CN109053193B

CN109053193B - Silicon nitride ceramic nozzle and preparation method thereof

Info

Publication number: CN109053193B
Application number: CN201810810657.2A
Authority: CN
Inventors: 周存龙; 王强; 郭瑞; 高全宏
Original assignee: Taiyuan University of Science and Technology
Current assignee: Taiyuan University of Science and Technology
Priority date: 2018-07-23
Filing date: 2018-07-23
Publication date: 2021-05-07
Anticipated expiration: 2038-07-23
Also published as: CN109053193A

Abstract

The invention relates to a silicon nitride ceramic nozzle and a preparation method thereof, wherein the silicon nitride ceramic nozzle comprises the following raw materials: 65-7% of silicon nitride submicron powder0％，Y₂O₃5-10% of submicron powder, 5-8% of TiC submicron powder and Al₂O₃3% -5% of fine-grain powder and Li₂CO₃3-7% of submicron powder and ZrO₂1-3% of submicron powder and 2-5% of kaolin, and sintering and forming are carried out by using an SPS sintering technology. Compared with the traditional metal nozzle, the nozzle with wear resistance, good toughness and ultra-long service life, the preparation method and the installation method thereof can be provided, the wear resistance of the nozzle is effectively improved, and the time for replacing the nozzle is shortened.

Description

Silicon nitride ceramic nozzle and preparation method thereof

Technical Field

The invention belongs to the technical field of preparation of advanced structural materials and functional materials, and particularly relates to a silicon nitride ceramic nozzle and a preparation method thereof, wherein the product is applied to the technical field of ecological environment-friendly metal strip descaling.

Background

The traditional method for removing the oxide layer on the surface of the metal plate mainly relies on acid cleaning. The acid washing has great pollution to the environment, the treatment cost of waste acid is high, and the mixed slurry spray descaling technology is further promoted to be popularized and applied on the production line of hot rolled plates and strips along with the increase of the treatment intensity of the atmospheric environment on the surface quality of products. However, one of the bottlenecks restricting the massive popularization and application of the technology at present is that the nozzle made of wear-resistant alloy has short service life, short continuous working time and frequent replacement, and the production efficiency is influenced; and the time-varying size and shape of the nozzle outlet affects the precise control of the flow rate, resulting in unstable metal surface quality.

Si₃N₄The ceramic serving as a novel high-temperature structural ceramic has the excellent characteristics of wear resistance, corrosion resistance, creep resistance, high strength, thermal shock resistance, good thermal stability and the like, can be used for manufacturing wear-resistant, high-temperature-resistant and corrosion-resistant parts and the like, and is applied to extreme environments such as aerospace, metallurgy, machinery, chemical industry and the like.

Spark plasma sintering is a novel powder curing and forming technology for preparing functional materials. Compared with the traditional process, the SPS technology is mainly characterized in that the ultra-fast densification sintering of the material is realized by utilizing body heating and surface activation, and has the advantages of fast temperature rise, short sintering time, low sintering temperature, uniform heating, high production efficiency, energy conservation and the like. In addition, due to the comprehensive action of plasma activation and rapid heating sintering, the growth of crystal grains is inhibited, and the microstructure of original particles is maintained, so that the performance of a sintered body is essentially improved, and the final product has the characteristics of fine and uniform structure, capability of keeping the natural state of raw materials, high density and the like.

Chinese patent CN201010600974.5 discloses a method for producing high-performance silicon nitride (Si3N4) ceramic by pressureless sintering with cerium oxide and erbium oxide as additives. The composition comprises the following components in percentage by mass: 3 to 7 percent of cerium oxide, 5 to 8 percent of erbium oxide and 85 to 92 percent of silicon nitride. Aims to overcome the defects of the prior art, provides a method for producing high-performance silicon nitride ceramics by pressureless sintering by taking cerium oxide and erbium oxide as additives, and can be widely used for preparing parts in the fields of chemical industry, machinery, metallurgy, aerospace and the like.

Chinese patent CN201810059357.5 discloses a high-performance silicon-aluminum nitride-based composite material and a preparation method thereof, and relates to a high-performance silicon-aluminum nitride-based composite material and a preparation method thereof. The invention aims to solve the problem that the adding content of the reinforcement is limited by the conventional method. The high-performance silicon nitride aluminum-based composite material consists of 5-45% of Si in percentage by volume₃N₄The reinforcing body is made of 55 to 95 percent of aluminum matrix. The method comprises the following steps: firstly, calculating the mass of powder and weighing; secondly, ball milling and mixing the powder; thirdly, sieving the powder; fourthly, prepressing; and fifthly, performing discharge plasma sintering (SPS) in a protective atmosphere. The method is used for preparing the aluminum matrix composite.

Aiming at the problem of short service life of the wear-resistant metal nozzle, the invention provides a long-service-life composite wear-resistant nozzle which is prepared by adding different elements into non-metallic silicon nitride which is one of the hardest materials in the world, manufacturing a wear-resistant part of a nozzle outlet by using an SPS sintering technology and then connecting the wear-resistant part with a metal outer wall body.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides a silicon nitride ceramic nozzle and a preparation method thereof. Compared with the traditional metal nozzle, the nozzle with wear resistance, good toughness and ultra-long service life and the preparation method thereof can be provided, and the installation method of the nozzle is provided, so that the wear resistance of the nozzle is effectively improved, and the installation time of the nozzle is shortened.

In order to achieve the purpose, the invention adopts the following scheme:

a preparation method of a silicon nitride ceramic nozzle comprises the following raw materials: 65-70% of silicon nitride submicron powder and Y₂O₃5-10% of submicron powder, 5-8% of TiC submicron powder and Al₂O₃3% -5% of fine-grain powder and Li₂CO₃3-7% of submicron powder and ZrO₂1-3% of submicron powder and 2-5% of kaolin, and sintering and forming are carried out by using an SPS sintering technology.

As a further preferable scheme, the sintering comprises batching, ball milling, drying, die filling, low-temperature inner hole preforming, high-temperature sintering and product post-treatment.

Preferably, the silicon nitride in the raw material is alpha-Si₃N₄。

As a further preferable mode, the particle size of silicon nitride in the raw material used is 0.8 μm.

As a further preferable scheme, the preparation process of the raw materials comprises the steps of taking silicon nitride as a main raw material, adding other components, taking absolute ethyl alcohol as a solvent, and carrying out wet ball milling to uniformly mix powder materials.

In a further preferred embodiment, the abrasive used in the ball milling is silicon nitride beads.

As a further preferred scheme, the SPS sintering operation is as follows: putting the prepared powder into a graphite mold, separating the powder from the inner wall of the mold by carbon paper, putting the powder into an SPS sintering furnace, fixing two sections of graphite electrodes, vacuumizing to be within 20Pa, adjusting the lifting and falling of the upper and lower electrodes to keep the pressure at 25MPa in the sintering process, heating to 800 ℃ at the speed of 2 ℃/s, preserving heat for 1min, keeping the pressure, cooling for 20 min along with the furnace, taking out, removing a core mold, putting the core mold into the SPS sintering furnace again, adjusting the lifting and falling of the upper and lower electrodes to keep the pressure at 12.5MPa, heating to 1400 ℃ at the speed of 2 ℃/s, increasing the pressure to 35MPa and keeping the pressure when the temperature is increased to 1200 ℃, heating to 1780 ℃ at the speed of 0.8 ℃/s, preserving heat for 5min, sintering, keeping the pressure, cooling for 40min along with the furnace, taking out, wherein the pulse output pressure range is 2-12V, and the output.

In a further preferable scheme, the inner hole of the nozzle is processed by adopting a preforming method, and the core die material used for preforming is die steel.

The invention also provides an installation method of the silicon nitride ceramic nozzle prepared by the preparation method, which comprises the following steps: the silicon nitride and metal jacket are installed in a composite forming mode, wherein the composite forming mode of the silicon nitride and the metal jacket is divided into four parts: the mixing device comprises a mixing cavity, a silicon nitride ceramic nozzle, a metal sleeve and an adjusting ring; the mixing cavity is in threaded connection with the metal sleeve, so that the silicon nitride ceramic nozzle can be conveniently replaced; the adjusting ring is in threaded connection with the metal sleeve and is used for axially fixing the silicon nitride ceramic nozzle.

Compared with the prior art, the invention has the following beneficial effects: firstly, adding elements of different types and different proportions into silicon nitride powder, then using the silicon nitride powder as a raw material for manufacturing the nozzle, sintering and forming by utilizing an SPS (plasma sintering system) sintering technology, and finally combining the silicon nitride powder with a metal jacket to obtain the nozzle for spraying the abrasive mixed slurry. The wear resistance of the nozzle is effectively improved by optimizing the nozzle formula. And then, the sintering process is further optimized and improved, so that the density of the finally obtained sintered body can reach more than or equal to 99 percent, the Vickers hardness is more than or equal to 1656, and the bending strength is more than or equal to 900MPa, and the nozzle with wear resistance, good toughness and ultra-long service life is provided for the industry. The invention adopts the composite molding mode of silicon nitride and the metal jacket for installation, thereby being more convenient for replacing and axially fixing the silicon nitride ceramic nozzle.

Drawings

The following is further described with reference to the accompanying drawings:

fig. 1 and 2 are external views of a core mold;

FIGS. 3 and 4 are schematic diagrams of a preform; 1. an upper pressing block, 2, a core mould, 3, sintering powder, 4, a female mould and 5, a lower pressing block;

FIGS. 5 and 6 are schematic illustrations of continued sintering after preforming;

FIGS. 7 and 8 are untreated sintered bodies;

FIGS. 9 and 10 are final nozzle shapes;

FIG. 11 is a schematic view of a silicon nitride nozzle formed in combination with metal;

wherein, 1, a metal sleeve; 2. a gasket; 3. A mixing chamber; 4. A silicon nitride ceramic nozzle; 5. An adjusting ring;

FIG. 12 is a schematic view of the threaded connection of the adjustment ring to the metal sleeve;

FIG. 13 is a schematic view of the threaded connection of the metal sleeve to the mixing chamber.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in detail and completely with reference to the following embodiments. It should be understood that the described embodiments are only a few embodiments of the present invention, not all embodiments, and are not to be construed as limiting the present invention. Based on the embodiments of the present invention, any person skilled in the art can make no creative effort or substantial adjustment according to the present invention, and the protection scope of the present invention is still covered.

Example 1

Proportioning: alpha-Si with average grain size of 0.8 mu m₃N₄TiC having an average particle size of 0.8 [ mu ] m, Y having an average particle size of 0.8 [ mu ] m₂O₃And Al having an average particle diameter of 1 μm₂O₃And Li having an average particle diameter of 0.8 [ mu ] m₂CO₃ZrO having an average particle size of 1 μm₂And kaolin is weighed according to the following mixture ratio: alpha-Si₃N₄Submicron powder 65%, Y₂O₃8% of submicron powder, 5% of TiC submicron powder and Al₂O₃Fine grain powder 3%, Li₂CO₃Submicron powder 3%, ZrO₂1% of submicron powder and 2% of kaolin.

Ball milling: ball milling is carried out by utilizing a planetary ball mill. The grinding ball material is silicon nitride, the ratio of ground hot 10mm and ground hot 5mm is 1: 5, the rotating speed of the ball mill is 280r/min, positive and negative rotation is alternated every 20 minutes, and the ball: material preparation: the proportion of the absolute ethyl alcohol is 4:2:1, and the ball milling time is 10 h.

Thirdly, drying: and drying the ball-milled powder in an oven at a constant temperature of 353K (80 ℃) for 5 hours.

Fourthly, die filling: the prepared powder is filled into a graphite mould, and carbon paper is pasted on the inner wall of the mould to separate the powder, so that the powder is prevented from being bonded with the mould. During charging, the powder is properly pressurized on a press machine after being charged, so that the powder is compact.

Performing low-temperature inner hole: as shown in figures 3 and 4, the graphite mould filled with the powder is placed in an SPS sintering furnace, two sections of graphite electrodes are added and fixed, after the SPS sintering furnace is vacuumized to be within 20Pa, the lifting of the upper electrode and the lower electrode is adjusted to keep the pressure at 25MPa in the sintering process, the graphite mould is heated to 800 ℃ at the speed of 2 ℃/s, the graphite mould is taken out after the graphite mould is cooled for 20 minutes along with the furnace, and the core mould is removed.

Sixthly, high-temperature sintering: after the core mold is removed, the upper pressing block is changed into a solid pressing block, as shown in fig. 5 and 6, the mold filled with the powder is placed into the SPS sintering furnace again, the lifting and the lowering of the upper electrode and the lower electrode are adjusted to keep the pressure at 12.5MPa, the temperature is heated to 1400 ℃ at the speed of 2 ℃/s, and the pressure is raised to 35MPa and kept when the temperature is raised to 1200 ℃. Then heating to 1780 deg.C at a speed of 0.8 deg.C/s, maintaining the temperature for 5min for sintering, maintaining the pressure, furnace cooling for 40min, and taking out. The pulse output pressure range is 2-12V, and the output current range is 0-5000A.

And (c) demoulding: the die is placed on a press machine workbench, a press machine piston props against an upper pressing block of the die, the lower portion of the press machine piston supports the die and makes a lower pressing block overhead, manual pressure is applied until the material is extruded, the die is shielded by a shielding object in the pressure applying process, and the die is prevented from bursting and hurting people.

B, post-treatment of the product: and grinding the sintered body by using a diamond grinding wheel, wherein the metal bond diamond grinding wheel with the granularity of 160/125-80/63 and the concentration of 100% is adopted during grinding. The grinding dosage is as follows: and the grinding wheel speed V = 20-35 m/s.

Example 2

Proportioning: alpha-Si with average grain size of 0.8 mu m₃N₄TiC having an average particle size of 0.8 [ mu ] m, Y having an average particle size of 0.8 [ mu ] m₂O₃And Al having an average particle diameter of 1 μm₂O₃And Li having an average particle diameter of 0.8 [ mu ] m₂CO₃ZrO having an average particle size of 1 μm₂And kaolin is weighed according to the following mixture ratio: alpha-Si₃N₄Submicron powder 70%, Y₂O₃10% of submicron powder, 8% of TiC submicron powder and Al₂O₃ Fine grain powder 5%, Li₂CO₃Submicron powder 5%, ZrO₂2% of submicron powder and 4% of kaolin.

Example 3

Proportioning: alpha-Si with average grain size of 0.8 mu m₃N₄TiC having an average particle size of 0.8 [ mu ] m, Y having an average particle size of 0.8 [ mu ] m₂O₃And Al having an average particle diameter of 1 μm₂O₃And Li having an average particle diameter of 0.8 [ mu ] m₂CO₃ZrO having an average particle size of 1 μm₂And kaolin is weighed according to the following mixture ratio: alpha-Si₃N₄Submicron powder 70%, Y₂O₃10% of submicron powder, 8% of TiC submicron powder and Al₂O₃ Fine grain powder 5%, Li₂CO₃Submicron powder 7%, ZrO₂3% of submicron powder and 5% of kaolin.

The density of the sintered body of the sample is calculated by an Archimedes drainage method, the Vickers hardness (load of 5 kg) of the product is measured by an indentation method, and the density of the sintered body is measured by a boiling method.

The density, vickers hardness, and flexural strength of the sintered bodies of the articles of examples 1-3 above are shown in table 1 below:

TABLE 1

The installation mode of the silicon nitride ceramic nozzle is as follows: the silicon nitride and metal jacket are installed in a composite forming mode, wherein the composite forming mode of the silicon nitride and the metal jacket is divided into four parts: the mixing device comprises a mixing cavity, a silicon nitride ceramic nozzle, a metal sleeve and an adjusting ring; the mixing cavity is in threaded connection with the metal sleeve, so that the silicon nitride ceramic nozzle can be conveniently replaced; the adjusting ring is in threaded connection with the metal sleeve and is used for axially fixing the silicon nitride ceramic nozzle.

The metal sleeve 1 is in threaded connection with the mixing cavity 3, so that the failed nozzle 4 is convenient to replace in the future, and the failed nozzle can be replaced only by unscrewing the metal sleeve and drawing out the nozzle. This saves both costs and also reduces the time to change nozzles. The adjusting ring 5 is also in threaded connection with the metal sleeve, and the function of the adjusting ring is to fix the nozzle in the axial direction through the movement of the adjusting ring in the axial direction, so that the problem that the axial size of each nozzle is deviated and cannot be fixed is solved.

The above description is only for the purpose of illustrating preferred embodiments of the present invention and is not to be construed as limiting the present invention, and any modifications, improvements, equivalents and the like that fall within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims

1. The preparation method of the silicon nitride ceramic nozzle is characterized in that the silicon nitride ceramic nozzle comprises the following raw materials: 65-70% of silicon nitride submicron powder and Y₂O₃5-10% of submicron powder, 5-8% of TiC submicron powder and Al₂O₃3% -5% of fine-grain powder and Li₂CO₃3-7% of submicron powder and ZrO₂1-3% of submicron powder and 2-5% of kaolin, and sintering and forming the submicron powder by using an SPS sintering technology, wherein the SPS sintering operation is as follows: putting the prepared powder into a graphite mould, separating the powder from the inner wall of the mould by carbon paper, putting the powder into an SPS sintering furnace, fixing the two sections by adding graphite electrodes, vacuumizing to be within 20Pa, adjusting the lifting and falling of the upper and lower electrodes to keep the pressure at 25MPa in the sintering process, heating to 800 ℃ at the speed of 2 ℃/s, keeping the temperature for 1min, keeping the pressure, cooling for 20 min along with the furnace, taking out, removing the core mould, putting the core mould into the SPS sintering furnace again, adjusting the lifting and falling of the upper and lower electrodes to keep the pressure at 12.5MPa, heating to 1400 ℃ at the speed of 2 ℃/s, increasing the pressure to 35MPa and keeping the pressure when the temperature is increased to 1200 ℃, heating to 1780 ℃ at the speed of 0.8 ℃/s, keeping the temperature for 5minAnd (4) maintaining the pressure, cooling the pressure along with the furnace for 40min, and taking out the pressure, wherein the pulse output pressure is 2-12V, and the output current is 0-5000A.

2. The method of claim 1, wherein the core material for preforming is die steel.

3. The method according to claim 1, wherein the raw material used is silicon nitride of alpha-Si₃N₄。

4. The preparation method according to claim 1, characterized in that the particle size of silicon nitride in the used raw materials is 0.8 μm, silicon nitride is used as a main raw material, other components are added, and absolute ethyl alcohol is used as a solvent to perform wet ball milling, so that the powder materials are uniformly mixed.

5. The method according to claim 4, wherein the abrasive used in the ball milling is silicon nitride beads.

6. A silicon nitride ceramic nozzle produced by the production method according to any one of claims 1 to 5.