Austenitic steel for spring technology

Austenitic steels are used in many branches of industry and have a total global consumption of around 70% in the stainless steel group. Austenitic steels are best known under the name chromium-nickel steels. Austenitic steel is the most common type of stainless steel.

Corrosion resistance
under different environmental conditions

Preservation of the surface
Good chemical resistance to liquid and gaseous media

Machanic-technological
Strength and toughness vs. good formability

A good combination of mechanical properties in conjunction with corrosion resistance are the clear advantages. Advantages of austenitic steel. Steels with an austenitic microstructure have excellent strength and toughness properties, even at low operating temperatures. Due to their comparatively low hardness, stainless steels exhibit good forming behaviour, making them suitable for a wide range of different applications. Even in the Production of flat springs steel has proven its worth due to its properties and advantages. The High elongation capacity of austenitic steel guarantees good cold formability. It is also largely non-magnetic and is easy to weld.

In accordance with the application requirements, austenitic stainless steel therefore has properties that are in demand in industry, automotive and shipbuilding, construction, medical technology and the chemical industry. The high corrosion resistance is the most important property of this stainless steel grade.

As a spring steel wire, austenitic chromium-nickel spring steel is ideal for corrosion-resistant springs for medium and high loads, depending on the environmental conditions. For this reason, the material is often used in the production of corrosion-resistant springs. Steel springs Utilisation.

Austenitic stainless steels are thermally post-treated for two reasons.

I.
Reduction of tensions
Increasing elasticity
Reduction of material fatigue

The first reason is the so-called reduction of the stresses introduced into the material during forming.

This process reduces existing stresses in the workpiece that have arisen during cold forming. It also significantly reduces the risk of internal tensile stresses being released by further processing and the mould springs, leaf springs and flat springs becoming distorted. What's more, because the internal stresses and external stresses add up, this can impair the load-bearing capacity of the moulded spring. This process therefore also results in an increase in elasticity and thus a reduction in material fatigue.

II.
Increase in strength
Wear resistance

The second reason is the possibility of increasing strength. The increase in dislocation density reduces the plastic deformability, which results in an increase in strength and hardness.

The increase in strength starts at a temperature of approx. 100°C and is then already at 100 MPa. At the peak, an increase of approx. 270 MPa can be achieved. These values are achieved with a holding time of 24 hours (see table). However, 80% of the path is probably already achieved with a holding time of 30 minutes.

For economic reasons, we at Mario Schaaf Technische Federn have therefore decided to always temper the material after forming. We currently have a holding time of 30 minutes and a temperature of 270°C, provided there are no deviating customer specifications. We have had the best experience with this value over the last 20 years.