TPi May 2014

products & developments

Composite tubes

Extruded tubing with internal and external layer

Hoesch Schwerter Profile develops products in collaboration with specific fields of industry and customers. Modern power stations and industrial plants are two areas where special steel solutions are used that are required to withstand extreme loads. The classic seamless steel tube for pressure vessels represents a key construction element in the building of thermal plants. The requirements for boiler construction steels become 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, fundamentally 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 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.

forming process at around 1,150- 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. Smooth surface structures avoid deposition of corrosion- promoting ash and salt particles from the flue gas. Special cross-section forms such as fin tubes, omega tubes or double omega tubes are possible. Cold bending is also possible, since there is no cast structure created by cladding.

Clad pipes (where the corrosion- resistant layer is applied to the tube body by welding) have one or two layers of corrosion-resistant outer covering, approximately 2.5mm thick. This is applied using fusion welding, which creates overlapping welding beads. During welding, there is an intermixing of a few tenths of a millimetre between the carbon steel and the austenite. In metallurgical terms this is equivalent to a ‘dilution’ of the high-alloy layer material. Since it is obtained via the liquid phase, the layer material is characterised by a casting structure typical of welding. The development of composite tubing pursued by Hoesch Schwerter Profile GmbH was undertaken with the aim of overcoming the known disadvantages particular to clad pipes. The carbon steel component and austenitic layer of the extrusion billet are manufactured in a common hot

Hoesch Schwerter Profile GmbH – Germany

info@hoesch-profile.com www.hoesch-profile.com

New name for continuous weld product Wheatland Tube, a manufacturer of steel pipe and tube solutions, has announced a new name for its continuous weld (CW) pipe. Wheatland CW pipe will now be manufactured and sold under the SureThread™ brand name. commonly seen on imported ERW pipe, so the SureThread name just made sense.” SureThread pipe features a uniform grain pattern and smooth surface that the company says is proven to cause less wear and tear on tools and dies than traditional ERW pipe. SureThread ASTM A53 CW and electric resistance weld (ERW) standard steel pipe. “We recently surveyed contractors, and 72 per cent of respondents indicated they believe our SureThread product to be easier on their tools. That means reduced wear and tear, which helps tools last longer,” added Mr Magno.

“This name speaks to the excellent threading and fabrication characteristics of CW pipe,” said Mark Magno, president of Wheatland Tube’s pipe division. “Many of our customers tell us that our CW pipe ‘threads like butter’ and doesn’t have hard spots

SureThread is used for mechanical and low-pressure applications, as well as steam, water, gas and air lines applications. Wheatland Tube is North America’s only full-line producer of

Wheatland Tube – USA info@wheatland.com www.wheatland.com

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May 2014 Tube Products International