Process method for purifying and refining brass and removing impurity elements of iron, lead and aluminum

Abstract

The invention provides a process method for purifying and refining brass and removing impurity elements of iron, lead and aluminum, and belongs to the technical field of brass purification and refining and continuous casting processing. According to the process method, a horizontal continuous casting furnace is used as core production equipment, sodium borate and calcium oxide are compounded to serve as a covering agent, the impurity elements of iron, lead, aluminum and phosphorus in the molten brass are efficiently removed through the integrated process of smelting, refining and impurity removal and continuous casting, non-magnetic brass and lead-free brass can be flexibly produced, and the production efficiency is improved. And a key process support is provided for subsequent quality upgrading of brass products. According to the method, technological parameters are easy to control, a covering agent is easy to purchase, cost is low, continuous casting forming defects are few, the rejection rate of finished product machining is reduced to 2% or below, production efficiency is improved by 15%-20%, and the method can be widely applied to large-scale production of brass products. The problems that when brass is produced through an existing horizontal continuous casting furnace, impurities such as iron, lead and aluminum are difficult to remove, and therefore finished brass cannot meet the non-magnetic and lead-free specification requirements are well solved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of brass purification refining and continuous casting processing, and particularly relates to a process method for purifying and refining brass and removing iron, lead and aluminum impurity elements, which can be used for simultaneously producing non-magnetic brass and lead-free brass. BACKGROUND

[0002] Brass is widely used in the fields of pipeline fittings, electronic components, hardware products and the like due to its low cost and good processing performance. Among them, non-magnetic brass (the "non-magnetic brass" mainly refers to brass in a single alpha phase (face-centered cubic structure) at room temperature, which is usually high-zinc brass, and the iron content needs to be strictly controlled to avoid magnetism) is suitable for precision electronic components, and lead-free brass (the "lead-free brass" refers to brass in which lead is replaced by elements such as bismuth (Bi), silicon (Si), antimony (Sb), tellurium (Te) and magnesium (Mg), and the "lead replacement element" needs to be effectively controlled, and the lead content needs to be strictly controlled to meet environmental protection standards) is suitable for drinking water pipelines and food contact components, both of which have strict requirements on the content of impurities such as iron, lead and aluminum.

[0003] The existing brass production mostly uses horizontal continuous casting furnaces, but there are obvious deficiencies in the purification and refining link: first, the commonly used single covering agent (such as sodium borate alone) has poor targeting for the adsorption of iron, lead and aluminum, especially the iron impurities are easy to form stable compounds and are difficult to remove, which leads to the inability to produce qualified non-magnetic brass; second, lead impurities are easy to disperse in the molten liquid, and ordinary refining methods are difficult to reduce them to the lead-free standard (≤0.01%); third, aluminum impurities are easy to combine with oxygen to form oxide inclusions, which not only affects the purity of brass, but also causes cracks during continuous casting.

[0004] In summary, when refining and purifying brass for continuous casting production, the above-mentioned problems exist, which leads to the fact that the produced brass cannot meet the specifications of non-magnetic and lead-free at the same time, and the excessive impurities also reduce the subsequent processing qualification rate. Therefore, how to provide a process for purifying and refining brass so as to efficiently remove impurity elements such as iron, lead and aluminum and realize the production of non-magnetic and lead-free brass has become a technical problem to be solved. SUMMARY

[0005] The present application is to solve the above technical problems, and provides a process method for purifying and refining brass and removing iron, lead and aluminum impurity elements. The technical purpose of the present application is to provide a process for purifying and refining brass, so as to efficiently remove impurity elements such as iron, lead and aluminum and achieve the purpose of producing high-quality non-magnetic and lead-free brass, and to solve the problem that the impurities such as iron, lead and aluminum are difficult to remove when the existing horizontal continuous casting furnace produces brass, which leads to the fact that the finished brass cannot meet the specifications of non-magnetic and lead-free.

[0006] In order to achieve the above technical purpose, the technical solution adopted by the present application is as follows: The application provides a process method for purifying refined brass and removing iron, lead and aluminum impurity elements, comprising the following steps: (1) preparing materials according to target brass components: when producing lead-free brass, electrolytic copper and zinc ingot with lead content less than or equal to 0.008% are selected as raw materials of the lead-free brass; when producing non-magnetic brass, electrolytic copper and zinc ingot with iron content less than or equal to 0.008% are selected as raw materials of the non-magnetic brass; the raw materials of the corresponding brass are put into a horizontal continuous casting furnace for smelting; (2) heating and controlling the smelting temperature to be 1050-1150 DEG C; after the electrolytic copper and zinc ingot raw materials are completely melted to form a brass melt, the melt is uniformly stirred for 15-30 min to make the melt components uniform; (3) uniformly scattering a composite covering agent of sodium borate and calcium oxide on the surface of the brass melt in step (2), the weight ratio of the sodium borate and the calcium oxide is 3:1-5:1, the amount of the composite covering agent is 0.8%-1.5% of the total weight of the brass melt, then the temperature is kept for 20-40 min for refining, and stirring is carried out during the period to realize the adsorption and removal of iron, lead and aluminum impurities; (4) after the refining is completed, the brass melt is placed for 10-20 min to make the covering agent dregs that adsorb impurities completely separated, the dregs are removed, and then a high-purity brass melt after purification is obtained, then the composite covering agent is replaced by high-purity flake graphite after baking; (5) the continuous casting temperature of the horizontal continuous casting furnace is controlled to be 1020-1100 DEG C, the drawing speed is 80-180 mm / min, and the cooling water amount is 1000-2000 L / h; the high-purity brass melt in step (4) is introduced into a continuous casting chamber to complete continuous casting forming, and after cooling to room temperature, lead-free brass or non-magnetic brass is obtained.

[0007] The process method provided by the application has the following advantages: (1) synergistic impurity removal effect of the composite covering agent: sodium borate has excellent solubility and adsorption, and can quickly adsorb lead impurities (forming lead acetate that is easy to float off) and aluminum impurities (forming soluble aluminum borate) in the melt; calcium oxide can react with iron impurities in the melt to generate iron calcium compounds that are stable and have a density much smaller than that of the melt; meanwhile, the calcium oxide can adjust the viscosity of the covering agent, avoiding that the high viscosity of the sodium borate causes impurities to be difficult to float off due to being wrapped, and the two can synergistically realize efficient removal of iron, lead and aluminum impurities.

[0008] (2) adaptability of the horizontal continuous casting furnace: the smelting, refining and continuous casting of the horizontal continuous casting furnace are integrated, which can reduce secondary pollution of the brass melt in the transfer process, and the continuous casting temperature and drawing speed are easy to accurately control, which can adapt to the forming requirements of the high-purity melt after purification, and avoid the re-precipitation of impurities.

[0009] (3) Differentiated production of non-magnetic brass or lead-free brass: By controlling the impurity content of raw materials at the source (strict control of iron raw materials for non-magnetic brass and strict control of lead raw materials for lead-free brass), and with the targeted removal of impurities by composite covering agents, production modes can be flexibly switched without the need to replace core equipment, thus reducing production switching costs.

[0010] Furthermore, the raw material composition of lead-free brass or non-magnetic brass in step (1) is as follows by weight percentage: copper 60.5-71.5%, zinc 28.5-39.5%, with the remainder being iron and unavoidable trace impurities.

[0011] Furthermore, in step (2), the heating rate is controlled to be 5-8℃ / min.

[0012] Furthermore, in step (2), high-purity argon gas is introduced for protection during heat preservation and stirring, and the argon gas flow rate is controlled to be 1.0-2.5 L / min.

[0013] Furthermore, in step (3), the purity of sodium borate is ≥99.5% and the purity of calcium oxide is ≥98.5%.

[0014] Furthermore, in step (3), the composite covering agent is applied in two stages. The first application is 60% of the total weight, and the remaining 40% is applied after a 10-minute interval.

[0015] Furthermore, in step (3), the impurity content of the brass melt is detected by sampling in front of the furnace during the heat preservation refining process. When the iron content is ≤0.002%, the lead content is ≤0.002%, and the aluminum content is ≤0.003%, the refining is stopped.

[0016] Furthermore, in step (3), the stirring is performed 2-3 times, with each stirring session lasting 5-8 minutes and the stirring speed being 25-45 rpm.

[0017] Furthermore, in step (5), the cooling water is circulating deionized water, and the temperature of the cooling water is controlled at 20-30℃; the temperature of the molten liquid is monitored in real time during the continuous casting process, and the temperature fluctuation range is controlled within ±20℃ to avoid continuous casting defects caused by temperature fluctuation.

[0018] Furthermore, in step (5), the lead content in the lead-free brass is ≤0.005%; the iron content in the non-magnetic brass is ≤0.005%, and the remaining magnetic properties are ≤0.01 mT.

[0019] The beneficial effects of this invention are as follows: (1) Precise impurity removal effect: Sodium borate + calcium oxide composite covering agent can simultaneously reduce iron, lead and aluminum impurities to non-magnetic / lead-free standards, iron ≤0.005%, lead ≤0.005% and aluminum ≤0.003%, solving the problem of single impurity removal in traditional processes.

[0020] (2) High production flexibility: The method of the present invention does not require the replacement of the core equipment of the horizontal continuous casting furnace. It can quickly switch between non-magnetic and lead-free brass by simply adjusting the raw materials and process parameters, and adapt to the production needs of multiple specifications.

[0021] (3) Strong industrial adaptability: The process parameters of this method are easy to control, the covering agent is easy to purchase and has low cost, the continuous casting has fewer defects, the scrap rate of finished product processing is reduced to less than 2%, and the production efficiency is increased by 15%-20%. It can be widely used in the large-scale production of brass products. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described in detail below with reference to embodiments. It should be noted that the following embodiments are for explanation and illustration only and are not intended to limit the invention. Non-essential improvements and adjustments made by those skilled in the art based on the above description are still within the scope of protection of this invention.

[0023] It should be noted that the percentage of element content mentioned in the following examples are all mass percentages.

[0024] Example 1

[0025] A process for purifying and refining brass and removing iron, lead, and aluminum impurities for the production of lead-free brass includes the following steps: (1) Prepare materials according to the composition of lead-free brass (68% copper and 32% zinc): Select 680 kg of electrolytic copper with a lead content of 0.008% and 320 kg of zinc ingots with a lead content of 0.008% and put them into the melting chamber of a 1000 kg horizontal continuous casting furnace; (2) Control the heating rate to 6℃ / min, raise the temperature of the melting chamber to 1100℃, and after the raw material is completely melted, argon gas (flow rate 1.8 L / min) is introduced for protection, and the mixture is kept warm and stirred for 22 min (rotation speed 35 r / min) to obtain a brass melt with uniform composition. (3) Prepare a composite covering agent of sodium borate and calcium oxide (mass ratio of the two is 4:1, sodium borate purity is 99.6% and calcium oxide purity is 98.8%). Calculate 6 kg of covering agent based on 1.2% of the total mass of brass melt (about 500 kg); spread it in two batches (3.6 kg for the first batch, and 2.4 kg for the second batch after a 10 min interval). After spreading, keep it warm and refine it for 30 min, stirring twice during the process (stirring for 6 min each time at a speed of 30 r / min). (4) After refining, samples were taken for testing. The iron content in the melt was 0.003%, the lead content was 0.004%, and the aluminum content was 0.002%. After meeting the standards, the melt was left to stand for 15 minutes, and the surface slag was removed to obtain the purified lead-free brass melt. (5) Control the continuous casting temperature of the horizontal continuous casting furnace to 1060℃ and the casting speed to 130 mm / min. Circulate deionized cooling water (water temperature 25℃, flow rate 1500 L / h) is introduced to the continuous casting chamber to continuously cast Φ120mm lead-free brass ingots and cool them to room temperature.

[0026] The samples obtained from the above process were subjected to chemical composition testing. The finished lead-free brass has a lead content of 0.004% (meeting lead-free standards), an iron content of 0.003%, and an aluminum content of 0.002%, with no oxide inclusions. The scrap rate in subsequent processing (bending and cutting) is reduced from 5% in the traditional process to 1.5%, which is suitable for the production needs of drinking water pipes.

[0027] Example 2

[0028] A process for purifying and refining brass and removing iron, lead, and aluminum impurities for the production of non-magnetic brass includes the following steps: (1) Prepare materials according to the composition of non-magnetic brass (62% copper and 38% zinc): Select 620 kg of electrolytic copper with an iron content of 0.005% and 380 kg of zinc ingots with an iron content of 0.004% and put them into the melting chamber of a 1000 kg horizontal continuous casting furnace. (2) Control the heating rate to 7℃ / min, raise the temperature of the melting chamber to 1120℃, and after the raw material is completely melted, argon gas (flow rate 2.2 L / min) is introduced for protection, and the mixture is kept at the temperature and stirred for 25 min (rotation speed 40 r / min) to obtain a uniform brass melt. (3) Prepare sodium borate + calcium oxide composite covering agent (mass ratio 4.5:1, sodium borate purity 99.7%, calcium oxide purity 98.9%), take 7 kg at 1.4% of the total mass of the melt, spread it in two batches (4.2 kg the first time, 2.8 kg the next time at 10 min interval), keep it warm and refine for 35 min, and stir it 3 times during the process (stir for 5 min each time, speed 35 r / min). (4) Sampling and testing: the iron content in the melt is 0.002%, the lead content is 0.004%, and the aluminum content is 0.002%. After meeting the standards, the melt is left to stand for 18 minutes, and the scum is removed to obtain the purified non-magnetic brass melt.

[0029] The continuous casting temperature was controlled at 1080℃, the casting speed at 110mm / min, and the cooling water (temperature at 26℃, flow rate at 1400L / h) to obtain a Φ120mm non-magnetic brass ingot, which was then cooled to room temperature. The samples produced were tested and found that the finished non-magnetic brass had an iron content of 0.002%, a remanence of about 0.008 mT (meeting the non-magnetic standard), a lead and aluminum content of ≤0.003%, and a conductivity of 65% IACS. It is suitable for the processing and use of precision electronic components and the production efficiency is 20% higher than that of traditional non-magnetic brass processes.

[0030] The above embodiments are only some implementations of the present invention. Various improvements and modifications can be made without departing from the principle of the present invention, and all such improvements and modifications fall within the protection scope of the present invention.

Claims

1. A process for purifying and refining brass and removing iron, lead, and aluminum impurities, characterized in that, Includes the following steps: (1) Prepare materials according to the target brass composition: When producing lead-free brass, select electrolytic copper and zinc ingots with lead content ≤0.008% as raw materials for lead-free brass; when producing non-magnetic brass, select electrolytic copper and zinc ingots with iron content ≤0.008% as raw materials for non-magnetic brass; put the corresponding brass raw materials into a horizontal continuous casting furnace for smelting. (2) Heat up the temperature and control the melting temperature to 1050-1150℃. After the electrolytic copper and zinc ingot raw materials are completely melted to form brass melt, keep it warm and stir for 15-30 minutes to make the melt composition uniform. (3) Spread a composite covering agent of sodium borate and calcium oxide evenly on the surface of the brass melt in step (2), wherein the weight ratio of sodium borate and calcium oxide is 3:1-5:1, and the amount of composite covering agent is 0.8%-1.5% of the total weight of the brass melt. Then keep it warm and refine for 20-40 minutes, stirring during the process, to achieve the adsorption and removal of iron, lead and aluminum impurities. (4) After refining, let the brass melt stand for 10-20 minutes to completely separate the scum of the covering agent that adsorbs impurities. Remove the scum to obtain the purified high-purity brass melt. Then replace the composite covering agent with baked high-purity flake graphite. (5) Control the continuous casting temperature of the horizontal continuous casting furnace to 1020-1100℃, the casting speed to 80-180 mm / min, and the cooling water volume to 1000-2000 L / h. Introduce the high-purity brass melt from step (4) into the continuous casting chamber to complete the continuous casting. After cooling to room temperature, lead-free brass or non-magnetic brass are obtained respectively.

2. The method according to claim 1, characterized in that, The raw material composition of lead-free brass or non-magnetic brass in step (1) is as follows by weight percentage: copper 60.5-71.5%, zinc 28.5-39.5%, with the remainder being iron and unavoidable trace impurities.

3. The method according to claim 1, characterized in that, In step (2), the heating rate is controlled to be 5-8℃ / min.

4. The method according to claim 1, characterized in that, In step (2), high-purity argon gas is introduced for protection during heat preservation and stirring, and the argon gas flow rate is controlled at 1.0-2.5 L / min.

5. The method according to claim 1, characterized in that, In step (3), the purity of sodium borate is ≥99.5% and the purity of calcium oxide is ≥98.5%.

6. The method according to claim 1, characterized in that, In step (3), the composite covering agent is applied in two stages. The first application is 60% of the total weight, and the remaining 40% is applied after a 10-minute interval.

7. The method according to claim 1, characterized in that, Step (3) During the heat preservation and refining process, the impurity content of the brass melt is detected by sampling in front of the furnace. When the iron content is ≤0.002%, the lead content is ≤0.002%, and the aluminum content is ≤0.003%, the refining is stopped.

8. The method according to claim 1, characterized in that, In step (3), the stirring is performed 2-3 times, with each stirring session lasting 5-8 minutes and the stirring speed being 25-45 rpm.

9. The process method according to claim 1, characterized in that, In step (5), the cooling water is circulating deionized water, and the temperature of the cooling water is controlled at 20-30℃. During the continuous casting process, the temperature of the melt is monitored in real time, and the temperature fluctuation range is controlled within ±20℃ to avoid continuous casting defects caused by temperature fluctuation.

10. The process method according to claim 1, characterized in that, In step (5), the lead content in lead-free brass is ≤0.005%; the iron content in non-magnetic brass is ≤0.005%, and the remaining magnetic properties are ≤0.01 mT.