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DEFINITION OF SPRAY TRANSFER

DEFINITION OF SPRAY TRANSFER. KELVIN LONGDEN PROCEDURES DEPARTMENT. PRESENTATION OVERVIEW. Modes of metal transfer Factor affecting metal transfer Spray transfer data Guidelines for spray transfer. MODES OF METAL TRANSFER. Short-Circuiting Transfer (GMAW-SC) Globular Transfer (GMAW-GL)

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DEFINITION OF SPRAY TRANSFER

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  1. DEFINITION OF SPRAY TRANSFER KELVIN LONGDEN PROCEDURES DEPARTMENT

  2. PRESENTATION OVERVIEW • Modes of metal transfer • Factor affecting metal transfer • Spray transfer data • Guidelines for spray transfer

  3. MODES OF METAL TRANSFER • Short-Circuiting Transfer (GMAW-SC) • Globular Transfer (GMAW-GL) • Spray Transfer (GMAW-SP) • Pulsed Transfer (GMAW-P)

  4. SHORT-CIRCUITING TRANSFER MODE (GMAW-SC) • Repetitive short-circuits (the arc is extinguished) between the wire and the welding puddle. • The parameters are at their lowest range for the GMAW process • Application in all positions for thin sheet and for the root pass welding of pipe. • Difficult to apply successfully to thicker materials because of the low values of amperage and voltage may result in fusion problems. • Not prequalified.

  5. GLOBULAR TRANSFER (GMAW-GL) • Droplet transfer is nonaxial with a diameter larger that the wire size. • In argon-rich gases this mode of metal transfer occurs with parameters below the spray transition but above that for short-circuiting. • Spatter can be excessive, rough-looking beads, glass-like silica island formations. • Limited use compared to short-circuit and spray transfer modes. • Not considered prequalified.

  6. SPRAY TRANSFER (GMAW-SP) • Molten metal is transferred across the arc in a continuous stream of fine droplets. • The arc is stable. • Current and voltage above critical transition values and the use of argon-rich gas mixtures. • High deposition rates and desirable fusion and penetration characteristics. • Considered prequalified.

  7. PULSED TRANSFER (GMAW-P) • Periodic surges or pulses of current above the transition value for spray transfer which causes the detachment of droplets. • Between the current pulses, the arc is maintained by a relatively low background current. • Average current can be well below the transition value - weld appearance resembling that obtained in spray transfer. • Not prequalified

  8. METAL TRANSFER ACROSS THE ARC IN GMAW • The mode of the weld metal transfer is determined by the following factors: • Welding current • Electrode size • Electrode composition • Electrode stick out • Shielding gas

  9. GAS MIXTURES FOR GMAW FOR CARBON STEELS • The gas mixtures commonly used for gas metal arc welding of carbon steel are: • Argon / Oxygen - 98% Ar / 2% O2 , 95%Ar / 5% O2 • Argon / Carbon dioxide - 90% Ar / 10% CO2 , 85% Ar / 15% CO2 , 75% Ar / 25% CO2 • Argon / Carbon dioxide / oxygen - 91% Ar / 5% CO2 / 4% O2, 90% Ar / 8% CO2 / 2% O2,

  10. Group A - Lows Energy Mixes Argon + 1-10% oxygen Argon + 2-10% CO2 Argon + 1-10% oxygen + 2-10% CO2 Group B – Medium Energy Mixes Argon + 14-20% CO2 Argon + 1-5% oxygen + 14-20% CO2 GMAW Gases That Produce Similar Results

  11. Spray Transfer Guidelines • Shielding Gas – Argon rich - maximum 20% CO2 • Welding parameters in accordance with graphs • Look and sound of the arc

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