RU2521764C1 - Step-by-step rolling method - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method involves deformation of a workpiece by direct and reverse travel at back-and-forth movement of axes of rolls and free movement of the workpiece along the rolling axis to the side opposite to direction of movement of axes of rolls during deformation of the workpiece, forced movement of the workpiece towards a ready-made channel during formation of a gap between the workpiece and the working surface of rolls. Reduction of axial forces in the workpiece at its deformation by reverse travel is provided owing to the fact that forced movement of the workpiece prior to reverse travel is performed additionally by the value of free movement of the workpiece; with that, free movement of the workpiece does not exceed m×(λ-1), where λ - ratio of cross-sectional areas of the initial workpiece and the ready-made channel; m - design supply.

EFFECT: improving efficiency of a step-by-step rolling process and reliability of process equipment.

6 dwg

Description

The invention relates to rolling production, and in particular to methods of step rolling.

A known method of step rolling, carried out on mills with oscillating rolls / Koval G.I. The use of rolling and forging mills for long products from special alloys of ferrous and non-ferrous metals / Procurement in mechanical engineering. - 2012. No. 7. P.33 ... 36 /, in which the deformation of the workpiece is performed during the reciprocating movement of the axes of the rolls and the free movement of the workpiece along the axis of rolling in the direction opposite to the direction of movement of the axes of the rolls during deformation of the workpiece, forced movement of the workpiece towards the finished profile during the formation of the gap between the workpiece and the working surface of the rolls.

The disadvantage of this method is the implementation of step rolling only in direct motion, which reduces the performance of the step rolling process.

In this case, the forced movement of the workpiece by the feed rate before the forward stroke is carried out by a continuously moving mechanism damped with a spring. During the forward stroke, the free movement of the workpiece along the rolling axis towards the original workpiece and the indicated movement of the mechanism by the amount of feed in the opposite direction are accumulated in a compressible spring. Due to this, during the reverse stroke, an axial force acts on the workpiece from the compressed spring, which is transmitted both to the deforming device and to the mechanism for forced movement of the workpiece. In addition, at the end of the return stroke at the time of the formation of the gap between the original workpiece and the working surface of the rolls, the workpiece is accelerated by the feed rate by means of a compressed spring. This situation leads to the action of dynamic forces on the workpiece and the mechanism of its forced movement. The action of dynamic forces on the mechanism of forced movement of the workpiece reduces the reliability of its work. Accelerated movement of the workpiece along the rolling axis by the feed amount causes uncontrolled movement of the workpiece and the possibility of exceeding the movement of the workpiece by an amount exceeding the feed amount. Exceeding the feed rate compared to the design feed will result in increased strain on the deforming equipment, reducing its reliability.

Thus, the disadvantage of this analogue is its low productivity, the effect of increased technological loads on deforming equipment and the mechanism of forced movement of the workpiece, reducing the reliability of their work.

Closest to the proposed solution on the technical nature and the achieved effect is the method of step rolling on cold rolling mills / Verderevsky V.A., Gleyberg A.Z., Nikitin A.S. Pipe rolling mills. - M.: Metallurgy, 1983, 240 p. (on page 188) /, in which the workpiece is deformed by both direct and reverse when the axes of the rolls are reciprocated and the workpiece is freely moved along the rolling axis in the direction opposite to the direction of movement of the roll axes during the workpiece deformation. In this case, the workpiece is forcibly moved towards the finished profile during the formation of the gap between the workpiece and the working surface of the rolls. The implementation of the deformation of the workpiece not only direct but also in reverse increases the productivity of the step rolling process.

However, during step rolling according to the prototype before the reverse stroke, the forced movement of the workpiece is carried out only by the value of the project feed. According to the well-known patterns of step rolling in the reverse course due to the linear displacement of the metal towards the initial billet, the actual deformable feed volume is λ times smaller than the projected feed volume (λ is the ratio of the cross-sectional areas of the initial billet and the finished profile) carried out in the forward stroke. Due to this, the productivity of the step rolling process during the reverse stroke decreases by a factor of λ. Therefore, the total productivity of the step rolling process is reduced by 2λ / (λ + 1) times. At the same time, significant axial forces act on the workpiece and the mechanism forcing the workpiece to move during reverse deformation (especially at its beginning). This is due to the fact that during deformation by the forward stroke due to the excess of movement of the workpiece by the rolls over the movement of the axis of the rolls, the workpiece is shifted relative to the stationary frame of the stepping mill towards the mechanism for forcing the workpiece. The specified movement during deformation of the workpiece in direct motion accumulates in the damping device of the mechanism, forcing the workpiece to move. The action of axial forces on the workpiece and the mechanism for the forced movement of the workpiece leads to an increase in technological loads on both the specified mechanism and deforming equipment.

Thus, the main disadvantage of this method is its low productivity and increased technological load on the equipment, reducing the reliability of its operation.

The objective of the invention is to increase the productivity of the step rolling process and increase the reliability of technological equipment.

The problem is achieved in that in the inventive method of step rolling, including deformation of the workpiece by forward and reverse motion with the reciprocating movement of the roll axes and free movement of the workpiece along the rolling axis in the direction opposite to the direction of movement of the roll axes during workpiece deformation, forced movement of the workpiece in side of the finished profile during the formation of the gap between the workpiece and the working surface of the rolls, according to the invention, the forced movement of the workpiece before the return stroke, they additionally carry out the amount of free movement of the workpiece, and the free movement of the workpiece does not exceed m × (λ-1), where λ is the ratio of the cross-sectional areas of the original workpiece and the finished profile; m - design feed.

The use of forced movement of the workpiece before the reverse stroke additionally by the amount of free movement of the workpiece allows you to return the workpiece to its position before the direct stroke, eliminating the axial forces on the workpiece and the mechanism that forces the workpiece to be forced backward, and increasing the productivity of the step rolling process.

The free movement of the workpiece by the value of m × (λ-1) makes it possible to set the workpiece in front of the forward stroke in a position that ensures the projected supply of the workpiece m when it is deformed by the direct course and the projected supply of the workpiece mλ when it is deformed by the reverse course.

Before the direct stroke, when setting the free movement of the workpiece less than m × (λ-1) using the mechanism forcing the workpiece to move, while there is a gap between the working surface of the rolls and the workpiece, the latter will additionally move to the desired design position. This will ensure the fulfillment of conditions under which the projected supply of the workpiece before its deformation by a direct stroke will be equal to m.

Before the return stroke, when setting the free movement of the workpiece less than m × (λ-1), the reverse rolling will be carried out with a feed not exceeding the design value mλ.

The free movement of the workpiece in excess of m × (λ-1) during the reverse stroke will lead to step rolling with an increased supply of the workpiece. This will increase the design technological load, leading to the failure of the technological equipment, reduce the quality of the rental.

Therefore, the application of the proposed method of step rolling provides an increase in the productivity of the step rolling process under technological conditions not exceeding design conditions, reducing axial forces in the workpiece, increasing the reliability of the process equipment.

Thus, the application of the proposed method increases the productivity of step rolling and increases the reliability of the process equipment.

The proposed method of step rolling is illustrated in the drawings.

Figure 1 shows the beginning of the process of deformation of the workpiece in direct motion.

Figure 2 shows the end of the process of deformation of the workpiece in direct motion.

Figure 3 shows the moment of the presence of a gap between the workpiece and the working surface of the rolls at the end of the forward and the beginning of the return stroke.

Figure 4 shows the beginning of the process of deformation of the workpiece in reverse.

Figure 5 shows the end of the process of deformation of the workpiece in reverse.

Figure 6 shows the moment of the presence of a gap between the workpiece and the working surface of the rolls at the end of the reverse and the beginning of the forward stroke.

Using figure 1 ... 6 consider the implementation of the technology of step rolling using the proposed method.

Step rolling of the workpiece 1 is carried out by two rolls 2 of variable radius. The axis of the rolls (t. O) make a reciprocating movement from the position of O ₂ in O ₃ and vice versa. The workpiece from the side of its original dimensions through a damping element in the form of a spring 3 is constantly acted along the rolling axis by a mechanism 4 of forced movement of the workpiece. In the future, for brevity, this mechanism will be called simply a mechanism.

The description of the implementation of the step rolling process will start from the position of the beginning of the deformation of the workpiece in reverse (figure 1). On the workpiece 1, a deformation cone is pre-rolled out with cross-sectional dimensions gradually changing from the initial workpiece S ₀ to the finished profile S ₁ and a certain part of the finished profile is obtained on it. In this position, the distance from the mechanism 4 (t. B) to the rear end of the workpiece 1 (t. A) is maximum and equal to a. The mechanism 4 through the spring 3 is in contact with the rear end of the workpiece 1. When compressing the O axis of the rolls 2 and the workpiece 1 in a straight way, they move in opposite directions (arrows), and the rolls 2 rotate (arrow). In this case, the mechanism 4 moves towards the finished profile with a constant predetermined speed along the rolling axis (in the direction of the arrow), providing for one cycle of the reciprocating movement of the roll axes its movement to the design doubled feed rate of 2 m. The indicated speed may vary depending on the design value of the feed m. When moving the mechanism 4 through the spring 3 acts on the end face of the workpiece 1. When changing the distance between the mechanism 4 and the end face of the workpiece 1, the spring 3 is compressed and expanded. The maximum distance between the mechanism 4 and the end face of the workpiece 1 is determined by the design of the mechanism 4. In this case, this distance is equal to a.

During crimping in direct motion (FIGS. 1 and 2), the roll axes move from position O to position O ₁ by a distance L ₀ . On the workpiece 1, a deformation cone of length L _{3 is} rolled out (the distance between points C and D). In this case, the workpiece 1 due to the difference in its movement and the O-axes of the rolls 2 during deformation freely moves along the rolling axis in the direction opposite to the specified direction of movement of the roll axes by ΔL = L ₃ -L ₀ (figure 2). In this case, the mechanism 4 due to constant movement will move a distance m in the direction of the finished profile. (In the figures, the movement of the mechanism 4 by the value of m is shown conditionally. (Actually, such a movement of the mechanism 4 is achieved in half the rolling cycle corresponding to the movement of the axis of rotation of the rolls 2 from the position O ₂ to O ₃ , or vice versa (Figs. 1 ... 6)). The distance between the end face of the workpiece 1 and the mechanism 4 will decrease, the spring will compress by m + ΔL.

With a further rotation of the rolls 2 and the movement of their axes from t. O ₁ to t. O ₂ (Fig.3) between the working surface of the rolls and the workpiece, a gap is formed. At this time, the workpiece 1 by means of mechanism 4 by fully unloading the spring 3 to a value a will move towards the finished profile along the rolling axis by the feed quantity m and additionally by the amount of free movement of the workpiece ΔL. For a given free movement of the workpiece not exceeding m × (λ-1), the total movement of the workpiece will not exceed m + m × (λ-1) = mλ. According to the well-known patterns of step rolling, this value of the movement of the workpiece during compression by reverse motion does not exceed the design technological modes. The maximum design value of the movement of the workpiece during step rolling in reverse motion, as is known, is m × λ.

Next, the return stroke begins. The axis of the rolls 2 from position O ₂ (figure 3) are moved to position O ₁ (figure 4). During this time, between the working surface of the rolls 1 and the workpiece 2, the gap is eliminated. After the deformation of the workpiece 1 in reverse (Fig. 5), the axis of the rolls 2 will move from position O ₁ to position O, having followed the path L ₀ . A new deformation cone FE of length L _{3 is} rolled out on the workpiece 1. In this case, the workpiece 1 from the side of the finished profile freely moves along the axis of rolling by the value ΔL = L ₃ -L ₀ towards the finished profile. Billet 1 from the side of its initial dimensions will also freely move in the same direction by the same amount and due to the known regularities of step rolling associated with the linear displacement of the metal during its deformation, will receive a shift in the opposite direction by (ΔL + m) × (λ -1) / λ. This expression is obtained as follows. The movement of the workpiece 1 before the reverse stroke, as shown earlier, is equal to (ΔL + m). During step rolling, equal feed volumes are observed

$$\left(\Delta L+m\right)\times S_{\mathrm{one}}=X\times S_0,\left(\mathrm{one}\right)$$

where X is the value of the accepted conditional feed of the workpiece during deformation by the forward stroke, corresponding to the forced movement of the workpiece 1 by the amount (ΔL + m) before the deformation by the reverse stroke;

S ₁ and S ₀ - the cross-sectional area of the finished profile and the original workpiece.

From equation (1) we can determine

$$X=\left(\Delta L+m\right)\times S_{\mathrm{one}}/S_0\mathrm{,.}\left(2\right)$$

Given that

$$\lambda =S_0/S_{\mathrm{one}},\left(3\right)$$

we get

$$X=\left(\Delta L+m\right)/\lambda .\left(\mathrm{four}\right)$$

The linear displacement of the metal during step rolling is (λ-1) times higher than the feed, then, taking into account dependence (4), the linear displacement of the workpiece metal during deformation by the reverse stroke is

$$X\left(\lambda -\mathrm{one}\right)=\left(\Delta L+m\right)\left(\lambda -\mathrm{one}\right)/\lambda .\left(5\right)$$

Finding the difference between the indicated movements of the workpiece 1 from the side of its original dimensions, we obtain

$$\left(\Delta L+m\right)\left(\lambda -\mathrm{one}\right)/\lambda -\Delta L=m-\left(\Delta L+m\right)/\lambda .\left(6\right)$$

The resulting expression determines the value of the movement of the workpiece 1 from the side of its original dimensions (figure 5). Those. point G (Fig. 4) will move by the value m- (ΔL + m) / λ (Fig. 5).

In this case, the mechanism 4 due to the constant movement during deformation by the reverse stroke will move by a predetermined value of the project feed m. Spring 3 is compressed by the value m + m- {ΔL + m) / λ = 2m- (ΔL + m) / λ (Fig. 5).

In the future, the axis of the rolls 2 are moved from position O to position O ₃ . When this rolls 2 are rotated, forming a gap between their working surface and the workpiece 1 (Fig.6). After the clearance is formed, the workpiece 1 (i.e., G, F), using mechanism 4, by fully unloading the spring 3 to a value a, moves to the side of the finished profile along the rolling axis by 2m- (ΔL + m) / λ.

For a given value of the free movement of the workpiece 1, not exceeding

m × (λ-1),

the maximum value of the obtained movement of the workpiece 1 will be

2m- (ΔL + m) / λ = 2m- (m × (λ-1) + m) / λ = m.

Thus, the maximum value of the movement of the workpiece before the forward stroke is equal to the value of the project feed m. This makes it possible to conduct the process of step rolling in direct motion in predetermined technological modes.

Next, the step rolling cycles are repeated.

Consider a specific example of the implementation of the proposed method of step rolling on the mill ШП175 with a lever system for driving rolls / G. Koval. The use of rolling and forging mills for long products from special alloys of ferrous and non-ferrous metals / Procurement in mechanical engineering. - 2012. No. 7. P.33 ... 36 /.

At ШП175, the following roll parameters can be used. The eccentricity e = 57.5 mm, the radius of curvature ρ = 110 mm, the distance between the axes of the rolls D ₀ = 350 mm. The height of the initial workpiece H ₀ = 60 mm, the height of the obtained profile H ₁ = 15 mm When rolling in two rolls, the absence of broadening of the workpiece is accepted. Then the ratio of the cross-sectional areas of the initial billet and the finished profile is λ = 4.

Using the method / Vydrin V.N., Berezin E.N., Koval G.I. Shaping, geometry of work rolls and deformation cone during multi-strand rolling in a rolling-forging mill. University News. Ferrous metallurgy. - 1980. No. 4. p.67 ... 71 / taking into account rolling in rolls with a smooth working surface, the length of the deformation cone L _{3 is} determined when the workpiece is crimped according to the formula, which in the accepted notation has the form

$$Ls=\rho \times {\delta }_{n\mathrm{to}}+e\times \sin {\delta }_{n\mathrm{to}}.\left(7\right)$$

In this formula

$${\delta }_{n\mathrm{to}}=\arccos ({(D_0-H_0)}^2-\mathrm{four}{e}^2-\mathrm{four}{\rho }^2)/(\mathrm{four}e\times (D_0-H_0)).\left(8\right)$$

After substituting the parameters in formulas (6) and (7) and calculating, we obtain

δ _nk ≈70 deg, L ₃ ≈186 mm.

According to the method described, for example, in / Fundamentals of design and calculation of rolling mills. Textbook for coursework and diploma design. V.N. Vydrin, E.N. Berezin, G.I. Koval, V.G. Dremin. - Chelyabinsk: ChPI, 1983. 44 p., On p. 18 ... 20 / using the value of L _nk ≈70 degrees, using the graphic-analytical method, the movement of the axes of the rolls L ₀ ≈164 mm is determined.

Then from the condition

$$m\times \left(\lambda -\mathrm{one}\right)\ge Ls-L_0\left(9\right)$$

the feed quantity m≥1.13 mm is determined, which ensures the fulfillment of the technological conditions required for the implementation of the proposed method of step rolling.

To calculate specific technological parameters using the above formulas and recommended methods, other calculation algorithms can be used. For example, for a given value of m, λ is determined, and therefore, the values of H ₀ and H ₁ . In any case, condition (9) must be satisfied.

The proposed method of step rolling is planned to be used on mills ШП175, ШП200, ШП280 and PK600.

Claims (1)

Method of step rolling, including deformation of the workpiece by forward and backward movement with reciprocating movement of the roll axes and free movement of the workpiece along the rolling axis to the side opposite to the direction of movement of the roll axes during workpiece deformation, forced movement of the workpiece towards the finished profile during the clearance between the workpiece and the working surface of the rolls, characterized in that the forced movement of the workpiece before the return stroke is additionally carried out on the reason for the free movement of the workpiece, while the free movement of the workpiece does not exceed m × (λ-1), where λ is the ratio of the cross-sectional areas of the original workpiece and the finished profile; m - design feed of the workpiece when it is deformed by a direct stroke.

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