SU1729636A1 - Tool for lengthwise hot rolling of tubes - Google Patents

Abstract

This invention relates to longitudinal rolling of pipes. The purpose of the invention is to improve the quality of rolled tubes. A technological tool for the longitudinal hot rolling of pipes consists of a conical mandrel 2 held on a rolling axle and rolls 3 with strands made therein. The larger base of the mandrel is advanced in the course of rolling beyond the line of roll centers. In the plane of the larger base of the mandrel, the tools form a gap d constant around the perimeter of the gauge. The roll stream is shaped by a symmetric curve, described by the equation U RB | (nv + L / 2- y () where y, x are the coordinates of the points of the curve; RB is the radius of the roll barrel, mm; L is the distance from the center line of the rolls to the larger base of the mandrel, mm; Do is the diameter of the larger base of the mandrel, mm ; d - gap between the tools in the plane of the larger base of the mandrel, mm; A - gap between the flanges of the rolls in the plane of the line of the centers of the rolls, mm. 4 ill., table 3 sl.

Description

The invention relates to pipe production, in particular, to the main tool of longitudinal rolling mills for hot rolled seamless pipes, and can be used for longitudinal rolling of pipes with distribution.

A known tool for the longitudinal rolling of pipes, comprising a series of successive calibers and a retained stepped mandrel having annular projections on the idle sections.

The disadvantage of such a tool is that the pipes are rolled in alternating crimping and expanding operations. In this case, the total amount of lift along the diameter of the pipe on the protrusions decreases by the amount of total diameter reduction in subsequent calibers. This reduces the total degree of distribution and requires high energy costs. In addition, the distribution of the pipe on the annular protrusions is carried out beyond the limits of the contact of the pipe with the rollers and the flow of metal in the transverse direction occurs mainly in areas with a smaller wall thickness. Therefore, the available cross-pipe pipes are aggravated.

There is also known a method for the longitudinal rolling of pipes with distribution, according to which the rolled pipes are successively deformed in two calibers on cylindrical mandrels with the distribution of the pipe by the conical part of the mandrel located in front of the caliber of the second stand.

The disadvantage of the tool that implements this method is the transverse difference in thickness caused by the deformation of the pipe on cylindrical mandrels, as well as the limited amount of lifting along the pipe diameter by the amount of axial forces generated by the first cage.

The technological tool for the longitudinal hot rolling of tubes includes two strand rolls, the depth of which is less than half the width, and the retained conical mandrel placed between the rolls, the larger base of which is located behind the roll center line, is closest to the proposed one.

The disadvantages of this tool when rolling tubes with dispensing is the rolling cross-sectional and ovality of the tubes that occur during rolling.

When using well-known calibrations of the rolls of the mill longitudinal rolling of pipes and a conical mandrel, streams of rolls for

the line of roll centers in the plane of the larger base of the mandrel forms a curve different from the circle. As a consequence, the gap between the surface of the streams and the conical mandrel in the plane of its larger base will be variable, namely, decreasing in the direction of the outlets. The deformation of the pipe along the wall is carried out in areas with a smaller gap and is localized in the course of rolling in the zones adjacent to the release. Reducing the gap in the release for large degrees of distribution leads to a roll in the flanges of the roll into the outer surface of the pipe. This limits the length and angle of taper of the calibrating portion of the mandrel, and, consequently, the degree of distribution. The unevenness of the gap between the tools in the plane of the larger base of the mandrel also leads to the guidance when rolling the transverse difference and ovality of the pipes.

The purpose of the invention is to improve the quality of rolled tubes.

This goal is achieved by the fact that in a technological tool for longitudinal hot rolling of tubes, including two strand rolls, the depth of the streams of which is less than half the width, and a conical mandrel held between the rollers, the larger base of which is located in the rolling direction, the roll stream outlined by an axisymmetric curve relative to the line of the centers of the rolls, described by the equation

V-RB-y RB + A.

0)

where y is the current coordinate of the depth of the stream, mm;

x - the current coordinate of the width of the stream, mm;

RB is the radius of the roll barrel, mm;

L is the distance from the center line of the rolls to the larger base of the mandrel, mm;

Do is the diameter of the larger base of the mandrel, mm;

d is the size of the annular gap between the caliber and the mandrel in the plane of the larger base of the mandrel, mm;

A - the value of the annular gap between the flanges of the rolls in the plane of the line of the centers of the rolls, mm.

The proposed technological tool forms, in the plane of the larger base of the mandrel extended as the rolling progresses beyond the line of roll centers, a constant annular gap around the perimeter of the gauge. For this, the roll stream is profiled by the curve described by equation (1), which is obtained from the condition that in the plane of the larger base of the mandrel the surface of the brook forms a part of a circle concentric to the larger base of the mandrel. Since the surface of the gauge forms a circle in the plane of the tube’s exit from the deformation zone and provides an annular gap constant around the perimeter with a large mandrel base, the tube wall formed in the annular gap will be constant along the tube perimeter, and the outer surface of the tube will have a circle in cross section . This provides, compared with the prototype, a decrease in the ovality and the transverse differential coatings of the rolled tubes. Due to the continuous increase in the rolling direction of the diameter of the mandrel, the tube also continuously increases its diameter. At the beginning of the deformation zone, the compression of the pipe along the wall is carried out by the top of the gauge. As the pipe moves, the compression zone along the wall expands around the perimeter of the gauge in the direction of the outlets and at the exit from the deformation zone is carried out by the entire perimeter of the gauge. The increase in the direction of rolling of the contact area of the surface of the streams of the rolls and the pipe leads to an increase in the course of rolling forces of friction, and hence the transporting forces. This contributes to the implementation of the process of distribution of the pipe in the roller caliber and increases the distributing cnqco6-instrument.

FIG. 1 shows the proposed technological tool; figure 2 - profile stream roll; Fig. 3 shows a mandrel, a cross-section in the plane of the larger base; figure 4 - the deformation zone, a longitudinal section.

The proposed technological tool (Fig. 1) consists of a taper mandrel 2 pivotally supported on the axis (axis O Z) and rod 1 as well as roll rollers 3. A larger base of mandrel 2 with a diameter Do extends beyond the center of the rolls (axis O Y) over the distance L. In the plane of the line of the centers of the rolls (plane Y О1 X) the rolls with the radius of the barrel RB are installed with an annular gap D (Fig 2) relative to each other. In the plane of the larger base of the mandrel (plane 1-1), the tools form an annular gap b, constant around the perimeter of the gauge (Fig. 3).

The tool works as follows.

The tube billet 4 (Fig. 4) is heated by axial forces Q, generated, for example, by a group of longitudinal rolling stands, freely distributed by the mandrel section 5 located in front of the roll gauge. After the rolls are gripped, the workpiece is distributed by the section 6 of the mandrel 2, races; 0 laid behind the line of the centers of the rolls with compression on the wall. In the plane of the larger base of the mandrel (plane I-I), the final formation of the wall and the diameter of the finished pipe takes place. five ; .. .

Example. Calibration construction of a roll stream using the example of hot rolling with the distribution of 244.5 x 12 mM pipes in a 3-stand mill expander. Rolling is carried out at 1100 ° C. After reduction in diameter in the first two cells, the tube is freely distributed in a 4% conical section of the mandrel located in front of the roll with the caliber of the third stand. After the shaft is gripped by the 5th cam of the third stand, the pipe is divided into a 10% section of the mandrel located in the caliber of the third stand with a compression on the wall of 2 mm. The larger base of the mandrel is advanced in the course of rolling for 0 line of roll centers at a distance of 68 mm. Rolling is carried out in two-roll cages with a roll barrel radius of 315 mm and an annular gap between the roll flanges of 10 mm. five

When calculating, the following notation is accepted: ...-.- T is the temperature = H = 0 ° C; g is the coefficient of thermal expansion of the metal; ... j -.-,

D is the diameter of the pipe before rolling i mm; Dr is the outer diameter of the pipe after rolling in a hotter state.

So.S - pipe wall thickness before and after rolling, mm;

5D - the value of the annular gap between

caliber and mandrel in the plane of the larger base of the mandrel, mm;

L is the distance from the center line of the rolls to the larger base of the mandrel, mm; 0 Do - diameter of the larger base of the mandrel, mm;

RB is the radius of the roll barrel, mm; A is the size of the annular gap between the roll flanges in the plane of the center of the rolls, mm;

AS - compression of the pipe wall, mm. Determine the coefficient of thermal expansion of the metal.

ij 1 + 0.000015 x T - 1 + 0.000015 x x1100 1.017.

Outer diameter of finished pipe in hot condition

Dr rj (D + D x 0.04 + D x 0.1) - -1.017 (244.5 + 244.5 x 0.01 + 244.5 x 0.1) 283.5 MM.

Pipe wall thickness after rolling

S So-AS 12-2 10mm.

Wall thickness of the finished pipe Corresponds to the size of the annular gap between the mandrel and the roll gauge in the plane of the larger base of the mandrel, i.e. d 10 mm. The diameter of the larger base of the mandrel corresponds to the internal diameter of the finished pipe in a hot condition, i.e. D0 Dr - 2S -283.5-2x10 263.5.

After substitution in equation (1), describing the stream roll profile, of the found numerical values, the curve equation takes

y-315jf 315+ -ylP 5 + 2 10f-x2f + 68g

To find the current coordinates of the depth of the stream (y) points of the curve in the resulting equation by substituting values.

The calculation results are shown in Table 1.

Due to the axisymmetry of the curve, the points for the first quadrant are presented in table 1. To prevent eadir and scratch marks on the outer surface of the pipe, the stream is mated with a radius of 25 mm to the roll flange.

The proposed technological tool was tested under conditions of longitudinal hot rolling with distribution in an experimental three-mill mill of pipes of 244.5 x 12 mm in size made of steel ZOG2SF heated to 1150-1200 ° С.

In the course of the experiments, rolls with a diameter of 630 mm and a barrel width of 370 mm were used. In the first two squares, a round calibration stream with radius-rounded outlets was applied. In the third stand, we used the proposed calibration stream, the parameters of which are listed in Table 1. The total compression of the pipe over the outer diameter in the first two cages was 6.5%. The experiments were carried out at a speed of axial displacement of the pipe of 0.75 m / s. In the experiments, conical mandrels with an angle of inclination of 12.5 ° forming a smaller diameter of 218 mm and a larger base of 263.5 mm were used. The larger base of the mandrel extends along the rolling line.

the centers of the rolls of the third stand 68 mm. Tripolyphosphate salt grease was used as a lubricant.

The results of the experiments are given

in table.2.

To compare the results obtained, the rolling was carried out using the technological tool described in the prototype. In this case, in the third stand, an oval calibration of the roll of the roll with the same coefficient of ovality of the gauge as in the calibration of the roll of the roll shown in Table 1 was applied. The radius of the caliber was 142 mm, the eccentricity was 13 mm. With

A cone-cylindrical mandrel consisting of inlet and calibrating conic sections, conjugated with a cylindrical face of 233 mm in diameter, 35 mm long, was used for rolling. Diameter

the smaller base of the entrance section is 218 mm, and the diameter of the larger base of the calibrating section is 263.5 mm. The results of pipe rolling with the use of the tool specified in the prototype are shown in Table 3.

From the results of the experiment, it can be seen that with the rolling pipe using the prototype technological tool, the distribution coefficient is 10 ± 0.13%,

the transverse differential wall is 7.8 ± 0.3% and the deviation of the outer diameter is 1.5 ± 0.02%. Rolling pipes using the proposed technological tool allows you to increase the distribution ratio

to T4 ± 0.04% and to ensure the accuracy of the pipes on the outer diameter in the range of 0.6 ± 0.2%, while reducing the transverse difference in wall pipes to 2.4 ± 0.02%.

Experimental studies

of the proposed technological tool for the longitudinal hot rolling of pipes showed that in comparison with the technological tool of a similar purpose (prototype) the proposed

the tool allows you to increase (at least 1.4 times) by raising the diameter of the rolled tubes. Thus, the use of the claimed tool, for example, in the lines of reduction-calibration mills

in the production of hot-rolled thin-walled seamless pipes of large diameter, it allows rolling with distribution with a minimum number of expansion stands, thereby increasing

performance tube rolling units.

In addition, the application of the proposed tool improves the quality of rolled pipes, increasing the accuracy of pipes by 1%.

on the outer diameter, while ensuring a reduction in the transverse differential wall thickness of pipes by 5%.

Invention Formula

Technological tool for longitudinal hot rolling of tubes, including two brook rolls, the depth of the streams of which is less than half the width, and a retained conical mandrel between the rollers, the larger base of which is located behind the line of roll centers in the rolling direction, characterized in that the quality of rolled pipes, the roll stream is outlined by an axisymmetric curve relative to the line of the centers of the rolls described by the equation

in RB in Q4- | - yfoo + f f + L8,

where y is the current coordinate of the depth of the stream;

x - the current coordinate width of the stream;

RB is the radius of the roll barrel, mm;

- distance from the center line of the rolls to the larger base of the mandrel, mm;

6 - the size of the annular gap between the caliber and the mandrel in the plane of the larger base of the mandrel, mm;

L is the size of the annular gap between the flanges of the rolls in the plane of the line of the centers of the rolls, mm.

Table 1

Table 2

Table 3

FIG. 2

Claims (1)

FORMULA AND SECTION 5 A technological tool for longitudinal hot rolling of pipes, including two groove rolls, the depth of the grooves of which is less than half the width, and a held conical mandrel placed between the rolls, the larger base of which is located behind the line of roll centers in the rolling direction, characterized in that, for the purpose of to improve the quality of rolled tubes 15, the roll creek is outlined by an axisymmetric curve with respect to the line of roll centers, described by the equation ^{y = RB} 'i [R _B + | - yEq ^ -x ^ + L ⁵ ,' ♦ where y is the current coordinate of the depth of the stream; x is the current coordinate of the width of the stream; Rb is the radius of the roll barrel, mm; L ^{is the} distance from the line of the centers of the rolls to the larger base of the mandrel, mm; d - the size of the annular gap between the caliber and the mandrel in the plane of the larger base of the mandrel, mm; Δ is the magnitude of the annular gap between the flanges of the rolls in the plane of the line of the centers of the rolls, mm Table 1 X 6 • 10 26 thirty 40 fifty 60 70 80 90 100 110 120 130 135 141.2 Y 124.2 123.9 122.9 121.2 118.8 115.7 111.7 106.8 100.9 93.8 85.2 74.6 61.2 ’42 .9 30.0 0 Table 2 Experience Pipe dimensions before rolling Pipe dimensions after rolling Distribution ratio * Outside Diameter (Do) mm Wall thickness (So), mm Outer Diameter (O) mm Wall thickness (S) mm The standard deviation of the diameter (ad.% Standard deviation of wall thickness% 1 244.74 12.15 278.76 9.98 0.56 2,34 13.90 2 244.63 12.13 279.01 10.01 0.61 2.36 14.05 3 244.58 12.08 278.83 10.01 0.62 2.35 2 p.m. 4 244.64 12.11 278.95 9.95 0.55 2.40 14.02 5 244.69 12.20 278.83 9.97 0.56 2.37 '13.95 6 244.59 12.14 278.78 10.03 0.60 2.41 • 13.98 7 244.66 12.11 278.81 . 9.97 0.57 2.37 13.96 8 244.71 12.12 278.94 9.96 0.57 2.36 13.99 9 244.66 12.14 278.96 10.02 0.59 2.38 14.02 Table 3 Experience Pipe dimensions before rolling Pipe dimensions after rolling Distribution coefficient ΡθΡο. Note Outside Diameter (Do) mm Wall thickness (So), mm Outside Diameter (D). mm Wall thickness (S) mm The standard deviation of the diameter (dr)% Standard deviation of wall thickness (ds \% 1 244.59 12.13 270.12 10.95 1.50 7.38 10.44 Braking on the cone, plunging the roll flanges and the outer surface of the pipe 2 244.62 12.07 269.77 10.81 1.55 8.11 10.28 Also 3 244.56 12.18 269.85 10.78 1.54 7.64 1034 - · - 4 244.64 12.16 270.60 10.88 1.55 8.05 10.61 5 24,475 ’ 12.22 270.40 10.74 1.52 7.77 10.48 Fig.Z Figure 2