SU1704993A1 - Method of preparing tubes with inner protective coating for welding - Google Patents

Abstract

The invention relates to welding, in particular, to methods of preparation for the welding of pipes with an internal protective coating, and can be used in the oil and gas, chemical and other industries in the construction of pipelines for the transport of chemically active substances. The purpose of the invention is to provide high-quality corrosion protection in the area of the spa. A sublayer of the thermo-reactive composite material is applied to the inner surface of the pipe end to be shed at a length not less than the expected seam width. Then, a layer of a metal-based semofluxing alloy and a protective coating are applied over the length exceeding the expected extent of the heat-affected zone. When welding into the sublayer of the thermo-reactive composite material, an exothermic reaction proceeds and the additional heat released provides reliable fusion of the metal-ceramic self-fluxing alloy at the root of the seam. 1 tab. with C

Description

The invention relates to welding, in particular, to methods of preparing pipes with an internal protective coating for ssarku, and can beat-used keftegasto- vzazhegchch. Chemical No; ECO and other industries in the construction of pipelines for the transport of chemically sensitive materials.

The chain of the invention is to protect the quality against corrosion in the weld zone.

The method is carried out as follows.

Vnutrmkyu o and tori.opuk gyrmnosti tru & and the floor crргlut 01chch tks ilrest; yl; and ways. r example. shot-blasting method, and dodging on the post application

internal coating on the ends of the pipes. After preliminary drying up to 250-270 ° C, an underlayer of a thermo-reactive composite powder material, such as NI-AI or, is applied to the inner surface of the tongue width to the width of the stick. Ni-ti. The thickness of the applied coating is 150-300 microns. From the end of the pipe, the coating of thermosetting material is worn out at the width of the seam. Then, the metalloermic self-fluxing alloy i i i the inner ryu and the tertiary surface of the pipe with a length overlapping the zone of thermal velocity of the alloy are applied. The lems are prepared in such a way that the pipes will be covered with the chosen coating of the whole inner surface, for example,

x O .1 O

Yu

with

enamel, varnish, polymer, glass, etc. Pipe joints for crpoi pipelines are produced by manual electric arc welding.

Welding of thin-walled pipes (1-4 mm) is carried out on small currents, which leads to a decrease in EFFGZHNAYA TG P YuPY POWER

welding flyi: i. but it is worth getting a monolithic coating on the root of the welded spur, because due to insufficient heat supply from the welding, the metal / yukeramichesky-self-fluxing bearing of the alloy does not completely melt and the alloy does not connect at the ends of the pipe . However, the sublayer of the thermoregulating composite material increases the temperature around the weld zone during the welding process due to the exothermic reaction. In this case, a high-quality coating of a self-fluxing alloy is formed.

It has been established that with a width of the sublayer of the thermoreactive composite material less than the width of the shock, the additionally released heat is not enough to form a high-quality coating of the self-fluxing alloy.

PRI me R. On a pipe with a diameter of 114 mm and a wall thickness of 3 mm, the end and inner surfaces were cleaned by a shot blasting method. Next, the pipe was fed through a roller table to the post of gas thermal coating. The post is equipped with two plasma spraying units of the UMP-6 type, which are improved and have a powder dosing unit per dose. In one dispenser, there was a thermo-reactive composite material of the PN70GOZO brand according to TU 14-1-3280-81, and in the other - self-fluxing: with an alloy of the PR-H80X13C2P brand according to TU 14-1-3795-84. Installations for plasma spraying were placed at the ends of the pipes, and the process of spraying powder materials was carried out automatically and simultaneously on both ends of the pipe. Preliminarily, the ends of the tubes were heated with a gas burner flame to 250-260 ° C (temperature control was carried out using a TE PA-50 radiation n-meter) and applied by plasma spraying to a distance of 4-5 mm (seam width), sublayer of thermo-reactive composite powder material PN70UZO. The coating thickness was 150-200 µm. After the termination of the supply of the thermosetting material from the caustic dispenser, another powder dispenser was automatically turned on and the front and inner surfaces of the pipe were coated with

self-fluxing alloy PR-H8GX13C2P for a length of 120 mm, overlapping the heat-affected zone of welding with a thickness of 120-150

um The pipes were then applied to the post coating of the entire inner surface of the pipe. The coating material is glass. The two pipes manufactured in this way were connected by electric arc welding at optimum technological conditions in accordance with industry standard OST 36-60-81 Welding during the installation of steel building structures. Inspection of the joint showed that a weld root was formed on the inner surface of the pipe, protected by a monolithic smooth coating of a self-fluxing alloy, which during the welding process due to heat generation during the exothermic intermetallic reaction (Ni + Al NiAl + Q) the alloy also joined due to wettability closed) at the two ends of the pipes, protecting the root of the weld from the effects of the pumped corrosive medium.

Accelerated comparative testing of welded specimens prepared by this method (sample 1) and the prototype method (samples 2 and 3) were carried out. Corrosion resistance was evaluated by reducing the mass of the samples in the waste hydrogen sulfide-containing medium (NC-300 mg / l), with the content of solid abrasive particles 200 mg / l (abrasive particles, quartz sand by granulation 200 microns). Only a coating of a self-fluted metal-ceramic alloy obtained at the root of the weld after welding was tested. The rest of the samples

when tested, they were isolated from contact with aggressive media. The test results are shown in the table.

The application of this method allows to increase the service life of the pipeline in 2

and more time and reduce the cost of repair and restoration work.

Claims (1)

The invention of the method of preparation for welding pipes with an internal protective coating, in which the inner surface of the pipes is cleaned, is applied to the internal surface of the welded ends at a length exceeding the expected length heat-affected zones of the seam, a metal layer of a ceramic self-fluxing alloy, and from the entire inner surface of the pipes a layer of protective coating, which is in order to provide high-quality corrosion protection about the seam zone. before applying the layer of the Metlaus-ceramic self-fluxing alloy on the welded ends of the pipes at a length not less than The expected weld width is additionally applied with a sublayer of a thermo-reactive composite material.