Ductile Iron Gears

Ductile iron is basically a cast iron in which the flakes of graphite are changed by the process of chemical reaction. They are transformed into nodules or spheres. In recent times, gear makers are increasingly opting for Ductile Iron Gears as a cost saving alternative to steel gears.

Comparison with Steel Gears
Those vouching for Ductile iron Gears stresses the distinct advantages of them over cast steel gears. These are the following:

• Ductile iron is similar in strength to a cast steel.
• Ductile iron is easier to pour.
• High hardness is easily obtainable.
• Supposedly better sliding wear against the steel pinions.
• After machining Ductile iron gives better dimensional stability.
• Weight reduction by at least 10%.
• Reduced gear noise.
• Increase in machine shop productivity.

Comparison of energy requirements : ADI vis-a-vis Forged steel gears

Energy consumption (kWh/ Tonne)
Operation	Austempered Ductile Iron	Forged steel Gears
Production of blank Annealing	2500	4,500 500
Austempering	600	---
Case-hardening	---	800-1,200
Total	3,100	5,800-6,200

Ductile Iron Gears in Mining Applications
ADI (Austempered Ductile Iron) gear segments is an integral feature of the mining industry. The gear segments are applied in rail tipping assemblies for emptying entire rail cars filled with ore.
The alloys for the gears has:
Tensile strength: 150,000 PSI
Yield strength: 100,000 PSI

Buyer's Consideration in Ductile iron Gears
As an informed buyer the following things needs to be checked for zeroing on to the best ductile iron gears:

• Tensile strength
• Chemical analysis
• Material hardness
• Required AGMA levels
• Inspection of - magnetic particle - dimensions
• Ultrasonic inspection