Method for micro-alloying in steel material based on adsorption of rare earth elements by carbon carrier
Technical Field
The invention relates to a microalloying method in steel materials based on rare earth elements adsorbed by a carbon carrier, belonging to the technical field of material preparation.
Background
Rare earth is used as a characteristic resource in Baotou areas of inner Mongolia, and Baotou iron and steel group holds great hope for the efficient utilization of rare earth in iron and steel materials for many years. Especially, a great deal of research and practice is carried out on the addition method of the rare earth. As early as the 70 th 20 th century, rare earth metals are added into a steel furnace or in the process of tapping molten steel, but because the chemical activity of the rare earth elements is very high, the addition method ensures that the rare earth metals rapidly react with oxygen, sulfur and the like in steel to generate oxides or oxysulfides which float upwards for slagging, thereby causing low yield of the rare earth elements, poor uniformity in the molten steel and simultaneously reducing the cleanliness of the molten steel.
The subsequent research mainly adopts the steps of adding rare earth metal or rare earth intermediate alloy into a steel ladle or a tundish, and fully deoxidizing and desulfurizing the molten steel before adding the rare earth metal or the rare earth intermediate alloy, so that the yield of the rare earth can be improved to 30-50%, and the uniformity of the rare earth element in the molten steel is improved when the intermediate alloy is added. However, this method has problems in that the main reaction involving rare earth elements is an oxidation reaction after the rare earth elements are added, and rare earth oxides existing in molten steel easily interact with nozzle refractories to cause nozzle flocculation, and deteriorate the properties of ladle top slag and tundish covering flux.
The current commonly used adding method is a continuous casting crystallizer wire feeding method, and rare earth wires are fed into molten steel in a crystallizer in the continuous casting process, so that the occurrence of water gap flocculation flow is avoided. Because the time interval between the addition and the solidification of the rare earth element is short, the rare earth element is not fully diffused, the oxidation chance of the rare earth element is reduced, and meanwhile, the rare earth element is basically not contacted with the refractory material, the utilization rate of the rare earth is greatly improved, and the yield can reach 90 percent in the best state. However, the rare earth element does not have a time to sufficiently diffuse just because the time interval between the addition and solidification of the rare earth element is short, and thus, the uniformity of the rare earth in the steel is poor.
Because of the large reserves of rare earth resources in China and the superior microalloying effect of 'four-two stirring jacks' of rare earth elements in steel, experts and professionals in the steel industry in China expect to effectively utilize the rare earth resources in steel materials, but because of the existing rare earth adding method, the method has obvious technical bottleneck problems and seriously restricts the application and development of the rare earth in the steel industry.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a method for microalloying rare earth elements in steel materials based on carbon carrier adsorption, which can effectively microalloy the rare earth elements in the steel materials so as to play a microalloying role.
In order to achieve the purpose, the invention adopts the technical scheme that:
a method for micro-alloying in steel materials based on rare earth element adsorbed by carbon carrier comprises the following steps:
(1) the raw material sources are as follows: selecting soluble rare earth salt, and preparing a rare earth salt solution after dissolving;
(2) adsorption carrier: adsorbing and fixing rare earth elements in the rare earth salt solution through a carbon carrier to form a rare earth compound taking carbon as a carrier;
(3) the adding mode is as follows: uniformly mixing the rare earth compound taking carbon as a carrier with a deoxidizer to prepare a briquette or a cored wire; adding the pressing block in the molten steel smelting process, and feeding the core-spun yarn into the molten steel by a wire feeding method;
(4) micro-alloying: and (3) performing reduction reaction on the rare earth compound taking carbon as a carrier in the pressed block or the cored wire and a deoxidizer by utilizing the temperature of the molten steel, so that the rare earth element is reduced and dissolved in the molten steel, and completing the microalloying process of the rare earth element in the steel material.
The soluble rare earth salt is one or a mixture of lanthanum chloride and cerium chloride.
The mass concentration of the rare earth salt solution is more than or equal to 1%, the pH value is 5-8, and the solvent for dissolving the rare earth salt is water, ethanol, a TBP extractant or a P350 extractant.
The carbon carrier is expanded graphite, graphite oxide, graphene oxide, coke or activated carbon.
The temperature in the adsorption and fixation process is 20-99 ℃, and the adsorption time is 25-35 min.
In the rare earth compound taking carbon as a carrier, the mass of the rare earth element accounts for 5-75% of the total mass of the carbon carrier and the rare earth compound after adsorption.
The deoxidizer is any one of silicon powder, calcium powder, aluminum powder and magnesium powder, or a mixture of two or more of the silicon powder, the calcium powder, the aluminum powder and the magnesium powder.
The dosage of the deoxidizer in the briquette or the cored wire is 1 to 50 percent of the mass of the rare earth compound taking carbon as a carrier.
The dosage of the rare earth compound taking carbon as a carrier is 0.01-2% of the mass of the molten steel.
The invention has the beneficial effects that:
the raw materials selected by the invention are common materials of factories and enterprises, are cheap and easily available, wherein the rare earth element in the rare earth salt solution has wide sources, soluble rare earth salt directly purchased or rare earth ions recovered from secondary resources by a wet method and the like can be selected, the related chemical reaction is stable, and the invention is safe and controllable and does not need to make special adjustment on the working condition of field production.
The invention selects soluble rare earth salt, prepares rare earth salt solution after dissolving, adsorbs and fixes rare earth elements in the solution through carbon carrier with adsorption performance, and forms rare earth compound taking carbon as carrier. The carbon carrier with adsorption performance has a porous structure or a carbon ring structure containing oxygen-containing functional groups, and the chemical stability of the formed carbon carrier rare earth compound is between that of a rare earth intermediate alloy and a rare earth oxide (sulfide), so that the reduction reaction can be carried out in molten steel for a sufficient time, the uniformity of microalloyed rare earth elements in the molten steel is ensured, and the reduction product can be effectively dissolved in the molten steel.
The microalloying method of the invention provides a brand new thought for microalloying rare earth elements in the production of steel materials, and finds a new application approach for soluble rare earth salts. The method has the advantages of safe production process, simple and easily-obtained material source, easy industrial production, no need of refining rare earth metal or intermediate alloy, energy conservation and environmental protection. The microalloying amount of the rare earth in the obtained steel material is high and can reach 10-100 ppm, the yield of the rare earth element is high and can reach 77.5%, the uniformity is good, the relative standard deviation RSD of the microalloying amount of different positions of a billet is not more than 18%, and the residual rare earth solution after the adsorption is finished can be recycled, the resource allocation and utilization are efficient and reasonable, and the application prospect is good.
Drawings
FIG. 1 is an XRD powder diffraction pattern of a carbon carrier having rare earth ions adsorbed thereon according to example 1 of the present invention;
wherein (a) before burning in air; (b) after the burning oxidation reaction in the air is finished;
FIG. 2 is a microscopic morphology of a carbon carrier adsorbing rare earth ions according to example 1 of the present invention;
FIG. 3 is a schematic view showing the structure of a carbon carrier having rare earth ions adsorbed thereon according to example 1 of the present invention;
wherein (a) is the whole; (b) a single layer.
Detailed Description
The following examples further illustrate the embodiments of the present invention in detail.
Example 1
A microalloying method for adsorbing rare earth elements in steel materials based on carbon carriers comprises the following specific steps:
(1) the main raw materials are as follows: lanthanum chloride is used as a raw material and dissolved in water to prepare a lanthanum chloride solution with 10 percent (wt%) of lanthanum ion concentration, and the pH value of the solution is controlled to be 5-7;
(2) adsorption carrier: taking 50g of graphite oxide and 50mL of lanthanum chloride solution, adsorbing and fixing rare earth lanthanum in the solution in the graphite oxide with adsorption performance, controlling the adsorption temperature at 60-70 ℃ and the adsorption time at 30min to form a rare earth lanthanum compound taking carbon as a carrier; after the carbon carrier is adsorbed, the mass of lanthanum element in the carbon carrier accounts for 5.4% of the total mass of the carbon carrier (including rare earth compounds, the same below);
recovering the adsorbed lanthanum chloride aqueous solution, supplementing lanthanum chloride to enable the mass concentration of rare earth lanthanum ions in the solution to reach 10%, adjusting the pH value of the solution to 5-7 by using ammonia water, and repeating the process for continuous use;
(3) the adding mode is as follows: mixing 10g of the rare earth lanthanum compound taking carbon as a carrier with 4g of aluminum powder, uniformly mixing, and pressing into a cylindrical briquette with the diameter of phi 15mm multiplied by 10mm (length); adding the pressing block into molten steel after the molten steel is completely melted in the process of smelting 10kg of molten steel in a medium-frequency induction furnace;
(4) a micro-alloying process: the carbon carrier rare earth lanthanum compound in the pressing block and deoxidizer aluminum are subjected to reduction reaction at the temperature of 1560-1600 ℃ of the molten steel, so that the rare earth elements are reduced and dissolved in the molten steel, and the rare earth element microalloying process is completed.
XRD powder diffraction experiments were performed on the carbon carrier adsorbed with rare earth ions to study the composition before and after firing in air, and the results are shown in fig. 1. As can be seen from fig. 1, the carbon carrier after adsorption is burned in air, and then is continuously oxidized to obtain the rare earth oxide, and since the carbon carrier does not change the valence state of the rare earth ions, the valence state of the rare earth elements on the carbon carrier is higher than that of the rare earth metals, i.e., the reducibility is lower than that of the rare earth metals. And because the carbon carrier with adsorption performance has a porous structure or a carbon ring structure containing oxygen-containing functional groups, the chemical stability of the formed carbon carrier rare earth compound is between that of the rare earth intermediate alloy and that of the rare earth oxide (sulfide), so that the reduction reaction can be ensured to be carried out in the molten steel for a sufficient time, the uniformity of the microalloyed rare earth elements in the molten steel can be ensured, and the reduction product can be effectively dissolved in the molten steel.
After microalloying, the microalloying amount of the rare earth lanthanum (the mass concentration of the rare earth lanthanum element in the billet) detected at 6 points in the billet is 27ppm, 26.5ppm, 31ppm, 32.5ppm, 28ppm and 27.3ppm respectively; the average microalloying amount was 28.7 ppm; relative Standard Deviation (RSD) 8.4%; the yield of the rare earth lanthanum element is 53 percent.
Example 2
A microalloying method for adsorbing rare earth elements in steel materials based on carbon carriers comprises the following specific steps:
(1) the main raw materials are as follows: dissolving cerium chloride serving as a raw material in water to prepare a cerium chloride solution with the cerium ion concentration of 36% (wt%), and controlling the pH value of the solution to be 5-7;
(2) adsorption carrier: taking 6g of coke and 100mL of a cerium chloride aqueous solution, adsorbing and fixing rare earth cerium in the solution in the coke with adsorption performance, controlling the adsorption temperature at 70-80 ℃ and the adsorption time at 25min to form a rare earth cerium compound taking carbon as a carrier; after adsorption, the mass of the rare earth cerium element in the carbon carrier accounts for 39.6 percent of the total mass of the adsorbed carbon carrier;
recovering the adsorbed cerium chloride aqueous solution, supplementing cerium chloride to enable the mass concentration of rare earth cerium ions in the solution to reach 36%, adjusting the pH value of the solution to 5-8 by using ammonia water, and repeating the process, namely enabling the cerium chloride aqueous solution to be continuously used;
(3) the adding mode is as follows: 2g of the above rare earth cerium compound using carbon as a carrier was mixed with 1g of aluminum powder, and after mixing uniformly, a long wire-shaped cored wire was produced. Feeding the cored wire into molten steel by a wire feeding method in the process of smelting 10kg of molten steel in a medium-frequency induction furnace;
(4) a micro-alloying process: the carbon carrier rare earth cerium compound in the cored wire and deoxidizer aluminum are subjected to reduction reaction at the temperature of 1560-1600 ℃ of the molten steel, so that rare earth elements are reduced and dissolved in the molten steel to complete the microalloying process of the rare earth elements.
After microalloying, the microalloying amount of rare earth cerium detected at 6 points in a billet is 61.3ppm, 53.2ppm, 56.7ppm, 63ppm, 65.9ppm and 67.4ppm respectively; the average microalloying amount was 61.3 ppm; relative Standard Deviation (RSD) 8.9%; the yield of the rare earth cerium element is 77.4%.
Example 3
A microalloying method for adsorbing rare earth elements in steel materials based on carbon carriers comprises the following specific steps:
(1) the main raw materials are as follows: lanthanum chloride and cerium chloride obtained by wet recovery of secondary resources are used as raw materials (wherein the mass ratio of lanthanum to cerium is 1:2, and the total amount of other impurity elements is less than 5%), the raw materials are dissolved in an ethanol solution to prepare an ethanol mixed solution of lanthanum chloride and cerium chloride (wherein the mass concentration of lanthanum ions is 10.1%, and the mass concentration of cerium ions is 20.1%), and the pH value of the solution is controlled to be 5-7;
(2) adsorption carrier: taking 60kg of graphite oxide and 100L of ethanol mixed solution of lanthanum chloride and cerium chloride, adsorbing and fixing rare earth lanthanum and cerium in the solution in the graphite oxide with adsorption performance, controlling the adsorption temperature at 50-60 ℃ and the adsorption time at 35min to form rare earth lanthanum and cerium compounds taking carbon as a carrier; after adsorption, the mass of the rare earth lanthanum and the mass of the rare earth cerium in the carbon carrier respectively account for 11.4 percent and 20.3 percent of the total mass of the carbon carrier after adsorption;
recovering the adsorbed ethanol mixed solution of lanthanum chloride and cerium chloride, supplementing lanthanum chloride and cerium chloride raw materials to ensure that the mass concentration of rare earth lanthanum ions in the solution reaches 10.1 percent and the mass concentration of cerium ions reaches 20.1 percent, adjusting the pH value of the solution to 5-7 by using ammonia water, and repeating the process for continuous use;
(3) the adding mode is as follows: 20kg of the rare earth lanthanum and cerium compounds taking carbon as a carrier are mixed with 10kg of aluminum powder and 2kg of silicon calcium powder (the mass ratio of silicon to calcium is 3:2), and after uniform mixing, the long-line-shaped core-spun yarn is prepared. Feeding the cored wire into molten steel by a wire feeding method in the process of refining 100t of molten steel in an LF ladle furnace;
(4) a micro-alloying process: the carbon carrier rare earth lanthanum and cerium compound in the cored wire and deoxidizer aluminum and silicon calcium are subjected to reduction reaction by utilizing the temperature of molten steel of 1550-1600 ℃, and rare earth elements are reduced and dissolved in the molten steel to complete the microalloying process.
The method finally takes 6 points in the billet after microalloying, and detects that the microalloying amount of the rare earth lanthanum is 10ppm, 12.5ppm, 13.9ppm, 14.6ppm, 15.3ppm and 15.4ppm respectively; the average microalloying amount was 13.6 ppm; relative Standard Deviation (RSD) 15%; the yield of the rare earth lanthanum element is 59.6 percent. Detecting that the microalloying amounts of the rare earth cerium are 31.6ppm, 28.5ppm, 33.4ppm, 35.2ppm, 32.3ppm and 27.5ppm respectively; the average microalloying amount was 31.4 ppm; relative Standard Deviation (RSD) 9.2%; the yield of the rare earth cerium element is 77.3 percent.
Example 4
A microalloying method for adsorbing rare earth elements in steel materials based on carbon carriers comprises the following specific steps:
(1) the main raw materials are as follows: dissolving cerium chloride serving as a raw material in water to prepare a cerium chloride aqueous solution with cerium ions of which the mass concentration is 36%, and controlling the pH value of the solution to be 5-7;
(2) adsorption carrier: taking 6g of graphene oxide and 50mL of cerium chloride solution, adsorbing and fixing rare earth cerium in the solution in the graphene oxide with adsorption performance, controlling the adsorption temperature at 30-45 ℃ and the adsorption time at 25min to form a rare earth cerium compound taking carbon as a carrier; after adsorption, the mass of the rare earth cerium in the carbon carrier accounts for 65.3 percent of the total mass of the adsorbed carbon carrier;
recovering the adsorbed cerium chloride aqueous solution, supplementing cerium chloride to enable the concentration of rare earth cerium ions in the solution to reach 36%, adjusting the pH value of the solution to 5-7 by using ammonia water, and repeating the process, namely enabling the cerium chloride aqueous solution to be continuously used;
(3) the adding mode is as follows: 2g of the above rare earth cerium compound using carbon as a carrier was mixed with 1g of aluminum powder, and after mixing uniformly, a long wire-shaped cored wire was produced. Feeding the cored wire into molten steel by a wire feeding method in the process of smelting 10kg of molten steel in a medium-frequency induction furnace;
(4) a micro-alloying process: the carbon carrier rare earth cerium compound in the cored wire and deoxidizer aluminum are subjected to reduction reaction at the temperature of 1560-1600 ℃ of the molten steel, so that rare earth elements are reduced and dissolved in the molten steel to complete the microalloying process of the rare earth elements.
After microalloying, the microalloying amount of rare earth cerium detected at 6 points in a billet is 91.3ppm, 89.5ppm, 93.4ppm, 92.7ppm, 85.6ppm and 93.6ppm respectively; the average microalloying amount was 91 ppm; relative Standard Deviation (RSD) 3.4%; the yield of the rare earth cerium element was 69.7%.
In addition to the above embodiments, the embodiments of the present invention may also have the following changes, for example, the solvent for dissolving the rare earth salt is TBP (tributyl phosphate) extractant or P350 extractant, the carbon carrier may be one of expanded graphite or activated carbon, and the deoxidizer may be one or two or more of silicon, calcium, aluminum and magnesium, and the changes or combinations of the embodiments can realize the present invention, which is not listed.
The above examples are merely illustrative for clearly illustrating the present invention and are not intended to limit the embodiments. Other variations will be apparent to persons skilled in the art upon consideration of the foregoing description. And obvious variations are contemplated as falling within the scope of the present invention.