JP2516187B2 - Refractory for molten steel container - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a molten steel container such as a converter, a ladle, a refining ladle, and an RH.

Here, the carbonaceous material means a material added as a refractory material, and is different from the carbonaceous material generated from the binder or the like.

<Prior art> With the progress of steelmaking technology in recent years, basic containers such as MgO-C bricks or MgO-CaO-C bricks have been used in containers for molten steel treatment such as converters, ladles, refining ladles, and RHs. Brick made of a combination of refractory material and carbonaceous material has come into widespread use.

However, recently, since various kinds of molten steel treatment have been performed, the operation has been carried out at ultrahigh temperatures, and the characteristics required for the lining material have become remarkably severe, and corrosion resistance and corrosion resistance at high temperatures have been increasing. Poling properties and wear resistance have become important.

The carbon-containing refractory has exerted its excellent corrosion resistance and spalling resistance against such severe operating conditions, but oxidation resistance has become a problem because a carbonaceous material is used.

By adding a metal powder such as aluminum to this MgO-C brick, etc., it is attempted to improve the oxidation resistance and hot strength at the same time.

However, with this method of adding aluminum powder, although corrosion resistance and microstructural stability were improved by densification due to the formation of carbides in the metal powder, the stress relaxation function decreased and brittleness proceeded, and the durability under mechanical and thermal stress was increased. I'm having problems with sex.

Further, the added aluminum reacts with the carbonaceous material to form aluminum carbide, and when the molten steel container operates intermittently and the container temperature decreases, this aluminum carbide causes a digestion reaction with water vapor in the air, resulting in bricks. A flaw has been discovered that makes it vulnerable.

Furthermore, when high temperature in a reducing atmosphere causes the reaction between magnesia and carbonaceous matter, a phenomenon (MgO + C → CO + Mg ↑) in which reduced magnesium vaporizes and scatters (magnesia-carbon reaction), which may deteriorate the texture. The bricks are heavily worn out. This magnesia-carbon reaction cannot be prevented by the addition of metal powder.

The present inventors have solved the above two problems by adding a metal powder and a certain boron compound to a basic material-carbonaceous material type brick,
Solved by the interaction (Japanese Patent Application No. 62-219699)
issue).

<Problems to be solved by the invention> However, in addition to the operation under super high temperature as in the case of melting stainless steel, in the operation under low basicity slag,
Further improvement in oxidation resistance, corrosion resistance, and prevention of magnesia-carbon reaction are desired.

<Means for Solving Problems> Therefore, as an improvement of the above-mentioned application, the inventors of the present invention applied to 100 parts by weight of a refractory material composed of 70 to 97% by weight of a magnesia raw material and 3 to 30% by weight of a carbonaceous material. 1 to 15 parts by weight of calcium metal-containing alloy powder and SiO ₂ 5 to 50 wt% a and glass or flux 0.5-10 parts by weight containing an alkali content of 10 wt% or less of SiO ₂ or the glass or flux and magnesium borate, The present invention has succeeded in solving the problem by using a refractory having a total amount of 0.5 to 10 parts by weight of a boron compound containing one or more selected from the group consisting of calcium borate and aluminum borate.

<Operation> The present invention is based on the interaction between the metal powder mainly composed of calcium and the boron compound, glass or flux, and MgO-C, MgO-CaO-C or a brick having a similar composition is added. Then, when the brick is heated, softening and melting of the glass and the like and melting of the metal occur, and then the boron compound and the glass and the like melt into the molten metal. Therefore, metals such as calcium reduce boron compounds and SiO ₂ components in glass, and at the same time, the metals are oxidized to metal oxides. At that time, the volume expansion expands the pores, blocks the inflow of air from the outside into the refractory, and prevents the carbonaceous material, which is a constituent component of the refractory, from being oxidized.

The dissolved boron compound or glass covers the carbonaceous material, but the viscosity increases due to the addition of oxidized calcium, so that the carbonaceous material does not flow away even at high temperatures Continues, and the antioxidant effect lasts up to high temperatures.

In this way, the coating of carbon material lasts up to high temperature,
The contact between magnesia and carbon is broken, and the magnesia-carbon reaction at high temperatures is suppressed.

At the same time, when a part of the melt precipitates as a new mineral component, a bond with the refractory component is generated, and the bond of the refractory component is strengthened, so that the strength of the entire refractory is improved.

The reduction of components such as boron compounds and glass by this metal and the reaction of the oxidized metal with the boron compounds and glass components are faster than the dissolution of aggregate particles in glass. In the case of adding only the above, deterioration of the aggregate and deterioration of the characteristics of the matrix due to the dissolution of the aggregate particles are prevented.

Furthermore, unlike a binder, molten boron compounds, glass, and other metals and metals, which flow down and fill the space between aggregate particles due to capillary action, causing a mineral change, so that the contact angle between particles becomes obtuse. Since the concentration of stress is relaxed by, the structure becomes excellent in toughness.

Further, the coating of the melt by the interaction between the metal mainly composed of calcium and the boron compound or the glass or the flux covers not only the carbonaceous material but also the refractory material, so that it has an action of preventing the digestive reaction of the refractory material. is there. Particularly, it is useful when a free CaO component is contained. This anti-digestion effect is particularly remarkable when calcium is contained as a metal.

<Structure of the Invention> As the magnesia raw material used in the present invention, electro-melted magnesia, sintered magnesia, dolomite, magcalcia clinker and the like can be used, but particularly for use at high temperature, high purity magnesia clinker and Magcalcia clinker is preferred. How much magnesia is used
It is 70 to 97% by weight. If it is less than 70% by weight, the corrosion resistance cannot be sufficiently exhibited, and if it exceeds 97% by weight, the spalling resistance is poor.

The carbonaceous materials are natural graphite, artificial graphite, electrode scraps, petroleum coke, carbon black, etc., but from the viewpoint of corrosion resistance at high temperatures, highly pure crystalline materials such as natural or artificial graphite are suitable, especially scales. More preferred is a shape. The crystalline carbonaceous material is excellent in oxidation resistance and also has a good filling property during molding, and as a result, a refractory having superior corrosion resistance can be obtained. The amount of carbonaceous material used is 3 to 30% by weight. Preferably, a crystalline carbon material having a particle size of 0.1 mm or more is at least 10
It may be contained in an amount of not less than wt%.

Calcium is essential as the metal powder, and it is used as an alloy powder of this and silicon, magnesium or aluminum. Specific examples of this metal alloy powder include Ca-Si and C
a-Al, Ca-Si-Mg, Ca-Al-Si, Ca-Al-Mg, Ca-Al-Si-Mg, etc., the amount of which is the total amount of the magnesia raw material and the carbonaceous refractory material. It is 1 to 15 parts by weight with respect to 100 parts by weight, and is out of the range, and is inferior in oxidation resistance, corrosion resistance, abrasion resistance and spalling resistance.

The metal alloy powder does not necessarily need to contain aluminum, but it is more preferable to use an alloy containing aluminum or a mixed powder of aluminum and a calcium alloy containing no aluminum. This case does not contain aluminum, calcium and generates the CaO · MgO · SiO ₂ and 2MgO · SiO ₂ was like a silicon oxide or magnesium present in the matrix, it is possible to reduce the slag corrosion resistance. However, when aluminum is present, the oxide of magnesium becomes spinel, so that calcium is changed to Ca.
O.Al ₂ O _{3 is formed} , and in the glass, silicon is mainly SiC and the low melting point compound is not formed, so that the corrosion resistance is not deteriorated. Also when aluminum is included, the total amount of the metal powder is 1 to 15 parts by weight based on 100 parts by weight of the total amount of refractory material.

In the present invention, glass or flux or a boron compound is used as a substance that interacts with the metal powder. In this case, glass or flux alone or in combination with a boron compound is used. The total amount used is 0.5 to 10 parts by weight with respect to 100 parts by weight of the refractory material. If it is less than 0.5 parts by weight, the interaction with the metal hardly occurs, and if it exceeds 10 parts by weight, the corrosion resistance is poor.

As the glass or the flux, those containing SiO ₂ are desirable in relation to the reaction with calcium and the product,
Use glass or flux that softens and melts near the temperature at which the added metal forms carbides (about 800 ° C). The glass or flux has an alkali content of 10% by weight or less
It is necessary that the SiO ₂ is 5 to 50% by weight. If the alkali content is 10% by weight or more, the corrosion resistance of bricks decreases.

In addition, SiO ₂ in glass or flux is 5% by weight
In the following, the effect of interaction with the above metal is not exhibited,
When more than 50% by weight, SiO ₂ which does not react with metal reacts with the refractory material components when it covers the refractory material, 2MgO ・ SiO ₂ and CaO.
・ MgO ・ SiO _{2 is} dissolved and the structure deteriorates. S
If the iO ₂ content is 50% by weight or less, there is no risk of tissue deterioration due to the effect of increasing the viscosity of the added calcium oxide. Other components are not particularly limited, but among them, Al ₂ O ₃ , MgO, and CaO are preferable, and components such as FeO and MnO tend to form refractory materials and low-melting-point substances, and therefore their presence is not preferable.

In the present invention, glass or flux is not specified, and similar substances other than glass and flux are included as long as they satisfy the above conditions.

Boron compounds are aluminum borate, magnesium borate,
One or more selected from calcium borate. These boron compounds can be used in the form of crystals or glass.

If the boron compound, glass or flux is a glass body, it is easier to react than a crystal body having a copper composition,
Since the interaction with the metal occurs at a lower temperature and the softening and melting of the glass material itself also occurs at a lower temperature, the effect of coating the carbon material to prevent oxidation is greater than that of the crystalline body.

A resin binder is added to the mixture containing the above-mentioned raw materials, and the mixture is kneaded and heat-treated after molding to obtain an unfired brick. The resin binder is not particularly limited as long as it can be hardened by heat treatment, but a phenol resin is preferable.

Good results can be obtained by using the above-mentioned unfired bricks for the entire lining of molten steel containers such as converters and ladle, or when lining a part of them, for slag lines and hot water contact areas where significant melting loss occurs. To be

<Example> The composition shown in Table 1 was molded by a friction press, and this molded product was heat-treated at 300 ° C for 10 hours to obtain an unfired brick.

The composition of the flux used is (A) 40% by weight of SiO ₂ ,
CaO 30% by weight, Al ₂ O ₃ 15% by weight, MgO 10% by weight, others 5
% By weight, (B) is 45% by weight of SiO _2, 15% by weight of MgO, ZrO ₂ 2
0% by weight, Al ₂ O ₃ 14% by weight, other 6% by weight, (C) is Si
60% by weight of O ₂ , 20% by weight of CaO, 5% by weight of Al ₂ O ₃ , 12% by weight of MgO and 3% by weight of others, and the composition of the silicate glass is 60% by weight of SiO ₂ , ₂₀ % by weight of Na ₂ O, Al ₂ O _{3 was} 10% by weight, CaO was 5% by weight, and others were 5% by weight.

The toughness was obtained by measuring a stress-strain curve by a three-point bending test method at 1400 ° C. in a reducing atmosphere.

The slag test is 5 at 1700 ° C using a rotary slag tester.
I went on time. The slag composition used was SiO ₂ 14 wt%, Al ₂ O ₃ 6 wt%, FeO + Fe ₂ O ₃ 15 wt%, CaO 50 wt%, MgO 10 wt%, and MnO 5 wt%.

The oxidation test was conducted for 10 hours at 1400 ° C. in an air atmosphere using a silicon carbide heating element electric furnace.

The toughness value ratio, the erosion area ratio, and the decarburized area ratio are shown in Table 1 by the ratio of Comparative Example 1 as 100.

Next, as a digestion test, the samples of Examples 2 and 7 and Comparative Examples 1 and 5 were heat-treated at 1400 ° C. for 5 hours, respectively, and then allowed to stand in saturated steam at 50 ° C. to measure the weight increase. did. Table 2 shows the results.

<Effects of the Invention> As is clear from the results shown in Table 1, the examples in which the metal powder mainly containing calcium and the boron compound were used in comparison with the comparative example in which only aluminum metal was added and the boron compound, glass or flux was added. And has excellent toughness, corrosion resistance and oxidation resistance. In particular, the improvement in corrosion resistance at 1700 ° C seems to be partly due to the suppression of the magnesia-carbon reaction.

In addition, flux C containing more than 50% by weight of SiO ₂ and
It can be seen that the use of silicate glass rich in SiO ₂ and Na ₂ O (Comparative Examples 2, 4 and 6) significantly reduces the slag corrosion resistance.

Among these examples, particularly good results were obtained by using a mixed powder of Ca-Si-Mg alloy and Al metal and Ca-Si-Mg alloy powder. Especially, calcium metal is MgO-CaO-C
It can be seen that the use as a material for the system is effective.

Further, according to the digestion test in Table 2, the sample to which only aluminum is added shows a significant weight increase by about 48 hours. This is due to the digestion of the metal carbide generated in the brick, and when calcium metal is added to this, the formation of carbide is suppressed in both the MgO-C type brick and the MgO-CaO-C type, There is little weight increase due to digestion. In particular, MgO-CaO-C type bricks prevent the formation of carbides and suppress the digestion of CaO, and it can be seen that the combined use of the metal and the boron compound of the present invention is exhibited.

In the molten steel container of the present invention, the metal powder mainly containing calcium is used in combination with the boron compound, glass or flux to improve the oxidation resistance, the corrosion resistance and the toughness due to their interaction.
Since the carbon reaction is suppressed and further the generation of aluminum carbide is suppressed, when it is used for a molten steel container that is operated intermittently or at a high temperature, operational stability and durability are significantly improved.

Front page continued (72) Inventor Akira Watanabe 12 at 102 Shiomigami, Okayama City, Okayama Prefecture (72) Inventor Shigeyuki Takanaga 2 at 433, Kato Nishi, Bizen City, Okayama Prefecture (56) Reference JP-A-56-59668 (JP, A)

Claims (2)

(57) [Claims] 1. A refractory material consisting of 70 to 97% by weight of a magnesia raw material and 3 to 30% by weight of a carbonaceous material,
Metal calcium-containing alloy powder 1 to 15 parts by weight and SiO ₂
A refractory for a molten steel container, characterized by comprising 0.5 to 10 parts by weight of glass or flux containing SiO ₂ in an amount of 5 to 50% by weight and having an alkali content of 10% by weight or less. 2. A refractory material consisting of 70 to 97% by weight of a magnesia raw material and 3 to 30% by weight of a carbonaceous material,
A material containing 1 to 15 parts by weight of a metal calcium-containing alloy powder and one or more selected from the group consisting of magnesium borate, calcium borate, and aluminum borate, and
SiO ₂ 5 to 50% by weight and alkali content of 10% by weight or less SiO ₂
A refractory for a molten steel container, characterized in that it comprises 0.5 to 10 parts by weight in a total amount of glass or flux.