Economical high-hardness low-grade aluminum-free non-oriented silicon steel and preparation method thereof

Abstract

The invention discloses economical high-hardness low-grade aluminum-free non-oriented silicon steel and a preparation method thereof. The economical high-hardness low-grade aluminum-free non-oriented silicon steel comprises the following components in percentage by mass: less than or equal to 0.003% of C, 0.50-0.70% of Si, 0.25-0.65% of Mn, 0.09-0.10% of P, less than or equal to 0.0040% of S, less than or equal to 0.0010% of Al and the balance of Fe and inevitable impurities. On the basis of low-cost aluminum-free high-phosphorus component design, the electromagnetic performance and the mechanical performance are improved by increasing the content of Si, adding and controlling strengthening elements, strictly controlling the process temperature control precision in the hot rolling production process and optimizing the temperature and speed process setting of the continuous annealing process; the high-hardness low-cost aluminum-free non-oriented silicon steel suitable for the high-speed punching machine is produced, so that the aluminum-free non-oriented silicon steel has excellent magnetic characteristics and high hardness, and the requirement of a user for high efficiency in motor stator and rotor punching sheet production is met.

Description

Technical Field

[0001] This invention relates to the fields of materials and metallurgy, and more specifically, to an economical, high-hardness, low-grade aluminum-free, non-oriented silicon steel and its preparation method. Background Technology

[0002] To achieve stability and quality in high-speed stamping production, non-oriented silicon steel has stricter requirements for magnetic properties, machinability, and high hardness. Among these, the magnetic properties require low iron loss and high magnetic induction. High hardness, on the other hand, can greatly improve its service life and safety.

[0003] However, the market currently uses a large amount of ordinary non-oriented silicon steel, whose chemical composition is mostly a combination of Si and Al. Its magnetic properties and strength requirements are insufficient to meet the demands for high precision, high stability, and high efficiency. Under these circumstances, with the increasingly fierce competition in the non-oriented silicon steel market, how to prepare non-oriented silicon steel that balances both magnetic properties and high hardness has become a hot research topic.

[0004] Therefore, it is of great significance to provide a non-oriented silicon steel with both low iron loss and high hardness and its preparation process. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned defects in the prior art and provide an economical, high-hardness, low-grade aluminum-free, non-oriented silicon steel and its preparation method.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: An economical, high-hardness, low-grade aluminum-free, non-oriented silicon steel comprises the following components by mass percentage: C ≤ 0.003%, Si: 0.50%–0.70%, Mn: 0.25%–0.65%, P: 0.09%–0.10%, S ≤ 0.0040%, Al ≤ 0.0010%, with the balance being Fe and unavoidable impurities.

[0007] Optionally, the magnetic induction intensity B of the aluminum-free, non-oriented silicon steel 50 ≥1.75T, iron loss P 15 / 50 ≤5.8W / kg, hardness ≥120HV.

[0008] This invention also discloses a method for preparing the above-mentioned economical, high-hardness, low-grade aluminum-free, non-oriented silicon steel, comprising the following steps: In the smelting process, steel grades are smelted according to their composition, and after tapping, the molten steel is continuously cast into slabs. In hot rolling, the slab is subjected to a hot charging process with a furnace charging temperature ≥600℃; the slab is in the furnace for ≥160 min; the slab exits the furnace at a temperature of 1150~1200℃; the hot rolling finishing temperature is 860~900℃; and the coiling temperature is 680~720℃. In cold rolling, the hot-rolled coil is pickled and then cold-rolled to obtain a cold-rolled steel coil with a thickness of 0.5 mm; the cold rolling is carried out in 5 passes using a 20-roll single-stand cold rolling mill. In the annealing process, the cold-rolled steel coil is annealed in a continuous annealing furnace at a temperature of 840–900°C. The proportion of the SF section in the continuous annealing furnace is 8–15 sections, the annealing process speed is 100–160 m / min, and the high cooling rate is ≥15°C / s, to obtain the aluminum-free, non-oriented silicon steel.

[0009] Optionally, in the cold rolling process, the reduction rate of the first four passes is 25-40%, the reduction rate of the last pass is ≤10%, the rolling force is 350-650 tons, the rolling speed is 400-750 mpm, and the unit tension of each pass is maintained at 10-40 N / mm during the rolling process. 2 .

[0010] Optionally, in the continuous casting, the thickness of the slab is 220-240 mm.

[0011] Optionally, in the hot rolling process, the thickness of the hot-rolled coil is 2.5 mm to 2.75 mm.

[0012] Optionally, the pickling solution used is a hydrochloric acid solution with a concentration of 5% to 20%.

[0013] Optionally, in the hot rolling process, the slab sequentially passes through a preheating section, a first heating section, a second heating section, and a soaking section in a heating furnace; the heating temperature of the preheating section is 900–1000℃, and the heating time of the preheating section is 30–40 min; the heating temperature of the first heating section is 1000–1100℃, and the heating time of the first heating section is 40–60 min; the heating temperature of the second heating section is 1100–1200℃, and the heating time of the second heating section is 40–60 min; the heating temperature of the soaking section is 1150–1220℃, and the heating time of the soaking section is 40–50 min.

[0014] Implementing the embodiments of the present invention will have the following beneficial effects: (1) Based on the low-cost aluminum-free high-phosphorus composition design, this invention reduces costs by increasing the Si content and adding and controlling the strengthening elements, while ensuring magnetic properties and significantly improving the stamping properties; and strictly controls the process temperature control accuracy in the hot rolling process, optimizes the temperature and speed process settings of the continuous annealing process, and improves electromagnetic and mechanical properties, producing a high-hardness, low-cost aluminum-free non-oriented silicon steel suitable for high-speed punching machines, so that the aluminum-free non-oriented silicon steel has excellent magnetic properties and high hardness, thereby meeting the user's high-efficiency needs in the production of motor stator and rotor laminations.

[0015] (2) High-hardness, low-grade non-oriented silicon steel is rolled using a single stand with 20 rolls to ensure stable production.

[0016] (3) The non-oriented silicon steel with grade 50W1300 and thickness of 0.5mm produced by this invention can achieve the following magnetic properties: magnetic induction intensity B 50 ≥1.75T, iron loss P 15 / 50 With a strength of ≤5.8W / kg and a hardness of ≥120HV, the finished steel meets the requirements of high-end users in terms of magnetic induction, hardness, and iron loss, while also exhibiting high punching performance. Detailed Implementation

[0017] The present invention will be further described below with reference to specific embodiments, but this does not limit the present invention in any way.

[0018] This invention discloses an economical, high-hardness, low-grade aluminum-free, non-oriented silicon steel, comprising the following components by mass percentage: C ≤ 0.003%, Si: 0.50%–0.70%, Mn: 0.25%–0.65%, P: 0.09%–0.10%, S ≤ 0.0040%, Al ≤ 0.0010%, with the balance being Fe and unavoidable impurities. This invention reduces costs and decreases the formation of aluminum carbonitride inclusions through aluminum-free composition design, improving slab quality; it also increases the P content, enhancing the strength of the finished product while strengthening grain boundary segregation and improving overall magnetic properties.

[0019] In one specific embodiment, the magnetic induction intensity B of aluminum-free, non-oriented silicon steel 50 ≥1.75T, iron loss P 15 / 50 ≤5.8W / kg, hardness ≥120HV.

[0020] This invention also discloses a method for preparing the above-mentioned economical, high-hardness, low-grade aluminum-free, non-oriented silicon steel, comprising the following steps: S1. In the smelting process, steel grades are smelted according to their composition, and after tapping, the molten steel is continuously cast into slabs.

[0021] In one specific embodiment, the thickness of the slab in continuous casting is 220–240 mm.

[0022] S2. In hot rolling, the slab is charged and delivered using a hot-feeding process, with a furnace charging temperature ≥600℃; the slab time in the furnace is ≥160min; and the slab exiting the furnace is 1150~1200℃. The main purpose is to control the solid solution and precipitation of second phases such as MnS and AlN, and to prevent a large number of fine and dispersed second phases from being distributed at grain boundaries. The finishing rolling temperature of hot rolling is 860~900℃, and the coiling temperature is 680~720℃, in order to increase the grain size and optimize the microstructure. The thickness of the hot-rolled coil is 2.5mm~2.75mm, which is beneficial to the optimization and realization of the reduction rate of the cold rolling process.

[0023] In one specific embodiment, during hot rolling, the slab sequentially passes through a preheating section, a first heating section, a second heating section, and a soaking section in a heating furnace; the heating temperature of the preheating section is 900–1000°C, and the heating time of the preheating section is 30–40 min; the heating temperature of the first heating section is 1000–1100°C, and the heating time of the first heating section is 40–60 min; the heating temperature of the second heating section is 1100–1200°C, and the heating time of the second heating section is 40–60 min; the heating temperature of the soaking section is 1150–1220°C, and the heating time of the soaking section is 40–50 min.

[0024] S3. In cold rolling, the hot-rolled coil is pickled and then cold-rolled to obtain a cold-rolled steel coil with a thickness of 0.5mm. The cold rolling is carried out in 5 passes using a 20-roll single-stand cold rolling mill.

[0025] In one specific embodiment, during cold rolling, the reduction rate of the first four passes is 25-40%, the reduction rate of the last pass is ≤10%, the rolling force is 350-650 tons, the rolling speed is 400-750 mpm, and the unit tension of each pass is maintained at 10-40 N / mm during the rolling process. 2 .

[0026] In one specific embodiment, the pickling solution used is a hydrochloric acid solution with a concentration of 5% to 20%.

[0027] S4. In the annealing process, the cold-rolled steel coil is annealed in a continuous annealing furnace. The annealing temperature is 840-900℃, the input ratio of the SF section of the continuous annealing furnace is 8-15 sections, the annealing process speed is 100-160m / min, the high cooling rate is ≥15℃ / s, and the strip surface is coated with insulating varnish to obtain aluminum-free and non-oriented silicon steel.

[0028] The following are specific embodiments. Example 1 The economical, high-hardness, low-grade aluminum-free, non-oriented silicon steel of this embodiment comprises the following components by mass percentage: C: 0.0022%; Si: 0.60%; Mn: 0.35%; P: 0.095%; S: 0.0035%; Al: 0.0010%; with the balance being Fe and unavoidable impurities.

[0029] The method for preparing economical, high-hardness, low-grade aluminum-free, non-oriented silicon steel in this embodiment includes the following steps: S1. In the smelting process, steel grades are smelted according to their composition, and after tapping, the molten steel is continuously cast into slabs with a thickness of 230mm.

[0030] S2. In hot rolling, the slab is charged using a hot delivery and charging process, with a furnace charging temperature of 602℃; the slab is in the furnace for 164 minutes; the slab exits the furnace at 1158℃; the hot rolling finishing temperature is 878℃, the coiling temperature is 706℃, and the thickness of the hot-rolled coil is 2.75mm. Specifically, in the slab heating step, the slab sequentially passes through a preheating section, a first heating section, a second heating section, and a soaking section in the heating furnace. The preheating section has a heating temperature of 955℃ and a heating time of 38 minutes; the first heating section has a heating temperature of 1050℃ and a heating time of 48 minutes; the second heating section has a heating temperature of 1180℃ and a heating time of 52 minutes; and the soaking section has a heating temperature of 1190℃ and a heating time of 46 minutes.

[0031] S3. In cold rolling, the obtained hot-rolled coil is pickled with 10% hydrochloric acid and then cold-rolled to obtain a cold-rolled steel coil with a thickness of 0.5 mm. The cold rolling is carried out in 5 passes using a 20-roll single-stand cold rolling mill. The reduction rate of the first four passes is 30%, and the reduction rate of the last pass is 8%. The rolling force is 550 tons, the rolling speed is 650 mpm, and the unit tension of each pass is maintained at 25 N / mm during the rolling process. 2 .

[0032] S4. In the annealing process, the cold-rolled steel coil is annealed in a continuous annealing furnace at a temperature of 860℃. Eight sections of the SF section of the continuous annealing furnace are fed in, the annealing process speed is 130m / min, the high cooling rate is 15℃ / s, and the steel strip surface is coated with insulating varnish to obtain the 1300 grade high-hardness, low-cost aluminum-free, non-oriented silicon steel for high-speed punching.

[0033] Example 2 The economical, high-hardness, low-grade aluminum-free, non-oriented silicon steel of this embodiment comprises the following components by mass percentage: C: 0.0018%; Si: 0.65%; Mn: 0.30%; P: 0.090%; S: 0.0030%; Al: 0.0010%; with the balance being Fe and unavoidable impurities.

[0034] The method for preparing economical, high-hardness, low-grade aluminum-free, non-oriented silicon steel in this embodiment includes the following steps: S1. In the smelting process, steel grades are smelted according to their composition, and after tapping, the molten steel is continuously cast into slabs with a thickness of 230mm.

[0035] S2. In hot rolling, the slab is charged using a hot delivery and charging process, with a furnace charging temperature of 600℃; the slab is in the furnace for 161 minutes; the slab exits the furnace at 1185℃; the hot rolling finishing temperature is 875℃, the coiling temperature is 710℃, and the thickness of the hot-rolled coil is 2.75mm. Specifically, in the slab heating step, the slab sequentially passes through a preheating section, a first heating section, a second heating section, and a soaking section in the heating furnace. The preheating section has a heating temperature of 980℃ and a heating time of 40 minutes; the first heating section has a heating temperature of 1070℃ and a heating time of 50 minutes; the second heating section has a heating temperature of 1180℃ and a heating time of 48 minutes; and the soaking section has a heating temperature of 1185℃ and a heating time of 43 minutes.

[0036] S3. In cold rolling, the obtained hot-rolled coil is pickled with 10% hydrochloric acid and then cold-rolled to obtain a cold-rolled steel coil with a thickness of 0.5 mm. The cold rolling is carried out in 5 passes using a 20-roll single-stand cold rolling mill. The reduction rate of the first four passes is 35%, and the reduction rate of the last pass is 9%. The rolling force is 600 tons, the rolling speed is 550 mpm, and the unit tension of each pass is maintained at 38 N / mm during the rolling process. 2 .

[0037] S4. In the annealing process, the cold-rolled steel coil is annealed in a continuous annealing furnace at a temperature of 890℃. The furnace has 7 sections in the SF section, the annealing process speed is 145m / min, the high cooling rate is 16℃ / s, and the steel strip surface is coated with insulating varnish to obtain the 1300 grade high-hardness, low-cost aluminum-free, non-oriented silicon steel for high-speed punching.

[0038] Example 3 The economical, high-hardness, low-grade aluminum-free, non-oriented silicon steel of this embodiment comprises the following components by mass percentage: C: 0.0016%; Si: 0.55%; Mn: 0.32%; P: 0.096%; S: 0.0030%; Al: 0.0010%; with the balance being Fe and unavoidable impurities.

[0039] The method for preparing economical, high-hardness, low-grade aluminum-free, non-oriented silicon steel in this embodiment includes the following steps: S1. In the smelting process, steel grades are smelted according to their composition, and after tapping, the molten steel is continuously cast into slabs with a thickness of 230mm.

[0040] S2. In hot rolling, the slab is charged using a hot delivery and charging process, with a furnace charging temperature of 602℃; the slab is in the furnace for 168 minutes; the slab exits the furnace at 1192℃; the hot-rolled finishing temperature is 887℃, the coiling temperature is 711℃, and the thickness of the hot-rolled coil is 2.75mm. Specifically, in the slab heating step, the slab sequentially passes through a preheating section, a first heating section, a second heating section, and a soaking section in the heating furnace. The preheating section has a heating temperature of 956℃ and a heating time of 38 minutes; the first heating section has a heating temperature of 1070℃ and a heating time of 46 minutes; the second heating section has a heating temperature of 1180℃ and a heating time of 56 minutes; and the soaking section has a heating temperature of 1195℃ and a heating time of 48 minutes.

[0041] S3. In cold rolling, the obtained hot-rolled coil is pickled with 10% hydrochloric acid and then cold-rolled to obtain a cold-rolled steel coil with a thickness of 0.5 mm. The cold rolling is carried out in 5 passes using a 20-roll single-stand cold rolling mill. The reduction rate of the first four passes is 32%, and the reduction rate of the last pass is 10%. The rolling force is 580 tons, the rolling speed is 650 mpm, and the unit tension of each pass is maintained at 35 N / mm during the rolling process. 2 .

[0042] S4. In the annealing process, the cold-rolled steel coil is annealed in a continuous annealing furnace at a temperature of 882℃. Eight sections of the SF section of the continuous annealing furnace are fed in, the annealing process speed is 140m / min, the high cooling rate is 17℃ / s, and the steel strip surface is coated with insulating varnish to obtain the 1300 grade high-hardness, low-cost aluminum-free, non-oriented silicon steel for high-speed punching.

[0043] Comparative Example 1 The non-oriented silicon steel grade 50W1300 in this comparative example comprises the following components by mass percentage: C: 0.0022%; Si: 0.43%; Mn: 0.28%; P: 0.065%; S: 0.0030%; Al: 0.0010%; with the balance being Fe and unavoidable impurities.

[0044] The preparation method of ordinary low-grade non-oriented silicon steel in this comparative example includes the following steps: S1. In the smelting process, steel grades are smelted according to their composition, and after tapping, the molten steel is continuously cast into slabs with a thickness of 230mm.

[0045] S2. In hot rolling, the slab is charged and loaded using a hot-feeding process, with a furnace loading temperature of 350℃; the slab is in the furnace for 188 minutes; the slab exits the furnace at 1152℃; the hot-rolled finishing temperature is 870℃, the coiling temperature is 711℃, and the thickness of the hot-rolled coil is 2.75mm. Specifically, in the slab heating step, the slab sequentially passes through a preheating section, a first heating section, a second heating section, and a soaking section in the heating furnace. The preheating section has a heating temperature of 950℃ and a heating time of 37 minutes; the first heating section has a heating temperature of 1065℃ and a heating time of 40 minutes; the second heating section has a heating temperature of 1160℃ and a heating time of 50 minutes; and the soaking section has a heating temperature of 1155℃ and a heating time of 45 minutes.

[0046] S3. In cold rolling, the obtained hot-rolled coil is pickled with 10% hydrochloric acid and then cold-rolled to obtain a cold-rolled steel coil with a thickness of 0.5 mm. The cold rolling is carried out in 5 passes using a 20-roll single-stand cold rolling mill. The reduction rate of the first four passes is 30%, and the reduction rate of the last pass is 9%. The rolling force is 550 tons, the rolling speed is 600 mpm, and the unit tension of each pass is maintained at 33 N / mm during the rolling process. 2 .

[0047] S4. In the annealing process, the cold-rolled steel coil is annealed in a continuous annealing furnace at a temperature of 862℃. The furnace consists of seven SF sections, with a annealing speed of 120m / min and a cooling rate of 8℃ / s. The steel strip is coated with insulating varnish to produce ordinary non-oriented silicon steel grade 1300 as shown in Comparative Example 1.

[0048] Test case Compared with Comparative Example 1, the high-strength 1300 produced using this invention not only has excellent electromagnetic properties, but also, due to its higher hardness, is more suitable for high-speed stamping production, improving production stability, stamping quality, and throughput. Furthermore, the method of this invention is simple, easy to operate, and yields quick results without investment, making it of significant value for widespread application. Specific effects are shown in Table 1.

[0049] Table 1 Mechanical properties of the embodiments and comparative examples

[0050] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. An economical, high-hardness, low-grade, aluminum-free, non-oriented silicon steel, characterized in that, The components include the following percentages by mass: C ≤ 0.003%, Si: 0.50%–0.70%, Mn: 0.25%–0.65%, P: 0.09%–0.10%, S ≤ 0.0040%, Al ≤ 0.0010%, with the balance being Fe and unavoidable impurities.

2. The economical, high-hardness, low-grade aluminum-free, non-oriented silicon steel according to claim 1, characterized in that, The magnetic induction intensity B of the aluminum-free, non-oriented silicon steel 50 ≥1.75T, iron loss P 15 / 50 ≤5.8W / kg, hardness ≥120HV.

3. A method for preparing an economical, high-hardness, low-grade aluminum-free, non-oriented silicon steel as described in any one of claims 1-2, characterized in that, Includes the following steps: In the smelting process, steel grades are smelted according to their composition, and after tapping, the molten steel is continuously cast into slabs. In hot rolling, the slab is subjected to a hot charging process with a furnace charging temperature ≥600℃; the slab is in the furnace for ≥160 min; the slab exits the furnace at a temperature of 1150~1200℃; the hot rolling finishing temperature is 860~900℃; and the coiling temperature is 680~720℃. In cold rolling, the hot-rolled coil is pickled and then cold-rolled to obtain a cold-rolled steel coil with a thickness of 0.5 mm; the cold rolling is carried out in 5 passes using a 20-roll single-stand cold rolling mill. In the annealing process, the cold-rolled steel coil is annealed in a continuous annealing furnace at a temperature of 840–900°C. The proportion of the SF section in the continuous annealing furnace is 8–15 sections, the annealing process speed is 100–160 m / min, and the high cooling rate is ≥15°C / s, to obtain the aluminum-free, non-oriented silicon steel.

4. The preparation method according to claim 3, characterized in that, In the cold rolling process, the reduction rate of the first four passes is 25-40%, the reduction rate of the last pass is ≤10%, the rolling force is 350-650 tons, the rolling speed is 400-750 mpm, and the unit tension of each pass is maintained at 10-40 N / mm during the rolling process. 2 .

5. The preparation method according to claim 3, characterized in that, In the continuous casting process, the thickness of the slab is 220–240 mm.

6. The preparation method according to claim 3, characterized in that, In the hot rolling process, the thickness of the hot-rolled coil is 2.5 mm to 2.75 mm.

7. The preparation method according to claim 3, characterized in that, The pickling solution used is a hydrochloric acid solution with a concentration of 5% to 20%.

8. The preparation method according to claim 3, characterized in that, In the hot rolling process, the slab sequentially passes through a preheating section, a first heating section, a second heating section, and a soaking section in a heating furnace. The heating temperature of the preheating section is 900–1000°C, and the heating time is 30–40 min. The heating temperature of the first heating section is 1000–1100°C, and the heating time is 40–60 min. The heating temperature of the second heating section is 1100–1200°C, and the heating time is 40–60 min. The heating temperature of the soaking section is 1150–1220°C, and the heating time is 40–50 min.

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