Narrow Gap Welding Process

Tandem Submerged Arc

The Lincoln Electric Narrow Gap Welding Process is designed to meet the quality, mechanical properties and overall cost requirements of heavy wall fabrication. It is a submerged arc process designed to weld thick walled steel plate [from 2 in. up to 13.8 in. (51 mm up to 350 mm)] using a nearly parallel-sided, narrow gap plate preparation. The process is appropriate for both flat and circumferential welding.

A multi-layer (two passes per layer) technique is recommended in place of one large pass per layer. This minimizes undercut, trapped or mechanically locked slag and concave weld profiles. The Narrow Gap Process produces a multi-layer weld with uniform side wall penetration, maintaining low parent metal dilution and low heat input.

The outstanding results of the Narrow Gap Process are made possible by several new submerged arc flux/electrode combinations and a specially designed deep groove nozzle assembly. Only the recommended flux/ electrode combinations should be used. When properly selected to meet the job requirements, these flux/electrode combinations will deliver excellent welding characteristics and mechanical properties. When following the recommended procedures, very good bead shape and self-releasing slag will result.

The Narrow Gap Process results in lower cost welding by reducing the volume of weld metal required for heavy plate thicknesses. The cost of consumables, welding time and preparation time is reduced when compared to more conventional methods.

INDUSTRY APPLICATIONS
• Power Generation
• Petrochemical
• Shipbuilding
• Heavy Fabrication
• Nuclear

BENEFITS
• Minimum joint preparation, minimum joint
volume.
• Good mechanical properties.
• Low heat input.
• Low parent metal dilution, small heat
affected zone.
• High quality weld—without turning plate.
• Simple “off-the-shelf” equipment solution.
• Low distortion.

 

AN UNBEATABLE SOLUTION: POWER WAVE® TECHNOLOGY
Increase Productivity, Quality and Flexibility
The Power Wave® AC/DC 1000® SD delivers Waveform Control Technology® to submerged arc welding. Choose constant current or constant voltage operation and set variable frequency and amplitude. Software driven AC, DC positive or DC negative output allows the user to control the deposition rate and penetration. The result over conventional power sources is increased weld speeds, consistently higher quality welds and improved efficiencies in a single or multi-arc environment.

NARROW GAP WELDING
SYSTEM FEATURES
Programmable Sidewall Offset—The combination of accurate laser tracking and precision wire servo tilt nozzles allow the system to be programmed to maintain a specific sidewall offset. If enabled, the controller also allows this offset to be overridden by the operator during welding.

Multi-Pass Sequencing—The number of passes, as well as the control of pass transition, overlap positions and durations, are all completely programmable.

Adaptive Fill—The laser scanning system is also capable of joint volume measurements. This information, combined with control of the welding parameters and travel rate, can be used to automatically adjust to maintain even fill.

Independently Adjustable Torch Tilt—The lead and trail arcs are programmed with independent tilt angles to more accurately and consistently control bead placement. Programmable Pass Overlap Positioning of the pass overlap is programmable to allow the pass transitions to be staggered.

Scanning Laser Tracking Sensor—Precision sensor for reliable sidewall offset and height control.

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