Summary of the invention
Object of the present invention, is to have unstable properties, burn till and shrink the problem large, firing temperature is high for above-mentioned alumina based ceramic core, and a kind of directional freeze alumina based ceramic core is provided.By adding suitable additive, make the bending strength >=5MPa of 1550 DEG C of alumina based ceramic cores, deformation induced by gravity amount≤1mm, burns till contraction≤1%, and firing temperature is lower than 1450 DEG C.Can ensure the dimensional precision of superalloy turbine blade and good surface of internal cavity quality.
Another object of the present invention, is to provide the preparation method of a kind of directional freeze oxygen Al-base ceramic core.
The technical scheme adopting is:
A kind of directional freeze alumina based ceramic core, is characterized in that taking EC95 electrofused mullite as base-material, and EC95 electrofused mullite is to add weight percent taking high-quality alundum to form as mineralizer >=2000 DEG C of pyrotic smeltings of warp in electric arc furnace of 2~6%.
EC95 electrofused mullite after smelting is with a-Al
2o
3, 3Al
2o
32SiO
2for main xln, wherein α-Al
2o
3content 80~95%, 3Al
2o
32SiO
2content 5~20%, be a kind of have compact structure, folding strength large, expand evenly, the good high-temperature creep resistance such as thermal stability is good, refractoriness under load is high, high temperature creep value is little and the high grade refractory of high-temperature stability.Through pulverizing shaping, magnetic separation de-iron, is sieved into granularity and is the powder of No. F200, No. F320, No. F600, and pickling is dry.
Mineralizer adopts zirconium silicate, silicon dioxide powder, titanium dioxide powder and aluminium powder.Zirconium silicate granularity is No. F320, silicon dioxide powder, and granularity is No. F320, SiO in powder
2content>=96%, titanium dioxide powder size≤30 μ m, TiO
2content>=97%, aluminum powder size≤50 μ m, active A l content>=98%.
A preparation method for alumina based ceramic core for directional freeze, is characterized in that comprising following processing step:
1, take powder: the EC95 electrofused mullite powder, zirconium silicate powder, silicon dioxide powder, titanium dioxide powder, the aluminium powder that weigh respectively certainweight are put into ball grinder.EC95 electrofused mullite 65~95% by weight percentage in powder, zirconium silicate 5~30%, silicon dioxide powder 2~8%, titanium dioxide powder 1~5%, aluminium powder 1~10%.Wherein in EC95 electrofused mullite, F200 powder accounts for 10~30%, F320 powder content 40~70%, and F600 powder accounts for 10~30%.
2, ball is mixed: add the oleic acid that accounts for powder weight 0.5~2%, add zirconia ceramics ball to mix by ratio of grinding media to material 1.5:1, the ball 4~8h that does time.
3, join softening agent: take the softening agent that accounts for the weight of mixed powder described in step 1 14~18%, in softening agent, paraffin and poly ratio are 46~49:1.Softening agent is put into core material stirrer heat fused, and temperature of fusion is 90~110 DEG C.
4, mixing: the mixed powder mixing described in step 1 slowly to be joined in core material stirrer, continue to stir 6~8h, make softening agent and powder mixing evenly.
5, hot-injection molding.Utilize ceramic core press injector, according to the size of ceramic core and complexity, controlling injection temperature is the molding parameters such as 90 DEG C, 45 DEG C of die temperatures, injection pressure 2MPa, dwell time 120s, and mixing uniform core material pressure injection, in ceramic core mould, is made to ceramic core biscuit.
6, finishing, school type: ceramic core biscuit, after finishing, school type, is put into the industrial alumina packing of saggar and buried reality.
7, roasting.The saggar that ceramic core biscuit and commercial alumina filler are housed is put into chamber type electric resistance furnace and carry out roasting, roasting system is: be warming up to 200~300 DEG C with the temperature rise rate of 2~5 DEG C/min, insulation 3~6h, be warming up to 400~500 DEG C with the temperature rise rate of 3~6 DEG C/min, insulation 2~4h, be warming up to 600~700 DEG C with the temperature rise rate of 4~7 DEG C/min, insulation 1~2h, be warming up to 900~1000 DEG C with 6~9 DEG C/min temperature rise rate, insulation 1~2h, be warming up to 1100~1200 DEG C with the temperature rise rate of 6~9 DEG C/min, insulation 2~3h, be warming up to 1300~1450 DEG C with the temperature rise rate of 1~2 DEG C/min, insulation 4~8h, then cool to room temperature with the furnace.
In roasting process there is complicated physicochemical change in alumina based ceramic core.Lower than 500 DEG C, the softening agent in ceramic core biscuit melts, in filler, moves, until decompose volatilization.Generate γ-Al at 500~1100 DEG C of aluminium powder oxidations
2o
3and follow 28% volumetric expansion, be oxidized the γ-Al generating
2o
3there is very high activity.Temperature is elevated to 1200 DEG C, and under the katalysis of titanium dioxide, zirconium silicate decomposes generation SiO
2and ZrO
2, decompose the SiO generating
2there is high reactivity.Highly active SiO
2high reactivity γ-Al with aluminium powder oxidation generation
2o
3reaction generates mullite.Temperature is higher than 1200 DEG C, at highly active SiO
2high reactivity Al with aluminium powder oxidation generation
2o
3in the mullite seed crystal matrix that reaction generates, the α-Al in additive silicon-dioxide and EC95
2o
3reaction generates mullite.The generation of mullite is accompanied by 6~10% volumetric expansion.Meanwhile, titanium dioxide is solidly soluted in zirconium dioxide, plays stabilized zirconia, has avoided zirconium dioxide to change low temperature monoclinic form into from high temperature tetragonal structure.Have neither part nor lot in the γ-Al of reaction
2o
3be greater than 1200 DEG C of generation crystal conversions generation α-Al
2o
3.The chemical reaction of whole process is as follows:
4Al+3O
2
→2γ-Al
2
O
3
ZrSiO
4
→ZrO
2
+SiO
2
3γ-Al
2
O
3
+2SiO
2
→3Al
2
O
3
·2SiO
2
3α-Al
2
O
3
+2SiO
2
→3Al
2
O
3
·2SiO
2
ZrO
2
+TiO
2
→ZrO
2
·TiO
2
γ-Al
2
O
3
→α-Al
2
O
3
8, High-Temperature Strengthening.Ceramic core after coming out of the stove adopts silicate hydrolyzate liquid to carry out High-Temperature Strengthening.Reinforcer contains tetraethyl silicate 81~83% by weight percentage, alcohol 11~12%, and distilled water 4~6%, hydrochloric acid 1~1.5% content carries out proportioning, the temperature of strict controlled hydrolysis liquid in hydrolytic process, temperature will be used water quench at once higher than 54 DEG C.
9, room temperature strengthening.High-Temperature Strengthening dried ceramic core are carried out to room temperature strengthening, in reinforcer, contain by weight percentage phenolic aldehyde spirit varnish 50~55%, ethanol 40~45%, hexamethylenetetramine 2~5%.
The invention has the advantages that:
(1) reduce and burn till contraction.In roasting process, aluminium powder oxidation generates aluminum oxide and silicon-dioxide reacts the volumetric expansion that generates mullite generation with aluminum oxide, has compensated the volumetric shrinkage that core roasting occurs.Burning till of alumina-based ceramic core shunk to be reduced to below 1%.
(2) reduce firing temperature.The decomposition temperature of zirconium silicate is 1540 DEG C, and titanium dioxide promotes zirconium silicate to decompose, and makes the decomposition temperature of zirconium silicate be reduced to 1200 DEG C.The generation temperature of mullite is also 1540 DEG C of left and right.And the temperature of the high reactivity silicon dioxde reaction generation mullite that the oxide of high activity aluminium that aluminium powder oxidation generates and zirconium silicate decomposition generate is 1200 DEG C, greatly reduces the generation temperature of mullite.The firing temperature of alumina-based ceramic core is reduced to 1300~1450 DEG C.
(3) improve high-temperature behavior.The high-temperature agglomerant mullite that chemical reaction generates is a kind of refractory materials of excellent performance.Fusing point is 1890 ± 90 DEG C, and hot strength and refractoriness under load are high, has good thermal shock resistance and high temperature creep property.And zirconium silicate decomposes the zirconium dioxide fusing point generating up to 2680 DEG C, strengthen the high-temperature behavior of alumina-based ceramic core.By the strengthening effect of mullite and zirconium dioxide, bending strength >=5MPa that alumina-ceramic core is 1550 DEG C, deformation induced by gravity amount≤1mm.
Embodiment
specific embodiment 1
A kind of directional freeze alumina based ceramic core, is characterized in that taking EC95 electrofused mullite as base-material, and EC95 electrofused mullite is to add weight percent taking high-quality alundum in electric arc furnace, to form through 2100 DEG C of pyrotic smeltings as 2% mineralizer.EC95 electrofused mullite after smelting is with a-Al
2o
3, 3Al
2o
32SiO
2for main xln, wherein α-Al
2o
3content 93%, 3Al
2o
32SiO
2content 7%.
A preparation method for alumina based ceramic core for directional freeze, comprises the steps:
1, take powder: the EC95 electrofused mullite after smelting is pulverized to shaping, and magnetic separation de-iron, is sieved into granularity and is the powder of No. F200, No. F320, No. F600, and pickling is dry.Take by weight percentage 15% F200 EC95,50% F320 EC95,15% F600 EC95,10% zirconium silicate powder, 5% silicon dioxide powder, 2% titanium dioxide, 3% aluminium powder.
2, ball is mixed: add the oleic acid that accounts for the weight of mixed powder described in step 1 1%, add zirconia ceramics ball to mix by ratio of grinding media to material 1.5:1, the ball 4h that does time.
3, join softening agent: take the softening agent that accounts for the weight of mixed powder described in step 1 14%, in softening agent, paraffin and poly ratio are 49:1.Softening agent is put into core material stirrer heat fused, and temperature of fusion is 110 DEG C.
4, mixing: the mixed powder mixing described in step 1 slowly to be joined in core material stirrer, continue to stir 8h, make softening agent and powder mixing evenly.
5, hot-injection molding: utilize ceramic core press injector, controlling injection temperature is 90 DEG C, 45 DEG C of die temperatures, injection pressure 2MPa, dwell time 120s, and mixing uniform core material pressure injection, in ceramic core mould, is made to ceramic core biscuit.
6, finishing, school type: ceramic core biscuit, after finishing, school type, is put into the industrial alumina packing of saggar and buried reality.
7, roasting: the saggar that ceramic core biscuit and commercial alumina filler are housed is put into chamber type electric resistance furnace and carry out roasting, roasting system is: be warming up to 240 DEG C with the temperature rise rate of 2 DEG C/min, insulation 4h, be warming up to 500 DEG C with the temperature rise rate of 3 DEG C/min, insulation 4h, be warming up to 700 DEG C with the temperature rise rate of 4 DEG C/min, insulation 1.5h, be warming up to 1000 DEG C with 6 DEG C/min temperature rise rate, insulation 1h, is warming up to 1200 DEG C with the temperature rise rate of 7 DEG C/min, insulation 2.5h, be warming up to 1350 DEG C with the temperature rise rate of 2 DEG C/min, insulation 6h, then cools to room temperature with the furnace.
8, High-Temperature Strengthening: the ceramic core after coming out of the stove adopts silicate hydrolyzate liquid to carry out High-Temperature Strengthening.Reinforcer contains tetraethyl silicate 81% by weight percentage, alcohol 12%, and distilled water 6%, hydrochloric acid 1% content carries out proportioning, the temperature of strict controlled hydrolysis liquid in hydrolytic process, temperature will be used water quench at once higher than 54 DEG C.
9, room temperature strengthening: High-Temperature Strengthening dried ceramic core are carried out to room temperature strengthening, contain by weight percentage phenolic aldehyde spirit varnish 53%, ethanol 44%, hexamethylenetetramine 3% in reinforcer.
specific embodiment 2
A kind of directional freeze alumina based ceramic core, is characterized in that taking EC95 electrofused mullite as base-material, and EC95 electrofused mullite is to add weight percent taking high-quality alundum in electric arc furnace, to form through 2150 DEG C of pyrotic smeltings as 3.5% mineralizer.EC95 electrofused mullite after smelting is with a-Al
2o
3, 3Al
2o
32SiO
2for main xln, wherein α-Al
2o
3content 88%, 3Al
2o
32SiO
2content 12%.
A preparation method for alumina based ceramic core for directional freeze, comprises the steps:
1, take powder: the EC95 electrofused mullite after smelting is pulverized to shaping, and magnetic separation de-iron, is sieved into granularity and is the powder of No. F200, No. F320, No. F600, and pickling is dry.Take by weight percentage 10% F200 EC95,45% F320 EC95,12% F600 EC95,20% zirconium silicate powder, 2% silicon dioxide powder, 1% titanium dioxide, 10% aluminium powder.
2, ball is mixed: add the oleic acid that accounts for the weight of mixed powder described in step 1 1.5%, add zirconia ceramics ball to mix by ratio of grinding media to material 1.5:1, the ball 6h that does time.
3, join softening agent: take the softening agent that accounts for the weight of mixed powder described in step 1 16%, in softening agent, paraffin and poly ratio are 48:1.Softening agent is put into core material stirrer heat fused, and temperature of fusion is 100 DEG C.
4, mixing: the mixed powder mixing described in step 1 slowly to be joined in core material stirrer, continue to stir 7h, make softening agent and powder mixing evenly.
5, hot-injection molding: utilize ceramic core press injector, controlling injection temperature is 95 DEG C, 40 DEG C of die temperatures, injection pressure 3MPa, dwell time 150s, and mixing uniform core material pressure injection, in ceramic core mould, is made to ceramic core biscuit.
6, finishing, school type: ceramic core biscuit, after finishing, school type, is put into the industrial alumina packing of saggar and buried reality.
7, roasting: the saggar that ceramic core biscuit and commercial alumina filler are housed is put into chamber type electric resistance furnace and carry out roasting, roasting system is: be warming up to 260 DEG C with the temperature rise rate of 2.5 DEG C/min, insulation 5h, be warming up to 480 DEG C with the temperature rise rate of 4 DEG C/min, insulation 3h, be warming up to 650 DEG C with the temperature rise rate of 5 DEG C/min, insulation 2h, be warming up to 950 DEG C with 7 DEG C/min temperature rise rate, insulation 1.5h, is warming up to 1150 DEG C with the temperature rise rate of 9 DEG C/min, insulation 3h, be warming up to 1400 DEG C with the temperature rise rate of 1.5 DEG C/min, insulation 4h, then cools to room temperature with the furnace.
8, High-Temperature Strengthening: the ceramic core after coming out of the stove adopts silicate hydrolyzate liquid to carry out High-Temperature Strengthening.Reinforcer contains tetraethyl silicate 82% by weight percentage, alcohol 11%, and distilled water 5.5%, hydrochloric acid 1.5% content carries out proportioning, the temperature of strict controlled hydrolysis liquid in hydrolytic process, temperature will be used water quench at once higher than 54 DEG C.
9, room temperature strengthening: High-Temperature Strengthening dried ceramic core are carried out to room temperature strengthening, contain by weight percentage phenolic aldehyde spirit varnish 50%, ethanol 45%, hexamethylenetetramine 5% in reinforcer.
specific embodiment 3
A kind of directional freeze alumina based ceramic core, is characterized in that taking EC95 electrofused mullite as base-material, and EC95 electrofused mullite is to add weight percent taking high-quality alundum in electric arc furnace, to form through 2200 DEG C of pyrotic smeltings as 5.5% mineralizer.EC95 electrofused mullite after smelting is with a-Al
2o
3, 3Al
2o
32SiO
2for main xln, wherein α-Al
2o
3content 80.5%, 3Al
2o
32SiO
2content 19.5%.
A preparation method for alumina based ceramic core for directional freeze, comprises the steps:
1, take powder: the EC95 electrofused mullite after smelting is pulverized to shaping, and magnetic separation de-iron, is sieved into granularity and is the powder of No. F200, No. F320, No. F600, and pickling is dry.Take by weight percentage 12% F200 EC95,40% F320 EC95,13% F600 EC95,25% zirconium silicate powder, 1% silicon dioxide powder, 4% titanium dioxide, 5% aluminium powder.
2, ball is mixed: add the oleic acid that accounts for the weight of mixed powder described in step 1 0.5%, add zirconia ceramics ball to mix by ratio of grinding media to material 1.5:1, the ball 8h that does time.
3, join softening agent: take the softening agent that accounts for the weight of mixed powder described in step 1 16%, in softening agent, paraffin and poly ratio are 47:1.Softening agent is put into core material stirrer heat fused, and temperature of fusion is 105 DEG C.
4, mixing: the mixed powder mixing described in step 1 slowly to be joined in core material stirrer, continue to stir 8h, make softening agent and powder mixing evenly.
5, hot-injection molding: utilize ceramic core press injector, controlling injection temperature is 100 DEG C, 50 DEG C of die temperatures, injection pressure 5MPa, dwell time 180s, and mixing uniform core material pressure injection, in ceramic core mould, is made to ceramic core biscuit.
6, finishing, school type: ceramic core biscuit, after finishing, school type, is put into the industrial alumina packing of saggar and buried reality.
7, roasting: the saggar that ceramic core biscuit and commercial alumina filler are housed is put into chamber type electric resistance furnace and carry out roasting, roasting system is: be warming up to 300 DEG C with the temperature rise rate of 4 DEG C/min, insulation 6h, be warming up to 500 DEG C with the temperature rise rate of 6 DEG C/min, insulation 2h, be warming up to 600 DEG C with the temperature rise rate of 6 DEG C/min, insulation 1h, be warming up to 900 DEG C with 8 DEG C/min temperature rise rate, insulation 2h, is warming up to 1100 DEG C with the temperature rise rate of 8 DEG C/min, insulation 2h, be warming up to 1450 DEG C with the temperature rise rate of 2 DEG C/min, insulation 8h, then cools to room temperature with the furnace.
8, High-Temperature Strengthening: the ceramic core after coming out of the stove adopts silicate hydrolyzate liquid to carry out High-Temperature Strengthening.Reinforcer contains tetraethyl silicate 82% by weight percentage, alcohol 12%, and distilled water 5%, hydrochloric acid 1% content carries out proportioning, the temperature of strict controlled hydrolysis liquid in hydrolytic process, temperature will be used water quench at once higher than 54 DEG C.
9, room temperature strengthening: High-Temperature Strengthening dried ceramic core are carried out to room temperature strengthening, contain by weight percentage phenolic aldehyde spirit varnish 55%, ethanol 43%, hexamethylenetetramine 2% in reinforcer.