SteelKey facts
- Spring steel is a name for a wide range of steels, most of them medium- or high-carbon grades.
- Its defining property is a very high yield strength, which lets a part recover its shape after large deflection.
- Coil springs are made by winding wire around a former such as a cylinder.
- EN 10270-1 covers patented cold drawn unalloyed steel wire for mechanical springs under static and dynamic duty.
- ASTM A227 covers two classes of round cold-drawn steel wire for springs that are not highly stressed.
What makes wire suitable for springs?
A spring stores energy by deflecting and gives it back by recovering. For that to work again and again, the wire must stay inside its elastic range: the stresses at which steel stretches or twists and then returns fully once the load is gone. The upper edge of that range is the yield point. Push beyond it and some of the deformation becomes permanent.
Ordinary soft wire has a low yield point, so it bends and stays bent, which is exactly what a tie wire should do. Spring steel sits at the other extreme. Its yield strength is very high, so a spring wound from it can be compressed, pulled or twisted a long way and still come back to its starting length. That is the whole point of spring wire, and it is why the material, not the coiling, is the first question in any spring order.
What is spring wire made of?
Most spring wire is spring steel. The term does not name one alloy; it covers a broad family, mostly low-alloy manganese steels and medium- or high-carbon steels. Carbon steel references list springs and high-strength wire among the main uses of high-carbon steel. What the carbon does to the wire is in our guide to high carbon steel wire.
Heat treatment plays a part as well. Many spring steels can be hardened and tempered, and springs are often tempered after coiling. The exact route depends on the steel and the size of the spring. For hard drawn against oil hardened wire, read oil tempered vs hard drawn spring wire.
Springs can be made from other metals too, but steel is by far the usual choice, and steel spring wire is what this guide and our range deal with.
Which springs are made from wire?
Coil springs are formed by winding wire around a former, often a cylinder. The three main kinds differ in how the load is applied.
| Spring type | Load it resists | How it works |
|---|---|---|
| Compression | Being pushed shorter | Shortens under load and pushes back |
| Extension (tension) | Being pulled longer | Stretches under load; usually has hooks or eyes at the ends |
| Torsion | Being twisted | Turns under load and twists back |
Wire forms, such as clips and shaped parts that flex and recover, use the same kind of wire without being coiled into a helix.
Which standards cover spring wire?
A spring wire standard fixes the steel, the properties and the tests, so a spring maker gets the same behaviour from one coil to the next. Two are widely named.
EN 10270-1 deals with patented cold drawn unalloyed steel wire of round section for mechanical springs. It covers wire for springs under static duty and under dynamic duty.
ASTM A227 covers two classes of round cold-drawn steel spring wire, Class I and Class II. It is meant for mechanical springs and wire forms that are not under high stress and do not need high fatigue properties. Specimens are tension and wrap tested, and carbon, manganese, phosphorus, sulfur and silicon are checked in the chemistry.
Classes, grades and strength levels within these standards vary by diameter and duty. Our spring wire standards guide explains each one separately. We do not publish grade values for our own range: the grade and standard available for an order are confirmed in the quotation.
Spring wire vs cold drawn wire
Both are drawn steel wire, and drawing work hardens the steel in each case. The difference lies in the steel and the target property.
| Feature | Spring wire | Cold drawn wire |
|---|---|---|
| Steel | Spring steel, mostly medium or high carbon | Steel drawn for general use |
| Key property | Very high yield strength, elastic recovery | Strength and accurate size |
| Typical standards | EN 10270-1, ASTM A227 | EN 10218-2 on our range |
| Diameter on our range | 1.3 to 4 mm | 0.8 to 6 mm |
| Strength on our range | On request | 500 to 1,000 N/mmยฒ |
| Typical jobs | Coil springs, formed parts | Nails, staples, bolts, screws |
For how drawing raises strength, and how that strength is tested and written, read our explainer what is high tensile wire. The drawn product itself is on our cold drawn wire page.
Where is spring wire used?
Coil springs are the main outlet, and vehicle suspension is the example both spring references give. Beyond coils, spring steel goes into many parts that have to flex in service and then snap back to where they started.
Our spring steel wire is offered in diameters from 1.3 to 4 mm for coil springs, vehicle springs such as suspension springs, and formed parts that must return to shape after bending. Other wire types are on the steel wire hub.
How do you specify spring wire in a quote request?
- Diameter in millimetres. A gauge number from an old drawing can be converted with the wire gauge chart.
- Standard and class or grade exactly as your spring drawing or customer names them.
- Duty: whether the spring works under a static or a dynamic load.
- Surface and packing, if your coiling line needs a particular finish or coil format.
- Quantity and destination.
For buying from abroad, see spring steel wire from Tรผrkiye, and the container loading guide for wire coils for how coils travel. Reinwent is a trading and sourcing company, not a producer. Request a quote and we check your specification with manufacturers.
