CN109400128B

CN109400128B - Pyrophyllite powder-containing aluminum-carbon refractory material and preparation method thereof

Info

Publication number: CN109400128B
Application number: CN201811326285.2A
Authority: CN
Inventors: 陈雄春; 苏月斌; 郑精武
Original assignee: Zhejiang Haoxiang Mining Co ltd
Current assignee: Zhejiang Haoxiang Mining Co ltd
Priority date: 2018-11-08
Filing date: 2018-11-08
Publication date: 2021-11-30
Anticipated expiration: 2038-11-08
Also published as: CN109400128A

Abstract

The invention discloses an aluminum-carbon refractory material containing pyrophyllite powder and a preparation method thereof. On the one hand, the pyrophyllite powder is used for replacing alumina powder, so that the cost of the aluminum-carbon refractory material is reduced. On the other hand, a thin carbon layer is generated on the surfaces of the alumina and the pyrophyllite by utilizing a spray calcination method, so that carbon and alumina or pyrophyllite powder are fully mixed, and meanwhile, the aluminum-carbon refractory material has better comprehensive performance on the premise of lower carbon content.

Description

Pyrophyllite powder-containing aluminum-carbon refractory material and preparation method thereof

Technical Field

The invention relates to a pyrophyllite powder-containing aluminum-carbon refractory material and a preparation method thereof, which comprises the steps of preparing aluminum oxide and pyrophyllite composite powder coated with carbon on the surface by a spray calcination method, mixing the powder with a binder and an antioxidant, pressing and calcining to obtain the low-carbon high-performance aluminum-carbon refractory material, and belongs to the technical field of refractory material preparation.

Background

In recent years, with the development of new steel-making technologies such as continuous casting and external refining, higher demands have been made on the service performance of refractory materials. Aluminum carbon (Al)₂O₃the-C) refractory material has the characteristics of good slag resistance, thermal shock resistance, high strength and the like, and is widely applied to the ferrous metallurgy industry. Carbon (C) has a very low coefficient of thermal expansion and a high thermal conductivity, does not soften after long-term use at high temperatures, is hardly attacked by acids, alkalis, salts and organic substances, and is a high-quality refractory material. In addition, carbon has difficult wettability to slag and has excellent slag corrosion resistance in the using process. Conventional Al₂O₃The carbon content fraction of the-C refractory material is higher and is about 10-30wt%. However, in the casting of clean steel, Al₂O₃-C the refractory material contacts the molten steel, which causes carburisation of the molten steel; the density of carbon is less than that of alumina, and when the carbon content is too high, the bulk density of the refractory material is reduced; in addition, C is highly reactive with oxidizing gases (e.g., O) at higher temperatures₂) A chemical reaction occurs that results in the loss of the superior properties of the carbonaceous refractory material. Therefore, in order to meet the requirements of smelting clean steel and saving energy and reducing consumption at present, Al₂O₃The development of-C refractory materials is directed toward low carbonization and low cost. However, low carbon does not mean that the carbon content tends to zero, which would result in poor thermal shock and slag erosion resistance of the refractory, thereby affecting the service life of the refractory. And when the carbon content is reduced, the volume fraction is correspondingly reduced, and how to realize the carbon and the Al₂O₃The thorough mixing of the components affects the Al₂O₃-C key factors in refractory performance. Thus in Al₂O₃The surface of the powder is coated with a thin carbon layer, so that the content of carbon can be reduced, the carbon and the aluminum can be fully mixed, and Al at high temperature can be favorably mixed₂O₃Reacts with carbon to generate Al on the surface of the powder₃C₃And the volume density and compressive strength of the refractory material are improved. The spray calcining method is to dissolve soluble carbon source in water solution, when the inorganic powder is soaked in the water solution and fully wetted, the surface will be soaked with a layer of water film containing carbon source, then through spray high temperature calcining, water in the water film is evaporated and the organic carbon source is decomposed to generate carbon, thus obtaining the inorganic powder material coated with thin carbon layer.

The alumina is replaced by abundant natural mineral material, and the alumina is aluminum carbon (Al)₂O₃-C) one way of cost reduction of the refractory material. And pyrophyllite of formula 2Al₂O₃·4SiO₂·H₂O, as a refractory material with excellent performance, has good high-temperature volume stability, can not be cracked under the condition of temperature drastic change and has good high-temperature creep resistance. The pyrophyllite is added into the aluminum-carbon refractory material, so that the production cost of the aluminum-carbon refractory material can be reduced. Meanwhile, the pyrophyllite belongs to a layered structure,the structure of the material is the same as that of the talc, and the material can expand during high-temperature calcination to offset the shrinkage of the green body during high-temperature calcination, so that the green body is prevented from cracking due to the shrinkage during the high-temperature calcination.

In summary, the prior art has been shown to contain aluminum-carbon (Al)₂O₃and-C) the refractory material has a high carbon content fraction (about 10-30 wt%), and the graphite and the alumina are not uniformly dispersed by using the crystalline flake graphite as a carbon source, so that the cost of the raw material is high, and the like.

Disclosure of Invention

In order to reduce the cost of the refractory material and reduce the carbon content on the premise of ensuring the uniform distribution of carbon in the aluminum-carbon material, the invention provides an aluminum-carbon refractory material containing pyrophyllite powder and a preparation method thereof.

The technical scheme adopted by the invention to achieve the aim of the invention is as follows: the method comprises the following steps of coating a carbon layer on the surfaces of alumina powder and pyrophyllite powder by a spray roasting method, uniformly mixing the coated alumina powder and pyrophyllite powder with thermosetting phenolic resin and an antioxidant according to a certain mass ratio, pressing the mixture into a green body by a press machine, drying and curing the formed green body in a drying box, and finally embedding carbon in a high-temperature furnace for sintering and forming, and specifically comprises the following steps:

s1: mixing alumina powder with the particle size of 50-500 mu m and pyrophyllite powder with the particle size of 50-500 mu m, then adding a soluble carbon source, uniformly mixing, finally adding water, and blending into paste; wherein the mass ratio of the alumina powder to the pyrophyllite powder is 86-46: 5-45; the soluble carbon source is an organic alcohol compound consisting of carbon, hydrogen and oxygen, and the ratio of the mass of carbon atoms in the added soluble carbon source to the total mass of the alumina powder and the pyrophyllite powder is 5-10: 100, respectively;

s2: the paste is sent into a two-temperature-zone tubular furnace which is connected with a high-pressure spraying device and is heated in advance in a mist form through the high-pressure spraying device, and a high-pressure gas source is nitrogen. Setting temperatures corresponding to two temperature intervals encountered in sequence to be 300 ℃ and 700 ℃ respectively according to the moving direction of the material; the corresponding length of the two temperature intervals is half of that of the tube furnace. Drying the water on the surfaces of the alumina and pyrophyllite powder at the temperature of 300 ℃, wherein the soluble carbon source is in a caramel state; in the temperature range of 700 ℃, the carbon source in the caramel state is thermally decomposed into carbon spheres which are coated on the surfaces of the alumina and pyrophyllite powder.

S3: then, uniformly mixing 100 parts by weight of the mixture of the alumina powder and the pyrophyllite powder coated with the carbon, 3-6 parts by weight of phenolic resin binder and 1-3 parts by weight of antioxidant by using a press machine at 15 MPa-cm^-2Pressing the mixture into a green body, and drying and curing the formed green body in a drying oven at the drying temperature of 150-200 ℃ for 24 hours.

S4: and (3) carrying out carbon burying sintering molding on the dried and solidified sample of S3 in a high-temperature furnace. The sintering molding temperature is 1250-1350 ℃, and the sintering time is 3-6 hours.

The beneficial effects of the pyrophyllite powder-containing aluminum-carbon refractory material and the preparation method thereof are mainly reflected in that: (1) a thin carbon layer is generated on the surfaces of the alumina and the pyrophyllite by utilizing a spray calcination method, so that carbon and alumina or pyrophyllite powder are fully mixed, and meanwhile, the aluminum-carbon refractory material has better comprehensive performance on the premise of lower carbon content. (2) The pyrophyllite powder is used to replace alumina powder, so that the cost of the aluminum-carbon refractory material is reduced.

Detailed description of the preferred embodiments

The invention is further described below with reference to specific examples, but the methods and technical parameters involved in the schemes should not be construed as limiting the invention.

Example 1:

step 1: mixing 66 parts by weight of alumina powder with the particle size of 50-500 mu m and 20 parts by weight of pyrophyllite powder with the powder size of 50-500 mu m, then adding 15 parts by weight of glucose, fully mixing uniformly, finally adding water, and blending into paste.

Step 2: and (3) feeding the paste into a two-temperature-area tubular furnace which is connected with the high-pressure spraying device and is preheated through the high-pressure spraying device in a mist form, wherein a high-pressure gas source is nitrogen, and the pressure is 2 MPa. According to the material moving direction, the corresponding set temperatures of two temperature intervals of the tubular furnace encountered successively are 300 ℃ and 700 ℃; the corresponding length of the two temperature intervals is half of that of the tube furnace.

After scanning and transmission tests, the carbon spheres are coated on the surfaces of the alumina and pyrophyllite powder after passing through the tubular furnace. In addition, samples are taken out in a segmented mode for characterization, and the result shows that the moisture on the surfaces of the alumina and pyrophyllite powder is dried in a temperature range of 300 ℃, and the soluble carbon source is in a caramel state; in the temperature range of 700 ℃, the carbon source in the caramel state is thermally decomposed into carbon spheres which are coated on the surfaces of the alumina and pyrophyllite powder.

And step 3: then, 100 parts by weight of the mixture of the alumina powder and the pyrophyllite powder, the surface of which is coated with carbon, is uniformly mixed with 4 parts by weight of phenolic resin binder and 2 parts by weight of SiC antioxidant, the mixture is pressed into a cylindrical blank body with phi 35mm multiplied by 35mm by a press machine under the pressure of 144MPa, and the formed blank body is put into a drying oven for drying and curing, wherein the drying temperature is 200 ℃, and the drying time is 24 hours.

And 4, step 4: and (3) carrying out carbon burying sintering molding on the dried and solidified sample in a silicon-molybdenum rod high-temperature furnace. The sintering and forming temperature is 1300 ℃, and the sintering time is 5 hours.

The test shows that the carbon content is 4.6 percent, the apparent porosity is 7.2 percent, and the volume density is 2.65g cm^-3The normal temperature compressive strength is 75MPa, and all indexes meet the use requirements of the steelmaking foundry ladle.

Example 2:

step 1: mixing 86 parts by weight of alumina powder with the particle size of 50-500 mu m and 5 parts by weight of pyrophyllite powder with the powder size of 50-500 mu m, then adding 11.4 parts by weight of glucose, fully mixing uniformly, finally adding water, and blending into paste.

Step 2: the paste is sent into a two-temperature-zone tubular furnace which is connected with a high-pressure spraying device and is preheated through the high-pressure spraying device in a mist form, wherein a high-pressure gas source is nitrogen, and the pressure is 1 MPa. According to the material moving direction, the corresponding set temperatures of two temperature intervals of the tubular furnace encountered successively are 300 ℃ and 700 ℃; the corresponding length of the two temperature intervals is half of that of the tube furnace.

And through scanning and transmission tests, after passing through a tube furnace, the surfaces of the alumina and pyrophyllite powder are coated with carbon spheres.

And step 3: then, 100 parts by weight of the mixture of the alumina powder and the pyrophyllite powder, the surface of which is coated with carbon, is uniformly mixed with 3 parts by weight of phenolic resin binder and 3 parts by weight of SiC antioxidant, the mixture is pressed into a cylindrical blank body with phi 35mm multiplied by 35mm by a press machine under the pressure of 144MPa, and the formed blank body is put into a drying oven for drying and curing, wherein the drying temperature is 200 ℃, and the drying time is 24 hours.

And 4, step 4: and (3) carrying out carbon burying sintering molding on the dried and solidified sample in a silicon-molybdenum rod high-temperature furnace. The sintering and forming temperature is 1250 ℃, and the sintering time is 6 hours.

The test shows that the carbon content is 3.2 percent, the apparent porosity is 5.8 percent, and the volume density is 2.72g cm^-3The normal temperature compressive strength is 82MPa, and all indexes meet the use requirements of the steelmaking foundry ladle.

Example 3:

step 1: mixing 46 parts by weight of alumina powder with the particle size of 50-500 mu m and 45 parts by weight of pyrophyllite powder with the powder size of 50-500 mu m, then adding 21.6 parts by weight of cane sugar, fully mixing uniformly, finally adding water, and blending into paste.

Step 2: the paste is sent into a two-temperature-zone tubular furnace which is connected with a high-pressure spraying device and is preheated through the high-pressure spraying device in a mist form, wherein a high-pressure gas source is nitrogen, and the pressure is 3 MPa. According to the material moving direction, the corresponding set temperatures of two temperature intervals of the tubular furnace encountered successively are 300 ℃ and 700 ℃; the corresponding length of the two temperature intervals is half of that of the tube furnace.

And step 3: then, 100 parts by weight of the mixture of the alumina powder and the pyrophyllite powder, the surface of which is coated with carbon, is uniformly mixed with 6 parts by weight of phenolic resin binder and 1 part by weight of SiC antioxidant, the mixture is pressed into a cylindrical blank body with phi 35mm multiplied by 35mm by a press machine under the pressure of 144MPa, and the formed blank body is put into a drying oven for drying and curing, wherein the drying temperature is 150 ℃, and the drying time is 24 hours.

And 4, step 4: and (3) carrying out carbon burying sintering molding on the dried and solidified sample in a silicon-molybdenum rod high-temperature furnace. The sintering and forming temperature is 1350 ℃, and the sintering time is 3 hours.

The test shows that the carbon content is 7.5 percent, the apparent porosity is 9.2 percent, and the volume density is 2.54g cm^-3The normal temperature compressive strength is 73MPa, and all the indexes meet the use requirements of the steelmaking foundry ladle.

Example 4

On the basis of example 1, the change in the performance of the refractory material was studied by changing the weight ratio of pyrophyllite to alumina as shown in table 1, respectively, while ensuring that the total weight of pyrophyllite and alumina was not changed, and the results are shown in table 1.

TABLE 1

Pyrophyllite weight fraction	5	13.5	20	22.4	35	45.5
							Alumina weight parts	86	77.5	66	68.6	56	45.5
Carbon content of the product%	4.7	4.5	4.6	4.5	4.8	4.4
							The apparent porosity of the product%	6.5	6.9	7.2	7.9	10.1	11.7
Bulk density of the product g cm^-3	2.72	2.67	2.65	2.62	2.41	2.34
							Compressive strength of the product MPa	81	77	75	74	67	58

Note: the tests of this example were the same as example 1 except that the relative contents of pyrophyllite and alumina were different from those of example 1.

It can be seen from table 1 that the pyrophyllite content affects the performance of the refractory material, the pyrophyllite content is high, which is beneficial to reducing the cost, but when the pyrophyllite is too high, the pyrophyllite is decomposed at high temperature to generate mullite and amorphous quartz phase with density lower than that of the pyrophyllite, so that the volume density of the refractory material is reduced, the corresponding apparent porosity is increased, and the normal-temperature compressive strength is also reduced correspondingly. The optimum pyrophyllite content is 5-45%, and the optimum cost performance content is 15-25%.

Example 5

The amount of the soluble carbon source added was investigated on the basis of example 1, and the results of the reaction using glucose in the amounts shown in Table 2 are shown in Table 2.

TABLE 2

Glucose weight parts	9	12	15	20	25
						Carbon content of the product%	2.9	3.5	4.6	5.5	6.1
The apparent porosity of the product%	7.9	7.4	7.2	6.7	7.3
						Bulk density of the product g cm^-3	2.52	2.63	2.65	2.74	2.58
Compressive strength of the product MPa	68	73	75	81	73

Note: the tests of this example were the same as those of example 1 except that the glucose content was different from that of example 1.

As can be seen from Table 2, the carbon content also affects the performance of the refractory, since carbon reacts with Al at high temperatures₂O₃Or, SiO2 produces Al3C3 or SiC to increase the bulk density and improve the compressive strength of the refractory, but since the density of carbon is lower than that of alumina, the bulk density of the sample decreases rather with an increase in the amount of carbon added, and the performance deteriorates accordingly. The carbon content in the actual refractory material is best between 3.5 and 5.5 percent. Because of the loss of the soluble carbon source by the spray calcination method, the mass fraction of the soluble liquid carbon source of the polyol carbohydrate is 5 to 10% in terms of carbon atom concentration.

Example 6

The sintering temperature was examined in addition to example 1, and the results of the reactions using glucose in the amounts shown in Table 3 are shown in Table 3.

TABLE 3

Sintering temperature	1200	1250	1300	1350	1400	1450
							The apparent porosity of the product%	7.9	7.4	7.2	6.8	7.0	7.5
Bulk density of the product g cm^-3	2.53	2.61	2.65	2.68	2.67	2.59
							Compressive strength of the product MPa	69	72	75	78	77	70

Note: the tests of this example were the same as those of example 1 except that the sintering temperature was different from that of example 1.

Since pyrophyllite decomposes at high temperatures to form mullite and amorphous quartz phases, the firing temperatures mentioned in the above steps are relative to Al₂O₃The performance of the-C refractory material is greatly influenced, when the firing temperature is less than 1400 ℃, the volume density and the compressive strength of the refractory material are improved along with the increase of the firing temperature, and when the firing temperature is higher than 1400 ℃, the Al is caused to be further improved by further increasing the firing temperature₂O₃The deterioration of the refractory material at-c. A large number of experiments show that Al₂O₃The most suitable firing temperature of the-C refractory material is 1250-1350 ℃, and the firing time is 3-6 hours.

Claims

1. A preparation method of an aluminum-carbon refractory material containing pyrophyllite powder is characterized by comprising the following steps:

s1: mixing alumina powder with the particle size of 50-500 mu m and pyrophyllite powder with the particle size of 50-500 mu m, then adding a soluble carbon source, uniformly mixing, finally adding water, and blending into paste; wherein the mass ratio of the alumina powder to the pyrophyllite powder is 17.2-1: 1; the soluble carbon source is an organic alcohol compound consisting of carbon, hydrogen and oxygen, and the ratio of the mass of carbon atoms in the added soluble carbon source to the total mass of the alumina powder and the pyrophyllite powder is 5-10: 100, respectively;

s2: feeding the paste into a pre-heated two-temperature-area tubular furnace connected with a high-pressure spraying device in a mist form through the high-pressure spraying device, wherein a high-pressure gas source is nitrogen; setting temperatures corresponding to two temperature intervals encountered in sequence to be 300 ℃ and 700 ℃ respectively according to the moving direction of the material; the corresponding lengths of the two temperature intervals are respectively half the length of the tube furnace;

s3: then, uniformly mixing 100 parts by weight of the mixture of the alumina powder and the pyrophyllite powder coated with the carbon, 3-6 parts by weight of phenolic resin binder and 1-3 parts by weight of antioxidant by using a press machine at 15 MPa-cm^-2Pressing the mixture into a green body, and drying and curing the formed green body in a drying oven at the drying temperature of 150-200 ℃ for 24 hours;

s4: carrying out carbon burying sintering molding on the sample dried and solidified by S3 in a high-temperature furnace; the sintering forming temperature is 1250-1350 ℃, and the sintering time is 3-6 hours.

2. The preparation method according to claim 1, wherein the mass ratio of the alumina powder to the pyrophyllite powder is 3.07-5.73: 1.

3. The method according to claim 1, wherein the antioxidant is silicon carbide (SiC), boron carbide (B)₄C) Aluminum nitride (AlN) or silicon nitride (Si)₃N₄) One or any combination of several of them.

4. An alumino-carbonaceous refractory material obtainable by a process as claimed in any one of claims 1 to 3.