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CN-122007341-A - Silica sol investment precision casting process

CN122007341ACN 122007341 ACN122007341 ACN 122007341ACN-122007341-A

Abstract

The invention relates to the technical field of silica sol investment, and discloses a silica sol investment precision casting process which comprises alkaline silica sol, refractory powder, polyethylene glycol-400, ammonium zirconium carbonate aqueous solution and propylene carbonate, wherein the alkaline silica sol, the polyethylene glycol-400 and the ammonium zirconium carbonate aqueous solution are mixed to form a high-steady-state cross-linking precursor silica sol, the propylene carbonate is used for hydrolysis and acid production to trigger the ammonium zirconium carbonate to release zirconium hydroxyl, the zirconium hydroxyl and the silica sol are dehydrated and condensed, so that a coating is converted into internal chemical homogeneous cross-linking from external physical dehydration, and the shell drying is completed by matching with a two-stage dynamic temperature and humidity induction curing process in the shell manufacturing process. The invention eliminates the problem of coating surface crust sealing internal moisture, reduces the peeling risk in the dewaxing stage, utilizes zirconium element phase change to generate zirconia crystals to participate in solid phase sintering in the high temperature roasting stage, makes up the defect of sintering activity of a pure silica sol system, and improves the normal temperature wet strength and high temperature roasting compactness of the shell.

Inventors

  • SONG GUANGQIANG
  • XU ZHENGWEI
  • ZHANG ZHIYUAN

Assignees

  • 辽宁华沣精密金属有限公司
  • 东营华洋金属制品有限公司

Dates

Publication Date
20260512
Application Date
20260413

Claims (10)

  1. 1. The silica sol investment is characterized by comprising, by mass, 1000 parts of alkaline silica sol, 1500-2500 parts of refractory powder, 1500-400,2-8 parts of polyethylene glycol, 5-15 parts of ammonium zirconium carbonate aqueous solution and 10-20 parts of propylene carbonate.
  2. 2. The investment for silica sol of claim 1, wherein the alkaline silica sol is mixed with the aqueous solution of polyethylene glycol-400 and ammonium zirconium carbonate to form a high steady state cross-linked precursor silica sol.
  3. 3. The silica sol investment according to claim 1, wherein the refractory powder is divided into powder for a surface layer and powder for a back layer, the powder for a surface layer is zircon powder or corundum powder having a particle size of 320 meshes, and the powder for a back layer is mullite powder or corundum powder having a particle size of 80 meshes.
  4. 4. The investment pattern of claim 2, wherein the method of preparing the Gao Wentai cross-linked precursor silica sol comprises the steps of: A. Adding the alkaline silica sol into a reaction kettle, dispersing the refractory powder at a high shearing rotation speed of 800-1200rpm for 15-20 minutes at 20-26 ℃, then reducing the rotation speed to 100-300rpm, slowly dropwise adding the polyethylene glycol-400 and the ammonium zirconium carbonate aqueous solution in sequence, and continuously stirring for 20-30 minutes to prepare a high-steady-state crosslinking precursor silica sol; B. And (3) dripping the propylene carbonate into the Gao Wentai cross-linked precursor silica sol at a constant speed for 15-25 minutes before the scheduled module coating operation at a low shearing rotating speed of 30-60rpm, and uniformly mixing for 10-15 minutes to obtain the product.
  5. 5. A silica sol investment casting process, characterized in that the process for manufacturing shells by adopting the silica sol investment according to any one of claims 1-4 comprises the following steps: S1, immersing a wax mould assembly into surface layer working silica sol to perform single-layer coating and slurry control, and then uniformly spreading surface layer sanding materials on the surface of the silica sol; s2, sending the module into an environment-controllable drying chamber, and performing two-stage dynamic temperature and humidity induction curing to dry and cure the single-layer surface layer; S3, immersing the module with the solidified single-layer surface layer into back layer working silica sol for coating and controlling slurry, spreading back layer sand-spreading material, performing two-stage dynamic temperature and humidity induction solidification the same as that of S2, repeating the steps for constructing the back layer by layer, and finally coating only without sand-spreading to obtain the shell; s4, feeding the completely dried shell into a high-pressure steam dewaxing kettle for dewaxing treatment; s5, transferring the dewaxed shell into a roasting furnace for high-temperature constant-temperature roasting, and cooling along with the furnace to obtain the final silica sol investment precision casting shell.
  6. 6. The silica sol investment casting process according to claim 5, wherein the two-stage dynamic temperature and humidity induction curing in S2 and S3 is specifically implemented by: The first stage, maintaining the environment of the drying chamber in a high humidity and low wind speed state so as to inhibit the moisture on the surface of the coating from volatilizing and skinning, and carrying out homogeneous cross-linking by matching with hydrolysis acid production of propylene carbonate in the coating; And in the second stage, the ambient temperature of the drying chamber is kept unchanged, the relative humidity is reduced by a linear speed program, and meanwhile, the ambient wind speed is smoothly increased, so that deep pore water is removed.
  7. 7. The silica sol investment casting process according to claim 6, wherein the two-stage dynamic temperature and humidity induction curing process parameters are as follows: The first stage, the ambient temperature is controlled at 22-26 ℃, the relative humidity is controlled at 80% -90%, the ambient wind speed is controlled at 0.3-0.8m/s, and the maintenance time is 25-40 minutes; And in the second stage, the ambient temperature is kept unchanged at 22-26 ℃, the relative humidity is reduced to 35-45% in a linear speed program in 50-70 minutes, and the ambient wind speed is smoothly increased to 2.0-3.0m/s.
  8. 8. The silica sol investment precise casting process according to claim 5, wherein the surface layer sand-spreading material in S1 is mullite sand or corundum sand with 200 meshes, and the back layer sand-spreading material in S3 is mullite sand or corundum sand with 60 meshes.
  9. 9. The silica sol investment casting process according to claim 5, wherein in S4, the dewaxing process parameters are: the steam pressure is set to be 0.5-0.8MPa, the dewaxing temperature is controlled to be 150-170 ℃, and the pressure maintaining time is 10-20 minutes.
  10. 10. The silica sol investment precise casting process according to claim 5, wherein in S5, the technological parameters of high-temperature constant-temperature roasting are as follows: heating to 850-1050 ℃ at a heating rate of 5-10 ℃ per min, and roasting for 1-3 hours at constant temperature.

Description

Silica sol investment precision casting process Technical Field The invention relates to the technical field of silica sol investment, in particular to a precise casting process of a silica sol investment. Background The silica sol investment precision casting is commonly used for manufacturing metal castings with higher dimensional precision requirements, wherein the preparation process of a shell has direct influence on the quality of the final casting, in the existing shell manufacturing process, the solidification of the silica sol shell mainly depends on the physical volatilization of moisture from outside to inside, the physical dehydration mode can lead to the preferential drying of the surface of a coating and the skinning of the coating, the formed surface layer colloid structure can prevent the further drainage of internal moisture, the phenomenon can prolong the integral drying period of the shell, and in the subsequent high-pressure steam dewaxing stage, the retained moisture in the shell is heated, rapidly gasified and expanded, the coating structure is easily damaged, and the defects of interlayer skinning or delamination peeling and the like are caused. Meanwhile, in order to meet the stress requirements of the module in dewaxing and carrying processes, the normal-temperature wet strength of the shell is improved, a part of organic polymers are usually added into a silica sol slurry system to serve as reinforcing components in the traditional shell manufacturing process, but the organic components are pyrolyzed and volatilized in the subsequent high-temperature roasting stage of the shell, so that microscopic holes are left in an inorganic silica skeleton, the compactness and continuity of a matrix structure of the shell are damaged due to the generation of the holes, the high-temperature roasting strength of the shell is reduced, and the shell is easy to peel in the subsequent dewaxing stage. Disclosure of Invention Aiming at the defects of the prior art, the invention provides a silica sol investment precision casting process, which solves the problem that the existing silica sol shell is long in drying period, so that the subsequent dewaxing stage is easy to peel. The invention aims at realizing the technical scheme that the precise investment casting process of the silica sol comprises the following raw materials, by mass, 1000 parts of alkaline silica sol, 1500-2500 parts of refractory powder, 2-8 parts of polyethylene glycol-400, 5-15 parts of ammonium zirconium carbonate aqueous solution and 10-20 parts of propylene carbonate. By adopting the technical scheme, as the propylene carbonate is matched with the ammonium zirconium carbonate and the polyethylene glycol-400, an internal crosslinking and tension regulating mechanism is established in the system, so that the effect of improving the normal-temperature wet strength and the high-temperature roasting strength is obtained, and the specific mechanism is carried out according to the following steps: Propylene carbonate undergoes hydrolysis reaction in the water phase of alkaline silica sol, hydroxyl ions in the system are consumed, propylene glycol and carbon dioxide are generated, and the pH value of the system is promoted to be reduced homogeneously; when the pH value of the system is reduced to a specific threshold value, decomplexing reaction is carried out on ammonium zirconium carbonate distributed in the system, and zirconium hydroxyl is released; The free zirconium hydroxyl groups and the silicon hydroxyl groups on the surfaces of the silica sol particles undergo dehydration polycondensation reaction, and are synchronously crosslinked and solidified in a coating space to construct a silica-zirconium inorganic network, and the process converts the drying mode of the coating from external dehydration to internal chemical gelation; Propylene glycol generated by propylene carbonate hydrolysis is mixed with preset polyethylene glycol-400 to form a binary tension reducing system. The system can reduce the surface tension of the coating pore liquid and relieve the damage of capillary shrinkage stress to the inorganic framework by spatially distributing hydrogen bonds which interfere water molecules in the pore liquid. Preferably, the Gao Wentai cross-linked precursor silica sol is formed by mixing the alkaline silica sol with the polyethylene glycol-400 and the ammonium zirconium carbonate aqueous solution. By adopting the technical scheme, because polyethylene glycol-400 and ammonium zirconium carbonate aqueous solution are adopted to be premixed with alkaline silica sol, the effects of uniformly dispersing each component and keeping rheological stability are obtained. Preferably, the refractory powder is divided into powder for a surface layer and powder for a back layer, wherein the powder for the surface layer is zircon powder or corundum powder with the granularity of 320 meshes, and the powder for the back layer is mullite powde