GlossaryKind of term: Manufacturing termC45
What is C45?
C45 is a non-alloy quenching and tempering steel with about 0.45 % carbon, used for shafts, pins and machine parts that must be stronger than structural steel.
Its material number is 1.0503, and the number in the name is the carbon content times one hundred. Apart from carbon, manganese and silicon it contains no significant alloying elements. It is supplied in conditions such as normalised (+N), soft annealed (+A), quenched and tempered (+QT) and, as bright bar, cold drawn (+C). Typical parts are shafts, pins, spindles, small gears and machine parts that must be stronger than structural steel.
What does the standard say about C45?
C45 is listed in EN ISO 683-1, the standard for non-alloy quenching and tempering steels that replaced EN 10083-2; bright bar is also covered by EN 10277. The name follows EN 10027-1 and the material number EN 10027-2. Besides C45 the standard lists C45E (1.1191), with lower maximum phosphorus and sulphur, and C45R (1.1201), with sulphur held within a range for better machinability. Ck45 is the old DIN name for C45E. A grade without a condition does not fix the strength: that depends on condition and section size, so the condition belongs on the drawing and the order.
How does C45 behave in the shop?
C45 machines well in +N. In +A it is softer but can smear more, and chips break less readily; quenched and tempered it is harder and needs lower cutting data. A running surface or bearing seat that must be hard is often induction or flame hardened, usually by a subcontractor, with stock left for grinding afterwards. How far C45 hardens through depends on section size: in larger diameters the core stays softer than in an alloy steel such as 42CrMo4. It can be welded, but usually needs preheating and sometimes a post-weld treatment, depending on thickness and process. Whether C45 works out cheaper than an alloy steel depends on price per kilo, condition, heat treatment and finishing taken together.
What is C45 often confused with?
C45 is not a structural steel such as S355, which is designed for welding and is not quenched and tempered. Nor is it 42CrMo4: without chromium and molybdenum C45 hardens less deeply, so it falls short in larger sections or where higher strength and toughness are required. Load, section and specified condition decide which of the two will do.
Frequently asked questions
What is the difference between C45 and 42CrMo4?
C45 is non-alloy; 42CrMo4 contains chromium and molybdenum. That lets 42CrMo4 harden more deeply and stay stronger and tougher in larger sections. Which will do depends on the load, the section and the condition the designer specifies.
Can C45 be hardened?
Yes. C45 can be quenched and tempered, and induction or flame hardened locally, on a bearing seat for example. The hardness and case depth you reach depend on section and process. Dimensions that must hold after hardening usually get grinding stock and are ground afterwards.
Is C45 the same as Ck45?
Nearly. Ck45 is the old DIN name for the variant with lower limits for phosphorus and sulphur, now called C45E. If an older drawing says Ck45, order C45E unless the customer says otherwise.