阅读说明：本技术 一种冶金铸造炉用碳纤维石墨坩埚及其制备方法 (Carbon fiber graphite crucible for metallurgical casting furnace and preparation method thereof ) 是由 闵洁 张培林 庞中海 武建军 雷涛 刘伟凯 纪永良 霍有 张彦举 于 2019-09-02 设计创作，主要内容包括：本发明涉及石墨坩埚材料的技术领域,特别是涉及一种冶金铸造炉用碳纤维石墨坩埚及其制备方法,其制备工艺科学,原料选择合理,可以提高石墨坩埚的各项理化性能；包括骨料、粉料和粘结剂,骨料为针状石油焦,粉料由碳纤维、沥青焦和炭黑成,粘结剂由中温煤沥青和改性煤沥青组成,骨料与粉料的组合和粘结剂的重量比为(70~75)：(25~30),骨料与粉料的重量比为(60~70)：(30~40)；其制备方法包括原料的碾磨筛分配料、混捏、预成型、破碎、磨粉、筛分、混合、等静压成型、炭化、浸渍、二次炭化、二次浸渍、固化、石墨化、喷涂料和三次炭化。(The invention relates to the technical field of graphite crucible materials, in particular to a carbon fiber graphite crucible for a metallurgical casting furnace and a preparation method thereof, the preparation process is scientific, the raw materials are reasonably selected, various physical and chemical properties of the graphite crucible can be improved, the carbon fiber graphite crucible comprises aggregate, powder and a binder, the aggregate is needle-shaped petroleum coke, the powder is prepared from carbon fiber, pitch coke and carbon black, the binder is prepared from medium-temperature coal pitch and modified coal pitch, the weight ratio of the aggregate to the powder and the binder is (70 ~ 75) to (25 ~ 30), the weight ratio of the aggregate to the powder is (60 ~ 70) to (30 ~ 40), and the preparation method comprises the steps of grinding, screening and batching, mixing and kneading, crushing, grinding, sieving, pre-forming, isostatic pressing, carbonization, impregnation, secondary carbonization, secondary impregnation, solidification, graphitization, spraying and tertiary carbonization of the raw materials.)

1. The carbon fiber graphite crucible for the metallurgical casting furnace is characterized by comprising aggregate, powder and a binder, wherein the aggregate is acicular petroleum coke, the powder consists of carbon fibers, pitch coke and carbon black, the binder consists of medium-temperature coal pitch and modified coal pitch, the weight ratio of the aggregate to the powder to the binder is (70 ~ 75): (25 ~ 30), and the weight ratio of the aggregate to the powder is (60 ~ 70): (30 ~ 40).

2. The carbon fiber graphite crucible for the metallurgical casting furnace as claimed in claim 1, wherein the weight ratio of the aggregate to the powder and the binder is preferably 72: 28.

3. the carbon fiber graphite crucible for the metallurgical casting furnace as claimed in claim 1, wherein the carbon fiber, the pitch coke and the carbon black are added in a weight ratio of 30:40: 30.

4. The method for preparing the carbon fiber graphite crucible for the metallurgical casting furnace as claimed in claim 1, which comprises the following steps:

(1) grinding and screening ingredients: processing the aggregate and the powder into required particle size by grinding equipment, and proportioning the materials after screening;

(2) kneading: adding the graded ingredients into a kneading pot for stirring;

(3) preforming: pouring the kneaded paste into a forming container, and performing pre-pressing forming to obtain a blank;

(4) crushing, namely crushing the pre-pressed and molded blank by using a crusher, wherein the crushed granularity is 100 ~ 250 mu m;

(5) grinding, namely grinding the crushed blank by using a grinder, wherein the grain size of the ground powder is 15 ~ 35 mu m;

(6) screening: the powder after being milled is screened and classified and is stored in separate bins, wherein the powder at each level accounts for the following proportions:

15~20μm 30%；

20~25μm 30%；

25~35μm 40%；

(7) mixing: uniformly mixing the graded powder by using a cyclone mixer;

(8) isostatic pressing, namely filling the uniformly mixed powder into a rubber mould, sealing the rubber mould, and carrying out cold isostatic pressing to obtain a molded green body with the volume density of 1.8 ~ 2.2.2 g/cm³；

(9) Carbonizing: filling metallurgical coke powder in the formed green body, vibrating, filling the green body into a carbonization furnace, filling the furnace with the coke powder, quartz sand and river sand, introducing inert gas into the furnace, and carbonizing the green body under the condition of isolating air;

(10) impregnating, namely preheating the carbonized product to 300 ~ 350 ℃, keeping the temperature for 8 hours, putting the carbonized product into an impregnating tank, vacuumizing the impregnating tank, pressurizing the carbonized product for 2.5 hours under the pressure of 3MPa ~ 5MPa, injecting an impregnant into the impregnating tank, and maintaining the pressure for 2 hours to ensure that the impregnant impregnates asphalt to impregnate the pores of the carbonized product for impregnation;

(11) secondary carbonization, namely putting the dipped product into a carbonization furnace for secondary carbonization at the temperature of 20 ℃ of ~ 1200 ℃ and keeping the temperature at the temperature of 1200 ℃ for 48 hours, wherein the carbonization time is 550 ~ 660 hours, and naturally cooling the product to normal temperature and discharging the product;

(12) secondary impregnation: placing the product after the secondary carbonization in an impregnation tank, and carrying out secondary impregnation to ensure that the impregnating agent impregnating pitch is immersed in the pores of the product;

(13) curing, namely drying the dipped product at 85 ~ 95 ℃, putting the product into a curing furnace for pressurizing and curing, wherein the curing pressure is 2MPa ~ 5MPa, the heating speed is 5 ℃/h ~ 10 ℃/h, the curing temperature is 140 ℃ ~ 180 ℃, and the heat preservation time is 3h ~ 6 h;

(14) graphitizing, namely putting the cured product into a graphitizing furnace, uniformly heating to 1500 ~ 2300 ℃, preserving heat for 6 ~ 8h, uniformly heating to 2300 ~ 2800 ℃, preserving heat for 2 ~ 4h, introducing halogen gas at a rate of 10 ~ 15m³Heating to 2800 ~ 3200 deg.C, maintaining for 48h, stopping introducing halogen gas, and cooling to room temperature by air cooling and water cooling;

(15) spraying a layer of silicon nitride layer on the inner and outer surfaces of the die after the die is discharged from the furnace, wherein the spraying flow rate is 120 ~ 150ml/10 s;

(16) and (3) performing third carbonization, namely finally placing the product in a carbonization furnace for third carbonization at the temperature of 20 ℃ and ~ 1400 ℃, preserving heat for 48 hours at the temperature of 1400 ℃, wherein the carbonization time is 30 ~ 60 hours, naturally cooling to normal temperature, discharging, and cleaning the obtained graphite crucible after discharging.

5. The method for preparing the carbon fiber graphite crucible for the metallurgical casting furnace according to claim 4, wherein the kneading manner in the step (2) is divided into dry blending and wet blending, wherein the dry blending is to put the prepared materials into a kneading machine and stir the materials at a speed of 50 ~ 80r/min for 60 ~ 80min, the dry blending temperature is 130 ~ 140 ℃ and the wet blending is to pour the binding agents into a kneading pot twice for kneading, 40% of the binding agents are added for the first time, the temperature is 140 ~ 150 ℃, the wet blending time is 20 ~ 30min, 60% of the binding agents are added for the second time, the temperature is 150 ~ 160 ℃, and the wet blending time is 30 ~ 40 min.

6. The method for preparing the carbon fiber graphite crucible for the metallurgical casting furnace as claimed in claim 4, wherein the prepressing pressure of the prepressing forming in the step (3) is 25MPa, and the prepressing time is 5 min.

7. The method for preparing the carbon fiber graphite crucible for the metallurgical casting furnace as claimed in claim 4, wherein the concrete operation of isostatic pressing in the step (8) is to firstly vacuumize the inside of the isostatic pressing machine to 10Kpa ~ 30KPa, then move the rubber mold filled with the powder into the isostatic pressing machine for press forming, the pressing pressure is 100Mpa ~ 150MPa, the pressure is increased to the set forming pressure at the pressure increasing rate of 10 ~ 12MPa/min, the pressure is stabilized for 5 ~ 10min, then the pressure is released to 80 ~ 90MPa at the pressure releasing rate of 8 ~ 12MPa/min, the pressure is stabilized for 5 ~ 10min, then the pressure is released to 40 ~ 50MPa at the pressure releasing rate of 8 ~ 12MPa/min, the pressure is stabilized for 2 ~ 5min, and finally the pressure is released to the room pressure at the pressure releasing rate of 8 ~ 12 MPa/min.

8. The method for preparing the carbon fiber graphite crucible for the metallurgical casting furnace according to claim 4, wherein the temperature rise process of the carbonization treatment in the step (9) is that the temperature rise rate is 2 ℃/h and 65h at the room temperature of ~ 150 ℃, the temperature rise rate is 3 ℃/h and 67h at the temperature rise rate of 150 ~ 350 ℃, the temperature rise rate is 3 ℃/h and 57h at the temperature rise rate of 350 ~ 550 ℃, the temperature rise rate is 4 ℃/h and 75h at the temperature rise rate of 550 ~ 850 ℃, the temperature rise rate is 3 ℃/h and 100h at the temperature rise rate of 850 ~ 1150 ℃, the temperature rise rate is 3 ℃/h and 33h at the temperature rise rate of 1150 ~ 1250 ℃, the temperature is kept for 48h at 1250 ℃, the temperature is reduced to 90 ℃ at the temperature reduction rate of 1 ℃/h ~ 2 ℃/h after the carbonization is stopped and then the temperature is discharged, and finally the temperature is naturally reduced in the room temperature.

Technical Field

The invention relates to the technical field of graphite crucible materials, in particular to a carbon fiber graphite crucible for a metallurgical casting furnace and a preparation method thereof.

Background

As is well known, the graphite crucible has good thermal conductivity and high temperature resistance, and has small thermal expansion coefficient and certain strain resistance to rapid heating and rapid cooling in the high-temperature use process; has strong corrosion resistance to acid and alkaline solutions and excellent chemical stability.

The graphite crucible, because of its excellent properties, is widely used in the metallurgy, casting, machinery, chemical industry and other industrial departments for the smelting of alloy tool steel and the smelting of non-ferrous metals and their alloys, and has better technical and economic effects.

The domestic graphite crucible has the following characteristics:

1. the higher density of the graphite crucible enables the crucible to have the best heat conducting performance, and the heat conducting effect of the graphite crucible is obviously better than that of other imported crucibles;

2. the graphite crucible is provided with a special glaze layer and compact molding materials on the surface, so that the corrosion resistance of the product is greatly improved, and the service life of the product is prolonged;

3. the graphite in the graphite crucible is made of natural graphite, so that the heat conductivity is very good. The graphite crucible cannot be placed on a cold metal table surface immediately after being heated, so that the graphite crucible is prevented from being broken due to rapid cooling;

4. the service life of the graphite crucible for the metallurgical furnace reaches more than 120 times.

A crucible is most suitable for melting a plurality of types and a small amount of alloys, when the types of the alloys are required to be changed, only a graphite crucible needs to be exchanged, when other melting methods such as a reverberatory furnace and a non-crucible induction furnace are used for melting, the crucible is suitable for melting a large amount of single alloys, and if the types of the alloys are changed and melted, metal pollution can occur if a lining refractory material is not replaced, so that the graphite crucible is used for melting the alloys, and the currently used crucible has certain defects in certain aspects, so that certain improvement needs to be carried out on the existing graphite crucible, and various physicochemical new performances of the graphite crucible are improved.

Disclosure of Invention

In order to solve the technical problems, the invention aims to provide the carbon fiber graphite crucible for the metallurgical casting furnace, which has reasonable raw material selection and can improve various physical and chemical properties of the carbon fiber graphite crucible;

the invention also aims to provide a preparation method of the carbon fiber graphite crucible for the metallurgical casting furnace, which has scientific preparation process.

The carbon fiber graphite crucible for the metallurgical casting furnace comprises aggregate, powder and a binder, wherein the aggregate is needle petroleum coke, the powder consists of carbon fibers, pitch coke and carbon black, the binder consists of medium-temperature coal pitch and modified coal pitch, the weight ratio of the aggregate to the powder to the binder is (70 ~ 75): (25 ~ 30), and the weight ratio of the aggregate to the powder is (60 ~ 70): (30 ~ 40).

The aggregate acicular petroleum coke has the granularity of 3 ~ 5 mu m and the true density of more than or equal to 2.13g/cm³Ash content is less than or equal to 0.20 percent, volatile matter is less than or equal to 0.25 percent, and sulfur content is less than or equal to 0.40 percent;

the granularity of the powdery carbon fiber is 2 ~ 4 mu m, the tensile strength is 7.0Gpa, and the density is 2.10g/cm³The resistivity is less than or equal to 55 mu omega cm;

the granularity of the powder asphalt coke is 2 ~ 3 mu m, and the true density is more than or equal to 2.13/cm³Ash content is less than or equal to 0.25 percent, sulfur content is less than or equal to 0.3 percent, and volatile matter is less than or equal to 0.5 percent;

the purity of the powder carbon black is 99 percent, and the granularity is 1 ~ 3 mu m;

the softening point of the medium-temperature coal pitch in the binder is 83 ~ 88 ℃, the coking value is more than or equal to 48 percent, and the quinoline insoluble substance is less than or equal to 3 percent;

the modified coal tar pitch has a softening point of 105 ~ 120 ℃, a coking value of more than or equal to 58%, ash content of less than or equal to 0.3%, quinoline insoluble substance of less than or equal to 2% and toluene insoluble substance of less than or equal to 20%.

According to the carbon fiber graphite crucible for the metallurgical casting furnace, the weight ratio of the aggregate to the powder and the binder is preferably 72: 28.

the carbon fiber graphite crucible for the metallurgical casting furnace is characterized in that the adding weight ratio of carbon fibers, pitch coke and carbon black is 30:40: 30.

The invention discloses a preparation method of a carbon fiber graphite crucible for a metallurgical casting furnace, which comprises the following steps:

(1) grinding and screening ingredients: processing the aggregate and the powder into required particle size by grinding equipment, and proportioning the materials after screening;

(2) kneading: adding the graded ingredients into a kneading pot for stirring;

(3) preforming: pouring the kneaded paste into a forming container, and performing pre-pressing forming to obtain a blank;

(4) crushing, namely crushing the pre-pressed and molded blank by using a crusher, wherein the crushed granularity is 100 ~ 250 mu m;

(5) grinding, namely grinding the crushed blank by using a grinder, wherein the grain size of the ground powder is 15 ~ 35 mu m;

(6) screening: the powder after being milled is screened and classified and is stored in separate bins, wherein the powder at each level accounts for the following proportions:

15~20μm 30%；

20~25μm 30%；

25~35μm 40%；

(7) mixing: uniformly mixing the graded powder by using a cyclone mixer;

(8) isostatic pressing, namely filling the uniformly mixed powder into a rubber mould, sealing the rubber mould, and carrying out cold isostatic pressing to obtain a molded green body with the volume density of 1.8 ~ 2.2.2 g/cm³；

(9) Carbonizing: filling metallurgical coke powder in the formed green body, vibrating, filling the green body into a carbonization furnace, filling the furnace with the coke powder, quartz sand and river sand, introducing inert gas into the furnace, and carbonizing the green body under the condition of isolating air;

(10) impregnating, namely preheating the carbonized product to 300 ~ 350 ℃, keeping the temperature for 8 hours, putting the carbonized product into an impregnating tank, vacuumizing the impregnating tank, pressurizing the carbonized product for 2.5 hours under the pressure of 3MPa ~ 5MPa, injecting an impregnant into the impregnating tank, and maintaining the pressure for 2 hours to ensure that the impregnant impregnates asphalt to impregnate the pores of the carbonized product for impregnation;

(11) secondary carbonization, namely putting the dipped product into a carbonization furnace for secondary carbonization at the temperature of 20 ℃ of ~ 1200 ℃ and keeping the temperature at the temperature of 1200 ℃ for 48 hours, wherein the carbonization time is 550 ~ 660 hours, and naturally cooling the product to normal temperature and discharging the product;

(12) secondary impregnation: placing the product after the secondary carbonization in an impregnation tank, and carrying out secondary impregnation to ensure that the impregnating agent impregnating pitch is immersed in the pores of the product;

(13) curing, namely drying the dipped product at 85 ~ 95 ℃, putting the product into a curing furnace for pressurizing and curing, wherein the curing pressure is 2MPa ~ 5MPa, the heating speed is 5 ℃/h ~ 10 ℃/h, the curing temperature is 140 ℃ ~ 180 ℃, and the heat preservation time is 3h ~ 6 h;

(14) graphitizing, namely putting the cured product into a graphitizing furnace, uniformly heating to 1500 ~ 2300 ℃, preserving heat for 6 ~ 8h, uniformly heating to 2300 ~ 2800 ℃, preserving heat for 2 ~ 4h, introducing halogen gas at a rate of 10 ~ 15m³Heating to 2800 ~ 3200 deg.C, maintaining for 48h, stopping introducing halogen gas, and cooling to room temperature by air cooling and water cooling;

(15) spraying a layer of silicon nitride layer on the inner and outer surfaces of the die after the die is discharged from the furnace, wherein the spraying flow rate is 120 ~ 150ml/10 s;

(16) and (3) performing third carbonization, namely finally placing the product in a carbonization furnace for third carbonization at the temperature of 20 ℃ and ~ 1400 ℃, preserving heat for 48 hours at the temperature of 1400 ℃, wherein the carbonization time is 30 ~ 60 hours, naturally cooling to normal temperature, discharging, and cleaning the obtained graphite crucible after discharging.

The preparation method of the carbon fiber graphite crucible for the metallurgical casting furnace comprises the step (2) of mixing and kneading, wherein the dry mixing is to put the prepared materials into a mixing and kneading machine and stir the materials for 60 ~ 80min at the speed of 50 ~ 80r/min, the dry mixing temperature is 130 ~ 140 ℃, the wet mixing is to pour the binding agent into a mixing and kneading pot for mixing and kneading twice, 40% of the binding agent is added for the first time, the temperature is 140 ~ 150 ℃, the wet mixing time is 20 ~ 30min, 60% of the binding agent is added for the second time, the temperature is 150 ~ 160 ℃, and the wet mixing time is 30 ~ 40 min.

The invention discloses a preparation method of a carbon fiber graphite crucible for a metallurgical casting furnace, wherein the prepressing pressure of the prepressing forming in the step (3) is 25MPa, and the prepressing time is 5 min.

The invention relates to a preparation method of a carbon fiber graphite crucible for a metallurgical casting furnace, which comprises the specific operation of carrying out isostatic pressing in the step (8), firstly vacuumizing the interior of an isostatic pressing machine to 10Kpa ~ 30KPa, then transferring a rubber mold filled with powder into the isostatic pressing machine for press forming, wherein the pressing pressure is 100Mpa ~ 150MPa, the pressing speed is increased to the set forming pressure at 10 ~ 12MPa/min, the pressure is stabilized for 5 ~ 10min, then the pressure is released to 80 ~ 90MPa at 8 ~ 12MPa/min, the pressure is stabilized for 5 ~ 10min, then the pressure is released to 40 ~ 50MPa at 8 ~ 12MPa/min, the pressure is stabilized for 2 ~ 5min, and finally the pressure is released to room pressure at 8 ~ 12 MPa/min.

The invention relates to a preparation method of a carbon fiber graphite crucible for a metallurgical casting furnace, wherein the temperature rise process of carbonization treatment in the step (9) is that the temperature rise rate is 2 ℃/h and 65h at the room temperature of ~ 150 ℃, the temperature rise rate is 3 ℃/h and 67h at the temperature rise rate of 150 ~ 350 ℃, the temperature rise rate is 3.5 ℃/h and 57h at the temperature of 350 ~ 550 ℃, the temperature rise rate is 4 ℃/h and 75h at the temperature of 550 ~ 850 ℃, the temperature rise rate is 3 ℃/h and 100h at the temperature rise rate of 850 ~ 1150 ℃, the temperature rise rate is 3 ℃/h and 33h at the temperature rise rate of 1150 ~ 1250 ℃, the temperature is kept for 48h at 1250 ℃, the temperature is kept for 24h after carbonization is stopped, and finally the temperature is reduced to 90 ℃ at the temperature reduction rate of 1 ℃/h ~ 2 ℃/h and taken out of the furnace, and finally the temperature is naturally reduced in the room temperature.

Compared with the prior art, the invention has the beneficial effects that: the graphite crucible prepared by the invention has the following advantages:

1. the manufacturing process of the existing graphite crucible material is substantially improved, the raw material selection is reasonable, the preparation process is scientific, and the method and the material are used for producing the high-purity large-scale graphite crucible material with excellent physical and chemical properties;

2. the structure is uniform and fine, and the volume density is high;

3. the carbon fiber is used as a main raw material, so that the original various physical and chemical properties of the carbon fiber are maintained, the graphite crucible has good thermal conductivity and high temperature resistance, and in the high-temperature use process, the graphite crucible has small thermal expansion coefficient, certain strain resistance to rapid heating and rapid cooling, strong corrosion resistance to acid and alkaline solutions and excellent chemical stability;

4. the physical and chemical indexes of the graphite are excellent: the volume density of the obtained graphite crucible material for the metallurgical casting furnace is more than or equal to 2.0g/cm³The resistivity is less than or equal to 5.0 mu omega m, the breaking strength is more than or equal to 60Mpa, the compressive strength is more than or equal to 110Mpa, the ash content is less than or equal to 0.30 percent, and the purity is more than or equal to 99 percent.

Detailed Description

The following examples are given to further illustrate the embodiments of the present invention. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.