TPT March 2016

4-8 April 2016

Composite tubes with powerful bonding HOESCH Schwerter Profile GmbH develops its products in collaboration with specific fields of industry and customers. Modern power stations and industrial plants are just two areas where special steel solutions are used that are required to withstand the most extreme loads.

The development of composite tubing pursued by Hoesch Schwerter Profile was undertaken with the aim of overcoming the known disadvantages of clad pipes. The carbon steel component and austenitic layer of the extrusion billet are manufactured in a common hot forming process at around 1,150°C to 1,250°C. The metallurgical connection between the two materials is achieved in the solid state using pressure-accelerated solid state diffusion. A diffusion zone approximately 10μm thick forms between the materials, which is responsible for a high-strength, oxide-free metallurgical bond of materials. The fine microstructure configuration of the layer and base material is preserved, with no variation in the alloy concentration. Hoesch Schwerter Profile GmbH – Germany Email: info@hoesch-profile.com Website: www.hoesch-profile.com

The classic seamless steel tube for pressure vessels is a key construction element in the building of thermal plants. The requirements for boiler construction steels become significantly more exacting if – instead of conventional boiler fuels such as coal, oil or gas – other sources of energy are used that result in strongly corrosive combustion products. For instance, boiler tubes in a waste incineration plant are not only exposed to thermal loads, but are also subject to corrosive attack, triggered by the chemical element chlorine. For this specific application, the conventional boiler tube used in plant construction with its proven component strength was equipped with a ‘coating’ using a corrosion-resistant austenitic

Extruded tubing with internal and external layer

material. The intention behind this combination of materials is to allow the carbon steel to handle the thermal- mechanical load on the tube, while the austenite provides protection against corrosion from the prevailing environment. ‘Combined materials’ tubing of this kind is often referred to as composite. If produced using the extrusion process, the term used to describe this is co- extruded tubing. The high temperature structure steel and high alloy layer are formed simultaneously during the hot extrusion process at temperatures from 1,150°C to 1,250°C.

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M ARCH 2016