A non-oriented silicon steel secondary refining process

Abstract

The application discloses an outside-furnace refining process of non-oriented silicon steel and belongs to the technical field of steelmaking. The process flow of the application is: desulfurization station, top and bottom combined blowing converter, VD refining furnace, LF refining furnace and continuous casting, and specifically comprises the following steps. Step one, converter smelting: smelting molten iron and scrap steel into initial smelting molten steel; step two, VD refining furnace: deep decarburization and rough adjustment of alloy components of the molten steel; and step three, LF refining furnace: temperature adjustment, strong stirring desulfurization, fine adjustment of alloy components, calcium treatment and then continuous casting pouring of the molten steel. The application combines the component characteristics of non-oriented silicon steel and the actual situation of the process equipment of a steel plant, scientifically matches and designs a smelting process, utilizes the thermodynamic and kinetic advantages of deep desulfurization of high Als content of non-oriented silicon steel and good strong stirring effect of the LF furnace, performs deep desulfurization on the molten steel in the LF furnace process, thereby relaxing the requirement of the S content of the molten steel tapped from the converter, and smelting by adopting the technology of the application can accurately hit the component range and continuously cast and pour normally.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of steelmaking, and particularly relates to a secondary refining process for non-oriented silicon steel. BACKGROUND

[0002] Silicon steel is a binary alloy of silicon and iron with a silicon content of 0.5% to 4.5% and a very low carbon content, which is developed from industrial pure iron and is mainly used for manufacturing various generators, generator cores and transformer cores. It is an irreplaceable soft magnetic alloy material in the electronic, electric power and military industries. According to different production processes, silicon steel can be divided into hot-rolled silicon steel and cold-rolled silicon steel. Cold-rolled silicon steel includes cold-rolled non-oriented silicon steel and cold-rolled oriented silicon steel. The Si content of cold-rolled non-oriented silicon steel is generally between 0.5% and 3.0%, and its iron loss and magnetic induction intensity are relatively low. It is mainly used for medium and large-sized motors and generators with large capacity.

[0003] At present, the general smelting process path of non-oriented high-grade silicon steel is "desulfurization station→top and bottom combined blowing converter→RH vacuum furnace→continuous casting". The main functions of each process are as follows: 1) molten iron desulfurization process: desulfurizer is added to the molten iron, and then stirring is performed to reduce the sulfur content in the molten iron. After stirring, the desulfurization slag is removed; 2) converter smelting: generally, top and bottom combined blowing converter is used for smelting. The mass fraction of carbon in the steel is ensured to be ≤0.05% when tapping, the oxygen mass fraction is 0.0500%-0.0800%, the tapping temperature is ≥1650℃, and the amount of slag discharged from the converter is controlled when tapping; 3) RH vacuum treatment: its main purpose is decarburization, deoxidation and alloying. The RH vacuum treatment process has high production efficiency and has the functions of decarburization, deoxidation, oxygen blowing and temperature rising, and composition control; 4) continuous casting: qualified molten steel is cast into continuous casting billets. The whole process adopts protective casting.

[0004] Through retrieval, a non-oriented silicon steel for transformers and a preparation method thereof are disclosed in Chinese patent (authorized publication number: CN 109943766 B), and the steelmaking process flow is: molten iron pretreatment→converter smelting→RH refining→continuous casting. Also, a steelmaking method of non-oriented silicon steel is disclosed in Chinese patent (authorized publication number: CN 110592460 B), and the process flow is: after molten iron desulfurization, converter smelting-RH vacuum refining-continuous casting and other processes. The main technology is to propose a method for smelting non-oriented silicon steel by using electroplated tin mud instead of pure tin ingot. The tin mud powder is obtained by drying the waste electroplated tin mud generated from the electroplated tin production line, and the tin mud powder is jointly sprayed and stirred with the desulfurizer in the molten iron desulfurization station to perform desulfurization operation. Most of the tin oxide in the tin mud powder reacts with carbon in the molten iron to generate metallic tin and remains in the molten iron. After the molten iron is desulfurized, the smelting of Sn-containing non-oriented silicon steel is completed through the processes of converter smelting, RH vacuum refining-continuous casting and the like. Pure tin ingot can be appropriately supplemented during vacuum refining according to the composition detection results. The main purpose is to reduce the production cost.

[0005] For example, Chinese patent (authorization announcement number: CN 108660294 A) discloses "A method for controlling inclusions in silicon-manganese killed non-oriented silicon steel," the process flow of which is: converter smelting → RH vacuum refining → continuous casting. By strictly controlling the slag amount at the converter tapping, adding lime, synthetic slag, and calcium carbide to adjust the slag; RH vacuum refining, using a deep decarburization mode, after decarburization, first adding metallic aluminum for pre-deoxidation, and simultaneously adding SiC to the slag surface of the ladle to deoxidize and modify the slag, circulating for 1-3 minutes, then adding low-carbon, low-titanium ferrosilicon for final deoxidation, circulating for 3-6 minutes, and then adding metallic manganese, ferrophosphorus, etc. for alloying. After alloying, the net circulation time is greater than 8 minutes, which can improve the composition of non-metallic inclusions in the steel and thus improve the performance of non-oriented silicon steel.

[0006] The scientific paper "Research on Inclusion Control in the Refining Process of Non-oriented Silicon Steel" (Continuous Casting - Issue 2, 2016) mentions that the silicon steel production process is "desulfurization → 150t top and bottom blowing converter → argon station → 150t RH vacuum furnace → slab continuous casting machine".

[0007] In summary, the publicly available information retrieved above indicates that the mainstream smelting process for non-oriented high-grade silicon steel is "desulfurization station → top and bottom combined blowing converter → RH vacuum furnace → continuous casting". For steel mills equipped only with VD refining furnaces and not RH refining furnaces, or those equipped with RH refining furnaces but with insufficient RH capacity, finding a new smelting process route that can achieve high-quality, low-cost smelting of non-oriented silicon steel without RH treatment is particularly important. Summary of the Invention

[0008] 1. The problem to be solved

[0009] The purpose of this invention is to provide a ladle refining process for non-oriented silicon steel. By optimizing the smelting process and combining the strong desulfurization capabilities of the LF furnace and the strong decarburization capabilities of the VD furnace, non-oriented silicon steel can be smelted without RH treatment. Furthermore, the method of this invention significantly relaxes the requirements for sulfur content in converter steel, thereby reducing production costs.

[0010] 2. Technical Solution

[0011] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0012] The ladle refining process for non-oriented silicon steel of the present invention adopts a process flow of desulfurization station → top and bottom combined blowing converter → VD refining furnace → LF refining furnace → continuous casting to produce non-oriented silicon steel. Among them, the VD refining furnace and LF refining furnace are ladle refining processes of converter, specifically including the following steps:

[0013] Step 1, Converter smelting: smelting molten iron and scrap steel into primary molten steel;

[0014] Step two: VD refining furnace: deep decarburization and rough adjustment of alloy composition for the molten steel;

[0015] Step three: LF refining furnace: temperature adjustment, strong stirring desulfurization, fine adjustment of alloy composition, calcium treatment, and then continuous casting.

[0016] As a further improvement of the present application, the non-oriented silicon steel comprises the following components by weight percentage: carbon ≤0.0050%, silicon: 0.20-2.0%, manganese: 0.20-0.50%, phosphorus: ≤0.090%, sulfur: ≤0.005%, acid-soluble aluminum: 0.20-0.80%, nitrogen ≤0.0030%, and the balance being iron and unavoidable impurities.

[0017] As a further improvement of the present application, in step one, the charging amount of the converter is controlled to ensure that the free space height of the ladle after the primary molten steel from the converter is poured into the ladle is between 800mm-1200mm.

[0018] As a further improvement of the present application, in step one, the converter tapping temperature is: 1680-1700℃, the converter tapping carbon content is: ≤0.040%, the converter tapping oxygen content is ≥600ppm, and the converter tapping sulfur content is ≤0.020%; no deoxidizer and slagging material is added during the converter tapping process, the amount of slag is controlled, and the thickness of the slag in the ladle is required to be ≤80mm.

[0019] As a further improvement of the present application, in step two, after the molten steel is poured out of the VD process, the oxygen is set and the molten steel sample 1 is taken to analyze the composition of the molten steel. Before the oxygen setting and sampling, the ladle is opened for bottom argon blowing, and the argon flow rate is controlled at 20-80NL / min, with the principle of having obvious fluctuations in the steel liquid surface and not exposing the steel liquid.

[0020] As a further improvement of the present application, in step two, after the VD starts processing, due to the combined effect of the exhaust of a large amount of CO gas generated by the decarburization reaction in the molten steel and the reduction of the vacuum degree, the molten steel violently churns in the ladle. During the processing, the principle is to have as large a bright surface of the molten steel as possible and not to pour out of the ladle, dynamically adjust the argon flow rate and the vacuum pump start-up speed, gradually open the vacuum pump to the limit vacuum degree <67Pa, the argon flow rate is 50-300NL / min, the vacuum degree is to the limit vacuum degree and is maintained for 15-20min, then aluminum particles are added for deoxidation, and the amount of aluminum particles added is calculated according to the following formula:

[0021] Aluminum particle addition amount (kg) = molten steel amount (t) × 1000 × [54 / 48 × ([O]inlet - 16 / 12 × [C]inlet)] + molten steel amount (t) × 1000 × target Al content / (aluminum particle Al content × Al recovery rate)

[0022] Wherein, [O]inlet represents the inlet oxygen content, unit is %; [C]inlet represents the inlet carbon content, unit is %; the aluminum particle Al content is 99%; the Al yield is 82%.

[0023] As a further improvement of the present application, in step two, after the aluminum particle is added for 3 minutes, low-carbon ferrosilicon, electrolytic manganese and other alloying elements are added to roughly adjust the chemical composition, and the alloying element addition amount is calculated according to a general metallurgical formula. After the low-carbon ferrosilicon, electrolytic manganese and other alloying elements are added for 5 minutes, the vacuum is broken, and after the vacuum is broken, the molten steel sample 2 is taken to analyze the molten steel composition.

[0024] As a further improvement of the present application, in step three, the temperature of the molten steel is measured after the molten steel is tapped in the LF process, the ladle bottom argon blowing is started, the argon flow rate is controlled according to the principle that the molten steel bright surface reaches 0-50 mm, and the argon flow rate is controlled at 50-100 NL / min.

[0025] As a further improvement of the present application, in step three, the lower electrode heating is performed: when the electrode is about to contact the slag, 1-2 kg / t of steel of lime is added, the lime is added in two batches during the heating period, the lime addition amount is 1-2 kg / steel, and during the heating period, 0.5-1.0 kg / t of steel of calcium carbide is added for submerged arc. The purpose of adding lime is to adjust the ladle slag system and improve the ladle slag basicity to create thermodynamic conditions for desulfurization. The purpose of adding calcium carbide is to generate CO2 by chemical reaction between calcium carbide and carbon in the electrode to foam the slag and reduce the carbon pick-up of the molten steel. After 2-4 minutes of heating, the argon flow rate is adjusted so that the molten steel bright surface reaches 100-200 mm, and the purpose is to uniform the ladle molten steel temperature. The heating time is considered at a heating rate of 4 ℃ / min, and the heating is stopped when the molten steel temperature reaches 1620 ℃.

[0026] As a further improvement of the present application, in step three, after the heating is stopped, the molten steel is subjected to strong stirring desulfurization. The strong stirring time is determined according to the sulfur content in the VD molten steel sample 2, and the specific values are shown in Table 1:

[0027] Table 1 LF strong stirring desulfurization time table

[0028]

[0029] During the strong stirring desulfurization, the Als content attenuation is calculated at 0.005% / min, and during the strong stirring desulfurization, the argon flow rate is controlled according to the principle that the molten steel bright surface reaches 400-600 mm, and the argon flow rate is controlled at 500-700 NL / min.

[0030] As a further improvement of the present application, in step three, before the end of the strong stirring desulfurization of the molten steel, the amount of aluminum particles to be added is calculated according to the following formula according to the composition analysis result of the VD molten steel sample 2, and then other alloying amounts are calculated according to the general metallurgical formula. After the addition of the alloy, the temperature is measured after stirring for 3-5 minutes. If the temperature of the molten steel is lower than the target temperature before the calcium wire feeding, the electrode is raised to the target temperature before the wire feeding.

[0031] The amount of aluminum particles to be added (kg) = (the amount of molten steel (t) x 1000 + the sum of VD alloying amounts) x (the target Als content - the Als content in the VD molten steel sample 2 - the strong stirring time x 0.005%) / (the Al content of the aluminum particles x the Al recovery rate), wherein the Al content of the aluminum particles is 99%, and the Al recovery rate is 90%.

[0032] As a further improvement of the present application, in step three, the calcium wire is fed, and the target range of the calcium content is 0.0020-0.0035%. After the wire feeding, the molten steel is weakly stirred for 6-8 minutes, and the molten steel sample 3 is taken for the outbound. Before and after the calcium wire feeding, the argon flow is adjusted according to the principle that the molten steel surface has obvious fluctuation and the molten steel is not exposed, and the argon flow is controlled at 20-80 NL / min.

[0033] 3. Beneficial effects

[0034] Compared with the prior art, the present application has the following beneficial effects:

[0035] (1) The present application achieves the purpose of deep decarburization of the molten steel by relying on the CO gas bubbles in the molten steel, the argon gas bubbles and the decarburization of the free surface of the molten steel in the VD refining furnace, solves the problem that in some steel plants, the RH refining furnace is not equipped, or although the RH refining furnace is equipped, the RH production capacity is insufficient, and realizes the smelting of non-oriented silicon steel by utilizing the VD refining furnace and the LF refining furnace;

[0036] (2) The present application realizes the deep desulfurization of the molten steel in the LF furnace process by utilizing the thermodynamic and kinetic advantages of the high Als content of non-oriented silicon steel and the good LF furnace strong stirring effect, significantly relaxes the requirement for the S content of the converter tapping compared with the conventional RH process path, so that other means are not needed to strictly control the S content of the converter tapping to be low enough during smelting, and compared with the conventional RH smelting process which needs to strictly control the S content of the converter tapping, the production cost can be significantly reduced.

[0037] (3) The key points of smelting non-oriented silicon steel by utilizing the smelting process of the present application are:

[0038] 1) The size of the ladle bottom argon flow and the opening timing of the vacuum degree pump stage are controlled during the VD treatment to prevent the molten steel from being poured out of the ladle to cause safety or equipment and production accidents;

[0039] 2) In LF furnace, the carbon pick-up of molten steel is reduced by adding calcium carbide to strengthen the submerged arc, and controlling the argon flow rate of ladle bottom blowing during heating, the slag basicity of ladle is adjusted by adding lime, and the deep desulfurization is realized in the stage of slagging;

[0040] 3) The attenuation law of Als in the process of LF strong stirring desulfurization is explored, and the Als content can be accurately hit at the outlet of LF furnace;

[0041] The technical scheme of the present application can accurately hit the composition range, continuously cast and pour normally, and effectively avoid the safety hazard of "VD furnace molten steel pouring out of the ladle and burning the equipment". BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 It is a flowchart of a non-oriented silicon steel external refining process; DETAILED DESCRIPTION

[0043] The technical scheme and effect of the present application will be described in detail below by taking the smelting of non-oriented silicon steel W800 by 120-ton VD refining furnace and LF refining furnace as an example.

[0044] (1) Converter: smelt the molten iron and scrap steel into primary molten steel, and control the molten steel quantity, tapping temperature, tapping carbon, sulfur, oxygen and slag quantity, etc. The main parameter control conditions are shown in Table 2:

[0045] Table 2 Main process parameters of converter in each example

[0046]

[0047] (2) VD refining furnace: deep decarburization and alloy composition rough adjustment of molten steel. The specific operation steps are as follows:

[0048] 1) Ladle bottom blowing flow rate control before VD refining furnace starts: connect the ladle bottom blowing argon when the molten steel enters the VD process. After the ladle is dropped, open the argon cut-off valve, and adjust the argon flow rate according to the principle that there is obvious fluctuation of the molten steel surface, and the molten steel is not exposed, and the argon flow rate is generally controlled at 20-80 NL / min;

[0049] 2) After the molten steel is dropped in the VD process, the oxygen is determined, and the molten steel sample ① is analyzed to analyze the carbon content, silicon content, manganese content and phosphorus content of the molten steel;

[0050] 3) Cover the vacuum tank cover to perform vacuum pumping operation. During the vacuum pumping process after starting the vacuum pump (i.e. from starting the vacuum pump to reaching the limit vacuum degree), the rolling condition of the molten steel surface is observed through the manual observation hole, the pump starting speed and the ladle bottom blowing argon flow rate are controlled according to the principle that the molten steel does not splash out of the ladle, the vacuum pump is gradually started to the limit vacuum degree (<67 Pa), and the argon flow rate is generally controlled at 20-150 NL / min;

[0051] 4) After the vacuum reaches the ultimate vacuum (less than 67 Pa), the vacuum holding stage, i.e. the deep decarburization stage, is entered, and the holding time is 15-20 min. During this period, the argon flow is controlled so that the molten steel is stirred violently, but the stirring height is not too high. Generally, the argon flow is controlled at 50-300 NL / min;

[0052] 5) After the vacuum reaches the ultimate vacuum and is maintained for 15-20 min, aluminum particles are added for deoxidization and alloying. The amount of the aluminum particles added is calculated according to the following formula:

[0053] Aluminum particle addition amount (kg) = tundish t x 1000 x [54 / 48 x ([O]inlet-16 / 12 x [C]inlet)] + tundish t x 1000 x target Als content / (aluminum particle Al content x Al recovery rate),

[0054] wherein [O]inlet represents the inlet oxygen content, in %; [C]inlet represents the inlet carbon content, in %; the target Als content is 0.25%; the aluminum particle Al content is 99%; and the Al recovery rate is 82%;

[0055] 6) After the aluminum particles are added for 3 min, low-carbon ferrosilicon, electrolytic manganese, and low-carbon ferrophosphorus are added to roughly adjust the chemical composition. The alloy addition amount is calculated according to the following formula:

[0056] Low-carbon ferrosilicon addition amount (kg) = tundish t x 1000 x (target Si content - Si content in molten steel sample ①) / (low-carbon ferrosilicon Si content x Si recovery rate), wherein the target Si content is 0.35%, the low-carbon ferrosilicon Si content is 75%, and the Si recovery rate is 92%;

[0057] Electrolytic manganese addition amount (kg) = tundish t x 1000 x (target Mn content - Mn content in molten steel sample ①) / (electrolytic manganese Mn content x Mn recovery rate), wherein the target Mn content is 0.35%, the electrolytic manganese Mn content is 99%, and the Mn recovery rate is 94%;

[0058] Low-carbon ferrophosphorus addition amount (kg) = tundish t x 1000 x (target P content - P content in molten steel sample ①) / (low-carbon ferrophosphorus P content x P recovery rate), wherein the target P content is 0.085%, the low-carbon ferrophosphorus P content is 23%, and the P recovery rate is 96%;

[0059] 7) During the rough adjustment period of the alloy composition, the argon flow is controlled so that the molten steel is stirred violently, but the stirring height is not too high. Generally, the argon flow is controlled at 50-300 NL / min;

[0060] 8) After the low-carbon ferrosilicon, electrolytic manganese, and low-carbon ferrophosphorus are added for 5 min, the vacuum is broken;

[0061] 9) After breaking the vacuum, take sample ② of the molten steel to analyze the carbon content, silicon content, manganese content, phosphorus content, and acid-soluble aluminum content of the molten steel;

[0062] The main parameter control conditions of the VD refining furnace of each example are shown in Table 3.

[0063] Table 3 Main process parameters of VD refining furnace of each example

[0064]

[0065] Table 3 (continued):

[0066]

[0067]

[0068] Table 3 (continued):

[0069]

[0070] Table 3 (continued):

[0071] Furnace number Steel sample number [C] / ％ [Si] / % [Mn] / % [P] / ％ [S] / ％ [Als] / % [N] / ％ Example 1 ② 0.0013 0.34 0.35 0.088％ 0.017 0.24 0.0023 Example 2 ② 0.0014 0.35 0.34 0.081％ 0.012 0.23 0.0022 Example 3 ② 0.0012 0.36 0.33 0.082％ 0.008 0.26 0.0022 Example 4 ② 0.0015 0.35 0.36 0.080％ 0.010 0.25 0.0021

[0072] (3) LF refining furnace: temperature adjustment, desulfurization, alloy composition fine adjustment, and calcium treatment of the molten steel. Specifically, the following steps are included:

[0073] 1) Connect the ladle bottom argon blowing before the molten steel is discharged from the LF process, and measure the temperature after discharging;

[0074] 2) Start the ladle bottom argon blowing, and control the argon flow rate according to the principle of reaching 100-300 mm of molten steel bright surface, and the argon flow rate is generally controlled at 100-200 NL / min;

[0075] 3) Lower electrode heating. When the electrode is about to contact the slag, add lime 1.0-2.0 kg / t steel; During heating, add lime 1.0-2.0 kg / t steel for arc burial in two batches. The heating time is considered at a heating rate of 4℃ / min, and when the molten steel temperature is expected to reach 1620℃, stop heating;

[0076] 4) After stopping heating, perform strong stirring desulfurization on the molten steel. The strong stirring time is determined according to the sulfur content in sample ② of the VD molten steel, and the specific conditions are shown in Table 4.

[0077] Table 4 LF strong stirring desulfurization time table

[0078]

[0079] Remark: During the period of strong stirring desulphurization, the Als content attenuation is calculated at 0.005% / min, and the argon flow is controlled at 500-700 NL / min based on the principle that the bright surface of the molten steel reaches 400-600 mm.

[0080] 5) 3 minutes before the end of the strong stirring desulphurization of the molten steel, the calculated results are added to the molten steel according to the following formula based on the analysis results of the VD molten steel sample ② to fine-tune the acid-soluble aluminum content, silicon content, manganese content, and phosphorus content of the molten steel to the target values (when the calculated result is ≤0, no alloy is added).

[0081] Aluminum particle addition amount (kg) = (tapping amount (t) x 1000 + VD low-carbon ferrosilicon addition amount + VD electrolytic manganese addition amount + VD aluminum particle addition amount + VD low-carbon ferrophosphorus addition amount) x (LF target Als content - Als content in VD molten steel sample ② - strong stirring time x 0.005%) / (aluminum particle Al content x Al recovery rate)

[0082] Wherein, the target Als content is 0.25% during LF smelting; the aluminum particle Al content is 99%; and the Al recovery rate is 90%.

[0083] Low-carbon ferrosilicon addition amount (kg) = (tapping amount (t) x 1000 + VD low-carbon ferrosilicon addition amount + VD electrolytic manganese addition amount + VD aluminum particle addition amount + VD low-carbon ferrophosphorus addition amount) x (LF target Si content - Si content in VD molten steel sample ②) / (low-carbon ferrosilicon Si content x Si recovery rate)

[0084] Wherein, the target Si content is 0.35%, the low-carbon ferrosilicon Si content is 75%, and the Si recovery rate is 95%.

[0085] Electrolytic manganese addition amount (kg) = (tapping amount (t) x 1000 + VD low-carbon ferrosilicon addition amount + VD electrolytic manganese addition amount + VD aluminum particle addition amount + VD low-carbon ferrophosphorus addition amount) x (LF target Mn content - Mn content in VD molten steel sample ②) / (electrolytic manganese Mn content x Mn recovery rate)

[0086] Wherein, the target Mn content is 0.35%, the electrolytic manganese Mn content is 99%, and the Mn recovery rate is 98%.

[0087] Low-carbon ferrophosphorus addition amount (kg) = (tapping amount (t) x 1000 + VD low-carbon ferrosilicon addition amount + VD electrolytic manganese addition amount + VD aluminum particle addition amount + VD low-carbon ferrophosphorus addition amount) x (LF target P content - P content in VD molten steel sample ②) / (low-carbon ferrophosphorus P content x P recovery rate)

[0088] Wherein, the target P content is 0.085%, the low-carbon ferrophosphorus P content is 23%, and the P recovery rate is 98%.

[0089] 6) After the end of strong stirring, the temperature of the molten steel is measured, if the temperature of the molten steel is lower than the target temperature (1585-1605℃) before feeding calcium wire, the lower electrode is heated, the heating time is considered at the heating speed of 4℃ / min, when the temperature of the molten steel is expected to reach 1595℃, the heating is stopped; during the heating, the argon flow is controlled according to the principle that the bright surface of the molten steel reaches 100-300mm, and the argon flow is generally controlled at 100-200NL / min;

[0090] 7) After the temperature reaches the target temperature before feeding calcium wire, the calcium wire is fed, the target range of calcium content is 0.0020-0.0035%, after the end of feeding the wire, the molten steel is weakly stirred for 6-8min, and the molten steel sample ③ is taken out. Before and after feeding the calcium wire, the argon flow is adjusted according to the principle that the molten steel surface has obvious fluctuation and the molten steel is not exposed, and the argon flow is generally controlled at 20-80NL / min.

[0091] The control conditions of the main parameters of the LF refining of each embodiment are shown in Table 5:

[0092] Table 5 Main process parameters of the LF refining furnace of each embodiment

[0093]

[0094]

[0095] Table 5 (continued):

[0096]

[0097] Table 5 (continued):

[0098]

[0099] Table 5 (continued):

[0100]

[0101] The above describes the present application and its embodiments in a schematic manner, which is not limited, and the drawings only show one of the embodiments of the present application, and the actual structure is not limited thereto. Therefore, if a person skilled in the art is inspired thereby, without departing from the purpose of the present application, similar structural modes and embodiments are not creatively designed, which should all belong to the protection scope of the present application.

Claims

1. A process for the secondary refining of non-oriented silicon steel, characterized in that, The process flow is: desulfurization station→top and bottom combined blowing converter→VD refining furnace→LF refining furnace→continuous casting, wherein the VD refining furnace and the LF refining furnace are the converter external refining process, and specifically comprising the following steps: Step one, converter smelting: smelting molten iron and scrap steel into initial molten steel; Step two: VD refining furnace: deep decarburization and alloy component rough adjustment of the molten steel; After the VD starts processing, the principle is to make the molten steel bright surface as large as possible and not to pour out the ladle, dynamically adjust the argon flow and the vacuum pump start-up speed, open the vacuum pump step by step to the limit vacuum degree <67Pa, and the argon flow is 20-150NL / min; In the deep decarburization stage, the holding time is 15-20min, and the argon flow is 50-300NL / min; Step three: LF refining furnace: temperature adjustment, strong stirring desulfurization, alloy component fine adjustment, calcium treatment of the molten steel, and then continuous casting; In step three, the lower electrode is heated: when the electrode is close to the slag, 1-2kg / t of steel of lime is added, and the lime is added in two batches during heating, and the amount of lime added is 1-2kg / t of steel. During heating, 0.5-1.0kg / t of steel of calcium carbide is added for submerged arc; After heating for 2-4 minutes, adjust the argon flow to make the molten steel bright surface reach 100-200mm; After stopping heating, the molten steel is subjected to strong stirring desulfurization, and during the process, the argon flow is controlled according to the principle that the molten steel bright surface reaches 400-600mm, and the argon flow is controlled at 500-700NL / min; The non-oriented silicon steel comprises the following components by weight percentage: carbon ≤0.0050%, silicon: 0.20-2.0%, manganese: 0.20-0.50%, phosphorus: ≤0.090%, sulfur: ≤0.005%, acid-soluble aluminum: 0.20-0.80%, nitrogen ≤0.0030%, and the balance is iron and unavoidable impurities.

2. A process for the production of non-oriented silicon steel outside the ladle refining process as claimed in claim 1, wherein: In step one, the amount of converter charging is controlled to ensure that the amount of initial molten steel when the converter is tapped is mixed into the ladle, and the free space height of the ladle is between 800mm-1200mm; The converter tapping temperature is 1680-1700℃, the converter tapping carbon content is ≤0.040%, the converter tapping oxygen content is ≥600ppm, and the converter tapping sulfur content is ≤0.020%; No deoxidizer and slag forming material is added during the converter tapping process, the amount of slag is controlled, and the thickness of the ladle slag is required to be ≤80mm.

3. A process for the secondary refining of non-oriented silicon steel according to any one of claims 1-2, characterized in that: In step two, the molten steel is sampled after the VD process to analyze the composition of the molten steel; The ladle is opened for bottom argon blowing before oxygen sampling, and the argon flow is controlled at 20-80NL / min, according to the principle that the molten steel surface has obvious fluctuation and the molten steel is not exposed.

4. A process for the production of non-oriented silicon steel outside the furnace refining process as claimed in claim 3, wherein: In step two, after the vacuum degree reaches the limit vacuum degree and is maintained for 15-20min, aluminum particles are added for deoxidization, 3min after the addition of aluminum particles, the alloy rough adjustment chemical components are added, 5min after the addition of the alloy, the vacuum is broken, and the molten steel sample 2 is taken after the vacuum is broken to analyze the composition of the molten steel.

5. A process for the production of non-oriented silicon steel as claimed in any one of claims 1-2, wherein: In step three, the temperature of the molten steel is measured after the LF process, the ladle is opened for bottom argon blowing, and the argon flow is controlled according to the principle that the molten steel bright surface reaches 0-50mm, and the argon flow is controlled at 50-100NL / min.

6. A process for the production of non-oriented silicon steel as claimed in claim 4 wherein: In step three, before the end of the strong stirring desulfurization, according to the analysis results of the VD molten steel sample 2, aluminum particles and alloy are added, the temperature is measured after stirring for 3-5 minutes after the addition of the alloy, and if the temperature of the molten steel is lower than the target temperature before the calcium wire feeding, the electrode is powered on to increase the temperature to the target temperature before the calcium wire feeding.

7. A process for the production of non-oriented silicon steel as claimed in claim 6 wherein: During the strong stirring desulfurization, the strong stirring time is determined according to the sulfur content in the VD molten steel sample 2, as shown below: When [S] in the VD molten steel sample 2 is less than or equal to 0.008%, the strong stirring time is 3-4 minutes; When 0.008% < [S] in the VD molten steel sample 2 is less than or equal to 0.010%, the strong stirring time is 5-7 minutes; When 0.010% < [S] in the VD molten steel sample 2 is less than or equal to 0.012%, the strong stirring time is 8-9 minutes; When 0.012% < [S] in the VD molten steel sample 2 is less than or equal to 0.020%, the strong stirring time is 10-11 minutes.

8. A process for the production of non-oriented silicon steel as claimed in claim 6 wherein: In step three, the calcium wire is fed, the target range of the calcium content is 0.0020-0.0035%, the molten steel is weakly stirred for 6-8 minutes after the wire feeding is completed, the molten steel sample 3 is taken for the outbound, and before and after the calcium wire feeding, the argon flow is adjusted according to the principle that the molten steel surface has obvious fluctuation and the molten steel is not exposed, and the argon flow is controlled at 20-80 NL / min.

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