JPH02199088A - Production of metal-impregnated non-calcined refractory - Google Patents

Abstract

PURPOSE:To readily provide a metal-impregnated non-calcined refractory having excellent spalling resistance and slag wetting resistance by pre-heating a porous non-calcined refractory, deaerating the gas existing in the open pores of the treated refractory, immersing the refractory in a melted metal and subsequently pressing the melted metal with a pressing plate to impregnate the melted metal into the open pores. CONSTITUTION:A pressing device comprising a piston 1a and a cylinder 1b is disposed in a metal-impregnating and pressing oven. A non-calcined refractory 13 is held with a piston 1a, inserted into a cylinder 1b, pre-heated with a pre- heating coil 9 and subsequently subjected to an evacuation treatment with a vacuum pump 7 to deaerate a gas existing in the open pores of the refractory 13. The piston is subsequently moved downward to immerse the melted metal 2 in the refractory 13 and simultaneously a pressure is applied to the melted metal 2 with the piston 1a to impregnate the melted metal 2 into the open pores of the refractory 13, thereby providing the metal-impregnated non-calcined refractory.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing unfired refractories used in metal manufacturing furnaces, heat treatment furnaces, and the like.

[Prior art] Refractories used for the inner walls of heat treatment furnaces such as pressurized furnaces have a
Since it is exposed to harsh conditions of 000°C or higher, surface peeling gradually occurs. On the other hand, the inner walls of molten metal containers such as converters, ladles, and degassing furnaces come into contact with molten metal and slag, causing erosion and peeling.

In particular, in slag lines, the inner wall refractories are severely eroded and
Furthermore, the molten slag penetrates into the interior of the refractory and the refractory is destroyed. In order to solve the above problems, refractories are required to have spalling resistance and slag infiltration resistance.

Spalling refers to the reduction in refractories that crack and fail due to thermal shock, mechanical or structural causes. Spalling due to thermal shock (hereinafter referred to as thermal spalling) occurs due to thermal stress during rapid heating and cooling. Spalling due to mechanical causes (hereinafter referred to as mechanical spalling) mainly occurs due to damage to refractories caused by mechanical operation. Furthermore, spalling due to structural causes (hereinafter referred to as structural spalling) mainly occurs in association with slag infiltration. That is, the slag infiltrated into the open pores of the brick increases thermal stress in the brick base material, causing damage to the base material.

Of these spalling types, mechanical spalling can be improved to a certain extent by improving equipment, etc. Therefore, in terms of the properties of firebricks, especially heat-resistant spalling properties and structural spalling properties can be improved. In order to improve the structural spalling resistance, it is necessary to improve the slag infiltration resistance for the reasons mentioned above.Slag infiltration also prevents erosion of the base material from the brick surface. Therefore, refractories with excellent slag infiltration resistance are desired from the viewpoint of suppressing melting loss.

Refractory bricks with relatively excellent properties include high alumina bricks, chamotte bricks, magnesia bricks,
Chrome and magnesia bricks are used. Recently, graphite-added refractories such as magnesia-carbon bricks with improved heat-resistant spalling properties and castables containing metal fibers have been put into practical use.

Further, in order to improve slag infiltration resistance, tar-impregnated bricks, which are porous bricks impregnated with tar, are used for lining converters, stainless steel smelting furnaces, and the like. In tar-impregnated bricks, the open pores of the bricks are filled with tar, which prevents slag infiltration and suppresses structural spalling.

One of the methods for manufacturing tar-impregnated bricks is to mix and mold dolomite powder with tar as a binder, then sinter it to obtain the desired apparent porosity, and then mix the tar diluted with a solvent in a vacuum chamber at room temperature. There is a method of immersion under pressure.

Also, one of the other methods of producing tar-impregnated bricks is
Dolomite powder is mixed and molded using tar as a binder, then fired to obtain the desired apparent porosity, immersed in a tar bath at a temperature of 200 to 300°C in a vacuum chamber, and 3 to 4 kg/cj of There is a way to apply pressure.

[Problem to be solved by the invention] However, when the above tar-impregnated brick is used in a furnace, etc., the solvent used to impregnate the tar evaporates due to high heat, and the apparent porosity of the brick increases. Resulting in. For this reason, it is not possible to sufficiently prevent slag infiltration, and the effect is small.

Generally, in order to improve the slag infiltration resistance, it is sufficient to densify the refractory, but if it is densified too much, thermal spalling tends to occur. Thus, it is difficult to achieve both slag infiltration resistance and spalling resistance.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for manufacturing an unfired refractory having excellent slag infiltration resistance, structural spalling resistance, and heat resistant spalling resistance.

[Means for Solving the Problems] The object of the present invention is to preheat a porous unfired refractory, to degas the gas present in the open pores of the preheated unfired refractory, A step of immersing the degassed unfired refractory into molten metal in a cylindrical container, and the unfired refractory is immersed by a piston-shaped pressure plate slidably provided in the cylindrical container. This can be achieved by a method for producing a gold scrap-impregnated unfired refractory, which includes the step of impregnating the unfired refractory with the molten metal by applying pressure to the molten metal.

Unfired refractories are refractories manufactured by molding using a binder such as phenolic resin and then baking at a temperature of about 200 to 300°C, such as magnesia bricks, chromium-magnesia bricks, There are high alumina bricks and chamotte bricks.

In addition, in the method for manufacturing a metal-impregnated unfired refractory of the present invention, before the step of immersing the unfired refractory in molten metal,
As long as the process of TMing the unfired refractory is always performed, the preheating process, degassing process, and dipping process can be performed in any order.

[Function] The reason why the preheating step is provided in the present invention is that if the unfired refractory is immersed in the molten metal at the same temperature (that is, room temperature) without preheating, the temperature difference between the surface of the unfired refractory and the molten metal will increase. is quite large, the molten metal is rapidly cooled and solidified on the surface of the unfired refractory, and a film of molten metal is formed on the surface of the unfired refractory. When a metal wave film is formed on the surface of the unfired refractory, it becomes impossible to further impregnate a portion of the unfired refractory with metal. Therefore, it is necessary to preheat the unfired refractory before immersing it in molten metal to minimize the temperature difference between it and the molten metal and prevent the molten metal from solidifying on the surface of the unfired refractory. be.

The reason for providing the degassing step in the present invention is that if air remains in the open pores of the unfired refractory, impregnation of the metal will be inhibited by the remaining air, making it difficult. Even if the metal could be impregnated by applying pressure, a portion of the metal would be extruded by the compressed air in the open pores after the pressure was restored. Therefore, in this degassing step, it is important to degas the unfired refractory almost completely.

The reason why the pressure step is provided in the present invention is that if pressure is not applied to the molten metal in which the unfired refractory is immersed, the internal pressure of the unfired refractory and the molten metal pressure will be balanced, and the molten metal will become unfired. This is because it is not impregnated into the open pores of the fired refractory. Conversely, if the applied pressure exceeds the compressive strength of the unfired refractory, the unfired refractory itself will be damaged, the amount of metal impregnated will decrease, and the hot strength of the unfired refractory after metal impregnation will decrease. , the pressure must be less than the compressive strength of the unfired refractory.

Hereinafter, the present invention will be described in more detail in Examples with reference to the drawings, but the present invention is not limited to the Examples.

[Example] First, an apparatus used in the method for manufacturing a metal-impregnated unfired refractory of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing an example of a metal-impregnated unfired refractory manufacturing apparatus that can be used in the present invention.

According to Figure 1, the metal-impregnated unfired refractory production equipment includes a preheating furnace (■) and a metal-impregnated pressure furnace (!). and an annealing furnace ■.

The preheating furnace (2) is a device for heating the unfired refractory to around the melting point of the metal with which it is pre-impregnated. Therefore, the performance required of a preheating furnace is that the walls of the preheating furnace can withstand near the melting point of the metal to be impregnated, and that the preheating coil 1
Second, it can be heated to around the melting point of the metal with which the unfired refractory is impregnated. Any heating furnace that achieves the above performance can be used in the present invention. As will be described later, when the preheating step is carried out in the metal-impregnated pressurized furnace 1, it is not necessary to provide the preheating furnace 2.

The metal impregnation pressure furnace 1 is a device that deaerates the unfired refractory, immerses it in the molten metal 2, and impregnates it with metal by applying pressure. FIG. 2 is an enlarged view of the metal impregnation pressurized furnace 1. According to this, a pressurizing device 1 is arranged in a metal impregnating pressurizing furnace I. The pressurizing device 1 is a piston 1a
and cylinder 1b. A completely sealed space 3 is formed by inserting the piston 1a into the cylinder 1b, and pressure can be applied to the sealed space 3 by withdrawing the piston 1a into the cylinder 1b. Therefore, the contact portion 4 between the piston 1a and the cylinder 1b must have excellent sealing properties and sliding properties. Furthermore, as will be described later, the pressurizing device 1 needs to be heat resistant because it comes into contact with or approaches the molten metal 2, and it needs to be pressure resistant because it applies a considerable pressure. In order to satisfy these conditions, the material of the pressurizing device 1 is Cr4C3.
It is preferable to use ceramic materials such as and ZrB2, and it is particularly preferable to use graphite-ceramic materials.

The piston 1a is a device that applies pressure to the sealed space 3 by being inserted and lowered into the cylinder 1b. The piston 1a is equipped with an unfired refractory holding device 5, a conveying device 6, and a vacuum valve 7.

The unfired refractory holding device 5 holds the unfired refractory and the piston 1.
This is a device that connects a. Unfired refractory holding device 5
First, it is necessary to have the ability to firmly connect the unfired refractory to the cylinder 1b or the piston 1a so as not to drop it during the processing process, and since the holding device 5 comes into contact with or approaches the molten metal 2, It requires heat resistance and pressure resistance since it is exposed to pressure in the sealed space 3. Any conventional holding device can be used as long as it satisfies these conditions. The transport device 6 mainly includes rails 8 and a drive device (
(not shown), and a control device (not shown). By providing this conveying device 6, the present invention can be made continuous or automated. The transport device 6 includes
Conventional ones can be used. The vacuum valve 7 is equipped with a vacuum pump (not shown), etc., and is a device for reducing the pressure in the sealed space 3. As a result, the unfired refractory 1
The gas present in the open pores of No. 3 can be evacuated.

The cylinder 1b is a device that stores molten metal 2 to be impregnated into the open pores of the unfired refractory 13. cylinder 1
A heating coil 9 is arranged around b. This heating coil 9 is for heating the cylinder 1b and maintaining the metal in a molten state. Therefore, the heating coil 9 is one that can be heated to the melting point of the metal to be impregnated.

The annealing furnace (2) is for annealing the unfired refractory impregnated with metal, and a conventional annealing furnace can be used.

In addition, the above preheating furnace ■, metal impregnated pressure furnace! and annealing furnace (2) do not necessarily need to be integrated.

Hereinafter, the method for manufacturing the metal-impregnated unfired refractory of the present invention will be explained in detail.

The method for producing a metal-impregnated unfired refractory of the present invention includes the steps of preheating the unfired refractory, impregnating the open pores of the unfired refractory with metal, and annealing the unfired refractory impregnated with the metal. It can be divided into two steps:

Each step will be explained below with reference to the drawings.

Preheating Step The preheating step is to preheat the unfired refractory before immersing it in molten metal.

The purpose of the preheating step is as follows.

The unfired refractory is immersed in molten metal in the next step. Molten metal is at a fairly high temperature (for example, 1450°C or higher for stainless steel), and if unfired refractories are directly impregnated into molten metal without preheating, the molten metal will come into contact with the unfired refractories due to the temperature difference. It cools rapidly on the surface and solidifies.

Furthermore, since unfired refractories are rapidly cooled, they may undergo severe thermal spalling and may be damaged. As a result, a metal film is formed on the surface of the unfired refractory, and no further metal can be impregnated therein. Therefore, by preheating the unfired refractory before immersion, the temperature difference between the surface of the unfired refractory and the molten metal is made as small as possible, and solidification of the molten metal on the surface of the unfired refractory is prevented.

The preheating temperature is preferably higher than the melting point of the metal to be impregnated, but may be lower than the melting point as long as the purpose of the preheating step can be achieved. As the preheating furnace (2) used in the preheating step, a conventional one can be used as long as it can obtain the desired temperature and is heat resistant.

Note that the preheating step can also be performed in the metal impregnated pressurized furnace I. In this case, the preheating furnace (2) is not necessary. To perform preheating in the metal impregnation pressurized furnace I, the piston 1a holding the unfired refractory may be inserted into the cylinder 1b and then heated by the heating coil 9 before being impregnated into the molten metal. As described above, by performing the preheating step in the metal-impregnated pressurized furnace 1, the apparatus used in the present invention can be simplified.

Metal Impregnation Process This metal impregnation process can be further divided into the following three steps.

(a) Deaeration step The purpose of this deaeration step is to remove air present in the open pores of the unfired refractory.

The reason for removing gas from the open pores of the unfired refractory 13 is as follows:
This is because if gas exists in the open pores, the metal impregnated by pressurization in the following pressurizing step (c) will be discharged by the compressed gas in the open pores after pressure is restored. The degassing step may be performed either before or after the preheating step described above.

The deaeration process is performed using a piston 1a holding an unfired refractory 13.
This can be done by inserting the cylinder into the cylinder lb to form a sealed space 3, and then reducing the pressure using a vacuum valve 7 equipped with a vacuum pump (not shown) or the like. At that time, when inserting the piston 1a holding the unfired refractory 13 into the cylinder lb, a certain distance is provided between the upper surface 10 of the molten metal accommodated in the cylinder 1b and the lower surface 11 of the piston 1a. There is a need. This is because if this distance is too small, the molten metal 2 will be sucked out from the vacuum valve 7 when the pressure is reduced. This distance depends on the degree of pressure reduction, the weight of the molten metal 2, etc., and changes depending on the combination thereof. Therefore, the distance is conveniently selected so as to obtain a desired effect by adjusting the amount of molten metal in the cylinder lb or by adjusting the distance by which the piston 1a is inserted into the cylinder 1b.

Moreover, the entire metal-impregnated pressure furnace 1 can be depressurized and the unfired refractory can be degassed while the unfired refractory held by the piston 1a is outside the cylinder 1b. However, this method requires a relatively large-scale vacuum pump to reduce the pressure in the entire metal impregnation pressurized furnace I.

In order to degas the unfired refractories, it is desirable to reduce the pressure in the sealed space 3 or the entire metal-impregnated pressurized furnace I as much as possible. However, in reality, since the molten metal 2 exists in the sealed space 3, the pressure must be reduced in consideration of the vapor pressure of the molten metal 2. In the present invention, 10-
A reduced pressure of about 2 to 20 torr is preferred.

(b) Immersion process The main dipping process is a process in which the unfired refractory is immersed in molten metal, and the unfired refractory 13 held by the piston 1a
This is done by immersing it in molten metal 2. this is,
This can be easily done by lowering the piston 1a until the unfired refractory 13 is immersed in the molten metal 2. Alternatively, the unfired refractory 13 may be removed from the holding device 5 and dropped. Note that when performing the dipping step, it is preferable to keep the vacuum valve 7 closed.

The metal impregnation rate depends on the wettability of the molten metal 2 to the unfired refractory 13, the porosity of the unfired refractory 13, and the pressure of the next step. Therefore, the impregnation time varies depending on the combination of the type of unfired refractory used and the type of metal to be impregnated, so it cannot be stated unconditionally, but it is 5 to 3
It takes about 0 minutes.

The previous degassing step (a) and the main dipping step (b) can be performed in any order. That is, the degassing step may be performed with the unfired refractory immersed in the molten metal 2. However, a preheating step must be performed before the main impregnation step. This is because, as described above, preheating the unfired refractory before immersing it in molten metal prevents the molten metal from solidifying on the surface of the unfired refractory.

In addition, from the viewpoint that the unfired refractory can be completely degassed, it is preferable to perform the deaeration process before the dipping process.

(c) Pressurizing process The purpose of this pressurizing process is to apply pressure with the piston 1a while the unfired refractory 13 is immersed in the molten metal 2, and use that pressure to push the metal through the open pores of the unfired refractory 13. It is to impregnate the inside of the body.

As a pressurizing method, for example, the following means can be used.

When the piston 1a is separated from the liquid level of the molten metal 2 after the dipping step (b), high pressure gas is introduced into the sealed space 3 between the piston 1a and the molten metal 2. pressure can be applied. In that case, the pressurizing effect can be enhanced by further lowering the piston 1a. In some cases, desired pressurization can be achieved by simply lowering the piston 1a after returning the sealed space 3 to normal pressure, without using particularly high-pressure gas. Furthermore, if conditions permit, the molten metal 2 may be directly pressurized by pressing the piston 1a downward while in contact with the liquid surface of the molten metal 2.

As mentioned earlier, the difficulty of impregnating the unfired refractory 13 with metal (impregnation speed) depends on the wettability of the molten metal 2 to the unfired refractory 13, and the apparent porosity of the unfired refractory 13. , and the pressure applied in the main pressurization step. however,
There are certain limits to improving the wettability and apparent porosity. Therefore, the difficulty of impregnating the unfired refractory 13 with metal depends mainly on the pressure applied in the main pressurization step. Generally, the higher the pressure applied, the more metal can be impregnated. However, if the applied pressure exceeds the compressive strength of the unfired refractory, the unfired refractory itself may be destroyed, the amount of metal impregnated may decrease, or the hot strength of the unfired refractory after metal impregnation may decrease.
A pressure less than the compressive strength of the unfired refractory must be applied. In addition, if no pressure is applied to the unfired refractory, the internal pressure of the unfired refractory and the pressure of the molten metal blades will be balanced, and the molten metal will not be able to penetrate into the open pores, so a certain amount of pressure must be applied. Must be.

Therefore, the pressure applied in the main pressurization step varies depending on the combination of the type of unfired refractory and the type of metal to be impregnated, so it cannot be generalized, but it is approximately 1 kg / c-
The compressive strength of the unfired refractory used in the present invention must be lower than the compressive strength of the unfired refractory used in the present invention.

Annealing Step In the immersion step, the unfired refractory 13 is immersed in the molten metal 2, and the unfired refractory itself is at a fairly high temperature. If the unfired refractory is cooled rapidly to room temperature, the metal impregnated in the unfired refractory will rapidly solidify, causing cracks or cracks in the unfired refractory. Therefore, in the main annealing step, the unfired refractory heated to a high temperature is gradually cooled to room temperature. A conventional annealing furnace can be used in the main annealing step.

The open pores of the unfired refractory can be impregnated with metal by the above-mentioned preheating step, metal impregnation step, and annealing step. For example, a magnesia brick with an apparent porosity of 19.5% by volume is degassed and immersed in molten Fe, and the porosity is 23 kg/
When a pressure of CD was applied to impregnate metal, the apparent porosity decreased to 0.01% by volume.

[Effects of the Invention] By the method of the present invention, the open pores of an unfired refractory can be impregnated with metal, and a metal-impregnated unfired refractory having excellent spalling resistance and slag infiltration resistance can be manufactured. Can be done.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of an apparatus that can be used in the method for producing a metal-impregnated unfired refractory of the present invention. FIG. 2 is a sectional view of the metal impregnating pressurized furnace. DESCRIPTION OF SYMBOLS 1... Pressure device, 2... Molten metal, 3... Sealed space, 5... Unfired refractory holding device, 6... Transfer device, 8... Vacuum valve, 9...・Heating coil, 12... Preheating coil, 13... Patent attorney Takehiko Suzue, representative of the applicant for unfired refractories

Claims (3)

[Claims] (1) A step of preheating a porous unfired refractory, a step of deaerating the gas present in the open pores of the preheated unfired refractory, and a step of storing the degassed unfired refractory in a cylindrical container. By applying pressure to the molten metal in which the unfired refractory is immersed by a piston-shaped pressure plate slidably provided in the cylindrical container, the molten metal is immersed in the molten metal. A method for producing a metal-impregnated unfired refractory, comprising the step of impregnating the unfired refractory with a metal-impregnated unfired refractory. (2) A step of preheating a porous unfired refractory, a step of immersing the preheated unfired refractory into molten metal in a cylindrical container, and a step of immersing the unfired refractory into the molten metal. By degassing the gas present in the open pores and applying pressure to the molten metal in which the unfired refractory is immersed by a piston-shaped pressure plate slidably provided in the cylindrical container. A method for producing a metal-impregnated unfired refractory, comprising the steps of: impregnating the unfired refractory with molten metal. (3) A step of degassing the gas present in the open pores of the porous unfired refractory, a step of preheating the degassed unfired refractory, and a step of storing the preheated unfired refractory in a cylindrical container. By applying pressure to the molten metal in which the unfired refractory is immersed by a piston-shaped pressure plate slidably provided in the cylindrical container, the molten metal is immersed in the molten metal. A method for producing a metal-impregnated unfired refractory, comprising the step of impregnating the unfired refractory with a metal-impregnated unfired refractory.