RU2308339C1 - Line for manufacturing helical-seam tubes from separate sheets - Google Patents

Abstract

FIELD: tube production, possibly manufacture of helical-seam large-diameter tubes for main and enterprise gas and oil conduits.

SUBSTANCE: line includes stationary and mobile plants for butt welding of two sheets by cross seams to one section and welding said section to continuous strip; shaping-welding mill; plant for welding outer cross seams in tube. In front of stationary and mobile butt-welding plants there are apparatuses for heating before welding end portions of sheets, sections and continuous strip along length 150-200 mm. First of such apparatuses is mounted stationary and second apparatus may move together with butt-welding plant. In front of plant for welding outer cross seam there is apparatus for heating tube portion including inner cross seam plus 100-300 mm at each side of it.

EFFECT: improved operational reliability of helical-seam tubes due to their enhanced ductile properties, improved shape of cross seams of helical-seam tubes, lowered trend to cracking.

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Description

The invention relates to pipe production and can be used for the manufacture of spiral-seam pipes of large diameter for infield and main gas and oil pipelines.

The closest solution from the known ones is the production line for the manufacture of spiral-seam pipes of large diameter from sheets, containing aggregates connected by vehicles for processing the longitudinal and transverse edges of a rolled product, a stationary butt welding machine for welding two sheets into a section with a transverse seam forming an internal transverse seam in a pipe, a mobile butt welding machine for welding sections to a continuous strip with a transverse seam forming an internal transverse seam in the pipe, ph a welding and welding mill, an ultrasonic flaw detector for checking spiral welds, a unit for welding external transverse welds in a pipe [1] (Zaritsky VN, Sabun LB, Raichuk Yu.I. et al. Spiral-suture pipes for pipelines thermal and nuclear power plants. M., Energy, 1980. 72 S.).

The features of this line include:

1. The lack of devices for heating the end sections of sheets, sections and a continuous strip before welding transverse seams.

Welding of cold transverse edges of steel sheets of type 10G2FBYu, X-70, X-80 causes:

- the formation of structures of an intermediate type in the heat-affected zone with increased hardness and brittleness;

- deterioration of the conditions for the formation of the weld;

- slowing down the removal of hydrogen from the weld pool and the cooling weld.

At the same time, the presence of structures with a reduced viscosity, a non-smooth transition of the weld reinforcement bead into the base metal and an increased hydrogen content increase the tendency to crack in the transverse weld, which undergoes significant deformations during the formation of spiral-seam pipes from a continuous strip.

2. The line does not provide a device for removing moisture remaining on the pipe surface after ultrasonic inspection of spiral joints, in which water is a contact medium.

If a wet pipe enters the weld zone of the external transverse welds, it leads to an increase in the hydrogen content in the weld metal, which determines a decrease in mechanical properties and an increased tendency to form defects in the welded joint.

The degree of reduction in the quality of transverse joints increases when used for welding ceramic fluxes with high hygroscopicity.

The objective of the invention is to improve the described line to improve the quality of transverse seams and, therefore, the health of spiral-seam pipes in General.

This goal is achieved by the fact that the known line containing aggregates connected by vehicles for processing the longitudinal and transverse edges of the sheet, a stationary butt welder for welding two sheets into a section with a transverse seam forming an internal transverse seam in the pipe, a movable butt welder for welding sections to continuous strip with a transverse seam forming an internal transverse seam in a pipe, a molding and welding mill, an ultrasonic flaw detector for controlling spiral seams, set for welding of external transverse welds in a pipe, it is additionally equipped with devices for preheating the end sections of sheets, sections and a continuous strip at a length of 150-200 mm, installed both in front of the stationary and in front of the movable butt welding installations, the first of which is fixed and the second moves together with the butt welding installation, as well as the device installed before installation for welding the external transverse seams to heat the pipe section, including the internal transverse seam plus with 100-300 mm on each side of it.

The proposed production line is schematically depicted in the drawing.

The production line contains a unit 1 for processing the transverse edges of the sheet, a stationary device 2 for heating the end sections of the sheets before welding, a stationary butt welding machine 3 for welding with a transverse seam (forming an internal transverse seam in the pipe) of two sheets per section, a device 4 for heating the ends of the sections and continuous strip before welding, a movable butt welding machine 5 for welding sections to a continuous strip, the device 4 and the installation 5 moving together, the unit 6 for longitudinal processing x edges of the strip, a molding and welding mill 7 for forming the strip into a pipe billet and welding longitudinal edges, an ultrasonic flaw detector 8 for controlling spiral seams, a device 9 for heating a pipe section, including an internal transverse seam plus 100-300 mm on each side, installation 10 for welding external transverse welds in a pipe.

The line works as follows.

The sheets are fed one at a time to unit 1, where the transverse edges of the sheet are machined, then transferred to device 2, where the end sections of the sheets, 150-200 mm long, are heated by high-frequency currents or otherwise to a temperature of 100-200 ° C and in a fixed butt welding Installation 3 is welded by electric arc welding two sheets into a section with a transverse seam forming an internal transverse seam in the pipe. Then, in the device 4, the end sections of the sections and the continuous strip over a length of 150-200 mm are heated by high-frequency currents or in another way to a temperature in the range (depending on steel grade and sheet thickness) of 100-200 ° C and in a mobile welding unit 5 welded transverse a seam forming an internal transverse seam in the pipe, and in the unit 6, the longitudinal edges of the continuous strip are machined for subsequent welding of spiral seams. Further, in the molding and welding mill 7, a continuous strip is formed into a tube billet and longitudinal edges are welded with technological and working seams. The resulting spiral seams are tested using an ultrasonic flaw detector 8, while the contact medium is water. Then, in the device 9, the inner transverse seam and pipe sections of 200-300 mm on each side of it are heated by high-frequency currents or otherwise to 110-150 ° C to completely remove moisture. The dry pipe enters the installation 10, where the welding of the outer transverse joints.

Technical results from the use of the invention in comparison with the prototype are:

- preheating before welding of the end sections of sheets, sections and a continuous strip to a temperature of 100-200 ° C prevents the formation of intermediate structures in the weld zone of the transverse weld, helps to reduce the hydrogen content in the weld metal and a smoother transition of the weld bead to the base metal, which determines a decrease in the tendency to crack in the transverse seam during pipe forming;

- heating to a temperature of 110-150 ° C of the inner transverse seam and adjacent pipe sections after ultrasonic inspection of the spiral seams prevents the wet pipe from entering the weld zone of the outer seam. Due to this, the hydrogen content in the weld metal is reduced, which leads to an increase in its mechanical properties and resistance to the formation of cold cracks.

Achieved by preheating the welded edges of sheets, sections and continuous strip, and heating the pipe section, including the inner transverse seam, improving the metal structure and geometry of the welded joints, as well as reducing the hydrogen content, provide the most efficient use of ceramic welding fluxes, which can significantly increase the visco-plastic characteristics of welded metal joints of spiral-seam pipes to the level of modern and perspective requirements of domestic and foreign countries artifacts.

Claims (1)

A technological line for the manufacture of large-diameter spiral-seam pipes from separate sheets, containing vehicles connected to each other for processing the longitudinal and transverse edges of a rolled product, a stationary butt welding machine for welding two sheets into a section with a transverse seam forming an internal transverse seam in a pipe, and a mobile butt welding installation for welding sections to a continuous strip with a transverse seam forming an internal transverse seam in the pipe, molding and welding mill, ultrasonic a flaw detector for controlling spiral welds in a pipe, an installation for welding external transverse welds in a pipe, characterized in that it is equipped with devices for heating the end sections of sheets, sections and a continuous strip on a length of 150-200 mm, installed both in front of the stationary and and in front of the mobile butt welding installations, the first of which is fixedly mounted, and the second with the possibility of moving together with the butt welding installation, as well as installed before installation for welding external transverse welds a heating device for the pipe section comprising an inner transverse seam plus 100-300 mm on each side thereof.