SU1523201A1 - Method of rolling tubes on sinking mill and rolling mill tools for effecting same - Google Patents

Abstract

The invention relates to pipe production and can be used on reduction mills. The purpose of the invention is to increase productivity and reduce metal consumption. When a pipe is reduced in three-roll calibers simultaneously with axial stretching, it is subjected to alternating bending deformations in draft calibers in a vertical plane with the direction of pipe bending with concavity towards the horizontal roll by displacing the axis of the gauge relative to the mill by the calculated value. The technological tool for carrying out the method contains a series of three roll gauges. In each caliber formed by the streams of three rolls, one roll 1 is horizontal, and the other two rolls 2 and 3 are inclined. Each inclined swath is made with flanges of unequal diameter. Moreover, the large diameter flange facing the flanges of a horizontal roll. 3 silt, 2 tab.

Description

The invention relates to pipe production and can be used in tube rolling in non-continuous unbinding mills.

The purpose of the invention is to increase productivity and reduce metal consumption "

Figure 1 shows schematically the technological tool of the reduction mill; figure 2 - three-roll caliber of the i-th stand; on fig.Z - the same, (1-1) -th stands,

The proposed method is carried out on a reduction mill, on which the rotational speeds of the rolls are set so that their ratio at given total reduction and initial dimensions of the billet provides the total tension, allowing the kit to obtain the required size of the pipe wall without taking into account the axial deformations determined bend. In this case, the first and last gauges are set along the mill axis, and the inner gauges so that their centers are offset relative to the mill axis in the direction opposite to the roll, whose axis is horizontal. The billet pipe is then set into rolls, where it is pierced, subjecting the deformation and bending and tensioning simultaneously.

The required magnitudes of the displacement of the gauge center are determined from the following considerations. The pipe is considered as a beam of variable section, i.e. in each i-M gap between gauges, the cross-section is determined by the diameter of the gauge and the wall in the previous caliber

As a first approximation, the tube-beam under the action of displacement (h;) i-ro caliber is bent along an arc of a circle of radius R, and the circles along which two adjacent sections of the tube-beam are bent smoothly mate (see Fig. 1) e,

From the geometric relationships, the magnitude of the displacement, defined as the height of a segment formed by a circle of radius R and a chord equal to the length 1 of the intercalibration gap, is calculated by the formula

I 1

i i

where is the bend radius of the pipe in the i-th caliber Rj. R; 250dT; ,,,

0

5 0 5 o

About 5

five

d. - diameter of the pipe entering the i-th caliber.

During the rolling process between the gauges, the pipe is exposed to two force factors - stretching and bending.

The simultaneous action of tension and bending in opposite directions blocks compressive deformations due to the displacement of the neutral section and provides additional stretching. This means that strain-related strain-only stresses will be significantly less than deformations due to joint stress and bending.

To implement the proposed method, the technological tool contains gauges formed by a stream — Nffl of three rolls, while the flanges of roll 1, whose axis is horizontal, are of the same diameter pi, and for rolls 2 and 3, whose axes are at an angle to the horizon, the flanges are different diameter D; , with larger flange facing the reb.ordam horizontal roll.

This embodiment of the tool provides during rolling offset caliber relative to the mill axis when installing calibers (Fig about 1). The pipe is gripped by rolls of the first caliber, whose center is not shifted, and moves along the mill axis, then it falls into the second gauge and is shifted upwards, as its axis is shifted in this direction. Then, the pipe in the subsequent caliber deflects downwards, which causes the direction of the bending of the pipe to be reversed, since the roller, having a horizontal axis in a three-roll mill, is alternately set up or down.

Thus, the technological tool provides alternating bends of the pipe from gauge to gauge, which is required for carrying out the proposed method of straight-through continuous rolling.

Since the rigidity of the section of the rolled pipe for bending from the beginning to the end of the mill decreases due to an intense decrease in diameter with an almost unchanged wall, the magnitude of the displacement of the caliber from the beginning of the mill to the end also decreases and the bending radii K - increase (Fig. 1). it

This is explained by the fact that the cross section of lesser rigidity at the lowest values of the acting bending moments passes into the plastic state. The actual wall thickness at the outlet of the mill, corresponding to the total actual tension, is defined as

"Act

US

and

where S is the wall thickness obtained at the outlet of the mill, s

., working-tension Z, calculated without bending;

& 5z - additional wall thinning due to the introduction of pipe bends

The test of the effect of the appearance of additional stretching from the imposition of pipe bends during its straight-line rolling with tension was carried out in a simple laboratory setup. This installation consisted of a rolling stand, duo, on whose rolls the streams forming an oval gauge were cut. The front and rear tensions were created by loads fixed to the ropes, which were connected to the ends of the pipe to be painted through the blocks. The displacement of the center of the caliber h |. from the mill was modeled by the displacement of the axes of the blocks along the vertical axis. This displacement was recorded as an angle between the axis of the pipe entering (or leaving) the blocks and the horizontal axis passing through the center of the gauge formed by the strands of rolls of the rolling stand.

The copper cold chickpea tube is 4.95x0.636 mm in size, the specimen is the yield strength G, equal to 23.20 kg / mm, and the tensile strength equal to 25.58 kg / mm, was rolled into a caliber having a height of 4.38 mm and a width 4.68 mm (average caliber diameter 4.52 mm), which corresponds to a reduction (t) equal to 8.48%. The tension is created by a constant load (a set of calibrated weights) of 47.5 and 52.5 kg, with the front and rear tension for a particular experiment being created by the same weights.

Axial deformation was recorded by measuring with a caliper the distance between the risks applied on the outer surface of the pipe, as well as measuring

0

five

0

five

0

5 0 5

five

0

tube cross section before and after rolling with a micrometer „

The results of the experiments are presented in tabLo1 o

From Table 1 it can be seen that the axial deformation of the pipe increases with increasing tension and with the application of pipe bends in caliber. Thus, the axial deformation during tension with weights of 47.5 kg with a displacement of the caliber relative to the mill axis, which was specified by the angle of exit of the front end of the pipe from the caliber equal to 17.0 ° and the entrance at an angle of 15.5 °, is greater than the same deformation without displacement of caliber, by 1.42%. A similar pattern is observed when rolling with tension, provided with weights of 52.5 kg. Axial deformation of pipe 5, rolled with a bend, is more than pipe 4, rolled without bending, by 1.44%.

Thus, laboratory studies have shown the presence of additional axial stretching of the pipe when introducing bends during roll-up rolling. In these studies, small values of plastic tension Zn were used (cm „

OVI

Table 1) and beats obtained relatively large additional deformations of the draw. Extrapolating the results obtained in the case of hot, smooth rolling of pipes with plastic tension of 0.40-0.75, determines the additional axial stretch from the bend of the pipe within one caliber, equal to 1.5-2.0%.

Additional stretching from pipe bends during rolling with tension, which is implemented in the proposed method, allows to increase the productivity of the tube-rolling unit and reduce the specific metal consumption.

The tabLo2 presents the elements of the rolling strip of a pipe, 5 mm in size, constructed using known technology and the proposed method.

As can be seen from table 2, the performance of the proposed method for rolling a pipe with a size of 5 mm is 7.7% higher than that of the known method. This increase in productivity is achieved by the possibility of rolling a thicker pipe after a continuous mill, a thicker sleeve and an increase in the length of the workpiece, which is 1523201

These are determined by the increased exhaust where the radius of the bending of the pipe in the ith caliber is the capacity of the reduction mill. camp

Claims (2)

Invention Formula 1 A method of rolling tubes in a reduction mill, including deforming with a decrease in pipe diameter in black and finishing three-wrap gauges with axial stretching of the pipe between gauges, distinguished by the fact that, in order to increase productivity and reduce metal consumption, the pipe is subjected to alternating deformation of bending in draft calibers in the vertical plane with the pipe bending direction of concavity towards the roll located horizontally, and the displacement of the axis of the pipe hj relative to the mill axis in the output section and caliber set of ratio h; R; - -one) at;  R; 250dT.,, . i 5 0 1-1 at; five spacing between gauge-f mm} diameter of the pipe entering the i-th caliber horizontal roll radius along the vertex of the i-ro caliber, mm. 2. Technological tool for rolling tubes on a reduction mill containing successively placed gauges of diameter decreasing in the course of rolling, formed by streams of three rolls, one roll of which is horizontal, and the other two are inclined, characterized by the fact that each inclined horizontal roller is with unequal diameter flanges, and large in di-. The diameter of the flange faces the flanges of a horizontal roll. r R about Ol m Ot en s 1L ffl in J5 five "G4 ve to M eat - in CM m GM O t in 4 M GM (H to CO in to about tk to in so about in eat in G4 m m CM about in n about to about to ““ I have i-l s X t to n. a "o (xa §0) "1 e eg e and v-