High-efficiency non-oriented silicon steel for variable frequency compressor and manufacturing method thereof

Abstract

The application provides a high-efficiency non-oriented silicon steel for a variable frequency compressor and a manufacturing method thereof, wherein, compared with the prior art, the last machine frame of acid continuous rolling is used as a skin pass mill, and influence of switching of an emulsion system on production efficiency is avoided; welding wire is not added, and welding quality is ensured; the strip steel does not need to be inductively heated before cold rolling, and cost is saved; the finished product is cut once, and the yield is improved, and the production efficiency is high; the composition is simple, and the cost is low; the rolling speed reaches 600-800 m / min, the longitudinal thickness fluctuation is within ±3 mu m, the same plate difference is less than or equal to 5 mu m, and the requirements of a stator and a rotor for a high-efficiency variable frequency compressor are met.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of non-oriented silicon steel, and particularly relates to a high-efficiency non-oriented silicon steel for a variable-frequency compressor and a manufacturing method thereof. BACKGROUND

[0002] The high-efficiency non-oriented silicon steel can be used to produce a motor core of a variable-frequency compressor. With the development of global manufacturing industry, green production and the compressor field, high efficiency and energy saving have become a consensus in the development of the compressor industry. Therefore, the market demand for the high-efficiency non-oriented silicon steel is increasing.

[0003] The traditional high-efficiency non-oriented silicon steel is mainly rolled by a 20-roll single-stand rolling mill after edge cutting after normalizing. The low rolling efficiency causes insufficient production capacity, and the production cost is high. Normalizing and the finished product each perform edge cutting once, and in order to eliminate edge waves, the edge cutting amount is large, causing a low material yield. Another approach is to produce by a continuous rolling mill after edge cutting after normalizing. However, the welding machine of the continuous rolling mill needs to add welding wires for welding, and the strip steel needs to be inductively heated before rolling. The cost is high, and the last stand adopts a large reduction mode during rolling. The emulsion system needs to be switched, which affects production.

[0004] A Chinese patent with the publication number CN 112501407 A disclosed on March 16, 2021 discloses a high-efficiency non-oriented silicon steel plate for a variable-frequency compressor and a production method thereof. The disclosure discloses that the composition of the cast blank is 2.8%≤(Si+Als+Mn)%≤4.0%, (V+Nb+Ti+N+S+C)%≤0.012%. The continuous casting blank is heated and kept warm, and then hot-rolled and coiled. Normalizing and keeping warm are performed, and then cooling is performed. The cooling speed V satisfies: V≤105×(V+Nb+Ti+N+S+C)%. After pickling, cold rolling is performed to a thickness of 0.25 mm and above. Recrystallization annealing and keeping warm are performed by using a continuous annealing furnace. The steel strip tension F in the furnace satisfies: 30×

[0005] (Si+Als+Mn)%≤F≤15×d. A coating layer is coated, and the high-efficiency non-oriented silicon steel plate for the variable-frequency compressor is obtained. However, how to improve the production efficiency is not disclosed. SUMMARY

[0006] The application aims to provide a high-efficiency non-oriented silicon steel for a variable-frequency compressor and a manufacturing method thereof. Through component design, process and parameter control, the last stand of the acid continuous rolling mill is used as a flattening mill, which avoids the influence of switching the emulsion system on the production efficiency. The welding quality can be ensured without adding welding wires. The strip steel does not need to be inductively heated before cold rolling. Only the finished product is cut once, the material yield is improved, and the cost is saved.

[0007] The specific technical scheme of the application is as follows:

[0008] A high-efficiency non-oriented silicon steel for variable frequency compressor comprises the following components by mass percentage:

[0009] C≤0.0025%, Si 2.0%-2.5%, Al 0.3%-0.45%, Mn 0.15-0.35%, S≤0.0035%, P≤0.04%, N≤0.002%, Ti≤0.002%, Cu≤0.03%, Cr≤0.03%, Ni≤0.02%, the balance being Fe and inevitable impurities.

[0010] The microstructure of the high-efficiency non-oriented silicon steel for variable frequency compressor is ferrite.

[0011] The high-efficiency non-oriented silicon steel for variable frequency compressor has a cold-rolled finished product thickness of 0.345-0.350 mm, and a strip breaking rate of ≤2 times per 10,000 tons; after cold rolling, the plate shape is good, the plate shape value is ≤7I, the longitudinal thickness fluctuation is ±3 μm, and the transverse same plate difference after edge cutting is ≤5 μm.

[0012] The high-efficiency non-oriented silicon steel for variable frequency compressor has an iron loss of ≤2.8 W / kg and a magnetic induction of ≥1.7 T.

[0013] The application provides a manufacturing method of the high-efficiency non-oriented silicon steel for variable frequency compressor, which comprises hot rolling, normalizing, cold rolling and annealing.

[0014] In the hot rolling, the heating furnace has a furnace time of 160-220 minutes, a heating temperature of 990-1130 DEG C, and an RT2 outlet temperature of 965-1050 DEG C; in order to reduce the slab temperature drop, the rough rolling adopts a 1+5 mode, i.e., R1 is rolled for one pass, R2 is rolled for five passes, FT7 is at a temperature of 850-900 DEG C, and the coiling temperature is 560-580 DEG C.

[0015] In the hot rolling, the thickness of the hot rolling raw material is controlled to be 2.1-2.3 mm, and in order to ensure the same plate difference of the finished product, the hot coil convexity is required to be 15-35 μm, and the wedge shape is controlled to be within ±15 μm.

[0016] In the normalizing, the normalizing speed is 40-58 m / min, and the temperature is 920-950 DEG C; the acid liquid concentration of the 4# tank is 200-280 g / l, and the acid liquid temperature is 75-85 DEG C; and the normalizing line is not edge-cut.

[0017] The cold rolling is produced by using an acid continuous rolling mill set, and the following parameters are mainly controlled: the welding quality is ensured without using welding wire, and the welding parameters are as follows: the welding speed is 3.6-4.2 m / min, the welding power is 9.6-10.8 kW, the preheating power is 15-22.5 kW, the welding seam is preheated, after the welding is completed, the welding seam area is post-heated for the first time, the first post-heating power is 22.5-30 kW, after the first post-heating treatment, the welding seam area is post-heated for the second time by using an auxiliary heating device, the second post-heating temperature is 500-600℃, and the heating time is 30-40 s;

[0018] Since the hot coil has been shot-blasted and pickled, the acid continuous rolling stretch-reducing extension rate and the bending unit and straightening unit roll gap value are reduced, the extension rate is 0.5-1.0%, the roll gap value of the 1# bending unit is 15-20 mm, the roll gap value of the 2# bending unit is 10-16 mm, and the roll gap value of the straightening unit is 8-15 mm, and the main purpose is to improve the plate shape. In order to prevent the welding seam from breaking, the stretch-reducing mode through the welding seam is non-stretch-reducing. The acid concentration is reduced, and the acid concentrations in the three pickling tanks are respectively set to 30-50 g / l, 60-90 g / l and 100-130 g / l, the acid temperatures in the three pickling tanks are 60-75℃, and the pickling speed is 150-200 m / min.

[0019] In order to reduce the transverse plate difference: the work rolls of the first and second stands of the continuous rolling mill are chamfered. The chamfer height of the work roll is 0.3-0.5 mm, and the chamfer length is 275-300 mm. The reduction rate of each stand and the inter-stand tension are as follows:

[0020] After pickling, the edges are not cut, which can prevent edge cracks from occurring during rolling and causing the strip to break. The induction heater is not needed at the entrance of the rolling mill, which saves energy consumption and reduces cost.

[0021] The main deformation is completed by the first four stands, and the fifth stand is used as a temper mill, which avoids the influence of switching the emulsion system on production efficiency. The reduction rates of the first, second, third, fourth and fifth cold rolling mills are respectively 38%-40%, 36%-39%, 28%-31%, 24%-27% and 0.5%-1%. In order to reduce the rolling force, small-diameter work rolls are used for the first to fourth work rolls, and the diameters of the work rolls of the first and second stands are ≤400 mm, and the diameters of the work rolls of the third and fourth stands are ≤420 mm. In order to reduce the rolling force, work rolls with low roughness are used, but at the same time, the roughness is prevented from being too low to cause slipping, and the roughness of the work rolls of the first and second stands is set to 0.8-1.2 μm, and the roughness of the work rolls of the third and fourth stands is set to 0.4-0.6 μm. In order to improve the lubrication performance and reduce the rolling force while preventing slipping, the emulsion concentration is controlled to be 2.6-3.0%.

[0022] To prevent strip breakage during rolling, the tension between the stands was reduced. The unit tension between the first and second cold rolling mills was 120-130 N / mm. 2 The unit tension between the second and third cold rolling mills is 130-140 N / mm. 2 The unit tension between the third and fourth cold rolling mills is 140-160 N / mm. 2 The unit tension between the fourth and fifth cold rolling mills is 150-170 N / mm. 2 The unit tension at the outlet is 40-50 N / mm. 2 .

[0023] Compared to other silicon steel continuous rolling mills, this unit has a larger roll diameter, resulting in greater rolling force and making it difficult to control edge waviness. Edge waviness is controlled by increasing the bending force of the fourth stand work roll, but excessive bending force can easily cause excessive tensile stress on the strip edge and lead to strip breakage. This invention controls the bending force of the intermediate roll to 480-720KN and the bending force of the fourth stand work roll to 400-600KN.

[0024] The cold rolling process involves a rolling speed of 600-800 m / min, with longitudinal thickness fluctuations within ±3 μm and plate-to-plate thickness differences ≤5 μm, meeting the requirements for stators and rotors in high-efficiency variable frequency compressors.

[0025] The cold-rolled product has a thickness of 0.345-0.350 mm and a strip breakage rate of ≤2 times / 10,000 tons. After cold rolling, the sheet shape is good, with a sheet shape value of ≤7I, longitudinal thickness fluctuation of ±3μm, and transverse thickness difference of ≤5μm after edge trimming.

[0026] The annealing is performed in a horizontal annealing furnace at a speed of 100-150 m / min and a temperature of 930-950℃. The surface coating is applied after annealing.

[0027] The high-efficiency non-oriented silicon steel used in the manufactured variable frequency compressors has an iron loss of ≤2.8W / kg and a magnetic induction of ≥1.7T.

[0028] The design concept of this invention is as follows:

[0029] C, S, N, Cr, Cu, Ni, and Ti are harmful elements in silicon steel, so their levels should be kept as low as possible. Si and Al play important roles in magnetism; as Si and Al content increases, resistivity increases and iron loss decreases, but magnetic induction also decreases. However, the effect of adding Al on the strength and hardness of steel is not as significant as that of Si. Adding Al causes less lattice distortion in iron than adding Si, with a smaller increase in brittleness and a lower increase in hardness. Therefore, adding Al can reduce the strength of steel while maintaining magnetic properties, which is beneficial for production and post-processing. Mn partially forms MnS compounds with S. The solid solubility of MnS in the γ phase is lower than in the α phase, thus promoting MnS coarsening and grain growth. Part of it exists in solid solution, increasing hardness. Mn also improves stamping properties and machinability, reducing adhesion during stamping. P increases resistivity and reduces iron loss, but excessive P content can lead to embrittlement.

[0030] In the production process of this invention, the absence of welding wire ensures weld quality and controls welding parameters; the main deformation is completed in the first four stands, with the last stand used as a leveling machine, avoiding the impact of switching emulsion systems on production efficiency; induction heating is not required, saving energy and reducing costs; no edge trimming during rolling avoids edge cracking and strip breakage during the rolling process; only one edge trimming is performed on the finished product, requiring a smaller hot-rolled coil width for the same order width, resulting in a higher yield; the S4 bending roll force is controlled to prevent edge waviness; small roll diameter and low roughness reduce rolling force; reduced tension prevents strip breakage; the rolling speed is 600-800m / min, and the transverse thickness difference after edge trimming is ≤5μm, with longitudinal thickness fluctuation of ±3μm, meeting the requirements of stator and rotor for high-efficiency variable frequency compressors.

[0031] Compared with existing technologies, the acid continuous rolling mill stand of this invention is used as a leveling machine, avoiding the impact of switching emulsion systems on production efficiency. The absence of welding wire ensures weld quality, and the strip does not require induction heating before cold rolling, saving costs. Only one edge trimming is required for the finished product, improving yield and increasing production efficiency. Furthermore, the composition is simple and the cost is low. Rolling speeds reach 600-800 m / min, with longitudinal thickness fluctuations within ±3 μm and plate thickness differences ≤5 μm, meeting the requirements for stators and rotors in high-efficiency variable frequency compressors. Attached Figure Description

[0032] Figure 1 The image shows the metallographic structure of Example 1, which is ferrite. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Examples 1-3

[0035] A high-efficiency non-oriented silicon steel for variable frequency compressors comprises the following components by mass percentage as shown in Table 1, where the balance not shown in Table 1 is Fe and unavoidable impurities.

[0036] Comparative Examples 1-3

[0037] A high-efficiency non-oriented silicon steel for variable frequency compressors comprises the following components by mass percentage as shown in Table 1, where the balance not shown in Table 1 is Fe and unavoidable impurities.

[0038] Table 1. Composition (%) of high-efficiency non-oriented silicon steel in each embodiment and comparative example

[0039] Examples C Si Als Mn S P N Ti Cu Cr Ni Example 1 0.0020 2.15 0.35 0.18 0.0028 0.022 0.0018 0.001 0.024 0.028 0.011 Example 2 0.0018 2.35 0.4 0.25 0.0019 0.018 0.0005 0.0011 0.025 0.029 0.018 Example 3 0.0015 2.45 0.45 0.33 0.0025 0.032 0.002 0.0009 0.027 0.024 0.012 Comparative Example 1 0.0023 1.85 0.356 0.155 0.0030 0.028 0.0014 0.0008 0.026 0.025 0.008 Comparative Example 2 0.0020 2.86 0.422 0.256 0.0025 0.030 0.0008 0.0013 0.028 0.027 0.01 Comparative Example 3 0.0018 1.00 0.226 0.324 0.0023 0.020 0.0010 0.0011 0.023 0.024 0.01

[0040] The manufacturing methods of high-efficiency non-oriented silicon steel for variable frequency compressors in each embodiment and comparative example include: hot rolling, normalizing, cold rolling, and annealing;

[0041] The hot rolling process involves a furnace time of 160-220 minutes, a heating temperature of 990-1130℃, an RT2 outlet temperature of 965-1050℃, and a roughing process using a 1+5 mode to reduce slab temperature drop, i.e., R1 is rolled in 1 pass, R2 is rolled in 5 passes, FT7 temperature is 850-900℃, and coiling temperature is 560-580℃.

[0042] The hot-rolled material has a thickness of 2.1-2.3 mm, a hot-roll crown of 15-35 μm, and a wedge shape controlled within ±15 μm.

[0043] The normalizing process is carried out at a rate of 40-58 m / min and a temperature of 920-950℃. The acid concentration in tank #4 is 200-280 g / L, and the acid temperature is 75-85℃. The normalizing line is not trimmed.

[0044] The cold rolling process employs pickling and continuous rolling. No welding wire is added during welding. The welding speed is 3.6-4.2 m / min, the welding power is 9.6-10.8 kW, the preheating power is 15-22.5 kW, and the initial post-heating power is 22.5-30 kW. Preheating is applied to the weld area. After welding, the weld area undergoes initial post-heating. Following the initial post-heating, auxiliary heating equipment is used for a second post-heating of the weld area. The second post-heating temperature is 500-600℃, and the heating time is 30-40 seconds.

[0045] Since the hot-rolled coils have already undergone shot blasting and pickling during normalizing, the elongation rate and the roll gap values ​​for bending and straightening units are reduced during continuous pickling and straightening. The elongation rate is 0.5-1.0%, the roll gap value for bending unit #1 is 15-20mm, the roll gap value for bending unit #2 is 10-16mm, and the roll gap value for straightening unit is 8-15mm. The main purpose is to improve the strip shape. To prevent weld strip breakage, the weld straightening mode is changed to no straightening. The acid concentration is reduced, with the acid concentrations in the three pickling tanks set to 30-50g / l, 60-90g / l, and 100-130g / l, respectively. The temperature of the acid in the three pickling tanks is 60-75℃, and the pickling speed is 150-200m / min.

[0046] To reduce transverse sheet thickness variation, chamfered rolls are used on the work rolls of the first and second stands of the continuous rolling mill. The chamfer height of the work rolls is 0.3-0.5 mm, and the chamfer length is 275-300 mm. The reduction rate of each stand and the tension between stands are as follows:

[0047] Not trimming the edges after pickling prevents edge cracking and strip breakage during rolling. Induction heaters are not required at the mill inlet, saving energy and reducing costs.

[0048] The main deformation is completed by the first four stands, with the fifth stand used as a leveling machine to avoid impacting production efficiency by switching emulsion systems. The reduction rates for the first, second, third, fourth, and fifth cold rolling mills are 38%-40%, 36%-39%, 28%-31%, 24%-27%, and 0.5%-1%, respectively. To reduce rolling force, small-diameter work rolls are used for S1-S4: S1 and S2 work roll diameters ≤400mm, and S3 and S4 work roll diameters ≤420mm. Low-roughness work rolls are required to reduce rolling force, but slippage must be prevented due to excessively low roughness. The roughness of the work rolls for the first and second cold rolling mills is set at 0.8-1.2μm, and the roughness of the work rolls for the third and fourth cold rolling mills is set at 0.4-0.6μm. To improve lubrication performance and reduce rolling force, the emulsion concentration is controlled at 2.6-3.0%.

[0049] To prevent strip breakage during rolling, the tension between the stands was reduced. The unit tension between the first and second cold rolling mills was 120-130 N / mm. 2The unit tension between the second and third cold rolling mills is 130-140 N / mm. 2 The unit tension between the third and fourth cold rolling mills is 140-160 N / mm. 2 The unit tension between the fourth and fifth cold rolling mills is 150-170 N / mm. 2 The unit tension at the outlet is 40-50 N / mm. 2 The cold rolling speed is 600-800m / min, the longitudinal thickness fluctuation is within ±3μm, and the difference between the same plate is ≤5μm, which meets the requirements of stator and rotor for high-efficiency variable frequency compressors.

[0050] Compared to other silicon steel continuous rolling mills, this unit has a larger roll diameter, resulting in greater rolling force and making it difficult to control edge waviness. Edge waviness is controlled by increasing the bending force of the work roll and intermediate roll of the fourth stand. However, if the bending force is too large, it can easily cause excessive tensile stress on the edge of the strip and lead to strip breakage. The bending force of the intermediate roll is controlled at 480-720KN, and the bending force of the work roll is controlled at 400-600KN.

[0051] The cold-rolled product has a thickness of 0.345-0.350 mm.

[0052] The annealing is performed in a bedroom annealing furnace at a speed of 100-150 m / min and a temperature of 930-950℃, resulting in a surface coating after annealing.

[0053] The main manufacturing parameters of each embodiment and comparative example are shown in Tables 2-6.

[0054] Table 2 Hot rolling parameters for each embodiment and comparative example

[0055]

[0056]

[0057] Table 3. Normalization parameters for each embodiment and comparative example.

[0058]

[0059] Table 4 Cold rolling parameters for each embodiment and comparative example

[0060]

[0061]

[0062]

[0063] In Comparative Example 1, during acid continuous rolling with edge trimming, multiple edge cracks occurred at the hardened edge, affecting the annealing process and requiring repair at the recoiling unit, increasing costs and causing width defects. The low elongation of the tension leveler resulted in poor sheet shape, leading to large edge waviness after rolling (sheet shape value 8I). Excessive welding speed resulted in numerous weld cracks. In Comparative Example 2, the tension between the first and second cold rolling mills, the second and third cold rolling mills, the third and fourth cold rolling mills, and the fourth and fifth cold rolling mills was high. The chamfer height of the work rolls on the first and second stands was excessive, easily causing strip breakage accidents during rolling, with a breakage rate reaching 50 times / 10,000 tons. High roughness of the work rolls from the first to fourth stands resulted in excessive rolling force. The low concentration of the emulsion in the large tank caused excessive rolling force and poor sheet shape. Low welding power resulted in numerous weld cracks. In Comparative Example 3, the acid concentration in tank #3 was too high, resulting in blackening of the over-pickled plate surface; the bending force of the work rolls and intermediate rolls in the fourth stand was too small, resulting in large edge waviness of the finished product and a plate shape value ≥20I; the diameter of the work rolls in S1-S4 was too large, resulting in excessive rolling force and poor plate shape; the low roughness of the work rolls in the first to fourth stands caused slippage and scratches during rolling; the chamfer height of the work rolls in the first and second stands was too small, and the plate difference did not meet the requirements; the secondary heating time was short, the stress was not eliminated, and the number of weld cracks was high.

[0064] Table 5. Impact of each embodiment and comparative example on cold rolling production and quality.

[0065]

[0066] Table 6 Annealing parameters for each embodiment and comparative example

[0067]

[0068] The high-efficiency non-oriented silicon steel produced in the above embodiments and comparative examples was tested, as shown in Table 7. Iron loss and magnetic induction were tested according to GB / T 3655-2022 standard. In-plate difference was measured using an offline in-plate difference measuring instrument.

[0069] Table 7 shows the magnetic properties and differences between the non-oriented silicon steels in each embodiment and comparative example.

[0070]

[0071] Comparative Example 1: Low normalizing temperature and fast annealing speed led to high iron loss; high hot-rolled coil crown resulted in large plate-to-plate difference. Comparative Example 2: High hot-rolling temperature led to coarse grains; low annealing temperature led to high iron loss; large hot-rolled coil wedge shape led to large plate-to-plate difference. Comparative Example 3: High hot-rolling temperature led to coarse grains and high iron loss; low annealing speed affected production output; low chamfer height of cold-rolled work rolls led to large plate-to-plate difference.

[0072] The data underlined above do not meet the requirements of this invention.

[0073] The above description of the embodiments is intended to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A high-efficiency non-oriented silicon steel for a variable frequency compressor, characterized in that, The high-efficiency non-oriented silicon steel for the variable frequency compressor comprises the following components by mass percentage: C≤0.0025%, Si 2.0%-2.5%, Als 0.3%-0.45%, Mn 0.15-0.35%, S≤0.0035%, P≤0.04%, N≤0.002%, Ti≤0.002%, Cu≤0.03%, Cr≤0.03%, Ni≤0.02%, with the balance being Fe and unavoidable impurities; The manufacturing method of the high-efficiency non-oriented silicon steel for the variable frequency compressor includes the following steps: Hot rolling, normalizing, cold rolling, and annealing; The normalizing process is carried out at a rate of 40-58 m / min and a temperature of 920-950℃; the normalizing line is not trimmed. In the cold rolling mill, the work rolls of the first and second stands of the continuous rolling mill are chamfered rolls, with a chamfer height of 0.3-0.5mm and a chamfer length of 275-300mm; the bending force of the work rolls of the fourth stand is controlled at 400-600KN. Cold rolling speed is 600-800 m / min; produced using a continuous acid rolling mill. The annealing process is carried out at a speed of 100-150 m / min and a temperature of 930-950℃. The variable frequency compressor uses high-efficiency non-oriented silicon steel with a cold-rolled finished product thickness of 0.345-0.350mm, a cold-rolled strip breakage rate of ≤2 times / 10,000 tons, a plate shape value of ≤7I, a longitudinal thickness fluctuation of ±3μm, and a transverse difference of ≤5μm after trimming. The microstructure of the high-efficiency non-oriented silicon steel used in the variable frequency compressor is ferrite.

2. The high-efficiency non-oriented silicon steel for variable frequency compressors according to claim 1, characterized in that, The variable frequency compressor uses high-efficiency non-oriented silicon steel with an iron loss ≤2.8W / kg and a magnetic induction ≥1.7T.

3. A method for manufacturing high-efficiency non-oriented silicon steel for a variable frequency compressor as described in claim 1 or 2, comprising the following steps: Hot rolling, normalizing, cold rolling, and annealing; The normalizing process is carried out at a rate of 40-58 m / min and a temperature of 920-950℃; the normalizing line is not trimmed. In the cold rolling mill, the work rolls of the first and second stands of the continuous rolling mill are chamfered rolls, with a chamfer height of 0.3-0.5mm and a chamfer length of 275-300mm; the bending force of the work rolls of the fourth stand is controlled at 400-600KN. Cold rolling speed: 600-800 m / min; The annealing process is carried out at a speed of 100-150 m / min and a temperature of 930-950℃.

4. The manufacturing method according to claim 3, characterized in that, The hot rolling process involves a furnace time of 160-220 minutes, a heating temperature of 990-1130℃, an RT2 outlet temperature of 965-1050℃, an FT7 temperature of 850-900℃, and a coiling temperature of 560-580℃. The hot-rolled coil crown is 15-35μm, and the wedge shape is controlled within ±15μm.

5. The manufacturing method according to claim 3, characterized in that, The cold rolling process does not use welding wire, and the welding parameters are as follows: welding speed is 3.6-4.2 m / min, welding power is 9.6-10.8 kW, preheating power is 15-22.5 kW, and initial postheating power is 22.5-30 kW; after the initial postheating treatment, the weld area is subjected to secondary postheating at a temperature of 500-600℃ for 30-40 seconds.

6. The manufacturing method according to claim 3, characterized in that, The annealing is performed in a horizontal annealing furnace.

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