Efficient non-oriented silicon steel for inverter compressor and manufacturing method of efficient non-oriented silicon steel

Abstract

According to the efficient non-oriented silicon steel for the inverter compressor and the manufacturing method of the efficient non-oriented silicon steel, compared with the prior art, an acid continuous rolling tail rack serves as a temper mill, and the situation that the production efficiency is affected by switching of an emulsion system is avoided. The welding quality can be guaranteed without adding welding wires, induction heating of strip steel is not needed before cold rolling, and cost is saved. And the finished product is cut once, so that the yield is improved, and the production efficiency is high. And the components are simple, and the cost is low. And the rolling speed reaches 600-800m / min, the longitudinal thickness fluctuation is within + / -3mu m, the same plate difference is less than or equal to 5mu m, and the stator and rotor requirements for the high-efficiency variable-frequency compressor are met.

Description

Technical Field

[0001] The invention belongs to the technical field of non-oriented silicon steel, and in particular relates to a high-efficiency non-oriented silicon steel for a variable frequency compressor and a manufacturing method thereof. Background Art

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

[0003] Traditional high-efficiency non-oriented silicon steel is mainly produced by hot-rolled coils that are normalized and trimmed and then rolled using a 20-roll single-stand mill. The low rolling efficiency results in insufficient production capacity and high production costs. The normalization and finished products are trimmed once each, and in order to eliminate the edge waves, the trimming amount is large, resulting in a low yield rate. Another way is to use a continuous rolling mill to produce the hot-rolled coils after normalization and trimming, but the continuous rolling mill welder needs to add welding wire for welding, and the strip needs to be induction heated before rolling, which is costly. In addition, the last stand uses a large pressure reduction mode during rolling, and the emulsion system needs to be switched off, which affects production.

[0004] The Chinese patent with publication number CN 112501407 A published on March 16, 2021, discloses a non-oriented silicon steel sheet for a high-efficiency variable frequency compressor and a production method thereof. It discloses that the composition of the ingot is 2.8%≤(Si+Als+Mn)%≤4.0%, (V+Nb+Ti+N+S+C)%≤0.012%; the continuous casting ingot is heated and kept warm, and then hot rolled and coiled; normalized and kept warm, and then cooled, and the cooling rate V satisfies: V≤105×(V+Nb+Ti+N+S+C)%; after pickling, cold rolled once to a thickness of 0.25mm and above; a continuous annealing furnace is used for recrystallization annealing and insulation, and the steel strip tension F in the furnace satisfies: 30×

[0005] (Si+Als+Mn)%≤F≤15×d; coating, thus obtaining a non-oriented silicon steel sheet for high-efficiency variable frequency compressor. However, it does not disclose how to improve production efficiency. Summary of the invention

[0006] The object of the present invention is to provide a high-efficiency non-oriented silicon steel for variable frequency compressor and a manufacturing method thereof. Through component design, process and parameter control, the acid continuous rolling end frame is used as a leveling machine, thereby avoiding the switching of the emulsion system to affect the production efficiency; the weld quality can be guaranteed without adding welding wire, the strip does not need to be induction heated before cold rolling, and the finished product only needs to be trimmed once, thereby improving the yield rate and saving costs.

[0007] The specific technical solutions of the present invention are as follows:

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

[0009] 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%, and the balance is Fe and unavoidable impurities.

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

[0011] The variable frequency compressor uses high-efficiency non-oriented silicon steel, the cold-rolled finished 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 plate shape is good, the plate shape value is ≤7I, the longitudinal thickness fluctuation is ±3μm, and the transverse plate difference after trimming is ≤5μm;

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

[0013] The present invention provides a method for manufacturing high-efficiency non-oriented silicon steel for a variable frequency compressor, comprising hot rolling, normalizing, cold rolling, and annealing;

[0014] For the hot rolling, the hot rolling heating furnace is in the furnace for 160-220 minutes, the heating temperature is 990-1130°C, the RT2 outlet temperature is 965-1050°C, and in order to reduce the temperature drop of the slab, the rough rolling adopts the 1+5 mode, that is, R1 rolling is 1 pass, R2 rolling is 5 passes, FT7 temperature is 850-900°C, and the coiling temperature is 560-580°C.

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

[0016] The normalization process has a normalization speed of 40-58 m / min and a temperature of 920-950° C.; the acid concentration of tank 4 is 200-280 g / l and the acid temperature is 75-85° C.; and the normalization line is not trimmed.

[0017] The cold rolling is produced by an acid continuous rolling unit, and the main control is as follows: the quality of the weld can be guaranteed without using welding wire, and the welding parameters are as follows: the welding speed is 3.6-4.2m / min, the welding power is 9.6-10.8kW, the preheating power is 15-22.5kW, the weld is preheated, and after welding, the weld area is initially post-heated, the initial post-heating power is 22.5-30kW, and after the initial post-heating treatment, the weld area is secondary post-heated using an auxiliary heating device, the secondary post-heating temperature is 500-600°C, and the heating time is 30-40s;

[0018] Since the hot coil has been shot blasted and pickled in normalizing, the elongation of the acid continuous rolling straightening and the roll gap value of the bending unit and the straightening unit are reduced. The elongation is 0.5-1.0%, the roll gap value of the 1# bending unit is 15-20mm, the roll gap value of the 2# bending unit is 10-16mm, and the roll gap value of the straightening unit is 8-15mm. The main purpose is to improve the plate shape. In order to prevent the weld from breaking, the straightening weld mode is no straightening. Reduce the acid concentration. The concentrations of the acid in the three pickling tanks are 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.

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

[0020] No trimming after pickling can prevent edge cracking and strip breakage during rolling. No induction heater is required at the mill entrance, saving energy and reducing costs.

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

[0022] In order to prevent the strip from breaking during rolling, the tension between the stands is reduced. The unit tension between the first and second cold rolling mills is 120-130N / mm 2 , the unit tension between the second and third cold rolling mills is 130-140N / mm 2 The unit tension between the third and fourth cold rolling mills is 140-160N / mm 2 The unit tension between the fourth and fifth cold rolling mills is 150-170N / mm 2 , export unit tension 40-50N / mm 2 .

[0023] Compared with other silicon steel dedicated continuous rolling mills, this unit has a larger roll diameter, resulting in a large rolling force and edge waves that are difficult to control. The edge waves are controlled by increasing the bending force of the working rolls of the fourth frame, but too much bending force can easily cause excessive tensile stress on the edge of the strip and cause strip breakage. The present invention controls: the bending force of the intermediate roll is controlled at 480-720KN, and the bending force of the working rolls of the fourth frame is controlled at 400-600KN.

[0024] The cold rolling has a rolling speed of 600-800 m / min, a longitudinal thickness fluctuation within ±3 μm, and a difference of ≤5 μm for the same plate, which meets the requirements for stators and rotors for 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 plate shape is good, the plate shape value is ≤7I, the longitudinal thickness fluctuation is ±3μm, and the transverse plate difference after trimming is ≤5μm.

[0026] The annealing is carried out in a horizontal annealing furnace at a speed of 100-150 m / min and a temperature of 930-950° C. The surface is coated after annealing.

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

[0028] The design ideas of the present invention are as follows:

[0029] C, S, N, Cr, Cu, Ni, and Ti are harmful elements in silicon steel, so they should be controlled as low as possible. Si and Al play an important role in magnetism. As the content of Si and Al increases, the resistivity increases, the iron loss decreases, but the magnetic induction also decreases. However, the effect of adding Al on the strength and hardness of steel is not as obvious as that of Si. Adding Al makes the lattice distortion of iron lighter than adding Si, the degree of brittleness increase is small, and the degree of hardness increase is lower. Therefore, adding Al can reduce the strength of steel while ensuring magnetic properties, and can be used in production and post-processing. A part of Mn forms MnS compound with S. The solid solubility of MnS in the γ phase is smaller than that in the α phase, so it can promote the coarsening of MnS, which is conducive to grain growth; a part of it can increase hardness in the form of solid solution. Mn can also improve the punching and cutting properties and reduce the bonding phenomenon during punching. P increases the resistance and reduces the iron loss, but if the P content is too high, embrittlement will occur.

[0030] In the production of the present invention, welding wire is not used to ensure the quality of the weld and control welding parameters; the main deformation is completed in the first four frames, and the last frame is used as a leveling machine, avoiding the switching of the emulsion system to affect the production efficiency; no induction heating is required, saving energy consumption and reducing costs; no trimming and rolling are performed to avoid edge cracks and broken strips during the rolling process; the finished product is trimmed only once, the hot coil width required for the same order width is smaller, and the yield rate is higher; the S4 bending roll force is controlled to control the edge waves; the small roll diameter and low roughness reduce the rolling force; the tension is reduced to prevent broken strips; the rolling speed is 600-800m / min, the lateral same-plate difference of the finished product after trimming is ≤5μm, and the longitudinal thickness fluctuation is ±3μm, which meets the requirements of the stator and rotor for high-efficiency variable frequency compressors.

[0031] Compared with the prior art, the acid continuous rolling mill stand of the present invention is used as a leveling machine, avoiding the influence of the switching emulsion system on the production efficiency. The quality of the weld can be guaranteed without adding welding wire, and the strip does not need to be induction heated before cold rolling, which saves costs. The finished product is trimmed only once, which improves the yield rate and has high production efficiency. Moreover, the composition is simple and the cost is low. The rolling speed reaches 600-800m / min, the longitudinal thickness fluctuation is within ±3μm, and the difference between the same plate is ≤5μm, which meets the requirements of the stator and rotor for high-efficiency variable frequency compressors. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is the metallographic structure diagram of Example 1, and the structure is ferrite. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] Example 1-Example 3

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

[0036] Comparative Example 1-Comparative Example 3

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

[0038] Table 1 Composition of high-efficiency non-oriented silicon steel in various embodiments and comparative examples (%)

[0039] Example 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 method of high-efficiency non-oriented silicon steel for variable frequency compressor of each embodiment and comparative example comprises: hot rolling, normalizing, cold rolling and annealing;

[0041] For the hot rolling, the hot rolling heating furnace is in the furnace for 160-220 minutes, the heating temperature is 990-1130°C, the RT2 outlet temperature is 965-1050°C, and in order to reduce the temperature drop of the slab, the rough rolling adopts the 1+5 mode, that is, R1 rolling is 1 pass, R2 rolling is 5 passes, FT7 temperature is 850-900°C, and the coiling temperature is 560-580°C.

[0042] In the hot rolling, the hot rolled raw material thickness is 2.1-2.3 mm, the hot coil convexity is 15-35 μm, and the wedge shape is controlled within ±15 μm.

[0043] The normalization process has a normalization speed of 40-58 m / min and a temperature of 920-950° C. The acid concentration of tank 4 is 200-280 g / l, the acid temperature is 75-85° C., and the normalization line is not cut.

[0044] The cold rolling is produced by pickling and continuous rolling. No welding wire is added during welding. The welding speed is 3.6-4.2m / min, the welding power is 9.6-10.8kW, the preheating power is 15-22.5kW, and the initial post-heating power is 22.5-30kW. The weld is preheated, and after welding, the weld area is initially post-heated. After the initial post-heating treatment, the weld area is post-heated for a second time using an auxiliary heating device. The temperature of the second post-heating is 500-600°C, and the heating time is 30-40s.

[0045] Since the hot coil has been shot blasted and pickled in normalizing, the elongation of the acid continuous rolling straightening and the roll gap value of the bending unit and the straightening unit are reduced. The elongation is 0.5-1.0%, the roll gap value of the 1# bending unit is 15-20mm, the roll gap value of the 2# bending unit is 10-16mm, and the roll gap value of the straightening unit is 8-15mm. The main purpose is to improve the plate shape. In order to prevent the weld from breaking, the straightening weld mode is no straightening. Reduce the acid concentration. The concentrations of the acid in the three pickling tanks are 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] In order to reduce the horizontal plate difference: the working rolls of the first and second stands of the continuous rolling mill are chamfered. The chamfer height of the working roll is 0.3-0.5mm, and the chamfer length is 275-300mm. The reduction rate of each stand and the tension between stands are as follows:

[0047] No trimming after pickling can prevent edge cracking and strip breakage during rolling. No induction heater is required at the mill entrance, saving energy and reducing costs.

[0048] The main deformation is completed by the first four stands, and the fifth stand is used as a leveling machine to avoid the impact of switching the emulsion system on production efficiency. The reduction rates of the first, second, third, fourth and fifth cold rolling mills are 38%-40%, 36%-39%, 28%-31%, 24%-27% and 0.5%-1% respectively. In order to reduce the rolling force, the S1-S4 working rolls use small roll diameters, the diameters of the S1 and S2 working rolls are ≤400mm, and the diameters of the S3 and S4 working rolls are ≤420mm. In order to reduce the rolling force, working rolls with low roughness need to be used, but at the same time, it is necessary to prevent the roughness from being too low and causing slipping. The roughness of the working rolls of the first and second cold rolling mills is set to 0.8-1.2μm, and the roughness of the working rolls of the third and fourth cold rolling mills is set to 0.4-0.6μm. In order to improve lubrication performance and reduce rolling force, the emulsion concentration is controlled at 2.6-3.0%.

[0049] In order to prevent the strip from breaking during rolling, the tension between the stands is reduced. The unit tension between the first and second cold rolling mills is 120-130N / mm 2, the unit tension between the second and third cold rolling mills is 130-140N / mm 2 The unit tension between the third and fourth cold rolling mills is 140-160N / mm 2 The unit tension between the fourth and fifth cold rolling mills is 150-170N / mm 2 , export unit tension 40-50N / 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 stators and rotors for high-efficiency variable frequency compressors.

[0050] Compared with other silicon steel dedicated continuous rolling mills, this unit has a larger roll diameter, resulting in a large rolling force and edge waves that are difficult to control. The edge waves are controlled by increasing the bending force of the working rolls and intermediate rolls of the fourth stand. However, excessive bending force can easily cause excessive tensile stress on the edge of the strip and cause strip breakage. The bending force of the intermediate roll is controlled at 480-720KN, and the bending force of the working roll is controlled at 400-600KN.

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

[0052] The annealing is carried out in a bedroom annealing furnace at a speed of 100-150 m / min and a temperature of 930-950° C. The surface is coated after annealing.

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

[0054] Table 2 Hot rolling parameters of various embodiments and comparative examples

[0055]

[0056]

[0057] Table 3 Normalization parameters of various embodiments and comparative examples

[0058]

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

[0060]

[0061]

[0062]

[0063] In comparative example 1, during the trimming rolling of acid continuous rolling, multiple edge cracks occurred on the edge of the hardened coil, which affected the production of the annealing process. The re-coiling unit was required to trim and repair the edges, resulting in increased costs and unqualified width. The low elongation of the straightening machine caused the plate shape to be poor, resulting in large edge waves after rolling, and the plate shape value was 8I. The welding speed was too fast, and the weld cracked many times. In comparative example 2, the tension between the first and second cold rolling mills, the tension between the second and third cold rolling mills, the tension between the third and fourth cold rolling mills, and the tension between the fourth and fifth cold rolling mills were large, and the chamfer height of the working rolls of the first and second stands was too large, which made it easy for the strip to break during rolling, and the strip break rate reached 50 times / 10,000 tons. The roughness of the working rolls of the first to fourth stands was high, resulting in large rolling force. The concentration of the large box emulsion was low, resulting in large rolling force and poor plate shape. The welding power was low, and the weld cracked many times. In Comparative Example 3, the acid concentration in tank 3# is too high, resulting in the blackening of the pickled plate surface; the bending force of the working rolls and intermediate rolls of the fourth frame is too small, resulting in large edge waves of the finished product and a plate shape value ≥20I; the diameter of the S1-S4 working rolls is too large, resulting in large rolling force and poor plate shape; the working rolls of the first to fourth frames have low roughness, resulting in slippage and scratches during rolling; the chamfer height of the working rolls of the first and second frames is too small, and the difference between the same plates does not meet the requirements; the secondary post-heating time is short, the stress is not eliminated, and the weld cracks many times.

[0064] Table 5 Effects of various embodiments and comparative examples on cold rolling production and quality

[0065]

[0066] Table 6 Annealing parameters of various embodiments and comparative examples

[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. The same plate difference was measured using an offline same plate difference measuring instrument.

[0069] Table 7 Magnetic properties of non-oriented silicon steel in various embodiments and comparative examples and the difference between the same plate

[0070]

[0071] Comparative Example 1: The normalizing temperature is too low and the annealing speed is too fast, resulting in high iron loss; the convexity of the hot coil is too high, resulting in a large difference between the same plate. Comparative Example 2: The hot rolling temperature is too high, resulting in coarse grains, and the annealing temperature is too low, resulting in high iron loss; the wedge shape of the hot coil is too large, resulting in a high difference between the same plate. Comparative Example 3: The hot rolling temperature is too high, resulting in coarse grains and high iron loss; the annealing speed is too low, affecting the output; the chamfer height of the cold rolling work roll is too low, resulting in a high difference between the same plate.

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

[0073] The description of the above embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and 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 present invention should be within the protection scope of the present invention.

Claims

1. A high-efficiency non-oriented silicon steel for variable frequency compressor, characterized in that: The high-efficiency non-oriented silicon steel for variable frequency compressor comprises the following components in 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%, the balance is Fe and unavoidable impurities.

2. The high-efficiency non-oriented silicon steel for variable frequency compressor according to claim 1, characterized in that: The variable frequency compressor uses high-efficiency non-oriented silicon steel, with 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 plate difference of ≤5μm after trimming.

3. The high-efficiency non-oriented silicon steel for variable frequency compressor according to claim 1, characterized in that: The high-efficiency non-oriented silicon steel used in the variable frequency compressor has an iron loss of ≤2.8W / kg and a magnetic induction of ≥1.7T.

4. A method for manufacturing high-efficiency non-oriented silicon steel for variable frequency compressors as described in any of claims 1 to 3, comprising the following steps of hot rolling, normalizing, cold rolling and annealing.

5. The manufacturing method according to claim 4, characterized in that: For the hot rolling, the hot rolling heating furnace time is 160-220 minutes, the heating temperature is 990-1130°C, the RT2 outlet temperature is 965-1050°C, the FT7 temperature is 850-900°C, and the coiling temperature is 560-580°C; the hot coil convexity is 15-35μm, and the wedge shape is controlled within ±15μm.

6. The manufacturing method according to claim 4, characterized in that: The normalization process has a normalization speed of 40-58 m / min and a temperature of 920-950° C.; the normalization line is not cut.

7. The manufacturing method according to claim 4, characterized in that: The cold rolling does not use welding wire, and the welding parameters are as follows: the welding speed is 3.6-4.2m / min, the welding power is 9.6-10.8kW, the preheating power is 15-22.5kW, and the initial post-heating power is 22.5-30kW; after the initial post-heating treatment, the weld area is subjected to secondary post-heating, the secondary post-heating temperature is 500-600°C, and the heating time is 30-40s.

8. The manufacturing method according to claim 4 or 7, characterized in that: The working rolls of the first and second stands of the cold rolling and continuous rolling are chamfered rolls, the chamfer height of the working rolls is 0.3-0.5mm, and the chamfer length is 275-300mm; the bending force of the working rolls of the fourth stand is controlled at 400-600KN.

9. The manufacturing method according to claim 4 or 8, characterized in that: Cold rolling speed is 600-800m / min.

10. The manufacturing method according to claim 4, characterized in that: The annealing is carried out in a horizontal annealing furnace at a speed of 100-150 m / min and a temperature of 930-950°C.

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