Are ASTM A307 bolts and rods always weldable?

A307 bolts, rods, and studs are not always weldable.  For this grade to be weldable it must meet the supplementary requirement S1 of the ASTM A307 specification.  This supplement provides assurances of weldability by additional chemical composition restrictions and by a carbon equivalent formula.  In addition, “Because of the embrittling effects of welding temperatures on cold-forged steel, this supplemental section is limited to hot-forged bolts, or, if not forged, then to bolts produced from hot-rolled bars without forging or threaded bars, bars studs, or stud bolts produced from hot-rolled bars without forging. Cold-forged bolts, or cold-drawn threaded bars, if they are given a thermal treatment by heating to a temperature of not less than 1500°F (815°C) and air-cooled are also suitable.”

To manufacture bolts that meet supplement S1, the following additional analysis limitations shall be used:

Element Composition
Carbon 0.30% Max
Manganese 1.00% Max
Phosphorus 0.04% Max
Sulfur 0.05% Max
Silicon 0.50% Max

In addition to the chemical analysis requirements above, the heat analysis shall be such as to provide a carbon equivalent (CE) not exceeding .55.  CE is calculated using the following formula:

CE = %C + (%Mn/6) + (%Cu/40) + (%Ni/20) + (%Cr/10) + (%Mo/50) + (%V/10)

Since many A307 bolts are cold formed, with little in the way of certification documents, if your project requires weldable A307 bolts, give one of our team members a call and we can help you with a quote that guarantees your bolts meet supplement S1 and are therefore weldable.


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