Agricultural
Farming and agricultural applications for ADI include plow points, till points, trash cutters, seed boots, ammonia knives, gears, sprockets, knotter gears, ripper points, tractor wheel hubs, rasp bars, disk parts, bell cranks, lifting arms, and a great variety of parts for planters, plows, sprayers and harvesters.
Defense
The defense industry has been relatively slow to adopt ADI, however some of the applications include track links, armor, ordnance and various hardware for trucks and armored vehicles.
Special Product Categories
Gears
Gears represent some of the best known, most widely publicized and high potential uses of ADI. During the early 1970’s the Finnish company Kymi Kymmene Metall began to replace forged steel with ADI in a in a wide range of gears, with highly satisfactory results.
In North America, ADI achieved a major breakthrough in 1977, when General Motors converted a forged and case hardened steel ring gear and pinion to ADI for Pontiac rear drive cars and station wagons. The decision came after nine years of development work and six years of field testing. The automaker was able to gain both significant cost savings and product improvement by changing to ADI.
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ADI Timing Gears for Cummins B-Series diesel engines. Replaced forged and case carburised 1022 steel with 30% cost saving.
In 1983, the Cummins Engine Co. began to use ADI timing gears, produced to AGMA class 8 standards, in its B and C series diesel engines. These gears were machined and hobbed from annealed Ductile Iron castings. A crown shaving operation was carried out on the gear teeth prior to austempering, and the only operations performed after
austempering were the grinding of the bore diameter and shot peening. Annual production exceeds 30,000 sets and the cost savings are estimated at 30% compared to the forged and carburized 1022 steel gears previously used.
Table 4.8 Comparison of energy requirements for the production of ADI and forged and carburized steel gears.
Energy consumption kWh per Tonne
Operation ADI Forged steel
Production of blank Annealing 2,500 4,500 500 Austempering 600 --- Case-hardening --- 800-1,200 Total 3,100 5,800-6,200
Table 4.8 describes the energy savings of almost 50% resulting from the conversion to ADI gears. In addition to
savings in energy and overall production costs, ADI gears offer the following advantages:
increased machine shop productivity
reduction in weight of up to 10%
reduced gear noise
rapid "break in" of new gears and,
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Austempered Ductile Iron gears to patented specifications K9805.
Courtesy: Hymi Kymmene Engineering, Finland.
Austempered Ductile Iron Hypoid Axle Gears: Conversion to Cast Ductile Iron from Forged Steel gave: major production cost saving, better machinability, quieter operation, reduced weight.
Courtesy: General Motors Corp. Central Foundry Div., Saginaw, Michigan, USA
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Crankshafts are another potentially significant application for Austempered Ductile Iron. The first commercially produced ADI part was a small crankshaft for a hermetically sealed refrigerator compressor. It was cast by Wagner Castings Company (US) for Tecumseh Products. Production of that part was initiated in 1972 and since that time, millions of those crankshafts have been produced.
Engines being developed by the automotive industry require weight reduction in parts that will be required to handle increased power. Automotive design engineers have evaluated ADI as a candidate for both the replacement of forged steel crankshafts and the upgrading of existing Ductile Iron crankshafts. The Ford Motor Company made an exhaustive, three year study of ADI crankshafts and concluded that they met all design criteria. During this study, the importance of fatigue testing was identified, and the following results were obtained:
Fatigue Test Method Fatigue Strength
ksi MPa
Constant Strain Amplitude 55 380
Rotating Bending 65 450
Reversed Bending 60 415
Reversed Bending (fillet rolled) 90 620
A thorough, joint Motor Industry Research Association / Cast Metals Development Laboratories study on ADI crankshafts concluded that properly fillet rolled ADI crankshafts exhibited fatigue properties comparable to, or better than, the best forged and heat treated steel crankshafts.
In another documented crankshaft study conducted at the Manchester (England) Materials Science Center, the authors demonstrated the performance capability of ADI crankshafts in one cylinder commercial and four cylinder automotive engines. They noted a 10% rotating weight reduction and an estimated 30% cost savings.
As of this writing ADI crankshafts are employed in high volume commercial applications and low volume automotive applications. As the specific power requirements for automotive engines are increased, ADI will become a more viable alternative to the heavier, more expensive forged steel crankshaft.
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An assortment of ADI "ground engaging" parts. Courtesy of Applied Process Inc.
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ADI crankshaft for a hermetically sealed compressor (first produced in 1972).
Courtesy of Wagner Castings and Tecumsen Products.
Conclusion
As design engineers become more familiar with ADI’s strength, toughness, wear resistance and noise damping properties and learn about the impressive cost and weight savings reported in successful ADI conversions from steel castings, weldments and forgings and aluminum castings and forgings, ADI will continue its remarkable growth.