In the conventional austempering process, the casting material is allowed to stand for a sufficient time (usually 1-2 hours) until a completely austenite (γ) matrix is obtained in the temperature range 850-950 ° C. Thereafter, it is rapidly cooled to a temperature range of 250-400 ° C and allowed to stand at the selected temperature for 1 to 4 hours, then cooled to room temperature in air.
The main purpose of the austempering heat treatment in spheroidal graphite cast irons is to form an acicular (beynitic) matrix structure composed of carbide-free ferrite, in which high-carbon austeniticity occurs.
Application Areas of Austempered Cast Iron Parts
Automotive
- timing gear
- output shaft
- control arm
- Joint
- engine mount
- Differential crankcase
- crankshaft
- ball joint
- tow hook
Agricultural Machinery
- plow tip
- control arm
- bucket teeth
- J-Hook
- pruner gear
Heavy Vehicles
- torqueplate
- U bolt bridge
- tail bracket
- wheel hubs
- Differential case and clutch ring
- spindle hook
Limitations of Austempering Process;
- Applies to parts where perch conversion can be avoided.
- The piece should be cooled fast enough to prevent perlite conversion.
- Thin section parts can be cooled faster.
Grades of spheroidal graphite cast iron according to DIN standard
Advantages of austempering process;
- Low distortion
- High ductility
- Homogeneous and consistent stiffness
- toughness and greater wear resistance
- High impact and fatigue strength
- Resistant to hydrogen brittleness
- High toughness
- High wear resistance
- Increase in fatigue strength
- Increase in hardness
- Increase in tensile and yield strengths