SteelKey facts
- Tensile strength is the highest stress a material carries while being pulled, just before it fractures.
- It is found with a tensile test, in which a sample is pulled to failure while force and stretch are recorded.
- For steel wire it is usually written in N/mm², which is numerically the same as MPa.
- Cold working, which includes drawing wire through dies, raises tensile strength and lowers ductility.
- Annealing reverses that cold work and makes the wire soft again.
What does high tensile mean?
The word tensile refers to tension, a load that pulls a piece of material along its length and tries to stretch it. A wire under tension has a stress in it equal to the pulling force divided by its cross-sectional area. Raise the force far enough and the wire first stretches permanently and then snaps.
High tensile wire is wire picked because it can carry a large stress of this kind before it gives way. The term is relative. No standard we found sets one number above which wire becomes “high tensile”, and the threshold a buyer has in mind depends on the job. That is why a serious enquiry always replaces the phrase with a strength band in N/mm², checked against a named standard.
Tensile strength and yield strength
Two figures describe how wire behaves under pulling, and they are easy to confuse.
| Feature | Tensile strength | Yield strength |
|---|---|---|
| What it marks | The maximum stress before the sample breaks | The stress at which permanent deformation starts |
| Below this point | The sample still holds together | The sample springs back fully when unloaded |
| For a ductile steel | The higher of the two figures | The lower of the two figures |
| Effect of work hardening | Rises | Rises |
| Unit for wire | N/mm² or MPa | N/mm² or MPa |
Designers of ductile structures tend to work from yield strength, since a part that has yielded is already bent out of shape. Tensile strength is the figure buyers usually see on a wire offer. Both rise when steel is cold worked.
How is tensile strength measured?
The measurement is a tensile test. A sample of wire is gripped at both ends in a universal testing machine and pulled at a controlled rate until it breaks. The machine logs the force and the extension the whole way through. Dividing force by the original cross-section turns the record into a stress-strain curve, and the highest point on that curve is the ultimate tensile strength.
Because the result is a stress, the force is divided by the area. A thick wire needs a far bigger force to break than a thin one, yet the two can show the same tensile strength in N/mm².
N/mm², MPa and psi
Stress is force per area. In SI units that is the pascal, one newton per square metre, and for metals the megapascal is the preferred multiple. One megapascal is a million newtons per square metre. A square metre holds a million square millimetres, so one megapascal also equals one newton per square millimetre.
In practice, N/mm² and MPa are the same number: 1,000 N/mm² reads as 1,000 MPa. Our product pages use N/mm². American documents often use psi, pounds-force per square inch, or ksi, which is a thousand psi. When you compare offers, convert everything into one unit first.
How does wire become high tensile?
Two levers set the strength of steel wire: how much it has been cold worked, and what steel it was drawn from.
Cold drawing. Wire is made by pulling rod through a die with a smaller hole, usually through a run of dies that each reduce it a little. This is done below the recrystallization temperature of the steel, typically at room temperature, so it counts as cold work. Each pass deforms the metal plastically. The steel gets harder, stronger in tension and higher in yield strength. This is work hardening. The cost is ductility: the wire bends less readily than before.
Steel grade. Carbon steel references group high-carbon steel with springs and high-strength wire, and most spring steels are medium- or high-carbon grades. The trade-off is the same as with cold work. Strength comes with lower ductility, so the grade is chosen for the job rather than simply pushed to the top. The material side is in high carbon steel wire.
Large reductions can make wire too hard to draw any further, so an intermediate anneal may be added between passes. A final anneal undoes the hardening completely. That is the step that separates soft tie wire from strong drawn wire (see hard drawn vs annealed wire); our explainer on cold drawn wire walks through the drawing line step by step.
What is high tensile wire used for?
Strength in tension is the property most wire is valued for, so the list is long. Drawing references name springs, paper clips, wheel spokes and tension-loaded structural parts among the products made from drawn wire.
Springs are the clearest case. Spring steels have a very high yield strength, which lets a part bend or twist a long way and still return to shape. For that application, read our companion explainer what is spring wire, and see our spring steel wire page for the range we source.
Our cold drawn wire is offered in diameters from 0.8 to 6 mm with a tensile strength of 500 to 1,000 N/mm², to EN 10218-2. It goes into nails, staples, bolts, screws and other fasteners and small hardware. All wire types are listed on the steel wire hub.
How do you specify high tensile wire in a quote request?
A useful request leaves no room for two offers that look alike but test differently. Include:
- Diameter in millimetres. If your drawing uses gauge numbers, convert them with the wire gauge chart.
- Tensile strength band in N/mm², as a minimum and maximum. A band, not the word “high”, is what suppliers can test against.
- Standard, so the test method and tolerances are fixed.
- Surface, for example bright or coated (see what bright wire is).
- Quantity, coil format and destination.
For zinc-coated wire, see galvanized wire tensile strength. If you are buying from abroad, our page on cold drawn wire from Türkiye covers ordering, and the container loading guide for wire coils explains how coils ship. Reinwent is a sourcing company, not a mill. Request a quote and we collect offers from manufacturers for you.
