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

Abstract

The invention belongs to the technical field of manufacturing of non-oriented electrical steel, and relates to a method for producing non-oriented silicon steel for a compressor based on thin-strip cast rolling. According to the invention, the low-silicon component design without adding Al, P, Sn and Sb is adopted, a hot-rolled thin substrate with the thickness of 0.60-0.80 mm is directly obtained through thin strip cast rolling, the finish rolling temperature T is controlled to be equal to (Ar1-70)-(Ar1-30) DEG C, and Ar1 is equal to 872 DEG C + 1000 (11 * [Si]-14 * [Mn] + 21 * [Al]); the coiling temperature is not less than 650 DEG C; after acid pickling and one-pass cold rolling, iron core blanking and stacking are directly carried out; and heat preservation is conducted for 120-180 min within the temperature range of 850-950 DEG C, and complete recrystallization annealing is conducted on the iron core. Compared with the 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 method is an energy-saving and environment-friendly short-process production technology.

Description

Technical Field

[0001] 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 compressors based on thin strip casting and rolling. Background Art

[0002] Non-oriented silicon steel, an important soft magnetic material, is primarily used in the manufacture of cores for various motors. The home appliance industry is one of the most important downstream industries for non-oriented silicon steel, consuming approximately 4 million tons of the steel annually. The majority of silicon steel raw materials used in this industry are medium- and low-grade non-oriented silicon steels, such as 50W1300 and 50W800, used in the manufacture of components such as refrigerator and air-conditioning compressor cores. Cast aluminum cores, due to their simple structure and ease of manufacture, are widely used in small and medium-sized motors and fixed-frequency compressors. During the core production process, finished silicon steel sheets are typically punched into stator and rotor laminations according to specific shapes and sizes. These laminations are then riveted together to form the stator and rotor core. To eliminate shear stress on the edges of the silicon steel sheets and reduce core losses, the core is annealed before assembly. Annealing temperatures for stator and rotor cores are typically between 700°C and 800°C, with a holding time of 120 to 180 minutes. This ensures recovery and recrystallization of the metal in the deformed areas of the stator and rotor cores, reducing core hysteresis losses.

[0003] Medium- and low-grade non-oriented silicon steels such as 50W1300 and 50W800 are generally produced through a sequential process of steelmaking, continuous casting, hot rolling, pickling, cold rolling, recrystallization annealing, coating, and finishing. Hot-rolled thicknesses range from 2.50 to 3.00 mm, cold-rolled thicknesses from 0.50 mm, and annealing temperatures from 800 to 950°C for 60 to 120 seconds. Compared to the 120 to 180-minute annealing times of compressor stator and rotor cores, the recrystallization annealing phase for non-oriented silicon steel is significantly shorter. Therefore, the possibility of integrating the two annealing steps is worth exploring. The finished silicon steel sheets are blanked and stacked between the two annealing steps. Conventional processes, such as eliminating the recrystallization annealing step and directly blanking the hardened sheet, present significant difficulties due to the high cold-rolling reduction (typically exceeding 80%) and severe work hardening. The resulting strength exceeds 900 MPa, making blanking difficult. Summary of the Invention

[0004] To address the aforementioned issues with conventional processes for producing non-oriented silicon steel and iron cores for compressors, the present invention provides a method for producing non-oriented silicon steel and iron cores for compressors based on thin strip casting. This method utilizes a low-silicon, aluminum-free design to directly produce a hot-rolled thin base plate with a thickness of 0.60-0.80 mm through thin strip casting, eliminating the need for continuous casting and heating of the ingot and significantly reducing the amount of hot rolling reduction. After pickling and a single cold rolling, the hot-rolled thin base plate is directly punched and stacked for iron core assembly. The core is then subjected to a bluing treatment and recrystallization annealing in a core annealing process.

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

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

[0007] 1) Molten steel smelting

[0008] Without adding Al, P, Sn and Sb, molten steel is obtained through converter steelmaking, vacuum smelting and alloying with the following mass percentage composition:

[0009] C: ≤0.0030%, S: ≤0.0030%, Si: 0.40~1.20%,

[0010] Mn: 0.20~0.30%, P: ≤0.03%, 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%, the rest is Fe and unavoidable inclusions;

[0013] 2) Thin strip casting

[0014] The cast strip is continuously cast using a twin-roll casting process to obtain a thickness of 1.60±0.20 mm at a continuous casting speed of 60-70 m / min, and then hot-rolled into a hot-rolled thin strip with a thickness of 0.60-0.80 mm in a single pass;

[0015] The finishing rolling temperature is controlled to be T, and T=(Ar1-70)~(Ar1-30)°C, where Ar1 is the γ / α phase transition temperature, unit: °C;

[0016] After hot rolling, the coiling temperature is controlled to be ≥650℃, and the coiling temperature is air-cooled to room temperature to obtain a hot-rolled coil with a thickness of 0.60-0.80mm. The calculation formula of Ar1 is:

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

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

[0019] 3) Pickling process

[0020] Use hydrochloric acid pickling, and the acid temperature is controlled at 75-85℃;

[0021] The rinsing water temperature is controlled at 45-55°C, the pickling and rinsing speeds are controlled at 150-200 mpm, and the pickling time is controlled at no less than 45-60 seconds;

[0022] 4) Cold rolling process

[0023] A single-stand rolling mill is used to carry out one-pass cold rolling with a cold rolling reduction rate of 10-40%, and the steel is rolled into a hardened steel coil with a thickness of 0.50 mm.

[0024] 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 comprises:

[0025] 5) Slitting-punching-stacking

[0026] The hardened steel coil is slit to obtain slit coils, which are punched into stator and rotor single pieces in a high-speed punching machine. The stator and rotor single pieces are stacked to form the stator and rotor core for the compressor.

[0027] 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 comprises:

[0028] 6) Core annealing preparation

[0029] The compressor stator and rotor cores are kept at 850-950°C for 120-180 minutes to ensure that the silicon steel matrix of the stator and rotor cores and the metal in the punching deformation area are completely recrystallized, with the grain size controlled to be 80-100 μm.

[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 molten steel smelting process, 60-80% molten iron + 20-40% scrap steel are used for converter steelmaking, and the converter end point C is: 0.020-0.050%, S≤0.0025%, and P≤0.03%.

[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 molten steel smelting process, the mass percentage of Si in the molten steel is 0.40-0.70%.

[0032] 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 molten steel smelting process, the mass percentage of Si in the molten steel is 0.70-0.90%.

[0033] 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 molten steel smelting process, the mass percentage of Si in the molten steel is 0.90-1.20%.

[0034] 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, the initial 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 roller and a side sealing plate through a tundish, the molten steel rapidly solidifies and forms after contacting the crystallization roller surface of the steel roller, the continuous casting speed is controlled to be 60-70m / min, and a cast strip with a thickness of 1.60±0.20mm is obtained.

[0035] 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, the cast strip enters the rolling mill through a hot box under the protection of inert gas, and is hot-rolled in one pass at a reduction rate of 50 to 70% into a hot-rolled thin strip with a thickness of 0.60 to 0.80 mm.

[0036] 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:

[0037] The concentration of level 1 acid solution is 30-50 g / L.

[0038] The concentration of the second-level acid solution is 70-90 g / L.

[0039] The concentration of level 3 acid is 100-120 g / L.

[0040] The concentration of level 4 acid is 140-160 g / L.

[0041] Fe in 1st grade acid 2+ Concentration ≤130g / L,

[0042] Fe in 2nd grade acid solution 2+ Concentration ≤ 100g / L,

[0043] Fe in 3-grade acid solution 2+ Concentration ≤85g / L,

[0044] Fe in 4-grade acid solution 2+ Concentration ≤50g / L.

[0045] 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 cold rolling process, the roughness of the working rolls is controlled to be 1.5-2.5 μm to obtain a hardened steel coil with a surface roughness of ≥0.80 μm.

[0046] 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 stripping-punching-stacking process, the gap between the male and female dies in the high-speed punching die is controlled to 0.25-0.50 mm, and the tearing area of ​​the punching section is controlled to 40-60%.

[0047] 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 iron core annealing preparation step, pure N2 is used for protection during the heating and insulation processes.

[0048] 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 iron core annealing preparation process, after the insulation is completed, cooling is carried out at a rate of 2 to 10°C / min, and after cooling to the bluing temperature of 450 to 550°C, water vapor is introduced and the heat is maintained for 1 hour; after the bluing treatment is completed, the steam valve is closed, and then pure N2 is continued to be introduced for protection, and the iron core is cooled to 100°C with the furnace, and then the iron core is taken out.

[0049] According to a second aspect of the present invention, there is provided a non-oriented silicon steel, which is produced by the above method, wherein the steel is smelted according to the chemical composition Si: 0.40-1.20%, and the iron loss P of the non-oriented silicon steel is 1.5 / 50 ≤4.5W / kg, magnetic induction B 5000 ≥1.76T.

[0050] According to a third aspect of the present invention, there is provided a non-oriented silicon steel, which is produced by the above method, wherein the steel is smelted according to the chemical composition Si: 0.40-0.70%, and the iron loss P of the non-oriented silicon steel is 1.5 / 50 ≤4.5W / kg, magnetic induction B 5000 ≥1.78T.

[0051] According to a fourth aspect of the present invention, there is provided a non-oriented silicon steel, which is produced by the above method, wherein the steel is smelted according to the chemical composition Si: 0.70-0.90%, and the iron loss P of the non-oriented silicon steel is 1.5 / 50 ≤4.0W / kg, magnetic induction B 5000 ≥1.77T.

[0052] According to a fifth aspect of the present invention, there is provided a non-oriented silicon steel, which is produced by the above method, wherein the steel is smelted according to the chemical composition Si: 0.90-1.20%, and the iron loss P of the non-oriented silicon steel is 1.5 / 50 ≤3.5W / kg, magnetic induction B 5000 ≥1.76T.

[0053] The role of each element in the present invention is analyzed as follows:

[0054] C: ≤0.0030%, S: ≤0.0030%, Si: 0.40~1.20%, Mn: 0.20~0.30%,

[0055] P: ≤0.03%, Al: ≤0.003%, Nb: ≤0.003%, V: ≤0.003%,

[0056] Ti: ≤0.003%, Cr: ≤0.02%, Ni: ≤0.02%, Cu: ≤0.02%,

[0057] N: ≤0.0020%, the rest is Fe and unavoidable inclusions.

[0058] C, S, N:

[0059] In non-oriented silicon steel, C, S, and N are all harmful elements, which lead to increased iron loss and reduced magnetic induction. In order to meet the magnetic property requirements of the finished non-oriented silicon steel for compressors based on thin strip casting, C≤0.0030%, S≤0.0030%, and N≤0.0020%.

[0060] Si, Al, Mn:

[0061] Si and Al can increase the resistivity of the steel plate and thus reduce the steel loss of non-oriented silicon steel; Mn forms MnS with S, which affects grain growth but avoids the formation of low-melting-point FeS at the grain boundaries to avoid hot brittleness. Therefore, when preparing non-oriented silicon steel in the traditional process, the design of Si+Al+Mn is 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 sealing plates of the molten pool. Once the nodules are washed down by the steel flow and enter the casting rollers, it will cause the continuous casting strip to break. Therefore, the present invention strictly controls Al≤0.003%; Si can reduce the steel loss of non-oriented silicon steel, but at the same time it will reduce the magnetic induction. Taking into account the magnetic properties, rollability and cost of the non-oriented silicon steel finished product for compressors based on thin strip casting and rolling, the Si content is controlled between 0.40 and 1.20%, and the Mn content is controlled between 0.20 and 0.30%.

[0062] Nb, V, Ti, Cr, Ni, Cu:

[0063] Nb, V, Ti, Cr, Ni, and Cu in non-oriented silicon steel will increase iron loss and reduce magnetic induction. Therefore, control Nb≤0.003%, V≤0.003%, Ti≤0.003%, Cr≤0.02%, Ni≤0.02%, and Cu≤0.02%.

[0064] Phosphorus (P) is a residual element that, in conventional processes, can segregate in the core of the ingot, affecting rollability and microstructure uniformity in the finished product. Therefore, P is typically controlled to 0.015% or less, significantly increasing steelmaking costs. However, in the thin strip casting and rolling process of the present invention, P does not segregate due to the high cooling rate of the strip at 1000°C / s. Therefore, the present invention relaxes the P control standard to 0.03% or less, reducing steelmaking costs.

[0065] From the above content, it can be seen that the present invention uses a special process for annealing the compressor core to obtain a hot-rolled coil with a thickness of 0.60 to 0.80 mm through a casting and rolling process, and obtains a hard-rolled coil with a thickness of 0.50 mm after one cold rolling; the hard-rolled coil is directly striped, punched, and stacked without annealing to obtain the stator and rotor core for the compressor; not only by saving steps, improving production efficiency and reducing production costs, but also by giving full play to the advantages of the casting and rolling process and the core annealing process, the non-oriented silicon steel for the compressor can meet the requirements of low iron loss and high magnetic induction at the same time.

[0066] Beneficial technical effects

[0067] Compared with the prior art, the technical concept and corresponding technical solutions of the present invention can at least achieve the following beneficial technical effects:

[0068] (1) The molten steel is directly cast into a strip with a thickness of 1.60±0.20 mm by two rotating steel rollers. Compared with the conventional process using 220 mm ingot, the subsequent hot rolling and cold rolling reduction is greatly reduced, and the high reduction ratio hot rolling + cold rolling is avoided, which causes a significant increase in the α and γ components in the non-oriented silicon steel texture, including {111} <110> 、{111} <112> 、{112} <100> components; thereby increasing the proportion of the ideal {100}<0vw> texture and improving the magnetic induction of the finished product.

[0069] (2) Through thin strip casting and rolling, hot-rolled coils with a thickness of 0.60-0.80 mm are directly obtained. Compared with the traditional process of low-silicon non-oriented silicon steel, which uses 2.50-2.75 mm hot-rolled coils to produce 0.50 mm cold-rolled coils through five stands, the 0.50 mm cold-rolled coils can be directly produced by rolling on a single stand mill in one pass. This not only reduces the difficulty of cold rolling production and improves production efficiency, but also greatly reduces the amount of work hardening, allowing the cold-rolled coils to be directly slit-punched-stacked to obtain the stator and rotor cores for compressors.

[0070] (3) By precisely controlling the hot rolling finishing temperature, the finishing temperature T = (Ar1-70) ~ (Ar1-30) ° C, hot rolling is completed in the high temperature ferrite region. This avoids the grain refinement caused by the phase transformation after rolling. At the same time, with the help of high temperature annealing of the core, the finished steel plate is controlled to undergo complete recrystallization, with a grain size of 80 ~ 100 μm; the finished non-oriented silicon steel product with a thickness of 0.50 mm has an iron loss of P 1.5 / 50 3.0~4.3W / kg, magnetic induction B 5000 It is 1.76~1.80T.

[0071] (4) A single-stand rolling mill is used for one-pass cold rolling, and the roughness of the working roll is controlled to be 1.5-2.5 μm, so as to obtain a hardened steel coil with a surface roughness of ≥0.80 μm, thereby creating conditions for subsequent bluing treatment; and through the bluing treatment, an iron oxide insulating coating is formed between the silicon steel sheets, thereby reducing the coating process in the conventional process.

[0072] (5) The strip rolls are punched into stator and rotor single pieces in a high-speed punching machine. The gap between the male and female dies in the punching die is 0.25 to 0.50 mm, and the tearing area of ​​the punched section is controlled to be 40 to 60%, which is conducive to the formation of a thicker oxide layer during the subsequent heat treatment process, increasing the contact resistance between the rotor cage bar and the iron core, reducing stray losses, and improving the efficiency of the motor.

[0073] (6) The present invention adopts a method of double-roll thin strip continuous casting + annealing-free iron core stamping + iron core high-temperature annealing. Compared with the conventional process, it omits the processes of hot rolling heating, normalizing, steel plate annealing before iron core stamping and coating, and greatly reduces the hot and cold rolling reduction. It is an energy-saving and environmentally friendly short-process production technology. DETAILED DESCRIPTION

[0074] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the described 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.

[0075] Unless otherwise defined, technical or scientific terms used in the present invention shall have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

[0076] The following are embodiments of the present invention. The described embodiments are only part of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments that can be obtained by ordinary technicians in this field without making any creative work are within the scope of protection of the present invention.

[0077] The following four examples further illustrate the beneficial effects of this embodiment. Of course, these four examples are only a part of the many variations of the present invention, not all of them. The four examples each provide a non-oriented silicon steel and iron core for a compressor based on strip casting, and the specific production methods are as follows:

[0078] (1) Examples 1 to 4 were all subjected to converter steelmaking, vacuum smelting and alloying to obtain molten steel with qualified composition, as shown in Table 1 by mass percentage.

[0079] Table 1 Chemical composition of molten steel of Examples 1-4

[0080]

[0081] The molten steel smelting adopts molten iron + scrap steel for converter steelmaking. The ratio of molten iron and scrap steel, as well as the mass percentage of C, S, and P at the converter end point in Examples 1 to 4 are shown in Table 2.

[0082] Table 2 The ratio of molten iron to scrap steel and the mass percentage of C, S and P at the converter end point in Examples 1-4

[0083] Converter steelmaking parameters Molten iron ratio Scrap steel ratio Converter end point C Converter end point S Converter end point P Example 1 63％ 37％ 0.035 0.0017 0.016 Example 2 67％ 33％ 0.028 0.0025 0.013 Example 3 73％ 27％ 0.039 0.0022 0.022 Example 4 75％ 25％ 0.045 0.0018 0.012

[0084] (2) Examples 1-4: The qualified molten steel obtained in Step 1 was cast and rolled. Each was cast using a twin-roll casting process to produce a cast strip; this was then hot-rolled into a hot-rolled thin strip in a single pass. The corresponding pouring temperature, continuous casting speed, cast strip thickness, reduction ratio, hot-rolled thin strip thickness, finishing temperature, coiling temperature, and Ar1 for Examples 1-4 are shown in Table 3.

[0085] Table 3 Parameters such as pouring temperature, continuous casting speed, etc. corresponding to Examples 1-4

[0086]

[0087] (3) Examples 1 to 4: The hot-rolled thin strip obtained in step 2 was pickled. Hydrochloric acid was used for four-stage pickling. The concentration of the first-stage acid solution was 38 g / L, the concentration of the second-stage acid solution was 82 g / L, the concentration of the third-stage acid solution was 105 g / L, and the concentration of the fourth-stage acid solution was 156 g / L. 2+ Concentration ≤130g / L, Fe in 2nd grade acid solution 2+ Concentration ≤100g / L, Fe in grade 3 acid solution 2+ Concentration ≤85g / L, Fe in 4-grade acid solution 2+ Concentration ≤50g / L, acid solution temperature 81℃; rinse water temperature 48℃, pickling and rinsing speeds controlled at 180mpm, pickling time 50s.

[0088] (4) Examples 1-4: The pickled hot-rolled thin strip obtained in Step 3 was cold rolled in a single-stand rolling mill to form a 0.50 mm thick hardened steel coil. The cold rolling reduction in Example 1 was 33.3%; in Example 2, 23.1%; in Example 3, 23.1%; and in Example 4, 28.6%.

[0089] (5) Examples 1-4: The hardened steel coil obtained in step 4 was slit to obtain slit coils, which were then punched into stator and rotor monoliths in a high-speed punch press. The stator and rotor monoliths were then stacked to form a stator and rotor core for a compressor. In Example 1, the punch die gap was 0.30 mm, and the punched cross-section tear area was 48%; in Example 2, the punch die gap was 0.40 mm, and the punched cross-section tear area was 55%; in Example 3, the punch die gap was 0.40 mm, and the punched cross-section tear area was 52%; in Example 4, the punch die gap was 0.30 mm, and the punched cross-section tear area was 44%.

[0090] (6) Examples 1 to 4 anneal the compressor stator and rotor core obtained in step 5 to ensure that the silicon steel matrix of the stator and rotor core and the metal in the punching deformation area are completely recrystallized. Pure N2 is used for protection during the heating and insulation process. After the insulation is completed, it is cooled at a rate of 5°C / min. After cooling to the blueing temperature of 500°C, water vapor is introduced and the temperature is kept for 1 hour; after the bluing treatment is completed, the steam valve is closed, and then pure N2 is continued to be introduced for protection. It is cooled to 100°C with the furnace and the sample is taken out. The core annealing temperature, insulation time, finished product grain size, iron loss and magnetic induction are shown in Table 4.

[0091] Table 3 Parameters such as pouring temperature, continuous casting speed, etc. corresponding to Examples 1-4

[0092]

[0093] Comparative Example 1

[0094] The non-oriented silicon steel and iron core of this comparative example compressor are manufactured by sequentially performing molten steel smelting, thin strip casting and rolling, pickling, cold rolling, stripping-punching-stacking, and iron core annealing. The final rolling temperature T of the thin strip casting and rolling process is controlled to be 900°C; other process parameters are the same as those of Example 1. The thickness is 0.50mm, the finished grain size is 65μm, and the iron loss P is 0.50mm. 1.5 / 50 is 4.75W / kg, magnetic induction B 5000 It is 1.778T.

[0095] Comparative Example 2

[0096] The non-oriented silicon steel and iron core of this comparative example compressor are manufactured by sequentially smelting steel, casting and rolling thin strips, pickling, cold rolling, stripping, blanking, laminating, and iron core annealing. The final rolling temperature T of the thin strip casting process is controlled to be 855℃; other process parameters are the same as those of Example 2. The thickness is 0.50mm, the finished grain size is 72μm, and the iron loss P is 0.50mm. 1.5 / 50 is 4.35W / kg, magnetic induction B 5000 It is 1.768T.

[0097] Comparative Example 3

[0098] This comparative example used non-oriented silicon steel for the compressor, which was produced through a sequential process of molten steel smelting and strip casting and rolling. The cast strip thickness during the casting and rolling process was controlled to be 1.60 mm, and the hot-rolled strip thickness was 0.54 mm; other process parameters were the same as those in Example 3. Due to the high reduction ratio of over 65% in a single hot-rolling pass, large edge waves on both sides resulted in unstable rolling and coiling.

[0099] Comparative Example 4

[0100] The non-oriented silicon steel used in this comparative example for the compressor was subjected to a sequential process of molten steel smelting, strip casting, pickling, cold rolling, and slitting-blanking. The casting process controlled the thickness of the cast strip to 2.0 mm, and the hot-rolled strip to 1.0 mm. The cold rolling process controlled the cold rolling reduction to 50% to produce a 0.50 mm thick hardened steel coil. Other process parameters were the same as those in Example 4. Cracking of the hardened steel sheet occurred during the blanking process, preventing the core assembly and annealing from being completed.

[0101] The above description is only a specific embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, they can make several improvements and modifications without departing from the principles of the present invention. These improvements and modifications should also be considered within the scope of protection 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 Without adding Al, P, Sn and Sb, molten steel is obtained through converter steelmaking, vacuum smelting and alloying with the following mass percentage composition: C: ≤0.0030%, S: ≤0.0030%, Si: 0.40~1.20%, Mn: 0.20~0.30%, P: ≤0.03%, 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) Thin strip casting The cast strip is continuously cast using a twin-roll casting process to obtain a thickness of 1.60±0.20 mm at a continuous casting speed of 60-70 m / min, and then hot-rolled into a hot-rolled thin strip with a thickness of 0.60-0.80 mm in a single pass; The finishing rolling temperature is controlled to be T, and T=(Ar1-70)~(Ar1-30)°C, where Ar1 is the γ / α phase transition temperature, unit: °C; After hot rolling, the coiling temperature is controlled to be ≥650℃, and the coiling temperature is air-cooled to room temperature to obtain a hot-rolled coil with a thickness of 0.60-0.80mm. The calculation formula of Ar1 is: Ar1=872℃+1000(11*[Si]-14*[Mn]+21*[Al]), Wherein, [Si], [Mn], and [Al] are the mass percentages of Si, Mn, and Al, respectively; 3) Pickling process Use hydrochloric acid pickling, and the acid temperature is controlled at 75-85℃; The rinsing water temperature is controlled at 45-55°C, the pickling and rinsing speeds are controlled at 150-200 mpm, and the pickling time is controlled at no less than 45-60 seconds; 4) Cold rolling process A single-stand rolling mill is used to carry out one-pass cold rolling with a cold rolling reduction rate of 10-40%, and the steel is rolled into a hardened steel coil with a thickness of 0.50 mm.

2. The method for producing non-oriented silicon steel for compressors 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, which are punched into stator and rotor single pieces in a high-speed punching machine. The stator and rotor single pieces are stacked to form the stator and rotor core for the compressor.

3. The method for producing non-oriented silicon steel for compressors 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 are kept at 850-950°C for 120-180 minutes to ensure that the silicon steel matrix of the stator and rotor cores and the metal in the punching deformation area are completely recrystallized, with the grain size controlled to be 80-100 μm.

4. The method for producing non-oriented silicon steel for compressors 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 are used for converter steelmaking, and the converter end point C is: 0.020-0.050%, S≤0.0025%, and P≤0.03%.

5. The method for producing non-oriented silicon steel for compressors based on thin strip casting and rolling according to claim 1, characterized in that: In the molten steel smelting process, the mass percentage of Si in the molten steel is 0.40~0.70%.

6. The method for producing non-oriented silicon steel for compressors based on thin strip casting and rolling according to claim 1, characterized in that: In the molten steel smelting process, the mass percentage of Si in the molten steel is 0.70~0.90%.

7. The method for producing non-oriented silicon steel for compressors based on thin strip casting and rolling according to claim 1, characterized in that: In the molten steel smelting process, the mass percentage of Si in the molten steel is 0.90~1.20%.

8. The method for producing non-oriented silicon steel for compressors based on thin strip casting and rolling according to claim 1, characterized in that: In the thin strip casting and rolling process, the initial pouring temperature of the molten steel is controlled at 1580-1590°C. The molten steel is poured into a molten pool composed of rotating steel rollers and side sealing plates through a tundish. The molten steel quickly solidifies and forms after contacting the crystallization roller surface of the steel roller. The continuous casting speed is controlled at 60-70m / min to obtain a cast strip with a thickness of 1.60±0.20mm.

9. The method for producing non-oriented silicon steel for compressors based on thin strip casting and rolling according to claim 1, characterized in that: In the thin strip casting and rolling process, the cast strip enters the rolling mill through a hot box under the protection of inert gas, and is hot rolled in one pass at a reduction rate of 50-70% into a hot-rolled thin strip with a thickness of 0.60-0.80 mm.

10. The method for producing non-oriented silicon steel for compressors 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 solution 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 solution 2+ Concentration ≤ 100g / L, Fe in 3-grade acid solution 2+ Concentration ≤85g / L, Fe in 4-grade acid solution 2+ Concentration ≤50g / L.

11. The method for producing non-oriented silicon steel for compressors 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 to 2.5 μm, and a hardened steel coil with a surface roughness of ≥0.80 μm is obtained.

12. The method for producing non-oriented silicon steel for compressors based on thin strip casting and rolling according to claim 2, characterized in that: In the stripping-punching-stacking process, the gap between the male and female dies in the high-speed punching die is controlled to 0.25-0.50 mm, and the tearing area of ​​the punching section is controlled to 40-60%.

13. The method for producing non-oriented silicon steel for compressors based on thin strip casting and rolling according to claim 3, characterized in that: During the core annealing preparation process, pure N2 is used for protection during the heating and insulation processes.

14. The method for producing non-oriented silicon steel for compressors based on thin strip casting and rolling according to claim 13, characterized in that: In the iron core annealing preparation process, after the heat preservation is completed, the core is cooled at a rate of 2 to 10°C / min. After cooling to the blueing temperature of 450 to 550°C, water vapor is introduced and the core is kept warm 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.

15. 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 14, wherein the steel is smelted according to the chemical composition Si: 0.40-1.20%, and the iron loss P of the non-oriented silicon steel is 1.5 / 50 ≤4.5W / kg, magnetic induction B 5000 ≥1.76T.

16. 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 14, wherein the steel is smelted according to the chemical composition Si: 0.40-0.70%, and the iron loss P of the non-oriented silicon steel is 1.5 / 50 ≤4.5W / kg, magnetic induction B 5000 ≥1.78T.

17. 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 14, wherein the steel is smelted according to the chemical composition Si: 0.70-0.90%, and the iron loss P of the non-oriented silicon steel is 1.5 / 50 ≤4.0W / kg, magnetic induction B 5000 ≥1.77T.

18. 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 14, wherein the steel is smelted according to the chemical composition Si: 0.90-1.20%, and the iron loss P of the non-oriented silicon steel is 1.5 / 50 ≤3.5W / kg, magnetic induction B 5000 ≥1.76T.

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