Manufacturers' use of cast austempered ductile iron components in new machinery should be a selling point for dealers.

The booming North American farm economy of the past few years has resulted in a bevy of new ag technologies, equipment advancements and wide ranging product innovations. Buried in the multitude of new product announcements coming from manufacturers is a shift in materials and processes used to produce key components in the new equipment. One example is the use of austempered ductile iron (ADI).

According to Vasko Popovski of Applied Process, a commercial heat treater that specializes in austempering, ADI isn't a new engineering material, but it is experiencing significant growth in agricultural applications for a number of reasons. Austempering isn't a new process either, having been developed in the 1930s.

It is described as a specialized "isothermal heat treating process that imparts superior properties to ferrous materials." These properties include improved wear resistance and impact toughness that cannot be achieved in the as-cast state of irons or by using other heat treat processes.

He says in addition to its excellent mechanical properties, ADI parts can often produce significant cost savings compared with forgings or machined and welded components. Coupled with casting's design flexibility that can integrate several components into a single part, engineers are giving cast ADI a long look, especially for demanding applications.

Popovski says the lack of skilled welders is also driving design engineers to take a long, hard look at cast austempered ductile iron.

"Most manufacturers base their operations on welding, and not too many have foundries. So they've traditionally welded several parts together to form a single component that becomes part of their finished equipment. I've heard from many of them that they just can't find skilled welders these days," says Popovski.

He adds that manufacturers he's working with have also expressed a desire to reduce or eliminate as many part numbers as they can. "If you go from 5 pieces welded to one piece cast, you're able to eliminate 4 part numbers," he explains. "Mechanically inclined farmers also appreciate the simplicity of a single cast part vs. a complex weldment."

Trunnion Bracket & Guard

According to Popovski, dozens of machined from barstock, welded and forged parts have been converted to ductile iron and ADI castings in recent years. He points to AerWay, a tillage equipment manufacturer, as a firm that has successfully performed multiple forging to casting conversions.

One half of AerWay's trunnion bracket is as-cast ductile iron, while the other half of the trunnion bracket with guard utilizes austempered ductile iron. This was originally an 8-piece assembly.

According to Matt Mayer, regional sales manager for AerWay, the lack of welders is not why the company is pursuing ADI. In fact, several conversions the company has undertaken resulted from conversations with farmers. In one case, a trunnion bracket was originally fabricated from carbon steel barstock and a trunnion bracket guard was designed as a piece of bent steel with two ears welded on. One bracket was mounted to the implement, and the mating bracket was assembled to the trunnion bracket guard with four fasteners. Together they surrounded a bearing. "We chose the ADI route to save labor and to integrate protection of the bearing.

Mayer and AerWay engineers determined that one of the brackets could be cast in ductile iron at a cost savings with no loss in performance. They also decided to combine the other trunnion bracket with the accompanying guard into a one-piece ADI casting with increased wear resistance.

While the initial design was well suited for the implement, working with Applied Process and Urick Foundry of Erie, Pa., it was determined that the assembly design could be further optimized for cost purposes.

Popovski explains that natural flowability and near-net shape capabilities of ductile iron were exploited to minimize section size and reduce the need for alloying in advance of heat treatment. This, in turn, reduced the weight and cost of the part. The final design resulted in both weight and cost savings because it fully exploited the iron casting process' ability to put material where it is needed and to remove material from where it is not necessary. Specifically, the regular ductile iron trunnion bracket did not incur the cost of heat treatment while the more demanding trunnion bracket with guard was properly austempered.

The new trunnion bracket with guard can also be retrofitted to previous units for users who want to upgrade the front only and not buy both halves. It also provides additional coverage of the bearing housing over the previous model by approximately 0.25 inch on either side (0.50 inch total) for increased protection.

The original design of the trunnion bracket with guard was an 8-piece assembly, which included the bracket machined from barstock, a 3-piece weldment and 4 fasteners. The final design was a 1-piece casting that reduced overall costs by 43%.

For the farmer, the new design improved field performance by providing better wear resistance, which means less labor is involved for changing parts and more protection for the bearing. And it's a far less complex part.

Finger Drive & Gears

Pequea, a manufacturer of hay rakes, tedders and a variety of other ag machinery and turf equipment, has also successfully converted forged and machined parts to ADI castings.

The design of Pequea's new gearboxes for its hay tedders features cast austempered ductile iron gear, pinion and finger drives. These were previously steel forgings.

According to Jim Westlake, Pequea's engineering manager, when the company decided to stop sourcing gearboxes for its tedders from China, they also decided to redesign them and specified ADI at the same time. He says the gears were originally steel forgings, and the finger drives were made from case-hardened steel.

Westlake says Pequea went to ADI for several reasons. While cost played a role in the conversions, more consistent quality material available from domestic suppliers provided the confidence needed to make the switch. "With our current casting suppliers we're getting good process control and the consistency of the heat treat was better than we were getting with the steel parts." He says gearbox to gearbox, the cost of those produced domestically are competitive with what they were getting from China.

Pequea also made the transition from forecasting production to lean manufacturing where the company fills orders as needed instead of anticipating what they would sell. "We're a small shortline company and we weren't necessarily getting the same attention the big manufacturers could demand from their overseas suppliers. With our casting suppliers being local, our supply chain improved dramatically and we have better control of our production and inventory."

But Westlake says it came back to the dependability of the parts themselves and its farm customers have seen improved performance and reliability from the equipment since they made the switch. "We've been using ADI for almost 4 full years and have not had a single failure in that time."

Talking Points

Popovski says their dealers have several talking points when selling equipment that utilizes ADI. "Most farmers are mechanically inclined and curious about how their equipment is made and from what. Salespeople who understand how castings are being used to reduce the complexity of farm machinery and that ADI is outperforming steel forgings in the field can differentiate their equipment from the others because it provides increased wear and abrasion resistance, and by reducing the potential for impact damage."

He adds that the integrated design of cast ADI parts can also reduce downtime as well as operating costs associated with parts and labor.