High Surface Quality Control Method for Non-Oriented Electrical Steel Strip

Abstract

The present invention relates to a high surface quality control method for a non-oriented electrical steel strip, and belongs to the field of metallurgy. The non-oriented electrical steel strip is produced by the process steps of molten iron pretreatment, converter smelting, refining outside the furnace, slab continuous casting, slab heating, high-pressure dephosphorization, rough rolling, finishing rolling, laminar cooling, coiling by a coiler, and post-treatment. The chemical composition of the non-oriented electrical steel strip includes, by weight, C: ≤0.006%, Si: 0.6% to 0.9%, Mn: 0.25% to 0.35%, ALs: 0.09% to 0.15%, N: ≤0.005%, and the rest is Fe and unavoidable impurities. The steel grade process design of the present invention is reasonable, no additional production equipment conditions are required, the production process is controllable, and there are no holes, edge cracks, or edge warping defects on the surface; the product is successfully developed under existing conditions and has good mechanical processing capabilities.

Description

Technical Field

[0001] The invention belongs to the field of metallurgy and relates to a method for controlling high surface quality of a non-oriented electrical steel strip. Background Art

[0002] Electrical steel, also known as silicon steel, is divided into two types: oriented electrical steel and non-oriented electrical steel. Oriented electrical steel is mainly used to manufacture the core of transformers and mutual inductors, while non-oriented electrical steel is mainly used to manufacture the core of motors. The improvement of electrical steel quality is directly related to the operating quality of transformers and motors. Summary of the invention

[0003] In view of this, the object of the present invention is to provide a method for controlling high surface quality of non-oriented electrical steel strip, so as to produce products with multiple advantages such as high surface quality, good formability, and high magnetic properties.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] A method for controlling high surface quality of a non-oriented electrical steel strip comprises the following steps:

[0006] The non-oriented electrical steel strip is produced by the process steps of molten iron from blast furnace, molten iron pretreatment, converter smelting, refining outside the furnace, slab continuous casting, slab heating, high-pressure descaling, rough rolling, finishing rolling, laminar cooling, coiling by a coiler and post-treatment.

[0007] Optionally, the chemical composition of the non-oriented electrical steel strip includes, by weight: C: ≤0.006%, Si: 0.6%-0.9%, Mn: 0.25%-0.35%, ALs: 0.09%-0.15%, N: ≤0.005%, and the rest is Fe and unavoidable impurities.

[0008] Optionally, the heating temperature of the slab heating process is 1120-1170°C, the total time in the heating furnace is ≥160min, the finishing rolling inlet temperature is 900°C-1020°C, the final rolling temperature is 840°C-880°C, the coiling temperature is between 570 and 640°C, the layer cooling mode is front-stage cooling, and the water cooling rate is ≤10°C / s.

[0009] Optionally, during the slab heating process, the preheating section temperature is 900℃-1000℃, the heating section temperature is 1150℃-1190℃, the soaking section temperature is 1140℃-1170℃, the cumulative heating time of the heating section and the soaking section is ≥80min, the total heating furnace time is 160-200min, the slab charging temperature is ≥500℃, and the slab out-of-furnace temperature is designed to be 1140-1170℃.

[0010] Optionally, in the high-pressure descaling step, 2 groups of rough descaling boxes are opened to ensure a water spray pressure of 20 to 22.5 MPa, and the 2nd and 4th passes of rough rolling mill descaling are opened to ensure a water spray pressure of 20 to 22 MPa. The rough descaling and rough rolling mill descaling water cannot be used at the same time. There are 2 groups of finishing rolling descaling boxes with a water spray pressure of 18 to 20 MPa.

[0011] Optionally, the requirements for cooling water of the roughing mill during rough rolling are as follows: the opening degree of the vertical roll cooling water flow valve is adjusted to 30%; the water flow rate is 400m³ / h; the descaling pre-flushing water valve is closed; the roughing vertical roll slag flushing water is closed; a vertical roll cooling water cutting device is added, and the cooling water flow of the roughing flower rack roll and working roll is reduced by 20%.

[0012] Optionally, all cooling water between the finishing mill stands is closed during the finishing rolling process.

[0013] Optionally, the side pressure of the roughing vertical rolls can be reduced by 15-25mm during the roughing rolling process, and the side pressure load of the 1st pass can be reduced by 30%, and the side pressure load of the 3rd and 5th passes can be increased by 20%.

[0014] Optionally, during the finishing rolling process, the finishing strip threading speeds are specifically: F1 1.6 mps, F2 2.9 mps, F3 4.6 mps, F4 5.9 mps, F5 6.5 mps, F6 7.8 mps, and F7 8.7 mps.

[0015] Optionally, during the coiling process of the coiler, the pressure compensation of the coiling side guide plate is -10KN.

[0016] The beneficial effects of the present invention are:

[0017] The steel grade process design of the present invention is reasonable, no new production equipment is required, the production process is controllable, the surface has no holes, edge cracks, edge warping defects, the product is successfully developed under existing conditions, and has good mechanical processing capabilities. The high surface quality of the product produced by the invention meets all the ordering standards, and at the same time meets the internal control requirements and user use, with good surface quality, especially the product has excellent performance and good comprehensive mechanical processing performance.

[0018] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. DETAILED DESCRIPTION

[0019] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0020] The invention discloses a high surface quality control method for a non-oriented electrical steel strip, which specifically comprises the following steps: blast furnace molten iron→molten iron pretreatment→converter smelting→external refining→slab continuous casting→slab heating→high-pressure descaling→rough rolling with vertical rollers→finishing high-pressure descaling→finishing 7-stand continuous rolling→U-tube laminar cooling→coiler coiling and packaging→face and side spraying of steel coil information→surface size and quality inspection→batch sampling and inspection→labeling after qualified inspection→warehousing and delivery.

[0021] The present invention discloses a method for controlling high surface quality of a non-oriented electrical steel strip, adopts a design concept of ultra-low carbon, ultra-low sulfur and high aluminum components, and the contents of the chemical components are as follows (by weight percentage): C: ≤0.006%, Si: 0.6%-0.9%, Mn: 0.25%-0.35%, ALs: 0.09%-0.15%, N: ≤0.005%, and the rest are Fe and unavoidable impurities. At the same time, the heating temperature, rough rolling mill, finishing rolling mill and coiling process parameter control are specified.

[0022] Process characteristics: using blast furnace molten iron, through molten iron pretreatment, converter smelting, RH vacuum degassing treatment, appropriate billet drawing speed, heating temperature 1120 ~ 1170 ℃, total time in the heating furnace ≥ 160min, finishing rolling entrance temperature 900 ℃ ~ 1020 ℃, final rolling temperature 840 ℃ -880 ℃, coiling temperature between 570 ~ 640 ℃, layer cooling mode is front section cooling, water cooling rate ≤ 10 ℃ / s.

[0023] Heating process: According to the composition and process characteristics, silicon element expands the austenite phase region significantly, the Ar3 temperature is relatively low, and the furnace gas temperature of the heating furnace is controlled. The preheating section temperature is 900℃-1000℃, the heating section temperature is 1150℃-1190℃, the soaking section temperature is 1140℃-1170℃, the cumulative heating time of the heating section and the soaking section is ≥80min, the total heating furnace time is 160-200min, the slab charging temperature is ≥500℃, and the slab discharge temperature is designed to be 1140-1170℃.

[0024] Rolling process: Rough rolling with five passes, no hot coil box, finishing rolling with seven stands, full hydraulic coiler. In order to effectively control the surface quality, the descaling water and process cooling water and parameters are mainly optimized.

[0025] ① Open 2 groups of rough descaling boxes to ensure a water spray pressure of 20-22.5MPa, open the 2nd and 4th passes of roughing mill descaling (pre-flush water flow valve 60% of descaling water), and ensure a water spray pressure of 20-22MPa. Rough descaling and roughing mill descaling water cannot be used at the same time. There are 2 groups of finishing descaling boxes with a water spray pressure of 18-20MPa.

[0026] ②Cooling water

[0027] Roughing mill cooling water: The opening of the vertical roller cooling water flow valve is adjusted to 30%. The water flow is about 400m³ / h; the descaling pre-flushing valve is closed; the roughing vertical roller slag flushing water is closed; the vertical roller cooling water cut-off device is added, and the cooling water flow of the roughing flower rack roller and working roller is reduced by 20%.

[0028] Finishing rolling cooling water: Because the finishing rolling inlet temperature is low and the final rolling temperature is high, all cooling water between the finishing rolling stands are closed.

[0029] Laminar cooling water: Set the backward cooling mode and do not use the fault valve in the fine adjustment section.

[0030] ③Rolling parameters

[0031] Side pressure of rough rolling vertical roll: The width reduction of slab should not be too large, the width reduction range is 15-25mm, and at the same time, the side pressure load of pass 1 is reduced by 30%, and the side pressure load of passes 3 and 5 is increased by 20%.

[0032] Finishing rolling: One group of finishing descaling is retained, the rolling speed should not be too fast, and the specific threading speeds are: F1 1.6, F2 2.9, F34.6, F4 5.9, F5 6.5, F6 7.8, F7 8.7 [mps]; since there is no guide wheel to guide, the side guide plate of each frame is increased by 15mm to avoid serious scratching.

[0033] Coiling: The pressure compensation of the coiling side guide is -10KN. This process parameter design has not been used for other steel types of this thickness specification.

[0034] Appendix 1 shows examples of the smelting compositions of 4 batches of steel strips.

[0035]

[0036] Appendix 2 is an example of process control for 4 batches of steel strips.

[0037]

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A method for controlling high surface quality of non-oriented electrical steel strip, characterized in that: The following steps are involved: The blast furnace molten iron is subjected to the process steps of molten iron pretreatment, converter smelting, refining outside the furnace, slab continuous casting, slab heating, high pressure descaling, rough rolling, finishing rolling, laminar cooling, coiling by a coiler and packaging to produce non-oriented electrical steel strip; Wherein, in the high pressure descaling step: Open 2 groups of coarse descaling boxes, with a water spray pressure of 20-22.5MPa; During the rough rolling process: The opening of the vertical roller cooling water flow valve is adjusted to 30%, and the water flow is 400m 3 / h; close the descaling pre-flushing valve and the roughing vertical roll slag flushing water; add the vertical roll cooling water cutting device, and reduce the cooling water flow of the roughing flower rack roll and working roll by 20%; start the second and fourth passes of roughing mill descaling, with a water spray pressure of 20-22MPa, and the roughing descaling and roughing mill descaling water are not used at the same time; During the finishing rolling process: All cooling water between the finishing mill stands is closed, and the finishing strip threading speed is F1 1.6mps, F2 2.9mps, F3 4.6mps, F4 5.9mps, F5 6.5mps, F6 7.8mps, F7 8.7mps; 2 groups of finishing descaling boxes are opened, and the water spray pressure is 18-20MPa; During the coiling process of the coiler: The pressure compensation of the winding side guide is -10KN.

2. The method according to claim 1, characterized in that The chemical composition of the non-oriented electrical steel strip is calculated by weight as follows: C: ≤0.006%; Si: 0.6%-0.9%; Mn: 0.25%-0.35%; Als: 0.09%-0.15%; N: ≤0.005%, and the rest is Fe and unavoidable impurities.

3. The method according to claim 1, characterized in that During the slab heating process, the preheating section temperature is 900℃-1000℃, the heating section temperature is 1150℃-1190℃, the soaking section temperature is 1140℃-1170℃, the cumulative heating time of the heating section and the soaking section is ≥80min, the total heating furnace time is 160-200min, the slab charging temperature is ≥500℃, and the slab out-of-furnace temperature is 1140-1170℃.

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