Molybdenum oxide composite press ball formula process

Abstract

The invention belongs to the technical field of steelmaking, and particularly relates to a molybdenum oxide composite pressed ball formula process which comprises the following components: 5-30% of lime powder, 5-20% of dolomite powder, 3-8% of anthracite powder, 3-6% of magnesium particles, 40-80% of molybdenum oxide powder, 3-10% of AD powder and 1-3% of binder. CaO in the lime, MgO in the dolomite and molybdenum oxide generate molybdate with a relatively high melting point through presintering in the rotary kiln, so that volatilization of the molybdenum oxide during direct alloying is effectively inhibited; in the pre-sintering process, C, Mg and Al can pre-reduce part of molybdenum oxide in advance; in the early stage of converter smelting, the molybdenum oxide composite pressed balls are added into a converter, C, Mg and Al in the molybdenum oxide composite pressed balls and C in molten iron can reduce molybdate and molybdenum oxide, and the generated molybdenum element enters molten steel to achieve the purpose of molten steel alloying. As the price of molybdenum oxide is far lower than that of ferromolybdenum, the economic benefit is remarkable.

Description

Technical Field

[0001] The invention relates to the technical field of steelmaking and is a formula process for molybdenum oxide composite ball pressing. Background Art

[0002] As an alloying element of steel, molybdenum can improve the repassivation ability, pitting and crevice corrosion resistance of steel, improve the high temperature strength of steel, greatly improve the high temperature durability and creep performance of steel, improve the acid and alkali resistance, wear resistance and improve the hardenability and weldability of steel. The most widely distributed and industrially valuable molybdenum-containing mineral in the earth's crust is molybdenite. Molybdenum exists in the form of MoS2. Generally, molybdenite (MoS2) is first oxidized and roasted into molybdenum oxide (MoO3), and then reduced with coke, aluminum particles, ferrosilicon, etc. to produce ferromolybdenum. Then, ferromolybdenum alloy is added to molten steel as a metallurgical additive for full alloying. At present, 1243kg of molybdenum ore, 339-350kg of ferrosilicon, 50kg of aluminum particles, hundreds of kilograms of other raw materials and 3800KWh of electricity consumption are required to smelt 1t of ferromolybdenum. At the same time, a large amount of CO, CO2, SO2, NOx and smoke will be generated, causing serious pollution to the environment. Therefore, developing a smelting process that does not use ferromolybdenum or uses less ferromolybdenum is of great strategic significance for achieving energy conservation and emission reduction.

[0003] Using molybdenum oxide briquettes instead of ferromolybdenum to directly alloy molybdenum is beneficial to reducing smelting costs, eliminating the alloying process in the smelting process, and saving a lot of energy. It has very important practical significance for the comprehensive and efficient use of my country's molybdenum resources, improving the economic benefits of enterprises, reducing the production costs of steel enterprises, reducing the pollution of steel production to the environment, and realizing the green and sustainable development of the steel industry.

[0004] However, the melting point and boiling point of molybdenum trioxide are relatively low, at 795°C and 1155°C respectively. Molybdenum trioxide begins to sublime at 600°C, and the sublimation rate increases when the temperature reaches 900-1100°C. Due to the volatile nature of molybdenum oxide, the recovery rate of molybdenum element in the direct alloying process of steelmaking is not high. Research on how to inhibit the volatilization of molybdenum oxide and improve the reduction rate of molybdenum oxide has become the focus of research in many scientific research institutions. Summary of the invention

[0005] The purpose of the present invention is to provide a molybdenum oxide composite ball pressing formula process, which solves the disadvantage that molybdenum oxide is easy to volatilize during use and achieves the purpose of replacing ferromolybdenum in the steelmaking alloying process of molybdenum-containing steel to reduce production costs.

[0006] The technical problem to be solved by the present invention is achieved by adopting the following technical scheme: a molybdenum oxide composite ball pressing formula process, comprising the following steps:

[0007] S1. Ingredients: Based on the total weight of the composite briquette, it includes 5-30% lime powder, 5-20% dolomite powder, 3-8% anthracite powder, 3-6% magnesium particles, 40-80% molybdenum oxide powder, 3-10% AD powder, and 1-3% binder;

[0008] S2. Pressing: Mix the lime powder, dolomite powder, anthracite powder, magnesium particles, molybdenum oxide powder and AD powder prepared in the above proportions, add a binder, stir evenly for 10 to 30 minutes, and press into shape;

[0009] S3. Sintering: Pre-sintering in a rotary kiln at 400-500°C for 2-3 hours to produce molybdenum oxide composite pressed balls.

[0010] Preferably, the lime powder is active lime powder, wherein CaO≥85%, SiO2≤5%, and the content of particles smaller than 3 mm is ≥90%. The lime powder plays a role in inhibiting the volatilization of molybdenum oxide.

[0011] The present invention preferably comprises dolomite powder, wherein MgO is ≥ 26%, CaO is ≥ 45%, and the content of particles smaller than 3 mm is ≥ 90%. MgO and CaO in the dolomite powder play a role in inhibiting the volatilization of molybdenum oxide. MgO also has the function of protecting the furnace lining.

[0012] Preferably, the anthracite powder has a carbon content of ≥90%, Sd ≤0.5%, and a content of particles smaller than 2 mm of ≥90%. The anthracite powder acts as a reducing agent.

[0013] Preferably, the magnesium particles contain Mg≥92%, CaO<0.3%, MgO<4.5, and the content of particles smaller than 5 mm is ≥90%. The magnesium particles act as a reducing agent.

[0014] Preferably, the molybdenum oxide powder contains Mo≥50%, P≤0.05%, S≤0.15%, and the content of particles smaller than 5 mm is ≥90%.

[0015] Preferably, the AD powder contains 10-30% Al, 30%-50% Al2O3, and ≥90% of the particle size less than 1 mm. The AD powder acts as a reducing agent.

[0016] Preferably, the molybdenum oxide composite pressed ball is ellipsoidal in shape and has a length of 10-40 mm.

[0017] Preferably, the molybdenum oxide composite briquettes obtained in step S3 are added into the converter from the scrap steel bucket before converter smelting, and the amount of addition is calculated and determined according to the requirement of the molybdenum element in the target molten steel composition.

[0018] The inventive concept of the present invention:

[0019] 1. The lime powder and dolomite powder mentioned in the present invention can both play a role in inhibiting the volatilization of molybdenum oxide. The main reason is that CaO in the lime and MgO in the dolomite react with molybdenum oxide as follows during the pre-sintering process in the rotary kiln: CaO+MOO3=CaMOO4, MgO+MOO3=MgMOO4. MoO3 has a strong binding force with CaO and can react to generate CaMoO4 and MgMOO4 at 400-500°C. The melting points of CaMoO4 and MgMOO4 are as high as about 1400°C, which are difficult to volatilize. This solves the problem of the volatilization of molybdenum oxide.

[0020] 2. In the present invention, since the main component of anthracite is C, part of the C will undergo a reduction reaction with the molybdenum oxide composite pellets during the pre-sintering process in the rotary kiln, and the reaction chemical equation is as follows: 3C+MOO3=MO+3CO.

[0021] 3. Since the present invention contains AD powder, the main components of which are Al and Al2O3, part of the Al will undergo a reduction reaction with the molybdenum oxide composite pellets during the pre-sintering process in the rotary kiln, and the reaction chemical equation is as follows: 2Al+MOO3=MO+Al2O3.

[0022] 4. Since the present invention contains magnesium particles, the main component of which is Mg, part of the Mg will undergo a reduction reaction with the molybdenum oxide composite pressed ball, and the reaction chemical equation is as follows: 3Mg+MOO3=MO+3MgO.

[0023] 5. After being added into the converter furnace, CaMOO4 and MgMOO4 will be reduced by the carbon and silicon elements in the molten iron.

[0024] 6. The present invention contains dolomite powder, the main component of which is MgO, so the MgO content in the slag can be increased, thereby increasing the melting point of the slag and improving the slag splashing furnace protection effect.

[0025] The molybdenum oxide composite briquette involved in the present invention can generate non-volatile CaMOO4 and MgMOO4 with MOO3 due to the presence of lime powder and dolomite powder, thereby effectively inhibiting the volatilization of MOO3; the C, Mg, and Al deoxidizers in the briquette can quickly reduce MOO3 in the early stage of converter smelting, thereby effectively improving the recovery rate of the molybdenum element.

[0026] Compared with the prior art, the invention has the following beneficial effects: based on the total weight of the composite briquette, the composite briquette contains 5-30% lime powder, 5-20% dolomite powder, 3-8% anthracite powder, 3-6% magnesium particles, 40-80% molybdenum oxide powder, 3-10% AD powder, and 1-3% binder. Through rotary kiln pre-sintering, CaO in lime and MgO in dolomite generate molybdate with a higher melting point with molybdenum oxide, which effectively inhibits the volatilization of molybdenum oxide during direct alloying; during the pre-sintering process, C, Mg, and Al will pre-reduce part of molybdenum oxide in advance; in the early stage of converter smelting, the molybdenum oxide composite briquette is added to the furnace, and the C, Mg, Al in the molybdenum oxide composite briquette and the C in the molten iron can reduce the molybdate and molybdenum oxide, and the generated molybdenum element enters the molten steel to achieve the purpose of molten steel alloying, ensuring that the molybdenum element recovery rate is above 97%. Since the price of molybdenum oxide is much lower than that of ferromolybdenum, the economic benefits are significant. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The present invention is a flow chart of the process for preparing the molybdenum oxide composite pellets. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0029] Example 1

[0030] like Figure 1 As shown, according to the molybdenum oxide composite ball pressing formula process provided by the present invention, the following steps are included:

[0031] Raw materials are prepared, including active lime powder with a lime content of 90%, AD powder with an Al content of 20%, anthracite powder with a C content of 90%, magnesium particles with a Mg content of 95%, dolomite powder with a MgO content of 26%, and molybdenum oxide powder with a molybdenum content of 57%. The binder is selected from at least one of caustic soda, white cement, biological starch and hydroxycellulose.

[0032] The above raw materials are mixed in the proportion of 10% lime powder, 5% AD powder, 5% magnesium particles, 5% anthracite powder, 5% dolomite powder, 67% molybdenum oxide powder and 3% binder. The prepared raw materials are fully stirred in a mixer for 25 minutes and pressed into balls.

[0033] The molybdenum oxide composite pressed balls are pre-fired at 400-500°C for 2-3 hours in a rotary kiln. The molybdenum oxide composite pressed balls are ellipsoidal in shape and 20 mm in length.

[0034] In the smelting of molybdenum-containing steel 15CrMoR for pressure vessels, the molybdenum oxide composite balls are added into the converter from the scrap steel bucket before converter smelting. The auxiliary gun is sampled and analyzed at the end of converter blowing, and the molybdenum recovery rate is measured to be 98%.

[0035] Example 2

[0036] like Figure 1 As shown, according to the molybdenum oxide composite ball pressing formula process provided by the present invention, the following steps are included:

[0037] Raw materials are prepared, including active lime powder with a lime content of 95%, AD powder with an Al content of 15%, anthracite powder with a C content of 12%, magnesium particles with a Mg content of 96%, dolomite powder with a MgO content of 28%, and molybdenum oxide powder with a molybdenum content of 55%. The binder is selected from at least one of caustic soda, white cement, biological starch and hydroxycellulose.

[0038] The above raw materials are mixed in the proportion of 5% lime powder, 3% AD powder, 4% anthracite powder, 5% magnesium particles, 8% dolomite powder, 72% molybdenum oxide powder and 3% binder. The prepared raw materials are fully stirred in a mixer for 30 minutes and pressed into balls.

[0039] The molybdenum oxide composite pressed balls are pre-fired at 400-500°C for 2-3 hours in a rotary kiln. The molybdenum oxide composite pressed balls are ellipsoidal in shape and 25 mm in length.

[0040] To smelt molybdenum-containing steel NM360 high-strength wear-resistant steel, the molybdenum oxide composite pellets were added into the converter from the scrap steel bucket before converter smelting. The auxiliary gun was sampled and analyzed at the end of converter blowing, and the molybdenum recovery rate was measured to be 99%.

[0041] Comparative Example 1

[0042] Molybdenum oxide powder containing 55% molybdenum is used as a raw material ingredient, and the ingredients are mixed in a ratio of 96% molybdenum oxide and 4% binder. The prepared raw materials are fully stirred and mixed in a blender for 30 minutes, and heated and dried in an electric blast drying oven at 200°C for 3 hours to make molybdenum oxide composite pressed balls with a particle diameter of 25 mm.

[0043] To smelt molybdenum-containing steel NM360 high-strength wear-resistant steel, the molybdenum oxide composite pellets were added into the converter from the scrap steel bucket before converter smelting. The auxiliary gun was sampled and analyzed at the end of converter blowing, and the molybdenum recovery rate was measured to be 86%.

[0044] Comparative Example 2

[0045] Active lime powder with a lime powder content of 95% and molybdenum oxide powder containing 55% molybdenum are prepared as raw material ingredients, and the above raw materials are mixed in a ratio of 10% lime powder, 85% molybdenum oxide powder, and 5% binder. The prepared raw materials are fully stirred and mixed with a blender for 30 minutes, and heated and dried at 220° C. in an electric blast drying oven for 2 hours to prepare molybdenum oxide composite pressed balls. The molybdenum oxide composite pressed balls are ellipsoidal in shape and 30 mm in length.

[0046] In the smelting of Q690 high-strength steel containing molybdenum, the molybdenum oxide composite pellets are added into the converter from the scrap steel bucket before converter smelting. The auxiliary gun is sampled and analyzed at the end of converter blowing, and the molybdenum recovery rate is measured to be 90%.

[0047] By comparison, it can be seen that when no inhibitor is added or only an inhibitor is added without a pre-reducing agent, the molybdenum recovery rate is relatively low.

[0048] When using the molybdenum oxide composite pressed balls of the present invention, the volatilization of molybdenum oxide is effectively suppressed, and the recovery rate of the molybdenum element is ensured. Since the price of molybdenum oxide is much lower than that of ferromolybdenum, the cost reduction effect is significant.

Claims

1. A molybdenum oxide composite ball pressing formula process, characterized in that: The following steps are involved: S1. Ingredients: Based on the total weight of the composite briquette, it includes 5-30% lime powder, 5-20% dolomite powder, 3-8% anthracite powder, 3-6% magnesium particles, 40-80% molybdenum oxide powder, 3-10% AD powder, and 1-3% binder; S2. Pressing: Mix the lime powder, dolomite powder, anthracite powder, magnesium particles, molybdenum oxide powder and AD powder prepared in the above proportions, add a binder, stir evenly for 10 to 30 minutes, and press into shape; S3. Sintering: Pre-sintering in a rotary kiln at 400-500°C for 2-3 hours to produce molybdenum oxide composite pressed balls.

2. The molybdenum oxide composite ball pressing formula process according to claim 1, characterized in that: The lime powder is active lime powder, wherein CaO≥85%, SiO2≤5%, and the content of particles smaller than 3mm is ≥90%.

3. The molybdenum oxide composite ball pressing formula process according to claim 1 is characterized in that: The dolomite powder has MgO≥26%, CaO≥45%, and the content of particles smaller than 3 mm is ≥90%.

4. The molybdenum oxide composite ball pressing formula process according to claim 1, characterized in that: The anthracite powder has a carbon content of ≥90%, Sd ≤0.5%, and a content of particles smaller than 2 mm of ≥90%.

5. The molybdenum oxide composite ball pressing formula process according to claim 1 is characterized in that: The magnesium particles contain Mg≥92%, CaO<0.3%, MgO<4.5, and the content of particles smaller than 5mm is ≥90%.

6. The molybdenum oxide composite ball pressing formula process according to claim 1, characterized in that: The molybdenum oxide powder contains Mo≥50%, P≤0.05%, S≤0.15%, and the content of particles smaller than 5mm is ≥90%.

7. The molybdenum oxide composite ball pressing formula process according to claim 1, characterized in that: The AD powder contains 10-30% Al, 30%-50% Al2O3, and the content of particles smaller than 1 mm is ≥90%.

8. The molybdenum oxide composite ball pressing formula process according to claim 1, characterized in that: The molybdenum oxide composite pressed ball is in the shape of an ellipsoid and has a length of 10-40 mm.

9. The molybdenum oxide composite ball pressing formula process according to claim 1, characterized in that: The molybdenum oxide composite pressed balls prepared in step S3 are added into the converter furnace before smelting in the converter, and the amount of addition is calculated and determined according to the requirement of the molybdenum element in the target molten steel composition.

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