RU2308337C1 - Line for manufacturing helical-seam tubes from rolled strip coils - Google Patents

Abstract

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

SUBSTANCE: line includes mobile butt-welding plant for welding end portions of coils by cross seam; shaping-welding mill; ultrasonic flaw detector for helical seams; plant for welding outer cross seams in tube. In front of butt-welding plant apparatus for heating strip along its whole width is arranged. In front of plant for welding outer cross seams there is apparatus for heating tube portions including inner cross seams plus 100-300 mm at both sides.

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

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 production line for the manufacture of large-diameter spiral-seam pipes from rolled steel, containing vehicles connected to each other for processing the longitudinal and transverse edges of the rolling, a mobile butt welding machine for welding the end sections of coils with a transverse seam, a molding and welding mill, ultrasonic flaw detector for controlling spiral welds, installation for welding external transverse welds in a pipe [1] (Zaritsky V.N., Sabun LB, Raichuk Yu.I. . and others. Spiral-seam pipes for pipelines of thermal and nuclear power plants. M.: Energy, 1980. - 72 S.).

The features of this line include:

1. The lack of devices for heating the transverse and longitudinal edges of the rolled steel before welding.

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

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

- deterioration of the weld formation conditions;

- 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 reduce the structural strength of the welded joint.

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

This goal is achieved by the fact that the well-known line containing aggregates connected by vehicles 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 controlling spiral seams, a welding machine external transverse welds in the pipe, is additionally equipped with a device for heating the strip along its entire width, located in front of the mobile butt welder, and also installed before installation for welding the external transverse seam device for heating sections of the pipe, including the 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 roll, a device 2 for heating the roll over its entire width, a mobile butt welding machine 3 for welding the ends of the rolls with a transverse seam, an assembly 4 for processing the longitudinal edges of the strip, a forming and welding mill 5 for forming the strip into a pipe preparation and welding of longitudinal edges, ultrasonic flaw detector 6 for controlling spiral welds, device 7 for heating a pipe section, including an internal transverse seam plus 100-300 mm on each side, installation 8 for welding external transverse welds in a pipe.

The line works as follows.

The rolls enter the unit 1, where they are machining the transverse edges of the strip, then they are transferred to the device 2, in which the coil is heated by high-frequency currents or in another way over its entire width to a temperature of 100-200 ° C. In the movable butt welding machine 3, the end sections of the rolls are welded with a transverse seam, in the machine 4, the longitudinal edges of the strip are machined for subsequent welding of spiral seams, and in the forming 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, and 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.

An additional installation in the line of the heating device provides heating of the rolls over the entire width to a temperature of 100-200 ° C. Preheating the rolls before welding eliminates the possibility of 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 cracking and an increase in the structural strength of welded joints.

Additional installation in the line of the device for heating to a temperature of 110-150 ° C of the internal transverse weld and adjacent pipe sections prevents the wet pipe from entering the weld zone of the outer weld. 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 and longitudinal edges of the rolled steel 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-welded pipes to the level of modern and perspective requirements of domestic and foreign standards.

Claims (1)

A technological 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 strip, a mobile butt welding machine for transverse seam welding of the end sections of coils, a forming and welding mill, an ultrasonic flaw detector for controlling spiral seams, installation for welding external transverse seams in the pipe, characterized in that it is equipped with a device for heating the strip along its entire width placed in front of the mobile butt welding machine, and also installed before installation for welding external transverse seams with a device for heating pipe sections, including an internal transverse seam plus 100-300 mm on each side.