Mud core molding sand for casting and preparation method thereof

Abstract

The invention discloses loam core molding sand for casting and a preparation method thereof, and relates to the field of casting. The molding sand is prepared from quartz sand, attapulgite, perlite, sepiolite, glass fibers, aluminum oxide, aminopropyltriethoxysilane, cellulose gum and glycerol monostearate according to specific parts by weight through the processes of step-by-step calcination, grinding, mixing and the like. The molding sand solves the problems that existing molding sand is insufficient in strength, poor in air permeability, large in gas generation amount and the like, has the characteristics that the dry compressive strength is not lower than 8 MPa, the wet compressive strength is not lower than 1.5 MPa, the air permeability index is not lower than 150, and the gas generation amount does not exceed 15 ml / g, and is wide in raw material source, moderate in cost, simple in preparation process and excellent in collapsibility. And the method is suitable for industrial large-scale production and can meet the production requirements of complex castings. The invention has the advantages of high strength, good air permeability, small gas generation amount, excellent collapsibility and simple preparation process.

Description

Technical Field

[0001] The present invention relates to the technical field of casting, in particular to a mud core molding sand for casting and a preparation method thereof. Background Art

[0002] In casting production, mud core sand is the key material for forming the inner cavity structure of the casting, and its performance directly affects the dimensional accuracy, surface quality and internal quality of the casting. At present, the commonly used casting mud core sands mainly include clay sand, water glass sand, resin sand and other types. Clay sand has a low cost, but it has the problems of insufficient strength in the wet state and easy to break after drying. It is prone to core collapse in the production of complex castings. Although water glass sand has high strength, it has poor disintegration, making it difficult to clean the casting, and the residual sand core is difficult to remove, which increases the subsequent processing cost. Resin sand has good strength and disintegration, but it has a large amount of gas emission, which can easily lead to defects such as pores and pinholes in the casting. At the same time, the resin cost is high and it is easy to produce harmful gases at high temperatures, which is not conducive to environmental protection and the health of operators.

[0003] In addition, the air permeability of existing mud core sand is often difficult to meet the production needs of high-demand castings. When the air permeability is insufficient, the gas generated during the pouring process cannot be discharged in time, forming pores inside the casting, reducing the mechanical properties of the casting. At the same time, some molding sands have poor high-temperature stability and are prone to softening and deformation during pouring, resulting in dimensional deviations in the castings. As the foundry industry continues to increase its requirements for casting quality and production efficiency, it is of great practical significance to develop a mud core sand for casting that has high strength, good air permeability, low gas emission, good disintegration and moderate cost, and a preparation method thereof. Summary of the Invention

[0004] In order to solve the above-mentioned problems, the present invention proposes a kind of mud core sand for casting with high strength, good air permeability, small gas emission, excellent disintegration and simple preparation process and its preparation method.

[0005] In order to solve the above technical problems, the technical solution proposed in the present invention is: a mud core sand for casting, which is made of the following raw materials in parts by weight: 200 to 240 parts of quartz sand, 30 to 35 parts of attapulgite, 50 to 55 parts of perlite, 30 to 35 parts of sepiolite, 12 to 17 parts of glass fiber, 30 to 40 parts of alumina, 2 to 3 parts of aminopropyltriethoxysilane, 10 to 12 parts of cellulose gum, and 1 part of stearic acid monoglyceride.

[0006] Preferably, the particle size of the quartz sand is 40 to 70 meshes, the particle size of the flake graphite is 50 meshes, the particle size of the amorphous graphite is 200 meshes, and the particle size of the white mud is 200 meshes.

[0007] Preferably, the glass fiber has a length of 2 to 5 mm and a diameter of 5 to 10 μm.

[0008] Preferably, the purity of the alumina is not less than 95%, and the particle size is 100 to 200 meshes.

[0009] A method for preparing clay core sand for casting comprises the following steps:

[0010] Step 1: Place quartz sand, attapulgite, and perlite in a calcining furnace at 490 to 520 degrees Celsius and calcine for 4 to 5 hours. After taking out, crush them into 200 to 400 mesh powder;

[0011] Step 2: Add aminopropyl triethoxysilane, stearic acid monoglyceride and an appropriate amount of water to the powder obtained in step 1, stir and disperse, then knead the slurry, and then send it into a calcining furnace at 1410 to 1430 degrees Celsius for 4 to 5 hours, take it out and crush it into 50 to 100 mesh to obtain a calcined material;

[0012] Step 3: Mix the sepiolite, glass fiber, alumina, and cellulose gum, and grind and disperse for 30 to 45 minutes to obtain a 100 to 150 mesh powder;

[0013] Step 4: Mix the powder obtained in step 3 with the calcined material obtained in step 2 and other remaining ingredients, add water equivalent to 3% to 6% of the weight of the mixture, and wet mix for 10 to 15 minutes.

[0014] Preferably, the heating rate of the calcining furnace is 5 to 10 degrees Celsius per minute, and the cooling rate is 3 to 5 degrees Celsius per minute.

[0015] Preferably, the grinding and dispersing process in step three uses a planetary ball mill with a ball-to-material ratio of 3:1 to 5:1 and a rotation speed of 200 to 300 revolutions per minute.

[0016] Preferably, the wet mixing process in step 4 uses a double-shaft mixer with a stirring speed of 100 to 150 revolutions per minute and a stirring time of 10 to 15 minutes.

[0017] Preferably, the dry compressive strength of the molding sand is not less than 8 MPa, the wet compressive strength is not less than 1.5 MPa, the permeability index is not less than 150, and the gas evolution amount does not exceed 15 ml / g.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] Excellent and stable performance: The dry compressive strength of the mud core sand is not less than 8 MPa, and the wet compressive strength is not less than 1.5 MPa, which can meet the stress requirements of complex casting molding and reduce core collapse and deformation; the permeability index is not less than 150, which can effectively discharge the pouring gas and avoid defects such as pores and pinholes; the gas emission does not exceed 15 ml per gram, which can reduce casting problems caused by gas, while reducing harm to the environment and operators, and comprehensively guaranteeing the quality of castings.

[0020] The economical efficiency and practicality are outstanding: the raw materials such as quartz sand and attapulgite used are widely available and inexpensive, which is conducive to reducing production costs; the preparation process steps are clear and easy to operate and control, suitable for industrial large-scale production, and can improve production efficiency; and the sand core has excellent disintegration properties and is easy to clean after the casting is formed, which can reduce the workload of subsequent processing, reduce labor intensity, and further optimize production benefits. DETAILED DESCRIPTION

[0021] The present invention is described in further detail below.

[0022] Example 1

[0023] A mud core molding sand for casting is prepared from the following raw materials in parts by weight: 200 parts of quartz sand, 30 parts of attapulgite, 50 parts of perlite, 30 parts of sepiolite, 12 parts of glass fiber, 30 parts of aluminum oxide, 2 parts of aminopropyltriethoxysilane, 10 parts of cellulose gum, and 1 part of stearic acid monoglyceride.

[0024] The preparation method is as follows:

[0025] Step 1: calcining quartz sand, attapulgite, and perlite in a calcining furnace at 490 degrees Celsius for 4 hours at a heating rate of 5 degrees Celsius per minute and a cooling rate of 3 degrees Celsius per minute. After taking out, crush into 200 mesh powder;

[0026] Step 2: Add aminopropyl triethoxysilane, stearic acid monoglyceride and an appropriate amount of water to the powder obtained in step 1, stir and disperse, and then perform mud kneading. Then, send it into a calcining furnace at 1410 degrees Celsius and calcine for 4 hours. The heating rate of the calcining furnace is 5 degrees Celsius per minute and the cooling rate is 3 degrees Celsius per minute. Take it out and crush it into 50 mesh to obtain a calcined material;

[0027] Step 3: Mix sepiolite, glass fiber, alumina, and cellulose gum, and grind and disperse them in a planetary ball mill for 30 minutes at a ball-to-material ratio of 3:1 and a rotation speed of 200 rpm to obtain a 100-mesh powder;

[0028] Step 4: Mix the powder obtained in step 3 with the calcined material obtained in step 2 and other remaining ingredients, add water equivalent to 3% of the weight of the mixture, and use a twin-shaft mixer to wet mix for 10 minutes at a stirring speed of 100 revolutions per minute.

[0029] According to tests, the molding sand prepared in this embodiment has a dry compressive strength of 8.2 MPa, a wet compressive strength of 1.6 MPa, an air permeability index of 155, and a gas evolution amount of 14 ml / g.

[0030] Example 2

[0031] A mud core molding sand for casting is prepared from the following raw materials in parts by weight: 220 parts of quartz sand, 33 parts of attapulgite, 53 parts of perlite, 33 parts of sepiolite, 15 parts of glass fiber, 35 parts of aluminum oxide, 2.5 parts of aminopropyltriethoxysilane, 11 parts of cellulose gum, and 1 part of stearic acid monoglyceride.

[0032] The preparation method is as follows:

[0033] Step 1: calcining quartz sand, attapulgite, and perlite in a calcining furnace at 505 degrees Celsius for 4.5 hours at a heating rate of 8 degrees Celsius per minute and a cooling rate of 4 degrees Celsius per minute. After taking out, crush into 300 mesh powder;

[0034] Step 2: Add aminopropyl triethoxysilane, stearic acid monoglyceride and an appropriate amount of water to the powder obtained in step 1, stir and disperse, then knead the mud, and then send it into a calcining furnace at 1420 degrees Celsius for 4.5 hours. The heating rate of the calcining furnace is 8 degrees Celsius per minute and the cooling rate is 4 degrees Celsius per minute. Take it out and crush it into 75 mesh to obtain a calcined material;

[0035] Step 3: Mix the sepiolite, glass fiber, alumina, and cellulose gum, and grind and disperse them in a planetary ball mill for 38 minutes at a ball-to-material ratio of 4:1 and a rotation speed of 250 rpm to obtain a 125-mesh powder;

[0036] Step 4: Mix the powder obtained in step 3 with the calcined material obtained in step 2 and other remaining ingredients, add water equivalent to 4.5% of the weight of the mixture, and use a twin-shaft mixer to wet mix for 13 minutes at a stirring speed of 125 revolutions per minute.

[0037] According to tests, the molding sand prepared in this embodiment has a dry compressive strength of 8.5 MPa, a wet compressive strength of 1.7 MPa, an air permeability index of 160, and a gas evolution amount of 13 ml / g.

[0038] Example 3

[0039] A mud core molding sand for casting is prepared from the following raw materials in parts by weight: 240 parts of quartz sand, 35 parts of attapulgite, 55 parts of perlite, 35 parts of sepiolite, 17 parts of glass fiber, 40 parts of aluminum oxide, 3 parts of aminopropyltriethoxysilane, 12 parts of cellulose gum, and 1 part of stearic acid monoglyceride.

[0040] The preparation method is as follows:

[0041] Step 1: calcining quartz sand, attapulgite, and perlite in a calcining furnace at 520 degrees Celsius for 5 hours at a heating rate of 10 degrees Celsius per minute and a cooling rate of 5 degrees Celsius per minute. After taking out, crush into 400 mesh powder;

[0042] Step 2: Add aminopropyl triethoxysilane, stearic acid monoglyceride and an appropriate amount of water to the powder obtained in step 1, stir and disperse, then knead the mud, and then send it into a calcining furnace at 1430 degrees Celsius for calcining for 5 hours. The heating rate of the calcining furnace is 10 degrees Celsius per minute and the cooling rate is 5 degrees Celsius per minute. Take it out and crush it into 100 mesh to obtain a calcined material;

[0043] Step 3: Mix the sepiolite, glass fiber, alumina, and cellulose gum, and grind and disperse them in a planetary ball mill for 45 minutes at a ball-to-material ratio of 5:1 and a rotation speed of 300 rpm to obtain a 150-mesh powder;

[0044] Step 4: Mix the powder obtained in step 3 with the calcined material obtained in step 2 and other remaining ingredients, add water equivalent to 6% of the weight of the mixture, and use a twin-shaft mixer to wet mix for 15 minutes at a stirring speed of 150 revolutions per minute.

[0045] According to tests, the molding sand prepared in this embodiment has a dry compressive strength of 8.8 MPa, a wet compressive strength of 1.8 MPa, an air permeability index of 165, and a gas evolution amount of 12 ml / g.

[0046] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A clay core sand for casting, characterized in that: The invention is made from the following raw materials in parts by weight: 200 to 240 parts of quartz sand, 30 to 35 parts of attapulgite, 50 to 55 parts of perlite, 30 to 35 parts of sepiolite, 12 to 17 parts of glass fiber, 30 to 40 parts of aluminum oxide, 2 to 3 parts of aminopropyltriethoxysilane, 10 to 12 parts of cellulose gum, and 1 part of stearic acid monoglyceride.

2. The clay core sand for casting according to claim 1, characterized in that: The particle size of the quartz sand is 40 to 70 meshes, the particle size of the flake graphite is 50 meshes, the particle size of the amorphous graphite is 200 meshes, and the particle size of the white mud is 200 meshes.

3. The clay core sand for casting according to claim 1, characterized in that: The glass fibers have a length of 2 to 5 mm and a diameter of 5 to 10 μm.

4. The clay core sand for casting according to claim 1, characterized in that: The purity of the aluminum oxide is not less than 95%, and the particle size is 100 to 200 meshes.

5. The method for preparing clay core sand for casting according to claim 1, wherein: The following steps are involved: Step 1: Place quartz sand, attapulgite, and perlite in a calcining furnace at 490 to 520 degrees Celsius and calcine for 4 to 5 hours. After taking out, crush them into 200 to 400 mesh powder; Step 2: Add aminopropyl triethoxysilane, stearic acid monoglyceride and an appropriate amount of water to the powder obtained in step 1, stir and disperse, then knead the slurry, and then send it into a calcining furnace at 1410 to 1430 degrees Celsius for 4 to 5 hours, take it out and crush it into 50 to 100 mesh to obtain a calcined material; Step 3: Mix the sepiolite, glass fiber, alumina, and cellulose gum, and grind and disperse for 30 to 45 minutes to obtain a 100 to 150 mesh powder; Step 4: Mix the powder obtained in step 3 with the calcined material obtained in step 2 and other remaining ingredients, add water equivalent to 3% to 6% of the weight of the mixture, and wet mix for 10 to 15 minutes.

6. The preparation method according to claim 5, characterized in that: The calcining furnace has a heating rate of 5 to 10 degrees Celsius per minute and a cooling rate of 3 to 5 degrees Celsius per minute.

7. The preparation method according to claim 5, characterized in that: The grinding and dispersing process in step 3 uses a planetary ball mill with a ball-to-material ratio of 3:1 to 5:1 and a rotation speed of 200 to 300 revolutions per minute.

8. The preparation method according to claim 5, characterized in that: The wet mixing process in step 4 uses a double-shaft mixer with a stirring speed of 100 to 150 revolutions per minute and a stirring time of 10 to 15 minutes.

9. The casting core sand and the preparation method thereof according to any one of claims 1 to 8, characterized in that: The dry compressive strength of the molding sand is not less than 8 MPa, the wet compressive strength is not less than 1.5 MPa, the permeability index is not less than 150, and the gas evolution volume does not exceed 15 ml / g.