Method for directly alloying molybdenum concentrate in RH furnace

Abstract

The invention belongs to the technical field of ferrous metallurgy, and discloses a method for directly alloying molybdenum concentrate in an RH furnace, which specifically comprises the following steps: before vacuum treatment of the RH furnace, adding 0.5-5kg / t of molybdenum concentrate with the diameter of 10-50mm into molten steel, then carrying out vacuum treatment under the conditions that the vacuum degree is less than or equal to 67Pa and the vacuum treatment time is 10-30 minutes, feeding 1-3m / t of calcium line after vacuum breaking, and carrying out static blowing for 10-30 minutes. According to the method, the molybdenum concentrate is used as the ferro-molybdenum alloy to directly alloy the molten steel, the procedure of refining the ferro-alloy is omitted, and the purposes of reducing pollution, saving energy and reducing consumption are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of iron and steel metallurgy and relates to a method for directly alloying molybdenum concentrate in an RH furnace. Background Art

[0002] During the RH smelting process, a certain amount of ferroalloy will be added according to the incoming molten steel composition to make the molten steel composition meet the target requirements of the steel grade and ensure the steel quality and performance. At present, the main method of RH alloying is: adding molybdenum-iron alloy (molybdenum content: 55% to 60%) into the ladle during the RH treatment process, but the price of molybdenum-iron alloy is generally relatively high, which affects the cost of molten steel. Summary of the invention

[0003] The present invention aims to provide a method for directly alloying molybdenum concentrate in an RH furnace, which method saves the process of smelting ferroalloys, reduces pollution, and saves energy and reduces consumption.

[0004] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is: A method for directly alloying molybdenum concentrate in an RH furnace, specifically: before vacuum treatment in the RH furnace, molybdenum concentrate is added to molten steel, then vacuum treatment is performed, calcium wire is fed after breaking the air, and static blowing is performed for 10-30 minutes.

[0005] Furthermore, the chemical composition and weight percentage of the molybdenum concentrate described in the present invention are: Mo: 45% to 55%, S: 25% to 35%, SiO2: 7% to 15%, CaO≤3%, and the rest are impurity elements that do not participate in the reaction.

[0006] Furthermore, the amount of molybdenum concentrate added in the present invention is 0.5-5 kg / t, which is specifically calculated based on the composition of the molybdenum concentrate, the composition of the molten steel entering the station, and the target composition requirements of the steel grade.

[0007] Furthermore, the diameter of the molybdenum concentrate of the present invention is 10-50 mm, so as to ensure that the molybdenum concentrate can react with molten steel as quickly as possible and dissolve the molybdenum element in the molten steel.

[0008] Furthermore, the vacuum degree of the vacuum treatment of the present invention is ≤67Pa, and the vacuum treatment time is 10-30min. The decomposition of molybdenum concentrate can be accelerated under vacuum conditions, and the decomposed molybdenum element is dissolved in molten steel; most of the decomposed sulfur vapor is extracted by vacuum, and a small part enters the molten steel.

[0009] Furthermore, the calcium wire feeding amount of the present invention is 1-3 m / t, the purpose of which is to ensure that a small amount of sulfur entering the molten steel after the molybdenum concentrate is thermally decomposed reacts with calcium to form CaS, so as to reduce the sulfur element in the molten steel.

[0010] Furthermore, the calcium wire of the present invention is a double-layer pure calcium wire.

[0011] Furthermore, the static blowing standard of the present invention is that the slag layer on the slag surface of the ladle surges but the molten steel is not exposed, in order to promote the floating of CaS.

[0012] Furthermore, the temperature of the molten steel entering the RH station of the present invention is ≥1600°C to ensure that the molybdenum concentrate has sufficient heat for decomposition.

[0013] The inventive principle and beneficial effects of the calculation scheme of the present invention are: The present invention adds molybdenum concentrate (main component MoS2) before RH vacuum treatment. During the vacuum treatment, the molybdenum element decomposed from the molybdenum concentrate is dissolved in the molten steel. Most of the decomposed sulfur vapor is extracted by vacuum, and a small part enters the molten steel to react with calcium to generate CaS that floats and is absorbed by the top slag. The method uses molybdenum concentrate as molybdenum-iron alloy to directly alloy the molten steel, eliminating the process of refining ferroalloys, and achieving the purpose of reducing pollution, energy saving and consumption reduction. DETAILED DESCRIPTION

[0014] In order to make the purpose, technical solution and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the embodiments described herein are only used to explain the present invention and are not used to limit the present invention. Examples 1-5

[0015] A method for directly alloying molybdenum concentrate in an RH furnace, specifically: before vacuum treatment in the RH furnace, molybdenum concentrate is added to molten steel, then vacuum treatment is performed, calcium wire is fed after breaking the air, and static blowing is performed for 10-30 minutes.

[0016] The chemical composition and weight percentage of the molybdenum concentrate are: Mo: 45% to 55%, S: 25% to 35%, SiO2: 7% to 15%, CaO ≤ 3%, and the rest are impurity elements that do not participate in the reaction; the diameter is: 10-50 mm. The chemical composition and diameter of the molybdenum concentrate of each embodiment are shown in Table 1.

[0017] The amount of molybdenum concentrate added is 0.5-5 kg / t, which is calculated based on the composition of the molybdenum concentrate, the composition of the molten steel entering the station, and the target composition requirements of the steel grade.

[0018] The vacuum degree of the vacuum treatment is ≤67Pa, and the vacuum treatment time is 10-30min.

[0019] The calcium wire is a double-layer pure calcium wire, and the feeding amount is 1-3m / t.

[0020] The RH inlet molten steel temperature is ≥1600°C.

[0021] The process parameters such as the amount of molybdenum concentrate added, vacuum degree, vacuum treatment time, double-layer pure calcium line feed amount, static blowing time, RH inlet molten steel temperature in each embodiment are shown in Table 2.

[0022] The sulfur content, molybdenum content and molybdenum concentrate absorption rate of the molten steel in each example are shown in Table 3.

[0023] Table 1 Chemical composition (%) and diameter (mm) of molybdenum concentrate in each example

[0024] Table 2 Process parameters of each embodiment

[0025] Table 3 Sulfur content, molybdenum content and molybdenum concentrate absorption rate of each example in molten steel

[0026] As can be seen from Table 3, the present invention adds molybdenum concentrate in the RH smelting process, the molybdenum element in the molybdenum concentrate can be completely dissolved in the molten steel, the molybdenum absorption rate is 97.54%-99.52%, and the sulfur content of the molten steel shows a decreasing trend, which meets the process quality requirements of the steel grade.

[0027] The above embodiments are only used to illustrate rather than limit the technical solutions of the present invention. Although the present invention is described in detail with reference to the above embodiments, those skilled in the art should understand that the present invention can still be modified or replaced by equivalents. Any modification or partial replacement that does not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A method for direct alloying of molybdenum concentrate in an RH furnace, characterized in that: Before the RH furnace vacuum treatment, add molybdenum concentrate into the molten steel, then carry out vacuum treatment, feed calcium wire after breaking the air, and blow quietly for 10-30 minutes.

2. The method for direct alloying of molybdenum concentrate in an RH furnace according to claim 1, characterized in that: The chemical composition and weight percentage of the molybdenum concentrate are: Mo: 45% to 55%, S: 25% to 35%, SiO2: 7% to 15%, CaO ≤ 3%, and the rest are impurity elements that do not participate in the reaction.

3. The method for direct alloying of molybdenum concentrate in an RH furnace according to claim 1, characterized in that: The amount of molybdenum concentrate added is: 0.5-5kg / t.

4. The method for direct alloying of molybdenum concentrate in an RH furnace according to claim 1, characterized in that: The diameter of the molybdenum concentrate is 10-50 mm.

5. The method for direct alloying of molybdenum concentrate in an RH furnace according to claim 1, characterized in that: The vacuum degree of the vacuum treatment is ≤67Pa, and the vacuum treatment time is 10-30min.

6. The method for direct alloying of molybdenum concentrate in an RH furnace according to claim 1, characterized in that: The calcium wire feeding amount is 1-3 m / t.

7. The method for direct alloying of molybdenum concentrate in an RH furnace according to claim 1, characterized in that: The calcium wire is a double-layer pure calcium wire.

8. The method for direct alloying of molybdenum concentrate in an RH furnace according to claim 1, characterized in that: The RH inlet molten steel temperature is ≥1600°C.

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