Slagging material for producing niobium-containing hypereutectoid wear-resistant alloy steel by medium-frequency induction furnace as well as preparation method and application of slagging material

Abstract

The invention discloses a slagging material for producing niobium-containing hypereutectoid wear-resistant alloy steel in a medium-frequency induction furnace as well as a preparation method and application of the slagging material. The slagging material comprises various raw materials such as fluorite and lime in specific parts by mass. The preparation method comprises the steps of weighing, mixing, drying, compacting and cutting, melting and the like. When the niobium-containing hypereutectoid wear-resistant alloy steel is produced, a component system is designed firstly, raw materials are put into a medium-frequency induction furnace to be melted and heated, the raw materials are treated through a converter and then return to the electric furnace to be alloyed and compounded for slagging, and then the procedures of heating, calcification, casting, heat treatment and the like are further performed. Steel components and slagging materials can be accurately controlled, the environment in the furnace is optimized, the steel quality is improved, impurities are reduced, the abrasion resistance is improved, the process is reasonable and efficient, and the method is suitable for industrial large-scale production of the niobium-containing hypereutectoid abrasion-resistant alloy steel.

Description

Technical Field

[0001] The invention relates to the technical field of iron and steel metallurgy, and in particular to a slag-making material, a preparation method and application thereof for producing niobium-containing hypereutectoid wear-resistant alloy steel in a medium-frequency induction furnace. Background Art

[0002] In modern industrial production, the demand for wear-resistant alloy steel is growing day by day, and it is widely used in many fields such as mining, machinery manufacturing, and construction. Due to its special organizational structure and the synergistic effect of alloying elements, niobium-containing hypereutectoid wear-resistant alloy steel has excellent wear resistance, high strength and certain toughness, and has become a research hotspot for high-performance wear-resistant materials.

[0003] There are many problems with the traditional production process of wear-resistant alloy steel. First, in the slag-making process, the commonly used slag-making materials have a simple formula and cannot meet the complex refining requirements of niobium-containing hypereutectoid steel. For example, it is difficult for ordinary slag-making materials to effectively remove harmful impurities such as sulfur and phosphorus in molten steel, resulting in low purity of the finished steel. In the subsequent use process, defects such as cracks and embrittlement are prone to occur, which greatly reduces the service life of the steel. Moreover, the recovery rate of precious alloy elements such as niobium is low, resulting in waste of resources and increased production costs.

[0004] Secondly, the temperature control and process connection in the production process are not accurate. The lack of optimization of operations such as heating, standing, and oxygen blowing at different stages makes the uniformity of molten steel composition poor and prone to segregation, which not only affects the mechanical properties of steel, but also leads to unstable product quality and large differences between batches. Furthermore, the heat treatment process in traditional processes is often not carefully designed for the characteristics of niobium-containing hypereutectoid steel. The quenching and tempering temperature and time are not properly controlled, and the strengthening effect of alloy elements cannot be fully exerted, so that the hardness, toughness and wear resistance of steel cannot achieve the best balance.

[0005] In addition, from an environmental protection perspective, some old processes will produce a large amount of waste residue and waste gas, which are difficult to handle and put great pressure on the environment. In terms of energy utilization, due to unreasonable processes, energy consumption is high, which does not conform to the current development trend of energy conservation and emission reduction. Summary of the invention

[0006] The existing wear-resistant alloy steel production technology urgently needs to be improved to meet the increasing industrial needs. The present invention is a brand-new slag-making material, preparation method and application for producing niobium-containing hypereutectoid wear-resistant alloy steel in a medium-frequency induction furnace developed based on the background technology, aiming to solve the above-mentioned series of problems.

[0007] The present invention adopts the following technical solutions:

[0008] A slag-making material for producing niobium-containing hypereutectoid wear-resistant alloy steel in a medium-frequency induction furnace comprises the following raw materials, in parts by mass: 16-22 parts of fluorite, 11-19 parts of lime, 2-12 parts of borax, 3-7 parts of magnesite, 2-9 parts of dolomite, 7-13 parts of quartz, 2-5 parts of gypsum, 6-17 parts of high-alumina laterite, 1-4 parts of nickel ore powder, 2-3 parts of titanium nitride, 1-2 parts of zircon, 0.8-1.4 parts of aluminum-vanadium master alloy and 1.2-2.5 parts of lithium carbonate.

[0009] Preferably, the slag-forming material for producing niobium-containing hypereutectoid wear-resistant alloy steel in the medium frequency induction furnace includes the following raw materials, in parts by mass: 18 parts of fluorite, 14 parts of lime, 8 parts of borax, 5 parts of magnesite, 6 parts of dolomite, 10 parts of quartz, 3 parts of gypsum, 12 parts of high-alumina laterite, 2 parts of nickel ore powder, 2.5 parts of titanium nitride, 1.5 parts of zircon, 1.1 parts of aluminum-vanadium master alloy, and 1.8 parts of lithium carbonate.

[0010] Preferably, the slag-forming material for producing niobium-containing hypereutectoid wear-resistant alloy steel in the medium frequency induction furnace includes the following raw materials, in parts by mass: 20 parts of fluorite, 16 parts of lime, 10 parts of borax, 6 parts of magnesite, 7 parts of dolomite, 12 parts of quartz, 4 parts of gypsum, 15 parts of high-alumina laterite, 3 parts of nickel ore powder, 2.8 parts of titanium nitride, 1.8 parts of zircon, 1.3 parts of aluminum-vanadium master alloy, and 2.2 parts of lithium carbonate.

[0011] Preferably, the slag-forming material for producing niobium-containing hypereutectoid wear-resistant alloy steel in the medium frequency induction furnace includes the following raw materials, in parts by mass: 19 parts of fluorite, 15 parts of lime, 9 parts of borax, 5.5 parts of magnesite, 6.5 parts of dolomite, 11 parts of quartz, 3.5 parts of gypsum, 13 parts of high-alumina laterite, 2.5 parts of nickel ore powder, 2.6 parts of titanium nitride, 1.6 parts of zircon, 1.2 parts of aluminum-vanadium master alloy, and 2.0 parts of lithium carbonate.

[0012] Preferably, the slag-forming material for producing niobium-containing hypereutectoid wear-resistant alloy steel in the medium frequency induction furnace includes the following raw materials, in parts by mass: 21 parts of fluorite, 17 parts of lime, 11 parts of borax, 6.5 parts of magnesite, 8 parts of dolomite, 12.5 parts of quartz, 4.5 parts of gypsum, 16 parts of high-alumina laterite, 3.5 parts of nickel ore powder, 2.9 parts of titanium nitride, 1.9 parts of zircon, 1.4 parts of aluminum-vanadium master alloy, and 2.4 parts of lithium carbonate.

[0013] Preferably, the slag-forming material for producing niobium-containing hypereutectoid wear-resistant alloy steel in the medium frequency induction furnace includes the following raw materials, in parts by mass: 17 parts of fluorite, 13 parts of lime, 7 parts of borax, 4.5 parts of magnesite, 5.5 parts of dolomite, 9 parts of quartz, 2.5 parts of gypsum, 11 parts of high-alumina laterite, 1.5 parts of nickel ore powder, 2.3 parts of titanium nitride, 1.3 parts of zircon, 0.9 parts of aluminum-vanadium master alloy, and 1.6 parts of lithium carbonate.

[0014] Preferably, the slag-forming material for producing niobium-containing hypereutectoid wear-resistant alloy steel in the medium frequency induction furnace includes the following raw materials, in parts by mass: 21 parts of fluorite, 18 parts of lime, 10 parts of borax, 7 parts of magnesite, 8 parts of dolomite, 11 parts of quartz, 5 parts of gypsum, 15 parts of high-alumina laterite, 4 parts of nickel ore powder, 2 parts of titanium nitride, 1.8 parts of zircon, 1.2 parts of aluminum-vanadium master alloy, and 2.2 parts of lithium carbonate.

[0015] The present invention also provides a method for preparing a slag-making material for producing niobium-containing hypereutectoid wear-resistant alloy steel in a medium-frequency induction furnace, comprising the following steps:

[0016] Step 1, weighing the slag-making material raw materials according to the mass ratio;

[0017] Step 2: Mix the raw materials weighed in step 1 thoroughly;

[0018] Step 3, drying the raw materials fully mixed in step 2 at 45-70° C. for 1.5-3.5 hours, keeping the moisture content ≤ 0.6%, to obtain a dry raw material;

[0019] Step 4: compacting and cutting the raw materials dried in step 3 to make slag-making agent blocks;

[0020] Step 5: Place the slag-forming agent block prepared in step 4 into a graphite crucible heated by medium frequency induction heating, heat it up and melt it, let it stand at 1800-2400°C for 10-20 minutes, then pour it into a designated metal mold into blocks of different sizes, and finally cool and crush it to obtain the slag-forming material.

[0021] Preferably, the particle size of the slag-forming material is 5-10 mm.

[0022] The invention also provides an application of a slag-making material in producing niobium-containing hypereutectoid wear-resistant alloy steel.

[0023] Compared with the prior art, the present invention has the following technical advantages:

[0024] (1) Improve the purity of molten steel

[0025] The slag-making material of the present invention has a unique formula, and the lime, gypsum and other components work synergistically, and the removal effect of sulfur and phosphorus is significantly better than that of traditional slag-making materials. In actual production monitoring, the sulfur content in molten steel produced by traditional processes is often as high as 0.06%-0.08%, and the phosphorus content is 0.05%-0.07%. After adopting the process of the present invention, the sulfur content can be stably controlled within 0.04%, and the phosphorus content is reduced to below 0.05%. This is because the strong alkalinity of lime and the gas produced by the decomposition of gypsum can form a good reaction atmosphere, promote the transfer of sulfur and phosphorus to slag, reduce harmful impurities in molten steel, greatly improve the purity of molten steel, greatly reduce defects such as cracks and embrittlement in finished steel, and significantly extend the service life of steel.

[0026] The process of combining the converter with the medium frequency induction furnace, with the oxygen and argon blowing operations, further enhances the ability to remove inclusions. The basic lining in the converter absorbs sulfur and phosphorus, the oxygen blowing decarburization and temperature increase cause the inclusions to float, and the argon blowing stirs the molten steel, making it easier for the floating inclusions to be discharged from the molten steel system. Compared with the simple electric furnace process, the inclusion content is reduced by more than 30%, which effectively improves the purity of the molten steel. The niobium-containing hypereutectoid wear-resistant alloy steel prepared by the present invention has an oxygen content of less than 15ppm and a hydrogen content of less than 5ppm, which improves the mechanical properties of the product.

[0027] (2) Improve the recovery rate of alloy elements

[0028] Fluorite, magnesite and other slag-making materials adjust the slag properties and provide a good smelting environment for alloy elements. Taking niobium as an example, the niobium recovery rate of traditional processes is only 60%-70%. Due to the high viscosity and unreasonable composition of the slag, part of the niobium is lost in the slag. The present invention optimizes the slag composition and reduces the viscosity, thereby increasing the niobium recovery rate to 80%-89%. Similarly, the recovery rate of alloy elements such as nickel and titanium has also been significantly improved, reducing the waste of precious alloy elements and reducing production costs. At the same time, the alloy element content in the steel is guaranteed to be stable, and the steel performance is more reliable.

[0029] Precise process temperature control and fast process connection reduce the burning time of alloy elements at high temperature. For example, the rapid transfer of molten steel between the converter and the medium frequency induction furnace avoids the oxidation loss of alloy elements caused by long-term high temperature exposure, further ensuring the recovery rate of alloy elements.

[0030] (3) Optimizing the mechanical properties of steel

[0031] Grain refiners such as titanium nitride and zircon in the slag-making material, combined with a reasonable heat treatment process, effectively refine the steel grains. Through metallographic analysis and comparison, the average grain size of steel produced by traditional processes is 50-60μm, and the grain size of steel produced by the present invention can be refined to 30-45μm. Grain refinement increases the strength of steel by more than 15% and the toughness by more than 20%. When subjected to external forces, the fine grain structure can hinder crack propagation, improve the comprehensive mechanical properties of steel, and meet more stringent working conditions.

[0032] Alloying treatment is combined with composite slag making to accurately control the composition of molten steel, ensuring the uniform distribution of carbon, silicon, manganese, chromium and other elements in the steel to avoid segregation. The uniform distribution of components makes the performance of each part of the steel consistent, avoiding local weak points and further improving the overall mechanical properties.

[0033] (4) Enhance the wear resistance of steel

[0034] Hypereutectoid steel containing niobium itself has a certain wear resistance. The present invention improves the corrosion resistance of steel by optimizing slag-making materials and introducing nickel ore powder and other ingredients, reduces the erosion of the steel surface by the external corrosive environment, and indirectly enhances the wear resistance. In the test of simulated mine wear and corrosion environment, the wear amount of traditional steel is 1.2-1.5g / h, and the wear amount of the steel of the present invention is reduced to 0.82-0.95g / h, and the wear resistance is improved by more than 20%.

[0035] Reasonable quenching and tempering process parameters enable the steel to form a stable martensitic structure. At the same time, the tempering process eliminates quenching stress and improves the toughness of the steel, making the steel wear-resistant and not easy to break, and has excellent comprehensive wear resistance.

[0036] (5) Energy conservation and emission reduction

[0037] The optimization of slag materials makes the melting process more efficient and reduces energy consumption. For example, the appropriate slag melting point and fluidity reduce the melting time, and the energy consumption per ton of steel melting is reduced by more than 10% compared with the traditional process.

[0038] Precise process control reduces scrap rate, energy consumption and waste of raw materials caused by rework and scrapping. At the same time, it reduces the amount of waste residue and waste gas, alleviates environmental pressure and meets the requirements of sustainable development.

[0039] (6) Improve production efficiency

[0040] The compact and reasonable process flow and the close connection of each link shorten the production cycle. From the input of raw materials to the output of finished castings, the process of the present invention has a shorter production cycle than the traditional process, improves production efficiency, and meets the needs of large-scale industrial production.

[0041] The prefabricated block form of the slag-making material is convenient for storage, transportation and subsequent operation, and improves production efficiency. DETAILED DESCRIPTION

[0042] The present invention will be further described in detail below in conjunction with specific embodiments. It should be emphasized that the following description is merely exemplary and is not intended to limit the scope of the present invention and its application.

[0043] In the present invention, a slag-making material for producing niobium-containing hypereutectoid wear-resistant alloy steel in a medium-frequency induction furnace comprises the following raw materials, in parts by mass: 16-22 parts of fluorite, 11-19 parts of lime, 2-12 parts of borax, 3-7 parts of magnesite, 2-9 parts of dolomite, 7-13 parts of quartz, 2-5 parts of gypsum, 6-17 parts of high-alumina laterite, 1-4 parts of nickel ore powder, 2-3 parts of titanium nitride, 1-2 parts of zircon, 0.8-1.4 parts of aluminum-vanadium master alloy, and 1.2-2.5 parts of lithium carbonate.

[0044] The method for preparing slag-making material for producing niobium-containing hypereutectoid wear-resistant alloy steel in a medium-frequency induction furnace comprises the following steps:

[0045] Step 1, weighing the slag-making material raw materials according to the mass ratio;

[0046] Step 2: Mix the raw materials weighed in step 1 thoroughly;

[0047] Step 3, drying the raw materials fully mixed in step 2 at 52-63°C for 2-3h, keeping the moisture content ≤0.6%, to obtain a dry raw material;

[0048] Step 4: compacting and cutting the raw materials dried in step 3 to make slag-making agent blocks;

[0049] Step 5: Place the slag-forming agent block prepared in step 4 into a graphite crucible heated by medium frequency induction heating, heat it up and melt it, let it stand at 1800-2400°C for 10-20 minutes, then pour it into a designated metal mold into blocks of different sizes, and finally cool and crush it to obtain the slag-forming material.

[0050] A method for producing niobium-containing hypereutectoid wear-resistant alloy steel using a medium frequency induction furnace comprises the following steps:

[0051] (1) Design the composition system according to the chemical composition in terms of mass percentage;

[0052] (2) adding raw materials including scrap steel into a medium frequency induction furnace and melting and heating to 1542°C;

[0053] (3) Then raise the temperature to 1630°C and let stand for 11 minutes;

[0054] (4) After standing still, the furnace was quickly transferred to the converter, which was lined with alkaline material. Oxygen was blown quickly at the bottom of the converter for 6 minutes. After the oxygen was stopped, argon was blown for 6 minutes at a flow rate of 8 L / min, and then the furnace was allowed to stand for 7 minutes.

[0055] (5) After the converter molten steel is left to stand, it is quickly transferred to a medium frequency induction furnace, and ferrochromium alloy, ferroniobium alloy and nickel are added for alloying treatment and composite slag treatment. After sampling and analysis are qualified, the molten steel temperature is adjusted to 1530°C. The composite slag treatment method is to add slag materials to the molten steel after the alloying treatment is completed and perform composite slag treatment. The amount of slag materials added is 8 kg / t;

[0056] (6) Then raise the temperature to 1620°C and let stand for 8 minutes;

[0057] (7) Add calcium iron alloy into the ladle for calcification treatment for 7 minutes, and control the tapping temperature at 1580°C;

[0058] (8) Adjusting the temperature of the molten steel to 1530°C according to the size of the casting, and then casting the casting;

[0059] (9) The casting is cleaned and heat treated to obtain niobium-containing hypereutectoid wear-resistant alloy steel. The heat treatment method is as follows: during quenching treatment, the quenching temperature is 980°C and the holding time is 7 hours; during tempering treatment, the tempering temperature is 500°C and the holding time is 7 hours.

[0060] Technical principle of the present invention:

[0061] 1. Technical principle of slag-making materials:

[0062] Fluorite (16-22 parts)

[0063] The main component of fluorite is calcium fluoride, which has a strong fluxing effect in the slag-making process. At high temperatures, fluorite can significantly reduce the melting point and viscosity of the slag, making the slag thinner and more fluid. This is conducive to full contact between the slag and the molten steel, promoting the transfer of inclusions in the molten steel to the slag, thereby improving the purity of the molten steel. At the same time, good fluidity also makes it easier to remove the oxide slag layer on the surface of the molten steel in a timely manner, reducing the chance of contact between the molten steel and oxygen, and indirectly reducing the oxygen content in the molten steel.

[0064] Lime (11-19 parts)

[0065] Lime, also known as calcium oxide (CaO), is a strong alkaline slag-making raw material. It can react chemically with acidic impurities such as sulfur and phosphorus in molten steel to generate stable sulfides and phosphides that enter the slag and are removed, effectively reducing the sulfur and phosphorus content in the molten steel and improving the quality of the steel. Moreover, calcium oxide can also play a key role in regulating the alkalinity of the slag in the slag-making system. The appropriate alkalinity helps to create a chemical environment that is conducive to removing harmful impurities in the molten steel, further improving the purity of the molten steel, and laying the foundation for the subsequent reduction of hydrogen and oxygen content.

[0066] Borax (2-12 parts)

[0067] When borax is used to make slag, on the one hand, the boron element in borax has a certain deoxidation ability, which can combine with oxygen in molten steel to form borates and enter the slag, playing a preliminary deoxidation effect; on the other hand, the viscous melt formed after the borax is melted can absorb tiny inclusions in the molten steel, entrain the inclusions and take them out of the molten steel, thus purifying the molten steel. In addition, a small amount of boron element may also be integrated into the steel matrix, which has a certain strengthening effect on the grain boundary of the steel and improves the strength and toughness of the steel.

[0068] Magnesite (3-7 parts)

[0069] The main component of magnesite is magnesium carbonate, which decomposes into magnesium oxide (MgO) at high temperature. Magnesium oxide has a high melting point and stability. It can increase the viscosity and stability of slag in slag, prevent the slag from being too thin and lost, and ensure that the slag can continue to effectively cover the surface of molten steel, isolate the air, reduce the absorption of molten steel, and thus reduce the hydrogen content in molten steel. At the same time, magnesium oxide also participates in the chemical reaction of slag, and cooperates with other components to optimize the performance of slag and promote the removal of impurities in molten steel.

[0070] Dolomite (2-9 parts)

[0071] Dolomite is a mineral of calcium magnesium carbonate, which generates calcium oxide and magnesium oxide after thermal decomposition. It has some characteristics of lime and magnesite, which can provide alkaline oxide (CaO) for slag to remove impurities such as sulfur and phosphorus, and can also contribute magnesium oxide to stabilize the slag and isolate the air. This dual role enables dolomite to flexibly adjust the performance of slag in the slag-making material system, and cooperate with other raw materials according to the actual conditions of molten steel to better achieve the goal of reducing hydrogen and oxygen content and purifying molten steel.

[0072] Quartz stone (7-13 parts)

[0073] The main component of quartz is silicon dioxide, which reacts with alkaline oxides (such as CaO, MgO, etc.) during the slag-making process to form silicate slag. These silicate slags have a certain viscosity and adsorption capacity, which can effectively adsorb inclusions in the molten steel and promote the purification of the molten steel. At the same time, an appropriate amount of silicon dioxide can also adjust the fluidity of the slag, prevent the slag from being too viscous or thin, ensure that the slag forms a stable covering layer on the surface of the molten steel, reduce the gas exchange between the molten steel and the external environment, and help control the hydrogen and oxygen content in the molten steel.

[0074] Gypsum (2-5 parts)

[0075] Gypsum will lose its crystal water at high temperature, and the released sulfur dioxide has a certain deoxidation effect, which can react with oxygen in the molten steel to generate oxides and enter the slag. In addition, the calcium ions in the gypsum also participate in the alkalinity regulation of the slag, enhance the slag's ability to remove acidic impurities in the molten steel, and cooperate with other alkaline raw materials to further purify the molten steel, reduce the oxygen content in the molten steel, and create favorable conditions for improving the mechanical properties of alloy steel.

[0076] High alumina laterite (6-17 parts)

[0077] High-alumina laterite is rich in alumina, which is an amphoteric oxide that can react with both acidic and alkaline substances during the slag-making process. It can combine with impurities such as sulfur and oxygen in the molten steel to form complex aluminates that enter the slag, achieving the effects of deoxidation and desulfurization. At the same time, a high content of alumina can increase the viscosity and stability of the slag, allowing the slag to form a stronger protective barrier on the surface of the molten steel, reduce the inhalation of molten steel, reduce the hydrogen content, and help control the fluidity of the slag, so that its interaction with the molten steel reaches the best state.

[0078] Nickel ore powder (1-4 parts)

[0079] Although the amount of nickel ore powder used is relatively small, a small amount of nickel in it will be incorporated into the molten steel during the slag-making process. Nickel is an element that can significantly improve the comprehensive mechanical properties of steel. It can improve the strength, toughness and corrosion resistance of steel. During slag-making, the addition of nickel ore powder not only supplements the nickel element to the molten steel, but also the other impurities it contains can also optimize the slag performance to a certain extent in the process of interacting with other slag-making raw materials, promote the purification of the molten steel, and indirectly help reduce the hydrogen and oxygen content in the molten steel.

[0080] Titanium nitride (2-3 parts)

[0081] Titanium nitride (TiN) has the characteristics of high hardness and high melting point. In the slag-making process, it can exist in the slag in the form of tiny particles. On the one hand, it enhances the hardness of the slag, so that it can more effectively scrape the surface of the molten steel during the flow of the molten steel, peel off the attached oxide film and inclusions, and play a role in purifying the molten steel; on the other hand, the titanium element in titanium nitride may enter the molten steel under certain conditions and combine with the nitrogen in the steel to form tiny titanium nitride particles. These particles are distributed at the grain boundaries of the steel, playing a role in pinning the grain boundaries, refining the grains, and improving the strength and toughness of the steel. At the same time, it also helps to reduce the nitrogen content in the molten steel and indirectly reduce the hydrogen content, because nitrogen and hydrogen have interrelated dissolution behaviors in the molten steel.

[0082] Zircon (1-2 parts)

[0083] The zircon element in zircon has a strong deoxidizing ability. It can react with oxygen in the molten steel to form zirconium oxide that enters the slag, effectively reducing the oxygen content in the molten steel. At the same time, the zircon element can also react with impurities such as carbon and sulfur in the steel to reduce the negative impact of these harmful impurities on the performance of the steel. In addition, the silicon dioxide produced by the decomposition of zircon at high temperature also participates in the silicate formation process of the slag, regulates the fluidity and adsorption of the slag, and cooperates with other raw materials to purify the molten steel and improve the quality of the steel.

[0084] Aluminum-vanadium master alloy (0.8-1.4 parts)

[0085] Aluminum-vanadium master alloy mainly provides aluminum and vanadium elements for molten steel. Aluminum is a commonly used deoxidizer that can quickly combine with oxygen in molten steel to form aluminum oxide, which floats up into the slag to achieve the purpose of deoxidation and reduce the oxygen content in molten steel. Vanadium has the function of refining grains in steel. It can form fine carbides and nitrides, which are distributed around the grain boundaries of steel, hindering the movement of grain boundaries and refining grains, thereby improving the strength and toughness of steel. The combination of the two can both deoxidize and strengthen grains, effectively improving the mechanical properties of niobium-containing hypereutectoid wear-resistant alloy steel.

[0086] Lithium carbonate (1.2-2.5 parts)

[0087] Lithium carbonate decomposes into lithium oxide at high temperature. Lithium oxide has the effect of reducing the melting point of slag, similar to fluorite, which can make slag easier to flow, promote the material exchange between molten steel and slag, facilitate the transfer of inclusions to slag, and purify molten steel. At the same time, lithium element has a certain tendency to absorb air in molten steel. It can preferentially absorb hydrogen in molten steel to form lithium hydride (LiH), which is taken out of the molten steel with the discharge of slag, effectively reducing the hydrogen content in molten steel, and playing a unique role in improving the quality and mechanical properties of alloy steel.

[0088] Synergy between raw materials

[0089] These raw materials cooperate with each other to form an organic slag-making system. First, raw materials such as fluorite and lithium carbonate that adjust the fluidity of the slag work together with raw materials such as lime and high-alumina laterite that adjust the alkalinity of the slag to ensure that the slag has good fluidity and can fully contact the molten steel, and has a suitable alkalinity to effectively remove impurities such as sulfur and phosphorus, creating a chemical environment that is conducive to the purification of the molten steel. Secondly, raw materials with deoxidation ability such as borax, gypsum, zircon, and aluminum complement each other, deoxidize the molten steel from different angles and at different rates, and control the oxygen content in the molten steel at an extremely low level. Furthermore, magnesite, dolomite, quartz stone, etc. reduce the absorption of molten steel and reduce the hydrogen content by stabilizing the slag and adsorbing inclusions. At the same time, the slag components generated by their reaction with other raw materials can continuously purify the molten steel. Finally, while nickel ore powder, titanium nitride, aluminum-vanadium intermediate alloy, etc. introduce beneficial elements (nickel, titanium, etc.) into the molten steel to improve the mechanical properties, their impurity components or decomposition products also participate in the optimization of the slag, complementing the overall slag-making process, and jointly achieving the goal of reducing the hydrogen and oxygen content of the molten steel and improving the mechanical properties of niobium-containing hypereutectoid wear-resistant alloy steel, achieving results far exceeding the use of a single raw material.

[0090] 2. Technical principle of preparation of hypereutectoid wear-resistant alloy steel containing niobium:

[0091] (1) Chemical composition design

[0092] Designing the composition system according to the mass percentage is the cornerstone of the entire preparation process. Different elements and their content ratios determine the final performance trend of alloy steel. For example, the addition of niobium can effectively refine the grains, improve the strength and toughness of steel, and enhance wear resistance; chromium can improve the corrosion resistance of steel, and nickel can help improve the comprehensive mechanical properties of steel, so that it can achieve a better balance in hardness, toughness, etc.

[0093] (2) Raw materials are melted and heated to 1542°C

[0094] Raw materials such as scrap steel are added to the medium frequency induction furnace and heated to this temperature. The purpose is to initially melt the raw materials and transform them from solid to liquid, in preparation for further refining and alloying. At this temperature, most of the metal begins to melt and form initial molten steel, but at this time the molten steel has a complex and uneven composition and contains many impurities, which requires further processing in subsequent steps.

[0095] (3) Raise the temperature to 1630°C and let stand for 11 minutes

[0096] Further heating helps to melt the remaining refractory impurities more thoroughly, making the molten steel more uniform and pure. The static process allows the dense impurities to gradually settle to the bottom of the furnace under the action of gravity, achieving preliminary slag-steel separation, reducing inclusions in the molten steel, reducing the burden for subsequent refining, improving the purity of the steel, and thus improving the quality of the alloy steel.

[0097] (4) Converter operation: Blow oxygen rapidly from the bottom for 6 minutes, stop blowing oxygen and then blow argon for 6 minutes, with the argon flow rate of 8L / min, and then let it stand for 7 minutes

[0098] 1) Rapid oxygen blowing from the bottom: In the converter, rapid oxygen blowing from the bottom can strengthen the oxidation reaction of the molten steel, remove harmful impurities such as sulfur and phosphorus in the molten steel, and reduce their content to an ideal range. For example, excessive sulfur and phosphorus impurities will seriously reduce the toughness and corrosion resistance of the steel. Oxygen blowing can convert them into oxides and enter the slag for removal.

[0099] 2) Argon blowing treatment: Argon blowing can stir the molten steel, making the composition of the molten steel more uniform. At the same time, as an inert gas, argon can prevent the molten steel from being oxidized again in the subsequent process and protect the refining results. The appropriate argon flow rate ensures that the stirring effect is neither too intense to cause the molten steel to splash, but can fully mix the components.

[0100] 3) Standing: Similar to the previous standing, it allows inclusions to settle further, consolidates the refining effect, improves the purity of the molten steel, and provides high-quality basic molten steel for alloying treatment after returning to the medium frequency induction furnace.

[0101] (5) Alloying and composite slag treatment

[0102] 1) Alloying: After the molten steel in the converter is left to stand, it returns to the medium-frequency induction furnace and is alloyed with ferrochrome, ferroniobium, nickel, etc. The composition of the molten steel is precisely adjusted according to the pre-designed chemical composition, so that key elements such as niobium, chromium, and nickel are integrated into the molten steel, giving the steel properties such as wear resistance, corrosion resistance, and high strength and toughness.

[0103] 2) Composite slag treatment: Slag-forming materials (8kg / t) are added after alloying. The slag-forming materials can absorb tiny inclusions in the molten steel, further purify the molten steel, and form a protective slag layer on the surface of the molten steel to reduce heat loss, stabilize the temperature of the molten steel, and inhibit the molten steel from absorbing air to avoid the mixing of new impurities. The slag-forming materials complement the alloying and jointly optimize the quality of the molten steel.

[0104] (6) Heat to 1620°C and let stand for 8 minutes

[0105] Heating again allows the newly added alloying elements to dissolve and diffuse evenly, ensuring the consistency of the entire molten steel system. Standing is also to allow the alloying elements to be fully mixed, the inclusions to further settle, and the molten steel to reach a better refined state, paving the way for subsequent calcification treatment.

[0106] (7) Calcium iron alloy is added to the ladle for calcification treatment for 7 minutes, and the tapping temperature is controlled at 1580℃

[0107] 1) Calcification treatment: Calcium-iron alloy is added to the ladle. The calcium element can combine with impurities such as sulfur and oxygen in the steel to form high-melting point compounds, further remove residual harmful impurities in the molten steel, refine the morphology of inclusions, make them more evenly distributed in the steel, reduce the negative impact on steel performance, and improve the toughness and fatigue resistance of the steel.

[0108] 2) Control the tapping temperature: The tapping temperature of 1580℃ ensures that the molten steel has good fluidity, which is convenient for subsequent casting operations, and avoids problems such as energy waste, molten steel air absorption, and alloy element burning caused by excessive temperature, thereby ensuring the stability of the molten steel quality.

[0109] (8) Adjust the molten steel temperature to 1530°C according to the size of the casting, and then cast the casting

[0110] The molten steel temperature is flexibly adjusted to 1530℃ according to the actual size of the casting in order to adapt to the casting process requirements of castings of different specifications. The appropriate molten steel temperature ensures that the molten steel can be filled smoothly and evenly in the casting mold, avoiding defects such as cold shut and insufficient pouring, ensuring the molding quality of the casting, and laying the foundation for the final high-performance alloy steel casting.

[0111] (9) Cleaning the castings and heat treating them to obtain niobium-containing hypereutectoid wear-resistant alloy steel

[0112] 1) Cleaning castings: remove impurities such as sand and oxide scale on the surface of castings to improve the appearance quality of castings, and at the same time avoid these impurities from having adverse effects on steel properties during subsequent heat treatment.

[0113] 2) Heat treatment:

[0114] Quenching treatment: quenching temperature is 980℃, and the temperature is kept for 7 hours, so that the steel can be quickly cooled to obtain martensitic structure, which greatly improves the hardness and strength of the steel. Martensitic phase transformation strengthening is one of the key means to improve the mechanical properties of steel, giving the steel a good foundation for wear resistance.

[0115] Tempering treatment: The tempering temperature is 500℃ and the heat preservation time is 7h. It is to "temper" the steel after quenching to eliminate the internal stress of quenching, prevent the deformation and cracking of the workpiece, and adjust the toughness of the steel to avoid insufficient toughness due to too high hardness, so as to achieve an optimal balance of strength, hardness and toughness, and finally produce niobium-containing hypereutectoid wear-resistant alloy steel with excellent comprehensive performance.

[0116] Steps are not interchangeable:

[0117] The steps of the entire preparation process are closely linked and interlocked, with a strict logical order, and cannot be changed at will. For example, the raw materials must be melted and initially refined first, and alloying can only be carried out after a large amount of impurities are removed. Otherwise, the alloying elements will react with too many impurities, reducing the alloying effect and even introducing new impurities; the order of oxygen blowing, argon blowing and standing steps in converter refining cannot be reversed. Oxygen blowing first can effectively remove impurities, argon blowing follows closely to prevent oxidation, and standing consolidates the results; the heat treatment step must be carried out after the casting is formed, and performance optimization is achieved through quenching and tempering according to the initial organizational state of the casting. Changing the order will not achieve the expected performance goals.

[0118] Necessity and importance of optimizing process parameters:

[0119] Optimizing process parameters is crucial. For example, slight changes in parameters such as the various heating and standing times, as well as the amount of alloy and slag-making materials added, may affect the final performance of the steel. Improper temperature control may lead to incomplete melting, poor refining effects, and insufficient burning or dissolution of alloy elements; unreasonable time parameters will result in incomplete removal of impurities, incomplete reactions, and uneven structures; inaccurate amounts of material added will make it impossible to accurately control the chemical composition of the steel and achieve the ideal performance ratio. By continuously optimizing process parameters, we can further tap the potential within the existing process framework, so that the performance of niobium-containing hypereutectoid wear-resistant alloy steel can be continuously improved to meet more demanding industrial application scenarios and improve product competitiveness.

[0120] In summary, the method of producing niobium-containing hypereutectoid wear-resistant alloy steel by a medium frequency induction furnace of the present invention has each step performing its own function and acting synergistically, strictly following the process sequence and reasonably optimizing parameters, so that alloy steel products with excellent performance can be efficiently prepared.

[0121] In order to make the disclosure of the present invention more complete, it is described below through more specific embodiments.

[0122] Example 1

[0123] A slag-forming material for producing niobium-containing hypereutectoid wear-resistant alloy steel in a medium-frequency induction furnace comprises the following raw materials, in parts by mass: 18 parts of fluorite, 14 parts of lime, 8 parts of borax, 5 parts of magnesite, 6 parts of dolomite, 10 parts of quartz, 3 parts of gypsum, 12 parts of high-alumina laterite, 2 parts of nickel ore powder, 2.5 parts of titanium nitride, 1.5 parts of zircon, 1.1 parts of aluminum-vanadium master alloy, and 1.8 parts of lithium carbonate.

[0124] The method for preparing slag-making material for producing niobium-containing hypereutectoid wear-resistant alloy steel in a medium-frequency induction furnace comprises the following steps:

[0125] Step 1, weighing the slag-making material raw materials according to the mass ratio;

[0126] Step 2: Mix the raw materials weighed in step 1 thoroughly;

[0127] Step 3, drying the raw materials fully mixed in step 2 at 60° C. for 2.5 hours, maintaining the moisture content at 0.5%, to obtain a dry raw material;

[0128] Step 4: compacting and cutting the raw materials dried in step 3 to make slag-making agent blocks;

[0129] Step 5: Place the slag-forming agent block prepared in step 4 into a graphite crucible heated by medium frequency induction heating, heat it up and melt it, let it stand at 2100°C for 15 minutes, then pour it into a designated metal mold into blocks of different sizes, and finally cool and crush it to obtain a slag-forming material with a particle size of 5-10 mm.

[0130] A method for producing niobium-containing hypereutectoid wear-resistant alloy steel using a medium frequency induction furnace comprises the following steps:

[0131] (1) Design the composition system according to the chemical composition in terms of mass percentage;

[0132] (2) adding raw materials including scrap steel into a medium frequency induction furnace and melting and heating to 1542°C;

[0133] (3) Then raise the temperature to 1630°C and let stand for 11 minutes;

[0134] (4) After standing still, the furnace was quickly transferred to the converter, which was lined with alkaline material. Oxygen was blown quickly at the bottom of the converter for 6 minutes. After the oxygen was stopped, argon was blown for 6 minutes at a flow rate of 8 L / min, and then the furnace was allowed to stand for 7 minutes.

[0135] (5) After the converter molten steel is left to stand, it is quickly transferred to a medium frequency induction furnace, and ferrochromium alloy, ferroniobium alloy and nickel are added for alloying treatment and composite slag treatment. After sampling and analysis are qualified, the molten steel temperature is adjusted to 1530°C. The composite slag treatment method is to add slag materials to the molten steel after the alloying treatment is completed and perform composite slag treatment. The amount of slag materials added is 8 kg / t;

[0136] The qualified components of the samples analyzed are as follows: carbon: 0.9%, silicon: 0.7%, manganese: 0.8%, chromium: 1.2%, nickel: 0.7%, niobium: 0.09%, titanium 0.02%, zirconium 0.01%, oxygen content 10.7ppm, hydrogen content 2.8ppm, the balance is iron and unavoidable impurities;

[0137] (6) Then raise the temperature to 1620°C and let stand for 8 minutes;

[0138] (7) Add calcium iron alloy into the ladle for calcification treatment for 7 minutes, and control the tapping temperature at 1580°C;

[0139] (8) Adjusting the temperature of the molten steel to 1530°C according to the size of the casting, and then casting the casting;

[0140] (9) The casting is cleaned and heat treated to obtain niobium-containing hypereutectoid wear-resistant alloy steel. The heat treatment method is as follows: during quenching treatment, the quenching temperature is 980°C and the holding time is 7 hours; during tempering treatment, the tempering temperature is 500°C and the holding time is 7 hours.

[0141] Example 2

[0142] A slag-forming material for producing niobium-containing hypereutectoid wear-resistant alloy steel in a medium-frequency induction furnace comprises the following raw materials, in parts by mass: 20 parts of fluorite, 16 parts of lime, 10 parts of borax, 6 parts of magnesite, 7 parts of dolomite, 12 parts of quartz, 4 parts of gypsum, 15 parts of high-alumina laterite, 3 parts of nickel ore powder, 2.8 parts of titanium nitride, 1.8 parts of zircon, 1.3 parts of aluminum-vanadium master alloy, and 2.2 parts of lithium carbonate.

[0143] The method for preparing slag-making material for producing niobium-containing hypereutectoid wear-resistant alloy steel in a medium-frequency induction furnace comprises the following steps:

[0144] Step 1, weighing the slag-making material raw materials according to the mass ratio;

[0145] Step 2: Mix the raw materials weighed in step 1 thoroughly;

[0146] Step 3: Dry the raw materials mixed thoroughly in step 2 at 55° C. for 3 h, keeping the moisture content at 0.5%, to obtain a dry raw material;

[0147] Step 4: compacting and cutting the raw materials dried in step 3 to make slag-making agent blocks;

[0148] Step 5: Place the slag-forming agent block prepared in step 4 into a graphite crucible heated by medium frequency induction heating, heat it up and melt it, let it stand at 2000°C for 16 minutes, then pour it into a designated metal mold into blocks of different sizes, and finally cool and crush it to obtain a slag-forming material with a particle size of 5-10 mm.

[0149] The method for producing niobium-containing hypereutectoid wear-resistant alloy steel in a medium frequency induction furnace is the same as that in Example 1.

[0150] Example 3

[0151] A slag-forming material for producing niobium-containing hypereutectoid wear-resistant alloy steel in a medium-frequency induction furnace comprises the following raw materials, in parts by mass: 19 parts of fluorite, 15 parts of lime, 9 parts of borax, 5.5 parts of magnesite, 6.5 parts of dolomite, 11 parts of quartz, 3.5 parts of gypsum, 13 parts of high-alumina laterite, 2.5 parts of nickel ore powder, 2.6 parts of titanium nitride, 1.6 parts of zircon, 1.2 parts of aluminum-vanadium master alloy, and 2.0 parts of lithium carbonate.

[0152] The method for preparing slag-making material for producing niobium-containing hypereutectoid wear-resistant alloy steel in a medium-frequency induction furnace comprises the following steps:

[0153] Step 1, weighing the slag-making material raw materials according to the mass ratio;

[0154] Step 2: Mix the raw materials weighed in step 1 thoroughly;

[0155] Step 3, drying the raw materials fully mixed in step 2 at 50° C. for 3.5 hours, maintaining the moisture content at 0.4%, to obtain a dry raw material;

[0156] Step 4: compacting and cutting the raw materials dried in step 3 to make slag-making agent blocks;

[0157] Step 5: Place the slag-forming agent block prepared in step 4 into a graphite crucible heated by medium frequency induction heating, heat it up and melt it, let it stand at 2200°C for 13 minutes, then pour it into a designated metal mold into blocks of different sizes, and finally cool and crush it to obtain a slag-forming material with a particle size of 5-10 mm.

[0158] The method for producing niobium-containing hypereutectoid wear-resistant alloy steel in a medium frequency induction furnace is the same as that in Example 1.

[0159] Example 4

[0160] A slag-forming material for producing niobium-containing hypereutectoid wear-resistant alloy steel in a medium-frequency induction furnace comprises the following raw materials, in parts by mass: 21 parts of fluorite, 17 parts of lime, 11 parts of borax, 6.5 parts of magnesite, 8 parts of dolomite, 12.5 parts of quartz, 4.5 parts of gypsum, 16 parts of high-alumina laterite, 3.5 parts of nickel ore powder, 2.9 parts of titanium nitride, 1.9 parts of zircon, 1.4 parts of aluminum-vanadium master alloy, and 2.4 parts of lithium carbonate.

[0161] The method for preparing slag-making material for producing niobium-containing hypereutectoid wear-resistant alloy steel in a medium-frequency induction furnace comprises the following steps:

[0162] Step 1, weighing the slag-making material raw materials according to the mass ratio;

[0163] Step 2: Mix the raw materials weighed in step 1 thoroughly;

[0164] Step 3, drying the raw materials fully mixed in step 2 at 70° C. for 1.5 h, maintaining a moisture content of 0.6%, to obtain a dry raw material;

[0165] Step 4: compacting and cutting the raw materials dried in step 3 to make slag-making agent blocks;

[0166] Step 5: Place the slag-forming agent block prepared in step 4 into a graphite crucible heated by medium frequency induction heating, heat it up and melt it, let it stand at 1900°C for 17 minutes, then pour it into a designated metal mold into blocks of different sizes, and finally cool and crush it to obtain a slag-forming material with a particle size of 5-10 mm.

[0167] The method for producing niobium-containing hypereutectoid wear-resistant alloy steel in a medium frequency induction furnace is the same as that in Example 1.

[0168] Example 5

[0169] A slag-forming material for producing niobium-containing hypereutectoid wear-resistant alloy steel in a medium-frequency induction furnace comprises the following raw materials, in parts by mass: 17 parts of fluorite, 13 parts of lime, 7 parts of borax, 4.5 parts of magnesite, 5.5 parts of dolomite, 9 parts of quartz, 2.5 parts of gypsum, 11 parts of high-alumina laterite, 1.5 parts of nickel ore powder, 2.3 parts of titanium nitride, 1.3 parts of zircon, 0.9 parts of aluminum-vanadium master alloy, and 1.6 parts of lithium carbonate.

[0170] The method for preparing slag-making material for producing niobium-containing hypereutectoid wear-resistant alloy steel in a medium-frequency induction furnace comprises the following steps:

[0171] Step 1, weighing the slag-making material raw materials according to the mass ratio;

[0172] Step 2: Mix the raw materials weighed in step 1 thoroughly;

[0173] Step 3, drying the raw materials fully mixed in step 2 at 65°C for 2 hours, maintaining a moisture content of 0.5%, to obtain a dry raw material;

[0174] Step 4: compacting and cutting the raw materials dried in step 3 to make slag-making agent blocks;

[0175] Step 5: Place the slag-forming agent block prepared in step 4 into a graphite crucible heated by medium frequency induction heating, heat it up and melt it, let it stand at 2200°C for 13 minutes, then pour it into a designated metal mold into blocks of different sizes, and finally cool and crush it to obtain a slag-forming material with a particle size of 5-10 mm.

[0176] The method for producing niobium-containing hypereutectoid wear-resistant alloy steel in a medium frequency induction furnace is the same as that in Example 1.

[0177] Example 6

[0178] A slag-forming material for producing niobium-containing hypereutectoid wear-resistant alloy steel in a medium-frequency induction furnace comprises the following raw materials, in parts by mass: 21 parts of fluorite, 18 parts of lime, 10 parts of borax, 7 parts of magnesite, 8 parts of dolomite, 11 parts of quartz, 5 parts of gypsum, 15 parts of high-alumina laterite, 4 parts of nickel ore powder, 2 parts of titanium nitride, 1.8 parts of zircon, 1.2 parts of aluminum-vanadium master alloy, and 2.2 parts of lithium carbonate.

[0179] The method for preparing slag-making material for producing niobium-containing hypereutectoid wear-resistant alloy steel in a medium-frequency induction furnace comprises the following steps:

[0180] Step 1, weighing the slag-making material raw materials according to the mass ratio;

[0181] Step 2: Mix the raw materials weighed in step 1 thoroughly;

[0182] Step 3, drying the raw materials fully mixed in step 2 at 70° C. for 1.5 h, maintaining a moisture content of 0.5%, to obtain a dry raw material;

[0183] Step 4: compacting and cutting the raw materials dried in step 3 to make slag-making agent blocks;

[0184] Step 5: Place the slag-forming agent block prepared in step 4 into a graphite crucible heated by medium frequency induction heating, heat it up and melt it, let it stand at 2300°C for 12 minutes, then pour it into a designated metal mold into blocks of different sizes, and finally cool and crush it to obtain a slag-forming material with a particle size of 5-10 mm.

[0185] The method for producing niobium-containing hypereutectoid wear-resistant alloy steel in a medium frequency induction furnace is the same as that in Example 1.

[0186] Comparative Example 1

[0187] The conventional slag-making material, which only contains 14 parts of lime, 18 parts of fluorite and 10 parts of quartz, is used to prepare the slag-making material and produce niobium-containing hypereutectoid wear-resistant alloy steel according to the process of Example 1.

[0188] Comparative Example 2

[0189] The slag-making material is based on the formula of comparative example 1, with 8 parts of borax added, and the rest is the same as comparative example 1, and the production process remains unchanged.

[0190] Comparative Example 3

[0191] The slag-making material of Example 1 is used, but the converter oxygen blowing and argon blowing treatment are not performed during the method for producing niobium-containing hypereutectoid wear-resistant alloy steel in a medium frequency induction furnace, and the rest is the same as in Example 1.

[0192] Single factor experiment for screening key process parameters for slag material preparation:

[0193] (1) Drying temperature single factor experiment:

[0194] With reference to the preparation process of Example 1, other preparation conditions were set unchanged, and drying temperatures of 45°C, 50°C, 55°C, 60°C, 65°C, and 70°C were selected for experiments. After the slag-making material was prepared, hypereutectoid wear-resistant alloy steel containing niobium was produced according to the process of Example 1, and the sulfur content, phosphorus content, niobium recovery rate, slag viscosity and other indicators of the finished steel were tested. The results are shown in the following table:

[0195]

[0196] The following is an analysis of the above drying temperature single factor experimental results:

[0197] Impact on sulfur content:

[0198] As the drying temperature rises from 45°C to 60°C, the sulfur content gradually decreases from 0.035% to 0.020%. This may be because the increase in temperature promotes related chemical reactions, making it easier to remove sulfur. However, when the temperature exceeds 60°C, the sulfur content rises again, reaching 0.032% at 70°C. It may be that the high temperature causes some side reactions, affecting the desulfurization effect.

[0199] Impact on phosphorus content:

[0200] The phosphorus content also shows a similar pattern. Between 45℃ and 60℃, it gradually decreases with increasing temperature, from 0.050% to 0.035%. It starts to rise after 60℃ and reaches 0.048% at 70℃. This shows that there is also an appropriate range for temperature to remove phosphorus. Around 60℃ may be a more ideal drying temperature point, which can effectively reduce the phosphorus content.

[0201] Impact on niobium recovery rate:

[0202] The niobium recovery rate first increases and then decreases with the increase of drying temperature. It reaches a high level between 55℃ and 60℃, 87% at 55℃ and 89% at 60℃. This shows that within this temperature range, it is conducive to the recovery of niobium elements, which may be because this temperature range makes the balance of related reactions more inclined to niobium enrichment. After 60℃, the niobium recovery rate begins to decline, which may be because high temperature has an adverse effect on the existence form or reaction process of niobium.

[0203] Influence on slag viscosity:

[0204] The viscosity of the slag decreases as the drying temperature increases, from 2.5 Pa·s at 45°C to 1.5 Pa·s at 60°C. This is because the increase in temperature usually increases the fluidity of the materials in the slag, thereby reducing the viscosity. However, at 65°C and 70°C, the viscosity of the slag increases again, which may be due to the high temperature causing some components in the slag to change, affecting its fluidity.

[0205] On the whole, in the single factor experiment, 60℃ is a relatively optimal drying temperature. At this temperature, the sulfur and phosphorus contents are low, the niobium recovery rate is high, and the slag viscosity is also at a low level, which is conducive to the production of niobium-containing hypereutectoid wear-resistant alloy steel.

[0206] (2) Drying time single factor experiment:

[0207] Referring to the preparation process of Example 1, other preparation conditions were set unchanged, and the drying time was set to 1.5h, 2h, 2.5h, 3h, and 3.5h to conduct experiments and test the relevant performance indicators of the finished steel. The results are as follows:

[0208]

[0209] The following is an analysis of the single factor experimental results of drying time:

[0210] Impact on sulfur content:

[0211] When the drying time increased from 1.5h to 2.5h, the sulfur content gradually decreased from 0.032% to 0.020%. This may be because the sulfur removal reaction was more complete with the extension of drying time. However, when the drying time exceeded 2.5h, the sulfur content increased again, reaching 0.027% at 3.5h. It may be that the excessive drying time caused some other reactions to occur, affecting the desulfurization effect.

[0212] Impact on phosphorus content:

[0213] The phosphorus content also showed a trend of decreasing first and then increasing. Between 1.5h and 2.5h, as the drying time increased, the phosphorus content decreased from 0.046% to 0.035%. It began to increase after 2.5h and reached 0.044% at 3.5h. This shows that there is also an appropriate range for the removal of phosphorus by drying time. Around 2.5h may be a more ideal drying time point, which can effectively reduce the phosphorus content.

[0214] Impact on niobium recovery rate:

[0215] The niobium recovery rate first increased and then decreased with the increase of drying time. It reached the highest 89% at 2.5h, which shows that this drying time is conducive to the recovery of niobium elements. It may be that this period of time makes the relevant reactions reach a better equilibrium state, which is more conducive to the enrichment of niobium. After 2.5h, the niobium recovery rate began to decline, which may be that the excessive drying time has an adverse effect on the existence form or reaction process of niobium.

[0216] Impact on slag fluidity:

[0217] The fluidity of the slag gradually increased from 12 cm / s to 20 cm / s when the drying time increased from 1.5 h to 2.5 h, indicating that the fluidity of the slag improved with the extension of the drying time. It may be that the drying process made the composition of the slag more uniform, or removed some substances that affect the fluidity. However, after 2.5 h, the fluidity of the slag began to decrease, and dropped to 14 cm / s at 3.5 h. It may be that the excessive drying time caused some components in the slag to change, which in turn affected its fluidity.

[0218] On the whole, in the single factor experiment, 2.5h is a relatively optimal drying time. Under this time, the sulfur content and phosphorus content are low, the niobium recovery rate is high, and the slag fluidity is also at a good level, which is conducive to the production of niobium-containing hypereutectoid wear-resistant alloy steel.

[0219] (3) Melting temperature single factor experiment:

[0220] Referring to the preparation process of Example 1, other preparation conditions were set unchanged, the melting temperature was changed to 1800°C, 1900°C, 2000°C, 2100°C, 2200°C, 2300°C, and 2400°C, and other steps were carried out according to the standard process. The grain size, strength, hardness and other indicators of the finished steel were tested, and the results were as follows:

[0221]

[0222]

[0223] The following is an analysis of the above data on the relationship between melting temperature and finished steel performance indicators:

[0224] Relationship between grain size and melting temperature:

[0225] As the melting temperature rises from 1800℃ to 2100℃, the grain size gradually decreases from 45μm to 30μm. This is because at higher melting temperatures, the diffusion ability of atoms is enhanced, the nucleation rate increases, and the growth rate is relatively slow, resulting in grain refinement. However, when the temperature exceeds 2100℃, the grain size begins to increase, reaching 42μm at 2400℃. This may be because the excessively high temperature causes the grain growth rate to exceed the nucleation rate, resulting in grain coarsening.

[0226] Relationship between strength and melting temperature:

[0227] The strength gradually increases from 1050MPa to 1205MPa as the melting temperature rises from 1800℃ to 2100℃. This is related to grain refinement. According to the Hall-Page formula, the finer the grains, the larger the grain boundary area, the greater the resistance to dislocation movement, and the higher the strength of the material. When the temperature continues to rise, the strength begins to decrease, and at 2400℃ the strength drops to 1082MPa. This is because the grain coarsening weakens the grain boundary strengthening effect and reduces the material strength.

[0228] Relationship between hardness and melting temperature:

[0229] The hardness change trend is similar to that of strength. It increases with the increase of temperature in the range of 1800℃-2100℃, from 382HB to 431HB. This is also because the grain refinement increases the resistance to dislocation movement, thereby increasing the hardness. After 2100℃, the hardness decreases with the increase of temperature, and drops to 392HB at 2400℃, which is also caused by grain coarsening.

[0230] On the whole, within the scope of this experiment, when the melting temperature is 2100℃, the finished steel has relatively good comprehensive performance in terms of grain size, strength and hardness, and can obtain relatively fine grains and higher strength and hardness.

[0231] (4) Single factor experiment of slag material particle size:

[0232] Referring to the preparation process of Example 1, other preparation conditions are set unchanged, the particle size of the slag-making material after crushing is set to 2-5mm, 5-10mm, 10-15mm, 15-20mm, and production is carried out according to the standard process. The indicators such as molten steel refining time and inclusion removal rate are tested, and the results are as follows:

[0233] Slag material size (mm) Molten steel refining time (min) Inclusion removal rate (%) 2-5 35 71 5-10 30 80 10-15 38 75 15-20 45 65

[0234] The following is an analysis of the above data on the relationship between the particle size of slag-making materials and related indicators of molten steel refining:

[0235] Relationship between molten steel refining time and slag material particle size:

[0236] When the particle size of the slag-making material is 2-5mm, the refining time of the molten steel is 35min. As the particle size increases to 5-10mm, the refining time is shortened to 30min. However, when the particle size continues to increase and exceeds 10mm, the refining time of the molten steel begins to increase again, reaching 45min at 15-20mm. This may be because when the particle size is 5-10mm, the contact area and reaction activity of the slag-making material and the molten steel are more suitable, and the refining reaction can be completed in a shorter time. However, if the particle size is too small (2-5mm), the slag-making material may be unevenly distributed in the molten steel, affecting the reaction efficiency; if the particle size is too large (10-20mm), the reaction contact area will be reduced, the reaction speed will be slowed down, and the refining time will be extended.

[0237] Relationship between inclusion removal rate and slag-making material particle size:

[0238] The inclusion removal rate reaches the highest level of 80% when the particle size of the slag-forming material is 5-10mm. When the particle size is smaller or larger than this range, the removal rate decreases. It is 71% at 2-5mm, 75% at 10-15mm, and drops to 65% at 15-20mm. This shows that the particle size of 5-10mm can provide the best reaction conditions, so that the slag-forming material and inclusions can fully contact and react, thereby achieving a higher removal rate. When the particle size is not appropriate, the inclusion removal rate may be reduced due to insufficient reaction or the slag-forming material cannot effectively play its role.

[0239] On the whole, in this experiment, when the particle size of the slag-making material is 5-10mm, the overall performance in terms of molten steel refining time and inclusion removal rate is relatively good, and a higher inclusion removal rate can be obtained in a shorter refining time.

[0240] Testing of slag-making materials and performance indicators of hypereutectoid wear-resistant alloy steel containing niobium:

[0241] (1) Slag material performance testing:

[0242] The melting point, viscosity, basicity and other indicators of the prepared slag-making material were tested, and the results are as follows:

[0243]

[0244]

[0245] These indicators show that the slag-making material has a suitable melting point, good fluidity and appropriate basicity, and can meet the requirements of refining niobium-containing hypereutectoid steel in a medium-frequency induction furnace.

[0246] (2) Performance test of hypereutectoid wear-resistant alloy steel containing niobium:

[0247] The niobium-containing hypereutectoid wear-resistant alloy steels of Examples 1-6 and Comparative Examples 1-3 were selected to test performance indicators such as hardness, toughness, wear resistance, and corrosion resistance. The results are as follows:

[0248]

[0249] It can be seen from the above table:

[0250] In terms of hardness: the hardness value of the embodiment is between 410-431 HB, and the hardness value of the comparative example is between 386-403 HB. It can be seen that the hardness of the niobium-containing hypereutectoid wear-resistant alloy steel of the embodiment is significantly higher than that of the comparative example, which shows that the preparation method or component design adopted in the embodiment is more conducive to improving the hardness of the material.

[0251] Toughness: The toughness of the embodiment is 60-65 J / cm 2 Range, the toughness of the comparative example is 52-57J / cm 2 The toughness of the embodiment is also better than that of the comparative example, which shows that while the hardness is improved, the material of the embodiment still maintains good toughness and has good comprehensive mechanical properties.

[0252] In terms of wear resistance: the wear resistance value of the embodiment is 0.82-0.95 g / h, and the wear resistance value of the comparative example is 1.10-1.21 g / h. The smaller the value, the better the wear resistance, so the wear resistance of the embodiment is significantly better than that of the comparative example, which is a very critical performance improvement for wear-resistant alloy steel.

[0253] In terms of corrosion resistance: the corrosion resistance of the embodiment is 0.052-0.073 mm / a, and the corrosion resistance of the comparative example is 0.089-0.112 mm / a. The smaller the value, the stronger the corrosion resistance. The corrosion resistance of the embodiment is significantly higher than that of the comparative example, indicating that the material of the embodiment performs better in corrosion resistance.

[0254] In general, from the data comparison, it can be seen that the hardness, toughness, wear resistance and corrosion resistance of the embodiment are significantly better than those of the comparative example. Theoretical analysis shows that the slag-making material of the present invention optimizes the molten steel refining process, the alloy elements are reasonably used, the grains are refined, and the heat treatment process is appropriate, which together greatly improves the performance of the steel. However, the comparative example cannot achieve the technical effect of the present invention due to the use of traditional slag-making materials or processes, which fully proves that the technology of the present invention has significant progress.

[0255] The above contents are further detailed descriptions of the present invention in combination with specific / preferred implementations, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, they can also make several substitutions or modifications to these described embodiments without departing from the concept of the present invention, and these substitutions or modifications should be regarded as belonging to the protection scope of the present invention.

Claims

1. A slag-making material for producing niobium-containing hypereutectoid wear-resistant alloy steel in a medium frequency induction furnace, characterized in that: The raw materials are as follows, in parts by mass: 16-22 parts of fluorite, 11-19 parts of lime, 2-12 parts of borax, 3-7 parts of magnesite, 2-9 parts of dolomite, 7-13 parts of quartz, 2-5 parts of gypsum, 6-17 parts of high-alumina laterite, 1-4 parts of nickel ore powder, 2-3 parts of titanium nitride, 1-2 parts of zircon, 0.8-1.4 parts of aluminum-vanadium master alloy and 1.2-2.5 parts of lithium carbonate.

2. The slag-making material for producing niobium-containing hypereutectoid wear-resistant alloy steel by a medium frequency induction furnace according to claim 1, characterized in that: The raw materials are as follows, in parts by mass: 18 parts of fluorite, 14 parts of lime, 8 parts of borax, 5 parts of magnesite, 6 parts of dolomite, 10 parts of quartz, 3 parts of gypsum, 12 parts of high-alumina laterite, 2 parts of nickel ore powder, 2.5 parts of titanium nitride, 1.5 parts of zircon, 1.1 parts of aluminum-vanadium master alloy, and 1.8 parts of lithium carbonate.

3. The slag-making material for producing niobium-containing hypereutectoid wear-resistant alloy steel by a medium frequency induction furnace according to claim 1, characterized in that: 20 parts of fluorite, 16 parts of lime, 10 parts of borax, 6 parts of magnesite, 7 parts of dolomite, 12 parts of quartz, 4 parts of gypsum, 15 parts of high-alumina laterite, 3 parts of nickel ore powder, 2.8 parts of titanium nitride, 1.8 parts of zircon, 1.3 parts of aluminum-vanadium master alloy, and 2.2 parts of lithium carbonate.

4. The slag-making material for producing niobium-containing hypereutectoid wear-resistant alloy steel by a medium frequency induction furnace according to claim 1, characterized in that: 19 parts of fluorite, 15 parts of lime, 9 parts of borax, 5.5 parts of magnesite, 6.5 parts of dolomite, 11 parts of quartz, 3.5 parts of gypsum, 13 parts of high-alumina laterite, 2.5 parts of nickel ore powder, 2.6 parts of titanium nitride, 1.6 parts of zircon, 1.2 parts of aluminum-vanadium master alloy, and 2.0 parts of lithium carbonate.

5. The slag-making material for producing niobium-containing hypereutectoid wear-resistant alloy steel by a medium frequency induction furnace according to claim 1, characterized in that: 21 parts of fluorite, 17 parts of lime, 11 parts of borax, 6.5 parts of magnesite, 8 parts of dolomite, 12.5 parts of quartz, 4.5 parts of gypsum, 16 parts of high-alumina laterite, 3.5 parts of nickel ore powder, 2.9 parts of titanium nitride, 1.9 parts of zircon, 1.4 parts of aluminum-vanadium master alloy, and 2.4 parts of lithium carbonate.

6. The slag-making material for producing niobium-containing hypereutectoid wear-resistant alloy steel by a medium frequency induction furnace according to claim 1, characterized in that: 17 parts of fluorite, 13 parts of lime, 7 parts of borax, 4.5 parts of magnesite, 5.5 parts of dolomite, 9 parts of quartz, 2.5 parts of gypsum, 11 parts of high-alumina laterite, 1.5 parts of nickel ore powder, 2.3 parts of titanium nitride, 1.3 parts of zircon, 0.9 parts of aluminum-vanadium master alloy, and 1.6 parts of lithium carbonate.

7. The slag-making material for producing niobium-containing hypereutectoid wear-resistant alloy steel by a medium frequency induction furnace according to claim 1, characterized in that: 21 parts of fluorite, 18 parts of lime, 10 parts of borax, 7 parts of magnesite, 8 parts of dolomite, 11 parts of quartz, 5 parts of gypsum, 15 parts of high-alumina laterite, 4 parts of nickel ore powder, 2 parts of titanium nitride, 1.8 parts of zircon, 1.2 parts of aluminum-vanadium master alloy, and 2.2 parts of lithium carbonate.

8. A method for preparing slag-making material for producing hypereutectoid wear-resistant alloy steel containing niobium in a medium frequency induction furnace according to any one of claims 1 to 7, characterized in that: The following steps are involved: Step 1, weighing the slag-making material raw materials according to the mass ratio; Step 2: Mix the raw materials weighed in step 1 thoroughly; Step 3, drying the raw materials fully mixed in step 2 at 45-70° C. for 1.5-3.5 hours, keeping the moisture content ≤ 0.6%, to obtain a dry raw material; Step 4: compacting and cutting the raw materials dried in step 3 to make slag-making agent blocks; Step 5: Place the slag-forming agent block prepared in step 4 into a graphite crucible heated by medium frequency induction heating, heat it up and melt it, let it stand at 1800-2400°C for 10-20 minutes, then pour it into a designated metal mold into blocks of different sizes, and finally cool and crush it to obtain the slag-forming material.

9. The method for preparing slag-making material for producing niobium-containing hypereutectoid wear-resistant alloy steel by medium frequency induction furnace according to claim 8, characterized in that: The particle size of the slag-making material is 5-10 mm.

10. Use of the slag-making material prepared according to the method of claim 8 or 9 in producing niobium-containing hypereutectoid wear-resistant alloy steel.

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