RU2062195C1 - Method of pipes laser welding - Google Patents

Abstract

FIELD: welding, in particular laser welding of small diameter pipes made of different materials. SUBSTANCE: laser emission feeding is exercised using turning device situated in front of focusing system at distance equal to l = F (1 + F/R) and turning device angle of turning is equal to α = arctgX/F/2 with F -focal distance of focusing system; R - radius of welded pipe; X - deviation of welded butt from normal position. Any deflecting member - mirror, prism may be used as turning device in the method. Method provides for usage of mirror type or transient type focusing system. EFFECT: usage of the method of welding allows to increase quality of welding seam and to improve dynamic characteristics of butt position control system relatively to dropping emission. 2 cl, 1 dwg

Description

 The invention relates to the field of radiation methods for processing materials and can be used for laser welding of pipes with a longitudinal seam.

 Known methods for welding pipes with a longitudinal seam [1] [2] [3] are as follows. The pipe intended for welding is installed in special devices. For the most optimal weld formation, the joint is exposed at the top. The radiation emerging from the laser is directed through the transportation system to a rotary mirror, reflected from which it is directed to a focusing device (lens). In it, the radiation is focused and directed to the longitudinal joint of the pipe. Under the influence of focused radiation at the edge of the joint, a fusion point is formed. When moving the lens and the swivel mirror using a drive along the pipe joint, a longitudinal weld is formed.

 The control over the location of the lens nozzle directly above the joint is carried out by the joint control sensor and the lens and rotary mirror actuator, united in a single unit perpendicular to the longitudinal seam. When the joint deviates from the normal position, the sensor located directly in front of the lens nozzle supplies a control signal to the lens and rotary mirror displacement drive perpendicular to the longitudinal seam and it fulfills the necessary movement.

 The above methods have the following disadvantages.

 1. To practice displacements when the joint deviates from the normal position during the welding process, it is necessary to reverse the massive structure, consisting of a focusing device and a swivel mirror, and the accelerations will constantly change. This requires the installation of a sufficiently powerful additional drive with a mechanical transmission.

 2. In the process of welding, despite the control of the joint in the horizontal plane, the beam is constantly directed vertically downward at a time when the joint deviates around the circumference. As a result, the necessary condition for the quality of the weld formation is perpendicular to the incident radiation in the plane to which the contact point of the part with the radiation belongs and which is perpendicular to the radiation axis.

 The beam hits the top of the junction, but does not go along it, but hits one of its edges. As a result, improper formation of the weld and, consequently, a sharp deterioration in its quality. In case of large deviations of the joint from the normal position, a lack of penetration of the weld occurs.

 The objectives of the invention are: improving the quality of the weld, improving the dynamic characteristics of the control system of the position of the joint relative to the incident radiation.

,
где F фокусное расстояние фокусирующей системы;
R радиус свариваемой трубы.In the proposed method, in the process of laser welding, the radiation is directed to the welded joint by a rotary device located in front of the focusing device at a distance l equal to

,
where F is the focal length of the focusing system;
R is the radius of the pipe being welded.

Поворотным устройством, направляющим излучение в фокусирующее устройство, может быть любое как плоское, так и имеющее определенный фокус устройство, элемент, позволяющий отклонять излучение: зеркало, призма и т.д. Фокусирующее устройство может быть как зеркального, так и проходного типов.In this case, the rotation angle of the rotary device depends on the deviation of the joint X from the normal position:

A rotary device directing radiation to a focusing device can be any device, either flat or having a certain focus, an element that allows deflecting radiation: a mirror, a prism, etc. The focusing device can be either a mirror or a walk-through type.

Technical results obtained by carrying out the invention:
1. The supply of laser radiation, the axis of which is perpendicular to the plane to which the point of contact of the part with the radiation during welding, allows you to form a high-quality seam regardless of the deviation of the joint from the normal position.

 2. Using this method allows you to abandon the powerful drive, moving in the direction perpendicular to the weld, a structure consisting of a focusing system and a rotary device. When implementing the proposed method, a low-power engine is required, which rotates the rotary device by a small angle. The focusing system remains motionless.

где δ неизвестная величина, отклонение центральной оси излучения от нормального положения на фокусирующем устройстве:
X' неизвестная величина, отклонение центральной оси излучения от нормального положения на уровне верхней фокальной плоскости;
l расстояние между поворотным и фокусирующим устройствами;
F фокусное расстояние фокусирующей системы;
X неизвестная величина, отклонение свариваемого стыка на трубе от нормального положения;
R радиус свариваемой трубы;
Выделив и Х во втором и третьем соответственно уравнениях и подставляя их в первое, находим зависимость L от F и R. Х при этой операции сокращается.The above formulas are obtained from the following ratio (figure 1). From the relations of the legs of the triangles, three equations with three unknowns are obtained:

where δ is an unknown quantity, the deviation of the central axis of the radiation from its normal position on the focusing device:
X 'unknown quantity, deviation of the central axis of radiation from a normal position at the level of the upper focal plane;
l distance between the rotary and focusing devices;
F the focal length of the focusing system;
X unknown value, deviation of the welded joint on the pipe from its normal position;
R is the radius of the welded pipe;
Selecting and X in the second and third equations, respectively, and substituting them in the first, we find the dependence of L on F and R. X during this operation is reduced.

Известно, что угол отклонения излучения β равен двум углам поворота поворотного устройства a:β=2α..

It is known that the angle of deviation of radiation β is equal to two angles of rotation of the rotary device a: β = 2α ..

. Подставляя вместо δ выражение, полученное из уравнения (3), а вместо l уравнение (4), получаем:

Способ иллюстрируется чертежом.From the ratio of the legs of the triangle we get:

. Substituting instead of δ the expression obtained from equation (3), and instead of l equation (4), we obtain:

The method is illustrated in the drawing.

 An example of a specific use of the method. Welded pipe 1 with a diameter of 40 mm. The laser beam 2 is fed to the mirror 3 and after it is directed to the lens 4. The focal length of the lens F 200 mm Hence the required distance from the mirror to the lens is: l 2200 mm.

If the joint deviates from the normal position X 2 mm, the angle of inclination of the mirror will be:

Claims (2)

1. The method of laser welding of pipes, in which the laser beam is directed by a rotary device through the focusing system to the welded joint, characterized in that the rotary device is placed in front of the focusing system at a distance

and the rotation angle α of the rotary device is set depending on the deviation of the joint from the normal position, based on the following ratio:

where F is the focal length of the focusing system;
R is the radius of the welded pipe;
X deviation of the joint from the normal position.  2. The method according to claim 1, characterized in that they use a focusing system of mirror or pass-through types.