RU2706988C1 - Method of multilayer hybrid laser-arc welding of steel clad pipes - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention relates to welding of metal structures, in particular to welding of longitudinal seams of molded cylindrical billet, and can be used in production of large-diameter steel welded pipes with wall thickness from 12 to 25 mm and higher to 50 mm with inner and outer clad layers. Multilayer hybrid laser-arc welding of working seam of steel clad tubes with inner and outer clad layers, assembled butt-joint with a gap of up to 1 mm. Edge slotting of edges is performed with size of blunting equal to thickness of base metal. Apply electric arc with consumable electrode. Then they are exposed to a laser beam. Facing internal seam and outer seam are applied by arc welding.

EFFECT: increased efficiency of welding due to minimization of weld seam relative to the base metal and clad layer with preservation of anticorrosive properties of the clad layer.

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Description

The invention relates to the welding of metal structures, in particular, to the welding of longitudinal seams of a formed cylindrical billet and can be used in the production of steel welded pipes of large diameter with a wall thickness of 12 to 25 mm and above up to 50 mm with inner and outer cladding layers.

Clad steel pipes are widely used in the oil and gas industry due to the impact of aggressive media on the surface of the pipe. One of the methods for producing large-diameter clad pipes is the molding of a tubular billet from clad sheet metal, followed by welding on a pipe-welding mill. Clad sheet metal is obtained by the method of batch rolling - hot rolling of two or more layers of metal.

The disadvantage of this method of manufacturing clad pipes is that the welds of these pipes are formed by filler material, which differs in its composition from the composition of the cladding layer and is therefore subject to accelerated corrosion.

A known method from the patent CN 103722346, according to which a steel bimetallic pipe is made with a corrosion-resistant coating by hot batch rolling with the subsequent formation of a tube billet from the resulting bimetal sheet metal, and followed by submerged arc welding of a longitudinal seam.

However, this method has insufficient productivity of arc welding, in which there is a violation of the integrity of the cladding layer, expressed in the melting of the cladding layer due to the extensive thermal effects of the current electric arc during submerged arc welding, and mixing of the cladding layer with the base metal.

A known method from patent RU 2108178, according to which the surface to be welded (clad strip) is cleaned of the clad layer, then the tube stock is formed, the welded edges are heated with two or more laser beams to the melting temperature and squeezed to form a durable welded joint followed by clad layer cladding in the form fine powder.

However, in this method, after squeezing the fused edges, the formation of excess (displacement) of the edges is possible, which is an unacceptable defect. In addition, it is difficult to apply sufficient compressive force to form a high-quality welded joint in the production of thick-walled pipes of large diameter.

Known from patent EP 1878531 is a method of hybrid laser-arc welding of metal blanks coated with a layer of aluminum.

However, this method is used for pipes with a small wall thickness of 0.5 to 4 mm, and it is not suitable for the production of steel welded pipes of large diameter with a wall thickness of 12 to 25 mm and above, and the method also has insufficient productivity due to welding with a non-consumable electrode .

The closest analogue of the claimed invention is a method of welding large diameter pipes by laser and hybrid laser-arc welding, known from patent RU 2609609, according to which hybrid laser-arc welding is used to produce large diameter pipes.

However, hybrid laser-arc welding is carried out with through-penetration, which leads to sagging of the weld in the production of clad pipes, and this entails an increase in the volume of sprayed metal, which significantly reduces productivity.

The technical problem to be solved by the claimed invention is directed, is the low productivity of welding clad pipes of large diameter.

The technical result of the claimed invention is to increase the welding productivity by minimizing the proportion of the weld in relation to the base metal and the cladding layer while maintaining the anticorrosive properties of the cladding layer.

The claimed technical result is achieved due to the fact that in the method of multilayer hybrid laser-arc welding of steel clad pipes on assembled end-to-end with a gap from 0 to 1 mm of the edge of the tube billet with inner and outer cladding layers and with a groove in which the bluntness is equal to the thickness of the main metal, they are exposed to an electric arc with a melting electrode, after which they are exposed to a laser beam, a facing inner seam and an outer seam are arc welded.

The method may use an X, Y or U-shape cut.

Before making a working seam can perform a technological seam.

They can use a slotted groove with a bevel angle of 1-5 °.

The laser seam is several times narrower than the seam obtained by arc welding. For example, for a wall thickness of a tube billet of 21.7 mm, the width of the root laser seam is 5 times smaller than the width of the seam obtained by arc welding. And the area of the seam obtained by arc welding is 2.36 times larger than the area of the seam obtained by hybrid laser-arc welding, respectively, the number of cladding layer removed to perform laser welding is several times less than the number of clad layer removed to perform arc welding . Increased productivity is also achieved by reducing the consumption of flux, electricity and welding wire.

The inventive method is illustrated using FIG. 1-4, which depict:

FIG. 1 - view of the welded edges;

FIG. 2 is a view of the edges to be welded, section AA;

FIG. 3 is a view of the edges to be welded after facing joints;

FIG. 4 is a view of the welded edges for the wall thickness of the pipe billet more than 25 mm, section AA.

In FIG. 1-4 positions 1-7 show:

1 - pipe billet;

2 - arc welding torch;

3 - a laser beam;

4 - cladding layer;

5 - a working seam;

6 - outer facing seam;

7 - inner facing seam.

The method is as follows.

Use edges with the shape of cutting X, Y or U-shaped, which is selected depending on the wall thickness and the complexity of the milling. For example, with a wall thickness of 45 mm it is more expedient to use an X-shaped groove or slotted shape, and for a smaller wall thickness Y or U, but a U-shaped groove is rarely used. The presence of an inner cladding layer does not oblige it to be cut. without welding, you can also perform a welding seam with an electric arc.

The amount of blunting is approximately equal to the thickness of the base metal, so that the volume of the removed cladding layer is minimal.

A technological (assembly) seam is applied by the arc welding method to fix the edges relative to each other to prevent their warping during subsequent welding on welded edges of the tube billet, assembled end-to-end without a gap or with a normalized gap of up to 1 mm, which excludes laser beam fading and lack of penetration. It should be noted that the step of applying the technological seam is not necessary to obtain the specified technical result and can be excluded.

Then, an arc welding torch 2 with a consumable electrode is directed to the welded edges with a technological seam applied. An electric arc melts the surface metal, introduces alloying elements and performs the function of preheating. After the arc welding torch 2 is affected by a laser beam 3, providing through penetration and mixing of the base metal and filler material in a single weld pool. Due to the narrowly targeted action of the laser beam 3, fusing the edges, the cladding layer 4 in the edge zone remains unharmed.

Then, after applying the working seam 5 by the method of hybrid laser-arc welding, a facing inner seam 7 and the outer seam 6 are applied by the method of arc welding (surfacing) with minimal penetration of the base metal. The size of the penetration depends on the thickness of the cladding layer 4. Facing seams 6 and 7 should at least melt the working seam 5 so that the metal of the cladding layer 4 does not mix with the working seam, because they differ in chemical composition. It is also possible to overlay the outer 6, and then the inner 7 facing seam after the working seam 5. Depending on the wall thickness and the number of cladding layers 4, it is possible to apply only one facing seam, outer 6 or inner 7 depending on which clad layer 4 is present, or dispense with facing seams at all, when it is allowed that the working seam is not shielded by cladding. For welding (surfacing), an alloying wire with a high content of chromium and nickel is used to form a corrosion-resistant coating at the level of the cladding layer, for example, grade SV-08X21N10G2.

For the production of steel clad welded pipes of large diameter with a wall thickness of 25 mm or more, a slotted groove is used with a bevel angle of 1-5 °, which minimizes the amount of cladding to be removed.

The method was tested on plates with a thickness of 24 mm from structural low-alloy steel of strength class K60, the thickness of the outer and inner cladding layer is 3 mm from stainless steel, the dullness is 17 mm, the value of the inner bevel is 2.5 mm, the angle of 10 bevels of the edges is 45 ° . After applying the technological seam, the working seam was welded in a protective environment of argon and carbon dioxide. The arc current was 400-500 A, voltage 34-38 V, laser power 25-30 kW.

The outer and inner facing seams are made by the method of arc welding in a protective environment of argon and carbon dioxide. The arc current was 400-500 A, voltage 34-38 V.

Claims (3)

1. The method of welding a steel clad pipe, characterized in that on assembled end-to-end with a gap of up to 1 mm, the edges of the tube billet with inner and outer cladding layers with slit grooves with an oblique angle of edges of 1–5 ° and a dullness equal to the thickness of the base metal, carry out multilayer hybrid laser-arc welding of the working seam by applying an electric arc with a consumable electrode and a laser beam, and then perform facing the inner seam and the outer seam by arc welding. 2. The method according to p. 1, characterized in that carry out X, Y or U-shaped cutting edges. 3. The method according to p. 1, characterized in that Before making a working seam, a technological seam is performed.

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