Small graphite crucible and preparation method thereof

Abstract

The invention relates to the technical field of crucible preparation, in particular to a small graphite crucible and a preparation method thereof. Comprising the following components in percentage by mass: 30-50% of graphite; 30%-50% of low-moisture clay; 5%-15% of high bauxite; 1%-10% of a binding agent; wherein the binding agent is hydrogel or lignin. The preparation method of the small graphite crucible comprises the following steps: S1, taking a proper amount of graphite, low-moisture clay, high-alumina bauxite and a binding agent, and uniformly mixing the graphite, the low-moisture clay, the high-alumina bauxite and the binding agent; s2, loading the uniformly mixed powder in the step S1 into a two-way pressurizing mold, and carrying out compression molding; and S3, carrying out drying and firing treatment on a green body subjected to compression molding. The production period is greatly shortened through proper formula design and a redesigned pressing method. And moreover, under the condition that the production procedures are greatly reduced, the product quality can be effectively controlled only by effectively managing key procedures, and the degree of dependence on manpower is low.

Description

Technical Field

[0001] The present invention relates to the technical field of crucible preparation, and in particular to a small graphite crucible and a preparation method thereof. Background Art

[0002] In the metallurgical industry, crucibles are the core containers for high-temperature smelting and are widely used in the smelting process of alloy tool steel and non-ferrous metal alloys.

[0003] The current method for making small graphite clay crucibles mainly follows the following process: first, sufficient water is added to the main raw materials of graphite and clay. After simple mixing, the crucible is put into an extruder to be extruded into mud strips. The mud strips are then piled into piles and sealed for a period of time (this time generally takes about a month). After a long period of storage, the mud strips are taken out and put into a large mill for adding water and crushing. It takes about one to two hours, and water needs to be added several times in the middle. After the mud is crushed to meet the standard, the mud is put into a crusher. After crushing, the mud will form mud particles of relatively uniform size. At this point, the raw materials that can be used to make crucibles are prepared.

[0004] Traditionally, small graphite clay crucibles are formed using two main methods: rotational molding, where workers use a rotary machine to drive the mold and use internal knives to squeeze the clay into the crucible. Compression molding, on the other hand, uses hydraulic, water, or air pressure as kinetic energy to form the crucible using a steel mold. These crucibles need to be left to rest for at least a week after forming to allow the body to gradually lose moisture. Only when the moisture content reaches a certain level can they be fired in a kiln, ultimately creating the finished crucible.

[0005] Traditional small graphite crucibles have defects such as long production cycle, low efficiency, high dependence on workers, and unstable product quality.

[0006] Prior art patent CN102249237B discloses a graphite crucible that incorporates liquid asphalt into the raw material. The calcined graphite crucible is then impregnated with the liquid asphalt in an impregnation tank. This results in a denser surface, making it difficult for liquid metal to penetrate, significantly improving the crucible's lifespan. However, liquid asphalt is prone to "surface encrustation" during the high-pressure impregnation process. Furthermore, the addition of asphalt to the raw material during calcination produces toxic substances. Furthermore, the disposal cost of the used asphalt-impregnated crucible is higher. Summary of the Invention

[0007] The present invention provides a small graphite crucible and a preparation method thereof, so as to solve the technical problems of traditional small graphite crucibles in the prior art, such as long production cycle, low efficiency, high dependence on workers, unstable product quality and the like.

[0008] To solve the above problems, a small graphite crucible and its preparation method provided by the present invention adopt the following technical solutions:

[0009] A small graphite crucible, comprising components in the following mass percentages:

[0010] Graphite: 30%-50%;

[0011] Low-moisture clay: 30%-50%;

[0012] High-alumina bauxite: 5%-15%;

[0013] Binder: 1%-10%;

[0014] Among them, the binder is a hydrogel or lignin.

[0015] Further, the water content of the low-moisture clay is less than 5%.

[0016] Further, the content of iron oxide in the high-alumina bauxite is less than 3%.

[0017] Further, the particle size of the graphite is 90-110 mesh; the particle size of the low-moisture clay is 190-210 mesh; the particle size of the high-alumina bauxite is 0.3-0.8 mm.

[0018] The preparation method of the above small graphite crucible comprises the following steps:

[0019] S1. Take appropriate amounts of graphite, low-moisture clay, high-alumina bauxite and binder and mix them evenly;

[0020] S2. Load the evenly mixed powder in S1 into a two-way pressing mold and press it into shape;

[0021] S3. Perform drying and firing treatment on the pressed green body.

[0022] Further, in S1, the moisture content of the mixed materials is less than 10%.

[0023] Further, in S2, when the two-way pressing mold is pressing, the pressure is 5-15 MPa, and the pressure ratio of the upper punch and the lower punch is 1:1.

[0024] Further, in S2, it is necessary to keep the pressure for 5 s-60 s before demolding after pressing.

[0025] Further, in S2, the flexural strength of the green body formed after demolding is 1-2 MPa.

[0026] Further, in S3, during the firing and drying treatment, the drying temperature is 200 °C and the drying time is 48 h;

[0027] During firing, the firing temperature is 1000 - 1200 °C, and the total firing time is 30 h.

[0028] Further, in S3, the density of the fired and formed small graphite crucible is 2 - 2.2 g / cm 3 , the flexural strength is 3 - 4 MPa, and the difference in porosity between the upper and lower surfaces of the bottom of the small graphite crucible is less than 2%.

[0029] The beneficial effects of the small graphite crucible and its preparation method provided by the present invention are as follows:

[0030] 1. In the present invention, through appropriate formulation design and redesigned pressing method, it is achieved that: after the raw materials are kneaded, they can be pressed and formed only after one day of aging. The pressed products can be dried and fired into finished products after a short period of placement, greatly shortening the production cycle. The new press has a high degree of automation, and the production efficiency is 2 to 3 times that of the traditional production method. Moreover, when the production process is greatly reduced, only the key processes need to be effectively managed to achieve effective control of product quality.

[0031] 2. In the present invention, the particle sizes of graphite (90 - 110 mesh), clay (190 - 210 mesh), and bauxite (0.3 - 0.8 mm) are matched. The fine - grained clay fills the gaps between the coarse particles, improving the density. The medium - grained bauxite enhances the skeleton support effect. The porosity is reduced, and the density and mechanical strength after sintering are improved.

[0032] In addition, a hydrogel is used as an environmentally friendly binder. The three - dimensional network structure of the hydrogel forms a composite system with graphite particles, enhancing the binding strength through physical adsorption or chemical bonding. Its high elasticity can absorb stress, reduce crack propagation, and improve the overall impact resistance of the crucible. The dual selection of hydrogel and lignin as binders takes into account both environmental protection and cost requirements.

[0033] 3. In the present invention, two - way pressing is achieved (pressure 5 - 15 MPa, the pressure ratio of the upper and lower punches is 1:1). After pressing, the pressure is maintained for 5 - 60 seconds. The flexural strength of the green body after demolding reaches 1 - 2 MPa, significantly improving the production efficiency and product consistency. After firing, the density of the crucible reaches 2 - 2.2 g / cm 3 , the flexural strength is 3 - 4 MPa, significantly higher than that of traditional crucibles, improving the service life and reliability. The difference in porosity between the upper and lower surfaces of the bottom is less than 2%, reducing the thermal stress concentration caused by uneven pores and lowering the cracking risk. Description of the Drawings

[0034] By reading the following detailed description with reference to the accompanying drawings, the above and other objects, features, and advantages of the exemplary embodiments of the present invention will become readily understood. In the drawings, several embodiments of the present invention are shown in an exemplary rather than restrictive manner, and the same or corresponding reference numerals denote the same or corresponding parts, wherein:

[0035] Figure 1 It is a physical diagram of the finished graphite crucible after the high-temperature resistance test in Example 1 of the present invention;

[0036] Figure 2 It is a physical diagram of the finished graphite crucible after the high-temperature resistance test in Comparative Example 1 of the present invention. Detailed Embodiments

[0037] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Those skilled in the art should know that the embodiments described below are a part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts fall within the scope of protection of the present invention.

[0038] The quantity of any element in the drawings is for illustration rather than limitation, and any naming is only for distinction and does not have any limiting meaning.

[0039] Next, with reference to several representative embodiments of the present invention, the principles and spirit of the present invention will be elaborated in detail.

[0040] Example 1:

[0041] A small graphite crucible provided in this embodiment includes components with the following mass percentages:

[0042] Graphite: 30%;

[0043] Low-moisture clay: 45%; wherein, the water content of the low-moisture clay is less than 5%.

[0044] High-alumina bauxite: 15%; wherein, the iron oxide content in the high-alumina bauxite is less than 3%

[0045] Hydrogel: 10%; <(

[0046] In this embodiment, the hydrogel is an environmentally friendly binder produced by Binxia New Materials Co., Ltd. in Zouping City. Among them, the particle size of the graphite is 90 - 110 mesh; the particle size of the low-moisture clay is 190 - 210 mesh; the particle size of the high-alumina bauxite is 0.3 - 0.8 mm.

[0047] The preparation method of the small graphite crucible with the above components includes the following steps:

[0048] S1. Weigh graphite, low-moisture clay, bauxite and binder according to the above proportions and mix them evenly through a mixer. The moisture content of the evenly mixed material is less than 10%.

[0049] S2. Load the evenly mixed powder in S1 into a two-way pressing die and press it into shape. Among them, the pressure during pressing of the two-way pressing die is 5 MPa, and the pressure ratio of the upper punch and the lower punch is 1:1.

[0050] The diameter of the green body after pressing is 70 mm, the thickness is 9 mm, and the height is 80 mm.

[0051] Among them, after the green body is pressed, it needs to be pressure-held for 60 s before demolding. The flexural strength of the green body formed after demolding is 1 - 2 MPa.

[0052] S3. Just perform drying and firing treatment on the green body pressed into shape.

[0053] Among them, during the drying and firing treatment, the maximum drying temperature is 200 °C, and the drying time is 48 h.

[0054] During firing, the firing temperature is 1000 - 1200 °C, and the total firing time is 30 h.

[0055] Example 2:

[0056] A small graphite crucible provided in this example includes components with the following mass percentages:

[0057] Graphite: 50%;

[0058] Low-moisture clay: 44%; among them, the water content of the low-moisture clay is less than 5%.

[0059] Bauxite: 5%; among them, the iron oxide content in the bauxite is less than 3%

[0060] Hydrogel: 1%;

[0061] In this example, the hydrogel is an environmentally friendly binder produced by Binxia New Materials Co., Ltd. in Zouping City. Among them, the particle size of the graphite is 90 - 110 mesh; the particle size of the low-moisture clay is 190 - 210 mesh; the particle size of the bauxite is 0.3 - 0.8 mm.

[0062] The preparation method of the small graphite crucible with the above components includes the following steps:

[0063] S1. Weigh graphite, low-moisture clay, bauxite and binder according to the above proportions and mix them evenly through a mixer. The moisture content of the evenly mixed material is less than 10%.

[0064] S2. Load the uniformly mixed powder in S1 into a two-way pressing mold and press it into shape. Among them, the pressure during pressing with the two-way pressing mold is 10 MPa, and the pressure ratio of the upper punch to the lower punch is 1:1.

[0065] The diameter of the green compact after pressing is 85 mm, the thickness is 10 mm, and the height is 100 mm.

[0066] Among them, after the green compact is pressed, it needs to be pressure-held for 30 s before demolding. The flexural strength of the green compact formed after demolding is 1 - 2 MPa.

[0067] S3. Just perform drying and firing treatment on the green compact pressed into shape.

[0068] Among them, during the drying and firing treatment, the maximum drying temperature is 200 °C, and the drying time is 48 h.

[0069] During firing, the firing temperature is 1000 - 1200 °C, and the total firing time is 30 h.

[0070] Example 3

[0071] A small graphite crucible provided in this example includes components with the following mass percentages:

[0072] Graphite: 42%;

[0073] Low-moisture clay: 50%; among them, the water content of the low-moisture clay is less than 5%.

[0074] High-aluminum bauxite: 6%; among them, the iron oxide content in the high-aluminum bauxite is less than 3%

[0075] Hydrogel: 2%;

[0076] In this example, the hydrogel is an environmentally friendly binder produced by Binxia New Materials Co., Ltd. in Zouping City. Among them, the particle size of the graphite is 90 - 110 mesh; the particle size of the low-moisture clay is 190 - 210 mesh; the particle size of the high-aluminum bauxite is 0.3 - 0.8 mm.

[0077] The preparation method of the small graphite crucible with the above components includes the following steps:

[0078] S1. Weigh graphite, low-moisture clay, high-aluminum bauxite and binder according to the above ratio and mix them evenly through a mixer. The moisture content of the evenly mixed material is less than 10%.

[0079] S2. Load the uniformly mixed powder in S1 into a two-way pressing mold and press it into shape. Among them, the pressure during pressing with the two-way pressing mold is 15 MPa, and the pressure ratio of the upper punch to the lower punch is 1:1.

[0080] The diameter of the green compact formed by pressing is 105 mm, the thickness is 11 mm, and the height is 120 mm.

[0081] Among them, after the green compact is pressed and before demolding, it needs to be pressure-held for 30 s. The flexural strength of the green compact formed after demolding is 1-2 MPa.

[0082] S3. Just perform drying and firing treatment on the green compact formed by pressing.

[0083] Among them, during the drying and firing treatment, the maximum drying temperature is 200 °C, and the drying time is 48 h.

[0084] During firing, the firing temperature is 1000-1200 °C, and the total firing time is 30 h.

[0085] Example 4

[0086] A small graphite crucible provided in this example includes components with the following mass percentages:

[0087] Graphite: 50%;

[0088] Low-moisture clay: 30%; among them, the water content of the low-moisture clay is less than 5%.

[0089] High-alumina bauxite: 10%; among them, the iron oxide content in the high-alumina bauxite is less than 3%

[0090] Hydrogel: 10%;

[0091] In this example, the hydrogel is an environmentally friendly binder produced by Zouping Binxia New Materials Co., Ltd. Among them, the particle size of the graphite is 90-110 mesh; the particle size of the low-moisture clay is 190-210 mesh; the particle size of the high-alumina bauxite is 0.3-0.8 mm.

[0092] The preparation method of the small graphite crucible with the above components includes the following steps:

[0093] S1. Weigh graphite, low-moisture clay, high-alumina bauxite and binder according to the above ratio and mix them evenly by a mixer. The moisture content of the evenly mixed material is less than 10%.

[0094] S2. Load the evenly mixed powder in S1 into a bi-directional pressing mold and press it into shape. Among them, the pressure during pressing by the bi-directional pressing mold is 5 MPa, and the pressure ratio of the upper punch and the lower punch is 1:1.

[0095] The diameter of the green compact formed by pressing is 70 mm, the thickness is 9 mm, and the height is 80 mm.

[0096] Among them, after the green compact is pressed and before demolding, it needs to be pressure-held for 1 s. The flexural strength of the green compact formed after demolding is 1-2 MPa.

[0097] S3. Just perform the drying and firing treatment on the compression-molded green body.

[0098] Among them, during the drying and firing treatment, the maximum drying temperature is 200 °C, and the drying time is 48 h.

[0099] During firing, the firing temperature is 1000 - 1200 °C, and the total firing time is 30 h.

[0100] Example 5

[0101] A small graphite crucible provided in this example includes components with the following mass percentages:

[0102] Graphite: 44%;

[0103] Low-moisture clay: 38%; among them, the water content of the low-moisture clay is less than 5%.

[0104] High-aluminum bauxite: 12%; among them, the iron oxide content in the high-aluminum bauxite is less than 3%

[0105] Lignin: 6%;

[0106] In this example, the lignin is the lignin liquid produced by Jinan Shengquan Group Co., Ltd. and the model is SQBS-1.

[0107] Among them, the particle size of the graphite is 90 - 110 mesh; the particle size of the low-moisture clay is 190 - 210 mesh; the particle size of the high-aluminum bauxite is 0.3 - 0.8 mm.

[0108] The preparation method of the small graphite crucible with the above components includes the following steps:

[0109] S1. Weigh graphite, low-moisture clay, high-aluminum bauxite and binder according to the above ratio and mix them evenly through a mixer. The moisture content of the evenly mixed material is less than 10%.

[0110] S2. Load the evenly mixed powder in S1 into a two-way pressure die for compression molding. Among them, the pressure during the compression of the two-way pressure die is 5 MPa, and the pressure ratio of the upper punch and the lower punch is 1:1.

[0111] The diameter of the compression-molded green body is 70 mm, the thickness is 9 mm, and the height is 80 mm.

[0112] Among them, it is necessary to maintain pressure for 20 s before demolding after the green body is pressed. The flexural strength of the green body formed after demolding is 1 - 2 MPa.

[0113] S3. Just perform the drying and firing treatment on the compression-molded green body.

[0114] Among them, during the firing and drying process, the maximum drying temperature is 200°C, and the drying time is 48 hours.

[0115] During firing, the firing temperature is 1000 - 1200°C, and the total firing time is 30 hours.

[0116] Comparative Example 1

[0117] A small graphite crucible was prepared by a traditional process. Graphite 40%, clay 50%, and bauxite 10% were weighed in proportion.

[0118] The preparation method includes the following steps:

[0119] S1. Add sufficient water to the above-mentioned proportion of materials and preliminarily knead them into a uniform mud state.

[0120] S2. Put the mixed mud into an extrusion machine and extrude mud strips with a diameter of about 5 - 10 cm.

[0121] S3. Stack the mud strips, cover them with a plastic film and seal them for 1 month of aging to promote the uniform distribution of moisture and the decomposition of organic matter.

[0122] S4. Put the aged mud strips into a large rolling mill, add water while rolling, and continue for 1 - 2 hours.

[0123] S5. The rolled mud is crushed by a crusher to form uniform mud particles.

[0124] S6. The mud particles are the raw materials for crucible pressing, and the forming method is rotational molding, that is, the worker uses a rotational canning machine to drive the plastic mold to rotate and uses an internal knife to extrude the mud to complete the crucible shaping.

[0125] The diameter of the green body after pressing is 85 mm, the thickness is 10 mm, and the height is 10 mm.

[0126] S7. Place the green body for one week to allow the body to gradually lose moisture, and then enter the kiln for firing at a temperature of 1100 - 1300°C for 30 - 40 hours.

[0127] Comparative Example 2

[0128] A small graphite crucible was prepared by a traditional process. Graphite 40%, clay 50%, and bauxite 10% were weighed in proportion.

[0129] The preparation method includes the following steps:

[0130] S1. Add sufficient water to the above-mentioned proportion of materials and preliminarily knead them into a uniform mud state.

[0131] S2. Put the mixed mud into an extrusion machine and extrude mud strips with a diameter of about 5 - 10 cm.

[0132] S3. Stack the clay strips, cover them with plastic film and seal for 1 month of aging to promote the uniform distribution of moisture and the decomposition of organic matter.

[0133] S4. Put the aged clay strips into a large rolling mill, add water while rolling, and continue for 1 - 2 h.

[0134] S5. The rolled clay material is crushed by a crusher to form uniform clay particles;

[0135] S6. The clay particles are used as raw materials for crucible pressing, and the molding method is selected as compression molding;

[0136] The diameter of the green body formed by compression molding is 85 mm, the thickness is 10 mm, and the height is 10 mm.

[0137] S7. Place the green body for one week to allow the embryo body to gradually lose moisture, and then enter the kiln for firing at a temperature of 1100 - 1300 °C for 30 - 40 h.

[0138] Experimental example:

[0139] Take the small graphite crucibles prepared in Examples 1 - 5 and Comparative Examples 1 - 2 for measurement. The results are shown in the following table.

[0140]

[0141] Take the finished graphite crucible in Example 1 and the crucible in Comparative Example 1 for high-temperature resistance test. The temperature is raised to 1650 °C. Among them, the finished crucible in Example 1 has a fast heating rate and good appearance without cracks. The crucible in Comparative Example 1 has a slow heating rate and damaged appearance with cracks.

[0142] Comparative analysis:

[0143] In Examples 1 - 5 of the present invention, the density is 2 - 2.2 g / cm 3 , and the flexural strength is high. The density is increased by 15% - 23%, the structure is more compact, and the anti-permeability and thermal conductivity are better. The upper limit of strength is increased by 33%, and the durability is enhanced. In the examples of the present invention, through bi-directional isostatic pressing (5 - 15 MPa) and particle size optimization (graphite 90 - 110 mesh + clay 190 - 210 mesh), the particle packing is tighter and the pores are reduced. The binder (hydrogel / lignin) is uniformly dispersed and forms a stable network structure after sintering.

[0144] In Examples 1 - 5 of the present invention, the difference in porosity is less than 2%: The bi-directional pressing + pressure holding process (5 - 60 s) ensures that the density gradient of the green body is extremely small, avoiding the density stratification problem of the traditional single pressing process (the porosity difference in the comparative example is greater than 2.2%).

[0145] The crucible of the embodiment of the present invention has high-temperature stability, can avoid the risk of melting through, and is suitable for the smelting of superalloys.

[0146] As described above, it is only the preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent replacements or changes, and should be covered by the protection scope of the present invention.

Claims

1. A small graphite crucible, characterized in that, Comprising components with the following mass percentages: Graphite: 30% - 50%; Low - moisture clay: 30% - 50%; High - alumina bauxite: 5% - 15%; Binder: 1% - 10%; Among them, the binder is a hydrogel or lignin.

2. The small graphite crucible according to claim 1, wherein The water content of the low - moisture clay is less than 5%.

3. The small graphite crucible according to claim 1, wherein The content of iron oxide in the high - alumina bauxite is less than 3%.

4. The small graphite crucible according to claim 1, wherein, The particle size of the graphite is 90 - 110 mesh; the particle size of the low - moisture clay is 190 - 210 mesh; the particle size of the high - alumina bauxite is 0.3 - 0.8 mm.

5. The preparation method of the small graphite crucible according to any one of claims 1-4, characterized in that, Including the following steps: S1. Take appropriate amounts of graphite, low - moisture clay, high - alumina bauxite and binder and mix them evenly; S2. Load the evenly - mixed powder in S1 into a double - sided pressing die and press it into shape; S3. Bake and fire the pressed green body.

6. The preparation method of the small graphite crucible according to claim 3, characterized in that, In S1, the moisture content of the mixed materials is less than 10%.

7. The preparation method of the small graphite crucible according to claim 3, characterized in that, In S2, when the double - sided pressing die is pressing, the pressure is 5 - 15 MPa, and the pressure ratio of the upper punch to the lower punch is 1∶1.

8. The preparation method of the small graphite crucible according to claim 3, characterized in that In S2, it is necessary to keep the pressure for 5 s - 60 s before demolding after pressing; In S2, the flexural strength of the green body formed after demolding is 1 - 2 MPa.

9. The preparation method of the small graphite crucible according to claim 3, characterized in that, In S3, during the baking and firing treatment, the drying temperature is 200 °C and the drying time is 48 h; During firing, the firing temperature is 1000 - 1200 °C and the total firing time is 30 h.

10. The preparation method of the small graphite crucible according to claim 3, characterized in that, In S3, the density of the fired and formed small graphite crucible is 2 - 2.2 g / cm 3 , the flexural strength is 3 - 4 MPa, and the difference in porosity between the upper and lower surfaces of the bottom of the small graphite crucible is less than 2%.

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