A pre-filled powder plasma arc welding method for titanium / steel

Abstract

This invention discloses a plasma arc welding method for titanium / steel with pre-filled powder, belonging to the field of arc welding. The invention involves a bevel on the steel plate side of the weld joint, where a multi-element alloy powder is pre-filled. This multi-element alloy powder is a copper-titanium-iron-nickel-niobium alloy powder, with the following mass percentages: Cu: 35-45 wt%, Ti: 15-20 wt%, Fe: 15-20 wt%, Ni: 15-20 wt%, Nb: 3-5 wt%, to optimize the metallurgical properties of the titanium-steel interface. The upper part of the bevel is tightly fitted with the titanium, leaving a gap at the bottom for the multi-element alloy powder. During welding, the pre-filled multi-element alloy powder forms an alloy transition layer with the titanium-steel interface. After the welding wire melts, it fills the weld joint, forming the weld area together with the pre-filled powder. This method maintains the stability of the multi-element alloy powder and prevents it from being dispersed by the gas flow. This method overcomes the shortcomings of filler materials in traditional welding, avoids the high cost of laser coaxial powder feeding, and significantly reduces powder loss and particle size limitations in arc powder feeding.

Description

Technical Field

[0001] This invention belongs to the field of arc welding, specifically relating to a plasma arc welding method for titanium steel with pre-filled powder. Background Technology

[0002] Titanium-steel dissimilar metal welding has encountered many challenges in its widespread application, particularly in ensuring high strength and toughness of the weld while meeting the physical property differences between titanium and steel. Traditional filler wires lack suitable alloy materials for brazing, making it difficult to achieve excellent metallurgical bonding at the titanium-steel joint. Although multi-alloy powders can be used as brazing filler metals, current laser coaxial powder feeding technology is costly and complex, making it unsuitable for large-scale applications. Furthermore, the powder feeding process in arc welding suffers from poor stability, high powder loss rate, and strict requirements for powder size and shape, making it difficult to meet application needs. Therefore, this invention provides a method for pre-filling titanium-steel butt welds with powder. By designing a special bevel structure, the powder is prevented from being blown away by the shielding gas during welding, ensuring welding quality and joint performance. Summary of the Invention

[0003] This invention proposes a joint design method for arc welding of titanium and steel dissimilar metals. The core of this method involves pre-filling the weld bevel with multi-element alloy powder to optimize the metallurgical properties of the titanium-steel joint. Specifically, the bevel is designed as a semi-inverted U-shape, with a tight fit and no gaps at the top, while a gap is left at the bottom specifically for filling the powder. During welding, this structure effectively maintains the stability of the powder and prevents it from being blown away by the gas flow. This method overcomes the shortcomings of filler materials in traditional welding, avoids the high cost of laser coaxial powder feeding, and significantly reduces powder loss and particle size limitations in arc powder feeding.

[0004] This invention provides a plasma arc welding method for titanium / steel with pre-filled powder. A welding bevel is processed at the titanium-steel interface of the titanium-steel dissimilar metal workpiece, and a multi-element alloy powder is pre-filled in the welding bevel. During the welding process, the pre-filled multi-element alloy powder forms an alloy transition layer with the titanium-steel interface. After the welding wire melts, it fills the weld and together with the pre-filled powder, it constitutes the weld area. The welding bevel maintains the stability of the multi-element alloy powder and prevents it from being blown away by the airflow.

[0005] Furthermore, the welding bevel is a semi-U-shaped groove arc; the steel plate thickness a, the semi-U-shaped groove arc width b: 0.08a≤b≤0.12a, the semi-U-shaped groove arc top thickness d: 0.02a≤d≤0.04a, the semi-U-shaped groove arc height h1: 0.04a≤h1≤0.1a, the semi-U-shaped groove arc radius r: 0.04a≤r≤0.06a, and the semi-U-shaped groove straight wall height h2: 0.86a≤h2≤0.94a.

[0006] Furthermore, the multi-element powder is a copper-titanium-iron-nickel-niobium alloy powder; by mass percentage: Cu: 35-45 wt%, Ti: 15-20 wt%, Fe: 15-20 wt%, Ni: 15-20 wt%, Nb: 3-5 wt%.

[0007] Furthermore, Cu powder, Ti powder, Fe powder, Ni powder, and Nb powder are mixed and ground using a ball mill under argon protection at a grinding speed of 150–250 rpm for 7–9 hours. During the grinding process, the milling is paused for 10 minutes every hour. After grinding and mixing, the powder is dried at 120–180°C for 1–3 hours. The Cu powder has a size of 500–800 nm, the Ti powder has a size of 100–200 nm, the Fe powder has a size of 100–200 nm, the Ni powder has a size of 200–500 nm, and the Nb powder has a size of 50–200 nm.

[0008] Furthermore, the multi-element powder occupies 80% to 90% of the groove area.

[0009] Furthermore, the distance between the tungsten electrode of the plasma welding torch and the steel-titanium interface is 1.5–2 mm.

[0010] Furthermore, the welding current is 150-180A, the voltage is 22-25V, the wire feed speed is 1.5-2.5m / min, and the shielding gas flow rate is 10-15L / min.

[0011] Furthermore, the welding process employs coaxial or off-axis wire feeding, and the welding wire is preferably Cu-(20~30)Zn welding wire, utilizing the good fluidity of Zn to achieve uniform melting and mixing of powder elements.

[0012] Furthermore, the titanium steel dissimilar metal workpiece is placed on an aluminum alloy plate.

[0013] Furthermore, during the welding process, a plasma arc welding gun is used to weld on the surface of the steel plate on one side of the weld. The arc generated by the tungsten electrode rapidly heats the titanium-steel weld area, and the multi-element powder in the semi-U-shaped groove melts to form a molten pool, while simultaneously undergoing a metallurgical reaction with the titanium plate and the steel plate.

[0014] The beneficial effects of this invention are as follows:

[0015] 1. The method of this invention improves weld quality; by pre-filling multi-element alloy powder, a more uniform metallurgical bond is obtained in the welding of dissimilar titanium and steel, which effectively improves the strength and toughness of the joint.

[0016] 2. This invention reduces welding costs; compared with laser coaxial powder feeding technology, this method does not require expensive equipment, reduces powder material waste, and is more economical for large-scale industrial applications.

[0017] 3. This invention improves powder utilization, the bevel structure design can effectively reduce powder loss, and allows the use of powders with different particle sizes and shapes, enhancing the flexibility of the welding process.

[0018] 4. The method of this invention designs the dimensions of the arc-shaped groove based on the plasma arc temperature. The center of the plasma arc has the highest temperature, corresponding to the thick-walled part of the arc-shaped groove, while the edge of the plasma arc has a lower temperature, corresponding to the thin-walled part of the arc-shaped groove. Compared with a straight wall, this ensures that heat is uniformly melted on the powder, avoiding excessive local heat that could cause the molten pool to collapse and the powder to be blown away. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of plasma arc welding of titanium steel dissimilar metals with pre-filled powder.

[0020] Figure 2 Schematic diagram of the joint shape with pre-filled powder;

[0021] Figure 3 Schematic diagram of pre-filled powder bevel dimensions.

[0022] Among them, 1-tungsten electrode, 2-plasma welding torch, 3-wire feeder, 4-welding wire, 5-electric arc, 6-steel plate, 7-titanium plate, 8-plasma welding machine, 9-aluminum alloy water-cooled plate, 10-multi-element alloy powder, 11-titanium steel butt joint interface, 12-groove width, 13-groove top wall thickness, 14-arc groove height, 15-straight wall groove height, 16-arc groove radius. Detailed Implementation

[0023] The present invention will now be further described with reference to the accompanying drawings.

[0024] This invention provides a method for designing a pre-filled powder titanium-steel plasma arc welding joint, comprising the following steps:

[0025] Step 1: Fix the titanium-steel dissimilar metal workpiece onto the welding fixture and perform surface cleaning to remove oxides, oil, and other impurities, ensuring the cleanliness and uniformity of the weld joint. According to the joint design requirements, prepare an inverted U-shaped bevel on the steel side, ensuring a tight, gapless fit at the top and a dedicated gap at the bottom for filling with multi-element alloy powder. The bevel shape and size should match the workpiece thickness to ensure the stability of the weld joint.

[0026] Step 2: Select Cu-(20-30)Zn welding wire and Cu powder, Ti powder, Fe powder, Ni powder, and Nb powder. The Cu powder size is 500nm–800nm, the Ti powder is 100nm–200nm, the Fe powder is 100–200nm, the Ni powder is 200–500nm, and the Nb powder is 50–200nm. The weight ratio of the powders is Cu: 35–45wt%, Ti: 15–20wt%, Fe: 15–20wt%, Ni: 15–20wt%, and Nb: 3–5wt%. Mix the powders uniformly using a ball mill. Improve the powder flowability and uniformity through powder spheroidization or surface modification techniques. The ball mill main disc rotates at 200rpm for 8 hours under argon protection. The mixture is circulated every hour with a 10-minute pause. After 8 hours of ball milling, the composite powder system exhibits good flowability, and the composite powder particles maintain a spherical shape. The mixed powder was dried at 120℃~180℃ for 2 hours.

[0027] Step 3: Fill the bottom of the bevel with screened multi-element alloy powder (such as alloy powder containing elements like titanium, nickel, and copper). The filling amount must ensure uniform powder distribution and close contact with the bevel wall to achieve a sufficient metallurgical reaction. Simultaneously, select a suitable Cu-(20-30)Zn welding wire, utilizing the Zn in the wire to improve powder flowability, and place it at the prepared weld position. The welding wire's compatibility with the base metal and filler powder composition effectively improves the metallurgical bonding effect at the titanium-steel interface.

[0028] Step 4: Start the arc welding equipment and set the appropriate welding current, voltage, and welding speed. Ignite the arc and begin welding, turning on the shielding gas (99.9% argon) to prevent oxidation. During welding, the filler wire should be fed evenly into the molten pool and kept at a proper angle to the welding torch to reduce spatter.

[0029] Under the heat of the electric arc, the multi-element alloy powder pre-filled at the bottom of the bevel forms an alloy transition layer with the titanium-steel interface, significantly improving the metallurgical bond between titanium and steel and reducing the tendency to crack. After the welding wire melts, it fills the weld, forming a high-strength, corrosion-resistant weld area together with the pre-filled powder.

[0030] Step 5: After welding, allow the joint to cool naturally without additional heat treatment. After cooling, perform non-destructive testing (such as X-ray inspection) and mechanical property testing on the welded joint to ensure that the weld quality and bond strength meet the expected requirements.

[0031] Example

[0032] Combined with appendix Figure 1 , 2 The following is a specific implementation method based on a 10mm thick titanium steel butt joint:

[0033] First, the tungsten electrode 1 and the plasma welding torch 2 are assembled onto the welding device. The welding wire 4 is continuously fed into the welding area via the wire feeder 3, forming a stable arc 5. A 10mm thick steel plate 6 and a 10mm thick titanium plate 7 are butt-jointed and mounted on the plasma welding machine 8. To prevent overheating, an aluminum alloy water-cooling plate 9 is placed below the welding area for cooling. The choice of aluminum alloy for the water-cooling plate also serves the purpose of ensuring a stable bond between the aluminum alloy and the titanium and steel, facilitating cleaning. Multi-element alloy powder 10 is pre-filled into the bevel on the steel plate side, forming a transition zone at the titanium-steel butt joint interface 11, ensuring good metallurgical bonding between the titanium and steel during welding. The multi-element alloy powder is a copper-titanium-iron-nickel-niobium alloy powder, with the following mass percentages: Cu: 35%, Ti: 20wt%, Fe: 20wt%, Ni: 20wt%, Nb: 5wt%. The welding wire 10 is a Cu-30Zn welding wire, utilizing the good fluidity of Zn to achieve uniform melting and mixing of the powder elements. The Cu powder had a size of 500 nm, Ti powder 100 nm, Fe powder 100 nm, Ni powder 200 nm, and Nb powder 200 nm. These powders were uniformly mixed using a ball mill. Powder spheroidization or surface modification techniques were employed to improve powder flowability and uniformity. The ball mill main disc rotated at 200 rpm for 8 hours under argon protection. The mixture was circulated every hour with a 10-minute pause. After 8 hours of ball milling, the composite powder system exhibited good flowability, and the particles maintained a spherical shape. The mixed powder was then dried at 120℃–180℃ for 2 hours.

[0034] Combined with appendix Figure 2 The inward reduction of the tungsten electrode 1 is set to 2–2.5 mm to ensure that the arc center is located at the edge of the titanium-steel butt interface 11. The horizontal distance between the tungsten electrode and the titanium-steel interface is set to 1.5–2 mm to avoid excessive melting of the titanium alloy. The distance between the plasma welding torch 2 and the sample surface is adjusted to 5–6 mm to ensure uniform heat input and stable molten pool formation.

[0035] Combined with appendix Figure 3 The pre-filled powder groove is designed on one side of the steel plate 6. The specific dimensions of the groove are as follows: the groove width 12 is 0.8 to 1.2 mm, the top wall thickness of the groove 13 is 0.2 to 0.4 mm, the height of the arc-shaped groove 14 is 0.4 to 1 mm, the radius of the arc-shaped groove 16 is 4 to 6 mm to increase the stability of the powder, and the height of the straight wall groove 15 is 9 mm to ensure the uniformity of the powder filling amount and the shape of the molten pool.

[0036] The arc-shaped grooves serve to protect the powder from being blown away by the electric arc. Their design is based on the arc temperature; the center of the plasma arc has the highest temperature, corresponding to the thicker wall of the arc-shaped groove, while the edge of the plasma arc has a lower temperature, corresponding to the thinner wall of the arc-shaped groove. Compared to straight walls, this ensures that heat is evenly distributed on the powder, preventing localized overheating that could cause the molten pool to collapse and the powder to be blown away.

[0037] After preliminary preparations are completed, the plasma arc welding machine is operated. The plasma welding machine 8 is turned on, and the flow of the shielding gas argon is initiated at a flow rate of 10–15 L / min. The tungsten inert gas (TIG) arc is activated, bringing it into contact with the butt joint interface 11. The current is adjusted to 150–180 A and the voltage to 22–25 V. The arc generated by the tungsten electrode rapidly heats the titanium-steel interface area, melting the pre-filled powder within the bevel to form a molten pool, which simultaneously undergoes a metallurgical reaction with the titanium and steel plates. The wire feeder delivers the welding wire into the molten pool at a speed synchronized with the arc (1.5–2.5 m / min). The welding wire, together with the powder, forms an alloyed weld in the molten pool. Throughout the welding process, most of the heat is used to melt the powder and steel plate, with only a small amount of titanium alloy melting. Therefore, the molten pool does not form brittle Fe-Ti intermetallic compounds, effectively improving the joint strength.

[0038] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for plasma arc welding of titanium / steel with pre-filled powder, characterized in that, A welding bevel is processed at the titanium-steel interface of a titanium-steel dissimilar metal workpiece, wherein the titanium-steel dissimilar metal workpiece is a titanium plate and a steel plate. Multi-element alloy powder is pre-filled in the welding bevel. During the welding process, the pre-filled multi-element alloy powder forms an alloy transition layer with the titanium-steel interface. After the welding wire melts, it fills the weld and together with the pre-filled powder, it forms the weld area. The welding bevel maintains the stability of the multi-element alloy powder and prevents it from being blown away by the airflow. The welding bevel is a semi-inverted U-shaped groove arc; the steel plate thickness a, the semi-inverted U-shaped groove arc width b: 0.08a≤b≤0.12a, the semi-inverted U-shaped groove arc top thickness d: 0.02a≤d≤0.04a, the semi-inverted U-shaped groove arc height h1: 0.04a≤h1≤0.1a, the semi-inverted U-shaped groove arc radius r: 0.04a≤r≤0.06a, and the semi-inverted U-shaped groove straight wall height h2: 0.86a≤h2≤0.94a; The multi-element alloy powder is a copper-titanium-iron-nickel-niobium alloy powder, with the following mass percentages: Cu: 35~45wt%, Ti: 15~20wt%, Fe: 15~20wt%, Ni: 15~20wt%, Nb: 3~5wt%.

2. The method for pre-filled powder plasma arc welding of titanium / steel according to claim 1, characterized in that, Cu powder, Ti powder, Fe powder, Ni powder, and Nb powder were mixed and ground in a ball mill under argon protection at a speed of 150-250 rpm for 7-9 hours. During the grinding process, the milling was paused for 10 minutes every hour. After grinding and mixing, the powder was dried at 120-180℃ for 1-3 hours. The Cu powder had a size of 500-800 nm, the Ti powder had a size of 100-200 nm, the Fe powder had a size of 100-200 nm, the Ni powder had a size of 200-500 nm, and the Nb powder had a size of 50-200 nm.

3. The method for pre-filled powder plasma arc welding of titanium / steel according to claim 1, characterized in that, The multi-element alloy powder occupies 80% to 90% of the groove area.

4. The method for pre-filled powder plasma arc welding of titanium / steel according to claim 1, characterized in that, The distance between the tungsten electrode of the plasma arc welding torch and the steel-titanium interface is 1.5~2mm.

5. The method for pre-filled powder plasma arc welding of titanium / steel according to claim 1, characterized in that, The welding process employs coaxial or off-axis wire feeding, and the welding wire is Cu-(20~30)Zn welding wire, utilizing the good fluidity of Zn to achieve uniform melting and mixing of multi-element alloy powder elements.

6. The method for pre-filled powder plasma arc welding of titanium / steel according to claim 1, characterized in that, The welding current is 150~180 A, the voltage is 22~25 V, the wire feed speed is 1.5~2.5 m / min, and the shielding gas flow rate is 10~15 L / min.

7. The method for pre-filled powder plasma arc welding of titanium / steel according to claim 1, characterized in that, The titanium steel dissimilar metal workpiece is placed on an aluminum alloy water-cooled plate.

8. The method for pre-filled powder plasma arc welding of titanium / steel according to claim 1, characterized in that, During the welding process, a plasma arc welding gun is used to weld on the surface of the steel plate on one side of the weld. The arc generated by the tungsten electrode rapidly heats the titanium-steel weld area, and the multi-element alloy powder in the semi-inverted U-shaped groove melts to form a molten pool, which at the same time undergoes a metallurgical reaction with the titanium plate and the steel plate.

Images