JP2002356723A - Method for dissolving and dehydrogenating copper scrap alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for dissolving a copper scrap alloy by which, on dissolution of a copper scrap alloy, hydrogen in a molten metal can rapidly be removed as possible. SOLUTION: In the copper scrap alloy adhered with emulsion, rolling oil, or lubricating oil, a metallic reducing agent such as Mg, Si, Zr, Ti and Al is contained by >=20 wt.%. This alloy is subjected to reducing dissolution and then, the surface of the molten metal is coated with charcoal only for preventing reoxidation. Next, bubbling by an inert gas such as gaseous Ar is performed to control the concentration of hydrogen to <=3 ppm, so that casting defects such as splitting and blistering are prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for melting a scrap copper alloy, and more particularly, to a method for melting a scrap copper alloy capable of removing hydrogen in a molten metal as quickly as possible when melting the scrap copper alloy. It is about.

[0002]

2. Description of the Related Art Copper alloys have excellent heat conductivity and conductivity as well as very good corrosion resistance and workability. Widely used. However, copper has low reserves of raw material ores compared to steel materials and is expensive, and therefore, from the viewpoint of resource protection, the recovery and reuse of scrap is an important issue. Particularly in recent years, high-performance materials to which active metal elements have been added as copper alloys for electric and electronic use have come to be used in large quantities, but even in these high-performance copper alloys, it is inevitable to collect and reuse scrap. It is an issue.

[0003] However, a large amount of emulsion or rolling oil is attached to scraps generally produced during the production of such high-performance copper alloys, and these copper alloys are used when processing into various electric and electronic parts. A large amount of lubricating oil and the like adheres to the scrap generated in the above. It is not possible to re-dissolve these scraps with a large amount of emulsion, rolling oil, and lubricating oil as they are. If these scraps are used as the raw material for melting, 5 wt% of the total molten metal in the melting furnace is used. Failure to do so would result in significant defects to the product.

[0004]

In order to improve the quality of copper alloy products, it is necessary to minimize impurity inclusions in the raw material melting stage. Things. In particular, in the dissolution of a high-performance copper alloy to which an active metal element is added, when the oxygen concentration in the molten metal is high, the added element is oxidized to become inclusions, so deoxidation of the molten metal, that is, reduction melting is indispensable in advance. .

[0005] This reduction dissolution is a method in which Mg, Si, Zr, Ti, Al, charcoal and the like are added to the molten metal as a solid reducing agent, whereby the oxygen concentration in the molten metal is reduced to clean the molten metal. However, suspension of oxides generated during the deoxidation of the reduction dissolution in the molten metal is also one of the factors that cause inclusions to remain in the copper alloy product.

An active metal is used as an additive element in a high-performance copper alloy, and the inventor of the present invention has found that when a large amount of scrap of such a high-performance copper alloy is used as a melting raw material, the oxygen in the molten metal immediately after melting is dropped. The concentration can be quite low,
The inventors invented that the above-mentioned reduction dissolution can be omitted.

However, when the above-mentioned emulsion, rolling oil or scrap containing a large amount of lubricating oil is used as a raw material, there is a problem that the hydrogen concentration in the molten metal after melting increases. Of the defects found in copper alloy products, hydrogen is considered to be the main cause of gas-related defects such as pinholes, blowholes, and blisters.To avoid these defects, lower the hydrogen concentration in the molten metal. There is a need to.

In view of the above-mentioned problems relating to the dissolution of conventional copper alloys, the present inventors have conducted intensive studies and conducted extensive studies. As a result, a large amount of copper alloys was produced by relatively simple means. We developed a method to use it.

That is, the present invention relates to a scrap copper alloy to which an emulsion, a rolling oil, a lubricating oil, or the like has adhered, wherein Mg, Si, Z
20% by weight or more of scrap copper alloy containing a metallic reducing agent such as r, Ti, Al, etc., is reduced and melted, and after melting, the surface of the molten metal is coated with charcoal only to prevent re-oxidation. Bubbling with active gas is performed to reduce the hydrogen concentration to 3
Provided is a method for dehydrogenating scrap copper alloy, which prevents casting defects such as scabs and blisters by controlling the content to less than ppm.

According to a second aspect of the present invention, in the method for dehydrogenating scrap copper alloy, the scrap copper alloy is a C7025 alloy to which an emulsion, rolling oil, lubricating oil or the like is attached. Is the law.

The method for dissolving scrap copper alloy according to the present invention will be described in detail below. Active metal element Mg,
In the case where pure copper yarn scrap is melted at 100 wt% without using scrap copper alloy containing Si, Zr, Ti, Al, etc., the oxygen concentration in the molten metal increases to about 2000 ppm, and in order to lower the oxygen concentration in the molten metal, Reductive dissolution is essential. By the way, in the most frequently used charcoal addition, even after 90 minutes from the addition, the oxygen concentration is about 1000 ppm. For this reason, addition of solid reducing agents such as Mg, Si, Zr, Ti, and Al cannot be avoided. By these additions, the oxygen concentration in the molten metal is reduced to 50 ppm or less, where the subsequent addition of alloying components is allowed. However, the oxide generated during the reduction melting is suspended in the molten metal and cast as it is, so that the product However, it remains in the form of oxide-based inclusions, and causes surface defects such as soot and the like generated in the subsequent processing step.

On the other hand, the method for dissolving scrap copper alloy according to the present invention uses the active metal elements Mg, Si, Zr,
The scrap copper alloy containing Ti, Al, etc. is melted to 20 w
By blending and dissolving so as to contain at least t%,
XCu2O in lysis + yM → 2xCu + MyOx: occur reaction (M active metal element) x O + yM → MyOx, the oxygen concentration in the melt immediately after burn through 50p
pm or less, and does not require the above-mentioned reductive dissolution at all. Thereafter, the surface is protected by a coating material such as charcoal in order to shield the surface of the molten metal from the atmosphere.

Some of the melts melted by such a melting method have a high hydrogen concentration in the melt and reach a high concentration of 6 ppm. According to the investigation by the present inventors, when such a high concentration of hydrogen is contained, a serious surface defect called blister is necessarily generated in a later processing step. Investigation of the relationship between this blister and the hydrogen concentration in the molten metal revealed that if the hydrogen concentration in the molten metal was reduced to 3 ppm or less, blisters would not be generated in the subsequent processing steps.

Therefore, an inert gas such as Ar gas is blown into the molten metal having a low oxygen concentration obtained by the above-described melting method, and hydrogen in the molten metal is taken into the inert gas bubbles by utilizing a partial pressure difference. This is to reduce the amount of hydrogen in the molten metal by releasing an inert gas containing hydrogen into the atmosphere or the atmosphere.

According to the melting method of the present invention, it is possible to obtain a molten metal having a low oxygen concentration, omit the reductive melting, facilitate the subsequent addition of alloy components, and prevent surface defects such as blisters and scabs in the subsequent steps.

[0016]

EXAMPLE 1 Only the scrap containing an active metal element to which a large amount of emulsion, rolling oil and lubricating oil adhered was used as a raw material, and the gas concentration in the molten metal was examined. After melting, dehydrogenation was performed by blowing Ar gas. [Procedure] Raw material (10 Ton) → melting in crucible furnace (1200 ± 30 ° C)
→ Sampling for gas analysis → Charcoal addition (40 kg) → Injection of Ar gas for a predetermined time → Component adjustment (C7025) → Sampling for gas analysis → Casting → Rolling to product thickness → Surface inspection [Ar injection conditions] Ar flow rate 20000Nl / hr

Table 1 shows the results of the investigation in Example 1. Further, Table 1 also shows the investigation results of Comparative Example 1 and Comparative Example 2. Table 2 shows changes over time in the oxygen concentration in the molten metal of Comparative Example 1.

[Table 1] (Note) Scraps containing active metal elements with a large amount of emulsion, rolling oil and lubricating oil attached.

No. In all of the raw materials 4 to 7, emulsions, rolling oils and lubricating oils with a large amount of
Since 0 wt% was used, the oxygen concentration in the molten metal immediately after melting was 50 ppm or less, and no reductive dissolution was required. Since the hydrogen concentration in the molten metal immediately after the meltdown exceeded 3 ppm, dehydrogenation treatment was required. No. 4, no. 5
No. for 120 minutes. 6, no. 7 is A for 60 minutes
r gas was blown. After the Ar injection, the hydrogen concentration in the molten metal was less than 3 ppm, and no blisters were generated in the products. Also, no shavings were generated on the product surface.

[0019]

Comparative Example 1 Pure copper yarn waste containing no active metal element and having no emulsion, rolling oil, or lubricating oil attached was used as a raw material, and the gas concentration in the molten metal was examined. With respect to the oxygen concentration in the molten metal, the change over time due to reduction and dissolution was examined. [Procedure] Raw material (10 Ton) → melting in crucible furnace (1200 ± 30 ° C)
→ Sampling for gas analysis → Charcoal addition (40kg) → 3
Sample collection for gas analysis after 0 minutes → Sample collection for gas analysis after 60 minutes → Addition of active metal → Component adjustment (C702
5) → sampling for gas analysis → casting → rolling to product thickness → surface inspection

No. In No. 1, since only pure copper waste was melted, the oxygen concentration in the molten metal immediately after the melting exceeded 2000 ppm, and reduction and dissolution were indispensable to lower the oxygen concentration in the molten metal. Even after 90 minutes from the addition of the charcoal most frequently used as a solid reducing agent, the oxygen concentration exceeded 1000 ppm. Thereafter, reduction and dissolution by addition of an active metal element were performed, so that the oxygen concentration immediately before casting was reduced to 4 ppm, but sodging was generated on the product surface due to turbidity of the oxide generated by the reduction and dissolution. The hydrogen concentration in the molten metal immediately after melting was lower than 3 ppm, and no blistering occurred on the product surface without performing the dehydrogenation treatment.

[0021]

[Table 2] Comparative Example 1

[0022]

Comparative Example 2 Scraps containing an active metal element to which a large amount of emulsion, rolling oil, and lubricating oil adhered were used as a part of raw materials, and the gas concentration in the molten metal was examined. [Procedure] Raw material (10 Ton) → melting in crucible furnace (1200 ± 30 ° C)
→ Sampling for gas analysis → Charcoal addition (40 kg) → Component adjustment (C7025) → Sampling for gas analysis → Casting → Rolling to product thickness → Surface inspection

No. 2, No. In all of the raw materials of No. 3, scrap containing a large amount of emulsion, rolling oil and lubricating oil was used in an amount of 30 wt% based on the total amount of molten metal in the melting furnace. I didn't need it. The hydrogen concentration in the molten metal immediately after the meltdown exceeded 3 ppm in all cases, and no swelling was generated on the product surface, but blisters were generated.

[0024]

As described above, according to the present invention, scrap containing an active metal element is used as a raw material. (1) Since deoxidation is completed during dissolution, reduction dissolution is unnecessary, and No suspension of oxides due to the addition of the active metal element and sodging caused by the suspension are not generated.

(2) After the melt-down, dehydrogenation is performed by blowing an inert gas to prevent blisters on the product surface. (3) According to the present invention, a scrap to which a large amount of emulsion, rolling oil, or lubricating oil has adhered can be used without limitation without causing casting defects such as shavings and blisters in the product.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroyuki Nishida 3rd Kurami, Samukawa-cho, Koza-gun, Kanagawa Prefecture F-term in Nippon Mining & Metals Co., Ltd. Kurami Factory 4K001 AA09 BA22 EA03 EA04 HA01 HA02

Claims (2)

[Claims] 1. A scrap copper alloy to which an emulsion, rolling oil, lubricating oil or the like has adhered, wherein a scrap copper alloy containing a metallic reducing agent such as Mg, Si, Zr, Ti, or Al is contained in an amount of 20 wt% or more. After reducing and dissolving, the surface of the molten metal is coated with charcoal only to prevent re-oxidation, and then bubbling with an inert gas such as Ar gas is performed to reduce the hydrogen concentration to 3 ppm or less to reduce casting defects such as soges and blisters. A dehydrogenation method for scrap copper alloys, characterized by preventing the occurrence of waste. 2. The method for dehydrogenating scrap copper alloy according to claim 1, wherein said scrap copper alloy is a C7025 alloy to which an emulsion, rolling oil, lubricating oil or the like has adhered. Dehydrogenation method.