Method for welding ultra-high strength steel cylinder

Abstract

This invention provides a method for welding ultra-high strength steel cylinders, comprising the following steps: Step S1, grinding away the oxide film on the surface of the area to be welded; Step S2, mounting the cylinder to be welded onto an internal support mechanism; Step S3, a robot moves the laser welding head to align it with the weld seam; Step S4, laser spot welding is performed first; Step S5, figure-eight laser oscillation welding is performed. This invention uses an internal support mechanism to tighten the cylinder to be welded, and the extension degree of the support block is adjustable, adapting to cylinders of various sizes; through the cooperation of the welding fixture and the laser head, figure-eight oscillation laser welding is used, resulting in better forming effect and lower porosity; the longer arc-ending time allows for complete melting on the back side of the weld while maintaining a higher weld height on the front side; the structure is simple, the operation is convenient, and it is applicable to various types of cylinders, effectively reducing welding costs while ensuring welding efficiency and quality.

Description

Technical Field

[0001] This invention relates to the field of engine casing welding, and more specifically, to a method for welding ultra-high strength steel cylinders. Background Technology

[0002] Ultra-high strength steel 30Si2MnCrMoVE (abbreviated as D406A) has a tensile strength higher than 1620MPa and an elongation greater than 8%, and is mainly used for solid rocket motor housings.

[0003] A Chinese patent with publication number CN105234535A discloses a cylindrical welding process, including: an internal beveling step, where an internal beveling is formed by machining and assembling the internal beveling, which is an inverted V-shaped beveling; an internal beveling welding step, where the internal beveling is welded using a double-wire three-wire submerged arc welding process; an external beveling and internal beveling mechanical cleaning step, where the external beveling and internal beveling mechanical cleaning are completed in one step, and the external beveling is a U-shaped beveling; and an external beveling welding step, where the external beveling is welded using a double-wire three-wire submerged arc welding process.

[0004] Traditional casings primarily use TIG welding, which offers relatively stable weld quality but is slow. For casings larger than 2mm, beveling and multi-layer, multi-pass welding are required. While electron beam welding is more efficient, the equipment is more expensive, and vacuuming takes longer. In comparison, laser welding is less expensive.

[0005] Laser welding boasts high energy density, resulting in a small heating area, a small heat-affected zone, minimal deformation, a large weld depth-to-width ratio, high weld quality, and low residual stress and deformation. Laser welding is fast and efficient, can be performed in atmospheric or vacuum environments, and can weld materials that are difficult or impossible to weld, such as high-melting-point metals, ceramics, and glass. Laser welding is simple to operate, allowing for automation and intelligent control, long-distance transmission, and flexible control. It can be combined with other processes, such as laser-arc welding and laser-resistance welding. Laser welding is highly safe, producing no pollution, noise, radiation, or electric arc.

[0006] Therefore, there is a need to provide a welding method for ultra-high strength steel cylinders made of 30Si2MnCrMoVE (D406A) to reduce welding costs while ensuring welding efficiency and quality. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the purpose of this invention is to provide a welding method for ultra-high strength steel cylinders.

[0008] A welding method for ultra-high strength steel cylinders according to the present invention includes the following steps:

[0009] Step S1: Grind off the oxide film on the surface of the four parts to be welded: left end cap, spun cylinder, right end cap, and front skirt.

[0010] Step S2: Install the left end cap, the spun cylinder, and the right end cap from left to right on the inner support mechanism. The tensioning block on the inner support mechanism extends outward and presses against the inner wall of the spun cylinder, so that the left end cap, the spun cylinder, and the right end cap are tightly attached to form the cylinder to be welded. Install the front skirt clamping block and the rear end cap fixing ring at both ends of the cylinder to be welded, and then lock them with the nut cap. Install the front skirt head on the front skirt clamping block and fix it with the front skirt fixing ring.

[0011] Step S3: Install the laser welding head on the robot, and move the laser welding head so that it is aligned with a weld seam of the cylinder to be welded.

[0012] Step S4: First, rotate the center rod to perform laser spot welding, spot welding 8-12 points in one circle, with the spot welding power being 70% of the welding power;

[0013] Step S5: The central rod rotates synchronously with the robot to perform laser oscillation scanning welding. The laser beam advances along the axis parallel to the weld seam. With the weld seam as the center point, the laser oscillation welding is performed in a figure-eight pattern. The laser welding power is 1500-2500W, the laser welding speed is 300-500mm / min, the laser welding defocusing amount is 0-13mm, the shielding gas flow rate is 30-50L / min, the oscillation frequency is 100-200Hz, the oscillation amplitude is 2-3mm, and the arc termination arc is 120°-360°.

[0014] Step S6: After one weld seam of the cylinder to be welded is completed, the moving robot aligns the laser welding head with another weld seam of the cylinder to be welded, and repeats steps S4 and S5 until the welding is completed.

[0015] Step S7: After welding is completed, remove the cylinder.

[0016] In step S2, the inner support mechanism includes a tensioning block, a tensioning block driving device, a positioning end cap, and a central rod. Two positioning end caps are respectively disposed at both ends of the central rod. Multiple tensioning blocks are evenly arranged around the central rod on the inner side of each positioning end cap. Two sets of tensioning block driving devices are correspondingly disposed on the central rod. The tensioning block driving devices are drivenly connected to the tensioning blocks. The tensioning blocks can extend outward or retract inward perpendicular to the central axis of the central rod.

[0017] The left and right end caps are respectively fitted to the positioning end caps on both sides.

[0018] The outer periphery of the positioning end cap is provided with a back protective air groove.

[0019] Each of the aforementioned tensioning blocks includes a movable tensioning member and a U-shaped tensioning seat. The opening of the U-shaped tensioning seat is perpendicular to the central axis of the central rod and extends outward. The movable tensioning member is disposed within the opening of the U-shaped tensioning seat, and the end faces of the two straight sections of the U-shaped tensioning seat are arc-shaped.

[0020] The tensioning block driving device is disposed on the inner side of the tensioning block. The tensioning block driving device includes a plurality of sliders evenly arranged around the central rod in the circumferential direction, and the sliders are arranged in a one-to-one correspondence with the movable tensioning member.

[0021] The central rod has a guide groove that matches the slider. The slider is installed in the guide groove and the two slide together. The slider can move closer to or further away from the movable support. The bottom end of the slider is connected to the movable support through the central rod via a connecting rod. The movable support can extend or retract by the connecting rod.

[0022] Each of the two tensioning block drive devices is connected to a control device. Multiple sliders of any one of the tensioning block drive devices move synchronously. The central rod is connected to a drive device, and the central rod can rotate around its central axis by being driven by the drive device.

[0023] In step S2, the assembly gap is less than 0.02 mm.

[0024] In step S2, the coaxiality of the inner holes of the cylinder to be welded, the front skirt fixing ring, and the rear end fixing ring is less than 0.1 mm.

[0025] In step S5, the arc initiation time is 20s and the arc termination time is 70s.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] This invention uses an internal support mechanism to tighten the cylinder to be welded, and the extension degree of the support block is adjustable, making it adaptable to cylinders of various sizes and greatly expanding its application range. Through the cooperation of the welding fixture and laser head, it employs 8-shaped oscillating laser welding, resulting in better forming effect and lower porosity. The longer arc-ending time allows for complete penetration of the weld on the back side, while maintaining a higher weld height on the front side. The invention features a simple structure, convenient operation, and applicability to various types of cylinders, effectively reducing welding costs while ensuring welding efficiency and quality. Attached Figure Description

[0028] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0029] Figure 1This is a schematic diagram of the welding fixture used in the welding method for ultra-high strength steel cylinders, which is the main feature of this invention.

[0030] Figure 2 This is a schematic diagram illustrating the main features of the invention, showing the workpiece to be welded mounted on a welding fixture.

[0031] Figure 3 This is a schematic diagram showing the structure of the left end of the welding fixture, which is the main feature of this invention.

[0032] Figure 4 This is a schematic diagram showing the structure of the right end of the welding fixture, which is the main feature of this invention.

[0033] Figure 5 This is a schematic diagram illustrating the figure-eight laser oscillation welding pattern, which is the main feature of this invention.

[0034] As shown in the figure:

[0035] Left end cap 10, spun cylinder 20, right end cap 30

[0036] Nut cover 1; Front skirt clamping block 2; Front skirt retaining ring 3

[0037] 4. Back protective air groove; 5. Internal support mechanism; 6. Rear end cap fixing ring.

[0038] 51 Tensioning block 52 Tensioning block drive device 53 Positioning end cover

[0039] Center rod 54 Detailed Implementation

[0040] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0041] like Figure 1-5 As shown, a welding method for ultra-high strength steel cylinders according to the present invention includes the following steps:

[0042] Step S1: Use sandpaper to sand off the oxide film on the surface of the four parts to be welded: left end cap 10, spinning cylinder 20, right end cap 30, and front skirt, so that the material in the area to be welded shows a metallic luster.

[0043] Step S2: Install the left end cap 10, the spinning cylinder 20, and the right end cap 30 from left to right on the inner support mechanism 5. The tensioning block 51 on the inner support mechanism 5 extends outward and presses against the inner wall of the spinning cylinder 20, so that the left end cap 10, the spinning cylinder 20, and the right end cap 30 are tightly attached to form the cylinder to be welded. Install the front skirt clamping block 2 and the rear end cap fixing ring 6 at both ends of the cylinder to be welded, and then lock them with the nut cover 1. Install the front skirt head on the front skirt clamping block 2 and fix it with the front skirt fixing ring 3.

[0044] Step S3: Install the laser welding head on the robot, and move the laser welding head so that it is aligned with a weld seam of the cylinder to be welded.

[0045] Step S4: First, rotate the center rod 54 to perform laser spot welding. Weld 8-12 points in one circle, and the spot welding power is 70% of the welding power.

[0046] In step S5, the central rod 54 rotates synchronously with the robot to perform laser oscillation scanning welding. The laser beam advances along the axis parallel to the weld seam, and with the weld seam as the center point, it performs figure-eight laser oscillation welding. The laser welding power is 1500-2500W, the laser welding speed is 300-500mm / min, the laser welding defocusing amount is 0-13mm, the shielding gas flow rate is 30-50L / min, the oscillation frequency is 100-200Hz, the oscillation amplitude is 2-3mm, and the arc termination arc is 120°-360°.

[0047] Step S6: After one weld seam of the cylinder to be welded is completed, the moving robot aligns the laser welding head with another weld seam of the cylinder to be welded, and repeats steps S4 and S5 until the welding is completed.

[0048] Step S7: After welding is completed, remove the cylinder.

[0049] The engine casing is constructed as follows: a 1.3mm spun section (without end caps) in the middle, approximately 1.5m in length, with two end caps of the same wall thickness aligned and welded to the spun section cylinder. The weld thickness is 1.3mm. A 3mm front skirt is then welded to the front. Traditional casing construction primarily uses TIG welding, which offers relatively stable weld quality but is slow. For casings thicker than 2mm, beveling and multi-layer, multi-pass welding are required. While electron beam welding is more efficient, the equipment is more expensive, and vacuuming takes longer. In comparison, laser welding is less expensive.

[0050] In step S2, the inner support mechanism 5 includes a support block 51, a support block drive device 52, a positioning end cover 53, and a central rod 54. Two positioning end covers 53 are respectively set at both ends of the central rod 54. Multiple support blocks 51 are evenly arranged around the central rod 54 on the inner side of any positioning end cover 53. Two sets of support block drive devices 52 are correspondingly set on the central rod 54. The support block drive devices 52 are driven to connect with the support blocks 51. The support blocks 51 can extend outward or retract inward perpendicular to the central axis of the central rod 54.

[0051] The left end cap 10 and the right end cap 30 are respectively fitted to the positioning end caps 53 on both sides. That is, the end face and inner circle of the left end cap 10 are positioned by the positioning end cap 53, so that the left end face of the spinning cylinder 20 is close to the left end cap 10, and then pressed by the nut cover 1; the end face and inner circle of the right end cap 30 are positioned by the positioning end cap 53, so that the right end face of the spinning cylinder 20 is close to the right end cap 30, then fixed by the rear end cap fixing ring 6, and finally pressed by the nut cover 1.

[0052] The outer periphery of the positioning end cover 53 is provided with a back protective air groove 4.

[0053] Each of the tensioning blocks 51 includes a movable tensioning element and a U-shaped tensioning seat. The opening of the U-shaped tensioning seat is perpendicular to the central axis of the central rod 54 and outward. The movable tensioning element is set inside the opening of the U-shaped tensioning seat. The end faces of the two straight sections of the U-shaped tensioning seat are arc-shaped.

[0054] The tension block drive device 52 is located inside the tension block 51. The tension block drive device 52 includes multiple sliders evenly arranged around the central rod 54, and each slider corresponds to a movable tension member. The central rod 54 has a guide groove that matches the slider. The slider is installed in the guide groove and the two slide together. The slider can move closer to or away from the movable tension member. The bottom end of the slider is connected to the movable tension member through the central rod 54 via a connecting rod. The movable tension member can extend or retract via the connecting rod.

[0055] Two tensioning block drive devices 52 are each connected to a control device, and multiple sliders of any one tensioning block drive device 52 move synchronously. The center rod 54 is connected to a drive device, typically a servo motor, which drives the center rod 54 to rotate around its central axis, thereby causing the cylinder to rotate.

[0056] This application uses two internal support mechanisms 5 to tighten the cylinder, and the extension degree of the support block 51 is adjustable, which can be adapted to cylinders of various sizes, greatly improving the application range and effectively reducing costs.

[0057] In step S2, the assembly gap is less than 0.02mm to ensure that the welding will not burn through.

[0058] In step S2, the coaxiality of the inner holes of the cylinder to be welded, the front skirt fixing ring 3, and the rear end fixing ring 6 is less than 0.1 mm.

[0059] In step S5, a two-dimensional oscillating laser head is used. The welding head is controlled by motor-driven X-axis and Y-axis oscillating mirrors to perform laser oscillation scanning welding in a high-frequency scanning mode, thereby improving the stability of the welding process.

[0060] In step S5, the arc initiation time is 20 seconds, and the arc termination time is 70 seconds. When welding ultra-high-strength steel thicker than 2mm, rapid laser power decay during arc termination can easily cause pitting. By using a slower laser power decay, pitting can be prevented from forming in the weld, while simultaneously providing secondary heating to the first pass of welding, resulting in a fuller weld reinforcement on the front side. A longer, slower arc termination time allows for even greater reinforcement on the front side, provided the back side is fully penetrated.

[0061] In step S4, if the spot welding power is too low, the weld may be subjected to tensile stress during full welding, leading to deformation. As welding progresses, the stress received by the weld increases, the weld gap widens, and the inherent stability of the molten pool is compromised, resulting in porosity. In step S5, if O-shaped oscillation is used, the unidirectional rotation can easily cause the molten pool material on one side to be oscillated to the other, resulting in poor weld formation. The thicker the weld plate, the more pronounced the poor formation effect. In contrast, 8-shaped oscillation, because the laser has two O-shaped oscillations in opposite directions, results in better formation, lower porosity, and the weld meets QJ175-1993 grade 0.

[0062] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0063] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A method for welding ultra-high strength steel cylinders, characterized in that, Includes the following steps: Step S1: Grind off the oxide film on the surface of the four parts to be welded: left end cap (10), spun cylinder (20), right end cap (30), and front skirt. Step S2: Install the left end cap (10), the spinning cylinder (20), and the right end cap (30) from left to right on the inner support mechanism (5). The support block (51) on the inner support mechanism (5) extends outward and presses against the inner wall of the spinning cylinder (20), so that the left end cap (10), the spinning cylinder (20), and the right end cap (30) are close together to form the cylinder to be welded. Install the front skirt pressing block (2) and the rear end cap fixing ring (6) at both ends of the cylinder to be welded, and then lock them with the nut cover (1). Install the front skirt head on the front skirt pressing block (2) and fix it with the front skirt fixing ring (3). Step S3: Install the laser welding head on the robot, and move the laser welding head so that it is aligned with a weld seam of the cylinder to be welded. Step S4: First, rotate the center rod (54) to perform laser spot welding. Weld 8-12 points in one circle, and the spot welding power is 70% of the welding power. Step S5: The center rod (54) rotates synchronously with the robot to perform laser oscillation scanning welding. The laser beam moves forward along the axis parallel to the weld seam. With the weld seam as the center point, the laser oscillation welding is performed in a figure-eight pattern. The laser welding power is 1500-2500W, the laser welding speed is 300-500mm / min, the laser welding defocusing amount is 0-13mm, the shielding gas flow rate is 30-50L / min, the oscillation frequency is 100-200Hz, the oscillation amplitude is 2-3mm, the arc termination arc is 120°-360°, the arc starting time is 20s, and the arc termination time is 70s. Step S6: After one weld seam of the cylinder to be welded is completed, the moving robot aligns the laser welding head with another weld seam of the cylinder to be welded, and repeats steps S4 and S5 until the welding is completed. Step S7: After welding is completed, remove the cylinder.

2. The welding method for ultra-high strength steel cylinders as described in claim 1, characterized in that, In step S2, the inner support mechanism (5) includes a support block (51), a support block drive device (52), a positioning end cap (53), and a central rod (54). The two positioning end caps (53) are respectively disposed at both ends of the central rod (54). Multiple support blocks (51) are evenly arranged around the central rod (54) on the inner side of any positioning end cap (53). Two sets of support block drive devices (52) are correspondingly disposed on the central rod (54). The support block drive device (52) is drivenly connected to the support block (51). The support block (51) can extend outward or retract inward perpendicular to the central axis of the central rod (54).

3. The welding method for ultra-high strength steel cylinders as described in claim 2, characterized in that, The left end cap (10) and the right end cap (30) are respectively fitted to the positioning end caps (53) on both sides.

4. The welding method for ultra-high strength steel cylinders as described in claim 2, characterized in that, The outer periphery of the positioning end cap (53) is provided with a back protective air groove (4).

5. The welding method for ultra-high strength steel cylinders as described in claim 2, characterized in that, Each of the aforementioned support blocks (51) includes a movable support member and a U-shaped support seat. The opening of the U-shaped support seat is perpendicular to the central axis of the central rod (54) and outward. The movable support member is disposed inside the opening of the U-shaped support seat. The end faces of the two straight sections of the U-shaped support seat are arc-shaped.

6. The welding method for ultra-high strength steel cylinders as described in claim 5, characterized in that, The tensioning block driving device (52) is disposed inside the tensioning block (51). The tensioning block driving device (52) includes a plurality of sliders evenly arranged around the central rod (54), and the sliders are arranged one-to-one with the movable tensioning member. The central rod (54) is provided with a guide groove that matches the slider. The slider is installed in the guide groove and the two slide together. The slider can move closer to or further away from the movable support member. The bottom end of the slider is connected to the movable support member through the central rod (54) via a connecting rod. The movable support member can extend or retract by the connecting rod.

7. The welding method for ultra-high strength steel cylinders as described in claim 6, characterized in that, The two support block drive devices (52) are respectively connected to control devices. Multiple sliders of any support block drive device (52) move synchronously. The central rod (54) is connected to a drive device. The central rod (54) can rotate around its central axis by the drive device.

8. The welding method for ultra-high strength steel cylinders as described in claim 1, characterized in that, In step S2, the assembly gap is less than 0.02 mm.

9. The welding method for ultra-high strength steel cylinders as described in claim 1, characterized in that, In step S2, the coaxiality of the inner holes of the cylinder to be welded, the front skirt fixing ring (3), and the rear end fixing ring (6) is less than 0.1 mm.

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