RU2320438C2 - Line for manufacturing helical-seam tubes of rolled strip coils - Google Patents

Abstract

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

SUBSTANCE: line includes movable butt-welding plant for welding end portions of coils by cross seam; molding/welding mill; plant for welding outer cross seams of tubes. In front of butt welding plant there is apparatus joined with said plant by means of kinematics links for preheating before welding ends portions of coil with length 150 - 200 mm. 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 said seam.

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

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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 a production line for the production of large-diameter spiral-seam pipes from rolled steel, containing vehicles connected to each other for processing the longitudinal and transverse edges of the rolls, a mobile butt welding machine for welding the end sections of the rolls with a transverse seam, a molding and welding machine , ultrasonic flaw detector for checking spiral welds, installation for welding external transverse welds in a pipe [1] (Zaritsky VN, Sabun LB, Raichuk Yu. And others. Spirally welded pipes for pipelines of thermal and nuclear power plants M, Energy, 1980. -.. 72)..

The features of this line include:

1. The lack of devices for heating the end sections of the rolls before welding transverse seams.

Welding cold transverse edges of a 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 cooling

welded joint.

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 well-known line in which, during the technological process, units are connected to each other for processing the longitudinal and transverse edges of the strip, a mobile butt welding machine for transverse seam welding of the end sections of rolls, a molding and welding mill, an ultrasonic flaw detector for inspection spiral welds, installation for welding external transverse welds in a pipe, is additionally equipped with devices installed in front of a mobile butt welding machine a property for preheating the end sections of rolls 150-200 mm long, which is kinematically connected with a butt welding machine, and also a device for heating a pipe section including an internal transverse seam plus 100-300 mm on each side installed before installation for welding an external transverse weld .

The proposed production line is schematically depicted in the drawing.

The production line contains a unit 1 for processing the transverse edges of the strip, a device 2 for heating the ends of the rolls before welding, a mobile butt welder 3 for transverse seam welding of the end sections of the rolls, the device 2 and the installation 3 kinematically connected to each other; unit 4 for processing the longitudinal edges of the strip; molding and welding mill 5 for forming a strip into a pipe billet and welding longitudinal edges, an ultrasonic flaw detector 6 for controlling spiral seams, a device 7 for heating to a temperature of 110-150 ° C from a pipe section, including an internal transverse seam plus 100-300 mm each its sides, an installation 8 for welding external transverse welds in a pipe.

The line works as follows.

The roll strip enters the unit 1, where the transverse edges are machined, then to the device 2, where the end sections of the rolls are heated at a length of 150-200 mm to a temperature of 100-200 ° C, and in a mobile welding unit 3 welded with a transverse seam. Then, in the unit 4, the longitudinal edges of the strip are machined for subsequent welding of spiral seams. Further, in a molding and welding mill 5, 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 6, while the contact medium is water. Then, in the device 7, the inner transverse seam and pipe sections of 100-300 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 8, where the welding of the outer transverse seam.

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

- preheating before welding the transverse edges of the rolls to a temperature of 100-200 ° C, which prevents the formation of intermediate structures in the heat-affected zone of the transverse weld, helps to reduce the hydrogen content in the weld metal and to obtain a smoother transition of the weld bead into the base metal. This determines a decrease in the tendency to crack in the transverse seam when forming pipes;

- heating to a temperature of 110-150 ° C of the transverse seam and adjacent pipe sections after ultrasonic inspection of 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 transverse edges of the rolls 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 suture pipes to the level of modern and future requirements of domestic and foreign standards.

Claims (1)

Technological line for the manufacture of large-diameter spiral suture pipes from rolled steel, containing vehicles connected to each other for processing the longitudinal and transverse edges of the strip, a mobile butt welding machine for welding the end sections of rolls with a transverse seam, a molding and welding mill, an ultrasonic flaw detector for controlling spiral seams in the pipe, installation for welding external transverse seams in the pipe, characterized in that it is equipped with installed in front of the butt welder a device for heating the end sections of rolls 150-200 mm long before welding, which is kinematically connected with a butt welding machine, and also a device for heating pipe sections including a transverse seam plus 100-300 mm on each side installed before installation for welding external transverse seams .