TPT January 2014

Technology News

Annealing stainless steel pipe IN-LINE bright annealing equipment is mainly used to in-line anneal AISI 300 and AISI 400 stainless steel pipe. The annealing process is completed under a controlled atmosphere (pure hydrogen) in order to assure the brightness of the surface and to regain the natural hardness of the material before forming and welding. Tube straightening is not required after the process. The in-line bright annealing systems developed and produced by EMMEDI resemble a tunnel through which the stainless steel tube passes at the out- feed of the profiling machine. The tunnel is filled with reducing gas for cleaning and inhibiting oxidations of the tube surface. Induction heating reduces start-up times to a minimum and permits a much higher power density than conventional furnaces with a consequent reduction in the length of the heating. Since dwell time inside the inductor is restricted, treatment temperature must be increased to almost 1,200°C.

A special cooling section located immediately after the heating inductor reduces the tube temperature to the values required for the annealing cycle. This system uses non-recycled pure hydrogen gas at a low flow rate for a perfect cleaning of tube surface in excellent safety condition. The outgoing hydrogen is burned to prevent gas dispersion in the environment. The heating section includes the heating inductor and the generator. In this section the tube can be heated up to 1,200°C. The heating inductor is a multi-turn coil, made of copper tube, internally cooled with demineralised water. The tube enters the heating inductor through a special adjustable seal, which prevents gas leaks at various tube sizes. As in the heating inductor, the entire cooling operation is carried out in a reducing gas controlled atmosphere. At the end of the cooling tunnel, the tube temperature drops below 150°C so the tube can be exposed to the external atmosphere. Two main gases are used to fill the controlled atmosphere treatment area: nitrogen to purge and hydrogen to clean the product. Nitrogen evacuates the air and other gases from the heat treatment area, but is unable to exert the same strong reducing effect on the material as hydrogen. Nitrogen is used therefore simply to fill the area in order to eliminate the oxygen before introducing the hydrogen. Both the heating inductor and the cooling section are assembled on a specific support frame, able to traverse on rails, perpendicularly to the production line, in order to clear the mill area when heat treatment is not required. The closed loop demineralised water cooling system is mounted on an independent structure. The unit includes the stainless steel collection tank, the stainless steel pump and the heat exchanger, also made of stainless steel. It cools the demineralised water of the closed loop with plant industrial water. The temperature of the treated tube is measured at the outlet of the heating inductor by means of an IR pyrometer.

C O N T R A S T

info@contrastsale.com Tel. ++39 0421 271699

Via Umbria, 15 30026 Portogruaro - VE - Italy

www.contrastsale.com Fax ++39 0421 770571

• Impeder cores • Fiberglass tubes • Complete impeders • Copper inductors

• HSS blades

• Hard metal inserts • Carbide base plates

• Fiction circular saw blades • Knives for guillottine cut-off

• Tool holders • Cutting rings

• Tools for slitting lines

• Inside scarfing tools

• Capacitors for H.F. welders

• Rolls for tubes

• Tube’s cleaners

Saet SpA – Italy Website: www.saetgroup.com

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J anuary 2014