CN102744367A - Lost foam-shell mold casting vibration and solidification method based on foam mold - Google Patents

Abstract

The invention relates to a lost foam-shell mold casting vibration and solidification method based on a foam mold, comprising the following steps of: (1) manufacturing the foam mold with a ceramic shell on a surface thereof; (2) after the foam mold is subjected to lost foam mold and baking, putting the foam mold into a bottom-drawing sandbox, filling scattered molded dry sand into the bottom-drying sandbox, closing a vibrating table after vibrating and compacting the scattered dry sand pass through the vibrating table, coating a layer of plastic film on the upper part of the bottom-drawing sandbox, and placing a pouring cup on the upper part of the bottom-drawing sandbox to be poured; and (3) opening a vacuum device and the vibrating table, injecting metal liquid into a ceramic shell through the pouring cup, vibrating and solidifying, closing the vibrating table and the vacuum device after the metal liquid is solidified into a cast completely, and opening the sandbox to perform cleaning. The lost foam-shell mold casting vibration and solidification method based on the foam mold is simple, lower in cost, convenient to operate and environmental-friendly. An effective method with the characteristics of convenience, quickness, low cost, environmental-friendly grain size of refined casts and enhanced performances of the casts is provided for lost foam-shell mold casting enterprises.

Description

Vibration Solidification Method of Lost Pattern Shell Mold Casting Based on Foam Plastic Mold

technical field

The invention relates to the field of precision casting, in particular to a vibration solidification method for lost pattern shell casting based on a foam plastic mold.

Background technique

Lost foam casting is a new technology with nearly no allowance and precise forming. It is called "new casting technology in the 21st century" and "green engineering in casting". It has been greatly developed and widely used at present. However, there are also certain problems in lost foam casting. For example, the decomposition of the foamed plastic pattern used in the pouring process will bring many defects such as pores, wrinkles, inclusions, and carburization. The grains are coarse, and the performance of the casting is low, especially for the lost foam casting of aluminum and magnesium alloys.

Lost foam shell casting is a new composite casting process developed by combining lost foam casting and investment casting. After taking off the foam mold and roasting, the mold shell is put into the sand box, and the sand box is filled with sand, vibrated and compacted, and then poured, so as to obtain a new method of precision casting. This process has flexible structural design, stable size, small shrinkage and low cost of lost foam casting foam pattern, and can produce medium and large complex thin-walled castings. Defects such as pores, wrinkled skin, inclusions and carburization are easy to appear, and can overcome the problems of traditional investment casting that cannot produce large castings and high cost. The castings also have the precision and surface quality of investment casting. Although lost foam shell casting solves some problems of lost foam casting and investment casting, it also has certain problems. Because the molten metal only solidifies naturally under gravity, and the loose dry sand of the shape is slow to dissipate heat, the final The casting structure presents obvious dendrites, and the grain size is too large. The grain size of the casting has an important influence on the mechanical properties of the casting. The smaller the grain size, the higher the strength and hardness, and the better the performance of the casting. Therefore, the refinement of casting grain size is an important means to improve the performance of castings.

Contents of the invention

The invention provides a vibratory solidification method for lost foam shell casting based on a foam plastic mold, which solves the problem of coarse grain size of lost foam shell castings and aims at refining the grain size of lost foam shell castings and improving the performance of castings Methods.

The technical solution adopted by the present invention to solve the above-mentioned technical problems is: the vibration solidification method of lost foam shell mold casting based on foamed plastic mold, it is characterized in that comprising the following steps:

1) First make a foam plastic mold, soak the foam plastic mold with paint, then sprinkle sand on it, and repeat the above operation 2-3 times after drying, so as to obtain a foam plastic mold with 2-3 layers of ceramic shells on the surface;

2) Put the foamed plastic mold with 2-3 layers of ceramic shells on the surface obtained in step 1) into the bottom-drawing sand box after losing the foam plastic mold and roasting, and the bottom-drawing sand box is connected to the vibrating table by fixing screws ; Then fill the modeling loose dry sand into the bottom pumping sand box, after the loose dry sand is vibrated and compacted by the vibrating table, close the vibrating table, and cover a layer of plastic film on the top of the bottom pumping sand box. The sprue cup is placed on the upper part of the type sand box to be poured;

3) Turn on the vacuum device and the vibrating table, inject the molten metal into the ceramic shell through the sprue cup, and make it solidify under vibration. After the molten metal is completely solidified into castings, turn off the vibrating table and the vacuum device, and you can get it after unpacking and cleaning. High performance castings.

According to the above scheme, the modeling loose dry sand is pearl sand or silica sand.

According to the above scheme, the vibration direction of the vibrating table is horizontal or vertical.

According to the above scheme, the vibration frequency of the vibrating table is 25-500 Hz, the amplitude is 0.04-4 mm, and the acceleration is 2-16 g.

The vibration solidification method of lost foam shell casting based on the foamed plastic mold of the present invention is suitable for lost foam shell casting of non-ferrous metals such as aluminum alloys and magnesium alloys, and is also suitable for lost foam shell casting of ferrous metals such as cast iron and cast steel .

The beneficial effects of the present invention are as follows: (1) The present invention vibrates the solidification process of molten metal in the process of lost pattern shell casting, so that the dendrite arms formed in the early stage of solidification are sheared and broken, broken and proliferated, and the fineness and disappearance are achieved. The grain size of mold shell castings improves the performance of castings. After vibration, the grain size can be reduced to 35-45% of that before vibration; (2) At the same time, the invention can solve the porosity that is easy to appear in ordinary lost foam casting , carburization, inclusions and other casting defects, to overcome the traditional investment casting can not produce large castings and high cost problems, with lost foam casting foam pattern structure design flexible, dimensional stability, small shrinkage and low cost, and investment casting With the advantages of high precision and excellent surface quality, it can produce medium and large complex thin-walled precision castings. Combined with vibration solidification, it can finally obtain medium and large complex thin-walled castings with good surface quality, high dimensional accuracy, excellent internal quality and high mechanical properties. Precision castings; (3) The invention is simple in process, low in cost, convenient in operation, and environment-friendly, and can provide a convenient, quick, low-cost, and environmentally friendly refinement of casting grain size for lost-form shell casting enterprises, and improve casting The effective method of performance can greatly improve the competitiveness of high-quality medium-to-large complex thin-walled precision castings produced by lost-form shell casting, has broad application prospects, and can realize large-scale industrial production.

Description of drawings

Fig. 1 is the concrete example schematic diagram of the present invention;

1. Vibration table; 2. Fixing screw; 3. Isolation layer; 4. Bottom pumping sand box; 5. Loose dry sand; 6. Ceramic shell; 7. Metal liquid; 8. Vacuum port; 9. Plastic film .

Detailed ways

The present invention will be described in further detail below in conjunction with the examples, but this description will not constitute a limitation to the present invention.

Embodiment 1 :

Vibration Solidification of Lost Pattern Shell Mold Casting of AZ91D Magnesium Alloy

(1) Prepare the foam plastic pattern, soak the foam mold with paint, then sprinkle sand, repeat the above operation twice after drying, and form 2 layers of ceramic shells on the surface of the foam mold;

(2) After losing the foam plastic mold and firing, the ceramic shell 6 is put into the bottom-drawing sand box 4, and the bottom-drawing sand box is connected with the vibrating table through fixing screws 2, and then filled with loose powder into the bottom-drawing sand box. Dry pearl sand 5, after loose dry sand is vibrated and compacted by the vibrating table 1, close the vibrating table, cover the upper part of the sand box with a layer of plastic film 9, and then place the sprue cup on the upper part of the sand box to be poured;

(3) Turn on the vacuum device and the vibrating table, and the vacuum device implements vacuuming through the vacuum port 8 and the space formed by the bottom pumping sand box and the isolation layer 3, and the vibration process parameters are set as: vibration frequency 25 Hz, The amplitude is 4.0 mm, the vibration acceleration is 10 g, and the vibration direction is horizontal. The AZ91D magnesium alloy molten metal 7 is poured into the ceramic shell after melting, refining, resting and reaching the pouring temperature. After the casting is completely solidified, the vibration table and the vacuum device 8 are turned off, and the AZ91D magnesium alloy casting can be obtained after unpacking and cleaning , the tensile strength and elongation of the castings were increased by 15-20% and 20-25% respectively compared with those without vibration, reaching 175-185 MPa and 2.5-3.5% respectively.

Embodiment 2 :

Vibration Solidification of A356 Aluminum Alloy Lost Form Shell Mold Casting

(1) Prepare the foam plastic pattern, soak the foam mold with paint, then sprinkle sand, repeat the above operation twice after drying, and form 2 layers of ceramic shells on the surface of the foam mold;

(2) Ceramic mold shell 6 is put into the bottom-drawing sand box 4 after losing the shape of foam plastic and roasted. The bottom-drawing sand box is connected with the vibrating table through fixing screws 2, and then the bottom-drawing sand box is filled with pearls. Sand 5. After the loose dry sand is vibrated and compacted by the vibrating table 1, the vibrating table is closed, and the upper part of the sand box is covered with a layer of plastic film 9, and then the sprue cup is placed on the upper part of the sand box to be poured;

(3) Turn on the vacuum device and the vibrating table, and the vacuum device implements vacuuming through the vacuum port 8 and the space formed by the bottom pumping sand box and the isolation layer 3, and the vibration process parameters are set as: vibration frequency 50 Hz, The amplitude is 4.0 mm, the vibration acceleration is 15 g, and the vibration direction is vertical. A356 aluminum alloy molten metal 7 is poured into the ceramic shell after melting, refining, resting and reaching the pouring temperature, and the vibrating table is quickly started, and the vibrating table and the vacuum device are turned off after the casting is completely solidified, and it can be obtained after unpacking and cleaning For A356 aluminum alloy castings, the tensile strength and elongation of the castings are 13-20% and 18-25% higher than those without vibration, reaching 180-195 MPa and 3-5% respectively.

Example 3:

Vibration Solidification of Gray Iron Lost Form Shell Mold Casting

(1) Prepare the foam plastic pattern, soak the foam mold with paint, then sprinkle sand, repeat the above operation 3 times after drying, and form 3 layers of ceramic shells on the surface of the foam mold;

(2) After the ceramic mold shell 6 loses the shape of the foam plastic and is roasted, it is put into the bottom-drawing sand box 4, and the bottom-drawing sand box is connected with the vibrating table through the fixing screw 2, and then filled with loose powder into the bottom-drawing sand box. Dry pearl sand 5, after loose dry sand is vibrated and compacted by the vibrating table 1, close the vibrating table, cover the upper part of the sand box with a layer of plastic film 9, and then place the sprue cup on the upper part of the sand box to be poured;

(3) Turn on the vacuum device and the vibrating table, and the vacuum device implements vacuuming through the vacuum port 8 and the space formed by the bottom pumping sand box and the isolation layer 3, and the vibration process parameters are set as: vibration frequency 100 Hz, The amplitude is 0.8 mm, the vibration acceleration is 16 g, and the vibration direction is vertical. Pour the gray cast iron molten metal 7 into the ceramic mold shell after melting, resting and reaching the pouring temperature, start the vibrating table quickly, and turn off the vibrating table and vacuum device after the castings are completely solidified, and the gray cast iron castings can be obtained after unpacking and cleaning. The tensile strength and hardness of the castings are increased by 15-20% and 18-22% respectively compared with those without vibration.

Example 4:

Vibration Solidification of Low Carbon Steel Parts in Lost Form Shell Mold Casting

(1) Prepare the foam plastic pattern, soak the foam mold with paint, then sprinkle sand, repeat the above operation 3 times after drying, and form 3 layers of ceramic shells on the surface of the foam mold;

(2) After the ceramic mold shell 6 loses the shape of the foam plastic and is roasted, it is put into the bottom-drawing sand box 4, and the bottom-drawing sand box is connected with the vibrating table through the fixing screw 2, and then filled with loose powder into the bottom-drawing sand box. Dry pearl sand 5, after loose dry sand is vibrated and compacted by the vibrating table 1, close the vibrating table, cover the upper part of the sand box with a layer of plastic film 9, and then place the sprue cup on the upper part of the sand box to be poured;

(3) Turn on the vacuum device and the vibrating table. The vacuum device is vacuumed through the vacuum port 8 and the space formed by the bottom pumping sand box and the isolation layer 3, and the vibration process parameters are set as: vibration frequency 500 Hz, The amplitude is 0.04 mm, the vibration acceleration is 15 g, and the vibration direction is vertical. The low-carbon steel molten metal 7 is melted, rested and poured into the ceramic shell after reaching the pouring temperature. After all the castings are solidified, turn off the vibrating table and the vacuum device. After unpacking and cleaning, you can get low-carbon steel castings. There is no carburization defect in the castings, and the tensile strength and hardness of the castings are respectively increased by 12-18% compared with those without vibration. 15-20%.

Claims (4)

1. based on the disappearance formwork mold casting vibration clotting method of foam mould, it is characterized in that may further comprise the steps:

1) at first make foam mould, foam mould dipping coating, stucco is above that afterwards carried out above operation 2-3 time repeatedly after to be dried, thereby is obtained the foam mould that the surface has the layer 2-3 ceramic shell;

2) foam mould that step 1) gained surface is had the layer 2-3 ceramic shell is put into the bottom pumping type sandbox after losing foam mould and roasting, the bottom pumping type sandbox is connected through hold-down screw with shake table; In the bottom pumping type sandbox, fill the diffusing dry sand of moulding then, the dry sand that will loose is closed shake table after carrying out vibration ramming through shake table, and covers layer of plastic film on bottom pumping type sandbox top, and place cup afterwards on bottom pumping type sandbox top to be poured;

3) open vacuum device and shake table inject ceramic shell with molten metal through cup, and it is solidified under vibration, treat to close shake table and vacuum plant after molten metal all is frozen into foundry goods, can obtain the high-performance foundry goods after the cleaning of unpacking.

2. the disappearance formwork mold casting vibration clotting method based on foam mould as claimed in claim 1 is characterized in that the diffusing dry sand of moulding is mound sand or silica sand.

3. according to claim 1 or claim 2 the disappearance formwork mold casting vibration clotting method based on foam mould is characterized in that the direction of vibration of shake table is horizontal direction or vertical direction.

4. according to claim 1 or claim 2 disappearance formwork mold casting vibration clotting method based on foam mould, the vibration frequency that it is characterized in that shake table is 25-500Hz, and amplitude is 0.04-4 mm, and acceleration is 2-16 g.

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