JPH02199087A - Production of metal-impregnated non-calcined refractory - Google Patents

Abstract

PURPOSE:To readily provide a metal-impregnated refractory having excellent spalling resistance and slag wetting resistance by preheating a porous non- calcined refractory, deaerating a gas in the open pores of the refractory, immersing the deaerated refractory in a melted metal and subsequently pressing the melted metal to impregnate the refractory with the melted metal. CONSTITUTION:A porous non-calcined refractory 11 (e.g. magnesia brick) is pre-heated in a pre-heating oven 2 and introduced into an evacuating and pressing oven 1 with a carrying holding arm 10. The oven 1 is evacuated with a vacuum pump through a suction pipe 8 to deaerate a gas contained in the open pores of the non-calcined refractory 11. The non-calcined refractory 11 is immersed in a metal bath 4. A pressure of 0.1-2000kg/cm<2> is applied to a metal metal 12 through a pressed gas-supplying pipe 7 to impregnate the melted metal 12 into the open pores of the non-calcined refractory 11. The treated non- calcined refractory 11 is taken out through an annealing oven 3 to provide the metal-impregnated non-calcined refractory.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for manufacturing an unfired refractory 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 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 refractory structure.

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.

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. In addition, 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, castables containing metal fibers, and the like 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 obtain the desired apparent porosity, immersed in a tar bath at a temperature of 200 to 300°C in a vacuum chamber, and then 3 to 4 kg/cd 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 or the like, the solvent used to impregnate the tar evaporates due to high heat, and the apparent porosity of the brick is reduced. It will rise. For this reason, it is not possible to sufficiently prevent slag infiltration, and the effect of tar impregnation 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 objects of the present invention include a step of preheating a porous unfired refractory, a step of degassing gas present in the open pores of the preheated unfired refractory, By immersing the degassed unfired refractory into molten metal and applying a pressure of 0.1 to 2000 kg/c to the molten metal in which the unfired refractory is immersed, the molten metal is unfired. This can be achieved by a method for producing a metal-impregnated unfired refractory, which comprises a step of impregnating the open pores of the refractory.

Unfired refractories are refractories manufactured by molding using a binder such as phenolic resin and then baking at a temperature of approximately 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, deaeration may be performed after the unfired refractory is immersed in molten metal.

(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, there will be a temperature difference between the surface of the unfired refractory and the molten metal. 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 impregnate the inside of the unfired refractory with metal any further. Therefore, by preheating the unfired refractory before immersing it in molten metal, the temperature difference between it and the molten metal can be minimized.
It is necessary to prevent molten metal from solidifying on the surface of the unfired refractory.

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 pressure in the pressurization process of the present invention is 0.1 to 2000k.
The reason for choosing the g/cJ range is that if no external pressure is applied,
This is because the internal pressure of the unfired refractory porous body and the molten metal pressure are balanced, and the molten metal does not penetrate into the open pores. Conversely, if the pressure exceeds 2000 kH/cd, the unfired refractory itself may be damaged. Generally, if the pressure exceeds the compressive strength of the unfired refractory, the unfired refractory die will be damaged, the amount of metal impregnated will decrease, and the hot strength of the unfired refractory after metal impregnation will decrease. shall 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, with reference to FIG. 1, an apparatus used in the method for producing a metallic impregnated unfired refractory of the present invention will be explained.

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 FIG. 1, the metal-impregnated unfired 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 unfired refractory to around the melting point of the metal with which it is pre-impregnated. Therefore, the performance required of the preheating furnace is that the preheating furnace wall 2' can withstand up to around the melting point of the metal to be impregnated, and that the preheating coil 5 can be heated up to around the melting point of the metal with which the unfired refractory is impregnated. It is. Any heating furnace having the above performance can be used in the present invention.

The vacuum pressure furnace 1 is a device that deaerates unfired refractories and impregnates them with metal. The vacuum pressurized furnace 1 includes a pressurized gas supply pipe 7 and a suction pipe 8.

The suction pipe 8 lowers the pressure inside the vacuum pressurizing furnace 1 to approximately 20 to 10-4.
This is for reducing the pressure to Lorr. On the contrary,
The pressurized gas supply pipe 7 is for injecting and pressurizing gas into 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 . Since the metal bath 4 is a container for storing molten metal, it needs to be heat resistant. For this metal bath 4, ordinary refractories can be used, but a dense one is particularly desirable, and a magnesia crucible is preferable. 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 unfired 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.
By holding and transporting the unfired refractories in this order to the annealing furnace 3 and the annealing furnace 3, continuous operation is possible.

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 This preheating step is to preheat the unfired refractory before immersing it in molten metal.

The purpose of this 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 an unfired refractory is directly impregnated into the molten metal without preheating, the molten metal will come into contact with the large unfired refractory due to the temperature difference. It cools rapidly on the surface and solidifies.

Moreover, unfired refractories are rapidly heated by metal, causing thermal spalling and cracking. 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 plA temperature is preferably higher than the melting temperature of the metal to be impregnated, but may be lower than the melting point if 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.

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 why air is removed from the open pores of unfired refractories is that if air exists in the open pores, the metal impregnated by the pressurization in the following pressure process This is because they are exhausted by the compressed air.

The purpose of this deaeration process is achieved by introducing the unfired refractory 11 from the preheating furnace 2 into the vacuum pressure inner furnace 1 using the conveying and holding arm 10, and reducing the pressure using a vacuum pump (not shown) or the like. be able to.

In order to degas the unfired refractories, it is desirable to reduce the pressure in the vacuum pressure 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 of immersing the degassed unfired refractory 11 in molten metal, and the degassed unfired refractory 11 is immersed in the molten metal.
is immersed in the metal bath 4 by the transport holding arm 10.

The rate of metal impregnation depends on the wettability of the molten metal to the unfired refractory, the porosity of the unfired refractory, 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 generalized, but it is about 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 unfired refractory, degassing is performed before the dipping step. Preferably, the process is carried out.

(c) Pressurizing process The purpose of this pressurizing process is to press the unfired refractory 11 into the metal bath 4.
While the unfired refractory is immersed in the material, pressure is applied, and the pressure is used to impregnate the metal into the open pores of the unfired refractory 11.

The pressurization method is carried out by supplying pressurized gas to the vacuum pressurizing furnace 1 from the pressurized gas supply pipe 7. It is preferable to use an inert gas or nitrogen gas as the pressurized gas. 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 difficulty of impregnating metal into the unfired refractory 11 (impregnation speed) depends on the wettability of the molten metal 12 to the unfired refractory, the apparent porosity of the unfired refractory, and the porosity of the unfired refractory. It depends on the pressure applied in the pressurization process. However, there are certain limits to improving the wettability and apparent porosity.

Therefore, the difficulty of impregnating unfired refractories with metal is
It mainly depends on the pressure applied in the main pressurization step.

Generally, the higher the pressure applied, the more metal can be impregnated. However, when the applied pressure exceeds the compressive strength of the unfired refractory, the unfired refractory itself may be destroyed.
This results in a decrease in the amount of metal impregnated or a decrease in the hot strength of the unfired refractory after metal impregnation. Therefore, a pressure lower than the compressive strength of the unfired refractory must be applied.

The pressure applied in this pressurizing 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 approximately 0.1 to 2000 kg/14 is appropriate.

Annealing Step In the immersion step, the unfired refractory 11 is immersed in the metal bath 4 at about 1500° C. or higher, and the unfired refractory itself is at about the same 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. Furthermore, thermal stress caused by a temperature difference between the inside and outside of the unfired refractory may cause thermal spalling. 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 preheating step, metal impregnation step, and annealing step described in . For example, if a magnesia-chromium brick with an apparent porosity of 13.5% by volume is deaerated, immersed in molten 5US304, and impregnated with metal by applying a pressure of 4 kg/c, the apparent The porosity decreased to 0.3% by volume.

Moreover, as a modification, there is a method in which the above-mentioned pressurizing step (C) is not used.

FIG. 3 shows a modified example.

According to this, a metal bath 4' having a height of several meters is provided in the vacuum pressure furnace. In this modification, the preheated unfired refractory 11 is
is immersed to the bottom of the metal bath 4'. In this modification, the unfired refractory 11 is compressed by the weight of the molten metal 12 instead of gas pressurization, and the other steps are the same as the above.

(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 an enlarged view of the vacuum pressure furnace. FIG. 3 is a diagram showing a modification of the vacuum pressure furnace. 1... Vacuum pressure furnace, 2... Preheating furnace, 3... Annealing furnace, 4.4'... Metal bath, 5... Preheating coil, 6
... Heating coil, 7... Pressurized gas supply pipe, 8...
Suction pipe, 10... Conveyance holding arm, 11... Unfired refractory, 12... Molten metal Applicant's representative Patent attorney Takehiko Suzue

Claims (3)

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