阅读说明：本技术 一种铸造用无机粘结剂砂冷芯盒制型芯方法 (Method for making core of inorganic binder sand cold core box for casting ) 是由 张宏奎 于 2019-11-06 设计创作，主要内容包括：本发明公开了一种铸造用无机粘结剂砂冷芯盒制型芯方法。所述方法包括：将铸造用无机粘结剂、可选的添加剂和原砂的混合物填入模具,通过吹气硬化制型芯,吹气工艺为方式一或方式二,方式一为：通过CO<Sub>2</Sub>气体和压缩气体先后吹气的方式；方式二为：通过压缩气体、CO<Sub>2</Sub>气体和压缩气体的先后吹气方式,所述CO<Sub>2</Sub>气体和压缩气体都具有压力。本发明能够解决现有技术中铸造用水玻璃砂吹CO<Sub>2</Sub>硬化制型、芯工艺存在的易过吹、粘结剂加入量高、砂型强度低等问题。与普通吹CO<Sub>2</Sub>法比,能够使制得的型、芯强度得到明显提高,旧砂可再生回用。(The invention discloses a method for making a core of a sand cold core box by using an inorganic binder for casting. The method comprises the following steps: filling a mixture of inorganic binder for casting, optional additive and raw sand into a mould, and hardening to prepare a core by blowing, wherein the blowing process is a first mode or a second mode, and the first mode is as follows: by CO 2 The gas and the compressed gas are blown in sequence; the second method is as follows: by compressing gas, CO 2 Sequential blowing of gas and compressed gas, said CO 2 Both the gas and the compressed gas have a pressure. The invention can solve the problem that the water glass sand for casting blows CO in the prior art 2 Easy over-blowing, high binder addition, low sand mold strength and the like in the hardening and core-making processAnd (5) problems are solved. With ordinary blowing of CO 2 Compared with the method, the strength of the prepared mould and core is obviously improved, and the used sand can be recycled.)

1. A method for making a core of a sand cold core box by using an inorganic binder for casting is characterized by comprising the following steps:

filling a mixture of inorganic binder for casting, optional additive and raw sand into a mould, hardening the mould core by blowing, wherein the blowing process is any one of the first mode or the second mode,

the first method is as follows: by CO₂The gas and the compressed gas are blown in sequence;

the second method is as follows: by compressing gas, CO₂The gas and compressed gas are blown in sequence;

the CO is₂Both the gas and the compressed gas have a pressure.

2. The method of claim 1, wherein the pressure is in the range of 0.1MPa to 0.8 MPa.

3. The method of claim 1 or 2, wherein the CO is present in a gas phase₂The gas being pure CO₂A gas.

4. The method according to any one of claims 1 to 3, wherein in the second mode, the compressed gas comprises any one or more of nitrogen, argon, air, helium, neon, krypton, xenon or radon.

5. The method according to any one of claims 1 to 4, wherein the composition of the inorganic binder for casting is: any one or the combination of at least two of sodium water glass, potassium water glass, lithium water glass and modified water glass;

preferably, the moduli of the sodium, potassium and lithium water glasses are independently in the range of 1 to 3.

6. The method of any one of claims 1 to 5, wherein the additive comprises any one of silica, a surfactant, or an additive that improves the performance of the sodium silicate-bonded sand, or a combination of at least two thereof.

7. A method according to any one of claims 1 to 6, wherein the raw sand comprises any one of foundry silica sand, zircon sand, forsterite sand, chromite sand or a combination of at least two thereof.

8. The method according to any one of claims 1 to 7, wherein the raw material composition of the core sand-making mixture comprises 2.0 to 4.0 wt% of the inorganic binder for foundry, 0 to 2.0 wt% of an additive, and the balance of raw sand.

9. The method according to any one of claims 1 to 8, wherein the first mode is: blowing CO firstly through the blowing plate₂Time of air blowing t₁Blowing compressed gas for 5-150s for blowing time t₂＝5-200s。

10. The method according to any one of claims 1 to 9, wherein the second mode is: compressed gas is firstly blown into a die cavity through a blowing plate for a blowing time t₃5-100s, followed by blowing CO₂Time of air blowing t₄5-150 s; blowing CO₂After the gas is finished, blowing the compressed gas again for a blowing time t₅Hardening is achieved in 5-200s。

Technical Field

The invention relates to the technical field of casting, in particular to a method for making a core of a cold core box by using inorganic binder sand for casting.

Background

CO₂The hardened water glass is applied to casting production as early as the 50 th of the 20 th century, and the method has the advantages of simple equipment, low cost, no need of kiln feeding and drying of a mold core, high hardening speed, short production period and labor intensityThe casting mold has the advantages of good casting quality, mold stripping of the core after hardening, clear casting size precision, clear contour, low surface roughness and the like. However, sodium silicate sand blows CO₂The hardening core-making process has the following problems in application: the over-blowing is easy, the mechanical property of the sand core is low, and in order to ensure that the water glass sand core has enough technological properties, the adding amount of water glass has to be increased, and the adding amount of the water glass is up to 5-8 percent, so that the collapsibility of the water glass sand is extremely poor, and the application and the development of the water glass sand in casting are influenced.

CN 106925717a discloses an inorganic binder for casting materials, the main components of the binder include: water glass, polyacrylamide solution, sodium tetraborate and sodium stearate. The synthesis process comprises the steps of adding 80 kg of water glass into a YT22 high-speed dispersion machine, starting stirring, slowly adding 10 kg of polyacrylamide solution, 4 kg of sodium tetraborate and 3 kg of sodium stearate, and mixing for two hours to obtain the binder. The product has good storage property, does not precipitate after being stored for a long time, and keeps a transparent and uniform solution. The zero emission of the waste sand is realized in the production, the regeneration efficiency of the used sand is improved, and the cleaning efficiency is improved. The working environment of workers is improved, the environmental and atmospheric pollution is reduced, and the quality of castings is improved. However, the core made by molding water glass has the technical defects of large gas evolution and poor collapsibility.

CN 103521709A discloses a CO₂Method for making core by coupling gas hardening and self hardening with water glass sand core without changing existing CO₂The core making production of the sodium silicate sand core is realized by sodium silicate sand core process equipment, a sand mulling process and a core making process, and the process steps are as follows: weighing raw materials, preparing water glass sand, detecting molding sand performance, compacting filled sand in a mold core box, blowing CO₂The method comprises the following steps of primary hardening and forming of the gas core, demoulding, self-hardening and complete hardening, and finished product core. The method has the advantage that the blowing time is longer than that of common CO₂The gas hardening method shortens 2/3, and the blowing efficiency is higher than that of CO₂The gas hardening method is improved by 2-3 times; production cost ratio of CO₂The air hardening method reduces 15%, reduces the labor intensity 1/3 and improves the production efficiency. However, the hardening method described in this patent is liable to cause over-blowing, resulting in low core strength, and liable to cause casting defects such as core breakage, sand inclusion, and sand adhesion.

CN 101985157A discloses a CO₂A method for making a gas hardened 'dual phase' sand core by using a CO2 gas hardened sodium silicate sand phase as the core internal body and CO₂Filling the core box with air-hardened water-soluble resin sand phase as the surface of the core, wherein CO on the surface of the sand core₂The thickness of the resin sand phase is 15 mm-25 mm, and after sand filling is finished, CO is introduced into the core box₂Gas, introduction of CO₂The pressure of the gas is controlled between 0.3MPa and 0.5MPa until the sodium silicate sand phase is completely hardened, so that the whole core sand is hardened and formed into a whole. The method not only solves CO₂The problems of poor collapsibility, poor cleaning of core sand, sand sticking on the surface of a cast after pouring and the like in the production of the air-hardened sodium silicate sand; and CO₂The air-hardening alkaline phenolic resin sand has poor control on air blowing and CO₂The requirements of pressure and flow of gas are strict, the strength is low, the cost is high, the smell is large, phenol and formaldehyde are diffused after casting pouring to cause the problems of environmental pollution and the like, and the method also has CO₂Fast setting effect and CO of sodium silicate sand₂The resin sand has the advantages of good collapsibility, no harmful gas generation in the whole production process of core making and casting, and convenient use. However, according to this patent, the molding process is complicated, and the contact surfaces of the two types of molding sand are easily separated from each other, and cannot be tightly bonded, so that the molding sand is likely to have defects such as collapse and core breakage during the mold stripping and mold closing processes.

Therefore, there is a need to provide a novel inorganic binder for casting to solve the problem of blowing CO by using water glass sand for casting in the prior art₂The hardening and core-making process has the problems of easy over-blowing, high binder addition amount, low sand mold strength and the like.

Disclosure of Invention

In view of the above problems in the prior art, an object of the present invention is to provide an inorganic binder for casting and a method for making a core with a cold core box. Can solve the problem that the water glass sand for casting blows CO in the prior art₂The hardening and core-making process has the problems of easy over-blowing, high binder addition amount, low sand mold strength and the like.

In order to achieve the purpose, the invention adopts the following technical scheme:

the invention aims to provide a method for making a core of a cold core box by using inorganic binder sand for casting, which comprises the following steps:

filling a mixture of inorganic binder for casting, optional additive and raw sand into a mould, hardening the mould core by blowing, wherein the blowing process is any one of the first mode or the second mode,

the first method is as follows: by CO₂The gas and the compressed gas are blown in sequence;

the second method is as follows: by compressing gas, CO₂The gas and the compressed gas are blown in sequence.

Wherein said CO is₂Both the gas and the compressed gas have a certain pressure.

The method of the invention adopts the inorganic binder for casting formed by the three different series of water glass and modified water glass, combines the core making process of the carbon dioxide and air composite hardening process, and can effectively avoid CO₂The compressed gas stays in the core and can effectively avoid CO₂The produced over-blowing defect ensures the strength of the mold core. The invention solves the problem of CO₂The problem of over-blowing in the process of manufacturing the mold and the core by the method leads the addition amount of the inorganic binder to be low, the mold and the core manufacturing speed to be high, the strength of the mold core to be high, the gas evolution to be low, the method is nontoxic and environment-friendly, and the working environment of casting is improved.

The "optional additives" refer to: the raw material composition of the core sand mixture may or may not contain additives.

The mixture of the invention can be mixed evenly before filling into the mould, and the additive can be added in the sand mixing process in the form of powder or liquid.

The method for filling the mold is not limited in the present invention, and may be, for example: the mold is filled by a core shooter or by manual methods.

As a preferred embodiment of the process of the present invention, the pressure is in the range of 0.1MPa to 0.8MPa, for example, 0.1MPa, 0.2MPa, 0.3MPa, 0.4MPa, 0.5MPa, 0.6MPa, 0.7MPa or 0.8 MPa. If the pressure is less than 0.1MPa, the phenomena of uneven hardening and hard impermeability are caused, and the strength of the sand core is reduced; if the pressure is more than 0.8MPa, the sand guide is over compacted, the hardening quality is influenced, and the strength of the sand core is further reduced.

Preferably, the CO is₂The gas being pure CO₂A gas.

Preferably, in the second mode, the compressed gas includes any one or more of nitrogen, argon, air, helium, neon, krypton, xenon, and radon.

The method of the present invention is applicable to various inorganic binders for casting, and may be any one of sodium water glass, potassium water glass, lithium water glass and modified water glass or a combination of at least two of them, for example.

Preferably, the moduli of the sodium, potassium and lithium water glasses are independently in the range of 1-3, such as 1, 1.5, 1.8, 2, 2.5, 2.7, or 3, and the like.

The modified water glass of the present invention may be, for example: the modified water glass is obtained by using sodium silicate, potassium silicate or lithium silicate as main components and performing electromagnetic treatment or magnetic field treatment, or the silicate solution is obtained by performing chemical modification treatment on inorganic salt and organic matters.

Preferably, the additive comprises any one of silica, a surfactant or an additive for improving the performance of the sodium silicate-bonded sand or a combination of at least two of the same. The silica may be one or more of silicas produced by different processes.

Preferably, the raw sand comprises any one of or a combination of at least two of foundry silica sand, spherical sand, zircon sand, forsterite sand and chromite sand.

The shape of the raw sand is not limited in the invention, and the raw sand can be spherical sand, for example.

As a preferable technical scheme of the method, the raw material composition of the core-making sand mixture comprises 2.0-4.0 wt% of the inorganic binder for casting, 0-2.0 wt% of additive and the balance of raw sand. The content of the inorganic binder for casting is, for example, 2.0 wt%, 2.3 wt%, 2.5 wt%, 2.6 wt%, 2.8 wt%, 3.0 wt%, 3.5 wt%, or 4.0 wt%, etc.; the additive is contained in an amount of, for example, 0, 0.02 wt%, 0.05 wt%, 0.1 wt%, 0.3 wt%, 0.5 wt%, 0.8 wt%, 1.0 wt%, 1.5 wt%, 2.0 wt%, or the like. The content of the raw sand is, for example, 94.0 wt%, 95.0 wt%, 96.0 wt%, 97.0 wt%, 98.0 wt%, or the like.

Preferably, the first mode is: blowing CO firstly through the blowing plate₂Time of air blowing t₁5-150s, for example, 5s, 10s, 20s, 30s, 45s, 55s, 70s, 80s, 100s, 110s, 125s, 135s, 150s, etc., and then blowing the compressed gas for a blowing time t₂For example, 5s, 10s, 20s, 30s, 40s, 45s, 55s, 70s, 80s, 90s, 100s, 110s, 120s, 130s, 140s, or 150 s.

Preferably, the second mode is: compressed gas is firstly blown into a die cavity through a blowing plate for a blowing time t₃5-100s, followed by blowing CO₂Time of air blowing t₄5-150 s; blowing CO₂After the gas is finished, blowing the compressed gas again for a blowing time t₅Hardening was achieved for 5-200 s.

Compared with the prior art, the invention has the following beneficial effects:

(1) the invention provides a method for making a core of a sand cold core box, in particular to a method for making a core by blowing and hardening inorganic binder sand for casting, which can solve the problem of blowing CO into the inorganic binder sand₂The method has the problem of over-blowing, so that the addition amount of the inorganic binder can be reduced to 2.0-4.0%; the method and the common CO blowing method provided by the invention₂Compared with the method, the strength of the prepared mould and core is obviously improved, and the used sand can be recycled. In addition, the method is nontoxic and free of pungent smell in the molding and core making process, can improve the casting production environment, and is beneficial to realizing environment-friendly production in the casting industry.

(2) The method of the invention has no toxicity and no pungent smell in the molding and core making process, can improve the casting production environment, and is beneficial to realizing the environment-friendly production in the casting industry.

Detailed Description

The technical solution of the present invention is further explained by the following embodiments.

To avoid the influence of environmental changes (temperature and humidity changes), the ambient temperature was maintained at 30 ℃ and the humidity at 40% RH. In addition, the gas flow and the blowing time can be adjusted according to the thickness and the complexity of the sand core and the structural design of a core box die in actual production.