CN111203515B - Preparation method of surface layer shell mold capable of effectively improving small-size concave surface cast tumor - Google Patents
Preparation method of surface layer shell mold capable of effectively improving small-size concave surface cast tumor Download PDFInfo
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- CN111203515B CN111203515B CN202010028438.6A CN202010028438A CN111203515B CN 111203515 B CN111203515 B CN 111203515B CN 202010028438 A CN202010028438 A CN 202010028438A CN 111203515 B CN111203515 B CN 111203515B
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- coating
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- wax
- aggregate
- silica sol
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C7/00—Patterns; Manufacture thereof so far as not provided for in other classes
- B22C7/02—Lost patterns
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C3/00—Selection of compositions for coating the surfaces of moulds, cores, or patterns
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C9/00—Moulds or cores; Moulding processes
- B22C9/02—Sand moulds or like moulds for shaped castings
- B22C9/04—Use of lost patterns
Abstract
The invention relates to the field of shell mold preparation of investment precision casting, in particular to a surface layer shell mold preparation method capable of effectively improving small-size concave surface casting nodules, which comprises the following steps: preparing a coating: preparing a first coating: preparing 1 part of silica sol, 0.5-1 part of water, 2.5-3.5 parts of aggregate and 0.001-0.005 part of wetting agent by weight, sequentially adding the silica sol, the water, the aggregate and the wetting agent into a first batching barrel, and uniformly stirring to form a first coating; preparing a second coating: preparing 1 part of silica sol and 2.5-3.5 parts of aggregate by weight, sequentially adding the silica sol and the aggregate into a second batching barrel, and uniformly stirring to form a second coating; pre-coating a wax mould; and (5) preparing a shell. The wax mould is precoated by the first coating with low viscosity and low surface tension, so that a wet precoating layer is formed between the surface coating and the wax mould, the surface coating is prevented from being in direct contact with the wax mould, the phenomenon that the small-size concave surface of the wax mould is blocked due to bubbles caused by the overlarge surface tension of the surface coating can be avoided, and casting nodules of the casting are effectively reduced.
Description
Technical Field
The invention relates to the field of shell mold preparation of investment precision casting, in particular to a surface layer shell mold preparation method capable of effectively improving small-size concave surface cast nodules.
Background
Precision investment casting, also known as lost wax casting, is widely applied to the production of precision castings of aeroengines due to high molding precision and less inclusions of the castings. With the continuous improvement of the performance requirements of the engine, the size design of part of parts is more complicated, and higher requirements are provided for the forming precision of castings. In investment casting, the key factors influencing the molding precision of a casting are mainly influenced by a shell making process except the size precision of a wax mould. In recent years, silica sol has been favored in the field of shell-forming binders for investment casting, and has gradually replaced ethyl silicate. The shell mold prepared by taking silica sol as a binder has high molding precision, high shell mold strength and better high-temperature stability, and can better meet the ultrahigh-temperature melt injection requirement in precision casting of an aircraft engine. In order to improve the copying precision of the shell to the shape of the wax piece and reduce interface reaction and casting inclusion, the density of the surface coating needs to be increased and the compactness of the inner cavity of the shell needs to be improved on the premise of ensuring certain fluidity.
However, the surface layer coating prepared by taking silica sol as a binder has the advantages that the viscosity of the coating is increased due to the higher density, the surface tension is increased rapidly, and the wettability of the coating on a wax mold is reduced seriously, which is particularly obvious on the surface of the wax mold with complex size, especially the surface of the wax mold with a small-size concave surface; when the wax mold with the small-size concave surface is coated, the large surface tension of the surface layer coating also easily causes the accumulation of bubbles on the small-size concave surface, so that the small-size concave surface cannot be accurately copied by the shell mold, the casting edge of the casting is formed at the position, the casting is scrapped, the production efficiency is reduced, and the production cost is improved. Therefore, there is an urgent need to develop a method for preparing a surface shell mold that can effectively improve the small-sized concave surface nodules.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a preparation method of a surface layer shell mold capable of effectively improving small-size concave surface cast nodules, so that small-size concave surface air holding in the precision investment casting coating process is improved, the cast nodules are reduced, the casting yield is improved, and the production cost is reduced.
The technical scheme adopted by the invention for realizing the purpose is as follows:
a preparation method of a surface layer shell mold capable of effectively improving small-size concave surface cast tumors comprises the following steps:
(1) preparing a coating:
a. preparing a first coating:
preparing 1 part of silica sol, 0.5-1 part of water, 2.5-3.5 parts of aggregate and 0.001-0.005 part of wetting agent by weight, sequentially adding the silica sol, the water, the aggregate and the wetting agent into a first batching barrel, and uniformly stirring to form a first coating;
b. preparing a second coating:
preparing 1 part of silica sol and 2.5-3.5 parts of aggregate by weight, sequentially adding the silica sol and the aggregate into a second batching barrel, and uniformly stirring to form a second coating;
(2) pre-coating a wax mould:
inclining the wax mould by 30-60 degrees, slowly rotating and immersing the wax mould into the first coating for pre-coating, taking out the wax mould after the pre-coating is finished, placing the wax mould on a first drying rack for drying, and evaporating water until the pre-coating does not flow and is still in a wet state;
(3) preparing a shell:
and immediately inclining the dried wax mold by 30-60 degrees, slowly rotating and immersing the wax mold into the second coating, performing surface coating and sanding, and placing the wax mold on a second drying rack for drying.
Further, the stirring time of the first coating and the second coating is more than 12 hours.
Further, the viscosity of the first dope is 5 to 15s as measured with a paint-4 cup.
Further, the viscosity of the second dope is 40 to 80s as measured with a paint-4 cup.
Further, the drying time in the step (2) is 3-5 min.
Further, the air humidity of the space where the first drying rack and the second drying rack are located is kept between 50% and 70%.
Has the advantages that: the viscosity and the surface tension of the first coating prepared by the method are low, the viscosity and the surface tension of the second coating are high, and the wax mold is precoated by using the first coating with low viscosity and low surface tension, so that a wet precoating layer is formed between the surface coating and the wax mold, the surface coating is prevented from directly contacting the wax mold, the phenomenon that bubbles are blocked on the small-size concave surface of the wax mold due to the fact that the surface tension of the surface coating is too high can be avoided, casting nodules of castings are effectively reduced, post-processing cost is reduced, and casting yield is improved. The surface layer coating has high viscosity, so that the surface of the inner cavity of the shell is more compact, the strength and the shape replication precision of the inner cavity of the shell are effectively improved, the mechanical sand adhesion and the inclusion defect of the casting between the shell and the casting are reduced, the qualified rate of the casting is improved, and the post-processing cost is reduced.
Detailed Description
The technical solution of the present invention is further described below, but the scope of the present invention is not limited thereto.
A preparation method of a surface layer shell mold capable of effectively improving small-size concave surface cast tumors comprises the following steps:
(1) preparing a coating:
a. preparing a first coating:
preparing 1 part of silica sol, 0.5-1 part of water, 2.5-3.5 parts of aggregate and 0.001-0.005 part of wetting agent by weight, sequentially adding the materials into a first batching barrel, stirring for at least 12 hours to uniformly mix the materials to form a first coating, and ensuring that the viscosity value of the first coating measured by a coating-4 cup is between 5 and 15 seconds.
b. Preparing a second coating:
preparing 1 part of silica sol and 2.5-3.5 parts of aggregate according to parts by weight, sequentially adding the silica sol and the aggregate into a second batching barrel, stirring for at least 12 hours, uniformly mixing to form a second coating, and ensuring that the viscosity value of the second coating measured by a coating-4 cup is between 40 and 80 s.
(2) Pre-coating a wax mould:
inclining the wax mould by 30-60 degrees, slowly rotating and immersing the wax mould into the first coating for pre-coating, taking out the wax mould after the pre-coating is finished, placing the wax mould on a first drying rack for drying, and evaporating water until the pre-coating does not flow and is still in a wet state; the drying time is kept within 3-5 min, and the air humidity of the space where the first drying rack is located is kept within 50% -70%, so that the precoat is prevented from being too dry, and the precoat can be kept in a wet state after being dried.
(3) Preparing a shell:
and immediately inclining the dried wax mold by 30-60 degrees, slowly rotating and immersing the wax mold into the second coating, performing surface coating and sanding, placing the wax mold on a second drying rack for drying, and keeping the air humidity of the space where the second drying rack is located between 50% and 70% so as to avoid over-drying of the precoating layer.
In the steps (2) and (3), the wax pattern is slowly immersed into the coating in an inclined manner of 30-60 degrees, so that the initial contact area between the wax pattern and the coating is reduced, the coating is slowly dip-coated on the surface of the wax pattern, and the gas on the surface of the wax pattern can be promoted to thoroughly escape, so that the coating is more tightly contacted with the surface of the wax pattern, fine bubbles are reduced to be retained on the surface of the wax pattern, and the shape replication precision of the shell mold is improved.
The viscosity and the surface tension of the first coating prepared by the method are low, the viscosity and the surface tension of the second coating are high, and the wax mold is precoated by using the first coating with low viscosity and low surface tension, so that a wet precoating layer is formed between the surface coating and the wax mold, the surface coating is prevented from directly contacting the wax mold, the phenomenon that bubbles are blocked on the small-size concave surface of the wax mold due to the fact that the surface tension of the surface coating is too high can be avoided, casting nodules of castings are effectively reduced, post-processing cost is reduced, and casting yield is improved. The surface layer coating has high viscosity, so that the surface of the inner cavity of the shell is more compact, the strength and the shape replication precision of the inner cavity of the shell are effectively improved, the mechanical sand adhesion and the inclusion defect of the casting between the shell and the casting are reduced, the qualified rate of the casting is improved, and the post-processing cost is reduced.
Specifically, on the basis of the foregoing embodiments, the present invention can be specifically implemented by the following steps:
step one, coating preparation: preparing 1 part of silica sol, 0.5 part of water, 2.5 parts of aggregate and 0.003 part of wetting agent by weight, sequentially adding the silica sol, the water, the aggregate and the wetting agent into a first batching barrel, and stirring for 24 hours to form uniform first coating as precoating coating; preparing 1 part of silica sol and 3 parts of aggregate by weight, sequentially adding the silica sol and the aggregate into a second batching barrel, and stirring for 24 hours to form a second coating as a surface coating.
Secondly, pre-coating the wax pattern: and inclining the wax pattern by 45 degrees, slowly rotating and immersing the wax pattern into the first coating, rotating for 1 circle for pre-coating, taking out the pre-coated wax pattern, placing the pre-coated wax pattern on a first drying rack, and drying for 3min to ensure that the pre-coated layer does not flow and is still in a wet state.
Step three, preparing a shell: and (3) slowly rotating and immersing the wax mould subjected to the second-step drying in a second coating in a 45-degree inclined manner, coating the surface coating, sanding, and placing on a second drying rack for drying.
In this example, after the first dope and the second dope were stirred for 24 hours, viscosity measurement was performed with a paint-4 cup, and the viscosity of the first dope was 6s and the viscosity of the second dope was 50 s; the air humidity of the space where the first drying rack and the second drying rack are located is 60%. The surface layer shell mold is prepared through the steps of the embodiment, the obtained shell mold is used for pouring after the whole shell making process is finished, and after the finally obtained casting is subjected to shell removal, the surface of the casting is less in sand adhesion, high in smoothness, good in size precision, and free of casting nodules on the small-size concave surface.
In another embodiment, the invention may also be implemented by:
preparing a coating: preparing 1 part of silica sol, 1 part of water, 2.5 parts of aggregate and 0.004 part of wetting agent by weight, sequentially adding the silica sol, the water, the aggregate and the wetting agent into a first batching barrel, and stirring for 24 hours to form uniform first coating as precoating coating; preparing 1 part of silica sol and 3.2 parts of aggregate by weight, sequentially adding the silica sol and the aggregate into a second batching barrel, and stirring for 24 hours to form a second coating as a surface coating.
(II) pre-coating a wax pattern: and inclining the wax pattern by 45 degrees, slowly rotating and immersing the wax pattern into the first coating, rotating for 1 circle for pre-coating, taking out the pre-coated wax pattern, placing the pre-coated wax pattern on a first drying rack, and drying for 4min to ensure that the pre-coated layer does not flow and is still in a wet state.
(III) preparing a shell: and (5) immediately inclining the wax mould after the drying in the step (II) for 45 degrees, slowly rotating and immersing the wax mould into a second coating, performing surface coating and sanding, and placing the wax mould on a second drying rack for drying.
In this example, after the first dope and the second dope were stirred for 24 hours, viscosity measurement was performed with a paint-4 cup, and the viscosity of the first dope was 10s and the viscosity of the second dope was 70 s; the first drying rack and the second drying rack are located at an air humidity of 60%. The surface layer shell mold is prepared through the steps of the embodiment, the whole shell making process is finished, the obtained shell mold is used for pouring, and after the finally obtained casting is subjected to shell removal, the surface of the casting is less in sand adhesion, high in smoothness, good in size precision, and free of casting nodules on the small-size concave surface.
The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (6)
1. A preparation method of a surface layer shell mold capable of effectively improving small-size concave surface cast tumors is characterized by comprising the following steps:
(1) preparing a coating:
a. preparing a first coating:
preparing 1 part of silica sol, 0.5-1 part of water, 2.5-3.5 parts of aggregate and 0.001-0.005 part of wetting agent by weight, sequentially adding the silica sol, the water, the aggregate and the wetting agent into a first batching barrel, and uniformly stirring to form a first coating;
b. preparing a second coating:
preparing 1 part of silica sol and 2.5-3.5 parts of aggregate by weight, sequentially adding the silica sol and the aggregate into a second batching barrel, and uniformly stirring to form a second coating;
(2) pre-coating a wax mould:
inclining the wax mould by 30-60 degrees, slowly rotating and immersing the wax mould into the first coating for pre-coating, taking out the wax mould after the pre-coating is finished, placing the wax mould on a first drying rack for drying, and evaporating water until the pre-coating does not flow and is still in a wet state;
(3) preparing a shell:
and immediately inclining the dried wax mold by 30-60 degrees, slowly rotating and immersing the wax mold into the second coating, performing surface coating and sanding, and placing the wax mold on a second drying rack for drying.
2. The method of claim 1, wherein the first coating and the second coating are stirred for a period of time greater than 12 hours.
3. The method of claim 1, wherein the viscosity of the first coating is 5-15 s as measured in a paint-4 cup.
4. The method of claim 1, wherein the viscosity of the second coating is 40-80 s as measured in a paint-4 cup.
5. The method for preparing the surface shell mold capable of effectively improving the small-size concave surface cast tumor according to claim 1, wherein the drying time in the step (2) is 3-5 min.
6. The method of claim 1, wherein the first drying rack and the second drying rack are configured to maintain an air humidity in a space between 50% and 70%.
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| CN202010028438.6A CN111203515B (en) | 2020-01-10 | 2020-01-10 | Preparation method of surface layer shell mold capable of effectively improving small-size concave surface cast tumor |
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| CN112371914B (en) * | 2020-10-28 | 2021-12-28 | 上海交通大学 | Pretreatment method for eliminating bubbles in deep groove and corner in product structure in shell manufacturing process |
| CN113145801B (en) * | 2021-04-30 | 2023-01-31 | 荃胜精密机械工业（中山）有限公司 | Manufacturing method of golf head casting |
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| CN104439067B (en) * | 2014-10-09 | 2017-08-29 | 湖南先淘不锈钢卫浴有限公司 | Core shell unifies deep hole part process for making shell |
| CN106914587A (en) * | 2017-01-10 | 2017-07-04 | 浙江美德光学有限公司 | A kind of processing technology of precision-investment casting housing |
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