JP2019136753A - Cobalt-nickel alloy material, continuous casting mold using same and method for manufacturing same - Google Patents

Abstract

To provide a cobalt-nickel alloy material adapted to form a protection layer having both of high strength and thermal shock resistance in addition to excellent heat resistance, corrosion resistance and wear resistance on a surface of a base substance of a continuous casting mold.SOLUTION: A cobalt-nickel alloy material is provided for forming on a surface of a mold base substance a Co-Ni alloy plating layer with a total film thickness of 30-500 μm by alternately laying two types of crystallized electric plating layers of hexagonal crystal and face-centered cubic crystal different in crystal structures with each film thickness of 0.1-50 μm. The two types of electric plating layers, which are a plating layer having a hexagonal crystal structure consisting of 10-20 wt.% of Ni and a balance of Co and a plating layer having a face-centered cubic crystal structure consisting of 21-60 wt.% of Ni and a balance of Co, are alternately layered, and these layers are respectively crystallized into hexagonal and face-centered cubic crystals by a heat treatment at 200-500°C. Further, while supplying a Ni-based heat-resistant alloy powder to the surface, a laser is radiated to fuse and solidify the powder so as to form a 0.1-10 mm thick Ni-based alloy coat layer formed with a rise.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a cobalt-nickel alloy material, a continuous casting mold having high heat resistance and wear resistance, and a method for producing the same.

  Copper and copper alloys that are excellent in thermal conductivity are often used from the viewpoint of the cooling effect as continuous casting mold materials used in the steel making process in which the molten steel is solidified and molded while cooling. However, since copper and copper alloys are low in hardness and inferior in wear resistance, for the purpose of extending the life of the mold, the surface of the mold base made of copper or copper alloy has higher wear resistance and excellent heat resistance. A continuous casting mold in which a cobalt plating layer, a metal layer by spraying, or a ceramic layer is formed is known.

  The mold surface is exposed to severe thermal shock due to the temperature difference between the hot molten steel and the cooled mold, especially at the upper part of the continuous casting mold during solidification and molding. On the other hand, at the lower part of the mold, the mold is rubbed strongly by the cooled and solidified slab, and the mold wears heavily. Therefore, a continuous casting mold surface made of copper or copper alloy by plating or spraying an alloy layer of nickel and iron, manganese, cobalt, chromium, tungsten, etc., which has excellent characteristics such as heat fatigue resistance, wear resistance, and corrosion resistance. A method for extending the life of a mold by forming the film is generally known.

  Patent Document 1 reports an example in which tensile strength and wear resistance are improved by coating the surface of a continuous casting mold with a layer in which two layers having different nickel contents are alternately laminated with a cobalt-nickel alloy. Has been.

  In Patent Document 2, Ni is plated on the surface of copper or a copper alloy, a plate-shaped Ni-based alloy is temporarily attached to the surface, and then is built up using a laser or an electron beam to provide high adhesion strength and wear resistance. A method for forming a film excellent in corrosion resistance and corrosion resistance is shown. Further, for the plate-shaped material of the Ni-based alloy for overlaying, Hastelloy C (53Ni19Mo17Cr), Inconel (80Ni13Cr), Monel (65Ni31Cu4 (Fe + Mn)), NiCoCrAlY (23Co20Cr8.5Al0.6Y remaining Ni), NiCr (50Ni50Cr) Used. Also shown is a method of melting the boundary between the plate-shaped material and the Ni plating layer when the plate-shaped material is built up using a laser or an electron beam, and the molten portion of the adjacent plate-shaped material forms an overlapped portion. ing.

Japanese Patent Laying-Open No. 2015-166383 Japanese Patent Laid-Open No. 10-85972

  In the technique of Patent Document 2, when a plate-shaped material is built up using a laser, it is necessary to supply a sufficient amount of heat to melt the plate-shaped material, and much of the supplied heat is a plate-shaped material. Therefore, there is a problem that the amount of heat to be applied to the copper or copper alloy substrate is increased and thermal deformation is not small. Further, the strength and heat resistance of the Ni plating as the base were not sufficient.

  The present invention has been made in view of such points, and in order to achieve a longer life of the continuous casting mold, the surface of the copper or copper alloy mold base has excellent wear resistance and corrosion resistance. Furthermore, by extending two types of cobalt-nickel alloy plating layers with different crystal structures and improved tensile strength and thermal shock resistance, the life of the continuous casting mold can be extended. In addition, a nickel-based alloy overlay layer with excellent heat resistance and corrosion resistance by a laser overlay method using metal powder on the surface of the cobalt-nickel alloy plating layer on which different crystal structures are alternately stacked. By suppressing and laminating, a continuous casting mold having high strength and excellent heat resistance and wear resistance is realized.

  The invention of claim 1 is a plating layer composed of 10 to 20% by weight of nickel, the remaining cobalt and unavoidable impurities and having a hexagonal crystal structure, and 21 to 60% by weight of nickel, the remaining cobalt and unavoidable impurities. It is a cobalt-nickel alloy material characterized by having a structure in which plating layers having a cubic crystal structure are alternately laminated.

  According to the second aspect of the present invention, a layer of 10 to 20% by weight of nickel, the remaining cobalt and unavoidable impurities, 21 to 60% by weight of nickel, the remaining cobalt and unavoidable are formed on the surface of the copper or copper alloy substrate by electroplating. Layers made of impurities are alternately stacked, and each layer has a thickness of 0.1 to 50 μm, and an alternate stacked plating layer having a total thickness of 50 to 2000 μm is formed at 200 to 500 ° C. It is a continuous casting mold in which each layer is crystallized into hexagonal crystals and face-centered cubic crystals by heat treatment.

  The invention according to claim 3 is an electroplated layer of two types which is made of nickel and cobalt and has a crystal structure different from hexagonal crystal and face centered cubic crystal on the surface of a copper or copper alloy substrate. A single layer or multiple layers formed by forming a plating layer with a total film thickness of 30 to 500 μm by alternately stacking ˜50 μm, and irradiating a laser while supplying nickel-base heat-resistant alloy powder to the surface to melt and solidify the powder Is a continuous casting mold in which a nickel-based alloy coating layer having a thickness of 0.1 to 10 mm is formed.

  The invention of claim 4 is the continuous casting mold according to claim 3, wherein the nickel-base heat-resistant alloy powder forming the laser build-up layer is Hastelloy C (53Ni19Mo17Cr), Inconel (80Ni13Cr), Monel (65Ni31Cu4 (Fe + Mn)), It is characterized by comprising one kind of NiCoCrAlY (47.9Ni23Co20Cr8.5Al0.6Y), NiCr (80Ni20Cr), Waspaloy (58Ni19Cr14Co4.5Mo3Ti).

  The invention of claim 5 is the method for producing a casting mold for continuous casting according to claim 3 or 4, wherein nickel and cobalt from the electroplated layer are formed by repeating the laser build-up layer formation two or more times. It is characterized by making it the multilayer laser build-up layer which decreased the diffusion of this from the inside to the surface.

  According to invention of Claim 1 or 2, the plating layer which consists of 10-20 weight% nickel, remainder cobalt, and an unavoidable impurity and has a hexagonal crystal structure, 21-60 weight% nickel, remainder cobalt, and an unavoidable impurity And has a structure in which plating layers having a face-centered cubic crystal structure are alternately laminated, and therefore has excellent crack resistance against thermal shock. In particular, according to the second aspect of the present invention, the alternately stacked plating layers having a thickness of each layer of 0.1 to 50 μm and a total thickness of 50 to 2000 μm are formed on the surface of the copper or copper alloy substrate. Since it is a continuous casting mold in which each layer is crystallized into hexagonal crystals and face-centered cubic crystals by heat treatment at 200 to 500 ° C., the crack resistance against thermal shock is improved, and heat cracks It can be set as a casting mold for continuous casting.

  According to the invention of claim 3, a build-up layer is formed by irradiating a laser while supplying nickel-base heat-resistant alloy powder to the surface of an electroplating layer made of nickel and cobalt, which absorbs laser energy better than copper or a copper alloy. Compared to the conventional example in which build-up welding is performed using a laser after temporarily attaching a plate-shaped nickel-base alloy, the supplied powder can be efficiently melted. The heat distortion of the alloy base and the entire coating layer can be suppressed. In addition, since the plating layer has a structure in which two types of electroplating layers having different crystal structures with a thickness of each layer of 0.1 to 50 μm are alternately stacked, compared to a single-layer plating layer, Crack resistance against thermal shock is improved. Furthermore, since the electroplating layer has a thickness of 30 to 500 μm, it is possible to suppress the dissolution of copper from the copper or copper alloy substrate to the laser build-up layer, and the original heat resistance, corrosion resistance, Abrasion can be demonstrated.

  According to the invention of claim 4, an alloy that is known to be excellent in heat resistance, corrosion resistance, and wear resistance can be applied to the surface of a copper or copper alloy substrate with almost no change in composition and good adhesion. Since it can be coated, superior heat resistance, corrosion resistance, and wear resistance can be exhibited as compared with a continuous casting mold in which a surface protective film is formed by an alloy plating method or a thermal spraying method.

  According to the invention of claim 5, the multilayer laser build-up layer in which the diffusion of cobalt and nickel from the plating layer is gradually decreased from the inside to the surface by repeating the laser build-up layer formation two or more times. Therefore, the surface of the build-up layer in contact with the molten steel has an effect that it can have a composition that approximates the composition of the nickel-based alloy supplied in powder form.

It is a photograph which shows the cross-section of Example 2 of this invention. It is a photograph which shows the expanded structure of the cross section of Example 2 of this invention.

  In a continuous casting mold, molten steel is poured into the mold, and at the same time, the molten steel is removed and solidified on the mold surface whose back surface is cooled with cooling water to continuously cast and mold the steel. The vicinity of the meniscus portion at the top of the mold is a portion where the molten steel and the mold are in direct contact, and high heat resistance and corrosion resistance are required. At the same time, it is subjected to the strongest thermal stress due to the temperature difference from the cooling water, and thermal cracking is likely to occur, and thermal shock resistance and high strength are required. Further, in a surface-coated mold having a coating layer having excellent heat resistance and corrosion resistance on the surface of a copper or copper alloy mold substrate, strong adhesion strength is required between the substrate and the coating layer.

  On the other hand, at the lower part of the mold where the molten steel is cooled and solidified, the mold surface is removed due to frictional wear of the vitreous ceramic powder contained in the mold powder and weight increase of the steel itself whose density has increased after the molten steel has solidified and volume contracted. Mold life due to strong rubbing can lead to life. Furthermore, it is necessary to take measures against chemical corrosion due to sulfur components in the molten steel and corrosive wear at the bottom of the mold due to the steam of water for cooling the steel after passing through the mold.

  Cobalt-nickel alloys with two types of compositions are alternately stacked as a protective layer that can handle all of the thermal cracks caused by the thermal load, which is the life factor of continuous casting molds, rubbing wear and chemical corrosion. The present inventors have found an alternately stacked crystal layer whose structure has been changed to a different crystal structure.

  By making the cobalt-nickel alloy have a different alternately stacked crystal structure, it becomes chemically more stable than the amorphous structure in which the alternately stacked layers are not stacked, and the corrosion resistance is improved. In addition, alternating layers with multiple components that have different compositional ratios but have similar compositions with hexagonal crystals and face-centered cubic crystals, and have many interfaces maintain strong film stress and flexible elongation characteristics. In particular, the elongation property was improved by 5 times or more than amorphous. Furthermore, because of the alternately stacked layers having a small film thickness, the crystal grain size was kept small, and the hardness was improved by about 130% as compared with the amorphous case. Since the film thickness of each layer of the alternately stacked layers affects the crystal grain size and crystallinity, the film thickness of each layer is preferably 0.1 to 50 μm, more preferably 0.5 to 20 μm. If the film thickness is 0.1 μm or less, it is difficult to control the film thickness at the time of plating, and if it is 50 μm or more, it is difficult to increase the number of alternating layers, and as a result, a high-strength film cannot be obtained.

  With the progress of continuous casting technology, continuous casting of different steel types and high-speed casting with more emphasis on efficiency are desired, and continuous casting molds are expected to withstand greater thermal loads, wear and corrosion resistance. Is done. From the viewpoint of reducing the thermal load on copper or copper alloy, it is preferable that the film thickness of the entire alternate multi-layered film is thick. However, if the plating thickness is increased in the vicinity of the meniscus where the heat load is the highest, the heat removal effect is reduced and the thermal effect on the plating film is further increased, inducing the occurrence of heat cracks, and further the plating peeling. It reaches. On the other hand, wear and corrosion reactions are intense at the lower end of the mold, and in order to withstand the environment, it is essential to increase the thickness of the plating film. From this, the film thickness of the entire alternating multi-layer was set to 50 to 2000 μm.

  In the alternately stacked crystal layer, the alloy composition of the layer having a hexagonal crystal structure is preferably a nickel content of 10 to 20% by weight and the balance cobalt. Outside this composition, it becomes difficult to exhibit a hexagonal crystal structure. Further, when the nickel content is low, the characteristics of cobalt metal become strong and the film becomes brittle. On the other hand, the alloy composition of the layer having the face-centered cubic structure is preferably nickel content of 21 to 60% by weight and the balance cobalt. When the amount is less than 20% by weight, a face-centered cubic structure is difficult to be formed, and when the nickel content is high, corrosion resistance tends to be improved. The elongation characteristics of the product crystal layer tend to be lowered and the thermal shock resistance tends to be lowered. For this reason, the nickel content is more preferably 21 to 60% by weight. The cobalt-nickel alloy plating composition contains inevitable impurities.

  In order to change the structure of layers alternately stacked by plating, it is preferable to crystallize into hexagonal crystals (hcp) and face-centered cubic crystals (fcc) by heat treatment at 200 to 500 ° C. for 10 to 480 minutes. When heat treatment is performed at a temperature higher than 500 ° C., the mold base made of copper and copper alloy is likely to be deformed, and it is preferable to perform the heat treatment at as low a temperature as possible. On the other hand, unless it is 200 degreeC or more, the crystal structure of each layer cannot be changed efficiently.

  In this way, by forming an alternating multi-layered structure composed of two types of plating layers whose structures are changed to hexagonal crystals and face-centered cubic crystals on the surface of the copper or copper alloy substrate, heat resistance, corrosion resistance, and wear resistance are improved. . Furthermore, it is possible to further extend the life by forming a protective layer having excellent heat resistance and corrosion resistance on the surface with good adhesion. In other words, while supplying nickel-based alloy powder with excellent heat resistance and corrosion resistance, the irradiated laser is irradiated to efficiently melt the supplied powder, and this powder supply and laser irradiation are linearly applied to the plating layer surface. By forming a laser build-up layer solidified from the powder melt by scanning in a shape, a protective layer having excellent interlayer adhesion and excellent heat resistance, corrosion resistance, and wear resistance could be formed.

  In order for the built-up nickel-based alloy layer to exhibit the characteristics inherent in the alloy, it is necessary that the alloy layer has no defects such as vacancies and reaches the original density of the alloy. In order for the alloy layer to obtain a true density without voids, it is required to completely melt the alloy part that contributes to build-up once. Energy for completely melting the alloy part is supplied by a laser, but escapes from a copper substrate having good thermal conductivity by heat conduction. Therefore, in order to obtain a good quality alloy layer, it is important to be able to control all of the energy supply amount, the heat of fusion of the metal powder, and the heat diffusion amount.

  As an intermediate layer between the copper substrate and the laser build-up layer, it is advantageous for thermal control during laser build-up to arrange an electroplating layer of cobalt and nickel having a thermal conductivity of about 1/4 that of pure copper. In addition, the laser energy absorption rate at a wavelength of around 1000 nm that can be industrially used for laser overlaying is approximately three times that of copper for nickel, and by providing an electroplated layer of cobalt and nickel on the surface of the copper substrate, it is efficient. A metal molten pool can be formed, which is extremely advantageous from the viewpoint of thermal efficiency and thermal control.

  In the metal overlaying method using a laser, there are a method of using a welding rod and a method of melting an alloy plate, but these methods are different from the method using a powder in that heat from a welding rod or an unmelted alloy plate is used. Because the heat energy that escapes by conduction is large, not only is it difficult to control the amount of heat, but if the entire thickness of the welding rod and alloy plate is not melted, high strength including adhesion strength to the base can be obtained. It is difficult and it is necessary to supply excessive energy from the outside. When the laser energy becomes excessive, it has a great influence on the mold copper base, and at the same time, a large thermal strain is generated. Excessive energy is also significant in the characteristics of the build-up layer itself, such as when the plating layer is thin, the entire thickness of the plating layer is dissolved, and a part of the mold copper base is dissolved in the laser build-up layer. There is a risk of impact.

  As in the present invention, while supplying the alloy powder to be used together with the laser beam from the laser irradiation nozzle, the laser is used for melting only the alloy powder to be supplied by scanning the nozzle on the surface of the substrate to build up the laser. Is the most efficient. Specifically, it is possible to control the required laser energy while managing the size of the molten pool formed by melting the powder and the temperature of the molten pool. By controlling the required laser energy in this way, it is also easy to dissolve a part of the surface portion of the plating layer in the molten pool generated from the alloy powder without excessively dissolving the plating base layer. It has become possible to form a strong build-up layer with no defects between the formation and excellent adhesion. At the same time, the amount of solid solution from the plating layer can be kept low, and the composition change of the alloy build-up layer can be reduced to 0 to 10% by weight.

  In the present invention, a nickel-based heat-resistant alloy build-up layer is formed by melting and solidifying on the surface of an intermediate layer in which cobalt-nickel alloy plating layers having two different compositions and different crystal structures are alternately stacked. However, since the cobalt and nickel plating layer components of the intermediate layer are components also included in the nickel-based heat-resistant alloy, the alloy composition is not greatly impaired even if the plating layer component is dissolved in the build-up layer. The heat resistance and corrosion resistance of the alloy can be maintained at a high level. Further, when two or more build-up layers are repeated, the solid solution amount of the cobalt and nickel plating components decreases in a stepwise gradient, and the surface of the second and higher layers has almost the same composition as the nickel-based alloy powder used. A build-up layer could be formed.

  When forming a nickel-based heat-resistant alloy build-up layer on the surface, the total film thickness (total film thickness of the plating layer) of the plating intermediate layer in which cobalt and nickel alloy plating layers having two types of crystal structures are alternately stacked is Instead of the above-mentioned 50 to 2000 μm, it is preferable that the thickness is 30 to 500 μm.

  If the total film thickness is less than 30 μm, the entire plating layer may be melted in the molten pool formed during laser cladding. In the unlikely event that a part of the copper or copper alloy substrate is also solid-dissolved under the plating layer, the melting point of the solid-solution alloy is greatly lowered, and the strength of the entire coating layer is lowered. In addition, if the total film thickness is less than 30 μm, the strength improvement rate is low and the alternate stacking effect is not sufficient other than the problem of melting during laser cladding. The cobalt and nickel electroplating layer is in the middle of the copper or copper alloy substrate and the laser build-up layer, and also has a role to alleviate thermal strain during build-up, and the total film thickness is preferably 30 μm or more. On the other hand, it is possible to make the total film thickness larger than 500 μm, but even if it is larger than 500 μm, the further improvement of the thermal strain relaxation effect is reduced. Further, even if the thickness is larger than 500 μm, it is difficult to obtain further improvement in strength.

  The laser build-up layer on the plating layer is formed by one layer or multiple layers by repetition, and the total film thickness is preferably 0.1 to 10 mm. When the thickness is less than 0.1 mm, it is necessary to reduce the powder particle size. Since the fine powder easily scatters and floats in the air for a long time, its use is not preferable from the viewpoint of working environment and yield.

  On the other hand, it is not very preferable to make the thickness of one layer of the laser build-up greater than 3 mm. In order to make it thicker than 3 mm, the alloy molten pool size and the laser energy become large, and it becomes difficult to control the laser build-up and the solid solution amount of the underlayer. For this reason, in order to increase the thickness of the laser build-up layer for the purpose of extending the life of the mold, it is realized by making the laser build-up layer multi-layered.

  Although it is possible to make the entire film thickness larger than 10 mm by the multi-layer method, the thickness larger than 10 mm is considered in consideration of the lifetime of the entire mold caused by other reasons than the effect of improving the wear resistance by increasing the film thickness. At this time, it was judged that it was not particularly necessary. The laser overlay layer may be formed in the vicinity of the meniscus portion at the upper part of the inner surface of the mold in addition to the lower part of the inner surface of the mold.

  The nickel-based alloy build-up layer was prepared by a method in which an alloy composition excellent in heat resistance and corrosion resistance was selected, and laser irradiation was performed while supplying these alloy powders. As nickel-based alloys having excellent heat resistance and corrosion resistance, Hastelloy C (53Ni19Mo17Cr), Inconel (80Ni13Cr), Monel (65Ni31Cu4 (Fe + Mn)), NiCoCrAlY (47.9Ni23Co20Cr8.5Al0.6Y), NiCr (80Ni20Cr), Waspaloy (58Ni19Cr14Co4. 5Mo3Ti) was selected, and commercially available alloy powders were used. The composition of the alloy powder is% by weight, and the part less than 100% is other components or inevitable impurities.

  In addition, the alloy powder which can be used is not limited to these, By weight%, Ni: 30% to 93%, Co: 1% or more, Cr: 8% or more, Mo: 1% or more, W: 0.5% or more, Al: 0.2% or more, Ti: 0.4-6%, Nb: 0.4-6%, Ta: 0.1-4%, Y: 0.1% or more As described above, the remainder, inevitable impurities, and the like can be used.

  Further, the copper alloy used for the mold base is not particularly limited, and those conventionally used in this technical field are appropriately used. For example, a copper material for chromium-zirconium-added precipitation hardening mold (preferably Cr: 0.5 to 1.5% by weight, Zr: 0.08 to 0.30% by weight), a chromium / zirconium / aluminum-added mold for electromagnetic stirring Copper materials (preferably Cr: 0.50 to 1.50% by weight, Zr: 0.08 to 0.30% by weight, Al: 0.7 to 1.1% by weight) are used. In some cases, pure copper is used for the mold base instead of these copper alloys.

When the build-up layer becomes thick, the roughness of the build-up layer surface becomes worse. For this reason, after the formation of the laser build-up layer, the surface thereof is polished and the surface roughness is flattened to Ry 10 μm or less, thereby suppressing abnormal wear of the build-up layer.
Hereinafter, the present invention will be described in detail based on the test results of the present invention.

The surface of the copper base material was coated with an alternating stack plating layer of Co—Ni alloys having two different compositions and different crystal structures. Table 1 shows the configuration and conditions of the plating bath. A sulfuric acid bath was used as the plating bath, and the difference in Ni content was caused by the strength of air aeration air flow during plating. First, one type of plating layer (referred to as A layer) is selected from the remaining Co with a Ni content of 10 to 20 wt%, and the other type of plating layer (referred to as B layer) is selected from the remaining Co with a Ni content of 21 to 60 wt%. A film was prepared by alternately stacking the Co-Ni alloy plating layers of the A layer and the B layer. Specifically, the air vent amount based on a current density of 3A / dm ^2: 0.1m with a strength at ³ / m ² and 0.4 m ³ / m ^2, the thickness of each layer by controlling the aeration time Changed. After plating, the film thickness was adjusted to 500 μm by machining. Out-of-range plating samples were produced together with the range-plating samples of the present invention and are shown in Table 2.

  As a comparative example of the present invention, an alternating stack plating layer and a single layer plating layer of a Co—Ni alloy having two kinds of compositions which are amorphous without heat treatment were coated. Table 3 shows Comparative Examples 2 to 3 having the same composition as Examples 1 and 2 of the present invention but amorphous and Comparative Example 4 which is a single-layer plating layer.

  Table 4 shows the tensile strength, breaking elongation, and film hardness of each sample. A tensile test was conducted only with the plating film, and the elongation at break of the film was determined from the tensile strength of the film and the maximum strain displacement at the time when the test piece broke. Inventive Examples 1 to 3, in which two kinds of crystal phases are alternately stacked, have a tensile strength and an elongation at break in contrast to the alternating stacked layers in which the plating layers are amorphous (Comparative Examples 2 to 3) and the comparative example 4 having a single layer. large. Table 4 also shows the results of measuring the micro Vickers hardness from the plating layer cross section with a load of 200 gf. It can be seen that the hardness is higher as the number of crystal alternate stacks is increased.

  The surface of a Cr—Zr—Cu mold base (size 230 mm × 900 mm × 50 mm) was coated with the Co—Ni alloy plating of Invention Examples 1 to 3 shown in Table 2 and the single layer Comparative Example 4 shown in Table 3, A laser build-up layer of Ni—Cr-based material (80Ni20Cr) was formed to 1.0 mm on the surface of which the film thickness was adjusted to 200 μm by machining. The laser build-up conditions were as follows: Ni—Cr-based material powder having an average particle size of 65 μm, powder supply rate of 7.2 g / min, nozzle scan rate of 600 mm / min, semiconductor laser wavelength of 950 to 1070 nm, and laser output of 2000 W. The build-up layer composition of each sample was analyzed by EPMA, and the results are shown in Table 5. The plating layer components dissolved in the build-up layer of each sample showed a substantially constant ratio. Moreover, the cross section which carried out the laser deposition on the Co-Ni alloy plating layer of this invention example 2 is shown in FIG. 1, FIG. In the figure, 1 is a laser build-up layer, 2 is a Co—Ni alternating stacked plating layer, and 3 is a copper alloy substrate.

  Moreover, the thermal shock test of each sample was conducted, and the test results are also shown in Table 5. In the thermal shock test, heating was performed at 800 ° C. for 20 minutes in the air atmosphere, and then water cooling was performed in one cycle, and evaluation was performed by the number of tests until a crack was confirmed on the surface with a magnifier. Compared to Comparative Example 4 where the plating layer has a single crystal structure, Invention Examples 1 to 3 in which two types of crystal structures are alternately stacked greatly increase the number of thermal shocks, and have a remarkable effect in preventing cracking due to thermal shock. Indicated.

  On the Co—Ni alloy plating layer in which the two types of crystal structures of Example 1 of the present invention of Example 1 are alternately stacked, a laser beam is applied while supplying an alloy powder of Hastelloy C276 to form a stacking layer of 3 This was repeated to form a built-up layer having a total film thickness of 1.5 mm. The laser build-up conditions are as follows. While supplying Hastelloy C276 powder having a particle size of 45 to 125 μm at a powder supply rate of 8 g / min, a semiconductor laser having a wavelength of 950 to 1070 nm was applied to the first layer at a laser output of 2000 W and a nozzle scan speed of 600 mm / min. In the second and subsequent layers, the laser output was changed to 1600 W and the nozzle scan speed was changed to 1000 mm / min. Table 6 shows the results of EPMA analysis of the composition of each overlay layer. The build-up layer shows a value closer to the original Hastelloy C276 composition (Ni59Cr15Mo16W5Fe3) as the outer layer, but it was confirmed that the second layer was closer to the original composition.

  The continuous casting mold according to the present invention has high strength and thermal shock resistance in addition to excellent heat resistance, corrosion resistance, and wear resistance as a steelmaking mold from molten steel. High accuracy maintainability can also be used for high quality molded product mold applications in high temperature and corrosive environments.

DESCRIPTION OF SYMBOLS 1 Laser build-up layer 2 Co-Ni alternating stacked plating layer 3 Copper alloy base | substrate

Claims (5)

A plating layer composed of 10 to 20% by weight of nickel, the remaining cobalt and unavoidable impurities and having a hexagonal crystal structure, and 21 to 60% by weight of nickel, the remaining cobalt and unavoidable impurities and having a face-centered cubic crystal structure A cobalt-nickel alloy material having a structure in which plating layers are alternately laminated. On the surface of the copper or copper alloy substrate, 10 to 20% by weight of nickel, the remaining cobalt and unavoidable impurities, and 21 to 60% by weight of nickel, the remaining cobalt and unavoidable impurities are alternately formed by electroplating. Each layer is formed in an alternating stacked plating layer having a thickness of 0.1 to 50 μm and a total thickness of 50 to 2000 μm, and heat-treated at 200 to 500 ° C. Continuous casting mold with layers crystallized into hexagonal crystals and face-centered cubic crystals. Two kinds of crystallized electroplating layers made of nickel and cobalt, which are different from hexagonal and face-centered cubic crystals, are stacked on the surface of the copper or copper alloy substrate in a thickness of 0.1 to 50 μm alternately. By forming a plating layer having a total film thickness of 30 to 500 μm and irradiating a laser while supplying nickel-base heat-resistant alloy powder to the surface, the layer is formed by building up one or more layers formed by melting and solidifying the powder. A continuous casting mold having a nickel-based alloy coating layer of 0.1 to 10 mm. The nickel-based heat-resistant alloy powder forming the laser build-up layer is Hastelloy C (53Ni19Mo17Cr), Inconel (80Ni13Cr), Monel (65Ni31Cu4 (Fe + Mn)), NiCoCrAlY (47.9Ni23Co20Cr8.5Al0.6Y), NiCr (80Ni20Cr), Waspaloy The continuous casting mold according to claim 3, wherein the casting mold is made of one of (58Ni19Cr14Co4.5Mo3Ti). The multilayer laser build-up layer in which the diffusion of nickel and cobalt from the plating layer is gradually reduced from the inside to the surface by repeating the laser build-up layer formation many times at least twice. 3. A method for producing a continuous casting mold according to 3 or 4.