A method for preparing copper ingot

Abstract

The invention discloses a method for preparing a copper ingot, which is characterized by comprising the following preparation steps: 1) raw material preparation: including pure electrolytic plates; 2) smelting: the smelting temperature is 1200-1250°C, charcoal is used for covering during the melting process, the covering thickness is 3-10cm, and the copper is transferred to a holding furnace after being completely melted; 3) covering and oxygenating: after the converter, the charcoal and oxidized slag on the surface of the copper water are removed, and a covering agent is used for covering, the covering thickness is 5-15cm, the temperature of the holding furnace is adjusted to 1150-1250°C, and a mixed gas is introduced from the bottom of the holding furnace, wherein the volume ratio of oxygen in the mixed gas is 30-80%. By introducing a mixed gas with oxygen into the bottom of the holding furnace, impurities in the copper water can be quickly oxidized and the impurities can be attracted to float up by inert gas, and then oxygenating is performed by adding copper oxide, so that the oxygen content of the copper water can be accurately controlled to 200-400ppm, and the deviation of the oxygen content at the head and tail of the ingot does not exceed 20ppm.

Description

Technical Field

[0001] The invention belongs to the technical field of copper alloys, and in particular relates to a method for preparing a red copper ingot. Background Art

[0002] High-purity copper is mainly used in relays and connectors due to its high conductivity and elongation. There are usually two ways to form it, copper rod and copper strip. The oxygen content of the upper copper rod is mainly controlled below 20ppm by covering it with charcoal, but the oxygen content fluctuates between 5-20ppm and is easy to inhale. The oxygen content of the continuously cast and rolled copper rod is controlled between 200-400ppm, mainly by reducing the combustion of CO gas to control the oxygen content. However, under the condition of lax combustion control, the difference in oxygen content between the head and tail of the same batch of materials fluctuates by more than 20ppm. In addition, copper rods are only suitable for small wire products. The production of copper strip mainly adopts the method of hot rolling of large ingots, but because large ingots are easy to inhale during the melting and casting process, peeling defects occur when rolling the strip, resulting in unstable quality and a large amount of scrap. The gas in the copper solution is basically hydrogen. According to the hydrogen-oxygen balance theory, if the oxygen content in the copper melt is increased, it can react with the hydrogen in the copper melt to generate water molecules that escape. In addition, a part of the oxygen can oxidize impurity elements such as phosphorus, iron, and tin in high-purity copper to improve the conductivity of pure copper. However, if the oxygen content is too high, the melt will be oxidized in large quantities, and a large number of oxide particles will cause peeling, which will also reduce the conductivity of high-purity copper. Generally, the oxygen content is controlled between 200 and 400 ppm. In addition, the oxygen content is uneven, and the cuprous oxide is unevenly distributed or locally concentrated. When rolled into thin strips, the enriched cuprous oxide particles are inconsistent with the deformation of the surrounding copper, which will also cause peeling. Therefore, it is necessary to control the uniform distribution of oxygen, but how to control the oxygen content within this range and the oxygen uniformity part is a technical problem.

[0003] For example, the Chinese invention patent "A Melting and Casting Production Process for High-Oxygen Tough Copper" with announcement number CN106086484A (application number 201610493637.8) discloses the following steps: (1) first add the cathode copper to the preheating furnace for preheating, and set the temperature of the preheating furnace to 400°C. After preheating, the surface of the cathode copper remains dry, oil-free and water-free, and the furnace temperature is greater than 90°C. (2) Then put the cathode copper taken out of the furnace into a melting furnace for smelting to produce high-oxygen tough copper, and the charcoal covering thickness is less than 100mm. (3) Then put the high-oxygen tough copper produced above into an insulation furnace and cover it with graphite particles with a thickness of less than 100mm. (4) Finally, put the high-oxygen tough copper into a casting box and a crystallizer for casting, and then cool the high-oxygen tough copper crystals through the crystallizer. This invention realizes the industrialization of high-oxygen tough copper through the technology of melting and casting oxygenation and homogenization, greatly improves its output, and meets the special requirements of downstream copper foil production for composition and performance, namely, O content of 80-350PPM, P<3PPM, and Fe<5PPM. In this scheme, the purpose of controlling the oxygen content is achieved by controlling the preheating of the raw materials, opening the doors of the smelting furnace and the insulation furnace three hours in advance, peeling off the graphite, and exposing one-third of the molten copper. This method first has high requirements for raw materials, and secondly, it has high requirements for slag removal and control time. Sampling and measuring the oxygen content on site for many times to detect changes in the oxygen content is difficult to operate and has low production efficiency. In addition, the higher the oxygen content, the more difficult it is to control the stability of the oxygen content at the head and tail of the ingot. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing a copper ingot with reasonably controlled oxygen content and uniform oxygen distribution.

[0005] The technical solution adopted by the present invention to solve the above technical problem is: a method for preparing a copper ingot, characterized in that it comprises the following preparation steps:

[0006] 1) Raw materials preparation;

[0007] 2) Melting: The melting temperature is 1200-1250°C. Charcoal is used to cover the melting process with a thickness of 3-10 cm. After it is completely melted, it is transferred to a holding furnace;

[0008] 3) Covering and oxygenation: After the converter, remove the charcoal and slag on the surface of the copper water, and cover it with a covering agent with a thickness of 5 to 15 cm. The temperature of the insulation furnace is adjusted to 1150 to 1250°C, and a mixed gas is introduced from the bottom of the insulation furnace, wherein the volume ratio of oxygen in the mixed gas is 30 to 80%, the remainder is inert gas, the gas pressure is 0.4 to 0.6 MPa, the gas flow rate V is 100 to 150 L / min, and the ventilation time T of the mixed gas meets:

[0009] T=W*10 3*(100~200ppm) / 1.42 / (V*(0.3~0.8)),

[0010] Wherein, the unit of T is min;

[0011] W is the total weight of molten copper in the holding furnace, in kg;

[0012] 100-200ppm is the control range of oxygen content in copper water after mixed gas oxygenation;

[0013] 1.42 is the weight of one liter of oxygen, in g / L;

[0014] 4) Keep the mixture at a temperature of 10 to 50 minutes, then test the oxygen content in the copper solution, which is recorded as a0 in ppm.

[0015] 5) Adding copper oxide: Heat the copper water to 1250-1300°C, press the copper oxide into the copper water through a graphite bell, keep it for 15-60 minutes after melting, and then let it stand for more than 15 minutes; the amount of copper oxide M added meets:

[0016] M=W*(a-a0) / 0.2,

[0017] Wherein, the unit of M is kg;

[0018] a is the target oxygen content of the ingot, in ppm;

[0019] 6) Casting: Open the graphite stopper rod, and pour the molten copper into the crystallizer through the graphite pouring pipe. The pouring pipe is placed 4 to 6 cm below the molten copper liquid level. The molten copper liquid level in the crystallizer is covered with a covering agent with a thickness of 3 to 5 cm. After the molten copper is cooled, an ingot is cast.

[0020] In step 3), the oxygen content is controlled between 100 and 200 ppm during the oxygenation process. The main reason is that when the temperature of the molten copper is between 1250 and 1300° C., when the oxygen content exceeds 100 ppm, according to the hydrogen-oxygen balance theory, the hydrogen content is below 1 ppm, and the purpose of degassing is achieved; the lower the oxygen content, the faster the oxidation rate, and the oxygen in the mixed gas is basically utilized. When the oxygen content exceeds 200 ppm, the oxidation rate decreases, and the difficulty of controlling the oxygen content increases, and the utilization efficiency of oxygen decreases.

[0021] After air blowing, copper oxide is added to increase oxygen. The main reason is that after the oxygen content exceeds 200ppm, air blowing cannot be controlled. Adding an oxidant is the most stable and effective means. Solid copper oxide is stable and does not affect the melt composition.

[0022] In step 5), the holding temperature is 1250-1300° C. A temperature higher than 1250° C. ensures sufficient dissolution and rapid diffusion of copper oxide, and a temperature lower than 1300° C. ensures low power consumption and prevents excessive volatilization of the covering agent due to high temperature.

[0023] Preferably, in step 3) and step 6), the covering agent is selected from at least one of sodium carbonate, potassium carbonate and sodium silicate. At high temperature, oxygen exists in the form of cuprous oxide, which is alkaline. The covering agent is preferably alkaline to avoid slagging by reaction between cuprous oxide and the covering agent, destroying the covering film, and air entering the copper water, which affects oxidation control.

[0024] Preferably, the step 1) further comprises no more than 50wt% of recycled copper.

[0025] Preferably, the Cu content in the red copper ingot is ≥99.99wt%, the oxygen content is 200-400ppm, and the deviation of the oxygen content between the head and the tail of the ingot does not exceed 20ppm.

[0026] Compared with the prior art, the advantages of the present invention are as follows: according to the oxidation kinetics of the high-temperature melt, the oxidation rate of the melt is a logarithmic function (first fast and then slow), so a mixed gas containing oxygen is introduced into the bottom of the insulation furnace, which can quickly oxidize impurities in the copper water and attract the impurities to float up through the inert gas. At the same time, the hydrogen can be controlled below 1 ppm to achieve the purpose of eliminating pores. Then, in order to ensure the oxygenation effect and stabilize the oxygen content, oxygenation is performed by adding copper oxide, so that the oxygen content of the copper water can be accurately controlled at 200-400 ppm, and the oxygen content deviation at the head and tail of the ingot does not exceed 20 ppm. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below with reference to the embodiments.

[0028] Example 1 A 40-ton industrial frequency furnace was used to trial-produce a 350ppm copper ingot, comprising the following preparation steps:

[0029] 1) Raw materials: electrolytic plates with a copper content of more than 99.9wt% and 15wt% T2 recycled materials, which are compressed into a 1m*1m cube;

[0030] 2) Melting: The melting temperature is 1200-1250℃. Charcoal is used to cover the melting process with a thickness of 5cm. After it is completely melted, it is transferred to the holding furnace;

[0031] 3) Covering and oxygenation: After the converter, remove the charcoal and slag on the surface of the copper water, and cover it with a covering agent, which is selected from 50wt% sodium carbonate and 50wt% potassium carbonate, with a covering thickness of 10cm. The temperature of the insulation furnace is adjusted to 1160-1180°C, and a mixed gas is introduced from the bottom of the insulation furnace, wherein the volume ratio of oxygen in the mixed gas is 60%, the remainder is inert gas, the gas pressure is 0.6MPa, the gas flow rate V is 120L / min, and the ventilation time T of the mixed gas meets:

[0032] T = 40000 * 1000 * 150ppm / 1.42 / (120 * 0.6) = 50.7min, where 40000 is the total weight of the copper water in the holding furnace, in kg, i.e. W; 150ppm is the control range of the oxygen content in the copper water after the mixed gas is oxygenated; 1.42 is the weight of one liter of oxygen, in g / L;

[0033] 4) Keep warm and let it stand for 30 minutes, and detect the oxygen content in the copper water, recorded as a0, and a0 is 180 ppm.

[0034] 5) Adding copper oxide: Heat the copper water to 1280°C, press the copper oxide into the copper water through a graphite bell, keep it for 30 minutes after melting, and then let it stand for 30 minutes; the amount of copper oxide M added meets:

[0035] M = W*(a-a0) / 0.2, where a is the target oxygen content of the ingot, in ppm; M is in kg;

[0036] W=40*1000(350-180) / 1000000 / 0.2=37kg.

[0037] 6) Casting: Open the graphite stopper rod, and pour the molten copper into the crystallizer through the graphite pouring pipe. The pouring pipe is placed 5 cm below the copper liquid level. The copper liquid level in the crystallizer is covered with a covering agent. The covering agent is selected from 50wt% sodium carbonate and 50wt% potassium carbonate, and the covering thickness is 4cm. After the copper liquid is cooled, an ingot is cast. The ingot specification is 650mm*220mm*8000mm.

[0038] Example 2 A 300ppm copper ingot was produced by trial production in a 40-ton industrial frequency furnace, comprising the following preparation steps:

[0039] 1) Raw materials: electrolytic plates with a copper content of more than 99.9wt% and 30wt% T2 recycled materials, which are compressed into a cube of 1m*1m;

[0040] 2) Melting: The melting temperature is 1200-1250℃. Charcoal is used to cover the melting process with a thickness of 10cm. After it is completely melted, it is transferred to the holding furnace;

[0041] 3) Covering and oxygenation: After the converter, remove the charcoal and slag on the surface of the copper water, and cover it with a covering agent, which is selected from 50wt% sodium carbonate and 50wt% potassium carbonate, with a covering thickness of 10cm. The temperature of the insulation furnace is adjusted to 1160-1180°C, and a mixed gas is introduced from the bottom of the insulation furnace, wherein the volume ratio of oxygen in the mixed gas is 60%, the remainder is inert gas, the gas pressure is 0.7MPa, the gas flow rate V is 150L / min, and the ventilation time T of the mixed gas meets:

[0042] T = 40000 * 1000 * 150ppm / 1.42 / (120 * 0.7) = 40.2min, where 40000 is the total weight of the copper water in the holding furnace, in kg, i.e. W; 150ppm is the control range of the oxygen content in the copper water after the mixed gas is oxygenated; 1.42 is the weight of one liter of oxygen, in g / L;

[0043] 4) Keep the mixture warm and let it stand for 30 minutes, and detect the oxygen content in the copper water, which is recorded as a0. A0 is 172 ppm.

[0044] 5) Adding copper oxide: Heat the copper water to 1260°C, press the copper oxide into the copper water through a graphite bell jar, keep it for 40 minutes after melting, and then let it stand for 40 minutes; the amount of copper oxide M added satisfies:

[0045] M = W*(a-a0) / 0.2, where a is the target oxygen content of the ingot, in ppm; M is in kg;

[0046] W=40*1000(300-172) / 1000000 / 0.2=25.6kg.

[0047] 6) Casting: Open the graphite stopper rod, and pour the molten copper into the crystallizer through the graphite pouring pipe. The pouring pipe is placed 5 cm below the copper liquid level. The copper liquid level in the crystallizer is covered with a covering agent. The covering agent is selected from 50wt% sodium carbonate and 50wt% potassium carbonate. The covering thickness is 4cm. After the copper liquid is cooled, it is cast into an ingot. The ingot specification is 650mm*220mm*8000mm

[0048] Example 3 A 200ppm copper ingot was produced by trial production in a 40-ton industrial frequency furnace, comprising the following preparation steps:

[0049] 1) Raw materials: electrolytic plates with a copper content of more than 99.9wt% and 45wt% T2 recycled materials, which are compressed into a cube of 1m*1m;

[0050] 2) Melting: The melting temperature is 1200-1250℃. Charcoal is used to cover the melting process with a thickness of 10cm. After it is completely melted, it is transferred to the holding furnace;

[0051] 3) Covering and oxygenation: After the converter, remove the charcoal and slag on the surface of the copper water, and cover it with a covering agent, which is selected from 50%wt sodium carbonate and 50%wt potassium carbonate, with a covering thickness of 10cm. The temperature of the insulation furnace is adjusted to 1160-1180°C, and a mixed gas is introduced from the bottom of the insulation furnace, wherein the volume ratio of oxygen in the mixed gas is 80%, the remainder is inert gas, the gas pressure is 0.8MPa, the gas flow rate V is 150L / min, and the ventilation time T of the mixed gas meets:

[0052] T = 40000 * 1000 * 150ppm / 1.42 / (120 * 0.8) = 44min, where 40000 is the total weight of the copper water in the holding furnace, in kg, i.e. W; 150ppm is the control range of the oxygen content in the copper water after the mixed gas is oxygenated; 1.42 is the weight of one liter of oxygen, in g / L;

[0053] 4) Keep warm and let it stand for 30 minutes, and detect the oxygen content in the copper water, recorded as a0, which is 185 ppm.

[0054] 5) Adding copper oxide: Heat the copper water to 1260°C, press the copper oxide into the copper water through a graphite bell jar, keep it for 40 minutes after melting, and then let it stand for 40 minutes; the amount of copper oxide M added satisfies:

[0055] M = W*(a-a0) / 0.2, where a is the target oxygen content of the ingot, in ppm; M is in kg;

[0056] W=40*1000(200-185) / 1000000 / 0.2=3kg.

[0057] 6) Casting: Open the graphite stopper rod, and pour the molten copper into the crystallizer through the graphite pouring pipe. The pouring pipe is placed 5 cm below the copper liquid level. The copper liquid level in the crystallizer is covered with a covering agent. The covering agent is selected from 50wt% sodium carbonate and 50wt% potassium carbonate, and the covering thickness is 4cm. After the copper liquid is cooled, an ingot is cast. The ingot specification is 650mm*220mm*8000mm.

[0058] The difference between the comparative example and Example 1 is that the ventilation time T is 10 minutes and the amount of copper oxide M added is 60 kg.

[0059] The oxygen content of the copper ingots obtained in the embodiment and the comparative example was detected:

[0060] Oxygen was measured by infrared absorption method: GB / T 5121.8-2008 Chemical analysis methods for copper and copper alloys Part 8: Determination of oxygen content was used for testing.

[0061] Sampling method: Cut a 2 cm thin slice 20 cm away from the head and tail of the pull casting ingot and cut off the 2 cm area on the outer edge, and sample the rest;

[0062] The calculation formula for head and tail deviation is: (tail oxygen content - head oxygen content) / head oxygen content.

[0063] Table 1 Test results of copper ingots of embodiments and comparative examples

[0064]

Claims

1. A method for preparing a copper ingot, characterized in that: The method comprises the following preparation steps: 1) Raw materials preparation; 2) Melting: The melting temperature is 1200-1250°C. Charcoal is used to cover the melting process with a thickness of 3-10 cm. After it is completely melted, it is transferred to a holding furnace; 3) Covering and oxygenation: After the converter, remove the charcoal and slag on the surface of the copper water, and cover it with a covering agent with a thickness of 5 to 15 cm. The temperature of the insulation furnace is adjusted to 1150 to 1250°C, and a mixed gas is introduced from the bottom of the insulation furnace, wherein the volume ratio of oxygen in the mixed gas is 30 to 80%, the remainder is inert gas, the gas pressure is 0.4 to 0.6 MPa, the gas flow rate V is 100 to 150 L / min, and the ventilation time T of the mixed gas meets: T=W*10 3 *(100~200ppm) / 1.42 / (V*(0.3~0.8)), Wherein, the unit of T is min; W is the total weight of molten copper in the holding furnace, in kg; 100-200ppm is the control range of oxygen content in copper water after mixed gas oxygenation; 1.42 is the weight of one liter of oxygen, in g / L; 4) Keep the mixture at a temperature of 10 to 50 minutes, then detect the oxygen content in the copper water, which is recorded as a0 in ppm; 5) Adding copper oxide: Heat the copper water to 1250-1300°C, press the copper oxide into the copper water through a graphite bell, keep it for 15-60 minutes after melting, and then let it stand for more than 15 minutes; the amount of copper oxide M added meets: M=W*(a-a0) / 0.2, Wherein, the unit of M is kg; a is the target oxygen content of the ingot, in ppm; 6) Casting: Open the graphite stopper rod, and pour the molten copper into the crystallizer through the graphite pouring pipe. The pouring pipe is placed 4 to 6 cm below the molten copper liquid level. The molten copper liquid level in the crystallizer is covered with a covering agent with a thickness of 3 to 5 cm. After the molten copper is cooled, an ingot is cast.

2. The method for preparing a copper ingot according to claim 1, characterized in that: In step 3) and step 6), the covering agent is selected from at least one of sodium carbonate, potassium carbonate and sodium silicate.

3. The method for preparing a copper ingot according to claim 1, characterized in that: In the step 1), no more than 50 wt % of red copper recycled material is also included.

4. The method for preparing a copper ingot according to claim 1, 2 or 3, characterized in that: The Cu content in the red copper ingot is ≥99.99wt%, the oxygen content is 200-400ppm, and the deviation of the oxygen content between the head and the tail of the ingot does not exceed 20ppm.

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