Guide
Rolled vs forged bars
The same 42CrMo4 in Ø80 and Ø400 is not the same piece. The small bar is typically hot rolled. The large one is often forged. The core has seen less deformation and takes hardening less well. That is why we change grade or process as the diameter grows – not only the price.
What the difference is
Rolling gives long bars with a uniform cross-section. Forging gives short, coarse pieces with a different grain flow. Both can carry the same W.Nr. The certificate must describe the material you received – rolled bar or forged piece.
- Up to approx. Ø400: most grades as hot-rolled bar
- Large diameters and short pieces: forged round
- The core of the large bar is not the small bar scaled up
What it means for the choice
In 42CrMo4, many switch to 34CrNiMo6 when the core of the large bar no longer holds. In structural steel it is still S355J2 – but as plate or forging, not as a rolled Ø80. The guide to bar condition explains +N and +QT on top of that.
What you write on the order
Grade, Ø, length and whether the part may be rolled bar or has to be forged. We tell you what the mill can supply in that diameter. We do not invent a rolled Ø800.
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Send your enquiry
State grade, dimensions and quantity — or attach a drawing. We reply with a quote.