How to choose the best grade for heavy-duty stainless steel springs

With over 150 types of stainless steel, it can be confusing to know which grade is the best for your spring project solution.

At Plymouth Spring, we use various materials, including stainless steel for springs.

But what is stainless steel?

Stainless steel is a corrosion-resistant iron alloy with at least 10.5% chromium, but it can also include other alloys like nickel, molybdenum, and carbon, to enhance strength and resistance to heat or chemicals. When used in springs it provides strength, flexibility, and corrosion resistance in harsh environments, such as high stress, extreme temperatures, moisture, or corrosive chemicals.

Stainless steel is used to manufacture various components, including compression, tension and torsion springs.

Compression Springs

Stainless steel is an ideal material for compression springs that need to resist significant weight without breaking or deforming. It also has good fatigue resistance, which makes it useful in applications where springs experience repeated compression cycles.

Tension Springs

Its corrosion-resistant property makes stainless steel suitable for manufacturing extension springs that will be used in extreme environments like moisture, salt and chemicals. For example, in tractors and harvesters to control the movement of gates, hatches and levers whilst protecting them from rain, mud, and pesticides. It also provides corrosion resistance in energy, mining and fishing industries.

Torsion Springs

Specific grades of stainless steel, like 304 and 316, can withstand extreme temperatures and is therefore suitable for torsion springs that need to function in environments with high heat or cold conditions. For example, these alloys can be used in torsion springs in anti-roll bars for motorsports to withstand heat resistance generated by the engine.

The Five Types of Stainless Steel

There are five main type of stainless steel based on the composition of alloying elements and their microstructure.

Austenitic Stainless Steel
It is popular because of its high chromium (16-26%) composition, which gives it high levels of corrosion resistance. Austenitic steels also include nickel (up to 35%) and often molybdenum.

Ferritic Stainless Steel
Affordable and with moderate corrosion resistance. This group include chromium (10.5-27%), but little or no nickel in the composition, lower toughness than austenitic types, as well as magnetic properties.

Duplex Stainless Steel
Combining austenitic and ferritic stainless steels, this category offers superior resistance in marine and saltwater environments and is made from chromium (18-28%), nickel (4.5-8%), molybdenum and nitrogen. However, they are magnetic due to their ferretic content.

Martensitic Stainless Steel
Martensitic steel, less common, high-strength group with moderate corrosion resistance, is composed of chromium (11.5-18%) and higher carbon content. They can be hardened by heat treatment to improve strength and toughness further and are ideal for applications that require high tensile strength and impact resistance.

Precipitation Hardening Stainless Steel
This group uses precipitation hardening to add strength to its key elements, which include chromium (15-17%), nickel and other elements such as copper and niobium. They provide high strength and good corrosion resistance and can be magnetic or non-magnetic, depending on the base structure.