Plasma chosen for annealing of SS wires and tubes in US, Asia and Europe

Plasmait GmbH from Austria is seeing an increasing demand for its new high-output plasma heat treatment lines for stainless steel products globally. One annealer was deployed in Asia last autumn. In 2018 another two are being built for renowned US nickel wire maker and a leading European stainless steel tube manufacturer.

A 30kW plasma annealer was commissioned to a renowned stainless steel wire producer in South East Asia, who used plasma to replace its traditional tube furnace for production of flat ferritic and austenitic product with widths up to 30mm (1.2 inch). The HPA30 plasma annealer with output capacity of 100kg per hour will allow the manufacturer to half the energy cost per kilogram of output whilst allowing for a considerable cost saving in terms of peak power consumption. Much lower power connection requirements of plasma annealer yielded also major savings in cabling installations.

Plasmait is now building another HPA10 PlasmaANNEALER to be integrated into a drawing line for fine stainless and nickel coated wires. The annealer will run in-line with a wet drawing machine to produce wires diameters between 0,1mm-1mm (0.004 inch – 0.04 inch).

The annealer destined to Europe will produce stainless steel tubes of various grades and diameters up to 1 inch OD. The 50kW annealer will have output well over 200kg/h for austenitic stainless steel tubes and more so for many ferritic and martensitic grades. Rapid cooling will ensure small grain size for improved product quality.

Plasma annealer allows accurate heat input and hence more uniform recrystallization, which is reflected in homogenous grain size in the longitudinal and transversal direction. Plasma annealers can feature also an extended tempering zone to allow for dwell time or slow cooling, which is necessary for selected ferritic grades of stainless steel.

The new compact single-line production concept takes just one third of shop floor space compared to the space required by the same output multiline furnace. A single-line production reduces material manipulation and reduces the investment into the associated takeups, payoffs and transport system. A typical plasma annealer installation for stainless steel applications can substitute 10-20 traditional lines on a conventional strand furnace.

Plasma annealer combines the advantages high speed bright annealing and superior scratch-free surface finish. Processed material does not touch plasma chamber when at high temperature which reduces the risk of surface scratching. This is different to the conventional strand furnace where hot materials rub against the heating tubes resulting in surface damage.

A unique feature of plasma annealing is that heating is conducted in low-pressure inert atmosphere, for which a vacuum installation and accurate material guiding is necessary. The advantage of vacuum system is that purging gas (usually hydrogen or forming gas) is supplied at low pressure, which reduces overall purging gas consumption.