CN108655173B - A rolling method of non-oriented high-grade silicon steel - Google Patents

Abstract

The invention relates to a rolling method of non-oriented high-grade silicon steel. Through four-pass rolling, the reduction rate is increased to increase the deformation heat of the strip steel, and the rolling temperature of the strip steel is increased. The temperature of the incoming material is controlled at 55°C~ 60°C, the four-pass reduction rates are as follows: the first pass reduction rate is 37%-41%, the second pass reduction rate is 36%-39%, and the third pass reduction rate is 34% %‑37%; the rolling forces of the four passes are respectively controlled at: 4750‑5000kN, 4600‑5000kN, 4400‑4600kN, 3900‑4200kN; the unit tension is adjusted for the first two passes. The advantages are: the rolling pass is simplified, the edge cracking trend of the strip is reduced, and the generation of second rib waves is reduced.

Description

A rolling method of non-oriented high-grade silicon steel

technical field

The invention belongs to the field of cold-rolled strip rolling, and in particular relates to a rolling method of non-oriented high-grade steel.

Background technique

Non-oriented high-grade silicon steel, such as: 35AW230, 35AW210 and other strip steels have high silicon content, and the Si content is as high as 3.10%, resulting in high hardness, high brittleness, and difficult deformation of the product, which makes the rolling process of the 20-high rolling mill more difficult. When rolling these high grades, the broken strip rate is very high, and the finished product rate is extremely low. There are mainly the following problems:

1. In the first pass, because the strip steel is too brittle, it is prone to brittle fracture during the threading process, resulting in failure to thread the strip and scrap it;

2. After the first pass, there is a large edge crack, which makes the second pass unable to be rolled and scrapped;

3. In the second pass, due to the high brittleness of the strip steel, it is prone to brittle fracture during strip threading, resulting in the failure to thread the strip and scrap it, or the strip is broken due to edge cracks during the rolling process.

4. Edge cracks occur during the third and fourth rolling passes, and it is necessary to go to the tailor welding unit for edge trimming and return to the rolling mill to continue rolling. The production efficiency is low and the yield rate is affected.

After several tests, the yield of non-oriented high-grade silicon steel sheets such as 35AW230 and 35AW210 is only about 60%, which is far below the target requirements.

Contents of the invention

In order to overcome the deficiencies of the prior art, the object of the present invention is to provide a rolling method for non-oriented high-grade steel, which saves rolling time, reduces edge cracks, and improves yield.

To achieve the above object, the present invention is achieved through the following technical solutions:

A method for rolling non-oriented high-grade silicon steel, through four-pass rolling, increasing the reduction ratio and then increasing the deformation heat of the strip steel, and increasing the rolling temperature of the strip steel, comprising the following steps:

1) The temperature of the incoming material is controlled at 55°C to 60°C, and the reduction rate schemes of the four passes are as follows: the reduction rate of the first pass is 37%-41%, and the reduction rate of the second pass is 36%-39% , the reduction rate of the third pass is 34%-37%, and the reduction rate of the fourth pass is 32%-35%; the first two passes use a larger reduction rate to increase the deformation temperature and increase the relative edge deformation , to control the edge cracking of the strip and reduce the number of broken strips;

2) As the reduction rate changes, the rolling force of the four passes is controlled at: the first pass is 4750-5000kN, the second pass is 4600-5000kN, the third pass is 4400-4600kN, and the fourth pass is 3900- 4200kN; the rolling force mode is adopted when starting the machine, that is, the rolling force is constant to ensure the stability of the strip;

³ ) Tension distribution: Due to the increase of the reduction rate and the reduction of edge cracks, the tension can be increased to improve the strip shape and prevent the strip deviation; The unit tension is 5.8～7kg/mm ² , and gradually increase the front unit tension to 16.2～18.2kg/mm ² after starting to stabilize; after the second pass, the unit tension is 5.6～6.8kg/mm ² , and the front unit tension is 11.1～ 12.6kg/mm ² , gradually increase the front unit tension to 18.38～19.5kg/mm ² after the car is stable.

In the first pass, export closed milk rolling is adopted.

The rolling temperature is controlled at: the first pass: 130°C to 140°C.

The rolling speed is controlled at: the first pass: 120m/min～150m/min.

Compared with prior art, the beneficial effect of the present invention is:

The present invention simplifies the rolling passes, from the original five-pass rolling to four passes, and at the same time adjusts the reduction rate of each pass, increases the deformation of the edge, reduces the edge cracking tendency of the strip, and eliminates or Reduced the generation of second-rib waves. At the same time, a large reduction rate can increase the deformation heat of the strip, increase the rolling temperature of the strip, significantly reduce the number of broken strips and the degree of edge cracking, and improve production efficiency. The reduction rate is gradually reduced. The first two steps use a larger reduction rate to increase the deformation temperature and increase the relative edge deformation to control the edge cracking of the strip and reduce the number of broken strips. With the increase of the reduction rate, the rolling force also increases appropriately to ensure the stability of the strip. After adopting the method of the invention, the finished product is directly put on the line without edge trimming and continuous retreat, which saves the program of edge trimming of tailor welding unit; saves rolling time and improves rolling speed.

The first two steps use a larger reduction rate to increase the deformation temperature to improve the toughness and plasticity of the strip, increase the deformation of the edge of the strip to make the strip have a slight double-sided wave, and reduce the tensile stress at the edge of the strip to control the strip. The edge cracking of the steel reduces the number of broken strips. In addition, a larger reduction rate can crush the coarse grains, refine the grains, improve the toughness and plasticity of the strip, and make the strip more conducive to rolling.

Detailed ways

The present invention will be described in detail below, but it should be noted that the implementation of the present invention is not limited to the following embodiments.

A rolling method for non-oriented high-grade silicon steel. According to the characteristics of non-oriented high-grade silicon steel that is sensitive to temperature and easy to be brittle, through four-pass rolling, the reduction rate is increased to increase the deformation heat of the strip steel, and the rolling strength of the strip steel is improved. control temperature, including the following steps:

1) The temperature of the incoming material is controlled at 55°C to 60°C; the four-pass reduction rate plan is that the reduction rate of the first pass is 37%-41%, and the reduction rate of the second pass is 36%-39%. The reduction rate of the third pass is 34%-37%, and the reduction rate of the fourth pass is 32%-35%. The first two passes use a larger reduction rate to increase the deformation temperature and increase the deformation of the relative edge. To control the edge cracking of the strip and reduce the number of broken strips; in addition, a larger reduction rate can crush the coarse grains, refine the grains, improve the toughness and plasticity of the strip, and make the strip more conducive to rolling.

2) As the reduction rate changes, the rolling force of the four passes is controlled at: the first pass is 4750-5000kN, the second pass is 4600-5000kN, the third pass is 4400-4600kN, and the fourth pass is 3900- 4200kN; the rolling force mode is adopted when starting the machine, that is, the rolling force is constant to ensure the stability of the strip;

The control mode of the 20-high rolling mill is divided into two types: rolling force mode and position mode. The rolling force mode is to ensure that the rolling force is constant during the rolling process, and the position mode is to ensure that the strip thickness is constant during the rolling process. Normal rolling adopts the position mode for thickness control, and the two modes can be switched at any time during the rolling process.

³ ) Tension distribution: Due to the increase of the reduction rate and the reduction of edge cracks, the tension can be increased to improve the strip shape and prevent the strip deviation; The unit tension is 5.8～7kg/mm ² , and gradually increase the front unit tension to 16.2～18.2kg/mm ² after starting to stabilize; after the second pass, the unit tension is 5.6～6.8kg/mm ² , and the front unit tension is 11.1～ 12.6kg/mm ² , gradually increase the front unit tension to 18.38～19.5kg/mm ² after the car is stable.

In the first pass, export closed milk rolling is adopted.

The rolling temperature is controlled at: the first pass: 130℃～140℃;

The rolling speed is controlled at: the first pass: 120m/min～150m/min.

Example: rolling 35AW230, 35AW210, 35AW270 (some operation methods of oriented silicon steel 30AG120 are still applicable)

The non-oriented high-grade silicon steel rolling method specifically includes the following steps:

1) The first pass, the adjustment of the reduction rate of the rolling force: the preset rolling force is 4900kN, a large reduction rate of 39.2% is adopted, and the reduction rate is increased to increase the deformation temperature of the strip and increase the edge pressure of the strip Next, micro-edge wave rolling is adopted, that is, the pressure rate at the edge of the strip is slightly greater than the reduction rate at other positions of the strip. The rolling force mode (constant rolling force) is adopted when the machine is started to reduce the variation range of the strip shape, and the operator is given time to adjust the shape, so that the rolling is more stable and then switched to the position mode.

Adjustment of unit tension: small tension is used when starting the car, the rear tension is 1.32kg/mm ² , and the front tension is 5.92kg/mm ² to prevent edge cracks on both sides of the strip when the thickness does not reach the target thickness when starting the car. Excessive tensile stress causes broken belts. After the target thickness is rolled, the tension is gradually increased after the rolling is stable (the front tension can be increased to 17.41kg/mm ² ) and the rolling speed, and the tension refers to the unit tension.

Emulsion control: Ensure that the temperature of the emulsion is 58°C before rolling, and it cannot be too low or it is not conducive to strip rolling. The inlet emulsion flow rate is 1000L/M, and the outlet closed milk rolling is used to increase the deformation temperature of the strip steel, reduce the brittleness of the strip steel, and improve the toughness and plasticity.

Through the above operations, the broken strip of the strip can be significantly reduced, and the edge crack of the strip can be reduced to prepare for the subsequent rolling and speed-up.

2) The second pass, the adjustment of the rolling force reduction rate: the preset rolling force is 4750kN, and a larger reduction rate of 37.5% is also used to start the car in a constant rolling force mode to make the strip more stable, and adopt The micro-edge wave mode can control the rolling to -30μm, which can reduce the tensile stress at the edge of the strip, inhibit the extension of edge cracks, and reduce the tendency of broken strips.

Adjustment of unit tension: the preset rear tension is 5.8kg/mm ² and the front tension is 11.61kg/mm ² when starting the car. After the strip reaches the target thickness, gradually increase the rolling speed and front tension of the strip to 18.58kg/mm ² , and the tension refers to the unit tension.

Emulsion control: Use a small emulsion flow rate to start the car: the inlet emulsion flow rate is 1000L/m, and the outlet emulsion flow rate is 600L/m. The emulsion gradually increases with the increase of rolling speed. The speed is increased to 200m/min, the emulsion inlet flow is 1400L/m, and the outlet flow is 1000L/m.

3) The reduction rates of the third and fourth passes are 36.5% and 34.1% respectively; because as the rolling passes increase, the work hardening of the strip increases, the deformation resistance increases, and the edge cracks increase. So use a smaller reduction rate. Under the premise of ensuring edge cracking, the rolling speed can be increased. Because the strip steel becomes thinner, control the pressing of the edge to make the strip steel have micro-edge waves, and the degree of edge waves should be increased appropriately (compared with other strip steel positions, the pressure should be about 50 μm more), so as to reduce the tensile stress on both sides of the strip steel and prevent edge cracking. fault zone.

According to the direction of rolling, the tension before the roll gap is the back tension, and the tension after the roll gap is the front tension.

Control of the second type of rib wave: In the third and fourth passes of rolling, the second rib wave is likely to occur, which affects the shape of the strip and is not conducive to rolling. It can be reduced by reducing the AS-U-ROLL (referring to the roll shape adjustment mechanism of the 20-high rolling mill) , on the B and C rolls of the support roll, it is composed of 7 racks and 6 eccentric rings. The rack drives the rotation of the eccentric ring to adjust the local strip shape of the strip. The surface is evenly divided into 7 parts corresponding to No. 1-7 racks) reducing No. 2 and No. 6 racks to reduce the compression of the second rib and increasing the compression of No. 1 and No. 7 racks. At the same time, reducing the overlapping amount of a middle taper and the strip steel and increasing the side pressure can effectively drive the second rib wave to the edge to form a micro edge wave, and achieve the purpose of eliminating or reducing the second rib wave.

Effect comparison after implementation: Since the silicon content of 35AW210 and 35AW230 without destination is very high, even exceeding the grain-oriented silicon steel (30AG120), 35AW210 and 35AW230 are more sensitive to temperature than 30AG120, and are more brittle and easier to break. Before adopting the new rolling method, the normal shift produced 2 coils. If the rolling was not smooth, or the temperature of the incoming material was low, and the temperature of the factory building was low, the shift production would even be lower than 2 coils due to strip breakage and difficulty in threading. The new rolling method not only reduces the rolling time of one pass, but also significantly reduces the broken strip and edge cracks. It not only reduces the labor intensity but also improves the production efficiency, and the average shift production can roll 4 coils. The success rate has also reached more than 80% from 60%.

Claims (1)

1. a kind of non-oriented high grade silicon steel milling method, which is characterized in that rolled by four-pass, increase reduction ratio and then increase The deformation heat for adding strip improves the rolling temperature of strip, comprising the following steps:

1) for the control of supplied materials temperature at 55 DEG C~60 DEG C, it is 37%- that four-pass reduction ratio scheme, which is respectively as follows: the first percentage pass reduction, 41%, the second percentage pass reduction is 36%-39%, and third percentage pass reduction is 34%-37%, and four-pass reduction ratio is 32%-35%；Preceding twice are increased deformation temperature using biggish reduction ratio and increase opposing edge's deflection, to control strip Side split, reduce disconnected band number；

2) with the change of reduction ratio, the roll-force control of four-pass exists: the first passage 4750-5000kN, the second passage 4600- 5000kN, third passage 4400-4600kN, four-pass 3900-4200kN；When playing vehicle using rolling force mode, that is, roll Power is invariable, guarantees that strip is steady；

3) tension distributes: the reduction that increase and side due to reduction ratio are split, and can increase tension improves belt plate shape and prevent strip Sideslip；Tension presets 1.28~1.34kg/mm of unit tension after the first passage², preceding 5.8~7kg/mm of unit tension², after playing vehicle Preceding unit tension is gradually increased after stabilization to 16.2~18.2kg/mm²；5.6~6.8kg/ of unit tension after second passage is default mm², preceding 11.1~12.6kg/mm of unit tension², rise and gradually add preceding unit tension to 18.38~19.5kg/mm after vehicle is stablized²；

Newborn rolling is closed using outlet in the first passage；

Rolling temperature control exists: the first passage: 130 DEG C~140 DEG C；

Mill speed control exists: the first passage: 120m/min~150m/min.