A method for reducing indentation defects on the lower surface of an electrical steel slab

Abstract

The application provides a method for reducing indentation defects on the lower surface of an electrical steel slab, belonging to the field of hot rolling. The method comprises: placing an electrical steel slab in a heating furnace with multiple heating furnace sections; obtaining furnace gas target temperatures and target power loads of the multiple heating furnace sections according to the entry temperature of the electrical steel slab; obtaining a flame length control mode of the multiple heating furnace sections according to the single burner gas consumption of the heating furnace; and sequentially passing the electrical steel slab through the multiple heating furnace sections under the process conditions of the furnace gas target temperatures, the target power loads and the flame length control mode to perform staged heating. According to different entry temperatures of the electrical steel slab, corresponding heating processes are formulated to avoid the increase of surface defect occurrence rate caused by the occurrence of more indentations on the high-entry-temperature slab under the premise of ensuring the uniformity of the slab heating temperature and the target temperature of the slab.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hot rolling, in particular to a method for reducing indentation defects on the lower surface of an electrical steel slab. BACKGROUND

[0002] Electrical steel, also known as silicon steel sheet. Electrical steel has high magnetic permeability, low iron loss, high saturation magnetic induction, excellent magnetic property stability, good processing performance and good corrosion resistance, etc. It is an important soft magnetic alloy indispensable in the power, electronics and military industries. As one of the largest metal functional materials, it is mainly used to manufacture the cores of various motors, generators and transformers.

[0003] During the heating process of the electrical steel slab in the heating furnace, as the temperature rises, the strength at high temperature also rapidly decreases, and when the slab temperature reaches 1000℃, the strength approaches 0. During the transportation of the slab on the walking beam in the furnace, the contact with the oxide scale nodules formed by the water beam pad or the water beam is extremely easy to cause indentation on the lower surface of the slab. Therefore, how to reduce the occurrence rate of indentation defects on the lower surface of the electrical steel slab is a technical problem that needs to be solved at present. SUMMARY

[0004] The present application provides a method for reducing indentation defects on the lower surface of an electrical steel slab to solve the technical problem of how to reduce the occurrence rate of indentation defects on the lower surface of the electrical steel slab.

[0005] The present application provides a method for reducing indentation defects on the lower surface of an electrical steel slab, which comprises:

[0006] placing the electrical steel slab in a heating furnace with multiple heating furnace sections;

[0007] obtaining furnace gas target temperatures and target power loads of the multiple heating furnace sections according to the entry temperature of the electrical steel slab;

[0008] obtaining flame length control modes of the multiple heating furnace sections according to the single burner gas consumption of the heating furnace; and

[0009] under the process conditions of the furnace gas target temperatures, the target power loads and the flame length control modes, sequentially passing the electrical steel slab through the multiple heating furnace sections for staged heating.

[0010] Optionally, the multiple heating furnace sections include a preheating section, a first heating section, a second heating section and a soaking section.

[0011] Optionally, obtaining the furnace gas target temperatures and the target power loads of the multiple heating furnace sections according to the entry temperature of the electrical steel slab comprises:

[0012] obtaining a furnace gas target temperature of a first heating section of the plurality of heating sections according to the entry temperature of the electrical steel slab;

[0013] obtaining target power loads of a preheating section, the first heating section, the second heating section and a soaking section of the plurality of heating sections according to the entry temperature of the electrical steel slab.

[0014] Optionally, the obtaining the furnace gas target temperature of the first heating section of the plurality of heating sections according to the entry temperature of the electrical steel slab comprises:

[0015] obtaining a furnace gas target temperature of a first heating section of the plurality of heating sections according to the entry temperature of the electrical steel slab;

[0016] if the entry temperature ≥ 600℃, the furnace gas target temperature of the first heating section is a first furnace gas target temperature;

[0017] if the entry temperature < 600℃, the furnace gas target temperature of the first heating section is a second furnace gas target temperature;

[0018] wherein the first furnace gas target temperature < the second furnace gas target temperature.

[0019] Optionally, the first furnace gas target temperature is 1100℃-1160℃, and the second furnace gas target temperature is 1120℃-1170℃.

[0020] Optionally, the obtaining the target power loads of the preheating section, the first heating section, the second heating section and the soaking section of the plurality of heating sections according to the entry temperature of the electrical steel slab comprises:

[0021] obtaining target power loads of a preheating section, the first heating section, the second heating section and a soaking section of the plurality of heating sections according to the entry temperature of the electrical steel slab.

[0022] if the entry temperature ≥ 600℃, the target power loads of the preheating section, the first heating section, the second heating section and the soaking section are 26%-31%, 22%-25%, 18%-22% and 16%-22% respectively;

[0023] if the entry temperature < 600℃, the target power loads of the preheating section, the first heating section, the second heating section and the soaking section are 35%-39%, 26%-28%, 16%-19% and 15%-20% respectively.

[0024] Optionally, if the entry temperature ≥ 600℃, the target power loads of the preheating section, the first heating section, the second heating section and the soaking section are 31%, 25%, 22% and 22% respectively.

[0025] Optionally, if the furnace entry temperature < 600℃, the target power load of the preheating section, the first heating section, the second heating section and the soaking section is 35%, 26%, 19% and 20% respectively.

[0026] Optionally, the flame length control mode of the plurality of heating furnace sections is obtained according to the single burner gas consumption of the heating furnace, and the flame length control mode comprises:

[0027] The flame length control mode of the first heating section, the second heating section and the soaking section of the plurality of heating furnace sections is obtained according to the single burner gas consumption of the heating furnace;

[0028] If the single burner gas consumption is 400Nm 3 / h~800Nm 3 / h, the flame length control mode of the first heating section, the second heating section and the soaking section is short flame mode;

[0029] If the single burner gas consumption is 800Nm 3 / h~1200Nm 3 / h, the flame length control mode of the first heating section and the second heating section is short flame mode, and the flame length control mode of the soaking section is long flame mode.

[0030] Optionally, the surface skin defect occurrence rate of the electrical steel slab after the stage heating is ≤6%.

[0031] The above technical solutions provided by the embodiments of the present application have the following advantages compared with the prior art:

[0032] The present application provides a method for reducing the indentation defect of the lower surface of an electrical steel slab, comprising: placing the electrical steel slab in a heating furnace with a plurality of heating furnace sections; obtaining the furnace gas target temperature and the target power load of the plurality of heating furnace sections according to the furnace entry temperature of the electrical steel slab; obtaining the flame length control mode of the plurality of heating furnace sections according to the single burner gas consumption of the heating furnace; and sequentially passing the electrical steel slab through the plurality of heating furnace sections under the process conditions of the furnace gas target temperature, the target power load and the flame length control mode for stage heating. According to the different furnace entry temperatures of the electrical steel slab, by formulating the corresponding heating process, the increase of the surface defect occurrence rate caused by the high furnace entry temperature slab is avoided under the premise of ensuring the uniformity of the slab heating temperature and the target temperature of the furnace exit. BRIEF DESCRIPTION OF DRAWINGS

[0033] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and serve to explain the principles of the present application together with the specification.

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without any creative effort.

[0035] Figure 1 A flowchart of a method for reducing indentation defects on the lower surface of an electrical steel slab provided by the embodiments of the present application;

[0036] Figure 2 A high-temperature strength curve of electrical steel provided by the embodiments of the present application;

[0037] Figure 3 A diagram of indentation on the lower surface of an electrical steel slab after staged heating provided by Embodiment 1 of the present application;

[0038] Figure 4 A diagram of indentation on the lower surface of an electrical steel slab after staged heating provided by Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0039] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will combine the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without any creative effort fall within the scope of the present application.

[0040] Various embodiments of the present application can exist in the form of a range; it should be understood that the description in the form of a range is merely for the convenience and brevity, and should not be understood as a hard limitation on the scope of the present application; therefore, it should be considered that the described range has specifically disclosed all possible sub-ranges and single values within the range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the described range, such as 1, 2, 3, 4, 5 and 6, regardless of the range. In addition, whenever a numerical range is indicated in this document, it refers to any cited number (fraction or integer) within the indicated range.

[0041] In addition, in the description of the present application, the terms "comprise", "contain" and the like are intended to mean "including but not limited to". In this document, relational terms such as "first" and "second", and the like can be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. In this document, the term "and / or" describes the associated relationship of associated objects, which means that there can be three kinds of relationships, for example, A and / or B can represent: the existence of A alone, the existence of A and B at the same time, and the existence of B alone. Wherein A and B can be singular or plural. In this document, "at least one" means one or more, and "multiple" means two or more. "At least one", "at least one of the following" or the like means any combination of these items, including single item or any combination of multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can mean a, b, c, a-b (i.e. a and b), a-c, b-c, or a-b-c, where a, b, and c can be single or multiple.

[0042] Unless otherwise specifically stated, the various raw materials, reagents, instruments and equipment used in the present application can be purchased from the market or can be prepared by existing methods.

[0043] The creative idea of the present application is:

[0044] During the heating process of the electrical steel slab in the heating furnace, as the temperature rises, its strength at high temperature also rapidly decreases, and when the slab temperature reaches 1000℃, its strength approaches 0. During the transportation of the slab on the walking beam in the furnace, it is in contact with the oxide scale nodule formed by the water beam pad or the water beam, which is extremely easy to cause the appearance of indentation on the lower surface of the slab. Since the electrical steel is high-Si steel, the fayalite phase is a unique internal oxidation structure layer of high-Si steel, and its equilibrium melting point temperature is 1173℃, which is higher than the melting point temperature. When the temperature is higher than the melting point temperature, the fayalite phase will melt and form an anchor-shaped combined form with the steel matrix, greatly increasing the difficulty of removing the scale. Although the electrical steel slab has an out-of-furnace temperature of <1150℃, but since the silicon steel slab must be hot-charged, the uniform in-furnace temperature is relatively high, and the actual furnace gas temperature in the heating furnace is mostly higher than 1173℃ for most of the time. In addition, the electrical steel has fewer descaling passes in the hot rolling process, which further increases the difficulty of removing the oxide scale, especially for the oxide scale in the indentation on the lower surface of the slab. This leads to the appearance of more surface curling defects of the electrical steel strip after rolling or pickling. In general, the higher the heating temperature and the longer the high-temperature furnace section in the furnace, the more difficult it is to remove the oxide scale in the indentation on the lower surface of the electrical steel slab, and the more likely the indentation causes surface quality defects of the subsequent product.

[0045] In the prior art, in the hot rolling process of the electrical steel slab, (1) there is no special heating process set for different charging temperatures of the electrical steel slab. (2) A higher temperature control of the furnace gas is emphasized, and the temperature of the furnace gas is mostly above 1170℃. (3) The target power loads of the preheating section, the first heating section, the second heating section and the soaking section are 35%, 37%, 16% and 12% respectively. (4) The flame regulating side burners of the lower section of each furnace section adopt a long flame mode. Therefore, the prior art has the following defects: (1) The strength of the slab at different temperature stages is quite different at high temperature, and the prior art does not develop a targeted heating process according to different charging temperatures, for example, for the slab with high charging temperature, the heating temperature in the subsequent high-temperature furnace section should be as low as possible under the condition of ensuring the uniformity of the heating temperature and the target discharge temperature; (2) The temperature of the first heating furnace gas is too high, which can cause overburning of the slab surface and aggravate the liquefaction of fayalite phase; (3) The flame rigidity is not good, and the flame floats up, resulting in the temperature of the lower surface of the slab being too high and aggravating the softening and oxidation.

[0046] To solve the above technical problems, the present application develops a corresponding heating process according to the different charging temperatures of the electrical steel slab, and avoids the increase of the surface defect rate of the slab with high charging temperature due to the occurrence of more indentation under the premise of ensuring the uniformity of the slab heating temperature and the target discharge temperature.

[0047] Figure 1 A flowchart of a method for reducing indentation defects on the lower surface of an electrical steel slab is provided.

[0048] Please refer to Figure 1 The present application provides a method for reducing indentation defects on the lower surface of an electrical steel slab, which comprises:

[0049] S1, placing the electrical steel slab in a heating furnace with multiple heating furnace sections;

[0050] In some embodiments, the multiple heating furnace sections include a preheating section, a first heating section, a second heating section and a soaking section.

[0051] It should be noted that the heating furnace section, in the field of steel production, especially in the heating furnace, refers to the heating part divided into different regions or sections in the furnace. These parts have different heating tasks according to the heating needs and process requirements of the slab. The heating furnace is usually designed to have multiple heating furnace sections, each of which is heated by different heating methods (such as direct flame heating, radiation heating, convection heating, etc.) and temperature control to gradually heat the slab to the required temperature. These furnace sections may include preheating sections, heating sections, soaking sections, etc., each of which has its specific function and temperature range.

[0052] S2, obtaining a furnace gas target temperature and a target power load of each of the plurality of reheating furnace sections according to the entry temperature of the electrical steel slab;

[0053] In some embodiments, the obtaining the furnace gas target temperature and the target power load of each of the plurality of reheating furnace sections according to the entry temperature of the electrical steel slab comprises:

[0054] obtaining a furnace gas target temperature of a first reheating furnace section of the plurality of reheating furnace sections according to the entry temperature of the electrical steel slab;

[0055] obtaining a target power load of a preheating section, the first reheating furnace section, a second reheating furnace section and a soaking section of the plurality of reheating furnace sections according to the entry temperature of the electrical steel slab.

[0056] Figure 2 A high temperature strength curve of the electrical steel is provided in an embodiment of the present application. It can be seen that the high temperature strength of the electrical steel slab at 600℃ is a turning point, and the high temperature strength decreases rapidly when the temperature exceeds 600℃. Therefore, in order to reduce the indentation defects on the lower surface of the slab, the entry temperature of the electrical steel slab should not be too high. When the temperature exceeds 600℃, the process load of the heating furnace should be optimized and adjusted. Thus, the present application optimizes and adjusts the target temperature of the first reheating furnace and the target power load of each furnace section according to different entry temperatures. Figure 2

[0057] In some embodiments, the obtaining the furnace gas target temperature and the target power load of each of the plurality of reheating furnace sections according to the entry temperature of the electrical steel slab comprises:

[0058] obtaining a furnace gas target temperature of a first reheating furnace section of the plurality of reheating furnace sections according to the entry temperature of the electrical steel slab;

[0059] if the entry temperature is greater than or equal to 600℃, the furnace gas target temperature of the first reheating furnace section is a first furnace gas target temperature;

[0060] if the entry temperature is less than 600℃, the furnace gas target temperature of the first reheating furnace section is a second furnace gas target temperature;

[0061] wherein the first furnace gas target temperature is less than the second furnace gas target temperature.

[0062] In some embodiments, the first furnace gas target temperature is 1100℃ to 1160℃, and the second furnace gas target temperature is 1120℃ to 1170℃.

[0063] ​The first furnace gas target temperature is defined as 1100-1160°C, and the second furnace gas target temperature is defined as 1120-1170°C, so as to ensure that the slab obtains sufficient heat at this furnace section, while avoiding the formation of iron olivine from surface iron scale due to excessively high furnace gas temperature, and thus avoiding the difficulty in removing the scale. For example, the first furnace gas target temperature can be 1100°C, 1110°C, 1120°C, 1130°C, 1140°C, 1150°C, 1160°C, etc., and the second furnace gas target temperature can be 1120°C, 1130°C, 1140°C, 1150°C, 1160°C, 1170°C, etc.

[0064] In some embodiments, the target power loads of the preheating section, the first heating section, the second heating section and the soaking section of the plurality of heating furnace sections are obtained according to the entry temperature of the electrical steel slab, including:

[0065] The target power loads of the preheating section, the first heating section, the second heating section and the soaking section of the plurality of heating furnace sections are obtained according to the entry temperature of the electrical steel slab;

[0066] If the entry temperature is ≥600°C, the target power loads of the preheating section, the first heating section, the second heating section and the soaking section are 26-31%, 22-25%, 18-22% and 16-22%, respectively.

[0067] If the entry temperature is <600°C, the target power loads of the preheating section, the first heating section, the second heating section and the soaking section are 35-39%, 26-28%, 16-19% and 15-20%, respectively.

[0068] In some embodiments, if the entry temperature is ≥600°C, the target power loads of the preheating section, the first heating section, the second heating section and the soaking section are 31%, 25%, 22% and 22%, respectively.

[0069] In some embodiments, if the entry temperature is <600°C, the target power loads of the preheating section, the first heating section, the second heating section and the soaking section are 35%, 26%, 19% and 20%, respectively.

[0070] It should be noted that the heating furnace power load refers to the amount of energy, such as electrical energy or fuel energy, that the heating furnace can consume or convert in a unit of time. It reflects the working intensity and energy conversion efficiency of the heating furnace. Generally speaking, the higher the power load of the heating furnace, the more energy it can convert and provide in a unit of time. This high energy conversion rate is directly related to the heating capacity of the heating furnace.

[0071] According to different furnace inlet temperatures, the target power load of each furnace section is optimized and adjusted, so that sufficient heat is ensured for the slab at the furnace section, while the surface iron scale is prevented from generating iron olivine, thereby avoiding the difficulty in removing the iron scale.

[0072] S3, obtaining a flame length control mode of the plurality of heating furnace sections according to the single burner gas consumption of the heating furnace; and

[0073] In some embodiments, the obtaining a flame length control mode of the plurality of heating furnace sections according to the single burner gas consumption of the heating furnace comprises:

[0074] According to the single burner gas consumption of the heating furnace, the flame length control mode of the first heating section, the second heating section and the soaking section is obtained.

[0075] If the single burner gas consumption is 400 Nm 3 / h~800 Nm 3 / h, the flame length control mode of the first heating section, the second heating section and the soaking section is short flame mode.

[0076] If the single burner gas consumption is 800 Nm 3 / h~1200 Nm 3 / h, the flame length control mode of the first heating section and the second heating section is short flame mode, and the flame length control mode of the soaking section is long flame mode.

[0077] It should be noted that the same flame adjusting side burner has long flame and short flame modes. Long flame mode: gas and air flow in parallel, and the two begin to mix after leaving the burner. Such a structure slows down the mixing speed and lengthens the flame profile, but the flame end is prone to flame floating. Short flame mode: air passes through the swirl disc in the burner, which is divided into 30 degrees, 45 degrees and 60 degrees, so that the tangential component speed of the air is perpendicular to the gas in the rotating process, thereby strengthening the mixing of air and gas, accelerating the mixing speed, shortening the mixing time, and the silicon carbide structure of the combustion cylinder allows part of the mixed gas to mix in the sleeve. When the high-speed airflow is ejected, the flame profile will be shortened, the flame rigidity will be enhanced, and the flame end will not appear the flame floating.

[0078] To avoid the flame end of the burner floating to the lower surface of the slab and causing the local temperature of the lower surface of the slab to be too high and softening, the flame length control mode is adjusted according to the single burner gas consumption load, so as to ensure the flame rigidity of the flame adjusting side burner of the lower section of each furnace section. For example, when the single burner gas consumption is 400 Nm 3 / h, 500 Nm 3 / h, 600 Nm3 / h, 700 Nm 3 / h, 800 Nm 3 / h, etc., the flame length control mode of the first adding section, the second adding section and the soaking section is short flame mode; when the single burner gas consumption is 800 Nm 3 / h, 900 Nm 3 / h, 1000 Nm 3 / h, 1100 Nm 3 / h, 1200 Nm 3 / h, etc., the flame length control mode of the first adding section and the second adding section is short flame mode, and the flame length control mode of the soaking section is long flame mode.

[0079] S4, under the process conditions of the furnace gas target temperature, the target power load and the flame length control mode, sequentially passing the electric steel slab through the plurality of heating furnace sections to perform staged heating.

[0080] In some embodiments, the surface skin defect occurrence rate of the electric steel slab after the staged heating is ≤6%.

[0081] According to different slab entry temperatures, the present application formulates corresponding heating processes, under the premise of ensuring slab heating temperature uniformity and target temperature, avoids the increase of surface defect occurrence rate caused by the occurrence of more indentation pits in high entry temperature slabs. For example, the surface skin defect occurrence rate of the electric steel slab after the staged heating can be 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, etc.

[0082] The present application will be further described in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present application and not to limit the scope of the present application. The experimental methods not specified in the following examples are generally determined according to the industry standard. If there is no corresponding industry standard, it is determined according to the general international standard, the conventional condition, or according to the conditions suggested by the manufacturer.

[0083] The present embodiment provides a method for reducing the indentation pit defect of the lower surface of an electric steel slab, the method comprising:

[0084] S11, placing an electric steel slab in a heating furnace with a plurality of heating furnace sections;

[0085] S21, obtaining the furnace gas target temperature and the target power load of the plurality of heating furnace sections according to the entry temperature of the electric steel slab;

[0086] S31, obtaining the flame length control mode of the plurality of heating furnace sections according to the single burner gas consumption of the heating furnace; and

[0087] S41, under the process conditions of the furnace gas target temperature, the target power load and the flame length control mode, sequentially passing the electrical steel slab through the plurality of heating furnace sections to perform staged heating, to reduce the method of reducing the indentation defects of the lower surface of the electrical steel slab. The process parameters of the method for reducing the indentation defects of the lower surface of the electrical steel slab in the examples and the comparative examples are shown in Table 1.

[0088] Table 1 Process parameters of the method for reducing the indentation defects of the lower surface of the electrical steel slab in the examples and the comparative examples

[0089]

[0090]

[0091] The surface skin defects of the electrical steel slab after staged heating obtained in Examples 1-4 and Comparative Examples 1-4 were measured, and the subsequent rolling stability of the electrical steel slab after staged heating was observed, and the results are shown in Table 2. The specific measurement method is as follows: the surface skin defects of the strip surface were observed by following the track, and the occurrence period was corresponded to the indentation of the water beam pad of the lower surface of the slab.

[0092] Table 2 Surface skin defects of the electrical steel slab after staged heating and subsequent rolling stability

[0093] Group Surface buckling defects Whether rolling is stable Example 1 5.37％ Yes Example 2 5.18％ Yes Example 3 5.24％ Yes Example 4 5.42％ Yes Comparative Example 1 31.37％ Yes Comparative Example 2 15.19％ Yes Comparative Example 3 17.22％ Yes Comparative Example 4 4.67％ No, it is very easy to cause a belt stoppage accident

[0094] Figure 3 The indentation condition diagram of the lower surface of the electrical steel slab after staged heating provided in Example 1 of the present application is shown in Figure 1. Figure 4 The indentation condition diagram of the lower surface of the electrical steel slab after staged heating provided in Comparative Example 1 of the present application is shown in Figure 2. Figure 3 And Figure 4 It can be seen that the indentation condition of the lower surface of the electrical steel slab after staged heating obtained in the comparative example is more obvious, and there are more surface skin defects, which seriously affects the comprehensive performance of the electrical steel.

[0095] In addition, one or more technical solutions in the embodiments of the present application have at least the following technical effects or advantages:

[0096] In the embodiments of the present application, corresponding heating processes are developed according to different slab inlet temperatures, which avoids the increase of surface defect rate caused by the occurrence of more indentation of high inlet temperature slab under the premise of ensuring uniform slab heating temperature and target outlet temperature.

[0097] In the embodiments of the present application, the surface skin defect rate of the electrical steel slab after staged heating is ≤6%, and the subsequent rolling is stable, which does not affect the subsequent production process.

[0098] The foregoing detailed description of the application has been presented for purposes of illustration and description. Various modifications and changes can be made to these embodiments without departing from the spirit and scope of the application. It is intended that the scope of the application should not be limited by the particular representative embodiments described above.

Claims

1. A method of reducing crater defects on the lower surface of an electrical steel slab, characterized in that, The method comprises: placing an electrical steel slab into a heating furnace with multiple heating furnace sections; obtaining furnace gas target temperatures and target power loads of the multiple heating furnace sections according to an entry temperature of the electrical steel slab; obtaining a flame length control mode of the multiple heating furnace sections according to a single burner gas consumption of the heating furnace; and sequentially passing the electrical steel slab through the multiple heating furnace sections under process conditions of the furnace gas target temperatures, the target power loads and the flame length control mode to perform staged heating; wherein the multiple heating furnace sections comprise a preheating section, a first heating section, a second heating section and a soaking section; the obtaining of the furnace gas target temperatures and the target power loads of the multiple heating furnace sections according to the entry temperature of the electrical steel slab comprises: obtaining a furnace gas target temperature of the first heating section of the multiple heating furnace sections according to the entry temperature of the electrical steel slab; obtaining target power loads of the preheating section, the first heating section, the second heating section and the soaking section of the multiple heating furnace sections according to the entry temperature of the electrical steel slab; the obtaining of the furnace gas target temperature of the first heating section of the multiple heating furnace sections according to the entry temperature of the electrical steel slab comprises: obtaining a furnace gas target temperature of the first heating section of the multiple heating furnace sections according to the entry temperature of the electrical steel slab; if the entry temperature is ≥600℃, the furnace gas target temperature of the first heating section is a first furnace gas target temperature; if the entry temperature is <600℃, the furnace gas target temperature of the first heating section is a second furnace gas target temperature; wherein the first furnace gas target temperature < the second furnace gas target temperature.

2. The method of claim 1, wherein, the first furnace gas target temperature is 1100℃-1160℃, and the second furnace gas target temperature is 1120℃-1170℃.

3. The method of claim 1, wherein, the obtaining of the target power loads of the preheating section, the first heating section, the second heating section and the soaking section of the multiple heating furnace sections according to the entry temperature of the electrical steel slab comprises: obtaining target power loads of the preheating section, the first heating section, the second heating section and the soaking section of the multiple heating furnace sections according to the entry temperature of the electrical steel slab; if the entry temperature is ≥600℃, the target power loads of the preheating section, the first heating section, the second heating section and the soaking section are 26%-31%, 22%-25%, 18%-22% and 16%-22% respectively; if the entry temperature is <600℃, the target power loads of the preheating section, the first heating section, the second heating section and the soaking section are 35%-39%, 26%-28%, 16%-19% and 15%-20% respectively.

4. The method of claim 3, wherein, if the entry temperature is ≥600℃, the target power loads of the preheating section, the first heating section, the second heating section and the soaking section are 31%, 25%, 22% and 22% respectively.

5. The method of claim 3, wherein, if the entry temperature is <600℃, the target power loads of the preheating section, the first heating section, the second heating section and the soaking section are 35%, 26%, 19% and 20% respectively.

6. The method of claim 1, wherein, the obtaining of the flame length control mode of the multiple heating furnace sections according to the single burner gas consumption of the heating furnace comprises: According to the single burner gas consumption of the heating furnace, a flame length control mode of a first section, a second section and a soaking section of the plurality of heating furnace sections is obtained. If the single burner gas consumption is 400 Nm 3 / h~800 Nm 3 / h, the flame length control mode of the first adding section, the second adding section and the soaking section are all short flame mode. If the single burner gas consumption is 800 Nm 3 / h~1200 Nm3 / h, the flame length control mode of the first and second adding sections is short flame mode, and the flame length control mode of the soaking section is long flame mode.

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