An efficient welding method for thick-walled titanium butt welds

Abstract

The present invention belongs to the technical field of metal material welding, and specifically relates to an efficient welding method for thick-walled titanium butt welds, comprising the following steps: S1. conducting quality inspection and analysis on the butt joint of the workpiece to be welded; S2. designing the groove structure of the butt joint to be U-shaped, and ensuring that the groove parameters and tolerances are within the control range through precision machining; S3. performing quality control before welding; and S4. performing layered welding according to a set sequence and welding method. This method has excellent internal weld surface quality, high welding deposition efficiency, and a deposition efficiency of up to 3.0 kg / hour. This method can increase production efficiency by 40%, reduce material consumption, and reduce parent material and welding material losses by 30%. For the first time, this method achieves fully automatic, continuous, high-quality, and efficient intelligent welding of thick-walled titanium weld joints with large blunt edges, achieving full penetration at the root, efficient filling, and an aesthetically pleasing finish.

Description

Technical Field

[0001] The invention belongs to the technical field of metal material welding, and in particular relates to a high-efficiency welding method for thick-walled titanium material butt welds. Background Art

[0002] Titanium has a low density and high strength-to-weight ratio. Compared to titanium alloys, industrial pure titanium exhibits excellent corrosion resistance. While its strength is lower than titanium alloys, it is economical and practical, and its excellent processability makes it widely used in specific corrosion-resistant applications. With the increasing demand for larger, more energy-efficient, more efficient, and more durable petrochemical facilities, as well as the rapid development of deep space and deep-sea exploration, titanium processing capabilities and performance research continue to improve, leading to a strong demand for large, thick-walled titanium and titanium alloy vessels. To improve investment returns and efficiency, titanium vessel components are shifting towards higher-strength alloys and thicker walls.

[0003] As technical requirements become more stringent, R&D and manufacturing cycles are repeatedly shortened. Existing welding processing technologies: ordinary tungsten inert gas arc welding has shallow penetration and low deposition efficiency. Although the weld quality is excellent, the process quality stability is greatly affected by environmental and human factors, and material loss is high. This leads to low welding production efficiency and high costs.

[0004] Plasma arc welding and deep penetration welding are penetrating welding methods, which are limited by the one-time penetration capability (one-time penetration depth is ≤16mm). They are mainly used for one-time penetration of workpieces and base welding. Subsequent welding needs to be completed by other methods of filling and covering. For titanium materials with a thickness of less than 16mm, they can complete high-quality and efficient welding well. For materials above 20mm, they can only be used for base welding of thick-walled titanium alloy butt welds ≥20mm. Filling and covering cannot meet the requirements, and general automatic tungsten inert gas arc welding is required. It cannot meet the needs of high-quality and efficient continuous production of large, high-strength, thick-walled titanium containers.

[0005] Electron beam welding is an efficient welding method for large thick-walled titanium and titanium alloys. However, it is limited by the electron beam penetration ability and the vacuum chamber. The quality stability during continuous operation is insufficient and the operating cost is high. Large titanium devices that exceed the vacuum chamber specifications require continuous updates of the vacuum chamber and have poor adaptability. In addition, the electron beam welding system is expensive and has a low input-output ratio, which is not conducive to the efficient and high-quality manufacturing of large, high-strength, thick-walled containers or products.

[0006] Narrow gap tungsten inert gas welding is an economical and practical welding method for welding thick-walled titanium joints. It uses a narrow groove, which significantly reduces material consumption and reduces groove processing and welding time, thereby significantly shortening the production cycle. Ordinary tungsten inert gas welding can be used to carry out narrow gap welding of thick-walled titanium flat plates / arc-shaped butt joints. Manual welding has strong adaptability, but it has many welding layers, low deposition efficiency, welding quality is greatly affected by human factors, and weld quality stability is poor. The welding process requires personnel to concentrate and the labor intensity is high. Quality problems such as tungsten clamping, arcing, and non-fusion between side wall layers are prone to occur, which seriously affect the quality of the continuous welding process of titanium thick-walled welds. Mechanical narrow gap tungsten electrode argon arc welding uses motorized control of tungsten electrode swing to achieve arc swing to solve the side wall fusion problem in the narrow gap welding process of titanium thick-walled workpieces. However, the selected tungsten electrode has a small diameter and low heat input. The filling material is generally a thin wire with a diameter of Φ0.8 to 1.2 mm. While solving the side wall fusion problem, continuous high-quality welding of titanium thick-wall welds is achieved. However, the mechanical method has large wear, high control accuracy requirements, relatively small heat input, and low deposition efficiency. It is now widely used in automatic welding of thick-walled pipes, and the titanium thick-wall welding process is still in the research stage. Summary of the Invention

[0007] In order to solve the above technical problems, the purpose of the present invention is to provide an efficient welding method for thick-walled titanium butt welds that can achieve high-quality and efficient welding of thick-walled titanium butt welds with a thickness of more than 20 mm.

[0008] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0009] An efficient welding method for thick-walled titanium butt welds comprises the following steps:

[0010] S1. Perform quality inspection and analysis on the butt joints of the workpieces to be welded. The tensile strength of the butt joints must be at least 0.9 times the tensile strength of the corresponding base material.

[0011] S2. Design the groove structure of the butt joint into a U-shape, and ensure that the groove parameters and tolerances are within the control range through precision machining;

[0012] S3. Quality control before welding:

[0013] S31. Cleaning before welding: Grind and scrub the surface of the base material on each side of the groove of the workpiece to be welded and the edge of the groove to remove surface oxide scale and dirt;

[0014] S32, Pairing and Forming: Pair the two workpieces to be welded together, ensuring that the front groove surfaces of the blunt edges of the two workpieces are flush, with the back misalignment of the blunt edges controlled to be ≤1.0mm and the root gap between 0 and 1mm. Spot weld an arc starting plate and an arc extinguishing plate of the same thickness as the blunt edges on each end of the workpieces to be welded. Depending on the length of the workpieces to be welded, spot weld fixtures at intervals on one side of the bottom groove to prevent the workpiece opening from affecting the welding during the base welding process. The workpieces to be welded are then fixed on the welding positioner. Debug the protection system effect and the shielding gas quality. After welding, the heat-affected zone of the weld is silvery white and qualified, and debug the welding system to ensure that it is operating properly.

[0015] S4. Welding

[0016] Adjust the welding system to identify and memorize the arc starting point, arc ending point and motion trajectory of the workpiece to be welded; start welding at the selected welding position; the welding robot starts the arc on the arc starting plate, and the welding robot is linked with the welding positioner. During the welding process, the welding pool is always in the best position for crystallization and formation to ensure welding quality, and welding is carried out according to the following welding methods:

[0017] S41, use pulsed tungsten inert gas welding process to perform front bottom welding;

[0018] S42, use thick wire magnetron narrow gap tungsten inert gas arc welding to perform filler welding in the front narrow groove to a certain weld thickness;

[0019] S43, using pulsed tungsten inert gas arc welding process to perform back-end penetration welding;

[0020] S44. Use thick wire magnetron narrow gap tungsten inert gas arc welding to fill the back groove. According to the deformation amount, alternate filling welding is performed on the front and back grooves until the distance from the parent material surface is 2 to 3 mm.

[0021] S45. Use pulsed tungsten inert gas arc welding to weld the cover layer and complete the butt weld of thick-walled titanium material.

[0022] As a preferred technical solution, the thickness of the thick-walled titanium material is ≥20 mm.

[0023] As a preferred technical solution, in step S2, the main groove parameters and tolerances of the butt joint are as follows:

[0024] Blunt edge b = 4 ~ 8mm, processing tolerance is controlled at 0 ~ 0.5mm;

[0025] The groove angle α is 6-12°, and the processing tolerance is controlled at 0-1.0°;

[0026] The root fillet R=4~6mm, and the processing tolerance is controlled at 00.5mm;

[0027] The machining tolerance of the distance H between the center line of the blunt edge and the single layer is controlled within 0 to 0.2 mm.

[0028] As a preferred technical solution, in step S4, the shielding gas for welding is 99.99% Ar.

[0029] As a preferred technical solution, in step S4, the welding electrode is a cerium tungsten electrode, and the diameter of the tungsten electrode is 4 to 6 mm.

[0030] As a preferred technical solution, in step S4, the diameter of the filling thick wire is 2 to 3 mm.

[0031] As a preferred technical solution, in step S4, the power supply of the welding system is a DC digital pulse welding power supply with a rated current of more than 1000A.

[0032] As a preferred technical solution, in step S41, the bottoming process parameters are controlled to be between 55% and 70% of the thickness of the blunt edge.

[0033] As a preferred technical solution, in step S42, thick wire magnetron narrow gap tungsten inert gas arc welding is used to fill and weld the front narrow groove to two layers of 6 to 8 mm weld thickness.

[0034] Due to the adoption of the above technical solution, the present invention has at least the following beneficial effects:

[0035] (1) Through the quality inspection and analysis of the butt joints of the workpieces to be welded, the tensile strength of the butt joints is at least 0.9 times the tensile strength of the corresponding base material. This can ensure the quality of welding in the best welding position, avoid the problem of large welding thickness, large changes in welding position when the workpiece is thick and the arc is shaped, many welding layers, long duration, unstable welding process and welding position changes causing unstable welding quality factors that make the quality control of the welding process difficult.

[0036] (2) By designing the groove structure of the butt joint to be U-shaped and maintaining a certain amount of blunt edge, the quality of the assembly can be easily guaranteed. Secondly, this design structure facilitates the use of fully automatic magnetically controlled narrow gap tungsten inert gas arc welding to achieve full penetration of the bottom and bottom sealing on both sides, and is conducive to shrinkage deformation control.

[0037] (3) The main groove parameters and tolerances of the butt joint are controlled at blunt edge b = 4 ~ 8 mm, groove angle α = 6 ~ 12 °, and root fillet R = 4 ~ 6 mm. This structural design has a small groove width, less parent material loss, less filler wire and short filling time, which provides a good technical guarantee for high-quality and efficient full-process automated welding of thick-walled titanium flat plates or arc-shaped butt welds.

[0038] (4) Through pre-welding quality control technology, titanium welding is avoided from being easily contaminated by dirt and air, and weld welding is prone to welding quality problems. Pre-welding groove cleaning, welding system integrity, protection system protection effect and gas quality, and assembly quality ensure efficient and high-quality welding in the welding process.

[0039] (5) The welding method adopts a unique welding method that is suitable for thick-walled titanium materials. The intelligent welding of the weld is completed according to the set welding sequence and welding parameters. During the welding process, the welding robot is linked with the welding positioner to always keep the welding pool in the best position that can effectively ensure the quality of the weld, such as the horizontal position or the specified position. A high-power pulsed tungsten electrode argon arc welding DC power supply, a large-diameter tungsten electrode, and thick wire filling are used. The internal surface quality of the weld is good, the welding deposition efficiency is high, the deposition efficiency can reach 3.0kg / hour, the production efficiency can be increased by 40%, the material consumption is small, and the loss of parent material and welding material is reduced by 30%. For the first time, the fully automatic continuous high-quality and efficient intelligent welding of the root of the thick-walled titanium weld joint with large blunt edges (4-8mm) is achieved, with full penetration, efficient filling and beautiful cover. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The following drawings are intended only to illustrate and explain the present invention, and are not intended to limit the scope of the present invention.

[0041] Figure 1 Schematic diagram of the groove structure of the butt joint of workpieces to be welded in an embodiment of the present invention;

[0042] Figure 2 The groove structure and parameter dimensions of the butt joint of the workpieces to be welded in the embodiment of the present invention;

[0043] Figure 3 Schematic diagram of the welding layers of the weld in the embodiment of the present invention. DETAILED DESCRIPTION

[0044] The present invention will be further described below with reference to the accompanying drawings and examples. In the following detailed description, certain exemplary embodiments of the present invention are described by way of illustration only. It is understood that those skilled in the art will recognize that the described embodiments may be modified in various ways without departing from the spirit and scope of the present invention. Therefore, the drawings and description are illustrative in nature and are not intended to limit the scope of the claims.

[0045] The following takes the welding of 42mm thick TA2 arc butt weld as an example.

[0046] An efficient welding method for thick-walled titanium butt welds comprises the following steps:

[0047] S1. Perform quality inspection and analysis on the butt joints of the workpieces to be welded. The tensile strength of the butt joints must be at least 0.9 times the tensile strength of the corresponding base material.

[0048] S2, such as Figure 1 As shown, the groove structure of the designed butt joint is U-shaped. Precision machining is used to ensure that the groove parameters and tolerances are within the control range. The main groove parameters and tolerances of the butt joint are as follows:

[0049] Blunt edge b = 4 ~ 8mm, processing tolerance is controlled at 0 ~ 0.5mm;

[0050] The groove angle α is 6-12°, and the processing tolerance is controlled at 0-1.0°;

[0051] The root fillet R=4~6mm, and the processing tolerance is controlled at 00.5mm;

[0052] The machining tolerance of the distance H between the center line of the blunt edge and the single layer is controlled within 0 to 0.2 mm;

[0053] like Figure 2 As shown, in this embodiment, the main groove parameters are blunt edge b=4mm, groove angle α=10°, root fillet R=4mm, and the distance between the blunt edge center line and the single layer is 21mm.

[0054] S3. Quality control before welding:

[0055] S31. Cleaning before welding: Grind and scrub the surface of the base material within 25mm of the groove and the edge of each side of the workpiece to be welded: clean and remove the surface oxide scale, and use acetone or anhydrous alcohol to scrub and remove dust, oil stains and other contaminants within 40mm of the groove and the edge of the groove;

[0056] S32, group forming: press Figure 1 As shown in the figure, two workpieces to be welded are aligned. When aligning, ensure that the front groove surfaces of the blunt edges of the two workpieces to be welded are flush, control the misalignment of the back edges of the blunt edges to be ≤1.0mm, and the root gap p is between 0 and 1mm. Spot weld an arc starting plate and an arc extinguishing plate of 80mm long and 60mm wide, made of TA2, with the same thickness as the blunt edges, at each end of the workpieces to be welded. According to the length of the workpieces to be welded, spot weld a saddle-shaped TA2 fixture at a certain distance on one side of the bottom groove to be sealed to prevent the workpiece opening from affecting the welding during the base welding process, and fix the workpieces to be welded on the welding positioner. Protect the welding area of ​​the workpieces to prevent dust from entering. Debug the protection system effect and the shielding gas protection quality. After welding, the heat-affected zone of the weld reaches a silvery white color and is qualified. Debug the welding system to ensure that it is running properly.

[0057] S4. Welding

[0058] Adjust the welding robot so that the electrode end is aligned with the center of the groove, adjust the welding robot to identify the welding starting point, groove area and workpiece groove welding trajectory, adjust the arc starting point to the flat welding position or the specified position suitable for the crystallization of the welding pool; start welding, the welding robot strikes the arc on the arc starting plate, and the welding robot is linked with the welding positioner. During the welding process, the welding pool is always in the best position for crystallization and forming to ensure welding quality, so that efficient welding can be implemented in the best and easiest position to ensure quality; the specific welding sequence is as follows: (reference Figure 3 , numbers 1-14 represent the welding levels of the welds)

[0059] S41. Use pulsed tungsten inert gas welding autogenous welding process for front root welding, and control the root process parameters to be able to penetrate 55% to 70% of the blunt edge thickness;

[0060] S42, use thick wire (diameter 2-3mm) magnetron narrow gap tungsten inert gas arc welding according to the process parameters in Table 1 to perform fill welding in the narrow groove on the front side, filling to a two-layer weld thickness of 6-8mm;

[0061] S43, using pulsed tungsten inert gas arc welding process with large heat input to perform back-end penetration welding;

[0062] S44. Use thick wire magnetron narrow gap tungsten inert gas arc welding according to the process parameters in Table 1 to perform fill welding in the back groove. According to the deformation amount, alternate fill welding is performed on the front and back grooves until the distance from the parent material surface is 2 to 3 mm.

[0063] S45. Use pulsed tungsten inert gas arc welding to weld the cover layer and complete the butt weld of thick-walled titanium material.

[0064] The shielding gas for welding is 99.99% Ar, the welding electrode is a cerium tungsten electrode, and the diameter of the tungsten electrode is 4 to 6 mm.

[0065] Preheating is not required for welding. The welding system is powered by a DC digital pulse welding power supply with a rated current of 1000A. A welding robot grasps the magnetically controlled narrow-gap welding gun and is linked to a welding positioner. The power supply polarity is DC positive. Specific welding parameters are shown in Table 1.

[0066] Table 1 Welding process parameters

[0067]

[0068]

[0069] S5. Weld quality inspection and testing

[0070] The appearance inspection of the 42mm thick-walled titanium arc-shaped butt weld showed good surface formation without defects such as undercuts, pores, and cracks. The weld and heat-affected zone were silvery white.

[0071] According to NB / T47013-2015, 100% non-destructive testing and assessment such as radiography, ultrasonic testing and surface coloring are carried out. The specific test results are as follows:

[0072] A. Radiographic testing is conducted at the highest technical level B, and the qualified level of welded joints is all at level I;

[0073] B. Ultrasonic testing is carried out at the highest technical level B, and the qualified level of welding joints is up to level I;

[0074] C. The color test is carried out at the highest technical level C, and the qualified level of the welded joints is up to level I;

[0075] Various mechanical performance tests such as tensile, bending and impact are carried out as required, and various mechanical performance indicators also meet the standard requirements.

[0076] The above test results show that the present invention performs titanium thick-walled (≥20mm) arc or flat plate butt welding. Based on the analysis of weld quality, performance and shape requirements, the selected welding equipment is reasonably matched, the designed groove structure, parameter size and tolerance, pre-weld preparation quality control technology and the set welding method and parameters meet the quality and performance control requirements of titanium thick-walled arc or flat plate butt joints.

[0077] Compared with the existing process, the method of the present invention has high welding deposition efficiency, the deposition efficiency can reach 3.0kg / hour, the production efficiency can be increased by 40%, the material consumption is small, and the loss of parent material and welding material is reduced by 30%. For the first time, it realizes the full penetration of the root of the thick-walled titanium weld joint with large blunt edge (4-8mm), efficient filling and beautiful covering, and realizes fully automatic continuous high-quality and efficient intelligent welding.

[0078] The above description is only an illustrative embodiment of the present invention and is not intended to limit the scope of the present invention. Any equivalent changes and modifications made by those skilled in the art without departing from the concept and principle of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A method for welding thick-walled titanium butt welds, characterized in that: The steps include: S1. Perform quality inspection and analysis on the butt joints of the workpieces to be welded. The tensile strength of the butt joints must be at least 0.9 times the tensile strength of the corresponding base material. S2. Design the groove structure of the butt joint into a U-shape, and ensure that the groove parameters and tolerances are within the control range through precision machining; S3. Quality control before welding: S31. Cleaning before welding: Grind and scrub the surface of the base material on each side of the groove of the workpiece to be welded and the edge of the groove to remove surface oxide scale and dirt; S32, Pairing and Forming: Pair the two workpieces to be welded together, ensuring that the front groove surfaces of the blunt edges of the two workpieces are flush, with the back misalignment of the blunt edges controlled to be ≤1.0mm and the root gap between 0 and 1mm. Spot weld an arc starting plate and an arc extinguishing plate of the same thickness as the blunt edges on each end of the workpieces to be welded. Depending on the length of the workpieces to be welded, spot weld fixtures at intervals on one side of the bottom groove to prevent the workpiece opening from affecting the welding during the base welding process. The workpieces to be welded are then fixed on the welding positioner. Debug the protection system effect and the shielding gas quality. After welding, the heat-affected zone of the weld is silvery white and qualified, and debug the welding system to ensure that it is operating properly. S4. Welding Adjust the welding system to identify and memorize the arc starting point, arc ending point and motion trajectory of the workpiece to be welded; start welding at the selected welding position; the welding robot starts the arc on the arc starting plate, and the welding robot is linked with the welding positioner. During the welding process, the welding pool is always in the best position for crystallization and formation to ensure welding quality, and welding is carried out according to the following welding methods: S41, use pulsed tungsten inert gas welding process to perform front bottom welding; S42, using thick wire magnetron narrow gap tungsten inert gas arc welding to fill weld in the front narrow groove to a two-layer weld thickness of 6 to 8 mm; S43, using pulsed tungsten inert gas arc welding process to perform back-end penetration welding; S44. Use thick wire magnetron narrow gap tungsten inert gas arc welding to fill the back groove. According to the deformation amount, alternate filling welding is performed on the front and back grooves until the distance from the parent material surface is 2 to 3 mm. S45. Use pulsed tungsten inert gas arc welding to weld the cover layer weld to complete the butt weld of the thick-walled titanium material; the thickness of the thick-walled titanium material is ≥20 mm.

2. The method for welding thick-walled titanium butt welds according to claim 1, wherein: In step S2, the main groove parameters and tolerances of the butt joint are as follows: Blunt edge b = 4 ~ 8mm, processing tolerance is controlled at 0 ~ 0.5mm; The groove angle α is 6-12°, and the processing tolerance is controlled at 0-1.0°; The root fillet R is 4-6mm, and the processing tolerance is controlled within 0.5mm; The machining tolerance of the distance H between the center line of the blunt edge and the single layer is controlled within 0 to 0.2 mm.

3. The method for welding thick-walled titanium butt welds according to claim 1, wherein: In step S4 , the shielding gas for welding is 99.99% Ar.

4. The method for welding thick-walled titanium butt welds according to claim 1, wherein: In step S4, the welding electrode is a cerium tungsten electrode, and the diameter of the tungsten electrode is 4 to 6 mm.

5. The method for welding thick-walled titanium butt welds according to claim 1, wherein: In step S4, the diameter of the filling thick wire is 2 to 3 mm.

6. The method for welding thick-walled titanium butt welds according to claim 1, wherein: In step S4, the power supply of the welding system is a DC digital pulse welding power supply with a rated current of more than 1000A.

7. The method for welding thick-walled titanium butt welds according to claim 1, wherein: In step S41, the bottoming process parameters are controlled to be between 55% and 70% of the thickness of the blunt edge.

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