Plasmait: high-output annealer for stainless steel tubes

Plasmait GmbH from Austria has introduced the largest annealer for stainless steel tubes to date. The new annealer HPA60 features 60kW plasma power and is capable to anneal up to 250kg (550lb) of austenitic stainless steel tubes per hour. The new annealer is designed for OD range of 1/8– 1/2inch.

The output of the annealer is comparable to the outputs of similar induction annealers, yet its power consumption is up to 3 times smaller for the same output. The required power connection is therefore also 3 times smaller when compared to induction or conventional furnace. This alone could represent a considerable cost saving in terms of peak power consumption and expensive cabling installation.

Efficient energy coupling also allows accurate heat input and hence more uniform recrystallization, which is reflected in homogenous grain size in the longitudinal and transversal direction.

The new annealer combines the advantages high speed bright annealing and superior scratch-free surface finish. Processed material does not touch plasma chamber when hot which reduces the risk of surface scratching. This is different to the conventional strand furnace where tubes remain in contact with the furnace guiding supports also during the maximum elevated temperatures when they are most vulnerable to the 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) is supplied at low pressure, which reduces overall purging gas consumption.

The new facility occupies about 1/3 of the shop-floor area that is required by a conventional multiline annealing furnace of the same capacity. A single plasma line can substitute around 10 traditional lines on a conventional strand furnace, which reduces the investment required for transport systems, takeups and payoffs.