RU2436640C1 - Method of cold deformed bar rolling of pipes - Google Patents

Abstract

FIELD: technological processes. ^ SUBSTANCE: in method of cold deformed bar rolling of pipes a rolled cartridge prior to each forward motion of deformed bar rolling is fed by one step, fixed relative to a mill stand and then deformed plastically by rollers of a double-roller rolling mill that makes reciprocal movement, besides, rollers have a pass of alternating radius. Reduced values of tension or backing that occur in process of plastic deformation of the cartridge are provided as a result of the fact that forward displacement of a mill accompanied with rotation of rollers is carried out so that displacement of the mill and the angle of rotation of each rolling mill are in a ratio regulated by a mathematical dependence. ^ EFFECT: expansion of technological capabilities of equipment during cold longitudinal cold deformed rolling of pipes on a mandrel. ^ 3 dwg

Description

The invention relates to pipe rolling production, namely to cold longitudinal periodic rolling of pipes on a mandrel.

A known method of cold periodic rolling of pipes by rollers (see, for example, Verderevsky V.A. Roller mills of cold rolling pipes. M., Metallurgy, 1992. 240 S.), in which a cold tube billet (sleeve) is crimped with three rollers with a constant section creek profile. The rollers are supported by profiled support strips installed in a rigid thick-walled sleeve that receives rolling force. The rollers are located in a separator, which receives a reciprocating movement along the mandrel from the housing through a lever and an earring.

The disadvantage of this method is the reduced ability to obtain significant plastic deformation of the sleeve due to the small diameter of the deforming rollers.

The closest in technical essence and the achieved effect to the proposed one is the method of cold periodic rolling of pipes, including crimping the sleeve on the mandrel with two rolls having streams of variable radius (Vinogradov A.G. Pipe production. M., Metallurgy, 1981. 340 p.). With this rolling method, after the end of the reverse stand of the stand and, accordingly, before the start of the direct course of the stand between the sleeve and the rolls, a gap is formed. In the period of time when there is a gap between the rollers and the sleeve, the sleeve is fed one step, it is rotated and fixed in a new position. After that, the crate is moved in the forward direction relative to the stationary sleeve. In the process of moving the cage, plastic deformation of the sleeve is carried out.

In the absence of tension or back-up of the rolled pipe, taking into account the shape of the stream and the contact conditions of the rolled pipe with the rolls, you can determine the points of the pipe surface at which the sliding speed of the material of the deformable pipe relative to the roll surface will be zero. The distance from these points of the pipe surface to the axis of rotation of the roll is the roll radius of the roll R _K. Given that the stream profile is a variable, depending on the angular coordinate of the roll, the rolling radius R _K will also be a variable. Considering that the sleeve remains stationary during the rolling process, the absence of tension or back-up in the pipe can be ensured if the speed of the points belonging to the roll surface and at a distance equal to the rolling diameter is zero in the plastic deformation zone.

When the radius of the stream cut on the roll is variable, the roll radius R _{K of the} roll in the zone of plastic deformation of the sleeve is also variable.

In the rolling method under consideration, the rolls are rotated from the gear put on the roll shank. This gear is meshed with a gear rack having a constant tooth pitch and fixedly mounted on the bed of the mill. The ratio between the movement x of the stand and the angle φ of rotation of the roll is determined by the following relationship:

where R _D is the radius of the pitch circle of the gear worn on the shank of the rolling roll. This radius is a constant.

The radius of the pitch circle is determined by the average rolling radius R _KCP

where z is the number of sections of the working cone in which the rolling radius R _Ki is determined.

From (1) it follows that the derivative of the displacement x of the stand along the angle φ of rotation of the rolls is a constant value equal to the radius R _{D of the} pitch circle of the gear worn on the shank of the rolling roll

The disadvantage of this method is that most of the plastic deformation of the sleeve is carried out in the absence of coincidence of the values of the variable rolling radius R _K with a constant value of the radius R _{D of the} pitch circle of the gear. If the values of the rolling radius and the radius of the pitch circle of the gear do not coincide in the rolled pipe, either tension or support is formed. A tension or support is formed on the sleeve section located between the cage and the device, which ensures that the sleeve is fixed relative to the bed. The presence of tension or back pressure negatively affects both the surface quality of the rolled pipe and the operation of the mill mechanisms.

The technical result of the invention is the expansion of the technological capabilities of the equipment by reducing the values of tension or backwater arising in the process of plastic deformation of the sleeve.

The technical result of the proposed invention is achieved by the fact that in the forward and reverse stroke of the stand, the relationship between the movement x of the stand and the angle φ of rotation of each rolling roll is determined from the following relationship:

where R _K is the variable rolling radius of the roll in the zone of contact of the deformable pipe with the streams of the rolls.

A method of rolling pipes is presented in figures 1-3, where:

- figure 1 shows the working stand, located in the initial position and in the intermediate position, and also shows the sleeve and work rolls;

- figure 2 shows the position of the work rolls, liners and mandrels at the time of the working stand in the initial position, when there is a feed and rotation of the sleeve, and also shows the direction of the angle φ of rotation of the rolls and the direction of movement x of the stand;

- figure 3 shows the position of the work rolls, sleeves and mandrels at the time of plastic deformation of the sleeve, and also shows the direction of the angle φ of rotation of the rolls, the direction of movement x of the stand and the rolling radius R of the rolls, while the figures indicate elements with positions:

- 1 - upper work roll;

- 2 - lower work roll;

- 3 - sleeve;

- 4 - mandrel.

The rolling method is as follows.

Before the beginning of each cycle of periodic rolling, when the crate is in the initial (extreme rear) position (figure 1). The dimensions of the caliber, formed by the profile of the streams cut on the rolls 1 and 2, in this position are larger than the dimensions of the sleeve 3. In this case, a gap is formed between the rollers 1, 2 and the sleeve 3 (Fig. 2). In this position, the supply of the sleeve by the value of m or the supply of the sleeve by the value of m, accompanied by its rotation. After feeding the sleeve by the value of m or feeding the sleeve by the value of m, accompanied by its rotation, the gap between the sleeve and the rolls remains, and also a gap Δ _m appears between the sleeve 3 and the mandrel 4. When the working stand moves forward, accompanied by rotation of the rolls, the sleeve is crimped until the inner surface comes into contact with the mandrel (reduction), then rolling of the displaced part of the metal on the mandrel follows (Fig. 3).

Thus, the proposed method for cold periodic rolling of pipes allows to expand technological capabilities:

- due to the presence in the elements of the tube mill of rolls of a special profile for feeding the pipe to a new step without deformation,

- rolling pipes of various materials with different indicators of hardness and strength due to the implementation of rolling to the required dimensions,

- as a result of calculation and sizing of the elements of the rolling rolls, which affect the technical characteristics of the proposed range of pipes prepared for cold rolling,

- since on some rolls it is possible to carry out a certain assortment of pipes with minor profile changes in the form of reprofiling,

- when replacing the rolls with the necessary profiles without significant labor costs.

Claims (1)

The method of cold periodic rolling of pipes, in which the rolled sleeve before each direct stroke of the periodic rolling is fed one step, is fixed motionless relative to the bed of the mill and then plastically deformed by the rolls of a two-roll rolling mill, which performs a reciprocating movement, and the rolls have a stream of variable radius, characterized in that the movement of the stand forward, accompanied by the rotation of the rolls, is carried out in such a way that the movement x of the stand and the angle φ of rotation of each rolling roll n hodyatsya in a ratio determined from the following relationship:

where R _K is the variable rolling radius of the roll in the zone of contact of the deformable pipe with the streams of the rolls.

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