Causes of Porosity
Possible Solutions
BASE METAL CONTAMINATION
Impurities on base metal
- Remove contamination; clean surfaces
- Use of specific wire/gas mix for specific types of impurities
FILLER METAL CONTAMINATION
Impurities on filler metal (wire)
- Replace wire
- Install wire-cleaning system
- Prevent industrial dust/dirt/grit from contaminating wire during storage or use
- Prevent build-up of aluminum oxide on exposed aluminum wire surface by using up quickly
- Remove wire from wire drive unit and store in a sealed plastic bag when not in use for long periods
ATMOSPHERIC CONTAMINATION
Drafts, wind, fans, etc.
- Protect weld from drafts (curtains/screens)
- Use tapered or bottleneck gas nozzles when drafts cannot be avoided
GAS MIXING APPARATUS
- Too high a gas flow, causing turbulence, and/or sucking air at hose connections; creating the venturi effect at end of gas nozzle
- Too low a gas flow, causing insufficient gas coverage
- Damaged or kinked gas lines
- Too high an oxygen content
- Leaks in gas distribution system
- Other impurities in gas - moisture, etc.
- Inconsistent gas flow (cfh) at the torch connection
- a. Reduce gas flow
b. Tighten all hose connection points - Increase gas flow
- Repair or replace
- Adjust mixer
- Repair leaks
- Overhaul system; fit filters and/or dryers
- Regulate pressure into flow meter for consistent cfh delivery of gas
GAS TURBULENCE
- Excessive spatter build-up in gas nozzle and on current tip
- Nozzle damage, causing uneven gas coverage
- Torch gas ports clogged or deformed
- Super-heated nozzle, causing shielding gas to expand rapidly and create return effect at end of nozzle
- Gas diffuser/nozzle insulator missing
- Too high a gas flow causing the venturi effect
- Clean nozzle and tip regularly; spray with anti-spatter fluid
- Replace nozzle
- Clean or replace
- Check duty cycle rating of torch
- Replace
- Reduce gas flow
WELDING PARAMETERS, ETC.
- Too long a wire stick-out; gas nozzle too far from weld puddle
- Bad torch position - too sharp a torch incline causing the venturi effect at the end of the nozzle leading to atmospheric contamination
- Excessively wide weld pool for nozzle I.D.
- Arc voltage too high
- Too high a travel speed
- Use longer nozzle or adjust stick-out (3/8" minimum or 15 times wire diameter)
- Correct torch angle
- Width of the weld pool should be 1.3 times the nozzle I.D.; use suitable wider gas nozzle
- Reduce voltage
- Reduce speed