Steel

Low Carbon free cutting steels
Used extensively for turned parts for general engineering and more specifically the automotive industry.

Table 1

Low carbon steels
The steels in this category are usually referred to as mild steels. They are particularly useful for bending, forming and case-hardening. They are useful for lightly stressed components and are available in several different forms including round, square, hexagonal and flat section.

Table 2

Medium carbon and carbon manganese steels
Of higher strength than mild steels these respond to heat treatment and include some types suitable for induction and flame hardening Depending on analysis and ruling section tensile strengths up to the T range 850-1000 N/mm may be obtained although 700-850 N/mm is more common. Applications include gears, shafts, racks, pinions, studs, bolts, nuts, rollers, etc.

Table 3

Alloy Case-hardening Steels
When a hard wear resisting surface and a tough supporting core is required the choice of steel will depend on the ruling section and core strength required for the. component. Care should be taken in selecting heavily alloyed types for parts with a thin cross section such as gear teeth as through hardening can result in brittleness and loss of shock resistance.

Table 4

Alloy Direct Hardening Steels
Steels in this group are available with a combination of alloying elements including nickel, chromium, molybdenum and vanadium. They are supplied in the softened condition. After machining they can be hardened and tempered to a range of tensile strengths. They can also be supplied in the finally heat treated condition, where they are machinable and can be put into service without further heat treatment. Induction hardening of the surface can also be carried out on many of the specifications if required. Suitable for a wide range of applications where high strength and resistance to shock is important.

Table 5

Stainless Steels

Ferritic
These stainless steels are mostly used for decorative trim. They are low strength but have good ductility and can be easily formed. These steels are mostly used for domestic and automotive trim, food processing and catering equipment, vehicle exhaust systems etc.

Table 6

Martensitic
These grades can be hardened and tempered to give tensile strengths in the range 550-1000 N/mm. Typical applications include cutlery, surgical instruments, fasteners, valves, spindles and shafts. Martensitic steels are magnetic.

Table 7

Austenitic
These steels are non-magnetic and cannot be hardened and tempered in the normal manner although they do work harden. This group offers the highest resistance to corrosion and is used for components in the food, chemical, gas and oil industries as well as for domestic appliances, automotive parts, hospital equipment, yacht fittings etc.

Table 8