US 4,543,060 A · Heat treatment of workpieces

Abstract

A continuous heat treatment furnace has an entrance, a preheat zone, a thermal treatment zone, a cooling zone and an exit. Curtains are provided at the entrance and exit respectively. Nitrogen and hydrogen (or other reducing gas) are supplied to the furnace to create a non-oxidizing or reducing atmosphere in the thermal treatment and cooling zones. Elongate workpieces such as tubes are advanced through the furnace and thereby heat treated (e.g. annealed). As the workpieces pass through the curtains so the tendency for air to leak into the furnace is increased. To counteract this tendency, position sensing plates are adapted to actuate a signal generator controlling a valve which in turn controls flow of e.g. nitrogen to the furnace. The arrangement is such that the flow of nitrogen to the furnace is increased wherever a workpiece is sensed, thereby enabling the essentially reducing or non-oxidizing character of the atmosphere to be sustained. If desired, the oxygen potential in the vicinity of the furnace entrance and exit can alternatively be monitored and used to modulate the flow of gas into the furnace.

Claims10

Dependent claims

A method of heat treating workpieces in a continuous furnace having an entrance, a thermal treatment region, a cooling region, and an exit and at least one curtain located at said entrance or exit comprising the steps of:

(a) supplying reducing gas or non-oxidizing gas to at least one location in said furnace remote from said curtain to form in said thermal treatment and cooling regions an atmosphere which is essentially reducing or non-oxidizing to said workpieces;
(b) passing said workpieces through the furnace to effect the desired heat treatment with said workpieces disturbing said said curtain upon passage into or from said furnace;
(c) establishing a flow rate of said reducing and non-oxidizing gas at a level when said curtains are not disturbed by passage of said workpieces through said furnace sufficient to maintain a substantially non-oxidizing or reducing atmosphere in said furnace;
(d) detecting disturbance of said curtain by said workpieces;
and
(e) increasing the flow rate of said gas upon detecting a disturbance of said curtain such that the atmosphere in said cooling and thermal treatment regions of said furnace is maintained substantially reducing or non-oxidizing.

3 more elements

Dependencies are inferred from the claim text.

Heat treatment of workpieces

Life of this patent

Heat treatment of workpieces

Life of this patent

Abstract

Claims10