Industrial pure iron plate blank and manufacturing method thereof

Abstract

The invention belongs to the technical field of metallurgical steelmaking, and discloses an industrial pure iron plate blank and a manufacturing method thereof. The industrial pure iron plate blank comprises the following chemical components in percentage by weight: less than or equal to 0.0015% of C, less than or equal to 0.015% of Mn, less than or equal to 0.003% of P, less than or equal to 0.003% of S, less than or equal to 0.01% of Cu, less than or equal to 0.02% of Al, less than or equal to 0.003% of T [O], less than or equal to 0.015% of Ni + Cr + Mo and the balance of Fe and other inevitable impurities. According to the manufacturing method disclosed by the invention, the content of Mn, P, S, O and the like can be controlled at a lower level through KR desulfurization, the converter smelting adopts double slag, low temperature and peroxidation to reduce converter end point manganese and phosphorus, ladle furnace refining demanganization, dephosphorization and temperature regulation, RH vacuum refining oxygen blowing demanganization, deep decarburization and aluminum addition for deoxygenation, and the production cost is reduced. And stable production of the industrial pure iron plate blank with lower impurity content is realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of metallurgical steel practice, and particularly relates to an industrial pure iron slab and a manufacturing method thereof. BACKGROUND

[0002] The industrial pure iron slab is a slab with very little impurity elements and an iron content of not less than 99.9% in steel production, and is a main raw material for producing industrial pure iron. The industrial pure iron has high magnetic permeability, low coercivity, low iron loss and excellent magnetization performance, and is widely used in fields requiring high efficient magnetic performance, such as medical equipment, industrial production, scientific research, shielding covers of electronic equipment (such as CRT display and precision sensor) and aerospace, etc. With the rapid development of downstream industries, the quality requirements for industrial pure iron are higher and higher, and the content of impurity elements is lower and lower.

[0003] In the search of prior art documents, the industrial pure iron steelmaking process in the book “Industrial Pure Iron Steelmaking Process Control Practice” written by Zhang Yuxiu of Tangshan Stainless Steel Company controls the key elements as C≤0.005%, Mn≤0.05%, P≤0.009%, S≤0.007%, Cu≤0.05%, and the composition range cannot meet the use requirements of most end users. In the book “High-end Industrial Pure Iron Desulfurization Process Research” written by Li Yang, the key element Mn is controlled between 0.013~0.02%, and the O content is not controlled. With the rapid development of the soft magnetic industry, users have higher requirements for the total oxygen T[O] in the slab, and high oxygen affects the yield of valuable alloy added by the user and the stability of the secondary melting production process. In order to meet the needs of users, the quality requirements for the slab produced by steelmaking are further improved, and the impurity elements in the slab are reduced as much as possible, and the iron content is increased. SUMMARY

[0004] The present application provides an industrial pure iron slab and a manufacturing method thereof to solve the technical problems existing in the prior art, and realizes stable production of an industrial pure iron slab with lower impurity content.

[0005] To solve the technical problems proposed in the present application, the present application provides an industrial pure iron slab, and the chemical composition and weight percentage content are as follows: C≤0.0015%, Mn≤0.015%, P≤0.003%, S≤0.003%, Cu≤0.01%, Al≤0.02%, T[O]≤0.003%, Ni+Cr+Mo≤0.015%, and the balance is Fe and other unavoidable impurities.

[0006] The present application also provides a manufacturing method of the above industrial pure iron slab, which comprises KR desulfurization, converter smelting, argon station treatment, ladle furnace refining, RH vacuum refining and continuous casting, guarantees the purity of molten steel after RH vacuum refining, reduces secondary oxidation during casting, and thus produces high-quality slabs.

[0007] In the above scheme, the KR desulfurization adopts calcium oxide as a desulfurizer to desulfurize the molten iron, and the molten iron before desulfurization has Mn≤0.220%, S≤0.05%, Cu≤0.008%, and Ni+Cr+Mo≤0.012%.

[0008] In the above scheme, the KR desulfurization is performed three times of slag skimming: first, the first slag skimming is performed, and the bright surface area after the slag skimming is ≥70%; then, the first batch of calcium oxide 8~10kg / t is added, and stirred for 12~15min, the second slag skimming is performed, and the bright surface area after the slag skimming is ≥85%; then, the second batch of calcium oxide 3~5kg / t is added, and stirred for 12~15min, the third slag skimming is performed, and the bright surface area after the slag skimming is ≥95%.

[0009] In the above scheme, the molten iron after the KR desulfurization treatment has S≤0.0008%.

[0010] In the above scheme, the converter smelting adopts the desulfurized molten iron and low-sulfur, low-copper and low-manganese scrap steel, and the low-sulfur, low-copper and low-manganese scrap steel has S content≤0.02%, Cu content≤0.05%, and Mn content≤0.1%.

[0011] In the above scheme, the converter smelting adopts a combined blowing mode of top blowing oxygen and bottom blowing argon, and the argon blowing flow rate is 350~400Nm 3 / h.

[0012] In the above scheme, the converter smelting adopts a double slag method, and the double slag operation is performed at 25~30% of the total time process of blowing and refining, 1 / 2~2 / 3 volume of the slag is poured out, and the slag is reformed, which is beneficial to dephosphorization and demanganization.

[0013] Further, after the double slag operation, flux 20~25kg / t and cooling agent 15~20kg / t are added to control the heat balance; the total amount of the flux added in the converter smelting process is ≥35kg / t, and the total amount of the cooling agent added is ≥20kg / t.

[0014] Further, the flux is high-quality lime, and the calcium oxide content is ≥85% and the sulfur content is ≤0.015%; the cooling agent is ore or cold-pressed ball of the skin slag, and the sulfur content is ≤0.015%.

[0015] In the above scheme, the end point temperature of the converter smelting is 1590~1620℃, the end point oxygen is ≥750ppm, if the end point oxygen is <750ppm, secondary oxygen blowing is performed to increase the oxidizability of the molten steel, the end point Mn is ≤0.030%, and the end point P is ≤0.010%.

[0016] In the above scheme, the active lime is added to form slag when the converter tapping is to 100~150s, and the addition amount is 1.5~3.0kg / t.

[0017] In the above scheme, the slide plate slag stopping is used when the converter is tapped, the under-slag alarm value is set to 15%~20%, and the infrared identification slag flow area ratio reaches the under-slag alarm value to automatically stop the slag, thereby controlling the under-slag amount.

[0018] In the above scheme, the argon station treatment is blowing argon stirring, the blowing argon flow is 15~35Nm 3 / h, the stirring time is 3~5min, and the molten steel surface is modified.

[0019] In the above scheme, the ladle furnace refining uses a ladle for containing molten steel of low-sulfur, low-copper and low-manganese, or a clean red-hot ladle after heating and baking after minor repair.

[0020] Further, the ladle for containing molten steel of low-sulfur, low-copper and low-manganese contains molten steel of low-sulfur, low-copper and low-manganese for at least the first four ladle times, and the molten steel of low-sulfur, low-copper and low-manganese has a S content of ≤0.008%, a Cu content of ≤0.03% and a Mn content of ≤0.2%.

[0021] In the above scheme, the purpose of the ladle furnace refining is to remove manganese and phosphorus from the molten steel and adjust the temperature.

[0022] In the above scheme, the ladle furnace refining uses two-stage heating, in each stage of heating, the argon blowing flow is first controlled to 80~100L / min, and lime and fluorite are added for slagging, after heating, the argon blowing flow is adjusted to 500~600L / min for strong stirring.

[0023] Further, the first stage of heating lasts for 10~12min, lime 2.5~5.0kg / t and fluorite 0.25~0.5kg / t are added for first slagging during heating, and the strong stirring time after heating is ≥3min.

[0024] Further, the second stage of heating lasts for 10~12min, lime 1.0~1.5kg / t and fluorite 0.1~0.15kg / t are added for second slagging during heating, and the strong stirring time after heating is ≥4min.

[0025] In the above scheme, after the ladle furnace refining treatment is completed, 0.8~1.5kg / t of aluminum slag balls are added to modify the top slag of the ladle, reduce the TFe content in the slag to below 10%, and reduce the oxygen return in the slag in the subsequent RH vacuum refining process.

[0026] In the above scheme, the outlet temperature of the ladle furnace refining is 1600~1615℃, the final Mn is ≤0.02%, and the final P is ≤0.003%.

[0027] In the above scheme, the RH vacuum refining is carried out by blowing oxygen to reduce manganese within 0-10 min after the start of vacuum exhaust, and the Mn reduction efficiency is 2-3 ppm / 100 Nm according to the initial Mn in vacuum 3 The total oxygen content is set, and the driving gas flow is 130-150 Nm 3 / h.

[0028] In the above scheme, the RH vacuum refining is carried out within 10-15 min after the start of vacuum exhaust, and the driving gas flow is set to 180-220 Nm 3 / h, the vacuum degree is maintained ≤30 Pa, and the decarburization end point oxygen content is 800-1000 ppm.

[0029] In the above scheme, the RH vacuum refining is carried out by adding aluminum to reduce oxygen at the decarburization end point, and the aluminum is added at 2.0-2.5 kg / t to deoxidize and increase the Als content in the molten steel, and the last batch of material is added for 4-6 min of pure circulation time.

[0030] In the above scheme, after the end of the RH vacuum refining, 0.5-1.0 kg / t of aluminum slag balls are added to modify the top slag of the ladle.

[0031] In the above scheme, the end point of the RH vacuum refining is Mn ≤0.015%, Al 0.015%-0.022%, and free oxygen ≤5 ppm.

[0032] In the above scheme, the continuous casting process uses a slag down chain, and the slag down alarm value is set to 15%-20%, and the sliding plate is automatically closed when the coil magnetic induction triggers the slag down alarm value, and the slag down amount during casting is controlled.

[0033] In the above scheme, when the continuous casting is started, 2.0-3.0 kg / t of covering agent is added, the tundish liquid level is completely covered, the molten steel is isolated from the air, and the molten steel is prevented from being oxidized by the air.

[0034] In the above scheme, the continuous casting process uses a robot to replace the protective tube, and the sealing property is good.

[0035] In the above scheme, the tundish capacity of the continuous casting is 50-60 t, and the inclusions in the tundish are fully floated.

[0036] In the above scheme, the pulling speed of the continuous casting is controlled at 1.0-1.1 m / min to ensure the processing time of the previous process; the slab length is controlled at 6000-9000 mm by online cutting, and the tolerance is ±50 mm; the thickness is 230 mm, and the tolerance is ±3 mm; the width is 1000-1320 mm, and the tolerance is ±3 mm.

[0037] The design points of the manufacturing method of the application are as follows: The difficulty in the manufacturing process of the present application lies in controlling P, Mn, S and total oxygen content. High total oxygen content in the slab can cause pores in the interior of the slab, thereby causing tearing during cutting of the slab by the user, resulting in a rough cut surface of the slab. On the other hand, during the process of melting the slab with other rare earth elements by the user, the oxygen in the slab is prone to oxidation reaction with the rare earth elements, producing oxide inclusions, resulting in low yield of rare earth elements, and affecting the yield of finished products.

[0038] To this end, the KR desulfurization of the present application adopts secondary stirring and three times of slagging measures to ensure low sulfur in the molten iron entering the furnace, reduce sulfuration in the molten iron slag, and control the return of sulfur in the converter blowing process; the converter smelting adopts double slag + low temperature + over-oxidation to reduce the manganese at the end of the converter, adopts slide plate slag stopping for tapping, and controls the amount of slag; the ladle refining temperature is adjusted, the manganese and phosphorus are removed, the quality is improved, the oxidizability of the slag is reduced, the refining measures such as vacuum oxygen blowing for manganese removal, addition of aluminum for reducing free oxygen, and prolonging the pure circulation time ensure the purity of the molten steel; and finally the stable production of the slab of industrial pure iron raw material is realized.

[0039] Among them, when the infrared recognition of the converter tapping reaches the alarm value of 15%~20% of the amount of slag, the slide plate is automatically closed to control the amount of slag, reduce the content of oxidized phosphorus and oxidized manganese in the top slag of the ladle, which is beneficial to improve the efficiency of the ladle refining slag refining for removing manganese and phosphorus, and reduce the return of manganese and phosphorus after vacuum refining alloying. In the early stage of vacuum refining, a large amount of oxygen is blown to forcibly decarburize and remove manganese to ensure the low manganese and low phosphorus composition requirements of the present application, which inevitably makes the oxygen content in the molten steel high during the refining process, and the oxidizability of the molten steel is strong. Only by adding aluminum alloy can the oxidizability be reduced. Considering the secondary oxidation reaction in the casting process, there is a large loss of Al in the molten steel. In order to control the total oxygen content in the slab, the present application controls the Al content at the end point to be between 0.015% and 0.022% by precise control, effectively reduces the free oxygen content at the end of vacuum refining to be within 5ppm, at the same time, the top slag is re-qualified after vacuum refining to reduce the oxygen content in the slag, and the aluminum loss caused by secondary oxidation in the transfer process of the ladle is reduced. If the aluminum content at the end of vacuum is less than 0.015%, the total oxygen content in the slab will be high. If the aluminum content exceeds 0.022%, the composition requirement of Al≤0.02% in the slab cannot be met.

[0040] The large ladle slag alarm device is used in the continuous casting process to reduce the amount of slag and the enrichment amount of the top slag in the tundish, which can effectively reduce the oxidizability of the slag, so as to achieve the purpose of controlling the total oxygen content in the slab. The alarm value of the large ladle slag in the present application is set to 15%~20%. If it is set to be lower than 15%, it cannot be accurately identified, and false alarm may occur. If it is set to be more than 20%, the coil induction signal will be slightly delayed, which will cause the slide plate to close late, the amount of slag will be more, and the enrichment of the amount of top slag in the tundish will cause the total oxygen content in the slab to be high.

[0041] Compared with the prior art, the present application has the following advantages: The present application ensures low sulfur of hot metal into the furnace by KR desulfurization, reduces manganese and phosphorus at the end of converter by double slag + low temperature + over oxidation, removes manganese and phosphorus and adjusts temperature in ladle refining, removes manganese by blowing oxygen in RH vacuum refining, deeply removes carbon and reduces oxygen by adding aluminum, so that the chemical composition of industrial pure iron slab can be controlled as follows: C≤0.0015%, Mn≤0.015%, P≤0.003%, S≤0.003%, Cu≤0.01%, Al≤0.02%, T[O]≤0.003%, Ni+Cr+Mo≤0.015%, and stable production of industrial pure iron slab with lower impurity content is realized. DETAILED DESCRIPTION

[0042] In order to better understand the present application, the content of the present application is further illustrated below in combination with examples, but the content of the present application is not limited to the following examples only.

[0043] The manufacturing method of industrial pure iron slab in the following examples comprises the following steps: 1) KR desulfurization Before desulfurization, the hot metal has Mn≤0.220%, S≤0.05%, Cu≤0.008%, and Ni+Cr+Mo≤0.012%; Calcium oxide is used as a desulfurizer to desulfurize the hot metal, and a total of three times of slagging is performed: first, the first time of slagging is performed, and the bright surface area after slagging is ≥70%; then, the first batch of calcium oxide 8~10kg / t is added, stirring is performed for 12~15min, the second time of slagging is performed, and the bright surface area after slagging is ≥85%; then, the second batch of calcium oxide 3~5kg / t is added, stirring is performed for 12~15min, the third time of slagging is performed, and the bright surface area after slagging is ≥95%; The sulfur of the hot metal after KR desulfurization treatment is ≤0.0008%; 2) Converter smelting The desulfurized hot metal and low-sulfur low-copper low-manganese scrap steel are used for smelting, and the low-sulfur low-copper low-manganese scrap steel has S content≤0.02%, Cu content≤0.05%, and Mn content≤0.1%; The top blowing oxygen and bottom blowing argon combined blowing mode is used, and the argon flow is 350~400Nm 3 / h; the double slag method is used for smelting, and the double slag operation is performed at 25~30% of the total time process of blowing and refining, 1 / 2~2 / 3 volume of the slag is poured out, and the slag is reformed; After the double slag operation, the flux 20~25kg / t and the cooling agent 15~20kg / t are added to control the heat balance; the total amount of the flux added during the converter smelting process is ≥35 kg / t, and the total amount of the cooling agent added is ≥20 kg / t; wherein, the flux is high-quality lime, and the calcium oxide content thereof is ≥85% and the sulfur content thereof is ≤0.015%; the cooling agent is a cold-pressed ball of skin slag, and the sulfur content thereof is ≤0.015%; Converter smelting end point temperature is 1590~1620℃, end point oxygen ≥750ppm, if end point oxygen <750ppm, secondary oxygen blowing is carried out, the oxidizing property of molten steel is increased, end point Mn≤0.030%, P≤0.010%; Converter tapping to 100~150s adds active lime for slagging, the adding amount is 1.5~3.0kg / t; the end point of tapping adopts slide plate slag stopping, the alarm value of slag stopping is set to 15%~20%, when the infrared identification slag flow area ratio reaches and exceeds the alarm value of slag stopping, automatic slag stopping is carried out, the amount of slag stopping is controlled; 3) Argon station treatment The molten steel is hoisted to the argon station, argon blowing stirring is carried out, the argon blowing flow is 15~35Nm 3 / h, the stirring time is 3~5min, the molten steel surface is modified; 4) Ladle furnace refining The ladle used to hold the molten steel of low sulfur, low copper and low manganese (the content of S in the molten steel is ≤0.008%, the content of Cu is ≤0.03%, the content of Mn is ≤0.2%) of at least the first 4 heats, or a clean red-hot ladle heated and roasted after minor repair is used; Two-stage heating is adopted, during each stage of heating, the argon blowing flow is first controlled to be 80~100L / min, and lime and fluorite are added for slagging, after heating, the argon blowing flow is adjusted to 500~600 L / min for strong stirring; The first stage heating time is 10~12min, during heating, 2.5~5.0kg / t of lime and 0.25~0.5kg / t of fluorite are added for first slagging, the strong stirring time after heating is ≥3min; The second stage heating time is 10~12min, during heating, 1.0~1.5kg / t of lime and 0.1~0.15kg / t of fluorite are added for second slagging, the strong stirring time after heating is ≥4min; After the treatment of the ladle furnace refining is completed, 0.8~1.5kg / t of aluminum slag balls are added to modify the top slag of the ladle, the content of TFe in the slag is reduced to below 10%, and the oxygen return in the slag during the subsequent RH vacuum refining process is reduced; The ladle furnace exit station temperature is 1600~1615℃, the end point Mn is ≤0.02%, the end point P is ≤0.003%; 5) RH vacuum refining Within 0~10min after the start of vacuum exhaust, Mn is reduced by oxygen blowing, according to the initial Mn of vacuum, the Mn reduction efficiency is set to 2~3ppm / 100Nm 3 The total oxygen content is set, the driving gas flow (argon) is set to 130~150Nm 3 / h; Within 10~15min after the start of vacuum exhaust, deep decarburization is carried out, the driving gas flow (argon) is set to 180~220 Nm 3 / h, the process keeps the vacuum degree ≤30 Pa, the decarburization end point oxygen content is 800-1000 ppm; The decarburization end point is subjected to aluminum addition and oxygen removal, 2.0-2.5 kg / t of aluminum is added to remove oxygen and increase the Als content in the molten steel, and the last batch of material is added for 4-6 min of pure circulation time; After the RH vacuum refining is completed, 0.5-1.0 kg / t of aluminum slag balls is added to modify the top slag of the ladle; The end point of the RH vacuum refining is Mn ≤0.015%, Al 0.015%-0.022%, and free oxygen ≤5 ppm; 6) Continuous casting The ladle uses a slag down chain, and the slag down alarm value is set to 15%-20%. When the coil magnetic induction triggers the slag down alarm value, the sliding plate is automatically closed to control the amount of slag down during casting; When the continuous casting is started, 2.0-3.0 kg / t of covering agent is added to completely cover the tundish liquid level, isolate the molten steel from the air, and prevent the molten steel from being oxidized by the air. A robot is used to replace the protective tube to maintain good sealing. The tundish tonnage is 50-60 t to ensure that the inclusions in the tundish float up sufficiently; The continuous casting speed is controlled at 1.0-1.1 m / min to ensure the processing time of the previous process. The slab length is controlled to be 6000-9000 mm with a tolerance of ±50 mm, the thickness is 230 mm with a tolerance of ±3 mm, and the width is 1000-1320 mm with a tolerance of ±3 mm through online cutting.

[0044] The specific process parameters in the above method and the composition of the industrial slab prepared finally are shown in the following table.

[0045] Table 1 KR desulfurization process control process parameters (I)

[0046] Table 2 KR desulfurization process control process parameters (II)

[0047] Table 3 Converter smelting process control process parameters (I)

[0048] Table 4 Converter smelting process control process parameters (II)

[0049] Table 5 Ladle furnace refining process control process parameters (I)

[0050] Table 6 Ladle furnace refining process control process parameters (II)

[0051] Table 7 Process parameters for ladle furnace refining process control

[0052] Table 8 Process parameters for RH vacuum refining process control (1)

[0053] Table 9 Process parameters for RH vacuum refining process control (2)

[0054] Table 10 Process parameters for continuous casting process control

[0055] Table 11 Chemical composition of the obtained industrial pure iron slab

[0056] The above examples are merely intended for the purpose of illustration and are not intended to limit the embodiments. Based on the above description, those skilled in the art can make other variations or changes in different forms, and it is not necessary or possible to exhaust all the embodiments. The obvious variations or changes thus derived are still within the protection scope of the present application.

Claims

1. An industrial pure iron slab, characterized in that: Its chemical composition and weight percentage content are: C≤0.0015%, Mn≤0.015%, P≤0.003%, S≤0.003%, Cu≤0.01%, Al≤0.02%, T[O]≤0.003%, Ni+Cr+Mo≤0.015%, and the balance is Fe and other inevitable impurities.

2. A method for manufacturing industrial pure iron slabs according to claim 1, characterized in that: The following steps are involved: 1) KR desulfurization: before desulfurization, molten iron Mn≤0.220%, S≤0.05%, Cu≤0.008%, Ni+Cr+Mo≤0.012%; after desulfurization, molten iron S≤0.0008%; 2) Converter smelting: adopt top blowing oxygen and bottom blowing argon combined blowing mode, with argon blowing flow rate of 350~400Nm 3 / h; endpoint temperature 1590~1620℃, endpoint oxygen ≥750ppm, Mn ≤0.030%, P ≤0.010%; 3) Argon station treatment: blowing argon gas for stirring, flow rate 15~35Nm 3 / h, time 3~5min; 4) Ladle furnace refining: Two-stage heating is adopted. During each stage of heating, the argon blowing flow rate is first controlled to 80-100 L / min, and lime and fluorite are added to form slag. After heating, the argon blowing flow rate is adjusted to 500-600 L / min for strong stirring; the outlet temperature is 1600-1615℃, and the end point Mn ≤ 0.02%, P ≤ 0.003%; 5) RH vacuum refining: within 0-10 minutes after the start of vacuum exhaust, oxygen is blown to reduce manganese, and deep decarburization is carried out within 10-15 minutes. The oxygen content at the end of decarburization is 800-1000 ppm. At the end of decarburization, aluminum is added to reduce oxygen. At the end of RH vacuum refining, Mn≤0.015%, Al0.015%-0.022%, and free oxygen≤5ppm; 6) Continuous casting to obtain industrial pure iron slabs.

3. The method for manufacturing industrial pure iron slabs according to claim 2, characterized in that: In the oxygen blowing and manganese reduction stage, the Mn reduction efficiency is 2~3ppm / 100Nm according to the initial Mn in vacuum. 3 Set the total oxygen content and the driving gas flow rate to 130~150Nm 3 / h; in the deep decarburization stage, the driving gas flow rate is 180~220Nm 3 / h, maintain vacuum degree ≤30Pa.

4. The method for manufacturing industrial pure iron slabs according to claim 2, wherein: For the aluminum addition and oxygen reduction, 2.0-2.5 kg / t of aluminum is added, and the pure circulation time after the last batch of materials is 4-6 minutes; after the RH vacuum refining is completed, 0.5-1.0 kg / t of aluminum slag balls are added to modify the ladle top slag.

5. The method for manufacturing industrial pure iron slabs according to claim 2, characterized in that: The first stage heating time of the ladle furnace refining is 10-12 minutes, during which 2.5-5.0 kg / t of lime and 0.25-0.5 kg / t of fluorite are added for primary slagging, and the strong stirring time after heating is ≥3 minutes; the second stage heating time is 10-12 minutes, during which 1.0-1.5 kg / t of lime and 0.1-0.15 kg / t of fluorite are added for secondary slagging, and the strong stirring time after heating is ≥4 minutes.

6. The method for manufacturing industrial pure iron slabs according to claim 2, characterized in that: The ladle furnace refining uses a ladle that has contained low-sulfur, low-copper, and low-manganese molten steel for at least four previous heats, or a clean red-hot ladle that has been heated and baked after a minor repair; the low-sulfur, low-copper, and low-manganese molten steel has an S content of ≤0.008%, a Cu content of ≤0.03%, and a Mn content of ≤0.2%; after the ladle furnace refining treatment is completed, 0.8-1.5 kg / t of aluminum slag balls are added to modify the ladle top slag to reduce the TFe content in the slag to below 10%.

7. The method for manufacturing industrial pure iron slabs according to claim 2, characterized in that: The converter smelting uses low-sulfur, low-copper, and low-manganese scrap steel, whose S content is ≤0.02%, Cu content is ≤0.05%, and Mn content is ≤0.1%; the converter smelting performs double slag operation when the blowing time reaches 25-30% of the total process, pours out 1 / 2-2 / 3 of the volume of slag and then re-slags; active lime is added to slag when the converter taps steel for 100-150 seconds, and the added amount is 1.5-3.0 kg / t; a slide plate is used to block slag during converter tapping, and the slag lowering alarm value is set to 15%-20%.

8. The method for manufacturing industrial pure iron slabs according to claim 7, wherein: After the double slag operation, 20-25 kg / t of flux and 15-20 kg / t of coolant are added to control the heat balance; during the converter smelting process, the total amount of flux added is ≥35 kg / t, and the total amount of coolant added is ≥20 kg / t; the flux is high-quality lime, with a calcium oxide content of ≥85% and a sulfur content of ≤0.015%; the coolant is cold-pressed ore or peeling slag balls, with a sulfur content of ≤0.015%.

9. The method for manufacturing industrial pure iron slabs according to claim 2, characterized in that: The KR desulfurization is carried out for three times of slagging: the first slagging is carried out, and the bright surface area after slagging is ≥70%; then the first batch of calcium oxide 8-10 kg / t is added, stirred for 12-15 minutes, and the second slagging is carried out, and the bright surface area after slagging is ≥85%; then the second batch of calcium oxide 3-5 kg / t is added, stirred for 12-15 minutes, and the third slagging is carried out, and the bright surface area after slagging is ≥95%.

10. The method for manufacturing industrial pure iron slabs according to claim 2, characterized in that: The continuous casting process uses a slag discharge interlock, and the slag discharge alarm value is set at 15% to 20%; when the continuous casting starts, 2.0 to 3.0 kg / t of covering agent is added to completely cover the liquid surface of the tundish; the continuous casting speed is 1.0 to 1.1 m / min; the length of the industrial pure iron slab is 6000 to 9000 mm, with a tolerance of ±50 mm; the thickness is 230 mm, with a tolerance of ±3 mm; and the width is 1000 to 1320 mm, with a tolerance of ±3 mm.

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