Welding especially large and thick pieces of plate metal presents some unique challenges. Typically speaking, joining metal plates or pipes that are more than a foot thick requires intense heat, in a strong concentration, to achieve a solid and sound weld. Welding in this manner, however, can yield several undesirable results, all of which can ruin the overall weld. The following is a list of several chief problems encountered in welding large and heavy pieces of metal:
- High Shrinkage Strains – Occurs when one section of a weld cools and contracts, while another section is still super-heated
- High Restraint – Generally occurs when creating welds where the weld bead is in excess of 2 inches in width, or when welding an inordinately large joint groove
- Cracks or Stress Riser – Existing cracks or discontinuities in large structural steel components that interfere with the welding process
- Reduced Resistance to Fracture – If the weld metal is of a lower toughness than the base metal, the overall toughness of the metal can be compromised
Overcoming the barriers created by this issue has been an ongoing struggle in the various industrial and manufacturing fields that require welding for large sections of thick metal.
New Technology Offers a Solution
In an effort to address the issues commonly faced when welding thicker, heavier metals, Lincoln Electric has developed the Narrow Gap Welding Process, an exciting new technological advancement that makes thick metal welding easier, more effective, and lower cost.
Features & Benefits
The process employs a computer controlled, duel weld-head machine, using a submerged arc, paired with specifically selected electrodes, and specially designed deep groove nozzle welding tip.
The Narrow Gap Welding Process employs two, nearly parallel welding heads to create two passes per layer, suitable for flat and curved surfaces.
The two pass per layer technique minimizes undercut, trapped or mechanically locked slag and concave weld profiles, in addition to achieving uniform sidewall penetration while maintaining low metal distortion and low heat input.
The process is faster, and when electrodes are properly paired with the welding machine, a smaller amount of electrode is consumed (with greater results), making the overall process more efficient, less time consuming and is considerably more cost effective.
The process is well suited to a variety of industrial applications, including:
- Power stations and nuclear facilities
- Petrochemical manufacturing facilities
- Ship building
- Heavy industrial fabrication
