A composite welding method for laser keyhole-guided deep penetration argon arc welding

Abstract

The present invention discloses a composite welding method for laser keyhole-guided deep penetration argon arc welding, belonging to the field of welding technology. The method comprises the following steps: Step 1, fix the laser head to the welding torch and place the welding torch vertically above the workpiece to be welded, so that the intersection of the laser irradiation position and the extension line of the tungsten electrode is located at the molten layer on the front wall of the keyhole; and along the welding direction, the welding torch is located in front of the laser head; Step 2, set the welding parameters, introduce the shielding gas, start the welding torch, after the arc is struck and the working current is reached, turn on the laser head, and make the laser head and the welding torch move synchronously relative to the workpiece to be welded for composite welding. The laser is used to weaken or even offset the obstruction of the molten layer in front of the keyhole generated by the interaction between the welded part and the heat source on the arc, making the arc straighter, improving the welding speed and weldable thickness of the keyhole, and solving the problems of arc drag caused by too fast welding speed and instability of the keyhole when the weldable thickness is too thick during the keyhole welding process.

Description

Technical Field

[0001] The present invention relates to the field of welding technology, and particularly to a composite welding method for laser keyhole-guided deep penetration argon arc welding. Background Art

[0002] The statements in this section only mention the background technology related to the present invention and do not necessarily constitute prior art.

[0003] KD-TIG (Deep Penetration Argon Arc Welding) is based on the traditional TIG welding (Gas Tungsten Arc Welding). The TIG welding torch is modified into a high-current water-cooled welding torch. The water-cooled welding torch takes away more heat along the axial direction of the tungsten electrode, causing the cathode region at the tip of the tungsten electrode to contract, the current density to be more concentrated, the electromagnetic contraction effect to be strengthened, the arc energy density to be increased, generating a greater arc force to penetrate the workpiece, forming a small hole. Under the balance of the arc force, the molten pool gravity, and the surface tension, the small hole advances stably, realizing keyhole welding. In the welding of medium and thick plates, due to its high welding quality and the characteristic of single-sided welding with double-sided formation, it is widely used.

[0004] This welding mode uses the small hole for energy transmission. Therefore, the stability of the small hole is the key process of keyhole welding. For deep penetration argon arc welding, plasma welding, or other keyhole welding methods, the stability of the keyhole is a necessary and sufficient condition for process application, which limits the welding speed and weldable thickness of deep penetration argon arc welding and plasma welding.

[0005] That is to say, in KD-TIG keyhole welding, the penetration of the arc is used to penetrate the weld seam to form a small hole, and then a stable keyhole welding process is achieved under the interaction of the surface tension, the arc force, and the molten pool gravity. During this process, due to the interaction between the welded part and the heat source, the appearance of the back small hole has a lag, that is, the position of the small hole is behind the arc, and this distance will increase with the increase of the welding speed and thickness. Through metallographic experiments, it is observed that there is an unevenly thick molten layer in front of the small hole in KD-TIG, which will hinder the penetration of the arc, resulting in the arc dragging phenomenon and limiting the welding speed and welding thickness.

[0006] The Chinese patent with the patent publication number CN104985327A discloses a method of composite welding using dual-focus laser and InFocus. Two laser beams and the arc act on the welded area together, enabling the weld seam to be simultaneously affected by three heat sources, which can achieve the effect of increasing the penetration depth, but it causes the molten pool volume to be too large. When welding medium and thick plates, the keyhole is unstable, and it uses dual-focus laser-arc composite, with complex equipment and numerous parameters, making the operation difficult.

[0007] A Chinese patent with the patent publication number CN 107685193 A discloses a pulsed negative pressure laser enhanced keyhole TIG welding device. In this device, the laser and the arc are coaxially placed. The laser irradiates the workpiece through a hollow tungsten electrode and forms a heat source together with the arc for welding. A vacuum negative pressure device is equipped above the tungsten electrode, which can effectively constrain the arc, enhance the arc penetration ability. The current density of the hollow tungsten electrode arc shows a concave distribution, and its arc penetration ability is significantly reduced. Moreover, this coaxial composite gun head design is complex, with high processing difficulty and poor practicability. Summary of the Invention

[0008] To address the deficiencies of the prior art, the present invention provides a composite welding method for laser keyhole-guided deep penetration argon arc welding. Using deep penetration argon arc welding as the main heat source and laser as the auxiliary heat source, it can achieve single-sided welding with double-sided formation, improve the straightness of the arc, reduce the molten pool volume, improve the stability of the keyhole, and reduce the welding heat input.

[0009] The present invention provides a composite welding method for laser keyhole-guided deep penetration argon arc welding;

[0010] A composite welding method for laser keyhole-guided deep penetration argon arc welding includes the following steps:

[0011] Step 1: Fix the laser head to the welding torch and place the welding torch vertically above the workpiece to be welded, so that the intersection of the laser irradiation position and the extension line of the tungsten electrode is located at the molten layer on the front wall of the keyhole; and along the welding direction, the welding torch is in front of the laser head.

[0012] Step 2: Set the welding parameters, introduce the shielding gas, start the welding torch. After the arc is struck and reaches the working current, turn on the laser head, and make the laser head and the welding torch move synchronously relative to the workpiece to be welded for composite welding.

[0013] By adopting the above technical solution, the laser acts on the molten layer to weaken or even offset the obstructive effect brought by the molten layer, making the arc straighter; by the method of having the arc in front and the laser behind, it is ensured that the arc is the main heat source and plays a major role during welding, while the laser behind is the auxiliary heat source to assist the arc in piercing the hole. Compared with KTIG, the welding speed of the keyhole is increased and the weldable thickness is increased. Compared with the composite welding with the laser in front and the arc behind, high-quality welding joints can be obtained, and the requirement for the gap of the joint is much lower.

[0014] Further, the arc generated by the welding torch is the main heat source, and the low-power laser generated by the laser processing head is the auxiliary heat source.

[0015] By adopting the above technical solution, thick plate penetration can be achieved without increasing the welding current by adding a laser or increasing the laser power.

[0016] Further, the intersection point of the laser irradiation position and the extension line of the tungsten electrode is located at one-third to two-thirds of the workpiece thickness.

[0017] By adopting the above technical solution, one-third to two-thirds of the workpiece thickness is the area where the molten layer of the keyhole front wall changes most violently. Making the laser act on this area can improve the penetration and straightness of the arc.

[0018] Further, the welding speed of the composite welding is 0.2 m / min to 2 m / min.

[0019] Further, the thickness of the workpiece to be welded is 6 mm to 12 mm.

[0020] Further, the laser welding parameters include: the output power is 500 W to 20 KW, and the laser defocus amount is -6 mm to 0 mm; the deep penetration argon arc welding parameters include: the welding current is 300 A to 800 A, the tungsten electrode diameter is 8 mm, the tungsten electrode height is 3 mm to 10 mm, and the welding method is direct current straight polarity.

[0021] Further, before step 1, it also includes:

[0022] Grind and clean the groove and the surface to be welded of the workpiece to be welded, and use a fixture to fix the workpiece to be welded on the welding platform.

[0023] Further, the laser head has an angle with the normal direction of the surface of the workpiece to be welded, and the angle is 30° to 60°.

[0024] Further, the types of the laser head include a laser focusing welding head, a laser double pendulum welding head, and a laser galvanometer welding head.

[0025] Further, the laser irradiation methods include focused laser irradiation and laser swing irradiation. The swing path of the laser irradiation includes a straight line, a 1-shaped line, an 8-shaped line, a circle, and a polygon, and the swing amplitude of the laser irradiation is 0 mm to 12 mm.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] 1. For the technical solution provided by the present invention, the normal welding speed of the large penetration argon arc welding is 200 - 300 mm / min. Compared with the large penetration argon arc welding, at the same welding current and welding speed, the addition of the laser significantly improves the straightness of the arc, and increases the welding speed by 60% - 100%.

[0028] 2. For thick plate welding, simply using KD-TIG requires increasing the current and reducing the welding speed to ensure the formation of a keyhole. However, the corresponding molten pool volume is too large, resulting in a weld bead on the back and unstable keyholes. The technical solution provided by the present invention belongs to argon arc keyhole piercing, and the joint quality must be better than that of laser keyhole piercing. Moreover, by adding a laser or increasing the laser power, thick plate penetration can be achieved without increasing the welding current, reducing the current threshold for arc keyhole piercing.

[0029] 3. The technical solution provided by the present invention, during welding, due to the improved penetration and straightness of the arc; compared with KD-TIG, for 10 mm carbon steel welded without beveling, when the laser power is 1500 W and the welding current is 500 A, the welding speed of the hybrid welding can reach 400 mm / min. For 6 mm stainless steel welded without beveling, with a laser power of 1500 W and a welding current of 430 A, the hybrid welding speed can reach 800 mm / min. Using this method, arc keyhole welding can be maintained at low current and high welding speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings forming a part of this specification are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0031] Figure 1 It is a schematic diagram of the molten pool during the hybrid welding process of laser keyhole-guided deep penetration argon arc welding provided by an embodiment of the present invention; 1 - laser, 2 - molten pool, 3 - tungsten electrode, 4 - arc, 5 - keyhole, 7 - laser irradiation position;

[0032] Figure 2 It is a schematic diagram of the weld appearance of laser keyhole-guided KD-TIG welding of 10 mm stainless steel provided by an embodiment of the present invention. (a) is the front weld appearance diagram, and (b) is the back weld appearance diagram;

[0033] Figure 3 It is the weld appearance of KD-TIG welding of 10 mm stainless steel provided by an embodiment of the present invention. (a) is the front weld appearance diagram, and (b) is the back weld appearance diagram;

[0034] Figure 4 It is the weld appearance of laser keyhole-guided KD-TIG welding of 8 mm carbon steel provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0035] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0036] Without conflict, the embodiments in the present invention and the features in the embodiments may be combined with each other.

[0037] During the keyhole welding process in the prior art, simply relying on KD-TIG welding, when the welding speed is too fast, arc drag occurs, and when the weldable thickness is too thick, the keyhole is unstable. Therefore, the present invention provides a composite welding method of laser keyhole-guided deep penetration argon arc welding.

[0038] Next, in combination with Figures 1 - 4 A composite welding method of laser keyhole-guided deep penetration argon arc welding disclosed in this embodiment will be described in detail. The composite welding method of laser keyhole-guided deep penetration argon arc welding includes the following steps:

[0039] Step 1: Grind and clean the groove and the surface to be welded of the workpiece to be welded, and fix the workpiece to be welded on the welding platform using a fixture.

[0040] Step 2: Fix the laser head and the welding torch, and place the welding torch vertically above the workpiece to be welded so that the intersection of the laser irradiation position and the extension line of the tungsten electrode is located at the molten layer on the front wall of the keyhole; and along the welding direction, the welding torch is in front of the laser head.

[0041] Specifically, the intersection of the laser irradiation position and the extension line of the tungsten electrode is located at one-third to two-thirds of the workpiece thickness, and the laser head has an included angle with the normal direction of the surface of the tool to be welded, and the included angle is 30°.

[0042] Among them, the thicker the plate thickness, the smaller the included angle of the composite heat source for maintaining the keyhole stability.

[0043] Step 3: Set the welding parameters, introduce the shielding gas, start the running device and the arc starting device of the welding torch. After the arc starts and reaches the working current, turn on the laser head, and make the laser head and the welding torch move synchronously relative to the workpiece to be welded for composite welding.

[0044] Among them, the running device is a robot that drives the welding torch and the laser head to move, and the arc starting device is an argon arc high-frequency arc starting module. The arc starts to burn only after the argon arc high-frequency arc starting module is started.

[0045] Furthermore, the arc generated by the welding torch is the main heat source, and the low-power laser generated by the laser processing head is the auxiliary heat source; the welding speed of the hybrid welding is 0.4 m / min to 2 m / min, the thickness of the workpiece to be welded is 4 mm to 16 mm, and the laser welding parameters include: the output power is 500 W to 20 KW, and the laser defocus amount is -6 mm to 0 mm; the keyhole plasma arc welding parameters include: the welding current is 300 A to 800 A, the tungsten electrode diameter is 8 mm, the tungsten electrode height is 3 mm to 10 mm, and the welding method is straight polarity DC. The types of laser heads include laser focusing welding heads, laser double pendulum welding heads, and laser galvanometer welding heads. The laser irradiation methods include focused laser irradiation and laser oscillating irradiation. The oscillating paths of laser irradiation include straight line, "1" shape, "8" shape, circular, and polygonal, and the oscillating amplitude of laser irradiation is 0 mm to 12 mm.

[0046] Among them, the parameters of the laser power and the arc current depend on the welding speed and the plate thickness. The faster the welding speed, the higher the required laser power, and the thicker the plate thickness, the greater the arc current.

[0047] Next, the hybrid welding method of laser keyhole-guided keyhole plasma arc welding will be described in detail with the following embodiments:

[0048] Example 1:

[0049] In this example, a 10-mm-thick stainless steel plate is used for laser keyhole-guided KD-TIG hybrid welding. A 1500-W continuous fiber laser is used, with a laser wavelength of 1064 nm and a laser focus diameter of 0.45 mm. An Aotai WSM-1000 power supply is used with a KD-TIG welding torch. The specific process is as follows:

[0050] (1) The surface of the workpiece to be welded is polished and cleaned, and it is clamped on the welding platform using a fixture.

[0051] (2) The laser head and the KD-TIG welding torch are rigidly fixed using a tooling fixture. The welding torch is perpendicular to the workpiece surface, and the angle between the laser head and the normal direction of the workpiece surface is 30°.

[0052] (3) Set the welding parameters, specifically: the laser power is 1350 W, the defocus amount is -6 mm, the KD-TIG tungsten electrode diameter is 8 mm, the welding current is 540 A, on the workpiece surface, the distance between the laser spot and the tungsten electrode tip is 3 mm, the welding speed is 0.5 m / min, and the shielding gas used is 99.9% argon, which is ejected from the KD-TIG welding torch, and the gas flow rate is 20 L / min.

[0053] (3) Pre-flow the shielding gas, start the arc first, and after the arc is successfully started, start the laser, and make the laser head and the KD-TIG welding torch move synchronously relative to the workpiece to be welded to perform laser keyhole-guided KD-TIG hybrid welding, obtaining a weld seam as shown in Figure 2as shown

[0054] Example 2:

[0055] In this example, a low-carbon steel plate with a thickness of 8 mm was used for laser keyhole-guided KD-TIG welding; a 1500W continuous fiber laser with a laser wavelength of 1064 nm and a laser focus diameter of 0.45 mm was used; an Aotai WSM-1000 power source was used with a KD-TIG welding torch. The specific process is as follows:

[0056] (1) The surface of the workpiece to be welded was polished and cleaned, and it was clamped on the welding platform using a fixture.

[0057] (2) The laser head and the KD-TIG welding torch were rigidly fixed using a tooling fixture. The welding torch was perpendicular to the surface of the workpiece to be welded, and the angle between the laser head and the normal direction of the surface of the workpiece to be welded was 30°.

[0058] (3) The welding parameters were set as follows: the laser power was 1350 W, the defocus amount was -4 mm, the laser scanning mode was set as a straight line, the swing amplitude was 1 mm, the swing frequency was 100 HZ, the KD-TIG tungsten electrode diameter was 8 mm, the welding current was 480 A, the distance between the laser spot and the tip of the tungsten electrode on the surface of the workpiece to be welded was 2 mm, the welding speed was 0.54 m / min, and the shielding gas used was 99.9% argon, which was ejected from the KD-TIG welding torch with a gas flow rate of 20 L / min.

[0059] (4) The shielding gas was pre-passed, the arc was started first, and after the arc was successfully started, the laser was started, and the laser head and the KD-TIG welding torch were moved synchronously relative to the workpiece to be welded for laser keyhole-guided KD-TIG welding. The obtained weld seam is as Figure 4 as shown

[0060] Comparative Example 1:

[0061] In this example, a stainless steel plate with a thickness of 10 mm was used for KD-TIG welding, and an Aotai WSM-1000 power source was used with a KD-TIG welding torch. The specific process is as follows:

[0062] (1) The surface of the workpiece to be welded was polished and cleaned, and it was clamped on the welding platform using a fixture.

[0063] (2) The KD-TIG welding torch was rigidly fixed using a tooling fixture. The welding torch was perpendicular to the surface of the workpiece.

[0064] (3)Set the welding parameters, specifically: the diameter of the KD-TIG tungsten electrode is 8 mm, the welding current is 540 A, the welding speed is 0.24 m / min, the shielding gas used is 99.9% argon, which is ejected by the KD-TIG welding torch, the gas flow rate is 20 L / min, a back shielding gas and a shielding gas shroud for the welding torch are installed, and the shielding gases used are both 99.9% argon.

[0065] (4)Pre-flow the shielding gas, start the arc first, and after the arc is successfully started, perform KD-TIG welding, and the weld seam is as Figure 3 shown.

[0066] When comparing the butt joints of 8 mm carbon steel without bevel groove welded by KD-TIG and laser-guided keyhole KD-TIG, the welding speed can be increased by 120%, the current can be reduced by 10%, and the heat input can be reduced by 50%.

[0067] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A composite welding method for laser keyhole-guided deep penetration argon arc welding, characterized in that The method includes the following steps: Step 1: Fix the laser head and the welding torch, and place the welding torch vertically above the workpiece to be welded, so that the intersection point of the laser irradiation position and the extension line of the tungsten electrode is located on the molten layer of the front wall of the keyhole; and along the welding direction, the welding torch is located in front of the laser head; the intersection point of the laser irradiation position and the extension line of the tungsten electrode is located at one-third to two-thirds of the thickness of the workpiece; Step 2: Set the welding parameters, introduce the shielding gas, start the welding torch, after the arc is struck and the working current is reached, turn on the laser head, and make the laser head and the welding torch move synchronously relative to the workpiece to be welded for hybrid welding; the arc generated by the welding torch is the main heat source, and the low-power laser generated by the laser processing head is the auxiliary heat source; The welding speed of the hybrid welding is 0.4 m / min to 2 m / min; The laser welding parameters include: the output power is 500 W to 1500 W, and the laser defocus amount is -6 mm to 0 mm; the deep penetration argon arc welding parameters include: the welding current is 300 A to 800 A, the tungsten electrode diameter is 8 mm, the tungsten electrode height is 3 mm to 10 mm, and the welding method is DC straight polarity.

2. The composite welding method of laser keyhole-guided deep penetration argon arc welding according to claim 1, characterized in that, The thickness of the workpiece to be welded is 6 mm to 12 mm.

3. The composite welding method of laser keyhole-guided deep penetration argon arc welding according to claim 1, characterized in that, Before Step 1, it further includes: Grind and clean the groove and the surface to be welded of the workpiece to be welded, and fix the workpiece to be welded on the welding platform using a fixture.

4. The composite welding method of laser keyhole-guided deep penetration argon arc welding according to claim 1, characterized in that, The laser head has an angle with the normal direction of the surface of the workpiece to be welded, and the angle is 30° to 60°.

5. The composite welding method of laser keyhole-guided deep penetration argon arc welding according to claim 1, characterized in that, The types of the laser head include a laser focusing welding head, a laser double pendulum welding head, and a laser galvanometer welding head.

6. The composite welding method of laser keyhole-guided deep penetration argon arc welding according to claim 1, characterized in that, The laser irradiation methods include focused laser irradiation and laser swing irradiation, the swing path of the laser irradiation includes a straight line, a 1-shaped line, an 8-shaped line, a circle, and a polygon, and the swing amplitude of the laser irradiation is 0 mm to 12 mm.

Images