Speaking in Code – A Spotlight on Arc Spot Welds

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Steel floor deck and steel roof deck are very common building materials and are incorporated into a large segment of projects and project work being built today. Much of this steel deck installation is accomplished by welding the individual pieces of steel deck to the beam or joist of the structure being built. The type of weld that is used, in the field, to join this light-gauge metal to a structural member, in the flat position only, is called an “arc spot weld” and is often referred to as a puddle weld.

How Are Arc Spot Welds Made?

We’re glad you asked. The arc spot or “puddle weld” is started by striking an arc on the deck surface, causing a hole to form in the deck. The weld operation then continues by depositing electrode material on the beam or joist and allowing the molten “puddle” to engage the penetrated deck. It is essential that the finished weld penetrate into the supporting beam or joist and that the puddle completely engages the deck on the weld perimeter. The complete process usually requires three to six seconds, possibly more on multiple thicknesses or thicker deck. Arc spot welding methods and operator qualifications are described in the American Welding Society Structural Welding Code – Sheet Steel, AWS D1.3.

 

What Is the Most Common Filler Metal Used for Welding Steel Deck?

The most common filler metal used for welding steel deck is an E6022 shielded metal arc welding (SMAW) electrode due to the ability of this electrode to produce welds with good penetration and wetting of the weld puddle perimeter. The E6022 electrode is the “matching” electrode for the most commonly used composite deck, roof deck and noncomposite floor deck with thicknesses of 28 gage or greater.

Are Welding Procedure Specification (WPS) Documents Required?

Yes indeed. It is the deck installation contractor’s responsibility to ensure that all Weld Procedure Specifications (WPSs) and welders are qualified. It is the special inspector’s responsibility to verify that the WPSs and welders are qualified. A WPS is a detailed document providing variables for a specific welding application to assure repeatability by properly trained welders and welding operators. Often times, welders will think that they are qualified to preform arc spot welds due to being certified in accordance with the AWS D1.1 structural welding code. Usually, their welding certification is limited to thickness greater than 1/8 inch and they must be certified in welding sheet steel when welding less than this thickness, in accordance with AWS D1.3.

What Special Inspections Are Required for Deck Welding?

Visual inspection is required to determine if a weld meets the acceptance criteria of AWS D1.3 and 100% of the welds must be visually examined. Inspection tasks are also listed in Appendix 1 of the Steel Deck Institute (SDI) QA/QC-2011 Standard for “Quality Control and Quality Assurance for Installation of Steel Deck”. These tasks include, but are not limited to, the use of qualified welders, control and handling of welding consumables, environmental conditions, WPS followed, verification of size, spacing and location of welds (including support, sidelap and perimeter welds), verification of repair activities, and the documentation or acceptance or rejection of welds.

Miscellaneous Pearls of Wisdom…

It is very common for the welder responsible for performing “arc spot welds” in the field NOT TO BE properly certified to weld “arc spot welds” in accordance with AWS D1.3.

  • Most welders think their structural certification (AWS D1.1) covers decking. NOPE. The D1.1 certification is only good down to thicknesses of 1/8 inch material. For thicknesses less than 1/8 inch, the CODE says to go to D1.3 for certification.
  • Arc spot welds are “flat” positions only. Code allows plus or minus 15 degrees from level to still be flat. About a 4 to 12 pitch is as steep as you can weld in a “flat” position.
  • Full fusion around the spot weld is the KEY to acceptability. If you see a hole OR it is split at the edge, it has lost substantial “holding” ability.
  • Good fusion should be visible (visual inspection) over no less than 90% of the weld perimeter (Clause 6.1.1.4 of AWS D1.3 permits undercut on 12% of the weld perimeter).
  • The Steel Deck Institute (SDI) has developed the ANSI/SDI QA/QC-2011 “Standard for Quality Control and Quality Assurance for Installation of Steel Deck”. This valuable reference is available FREE from the SDI website.
  • Arc spot welds can be made through multiple thicknesses of steel deck as long as the TOTAL base metal thickness does not exceed 0.15 inches.
  • Visual inspection is required to determine if a weld meets the acceptance criteria of AWS D1.3, “Structural Welding Code Sheet Steel”.
  • When should weld washers be used? They should be specified for arc spot welds connections to the supporting steel frame when the deck is LESS than 0.028 inches thick.
  • Weld washers (due to their heat-sink effect) may actually create welds of lower quality and strength when used with a 22 gage or thicker deck.
  • Preheating is not generally required in deck welding. AWS D1.3 allow exceptions for the preheating rules of AWS D1.1, Clause 5.6.