The paper, titled Improved Quality by Carbon Potential Control in Metal Injection Moulding Sinter Furnace Atmospheres, was presented by Tony Palermo, metallurgy program manager for Linde in North America, and Akin Malas, head of heat treatment industry segment, at Powdermet, which took place in Nashville, Tennessee, USA, from 10-13 June.
The paper described a means to control the chemical carbon potential of the sintering atmosphere in order to produce higher quality product while lowering the cost of production.
"There are a number of practices which, if not controlled properly, may contribute to the generation of defects or insufficient sintered part properties or appearance, which reduce quality, increase costs, and lead to dissatisfied customers and, ultimately, diminished market share," Palermo said in his paper. "We have found that one of the root causes of these problems resides in the surface decarburization or carburization of the sintered parts which may be the result of carbon potential fluctuation in the sintering process."
The problem can be eliminated by using Linde’s Sinterflex carbon control system to control the carbon potential in the furnace throughout the sintering process. The technology uses continuous atmosphere sampling, a proprietary oxygen probe, and a carbon monoxide analyzer to continuously calculate atmosphere carbon potential and provide the addition, when needed, of an appropriate trim gas mixture to maintain carbon potential within a desired, pre-set range. "The objective of this technology is to maintain a furnace atmosphere carbon potential that contributes to the processing of sintered parts that meet required, or desired, carbon composition and consequent properties," Palermo added.