CN112008042A - Reinforced sand mold and method of making the same - Google Patents

Abstract

A reinforced sand mold and a manufacturing method thereof, comprising a sand mold, an inner cavity, and a reinforcement layer, wherein at least one inner cavity is arranged inside the sand mold, at least one end of the inner cavity is communicated with the outside world, the surface of the inner cavity is covered with a reinforcement layer, or the reinforcement layer penetrates into the surface of the inner cavity, The tensile strength of the sand mold with the strengthening layer in the inner cavity is not less than 4MPa. It is especially suitable for sand molds with complex inner cavity pipes or sand molds with insufficient strength. So that the sand mold with fragile structure will not break during the process of application, transportation, core grouping, and pouring, reducing the number of rework and improving efficiency.

Description

Reinforced sand mold and method of making the same

technical field

The invention relates to the field of sand moulds, in particular to a reinforced sand mould and a manufacturing method thereof.

Background technique

In the production process of some complex sand molds such as engine casings, casings, shell covers, etc., some small and special-shaped pipe structures in the product sand molds have a large number of sand molds, small diameters, large curvatures, and extremely irregular shapes, which are difficult to produce. It is very difficult to make this kind of sand mold through a mold, and the production process of the mold is also extremely difficult. At the same time, most of this kind of sand mold needs to be made of a core bone to increase its strength, and the core bone of this special-shaped structure is more difficult to make. As you can imagine.

With the promotion and application of 3D printing technology, the production of sand molds has become extremely simple. This technology does not need to make molds, and does not need to consider the problems of mold removal and material removal in traditional processes. Precision printing increases the flexibility of the casting process design method, saves the cost of mold manufacturing, and shortens the production cycle of sand molds.

However, for some sand molds with fragile structures, it is easy to break during the process of application, transportation and core casting. The problems that 3D printing sand molds cannot meet their high strength and cannot place core bones are exposed, especially for some small pipeline sand molds. Its structure has a large curvature and a small diameter. Even if it is produced by 3D printing technology, it is difficult to meet its due use requirements.

In view of the above problems, it is necessary to invent a strengthening method for 3D printing sand molds.

SUMMARY OF THE INVENTION

Aiming at the deficiencies of the prior art, the present invention provides a reinforced sand mold and a manufacturing method thereof. One technical problem solved by the present invention is to improve the strength of the structurally fragile sand mold, so that the sand mold can be applied, transported or cored, poured Process sand will not break. By combining the advantages and forming characteristics of 3D printing sand molds, this invention can effectively improve the strength and toughness of 3D printing cores, solve the problems of high strength requirements, easy fracture and fracture during application, transportation and core casting, and achieve casting production requirements.

A technical scheme adopted by the present invention to solve its technical problem is:

A reinforced sand mold, comprising a sand mold, an inner cavity, and a reinforcement layer. The interior of the sand mold is provided with at least one inner cavity, and at least one end of the inner cavity is communicated with the outside world. The surface of the inner cavity is covered with a reinforcement layer, or the reinforcement layer penetrates into the surface of the inner cavity. The sand mold tensile strength of the reinforcement layer is not less than 4MPa.

Especially for large sand molds, the internal structure is complex and there are many slender pipes or thin plate-like or long-striped plate-like structures. Because the structure itself is relatively easy to break, it is necessary to process any part of application, transportation, core formation, and pouring. Fractures may occur. As a result, the scrap rate will increase, the number of rework will increase, and the work efficiency will be seriously affected. Therefore, this solution is to set at least one inner cavity inside these fragile structures that need to be strengthened, and then inside the sand mold. A strengthening layer is arranged in the cavity, so that the tensile strength of the sand mold is not less than 4MPa, which can completely ensure that the sand mold will not break in any link of sand application, transportation, core assembly, and pouring, thereby improving efficiency.

Preferably, the compressive strength of the sand mold provided with the reinforcing layer in the inner cavity is not less than 4MPa.

Cooling liquid or a certain pressure of cooling gas may be introduced into the inner cavity during pouring, so it needs to have a certain compressive capacity, and the compressive strength of the inner cavity after the reinforcement layer is installed reaches 4MPa, which is enough to deal with the above situation.

Preferably, the sand mold is made of at least one granular material among silica sand, ceramsite sand, chrome ore sand, pearl sand, and zircon sand, and the granularity of the granular material is 50-200 mesh.

Selecting granular materials with high refractoriness can protect the reinforcement layer, especially during pouring. Particle size affects the gaps between the materials and thus the ease and thickness of penetration of the reinforcement layer.

Preferably, the diameter of the inner cavity is not less than 2 mm.

The cross section of the inner cavity can be a circle, a quadrilateral or a triangle, but the minimum aperture is 2 mm, because sand cleaning is still required, and if it is too small, it will be difficult to clean the sand, so there is a minimum aperture requirement.

Preferably, the distance between the inner surface of the inner cavity and the outer surface of the sand mold is greater than or equal to 2 mm.

This means that the minimum wall thickness of the inner cavity is 2 mm, because if it is too thin, the penetration thickness of the reinforcement layer will not meet the requirements and the desired tensile strength will not be achieved.

Preferably, the reinforcement layer adheres to the main body or penetrates into the surface of the main body in a liquid state, and the reinforcement layer is solid after curing.

The reinforcement layer needs to be in a liquid state so that it can penetrate into the main body. If it is solid, it will not be real-time. At the same time, the reinforcement layer must be able to adhere to or penetrate into the main body, so as not to separate from the main body and become one.

Preferably, the reinforcing layer comprises epoxy resin AB glue, epoxy-polyamide AB glue, phenolic-epoxy resin AB glue, phenolic resin, urea-formaldehyde resin, polyurea resin, polyurethane glue, melamine-formaldehyde resin, Epoxy resin, silicone resin, furan resin, unsaturated polyester, acrylic resin, polyimide, polybenzimidazole, phenolic-polyvinyl acetal, phenolic-polyamide, epoxy-polyamide, olefins Polymers, polyvinyl acetate, polyvinyl alcohol, perchloroethylene, polyisobutylene, polyester, polyether, polyamide, polyacrylate, a-cyanoacrylate, polyvinyl acetal, ethylene vinyl acetate At least one of copolymer, phenolic-nitrile butadiene glue, phenolic-chloroprene glue, phenolic-polyurethane glue, epoxy-nitrile-butadiene glue, epoxy-polysulfide glue; preferably, the strengthening agent includes epoxy resin At least one of AB glue, epoxy-polyamide AB glue, phenolic-epoxy AB glue, polyurea resin, epoxy resin, polyurethane glue, and phenolic resin.

The materials that can be used as strengthening agents are not limited to the above. The main requirement of the strengthening agent is that it can be in a liquid state, and the liquid state can be easily applied to the main body, and can be attached to the main body or penetrate into the main body, and then cured by heating or adding a curing agent. In short, the surface hardness and tensile hardness can meet the requirements after curing, and this material can be used as a strengthening agent. The above are common adhesives. On the one hand, they are sticky, which is conducive to sticking to the main body, and on the other hand, they have certain surface hardness and tensile hardness after curing, and are the preferred materials.

Preferably, the reinforcement layer covered on the surface of the inner cavity is 1-6 mm, or the reinforcement layer penetrates into the surface of the inner cavity by 1-6 mm.

If the reinforcing agent is attached to the main body, the hardness and tensile strength of the model depend on the tightness of the attachment on the one hand, and the thickness of the reinforcing agent itself on the other hand. Higher tensile hardness. If the reinforcing agent penetrates into the main body, the hardness and tensile strength of the model depend on the depth of the reinforcing agent. When it penetrates 1 mm, it can meet the requirements. The depth is determined according to the needs. The deeper the penetration, the hardness and tensile hardness The higher it is, but the reality takes into account the cost and the difficulty of regeneration, so the infiltration is controlled at 1 to 6 mm.

Preferably, the two-component glue in the reinforcing agent is at least one of epoxy resin AB glue, epoxy-polyamide AB glue, phenolic-epoxy resin AB glue, wherein the volume ratio of component A and component B is The ratio is 3:1 to 1:1, the component A is a resin, and the component B is a curing agent.

When using this two-component adhesive, it is necessary to control the proportion, so as to control the good viscosity and control the curing time, so that the adhesion or penetration of the strengthening agent on the main body can be completed before the curing agent is cured.

Preferably, the reinforcing agent further includes fibers, and fibers are added to the reinforcing agent, and the fibers account for 1-10% by volume of the reinforcing agent; preferably, the fibers account for 3-8% of the reinforcing agent volume percentage; or the strengthening agent further includes nano-silica.

In order to improve the surface hardness, hardness, tensile hardness, corrosion resistance and other properties of the model, fiber is added to the reinforcing agent. The fiber can choose chemical fiber or natural fiber. Fiber in the reinforcing agent can significantly improve the tensile strength of the reinforcing agent. At the same time, because the fiber can choose materials with higher hardness and hardness, it can improve the surface hardness and hardness. On the other hand, some fibers have certain corrosion resistance, which can improve the corrosion resistance.

A method of using a reinforced sand mold is to pour the molten metal in the above-mentioned reinforced sand mold, and in the process of pouring and cooling, cooling air or cooling liquid is introduced into the inner cavity.

In some cases where the temperature of the molten metal is too high, it is necessary to cool the strengthened sand mold, which can protect the strengthening layer on the one hand, and accelerate the cooling of the molten metal in this part, and improve the density of the casting. And because the cooling liquid or gas is introduced, the temperature of the sand mold in this part is also lower, so that the particles are not easy to stick to the casting liquid, which makes the cleaning of this part of the casting easier.

In the case of casting alloys, etc., because the temperature is low, it can be rapidly cooled, and there is no need to introduce cooling liquid or gas.

A method for making a reinforced sand mold. At least one inner cavity is arranged on the inner side of the sand mold to be reinforced, and at least one end of the inner cavity is connected to the outside world, and enough strengthening agent is injected into the inner cavity to keep the strengthening agent in the inner cavity for a period of time, Then take out the excess strengthening agent, and after the strengthening agent is cured, the strengthening agent forms a strengthening layer on the inner wall of the inner cavity.

One side of the inner cavity of the sand mold is not in contact with the casting liquid, and the outer surface of the sand mold is in contact with the casting liquid, so the outer surface of the sand mold should not be reinforced, so it cannot be dipped or brushed. Fill the opening of the enhancer, and seal the remaining openings with tape, stay for a period of time to allow the enhancer to penetrate or adhere, and then clean up the excess enhancer. If necessary, blow in a certain pressure of gas to improve the cleaning effect. it is good.

It can be seen from the above technical solutions that one of the beneficial effects of the disclosed aspect of the present invention is that the tensile strength of the sand mold is not less than 4MPa by setting an inner cavity in the fragile sand mold, and then setting a strengthening layer on the surface of the inner cavity. , fully meet the requirements of the sand mold production process and casting process, so that the sand mold will not break during the application, transportation, core formation, and pouring process. The treated sand mold can be used for casting of ferrous metals as well as non-ferrous metals.

Description of drawings

FIG. 1 is a schematic structural diagram of a reinforced sand mold according to the first embodiment disclosed in the present invention.

FIG. 2 is a schematic structural diagram of a reinforced sand mold according to the second embodiment disclosed in the present invention.

FIG. 3 is a schematic structural diagram of a reinforced sand mold according to a third embodiment disclosed in the present invention.

In the figure: sand mold 10, inner cavity 20, strengthening layer 30.

Detailed ways

With reference to the accompanying drawings of the present invention, a technical solution of the embodiment of the present invention is further elaborated.

The sand mold 10 can be used for casting of ferrous metals and non-ferrous metals. The sand mold 10, which could not be done in the past, can be printed due to the development of current printing technology. The one-time high-precision printing of various complex structural cores increases the flexibility of the casting process design method and saves the cost of mold manufacturing. The production cycle of the sand mold 10 is shortened. However, some of the sand molds 10 have a large number of small special-shaped pipe structures, small diameters, large curvatures, extremely irregular shapes, and are extremely difficult to produce. The sheet-like structure will be connected with some installation parts, and the installation parts will be relatively heavy, so these fragile sand molds 10 often break accidentally before they are assembled, and some of them will be poured due to the low density of the pouring liquid. Therefore, it is necessary to improve the tensile strength of the local sand mold 10, thereby reducing the number of rework and improving the work efficiency.

Referring to Figures 1-3, a reinforced sand mold includes a sand mold 10, an inner cavity 20, and a reinforced layer 30. The sand mold 10 is formed by pressing or printing at least one granular material among silica sand, ceramsite sand, chrome ore sand, pearl sand, and zircon sand, and has high refractoriness and the granularity of the granular material is 50-200 mesh. The sand mold 10 that needs to be strengthened is provided with an inner cavity 20, the tubular sand mold 10 is generally provided with one inner cavity 20, and the plate-shaped sand mold 10 is generally provided with multiple inner chambers 20 side by side, and the inner cavity 20 has a diameter of not less than 2 mm. The distance between the inner surface of the inner cavity 20 and the outer surface of the sand mold 10 is greater than or equal to 2 mm. At least one end of the inner cavity 20 is communicated with the outside world, the surface of the inner cavity 20 is covered with the reinforcement layer 30, or the reinforcement layer 30 penetrates into the surface of the inner cavity 20, and the reinforcement layer 30 adheres to the main body in a liquid state for 1-6 mm or penetrates into the main body surface in a liquid state for 1-6 mm. 6 mm, the reinforcement layer 30 is solid after curing. The tensile strength of the sand mold 10 provided with the reinforcing layer 30 in the inner cavity 20 is not less than 4MPa. The compressive strength of the sand mold 10 provided with the reinforcing layer 30 in the inner cavity 20 is not less than 4MPa.

The reinforcing layer 30 includes epoxy resin AB glue, epoxy-polyamide AB glue, phenolic-epoxy resin AB glue, phenolic resin, urea-formaldehyde resin, polyurea resin, polyurethane glue, melamine-formaldehyde resin, epoxy resin, Silicone resin, furan resin, unsaturated polyester, acrylic resin, polyimide, polybenzimidazole, phenolic-polyvinyl acetal, phenolic-polyamide, epoxy-polyamide, vinyl polymer, polyamide Vinyl acetate, polyvinyl alcohol, vinyl perchloride, polyisobutylene, polyester, polyether, polyamide, polyacrylate, a-cyanoacrylate, polyvinyl acetal, ethylene-vinyl acetate copolymer, phenolic - at least one of nitrile glue, phenolic-chloroprene glue, phenolic-polyurethane glue, epoxy-nitrile glue, epoxy-polysulfide glue; preferably, the strengthening agent includes epoxy resin AB glue, ring At least one of oxygen-polyamide AB glue, phenolic-epoxy resin AB glue, polyurea resin, epoxy resin, polyurethane glue, and phenolic resin.

The two-component adhesive in the strengthening agent is at least one of epoxy resin AB adhesive, epoxy-polyamide AB adhesive, and phenolic-epoxy resin AB adhesive, wherein the volume ratio of component A to component B is 3:1～ 1:1, the component A is a resin, and the component B is a curing agent.

Fibers are added to the reinforcing agent, and the fibers account for 1-10% by volume of the reinforcing agent; preferably, the fibers account for 3-8% by volume of the reinforcing agent; or the reinforcing agent further comprises nanometers Silica.

The specific implementation process is as follows:

Firstly, according to the structure of the casting, the parts of the sand mold 10 that need to be strengthened are separated separately, and assembled together with the whole through the assembly parts, and an appropriate number of inner cavities 20 are designed in the sand mold to be strengthened. At least one end of the inner cavity 20 is connected to the outside world. According to the design The sand mold 10 is printed out, and the loose sand in the inner cavity 20 is removed by cleaning the sand, and then one inner cavity 20 is left with an opening, and the remaining openings are blocked with tape. After a period of time, let the strengthening agent infiltrate into the sand mold 10, then open the opening at the other end of the opposite opening, and push out the remaining strengthening agent in the inner cavity 20. It is pushed out, so that the strengthening agent penetrates into the sand mold more than 101 mm, and then the strengthening agent is cured by natural curing or heating curing or microwave curing, so as to meet the requirements of tensile strength and compressive strength.

In some cases, for example, when the sand mold 10 is too thin and cooling gas does not need to be introduced, the strengthening agent in the inner cavity 20 can be retained to improve the tensile strength of the sand mold 10.

When the obtained sand mold 10 is poured, cooling liquid or cooling gas is introduced into the inner cavity 20 as required, so as to reduce the temperature of the inner cavity 20, and at the same time, the casting can be cooled as soon as possible, thereby improving the layout density of the casting.

In this scheme, by strengthening the internal adhesive of the sand mold 10, the properties such as the tensile strength and compressive strength of the sand mold 10 can meet the production requirements, so that the sand core can be suitable for actual production and ensure the quality of the mold and castings. ,Improve work efficiency.

Claims (12)

1. a reinforced sand mould, it is characterized in that: comprise sand mould, inner cavity, strengthening layer, sand mould is provided with at least one inner cavity inside, inner cavity at least one end is communicated with the outside world, inner cavity surface covers reinforcement layer, or reinforcement layer penetrates inner cavity The tensile strength of the sand mold with a strengthening layer on the surface and the inner cavity is not less than 4MPa. 2 . The reinforced sand mold according to claim 1 , wherein the compressive strength of the sand mold with a reinforced layer in the inner cavity is not less than 4 MPa. 3 . 3. The reinforced sand mold according to claim 1, characterized in that: the sand mold is made of at least one granular material among silica sand, ceramsite sand, chrome ore sand, pearl sand, and zircon sand, and the particle size of the granular material is 50- 200 mesh. 4 . The reinforced sand mold according to claim 1 , wherein the diameter of the inner cavity is not less than 2 mm. 5 . 5 . The reinforced sand mold according to claim 4 , wherein the distance between the inner surface of the inner cavity and the outer surface of the sand mold is greater than or equal to 2 mm. 6 . 6 . The reinforced sand mold according to claim 1 , wherein the reinforced layer adheres to the main body or penetrates into the surface of the main body in a liquid state, and the reinforced layer is solid after curing. 7 . 7 . The reinforced sand mold according to claim 6 , wherein the reinforced layer comprises epoxy resin AB glue, epoxy-polyamide AB glue, phenolic-epoxy resin AB glue, phenolic resin, urea-formaldehyde resin, polyamide Urea resin, polyurethane glue, melamine-formaldehyde resin, epoxy resin, silicone resin, furan resin, unsaturated polyester, acrylic resin, polyimide, polybenzimidazole, phenolic-polyvinyl acetal, Phenolic-polyamide, epoxy-polyamide, vinyl polymers, polyvinyl acetate, polyvinyl alcohol, perchloride, polyisobutylene, polyester, polyether, polyamide, polyacrylate, a-cyanoacrylic acid At least one of ester, polyvinyl acetal, ethylene-vinyl acetate copolymer, phenolic-nitrile rubber, phenolic-chloroprene rubber, phenolic-polyurethane rubber, epoxy-nitrile rubber, epoxy-polysulfide rubber Preferably, the reinforcing agent includes at least one of epoxy resin AB glue, epoxy-polyamide AB glue, phenolic-epoxy AB glue, polyurea resin, epoxy resin, polyurethane glue, and phenolic resin . 8 . The reinforced sand mold according to claim 7 , wherein the reinforced layer covering the surface of the inner cavity is 1-6 mm, or the reinforced layer penetrates into the surface of the inner cavity by 1-6 mm. 9 . 9. The reinforced sand mold according to claim 7, characterized in that: the two-component glue in the reinforcing agent, namely epoxy resin AB glue, epoxy-polyamide AB glue, and phenolic-epoxy resin AB glue. At least one, wherein the volume ratio of component A to component B is 3:1 to 1:1, the component A is a resin, and the component B is a curing agent. 10 . The reinforced sand mold according to claim 6 , wherein the reinforcing agent further comprises fibers, and fibers are added to the reinforcing agent, and the fibers account for 1-10% by volume of the reinforcing agent; preferably , the fiber accounts for 3-8% by volume of the reinforcing agent; or the reinforcing agent further includes nano-silica. 11. A method of using a reinforced sand mold, characterized in that: pouring molten metal into the reinforced sand mold according to any one of the above claims 1 to 9, in the process of pouring and cooling, pouring into the inner cavity Cooling air or cooling liquid. 12. A method for making a reinforced sand mold, characterized in that: at least one inner cavity is provided inside the sand mold to be reinforced, and at least one end of the inner cavity is communicated with the outside world, and enough strengthening agent is injected into the inner cavity, so that the strengthening agent is inside. It is kept in the cavity for a period of time, and then the excess strengthening agent is taken out. After the strengthening agent is cured, the strengthening agent forms a strengthening layer on the inner wall of the cavity.

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