BN-based composite ceramics for side seal plate of strip continuous casting and its preparation method

Abstract

The present invention discloses a boron nitride-based composite ceramic for thin strip continuous casting side seal plates and a preparation method thereof. The technical solution is as follows: Mix elemental Si powder, h-BN powder, elemental Ti powder and a conditioning agent to obtain a mixed powder; place the mixed powder, absolute ethanol and ball milling beads in a high-speed ball mill for ball milling to obtain a slurry; dry and screen the slurry to obtain a screened material; place the hot pressing die I containing the screened material in a hot pressing sintering furnace, keep the temperature and pressure constant at 10-30 MPa, 1300-1450 °C and in nitrogen, cool and release pressure with the furnace to obtain a pre-sintered side seal plate, and then place the hot pressing die II containing the pre-sintered side seal plate in a hot pressing sintering furnace, keep the temperature and pressure constant at 100-200 MPa, 1400-1500 °C and in an inert atmosphere, cool and release pressure with the furnace to prepare the boron nitride-based composite ceramic for thin strip continuous casting side seal plates. The product prepared by the present invention has the characteristics of low thermal conductivity, good erosion resistance, high high-temperature bending strength and long service life.

Description

Technical Field

[0001] The present invention relates to the technical field of composite ceramic side seal plates. Specifically, it relates to a boron nitride-based composite ceramic for a thin strip continuous casting side seal plate and a preparation method thereof. Background Art

[0002] Thin strip continuous casting is a process that uses reversely rotating roller shafts and side seal plates to continuously form strips without hot rolling. The side seal technology is one of the most critical technologies in the twin-roll thin strip continuous casting technology. It is a key factor affecting the quality of the cast strip and the process stability during thin strip continuous casting, and ultimately determines whether the thin strip continuous casting technology can be widely applied in industrial production. However, with the higher requirements for thin strip steel and the continuous development of the thin strip continuous casting process, the existing side seal materials are difficult to meet the higher production requirements. Whether it is side seal material systems such as sialon-BN, AlN-BN, and mullite-BN, they have disadvantages such as high temperature instability, high thermal conductivity, and easy erosion, which are difficult to be applied industrially. The instability during the thin strip continuous casting process and the quality problems of the cast strip have hindered the industrialization process of thin strip continuous casting. Therefore, the research and preparation of new side seal plates have attracted the attention of technicians.

[0003] Barick P et al. (Barick P, Saha B P. Effect of boron nitride addition on densification, microstructure, mechanical, thermal, and dielectric properties of β-SiAlON ceramic [J]. Journal of Materials Engineering and Performance, 2021, 30: 3603-3611) mixed Si3N4 powder, BN powder, AlN powder, and Al2O3 powder and obtained a high-strength β-SiAlON / BN ceramic composite material by holding at 1800 °C for 4 h. However, due to the too high thermal conductivity, local condensation and caking occurred on the side seal plate, and it was easily eroded by molten steel, affecting the service life of the side seal plate.

[0004] The patented technology of "Max phase-boron nitride composite ceramic side sealing plate for thin strip continuous casting and its manufacturing method" (CN 104876598A) uses 40-70% h-BN powder, 10-30% Max phase powder, 5-20% AlN powder, 5-20% AlB2 powder and 0.5-5% Al2O3 powder as raw materials, mixes them, and keeps them warm for 10-30 minutes at 1300-1600℃ and 5-60MPa by spark plasma sintering. The prepared side sealing plate material has low thermal conductivity and high strength. However, since the Max phase is easily oxidized at high temperature, the thermal expansion coefficient of the side sealing plate material increases, cracking occurs, and the high-temperature bending strength of the side sealing plate is reduced. Summary of the invention

[0005] The present invention aims to overcome the defects of the prior art and aims to provide a boron nitride-based composite ceramic for a thin strip continuous casting side sealing plate having low thermal conductivity, good resistance to molten steel corrosion, high high temperature bending strength and long service life and a preparation method thereof.

[0006] To achieve the above object, the steps of the technical solution adopted by the present invention are:

[0007] Step 1: 15-30 wt% of silicon powder, 55-70 wt% of boron nitride powder, 5-10 wt% of titanium powder and 5-15 wt% of a tempering agent are mixed to obtain a mixed powder.

[0008] Step 2: prepare the mixed powder, anhydrous ethanol, and ball milling beads in a ball mill according to a mass ratio of 1:8-12:2-4, place the mixed powder, anhydrous ethanol, and ball milling beads in a ball mill, and mill them at 250-350 r / min for 6-9 hours to obtain a slurry.

[0009] Step 3: Dry the slurry at 80-200° C. for 12-48 hours to obtain a powder; and then sieve the powder to obtain a sieved material with a particle size of less than 75 μm.

[0010] Step 4: Place the screened material in a hot pressing mold I, then place the hot pressing mold I in a hot pressing sintering furnace, and heat it to 950-1050°C at a rate of 600-1200°C / h under 0.1-0.2Pa conditions; then pressurize and heat it and introduce nitrogen at the same time, and keep the temperature and pressure at 10-30MPa, 1300-1450°C and nitrogen atmosphere for 0.5-4h, cool it down and release the pressure along with the furnace to obtain a pre-sintered side sealing plate.

[0011] Step 5: Place the pre-sintered side seal plate into the hot pressing die II, then place the hot pressing die II into the hot pressing sintering furnace, and heat it to 950 - 1050°C at a rate of 800 - 1100°C / h in an inert atmosphere; then simultaneously apply pressure, heat up, and introduce an inert gas, keep the temperature and pressure constant for 2 - 6 h under the conditions of 100 - 200 MPa, 1400 - 1500°C, and an inert atmosphere, and cool down and relieve pressure with the furnace to obtain a boron nitride-based composite ceramic for thin strip continuous casting side seal plates.

[0012] The Si content of the elemental silicon powder ≥ 99 wt%; the particle size of the elemental silicon powder is less than 30 μm.

[0013] The BN content of the boron nitride powder ≥ 95 wt%; the particle size of the boron nitride powder is less than 48 μm.

[0014] The Ti content of the elemental titanium powder ≥ 99 wt%, and the particle size of the elemental titanium powder is less than 75 μm.

[0015] The tempering agent is one or two of titanium boride powder, flaky nano-silicon powder, and boron powder, where: the TiB2 content of the titanium boride powder ≥ 98 wt%, the Si content of the flaky nano-silicon powder ≥ 99 wt%, and the B content of the boron powder ≥ 98 wt%; the particle size of the tempering agent ≤ 75 μm.

[0016] The ball milling beads are agate or corundum.

[0017] The inert atmosphere is nitrogen or argon.

[0018] Due to the adoption of the above technical solution, the present invention has the following positive effects compared with the prior art:

[0019] The present invention uses boron nitride powder, elemental silicon powder, and elemental titanium powder as raw materials, adds a tempering agent and mixes them, and in-situ generates layered Ti2SiB during the pre-sintering process. The generated layered Ti2SiB combines with BN particles to form an interlaced network structure. At the same time, in the high-pressure environment of secondary sintering, SiTi2N4 particles are in-situ generated. The generated SiTi2N4 particles complement the BN-Ti2SiB structure. Under the coupling effect of the BN-Ti2SiB network structure and the filling of pores by SiTi2N4 particles, the boron nitride-based composite ceramic for thin strip continuous casting side seal plates prepared has low thermal conductivity and good resistance to molten steel erosion.

[0020] The interaction between the high-temperature damage tolerance of the ternary MAB phase Ti2SiB in the boron nitride-based composite ceramic for thin strip continuous casting side seal plates prepared by the present invention and the high strength of the covalent ternary nitride SiTi2N4 with a spinel structure enables the boron nitride-based composite ceramic for thin strip continuous casting side seal plates to have good high-temperature stability with the crystallization roll, and enhances the high-temperature bending strength of the boron nitride-based composite ceramic for thin strip continuous casting side seal plates.

[0021] In the boron nitride-based composite ceramic for the side sealing plate of thin strip continuous casting prepared by the present invention, SiTi2N4 is pinned in the BN-Ti2SiB network structure and is tightly combined. In a high-temperature environment, the crack propagation of the boron nitride-based composite ceramic for the side sealing plate of thin strip continuous casting is suppressed, the thermal expansion coefficient is reduced, the high-temperature service life is enhanced, and the service life of the boron nitride-based composite ceramic for the side sealing plate of thin strip continuous casting is further improved.

[0022] The boron nitride-based composite ceramic for the thin strip continuous casting side sealing plate prepared by the present invention has been tested to have a high-temperature bending strength of 105.4-112.8 MPa and a thermal expansion coefficient of 3.12-3.45×10 -6 ·K -1 ; Thermal conductivity is 11~15W / (m·K); Wetting angle is 75~90°.

[0023] Therefore, the boron nitride-based composite ceramic for the thin strip continuous casting side sealing plate prepared by the present invention has the characteristics of low thermal conductivity, good resistance to molten steel corrosion, high high-temperature bending strength and long service life. DETAILED DESCRIPTION

[0024] The present invention is further described below in conjunction with specific implementation modes, but is not intended to limit the protection scope thereof.

[0025] A boron nitride-based composite ceramic for a thin strip continuous casting side sealing plate and a preparation method thereof. The steps of the preparation method described in this specific embodiment are:

[0026] Step 1: 15-30 wt% of silicon powder, 55-70 wt% of boron nitride powder, 5-10 wt% of titanium powder and 5-15 wt% of a tempering agent are mixed to obtain a mixed powder.

[0027] Step 2: prepare the mixed powder, anhydrous ethanol, and ball milling beads in a ball mill according to a mass ratio of 1:8-12:2-4, place the mixed powder, anhydrous ethanol, and ball milling beads in a ball mill, and mill them at 250-350 r / min for 6-9 hours to obtain a slurry.

[0028] Step 3: Dry the slurry at 80-200° C. for 12-48 hours to obtain a powder; and then sieve the powder to obtain a sieved material with a particle size of less than 75 μm.

[0029] Step 4: Place the sieved material in Hot Pressing Mold I, then place Hot Pressing Mold I in a hot press sintering furnace, and heat it to 950 - 1050°C at a rate of 600 - 1200°C / h under the condition of 0.1 - 0.2 Pa; then apply pressure, heat up, and introduce nitrogen simultaneously, keep it warm for 0.5 - 4 h under the conditions of 10 - 30 MPa, 1300 - 1450°C, and nitrogen atmosphere, cool down with the furnace and relieve pressure to obtain a pre-sintered side seal plate.

[0030] Step 5: Place the pre-sintered side seal plate in Hot Pressing Mold II, then place Hot Pressing Mold II in a hot press sintering furnace, and heat it to 950 - 1050°C at a rate of 800 - 1100°C / h in an inert atmosphere; then apply pressure, heat up, and introduce an inert gas simultaneously, keep it warm for 2 - 6 h under the conditions of 100 - 200 MPa, 1400 - 1500°C, and inert atmosphere, cool down with the furnace and relieve pressure to prepare a boron nitride-based composite ceramic for thin strip continuous casting side seal plate.

[0031] The tempering agent is one or two of titanium boride powder, flaky nano silicon powder, and boron powder.

[0032] The ball milling beads are agate or corundum.

[0033] The inert atmosphere is nitrogen or argon.

[0034] In this specific embodiment:

[0035] The Si content of the elemental silicon powder ≥ 99 wt%; the particle size of the elemental silicon powder is less than 30 μm.

[0036] The BN content of the boron nitride powder ≥ 95 wt%; the particle size of the boron nitride powder is less than 48 μm.

[0037] The Ti content of the elemental titanium powder ≥ 99 wt%, and the particle size of the elemental titanium powder is less than 75 μm.

[0038] The particle size of the tempering agent ≤ 75 μm.

[0039] The TiB₂ content of the titanium boride powder ≥ 98 wt%, the Si content of the flaky nano silicon powder ≥ 99 wt%, and the B content of the boron powder ≥ 98 wt%.

[0040] Details in the examples will not be elaborated again.

[0041] Example 1

[0042] A boron nitride-based composite ceramic for thin strip continuous casting side seal plate and its preparation method. The steps of the preparation method in this embodiment are as follows:

[0043] Step 1: 18 wt% of elemental silicon powder, 60 wt% of boron nitride powder, 7 wt% of elemental titanium powder and 15 wt% of flaky nano silicon powder are mixed to obtain a mixed powder.

[0044] Step 2: The mixed powder, anhydrous ethanol and ball milling beads are placed in a ball mill according to a mass ratio of 1:8:2, and ball milled at 300 r / min for 9 hours to obtain a slurry.

[0045] Step 3: Dry the slurry at 80° C. for 48 hours to obtain a powder; and then sieve the powder to obtain a sieved material with a particle size of less than 75 μm.

[0046] Step 4: Place the screened material in a hot pressing mold I, then place the hot pressing mold I in a hot pressing sintering furnace, and heat it to 950°C at a rate of 600 / h under 0.1Pa conditions; then pressurize, heat up, and introduce nitrogen at the same time, and keep the temperature and pressure at 30MPa, 1300°C and nitrogen atmosphere for 0.5h, cool down and release the pressure with the furnace to obtain a pre-sintered side sealing plate.

[0047] Step 5: Place the pre-sintered side sealing plate in a hot pressing mold II, then place the hot pressing mold II in a hot pressing sintering furnace, and heat it to 950°C at a rate of 1000°C / h in an inert atmosphere; then pressurize, heat up, and introduce inert gas at the same time, and keep the temperature and pressure at 200MPa, 1500°C and inert atmosphere for 4 hours, cool down and release the pressure along with the furnace to obtain a boron nitride-based composite ceramic for thin strip continuous casting side sealing plates.

[0048] The ball milling beads are agate.

[0049] The inert atmosphere is nitrogen.

[0050] The boron nitride-based composite ceramic for the thin strip continuous casting side sealing plate prepared in this embodiment has been tested: the high temperature bending strength is 110.2MPa; the thermal expansion coefficient is 3.12×10 -6 ·K -1 ; Thermal conductivity is 15W / (m·K); Wetting angle is 85°.

[0051] Example 2

[0052] A boron nitride-based composite ceramic for a thin strip continuous casting side sealing plate and a preparation method thereof. The steps of the preparation method described in this embodiment are:

[0053] Step 1: 30 wt% of silicon powder, 55 wt% of boron nitride powder, 5 wt% of titanium powder and 10 wt% of boron powder are mixed to obtain a mixed powder.

[0054] Step 2: Weigh the mixture powder, absolute ethanol, and grinding beads according to the mass ratio of 1:9:4. Place the mixture powder, absolute ethanol, and grinding beads into a ball mill, and ball mill for 6 hours at 250 r / min to obtain a slurry.

[0055] Step 3: Dry the slurry at 150 °C for 24 hours to obtain a powder; then screen the powder to obtain a screened material with a particle size less than 75 μm.

[0056] Step 4: Place the screened material into hot pressing mold I, and then place hot pressing mold I into a hot press sintering furnace. Heat it to 1000 °C at a rate of 800 °C / h under the condition of 0.15 Pa; then simultaneously apply pressure, heat up, and introduce nitrogen gas. Keep the temperature and pressure constant for 1 hour under the conditions of 20 MPa, 1400 °C, and nitrogen atmosphere. Cool down and relieve pressure with the furnace to obtain a pre-sintered side seal plate.

[0057] Step 5: Place the pre-sintered side seal plate into hot pressing mold II, and then place hot pressing mold II into a hot press sintering furnace. Heat it to 1000 °C at a rate of 800 °C / h in an inert atmosphere; then simultaneously apply pressure, heat up, and introduce an inert gas. Keep the temperature and pressure constant for 6 hours under the conditions of 150 MPa, 1400 °C, and inert atmosphere. Cool down and relieve pressure with the furnace to prepare a boron nitride-based composite ceramic for a thin strip continuous casting side seal plate.

[0058] The grinding beads are corundum.

[0059] The inert atmosphere is argon.

[0060] The boron nitride-based composite ceramic for a thin strip continuous casting side seal plate prepared in this example is detected: the high-temperature bending strength is 105.4 MPa; the thermal expansion coefficient is 3.45×10 -6 ·K -1 ; the thermal conductivity is 14 W / (m·K); the wetting angle is 90°.

[0061] Example 3

[0062] A boron nitride-based composite ceramic for a thin strip continuous casting side seal plate and a preparation method thereof. The steps of the preparation method described in this embodiment are as follows:

[0063] Step 1: Mix 15 wt% of elemental silicon powder, 70 wt% of boron nitride powder, 10 wt% of elemental titanium powder, and 5 wt% of titanium boride powder to obtain a mixture powder.

[0064] Step 2: Weigh the mixture powder, absolute ethanol, and grinding beads according to the mass ratio of 1:12:3. Place the mixture powder, absolute ethanol, and grinding beads into a ball mill, and ball mill for 7 hours at 350 r / min to obtain a slurry.

[0065] Step 3: Dry the slurry at 200° C. for 12 hours to obtain a powder; and then sieve the powder to obtain a sieved material with a particle size of less than 75 μm.

[0066] Step 4: Place the screened material in a hot pressing mold I, then place the hot pressing mold I in a hot pressing sintering furnace, and heat it to 1050°C at a rate of 1200°C / h under 0.2Pa conditions; then pressurize, heat up and introduce nitrogen at the same time, keep the temperature and pressure at 10MPa, 1450°C and nitrogen atmosphere for 4 hours, cool down and release the pressure along with the furnace to obtain a pre-sintered side sealing plate.

[0067] Step 5: Place the pre-sintered side sealing plate in a hot pressing mold II, then place the hot pressing mold II in a hot pressing sintering furnace, and heat it to 1050°C at a rate of 1100°C / h in an inert atmosphere; then pressurize, heat up and introduce inert gas at the same time, keep the temperature and pressure at 100MPa, 1450°C and inert atmosphere for 2h, cool down and release the pressure along with the furnace, and obtain a boron nitride-based composite ceramic for thin strip continuous casting side sealing plates.

[0068] The ball milling beads are agate.

[0069] The inert atmosphere is argon.

[0070] The boron nitride-based composite ceramic for the thin strip continuous casting side sealing plate prepared in this embodiment has been tested: the high temperature bending strength is 111.4MPa; the thermal expansion coefficient is 3.28×10 -6 ·K -1 ; Thermal conductivity is 11W / (m·K); Wetting angle is 75°.

[0071] Example 4

[0072] A boron nitride-based composite ceramic for a thin strip continuous casting side sealing plate and a preparation method thereof. The steps of the preparation method described in this embodiment are:

[0073] Step 1: 30 wt% of elemental silicon powder, 60 wt% of boron nitride powder, 5 wt% of elemental titanium powder, 2 wt% of titanium boride and 3 wt% of flaky nano silicon powder are mixed to obtain a mixed powder.

[0074] Step 2: The mixed powder, anhydrous ethanol and ball milling beads are placed in a ball mill and milled at 330 r / min for 9 hours to obtain a slurry according to the mass ratio of the mixed powder, anhydrous ethanol and ball milling beads of 1:10:4.

[0075] Step 3: Dry the slurry at 80° C. for 48 hours to obtain a powder; and then sieve the powder to obtain a sieved material with a particle size of less than 75 μm.

[0076] Step 4: Place the screened material in a hot pressing mold I, then place the hot pressing mold I in a hot pressing sintering furnace, and heat it to 1000°C at a rate of 1000°C / h under 0.12Pa conditions; then pressurize, heat up and introduce nitrogen at the same time, keep the temperature and pressure at 30MPa, 1450°C and nitrogen atmosphere for 4 hours, cool down and release the pressure with the furnace to obtain a pre-sintered side sealing plate.

[0077] Step 5: Place the pre-sintered side sealing plate in a hot pressing mold II, then place the hot pressing mold II in a hot pressing sintering furnace, and heat it to 1000°C at a rate of 900°C / h in an inert atmosphere; then pressurize, heat up and introduce inert gas at the same time, keep the temperature and pressure at 180MPa, 1500°C and inert atmosphere for 3 hours, cool down and release the pressure along with the furnace, and obtain a boron nitride-based composite ceramic for thin strip continuous casting side sealing plates.

[0078] The ball milling beads are corundum.

[0079] The inert atmosphere is nitrogen.

[0080] The boron nitride-based composite ceramic for the thin strip continuous casting side sealing plate prepared in this embodiment has been tested: the high temperature bending strength is 100.8MPa; the thermal expansion coefficient is 3.36×10 -6 ·K -1 ; Thermal conductivity is 12W / (m·K); Wetting angle is 80°.

[0081] Example 5

[0082] A boron nitride-based composite ceramic for a thin strip continuous casting side sealing plate and a preparation method thereof. The steps of the preparation method described in this embodiment are:

[0083] Step 1: 15 wt% of elemental silicon powder, 70 wt% of boron nitride powder, 7 wt% of elemental titanium powder, 5 wt% of flaky nano silicon powder and 3 wt% of boron powder are mixed to obtain a mixed powder.

[0084] Step 2: prepare the mixed powder, anhydrous ethanol and ball milling beads in a ball mill at a mass ratio of 1:8:3, place the mixed powder, anhydrous ethanol and ball milling beads in a ball mill, and ball mill at 250 r / min for 8 hours to obtain a slurry.

[0085] Step 3: Dry the slurry at 200° C. for 12 hours to obtain a powder; and then sieve the powder to obtain a sieved material with a particle size of less than 75 μm.

[0086] Step 4: Place the sieved material in Hot Pressing Die I, then place Hot Pressing Die I in a hot press sintering furnace, and heat it to 1050°C at a rate of 1200°C / h under the condition of 0.2 Pa; then simultaneously apply pressure, heat up, and introduce nitrogen gas, keep the temperature and pressure constant for 2 h under the conditions of 25 MPa, 1350°C, and nitrogen gas atmosphere, and cool down and relieve pressure with the furnace to obtain a pre-sintered side seal plate.

[0087] Step 5: Place the pre-sintered side seal plate in Hot Pressing Die II, then place Hot Pressing Die II in a hot press sintering furnace, and heat it to 1050°C at a rate of 1100°C / h in an inert atmosphere; then simultaneously apply pressure, heat up, and introduce an inert gas, keep the temperature and pressure constant for 6 h under the conditions of 100 MPa, 1450°C, and inert atmosphere, and cool down and relieve pressure with the furnace to obtain a boron nitride-based composite ceramic for thin strip continuous casting side seal plate.

[0088] The ball milling beads are agate.

[0089] The inert atmosphere is argon.

[0090] The boron nitride-based composite ceramic for thin strip continuous casting side seal plate prepared in this example is detected: the high-temperature bending strength is 112.8 MPa; the thermal expansion coefficient is 3.3×10 -6 ·K -1 ; the thermal conductivity is 13 W / (m·K); the wetting angle is 78°.

[0091] Example 6

[0092] A boron nitride-based composite ceramic for thin strip continuous casting side seal plate and a preparation method thereof. The steps of the preparation method described in this embodiment are:

[0093] Step 1: Mix 20 wt% of elemental silicon powder, 55 wt% of boron nitride powder, 10 wt% of elemental titanium powder, 8 wt% of titanium boride powder conditioner, and 7 wt% of boron powder to obtain a mixed powder.

[0094] Step 2: According to the mass ratio of the mixed powder: absolute ethanol: ball milling beads of 1:12:2, place the mixed powder, the absolute ethanol, and the ball milling beads in a ball mill, and ball mill for 6 h at 350 r / min to obtain a slurry.

[0095] Step 3: Dry the slurry at 160°C for 36 h to obtain a powder; then sieve the powder to obtain a sieved material with a particle size less than 75 μm.

[0096] Step 4: Place the sieved material in Hot Pressing Die I, then place Hot Pressing Die I in a hot press sintering furnace, and heat it to 950°C at a rate of 600°C / h under the condition of 0.1 Pa; then simultaneously apply pressure, heat up, and introduce nitrogen, keep the temperature and pressure constant for 0.5 h under the conditions of 10 MPa, 1300°C, and nitrogen atmosphere, and cool down and relieve pressure along with the furnace to obtain a pre-sintered side seal plate.

[0097] Step 5: Place the pre-sintered side seal plate in Hot Pressing Die II, then place Hot Pressing Die II in a hot press sintering furnace, and heat it to 950°C at a rate of 800°C / h in an inert atmosphere; then simultaneously apply pressure, heat up, and introduce an inert gas, keep the temperature and pressure constant for 2 h under the conditions of 200 MPa, 1400°C, and inert atmosphere, and cool down and relieve pressure along with the furnace to obtain a boron nitride-based composite ceramic for thin strip continuous casting side seal plate.

[0098] The ball milling beads are corundum.

[0099] The inert atmosphere is argon.

[0100] The boron nitride-based composite ceramic for thin strip continuous casting side seal plate prepared in this example is detected: the high-temperature bending strength is 106.5 MPa; the thermal expansion coefficient is 3.41×10 -6 ·K -1 ; the thermal conductivity is 15 W / (m·K); the wetting angle is 86°.

[0101] This specific embodiment has the following positive effects compared with the prior art:

[0102] This specific embodiment uses boron nitride powder, elemental silicon powder, and elemental titanium powder as raw materials, adds a conditioning agent and mixes them. In the pre-sintering process, layered Ti2SiB is in-situ generated, and the generated layered Ti2SiB combines with BN particles to form an interlaced network structure. At the same time, in the high-pressure environment of secondary sintering, SiTi2N4 particles are in-situ generated, and the generated SiTi2N4 particles are complementary to the BN-Ti2SiB structure. Under the coupling action of the BN-Ti2SiB network structure and the filling of pores by SiTi2N4 particles, the boron nitride-based composite ceramic for thin strip continuous casting side seal plate prepared has low thermal conductivity and good resistance to molten steel erosion.

[0103] The high-temperature damage tolerance of the ternary MAB phase Ti2SiB in the boron nitride-based composite ceramic for thin strip continuous casting side seal plate prepared in this specific embodiment and the high strength of the covalent ternary nitride SiTi2N4 with a spinel structure interact with each other, making the boron nitride-based composite ceramic for thin strip continuous casting side seal plate have good high-temperature stability with the crystallizing roll, and enhancing the high-temperature bending strength of the boron nitride-based composite ceramic for thin strip continuous casting side seal plate.

[0104] In the boron nitride-based composite ceramic for the thin strip continuous casting side seal plate prepared by this specific embodiment, SiTi2N4 is pinned in the BN-Ti2SiB network structure, with tight combination. In a high-temperature environment, it inhibits the crack propagation of the boron nitride-based composite ceramic for the thin strip continuous casting side seal plate, reduces the thermal expansion coefficient, enhances the high-temperature service life, and further improves the service life of the boron nitride-based composite ceramic for the thin strip continuous casting side seal plate.

[0105] The boron nitride-based composite ceramic for the thin strip continuous casting side seal plate prepared by this specific embodiment is detected as follows: the high-temperature bending strength is 105.4 - 112.8 MPa; the thermal expansion coefficient is 3.12 - 3.45×10 -6 ·K -1 ; the thermal conductivity is 11 - 15 W / (m·K); the wetting angle is 75 - 90°.

[0106] Therefore, the boron nitride-based composite ceramic for the thin strip continuous casting side seal plate prepared by this specific embodiment has the characteristics of low thermal conductivity, good resistance to molten steel erosion, high high-temperature bending strength, and long service life.

Claims

1. A preparation method of a boron nitride-based composite ceramic for a side seal plate of thin strip continuous casting, characterized in that The steps of the preparation method are: Step 1, 15-30wt% of elemental silicon powder, 55-70wt% of boron nitride powder, 5-10wt% of elemental titanium powder and 5-15wt% of a tempering agent are mixed to obtain a mixed powder; The conditioning agent is one or two of titanium boride powder, flaky nano silicon powder and boron powder; Step 2, according to the mass ratio of the mixed powder: anhydrous ethanol: ball milling beads of 1: 8-12: 2-4, the mixed powder, the anhydrous ethanol and the ball milling beads are placed in a ball mill, and ball milled at 250-350 r / min for 6-9 hours to obtain a slurry; Step 3, drying the slurry at 80-200° C. for 12-48 hours to obtain a powder; and then sieving the powder to obtain a sieved material with a particle size of less than 75 μm; Step 4: placing the sieved material in a hot pressing mold I, and then placing the hot pressing mold I in a hot pressing sintering furnace, heating to 950-1050°C at a rate of 600-1200°C / h under 0.1-0.2Pa conditions; then pressurizing, heating and introducing nitrogen at the same time, keeping the temperature and pressure for 0.5-4h under 10-30MPa, 1300-1450°C and nitrogen atmosphere conditions, cooling and releasing the pressure with the furnace, to obtain a pre-sintered side sealing plate; Step 5: Place the pre-sintered side sealing plate in a hot pressing mold II, then place the hot pressing mold II in a hot pressing sintering furnace, and heat it to 950-1050°C at a rate of 800-1100°C / h in an inert atmosphere; then pressurize, heat up, and introduce inert gas at the same time, and keep the temperature and pressure for 2-6 hours under the conditions of 100-200MPa, 1400-1500°C and inert atmosphere, cool down and release the pressure along with the furnace to obtain a boron nitride-based composite ceramic for thin strip continuous casting side sealing plates.

2. The preparation method of the boron nitride-based composite ceramic for the side seal plate of thin strip continuous casting according to claim 1, characterized in that The Si content of the elemental silicon powder is ≥99wt%; and the particle size of the elemental silicon powder is less than 30μm.

3. The preparation method of the boron nitride-based composite ceramic for the side seal plate of thin strip continuous casting according to claim 1, characterized in that The BN content of the boron nitride powder is ≥95wt%; and the particle size of the boron nitride powder is less than 48μm.

4. The preparation method of the boron nitride-based composite ceramic for the side seal plate of thin strip continuous casting according to claim 1, characterized in that The Ti content of the single-substance titanium powder is ≥99wt%, and the particle size of the single-substance titanium powder is less than 75μm.

5. The preparation method of the boron nitride-based composite ceramic for the side seal plate of thin strip continuous casting according to claim 1, characterized in that The particle sizes of the titanium boride powder, flaky nano silicon powder and boron powder are ≤75 μm; the TiB2 content of the titanium boride powder is ≥98wt%, the Si content of the flaky nano silicon powder is ≥99wt%, and the B content of the boron powder is ≥98wt%.

6. The preparation method of the boron nitride-based composite ceramic for the side seal plate of thin strip continuous casting according to claim 1, characterized in that The ball milling beads are agate or corundum.

7. The preparation method of the boron nitride-based composite ceramic for the side seal plate of thin strip continuous casting according to claim 1, characterized in that The inert atmosphere is nitrogen or argon.

8. A boron nitride-based composite ceramic for side seal plates of thin strip continuous casting, characterized in that The boron nitride-based composite ceramic for side sealing plates of thin strip continuous casting is a boron nitride-based composite ceramic for side sealing plates of thin strip continuous casting prepared by the preparation method of the boron nitride-based composite ceramic for side sealing plates of thin strip continuous casting according to any one of claims 1 to 7.