CN102873263B - Lost foam casting technology for sand burning-resistance cast steel - Google Patents

Abstract

The invention relates to an anti-adhesive sand cast steel lost foam casting process, including making model clusters, preparing inner coatings, preparing outer coatings, using inner coatings and outer coatings to treat lost foam patterns, vibration modeling, casting replacement and cooling and other steps. According to the analysis of paint fragments, the coating was not invaded by molten steel, and the refractory aggregate particles in the inner layer of the coating were filled with molten glass phase, which prevented the intrusion of molten steel and also avoided the phenomenon of sand sticking in castings.

Description

A lost foam casting process for anti-stick sand cast steel

technical field

The invention relates to the field of casting, in particular to the technical field of lost foam cast steel manufacturing, in particular to an anti-sticking sand cast steel lost foam casting process.

Background technique

Lost foam casting (also known as solid casting) is to bond and combine foam models similar in size and shape to castings to form a model cluster. After brushing refractory paint and drying, it is buried in dry quartz sand for vibration molding, and poured under negative pressure. , the model is vaporized, the liquid metal occupies the position of the model, solidified and cooled to form a new casting method of castings.

Compared with traditional casting technology, lost foam casting has the following characteristics: 1. Good casting quality and low cost; 2. Unlimited material and suitable size; 3. High dimensional accuracy, smooth surface, reducing cleaning workload; 4. Internal The defects are greatly reduced and the organization is dense; 5. It can realize large-scale and mass production, which can greatly improve the working environment, reduce labor intensity, and reduce energy consumption.

Although the lost foam casting process has been developed rapidly, the coating technology has not yet met the ideal requirements. Because the performance of the coating directly affects the quality of the casting, the coating has an important role in addition to isolating the direct contact between the molten metal and the molding sand and preventing the mechanical and chemical sticking of the casting: forming and maintaining the casting cavity. Therefore, it must have high normal temperature strength and high temperature strength, and must have suitable high temperature air permeability.

However, the quality of the current coatings still has shortcomings in various aspects. For example, in the production of cast steel, the lost foam coating is not easy to peel off from the casting after casting cooling, which greatly increases the cost of subsequent grinding wheel grinding.

In response to the above phenomenon, the applicant analyzed the coating fragments, and found that the inner layer of the coating was in direct contact with the molten steel, and the outer layer was in direct contact with the molding sand. During casting, the high-temperature molten steel will wet the inner layer of the paint and immerse into the gaps between the paint aggregate particles. After casting, during the slow cooling process of the casting, the molten steel condenses the coating and the casting into one, making it difficult for the coating to peel off from the surface of the casting.

From the above analysis, it is known that this phenomenon can only be avoided by preventing molten steel from immersing into the gaps between aggregate particles and forming a clear dividing line. However, because the aggregate particles should not be too small, otherwise the air permeability will decrease, and the appearance gasification products will not be able to penetrate smoothly, which will cause pores and slag inclusions, which will reduce the quality of castings.

Contents of the invention

In view of the defects in the prior art, the applicant adjusted the formulation of the coating so that a layer of molten glass phase can be formed inside the coating when pouring at high temperature, so that it can successfully block the penetration of molten steel between the refractory aggregates.

The object of the present invention is to provide an anti-stick sand cast steel lost foam casting process.

In order to realize the foregoing invention object, the technical scheme that the present invention adopts is as follows:

A lost foam casting process for anti-stick sand cast steel, comprising the following steps:

1) Bond and combine foam models similar in size and shape to castings to form model clusters;

2) Prepare inner coating:

a) adding water to the bentonite and stirring at a high speed to obtain bentonite slurry;

b) Add water glass, sodium carboxymethyl cellulose, n-octanol and fatty alcohol polyoxyethylene ether to water to prepare an aqueous solution;

c) Add the bentonite slurry and quartz powder obtained in step a) to the aqueous solution obtained in step b), and add water under constant stirring to make an inner coating;

3) Prepare the outer coating:

d) adding water to the sodium-based bentonite, and stirring at a high speed to obtain a sodium-based bentonite slurry;

e) Add white sol, sodium carboxymethyl cellulose, n-octanol, and fatty alcohol polyoxyethylene ether into water to prepare an aqueous solution;

f) Add the sodium-based bentonite slurry and high-chromium corundum obtained in step d) to the aqueous solution obtained in step e), and add water to mix under constant stirring to form an outer coating;

4) The appearance of the lost pattern is first immersed in the inner layer of paint, taken out and then dried; after drying, the outer layer of paint is hung and dried;

5) Put the model obtained in step 4) in the sandbox, fill it with dry sand, vibrate and compact it, cover the sandbox with a plastic film and vacuum the sandbox;

6) The molten metal is cast into the model area, the lost foam is gasified, the metal replaces the model, and the casting is taken out after cooling.

Further, in step 2), the ratio of each component for preparing the inner coating is: 25-75 parts by weight of quartz powder, 1-3 parts by weight of bentonite, 0.5-1.5 parts by weight of water glass, 0.75 parts by weight of sodium carboxymethyl cellulose ~2.25 parts by weight, 0.15~0.45 parts by weight of n-octanol, and 0.15~0.45 parts by weight of fatty alcohol polyoxyethylene ether.

In the embodiment of the present invention, the ratio of the components of the inner coating in step 2) is: 50 parts by weight of quartz powder, 2 parts by weight of bentonite, 1 part by weight of water glass, and 1.5 parts by weight of sodium carboxymethyl cellulose 0.3 parts by weight of n-octanol, 0.3 parts by weight of fatty alcohol polyoxyethylene ether.

In step a), the weight ratio of bentonite to added water is 1:10; in step b), the weight ratio of water glass to added water is 1:20; in step c), quartz powder is added with constant stirring The weight ratio of water is 1:1.

Further, in step 3), the ratio of each component for preparing the outer coating is: 25-75 parts by weight of high-chromium corundum, 1.5-4.5 parts by weight of sodium bentonite, 0.25-0.75 parts by weight of white sol, carboxymethyl 0.75-2.25 parts by weight of sodium cellulose, 0.15-0.45 parts by weight of n-octanol, and 0.15-0.45 parts by weight of fatty alcohol polyoxyethylene ether.

In the embodiment of the present invention, the ratio of the components of the outer coating in step 3) is: 50 parts by weight of high chromium corundum, 3 parts by weight of sodium bentonite, 0.5 parts by weight of white sol, carboxymethyl fiber 1.5 parts by weight of plain sodium, 0.3 parts by weight of n-octanol, and 0.3 parts by weight of fatty alcohol polyoxyethylene ether.

In step d), the weight ratio of sodium bentonite to added water is 1:10; in step e), the weight ratio of white sol to added water is 1:40; in step f), high chromium corundum is mixed with The weight ratio of water added under constant stirring is 1:1.

Further, the stirring method in steps c) and f) is: first stir at high speed for 1 hour, then stir at low speed to discharge the gas involved in the inner coating and outer coating, and keep stirring at low speed for about 10 hours.

In an embodiment of the present invention, the number of times of hang-coating the outer coating in step 4) is 2-5 times. The drying temperature is 40~60℃, and the drying time is 2-8 hours.

The invention has the following beneficial effects: after the casting is cooled, most of the smears are automatically peeled off from the surface of the casting, and the peeling effect is outstanding. Even if there is a small part of the coating that does not peel off, the subsequent processing is greatly simplified and a lot of labor is saved. According to the analysis of coating fragments, the coating has not been invaded by molten steel, and the refractory aggregate particles in the inner layer of the coating are filled with molten glass phase, which prevents the intrusion of molten steel and also avoids the phenomenon of sand sticking in castings.

Description of drawings

Fig. 1 is a flow chart of the lost foam casting process of anti-stick sand cast steel disclosed by the present invention.

Detailed ways

The present invention will be further described below in conjunction with the examples, but the scope of application of the present invention is not limited.

Example 1

A lost foam casting process for anti-stick sand cast steel, comprising the following steps:

1) Bond and combine foam models similar in size and shape to castings to form model clusters;

2) Prepare inner coating:

a) Add 10 parts by weight of water to 1 part by weight of bentonite, and stir at a high speed for 5 hours to obtain bentonite slurry;

b) Add 1.5 parts by weight of water glass, 2.25 parts by weight of sodium carboxymethyl cellulose, 0.15 parts by weight of n-octanol, and 0.45 parts by weight of fatty alcohol polyoxyethylene ether into 30 parts by weight of water to prepare an aqueous solution;

c) Add the bentonite slurry obtained in step a) and 25 parts by weight of quartz powder to the aqueous solution obtained in step b), and add 25 parts by weight of water under continuous stirring to make an inner coating. The stirring method is: first stir at high speed for 1 hour Then stir at a low speed to discharge the gas involved in the inner coating, and keep stirring at a low speed for 8 hours;

3) Prepare the outer coating:

d) Add 15 parts by weight of water to 1.5 parts by weight of sodium bentonite, and stir at a high speed for 7 hours to obtain sodium bentonite slurry;

e) adding 0.75 parts by weight of white sol, 2.25 parts by weight of sodium carboxymethyl cellulose, 0.15 parts by weight of n-octanol, and 0.45 parts by weight of fatty alcohol polyoxyethylene ether into 30 parts by weight of water to prepare an aqueous solution;

f) Add the sodium-based bentonite slurry obtained in step d) and 25 parts by weight of high-chromium corundum to the aqueous solution obtained in step e), and add 25 parts by weight of water under continuous stirring to make an outer coating. The stirring method is: first Stir at high speed for 1 hour, then stir at low speed to discharge the gas involved in the outer coating, and keep stirring at low speed for 11 hours;

4) The appearance of the lost pattern is first immersed in the inner layer of paint, taken out and then dried; after drying, the outer layer of paint is hung and dried;

5) Put the model obtained in step 4) in the sandbox, fill it with dry sand, vibrate and compact it, cover the sandbox with a plastic film and vacuum the sandbox;

6) The molten metal is cast into the model area, the lost foam is gasified, the metal replaces the model, and the casting is taken out after cooling.

Example 2

A lost foam casting process for anti-stick sand cast steel, comprising the following steps:

1) Bond and combine foam models similar in size and shape to castings to form model clusters;

2) Prepare inner coating:

a) Add 30 parts by weight of water to 3 parts by weight of bentonite, and stir at a high speed for 7 hours to obtain bentonite slurry;

b) Add 0.5 parts by weight of water glass, 0.75 parts by weight of sodium carboxymethyl cellulose, 0.45 parts by weight of n-octanol, and 0.15 parts by weight of fatty alcohol polyoxyethylene ether into 10 parts by weight of water to prepare an aqueous solution;

c) Add the bentonite slurry obtained in step a) and 75 parts by weight of quartz powder to the aqueous solution obtained in step b), and add 75 parts by weight of water under continuous stirring to make an inner coating. The stirring method is: first stir at high speed for 1 hour Then stir at a low speed to discharge the gas involved in the inner coating, and keep stirring at a low speed for 10 hours;

3) Prepare the outer coating:

d) Add 45 parts by weight of water to 4.5 parts by weight of sodium bentonite, and stir at a high speed for 5 hours to obtain sodium bentonite slurry;

e) adding 0.75 parts by weight of white sol, 0.75 parts by weight of sodium carboxymethyl cellulose, 0.15 parts by weight of n-octanol, and 0.45 parts by weight of fatty alcohol polyoxyethylene ether into 30 parts by weight of water to prepare an aqueous solution;

f) Add the sodium-based bentonite slurry obtained in step d) and 75 parts by weight of high-chromium corundum into the aqueous solution obtained in step e), and add 75 parts by weight of water under continuous stirring to make an outer coating. The stirring method is: first Stir at high speed for 1 hour, then stir at low speed to discharge the gas involved in the outer coating, and keep stirring at low speed for 10 hours;

4) The appearance of the lost pattern is first immersed in the inner layer of paint, taken out and then dried; after drying, the outer layer of paint is hung and dried;

5) Put the model obtained in step 4) in the sandbox, fill it with dry sand, vibrate and compact it, cover the sandbox with a plastic film and vacuum the sandbox;

6) The molten metal is cast into the model area, the lost foam is gasified, the metal replaces the model, and the casting is taken out after cooling.

Example 3

A lost foam casting process for anti-stick sand cast steel, comprising the following steps:

1) Bond and combine foam models similar in size and shape to castings to form model clusters;

2) Prepare inner coating:

a) Add 20 parts by weight of water to 2 parts by weight of bentonite, and stir at a high speed for 6 hours to obtain bentonite slurry;

b) Add 1 part by weight of water glass, 1.5 parts by weight of sodium carboxymethyl cellulose, 0.3 part by weight of n-octanol, and 0.3 part by weight of fatty alcohol polyoxyethylene ether into 20 parts by weight of water to prepare an aqueous solution;

c) Add the bentonite slurry obtained in step a) and 50 parts by weight of quartz powder to the aqueous solution obtained in step b), and add 50 parts by weight of water under continuous stirring to make an inner coating. The stirring method is: first stir at high speed for 1 hour Then stir at a low speed to discharge the gas involved in the inner coating, and keep stirring at a low speed for 11 hours;

3) Prepare the outer coating:

d) Add 30 parts by weight of water to 3 parts by weight of sodium bentonite, and stir at a high speed for 6 hours to obtain sodium bentonite slurry;

e) Add 0.5 parts by weight of white sol, 1.5 parts by weight of sodium carboxymethyl cellulose, 0.3 parts by weight of n-octanol, and 0.3 parts by weight of fatty alcohol polyoxyethylene ether into 20 parts by weight of water to prepare an aqueous solution;

f) Add the sodium-based bentonite slurry obtained in step d) and 50 parts by weight of high-chromium corundum to the aqueous solution obtained in step e), and add 50 parts by weight of water under continuous stirring to make an outer coating. The stirring method is: first Stir at high speed for 1 hour, then stir at low speed to discharge the gas involved in the outer coating, and keep stirring at low speed for 11 hours;

4) The appearance of the lost pattern is first immersed in the inner layer of paint, taken out and then dried; after drying, the outer layer of paint is hung and dried;

5) Put the model obtained in step 4) in the sandbox, fill it with dry sand, vibrate and compact it, cover the sandbox with a plastic film and vacuum the sandbox;

6) The molten metal is cast into the model area, the lost foam is gasified, the metal replaces the model, and the casting is taken out after cooling.

In the embodiment of the present invention, the outer coating can be hang-coated multiple times, such as 2-5 times, according to the condition of the casting. In addition, in order to reduce the amount of gas generated during pouring and ensure the quality of the casting, the foamed plastic pattern must be dried after being coated with paint to ensure sufficient drying time to dry and thoroughly dry the paint. The temperature is controlled at 40-60 degrees, and the time is 2-8. Hours, if necessary, use microwave drying to complete the drying process in a short time.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the implementation scope of the present invention; if it does not depart from the spirit and scope of the present invention, any modification or equivalent replacement of the present invention shall be covered by the claims of the present invention. within the scope of protection.

Claims (8)

1. The sand adhesion preventing lost foam casting process for the cast steel is characterized by comprising the following steps of:

1) bonding and combining foam models with similar sizes and shapes with the castings to form a model cluster;

2) preparing an inner layer coating:

a) adding water into bentonite, and stirring at a high speed to obtain bentonite slurry;

b) adding water glass, sodium carboxymethylcellulose, n-octanol and fatty alcohol-polyoxyethylene ether into water to prepare an aqueous solution;

c) adding the bentonite slurry and the quartz powder obtained in the step a) into the aqueous solution obtained in the step b), and adding water under continuous stirring to prepare an inner layer coating;

3) preparing an outer layer coating:

d) adding water into sodium bentonite, and stirring at a high speed to obtain sodium bentonite slurry;

e) adding the white sol, sodium carboxymethylcellulose, n-octanol and fatty alcohol-polyoxyethylene ether into water to prepare an aqueous solution;

f) adding the sodium bentonite slurry obtained in the step d) and the high-chromium corundum into the aqueous solution obtained in the step e), and adding water under continuous stirring to prepare an outer layer coating;

4) firstly immersing the lost foam pattern into the inner layer coating, taking out and drying; after drying, coating an outer layer coating in a hanging way, and drying;

5) placing the model obtained in the step 4) in a sandbox, filling dry sand, vibrating to compact, covering a plastic film on the sandbox, and vacuumizing the sandbox;

6) casting the molten metal into a model area, gasifying the lost foam, replacing the model with the metal, and cooling and taking out the casting; wherein,

the mixture ratio of each component for preparing the inner layer coating in the step 2) is as follows: 25-75 parts of quartz powder, 1-3 parts of bentonite, 0.5-1.5 parts of water glass, 0.75-2.25 parts of sodium carboxymethylcellulose, 0.15-0.45 part of n-octanol and 0.15-0.45 part of fatty alcohol-polyoxyethylene ether;

the mixture ratio of the components for preparing the outer layer coating in the step 3) is as follows: 25-75 parts of high-chromium corundum, 1.5-4.5 parts of sodium bentonite, 0.25-0.75 part of white sol, 0.75-2.25 parts of sodium carboxymethylcellulose, 0.15-0.45 part of n-octanol and 0.15-0.45 part of fatty alcohol-polyoxyethylene ether.

2. The sand adhesion preventing cast steel lost foam casting process according to claim 1, wherein the ratio of each component for preparing the inner layer coating in the step 2) is as follows: 50 parts of quartz powder, 2 parts of bentonite, 1 part of water glass, 1.5 parts of sodium carboxymethylcellulose, 0.3 part of n-octanol and 0.3 part of fatty alcohol-polyoxyethylene ether.

3. The sand adhesion preventing cast steel lost foam casting process according to claim 1 or 2, characterized in that in step a), the weight ratio of bentonite to added water is 1: 10; in the step b), the weight ratio of the water glass to the added water is 1: 20; in step c), the weight ratio of the quartz powder to the water added under continuous stirring is 1: 1.

4. The sand adhesion preventing cast steel lost foam casting process according to claim 1, wherein the mixture ratio of the components for preparing the outer coating in the step 3) is as follows: 50 parts of high-chromium corundum, 3 parts of sodium bentonite, 0.5 part of white sol, 1.5 parts of sodium carboxymethylcellulose, 0.3 part of n-octanol and 0.3 part of fatty alcohol-polyoxyethylene ether.

5. The sand adhesion preventing cast steel lost foam casting process according to claim 1 or 4, characterized in that in step d), the weight ratio of sodium bentonite to added water is 1: 10; in the step e), the weight ratio of the white sol to the added water is 1: 40; in step f), the weight ratio of the high-chromium corundum to the water added under continuous stirring is 1: 1.

6. The sand release resistant cast steel lost foam casting process of claim 1, wherein the stirring mode in steps c) and f) is as follows: firstly stirring at a high speed for 1 hour, then stirring at a low speed to discharge gas involved in the inner layer coating and the outer layer coating, and keeping stirring at the low speed for about 10 hours.

7. The sand adhesion preventing cast steel lost foam casting process according to claim 1, wherein in step 4), the outer layer coating is hung 2-5 times.

8. The sand adhesion preventing cast steel lost foam casting process as claimed in claim 1, wherein in the step 4), the drying temperature is 40-60 ℃ and the drying time is 2-8 hours.