Layered composite plate type continuous casting machine crystallizer copper plate and preparation method thereof

Abstract

The invention discloses a layered composite plate type continuous casting machine crystallizer copper plate and a preparation method thereof.The layered composite plate type continuous casting machine crystallizer copper plate comprises a layered composite structure, the layered composite structure comprises a front face layer serving as a working face, a back face layer serving as a cooling face and a middle layer serving as a heat dissipation layer, and the middle layer is made of copper-silver alloy; the back surface layer is made of high-strength steel and is in metallurgical joint with the first surface of the middle layer; the front layer is a high-temperature alloy sheet and is in metallurgical joint with the second surface, opposite to the first surface, of the middle layer. According to the layered composite plate type continuous casting machine crystallizer copper plate, the overall rigidity and the cooling strength of a composite plate crystallizer are improved through the optimized design of the layered composite plate according to the using working condition of a continuous casting crystallizer, the hot surface temperature of an eddy current area with large heat flux density can be avoided, the phenomenon of cracks of the copper plate can be improved or thoroughly eliminated, and the service life of the continuous casting crystallizer is prolonged. Meanwhile, the service life of the crystallizer composite plate is prolonged, and the overall manufacturing cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of metallurgical continuous casting, and in particular to a novel layered composite plate type continuous casting machine crystallizer copper plate. 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 down from the tundish passes through the water-cooled copper plate of the crystallizer to form a certain billet shell, and is continuously pulled out from the lower mouth 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 operating requirements, the crystallizer should have good thermal conductivity and rigidity. The thermal conductivity makes the molten steel solidify quickly, which is an important prerequisite for achieving high drawing speed. The rigidity can adapt to large thermal stress, is not easy to deform and has the advantages of wear resistance on the inner surface, and the structure should be simple and easy to manufacture and maintain.

[0003] The working surface of the continuous casting mold is a key component for heat exchange and forming of molten steel during solidification, so it is required to be made of materials with good thermal conductivity. Copper plate has good thermal conductivity, but its strength and hardness are low, especially at high temperatures, so its 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 main technical means at present are: first, the chromium-zirconium-copper alloy is generally used, and the nickel-iron coating is applied on the working surface to improve the surface hardness and wear resistance; second, the cooling water tank is set on the cooling surface to improve the cooling strength. For example: The Chinese utility model patent with announcement number CN202155493U discloses a wide copper plate cooling structure for a thin slab continuous casting crystallizer. By setting cooling water channels, the non-uniform distribution of the water channels is optimized, specifically by reducing the diameter of the water channels, increasing the number of water channels, and reasonably distributing them according to the temperature of the molten steel, thereby improving the cooling intensity of the crystallizer and improving the quality of the casting.

[0005] A Chinese invention patent application with publication number CN102581239A discloses a wide copper plate for a crystallizer of an efficient slab continuous casting machine. Deep water troughs and shallow water troughs of different depths are set to optimize the heat dissipation uniformity of the crystallizer copper plate. However, there are problems such as difficulty in processing water holes and high scrap rate, and the thermal conductivity of the copper plate is not greatly improved.

[0006] The Chinese invention patent application with the publication number CN107116186A discloses an ultra-thin slab crystallizer copper plate with a composite cooling structure, in which multiple cooling water grooves and multiple cooling water holes are arranged on the cooling surface to optimize the uneven cooling phenomenon in the area of ​​the primary shell. However, in actual applications, in the cooling structure of the full water groove or water groove + water hole, the copper plate has serious cracks within the range of 90-120mm from the upper edge to the center of the copper plate and 320-460mm from the edge to the center, that is, the straight part of the high temperature zone, the position of the reinforcing rib where the pin is located, which affects the service life of the copper plate.

[0007] The Chinese invention patent application with publication number CN115007816A discloses a thin slab continuous casting crystallizer copper plate with a cooling structure. By optimizing the design of the high-temperature area, the cooling capacity of the copper plate is improved, and the hot surface temperature of the eddy current area with high 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.

[0008] The above-mentioned disclosures are limited to optimizing the diameter, quantity, distribution, etc. of cooling water channels under the existing materials, i.e., chromium-zirconium-copper alloy, and the existing structure, i.e., chromium-zirconium-copper plus surface-plated nickel-iron, to improve the working performance and life of the crystallizer copper plate. Although there are certain effects, it is difficult to significantly change the performance and life of the crystallizer if the thermal conductivity of the material itself is not significantly improved and the processing technology is not changed. Summary of the invention

[0009] The purpose of the present invention is to address the deficiencies in the prior art and to provide a layered composite plate continuous casting machine crystallizer copper plate that significantly improves the working performance, including thermal conductivity, rigidity and life of the continuous casting machine crystallizer copper plate by changes in material, structure and production process.

[0010] To achieve the above objectives, some embodiments of the present invention provide a layered composite plate type continuous casting machine crystallizer copper plate, which includes a layered composite structure, wherein the layered composite structure includes 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 material; the back layer is high-strength steel, which is metallurgically bonded to the first surface of the intermediate layer; the front layer is a high-temperature alloy thin plate, which is metallurgically bonded to the second surface of the intermediate layer opposite to the first surface.

[0011] In some embodiments, the back layer is metallurgically bonded to the first surface of the middle layer by diffusion welding or rolling bonding.

[0012] In some embodiments, the front layer is metallurgically bonded to the second surface of the intermediate layer by surfacing welding or rolling bonding.

[0013] In some embodiments, the thickness of the middle layer and the back layer is the same and much greater than the thickness of the front layer.

[0014] In some embodiments, the thickness of the high temperature alloy sheet is about 1-2 mm.

[0015] In some embodiments, 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.

[0016] Preferably, the copper-silver alloy has a composition of Cu 99.5% and Ag 0.07-0.1%, and its thermal conductivity can reach 450 W / (m·K).

[0017] Preferably, the material of the high-temperature alloy sheet is Inconel600.

[0018] Preferably, the process and cooling water channel settings and optimization can be performed according to the operating conditions.

[0019] Some embodiments of the present application also disclose a method for preparing a layered composite plate continuous casting machine crystallizer copper plate of any of the above-mentioned items, which comprises: respectively compounding the middle layer with the front layer and the back layer, 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.

[0020] In some embodiments, 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.

[0021] In some embodiments, 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.

[0022] In some embodiments, the metallurgical bonding method of the front layer and the second surface of the middle layer is diffusion welding, and 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 30.

[0023] In some embodiments, the current front layer is thermally peeled off, 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; assembling and positioning the new front layer; and performing diffusion welding.

[0024] The beneficial effects of the present invention include: On the one hand, the layered composite plate type continuous casting machine crystallizer copper plate of the present invention improves the overall rigidity and cooling strength of the composite plate crystallizer through the optimized design of the layered composite plate according to the operating conditions of the continuous casting crystallizer, which can avoid the hot surface temperature of the eddy current zone with large heat flux density, thereby helping to improve or completely eliminate the occurrence of copper plate cracks. After the rigidity is improved, it can give the cooling water channel design and optimization greater flexibility and freedom, while extending the service life of the crystallizer composite plate and reducing the overall manufacturing cost.

[0025] On the other hand, the composite method in the production process of the layered composite plate type continuous casting machine crystallizer copper plate of the present invention is rolling composite or diffusion welding, which reduces the electroplating link and is more energy-saving and environmentally friendly.

[0026] On the other hand, the layered composite plate continuous casting machine crystallizer copper plate of the present invention only replaces the material of the existing crystallizer copper plate, and then composites other materials to improve the wear resistance and rigidity requirements. This allows the water trough depth and layout, the position and depth of the pin screw holes, and the position and depth of the thermocouple to remain original, and the back panel and the overall assembly structure may not change. This allows steel companies to make full use of the existing back panel without purchasing a new one, which is conducive to cost savings and the promotion of the crystallizer of the present application.

[0027] On the other hand, the continuous casting process parameters of the continuous casting machine using the layered composite plate type continuous casting machine crystallizer copper plate of the present invention do not need to be greatly adjusted, the adaptation is convenient, and it has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the three-dimensional structure of a copper plate continuous casting combined crystallizer in the prior art.

[0029] Figure 2 It is a schematic diagram of the main view of the copper plate continuous casting combined crystallizer in the prior art.

[0030] Figure 3 for Figure 2 AA cross-sectional schematic diagram of the copper plate continuous casting combined crystallizer is shown.

[0031] Figure 4It is a schematic diagram of the three-dimensional structure of the copper plate of the crystallizer of the layered composite plate type continuous casting machine according to an embodiment of the present application.

[0032] Figure 5 It is a front schematic view of a copper plate of a crystallizer of a layered composite plate type continuous casting machine according to an embodiment of the present application.

[0033] Figure 6 for Figure 5 The schematic diagram of the BB cross-section side view of the layered composite plate continuous casting machine crystallizer copper plate is shown. DETAILED DESCRIPTION

[0034] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0035] like Figure 4 , Figure 5 , Figure 6 As shown, a layered composite plate type continuous casting machine crystallizer copper plate 100 according to an embodiment of the present invention comprises a layered composite plate structure, wherein the layered composite plate structure comprises a front layer 10 as a working surface, a back layer 20 as a cooling surface, and an intermediate layer 30 as a heat dissipation layer.

[0036] The intermediate layer 30 as a heat dissipation layer is plate-shaped and includes a first surface 31 and a second surface 32 arranged opposite to the first surface. The intermediate layer 30 can be made of a copper-silver alloy, the composition of which is: Cu 99.5%, Ag 0.07-0.1%, and its thermal conductivity can reach 450W / (m·K). The thermal conductivity of the copper-silver alloy used in this embodiment is much higher than that of the existing chromium-zirconium-copper alloy layer 801 (290-340W / (m·K), which can greatly improve the cooling strength of the crystallizer.

[0037] The back layer 20 as the cooling surface can be made of high-strength steel, and the back layer 20 is metallurgically bonded 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 the like. For example, high-temperature rolling, or hot rolling, the temperature is controlled between 850°C and 950°C to prevent the copper layer from overheating and deformation, and the rolling force is generally between 500 tons and 1500 tons, which varies according to the thickness ratio of copper and steel. Diffusion welding can also be used to metallurgically bond the back layer 20 and the intermediate layer 30. The temperature range of the diffusion welding is 800°C to 950°C; the insulation time is usually 30 minutes to 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 between the interface, usually 5MPa~20MPa, which is appropriately adjusted according to the shape and thickness of the material.

[0038] This type of composite can improve the overall strength of the composite plate and reduce its weight without changing the thickness of the crystallizer, thereby reducing the inertia force of the composite plate when it vibrates. In addition, the price difference of the materials can be used to reduce costs. For example, the current copper alloy price is about 80,000 yuan / ton, while steel is about 6,000 yuan / ton, which can save more than 90% of the cost.

[0039] The front layer 10 as the working surface can be a high-temperature alloy sheet with a thickness of about 1 to 2 mm to replace the coating 802 (nickel-iron plating) in the prior art. The front layer 10 is metallurgically bonded to the second surface 32 of the intermediate layer 30. As an optional bonding method, the high-temperature alloy sheet is bonded to the copper-silver alloy of the intermediate layer 20 by rolling bonding methods such as hot, warm, and cold rolling bonding or surfacing. This bonding can solve the problem of insufficient surface strength of the copper-silver alloy and meet the hardness and wear resistance requirements of the working surface, while simplifying the processing technology and reducing costs.

[0040] In this embodiment, the material of the high temperature alloy sheet can be Inconel600 (implementation standard ASTMB168), the composition is: nickel (Ni) 72%, chromium (Cr) 14%, iron (Fe) 6%, molybdenum (Mo) 0.5%, and other elements in trace amounts. The material is characterized by excellent oxidation resistance and corrosion resistance, and is suitable for high temperature environments.

[0041] The material's oxidation resistance, corrosion resistance, creep strength and toughness can also be considered comprehensively to adapt to the specific working environment and use requirements of the continuous casting combined crystallizer, and select suitable high-temperature alloy sheet materials. For example, the optional materials include: Inconel625: It has excellent corrosion resistance and oxidation resistance, suitable for use at temperatures up to 1000°C, while providing good strength and toughness. Inconel718: It has high strength and good creep resistance, and is particularly suitable for high-temperature environments that require oxidation resistance and corrosion resistance. HastelloyX: This nickel-based high-temperature alloy has good high-temperature oxidation resistance and weldability, is suitable for environments of 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 well under extreme high temperature conditions (above 1000°C). Fe-Ni-Cr alloy (such as Incoloy800H / 800HT): This alloy provides a stable structure and good oxidation resistance at higher temperatures (up to 870°C).

[0042] The composite structure proposed in this application can greatly reduce the thickness of the copper plate of the crystallizer. Figure 1 , Figure 2 , Figure 3The conventional 41mm thick chromium-zirconium-copper alloy composite plate crystallizer to be replaced is shown in the figure. In terms of the dimensions of each layer of the layered composite plate proposed by the present invention, the thickness of the middle layer 30 of the copper-silver alloy is about 20mm, which is about 1 / 2 of the thickness of the chromium-zirconium-copper alloy layer 801 of the crystallizer copper plate to be replaced; the thickness of the front layer 10 of the high-temperature alloy sheet, i.e. the working surface, is about 1-2mm, which is roughly equal to the thickness of the coating 802 of the conventional crystallizer copper plate; the thickness of the back layer 20 of the high-strength steel material, i.e. the cooling surface, is about 20mm, which is about 1 / 2 of the original thickness of the crystallizer copper plate to be replaced. The overall size can be reduced by about 1 / 4.

[0043] In addition, the inventors found that when the front layer 10 as a high-temperature alloy sheet is combined with the middle layer 30 of the copper-silver alloy, due to the large difference in thermal expansion coefficients between the two, large stress may be generated during the temperature change process. In view of this situation, as an optional treatment method, the atoms of the two materials of the front layer 10 and the middle layer 20 can be diffused 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.

[0044] The diffusion welding temperature of the front layer 10 and the middle layer 30 is 800-950°C. Due to the different thermal expansion coefficients of copper and high-temperature alloys, the temperature should not be too high to prevent excessive thermal expansion stress from affecting the interface bonding. The pressure is 500-600MPa. Maintaining appropriate pressure can promote interface contact, but excessive pressure should be avoided to prevent deformation of the alloy sheet or indentation of the copper plate. The insulation time should ensure sufficient diffusion, for example, the insulation time is 12 hours, so as to achieve atomic diffusion bonding between alloy elements. In addition, a vacuum degree of <10 3 The vacuum degree is Pa, and the 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.

[0045] Alternatively, as another optional treatment method, the front layer 10 and the middle layer 30 are brazed with silver-based solder, which can also effectively relieve the stress caused by the difference in thermal expansion coefficient, has good thermal conductivity, and can also improve the interface bonding strength.

[0046] The inventors have found that diffusion welding is helpful for replacing the high-temperature alloy sheet of the front layer in subsequent processing after it is damaged.

[0047] The worn surface layer 10 of the high-temperature alloy sheet can be peeled off by heating under certain conditions and replaced with a new surface layer of the high-temperature alloy sheet, so that the copper-silver alloy of the middle layer 30 and the high-strength steel of the back layer 20 can be reused.

[0048] The implementation steps for replacing the front layer include: Step S201, preliminary preparation. Including material inspection, that is, checking the state of the front layer, middle layer of the worn high-temperature alloy plate and the back layer of the high-strength steel. Confirm that the middle layer and the back layer have no structural damage and are suitable for reuse; surface cleaning, that is, thoroughly cleaning the surface of each layer, especially the contact surface of the copper plate and the high-strength steel, to remove oxides, oil stains, etc., to ensure a good effect of diffusion welding; and equipment preparation, that is, preparing diffusion welding equipment, such as a vacuum diffusion welding furnace or a high-temperature and high-pressure diffusion welding equipment, and corresponding fixtures.

[0049] Step S202, heating and peeling. It includes heating, that is, 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 high-temperature alloy and the copper-silver alloy are different. Heating will produce interface stress, which will help to separate the worn alloy plate; peeling, that is, gradually applying a slight mechanical force at high temperature after heating to separate the worn high-temperature alloy plate from the silver-copper matrix. The direction and strength of the force should be controlled to prevent damage to the matrix of the intermediate layer of the copper-silver alloy; cooling, that is, after the peeling is completed, slowly cool it to room temperature to prevent cracks caused by rapid cooling of the material.

[0050] Step S203, interface cleaning. This includes surface cleaning, i.e., the second surface 32 of the intermediate layer 30 after stripping may have residues or oxides, and polishing or grinding tools are used to remove the residues to ensure that the surface is smooth and free of pollution. Surface activation, i.e., if necessary, the surface can be activated after cleaning, such as pickling and ultrasonic cleaning, to ensure that the new high-temperature alloy sheet can achieve the required welding strength.

[0051] Step S204, assembly and positioning of the new plate. This includes preparation of the new plate, i.e. ensuring that the new high-temperature alloy plate meets the size requirements and has no surface defects, and performing necessary surface cleaning to ensure its cleanliness; positioning and clamping, i.e. aligning the new high-temperature alloy plate with the copper plate, installing it in the diffusion welding fixture, ensuring that the contact surfaces fit tightly, and applying appropriate uniform clamping pressure; and vacuum environment preparation, i.e. placing the assembly into a vacuum diffusion welding furnace and evacuating it to <10 3 Pa prevents oxidation and ensures welding quality.

[0052] Step S205, diffusion welding. It includes welding parameter setting, i.e. re-welding according to the original diffusion welding parameters, such as temperature 800-950°C, pressure 500-600MPa, 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 high-temperature alloy sheet and the copper matrix; and slow cooling, i.e. slow cooling after welding to avoid cracks or delamination caused by internal stress.

[0053] Step S206 may also include quality inspection, including interface bonding strength test, i.e. ultrasonic testing or microhardness test, to confirm that the bonding strength of the new welding interface meets the requirements; and non-destructive testing, i.e. ultrasonic or X-ray non-destructive testing of the welding interface to ensure that the welding quality is qualified and the bonding is firm.

[0054] The crystallizer copper plate structural design proposed in the present invention can not only greatly improve the thermal conductivity of the crystallizer copper plate, but also improve the overall rigidity of the crystallizer plate through layered composite, and 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, while making the formation and growth of the billet shell more uniform and the quality of the steel billet better. The above is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various changes and variations. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should 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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