A method and apparatus for repairing a crystallizer surface

Abstract

The application discloses a kind of crystallizer surface repair method and device, it is related to continuous casting crystallizer cold spraying repair coating structure design field.In the crystallizer matrix of damaged layer has been removed with the method of cold spraying preparation heat conduction layer;Then preparation main body coating on heat conduction layer;Solid powder used in preparation heat conduction layer is one or more than two mixed microparticles of pure copper, copper alloy and copper-coated carbon nanotube;Solid powder used in preparation main body coating is selected from at least one of CuCrZr, CuCrZr+ceramic, iron and iron alloy, nickel and nickel alloy and chromium and chromium alloy.Before spraying main body coating, first bottom heat conduction layer, so on the one hand, it can solve the problem of reduced heat conductivity when cold spraying main body coating, on the other hand, can increase the deposition efficiency of main body coating, greatly improve the range of repairable thickness.Moreover, the crystallizer surface repair method provided by the application is simple and easy to operate, and can realize size recovery and function recovery simultaneously.

Description

Technical Field

[0001] This invention relates to the fields of surface engineering, metallurgy, and machinery, and specifically to the design of a cold spray repair coating structure for continuous casting crystallizers. More specifically, it relates to a method and apparatus for repairing the surface of a crystallizer. Background Technology

[0002] The crystallizer is a key cooling device in continuous casting technology, often referred to as the "heart" of the equipment, and has a significant impact on the production of high-quality, high-efficiency steel. During operation, the inner surface of the crystallizer comes into contact with solid protective slag and molten steel, while the outer surface undergoes forced cooling by water spray. Operating under rapid heating and cooling conditions for extended periods, it also endures chemical corrosion from the cooling water and fluoride protective slag, friction from ingot pulling, and abrasion. This often leads to the failure of the electroplated coating on its surface, resulting in wear, thermal cracking, and deformation, and a short lifespan. If the copper crystallizer's surface coating is damaged or scratched, the original coating must first be completely ground off, along with a layer of the crystallizer's copper alloy matrix, to obtain a smooth copper surface before a new electroplated layer can be prepared. With each grinding cycle, the copper alloy matrix of the crystallizer becomes increasingly thin, and after several grinding cycles, the crystallizer no longer meets dimensional requirements and must be scrapped, resulting in significant resource waste.

[0003] Based on currently available papers and patent reports, crystallizer repair methods can be divided into three main categories according to the size of the heat source: high-temperature technology: welding, laser cladding; medium-temperature technology: electroplating, composite electroplating, supersonic flame spraying, plasma spraying, etc.; low-temperature technology: cold spraying.

[0004] Different repair techniques each have their advantages and disadvantages. Specifically, laser cladding technology requires less heat input than welding, and the coating is metallurgically bonded to the substrate. However, the copper alloy in the crystallizer has a high reflectivity to conventional lasers, resulting in low cladding efficiency. Furthermore, the cladding process is prone to practical problems such as deformation and cracking. In addition, the material system used in this technology is mainly Fe / Co / Ni-based hard materials, which have higher wear and corrosion resistance than the copper alloy body, but their thermal conductivity is much lower than that of copper alloy. Therefore, its main purpose is to replace the current electroplating layer.

[0005] Thermal spraying technology is a medium-temperature technology that uses high-speed, high-temperature flames or plasma as heat sources. If CuCrZr, the main material of the crystallizer copper alloy, is used as the spraying material, oxidation is very likely to occur during the spraying process, which weakens the bond between the coating and the substrate and also reduces the thermal conductivity of the material. Therefore, the material systems currently used for thermal spraying repair are mostly metal ceramics, such as WC-Co, CoCrMoSi, and Cr3C2-25NiCr. Similar to laser cladding, their wear resistance and corrosion resistance are enhanced, but their thermal conductivity as a cooling device is weakened.

[0006] Cold spraying technology does not use any external heating source. It accelerates the material to be sprayed with high-pressure gas and impacts the substrate in solid form. Therefore, the properties of the powder can be transferred to the coating. Moreover, it has no thermal impact on the copper alloy body material of the crystallizer and can directly repair the copper crystallizer body.

[0007] CN200410084779.6 discloses a pneumatic spraying method for repairing copper plates in copper crystallizers, primarily used to fill cracks and worn grooves, forming a new surface and restoring the dimensions of the crystallizing roller. This patent mainly relates to cold spraying processes, such as the sprayed metal particle size, gas pressure, flow rate and temperature, nozzle-substrate distance, and materials. Materials used include pure copper (Cu), silver-copper alloy (AgCu), chromium-zirconium copper alloy (CrZrCu), beryllium-nickel-zirconium copper alloy (BeNiZrCu), or nickel alloys. While this patent can restore the dimensions of the grooves in the copper crystallizer, in actual factory processing, the grooved surface is completely removed. If this patented technology is used, the spraying thickness is limited (≤2mm), and cracks may occur at the interface between the coating and the substrate due to accumulated internal stress. CN201010117519.X discloses a method for creating a roughened morphology with naturally streamlined pits on the surface of a copper plate to be repaired using supersonic hard microparticles. This increases the bonding area and strength between the repair layer and the copper plate surface, thereby improving the thermal conductivity and resistance to alternating thermal stress of the repair layer. This patent primarily addresses roughening parameters related to the copper plate, such as hard particle material parameters, spraying process, and annealing process parameters. Its main purpose is to enhance the bonding between the repair layer and the substrate through roughening treatment. The patent application shows that, compared to samples treated only by surface sandblasting, the bonding strength is increased by 15-22%, and the thermal conductivity is increased by 10%-16%. However, it should be noted that the roughening method in this patent involves two steps: surface sandblasting followed by pit enhancement. This pretreatment procedure is complex and presents many difficulties for operators. The reasons are as follows: First, the crystallizer is relatively large, requiring a large closed sandblasting chamber; second, the pits are prone to containing ceramic phases, requiring additional high-pressure gas removal; furthermore, the pit-enhancing powder used has a certain particle size range, making it difficult to obtain a uniform pit morphology. CN201010596518.8 discloses a method for preparing a thermally conductive and wear-resistant coating on the surface of a continuous casting crystallizer. First, alloy powder is prepared using a ball milling method, then a coating is prepared using cold spraying technology, and finally, the coating is thermally diffused and alloyed to prepare a NiAl intermetallic compound-based composite structure coating. The main components are Ni powder, Al powder, and thermally conductive and wear-resistant ceramic content. This patent can obtain a thermally conductive and wear-resistant coating, but the coating thickness is limited, and it does not involve dimensional repair of the copper alloy body of the crystallizer; it is mainly used to replace electroplating coatings. CN201310352334.0 discloses a method for overall repair of the crystallizer using cold spraying and a clamping device specifically for edge and corner treatment, mainly providing a method for treating the edges and corners of the crystallizer.

[0008] In summary, cold spraying for repairing crystallizer bodies has certain technical advantages, but there are still technical difficulties in solving the problem of repairing large areas and thick layers. In addition, current patented repair strategies for improving the performance of the repair layer have complicated procedures, which brings difficulties to practical applications.

[0009] In view of this, the present invention is proposed. Summary of the Invention

[0010] The purpose of this invention is to provide a method and apparatus for repairing the surface of a crystallizer, thereby simplifying the processing while ensuring the restoration of the size and function of a large-area, thick copper alloy body.

[0011] This invention is implemented as follows:

[0012] In a first aspect, the present invention provides a method for repairing the surface of a crystallizer, comprising:

[0013] A thermally conductive layer is prepared on a crystallizer substrate with the damaged layer removed by cold spraying; then a main coating layer is prepared on the thermally conductive layer.

[0014] The solid powder used in preparing the thermal conductive layer is one or more mixed particles of pure copper, copper alloy and copper-coated carbon nanotubes.

[0015] The solid powder used in preparing the main coating is selected from at least one of CuCrZr, CuCrZr+ ceramics, iron and iron alloys, nickel and nickel alloys, and chromium and chromium alloys.

[0016] The inventors first apply a thermally conductive primer layer before spraying the main coating. This compensates for the reduced thermal conductivity of the main coating (e.g., CuCrZr) after cold spraying and increases the deposition efficiency of the main coating (e.g., CuCrZr), significantly expanding the range of repairable thicknesses. Therefore, the crystallizer surface repair method provided by this invention not only ensures the thermal conductivity of the coating (functional restoration) but also restores the dimensions of large-area, thick copper alloy main bodies. Moreover, the crystallizer surface repair method provided by this invention is simple and easy to implement.

[0017] Methods for removing damaged coatings include, but are not limited to: thoroughly grinding the damaged surface of the failed crystallizer with a conventional grinding wheel or sandpaper to remove the damaged layer and expose a fresh surface. This pretreatment step is simple.

[0018] In a preferred embodiment of the present invention, the crystallizer is a copper crystallizer.

[0019] In a preferred embodiment of the present invention, the average particle size of the solid powder is 15-45 μm when preparing the thermally conductive layer. For example, 15-35 μm, or 20-45 μm, or 20-30 μm. Particle sizes that are too small or too large will prevent the thermally conductive layer from being sprayed onto the surface of the crystallizer.

[0020] In one alternative embodiment, when preparing the thermally conductive layer, the solid powder is pure copper or copper-coated carbon nanotubes with an oxygen content of less than 0.1 wt%.

[0021] In a preferred embodiment of the present invention, the average particle size of the solid powder (e.g., CuCrZr) is 15-45 μm when preparing the main coating. For example, 15-30 μm or 20-45 μm. Within the above particle size range, better uniformity of the coating can be ensured.

[0022] In one optional embodiment, the chemical composition of CuCrZr is Cu: 0.5-1.5 wt.%, Cr: 0.02-0.2 wt.%, Zr: 1 wt.%. For example, the chemical composition of CuCrZr is Cu: 0.5-1 wt.%, Cr: 0.02-0.1 wt.%, Zr: 1 wt.%.

[0023] In a preferred embodiment of the present invention, when preparing the main coating, the solid powder used also includes a reinforcing phase powder, which is one or more mixed particles selected from alumina, aluminum nitride, titanium oxide, zirconium oxide, yttrium oxide, silicon dioxide, boron nitride, silicon nitride, silicon carbide, tungsten carbide, diamond, hard chrome, tungsten alloy, high-speed steel, high-temperature alloy, tantalum alloy, and amorphous alloy.

[0024] Reinforcing phase powders such as SiC, Al2O3, and AlN help improve the deposition efficiency of the main coating, increasing the repair depth and improving the wear resistance of the coating.

[0025] In one alternative embodiment, the average particle size of the reinforcing phase powder is 30-60 μm.

[0026] For example, 30-40μm, or 40-45μm.

[0027] In one alternative embodiment, the reinforcing phase powder comprises 15-60 vol% of the total solid powder used in preparing the main coating. For example, 20-60 vol%, or 25-50 vol%.

[0028] In a preferred embodiment of the present invention, the solid powder used in preparing the main coating is CuCrZr and 15-45 vol% Al2O3.

[0029] In a preferred embodiment of the present invention, the thickness of the thermally conductive layer and the main coating is (1:3) to (1:9). For example, the thickness of the thermally conductive layer and the main coating is 1:3, 1:4, 1:8, or 1:9.

[0030] In a preferred embodiment of the present invention, the maximum thickness of the thermally conductive layer is 2.5 mm, and the maximum thickness of the main body layer is 9 mm.

[0031] In a preferred embodiment of the present invention, the gas pressure is 3–5 MPa and the temperature is 300–550°C during the preparation of the thermally conductive layer and the main coating. A dual-path negative pressure powder feeding method is used. Dual-path negative pressure powder feeding ensures that the thermally conductive layer is in a well-preheated state, which helps to enhance the deposition efficiency during the preparation of the main coating and avoids the pressure reduction and powder replacement required by traditional powder feeding methods, which leads to cooling of the underlying layer and thus reduces operational efficiency.

[0032] In one optional embodiment, when using dual-path negative pressure powder feeding, the powder feeding rate is 10-30 g / min and the powder feeding pressure is 0.3-2 MPa.

[0033] In a preferred embodiment of the present invention, after the main coating is completed, a heat treatment step is also included.

[0034] In one alternative implementation, the heat treatment involves applying heat to the coating using spray gun gas. Post-heat treatment of the repair coating with high-temperature spray gas can slowly cool the coating, release stress, prolong the interdiffusion process between particles, and enhance bonding. Compared to traditional heat treatment in a furnace, this significantly improves efficiency and helps avoid thermal impact on the original substrate area.

[0035] In a preferred embodiment of the present invention, the temperature of the spraying gas during heat treatment is 350–550°C, the pressure is 3–5 MPa, and the gas bombardment density is 1.5–5 L / mm². 2 The distance is 15-30mm.

[0036] Secondly, the present invention also provides an apparatus for implementing a method for repairing the surface of a crystallizer: the apparatus includes a dual-barrel powder feeding device, a heater, a main gas storage device, and a nozzle.

[0037] The main gas storage device stores inert gases, such as argon.

[0038] The present invention has the following beneficial effects:

[0039] This invention applies a thermally conductive primer layer before spraying the main coating. This addresses the issue of reduced thermal conductivity during cold spraying of the main coating and increases the deposition efficiency of the main coating, significantly expanding the range of repairable thicknesses. Therefore, the crystallizer surface repair method provided by this invention not only ensures the thermal conductivity of the coating (functional restoration) but also restores the dimensions of large-area, thick copper alloy bodies. Furthermore, the crystallizer surface repair method provided by this invention is simple and easy to implement. Attached Figure Description

[0040] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 This is a schematic diagram of the coating cross-section structure;

[0042] Figure 2 Schematic diagram of negative pressure dual-barrel powder feeding;

[0043] Figure 3 Metallographic microscope image of the cross section of the coating prepared in Example 1;

[0044] Figure 4 Scanning electron microscope (SEM) images of the coating structures of the prepared coating sections in Examples 2(a) and 3(b);

[0045] Figure 5 The image shows a scanning electron microscope (SEM) image of the coating structure of the cross section prepared in Comparative Example 1.

[0046] Figure 6 The image shows the scanning electron microscope (SEM) structure of the coating cross-section prepared for Comparative Example 2. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0048] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0049] Example 1

[0050] This embodiment uses a pure Cu-CuCrZr structure as an example. For a copper alloy body with a wear thickness of 0.5mm, the thermal conductive layer material is Cu particles with an average particle size of 34.36μm, and the repair layer material is CuCrZr particles with an average particle size of 30.17μm. The spraying gas temperature is set at 500℃, the pressure at 3.4MPa, and the powder feeding rate of both barrels is 20g / min with a pressure of 0.7MPa.

[0051] Reference for cold spray copper alloy body repair coating structure Figure 1 As shown, the bottom layer is a heat-conducting layer, and the top layer is the main coating (i.e., the reinforcing layer). The negative pressure dual-barrel powder feeding device is described in reference... Figure 2As shown, it includes a main gas storage device, a heater, a dual-barrel powder feeding device, and nozzles.

[0052] The specific repair methods are as follows:

[0053] (1) First, use 100# sandpaper to clean and polish the surface of the substrate.

[0054] (2) Turn on the pure Cu powder feeder to feed powder, spray one coat, and prepare a 60um copper coating.

[0055] (3) Turn off the pure Cu powder feeder, turn on the CuCrZr powder feeder, and spray 450um CuCrZr;

[0056] (4) Turn off the CuCrZr powder feeding switch, spray five coats with 500℃ high temperature and high pressure gas, then stop the gas supply and wait for the coating to cool naturally to room temperature.

[0057] Scanning electron microscope (SEM) image of the cold-sprayed Cu-CuCrZr repair coating structure (after corrosion) (see reference). Figure 3 As shown.

[0058] Example 2

[0059] This embodiment uses a pure Cu-CuCrZr+15 vol% Al2O3 structure as an example. For a copper alloy body with a wear thickness of 1 mm, the heat-conducting layer material is Cu particles with an average particle size of 34.36 μm. The repair layer consists of CuCrZr particles (average particle size of 30.17 μm) and Al2O3 ceramic phase particles (average particle size of approximately 56 μm) mechanically mixed powder, with a ceramic phase content of 15 vol%. The spraying gas temperature is set at 500℃ and the pressure at 3.4 MPa. The powder feeding rate for both barrels is 20 g / min and the pressure is 0.7 MPa. The negative pressure double-barrel powder feeding device is the same as in Embodiment 1.

[0060] The specific repair methods are as follows:

[0061] (1) First, use 100# sandpaper to clean and polish the surface of the substrate.

[0062] (2) Turn on the pure Cu powder feeder to feed powder, spray one coat, and prepare a 200um copper coating.

[0063] (3) Turn off the pure Cu powder feeder, turn on the CuCrZr / Al2O3 composite powder feeder, and spray 800um CuCrZr;

[0064] (4) Turn off the powder feeding switch, spray five coats with 500℃ high temperature and high pressure gas, then stop the gas supply and wait for the coating to cool naturally to room temperature.

[0065] Reference to the coating structure of cold-sprayed CuCrZr+15 vol% Al2O3 repair coating (after corrosion) Figure 4 As shown in (a).

[0066] Example 3

[0067] This embodiment uses a pure Cu-CuCrZr+30 vol.% Al2O3 structure as an example. For a copper alloy body with a wear thickness of 2 mm, the thermally conductive layer material is Cu particles with an average particle size of 34.36 μm. The repair layer consists of CuCrZr particles (average particle size of 30.17 μm) and Al2O3 ceramic phase particles (average particle size of approximately 56 μm) mechanically mixed powder, with a ceramic phase content of 45 vol.%. The spraying gas temperature is set at 500℃, the pressure at 3.4 MPa, and the powder feeding rate of both barrels is 20 g / min with a pressure of 0.7 MPa.

[0068] The specific repair methods are as follows:

[0069] (1) Specifically, first use 100# sandpaper to clean and polish the surface of the substrate;

[0070] (2) Turn on the pure Cu powder feeder to feed powder, spray one coat, and prepare a 400um copper coating.

[0071] (3) Turn off the pure Cu powder feeder, turn on the CuCrZr / Al2O3 composite powder feeder, and spray 1600um CuCrZr.

[0072] (4) Turn off the powder feeding switch, spray five coats with 500℃ high temperature and high pressure gas, then stop the gas supply and wait for the coating to cool naturally to room temperature.

[0073] Cold spray CuCrZr+30 vol% Al2O3 repair coating structure reference Figure 4 As shown in (b).

[0074] Example 4

[0075] Compared to Example 2, taking the Cu-coated carbon nanotube-CuCrZr+15vol%Al2O3 structure as an example, for a copper alloy body with a wear thickness of 1mm, the only difference in the repair method is that the thermally conductive layer material is Cu-coated carbon nanotubes with an average particle size of 30μm. The rest of the repair method is the same as in Example 2.

[0076] The thickness of the thermally conductive layer is 100μm, and the thickness of the main coating is 900μm.

[0077] Example 5

[0078] Compared to Example 2, the only difference is the reinforcing phase. The reinforcing phase is SiC. The repair layer consists of a mechanically mixed powder of CuCrZr particles (average particle size 30.17 μm) and SiC particles (average particle size approximately 60 μm), with a SiC content of 40 vol.%. The remaining repair methods are the same as in Example 2.

[0079] The thickness of the thermally conductive layer is 200μm, and the thickness of the main coating is 800μm.

[0080] Example 6

[0081] Compared to Example 2, the only difference is the reinforcing phase. The reinforcing phase is AlN. The repair layer consists of a mechanically mixed powder of CuCrZr particles (average particle size 30.17 μm) and AlN particles (average particle size approximately 50 μm), with an AlN content of 20 vol.%. The remaining repair methods are the same as in Example 2.

[0082] Comparative Example 1

[0083] Compared with Example 1, the only difference is that: no thermally conductive layer is prepared, and the main coating is prepared directly (the scanning electron microscope structure diagram of the coating cross-section is shown in the figure). Figure 5 (As shown).

[0084] Comparative Example 2

[0085] The only difference from Example 2 is that the ceramic phase content is 50 vol% (see the scanning electron microscope image of the coating structure). Figure 6 (As shown).

[0086] Experimental Example 1

[0087] The thermal conductivity of the copper crystallizers repaired in Examples 1-3 and Comparative Example 1, as well as the copper crystallizer repaired with CuCrZr, was measured respectively. The results show that:

[0088] Example 1: The thermal conductivity of the copper crystallizer repaired with the Cu-CuCrZr structure is 30% higher than that of the copper crystallizer repaired with CuCrZr (Comparative Example 1). Example 2: The thermal conductivity of the copper crystallizer repaired with the Cu-CuCrZr / Al2O3 structure is 35% higher than that of the copper crystallizer repaired with CuCrZr (Comparative Example 1). Example 3: The thermal conductivity of the copper crystallizer repaired with the Cu-CuCrZr / Al2O3 structure is approximately 50% higher than that of the copper crystallizer repaired with CuCrZr (Comparative Example 1).

[0089] Furthermore, the copper crystallizer repaired in Comparative Example 2 with a ceramic phase content of 50 vol% resulted in a decrease in thermal conductivity.

[0090] Experiment Example 2

[0091] Wear resistance tests were conducted. In Example 1, the copper crystallizer repaired with the Cu-CuCrZr structure had a wear rate comparable to that repaired with CuCrZr. In Example 2, the copper crystallizer repaired with the Cu-CuCrZr / Al2O3 structure showed a 23.2% lower wear rate than that repaired with CuCrZr. In Example 3, the copper crystallizer repaired with the Cu-CuCrZr / Al2O3 structure showed an approximately 59% lower wear rate than that repaired with CuCrZr.

[0092] Experimental Example 3

[0093] Tissue observation revealed that the Al2O3 ceramics in Example 2 and Experimental Example 3 remained intact, while those in Comparative Example 2 ( Figure 6 The Al2O3 ceramic in the sample was broken and did not meet the requirements.

[0094] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for repairing the surface of a crystallizer, characterized in that, It includes: A thermally conductive layer was prepared on a crystallizer substrate with the damaged layer removed by cold spraying. Then, a main coating is prepared on the thermally conductive layer; The solid powder used in preparing the thermal conductive layer is one or more mixed particles of pure copper, copper alloy and copper-coated carbon nanotubes; The solid powder used in preparing the main coating is selected from at least one of CuCrZr, CuCrZr+ ceramics, iron and iron alloys, nickel and nickel alloys, and chromium and chromium alloys.

2. The method for repairing the surface of a crystallizer according to claim 1, characterized in that, When preparing the thermally conductive layer, the average particle size of the solid powder is 15-45 μm.

3. The method for repairing the surface of a crystallizer according to claim 2, characterized in that, When preparing the thermally conductive layer, the solid powder is pure copper or copper-coated carbon nanotubes with an oxygen content of less than 0.1 wt%.

4. The method for repairing the surface of a crystallizer according to claim 1 or 2, characterized in that, When preparing the main coating, the average particle size of the solid powder is 15-45 μm.

5. The method for repairing the surface of a crystallizer according to claim 4, characterized in that, When preparing the main coating, the solid powder used also includes reinforcing phase powder, which is one or more mixed particles selected from aluminum oxide, aluminum nitride, titanium oxide, zirconium oxide, yttrium oxide, silicon dioxide, boron nitride, silicon nitride, silicon carbide, tungsten carbide, diamond, hard chrome, tungsten alloy, high-speed steel, high-temperature alloy, tantalum alloy, and amorphous alloy. The average particle size of the reinforcing phase powder is 30-60 μm; The reinforcing phase powder accounts for 15-60 vol of the total solid powder used in preparing the main coating.

6. The method for repairing the surface of a crystallizer according to claim 5, characterized in that, The solid powder used in preparing the main coating is CuCrZr and 15-45 vol% Al2O3.

7. The method for repairing the surface of a crystallizer according to claim 1 or 2, characterized in that, The thickness ratio of the thermally conductive layer to the main coating is (1:3) - (1:9). The crystallizer is a copper crystallizer.

8. The method for repairing the surface of a crystallizer according to claim 1 or 2, characterized in that, When preparing the thermally conductive layer and the main coating, the gas pressure is 3~5MPa, the temperature is 300~550℃, and the powder is fed using a dual-path negative pressure powder feeding method.

9. The method for repairing the surface of a crystallizer according to claim 8, characterized in that, When the dual-path negative pressure powder feeding is used, the powder feeding rate is 10~30g / min and the powder feeding pressure is 0.3~2MPa.

10. The method for repairing the surface of a crystallizer according to claim 1 or 2, characterized in that, After the main coating is completed, a heat treatment step is also included; The heat treatment is performed by applying heat to the coating using a spray gun.

11. The method for repairing the surface of a crystallizer according to claim 10, characterized in that, The spraying gas temperature during the heat treatment is 350~550℃, the pressure is 3~5MPa, and the gas bombardment density is 1.5~5L / mm. 2 The distance is 15~30mm.

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