TESTING 1-2-3
IMPROVING ADI WITH V & NB
A 1
2 3
An experiment sought to determine whether microalloying ductile iron with vanadium and niobium would have the same benefi cial effects as microalloying steel with those same elements.
AN MCDP STAFF REPORT
ustempered ductile iron’s (ADI) engineering prop- erties, such as tensile strength, elongation and wear resistance, are comparable to that of steel, and the material has been used as a forged steel replace- ment in several applications, such as crankshafts, camshafts, diff erential gears, chain links, spiral, ring and pinion gears, and universal joints. Curious about improving ADI’s properties
further, Devinder Padan, assistant general man- ager, Tata Motors Ltd., Jamshedpur, India, led a study to test the material’s ability to replicate
other steel characteristics, namely, the ability to be microalloyed. Microalloying is the addition of certain elements in very small quantities, usually between 0.05 to 0.15%, to meet certain mechanical properties rather than a specifi c chemical com- position. T e development of microalloyed steel with small amounts of elements like vanadium and niobium has led to signifi cantly improved mechanical proper- ties, superior to that of the usual structural steels. In the paper, “Microalloying in Austempered Ductile Iron,” Padan discusses the promising results of microalloying ADI with vanadium and niobium.
ADDING IT ALL UP
Microalloying in Austempered Ductile Iron (ADI) Devinder Padan, Tata Motors Ltd., Jamshedpur, India Background—Microalloyed steel with vanadium and niobium exhibits signifi cantly improved mechanical properties. Would microalloying austempered ductile iron with those same elements provide similar results?
Procedure—Quantities of nickel, Fe-V, Fe-Nb and Fe-Mo were added to the molten metal after it was poured into a ladle to produce the experimental alloys. The metal was cast into standard test bars and given austempering treatment. Results and Conclusions—The addition of microalloying elements V or Nb increased the tensile strength of as-cast ductile iron and did not affect the ability of the metal to be austempered. The microalloyed ADI castings showed improvement in mechanical properties, such as tensile strength and increased wear resistance.
Question
Considering microalloyed steel with vanadium and niobium exhibits significantly improved mechanical properties, would microalloying austempered ductile iron with those same elements provide similar results?
1
Background Austempered ductile
iron (ADI) commonly is alloyed with elements like molybdenum, nickel, and
copper, which are used to improve hardenability and help stabilize austenite. Vanadium and niobium are considered for microalloying because they facilitate grain refin- ing and age hardening. Higher properties can be achieved without additional heat treatment. Previous studies on microalloy- ing with niobium and vanadium have been conducted on iron but limited to ferrite-pearlite grades of ductile irons. Padan antici- pated the benefits of the addition of the elements would justifying microalloying ADI. He designed an experiment to study the effects of microstructure, mechanical properties, wear characteristics and austempering response when microalloying ADI with 0.1% vanadium or 0.043% niobium. The results were compared with the results of a standard ADI containing 0.3% molybdenum and 1.4% nickel.
42 | METAL CASTING DESIGN & PURCHASING | Nov/Dec 2012
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