Metcalf Speech to IMM About Their Superalloy Furnace
The Vacuum Induction Melting Facility located here has many features which make it unique in the world. It is a facility capable of producing new and high quality metals with new shapes well into the twenty first century.
The staff of IMM and Iwakuni have fully explained the physical features of the facility. You have been able to see the features including a three chamber design that allows for several melts to be completed without exposing the melt chamber to atmosphere.
You have seen the deep pit which extends more than ten meters below the pouring point. This feature allows batch continuous casting of remelt bars and electrodes. Metal bars without center porosity will be produced here in the near future. This feature offers a major improvement in the quality of superalloy.
You have seen the long pouring launder, that can be inserted in a hot condition just prior to pouring. This long launder along with furnace movement, allows skimming and pouring of metal at various points on the turntable.
The things you can not see may be the most important. Partial pressure of offending gases is the key to the thermodynamics and the end point equilibrium of the vacuum melting process. This facility is equipped with features which allow the control of partial pressure of offending gases several decades lower than any other facility in the world.
Many assume that a lower vacuum level provides better quality. The quality of the vacuum counts more than the actual pressure. If the pump size is increased a thousandfold the leak can be one thousand times larger with the same vacuum level.
The liquid metal contains reactive metals such as aluminum and titanium that absorb and fix oxides and nitrides from any vacuum leaks or carry in through opening of the locks.
This vacuum melting and casting facility is constructed with a zero leak concept. ZERO LEAK is a construction which allows checking and control of all points which normally leak in operation. This facility will operate with inleakage much lower than any other facility.
MAINTAINING A VERY LOW PARTIAL PRESSURE OF NITROGEN REQUIRES THAT MINIMUM NITROGEN IS ALLOWED IN THE SYSTEM FROM CARRY IN THROUGH THE LOCKS. THIS IS A VERY IMPORTANT POINT. No other furnace in the world controls and records cross valve leaks and carry in from the lock. The entire vacuum pumping system can be used to pump the charging and pouring chambers. This unique valving system precludes leaks through the valves by utilizing a double valve system with holding pumps between the valves.
Allowing the pressure to rise in the melting chamber while pumping the locks to a lower pressure allows flushing the lock when it is opened. Most operations in the world continue to pump the melting chamber and open the locks at a higher pressure. This is a major error since it allows a major nitrogen intake.
This facility is equipped with internal valving which allows the use of gettering pumps and controlled leaks of useful gases.
This facility offers the customers the possibility to purchase new shapes and quality which can only be produced here.