CN108752002B

CN108752002B - SiC ceramic-based hot bending die and preparation method thereof

Info

Publication number: CN108752002B
Application number: CN201810841072.7A
Authority: CN
Inventors: 刘荣军; 孙海侠; 贺鹏博; 王衍飞; 缪花明
Original assignee: National University of Defense Technology
Current assignee: National University of Defense Technology
Priority date: 2018-07-27
Filing date: 2018-07-27
Publication date: 2020-08-07
Anticipated expiration: 2038-07-27
Also published as: CN108752002A

Abstract

The invention discloses a preparation method of a SiC ceramic-based hot bending die, which comprises the following steps of mechanically stirring a solid-phase raw material, a dispersing agent, a curing crosslinking agent and alcohol to obtain mixed slurry, drying and crushing the mixed slurry to obtain mixed powder, carrying out compression molding on the mixed powder, carrying out isostatic pressing, finally curing and crosslinking to obtain a molded biscuit, carrying out gas-phase siliconizing sintering on the molded biscuit to obtain a SiC-based complex-phase ceramic blank, and machining the SiC-based complex-phase ceramic blank to obtain the glass hot bending die.

Description

SiC ceramic-based hot bending die and preparation method thereof

Technical Field

The invention relates to the technical field of preparation of forming processing molds, in particular to a SiC ceramic-based hot bending mold and a preparation method thereof.

Background

Hot bending glass refers to heating and softening a flat glass into a mold to form a curved glass. The traditional glass hot bending die comprises a male die 1 and a female die 2, as shown in figure 1, a profiling block 11 is arranged on the male die 1, a profiling groove 21 matched with the profiling block 11 is arranged on the female die 2, and a cavity for glass hot bending forming is formed between the profiling groove 21 and the profiling block 11 after die assembly. When the glass is hot-bent, the glass 3 is placed on the contour block, the two-dimensional size of the glass 3 is larger than that of the contour block 11, the lower surface of the concave die 2 presses the periphery of the glass 3 downwards and conducts heat to the glass 3 until the glass 3 is heated to be close to the softening temperature, and the glass 3 is pressed into the cavity to form a finished product.

Because the mold needs to transfer heat and force to the glass and does not affect the forming precision of the finished glass product, the mold is required to have high temperature resistance, high thermal conductivity, low thermal expansion rate, wear resistance, high polishing performance, high mechanical property and high thermal shock resistance in the aspect of material, but the mold is mostly prepared from metal or graphite in the traditional technology, the metal material has slow heat transfer, long heat transfer time and large thermal expansion coefficient, and is easy to deform at high temperature, so that the surface of the glass has defects, for example, the shape radian of the finished glass product has deviation, and the forming precision of the finished glass product is affected. The graphite material has poor oxidation resistance and is easy to oxidize at high temperature, so that the service life of the mold is shortened, and the graphite mold has poor thermal shock resistance and can also influence the forming precision of finished glass.

Disclosure of Invention

In view of the above, it is necessary to provide a hot bending die with high molding accuracy and a method for manufacturing the same.

The preparation method of the SiC ceramic-based hot bending die is characterized by comprising the following steps of:

(1) mechanically stirring a solid-phase raw material, a dispersing agent, a curing cross-linking agent and alcohol to obtain mixed slurry, wherein the solid-phase raw material consists of carbon black, graphite and α -SiC ceramic powder;

(2) drying and crushing the mixed slurry obtained in the step (1) to obtain mixed powder;

(3) carrying out compression molding on the mixed powder obtained in the step (2), carrying out isostatic pressing, and finally curing and crosslinking to obtain a molded biscuit;

(4) carrying out gas-phase siliconizing sintering on the molded biscuit obtained in the step (3) to obtain a SiC-based complex-phase ceramic blank;

(5) and machining the SiC-based complex phase ceramic blank to obtain the glass hot bending die.

The SiC-based ceramic blank prepared by the invention has the characteristics of high thermal conductivity, low thermal expansion coefficient, good polishing property, good wear resistance, excellent thermal shock resistance and cold and hot fatigue resistance and the like, and the processed glass hot bending die does not influence the forming precision of a glass finished product and has long service life.

In one embodiment, the dispersing agent is polyvinylpyrrolidone and Dolapix CE64, the mass of the polyvinylpyrrolidone is 10% -65% of that of the carbon black, and the mass of the Dolapix CE64 is 0.2% -1% of that of the α -SiC ceramic powder.

In one embodiment, the α -SiC ceramic powder consists of α -SiC ceramic powders with F1200 and F240 different in particle size, and the mass ratio of the α -SiC ceramic powder with the F1200 particle size to the α -SiC ceramic powder with the F240 particle size is 1: 1-1.8.

In one embodiment, in the step (1), the solid content of the mixed slurry is 50% to 80%, in the solid-phase raw material, the carbon black accounts for 10% to 15% by mass of the solid-phase raw material, the graphite accounts for 2% to 10% by mass of the solid-phase raw material, and the α -SiC ceramic powder accounts for 75% to 88% by mass of the solid-phase raw material.

In one embodiment, the curing crosslinking agent is thermosetting phenolic resin, and the curing crosslinking agent accounts for 1-10% of the total mass of the solid phase raw material, the dispersing agent and the curing crosslinking agent.

In one embodiment, in the step (3), the compression molding pressure is 8-15 MPa, and the compression molding time is 60-120 s; the isostatic compaction pressure is 50-150 Mpa, and the isostatic compaction time is 60-300 s; the curing and crosslinking temperature is 150-180 ℃, and the curing and crosslinking time is 2-4 h.

In one embodiment, in the step (4), the temperature of the gas phase siliconizing sintering is 1500-1700 ℃, and the time is 1-3 h.

In one embodiment, in the step (2), the drying temperature of the mixed slurry is 25-30 ℃, and the mixed slurry is crushed until the particle size of the mixed powder is less than or equal to 60 meshes.

As a general inventive concept, the invention also provides a SiC ceramic-based hot bending die prepared by the preparation method.

In one embodiment, the SiC ceramic-based hot bending die is a glass hot bending die, the glass hot bending die comprises a female die and a male die, a contour groove is formed in the female die, a contour block matched with the contour groove is arranged on the male die, the height of the contour block is smaller than the depth of the contour groove, and the contour groove is matched with the contour block to form a cavity for glass hot bending forming.

In one embodiment, the female die comprises a base, a boss is arranged on the base, the profiling groove is formed in the middle of the boss, and an annular frame is formed between the outer wall of the boss and the wall of the profiling groove;

the male die is provided with a groove, the profiling block is arranged on the bottom wall of the groove, the height of the profiling block is smaller than the depth of the profiling groove, and the profiling groove and the profiling block are matched to form a cavity for hot bending forming of glass; an annular groove matched with the annular frame is formed between the inner wall of the groove and the outer wall of the contour block.

Drawings

FIG. 1 is a schematic structural view of a glass hot bending mold according to an embodiment;

FIG. 2 is a schematic front view of a female mold according to another embodiment;

FIG. 3 is a schematic top view of another embodiment of a female mold;

FIG. 4 is a schematic right view of a female mold according to another embodiment;

FIG. 5 is a schematic front view of a male mold of another embodiment;

FIG. 6 is a schematic top view of another embodiment of a male mold;

FIG. 7 is a schematic right view of another embodiment of a male mold;

FIG. 8 is a metallographic microstructure diagram of a SiC-based complex phase ceramic prepared in example 1;

FIG. 9 is a photomicrograph of a polished sample of the SiC-based composite ceramic obtained in example 1.

Detailed Description

In order that the invention may be more fully understood, a more particular description of the invention will now be rendered by reference to specific embodiments thereof that are illustrated in the appended drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

The invention provides a preparation method of a SiC ceramic-based hot bending die, which comprises the following steps:

(5) and machining the SiC-based complex phase ceramic blank to obtain the SiC-based hot bending die.

The silicon carbide as a structural ceramic has excellent physicochemical properties such as high bending resistance, high temperature resistance, oxidation resistance, high thermal conductivity, low thermal expansion rate, excellent chemical stability and the like, the silicon carbide ceramic prepared by the conventional method has extremely high brittleness, and the silicon carbide is difficult to sinter and compact, so the silicon carbide ceramic has poor bending property and thermal shock resistance, is easy to crack in the processing and high-temperature application processes, and cannot meet the processing and using requirements of a glass hot bending die.

The traditional method mainly adopts the combination of slip casting and reactive sintering process to form the SiC-based ceramic material, or adopts the combination of dry pressing biscuit and reactive sintering process to form the SiC-based ceramic material.

According to the invention, researches show that the slip casting process has long forming period, so that a slip casting green body has obvious density gradient, the density and the carbon content of the prepared biscuit are low, the free Si content in the SiC ceramic after siliconizing sintering is high, the thermal shock resistance is poor due to the difference of expansion coefficients of Si and SiC, and the processing and using requirements of a hot bending die cannot be met, while the dry pressing formed biscuit has poor uniformity, and in gas phase siliconizing sintering, the prepared SiC-based ceramic material has uneven and discontinuous internal structure, the residual C in a region with high C content and the residual free Si. in a place with low C content can cause the existence of a large amount of Si, the formation of β -SiC continuous phase is influenced, the mechanical property and the thermal shock property of the material are low, and the processing and using requirements of the hot bending die cannot be met.

Further research shows that the mechanical property and the thermal shock resistance of the SiC-based complex phase ceramic prepared by combining the wet-process forming biscuit with the siliconizing reaction sintering process are greatly improved compared with the SiC-based complex phase ceramic prepared by combining the slip casting forming process with the reaction sintering process or by combining the dry-pressing forming biscuit with the reaction sintering process.

The specific process of the invention is as follows: firstly, dispersing the preparation raw materials in alcohol, uniformly mixing the raw materials by adopting a mechanical stirring method, then air-drying the uniformly mixed slurry at room temperature, and crushing the slurry by adopting a crusher to ensure that the raw materials are fully and uniformly mixed; and then adopting a mould pressing/isostatic pressing forming process to form a biscuit, and carrying out gas-phase siliconizing reaction on pyrolytic carbon generated by cracking carbon black, graphite and a cured crosslinking agent phenolic resin in the biscuit to sinter the pyrolytic carbon to form the SiC-based complex phase ceramic.

The wet mixing is adopted, so that compared with the dry mixing, the uniformity of raw material mixing is ensured, the uniformity of a biscuit formed by mould pressing/isostatic pressing is very high, the uniformity and the tissue continuity of the prepared SiC-based ceramic material can be ensured after siliconizing reaction sintering, the content of residual C and Si in the SiC ceramic is obviously reduced, the content of SiC is improved, and the problem that the mechanical property and the thermal shock resistance of the SiC-based ceramic material formed by combining the traditional dry pressing biscuit and the reaction sintering process are poor due to overhigh content of residual Si is solved. And the molding/isostatic pressing time is short, and the biscuit can be controlled to be in proper density by adjusting the pressure and the pressing time of the biscuit molding process. Compared with the traditional slip casting, the density gradient phenomenon can not exist, and the problem that the thermal shock resistance is poor due to the high content of residual Si in the SiC-based ceramic material formed by combining the traditional slip casting and the reactive sintering process due to the density gradient is solved.

In addition, because the raw material mixing and biscuit uniformity are higher and more uniform, only a small amount of dispersed free silicon exists in the prepared SiC-based multiphase ceramic material, so that the SiC-based multiphase ceramic material has the characteristics of high thermal conductivity, low thermal expansion coefficient, high polishing property, excellent wear resistance, mechanical property and thermal shock resistance and the like, and meets the processing and using requirements of a hot bending die.

Through further research, the invention discovers that compared with the traditional mould pressing mixed material, the invention adds graphite into the wet mixed material, the graphite is a crystal form of carbon, has hexagonal crystal lattices, atoms are arranged in layers, the distance between carbon atoms on the same layer of crystal face is 0.142nm, and the graphite and the carbon atoms are combined by covalent bonds; the distance between layers is 0.34nm, the atoms form molecular bonds, the acting force between layers is very small, relative sliding is easy to occur between layers, the structural characteristics lead to low graphite strength/hardness and poor plasticity, the graphite has good lubricating effect in the powder preparation and compression molding process, and the uniformity of a biscuit can be obviously improved, so that the mechanical property and the thermal shock resistance of the prepared SiC-based complex phase ceramic material are further improved.

Furthermore, the research of the invention discovers that the traditional mould pressing mixing material is generally added with the curing cross-linking agent phenolic resin for curing and cross-linking after the preparation and drying of the slurry are finished, so that the dispersion is easy to be uneven, and the residual silicon aggregation phenomenon is easy to occur after siliconizing and sintering, thereby influencing the comprehensive performance of the composite ceramic. According to the invention, the curing crosslinking agent is added in advance when the wet mixing is carried out, so that the uniformity of the curing crosslinking agent phenolic resin in powder can be realized, and the curing crosslinking effect of the curing crosslinking agent phenolic resin can not be influenced, thereby avoiding the occurrence of residual silicon aggregation and improving the comprehensive performance of the complex phase ceramic.

In the embodiment, the dispersing agents are polyvinylpyrrolidone and Dolapix CE64, the polyvinylpyrrolidone is mainly used as a dispersing agent of carbon black, and the Dolapix CE64 (the main component is polymethacrylamide) is mainly used as a dispersing agent of SiC ceramic powder.

The mass of the polyvinylpyrrolidone is preferably 10-65% of that of the carbon black, and the mass of the Dolapix CE64 is preferably 0.2-1% of that of the α -SiC ceramic powder.

In the present embodiment, the α -SiC ceramic powder is preferably composed of α -SiC ceramic powders having two different particle sizes of F1200 and F240, and tests show that the particle packing density can be increased by using the above-mentioned silicon carbide having a particle size distribution, and the bulk density of the green body can be increased, and the amount of residual silicon in the sintered body can be reduced.

In this embodiment, in the step (1), the solid content of the mixed slurry is preferably 50% to 80%;

in the embodiment, in the step (1), the mass percentage of carbon black in the solid phase raw material is preferably 10-15%, the mass percentage of graphite in the solid phase raw material is preferably 2-10%, and the mass percentage of α -SiC ceramic powder in the solid phase raw material is preferably 75-88%, wherein the mass ratio of α -SiC ceramic powder with the grain size of F1200 to α -SiC ceramic powder with the grain size of F240 is preferably 1: 1-1.8.

In this embodiment, the curing crosslinking agent is thermosetting phenolic resin, and the percentage content of the curing crosslinking agent in the total mass of the solid phase raw material, the dispersing agent and the curing crosslinking agent is preferably 1% to 10%.

In the embodiment, in the step (2), the drying temperature of the mixed slurry is 25 to 30 ℃, and the mixed powder is crushed to have a particle size of not more than 60 meshes.

In the embodiment, in the step (3), the pressure for compression molding is preferably 8-15 MPa, and the compression molding time is preferably 60-120 s; the pressure of isostatic pressing is preferably 50-150 MPa, and the isostatic pressing time is preferably 60-300 s.

In the present embodiment, in the step (3), the curing and crosslinking temperature is preferably 150 ℃ to 180 ℃, and the curing and crosslinking time is preferably 2 to 4 hours.

In this embodiment, in the step (4), the temperature of the gas phase siliconizing sintering is preferably 1500 to 1700 ℃, and the time is preferably 1 to 3 hours.

The invention also provides a glass hot bending die of one embodiment prepared by the method, which comprises a female die 1 and a male die 2, wherein the female die 1 is internally provided with a profile groove 21, the male die 2 is provided with a profile block 11 matched with the profile groove 21, the height of the profile block 11 is smaller than the depth of the profile groove 21, and the profile groove 21 is matched with the profile block 11 to form a cavity for glass hot bending forming.

The shape of the surface of the profile groove 21 and the profile block 11 is the same as the shape of the glass article to be hot bent.

The working process of the hot bending forming curved glass of the embodiment is as follows: the glass 3 is placed on the contour block 11, the two-dimensional size of the glass 3 is larger than that of the contour block 11, the periphery of the glass is pressed downwards by the lower surface of the concave die 1, heat is conducted to the glass, the glass is heated to be close to the softening temperature of the glass, and the glass 3 is pressed into the cavity to form a finished product.

When the processing and installation errors of the mold are small, the curved glass is formed by hot bending in the embodiment, because the lower surface of the female die 1 is adopted to press the glass 3, the contact area between the female die 1 and the glass 3 is large and uniform, the periphery of the glass 3 is uniformly stressed and heated, the glass is not easy to deform, and the forming precision of the curved glass is high.

The present invention also provides another embodiment of a glass hot-bending mold manufactured by the above method, comprising a female mold 10 and a male mold 20; referring to fig. 2 to 4, the female die comprises a base 130, a boss 100 is arranged on the base, a profile groove 110 is arranged in the middle of the boss 100, and an annular frame 120 is formed between the outer wall of the boss 100 and the wall of the profile groove 110; wherein, the material of the boss 100 is SiC-based complex phase ceramic;

referring to fig. 5 to 7, a groove 200 is formed on the male mold 20, a profiling block 210 for matching with the profiling groove 110 is arranged on the bottom wall of the groove 200, the height of the profiling block 210 is greater than the depth of the annular groove 110, and the profiling groove 110 and the profiling block 210 match to form a cavity for glass hot bending molding; an annular groove 220 is formed between the inner wall of the groove 200 and the outer wall of the contour block 210 for cooperation with the annular frame 120.

The working process of the hot bending forming curved glass of the embodiment is as follows: the flat glass is placed on the contour block 210, the two-dimensional size of the glass is larger than that of the contour block 210, the lower surface of the ring frame 120 presses the periphery of the flat glass and conducts heat to the flat glass until the glass is heated to the temperature near the softening temperature of the glass, and the flat glass is pressed into the cavity to form a curved glass finished product.

When the die cannot be in an ideal assembling state when the female die and the male die are assembled due to errors in die machining and installation, the stress and the heating of the periphery of the glass are relatively more uniform, the glass is deformed and the forming precision is higher because the periphery of the annular frame is smaller in size.

Because the glass hot bending die generally needs higher temperature and larger pressure when forming the bent glass with small bending radius, after the annular frame 120 is used for transferring heat and force, because the contact area of the annular frame 120 and the glass is smaller than that of the traditional female die and the glass, the heat transfer and force transfer capability of the glass is not as good as that of the traditional female die, if the annular frame 120 is prepared by adopting the traditional metal material, the metal is slower in heat transfer, the thermal expansion coefficient is large, the thermal shock performance is poor, the glass is easy to deform at high temperature, the glass moves and deforms in the hot bending process, the shape radian of the finished glass is deviated, and the forming precision is influenced; if the annular frame 120 is made of graphite, the graphite material has poor oxidation resistance and is easily oxidized at high temperature, so that the service life of the mold is shortened, and the graphite material has poor wear resistance and thermal shock resistance, which also affects the forming precision of the finished glass.

The utility model discloses a SiC base multiphase ceramic preparation annular frame 120 compares with traditional metal material, and SiC base multiphase ceramic has better heat conductivity, and the heat transfer piece is heated evenly to thermal expansion coefficient is less, and the wearability is good, polishing nature and thermal shock ability are good, and the curved in-process of heat can not arouse glass drunkenness and deformation, has guaranteed the machining precision of the curved forming in-process of heat. Compared with graphite materials, the SiC-based complex phase ceramic has better oxidation resistance, polishing property and thermal shock resistance, the service life of a die is longer and the forming precision of a finished product is higher.

The following are specific examples.

Example 1:

a preparation method of a SiC ceramic-based hot bending die comprises the following steps:

(1) preparing mixed slurry:

the method comprises the steps of adding a dispersing agent (polyvinylpyrrolidone and Dolapix CE64) and a solid phase raw material into alcohol to obtain a premixed slurry, adding an alcohol solution of a curing cross-linking agent (phenolic resin) into the premixed slurry, and mechanically stirring for 5 hours to obtain a mixed slurry, wherein the solid phase raw material consists of carbon black, graphite and α -SiC ceramic powder (including F240 and F1200), the mass percentage of the carbon black in the solid phase raw material is 13%, the mass percentage of the graphite in the solid phase raw material is 4%, the mass percentage of the α -SiC ceramic powder in the mixed solid phase is 83%, the mass percentage of the F240/F1200 in the α -SiC ceramic powder is 1.72, the mass percentage of the polyvinylpyrrolidone in the carbon black is 50%, the mass percentage of the Dolapix CE64 in the solid phase is α -SiC ceramic powder, and the mass percentage of the phenolic resin in the solid phase raw material, the dispersing agent and the curing cross-linking agent is 5%.

(2) Drying and crushing the mixed slurry:

and (2) pouring the mixed slurry obtained in the step (1) into a drying tray, drying the mixed slurry in air at room temperature for 48 hours, crushing the dried mixed slurry by using a crusher, and sieving the powder by using a 60-mesh sieve to obtain mixed powder.

(3) Die pressing/isostatic pressing:

and (3) taking the mixed powder obtained in the step (2), and forming by adopting a die pressing/isostatic pressing process to obtain a die pressing biscuit. The pressure intensity for mould pressing is 15MPa, the pressure maintaining time is 60s, the pressure intensity for isostatic pressing is 92MPa, and the pressure maintaining time is 60 s.

(4) Curing and crosslinking:

and (4) carrying out curing and crosslinking reaction on the molded biscuit obtained in the step (3) at 180 ℃, wherein the reaction time is 2h, and thus obtaining the molded biscuit.

(5) Gas-phase siliconizing and sintering:

and (4) carrying out gas-phase siliconizing sintering on the molded biscuit obtained in the step (4), wherein the siliconizing sintering temperature is 1700 ℃, and the time is 1h, so as to obtain a compact SiC-based complex-phase ceramic blank.

(6) And machining the SiC-based complex phase ceramic blank to obtain the SiC-based hot bending die.

Fig. 8 is a metallographic microscopic structure diagram of the SiC-based multiphase ceramic prepared in this example after surface polishing, which shows that the SiC-based multiphase ceramic prepared by the present invention has SiC grains continuously stacked, only a small amount of free phase Si is dispersedly distributed in the SiC continuous phase, and the Si free phase is formed by the condensation of gas phase silicon that does not participate in the reaction in the SiC-based ceramic material. FIG. 9 is a photomicrograph of a polished SiC-based multiphase ceramic obtained in example 1, wherein the RMS value of the polished surface reaches 0.024 lambda, the surface roughness Ra reaches 0.57nm, and the use requirement of a hot bending die is completely met.

Example 2:

(1) preparing mixed slurry:

the method comprises the steps of adding a dispersing agent (polyvinylpyrrolidone and Dolapix CE64) and a solid-phase raw material into alcohol to obtain a premixed slurry, adding an alcohol solution of a curing cross-linking agent (phenolic resin) into the premixed slurry, and mechanically stirring for 5 hours to obtain a mixed slurry, wherein the solid-phase raw material consists of carbon black, graphite and α -SiC ceramic powder (including F240 and F1200), the mass percentage of the carbon black in the solid-phase raw material is 15%, the mass percentage of the graphite in the solid-phase raw material is 3.9%, the mass percentage of α -SiC ceramic powder in the solid-phase raw material is 81.1%, the mass ratio of F240/F1200 in the α -SiC ceramic powder is 1.5, the mass percentage of the polyvinylpyrrolidone in the carbon black is 71%, the mass percentage of the Dolapix CE64 in the solid-phase raw material is α -SiC ceramic powder, and the mass percentage of the phenolic resin in the solid-phase raw material, the dispersing agent and the curing cross-linking agent is 3%.

(2) Drying and crushing the mixed slurry:

(3) Die pressing/isostatic pressing:

and (3) taking the mixed powder obtained in the step (2), and forming by adopting a die pressing/isostatic pressing process to obtain a die pressing biscuit. The pressure for mould pressing is 10.3MPa, the pressure maintaining time is 60s, the pressure for isostatic pressing is 80MPa, and the pressure maintaining time is 60 s. (4) Curing and crosslinking:

and (4) carrying out curing and crosslinking reaction on the die-pressed biscuit obtained in the step (3) at 170 ℃, wherein the reaction time is 2.5h, and thus obtaining the formed biscuit.

(5) Gas-phase siliconizing and sintering:

and (4) carrying out gas-phase siliconizing sintering on the molded biscuit obtained in the step (4), wherein the siliconizing sintering temperature is 1600 ℃, and the time is 2 hours, so as to obtain a compact SiC-based complex-phase ceramic blank.

(6) And machining the SiC-based complex phase ceramic blank to obtain the SiC-based hot bending die. The surface roughness Ra of the hot bending die of the embodiment after polishing is detected to be 0.468 nm.

Example 3:

(1) preparing mixed slurry:

the method comprises the steps of adding a dispersing agent (polyvinylpyrrolidone and Dolapix CE64) and a solid-phase raw material into alcohol to obtain a premixed slurry, adding an alcohol solution of a curing cross-linking agent (phenolic resin) into the premixed slurry, and mechanically stirring for 5 hours to obtain a mixed slurry, wherein the solid-phase raw material consists of carbon black, graphite and α -SiC ceramic powder (including F240 and F1200), the mass percentage of the carbon black in the solid-phase raw material is 13.6%, the mass percentage of the graphite in the solid-phase raw material is 3.6%, the mass percentage of α -SiC ceramic powder in the solid-phase raw material is 82.8%, the mass percentage of F240/F1200 in the α -SiC ceramic powder is 1.5%, the mass percentage of the polyvinylpyrrolidone in the solid-phase raw material is 16.7%, the mass percentage of the Dolapix CE64 in the solid-phase raw material is α -SiC ceramic powder is 0.3%, and the mass percentage of the phenolic resin in the solid-phase raw material, the dispersing agent and the curing cross-linking agent is.

(2) Drying and crushing the mixed slurry:

(3) Die pressing/isostatic pressing:

and (3) taking the mixed powder obtained in the step (2), and forming by adopting a die pressing/isostatic pressing process to obtain a die pressing biscuit. The pressure for mould pressing is 10.3MPa, the pressure maintaining time is 60s, the pressure for isostatic pressing is 50MPa, and the pressure maintaining time is 60 s.

(4) Curing and crosslinking:

and (4) carrying out curing and crosslinking reaction on the die-pressed biscuit obtained in the step (3) at 170 ℃, wherein the reaction time is 3h, and thus obtaining the formed biscuit.

(5) Gas-phase siliconizing and sintering:

and (4) carrying out gas-phase siliconizing sintering on the molded biscuit obtained in the step (4), wherein the siliconizing sintering temperature is 1650 ℃, and the time is 2 hours, so as to obtain a compact SiC-based complex-phase ceramic blank.

Example 4:

(1) preparing mixed slurry:

the method comprises the steps of adding a dispersing agent (polyvinylpyrrolidone and Dolapix CE64) and a solid phase raw material into alcohol to obtain a premixed slurry, adding an alcohol solution of a curing cross-linking agent (phenolic resin) into the premixed slurry, and mechanically stirring for 5 hours to obtain a mixed slurry, wherein the solid phase raw material consists of carbon black, graphite and α -SiC ceramic powder (including F240 and F1200), the mass percentage of the carbon black in the solid phase raw material is 5%, the mass percentage of the graphite in the solid phase raw material is 91%, the mass percentage of the α -SiC ceramic powder in the mixed solid phase is 91%, the mass percentage of the F240/F1200 in the α -SiC ceramic powder is 1.72%, the mass percentage of the polyvinylpyrrolidone in the carbon black is 50%, the mass percentage of the Dolapix CE64 in the α -SiC ceramic powder is 0.3%, and the mass percentage of the phenolic resin in the solid phase raw material, the dispersing agent and the curing cross-linking agent is 5%.

(2) Drying and crushing the mixed slurry:

(3) Die pressing/isostatic pressing:

(4) Curing and crosslinking:

(5) Gas-phase siliconizing and sintering:

The surface roughness Ra of the hot bending die of the embodiment after polishing is detected to be 0.9 nm.

Comparative example 1:

a method for preparing a SiC ceramic-based hot bending die by slip casting comprises the following steps:

(1) preparing mixed slurry:

(1.1) dissolving tetramethylammonium hydroxide and polyvinylpyrrolidone (PVP K30) in water to obtain a mixed solution, wherein the mass of the tetramethylammonium hydroxide is 10% of that of deionized water, the mass of the polyvinylpyrrolidone (PVP K30) is 2% of that of the deionized water, adding a mixed solid phase consisting of carbon black, graphite and α -SiC ceramic powder into the mixed solution, wherein the mass percentage of the carbon black in the mixed solid phase is 15%, the mass percentage of the graphite in the mixed solid phase is 3.9%, the mass percentage of the α -SiC ceramic powder in the mixed solid phase is 81.1%, the mass ratio of F240/F1200 in the α -SiC ceramic powder is 1.5, and performing ball milling for 8 hours to obtain a premixed slurry with the solid content of 65 wt.%.

(1.2) the premixed slurry was vacuum-degassed for 30 minutes to obtain a mixed slurry.

(2) Grouting and forming: and (2) injecting the mixed slurry obtained in the step (1) into a gypsum mould for 60 min. Demoulding and drying to obtain a biscuit;

(3) gas-phase siliconizing and sintering: and (3) carrying out gas-phase siliconizing sintering on the gel biscuit obtained in the step (2), wherein the sintering temperature is 1700 ℃, and the time is 2.5 hours, so as to obtain a compact Si/SiC complex-phase ceramic blank.

(6) And machining the SiC-based complex phase ceramic blank to obtain the hot bending die.

Comparative example 2:

a method for preparing a SiC ceramic-based hot bending die by adopting dry compression molding comprises the following steps:

(1) preparing mixed powder:

the solid-phase raw materials and the phenolic resin are placed in a ball milling tank to be ball-milled for 6 hours to obtain mixed powder, wherein the solid-phase raw materials consist of carbon black, graphite and α -SiC ceramic powder (including F240 and F1200), the mass percentage of the carbon black is 15% of the solid-phase raw materials, the mass percentage of the α -SiC ceramic powder is 81.1% of the solid-phase raw materials, the mass percentage of the graphite is 3.9% of the solid-phase raw materials, the mass percentage of the phenolic resin is 3.9% of the total mass of the solid-phase raw materials and the phenolic resin, and the mass ratio of graded F240/F1200 in the α -SiC ceramic powder is 1.72.

(2) Die pressing/isostatic pressing:

and (2) taking the mixed powder obtained in the step (1), and forming by adopting a die pressing/isostatic pressing process to obtain a die pressing biscuit. The pressure for mould pressing is 10.3MPa, the pressure maintaining time is 60s, the pressure for isostatic pressing is 80MPa, and the pressure maintaining time is 60 s.

(3) Curing and crosslinking:

and (3) carrying out curing and crosslinking reaction on the die-pressed biscuit obtained in the step (2) at 170 ℃, wherein the reaction time is 2.5h, and thus obtaining the formed biscuit.

(5) Gas-phase siliconizing and sintering:

and (4) carrying out gas-phase siliconizing sintering on the molded biscuit obtained in the step (4), wherein the siliconizing sintering temperature is 1700 ℃, and the time is 2 hours, so as to obtain a compact SiC-based complex-phase ceramic blank.

Mechanical property tests were performed on the glass hot bending dies of examples 1 to 5 and comparative examples 1 and 2 and the SiC ceramic-based hot bending die prepared from the graphite material, and the test results are shown in table 1.

The SiC ceramic-based hot-bending dies of examples 1-5 and comparative examples 1 and 2 were tested for thermal shock resistance by heating the sample in a muffle furnace to a specific temperature, taking out the sample, cooling the sample in air for 5min, placing the cooled sample in water at 25 ℃, and observing the cracking of the sample, the experimental results are shown in Table 2, wherein the symbol "√" in Table 2 indicates that there is no cracking after the thermal shock test, and the symbol × indicates that the sample cracks after the thermal shock test.

TABLE 1

Hot bending die	Flexural strength Mpa	Flexural modulus GPa	Fracture toughness Mpa m^1/2
				Example 1	251.6	165	3.72
Example 2	276.4	180.2	3.92
				Example 3	263.7	171.3	3.84
Comparative example 1	216.7	132.4	3.25
				Comparative example 2	230.9	148.3	3.41

TABLE 2

200℃

300℃

400℃

500℃

600℃

700℃

750℃

Example 1

√

Example 2

√

Example 3

√

Comparative example 2

√

×

Comparative example 3

√

×

As can be seen from tables 1 and 2, compared with the hot bending mold made of SiC-based complex phase ceramic material obtained by slip casting, sintering after sintering, and dry mold pressing, the hot bending mold of the present invention has better mechanical properties and thermal shock properties, and completely meets the use requirements of the hot bending mold. Compared with a hot bending die made of graphite materials, the hot bending die provided by the invention has the advantages that the oxidation resistance, the wear resistance and the thermal shock resistance are more excellent, the service life of the die is longer, and the precision of the formed curved glass is higher.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. The preparation method of the SiC ceramic-based hot bending die is characterized by comprising the following steps of:

(5) machining the SiC-based complex-phase ceramic blank to obtain a SiC-based hot bending die;

the dispersing agent is polyvinylpyrrolidone and Dolapix CE64, the mass of the polyvinylpyrrolidone is 10-65% of that of the carbon black, and the mass of the Dolapix CE64 is 0.2-1% of that of the α -SiC ceramic powder;

the α -SiC ceramic powder consists of α -SiC ceramic powder with different grain sizes of F1200 and F240, and the mass ratio of α -SiC ceramic powder with the grain size of F1200 to α -SiC ceramic powder with the grain size of F240 is 1: 1-1.8;

in the step (1), the solid content of the mixed slurry is 50-80%, in the solid-phase raw material, the carbon black accounts for 10-15% of the solid-phase raw material by mass, the graphite accounts for 2-10% of the solid-phase raw material by mass, and the α -SiC ceramic powder accounts for 75-88% of the solid-phase raw material by mass.

2. The method for preparing the SiC ceramic-based hot bending die of claim 1, wherein the curing crosslinking agent is thermosetting phenolic resin, and the curing crosslinking agent accounts for 1-10% of the total mass of the solid phase raw material, the dispersing agent and the curing crosslinking agent.

3. The method for preparing the SiC ceramic-based hot bending die of claim 1, wherein in the step (3), the compression molding pressure is 8-15 MPa, and the compression molding time is 60-120 s; the isostatic compaction pressure is 50-150 Mpa, and the isostatic compaction time is 60-300 s.

4. The method for preparing the SiC ceramic-based hot bending die according to claim 1, wherein in the step (4), the temperature of the gas phase siliconizing sintering is 1500-1700 ℃, and the time is 1-3 h.

5. A SiC ceramic-based hot-bending die produced by the production method according to any one of claims 1 to 4.

6. The SiC ceramic-based hot bending die according to claim 5, wherein the SiC ceramic-based hot bending die is a glass hot bending die, the glass hot bending die comprises a female die and a male die, a contour groove is formed in the female die, a contour block matched with the contour groove is arranged on the male die, the height of the contour block is smaller than the depth of the contour groove, and the contour groove is matched with the contour block to form a cavity for glass hot bending.

7. The SiC ceramic based hot bending die of claim 6,

the female die comprises a base, a boss is arranged on the base, the profiling groove is formed in the middle of the boss, and an annular frame is formed between the outer wall of the boss and the wall of the profiling groove;