The invention relates to a substrate for reinforcing elastomeric polymers whereby at least part of the substrate is made of steel, said part being covered by a layer of an alloy consisting of, apart from impurities, between 4.2 and 6.5% weight of aluminum, possibly less than 0.1% of at least one element stimulating the wetting ability of the liquid alloy to the substrate and the balance zinc.

A double-twisting device (2) includes two half-shafts (4) and at least one flyer (6). The flyer (6) connects the two half-shafts (4) and causes axial forces F.sub.a which are exerted upon the half shafts (4) during rotation. The double-twisting device (2) further includes a magnetic device (22, 24) which are suited to compensate at least partially for the axial forces F.sub.a. This increases the life span of the bearings (8) and considerably reduces the maintenance costs of the double-twisting device.

A steel strip (1) comprises two to seven round steel filaments (2) lying in parallel adjacent to one another so as to form a single plane of core filaments and one or more filaments (4) which are wrapped around the core filaments in one single wrapping direction. One or more core filaments, individually, or the plane of the core filaments as a whole have residual elastic torsions to such an extent that the strip remains substantially flat over the whole length of the strip if the strip is not subjected to external forces.

The granular composite is obtained by chopping a composite strand containing metal fibers, said fibers being embedded as bundles in a plastic and is to be used for the shaping of plastic articles. The metal fibers comprise hardened material which has been derived from an austenitic ferric alloy in which the austenite has been converted into martensite for at least 75 vol. %.

The invention relates to a burner membrane (1) for radiant burner comprising a porous sintered web of inorganic fibres that are resistant to high temperatures, wherein at least the membrane surface (3) opposite from the fuel supply side (2) has been provided with grooves (4) in the shape of a grid and which grooves bound the meshes (5) of the grid. Preferably, the meshes are regular polygons with a surface area of between 4 and 400 mm.sup.2. The porosity is between 70% and 90% and the permeability variation over its surface is less than 25%.