A method for producing low-carbon and low-silicon electrical steel

Abstract

The present invention discloses a method for producing low-carbon and low-silicon electrical steel, and relates to the technical field of steel rolling. The electrical steel raw material is rolled by a profile cold rolling mill to thin the electrical steel raw material to form an intermediate electrical steel; the intermediate electrical steel is rolled by a shaping cold rolling mill to flatten the intermediate electrical steel to form a flat electrical steel; the flat electrical steel is annealed by a vertical annealing furnace to obtain an electrical steel product. Compared with the prior art, the method for producing low-carbon and low-silicon electrical steel provided by the present invention adopts the step of rolling the intermediate electrical steel by a shaping cold rolling mill to flatten the intermediate electrical steel to form a flat electrical steel, so that the low-carbon and low-silicon electrical steel can be effectively shaped, the shaping effect is good, the flatness is improved, the plate shape is good, and the product quality is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of steel rolling, and in particular to a method for producing low-carbon and low-silicon electrical steel. Background Art

[0002] At present, low-carbon, low-silicon electrical steel is generally used to make stators and rotors of small motors, and low-carbon, low-silicon electrical steel is generally rolled by cold rolling mills. However, the current low-carbon, low-silicon electrical steel is not shaped during the rolling process, resulting in poor plate shape and unsatisfactory flatness, which affects product quality.

[0003] In view of this, it is particularly important to design a method for producing low-carbon and low-silicon electrical steel with good shaping effect, especially in steel rolling production. Summary of the invention

[0004] The purpose of the present invention is to provide a method for producing low-carbon and low-silicon electrical steel, which can effectively shape the low-carbon and low-silicon electrical steel, has a good shaping effect, improves flatness, ensures a good plate shape, and improves product quality.

[0005] The present invention is achieved by adopting the following technical solutions.

[0006] A method for producing low-carbon and low-silicon electrical steel comprises: rolling electrical steel raw materials by using a profile cold rolling mill to thin the electrical steel raw materials to form intermediate electrical steel; rolling the intermediate electrical steel by using a profile cold rolling mill to flatten the intermediate electrical steel to form flat electrical steel; and annealing the flat electrical steel by using a vertical annealing furnace to obtain an electrical steel product.

[0007] Optionally, the carbon content in the electrical steel raw material is less than or equal to 0.005%, the silicon content ranges from 0.4% to 0.6%, the manganese content ranges from 0.21% to 0.4%, the sulfur content is less than or equal to 0.01%, and the phosphorus content ranges from 0.07% to 0.1%.

[0008] Optionally, before the step of rolling the electrical steel raw material by a profile cold rolling mill to thin the electrical steel raw material to form intermediate electrical steel, the low-carbon and low-silicon electrical steel production method further includes: immersing the electrical steel raw material in an acid solution to pickle the electrical steel raw material.

[0009] Optionally, the step of rolling the electrical steel raw material by using a profile cold rolling mill to thin the electrical steel raw material to form intermediate electrical steel includes: rolling the electrical steel raw material by using a first profile cold rolling mill to form a first electrical steel; rolling the first electrical steel by using a second profile cold rolling mill to form a second electrical steel; rolling the second electrical steel by using a third profile cold rolling mill to form a third electrical steel; and rolling the third electrical steel by using a fourth profile cold rolling mill to form intermediate electrical steel.

[0010] Optionally, the reduction ratio of the first profile cold rolling mill ranges from 36% to 39%, the reduction ratio of the second profile cold rolling mill ranges from 32% to 35%, the reduction ratio of the third profile cold rolling mill ranges from 28% to 31%, and the reduction ratio of the fourth profile cold rolling mill ranges from 26% to 29%.

[0011] Optionally, the first profile cold rolling mill, the second profile cold rolling mill, the third profile cold rolling mill, the fourth profile cold rolling mill and the forming cold rolling mill are arranged in sequence, and the unit tension range of the first electrical steel between the first profile cold rolling mill and the second profile cold rolling mill is 120N / mm 2 Up to 130N / mm 2 The unit tension range of the second electrical steel between the second and third cold rolling mills is 130N / mm 2 Up to 140N / mm 2 The unit tension range of the third electrical steel between the third and fourth cold rolling mills is 150N / mm 2 Up to 160N / mm 2 The unit tension range of the intermediate electrical steel between the fourth profile cold rolling mill and the full profile cold rolling mill is 160N / mm 2 Up to 180N / mm 2 The unit tension range of the flat electrical steel output by the cold rolling mill is 40N / mm 2 Up to 50N / mm 2 .

[0012] Optionally, in the step of rolling the intermediate electrical steel by a truing cold rolling mill to flatten the intermediate electrical steel to form flat electrical steel, the reduction ratio of the truing cold rolling mill is in the range of 2% to 5%.

[0013] Optionally, the step of annealing the flat electrical steel using a vertical annealing furnace to obtain an electrical steel product includes: controlling the flat electrical steel to pass through the preheating section, heating section, soaking section, slow cooling section, fast cooling section, over-aging section and final cooling section of the vertical annealing furnace in sequence.

[0014] Optionally, the temperature range of the preheating section is 120°C to 130°C, the temperature range of the heating section and the soaking section is 825°C to 835°C, the temperature range of the slow cooling section is 645°C to 655°C, the temperature range of the fast cooling section is 495°C to 505°C, the temperature range of the aging section is 395°C to 405°C, and the temperature range of the final cooling section is 180°C to 190°C.

[0015] Optionally, the movement speed of the flat electrical steel ranges from 4m / s to 5m / s, the time required for the flat electrical steel to pass through the preheating section ranges from 11s to 13s, the time required for the flat electrical steel to pass through the heating section ranges from 107s to 118s, the time required for the flat electrical steel to pass through the equalizing section ranges from 60s to 68s, the time required for the flat electrical steel to pass through the slow cooling section ranges from 16s to 19s, the time required for the flat electrical steel to pass through the fast cooling section ranges from 6s to 7s, the time required for the flat electrical steel to pass through the aging section ranges from 205s to 230s, and the time required for the flat electrical steel to pass through the final cooling section ranges from 45s to 50s.

[0016] The method for producing low-carbon and low-silicon electrical steel provided by the present invention has the following beneficial effects:

[0017] The method for producing low-carbon and low-silicon electrical steel provided by the present invention uses a profile cold rolling mill to roll the electrical steel raw material to thin the electrical steel raw material to form an intermediate electrical steel; uses a shaping cold rolling mill to roll the intermediate electrical steel to flatten the intermediate electrical steel to form a flat electrical steel; and uses a vertical annealing furnace to anneal the flat electrical steel to obtain an electrical steel product. Compared with the prior art, the method for producing low-carbon and low-silicon electrical steel provided by the present invention uses a shaping cold rolling mill to roll the intermediate electrical steel to flatten the intermediate electrical steel to form a flat electrical steel. Therefore, the low-carbon and low-silicon electrical steel can be effectively shaped, the shaping effect is good, the flatness is improved, the plate shape is good, and the product quality is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0019] Figure 1 A flowchart of the steps of a method for producing low-carbon and low-silicon electrical steel provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0021] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0023] In the description of the present invention, it should be noted that the terms "inside", "outside", "upper", "lower", "horizontal", etc. indicate the orientation or position relationship based on the orientation or position relationship shown in the drawings, or the orientation or position relationship in which the product of the invention is usually placed when in use, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0024] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "connect", "install", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0025] Some embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the absence of conflict, the features of the following embodiments can be combined with each other.

[0026] Please refer to Figure 1 The embodiment of the present invention provides a method for producing low-carbon and low-silicon electrical steel, which is used to produce low-carbon and low-silicon electrical steel. The method can effectively shape the low-carbon and low-silicon electrical steel, has a good shaping effect, improves flatness, ensures a good plate shape, and improves product quality.

[0027] It should be noted that the low-carbon, low-silicon electrical steel production method is used to roll and anneal electrical steel raw materials with a thickness of 2.5mm (millimeter) to 3mm to form electrical steel products with a thickness of 0.5mm. During this process, the electrical steel raw materials can be effectively shaped to ensure that the produced electrical steel products have high flatness and good plate shape.

[0028] Specifically, the carbon content in the electrical steel raw material is less than or equal to 0.005%, the silicon content ranges from 0.4% to 0.6%, the manganese content ranges from 0.21% to 0.4%, the sulfur content is less than or equal to 0.01%, and the phosphorus content ranges from 0.07% to 0.1%. Furthermore, carbon is a harmful element in the electrical steel raw material, so it is necessary to control the carbon content in a very low range as much as possible. With the increase of silicon content, the resistivity of the electrical steel raw material increases, the iron loss decreases, but the magnetic induction also decreases, so the silicon content should be reasonably controlled according to product requirements. A part of manganese combines with sulfur to form manganese sulfide compounds. The solid solubility of manganese sulfide in the γ phase is smaller than that in the α phase, so it can promote the coarsening of manganese sulfide and is conducive to grain growth; another part of manganese exists in the form of solid solution, which can increase the hardness of the electrical steel raw material. Phosphorus can increase the resistance of the electrical steel raw material and reduce iron loss. At the same time, phosphorus can also increase the hardness of the electrical steel raw material and improve the punching performance.

[0029] The method for producing low carbon and low silicon electrical steel comprises the following steps:

[0030] Step S110: immersing the electrical steel raw material in an acid solution to pickle the electrical steel raw material.

[0031] It should be noted that, in step S110, the electrical steel raw material is fed in a preset direction so that the electrical steel raw material is immersed in the acid solution and moves forward in the acid solution. During this process, the acid solution reacts chemically with the oxide scale and rust on the surface of the electrical steel raw material to remove the oxide scale and rust on the surface of the electrical steel raw material, thereby ensuring that the subsequent rolling process can be carried out stably.

[0032] Specifically, in step S110, the stretching elongation is increased to 1.5 to 2.0%, and the stretching mode over the weld is adjusted to continuous stretching. In this way, the oxide scale on the surface of the electrical steel raw material can be effectively broken, thereby improving the pickling quality and pickling speed.

[0033] Step S120: rolling the electrical steel raw material by using a profile cold rolling mill to thin the electrical steel raw material to form intermediate electrical steel.

[0034] It should be noted that in step S120, since the strength of low-carbon, low-silicon electrical steel is not high, the main deformation of the low-carbon, low-silicon electrical steel is completed by four cold rolling mills. Affected by work hardening, the reduction rates of the four cold rolling mills are reduced successively.

[0035] Specifically, step S120 includes four steps, namely:

[0036] Step S121: using a first profile cold rolling mill to roll the electrical steel raw material to form the first electrical steel.

[0037] It should be noted that, in step S121, the reduction ratio of the first cold rolling mill is in the range of 36% to 39%, that is, the first cold rolling mill can reduce the electrical steel raw material by 36% to 39% to form the first electrical steel.

[0038] Step S122: using a second cold rolling mill to roll the first electrical steel to form a second electrical steel.

[0039] It should be noted that, in step S122, the reduction ratio of the second cold rolling mill is in the range of 32% to 35%, that is, the second cold rolling mill can reduce the first electrical steel by 32% to 35% to form the second electrical steel.

[0040] Step S123: using a third cold rolling mill to roll the second electrical steel to form a third electrical steel.

[0041] It should be noted that, in step S123, the reduction ratio of the third cold rolling mill is in the range of 28% to 31%, that is, the third cold rolling mill can reduce the second electrical steel by 28% to 31% to form the third electrical steel.

[0042] Step S124: using a fourth cold rolling mill to roll the third electrical steel to form intermediate electrical steel.

[0043] It should be noted that, in step S124, the reduction ratio of the fourth cold rolling mill is in the range of 26% to 29%, that is, the fourth cold rolling mill can reduce the third electrical steel by 26% to 29% to form intermediate electrical steel.

[0044] Step S130: rolling the intermediate electrical steel using a cold rolling mill to flatten the intermediate electrical steel to form flat electrical steel.

[0045] It should be noted that in step S130, the reduction ratio of the shaping cold rolling mill is relatively low. The shaping cold rolling mill is used to shape the intermediate electrical steel to form flat electrical steel, and the flat electrical steel has a high flatness and a good plate shape. Specifically, the reduction ratio of the shaping cold rolling mill ranges from 2% to 5%, that is, the shaping cold rolling mill can thin the intermediate electrical steel by 2% to 5% to form flat electrical steel.

[0046] Furthermore, the surface roughness of the working rolls of the cold rolling mill ranges from 0.8 μm (micrometer) to 1.2 μm, and the plate shape of the flat electrical steel formed is a slightly wavy plate shape.

[0047] It is worth noting that the first profile cold rolling mill, the second profile cold rolling mill, the third profile cold rolling mill, the fourth profile cold rolling mill and the whole profile cold rolling mill are arranged in sequence. The unit tension range of the first electrical steel between the first profile cold rolling mill and the second profile cold rolling mill is 120N / mm 2 (Newton per square millimeter) to 130N / mm2 The unit tension range of the second electrical steel between the second and third cold rolling mills is 130N / mm 2 Up to 140N / mm 2 The unit tension range of the third electrical steel between the third and fourth cold rolling mills is 150N / mm 2 Up to 160N / mm 2 The unit tension range of the intermediate electrical steel between the fourth profile cold rolling mill and the full profile cold rolling mill is 160N / mm 2 Up to 180N / mm 2 The unit tension range of the flat electrical steel output by the cold rolling mill is 40N / mm 2 Up to 50N / mm 2 .

[0048] Specifically, low-carbon, low-silicon electrical steel is a strip material. Reasonable control of the unit tension of low-carbon, low-silicon electrical steel between multiple cold rolling mills and the full-forming cold rolling mill can effectively reduce the unit rolling force, prevent the strip from deviating, and ensure stable rolling. Furthermore, the unit tension of low-carbon, low-silicon electrical steel cannot exceed the yield limit σ of the strip material, otherwise it is easy to cause strip breakage; and if the edge of the low-carbon, low-silicon electrical steel has defects such as edge cracks, excessive unit tension of the low-carbon, low-silicon electrical steel will cause the strip to break at the edge cracks.

[0049] In this embodiment, since the strength of the low-carbon, low-silicon electrical steel is not high, the rolling force will not be too large. At the same time, since the edges are not trimmed, the edge quality of the low-carbon, low-silicon electrical steel is poor. Therefore, the unit tension of the low-carbon, low-silicon electrical steel between multiple profile cold rolling mills and the full-form cold rolling mill cannot be set too large, and can be kept within the range of 0.3σ to 0.5σ.

[0050] Step S140: annealing the flat electrical steel in a vertical annealing furnace to obtain an electrical steel product.

[0051] It should be noted that in step S140, the flat electrical steel is controlled to pass through the preheating section, heating section, soaking section, slow cooling section, rapid cooling section, over-aging section and final cooling section of the vertical annealing furnace in sequence to perform continuous annealing on the flat electrical steel, so that the flat electrical steel undergoes the preheating process, heating process, slow cooling process, rapid cooling process, over-aging process and final cooling process in sequence.

[0052] Specifically, the temperature range of the preheating section is 120℃ (degrees Celsius) to 130℃, the temperature range of the heating section and the soaking section is 825℃ to 835℃, the temperature range of the slow cooling section is 645℃ to 655℃, the temperature range of the fast cooling section is 495℃ to 505℃, the temperature range of the over-aging section is 395℃ to 405℃, and the temperature range of the final cooling section is 180℃ to 190℃.

[0053] In this embodiment, the heat generated by the exhaust gas recovery in the heating section and the soaking section is used to heat the protective gas, and the protective gas is sprayed onto the flat electrical steel in the preheating section to heat the flat electrical steel, which is energy-saving and environmentally friendly. Furthermore, the flat electrical steel is heated to below the phase change point by the heating section and the soaking section to avoid the generation of mixed crystals by the phase change, and the temperature of the flat electrical steel is increased in the α phase region, so that the grains grow and the iron loss is reduced.

[0054] It is worth noting that the movement speed of flat electrical steel ranges from 4m / s (meters per second) to 5m / s. The time required for flat electrical steel to pass through the preheating section ranges from 11s (seconds) to 13s, that is, the time range for the preheating process of flat electrical steel is 11s to 13s. The time required for flat electrical steel to pass through the heating section ranges from 107s to 118s, that is, the time range for the heating process of flat electrical steel is 107s to 118s. The time required for flat electrical steel to pass through the soaking section ranges from 60s to 68s, that is, the time range for the soaking process of flat electrical steel is 60s to 68s. The time required for flat electrical steel to pass through the slow cooling section ranges from 16s to 19s, that is, the time range for the slow cooling process of flat electrical steel is 16s to 19s. The time required for flat electrical steel to pass through the rapid cooling section ranges from 6s to 7s, that is, the time range for the rapid cooling process of flat electrical steel is 6s to 7s. The time required for flat electrical steel to pass through the aging section ranges from 205s to 230s, that is, the time range for the aging process of flat electrical steel is 205s to 230s. The time required for flat electrical steel to pass through the final cooling section ranges from 45s to 50s, that is, the time range for the final cooling process of flat electrical steel is 45s to 50s.

[0055] In this embodiment, the vertical annealing furnace is divided into seven sections. The flat electrical steel passes through the preheating section, heating section, soaking section, slow cooling section, fast cooling section, over-aging section and final cooling section in sequence during the feeding process, so that different positions of the flat electrical steel are in different annealing processes at the same time, which greatly improves the annealing efficiency. Compared with the method of annealing low-carbon and low-silicon electrical steel using a horizontal annealing furnace in the prior art, the length of low-carbon and low-silicon electrical steel in the vertical annealing furnace at the same time is longer, the annealing time is shorter, the annealing efficiency is higher, and the production efficiency of low-carbon and low-silicon electrical steel is improved.

[0056] The method for producing low-carbon, low-silicon electrical steel provided in the embodiment of the present invention uses a profile cold rolling mill to roll the electrical steel raw material to thin the electrical steel raw material to form an intermediate electrical steel; uses a shaping cold rolling mill to roll the intermediate electrical steel to flatten the intermediate electrical steel to form a flat electrical steel; and uses a vertical annealing furnace to anneal the flat electrical steel to obtain an electrical steel product. Compared with the prior art, the method for producing low-carbon, low-silicon electrical steel provided in the present invention uses a step of using a shaping cold rolling mill to roll the intermediate electrical steel to flatten the intermediate electrical steel to form a flat electrical steel, so that the low-carbon, low-silicon electrical steel can be effectively shaped, the shaping effect is good, the flatness is improved, the plate shape is good, and the product quality is improved.

[0057] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for producing low-carbon and low-silicon electrical steel, characterized in that: include: Using a profile cold rolling mill to roll an electrical steel raw material to thin the electrical steel raw material to form an intermediate electrical steel, comprising: using a first profile cold rolling mill to roll the electrical steel raw material to form a first electrical steel; using a second profile cold rolling mill to roll the first electrical steel to form a second electrical steel; using a third profile cold rolling mill to roll the second electrical steel to form a third electrical steel; using a fourth profile cold rolling mill to roll the third electrical steel to form an intermediate electrical steel; wherein the reduction ratio of the first profile cold rolling mill is in the range of 36% to 39%, the reduction ratio of the second profile cold rolling mill is in the range of 32% to 35%, the reduction ratio of the third profile cold rolling mill is in the range of 28% to 31%, and the reduction ratio of the fourth profile cold rolling mill is in the range of 26% to 29%; Rolling the intermediate electrical steel by a cold rolling mill to flatten the intermediate electrical steel to form flat electrical steel, wherein the reduction ratio of the cold rolling mill is in a range of 2% to 5%; The flat electrical steel is annealed in a vertical annealing furnace to obtain an electrical steel product.

2. The method for producing low-carbon and low-silicon electrical steel according to claim 1, characterized in that: The electrical steel raw material has a carbon content less than or equal to 0.005%, a silicon content ranging from 0.4% to 0.6%, a manganese content ranging from 0.21% to 0.4%, a sulfur content less than or equal to 0.01%, and a phosphorus content ranging from 0.07% to 0.1%.

3. The method for producing low-carbon and low-silicon electrical steel according to claim 1, characterized in that: Before the step of rolling the electrical steel raw material by a profile cold rolling mill to thin the electrical steel raw material to form intermediate electrical steel, the method for producing low-carbon and low-silicon electrical steel further comprises: The electrical steel raw material is immersed in an acid solution to pickle the electrical steel raw material.

4. The method for producing low-carbon and low-silicon electrical steel according to claim 1, characterized in that: The first profile cold rolling mill, the second profile cold rolling mill, the third profile cold rolling mill, the fourth profile cold rolling mill and the forming cold rolling mill are arranged in sequence, and the unit tension range of the first electrical steel between the first profile cold rolling mill and the second profile cold rolling mill is 120N / mm 2 Up to 130N / mm 2 The unit tension range of the second electrical steel between the second cold rolling mill and the third cold rolling mill is 130N / mm 2 Up to 140N / mm 2 The unit tension range of the third electrical steel between the third cold rolling mill and the fourth cold rolling mill is 150N / mm 2 Up to 160N / mm 2 The unit tension range of the intermediate electrical steel between the fourth profile cold rolling mill and the full profile cold rolling mill is 160N / mm 2 Up to 180N / mm 2 The unit tension range of the flat electrical steel output by the cold rolling mill is 40N / mm 2 Up to 50N / mm 2 .

5. The method for producing low-carbon and low-silicon electrical steel according to claim 1, characterized in that: The step of annealing the flat electrical steel using a vertical annealing furnace to obtain an electrical steel product comprises: The flat electrical steel is controlled to sequentially pass through the preheating section, heating section, soaking section, slow cooling section, fast cooling section, over-aging section and final cooling section of the vertical annealing furnace.

6. The method for producing low-carbon and low-silicon electrical steel according to claim 5, characterized in that: The temperature range of the preheating section is 120°C to 130°C, the temperature range of the heating section and the soaking section are both 825°C to 835°C, the temperature range of the slow cooling section is 645°C to 655°C, the temperature range of the fast cooling section is 495°C to 505°C, the temperature range of the over-aging section is 395°C to 405°C, and the temperature range of the final cooling section is 180°C to 190°C.

7. The method for producing low-carbon and low-silicon electrical steel according to claim 5, characterized in that: The movement speed of the flat electrical steel ranges from 4m / s to 5m / s, the time required for the flat electrical steel to pass through the preheating section ranges from 11s to 13s, the time required for the flat electrical steel to pass through the heating section ranges from 107s to 118s, the time required for the flat electrical steel to pass through the equalizing section ranges from 60s to 68s, the time required for the flat electrical steel to pass through the slow cooling section ranges from 16s to 19s, the time required for the flat electrical steel to pass through the fast cooling section ranges from 6s to 7s, the time required for the flat electrical steel to pass through the over-aging section ranges from 205s to 230s, and the time required for the flat electrical steel to pass through the final cooling section ranges from 45s to 50s.

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