Method for smelting high-cleanliness steel through molybdenum oxide alloying

Abstract

The invention belongs to the technical field of alloy steel smelting, and particularly relates to a method for smelting high-cleanliness steel through molybdenum oxide alloying. According to the method for smelting the high-cleanliness steel through alloying of the molybdenum oxide, the electric furnace smelting process and the molten steel tapping process are strictly controlled, different deoxidation modes are adopted at different times, the oxygen content in the molten steel is reduced, the molybdenum oxide is added when the tapping amount is 23%-25%, and therefore the yield of the molybdenum element can be increased. After the specific deoxidation process, the refining slag system is further stabilized by precisely controlling the addition amount of each material in the steps of secondary slagging, diffusion deoxidation, desulfurization and the like in the refining process, the refining slag with specific quantitative relation among the components is obtained, and a guarantee is provided for ensuring the cleanliness of molten steel. According to the method for smelting the high-cleanliness steel through molybdenum oxide alloying, the yield of molybdenum reaches up to 99.8%, the total rating of inclusions in molten steel is smaller than or equal to 0.5 grade, and the win-win situation of cost reduction and quality improvement is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of alloy steel smelting, and in particular relates to a method for smelting high-clean steel by alloying molybdenum oxide. Background Art

[0002] Molybdenum is one of the conventional alloying elements in alloy steel. Molybdenum can work together with other alloying elements in steel materials to improve the performance of steel materials. At present, most alloy steel smelting companies use the method of adding molybdenum-iron alloy to the smelting furnace to achieve the alloying of molybdenum elements in steel or molten iron during the smelting of molybdenum-containing alloy steel. This alloying method is simple and fast, but the high cost of molybdenum-iron alloy leads to increased smelting costs. For this reason, metallurgical workers have developed a method of using cheap primary raw material molybdenum oxide as an alloying additive for molybdenum. The melting rate of molybdenum oxide in molten steel is faster than that of ferromolybdenum, and the temperature drop of molten steel after alloying is smaller. Therefore, it has more advantages than molybdenum-iron alloy in terms of price, energy, and environmental protection. Therefore, the metallurgical process of using molybdenum oxide for direct alloying steelmaking has developed rapidly in recent years.

[0003] Molybdenum oxide is mainly MoO3, but in the high-temperature steelmaking process, molybdenum oxide is easily reduced by other elements in the molten steel, and even iron can reduce MoO3, resulting in some problems in the application of molybdenum oxide. For example, molybdenum oxide alloying will transfer and provide oxygen to the molten steel, affecting the cleanliness of the molten steel. The presence of oxygen also reduces the yield of molybdenum oxide. Summary of the invention

[0004] In view of this, the present invention provides a method for smelting high-clean steel by alloying with molybdenum oxide. The method uses molybdenum oxide to replace part of the ferro-molybdenum alloy for alloying smelting, and cooperates with the electric furnace control process, the appropriate amount and timing of molybdenum oxide addition, deoxidation and refining slag making process, which not only reduces the cost of molybdenum alloying, but also improves the cleanliness of molten steel and the molybdenum yield, achieving a win-win situation in cost and quality.

[0005] In order to solve the above technical problems, the first aspect of the present invention provides a method for smelting high-clean steel by molybdenum oxide alloying, the steps comprising:

[0006] S1, tapping molten steel from an electric furnace into a ladle, adding a diffusion deoxidizer to the ladle for pre-deoxidation when 5% to 10% of the steel is tapped, adding an aluminum ingot to the ladle for precipitation deoxidation when 17% to 18% of the steel is tapped, adding a carburizer to the ladle when 20% to 22% of the steel is tapped, adding molybdenum oxide to the ladle when 23% to 25% of the steel is tapped, adding alloy materials to the ladle when 29% to 31% of the steel is tapped, adding lime and synthetic slag to the ladle when 35% to 37% of the steel is tapped, and adding calcium carbide to the ladle when 48% to 52% of the steel is tapped;

[0007] S2, refining the ladle: when power is supplied for 1 to 2 minutes, 4±1kg / t steel lime and 2.5±0.5kg / t steel synthetic slag are added for secondary slagging; when power is supplied for 3 to 4 minutes, 0.8±0.2kg / t steel silicon carbide, 1±0.2kg / t steel calcium carbide and 1±0.1kg / t steel aluminum particles are added for diffusion deoxidation; when power is supplied for 5 to 6 minutes, 3±0.2kg / t steel lime is added to continue slagging; when power is supplied for 7 to 8 minutes, 0 .25~0.83kg / t steel calcium carbide and 0.06~0.64kg / t steel silicon carbide, keep refining white slag for 12~15min, analyze the slag system and adjust the composition appropriately to finally obtain refined slag; within 5min before the end of refining and the next process, evenly sprinkle 0.15kg / t steel aluminum particles on the surface of the refined slag to further reduce the oxygen content in the refining slag during light vacuum and prevent resulfurization; during the whole refining process, control Al in molten steel ≥ 0.015%;

[0008] Within 1 minute from the end of refining to the next process, the refined slag samples were taken for component analysis. The chemical composition contents in the refined slag satisfied the following relationship:

[0009] CaO: bx; SiO2: x; Al2O3: bx / c; MgO: x / a; FeO+MnO: dx; 95%≤y=F(x);

[0010] Wherein: F(x)=[a(1+b)+1]x / a+bx / c+dx;a:1.9~2.0,b:5~6,c:1.7~1.8,d:0.05~0.1.

[0011] The method for smelting high-clean steel by alloying molybdenum oxide provided by the present invention strictly controls the steel tapping process, adopts different deoxidation methods at different times, and adds molybdenum oxide when the tapping amount is 23% to 25%, thereby reducing the oxygen content in the steel, thereby facilitating improving the yield of the molybdenum element. After the above specific deoxidation process is completed, the refined slag system is further stabilized by strictly coordinating the steps of secondary slag making, diffusion deoxidation and desulfurization, and accurately controlling the addition amount of each material in the refining process, so as to obtain a refined slag with a specific quantitative relationship between the components, which provides a guarantee for ensuring the cleanliness of the molten steel.

[0012] In combination with the first aspect, the method for smelting high-clean steel by alloying molybdenum oxide further includes: setting the oxygen supply intensity to 0.6 Nm before the molten steel is tapped from the electric furnace to the ladle, in the late stage of electric furnace smelting, after taking the spectrum sample and within 3 minutes before tapping, 3 / min·t~0.8Nm 3 / min·t, control the flow rate of inching type carbon powder injection to 0.7kg / min·t~0.9kg / min·t, and the amount of steel left in the electric furnace after steel tapping is ≥30 tons.

[0013] In the later stage of electric furnace smelting, the oxygen supply and carbon injection process are adjusted to control the oxidizability of the electric furnace slag in the later stage, ensuring that FeO in the electric furnace slag is ≤17% and the amount of slag under the electric furnace is ≤0.5kg / t steel, thereby reducing the oxidizability of the "primary slag" of the ladle top slag, and prompting carbon powder to reduce the metal oxides in the electric furnace slag. Even if a small amount of slag curling and slag under the ladle occurs, its lower oxidizability can also achieve rapid modification of the top slag, thereby reducing the impact on the oxidizability of the ladle top slag.

[0014] In combination with the first aspect, in step S1, the diffusion deoxidizer includes at least one of calcium carbide and silicon carbide.

[0015] In combination with the first aspect, in step S1, the amount of the diffusion deoxidizer added is 0.45±0.01 kg / t steel.

[0016] Before precipitation deoxidation, the molten steel is pre-deoxidized using a diffusion deoxidizer, making full use of the molten steel dynamics conditions during the steel-tapping process to fully mix the slag pre-diffusion deoxidizer and obtain a better pre-deoxidation effect.

[0017] In combination with the first aspect, in step S1, the amount of the aluminum ingot added is 1.6±0.1 kg / t steel.

[0018] In combination with the first aspect, in step S1, the alloy material includes ferromolybdenum alloy, silicon-manganese alloy, ferrosilicon alloy, high carbon ferromanganese alloy, high carbon ferrochromium alloy and ferrovanadium alloy.

[0019] In combination with the first aspect, the amount of the silicon manganese alloy added is 4-9 kg / t steel, the amount of the ferrosilicon alloy added is 0-2 kg / t steel, the amount of the high carbon ferromanganese alloy added is 0-5 kg / t steel, the amount of the high carbon ferrochromium alloy added is 12-24 kg / t steel, the amount of the ferrovanadium alloy added is 0-8 kg / t steel, and the amount of the ferromolybdenum alloy added can be determined according to the actual type of steel produced.

[0020] In combination with the first aspect, in step S1, the amount of molybdenum oxide added does not exceed 3.5 kg / t steel. This amount of molybdenum oxide added can reduce the cost of alloying without affecting the cleanliness of the final molten steel.

[0021] In combination with the first aspect, in step S1, the amount of lime added is 5.8-6.0 kg / t steel, the amount of synthetic slag added is 3.4-3.6 kg / t steel, and the amount of calcium carbide added is 0.68-0.72 kg / t steel.

[0022] In combination with the first aspect, the chemical components of the synthetic slag include by mass percentage: Al2O3: 45% to 50%, CaO: 32% to 40%, SiO2: 4% to 10%, and MgO: <3%.

[0023] In combination with the first aspect, in step S2, the controlling Al in the molten steel ≥ 0.015% is specifically: taking the molten steel for component analysis, when Al in the molten steel is < 0.015%, adding aluminum wire and alloy materials to adjust the composition to an Al content in the molten steel of 0.025% to 0.035%, and ensuring that other components meet the process requirements.

[0024] Preferably, the alloy material includes at least one of ferromolybdenum alloy, silicon-manganese alloy, ferrosilicon alloy, high-carbon ferromanganese alloy, high-carbon ferrochrome alloy and ferrovanadium alloy, and the aluminum wire is φ9 mm and contains ≥97% Al.

[0025] In combination with the first aspect, step S2 also includes: when the power is supplied for 22 to 24 minutes, the molten steel is taken for component analysis, and the composition of the molten steel is adjusted according to the results of the chemical composition so that S in the molten steel is ≤0.002%, and aluminum wire is added ≤5 minutes away from LF steel tapping to adjust the Al content to 0.035% to 0.045%, and according to the composition test results, a small amount of required alloy elements is added.

[0026] The amount of alloy material added is accurately calculated to ensure that when the amount of alloy added is fine-tuned in the LF process, the total amount of alloy added is ≤1.5kg / t steel, so as to reduce the free oxygen content introduced during the alloying process of the LF process.

[0027] In combination with the first aspect, the chemical composition and proportion of the refined slag are as follows: CaO: 49%~53%, SiO2: 8%~12%, Al2O3: 28%~32%, MgO: 4%~8%, FeO+MnO<0.6%, in the ladle top slag: CaO / Al2O3 is 1.7±0.1, binary basicity CaO / SiO2 is 5.5±0.5; the refined slag with the chemical composition and proportion within the above range can ensure that the molten steel has good cleanliness.

[0028] Preferably, the main chemical components and proportions of the refined slag are as follows: CaO: 50.8% to 52.5%, SiO2: 8.8% to 10.4%, Al2O3: 28.9% to 28.3%, MgO: 4.8% to 5.3%, FeO+MnO: 0.47% to 0.52%, and in the ladle top slag: CaO / Al2O3 is 1.76 to 1.79, and binary basicity CaO / SiO2: 5.04 to 5.8.

[0029] Further preferably, the main chemical components and proportions of the refined slag are as follows: CaO: 50.8%, SiO2: 9.2%, Al2O3: 28.9%, MgO: 5.1%, FeO+MnO: 0.47%, and in the ladle top slag: CaO / Al2O3 is 1.76, and binary basicity CaO / SiO2: 5.5.

[0030] The beneficial effects obtained by the present invention are as follows: the present invention strictly controls the deoxidation process during the steel tapping process, reduces the oxygen content in the steel, and combines the LF refining process with slag making, which not only makes the molybdenum recovery rate as high as 99.8%, but also makes the total rating of inclusions in the steel molten ≤0.5, thus achieving a win-win situation of cost reduction and quality improvement. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a metallographic micrograph of the steel obtained in Example 1;

[0032] Figure 2 This is a metallographic micrograph of the steel obtained in Example 1;

[0033] Figure 3 This is a metallographic micrograph of the steel obtained in Example 1;

[0034] Figure 4 This is a metallographic micrograph of the steel obtained in Comparative Example 3;

[0035] Figure 5 This is a metallographic micrograph of the steel obtained in Comparative Example 4. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0037] Since the cost of smelting molybdenum-iron alloy is relatively high, using molybdenum oxide instead of molybdenum-iron alloy has gradually become a feasible new method for smelting molybdenum alloy. However, there are the following problems when using molybdenum oxide alloying: (1) Molybdenum oxide alloying will transfer oxygen to the molten steel. Therefore, it is necessary to ensure that the molten steel has a low original oxygen content when tapping, and a good electric furnace smelting control process is very important; (2) Since molybdenum oxide alloying will supply oxygen to the molten steel, it is necessary to strictly control the amount and timing of molybdenum oxide addition; (3) Since the use of molybdenum oxide alloying undoubtedly supplies oxygen to the molten steel compared to the use of molybdenum-iron alloy. Therefore, how to control the deoxidation timing and deoxidation process to achieve the reaction of aluminum with molybdenum oxide and remove oxygen from it to increase the yield of molybdenum oxide is also one of the key points of research at this stage; (4) Since the oxygen content in the molten steel determines the cleanliness of the molten steel to a certain extent, the slag making process and slag system composition control after deoxidation have become a key research point for smelting high-clean steel.

[0038] Through a large number of experimental studies on various process links, the inventors proposed a method for smelting high-clean steel by alloying with molybdenum oxide. By using molybdenum oxide to replace part of ferromolybdenum for alloying, and combining with a good electric furnace control process, a suitable amount and timing of molybdenum oxide addition, and a good deoxidation and refining slag making process, the cost of molybdenum alloying is reduced and the cleanliness of molten steel is improved.

[0039] In the following examples and comparative examples, the total amount of molten steel in the ladle is 87-89 t, and the proportion of each material added is the ratio to the total amount of molten steel.

[0040] Example 1

[0041] This embodiment provides a method for smelting high-clean steel by alloying molybdenum oxide, producing steel grade 25CrMo, the main components of which are C: 0.23%-0.27%, Si: 0.15%-0.40%, Mn: 0.4%-0.7%, Cr: 0.8%-1.0%, Mo: 0.15%-0.30%, and the specific steps are:

[0042] (1) Put the smelting raw materials (35% of automobile cold plate briquettes, 15% of pipe heads, 12% of graphite balls and 38% of scrap steel) into the furnace body and send it to the electric furnace for smelting. In the later stage of electric furnace smelting, the oxygen supply intensity is set to 0.6Nm within 3 minutes after taking the spectrum sample and before steel tapping. 3 / min·t, the flow rate of the inching type carbon powder injection is controlled to be 0.7kg / min·t; the carbon content of the molten steel at the end of the electric furnace is 0.07%, and the temperature of the molten steel at the end of the electric furnace is 1610℃;

[0043] (2) When the molten steel is tapped from the electric furnace into a ladle, when the tapping amount reaches 5%, silicon carbide is added at a ratio of 0.45 kg / t steel for pre-deoxidation, and the ladle is opened to blow argon gas to stir the molten steel; when the tapping amount reaches 17%, aluminum ingots are added at a ratio of 1.5 kg / t steel for precipitation deoxidation; when the tapping amount reaches 24%, molybdenum oxide alloy is added at a ratio of 2.8 kg / t steel; when the tapping amount reaches 30%, silicon manganese alloy is added at a ratio of 6.3 kg / t steel, and high carbon ferrochrome alloy is added at a ratio of 18.5 kg / t steel; when the tapping amount reaches 35%, lime is added at a ratio of 5.8 kg / t steel, and synthetic slag is added at a ratio of 3.4 kg / t steel for primary slag making; when the tapping amount reaches 50%, calcium carbide is added at a ratio of 0.69 kg / t steel. After the tapping is completed, the amount of steel left in the electric arc furnace is 32 tons.

[0044] (3) After EAF smelting, ladle refining is carried out: the ladle is hoisted to the refining station for smelting. When the power is supplied for 1 minute, 3.9 kg / t of lime and 2.0 kg / t of synthetic slag are added for secondary slag making. When the power is supplied for 3 minutes, 0.6 kg / t of silicon carbide, 0.8 kg / t of calcium carbide and 0.9 kg / t of aluminum particles are added for diffusion deoxidation. When the power is supplied for 5 minutes, 2.8 kg / t of lime is added to continue slag making. When the power is supplied for 7 minutes, 0.25 kg / t steel calcium carbide and 0.06kg / t steel silicon carbide, keep refining white slag for 12 minutes, analyze the slag system and adjust the composition appropriately to get refined slag; when the power is sent for 22 minutes, take the molten steel for composition analysis, adjust the molten steel composition according to the results of chemical composition, make S ≤ 0.002% in the molten steel, add aluminum wire ≥ 5 minutes before LF steel tapping, adjust Al content to 0.035% ~ 0.045%, and according to the composition test results, add a small amount of required alloy elements.

[0045] Within 5 minutes from the end of refining to the next process, aluminum particles are evenly sprinkled on the surface of the refining slag at a ratio of 0.15kg / t steel to further reduce the oxygen content in the refining slag during vacuum and prevent resulfurization. During the entire refining process, the Al content in the molten steel is controlled to be ≥ 0.015%. When the Al content in the molten steel is < 0.015%, the composition is adjusted by adding aluminum wire and alloy materials to the Al content in the molten steel of 0.025% to 0.035%, and other components meet the process requirements. Within 1 minute from the end of refining to the next process, the refined slag sample is taken for component analysis. The slag system components are shown in Table 1 below, which meet the requirements.

[0046] Table 1

[0047] Slag components CaO MgO <![CDATA[SiO2]]> <![CDATA[Al2O3]]> FeO+MnO <![CDATA[CaO / SiO2]]> <![CDATA[CaO / Al2O3]]> content(%) 52.5 5.3 10.4 29.3 0.49 5.04 1.79 .

[0048] Example 2

[0049] This embodiment provides a method for smelting high-clean steel by molybdenum oxide alloying, producing steel grade 27CrMo48V, the main components of which are C: 0.25%-0.29%, Si: 0.15%-0.40%, Mn: 0.8%-1.1%, Cr: 0.9%-1.1%, Mo: 0.4%-0.7%, V: 0.06%-0.12%, and the specific steps are:

[0050] (1) Put the smelting raw materials (34% of automobile cold plate briquettes, 16% of pipe heads, 11% of graphite balls and 39% of scrap steel) into the furnace body and send it to the electric furnace for smelting. In the later stage of electric furnace smelting, the oxygen supply intensity is set to 0.8Nm within 3 minutes after taking the spectrum sample and before steel tapping. 3 / min·t, the flow rate of the inching type carbon powder injection is controlled to be 0.9kg / min·t; the carbon content of the molten steel at the end of the electric furnace is 0.07%, and the temperature of the molten steel at the end of the electric furnace is 1610℃.

[0051] (2) When the molten steel is tapped from the electric furnace into a ladle, when the tapping amount reaches 10%, calcium carbide is added at a ratio of 0.44 kg / t steel for pre-deoxidation, and the ladle is opened to blow argon to stir the molten steel; when the tapping amount reaches 18%, aluminum ingots are added at a ratio of 1.6 kg / t steel for precipitation deoxidation; when the tapping amount reaches 25%, molybdenum oxide alloy is added at a ratio of 3.5 kg / t steel; when the tapping amount reaches 29%, silicon manganese alloy is added at a ratio of 6.3 kg / t steel and silicon is added at a ratio of 1 kg / t steel. Ferroalloy, high carbon ferromanganese alloy at a ratio of 6.5kg / t steel, high carbon ferrochromium alloy at a ratio of 20kg / t steel, ferromolybdenum alloy at a ratio of 4.4kg / t steel, and ferrovanadium alloy at a ratio of 1.4kg / t steel for alloying; when the molten steel volume reaches 37%, lime is added at a ratio of 6.0kg / t steel, and synthetic slag is added at a ratio of 3.6kg / t steel for primary slag making; when the molten steel volume reaches 50%, calcium carbide is added at a ratio of 0.72kg / t steel. After the steel is tapped, the amount of steel left in the electric arc furnace is 32t.

[0052] (3) After EAF smelting, ladle refining is carried out: the ladle is hoisted to the refining station for smelting. After power supply for 2 minutes, 3kg / t steel of lime and 2.5kg / t steel of synthetic slag are added for secondary slag making. After power supply for 4 minutes, 0.8kg / t steel of silicon carbide, 1.0kg / t steel of calcium carbide and 1.0kg / t steel of aluminum particles are added for diffusion deoxidation. After power supply for 6 minutes, 3.2kg / t steel of lime is added to continue slag making. After power supply for 8 minutes, 0.83kg / t steel of silicon carbide, 1.0kg / t steel of calcium carbide and 1.0kg / t steel of aluminum particles are added for diffusion deoxidation. g / t steel calcium carbide and 0.64kg / t steel silicon carbide, keep refining white slag for 15 minutes, analyze the slag system and adjust the composition appropriately to get refined slag; 24 minutes after power supply, take molten steel for composition analysis, adjust the composition of molten steel according to the results of chemical composition, make S ≤ 0.002% in the molten steel, add aluminum wire ≥ 5 minutes before LF steel tapping, adjust Al content to 0.035% ~ 0.045%, and according to the composition test results, add a small amount of required alloy elements.

[0053] Within 5 minutes from the end of refining to the next process, aluminum particles are evenly sprinkled on the surface of the refining slag at a ratio of 0.14kg / t steel to further reduce the oxygen content in the refining slag during vacuum and prevent resulfurization. During the entire refining process, the Al content in the molten steel is controlled to be ≥ 0.015%. When the Al content in the molten steel is < 0.015%, the composition is adjusted by adding aluminum wire and alloy materials to the Al content in the molten steel of 0.025% to 0.035%, and other components meet the process requirements. Within 1 minute from the end of refining to the next process, the refined slag sample is taken for component analysis. The slag system components are shown in Table 2 below, which meet the requirements.

[0054] Table 2

[0055] Slag components CaO MgO <![CDATA[SiO2]]> <![CDATA[Al2O3]]> FeO+MnO <![CDATA[CaO / SiO2]]> <![CDATA[CaO / Al2O3]]> content(%) 51.3 4.8 8.8 29.2 0.52 5.8 1.76 .

[0056] Example 3

[0057] This embodiment provides a method for smelting high-clean steel by alloying molybdenum oxide, producing steel grade 26CrMo, the main components of which are C: 0.24%-0.28%, Si: 0.15%-0.40%, Mn: 0.4%-0.7%, Cr: 0.9%-1.1%, Mo: 0.4%-0.6%, and the specific steps are:

[0058] (1) Put the smelting raw materials (38% of automobile cold plate briquettes, 13% of pipe heads, 11% of graphite balls and 38% of scrap steel) into the furnace body and send it to the electric furnace for smelting. In the later stage of electric furnace smelting, the oxygen supply intensity is set to 0.7Nm within 3 minutes after taking the spectrum sample and before steel tapping. 3 / min·t, the flow rate of the inching type carbon powder injection is controlled to be 0.8kg / min·t; the carbon content of the molten steel at the end of the electric furnace is 0.07%, and the temperature of the molten steel at the end of the electric furnace is 1610℃.

[0059] (2) When the molten steel is tapped from the electric furnace into a ladle, when the tapping amount reaches 8%, calcium carbide is added at a ratio of 0.46 kg / t steel for pre-deoxidation, and the ladle is opened to blow argon to stir the molten steel; when the tapping amount reaches 18%, aluminum ingots are added at a ratio of 1.7 kg / t steel for precipitation deoxidation; when the tapping amount reaches 21%, a carburizer is added to the ladle at a ratio of 0.2 kg / t steel; when the tapping amount reaches 23%, molybdenum oxide alloy is added at a ratio of 3.2 kg / t steel; when the tapping amount reaches 3 When the steel volume reaches 1%, silicon-manganese alloy is added at a ratio of 7kg / t steel, ferrosilicon alloy is added at a ratio of 1kg / t steel, high carbon ferrochrome alloy is added at a ratio of 19kg / t steel, and ferromolybdenum alloy is added at a ratio of 3.3kg / t steel for alloying; when the steel volume reaches 36%, lime is added at a ratio of 5.9kg / t steel, and synthetic slag is added at a ratio of 3.5kg / t steel for primary slag making; when the steel volume reaches 52%, calcium carbide is added at a ratio of 0.68kg / t steel. After the steel is tapped, the amount of steel left in the electric arc furnace is 32t.

[0060] (3) After EAF smelting, ladle refining is carried out: the ladle is hoisted to the refining station for smelting. After power supply for 2 minutes, 4.9 kg / t steel of lime and 3.0 kg / t steel of synthetic slag are added for secondary slag making. After power supply for 3 minutes, 1.0 kg / t steel of silicon carbide, 1.2 kg / t steel of calcium carbide and 1.0 kg / t steel of aluminum particles are added for diffusion deoxidation. After power supply for 5 minutes, 3.0 kg / t steel of lime is added to continue slag making. After power supply for 7 minutes, 0.65 kg / t steel calcium carbide and 0.43kg / t steel silicon carbide, keep refining white slag for 13 minutes, analyze the slag system and adjust the composition appropriately to get refined slag; 23 minutes after power supply, take molten steel for composition analysis, adjust the composition of molten steel according to the results of chemical composition, make S ≤ 0.002% in the molten steel, add aluminum wire ≥ 5 minutes before LF steelmaking, adjust Al content to 0.035% ~ 0.045%, and according to the composition test results, add a small amount of required alloy elements.

[0061] Within 5 minutes from the end of refining to the next process, aluminum particles are evenly sprinkled on the surface of the refining slag at a ratio of 0.16kg / t steel to further reduce the oxygen content in the refining slag during vacuum and prevent resulfurization. During the entire refining process, the Al content in the molten steel is controlled to be ≥ 0.015%. When the Al content in the molten steel is < 0.015%, the composition is adjusted by adding aluminum wire and alloy materials to the Al content in the molten steel of 0.025% to 0.035%, and other components meet the process requirements. Within 1 minute from the end of refining to the next process, the refined slag sample is taken for component analysis. The slag system components are shown in Table 3 below, which meet the requirements.

[0062] Table 3

[0063] Slag components CaO MgO <![CDATA[SiO2]]> <![CDATA[Al2O3]]> FeO+MnO <![CDATA[CaO / SiO2]]> <![CDATA[CaO / Al2O3]]> content(%) 50.8 5.1 9.2 28.9 0.47 5.5 1.76 .

[0064] Comparative Example 1

[0065] This comparative example provides a method for smelting high-clean steel by alloying molybdenum oxide, and the specific steps are similar to those of Example 1, except that the amount of molybdenum oxide added is 5 kg / t steel, and the remaining steps and parameters are the same as those of Example 1. The slag system components are shown in Table 4 below.

[0066] Table 4

[0067] Slag components CaO MgO <![CDATA[SiO2]]> <![CDATA[Al2O3]]> FeO+MnO <![CDATA[CaO / SiO2]]> <![CDATA[CaO / Al2O3]]> content(%) 50.8 5.1 9.2 30.4 0.58 5..5 1.69 .

[0068] Comparative Example 2

[0069] This comparative example provides a method for smelting high-clean steel by alloying molybdenum oxide, and the specific steps are similar to those of Example 1, except that the slag system components are not adjusted after the refined white slag is kept for 12 minutes. The slag system components are shown in Table 5 below.

[0070] Table 5

[0071] Slag components CaO MgO <![CDATA[SiO2]]> <![CDATA[Al2O3]]> FeO+MnO <![CDATA[CaO / SiO2]]> <![CDATA[CaO / Al2O3]]> content(%) 48.7 7.2 11.8 32.4 0.55 4.1 1.5 .

[0072] Comparative Example 3

[0073] This comparative example provides a method for smelting high-clean steel by alloying molybdenum oxide, and the specific steps are similar to those of Example 1. When 30% to 33% of the steel is tapped, lime and synthetic slag are added to the ladle, and the remaining steps and parameters are the same as those of Example 1. The slag system components are shown in Table 6 below.

[0074] Table 6

[0075] Slag components CaO MgO <![CDATA[SiO2]]> <![CDATA[Al2O3]]> FeO+MnO <![CDATA[CaO / SiO2]]> <![CDATA[CaO / Al2O3]]> content(%) 50.2 7.2 9.8 30.4 0.51 5.1 1.65 .

[0076] Comparative Example 4

[0077] This comparative example provides a method for smelting high-clean steel by alloying molybdenum oxide, and the specific steps are similar to those of Example 1. Molybdenum oxide is added to the ladle when 30% to 35% of the steel is tapped, and the remaining steps and parameters are the same as those of Example 1. The slag system components are shown in Table 7 below.

[0078] Table 7

[0079] Slag components CaO MgO <![CDATA[SiO2]]> <![CDATA[Al2O3]]> FeO+MnO <![CDATA[CaO / SiO2]]> <![CDATA[CaO / Al2O3]]> content(%) 52.4 5.3 10.5 29.3 0.68 5.04 1.79 .

[0080] Test example

[0081] According to the standard "Standard Rating Chart Microscopic Examination Method for Determination of Non-metallic Inclusions in Steel" (GB / T 10561-2005), the molten steel obtained in Examples 1 to 3 and Comparative Examples 1 to 4 was prepared into steel, and the inclusion contents thereof were determined by metallographic microscope (the metallographic micrographs of Examples 1 to 3 correspond to Figures 1 to 3 The metallographic micrographs of Comparative Examples 3 to 4 correspond to Figures 4-5 ), and the molybdenum yield was determined simultaneously. The results are shown in Table 8.

[0082] Table 8

[0083]

[0084] .

[0085] It can be seen from Table 8 that the non-metallic inclusion contents in the corresponding steels of Examples 1 to 3 all meet the standard requirements, indicating that the method provided by the present invention can not only ensure a higher molybdenum element yield, but also reduce the content of non-metallic inclusions in the alloy steel and improve the purity of the steel.

[0086] Depend on Figures 1 to 5 It can be seen from the metallographic detection diagrams of inclusions (corresponding to Examples 1 to 3 and Comparative Examples 3 to 4, respectively) that by using molybdenum oxide to replace part of ferromolybdenum for alloying, in combination with a good electric furnace control process, a suitable amount and timing of molybdenum oxide addition, and a good deoxidation and refining slag making process, the inclusions after detection are significantly better than those of the comparative examples.

[0087] What is described above is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for smelting high-clean steel by alloying molybdenum oxide, characterized in that the steps include: S1, tapping molten steel from an electric furnace into a ladle, adding a diffusion deoxidizer to the ladle for pre-deoxidation when 5% to 10% of the steel is tapped, adding an aluminum ingot to the ladle for precipitation deoxidation when 17% to 18% of the steel is tapped, adding a carburizer to the ladle when 20% to 22% of the steel is tapped, adding molybdenum oxide to the ladle when 23% to 25% of the steel is tapped, adding an alloy material to the ladle when 29% to 31% of the steel is tapped, adding lime and synthetic slag to the ladle when 35% to 37% of the steel is tapped, and adding calcium carbide to the ladle when 48% to 52% of the steel is tapped; S2, refining the ladle: when power is supplied for 1 to 2 minutes, 4±1kg / t steel lime and 2.5±0.5kg / t steel synthetic slag are added for secondary slag making; when power is supplied for 3 to 4 minutes, 0.8±0.2kg / t steel silicon carbide, 1±0.2kg / t steel calcium carbide and 1±0.1kg / t steel aluminum particles are added for diffusion deoxidation; when power is supplied for 5 to 6 minutes, 3±0.2kg / t steel lime is added to continue slag making; when power is supplied for 7 to 8 minutes, 0.25 to 0.83kg / t steel calcium carbide and 0.06 to 0.64kg / t steel silicon carbide are added, and the white slag is kept refined for 12 to 15 minutes. After analyzing the slag system components and adjusting the components appropriately, refined slag is finally obtained; Within 5 minutes from the end of refining to the next process, 0.15kg / t steel aluminum particles are evenly spread on the surface of the refining slag to further reduce the oxygen content in the refining slag during light vacuum and prevent resulfurization; during the entire refining process, the Al content in the molten steel is controlled to be ≥ 0.015%; Within 1 minute from the end of refining to the next process, the refined slag samples were taken for component analysis. The chemical composition contents in the refined slag satisfied the following relationship: CaO: bx; SiO2: x; Al2O3: bx / c; MgO: x / a; FeO+MnO: dx; 95%≤y=F(x); Wherein: F(x)=[a(1+b)+1]x / a+bx / c+dx;a:1.9~2.0,b:5~6,c:1.7~1.8,d:0.05~0.

1.

2. The method for smelting high-clean steel by alloying molybdenum oxide according to claim 1, characterized in that: The steps also include: setting the oxygen supply intensity to 0.6 Nm before the molten steel is tapped from the electric furnace to the ladle, in the late stage of electric furnace smelting, after taking the spectrum sample and within 3 minutes before tapping, 3 / min·t~0.8Nm 3 / min·t, control the flow rate of inching type carbon powder injection to 0.7kg / min·t~0.9kg / min·t, and the amount of steel left in the electric furnace after steel tapping is ≥30 tons.

3. The method for smelting high-clean steel by alloying molybdenum oxide according to claim 1, characterized in that: In step S1, the diffusion deoxidizer includes at least one of calcium carbide and silicon carbide.

4. The method for smelting high-clean steel by alloying molybdenum oxide according to claim 3, characterized in that: The added amount of the diffusion deoxidizer is 0.45±0.01kg / t steel.

5. The method for smelting high-clean steel by alloying molybdenum oxide according to claim 1, characterized in that: In step S1, the alloy material is selected from molybdenum-iron alloy, silicon-manganese alloy, silicon-iron alloy, high-carbon manganese-iron alloy, high-carbon chromium-iron alloy and vanadium-iron alloy.

6. The method for smelting high-clean steel by alloying molybdenum oxide according to claim 5, characterized in that: The amount of silicon manganese alloy added is 4-9 kg / t steel, the amount of ferrosilicon alloy added is 0-2 kg / t steel, the amount of high carbon ferromanganese alloy added is 0-5 kg / t steel, the amount of high carbon ferrochrome alloy added is 12-24 kg / t steel, and the amount of ferrovanadium alloy added is 0-8 kg / t steel.

7. The method for smelting high-clean steel by alloying molybdenum oxide according to claim 1, characterized in that: In step S1, the amount of molybdenum oxide added does not exceed 3.5 kg / t steel.

8. The method for smelting high-clean steel by alloying molybdenum oxide according to claim 1, characterized in that: In step S2, the control of Al in the molten steel ≥ 0.015% is specifically as follows: taking the molten steel for component analysis, when Al in the molten steel is less than 0.015%, adding aluminum wire and alloy materials to adjust the composition, and the Al content in the molten steel is 0.025% to 0.035% before the end of refining and the next process, and other components meet the process requirements.

9. The method for smelting high-clean steel by alloying molybdenum oxide according to claim 1, characterized in that: In step S2, when power is supplied for 22 to 24 minutes, the molten steel is taken for component analysis, and the composition of the molten steel is adjusted according to the results of the chemical composition so that S in the molten steel is ≤0.002%, and aluminum wire is added ≤5 minutes before LF steel tapping to adjust the Al content to 0.035% to 0.045%, and a small amount of required alloy elements is added according to the composition test results.

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