EuroWire March 2015

News Technology

Versatile heat and surface treatment process

Plasma proves itself in a range of continuous applications from mainstream stainless steel annealing to precision alloy wire cleaning and heat-treating. The past two years have been an exciting and productive time for the Plasmait team. The company sold a range of plasma machines in the ferrous and non-ferrous markets, and it is proving its performance in an increasingly wide range of materials, from mainstream copper alloy and aluminium wire to specialist medical tubes and ropes, jewellery strands, aerospace materials, electronics and semiconductor wire and strip. Most significant is Plasmait’s success in the stainless steel and nickel alloy wire and tube markets with new deployments in fine, medium and large cross-section materials. Deployments included annealing of various forms, ie wire, tube, strip, strand and ropes. For example, Plasmait’s most recent annealer for large and intermediate stainless steel wire boasts a single line output of 130kg/h (250lb/h). Stainless steel wires from 1mm-6mm can now be produced scratch-free and pile-free at high speed. and homogeneous recrystallisation with small grain improves subsequent drawing by reducing the number of wire breaks on the drawing machine. Die wear is also reduced. The Plasma annealer can cold start production in a few minutes and can be stopped immediately. This avoids the lengthy heating-up and cooling-down times and associated energy costs that are symptomatic of a conventional tube furnace. Equally important was the introduction of a new fine wire annealing line, allowing recrystallisation annealing at up to 25m/s (5,000ft/min) on a range of fine stainless steel and nickel alloy wires. It is now possible to anneal fine stainless wires in-line with the drawing machine. The annealer features compact design, high-energy conversion efficiency and low gas consumption. Annealing fine wire at up to 20 times the speed of a traditional strand furnace means fewer take-ups and payoffs and hence lower cost of total capital investment. Furthermore, superior surface

▲ ▲ Plasmait is proving its performance in an increasingly wide range of materials

Better surface finish also results in superior tape adhesion. The latest deployment of PlasmaCleaner features plasma surface activation for improvement of lubricant pickup in a rod drawing line. Plasma surface treatment ensures good lubricant adhesion during drawing of stainless steel or titanium rods. Surface activation is achieved at low temperatures, which makes the process particularly economical compared to expensive-to-run traditional processes such as brushing, acid treatment or sand blasting. Among the latest deployments is a plasma annealer for stranded conductors and ropes. The annealer was designed to allow for rapid heat penetration through the cross-section of the stranded construction so that individual wires in a strand/rope can be heat-treated to an equal temper. Accurate control of heat transfer and thereby resulting mechanical properties can be achieved on a wide range of stranded constructions and materials from copper, aluminium, stainless steel and alloys.

With the introduction of high-output annealers Plasmait also became competitive in the mainstream stainless steel markets in the fine, small and large diameter ranges. A single line of a high output plasma annealer can replace five to 20 annealing lines of a conventional annealing furnace. This means a considerably lower investment in transport and winding equipment, which often bears the brunt of the cost of annealing equipment. The savings are even more pronounced on fine sizes where a plasma annealer runs in-line with a drawing machine. The first plasma annealer for taped copper conductors has been in operation now for more than a decade. The latest one was installed in 2014 with another one scheduled for delivery in early 2015. Taped conductors have traditionally been annealed in bell furnaces, which may result in uneven recrystallisation and surface quality issues like sticking of flat products. Round or rectangular conductors can now be plasma annealed and cleaned continuously in-line with a conventional taping line.

Plasmait GmbH – Austria Website : www.plasmait.com

Plasma annealed conductors feature better accuracy in mechanical properties.

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March 2015