Preparation method of pulverized iron alloy

Abstract

The invention provides a preparation method of pulverized iron alloy. The preparation method comprises the steps that target pulverized iron alloy components are set; the phosphated residues obtained after zinc removal treatment, coke and ferrosilicon blocks are put into a smelting furnace to be smelted, and molten metal is obtained; and the molten metal is discharged to a tundish of high-pressure water atomization equipment, water atomization treatment is conducted through the high-pressure water atomization equipment, and the pulverized iron alloy is obtained after dewatering and drying. The problems that in the prior art, due to the fact that molten iron alloy has surface tension, the particle size of prepared pulverized iron is large, and the proportion of collected pulverized iron alloy meeting the requirement that the particle size is smaller than 300 meshes is small are solved.

Description

Technical Field

[0001] This application relates to the technical field of ferroalloy preparation, and particularly relates to a method for preparing pulverized ferroalloy. Background Art

[0002] The pulverization phenomenon of ferroalloy refers to the fragmentation and decomposition of iron-based alloys caused by composition segregation, impurity element influence or environmental factors. Impurities such as phosphorus and sulfur in ferroalloys will exacerbate the pulverization of ferroalloys.

[0003] In general ferroalloy preparation, it is necessary to avoid the pulverization of ferroalloy into pulverized ferroalloy. However, pulverized ferroalloy has special uses in fields such as powder metallurgy, coatings, and ferromagnetic materials.

[0004] The existing methods for preparing pulverized ferroalloy mainly include dispersing molten ferroalloy into fine droplets by high-pressure gas or high-speed water flow impact and rapidly solidifying them to form metal powder, or pulverizing ferroalloy into pulverized ferroalloy by crushing and grinding.

[0005] However, in the conventional method of preparing pulverized ferroalloy by high-pressure gas or high-speed water flow impact on molten ferroalloy, due to the surface tension of molten ferroalloy, the particle size of the prepared pulverized ferroalloy is relatively large, resulting in a small proportion of pulverized ferroalloy that meets the requirement of "particle size less than 300 mesh" collected.

[0006] Phosphating treatment on the surface of steel will produce phosphating slag solid waste. The main component of phosphating slag is iron phosphate, and the content of iron phosphate is above 75%. At present, the method of separating iron phosphate from phosphating slag is already very mature, and the impurity content can be less than 0.5%. Common methods include pickling method, complexing method, precipitation method, etc. At present, the recycling of phosphating slag is mainly used for the precursor of lithium iron phosphate cathode material. However, due to the high purity requirement of battery-grade lithium iron phosphate, a large amount of iron phosphate recycled from phosphating slag cannot be directly used for the precursor of lithium iron phosphate cathode material, resulting in waste of phosphating slag resources. Summary of the Invention

[0007] The technical problem to be solved by this application is that in the existing water atomization method for preparing pulverized ferroalloy, the proportion of pulverized ferroalloy with a particle size less than or equal to 300 mesh is relatively small.

[0008] To solve the above problems, this application provides a method for preparing pulverized ferroalloy, including: Setting the target composition of pulverized ferroalloy; Putting the zinc-removed phosphating slag, coke, and silicon iron blocks into a smelting furnace for smelting to obtain a metal melt; Pouring the metal melt into a tundish of a high-pressure water atomization device, performing water atomization treatment using the high-pressure water atomization device, and obtaining pulverized ferroalloy after dehydration and drying.

[0009] In this application, the main component of the phosphating slag after zinc removal is iron phosphate. Iron phosphate reacts with coke at high temperature to produce ferrophosphorus and carbon monoxide gas or carbon dioxide gas. Ferrophosphorus tends to accumulate at the grain boundaries of ferroalloy grains. When the phosphorus-containing metal melt is subjected to water atomization, the phosphide will undergo a hydrolysis reaction with water to generate PH3 gas, which destroys the grain boundary structure and promotes the disintegration of the ferroalloy from the inside, thereby promoting the pulverization of the ferroalloy. On the other hand, phosphorus will form eutectic phases with low melting points with elements such as iron and silicon. These eutectic phases produce volume changes and thermal stresses during temperature fluctuations or solidification processes, which will cause the alloy to crack, thereby promoting the pulverization of the ferroalloy. Through the above solution, the problem in the prior art that due to the surface tension of the molten ferroalloy, the particle size of the pulverized iron obtained is too large, resulting in a small proportion of the pulverized ferroalloy that meets the requirement of a particle size less than 300 mesh being collected is solved.

[0010] Optionally, the phosphating slag after zinc removal accounts for 16-18 wt% of the total amount of the smelting materials.

[0011] Optionally, the mass ratio of the zinc-removed phosphating slag to coke is 12-13:1.

[0012] Optionally, the mass ratio of the ferrosilicon block to the phosphating slag after zinc removal is 4-5:1.

[0013] In order to obtain a pulverized ferroalloy with the target composition, optionally, iron blocks are also added to the smelting furnace.

[0014] Optionally, the smelting temperature is 1420-1550 °C.

[0015] In order to promote the reaction between the phosphating slag and coke, and to promote the reaction products to be better dispersed and mixed in the ferrosilicon metal melt, preferably, the phosphating slag after zinc removal and coke are added to the ferrosilicon melt by means of powder spraying.

[0016] Specifically: after grinding the phosphating slag after zinc removal and coke into powders, they are mixed and introduced into the ferrosilicon melt by means of powder spraying under the protection of an inert gas.

[0017] The technical effect of this application lies in: This application makes full use of phosphating slag waste and the property of phosphorus to promote alloy pulverization, realizing the preparation of pulverized ferroalloy with a particle size less than 300 mesh. In this application, the main component of the phosphating slag after zinc treatment is iron phosphate, and iron phosphate reacts with coke at high temperature to produce ferrophosphorus and carbon monoxide gas or carbon dioxide gas. Ferrophosphorus tends to accumulate at the grain boundaries of ferroalloy. When the phosphorus-containing metal melt is subjected to water atomization, the phosphide will undergo a hydrolysis reaction with water to generate PH3 gas, which destroys the grain boundary structure and promotes the disintegration of the ferroalloy from the inside, thus promoting the pulverization of the ferroalloy. On the other hand, phosphorus will form eutectic phases with low melting points with elements such as iron and silicon. These eutectic phases produce volume changes and thermal stresses during temperature fluctuations or solidification processes, which will cause the alloy to crack, thus promoting the pulverization of the ferroalloy. Through the above solutions, the problems in the prior art are solved, that is, due to the surface tension of the molten ferroalloy, the particle size of the prepared pulverized iron is too large, resulting in a relatively small proportion of the pulverized ferroalloy that meets the requirement of a particle size less than 300 mesh being collected. Detailed Embodiments

[0018] The embodiments of the technical solutions of this application will be described in detail below. The following embodiments are only used to illustrate the technical solutions of this application more clearly, so they are only examples and cannot be used to limit the protection scope of this application.

[0019] The following specific embodiments of this application provide a method for preparing pulverized ferroalloy. This method is used to prepare pulverized ferroalloy, solving the problems that in the preparation of pulverized iron by impacting molten ferroalloy with high-pressure gas or high-speed water flow, due to the surface tension of the molten ferroalloy, the particle size of the prepared pulverized iron is too large, resulting in a relatively small proportion of the pulverized ferroalloy that meets the requirement of a particle size less than 300 mesh being collected. And the problem of waste of phosphating slag resources.

[0020] The method for preparing pulverized ferroalloy provided by this application includes: Setting the target composition of the pulverized ferroalloy; Putting the phosphating slag after zinc treatment, coke, and silicon iron blocks into a smelting furnace for smelting to obtain a metal melt, and the smelting temperature is 1420 - 1550 °C; Transferring the metal melt to a tundish of a high-pressure water atomization device, and performing water atomization treatment using the high-pressure water atomization device, and obtaining pulverized ferroalloy after dehydration and drying.

[0021] This application makes full use of the characteristics that the main component of the phosphating slag after zinc treatment is iron phosphate, and the fact that iron phosphate reacts with coke at high temperature to produce ferrophosphorus, so that more phosphorus is incorporated into the ferroalloy melt. Thus, in the high-pressure water atomization of the ferroalloy melt, phosphorus reacts with water, promoting the fragmentation and decomposition of the ferroalloy and the pulverization of the ferroalloy, thereby improving the pulverization efficiency of the ferroalloy, and significantly increasing the proportion of pulverized iron with a particle size less than 300 mesh obtained.

[0022] The chemical reaction formula for the reaction of iron phosphate and coke at high temperature to produce ferrophosphorus is: FePO4 + 4C → FeP + 4CO↑, or 2FePO4 + 5C → Fe2P + 5CO2↑ In some examples of the present application, the proportion of the phosphating slag after zinc removal in the total amount of the smelting materials is 16 - 18 wt%, specifically including but not limited to 16 wt%, 17 wt%, 18 wt%, and any proportion value with valid decimals between 16 - 18 wt%.

[0023] In some examples of the present application, the mass ratio of the phosphating slag after zinc removal to coke is 12 - 13:1, specifically including but not limited to 12:1, 13:1, and any proportion value with valid decimals between 12 - 13:1.

[0024] In some examples of the present application, the mass ratio of the ferrosilicon block to the phosphating slag after zinc removal is 4 - 5:1.

[0025] In order to achieve the target pulverized ferroalloy composition, in some embodiments, iron blocks are also added to the smelting furnace.

[0026] In some preferred embodiments, the phosphating slag after zinc removal and coke are added to the ferrosilicon melt by powder spraying; specifically: after grinding the phosphating slag after zinc removal and coke into powders, they are mixed and introduced into the ferrosilicon melt by powder spraying under the protection of an inert gas. The inert gas can be selected as argon, helium, etc. In the following specific embodiments, high-purity argon is used as the inert gas, the powder spraying feeding flow rate is 15 kg / min, the powder spraying pressure is 6 Mpa, the powder is sprayed from the bottom upwards, and the distance between the powder spraying port and the furnace bottom is 20 cm. Those skilled in the art can also select other powder spraying parameters according to actual needs under the inspiration of the embodiments of the present invention.

[0027] In the following specific embodiments, the water atomization equipment used is the LD-WA / 100 ultra-high pressure water atomization powder making (granulation) device of Handan Land Atomization Powder Making Equipment Co., Ltd. In the water atomization treatment, the pressure is 50 MPa and the water flow is 60 L / min. Those skilled in the art can also select other water atomization parameters according to actual needs under the inspiration of the embodiments of the present invention.

[0028] The present invention will be described below in conjunction with specific examples and comparative examples. In the following examples, the phosphating slag after zinc removal is an externally purchased phosphating slag, and the content of iron phosphate in the phosphating slag after zinc removal is ≥98%wt.

[0029] Example 1: Set the target mass ratio of the components of the pulverized ferroalloy as Si 68% - 72%, Al ≤ 1.5%, and Fe ≥ 25%.

[0030] Put 75.5 kg of zinc-removed phosphating slag, 6.0 kg of coke, and 312.5 kg of ferrosilicon blocks into a smelting furnace for smelting. When the smelting temperature in the furnace reaches 1420°C - 1550°C, maintain the smelting temperature at 1420°C - 1550°C for 40 minutes to obtain a metal melt, and detect the mass ratio of each element in the metal melt. See Table 1 for details; in this step, the mass ratio of iron phosphate in the zinc-removed phosphating slag is 98.5%, the proportion of Si in the ferrosilicon blocks is 78.6%, the proportion of Al is 0.5%, and the proportion of Fe is 19.4%. After removing the slag layer in the smelting furnace, when the metal melt is poured into the tundish of the water atomization equipment, control the temperature in the tundish at 1420°C - 1550°C, and perform water atomization treatment to obtain ferroalloy powder, which is dehydrated and dried to obtain pulverized ferroalloy.

[0031] Screen the pulverized ferroalloy through a 300-mesh sieve, calculate the weight of the pulverized ferroalloy with a particle size ≤ 300 mesh, and detect the composition of the pulverized ferroalloy with a particle size ≤ 300 mesh. See Table 1 for details.

[0032] Example 2 Set the target mass ratio of the components of the pulverized ferroalloy as Si 68% - 72%, Al ≤ 1.5%, and Fe ≥ 25%.

[0033] Put 65.9 kg of zinc-removed phosphating slag, 5.2 kg of coke, and 316.1 kg of ferrosilicon blocks into a smelting furnace for smelting. When the smelting temperature in the furnace reaches 1420°C - 1550°C, maintain the smelting temperature at 1420°C - 1550°C for 40 minutes to obtain a metal melt, and detect the mass ratio of each element in the metal melt. See Table 1 for details; in this step, the mass ratio of iron phosphate in the zinc-removed phosphating slag is 98.5%, the proportion of Si in the ferrosilicon blocks is 76.6%, the proportion of Al is 0.5%, and the proportion of Fe is 21.4%. After removing the slag layer in the smelting furnace, when the metal melt is poured into the tundish of the water atomization equipment, control the temperature in the tundish at 1420°C - 1550°C, and perform water atomization treatment to obtain ferroalloy powder, which is dehydrated and dried to obtain pulverized ferroalloy.

[0034] Screen the pulverized ferroalloy through a 300-mesh sieve, calculate the weight of the pulverized ferroalloy with a particle size ≤ 300 mesh, and detect the composition of the pulverized ferroalloy with a particle size ≤ 300 mesh. See Table 1 for details.

[0035] Example 3 Set the target mass ratio of the components of the pulverized ferroalloy as Si 68% - 72%, Al ≤ 1.5%, and Fe ≥ 25%.

[0036] Put 316.1 kg of ferrosilicon blocks into a smelting furnace for smelting. When the smelting temperature in the furnace reaches 1420 °C to 1550 °C, maintain the smelting temperature at 1420 °C to 1550 °C for smelting for 25 minutes to obtain a molten metal, and detect the mass ratio of each element in the molten metal. See Table 1 for details; in this step, the proportion of Si in the ferrosilicon blocks is 76.6%, the proportion of Al is 0.5%, and the proportion of Fe is 21.4%. Crush 65.9 kg of zinc-removed phosphating slag and 5.2 kg of coke into powders with a mesh size of 80 - 100, and then mix them. Under the protection of argon, use a powder spraying machine to blow the mixed powder of phosphating slag and coke into the molten metal by powder spraying and continue smelting for 15 minutes; in this step, the mass proportion of iron phosphate in the zinc-removed phosphating slag is 98.5%. After removing the slag layer in the smelting furnace, transfer the molten metal to the tundish of the water atomization equipment. Control the temperature in the tundish at 1420 °C to 1550 °C, and perform water atomization treatment to obtain ferroalloy powder. After dehydration and drying, powdered ferroalloy is obtained.

[0037] Sieve the powdered ferroalloy through a 300-mesh sieve, calculate the weight of the powdered ferroalloy with a particle size ≤ 300 mesh, and detect the composition of the powdered ferroalloy with a particle size ≤ 300 mesh. See Table 1 for details.

[0038] Example 4 Set the target mass ratio of the components of the powdered ferroalloy as Si 68% - 72%, Al ≤ 1.5%, Fe ≥ 27%.

[0039] Put 75.5 kg of zinc-removed phosphating slag, 6.0 kg of coke, and 316.1 kg of ferrosilicon blocks into a smelting furnace for smelting. When the smelting temperature in the furnace reaches 1420 °C to 1550 °C, maintain the smelting temperature at 1420 °C to 1550 °C for smelting for 40 minutes to obtain a molten metal, and detect the mass ratio of each element in the molten metal. See Table 1 for details; in this step, the mass proportion of iron phosphate in the zinc-removed phosphating slag is 98.5%, the proportion of Si in the ferrosilicon blocks is 76.6%, the proportion of Al is 0.5%, and the proportion of Fe is 21.4%. After removing the slag layer in the smelting furnace, transfer the molten metal to the tundish of the water atomization equipment. Control the temperature in the tundish at 1420 °C to 1550 °C, and perform water atomization treatment to obtain ferroalloy powder. After dehydration and drying, powdered ferroalloy is obtained.

[0040] Sieve the powdered ferroalloy through a 300-mesh sieve, calculate the weight of the powdered ferroalloy with a particle size ≤ 300 mesh, and detect the composition of the powdered ferroalloy with a particle size ≤ 300 mesh. See Table 1 for details.

[0041] Comparative Example 1 Set the target mass ratio of the pulverized ferroalloy components as Si 68% - 72%, Al ≤ 1.5%, Fe ≥ 24%.

[0042] Put 338 kg of ferrosilicon blocks into a smelting furnace for smelting. When the smelting temperature in the furnace reaches 1420°C - 1550°C, maintain the smelting temperature at 1420°C - 1550°C for 40 minutes to obtain a molten metal, and detect the mass ratio of each element in the molten metal. See Table 1 for details; in this step, the proportion of Si in the ferrosilicon blocks is 71.4%, the proportion of Al is 0.9%, and the proportion of Fe is 25.4%. After removing the slag layer in the smelting furnace, after the molten metal is discharged into the tundish of the water atomization equipment, control the temperature in the tundish at 1420°C - 1550°C, and perform water atomization treatment to obtain ferroalloy powder, and obtain pulverized ferroalloy after dehydration and drying.

[0043] Sieve the pulverized ferroalloy through a 300 - mesh sieve, calculate the weight of the pulverized ferroalloy with a particle size ≤ 300 mesh, and detect the composition of the pulverized ferroalloy with a particle size ≤ 300 mesh. See Table 1 for details.

[0044] Table 1 Detection table of molten metal and pulverized ferroalloy obtained in each example and comparative example The mass ratio values of each component in the molten metal in Table 1 are the average detection values of 5 detection samples, and the mass ratio values of each component in the pulverized iron are the average detection values of 5 detection samples.

[0045] As can be seen from Table 1, among the pulverized iron obtained in Examples 1 - 4, the mass ratio of the pulverized iron with a particle size less than or equal to 300 mesh is above 89%, while the mass of the pulverized iron with a particle size less than or equal to 300 mesh obtained in Comparative Example 1 is only 58.7%, indicating that the solution in this application is beneficial to promoting the pulverization of ferroalloy.

[0046] In Examples 1 and 2, phosphating slag, coke and ferrosilicon were added to the smelting furnace for smelting simultaneously. In Example 3, phosphating slag and coke were added to the ferrosilicon molten metal by means of powder spraying. The proportion of the pulverized ferroalloy with a particle size less than or equal to 300 mesh obtained in Example 3 is higher than that obtained in Examples 1 and 2, indicating that the powder spraying method is beneficial to promoting the reaction of phosphating slag and coke to generate ferrophosphorus, which is further beneficial to promoting the dispersion and mixing of ferrophosphorus in the ferrosilicon melt, and thus is beneficial to the pulverization of the phosphorus - containing molten metal into pulverized ferroalloy with a particle size less than or equal to 300 mesh.

[0047] As can be seen from Table 1, in Examples 1 to 4, the phosphorus content in the molten metal accounts for about 4%, while the phosphorus content in the pulverized ferroalloy is 0.134 - 0.146%. This shows that during the pulverization process of high-pressure water atomization, phosphorus in the molten metal is released from the ferroalloy. The speculated reason is that phosphides will undergo hydrolysis reactions with water to generate PH3 gas and be released.

[0048] It should be noted that in Table 1, in the smelting furnace, part of Si is oxidized to form SiO2 and enters the slag, and part of P will also be discharged with the slag. Therefore, there will be a deviation between the mass percentage of each component in the actually detected molten metal and the theoretically calculated value. In addition, due to factors such as ladle transfer losses and some extremely fine particles being discharged as water slag with the atomized water, the total amount of pulverized iron obtained is less than the theoretical value.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and are not intended to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing powdered ferroalloy, characterized in that, Including: Setting the target composition of pulverized ferroalloy; Putting the zinc-removed phosphating slag, coke, and ferrosilicon blocks into a smelting furnace for smelting to obtain a molten metal; Pouring the molten metal into a tundish for a high-pressure water atomization device, performing water atomization treatment with the high-pressure water atomization device, and obtaining pulverized ferroalloy after dehydration and drying.

2. The method according to claim 1, characterized in that, The zinc-removed phosphating slag accounts for 16 - 18 wt% of the total amount of smelting materials.

3. The method according to claim 1, characterized in that, The mass ratio of the zinc-removed phosphating slag to coke is 12 - 13:

1.

4. The method according to claim 1, wherein The mass ratio of the ferrosilicon block to the zinc-removed phosphating slag is 4 - 5:

1.

5. The method according to claim 1, wherein Adding iron blocks is also included in the smelting furnace.

6. The method according to claim 1, wherein The smelting temperature is 1420 - 1550 °C.

7. The method according to claim 1, wherein The zinc-removed phosphating slag and coke are added to the ferrosilicon melt by powder spraying.

8. The method according to claim 7, wherein Specifically: After grinding the zinc-removed phosphating slag and coke into powders, they are mixed and introduced into the ferrosilicon melt by powder spraying under the protection of inert gas.

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