CN108856989B

CN108856989B - Priming method for fusion electrode MIG welding in pipeline welding

Info

Publication number: CN108856989B
Application number: CN201810791200.1A
Authority: CN
Inventors: 梁恩荣; 王跃峰; 何耀飞; 鲁晓欣
Original assignee: Pangang Group Engineering Technology Co Ltd
Current assignee: Pangang Group Engineering Technology Co Ltd
Priority date: 2018-07-18
Filing date: 2018-07-18
Publication date: 2020-11-10
Anticipated expiration: 2038-07-18
Also published as: CN108856989A

Abstract

The invention relates to a bottoming method for metal-inert gas (MIG) welding in pipeline welding, belonging to the technical field of pipeline welding. During welding, two pipes to be welded are respectively provided with welding grooves on the butt joint end faces and are oppositely arranged to form a V-shaped groove, the root gap of the V-shaped groove is 3-5 mm, the angle of the single groove is 30-35 degrees, a welding machine for backing welding adopts semi-automatic consumable electrode MAG welding equipment, the protective gas adopts mixed gas of argon and carbon dioxide, and the proportion of argon is 95% and the proportion of carbon dioxide is 5% according to volume percentage. The invention adopts the ordinary semi-automatic consumable electrode MAG welding equipment to realize the MIG welding effect, can reduce the construction cost, improve the construction efficiency and avoid the welding defects of the conventional operation method.

Description

Priming method for fusion electrode MIG welding in pipeline welding

Technical Field

The invention relates to a bottoming method for metal-inert gas (MIG) welding in pipeline welding, belonging to the technical field of pipeline welding.

Background

The chemical industry has higher requirements on the strength and compactness of the pipeline and the tank body, so that the requirement on the welding quality of the pipeline is strict, and the requirement on the radiographic inspection of partial pipelines reaches the first level. In the prior art, the welding method with high requirements on the pipeline adopts argon arc welding to perform single-side welding and double-side forming of a root backing weld bead, and manual welding is performed to perform welding of a filling cover surface. However, when a large-diameter pipeline is welded, the lower half circle of the large pipeline is almost positioned at the overhead welding position and the climbing overhead welding position, and the argon arc welding operation needs to hold a welding gun by one hand and send a welding wire by the other hand, and the two hands need to be matched and coordinated to ensure the quality of a welding seam. The conventional argon arc welding pipeline wire feeding method comprises an inner filler wire (figure 1) and an outer filler wire (figure 2), the large-diameter pipeline can be completed only by matching two wires if one person cannot complete the operation by adopting the inner filler wire, the requirement on the tacit degree and the operation proficiency degree of the matching of the two persons is high, the investment of a welder is obviously increased, and the outer filler wire is adopted for welding according to the conditions of enterprises and the preparation of the personnel in many aspects. When the external wire filling method is adopted, two welding hands at the overhead welding part are in suspended positions, the stability of the two hands can be ensured without any leaning and supporting points, the head part is still in a long-term upward looking state, the operation posture naturally increases the difficulty for welding, the instability of the hands of an operator cannot ensure that the welding wire is correctly sent to the root part of a welding seam, if the welding wire is only sent to the middle of a groove, when the welding wire is melted and combined with a base metal, the welding seam naturally collapses due to the dead weight of molten iron at the overhead welding part, the natural sunken state appears at the back, the phenomenon is avoided, the condition that the gap of the groove must be larger than the diameter of the welding wire is ensured, the welding wire can be normally sent to the back of a near welding seam through the groove, the condition that the surplus height and the base metal at the back of the welding seam are flush and slightly higher than the base metal even if a certain amount of the molten, the operation difficulty is increased, and the welding of the overhead welding part always has depressions with different depths (as shown in figure 3), so that the welding quality cannot be guaranteed.

Adopt consumable electrode MIG to weld and replace manual tungsten electrode argon arc to weld and carry out backing weld, can guarantee the stationarity of hand because consumable electrode MIG welds and is semi-automatic welding, and the welding wire just need not send the silk alone like argon arc welding through welder automatic feed, just at this moment can adopt both hands to control welder, and the arm of one hand can also lean on the pipe wall, greatly increased welding operation's stability like this. And the welding wire of consumable electrode MIG welding is thin, the welding wire can easily reach the root of the groove, the molten pool can be prevented from collapsing due to short existing time during welding, the depression of the welding overhead welding part of argon arc welding backing welding can be effectively avoided, the construction efficiency can be obviously improved, meanwhile, the heat affected zone of the consumable electrode MIG welding is narrow, the welding seam cooling speed is high, and the deformation of a weldment is small.

At present, the consumable electrode MIG welding process is widely applied to petroleum and natural gas pipelines at home and abroad, but the cost investment of a welding machine is large, the lowest price of a professional consumable electrode MIG welding machine is more than 5 thousands, some semi-automatic welding equipment is as high as hundreds of thousands, the equipment is more complicated than common consumable electrode equipment, the construction cost investment and profit return of the common industry are not directly proportional, and the use of the equipment is limited in places with complicated construction sites.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the bottoming method for the metal-inert gas (MIG) welding in the pipeline welding is provided, and the MIG welding effect is realized by adopting common semi-automatic MAG welding equipment so as to reduce the construction cost.

In order to solve the technical problems, the invention adopts the technical scheme that: a bottoming method of consumable electrode MIG welding in pipeline welding is characterized in that during welding, two pipes to be welded are respectively provided with welding grooves on butt joint end faces and are oppositely arranged to form a V-shaped groove, the root gap of the V-shaped groove is 3-5 mm, the angle of a single-side groove is 30-35 degrees, a welding machine for bottoming welding adopts semi-automatic consumable electrode MAG welding equipment, protective gas adopts mixed gas of argon and carbon dioxide, the argon accounts for 95% and the carbon dioxide accounts for 5% according to volume percentage.

Further, the method comprises the following steps: when the welding pipeline is in a horizontal fixed position, marking the lowest point as M and the highest point as N in the circumferential direction of a welding line, marking a point on the welding line at one side of a straight line MN as P, marking a point on the welding line at the other side of the straight line MN as Q, marking the central angle of an arc line MP as a, wherein the value of the a is 55-65 degrees, the central angle of an arc line MQ is marked as b, and the value of the b is 55-65 degrees;

when backing welding is carried out, a straight line MN is used as a boundary line to weld a welding line in two halves, and M points are used as starting points during welding; the welding current is 150A-180A, and the voltage is 14V-17V.

Welding seams in the range from M point to P point and welding seams in the range from M point to Q point are welded by adopting a welding gun forward tilting method, the included angle between the welding gun and the pipe skin is 100-105 degrees, the welding mode is one-point wire feeding, each time of arc striking is carried out in the middle of the welding seams, the molten pool is observed to be fused with the grooves on the two sides, the arc is extinguished immediately, and the wire feeding position is at the root part of the pipe skin;

welding seams in the range from P point to N point and welding seams in the range from Q point to N point are welded by adopting a welding gun backward tilting method, the included angle between a welding gun and a pipe skin is 80-90 degrees, the welding mode adopts a method of arc striking on two sides and arc extinguishing on two sides, an electric arc is ignited at one time at a groove of the pipe skin and immediately swings to the other groove, the electric arc is observed to be fused at the other side and immediately extinguished, then the electric arc is ignited at the arc extinguishing position and swings to be fused well at the other side and then is extinguished, and the actions are repeated until the bottoming welding of the whole welding seams is completed.

Further, the method comprises the following steps: when the outer diameter phi of the pipe is larger than 400mm, the welding seam is divided into four sections from M point to P point, from M point to Q point, from P point to N point and from Q point to N point for backing welding.

Further, the method comprises the following steps: when the welding pipeline is in a vertical fixed position, the welding current of the backing welding is 120-130A, and the voltage is 13-14V; the arc striking position is close to the edge of the upper groove, welding is carried out in a gun carrying mode of an inclined circle from top to bottom, and a gun carrying track finally forms a spiral shape; when the thickness of the pipe skin is larger than 16mm, continuous arc welding is adopted, and when the thickness of the pipe skin is smaller than or equal to 16mm, broken arc welding is adopted, arc blowout is carried out after the broken arc welding winds one inclined circle, then the electric arc is ignited from the arc blowout position, and the next inclined circle is operated, so that the welding of the bottoming welding bead is completed in sequence.

Further, the method comprises the following steps: before backing welding, performing positioning welding at a welding seam, wherein the length of the positioning welding seam is 20-30 mm, and two ends of the positioning welding seam are ground into a gentle slope by an angular grinding machine.

The invention has the beneficial effects that: practice shows that the quality of the welding seam of the invention can meet the use performance. The invention adopts a proper welding method and an effective operation method, and adopts common semi-automatic consumable electrode MAG welding equipment to realize the MIG welding effect, thereby solving the welding quality problem, reducing the deformation and stress of a weldment, improving the welding production efficiency, shortening the construction period and saving the construction cost. The invention is particularly suitable for parts with complex construction environment and limited construction site, can meet the construction requirements of argon tungsten-arc welding, can avoid the phenomenon that the welding part is concave upwards when the argon tungsten-arc welding is used for welding large-diameter pipelines, is suitable for all metallurgy, building industries and private enterprises to be applied to the welding of large-diameter pipelines, is favorable for improving the qualification rate and the construction efficiency of flaw detection, and reduces the labor cost.

Drawings

FIG. 1 is a schematic structural diagram of a prior art welding process using an internal filler wire;

FIG. 2 is a schematic structural diagram of a prior art welding process using an external filler wire;

FIG. 3 is a schematic structural diagram of a weld seam overhead welding portion indent defect in the prior art;

FIG. 4 is a schematic view of a segmented weld configuration of the present invention;

FIG. 5 is a schematic view of the angle change of the welding torch according to the present invention;

FIG. 6 is a schematic view of a welding method using one-spot wire feeding according to the present invention;

FIG. 7 is a schematic view of a welding mode of arc striking on two sides and arc extinguishing on two sides in the invention;

FIG. 8 is a schematic diagram of the inclined circular gun transportation mode in the invention.

Detailed Description

The invention is further explained below with reference to the drawings and examples.

A bottoming method of consumable electrode MIG welding in pipeline welding is characterized in that during welding, two pipes to be welded are respectively provided with welding grooves on butt joint end faces and are oppositely arranged to form a V-shaped groove, the root gap of the V-shaped groove is 3-5 mm, the angle of a single-side groove is 30-35 degrees, a welding machine for bottoming welding adopts semi-automatic consumable electrode MAG welding equipment, protective gas adopts mixed gas of argon and carbon dioxide, the argon accounts for 95% and the carbon dioxide accounts for 5% according to volume percentage.

Before backing welding, the welding seam is subjected to positioning welding, the length of the positioning welding seam is 20-30 mm, and two ends of the positioning welding seam are ground into a gentle slope by an angular grinding machine so as to ensure the quality of a joint. Before welding, rust oil stains in the range of 10 mm-20 mm on the inner side and the outer side of a weld groove are cleaned, and the welding wire is ER49-1 phi 1.2mm and is consistent with a formal weld when positioning welding is carried out.

As shown in fig. 4 to 7, when the welding pipe is in the horizontal fixed position, in the circumferential direction of the welding line, the lowest point is marked as M, the highest point is marked as N, a point is taken from the welding line on one side of the straight line MN and is marked as P, a point is taken from the welding line on the other side of the straight line MN and is marked as Q, the central angle of the arc line MP is marked as a, the value of a is 55-65 degrees, the central angle of the arc line MQ is marked as b, and the value of b is 55-65 degrees; the values of a and b are generally the same;

Welding seams in the range from M point to P point and welding seams in the range from M point to Q point are welded by adopting a welding gun forward tilting method, the included angle between the welding gun and the pipe skin is 100-105 degrees, the welding mode is one-point wire feeding, each time of arc striking is carried out in the middle of the welding seams, the molten pool is observed to be fused with the grooves on the two sides, the arc is extinguished immediately, and the wire feeding position is at the root part of the pipe skin; the wire feeding position cannot be only fed to the middle of the groove, otherwise, due to the gravity action of a molten pool, the phenomenon that the welding seam on the inner side of the groove is too high and the back of the welding seam is sunken and too deep is easy to occur.

Welding seams in the range from the point P to the point N and welding seams in the range from the point Q to the point N are welded by adopting a welding gun backward tilting method, the included angle between a welding gun and a pipe skin is 80-90 degrees, the welding mode adopts a method of arc striking on two sides and arc extinguishing on two sides, an electric arc is ignited at one time at a groove of the pipe skin and swings to the other groove immediately, the electric arc is observed to be melted at the other side and is extinguished immediately, then the electric arc is ignited at the arc extinguishing position and swings to the groove at the other side and is extinguished well, and the actions are repeated until the bottoming welding of the whole welding seam is completed, so that the internal welding bead.

In addition, in order to further ensure the welding quality, when the pipe diameter is larger, the welding seam can be divided into a plurality of sections for welding, and the invention preferably adopts the embodiment that when the outer diameter phi of the pipe is more than 400mm, the welding seam is divided into four sections from M point to P point, from M point to Q point, from P point to N point and from Q point to N point for backing welding.

When the welding pipeline is in a vertical fixed position, the welding current of the backing welding is 120-130A, and the voltage is 13-14V; the arc striking position is close to the edge of the upper groove, welding is carried out in a gun conveying mode of an inclined circle from top to bottom, and as shown in fig. 8, a gun conveying track finally forms a spiral shape; when the thickness of the pipe skin is larger than 16mm, continuous arc welding is adopted, and when the thickness of the pipe skin is smaller than or equal to 16mm, broken arc welding is adopted, arc blowout is carried out after the broken arc welding winds one inclined circle, then the electric arc is ignited from the arc blowout position, and the next inclined circle is operated, so that the welding of the bottoming welding bead is completed in sequence.

After the backing weld bead is welded, in order to avoid the phenomena of slag inclusion and incomplete fusion between layers, the positions of the joints and the parts with the clamping grooves on two sides of the middle bulges are polished and leveled by an angular grinder and then welded in the next procedure, and the methods of manual welding and gas metal arc welding can be selected for welding between layers and the cover layer according to actual conditions.

The first embodiment is as follows:

welding base materials: the material of the tube is 20, the outer diameter phi of the tube is 273mm, and the wall thickness is 8 mm; the two pipes are welded in a horizontal fixed position.

Welding equipment and materials: the welding machine is protected by conventional NBC-350 carbon dioxide gas, the protective gas is mixed gas of argon and carbon dioxide, and the proportion of argon is 95% and the proportion of carbon dioxide is 5% according to volume percentage; the welding wire adopts ER49-1 phi 1.2 mm.

Groove setting: a V-shaped groove is adopted, the root gap is 4mm, and the angle of the single-side groove is 30 degrees.

Working parameters of the welding equipment: the welding current is 150A-180A, and the voltage is 14V-17V.

And (3) welding operation: marking the lowest point as M and the highest point as N in the circumferential direction of a welding line, marking a point on the welding line at one side of a straight line MN as P, marking a point on the welding line at the other side of the straight line MN as Q, marking the central angle of an arc line MP as a, the value of a as 60 degrees, marking the central angle of an arc line MQ as b, and marking the value of b as 60 degrees;

when backing welding is carried out, a straight line MN is used as a boundary line to weld a welding line in two halves, and M points are used as starting points during welding;

welding seams in the range from M point to P point and welding seams in the range from M point to Q point are welded by adopting a welding gun forward tilting method, the included angle between the welding gun and the pipe skin is 100-105 degrees, the welding mode is one-point wire feeding, each time of arc striking is carried out in the middle of the welding seams, the molten pool is observed to be fused with the grooves on the two sides, the arc is extinguished immediately, and the wire feeding position is at the root part of the pipe skin.

And (3) welding quality inspection: visual inspection is adopted outside, no inspection is carried out, no air holes, slag inclusion, no fusion and undercut with the depth of more than 0.5mm are qualified, radiographic inspection is adopted for internal inspection of the welded junction of the pipeline, and the welded junction can achieve the radiographic inspection quality of more than two levels.

Example two:

welding base materials: the material of the tube is 20, the outer diameter phi of the tube is 600mm, and the wall thickness is 6 mm; the two pipes are welded in a horizontal fixed position.

Groove setting: a V-shaped groove is adopted, the root gap is 4mm, and the angle of the single-side groove is 35 degrees.

dividing a welding line into four sections from M point to P point, from M point to Q point, from P point to N point and from Q point to N point for backing welding, wherein the M point is taken as an initial starting point during welding;

And (3) welding quality inspection: visual inspection is adopted outside, no air holes, slag inclusion, incomplete fusion and undercut with the depth of more than 0.5mm are qualified, ultrasonic is adopted for detecting the internal quality of the pipeline, and the welding quality can reach the ultrasonic level.

Example three:

welding base materials: the material of the tube is 20, the outer diameter phi of the tube is 325mm, and the wall thickness is 6 mm; the two pipes are welded in a vertical fixed position.

Working parameters of the welding equipment: the welding current is 120A-130A, and the voltage is 13V-14V.

And (3) welding operation: the arc striking position is close to the edge of the upper groove, welding is carried out in a gun conveying mode of an inclined circle from top to bottom, and as shown in fig. 8, a gun conveying track finally forms a spiral shape; arc-breaking welding is adopted.

Claims

1. Consumable utmost point MIG welds bottoming method in the pipeline welding, and during the welding, two pipes that wait to weld set up the welding groove respectively at the butt joint terminal surface to be relative arrangement in order to form V type groove, its characterized in that: the root gap of the V-shaped groove is 3-5 mm, the angle of the single-side groove is 30-35 degrees, a welding machine for backing welding adopts semi-automatic consumable electrode MAG welding equipment, a mixed gas of argon and carbon dioxide is adopted as a protective gas, and the proportion of argon is 95% and the proportion of carbon dioxide is 5% according to volume percentage;

when the welding pipeline is in a horizontal fixed position, marking the lowest point as M and the highest point as N in the circumferential direction of a welding line, marking a point on the welding line at one side of a straight line MN as P, marking a point on the welding line at the other side of the straight line MN as Q, marking the central angle of an arc line MP as a, wherein the value of the a is 55-65 degrees, the central angle of an arc line MQ is marked as b, and the value of the b is 55-65 degrees;

when backing welding is carried out, a straight line MN is used as a boundary line to weld a welding line in two halves, and M points are used as starting points during welding; the welding current is 150A-180A, and the voltage is 14V-17V;

welding seams in the range from the point P to the point N and welding seams in the range from the point Q to the point N are welded by adopting a welding gun backward tilting method, the included angle between a welding gun and a pipe skin is 80-90 degrees, the welding mode adopts a method of arc striking on two sides and arc extinguishing on two sides, an electric arc is ignited on one side of a groove of the pipe skin and immediately swings to a groove on the other side, the electric arc is observed to be instantly extinguished after the groove on the other side is fused well, then the electric arc is ignited at the arc extinguishing position and swings to be fused well to the groove on the other side and then is extinguished, and the actions are repeated;

when the welding pipeline is in a vertical fixed position, the welding current of the backing welding is 120-130A, and the voltage is 13-14V; the arc striking position is close to the edge of the upper groove, welding is carried out in a gun carrying mode of an inclined circle from top to bottom, and a gun carrying track finally forms a spiral shape; when the thickness of the pipe skin is larger than 16mm, continuous arc welding is adopted, and when the thickness of the pipe skin is smaller than or equal to 16mm, broken arc welding is adopted, arc blowout is carried out after the broken arc welding winds one inclined circle, then the electric arc is ignited from the arc blowout position, and the next inclined circle is operated, so that the welding of the bottoming welding bead is completed in sequence.

2. A bottoming method for metal MIG welding in pipe welding as claimed in claim 1, wherein: when the outer diameter phi of the pipe is larger than 400mm, the welding seam is divided into four sections from M point to P point, from M point to Q point, from P point to N point and from Q point to N point for backing welding.

3. A bottoming method for metal-MIG welding in pipe welding as claimed in claim 1 or 2, characterized in that: before backing welding, performing positioning welding at a welding seam, wherein the length of the positioning welding seam is 20-30 mm, and two ends of the positioning welding seam are ground into a gentle slope by an angular grinding machine.