1.1248 - C75S soft

Unhardened, easily hardenable carbon steel W.-Nr. 1.1248 (C75S)

1. Application examples
With a carbon content of over 0.75%, this material is very well suited for springs and wear parts that are not subject to corrosion requirements.

In DIN EN 10 132-4, the hardened version of 1.1248 is approved as a material for springs.

If there is a risk of corrosion and the highest demands on the mechanical load, we recommend the material 1.4031Mo, which is available in thicknesses of 0.10 to 0.80 mm.

2. Material codes
German Norm: 1.1248 C75S (former Ck75)
AISI: 1075
ASTM: G 10750
Engl. Norm: 75 (B.S. 5770 Part 1)
Franz. Norm: XC 75
Japanese Norm: C75 C CSP (Norm G 4802)

3. Alloy Composition *
C: 0,70-0,80 %
Si: 0,15-0,30 %
Mn: 0,30-0,45 %
P: max. 0,02 %
S: max. 0,02 %
Cr: ca. 0,01 %

* the exact composition of each batch can be documented by a material certificate 2.2 or 3.1 according to DIN EN 10 204.

4. Delivery condition
Condition: cold rolled, non-hardened (ferritic condition)
Surface: MA, please ask for roughness values
flatness: no data available
Ultimate tensile strength: 490-790 N/mm²

In the thicknesses 4,0+5,0mm, our material on stock is hot-rolled and sandblasted.

Further mechanical data: see chapter 7 and 8.

5. Sizes
thicknesses: 0,20-5,00 mm
raw material width: ca. 300-330 mm (see table)
edges: cut

Lengths: only available in a length of 1000mm

6. Tolerances
thickness tolerace: DIN EN 10 140 and DIN EN 10 051
width tolerance: -
straightness: normal

7. Further mechanical data
Yield strength Rp0,2: ca. 360-460 N/mm²
Elongation A80: no values available

The highest application temperature is around 200° Celsius, depending on the load. Please note that Young's modulus values drop as temperature increases.
For higher operation temperatures we suggest the stainless hardened steels like the alloys 1.4031Mo (up to 0.80 mm thickness) and 1.4034 (from 1.0 to approx. 10.0 mm thickness)

8. Physical properties
Density: 7,9 g/cm³
Thermal conductivity: 35-45 W/(m °C) bei 20 °C
Heat capacity: 460 J/(kg °C) mean value at 50 – 100 °C
Thermal expansion:
10,5 x 10 -6 (between 30 - 100 °C)
11,5 x 10 -6 (between 30 - 200 °C)
12,5 x 10 -6 (between 30 - 300 °C)
Electric resistance: ca. 0,20 Ohm x mm²/m (for 1.1231= C67S hardened)
Modus of elasticity: 210 000 MPa at 20 °C
Relative permeability µr: ca. 400 (for 1.1231= C67S hardened)

9. Blanking
The alloy 1.1248 can be stamped and drawn easily in the non hardened condition. We recommend a punch-to-die clearance of 4-10 % of the strip thickness. The corner radius should be at least 0.25 mm and the punching die should be at least twice the strip thickness.
The pieces should then be tumbled to receive a good edge roundness.

10. Laser cutting
As the material melts at the edge during laser cutting, a higher hardness and therefore a lower toughness at the cutting zone is possible. We suggest to produce critical pieces by water jet cutting.

11. Photo etching
This alloy is very easy to etch.

12. Bending
As this material need to be hardened after forming, the rolling direction is not important regarding the bending.

Bending radius: minimum 10 times of the strip thickness.
Spring back angle: As the spring back angle depends on several factors, bending tests are necessary. As guidance an angle of 10° at a strip thickness of 0.20 mm and an angle of 20° at a strip thickness of 0.60 mm can be expected.

13. Flat grinding
The alloy 1.1248 is magnetisable and can be fixed by magnetic clamping devices of flat grinding machines.

14. Welding
Due to a high content of carbon of ca. 0,75% the alloy 1.1248 should not be welded.

15. Corrosion resistance
The alloy 1.1248 is not corrosion resistant. We supply this alloy with a light oil film. If used at normal conditions this alloy needs to be painted or galvanized.

Important Annotation
The specifications which are given in this technical information sheet about the condition and application of the alloys are only for reference and are no confirmation about certain performances and characteristics.
The information correspond to our own experiences and experiences of our suppliers. We can not guarantee for the results during processing and utilisation.

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