CN1285431C - Mold copper plate for continuous casting and its production method - Google Patents

Abstract

To provide a mold copper sheet for continuous casting having a high adhesion to the mold copper sheet base even when it is actually used for continuous casting and comprising a surface coating layer excellent in wear resistance. A metal layer of one or more kinds of metals selected from Ti, Cr, Ni, B, Si, and Al is formed as the innermost layer on the surface of a mold copper sheet base. Layers of a nitride or carbide of the metals of the metal layer or of a carbonitride and layers of the metals are alternated on the metal layer. A nitride, carbide, or carbonitride layer is formed as the outermost layer. The layers are preferably formed by PVD. At least the metal layer, the innermost layer, is desirably formed by using a bias voltage of the arc cut.

Description

Mold copper plate for continuous casting and manufacturing method thereof

technical field

The present invention relates to structural parts suitable for molds used in the continuous casting of molten metal, especially molten steel, in particular copper plates suitable for use as mold copper plates for casting molten metal. Furthermore, it relates to a technology that is advantageous for improving the durability of the mold copper plate or a technology that enables forced cooling.

Moreover, this invention also relates to the manufacturing method of the said mold copper plate for continuous casting. In particular, it relates to the manufacturing technology of effectively improving the adhesion of the wear-resistant coating layer covered on the surface of the crystallizer copper plate, and further improving the durability of the crystallizer copper plate.

Background technique

In the continuous casting of molten metal, especially molten steel, efforts have been made in recent years to increase productivity by increasing the casting speed. At the same time, it is also required to more efficiently produce multi-type and multi-size billets.

Continuous casting of molten metal generally uses a water-cooled mold that is open on the upstream and downstream sides of the casting direction. That is, a casting method is adopted in which molten metal is injected into the mold, and the molten metal is solidified due to heat dissipation from the molten metal to the mold, and at the same time, the casting slab to be cast is pulled out in the downstream direction. In this case the mold is fixed or vibrates repeatedly in the casting direction, in each case friction occurs between the strand and the mold. Since the surfaces of the mold in contact with the strand are constantly exposed to high temperatures, especially its surfaces are subjected to high thermal loads.

Of course, in order to lubricate the mold/slab and keep the molten metal surface warm and prevent oxidation, mold powder with oxide as the main component is used. However, especially in the case of high-speed casting, the mold is subjected to significantly increased friction due to the increased relative speed of the strand and the mold. Moreover, due to the increase in speed, the temperature of the slab in the mold increases, and the heat load on the mold increases significantly. As a result, cracks tend to form on the surface of the crystallizer as the number of times of use increases.

In addition, in continuous casting of slabs, the width of the slab is often changed during casting in order to perform casting efficiently. This situation also often produces significantly greater frictional forces between the mold and the strand than when casting in a steady state.

In addition, in the case of continuous casting of high-grade steel such as stainless steel and high-carbon steel with high thermal strength, the wear of the mold surface is remarkable because the hardness of the solidified shell is higher than that of ordinary steel.

Therefore, various researches and developments have been conducted in order to improve the durability of the conventional crystallizer.

In general, in order to improve the cooling efficiency of the casting slab, the mold for continuous casting is arranged such that a copper plate (hereinafter referred to as a mold copper plate) is used as a component on the side in contact with the casting slab. In order to prolong the service life of the copper plate and ensure the high-temperature-resistant material strength on the existing crystallizer copper plate, the precipitation-hardened copper alloy material is mainly used.

In general, alloys such as Ni-Cr, Fe-Ni, Co-Ni, etc. are coated on the surface of such mold copper plate by wet coating method, molten spraying method and the like.

However, for example, on the surface of the above-mentioned precipitation-hardened copper alloy material base material, it is coated with the above-mentioned wet coating method and melt spraying method, and used as a crystallizer copper plate (surface treatment material) for continuous use in stainless steel and high carbon steel. The life in the case of casting may be the same as or lower than that in the case of continuous casting of ordinary steel.

Therefore, in order to prolong the life of mold copper plates used for continuous casting of high-strength steel such as stainless steel and high-carbon steel, it is necessary to develop a new mold surface treatment material that has not been hitherto.

From this point of view, it is proposed to use metals (Al, 4A group elements (Ti, Zr, etc.), 5A group elements (V, Nb, Ta, etc.), 6A group elements (Cr, etc.) Mo, W, etc.), Fe) nitrides covering the surface of the crystallizer copper plate. Since such a nitride has very high hardness, it can be expected to improve the wear resistance of the mold copper plate.

Such a nitride covering layer has poor adhesion to the base material of the crystallizer copper plate. In this publication, it is recommended that Fe alloy, Ni alloy, Co alloy and other alloys be plated on the nitride-coated base layer.

In the above-mentioned Japanese Unexamined Patent Application Publication No. 9-314288, it is disclosed that the crack resistance and the wear resistance are good in laboratory tests.

However, the inventors of the present invention have found that cracks occur in the covering nitride layer during actual continuous casting in a continuous casting machine, and such a nitride layer peels off in many cases, making continuous use impossible for a long time. In addition, there is concern that a ceramic layer such as a nitride is less effective in heat extraction from a molten metal by a copper plate.

Contents of the invention

The present invention is an invention developed according to the above-mentioned actual situation. The purpose of the present invention is to provide a continuous casting crystal with good adhesion to the copper plate base material in actual use, excellent wear resistance, and a surface covering layer with good heat dissipation effect. device copper plate, while proposing an effective manufacturing method.

In addition, the purpose of the present invention is to further improve the above-mentioned technology, to provide further improved adhesion of the wear-resistant coating of the mold copper plate, to further improve the durability of the mold copper plate, etc. Effective production of mold copper plates for continuous casting method.

In order to achieve the above object, the inventor aimed at how to coat carbides and nitrides of various metals with high hardness and excellent wear resistance on the substrate of copper or copper alloy, so that they can be firmly attached, so that in the actual continuous casting environment Intensive research has been carried out to prevent peeling and cracking under long-term use.

As a result, it was newly discovered that the dry coating method was adopted, among which PVD (Physical Vapor Deposition, physical vapor deposition) method with high ionization rate and high-speed film formation, especially HCD (Hollow Cathode Discharge, hollow cathode discharge) method and arc discharge method,

(1) The metal layer composed of one or more metals selected from Ti, Cr, Ni, B, Si and Al is used as the innermost layer of the wear-resistant film on the surface of the crystallizer copper plate, which can ensure the same Strong adhesion of copper plate,

(2) As the outermost layer of the wear-resistant film, one or two or more nitride-based or carbide-based ( Including carbon-nitride system, hereinafter the same) ceramic film can not only ensure high strength, but also can ensure excellent wear resistance and heat resistance, and can also ensure heat dissipation effect,

(3) In addition, between the above-mentioned innermost layer and the outermost layer, ceramic layers composed of nitrides or carbides of one or two or more metals selected from the above-mentioned metal group and ceramic layers selected from the above-mentioned metal group are alternately laminated. The metal layer composed of one or more than two metals in the group can effectively alleviate the internal distortion of the wear-resistant composite coating, not only can further improve the adhesion with the copper plate, but also can effectively prevent the wear-resistant composite coating. Peeling and cracks occur in the composite film, especially in the ceramic film.

The present invention is based on the above knowledge.

That is, the main contents of the present invention are as follows.

1. The mold copper plate for continuous casting is characterized in that: in the mold copper plate for continuous casting of molten metal, the plate surface made of copper or copper alloy as base material is provided with metal groups Ti, Cr, Ni, B The innermost layer consists of one or two or more metals selected from Si, Al, and Al, and one or more groups of one or two or more metals selected from the above metal groups are alternately laminated on it. A nitride or carbide layer and a layer composed of one or two or more metals selected from the above metal groups, and a nitride of one or two or more metals selected from the above metal groups is provided as the outermost layer or carbide layer.

2. The mold copper plate for continuous casting according to the above 1, characterized in that a mixed layer of the innermost layer metal and the metal constituting the base material is formed at the boundary between the innermost layer and the base material.

3. The mold copper plate for continuous casting as described in the above 1 or 2 is characterized in that: the plate made of copper or copper alloy constituting the above-mentioned base material is implemented on its surface in advance to select from Ni, Cr, Fe and Co One or more than two kinds of coatings are the main components.

4. A method for manufacturing a mold copper plate for continuous casting, which is characterized in that one or both of Ti, Cr, Ni, B, Si and Al are formed by PVD on the surface of a copper or copper alloy plate constituting the base material. A metal layer composed of more than one metal is used as the innermost layer, and more than one group of metal nitride or carbide layers selected from the above metal group or two or more metal nitrides or carbide layers from the above metal group are alternately laminated on it. A metal layer composed of one or two or more metals is selected, and then the outermost layer of a nitride or carbide layer of one or two or more metals selected from the above metal group is formed.

5. The method for manufacturing the mold copper plate for continuous casting as described in the above 4 is characterized in that: the method of forming the innermost layer is a high bias voltage discharge coating method.

6. The above-mentioned 4 or 5 described method for manufacturing mold copper plate for continuous casting is characterized in that: the plate made of copper or copper alloy of the above-mentioned base material is to be coated on its surface to form Ni, Cr, Fe and Co Choose one or more boards with two or more main ingredients.

The above "nitride or carbide" also includes carbon-nitride.

7. On the surface of the copper or copper alloy plate of the base material, the innermost layer of the metal layer composed of one or more metals selected from Ti, Cr, Ni, B, Si and Al is formed by PVD method. It is alternately laminated with more than one set of metal nitride or carbide layers selected from the above-mentioned metal groups and metal layers composed of one or more metals selected from the above-mentioned metal groups, Then, in the method of manufacturing a mold copper plate for continuous casting that forms the outermost layer of one or more metal nitrides or carbide layers selected from the above-mentioned metal groups, it is characterized in that: at least in the metal layer that forms the innermost layer , the bias voltage for arc interruption is used.

8. The above-mentioned 7 described method for manufacturing mold copper plate for continuous casting is characterized in that: the plate material of copper or copper alloy of the above-mentioned base material is coated on its surface to select one of Ni, Cr, Fe and Co One or more kinds of boards as the main components.

In the above 1 to 8, each metal layer does not have to be made of the same metal, and if one or two or more of Ti, Cr, Ni, B, Si and Al are selected, different metals may be used for each layer. Likewise, the individual layers of carbides, nitrides or carbon-nitrides do not necessarily consist of the same compound.

Description of drawings

FIG. 1A is a schematic cross-sectional view of a surface-covered crystallizer copper plate of the present invention.

FIG. 1B is a schematic cross-sectional view of a conventional surface-covered crystallizer copper plate.

FIG. 2A is a graph showing the hardness comparison of the surface-covered mold copper plate of the present invention and the existing surface-covered mold copper plate.

Fig. 2B is a graph showing the adhesion of the surface-covered mold copper plate of the present invention compared with the conventional surface-covered mold copper plate.

FIG. 3A is a schematic diagram showing arc-interruption bias voltage waveforms.

FIG. 3B is a schematic diagram showing another waveform of an arc-interruption bias voltage.

Detailed ways

The present invention will be described in detail below according to the figures.

1A shows a schematic cross-sectional view of a crystallizer surface treatment material that alternately covers 6 groups (a total of 12 layers) of metal layers of Ti metal films and ceramic layers of TiN films on the surface of the copper plate base material of the crystallizer according to the present invention. On the other hand, FIG. 1B shows a schematic cross-sectional view of a conventional mold surface treatment material covered with two layers of Ni plating and then Cr plating on the surface of the mold copper plate.

As can be seen from the situation shown in FIG. 1A, the core of the mold surface treatment material (mold copper plate) of the present invention is as follows.

1) In order to closely adhere to the copper plate of the crystallizer, a metal layer composed of one or more metals selected from the metal group Ti, Cr, Ni, B, Si and Al and a metal layer selected from the above metal group should be used. One or more than two kinds of ceramic films of nitrides, carbides or carbon-nitrides of two or more metals constitute the wear-resistant coating layer.

2) Coating the above-mentioned metal layer as the innermost layer of the film-resistant film on the surface of the copper plate base material of the crystallizer to ensure firm adhesion. That is to make sure that there is no peeling between the surface of the base material and the metal coating composed of one or two or more metals selected from the above metal groups.

3) The outermost layer of the coating film on the base material of the crystallizer copper plate should use a ceramic film with high hardness (metal nitride, carbide or carbon-nitrogen composed of one or more metals selected from the above metal group) compound composed of ceramic film) to ensure improved strength, wear resistance, heat resistance, and heat dissipation.

4) In order to alleviate the internal distortion of the wear-resistant covering mill on the copper plate base material of the crystallizer, a metal layer composed of one or more than two metals selected from the above metal groups and a metal layer selected from the above metal groups Ceramic layers composed of metal nitrides, carbides or carbon-nitrides composed of one or more than two metals are used as a group, and they are coated with multiple groups to prevent the peeling off of the wear-resistant film and prevent wear resistance. Cracks occur in the film.

Among them, at least when forming the innermost metal layer, the adhesion of the above-mentioned 2) is further improved by using an arc cutoff bias voltage as a bias voltage.

In order to make the above-mentioned Ti and Cr, Ni, B, Si, and Al excellent in adhesion with various metals, especially copper or copper alloys, etc., in the present invention, it is necessary to use it as a base material for the copper plate of the crystallizer. The middle layer between the innermost layer and the ceramic membrane.

On the other hand, ceramic films composed of nitrides, carbides, or carbon-nitrides of these metals are used as the outermost layer that requires high strength, wear resistance, and heat resistance because of their extremely high hardness.

And between the innermost layer of the above-mentioned metal and the outermost layer of ceramics, with the above-mentioned ceramic layer and metal layer as a group, by at least one group of coating, the adhesion between the films can be further improved, and at the same time Cracks can be prevented from being generated in the wear-resistant coating.

The reason why the above-mentioned effect is obtained is not clear, but the inventor's opinion is as follows.

That is to say, the ceramic film generally has high hardness, and its thermal expansion coefficient is smaller than that of the metal coating. Therefore, when a thick ceramic film is applied to ensure high strength, wear resistance, and heat resistance, distortion tends to accumulate at the interface with the base material, and as a result, it tends to peel off. It is therefore difficult to secure adhesion performance.

On the contrary, it is considered that in the case of alternate lamination of several metal layers and ceramic layers, the distortion between each metal layer-ceramic layer is effectively released (the distortion of the ceramic layer is transferred to the metal layer), and as a result, the adhesion is significantly improved . It is considered that the metal layer-ceramic layer is alternately laminated in atomic units, which is most suitable for the release of distortion.

Surprisingly, it was found that even if the ceramic layer of the present invention is used as the covering layer, not only the heat dissipation performance does not deteriorate, but it can be significantly improved depending on the situation. This is considered to be due to the fact that when the outermost layer uses the selected component ceramics of the present invention, the wettability of the ceramics and the molten crystallizer co-solvent as a lubricant is significantly improved, and as a result, the thermal conductivity of the coating due to the ceramic layer is filled. of the reduction, and get redundant thermal performance.

In order to obtain the above-mentioned heat dissipation effect, it is desirable that the arithmetic mean roughness Ra of the surface roughness of the outermost ceramic layer is in the range of 5 μ or less. In addition, especially when Ti-based carbide-nitride, especially TiN, is used for the ceramic layer, it has a remarkable effect, and the heat dissipation of the general mold copper plate plated with metal is increased by 10 to 40%.

In the present invention, the thickness of each metal layer including the innermost layer is preferably about 0.1 to 5.0 μm, and the thickness of each ceramic layer including the outermost layer is about 0.1 to 5.0 μm, and the total thickness, that is, the thickness of the wear-resistant coating is about 1.0 to 50 μm. .

In addition, in the present invention, at least two sets of metal layers and ceramic layers (including the innermost layer and the outermost layer) are required on the surface of the base material. It is desirable that the above-mentioned number of groups is 3 or more, more preferably 5 or more.

The film thickness, number of layers, and total thickness of each layer can be determined by taking into account the above-mentioned effect of improving adhesion, the required wear resistance of the coating, and the cost required for multilayering of the coating-increasing thickness.

In order to further improve the strength, wear resistance, and heat resistance without loss of adhesion, it is suitable to change the composition of the metal layer and the ceramic layer and the thickness of their plating layer in the thickness direction. Specifically, the coating thickness of each layer is gradually increased from the innermost layer to the outermost layer, and it is suitable to perform coating so that the coefficient of thermal expansion gradually decreases especially for the ceramic layer. Furthermore, the coefficient of thermal expansion of the ceramic layer can be controlled by the composition, surface state, and the like.

As an example, the coefficient of linear expansion depends on the type of substance, for example at 20°C:

In case of TiN 9.4×10 ^-6 /℃

Ti 8.6×10 ^-6 /°C

Cu 16.5×10 ^-6 /℃

The coefficients of linear expansion therefore change in the case of these composite substances compared to the case of pure substances, depending on the ratio of their composition. Therefore, if the relationship between the composition ratio and the linear expansion coefficient is determined in advance, the expansion coefficient can be controlled by controlling the composition ratio of the layer. Of course, it is not limited to the above methods.

Furthermore, from the viewpoint of improving adhesion, it is desirable to perform coating in a state where the surface to be coated is cleaned before coating.

The core of the production method for obtaining such a mold surface-treated material for continuous casting is as follows.

5) In order to make the crystallizer copper plate base material and the above-mentioned metal layer, the above-mentioned metal layer and the above-mentioned ceramic layer firmly bonded, and in order to avoid the change of the base material caused by the high temperature thermal influence of the surface coating treatment, at a relatively low temperature (300 Below ℃) PVD should be used for coating.

6) It is especially hoped that HCD and arc discharge method with excellent ionization rate will be used in PVD to firmly combine the base material of the mold copper plate with the above-mentioned metal layer, the above-mentioned metal layer and the above-mentioned ceramic layer, and avoid the base material caused by the thermal influence of high temperature. The change.

7) It is particularly desirable to further improve the adhesion of the plating layer to the base material by using an arc-interruption bias voltage as a bias voltage at least when the innermost metal layer is coated.

8) It is hoped that a high bias voltage will be added when plating the innermost metal layer, and a mixed layer will be formed at the boundary between the base material of the crystallizer copper plate and the above metal layer.

In the coating treatment of the present invention, the PVD method is mainly used. In the PVD method, there are dry plating methods such as HCD and arc discharge, EB (Electron beam, electron beam) + RF (Radio Frequency, radio frequency), etc. In particular, it is desirable to use an HCD method or an arc discharge method that is excellent in ionization rate and can form a film quickly. At this time, the two methods can also be combined. In addition, when coating the outermost layer, the HCD method that enables smooth and dense ceramic coating is particularly suitable.

It goes without saying that the inventors have conducted studies on improving durability in the composite layer of the present invention, and as a result, have recognized that the use of an arc-cutting bias voltage as a bias voltage has a significant effect on achieving the desired Goals are very effective. Among them, the bias voltage is added to the ground so that the copper plate is negative, and then the absolute value of the potential difference between the ground and the copper plate is used as the bias voltage. The so-called high bias means that the bias voltage is large.

That is, when the above-mentioned metal layer and ceramic layer are coated, if the bias voltage of arc cut-off is used as the bias voltage, abnormal discharge caused by foreign matter can be prevented, ionized particles can be stabilized, and the two can be supplied to the substrate. The adhesion of the layer is further improved, and as a result, occurrence of cracks and peeling of the plating layer are reduced, and durability can be improved.

Here, the bias voltage for arc interruption will be described. As for the waveform of the arc interception bias voltage, there are two situations shown in Fig. 3A and Fig. 3B. In these cases, when the voltage rises, it is not a sharp (linear) rise, but through a certain degree of gentle ground (radiation) type or segmented) rise, which can effectively prevent abnormal discharge.

Arc interruption of the type shown in FIG. 3A is also known as arc breaking or arc control and is generally used in DC power supplies that function as semiconductor switching elements. On the other hand the pattern shown in Fig. 3B is also called pulse. Generally, the type shown in FIG. 3A is used for arc interruption, and the type shown in FIG. 3B is used according to some cases where the effects are different.

As described above, using the bias voltage for arc cutoff can stably supply ionized particles, which further improves adhesion and is advantageous in avoiding peeling off of the wear-resistant coating.

Therefore, from the viewpoint of preventing peeling of the entire covering layer (abrasion-resistant film), it is strongly recommended to use a bias voltage for arc interruption at least when forming the innermost metal layer.

Of course, if the arc cut-off bias voltage is used when forming all the layers, it is beneficial to improve the adhesion between the coating layers, and it goes without saying that the best results can be obtained.

On the other hand, when the above-mentioned coating is used as the bias voltage to cut off the bias voltage by using an arc, the ionized metal particles are driven into the lower layer, and a thick and fine mixed layer of these metals is formed at the interface between the upper layer and the lower layer. As a result, The two are combined more firmly, and needless to say, the purpose of improving adhesion can be achieved.

Wherein, the suitable range of the voltage added by the above-mentioned arc interruption bias voltage is 10 to 1000V.

In order to ensure strong adhesion to the base material during coating, especially for the innermost metal coating, it is desirable to use a high bias voltage coating method in which a high bias voltage is applied and the coating is performed. Among them, the particularly suitable additional voltage in this high bias voltage discharge coating method is 50 to 1000V.

If such a high bias voltage power generation coating method is used, when the innermost metal is coated, the ionized metal particles are deeply driven into the base material, and these particles are formed at the interface between the copper plate base material and the innermost metal layer The mixed layer of metals results in a stronger combination of the two, which, of course, has the advantage of being able to achieve improved adhesion.

In the mixed layer formed by such a method, it is desirable that the ratio of the innermost layer metal in the layer is about 10 to 50%.

In the present invention, since high strength, wear resistance and heat resistance can be obtained by the above-mentioned surface covering layer (abrasion-resistant film), the material of the copper plate or copper alloy plate as the base material is not particularly limited. That is, in recent years, precipitation hardening copper alloys have been used as the base material of the mold copper plate in order to increase the strength at high temperatures. In the present invention, it is not necessary to specifically ensure the strength of the base material. Therefore, for example, there is no problem in using various commercially available copper plates and copper alloy plates for continuous casting.

In addition, the plate thickness of the copper plate is designed according to the application and the size of the cast slab, and in the case of a cast slab, it is generally 30 to 60 mm.

In addition, on the surface of the copper plate as the base of the above-mentioned wear-resistant film (including the innermost layer-outermost layer of multilayer covering layer composed of a metal layer and a ceramic layer), one or more layers can be set in advance. A base covering composed of a metal or ceramic. Especially due to selecting one or more of Ti, Cr, Ni, B, Si and Al as the main component (that is, more than 50% by mass of the substrate) of the coating (so-called metal coating) and the copper plate and the above-mentioned resistance Abrasive overlays adhere well and are therefore suitable for use as a base overlay. Among them, it is desirable to select one or two or more of Ni, Cr, Fe, and Co as the main component.

These coatings are now covered on the copper plate of the crystallizer by means of wet coating and melt spraying, so they generally have a thickness of about 30 to 2000 μm. In the present invention, the effect of plating of these metal elements is not necessarily essential, and since these metal elements have good adhesion to copper plates, there is no problem even if the wear-resistant film of the present invention is formed on these metals.

Therefore, in the case of implementing the wear-resistant film of the present invention on the existing copper plate of the crystallizer, there is no need to take the trouble and cost of peeling off these metal plating layers.

The mold copper plate of the present invention may be used for the entire inside of the mold, or may be used only for important parts. For example, if the heat dissipation function is emphasized, it can be considered to be used only on the inlet side of the crystallizer (from the upper end to at least about 100mm deep into the liquid surface), and it is suitable for the materials of the present invention with good heat dissipation function (such as using Ti system, especially TiN covering layer material). On the other hand, if durability is emphasized, it can be considered that the material of the present invention is only used in the lower part of the crystallizer (from the end of the lower half to the depth of 30mm), and is suitable for the material of the present invention with high hardness (such as Si-based, etc.). Of course, if the crystallizer is formed by using the copper plate of the present invention with a TiN coating on the upper half and the copper plate of the present invention with a SiC coating on the lower half, it will be a better combination.

(Example)

Example 1

The surface of the base material (Cr: 1.0% by mass, Zr: 0.1% by mass, and the rest is Cu) composed of a mold copper plate is formed by arc discharge method with an initial bias: 400V arc cut-off bias voltage. Ti metal innermost layer (thickness: 3.0 μm). Then, TiN (thickness: 3.0μm) → Ti (thickness: 3.0μm) → TiN (thickness: 3.0μm) → Ti (thickness: 3.0μm) → TiN (thickness: 3.0μm) is laminated in the same way to form a composite with a thickness of about 18μm. film. Then use the HCD method to form a Ti (thickness: 2.0μm) → TiN (thickness: 2.0μm) film under the condition of adding an initial bias: 400V (general bias voltage, the same below), and a total of 8 layers are made. Total thickness: Copper plate with wear-resistant coating of about 22 μm (invention example 1).

Also on the same base material surface, with an additional initial bias: 250V, a Ti metal innermost layer (thickness: 3.0 μm) was formed. Then, TiN (thickness: 3.0μm) → Ti (thickness: 3.0μm) → TiN (thickness: 3.0μm) → Ti (thickness: 3.0μm) → TiN (thickness: 3.0μm) is laminated in the same way to form a composite with a thickness of about 18μm. film. Then use the HCD method to form a Ti (thickness: 2.0μm)→TiN (thickness: 2.0μm) film with an additional initial bias: 400V, a total of 8 layers, and a wear resistance with a total thickness of about 22μm A coated copper plate (invention example 2).

2A and 2B show the results of hardness (surface hardness, test load 400 g) and adhesion studies of the surface-coated mold copper plates thus obtained. Among them, the adhesion is scraped with the tip of the Rockwell hardness C diamond indenter (tip radius 0.2mm, tip angle 120°, hardness Hv8000 or more), contacting the surface of the crystallizer copper plate covered by the surface, while continuously increasing the load on this tool, In general scraping substrates, the evaluation is performed by the critical load at which streak cracks (film peeling) occur at the scratched end.

For the comparative example, Ni (thickness: 0.5 mm) was plated on the surface of the same base material as the inventive example by the existing method, and then Cr (thickness: 30 μm) was plated on it. The same research method was used to obtain the obtained surface-covered crystallizer copper plate, and the results are shown in Fig. 2A and Fig. 2B.

It can be seen from Fig. 2A and Fig. 2B that the hardness and adhesion of Invention Example 1 and Invention Example 2 are greatly improved compared with Comparative Example. In addition, Invention Example 1 using an arc interruption bias voltage was better in adhesion than Invention Example 2.

In addition, when the stainless steel slabs were continuously cast with the above-mentioned copper plates covering the crystallizer on each surface, no cracks were produced after casting 1000 batches of Invention Example 1 and Invention Example 2, and the actual operation proved to have good durability. On the contrary, with the conventional surface-coated mold copper plate represented by the comparative example (comparative example), cracks occurred in the surface coating layer after casting 300 to 600 batches.

Example 2

As shown in Table 1, the base material (No.3-14: Cr: 1.5% by mass, Zr: 0.15% by mass, and the rest is Cu) composed of copper plate of the crystallizer, the base material (No. .15, 16) and the base material (No. 17, 18) composed of copper plates melt-sprayed on the surface of Ni-Cr (No. Crystallizer copper plate.

The hardness and adhesion of the obtained surface-covered mold copper plate were investigated in the same manner as in Example 1, and the results are shown in Table 1 together.

In the column "whether to use the arc cutoff bias voltage" in Table 1, the "yes" is written to use the arc cutoff bias voltage for the whole layer. In addition, the ones written with "None" use a bias voltage other than arc interception for the entire layer (the voltage intensity is the same as "Yes").

Table 1 No. Abrasion-resistant film: metal layer, type of ceramic layer, (thickness: μm) Number of laminated layers (thickness: μm) Plating method Whether to use arc cutoff bias voltage (additional voltage V) Hardness Hv Adhesion (Mpa) 3 Ti-TiN-Ti-TiN-Ti-TiC-Ti-TiC(2.5)(2.5)(2.5)(2.5)(2.5)(2.5)(2.5)(2.5) 8(20) HCD method yes(250) 2500 150 4 none 2300 125 5 Cr-CrN-Cr-CrN-Cr-CrN-(3.0)(3.0)(2.0)(2.0)(2.5)(2.5) 6(15) HCD method yes(150) 1900 161 6 none 1800 136 7 Ni-NiN-Ni-NiN-Ni-NiC-Ni-NiC-Ni-NiC(3.5)(3.5)(3.5)(3.5)(3.0)(3.0)(2.5)(2.5)(2.5)(2.5) 10(30) HCD method yes(100) 1700 160 8 none 1600 119 9 B-BN-B-BN-B-BN(3.0)(3.0)(3.0)(3.0)(3.0)(3.0) 6(18) arc discharge method yes(200) 2500 163 10 none 2400 139 11 Si-SiNx-Si-SiNx-Si-SiC-Si-SiC-Si-SiC(2.0)(2.0)(2.0)(2.0)(3.0)(3.0)(3.0)(3.0)(2.5)(2.5) 10(25) SiNx: Magnetron sputtering method SiC: Arc discharge method yes(80) 2700 150 12 none 2600 118 13 Al-AlN-Al-AlN-Al-AlC-Al-AlC(2.5)(2.5)(2.5)(2.5)(2.5)(2.5)(2.5)(2.5) 8(20) AlN: arc discharge method AlC: magnetron sputtering method yes(100) 2400 159 14 none 2200 124 15 Ti-TiN-Ti-TiN-Ti-TiC-Ti-TiC(2.5)(2.5)(2.5)(2.5)(2.5)(2.5)(2.5)(2.5) 8(20) HCD method yes(150) 2500 170 16 none 2300 115 17 Ti-TiN-Ti-TiN-Ti-TiC-Ti-TiC(2.5)(2.5)(2.5)(2.5)(2.5)(2.5)(2.5)(2.5) 8(20) HCD method yes(100) 2500 150 18 none 2300 120

As shown in this table, it can be seen that the surface-coated mold copper plates obtained according to the present invention not only have high hardness but also can obtain excellent adhesion. In addition, better adhesion can be obtained in the case of using an arc cutoff bias voltage.

Example 3

The crystallizer copper plate (invention example 1, 2) that has the Ti-TiN system surface coating layer shown in embodiment 1, 16 kinds of surface coating mold copper plates (invention examples 3-18) shown in embodiment 2 are prepared as the invention examples. ).

In addition, as a comparative example, a mold copper plate (Comparative Example 1) having a (Ni+Cr) plating layer shown in Example 1, and a mold copper plate (Comparative Example 2) in which 10 μm of TiN was laminated by an arc method on a copper plate base material were prepared. ), a crystallizer copper plate (comparative example 3) in which 10 μm of chromium nitride was laminated by the HCD method on the base material of the copper plate (comparative example 3), a substrate of Ni-P (thickness: 30 μm) plated by an arc method on the base material of the copper plate, and A crystallized copper plate (comparative example 4) on which titanium nitride (thickness: 7 μm) was laminated on the base by the HCD method, a base material on which the copper plate was plated with Cr (thickness: 30 μm) by wet plating, and on the base A crystallizer copper plate (comparative example 5) of chromium nitride (thickness: 5 μm) laminated by the HCD method, a substrate of melt-sprayed Ni-Cr (thickness: 1 mm) is used on the copper plate base material, and Cr (thickness: 1 mm) is plated on the substrate. : 30 μm) crystallizer copper plate (comparative example 6).

These surface-covered mold copper plates are used on the short side of the mold for continuous casting with a continuous casting machine.

The cast steel types are stainless steel (SUS 430 steel, SUS 304 steel) and high carbon steel (SK 5 to SK 2) specified in the JIS steel handbook. The continuous casting machine is vertical, and the mold size is a slab continuous casting machine with thickness: 200mm, width: 750-1240mm, and length: 915mm. The casting speed of stainless steel was 0.9-1.3m/min, the casting speed of high-carbon steel was 0.8-1.2m/min, the evaluation of heat dissipation was performed at 1.0m/min, and the slab width was 1000-1100mm. The physical properties of the mold flux used are that the solidification temperature is 1100° C., the viscosity at 1300° C. is 2.0 poise, and the basicity (CaO/SiO ₂ ) is 1.5.

One batch of 150 tons of molten steel was cast in each crystallizer for a total of 500 batches. After casting 500 furnaces like this, the situation (whether or not there are cracks, peeling, wear) of the crystallizer copper plate surface film was observed.

The obtained results are shown in Table 2.

Table 2 Mold short side copper plate With or without cracks With or without stripping Whether there is wear or tear Invention Example 1 none none none Invention Example 2 none none none Invention Example 3 none none none Invention Example 4 none none none Invention Example 5 none none none Invention Example 6 none none none Invention Example 7 none none none Invention Example 8 none none none Invention Example 9 none none none Invention Example 10 none none none Invention Example 11 none none none Invention Example 12 none none none Invention Example 13 none none none Invention Example 14 none none none Invention Example 15 none none none Invention Example 16 none none none Invention Example 17 none none none Invention Example 18 none none none Comparative example 1 none none Plating wear on the lower end Comparative example 2 There are many cracks on the whole surface Extensive peeling over the entire surface Copper wear at the stripped part Comparative example 3 There are many cracks on the whole surface Extensive peeling over the entire surface Copper wear at the stripped part Comparative example 4 There are a lot of cracks near the meniscus The lower end is stripped Copper plate wear at the stripped part of the lower end Comparative Example 5 There are a lot of cracks near the meniscus The lower end is stripped Copper plate wear at the stripped part of the lower end Comparative example 6 none none Copper plate wear at the stripped part of the lower end

It can be seen from Table 2 that none of the surface covering layers of the inventive examples had cracks, peeling and abrasion.

On the contrary, in Comparative Examples 1 and 6, abrasion of the plating layer at the lower end of the short side of the crystallizer was observed. In Comparative Example 2 and Comparative Example 3, a large number of cracks and peeling were observed on the entire surface, and in Comparative Example 4 and Comparative Example 5, a large number of cracks were observed near the meniscus, and peeling was observed at the lower end.

Example 4

Evaluation of the amount of heat dissipation was performed for each of the Examples and Comparative Examples employed in Example 3. The amount of heat dissipation was calculated from the temperature difference between the inlet side and the outlet side of the cooling water of the copper plate and the amount of cooling water, and expressed as a ratio to Comparative Example 1. In addition, in order to evaluate the uniformity of cooling, the temperature at 100 mm below the meniscus and 10 mm deep from the surface at the center of the short side width was measured at intervals of 1 second, and the standard deviation within 10 minutes was obtained. The results are shown in Table 3.

table 3 Surface roughness Ra(μm) heat dissipation ratio Copper plate temperature standard deviation (°C) Invention Example 1 1.34 1.11～1.35 1.9 Invention Example 2 0.12 1.15～1.45 2.1 Invention Example 3 0.34 1.01～1.09 2.5 Invention Example 7 3.19 1.051.11 2.7 Invention Example 9 0.12 0.94～1.05 3.5 Invention Example 11 1.26 0.97～1.07 4.1 Comparative example 1 0.11 1.0 5.5 Comparative example 2 5.3 1.05～1.20 3.3 Comparative example 4 6.5 1.03～1.15 2.8 Comparative Example 6 0.33 0.95～1.05 4.6

As can be seen from Table 3, the inventive examples all exhibit good heat dissipation properties at least equivalent to those of the conventional copper sheet material (Comparative Example 1). The difference in heat dissipation due to the position of the board surface is small. In particular, the heat dissipation of Ti-based (invention examples 1, 2, 3, and 7) is improved compared with conventional materials, and the Ti-based (invention examples 1 and 2) are improved by 15% or more. In addition, among these copper plates, the standard deviation of the temperature of the copper plates is small and has excellent heat dissipation uniformity. It is generally worried that fine longitudinal cracks will occur on the surface of the slab with the increase of heat dissipation, but such cracks do not occur on the slab cast by the mold of the present invention. Therefore, by using such a mold copper plate, the cast material can be forcibly cooled and uniformly cooled, and the slab casting speed can be increased.

On the contrary, in Comparative Examples 2 and 4 in which TiN was used as the outermost layer, the roughness was outside the appropriate range, and the effect of improving heat dissipation was also small.

In each of the above-mentioned embodiments, the case where the mold copper plate of the present invention is used for the short side of the mold is mainly explained. It was confirmed that the same effect can be obtained also when it is used on the long side of the crystallizer.

Possibility of industrial use

Adopting such a surface-covered mold copper plate of the present invention can maintain excellent durability and heat dissipation even if it is actually provided for continuous casting of stainless steel and high-carbon steel with high solidification shell hardness in a hot state, especially in High-speed casting can efficiently produce high-quality slabs, and it can be said to be very effective industrially.

Claims (8)

1. a mold copper plate for continuous casting is suitable for the mold copper plate of continuous casting molten metal, characterized in that, having a base material substantially composed of a plate made of copper or a copper alloy and a covering layer provided on the surface of the base material, The covering layer is composed of the following parts: The innermost layer is composed of one or more metals selected from the metal group Ti, Cr, Ni, B, Si and Al; The middle layer, formed on the innermost layer, is alternately laminated with one or more layers composed of nitrides, carbides or carbon-nitrides of one or more metals selected from the metal group, and a layer composed of one or more metals selected from the group of metals; and The outermost layer, formed on the intermediate layer, is composed of nitrides, carbides or carbon-nitrides of one or two or more metals selected from the metal group. 2. The mold copper plate for continuous casting according to claim 1, wherein a mixed layer of the metal constituting the innermost layer and the metal constituting the base material is formed at the boundary between the innermost layer and the base material . 3. The mold copper plate for continuous casting as claimed in claim 1 or 2, characterized in that, the base material is pre-implemented on the surface of the plate to be selected from one or both of Ni, Cr, Fe and Co. More than one kind of coating as the main component. 4. A method for manufacturing a crystallizer copper plate for continuous casting, characterized in that, on the surface of a plate made of copper or copper alloy constituting the base material, the PVD method is used to form the metal group Ti, Cr, Ni, B. A layer composed of one or two or more metals selected from Si and Al, on which one or more groups of nitrides and carbides of one or two or more metals selected from the metal group are alternately laminated Or a layer composed of carbon-nitride, and a layer composed of one or more metals selected from the metal group, and then form one or more than two metals selected from the metal group as the outermost layer Layers of metal nitrides, carbides or carbon-nitrides. 5. The manufacturing method of the mold copper plate for continuous casting according to claim 4, wherein the method of forming the innermost layer is a high bias voltage discharge coating method. 6. The method of manufacturing a mold copper plate for continuous casting according to claim 4, wherein a bias voltage for arc interruption is used at least when forming the innermost metal layer. 7. The method of manufacturing a mold copper plate for continuous casting according to claim 5, wherein a bias voltage for arc interruption is used at least when forming the innermost metal layer. 8. The method for manufacturing a mold copper plate for continuous casting as claimed in any one of claims 4 to 7, wherein the copper or copper alloy plate constituting the base material is previously carried out on its surface with Coating consisting mainly of one or two or more selected from Ni, Cr, Fe, and Co.

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