CN103304227A - Alumina-based ceramic core for directional solidification and preparation method thereof - Google Patents

Abstract

The invention relates to an alumina-based ceramic core for directional solidification and a preparation method thereof. The refractory materials used in the alumina-based ceramic core include EC95 fused mullite, zirconium silicate, silica powder, titanium dioxide powder, aluminum pink. The powder contains 65-95% EC95 fused mullite, 5-30% zirconium silicate, 2-8% silicon dioxide powder, 1-5% titanium dioxide powder and 1-10% aluminum powder in percentage by weight. Among them, in EC95 fused mullite, F200 powder accounts for 10-30%, F320 powder accounts for 40-70%, and F600 powder accounts for 10-30%. The preparation method is as follows: ball milling and mixing the above-mentioned powder materials evenly, putting them into molten plasticizer for mixing, and hot-pressing injection molding on a ceramic core molding machine. The hot-press injection molded ceramic core is put into a box-type resistance furnace for firing after trimming and calibration. After being released from the furnace, the ceramic core is strengthened at high temperature and at room temperature with high temperature strengthening agent and room temperature strengthening agent. The alumina-based ceramic core prepared by the invention has the characteristics of high high-temperature strength, good creep resistance, small firing shrinkage, low firing temperature and good metallurgical and chemical properties.

Description

Alumina-based ceramic core for directional solidification and preparation method thereof

technical field

The invention relates to a gas turbine component, in particular to an alumina-based ceramic core for directional solidification and a preparation method thereof. The alumina-based ceramic core has high high-temperature strength, good creep resistance, small firing shrinkage, low firing temperature, and no chemical reaction with high-temperature alloy melt. Not only can it be used to cast small-sized equiaxed, oriented and single-crystal blades for aero-engines, but it can also be used to cast large-sized equiaxed, oriented and single-crystal blades for heavy-duty gas turbines.

Background technique

High-pressure turbine blades are important components of gas turbines. In order to continuously increase the gas inlet temperature before the turbine, countries around the world have developed from solid blades to hollow blades, from polycrystalline blades to the current directional and single crystal blades. The purpose is to continuously improve gas turbines. comprehensive performance. At present, the temperature of the front inlet of the advanced aero-engine turbine has reached 1757°C, and the temperature of the front inlet of the heavy-duty gas turbine turbine has also reached 1600°C, and the heavy-duty gas turbine with a temperature of 1700°C before the turbine inlet is also being designed and manufactured. Therefore, it is necessary to improve the cooling structure of the inner cavity of the blade and improve the cooling efficiency. The more complex the cooling structure of the inner cavity of the blade, the higher the performance requirements for the ceramic core used to form the inner cavity. Silicon oxide-based ceramic cores are prone to softening and denaturation under high temperature conditions, core eccentricity, and core leakage. When the temperature is higher than 1550 ° C, silicon oxide is prone to chemical reactions with active elements Al, Hf, and C in superalloys, resulting in gas inside the blade. Chemical sticky sand occurs in the cold channel, which deteriorates the quality of the inner cavity of the blade and reduces the air cooling effect of the blade. Due to the high refractoriness, high chemical stability and high thermal stability of alumina itself, the alumina ceramic core made of it has stable chemical properties and good creep resistance.

The known matrix material used to prepare alumina-based ceramic cores is fused corundum powder, and other mineralizers and additives include activated alumina, porous alumina, alumina hollow spheres, silicon carbide, magnesia, yttrium oxide, oxide Lanthanum, graphite powder, etc. Chinese patent (patent number: CN1994964A) discloses a composite alumina ceramic core material and molding preparation process using alumina hollow balls. 20-50% balls, 3-5% silicon carbide, and the rest are plasticizers, injection molding. U.S. Patent (Patent No.: 5143777) discloses a fused alumina powder of 200 meshes and 0-0.25mm alumina hollow balls at a ratio of 30:70, adding a binder, and forming an alumina ceramic core by gravity grouting. method. Although these two methods increase the porosity of the alumina-based ceramic core, due to the low density of the alumina hollow sphere and the high density of the fused corundum, the raw materials are not mixed uniformly, and the performance of the ceramic core is unstable. Chinese patent (patent number: CN101229975A) discloses a hot press injection molding alumina-based ceramic type with 45-66% by weight of fused corundum powder, 15-30% of activated alumina, and 1-5% of graphite powder. The core method, because the porous active alumina is gradually transformed into γ-Al ₂ O ₃ and α-Al ₂ O ₃ during firing is accompanied by a large volume shrinkage, resulting in a large shrinkage rate of the ceramic core. U.S. patents (patent numbers: 4837187, 5409871, 5580837) respectively disclose adding 1-20% of yttrium oxide, 1-5% of MgO, 1-7% of graphite powder to alumina, or adding Adding 10-40% of yttrium-aluminum garnet and injection-molding the alumina-based ceramic core improves the high-temperature performance of the ceramic core, but the sintering temperature of the core is as high as 1600-1700°C.

Contents of the invention

The object of the present invention is to provide an alumina-based ceramic core for directional solidification to solve the problems of unstable performance, large firing shrinkage and high firing temperature of the above-mentioned alumina-based ceramic core. By adding appropriate additives, the bending strength of the alumina-based ceramic core at 1550 ° C is ≥ 5 MPa, the self-weight deformation is ≤ 1 mm, the firing shrinkage is ≤ 1%, and the firing temperature is lower than 1450 ° C. It can ensure the dimensional accuracy and excellent surface quality of the inner cavity of the superalloy turbine blade.

Another object of the present invention is to provide a method for preparing an alumina-based ceramic core for directional solidification.

The technical solutions adopted are:

An alumina-based ceramic core for directional solidification, which is characterized by using EC95 fused mullite as the base material, and EC95 fused mullite is a mineralizer with a weight percentage of 2-6% of high-quality alumina powder It is smelted at a high temperature of ≥2000°C in an electric arc furnace.

The EC95 fused mullite after smelting has a-Al ₂ O ₃ , 3Al ₂ O ₃ 2SiO ₂ as the main crystals, in which the content of α-Al ₂ O ₃ is 80-95%, and the content of 3Al ₂ O ₃ 2SiO ₂ is 5% ~20%, it is a kind of advanced refractory material with good high-temperature creep resistance and high-temperature stability, such as compact structure, high flexural strength, uniform expansion, good thermal stability, high load softening temperature, and low high-temperature creep value. . After crushing and shaping, magnetic separation to remove iron, sieve into powders with particle sizes of F200, F320, and F600, and pickle and dry.

The mineralizer adopts zirconium silicate, silicon dioxide powder, titanium dioxide powder and aluminum powder. The particle size of zirconium silicate is F320, the silica powder is F320, the _SiO2 content in the powder is ≥96%, the titanium dioxide powder size is ≤30μm, the _TiO2 content is ≥97%, the aluminum powder size is ≤50μm, and the active Al content ≥98%.

A method for preparing an alumina-based ceramic core for directional solidification, characterized in that it comprises the following process steps:

1. Weigh the powder: Weigh a certain weight of EC95 fused mullite powder, zirconium silicate powder, silicon dioxide powder, titanium dioxide powder and aluminum powder respectively and put them into the ball mill tank. In the powder, EC95 fused mullite is 65-95% by weight, zirconium silicate is 5-30%, silicon dioxide powder is 2-8%, titanium dioxide powder is 1-5%, and aluminum powder is 1-10%. Among them, F200 powder in EC95 fused mullite accounts for 10-30%, F320 powder accounts for 40-70%, and F600 powder accounts for 10-30%.

2. Ball mixing: Add 0.5-2% oleic acid in the weight of the powder, add zirconia ceramic balls for mixing according to the ball-to-material ratio of 1.5:1, and the ball mixing time is 4-8 hours.

3. Prepare plasticizer: weigh the plasticizer which accounts for 14-18% of the weight of the mixed powder mentioned in step 1. The ratio of paraffin wax to polyethylene in the plasticizer is 46-49:1. Put the plasticizer into the core material mixer and heat to melt, the melting temperature is 90-110°C.

4. Mixing: Slowly add the uniformly mixed powder described in step 1 into the core material mixer, and continue stirring for 6-8 hours to make the plasticizer and powder mix evenly.

5. Hot pressing injection molding. Using a ceramic core injection machine, according to the size and complexity of the ceramic core, control the molding parameters such as injection temperature at 90°C, mold temperature at 45°C, injection pressure at 2MPa, and pressure holding time at 120s to press the uniformly mixed core material Inject into the ceramic core mold to make the ceramic core blank.

6. Trimming and calibration: after trimming and calibration, the ceramic core blank is put into a sagger and buried with industrial alumina filler.

7. Roasting. Put the sagger with ceramic core blank and industrial alumina filler into a box-type resistance furnace for firing. The firing system is as follows: heat up to 200-300°C at a heating rate of 2-5°C/min, and keep warm for 3-6 hours , heat up to 400-500°C at a heating rate of 3-6°C/min, keep warm for 2-4 hours, heat up to 600-700°C at a heating rate of 4-7°C/min, keep warm for 1-2 hours, and keep warm at 6-9°C /min heating rate to 900-1000°C, keep warm for 1-2 hours, heat up to 1100-1200°C at a heating rate of 6-9°C/min, keep warm for 2-3 hours, and heat up at a heating rate of 1-2°C/min to 1300～1450℃, keep warm for 4～8h, then cool down to room temperature with the furnace.

Complex physical and chemical changes occur in the alumina-based ceramic core during the firing process. Below 500°C, the plasticizer in the ceramic core blank melts and migrates into the filler until it decomposes and volatilizes. At 500～1100℃, aluminum powder is oxidized to form γ-Al ₂ O ₃ with a volume expansion of 28%, and the γ-Al ₂ O ₃ produced by oxidation has high activity. When the temperature rises to 1200°C, zirconium silicate decomposes to generate SiO ₂ and ZrO ₂ under the catalysis of titanium dioxide, and the SiO ₂ generated by the decomposition has high activity. The highly active SiO ₂ reacts with the highly active γ-Al ₂ O ₃ generated by the oxidation of aluminum powder to form mullite. The temperature is higher than 1200 ℃, on the mullite seed matrix formed by the reaction of highly active SiO ₂ and the highly active Al ₂ O ₃ generated by the oxidation of aluminum powder, the additive silica reacts with α-Al ₂ O ₃ in EC95 Generate mullite. The formation of mullite is accompanied by a volume expansion of 6-10%. At the same time, titanium dioxide dissolves into zirconium dioxide to stabilize zirconium dioxide and prevent zirconium dioxide from changing from a high-temperature tetragonal crystal to a low-temperature monoclinic crystal. The γ-Al ₂ O ₃ that did not participate in the reaction undergoes a crystal transformation to α-Al ₂ O ₃ at temperatures above 1200°C. The chemical reaction of the whole process is as follows:

4Al+3O ₂ →2γ-Al ₂ o ₃

ZrSiO ₄ →ZrO ₂ +SiO2 ₂

3γ-Al ₂ o ₃ +2SiO ₂ →3Al ₂ o ₃ 2SiO2 ₂

3α-Al ₂ o ₃ +2SiO ₂ →3Al ₂ o ₃ 2SiO2 ₂

ZrO ₂ +TiO ₂ →ZrO ₂ ·TiO ₂

γ-Al ₂ o ₃ →α-Al ₂ o ₃

8. High temperature strengthening. After being fired, the ceramic core is strengthened at high temperature with ethyl silicate hydrolyzate. The strengthening agent contains 81-83% ethyl silicate, 11-12% alcohol, 4-6% distilled water, and 1-1.5% hydrochloric acid by weight. During the hydrolysis process, the temperature of the hydrolyzate is strictly controlled, and the temperature is higher than 54 ℃ to immediately cool with cooling water.

9. Room temperature strengthening. The room temperature strengthening is performed on the ceramic core after high temperature strengthening and drying, and the strengthening agent contains 50-55% of novolac varnish, 40-45% of ethanol, and 2-5% of hexamethylenetetramine in weight percentage.

The advantages of the present invention are:

(1) Reduce firing shrinkage. During the roasting process, the volume expansion of the aluminum powder oxidized to form alumina and the reaction of silica and alumina to form mullite compensates for the volume shrinkage of the core roasting. Reduce the firing shrinkage of the alumina-based ceramic core to less than 1%.

(2) Lower the firing temperature. The decomposition temperature of zirconium silicate is 1540°C, and titanium dioxide promotes the decomposition of zirconium silicate, reducing the decomposition temperature of zirconium silicate to 1200°C. The formation temperature of mullite is also about 1540°C. However, the high-activity alumina produced by the oxidation of aluminum powder and the high-activity silica produced by the decomposition of zirconium silicate react to form mullite at a temperature of 1200 ° C, which greatly reduces the formation temperature of mullite. The firing temperature of the alumina-based ceramic core is reduced to 1300-1450°C.

(3) Improve high temperature performance. The high-temperature binder mullite produced by chemical reaction is a refractory material with excellent performance. The melting point is 1890±90°C, the high temperature strength and load softening temperature are high, and it has good thermal shock resistance and high temperature creep performance. The melting point of zirconium dioxide produced by the decomposition of zirconium silicate is as high as 2680°C, which strengthens the high-temperature performance of the alumina-based ceramic core. Through the strengthening effect of mullite and zirconia, the bending strength of the alumina ceramic core at 1550°C is ≥5MPa, and the self-weight deformation is ≤1mm.

Description of drawings

Figure 1 is a flowchart of the preparation process of alumina-based ceramic cores.

Fig. 2 is a schematic diagram of the firing system of the alumina-based ceramic core.

Detailed ways

Specific embodiment 1

An alumina-based ceramic core for directional solidification, which is characterized in that it uses EC95 fused mullite as the base material, and the EC95 fused mullite is made of high-quality alumina powder plus a mineralizer with a weight percentage of 2%. It is smelted at a high temperature of 2100°C in a furnace. The smelted EC95 fused mullite has a-Al ₂ O ₃ and 3Al ₂ O ₃ ·2SiO ₂ as the main crystals, of which the content of α-Al ₂ O ₃ is 93%, and the content of 3Al ₂ O ₃ ·2SiO ₂ is 7%.

A method for preparing an alumina-based ceramic core for directional solidification, comprising the steps of:

1. Weigh the powder: crush and shape the smelted EC95 fused mullite, remove iron by magnetic separation, sieve into powders with particle sizes of F200, F320, and F600, and pickle and dry. Weigh 15% F200 EC95, 50% F320 EC95, 15% F600 EC95, 10% zirconium silicate powder, 5% silica powder, 2% titanium dioxide, 3% Aluminum powder.

2. Ball mixing: Add oleic acid accounting for 1% of the weight of the mixed powder mentioned in step 1, and add zirconia ceramic balls for mixing according to the ball-to-material ratio of 1.5:1, and the ball mixing time is 4 hours.

3. Prepare plasticizer: Weigh the plasticizer accounting for 14% of the weight of the mixed powder described in step 1. The ratio of paraffin wax to polyethylene in the plasticizer is 49:1. Put the plasticizer into the core material mixer and heat to melt, and the melting temperature is 110°C.

4. Mixing: Slowly add the homogeneously mixed powder described in step 1 into the core material mixer, and continue stirring for 8 hours to make the plasticizer and powder knead evenly.

5. Hot pressure injection molding: Use a ceramic core injection machine to control the injection temperature at 90°C, mold temperature at 45°C, injection pressure at 2MPa, and pressure holding time of 120s, and press-inject the uniformly mixed core material into the ceramic core mold , made of ceramic core blank.

6. Trimming and calibration: after trimming and calibration, the ceramic core blank is put into a sagger and buried with industrial alumina filler.

7. Roasting: put the sagger with ceramic core blank and industrial alumina filler into a box-type resistance furnace for roasting, the roasting system is: heat up to 240°C at a heating rate of 2°C/min, keep warm for 4h, and Heat up to 500°C at a heating rate of 3°C/min, hold for 4 hours, heat up to 700°C at a heating rate of 4°C/min, hold for 1.5 hours, heat up to 1000°C at a heating rate of 6°C/min, hold for 1 hour, and heat at 7°C Raise the temperature to 1200°C at a heating rate of 2°C/min, keep it warm for 2.5 hours, raise the temperature to 1350°C at a heating rate of 2°C/min, keep it warm for 6 hours, and then cool to room temperature with the furnace.

8. High temperature strengthening: The ceramic core after being released from the furnace is strengthened at high temperature with ethyl silicate hydrolyzate. The strengthening agent contains 81% ethyl silicate, 12% alcohol, 6% distilled water, and 1% hydrochloric acid by weight. During the hydrolysis process, the temperature of the hydrolyzate is strictly controlled. If the temperature is higher than 54°C, it should be cooled with cooling water immediately. .

9. Strengthening at room temperature: Carry out room temperature strengthening to the ceramic core after high temperature strengthening and drying. The strengthening agent contains 53% novolac varnish by weight, 44% ethanol, and 3% hexamethylenetetramine.

Specific embodiment 2

An alumina-based ceramic core for directional solidification, which is characterized in that it uses EC95 fused mullite as the base material, and the EC95 fused mullite is made of high-quality alumina powder plus a mineralizer with a weight percentage of 3.5% in the arc It is smelted at a high temperature of 2150°C in a furnace. The smelted EC95 fused mullite has a-Al ₂ O ₃ and 3Al ₂ O ₃ ·2SiO ₂ as the main crystals, of which the content of α-Al ₂ O ₃ is 88%, and the content of 3Al ₂ O ₃ ·2SiO ₂ is 12%.

A method for preparing an alumina-based ceramic core for directional solidification, comprising the steps of:

1. Weigh the powder: crush and shape the smelted EC95 fused mullite, remove iron by magnetic separation, sieve into powders with particle sizes of F200, F320, and F600, and pickle and dry. Weigh 10% F200 EC95, 45% F320 EC95, 12% F600 EC95, 20% zirconium silicate powder, 2% silica powder, 1% titanium dioxide, 10% Aluminum powder.

2. Ball mixing: Add oleic acid accounting for 1.5% of the weight of the mixed powder mentioned in step 1, and add zirconia ceramic balls for mixing according to the ball-to-material ratio of 1.5:1, and the ball mixing time is 6 hours.

3. Adding a plasticizer: Weigh a plasticizer accounting for 16% of the weight of the mixed powder described in step 1. The ratio of paraffin wax to polyethylene in the plasticizer is 48:1. Put the plasticizer into the core material mixer and heat to melt, and the melting temperature is 100°C.

4. Mixing: Slowly add the homogeneously mixed powder described in step 1 into the core material mixer, and continue stirring for 7 hours to make the plasticizer and powder knead evenly.

5. Hot pressure injection molding: use a ceramic core injection machine, control the injection temperature to 95°C, mold temperature to 40°C, injection pressure to 3MPa, pressure holding time to 150s, and inject the uniformly mixed core material into the ceramic core mold , made of ceramic core blank.

6. Trimming and calibration: after trimming and calibration, the ceramic core blank is put into a sagger and buried with industrial alumina filler.

7. Roasting: put the sagger with the ceramic core green body and the industrial alumina filler into the box-type resistance furnace for roasting, the roasting system is: heat up to 260 °C at a heating rate of 2.5 °C/min, keep the temperature for 5 hours, and Heat up to 480°C at a heating rate of 4°C/min, hold for 3 hours, heat up to 650°C at a heating rate of 5°C/min, hold for 2 hours, heat up to 950°C at a heating rate of 7°C/min, hold for 1.5 hours, and heat at 9°C Raise the temperature to 1150°C at a heating rate of 1.5°C/min, hold for 3 hours, raise the temperature to 1400°C at a heating rate of 1.5°C/min, hold for 4 hours, and then cool to room temperature with the furnace.

8. High temperature strengthening: The ceramic core after being released from the furnace is strengthened at high temperature with ethyl silicate hydrolyzate. The strengthening agent contains 82% ethyl silicate, 11% alcohol, 5.5% distilled water, and 1.5% hydrochloric acid by weight. During the hydrolysis process, the temperature of the hydrolyzate is strictly controlled. If the temperature is higher than 54°C, it should be cooled with cooling water immediately. .

9. Strengthening at room temperature: Carry out room temperature strengthening to the ceramic core after high temperature strengthening and drying. The strengthening agent contains 50% phenolic alcohol-soluble varnish, 45% ethanol, and 5% hexamethylenetetramine in the strengthening agent.

Specific embodiment 3

An alumina-based ceramic core for directional solidification, which is characterized in that it uses EC95 fused mullite as the base material, and the EC95 fused mullite is made of high-quality alumina powder plus a mineralizer with a weight percentage of 5.5% in the arc It is smelted at a high temperature of 2200°C in a furnace. The smelted EC95 fused mullite has a-Al ₂ O ₃ and 3Al ₂ O ₃ ·2SiO ₂ as the main crystals, of which the content of α-Al ₂ O ₃ is 80.5%, and the content of 3Al ₂ O ₃ ·2SiO ₂ is 19.5%.

A method for preparing an alumina-based ceramic core for directional solidification, comprising the steps of:

1. Weigh the powder: crush and shape the smelted EC95 fused mullite, remove iron by magnetic separation, sieve into powders with particle sizes of F200, F320, and F600, and pickle and dry. Weigh 12% F200 EC95, 40% F320 EC95, 13% F600 EC95, 25% zirconium silicate powder, 1% silica powder, 4% titanium dioxide, 5% Aluminum powder.

2. Ball mixing: add oleic acid accounting for 0.5% of the weight of the mixed powder described in step 1, and add zirconia ceramic balls for mixing according to the ball-to-material ratio of 1.5:1, and the ball mixing time is 8 hours.

3. Prepare plasticizer: Weigh the plasticizer accounting for 16% of the weight of the mixed powder described in step 1. The ratio of paraffin wax to polyethylene in the plasticizer is 47:1. Put the plasticizer into the core material mixer and heat it to melt, and the melting temperature is 105°C.

4. Mixing: Slowly add the homogeneously mixed powder described in step 1 into the core material mixer, and continue stirring for 8 hours to make the plasticizer and powder knead evenly.

5. Hot pressure injection molding: use a ceramic core injection machine, control the injection temperature to 100°C, the mold temperature to 50°C, the injection pressure to 5MPa, and the pressure holding time to 180s, and inject the uniformly mixed core material into the ceramic core mold , made of ceramic core blank.

6. Trimming and calibration: after trimming and calibration, the ceramic core blank is put into a sagger and buried with industrial alumina filler.

7. Roasting: Put the sagger with the ceramic core green body and the industrial alumina filler into the box-type resistance furnace for roasting. The roasting system is: heat up to 300 °C at a heating rate of 4 °C/min, keep the temperature for 6 hours, and Heat up to 500°C at a heating rate of 6°C/min, hold for 2 hours, heat up to 600°C at a heating rate of 6°C/min, hold for 1 hour, heat up to 900°C at a heating rate of 8°C/min, hold for 2 hours, and heat at 8°C/min Raise the temperature to 1100°C at a heating rate of 1 min, keep it warm for 2 hours, raise the temperature to 1450°C at a heating rate of 2°C/min, keep it warm for 8 hours, and then cool to room temperature with the furnace.

8. High temperature strengthening: The ceramic core after being released from the furnace is strengthened at high temperature with ethyl silicate hydrolyzate. The strengthening agent contains 82% ethyl silicate, 12% alcohol, 5% distilled water, and 1% hydrochloric acid by weight. During the hydrolysis process, the temperature of the hydrolyzate is strictly controlled. If the temperature is higher than 54°C, it should be cooled with cooling water immediately. .

9. Strengthening at room temperature: Carry out room temperature strengthening to the ceramic core after high temperature strengthening and drying. The strengthening agent contains 55% phenolic alcohol-soluble varnish, 43% ethanol, and 2% hexamethylenetetramine in the strengthening agent. the

Claims (2)

1. a directional freeze alumina based ceramic core is characterized in that take the EC95 electrofused mullite as base-material, and the mineralizer that adds weight per-cent and be 2-6% forms through 〉=2000 ℃ of pyrotic smeltings in electric arc furnace;

Mullite is with a-Al ₂O ₃, 3Al ₂O ₃2SiO ₂Be main xln, wherein α-Al ₂O ₃Content 80～95%, 3Al ₂O ₃2SiO ₂Content 5～20%, through pulverizing shaping, the magnetic separation de-iron be sieved into granularity and be F200 number, F320 number, F600 number powder, and pickling is dry;

Mineralizer adopts zirconium silicate, silicon dioxide powder, titanium dioxide powder and aluminium powder; The zirconium silicate granularity is F320 number, silicon dioxide powder, and granularity is F320 number, 2SiO in the powder ₂Content 〉=96%, titanium dioxide powder size≤30 μ m, TiO ₂Content 〉=97%, aluminum powder size≤50 μ m, active A l content 〉=98%.

2. a directional freeze is characterized in that comprising following processing step with the preparation method of alumina based ceramic core:

1) take by weighing powder: EC95 electrofused mullite powder, zirconium silicate powder, silicon dioxide powder, titanium dioxide powder, the aluminium powder of weighing certainweight are put into ball grinder respectively; EC95 electrofused mullite 65～95% by weight percentage in the powder, zirconium silicate 5～30%, silicon dioxide powder 2～8%, titanium dioxide powder 1～5%, aluminium powder 1～10%; Wherein the F200 powder accounts for 10～30%, F320 powder content 40～70% in the EC95 electrofused mullite, and the F600 powder accounts for 10～30%;

2) ball is mixed: add the oleic acid that accounts for powder weight 0.5～2%, add the zirconia ceramics ball by ratio of grinding media to material 1.5:1 and mix, the ball 4～8h that does time;

3) join softening agent: take by weighing the softening agent that accounts for the weight of mixed powder described in the step 1 14～18%, paraffin and poly ratio are 46～49:1 in the softening agent; Softening agent is put into core material stirrer heat fused, and temperature of fusion is 90～110 ℃;

4) mixing: as the mixed powder that mixes described in the step 1 slowly to be joined in the core material stirrer, continue to stir 6～8h, make softening agent and powder mixing evenly;

5) hot-injection molding; Utilize the ceramic core press injector, size and complexity according to ceramic core, the control injection temperature is 90 ℃, 450 ℃ of die temperatures, the molding parameters such as injection pressure 2MPa, dwell time 120s, and mixing uniform core material pressure injection in the ceramic core mould, is made the ceramic core biscuit;

6) finishing, school type: the ceramic core biscuit is put into saggar and is buried reality with industrial alumina packing behind finishing, school type;

7) roasting: the saggar that ceramic core biscuit and commercial alumina filler are housed is put into chamber type electric resistance furnace carry out roasting, the roasting system is: the temperature rise rate with 2～5 ℃/min is warming up to 200～300 ℃, insulation 3～6h, temperature rise rate with 3～6 ℃/min is warming up to 400～500 ℃, insulation 2～4h, temperature rise rate with 4～7 ℃/min is warming up to 600～700 ℃, insulation 1～2h, be warming up to 900～1000 ℃ with 6～9 ℃/min temperature rise rate, insulation 1～2h, temperature rise rate with 6～9 ℃/min is warming up to 1100～1200 ℃, insulation 2～3h, temperature rise rate with 1～2 ℃/min is warming up to 1300～1450 ℃, and then insulation 4～8h cools to room temperature with the furnace.

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