allaboutmyinterest: July 2009

Monday, July 6, 2009

W E L D E R ‘ SH A N D B O O K

TABLE OF CONTENTS

I. WELD DEFECTS, CAUSES AND CURE

A. Weld Spatter 3 –4

B. Overlap 4

C. Underfill 4

D. Arc Strikes 5

E. Undercut 5

F. Porosity 6 – 7

G. Slag Inclusion 7 – 8

H. Burn-Through 8

I. Internal Concavity 9

J. Incomplete Fusion 9 – 10

K. Incomplete Root Penetration 11

L. Excessive Reinforcement 11 – 12

M. Excessive Penetration 12

N. Cracking 13 – 14

O. Tungsten Inclusion 15

P. Insufficient Leg Size 15

II. ACCEPTABLE AND UNACCEPTABLE WELD PROFILES

A. Desirable Fillet Weld Profiles 16

B. Acceptable Fillet Weld Profiles 16

C. Unacceptable Fillet Weld Profiles 17

D. Acceptable Groove Weld Profile in Butt Joint 17

E. Unacceptable Groove Weld Profiles in Butt Joints 18

F. Tubular T, K, & Y Connections 18

1. Figure 3.8 – Standard Flat Profiles 19

2. Figure 3.9 – Profile with Toe Fillets 20

3. Figure 3.10 – Concave Improved Profile 21

4. Table 3.6 – Pre-qualified Joint Dimensions 22

III. WELDING POSITIONS

Plate
1. Groove 23 - 24
2. Fillet 24 – 25

TABLE OF CONTENTS (continuation…)

Pipe
1. Groove 26 - 28
2. Fillet 28 – 30

IV. HANDLING, STORAGE AND TREATMENT OF WELDING

CONSUMABLES

A. SMAW Consumables Other Than Low Hydrogen 30

B. Low Hydrogen Consumables 31

C. SAW FLUX 32

V. PREHEAT AND INTERPASS TEMPERATURE 33

VI. WELDMENT DISTORTION CONTROL 34 – 36

VII. BASIC MECHANICAL TESTINGS AND THE FACTORS

AFFECTING THE TEST RESULTS 36 - 37

VIII. APPROVED WPS

Structural Fabrication
Piping Fabrication

WELD DEFECTS, CAUSES AND CURE

Weld Spatter

Sketch:

Causes:

Current too high.
Wrong Polarity.
Arc length too long.
Presence of arc blow.
Wet electrodes

Cure:

Try lowering the current. Be sure the current is within the range for the type and diameter of the electrode.
Be sure the polarity is correct for the electrode type.
Try a shorter arc length.
If the molten metal is running in front of the arc, change the electrode angle.
Look for arc blow conditions, and control it as follows;
1. Change to AC welding.
2. Use lower current and smaller electrodes.
3. Try reducing the arc length.
4. Weld in the direction of the blow.
5. Change the electrical path to work by:
  1. Shifting the work connection to the other end of the work or making connections in several locations.
  2. Welding toward heavy tacks, finished welds, or back-stepping on long welds.
  3. Using run-out tabs, adding steel blocks to change work current path, or tacking small plates across the seam at weld ends.
Observe the proper handling of welding electrode.

Overlap
Sketch:

Causes:
1. Welding current too low and travel speed too slow.
2. Contaminated base metal.
Cure:
1. Increase the welding current and the travel speed.
2. Clean the joint properly.

C. Underfill

Sketch:

Causes:

Failure to fill the joint completely prior to the deposition of the cap pass.

Cure:

Fill the joint up to the base metal thickness or at least 1mm below prior to the deposition of cap pass.

Arc Strikes

Sketch:

Cause:

Carelessness of the welder.

Cure:

Properly secure all ground connections, welding cables and electrode handle/gun.

Undercut
Sketch:

Causes:
1. Current too high.
2. Wrong electrode angle.
Cure:
1. Decrease the current and the travel speed.
2. Change electrode angle so the arc force holds the metal in the corners. Use a uniform travel speed, and avoid excessive weaving.
Porosity
Sketch:

Cluster Porosity

Causes:
1. Unstable or poor shielding.
2. Improper initiation or termination of weld.
Cure:
1. Keep the arc length as close as possible.
2. For the initiation of the arc, use the back-stepping method to re-melt the cold start area and float the gas out of the bead. Whenever possible, use tab plates on each end of the joint.
Piping/Wormhole Porosity

Causes:
1. Contaminated base metal.
2. Poor or unstable shielding i.e. poor moisture and wind protection, too long arc length, unstable electrode manipulation.
3. The electrodes absorbed moisture.
Cure:
1. Observe proper cleaning of the joint for welding.
2. Keep the arc length as close as possible.
3. Avoid too wide weaving.
4. Install proper wind protection on the work area.
5. Observe the proper handling of welding electrode.
6. For GTAW process, increase the shielding gas flow rate as required. Also, check the gas hose and connections for possible leakage.

Slag Inclusion
Sketch:

Causes:
1. Poor inter-pass cleaning.
2. Current too low.
3. Unstable electrode manipulation
4. Groove angle too narrow.
5. Weld beads too convex.
Cure:
1. Observe proper inter-pass cleaning.
2. Increase the current.
3. Correct the too convex bead by grinding.

Burn-Through
Sketch:

Causes:
1. Too wide root gap, and too short root face.
Cure:
1. Correct the joint preparation.
2. Decrease the current, and increase the welding speed.

Internal Concavity
Sketch:

Causes:

Higher current.
Arc length too long.
Root gap too wide, and groove angle too narrow.

Cure:

Decrease the current, increase the welding speed.
Make arc length as close as possible.
Correct the joint preparation.

Incomplete Fusion

Causes:
1. Groove angle too narrow.
2. Welding speed too high.
3. Weld beads too irregular.

Cure:

Increase the current and decrease the welding speed.
Correct the joint preparation.
Correct the irregular bead by grinding.

Sketch:

Incomplete Root Penetration
Sketch:

Causes:
1. Current too low.
2. Arc length too long.
3. Improper joint preparation i.e. root face too long, root gap too narrow, groove angle too narrow.
Cure:
1. Increase the current.
2. Make arc length as short as possible.
3. Correct the joint preparation.

Excessive Reinforcement

Causes:
1. Welding speed too slow.
2. Improper welding technique.
Cure:
1. Increase the welding speed.
2. Grind the excess thickness of the last layer to base metal prior to deposition of cap pass.
3. Use the proper size of welding electrode.
Sketch:
Excessive Penetration

Sketch:

Causes:

Root gap too wide, and root face too short.
Current too high.

Cure:

Correct the joint preparation.
Decrease the current, and increase the travel speed.

Cracking
Sketch:

Cold Cracks (Toe/Underbead Cracks)

Causes:
1. Rapid cooling from the welding temperature of a relatively high carbon or alloy content steel.
2. Hydrogen pick-up during welding.
3. The joint is so restrained.

Cure:

Use low hydrogen welding electrodes.
1. Observe proper handling of electrodes, and cleanliness of the joint for welding.
Preheat the joint to reduce the cooling rate, and maintain the inter-pass temperature.
Reduce penetration by using low currents, small electrodes. This reduces the amount of alloy added to the weld from melted base metal.
For GTAW process, check the gas hose and connections for possible leaks. Verify also the purity of shielding gas and change with a higher grade if found necessary.

Hot Cracks (Crater/Throat/Root Cracks)
Causes:
1. Wrong welding technique.
Cure:
1. To control crater cracking, fill each crater before breaking the arc.
2. On multiple pass or fillet welds, be sure the first bead is of sufficient size and of flat or convex shape to resist cracking until the later beads can be added for support. To increase bead size, use slower travel speed, a short arc, or weld
  5^O uphill. Always continue welding while the plate is hot.
3. For rigid joints, whenever possible, weld towards the unrestrained end. Leave at least 1/32" gap between plates for free shrinkage as the weld cools.

Tungsten Inclusion (GTAW Process)
Sketch:

Cause:
1. Accidental touching of the tungsten electrode to the weld puddle.

Cure:

Avoid contact of the tungsten electrode with the molten weld puddle.

Insufficient Leg Size (Fillet Welds)

Sketch:

Cause:

Incorrect electrode angle.
Improper welding technique.

Cure:

Use the correct electrode angle.
For multi-pass fillet welds, follow the proper weld pass sequence to attain the required leg size.
Use the correct diameter of the electrode for each pass.

ACCEPTABLE AND UNACCEPTABLE WELD PROFILES

DESIRABLE FILLET WELD PROFILES

Size Size

Size Size C

ACCEPTABLE FILLET WELD PROFILES

Size Size

C C

Size Size

Note: Convexity "C" of a weld or individual surface bead with dimension "W" shall not exceed the following value;

Width of Weld Face or

Individual Surface Bead, W

Maximum Convexity, C

W < 5/16" (8mm)

W > 5/16" (8mm) to W < 1 IN. (25mm)

W > 1" (25mm)

1/16" (2mm)

1/8" (3mm)

3/16" (5mm)

UNACCEPTABLE FILLET WELD PROFILES

SIZE SIZE SIZE

INSUFFICIENT EXCESSIVE EXCESSIVE

THROAT CONVEXITY UNDERCUT

SIZE SIZE SIZE

OVERLAP INSUFFICIENT INCOMPLETE

LEG FUSION

ACCEPTABLE GROOVE WELD PROFILE IN BUTT JOINT

BUTT JOINT – EQUAL THICKNESS PLATE

BUTT JOINT (TRANSITION) – UNEQUAL THICKNESS PLATE

Note: Reinforcement "R" shall not exceed 1/8 in. (3 mm).

UNACCEPTABLE GROOVE WELD PROFILES IN BUTT JOINTS

EXCESSIVE INSUFFICIENT

CONVEXITY THROAT

EXCESSIVE OVERLAP

UNDERCUT

TUBULAR T, K & Y CONNECTIONS

Note:

See Table 3.6 for dimensions t_w, L, R, W, w, f.
Min. standard flat weld profile as shown by solid line.
A concave profile as shown by dashed lines, as applicable.

NOTE:

(1) See Table 3.6 for dimensions t_w, L, R, W, w, f.

(2) Min. standard flat weld profile as shown by solid line.

(3) A concave profile as shown by dashed lines, as applicable.

Note:

(1) See Table 3.6 for dimensions t_w, L, R, W, w, f.

WELDING POSITIONS

PLATE
1. Groove
  1. Flat Position (1G)

Plates Horizontal

Horizontal Posiiton (2G)

Plates vertical; axis of weld horizontal

Vertical Position (3G)

Plates vertical; axis of weld vertical

Overhead Position (4G)

Plates Horizontal

Fillet

Flat Position (1F)

Horizontal Position (2F)

Note: One plate must be horizontal

Vertical Position (3F)

Overhead Position (4F)

Note: One plate must be horizontal.

PIPE

Groove
1. 1G Rotated – pipe horizontal and rotated, weld flat (+15^O), deposit filler metal at or near the top.
Pipe horizontal and rotated. Weld flat (+15^O). Deposit filler metal at or near the top.
1. 2G – pipe or tube vertical and not rotated during welding, weld horizontal (+15^O).
Pipe or tube vertical and not rotated during welding. Weld horizontal (+15^O).
1. 5G – pipe or tube horizontal fixed (+15^O) and not rotated during welding. Weld flat, vertical and overhead.
  
  Pipe or tube horizontal fixed (+15^OC) and not rotated during welding. Weld flat, vertical and overhead.
1. 6G - pipe inclination fixed (45^O
  +5^O) and not rotated during welding.
  
  Pipe inclination fixed (45^O
  +5^O) and not rotated during welding.
1. 6GR – test position for T, K, Y connections. Pipe inclination fixed (45^O
  +5^O), with restriction ring and not rotated during welding.
Fillet

1F ROTATED – flat position

2F FIXED - horizontal position

2F ROTATED – horizontal position

4F FIXED - overhead position

5F FIXED – multiple position

HANDLING, STORAGE AND TREATMENT OF WELDING CONSUMABLES

SMAW WELDING CONSUMABLES OTHER THAN LOW HYDROGEN

CLASSIFICATION

TRADE NAME

BAKE - OUT

HANDLING

E7010

LINCOLN SHIELD ARC HYP

NONE

SEE NOTE "N1"

E6027

CHOSUN CF 120

ESAB E6027

NONE

SEE NOTE "N1"

E2XX-15 and

E3XX-16*

ALL

NONE

SEE NOTE "N1"

ECuNi

ALL

NONE

SEE NOTE "N1)

Note:

N1 – must be stored in a clean, dry area.

* - Arosta brand consumables requires baking when not packaged in hermetically sealed containers. See Item 2 below.

LOW HYDROGEN WELDING CONSUMABLES

Note:

Applicable for the following electrodes:
1. E316 –1 (Arosta), when not from hermetically sealed container.
2. E347 (Arosta), when not from hermetically sealed container.
3. E7016 (Kobelco LB-52U)
4. E7018-1 (Lincoln LH75)
5. E9018 (Tech Rod)
6. E11018 (Tech Rod)
Undamaged electrodes = no dirt, moisture, oil and the flux remains intact.

SAW FLUX

PREHEAT AND INTERPASS TEMPERATURE

Purpose of Preheating
1. To slow down the cooling rate, and allow more time for hydrogen, that is present, to diffuse away from the weld and adjacent plate.
2. To reduce shrinkage stresses in the weld and adjacent base metal, especially withhighly restrained joints.
3. To slow down the cooling rate through the critical temperature range (1600^OF to 1330^OF), preventing excessive hardening and lowering ductility of both weld and heat affected zone.
Problems Encountered When Proper Preheating is not Observed
1. Weld Cracking
Required Preheat and Interpass Temperature
1. As specified in the approved WPS.
Required Preheat Areas
1. Min. 3 inches (75mm) in all directions from the point of welding.
Method of Preheating
1. Torch Heating
2. Ceramic Heating Element
Means of Monitoring the Temperatures
1. Temperature Indicating Crayons
2. Portable Pyrometers
3. Thermocouples
1. WELDMENT DISTORTION CONTROL

Avoid overwelding.

Use intermittent welding.

Use as few weld passes as possible.

Good

Poor

Use backstep welding.

Prebending the parts to be welded

Weld

Wedge

Clamps along edges

Plan the welding sequence.

Minimize welding time. Use the welding process and electrodes that able to finish the weld quickly.

BASIC MECHANICAL TESTING AND THE FACTORS AFFECTING THE TEST RESULTS

Tensile Test – the testing used to determine the strength of the weldment to resist pulling forces.
Factors affecting the test results:
1. welding electrodes – the tensile strength of the welding electrodes must be greater than the min. tensile strength of the base metal
Bend Test – the testing used to determine the strength of the weldment to resist bending forces.
Factors affecting the test results:
1. Weld discontinuities such as inclusions, porosities, incomplete fusion, etc. that may cause openings beyond the acceptance criteria after bending.
  (See Section I for the causes of weld defects.)
Impact Test – the testing used to determine the strength of the weldment to absorb the energy of the load rapidly applied to the member.
Factors affecting the test results:
1. Weaving of electrodes beyond the maximum requirements.
2. Interpass temperatures beyond the maximum allowable.
Hardness Test – the testing used to determine the property of the weldment to resist indentation or penetration.
Factors affecting the test results:
1. Not enough preheat temperature.

Macro-etch Test – the testing used to verify the soundness of weld.
Factors affecting the test results:
1. Weld discontinuities such as lack of fusion, inclusions, porosities, etc. that beyond the acceptance criteria.
  (See Section I for the causes of weld defects.)

WELD DEFECTS, CAUSES AND CURE

I. SMAW PROCESS

Weld Spatter
Sketch:

Causes:
1. Current too high.
2. Wrong Polarity.
3. Arc length too long.
4. Presence of arc blow.
5. Wet electrodes
Cure:
1. Try lowering the current. Be sure the current is within the range for the type and diameter of the electrode.
2. Be sure the polarity is correct for the electrode type.
3. Try a shorter arc length.
4. If the molten metal is running in front of the arc, change the electrode angle.
5. Look for arc blow conditions, and control it as follows;
  1. Change to AC welding.
  2. Use lower current and smaller electrodes.
  3. Try reducing the arc length.
  4. Weld in the direction of the blow.

Change the electrical path to work by:
1. Shifting the work connection to the other end of the work or making connections in several locations.
2. Welding toward heavy tacks, finished welds, or back-stepping on long welds.
3. Using run-out tabs, adding steel blocks to change work current path, or tacking small plates across the seam at weld ends.

Be sure the electrode is not wet.

Underfill
Sketch:

Cause:
1. Improper welding technique.
Cure:
1. Ensure that the fill passes are enough prior to the deposition of cap pass.
Overlap
Sketch:

Cause:
1. Current too low.
2. Improper preparation of the joint.
Cure:
1. Use higher current.

Undercut
Sketch:

Causes:
1. Current too high.
2. Improper welding technique.
Cure:
1. Reduce current, travel speed, or electrode diameter until you have a puddle size you can handle.
2. Change electrode angle so the arc force holds the metal in the corners. Use a uniform travel speed and avoid excessive weaving.
Porosity
Sketch:

Cluster Porosity

Causes:

Unstable or poor shielding.
Improper initiation or termination of weld.

Cure:

Keep the arc length as close as possible.
For the initiation of the arc, use the backstepping method to re-melt the cold start area and float the gas out of the bead. Whenever possible, use tab plates on each end of the joint.

Piping/Wormhole Porosity

Causes:

Presence of foreign materials contaminating the weld metal i.e. moisture, rust, paint,oil, etc.
Poor or unstable shielding i.e. poor moisture and wind protection, too long arc length, unstable electrode manipulation.
Electrode

Cure:

Remove scale, rust, paint, moisture or dirt from the joint.
For the initiation of the arc, use the back-stepping method to re-melt the cold start area and float the gas out of the bead. Whenever possible, use tab plates on each end of the joint.
Keep the puddle molten for a longer time. This allows the gases to boil out before it freezes.
The steel may have a low carbon or manganese content or a high sulfur (free machining steel) or phosphorous content. Weld these steels with a low hydrogen electrode. Minimize admixture of base metal into weld metal by using low currents and fast travel speeds for less penetration.
Try using a shorter arc length. A light drag technique is recommended for low hydrogen electrodes.

Slag Inclusion
Sketch:

Causes:
1. Poor interpass cleaning.
2. Current too low.
3. Unstable electrode manipulation
4. Groove angle too narrow.
5. Weld bead too convex.

Cure:

Observe proper interpass cleaning.
Increase the current.
Correct the too convex bead by grinding.

Incomplete Fusion
Sketch:

Causes:
1. Welding speed too high.
2. Groove angle too narrow.
3. Too irregular beads.
Cure:
1. Increase the current and decrease the welding speed.
2. Observe proper joint preparation.
3. Correct the irregular bead by grinding.
Burn-Through
Sketch:

Causes:
1. Too wide root gap, and too short root face.
Cure:
1. Correct the joint preparation.
2. Decrease the current, and increase the welding speed.
Internal Concavity
Sketch:

Cause:
1. Higher current.
2. Arc length too long.
3. Root gap too wide, groove angle too narrow.
Cure:
1. Decrease the current.
2. Put the electrode deeper to the groove.
3. Correct the joint preparation.
Incomplete Root Penetration
Sketch:

Causes:
1. Current too low.
2. Arc length too long.
3. Improper joint preparation i.e. root face too long, root gap too narrow, groove angle too narrow.
Cure:
1. Increase the current.
2. Put the electrode deeper to the groove.
3. Correct the joint preparation.

Cracking
Sketch:

Cold Cracks (Toe/Underbead Cracks)

Causes:
1. Rapid cooling from the welding temperature of a relatively high carbon or alloy content steel.
2. Hydrogen pick-up during welding.
3. The joint is so restrained.
Cure:
1. Use low hydrogen welding electrodes.
  1. Observe proper handling of electrodes, and cleanliness of the joint for welding.
2. Preheat the joint to reduce the cooling rate. Use high preheats for heavier plate and rigid joints.
3. Reduce penetration by using low currents, small electrodes. This reduces the amount of alloy added to the weld from melted base metal.
Hot Cracks (Crater/Throat/Root Cracks)

Causes:
1. Wrong welding technique.
Cure:
1. To control crater cracking, fill each crater before breaking the arc.
2. On multiple pass or fillet welds, be sure the first bead is of sufficient size and of flat or convex shape to resist cracking until the later beads can be added for support. To increase bead size, use slower travel speed, a short arc, or weld
  5^O uphill. Always continue welding while the plate is hot.
3. For rigid joints, whenever possible, weld towards the unrestrained end. Leave at least 1/32" gap between plates for free shrinkage as the weld cools.

II. GTAW PROCESS

Incomplete Fusion
Sketch:

Cause:
1. Insufficient application of heat to all faces of the joint.
Cure:
1. Use higher current and decrease the travel speed.
Tungsten Inclusion
Sketch:

Cause:
1. Accidental touching of the tungsten electrode to the weld puddle.

Cure:

Avoid contact of the tungsten electrode with the molten weld puddle.

Porosity
Sketch:

Cause:
1. Impurities on the surface or within the base metal.
2. Inadequate shielding gas.
Cure:
1. Cleaning of the joint prior to welding.
2. Increase the shielding gas flow rate as required.
3. Check the shielding gas hose and connections for possible leaks.
Cracks
Sketch:
1. Hot Cracks (Longitudinal/Crater Cracks)
  Cause:
  1. High travel speed.
  2. Improper control of the welding current.
  Cure:
  1. Observe proper travel speed.
  2. Trail the bead up to the bevel of the groove to leave no crater.
2. Cold Cracks
Cause:
1. Water leaks into the shielding gas.
Cure:
1. Check the gas hose and connections for leaks
2. Verify the purity of the shielding gas and change with the higher grade when necessary.

ACCEPTABLE GROOVE WELD PROFILES IN BUTT JOINTS

(a) Butt Joint - Equal Thickness

(b) Butt Joint (Transition) – Unequal Thickness

Note: Reinforcement R shall not exceed 1/8" (3mm)

UNACCEPTABLE GROOVE WELD PROFILES IN BUTT JOINTS

DESIRABLE FILLET WELD PROFILES