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Tube sheet horizontal fixed all position TIG welding

TIG welding parameters
Tube sheet horizontal fixed all position TIG welding
TIG welding points

Two layers and two layers. Each layer of welding seam is divided into front and rear half circles, which are welded in turn, and a tack weld is at 7 o’clock of the clock.

① Make a bottom layer. Fix the axis of the test piece tube in a horizontal position, and the 0 o’clock position of the clock is directly above.

The inclination angle of the welding torch and the centering position of the arc are shown in Figure-Welding torch inclination angle and arc centering position of tube-sheet all-position welding. After igniting the arc at 10-20mm to the left of the 7 o’clock position of the clock, quickly retreat to the positioning welding seam, do not add welding wire first, wait for the positioning welding seam to melt and form a molten pool, start adding welding wire, and follow the clockwise direction Solder to 11 o’clock on the clock.

Welding torch inclination angle and arc centering position of tube-sheet all-position welding

Then start the arc from the 6 o’clock position of the clock, without adding welding wire, and move the arc counterclockwise to the end of the weld to preheat. After the end of the weld melts and forms a molten pool, add welding wire and weld counterclockwise to the clock On the left side at 11 o’clock, stop wire feeding, add wire when the weld seam melts, and finish welding the last closed joint of the bottom bead.

② Cover surface layer. Weld the cover weld bead in the order of welding the bottom weld bead, and the welding torch swings slightly wider during welding to ensure that the weld leg size meets the requirements.

Plug-in tube-sheet welding requiring penetration

The welding technology of the inserted tube sheet that requires penetration is an essential technology for welders in boilers, pressure vessels, and pressure pipes. It is also the most difficult joint form to weld. Welders must master the single-sided welding of flat-plate butt joints and double-sided forming and flat-plate butt joint welding at the same time. The welding technology of T-shaped joint fillet welds, and the ability to adjust the inclination angle of the welding torch, the position of the wire, and the position of the arc centering at any time according to the change of the curvature of the pipe circumference, can obtain satisfactory welding results.

Because the orifice plate selected for this type of tube plate test piece is relatively thick, usually a 12mm thick plate is used with a larger groove angle, and more welding meat needs to be filled. In order to improve the welding quality and reduce the cost, only manual tungsten chloride is usually used. Arc welding is used to make the bottom layer, and the filler layer and the cover layer are welded according to the requirements of the welding process. Electrode arc welding, CO2 gas shielded welding or mixed gas shielded welding are used for welding.

The insertion type tube-sheet welding that requires penetration mainly includes tube-sheet horizontal rotation bottom welding, tube-sheet vertical fixed bottom welding, tube-sheet vertical fixed overhead welding and tube-sheet horizontal fixed all-position welding.

Tube sheet horizontal rotation bottom welding

Assembly and tack welding

Insert the pipe in the middle of the orifice plate to ensure that the end surface of the pipe is flush with the lower plane of the orifice plate, and the gap between the pipe and the orifice plate is evenly distributed along the circumferential direction. Weld 3 tack welds, each with a length of 10~15mm, as small as possible, must be welded firmly, no defects are allowed, and evenly distributed along the circumferential direction.

The position of the test piece

The axis of the pipe is required to be perpendicular to the horizontal plane, and the orifice plate is placed on the horizontal plane.

Note: It must be ensured that the back of the tube-sheet joint welding area is suspended, the back weld bead can be formed freely, the electrical contact is reliable, and the arc can be reliably started and burned. One tack weld of the test piece is on the right side of the welder.

Welding key points

use the left welding method, the angle of the welding torch, the position of wire feeding and the centering position of the arc are shown in Figure Angle of TIG torch and centering position of arc in downward welding.

Angle of TIG torch and centering position of arc in downward welding
Welding parameters: see Table-Welding Parameters of Horizontal Turning Down Welding of Tube Sheet
Welding Parameters of Horizontal Turning Down Welding of Tube Sheet
Welding points

① Ignite the arc on the positioning weld on the right side of the weld, preheat in situ, and do not add wire for the time being. After the positioning weld and the grooves on both sides are melted to form a molten pool, the arc moves to the left side of the positioning weld, press down the arc, hear the breakdown sound, see the melting hole, and when the diameter of the melting hole is appropriate, turn to the formal left Solder and start adding wire.

② Weld to 1/4~1/3 of the bottom bead, and extinguish the arc. Turn the arc crater to the right, ignite the arc on the right side of the arc crater, do not add wire temporarily, preheat in situ, after the arc crater and the grooves on both sides melt to form a molten pool, the arc moves to the left end of the arc crater, press down Arc, when the breakdown sound is heard, the melting hole is seen, and the diameter of the melting hole is suitable, continue to weld to the left and start adding wire. Repeat this until the bottom layer is welded.

③ When welding to both ends of the positioning weld, stop adding wire, slow down the welding speed, and continue welding after seeing that the welding seam and the positioning weld are fused.

④ When welding to the closed part of the bottom welding bead, the last joint must be connected.

Tube sheet vertical fixed bottom welding

  • Assembly and positioning welding: the requirements for assembly and positioning welding are the same as those of the tube plate vertical fixed down welding of the impermeable penetration tube plate welding.

  • The position of the test piece: the content is the same as that of the tube-sheet vertical fixed bottom welding of the impermeable penetration tube-sheet welding. However, the test piece must be fixed firmly, and it is not allowed to move during the welding process.

  • Welding parameters: see Table Welding parameters of vertical fixed down welding of tube sheet.

Welding parameters of vertical fixed down welding of tube sheet
  • Welding points: It is exactly the same as the plug-in tube sheet that needs to be penetrated when the tube sheet is rotated horizontally, but the position of the test piece is not allowed to move during the welding process. The welder must turn around the test piece to complete the welding of the bottom bead.

Tube plate vertical fixed overhead welding

This position is more difficult than nose welding. When welding, the molten pool must be kept as small as possible to prevent the loss of liquid metal and ensure the appearance of the weld seam.

(1) Assembly and tack welding: the requirements are the same as those of the plug-in tube sheet that needs to be welded through when the tube sheet rotates horizontally.

(2) The position of the test piece: the axis of the pipe is vertically downward, the orifice plate is on top, and the weld is in the overhead welding position. Fix the test piece in a place convenient for welding.

(3) Welding parameters, see Table -Torch Angle and Arc Centering Position for Overhead Welding.

Torch Angle and Arc Centering Position for Overhead Welding

(4) Welding points:

①Left welding method, the inclination angle of the welding torch, the wire feeding position and the arc centering position are shown in Figure-Angle of tig torch and centering position of arc in overhead welding.

Angle of tig torch and centering position of arc in overhead welding

② Ignite the arc on the positioning weld on the right side of the welding seam, preheat in situ, do not add wire temporarily, wait for the positioning weld and the grooves on both sides to melt and form a molten pool, then move the arc to the left side of the positioning weld, Go up the top arc, when you hear the breakdown sound, see the melting hole, and when the diameter of the melting hole is appropriate, start welding to the left and add welding wire. The welder can follow the position of the molten pool and continue to weld to the left.
③ When welding to both ends of the tack weld, stop adding wire and slow down the welding speed to ensure that both ends of the tack weld are penetrated and fused well.
④ When welding to the closed part of the bottom welding bead, the last joint must be connected.

Tube sheet horizontal fixed all position welding

  • Assembly and tack welding: the requirements are the same as those of the plug-in tube sheet that requires penetration when the tube sheet rotates horizontally.

  • Test piece position: the axis of the pipe is in the horizontal plane, the orifice plate is in the vertical plane, a positioning weld is at the 7 o’clock position of the clock, and the 0 o’clock position is directly above.

  • Welding parameters: see Table-Welding Parameters for Horizontal Fixed All-position Welding of Tube Sheet.

Welding Parameters for Horizontal Fixed All-position Welding of Tube Sheet
  • Welding points: Divide the tube plate weld into left and right halves, and weld from bottom to top.

  • ① The welding torch angle, wire feeding position and arc centering position are shown in Figure- Tig welding torch angle and arc centering position.
Tig welding torch angle and arc centering position

② Ignite the arc on the positioning weld at 7 o’clock of the clock for preheating, do not add wire temporarily, wait for the positioning weld and the grooves on both sides to melt, and after the molten pool is formed, the arc moves counterclockwise to the positioning weld At the right end, press the arc inward, hear the breakdown sound, see the melting hole, and when the diameter of the melting hole is suitable, start welding upwards counterclockwise, add welding wire, and weld from the 3 o’clock position to the positioning weld at the 11 o’clock position to the right of the stop. Be careful to connect the connectors.
③ Ignite the arc on the tack weld at 7 o’clock, preheat in situ, and wait for the tack weld and both sides of the groove to melt to form a molten pool. Hear the sound of breakdown, see the melting hole, and when the diameter of the melting hole is suitable, start to turn clockwise to formally weld and add wire, until the position of 11 o’clock on the clock, pay attention to connecting the joints, and complete the welding of the bottom bead.

Tube sheet 45°fixed all-position welding

  • Assembly and tack welding: the requirements are the same as those of a plug-in tube sheet that requires penetration when the tube sheet rotates horizontally.

  • The position of the test piece: fix the pipe axis and the horizontal plane at an angle of 45°, and the position is not allowed to be changed during the welding process. A tack weld is at 7 o’clock, and 0 o’clock is at the top.

  • Welding parameters: see Table-Welding parameters of 45° fixed all-position welding of tube-sheet

Welding parameters of 45° fixed all-position welding of tube-sheet
  • Welding points: The welding steps are exactly the same as the welding steps for horizontally fixing the plug-in tube sheet that needs to be penetrated. Note: During the welding process, the inclination angle of the welding torch, the wire feeding position and the centering position of the arc must be moved horizontally at the position of the welding pool, and their relative positions must be kept unchanged. The arc swings in the horizontal direction, so the fish scale pattern on the weld seam The direction is at an angle of 45° to the axis of the pipe.