Refining Method

Abstract

A refining method comprising: a first step of obtaining a molten copper containing nickel as an impurity; a second step of contacting the molten copper with slag containing diphosphorus pentoxide; and a third step of removing the slag containing nickel from the molten copper.

Description

[Technical Field]

[0001] The present disclosure relates to a refining method and a refining apparatus. [Background technology]

[0002] Patent Document 1 discloses a copper refining method in which molten copper containing one or more metal elements selected from the group consisting of Sn, Pb, Ni, and Zn is brought into contact with slag containing SiO2 and FeO, and the metal elements are removed from the molten copper together with the slag. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-42162 Summary of the Invention

[0004] The refining method of the present disclosure includes a first step of obtaining molten copper containing nickel as an impurity, a second step of contacting the molten copper with slag containing diphosphorus pentoxide, and a third step of removing the slag containing nickel from the molten copper. [Brief explanation of the drawings]

[0005] [Figure 1] FIG. 1 is a schematic diagram illustrating an example of a refining method according to an embodiment. [Figure 2] FIG. 2 is a graph showing the change over time in the concentration of nickel in the molten metal measured in Test Example 1. [Figure 3] FIG. 3 is a graph showing the relationship between the phosphorus concentration in the molten metal and the oxygen concentration in the molten metal measured in Test Example 2. [Figure 4] FIG. 4 is a graph showing an enlarged portion of the graph of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0006] [Problem to be solved by this disclosure] In the copper refining method described in Patent Document 1, nickel (Ni) and lead (Pb) are more difficult to reduce from molten copper than tin (Sn) and zinc (Zn).

[0007] An object of the present disclosure is to provide a refining method that can easily reduce nickel, an impurity, from molten copper.

[0008] [Effects of this disclosure] The refining method of the present disclosure can easily reduce the impurity nickel from molten copper.

[0009] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described.

[0010] (1) A refining method according to an embodiment of the present disclosure includes a first step of obtaining molten copper containing nickel as an impurity, a second step of contacting the molten copper with slag containing diphosphorus pentoxide, and a third step of removing the slag containing nickel from the molten copper.

[0011] When molten copper containing nickel as an impurity is brought into contact with slag containing diphosphorus pentoxide, nickel is easily incorporated into the slag. By removing this nickel-containing slag from the molten copper, nickel can be easily reduced from the molten copper.

[0012] (2) In the refining method of (1) above, in the second step, the slag may be brought into contact with the molten metal so that the ratio of the mass of diphosphorus pentoxide to the mass of nickel in the molten metal is 1.5 or more and 700 or less.

[0013] If the mass ratio is 1.5 or more, nickel is easily incorporated into the slag. The higher the mass ratio, the greater the nickel reduction effect, but if the mass ratio is too high, copper is also easily incorporated into the slag. If the mass ratio is 700 or less, nickel can be reduced from the molten copper and copper loss can be reduced.

[0014] (3) In the refining method of (1) or (2) above, in the second step, an alloy containing copper and phosphorus and oxygen may be supplied to the molten metal.

[0015] When an alloy containing copper and phosphorus and oxygen are supplied to the molten metal, the alloy containing copper and phosphorus is oxidized to produce diphosphorus pentoxide. The production of diphosphorus pentoxide from the alloy containing copper and phosphorus results in a higher nickel reduction effect than when diphosphorus pentoxide is supplied to the molten metal. When oxygen is supplied to the molten metal, nickel oxide is produced. Nickel oxide is a basic oxide, and diphosphorus pentoxide is an acidic oxide. Nickel oxide and diphosphorus pentoxide are highly reactive. Therefore, nickel oxide reacts with diphosphorus pentoxide and is easily incorporated into the slag, improving the nickel reduction effect.

[0016] (4) In the refining method of (3) above, in the second step, the slag may be brought into contact with the molten metal so that the phosphorus concentration in the molten metal is 500 ppm by mass or less and the oxygen concentration in the molten metal is 300 ppm by mass or more.

[0017] If the phosphorus concentration in the molten metal is too high, nickel oxide is difficult to generate, and the nickel reduction effect is likely to decrease. If the phosphorus concentration in the molten metal is 500 ppm by mass or less and the oxygen concentration in the molten metal is 300 ppm by mass or more, both nickel oxide and diphosphorus pentoxide are likely to be generated, and the nickel reduction effect is high.

[0018] (5) In the refining method of (3) or (4) above, in the second step, air may be supplied into the molten metal by bubbling.

[0019] By bubbling air into the molten metal, the molten metal can be agitated, which makes it easier to produce both nickel oxide and diphosphorus pentoxide.

[0020] (6) In the refining method of (3) or (4) above, copper oxide or copper with an oxidized surface may be supplied to the molten metal in the second step.

[0021] By supplying copper oxide or copper with an oxidized surface to the molten metal, both nickel oxide and diphosphorus pentoxide can be produced, and even if copper from the molten metal is absorbed into the slag, the loss of copper can be compensated for.

[0022] (7) In any of the refining methods (1) to (6) above, the material of the furnace for storing the molten metal may contain at least one of aluminum oxide, magnesium oxide, chromium oxide, and silicon oxide.

[0023] Depending on the material of the furnace, oxygen supplied to the molten metal may react with the material of the furnace. If the furnace is made of the materials listed above, the oxygen supplied to the molten metal in the furnace is less likely to react with the material of the furnace, and both nickel oxide and diphosphorus pentoxide are likely to be produced.

[0024] (8) A refining apparatus according to an embodiment of the present disclosure includes a furnace for storing molten copper, a supply unit for supplying slag into the molten copper, and a first supply unit for supplying oxygen and a second supply unit for supplying an alloy containing copper and phosphorus.

[0025] When oxygen is supplied into the molten metal by the first supply unit and an alloy containing copper and phosphorus is supplied into the molten metal by the second supply unit, the alloy containing copper and phosphorus is oxidized in the molten metal to produce diphosphorus pentoxide. The production of diphosphorus pentoxide from the alloy containing copper and phosphorus results in a higher nickel reduction effect than when diphosphorus pentoxide is supplied to the molten metal. When oxygen is supplied into the molten metal, nickel oxide is produced. Nickel oxide is a basic oxide, and diphosphorus pentoxide is an acidic oxide. Nickel oxide and diphosphorus pentoxide are highly reactive. Therefore, nickel oxide reacts with diphosphorus pentoxide and is easily incorporated into the slag, improving the nickel reduction effect.

[0026] (9) In the refining apparatus of (8) above, the material of the furnace may contain at least one of aluminum oxide, magnesium oxide, chromium oxide, and silicon oxide.

[0027] Depending on the material of the furnace, oxygen supplied to the molten metal may react with the material of the furnace. If the furnace is made of the materials listed above, the oxygen supplied to the molten metal in the furnace is less likely to react with the material of the furnace, and both nickel oxide and diphosphorus pentoxide are likely to be produced.

[0028] [Details of the embodiments of the present disclosure] Specific examples of the refining method and refining apparatus of the present disclosure will be described with reference to the drawings. The same reference numerals in the drawings indicate the same or equivalent parts. In each drawing, for the convenience of explanation, some of the components may be exaggerated or simplified. The dimensional ratios of each part in the drawings may also differ from the actual ratios. Note that the present invention is not limited to these examples, but is defined by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0029] <Summary> A refining method and a refining apparatus according to an embodiment will be described with reference to Fig. 1. In the refining method according to the embodiment, as shown in the middle diagram of Fig. 1, molten metal 2 is brought into contact with slag 3, impurities in the molten metal 2 are incorporated into the slag 3, and the impurities are removed from the molten metal 2 together with the slag 3 as shown in the bottom diagram of Fig. 1, thereby reducing the concentration of impurities in the molten metal 2. The molten metal 2 is a copper molten metal and contains nickel 4 as an impurity.

[0030] The refining method of the embodiment includes a first step of obtaining a molten copper metal 2 containing nickel 4 as an impurity, a second step of bringing slag 3 into contact with the molten metal 2, and a third step of removing the slag 3 containing nickel 4 from the molten metal 2. One of the features of the refining method of the embodiment is that the slag 3 contains diphosphorus pentoxide 7. In the embodiment, a Cu-P alloy 5 and oxygen 6 are supplied to the molten metal 2, and diphosphorus pentoxide 7 is generated in the molten metal 2. The Cu-P alloy 5 is an alloy containing copper and phosphorus. When oxygen 6 is supplied to the molten metal 2, nickel oxide 8 and copper oxide 9 are generated in the molten metal 2.

[0031] In each figure, for ease of understanding, nickel 4, Cu-P alloy 5, oxygen 6, diphosphorus pentoxide 7, nickel oxide 8, and copper oxide 9 are shown as circles.

[0032] <Refining Device> The refining apparatus 1 includes a furnace 11 and a supply unit 12. The furnace 11 stores a molten copper metal 2. The material of the furnace 11 contains at least one of aluminum oxide, magnesium oxide, chromium oxide, and silicon oxide, for example. Depending on the material of the furnace 11, oxygen 6 supplied to the molten metal 2 may react with the constituent materials of the furnace 11. If the oxygen 6 supplied to the molten metal 2 reacts with the constituent materials of the furnace 11, the amount of oxygen 6 that reacts with the Cu-P alloy 5 or nickel 4 decreases, and diphosphorus pentoxide 7 and nickel oxide 8 are less likely to be produced. If the furnace 11 is made of the materials listed above, the oxygen 6 supplied to the molten metal 2 is less likely to react with the constituent materials of the furnace 11, and both diphosphorus pentoxide 7 and nickel oxide 8 are more likely to be produced.

[0033] The supply unit 12 in this example includes a first supply unit 13 and a second supply unit 14. The first supply unit 13 supplies oxygen 6. The first supply unit 13 includes, for example, piping that is resistant to the molten metal 2. The piping is made of, for example, aluminum oxide, magnesium oxide, chromium oxide, silicon oxide, silicon carbide, or stainless steel. The tip of the piping is immersed in the molten metal 2. The piping is arranged, for example, to supply oxygen 6 below the molten metal 2. The first supply unit 13, which is made of piping, is configured, for example, to supply air into the molten metal 2 by bubbling. The second supply unit 14 supplies the Cu-P alloy 5. The Cu-P alloy 5 is supplied, for example, in the form of a shot or a plate. The second supply unit 14 is, for example, a bag that contains the Cu-P alloy 5. The Cu-P alloy 5 contained in the bag is dropped into the molten metal 2 from above the molten metal 2 by, for example, a forklift.

[0034] The first supply unit 13 may be a bag containing copper oxide. Oxygen is supplied into the molten metal 2 by supplying the copper oxide. The copper oxide is contained in a bag and is then poured into the molten metal 2 from above using, for example, a forklift. In this case, the first supply unit 13 and the second supply unit 14 may be independent of each other, and the copper oxide and the Cu-P alloy 5 may be separately poured into the molten metal 2. Alternatively, the first supply unit 13 and the second supply unit 14 may be configured as a single supply unit, and the copper oxide and the Cu-P alloy 5 may be contained in the same bag, and the copper oxide and the Cu-P alloy 5 may be simultaneously poured into the molten metal 2. Copper with an oxidized surface may be supplied instead of copper oxide. Alternatively, both copper oxide and copper with an oxidized surface may be supplied.

[0035] <Refining method> In the first step, a copper molten metal 2 containing nickel 4 as an impurity is obtained. The molten metal 2 contains, for example, copper material that has been used once, i.e., copper scrap, in a melted state. At least a portion of the raw material for the molten metal 2 may contain copper scrap, or all of the raw material for the molten metal 2 may be copper scrap. Copper scrap tends to contain a large amount of impurities such as nickel 4.

[0036] In the second step, as shown in the middle diagram of Figure 1, molten metal 2 is brought into contact with slag 3 containing diphosphorus pentoxide 7. In the second step of this example, as shown in the top diagram of Figure 1, oxygen 6 is supplied to molten metal 2 by a first supply unit 13, and Cu-P alloy 5 is supplied to molten metal 2 by a second supply unit 14. When Cu-P alloy 5 and oxygen 6 are supplied to molten metal 2, Cu-P alloy 5 is oxidized in molten metal 2 to produce diphosphorus pentoxide 7.

[0037] When oxygen 6 is supplied to the molten metal 2, nickel oxide 8 is produced. Nickel oxide 8 is a basic oxide, and diphosphorus pentoxide 7 is an acidic oxide. Nickel oxide 8 and diphosphorus pentoxide 7 are highly reactive. Therefore, nickel oxide 8 reacts with diphosphorus pentoxide 7 and is incorporated into slag 3.

[0038] When oxygen 6 is supplied to the molten metal 2, copper oxide 9 is also produced. The copper oxide 9 is produced from the copper or Cu-P alloy 5 in the molten metal 2. The copper oxide 9 is also captured in the slag 3. As shown in the lower diagram of Figure 1, the slag 3 contains diphosphorus pentoxide 7, nickel oxide 8, and copper oxide 9.

[0039] In the second step, oxygen 6 is supplied by, for example, bubbling air into the molten metal 2. By bubbling air into the molten metal 2, the molten metal 2 can be stirred, which makes it easier to produce both diphosphorus pentoxide 7 and nickel oxide 8. The bubbling air may be oxygen-enriched air. In the second step, the Cu-P alloy 5 is supplied in a state in which oxygen 6 has been supplied by, for example, bubbling air into the molten metal 2.

[0040] In the second step, for example, the molten metal 2 is brought into contact with the slag 3 so that the mass ratio of diphosphorus pentoxide 7 to the mass of nickel 4 in the molten metal 2 is 1.5 or more and 700 or less. If this mass ratio is 1.5 or more, nickel oxide 8 is easily incorporated into the slag 3, and the nickel 4 removal effect is high. The higher this mass ratio, the greater the nickel 4 reduction effect; however, if this mass ratio is too high, copper oxide 9 generated from the copper in the molten metal 2 is easily incorporated into the slag 3. If this mass ratio is 700 or less, nickel 4 can be reduced from the molten metal 2 and copper loss from the molten metal 2 can be reduced. The mass ratio of diphosphorus pentoxide 7 to the mass of nickel 4 in the molten metal 2 may be 2.0 or more and 650 or less, 3.0 or more and 600 or less, or 4.0 or more and 550 or less.

[0041] In the second step, for example, the molten metal 2 is brought into contact with the slag 3 so that the phosphorus concentration in the molten metal 2 is 500 ppm by mass or less and the oxygen 6 concentration in the molten metal 2 is 300 ppm by mass or more. If the phosphorus concentration in the molten metal 2 is too high, the oxygen 6 is consumed in the production of diphosphorus pentoxide 7, making it difficult to produce nickel oxide 8, and the effect of reducing nickel 4 may be reduced. If the phosphorus concentration in the molten metal 2 is 500 ppm by mass or less and the oxygen 6 concentration in the molten metal 2 is 300 ppm by mass or more, both diphosphorus pentoxide 7 and nickel oxide 8 are easily produced, and the effect of reducing nickel 4 is high.

[0042] The phosphorus concentration in the molten metal 2 is, for example, 0.1 ppm by mass or more. The phosphorus concentration in the molten metal 2 is, for example, 0.1 ppm by mass or more and 500 ppm by mass or less. If the phosphorus concentration in the molten metal 2 is within the above range, both diphosphorus pentoxide 7 and nickel oxide 8 are likely to be produced. The phosphorus concentration in the molten metal 2 may be 0.5 ppm by mass or more and 450 ppm by mass or less, or 1.0 ppm by mass or more and 400 ppm by mass or less.

[0043] The concentration of oxygen 6 in the molten metal 2 is, for example, 50,000 ppm by mass or less. If the concentration of oxygen 6 in the molten metal 2 is too high, the copper in the molten metal 2 becomes copper oxide 9 and is easily taken up into the slag 3. If the concentration of oxygen 6 in the molten metal 2 is 50,000 ppm by mass or less, copper loss in the molten metal 2 can be reduced. The concentration of oxygen 6 in the molten metal 2 is, for example, 300 ppm by mass or more and 50,000 ppm by mass or less. The concentration of oxygen 6 in the molten metal 2 may also be 500 ppm by mass or more and 35,000 ppm by mass or less, or 700 ppm by mass or more and 20,000 ppm by mass or less.

[0044] In the second step, diphosphorus pentoxide 7 may be supplied into the molten metal 2 instead of the Cu-P alloy 5. In the second step, both the Cu-P alloy 5 and diphosphorus pentoxide 7 may be supplied into the molten metal 2. However, because the sublimation point of diphosphorus pentoxide 7 is 360°C, supplying diphosphorus pentoxide 7 into the molten metal 2 may cause diphosphorus pentoxide 7 to sublimate before nickel oxide 8 is incorporated into the slag 3. Therefore, supplying the Cu-P alloy 5 and oxygen 6 to generate diphosphorus pentoxide 7 in the molten metal 2 is more effective than supplying diphosphorus pentoxide 7 into the molten metal 2, as this allows nickel oxide 8 to be more easily incorporated into the slag 3 before diphosphorus pentoxide 7 sublimes, resulting in a greater nickel reduction effect.

[0045] In the second step, instead of supplying oxygen 6 by bubbling air into the molten metal 2, copper oxide or copper with an oxidized surface may be supplied into the molten metal 2. In the second step, copper oxide or copper with an oxidized surface may be supplied into the molten metal 2 while supplying oxygen 6 by bubbling air into the molten metal 2. By supplying copper oxide or copper with an oxidized surface into the molten metal 2, both nickel oxide 8 and diphosphorus pentoxide 7 can be produced, and even if copper from the molten metal 2 is taken up into the slag 3, the loss of that copper can be compensated for.

[0046] In the second step, copper oxide and copper phosphide may be supplied to the molten metal 2. The copper oxide and copper phosphide supplied to the molten metal 2 react with each other to produce diphosphorus pentoxide.

[0047] In the third step, as shown in the lower diagram of Figure 1, slag 3 containing nickel 4 is removed from molten metal 2. Slag 3 containing diphosphorus pentoxide 7, nickel oxide 8, and copper oxide 9 floats to the surface of molten metal 2. By removing this floating slag 3, the nickel 4 content in molten metal 2 can be reduced.

[0048] [Test Example 1] In Test Example 1, the nickel concentration in molten copper containing nickel as an impurity was measured over time when slag was brought into contact with the molten copper. The nickel concentration in the molten copper was measured using ICP (Inductively Coupled Plasma) atomic emission spectroscopy. In this example, measurements were taken on Test Specimen A, which used slag containing diphosphorus pentoxide, and Test Specimen B, which used slag containing silicon dioxide (SiO2) and iron oxide (FeO). The results are shown in Figure 2. In the graph shown in Figure 2, the horizontal axis represents time and the vertical axis represents the nickel concentration in the molten copper. In the graph shown in Figure 2, the results for Test Specimen A are indicated by black circles, and the results for Test Specimen B are indicated by black triangles.

[0049] For both specimen A and specimen B, the furnace was made of aluminum oxide.

[0050] <Test specimen A> For test specimen A, oxygen was supplied by bubbling air into the molten metal, and then an alloy containing copper and phosphorus (Cu-P alloy) was introduced, generating diphosphorus pentoxide in the molten metal. The nickel concentration in the molten metal was approximately 680 ppm at the start of the test. Air was blown into the molten metal at a flow rate of 300 cc / min. The oxygen concentration in the molten metal was gradually increased from the start of the test, and 87 g of Cu-P alloy was introduced into the molten metal at time A1. As shown in Figure 2, the introduction of Cu-P alloy into the molten metal at time A1 reduced the nickel concentration in the molten metal to below 200 ppm. Nickel oxide was generated by the introduction of oxygen, and diphosphorus pentoxide was generated by the introduction of Cu-P alloy. The nickel oxide reacted with diphosphorus pentoxide and was incorporated into the slag, which is thought to have reduced the nickel concentration in the molten metal.

[0051] As shown in Figure 2, gradually increasing the oxygen concentration in the molten metal after adding the Cu-P alloy resulted in a slight increase in the nickel concentration in the molten metal. Therefore, 87 g of Cu-P alloy was added to the molten metal at time A2. Adding the Cu-P alloy caused a slight decrease in the nickel concentration in the molten metal. However, the rate of decrease was smaller than the rate of decrease in the nickel concentration in the molten metal caused by adding the Cu-P alloy at time A1. The reason the rate of decrease in the nickel concentration in the molten metal caused by adding the Cu-P alloy at time A2 was small is thought to be because the phosphorus concentration in the molten metal became too high, so oxygen was consumed in the production of diphosphorus pentoxide, making it difficult to produce nickel oxide.

[0052] For specimen A, the equilibrium Ni distribution ratio resulting from supplying Cu-P alloy at time A1 was 211. The equilibrium Ni distribution ratio is an index of the ability to reduce nickel from the molten metal, and is the ratio of the nickel concentration in the slag to the nickel concentration in the molten metal. The higher the equilibrium Ni distribution ratio, the higher the ability to reduce nickel from the molten metal. The method for calculating the equilibrium Ni distribution ratio will be described later.

[0053] <Test specimen B> For test specimen B, oxygen was supplied by bubbling air into the molten metal, and slag containing SiO2 and FeO was added. The nickel concentration in the molten metal was approximately 970 ppm at the start of the test. Air was blown into the molten metal at a flow rate of 300 cc / min. The oxygen concentration in the molten metal was gradually increased from the start of the test, and at time B1, 25 g of the above slag was added to the molten metal. As shown in Figure 2, adding the above slag to the molten metal at time B1 reduced the nickel concentration in the molten metal to below 750 ppm. The equilibrium Ni distribution ratio at this time was 23. At time B2, 75 g of the above slag was added to the molten metal. Although the addition of the above slag reduced the nickel concentration in the molten metal, it was not able to reduce it below 400 ppm.

[0054] <Calculation method for equilibrium Ni distribution ratio> The equilibrium Ni distribution ratio is calculated by the following formula: L Ni =(1 / B)×{A×(β / α) 1 / n -A'} The notation for the above formula is as follows: L Ni is the equilibrium Ni distribution ratio. A is the weight of the molten metal at the start of refining. A' is the weight of the molten metal after a specified time has elapsed since the start of refining. B is the weight of the slag. The weight of the slag in the above formula is the weight of the slag excluding nickel oxide and copper oxide. Although slag contains nickel oxide and copper oxide, the weights of nickel oxide and copper oxide are ignored in the above formula. For specimen A, the weight of the slag in the above formula is the weight of diphosphorus pentoxide. For specimen B, the weight of the slag in the above formula is the combined weight of SiO2 and FeO. α is the nickel concentration in the molten metal after a specified time has elapsed since the start of refining. β is the nickel concentration in the molten metal at the start of refining. n is the number of times that one set of slag generation, impurity absorption, and slag removal is performed. A, A', and B are in kg. α and β are in ppm by mass.

[0055] [Test Example 2] In Test Example 2, specimens were prepared using Test Example 1, with the ratio of the mass of diphosphorus pentoxide to the mass of nickel in the molten metal varied from 1.5 to 700. The phosphorus and oxygen concentrations in the molten metal were varied, and the equilibrium Ni distribution ratio was determined. The phosphorus concentration in the molten metal was measured using ICP atomic emission spectroscopy. The oxygen concentration in the molten metal was measured using inert gas fusion-infrared absorption spectroscopy. The results are shown in Figures 3 and 4. The graph in Figure 4 shows an enlarged view of the region near the origin of the graph in Figure 3. In Figures 3 and 4, the horizontal axis represents the phosphorus concentration in the molten metal, and the vertical axis represents the oxygen concentration in the molten metal. In Figures 3 and 4, specimens with an equilibrium Ni distribution ratio of 23 or greater are indicated by black circles, and specimens with an equilibrium Ni distribution ratio of less than 23 are indicated by black triangles.

[0056] As shown in Figures 3 and 4, all of the test specimens with an equilibrium Ni distribution ratio of 23 or higher had a phosphorus concentration in the molten metal of 500 ppm by mass or less and an oxygen concentration in the molten metal of 300 ppm by mass or more. When the phosphorus concentration in the molten metal is 500 ppm by mass or less and the oxygen concentration in the molten metal is 300 ppm by mass or more, both nickel oxide and diphosphorus pentoxide are likely to be produced, and nickel oxide reacts with diphosphorus pentoxide and is incorporated into the slag, which is thought to have increased the nickel concentration in the slag and decreased the nickel concentration in the molten metal.

[0057] [Test Example 3] In Test Example 3, the oxygen concentration in the molten metal, the phosphorus concentration in the molten metal, and the equilibrium Ni distribution ratio were measured for Test Example A in Test Example 1, with the furnace material used changing. The results are shown in Table 1. In this example, Test Example α, whose furnace was made of aluminum oxide, and Test Examples β and γ, whose furnaces were made of graphite, were used. In Table 1, aluminum oxide is referred to as "alumina."

[0058] In this example, the oxygen concentration in the molten metal was measured at the start of the test and a predetermined time after the Cu-P alloy was added. The phosphorus concentration in the molten metal was measured a predetermined time after the Cu-P alloy was added. The phosphorus concentration in the molten metal at the start of the test is an estimated value. In Table 1, the value at the start of the test is referred to as the initial value, and the value a predetermined time after the Cu-P alloy was added is referred to as the equilibrium value.

[0059] [Table 1]

[0060] As shown in Table 1, in specimen α, whose furnace was made of aluminum oxide, both the oxygen and phosphorus concentrations in the molten metal decreased after the Cu-P alloy was added, and the equilibrium Ni distribution ratio was 51. Because the furnace was made of aluminum oxide, it is thought that the oxygen supplied to the molten metal was consumed in reactions with the Cu-P alloy or nickel without reacting with the furnace materials. In other words, in specimen α, both nickel oxide and diphosphorus pentoxide were easily produced, and nickel oxide reacted with diphosphorus pentoxide and was absorbed into the slag, which is thought to have increased the nickel concentration in the slag and decreased the nickel concentration in the molten metal.

[0061] In specimens β and γ, which had graphite furnaces, the oxygen concentration in the molten metal decreased after the Cu-P alloy was added, but the phosphorus concentration in the molten metal did not decrease significantly, and the equilibrium Ni distribution ratio was less than 23. Because the furnace was made of graphite, the oxygen supplied to the molten metal reacted easily with the furnace's constituent materials and was presumably consumed in reaction with the furnace rather than with the Cu-P alloy or nickel. Therefore, in specimens β and γ, which had graphite furnaces, the equilibrium Ni distribution ratio was low at less than 23. [Explanation of symbols]

[0062] 1. Refining equipment 11 Furnace 12 Supply section 13 First Supply Department 14 Second supply section 2 Molten metal 3. Slug 4 nickel 5 Cu-P alloy 6. Oxygen 7. Diphosphorus pentoxide 8 Nickel Oxide 9. Copper Oxide

Claims

1. A first step of obtaining a molten copper containing nickel as an impurity; a second step of contacting the molten metal with slag containing diphosphorus pentoxide; and a third step of removing the slag containing the nickel from the molten metal, In the second step, an alloy containing copper and phosphorus and oxygen are supplied to the molten metal, and the slag is brought into contact with the molten metal so that the phosphorus concentration in the molten metal is 500 ppm by mass or less, the oxygen concentration in the molten metal is 300 ppm by mass or more, and the ratio of the mass of the diphosphorus pentoxide to the mass of the nickel in the molten metal is 1.5 or more and 700 or less. Refining method.

2. The refining method according to claim 1, wherein in the second step, air is supplied into the molten metal by bubbling.

3. 3. The refining method according to claim 1, wherein copper oxide or copper having an oxidized surface is supplied to the molten metal in the second step.

4. 3. The refining method according to claim 1, wherein the material of the furnace for storing the molten metal contains at least one of aluminum oxide, magnesium oxide, chromium oxide, and silicon oxide.

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