JPS63104752A - Surface treatment method for continuous casting molds - Google Patents

Abstract

PURPOSE:To form the film having gradually transiting composition under good adhesion and to improve wear resistance and heat resistance of a mold by conducting between an anode and the mold and plating with a porous material while shifting it together with the anode along the mold wall face. CONSTITUTION:The graphite-made anode 4 is wrapped with the spongy porous material and is fitted in a stylus 5 and the positive electrode of electric source 6 is connected to the anode 4 by a lead wire and the negative electrode is connected to the mold 1. On the other hand, nickel plating liquid is supplied to the mold all 3 from a pump 8 through the anode 4 and at the same time, the anode 4 is shifted and the nickel in the plating liquid is plated on the surface of mold wall 3. Next, it is washed and dried, tungsten carbide powder containing nickel and cobalt on the nickel plating layer is used as a material and is thermal-sprayed, to form the film having gradually transiting composition com posed of the nickel as under-coating and tungsten carbide containing cobalt as top-coating.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a surface treatment method for continuous casting molds, and particularly a surface treatment method suitable for repairing continuous casting molds at their installation site without disassembling them. Regarding.

(Conventional technology) In recent years, in continuous casting, with the speeding up of operations and the development of on-line change during casting technology, the performance required of continuous casting molds has become harsher, and the durability of copper molds has been reduced. In order to improve the
or Cr plating layer (for example, JP-A-52
-52828), or those whose surface has been treated by thermal spraying with a self-fluxing alloy have been widely used.

(Problem to be Solved by the Invention) However, even if continuous casting molds with these protective films are used repeatedly, the protective layer at the bottom of the mold will wear out due to the sliding of the solidified shell, so the mold will need to be removed frequently. It is necessary to repair the worn surfaces. When repairing this mold, the casting equipment must first be stopped, the mold must be disassembled, and then reassembled after the mold is repaired. Disassembling and reassembling takes a lot of time, which reduces the operating rate of the casting equipment. There was a problem of bringing

Moreover, with a protective layer formed by plating, local repairs cannot be performed, so all plating layers remaining on the mold surface must be removed and a new plating layer must be formed, and each time repairs are made, The problem was that the thickness of the copper became thinner, making it unusable after several repairs. Further, in the case where the protective layer is formed from a self-melting alloy, heat treatment must be performed each time it is repaired, resulting in thermal deformation, which limits repeated use.

On the other hand, metal materials other than self-fluxing alloys as protective layer forming materials,
For example, it is possible to use chromium, cobalt, etc. and spray the powder onto the surface of a copper material using a plasma spraying method to form a protective layer, but the sprayed wave coating of these metals has weak adhesion to the copper material. Therefore, it was impossible to apply it to continuous casting molds operated in continuous mode.

Therefore, in order to improve the wear resistance and heat resistance of the mold, the present invention makes it possible to apply a thermally sprayed coating made of a metal compound composite material, and to repair the continuous casting mold at its installation site without disassembling it. This was done with the purpose of making it possible to do so.

(Means for Solving the Problems) The present invention, as a means for solving the above-mentioned problems, involves interposing a porous material to bring an anode into contact with the inner wall surface of a copper mold. Electricity is applied between the anode and the copper mold while continuously supplying the electrolytic plating solution to the surface of the copper mold through the electrolytic plating solution. The present invention provides a method for surface treatment of a continuous casting mold, characterized in that a nickel and/or metal carbide composite material is thermally sprayed onto a plating layer to form a gradual coating.

Although any electrolytic plating bath can be used,
It is preferable to use a nickel plating bath in order to improve the adhesion between the copper, which is the material of the mold, and the sprayed coating.

The gradual change film has an undercoat made of nickel,
Preferably, the top coat is formed from a metal carbide composite material.

As the metal carbide composite material, tungsten carbide or titanium carbide containing at least one of cobalt, nickel, and chromium is particularly suitable, but the material is not limited thereto.

(Function) Basically, in order to form a thermally sprayed coating made of a metal carbide composite material, the present invention basically uses a so-called brush plating method to coat metals such as nickel and copper prior to forming the thermally sprayed coating. This improves the adhesion between the thermal spray coating and the copper mold material, and at the same time suppresses the reaction with the slag by containing nickel in the interior of the multi-layer thermal spray coating. This is intended to compensate for the drawbacks of thermal sprayed coatings made of metal carbide composite materials, which have high hardness but are brittle and prone to cracking due to thermal shock.

However, in the ordinary electrolytic plating method, the use of a plating bath is unavoidable, and therefore the mold must be disassembled and reassembled. Therefore, in the method of the present invention, the inner wall surface of the copper mold is An electrolytic plating solution is continuously supplied to the porous material in contact with the porous material through the anode to form a fluidized plating bath layer between the inner wall surface of the mold and the anode, and electricity is applied between the anode and the mold to remove the porous material. The above-mentioned problem is solved by adopting a method of performing electrolytic plating while moving the material together with the anode along the inner wall surface of the mold.

In addition, as the thermal spraying method, it is preferable to use a gas flame thermal spraying method which can employ a simple and small-sized apparatus.

Furthermore, the content of nickel in the sprayed coating is increased stepwise or continuously from the surface to the inside. In other words, the metal carbide composite material increases from the mold surface to the surface of the sprayed coating. By increasing the content continuously or stepwise, thermal shock and interlayer peeling caused by differences in physical properties between each layer, which are defects in thermal sprayed coatings with a laminated structure, are alleviated, and the spreadability and adhesion of thermal sprayed coatings are improved. Improves strength and durability.

Hereinafter, a case where the method of the present invention is applied to repairing a continuous casting mold will be explained with reference to the attached drawings.

In the figure, 1 is a copper mold, 2 is the long side wall of the mold, 3
4 is the short side mold wall, 4 is the anode surrounded by porous material,
5 is a stylus, 6 is a power supply device, 7 is a tray, 8 is a plating solution circulation pump 8, the anode 4 is made of a conductive material such as graphite, and the plating solution is continuously supplied from the pump 8 to the anode 4. is the short side mold wall 3 through the porous material.
The overflowing plating solution is collected in a tray 7 and supplied to the anode 4 again by a pump 8.

According to the method of the present invention, repair of the mold is accomplished, for example, in the following manner. That is, the graphite anode 4 is wrapped in a sponge-like porous material, and this is attached to the stylus 5, and the positive electrode of the power supply device 6 is connected to the anode 4 with a lead wire 9.
Then, connect the negative electrode to the mold l. On the other hand, the nickel plating solution is supplied from the pump 8 to the short side mold wall 3 via the anode 4 and the porous material, while the nickel plating solution falling down along the mold wall is collected in the tray 7 and pump 8 Then, supply is made to the anode 4 again. At the same time, by applying a DC voltage from the power supply 6 between the anode 4 and the mold wall 3 and moving the anode 4 along the mold wall surface manually or by a drive mechanism, nickel in the plating solution is transferred to the mold wall. Electrodeposit on the surface of 3.

After nickel plating the mold wall in this way,
After cleaning and drying, the nickel plating layer is thermally sprayed using a powder flame spraying method using tungsten carbide powder containing nickel and cobalt as a material to form an undercoat of nickel and a top coat of tungsten carbide containing cobalt. Repair is performed by forming a gradual change film consisting of:

Separately, a bending test piece was prepared, electrolytically nickel plated using the method described above, and subjected to a U-shaped bending test. No peeling was observed at all.

(Effects of the Invention) As is clear from the above description, according to the present invention, a plating tank is not required, and disassembly and assembly of the mold are not required, and the plating device itself can be set in the mold device. All you need is an anode and a stylus, and you can also use a small thermal spraying device, so you can perform localized repairs on-site.

Furthermore, according to the method of the present invention, it is possible to form a graded film made of nickel and a metal compound composite material with good adhesion, which improves the abrasion resistance and heat resistance of the mold, and provides a highly durable continuous film. Not only can casting molds be manufactured, but even if there is local wear, the sprayed coating can be repaired without removing the entire thermal sprayed coating, providing excellent effects.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a main part showing an example of applying the method of the present invention to repair of a continuous casting mold. 1-copper mold, 2-long side mold wall, 3-short side mold wall, 4-anode surrounded by porous material, 5-stylus, 6-power supply device, 7-tray, 8-plating liquid Circulation pump.

Claims (4)

[Claims] (1) An anode is brought into contact with the inner wall surface of a copper mold through a porous material, and an electrolytic plating solution is continuously supplied to the surface of the copper mold through the anode and the porous material while the anode and the copper mold are brought into contact with each other. After electrolytically plating the anode while moving the anode along the inner wall surface of the mold, nickel and/or metal carbide-based composite material is thermally sprayed onto the formed electrolytically plated layer to form a gradual coating. 1. A method for surface treatment of a continuous casting mold, characterized by forming a continuous casting mold. (2) The method according to claim 1, wherein the electrolytic plating bath is a nickel plating bath. (3) The method according to claim 1 or 2, wherein the undercoat of the gradual change coating is formed of nickel, and the top coat is formed of a metal carbide composite material. (4) The method according to any one of claims 1 to 3, wherein the metal carbide composite material is tungsten carbide or titanium carbide containing at least one of cobalt, nickel, and chromium.