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B23K 26/00 |
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Technique of tubes laser welding. |
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The invention falls into field of beam techniques of materials treating and can be used for laser welding of tubes with a longitudinal seam. Known techniques for welding tubes with a longitudinal seam [1], [2], [3] are carried out as follows. The tube, intended for welding, is erected in special gadgets. For optimal shaping of a weld a junction is advanced overhead. The radiation, going out a laser, is guided through a system of transportation on a rotary mirror, being reflected from which it is guided to a focusing device (lens). In it a radiation is brought into focus and is guided on the longitudinal junction of a tube. Under action of focused radiation on a junction edge will be formed alloying point. At moving a lens and a rotary mirror along a tube junction with the help of a drive unit, will be formed a longitudinal weld. A control at a lens nozzle arrangement immediately above a junction is carried out with the help of a junction control data unit and a drive unit of a lens and a rotary mirror moving, integrated in a common unit, perpendicularly to a longitudinal seam. At a junction deflection from a normal standing taking place directly ahead of lens nozzle a data unit gives control signal on a drive unit of a lens and a rotary mirror moving perpendicularly to longitudinal seam, and it completes necessary moving. The above-stated techniques have the following disadvantages: 1. At a junction deflection from a normal standing during welding for working off moving it is necessary to move reversibly a massive construction, consisting of a focusing device and a rotary mirror, while an acceleration will vary permanently. It requires a presence in a composition of device enough high-power additional drive unit with mechanical transmission. 2. During welding, despite of junction control in a horizontal plane, the beam is permanently guided upright downwards when a junction is declined on a circle. In result is disturbed a necessary requirement of qualitative forming of a weld - a perpendicularity of an incident radiation to a plane, which has a touch point of a detail with radiation and which is perpendicular to an axes of radiation. A beam gets in an upper junction part, but does not go along it, and gets on one of its edges. In result – incorrect forming of a weld and, therefore, sharp aggravation of its quality. At major deflections of a junction from a normal standing there is an incomplete fusion of a weld. Problems of the invention: an improvement of a weld quality, an improvement of dynamic characteristics of junction standing monitoring system concerning an incident radiation. In an offered technique during laser welding radiation is guided on welded junction by a rotary device which is taking place before a focusing device at a distance l, peer l = F (1+ F / R), where F - focal distance of focusing system; R - radius of welded tube; Thus the angle of rotation of rotary device depends on a junction deflection - X from a normal standing: a = (arctg x / F) / 2 A rotary device, guiding radiation to focusing device can be anyone both flat, and device, having particular focus, element, permitting to decline radiation: a mirror, a prism, etc. Focusing device can be both reflecting, and flowing types. Technical results, gained at invention realization: 1. Delivery of a laser radiation, which axis is perpendicular to a plane, which has a touch point between a detail and radiation during welding, allows to shape a qualitative seam independently from junction deflections from a normal standing. 2. Usage of the given technique allows to refuse a high-power drive unit, moving in a direction, perpendicular a weld, a construction, consisting of focusing system and rotary device. At realization of an offered technique the low-power engine, rotating the rotary device on a small corner, is necessary. The focusing system thus remains fixed. The above-stated formulas are obtained from the following relations (fig.1): from ratio of triangle legs three equations with three unknowns are gained: d / l = x’ / (1-F) (1) x’ / F = x / R (2) x / R = d / (F+R) (3) , where d - an unknown quantity, a deflection of radiation central axis from a normal standing on a focusing device; x’ – an unknown quantity, a deflection of radiation central axis from a normal standing at a level of upper focal plane; l – a distance between rotary and focusing devices; F – a focal distance of focusing system; x – an unknown quantity, a deflection of welded junction on a tube from a normal standing; R – a radius of a welded tube; Having selected x’ and x in second and third equations accordingly and substitute them in first, we discover dependence l from F and R. X at this operation is reduced. L = F(1+ F / R) (4) It is known, that an angle of radiation deflection b , is peer to two angles of rotary device rotation a : b = 2a From a triangle legs ratio we have tg b = d / l. Substituting instead of d expression, obtained from the equation (3), and instead of l the equation (4), we gain: a = ( arctg x / F) / 2 (5) A technique is illustrated with the help of a plan. There is an example of technique concrete usage. A tube 1 with a diameter of 40 mm is welded. The laser beam 2 moves on a mirror 3 and after it is guided on a lens 4. A focal distance of a lens F=200 mm. From here, necessary distance from a mirror up to a lens is equal: l=2200 mm. At a junction deflection from a normal standing X=2 mm, a tilt angle of a mirror will make: a = ( arctg 2 / 200) / 2 = 0,573 degree. What is claimed is:
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