Lincoln Electric IM901-A manual Constant Current Wire Welding, Figure b-3

Page 23

b-8

OPERATION

b-8

 

 

 

CONSTANT CURRENT WIRE WELDING

(See Figure B.3)

Most semiautomatic welding processes perform better using constant voltage power sources.

Welding codes usually do not address the power source selection or specifically, whether the welding process is to be operated in the constant voltage or constant current mode. Instead, codes typically speci- fy limitations on the current, voltage, heat input and preheat temperature based on the material to be welded. The intention is to assure that proper weld material properties will develop.

Welding is sometimes performed using constant cur- rent power sources. The operation can be more con- venient because it may allow the use of an existing stick (SMAW) power source and the power source can be placed at a distant location without any provi- sion for adjusting the output settings.

For constant current operation, the power source is set to deliver the specified current. The power source regulates this current regardless of changes in the welding circuit, including cable length, electrode diam- eter, wire feed speed, contact tip to work distance, etc.

Changes in the wire feed speed (WFS) or contact tip to work distance (CTWD) affect the arc voltage when constant current power sources are used. Lowering the wire feed speed raises the voltage, raising the wire feed speed lowers the voltage. Lengthening the contact tip to work distance raises the voltage, short- ening the contact tip to work distance lowers the volt- age.

If the contact tip to work distance is properly main- tained, a satisfactory operating voltage range may be achieved, and a sound weld may result. However, when a welder uses a longer contact tip to work dis- tance, an arc-sensing wire feeder compensates by increasing the wire feed speed to regulate the voltage. Even if the voltage and current remain unchanged, the increased wire feed speed may result in a deposition rate well beyond the specified range of the electrode. Under these conditions, the specified weld metal prop- erties may not be achieved.

Constant voltage power sources deliver large current surges to stabilize the arc when the electrode is short- ed or the arc length is very short. However, a constant current power source does not provide such a response to stabilize the arc. It may be difficult to achieve required weld metal properties, or to achieve the required quality of welds needed to pass nonde- structive tests, when such welds are made under con- stant current operation.

For these reasons, Lincoln Electric does NOT recom- mend constant current semiautomatic welding for applications which need to meet specified weld metal chemical or mechanical property requirements or weld quality requirements.

Constant Current

Power Source

+

-

FIGURE b-3

Current

Wire

Feeder

CTWD

WFS

Current

LN-25™ PRO ACROSS THE ARC MODEL

Image 23
Contents LN-25PRO Safety Depends on YouCalifornia Proposition 65 Warnings SafetyElectric Shock can kill Iii Welding and Cutting Sparks can Cause fire or explosionPrécautions DE Sûreté On-Line Product Registration Please Examine Carton and Equipment For Damage ImmediatelyTAbLE of Contents Installation Weld CAbLE SIzE Safety PrecautionsLocation High Frequency ProtectionShielding GAS Connection 3INSTALLATIONA-3Function Pin Wiring CAbLE ConnectionsChanging the GUN Receiver bUSHING Procedure to Install Drive Rolls and Wire GuidesFe, CrNi Pressure ARM AdjustmentLoading Spools of Wire GUN ConnectionFigure A.5 Across the ARC SET-UPSFigure A.7 Figure A.9 8INSTALLATIONA-8Operation Process Limitations Recommended Power SourcesDefinition of Welding Terms Recommended ProcessesAnalog Voltmeter Case Front Controls See Figure b.1Description Extra Torque Wire Feed Speed KNObWire Feed Speed, CV Operation Minimum Arc Volts Maximum WFSPolarity LED Figure b.2 Internal ControlsCold Feed PUSHbUTTON CV/CC SwitchInternal Controls Description Figure b-3 Constant Current Wire WeldingRear Controls ItemdescriptionScfh POWER-UP SequenceGAS Purge PUSHbUTTON Flow MeterDrive Roll Kits AccessoriesFactory Installed Equipment Wire TypeAccessories Kit Accessories K1500-5 Gun Receiver Bushing compatible Installation of the K590-6 Water Cooling KIT CALIbRATION Specification MaintenanceRoutine Maintenance Periodic MaintenanceBOARD Wire Feed Speed ValidationTo change the wire feed speed calibration See Figure D.2 Model gearingElectric Shock can kill TROUbLESHOOTINGPOSSIbLE PRObLEMSSymptoms Fault Code Description Possible AdjustmentsOutput Problems TROUbLESHOOTING Model DiagramsLN-25 PRO Across the ARC Diagrams Dimension Print LN-25 PRO Across the ARC Model Precaucion Warnung