Welding defects, soldering and brazing

1. CRAFTED BY:
RAMESH KUMAR A
ASSISTANT PROFESSOR
SONA COLLEGE OF TECHNOLOGY
SALEM
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2. WELDING DEFECTS
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3. • A GOOD WELD OR WELD BEAD SHOULD
HAVE UNIFORMLY RIPPLED WELD
SURFACE WITH EVEN COUNTER AND
EVEN WIDTH OF THE BEAD
• BEAD SHOULD BE STRAIGHT
• DIVIDED INTO TWO CATEGORIES:
• EXTERNAL WELD DEFECT
• INCORRECT PROFILE
• CRACKS
• CRATER
• SPATTER
• EDGE OF PLATE MELTED OFF
• SURFACE POROSITY
• INCOMPLETE FILLED GROOVES
• DISTORTION
• INTERNAL WELD DEFECT
• BLOW HOLES AND INTERNAL
POROSITY
• CRACKS
• INCLUSIONS
• LACK OF FUSION
• INCOMPLETE PENETRATION
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4. EXTERNAL WELD DEFECTS
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5. • OVERLAP:
• IMPERFECTION AT THE TOE OR ROOT
OF A WELD BEAD
• CAUSED DUE TO THE FLOW OF METAL
ON THE SURFACE OF THE PARENT
METAL WITHOUT FUSION WITH THE
LATTER
• SLOW RATE OF WELDING
• INCORRECT SIZE AND ANGLE OF
ELECTRODE
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6. • UNDERCUT:
• GROOVE CUT INTO THE BASE METAL
ALONG THE TOE OF THE WELD
• EXCESSIVE ARC LENGTH, CURRENT AND
SPEED OF WELDING
• IMPROPER MANIPULATION OF
ELECTRODE AND DAMPNESS IN
ELECTRODE AND ARC BLOW ARE ALSO
THE FACTORS CONTRIBUTING TO
UNDERCUTTING
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7. • EXCESSIVE PENETRATION BEAD:
• INCORRECT JOINT PREPARATION
• HIGH CURRENT AND LARGER ARC
LENGTH
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8. • EXCESSIVE CONVEXITY:
• EXCESSIVE CURRENT AND IMPROPER
WELDING
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9. • EXCESSIVE CONCAVITY:
• EXCESSIVE CURRENT AND IMPROPER
WELDING
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10. • DISCONTINUITY GENERATED DUE TO
EITHER TEARING OR FRACTURE OF THE
METAL
• TEARING – DURING SOLIDIFICATION
FROM MOLTEN STATE
• FRACTURE – UNEVEN COOLING OF
WELD BESIDES IMPROPER WELDING
TECHNIQUE
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11. • FORMED AT THE END OF A WELD RUN
AND IS DUE TO IMPROPER WELDING
TECHNIQUE
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12. • METAL PARTICLES EXPELLED OUT FROM THE
MOLTEN METAL POOL UNDER THE EFFECT
OF HARSH ARC DURING WELDING
• SMALL TINY BALLS ALONG THE WELD BEAD
• EXCESSIVE CURRENT, A LONGER ARC AND
DAMP ELECTRODE CAUSE SPATTER
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13. • WRONG ELECTRODE, LONGER ARC,
IMPROPER WELDING CONDITIONS AND
TECHNIQUE
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14. • CHANGE IN THE SHAPE OF THE WORK
PIECE AFTER WELDING
• TEMPERATURE GRADIENTS THAT EXIT IN
DIFFERENT SECTIONS OF THE WORK PIECE
• WELDING FIXTURES AND PROPER
SEQUENCE OF WELDING MAY HELP IN
AVOIDING DISTORTION
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15. INTERNAL WELD DEFECTS
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16. • ATMOSPHERIC GASES THAT GET DISSOLVED
IN MOLTEN WELD POOL TRY TO GET
RELEASED DURING SOLIDIFICATION AND
COOLING OF THE WELD
• CROWDED GROUP OF GAS PORES IN THE
WELD IS CALLED POROSITY
• LARGE GAS CAVITY EXCEEDING 1.5MM IN
DIA IS CALLED A BLOW HOLE
• CAUSES:
• WRONG USE OF ELECTRODES
• EXCESSIVE CURRENT
• LONGER ARC
• POOR WELD ABILITY OF PARENT METAL
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17. • SLAG (OXIDES), NITRIDES AND OTHER
FOREIGN MATTER ENTRAPPED WITHIN
THE WELD
• CAUSES:
• INADEQUATE CLEANING OF EACH
WELD BEAD DEPOSITED DURING
MULTIPLE PASS WELDING
• IMPROPER AND DAMAGED FLUX
COATING ON THE ELECTRODE
• LONGER ARC
• IMPROPER JOINT PREPARATION
• IMPROPER WELDING TECHNIQUE
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18. • LACK OF UNION OF THE DEPOSITED
WELD METAL WITH THE PARENT METAL
• CAUSES:
• FAILURE IN RAISING THE TEMPERATURE
OF PARENT METAL TO THE MELTING
POINT
• FAILURE TO DISSOLVE DURING WELDING
THE OXIDES AND OTHER FOREIGN
MATERIAL PRESENT ON THE WORK
PIECE SURFACES
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19. • INCAPABILITY OF WELDING ARC TO REACH
OR PENETRATE A NARROW CORNER
• CAUSES:
• FAILURE OF ROOT FACE OF BUTT WELD
TO REACH FUSION TEMPERATURE FOR
ITS ENTIRE DEPTH
• FAILURE OF WELD METAL TO REACH THE
ROOT OF A FILLET WELD LEAVING A
VOID
• USE OF OVERSIZED ELECTRODE
• HIGHER WELDING SPEED
• LESS CURRENT
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20. SOLDERING AND BRAZING
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21. • SOLDERING IS A METAL JOINING PROCESS
WITH THE HELP OF A LOW MELTING POINT
METAL BY THE USE OF HEAT AND FILLER
MATERIAL
• MELTING POINT OF FILLER METAL IS LESS
THAN 427°C
• SOLDERING IRON:
• TOOL NORMALLY USED FOR APPLYING HEAT
TO TWO OR MORE ADJOINING METAL PARTS
SUCH THAT SOLDER MAY MELT AND FLOW
BETWEEN THOSE PARTS, BINDING THEM
SECURELY AND CONDUCTIVELY
• SOLDER:
• FUSIBLE METAL ALLOY WITH A MELTING
POINT RANGE OF 90 TO 450°C
• APPLICATIONS:
• ELECTRONICS, AUTOMOBILE PARTS, REPAIR
UTENSILS, ETC.,
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22. • JOINING TWO SIMILAR OR DISSIMILAR
MATERIALS BY ADDITION OF SPECIAL FILLER
METHOD
• MUCH STRONGER JOINT THAN SOLDERING
BUT REQUIRES GREATER HEAT WHICH
CANNOT BE OBTAINED FROM COPPER IN
SOFT SOLDERING
• NON FERROUS FILLER METAL HAVING ITS
MELTING POINT ABOVE 427°C
• APPLICATIONS:
• ELECTRICAL PARTS, REPAIR OF CASTINGS,
ASSEMBLY OF PIPES TO FITTINGS, HEAT
EXCHANGERS, ETC.,
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