Method for forming butt welded seams on tubes

FIELD: plastic working of metals, namely processes for forming butt welded seams on tubes at making tube studs of U-shaped tube bundles using effect of localized hot plastic deforming of welded seam and near-seam zones.

SUBSTANCE: method comprises steps of preliminarily working tube ends by expanding them from cylinder to cylinder; assembling tubes with use of mandrel and placing intermediate member of additive material between joined end surfaces of end portions of tubes sized by expansion and end surfaces of step ring. Welded seams are formed by argon-arc welding due to melting material of intermediate member at its both sides adjacent to tube ends. The intermediate member is heated up and it is subjected to hot radial squeezing while concentrating its initial deformation in surface layers according to position of ring steps, welded seams and near-seam zones on mandrel for providing size of their outer diameter equal to initial outer diameter of tubes.

EFFECT: improved quality of welded seams.

8 dwg

 

The invention relates to the field of metal forming, and in particular to the formation of butt welds when receiving pipe studs U-shaped beams using the localized effect of hot plastic deformation of the weld and the adjacent heat-affected zones.

A known method of forming a butt weld on the pipes in the production of tubular rods, including preparatory operations on the pipe for welding, assembling and subsequent argon-arc welding of the mating pipe ends with a filler material non-consumable electrode with the use of filler material, cut tube lengths of pipe for straight portions of the studs, length of pipe for flexible on the specified radius of the roll and the cleaning of the outer surface of the mating ends of the connected elements, and their subsequent welding with the formation of two weld seams in the resulting hairpin (see GOST 14245-79. Shell and tube heat exchangers with U-shaped tubes).

The main disadvantages of this method of education of butt welds should include the vulnerability of the internal interface from the impact of aggressive working environment during operation of the tube bundle, as well as increased production costs. First, large waste billets due to the multiplicity of ispolzuemykh working lengths. And secondly, increased cost, determined and a large percentage of defects in welds because of the defects identified by the presence in the welding process of the atmospheric gas (oxygen and nitrogen). Quality all-in-one compounds thus fully determined by the skills and ability of the welder to intensively perform necessary when welding steps. It should be emphasized, and such shortcomings as the presence of the heat-affected zones with reduced mechanical properties and internal grata, reducing the cross-section of the junction relative to the original cross-section of connected pipes.

There is also known a method of forming a butt weld on the pipes when receiving tube pins, including preparatory operations on the pipe for welding, assembling and subsequent argon-arc welding of the mating pipe ends non-consumable electrode with the use of filler material (see RD 153-34.1-003-01. Welding, heat treatment and the control pipe systems, boilers and pipelines during installation and repair of power equipment, Moscow, PIO MBT 2001 - prototype).

The disadvantage of this method is that the weld bead and heat-affected zone formed without cladding inner surface of the junction to improve anti-corrosion properties, and are not subjected to the finishing plastic deformation or the tion, eliminate possible defects in the welds and reinforcing material in the heat-affected zones. Due to possible defects in the welds, and similar studs drafted out. When welding control is not amenable to the formation of internal deburring and each time the resulting joint has its geometrical dimensions for the inner diameter, which requires controlling the operation of the testing pins control the ball with a diameter amounting to 0.8 D, where D is the internal pipe diameter.

Object of the invention is to provide such a method of education of butt welds when receiving pipe studs U-shaped beams, which would be localized amounts of melting of the material of the tubes, allowed to protect internal and external surfaces of the joint from corrosion during operation of the tube bundle, and eliminate defects in the welds, finish their hot stamping.

The technical result is achieved in that in the method of formation of butt welds on pipes in the production of tubular rods, including preparatory operations on the pipe for welding, assembling and subsequent argon-arc welding of the mating pipe ends non-consumable electrode with the use of filler material according to the invention as a filler material use intermediate element the form of stepped rings, which is installed between the mating ends of the tubes in the Assembly, while prior to Assembly, the mating ends of the distributing pipes from the cylinder into the cylinder, a collecting pipe with an intermediate element on the mandrel, apply axial force to the mating end surfaces of the calibrated distribution pipes, providing contact between them and the end surfaces of the stepped ring, carry out welding, melting stage speed rings on both their sides with the formation of two butt-welded seams provide additional heating of the pipe joint with subsequent hot radial crimping, reaching the outer diameter of the joint is equal to the original outer diameter of the welded tube and concentrating deformation in the surface layers at the location of the ring steps, welds and heat affected zones.

Implementation of the proposed method of education of butt-welded joints on pipes when receiving the pins of the U-shaped tube bundles allows you to localize the volume of molten material, and means to eliminate the possibility of burning out the carbon and to create the effect of welding-brazing, plastiroute internal and external interfaces, providing increased corrosion of their characteristics and to eliminate the defects in the welds, finish their hot plastic deformation, to change the structure and mechanical the properties in the heat-affected zones, to form the inner surface of the junction without Burr.

This is because:

- filler material is chosen from the condition of elevated its anticorrosive properties, and mechanical properties will not be below the relevant properties of the pipe material;

- carry out the activation of plastic deformation (by hand) amounts of the mating pipe ends to be welded later;

- using an intermediate element in the form of stepped rings of cladding material (e.g. stainless steel), achieve efficient melting of the filler material with a reactive melting of the material of the pipes in limited amounts;

- planiruet interface at reduced deforming force that increases the life work of technological equipment;

- plastic deformation of the weld and heat-affected zones eliminates possible defects in the welds, and strengthens the material in the heat-affected zones (hardening rate of the material in the heat-affected zones exceeds the rate of its softening from hot deformation).

The invention is illustrated by drawings, where figure 1 shows the mating Assembly pipe end, the last preparations for welding and hard punch before performing operations distribution pipes from the cylinder into the cylinder; figure 2 is an end stage hand end of pipe hard point the nom; figure 3 - the mating ends of the pipe, a stepped ring of filler material on the mandrel upon application of axial force compression; 4 - grooved ends of the pipes and the intermediate element after the formation of welds preferential melting of the filler material; figure 5 is heated junction of pipes placed in the plug (3-segment) matrix horizontal hydraulic press; figure 6 - stage hot pressing of the intermediate element in the outer layers; 7 - end of the hot forming of the intermediate element, welds and heat affected zones with the formation of the internal and external surfaces of the pipe joint; Fig - high quality welded connection.

A variant embodiment of the invention is as follows.

On rectilinear heat pipe 1 (Fig 1) perform operations with the aim of preparing the outer surface of each of the ends for welding: edit the pipes on konovalovas straightening machine, cutting their dimensional lengths and Stripping of the outer surfaces to the metal layer.

Next, make calibration of the mating pipe ends by operation of their distribution from the cylinder into the cylinder through a hard punch 2.

Bending forming of pipes forms within the thickness of their walls plastic hinges allocated in the form of a conical regions dots (figure 2).

The Assembly Proc. of the b on the mandrel 3 before welding is done with the use of a stepped ring 4 of the filler material, for example stainless steel 18CR10NITI. On the outer surface of the ring made of two steps, the external diameter of which exceeds the outer diameter of the grooved sections of the pipe ends.

Through the application of axial compressive force to the mating ends of the pipe reaches the desired contact between the end surfaces and the end surfaces of the intermediate element of the filler material (figure 3).

The formation of welds on both sides of the ring is performed by fusion (figure 4) modes, regulated technical documentation. In this exercise the preferential melting of the volume of the filler material, forming an electric arc non-consumable electrode according to the areas of speed. Melting the material of the pipes is reactive (including axial compressive efforts to pipes) the influence of the molten filler material on a face surface of the grooved pipe sections. In other words, there is a localization volume of the melt in the pipe material that does not cause negative impact of warming on the alloying elements of the pipe material.

The relatively large dimensions of the stepped rings along its length require additional heating of the pipe joint to the optimum temperature hot deformation. Temperature control is carried out re Osney thermocouple.

The hot junction of the pipes are placed in the plug (3-segment) matrix 5 horizontal hydraulic press (figure 5).

The message segments of the matrix radial displacement in the axis direction initially causes the impact of the scallops of the working surface of the die on the side surface of the stepped ring of filler material. Reduced overall dimensions of the ring causes the localization of deformation of the filler element initially in the outer volume with the formation of a zone of the complicated deformation (6).

The reactive force from the mandrel at the above-mentioned effect leads to localization of deformation of the intermediate element in the inner layers (Fig.7). Observed deformation of the intermediate element with simultaneous cladding inner surface of the pipe joint.

Thus, the movement of segments of the matrix in the radial direction is connected with the hot deformation of the filler material and through its plastic flow - deformation of welds and heat affected zones. We emphasize that the hot deformation of the material of the weld is performed in 3 Osney scheme stresses of uneven compression, preventing the destruction of the weld. When this axial compressive stresses occur at the stage of deformation of the pipe in transitional circular areas marked mn what photochemi.

Minimized the volume of welds subject to a comprehensive non-uniform compression, intensively worked out, which causes no loss in mechanical properties. In addition, in the pipe joint is observed the formation of axial compressive residual stresses of the first kind.

The formation of the inner surface of the junction reaches the plastic for filler material relative to the welded seam, providing a cladding of the latter.

The permanent connection (Fig) high mechanical properties (a significant role is played here by the material of graded rings, perceiving the effect of the working environment)that are generated residual compressive axial stresses, sufficient accuracy for such products, high technology, which determines and increased productivity. The lack of inner flash eliminates the need for control spinning rods ball.

Pilot verification of the developed method of forming a butt weld was in the manufacture of single seam pins of the tubes produced of steel 10.

The original geometric dimensions of the tubes were: outer diameter - 25 mm, wall thickness of 2.6 mm and a length of 9 and 3.6 m

Edit pipe, cut to measure and clean the mating surfaces of pipes made suitable for the equipment to achieve the required parameters.

Speed rings with dimensions 26,2×18,3×12 mm made of stainless steel AISI 18CR10NITI, steel 10 by deformation of the billets to the appropriate diameter and the necessary cutting operations. On the outer surfaces of the rings did stage a width of 3 mm from the ends) and a diameter equal to 25.8 mm

Hand-calibration of the mating pipe ends were conducted on a horizontal hydraulic press, double action design "Repair-mechanical plant" NK YUKOS when efforts within 35-40,0 kN.

The length of the calibrated section of pipe was 25 mm and the largest outer diameter of 25.5 mm, the Maximum diameter of the steel bar was equal 18,25 mm

The formation of welds performed argon-arc welding with non-consumable electrode according to well-known modes. Hot crimping the pipe joint made in the temperature range typical for steel 10, namely (1200-850)°also on a horizontal hydraulic press, double action with the effort of not more than 300 kN.

Removing the mandrel from long tubes produced using industrial complex, when the long-length tube hot junction was placed in a mechanical clamp, fixed against axial movement and applying pulling force to the mandrel, causing its axial movement. During this stroke of the mandrel with the axial force does not exceed the al 20 mm.

In further perform the bending of the pipe at a given radius.

It is established that the process of formation of a butt-welded joints with an intermediate element in the form of stepped rings stainless steel or steel 10 effectively planiruet surface of the pipe joint, strengthens the pipe material in the heat-affected zones, allows you to more efficiently carry out cutting billets, and reduces the number of workers by reducing the amount of manual work is not accompanied by the occurrence of defects such as pores, inclusions, etc.

The invention is applicable in the manufacture of the tube bundles of heat exchangers in the oil refining, petrochemical, gas and other industries.

The method of formation of butt welds on pipes in the production of tubular rods, including preparatory operations on the pipe for welding, assembling and subsequent argon-arc welding of the mating pipe ends non-consumable electrode with the use of a filler material, wherein the filler material use intermediate element in the form of a stepped ring, which is installed between the mating ends of the tubes in the Assembly, while prior to Assembly, the mating ends of the distributing pipes from the cylinder into the cylinder, a collecting pipe with an intermediate element on the rims is e, apply axial force to the mating end surfaces of the calibrated distribution pipes, providing contact between them and the end surfaces of the stepped ring, carry out welding, melting stage speed rings on both sides with the formation of two butt-welded seams provide additional heating of the pipe joint with subsequent hot radial crimping, reaching the outer diameter of the joint is equal to the original outer diameter of the welded tube and concentrating deformation in the surface layers at the location of the ring steps, welds and heat affected zones.



 

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