JP5640179B1 - Continuous casting mold - Google Patents

Abstract

The mold main bodies 11 a to 14 a are made of copper or a copper alloy, and have a diamond-like carbon layer 21 through a hard protective layer 20 inside the mold members 11 to 14 that are in contact with molten steel or a shell in which the molten steel is solidified. The mold members 11 to 14 in this case include a type having a short side and a long side that form a pair, and a cylindrical type. Since the diamond-like carbon layer 21 is formed through the hard protective layer 20 inside the mold members 11 to 14 with which the molten steel or slab comes into contact, the continuous casting mold 10 with extremely reduced friction between the molten steel and the slab is provided. Can be provided.

Description

The present invention relates to a continuous casting mold in which a diamond-like carbon layer (DLC) is formed on the inner side of a casting mold member in contact with molten steel or a slab (specifically, a shell).

As described in Patent Document 1, in the current continuous casting method, friction exists between the mold surface and the slab surface, and in order to reduce this, mold powder (lubricant) is used during casting, The casting equipment is equipped with an oscillation mechanism.
Further, in the first embodiment of Patent Document 2, a continuous casting mold is proposed in which a coating made of a material such as diamond having resistance to deterioration is formed on the mold surface. In the second embodiment, In the proposal, the entire mold is made of a non-metallic material such as diamond.
Furthermore, Non-Patent Document 1 describes the characteristics of DLC films and their applications, and in a durability test using a copper-based sintered alloy mold, the DLC-treated mold is untreated. In comparison, it is disclosed that the lifetime is greatly increased.

JP 2001-246449 A Special table 2002-522225 gazette

Shinya Ohira (Elemental Research Laboratory), “Characteristics of DLC film and its application”, NTN TECHNIC REVIEW No. 77 (2009), p. 87-93

However, in Patent Document 1, the frictional force between the mold surface and the slab surface causes wear of the mold surface, and the mold powder causes corrosion of the mold surface.
Further, in the technique in which the mold surface described in Patent Document 2 is directly covered with a diamond coating, the mold body is made of copper or copper alloy and is soft, so that the hardness of the surface is sufficient even if a diamond coating layer is formed thereon. Further, there is a problem that the coated diamond coating layer is easily peeled off and cannot exhibit a sufficient effect.
Non-Patent Document 1 describes that a DLC film is applied to a copper-based sintered alloy molding die. However, since a cemented carbide is used as a material, thermal conductivity is poor, and a continuous casting mold is used. There was a problem that could not be used as.

The present invention has been made in view of such circumstances, and provides a continuous casting mold in which a diamond-like carbon layer is formed at least on the inner side of a mold member in contact with molten steel or a cast slab, and friction with molten steel is extremely reduced. With the goal.

A continuous casting mold according to the present invention that meets the above-mentioned object is a molten steel or a shell (cast slab) in which the molten steel is solidified by coating a diamond-like carbon layer through a hard protective layer on the inside of a mold body made of copper or a copper alloy. ) Is formed. As the diamond-like carbon layer, for example, a layer having a high wear resistance in which the density ρ is in the range of 2.0 to 3.5 (more preferably 2.6 to 3.5) is used. Good.

In the continuous casting mold according to the present invention, each of the mold members has a pair of short side and long side, and the diamond-like carbon layer is formed on all or part of the inside of the short side and the long side. There are some types.
Further, in the continuous casting mold according to the present invention, the mold member is a tubular type, and the diamond-like carbon layer is formed on all or a part of an inner surface of the molten steel or a shell solidified by the molten steel. Some types are also available.

In the continuous casting mold according to the present invention, the hard protective layer may be formed by performing nitriding treatment and / or shot peening treatment on the mold body.
In the continuous casting mold according to the present invention, the hard protective layer is preferably composed of a hard plating layer formed on the mold body, and the hard plating layer in this case is, for example, Cr, Ni, Co, high hardness Cu or It consists of these alloy plating.
In the continuous casting mold according to the present invention, the hard protective layer can be formed by thermal spraying (for example, cermet thermal spraying, self-fluxing alloy thermal spraying).

In the continuous casting mold according to the present invention, it is more preferable that the hard protective layer is formed on the mold body after being subjected to concavo-convex treatment by blasting or etching.
In the continuous casting mold according to the present invention, the diamond-like carbon layer is preferably formed by a PVD method or a CVD method.

In the continuous casting mold of the present invention, it is preferable that a large number of vertical grooves or a large number of dimples are formed in the meniscus portion located at the upper part of the mold for the purpose of slow cooling. Here, the meniscus portion refers to, for example, a range of +80 mm to −100 mm (more preferably +50 mm to −60 mm) with respect to the average meniscus height. Moreover, it is preferable to make the width | variety and space | interval (namely, horizontal width of a non-groove part) of a vertical groove into the range of 0.4-15 mm (more preferably, 0.5-2.2 mm). In the case of dimples, the diameter is 0.5 to 3 mm (more preferably 0.7 to 1.5 mm), hemispherical, conical, cylindrical, or indefinite, and the gap between each dimple is 0.5 to It is preferable that they are arranged in a lattice shape or at an equal interval of about 3 mm.

In the continuous casting mold according to the present invention, the hard protective layer is formed by one or more of 1) nitriding treatment, shot peening treatment, 2) hard plating, 3) blast treatment, etching treatment, and 4) spraying treatment. It can also be done in combination.

The continuous casting mold according to the present invention has a diamond-like carbon layer covered with a hard protective layer on the inner side of a mold member made of copper or a copper alloy and in contact with a molten steel or a solidified shell of molten steel. Therefore, the coefficient of friction with respect to the molten steel and slab on the inner surface of the mold member is extremely reduced, and the slab can be manufactured smoothly.

By making the friction between the mold member and the slab extremely small, powderless casting or casting with a reduced amount of powder becomes possible, and wear and corrosion of the mold member are drastically reduced.
Further, by forming a hard protective layer below the diamond-like carbon layer, the diamond-like carbon layer is reinforced by the hard protective layer, and the diamond-like carbon layer is not peeled off. Furthermore, since the strength is provided by the hard protective layer, the diamond-like carbon layer can be made thinner.

Moreover, the following can be expected by using the continuous casting mold according to the present invention.
1) The continuous casting mold according to the present invention enables the production of ultra-high quality slabs without oscillation marks in addition to the reduction of steelmaking costs by simple powder reduction, which eliminates the need for scarfing treatment. .
2) In some cases, the installation of the oscillation device itself in the continuous casting mold facility can be omitted.

And, in the continuous casting mold according to the present invention, when the hard protective layer is formed by nitriding and shot peening the mold body, the processing becomes simpler, but further, plating or thermal spraying is performed on the upper layer. If done, a stronger coating can be formed.

Further, in the continuous casting mold according to the present invention, when the hard protective layer is formed on the concavo-convex process by blasting or etching, the joining area is increased by this, so that the continuous casting mold having a longer life is obtained. It can be.

And, in the continuous casting mold according to the present invention, when a large number of vertical grooves (extremely fine slits) and dimples are formed on the meniscus portion located above the mold member for slow cooling, It is possible to control the slow cooling during the initial solidification.

(A) is an exploded plan view of a continuous casting mold according to one embodiment of the present invention, and (B) to (D) are partially enlarged views of the continuous casting mold. (A), (B), and (C) are a diamond structural diagram, a graphite structural diagram, and a structural diagram of a DLC film, respectively. (D) is an explanatory diagram of an amorphous carbon film (Source: Non-Patent Document 1). It is a graph which shows the abrasion characteristic at the time of forming various protective films in a casting_mold | template main body. It is a graph which shows a friction coefficient at the time of forming various protective films in a casting_mold | template main body.

Then, the Example which actualized this invention is described and it uses for an understanding of this invention.
As shown in FIGS. 1 (A) and 1 (B), a continuous casting mold 10 according to an embodiment of the present invention includes opposing short sides 11 and 12 and opposing short sides 11 and 12 constituting a mold member. It has long sides 13 and 14 arranged so as to sandwich it, and has short sides 11 and 12 and back plates 15 to 18 having a water cooling structure arranged fixedly outside the long sides 13 and 14.

The short sides 11 and 12 and the long sides 13 and 14 are plate-shaped mold bodies 11a to 14a made of copper or copper alloy having good thermal conductivity, and hard protective layers formed on the inner surfaces of the mold bodies 11a to 14a, respectively. 20 and a diamond-like carbon layer (DLC) 21 formed on the surface of each hard protective layer 20.

The hard protective layer 20 includes: 1) a method of forming the inner surfaces of the mold bodies 11a to 14a by nitriding and / or shot peening; and 2) chromium (Cr), nickel (on the inner surfaces of the mold bodies 11a to 14a). A method of performing hard plating from Ni), cobalt (Co), high-hardness copper (Cu), or an alloy thereof (NiCo alloy) to form a hard plating layer; and 3) hard on the inner surfaces of the mold bodies 11a to 14a. There are a method of spraying a material (for example, a mixture of metal and hard ceramic powder), and 4) a method of forming two or more of these together. A cermet material (or a self-fluxing alloy) may be used as the material to be sprayed.

Specific examples of the hard plating include Ni-based alloy plating, Co—Ni-based alloy plating, and hard (high hardness) Cu plating (including alloy plating). In addition, the thermal spray material is 1) a Cr-Si-B alloy based on Ni or Co, and 2) a carbide, nitride, boride added to a Co, Ni or Co-Ni alloy. Etc.

Here, the thickness when the hard protective layer 20 is formed by plating is, for example, about 0.01 to 3 mm (more preferably 0.1 to 1 mm), and when formed by thermal spraying, for example, 0.01. About 3 mm (more preferably 0.05-1 mm).
In addition, when the thickness of the hard protective layer 20 is too thick, the heat removal of the continuous casting mold 10 is deteriorated, and when the hard protective layer 20 and the mold main bodies 11a to 14a have different thermal expansion coefficients, they are easily peeled off. Moreover, when the thickness of the hard protective layer 20 is too thin, the strength of the hard protective layer 20 is lost, and wrinkles are easily generated.

A diamond-like carbon layer 21 is formed on the surface (inner side surface) of the hard protective layer 20. The diamond-like carbon layer 21 has both the diamond structure (sp ³ ) and the graphite structure (sp ² ) shown in FIGS. 2A and 2B, and has the structure shown in FIG. In the state diagram shown in FIG. 2D, a-C (amorphous carbon) and ta-C (tetrahedral amorphous carbon) are used.

The hard protective layer 20 and the diamond-like carbon layer 21 are easy to construct on the entire inner surface of the mold bodies 11a to 14a. However, the inner surface of the mold bodies 11a to 14a may be directly applied to the molten steel and slab. You may form the hard protective layer 20 and the diamond-like carbon layer 21 only in a part with.
Moreover, before forming the hard protective layer 20, the inner surfaces of the mold bodies 11a to 14a may be subjected to hardening treatment by nitriding and / or shot peening, and the inner surfaces of the mold bodies 11a to 14a may be uneven by blasting or etching ( (Formation) treatment may be performed to increase the surface roughness, and adhesion of a plating layer or a sprayed layer to be further formed on the surface may be improved.

The diamond-like carbon layer 21 is formed by a CVD (Chemical Vapor Deposition) method using a hydrocarbon-based gas as a raw material, as shown in FIG. 2D, but PVD (Physical Vapor) using solid carbon as a raw material The Deposition method can also be used. In either case, the method itself is well known, and detailed description thereof is omitted.

The diamond-like carbon layer 21 has a very thin thickness of about 0.001 to 5 [mu] m (more preferably 1 to 5 [mu] m), but the present invention is also applied to a case where the thickness is even thicker. If the diamond-like carbon layer 21 is excessively thick, the adhesion to the base material (mold bodies 11a to 14a, hard protective layer 20) is reduced. Since the diamond-like carbon layer 21 has an amorphous structure, the atomic structure is uniform and stable, and has high corrosion resistance.
Further, since the inside of the short sides 11 and 12 and the long sides 13 and 14 formed in this way has a diamond-like carbon layer 21 on the surface, the friction coefficient with respect to the slab is 0, as shown in FIG. 1 or less (however, about 0.3 when Ni is a protective layer). In addition, although the characteristic comparison of a carbonaceous material is shown in Table 1, it turns out that DLC has very high hardness.

Further, in the continuous casting mold 10 according to this embodiment, by using the CVD method or the PVD method, the film-forming running cost of the diamond-like carbon layer 21 is 1) the material (hydrocarbon gas) cost is extremely low, 2) The cost of electricity required for the production is low, so it can be reduced. 3) The film formation time is about 2 μm / h, and the production cost is low.

Furthermore, when the diamond-like carbon layer 21 is directly formed on the copper or copper alloy mold main bodies 11a to 14a, the mold main bodies 11a to 14a themselves are soft, so that it can be said that the adhesion and wear resistance are excellent. However, by forming the hard protective layer 20 between the diamond-like carbon layer 21 and the mold main bodies 11a to 14a, it is possible to obtain a continuous casting mold 10 having a stronger and higher wear resistance and higher corrosion resistance. .

Further, as shown in FIGS. 1C and 1D, it is possible to form vertically long grooves 22 on the meniscus portions 23 of the mold bodies 11a to 14a at a predetermined pitch (a + b) for gentle cooling. . In this case, when the cross section of the vertical groove 22 is a semicircle, the width b and the interval (that is, the horizontal width of the non-groove portion) a of the vertical groove are 0.4 to 15 mm (more preferably 0.5 to 2.2 mm) ) Is preferable. As shown in FIG. 1D, the longitudinal groove 22 is preferably in the range of +80 mm to −100 mm (more preferably +50 mm to −60 mm) with respect to the average meniscus height (position). That is, c = 20 to 80 mm and d = about 40 to 100 mm are preferable.

In this way, by forming a plurality of vertical grooves 22 arranged in the meniscus portion 23 in the horizontal direction, the molten steel and the mold member (short sides 11 and 12 and the long sides) with which the solidified shell of the molten steel (part of the slab) comes into contact. Slow cooling by the continuous casting mold 10 composed of 13, 14) can be performed. In this case, the hard protective layer 20 and the diamond-like carbon layer 21 are formed along an uneven shape. The cross section of the longitudinal groove is not limited to a semicircular shape, and various cases such as a triangle, a quadrangle, and an arc shape can be adopted. A large number of dimples for slow cooling may be formed in the meniscus portion.

Experimental example

Next, FIG. 3 and FIG. 4 show data obtained by actually obtaining the wear index (wear amount) and the friction coefficient of the continuous casting mold 10 and the conventional continuous casting mold. 3 and 4, 1 is an example in which a diamond-like carbon layer is formed by performing Ni plating on the mold bodies 11 a to 14 a (base material), and 2 is a diamond-like carbon layer by performing Co plating on the base material. Example 3 shows an example in which a diamond-like carbon layer is formed by spraying a wear-resistant material on a base material. 4 shows an example in which only Ni plating is performed on the surface of the base material, 5 shows only Co plating on the surface of the base material, and 6 shows only thermal spraying on the surface of the base material.

Here, the thickness of the above plating and thermal spray coating is 0.1 to 0.2 mm, and a cermet containing a hard material (for example, WC) was used as the thermal spray material.
The “wear index” in FIG. 3 was the same as the wear amount represented by the following equation.
Amount of wear = μ · P · L / Hv
Here, μ: friction coefficient (see FIG. 4), P: surface pressure, L: sliding distance, Hv: strength of coating

From the above experiments, when Ni-plated on the base material and a diamond-like carbon layer was formed thereon, friction was greater than when a diamond-like carbon layer was formed by forming a Co-plated layer or a sprayed layer on the base material. Although the coefficient increases and the wear index increases, the effect (reduction of the friction coefficient, wear index) is significantly higher than when the conventional Ni-plated layer, Co-plated layer, and sprayed layer that do not form a diamond-like carbon layer are formed. Deceive). “No wear” indicates that the friction coefficient μ is 0.001 or less.

Next, a test example in which a heat cycle test of a mold member on which a DLC film is formed will be described. The heat cycle test was carried out by repeating heating at 400 ° C. and water cooling. In the following test examples, the diamond-like carbon layer had a thickness of about 0.5 to 2 μm (actually in the range of 0.001 to 5 μm), and the plating layer had a thickness of 0.5 to 1 mm.

As shown in Table 2, 1) copper plate (CCM-BS) + diamond-like carbon layer, 2) copper plate + Ni plating (hard protective layer) + diamond-like carbon layer, 3) copper plate + CoNi plating (hard protective layer) + diamond-like Carbon layer, 4) Copper plate + self-fluxing alloy spray (hard protective layer) + diamond-like carbon layer, 5) Copper plate + Ni plating + cermet spraying + diamond-like carbon layer, 6) Copper plate + cermet spraying (alloys such as WC, Ni) + It performed about the diamond-like carbon layer. The sprayed coating had a thickness of about 0.5 mm. In Test Examples 2 to 6 in Table 2, “copper plate +” is omitted.

In the above test examples 2) to 4), cracks did not occur even after 100 heat cycles. In Test Example 5), there was no damage at the 100th time, and in 6), peeling occurred at the 20th time. The reason of this 6) is that the non-self-soluble cermet material and the base material (copper) are not sufficiently joined. On the other hand, in self-fluxing alloy spraying, since it is heated after spraying, it is considered that the sprayed film and the base material are diffusion bonded.

Next, an acid resistance test of the mold member was performed for Test Examples 1) to 4) in which a diamond-like carbon layer was formed on the surface.
1) Corrosion occurs for copper plate (CCM-BS) + diamond-like carbon layer, 2) Ni plating (hard protective layer) + diamond-like carbon layer, 3) CoNi plating (hard protective layer) + diamond-like carbon layer 4) No corrosion reaction was observed after several hours for thermal spraying (hard protective layer) + diamond-like carbon layer. Therefore, it can be seen that by forming the hard protective layer + diamond-like carbon layer, it has excellent corrosion resistance.

The present invention is not limited to the above-described examples and experimental examples, and the present invention is also applied to the case where material change, thickness change, and numerical value change are made without changing the gist of the present invention.
Also, when a hard protective layer is formed by a combination of roughening treatment (unevenness treatment) of the mold body, surface hardening treatment of the mold body, formation of a plating layer, and formation of a sprayed layer, and finally a diamond-like carbon layer is formed. The present invention also applies.
Moreover, in the said Example, although the continuous casting mold has a long side and a short side, even if it is a cylindrical mold (substantially square cross section, circular cross section, tubular type), a hard protective layer and Any diamond-like carbon layer can be applied.

In the continuous casting mold according to the present invention, the diamond-like carbon layer is coated on the inner side of the mold body via the hard protective layer, so that the friction between the inner surface of the mold and the slab is remarkably reduced, and the lifetime is longer. A continuous casting mold can be provided.

10: Continuous casting mold, 11, 12: Short side, 13, 14: Long side, 11a-14a: Mold body, 15-18: Back plate, 20: Hard protective layer, 21: Diamond-like carbon layer, 22: Vertical Groove, 23: meniscus part

Claims (11)

A continuous casting mold characterized in that a mold member is formed in which a diamond-like carbon layer is coated on the inside of a mold body made of copper or a copper alloy via a hard protective layer, and a molten steel or a solidified shell of the molten steel contacts. . 2. The continuous casting mold according to claim 1, wherein each of the mold members has a pair of short side and long side, and the diamond-like carbon layer is formed on all or part of the inside of the short side and the long side. Continuous casting mold characterized by being made. 2. The continuous casting mold according to claim 1, wherein the mold member is a tubular type, and the diamond-like carbon layer is formed on all or a part of an inner surface of the molten steel or a solidified shell of the molten steel. Continuous casting mold characterized by. The continuous casting mold according to any one of claims 1 to 3, wherein the hard protective layer is formed by performing nitriding treatment and / or shot peening treatment on the mold body. . 5. The continuous casting mold according to claim 1, wherein the hard protective layer is formed of a hard plating layer formed on the mold body. 6. 6. The continuous casting mold according to claim 5, wherein the hard plating layer is made of Cr, Ni, Co, high hardness Cu or an alloy plating thereof. The continuous casting mold according to any one of claims 1 to 6, wherein the hard protective layer is formed by thermal spraying. The continuous casting mold according to any one of claims 1 to 7, wherein the hard protective layer is formed on the mold body after being subjected to concavo-convex treatment by blasting or etching. 9. The continuous casting mold according to claim 1, wherein the diamond-like carbon layer is formed by a PVD method or a CVD method. 10. The continuous casting mold according to any one of claims 1 to 9, wherein a plurality of long vertical grooves for gentle cooling are formed in a meniscus portion located at an upper portion of the mold member. Continuous casting mold. The continuous casting mold according to any one of claims 1 to 9, wherein a plurality of dimples for slow cooling are formed in a meniscus portion located at an upper portion of the mold member.

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