CN117123734A - VRH-CO 2 Is formed by vacuum sealing box - Google Patents

Abstract

The application relates to a VRH-CO ₂ The molding method and the vacuum seal box of the (2) comprise the steps of placing a sand mold: placing the sand mould into a vacuum box; vacuumizing for the first time: opening the vacuum pump, wherein the vacuum degree in the sealed space is more than or equal to 5KPa, and closing the vacuum pump; the pressure in the vacuum box is in a negative pressure state, and the range of the change is not more than 0.5Kpa; CO blowing in ₂ A gas; and vacuumizing for the second time: CO ₂ After the blowing device is closed, the vacuum pump is opened, vacuum is pumped, and then the vacuum pump is closed; decompression and taking of the vacuum sealing box; the application can produce thick and large sand molds, reduce the use amount of carbon dioxide gas, reduce the waste mold rate, improve the production efficiency and improve the production environment.

Description

VRH-CO 2 Is formed by vacuum sealing box

Technical Field

The application belongs to the technical field of casting, and relates to a VRH-CO ₂ (vacuity/vacuum replacement hardening-CO ₂ Vacuum displacement carbon dioxide hardening).

Background

The carbon dioxide hardening modeling method adopted in the prior art has the main problems that:

(1) the blown carbon dioxide leaks more, resulting in a thin hardened layer of sand mold/sand core, and the inside is not blown through, failing to produce thick and large sand mold.

(2) As the blowing pressure of the carbon dioxide is 0.5Mpa at most, the pressure gradually drops along with the extension of the service time, and when the blowing pressure is insufficient to extrude the residual air in the cavity, the hardening of the sand mould in the cavity can be affected.

(3) The residual air in the extrusion cavity is blown by only carbon dioxide, and even if the pressure is large enough, the partial hardening can be performed again under the condition of smooth air discharge.

Patent document 1 (CN 1061911C) discloses a molding (core) method comprising the steps of sand mixing, molding, vacuum-pumping, air-charging, and mold-drawing, characterized in that: uniformly mixing 100 parts of casting sand, 0.5-10 parts of water glass and 0.05-1.5 parts of organic ester (in mass) and filling into a sand box (core box) for molding; pumping out air in the sand box, wherein the vacuum degree reaches 0.01-0.09 MPa; filling a mixed gas of methyl formate with the concentration of 5-100% (by volume) and air or nitrogen, so that the air pressure in the sand box is increased to 0.05-0.098 MPa, and maintaining the pressure for 20-240 seconds; and (5) releasing pressure and stripping. The patent document uses a method of blowing after vacuumizing to realize the hardening, but the sand mould used by the method is a sodium silicate sand mould, the blown curing agent is a liquid material, the aerosol hardening is realized by taking compressed air or nitrogen as a carrier, and the liquid curing material is an acid ester organic matter, so that the environment is still polluted.

Patent document 2 (CN 1180002 a) discloses a carbon dioxide hardening resin sand, including quartz sand, sodium polyacrylate resin, and the like. The resin sand has the CO2 rapid curing effect of sodium silicate sand in casting production, and the residual strength after casting is lower than that of common resin sand, so that the resin sand is extremely easy to clean. The resin sand provided in the patent document does not generate any harmful gas in the core making and pouring processes, does not pollute the environment, but uses sodium polyacrylate resin with higher organic components, does not relate to a VRH method, has relatively simple process, and causes more CO2 usage and larger carbon emission.

Patent document 3 (CN 103028703 a) application relates to a sodium polyacrylate resin sand carbon dioxide hardening cold box core making method, which comprises: the method for preparing the core by using the cold core box through carbon dioxide hardening comprises the steps of adding sodium polyacrylate resin and a hardening accelerator into raw sand, mixing by adopting a sand mixer, adding sand into a sand hopper for preparing the core by using the cold core box, injecting carbon dioxide into a core, and hardening resin sand, wherein the raw sand is formed by mixing two shaping sand with the granularity of 40/70 meshes and 50/100 meshes. The method has the advantages of short hardening time, uniform hardening of the whole section from the surface to the core of the sand core, difficult deformation and cracking in the specified standing time, and environmental protection compared with other hardening methods. However, this patent document uses a two-component liquid material in which the second component is a hardening accelerator and is further assisted in hardening by carbon dioxide hardening, and, although the process has a low carbon dioxide consumption, the resin sand storage time is shortened due to the presence of the hardening accelerator, and the VRH hardening method is not involved due to the core-making process.

Patent document CN104439093a discloses a hardening process of a sodium silicate sand mold and a vacuum box used in the process, and a hardening process of a sodium silicate sand mold, wherein a sand mold made of sodium silicate sand is placed into the vacuum box, and the vacuum box is sealed; the temperature in the vacuum box is kept at 35-45 ℃, the vacuum box is slowly and continuously evacuated, and the air pressure of the vacuum box is kept at 0.8-0.9 pa for 1-2 min; the water molecules on the surface of the sand mold are gasified and discharged out of the vacuum box under the condition of preventing the sodium silicate sand from melting and keeping the higher temperature and the smaller air pressure as much as possible, because the sand mold is preventedDeforming for 1-2 min, and discharging most of water vapor. The temperature of the vacuum box is reduced to 25 ℃, the vacuum box is evacuated to 0.5pa, the evacuation is stopped, the vacuum box is sealed, and the CO is slowly filled in ₂ The air pressure of the vacuum box is 0.7pa, and the vacuum box is kept for 10 to 15 minutes; firstly, reducing the temperature, keeping the good hardness of the sand mold, then pumping air into the vacuum box to achieve the effect of reducing the pressure, and then filling CO ₂ The vacuum box still maintains lower air pressure and CO ₂ Fully contacts with water glass and achieves better hardening effect.

The above patent documents have low relevance to the present application.

Disclosure of Invention

The application aims to improve the hardening speed, reduce the use amount, ensure the uniformity of sand hardening and provide a VRH-CO in the process of hardening a sand mould by using carbon dioxide gas ₂ Is a molding method of (a).

It is noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions.

Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

In order to solve the technical problems, the application is realized by adopting the following technical scheme:

VRH-CO ₂ The modeling method of (2) comprises the following steps:

putting into a sand mold: placing the sand mould into a vacuum box;

vacuumizing for the first time: opening the vacuum pump, wherein the vacuum degree in the sealed space is more than or equal to 5KPa, and closing the vacuum pump; the pressure in the vacuum sealing box is in a negative pressure state, and the range of the change is not more than 0.5Kpa;

CO blowing in ₂ A gas;

and vacuumizing for the second time: CO ₂ After the blowing device is closed, the vacuum pump is opened, vacuum is pumped, and then the vacuum pump is closed;

and (5) decompressing and taking out the vacuum sealing box.

Further, the raw sand is selected from 50/100 or 70/140 of scouring silica sand or regenerated sand with the same type, resol is used, the addition amount is 2.5%, and the sand is discharged and molded after 60 seconds of mixing and grinding.

Further, the sand mould is placed in a vacuum sealing box, a mode of two layers of sealing covers is adopted, one layer of air blowing plate is buckled on the upper surface of the sand mould in a sealing mode, one layer of vacuum sealing box sealing plate guarantees that the vacuum sealing box is sealed, and the two layers of sealing plates are connected through hoses.

Further, the vacuum pump is opened for the first time, and the pressure in the sealed space is less than or equal to

0.1MPa, and the vacuumizing time is more than or equal to 60s.

Further, after the first vacuumizing, the vacuumizing is closed, the pressure maintaining time is more than or equal to 5 seconds, and CO is charged ₂ And (3) gas.

Further, CO ₂ The blowing pressure is more than or equal to 0.2MPa, and the blowing time is 30-40 seconds.

Further, CO ₂ After the blowing device is closed, the vacuum pump is turned on, and the vacuumizing time is more than or equal to 60 seconds.

Further, the length of the vacuum sealing box is 1800mm, the width is 1800mm, the height is 1000mm, the wall thickness of the vacuum sealing box and the thickness of the upper sealing plate are more than 100mm, and the thickness of the lower bottom plate is more than 150 mm;

the exhaust capacity of the vacuum pump is more than 7000l/min, and the vacuum degree is less than 133 Pa;

the air blowing plate is connected with a sealing top plate of the vacuum sealing box.

Further, the sand mould is placed into a vacuum sealing box, a mode of two layers of sealing covers is adopted, and the two layers of sealing covers are connected by a hose with the inner diameter of phi 10-phi 12 mm.

Further, the sand mold adopts a resol material, belongs to water-soluble alkaline materials, contains about 70 percent of inorganic components, adoptsBy CO ₂ Hardening.

VRH-CO used for the said ₂ The vacuum seal box in the molding method is 1800mm long, 1800mm wide and 1000mm high, the wall thickness of the vacuum seal box and the thickness of the upper sealing plate are more than 100mm, and the thickness of the lower bottom plate is more than 150 mm;

setting a vacuum pump and a blowing plate, wherein the exhausting capacity of the vacuum pump is more than 7000l/min, and the vacuum degree is less than 133 Pa;

the air blowing plate is connected with a sealing top plate of the vacuum sealing box.

Further, the vacuum seal box adopts a mode of two layers of seal covers, one layer of air blowing plate is buckled on the upper surface of the sand mold in a sealing way, one layer of vacuum seal box sealing plate ensures the sealing of the vacuum seal box, and the two layers of sealing are connected by a hose.

Compared with the prior art, the application has the beneficial effects that:

the application can produce thick and large sand molds, reduce the use amount of carbon dioxide gas, reduce the waste mold rate, improve the production efficiency and improve the production environment.

The selected resol belongs to water-soluble alkaline materials and contains 70 percent

The left and right inorganic components are CO ₂ The hardening is more environment-friendly than the original amine-hardened phenol urethane resin.

Drawings

The application is further described below with reference to the accompanying drawings:

FIG. 1 shows a VRH-CO according to the application ₂ A molding method flow chart of (2);

FIG. 2 is CO ₂ The gas enters the blowing plate through the gas blowing pipe, and after being dispersed, the pressure of the gas entering the sand mould is reduced.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application become more apparent, the technical solutions in the embodiments of the present application will be described in more detail below with reference to the accompanying drawings in the embodiments of the present application.

In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout.

The described embodiments are some, but not all, embodiments of the application. The embodiments described below by referring to the drawings are illustrative and intended to explain the present application and should not be construed as limiting the application.

All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application. Embodiments of the present application will be described in detail below with reference to the accompanying drawings.

In the description of the present application, it should be understood that the terms "center," "longitudinal," "lateral," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, merely to facilitate describing the present application and simplify the description, and do not indicate or imply that the devices or elements being referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore should not be construed as limiting the scope of the present application.

The application is described in detail below with reference to the attached drawing figures:

the resin selected by the application needs to pass through CO ₂ The gas effecting hardening, if CO ₂ The low or uneven gas concentration can lead to uneven sand hardening, thereby affecting the quality and strength of the sand mould.

In the gas hardening process, only the air in the cavity is completely replaced by CO ₂ The gas fully reacts with the resin on the surface of the sand grains to ensure uniform sand hardening and strength.

CO ₂ In the process of filling the gas, the air in the cavity is continuously compressed along with the increase of the filling amount to cause the internal pressure of the cavity to rise to a certain pressure to cause CO ₂ The gas pressure is insufficient to extend downward again, resulting in a failure of the bottom sand mold to harden.

At the time of CO filling ₂ When the gas cannot continuously extrude the air at the lower part of the cavity，CO ₂ The gas can disperse around, and the production requirement can not be reduced.

In order to solve the problems, the application adopts secondary VRH-CO ₂ The vacuumizing-inflating mode of the gas ensures uniform sand hardening and improves the strength of the sand mold.

Referring to fig. 1, preparation before operation:

1) And selecting a vacuum sealing box manufactured by a vacuum equipment factory. Length 1800mm, width

1800mm, 1000mm in height, the wall thickness of the vacuum box and the thickness of the upper sealing plate are more than 100mm, and the thickness of the lower bottom plate is more than 150 mm.

2) And selecting a vacuum pump with an exhaust capacity of 7000l/min or more and a vacuum degree of 133Pa or less.

3) The blowing plate is connected with the vacuum box sealing top plate.

The operation steps are as follows:

1) The raw sand is selected from 50/100 or 70/140 of scouring silica sand or regenerated sand with the same type, the resol is used, the addition amount is 2.5 percent, and the sand is discharged and molded after 60 seconds of mixing grinding.

2) Putting into a sand mold: and placing the sand mould into a vacuum sealing box, buckling the air blowing plate on the upper surface of the sand mould, and locking by using calipers. Then the sealing fixed plate of the vacuum sealing box is buckled and locked.

3) Vacuumizing: the vacuum pump is turned on, the vacuum degree in the sealed space is more than or equal to 5KPa, the vacuumizing time is more than or equal to 60s, and the vacuum pump is turned off.

4) The pressure in the vacuum sealing box is in a negative pressure state, the range of the change is not more than 0.5KPa, and the pressure maintaining time is more than or equal to 5S; otherwise the surrounding seal is checked. CO blowing in ₂ The blowing pressure of the gas and the carbon dioxide is more than or equal to 0.2MPa, and the blowing time is 30-40s.

5)CO ₂ After the blowing device of step (3) is turned off, the operation of step (4) is repeated.

6) The device is closed, the vacuum pump is opened to pump residual gas, the vacuumizing time is more than or equal to 60 seconds, the vacuum pump is closed, and the vacuum sealing box is depressurized and taken.

Explanation of the reason for hardening by secondary reciprocating vacuuming and blowing and related tests:

in the vacuum seal box, the surrounding environment of the sand mold and the sand box is in a vacuum state, and the sand mold is easily filled in the process of external inflation theoretically. However, in the actual process, it was found that the hardening problem locally occurs by only one vacuum hardening.

Analyzing the reason:

after the sand mold is sealed by the air blowing sealing plate, the sand mold is sealed by the sand box and the air blowing plate at the same time, so that the gas in the sand mold cannot be effectively discharged in the vacuumizing process, and CO ₂ The gas enters the blowing plate through the gas blowing pipe, and after being dispersed, the pressure of the gas entering the sand mold is reduced (see fig. 2).

If the number of the air inlet pipelines and the number of the air cylinders are increased, the pressure of the air entering the sand mould can be ensured; and the mode of adding the air inlet pipeline can influence the vacuum box sealing and the occupied space of the factory building.

When adopting the secondary reciprocating VRH-CO ₂ The strength of the bottom sand mould can be improved by more than 80% in a vacuumizing-inflating mode of gas, and the problem of poor hardening does not occur. The number of times of vacuumizing-inflating modes was further increased, and the strength was slightly increased, and even when the number of times exceeded 3, the strength tended to decrease, as shown in Table 1.

Table 1 shows the relationship between the number of times of evacuation and the strength.

TABLE 1

The number of times of vacuum pumping	1 time	2 times	3 times	4 times
					Tensile strength (MPa))	0.29	0.52	0.54	0.48

The reason why the two layers of seals are connected with a hose having an inner diameter of Φ8- Φ12mm is explained:

since the hose connected to the pressure reducing valve is only 12mm, if the hose connection between the sealing plates is too high or too low, the amount of blowing air in the upper and lower parts of the sand mold is uneven, as shown in Table 2.

Table 2 shows the relationship between the connection inner diameter and the strength (secondary evacuation-blowing).

TABLE 2

Description of the reason for the two-layer seal cap:

the sealing plate through the vacuum box blows, disperses around the vacuum box, and does not have sufficient pressure to fill the sand mould, leads to unable hardening of sand mould.

Determination of vacuumizing time and blowing time:

(1) connecting a sealing bag at an air inlet of a vacuum box, disconnecting connecting pipelines of two layers of sealing plates, starting a vacuumizing device, and recording time after air in the sealing bag is completely evacuated; the time is CO filling ₂ Minimum vacuum time before gas, 3.24m in vacuum box through test ³ When the sand mold occupies 50% of the space, the vacuumizing time is more than or equal to 60 seconds, and the sealed bag can be ensured to be in a vacuum state.

(2) And (3) determining the blowing time, and comparing the strength of the sand mold at the upper end and the lower end of the sand mold to obtain the highest value, namely the optimal blowing time, similar to the method for determining the blowing times. According to the experimental comparison, the intensity changes at different blowing times are shown in table 3.

Table 3 shows the relationship between the evacuation time and the amount of blowing air.

The tensile strength of the upper and lower positions of the sand mold is more than or equal to 0.5MPa.

TABLE 3 Table 3

And (3) setting vacuumizing pressure maintaining time, and keeping the negative pressure intensity of the connecting pressure gauge stable for more than 5 seconds without changing the numerical value.

The application adopts a secondary vacuumizing blowing mode, ensures uniform hardening and improves the strength of the sand mould.

The sand mould is placed in a vacuum box, a mode of two layers of sealing covers is adopted, one layer of blowing plate is buckled on the upper surface of the sand mould in a sealing mode, one layer of sealing plate of the vacuum box ensures the sealing of the vacuum box, and the two layers of sealing are connected by a hose with the inner diameter of phi 10-phi 12 mm.

The vacuum pump is turned on, the pressure in the sealed space is less than or equal to-0.1 MPa, and the vacuumizing time is more than or equal to 60s

Closing the vacuumizing, keeping the pressure for more than or equal to 5 seconds, and recharging CO ₂ And (3) gas.

CO ₂ The blowing pressure is more than or equal to 0.2MPa, and the blowing time is 30-40 seconds.

CO ₂ After the blowing device is closed, the vacuum pump is turned on, and the vacuumizing time is more than or equal to 60 seconds.

The present application provides another embodiment, a method for VRH-CO as described above ₂ The vacuum seal box in the molding method is 1800mm long, 1800mm wide and 1000mm high, the wall thickness of the vacuum seal box and the thickness of the upper sealing plate are more than 100mm, and the thickness of the lower bottom plate is more than 150 mm;

the exhaust capacity of the vacuum pump is more than 7000l/min, and the vacuum degree is less than 133 Pa;

the air blowing plate is connected with a sealing top plate of the vacuum sealing box.

The vacuum seal box adopts a mode of two layers of seal covers, one layer of air blowing plate is buckled on the upper surface of the sand mold in a sealing way, one layer of vacuum seal box sealing plate ensures the sealing of the vacuum seal box, and the two layers of sealing are connected by a hose with the inner diameter of phi 8-phi 12 mm.

The foregoing is merely illustrative of specific embodiments of the present application, and the scope of the application is not limited thereto, but any modifications, equivalents, improvements and alternatives falling within the spirit and principles of the present application will be apparent to those skilled in the art within the scope of the present application. And all that is not described in detail in this specification is well known to those skilled in the art.

Claims (10)

1. VRH-CO ₂ Is characterized by comprising the following steps:

putting into a sand mold: placing the sand mould into a vacuum sealing box;

vacuumizing for the first time: opening the vacuum pump, wherein the vacuum degree in the sealed space is more than or equal to 5KPa, and closing the vacuum pump; the pressure in the vacuum sealing box is in a negative pressure state, and the range of the change is not more than 0.5Kpa;

CO blowing in ₂ A gas;

and vacuumizing for the second time: CO ₂ After the blowing device is closed, the vacuum pump is opened, vacuum is pumped, and then the vacuum pump is closed;

and (5) decompressing and taking out the vacuum sealing box.

2. A VRH-CO according to claim 1 ₂ Is characterized in that:

the raw sand is selected from 50/100 or 70/140 of scouring silica sand or regenerated sand with the same type, the resol is used, the addition amount is 2.5 percent, and the sand is discharged and molded after 60 seconds of mixing grinding.

3. A VRH-CO according to claim 1 ₂ Is characterized in that:

the vacuum pump is turned on for the first time, the pressure in the sealed space is less than or equal to minus 0.1MPa, and the vacuum pumping time is more than or equal to 60 seconds.

4. A VRH-CO according to claim 1 ₂ Is characterized in that:

after the first vacuumizing, closing vacuumizing, keeping the pressure for more than or equal to 5 seconds, and recharging CO ₂ And (3) gas.

5. A VRH-CO according to claim 1 ₂ Is characterized in that:

CO ₂ the blowing pressure is more than or equal to 0.2MPa, and the blowing time is 30-40 seconds.

6. A VRH-CO according to claim 1 ₂ Is characterized in that:

CO ₂ after the blowing device is closed, the vacuum pump is turned on, and the vacuumizing time is more than or equal to 60 seconds.

7. A VRH-CO according to claim 3 ₂ Is characterized in that:

the sand mould is put into a vacuum sealing box, a mode of two layers of sealing covers is adopted, and the two layers of sealing are connected by a hose with the inner diameter of phi 10-phi 12 mm.

8. A VRH-CO according to claim 1 ₂ Is characterized in that:

the sand mold adopts a resol material, belongs to a water-soluble alkaline material, contains about 70 percent of inorganic components, adopts CO ₂ Hardening.

9. A VRH-CO for use as claimed in any one of claims 1 to 8 ₂ The vacuum seal box in the molding method is characterized in that:

the length of the vacuum sealing box is 1800mm, the width of the vacuum sealing box is 1800mm, the height of the vacuum sealing box is 1000mm, the wall thickness of the vacuum sealing box and the thickness of the upper sealing plate are more than 100mm, and the thickness of the lower bottom plate is more than 150 mm;

setting a vacuum pump and a blowing plate, wherein the exhausting capacity of the vacuum pump is more than 7000l/min, and the vacuum degree is less than 133 Pa;

the air blowing plate is connected with a sealing top plate of the vacuum sealing box.

10. The VRH-CO of claim 9 ₂ Is characterized in that:

the vacuum seal box adopts a mode of two layers of seal covers, one layer of air blowing plate is buckled on the upper surface of the sand mold in a sealing way, one layer of vacuum seal box sealing plate ensures the sealing of the vacuum seal box, and the two layers of sealing are connected by a hose with the inner diameter of phi 8-phi 12 mm.