B - Operations – Transporting – 23 – K
Patent
B - Operations, Transporting
23
K
B23K 26/02 (2006.01) B08B 7/00 (2006.01) B23K 26/06 (2006.01) B23K 26/067 (2006.01) B23K 26/073 (2006.01) B23K 26/12 (2006.01)
Patent
CA 2225507
The invention relates to a process and apparatus for using laser radiation to remove an oxide layer (scale) from a hot rolled or annealed steel strip (40) by vaporization traveling in a gravitationally vertical direction at a speed of at least 10 m/min. The process includes utilizing electromagnetic radiation from a high power laser such as a free electron laser whose radiation has a surface power density of at least about 5 MW/cm2 at a point of contact with the metal strip surface. The radiation is passed through an optical system of aligned lenses or mirrors for focusing the radiation into a straight line projected transversely completely across the strip. The radiation has a pulse width less than 100 picoseconds, a pulse repetition rate greater than 10 MHz and a high average power of at least 10 KW. A radiation beam (56) is passed through a homogenizer (60) having a linear diverging lens (74) for spreading the radiation in a linear transverse direction. The radiation is passed through a cylindrical convergent lens (78) or a long cylindrical mirror (132) and focused into a straight line beam (36) projected completely across the width of the strip to remove the oxide by vaporization by the interaction of one or more or the spatial elongated laser pulses thereby forming an oxide free surface. A sealed interaction chamber (90) contains a non-oxidizing gas (108), a slotted entry (91) for receiving the oxidized strip, a slotted exit (92) for a passage of the as-cleaned strip, at least one elongated window (93) for receiving the radiation into the chamber, an exhaust duct (94) for removing the non-oxidizing gas ladened with oxide debris from the chamber and a filter (106) for removing oxide powder from the gas. The non-oxidizing gas is directed into the chamber at a point just above a plasma plume (112) and just beyond incident focused radiation beam (36) through a long slot-like gas nozzle (114). By keeping the chamber sealed from the ambient atmosphere and by maintaining sufficient non-oxidizing gas adjacent to the plasma interaction zone and the cleaned metal surface, reoxidation of the cleaned steel surface can be prevented.
Armco Inc.
Riches Mckenzie & Herbert Llp
LandOfFree
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