Full-automatic welding process for low-alloy high-strength high-pressure thick-wall pipeline

Abstract

The invention relates to a full-automatic welding process for a low-alloy high-strength high-pressure thick-wall pipeline, and belongs to the technical field of welding. The method comprises the following specific steps that firstly, construction preparation work is made, and a pipeline welding joint groove is machined; 2, pipeline assembling work is carried out; (3) welding of a connector is carried out; and fourthly, appearance detection is conducted after welding. According to the method, the composite butt joint groove is independently designed, compared with a traditional groove angle, the deposited metal filling amount is reduced by 1 / 4, welding materials are saved, and the welding time of each welded junction of the full-automatic welding process is shortened by 1 / 3; and the number of welding layers, the number of channels and welding parameters are designed, secondary heat treatment is conducted between layers in the welding process, the metallographic structure of a molten pool is improved, the overflow time of gas molecules is prolonged, the circular defect of air holes is reduced, and the welding quality is improved.

Description

Technical Field

[0001] The invention relates to a full-automatic welding process for a low-alloy high-strength high-pressure thick-wall pipeline, belonging to the technical field of welding. Background Art

[0002] With the demand for national energy security, long-distance pipeline construction will be vigorously developed. With the arrival of the peak period of gas storage development and construction, the construction quality of supporting high-pressure thick-walled pipelines is getting higher and higher, and traditional manual welding and semi-automatic welding cannot meet the construction requirements.

[0003] The traditional welding method for high-pressure thick-walled long-distance pipelines is manual base welding + semi-automatic filling welding, cover welding and combined automatic welding. Affected by the wall thickness, multiple thin layers and the thickness of the welding process, thick-walled pipeline welding requires high skills of base welders. Taking a φ1219mm, 33mm wall thickness pipeline as an example, the average time for welding one pass is 7.5 hours. The long welding time also has high requirements on the physical fitness of welders, increases labor intensity, and poses safety risks. This is a technical problem that needs to be solved urgently in the development of the high-pressure thick-walled pipeline market. Summary of the invention

[0004] In order to solve the technical problems existing in the prior art, the present invention discloses a fully automatic welding process for low-alloy high-strength, high-pressure, thick-walled pipelines, and independently designs a composite butt groove, which reduces the amount of deposited metal filling by 1 / 4 compared with the traditional groove angle, saves welding materials, and shortens the welding time of each weld in the fully automatic welding process by 1 / 3; the number of layers and welding parameters of double-gun automatic welding are designed to perform secondary heat treatment between layers during the welding process, improve the metallographic structure of the molten pool, increase the overflow time of gas molecules, reduce the generation of circular defects of pores, and improve the welding quality.

[0005] The technical solution adopted by the present invention is a low-alloy high-strength high-pressure thick-walled pipeline fully automatic welding process, and the specific steps are as follows:

[0006] Step 1: Make good preparations for construction and process the groove of the pipeline welding joint;

[0007] Step 2: Carry out pipeline assembly work;

[0008] Step 3: Weld the interface;

[0009] Step 4: Perform appearance inspection after welding.

[0010] Furthermore, the step 1 specifically includes preparing personnel, materials, and machines and evaluating the construction environment before welding, and processing the groove of the pipe joint into a composite butt groove.

[0011] Furthermore, the technical requirements of the composite butt groove include groove surface angle β=5°±1°; groove angle a=45°±1; inner groove surface angle γ=37.5°±1°; blunt edge P=0.8±0.2mm; butt clearance b=0~0.5mm; height from inflection point to inner wall H=4.8±0.2mm; inner groove height h=1.7±0.2mm; misalignment ≤2.0mm; excess height=0~2.0mm, the continuous length of the weld excess height not exceeding 3.0mm locally is not greater than 50mm; the upper opening of the groove with a wide cover weld is widened by 1.0mm~2.0mm on each side; there is no back pad; and the half groove width W=4.3~4.8mm.

[0012] Furthermore, the weld excess height is no more than 2.0 mm.

[0013] Furthermore, the thickness of the pipe is 33 mm.

[0014] Furthermore, the step 2 specifically includes that debris inside each pipe should be cleaned before pipe assembly, no mechanical scratches exceeding 0.5m deep should be found on the pipe ends, the pipes should not be forcefully aligned during assembly, and the center deviation of the pipe assembly should not be greater than 1mm.

[0015] Furthermore, the step three is specifically as follows: first determine that the number of welding layers is 13 layers and the number of passes is 14, then determine to use the internal welding machine for base welding first, then use single torch hot welding, double torch filling welding, single torch filling welding, and finally use double torch cover welding.

[0016] Furthermore, in the step three, the base welding is one layer and one pass, the hot welding is one layer and one pass, the double-torch filling welding is nine layers and nine passes, the single-torch filling welding is one layer and one pass, and the cover welding is two layers and two passes.

[0017] Furthermore, the specific requirements for welding parameters in step 3 include:

[0018] When performing root welding, the arc voltage is 140-240V and the wire feed speed is 290-450in·min -1 , welding speed is 65-75cm·min -1 , heat input is 0.28-0.48kJ / mm;

[0019] When single-torch hot welding is performed, the arc voltage is 160-280V and the wire feed speed is 400-560in·min -1 , welding speed is 60-80cm·min -1 , heat input is 0.32-0.56kJ / mm, swing width is 1.0-4.0mm, edge dwell is 0.01-0.08s;

[0020] When double torch filling welding is performed, the arc voltage is 120-250V and the wire feed speed is 270-500in·min -1 , welding speed is 30-50cm·min -1 , heat input is 0.42-0.88 kJ / mm, swing width is 1.0-5.5 mm, and edge dwell is 0.01-0.10 s;

[0021] When performing single torch filling welding, the arc voltage is 120-250V and the wire feed speed is 300-500in·min -1 , welding speed is 30-50cm·min -1 , heat input is 0.42-0.88 kJ / mm, swing width is 2.0-6.5 mm, edge dwell is 0.01-0.10 s;

[0022] When double torch cap welding is performed, the arc voltage is 85-170V and the wire feed speed is 170-270in·min -1 , welding speed is 35-60cm·min -1 , heat input is 0.25-0.50kJ / mm, swing width is 2.0-6.5mm, edge dwell is 0.01-0.10s;

[0023] During the welding process, the welding method was GMAW, the welding direction was downward, the polarity was DCEP, the welding current was 18-26A, and the shielding gas flow rate was 24-36L / min.

[0024] Furthermore, the step 4 specifically includes performing an appearance inspection after the pipeline welding is completed and making welding construction records in time; the pipeline welds should be subjected to non-destructive testing in accordance with regulations.

[0025] Furthermore, the thickness of each layer does not exceed 3 mm.

[0026] The invention discloses a fully automatic welding process for a low-alloy high-strength, high-pressure, thick-walled pipeline. The beneficial effects are as follows: by independently designing a composite butt groove, the amount of deposited metal filling is reduced by 1 / 4 compared with a traditional groove angle, welding materials are saved, and the welding time of each weld in the fully automatic welding process is shortened by 1 / 3; the number of welding layers, the number of passes and the welding parameters are designed so that secondary heat treatment is performed between layers during the welding process, the metallographic structure of the molten pool is improved, the overflow time of gas molecules is increased, the generation of circular defects of pores is reduced, and the welding quality is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0028] Figure 1 Shown is a schematic diagram of the process of Example 1;

[0029] Figure 2 The figure shows a schematic diagram of the composite butt groove in Example 1;

[0030] Figure 3 Shown is a schematic diagram of the number of welding layers and passes in Example 1. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] In order to further understand the content of the present invention, the present invention is further described below in conjunction with specific implementation methods.

[0033] Embodiment 1:

[0034] like Figures 1 to 3 As shown in the figure, a low alloy high strength high pressure thick wall pipeline fully automatic welding process, the specific steps are as follows:

[0035] Step 1: Prepare the construction and process the groove of the pipeline welding joint; specifically, prepare the personnel, materials, and tools and evaluate the construction environment before welding, and process the groove of the pipeline joint into a composite butt joint groove. Figure 2As shown, the technical requirements of the composite butt groove include groove surface angle β=5°±1°; groove angle a=45°±1; inner groove surface angle γ=37.5°±1°; blunt edge P=0.8±0.2mm; butt clearance b=0~0.5mm; height from inflection point to inner wall H=4.8±0.2mm; inner groove height h=1.7±0.2mm; misalignment ≤2.0mm; excess height=0~2.0mm, weld excess height is not more than 2.0mm, and the continuous length of the weld excess height not more than 3.0mm locally is not more than 50mm; the upper opening of the groove with a wide cover weld is widened by 1.0mm~2.0mm on each side; no back pad; half groove width W=4.3~4.8mm; the thickness of the pipe is 33mm.

[0036] Step 2: Perform pipeline assembly work; specifically, before assembling the pipelines, the debris inside the pipelines should be cleaned one by one, the pipeline ends should not have mechanical scratches deeper than 0.5m, the pipelines should not be forcefully aligned, and the center deviation of the pipeline assembly should not be greater than 1mm.

[0037] Step 3: Weld the interface; specifically, Figure 3 As shown in Table 1, first determine the number of welding layers to be 13 layers, the number of passes to be 14, and the thickness of each layer to be no more than 3 mm; secondly determine to use the internal welding machine for base welding first, then use single torch hot welding, double torch filling welding, single torch filling welding, and finally double torch cover welding. Figure 3 As shown, the base welding is one layer and one pass, the hot welding is one layer and one pass, the double-torch filling welding is nine layers and nine passes, the single-torch filling welding is one layer and one pass, and the cover welding is two layers and two passes.

[0038] Table 1: Number of welding layers and passes

[0039]

[0040] As shown in Table 2, the specific requirements for welding parameters include:

[0041] When performing root welding, the arc voltage is 140-240V and the wire feed speed is 290-450in·min -1 , welding speed is 65-75cm·min -1 , heat input is 0.28-0.48kJ / mm;

[0042] When single-torch hot welding is performed, the arc voltage is 160-280V and the wire feed speed is 400-560in·min -1 , welding speed is 60-80cm·min -1 , heat input is 0.32-0.56kJ / mm, swing width is 1.0-4.0mm, edge dwell is 0.01-0.08s;

[0043] When double torch filling welding is performed, the arc voltage is 120-250V and the wire feed speed is 270-500in·min -1 , welding speed is 30-50cm·min -1 , heat input is 0.42-0.88 kJ / mm, swing width is 1.0-5.5 mm, and edge dwell is 0.01-0.10 s;

[0044] When performing single torch filling welding, the arc voltage is 120-250V and the wire feed speed is 300-500in·min -1 , welding speed is 30-50cm·min -1 , heat input is 0.42-0.88 kJ / mm, swing width is 2.0-6.5 mm, edge dwell is 0.01-0.10 s;

[0045] When double torch cap welding is performed, the arc voltage is 85-170V and the wire feed speed is 170-270in·min -1 , welding speed is 35-60cm·min -1 , heat input is 0.25-0.50kJ / mm, swing width is 2.0-6.5mm, edge dwell is 0.01-0.10s; during the welding process, the welding method is GMAW, the welding direction is downward, the polarity is DCEP, the welding current is 18-26A, and the shielding gas flow rate is 24-36L / min.

[0046] Table 2: Welding parameters

[0047]

[0048] Step 4: Perform appearance inspection after welding. Specifically, after the pipeline is welded, perform an appearance inspection and make welding construction records in time; the pipeline welds should be non-destructively tested according to regulations.

[0049] The invention was applied to the pilot test ground engineering injection, collection and transmission pipeline project of a gas storage reservoir in Dongnanbao, Jidong, and the length of the West-East Gas Transmission Line 4 was 11.6 km, and the pipeline was Φ1219×33mm. The first-time qualified rate of on-site application welding was increased to more than 97%, and the welding time of each intersection was shortened by 1 / 3 compared with the traditional process, achieving the purpose of reducing costs and increasing efficiency.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A fully automatic welding process for low alloy, high strength, high pressure, thick wall pipelines. It is characterized in that The specific steps are as follows: Step 1: Make good preparations for construction and process the groove of the pipeline welding joint; Step 2: Carry out pipeline assembly work; Step 3: Weld the interface; Step 4: Perform appearance inspection after welding.

2. According to claim 1, a low alloy high strength high pressure thick wall pipeline fully automatic welding process, It is characterized in that Step 1 specifically includes preparing personnel, materials, and machines and evaluating the construction environment before welding, and processing the groove of the pipe joint into a composite butt groove; The technical requirements of the composite butt groove include groove surface angle β=5°±1°; groove angle a=45°±1; inner groove surface angle γ=37.5°±1°; blunt edge P=0.8±0.2mm; butt clearance b=0-0.5mm; height from inflection point to inner wall H=4.8±0.2mm; inner groove height h=1.7±0.2mm; misalignment ≤2.0mm; excess height=0-2.0mm, weld excess height not more than 2.0mm; the upper opening of the groove with cover weld width is widened by 1.0mm-2.0mm on each side; no back pad; half groove width W=4.3-4.8mm.

3. According to claim 2, a low alloy high strength high pressure thick wall pipeline fully automatic welding process, It is characterized in that The pipe thickness is 33mm.

4. According to claim 3, a low alloy high strength high pressure thick wall pipeline fully automatic welding process, It is characterized in that Step 2: Before assembling the pipes, the debris inside each pipe should be cleaned one by one. There should be no mechanical scratches deeper than 0.5m on the pipe ends. The pipes should not be forcefully aligned during assembly, and the center deviation of the pipe assembly should not be greater than 1mm.

5. According to claim 3, a low alloy high strength high pressure thick wall pipeline fully automatic welding process, It is characterized in that Step three specifically includes first determining that the number of welding layers is 13 layers and the number of passes is 14, and secondly determining to use an internal welding machine for base welding first, followed by single torch hot welding, double torch filling welding, single torch filling welding, and finally double torch cover welding.

6. A fully automatic welding process for low alloy, high strength, high pressure, thick wall pipeline according to claim 5, It is characterized in that Step three: the base welding is one layer and one pass, the hot welding is one layer and one pass, the double-torch filling welding is nine layers and nine passes, the single-torch filling welding is one layer and one pass, and the cover welding is two layers and two passes.

7. A fully automatic welding process for low alloy, high strength, high pressure, thick wall pipelines according to claim 6, It is characterized in that The specific requirements for welding parameters in step 3 include: When performing root welding, the arc voltage is 140-240V and the wire feed speed is 290-450in·min -1 , welding speed is 65-75cm·min -1 , heat input is 0.28-0.48kJ / mm; When single-torch hot welding is performed, the arc voltage is 160-280V and the wire feed speed is 400-560in·min -1 , welding speed is 60-80cm·min -1 , heat input is 0.32-0.56kJ / mm, swing width is 1.0-4.0mm, edge dwell is 0.01-0.08s; When double torch filling welding is performed, the arc voltage is 120-250V and the wire feed speed is 270-500in·min -1 , welding speed is 30-50cm·min -1 , heat input is 0.42-0.88 kJ / mm, swing width is 1.0-5.5 mm, and edge dwell is 0.01-0.10 s; When performing single torch filling welding, the arc voltage is 120-250V and the wire feed speed is 300-500in·min -1 , welding speed is 30-50cm·min -1 , heat input is 0.42-0.88 kJ / mm, swing width is 2.0-6.5 mm, edge dwell is 0.01-0.10 s; When double torch cap welding is performed, the arc voltage is 85-170V and the wire feed speed is 170-270in·min -1 , welding speed is 35-60cm·min -1 , heat input is 0.25-0.50kJ / mm, swing width is 2.0-6.5mm, edge dwell is 0.01-0.10s; During the welding process, the welding method was GMAW, the welding direction was downward, the polarity was DCEP, the welding current was 18-26A, and the shielding gas flow rate was 24-36L / min.

8. A fully automatic welding process for low alloy, high strength, high pressure, thick wall pipelines according to any one of claims 5 or 6, It is characterized in that The thickness of each layer shall not exceed 3mm.

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