material will not be strong enough for
class,” he said. “For
di f ference in cost,
rather have less inventory
the 300-lb. the small I would on
This header for a radiant water heater was converted from bronze to gray iron for cost savings and weight reduction.
hand and reduce
the changes in patterns for switching materials. Therefore, I would rather invest in 65-45-12 ductile iron to have on hand in rough or fi nished stages for either class of valves.” According to Atkin and Peaslee,
who both work for companies pro- ducing ductile and gray iron castings, ductile iron parts can cost from 10 to 30% more than gray iron parts—a price difference that some customers, such as Sugarman, can live with. “Engineers in general will prefer to
use ductile iron over gray iron,” Atkin said. “From a mechanical standpoint of just strength and ductility, it has a tremendous advantage.”
Show Goes On Despite the conversions to other
materials, gray iron still does have a role to play in manufacturing, accord- ing to Kuehnel. One of gray iron’s main markets, machine tool, is a key cog to the global economy and technical developments, he said. “Machine tools use a considerable
amount of gray iron casting,” Kuehnel said. “As the economy grows and new products are developed, we have to look toward that industry to develop the new tools and machines needed to make them.” Sugarman said at his company,
most of the potential conversions to ductile iron have already been made. He continues to purchase gray iron Class 40 material for simple designs, such as housings, cover plates, adapter plates, bonnet extensions, levers, col- lars and nuts. “If you are making something to
shape that doesn’t have a lot of stress requirements, gray iron is the best mate- rial you can use,” Atkin said.
METAL Online Resource
Visit
www.metalcastingdesign. com/content/category/20/48/314/ for an article forecasting future shipments of gray iron castings and other metals.
32 METAL CASTING DESIGN AND PURCHASING SEPTEMBER/OCTOBER 2010
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