JPH0824997A - Mold for continuous casting - Google Patents

Abstract

PURPOSE:To improve the durability without easy peeling of a protecting layer formed on the surface with chromium. CONSTITUTION:A heat conductive layer 2 composed of anyone among silver, silver alloy, nickel or nickel alloy with an electric discharge coating on the contacting surface of molten metal of a copper base body 1 formed with copper or copper alloy, and an electro-deposition, etc., of the chromium is executed on the surface of the heat conductive layer 2 to form the protecting layer 3. Since the heat conductive layer 2 formed on the surface of the copper base body 1 is made with the electric discharge coating, the copper base body 1 and the heat conductive layer 2 are firmly combined. Further, the surface of the heat conductive layer 2 is made to be the rough surface, and the protecting layer 3 formed on the surface of the heat conductive layer 2 is firmly and closely combined with the heat conductive layer 2. Therefore, the protecting layer 3 from the heat conductive layer 2 or the heat conductive layer 2 from the copper base body 1 are not easily peeled and do not fall down, and the exposure of the copper base body 1 is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold used in a continuous casting machine, and more particularly to an improvement for improving durability.

[0002]

2. Description of the Related Art A continuous casting mold has a structure in which the inner surface is formed of copper or white copper having a good thermal conductivity, and the outer periphery thereof is water-cooled so that the heat taken from the molten steel is discharged by the cooling water. Molten steel injected into this mold contacts the mold wall,
The heat is removed by the heat transfer action, and the surface is solidified and contracted. When it contracts, it is separated from the mold wall and the amount of heat removed decreases, and the solidified portion is deformed by the heat from the unsolidified portion and the static pressure of the molten steel, and comes into contact with the mold wall again. Next, heat is removed and the molten steel is separated from the mold wall again. That is, the solidified layer advances by repeating contact and separation with the mold wall.

Therefore, the mold wall is required to have good heat conduction and wear resistance against contact and separation of the solidified layer. Further, the continuous casting mold is required to have further improved durability due to the speeding up of operations and the like.

In order to meet such demands, various improvements and developments of continuous casting molds have been made. A conventional mold for continuous casting of this type is plated with nickel (Ni) on a substrate of copper or copper alloy, and chromium (C
r) There is a plated structure.

[0005]

However, the conventional continuous casting mold in which the above-mentioned copper substrate is plated with Ni and Cr is repeated because the copper substrate and the Cr plating have different coefficients of thermal expansion. When used as a heat treatment, the Cr plating layer may peel off due to heat shock. When the Cr plating layer is peeled off, the copper substrate is exposed and copper of the substrate is attached to the molten steel, and many cracks are generated in the product, resulting in poor yield.

Therefore, an object of the present invention is to provide a continuous casting mold in which the peeling of the plating layer on the surface is prevented as much as possible and the durability is improved. Further, it is an object of the present invention to provide a continuous casting mold having sufficient wear resistance against contact and separation of molten steel.

[0007]

As a technical means for achieving the above object, a continuous casting mold according to the present invention is an electric discharge machining of a molten metal contact surface of a mold made of a copper base, and A heat transfer layer is formed, and a protective layer made of chromium is formed on the surface of the heat transfer layer, and the heat transfer layer is silver, or a silver alloy, nickel, or a nickel alloy. I am trying.

In addition, a good heat transfer effect is desired on the upstream side of the mold so that heat can be smoothly removed, and wear resistance is desired on the downstream side because the solidified layer contacts the mold surface.
On the surface of the molten metal contact surface of the mold made of a copper substrate on the upstream side in the flow direction of the molten metal, an electric discharge process is applied to form a heat transfer layer, and on the molten metal contact surface on the downstream side in the flow direction of the molten metal. The surface is subjected to electric discharge machining to form an intermediate layer, and the surface of the intermediate layer is subjected to electric discharge machining to form a wear resistant layer made of a material having wear resistance, and the surface of the heat transfer layer and the wear resistant layer are made of chromium. It is characterized in that a protective layer is formed.

Also in this case, the heat transfer layer and the intermediate layer are made of silver or any one of silver alloy, nickel and nickel alloy, and the wear resistant layer is made of tungsten carbide or stellite alloy. It is characterized by being either.

[0010]

Since the heat transfer layer formed on the surface of the copper base is formed by electric discharge machining, the copper base and the heat transfer layer are firmly bonded. In addition, the surface of the heat transfer layer becomes a rough surface, and the protective layer formed on the surface of the heat transfer layer is firmly and closely bonded to the heat transfer layer. Therefore, the protective layer does not easily peel off from the heat transfer layer or the heat transfer layer from the copper substrate and fall off. Therefore, the copper substrate is prevented from being exposed and copper is prevented from adhering to the surface of the product.

Further, since the surface of the copper substrate, the heat transfer layer is formed on the upstream side of the mold, and the wear resistant layer is formed on the downstream side, the cooling of the molten metal can be promoted, and when it solidifies, it contacts the mold. However, it does not easily wear.

[0012]

EXAMPLES The continuous casting mold according to the present invention will be specifically described below based on the illustrated examples.

FIG. 1 is a partial sectional view of a continuous casting mold according to the present invention, in which a copper base 1 made of copper or a copper alloy is provided with a cooling water passage (not shown). An electric circuit for this electric discharge machining is schematically shown in FIG. 3, in which a DC power source 11 is connected in series with a resistor 12 and a capacitor 13, and a connecting portion between the resistor 12 and the capacitor 13 is connected with, for example, an electrode 14. A copper base 1, which is, for example, a workpiece, is connected to the connection between the capacitor 13 and the power supply 11 so that the copper base 1 and the electrode 14 are discharged. This copper substrate 1 is used as a cathode, and silver (Ag) or a silver alloy, nickel, or a nickel alloy is used as a rod-shaped electrode, or vice versa, the atmosphere, oil, non-oxidizing gas such as Ar, N ₂ etc. In the inside, the copper base 1
The heat transfer layer 2 of Ag, silver alloy, Ni, or nickel alloy is formed on the molten metal contact surface. As a result, the copper substrate 1
A rough surface having a three-dimensional complex shape different from mechanical and chemical rough surface formation is formed on the surface of the. Then, chromium is electrodeposited on the surface of the heat transfer layer 2 to form the protective layer 3.

That is, since the copper substrate 1 is covered with the heat transfer layer 2 by electric discharge machining, the heat transfer layer 2 does not have a crack. Further, the surface of the copper substrate 1 is strengthened in physical bonding by electric discharge machining, and the surface is roughened which cannot be considered by other methods, and the heat transfer layer 2 tightly covers the surface of the copper substrate 1. At the same time, due to the alloying of the interface and the quenching effect of the base metal, the crystals become disordered and sometimes become amorphized, and a strong bond can be given to the subsequent treatment for activation. Therefore, the heat transfer layer 2 does not easily peel off from the copper substrate 1.

Furthermore, since the surface of the heat transfer layer 2 is formed in a peculiar three-dimensional space by electric discharge machining, the protective layer 3 covering the heat transfer layer 2 enters this peculiar space and adheres by an anchoring action. Strengthening and homogenization of the heat transfer layer 2 are achieved. For this reason, it is possible to prevent the protective layer 3 from peeling off from the heat transfer layer 2 and falling off as much as possible, and obtain high durability.

FIG. 2 shows another embodiment, in particular, one in which the wear resistance of the mold is improved. As shown in FIG. 2, a heat transfer layer 4 is formed on the molten metal contact surface of the copper substrate 1 by electric discharge machining on the upstream side in the molten metal flow direction of the mold, and on the downstream side the molten metal contact surface of the copper substrate 1 is formed. The intermediate layer 5 is formed by electric discharge machining. Similar to the above, the heat transfer layer 4 and the intermediate layer 5 are subjected to electric discharge machining using Ag or any one of silver alloy, Ni, and nickel alloy for the electrodes, and any one of these Ag, silver alloy, Ni, and nickel alloy is used. To form.

Further, the wear-resistant layer 6 is formed on the surface of the intermediate layer 5 by electric discharge machining using either wear-resistant tungsten carbide or stellite alloy as an electrode.
Are formed.

The surfaces of the heat transfer layer 4 and the wear resistant layer 6 are continuously plated with chromium to form a protective layer 7. The protective layer 7 formed by chrome plating is 10
So-called cracking does not occur even if it is formed to a thickness of -100 μm, but it is preferable to form it to a thickness of about 10 μm.

According to the continuous casting mold shown in FIG.
Since the heat transfer layer 4 having good heat transfer efficiency is formed on the upstream side, it is possible to efficiently remove heat of the supplied molten metal. Further, since the wear resistant layer 6 is formed on the downstream side, even if the solidified molten metal comes into contact with the mold, the mold is not easily worn. Therefore, the durability of the mold can be improved. Moreover, good heat removal and wear resistance can be combined to shorten the production time of the slab.

Further, the portion forming the heat transfer layer 4 and the intermediate layer 6
The ratio of the portion forming the slab may be designed according to the conditions of the molten metal and casting, but it may be formed in the range of 5: 5 to 2: 8.

[0021]

As described above, according to the continuous casting mold of the present invention, since the heat transfer layer is formed by performing the electric discharge machining on the copper base, the base and the heat transfer layer are firmly formed. To
Moreover, they can be brought into close contact with each other to be bonded. Therefore, it is possible to prevent the heat transfer layer from peeling off or falling off from the copper substrate as much as possible. Further, good heat conduction is ensured by the copper substrate and the heat transfer layer.

Further, a peculiar three-dimensional space is formed on the surface of the heat transfer layer, and the protective layer formed on the surface of the heat transfer layer is bonded while entering the peculiar space. The bond between the heat layer and the protective layer is tight and strong, and peeling of the protective layer from the heat transfer layer is prevented as much as possible. Therefore, durability can be improved.

[Brief description of drawings]

FIG. 1 is a partial sectional view of a molten metal contact surface of an embodiment of a continuous casting mold according to the present invention.

FIG. 2 is a partial sectional view of a molten metal contact surface of another embodiment of the continuous casting mold according to the present invention.

FIG. 3 is a schematic electric circuit diagram of an electric discharge machine.

[Explanation of symbols]

 1 Copper Substrate 2 Heat Transfer Layer 3 Protective Layer 4 Heat Transfer Layer 5 Intermediate Layer 6 Abrasion Resistant Layer 7 Protective Layer 14 Electrode

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hisaro Tashiro 1 17-2 Shinjuyo, Kashiwa-shi, Chiba Yoshizawa Elue Co., Ltd.

Claims (5)

[Claims] 1. A molten metal contact surface of a mold made of a copper base is subjected to electric discharge machining to form a heat transfer layer on the surface, and a protective layer made of chromium is formed on the surface of the heat transfer layer. Continuous casting mold. 2. The continuous casting mold according to claim 1, wherein the heat transfer layer is made of silver, a silver alloy, nickel, or a nickel alloy. 3. A molten metal contact surface of a mold made of a copper base, which is an upstream surface in a molten metal flow direction, is subjected to electric discharge machining to form a heat transfer layer. On the surface of the downstream side of the direction to form an intermediate layer by performing electrical discharge machining, the wear resistance layer is formed by a material having wear resistance by electrical discharge machining on the surface of the intermediate layer, the heat transfer layer and the wear resistant layer A continuous casting mold characterized in that a protective layer made of chromium is formed on the surface of the. 4. The continuous casting mold according to claim 3, wherein the heat transfer layer and the intermediate layer are made of silver, a silver alloy, nickel, or a nickel alloy. 5. The continuous casting mold according to claim 3, wherein the wear resistant layer is made of tungsten carbide or stellite alloy.