RU2492947C1 - Method of tempering annealed steel strips - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to metallurgy, particularly, to tempering of cold-rolled annealed strips at mills with at least one driven roll. Proposed method comprises strip threading in the mill by electrically driven working rolls at relative reduction of 0.5-2.0% and rolling at working rolls running at preset speed. Metal plastic yielding solely in direction of rolls rotation is ensured by switching off of working rolls drive after threading the strip to increase rear and front tension smoothly. Note here that rear tension is increased to specific magnitude equal to 0.05-0.20 of conventional yield point of annealed strip while front tension is increased to the start of working roll rotation at preset rolling speed. Front tension is increased to specific value not exceeding 0.8 of arbitrary yield point of annealed steel strip.

EFFECT: electric power savings.

1 tbl, 1 ex

Description

The invention relates to rolling production and can be used in the training of cold-rolled steel annealed strips in a stand with at least one drive roll.

There is a method of training steel annealed strips at a given speed with a relative compression of about 1% using a pair of electric drive work rolls with the rear and front tension created by the unwinder and reel [1] applied to the strip.

The disadvantage of this method is the high energy consumption for the implementation of training.

There is also a known method of rolling metal strips of aluminum and its alloys, including the first rolling in a quarto mill with drive backup rolls to an intermediate thickness and the final cold rolling in non-driving rolls with a specific front tension created by a coiler exceeding the specific rear tension, rolling speeds of 50-100 m / min and compression for the passage of 40-55% [2].

The disadvantages of this method are that it is not suitable for training steel annealed strips, and its implementation requires large energy costs. In addition, the front ends of the strips with a length equal to the distance from the non-driven rolls to the coiler are substandard.

The closest analogue to the present invention is a method of training steel annealed strips with a relative compression of from 0.5 to 8-10%, including installing the roll on the unwinder, dressing the strip in the mill using a pair of electric drive work rolls, securing the front end on the reel drum and training of the strip (rolling) with a given rolling speed with the application of rear and front tension created by the electric drives of the unwinder and coiler [3].

The disadvantages of this method are that when training the electric drives of the work rolls, unwinder and winder in the energy sense, they work counter-directionally. In addition, since the speed of entry of the strip into the electric drive work rolls is less than their peripheral speed (due to the lag effect), the metal in the deformation zone plastically flows towards the movement of the rolls, which increases the load on the drive. All this increases the energy consumption for training.

The technical problem solved by the invention is to reduce energy consumption.

To solve the technical problem in the known method of training steel annealed strips with the application of rear and front tension, comprising refueling the strip into the mill by means of electric drive work rolls with compression of the strip until the front end of the strip is fixed on the winder and subsequent training in work rolls rotated at a given speed, according to of the invention, after completing the filling of the strip, the electric drive of the work rolls is turned off, a smooth increase in the rear and front tension, and the rear tension at increase to a specific value equal to 0.05-0.20 from the conditional yield strength of the annealed steel strip, and the front tension to a specific value not exceeding 0.8 from the conditional yield strength of the annealed steel strip, with increasing front tension to the initial moment of rotation work rolls with a given rolling speed, while training is carried out with a relative compression of 0.5-2.0%.

The essence of the proposed technical solution is as follows. Filling the strip into the training mill with the help of electric drive work rolls allows transportation of the front end of the strip along the line of the training mill and contributes to its reliable binding to the reel drum. In the process of refueling, driven work rolls produce compression (training) of the front end of the strip, which eliminates the formation of substandard metal products.

With an increase in the specific forward tension σ ₁ to a value not exceeding 0.8 from the conditional yield strength σ _{0.2 of the} annealed steel strip, experiments have shown that training with a relative compression of 0.5-2.0% in notched and smooth work rolls proceeds stably over account of the force action of only the front tension, i.e. when the electric drive of the work rolls is off. Throughout the deformation zone, the metal flows plastic only in the direction of rotation of the work rolls. Due to this, a reduction in energy costs for the implementation of training is achieved.

With a specific rear tension of Hundred less than 0.05 of σ _{0.2, there} is a deterioration in the flatness of the strips without a decrease in energy consumption. An increase in the specific back tension σ _{0 of} more than 0.20 from σ _0.2 leads to an increase in energy consumption for training, which is therefore impractical.

It was experimentally established that, with a relative reduction of less than 0.5%, the steel annealed strips after training retain the area and the yield tooth in the tensile diagram of the samples, and their surface finish remains low, i.e. the goal of training is not achieved. With an increase in the relative compression of more than 2.0%, for a stable course of the training process with the electric drive of the work rolls turned off, an increase in σ _{1 of} more than 0.5 from σ _0.2 is required. At the same time, the band break in the training camp and the creation of an emergency are not excluded.

It was also established from experiments that an increase in the specific forward tension σ _{1 of} more than 0.8 from the conditional yield strength σ _{0.2 of the} annealed steel strip does not exclude strip breaks in the line of the temper mill, which is unacceptable.

Method implementation examples

A cold-rolled annealed strip with a cross section of 0.7 × 780 mm from steel grade 08Yu, wound into a roll, is installed on the uncoiler of a single-cage temper mill 1700. The conditional yield stress of the trained strip is: σ _0.2 = 295 MPa.

The front end of the strip at a filling speed of 0.5 m / s is set into a pair of work rolls rotated from electric motors. Using push mechanisms set the compression strip equal to: ε = 1.0%.

After exiting the rolls, the front end of the strip is transported to the winder drum and is attached to it by tightly winding 5 turns. Then the electric motors drive the work rolls are turned off.

By increasing the current of the armature of the unwinder motor, the rear tension of the strip is smoothly increased until a specific value is reached

σ ₀ = 0.12 · σ _0.2 = 0.12 · 295 MPa = 35.4 MPa.

At the same time, using a winder electric motor, the front tension of the strip is gradually increased first, before the work rolls begin to rotate, and then, until the rolling speed increases to a predetermined V _dr = 20 m / s. In this case, the specific front tension σ ₁ is:

σ ₁ = 118 MPa = 0.40 · σ _0.2 ,

those. σ ₁ <0.8 · σ _0.2 = 236 MPa.

Under the action of the front tension of the strip created by the winder electric motor, the strip extends through the gap formed by the work rolls and is crimped by them with a relative compression ε = 1.0%, which ensures its training. The presence of rear tension ensures high flatness of the strip (non-flatness A does not exceed 3 mm / m) and stability of the rolling process.

Total measured power, i.e. energy consumption for training consumed by the winder and unwinder electric motors in the process of training with the specified parameters is:

N _Σ = 137 kBt,

which is significantly less than in the known method [3].

Implementation options of the proposed method and indicators of their effectiveness are shown in the table.

Table. Training modes of annealed strips with a cross section of 0.7 × 780 mm from steel grade 08Yu on a single-chamber mill 1700 and their effectiveness Option No. ε,% σ ₀ / σ _0.2 σ ₁ / σ _0.2 N _Σ , kW A, mm / m Notes one. 0.4 0.04 0.20 280 8-10 Flatness 2. 0.5 0.05 0.30 130 four Without remarks 3. 1,0 0.12 0.40 137 3 Without remarks four. 2.0 0.20 0.80 137 3 Without remarks 5. 2,5 0.25 0.90 276 3-10 Break of bands 6. [3] 1,0 not regl. not regl. 298 3-5 Without remarks

From the data given in the table, it follows that when implementing the proposed method (options No. 2-4), a reduction in the total power consumed by the unwinder and winder electric motors is achieved, and, therefore, energy consumption for training. With exorbitant values of the declared parameters (options No. 1 and No. 5), the training process is unstable due to mill stops or band breaks. In the case of the implementation of the known method (option No. 6) with the drive of work rolls from electric motors in the process of training, there is an increase in the total power consumption and energy consumption for training.

As the base object, the closest analogue was adopted [3]. Using the proposed method will increase the profitability of the production of cold-rolled strips by 3-5% by reducing the cost of production.

Information sources

1. V.L. Mazur et al. Improving the quality of sheet metal. K .: Technics, 1979, pp. 106-109.

2. RF patent No. 2048217, IPC B21B 3/00, 1995

3. M.A. Benyakovsky et al. Automotive steel and thin sheet. Cherepovets, Publishing House "Cherepovets", 2007, p. 344-349.

Claims (1)

The method of training annealed steel strips with the application of back and front tension, comprising refueling the strip into the mill by means of electric drive work rolls with squeezing the strip until the front end of the strip is fixed on the winder and subsequent training in work rolls rotating at a given speed, characterized in that after refueling is completed the electric drive strips of the work rolls are turned off, a smooth increase in the rear and front tension, and the rear tension is increased to a specific value equal to 0.05 - 0.20 from the conditional yield strength of the annealed steel strip, and the front tension is up to a specific value not exceeding 0.8 from the conditional yield strength of the annealed steel strip, with an increase in front tension to the initial moment of rotation of the rolls with a given rolling speed, while training is performed with a relative compression of 0.5-2.0%.