RU2087226C1 - Method of making straight-seam electrically welded large diameter tubes for transporting abrasive loose materials and pulps and apparatus for performing the same - Google Patents

Abstract

FIELD: tube production, namely manufacture of large-diameter electrically welded tubes with oriented single-side wall thickness difference for transporting abrasive loose materials and pulps. SUBSTANCE: skelp sheet with thickness variable along its width is used as tube blank; thickened portion oriented along generatrix of tube is arranged in mean part of said sheet or near its edges. Thickness of sheet in zone of said thickened portion exceeds at least by 1.5 times nominal sheet thickness. Width of said thickened portion is determined according to given relations. As edge planed tube blank is guided to edge bending mill or press for bending up its edges in accordance with tube radius. Diameter of cylindrical portion of upper bending discs is selected in dependance upon shape of said blank and size of thickened portion of sheet. Sheet with bent up edges is fed to preshaping hydraulic press for bending central portion of sheet by means of punch. Radius of cylindrical portion of said punch is selected in dependance upon type of used blank. Then in finally shaping press semifinished product is shaped to tube to be fed to outer welding mill. Distance between centers of rollers of inner mandrel of said mill and distance between centers of rolls of vertical non-driven and horizontal driven stands are selected while taking into account size of said thickened portion of sheet. Welded tube is subjected to expanding in hydraulic press in which tube end portions are calibrated by means of calibrating cones and then tube is hydraulically expanded by diameter. Said calibrating cones have variable profile. At placing tube in hydraulic press it is oriented in such a way that profiles of said cones and profiles of tube end portions are coincided. EFFECT: enhanced efficiency, improved arrangement of units. 4 cl, 13 dwg

Description

 The invention relates to pipe production, in particular to the production of longitudinally welded large diameter pipes with oriented one-sided difference for transportation of abrasive bulk materials and pulps.

 In the pipe industry, methods are used to produce large-diameter pipes for transporting bulk materials and pulps, straight-seam with one or two seams and spiral-seam from a sheet with a relatively constant nominal wall thickness.

 A known method of manufacturing longitudinal welded pipes of large diameter for transporting abrasive bulk materials and pulps, including forming a pipe from a workpiece in the form of sheet strip, welding the edges, expanding the finished pipe and processing its ends.

 However, the known method has the following disadvantages. Pipes have the same nominal wall thickness around the perimeter, and during transportation of abrasive products in the form of bulk materials and pulps (1/3 of the perimeter filling), intensive wear of its lower part occurs. As a result, the product pipeline fails due to complete wear of its part, while the upper part (2/3 of the pipe perimeter) is in working condition, i.e. practically does not undergo wear, except for natural corrosion.

 A device is known for the manufacture of longitudinally-welded large-diameter electric pipes for transporting abrasive bulk materials and pulps, containing a bending mill with a tool in the form of upper and lower lower bending disks, as well as upper and lower central disks, preliminary and final molding presses with technological equipment, a mill for external welding of pipes, having an internal mandrel and stands with horizontal and vertical rolls, as well as a hydraulic press expander with calibrating my cones.

 The disadvantage of this known device is the production of pipes which, when transporting abrasive products in the form of bulk materials and pulps, undergo intensive wear.

 The technical problem to which the claimed inventions are directed is to extend the service life of product pipelines for transporting bulk materials and pulps by changing the perimeter of the wall thickness of the pipes.

 The problem is solved in that in the known method of manufacturing longitudinal seam welded pipes of large diameter for transporting abrasive bulk materials and pulps, including forming a pipe from a workpiece in the form of sheet strip, welding the edges, expanding the pipe and processing its ends, use sheet strip having a variable transverse cross-section along the width with a thickening in the middle part or in the region of the edges, while the thickness of the sheet strip in the thickening zone is at least one and a half times the nominal t lschinu sheet.

,
где В_ут.с. ширина утолщения в средней части листа;
В_ут.к. ширина утолщения в зоне, примыкающей к кромке листа;
В ширина листа.The width of the thickening in the middle part of the sheet and the width of the thickening in the area adjacent to the edge of the sheet are selected, respectively, from the following ranges:

,
where In _ut. the width of the thickening in the middle of the sheet;
In the _ut. the width of the thickening in the area adjacent to the edge of the sheet;
In sheet width.

 In addition, the goal is achieved by the fact that in the known device for the manufacture of longitudinal seam welded pipes of large diameter for transporting abrasive bulk materials and pulps, containing a bending mill with tools in the form of upper and lower lower bending disks, as well as upper and lower central disks, presses of preliminary and final molding with technological equipment, a mill for external welding of pipes, having an internal mandrel and stands with horizontal and vertical rolls as well as a hydraulic press expander with gauge cones, in the manufacture of sheets of sheet strip with a thickening in the middle part or in the region of the edges, the upper bending discs of the edging mill are made with a cylindrical section on the side surface whose diameter is larger or smaller than the diameter of the upper central disk the thickness of the sheet strip, respectively, in the middle part or in the region of the edges, the technological equipment of the pre-molding press is made in the form of a bed and a cylindrical the punch, the axis of the cylindrical surface of which is perpendicular to the bed, and the radius is the difference between the distance from the axis of the cylinder to the bed and the thickness of the sheet strip in the middle part, the technological equipment of the final molding press is made in the form of paired upper and lower liners, each of which is made in the form of a hollow half-cylinder with an internal working surface, the diameter of which is constant for a given pipe diameter in the entire range of thicknesses of the molded billets, the inner mandrel of techn The tooling of the external welding mill is made with horizontal and vertical rollers, the center-to-center distance of the first of which is equal to the difference between the center-to-center distance of the vertical rollers and the thickness of the sheet strip, and the center-to-center distance of the vertical rolls of the non-driven stand and the horizontal rolls of the driven stand are respectively larger and smaller than the outer diameter of the welded pipe the thickness of the sheet strip, with each calibrating cone of the press expander made with a transverse a section, one half of which is a circle with a radius equal to the radius of the inner surface of the calibrated pipe without thickening the wall, and the second half is a circle with a radius equal to the radius of the inner surface of the pipe in the zone of thickening of the wall.

 The upper liner of the tooling of the final molding press is equipped with a T-key for stopping the edges of the pipe billet during pipe forming.

 Figures 1 and 2 show two types of cross section of a sheet strip; in Fig.3 and 4 tool edging mill for bending the edges of the sheet strip with a thickening, respectively, in the middle part and in the region of the edges; 5 and 6, the technological equipment of the preform press for sheet strip with a thickening, respectively, in the middle part and in the region of the edges; 7 and 8, the technological equipment of the final molding press for sheet strip with a thickening, respectively, in the middle part and in the region of the edges; Figures 9 and 10, a tool for external welding of pipes for sheet strips with a thickening, respectively, in the middle part and in the region of the edges; 11, an electric welded pipe assembly with calibrating cones; in Fig.12 the same, section aa in Fig.11; 13 a calibration cone.

 The method is as follows.

 Sheet strip 1 with a variable cross-section in width, i.e. having a thickening in the middle part (Fig. 1) or the region of the edges (Fig. 2), the gouging of the edges in the beveling machine to the width dimension "B" is set in the bevelling machine, where the edges are bent to the radius of the pipe. The tool of the bending mill includes the upper 2 and lower 3 central disks and the upper bending 4 and 5 and the corresponding lower bending disks 6 and 7.

The diameter D _{1 of the} upper 4 and 5 bending discs and the diameter D _{2 of the} upper central disk are selected and calculated depending on the specified pipe diameter D _n . The diameter D _{3 of the} lower 6 and 7 bending disks and the diameter D of the lower central disk 3 (roll) are selected and calculated depending on the pipe diameter D _H and the rotation speed of the disks ω.

The upper bending discs 4 and 5 are made with a cylindrical section on the side surface, the diameter D _{c of} which is larger or smaller than the diameter D _{2 of the} upper central disc by the thickness of the sheet strip thickening, respectively, in the middle part or in the region of the edges.

After bending the edges, the sheet is set into a hydraulic preform press (Fig. 5, 6), the technological equipment of which is made in the form of bed 8 and a cylindrical punch 9, the axis of the cylindrical surface of which is perpendicular to the bed, and the radius (R ₁ , R ₂ ) of the punch is the difference between the distance from the axis of the cylinder to the bed and the thickness of the sheet strip in the middle part.

In the pre-molding press, the central part of the sheet is bent by the force P or P ₁ , the value of which depends on the thickness of the metal and its mechanical properties. Regulation of the size of the connector between the edges of the sheet (S and S ₁ ) produce the height of the bed. The height of the workpiece (H and H ₁ ) in this case varies depending on the initial sheet width (B), the height of the bed (h and h ₁ ) and the size of the connector between the edges (S and S ₁ ).

From the pre-molding press, the semi-finished product (curved sheet) is transferred to the final forming press, where they are molded into a round pipe by the force P. The technological equipment of the final forming press (Figs. 7 and 8) consists of the upper 10 and lower 11 die holders carrying the upper mates 12 and lower 13 replaceable calibrating inserts, each insert is made in the form of a hollow cylinder with an internal working surface, the diameter of which (D ₃ ) is constant for a given pipe diameter in the entire range of thicknesses of the molded workpieces. In the upper 12 insert, a T-key (14) can be mounted in which the edges of the pipe billet abut.

In the case of a faceless molding, there may not be a T-key, and the pipe billet is formed by abutting the edge against the edge. At the final molding, the force P is calculated to compress the workpiece and give it an irreversible shape. The value of P is calculated depending on the diameter of the manufactured pipes D _H and a variable wall thickness S _T and S _t + Δ.

 Pipe welding is carried out in a mill for external pipe welding, having an internal mandrel and stands with horizontal and vertical rolls. The inner mandrel is made with rollers 15, 16 and 17 and a shoe 18 equipped with a copper plate. The distance between the working surfaces of the vertical rolls 19 and 20 in the plane passing through the longitudinal axis of the pipe perpendicular to the axes of the said rolls exceeds the outer diameter of the pipe being welded by the thickness of the sheet strip and the distance between the working surfaces of the horizontal rolls 21 and 22 in the plane passing through the longitudinal axis pipes perpendicular to the axes of the said rolls, less than the outer diameter of the pipe being welded by the amount of thickening of the sheet strip, as a result of which the pipe in cross section at takes the form of an oval. The rollers 15 and 16 are parallel to the vertical rolls 19 and 20, and the distance between their working surfaces in the plane passing through the longitudinal axis of the pipe perpendicular to the axes of the rollers is equal to the difference between the above-mentioned distance between the working surfaces of the vertical rolls and twice the thickness of the sheet strip in the thickening zone . The stand with horizontal rolls 21 and 22 is driven, and the stand with vertical rolls 19 and 20 is non-driven.

 The welded pipe edges are assembled without a gap on the copper plate of the shoe 18.

 After welding in the external welding mill, the internal seam is welded on the internal welding mill.

 With the internal seam force removed on the milling machines, the pipes undergo expansion by hydraulic presses, where the calibrating cones 23 and 24 are introduced into the pipe cavity and mechanical ends are calibrated, then the pipes are hydraulically distributed in diameter.

 Each calibrating cone is made with a cross section, one half of which is a circle with a radius R equal to the radius of the inner surface of the calibrated pipe without thickening the wall, and the second half is a circle with a radius R-Δ equal to the radius of the inner surface of the pipe in the zone of wall thickening.

 Before feeding the pipe into the press, it is oriented in such a way that the dimensions of the pipe H coincide with the radius R, and H-Δ with the radius R-Δ.

 After distribution and calibration in the press, the pipe enters the beveling machines, where trimming and chamfering is performed.

 An example implementation of the method.

 A sheet was taken for the manufacture of pipes measuring 530x7 mm. A sheet was welded in the center of the sheet, with a width equal to 1/2 the width of the main sheet, with a wall thickness of 10 mm. Such a billet was molded in presses of preliminary and final molding and welded on mills for external and internal pipe welding. Thus, a semi-finished pipe was obtained, which proves the possibility of producing pipes according to this invention.

 Using this method of manufacturing longitudinal welded large diameter pipes for transporting abrasive bulk materials and pulps and a device for its implementation can increase the resistance of product pipelines by 1.5 or more times depending on the difference in the thickness of the pipe walls in the upper and lower parts, as well as on their conditions operation, and this, in turn, makes it possible to reduce metal consumption for pipe production by at least 1.5 times and increase the productivity of product pipelines for transporting abrasive bulk materials and pulps.

Claims (4)

 1. A method of manufacturing longitudinally welded large-diameter electric pipes for transportation and abrasive bulk materials and pulps, including forming a pipe from a workpiece in the form of sheet strip, welding edges, expansion of the finished pipe and processing of its ends, characterized in that they use sheet strip having a variable cross section in width with a thickening in the middle part or in the region of the edges, while the thickness of the sheet strip in the thickening zone is at least one and a half times the nominal thickness of the sheet. 2. The method according to claim 1, characterized in that the width B _{at t . with a} thickening in the middle of the sheet and a width B _{of t . to the} thickening in the area adjacent to the edge of the sheet, respectively, are selected from the following ranges:
B / 3 ≅ B _{y t. with} ≅ B / 2;
B / _y 6 ≅ B _{t. to} ≅ B / 4,
where B is the width of the sheet.  3. A device for the manufacture of longitudinally-welded large-diameter electric pipes for transporting abrasive bulk materials and pulps, containing a bending mill with tools in the form of upper and lower lower bending disks, as well as upper and lower central disks, preliminary and final molding presses with technological equipment, an external pipe welding mill with an internal mandrel and stands with horizontal and vertical rolls, as well as a hydraulic press expander with calibrating cones characterized in that in the manufacture of pipes from sheet strip with a thickening in the middle part or in the region of the edges, the upper bending discs of the edging mill are made with a cylindrical section on the side surface whose diameter is larger or smaller than the diameter of the upper central disk by the thickness of the sheet strip thickening, respectively in the middle part or in the region of the edges, the technological equipment of the preliminary molding press is made in the form of a bed and a cylindrical punch, the axis of the cylindrical surface which is perpendicular to the bed, and the radius is the difference between the distance from the axis of the cylinder to the bed and the thickness of the sheet strip in the middle part, the technological equipment of the final molding press is made in the form of paired upper and lower liners, each of which is made in the form of a hollow half cylinder with an inner the working surface, the diameter of which is constant for a given pipe diameter in the entire range of thicknesses of the formed workpieces, the distance between the working surfaces of the vertical rolls non-driven stand, and between the working surfaces of horizontal rolls of the stand, made drive, in planes passing through the longitudinal axis of the pipe perpendicular to the axes of the respective rolls, respectively, more and less than the outer diameter of the pipe being welded by the thickness of the sheet strip, and the inner mandrel of the technological equipment of the external welding mill made with rollers, the axes of which are located in the same plane with the axes of the vertical rolls parallel to the last, and the distance between their workers along the surfaces in the plane passing through the longitudinal axis of the pipe perpendicular to the axes of the rollers is equal to the difference between the above-mentioned distance between the working surfaces of the vertical rolls and twice the thickness of the sheet strip in the thickening zone, each calibrating cone of the press expander is made with a cross section, one half of which represents a circle with a radius equal to the radius of the inner surface of the calibrated pipe without thickening the wall, and the second half is a circle with a radius equal to the radius of the inside the lower surface of the pipe in the zone of thickening of the wall.  4. The device according to claim 3, characterized in that the upper liner of the technological tooling of the final molding press is equipped with a T-key for stopping the edges of the pipe billet during pipe forming.

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