CN111792927A

CN111792927A - Low-heat-conduction refractory brick for ladle working lining and preparation method thereof

Info

Publication number: CN111792927A
Application number: CN201910279973.6A
Authority: CN
Inventors: 甘菲芳; 王涛
Original assignee: Baoshan Iron and Steel Co Ltd
Current assignee: Baoshan Iron and Steel Co Ltd
Priority date: 2019-04-09
Filing date: 2019-04-09
Publication date: 2020-10-20

Abstract

The invention discloses a low-heat-conduction refractory brick for a ladle working lining and a preparation method thereof, wherein the refractory brick comprises the following raw materials in percentage by mass: 60-70% of calcium hexaluminate particles, 5-10% of corundum fine powder, 3-9% of alumina micro powder, 4-8% of silicon carbide, 5-9% of carbonaceous raw material, 3-5% of expanding agent, 1-3% of antioxidant and 3-4% of binding agent. The calcium hexaluminate particles have a porosity of 10-26% and a bulk density of 2.5-2.8g/cm³The diameter of the granules is 0.088-5 mm. The carbonaceous raw materials are at least two of graphite, carbon black and asphalt. The expanding agent is any one of kyanite, andalusite and sillimanite. The antioxidant is Al, Si, B₄One or two of C. The binding agent is phenolic resin. The ladle working lining made of the refractory brick has low heat conductivity coefficient, and has better erosion resistance, thermal shock resistance and heat preservation.

Description

Low-heat-conduction refractory brick for ladle working lining and preparation method thereof

Technical Field

The invention relates to a refractory material of a foundry ladle and a preparation method thereof, in particular to low-heat-conductivity Al for a foundry ladle working lining₂O₃-CaO-SiC-C refractory bricks and a preparation method thereof.

Background

The ladle in the steel smelting is a wide range of the current steel enterprisesThe adopted molten iron receiving, conveying and molten iron pretreatment container device is also an important carrier of an interface technology in an iron-making and steel-making section, and the temperature state of the container device directly influences the temperature of molten iron in a ladle, so that the technical and economic indexes of material consumption, energy consumption, operation time and the like of molten iron pretreatment and converter steel-making procedures are influenced. Therefore, the heat preservation and the service life of the ladle have important significance for cost reduction, efficiency improvement, energy conservation and consumption reduction of iron and steel enterprises. The desulfurization of the molten iron is usually carried out in a ladle, and the molten iron is stirred to increase the erosion of the refractory material of the working lining. Part of CaO and CaF in the desulfurizer₂With SiO in refractory materials₂、Al₂O₃The reaction to produce low melting point material results in erosion of the lining. And CaF in the desulfurizing agent₂The flux is a strong fluxing agent, reduces the melting point and viscosity of slag, and accelerates the erosion speed of the working lining refractory material. In the process of operation and deep desulfurization treatment of the ladle, the time interval is long, the temperature drop is too large, the consistency of molten iron and slag is increased, the phenomena of incomplete tapping, slag adhesion and iron adhesion after desulfurization are caused, slag skimming is needed, the slag skimming causes the working layer of a refractory material on the upper part of the ladle to be loosened and fall off, the maintenance has to be increased, and the comprehensive service life of the ladle is further shortened. At present, in order to further save energy and reduce consumption, a steel mill is pushed to add scrap steel into a ladle or increase the temperature of molten iron entering a furnace as much as possible. Therefore, the service life and the heat preservation of the ladle are more and more emphasized, and a plurality of new technologies are developed and researched to meet new requirements of energy conservation, environmental protection, high efficiency and the like of steel plants.

The invention discloses a lining brick for a desulfurization hot-metal bottle with publication number CN 101219901A, which adopts alumina clinker and brown corundum as high-alumina raw materials, adds silicon carbide and graphite, and improves the requirements of erosion resistance and expansibility by adding electric melting magnesia powder, improves the phenomenon of slag-iron adhesion of the brick lining and prolongs the service life.

In order to adapt to more severe use conditions, the Chinese invention patent application with the publication number of CN 106882969A discloses a zinc-aluminum-containing spinel aluminum silicon carbide carbon brick for a ladle, which takes tabular corundum as a high-alumina main raw material and adopts special raw materials such as zinc-aluminum spinel, stabilized zirconia, lanthanum oxide and the like to strengthen the thermal shock resistance stability, compactness and high-temperature strength of an ASC brick (aluminum silicon carbide carbon brick), improve the service life of the ladle and reduce the heat loss of molten iron. The thermal conductivity of the brick is 8.0-10.0 w/m.k, which is much lower than 14.1w/m.k in the prior art, and the brick is a new technical product of a foundry ladle.

The Chinese patent application with publication number CN 106495718A discloses a MgO-SiC-C working lining brick for a ladle made of iron and a preparation method thereof, magnesia is used as a main raw material to replace a high-alumina raw material, mainly aiming at improving the expansibility of refractory bricks and reducing the iron inclusion and erosion of brick joints, and meanwhile, the magnesia is considered to have good erosion resistance to desulfurized alkaline slag. The product has long service life and low ton iron cost.

In order to reduce the temperature drop in the molten iron process and be beneficial to adding scrap steel in a ladle or improving the temperature of molten iron entering a furnace, many steel plants are equipped with heat-preservation ladles. The insulating material is added between the steel shell of the ladle and the permanent layer of refractory material, the insulating material has good heat preservation performance, but the service temperature of the insulating material cannot exceed 1000 ℃, otherwise, the insulating material is rapidly failed and damaged, and serious accidents such as steel leakage of the ladle are easily caused. Although the above patents or patent applications extend the life of the working lining of the ladle and have good thermal insulation properties, the thermal conductivity of the working lining is not good for blocking heat transfer to the thermal insulation material, and the corrosion resistance and thermal shock resistance are not good.

Disclosure of Invention

The invention aims to provide a low-heat-conductivity refractory brick for a ladle working lining and a preparation method thereof.

The invention is realized by the following steps:

a low-heat-conduction refractory brick for a ladle working lining comprises the following raw materials in percentage by mass: 60-70% of calcium hexaluminate particles, 5-10% of corundum fine powder, 3-9% of alumina micro powder, 4-8% of silicon carbide, 5-9% of carbonaceous raw material, 3-5% of expanding agent, 1-3% of antioxidant and 3-4% of binding agent.

The calcium hexaluminate particles have a porosity of 10-26% and a bulk density of 2.5-2.8g/cm³The diameter of the granules is 0.088-5 mm.

The carbonaceous raw materials are at least two of graphite, carbon black and asphalt.

The expanding agent is any one of kyanite, andalusite and sillimanite.

The antioxidant is Al, Si, B₄One or two of C.

The binding agent is phenolic resin.

The particle diameter of the corundum fine powder is not more than 0.088mm, and the particle diameter of the alumina micro powder is not more than 8 um.

The particle diameter of the silicon carbide is not more than 0.074mm, the particle diameter of the carbonaceous raw material is not more than 0.154mm, and the particle diameter of the expanding agent is not more than 0.074 mm.

The heat conductivity coefficient of the refractory brick is 4.1-4.9w/m.k, the thermal shock resistance is 20-25 times, and the erosion index of the desulfurization agent is 165-190%.

A preparation method of a low-heat-conductivity refractory brick for a ladle working lining comprises the following steps:

step 1: weighing the following raw materials in percentage by mass: 60-70% of calcium hexaluminate particles, 5-10% of corundum fine powder, 3-9% of alumina micro powder, 4-8% of silicon carbide, 5-9% of carbonaceous raw material, 3-5% of expanding agent, 1-3% of antioxidant and 3-4% of binding agent;

step 2: mixing calcium hexaluminate particles, a carbonaceous raw material, silicon carbide and a swelling agent;

and step 3: adding a binding agent into the mixture obtained in the step 2, and continuously mixing;

and 4, step 4: adding corundum fine powder, alumina micro powder and an antioxidant into the mixture obtained in the step 3, and mixing;

and 5: pressing the mixture obtained in the step 4 into green bricks by a brick press, loading into a vehicle, pushing into a drying kiln and drying;

step 6: and (5) obtaining a finished product of the refractory brick after the overall dimension is qualified.

Compared with the prior art, the invention has the following beneficial effects:

1. compared with the ASC brick in the prior art, the heat conductivity coefficient of the refractory brick is reduced by more than 35%, the heat preservation performance of the ladle is better, the use temperature of a ladle steel shell and a heat insulation material is lowered, and the use safety of the ladle is greatly improved.

2. The refractory brick provided by the invention is excellent in thermal shock resistance and erosion resistance, and particularly has a better using effect under the conditions of ladle desulfurization process treatment and heat preservation requirement.

The raw materials of the refractory brick select the ladle with good adaptability to the slag system of the desulfurization ladle and good matching property to the performance requirement, so that the prepared ladle working lining has low heat conductivity coefficient, and the erosion resistance, the thermal shock resistance and the heat preservation performance are superior to those of the materials in the prior art, can meet the functional requirement of the ladle, and is particularly suitable for the ladle with the hot metal desulfurization pretreatment process and the heat preservation requirement.

Drawings

FIG. 1 shows CaO-Al₂O₃The system phase diagram of (1);

FIG. 2 is Al₂O₃-SiO₂The system phase diagram of (1).

Detailed Description

The invention is further described with reference to the following figures and specific examples.

A low-heat-conduction refractory brick for a ladle working lining comprises the following raw materials in percentage by mass: 60-70% of calcium hexaluminate particles, 5-10% of corundum fine powder, 3-9% of alumina micro powder, 4-8% of silicon carbide, 5-9% of carbonaceous raw material, 3-5% of expanding agent, 1-3% of antioxidant and 3-4% of binding agent. The calcium hexaluminate particles are used as the aggregate of the refractory brick, and the alumina raw material consisting of 5-10% of corundum fine powder and 3-9% of alumina micro powder is used as the matrix material of the refractory brick.

The calcium hexaluminate (CA)₆) The granules have a porosity of 10-26% and a bulk density of 2.5-2.8g/cm³The diameter of the granules is 0.088-5 mm. The calcium hexaluminate has CaO-Al₂O₃The phase with the best high temperature resistance is shown in figure 1, and the theoretical density is 3.79g/cm³The melting point is 1830 ℃, and the lower thermal expansion coefficient is 8.0 10^-6V. C. The solubility in the iron-containing slag is low, and the chemical stability in an alkaline environment is good, so the corrosion resistance of the CaO system desulfurizer is good; has low wettability to molten metal and slag, and thus has good erosion resistance and permeability. Artificially synthesized CA₆The microstructure of the raw material is mainly composed of plate-shaped CA₆The material is composed of crystals and air holes, so that the material has low thermal conductivity, and the heat preservation and thermal shock performance of the material are superior to those of other high-alumina raw materials.

Preferably, the alumina raw material adopts corundum fine powder (optional corundum fine powder with the particle diameter not more than 0.088 mm) and alpha-alumina micro powder (optional alpha-alumina micro powder with the particle diameter not more than 8 mu m) as the matrix material of the refractory brick, is a very excellent high-temperature refractory raw material, and has particularly good erosion resistance and wear resistance, so that Al with higher content in matrix chemical composition is kept₂O₃Content of high-temperature calcium-containing phase in refractory brick, and can protect CA₆An aggregate. Meanwhile, the refractory brick is also ensured to be not reacted by the desulfurizer or the CaO-rich slag to generate a low-melting-point new phase in the using process.

Referring to FIG. 1, Al in the matrix₂O₃High content, reacting with CaO in slag to generate a melting point of CA 1602 ℃, or generating CA₂Melting point 1762 ℃ and are phases with higher melting points. And at the moment, the temperature of molten iron does not exceed 1500 ℃, so the refractory brick is not easy to corrode, melt and damage. With excess Al₂O₃Can also contact SiO in the slag₂Formation of Al₂O₃-SiO₂Mullite phase (A)₃S₂) The melting point is above 1700 ℃, see figure 2, so that the thermal shock resistance and the erosion resistance of the refractory brick are further improved.

The silicon carbide SiC (silicon carbide with the particle diameter not more than 0.074mm can be selected) is a high-temperature refractory raw material, the molten iron has good erosion resistance and good thermal shock resistance, and the influence of the silicon carbide SiC on the thermal conductivity and the oxidation resistance of the refractory brick can be reduced by controlling the proper addition amount.

The carbonaceous raw materials (the carbonaceous raw materials with the particle diameter not more than 0.154mm can be selected) are at least two of graphite, carbon black and asphalt, and the carbonaceous raw material combination with different material properties has the best application effect, so that the infiltration resistance of molten iron and slag is good, the expansion is small, the erosion resistance of the refractory brick can be improved, the thermal shock resistance of the refractory material can be greatly improved, and the influence on the thermal conductivity of the refractory brick is reduced.

In order to avoid the problem of enlarging the brick joints caused by low expansibility of the raw materials, an expanding agent can be added to avoid safety accidents such as iron infiltration of the working lining, preferably, the expanding agent (the expanding agent with the particle diameter not more than 0.074mm can be selected) is any one of kyanite, andalusite and sillimanite, and the main component is Al₂O₃And SiO₂. The expanding agent is heated and converted into mullite and quartz to expand, and the decomposed quartz SiO₂And may further react with Al in the matrix₂O₃The reaction is carried out to regenerate mullite, so that the continuous expansion period is longer, and meanwhile, the thermal shock resistance of the refractory brick is improved due to the increase of the mullite amount.

Since the refractory brick of the present invention contains a carbonaceous material, it is necessary to add an appropriate amount of an antioxidant, preferably, Al, Si, B₄One or two of C.

Preferably, the binding agent is phenolic resin, and the refractory brick after being formed and dried by resin binding has high strength and can fully meet the requirements of transportation, construction and application.

step 1: weighing the following raw materials in percentage by mass: 60-70% of calcium hexaluminate particles, 5-10% of corundum fine powder, 3-9% of alumina micro powder, 4-8% of silicon carbide, 5-9% of carbonaceous raw material, 3-5% of expanding agent, 1-3% of antioxidant and 3-4% of binding agent.

Step 2: mixing the calcium hexaluminate particles, the carbonaceous raw material, the silicon carbide and the expanding agent in a mixing mill, preferably for 3-8 min.

And step 3: adding a binding agent into the mixture obtained in the step 2, and continuously mixing, wherein the mixing time is preferably 3-5 min.

And 4, step 4: adding corundum fine powder, alumina micro powder and an antioxidant into the mixture obtained in the step 3, and mixing, wherein the mixing time is preferably 10-20 min.

And 5: and (3) pressing the mixture obtained in the step (4) into green bricks by using a brick press, loading into a drying kiln, and drying at the drying temperature of 160-250 ℃ for 12-24 hours.

Step 6: and (5) obtaining a finished product of the refractory brick after the overall dimension is qualified. The compressive strength of the refractory brick prepared by the invention can reach 54-67MPa, the thermal conductivity coefficient can be reduced to 4.1-4.9w/m.k, the thermal shock resistance can reach 20-25 times, the erosion index of the desulfurization agent can reach 165-190% (the higher the erosion index of the desulfurization agent is, the better), and as shown in Table 2, all indexes are obviously superior to that of the ASC brick in the prior art.

The following 7 groups of refractory bricks were prepared according to the above raw material mass percentages and preparation methods, and the components and proportions thereof are shown in table 1.

TABLE 1 example composition of ladle refractory brick (% by mass)

The physical properties of the refractory bricks prepared in the above embodiments are tested and analyzed, and the physical properties include compressive strength (MPa), thermal conductivity, thermal shock resistance and desulfurization agent erosion resistance index; in the test of the erosion index of the desulfurization agent, the content of CaO in the desulfurizer is more than 70 percent. The results of the test analyses and their comparison with the physical properties of the aluminum silicon carbide carbon bricks are shown in Table 2.

TABLE 2 analysis and comparison of properties of refractory foundry ladle bricks prepared in the examples

As can be seen from Table 2, the refractory brick for the ladle working lining provided by the invention has the advantages that the heat preservation performance, the thermal shock resistance and the desulfurization agent erosion resistance are obviously improved, particularly, the heat conductivity coefficient is reduced by more than 35% compared with the conventional ASC brick, and the refractory brick is very beneficial to the heat preservation of the ladle and the reduction of the temperature drop of molten iron. Therefore, the refractory brick for preparing the foundry ladle ensures the service life and the heat preservation effect of the foundry ladle, and has great promotion effect on realizing energy conservation, consumption reduction and high-efficiency production of iron and steel enterprises.

Claims

1. A low heat conduction firebrick for a ladle working lining is characterized in that: the composite material comprises the following raw materials in percentage by mass: 60-70% of calcium hexaluminate particles, 5-10% of corundum fine powder, 3-9% of alumina micro powder, 4-8% of silicon carbide, 5-9% of carbonaceous raw material, 3-5% of expanding agent, 1-3% of antioxidant and 3-4% of binding agent.

2. The refractory brick for a ladle working lining as claimed in claim 1, wherein: the calcium hexaluminate particles have a porosity of 10-26% and a bulk density of 2.5-2.8g/cm³The diameter of the granules is 0.088-5 mm.

3. The refractory brick for a ladle working lining as claimed in claim 1, wherein: the carbonaceous raw materials are at least two of graphite, carbon black and asphalt.

4. The refractory brick for a ladle working lining as claimed in claim 1, wherein: the expanding agent is any one of kyanite, andalusite and sillimanite.

5. The refractory brick for a ladle working lining as claimed in claim 1, wherein: the antioxidant is Al, Si, B₄One or two of C.

6. The refractory brick for a ladle working lining as claimed in claim 1, wherein: the binding agent is phenolic resin.

7. The refractory brick for a ladle working lining as claimed in claim 1, wherein: the particle diameter of the corundum fine powder is not more than 0.088mm, and the particle diameter of the alumina micro powder is not more than 8 um.

8. The refractory brick for a ladle working lining as claimed in claim 1, wherein: the particle diameter of the silicon carbide is not more than 0.074mm, the particle diameter of the carbonaceous raw material is not more than 0.154mm, and the particle diameter of the expanding agent is not more than 0.074 mm.

9. The refractory brick for a ladle working lining as claimed in claim 1, wherein: the heat conductivity coefficient of the refractory brick is 4.1-4.9w/m.k, the thermal shock resistance is 20-25 times, and the erosion index of the desulfurization agent is 165-190%.

10. A method for preparing a refractory brick with low thermal conductivity for a ladle working lining as claimed in claim 1, which is characterized in that: the method comprises the following steps: