CN114685173A

CN114685173A - Thermal shock resistant corundum-mullite crucible for metal precision casting and preparation method thereof

Info

Publication number: CN114685173A
Application number: CN202210215982.0A
Authority: CN
Inventors: 于修水; ***; 许烨; 张振翀; 杜会军; 王鑫松; 刘德军; 郭兴龙; 韩恒; 苏峰; 马金秋; 曹冲; 顾晓峰
Original assignee: Zibo Guochuang Center Advanced Vehicle Material Technology Innovation Center
Current assignee: Zibo Guochuang Center Advanced Vehicle Material Technology Innovation Center
Priority date: 2022-03-07
Filing date: 2022-03-07
Publication date: 2022-07-01
Anticipated expiration: 2042-03-07
Also published as: CN114685173B

Abstract

The invention belongs to the technical field of high-temperature refractory materials, and particularly relates to a thermal shock resistant corundum mullite crucible for metal precision casting and a preparation method thereof, wherein the raw materials comprise the following components in percentage by mass: 15-25% of plate-shaped corundum, 15-25% of fused corundum, 25-35% of fused mullite, 20-30% of flake alumina, 5-15% of active alumina and 1-5% of silicon dioxide; 2-6% of binder and 2-6% of plasticizer are added. The grain composition percentage is as follows: 10-25% of grain size of more than 1mm and less than or equal to 3mm, 35-50% of grain size of more than or equal to 0.1mm and less than 0.1mm 30-45%. The crucible with extremely high quality, uniform density and consistent aperture size is prepared by adopting an isostatic pressing process, has the advantages of excellent thermal shock resistance, high temperature resistance, wear resistance, good acid and alkali resistance, good chemical stability and the like, is suitable for precision casting of metal materials, and has low production cost and high quality and yield.

Description

Thermal shock resistant corundum-mullite crucible for metal precision casting and preparation method thereof

Technical Field

The invention belongs to the technical field of high-temperature refractory materials, and particularly relates to a thermal shock resistant corundum mullite crucible for metal precision casting and a preparation method thereof.

Background

China is the largest casting production country in the world at present, and according to data introduction, in recent years, because the trades of castings are increased rapidly, the yield value of casting products in China accounts for about 9% in national economy. The number of foundries in China is as large as 2 thousands, and the number of workers is as large as 120 thousands. Currently, the precision casting industry in China has a considerable scale, a large amount of technological progress achievements of the casting industry enter the application field, and the manufacturing level of individual products is even close to the international advanced level. Some medium and high precision cast products also serve important fields such as automobiles, aerospace, ships, energy sources and the like.

The crucible is used as a main auxiliary tool for metal smelting in precision casting. The crucible has excellent corrosion resistance, erosion resistance, thermal shock resistance and other performances, can reduce casting inclusions, and improves quality and yield to the maximum extent. Particularly in aircraft engine and turbine manufacturing applications, the required melting vessel requires superior performance. The development of isostatic pressing crucibles is seen as a major breakthrough in the investment casting industry. The crucible is formed under a certain pressure, and the crucible with extremely high quality, uniform density and consistent aperture size can be produced. When complex and expensive castings are manufactured, the isostatic pressing crucible can be used for ensuring the purity of the melt, and the improvement of the quality and the yield of the castings is facilitated.

At present, few enterprises for producing corundum-mullite crucibles through isostatic pressing technology are available in China, most of the enterprises are silicon carbide and graphite crucibles, but carbon elements in the crucibles easily enter metal melts, and the corrosion resistance is poor; the magnesium oxide crucible is easy to generate reduction reaction with active elements such as carbon, titanium, aluminum and the like at high temperature, so that a melt is polluted, and the purity of a casting is reduced; the calcium oxide crucible is easy to have hydration reaction with water and is not easy to be pressed and formed; the corundum crucible has the advantages of good chemical stability, acid and alkali resistance, slag resistance and the like, but has poor thermal shock resistance, and is easy to crack when being quenched and heated.

The crucible belongs to a high-temperature refractory material product, generally according to the 'close packing' principle, the particles are divided into three particle sizes of coarse, medium and fine, the coarse particles and the medium particles form a framework, and fine powder is filled in gaps of the framework to form the closest packing. However, fines are the basis for forming the refractory matrix and are the weakest point in thermal shock resistance.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the defects of the prior art are overcome, and the thermal shock resistant corundum mullite crucible for metal precision casting, which has good thermal shock resistance, good slag resistance, high temperature resistance, wear resistance and good chemical stability, is provided; the invention also provides a preparation method of the composition.

The invention is realized by adopting the following technical scheme:

the thermal shock resistant corundum-mullite crucible for metal precision casting comprises the following raw materials in percentage by mass: 15-25% of plate-shaped corundum, 15-25% of fused corundum, 25-35% of fused mullite, 20-30% of flake alumina, 5-15% of active alumina and 1-5% of silicon dioxide; 2-6% of binder and 2-6% of plasticizer are added in the total mass of the raw materials. The adopted raw materials are high-purity raw materials, so that impurities are prevented from entering a melt to influence the purity and quality of a casting when the metal is smelted.

The raw material grain composition is designed according to the proportion, so that the thermal shock resistance of the corundum-mullite crucible is improved, the service life of the crucible is prolonged, and the grain composition percentage is as follows:

the grain diameter is more than 1mm and less than or equal to 3mm, and 10-25 percent

The grain diameter is not less than 0.1mm and not more than 1mm, and 35-50 percent

The grain size is less than 0.1mm and is 30-45%.

Flake alumina with the grain size less than 0.1mm is introduced, fine powder with the grain size less than 0.1mm is the weakest tissue of the refractory material, and the flake structure can greatly improve the thermal shock resistance, thereby prolonging the service life of the crucible.

Active alumina and silica micropowder with the grain size less than 0.1mm are subjected to solid phase reaction at high temperature to generate columnar or rodlike secondary mullite in situ, and the columnar or rodlike secondary mullite and flaky alumina form a continuous staggered network structure, so that the fiber-reinforced toughening effect can be achieved, and the thermal shock resistance of the crucible matrix can be improved.

The binder is preferably one or more of polyvinyl alcohol, acrylic acid polymer, starch, dextrin or methyl cellulose.

The plasticizer is preferably one or more of polyethylene glycol, polyglycerol or ester compounds.

The invention relates to a preparation method of a thermal shock resistant corundum-mullite crucible for metal precision casting,

the method comprises the following steps:

(1) weighing the required raw materials according to the mass percentage, grading the raw materials, and premixing the raw materials with the particle size of more than 1mm and less than or equal to 3mm and the particle size of more than 0.1mm and less than or equal to 1mm for 1-3 h; after uniformly mixing, adding a binder and a plasticizer, and uniformly mixing for 1-2 h; then adding raw materials with the particle size of less than 0.1mm, and mixing for 3-5 h;

(2) after uniformly mixing, aging the materials for 15-25 h to ensure that the water is more uniform;

(3) after the material is aged, putting the material into an isostatic pressing die, compacting, and pressing and forming in isostatic pressing equipment, wherein the forming pressure is 70-120 MPa;

(4) naturally drying the formed crucible green body for 24-48 h;

(5) and (3) sintering the dried crucible at a high temperature of 1600-1700 ℃, keeping the temperature for 3-6 h, and cooling along with the furnace.

The raw materials are mixed by a mixing mill. Mix mill inside lining and agitating unit and all adopt ceramic material, prevent that the metal material from being worn and torn, lead to the pollution in the abrasive dust sneaks into the raw materials.

The isostatic pressing mould steel core adopts the carbide material, the gum cover adopts the polyurethane material. The plate-shaped corundum, the fused corundum and the fused mullite in the raw materials have sharp structures, so that a steel core is easily damaged, the service life is shortened, and the demoulding is difficult; the polyurethane rubber sleeve has good rebound, is not sticky, can be rapidly demoulded after being pressed, and has high efficiency.

The compaction equipment is a three-dimensional vibration platform. The refractory material has particle grading, and a three-dimensional vibration platform is adopted to prevent particle layering caused by vibration.

The isostatic pressing process adopts a cold isostatic pressing device. The isostatic compaction crucible has high density and uniform density, reduces the usage amount of lubricant and reduces the pollution to the crucible.

The sintering process adopts electric furnace high-temperature sintering. The electric furnace sintering is easy to control the temperature, the heating speed is high, the cost is reduced, and the environment is protected.

The corundum-mullite not only utilizes the advantages of high melting point, low thermal expansion coefficient, creep resistance, thermal shock resistance and the like of mullite, but also utilizes the advantages of wear resistance, chemical erosion resistance, oxidation resistance and the like of corundum, so that the corundum-mullite has higher high-temperature performance, high-temperature mechanical strength, thermal shock resistance, refractoriness under load, higher use temperature and good chemical stability, and does not react with other products. In the corundum-mullite complex phase structure, mullite is generally columnar and rod-shaped crystals, corundum is generally granular, corundum-shaped crystals are filled in gaps of a mullite columnar crystal network structure to form a continuous staggered network framework structure, and corundum phase crystals can play roles in strengthening and toughening; or the mullite columnar crystals are filled in the gaps of the corundum phase crystals, the existence of the columnar mullite crystals can play a role in strengthening and toughening similar to fibers and particles, and the two filling states are very favorable for improving the high-temperature mechanical property of the corundum-mullite composite ceramic. The invention adopts isostatic pressing technology for pressing and forming, solves the defects of poor thermal shock resistance, poor slag resistance, poor chemical stability and the like of the crucible in the metal precision casting, thereby improving the service life of the crucible, the purity of the melt and the quality of the casting, being suitable for precision casting of metal materials such as common steel, stainless steel, nickel-based/cobalt-based high-temperature alloy and the like, reducing the production cost and improving the quality and the yield of the casting.

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

1. the thermal shock resistant corundum mullite crucible for metal precision casting is formed by an isostatic pressing process, and has the advantages of extremely high quality, uniform density and consistent aperture size.

2. The invention further improves the thermal shock resistance of the weakest structure of the crucible by introducing the flaky alumina fine powder with the grain diameter less than 0.1mm, and has the advantages of excellent slag resistance, chemical stability, high temperature resistance, wear resistance and the like, thereby prolonging the service life of the crucible, and improving the purity of the melt and the quality of the casting.

3. According to the invention, the columnar or rod-shaped secondary mullite is generated in situ by introducing the active alumina with the grain size less than 0.1mm and the silicon dioxide micro powder to perform a solid phase reaction at high temperature, and forms a continuous staggered network structure with the flaky alumina, so that the fiber-reinforced toughening effect can be achieved, and the thermal shock resistance of the crucible matrix can be improved.

4. In the preparation process, the lining and the stirring device are all made of ceramic materials, such as a mixing mill, a cold isostatic pressing device, a hard alloy steel core, an electric furnace and the like, so that the corundum-mullite crucible is ensured to have high-purity components, and the pollution probability during metal smelting is reduced.

5. The preparation process of the invention adopts the polyurethane rubber sleeve and the three-dimensional vibration platform, and can improve the production efficiency and the yield.

Drawings

FIG. 1 is a scanning electron microscope image of a high-temperature-fired crucible substrate in example 1 of the present invention.

Detailed Description

The present invention will be further described with reference to the following examples.

Example 1

Weighing the required raw materials, namely 17% of tabular corundum, 18% of fused corundum, 27% of fused mullite, 24% of flaky alumina, 11% of activated alumina, 3% of silicon dioxide, 3.5% of an additional binder and 4% of a plasticizer according to mass percentage. The grain composition percentage is as follows: the grain diameter is more than 1mm and less than or equal to 3mm 17%, the grain diameter is more than or equal to 0.1mm and less than or equal to 1mm 45%, and the grain diameter is less than 0.1mm 38%. Premixing raw materials with the particle size of more than 1mm and less than or equal to 3mm and the particle size of more than or equal to 0.1mm and less than or equal to 1mm for 1.5h, adding a binder and a plasticizer after uniformly mixing, and uniformly mixing for 1.5 h; then adding raw materials with the particle size less than 0.1mm, and mixing for 4 hours; after the materials are uniformly mixed, the materials are aged for 18 hours to ensure that the water content is more uniform; after the material is aged, the material is put into a die and is pressed and formed in isostatic pressing equipment, and the forming pressure is 90 MPa; naturally drying the formed crucible green body for 24 hours; and (4) sintering the dried crucible at a high temperature of 1650 ℃, keeping the temperature for 5h, and cooling along with the furnace.

Example 2

Weighing 15% of tabular corundum, 19% of fused corundum, 28% of fused mullite, 20% of flaky alumina, 15% of activated alumina, 3% of silicon dioxide, 3.5% of additional binder and 4% of plasticizer according to mass percentage. The grain composition percentage is as follows: the grain diameter is more than 1mm and less than or equal to 3mm 15%, the grain diameter is more than or equal to 0.1mm and less than or equal to 1mm 47%, and the grain diameter is less than 0.1mm 38%. Premixing raw materials with the particle size of more than 1mm and less than or equal to 3mm and the particle size of more than or equal to 0.1mm and less than or equal to 1mm for 2h, adding a binder and a plasticizer after uniformly mixing, and uniformly mixing for 2 h; then adding raw materials with the particle size less than 0.1mm, and mixing for 3 h; after the materials are uniformly mixed, the materials are aged for 24 hours to ensure that the water content is more uniform; after the material is aged, putting the material into a mold, and pressing and molding the material in isostatic pressing equipment, wherein the molding pressure is 90 MPa; naturally drying the formed crucible green body for 24 hours; and (3) sintering the dried crucible at a high temperature of 1600 ℃, keeping the temperature for 6h, and cooling along with the furnace.

Example 3

Weighing the required raw materials, namely 17% of tabular corundum, 16% of fused corundum, 27% of fused mullite, 26% of flaky alumina, 11% of activated alumina, 3% of silicon dioxide, 3.5% of an additional binder and 4% of a plasticizer according to mass percentage. The grain composition percentage is as follows: the grain diameter is more than 1mm and less than or equal to 3mm and 17 percent, the grain diameter is more than or equal to 0.1mm and less than or equal to 1mm and 43 percent, and the grain diameter is less than 0.1mm and less than 40 percent. Premixing raw materials with the particle size of more than 1mm and less than or equal to 3mm and the particle size of more than or equal to 0.1mm and less than or equal to 1mm for 3 hours, adding a binder and a plasticizer after uniformly mixing, and uniformly mixing for 1 hour; then adding raw materials with the particle size less than 0.1mm, and mixing for 5 hours; after the materials are uniformly mixed, the materials are aged for 18 hours to ensure that the water content is more uniform; after the material is aged, the material is put into a die and is pressed and formed in isostatic pressing equipment, and the forming pressure is 80 MPa; naturally drying the formed crucible green body for 24 hours; and (4) sintering the dried crucible at a high temperature of 1650 ℃, keeping the temperature for 4h, and cooling along with the furnace.

Example 4

Weighing the required raw materials by mass percent, namely 20 percent of plate-shaped corundum, 15 percent of fused corundum, 27 percent of fused mullite, 24 percent of flake alumina, 11 percent of activated alumina, 3 percent of silicon dioxide, 4.5 percent of additional binder and 2 percent of plasticizer. The grain composition percentage is as follows: the grain diameter is more than 1mm and less than or equal to 3mm and 20 percent, the grain diameter is more than or equal to 0.1mm and less than or equal to 1mm and 42 percent, and the grain diameter is less than 0.1mm and 38 percent. Premixing raw materials with the particle size of more than 1mm and less than or equal to 3mm and the particle size of more than or equal to 0.1mm and less than or equal to 1mm for 2 hours, adding a binder and a plasticizer after uniformly mixing, and uniformly mixing for 1.5 hours; then adding raw materials with the particle size of less than 0.1mm, and mixing for 4 hours; after the materials are uniformly mixed, the materials are aged for 18 hours to ensure that the water content is more uniform; after the material is aged, putting the material into a mold, and pressing and molding the material in isostatic pressing equipment, wherein the molding pressure is 80 MPa; naturally drying the formed crucible green body for 48 hours; and (4) sintering the dried crucible at a high temperature of 1650 ℃, keeping the temperature for 4h, and cooling along with the furnace.

Example 5

Weighing the required raw materials by mass percent, namely 23 percent of plate-shaped corundum, 10 percent of fused corundum, 27 percent of fused mullite, 24 percent of flaky alumina, 13 percent of activated alumina, 3 percent of silicon dioxide, 3.5 percent of additional binder and 4 percent of plasticizer. The grain composition percentage is as follows: the grain diameter is more than 1mm and less than or equal to 3mm 23%, the grain diameter is more than or equal to 0.1mm and less than or equal to 1mm 37%, and the grain diameter is less than 0.1mm 40%. Premixing raw materials with the particle size of more than 1mm and less than or equal to 3mm and the particle size of more than or equal to 0.1mm and less than or equal to 1mm for 3 hours, adding a binder and a plasticizer after uniformly mixing, and uniformly mixing for 2 hours; then adding raw materials with the particle size less than 0.1mm, and mixing for 4 hours; after the materials are uniformly mixed, the materials are aged for 24 hours to ensure that the water content is more uniform; after the material is aged, putting the material into a mold, and performing compression molding in isostatic pressing equipment, wherein the molding pressure is 120 MPa; naturally drying the formed crucible green body for 24 hours; and (4) sintering the dried crucible at a high temperature of 1700 ℃, keeping the temperature for 3h, and cooling along with the furnace.

Example 6

Weighing the required raw materials by mass percent, namely 20 percent of plate-shaped corundum, 20 percent of fused corundum, 27 percent of fused mullite, 20 percent of flake alumina, 10 percent of activated alumina, 3 percent of silicon dioxide, 3.5 percent of additional binder and 4 percent of plasticizer. The grain composition percentage is as follows: the grain diameter is more than 1mm and less than or equal to 3mm and 20 percent, the grain diameter is more than or equal to 0.1mm and less than or equal to 1mm and 47 percent, and the grain diameter is less than 0.1mm and less than 33 percent. Premixing raw materials with the particle size of more than 1mm and less than or equal to 3mm and the particle size of more than or equal to 0.1mm and less than or equal to 1mm for 2h, adding a binder and a plasticizer after uniformly mixing, and uniformly mixing for 2 h; then adding raw materials with the particle size less than 0.1mm, and mixing for 3 h; after the materials are uniformly mixed, the materials are aged for 18 hours to ensure that the water content is more uniform; after the material is aged, putting the material into a mold, and pressing and molding the material in isostatic pressing equipment, wherein the molding pressure is 90 MPa; naturally drying the formed crucible green body for 24 hours; and (3) sintering the dried crucible at a high temperature of 1600 ℃, keeping the temperature for 6h, and cooling along with the furnace.

Performance testing

As shown in figure 1, in the corundum-mullite crucible matrix, the flaky alumina and the secondary mullite generated in situ form a mutually closely staggered network structure, so that the corundum-mullite crucible matrix has the functions of strengthening and toughening similar to fibers and particles, and is favorable for improving the thermal shock resistance of the matrix, thereby prolonging the service life of the crucible and reducing the use cost.

The crucibles prepared in examples 1 to 6 were subjected to performance tests according to the conventional standards, and the test results are shown in Table 1.

TABLE 1 results of performance test of high temperature firing crucibles of examples 1-6

As can be seen from Table 1, the corundum-mullite crucible of the present invention has the advantages of high use temperature, high bulk density, low apparent porosity and water absorption, low thermal expansion coefficient, high thermal conductivity, and high retention rate of rupture strength after thermal shock, so that the corundum-mullite crucible of the present invention has excellent thermal shock resistance, and is beneficial to prolonging the service life of the crucible.

Table 2 comparison of the properties of example 1 and a homogeneous crucible

As can be seen from Table 2, by comparing the thermal shock resistance and the service life, the thermal shock resistance (1300 ℃, water cooling) of the corundum-mullite crucible of the invention reaches more than 20 times and the service life reaches more than 150 furnaces, and compared with a homogeneous crucible, the corundum-mullite crucible has obvious advantages, which shows that the thermal shock resistance of the crucible is improved by adding the flaky alumina and forming a continuous staggered network structure by the mullite synthesized in situ and the flaky alumina.

Of course, the foregoing is merely exemplary of the invention and is not to be construed as limiting the scope of the embodiments of the invention. The present invention is not limited to the above examples, and equivalent changes and modifications made by those skilled in the art within the spirit and scope of the present invention should be construed as being included in the scope of the present invention.

Claims

1. A thermal shock resistant corundum mullite crucible for metal precision casting is characterized in that: the raw materials comprise the following components in percentage by mass: 15-25% of plate-shaped corundum, 15-25% of fused corundum, 25-35% of fused mullite, 20-30% of flake alumina, 5-15% of active alumina and 1-5% of silicon dioxide; 2-6% of binder and 2-6% of plasticizer are added according to the total mass of the raw materials;

the raw material grain composition is designed in proportion, and the grain composition percentage is as follows:

The grain size is less than 0.1mm and is 30-45%.

2. The thermal shock resistant corundum-mullite crucible for metal precision casting according to claim 1, characterized in that: the binder is one or more of polyvinyl alcohol, acrylic polymer, starch, dextrin or methyl cellulose.

3. The thermal shock resistant corundum-mullite crucible for metal precision casting according to claim 1, characterized in that: the plasticizer is one or more of polyethylene glycol, polyglycerol or ester compounds.

4. A method for preparing the thermal shock resistant corundum mullite crucible for metal precision casting as claimed in any one of claims 1 to 3, which is characterized in that: the method comprises the following steps:

(1) weighing the required raw materials according to the mass percentage, grading the raw materials, and premixing the raw materials with the particle size of more than 1mm and less than or equal to 3mm and the particle size of 0.1mm and less than or equal to 1mm for 1-3 h; after uniformly mixing, adding a binder and a plasticizer, and uniformly mixing for 1-2 h; then adding raw materials with the particle size of less than 0.1mm, and mixing for 3-5 h;

(4) naturally drying the formed crucible green body for 24-48 h;

5. The preparation method of the thermal shock resistant corundum-mullite crucible for metal precision casting according to claim 4, which is characterized in that: the raw materials are mixed and are adopted the machine that thoughtlessly rolls, and thoughtlessly roll quick-witted inside lining and agitating unit all adopt ceramic material.

6. The preparation method of the thermal shock resistant corundum-mullite crucible for metal precision casting according to claim 4, which is characterized in that: the isostatic pressing mould steel core adopts the carbide material, and the gum cover adopts the polyurethane material.

7. The preparation method of the thermal shock resistant corundum-mullite crucible for metal precision casting according to claim 4, which is characterized in that: the compaction equipment is a three-dimensional vibration platform.

8. The preparation method of the thermal shock resistant corundum-mullite crucible for metal precision casting according to claim 4, which is characterized in that: the isostatic pressing process adopts a cold isostatic pressing device.

9. The preparation method of the thermal shock resistant corundum-mullite crucible for the precise casting of the metal according to claim 4, which is characterized by comprising the following steps: the sintering process adopts electric furnace high-temperature sintering.