A34-2 is the AFNOR designation for a basic unalloyed structural steel corresponding to the German DIN 17100 grade USt34-2, part of the same low-strength "Fe330" family as St33/A33 but one step up in guaranteed tensile strength. The "U" in USt34-2 signals an unkilled (rimming) deoxidation practice, a lower-cost steelmaking route that trades some internal uniformity and aging resistance for economy — a fair trade in applications where the steel isn't exposed to demanding fatigue or low-temperature service. Like the rest of this family, USt34-2 is specified by guaranteed mechanical minimums rather than a tight chemical window.

With its low carbon content and unalloyed chemistry, A34-2 has essentially no response to hardening heat treatment and isn't intended for wear-critical or high-strength applications. Instead, it's a general fabrication steel: sheet and strip products, light structural sections, enclosures, and formed parts where cost, weldability, and ease of forming matter more than strength margin. It bends and welds without special precautions, which is exactly why grades in this family remain common in general sheet metal and light structural work even where higher-strength alternatives exist.

USt34-2 / A34-2 is a mechanical-property specification under DIN 17100 rather than a tightly controlled chemical grade. It is an unalloyed, low-carbon rimming steel with phosphorus and sulfur held to basic structural-quality limits (typically 0.05% max each). No further verified composition data is presented here rather than publish an unreliable figure.

A34-2 machines much like the other low-carbon grades in the Fe330 family: cutting forces are low, power demand is modest, and tool wear in the base material is light. The main practical concern is built-up edge — the soft, unalloyed matrix can smear across the rake face at low cutting speeds rather than shearing away cleanly, which is more pronounced in rimming (unkilled) steel than in fully killed grades because of its slightly less uniform internal structure.

Chip control depends heavily on chipbreaker geometry rather than on the material fracturing on its own, so turning and drilling operations benefit from a geometry chosen specifically for chip curling rather than a general-purpose one. Because rimming steels can carry minor internal segregation near the surface of the bar or sheet, the first light pass sometimes reveals slightly inconsistent surface hardness compared with the bulk material.

In practice this is an easy, forgiving material to machine. Running speeds toward the upper end of the recommended range, keeping the edge sharp and positive, and matching the chipbreaker to the operation all help avoid BUE and keep chip evacuation clean.