JPH07101768A - Nitride bonded refractory and its production - Google Patents

Abstract

PURPOSE:To improve strength while maintaining corrosion and thermal shock resistances peculiar to carbon-contg. refractories. CONSTITUTION:A mixture of refractory stock with graphite and metal titanium is sintered by heat generated by the self-combustion reaction of the metal titanium in a nitrogen atmosphere under >=10kg/cm<2> pressure to produce the objective nitride bonded refractories contg. 20-80wt.% titanium nitride per 100wt.% blend of >70 to <97wt.% refractory stock with 3-30wt.% graphite.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refractory used as a lining material for an industrial furnace, particularly for a steel manufacturing furnace.

[0002]

2. Description of the Related Art Carbon-containing refractory materials have been applied as lining materials for molten metal refining furnaces and have achieved quite high performance. This refractory material is an aggregate made of an oxide such as MgO and bound with a binder made of graphite and pitch.

[0003] These refractories improve the corrosion resistance by utilizing the low wettability of graphite with respect to slag, and enhance the thermal shock resistance by utilizing the high thermal conductivity of graphite. For example, Ceramic Data Book 19
82 Industrial Products Technology Association).

On the other hand, these refractories have high strength at high temperature,
It has a weak point in oxidation resistance, and in order to improve it, various metals have been added, or metals and carbides have been added in combination (for example, JP-A-54-16391, JP-A-01-01). 320262).

[0005]

However, since these refractory materials are not fired and are formed by binding with a binder or graphite, there is a limit to the strength improvement.

The present invention aims to improve the strength while maintaining the corrosion resistance and thermal shock resistance of the carbon-containing refractory.

[0007]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention is as follows: 1) With respect to a compound 100 containing more than 70% by weight of refractory raw material and less than 97% by weight, and 3% by weight or more and 30% by weight or less of graphite. It is a refractory material containing 20% by weight or more and 80% by weight or less of titanium nitride.

2) A mixture of a refractory raw material, graphite and metallic titanium is sintered by heat generated by a self-combustion reaction of metallic titanium in a nitrogen atmosphere of 10 kg / cm ² or more.

[0009]

[Function] By using the heat generated by the self-combustion reaction when TiN is formed by metallic Ti and nitrogen gas in a nitrogen atmosphere of 10 kg / cm ² or more in a mixture of refractory raw material, graphite and metallic titanium, Oxide-carbon-titanium nitride refractory that is sintered in a short time can be obtained.

The refractory material in the present invention means a material mainly composed of an oxide having a Zegel cone melting point of 26 or higher.

When carbon is contained in the refractory material, the refractory material has the characteristics that carbon has poor wettability with slag and has extremely high thermal conductivity.

Since the wettability with respect to the slag is deteriorated, chemical corrosion due to the slag is less likely to occur and the corrosion resistance is improved.

When the thermal conductivity is increased, the temperature gradient generated in the refractory material is small and the thermal stress is less likely to occur, so that the thermal shock resistance is improved.

However, it is difficult to improve the strength of a refractory in which carbon is contained in the refractory in the form of a binder such as graphite and pitch and bonded with the carbon.

Therefore, in order to improve the bond strength, in the refractory material of the present invention, a nitride bond having a bond strength superior to that of carbon is formed between the refractory materials.

For example, 20% graphite T in Al ₂ O ₃
When a nitride bond is formed by containing 25% by weight of iN, the bending strength when TiN is not contained is 120M.
Compared with Pa, it is remarkably improved to 160 MPa.

In the conventional method, in order to obtain the above-mentioned nitride bond refractory, a mixture containing phosphorous graphite and metallic Ti as a refractory material is used in an atmosphere firing furnace in a nitrogen atmosphere.
The heat treatment is performed in the temperature range of 400 to 1600 ° C. for about 3 to 4 hours.

In this case, the atmospheric nitrogen pressure is mainly atmospheric pressure or 5 kg / cm ² or less.

Therefore, it is difficult to form a nitride bond uniformly inside the refractory, and in order to form a uniform nitride bond, it is necessary to perform heat treatment for several hours or tens of hours as described above. become.

In the present invention, metallic Ti is self-combusted in a nitrogen atmosphere to form a nitride bond. Here, the self-combustion method will be described in detail.

Combustion reaction occurs when one end of the green compact of the constituent elements of the compound is heated to about 1600 to 2000 ° C. using a carbon ribbon heater or the like and ignited.

After that, the combustion reaction continuously progresses due to the heat generated by the reaction itself, and the reaction is transmitted to the entire green compact. The self-burning reaction has the following characteristics.

1) The rate of combustion reaction is 1 to 15 mm / sec, and the synthesis time is extremely short. 2) The temperature during combustion reaches 1600 to 4000 ° C. 3) It does not require external heating for a long time and has high energy efficiency.

When the self-combustion method is used to obtain the nitride-bonded refractory material of the present invention, it is ignited by heating the end of the green compact of the mixture of the refractory material and the metal in a nitrogen atmosphere. Causes a combustion reaction.

The reaction and the heat of reaction form nitrides and simultaneously bond the refractory material and the nitrides.

In order to obtain a uniform nitride bond, it is preferable to cause self-combustion under a high pressure nitrogen atmosphere.

In the present invention, in order to uniformly form a nitride bond by the self-combustion method, the end portion of the green compact of the mixture of refractory, carbon and metal Ti is heated to 1700 ° C. by a carbon heater in a high pressure nitrogen atmosphere. It ignites and causes self-combustion.

When the nitrogen pressure exceeds 5 kg / cm ² , self-combustion propagates throughout the green compact. However, in order to form a uniform nitride bond, the nitrogen pressure is 10 kg / cm ²
Need to be super. Preferably, if it exceeds 30 kg / cm ² , a uniform nitride bond can be obtained in a shorter time.

The higher the nitrogen pressure is, the easier it is to obtain a uniform nitride bond. However, the nitrogen pressure is 100 kg in consideration of the pressure vessel manufacturing cost and the high pressure nitrogen gas manufacturing cost.
/ Cm ² or less is preferable.

This method is characterized in that the heat treatment or the sintering is completed in an extremely short time as compared with the heat treatment in the conventional atmosphere firing furnace.

Therefore, even if the refractory made of oxide and carbon and the metallic Ti are self-combusted in a nitrogen atmosphere, only TiN having a small free energy of formation is formed and the refractory exists in its original form. It is possible to achieve both the corrosion resistance and the thermal shock resistance of the TiN and the good bonding strength of TiN and the refractory.

For example, a refractory obtained by self-combusting a mixture of Al ₂ O ₃ , graphite and Ti is Al ₂ O ₃ , C and Ti.
The refractory obtained has only T so that it has only N mineral phases.
The i-carbide and the product formed by the reaction of Al ₂ O ₃ and TiN are not included.

In the present invention, the amount of carbon contained in the refractory material is specified to be 3% by weight or more because if it is less than 3% by weight, corrosion resistance and thermal shock resistance cannot be secured.

Further, the reason why the amount is defined as 30% by weight or less is that
This is because if it exceeds 30% by weight, it is not possible to secure the strength that can withstand use as a refractory material.

In the present invention, the amount of TiN is set to 20.
20% by weight is defined as more than 80% by weight
If it is less than 80% by weight, good bonding strength cannot be obtained, and if it exceeds 80% by weight, the characteristics such as corrosion resistance of the refractory material composed of oxide and carbon cannot be sufficiently obtained.

In order to obtain the above-mentioned amount of TiN, the total Ti content of the refractory material is 15.5% by weight or more and 61.9 or more.
%, It is sufficient to perform self-combustion in a nitrogen atmosphere by using a raw material made of a green compact of a mixture containing less than 100%.

[0037]

EXAMPLE As an example, a raw material having a composition as shown in Table 1 was molded into a size of 214 mm × 114 mm × 65 mm, and in a nitrogen atmosphere, the central portion of the upper surface of the sample was 15 m.
mφ is heated by a carbon ribbon heater and ignited, the sample is self-combusted, and the combustion is propagated throughout the sample.
A carbon-titanium nitride refractory was manufactured.

Table 1 also shows the nitrogen pressure, which is the condition at the time of manufacturing each sample, and the ignition temperature of the sample end portion by the carbon ribbon heater. The results of measuring the characteristics of the manufactured samples are shown in Table 1.

As a comparative example, refractory materials were manufactured by the self-combustion synthesis method using the raw materials having the composition shown in Table 1. The results are also shown in Table 1.

The strength in Table 1 is 3 mm × 4 mm ×
A 40 mm test piece was prepared and the bending strength was measured.

When the strength of the oxide-carbon refractory material to which TiN is not added at all is set to 100, 105 or more is ⊚, 9
5 to 105 were evaluated as ◯, and 95 or less were evaluated as x.

Corrosion resistance refers to the amount of erosion loss due to the reaction of the oxide-carbon refractory material containing no TiN with the slag.
When set to 0, less than 80 is ⊚, 80 to 100 is ∘, 10
0 or more was designated as x.

The thermal shock resistance was measured when the oxide-carbon refractory material to which TiN was not added at all was destroyed 1.2 times more than the number of times when it was subjected to the rapid heating and quenching cycle. The case where the same number of times is less than 1.2 times is marked as ◯, and the case where the same number of times is destroyed is marked as x.

Further, as a comprehensive evaluation, all the above three items were marked with ⊚ or ∘, and other than these were marked with x.

As shown in Table 1, the oxide-carbon-titanium nitride refractory material obtained by the present invention was excellent in strength, corrosion resistance and thermal shock resistance.

Further, the strength, corrosion resistance, and thermal shock resistance of the refractory material in the comparative example were inferior to those of the oxide-carbon-titanium nitride refractory material obtained by the present invention.

[0047]

[Table 1]

[0048]

[Table 2]

[0049]

INDUSTRIAL APPLICABILITY The refractory material of the present invention is excellent in strength, corrosion resistance, and thermal shock resistance, and is a refractory material for industrial furnaces, particularly steel manufacturing furnaces, such as ladle linings, tundish linings, and sliding nozzles. It is suitable for use as a refractory material such as a dipping nozzle, a refractory material for a heating furnace, or a refuse incinerator, and can extend the life of these refractory materials.

Claims (2)

[Claims] 1. A refractory raw material of more than 70% by weight and less than 97% by weight,
A nitride bond refractory, which is a refractory containing 20% by weight or more and 80% by weight or less of titanium nitride with respect to 100% of a compound containing 3% by weight or more and 30% by weight or less of graphite. 2. A nitride bond characterized in that a mixture of a refractory raw material, graphite, and metallic titanium is sintered by heat generated by a self-combustion reaction of metallic titanium in a nitrogen atmosphere of 10 kg / cm ² or more. Refractory manufacturing method.