JP4751260B2 - Continuous casting mold and manufacturing method thereof - Google Patents

Description

  The present invention relates to a continuous casting mold used for manufacturing steel materials and a manufacturing method thereof.

  The casting mold for continuous casting is required to have good heat conduction characteristics in order to efficiently remove heat from molten steel and solidify it, and a copper alloy containing a trace amount of Cr, Zr or the like is used as a base material. However, since the copper alloy itself has poor properties such as heat resistance, wear resistance, and corrosion resistance, various plating layers and sprayed coatings are formed on the inner surface of the continuous casting mold in contact with the molten steel. Until now, Ni plating, Ni alloy plating, Co plating, Co alloy plating, Cr plating, etc. have been mainly used for coating the mold surface. Among these, Cr plating is excellent in wear resistance and erosion resistance, and also has low reactivity with molten steel, so it is widely used for the purpose of prolonging mold life and preventing breakout due to adhesion of molten steel splash. Has been.

  In recent years, it has become common to use scrap as part of the raw material for molten steel for continuous casting, but since the scrap contains galvanized steel sheets, etc., zinc dissolved in molten steel Concentrates on the mold meniscus, causing a problem of damaging the mold surface. A specific form of damage of the continuous casting mold by zinc is a pitting that occurs in the meniscus portion, and the pitting is caused by the elution of the plating layer into zinc adhered and concentrated on the meniscus portion. When the depth becomes deep, when the width is changed during casting, there is a risk that the molten steel will be inserted into the gap between the short side and cause breakout.

  Further, cracks may occur in the meniscus portion of the continuous casting mold due to fluctuations in the molten metal surface or temperature changes of the mold between charges, that is, thermal cycles. When this crack grows and penetrates the plating layer applied to the mold surface and reaches the surface of the base material, zinc enters the crack and causes peeling of the plating layer and copper plate cracking, thereby accelerating the damage of the meniscus portion. Therefore, the galling of zinc in the continuous casting mold meniscus and the penetration of zinc into cracks due to thermal cycling are very serious problems from both operational and safety aspects, and have greatly limited the mold life.

  Various techniques for improving characteristics of Cr plating and applying to a mold against damage to a mold surface due to zinc, particularly damage to a meniscus portion, have been disclosed. General industrial Cr plating has high hardness and has many cracks in it, so there is a problem that peeling occurs at an early stage. For the purpose of improving the zinc resistance of continuous casting molds. Could not be used. On the other hand, for example, Patent Document 1 discloses a mold in which two or more layers of Cr electrolytic plating are provided on electrolytic Ni plating. Patent Document 2 discloses a mold in which two or more layers of Cr-based plating are formed, at least one of which has a compressive residual stress of 350 MPa or more. Patent Document 3 discloses a mold in which a Cr plating layer is formed at a temperature of 55 ° C. or higher and a Cr plating layer is further formed at a temperature of less than 55 ° C. Patent Document 4 discloses a mold having two or more layers of Cr plating having a Vickers hardness of 600 HV 0.01 or less and a crack density of 5 pieces / cm or less. Patent Document 5 discloses a mold in which the inside of a crack of Cr plating and / or the surface of a plating layer is entirely or partially coated with a metal oxide. However, no matter which method is used, when Cr plating is used, generation of cracks during use cannot be avoided, and sufficient durability cannot be obtained.

  As a technique other than Cr plating, Patent Document 6 discloses a template having a protective coating of Co or Co alloy, and Patent Document 7 describes a Co alloy containing C, Ni, Cr, W, and Ta under reduced pressure plasma. Although a mold coated by a thermal spraying method is disclosed, durability is insufficient because Co reacts with zinc. Patent Document 8 discloses a mold having a coating containing Mo and / or V at 60 at% or more on the surface of the coating. The conventional thermal spraying method cannot obtain a sufficiently dense coating, and does not provide a sufficient barrier against zinc penetration. Further, the vapor phase plating methods such as the sputtering method, the ion plating method, and the CVD method have a problem that the equipment is expensive and the running cost is high because the vacuum chamber for storing the mold is huge.

  In Patent Document 9, a film formed by cold spray is Cr, Ni, a Ni alloy, or a composite of 10 to 90% by mass of Ni or Ni alloy and the remaining high-hardness ceramic, and 0.01 A continuous casting mold is disclosed, which is made of ˜2% by volume of Cr, Ni, or an oxide of Ni alloy, and the porosity of the coating is 3% or less. There is no description about the property, and there is no provision for the elongation and adhesion strength of the film. Since the working gas pressure at the nozzle entrance is 1 to 3 MPa among the cold spray conditions, the coating described in Patent Document 9 is inferior in adhesion of the coating because the kinetic energy of the powder at the initial stage of film formation is not sufficient, There was a problem in durability when casting molten steel with a lot of scrap.

JP-A-7-284881 Japanese Patent Laid-Open No. 10-156490 Japanese Patent Laid-Open No. 1-271033 JP 2004-237315 A Japanese Patent Laid-Open No. 10-80753 JP 59-189037 A Japanese Patent Laid-Open No. 7-171661 JP-A-9-52152 JP 2004-306120 A

  The present invention provides a mold excellent in zinc resistance, which reduces the meniscus damage that becomes a problem when casting molten steel containing zinc as an impurity and extends the mold life.

As a result of investigating the characteristics required as a metal film to be applied to a necessary part of the mold surface in order to obtain a continuous casting mold made of copper or copper alloy having excellent zinc resistance, the present inventors have found the following 1) to It has been found that the item 5) may be appropriate or an appropriate value.
1) The group of the metal film is composed of group VIa elements (Cr, Mo, W) of the periodic table, group Va of the periodic table (V, Nb, Ta) and group IVa of the periodic table (Ti, Zr, Hf) 4) a metal comprising at least one element selected from the above and inevitable impurities; 2) the porosity of the film is 1.5% or less; 3) the elongation of the film is 4.0% or more. ) The adhesion strength between the film and the substrate is 35 MPa or more. 5) The thickness of the film is 0.02 to 0.2 mm.

  6) In order to obtain a metal film satisfying these conditions, it has been found that a method of forming a metal film by a cold spray method under a predetermined condition after blasting the surface of the material is suitable. .

7) The metal powder used in cold spray has a particle size of 1 μm or more and 50 μm or less, so that it can be stably supplied and sufficient powder acceleration can be achieved.
8) By having a metal underlayer composed of one or two elements of Co and Ni and unavoidable impurities between a continuous casting mold made of copper or a copper alloy and a metal film formed by a cold spray method. Reducing the risk of cracking and peeling due to thermal expansion differences during thermal cycling, and
9) After forming a metal film by cold spraying, it was found that the ductility of the film was remarkably improved by performing a heat treatment at a temperature of 200 ° C. to 500 ° C. for 1 hour to 5 hours.

The present invention has been obtained by such knowledge, and the gist thereof is as follows.
(1) copper or Ri name of copper alloy, in continuous casting mold for casting a molten steel containing zinc as impurities, in a range from at least the mold upper end of the mold inner surface to a height 300 mm, periodic table group VIa elements (Cr , Mo, W), at least one element selected from the group consisting of group Va of the periodic table (V, Nb, Ta) and group IVa of the periodic table (Ti, Zr, Hf), and a metal composed of inevitable impurities It has a film, and the film has a porosity of 1.5% or less, an elongation of 4.0% or more, an adhesion strength with a substrate of 35 MPa or more, and a thickness of 0.02 to 0.2 mm. Mold for continuous casting of steel materials.
(2) The continuous casting mold for a steel material according to (1), wherein the base layer of the coating has a metal layer made of one or two elements of Co and Ni and inevitable impurities.
(3) copper or copper alloy from Ri Na, in the manufacturing method of the continuous casting mold for casting a molten steel containing zinc as impurities, after blasting the range from at least the mold upper end of the mold inner to the height 300 mm, the periodic At least one element selected from the group consisting of Table VIa group elements (Cr, Mo, W), Periodic Table Group Va (V, Nb, Ta) and Periodic Table Group IVa (Ti, Zr, Hf); Using metal powder consisting of inevitable impurities, the working gas is helium, argon, nitrogen or a mixed gas thereof, the working gas pressure at the nozzle inlet is higher than 3 MPa, and the working gas temperature at the nozzle inlet is 200 ° C or higher and 800 ° C or lower. By performing a cold spray on the blasted surface under the conditions, the porosity is 1.5% or less, the elongation is 4.0% or more, and the adhesion strength with the substrate is 35M a or more and a manufacturing method of the continuous casting mold, wherein the thickness to form a metal film is 0.02 to 0.2 mm.
(4) The method for producing a continuous casting mold as described in (3) above, wherein a particle size of the metal powder used in the cold spray is 1 μm or more and 50 μm or less.
(5) In the above (3) or (4), a metal underlayer comprising one or two elements of Co and Ni and inevitable impurities is provided on the entire inner surface of the mold before the blast treatment. The manufacturing method of the casting mold for description.
(6) After forming a metal film by the cold spray, heat treatment is performed at a temperature of 200 ° C. or more and 500 ° C. or less for 1 hour or more and 5 hours or less, any of the above (3) to (5) A process for producing a casting mold for continuous casting as described in 1. above.

  According to the present invention, it is possible to prevent damage caused by erosion of a copper plate by zinc, which is a problem when manufacturing molten steel containing zinc as an impurity, and it is possible to extend the life of the mold, contributing to the industry. Is extremely large.

  It is necessary to provide the zinc-resistant metal coating at a site corresponding to the height of the meniscus of the continuous casting mold, where the mold damage due to zinc is a problem. The meniscus height is usually set at a position of 80 to 150 mm from the upper end of the mold, but it may fluctuate up and down due to disturbances such as fluctuations in the molten metal surface. Therefore, it is necessary to provide the zinc-resistant metal film in a range from at least the upper end of the mold to a height of 300 mm on the inner surface of the mold.

  In order to search for materials that are durable to zinc, the inventors investigated the reaction of various metal materials with zinc. The materials used were various metal plates having a purity of 99.9% or more shown in Table 1, and plate-like test pieces processed into dimensions of 15 mm in length, 15 mm in width, and 5 mm in height were used. A zinc plate having a purity of 99.9% and having a length of 10 mm, a width of 10 mm, and a height of 2 mm was placed on the surface of these plate-like test pieces. The test piece was placed in an electric furnace capable of adjusting the atmosphere and replaced with an argon atmosphere. After heating to 450 ° C. and heat treatment for 5 hours, the sample was gradually cooled to room temperature. After that, the test piece is cut in the center in the width direction in the thickness direction, embedded and polished to observe the cross-section, observation of the presence or absence of reaction layer formation at the interface between the test piece material and zinc, and measurement of the depth of pitting. went. In the measurement of the digging depth by cross-sectional observation, using the line connecting both ends of the test piece on which the zinc plate was not placed as a reference line, the interface between the zinc layer and the test piece in the center where the zinc plate was placed, and the reference The maximum distance between the lines was defined as the depth. In the case of a metal or alloy having durability against zinc, as shown in the schematic diagrams of the cross sections after the test shown in FIGS. 1A and 1B, the mounted zinc plate is only melted and solidified, respectively. The surface of the test piece is slightly damaged. On the other hand, in the case of a metal or alloy having no durability against zinc, as shown in the schematic diagram of the cross section after the test shown in FIG. 1 (c), the erosion caused by large erosion by molten zinc and the reaction between zinc and the metal A layer is seen.

  The results of evaluating the durability against zinc are shown in Table 1. Cases 1-1 to 1-3 are Cr, Mo, W which are elements of group VIa of the periodic table, Cases 1-4 to 1-6 are V, Nb, Ta, which are elements of group Va of the periodic table, case 1 -7 to 1-9 were Ti, Zr, and Hf which are groups IVa of the periodic table, and there was little or no reaction with zinc, and the depth of penetration was small. Case 1-10 and Case 1-11 are examples of alloys, respectively, TZM (Mo-0.5% Ti-0.07% Zr) which is a VIa group-IVa group alloy and Molly B60 (IVa group alloy) Mo70% -W30%), there was almost no reaction with zinc, and the depth of penetration was small. On the other hand, Cases 1-12 to 1-15 were metals other than those described above, and the metal plate and zinc reacted to form a reaction layer at the interface, and the depth of punching was also large. From these results, it was confirmed that the metals having durability against zinc are periodic group VIa group elements, periodic table Va group elements, periodic table group IVa elements and alloys thereof. Here, about the alloy powder used by cold spray, periodic table VI group element (Cr, Mo, W), periodic table Va group (V, Nb, Ta) and periodic table group IVa (Ti, Zr, Hf) If the metal contains at least one element selected from the group consisting of unavoidable impurities, any combination of the above groups and any composition as long as the alloy powder can be produced It doesn't matter.

  The porosity of the zinc-resistant metal film needs to be 1.5% or less. This is because if the porosity is larger than 1.5%, there is a risk that so-called through-holes are formed in which the pores are connected from the surface to the base material, and zinc penetrates between the metal film and the base material through the pores. However, there is a risk of peeling off the metal film. On the other hand, if the porosity is 1.5% or less, through-holes are unlikely to occur, so that zinc does not enter between the metal film and the substrate, and the metal film does not peel off. The porosity was determined by cutting a metal film formed by a cold spray method in the thickness direction, and performing cross-section observation test specimens embedded and polished using a scanning electron microscope at a magnification of 1000 at any of 10 locations in the metal film. For example, an instant film having a size of 10.2 mm × 13.1 mm is taken, and the area ratio of the pore portion is obtained from each photograph, and these are averaged.

  The elongation of the zinc-resistant metal film should be 4.0% or more. The mold, particularly the meniscus portion, is subjected to a large thermal cycle due to the fluctuation of the molten metal surface and the temperature change of the mold between charges. When cracks are generated by this thermal cycle, film peeling occurs due to zinc entering from the cracks. Therefore, it is necessary to prevent cracks from occurring during use of the mold. In general, there is a correlation between the probability of cracking due to thermal cycling and the elongation of the material, and cracks are easily generated when the elongation is less than 4%. The elongation of the metal film by cold spray can be measured as follows. That is, a tensile test piece (based on JIS Z 2201-1980, No. 6 test piece) having a thickness of 5 mm, a gauge distance of 70 mm, and a parallel part length of 80 mm was Cr: 1.2 mass%, Zr: 0.2 mass% , Al; containing 0.3% by mass, the balance being made of a copper alloy consisting of copper and unavoidable impurities, and applying a metal film by cold spraying on one side of the parallel part of the tensile test piece. It can be obtained by attaching to a general-purpose tensile testing machine, performing a tensile test, and measuring the elongation until the first crack occurs in the metal film.

  The adhesion strength between the metal film and the substrate by cold spray needs to be 35 MPa or more. This is because, in the range including the meniscus height of the mold, a thermal cycle occurs between molten metal surface fluctuations and charges, and therefore, if the adhesion strength is less than 35 MPa, the risk of peeling increases. The adhesion strength may be measured as follows. That is, with the same material as the mold, one of the bottom surfaces of a cylindrical test piece having a diameter of 25 mmφ and a height of 75 mm is roughened by blasting using an alumina grid, and the blasting surface is subjected to a cold spray method. A metal film having a thickness of 0.2 mm is formed. Create a tensile specimen bonded with an epoxy-based adhesive so that the coating surface of the test piece with the metal film and the bottom surface of another test piece without the coating are facing each other. Attached to a testing machine, a tensile test is performed parallel to the axial direction, and the load at which the specimen breaks is measured. Since there is a variation in tensile strength, at least five or more tensile tests may be performed, and the average may be used as the adhesion strength.

  The thickness of the zinc-resistant metal film needs to be 0.02 mm or more. This is because the film formation process by the cold spray method is a method in which the powder is deposited by colliding and deforming the substrate, and if the thickness is less than 0.02 mm, the deposited powder is less overlapped and the density is inferior. There is sex. A more preferable lower limit of the thickness for securing the denseness of the metal film and not hindering heat removal from the molten steel is 0.05 mm. On the other hand, the upper limit of the thickness needs to be 0.2 mm or less because when the coating applied to the meniscus portion becomes too thick, the heat removal from the molten steel decreases and the solidification of the molten metal is delayed.

  We focused on the cold spray method as a method for imparting a metal film having durability to these zincs to the mold surface. The cold spray method is disclosed in “Technical spray technology” vol. 21-No. 3, p29-p38 (Shinshu University Kazuhiko Tsuji), as described in “Cold Spray Technology”, the temperature of the powder does not melt, typically in a supersonic gas heated from 200 ° C. to 600 ° C. The coating is formed by accelerating and heating the powder in a supersonic gas and depositing the powder on the substrate mainly by collision and high-speed deformation due to the kinetic energy of the powder. Similarly, conventional thermal spraying methods such as gas spraying, plasma spraying, and high-speed flame spraying, which are film formation methods using powder as a raw material, heat and melt the powder in a high-temperature medium, In contrast to forming a film on the surface, the cold spray method forms a film on a completely different principle and forms a film on the workpiece without melting the powder. The powder is oxidized and denatured. Since the opportunity is reduced, it has a feature that a clean and dense film can be formed.

  Among the conventional thermal spraying methods, when a low-pressure plasma spraying method is used, a clean and dense film can be formed. However, in order to form a high-quality film, it is necessary to heat the substrate to a temperature of 600 ° C. or higher. Therefore, the deterioration of the base material is a problem, and further, since a vacuum chamber is required, there is a problem that the equipment cost and the running cost are high. In addition, in vapor phase plating methods such as sputtering, ion plating, and CVD, a clean and dense metal film can be formed. However, since the film formation rate is as small as several micrometers per hour, it is several tens of micrometers or more. As a method for forming this film, there is a problem that the equipment cost and the running cost are high because it is not practical and further requires a vacuum chamber.

  Next, cold spray conditions for producing the aforementioned zinc-resistant metal film will be described.

  First, since the adhesion mechanism of the metal film by the cold spray method is mainly an anchor ring to the substrate, the region where the metal film is formed needs to be roughened by blasting.

  As a gas used in the cold spray method, it is necessary to use a gas not containing oxygen in order to maintain the cleanliness of the raw material powder, and argon, helium, nitrogen, or a mixed gas thereof is preferable.

  The temperature of the gas used is preferably 200 ° C. or higher and 800 ° C. or lower. This is because if the gas temperature is less than 200 ° C., the heating of the powder is insufficient, and the denseness of the film and the adhesion efficiency of the powder may decrease. On the other hand, the reason why the temperature is set to 800 ° C. or lower is that, if the gas temperature is high, it is effective for heating the powder, but the equipment for heating the gas becomes large and not economical. Moreover, it is 400 to 600 degreeC more preferably.

  The gas pressure at the nozzle entrance of the working gas needs to be higher than 3 MPa in order to ensure 35 MPa or more as the adhesion strength of the film. This is because when the gas pressure is 3 MPa or less, the pressure in the cold spray nozzle is small, a sufficient gas velocity cannot be obtained, and the acceleration of the powder becomes insufficient. This is because the adhesion efficiency decreases. On the other hand, the upper limit of the gas pressure is not particularly limited. However, if the pressure is too large, the pressure resistance of the equipment, including the piping, must be increased, and the equipment becomes large. More preferably, it is higher than 3 MPa and 6 MPa or lower.

  The particle size of the metal powder used in the present invention is preferably 1 μm or more and 50 μm or less. This is the lower limit for powder powder having a particle size of less than 1 μm that is prone to agglomerate, making it difficult to supply a stable powder. On the other hand, a powder spray of 50 μm or less collides without melting the powder. When the particle size is larger than 50 μm, the acceleration of the powder is insufficient, and not only the adhesion efficiency of the powder is lowered but also stable film formation becomes difficult. More preferably, it is 10 μm to 30 μm. The metal powder to be used can be prepared by atomizing method or ingot pulverization method, etc., and classified so as to fall within the above particle size range, and primary particles having a particle size of 0.01 μm to 1 μm can be used. It is also possible to use a granulated powder produced by agglomerating particles having an appropriate size, firing the particles, and classifying the particles so as to fall within the above-mentioned particle size range.

  Since the metal film formed by the cold spray method has low hardness and ductility, it can be sufficiently used as it is.

On the surface of the mold of the present invention, it is preferable to form a metal underlayer comprising one or two elements of Co and Ni and inevitable impurities before forming a metal film by the cold spray method. This is because the thermal expansion coefficient of copper and copper alloys is about 17 × 10 ⁻⁶ / ° C., whereas the thermal expansion coefficient of zinc-resistant metal is as small as 5 to 9 × 10 ⁻⁶ / ° C. Thermal expansion during thermal cycling by interposing a metal underlayer having an intermediate thermal expansion coefficient (12 to 14 × 10 ⁻⁶ / ° C.) made of one or two elements of Co and Ni and inevitable impurities It can reduce the risk of cracking and peeling due to the difference, and also wear resistance and corrosion resistance at the part where the zinc-resistant metal film is not formed, that is, the middle part and the lower part in the mold height direction. It is because it can be provided. Here, the ratio of Co and Ni in the alloy composed of Co and Ni and inevitable impurities may be any ratio.

  The thickness of the metal underlayer formed of one or two elements of Co and Ni and unavoidable impurities in the portion forming the zinc-resistant metal film by the cold spray method is preferably 0.05 mm or more and 0.2 mm or less. Since the adhesion mechanism of the metal film by the cold spray method is mainly anchoring to the substrate, it is necessary to roughen the surface layer of the base layer by blasting also in the region where the metal film is formed. The reason why the thickness of the base layer of the metal composed of one or two elements of Co and Ni and inevitable impurities is set to 0.05 mm or more is that when the blast treatment is performed, a portion where the thickness of the base layer becomes thin appears. This is because at least 0.05 mm is necessary for the undercoat to remain even after blasting. In addition, the area where the zinc-resistant metal film is formed by cold spray is a range including meniscus, and since it is a part where it is desired to increase heat removal from the molten metal, providing a thick underlayer in this part It is not preferable for solidification of the slab. Therefore, the upper limit of the underlayer thickness is preferably 0.2 mm or less. The blasting process may be the same as the equipment and blasting conditions used in the normal thermal spraying method.

  Protection of copper or copper alloy inferior in wear resistance and corrosion resistance on the inner surface of the mold where the zinc-resistant metal film by the cold spray method is not formed, that is, in the middle and lower ends in the mold height direction Therefore, it is preferable to form a metal film composed of one or two elements of Co and Ni and unavoidable impurities having a thickness of 0.5 mm or more, and the film thickness gradually increases from the middle part of the mold to the lower end part. An increasing taper structure is more preferred. There are no particular limitations on the method for forming the metal underlayer comprising one or two elements of Co and Ni and unavoidable impurities, and a normal wet plating method using a sulfuric acid bath, chloride bath, sulfamic acid bath or the like is used. Alternatively, it may be formed using a cold spray method. However, even when the underlayer is formed by the cold spray method, it is desirable to perform roughening by blasting before that.

  Since the metal film formed by the cold spray method has low hardness and ductility, it can be used as it is, but it can be used in any temperature range of 200 ° C. to 500 ° C. for 1 hour to 5 hours. When the heat treatment is performed, the ductility of the film is remarkably improved, which is preferable. If the heat treatment temperature is less than 200 ° C., it does not change from the as-formed state, and therefore there is no meaning of heat treatment. On the other hand, if the temperature is higher than 500 ° C., the copper alloy of the mold body is altered. Moreover, if the heat treatment time is less than 1 hour, the effect of the heat treatment cannot be remarkably obtained, and even if the heat treatment is performed for longer than 5 hours, the heat treatment effect is saturated.

  The damage of the mold meniscus portion was evaluated by a continuous casting machine that casts 8 tons of molten steel per charge. The dimension of the mold made of copper alloy containing Cr: 1.2% by mass, Zr: 0.2% by mass, Al: 0.3% by mass, and the balance of copper and inevitable impurities, has a long side width of 400 mm. The short side has a width of 100 mm and a height of 900 mm. In the molten steel used here, zinc was added in a larger amount than when it was mixed from scrap put into normal molten iron to make Zn: 0.05% by mass.

As an example of the present invention, a Co-10% Ni plating with a thickness of 0.1 mm is provided on the entire inner surface of the long side and the short side, and further, the entire surface from the upper end to the 300 mm position (the meniscus position is 80 mm from the upper end). Next, after performing a blasting process using an alumina grid, molds on which various metal films as shown in Case 2-1 to Case 2-14 in Table 2 were formed by a cold spray method. Here, for Case 2-12, a metal film was formed as it was without providing Co-10% Ni plating in the range from the upper end of the copper alloy to the 300 mm position. The cold spray apparatus uses an apparatus similar to that described in the above technical document, working gas: helium, gas pressure at the nozzle inlet: 3.5 MPa or 6 MPa, gas temperature: 600 ° C. or 400 ° C., helium gas flow rate: Under the condition of 1 m ³ / min, powder particle size: 10 μm to 44 μm of metal powder is supplied into the nozzle at a supply rate of 4 kg / h, and the nozzle is kept at a constant distance of 20 mm between the nozzle and the copper plate. By traversing, a mold was prepared in which various metal films having a thickness of 0.05 mm were provided on the entire surface from the upper end of the long side and the short side to the position of 300 mm. The metal powder used was a pure metal except for an alloy film, and a metal powder having a purity of 99.0% or more was used. However, Zr and Hf contain about 2% Hf and about 3% Zr, respectively. For Case 2-14, a Cr film was formed by cold spraying and then heat treatment was performed at 400 ° C. for 2 hours.

  As a comparative example, as shown in Case 2-15 and Case 2-16 in Table 2, a mold was produced in which a Ni and Co film was formed under the same conditions as those shown in the above-mentioned Examples of the present invention. As another comparative example, as shown in cases 2-17 to 2-19 in Table 2, a mold on which a Cr film with different cold spray conditions was formed was produced. Case 2-17 has the same conditions as those shown in the above-described example of the present invention except that the gas pressure at the nozzle entrance is 3 MPa. Case 2-18 has the same gas temperature of 150 ° C. The conditions are the same as those shown in the above examples of the present invention. Case 2-19 is a condition in which the gas pressure at the nozzle entrance is 3 MPa and the gas temperature is 150 ° C.

  As yet another comparative example, a mold having a film formed by a conventional wet plating method was produced. Co-10% Ni plating with a thickness of 0.1 mm was provided on the entire inner surface of the long side and the short side, and an industrial Cr plating with a thickness of 0.05 mm was further provided on the entire surface from the upper end to the 300 mm position. Mold (Case 2-20), Mold (case 2-21) provided with 0.1 mm thick Co-10% Ni plating on the entire inner surface of the long side and the short side, and the entire inner surface of the long side and the short side And a mold (case 2-22) provided with Ni plating having a thickness of 0.1 mm.

  The porosity of the metal film shown in Table 2 is 50 mm square, 10 mm thick Cr; 1.2 mass%, Zr: 0.2 mass%, Al: 0.3 mass%, with the balance being copper and A test piece in which a Co-10% Ni plating having a thickness of 0.1 mm is provided on a copper alloy substrate made of inevitable impurities, and a sample in which a metal film is formed under the same conditions as those for forming on a mold is prepared. And measured. This sample was cut at the center of the width, embedded in resin, and the cut surface was polished to produce a cross-section observation specimen, and a scanning electron microscope was used to photograph 10 views of the cross section of the metal film at a magnification of 1000. From this, the porosity of the metal film was determined. The wet plating test piece of the comparative example was also measured by the same method.

  The elongation of the metal film is as follows: a tensile test piece (based on JIS Z 2201-1980, No. 6 test piece) having a thickness of 5 mm, a gauge distance of 70 mm, and a parallel part length of 80 mm is Cr; 1.2% by mass, Zr; 0 .2% by mass, Al; 0.3% by mass, and the balance is made of a copper alloy consisting of copper and inevitable impurities. The metal is formed under the same conditions as those for forming a mold on one side of the tensile test piece parallel part. A film was applied. The tensile test piece to which the metal film was applied was attached to a general-purpose tensile test apparatus, a tensile test was performed at a tensile speed of 0.1 mm / s, and the elongation until the first crack was generated in the metal film was measured. The wet plating test piece of the comparative example was also measured by the same method.

  Further, the adhesion strength was measured as follows. That is, a copper alloy cylindrical shape containing 25% in diameter and 75 mm in height of Cr; 1.2% by mass, Zr; 0.2% by mass, Al; 0.3% by mass, with the balance being copper and inevitable impurities. After providing Co-10% Ni plating with a thickness of 0.1 mm on one bottom surface of the test piece, the plated surface was roughened by blasting using an alumina grid, and the blasted surface was cold-coated. A metal film having a thickness of 0.2 mm was formed by a spray method. Five tensile test specimens bonded with an epoxy adhesive were prepared so that the coating surface of the test piece on which the metal film was formed and the bottom surface of another copper alloy cylindrical test piece on which no coating was formed. Then, this was attached to a general-purpose tensile testing machine, a tensile test was performed in parallel with the axial direction, the load at which each specimen was broken was measured, and this was averaged to determine the adhesion strength. In this measurement method, the adhesion strength of 90 MPa or more, which is the adhesion strength of the epoxy adhesive, cannot be measured. The wet plating test piece of the comparative example was also measured by the same method. In the case of the wet plating test piece, since the adhesion strength was 90 MPa or more which is the adhesion strength of the epoxy adhesive, the adhesion strength of the plating film could not be measured.

  Using the molds shown in Table 2, each of the above casting machines was subjected to a casting test with 20 charges, and then the mold was disassembled to investigate the damage state of the meniscus portion. The survey items are the presence or absence of cracks at the meniscus portion and the measurement of the depth of penetration. First, the presence or absence of cracks was observed with a microscope having a magnification of 100 after the surface of the disassembled mold was washed with high-pressure water to remove deposits on the mold surface. The punch depth was determined by placing a stretch gauge parallel to the casting direction of the mold and measuring the distance between the reference surface of the stretch gauge and the mold surface with a micro depth gauge.

  As a result, in the molds according to the present invention, that is, cases 2-1 to 2-14, the porosity of the metal film is 1.5% or less, the elongation is 4.0% or more, and the adhesion strength is 35 MPa or more. Even after the charge was cast, the metal film did not show any damage such as cracking or peeling. Case 2-13 is an example in which heat treatment was performed after film formation by cold spray, and the elongation of the film was large. Even in this example, even after casting of 20 charges, damage such as cracks and peeling was observed on the metal film. There was no excuse. In the mold of the present invention, as shown in FIG. 2 (a), it can be seen that the metal film provided in the range including the meniscus functions as a barrier against zinc contained in the molten steel. On the other hand, in case 2-15 and case 2-16 which are comparative examples, the porosity is 1.5% or less, the elongation is 4.0% or more, the adhesion strength is 35 MPa or more, and 20 charges Although no cracks or delamination were observed after casting, as shown in FIG. 2 (b), pitting was seen near the meniscus, and the depths were 28 μm and 15 μm, respectively. In the mold of case 2-17 as a comparative example, the porosity was 1.2% and the elongation was 4.1%, but the adhesion strength was 30 MPa, and after casting 20 charges, the entire surface of the Cr film was Peeling occurred. In the molds of case 2-18 and case 2-19, the porosity is 1.9% and 2.5%, the elongation is 2.4% and 1.8%, and the adhesion strength is 25 MPa and 18 MPa, respectively. After casting 20 charges, the entire surface of the Cr film peeled off. In these molds, as shown in FIG. 2 (c), the metal film is peeled off by zinc that has entered from pores or cracks generated during use. In the mold of case 2-20, which is a comparative example of the film by the wet plating method, macro cracking was hardly seen, but many cracks and partial peeling were observed in the Cr plating, and the peeling part was localized. Naegure was seen. In the mold of case 2-21, Co-10% Ni plating was found to have a 10 μm punch and a small number of cracks. Similarly, in the mold of case 2-22, no crack was observed in the Ni plating, but a 30 μm punch was observed.

  The present invention can be applied to a mold for continuous casting of a steel material containing zinc as an impurity.

It is a schematic diagram which shows the result of having test | inspected the durability with respect to zinc of a metal or an alloy, (a) and (b) are examples of a zinc-resistant metal or an alloy, (c) is a metal without zinc resistance Or an example of an alloy. It is a schematic diagram which shows the damage condition by the zinc in the mold meniscus part in use, (a) is a schematic diagram of the meniscus part of the mold which provided the metal film of this invention, (b) is zinc resistance of a comparative example. Schematic diagram of the meniscus part of the mold to which a metal film without a coating is applied, (c) is a comparative example, which has a zinc film resistance but a metal film with porosity, elongation or adhesion strength deviating from the scope of the present invention. It is a schematic diagram of the meniscus part of a casting_mold | template.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Test piece of metal or alloy 2 ... Zinc plate 3 ... Reaction layer 4 of metal or alloy and zinc ... Copper plate 5 of mold ... Underlayer 6 of Co-Ni alloy -Metal coating 7 ... Molten steel 8 ... Zinc adhering to the mold meniscus

Claims (6)

Ri name of copper or a copper alloy, in continuous casting mold for casting a molten steel containing zinc as impurities, in a range from at least the mold upper end of the mold inner surface to a height 300 mm, periodic table group VIa elements (Cr, Mo, W), at least one element selected from the group consisting of group Va of the periodic table (V, Nb, Ta) and group IVa of the periodic table (Ti, Zr, Hf), and a metal film made of inevitable impurities. The steel material is characterized in that the film has a porosity of 1.5% or less, an elongation of 4.0% or more, an adhesion strength of 35 MPa or more, and a thickness of 0.02 to 0.2 mm. Mold for continuous casting.   The mold for continuous casting of a steel material according to claim 1, wherein the base layer of the coating has a metal layer made of one or two elements of Co and Ni and inevitable impurities. Ri Na of copper or a copper alloy, in the manufacturing method of the continuous casting mold for casting a molten steel containing zinc as impurities, after blasting the range from at least the mold upper end of the mold inner to the height 300 mm, periodic table Group VIa From at least one element selected from the group consisting of elements (Cr, Mo, W), periodic table group Va (V, Nb, Ta) and periodic table group IVa (Ti, Zr, Hf) and inevitable impurities The working gas is helium, argon, nitrogen, or a mixed gas thereof, the working gas pressure at the nozzle inlet is higher than 3 MPa, and the working gas temperature at the nozzle inlet is 200 ° C. or higher and 800 ° C. or lower. By performing cold spray on the blasted surface, the porosity is 1.5% or less, the elongation is 4.0% or more, and the adhesion strength with the substrate is 35 MPa or more. And forming a metal film having a thickness of 0.02 to 0.2 mm.   The method for producing a continuous casting mold according to claim 3, wherein a particle size of the metal powder used in the cold spray is 1 µm or more and 50 µm or less.   5. The continuous casting mold according to claim 3, wherein a metal underlayer comprising one or two elements of Co and Ni and inevitable impurities is provided inside the mold before the blasting process. Production method.   6. The continuous casting according to claim 3, wherein after the metal film is formed by the cold spray, a heat treatment is performed at a temperature of 200 ° C. to 500 ° C. for 1 hour to 5 hours. Mold manufacturing method.

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