RU2300451C2 - Method for forming butt welded seams on tubes - Google Patents

Abstract

FIELD: plastic working of metals, possibly manufacture of tube studs.

SUBSTANCE: method comprises steps of preparing tubes to welding; assembling tubes and performing argon-arc welding of abutted ends of tubes with additive materials by means of non-consumable electrode. Preliminarily joined ends of tubes are calibrated by expanding them to cone. Assembling of tubes is realized on sleeve of cladding material. Said sleeve is mounted on mandrel while contact of sleeve end edges with inner cone surfaces of calibrated portions is provided. After welding hot joint is subjected to radial reduction on mandrel according to three-axial non-uniform compression pattern. Inner surface of butt after its final formation is clad due to cross shear deformations of tubes material and additive material.

EFFECT: enhanced quality of tube studs due to cladding inner and outer surfaces of welded seams and eliminating their flaws.

5 dwg

Description

The invention relates to the field of metal forming, and in particular to the processes of formation of butt welds upon receipt of tube hairpins of U-shaped beams using the effect of localized hot plastic deformation of the weld and adjacent heat-affected zones.

A known method of the formation of butt welds on pipes in the production of pipe rods, including the cut length of pipe lengths for straight sections of the studs, the measured length of the pipe for manufacturing flexible to a given radius of the thread, cleaning the outer surface of the mating ends of the elements to be joined, their subsequent welding with the formation of two welds in the obtained hairpin (see GOST 14245-79. Shell-and-tube heat exchangers with U-shaped pipes).

The main disadvantages of the known method of formation of butt welds should include the insecurity of the inner surface of the joint from the effects of an aggressive working environment during operation of the tube bundle, as well as the increased cost of their production. Firstly, large waste of pipe billets due to the multiplicity of used working lengths. And secondly, the increased cost, determined by a large percentage of defective welds due to defects determined by the presence of atmospheric gas (oxygen and nitrogen) during the welding process. The quality of one-piece joints in this case is entirely determined by professional skills and the ability of the welder to intensively perform the necessary actions during welding. It should be emphasized and such disadvantages as the presence of heat-affected zones with reduced mechanical characteristics and internal burr, which reduces the cross section of the joint relative to the original cross section of the connected pipes.

There is also a known method for the formation of butt welds on pipes when receiving pipe hairpins, including preparatory operations on pipes for welding, their assembly and subsequent argon-arc welding of the mating ends of pipes with filler material using a non-consumable electrode (see RD 153-34.1-003-01 Welding, heat treatment and control of pipe systems of boilers and pipelines during installation and repair of power equipment. M: PIO OBT, 2001 - prototype).

The disadvantage of this method is that the weld and heat-affected zones are formed without cladding the inner surface of the joint in order to increase its anticorrosion properties, and also do not undergo final plastic deformation, eliminating possible defects in the welds and hardening material in the heat-affected zones. As a result, defects in the welds are possible, and similar studs are rejected. During welding, the process of formation of an internal burr is not amenable and each time the resulting joint has its geometrical dimensions and inner diameter, which requires a control operation — rolling the stud around with a control ball with a diameter of 0.8 D, where D is the inner diameter of the pipe.

The objective of the invention is to develop such a method for the formation of butt welds when receiving pipe rods of U-shaped beams, which would protect the inner surface of the joint from the effects of aggressive working environment during operation of the tube bundle, as well as eliminate defects in welds by their finish hot stamping.

The technical result is achieved by the fact that in the method of forming butt welds on pipes in the manufacture of pipe rods, including preparatory operations on pipes for welding, their assembly and subsequent argon-arc welding of the mating ends of the pipes with filler material by means of a non-consumable electrode, according to the invention, are pre-mated the ends of the pipes are calibrated by distribution to the cone, the pipes are assembled on a sleeve of cladding material mounted on a mandrel with a contact between the edges of the ends of the sleeve on the inside them with conical surfaces of calibrated sections, and after welding, the hot joint is radially crimped on the mandrel according to the triaxial uneven compression scheme, with the inner surface of the joint cladding during its final formation by transverse shear deformations of the pipe material and filler material relative to the end edges of the sleeve of the cladding material.

Implementation of the proposed method for the formation of butt welds on pipes upon receipt of U-shaped tube bundle hairpins allows the inner surface of the joint to be clad, providing improved anti-corrosion characteristics, as well as eliminating defects in welds by their finish hot plastic deformation, changing the structure and mechanical properties in the heat-affected zones , to form the inner surface of the joint without burr.

This is explained by:

- carry out the activation by plastic deformation (distribution to the cone) of the volumes of the mating ends of the pipes, welded subsequently;

- using an intermediate element in the form of a sleeve of cladding material (for example, stainless steel), effective cladding of the working surface of the joint is achieved during operation of the tube bundle;

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

The invention is illustrated by drawings, where in Fig.1 shows the ends of the pipes mating in the assembly, having undergone preparatory operations for their welding, with a sleeve of cladding material placed between them, before forming a weld; figure 2 - hot joint of pipes after welding, placed in a detachable matrix containing three segments with a non-smooth working surface (combs with a triangular cross-section; figure 3 - deformation of the hot joint of pipes in reinforcing the weld with the formation of zones of difficult deformation; figure 4 - the end of the hot stamping process of the weld and heat-affected zones; figure 5 - high-quality one-piece connection with a clad inner surface.

An embodiment of the invention is as follows.

On rectilinear heat exchange tubes 1 (Fig. 1), operations are performed to prepare the outer surface of each end for welding: straightening the tubes in a straight-line straightening machine, cutting their measured lengths and cleaning the outer surfaces to a metallic sheen.

Next, the mating ends of the pipes are calibrated by the operation of distributing them to the cone by means of a rigid punch. The bending of the forming pipes forms, within the limits of their wall thickness, plastic hinges, selected in the form of areas of a triangular type by dots.

The assembly of the pipes before welding is performed on the sleeve 2 of cladding material (for example, stainless steel) located on the steel mandrel 3.

The gap between the ends of the pipes is controlled by means of a template.

The formation of the weld is carried out using filler wire, for example, from Article 3 with the modes regulated by technical documentation.

A hot joint of pipes is placed in a detachable (3-segment) matrix 4 of a horizontal hydraulic press (figure 2).

The message segments of the matrix of the radial movement in the direction of the axis initially causes the introduction of the scallops of the working surface of the matrix in the reinforcement of the weld and the formation of the outer zone of difficult deformation (figure 3). At the final stage of this introduction, there is also the formation of an internal zone of difficult deformation (due to friction forces on the surface of the mandrel).

Further movement of the matrix segments in the radial direction is associated with hot deformation of the weld material when the surfaces of the zones of difficult deformation approach each other (Fig. 4). We emphasize that the hot deformation of the weld material is carried out according to a 3-axis scheme of uneven compression stresses, which prevents the destruction of the weld. The formation of the inner surface of the joint is achieved both by the high quality of the surface of the sleeve of cladding material, and by transverse shear deformations of the material of the weld relative to the end edges of the said sleeve.

The one-piece connection (Fig. 5) is characterized by high mechanical properties (the sleeve material that perceives the action of the working medium plays an important role), formed by residual compressive axial stresses, sufficient accuracy for such products, and high manufacturability, which also determines increased productivity. The absence of an internal burr eliminates the need for a test ball rolling around the studs.

A pilot test of the developed method for the formation of butt welds was carried out in the manufacture of single-seam studs from pipes obtained from steel 10.

The initial geometric dimensions of the pipes were: outer diameter - 25 mm, wall thickness - 2.6 mm and lengths of 9 and 3.6 m.

Pipe straightening, cutting in moderation and cleaning of the surfaces of the mating pipes were carried out on the appropriate equipment with the achievement of the required parameters.

A sleeve with dimensions of 21.4 × 18.3 × 12.4 mm was made of X18H10T stainless steel by deformation of the pipe blanks to the appropriate diameter and the necessary cutting operations.

Distribution-calibration of the mating pipe ends was carried out on a double-action horizontal hydraulic press of the Yukos Repair and Mechanical Plant design with forces within 30 kN.

The length of the calibrated pipe section was 21.2 mm; the taper angle of the rigid punch was 1.2 °. The maximum diameter of the ends of the ends of the pipes after their distribution was 26.2 mm. The maximum diameter of the steel mandrel was 18.25 mm.

The weld was formed by argon-arc welding with a non-consumable electrode using filler wire from Art. 3.

Hot crimping of the pipe joint was carried out in the temperature range characteristic of steel 10, namely 1200 ÷ 850 ° C, also on a horizontal double-acting hydraulic press with forces of not more than 300 kN.

The mandrel removal from the long pipe was carried out using the production complex, when the long pipe was placed with a hot joint in a mechanical clamp, fixed from axial movements, and applying a pulling force to the mandrel caused its axial movement. In this case, the stroke of the mandrel with axial force did not exceed 20 mm.

Subsequently, pipes were bent to a given radius.

It has been established that the technological process of formation of butt welds clad the working surface of the pipe joint, strengthens the metal of the pipes in the heat-affected zones, allows more efficient cutting of pipe billets, and reduces the number of workers due to the reduction in the volume of manual work.

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

Claims (1)

A method of forming butt welds on pipes in the manufacture of pipe rods, including preparatory operations on pipes for welding, their assembly and subsequent argon-arc welding of the mating ends of the pipes with filler material using a non-consumable electrode, characterized in that the pre-mated ends of the pipes are calibrated by conical distribution, assembly pipes are carried out on a sleeve of cladding material mounted on a mandrel with contact, the edges of the ends of the sleeve, with internal conical surfaces calibrated sections, and after welding, the hot joint is subjected to radial crimping on the mandrel according to the triaxial uneven compression scheme with cladding of the inner surface of the joint when it is finally formed by transverse shear deformations of the pipe material and filler material relative to the end edges of the sleeve of the cladding material.

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