CN108705195A - Energy restrains type narrow gap laser welding with filler wire method - Google Patents

Abstract

The invention relates to an energy-constrained narrow-gap laser wire-filling welding method for thick plates, which belongs to the technical field of laser material processing. The feature of the present invention is that when the positively defocused laser beam enters the narrow gap groove of the workpiece to be welded for welding, the two front and rear wire feeding systems send the welding wire into the molten pool and form a semi-enclosed space that limits the reflection loss of laser energy, and the welding wire passes through the molten pool. The pool is heated and melted, the gap is filled to form a weld, and the connection of thick plates is realized by single-pass multi-layer welding. The invention adopts the mode of heat conduction welding and the mode of heating and melting the welding wire in the molten pool, and the welding process is stable. At the same time, the laser beam acts on the side wall of the groove, which can effectively avoid welding defects such as unfused side walls.

Description

Energy Constrained Narrow Gap Laser Wire Filler Welding Method

technical field

An energy-constrained narrow-gap laser wire-filling welding method for thick plates belongs to the technical field of material processing.

Background technique

Thick plate welded structures are widely used in shipbuilding, marine engineering, nuclear power equipment, aerospace and other fields, especially in the field of nuclear power equipment, thick plates are most widely used, and the thickness range is also the largest. For example, reactor pressure vessels are mostly welded with large thickness stainless steel plates. into, while some containers have a wall thickness of up to 250mm. At present, the welding methods of thick plates are mainly argon arc welding (TIG), narrow gap submerged arc welding and narrow gap MIG welding. Due to the large heat input of these welding methods, the structure of the welded joint is relatively coarse, and the residual stress and deformation of the joint are large.

Compared with the conventional welding method, the narrow gap laser wire filler welding method combines the dual advantages of laser welding and narrow gap welding, and has the advantages of small heat input, welding heat affected zone and welding deformation, etc., as an efficient thick plate welding method ,Gaining importance. The existing narrow-gap laser wire-filling welding technology for thick plates mostly uses a focused spot to act on the welding wire, and melts the welding wire to fill the gap to form a weld through the deep penetration welding mode. The plate thickness range that can be welded by this method is small, and defects such as welding pores and unfused bottom are prone to occur. This is due to the existence of the divergence angle of the laser beam, and the gap width must be large enough to ensure that the beam is not blocked by the upper surface or side of the groove and acts on the bottom of the groove. As the thickness of the welded plate increases, the gap width increases. However, when the gap is large, due to the high concentration of laser energy and the limited melting width of laser welding, there will be defects of side wall infusion. This contradiction between the accessibility of light and the lack of fusion of the sidewalls limits the range of weldable plate thickness for narrow gap laser welding. In addition, due to the multi-layer welding of the deep penetration welding mode, the unstable closure of the deep penetration small holes will generate a large number of welding pores and affect the stability of the welding quality.

For thick plates larger than 40 mm, in the existing narrow-gap laser wire-filled welding research, a gap of 6 mm to 10 mm is mostly used to focus the spot and cooperate with multi-spot combination or the beam swings in the gap to complete the welding. Combination of light spots and swinging of the beam increase the melting width to solve the unfused defect of the side wall. Due to the poor adaptability of the focused spot in the gap, the welding gap is wide. Although it can be solved by the above methods, the operation is difficult, the cost is high, and the thickness range of the weldable plate is still limited. Currently, single-sided The maximum plate thickness of narrow gap laser welding is only 60mm. In the paper "Experimental Research on Filled Hot Wire Laser Narrow Gap Welding", Wen Peng and others from Tsinghua University announced a narrow gap laser thermal conduction mode welding method filled with hot wire. The molten pool is formed at the bottom of the mouth, and the welding wire is fed into the molten pool from the rear, and the side wall is not melted. The welding wire heated by the current is melted and combined with the side wall. This method suppresses the occurrence of incomplete fusion of the side wall to a certain extent and increases the weldable plate thickness range of narrow-gap laser welding. When the welding wire is fed into an unstable situation, unfused defects on the side wall and bottom are prone to occur.

Contents of the invention

The purpose of the present invention is to avoid the side wall infusion and air hole defects in the narrow gap welding of large and thick plates, and to provide a stable and efficient narrow gap laser welding method for thick plates.

The object of the present invention is achieved by the following measures: using a positive defocused laser beam, the laser beam enters the narrow gap groove of the workpiece to be welded, and acts on the bottom and side walls of the groove at the same time to form a weld pool in a heat conduction welding mode, Two front and rear wire feeding systems feed the welding wire into the molten pool and form a semi-closed space together with the narrow gap side wall to limit the reflection loss of laser energy. The welding wire is heated and melted through the molten pool, and the gap is filled to form a weld. Single-pass multi-layer welding way to realize the connection of thick plates.

The narrow-gap laser wire-filling welding method for thick plates above is characterized in that: the two wire feeding systems are distributed on both sides of the laser beam and the included angle is less than 45 degrees.

The narrow-gap laser wire-filling welding method for thick plates described above is characterized in that the width of the narrow gap for thick plate welding is between 2 mm and 10 mm.

The principle of the present invention is to use the front and rear wire feeding systems to send the welding wire into the molten pool and form a semi-enclosed space together with the side wall of the narrow gap to limit the reflection loss of laser energy. Absorbed by the side wall of the gap and the welding wire, the energy utilization rate is greatly improved, and the laser welding of large and thick plates can be realized by using a low-power laser. In addition, laser irradiation and reflected energy are used to melt the sidewall, thereby reducing the occurrence of unfused sidewall. The heat conduction welding mode adopted avoids the generation of small pores in welding, and the way that the welding wire is melted by the molten pool by using a certain distance from the welding wire to the spot does not involve light directly acting on the welding wire to cause irregular reflection and splashing, so the molten pool Stable, avoiding the generation of welding porosity and spatter, ensuring the stability of welding quality. At the same time, because the defocused beam has better gap adaptability than the focused beam, it can be applied to a narrower gap, and the ultra-narrow gap is used to reduce the sensitivity of laser welding to the lack of fusion of the side wall. In addition, the narrow gap laser welding also significantly increases Weldable plate thickness range. Since heat conduction welding does not involve the eruption of particles such as metal vapor in small holes, the shielding gas can more easily reach the bottom of the gap, which can significantly increase the range of plate thickness that can be protected. It provides conditions for welding of large thickness plates, and also improves the protection effect. .

The advantages of the present invention are that compared with the conventional narrow gap laser welding technology, it has the advantages of more sufficient melting of the side wall, smaller tendency of welding porosity, less welding deformation, small heat-affected zone and high stability of welding quality.

Description of drawings

Figure 1: Schematic diagram of the method for ultra-narrow gap laser filler wire welding suitable for large and thick plates,

Figure 2: Schematic diagram of sidewall melting promoted by direct irradiation and reflection of laser beam.

In the figure: 1. Laser beam, 2. Welding groove, 3. Large thickness plate, 4. Welding pool, 5. Weld seam, 6. Shielding gas nozzle, 7. Welding wire.

Detailed ways

The implementation mode of this example is referred to accompanying drawing 1. The laser beam is perpendicular to the horizontal plane, the angle between the welding wire and the laser beam is 30°, and the front and rear simultaneous wire feeding is adopted.

In this example, the workpiece is two 60mm thick 304 stainless steel plates that are butted, the narrow gap groove width is 3.5mm, the blunt edge thickness is 2mm, and the groove depth is 58mm. Stainless steel welding wire ER347 with a diameter of 1mm is used. Using IPG company YLS-6000 fiber laser. The welding parameters are: welding speed 0.36m/min, welding power 4200W, wire feeding speed 3.1m/min, defocus distance 54mm, spot diameter 4mm. The distance between the welding wire and the beam is 2 mm. The side-blowing gas protection form is adopted, the flow rate of the protection gas is 25L/min, the protection gas is argon with a purity of 99.9%, and the diameter of the protection gas nozzle is 7mm.

Claims (3)

1. A narrow-gap laser wire-filling welding method for thick plates, characterized in that: when the positive defocus laser beam enters the narrow-gap groove of the workpiece to be welded for welding, two wire feeding systems before and after send the welding wire into the molten pool and form In the semi-enclosed space that limits the loss of laser energy reflection, the welding wire is heated and melted through the molten pool, and the gap is filled to form a weld. The connection of thick plates is realized by single-pass multi-layer welding. 2. The narrow-gap laser wire-fill welding method for thick plates according to claim 1, characterized in that: the two wire feeding systems are distributed on both sides of the laser beam and the included angle is less than 45 degrees. 3. The narrow-gap laser wire-filling welding method for thick plates according to claim 1, characterized in that the width of the narrow gap for thick plate welding is between 2 mm and 10 mm.