A laser welding groove structure for a medium plate and a welding method

Abstract

The present application discloses a kind of laser wire welding groove structure and welding method of medium plate, and the surface of both sides wall in the groove is formed into discontinuous convex structure along length direction.The present application adopts narrow gap welding groove, and by the design of groove size and shape, plasma is compressed, so that plasma heat is fully burned on weld side wall, and side wall unmelted defect is avoided, and the surface shape of weld is changed from convex to plane by compressed plasma, which is beneficial to the shape control of subsequent laser wire welding weld;Meanwhile, the present application reduces weld filling amount, improves welding efficiency, obtains better welding joint, and solves the problem of difficult fusion of laser wire welding side wall.

Description

Technical Field

[0001] This invention relates to the field of welding, and in particular to a laser filler wire welding groove structure and welding method for medium and thick plates. Background Technology

[0002] Laser filler wire welding of medium and thick plates generally uses the I-groove method, such as... Figure 1 As shown, when welding with this type I bevel, the laser plasma is not constrained by the bevel, causing the plasma to escape upwards and fail to heat the sidewall, resulting in incomplete fusion of the sidewall and thus forming a sidewall non-fusion defect.

[0003] In addition, V-groove welding is also used for laser filler wire welding, such as... Figure 2 As shown, the narrower lower part of the V-groove allows for better sidewall fusion, but as the filling depth increases, the upper part of the groove widens, leading to sidewall incomplete fusion defects, such as... Figure 3 As shown.

[0004] Therefore, the main problems faced in laser filler wire welding of medium-thick low-alloy high-strength steel plates include:

[0005] (1) The plasma region caused by the interaction between the laser and the material is narrow, which makes it impossible to burn to the sidewall or the sidewall heat is low, resulting in the formation of sidewall non-fusion defects.

[0006] (2) After laser filler wire welding, the weld surface becomes convex due to surface tension. Subsequent welding passes are prone to forming incomplete fusion defects at the root of the convex weld bead. To address these issues, some studies employ the laser positive defocusing method to increase the laser spot size and burn as much heat as possible to the weld sidewalls. Others use a narrow bevel design to make the bevel size very small, thus burning as much heat as possible to the sidewalls. Still others use laser filler hot wire welding to reduce the heat absorbed by the welding wire, allowing more heat to be absorbed by the sidewalls and preventing the formation of incomplete fusion defects on the sidewalls.

[0007] Chinese patent CN111618434A discloses a method for welding thick plates with narrow gaps based on laser scanning. The method controls sidewall incomplete fusion defects by designing a V-shaped groove with blunt edges, adjusting the laser spot size, laser frequency, and wire feeding angle.

[0008] Chinese patent CN111299828A discloses a method that uses laser to melt a post-placed welding wire in an ultra-narrow gap groove in a heat-conducting welding mode. The laser-wire interaction position is located above the molten pool at the bottom of the groove. The reflected laser from the molten surface of the welding wire acts on the bottom and sidewalls of the groove and preheats them. The molten droplets from the welding wire fill the groove gap to form a weld.

[0009] Chinese patent CN111515541 discloses a laser-arc-TIG composite welding method that avoids incomplete weld fusion caused by laser energy fluctuations due to laser melting of the welding wire, and improves the absorption rate of laser energy by the base material, thereby increasing welding efficiency. Summary of the Invention

[0010] The purpose of this invention is to provide a laser filler wire welding groove structure and welding method for medium and thick plates. This method ensures welding quality while improving welding efficiency, obtaining a well-formed welded joint, and solving the problem of difficult fusion of the sidewalls in laser filler wire welding.

[0011] To achieve the above objectives, the technical solution of the present invention is as follows:

[0012] A laser filler wire welding groove structure for medium-thick plates, wherein the inner two side walls of the groove form a discontinuous protruding structure along the length direction.

[0013] Preferably, the inner two side walls of the bevel are uniformly provided with raised structures, and / or the raised structures on the two side walls are symmetrically designed.

[0014] Preferably, the protruding structure is an arc surface.

[0015] Preferably, the distance between the vertices of the protruding structures on both sides of the bevel is a = 3-4 mm, the distance between the bottoms of adjacent protruding structures on one side of the bevel is b = 3-5 mm, the bottom width of the protruding structure is c = 4-6 mm, the thickness of the bevel's blunt edge is f = 4-6 mm, and the width d inside the bevel is 2-3 mm.

[0016] The welding method for laser filler wire welding bevel structure of medium and thick plate according to the present invention includes the following steps:

[0017] 1) Using machining methods, the bevel surfaces of the two butt joint medium-thick plates are machined to the bevel structure described above;

[0018] 2) Laser welding is used to perform root pass welding on the blunt edge of the bevel of the two butt joint medium-thick plates, that is, welding the blunt edge at the root of the butt weld to ensure that the blunt edge is fully penetrated; then laser filler wire welding is used to fill and build up the bottom of the adjacent protruding structures on the inner wall of the bevel; then laser filler wire welding is used again to fill the weld at the bottom of the protruding structure, and finally the laser filler wire butt weld of the medium-thick plates is completed; the laser filler wire welding process uses laser positive defocusing amount, the laser spot size is controlled above 1mm, and the welding speed is preferably controlled at 1±0.1m / min to ensure that the welding wire can be completely melted.

[0019] Preferably, in step 1), the machined bevel is cleaned with acetone to remove oil stains from the surface of the bevel caused by machining.

[0020] Preferably, in step 2) laser filler wire welding, the wire feed tube is in front of the laser beam, forming an angle of 40-50° with the laser beam, and the position where the welding wire is delivered should be tangential to the leading edge of the laser focusing spot; the shielding gas tube is behind the laser beam, forming an angle of 40-60° with the laser beam, and the blowing position should be aligned with the center of the laser spot.

[0021] Preferably, in step 2), when laser filler wire welding is used to weld the bottom of the adjacent protruding structure on one side wall of the groove, the filler thickness of the weld is ensured to be greater than the value b.

[0022] Preferably, in step 2), when the laser filler wire welding method fills the weld at the bottom position of the protruding structure on both sides of the groove, the weld filling thickness can be less than the c value.

[0023] Preferably, in step 2), when the laser filler wire welding process is unstable, if the weld surface is not smooth after the filler wire is completed, the weld surface can be laser remelted to make the surface smooth, which is beneficial to the formation of the filler wire weld in the next step.

[0024] Compared with other laser filler wire welding methods, the groove design and welding method described in this invention has the following advantages:

[0025] 1. The inner wall of the bevel described in this invention adopts a serrated design to prevent sharp areas from appearing between the weld bead and the side wall due to the planar structure used in traditional bevels, thereby forming welding inclusions and voids.

[0026] 2. The inner wall of the bevel described in this invention adopts a serrated design, which can change the plasma morphology, so that both sides of the weld sidewall can be fully heated and melted, avoiding the sidewall incomplete fusion defects caused by traditional planar bevels.

[0027] 3. The surface of the molten pool is subjected to compressed plasma, which changes the shape of the weld surface from a raised shape to a flat or concave shape. This is beneficial for the formation of the weld in the subsequent laser filler wire welding, improves the surface formation quality of the weld, and avoids the discontinuity defects of the weld bead formed by the traditional flat bevel.

[0028] 4. The bevel of the present invention is designed with a serrated shape, which, compared with the traditional planar structure bevel, can reduce the amount of weld filler, save welding materials, improve welding efficiency, and increase economic benefits.

[0029] The beneficial effects of this invention are:

[0030] The bevel of this invention adopts a discontinuous protrusion, serrated shape, and narrow gap design. Combined with the size and shape of the protrusion, on the one hand, the confined laser plasma can widen the plasma morphology, allowing the plasma heat to fully burn to the weld sidewall; on the other hand, the confined plasma generates pressure on the surface of the molten pool, causing the weld surface morphology to change from a protruding shape to a planar or concave shape, which is beneficial to the weld formation control of the subsequent laser filler wire welding. At the same time, by adopting this bevel design, the amount of filler wire is reduced, making it less likely for inclusions and incomplete fusion defects to form at the root on both sides of the weld, realizing laser filler wire welding of medium and thick plate steel, and also improving welding efficiency. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of an existing laser filler wire welding type I groove;

[0032] Figure 2 A schematic diagram of an existing laser filler wire welding V-groove;

[0033] Figure 3 This is a schematic diagram of the non-fusion defect in the sidewall of the groove in existing laser filler wire welding.

[0034] Figure 4 A schematic diagram of the bevel laser plasma morphology in existing laser welding methods;

[0035] Figure 5 This is a schematic diagram of the welding bevel structure described in this invention;

[0036] Figure 6 This is a schematic diagram of the laser plasma morphology obtained by the method of the present invention;

[0037] Figure 7 This is a schematic diagram of the laser spot, wire feed tube, and protective gas tube in the welding method described in this invention;

[0038] Figure 8 This is a macroscopic photograph of the weld formation obtained in Example 1 of the welding method described in this invention.

[0039] Figure 9 This is a macroscopic photograph of the weld formation obtained in Example 2 of the welding method described in this invention. Detailed Implementation

[0040] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0041] See Figures 5-8 The laser filler wire welding groove structure for medium and thick plates described in this invention, wherein discontinuous protrusion structures 2, 2', 2' are formed on the inner two side wall surfaces of groove 1 along the length direction.

[0042] Preferably, the inner two side walls of the bevel 1 are uniformly provided with raised structures 2, 2', 2'", and / or the raised structures on the two side walls are symmetrically designed.

[0043] Preferably, the protruding structures 2, 2', 2" are arc surfaces.

[0044] Preferably, the distance a between the vertices of the protruding structures 2 and 2' on the inner sidewalls of the bevel 1 is 3-4 mm, the bottom distance b between adjacent protruding structures 2 and 2' on one sidewall of the bevel 1 is 3-5 mm, the bottom width c of the protruding structure 2 is 4-6 mm, the blunt edge thickness f of the bevel 1 is 4-6 mm, and the inner width d of the bevel is 2-3 mm.

[0045] The welding method for laser filler wire welding bevel structure of medium and thick plate according to the present invention includes the following steps:

[0046] 1) Using machining methods, the bevel 1 surface of the two butt joint medium-thick plates 100 and 100' is machined as described above;

[0047] 2) Laser welding is used to perform root pass welding on the blunt edges of the bevel 1 of the two butt-welded medium-thick plates 100 and 100', that is, welding the blunt edge f at the root of the butt weld to ensure full penetration of the blunt edge; then laser filler wire welding is used to fill and build up the bottom of the adjacent protruding structures 2 and 2' on the inner sidewall of the bevel 1; then laser filler wire welding is used again to fill the weld at the bottom of the protruding structures 2 and 2', and finally the laser filler wire butt weld of the medium-thick plates is completed; the laser filler wire welding process uses laser positive defocusing amount, the laser spot size is controlled above 1mm, and the welding speed is preferably controlled at 1±0.1m / min to ensure that the welding wire can be completely melted.

[0048] Preferably, in step 1), the machined bevel is cleaned with acetone to remove oil stains from the surface of the bevel caused by machining.

[0049] Preferably, in step 2) laser filler wire welding, the wire feed tube 3 is in front of the laser beam 4, forming an angle of 40-50° with the laser beam 4, and the position where the welding wire is delivered should be tangential to the leading edge of the laser focusing spot; the protective gas tube 5 is behind the laser beam 4, forming an angle of 40-60° with the laser beam 4, and the blowing position should be aligned with the center of the laser spot.

[0050] Preferably, in step 2), when laser filler wire welding is used to weld the bottom of the adjacent protruding structure on one side wall of the groove, the filler thickness of the weld is ensured to be greater than the value b.

[0051] Preferably, in step 2), when the laser filler wire welding method fills the weld at the bottom position of the protruding structure on both sides of the groove, the weld filling thickness can be less than the c value.

[0052] Preferably, in step 2), when the laser filler wire welding process is unstable, if the weld surface is not smooth after the filler wire is completed, the weld surface can be laser remelted to make the surface smooth, which is beneficial to the formation of the filler wire weld in the next step.

[0053] Example 1

[0054] Two pieces of BG890QL low-alloy high-strength steel, with lengths of 200mm, widths of 100mm, and thicknesses of 50mm, were used to machine the bevel structure described in this invention using a CNC lathe. Specific parameters are shown in Table 1. After beveling, the bevel surface was cleaned with acetone and then fixed on a fixture. A fiber laser with a maximum power of 10kW was used, and the motion mechanism was controlled by a six-axis robot. The filler wire was X70 wire with a diameter of 1.2mm, and the wire feed tube had a diameter of 2mm. Pure argon gas was used for shielding, and the shielding gas tube was made of pure copper with a diameter of 3mm and a wall thickness of 0.5mm. The shielding gas flow rate was 15L / min.

[0055] During welding, the laser is incident perpendicularly to the welding position, and the wire feed tube 3 is in front of the laser beam 4, forming a 45° angle with the laser beam 4. Its wire feed position is tangent to the front of the laser focusing spot. The shielding gas tube 5 is positioned behind the laser beam 4, forming a 45° angle with the laser beam 4. Figure 7 As shown. The first root pass was performed using pure laser welding at a power of 6kW, a welding speed of 1m / min, and an argon shielding gas flow rate of 15L / min. After the first root pass, laser filler wire welding began. During filler wire welding, the laser power was 6kW, the welding speed was 0.8m / min, the wire feed speed was 4m / min, and the gas shielding flow rate was 20L / min. Welding continued according to this process until the entire weld joint was filled.

[0056] The weld formation obtained according to this method is as follows: Figure 8 As shown, there are no defects such as loading inside the weld or lack of fusion on the sidewalls, and the weld formation quality is stable and well formed.

[0057] The bevel size parameters for Example 2 are shown in Table 1, and the resulting weld formation is as follows: Figure 9 As shown.

[0058] Table 1 Unit: mm

[0059] Example 1 3 3 6 2 4 Example 2 4 5 6 3 4

[0060] Figure 1 , Figure 2 This illustrates the traditional I-groove and V-groove grooves used in laser welding and laser filler wire welding. These groove designs easily lead to sharp areas between the weld bead and the sidewall, resulting in weld inclusions and voids. Figure 3 , Figure 4 As shown.

[0061] use Figure 5 The welding bevel of the present invention shown in the figure, through different embodiments, can achieve good weld formation quality, without welding defects such as inclusions and lack of sidewall fusion, such as... Figure 8 , Figure 9 As shown.

[0062] The main reason is:

[0063] The bevel design described in this invention alters the plasma morphology, allowing both sides of the weld sidewall to be fully heated and melted, avoiding the sidewall incomplete fusion defects caused by traditional planar bevels. On one hand, the confined laser plasma widens the plasma morphology, enabling the plasma heat to fully reach the weld sidewall. On the other hand, the confined plasma exerts pressure on the molten pool surface, causing the weld surface morphology to change from a convex shape to a planar or concave shape, which is beneficial for the weld formation control in subsequent laser filler wire welding. At the same time, by adopting this bevel design, the amount of filler wire is reduced, making it less likely for inclusions and incomplete fusion defects to form at the root of the weld on both sides, thus realizing laser filler wire welding of medium and thick steel plates and improving welding efficiency.

[0064] The above embodiments are merely detailed descriptions of the present invention and are not intended to limit the scope of protection of the invention. They do not limit the present invention in any way, and subsequent changes and improvements to the present invention fall within the scope of the claims.

[0065] The welding method of this invention can be applied to laser filler wire welding of medium-thick plate low-alloy high-strength steel. The main application prospects of this invention include the following industries: engineering machinery, oil pipelines, and chemical industry.

Claims

1. A laser filler wire welding bevel structure for medium-thick plates, characterized in that, The inner two side walls of the bevel form a discontinuous raised structure along the length direction; the bevel is designed with a narrow gap; the inner two side walls of the bevel are uniformly provided with raised structures, the raised structures on the two side walls are symmetrically designed, and the raised structures are arc surfaces.

2. The welding method for laser-welded bevel structures of medium-thick plates as described in claim 1, characterized in that, Includes the following steps: 1) The bevel structure is machined on the bevel surfaces of the two butt joint medium-thick plates using machining methods; 2) Laser welding is used to perform root pass welding on the blunt edge of the bevel of the two butt joint medium-thick plates, that is, welding the blunt edge at the root of the butt weld to ensure full penetration of the blunt edge; then laser filler wire welding is used to fill and build up the bottom of the adjacent protruding structures on the inner wall of the bevel; then laser filler wire welding is used again to fill the weld at the bottom of the protruding structure, and finally the laser filler wire butt weld of the medium-thick plates is completed; the laser filler wire welding process uses laser positive defocusing amount, the laser spot size is controlled above 1mm, and the welding speed is controlled at 1±0.1 m / min to ensure that the welding wire can be completely melted.

3. The welding method for laser-welded bevel structures of medium-thick plates as described in claim 2, characterized in that, In step 1), the machined bevel is cleaned with acetone to remove oil stains from the surface of the bevel caused by machining.

4. The welding method for laser-welded bevel structures of medium-thick plates as described in claim 2, characterized in that, Step 2) During laser wire feeding, the wire feed tube is in front of the laser beam, forming an angle of 40-50° with the laser beam. The wire should be delivered to a position that is tangential to the leading edge of the laser focusing spot. The shielding gas tube is behind the laser beam, forming an angle of 40-60° with the laser beam. The blowing position should be aligned with the center of the laser spot.

5. The welding method for laser-welded bevel structures of medium-thick plates as described in claim 2 or 4, characterized in that, In step 2), when laser filler wire welding is used to weld the bottom of the adjacent protruding structure on one side wall of the groove, ensure that the filler thickness of the weld is greater than the b value.

6. The welding method for laser-welded bevel structures of medium-thick plates as described in claim 2 or 4, characterized in that, In step 2), when the laser filler wire welding method fills the weld at the bottom of the raised structure on both sides of the groove, the weld filling thickness can be less than the c value.

7. The welding method for laser-welded bevel structures of medium-thick plates as described in claim 5, characterized in that, In step 2), when the laser filler wire welding method fills the weld at the bottom of the raised structure on both sides of the groove, the weld filling thickness can be less than the c value.

8. The welding method for laser-welded bevel structures of medium-thick plates as described in claim 2 or 4, characterized in that, In step 2), if the laser filler wire welding process is unstable, and the weld surface is not smooth after the filler wire is completed, the weld surface can be laser remelted to make the surface smooth, which is beneficial to the formation of the filler wire weld in the next step.

9. The welding method for laser-welded bevel structures of medium-thick plates as described in claim 5, characterized in that, In step 2), if the laser filler wire welding process is unstable, and the weld surface is not smooth after the filler wire is completed, the weld surface can be laser remelted to make the surface smooth, which is beneficial to the formation of the filler wire weld in the next step.

10. The welding method for laser-welded bevel structures of medium-thick plates as described in claim 6, characterized in that, In step 2), if the laser filler wire welding process is unstable, and the weld surface is not smooth after the filler wire is completed, the weld surface can be laser remelted to make the surface smooth, which is beneficial to the formation of the filler wire weld in the next step.

11. The welding method for laser-welded bevel structures of medium-thick plates as described in claim 7, characterized in that, In step 2), if the laser filler wire welding process is unstable, and the weld surface is not smooth after the filler wire is completed, the weld surface can be laser remelted to make the surface smooth, which is beneficial to the formation of the filler wire weld in the next step.

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