustion with an oxygen flame to remove it from the counter hole.

The surfaces of the body can all be the same shape and size. The cubic shape is preferred.

10 The body may be a refractory material with solid metal particles distributed to increase its density. The metal particles may be spheres or fibers, or both, with the latter acting to increase the cohesiveness of the body. It is preferred to use carbon steel balls, while the fibers have a stainless steel composition.

The invention will now be described in more detail by way of example with reference to the accompanying drawings, in which Figure 1 is a cross-section of a furnace inclined to discharge molten metal through a furnace 20 countersink and showing the position of a floating plug;

Referring to Figure 1, there is shown a steelmaking converter 10 having a refractory cladding 12 and a counting hole 14 located near the mouth 16 of the converter vessel. The vessel is shown tilted downward from its normal vertical position so that molten metal 18 and slag 20 flow away therefrom. Cube 22 floats on the interface between the crank 30 and the metal during the descent. Referring to Figure 2, there is shown a cube 22 adhering to a counter hole 24, only partially blocking the counter hole opening. For a counting hole with a diameter of 15 cm, each cube with an area of 18 or 20 cm has been found to work satisfactorily. An 18 cm moon is preferred. It blocks about 40% of the counter hole with a cross-section of 15 cm in diameter.

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The cube can be any refractory material that resists dissolution in metal or slag at least sufficiently to maintain the minimum dimensions required to adhere to the downhole. A moldable tu-5 durable material is preferred. 18 cm cubes with a density of 4150-4710 kg / m 3 have been used, although any density between the densities of slag and metal should suffice. For example, the density of molten steel is n.

3 6920 kg / m while the density of steelmaking slag 3 10 is about 2770 kg / m. The following are examples of mixtures used to make typical cubes:

Table I

3

Cube A, each side 18 cm and density 4150 kg / m 15 weight, kg

Refractory cement 3.4

Fine iron ore concentrate 6.9

Steel balls 13.0

Water 1.1 20 Stainless steel fibers 0.7 3

Cube B, each side 18 cm and density 4710 kg / m weight, kg

Refractory cement 2.4

Fine iron ore concentrate 4.7 25 Steel balls 19.4

Water 1.1

Stainless steel fibers 0.7

Steel balls are of the readily available type and are used to increase the density of a cube. Iron ore 30 is used because it reacts with the carbon in the steel bath and indicates where the submerged cube is located. Stainless steel fibers tend to bind the refractory mass, preventing the cube from breaking into pieces prematurely.

It is, of course, desirable to dry the cubes completely to remove moisture that reacts with the metal, causing the cubes to crack and break.

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It is important that the cube is dropped into a limited area above the landing opening so as to ensure that it is transported by the currents in the metal during the landing to an area directly above the landing opening so that it adheres to it. It has been found that the downward tilt angle of the BOP or Q-BOP furnace at the end of the descent, if tilted to reach the maximum rate of flowing metal, varies between about 88-103 ° from the vertical. The area of the corners is due to various factors, such as the wear of the furnace lining and the accumulation of solid slag or metal at the mouth of the furnace. It has been found that you make sense. the location of the counting hole can be made by calculating the distance of the counting hole from the hinge pins of the furnace at different angles of inclination of the furnace. The location of the counter hole from the hinge-15 pins at the end of the descent varies by about 1.2 n. Thus, it has been found best to place the cube in the center of the calculated distance of 1.2 m. This can be done in various ways from floor level to the point next to the mouth of the oven.

20 The cube must also be placed in the oven just before a vortex forms, when the last part of the metal begins to drain out. This time can be calculated from the estimated tonnage of metal contained in the furnace, the size and shape of the counting hole relative to the metal bath to arrive at the critical tonnage of metal remaining in the furnace at which vortex formation begins to occur. This critical tonnage can be calculated for conventional steelmaking BOP or Q-BOP grades from the formula. Normally, it is preferable to add the cube in one or two minutes to 30 minutes before all the metal has drained from the furnace.

Claims (8)

1. A method of minimizing slag entrainment on the surface of molten metal flowing out of one through a tapping heel. furnace, according to which a method on the surface of the molten slag and metal in the furnace in the area above the tap hole is dropped a body whose density lies between the densities of the molten metal and the slag in the furnace and whose minimum dimension has a cross section which is larger than the largest cross-section of the tap heel opening, molten metal is discharged from the furnace through the tap heel opening, and then the flow through the tap hole is stopped to prevent slag from entering the furnace on the molten metal already taped out of the furnace, characterized in that it The body used has equilateral, generally planar surfaces, the connection points of which are arranged to adhere to the tappet so that the body blocks 20-80% of the tappet opening, as the body adheres to the tappet opening, and the state of flow through the tappet is monitored so that the enlargement is observed which occurs in the flow as the body gets stuck in the drain hole, whereby the flow through the drain hole is stopped. Method according to claim 1, characterized in that the body used is multilayered. Method according to claim 2, characterized in that the body used is cubic. 4. A method according to claim 3, characterized in that the body used is a cube. 5. Means for minimizing slag entrainment on the surface of molten metal flowing out of a furnace through a tap heel, which is a body whose density lies between the densities of the molten metal and the slag in the furnace and whose minimum dimension has a cross-section which is larger than the largest cross-section of the pinhole opening, characterized in that it has parallel, generally planar