TPi October 2009

Mater ials Tube and pipe

Hot roll bonding of various steel grades in itself is not new. However, to date it has not been used with coil material, but rather for heavy plates in the production of corresponding slabs. The procedure creates a homogenous metalline bond at the atomic level between the individual layers in a single step. The high adhesive power of this bond can be evidenced using shear tests, among other things. As a coil material, TriBond can be processed economically, and it can be etched, cold-rolled and processed like conventional steel strips. During production, the preliminary strips and the appropriately prepared slabs are first cleaned of any forging scales, placed on top of each other and connected with circular welds. The welds stabilise the steel package and prevent the intrusion of furnace atmosphere between the individual layers during the heating process, which leads to the creation of forging scales.

ThyssenKrupp Steel’s latest developments in tube steel grades involve higher tensile S S materials for standard grades and HIC steel grades

characteristics or to connect wear- resistant materials with weldable ones.

1,200ºC, is pre-rolled in the roughing stand of the hot strip mill at a pressure between 2,000 to 4,000 tons. Afterwards, the material may be rolled to hot strips of 2.5 to 7.5mm and cold strips of 0.1 to 2mm. The selected thickness ratio of the individual material layers remains stable during the entire process. The composite material can conceivably be used in automobiles, as a crash element, for example. During an axial crash test, a rectangular TriBond tube with the dimensions of 60mm x 60mm x 350mm and a wall thickness of 1.13mm was tested. The C70/C15 test sample made of cold- rolled, annealed plate, which had been formed into a tube using a longitudinal laser weld, showed very even energy absorption along the path of distortion and very symmetrical distortion. Researchers are currently working on the further exploitation of the potential of the procedure. For example, asymmetrical layer designs can be produced, where layers of varying thickness and strength enclose a core material that can be re-formed.

A further project in development is Nirosta ® TriBond as three-layer combination of high-grade steel with low carbon ratio with corrosion, acid and heat resistant steel grades. Possible uses in this regard are tubes with corrosion-resistant surfaces for the chemical industry as an economical alternative to stainless steel tubes. New developments in the tube material sector are a central topic of the international trade fair, Tube 2010, which will take place at the Düsseldorf exhibition grounds from 12 to 16 April 2010. In addition, the trade fair will again present the entire range, from tube production and processing to utilisation. After a successful premiere in 2008, the sections Pipelines and OCTG Technology will again be showcased.

The material bond is created when the steel package, heated to approximately

The TriBond crash element shows very ▼ ▼ symmetrical distortion after the axial crash test

Information supplied by Messe Düsseldorf GmbH

ThyssenKrupp Steel AG – Germany info@thyssenkrupp.com www.thyssenkrupp.com Messe Düsseldorf GmbH – Germany info@messe-duesseldorf.de www.messe-duesseldorf.de

In addition it is possible to combine high tensile strength and good re-forming

Photo credits: ThyssenKrupp Steel

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October 2009 Tube Products International