RU2320439C2 - Line for manufacturing helical-seam tubes of separate sheets - Google Patents

Abstract

FIELD: tube production, possibly manufacture of helical-seam tubes of large diameters for main and intrafield gas and oil pipelines.

SUBSTANCE: line includes stationary and movable butt welding plants for welding by cross seams of two sheets to section and sections one with other; molding-welding mill; plant for welding outer cross seams of tubes. In front of stationary butt-welding plant there is section type apparatus for heating sheet along its whole width. In front of plant for welding outer cross seams there is apparatus for heating tube portions including inner cross seam plus 100-300 mm at each side of it.

EFFECT: improved viscous-plastic properties, enhanced shape of helical seams of tubes, lowered trend to cracking, enhanced operational efficiency and reliability of helical seam tubes.

1 dwg

Description

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

The closest solution from the known ones is a technological line for the manufacture of large-diameter welded pipes, containing vehicles connected to each other for processing the longitudinal and transverse edges of the sheet, a stationary butt welding machine for welding two sheets with a transverse seam into a section, a mobile butt welding machine for welding with a transverse seam of sections to a continuous strip, molding and welding mill, ultrasonic flaw detector for controlling spiral seams, installation for external welding operechnyh seams in the pipe (Zaritskii VN Sabuni LB, Raychuk YI etc. Spiral pipe for pipelines thermal and nuclear power stations M, Energy, 1980. -.. 72 pp.).

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 of transverse welds and longitudinal edges of a continuous strip before welding.

Welding of cold transverse edges of sheets, sections and continuous strip and longitudinal edges of a continuous strip of steel type 10G2FBYu, X-70, X-80 causes:

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

- 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 roller into the base metal and a high hydrogen content increase the tendency to crack in welded joints and reduce their structural strength.

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 significantly 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 and spiral welds and, therefore, the health of spiral-seam pipes in general.

This goal is achieved by the fact that the known line for the manufacture of large-diameter spiral-seam pipes from sheets, in which, during the technological process, units are connected to each other for processing the longitudinal and transverse edges of the sheet, a stationary butt welding machine for welding two sheets with a transverse seam into a section, movable butt-welding machine for welding sections to a continuous strip with a transverse seam, molding and welding mill, ultrasonic flaw detector for monitoring spi welds, installation for welding of external transverse welds in a pipe, is additionally equipped with a sectional type device located in front of a stationary butt welder for heating the sheet along its entire width, and also installed after an ultrasonic flaw detector to control a spiral weld and before installation for welding an external transverse weld with a device for heating a pipe section, including an internal transverse seam plus 100-300 mm on each side.

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 sectional type device 2 for heating the sheet along its entire width, a stationary butt welder 3 for welding two sheets into a section with a transverse seam (forming an internal transverse weld in the pipe), and a mobile butt welder 4 for joining sections to a continuous strip; unit 5 for processing the longitudinal edges of the strip; molding and welding mill 6 for forming a strip into a pipe billet and welding longitudinal edges, an ultrasonic flaw detector 7 for controlling spiral welds, a device 8 for heating a pipe section to an internal transverse seam plus 100-300 mm each to a temperature of 110-150 ° С side, installation 9 for welding external transverse welds in the 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 sheets are heated over the entire width to a temperature of 100-200 ° C with high-frequency currents or otherwise, and in a stationary butt welder 3 are welded by electric arc two sheets with a transverse seam per section. Then, in a mobile welding installation, 4 end sections of sections and a continuous strip are welded with a transverse seam; and in the unit 5, the longitudinal edges of the continuous strip are machined for subsequent welding of the spiral seams. Next, in a molding and welding mill 6, a continuous strip is formed into a tube billet and longitudinal edges are welded with technological and working seams. The resulting spiral seams are controlled using an ultrasonic flaw detector 7, while the contact medium is water. Then, in the device 8, the inner transverse seam and pipe sections of 200-300 mm on each side of it are heated to 110-150 ° C with high-frequency currents or otherwise to completely remove moisture. The dry pipe enters the installation 9, where the welding of the outer transverse seam.

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

- preheating the sheets over the entire width before welding to temperatures of 100-200 ° C eliminates the possibility of the formation of intermediate structures in the heat-affected zone of transverse and spiral welds, helps to reduce the hydrogen content in the metal of welded joints and to obtain a smoother transition of the weld bead into the base metal. This determines a decrease in the tendency to crack and increase the structural strength of welded joints;

- heating to a temperature of 110-150 ° C of the transverse seam and adjacent pipe sections after ultrasonic testing 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 sheets before welding 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 the metal of the welded joints of spiral-seam pipes to the level of modern and promising requirements of domestic and foreign standards.

Claims (1)

A technological line for the manufacture of large-diameter spiral-seam pipes from separate sheets, containing vehicles connected to each other for preliminary processing of the longitudinal and transverse edges of the sheet, stationary and mobile butt welding machines, a molding and welding mill, an ultrasonic flaw detector for controlling spiral welds, an installation for welding external transverse joints in the pipe, characterized in that it is additionally equipped with a sectional type device for heating the sheet throughout width, placed in front of the stationary stykosvarochnoy installation and set before installation for welding the transverse seams external device to heat the pipe sections comprising an inner transverse seam plus 100-300 mm on each side thereof.