Stud Welding and Nut Welding to Press-Hardened Materials

Projection welding of fasteners, including flange nuts and threaded studs to hot-stamped boron and press-hardened steels, where an AlSi coating is present.

Stud welding and nut welding can be difficult. Fasteners are often considerably softer than the 1500 MPa stamping. With these large change in hardness, the projections in the fastener will collapse prior to a good weld being made. The end result is usually vaporized projections and extended weld times in an effort to forge the materials, instead of welding them. Furthermore, when this type of weld process is incorporated, the end result is weak, inconsistent torque and push-out values, as well as a large heat-affected zone (HAZ).

A M8 nut welded to 2-mm boron.	A M6 nut welded to 2-mm boron.

In addition, another concern is the consistency of the base material because of in-house processing.  The influences observed can be oven temperatures, heat cycle times, water flow rates, water temperatures, and quench times.

Fastener Projection Welding Challenge:

• Fasteners including flange nuts and threaded studs are extremely soft compared to the base material.
• Hot-stamp materials develop AlSi coating in the furnace.
• Resistive qualities of AlSi coating can be inconsistent across the part, and from batch to batch.
• Longer weld times with lower weld currents (as typically called for in projection welding charts) makes it difficult to deliver enough heat to the base material, often vaporizing the projections without welding.
• Consistent projection welding is difficult with most processes, and even with many Capacitor Discharge Welding machines, which may not be properly designed for the projection welding process.

Fastener Projection Welding Solution:

As a result, fastener welding using Capacitor Discharge Welders from Weld Systems Integrators (WSI) is your solution. Capacitor discharge resistance welding (sometimes referred to as capacitive discharge) stores energy for extremely fast release of energy with large peak currents. More energy into weld formation and less into heating the surrounding material. The heat-affected weld zone, where the properties of the metal have been changed is smaller, minimizing changes in the metallurgy of the workpiece.

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Fastener Welding Articles and News

• 12J Series CD Welder
• WSI Welding Seminar
• AWS Welding Journal – 10/2017
• Ask The Welding Engineer – 3/14/17
• The FABRICATOR – 8/2016