UA21300U - Method of cold or warm pilger rolling of tubes with external longitudinal ribs - Google Patents

Abstract

A method of cold or warm Pilger rolling of tubes with external longitudinal ribs includes deformation of stock tube on the internal tool in the rolls with grooves, cross sections of which decrease along reduction area. The deforming surfaces of the internal tool and groove along its development within the limits of the reduction area have a generatrix in the form of curves, which are described by parabolic type analogous functions, moreover, each generatrix of the surface of the groove is distanced from the axis of rolling, at the beginning of the groove - for the value of radius of external diameter of billet, and at the end of reduction area and on entire length of calibration section - for the value of distance from the axis of rolling to the corresponding point on external perimeter of the cross section of rolled pipe.

Description

Description of the invention

The utility model refers to pipe production and can be used for cold or warm 2-roll pilger rolling of pipes with external fins, for example, finned or polyhedral on the outside.

The usual cold rolling process involves the presence of a zone of free reduction before the crimping section (diameter crimping without wall crimping). In this zone, folds and cracks are formed on the inner surface of the pipes. Influence of reduction on the quality of the inner surface of the pipes during 70° cold rolling. Metallurgical and mining industry, 1979 Mob, pp. 41-50). In addition, as a result of the unfavorable state of stress in this zone, up to 7095 metal hardening takes place, because of which the main deformation has to be carried out with a material that has lost a significant part of its plastic properties.

Known methods of cold pilger rolling of finned tubes involve pressing the metal of the tube blanks in the grooves on the mandrel, the cross-sections of which decrease along the course of the rolls, and the ribs 72 of the finned tube are formed as a result of the free expansion of the metal into the shaped caliber releases.

Difficulties in forming ribs of the required height, thickness and dimensional accuracy under the conditions of using conventional groove and mandrel profiles are associated with insufficient plasticity of the metal until the pipe is given its final shape and dimensions, which forces additional calibration of the pipe in a bracket with non-drive rollers that are attached to of the front face of the HPT state on the rolling axis (New in the technology of production of cold-deformed profile pipes. V.M. Rebrin, Z.V. Nikulin et al. In coll. New technologies in the production of steel pipes. Moscow, Metallurgy, 1983, pp. 38-43 , as well as AS USSR Mo738714, Cl. B21337/22 v21821/00, 1980).

The strengthening of the metal in the zone of free reduction and at the beginning of the crimping zone does not allow forming ribs of the required size in one pass, which forces the profile pipe to be rolled from a pre-made semi-finished product. Ways to improve the quality of cold-rolled pipes. O.A. Plyatkovsky, V.I. Rebrin et al

Metallurgical and mining industry, 1978 Mo1, pp. 20-22, as well as a billet for rolling pipes with two outer symmetrical ribs. A.S. USSR Mob 47030, Cl. B21337/15, B21817/001, i.e. pipes are obtained by these methods in two passes: - semi-finished pipe pressing and cold rolling; o - cold cold rolling and roller calibration in a separate holder. Av

It is also known that during cold relief rolling, a reduction in the intensity of metal strengthening and an increase in the degree of its deformation per pass is achieved with a certain distribution of crimping along the crimping zone. According to such a distribution, which is provided by the corresponding profiles of the groove and the mandrel, the rational "-- ratio of deformations of the diameter and wall thickness along the crimping zone determines the partial compensation of 3o deformation stresses due to the annihilation of dislocations of opposite signs. |(Ways of intensification of the production of steel cold-deformed pipes. V.F. Frolov, Y.V. Frolov, T.V. Senina. Metallurgical and mining industry, 1998 Mo4, p.41-44).

There is also a known method of pilger rolling of pipes with external longitudinal ribs, which includes "deformation of the pipe-workpiece on a mandrel in gauges with grooves, the cross-sections of which decrease along the crimping zone. This method is carried out in grooves, the length of which along the circumference of the roll consists of zones of reduction, with crimping, pre-calibration with a reduced cross-section, as well as zones of constant calibration

From" the cross-section, and the profile of the cross-section is formed by a combination of central arcs and segments of straight lines (AS USSR Mob670350, Cl. B21821/02, 1979).

During the rolling of a profile pipe in such grooves, due to the presence of a zone of free reduction, the inner surface of the pipe deteriorates and a significant strengthening of the metal occurs even before the beginning of the main deformation. Deformation of the metal within the crimping zone occurs with an irrational ratio of crimp diameter and wall thickness, which makes it difficult to form ribs, especially from hard-to-deform metals and alloys, due to the metal losing a significant part of its plastic properties and excessive hardening, which necessitate the introduction of an additional pass. aw! 20 The task of this useful model is to create a method of cold or warm relief rolling of pipes with external longitudinal ribs by changing the mode of metal crimping along the course of the rolls, which is provided by changing the shape and size of the deforming surfaces of the grooves and the mandrel, which allows: - to expand the assortment of externally ribbed pipes both by shape and size, and by metal grades; - to increase the accuracy of the dimensions of ribbed pipes and the quality of their surfaces; 29 - to carry out rolling of ribbed pipes in one pass from an ordinary cylindrical pipe-workpiece. c This problem is solved by the fact that in the method, which includes the deformation of the pipe-workpiece on the mandrel in gauges with grooves, the cross sections of which decrease along the crimping zone, according to a useful model, the deforming surfaces of the mandrel and the grooves along its sweep within the crimping zone have generating in the form of curves, which are described by similar functions of the parabolic type, and each generating surface of the groove is distant 60 from the rolling axis at the beginning of the groove - by the value of the radius of the outer diameter of the workpiece, and at the end of the crimping and along the entire length of the calibration section - by the distance from the rolling axis to corresponding point on the outer perimeter of the transverse profile of the rolled pipe. In addition, the amount of free expansion that occurs in each instantaneous deformation zone during crimping of the horizontal ribs is added to the length of the crimping section in the area of the shaped gauge releases to the distance from the rolling axis to the corresponding curvilinear factory.

The differences between the proposed method and the closest analogues are that the deforming surfaces of the mandrel and the groove along its sweep within the crimping zone have generating curves in the form of curves described by similar functions of the parabolic type, and each generating surface of the groove is distant from the rolling axis at the beginning of the groove - by the value of the radius of the outer diameter of the workpiece, and at the end of the crimping and along the entire length of the calibration section - by the value of the distance from the rolling axis to the corresponding point on the outer perimeter of the transverse profile of the rolled pipe, and in the case of rolling, in particular, of finned pipes along the crimping section in the zone of shaped gauge releases to the distance from the rolling axis to the corresponding curvilinear generator, add the amount of free expansion that occurs in each instantaneous deformation zone under 7/0 the time of crimping the horizontal ribs.

The technical result of the application of this method, in comparison with the closest analogues, is: - expansion of the range of externally ribbed pipes, both in terms of shape and size, and by metal grades; - increasing the accuracy of the dimensions of ribbed pipes and the quality of their surfaces; - one-pass rolling of finned pipes from an ordinary cylindrical pipe-workpiece.

This is due to the fact that the use of the indicated distinctive features of the method allows to achieve, first of all, the expansion of the assortment due to the absence of a zone of free reduction and a decrease in the intensity of metal strengthening due to the optimal ratio of crimping diameter and wall thickness, which allows to achieve a greater height of ribs of a smaller thickness, and also roll pipes from metals and alloys that are difficult to deform.

In addition, the increase in the accuracy of the dimensions of ribbed pipes and the quality of their surfaces occurs as a result of 2o better use of the plastic properties of the metal, a decrease in its resistance to deformation and the absence of a reduction zone, which reduces the distortion of the dimensions of the rolled pipe from the elastic deformation of the working cage, and also excludes the formation of cracks and folds.

The rolling of most types of finned pipes in one pass is ensured by the better distribution of partial crimps along each forming groove with the correct (taking into account the specific properties of the metal and the preform) selection of the degree of their curvature, which reduces the unevenness of deformation in the transverse sections of the groove and reduces the probability of the formation of oblique cracks. In addition, in the case of rolling finned tubes, which takes place without canting, taking into account the amount of free expansion allows you to successfully form horizontal ribs of considerable height, which are formed mainly due to free expansion. In addition, the proposed profile makes it possible to carry out the rolling of ribbed bars similar to the mandrelless rolling of pipes.

Fig. 1, 2 shows the scheme of cold pile rolling of pipes with straight outer ribs. On

Fig. 1 shows the shape change of the blank pipe into a finned pipe, and Fig. 2 - into an octagonal pipe from the outside. with

Designation: 1 - section of pipe-workpiece; -- 2 - section of the rolled pipe; with

C - working cone; 4 - sweep of the groove (along the ridge); 5 - mandrel; p - the outer diameter of the pipe-workpiece; « dvn - the inner diameter of the pipe-workpiece; z c Z - thickness of the wall of the pipe-workpiece; r. - the outer diameter of the round part of the fin tube or the described diameter of the octagon; ;" 51 - the thickness of the wall of the round part of the fin pipe or the thickness of the wall of the octagonal pipe at the top of the gauge;

And the clearance between the inner surface of the pipe-workpiece and the surface of the cylindrical part of the mandrel; o I - the length of the crimped section; - Ikh - the length of the calibration section;

I. , Ш, M and M - cross sections of the working cone with the mandrel (M - cross section at the border of the crimping and calibrating sections - crimping); av | 20 vgYa release angle of the shaped gauge; o a,, - diameter of the cylindrical part of the mandrel; workpiece and working cone in a crimp (rolled pipe); 1,2,3...M - numbers of points on the perimeter of the cross-section of the pipe-workpiece and the working cone in the crimp (rolled pipe);

K, - the radius of the outer surface of the pipe-workpiece in cross-section 1 (the beginning of the crimping section); p o- radii (distances) from the rolling axis to the outer surface of the rolled pipe in the cross section M (in the crimp) at the control points; a, - the diameter of the mandrel in the clamp.

The proposed method is carried out as follows. 60 The rolls of the HPT state, performing a rotary-progressive-rotational movement, press the workpiece 1 in the grooves, the cross-section of which decreases, and the generating surfaces of which are described by functions of the parabolic type, on the mandrel, the generating surfaces of which are also described by a parabolic function, similar to the one that describes the generating grooves

Since each parabolic type generator is distant from the rolling axis at the beginning of the groove by 65 times the radius of the outer diameter of the workpiece (the first points of the parabolic generators 1,2,3...M), and the clearance A between the mandrel cylinder and the inner surface of the workpiece, as shown in the figure , very small (and vu-ac-0.2-0.5mm or Ad-0.1-0.25mm - per side), the "harmful" reduction zone is practically absent.

The second "binding" point of the parabolic generator to the rolling axis is located on the contour of the cross section of the outer surface of the working cone C at the end of the crimping section (at the beginning of the calibration section). This point (12.8...M) along the length of the calibration section is distant from the rolling axis by the distance to the outer surface of the finished pipe.

The parabolic type of the forming groove and mandrel, described by similar functions, ensures the constancy of the optimal ratio of deformations of the diameter and wall thickness over the entire length of the crimped section, which causes a decrease in the intensity of metal strengthening.

During the movement of the rolls, a series of instantaneous deformation zones creates a working cone 3, which ends with a section of the finished pipe. In the process of rolling in the instantaneous deformation zones, the metal flows in both longitudinal and transverse directions, successively taking the shape and dimensions of the gap between the surfaces of the grooves and the mandrel, as shown in sections 1, II, W, IM and M in Fig. 1, which corresponds to the rolling of finned tubes, as well as in 719 similar sections of Fig. 2, corresponding to the rolling of polyhedral tubes.

The inner surface of workpiece 1 in the first instantaneous deformation zone, due to a small gap between the cylinder of the mandrel and the inner surface of the workpiece (0.2-0.5 mm, only for the passage of the mandrel into the workpiece), is adjacent to the mandrel. There is currently no "harmful" reduction zone.

The peculiarity of the rolling of finned tubes is that it occurs without rotation (cantilevering) of the working cone around its axis (the rotation mechanism is disabled). As a result, the transverse flow of metal in the zones of gauge releases, marked by angles zv, occurs as a free expansion. In the process of this expansion, horizontal ribs are gradually formed, which take the required shape and size to the end of the working cone.

To construct the transverse profile of the groove in the zone of gauge releases, to the current (along the length of the crimping zone) distances from the rolling axis to the corresponding parabolic mill, it is necessary to add the values of the free - expansion of the horizontal ribs, which occurs during their crimping, in order to prevent the metal from flowing into the gaps between calibers and the formation of so-called "whiskers".

During the rolling of polygonal pipes, bending occurs at an angle multiple of the central angle between the ribs. In this case, the edges are formed as a result of successive crimping of the metal at the top of the gauge.

In both cases, rolling is carried out with a feed rate that corresponds to the complexity of the pipe profile and the properties of the metal. Steels and alloys, the properties of which significantly depend on the initial temperature of the metal, are rolled with heating of the workpiece (hot rolling), which, in turn, reduces the intensity of metal hardening and facilitates the formation of ribs. --

The distribution of metal crimping along the course of the rolls within the crimping zone (in each instantaneous deformation zone) c occurs in accordance with the dimensions (profiles) of the working surfaces of the grooves and the mandrel, which are calculated depending on the size of the selected pipe-workpiece, as well as the shape and dimensions of the ribbed pipe ( instrument calibration calculation).

The profile of the mandrel is calculated according to the formula: "

What am I I - she and B. Bey V Mi De BELA I. ANYA, i. is" and as x Kx I is where: a, - the diameter of the mandrel in the control section at the distance X from the beginning or from the end of the crimping zone; ду - the diameter of the cylindrical part of the mandrel, equal to the inner diameter of the workpiece (dvy) minus the minimum clearance A sufficient for the insertion of the mandrel into the workpiece (4у-авн-А); - a, - inner diameter of the finished pipe;

X is the current coordinate of the length of the crimped part; and I - the length of the crimped part; o 20 p o - an indicator that determines the steepness of the mandrel profile and is chosen in accordance with the nature of the change in the properties of the rolled metal depending on the degree of deformation; me, Oli" the minimum taper of the mandrel in the crimp;

The groove profile is calculated as follows.

Depending on the shape of the ribbed pipe on the outer contour of its cross-section, a sufficient number of points are assigned to determine the profiles of the groove surfaces. The profile of each generator is calculated according to the formula: what p in (2) ii ne y I neo V ze ES I on sha - bO NOT PRESS SN t flow TOWER y- XIANU goes: K, - distance from the rolling axis to the surface of the groove in the control cross section for each generator at the distance X from the beginning of the crimping zone; d - the distance from the rolling axis to the outer surface of the finished pipe in the control section for each 65 (corresponding) factory; p - outer diameter of the workpiece;

sho- the minimum taper of the groove in the crimp; ee AND the rest of the designations are as in formula (1).

For generators that lie within the limits of the release angles to the radii Ku, determined by formula (2), add the amount of expansion calculated for each control section according to the methodology outlined, for example, in the work (Expansion of metal during the rolling of finned tubes. O. A. Plyatkovsky, V. I. Rebrin. In sb.

Production of pipes for energy industry. Moscow, Metallurgizdat, 19811.

The grooves of the calculated profiles are cut on gauges or manually, according to patterns for control sections, 70 or on a five-coordinate CNC grinding machine, for example, type Z652СМС of the ZM5-MEEK company.

A mandrel with a curved tool is ground on a two-coordinate circular grinding machine, for example, type ZK1I528F20n80 of the Kharkiv Grinding Machine Plant. The manufactured tool is installed in the state of HPT with two working rolls of the appropriate standard size.

During rolling from a round pipe-workpiece in one pass of externally ribbed pipes made of 12X1MF steel and 75 steel 20 with relatively high ribs, in the crimping mode, provided by the profiles of the deforming surfaces of the grooves and the mandrel, which are made according to the claimed method, a satisfactory shape is achieved and the accuracy of the dimensions of both the ribs and the rest of the pipe. In addition, violations of the integrity of the metal on the outer and, especially, on the inner surfaces were not observed.

At the same time, similar rolling according to the method provided by A.S. Mob70350, did not ensure the formation of ribs of the specified shape and accuracy of pipes made of 12X1MF steel. Deviations in the height of fin tube ribs reached (minus) 0.5...0.6 mm. In addition, oblique cracks visible to the naked eye were observed at the base of the ribs, indicating the exhaustion of the plastic properties of the metal in this zone. Longitudinal folds were observed on the inner surface of these pipes, some of them (under the ribs) turned into cracks, which is due to the influence of the reduction zone.

During the rolling of pipes made of more ductile steel 20, the same defects as those of pipes made of steel Z 12X1MF were observed, but to a lesser extent. The number of cracks and their depth were smaller, and the deviations of the dimensions of the ribs reached (minus) 0.3...0.5 mm.

Thus, the application of the claimed method in industrial conditions, in comparison with the closest analogue, allows rolling from a round pipe-workpiece in one pass ribbed from the outside of the pipe with (а) relatively high ribs of satisfactory dimensional accuracy, without violations of the integrity of the metal. at

The formula of the invention "- 1. The method of cold or warm cold rolling of pipes with external longitudinal ribs, which includes the deformation of the pipe-workpiece on the mandrel in rolls with grooves, the cross-sections of which decrease along the crimping zone, which is characterized by the fact that the deforming surfaces of the mandrel and the grooves along its sweep within the crimping zone have generators in the form of curves, which are described by similar functions of the parabolic " type, in addition, each generator surface of the groove is distant from the rolling axis at the beginning of the groove - by the value of the radius of the outer diameter of the workpiece, and at the end of the crimping and along the entire length of the calibration section - na - s the value of the distance from the rolling axis to the corresponding point on the outer perimeter of the transverse profile ц of the rolled pipe. "» 2. The method according to item 1, which differs in that along the length of the crimping section in the area of the shaped gauge releases, the amount of free expansion is added to the distances from the rolling axis to the corresponding curvilinear factory, which

Occurs in each instantaneous deformation zone during crimping of horizontal ribs. name) - (95) o 50 (42) s 60 b5