Preparation method and application of a refiner for smelting scrap copper

Abstract

A preparation method of a refining agent for smelting of scrap copper, characterized in that the raw materials, based on 100%, comprise the following components by weight percentage: 30-50% of potassium fluoborate, 10-25% of zirconium oxide, 2-10% of titanium powder, 20-30% of dolomite powder and 5-10% of aluminum boron alloy, and the balance is inevitable impurities; the refining agent for smelting of scrap copper is prepared by sequentially melting, cooling, crushing or grinding the above raw materials, so that the prepared refining agent is not easy to lose the refining effect in the smelting process of scrap copper. An application of a refining agent for smelting of scrap copper, characterized in that the application sequentially comprises the following steps: Step one, material preparation: melting into copper water after adding scrap copper and the refining agent into a smelting furnace, and the use amount of the refining agent is 0.02-0.03% of the mass of the scrap copper; Step two, slag removal refining; Step three, degassing; Step four, casting: spraying fire for about 15s, and then casting at 1080-1100 DEG C.

Description

Technical Field

[0001] This invention relates to metallurgical casting, and more particularly to a method for preparing a refining agent for smelting scrap copper, and also to the application of a refining agent for smelting scrap copper. Background Technology

[0002] Grain refiners are added during the copper ingot smelting and casting process. These grain refiners promote the nucleation of metals or alloys or inhibit grain growth, thereby refining the grain size and improving the surface quality of the casting. This results in fine equiaxed grains in the casting, particularly reducing cold shuts and eliminating rough and columnar grains, effectively overcoming casting cracks and improving the appearance of the casting. In existing technologies, copper ingot smelting typically uses a single-system grain refiner, such as iron-based, titanium-based, or boron-based ones.

[0003] Scrap copper mainly refers to copper alloy products dismantled from discarded materials such as electronic appliances, industrial motors, electronic products, household hardware, and bathroom products. In current technology, scrap copper is often used as one of the main raw materials for smelting ordinary leaded brass ingots, in order to recycle copper and save on the production cost of copper ingots.

[0004] Because scrap copper is widely available, and because copper alloy products are manufactured with the addition of at least one of the following metals to the raw materials in order to impart special properties such as wear resistance, corrosion resistance, high temperature resistance, high fatigue resistance, easy machinability, high yield strength, and resistance to electro-ablation, scrap copper is often mixed with copper alloys during the manufacturing process. Currently, scrap copper is only simply classified before smelting, and the valuable metals added to the raw materials are not recovered, resulting in a complex composition of scrap copper.

[0005] Because of these uncertain metallic components, scrap copper is prone to chemical reactions during smelting due to the interaction between the raw material components and the main elements of single-system refining agents. For example, ZrAl3 (Zr poisoning) can combine with AlTi, AlB2, TiB2, etc., to form aggregates, preventing these second-phase particles (Al3Ti, AlB2, TiB2) from acting as nucleation sites. Consequently, during solidification and crystallization, the lack of sufficient crystallization nuclei leads to grain attachment and growth, resulting in coarse grains. This causes the refining agent to become "poisoned" and ineffective, causing the copper ingot to develop dendrites. The inner wall of the smelting cup has a noticeable granular texture, and the base has an uneven surface, making it impossible to obtain copper ingots with full shrinkage quality. Moreover, some single-system refining agents are also prone to oxidation and ineffectiveness during smelting. For example, common refining agents can combine iron and oxygen to form iron(III) oxide (Fe3O4), which forms slag and reduces iron particles. Summary of the Invention

[0006] The first technical problem to be solved by the present invention is to provide a method for preparing a refining agent for smelting scrap copper, in view of the above-mentioned technical status, so that the prepared refining agent does not easily lose its refining effect during the smelting of scrap copper.

[0007] The second technical problem to be solved by the present invention is to provide an application of a refining agent for smelting scrap copper, in view of the above-mentioned technical status quo.

[0008] The technical solution adopted by the present invention to solve the first technical problem mentioned above is: a method for preparing a refining agent for smelting scrap copper, characterized in that the raw materials, based on 100%, contain the following components in weight percentage: 30-50 wt% potassium fluoroborate, 10-25 wt% zirconium oxide, 2-10 wt% titanium powder, 20-30 wt% dolomite powder and 5-10 wt% aluminum-boron alloy, with the balance being unavoidable impurities;

[0009] The above raw materials are successively melted, cooled, crushed or ground to produce the refining agent for smelting scrap copper.

[0010] The content of potassium fluoroborate (KBF4) is 30-50 wt%. Below 30 wt%, some oxides cannot be completely compounded, resulting in insufficient grain refinement and a small number of nucleation centers. Above 50 wt%, the fluidity of molten copper is reduced, which can easily lead to cracking of the casting. At the same time, the number of polishing particles will also increase, resulting in poor grain refinement.

[0011] The content of zirconium oxide (ZrO2) is 10-25 wt%. If it is higher than 25 wt%, it will reduce the fluidity of molten copper and easily lead to cracking of the casting. If it is lower than 10 wt%, the number of AlTiZr and BTiZr core particles will be too low, which will not be conducive to the refinement process.

[0012] For aluminum-boron alloys (AlB2), the boron content is 5-10 wt%. If it exceeds 10 wt%, the increased boron content will form excessive oxides, resulting in hard spots during polishing, which is not conducive to the electroplating of subsequent products. It will also reduce the fluidity of molten copper, causing the ingot to shrink and crack.

[0013] Titanium powder (Ti), 2-10 wt%. A content above 10 wt% will reduce the fluidity of molten copper and easily lead to cracking of the casting. A content below 2 wt% is not conducive to the formation of nucleation points.

[0014] In order to make the refined agent for smelting scrap copper suitable for smelting scrap copper with more complex raw material composition, the component also includes 5-10 wt% of cerium rare earth.

[0015] Further design: the melting temperature of the raw material is 1300–1500℃.

[0016] Further design: the zirconium oxide content is 10-15 wt%.

[0017] The technical solution adopted by the present invention to solve the second technical problem mentioned above is: the application of a refining agent for smelting scrap copper, characterized by comprising the following steps in sequence:

[0018] Step 1, Material Processing: Add scrap copper and a refining agent to the smelting furnace and melt them into molten copper. The refining agent is prepared using the method described above for preparing refining agents for scrap copper smelting, and the amount of the refining agent used is 0.02 to 0.03% of the mass of the scrap copper.

[0019] Step 2: Slag removal and refining;

[0020] Step 3: Degas;

[0021] Step 4, casting: After about 15 seconds of flame spraying, stabilize the temperature at 1100-1080℃ and then cast.

[0022] Further design includes component analysis between steps two and three: taking a sample and performing component testing using spectroscopy; if the components are qualified, proceed to the next step; if not qualified, adjust the components by adding the corresponding metals until the components are qualified.

[0023] To facilitate a preliminary assessment of the refining effect, a cup-spinning test is included between steps three and four: the temperature is raised to 1080–1100℃, and a cup-spinning operation is performed. If the inner wall of the cup sample is smooth and flat, it is considered qualified. If it is not qualified, borax and a refining agent accounting for 0.02–0.04% of the mass of scrap copper are added to the raw material and left to stand until the cup-spinning test is qualified.

[0024] To facilitate a preliminary assessment of the refining effect, a small ingot sample is cast between steps three and four: the temperature is raised to 1080–1100°C, and a copper ingot is cast using a ladle. The shrinkage of the copper ingot during the later stages of crystallization is observed. If the shrinkage is not saturated, a refining agent of 0.01–0.02% of the mass of scrap copper is added to the raw material, and a rapid sample is cut and polished to preliminarily determine whether shrinkage porosity exists. Polishing is also included after step four.

[0025] Further design: In step two, 0.08–0.10% of a slag remover by weight of scrap copper is added to the smelting furnace and stirred evenly. Then, 0.08–0.10% of a refining agent by weight of scrap copper is injected into the molten copper and stirred. The temperature is raised to 1080–1100°C, and slag removal begins. After slag removal is completed, the temperature is lowered to 980–1000°C, and 0.006–0.008% of an aluminum rare earth element by weight of scrap copper is added and stirred evenly.

[0026] Further design involves adding magnesium blocks, accounting for 0.003 to 0.005% of the mass of scrap copper, to the smelting furnace for degassing in step three.

[0027] Compared with the prior art, the advantages of the present invention are as follows:

[0028] ① The preparation method of the refining agent for smelting scrap copper involves mixing potassium fluoroborate, zirconium oxide, dolomite powder and titanium powder, so that the mixture can be melted into a highly fluid complex salt and intermetallic compound ZrB2·TiB2 at high temperature. After cooling, it becomes honeycomb-like, and after being crushed or ground, it becomes powder. After entering the melt, it will form independent nucleation sites, which serve as attachment points for grain growth in the early stage of solidification. Due to the small size and uniform distribution of the particles, a large number of grains can be incubated, so a fine-structured polished copper ingot can be obtained after solidification.

[0029] ② The preparation method of the refining agent for smelting scrap copper is to add aluminum-boron alloy to the raw materials so that the boron enters the copper liquid and combines with metallic titanium powder to form the core AlTiB of heterogeneous nucleation. This compound is a metallic crystal compound with good stability. It will be evenly distributed in the melt and act as the nucleation core during solidification, that is, it is dissolved in the crystal.

[0030] ③ The method for preparing a refining agent for scrap copper smelting produces a composite refining agent that can form two refining systems: one with ZrB2·TiB2 as the main refining component and the other with AlTiB as the main refining component. The ZrB2·TiB2-based refining system is mainly for scrap copper containing high-melting-point metals such as zirconium, chromium, niobium, and titanium. Without a corresponding bonding system, these metals can easily lead to increased melt viscosity, reduced copper fluidity, and cracking of castings. The AlTiB-based refining system is mainly for scrap copper containing titanium. Since the prepared composite refining agent can refine copper alloys containing multiple elements, it is more suitable for smelting scrap copper with complex and uncertain compositions and is less likely to lose its refining effect during the scrap copper smelting process.

[0031] ④ The preparation method of the refining agent for scrap copper smelting involves adding cerium rare earth to the raw materials. Since cerium is CeO2 or CeO2·XO2, and lanthanum can also be LaO2 or LaO2·XO2, but mainly in the form of oxides, cerium rare earth will be evenly distributed after entering the melt. Due to its very high melting point, it can combine with oxides to play a role in refining and removing impurities. Due to the complexation effect of the composite salt, it can combine AlTiB, AlTiZr, and BTiZr to distribute throughout the melt, achieving maximum grain refinement. Cerium rare earth is mainly for smelting systems with various impurities and is suitable for smelting scrap copper containing unknown systems. Attached Figure Description

[0032] Figure 1 The sample obtained by applying the refining agent of Example 1 in this embodiment of the invention;

[0033] Figure 2 The sample obtained by applying the refining agent of Example 2 in this embodiment of the invention;

[0034] Figure 3 The sample obtained by applying the refining agent of Example 3 in this embodiment of the invention;

[0035] Figure 4 The sample obtained by applying the refining agent of Example 4 in this embodiment of the invention;

[0036] Figure 5 The sample cup used in this embodiment of the invention is a comparative example of a refining agent.

[0037] Figure 6 This is a small sample of an ingot using the refining agent from Example 1 in this invention.

[0038] Figure 7 This is a small sample of an ingot using the refining agent from Example 2 in this invention.

[0039] Figure 8 This is a small sample of an ingot using the refining agent from Example 3 in this invention.

[0040] Figure 9 This is a small sample of an ingot using the refining agent from Example 4 in this invention.

[0041] Figure 10 This is a small sample of an ingot using a comparative refining agent in an embodiment of the present invention;

[0042] Figure 11 is a metallographic image of a copper ingot using the refining agent of Example 1 in an embodiment of the present invention;

[0043] Figure 12 is a metallographic image of a copper ingot using the refining agent of Example 2 in an embodiment of the present invention;

[0044] Figure 13 is a metallographic image of a copper ingot using the refining agent of Example 3 in an embodiment of the present invention;

[0045] Figure 14 is a metallographic image of a copper ingot using the refining agent of Example 4 in an embodiment of the present invention;

[0046] Figure 15 is a metallographic image of a copper ingot using a comparative refiner in an embodiment of the present invention. Detailed Implementation

[0047] The embodiments of the present invention will be described in further detail below.

[0048] In this embodiment, the preparation method of the refining agent for smelting scrap copper includes the following components by weight percentage, based on 100% of the raw materials: 30-50 wt% potassium fluoroborate, 10-15 wt% zirconium oxide, 2-10 wt% titanium powder, 20-30 wt% dolomite powder, 5-10 wt% aluminum-boron alloy and 5-10 wt% cerium rare earth, with the balance being unavoidable impurities.

[0049] The above raw materials are successively melted, cooled, crushed or ground to produce the refining agent for smelting scrap copper.

[0050] The application of the refining agent in the smelting of scrap copper in this embodiment is characterized by comprising the following steps in sequence:

[0051] Step 1, Material Preparation: Raise the furnace and add the finer agent prepared using the method described above for preparing the finer agent for smelting scrap copper into the smelting furnace in advance. The amount of finer agent used is 0.02-0.03% of the mass of scrap copper. Add crushed copper to cover the scrap copper and add it in three batches. When adding the first batch, add 500g of borax with the furnace. Be sure to remove the slag before each addition. After the three additions are completed, the scrap copper will be melted into molten copper.

[0052] Step 2, Slag Removal and Refining: Add 0.08-0.10% of the slag removal agent (by weight of scrap copper) to the smelting furnace and stir evenly. Then, press 0.08-0.10% of the refining agent (by weight of scrap copper) into the molten copper and stir. Raise the temperature to 1080-1100℃ and begin slag removal. After slag removal, lower the temperature to 980-1000℃ and add 0.006-0.008% of the aluminum rare earth (by weight of scrap copper), stir evenly, take a sample, and let it stand.

[0053] Step 3: Composition Analysis: Take a sample and perform composition analysis using spectroscopy. If the composition is qualified, proceed to the next step. If it is not qualified, adjust the composition by adding the corresponding metal until the composition is qualified.

[0054] Step 4, Degassing: Add magnesium blocks, accounting for 0.003 to 0.005% of the mass of scrap copper, to the smelting furnace.

[0055] Step 5, Swing Cup Test: Raise the temperature to 1080-1100℃ and perform a swing cup operation. If the inner wall of the swing cup sample is smooth and flat, it is considered qualified. If it is not qualified, add borax and a refining agent accounting for 0.02-0.04% of the mass of scrap copper to the raw material and let it stand until the swing cup test is qualified.

[0056] Step 6: Casting a small ingot sample: Raise the temperature to 1080-1100℃ and cast a copper ingot using a ladle. Observe the shrinkage in the later stage of copper ingot crystallization. If the shrinkage is not saturated, add a refining agent of 0.01-0.02% of the mass of scrap copper to the raw material. At the same time, perform rapid cutting and polishing to preliminarily determine whether there are shrinkage pores.

[0057] Step 7, Casting: After about 15 seconds of flame spraying, stabilize the temperature at 1100-1080℃ and then cast.

[0058] Step 8: Polishing.

[0059] I. Preparation of Fine Refining Agent Samples

[0060] The raw materials involved in each refining agent sample are as follows:

[0061] Potassium fluoroborate KBF4: Particle size 200 mesh, Type: Industrial grade, Purity ≥ 98%, Manufacturer: Shandong Maofa Chemical Co., Ltd.

[0062] Zirconia (ZrO2): Particle size 300 mesh, model: hh-08, purity ≥ 99%, manufacturer: Shandong Hanhe New Materials Co., Ltd.

[0063] Aluminum-boron alloy AlB2: Al-B (5%), manufacturer: Jiangsu Xitike Metal Products Co., Ltd.

[0064] Titanium powder (Ti): particle size 200 mesh, purity 99.99%, Inner Mongolia Xiyuan New Technology Materials Co., Ltd.

[0065] Dolomite powder CaMg(CO3)2: particle size 325μm, purity over 99%, produced by Lingshou County Tiansen Mineral Products Processing Plant.

[0066] Lanzhou cerium rare earth: purity above 99.5%, Jiangsu Taicheng Metal Materials Products Co., Ltd.

[0067] Calcium carbonate: 50 mesh particle size, purity over 99%, produced by Shanggao County Huagui Mining Co., Ltd.

[0068] Iron powder: 20 mesh particle size, purity ≥ 99.5%, Shijiazhuang Jingsen Mineral Products Co., Ltd.

[0069] The composition of the samples in each embodiment is shown in Table 1 below:

[0070] Table 1. Raw material composition of samples from each embodiment.

[0071]

[0072] The raw material composition of the comparative sample was: calcium carbonate: iron powder = 30: 70.

[0073] The raw materials were prepared according to the above sample composition, and each group of raw materials was melted, cooled, crushed or ground in sequence to make each fine agent sample.

[0074] II. Application of Refining Agent Samples

[0075] Each group of refining agent samples was used, and the scrap copper was smelted in sequence according to the following steps:

[0076] Step 1, Material Preparation: In the furnace, take 840g of each group of refining agent samples and add them to the 3t industrial frequency furnace in advance. Add crushed copper to cover the furnace. Add 2800kg of scrap copper in three batches. Add 500g of borax with the furnace during the first addition. Be sure to remove slag before each addition. After the three additions are completed, melt it into molten copper.

[0077] Step 2, Slag Removal and Refining: Add 2.5 kg of slag removal agent to the smelting furnace and stir evenly. Then, press 2.5 kg of refining agent into the molten copper and stir. Raise the temperature to 980-1000℃ and start slag removal. After slag removal is completed, lower the temperature to 980-1000℃ and add 200 g of aluminum rare earth. Stir evenly, take a sample, and let it stand.

[0078] Step 3: Composition Analysis: Take a sample and perform composition analysis using spectroscopy. If the composition is qualified, proceed to the next step. If it is not qualified, adjust the composition by adding the corresponding metal until the composition is qualified.

[0079] Step 4, Degassing: Place 120g of magnesium block in the smelting furnace.

[0080] Step 5, Swing Cup Test: Raise the temperature to 1080-1100℃ and perform the swing cup operation. If the inner wall of the swing cup sample is smooth and flat, it is considered qualified. If it is not qualified, add borax and 840g of each group of refining agent samples to the raw materials and let it stand until the swing cup test is qualified.

[0081] Step 6: Casting a small ingot sample: Raise the temperature to 1080-1100℃ and cast a copper ingot using a ladle. Observe the shrinkage of the copper ingot in the later stage of crystallization. If the shrinkage is not saturated, add 280g of each group of refining agent samples to the raw materials and perform rapid cutting and polishing at the same time to preliminarily determine whether there is shrinkage porosity.

[0082] Step 7, Casting: After about 15 seconds of flame spraying, stabilize the temperature at 1100-1080℃ and then cast.

[0083] Step 8: Polishing to obtain HPb60-3 copper ingots.

[0084] III. Tests on the application of various refining agent samples in the copper ingot smelting process

[0085] 1. The copper molten metal from each group of refining agent samples used in the copper ingot smelting process was subjected to spectral composition analysis. The testing standard was YS / T 482-2005. The composition analysis results are shown in Table 2 below:

[0086] Table 2. Copper composition of each refining agent sample applied in the copper ingot smelting process.

[0087]

[0088] 2. A cup-swinging operation was performed on the molten copper from each group of refining agent samples. The operation method was as follows: using a graphite spoon, a small amount of molten copper was shaken out and poured into a small graphite mold. After cooling for 2 seconds, the small graphite mold was quickly tilted to obtain a copper cup attached to the inner wall of the small graphite mold. Figures 1-5 The comparison shows that the waste copper smelted by the refining agent sample in the example has a better cup-spinning quality. The fineness of the cup-spinning improves with the increase of borax content, and the degree of change is more easily distinguishable. In contrast, the waste copper smelted by the refining agent sample in the comparative example has a poor cup-spinning quality. The side and base surfaces of the cup sample have a very obvious grainy texture and a very obvious orange peel texture.

[0089] 3. For casting small-scale copper ingots from the molten copper of each group of refining agent samples, the procedure is as follows: Use an iron ladle to shake out a small amount of molten copper and pour it into an iron mold. After the iron mold cools, small-scale copper ingot samples can be obtained. Figures 6-10 The comparison shows that the small ingots cast from the scrap copper smelted by the refiner sample in the example have better shrinkage quality, higher identification, and uniform and saturated solidification in the later stage of crystallization; while the small ingots cast from the scrap copper smelted by the refiner sample in the comparative example have very poor shrinkage quality, high dendrite identification, very uneven solidification in the later stage of crystallization, with almost no grain refinement in the middle and dendrites visible to the naked eye.

[0090] 4. Metallographic analysis was performed on the copper ingots refined by each group of grain refiner samples. The testing standard was GB / T 6394-2017 Method for Determination of Average Grain Size of Metals. Comparison of Figures 11-15 shows that the copper ingots refined by the grain refiner samples in the examples mainly consist of α and β phases, with grains predominantly island-shaped and a small number of short rod-shaped grains, which are evenly distributed without any mixed crystal problem. Lead particles are evenly distributed at grain boundaries and within grains. By increasing the proportion of grain refiner, the grain size continuously decreased, all below 25 μm. In contrast, the copper ingots refined by the grain refiner samples in the comparative examples mainly consist of α and β phases, with grains predominantly short rod-shaped, showing a tendency towards dendrite formation and a small number of island-shaped grains, exhibiting mixed crystal problem. Lead particles are evenly distributed at grain boundaries and within grains, with a grain size greater than 45 μm.

[0091] 5. Grain size testing was performed on the copper ingots refined by each group of grain refiner samples. The testing standard was GB / T 6394-2017, "Method for Determination of Average Grain Size of Metals". The test results are shown in Table 3 below:

[0092] Table 3. Test results of each group of refining agent samples during the smelting of scrap copper.

[0093]

Claims

1. A method for preparing a refining agent for smelting scrap copper, characterized in that, The raw materials, on a 100% basis, contain the following components by weight percentage: 30-50 wt% potassium fluoroborate, 10-25 wt% zirconium oxide, 2-10 wt% titanium powder, 20-30 wt% dolomite powder and 5-10 wt% aluminum-boron alloy, with the balance being unavoidable impurities. The above raw materials are successively melted, cooled, crushed or ground to produce the refining agent for smelting scrap copper.

2. The preparation method according to claim 1, characterized in that, The composition also includes 5-10 wt% lanthanum, cerium, and rare earth elements.

3. The preparation method according to claim 1, characterized in that, The melting temperature of the raw material is 1300–1500℃.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The zirconium oxide content is 10-15 wt%.

5. The application of a refining agent for smelting scrap copper, characterized in that, The steps are as follows: Step 1, Material Preparation: Add scrap copper and a refining agent to a smelting furnace and melt them into molten copper. The refining agent is prepared using the method described in any one of claims 1 to 4 for preparing a refining agent for scrap copper smelting, and the amount of the refining agent used is 0.02 to 0.03% of the mass of the scrap copper. Step 2: Slag removal and refining; Step 3: Degas; Step 4, casting: After about 15 seconds of flame spraying, stabilize the temperature at 1080-1100℃ and then cast.

6. The application according to claim 5, characterized in that, Between steps three and four, a cup-spinning test is also included: the temperature is raised to 1080-1100℃ and a cup-spinning operation is performed. If the inner wall of the cup sample is smooth and flat, it is considered qualified. If it is not qualified, borax and a refining agent accounting for 0.02-0.04% of the mass of scrap copper are added to the raw material and left to stand until the cup-spinning test is qualified.

7. The application according to claim 5, characterized in that, Between steps three and four, a small sample of the ingot is also cast: the temperature is raised to 1080-1100℃, a copper ingot is cast using a ladle, and the shrinkage of the copper ingot in the later stage of crystallization is observed. If the shrinkage is not saturated, a refining agent of 0.01-0.02% of the mass of scrap copper is added to the raw material, and a rapid sample is cut and polished at the same time to preliminarily determine whether there are shrinkage pores. After step four, polishing is also included.

8. The application according to claims 5 to 7, characterized in that, In step two, 0.08–0.10% of a slag remover by mass of scrap copper is added to the smelting furnace and stirred until homogeneous. Then, 0.08–0.10% of a refining agent by mass of scrap copper is added to the molten copper and stirred. The temperature is raised to 1080–1100°C, and slag removal begins. After slag removal is completed, the temperature is lowered to 980–1000°C, and 0.006–0.008% of an aluminum rare earth element by mass of scrap copper is added and stirred until homogeneous.

9. The application according to claims 5 to 7, characterized in that, In step three, magnesium blocks accounting for 0.003 to 0.005% of the mass of scrap copper are added to the smelting furnace for degassing.

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