A molybdenum-containing steel and a method for smelting the same

Abstract

This application discloses a molybdenum-containing steel and its smelting method. The smelting method includes hot metal pretreatment, converter smelting, converter tapping, LF furnace refining, and continuous casting. Utilizing the scouring effect of blast furnace hot metal and the carbon element in the blast furnace hot metal, the molybdenum element in the first molybdenum oxide raw material is reduced to obtain molybdenum-containing hot metal. In the converter tapping process, a second molybdenum oxide raw material is added to the bottom of the ladle, and then the molten steel is poured into the ladle. During the pouring process, a deoxidizer is added, and argon gas is blown into the bottom of the ladle for stirring, thus obtaining molten steel. In the LF furnace refining process, the molten steel is heated, and the argon gas flow rate in the ladle is increased to promote the complete reduction of molybdenum from the molybdenum oxide in the molten steel. The molten steel is then fed into the LF furnace, where a ferromolybdenum alloy is added to fine-tune the molybdenum content to achieve the target value, resulting in finely tuned molten steel. The technical solution of this application can reduce the manufacturing cost of molybdenum-containing steel while ensuring its performance.

Description

Technical Field

[0001] This application relates to the field of iron and steel smelting, and in particular to a molybdenum-containing steel and a method for smelting the same. Background Technology

[0002] Molybdenum-containing steel, as an important alloy structural steel, plays an indispensable role in modern industry. The addition of molybdenum improves the overall performance of steel, with its main effects manifested in multiple dimensions. First, molybdenum effectively strengthens the steel matrix and refines the grain, thereby significantly improving the steel's high-temperature strength, creep resistance, and endurance strength, ensuring the steel remains stable under high-temperature environments and is less prone to deformation or failure. Second, molybdenum significantly enhances the hardenability and hot strength of steel, which is crucial for manufacturing critical components that bear heavy loads (such as pressure vessels, high-temperature valves, and aerospace fasteners). Furthermore, in stainless steel, molybdenum greatly enhances the material's corrosion resistance, particularly effectively inhibiting pitting and crevice corrosion, and improving the steel's stability in chloride media and acidic environments. Due to these excellent properties, molybdenum-containing steel is often used to manufacture high-temperature, high-pressure, and corrosion-resistant high-end components, becoming a key material in the energy, chemical, and special machinery fields.

[0003] However, despite the superior performance of molybdenum-containing steel, its widespread application has long been constrained by its high manufacturing costs. Currently, industrial production typically introduces molybdenum by directly adding high-purity ferromolybdenum alloys. Molybdenum, as a rare and precious metal, commands a market price far exceeding that of ordinary steel, and the complex preparation process of ferromolybdenum alloys results in extremely high raw material procurement costs. This direct alloying method makes the production cost of molybdenum-containing steel several times that of ordinary carbon steel, significantly weakening the product's market competitiveness. Therefore, how to effectively reduce the cost of introducing molybdenum without sacrificing steel performance and develop an economical and efficient method for smelting molybdenum-containing steel has become a pressing technical challenge for those skilled in the art. Summary of the Invention

[0004] In view of the above problems, this application provides a molybdenum-containing steel and its smelting method, which can reduce the manufacturing cost of molybdenum-containing steel while ensuring its performance.

[0005] In a first aspect, this application provides a method for smelting molybdenum-containing steel, comprising the following steps: The hot metal pretreatment involves adding a first molybdenum oxide raw material to the hot metal ladle beforehand, and then receiving the blast furnace hot metal at the blast furnace tap hole; by utilizing the scouring effect of the blast furnace hot metal and the carbon element in the blast furnace hot metal, the molybdenum element in the first molybdenum oxide raw material is reduced to obtain molybdenum-containing hot metal. In converter smelting, molten iron containing molybdenum is poured into a converter for oxygen blowing smelting to obtain converter steel. After tapping the steel from the converter, a second molybdenum oxide raw material is added to the bottom of the ladle. Then, the molten steel from the converter is poured into the ladle. During the process of pouring the molten steel from the converter into the ladle, a deoxidizer is added. At the same time, argon gas is blown into the bottom of the ladle for stirring to obtain molten steel. LF furnace refining involves feeding molten steel into the LF furnace, heating the molten steel, and adding aluminum blocks and lime for deoxidation and slagging. After deoxidation and slagging are completed, ferromolybdenum alloy is added to finely adjust the molybdenum content in the molten steel to achieve the target value, resulting in finely adjusted molten steel. During the heating process, the bottom blowing flow rate of the ladle is increased to promote the full reduction of molybdenum in the second molybdenum oxide raw material. Continuous casting involves continuously casting finely tuned molten steel to obtain molybdenum-containing steel slabs.

[0006] In some embodiments, the amount of the first molybdenum oxide raw material added to the molten iron ladle accounts for 85% to 90% of the total amount of molybdenum oxide raw material added; and / or, the mass of molybdenum element brought in by the first molybdenum oxide raw material accounts for 85% to 90% of the total mass of molybdenum element in the fine-tuned molten steel.

[0007] In some embodiments, the temperature of the blast furnace molten iron is 1450℃~1500℃, and the carbon mass percentage in the blast furnace molten iron is 4.3%~4.5%; the process of receiving the blast furnace molten iron lasts for 25~30 minutes.

[0008] In some embodiments, during the converter tapping step, the addition of the second molybdenum oxide raw material is initiated 2 to 5 minutes before the start of converter tapping and is completed before the start of converter tapping.

[0009] In some embodiments, during the converter tapping step, the ladle bottom blowing argon flow rate is 200–400 L / min.

[0010] In some embodiments, during the LF furnace refining step, the flow rate of bottom-blown argon gas in the ladle is controlled at 600-800 L / min to raise the temperature of the molten steel to 1580℃~1620℃; and during the refining process, aluminum blocks are added at a rate of 0.5~1.0 kg / ton of molten steel, and lime is added at a rate of 3~8 kg / ton of molten steel.

[0011] In some embodiments, the mass percentage content of each component in the first molybdenum oxide raw material and the second molybdenum oxide raw material is Mo ≤60%, sulfur (S) ≤0.15%, phosphorus (P) ≤0.05%, and Cu ≤1.0%.

[0012] In some embodiments, the amount of ferromolybdenum alloy added accounts for 5% to 10% of the total molybdenum metal content, and is used to fine-tune the molybdenum content in the molten steel to the target composition range.

[0013] Secondly, this application also provides a molybdenum-containing steel, which is prepared by the smelting method of the molybdenum-containing steel described in the above embodiments.

[0014] In some embodiments, molybdenum-containing steel comprises, by mass percentage: C: 0.05%-0.20%, Si: 0.10%-0.50%, Mn: 0.50%-1.50%, P≤0.015%, S≤0.005%, Mo: 0.15%-0.20%, with the balance being iron and unavoidable impurities.

[0015] The technical solution of this application utilizes the high temperature and high carbon environment of blast furnace molten iron in the ladle to pre-reduce molybdenum oxide, and combines secondary reduction during the converter tapping process with fine-tuning in the LF furnace refining process. This not only significantly reduces the dependence on expensive ferromolybdenum alloys and greatly saves production costs, but also utilizes the physical heat and chemical energy of molten iron to improve the reduction efficiency and yield of molybdenum, effectively avoiding the problems of compositional segregation and yield fluctuations caused by direct alloying. At the same time, the purity and compositional uniformity of the molten steel are ensured by high-flow-rate argon gas and bottom blowing agitation, ultimately obtaining high-quality molybdenum-containing steel with excellent high-temperature strength, corrosion resistance and high stability.

[0016] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0017] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings, in which the same or similar reference numerals denote the same or similar features, and the drawings are not drawn to scale.

[0018] Figure 1 This is a schematic flowchart of a method for smelting molybdenum-containing steel according to an embodiment of this application. Detailed Implementation

[0019] The features and exemplary embodiments of various aspects of the present invention will now be described in detail. To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only configured to explain the present invention and are not configured to limit the present invention. For those skilled in the art, the present invention can be practiced without some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the present invention by illustrating examples of the invention.

[0020] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes said element.

[0021] It should be understood that when describing the structure of a component, when referring to a layer or region as being "above" or "on top of" another layer or region, it can mean that it is directly above the other layer or region, or that it contains other layers or regions between it and the other layer or region. Furthermore, if the component is flipped over, that layer or region will be located "below" or "under" the other layer or region.

[0022] The features and exemplary embodiments of various aspects of the present invention will now be described in detail. Furthermore, the features, structures, or characteristics described below may be combined in any suitable manner in one or more embodiments.

[0023] In the smelting process of converter or electric arc furnace, if molybdenum oxide (MoO3) is added directly, it will easily volatilize at high temperatures or float on the surface of molten steel and be carried away by the smoke and dust due to its low melting point and low density. At the same time, the reduction reaction of molybdenum oxide requires a large amount of carbon or aluminum. If the reaction kinetics are not sufficient, the reduction of molybdenum will be incomplete, resulting in a large fluctuation in the yield of molybdenum. This not only wastes valuable resources, but also makes it difficult to accurately control the final composition of molten steel.

[0024] To address the aforementioned issues, embodiments of this application provide a method for smelting molybdenum-containing steel. By pre-reducing molybdenum oxide in the high-temperature and high-carbon environment of blast furnace molten iron within the ladle, the excess carbon in the molten iron is fully utilized as a reducing agent. This directly reduces and dissolves the inexpensive molybdenum oxide in the molten iron, replacing the expensive ferromolybdenum alloy used in traditional processes and significantly reducing alloy costs. Furthermore, by combining secondary reduction during converter tapping with fine-tuning in the LF furnace, a staged alloying strategy is employed to further improve the molybdenum yield, avoiding the compositional segregation and temperature drop problems caused by directly adding large amounts of ferromolybdenum alloy. Moreover, the physical heat and chemical energy of the molten iron effectively solve the problems of easy volatilization and low yield of molybdenum oxide when directly added to molten steel. Simultaneously, bottom blowing and stirring ensure the purity and compositional uniformity of the molten steel, ultimately achieving stable smelting of low-cost, high-quality molybdenum-containing steel.

[0025] like Figure 1 As shown, the smelting method for molybdenum-containing steel provided in the embodiments of this application includes: S1. Hot metal pretreatment: First molybdenum oxide raw material is added to the hot metal ladle in advance, and then the hot metal is collected at the tapping point of the blast furnace; the molybdenum element in the first molybdenum oxide raw material is reduced by the scouring action of the hot metal and the carbon element in the hot metal to produce molybdenum-containing hot metal. S2. Converter smelting: Molybdenum-containing molten iron is poured into a converter for oxygen blowing smelting to obtain converter steel liquid; S3. Converter tapping: Add second molybdenum oxide raw material to the bottom of the ladle, then pour the converter molten steel into the ladle. During the pouring process, add deoxidizer and blow argon gas into the bottom of the ladle for stirring to obtain molten steel. S4 and LF furnace refining: molten steel is fed into the LF furnace, heated, and aluminum blocks and lime are added for deoxidation and slag formation. After deoxidation and slag formation, ferromolybdenum alloy is added to finely adjust the molybdenum content in the molten steel to achieve the target value, resulting in finely adjusted molten steel. During the heating process, the bottom blowing flow rate of the ladle is increased to promote the full reduction of molybdenum in the second molybdenum oxide raw material. S5 continuous casting involves continuously casting finely tuned molten steel to obtain molybdenum-containing steel slabs.

[0026] In the hot metal pretreatment step, the high temperature (around 1500℃) and high carbon content (4.3%-4.5%) of the blast furnace hot metal are used to reduce molybdenum from molybdenum oxide, replacing the expensive ferromolybdenum alloy. In the converter smelting step, the molybdenum-containing hot metal is smelted together with scrap steel using oxygen blowing, ensuring the uniformity of the steel's basic composition. This creates favorable temperature and molten pool conditions for the subsequent addition of molybdenum oxide during tapping. Before tapping, molybdenum oxide is added to the bottom of the ladle, and the high temperature of the molten steel (>1600℃) and bottom argon stirring (600-800 L / min) rapidly melt and reduce the molybdenum oxide. The addition of deoxidizers (silicon manganese, ferrosilicon, aluminum blocks) creates a reducing environment, improving the molybdenum yield. This step can adjust the molybdenum content to approximately 95% of the target value, further reducing the amount of ferromolybdenum added to the LF furnace. Heating to 1600℃ improves the reduction kinetics of molybdenum oxide. Aluminum blocks and lime are added for deep deoxidation and desulfurization, reducing inclusions in the steel and improving its purity. A small amount of ferromolybdenum (e.g., 69 kg) is precisely added based on the molybdenum content in the steel sample (e.g., 0.174%) to achieve precise control of the molybdenum content, ensuring the finished product meets quality standards. Ultimately, the molybdenum reduction rate reaches over 95%.

[0027] The above-mentioned technical solution uses molybdenum oxide to replace 85%-90% of the ferromolybdenum alloy, making full use of the carbon elements in the blast furnace hot iron and the high-temperature conditions for reduction, significantly reducing the amount of expensive ferromolybdenum and effectively reducing the smelting cost of molybdenum-containing steel. Through the control of "hot iron pre-reduction + converter tapping with molybdenum oxide addition + early reduction in the LF furnace + fine-tuning of ferromolybdenum in the later stage", the overall molybdenum reduction rate reaches more than 95%, reducing the waste of molybdenum elements and improving resource utilization. In the LF furnace stage, a small amount of ferromolybdenum (e.g., 69 kg) is precisely added according to the actual molybdenum content of the molten steel (e.g., 0.174% in the example) to avoid excessive or insufficient composition and ensure that the final product meets the steel grade requirements. At the same time, it avoids the high-energy-consuming and high-polluting links in the ferromolybdenum smelting process, reduces the emission of harmful substances, and conforms to the development direction of green and low-carbon metallurgy. Furthermore, this invention can be implemented using existing converter-LF-continuous casting production lines without additional investment and is applicable to the production of various molybdenum-containing steel grades (e.g., molybdenum-containing high-strength steel).

[0028] In some embodiments of this application, the amount of the first molybdenum oxide raw material added to the molten iron ladle accounts for 85% to 90% of the total amount of molybdenum oxide raw material added; and / or, the mass of molybdenum element brought in by the first molybdenum oxide raw material accounts for 85% to 90% of the total mass of molybdenum element in the fine-tuned molten steel.

[0029] In the above method, 85%–90% of the molybdenum element is provided by molybdenum oxide, with only 10%–15% supplemented by fine-tuning with ferromolybdenum in the LF furnace stage. This significantly reduces dependence on high-cost ferromolybdenum and further compresses alloy costs. Blast furnace hot metal, with its high carbon content (4.3%–4.5%) and temperature (1500℃), is an ideal medium for reducing molybdenum oxide. Adding the majority of molybdenum oxide during the hot metal pretreatment stage maximizes the utilization of the hot metal's reduction potential and improves the pre-reduction rate of molybdenum. Since most of the molybdenum has already been reduced into the molten steel during the hot metal stage, only a small amount of molybdenum oxide and ferromolybdenum needs to be added during the converter tapping and LF furnace stages, reducing the reduction pressure and alloy adjustment difficulty in the converter and LF furnace. Furthermore, it avoids concentrating a large amount of molybdenum oxide into the converter tapping or LF furnace stages, reducing molybdenum loss due to factors such as strong oxidizing properties, large slag volume, and temperature fluctuations. The overall molybdenum yield can be stably controlled above 95%. A 10%–15% margin is reserved for molybdenum content, which can be fine-tuned during the LF furnace stage based on actual test results. This leverages the cost advantage of molybdenum oxide while ensuring that the finished product's molybdenum content accurately meets the target value for the steel grade, avoiding either excessive or insufficient content. Through this setup, the reducing power of blast furnace hot metal can be maximized to replace expensive ferromolybdenum, effectively reducing smelting costs while simultaneously improving molybdenum yield and stability, all while ensuring precise control over molybdenum content.

[0030] In some embodiments of this application, the temperature of the blast furnace molten iron is 1450℃~1500℃, and the carbon mass percentage of the blast furnace molten iron is 4.3%~4.5%; the process of receiving the blast furnace molten iron lasts for 25~30 minutes.

[0031] The high temperature of 450℃ to 1500℃ provides favorable thermodynamic and kinetic conditions for the reduction reaction between molybdenum oxide and molten iron, facilitating the rapid reduction of molybdenum from oxides by carbon. The high carbon content of 4.3% to 4.5% in the molten iron provides ample reducing agent for the reduction of molybdenum oxide. Carbon reacts with molybdenum oxide to generate CO or CO2, driving the reduction reaction continuously without the need for additional reducing agent. The tapping time is controlled at 25 to 30 minutes, allowing the molybdenum oxide to fully contact, mix, and react with the molten iron under the washing and stirring action, preventing incomplete reduction of molybdenum oxide that could be carried into subsequent processes due to insufficient reaction time. Under the synergistic effect of the above temperature, carbon content, and time conditions, most of the molybdenum in the molybdenum oxide can be reduced into the molten iron during the pretreatment stage, significantly improving the pre-reduction rate and laying the foundation for an overall molybdenum yield of over 95%. Since efficient reduction is achieved in the molten iron stage, only a small amount of residual molybdenum oxide needs to be treated in the converter tapping and LF furnace stages, reducing the risk of molybdenum loss due to the oxidizing atmosphere in the converter and also reducing the consumption of deoxidizer in the LF furnace.

[0032] In some embodiments of this application, the temperature of the blast furnace molten iron is 1450℃~1500℃, and the carbon content in the blast furnace molten iron is 4.3%~4.5% by mass; the process of receiving the blast furnace molten iron lasts for 25~30 minutes. By controlling the above conditions, the high temperature and high carbon characteristics of the blast furnace molten iron and the sufficient tapping time can be fully utilized to efficiently reduce molybdenum in molybdenum oxide during the molten iron pretreatment stage, improve the pre-reduction rate of molybdenum, reduce the reduction burden for subsequent processes, and ensure that the overall molybdenum yield consistently reaches over 95%.

[0033] In some embodiments of this application, in the converter tapping step, the addition of the second molybdenum oxide raw material is initiated 2 to 5 minutes before the start of converter tapping and is completed before the start of converter tapping.

[0034] Before tapping, the second molybdenum oxide is pre-added to the bottom of the ladle. During tapping, the high-temperature molten steel flows from the converter into the ladle, creating a strong impact and agitation on the molybdenum oxide at the bottom, causing it to disperse, melt, and react rapidly without the need for additional stirring equipment. At the end of the converter blowing process, the slag layer inside the furnace is highly oxidizing. If molybdenum oxide is added directly to the converter, some molybdenum may be oxidized and lost. Adding molybdenum oxide to the ladle instead of the converter effectively isolates the oxidizing slag and reduces the oxidation loss of molybdenum. During tapping, the temperature of the molten steel is usually above 1600℃. The second molybdenum oxide comes into contact with the high-temperature molten steel at the bottom of the ladle. Combined with deoxidizers added during tapping (such as ferrosilicon, ferrosilicon, and aluminum blocks), it can be rapidly reduced in a reducing atmosphere, improving the molybdenum yield. Adding molybdenum oxide before tapping ensures that molybdenum oxide reacts with the molten steel throughout the entire tapping process (usually several minutes). At the same time, the argon gas stirring at the bottom further enhances mass transfer, resulting in more complete reduction compared to adding it during or after tapping. This operating method is highly compatible with existing converter tapping processes. It only requires adding molybdenum oxide to the bottom of the empty ladle before tapping, without adding any additional equipment or operating steps, making it easy to promote and apply on existing production lines.

[0035] In the above technical solution, during the converter tapping process, the addition of the second molybdenum oxide raw material is initiated 2-5 minutes before the start of converter tapping and completed before tapping begins. This operation allows the second molybdenum oxide to be pre-placed at the bottom of the ladle, achieving rapid dispersion and reduction through the strong impact and stirring of the high-temperature molten steel during tapping. Simultaneously, it avoids contact between the molybdenum oxide and the highly oxidizing slag in the converter, reducing molybdenum oxidation loss, increasing molybdenum yield, and is simple to operate and easy to implement industrially.

[0036] In some embodiments of this application, during the converter tapping process, the ladle bottom blowing argon flow rate is 200-400 L / min.

[0037] This application has made targeted optimizations to the argon control process in the converter tapping and LF furnace refining stages. It abandons the complex staged flow control and soft blowing operation at the end of the tapping stage in the traditional process, and adopts a synergistic stirring strategy of large flow rate to enhance mixing in converter tapping and continuous large flow rate for deep reduction in LF furnace.

[0038] Specifically, in the converter tapping process, this application uniformly sets and controls the flow rate of bottom-blown argon gas in the ladle within a high flow range of 200–400 L / min. Within this flow range, the flow rate variation that distinguishes between the initial / middle / final stages of tapping, as in existing technologies, is eliminated, and there is no need for low-flow soft blowing treatment after tapping is completed.

[0039] The tapping process in a converter is a critical moment for the addition of alloys (especially high-density molybdenum oxide and ferromolybdenum). Using a constant high-flow-rate bottom blowing at 200–400 L / min utilizes the stirring kinetic energy of argon bubbles to rapidly break up the stagnant layer of molten steel, creating a strong circulating flow. This not only ensures the rapid melting and uniform dispersion of high-density alloys in the molten steel, effectively preventing alloy settling or localized aggregation, but also significantly shortens the homogenization time, providing a sound physical basis for subsequent chemical reduction reactions.

[0040] In traditional processes, the "soft blowing" process after tapping is typically used to remove inclusions or fine-tune the composition, but it requires high control precision and is time-consuming. This application achieves thorough mixing by using high-flow-rate stirring during the tapping stage. Therefore, omitting the soft blowing process after tapping not only simplifies the operation and reduces control errors caused by flow rate switching, but also directly shortens the occupancy time at the tapping position, thereby improving the converter's production efficiency.

[0041] The core idea of ​​this application is to transfer the burden of the reduction reaction to the LF furnace. Since physical mixing has already been achieved during the tapping stage using a high flow rate of argon gas, this application continues to maintain a high flow rate of argon gas for stirring after the molten steel enters the LF furnace (unlike the low flow rate in Comparative Example 1). Under the reducing atmosphere of the LF furnace, continuous high-flow-rate stirring significantly reduces the mass transfer resistance of the molybdenum oxide reduction reaction in the molten steel, promoting the diffusion of [MoO] from the molten steel into the molten metal pool, thereby greatly accelerating the reduction rate of molybdenum oxide by reducing agents such as carbon, silicon, and aluminum. This "one-step" high-flow-rate strategy, compared to segmented control, ensures a higher molybdenum yield (>95%), while simultaneously utilizing large-scale stirring to promote the flotation and removal of desulfurization and deoxidation products.

[0042] In summary, this application achieves a process division of "physical mixing in the converter and chemical reduction in the LF furnace" by setting the bottom blowing flow rate of 200-400 L / min and cooperating with the high flow rate of the LF furnace for continuous stirring. This simplifies the operation and ensures high quality and low cost of molybdenum-containing steel by strengthening the kinetic conditions.

[0043] In some embodiments of this application, during the LF furnace refining step, the flow rate of bottom-blown argon gas in the ladle is controlled at 600-800 L / min to raise the temperature of the molten steel to 1580℃-1620℃; and during the refining process, aluminum blocks are added at a rate of 0.5-1.0 kg / ton of molten steel, and lime is added at a rate of 3-8 kg / ton of molten steel.

[0044] An argon flow rate of 600–800 L / min provides adequate stirring power for the molten steel, allowing the added aluminum blocks and lime to disperse rapidly and make full contact with the molten steel. This enhances the kinetics of the deoxidation and desulfurization reactions, improving reaction efficiency and rate. Heating the molten steel to 1580℃–1620℃ provides sufficient thermodynamic driving force for the reduction of residual molybdenum oxide. Compared to the refining temperature of a conventional LF furnace (typically 1550℃–1570℃), this temperature range is more favorable for the reduction of molybdenum from oxides by reducing agents such as aluminum, further improving the overall molybdenum yield. Adding aluminum blocks at a rate of 0.5–1.0 kg / ton of molten steel effectively reduces the dissolved oxygen content in the molten steel, creating reducing conditions for molybdenum oxide reduction. It also avoids the increase in inclusions (such as Al2O3) or alloy costs caused by excessive aluminum, achieving a balance between deoxidation efficiency and economy. Adding lime (CaO) at a rate of 3-8 kg / ton of molten steel can form a high-basicity slag system (basicity R≥3), which effectively removes sulfur from the molten steel. At the same time, the lime slag layer can also adsorb deoxidation products (such as Al2O3), purify the molten steel, and improve its cleanliness.

[0045] Furthermore, at high temperatures of 1580℃~1620℃, the strong reducing environment created by aluminum deoxidation, combined with lime slag formation to reduce the activity of oxidizing components in the slag, results in a synergistic effect that significantly increases the reduction rate of residual molybdenum oxide in the molten steel, ensuring an overall molybdenum yield consistently above 95%. This thorough reduction process results in extremely low residual molybdenum oxide content in the molten steel, uniform molybdenum distribution, and highly representative sampling and testing results. This facilitates precise adjustments by adding ferromolybdenum based on the test values, ensuring accurate molybdenum content in the finished product meets the required standards.

[0046] In summary, during the LF furnace refining process, the argon flow rate at the bottom of the ladle is controlled at 600–800 L / min, and the molten steel is heated to 1580℃–1620℃. During the refining process, aluminum blocks are added at a rate of 0.5–1.0 kg / ton of molten steel, and lime is added at a rate of 3–8 kg / ton of molten steel. By controlling these parameters, the molybdenum element in the residual molybdenum oxide can be fully reduced under high-temperature reducing conditions, while simultaneously achieving efficient deoxidation and desulfurization, purifying the molten steel, and providing a uniform and stable steel base for subsequent fine-tuning of ferromolybdenum, ensuring an overall molybdenum yield of over 95% and precise controllable composition of the finished product.

[0047] In some embodiments of this application, the mass percentage content of each component in the first molybdenum oxide raw material and the second molybdenum oxide raw material is Mo ≤60%, sulfur (S) ≤0.15%, phosphorus (P) ≤0.05%, and Cu ≤1.0%.

[0048] By consistently controlling the molybdenum content in the molybdenum oxide feedstock within the high-grade range of 60%, a high metal yield was ensured. During the smelting process, the high-grade molybdenum oxide reduced slag volume and slag erosion of the furnace lining, while also reducing the amount of reducing agent required to reduce oxides, thereby effectively lowering smelting costs and energy consumption.

[0049] Secondly, strictly controlling the content of sulfur (S≤0.15%) and phosphorus (P≤0.05%) is crucial for improving the quality of the final steel. Sulfur and phosphorus are the main harmful impurity elements in steel, which can lead to hot brittleness and cold brittleness, respectively. The low-sulfur and low-phosphorus molybdenum oxide raw materials selected in this application significantly reduce the introduction of foreign impurity elements from the source. This allows the smelting process to easily meet the stringent requirements for sulfur and phosphorus content in high-quality steel grades without complex desulfurization and dephosphorization operations, significantly improving the purity of the molten steel and enhancing its impact toughness, weldability, and machinability.

[0050] Furthermore, limiting the copper (Cu) content to below 1.0% can effectively prevent surface hot cracking defects (copper embrittlement) caused by the segregation or enrichment of copper in steel. When smelting steel grades with high surface quality requirements, the use of low-copper raw materials ensures yield and product surface quality, and broadens the range of steel grades applicable to this process.

[0051] In summary, using molybdenum oxide raw materials within the aforementioned specific composition range not only ensures the stable alloying effect of molybdenum, but also significantly improves the cleanliness of molten steel through low impurity content, simplifies the refining process, and ultimately achieves low-cost, high-efficiency production of high-quality molybdenum-containing steel.

[0052] In some embodiments of this application, the amount of ferromolybdenum alloy added accounts for 5% to 10% of the total molybdenum metal content, which is used to fine-tune the molybdenum content in the molten steel to the target composition range.

[0053] Ferromolybdenum alloys are significantly more expensive than molybdenum oxide. Controlling its addition to 5%–10% of the total molybdenum metal content means that 85%–95% of the molybdenum comes from low-cost molybdenum oxide, maximizing the cost advantage of molybdenum oxide as a substitute for ferromolybdenum. Ferromolybdenum alloys have a clearly defined molybdenum content (typically around 60%) and a low melting point. Under LF furnace refining conditions, they can be rapidly and uniformly melted into molten steel with a stable yield (over 95%), making them ideal for precise fine-tuning of the final composition and ensuring that the finished product's molybdenum content strictly meets the target value for the steel grade. The reduction rate of molybdenum oxide may fluctuate between batches due to factors such as molten iron temperature, carbon content, and stirring intensity. Reserved 5%–10% of molybdenum for addition by ferromolybdenum, which can be flexibly adjusted based on LF furnace sampling and testing results, eliminates uncertainties in the molybdenum oxide reduction process and ensures a high finished product qualification rate. Since most of the molybdenum has already been alloyed during the hot metal pretreatment and converter tapping stages, the LF furnace only needs a small amount of ferromolybdenum to meet the required standards. This eliminates the need for extensive molybdenum oxide reduction in the LF furnace, reducing the complexity of aluminum block consumption, slag control, and stirring intensity adjustments. The yield of the molybdenum oxide reduction stage (approximately 95%) is comparable to that of the ferromolybdenum fine-tuning stage (approximately 95%–97%). This reasonable combination ensures a stable and controllable overall molybdenum yield, avoiding significant fluctuations caused by relying solely on molybdenum oxide reduction. If relying entirely on molybdenum oxide reduction (without ferromolybdenum), insufficient reduction will result in low molybdenum content in the molten steel, potentially even leading to the scrapping of the entire furnace. Retaining a 5%–10% fine-tuning margin for ferromolybdenum allows for immediate correction after laboratory results are available, preventing economic losses due to substandard composition.

[0054] In summary, the addition of ferromolybdenum alloy accounts for 5% to 10% of the total molybdenum metal content, used to fine-tune the molybdenum content in molten steel to the target composition range. Through this setup, the advantages of stable ferromolybdenum yield and precise composition control can be leveraged while maximizing the utilization of low-cost molybdenum oxide (85% to 90%). This eliminates potential fluctuations in the molybdenum oxide reduction process, ensures strict compliance with finished product molybdenum content standards, reduces scrap risk, and achieves an optimal balance between cost control and quality assurance.

[0055] An embodiment of this application also provides a molybdenum-containing steel, which is prepared using the smelting method for molybdenum-containing steel described in the above embodiments.

[0056] By controlling the pre-reduction of molten iron, the addition of molybdenum oxide during converter tapping, the initial reduction in the LF furnace, and the fine-tuning of ferromolybdenum in the later stage through the above smelting method, the molybdenum content in the finished molybdenum-containing steel can accurately reach the target composition range (such as 0.18% in the example), which is suitable for the production needs of different grades of molybdenum-containing steel. Argon gas stirring is used in each stage of molten iron pretreatment, converter tapping, and LF furnace refining, so that the molybdenum element is evenly dispersed in the molten steel, avoiding the uneven structure and performance fluctuations caused by local enrichment or depletion. Using molybdenum oxide (P≤0.1%, S≤0.15%), combined with aluminum block deoxidation in the LF furnace and lime slag desulfurization, the harmful elements (P, S) and non-metallic inclusions (such as Al2O3) in the steel are effectively controlled, improving the purity of the steel. Due to the uniform distribution of molybdenum and the high purity of the molten steel, the prepared molybdenum-containing steel can fully exert the alloying effect of molybdenum in terms of strength, hardness, wear resistance, toughness, and corrosion resistance, meeting the performance requirements of high-strength steel, wear-resistant steel, heat-resistant steel, and other high-end steels. The molybdenum-containing steel prepared using this low-cost molybdenum oxide substitution process is comparable to or even superior to the traditional all-molybdenum ferroalloy process in terms of finished product quality (compositional accuracy, purity, and mechanical properties), but with a significantly reduced alloy cost, giving it a clear competitive edge in the market. Because the parameters at each stage of the smelting process are clearly defined (temperature, time, flow rate, amount added, etc.), the molybdenum-containing steel prepared using this method exhibits good batch-to-batch consistency, and the product quality is traceable and repeatable, meeting the requirements of industrial-scale mass production.

[0057] In summary, the molybdenum-containing steel provided in this application has the characteristics of precise and controllable molybdenum content, uniform element distribution, high steel cleanliness, and excellent comprehensive mechanical properties. Moreover, its production cost is significantly lower than that of molybdenum-containing steel prepared by the traditional all-molybdenum-iron process, and its batch quality stability is good, making it suitable for industrial mass production.

[0058] In some embodiments of this application, the molybdenum-containing steel, by mass percentage, comprises: C: 0.05%-0.20%, Si: 0.10%-0.50%, Mn: 0.50%-1.50%, P≤0.015%, S≤0.005%, Mo: 0.15%-0.20%, with the balance being iron and unavoidable impurities.

[0059] The carbon (C) content is controlled between 0.05% and 0.20%, falling within the low-carbon or low-to-medium-carbon range. This allows for improved steel strength through solid solution strengthening and precipitation strengthening, while avoiding the reduced weldability and toughness caused by excessively high carbon content, resulting in steel with good strength, toughness, and weldability. The silicon (Si) content is 0.10% to 0.50%, providing solid solution strengthening and increasing steel strength. It also acts as a deoxidizing element in the steelmaking process, aiding in steel purification. This range avoids the reduced toughness and surface quality problems caused by excessively high silicon content (>0.5%). The manganese (Mn) content is 0.50% to 1.50%, an important solid solution strengthening element that improves hardenability and strength. It also combines with sulfur to form MnS, reducing the hot brittleness caused by sulfur. This range balances strengthening effect and cost control. P ≤ 0.015% indicates ultra-low phosphorus steel. Phosphorus tends to segregate at grain boundaries, significantly reducing the low-temperature impact toughness and resistance to hydrogen-induced cracking. Strict control of phosphorus content ensures excellent reliability of molybdenum-containing steel under low-temperature environments and harsh service conditions. ≤0.005% phosphorus content classifies it as ultra-low sulfur steel. Sulfur forms sulfide inclusions, reducing the steel's ductility, impact toughness, and pitting resistance. Ultra-low sulfur control combined with appropriate calcium treatment alters the sulfide morphology, further improving steel quality and service performance. Furthermore, this invention uses low-phosphorus (≤0.1%) molybdenum oxide raw materials, combined with hot metal pretreatment and LF furnace refining, controlling phosphorus and sulfur elements from both the source and process. This enables the stable production of high-quality molybdenum-containing steel with P≤0.015% and S≤0.005%, meeting the purity requirements of high-end steel. The rational proportions of C, Si, Mn, and Mo, combined with ultra-low P and S control, achieve a good balance between strength, toughness, wear resistance, heat resistance, and weldability, making it suitable for various high-end manufacturing fields such as engineering machinery, petrochemicals, power, and rail transportation.

[0060] In summary, the molybdenum-containing steel prepared by the method of this invention, with the help of low-phosphorus and low-sulfur molybdenum oxide raw materials and a reasonable refining process, can stably achieve ultra-low phosphorus and sulfur control (P≤0.015%, S≤0.005%). At the same time, the ratio of C, Si, Mn and Mo elements is reasonable, so that the steel achieves a good balance between strength, toughness, wear resistance, heat resistance and weldability, meeting the stringent requirements of high-end manufacturing fields for molybdenum-containing steel. Specific Implementation

[0061] Comparative Example 1 This comparative example uses the traditional ferromolybdenum alloying process and does not use molybdenum oxide.

[0062] Specific smelting steps: (1) No molybdenum-containing materials are added to the ladle. The ladle is directly connected to the blast furnace tap hole to collect molten iron. The molten iron temperature is 1500℃, the carbon content in the molten iron is 4.3%, and the tapping time is 27 minutes.

[0063] (2) Converter blowing: 165 tons of molten iron and 40 tons of scrap steel are poured into the converter for oxygen blowing and smelting. Molybdenum oxide is not added to the bottom of the ladle before tapping. After the blowing is completed, the steel is tapped from the converter. During the tapping process, 400 kg of ferrosilicon, 210 kg of ferrosilicon and 100 kg of aluminum blocks are added for deoxidation. Argon is blown and stirred at the bottom of the ladle throughout the process. The argon flow rate is 780 L / min.

[0064] (3) LF furnace refining: Molten steel enters the LF furnace, and is heated to 1600℃ by electric submerged arc heating. 300kg of aluminum blocks and 950kg of lime are added for deoxidation, slag formation, and desulfurization. All ferromolybdenum alloy is added according to the target value of 0.18% molybdenum content for the steel grade. The amount of ferromolybdenum added is calculated to be 560kg based on a 95% yield. After the composition is qualified, it is soft-blown out of the station.

[0065] (4) Molten steel is poured into the continuous casting table to obtain molybdenum-containing steel slabs.

[0066] Comparative Example 2 In this comparative example, all the required molybdenum element is added to the ladle in the form of molybdenum oxide at once, and no additional ferromolybdenum is added to the LF furnace.

[0067] Specific smelting steps: (1) Add molybdenum oxide (approximately 1700 kg) to the ladle according to 100% of the target molybdenum content, and then collect the molten iron at the blast furnace tapping point. The molten iron temperature is 1500℃, the carbon content in the molten iron is 4.3-4.5%, and the tapping time is 25-30 minutes.

[0068] (2) Converter blowing: 165 tons of molten iron and 40 tons of scrap steel are poured into the converter for oxygen blowing and smelting. Molybdenum oxide is not added to the bottom of the ladle before tapping. After the blowing is completed, the steel is tapped from the converter. During the tapping process, 400 kg of ferrosilicon, 200 kg of ferrosilicon and 110 kg of aluminum blocks are added for deoxidation. Argon is blown and stirred at the bottom of the ladle throughout the process. The argon flow rate is 740 L / min.

[0069] (3) LF furnace refining: Molten steel enters the LF furnace, is heated to 1600℃ by electric submerged arc heating, and 300kg of aluminum blocks and 980kg of lime are added for deoxidation, slag formation and desulfurization. No more ferromolybdenum is added. After the composition is qualified, it is soft blown out of the station.

[0070] (4) Molten steel is poured into the continuous casting table to obtain molybdenum-containing steel slabs.

[0071] Comparative Example 3 In this comparative example, the heating temperature was too low during refining in the LF furnace to verify the effect of temperature on the reduction effect of molybdenum oxide.

[0072] Specific smelting steps: (1) Add 1200 kg of molybdenum oxide (accounting for 88% of the target molybdenum content) to the ladle, and then collect the molten iron at the blast furnace tapping point. The molten iron temperature is 1500℃, the carbon content in the molten iron is 4.4%, and the tapping time is 26 minutes.

[0073] (2) Converter blowing: 165 tons of molten iron and 40 tons of scrap steel are poured into the converter for oxygen blowing and smelting. Before tapping, 800 kg of molybdenum oxide is added to the bottom of the ladle. After blowing is completed, the steel is tapped from the converter. During the tapping process, 400 kg of ferrosilicon, 200 kg of ferrosilicon and 100 kg of aluminum blocks are added for deoxidation. Argon is blown and stirred at the bottom of the ladle throughout the process. The argon flow rate is 710 L / min.

[0074] (3) LF furnace refining: Molten steel enters the LF furnace and is heated to 1530℃ by electric submerged arc heating (lower than the 1600℃ required by this invention). 300kg of aluminum blocks and 900kg of lime are added for deoxidation, slag formation, and desulfurization. 69kg of ferromolybdenum is added according to the test results. After the composition is qualified, it is soft-blown out of the station.

[0075] (4) Molten steel is poured into the continuous casting table to obtain molybdenum-containing steel slabs.

[0076] The experimental conditions for the comparative example are shown in the table below: Table 1 Example 1 Specific smelting steps: (1) Add 1200 kg of molybdenum oxide to the iron ladle. The molybdenum element in the molybdenum oxide accounts for 88% of the molybdenum content in the final product. Then, collect molten iron at the tapping point of the blast furnace. The temperature of the molten iron is 1500℃, the carbon content in the molten iron is 4.4%, and the tapping time is 28 minutes. The molybdenum element in the molybdenum oxide is reduced by the scouring effect of the molten iron and the carbon element in the molten iron.

[0077] (2) Converter blowing: 165 tons of molten iron and 40 tons of scrap steel are poured into the converter for oxygen blowing and smelting. Before tapping, 800 kg of molybdenum oxide is added to the bottom of the ladle. After blowing is completed, the steel is tapped from the converter. During the tapping process, 400 kg of ferrosilicon, 200 kg of ferrosilicon and 100 kg of aluminum blocks are added for deoxidation. Argon is blown and stirred at the bottom of the ladle throughout the process. The argon flow rate is 290 L / min.

[0078] (3) LF furnace refining: Molten steel enters the LF furnace, and the temperature is raised to 1600℃ by electric submerged arc heating. Argon is blown into the bottom of the ladle for stirring throughout the process, with an argon flow rate of 640L / min. 300kg of aluminum blocks and 880kg of lime are added for deoxidation, slag formation, and desulfurization. Temperature is measured and samples are taken. The molybdenum content is 0.174%. 69kg of ferromolybdenum is added, and after 5min of argon blowing and stirring, temperature is measured and samples are taken. After all components meet the standards, the steel is discharged from the station.

[0079] (4) The molten steel enters the continuous casting table and is cast to obtain the target molybdenum-containing steel slab. The reduction rate of molybdenum oxide in the molten steel reaches 96%.

[0080] Example 2 Specific smelting steps: (1) Add 850 kg of molybdenum oxide to the ladle (calculated as 90% of the target molybdenum content of 0.10%), and then collect the molten iron at the blast furnace tapping point. The molten iron temperature is 1500℃, the carbon content is 4.5%, and the tapping time is 27 minutes.

[0081] (2) Converter blowing: 165 tons of molten iron and 40 tons of scrap steel are poured into the converter for oxygen blowing and smelting. Before tapping, 300 kg of molybdenum oxide is added to the bottom of the ladle. During the tapping process, 400 kg of ferrosilicon, 200 kg of ferrosilicon and 100 kg of aluminum blocks are added for deoxidation. Argon gas is stirred at 330 L / min throughout the process.

[0082] (3) LF furnace refining: Heat to 1590℃, blow argon to the bottom of the ladle throughout the process, argon flow rate 660L / min, add 300kg of aluminum blocks and 920kg of lime for deoxidation, slag formation and desulfurization, after testing the molybdenum content, add about 30kg of ferromolybdenum, and after the composition is qualified, it leaves the station.

[0083] (4) The molybdenum-containing steel slab was obtained by continuous casting, with a molybdenum reduction rate of 95.5%.

[0084] Example 3 Specific smelting steps: (1) Add 1900 kg of molybdenum oxide to the iron ladle (calculated as 85% of the target molybdenum content of 0.35%), the molten iron temperature is 1510℃, the carbon content is 4.4%, and the tapping time is 28 minutes.

[0085] (2) Converter blowing: 165 tons of molten iron and 40 tons of scrap steel are poured into the converter for oxygen blowing and smelting. Before tapping, 900 kg of molybdenum oxide is added to the bottom of the ladle. During the tapping process, 450 kg of ferrosilicon, 220 kg of ferrosilicon and 120 kg of aluminum blocks are added for deoxidation. The argon flow rate is 290 L / min.

[0086] (3) LF furnace refining: heat up to 1620℃, blow argon to the bottom of the ladle throughout the process, argon flow rate 700L / min, add 350kg of aluminum blocks and 1000kg of lime, test the molybdenum content after desulfurization, add ferromolybdenum to adjust to 0.35%, and then leave the station.

[0087] (4) High molybdenum steel slabs were obtained by continuous casting, with a molybdenum reduction rate of 97.2%.

[0088] Example 4 Specific smelting steps: (1) Add 1250 kg of molybdenum oxide to the iron ladle (calculated as 88% of the target molybdenum content of 0.18%), the molten iron temperature is 1490℃, the carbon content is 4.3%, and the tapping time is 25 minutes.

[0089] (2) Converter blowing: 145 tons of molten iron and 60 tons of scrap steel are poured into the converter for oxygen blowing and smelting. Before tapping, 750 kg of molybdenum oxide is added to the bottom of the ladle. During the tapping process, 420 kg of ferrosilicon, 210 kg of ferrosilicon and 110 kg of aluminum blocks are added for deoxidation. The argon flow rate is 320 L / min.

[0090] (3) LF furnace refining: heat up to 1600℃, blow argon to the bottom of the ladle throughout the process, argon flow rate 720 / min, add 300kg of aluminum blocks and 900kg of lime, after testing the molybdenum content, add about 50kg of ferromolybdenum, and then leave the station.

[0091] (4) The slab obtained by continuous casting has a molybdenum reduction rate of 95.8%.

[0092] The experimental conditions for the examples are shown in the table below: Table 2 After the above steps, as shown in Table 3, in order to objectively evaluate the economic benefits of the present invention, calculations are performed using a steel grade with a target molybdenum content of 0.18% as an example.

[0093] The product test results for Comparative Examples 1-3 and Examples 1-4 are as follows: Table 3 The test results in Table 3 show that: Comparative Example 1 uses the traditional all-molybdenum iron process, which has a stable molybdenum yield (95.0%), but the alloy cost is the highest (100%).

[0094] Comparative Example 2 added all molybdenum oxide to the ladle at once, which reduced costs (65%), but the molybdenum oxide reduction rate was only 88.0%, and the finished product molybdenum content of 0.158% was lower than the target value of 0.18%. Comparative Example 3, under the condition of excessively low LF furnace temperature (1530℃), the molybdenum oxide reduction was insufficient, with a reduction rate of only 86.5%, and the finished product molybdenum content of 0.162% was still lower than the target value.

[0095] Examples 1-4 all adopted the stepwise addition method of the present invention (iron ladle + converter tapping + small amount of ferromolybdenum fine adjustment in LF). Under the condition of LF furnace temperature ≥1600℃, the molybdenum oxide reduction rate reached more than 95.5%, the molybdenum content of the finished product was accurately controlled within the target range, and the finished product qualification rate was 100%.

[0096] Compared to Comparative Example 1, the alloy cost of Example 1 was reduced by 32% (relative value 68) while maintaining the same or even higher molybdenum yield (96.0% vs 95.0%).

[0097] In Comparative Example 2, although a low-cost full molybdenum oxide solution was adopted, the addition of 100% molybdenum oxide to the iron ladle at one time exceeded the reduction capacity limit of the molten iron pretreatment stage, resulting in a significant reduction in the molybdenum oxide reduction rate (only 88.0%). As a result, the molybdenum content of the final product was lower than the target value, and the product was rejected.

[0098] This demonstrates that relying solely on ladle pre-reduction carries significant quality risks. In contrast, the control method employed in Examples 1-4 of this application—combining molten iron pre-reduction, converter tapping with molybdenum oxide addition, early-stage reduction in the LF furnace, and later fine-tuning of ferromolybdenum—utilizes the inexpensive reduction capability of molten iron through a step-by-step relay approach. Furthermore, the precise fine-tuning of the LF furnace compensates for fluctuations in the molybdenum oxide reduction rate, thereby achieving 100% product quality compliance while maintaining a cost advantage.

[0099] Example 3 achieved the highest molybdenum reduction rate (97.2%) by increasing the LF furnace temperature to 1620°C, which is suitable for the quality requirements of high-molybdenum high-strength steel.

[0100] Furthermore, Examples 2 and 3 demonstrate the adaptability of the present invention in the production of low-molybdenum steel (0.099%) and high-molybdenum steel (0.349%), respectively. Although the absolute cost is not directly comparable to the benchmark scheme due to the different target compositions, the high yields (95.5% and 97.2%, respectively) prove that the process of the present invention can maintain stable metallurgical effects under different alloying requirements, avoiding the waste of precious alloying elements.

[0101] Example 4 demonstrates that the process of the present invention remains stable and reliable even under conditions of a high scrap ratio (approximately 29%) and a slightly lower molten iron temperature (1490°C).

[0102] The above results indicate that the method for smelting molybdenum-containing steel by adding molybdenum oxide to iron ladles, as described in this invention, can significantly reduce alloy costs while ensuring precise control of the molybdenum content in the finished product, and has excellent industrial applicability and economic benefits.

[0103] The embodiments described above are not exhaustive, nor do they limit the application to the specific embodiments described herein. Clearly, many modifications and variations can be made based on the above description. These embodiments are selected and specifically described in this specification to better explain the principles and practical applications of this application, thereby enabling those skilled in the art to effectively utilize this application and its modifications. This application is limited only by the claims and their full scope and equivalents.

Claims

1. A method for smelting molybdenum-containing steel, characterized in that, include: Hot metal pretreatment involves adding molybdenum oxide raw material to the hot metal ladle beforehand, and then receiving the molten hot metal at the blast furnace taphole. By utilizing the scouring effect of molten iron in the blast furnace and the carbon element in the molten iron, the molybdenum element in the first molybdenum oxide raw material is reduced to obtain molybdenum-containing molten iron. In the converter smelting process, the molybdenum-containing molten iron is poured into a converter for oxygen blowing smelting to obtain the converter steel liquid; After tapping the steel from the converter, a second molybdenum oxide raw material is added to the bottom of the ladle. Then, the molten steel from the converter is poured into the ladle. During the process of pouring the molten steel from the converter into the ladle, a deoxidizer is added. At the same time, argon gas is blown into the bottom of the ladle for stirring to obtain molten steel. In the LF furnace refining process, the molten steel is fed into the LF furnace, heated, and aluminum blocks and lime are added for deoxidation and slag formation. After the deoxidation and slag formation is completed, ferromolybdenum alloy is added to finely adjust the molybdenum content in the molten steel to achieve the target value, thus obtaining finely adjusted molten steel. During the heating process, the bottom blowing flow rate of the ladle is increased to promote the full reduction of molybdenum in the second molybdenum oxide raw material. Continuous casting: The finely tuned molten steel is continuously cast to obtain a molybdenum-containing steel slab.

2. The method according to claim 1, characterized in that, The amount of the first molybdenum oxide raw material added to the molten iron ladle accounts for 85% to 90% of the total amount of molybdenum oxide raw material added; and / or, the mass of molybdenum element brought in by the first molybdenum oxide raw material accounts for 85% to 90% of the total mass of molybdenum element in the fine-tuned molten steel.

3. The method according to claim 1, characterized in that, The temperature of the blast furnace molten iron is 1450℃~1500℃, and the carbon content in the blast furnace molten iron is 4.3%~4.5% by mass; the process of receiving the blast furnace molten iron lasts for 25~30 minutes.

4. The method according to claim 1, characterized in that, In the converter tapping step, the addition of the second molybdenum oxide raw material is initiated 2 to 5 minutes before the start of converter tapping and is completed before the start of converter tapping.

5. The method according to any one of claims 1-4, characterized in that, In the converter tapping step, the flow rate of argon gas blown into the ladle during the tapping process is 200-400 L / min.

6. The method according to claim 1, characterized in that, In the LF furnace refining step, the flow rate of bottom-blown argon gas in the ladle is controlled at 600-800 L / min, and the molten steel is heated to 1580℃-1620℃; and during the refining process, aluminum blocks are added at a rate of 0.5-1.0 kg / ton of molten steel, and lime is added at a rate of 3-8 kg / ton of molten steel.

7. The method according to any one of claims 1-6, characterized in that, In the first and second molybdenum oxide raw materials, the mass percentage content of each component is Mo ≤60%, sulfur (S) ≤0.15%, phosphorus (P) ≤0.05%, and Cu ≤1.0%.

8. The method according to claim 1 or 6, characterized in that, The amount of the ferromolybdenum alloy added accounts for 5% to 10% of the total molybdenum metal content, and is used to fine-tune the molybdenum content in the molten steel to the target composition range.

9. A molybdenum-containing steel, characterized in that, It is prepared by the smelting method of molybdenum-containing steel according to any one of claims 1-8.

10. The molybdenum-containing steel according to claim 9, characterized in that, The molybdenum-containing steel comprises, by mass percentage: C: 0.05%-0.20%, Si: 0.10%-0.50%, Mn: 0.50%-1.50%, P≤0.015%, S≤0.005%, Mo: 0.15%-0.20%, with the balance being iron and unavoidable impurities.

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