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Surface Tension Transfer (abbreviated STT) is a welding method.

Definition
STT is a subset of gas metal arc welding and was developed by the Lincoln Electric Company.

How STT works
A background current between 50 and 100 amps maintains the arc and contributes to base metal heating. After the electrode initially shorts to the weld pool, the current is quickly reduced to ensure a solid short. PINCH CURRENT isthen applied to squeezemolten metal down into thepool while monitoring thenecking of the liquid bridgefrom electrical signals. Whenthe liquid bridge is about tobreak, the power sourcereacts by reducing the currentto about 45-50 amps. Immediately following thearcre-establishment, a PEAKCURRENT is applied toproduce plasma force pushingdown the weld pool to preventaccidental short and to heatthe puddle and the joint. Finally, exponential TAIL-OUTis adjusted to regulate overallheat input. BACKGROUNDCURRENT serves as a fineheat control.

Specifications

 * Open root - pipe and plate.
 * Stainless steel and other nickel alloys.
 * Thin gauge material
 * Silicon bronze
 * Galvanized steel

Weblinks
Lincoln Electric - Surface Tension Transfer (STT) Pipe Welding