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 /  /  /  / High-strength steels for cold-forming, normalized rolled

High-strength steels for cold-forming, normalized rolled

Usage

The steel grades of the S260NC to S355NC series are used for cold-formed components of the most varied designs. Their fields of application include above all the manufacture of

  • Longitudinal beams
  • Frames
  • Cold-pressed parts
  • Cold-rolled sections
  • Structural pipes

The user of these steel grades must make sure that his calculation, design and processing methods are appropriate for the material. The forming process used must be suitable for the intended application and comply with the state-of-the-art; it is of fundamental importance to the processing behaviour of these steel grades.

These steel grades offer excellent bending, flanging, cold-bordering and folding properties in both longitudinal and transverse direction. The bending radii specified below should be observed as minimum values.

Standards

Europe Material no. D GB Salzgitter Flachstahl FK1)
EN 10149-3 SEW 092 BS 1449 Sec. 1.4
S260NC 1.0971 QStE 260 N - PSQ 26 (SB 26 Q) A
S315NC 1.0973 - HR 40/30 SB 32 Q A
S355NC 1.0977 QStE 340 N HR 43/35 SB 36 Q B

Chemical composition in percent by weight [%] (Heat analysis)

Grade C Si Mn P S1) Altotal2) Nb3) V3) Ti3)
max. max. max. max. max. min. max. max. max.
S260NC 0.16 0.50 1.20 0.025 0.020 0.015 0.09 0.10 0.15
S315NC 0.16 0.50 1.40 0.025 0.020 0.015 0.09 0.10 0.15
S355NC 0.18 0.50 1.60 0.025 0.015 0.015 0.09 0.10 0.15

Mechanical properties1)

Grade Min. yield strength Tensile strength Min. total elongation [%]
MPa MPa L0 = 80 mm L0 = 5,65 √S0
e2) < 3 e2) ≥ 3
S260NC 260 370 - 490 24 30
S315NC 315 430 - 550 22 27
S355NC 355 470 - 610 20 25

Notch impact energy

If agreed in the order, the notch impact energy is proved using longitudinal samples at -20 °C. The average notch impact energy from 3 samples must be 40 J minimum. One individual value may fall short of the required minimum value by not more than 30 %. The sample width shall equal the product thickness if the latter is between 5 and 10 mm, the tests being performed using samples which are similar to Charpy-V samples. The required minimum values are to be reduced proportionally to the sample width.

Smallest bending radius

Grade Smallest recommended bending radius bending angles ≤ 90°1)
e ≤ 3 3 < e1) < 6 e > 6
S260NC 0.25 e 0.5 e 1.0 e
S315NC 0.25 e  0.5 e 1.0 e
S355NC 0.25 e 0.5 e 1.0 e

Heat treatment

These steel grades may be hot-formed without negatively affecting the material properties. This applies in particular to the temperature range of 850 - 1.050 °C. Normalized at 900 - 950 °C (holding time after temperature equalization: 1 - 2 minutes per millimeter of plate thickness) is required only if the mechanical and technological properties are to be restored to an ‘as-delivered condition following forming operations outside of the temperature range given above or after cold-forming or if the regulations in force call for normalized. However, such a heat treatment or stress relief annealing at 530 - 580 °C (holding time: 30 minutes after thermal equilibrium has been achieved for all product thicknesses) will not be necessary.

Welding 

These steel grades can be perfectly welded both manually and using automatic equipment by means of all known welding processes. However, the quality of the weld joint depends on the welding process, the welding conditions and the selection of the correct filler metals. The welding wires and electrodes approved in this strength category must be used as filler metals. Basic coated electrodes are recommended for manual welding.

In general, pre-heating prior to welding or torch-cutting is not necessary. At outside temperatures below +5 °C, pre-heating to approx. 150 °C should be carried out; the same applies to plate thicknesses ≥ 12,5 mm.

Subsequent normalized or stress relief annealing is required only if called for in the regulations or if operating and manufacturing conditions make a reduction of the residual welding stresses appear useful. In addition to this, the guidelines for processing weldable fine-grain structural steel grades according to ‘Stahl-Eisen- Werkstoffblatt’ (Iron and steel material sheet) 088 must be observed.

Condition of delivery, scope of testing and certificate

The provisions of EN 10149-3 shall apply for delivery and inspection.
The products are delivered in a condition obtained by normalized rolling.

Certificates according to DIN EN 10204 can be supplied as follows: IT, DUN, FAX, e-mail, paper.

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