Iron powder is one of the “long-seller” material because it has been used since B. C. 300. Iron powder is mainly used for powder metallurgy in recent years. On the other hands, it is also used for the functional applications by using chemical reaction, such as body warmer, deoxidant and agricultural application. There are the several methods to produce iron powder, and reduced and water atomized iron powders are mainly used for the powder metallurgy due to their good compactibilities. In this paper, the details of production process of iron powders containing alloyed steel powders in JFE steel, which produces both reduced and water atomized iron powders, are described. In addition, the powder characteristics of these two kinds of iron powders are also described. The expansion of functional applications such as additive manufacturing process or magnetic cores is expected in the future, thus additional improvement of iron powders quality will be required.
The filling density decreases rapidly in the initial stage of consecutive compacting. As one of the reasons, it was thought that the history of the movement given to the powder just before the filling would change flowability, and experiments in this study showed that the history affected significantly on it. Based on these results, a high-precision filling system was developed.
In addition, in order to minimize the amount of elastic deformation of the punch, which causes cracking, a tool and a compacting press with a minimum punch length were devised. From the experiments using them, the optimum balance of amount of the elastic deformation for each punch that prevent cracks was clarified. By using the high-precision filling system stabilizing the filling density and the compacting technology preventing cracks, a new system that reduced the number of defective green compacts without adjusting compacting conditions was able to be developed.
I have been engaged in high precision of sintered machine parts, small complex shape design, and high efficiency manufacturing technology development in metal powder metallurgy products. It is very important to quickly incorporate market needs trends in new technologies and new products, or to commercialize them to meet customer needs. The elementary materials industry is also competing with other construction methods such as forging, casting, and pressing, and it is necessary to develop technologies that achieve high quality and low cost by taking advantage of the characteristics of those that can only be made with powder metallurgy technology. We will introduce the developed products and evaluation technical examples.
Conventionally, high Cr cast steel having excellent oxidation resistance and wear resistance has been used for the heat resistant bearing of the turbocharger. In recent years, the usage environment has become more and more severe, and bearing materials are required to have higher wear resistance and oxidation resistance. Therefore, we have developed high heat resistant sintered material that is superior in wear resistance and oxidation resistance to high Cr cast steel in high temperature environment. In microstructure of the developed material, particulate fine carbides are dispersed in the matrix of densified ferritic high Cr steel. The feature of the developed material is that it has excellent wear resistance by dispersing about twice as much carbide as high Cr cast steel. Another feature is that the shape of the carbide is granular in order to minimize the decrease in oxidation resistance. In addition, the developed material is densified by liquid phase sintering to suppress the progress of internal oxidation. Despite the large amount of carbide dispersed in the developed material, it has become possible to achieve higher oxidation resistance than conventional high Cr cast steel.