UGI® S302 Solution-Annealed Stainless Steel Springs – Superior Corrosion Resistance & Fatigue Strength

UGI® S302 is the grade conventionally used to manufacture stainless steel springs. This grade offers good corrosion resistance and can be used at temperature levels close to 250°C. Springs in UGI® S302 have good fatigue strength and low relaxation compared with carbon steels.

For springs used in corrosive environments, UGI® S302 makes it possible to avoid the surface protection needed on carbon steel springs. To adapt to various cold transformation conditions, Ugitech has developed several versions of UGI® S302, such as UGI® S302-1, UGI® S302-2, and UGI® S302-6 to cover several CWH values (Cold Work Hardening factors). For applications which require high dynamic fatigue performances, a special grade is available on request: UGI® S302 HFS (HFS for High Fatigue Strength).

These Rm values are in conformance with the standard mechanical strength range indicated in Euronorm EN 10270-3 for grade 1.4310 (NS). The Rp 0.2 values are given as an indication.

The Rm/Rp 0.2 ratio on spring wires in UGI® S302 is generally around 0.9.

The range of strength (Rm) values is generally contained

within a manufacturing batch, at 100 MPa;

within a packaging unit (cable drums, coils, rims) at 60 Mpa.

The grade's magnetic permeability (µr) is heavily influenced by cold transformation of the material. In the solu-tion-annealed and non-cold-worked state, µr is less than 1.02, but in the cold-worked state with spring-wire properties, it can rise to a maximum of 10.

Properties

General

Property	Temperature	Value
Density	20 °C	7.9 g/cm³
	100 °C	7.9 g/cm³
	250 °C	7.9 g/cm³

Mechanical

Property	Temperature	Value	Comment
Elastic modulus	20 °C	200 GPa
	100 °C	194 GPa
	200 °C	183 GPa
Elongation		50 %	min.
Tensile strength		600 MPa	max.

Thermal

Property	Temperature	Value	Comment
Coefficient of thermal expansion		0.0000165 1/K	20 to 100°C
		0.0000175 1/K	20 to 200°C
Max service temperature		250.0 °C
Specific heat capacity		500 J/(kg·K)
Thermal conductivity	20 °C	15 W/(m·K)
	100 °C	16 W/(m·K)
	250 °C	18 W/(m·K)

Electrical

Property	Temperature	Value
Electrical resistivity	20 °C	0.00000078 Ω·m
	100 °C	0.00000083 Ω·m
	250 °C	0.00000090 Ω·m

Magnetic

Property	Value
Relative magnetic permeability	1.02 [-]

Chemical properties

Property	Value	Comment
Carbon	0.05 - 0.15 %
Chromium	16.0 - 19.0 %
Manganese	2.0	max.
Molybdenum	0.8	max.
Nickel	6.0 - 9.5 %
Nitrogen	0.11	max.
Phosphorus	0.045	max.
Silicon	1.0	max.
Sulfur	0.015	max.

Technological properties

Property

Application areas

Torsion bars, torsion springs

Compression springs

Draw spring

Cold Forming

Drawing – Profiling Like all high-carbon grade austenitic steels, UGI® S302 is hardened significantly during cold transformation. However, it has good ductility, with a potential reduction in cross section of up to 90% or more.

Corrosion properties

UGI® S302 has good corrosion resistance in moderately corrosive environments. It is widely used in humid or aqueous environments with a limited chloride content. The use of UGI® S302 in marine environments should be avoided, especially in its drawn spring-wire version.

Heat Treatment

Springs' mechanical strength can be increased up to 250 Mpa (depending on the diameter) by heat treatment performed on the springs. The Rp0.2/Rm ratio can increase by 5% after such a treatment.

Static treatment: Static treatment temp.: 350/425°C, Recommended duration 0.5 to 4 hours depending on batch size

Treatment in continuous oven: Heat treatment temp.: 25°C higher than in, Min. treatment duration: 3 minutes

Hot forming

UGI® S302 has good hot forgeability. Forging temperatures are between 900°C and 1100°C. Once forged, the parts must be cooled swiftly, i.e. chilled in water to avoid problems of sensitization of the grade to poten-tial grain-boundary corrosion

Other

Available products:

Product	Shape	Finish	Sizes
Wire rod	Round	Pickled	5.0 to 32 mm
Drawn wire	Round	Matt	0.2 to 1.0 mm
Bars	Round	Matt	1.0 to 15 mm
Rolled wire	Sections	Bright	2 to 70 mm²

Other: please consult the supplier

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