A cold rolling method of ultra-high grade non-oriented silicon steel

Abstract

The application relates to a cold rolling method of an unoriented silicon steel, and a cold rolling method of an ultra-high-grade unoriented silicon steel, which comprises the following steps: step one: first rolling process: a first cold rolling production method of a steel coil; and step two: second rolling process: a second cold rolling production method of the steel coil after first annealing. In the first rolling process, a small reduction of 26-30% is adopted in the first pass, and a micro-edge wave control standard is adopted at the edge, so that the generation of edge crack defects is reduced or avoided.

Description

TECHNICAL FIELD

[0001] The application relates to a cold rolling method of non-oriented silicon steel, in particular to a cold rolling method of two-rolling-process ultra-high-grade non-oriented silicon steel. BACKGROUND

[0002] With the rapid development of the electrical industry, the demand for the magnetic properties and mechanical properties of electromagnetic materials is higher and higher. However, with the increase of the silicon content, the brittleness of the strip steel increases, and the processing difficulty increases exponentially. In order to further improve the magnetic induction intensity of the silicon steel sheet, the ultra-high-grade non-oriented silicon steel (the silicon content is between 3.0-3.5%) is realized by adopting a twice annealing process during rolling. Compared with the process of the ordinary high-grade cold-rolled silicon steel, the characteristics are that the strip steel is first rolled to the intermediate thickness on the single-stand rolling mill after being heat-treated on the normalizing unit, is annealed for the first time on the continuous annealing unit, is secondly rolled to the final thickness on the single-stand rolling mill, is annealed for the second time on the continuous annealing unit, and is coated. The production method is more than the normal process once intermediate annealing and once cold rolling. The final thickness of the product is generally between 0.15-0.35 mm, the first rolling thickness is controlled between 0.4-0.7 mm according to the process design, and the billet thickness is between 2.1-2.3 mm. The process described in the application is in the cold rolling process.

[0003] The cold rolling described in the application is produced by adopting a twenty-roller rolling mill, in particular a split type 21 twenty-roller rolling mill, and the working roller diameter is used in the range of 65-100 mm.

[0004] The twice cold rolling and twice annealing are the process technical routes for improving the magnetic properties which are widely adopted at present. The difficulties of the process are that the strip steel surface is oxidized in the annealing furnace after the first annealing, the rolling pressure fluctuates greatly during the second rolling, the rolling difficulty is extremely great, the strip is broken more, the production efficiency is low, the yield is low, the surface has serious color difference after the second rolling, the plate shape is unstable, and the qualified product rate is low.

[0005] The application improves the cold rolling process from the mechanism of the surface oxidation of the strip steel after the first annealing, reduces the degree of the surface oxidation of the strip steel, improves the surface quality, reduces the generation of the crack defects, solves the problem of the strip breakage due to the crack in the second rolling process, optimizes the second rolling process, and solves the influence of the surface oxidation of the strip steel after the first annealing on the cold rolling. Finally, the rolling efficiency, the yield and the surface quality of the strip steel are improved. SUMMARY

[0006] The application aims at the above problems, and provides a cold rolling method of ultra-high-grade non-oriented silicon steel.

[0007] The purpose of the present application is achieved in that: a cold rolling method of ultra-high grade non-oriented silicon steel, comprising the following steps: step one: first rolling: the first cold rolling production method of the steel coil: (1) the thickness of the blank is 2.1-2.3mm, the thickness of the first rolling is between 0.4-0.7mm, and the total rolling pass number of the first rolling is 4; (2) the first pass reduction rate of the first rolling is controlled between 26-32%, the front tension is 7-10kg / mm², and the rear tension is between 2.5-3.5kg / mm²; (3) the intermediate pass reduction rate of the first rolling is controlled between 30-38%, the front tension is 8-15kg / mm², and the rear tension is between 4-12kg / mm²; (4) the last pass reduction rate of the first rolling is controlled between 25-33%, the front tension is 18-22kg / mm², and the rear tension is between 9-15kg / mm²; (5) the process lubricating medium used in the above rolling is emulsion; (6) after the first cold rolling, the first annealing is carried out, the annealing process speed is 80-150m / min, and the process temperature is 900-1000℃; step two: second rolling: the steel coil after the first annealing is subjected to the second cold rolling production method: (1) the second rolling adopts 2-3 passes of rolling, and the target thickness is 0.15mm-0.3mm; (2) the first pass reduction rate of the second rolling is controlled between 28-40%, the front tension is 18-22kg / mm², and the rear tension is between 12-17kg / mm²; (3) the second pass reduction rate of the second rolling is controlled between 28-40%, the front tension is 20-25kg / mm², and the rear tension is between 13-18kg / mm²; (4) the last pass reduction rate of the second rolling is controlled between 29-33%, the front tension is 22-25kg / mm², and the rear tension is between 13-18kg / mm²; (5) the process lubricating medium used in the above rolling is emulsion.

[0008] In the first cold rolling production method of the steel coil of step one, the first pass to the third last pass working roll roughness adopts a large roughness working roll of 1.2-2.0μm; the first pass working roll diameter is 70-100mm; the roughness of the last two passes working roll adopts a small roughness working roll of 0.15-0.4μm; the last two passes working roll diameter is 70-100mm; the leading strip is cut off before the last pass production, and the sleeve is fed; the first pass rolling speed is 80-260m / min, the second pass rolling speed is 200-400m / min, and the rolling speed of other passes is 400-800m / min; the first pass adopts micro edge wave control, that is, the wave shape displayed by the shape meter is 10-20I, and the other passes adopt small edge wave control, that is, the wave shape displayed by the shape meter is 25-35I.

[0009] If the second rolling pass is two rolling passes in the second cold rolling production method of step two, step (3) in the production method of the second rolling pass is omitted, and (2) directly jumps to (4); the first-pass work roll roughness adopts a work roll of 0.6-1.0 μm; the last-pass work roll roughness adopts a work roll of 0.15-0.4 μm; the absolute reduction of all passes of the second rolling pass is 0.05-0.3 mm, and the rolling speed of each pass is between 200-600 m / min; a steel sleeve is used on the coiler before the last-pass rolling; during the speed-up process of the first-pass rolling, an intermittent method is adopted, i.e. speed-up-keeping-speed-up-keeping……, and the speed is kept once every 30-80 m of speed-up.

[0010] The emulsion temperature of the first rolling pass is 45-60 ℃, and the emulsion concentration is 3-5%.

[0011] The emulsion temperature of the second rolling pass is 45-60 ℃, and the emulsion concentration is 6-8%.

[0012] The beneficial effects of the present application are: 1. The first-pass first-pass of the first rolling pass adopts a small reduction of 26-30%, and the edge part adopts a micro-edge wave control standard, which aims to reduce or avoid the generation of edge crack defects.

[0013] 2. All rolling passes before the last-pass of the first rolling pass adopt a large roughness work roll, which is beneficial to reduce rolling cracks and realize high-speed stable rolling under small tension.

[0014] 3. The plate shape control of the first rolling pass adopts a small edge wave control except the first-pass, which aims to reduce the stress of the strip edge and prevent crack generation or extension.

[0015] 4. The last-pass of the first rolling pass adopts a small roughness work roll, which aims to reduce the micro-surface area of the strip surface, reduce the contact area of the strip surface and the furnace atmosphere, and thus reduce the oxidation degree of the strip.

[0016] 5. The first-pass of the second rolling pass adopts a large roughness work roll, which aims to break the oxidation layer of the strip surface, reduce the fluctuation of rolling pressure in the rolling process, improve the uniformity of the surface and the stability of rolling, and avoid color difference of the strip surface.

[0017] 6. The last-pass of the second rolling pass adopts a small roughness work roll, which aims to ensure the final surface roughness of the strip and improve the consistency of the surface. DETAILED DESCRIPTION

[0018] The related industries such as electric vehicles develop rapidly, and the requirements for the electromagnetic properties and mechanical properties of silicon steel are higher and higher. With the upgrading of silicon steel process equipment, the cold-rolled silicon steel has great changes in the process flow, such as thin gauge high grade and ultra-high grade non-oriented silicon steel has been mass produced on the tandem cold rolling mill. However, the products with high electromagnetic properties and mechanical properties can only be produced by twice intermediate annealing and two rolling processes at present. The downstream market demands more and more high-performance products, but the production cost is high due to high rolling difficulty. The present application improves the production efficiency and product quality from the innovative design of cold rolling process, greatly reduces the production cost, and improves the market competitiveness.

[0019] The content of the present application mainly solves the above problems from the aspects of rolling design, optimization of roll system and process medium parameters. The specific process design and production scheme are as follows.

[0020] The production process before the first cold rolling is explained as follows: normalizing process: the hot-rolled material is treated by the CP unit, pickled and edge cut.

[0021] Preparation unit: the steel coil after normalizing is heated and the leading tape is welded in the preparation unit.

[0022] The above two processes are the conventional production process for producing ultra-high grade non-oriented silicon steel at present, and the present application does not make specific description. The scope involved in the present application is in the cold rolling process, which is specifically described as follows.

[0023] 1. The first cold rolling production method of the steel coil after normalizing and pickling: process design method and steps: (1) the thickness of the blank is 2.1-2.3 mm, the thickness of the first rolling is between 0.4-0.7 mm, and the total rolling pass number of the first rolling is generally 4.

[0024] (2) The first pass reduction rate of the first rolling is controlled between 26-32%. The front tension is 7-10 kg / mm², and the rear tension is between 2.5-3.5 kg / mm². Preferably, the front tension is 7.8 kg / mm², and the rear tension is 2.7 kg / mm².

[0025] (3) The intermediate pass reduction rate of the first rolling is controlled between 30-38%. The front tension is 8-15 kg / mm², and the rear tension is between 4-12 kg / mm².

[0026] (4) The last pass reduction rate of the first rolling is controlled between 25-33%. The front tension is 18-22 kg / mm², and the rear tension is between 9-15 kg / mm².

[0027] Further explanation: (1) The working roll roughness of the above first pass to the third last pass is 1.2-2.0 μm of large roughness working roll, and preferably 1.5 μm.

[0028] (2) The first pass work roll diameter is 70-100 mm, preferably 95-100 mm.

[0029] (3) The last two passes work roll roughness is 0.15-0.4 μm, preferably 0.2 μm.

[0030] (4) The last two passes work roll diameter is 70-100 mm, preferably 70-80 mm.

[0031] (5) The last pass production is preceded by cutting off the leading end and inserting the sleeve.

[0032] (6) The rolling speed of each pass is determined according to the design capacity of the mill train, and in theory can reach the design speed of the mill train, and is not limited by the process.

[0033] (7) The first pass uses micro edge waves for control, and the micro edge waves are 10-20 I as shown by the wave shape of the plate shape meter.

[0034] (8) The other passes use small edge waves for control, and the small edge waves are 25-35 I as shown by the wave shape of the plate shape meter.

[0035] 2. The production method of the second rolling pass (after the first annealing): process design method and steps: (1) According to the overall design of the process, the second rolling pass generally uses 2-3 passes of rolling.

[0036] (2) The first pass of the second rolling pass is controlled at a reduction of 28-40%. The front tension is 18-22 kg / mm2, and the back tension is 12-17 kg / mm2. Preferably, the front tension is 20 kg / mm2, and the back tension is 13 kg / mm2.

[0037] (3) The second pass of the second rolling pass is controlled at a reduction of 28-40%. The front tension is 20-25 kg / mm2, and the back tension is 13-18 kg / mm2. Preferably, the front tension is 20.5 kg / mm2, and the back tension is 14 kg / mm2.

[0038] (4) The last pass of the second rolling pass is controlled at a reduction of 29-33%. The front tension is 22-25 kg / mm2, and the back tension is 13-18 kg / mm2. Preferably, the front tension is 23.5 kg / mm2, and the back tension is 16.5 kg / mm2.

[0039] Further explanation: (1) If the second rolling pass is two rolling passes, then step (3) of the production method of the second rolling pass (after the first annealing) is omitted, and goes directly from (2) to (4).

[0040] (2) The roughness of the work roll in the first pass is 0.6-1.0 μm, preferably 0.75 μm.

[0041] (3) The roughness of the work roll in the last pass is 0.15-0.4 μm, preferably 0.2 μm.

[0042] (4) The absolute reduction in the pass is >0.05 mm.

[0043] (5) A steel sleeve is used on the coiler before the last pass to prevent coil collapse and coiler indentation.

[0044] (6) In the first pass, the speed is increased in steps using an intermittent process (speed-up-maintain-speed-up-maintain...), preferably maintaining the speed every 30 m.

[0045] 3. The process medium parameters in the two passes are as shown in the following table.

[0046]

[0047] The present case is applied to a 20-roll mill in the Silicon Steel Division of Baosteel Taigang Stainless Steel Co., Ltd. The specific embodiments are described as follows. Example 1

[0048] The steel grade is a super-high grade non-oriented silicon steel with a silicon content of 3.33%, a width of 1130 mm, a thickness of 2.25 mm after normalizing and pickling, a rolling thickness of 0.5 mm in the first pass, and a rolling thickness of 0.245 mm in the second pass. The specific rolling conditions are described as follows: 1. The strip steel is heated to 120°C and the leading strip is welded after being cut and edged by the CP unit.

[0049] 2. The specific cold rolling steps and parameters are as follows: First pass: (1) The work roll is replaced before rolling, preferably a work roll with a roughness of 1.5 μm and a roll diameter of 85-100 mm.

[0050] (2) The work roll is replaced and a sleeve is added before the finished product, preferably a work roll with a roughness of 0.2 μm and a roll diameter of 70-85 mm.

[0051] (3) The rolling procedure is as shown in the following table.

[0052]

[0053] Second pass: The blank is the material after the first annealing.

[0054] (1) The work roll is replaced before rolling, preferably a work roll with a roughness of 0.75 μm and a roll diameter of 70-85 mm.

[0055] (2) Change the work roll before the last pass of the finished product and sleeve on the coiler, preferably the work roll roughness is 0.2 μm, and the roll diameter is 70-85 mm.

[0056] (3) The rolling procedure is shown in the following table.

[0057] Example 2

[0058] The steel grade is ultra-high grade non-oriented silicon steel, the silicon content is 3.28%, the width is 1190 mm, the strip thickness after normalizing and pickling is 2.2 mm, the first rolling thickness is 0.47 mm, and the second rolling thickness is 0.15 mm. The specific rolling conditions are as follows: 1. The strip is heated to 120℃ and the leading tape is welded after the edge cutting of the CP unit.

[0059] 2. The specific cold rolling steps and parameters are as follows: the first rolling: (1) change the work roll before rolling, preferably the work roll roughness is 1.5 μm, and the roll diameter is 85-100 mm.

[0060] (2) Change the work roll before the last pass of the finished product and sleeve on the coiler, preferably the work roll roughness is 0.2 μm, and the roll diameter is 70-85 mm.

[0061] (3) The rolling procedure is shown in the following table.

[0062]

[0063] The second rolling: the blank is the material after the first annealing.

[0064] (1) Change the work roll before rolling, preferably the work roll roughness is 0.75 μm, and the roll diameter is 75-85 mm.

[0065] (2) Change the work roll before the last pass of the finished product and sleeve on the coiler, preferably the work roll roughness is 0.2 μm, and the roll diameter is 75-85 mm.

[0066] (3) The rolling procedure is shown in the following table.

[0067]

[0068] Note: Because the emulsion concentration is adjusted by on-site oil and water addition, a specific value cannot be achieved, and only a certain range can be controlled.

[0069] Example and comparative example effect comparison: 1. The silicon content of the ultra-high grade non-oriented silicon steel is 3.3±0.05%, the width is 1050-1200 mm. The hot rolling thickness of the blank is 2.1-2.3 mm, the first rolling thickness is 0.5 mm, and the second rolling thickness is 0.245 mm. The comparison is shown in the following table.

[0070]

[0071] The embodiments are only the best examples, and are not intended to limit the technical solutions of the present application.

[0072] The above only describes specific embodiments of the present application, but the structural features of the scope of protection of the present application are not limited thereto, and any changes or modifications made by those skilled in the art within the scope of the present application are covered by the patent scope of the present application.

Claims

1. A cold rolling method for ultra-high grade non-oriented silicon steel, characterized in that: Includes the following steps: Step 1: First Rolling Stroke: First Cold Rolling Production Method for Steel Coils (1) The billet thickness is 2.1-2.3 mm, the thickness of the first rolling pass is between 0.4-0.7 mm, and the total number of rolling passes in the first rolling pass is 4; (2) The first pass reduction rate of the first rolling stroke is controlled between 26-32%, the front tension is 7-10 kg / mm², and the back tension is between 2.5-3.5 kg / mm². (3) The reduction rate of the intermediate pass in the first rolling stroke is controlled between 30-38%, the front tension is 8-15 kg / mm², and the back tension is between 4-12 kg / mm². (4) The reduction rate of the last pass of the first rolling stroke is controlled between 25-33%, the front tension is 18-22 kg / mm², and the rear tension is between 9-15 kg / mm². (5) The process lubricating medium used in the above rolling process is an emulsion; (6) After the first cold rolling, the first annealing is carried out. The annealing process speed is 80-150m / min and the process temperature is 900-1000℃. Step Two: Second Rolling Stroke: The steel coil after the first annealing undergoes a second cold rolling process. (1) The second rolling process uses 2-3 passes to achieve a target thickness of 0.15mm-0.3mm; (2) The first pass reduction rate of the second rolling stroke is controlled between 28-40%, the front tension is 18-22 kg / mm², and the back tension is between 12-17 kg / mm². (3) The reduction rate of the second pass in the second rolling stroke is controlled between 28-40%, the front tension is 20-25 kg / mm², and the back tension is between 13-18 kg / mm². (4) The reduction rate of the last pass of the second rolling process is controlled between 29-33%, the front tension is 22-25 kg / mm², and the back tension is between 13-18 kg / mm². (5) The process lubricating medium used in the above rolling process is an emulsion; In the first cold rolling process of steel coils in step one, the roughness of the work rolls in the first to third-to-last passes is 1.2-2.0 μm, which is a large roughness. The roll diameter of the work rolls in the first pass is 70-100 mm. The roughness of the work rolls in the last two passes is 0.15-0.4 μm, which is a small roughness. The roll diameter of the work rolls in the last two passes is 70-100 mm. Before the last pass, the lead strip is removed and the steel sleeve is installed. The rolling speed is 80-260 m / min in the first pass, 200-400 m / min in the second pass, and 400-800 m / min in the other passes. The first pass is controlled with micro-edge waviness, i.e., the waviness displayed by the shape meter is 10-20I. The other passes are controlled with small edge waviness, i.e., the waviness displayed by the shape meter is 25-35I.

2. The cold rolling method for ultra-high grade non-oriented silicon steel according to claim 1, characterized in that: If the second rolling process in the second cold rolling production method of step two consists of two rolling passes, then step (3) in the production method of the second rolling process is omitted, and the process jumps directly from (2) to (4). The roughness of the work rolls used in the first pass is 0.6-1.0μm; the roughness of the work rolls used in the last pass is 0.15-0.4μm; the absolute reduction of all passes in the second rolling stroke is 0.05-0.3mm, and the rolling speed of each pass is between 200-600m / min; a steel sleeve is placed on the coiler before the last pass rolling; during the first pass rolling, the speed increase process is carried out intermittently, i.e., speed increase-hold-speed increase-hold... gradually, and the speed is held once every 30-80m increase.

3. The cold rolling method for ultra-high grade non-oriented silicon steel according to claim 1, characterized in that: The emulsion temperature in the first rolling pass is 45-60℃, and the emulsion concentration is 3-5%.

4. The cold rolling method for ultra-high grade non-oriented silicon steel according to claim 1, characterized in that: The emulsion temperature in the second rolling pass is 45-60℃, and the emulsion concentration is 6-8%.

Images