Rolling method for hot-rolled low-silicon electrical steel in low-temperature energy-saving mode

Abstract

The invention relates to the technical field of electrical steel rolling, in particular to a rolling method for hot-rolled low-silicon electrical steel in a low-temperature energy-saving mode, which specifically comprises the following steps: S1, blank heating: putting a low-silicon electrical steel continuous casting blank into a heating furnace, keeping the temperature of the blank entering the furnace to be above 350 DEG C, and adopting a segmented heating mode with the total heating time of 180-240 minutes; s2, rough rolling is conducted, specifically, the heated blank is subjected to rough rolling, six passes are set in total, the reduction rate is gradually decreased, and the rough rolling outlet temperature is controlled to be 900-950 DEG C; s3, finish rolling: after being uncoiled, the hot coil box enters a finish rolling unit for finish rolling, the finish rolling is set for 7 passes, and the temperature of a finish rolling outlet is controlled to be 800-850 DEG C; and S4, cooling is conducted, specifically, the strip steel obtained after finish rolling enters a laminar cooling system to be cooled. The method has the beneficial effects that the structure property and the plate shape quality of the low-silicon electrical steel are guaranteed, the rolling stability is improved on the premise that the product quality is guaranteed, and the energy consumption is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electric steel rolling technology, in particular to a rolling method of hot-rolled low-silicon electrical steel under low-temperature energy-saving mode. BACKGROUND

[0002] Low-silicon electrical steel has good magnetic properties and processing performance, and is widely used in the manufacture of electrical equipment such as motors, transformers, generators, etc. Hot rolling is a key link in the production of low-silicon electrical steel, and its process parameters directly affect the organization performance, shape quality and production energy consumption of the product. The traditional hot-rolled low-silicon electrical steel rolling method usually adopts a higher heating temperature, a higher finishing temperature and a coiling temperature to ensure the plasticity and rollability of the billet, but high heating temperature will increase the energy consumption of the heating furnace, and may cause problems such as intensified oxidation and burning loss of the billet surface, grain coarsening, etc., affecting the subsequent processing performance and product quality.

[0003] With the increasingly stringent requirements of energy saving and emission reduction, reducing the energy consumption of hot rolling process has become an important development direction for steel enterprises. As an effective energy-saving means, low-temperature rolling technology has been applied in the rolling of ordinary steel, but in the field of low-silicon electrical steel, due to its special composition and performance, low-temperature rolling is prone to problems such as increased rolling force, difficult to control the shape, unstable product performance, etc., which limits the popularization and application of this technology. Therefore, it is of great practical significance to develop a low-temperature energy-saving rolling method suitable for hot-rolled low-silicon electrical steel, which can reduce energy consumption while ensuring product quality. SUMMARY

[0004] In order to overcome the shortcomings of the prior art, the present application provides a rolling method of hot-rolled low-silicon electrical steel under low-temperature energy-saving mode, which can reduce the heating temperature and finishing temperature while ensuring the organization performance and shape quality of low-silicon electrical steel, and improve the stability of rolling and reduce energy consumption under the premise of ensuring product quality.

[0005] In order to achieve the above purpose, the present application adopts the following technical scheme: A rolling method of hot-rolled low-silicon electrical steel under low-temperature energy-saving mode, specifically including the following steps: S1, billet heating: put the low-silicon electrical steel continuous casting billet into the heating furnace, the billet inlet temperature is kept above 350℃, adopt segmented heating mode, the preheating segment temperature is controlled at 800-850℃, the heating segment temperature is controlled at 1050-1150℃, and the soaking segment temperature is controlled at 1000-1050℃, the total heating time is 180-240min; S2. Rough rolling: The heated billet is rough rolled. The rough rolling process consists of 6 passes. The first pass has a reduction rate of 30% to 35%, the second pass has a reduction rate of 25% to 30%, and the reduction rate of subsequent passes gradually decreases. The last pass has a reduction rate of 15% to 20%. The exit temperature of the rough rolling mill is controlled at 900 to 950℃. S3. Finishing Rolling: After the hot coil box is uncoiled, it enters the finishing rolling mill for finishing rolling. The finishing rolling is set with 7 passes. The reduction rate of the first two passes is 20% to 25%, the reduction rate of the middle passes is 15% to 20%, and the reduction rate of the last two passes is 10% to 15%. The finishing rolling exit temperature is controlled at 800 to 850℃, and the rolling speed is 8 to 12 m / s. S4. Cooling: The finished strip enters the laminar flow cooling system for cooling, using a method of rapid cooling in the front section and slow cooling in the back section. The cooling rate in the front section is 25-35℃ / s, cooling to 650-700℃, and the cooling rate in the back section is 5-10℃ / s, cooling to 500-550℃, and then it is coiled.

[0006] Furthermore, in step S1, the silicon content of the low-silicon electrical steel continuous casting billet is 0.5% to 1.0%.

[0007] Furthermore, in step S1, the heating rate of the preheating section is 5-8℃ / min, the heating rate of the heating section is 8-12℃ / min, and the heat soaking time is 40-60min.

[0008] Furthermore, in step S2, during the rough rolling process, the pre-mill descaling of odd-numbered passes is opened, and constant speed rolling is performed, with an interval of 30 to 60 seconds between adjacent passes.

[0009] Furthermore, in step S3, the work rolls in the finishing rolling process are made of high-speed steel, and the surface roughness of the rolls is 0.8 to 1.2 μm.

[0010] Furthermore, in step S4, the water flow ratio of the upper and lower manifolds of the laminar flow cooling system is 1:1.2 to 1:1.5.

[0011] Compared with the prior art, the beneficial effects of the present invention are: 1) This invention uses a low-temperature heating method, which reduces the heating temperature by 50-100°C compared to traditional methods. This can reduce the gas consumption of the heating furnace by 8%-12% and reduce the energy consumption per ton of steel by 15-20 kg of standard coal. The energy-saving effect is significant and the production cost is significantly reduced.

[0012] 2) By rationally controlling the process parameters during rolling, including heating temperature, rolling pass reduction rate, rolling speed, and cooling rate, the microstructure and sheet quality of the low-silicon electrical steel are guaranteed. The iron loss value of the product is reduced by 0.5–1.0 W / kg, and the magnetic induction intensity is increased by 0.05–0.1 T, meeting the application requirements of motors, transformers, and other fields, and the product quality is excellent.

[0013] 3) The rolling method of the present invention effectively solves the problems of increased rolling force and difficulty in controlling plate shape during low-temperature rolling by means of segmented heating, reasonable distribution of reduction rate and segmented cooling, etc., and has good process stability, ensuring the stability and continuity of the production process.

[0014] 4) This invention is applicable to the hot rolling production of low-silicon electrical steel with a silicon content of 0.5% to 1.0%, and can meet the production needs of products with different specifications and performance requirements. It has a wide range of applications and broad application prospects. Attached Figure Description

[0015] Figure 1 This is a flow chart of the hot rolling production process described in this invention.

[0016] Figure 2 This is a metallographic diagram of the ferrite + carbide structure described in this invention. Detailed Implementation

[0017] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings: like Figures 1-2 As shown, a rolling method for hot-rolled low-silicon electrical steel under low-temperature energy-saving mode includes the following steps: S1. Billet Heating: The low-silicon electrical steel continuous casting billet with a silicon content of 0.5% to 1.0% is placed in a heating furnace. Low-silicon electrical steel within this silicon content range has good magnetic properties and processing performance, making it suitable for the rolling method of this invention. The billet temperature is maintained above 350°C upon entering the furnace. A segmented heating method is adopted to avoid thermal stress caused by excessively rapid heating of the billet and to reduce cracking. The preheating section slowly raises the billet temperature to 800–850°C to prepare for subsequent heating; the heating section heats the billet to 1050–1150°C to ensure sufficient heating; the soaking section is controlled at 1000–1050°C, with a total heating time of 180–240 minutes, to ensure uniform billet temperature and reduce temperature gradients. Compared with traditional heating temperatures, the heating temperature in this step is reduced by 50–100℃, which can significantly reduce the energy consumption of the heating furnace. The heating rate in the preheating section is 5–8℃ / min, the heating rate in the heating section is 8–12℃ / min, and the holding time in the soaking section is 40–60min. Reasonable control of the heating rate and soaking time of each section can ensure uniform heating of the billet and reduce oxidation loss.

[0018] S2. Rough Rolling: The heated billet undergoes rough rolling, which consists of six passes. The first pass has a reduction rate of 30%–35%, the second pass 25%–30%, and subsequent passes gradually decrease the reduction rate, with the final pass having a reduction rate of 15%–20%. This allocation of reduction rates across the rough rolling passes, with the first pass using a larger reduction rate to break up coarse grains in the billet and refine the microstructure, and subsequent passes gradually decreasing the reduction rate, avoids excessive rolling force that could damage the equipment, and ensures uniform plastic deformation of the billet. The exit temperature of the rough rolling mill is controlled at 900–950℃ to provide suitable temperature conditions for subsequent finish rolling. After rough rolling, the strip billet is first coiled in a hot coiler. In the coiled state, the heat distribution inside the billet is more uniform, reducing the temperature difference between the head and tail and the temperature drop at the edges, which is beneficial for stable temperature control in the subsequent finish rolling process and improves the quality of the strip. During rough rolling, in order to prevent the intermediate billet temperature from dropping, only the odd-numbered descaling passes are opened in front of the mill to maintain constant rolling speed. The interval between adjacent passes is 30 to 60 seconds, which can ensure the temperature uniformity of the billet.

[0019] S3. Finishing Rolling: After uncoiling in the hot coil box, the strip enters the finishing mill for finishing rolling. The finishing mill has 7 passes. The reduction rate for the first two passes is 20%–25%, the reduction rate for the middle passes is 15%–20%, and the reduction rate for the last two passes is 10%–15%, with a rolling speed of 8–12 m / s. By rationally controlling the reduction rate and rolling speed of each pass, the grain size is further refined, improving the microstructure and properties of the product. The first two passes use a larger reduction rate to further refine the grain size; the reduction rate is gradually reduced in the middle and last two passes to ensure the strip's shape quality. The finishing mill exit temperature is controlled at 800–850℃, which is beneficial for subsequent cooling control and microstructure formation. To avoid thickness fluctuations caused by large changes in strip cooling water and finishing mill speed, the final rolling temperature model uses a control logic of uniformly adding cooling water at a small flow rate and avoiding frequent acceleration fluctuations. During finishing rolling, the work rolls are made of high-speed steel with a surface roughness of 0.8–1.2 μm. High-speed steel work rolls have high wear resistance and strength, which can ensure the stability of the rolling process; appropriate roll surface roughness can reduce frictional resistance during the rolling process and improve the quality of the strip shape.

[0020] S4. Cooling: After finishing rolling, the strip enters a laminar flow cooling system for cooling, employing a rapid cooling process in the first stage followed by a slow cooling process in the second stage. The first stage cooling rate is 25–35℃ / s, cooling to 650–700℃, while the second stage cooling rate is 5–10℃ / s, cooling to 500–550℃, before coiling. This segmented cooling method, with rapid cooling in the first stage to inhibit austenite grain growth and slow cooling in the second stage to promote uniform pearlite transformation and ensure stable microstructure and properties of the product, is beneficial. The water flow ratio of the upper and lower manifolds in the laminar flow cooling system is 1:1.2–1:1.5. Adjusting this ratio ensures uniform cooling of the upper and lower surfaces of the strip, reducing shape defects caused by uneven cooling. Controlling the final cooling temperature at 500–550℃ reduces internal stress in the strip and improves shape quality.

[0021] Example: The electrical steel of this invention is BW1300 as an example, and its chemical composition by weight percentage is shown in Table 1; like Figure 1 As shown, the hot-rolled steel coil process of this invention is as follows: molten steel pretreatment → converter smelting → ladle refining → continuous casting → hot rolling heating → rough rolling, hot coil box, and finish rolling → controlled cooling → coiling → surface and performance inspection → packaging → delivery.

[0022] The billet heating process parameters of the embodiments of the present invention are shown in Table 2; the roughing process parameters of the embodiments of the present invention are shown in Table 3; the finishing process parameters of the embodiments of the present invention are shown in Table 4; the cooling process parameters of the embodiments of the present invention are shown in Table 5; and the beneficial effects of the embodiments of the present invention are shown in Table 6.

[0023] Table 1 - Chemical composition of electrical steel in embodiments of the present invention, weight percentage: (wt, %).

[0024] Table 2 - Billet heating process parameters of the present invention:

[0025] Table 3 - Roughing process parameters of embodiments of the present invention: Table 4 - Finishing rolling process parameters of the present invention: Table 5 - Cooling process parameters of embodiments of the present invention: Table 6 - Beneficial effects of the embodiments of the present invention: As can be seen from the above embodiments, lowering the heating temperature by 50-100℃ compared to traditional methods can reduce the gas consumption of the heating furnace by 8%-12%, reduce the energy consumption per ton of steel by 15-20 kg of standard coal, reduce the iron loss value of the product by 0.5-1.0 W / kg, increase the magnetic induction intensity by 0.05-0.1 T, and improve the plate shape quality.

[0026] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A rolling method for hot-rolled low-silicon electrical steel under low-temperature energy-saving mode, characterized in that, The specific steps include the following: S1. Billet heating: Place the low-silicon electrical steel continuous casting billet into the heating furnace. The billet temperature is maintained above 350℃. A segmented heating method is adopted. The preheating section temperature is controlled at 800-850℃, the heating section temperature is controlled at 1050-1150℃, and the soaking section temperature is controlled at 1000-1050℃. The total heating time is 180-240 minutes. S2. Rough rolling: The heated billet is rough rolled. The rough rolling process consists of 6 passes. The first pass has a reduction rate of 30% to 35%, the second pass has a reduction rate of 25% to 30%, and the reduction rate of subsequent passes gradually decreases. The last pass has a reduction rate of 15% to 20%. The exit temperature of the rough rolling mill is controlled at 900 to 950℃. S3. Finishing Rolling: After the hot coil box is uncoiled, it enters the finishing rolling mill for finishing rolling. The finishing rolling is set with 7 passes. The reduction rate of the first two passes is 20% to 25%, the reduction rate of the middle passes is 15% to 20%, and the reduction rate of the last two passes is 10% to 15%. The finishing rolling exit temperature is controlled at 800 to 850℃, and the rolling speed is 8 to 12 m / s. S4. Cooling: The finished strip enters the laminar flow cooling system for cooling, using a method of rapid cooling in the front section and slow cooling in the back section. The cooling rate in the front section is 25-35℃ / s, cooling to 650-700℃, and the cooling rate in the back section is 5-10℃ / s, cooling to 500-550℃, and then it is coiled.

2. The rolling method for hot-rolled low-silicon electrical steel under low-temperature energy-saving mode according to claim 1, characterized in that, In step S1, the silicon content of the low-silicon electrical steel continuous casting billet is 0.5% to 1.0%.

3. The rolling method for hot-rolled low-silicon electrical steel under low-temperature energy-saving mode according to claim 1, characterized in that, In step S1, the heating rate of the preheating section is 5-8℃ / min, the heating rate of the heating section is 8-12℃ / min, and the heat soaking time is 40-60min.

4. The rolling method for hot-rolled low-silicon electrical steel under low-temperature energy-saving mode according to claim 1, characterized in that, In step S2, during the rough rolling process, the pre-mill descaling of odd-numbered passes is opened, and constant speed rolling is performed with an interval of 30 to 60 seconds between adjacent passes.

5. The rolling method for hot-rolled low-silicon electrical steel under low-temperature energy-saving mode according to claim 1, characterized in that, In step S3, the work rolls used in the finishing rolling process are made of high-speed steel with a surface roughness of 0.8 to 1.2 μm.

6. The rolling method for hot-rolled low-silicon electrical steel under low-temperature energy-saving mode according to claim 1, characterized in that, In step S4, the water flow ratio of the upper and lower manifolds of the laminar flow cooling system is 1:1.2 to 1:1.5.

Images