Method for producing non-oriented silicon steel for compressor based on thin-strip cast rolling

Abstract

The invention belongs to the technical field of thin-strip casting and rolling, and relates to a method for producing non-oriented silicon steel for a compressor based on thin-strip casting and rolling, and the non-oriented silicon steel produced by adopting the method. The method comprises the following steps: carrying out steelmaking according to 0.95-1.05% of Si and 0.20-0.30% of Mn without adding Al, P, Sn and Sb; continuous casting is conducted through a double-roller casting and rolling technology, and a cast strip with the thickness being 1.80 mm is obtained; the casting strip is subjected to hot rolling, acid pickling and small-reduction-rate cold rolling and then directly subjected to splitting, blanking and stacking, and the stator and rotor iron core for the compressor is obtained; the iron core is subjected to heat preservation for 150 min at the temperature of 925 DEG C, so that a silicon steel base body of the stator and rotor iron core and metal in a blanking deformation area are completely recrystallized, and the grain size is 80-100 microns. Compared with a conventional process, the process of hot rolling heating, normalizing, steel plate annealing before iron core stamping, coating and the like is omitted, the rolling reduction of hot rolling and cold rolling is greatly reduced, and the non-oriented silicon steel with excellent performance and the corresponding iron core product for the compressor are produced in a short-process mode.

Description

Technical Field

[0001] The present invention belongs to the technical field of thin strip continuous casting and rolling, and relates to a method for producing non-oriented electrical steel for compressors based on thin strip continuous casting and rolling. Background Art

[0002] As an important soft magnetic material, non-oriented electrical steel is mainly used to manufacture the iron cores of various motors. The household appliance industry is one of the most important downstream industries of non-oriented electrical steel, consuming approximately 4 million tons of non-oriented electrical steel annually. Most of the silicon steel raw materials in the household appliance industry are medium and low grade non-oriented electrical steels such as 50W1300 and 50W800, which are used to manufacture components such as the iron cores of refrigerators and air conditioner compressors. Cast aluminum cores are widely used in small and medium-sized motors and fixed-frequency compressors due to their simple structure and easy manufacturing. During the production of the iron core, generally, the finished silicon steel sheets are first blanked into stator and rotor laminations according to certain shapes and dimensions, and then the laminations are stacked into stator and rotor cores by riveting. In order to eliminate the blanking stress at the edges of the silicon steel sheets and reduce the iron core loss of the motor, annealing treatment is carried out before the iron core assembly. The common annealing temperature for stator and rotor cores is 700 - 800 °C, and the holding time is 120 - 180 min, ensuring that the metal in the blanking deformation area of the stator and rotor cores undergoes recovery and recrystallization to reduce the hysteresis loss of the iron core.

[0003] Medium and low grade non-oriented electrical steels such as 50W1300 and 50W800 are generally prepared through a series of processes including steelmaking, continuous casting, hot rolling, pickling, cold rolling, recrystallization annealing + coating + finishing. The hot rolling thickness is 2.50 - 3.00 mm, the cold rolling thickness is 0.50 mm, the annealing temperature is 800 - 950 °C, and the annealing time is 60 - 120 s. Obviously, compared with the annealing time of up to 120 - 180 min for the stator and rotor cores of compressors, the time for non-oriented electrical steel in the recrystallization annealing stage is very short. Therefore, it is worth exploring whether the two annealing processes can be integrated. Between the two annealing processes, there is the blanking and stacking process of the finished silicon steel sheets. In the conventional process, if the recrystallization annealing process is cancelled and the rolled hard sheet is directly blanked. Since the cold rolling reduction of the rolled hard sheet is large, generally greater than 80%, the work hardening is severe, and the steel plate strength reaches over 900 MPa, so it is difficult to carry out blanking. Summary of the Invention

[0004] Aiming at the above problems existing in the existing traditional processes for preparing non-oriented electrical steel for compressors and iron core preparation technologies, the present invention provides a non-oriented electrical steel for compressors based on thin strip continuous casting and rolling. In the method of the present invention, the steel water composition is designed with a low silicon and aluminum-free composition, and a hot-rolled thin substrate with a thickness of 0.65 mm is directly obtained through thin strip continuous casting and rolling, eliminating the continuous casting of billets and billet heating, and significantly reducing the hot rolling reduction; after the above hot-rolled thin substrate undergoes pickling and one-pass cold rolling, it is directly subjected to iron core blanking and stacking, and then through the iron core annealing process, bluing treatment and recrystallization annealing are carried out.

[0005] The present invention specifically adopts the following technical solutions:

[0006] According to the first aspect of the present invention, a method for producing non-oriented electrical steel for compressors based on thin strip casting and rolling is provided. The method includes the following steps:

[0007] 1) Molten steel smelting

[0008] Steelmaking is carried out without adding Al, P, Sn, and Sb. The chemical composition of the molten steel includes, by mass percentage:

[0009] C: 0.0015 - 0.0030%, S: 0.0015 - 0.0030%, Si: 0.95 - 1.05%,

[0010] Mn: 0.20 - 0.30%, P ≤ 0.015%, Al: ≤ 0.003%, Nb ≤ 0.003%,

[0011] V ≤ 0.003%, Ti ≤ 0.003%, Cr ≤ 0.02%, Ni ≤ 0.02%,

[0012] Cu ≤ 0.02%, N ≤ 0.0020%, and the rest is Fe and inevitable inclusions;

[0013] 2) Thin strip casting and rolling

[0014] Continuous casting is carried out by using a twin-roll casting and rolling process to obtain a cast strip, which is then hot-rolled into a hot-rolled thin strip in one pass. The final rolling temperature T is controlled to be 880 - 920 °C, and the final rolling temperature T is further controlled to be T = (Ar1 - 60) - (Ar1 - 50) °C, where Ar1 is the γ / α phase transformation temperature in °C;

[0015] After hot rolling, coiling is carried out. The coiling temperature is controlled to be ≥ 680 °C, and after coiling, it is air-cooled to room temperature to obtain a hot-rolled coil;

[0016] Among them, Ar1 is determined according to the following formula:

[0017] Ar1 = 872 °C + 1000(11*[Si] - 14*[Mn] + 21*[Al]),

[0018] Among them, [Si], [Mn], and [Al] are the mass percentages of Si, Mn, and Al respectively;

[0019] 3) Pickling process

[0020] Hydrochloric acid pickling is adopted. The acid solution temperature is controlled to be 75 - 85 °C; the rinsing water temperature is controlled to be 45 - 55 °C, the pickling and rinsing speed is controlled to be 150 - 200 mpm, and the pickling time is controlled to be 45 - 60 s;

[0021] 4) Cold rolling process

[0022] One - pass cold rolling is carried out using a single - stand rolling mill to roll the hot - rolled substrate into a cold - rolled hard coil.

[0023] According to the method for producing non - oriented silicon steel for compressors based on thin - strip casting and rolling of the present invention, preferably, the method further includes:

[0024] 5) Slitting - blanking - stacking

[0025] The cold - rolled hard coil is slit into slit coils, the slit coils are blanked into single stator and rotor sheets, and the single stator and rotor sheets are stacked into a stator and rotor core for compressors.

[0026] According to the method for producing non - oriented silicon steel for compressors based on thin - strip casting and rolling of the present invention, preferably, the method further includes:

[0027] 6) Core annealing preparation

[0028] The stator and rotor core of the compressor is held at 925 °C for 150 min to ensure that complete recrystallization occurs in both the silicon - steel matrix of the stator and rotor core and the metal in the blanking deformation area, and the grain size is controlled to be 80 - 100 μm.

[0029] According to the method for producing non - oriented silicon steel for compressors based on thin - strip casting and rolling of the present invention, preferably, in the steel - melting and smelting process, converter steelmaking is carried out using 60 - 80% hot metal + 20 - 40% scrap steel. The end - point C of the converter is 0.020 - 0.050%, S ≤ 0.0025%, P ≤ 0.015%; then molten steel is obtained through vacuum smelting and alloying.

[0030] According to the method for producing non - oriented silicon steel for compressors based on thin - strip casting and rolling of the present invention, preferably, in the thin - strip casting and rolling process, continuous casting is carried out using a twin - roll casting process. The starting pouring temperature of the molten steel is controlled to be 1580 - 1590 °C. The molten steel is poured into a molten pool composed of a rotating steel roll and side seals through a tundish. After the molten steel contacts the crystallizing roll surface of the steel roll, it rapidly solidifies and forms, obtaining a cast strip with a thickness of 1.80 mm. The continuous casting speed is 60 m / min; the cast strip enters the rolling mill through a hot box under the protection of inert gas and is hot - rolled into a hot - rolled thin strip with a thickness of 0.65 mm in one pass.

[0031] According to the method for producing non - oriented silicon steel for compressors based on thin - strip casting and rolling of the present invention, preferably, in the pickling process, four - stage hydrochloric acid pickling is adopted: the concentration of the first - stage acid solution is 30 - 50 g / L, the concentration of the second - stage acid solution is 70 - 90 g / L, the concentration of the third - stage acid solution is 100 - 120 g / L, the concentration of the fourth - stage acid solution is 140 - 160 g / L, and the Fe concentration in the first - stage acid solution 2+ ≤ 130 g / L, and the Fe concentration in the second - stage acid solution 2+Concentration ≤ 100 g / L, Fe in grade 3 acid solution 2+ Concentration ≤ 85 g / L, Fe in grade 4 acid solution 2+ Concentration ≤ 50 g / L.

[0032] According to the method for producing non-oriented electrical steel for compressors based on thin strip casting and rolling of the present invention, preferably, in the cold rolling process, the roughness of the work roll is controlled to be 1.5 - 2.5 μm, and a cold rolled steel coil with a surface roughness ≥ 0.80 μm is obtained.

[0033] According to the method for producing non-oriented electrical steel for compressors based on thin strip casting and rolling of the present invention, preferably, in the cold rolling process, the thickness of the cold rolled steel coil is controlled to be 0.50 mm.

[0034] According to the method for producing non-oriented electrical steel for compressors based on thin strip casting and rolling of the present invention, preferably, in the slitting - blanking - stacking process, the cold rolled steel coil is slit into slit coils, and the slit coils are blanked into stator and rotor single sheets in a high - speed punching machine; wherein the clearance between the punch and the die in the punching die is controlled to be 0.30 mm, and the area of the torn region of the blanking section is controlled to be 40 - 60%; the stator and rotor single sheets are stacked into a stator - rotor core for compressors.

[0035] According to the method for producing non-oriented electrical steel for compressors based on thin strip casting and rolling of the present invention, preferably, in the core annealing preparation process, the heating and heat preservation processes are protected by pure N2; then it is cooled at a speed of 2 - 10 °C / min. After cooling to the bluing temperature of 500 °C, steam is introduced and held for 1 hour; after the bluing treatment is completed, the steam valve is closed, and then pure N2 is continuously introduced for protection, and it is cooled in the furnace to 100 °C, and the core is taken out.

[0036] According to the second aspect of the present invention, there is provided a non-oriented electrical steel, which is produced by the aforementioned method, wherein the iron loss P of the non-oriented electrical steel 1.5 / 50 ≤ 3.5 W / kg, and the magnetic induction B 5000 ≥ 1.76 T.

[0037] The analysis of the functions of each element in the present invention is as follows:

[0038] C: 0.0015 - 0.0030%, S: 0.0015 - 0.0030%, Si: 0.95 - 1.05%, Mn: 0.20 - 0.30%, P ≤ 0.015%, Al ≤ 0.003%, Nb ≤ 0.003%, V ≤ 0.003%, Ti ≤ 0.003%, Cr ≤ 0.02%, Ni ≤ 0.02%, Cu ≤ 0.02%, N ≤ 0.0020%, and the rest are Fe and inevitable inclusions.

[0039] C, S, N: In non-oriented electrical steel, C, S, and N are all harmful elements, which lead to increased iron loss and reduced magnetic induction. However, the lower the contents of C and S, the higher the steelmaking cost. To meet the requirements for the magnetic properties of the finished non-oriented electrical steel for compressors based on thin strip casting and rolling, while taking into account the production cost, C: 0.0015 - 0.0030%, S: 0.0015 - 0.0030%, N ≤ 0.0020%;

[0040] Si, Al, Mn: Si and Al can increase the resistivity of the steel sheet and thus reduce the iron loss of non-oriented electrical steel; Mn forms MnS with S. Although it affects grain growth, it avoids the formation of low-melting-point FeS at the grain boundaries to avoid hot brittleness. Therefore, in the preparation of non-oriented electrical steel by traditional processes, the design of Si + Al + Mn is always adopted. However, in the thin strip casting and rolling process of the present invention, the Al2O3 inclusions formed by Al during the steelmaking process will gradually accumulate and form nodules on the side seal plate of the molten pool. Once the nodule is washed down by the steel flow and enters the casting roll, it will cause the continuous casting to break. Therefore, in the present invention, Al is strictly controlled to be ≤ 0.003%; Si can reduce the iron loss of non-oriented electrical steel, but at the same time it will reduce the magnetic induction. Considering comprehensively the magnetic properties, rollability and cost of the finished non-oriented electrical steel for compressors based on thin strip casting and rolling, the Si content is controlled between 0.95 - 1.05%, and the Mn content is controlled between 0.20 - 0.30%.

[0041] Nb, V, Ti, Cr, Ni, Cu: Nb, V, Ti, Cr, Ni, and Cu will simultaneously cause increased iron loss and reduced magnetic induction in non-oriented electrical steel. Therefore, Nb ≤ 0.003%, V ≤ 0.003%, Ti ≤ 0.003%, Cr ≤ 0.02%, Ni ≤ 0.02%, Cu ≤ 0.02%;

[0042] P: Phosphorus is a residual element, and it is required to control P ≤ 0.015%.

[0043] As can be seen from the above, by means of the special process of annealing the compressor iron core, the present invention obtains a hot-rolled coil with a thickness of 0.65 mm through the casting and rolling process, and obtains a cold-rolled hard coil with a thickness of 0.50 mm after one cold rolling; the cold-rolled hard coil is directly slit - blanked - stacked without annealing to obtain the stator and rotor cores for compressors; not only the production efficiency is improved and the production cost is reduced by saving processes, but also the requirements of low iron loss and high magnetic induction for the non-oriented electrical steel for compressors are achieved by giving full play to the advantages of the casting and rolling process and the iron core annealing process.

[0044] Beneficial technical effects

[0045] Compared with the prior art, the technical concept and corresponding technical solutions of the present invention can at least obtain the following beneficial technical effects:

[0046] (1) The molten steel directly obtains a cast strip with a thickness of 1.80 mm through two rotating steel rollers. Compared with the traditional process that uses a 220-mm cast slab, the reduction amount of subsequent hot rolling and cold rolling is significantly reduced, avoiding a significant increase in the α and γ components in the texture of non-oriented silicon steel caused by hot rolling + cold rolling with a large compression ratio, including {111}<110>, {111}<112>, and {112}<100> components; thereby increasing the proportion of the ideal {100}<0vw> texture and improving the magnetic induction of the finished product.

[0047] (2) A hot-rolled coil with a thickness of 0.65 mm is directly obtained through thin strip casting and rolling. Compared with the traditional process for low-silicon non-oriented silicon steel that uses a hot-rolled coil with a thickness of 2.50 - 2.75 mm and is rolled into a cold-rolled coil with a thickness of 0.50 mm through five stands of rolling, a cold-rolled coil with a thickness of 0.50 mm can be directly obtained through a single pass of rolling on a single stand rolling mill. This not only reduces the difficulty of cold rolling production and improves production efficiency, but also significantly reduces the work hardening amount from more than 80% to 23%, enabling the cold-rolled coil to be directly slit - blanked - stacked to obtain the stator and rotor cores for compressors.

[0048] (3) By precisely controlling the finish rolling temperature of hot rolling, the finish rolling temperature T is 880 - 920 °C, and T = (Ar1 - 60) - (Ar1 - 50) °C, enabling hot rolling to be completed in the high-temperature ferrite region. This avoids grain refinement caused by phase transformation after rolling, and at the same time, by means of high-temperature annealing of the core, complete recrystallization of the finished steel plate is controlled, with a grain size of 80 - 100 μm; for the finished non-oriented silicon steel with a thickness of 0.50 mm, the iron loss P 1.5 / 50 ≤ 3.5 W / kg, and the magnetic induction B 5000 ≥ 1.76 T.

[0049] (4) A single pass of cold rolling is carried out using a single stand rolling mill, controlling the roughness of the work roll to be 1.5 - 2.5 μm to obtain a cold-rolled hard coil with a surface roughness ≥ 0.80 μm, creating conditions for subsequent bluing treatment; and through bluing treatment, an iron oxide insulating coating is formed between the silicon steel sheets, reducing the coating process in the conventional process.

[0050] (5) The slit coil is blanked into stator and rotor single pieces in a high-speed punching machine. The clearance between the punch and die in the punching die is 0.30 mm, controlling the area of the torn region of the punching section to be 40 - 60%, which is conducive to the formation of a thicker oxide layer during subsequent heat treatment, increasing the contact resistance between the rotor cage bars and the core, reducing stray losses, and improving the motor efficiency.

[0051] (6) The method of the present invention uses twin-roll thin strip continuous casting + annealing-free core stamping + high-temperature annealing of the core, omitting processes such as hot rolling heating, normalizing, steel plate annealing before core stamping, and coating in the conventional process, and significantly reducing the reduction amount of hot and cold rolling. It is an energy-saving and environmentally friendly short-process production technology. Detailed implementation mode

[0052] 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 described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention.

[0053] Unless otherwise defined, the technical terms or scientific terms used in the present invention shall have the ordinary meanings understood by those of ordinary skill in the art to which the present invention pertains.

[0054] The following are the embodiments of the present invention. The described embodiments are only a part of the embodiments of the present invention. All other embodiments that those of ordinary skill in the art can obtain without creative efforts based on the embodiments of the present invention shall fall within the scope of protection of the present invention.

[0055] The technical solutions of the present invention are further illustrated below through specific Examples 1 to 3 and Comparative Examples 1 to 3:

[0056] Example 1

[0057] The non-oriented electrical steel and iron core for compressors based on strip casting of the present embodiment have the following chemical components by mass percentage:

[0058] C: 0.0022%, S: 0.0025%, Si: 0.98%, Mn: 0.28%, P: 0.012%, Al: 0.0023%, Nb: 0.0011%, V: 0.0023%, Ti: 0.0010%, Cr: 0.012%, Ni: 0.005%, Cu: 0.014%, N: 0.0013%, and the rest is Fe and inevitable inclusions.

[0059] It is prepared by successively performing molten steel smelting, strip casting, pickling, cold rolling, slitting-blanking-stacking, and iron core annealing. The thickness is 0.50 mm, the finished product grain size is 85 μm, and the iron loss P 1.5 / 50 is 3.45 W / kg, and the magnetic induction B 5000 is 1.782 T.

[0060] The preparation method of the above non-oriented electrical steel and iron core for compressors based on strip casting is carried out according to the following production steps:

[0061] (1) Molten steel smelting: Converter steelmaking is carried out using 63% hot metal + 37% scrap steel. The converter end-point C is 0.028%, S is 0.0016%, and P is 0.014%. Then, through vacuum smelting and alloying, molten steel with qualified composition is obtained, with the mass percentages being: C: 0.0022%, S: 0.0025%, Si: 0.98%, Mn: 0.28%, P: 0.012%, Al: 0.0023%, Nb: 0.0011%, V: 0.0023%, Ti: 0.0010%, Cr: 0.012%, Ni: 0.005%, Cu: 0.014%, N: 0.0013%, and the rest being Fe and inevitable inclusions.

[0062] (2) Thin strip continuous casting and rolling: Continuous casting is carried out using the twin-roll casting and rolling process. The starting pouring temperature of the molten steel is controlled at 1588°C. The molten steel is poured into the molten pool composed of a rotating steel roll and side seal plates through a tundish. After the molten steel contacts the crystallizing roll surface of the steel roll, it rapidly solidifies and forms, obtaining a cast strip with a thickness of 1.80 mm. The continuous casting speed is 60 m / min. The cast strip enters the rolling mill through a hot box under the protection of inert gas and is hot-rolled in one pass into a hot-rolled thin strip with a thickness of 0.65 mm. The final rolling temperature T is controlled at 885°C. After hot rolling, it is coiled, and the coiling temperature is controlled at 705°C. After coiling, it is air-cooled to room temperature to obtain a hot-rolled coil with a thickness of 0.65 mm.

[0063] (3) Pickling: Four-stage hydrochloric acid pickling is adopted. The concentration of the first-stage acid solution is 38 g / L, the second-stage is 82 g / L, the third-stage is 105 g / L, and the fourth-stage is 156 g / L. The Fe concentration in the first-stage acid solution ≤ 130 g / L, the Fe concentration in the second-stage acid solution ≤ 100 g / L, the Fe concentration in the third-stage acid solution ≤ 85 g / L, and the Fe concentration in the fourth-stage acid solution ≤ 50 g / L. The acid solution temperature is 81°C; the rinsing water temperature is 48°C. The pickling and rinsing speed is controlled at 180 mpm, and the pickling time is 50 s. 2+ concentration ≤ 130 g / L, the Fe concentration in the second-stage acid solution 2+ ≤ 100 g / L, the Fe concentration in the third-stage acid solution 2+ ≤ 85 g / L, the Fe concentration in the fourth-stage acid solution 2+ ≤ 50 g / L, the acid solution temperature is 81°C; the rinsing water temperature is 48°C. The pickling and rinsing speed is controlled at 180 mpm, and the pickling time is 50 s.

[0064] (4) Cold rolling: One-pass cold rolling is carried out using a single-stand rolling mill. The 0.65-mm-thick hot-rolled substrate is rolled into a 0.50-mm-thick cold-rolled hard coil; meanwhile, the roughness of the work roll is controlled at 2.2 μm to obtain a cold-rolled hard coil with a surface roughness of 0.92 μm.

[0065] (5) Slitting - Blanking - Stacking: The cold-rolled hard coil is slit to obtain slit coils, and the slit coils are blanked into single stator and rotor sheets in a high-speed punching machine. The clearance between the punch and die in the punching die is 0.30 mm, and the area of the torn region of the blanking section is controlled at 48%; the single stator and rotor sheets are stacked into a stator and rotor core for a compressor.

[0066] (6) Core annealing: The stator and rotor cores of the compressor are held at 925 °C for 150 min to ensure that complete recrystallization occurs in both the silicon steel matrix of the stator and rotor cores and the metal in the blanking deformation area, with a grain size of 85 μm. The heating and holding processes are protected by pure N2. Then, it is cooled at a rate of 5 °C / min. After cooling to the bluing temperature of 500 °C, steam is introduced and held for 1 hour. After the bluing treatment is completed, the steam valve is closed, and then pure N2 is continuously introduced for protection. It is cooled in the furnace to 100 °C, and the specimen is taken out.

[0067] After testing, the magnetic properties of the non-oriented silicon steel finished product for compressors based on strip casting are as follows: Iron loss P 1.5 / 50 is 3.45 W / kg, magnetic induction B 5000 is 1.782 T.

[0068] Example 2

[0069] The chemical composition of the non-oriented silicon steel and core for compressors based on strip casting in this embodiment is as follows by mass percentage:

[0070] C: 0.0027%, S: 0.0019%, Si: 1.03%, Mn: 0.23%, P: 0.009%, Al: 0.0027%, Nb: 0.0021%, V: 0.0027%, Ti: 0.0012%, Cr: 0.015%, Ni: 0.003%, Cu: 0.011%, N: 0.0007%, and the rest is Fe and inevitable inclusions.

[0071] It is prepared by sequentially performing molten steel smelting, strip casting, pickling, cold rolling, slitting-blanking-stacking, and core annealing. The thickness is 0.50 mm, the finished product grain size is 96 μm, and the iron loss P 1.5 / 50 is 3.28 W / kg, and the magnetic induction B 5000 is 1.775 T.

[0072] The preparation method of the non-oriented silicon steel and core for compressors based on strip casting is carried out according to the following production steps:

[0073] (1) Molten steel smelting: Converter steelmaking is carried out using 76% hot metal + 24% scrap steel. At the end of the converter process, C: 0.034%, S: 0.0023%, P: 0.012%; then through vacuum smelting and alloying, molten steel with qualified composition is obtained. Its chemical composition in mass percentage is: C: 0.0027%, S: 0.0019%, Si: 1.03%, Mn: 0.23%, P: 0.009%, Al: 0.0027%, Nb: 0.0021%, V: 0.0027%, Ti: 0.0012%, Cr: 0.015%, Ni: 0.003%, Cu: 0.011%, N: 0.0007%, and the rest is Fe and inevitable inclusions.

[0074] (2) Thin strip continuous casting and rolling: Continuous casting is carried out using the twin-roll casting and rolling process. The starting pouring temperature of the molten steel is controlled at 1583°C. The molten steel is poured into the molten pool composed of a rotating steel roll and side seal plates through a tundish. After the molten steel contacts the crystallizing roll surface of the steel roll, it solidifies rapidly and forms a cast strip with a thickness of 1.80 mm. The continuous casting speed is 60 m / min; the cast strip enters the rolling mill through a hot box under the protection of inert gas and is hot-rolled into a hot-rolled thin strip with a thickness of 0.65 mm in one pass. The final rolling temperature T is controlled at 900°C; after hot rolling, it is coiled, the coiling temperature is controlled at 712°C, and after coiling, it is air-cooled to room temperature to obtain a hot-rolled coil with a thickness of 0.65 mm.

[0075] (3) Pickling: Four-stage hydrochloric acid pickling is adopted. The concentration of the first-stage acid solution is 38 g / L, the second-stage is 82 g / L, the third-stage is 105 g / L, and the fourth-stage is 156 g / L. The Fe concentration in the first-stage acid solution ≤ 130 g / L, the Fe concentration in the second-stage acid solution ≤ 100 g / L, the Fe concentration in the third-stage acid solution ≤ 85 g / L, the Fe concentration in the fourth-stage acid solution ≤ 50 g / L, and the acid solution temperature is 81°C; the temperature of the rinsing water is 48°C. The pickling and rinsing speed is controlled at 180 mpm, and the pickling time is 50 s. 2+ The Fe concentration in the first-stage acid solution ≤ 130 g / L, and the Fe concentration in the second-stage acid solution 2+ ≤ 100 g / L. The Fe concentration in the third-stage acid solution 2+ ≤ 85 g / L, and the Fe concentration in the fourth-stage acid solution 2+ ≤ 50 g / L. The acid solution temperature is 81°C; the temperature of the rinsing water is 48°C. The pickling and rinsing speed is controlled at 180 mpm, and the pickling time is 50 s.

[0076] (4) Cold rolling: Single-stand rolling mill is used for one-pass cold rolling. The hot-rolled substrate with a thickness of 0.65 mm is rolled into a cold-rolled hard coil with a thickness of 0.50 mm; at the same time, the roughness of the work roll is controlled at 2.2 μm to obtain a cold-rolled hard coil with a surface roughness of 0.92 μm.

[0077] (5) Slitting - blanking - stacking: The cold-rolled hard coil is slit into slit coils, and the slit coils are blanked into single stator and rotor sheets in high-speed punching equipment. The clearance between the punch and die in the punching die is 0.30 mm, and the area of the torn region of the blanking section is controlled at 48%; the single stator and rotor sheets are stacked into a stator and rotor core for compressors.

[0078] (6) Core annealing: The stator and rotor cores of the compressor are kept at 925 °C for 150 min to ensure that complete recrystallization occurs in both the silicon steel matrix of the stator and rotor cores and the metal in the blanking deformation area, with a grain size of 96 μm. The heating and insulation processes are protected by pure N2. Then, it is cooled at a rate of 5 °C / min. After cooling to the bluing temperature of 500 °C, steam is introduced and kept for 1 hour. After the bluing treatment is completed, the steam valve is closed, and then pure N2 is continuously introduced for protection. The sample is taken out after furnace cooling to 100 °C.

[0079] After testing, the magnetic properties of the non-oriented silicon steel product for compressors based on strip casting are as follows: Iron loss P 1.5 / 50 is 3.28 W / kg, and magnetic induction B 5000 is 1.775 T.

[0080] Example 3

[0081] For the non-oriented silicon steel and core for compressors based on strip casting in this embodiment, their chemical compositions are in mass percentages as follows:

[0082] C: 0.0025%, S: 0.0018%, Si: 1.01%, Mn: 0.25%, P: 0.009%, Al: 0.0013%, Nb: 0.0015%, V: 0.0010%, Ti: 0.0009%, Cr: 0.012%, Ni: 0.005%, Cu: 0.003%, N: 0.0009%, and the rest are Fe and inevitable inclusions.

[0083] It is prepared by successively performing molten steel smelting, strip casting, pickling, cold rolling, slitting-blanking-stacking, and core annealing. The thickness is 0.50 mm, the finished product grain size is 92 μm, and the iron loss P 1.5 / 50 is 3.34 W / kg, and the magnetic induction B 5000 is 1.779 T.

[0084] The preparation method of the above non-oriented silicon steel and core for compressors based on strip casting is carried out according to the following production steps:

[0085] (1) Molten steel smelting: Converter steelmaking is carried out using 69% hot metal + 31% scrap steel. The converter end-point C is 0.042%, S is 0.0021%, and P is 0.008%. Then, through vacuum smelting and alloying, molten steel with qualified composition is obtained. Its chemical composition in mass percentage is: C: 0.0025%, S: 0.0018%, Si: 1.01%, Mn: 0.25%, P: 0.009%, Al: 0.0013%, Nb: 0.0015%, V: 0.0010%, Ti: 0.0009%, Cr: 0.012%, Ni: 0.005%, Cu: 0.003%, N: 0.0009%, and the rest is Fe and inevitable inclusions.

[0086] (2) Thin strip continuous casting and rolling: Continuous casting is carried out using the twin-roll casting and rolling process. The starting pouring temperature of the molten steel is controlled at 1586°C. The molten steel is poured into the molten pool composed of a rotating steel roll and side seal plates through a tundish. After the molten steel contacts the crystallizing roll surface of the steel roll, it solidifies rapidly and forms a cast strip with a thickness of 1.80 mm. The continuous casting speed is 60 m / min. The cast strip enters the rolling mill through a hot box under the protection of inert gas and is hot-rolled into a hot-rolled thin strip with a thickness of 0.65 mm in one pass. The final rolling temperature T is controlled at 892°C. After hot rolling, it is coiled, and the coiling temperature is controlled at 683°C. After coiling, it is air-cooled to room temperature to obtain a hot-rolled coil with a thickness of 0.65 mm.

[0087] (3) Pickling: Four-stage pickling with hydrochloric acid is adopted. The concentration of the first-stage acid solution is 38 g / L, the second-stage is 82 g / L, the third-stage is 105 g / L, and the fourth-stage is 156 g / L. The Fe concentration in the first-stage acid solution ≤ 130 g / L, the Fe concentration in the second-stage acid solution ≤ 100 g / L, the Fe concentration in the third-stage acid solution ≤ 85 g / L, and the Fe concentration in the fourth-stage acid solution ≤ 50 g / L. The acid solution temperature is 81°C; the rinsing water temperature is 48°C. The pickling and rinsing speed is controlled at 180 mpm, and the pickling time is 50 s. 2+ concentration ≤ 130 g / L, the Fe concentration in the second-stage acid solution 2+ ≤ 100 g / L, the Fe concentration in the third-stage acid solution 2+ ≤ 85 g / L, the Fe concentration in the fourth-stage acid solution 2+ ≤ 50 g / L, the acid solution temperature is 81°C; the rinsing water temperature is 48°C. The pickling and rinsing speed is controlled at 180 mpm, and the pickling time is 50 s.

[0088] (4) Cold rolling: One-pass cold rolling is carried out using a single-stand rolling mill. The hot-rolled substrate with a thickness of 0.65 mm is rolled into a cold-rolled hard coil with a thickness of 0.50 mm. At the same time, the roughness of the work roll is controlled at 2.2 μm to obtain a cold-rolled hard coil with a surface roughness of 0.92 μm.

[0089] (5) Slitting - Blanking - Stacking: The cold-rolled hard coil is slit into slit coils, and the slit coils are blanked into single stator and rotor sheets in a high-speed punching machine. The clearance between the convex and concave dies in the punching die is 0.30 mm, and the area of the torn region of the blanking section is controlled at 48%; the single stator and rotor sheets are stacked into a stator and rotor core for a compressor.

[0090] (6) Core annealing: The stator and rotor cores of the compressor are kept at 925 °C for 150 min to ensure that complete recrystallization occurs in both the silicon steel matrix of the stator and rotor cores and the metal in the blanking deformation area, with a grain size of 92 μm. The heating and insulation processes are protected with pure N2. Then, it is cooled at a rate of 5 °C / min. After cooling to the bluing temperature of 500 °C, steam is introduced and kept for 1 hour. After the bluing treatment is completed, the steam valve is closed, and then pure N2 is continuously introduced for protection. It is cooled in the furnace to 100 °C, and the specimen is taken out.

[0091] After testing, the magnetic properties of the non-oriented silicon steel finished product for compressors based on strip casting are as follows: Iron loss P 1.5 / 50 is 3.34 W / kg, and magnetic induction B 5000 is 1.779 T.

[0092] Comparative Example 1

[0093] For the non-oriented silicon steel and core for compressors based on strip casting in this comparative example, its chemical composition is by mass percentage:

[0094] C: 0.0022%, S: 0.0025%, Si: 0.98%, Mn: 0.28%, P: 0.012%, Al: 0.0023%, Nb: 0.0011%, V: 0.0023%, Ti: 0.0010%, Cr: 0.012%, Ni: 0.005%, Cu: 0.014%, N: 0.0013%, and the rest is Fe and inevitable inclusions.

[0095] It is prepared by sequentially performing molten steel smelting, strip casting, pickling, cold rolling, slitting-blanking-stacking, and core annealing. The final rolling temperature T of the strip casting process is controlled at 955 °C; other process parameters are the same as those in Example 1.

[0096] The thickness is 0.50 mm, the finished product grain size is 55 μm, and the iron loss P 1.5 / 50 is 4.01 W / kg, and the magnetic induction B 5000 is 1.758 T.

[0097] Comparative Example 2

[0098] For the non-oriented silicon steel and core for compressors based on strip casting in this comparative example, its chemical composition is by mass percentage:

[0099] C: 0.0027%, S: 0.0019%, Si: 1.03%, Mn: 0.23%, P: 0.009%, Al: 0.0027%, Nb: 0.0021%, V: 0.0027%, Ti: 0.0012%, Cr: 0.015%, Ni: 0.003%, Cu: 0.011%, N: 0.0007%, and the rest is Fe and inevitable inclusions.

[0100] It is prepared by sequentially performing molten steel smelting, thin strip continuous casting and rolling, pickling, cold rolling, slitting-blanking-stacking, and core annealing. Control the thin strip continuous casting and rolling process, and the final rolling temperature T is 862 °C; other process parameters are the same as those in Example 2.

[0101] The thickness is 0.50 mm, the finished product grain size is 68 μm, and the iron loss P 1.5 / 50 is 3.85 W / kg, and the magnetic induction B 5000 is 1.753 T.

[0102] Comparative Example 3

[0103] For the non-oriented electrical steel and core for compressors based on thin strip continuous casting and rolling in this comparative example, its chemical composition is by mass percentage:

[0104] C: 0.0025%, S: 0.0018%, Si: 1.01%, Mn: 0.25%, P: 0.009%, Al: 0.0013%, Nb: 0.0015%, V: 0.0010%, Ti: 0.0009%, Cr: 0.012%, Ni: 0.005%, Cu: 0.003%, N: 0.0009%, and the rest is Fe and inevitable inclusions.

[0105] It is prepared by sequentially performing molten steel smelting, thin strip continuous casting and rolling, pickling, cold rolling, slitting-blanking-stacking, and core annealing. Control the thin strip continuous casting and rolling process, and the final rolling temperature T is 873 °C; other process parameters are the same as those in Example 3.

[0106] The thickness is 0.50 mm, the finished product grain size is 78 μm, and the iron loss P 1.5 / 50 is 3.55 W / kg, and the magnetic induction B 5000 is 1.759 T.

[0107] The above are only specific embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for producing non-oriented silicon steel for compressors based on thin strip casting, characterized in that: The method comprises the following steps: 1) Molten steel smelting Steelmaking is carried out without adding Al, P, Sn and Sb. The chemical composition of molten steel in terms of mass percentage includes: C: 0.0015~0.0030%, S: 0.0015~0.0030%, Si: 0.95~1.05%, Mn: 0.20~0.30%, P≤0.015%, Al: ≤0.003%, Nb≤0.003%, V≤0.003%, Ti≤0.003%, Cr≤0.02%, Ni≤0.02%, Cu≤0.02%, N≤0.0020%, the rest is Fe and unavoidable inclusions; 2) Strip casting The cast strip is obtained by continuous casting using a twin-roll casting process, and then hot-rolled into a hot-rolled thin strip in one pass, wherein the final rolling temperature T is controlled to be 880-920°C, and the final rolling temperature T is further controlled to be T=(Ar1-60)-(Ar1-50)°C, wherein Ar1 is the γ / α phase transition temperature, in °C; After hot rolling, the coiling is carried out, and the coiling temperature is controlled to be ≥680°C. After coiling, the coiling is air-cooled to room temperature to obtain a hot-rolled coil; Where Ar1 is determined according to the following formula: Ar1=872℃+1000(11*[Si]-14*[Mn]+21*[Al]), Where [Si], [Mn], and [Al] are the mass percentages of Si, Mn, and Al, respectively; 3) Pickling process Use hydrochloric acid pickling, the acid solution temperature is controlled at 75-85℃; the rinsing water temperature is controlled at 45-55℃, the pickling and rinsing speeds are controlled at 150-200mpm, and the pickling time is controlled at 45-60s; 4) Cold rolling process The hot rolled base plate is rolled into hardened steel coils by a single stand rolling mill for one-pass cold rolling.

2. The method for producing non-oriented silicon steel for compressor based on thin strip casting and rolling according to claim 1, characterized in that: The method further comprises: 5) Slitting-punching-stacking The hardened steel coil is slit to obtain slit coils, the slit coils are punched into stator and rotor single pieces, and the stator and rotor single pieces are stacked to form stator and rotor cores for compressors.

3. The method for producing non-oriented silicon steel for compressor based on thin strip casting and rolling according to claim 2, characterized in that: The method further comprises: 6) Core annealing preparation The compressor stator and rotor cores were kept at 925°C for 150 minutes to ensure that the silicon steel matrix of the stator and rotor cores and the metal in the punching deformation area were completely recrystallized, with the grain size controlled to be 80-100 μm.

4. The method for producing non-oriented silicon steel for compressor based on thin strip casting and rolling according to claim 1, characterized in that: In the molten steel smelting process, 60-80% molten iron + 20-40% scrap steel is used for converter steelmaking, the converter end point C: 0.020-0.050%, S≤0.0025%, P≤0.015%; then vacuum smelting and alloying are performed to obtain molten steel.

5. The method for producing non-oriented silicon steel for compressor based on thin strip casting and rolling according to claim 1, characterized in that: In the thin strip casting and rolling process, the twin-roll casting and rolling process is used for continuous casting. The starting pouring temperature of the molten steel is controlled at 1580-1590°C. The molten steel is poured into a molten pool composed of a rotating steel roller and a side sealing plate through a tundish. The molten steel quickly solidifies and forms after contacting the crystallization roller surface of the steel roller to obtain a cast strip with a thickness of 1.80 mm. The continuous casting speed is 60 m / min. The cast strip passes through a hot box under the protection of inert gas and enters the rolling mill. After a single hot rolling, the cast strip with a thickness of 1.80 mm is hot rolled into a hot-rolled thin strip with a thickness of 0.65 mm.

6. The method for producing non-oriented silicon steel for compressor based on thin strip casting and rolling according to claim 1, characterized in that: In the pickling process, hydrochloric acid four-stage pickling is used: The concentration of level 1 acid is 30-50 g / L. The concentration of the second-level acid solution is 70-90 g / L. The concentration of level 3 acid is 100-120 g / L. The concentration of level 4 acid is 140-160 g / L. Fe in 1st grade acid 2+ Concentration ≤130g / L, Fe in 2nd grade acid 2+ Concentration ≤100g / L, Fe in 3-grade acid 2+ Concentration ≤85g / L, Fe in 4-grade acid 2+ Concentration ≤50g / L.

7. The method for producing non-oriented silicon steel for compressor based on thin strip casting and rolling according to claim 1, characterized in that: In the cold rolling process, the roughness of the working roll is controlled to be 1.5-2.5 μm, and the hardened steel coil with a surface roughness of ≥0.80 μm is obtained.

8. The method for producing non-oriented silicon steel for compressors based on thin strip casting and rolling according to claim 7, characterized in that: In the cold rolling process, the thickness of the hardened steel coil is controlled to be 0.50 mm.

9. The method for producing non-oriented silicon steel for compressor based on thin strip casting and rolling according to claim 1, characterized in that: In the slitting-punching-stacking process, the hardened steel coil is slid to obtain slitting coils, and the slitting coils are punched into stator and rotor single pieces in a high-speed punching machine. The gap between the male and female dies in the punch die is controlled to be 0.30 mm, and the tearing area of ​​the punching section is controlled to be 40-60%; The stator and rotor are stacked as a single piece to form a stator and rotor core for a compressor.

10. The method for producing non-oriented silicon steel for compressor based on thin strip casting and rolling according to claim 1, characterized in that: In the core annealing preparation process, pure N2 is used for protection during the heating and insulation process; Then, the mixture is cooled at a rate of 2 to 10°C / min until it reaches the blueing temperature of 500°C, and then steam is introduced and kept at this temperature for 1 hour. After the bluing treatment is completed, close the steam valve, and then continue to introduce pure N2 for protection. Cool down to 100℃ with the furnace and take out the iron core.

11. A non-oriented silicon steel, characterized in that: The non-oriented silicon steel is produced by the method according to any one of claims 1 to 10, wherein the iron loss P of the non-oriented silicon steel is 1.5 / 50 ≤3.5W / kg, magnetic induction B 5000 ≥1.76T.