How Does Composition Decide What Steel Can Do?
Every steel is iron plus carbon plus alloying elements. A few tenths of a percent of each changes strength, hardness, toughness and how the steel machines.
| Element | What it does |
|---|---|
| Carbon | Raises strength and hardness. Lowers ductility and weldability. |
| Manganese | Adds strength and hardenability. |
| Chromium | Adds hardenability and wear resistance. Above about 10.5% it makes steel stainless. |
| Molybdenum | Adds hardenability and strength at temperature. |
| Nickel | Adds toughness, including at low temperature. |
| Sulphur | Improves machinability in free-cutting grades. Lowers toughness. |
| Boron | A trace adds hardenability to low carbon steel. |
How Do You Select a Steel Grade?
Work through five questions, in this order.
- What load does the part carry: steady, repeated or shock?
- What is the section size? Thick sections need more hardenability.
- Does the surface wear or corrode?
- How is the part made: machined, forged or cold headed?
- What standard or customer specification applies?
OneKaizen's grade pages list each grade with its equivalents, rated direct, close or approximate, and its typical uses. Browse steel grades ↗
What Does Heat Treatment Do to Steel?
Heat treatment heats steel to a set temperature and cools it at a set rate to change its structure. The main treatments are:
- Annealing. Softens steel for machining.
- Normalising. Refines the structure for an even condition.
- Hardening and tempering. Quenching hardens the steel. Tempering restores toughness and sets the final strength.
- Case hardening. Gives a hard surface and a tough core on low carbon steels.
How deep a steel hardens is its hardenability. Estimate it with our Jominy calculator, or order bars already heat treated.
How Is Steel Tested?
| Test | What it tells you |
|---|---|
| Chemical analysis | Confirms the grade. |
| Tensile test | Yield strength, tensile strength and elongation. |
| Hardness test | Whether the heat treatment reached its target. |
| Jominy test | Hardenability of the steel. |
| Ultrasonic test (UT) | Internal defects in the bar. |
| Microstructure | Decarburisation, grain size and inclusions. |
Every heat we ship carries an EN 10204 3.1 mill test certificate. Tensile, hardness and ultrasonic testing are available on request.
How Do We Use Metallurgy in Steel Supply?
OneKaizen's metallurgists check your grade against the duty of the part, pick the mill and the heat, set the condition and the finish, and read the certificate before the steel leaves. That is what lets us supply steel that works the first time on your line.
Common Questions
What is metallurgy?
Metallurgy is the science of metals: how they are made, how their structure forms and how that structure decides their properties. For steel, it explains why one grade is hard, another tough and another easy to machine.
What does a metallurgist do?
A metallurgist chooses the steel grade and condition for a job, specifies heat treatment, interprets test results and investigates failures. Our metallurgists do this for the steel we supply.
Why do we heat treat steel?
Heat treatment changes a steel’s structure to reach a target hardness, strength and toughness. A grade that is soft as rolled can become a strong shaft or a hard gear once it is treated.
What is hardenability?
Hardenability is how deep a steel hardens when quenched. It depends on chemistry and section size. It is different from the maximum hardness the steel can reach.
What is the Jominy test?
The Jominy end quench test quenches one end of a steel bar and measures hardness along its length. The curve shows how hardenability falls with depth. Try our Jominy calculator for an estimate from chemistry.
How do I choose a steel grade?
Start with the load, the section size, the wear and the machining route. Then pick a grade and condition that meets the strength and toughness you need at that size. Our grade pages list equivalents and typical uses.
What is EN8 steel used for?
EN8 is a medium carbon steel used for shafts, studs, bolts and general engineering parts. Browse our grades for its equivalents and properties.