Martempering and Marquenching / Isothermal Heat Treatments

  • These processes are most commonly used in the hardening of complex shapes or for components with varying cross sections to allow equalisation before transformation to the hard structures.
  • Can be used with carburised parts, through hardened (quench) and tempered materials and tool steels.
  • These treatments use an interrupted elevated temperature quench.  Components are heated to the austenitising temperature and quenched, normally in molten salt, at a temperature just above the martensitic transformation start point (Ms). During the interrupted quench, the components are delayed in the quenching medium for sufficient time to equalise the temperature throughout the component and then air cooled through the martensite formation range.
  • Typical temperatures range between 180°C to 230°C.
  • The suitability of a particular material or section size for these processes is best determined by a metallurgist experienced in materials and heat treatments.  For these reasons these processes are considered Technical in nature.
  • Can also be used on most steels that respond to oil quenching as these are adaptable to martempering.  Exceptions might include low hardenability grades or larger cross sections.
  • All martempered components need a final temper after isothermal quenching. Suitable for components such as gears, shafts and rolls.
  • Components up to 680mm in diameter and 1200mm long can be treated vertically using special jigging.
  • Weight up to 400Kg.
  • Most common materials: ferrous metals, steels, cast iron, SG iron, 709M40 (EN19), 817M40 (EN24), 826M31 (EN25).
  • Annealing applied to cast iron castings to remove chilling from founding is a high temperature process. This process may not be suited to all chilled irons (for example those containing chromium or other elements that cause or contribute to excess carbide chilling).
  • Whilst most metallic materials can be “annealed” using an applicable process, commercial processes are more commonly limited to ferrous materials, aluminium alloys, copper alloys,  nickel alloys and titanium alloys.
  • For the most common range of ferrous materials KLL can often offer vertical or other special fixturing to minimise distortion – however, most distortion comes from the relief of uneven residual stresses and cannot be prevented.
  • Annealing at KLL is normally carried out in open atmospheres with no control of surface oxidation and scaling. This is usually applicable to un-machined or proof machined components or materials with shot blasting often used to clean parts up for subsequent machining.
  • Components up to 1120mm in diameter and 1730mm long can be treated vertically using special jigging.  Maximum weight 2000Kg.

James Menzies

Production

Leonard Powell

Technical Planner

David Wright

Production Director

Mark Barron

Business Development Manager

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

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