Hardening and Tempering
- The primary aim of the conventional Hardening and Tempering process is to enhance the mechanical properties of the bulk material, producing specific combinations of tensile/proof strengths, hardness and ductility (impact strengths).
- The process involves careful heating to high temperatures, typically between 780°C and 980°C, ‘soaking’ for specific times, quenching in air, oil, polymer or salt – depending on the material and requirements – followed by tempering of the hardened material to partly or substantially relieve quenching stresses and develop the particular properties required.
- Keighley Laboratories offers atmosphere controlled vertical pit batch furnaces, where long/large components can be treated or sealed quench furnaces where large numbers of smaller components are treated in batches.
- The primary benefit of through hardening and tempering is to give the best combination of bulk strength and ductility.
- For tool and die materials through hardening and tempering confers strength and wear resistance to suit specific applications.
- Harden and Temper treatment provides a vital basis for subsequent surface treatments such as Gas Nitriding, Nitrocarburising and even Induction hardening.
- When combined with our Press Quenching facility, shape and distortion can be controlled.
- The temperature used in final tempering can vary from less than 200° C to around 700° C, depending on many factors, and some materials may require more than one temper to achieve the desired stability and properties.
- Cryogenic (sub-zero) treatments (more commonly associated with the reduction of retained austenite levels in carburised alloy steel materials) may also be specified for particular through hardened/quenched and tempered materials, usually aimed at promoting full transformation and associated secondary hardening – most applicable to higher alloy steels including some tool steels.
- Scaling and surface oxidation is reduced using endothermic atmospheres with oxygen probe control on vertical pit and sealed quench furnaces.
- Components up to 1730mm long can be treated using special jigging to minimise distortion.
- Components up to 1120mm diameter and 1730mm long can be treated vertically using special jigging. Weight up to 2000Kg
- Fast quenching oils are available. Alternatively, a molten salt quench (180°C – 400°C marquench or martemper) may be used to minimise distortion as appropriate.
- This process is most commonly applied to steels although it can be applied to some other materials including SG cast irons and some non-ferrous alloys such as aluminium bronzes.
- Many common steels are routinely through hardened and tempered including but not restricted to the following: Carbon / carbon-manganese steels in smaller cross sections – 080M40 (EN8), 070M55 (EN9), 150M19 (EN14), 150M36 (EN15), low alloy steels in larger cross sections – 605M36 (EN16), 709M40 (EN19), 817M40 (EN24), 826M31 (EN25), 826M40 (EN26), 835M30 (EN30), Tool and Die steels -01, S1, D2, D3, H13. In addition, many cast steel grades can be hardened and tempered – advice must be sought before committing a design.
Keighley Laboratories Ltd
Registered Office:
Croft House
South Street
Keighley
West Yorkshire
BD21 1EG
Registered in England 164811
UK Tel: +44 (0)1535 664211
Email: info@keighleylabs.co.uk
