Non-oriented electrical steel for the armature core of a new energy heavy-duty truck electric drive and its manufacturing method

Abstract

The present invention discloses a non-oriented electrical steel for the electric drive iron core of new energy heavy trucks and a manufacturing method thereof. The non-oriented electrical steel contains the following components by weight percentage: Si: 2.90% - 3.30%; Al: 0.10% - 0.40%; Als: ≥0.95×Al; N: ≤Als / 130; C+N: ≤0.006%; C+Ti: ≤0.005%; Mn: 0.05% - 0.2%; P: 0.01% - 0.20%; S: ≤0.02%, and the balance is Fe and unavoidable impurities. Through composition design and coordinated adjustment of continuous casting, heating, hot rolling, normalizing, cold rolling and continuous annealing processes, the batch production and stable production of non-oriented electrical steel suitable for the electric drive iron core of new energy heavy trucks are realized, ensuring that the electrical steel has low iron loss and high magnetic induction performance in a relatively wide frequency range, and at the same time has high yield strength and fatigue resistance.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrical steel, and particularly relates to a non-oriented electrical steel for the armature of a new energy heavy truck electric drive and a manufacturing method thereof. Background Art

[0002] Heavy trucks are load-carrying or towing vehicles used in environments such as ports, mines, urban transportation, and large steel mills, and play an important role in the development of the national economy. However, they are also an important area with high emissions and heavy pollution. In recent years, the electrification of heavy trucks has developed rapidly, and the proportion of new energy heavy trucks, especially pure electric heavy trucks, in heavy trucks has gradually increased.

[0003] Affected by the working environment of the vehicle, the electric drive system of new energy heavy trucks needs to withstand impacts such as large torque, frequent starts, and high speeds; at the same time, to meet the requirements of long driving ranges, the electric drive system must have a high energy conversion efficiency. This poses more stringent requirements for the non-oriented electrical steel used in the armature of the electric drive, not only requiring the electrical steel to have low iron loss and high magnetic induction performance within a relatively wide frequency range (≤1000); at the same time, to ensure the safety of the vehicle drive system, the electrical steel is required to have a high yield strength and fatigue resistance. The performance of existing conventional non-oriented electrical steel sheets has been difficult to meet the high-performance and high-efficiency requirements of new energy heavy truck electric drive systems under complex working conditions.

[0004] Chinese Patent CN108570595A discloses a kind of electrical steel for a new energy vehicle drive motor and its production method. The component content is: C≤0.0030%, Si: 2.50% - 3.00%, Mn: 0.30% - 0.60%, P≤0.030%, Als: 0.50% - 0.70%, Cu: 0.20% - 0.50%, S≤0.004%, N≤0.004%, Ti≤0.004%, and the rest is Fe and inevitable impurities. This invention obtains a non-oriented electrical steel applicable to a new energy vehicle drive motor by adding copper element, and the iron loss P 1.0 / 400 ≤16W / kg, and the magnetic induction B 5000 ≥1.67T. The non-oriented electrical steel sheet produced by this technology is applied to the new energy vehicle drive system, and high efficiency can be obtained within a certain speed range, but the high efficiency within a relatively wide speed range and the safety of the electric drive system under high torque and high speed conditions are not considered, and it is difficult for the electrical steel to be used in manufacturing the electric drive system of new energy heavy trucks.

[0005] Chinese Patent CN108504926A discloses a non-oriented electrical steel for new energy vehicles and its production method. The component content is as follows: Si: 3.0 - 4.0%, Al: 1.0 - 2.0%, Si + Al ≥ 4.5%, Mn: 1.0 - 2.0%, S ≤ 30 ppm, O ≤ 30 ppm, C ≤ 20 ppm, N ≤ 20 ppm, Ti ≤ 30 ppm, S + O + C + N + Ti ≤ 80 ppm, Sn or Sb or Sn + Sb: 0.01 - 0.1%, rare earth elements: 0.001 - 0.1%, and the balance is Fe and other impurity elements. Through the addition of rare earth elements and in combination with the secondary cold rolling production process, the invention obtains a super-thin non-oriented electrical steel for the drive motor of new energy vehicles, with iron loss P 1.0 / 400 about 14.0 W / kg and magnetic induction B 5000 about 1.67; the thin-gauge non-oriented electrical steel sheet produced by the invention enables the electric drive system to obtain high-efficiency advantages in a relatively high-speed range, but the losses under low-speed operating conditions and the operating safety of the system are not considered, and it is difficult to obtain good comprehensive performance when the electrical steel is applied to the electric drive of heavy trucks. Summary of the Invention

[0006] The purpose of the present invention is to provide a non-oriented electrical steel for the iron core of the electric drive of new energy heavy trucks and its manufacturing method for the complex working environment of new energy heavy trucks. Through component design and coordinated adjustment of processes such as continuous casting, heating, hot rolling, normalizing, cold rolling, and continuous annealing, batch stable production of non-oriented electrical steel suitable for the iron core of the electric drive of new energy heavy trucks is achieved, ensuring that the electrical steel has low iron loss and high magnetic induction performance in a relatively wide frequency range of ≤ 1000 Hz, and at the same time has high yield strength and fatigue resistance.

[0007] To achieve the above purpose, the technical solutions adopted by the present invention are as follows:

[0008] A non-oriented electrical steel for the iron core of the electric drive of new energy heavy trucks, the non-oriented electrical steel contains the following components by weight percentage: Si: 2.90% - 3.30%; Al: 0.10% - 0.40%; Als: ≥ 0.95 × Al; N: ≤ Als / 130; C + N: ≤ 0.006%; C + Ti: ≤ 0.005%; Mn: 0.05% - 0.2%; P: 0.01% - 0.20%; S: ≤ 0.02%, and the remaining components are Fe and inevitable impurity elements.

[0009] The metallographic structure of the non-oriented electrical steel is a single-phase ferrite structure, the grain size rating is 4.0, the average grain size reaches 80 μm, and the maximum grain size - average grain size ≤ 15 μm.

[0010] The iron loss P of the non-oriented electrical steel 1.0 / 50≤0.90 W / kg, P 1.0 / 100 ≤2.15 W / kg,

[0011] P 1.0 / 400 ≤16.00 W / kg, P 1.0 / 600 ≤30.50 W / kg, P 1.0 / 800 ≤48.50 W / kg, P 1.0 / 1000 ≤70.10 W / kg, B 25 ≥1.59 T, B 50 ≥1.68 T, Rp 0.2 ≥440 MPa, fatigue strength ≥400 MPa; among them, the iron loss P 1.0 / 50 is the specific total loss measured at a magnetic polarization intensity of 1.0 T under an alternating magnetic field with a frequency of 50 Hz; the iron loss P 1.0 / 100 is the specific total loss measured at a magnetic polarization intensity of 1.0 T under an alternating magnetic field with a frequency of 100 Hz; the iron loss P 1.0 / 400 is the specific total loss measured at a magnetic polarization intensity of 1.0 T under an alternating magnetic field with a frequency of 400 Hz; the iron loss P 1.0 / 600 is the specific total loss measured at a magnetic polarization intensity of 1.0 T under an alternating magnetic field with a frequency of 600 Hz; the iron loss P 1.0 / 800 is the specific total loss measured at a magnetic polarization intensity of 1.0 T under an alternating magnetic field with a frequency of 800 Hz; the iron loss P 1.0 / 1000 is the specific total loss measured at a magnetic polarization intensity of 1.0 T under an alternating magnetic field with a frequency of 1000 Hz; the test of Rp0.2 is carried out with reference to the national standard "GB / T 228.1-2021 Metallic materials - Tensile testing", and Rp0.2 is the yield strength at a non-proportional elongation of 0.2%; the test conditions for fatigue strength are: strain ratio R = 0.05, conditional life Nf = 107, and failure probability P = 50%.

[0012] The manufacturing method of the non-oriented electrical steel for the new energy heavy truck electric drive iron core provided by the present invention includes the following steps:

[0013] (1) Converter smelting;

[0014] (2) RH vacuum treatment;

[0015] (3) Continuous casting: The mold adopts a fast cooling mode, and the electromagnetic stirring equipment is not put into use to increase the proportion of columnar crystals in the slab. The texture component in the columnar crystal is mainly {100} texture. Increasing the proportion of columnar crystals in the slab is beneficial for the texture component to be inherited to the finished product through hot rolling and cold rolling processes, increasing the beneficial texture component in the finished product and making the electromagnetic performance better;

[0016] (4) Heating: Heat to 1020 - 1120 °C, and the total heating and holding time shall not exceed 4 h; the heating temperature adopts a low-temperature heating method to avoid the solution of large-sized liquid segregation inclusions in the steel billet; because the dissolved inclusions will form precipitates during the laminar flow cooling process, and the small-sized precipitates cannot disappear during the subsequent heat treatment process, which hinders the growth of the finished product grains, affects the movement of magnetic domains, and deteriorates the electromagnetic properties of the product. At the same time, the large-sized precipitates have a greater impact on the fatigue resistance of the finished product, leading to fatigue aging of the finished product;

[0017] (5) Hot rolling;

[0018] (6) Normalizing treatment: The normalizing temperature is 900 - 980 °C, and the time is 1 - 5 min; in the present invention, a high-temperature and short-time normalizing treatment process is adopted. Increasing the normalizing temperature can effectively improve the favorable {100}, {110} texture in the steel plate, while the harmful {111} texture gradually decreases, effectively improving the electromagnetic properties of the finished product. However, a higher normalizing temperature will increase the average grain size in the steel plate, reduce the elongation rate, and increase the risk of breakage during the cold rolling process; increasing the normalizing temperature and reducing the normalizing time simultaneously can ensure that the steel plate obtains a higher heating rate, increase the nucleation ratio of the favorable texture structure, and reducing the normalizing time can effectively control the growth of the grain size of the steel plate after normalizing. Therefore, the normalizing adopts a high-temperature and short-time heating process, which can effectively improve the electromagnetic properties of the finished product while improving the cold rolling processing performance of the steel coil;

[0019] (7) Pickling;

[0020] (8) Cold rolling;

[0021] (9) Continuous annealing: The annealing temperature is 920 - 960 °C, and the holding time is 120 - 200 s;

[0022] (10) Coating with an insulating coating.

[0023] In the converter smelting step, a slide gate is used for slag blocking during converter tapping, the tapping time is within 15 min, and the thickness of the top slag in the ladle is controlled within 45 mm. Reducing the thickness of the top slag in the ladle can effectively reduce the content of harmful elements such as Ti and Nb in the steel billet.

[0024] In the RH vacuum treatment step, after the decarburization of the molten steel is completed, ferrosilicon alloy with a C content less than 0.01% is used for deoxidation, and alloying is carried out in the order of Si, Mn, and Al for alloy addition to reduce the formation of Al-based inclusions such as Al2O3 in the molten steel, and at the same time reduce the content of Ti element in the molten steel.

[0025] In the heating step, the steel billet enters the heating furnace at a temperature not lower than 450 °C.

[0026] In the hot rolling step, the slab is rough rolled in 5 passes and finish rolled in 7 passes to the target thickness of 2.0 - 3.0 mm. The final rolling temperature of hot rolling is 800 - 880 °C, and the coiling temperature is 600 - 680 °C.

[0027] In the pickling step, after normalization, the steel plate is tension leveled and then passes through a turbulent acid tank to remove the surface scale. Tension leveling can break and remove the surface scale of the steel plate. The relatively ductile Fe3O4 part in the surface scale is cracked, so that the acid solution can penetrate in the subsequent process to improve the surface pickling quality.

[0028] In the cold rolling step, a single stand reversing mill is used to cold roll the steel plate in 6 - 8 passes to the target thickness of 0.27 - 0.35 mm. The total cold rolling reduction rate is between 85% and 90%. The reversing rolling method can increase the stress direction during the strip rolling process, increase the selectivity of grain deformation and rotation direction, reduce the concentration degree of texture, and reduce the difference in transverse and longitudinal properties of the finished steel plate.

[0029] In the continuous annealing step, the temperature is raised to 920 - 960 °C at a heating rate greater than 60 °C / s and held for 120 - 200 s. The whole process in the furnace is protected by a mixed gas of 15% - 50% H2 and N2. The O2 content in the furnace is controlled below 40 ppm and the dew point is below -20 °C. Reducing the O2 content and oxidizing atmosphere in the furnace can effectively reduce the formation of an external oxide layer on the surface of the steel plate during annealing, and then increase the hysteresis loss and deteriorate the electromagnetic properties of the finished steel plate with an internal nitride layer formed; using a relatively fast heating rate for the steel plate can effectively increase the nucleation ratio of the cold-rolled banded structure, increase the proportion of softened structure during heating, effectively prevent the diffusion of some oxygen elements along the grain boundaries and deformed tissues, relieve the generation of internal oxidation and internal nitride layers in the steel plate, and the low-temperature annealing process can effectively control the grain growth size in the steel plate, increase the uniformity of the finished grains, increase the yield strength, and improve the fatigue resistance.

[0030] In the step of coating the insulating coating, an insulating coating is applied to the surface of the steel coil and cured at 350 - 600 °C for 35 - 70 s to ensure that the interlayer resistance of both sides of the steel plate is 150 - 500 Ω·mm 2 , and the coating thickness is controlled at 0.5 - 0.8 μm.

[0031] In the non-oriented electrical steel for the new energy heavy truck electric drive iron core provided by the present invention, the functions and controls of each component are as follows:

[0032] Si and Al: Both are alloying elements in non-oriented electrical steel. For magnetism, as the content of Si element increases, the resistivity increases and the iron loss decreases. However, for the strength of electrical steel, as the Si content increases, the yield strength increases, the plasticity decreases, the brittleness increases, and the cold working performance decreases; the addition of Al can improve the magnetism of electrical steel, and at the same time has an obvious effect on improving the plasticity of electrical steel, and the ductile-brittle transition temperature of the alloy can be significantly improved. However, a relatively high aluminum element is likely to reduce titanium in the steel slag during smelting, which has a certain harm to the performance of electrical steel. Therefore, to ensure excellent electromagnetic and mechanical properties of the product at the same time, the total content and ratio of Si and Als should be strictly controlled;

[0033] Als: It is acid-soluble aluminum in electrical steel and belongs to the part where Al plays an alloying role in electrical steel. To give full play to the addition of Al element in the steel and at the same time reduce the Al-based non-metallic inclusions in electrical steel and improve the electromagnetic and anti-fatigue properties of the product, while ensuring the accurate control of the total Al content in the steel, the content ratio of Als is used in more than 95% of the total Al content;

[0034] N, C, and Ti: They are harmful elements in electrical steel. N is likely to form second-phase inclusions such as AlN and TiN in electrical steel, strongly hindering grain growth, increasing the resistance to magnetic domain movement, and deteriorating the electromagnetic properties. Therefore, the content of N element should be controlled within the range of Als / 130; N and C elements make the magnetic time effect of electrical steel obvious. To ensure the stable performance of the product, the total amount of C+N elements should be controlled within 0.006%; the influence of Ti element on the electromagnetic properties of non-oriented electrical steel is particularly strong. The TiC and TiN inclusions precipitated by combining with N and C elements in the steel seriously hinder grain growth and the iron loss increases significantly. Therefore, the total amount of C+Ti elements should be controlled within 0.005%, and the lower the content, the better;

[0035] Mn: It is an alloying element of electrical steel. The addition of Mn can increase the proportion of {100} and {110} plane textures in the structure and reduce the proportion of {111} plane texture, improving the magnetism. At the same time, Mn can improve the plasticity of high electrical steel and increase the elongation;

[0036] P: P element can effectively narrow the γ phase region of electrical steel and promote grain growth. If the content exceeds 0.1%, the embrittlement effect of the material is enhanced, affecting the cold rolling and subsequent blanking performance and reducing the number of bending times. Therefore, the P content should be controlled within 0.01% - 0.20%;

[0037] S: It is a harmful element in electrical steel. S is likely to form second-phase inclusions such as MnS and Cu2S in electrical steel, strongly hindering grain growth and deteriorating the electromagnetic properties. Therefore, the P content should be controlled within 0.02%.

[0038] In the manufacturing method of non-oriented electrical steel for the electric drive iron core of new energy heavy trucks provided by the present invention, the molten iron is transported to RH for vacuum smelting after converter blowing. After alloying treatment, the molten steel with qualified chemical composition is continuously cast into slab billets with a thickness of 200 - 280 mm. The slab billets enter a walking beam reheating furnace for heating after being cooled to a temperature not lower than 450 °C, and then are hot-rolled into hot-rolled sheets with a thickness of 1.8 - 2.5 mm; the hot-rolled sheets are made into finished non-oriented electrical steel for the electric drive iron core of new energy heavy trucks through normalizing, pickling, cold rolling, continuous annealing, and coating with an insulating coating.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] 1) In the smelting process, by controlling the molten steel flowing time when tapping from the converter, the thickness of the top slag in the ladle, and the addition sequence of C content and alloying components in the RH vacuum treatment step, the harmful elements are controlled at a lower content;

[0041] 2) By adopting a fast cooling mode in the crystallizer and not using an electromagnetic stirring device in the continuous casting step, the proportion of columnar crystals in the slab billets is increased. The texture components in the columnar crystals are mainly {100} texture. Such favorable texture components can be inherited to the finished products through hot rolling and cold rolling processes, increasing the favorable texture components of the finished products and making the electromagnetic properties better;

[0042] 3) In the heating process before hot rolling, a low-temperature heating method is adopted to avoid the solid solution of large-size liquid segregation inclusions and affect the fatigue resistance of the finished products;

[0043] 4) A normalizing process with high temperature and short time is adopted. While increasing the normalizing temperature, the normalizing time is reduced, which can ensure that the steel plate obtains a higher heating rate, increase the nucleation proportion of favorable texture structures, improve the favorable plane textures of {100} and {110} in the steel plate, and reduce the harmful {111} texture. Reducing the normalizing time can effectively control the grain size growth of the steel plate after normalizing, and can effectively improve the electromagnetic properties of the finished products while improving the cold rolling processing performance of the steel coil;

[0044] 5) The cold rolling method of reciprocating rolling is adopted, which can increase the stress directions during the strip rolling process, increase the selectivity of grain deformation and rotation directions, reduce the concentration degree of texture, and reduce the difference in transverse and longitudinal properties of the finished steel plate;

[0045] 6) A low-temperature annealing process is adopted to effectively control the grain growth size in the steel plate, thereby increasing the grain uniformity of the finished products, increasing the yield strength, and improving the anti-fatigue performance. Description of the Drawings

[0046] Figure 1It is the finished product microstructure diagram of non-oriented electrical steel for the electric drive iron core of a new energy heavy truck in Example 1. It is a single-phase ferrite structure, with a grain size rating of 4.0, an average grain size reaching 80μm, and the maximum grain size - average grain size ≤ 15μm. Detailed implementation mode

[0047] The present invention will be described in detail below in conjunction with the embodiments.

[0048] Example 1

[0049] A manufacturing method of non-oriented electrical steel for the electric drive iron core of a new energy heavy truck specifically includes the following steps:

[0050] 1) After the molten iron is blown in the converter, it is transported to RH through the ladle. The converter tapping uses a slide gate to block slag, with a tapping time of 12 minutes, a top slag thickness of 40 mm in the ladle. The molten steel undergoes vacuum alloying smelting in RH. After decarburization, ferrosilicon alloy is used for deoxidation. Ferrosilicon, electrolytic manganese, and aluminum grain alloy are added in sequence for alloying. The chemical composition weight percentages of the molten steel out of RH are respectively: Si: 3.20%; Al: 0.35%; Als: 0.35%; N: 0.0023%; C: 0.0017%; Ti: 0.0016%; Mn: 0.12%; P: 0.11%; S: 0.011%, and the rest is Fe and inevitable impurity elements;

[0051] 2) The molten steel with qualified chemical composition is continuously cast into a slab with a thickness of 240 mm. During continuous casting, the mold uses a fast cooling mode and does not use electromagnetic stirring. The steel billet enters the walking beam reheating furnace when it is higher than 450°C, is heated to 1080°C, and the residence time in the furnace is 220 minutes. The slab is rough rolled through 5 passes + finish rolled through 7 passes to the target thickness of 2.3 mm. The hot rolling final rolling temperature is 860°C, and the coiling temperature is 640°C;

[0052] 3) The normalizing temperature of the hot rolled plate is 960°C and the time is 3.2 minutes. After normalizing, the steel plate is straightened and then the surface scale is removed through a turbulent acid tank;

[0053] 4) The pickled steel plate is cold rolled to the target thickness of 0.30 mm through 7 passes by a single-stand reciprocating rolling mill, and the total cold rolling reduction rate is 86.96%;

[0054] 5) The cold rolled plate is annealed at 955°C for 160 s, and the whole process in the furnace is protected by a mixed gas of 15% - 50% H2 and N2. The heating rate of the steel plate during the heating stage is 130°C / s, the O2 content in the furnace is 25 ppm, and the dew point is -35°C. After annealing, an insulating coating is applied to the surface of the steel coil and cured at 450°C for 52 s. The coating thickness is 0.7μm and the double-sided resistance is 320Ω·mm 2 .

[0055] The non-oriented electrical steel for the new energy heavy truck electric drive iron core manufactured by the above process has excellent surface quality, and the finished iron loss P 1.0 / 50 is 0.86 W / kg, P 1.0 / 100 is 2.07 W / kg, P 1.0 / 400 is 15.01 W / kg, P 1.0 / 600 is 28.61 W / kg, P 1.0 / 800 is 44.31 W / kg, P 1.0 / 1000 is 61.41 W / kg, B 25 is 1.600 T, B 50 is 1.683 T, the yield strength Rp0.2 is 449 MPa, and the fatigue strength is 416 MPa.

[0056] Example 2

[0057] A manufacturing method of non-oriented electrical steel for the new energy heavy truck electric drive iron core specifically includes the following steps:

[0058] 1) After the molten iron is blown in the converter, it is transferred to the RH through the ladle. The converter tapping uses a slide gate to block the slag, the molten steel flowing time is 13 min, the thickness of the top slag in the ladle is 42 mm, and the molten steel undergoes vacuum alloying smelting in the RH. After decarburization, ferrosilicon alloy is used for deoxidation. Ferro-silicon, electrolytic manganese, and aluminum grain alloy are sequentially added during alloying. The chemical composition weight percentages of the molten steel out of the RH are respectively: Si: 3.25%; Al: 0.30%; Als: 0.29%; N: 0.0017%; C: 0.0023%; Ti: 0.0024%; Mn: 0.19%; P: 0.14%; S: 0.017%, and the rest are Fe and inevitable impurity elements;

[0059] 2) The molten steel with qualified chemical composition is continuously cast into a slab with a thickness of 240 mm. The mold adopts a fast cooling mode and does not use electromagnetic stirring. The steel billet enters the walking beam reheating furnace when the temperature is higher than 450 °C, and is heated to 1100 °C, and the residence time in the furnace is 230 min. The slab is rough rolled in 5 passes + finish rolled in 7 passes to the target thickness of 2.3 mm. The hot rolling finishing rolling temperature is 860 °C, and the coiling temperature is 640 °C;

[0060] 3) The normalizing temperature of the hot rolled plate is 950 °C and the time is 3.0 min. After normalizing, the steel plate is straightened and then the surface scale is removed through a turbulent acid tank;

[0061] 4) The pickled steel plate is cold rolled to the target thickness of 0.30 mm in 7 passes by a single-stand reciprocating rolling mill, and the total cold rolling reduction rate is 86.96%;

[0062] 5) The cold-rolled sheet is annealed at 960°C for 160 s, and is protected by a mixed gas of 15% - 50% H2 and N2 throughout the furnace. The heating rate of the steel sheet during the heating stage is 130°C / s, the O2 content in the furnace is 33 ppm, and the dew point is -40°C. After annealing, an insulating coating is applied to the surface of the steel coil and cured at 450°C for 52 s. The coating thickness is 0.6 μm and the surface resistance of both sides is 421 Ω·mm 2 。

[0063] The non-oriented electrical steel for the electric drive iron core of new energy heavy trucks manufactured by the above process has excellent surface quality. The finished iron loss P 1.0 / 50 is 0.84 W / kg, P 1.0 / 100 is 2.07 W / kg, P 1.0 / 400 is 15.11 W / kg, P 1.0 / 600 is 29.21 W / kg, P 1.0 / 800 is 43.54 W / kg, P 1.0 / 1000 is 60.51 W / kg, B 25 is 1.601 T, B 50 is 1.684 T, the yield strength Rp0.2 is 450 MPa, and the fatigue strength is 408 MPa.

[0064] Example 3

[0065] A manufacturing method of non-oriented electrical steel for the electric drive iron core of new energy heavy trucks specifically includes the following steps:

[0066] 1) After the molten iron is blown in the converter, it is transferred to the RH through the ladle. The ladle slag is blocked by a slide plate during tapping, and the tapping time is 14 min. The thickness of the top slag in the ladle is 40 mm. The molten steel is subjected to vacuum alloying smelting in the RH. After decarburization, ferrosilicon alloy is used for deoxidation. Ferrosilicon, electrolytic manganese, and aluminum grain alloy are added in sequence during alloying. The chemical composition weight percentages of the molten steel out of the RH are Si: 3.18%; Al: 0.20%; Als: 0.15%; N: 0.0009%; C: 0.0017%; Ti: 0.0026%; Mn: 0.14%; P: 0.021%; S: 0.020%, and the rest are Fe and unavoidable impurity elements;

[0067] 2) The molten steel with qualified chemical composition is continuously cast into a slab with a thickness of 230 mm. The mold adopts a fast cooling mode and does not use electromagnetic stirring. The steel billet enters the walking beam reheating furnace at a temperature higher than 450°C and is heated to 1090°C. The residence time in the furnace is 220 min. The slab is rough rolled in 5 passes + finish rolled in 7 passes to the target thickness of 2.4 mm. The hot rolling finishing temperature is 870°C, and the coiling temperature is 650°C;

[0068] 3) The normalizing temperature of the hot-rolled sheet is 960°C and the time is 3.0 min. After normalizing, the steel sheet is straightened and then passes through a turbulent acid tank to remove the surface scale;

[0069] 4) The pickled steel plate is cold-rolled to the target thickness of 0.35 mm in 6 passes by a single-stand reciprocating rolling mill, and the total cold rolling reduction rate is 85.42%;

[0070] 5) The cold-rolled plate is annealed at 955 °C for 155 s, and is protected by a mixed gas of 15% - 50% H2 and N2 throughout the furnace. The heating rate of the steel plate during the heating stage is 125 °C / s, the O2 content in the furnace is 24 ppm, and the dew point is -35 °C. After annealing, an insulating coating is applied to the surface of the steel coil, and is cured at 470 °C for 50 s. The coating thickness is 0.71 μm and the surface resistance is 375 Ω·mm 2 .

[0071] The non-oriented electrical steel for the electric drive iron core of new energy heavy trucks manufactured by the above process has excellent surface quality. The finished iron loss P 1.0 / 50 is 0.88 W / kg, P 1.0 / 100 is 2.12 W / kg, P 1.0 / 400 is 15.90 W / kg, P 1.0 / 600 is 29.80 W / kg, P 1.0 / 800 is 47.75 W / kg, P 1.0 / 1000 is 66.23 W / kg, B 25 is 1.597 T, B 50 is 1.681 T, the yield strength Rp0.2 is 446 MPa, and the fatigue strength is 405 MPa.

[0072] Comparative Example 1

[0073] 1) After the hot metal is blown in the converter, it is transferred to the RH through the ladle. The converter tapping uses a slide gate to block the slag, the molten steel flowing time is 20 min, the thickness of the top slag in the ladle is 80 mm, and the molten steel is subjected to vacuum alloying smelting in the RH. After the decarburization is completed, aluminum pellets are used for deoxidation. Ferro-silicon, aluminum pellet alloy, and electrolytic manganese are added in sequence during alloying. The chemical composition weight percentages of the molten steel out of the RH are Si: 3.20%; Al: 0.45%; Als: 0.38%; N: 0.0026%; C: 0.0040%; Ti: 0.0054%; Mn: 0.20%; P: 0.031%; S: 0.040%, and the rest are Fe and inevitable impurity elements;

[0074] 2) The molten steel with qualified chemical composition is continuously cast into a slab with a thickness of 230 mm, and electromagnetic stirring is applied. The steel billet enters the walking beam reheating furnace when it is higher than 450 °C, and is heated to 1200 °C. The residence time in the furnace is 220 min. The slab is rough-rolled in 5 passes + finish-rolled in 7 passes to the target thickness of 2.3 mm. The hot rolling finishing rolling temperature is 880 °C, and the coiling temperature is 640 °C;

[0075] 3) The hot-rolled plate is normalized at a temperature of 850°C for 5.0 min. After normalization, the steel plate is straightened and passed through a turbulent acid tank to remove surface oxide scale.

[0076] 4) The pickled steel plate is cold rolled in 6 passes using a single-stand reciprocating rolling mill to a target thickness of 0.35 mm, with a total cold rolling reduction of 84.78%;

[0077] 5) The cold-rolled sheet was annealed at 970°C for 180 seconds, with a 15% to 50% H2 and N2 mixture in the furnace. The heating rate during the heating phase was 50°C / s, the O2 content in the furnace was 108 ppm, and the dew point was 10°C. After annealing, an insulating coating was applied to the surface of the steel coil and cured at 450°C for 50 seconds. The coating thickness was 0.65 μm and the double-sided resistance was 420 Ω·mm. 2 .

[0078] The surface quality of the non-oriented electrical steel for the electric drive core of new energy heavy trucks manufactured by the above process is excellent, but the iron loss of the finished product is 1.0 / 50 1.08W / kg, P 1.0 / 100 2.24W / kg, P 1.0 / 400 17.54W / kg, P 1.0 / 600 38.75W / kg, P 1.0 / 800 is 50.34W / kg, P 1.0 / 1000 is 74.62W / kg, B 25 1.461T, B 50 The yield strength Rp0.2 is 415 MPa, and the fatigue strength is 360 MPa. It can be seen that its electromagnetic performance and mechanical properties are inferior to those of the embodiments.

[0079] The above-mentioned detailed description of a non-oriented electrical steel for an electric drive core of a new energy heavy-duty truck and a method for manufacturing the same with reference to the embodiments is illustrative rather than restrictive, and several embodiments can be listed according to the limited scope. Therefore, changes and modifications without departing from the overall concept of the present invention should fall within the scope of protection of the present invention.

Claims

1. An non-oriented electrical steel for the armature core of a new energy heavy-duty truck electric drive, characterized in that, The non-oriented electrical steel contains the following components by weight percentage: Si: 2.90% - 3.30%; Al: 0.10% - 0.40%; Als: ≥0.95×Al; N: ≤Als / 130; C+N: ≤0.006%; C+Ti: ≤0.005%; Mn: 0.05% - 0.19%; P：0.01％～0.20％； S: ≤0.02%, and the remaining components are Fe and inevitable impurity elements; The manufacturing method of the non-oriented electrical steel for the new energy heavy truck electric drive iron core includes the following steps: (1) Converter smelting; (2) RH vacuum treatment; (3) Continuous casting: The mold adopts a fast cooling mode, and the electromagnetic stirring equipment is not put into use; (4) Heating: Heat to 1020 - 1120 °C, and the total heating and holding time does not exceed 4 h; (5) Hot rolling; (6) Normalizing treatment: The normalizing temperature is 900 - 980 °C, and the time is 1 - 5 min; (7) Pickling; (8) Cold rolling; (10) Continuous annealing: The annealing temperature is 920 - 960 °C, and the holding time is 120 - 200 s; (10) Coating with an insulating coating; In the continuous annealing step, heat up to 920 - 960 °C at a heating rate greater than 60 °C / s and hold for 120 - 200 s. The whole process in the furnace is protected by a mixed gas of 15% - 50% H2 and N2. The O2 content in the furnace is controlled below 40 ppm, and the dew point is below -20 °C; The Rp0.2 of the non-oriented electrical steel ≥ 440 MPa, and the fatigue strength ≥ 400 MPa.

2. The non-oriented electrical steel for the armature core of the new energy heavy truck electric drive according to claim 1, characterized in that, The metallographic structure of the non-oriented electrical steel is a single-phase ferrite structure, the grain size rating is 4.0, the average grain size reaches 80 μm, and the maximum grain size - average grain size ≤ 15 μm.

3. The non-oriented electrical steel for the armature core of the new energy heavy truck electric drive according to claim 1, wherein, The iron loss P of the non-oriented electrical steel 1.0 / 50 ≤0.90 W / kg, P 1.0 / 100 ≤2.15 W / kg, P 1.0 / 400 ≤16.00 W / kg, P 1.0 / 600 ≤30.50 W / kg, P 1.0 / 800 ≤48.50 W / kg, P 1.0 / 1000 ≤70.10 W / kg, B 25 ≥1.59 T, B 50 ≥1.68 T.

4. The manufacturing method of the non-oriented electrical steel for the electric drive iron core of the new energy heavy truck according to any one of claims 1-3, characterized in that, The manufacturing method includes the following steps: (1) Converter smelting; (2) RH vacuum treatment; (3) Continuous casting: The mold adopts a fast cooling mode, and the electromagnetic stirring equipment is not put into use; (4) Heating: Heat to 1020 - 1120 °C, and the total heating and holding time does not exceed 4 h; (5) Hot rolling; (6) Normalizing treatment: The normalizing temperature is 900 - 980 °C, and the time is 1 - 5 min; (7) Pickling; (8) Cold rolling; (9) Continuous annealing: The annealing temperature is 920 - 960 °C, and the holding time is 120 - 200 s; (10) Coating with an insulating coating.

5. The manufacturing method according to claim 4, wherein, In the converter smelting step, the converter tapping uses a slide gate to block slag, the tapping time is within 15 min, and the thickness of the top slag in the ladle is controlled within 45 mm.

6. The manufacturing method according to claim 4, characterized in that In the RH vacuum treatment step, after the decarburization of the molten steel is completed, ferrosilicon alloy with a C content less than 0.01% is used for deoxidation, and alloying is carried out in the order of Si, Mn, and Al for alloy addition.

7. The manufacturing method according to claim 4, characterized in that, In the heating step, the billet inlet furnace temperature is not lower than 450 °C.

8. The manufacturing method according to claim 4, characterized in that In the hot rolling step, the slab is rough rolled in 5 passes + finish rolled in 7 passes to the target thickness of 2.0 - 3.0 mm. The final rolling temperature of the hot rolling is 800 - 880 °C, and the coiling temperature is 600 - 680 °C.

9. The manufacturing method according to claim 4, wherein In the cold rolling step, a single-stand reciprocating rolling mill is used to cold roll in 6 - 8 passes to the target thickness of 0.27 - 0.35 mm, and the total cold rolling reduction rate is between 85% - 90%.

Images