Excerpt of a report from the Institut de Soudure, Villepinte, France reference 30065;
Rev n°1 from July 4, 1995

Introduction : With an aim to studying the possibilities of building a tubular cross structure in steel,... the problems and resulting solutions will be dealt with concerning the material (nuance, tenacity, elaboration of tubes, welding ability, "long-term" evolution of characteristics.

Conclusion : The study of feasibility made in the context of the present tubular construction leads to present industriel solutions or that could be in the near future.

As regards materials and semi-products for tubular elements, a solution finally appears as follows :

- rough shapes forged in treated steel for the tubes of large thickness (ie, + de 80 mm) and in microalloyed steel for the tubes having an average thickness (40 to 80 mm). NB : After discussion with the producing factory, supply could be established on a basis of variety of the sort 16MND5 (R 0,2 >400 MPa; R > 550 MPa)

- standard welded tubes or not in non-alloyed or microalloyed steel, for the elements of small thickness (- than 40 mm)

Concerning the nodes of the wire work, the most attractive solution would be that of slightly alloyed foundry steel of the type 12 MDV 6.M.
(R 0,2 > 350 MPa; R > 480 MPa)

Concerning the welded structures, we emphasize the advantage offered by the moulded nodes which would facilitate the production of single weldings end to circular end and which would be easy to automate, verify and perfect.

Finally regarding long term protection of the surface, our preference would run to a recharging of the exterior surfaces with the help of an alloy of the sort cupro-nickel.

A. MICHEL and D. MARGALIDA

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