Method for producing low-phosphorus oxygen-free copper ingot

Abstract

A preparation method of low-phosphorus-content oxygen-free copper ingot, characterized in that comprising the following steps: ① raw material preparation; ② smelting: the raw materials are added into a smelting furnace in batches for melting, and after all the raw materials are melted, the smelting furnace is transferred into a holding furnace; ③ first-time phosphor copper alloy addition; ④ phosphor copper supplement; ⑤ drawing and casting: the temperature of the holding furnace is controlled at 1160-1170 DEG C, and the drawing and casting is started, and inert gas is used to purge and protect the crystallizer before the drawing and casting. Oxygen in the melt is removed completely through the first-time phosphor copper addition and the bottom blowing oxygen removal, and the phosphor copper powder is blown into through a second-time graphite tube, so that the phosphor element is ensured not to be burned and lost and uniform, and the uniform ingot with a difference of not more than 10 ppm between the head and tail phosphor element is obtained.

Description

Technical Field

[0001] This invention relates to a method for preparing a copper alloy, belonging to the field of copper alloy technology. Background Technology

[0002] Phosphorus-containing oxygen-free copper, due to the addition of phosphorus, significantly improves the weldability of oxygen-free copper while ensuring excellent electrical and thermal conductivity and preventing hydrogen embrittlement. Generally, the oxygen content is below 10 ppm, and the phosphorus content is between 10 and 70 ppm. However, in actual production, the phosphorus requirements are more stringent, mainly because the addition of phosphorus drastically reduces the conductivity of copper. Therefore, it is generally controlled below 50 ppm, but below 20 ppm, the improvement in weldability is not significant. Thus, the phosphorus content is generally controlled between 20 and 50 ppm. However, because the casting time for oxygen-free copper thin strip ingots is long, phosphorus is easily burned off, making it difficult to stably control the phosphorus content in the ingot. If there is a large difference in phosphorus content between the beginning and end of the strip, the performance of the finished strip will also differ significantly. It is best to control the difference within a 10 ppm range.

[0003] Chinese invention patent ZL201110119494.1, entitled "An Oxygen-Free Copper Tube and Its Processing Method" (authorization announcement number CN102220511B), uses a phosphorus deoxidation method to trial-produce oxygen-free copper tubes. This mainly involves adding Ag, Bi, P, and Pb during the semi-continuous casting process to achieve oxygen-free copper tubes with P: 0.001%~0.006%, Ag≤0.015%, Bi≤0.0005%, and Pb≤0.005%. However, it does not provide a detailed explanation of the method for stabilizing and controlling the phosphorus element.

[0004] Referring to the Chinese invention patent application publication "A device for adding phosphorus and deoxidizing oxygen in an oxygen-free copper furnace by measuring the weight using a weight sensor" (application publication number CN111424181A), this document adds phosphorus based on the phosphorus and oxygen content in the oxygen-free copper furnace to control the oxygen content, but does not specify the standard range for phosphorus control. Moreover, semi-continuous casting ingots are calculated in tons, which places extremely high demands on the measurement of the sensor. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an easy-to-implement method for preparing low-phosphorus oxygen-free copper ingots, in light of the above-mentioned technical situation.

[0006] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: 1. A method for preparing low-phosphorus oxygen-free copper ingots, characterized by comprising the following steps:

[0007] ①Raw material preparation: Prepare raw materials according to the set specifications;

[0008] ② Smelting: Raw materials are added to the smelting furnace in batches for melting. After all the raw materials have melted, they are transferred to a holding furnace. Before the converter, the flow channel is cleaned and baked.

[0009] ③ First addition of phosphorus copper alloy: According to the converter volume, add phosphorus copper alloy at 0.003 to 0.005% of the total weight of the melt, and the phosphorus weight of the phosphorus copper alloy is 10% to 20%; after addition, bottom blowing gas is carried out through the blowing device pre-installed at the bottom of the holding furnace, and the gas is an inert gas.

[0010] ④ Phosphorus copper replenishment: A vacuum sampling tube is used to take a sample from the holding furnace to measure the phosphorus content of the furnace melt. Based on the difference between the phosphorus content and the target phosphorus content, phosphorus element is replenished. The replenished phosphorus copper needs to be vacuum ground into powder and then blown into the melt through a graphite blowing tube for heat preservation.

[0011] ⑤ Casting: Casting begins when the temperature of the holding furnace is controlled at 1160-1170℃. Before casting, the crystallizer is purged with inert gas for protection. After casting is completed, the P element content at the head and tail is tested.

[0012] As a preferred option, the raw material in step ① is pure electrolytic plate or a mixture of pure electrolytic plate and T2 copper recycled material, and the weight proportion of T2 copper recycled material in the mixture is not higher than 40%.

[0013] As a preferred option, calcined charcoal is used for covering during the melting process in step ②. The calcined charcoal covering conditions are as follows: the particle size is controlled between 5 and 10 cm, and the covering thickness is not less than 20 cm.

[0014] Preferably, natural gas is used for baking in step ②, and the baking time is not less than 3 hours.

[0015] As a preferred option, in step ②, the oven after baking is covered with calcined charcoal with a particle size of 3-5 cm, and the covering thickness is not less than 30 cm.

[0016] Preferably, the smelting temperature in step ② is no higher than 1200℃, and the holding furnace temperature is controlled between 1140℃ and 1160℃. As the temperature increases, the oxygen and hydrogen absorption of the melt increases exponentially, but if the temperature is too low, the melt has poor fluidity, which makes it difficult for the charcoal covering the surface to diffuse and deoxidize.

[0017] Preferably, in step ③, after blowing for at least 30 minutes, a mixture of reducing and inert gases is started. This is mainly because 0.005% phosphorus copper cannot completely remove oxygen from the melt. After the inert gas adsorbs the oxide slag in the melt, the reducing gas further eliminates trace amounts of oxygen. At this point, the proportion of reducing gas is increased, while some inert gas is retained to further adsorb oxide slag while deoxidizing. The proportion of reducing gas is 30–40%, the pressure is controlled at 0.4–0.8 MPa, and the gas flow rate is controlled at 30–80 L / min; the blowing time is no less than 30 minutes.

[0018] In step ③, the inert gas is either carbon dioxide or argon. Argon and carbon dioxide have a higher specific gravity than air. After floating to the surface of the melt, they can remove the oxygen from the surface of the melt and form a protective gas layer. Also, because argon and carbon dioxide have a relatively high specific gravity, the bubbles they form are small and rise relatively slowly, which allows for more thorough adsorption of oxide slag in the melt and is conducive to maximizing the complete deoxygenation. Carbon monoxide is chosen as the reducing gas.

[0019] Preferably, the heat preservation time in step ④ is 15 to 30 minutes.

[0020] Preferably, in step ④, while blowing in the phosphorus copper powder, the proportion of reducing gas in the bottom blowing gas is adjusted. The volume ratio of reducing gas is controlled at 40-60% (when blowing in the phosphorus copper alloy powder, the surface of the melt will fluctuate. In order to ensure that the melt does not absorb oxygen, the phosphorus element is not oxidized, and completely enters the copper melt, the proportion of reducing gas must be increased), the pressure is controlled at 0.4-0.8 MPa, the gas flow rate is controlled at 30-80 L / min, and the blowing time is not less than 30 minutes.

[0021] In step ④, the mesh size of the vacuum-ground phosphor bronze powder is controlled between 200 and 300 mesh, the inner diameter of the graphite tube is controlled between 20 and 30 cm, an inert gas is selected for blowing, and the depth of the graphite tube inserted into the molten copper is not less than 50 cm. The blowing pressure P0 is controlled according to the insertion depth h of the graphite tube, and the calculation formula is as follows:

[0022] P0 = α * ρ * g * h;

[0023] Where α is the pressure coefficient, taken as 1.2 to 1.5; ρ is 8.92 * 10 3 kg / m 3 g is the acceleration due to gravity, taken as 9.8 m / s². 2 .

[0024] By controlling the blowing pressure and the particle size of the ground phosphor bronze powder, it is ensured that when the phosphor bronze powder is blown through the graphite tube, the phosphor bronze is fully dissolved in the melt, and is not blown out of the melt or is not fully dissolved.

[0025] Compared with existing technologies, the advantages of this invention are as follows: by adding phosphorus copper in the first step and bottom blowing to remove oxygen from the melt, and then blowing phosphorus copper powder in a second step through a graphite tube, the loss of phosphorus element is minimized and the process is made uniform, resulting in a uniform ingot with a phosphorus element content difference of no more than 10 ppm between the beginning and end of the casting. The phosphorus element in the copper alloy can be stably controlled, and the overall process is easy to implement. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to the embodiments.

[0027] Example 1: A method for preparing oxygen-free copper ingots with a phosphorus content of 30 ppm to 40 ppm.

[0028] 1) Raw material preparation: The raw materials are electrolytic plates with a copper content of 99.9 wt% or more and 30% T2 copper recycled material;

[0029] 2) Smelting: Raw materials are added to the smelting furnace in batches for melting. During the melting process, calcined charcoal is used for covering, with the charcoal particle size controlled at 5-10 cm and the covering thickness not less than 20 cm. The smelting temperature does not exceed 1200℃. After all the raw materials have melted, they are transferred to the holding furnace. Before the transfer furnace, the flow channel is cleaned and baked using natural gas for a time of not less than 3 hours. The temperature of the molten copper in the holding furnace is controlled at 1140-1150℃, and calcined charcoal with a particle size of 3-5 cm is used for covering, with a covering thickness not less than 30 cm.

[0030] 3) First addition of phosphorus copper alloy: Based on the converter volume, add phosphorus copper alloy at 0.004% of the total melt weight, with a phosphorus content of 15%. After addition, bottom blowing gas is performed using a blowing device pre-installed at the bottom of the holding furnace. Carbon dioxide gas is selected. After blowing for 30 minutes, a mixture of carbon monoxide and carbon dioxide gas is started, with a reducing gas ratio of 30%. The pressure is controlled at 0.4–0.8 MPa, and the gas flow rate is controlled at 30–80 L / min. The blowing time is 40 minutes.

[0031] 4) Phosphorus Copper Replenishment: After 70 minutes of blowing, a sample is taken from the holding furnace using a vacuum sampling tube. The phosphorus content of the furnace melt is measured to be 15 ppm. Replenishment is made according to the 20 ppm content difference. The added phosphorus copper needs to be vacuum ground into powder, with the particle size of the powdered phosphorus copper alloy controlled at 200 mesh. Then, it is blown into the melt through a graphite blowing tube, with the graphite tube inserted to a depth of 55-60 cm. The blowing pressure is controlled at 0.1-0.15 MPa, and then the furnace is held for 15 minutes. After the holding period, the proportion of reducing gas in the bottom blowing gas is adjusted, with the proportion of reducing gas controlled at about 50%, the blowing pressure controlled at 0.4-0.6 MPa, and the gas flow rate controlled at 30-80 L / min. The blowing time is no less than 30 minutes.

[0032] Example 2: A method for preparing oxygen-free copper ingots with a phosphorus content of 40 ppm to 50 ppm.

[0033] 1) Raw material preparation: The raw materials are electrolytic plates with a copper content of 99.9 wt% or more and 20% T2 copper recycled material;

[0034] 2) Smelting: Raw materials are added to the smelting furnace in batches for melting. During the melting process, calcined charcoal is used for covering, with the charcoal particle size controlled at 5-10 cm and the covering thickness not less than 20 cm. The smelting temperature does not exceed 1200℃. After all the raw materials have melted, they are transferred to the holding furnace. Before the transfer furnace, the flow channel is cleaned and baked using natural gas for a time of not less than 3 hours. The temperature of the molten copper in the holding furnace is controlled at 1140-1150℃, and calcined charcoal with a particle size of 3-5 cm is used for covering, with a covering thickness not less than 30 cm.

[0035] 3) First addition of phosphorus copper alloy: Based on the converter volume, add phosphorus copper alloy at 0.005% of the total melt weight, with a phosphorus content of 15%. After addition, bottom blowing gas is performed using a blowing device pre-installed at the bottom of the holding furnace. Carbon dioxide gas is selected. After blowing for 30 minutes, a mixture of carbon monoxide and carbon dioxide gas is started, with a reducing gas ratio of 30%. The pressure is controlled at 0.4–0.8 MPa, and the gas flow rate is controlled at 30–80 L / min. The blowing time is 30 minutes.

[0036] 4) Phosphorus Copper Replenishment: After 70 minutes of blowing, a sample is taken from the holding furnace using a vacuum sampling tube. The phosphorus content of the furnace melt is measured to be 20 ppm. Replenishment is then carried out according to the 25 ppm content difference. The added phosphorus copper needs to be vacuum-ground into powder, with the particle size of the powdered phosphorus copper alloy controlled at 250 mesh. This powder is then blown into the melt through a graphite blowing tube, with the tube inserted to a depth of 55–60 cm. The blowing pressure is controlled at 0.1–0.15 MPa, followed by holding for 15 minutes. After holding, the proportion of reducing gas in the bottom blowing gas is adjusted, with the proportion controlled at approximately 50%. The blowing pressure is controlled at 0.4–0.6 MPa, and the gas flow rate is controlled at 30–80 L / min. The blowing time is no less than 30 minutes.

[0037] Example 1: A method for preparing oxygen-free copper ingots with a phosphorus content of 20 ppm to 30 ppm.

[0038] 1) Raw material preparation: The raw materials are electrolytic plates with a copper content of over 99.9 wt% and 40% recycled T2 copper;

[0039] 2) Smelting: Raw materials are added to the smelting furnace in batches for melting. During the melting process, calcined charcoal is used for covering, with the charcoal particle size controlled at 5-10 cm and the covering thickness not less than 20 cm. The smelting temperature does not exceed 1200℃. After all the raw materials have melted, they are transferred to the holding furnace. Before the transfer furnace, the flow channel is cleaned and baked using natural gas for a time of not less than 3 hours. The temperature of the molten copper in the holding furnace is controlled at 1140-1150℃, and calcined charcoal with a particle size of 3-5 cm is used for covering, with a covering thickness not less than 30 cm.

[0040] 3) First addition of phosphorus copper alloy: Based on the converter volume, add phosphorus copper alloy at 0.004% of the total melt weight, with a phosphorus content of 15%. After addition, bottom blowing gas is performed using a blowing device pre-installed at the bottom of the holding furnace. Carbon dioxide gas is selected. After blowing for 50 minutes, a mixture of carbon monoxide and carbon dioxide gas is started, with a reducing gas ratio of 30%. The pressure is controlled at 0.4–0.8 MPa, and the gas flow rate is controlled at 30–80 L / min. The blowing time is 40 minutes.

[0041] 4) Phosphorus Copper Replenishment: After 70 minutes of blowing, a sample is taken from the holding furnace using a vacuum sampling tube. The phosphorus content of the furnace melt is measured to be 20 ppm. Replenishment is made according to a 10 ppm content difference. The added phosphorus copper needs to be vacuum ground into powder, with the particle size of the powdered phosphorus copper alloy controlled at 300 mesh. Then, it is blown into the melt through a graphite blowing tube, with the graphite tube inserted to a depth of 55-60 cm. The blowing pressure is controlled at 0.1-0.15 MPa, and then the furnace is held for 15 minutes. After the holding period, the proportion of reducing gas in the bottom blowing gas is adjusted, with the proportion of reducing gas controlled at about 50%, the blowing pressure controlled at 0.4-0.6 MPa, and the gas flow rate controlled at 30-80 L / min. The blowing time is no less than 30 minutes.

[0042] The oxygen content of the oxygen-free copper ingots from the obtained examples and comparative examples was tested at both ends:

[0043] Oxygen content was measured by infrared absorption method according to GB / T 5121.8-2008 Chemical Analysis Methods for Copper and Copper Alloys Part 8: Determination of Oxygen Content.

[0044] Phosphorus content determination method: GB / T 5121.2-2008 Chemical analysis methods for copper and copper alloys – Part 2: Determination of phosphorus content

[0045] Table 1. Test results of oxygen and phosphorus content at the head and tail of the ingot in the example.

[0046]

Claims

1. A method for preparing a low-phosphorus oxygen-free copper ingot, characterized in that... Includes the following steps: Raw material preparation: Prepare raw materials according to the settings; Smelting: Raw materials are added to the smelting furnace in batches for melting. After all the raw materials have melted, they are transferred to a holding furnace. Before the converter, the flow channel is cleaned and baked. First addition of phosphorus copper alloy: According to the converter volume, add phosphorus copper alloy at 0.003~0.005% of the total weight of the melt, and the phosphorus weight of the phosphorus copper alloy is 10%~20%; after addition, bottom blowing gas is carried out through the blowing device pre-installed at the bottom of the holding furnace, and the gas is an inert gas. Phosphorus copper replenishment: A vacuum sampling tube is used to take a sample from the holding furnace to measure the phosphorus content of the furnace melt. Based on the difference between the phosphorus content and the target phosphorus content, phosphorus element is replenished. The replenished phosphorus copper needs to be vacuum ground into powder and then blown into the melt through a graphite blowing tube for heat preservation. Casting: Casting begins when the holding furnace temperature is controlled at 1160~1170℃. Before casting, the crystallizer is purged with inert gas for protection. After casting, the P element content at the head and tail is tested. step The mesh size of the phosphor bronze powder ground in medium vacuum is controlled at 200~300 mesh, the inner diameter of the graphite tube is controlled at 20~30cm, an inert gas is selected for blowing, and the depth of the graphite tube inserted into the molten copper is not less than 50cm. The blowing pressure P0 is controlled according to the insertion depth h of the graphite tube, and the calculation formula is as follows: P0 = α * ρ * g * h; Where α is the pressure coefficient, taken as 1.2~1.5; ρ is 8.92*10 3 kg / m 3 g is the acceleration due to gravity, taken as 9.8 m / s². 2 .

2. The preparation method according to claim 1, characterized in that... step The raw materials used are pure electrolytic plates or a mixture of pure electrolytic plates and T2 copper recycled material, with the weight proportion of T2 copper recycled material in the mixture not exceeding 40%.

3. The preparation method according to claim 1, characterized in that... step During the melting process, calcined charcoal is used for covering. The calcined charcoal covering conditions are as follows: the particle size is controlled at 5~10cm, and the covering thickness is not less than 20cm.

4. The preparation method according to claim 1, characterized in that... step The baking process uses natural gas and takes no less than 3 hours.

5. The preparation method according to claim 1, characterized in that... step After baking, the oven is covered with calcined charcoal with a particle size of 3-5cm, and the covering thickness is not less than 30cm.

6. The preparation method according to claim 1, characterized in that... step The smelting temperature should not exceed 1200℃, and the holding furnace temperature should be controlled at 1140~1160℃.

7. The preparation method according to claim 1, characterized in that... step The inert gas used is either carbon dioxide or argon.

8. The preparation method according to claim 1, characterized in that... step After blowing air for at least 30 minutes, start blowing a mixture of reducing and inert gases, with the proportion of reducing gas being 30-40%, the pressure controlled at 0.4-0.8 MPa, and the gas flow rate controlled at 30-80 L / min; the blowing time should be no less than 30 minutes.

9. The preparation method according to claim 8, characterized in that... step While blowing in the phosphorus copper powder, the proportion of reducing gas in the bottom blowing gas is adjusted. The proportion of reducing gas is controlled at 40-60%, the pressure is controlled at 0.4-0.8MPa, and the gas flow rate is controlled at 30-80L / min. The blowing time is not less than 30 minutes.

10. The preparation method according to claim 1, characterized in that... step The medium heat preservation time is 15-30 minutes.

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