Surface treatments for technical springs (Part 1)

Subsequent surface treatment gives customised technical springs a range of additional desired properties. In the majority of applications, the springs should be harder and/or more resistant to rust or heat. However, the desired effects also include electrical conductivity or extreme mechanical resilience. Our overview presents the "classic" processes, but also takes a look at special processes that can be used to achieve the desired properties. customised spring construction their special uniqueness.

Burnishing is a non-layer-forming process and is one of the classic optical surface treatments. During burnishing, oxygen is incorporated into the top layer. This forms a very thin, non-metallic black skin of iron oxide on the low-alloy steel nib. As it is part of an optical process, the coating, which is usually less than 1 micrometre thick, enhances the appearance of the nib and protects it at the same time. Apart from these properties, the process hardly changes the spring as it is located in a relatively low temperature range of up to 150 ° C. The minimal thermal stress has no effect on the roughness depth and structure of the spring, and the dimensional accuracy also remains the same. One of the main effects of the process is that the technical springs take on a uniform colour. However, the corrosion resistance is low.

In contrast to black oxidation, this optical process also offers a high level of corrosion protection. The principle of surface treatment is a galvanised protective system for steel surfaces. During electroplating, an extremely thin zinc metal layer is created, which is supplemented by passivation and chromatisation to provide the spring with a high level of protection against corrosion. The technical spring becomes significantly more durable. Bright galvanising also prevents traces of corrosion such as so-called "white rust". The visual effect is also important here. The spring looks better, but is also more thermally resistant and more adhesive.

Computerised load simulations are one of the services that Schaaf can carry out comprehensively and conclusively on request. More performance can mean fewer potential weak points. And sometimes a real "simulation", as in the case of pipette springs for medical technology described above, replaces any computer.

As technical springs are also generally made from stainless steel, the process typical of this material is relatively widespread. It is mainly used in medical technology to enhance the appearance of the material.
A thin surface layer of the workpiece is removed in a single operation by means of anodic dissolution. The effect is far-reaching. All impurities, cracks, stresses, particles and structural defects are removed. The result is impressive: Metallically pure, shiny, free of burrs and particles and closed in the micro range, the spring presents itself with optimal properties of the base material. The spring was neither mechanically nor thermally stressed. The advantages of this surface treatment are the good corrosion resistance with high fatigue strength and low product adhesion and coating formation.

As a specialist in customised technical springs for special applications, Schaaf naturally also has a wide range of different surface treatments for steel springs. Many years of experience guarantee the selection of the optimum process in each case in order to achieve additional effects by refining the workpieces.