Prewelding method of thin-wall longitudinal submerged-arc welded (LSAW) pipes with small bore diameter

A straight seam submerged arc and small-diameter technology, which is applied in the field of steel welding, can solve the problems of reducing the welding pass rate, the pre-weld seam is not full, and the welding seam repair rate increases, so as to reduce the number of pre-welding arc stop adjustments and improve The effect of one-time molding rate and shortened repair length

Inactive Publication Date: 2015-12-23
CNPC BOHAI EQUIP MFG +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The current longitudinal submerged arc welding pipe industry adopts the automatic gas-shielded welding method for pre-welding, and the diameters of the welding wires used are all φ2.4mm and φ3.2mm specified by the general standard. The welding current used by the gas-shielded welding wire with this diameter is too large. It is not suitable for welding small-caliber and thin-walled steel pipes: 1) During pre-welding, it is easy to cause burn-through, welding lumps on the inner welding groove, and the probability of internal welding deviation increases, resulting in the degradation and waste reduction of steel pipes; 2) Using large Current, high welding speed, the pre-weld seam is not full, resulting in internal welding burn-through, the weld seam needs to be repaired in light cases, and the base metal is damaged in severe cases, resulting in the waste of the steel pipe; 3) Due to the fast welding speed, the pre-weld seam Humps appear, the welding seam repair rate increases, and the welding pass rate is reduced

Method used

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  • Prewelding method of thin-wall longitudinal submerged-arc welded (LSAW) pipes with small bore diameter

Examples

Experimental program
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Effect test

Embodiment 1

[0014] The selected steel pipe specification is φ457X8.8mm steel grade L360MS, the pre-welding uses φ2.0mm gas shielded welding wire, and uses CO 2 Pre-weld with Ar mixed gas shielded automatic welding, welding current is 430A, welding voltage is 25V, welding wire elongation is 24mm, welding wire inclination is 0°, welding speed is 2.2m / min, shielding gas is 18% CO 2 +82% Ar, gas flow rate 25L / min.

[0015] Prepare the groove, and grind the groove and both sides of the inner and outer walls until the metallic luster is exposed, and then adopt gas shielded automatic welding for the counter pre-welding. The pre-welded seam obtained is full, smooth and uniform, and the inner groove has almost no welding tumor . 0% of internal welding burn-through defects, 0% of internal welding partial defects; the time consumption of each pre-welding repair process is reduced from 25min when using φ2.4mm gas shielded welding wire to 15min, and the production efficiency is reduced from φ2.4mm ga...

Embodiment 2

[0017] The selected steel pipe specification is φ406X11mm steel grade L360MS, the pre-welding uses φ2.0mm gas shielded welding wire, the welding current is 480A, the welding voltage is 26V, the elongation of the welding wire is 24mm, the inclination angle of the welding wire is 0°, and the welding speed is 1.8m / min , protective gas 18%CO 2 +82% Ar, gas flow rate 20L / min.

[0018] Prepare the groove, and grind the groove and both sides of the inner and outer walls until the metallic luster is exposed, and then adopt gas shielded automatic welding for the counter pre-welding. The pre-welded seam obtained is full, smooth and uniform, and the inner groove has almost no welding tumor . 0% of internal welding burn-through defects, 0% of internal welding partial defects; the time consumption of each pre-welding repair process is reduced from 20min when using φ2.4mm gas shielded welding wire to 14min, and the production efficiency is reduced from φ2.4mm gas shielded welding wire Ste...

Embodiment 3

[0020] The specification of the selected steel pipe is φ559X6.4mm steel grade L360M, the pre-welding uses the gas shielded welding wire of φ2.0mm, the welding current is 400A, the welding voltage is 27V, the elongation of the welding wire is 25mm, the inclination angle of the welding wire is 0°, and the welding speed is 2.9m / min, protective gas 18%CO 2 +82% Ar, gas flow rate 40L / min.

[0021] The theoretical groove width of the external welding of 6.4mm wall thickness steel pipe is 3.8mm. If φ2.4mm and φ3.2mm welding wires are used, the pre-welding automatic welding equipment cannot produce normally, and the steel pipe can only be pre-welded manually by semi-automatic gas-shielded welding, 8 hours The shift produces 10 to 12 roots. After adopting the gas shielded welding wire of φ2.0mm, the pre-welding is automated, the pre-weld seam is full, smooth and uniform, and there is almost no welding bump in the inner groove. Internal welding burn-through defects are 0%, internal w...

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Abstract

The invention discloses a prewelding method of thin-wall longitudinal submerged-arc welded (LSAW) pipes with a small bore diameter, and relates to the technical field of steel products welding. The prewelding method lies in that prewelding is carried out by adopting CO2 and Ar mixed gas protective automatic welding, and further comprises the following steps: firstly, determining welding technological parameters, determining the diameter of a welding wire as 2.0 mm and the welding speed as 1.8-2.9 m/min, and determining the proportion and flow of mixed gas, then carrying out preparation before welding, preparing a groove, determining the grade of the welding wire and the welding parameters. During the process of producing thin-wall steel pipes with a small bore diameter, prewelding is carried out by utilizing a shielding welding wire with the diameter of 2.0 mm, welding is carried out by adopting low current, the prewelding seam is plump, the overlaps of an internal groove are greatly reduced, the occurrence probability of defects like burning through and weld misalignment is reduced, and at the same time, the prewelding failure discharge regulation times is reduced, the prewelding once-shaping ratio is increased, and the production efficiency is improved.

Description

technical field [0001] The invention relates to the technical field of steel welding, in particular to a small-diameter, thin-walled straight seam submerged arc welding steel pipe pre-welding method. Background technique [0002] Welding is the core part of the production of LSAW pipes. The welding sequence of LSAW pipes is as follows: figure 1 Shown: First, automatic gas shielded welding is used for pre-welding, and the open tube blanks are bonded into steel pipes, and then the inner and outer "V" grooves of the steel pipes are sequentially filled by submerged arc welding to form inner welds and outer welds . As the root weld of submerged arc welding seam, the quality of pre-weld seam directly affects the first pass rate and production efficiency of steel pipe welding, especially for small-diameter and thin-walled steel pipes. The current longitudinal submerged arc welding pipe industry adopts the automatic gas-shielded welding method for pre-welding, and the diameters of...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): B23K9/18B23K9/025B23K9/235B23K35/38B23K101/06B23K103/04
CPCB23K9/18B23K9/0253B23K9/235B23K35/383B23K2101/06B23K2103/04
Inventor 葛玉宏刘鉴卫曹华勇刘增强杨魁张骅金博姚华
Owner CNPC BOHAI EQUIP MFG
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