JP2001259799A - Method for continuously casting copper and copper alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the entrainment of slag and oxide based inclusion devel oped at the initial stage of casting into a cast block when a continuous casting of copper and copper alloy is preformed. SOLUTION: An inert gas atmosphere or a reducing gas atmosphere having oxygen concentration less than 2,000 ppm in the mold is prepared at the initial stage of the casting from the starting time of the casting to the immersion of an immersion nozzle for supplying molten metal into a mold below the surface of the molten metal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention prevents slag and oxide inclusions generated in the early stage of casting from being entrained in an ingot in continuous casting or semi-continuous casting of copper and copper alloy (hereinafter referred to as continuous casting). And it is widely used in the field of continuous casting of copper and copper alloy which can obtain a good casting surface.

[0002]

2. Description of the Related Art In order to produce an ingot of copper and copper alloy by continuous casting, molten metal produced in a melting furnace is poured into a holding furnace or a tundish, and is vertically moved through an immersion nozzle. The molten metal is poured into the open cylindrical mold. When casting an ingot having a rectangular cross section, it was opened up and down through an inverted T-shaped immersion nozzle (a nozzle having a nozzle hole opened in the short side direction of the mold is called an inverted T-type immersion nozzle). Molten metal is injected in the short side direction of the cylindrical mold, and solidified in the mold cooled by cooling water. The ingot that has started solidifying in the mold is continuously drawn vertically downward by a dummy bar installed at the bottom of the mold, and the method of spraying cooling water directly onto the ingot when it exits the mold is widely used. ing.

[0003] At that time, the surface of the molten metal in the mold is made into a carbon powder or a powder or a molten state called a flux for casting in order to prevent oxidation of the molten metal in the mold and improve lubrication between the mold and the ingot. Coated with oxides, fluorides and chlorides.

[0004] The role of the casting flux is to prevent oxidation of the molten metal, lubricate between the mold and the ingot, keep the temperature of the molten metal, uniformity of heat removal, and the like. It is necessary to coat the surface of the molten metal with a casting flux in order to obtain an ingot having a sound surface and internal properties.

On the other hand, when continuously casting a copper alloy, after the molten metal is injected into the mold and the immersion nozzle hole is immersed in the molten metal, until the casting flux is injected,
Usually, it is cast in air atmosphere, but the part where casting has started is cut after manufacturing the ingot, or it is removed as unprocessed terminals etc. Then it was not a big problem.

However, a recent demand for a copper alloy material for electric and electronic parts is to improve properties such as strength and electric conductivity of the material.
Copper with trace amounts of various elements such as Mg, Si, Ti,
A precipitation hardening type copper alloy to which these elements are added, for example, C
u-Zr system, Cu-Cr-Zr system, Cu-Ti system, Cu
-Ni-Si-Mg series and the like have been developed and used as electronic components and terminal / connector components.

[0007] Such additional elements of copper or copper alloy include:
It is often an active metal with strong affinity for oxygen, and is easily oxidized by oxygen in the atmosphere to generate inclusions and large amounts of slag, which are mixed into the ingot during casting to form a casting surface or ingot. Quality deteriorates. In particular, when the molten metal discharged from the immersion nozzle at the start of casting is poured into the mold, it reacts with oxygen in the atmosphere, and a large amount of slag and oxide-based inclusions are easily generated.

[0008] The generation of slag and oxide inclusions in which the active metal in the molten metal has reacted with oxygen in the atmosphere depends on the oxygen concentration in the atmosphere to which the molten metal is exposed during melting and casting, and the contact area when contacting the atmosphere. It largely depends on the contact time. In particular, during the time from the start of casting until the immersion nozzle hole is immersed below the surface of the molten metal, the molten metal discharged from the nozzle involves a large amount of atmospheric gas and the molten metal-gas interface area increases, so that the oxidation reaction is accelerated. Is done.

Accordingly, a large amount of slag and oxide-based inclusions are generated in the early stage of casting, from the start of casting to the dipping nozzle hole being immersed below the surface of the molten metal. Slag and oxide inclusions generated at the start of casting float on the surface of the molten metal and are absorbed by the casting flux.However, when part of the slag is caught in the ingot, the surface of the ingot deteriorates. And the number of defects on the surface of the product material increases.

[0010]

In order to prevent such slag and oxide-based inclusions from being mixed into the ingot, the generation of slag and oxide-based inclusions should be suppressed, and the generated slag and oxide-based inclusions should be prevented. It is conceivable to consider measures to prevent the system inclusion from being caught in the ingot. In order to prevent the generated slag and oxide inclusions from being caught in the ingot, it is conceivable to change the shape of the immersion nozzle to change the flow state of the molten metal in the mold. It is difficult to absorb all the generated slag and oxide-based inclusions into the flux for casting, and it is necessary to minimize the generation of slag and oxide-based inclusions.

[0011] Therefore, there is a demand for a technique that does not oxidize molten metal and generate slag and oxide-based inclusions as much as possible before the casting flux is injected at the start of casting.

As a method of solving this problem, if the entire molten metal is manufactured in a vacuum atmosphere through melting and casting, the frequency of occurrence of slag and oxide-based inclusions can be reduced. However, since the manufacturing cost increases, it is inexpensive. Therefore, there is a demand for a method of producing a sound ingot that can be produced with a high yield, does not cause casting trouble, and minimizes the generation of slag and oxide inclusions.

[0013]

Means for Solving the Problems The present invention has been made in view of the above points, and controls the oxygen concentration in the atmosphere in a mold at the start of casting until casting flux is supplied, thereby preventing slag and oxidation. An object of the present invention is to provide a clean, sound surface ingot with stable components by reducing the generation of physical inclusions.

The gist of the present invention is as follows. (1) In a continuous casting method or a semi-continuous casting method of copper and a copper alloy that is vertically cast using a cylindrical mold that is opened up and down, an immersion nozzle hole that supplies molten metal into the mold from the start of casting is formed by molten metal. In the early stage of casting before immersion under the surface, the oxygen concentration in the mold is set to an inert gas atmosphere or a reducing gas atmosphere of less than 2000 ppm to prevent slag and oxide inclusions generated in the early stage of casting from being involved. Characteristic continuous casting method of copper and copper alloy. (2) At the beginning of casting, from the start of casting until the immersion nozzle hole for supplying the molten metal into the mold is immersed below the surface of the molten metal, the surface of the molten metal poured into the mold is heated with a butane gas burner. The method according to claim 1, wherein the initial casting is performed in an atmosphere.

That is, when copper and a copper alloy are manufactured by continuous casting, the immersion nozzle hole is formed on the surface of the molten metal in order to suppress the amount of slag and oxide-based inclusions generated at the start of casting to prevent entrapment. It is necessary to reduce the oxygen concentration of the atmosphere in the mold until it is immersed below, but in order to economically and efficiently produce an ingot, it is necessary to define the oxygen concentration, and You need to be able to control it.

Accordingly, in order to prevent entrapment of slag and oxide-based inclusions generated at the start of casting, the immersion nozzle hole for supplying the molten metal into the mold from the start of casting until the immersion nozzle hole is immersed under the surface of the molten metal. Initiate casting in an atmosphere of an inert gas or reducing gas with an oxygen concentration of less than 2000 ppm, and heat the surface of the molten metal poured into the mold with a butane gas burner to start initial casting in an atmosphere of the flame. This makes it possible to produce a defect-free ingot of a copper alloy containing an active metal particularly among copper and copper alloys.

[0017]

Next, the significance of the requirements in the present invention will be described. The oxygen concentration in the mold is set to an inert gas atmosphere or a reducing gas atmosphere of less than 2000 ppm in the initial stage of casting from the start of casting to the dipping nozzle hole for supplying the melt into the mold under the surface of the melt.
The reason for setting it as less than ppm is that the oxygen concentration in the mold is 2000
If the content is not less than ppm, the frequency of generation of slag and oxide-based inclusions becomes extremely high, and the slag becomes coarse and surface defects become apparent.

As the inert gas, an oxygen content of 20
Ar, N _2, etc. of less than 00 ppm are exemplified. CO-Ar or the like can be used as the reducing gas.

The method of heating with a butane gas burner is a simple method of creating an atmosphere containing less oxygen in a mold by the flame of butane gas, which is a reducing gas.
Still other combustion gases can be used as long as the oxygen concentration is less than 2000 ppm.

[0020]

EXAMPLES The semi-continuous casting equipment was used to obtain the composition shown in Table 1.
The test was performed using a copper alloy obtained by adding Cr, Zr, Si and Mg to Cu alone or in a composite. The mold is 200 thick
mm and a width of 500 mm were used, and the atmosphere in the mold was adjusted with a flame heated with a gas of various oxygen concentrations or a butane gas burner from the start of casting, and a 2,000 kg ingot was cast at a casting speed of 100 mm / min. .

[0021]

[Table 1]

FIG. 1 is a schematic view when heating with a butane gas burner during casting. Since the molten metal (6) flowing out from the immersion nozzle hole easily entrains oxygen in the atmosphere, the flame (7) from the burner is blown so as to block the molten metal from oxygen in the atmosphere.

After the immersion nozzle hole is immersed below the surface of the molten metal, the supply of the inert gas or the heating with the combustion gas of butane is stopped while continuing the casting, and the surface of the molten metal is immediately covered with a casting flux. And continued casting.

After completion of casting, the surface of the ingot is inspected for surface cracks and casting surface by visual inspection and color check (penetration inspection), and the ingot is hot-rolled, surface-faced, and cold-rolled.
It was processed to a 2 mm thick strip and evaluated.

Tables 2 and 3 show evaluation results of ingots cast under various oxygen concentrations and atmospheres in molds. The material cast in the atmosphere of the mold of the present invention does not involve encrustation of the slag in the ingot, has excellent surface properties, and does not require a large amount of surface shaving even during processing in a subsequent processing step. With no problems such as surface defects, it has become possible to produce with high yield and efficiency. Compared to the present invention, in the method of the comparative example having a high oxygen concentration, the amount of facing after hot rolling is increased, or the amount of facing is usually, even when the slag is wound with a 2 mm thick strip. Surface defects considered to be caused by oxide-based inclusions occurred.

[0026]

[Table 2]

[0027]

[Table 3]

In this embodiment, the total amount of the additional elements is 0.5
Tests were performed on copper alloys having a mass percentage of 1.3 to 1.3 mass% (hereinafter referred to as%). The same effect can be obtained with pure copper-based copper having a total amount of additional elements of 0.1% or less. Needless to say.

[0029]

According to the present invention, not only when producing ingots of ordinary copper and copper alloys such as copper, brass and nickel silver by a continuous casting method, but also an active element having a strong affinity for oxygen to copper. When slag is added, slag and oxide-based inclusions are entrained in the ingot and the surface of the ingot does not deteriorate, and the surface of the ingot is not peeled before hot rolling. It can be manufactured.

[Brief description of the drawings]

FIG. 1 is a schematic diagram in which the surface of a molten metal poured into a mold is covered with a butane gas burner.

[Explanation of symbols]

 1: Tundish 2: Immersion nozzle 3: Immersion nozzle hole 4: Burner 5a, 5b: Mold 6: Dummy bar 7: Molten metal 8: Burner flame

Claims (2)

[Claims] In a continuous casting method or semi-continuous casting method of copper and a copper alloy which is vertically cast using a cylindrical mold which is opened up and down, an immersion nozzle hole for supplying molten metal into the mold from the start of casting. In the early stage of casting before immersion under the surface of the molten metal, the oxygen concentration in the mold is set to an inert gas atmosphere or a reducing gas atmosphere of less than 2000 ppm to prevent entrapment of slag and oxide inclusions generated in the early stage of casting. A continuous casting method of copper and a copper alloy, characterized in that: In the early stage of casting, from the start of casting until the immersion nozzle hole for supplying the molten metal into the mold is immersed below the surface of the molten metal,
The continuous casting method or semi-continuous casting of copper and copper alloy according to claim 1, wherein the surface of the molten metal poured into the mold is heated by a butane gas burner, and the initial casting is performed in an atmosphere of the burner flame. Method.