CN112719515A

CN112719515A - Rail TIG welding method for black and white pipe

Info

Publication number: CN112719515A
Application number: CN202110100913.0A
Authority: CN
Inventors: 孙华; 刘磊; 方卫兵; 吕莽
Original assignee: Wuhan Boiler Co Ltd
Current assignee: Wuhan Boiler Co Ltd
Priority date: 2021-01-25
Filing date: 2021-01-25
Publication date: 2021-04-30

Abstract

The invention discloses a rail TIG welding method of a black and white pipe, and belongs to the technical field of welding. When the rail TIG welding is adopted to carry out the all-position welding of the black and white pipe, the difficulty lies in ensuring the stable transition of welding materials in all directions (flat, downhill, upward slope and the like) to a molten pool and the stress balance in the crystallization process of the molten pool, otherwise, the hot crack easily appears on a bottom layer, the concave position appears on the upward welding position and the like, and the rail TIG welding can not be successfully applied to the butt joint of the black and white pipe, thereby limiting the wide application of the rail TIG welding in the boiler manufacturing. The rail TIG welding method of the black and white tube is provided, welding parameters are set in a subarea mode, the welding rotating speed of the bottoming layer is increased, and the wire feeding amount and the welding current are reduced, so that the temperature of a molten pool at an upward welding position of 4-7 o' clock is reduced, and the generation of the inward recess of the upward welding position of the bottoming layer is effectively avoided; the welding speed of the first layer of filling layer at the overhead welding position is increased, the welding current is reduced, and the situation that the first layer of filling layer at the overhead welding position is welded to cause reverse melting to the bottoming layer to cause inward recess is effectively avoided; by optimizing the welding parameters of the bottom layer, the arc-closing decay time and the arc-closing stroke are prolonged, the arc length is increased, and the generation of arc-closing cracks of the bottom layer is effectively avoided; the heat input of each area is accurately controlled by changing the current and the wire feeding speed in different areas, so that the defect of poor fusion of various types is effectively avoided.

Description

Rail TIG welding method for black and white pipe

Technical Field

The invention relates to a rail TIG welding method of a black and white pipe, belonging to the technical field of welding.

Background

With the development of new technologies and the increasing shortage of high-skill welder resources in the market, boiler manufacturers are looking for solutions for automated and intelligent welding in order to improve welding productivity and market competitiveness. The application of rail TIG welding in the butt joint of small pipes can improve the welding production efficiency, reduce the labor intensity of welders and reduce the requirements of enterprises on all-position high-skill welders. However, in the current market, the rail TIG welding is only applied to the butt joint of carbon steel materials, the butt joint of low-alloy materials and the butt joint of stainless steel materials widely, and is never successfully applied to the butt joint of a novel heat-resistant steel material T91/T92 and an austenitic stainless steel material heterogeneous steel pipe (generally called a black and white pipe). The root causes are two: 1) the backing weld is prone to hot cracking. The filling material for welding the black and white pipe is a nickel-based material, and has a large thermal cracking tendency, and due to the difference of linear expansion coefficients of the T91/T92 material and austenitic stainless steel, the base metals on two sides can form large tensile stress on a weld joint in the welding process, so that the thermal cracking is easy to occur particularly at an arc-closing part during backing welding. 2) The indent is likely to occur at the overhead position. Molten iron flows downwards under the influence of gravity at the overhead welding position, so that the inward recess is generated. Both of these problems have not been solved, thereby limiting the widespread use of orbital TIG welding in boiler black and white pipe manufacture.

Disclosure of Invention

The invention aims to provide a rail TIG welding method of a black-and-white pipe, which can effectively avoid hot cracks and inward dents generated in the welding process of a T91/T92 pipe and an austenitic stainless steel black-and-white pipe. By setting welding parameters in different areas, the welding speed of the bottoming layer is increased, and the wire feeding amount and the welding current are reduced, so that the temperature of a molten pool at an upward welding position of 4-7 o' clock is reduced, and the generation of inward concave of the upward welding position of the bottoming layer is effectively avoided; the welding speed of the first layer of filling layer at the overhead welding position is increased, the welding current is reduced, and the situation that the first layer of filling layer at the overhead welding position is welded to cause reverse melting to the bottoming layer to cause inward recess is effectively avoided; by optimizing the welding parameters of the bottom layer, the arc-closing decay time and the arc-closing stroke are prolonged, the arc length is increased, and the generation of arc-closing cracks of the bottom layer is effectively avoided; the heat input of each area is accurately controlled by changing the current and the wire feeding speed in different areas, so that the defect of poor fusion of various types is effectively avoided.

The invention provides a rail TIG welding method of a black and white pipe. The welding method comprises the following steps:

step 1: and machining a T91/T92 pipe and an austenitic stainless steel pipe welding groove by adopting a machining method.

Step 2: the area to be welded is polished to see the metallic luster, the thickness or the width of the root is not influenced, and any foreign matter is ensured to be absent.

And step 3: and assembling spot welding, namely manually performing GTAW spot welding on the T91/T92 pipe and the stainless steel pipe, wherein wires are not filled in the spot welding process. The assembly clearance is 0-0.5 mm.

And 4, step 4: and selecting a proper top die according to the pipe diameter and installing the top die on the machine head. The top die needs to be ensured to be concentric with the pipe to ensure that the head remains concentric with the pipe during rotation, ensuring uniformity and consistency of the weld.

And 5: and placing the machine head on the pipe, observing the center position of the groove by naked eyes, and clamping and fixing.

Step 6: and grinding the tip of the tungsten electrode to form an angle of 30 degrees. And adjusting the length of the tungsten electrode according to the depth of the first layer of arc starting points. When the contact root of the tungsten needle tip is automatically lifted, the gap between the porcelain bushing and the surface of the workpiece is 1-2 mm.

And 7: the back-protection gas is Ar gas, the inlet end is sealed by a plastic plug matched with the tube, and the outlet end is sealed by about 2/3 by tinfoil to facilitate air discharge. The back protection gas should first drive out the air in the tube at a large flow rate and then be reduced to below 5L/min.

And 8: the machine head is rotated for one circle, all cables are loosely wound on the machine head, and the cables are prevented from falling off and affecting the following welding and swinging. The positional relationship of the welding wire and the tungsten needle was adjusted so that the welding wire was about 2.5mm just below the tungsten electrode.

And step 9: preheating the workpiece by adopting an electric arc self-preheating or flame preheating mode, wherein the preheating temperature is more than or equal to 150 ℃. The preheating temperature of the priming layer is 250 ℃.

Step 10: and carrying out multilayer welding. The multilayer welding comprises a priming layer, a filling layer and a cover layer in sequence. The welding wire adopts ERNiCr-3, 1.0 mm. Ar gas is used as protective gas, and the flow rate is 8-15L/min. The interlayer temperature is less than or equal to 300 ℃. The welding uses a pulse current in the form of a rapid pulse.

Wherein the content of the first and second substances,

the welding conditions of the bottom layer comprise: during parameter setting, zone control is adopted, wherein welding voltage is 9-10V, welding current is 90-100A, pulse current is 5A, and welding speed is as follows: 55mm/min, wire feed speed: 200 mm/min. Arc starting is carried out at 12 o 'clock position, the machine head rotates and welds along the clockwise direction, and arc extinguishing is carried out at 1 o' clock position. The welding position of the indent appears easily, and the mode of adopting undercurrent, rapid welding and reducing the wire feed speed can effectively reduce the molten pool temperature, avoids the production of indent. By prolonging the current attenuation time of arc striking and the attenuation stroke of arc striking, the length of the electric arc is increased, and the generation of arc striking cracks on the bottom layer can be effectively avoided.

The welding conditions of the first filling layer comprise: and the parameters are set by adopting zone control, wherein the welding voltage is 9-10V, the welding current is 100-120A, the pulse current is 5A, and the welding speed is as follows: 50-60mm/min, wire feed speed: 900-. Arc starting is carried out at the position of 12 o ' clock, the machine head rotates and welds in the clockwise direction, and arc extinguishing is carried out at the middle position of 12 o ' clock-1 o ' clock. In order to avoid the situation that the bottom layer is reversely melted to cause concave when the filling layer is welded at the upward welding position, the welding is carried out by adopting a small current and quick welding mode.

The welding conditions of the second filling layer and the cover surface layer comprise: during parameter setting, the welding voltage is controlled by zones to be 9-10V, the welding current is controlled by 100-120A, the pulse current is controlled by 5A, and the welding speed is controlled by the following steps: 50-55 mm/min. Wire feeding speed: 750-1000 mm/min. Arc starting is carried out at the position of 12 o ' clock, the machine head rotates and welds in the clockwise direction, and arc extinguishing is carried out at the middle position of 12 o ' clock-1 o ' clock.

The welding is initially observed for a transition of the wire in the weld pool, ensuring that the wire gently contacts the workpiece surface as it moves. After each layer is welded, a stainless steel wire brush is used for cleaning the welding bead so as to facilitate the welding of the next layer. Once welding is initiated, the entire weld must be completed.

The invention has the beneficial effects that: (1) the invention provides a welding method of TIG welding of a black and white pipe track, which increases the welding rotating speed of a bottoming layer and reduces the wire feeding amount and the welding current by setting welding parameters in different areas, thereby reducing the temperature of a molten pool at an upward welding position by 4-7 o' clock and effectively avoiding the generation of the inward recess of the upward welding position of the bottoming layer; the welding speed of the first layer of filling layer at the overhead welding position is increased, the welding current is reduced, and the situation that the first layer of filling layer at the overhead welding position is welded to cause reverse melting to the bottoming layer to cause inward recess is effectively avoided; by optimizing the welding parameters of the bottom layer, the arc-closing decay time and the arc-closing stroke are prolonged, the arc length is increased, and the generation of arc-closing cracks of the bottom layer is effectively avoided; the heat input of each area is accurately controlled by changing the current and the wire feeding speed in different areas, so that the defect of poor fusion of various types is effectively avoided. (2) The welding method for TIG welding of the black and white pipe track can bring considerable economic benefits for boiler manufacturing enterprises.

Drawings

FIG. 1 is a schematic view of a TIG welding groove of a black-and-white pipe track according to the present invention

FIG. 2 is a schematic view of the TIG welding layer path distribution of a black and white pipe track related to the invention

FIG. 3 is a sectional view of welding parameters of a black and white pipe track TIG welding backing layer according to the present invention

FIG. 4 is a sectional view of welding parameters of a first layer filling layer in TIG welding of a black-and-white pipe track according to the invention

FIG. 5 is a sectional view of welding parameters from a second layer filling layer to a cover layer in TIG welding of a black and white tube track according to the present invention

In the figure: 1-T91/T92 pipe, 2-stainless steel pipe, 3-welded joint

Detailed Description

The following further describes the practice of the present invention in conjunction with the accompanying drawings.

The invention provides a welding method for TIG welding of a black and white pipe track. As shown in fig. 1 to 5. The welding method comprises the following steps:

step 1: and machining the T91/T92 pipe 1 and the austenitic stainless steel pipe 2 welding groove by adopting a machining method. The groove size is shown in fig. 1. The J-shaped groove is adopted, and in order to ensure the opposite port quality of the TIG welding groove of the track, the inner wall of the pipe needs to be processed and welded with the inner diameter Dp which is Dw-1.8S, wherein Dw is the nominal outer diameter of the pipe, and S is the nominal thickness of the pipe. When the wall thickness S of the pipe is less than or equal to 16mm, the size of the truncated edge p of the groove is 1.6mm, the length of the truncated edge is 1.6mm, the truncated edge of the groove and the bevel surface are in transition by an arc of R1.2mm, and the size of the bevel angle beta is 28 degrees.

Step 2: grinding the area to be welded to see metallic luster, without affecting the thickness or width of the root, ensuring that there are no foreign bodies (if a cleaning chemical is required, a cleaning agent, such as acetone, may be used)

And step 3: and assembling spot welding, namely assembling the T91/T92 pipe 1 and the stainless steel pipe 2 by adopting manual GTAW spot welding, wherein no wire is filled in the spot welding process in order to reduce the influence of spot welding seams on the formation of the subsequent rail TIG welding seams. The assembly clearance is 0-0.5 mm.

And 8: the machine head is rotated for one circle, all cables are loosely wound on the machine head, and the cables are prevented from falling off and affecting the following welding and swinging. The position relation of the welding wire and the tungsten needle is adjusted, the welding wire is about 2.5mm below the tungsten electrode, and the distance can be adjusted by an inner hexagon with the diameter of 2.5 mm. Ensures that the welding wire can be gently transited to the molten pool during welding.

Step 10: and carrying out multilayer welding. The multilayer welding comprises a priming layer, a filling layer and a cover layer in sequence. A typical layer-by-layer layout of the weld seam 3 is shown in figure 2. The welding wire adopts ERNiCr-3, 1.0 mm. Ar gas is used as protective gas, and the flow rate is 8-15L/min. The interlayer temperature is less than or equal to 300 ℃. The welding uses a pulse current in the form of a rapid pulse. Wherein the content of the first and second substances,

the welding conditions of the bottom layer comprise: the parameter setting adopts zone control, and is divided into 6 zones (12 points-3 points-4 points-7 points-9 points-10 points-1 points), and the zone schematic diagram is shown in figure 3. Welding voltage is 9-10V, welding current is 90-100A, pulse current is 5A, welding speed is as follows: 55mm/min, wire feed speed: 200 mm/min. Arc starting is carried out at 12 o 'clock position, the machine head rotates and welds along the clockwise direction, and arc extinguishing is carried out at 1 o' clock position. The concave upward welding position (4-7 points) is easy to appear, the temperature of a molten pool can be effectively reduced by adopting a mode of low current, rapid welding and reduction of the wire feeding speed of a welding wire, and the generation of concave is avoided. By prolonging the current attenuation time of arc striking and the attenuation stroke of arc striking, the length of the electric arc is increased, and the generation of arc striking cracks on the bottom layer can be effectively avoided.

The welding conditions of the first filling layer comprise: the parameter setting adopts zone control, and is divided into 5 zones (12 points-3 points-4 points-8 points-10 points-1 points), and the zone schematic diagram is shown in figure 4. Welding voltage 9-10V, welding current 100-120A, pulse current 5A, welding speed: 50-60mm/min, wire feed speed: 900-. Arc starting is carried out at the position of 12 o ' clock, the machine head rotates and welds in the clockwise direction, and arc extinguishing is carried out at the middle position of 12 o ' clock-1 o ' clock. In order to avoid the situation that the bottom layer is subjected to reverse melting to cause concave indentation when the filling layer is welded at the upward welding position, the positions of 4-8 points are welded in a small current and rapid welding mode.

The welding conditions of the second filling layer and the cover surface layer comprise: the parameter setting adopts zone control, and is divided into 5 zones (12 points-3 points-4 points-8 points-10 points-1 points), and the zone schematic diagram is shown in figure 5. Welding voltage 9-10V, welding current 100-120A, pulse current 5A, welding speed: 50-55 mm/min. Wire feeding speed: 750-1000 mm/min. Arc starting is carried out at the position of 12 o ' clock, the machine head rotates and welds in the clockwise direction, and arc extinguishing is carried out at the middle position of 12 o ' clock-1 o ' clock.

The foregoing is only a preferred embodiment of this invention and it should be noted that modifications can be made by those skilled in the art without departing from the principle of the invention and these modifications should also be considered as the protection scope of the invention.

Claims

1. The invention provides a rail TIG welding method of a black and white pipe, which is characterized by comprising the following steps of:

step 1: machining a T91/T92 pipe and an austenitic stainless steel pipe welding groove by adopting a machining method, wherein a J-shaped groove is adopted;

step 2: polishing the area to be welded to see metal luster, so as to ensure no influence on the thickness or width of the root and no foreign matter;

and step 3: assembling spot welding, namely assembling the T91/T92 tube and the stainless steel tube by adopting manual GTAW spot welding, wherein no wire is filled in the spot welding process, and the assembling clearance is 0-0.5 mm;

and 4, step 4: selecting a proper top die according to the pipe diameter and installing the top die on a machine head;

and 5: placing the machine head on the pipe, observing the center position of the groove with naked eyes, and then clamping and fixing;

step 6: polishing the tip of the tungsten electrode to form a 30-degree angle, adjusting the length of the tungsten electrode according to the depth of a first layer of arc starting points, and when the contact root of the tungsten needle tip is automatically lifted, the gap between the porcelain bushing and the surface of the workpiece is 1-2 mm;

and 7: the back protection gas adopts Ar gas, the inlet end of the back protection gas is sealed by a plastic plug matched with the tube, the outlet end of the back protection gas is sealed by about 2/3 by tinfoil so as to be beneficial to air discharge, the back protection gas firstly drives the air in the tube out at a larger flow rate and then is reduced to be below 5L/min;

and 8: rotating the machine head for one circle, winding all cables on the machine head loosely, ensuring that the cables do not fall off and influence the subsequent welding and swinging, adjusting the position relation of a welding wire and a tungsten needle, wherein the welding wire is about 2.5mm below a tungsten electrode, and the distance can be adjusted by an inner hexagon with the diameter of 2.5mm, so that the welding wire can be enabled to be transited to a molten pool softly during welding;

and step 9: preheating the workpiece by adopting an electric arc self-preheating or flame preheating mode, wherein the preheating temperature is more than or equal to 150 ℃; preheating the priming coat at 250 ℃;

step 10: performing multilayer welding, wherein the multilayer welding sequentially comprises a bottom layer, a filling layer and a cover layer, welding wires adopt ERNiCr-3 of 1.0mm, protective gas adopts Ar gas, the flow is 8-15L/min, the interlayer temperature is less than or equal to 300 ℃, pulse current is adopted for welding, a rapid pulse mode is adopted,

the welding conditions of the bottom layer comprise: the parameters are set by adopting zone control and are divided into 6 zones (12 points-3 points-4 points-7 points-9 points-10 points-1 points), the welding voltage is 9-10V, the welding current is 90-100A, the pulse current is 5A, and the welding speed is as follows: 55mm/min, wire feed speed: 200mm/min, arcing at 12 o ' clock, rotating and welding a machine head in a clockwise direction, quenching at 1 o ' clock, and easily forming an inward-concave upward welding position (4 o-7 o ' clock), wherein the temperature of a molten pool can be effectively reduced by adopting a small current, fast welding and a mode of reducing the wire feeding speed of a welding wire, the generation of inward concave is avoided, and the generation of bottom layer arc-closing cracks can be effectively avoided by prolonging the current attenuation time of arc-closing and the attenuation stroke of arc-closing, increasing the length of an electric arc and effectively avoiding the generation of bottom layer arc-closing cracks;

the welding conditions of the first filling layer comprise: the parameters are set by adopting zone control and are divided into 5 zones (12 points-3 points-4 points-8 points-10 points-1 point), the welding voltage is 9-10V, the welding current is 100-120A, the pulse current is 5A, and the welding speed is as follows: 50-60mm/min, wire feed speed: 900 plus 1000mm/min, starting arc at the 12 o ' clock position, rotating the machine head for welding along the clockwise direction, extinguishing arc at the middle position of 12 o ' clock-1 o ' clock, avoiding the situation that the bottom layer is melted reversely to cause concave when the filling layer is welded at the upward welding position, welding at the 4 o ' clock-8 o ' clock position by adopting a small current and rapid welding mode,

the welding conditions of the second filling layer and the cover surface layer comprise: the parameters are set by adopting zone control and are divided into 5 zones (12 points-3 points-4 points-8 points-10 points-1 point), the welding voltage is 9-10V, the welding current is 100-120A, the pulse current is 5A, and the welding speed is as follows: 50-55mm/min, wire feed speed: 750-;

the transition condition of the welding wire in a molten pool is observed at the beginning of welding, the welding wire is ensured to lightly contact the surface of a workpiece when moving, a stainless steel wire brush is used for cleaning a welding bead to facilitate the welding of the next layer after one layer is welded, and once the welding is started, the whole welding seam is required to be finished.

2. The orbital TIG welding method for black-and-white tubes according to claim 1, wherein the TIG welding method comprises the following steps: in the J-shaped groove in the step 1, when the wall thickness S of the pipe is less than or equal to 16mm, the size of a truncated edge p of the groove is 1.6mm, the length of the truncated edge is 1.6mm, the truncated edge of the groove and the groove surface are in transition by an arc of R1.2mm, the size of a groove angle beta is 28 degrees, the inner diameter Dp of the processing and welding of the inner wall of the pipe is equal to Dw-1.8S, wherein Dw is the nominal outer diameter of the pipe, and S is the nominal thickness of the pipe.