Springs
“Spring design starts with application requirements, not material cost ”
In their day-to-day work, the engineers at Mollificio Modenese often come up with a seemingly simple question: which material should be selected to manufacture a spring?
In many cases, the choice starts with the raw material cost. It is not uncommon, for example, to receive requests for quotations for the same spring made from very different materials, such as AISI 302 and Inconel X-750, with the aim of identifying the most cost-effective solution.
According to Mollificio Modenese, this approach can lead to misleading assessments. Material selection should not start from the cost per kilogram but from the actual operating conditions of the component.
Temperature as the key selection criterion
Ambient temperature is generally considered to be within a range of approximately -20°C to +80°C. Within this range, most materials used for spring manufacturing can be employed without particular limitations: temperature is not a critical design variable.
At low temperatures, down to -200°C, austenitic stainless steels such as AISI 302 and AISI 316 are often used because they maintain good elasticity and toughness even under demanding conditions. These are the most widely used stainless spring steels on the market.
When special alloys are required
Austenitic stainless steels can also be successfully used at elevated temperatures, generally up to approximately 200–250°C.
Beyond this threshold, operating conditions often require materials specifically engineered for use in high-temperature environments, such as alloys from the Inconel, Nimonic, and Hastelloy families. In these applications, selecting a special alloy is not an optional enhancement but a design necessity.
Why comparing materials based only on price is misleading
The comparison between AISI 302 and Inconel X-750 is particularly effective in explaining this point.
If the operating temperature allows the use of a stainless steel such as AISI 302, choosing a high-performance alloy like Inconel can significantly increase the cost of the component without providing any real technical benefit.
Conversely, if the operating conditions genuinely require a high-temperature-resistant alloy, the price of a spring made from AISI 302 becomes irrelevant. Such a solution would simply be technically unsuitable and incapable of delivering the performance required by the application.
Mollificio Modenese's experience confirms that material selection should be approached by evaluating operating temperature, applied loads, working environment, and service life requirements as a whole. Only after identifying the materials that are truly compatible with the application does it make sense to compare costs. Real cost savings come from making the right technical choice at the design stage.
