摘要
The present investigation deals with hot powder preform forging technique for the development of high density iron-phosphorus based alloys. These alloys are known for hot-shortness and are therefore not considered suitable for high temperature working. To remove this problem proper soaking at high temperature to eliminate iron- phosphide eutectic and bring entire phosphorus into solution in iron was aimed. Attempting hot forging thereafter completely eliminates hot as well as cold shortness and thereby helps to form these alloys into very thin sheets. It has also been possible to eliminate the use of costly hydrogen atmosphere during sintering by use of addition of carbon as a reducing agent to form CO gas within the compact by reacting with oxygen of iron powder particles. The glassy ceramic coating applied over the compact serves as a protective coating to avoid atmospheric oxygen attack over the compact held at high temperature. Combined application of carbon and glassy ceramic coating has lead to economy in P/M processing for soft magnetic applications. Fe- 0.07C- 0.3O- 0.35wt% P- 0.35wt% Cr alloy so formed yielded coercivity as low as 0.42 Oe, resistivity as high as 21.8 μ cm and total loss as low as 0.170 W/Kg. Such a combination of properties may suit their application in magnetic relays and transformer cores.
The present investigation deals with hot powder preform forging technique for the development of high density iron-phosphorus based alloys. These alloys are known for hot-shortness and are therefore not considered suitable for high temperature working. To remove this problem proper soaking at high temperature to eliminate iron- phosphide eutectic and bring entire phosphorus into solution in iron was aimed. Attempting hot forging thereafter completely eliminates hot as well as cold shortness and thereby helps to form these alloys into very thin sheets. It has also been possible to eliminate the use of costly hydrogen atmosphere during sintering by use of addition of carbon as a reducing agent to form CO gas within the compact by reacting with oxygen of iron powder particles. The glassy ceramic coating applied over the compact serves as a protective coating to avoid atmospheric oxygen attack over the compact held at high temperature. Combined application of carbon and glassy ceramic coating has lead to economy in P/M processing for soft magnetic applications. Fe- 0.07C- 0.3O- 0.35wt% P- 0.35wt% Cr alloy so formed yielded coercivity as low as 0.42 Oe, resistivity as high as 21.8 μ cm and total loss as low as 0.170 W/Kg. Such a combination of properties may suit their application in magnetic relays and transformer cores.
