On-site circumferential connection method for duplex stainless steel pipes based on solid-phase welding

Abstract

The invention discloses an on-site annular connection method for duplex stainless steel pipes based on solid-phase welding, which comprises the following steps: pipe orifices of two sections of duplex stainless steel pipes and a welding short section are clamped on a welding tool, and the welding short section is positioned between the two sections of duplex stainless steel pipes; a solid-phase welding technology is adopted, positive pressure is applied to the welding pup joint by the two sections of duplex stainless steel pipes, and the welding pup joint is clamped for rotary welding; and carrying out post-treatment on the welded duplex stainless steel pipe. By adopting the solid-phase welding technology, the method has the advantages of self-cleaning effect, low possibility of generating weld defects, no need of welding flux or shielding gas, high welding efficiency and the like, realizes on-site circumferential, rapid and efficient welding of duplex stainless steel, obtains a joint with good tensile property and corrosion resistance, and can ensure good sealing property, pressure-bearing property and corrosion resistance.

Description

Technical Field

[0001] The present invention belongs to the field of stainless steel welding and relates to a method for on-site circumferential connection of duplex stainless steel pipes based on solid-phase welding. Background Art

[0002] For pipelines in oil and gas transportation stations, the medium has strong corrosivity and the service environment is harsh. Traditional carbon steel pipelines are difficult to meet on-site requirements. Therefore, each oilfield explores the application of stainless steel in oil and gas gathering and transportation. In duplex stainless steel, austenite and ferrite in the solid solution at room temperature each account for about half, with the characteristics of both two-phase structures. It retains the characteristics of ferritic stainless steel such as small thermal conductivity, resistance to pitting corrosion, crevice corrosion and chloride stress corrosion, and also has the advantages of good toughness of austenitic stainless steel, low brittle transition temperature, resistance to intergranular corrosion, good mechanical properties and welding properties. Therefore, domestic and foreign oilfields use 2205 duplex stainless steel pure materials as gas gathering main pipelines, process pipelines and station containers under harsh corrosion conditions. The application of duplex stainless steel effectively solves the corrosion problem. However, failures of 2205 duplex stainless steel circumferential welds also occur from time to time.

[0003] Traditional 2205 welding mainly uses TIG welding for backing, SMAW for filling and surfacing, requires a welding flux, Ar / N 2 protection, appropriate heat input, and the process control is relatively complex, with low welding efficiency. If the heat input used during welding is too large and the cooling rate of the workpiece is too slow, intermetallic compound phases may precipitate in the weld and the heat-affected zone, which will reduce the corrosion resistance and toughness of the welded joint.

[0004] Patent CN101537539A provides a stirring head for friction stir welding and a current-carrying friction stir welding method. This method breaks through the limitations of conventional friction stir welding technology, solves the dependence of the stirring head for friction stir welding of high-melting-point metals on high-quality materials and complex preparation technologies, enriches the quality control means for friction stir welding of low-melting-point light alloys, realizes the effective and reasonable matching of high quality and low cost of friction stir welding, and improves the friction stir welding technology. However, friction stir welding has high requirements for surface cleanliness and low welding efficiency.

[0005] Patent CN 114833438A provides a method for inertia friction welding of duplex stainless steel and austenitic stainless steel. Although this method has high material utilization rate, high welding efficiency and stable and good weld quality, it is only applicable to the welding of short pipe sections, cannot perform on-site circumferential connection, and does not provide the welding process for duplex stainless steel. Summary of the Invention

[0006] The purpose of the present invention is to solve the problems in the prior art and provide a method for on-site circumferential connection of duplex stainless steel pipes based on solid-phase welding, so as to solve the problems of complex process control and inability to perform on-site circumferential connection in the prior art.

[0007] To achieve the above object, the present invention is implemented by the following technical solutions:

[0008] A on-site circumferential connection method for duplex stainless steel pipes based on solid-phase welding, comprising:

[0009] Clamp the pipe ends of two sections of duplex stainless steel pipes and the welding stub between the welding tooling, and the welding stub is located between the two sections of duplex stainless steel pipes;

[0010] Adopt solid-phase welding technology, apply positive pressure to the welding stub by two sections of duplex stainless steel pipes, clamp the welding stub, and perform rotary welding;

[0011] Perform post-treatment on the welded duplex stainless steel pipes.

[0012] Furthermore, the material of the welding stub is duplex stainless steel pipe.

[0013] Furthermore, it also includes the pretreatment of the duplex stainless steel pipe. The pretreatment is to polish, round and clean the pipe ends of the duplex stainless steel pipes to be butted by using a wire brush.

[0014] Furthermore, the roundness of the pipe end of the duplex stainless steel pipe is less than 0.8%, and the end face is perpendicular to the pipe body.

[0015] Furthermore, the coaxiality between the duplex stainless steel pipe and the welding stub is less than 0.3 mm.

[0016] Furthermore, the clamping force of the welding tooling is 0 - 400 MPa.

[0017] Furthermore, the positive pressure is 20 - 80 MPa, the rotation speed is 30 - 100 r / s, and the welding time is 5 - 20 s.

[0018] Furthermore, the rotation direction during the rotary welding is co-rotating or reciprocating rotation, and the reciprocating rotation angle is greater than ±10°.

[0019] Furthermore, place a water-soluble paper plug made of water-soluble vinylon in the welding stub before welding.

[0020] Furthermore, the post-treatment is to grind the butt weld flash with a angle grinder until it is flush with the duplex stainless steel pipe.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention provides a method for on-site circumferential connection of duplex stainless steel pipes based on solid-phase welding. By clamping the pipe ends of two sections of duplex stainless steel pipes and a welding stub on a welding fixture, with the welding stub positioned between the two sections of duplex stainless steel pipes, applying a positive pressure to the welding stub by the two sections of duplex stainless steel pipes to clamp the welding stub, performing rotary welding, and then post-treating the flash of the welded duplex stainless steel pipes, the on-site circumferential connection of duplex stainless steel pipes is completed. The present invention adopts solid-phase welding technology, which has a self-cleaning effect, is not prone to weld defects, and also has advantages such as no need for flux, shielding gas, and high welding efficiency. It realizes on-site circumferential, rapid and efficient welding of duplex stainless steel, obtains joints with good tensile properties and corrosion resistance, and can ensure good sealing performance, pressure-bearing performance and corrosion resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other relevant drawings can also be obtained based on these drawings.

[0024] Figure 1 It is a schematic diagram of the solid-phase welding device of the present invention.

[0025] Figure 2 It is a physical drawing of the welding in Embodiment 1 of the present invention.

[0026] Figure 3 It is a material microstructure phase diagram of the duplex stainless steel pipe in Embodiment 1 of the present invention.

[0027] Figure 4 It is a physical drawing of the tensile fracture in Embodiment 1 of the present invention.

[0028] Figure 5 It is a corrosion potential comparison diagram of the weld and the base metal in Embodiment 1 of the present invention.

[0029] Wherein: 1 - welding fixture, 2 - the first section of duplex stainless steel pipe, 3 - the second section of duplex stainless steel pipe, 4 - flange. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] To enable those skilled in the art to understand the characteristics and effects of the present invention, the following provides a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meanings understood by those skilled in the art regarding the present invention. In case of conflicts, the definitions in this specification shall prevail.

[0031] The theories or mechanisms described and disclosed herein, whether right or wrong, shall not in any way limit the scope of the present invention, that is, the content of the present invention can be implemented without being limited by any specific theory or mechanism.

[0032] In this document, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are only for the sake of brevity and convenience. Accordingly, the description of a numerical range or percentage range should be regarded as having covered and specifically disclosed all possible sub-ranges and individual numerical values (including integers and fractions) within the range.

[0033] In this document, unless otherwise specified, the terms "comprising", "including", "containing", "having", or similar terms cover the meanings of "consisting of" and "consisting essentially of". For example, "A comprises a" covers the meanings of "A comprises a and others" and "A consists only of a".

[0034] In this document, for the sake of brevity, all possible combinations of all technical features in each embodiment or example are not described. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each embodiment or example can be combined arbitrarily, and all possible combinations should be considered as being within the scope described in this specification.

[0035] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0036] Conventional instrument and equipment in the art are used in the following embodiments. For the experimental methods without specific conditions noted in the following embodiments, they are generally carried out under conventional conditions or according to the conditions recommended by the manufacturer. Various raw materials are used in the following embodiments. Unless otherwise stated, commercially available products are used, and their specifications are conventional specifications in the art. In the specification of the present invention and the following embodiments, unless otherwise specified, "%" represents weight percentage, "parts" represents weight parts, and the ratio represents weight ratio.

[0037] The present invention will be further described in detail below:

[0038] The present invention provides a method for on-site circumferential connection of duplex stainless steel pipes based on solid-phase welding, comprising the following steps:

[0039] Step 1, pipe end treatment of duplex stainless steel pipes:

[0040] Use a wire brush to polish, round and clean the pipe ends of the first section of duplex stainless steel pipe 2 and the second section of duplex stainless steel pipe 3 that need to be butt-jointed. After rounding the pipe ends, the ovality of the pipe ends is less than 0.8%, and the end face is perpendicular to the pipe body.

[0041] Step 2, preparation of welding stub:

[0042] Use a cutting machine to cut a welding stub at one end of the duplex stainless steel pipe.

[0043] Step 3, alignment:

[0044] Clamp the pipe orifices of the two sections of duplex stainless steel pipe that need to be butt-jointed and the welding stub on the welding fixture 1, and the welding stub is located between the two sections of duplex stainless steel pipe.

[0045] Preferably, the coaxiality between the welding stub and the original fractured duplex stainless steel pipe is less than 0.3 mm, and the clamping force provided by the welding fixture 1 is 0 - 400 MPa.

[0046] Step 4, welding:

[0047] The welding method uses solid-phase welding technology. The two sections of duplex stainless steel pipe apply a positive pressure to the welding stub through the flange 4, clamp the welding stub, and give a certain rotational speed for welding.

[0048] Preferably, the welding parameters are: positive pressure: 20 - 80 MPa, rotational speed: 30 - 100 r / s, the rotational direction can be co-rotating or reciprocating rotation, the reciprocating rotation angle is greater than ±10°, the welding time is 5 - 20 s, and the welding parameters should be selected according to the material phase diagram.

[0049] Preferably, in order to control the morphology of the internal flash, a water-soluble paper plug can be placed inside the welding stub before welding. After welding, it is dissolved with a water medium. The water-soluble paper plug is made of water-soluble vinylon material.

[0050] Step 5, grinding:

[0051] Use a grinding machine to grind the flash of the butt weld until it is flush with the base metal.

[0052] The following further describes the present invention in detail with specific embodiments:

[0053] Embodiment 1:

[0054] Weld two pipe segments of S32205 pipe with a diameter of φ38.1mm×3.2mm. First, use a wire brush to grind, round, and clean the pipe ends of the two duplex stainless steel pipes to remove impurities; clamp the pipe orifices of the two duplex stainless steel pipes and the cut welding stub on the welding fixture. The coaxiality between the welding stub and the duplex stainless steel pipe is 0.2mm, and the clamping force provided by the clamping device is 20MPa; adopt a welding process with a positive pressure of 20MPa, a rotation speed of 40r / s, a welding time of 10s, and a rotation direction of co-rotation to obtain a joint morphology as Figure 2 shown. As Figure 3 shown, no harmful phase structure is shown at the joint. The obtained material tensile test results are shown in Table 1. The tensile test results show that during the tensile process, compared with the performance of the base material, the weld performance has good strength performance, and the joint tensile performance is better than that of the base material. The material fractures at the base material during the tensile test, as Figure 4 shown. Conduct an electrochemical experiment on the base material and the weld. It can be seen from Figure 5 that the weld has a higher corrosion potential than the base material and better corrosion resistance.

[0055] Table 1 Comparison of tensile properties between the base material and the weld

[0056]

[0057] Example 2:

[0058] Weld two pipe segments of S31803 pipe with a diameter of φ50.8mm×3.2mm. First, use a wire brush to grind and round the pipe ends of the two duplex stainless steel pipes, and use acetone to remove oil stains; clamp the pipe orifices of the two duplex stainless steel pipes and the cut welding stub on the welding fixture. The coaxiality between the welding stub and the duplex stainless steel pipe is 0.1mm, and the clamping force provided by the clamping device is 35MPa; adopt a welding process with a positive pressure of 35MPa, a rotation speed of 60r / s, a welding time of 7s, and a rotation direction of co-rotation; use an angle grinder to grind the butt weld flash to be flush with the base material, and no harmful phase structure is shown at the joint. The tensile test results show that during the tensile process, compared with the performance of the base material, the weld performance has good strength performance, and the joint tensile performance is better than that of the base material. The material fractures at the base material during the tensile test.

[0059] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A field circumferential connection method for duplex stainless steel pipes based on solid-phase welding, characterized in that, it includes: Clamp the pipe ends of two sections of duplex stainless steel pipes and the welding stub on the welding tooling, and the welding stub is located between the two sections of duplex stainless steel pipes; Adopt the solid-phase welding technology, apply a positive pressure to the welding stub by the two sections of duplex stainless steel pipes, clamp the welding stub, and perform rotary welding; Perform post-treatment on the welded duplex stainless steel pipes.

2. The field circumferential connection method for duplex stainless steel pipes based on solid-phase welding according to claim 1, characterized in that, the material of the welding stub is duplex stainless steel pipe.

3. The field circumferential connection method for duplex stainless steel pipes based on solid-phase welding according to claim 1, characterized in that, it also includes the pre-treatment of the duplex stainless steel pipes, and the pre-treatment is to polish, round and clean the pipe ends of the duplex stainless steel pipes to be butt-jointed with a wire brush.

4. The field circumferential connection method for duplex stainless steel pipes based on solid-phase welding according to claim 3, characterized in that, the roundness of the pipe ends of the duplex stainless steel pipes is less than 0.8%, and the end face is perpendicular to the pipe body.

5. The field circumferential connection method for duplex stainless steel pipes based on solid-phase welding according to claim 1, characterized in that, the coaxiality between the duplex stainless steel pipe and the welding stub is less than 0.3 mm.

6. The field circumferential connection method for duplex stainless steel pipes based on solid-phase welding according to claim 1, characterized in that, the clamping force of the welding tooling is 0 - 400 MPa.

7. The field circumferential connection method for duplex stainless steel pipes based on solid-phase welding according to claim 1, characterized in that, the positive pressure is 20 - 80 MPa, the rotation speed is 30 - 100 r / s, and the welding time is 5 - 20 s.

8. The field circumferential connection method for duplex stainless steel pipes based on solid-phase welding according to claim 1, characterized in that, the rotation direction during the rotary welding is co-rotating or reciprocating rotation, and the reciprocating rotation angle is greater than ±10°.

9. The field circumferential connection method for duplex stainless steel pipes based on solid-phase welding according to claim 1, characterized in that, place a water-soluble paper plug in the welding stub before welding, and the water-soluble paper plug is made of water-soluble vinylon.

10. The field circumferential connection method for duplex stainless steel pipes based on solid-phase welding according to claim 1, characterized in that, the post-treatment is to grind the butt weld flash with an angle grinder until it is flush with the duplex stainless steel pipe.

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