DD149378A5 - PERMANENT CLADDING FOR A CONVERTER - Google Patents

Abstract

The invention relates to the field of metallurgy and relates to converter for the Stahlgieszen. The aim and the object is to provide a specific lining for converters which has a long service life, temperature resistance, resistance to breakage and oxidation resistance. This is achieved by certain proportions of material according to the invention, e.g. This is achieved by using unburned carbon-bonded bricks with 3 to 40% by weight of carbonaceous material, 1 to 10% by weight of aluminum and as residual fraction of magnesite clinker for the converter lining.

Description

The invention relates to a permanent lining for a converter for steel production.

Characteristic of the known technical solutions

In general, calcined magnesite · dolomite bricks including synthetic magnesite dolomitic bricks are used as the permanent lining material of a converter. In addition to the use of these furnace components, the use of hot jet repair, slag monitoring, slag coating, or slag wrapping, etc. have significantly increased the life of the converter liner.

In connection with the recent aggravation of the energy situation and the problem of raw materials, a further reduction of steel production costs for the steel industry has become desirable.

The steel production by the oxygen blowing method is carried out in various manners, for example, as an oxygen blowing method, an oxygen blowing method, a combination of these methods and the like. This has the consequence that the thermal load ratios of the converter change frequently, whereby the refractory converter lining materials are subjected to a heavy load.

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It is well known that carbon has excellent refractory properties such as high thermal shock resistance, high impact corrosion resistance, high slag penetration resistance and the like.

Therefore, untethered tar digolite stones have been used. However, such stones have the disadvantage that their structure is impaired due to a reaction between the CaO in the dolomite and the carbon during use at high temperature.

Since the amount of carbon to be added to the tarsol earth is necessarily limited, the properties of the carbon can not be satisfactorily exploited.

Teerdolomite stones were actually replaced by burned tar-infused magnesite dolomite stones. However, since the carbon content obtained by tar permeation is insufficient to make satisfactory use of the properties of the carbon, the disadvantages of the calcined bricks could not be fundamentally eliminated.

Unfired carbon magnesia bricks (Japanese Patent Publication No. 756495, U.S. Patent No. 3,667,974, UK Patent No. 1,233,646 and Canadian Patent No. 896,629) have been widely used in electric arc furnaces, particularly as ceiling tiles and hot spots However, stones are unsuitable for use in a converter as they are prone to breakage upon impact

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or impacts when scrap metal is thrown into the converter and shows decoking when brought into contact with molten steel.

In order to improve the quality of unliberated carbon magnesia bricks, various advances have been made, for example, as shown in Japanese Patent Laid-Open Publication SHO-53-6312, in which silicon is added to improve the oxidation resistance, and as disclosed in, for example, Japanese Patent Laid-Open SHO -54-11113, in which the heat resistance is increased by overcoming various problems in the pressing process and as described, for example, in Japanese patent application no. SHO-53-104292 (US Patent Application 13478), in which the carbon content is increased substantially more than 55% to thereby enable the full utilization of the properties of the carbon, and alleviates various difficulties associated with the pressing operation become.

Nevertheless, this carbon-carbonaceous carbonaceous material is not such that they simultaneously exhibit both the property of oxidation resistance and a high modulus of rupture.

Object of the invention

The object of the invention is to provide a lining for converters, which is characterized by high utility properties, which is ensured in particular by a long service life.

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Explanation of the essence of the invention

According to this aim, the task for the invention results in a specific material composition for the blocks of the converter lining, which has high thermal changes with simultaneously low breakage sensitivity and sufficient oxidation resistance.

According to the invention this object is achieved in that the lining at least partially from unburned carbon-bonded bricks, from 3 to 40 wt .- / b carbonaceous material, 1 to 10 wt - . % Aluminum and / or less al * s 6 wt '.-% Silicon and a residual amount of magnesite clinker exists.

In the following, the green carbonaceous stones according to the invention will be described in detail.

The amount of carbonaceous material in the bricks is 3 to 40% by weight, preferably 5 to 30% by weight. The range of the content of carbonaceous material is limited for the following reasons. When the content is less than 3% by weight, it is impossible to fully exploit the thermal shock resistance, the slag corrosion resistance, the slag penetration resistance and the like, while when the content is over 40% by weight, the resistance to both impacts dropped scrap metal parts and against the wear by the molten steel decreases.

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For the following reasons, aluminum is added to the stone material, preferably in a proportion of 1 to 6% by weight. The aluminum added and mixed with the material prevents binding between the carbon and the oxygen from the outside by bonding with the residual carbon (A1.C-) in a structurally unstable state in the bonding material (resinous pitch, curable phenolic resins, etc.) in a high-temperature region whereby it is possible to prevent the decarburization of the binder material, to greatly increase the ratio of the residual carbon in the bonded portion and to show the effect of the carbon magnesia stones.

At the same time, aluminum reduces the volume of each pore due to spatial expansion while being converted to carbide in a reaction with carbonaceous materials. The stone structure is therefore more compact, and the strength of the stone is increased, making it particularly difficult in upper layers for slag and molten steel to corrode the stones.

The increased oxidation resistance can further preclude deterioration of the structure due to decarburization.

As described above, the addition of aluminum has the effect of simultaneously improving the breaking modulus and the oxidation resistance of the carbon bonded bricks.

The stones of the invention having from 3 to 40% by weight of carbonaceous material capable of exhibiting the above excellent properties are suitable

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Content of the aluminum at 1 to 10 wt .-%, preferably at 1 to 6 wt .-%.

If the aluminum content is less than 1% by weight, the addition is not only ineffective, but also makes it impossible to fully exploit the strong effect of the carbonaceous material because it is impossible to increase the carbon content in the stones, whereas if the aluminum content of about 10 wt -.%, the fire resistance is impaired.

If necessary, the properties of the stones according to the invention can be improved by a factor of 2 by adding silicon to the material.

That is, in detail, the aluminum added to the rock material in combination with the carbon generates carbide under the heating ratios of a converter, and when the carbide is contacted with water at a high temperature, the following reaction takes place

Al ₄ C ₃ + 12H ₂ O> 3CH ₄ + 4Al (OH) ₃ ,

whereby there is a risk that the stone structure is affected or even collapsed with an increase in cracks. When silicon is added, hydrogenation of the carbide is successfully prevented. The silicon content is less than 6 wt .-% and is preferably 1 to 4 Gow .-%. When the proportion is more than 6% by weight, the refractoriness of the stones is undesirably impaired.

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Preferably, the silicon addition is increased in conformity with the aluminum addition. The particularly suitable ratio of the addition is 0.2 to 1.0 wt .-% silicon to 1 wt .-% aluminum.

In addition to preventing the hydrogenation of the carbides, the addition of silicon makes it possible to improve the oxidation resistance of the carbon in cooperation with the aluminum. This effect is completely different from the effect intended in the conventional case, in which silicon is added independently to avoid oxidation.

embodiment

In the following, an example of a method for producing the non-fired carbonaceous bricks according to the invention and some embodiments will be described in detail.

As refractory materials Magnesitklinkor and a carbonaceous material are used. The magnesite clinker includes calcined magnesite, seawater magnesite clinker or electrofused magnesite, while the carbonaceous material includes graphite, artificial graphite, electrode residues, petroleum coke, foundry coke, carbon black and pitch coke.

These refractories are subjected to particle size control and then kneaded with binding materials which, when heated, provide carbon, such as tar, pitch, resin and the like.

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The kneaded mixture is pressed and heated by a conventional method to obtain the final product.

The most satisfactory results are obtained when the unburned carbonaceous stones obtained in this way are used as a permanent lining over the entire bottom, body and cone of a converter. A good result is obtained even if only the feed side and / or the turning side exposed to severe wear are lined.

In view of the fact that the cause and extent of wear are different according to the respective parts of each converter, the life of the converter can be further extended by lining it with unlubricated carbon-bonded bricks having a different content of carbon and metal powders , Specifically, it is recommended that unfired carbon-bonded bricks with 3 to 30 % carbonaceous material and more than 2 % metal powder for the bottom, the bath and the feed side of the converter body, stones with 5 to 35 % carbonaceous material and more than 1 Use % metal powder for the tapping side of the body and the journal side and stones with 10 to 40 % carbonaceous material and more than 3 % metal powder for the conical part respectively.

The green carbonaceous stones of the present invention have the following characteristics as compared with the conventional calcined stones:

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1. Due to the high resistance to thermal shock, the stones do not break even if the furnace body is heated quickly or cooled by the introduction of scrap metal.

2. The stones hardly corrode because they do not react with the slag.

Compared to the conventional non-fired carbon-bonded bricks without metal powder, the bricks of the invention have the following properties:

3. The structure is more compact and has greater strength.

4. The structure is less affected by decarburization because it hardly oxidizes.

5. The penetration of slag into the stone structure is thus prevented, and the stones show a high resistance to impacts of pieces of scrap metal and a high resistance to wear compared to the molten steel.

The characteristic properties described above ensure a long life of the lining of the converter, for which the stones according to the invention are used.

In the following the invention will be described in detail with reference to some examples.

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Examples 1 to 6

Examples 1 to 6 and Comparative Examples 1 to 3 are unfired stones. Mixtures having the mixing ratios shown in Table 1 were prepared, pressed and then heat-treated at 300 ^° C. for 4 hours to obtain the samples.

Comparative Sample 4 is a calcined Magnesltdolomitetein containing synthetic magnesitdolomitklinker and is traversed with tar. Its chemical composition is shown in Table 1.

The samples were subjected to measurement of physical property values and the modulus of rupture, as well as a temperature cycling test and a slag test.

The bricks obtained in this manner continued to be used as a lining for the trunnion walls of a 300 tonne converter manufactured by Company A. The results are shown in Table 1.

The temperature cycling test, the slag test and the actual furnace test were carried out according to the following procedures;

1. Temperature change test

The samples were heated in a carbon crucible in an electric furnace with a heating element of Siliziurncarbid for 15 minutes at 1400 ⁰ C and then cooled in ambient air for 15 minutes. After this

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The process was repeated 5 times in succession, the samples were cut to test the growth of the cracks.

2. Slag test

Each sample was shaped into a cylinder. The cylinder was rotated to the horizontal position and heated for 5 hours at 1750 C while the slag was thrown onto the cylinder. The sample was then cut through to measure the abrasion or wear and strength of the decarburized layer.

3. Actual oven test

The pivot walls of a 300 ton converter manufactured by Company A. were lined with the respective examples. After this converter was used until the back liner was exposed, the liner was removed and samples were collected to compare the extent of wear. The wear ratios were calculated with a wear ratio in Example 3 equal to 1.

Table 1

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Magnesite clinker graphite aluminum powder silicon powder resin pitch thermosetting phenolic resin Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Mixing ratio (% by weight ) apparent porosity {%) apparent specific gravity specific bulk density 2 breaking strength (kg / cm) M CD 04 N) UI UI O Ul Ul 82 15 3 2.5 3.5 79 15 3 3 2.5 3.5 90 7 3 2.0 3.0 83 7 6 4 2.0 3.0 83 15 1 1 2.5 3.5 Value of the physical property Modulus of rupture at ,, 1500 ⁰ C (kg / CNT) 5.4 2.92 2.76 408 5.2 2.93 2.79 422 4.0 2.92 2.81 435 5.2 3.07 2.91 507 4.5 3.05 2.91 520 5.0 2.96 2.81 410. Temperature change test Growth of cracks 115 86 180 100 110 82 Edge loss measurement (mm) decarburized layer (mm) no - - - ~ Slag test Wear ratio in an actual oven 19.5 0 20.5 O 16.0 0 21.0 0 22.5 0 19.2 0 1.2 1.2 1.0 1.3 1.4 1.2

Table 1

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ff Magnesite clinker graphite aluminum powder silicon powder resin pitch thermosetting phenolic resin Comparative Example 1 Comparative example 2 Comparative example 3 Comparative example 4 Mixed ratio (wt%) apparent porosity (%) apparent specific gravity specific bulk density ρ breaking strength (kg / cm) 85 15 2.5 3.5 93 7 2.0 3.0 68 15 15 2 2,5 3,5 Igloss 4.8. SiO-0.5 A1 "Ö, 0.2 FeJO-? 0.3 CaO "* 8.5 MgO 85.7 Vert dsr physical property Breaking modulus at ~ 1500 ⁰ C (kg / crn) 4.4 2.94 2.80 431 4.3 3.07 2.95 530 6.3 2.91 2.73 380 1.0 3.23 3.20 1100 Temperature change test Crack growth 50 60 45 30 Edge loss measurement (mm) decarburized layer (mm) no no no big cracks Schlak ken- test Wear ratio in. An actual oven 25.5 3.0 26.5 3.5 33.5 0 30 5.0 1.6 1.7 2.1 2.0

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From the above Table 1, it can be seen that each of the examples according to the invention shows better results than any comparative example with respect to the modulus of rupture, the thermal cycling test, the slag test and the actual furnace test.

Example 7

Unburned carbon bricks having a mixing ratio as shown in Table 2 were used on a 300 ton converter manufactured by Company A. as a lining of the floor, bath and body (pivot wall).

The wear rate until the back liner was exposed was compared with the conventional products under the same conditions to obtain the results shown in Table.

Place of use _ mm _ herkömm bath ungebrann herkömm 08/05/1980 herkömm material Table 2 royal coals royal royal ground Product A stone B Product B 57 063/16 > jngebrann- 88 80 ' 85 Pivot wall Magnesitklinker he coals 12 15 15 ungebrann graphite stone A 3 coals Product C • CD O) aluminum powder 83 2 stone C 82 > H silicon powder 12 86.2 78.8 83.3 78 18 -C C O + - » MgO 3 18 Mis hai Uo ) 2 12.0 14.6 14.6 2 R-i I H O CD O 4- » F.C 81.8 2 80.4  Μ "Ό 76.8 Q. C 12.0 17.2 CO 4 "££ J apparent porosity 4.5 4.0 4.5 17.2 X Ow ( <v \ I I C apparent specifi 3.03 2.98 3.01 Ή Ο O) O) nice weight 4.0 4.5 > H x: UY specific bulk 2.89 2.86 2.87 4.0 Q. C f *** mass 3.00 2.98 OJ = breaking strength 540 500 480 2.96 U w + * (Λ> + - i_j-j m (kg / cm) 2.88 1.6 1.0 1.6 2.85 ft> (Π Π Abnutzungsverhältni 2.84 \ & ^ u ^ yg ^. O) 550 460 i 1.6 450 1.7 1.0

The conventional products A, B and C are unfired carbon stones.

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From these results, it can be seen that the lining formed from unbaked carbonaceous bricks according to the invention exhibits high durability with less crumbling, less molten steel wear and less slag corrosion as compared to conventional products.

Thus, it has been confirmed that the permanent liner for a converter according to the invention has a longer life than the conventional liner of ordinary unburned carbonaceous bricks without metal powder, let alone conventional burned magnesite dolomite bricks containing synthetic magnesite dolomite clinker.

The invention thus relates to a permanent lining for a converter.

According to the invention, unfired carbon-bonded bricks are used with 3 to 40% by weight of carbonaceous material, 1 to 10% by weight of aluminum and as residual magnesite clinker for at least a portion of the permanent lining, to allow the lining of one converter to reach the different high withstand the thermal load ratios to which the refractory lining materials in the oxygen blowing process are exposed for producing steel in various forms such as the oxygen inflation method, the oxygen blowing method, combinations of these methods, and the like, thereby enabling the lining of the converter to operate even under these thermal load conditions has a long period of use.

Claims (7)

1. A liner for a converter, characterized in that unburnt carbon-bonded bricks weight having 3 to 40 -.% Carbonaceous material, 1 to 10 wt .-% aluminum and the balance proportion Magnesitklinker form at least a portion of the liner. 2. Lining according to item 1, characterized in that the proportion of the carbonaceous material 5 bis 30 wt .-% is. 3. Lining according to item 1, characterized in that the proportion of aluminum is 1 to 6 wt .-%. 4. Aue clothes according to item 1, characterized in that unburned carbon-bonded stones with 3 to 40 wt .-% of carbonaceous material, 1 to 10 wt .-% aluminum, less than 6 wt - . % Silicon and form as a residual magnesite clinker at least part of the lining. 5. Lining according to item 4, characterized in that the proportion of the carbonaceous material 5 bis 30 wt .-% is. 6. lining according to item 4, characterized in that the proportion of aluminum is 1 to 6 wt .-%. 7. lining according to point 4, characterized in that the proportion of silicon 1 to 4 wt - . % Is.