Applications of plain carbon steels
These are alloys of iron and carbon, chemically combined, with other elements such as manganese, silicon, sulphur, phosphorus, nickel and chromium. Properties are governed by the amount of carbon and the heat treatment used. Plain carbon steels are broadly classified as: low carbon (0.05-0.3%C), with high ductility and ease of forming; medium carbon (0.3-0.6%C), in which heat treatment can double the strength and hardness but retain good ductility; and high carbon (> 0.6%C), which has great hardness and high strength and is used for tools, dies, springs, etc.
Applications of plain carbon steels :
| % Carbon | Name | Applications |
| 0.05 | Dead mild | Sheet, strip, car bodies, tinplate, wire, rod, tubes |
| 0.08-0.15 | Mild | Sheet, strip, wire, rod, nails, screws, reinforcing bars |
| 0.15 | Mild | Case carburizing type |
| 0.10-0.30 | Mild | Steel plate, sections, structural steel |
| 0.25-0.40 | Medium carbon | Bright drawn bar |
| 0.30-0.45 | Medium carbon | High tensile tube, shafts |
| 0.40-0.50 | Medium carbon | Shafts, gears, forgings, castings, springs |
| 0.55-0.65 | High carbon | Forging dies, springs, railway rails |
| 0.65-0.75 | High carbon | Hammers, saws, cylinder liners |
| 0.75-0.85 | High carbon | Chisels, die blocks for forging |
| 0.85-0.95 | High carbon | Punches, shear blades, high tensile wire |
| 0.95-1.10 | High carbon | Knives, axes, screwing taps and dies, milling cutters |
Properties of carbon steels (BS 970) :
| Type | C (%) | Si (%) | Mn (%) | Tensile strength (Nmm-2) | Elongation (%) | Hardness, BHN* | Applications, etc. |
| 070 M20 | 0.2 | - | 0.7 | 400 | 21 | 150 | Easily machinable steels suitable for light stressing. Weldable |
| 070 M26 | 0.26 | - | 0.7 | 430 | 20 | 165 | Stronger than En2. Good machinability. Weldable |
| 080 M30 | 0.3 | - | 0.8 | 460 | 20 | 165 | Increased carbon improves mechanical properties, but slightly less machinable |
| 080 M36 | 0.36 | - | 0.8 | 490 | 18 | 180 | Tough steel used for forgings, nuts and bolts, |
| 080 M40 | 0.4 | - | 0.8 | 510 | 16 | 180 | Medium carbon steel, readily machinable |
| 080 M46 | 0.46 | - | 0.8 | 540 | 14 | 205 | Used for motor shafts, axles, brackets and couplings |
| 080 M50 | 0.5 | - | 0.8 | 570 | 14 | 205 | Used where strength is more important than toughness, e.g. machine tool parts |
| 216 M28 | 0.28 | 0.25 | 1.3 | 540 | 10 | 180 | Increased manganese content gives enhanced strength and toughness |
| 080 M15 | 0.15 | 0.25 | 0.8 | 460 | 16 | - | Case-hardening steel. Used where wear is important, e.g. gears and pawls |
| 060 A96^ | 0.99-1.0 | 0.1-0.7 | 0.5-0.7 | 1300 | - | 500 | High carbon spring steel |
*BHN =Brinell hardness number....^To BS 950.
Tempering temperature and clolour for carbon steels :
| Temperature ("C) | Colour | Applications |
| 220 | Pale yellow | Hacksaw blades |
| 230 | Light yellow | Planing and slotting tools, hammers |
| 240 | Straw yellow | Milling cutters, drills, reamers |
| 250 | Dark yellow | Taps, dies, shear blades, punches |
| 260 | Brown yellow | Wood drills, stone-cutting tools |
| 270 | Brown purple | Axe blades, press tools |
| 280 | Purple | Cold chisels, wood chisels, plane blades |
| 290 | Dark purple | Screw drivers |
| 300 | Dark blue | Wood saws, springs |
| 450-700 | Up to dark red | Great toughness at expense of hardness |
Labels: engineering materials