Aug 12 2008
SECO/WARWICK has recently patented a hydrogen closed-cycle hardening system where the heat treatment process is performed in vacuum, and the hydrogen atmosphere is recycled. This system produces excellent process results because the cooling cycle is performed in hydrogen.
The most useful application is for steels that are difficult to harden in other gases, and the user does not want to use an oil quench for environmental reasons. Gas quenching consistently provides superior metallurgical results in terms of uniformity and low part distortion.
How It Works
The hydrogen closed-cycle hardening unit consists of a vacuum oven having an internal quenching and circulation system that is adjusted to operate under a pressure of 2 MPa, the internal quenching and circulation system being fitted with conduits and valves for feeding and discharging of a quenching atmosphere; wherein: the oven is fitted with a hydrogen inlet line or a nitrogen inlet line and an operating gas outlet line; and wherein: (a) the oven is connected on one side to an inlet pipe, (i) the inlet pipe has a low-capacity fan; (ii) the inlet pipe is connected to a first conduit between two valves in the first conduit; and (iii) the first conduit is connected to a unit including a first container and a second container such that the first conduit is connected to the first container beyond one of the two valves in the first conduit and the first conduit is connected to the second container beyond the other of the two valves in the first conduit; (b) the oven is connected, on an opposite side from the connection to the inlet pipe, to an outlet pipe; (i) the outlet pipe is connected to a second conduit between two valves in the second conduit; and (ii) the second conduit is connected to the unit including the first container and the second container such that the second conduit is connected to the first container beyond one of the two valves in the second conduit and the second conduit is connected to the second container beyond the other of the two valves in the second conduit; (c) the first container is connected to a third conduit that contains a valve and a flow meter, the third conduit connecting to an external hydrogen source; (i) the first container is equipped with a first independent heating and cooling system; (ii) the first container contains a metal alloy that absorbs hydrogen as a high-pressure hydride, for which an equilibrium pressure of a reversible formation/dissociation reaction is about 0.01 to about 15 MPa at a temperature in a range of about 298 to about 533.degree. K.; (d) the second container contains a metal alloy that absorbs hydrogen as a low-pressure hydride, for which an equilibrium pressure of a reversible formation/dissociation reaction is about 10.sup.-6 to about 2 MPa at a temperature in a range of 293 to about 673.degree. K.; and (i) the second container is equipped with a second independent heating and cooling system; and (e) the first container and the second container are connected by a fourth conduit that contains a valve and a gas flow meter.
For more information on heat treatment , click here.