Method for improving iron and steel loss full-length uniformity of middle and low grade silicon steel

Abstract

The invention discloses a method for improving the overall-length uniformity of medium-low grade silicon steel iron loss, and belongs to the technical field of material processing. The method comprises the following steps that firstly, molten steel is subjected to KR desulfurization, converter treatment, refining and continuous casting in sequence, and a plate blank is obtained; secondly, the plate blank is sequentially subjected to hot rolling, coiling, rough rolling and finish rolling, the in-furnace time of hot rolling is controlled to range from 180 min to 210 min, the maximum rolling speed of a rough rolling R2 working roller is controlled to range from 4.5 m / s to 6.5 m / s, and the strip threading speed of finish rolling is controlled to range from 11 m / s to 13 m / s; thirdly, acid continuous rolling is conducted; and 4, annealing is conducted, the hydrogen content of annealing is controlled to be 5-15%, and the dew point is 10-20 DEG C. According to the method, on the basis that existing equipment is not transformed, the overall length uniformity of the silicon steel iron loss performance can be improved only by changing technological parameters.

Description

Technical Field

[0001] This invention belongs to the field of materials processing technology, specifically relating to a method for improving the uniformity of steel loss along the entire length of medium and low grade silicon steel. Background Technology

[0002] Medium and low grade silicon steel, as an important part of non-oriented electrical steel, is widely used in home appliances and industrial motors. Generally, the silicon content of medium and low grade silicon steel is required to be below 1.5%. The processing path for medium and low grade silicon steel differs from that of high grade silicon steel, as it omits a normalizing treatment step. Therefore, the iron loss performance after annealing is more sensitive to key control parameters in each process step, resulting in large fluctuations in iron loss throughout the entire process, with more severe fluctuations at the beginning and end, resembling a boat shape. This is detrimental to the stable production of the annealing process and downstream motor manufacturers. Summary of the Invention

[0003] Technical problem to be solved: In view of the above-mentioned technical problem, the present invention provides a method for improving the uniformity of steel loss along the entire length of medium and low grade silicon steel. It can improve the uniformity of steel loss performance along the entire length of silicon steel without modifying existing equipment, simply by changing process parameters.

[0004] Technical solution: A method for improving the uniformity of steel loss along the entire length of medium and low grade silicon steel, comprising the following steps: Step 1: Molten steel is sequentially desulfurized by KR, passed through a converter, refined and continuously cast to obtain the finished continuously cast slab. Step 2: The slab is subjected to hot rolling, coiling, rough rolling and finish rolling in sequence. The hot rolling time in the furnace is controlled to be 180~210min, the maximum rolling speed of the R2 work roll in the rough rolling is controlled to be 4.5~6.5m / s, and the strip threading speed in the finish rolling is controlled to be 11~13m / s. Step 3: Perform acid rolling; Step 4: Perform annealing, controlling the hydrogen content to be 5-15% and the dew point to be 10-20℃.

[0005] Preferably, in step one, the composition of the continuously cast slab is controlled to have a C content of no more than 0.0030%, a Si content of 1.0~1.5%, a Mn content of 0.2~0.5%, a Ti content of no more than 0.0025%, an Al content of 0.3~0.8%, and a S content of no more than 0.0035%.

[0006] Preferably, in step one, the slab drawing speed is controlled to be 0.9~1.4m / min.

[0007] Preferably, in step two, the furnace temperature of the slab during hot rolling is controlled to be no less than 300°C.

[0008] Preferably, in step two, the furnace temperature is controlled at 1120~1160℃ during hot rolling.

[0009] Preferably, in step two, the final rolling temperature is controlled at 840~880℃ during hot rolling.

[0010] Preferably, in step two, the winding temperature is controlled to be 630~680℃.

[0011] Preferably, in step three, the surface roughness of the first stand of the acid rolling mill is controlled to be 1.2~1.3.

[0012] Beneficial effects: This invention can improve the uniformity of silicon steel loss performance along the entire length without modifying existing equipment, and achieve continuous and stable production simply by changing process parameters.

[0013] Specifically, this invention ensures the uniformity of slab heating by strictly controlling the slab's furnace entry temperature and furnace time; reduces the temperature drop at the head of the intermediate slab and improves the final rolling temperature hit rate by controlling the rolling parameters of roughing and finishing rolling; avoids slippage caused by iron oxide on the surface of hot-rolled material, which would lead to thickness fluctuations and affect the uniformity of plate thickness; and ensures stable and continuous production at high annealing temperatures by using a low-hydrogen, low-dew-point furnace atmosphere in the annealing process, avoiding frequent nodulation that would cause speed reduction and thus fluctuations in iron loss performance. Attached Figure Description

[0014] Figure 1 This is a graph showing the total iron loss of the finished product from Example 1. Figure 2 This is the iron loss curve of the finished product in Comparative Example 1. Detailed Implementation

[0015] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Example 1

[0016] Using the methods and control measures involved in this invention, low-grade silicon steel is produced sequentially in a converter steelmaking unit, a 1450 hot rolling mill, a 1420 pickling and cold rolling combined unit, and a silicon steel continuous annealing unit.

[0017] The relevant control parameters are as follows: (1) Steelmaking adopts KR desulfurization-converter-refining-continuous casting production process. The composition C is controlled below 0.0030%, Si content is controlled at 1.0~1.5%, Mn content is controlled at 0.2~0.5%, Ti content is controlled below 0.0025%, Al content is controlled at 0.3~0.8% and S content is controlled below 0.0035%. The slab casting speed is controlled at 0.9~1.4m / min.

[0018] (2) The slab entry temperature is 300℃, the hot rolling furnace temperature is controlled at 1160℃, the furnace time is controlled at 210min, the final rolling temperature is controlled at 840℃, and the coiling temperature is controlled at 630℃. Strictly control the slab entry temperature and furnace time to ensure the uniformity of slab heating. The maximum rolling speed of roughing R2 is controlled at 4.5m / s, and the finishing rolling threading speed is controlled at 11m / s to reduce the temperature drop at the head of the intermediate slab and improve the final rolling temperature hit rate.

[0019] (3) The roughness of the first stand of the pickling continuous rolling mill is controlled at 1.2 to avoid slippage caused by iron oxide on the surface of the hot-rolled material, which would cause thickness fluctuation and affect the uniformity of the plate thickness.

[0020] (4) The annealing adopts a furnace atmosphere with low hydrogen and low dew point. The hydrogen content is controlled at 15% and the dew point is controlled at 20℃. This can ensure stable and continuous production at high annealing temperature and avoid frequent nodule formation leading to a decrease in speed, thus causing fluctuations in iron loss performance.

[0021] (5) After annealing, the online iron loss of the finished product fluctuates little along the entire length and remains basically uniform. The online range is controlled at around 100mW / kg. Specifically, as shown in the figure below. Figure 1 As shown. Example 2

[0022] Using the methods and control measures involved in this invention, low-grade silicon steel is produced sequentially in a converter steelmaking unit, a 1450 hot rolling mill, a 1420 pickling and cold rolling combined unit, and a silicon steel continuous annealing unit.

[0023] The relevant control parameters are as follows: (1) Steelmaking adopts KR desulfurization-converter-refining-continuous casting production process. The composition C is controlled below 0.0030%, Si content is controlled at 1.0~1.5%, Mn content is controlled at 0.2~0.5%, Ti content is controlled below 0.0025%, Al content is controlled at 0.3~0.8% and S content is controlled below 0.0035%. The slab casting speed is controlled at 0.9~1.4m / min.

[0024] (2) The slab temperature entering the furnace is maintained at 400℃, the hot rolling furnace temperature is controlled at 1120℃, the furnace time is controlled at 180min, the final rolling temperature is controlled at 880℃, and the coiling temperature is controlled at 680℃. Strict control of the slab temperature entering the furnace and the furnace time is required to ensure the uniformity of slab heating. The maximum rolling speed of roughing R2 is controlled at 6.5m / s, and the finishing rolling threading speed is controlled at 13m / s to reduce the temperature drop at the head of the intermediate slab and improve the final rolling temperature hit rate.

[0025] (3) The roughness of the first stand of the pickling continuous rolling mill is controlled at 1.3 to avoid slippage caused by iron oxide on the surface of the hot-rolled material, which would cause thickness fluctuation and affect the uniformity of the plate thickness.

[0026] (4) The annealing adopts a furnace atmosphere with low hydrogen and low dew point. The hydrogen content is controlled at 5% and the dew point is controlled at 10℃. This can ensure stable and continuous production at high annealing temperature and avoid frequent nodule formation leading to a decrease in speed, thus causing fluctuations in iron loss performance.

[0027] (5) After annealing, the online iron loss of the finished product fluctuates little along the entire length and remains basically uniform, with the online range controlled at around 100mW / kg. Comparative Example 1

[0028] Using the original process parameters, low and medium grade silicon steel was produced sequentially in a converter steelmaking unit, a 1450 hot rolling mill, a 1420 pickling and cold rolling combined unit, and a silicon steel continuous annealing unit.

[0029] The relevant control parameters are as follows: (1) Steelmaking adopts KR desulfurization-converter-refining-continuous casting production process. The composition C is controlled below 0.0030%, Si content is controlled at 1.0~1.5%, Mn content is controlled at 0.2~0.5%, Ti content is controlled below 0.0025%, Al content is controlled at 0.3~0.8% and S content is controlled below 0.0035%. The slab casting speed is controlled at 0.9~1.4m / min.

[0030] (2) The slab temperature entering the furnace is maintained at 200℃, the hot rolling furnace temperature is controlled at 1180℃, the furnace time is controlled at 200min, the final rolling temperature is controlled at 820℃, and the coiling temperature is controlled at 5800℃. The maximum rolling speed of roughing R2 is controlled at 2m / s, and the finishing rolling threading speed is controlled at 8m / s.

[0031] (3) The roughness of the first stand of the acid rolling mill is controlled at 0.8.

[0032] (4) The hydrogen content in the atmosphere inside the annealing furnace is controlled at 40%, and the dew point is controlled at 40℃.

[0033] (5) The online iron loss of the finished product after annealing fluctuates greatly along the entire length, especially the fluctuation at the beginning and end, which resembles a boat shape. The online range is around 450mW / kg, as detailed below. Figure 2 As shown.

Claims

1. A method for improving the uniformity of steel loss along the entire length in medium and low grade silicon steel, characterized in that, The steps include the following: Step 1: Molten steel is sequentially desulfurized by KR, passed through a converter, refined and continuously cast to obtain the finished continuously cast slab. Step 2: The slab is subjected to hot rolling, coiling, rough rolling and finish rolling in sequence. The hot rolling time in the furnace is controlled to be 180~210min, the maximum rolling speed of the R2 work roll in the rough rolling is controlled to be 4.5~6.5m / s, and the strip threading speed in the finish rolling is controlled to be 11~13m / s. Step 3: Perform acid rolling; Step 4: Perform annealing, controlling the hydrogen content to be 5-15% and the dew point to be 10-20℃.

2. The method for improving the uniformity of steel loss along the entire length of medium and low grade silicon steel according to claim 1, characterized in that, In step one, the composition of the continuously cast slab is controlled to have a C content of no more than 0.0030%, a Si content of 1.0~1.5%, a Mn content of 0.2~0.5%, a Ti content of no more than 0.0025%, an Al content of 0.3~0.8%, and a S content of no more than 0.0035%.

3. The method for improving the uniformity of steel loss along the entire length of medium and low grade silicon steel according to claim 1, characterized in that, In step one, the slab drawing speed is controlled at 0.9~1.4m / min.

4. The method for improving the uniformity of steel loss along the entire length of medium and low grade silicon steel according to claim 1, characterized in that, In step two, the furnace temperature of the slab during hot rolling is controlled to be no less than 300°C.

5. The method for improving the uniformity of steel loss along the entire length of medium and low grade silicon steel according to claim 1, characterized in that, In step two, the furnace temperature is controlled at 1120~1160℃ during hot rolling.

6. The method for improving the uniformity of steel loss along the entire length of medium and low grade silicon steel according to claim 1, characterized in that, In step two, the final rolling temperature is controlled at 840~880℃ during hot rolling.

7. The method for improving the uniformity of steel loss along the entire length of medium and low grade silicon steel according to claim 1, characterized in that, In step two, the winding temperature is controlled at 630~680℃.

8. The method for improving the uniformity of steel loss along the entire length of medium and low grade silicon steel according to claim 1, characterized in that, In step three, the surface roughness of the first stand of the acid rolling mill is controlled to be 1.2~1.3.

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