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AssigneeValinox Nucleaire
InventorsJean-Louis Buret, Denis Vuillaume
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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.
A process for increasing the signal/background noise ratio measured by an eddy-current sensor compared to the signal/background noise ratio attained when the eddy-current sensor is used for testing a metallic tube with a small diameter which has been formed to size by being subjected to a cold reduction of at least 30% using a cold pilger mill, said process comprising subjecting the metallic tube to at least one hollow drawing pass carried out, cold, thereon to further reduce the external diameter of the metallic tube by at least 0.1% and at most by 5% to thereby attain said increased signal/background noise ratio upon inspection by an eddy-current sensor.
A metallic safety tube in metal or alloys with a relatively small diameter, being formed to size by a reduction in section of at least 30% using a cold pilger mill followed by a hollow drawing pass in a manner such as to reduce its diameter by at least 0.1% and at most 5%.
Dependencies are inferred from the claim text.