JPH02172881A - Production of metal-impregnated refractories - Google Patents

Abstract

PURPOSE:To obtain the refractories having excellent slag swelling resistance, constitutional spalling resistance, and thermal spalling resistance by deaerating preheated porous refractories, then immersing the refractories in a molten metal and exerting a pressure to this molten metal. CONSTITUTION:The porous refractories are preheated to remove the gases existing in the open cells of the preheated refractories. The dearated refractories are then immersed in the molten metal and 0.1 to 2000kg/cm<2> pressure is exerted to the molten metal in which the refractories are immersed, by which the molten metal is impregnated into the open cells of the refractories and the desired refractories are obtd. The reason for providing the above mentioned preheating stage lies in that, if the refractories are immersed in the molten metal at the original temp. (room temp.) without preheating the retractories, the temp. difference between the surface of the refractories and the molten metal is fairly large and, therefore, the molten metal is rapidly cooled to solidify and the film of the molten metal is generated on the surface of the refractories.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for manufacturing 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 are exposed to harsh conditions of about 1000° C. or higher, so that surface peeling gradually occurs. On the other hand, the inner wall of a molten metal container such as a converter, a ladle, or a gas furnace comes into contact with elution and slag, causing erosion and peeling.

In particular, in a slag line, the inner wall refractories are significantly damaged by slag, and the molten slag penetrates into the refractories, resulting in destruction of the refractories. 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 applies thermal stress to the surrounding brick base material, causing damage to the base material.

Among these spallings, mechanical spalling is
This can be improved to some extent by improving equipment and the like. Therefore, in terms of the properties of refractory bricks, it is particularly desirable to improve the thermal spalling resistance and the structural spalling resistance. In order to improve the structural spalling resistance, the slag infiltration resistance must be improved for the above reasons. Furthermore, since slag infiltration increases erosion loss of the base material from the brick surface, a refractory with excellent slag infiltration resistance is desired in order to suppress erosion 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, fired to give the desired apparent porosity, and immersed in a tar bath at a temperature of 200 to 300°C in a vacuum chamber, and then 3 to 4 kg/c- There is a way to apply pressure.

(Problems to be Solved by the Invention) However, in the above method for manufacturing tar-impregnated bricks, there is a limit to the penetration depth of tar.

Furthermore, when a refractory is used in a furnace or the like, the solvent used to impregnate the refractory with tar evaporates due to high heat, resulting in an increase in the apparent porosity of the brick. For this reason, it is not possible to sufficiently prevent slag infiltration, and the life of the bricks is generally short. Also, it is difficult to manufacture large-sized bricks.

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 improve 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 producing a refractory that is excellent in slag infiltration resistance, structural spalling resistance, and heat resistant spalling resistance.

(Means for Solving the Problems) The object of the present invention is to provide a step of preheating a porous refractory, a step of deaerating the gas present in the open pores of the preheated refractory, and a step of deaerating the gas existing in the open pores of the preheated refractory. The step of immersing the refractory in the molten metal, and adding 0.1 to 200% to the molten metal in which the refractory is immersed.
This can be achieved by a method of manufacturing a metal-impregnated refractory, which comprises impregnating molten metal into the open pores of the refractory by applying a pressure of 0 ky/cI#.

In addition, in the method for manufacturing a metallic immersed refractory of the present invention, deaeration may be performed after the refractory is immersed in the molten metal.

(Function) The reason why the preheating step is provided in the present invention is that the refractory is not preheated,
If immersed in molten metal at the same temperature (that is, room temperature), the molten metal will rapidly cool and solidify on the refractory surface because the temperature difference between the refractory surface and the molten metal will be very large. This is because a film of molten metal will be formed. Once a metal film forms on the surface of the refractory, it becomes impossible to impregnate the interior of the refractory with metal any further. Therefore, it is necessary to preheat the refractory before immersing it in the molten metal to minimize the temperature difference between the refractory and the molten metal and to prevent the molten metal from solidifying on the surface of the refractory.

The reason for providing the degassing step in the present invention is that if air remains in the open pores of the refractory, impregnation of the metal will be inhibited by the remaining air, making it difficult.

Even if it were possible to impregnate metal by applying pressure,
After the pressure is restored, a portion of the metal is pushed out by the compressed air in the open pores. Therefore, in this degassing step, it is important to degas the refractory almost completely.

The pressure in the pressurization process of the present invention is 0.1 to 2000k.
The reason for setting it in the range of g/cm2 is that if no external pressure is applied, the internal pressure of the refractory porous body and the molten metal pressure will be balanced, and the molten metal will not penetrate into the open pores. Conversely, if the pressure exceeds 2000 kg/c-, the refractory itself may be damaged. Generally, if the pressure exceeds the compressive strength of the refractory, the refractory itself will be damaged, the amount of metal impregnated will decrease, and the hot strength of the refractory after metal impregnation will decrease. Must be small.

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, with reference to FIG. 1, an apparatus used in the method for manufacturing a metal-impregnated large-sized article of the present invention will be described.

FIG. 1 is a conceptual diagram of a metal-impregnated refractory manufacturing apparatus that can be used in the present invention. According to FIG. 1, the metal-impregnated refractory manufacturing apparatus includes a preheating furnace 2, a vacuum pressure furnace 1, and an annealing furnace 3.

The preheating furnace 2 is a device for heating the metal with which the refractory is pre-impregnated to around the melting point. Therefore, the performance required of the preheating furnace is that the preheating furnace wall 2'' can withstand temperatures close to the melting point of the metal to be impregnated, and that the preheating coil 5 be able to heat the refractory to near the melting point of the metal to be impregnated. Any heating furnace having the above performance can be used in the present invention.

The vacuum pressure furnace 1 is a device that deaerates refractories and impregnates them with metal. The vacuum pressure furnace 1 includes a pressurized gas common supply pipe 7 and a suction pipe 8. The suction pipe 8 is for reducing the pressure inside the vacuum pressurizing furnace 1 to about 20 to 10 −4 Lorr. On the contrary, the pressurized gas supply pipe 7 is for injecting and pressurizing the vacuum pressurizing furnace 1, which has been depressurized by the suction pipe. Furthermore, a metal bath 4 is arranged inside the vacuum pressurizing furnace 1 . Metal bus 4 is
Since it is a container for storing molten metal, it needs to be heat resistant. For this metal bath 4, ordinary refractories can be used, but particularly dense ones are preferable.
Magnesium crucibles are preferred.

A heating coil 6 is arranged around the outer wall of the metal bath 4. The heating coil 6 keeps the metal bath 4 at a temperature above the melting point of the metal.

The annealing furnace 3 is for annealing the refractory impregnated with metal, and a conventional annealing furnace can be used.

In the present invention, the preheating furnace 2, the vacuum pressurizing furnace 1, and the annealing furnace 3 do not necessarily need to be integrated. but,
As shown in Figure 1, these furnaces are integrated and the rail 9
, the r-thermal furnace 2 and the vacuum pressurizing furnace 1 by a holding and transporting device consisting of a transporting and holding arm 10, a drive device (not shown), etc.
Continuous operation is possible by holding and transporting the refractories in this order: and annealing furnace '3.

Hereinafter, the method for producing a metal-impregnated large-sized article of the present invention will be explained in detail.

The method for producing a metal-impregnated refractory of the present invention includes preheating the refractory: step 1, impregnating the open pores of the refractory with metal, and step Y of annealing the metal-impregnated refractory. Can be divided.

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

Preheating Step This preheating step preheats the refractory before immersing it in molten metal.

The purpose of this preheating step is as follows.

In the next step, the refractory is immersed in molten metal.

Molten metal is heated to a fairly high temperature (for example, stainless steel
1450° C. or higher), and if the refractory is directly impregnated into molten metal without preheating, the molten metal will rapidly cool and solidify at the contact surface with the refractory due to the temperature difference. Furthermore, refractories are rapidly heated by metal, causing thermal spalling and cracking. As a result, a metal film is formed on the surface of the refractory, and no further metal can be impregnated into the refractory. Therefore, by preheating the refractory before dipping,
Minimize the temperature difference between the refractory surface and the molten metal as much as possible,
This prevents molten metal from solidifying on the refractory surface.

The preheating temperature is preferably higher than the melting temperature 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. Further, as the preheating furnace used in this preheating step, a conventional one can be used as long as it can obtain the desired temperature and is heat resistant.

This metal impregnation step can be further divided into the following three steps.

(a) Degassing process The purpose of this degassing process is to remove the air present in the open pores of the refractory.

The reason why air is removed from the open pores of the refractory is that if air exists in the open pores, the metal impregnated by the pressurization in the pressurization step (e) below will absorb the compressed air in the open pores after the pressure is restored. This is because it is discharged by

The purpose of this degassing step can be achieved by introducing the refractory 11 from the preheating furnace 2 into the vacuum pressure furnace 1 using the transfer holding arm 10 and reducing the pressure using a vacuum pump (not shown) or the like. .

In order to degas the refractory, it is desirable to reduce the pressure in the vacuum pressurized furnace 1 as much as possible. However, in reality, since molten metal is present in the vacuum pressure furnace 1, the pressure must be reduced in consideration of the vapor pressure of the molten metal. In the present invention, a reduced pressure of about 20 to 10<-4 >torr is preferred.

(b) Immersion process The main dipping process is a process in which the degassed refractory 11 is immersed in molten metal. 5? , pickle.

The rate of metal impregnation depends on the wettability of the molten metal to the refractory, the porosity of the refractory, and the pressure of the next step.

Therefore, the impregnation time varies depending on the combination of the type of refractory used and the type of metal to be impregnated, so it cannot be stated unambiguously, but it is approximately 1 to 120 minutes.

The previous degassing step (a) and the main dipping step (b) can be performed in any order, but from the viewpoint of completely degassing the refractory, it is preferable to perform the degassing step before the dipping step. It is preferable to do so.

(c) Pressurization process The purpose of this pressurization process is to pressurize the refractory 11 while it is immersed in the metal bath 4, and use that pressure to impregnate the open pores of the refractory 1 with metal. .

The pressurization method is carried out by supplying pressurized gas (i) from the pressurized gas supply pipe 7 to the vacuum pressurizing furnace 1.
Preferably, inert gas or nitrogen gas is used. This is because by making the atmosphere in the vacuum pressurized furnace non-oxidizing, oxidation of the heating coil 6 can be prevented, and a decrease in thermal efficiency of the coil can be prevented.

As mentioned earlier, the impregnation rate of metal into the refractory 11 depends on the wettability of the molten metal 12 to the refractory,
The appearance of the refractory depends on the porosity and the pressure applied in the main pressurization step. However, there are certain limits to improving the wettability and apparent porosity. Therefore, the difficulty in impregnating the refractory with metal depends mainly on the pressure applied in the main pressurization step. in general,
The higher the pressure applied, the more metal can be impregnated. However, if the applied pressure exceeds the compressive strength of the refractory, the refractory itself may be destroyed, the amount of metal impregnated may decrease, or the hot strength of the refractory after metal impregnation may decrease. Therefore, a pressure less than the compressive strength of the refractory must be applied.

The pressure applied in this pressurizing step varies depending on the combination of the type of refractory and the type of metal to be impregnated, so it cannot be generalized, but approximately 0.1 to 2000 kg/c is appropriate.

Annealing Step In the immersion step, the refractory 11 is immersed in the metal bath 4 at about 1500° C. or higher, and the refractory itself is at about the same temperature. When cooling this refractory to Muronin,
When cooled rapidly, the metal impregnated in the refractory solidifies rapidly, causing cracks and cracks in the refractory. Furthermore, thermal stress caused by temperature differences between the inside and outside of the refractory may cause thermal spalling. Therefore, in the main annealing step, the 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 refractory can be impregnated with metal through the preheating step, metal impregnation step, and annealing step described above. For example, a high alumina brick with an apparent porosity of 13% by volume is degassed, immersed in Ni-Cr molten metal, and 20kg/cIiY
When the metal was impregnated under a pressure of

Moreover, as a modification, there is a method that does not use the above-mentioned pressurizing step (c).

FIG. 3 shows a modified example.

According to this, a metal bath 4'' having a height of several meters is provided in a vacuum pressurized furnace.In this modification, the preheated refractory 11 is transferred to the metal bath 4' by a conveying and holding arm 10'. In this modification, the refractory 11 is immersed in the !I!at of the molten metal 12 instead of gas pressurization.
The other steps are the same as above.

(Effects of the Invention) According to the method of the present invention, the open pores of a refractory can be impregnated with metal, and a metal-impregnated large-sized refractory can be manufactured that has excellent spalling resistance and slag infiltration resistance.

[Brief explanation of the drawing]

FIG. 1 is a diagram conceptually showing the method for manufacturing a metal-impregnated large-sized article of the present invention. FIG. 2 is an enlarged view of the vacuum pressure furnace. FIG. 3 is a diagram showing a modification of the vacuum pressure furnace. DESCRIPTION OF SYMBOLS 1... Vacuum pressure furnace, 2... Preheating furnace, 3... Annealing furnace, 44'... Metal bath, 5... Preheating coil, 6...
... Heating coil, 7... Pressurized gas common supply pipe, 8... Suction pipe, 10... Conveyance holding arm, 11... Refractory,
12...Representative for Fugan Metals Applicant Patent Attorney Takehiko Suzue Figure 3

Claims (3)

[Claims] (1) a step of preheating a porous refractory, a step of deaerating the gas present in the open pores of the preheated refractory, and a step of immersing the degassed refractory in molten metal; 0.1 to 2000 kg/c to the molten metal in which the refractory is immersed
A method for producing a metal-impregnated refractory, comprising the step of impregnating molten metal into the open pores of the refractory by applying a pressure of m^2. (2) Preheating the porous refractory, immersing the preheated refractory into molten metal, and degassing the gas present in the open pores of the refractory immersed in the molten metal. process and the molten metal in which the refractory is immersed.
A method for producing a metal-impregnated refractory, comprising the step of impregnating molten metal into the open pores of the refractory by applying a pressure of 00 kg/cm^2. (3) The method for manufacturing a metal-impregnated refractory according to claim 1 or 2, wherein the maximum value of the pressure is smaller than the compressive strength of the refractory.