Mould copper plate of a laminated composite slab continuous caster and its preparation method

Abstract

The present invention discloses a copper plate for a continuous casting mold of a laminated composite plate type and a preparation method thereof. It includes a laminated composite structure, and the laminated composite structure includes a front layer as the working surface, a back layer as the cooling surface, and an intermediate layer as the heat dissipation layer. Among them: the intermediate layer is made of a copper-silver alloy; the back layer is high-strength steel and is metallurgically bonded to the first surface of the intermediate layer; the front layer is a high-temperature alloy thin plate and is metallurgically bonded to the second surface of the intermediate layer opposite to the first surface. The copper plate for the continuous casting mold of the laminated composite plate type according to the present invention, through the optimized design of the laminated composite plate according to the working conditions of the continuous casting mold, improves the overall rigidity and cooling intensity of the composite plate continuous casting mold, can avoid the hot surface temperature in the eddy current area with a large heat flux density, and thus helps to improve or completely eliminate the occurrence of copper plate cracks. At the same time, it prolongs the service life of the continuous casting mold composite plate and reduces the overall manufacturing cost.

Description

Technical Field

[0001] The present invention relates to the technical field of metallurgical continuous casting, and more particularly, to a crystallizer copper plate of a novel laminated composite plate type continuous casting machine. Background Art

[0002] The crystallizer is the core of the continuous casting machine and is called the "heart" of the continuous casting equipment. The molten steel flowing from the tundish forms a certain billet shell through the water-cooled copper plate of the crystallizer and is continuously drawn out from the lower opening of the crystallizer and enters the secondary cooling zone. The performance of the crystallizer copper plate directly affects the service life of the crystallizer copper plate, the quality of the cast billet, and the operation rate of the continuous casting machine. According to the operation requirements, the crystallizer should have good thermal conductivity and rigidity. The thermal conductivity enables the molten steel to solidify quickly, which is an important prerequisite for achieving high casting speeds. Rigidity can adapt to large thermal stresses, is not easily deformed, has wear-resistant inner surfaces, etc., and the structure should be simple for easy manufacturing and maintenance.

[0003] The working surface of the continuous casting crystallizer is a key component for heat exchange and shaping of the molten steel during solidification. Therefore, it is required to be made of a material with good thermal conductivity. The copper plate has good thermal conductivity, but its strength and hardness are low, especially at high temperatures, its strength is even lower, so its service life is short.

[0004] In order to improve the heat transfer and high-temperature strength performance of the continuous casting crystallizer copper plate and increase its service life, the current main technical means are: one is to generally use chromium zirconium copper alloy and apply nickel-iron plating on the working surface to improve surface hardness and wear resistance; the other is to set cooling water channels on the cooling surface to enhance the cooling intensity. For example:

[0005] The Chinese utility model patent with the publication number CN202155493U discloses a cooling structure for the wide-face copper plate of a thin slab continuous casting crystallizer. By setting cooling water channels and optimizing the non-uniformity of the water channel distribution, specifically reducing the water channel diameter, increasing the number of water channels, and making a reasonable distribution according to the temperature of the molten steel, the cooling intensity of the crystallizer is improved, and the quality of the cast billet is enhanced.

[0006] The Chinese invention patent application with the publication number CN102581239A discloses a wide-face copper plate for a high-efficiency slab continuous casting machine. By setting deep water channels and shallow water channels with different depths to optimize the heat dissipation uniformity of the crystallizer copper plate, there are problems such as large processing difficulty of the water holes, high rejection rate, and little improvement in the thermal conductivity of the copper plate.

[0007] The Chinese patent application with the publication number CN107116186A discloses a copper plate for an ultra-thin slab mold with a composite cooling structure. Multiple cooling water channels and multiple cooling water holes are arranged on the cooling surface to optimize the uneven cooling phenomenon in the area of the initial solidified shell. However, in actual applications, in the cooling structure of all water channels or water channels + water holes, within the range of 90 - 120 mm downward from the upper opening of the copper plate and 320 - 460 mm from the edge to the center, that is, in the straight part of the high-temperature area, at the position of the reinforcing rib where the bolt is located, the copper plate has serious cracks, affecting the service life of the copper plate.

[0008] The Chinese patent application with the publication number CN115007816A discloses a copper plate for a thin slab continuous casting mold with a cooling structure. By optimizing the design of the high-temperature area, the cooling capacity of the copper plate is improved, the hot surface temperature of the eddy current area with a large heat flux density is reduced, which helps to improve or completely eliminate the occurrence of copper plate cracks and extend the service life of the copper plate.

[0009] The above-mentioned multiple disclosures are limited to optimizing the diameter, quantity, distribution, etc. of the cooling water channels under the existing materials, that is, chromium zirconium copper alloy, and the existing structure, that is, chromium zirconium copper plus nickel iron surface plating, to improve the working performance and service life of the copper plate for the mold. Although there is a certain effect, without a substantial improvement in the thermal conductivity of the material itself and no change in the processing technology, it is very difficult to significantly change the performance and service life of the mold. Summary of the Invention

[0010] The object of the present invention is to provide, in view of the deficiencies of the prior art, a laminated composite plate type copper plate for a continuous casting machine mold that can significantly improve the working performance and service life, including thermal conductivity and rigidity, of the copper plate for the continuous casting machine mold through changes in materials, structures, and production processes.

[0011] To achieve the above object, some embodiments of the present invention provide a laminated composite plate type copper plate for a continuous casting machine mold, which includes a laminated composite structure. The laminated composite structure includes a front layer as the working surface, a back layer as the cooling surface, and an intermediate layer as the heat dissipation layer, where: the intermediate layer is made of a copper-silver alloy material; the back layer is high-strength steel and is metallurgically joined to the first surface of the intermediate layer; the front layer is a high-temperature alloy thin plate and is metallurgically joined to the second surface of the intermediate layer opposite to the first surface.

[0012] In some embodiments, the back layer is metallurgically joined to the first surface of the intermediate layer by diffusion welding or rolling composite method.

[0013] In some embodiments, the front layer is metallurgically joined to the second surface of the intermediate layer by surfacing or rolling composite method.

[0014] In some embodiments, the thicknesses of the intermediate layer and the back layer are the same and much greater than that of the front layer.

[0015] In some embodiments, the thickness of the superalloy thin plate is about 1 - 2 mm.

[0016] In some embodiments, the thickness of the intermediate layer is about 20 mm, the thickness of the front layer is about 1 mm, and the thickness of the back layer is about 20 mm.

[0017] Preferably, the composition of the copper - silver alloy is: Cu 99.5%, Ag 0.07 - 0.1%, and its thermal conductivity can reach 450 W / (m·K).

[0018] Preferably, the material of the superalloy thin plate is Inconel600.

[0019] Preferably, the process and the cooling water channel can be set and optimized according to the operating conditions.

[0020] Some embodiments of the present application also disclose a preparation method of the crystallizer copper plate of the laminated composite slab continuous caster as described in any one of the above, which includes: respectively laminating the intermediate layer with the front layer and the back layer. The metallurgical bonding method between the back layer and the intermediate layer is hot rolling, warm rolling or cold rolling lamination, or diffusion welding; the metallurgical bonding method between the intermediate layer and the front layer is hot rolling, warm rolling or cold rolling lamination, or diffusion welding.

[0021] In some embodiments, the metallurgical bonding method between the back layer and the intermediate layer is hot rolling at a temperature controlled between 850°C and 950°C and a rolling force between 500 tons and 1500 tons, varying according to the thickness ratio of copper and steel.

[0022] In some embodiments, the metallurgical bonding method between the back layer and the intermediate layer is diffusion welding with parameters: temperature: 800 - 950°C; pressure: 500 - 600 MPa; holding time: 12 hours; vacuum degree: <10 3 Pa; followed by slow cooling.

[0023] In some embodiments, the metallurgical bonding method between the front layer and the second surface of the intermediate layer is diffusion welding. The temperature range of the diffusion welding is 800°C - 950°C; the holding time is usually between 30 minutes and 2 hours; a pressure of 5 MPa - 20 MPa is applied to the layer and the intermediate layer 30.

[0024] In some embodiments, heating and peeling the current front layer includes putting the copper plate of the mold about to be worn into a heating furnace, heating it to a welding temperature of 800 - 900 °C, gradually applying a slight mechanical force at high temperature to promote the separation of the worn front layer from the intermediate layer; after the peeling is completed, slowly cooling it to room temperature; cleaning the surface of the interface; assembling and positioning the new front layer; and performing diffusion welding.

[0025] The beneficial effects of the present invention include:

[0026] On the one hand, according to the operating conditions of the continuous casting mold, the copper plate of the layered composite plate type continuous casting mold of the present invention improves the overall rigidity and cooling intensity of the composite plate mold through the optimized design of the layered composite plate, can avoid the hot surface temperature of the eddy current area with a large heat flux density, and thus helps to improve or completely eliminate the occurrence of copper plate cracks. After the rigidity is improved, it can give greater flexibility and freedom to the design and optimization of the cooling water channels, while extending the service life of the mold composite plate and reducing the overall manufacturing cost.

[0027] On the other hand, during the production process of the copper plate of the layered composite plate type continuous casting mold of the present invention, the composite method is rolling composite or diffusion welding, reducing the electroplating link, and being more energy-saving and environmentally friendly.

[0028] On another hand, the copper plate of the layered composite plate type continuous casting mold of the present invention only replaces the material of the copper plate of the existing mold, and then composites other materials according to the requirements of improving wear resistance and stiffness. This enables the depth and layout of the water tank, the position and depth of the bolt holes, and the position and depth of the thermocouple to remain unchanged, and the back plate and the overall assembly structure do not need to change either. For steel enterprises, this can make full use of the existing back plate without the need to purchase new ones, which is beneficial to cost savings and the promotion of the mold of this application.

[0029] On yet another hand, the continuous casting process parameters of the continuous casting machine using the copper plate of the layered composite plate type continuous casting mold of the present invention do not need to be greatly adjusted, and it is convenient to adapt, having good application prospects. Description of the Drawings

[0030] Figure 1 It is a schematic three-dimensional structure diagram of a copper plate continuous casting combined mold in the prior art.

[0031] Figure 2 It is a schematic front view of a copper plate continuous casting combined mold in the prior art.

[0032] Figure 3 For Figure 2 The schematic A - A cross-sectional view of the copper plate continuous casting combined mold shown.

[0033] Figure 4Schematic three-dimensional structure of the copper plate of the mold for the slab continuous casting machine according to an embodiment of the present application.

[0034] Figure 5 Front view schematic of the copper plate of the mold for the slab continuous casting machine according to an embodiment of the present application.

[0035] Figure 6 For Figure 5 Side view schematic of the B-B cross-section of the copper plate of the mold for the slab continuous casting machine shown. Detailed implementation manners

[0036] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0037] As Figure 4 、 Figure 5 、 Figure 6 As shown, the copper plate 100 of the mold for the slab continuous casting machine according to an embodiment of the present invention includes a laminated composite plate structure, and the laminated composite plate structure includes a front layer 10 as the working surface, a back layer 20 as the cooling surface, and an intermediate layer 30 as the heat dissipation layer.

[0038] The intermediate layer 30 as the heat dissipation layer is plate-shaped and includes a first surface 31 and a second surface 32 opposite to the first surface. The intermediate layer 30 can be made of a copper-silver alloy, and the composition of the copper-silver alloy is: Cu 99.5%, Ag 0.07 - 0.1%, and its thermal conductivity can reach 450 W / (m·K). The thermal conductivity of the copper-silver alloy adopted in this embodiment is much higher than that of the existing chromium-zirconium copper alloy layer 801 (290 - 340 W / (m·K)), which can greatly improve the cooling intensity of the mold.

[0039] The back layer 20 as the cooling surface can be made of high-strength steel. The back layer 20 is metallurgically joined to the first surface 31 of the intermediate layer 30. That is, the composite method of high-strength steel and copper-silver alloy can be, for example, hot, warm, cold rolling composite rolling composite method, or diffusion welding and other methods. For example, high-temperature rolling, or hot rolling, with the temperature controlled between 850°C and 950°C to prevent the copper layer from overheating and deforming. The rolling force is generally between 500 tons and 1500 tons, which varies according to the thickness ratio of copper and steel. The back layer 20 and the intermediate layer 30 can also be metallurgically joined by diffusion welding. The temperature range of the diffusion welding is 800°C - 950°C; the holding time is usually between 30 minutes and 2 hours, depending on the specific thickness and diffusion requirements; a certain pressure needs to be applied between copper and steel to ensure close contact at the interface, usually 5 MPa - 20 MPa, which is appropriately adjusted according to the shape and thickness of the material.

[0040] This composite can enhance the overall strength of the composite plate, reduce the weight without changing the thickness dimension of the mold, so that the inertial force is small when the composite plate vibrates. In addition, the cost can be reduced by taking advantage of the price difference of materials. For example, the current price of copper alloy is about 80,000 yuan per ton, while that of steel is about 6,000 yuan per ton, saving more than 90% of the cost.

[0041] The front layer 10 serving as the working surface can be a superalloy thin plate with a thickness of about 1-2 mm to replace the plating 802 (nickel-iron plating) treatment in the prior art. The front layer 10 is metallurgically bonded to the second surface 32 of the intermediate layer 30. As an alternative bonding method, the superalloy thin plate is bonded to the copper-silver alloy of the intermediate layer 20 by rolling composite methods such as hot, warm, cold rolling composite or surfacing. This composite can solve the problem of insufficient surface strength of the copper-silver alloy and meet the requirements of the hardness and wear resistance of the working surface, while simplifying the processing technology and reducing the cost.

[0042] In this embodiment, the material of the superalloy thin plate can be Inconel600 (execution standard ASTMB168), and the composition is: nickel (Ni) 72%, chromium (Cr) 14%, iron (Fe) 6%, molybdenum (Mo) 0.5%, and trace amounts of other elements. The characteristics of this material are excellent oxidation resistance and corrosion resistance, and it is suitable for high-temperature environments.

[0043] It is also possible to comprehensively consider properties such as oxidation resistance, corrosion resistance, creep strength and toughness of the material to adapt to the specific working environment and usage requirements of the continuous casting combined mold, and select a suitable superalloy thin plate material. For example, optional materials include: Inconel625: It has excellent corrosion resistance and oxidation resistance, is suitable for use at temperatures up to 1000 °C, and provides good strength and toughness at the same time. Inconel718: It has high strength and good creep resistance, and is particularly suitable for high-temperature environments that require oxidation and corrosion resistance. HastelloyX: This nickel-based superalloy has good high-temperature oxidation resistance and weldability, is suitable for environments from 600 °C to 800 °C, and is widely used in gas turbines and petrochemical equipment. Haynes230: This alloy performs well at high temperatures and also has good creep resistance and oxidation resistance. Cobalt-based alloys (such as Haynes188): They perform excellently under extreme high-temperature conditions (above 1000 °C). Fe-Ni-Cr alloys (such as Incoloy800H / 800HT): This alloy provides a stable structure and good oxidation resistance at higher temperatures (up to 870 °C at most).

[0044] Adopting the composite structure proposed in this application can greatly reduce the thickness dimension of the mold copper plate. For example, for comparison Figure 1 、 Figure 2 、 Figure 3The existing 41-mm-thick conventional chromium-zirconium copper alloy composite slab mold to be replaced is presented. In terms of the dimensions of each layer of the laminated composite slab proposed by the present invention, the thickness of the copper-silver alloy intermediate layer 30 is about 20 mm, which is approximately 1 / 2 of the thickness of the chromium-zirconium copper alloy layer 801 of the copper slab of the mold to be replaced; the thickness of the front layer 10 of the superalloy thin sheet, that is, the working surface, is about 1-2 mm, which is roughly equal to the thickness of the plating layer 802 of the traditional copper mold; the thickness of the back layer 20 of the high-strength steel material, that is, the cooling surface, is about 20 mm, which is approximately 1 / 2 of the original thickness of the copper slab of the mold to be replaced. The overall size can be reduced by about 1 / 4.

[0045] In addition, the inventor found that when the front layer 10 of the superalloy thin sheet is combined with the copper-silver alloy intermediate layer 30, due to the large difference in the thermal expansion coefficients of the two, relatively large stresses may be generated during temperature changes. In response to this situation, as an optional treatment method, the atoms of the two materials of the front layer 10 and the intermediate layer 20 can be diffused with each other at the interface through a diffusion welding process to form a strong metallurgical bond, which can eliminate the interface stress caused by the difference in thermal expansion coefficients in the traditional welding method.

[0046] The diffusion welding temperature of the front layer 10 and the intermediate layer 30 is 800-950 °C. Since the thermal expansion coefficients of copper and superalloy are different, the temperature should not be too high to prevent excessive thermal expansion stress from affecting the interface bonding; the pressure is 500-600 MPa. Maintaining an appropriate pressure can promote interface contact, but excessive pressure should be avoided to prevent deformation of the alloy thin sheet or indentation of the copper slab; the holding time should ensure sufficient diffusion. For example, the holding time is 12 hours to achieve atomic diffusion bonding between alloy elements. In addition, a vacuum degree <10 3 Pa can be provided. A high-vacuum environment can prevent oxidation and improve the bonding quality; the cooling method is slow cooling to prevent cracks caused by thermal stress and is conducive to the formation of a uniform bonding layer.

[0047] Or as another optional treatment method, that is, using a silver-based filler metal to braze the front layer 10 and the intermediate layer 30 can also effectively relieve the stress caused by the difference in thermal expansion coefficients, has good thermal conductivity, and can also improve the interface bonding strength.

[0048] The inventor found that using diffusion welding helps to replace the damaged superalloy thin sheet in the front layer during subsequent processing.

[0049] The surface layer 10 of the worn superalloy thin sheet can be peeled off by heating under certain conditions, and a new surface layer of the superalloy thin sheet can be replaced, so that the copper-silver alloy of the intermediate layer 30 and the high-strength steel of the back layer 20 can be reused.

[0050] The implementation steps for replacing the front layer include:

[0051] Step S201, preliminary preparation. This includes material inspection, i.e., inspecting the states of the front layer of the worn superalloy plate, the middle layer, and the back layer of the high-strength steel. Confirm that there are no structural damages in the middle layer and the back layer and they are suitable for reuse; surface cleaning, i.e., thoroughly cleaning the surfaces of each layer, especially the contact surface between the copper plate and the high-strength steel, to remove oxides, oil stains, etc., to ensure good diffusion welding effect; and equipment preparation, i.e., preparing diffusion welding equipment, such as a vacuum diffusion welding furnace or a high-temperature and high-pressure diffusion welding equipment, and corresponding tooling fixtures.

[0052] Step S202, heating and peeling. This includes heating, i.e., putting the worn crystallizer copper plate into a heating furnace and heating it to a welding temperature of 800 - 900 °C to soften the interface bonding and increase the interface stress. This is because the expansion coefficients of the superalloy and the copper-silver alloy are different, and heating will generate interface stress, which will help to separate the worn alloy plate; peeling, i.e., gradually applying a slight mechanical force at high temperature after heating to promote the separation of the worn superalloy plate from the silver-copper matrix. The direction and intensity of the force application should be controlled to prevent damage to the matrix of the middle layer of the copper-silver alloy; cooling, i.e., after peeling is completed, slowly cooling to room temperature to prevent cracks caused by rapid cooling of the material.

[0053] Step S203, interface cleaning. This includes surface cleaning, i.e., the second surface 32 of the middle layer 30 after peeling may have residues or oxides, and polishing or grinding tools are used to remove the residues to ensure a smooth and pollution-free surface. Surface activation, i.e., when necessary, the surface can be activated after cleaning, such as pickling, ultrasonic cleaning, to ensure that the new superalloy thin plate can achieve the required welding bonding strength.

[0054] Step S204, new plate assembly and positioning. This includes new plate preparation, i.e., ensuring that the new superalloy thin plate meets the dimensional requirements, has no surface defects, and undergoes necessary surface cleaning to ensure its cleanliness; positioning and clamping, i.e., aligning the new superalloy thin plate with the copper plate and installing it in the diffusion welding tooling fixture to ensure tight contact of the contact surfaces and applying appropriate uniform clamping pressure; and vacuum environment preparation, i.e., putting the assembly into a vacuum diffusion welding furnace and evacuating to < 10 3 Pa to prevent oxidation and ensure welding quality.

[0055] Step S205, diffusion welding. This includes welding parameter setting, i.e., re-welding according to the original diffusion welding parameters, such as temperature 800 - 950 °C, pressure 500 - 600 MPa, and heat preservation for 12 hours; temperature and pressure control, i.e., keeping the welding parameters stable to ensure sufficient atomic diffusion bonding between the superalloy thin plate and the copper matrix; and slow cooling, i.e., after welding is completed, slowly cooling to avoid cracks or delamination caused by internal stress.

[0056] Step S206 may further include quality inspection, including interface bonding strength testing, i.e., performing ultrasonic testing or microhardness testing to confirm that the bonding strength of the new welding interface meets the requirements; and non-destructive testing, i.e., performing non-destructive testing such as ultrasonic or X-ray on the welding interface to ensure that the welding quality is qualified and the bonding is firm.

[0057] The mold copper plate structure design proposed by the present invention can not only greatly improve the thermal conductivity of the mold copper plate, but also improve the overall rigidity of the mold plate through laminated composite, and can meet the wear resistance requirements of the working surface, thereby improving or completely eliminating the copper plate crack phenomenon and extending the service life of the copper plate. At the same time, the formation and growth of the billet shell are more uniform and the quality of the steel billet is better. The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A layered composite plate type continuous casting machine crystallizer copper plate, characterized in that: The invention comprises a layered composite structure, wherein the layered composite structure comprises a front layer as a working surface, a back layer as a cooling surface, and an intermediate layer as a heat dissipation layer, wherein: the intermediate layer is made of a copper-silver alloy; the back layer is high-strength steel and is metallurgically bonded to a first surface of the intermediate layer; the front layer is a high-temperature alloy thin plate and is metallurgically bonded to a second surface of the intermediate layer opposite to the first surface.

2. The layered composite plate type continuous casting machine crystallizer copper plate according to claim 1, characterized in that: The thickness of the middle layer is the same as that of the back layer, and is much greater than the thickness of the front layer.

3. The layered composite plate type continuous casting machine crystallizer copper plate according to claim 1, characterized in that: The thickness of the high-temperature alloy sheet is about 1-2 mm; the thickness of the middle layer is about 20 mm, the thickness of the front layer is about 1 mm; and the thickness of the back layer is about 20 mm.

4. The layered composite plate type continuous casting machine crystallizer copper plate according to claim 1, characterized in that: The copper-silver alloy has the following components: Cu 99.5%, Ag 0.07-0.1%, and its thermal conductivity can reach 450W / (m·K). The material of the high-temperature alloy sheet is Inconel 600.

5. The method for preparing a layered composite plate type continuous casting machine crystallizer copper plate according to any one of the above claims, characterized in that include: The middle layer is compounded with the front layer and the back layer respectively by metallurgical bonding; the metallurgical bonding method of the back layer and the middle layer is hot rolling, warm rolling or cold rolling compound, or diffusion welding; the metallurgical bonding method of the middle layer and the front layer is hot rolling, warm rolling or cold rolling compound, or diffusion welding.

6. The preparation method according to claim 5, characterized in that: The metallurgical bonding method of the back layer and the middle layer is high temperature rolling, the temperature is controlled between 850°C and 950°C, and the rolling force is between 500 tons and 1500 tons, which varies according to the thickness ratio of copper and steel.

7. The preparation method according to claim 5, characterized in that: The metallurgical bonding method of the back layer and the middle layer is diffusion welding, and the parameters are: temperature: 800-950°C; pressure: 500-600MPa; insulation time: 12 hours; Vacuum degree: <10 3 Pa; then undergo slow cooling.

8. The preparation method according to claim 5, characterized in that: The metallurgical bonding method of the front layer and the second surface of the middle layer is diffusion welding, the temperature range of the diffusion welding is 800°C~950°C; the insulation time is usually 30 minutes to 2 hours; and a pressure of 5MPa~20MPa is applied to the layer and the middle layer.

9. The preparation method according to claim 5, characterized in that: Heat-peeling the current front layer, including placing the crystallizer copper plate that is about to be worn into a heating furnace, heating it to a welding temperature of 800-900°C, and gradually applying a slight mechanical force at high temperature to separate the worn front layer from the middle layer; after the peeling is completed, slowly cooling to room temperature; cleaning the interface surface; assembling and positioning the new front layer; and diffusion welding.

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