Abstract: The process relates to the aptitude for detectability of defects using eddy-currents on metal tubes cold laminated using a pilger mill and relates more particularly to the possibility of reducing the background noise and increasing the ratio between a standard signal and this background noise.The process consists of carrying out, after reduction in section by at least 30% in a cold pilger mill, a hollow drawing pass with a reduction in the external diameter of approximately 0.1% to 5%. The signal/background noise ratio can in this way be multiplied by a factor of between 2 and 3.7, in the case of a series of tubes made of INCO 690 alloy, as shown in the single figure.The invention also relates to tubes produced using this process.Application in production of steam generating tubes for nuclear power stations.

Abstract: An apparatus and a process for detecting surface defects on moving long metallic products utilizing linear CCD cameras for effecting exposures at successive times t1, t2,t3 . . . Tn. A processing device calculates differences observed for each pixel or assemble of pixels at the successive times and any variations in the differences makes it possible to detect defects and the extent of the defects. The use of thresholds allows for reduction in the background noise and different orientations of the optical axis of the camera permit the detection of different types of defects.

Abstract: The process and apparatus concern hot shaping by plastic deformation of metal alloys by means of a pressing tool.The process comprises effecting extrusion of a billet which is covered by at least one external sleeve, by a pushing force applied by means of a pressing tool, through a die. A thin layer of at least one compound comprising oxygen and at least one metal is deposited on one of the facing walls of the sleeve and the billet. The billet is preheated before being put into the container for the extrusion operation. Lubrication is effected by a lubricant such as a glass. The process is applied to the extrusion of solid or hollow billets of refractory alloys and also other alloys which involve difficulties in shaping them.

Abstract: An extraction device for a metal tube obtained by hot extrusion is located along an extrusion axis downstream of the die of an extrusion press. The extraction device has a group of elastic metal fingers for gripping the tube against a bearing surface of a discharge chute receiving the extruded tube. The fingers are joined at one end to a rotatable shaft in order to bring the fingers into elastic contact with an outer wall of the tube. A double-acting jack is connected directly or indirectly to the shaft in such a way as to permit the displacement of the tube clamped by the fingers towards the downstream end and to thereby extract its upstream end from the die.

Abstract: The method according to the invention relates to the production of a bimetallic tube, the cross-section of which comprises an outer annular zone and an inner annular zone, these zones being of different compositions. The method resides in preparing a blank (1) comprising two tubular components (2, 3) housed one inside the other and of different compositions and separated by an annular space (4) which is filled with divided metal. The whole assembly is made rigid by two end pieces (7, 8) and coextrusion is carried out at a suitable temperature to ensure a metallurgical bond between the inner component (2) and the outer component (3). The bimetallic tube obtained is particularly suitable for uses in which one of its two outer or inner walls is exposed to a medium which is more aggressive than the other.