Powder-prefilled titanium / steel plasma arc welding method

Abstract

The invention discloses a powder-prefilled titanium / steel plasma arc welding method, and belongs to the field of electric arc welding. A groove is formed in the side of a steel plate at a welding seam, the groove is pre-filled with multi-element alloy powder, and the multi-element alloy powder is copper-titanium-iron-nickel-niobium alloy powder and comprises, by mass, 35-45% of Cu, 15-20% of Ti, 15-20% of Fe, 15-20% of Ni and 3-5% of Nb, so that the metallurgical performance of the titanium-steel joint is optimized. Steel / titanium on the upper portion of the groove is tightly attached without gaps, and gaps filled with multi-component alloy powder are reserved in the bottom of the groove; in the welding process, an alloy transition layer is formed between the pre-filled multi-component alloy powder and a titanium steel interface; according to the method, the stability of the multi-element alloy powder is kept, and the multi-element alloy powder is prevented from being blown away by airflow; according to the method, the defect of filling materials in traditional welding is overcome, the problem of high cost of laser coaxial powder feeding is solved, and powder loss and particle size limitation in electric arc powder feeding are remarkably reduced.

Description

Technical Field

[0001] The invention belongs to the field of arc welding, and in particular relates to a titanium steel plasma arc welding method with prefilled powder. Background Art

[0002] Titanium-steel dissimilar metal welding has encountered many challenges in its wide application, especially in ensuring the high strength and high toughness of the weld while meeting the physical property differences between titanium and steel. Traditional filler wires are difficult to obtain excellent metallurgical bonding at the titanium-steel joint due to the lack of alloy materials suitable for brazing. Although multi-element alloy powders can be used as brazing materials, the current laser coaxial powder feeding technology is costly and complex in process, and is not suitable for large-scale application. The powder feeding process in arc welding is difficult to meet application requirements due to its poor stability, high powder loss rate, and strict requirements on powder size and shape. To this end, the present invention provides a method for pre-filling powder in a titanium-steel butt weld. By designing a special groove structure, the powder is not blown away by the shielding gas during the welding process, thereby ensuring the welding effect and joint performance. Summary of the invention

[0003] The present invention proposes a joint design method for arc welding of dissimilar metals of titanium and steel, the core of which is to pre-fill multi-element alloy powder in the welding groove to optimize the metallurgical properties of the titanium-steel joint. Specifically, the groove is designed to be a semi-inverted U-shape, with a tight fit and no gap at the top, and a gap at the bottom specifically filled with powder. During the welding process, this structure effectively maintains the stability of the powder and prevents it from being blown away by the airflow. This method makes up for the lack of filling materials in traditional welding, avoids the high cost problem of laser coaxial powder feeding, and significantly reduces the powder loss and particle size limitation in arc powder feeding.

[0004] The invention provides a titanium / steel plasma arc welding method with pre-filled powder, in which a welding groove is processed at the interface between titanium and steel of a titanium-steel dissimilar metal workpiece, and multi-element alloy powder is pre-filled in the welding groove; during the welding process, the pre-filled multi-element alloy powder forms an alloy transition layer with the titanium-steel interface; the welding wire fills the weld after being melted, and together with the pre-filled powder, forms a weld area, and the welding groove maintains the stability of the multi-element alloy powder to prevent it from being blown away by airflow.

[0005] Furthermore, the welding groove 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, 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; in terms of mass percentage: Cu: 35-45wt%, Ti: 15-20wt%, Fe: 15-20wt%, Ni: 15-20wt%, Nb: 3-5wt%.

[0007] Furthermore, Cu powder, Ti powder, Fe powder, Ni powder and Nb powder are mixed and ground in a ball mill under argon protection, with a grinding speed of 150-250 rpm and a grinding time of 7-9 h; during the grinding process, the grinding is paused for 10 min every 1 h, and the ground and mixed powders are dried at 120-180° C. for 1-3 h; the Cu powder size is 500-800 nm, the Ti powder size is 100-200 nm, the Fe powder size is 100-200 nm, the Ni powder size is 200-500 nm, and the Nb powder size is 50-200 nm.

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

[0009] Furthermore, the distance between the tungsten electrode of the plasma welding gun 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 feeding speed is 1.5-2.5m / min, and the shielding gas flow rate is 10-15L / min.

[0011] Furthermore, the welding process adopts coaxial wire feeding or side-axis wire feeding, and the welding wire is preferably Cu-(20-30)Zn welding wire, and the good fluidity of Zn is used 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 quickly heats the titanium steel weld area, and the multi-component powder in the semi-U-shaped groove melts to form a molten pool, while metallurgical reactions occur with the titanium plate and the steel plate.

[0014] The beneficial effects of the present invention are:

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

[0016] 2. The present 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. The present invention improves the utilization rate of powder. The groove structure design can effectively reduce the powder loss rate and allows the use of powders of different particle sizes and shapes, thereby enhancing the flexibility of the welding process.

[0018] 4. The method of the present invention designs the size of the arc groove according to the temperature of the plasma arc. The temperature at the center of the plasma arc is the highest, corresponding to the thick wall part of the arc groove, while the temperature at the edge of the plasma arc is lower, corresponding to the thin wall part of the arc groove. Compared with the straight wall, it can ensure that the heat is melted evenly on the powder, avoiding the collapse of the molten pool due to excessive local heat and the blowing away of the powder. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of titanium steel dissimilar metal plasma arc welding 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 groove dimensions.

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

[0023] The present invention is further described below in conjunction with the accompanying drawings.

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

[0025] Step 1: Fix the titanium steel dissimilar metal workpiece on the welding fixture and clean the surface to remove impurities such as oxides and oil stains on the surface to ensure the cleanliness and uniformity of the welded joint. According to the joint design requirements, prepare an inverted U-shaped groove on one side of the steel material so that the upper part fits tightly without gaps, and a special gap is left at the bottom for filling multi-element alloy powder. The shape and size of the groove should match the thickness of the workpiece to ensure the stability of the welded joint.

[0026] Step 2: Select Cu-(20-30)Zn welding wire and Cu powder, Ti powder, Fe powder, Ni powder and Nb powder, wherein the size of Cu powder is between 500nm and 800nm, Ti powder is between 100nm and 200nm, Fe powder is between 100nm and 200nm, Ni powder is between 200nm and 500nm, and Nb powder is between 50nm and 200nm. The weight ratio of the powder is Cu: 35-45wt%, Ti: 15-20wt%, Fe: 15-20wt%, Ni: 15-20wt%, Nb: 3-5wt%. The above powders are evenly mixed with a ball mill, and the powder fluidity and uniformity are improved by powder spheroidization or surface modification technology. The main disk speed of the ball mill is 200rpm, the grinding time is 8h, and the grinding process is carried out under argon protection. Cycle once every hour and pause for 10 minutes. After ball milling for 8h, the composite powder system shows good fluidity, and the particles of the composite powder remain spherical. The mixed powder is dried at 120°C to 180°C for 2 hours.

[0027] Step 3: Fill the bottom of the groove with screened multi-element alloy powder (such as alloy powder containing titanium, nickel, copper and other elements). The filling amount needs to ensure that the powder is evenly distributed and in close contact with the groove wall to achieve sufficient metallurgical reaction. At the same time, select suitable Cu-(20-30)Zn welding wire, use the Zn in the welding wire to improve the powder fluidity, and place it in the preparation position of the weld. The welding wire is compatible with the components of the base material and the filling powder, which can effectively improve the metallurgical bonding effect of the titanium steel interface.

[0028] Step 4: Start the arc welding equipment and set the appropriate welding current, voltage and welding speed. Start the arc and start welding, and turn on the shielding gas (99.9% argon) to prevent oxidation. When welding, the filler wire should be evenly fed into the molten pool and maintained at a reasonable angle to the welding gun to reduce spatter.

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

[0030] Step 5: After welding is completed, the joint is cooled naturally without additional heat treatment. After cooling, the welded joint is subjected to non-destructive testing (such as X-ray flaw detection) and mechanical property testing to ensure that the quality and bonding strength of the weld meet the expected requirements.

[0031] Example

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

[0033] First, tungsten electrode 1 and plasma welding gun 2 are assembled on the welding device, and welding wire 4 is continuously fed into the welding area through wire feeder 3 to form a stable arc 5. 10mm thick steel plate 6 and 10mm thick titanium plate 7 are butt-jointed and installed on plasma welding machine 8. To prevent overheating, aluminum alloy water cooling plate 9 is placed under the welding area for cooling. In addition, another function of choosing aluminum alloy for water cooling plate is that aluminum alloy will not form a stable connection with titanium and steel, which is easy to clean. Multi-element alloy powder 10 is pre-filled in the groove on the side of the steel plate, and titanium-steel butt interface 11 forms a transition zone to ensure good metallurgical bonding between titanium and steel during welding. Multi-element alloy powder selects copper-titanium-iron-nickel-niobium alloy powder, which is calculated by mass percentage: Cu: 35%, Ti: 20wt%, Fe: 20wt%, Ni: 20wt%, Nb: 5wt%; welding wire 10 selects Cu-30Zn welding wire, and the good fluidity of Zn is used to achieve uniform melting and mixing of powder elements. The size of Cu powder is 500nm, Ti powder is 100nm, Fe powder is between 100nm, Ni powder is 200nm, and Nb powder is 200nm. The above powders are evenly mixed in a ball mill, and the powder fluidity and uniformity are improved by powder spheroidization or surface modification technology. The main disk speed of the ball mill is 200rpm, the grinding time is 8h, and the grinding process is carried out under argon protection. Cycle once every hour and pause for 10 minutes. After 8h of ball milling, the composite powder system shows good fluidity, and the particles of the composite powder remain spherical. The mixed powder is dried at 120℃~180℃ for 2 hours.

[0034] Combined with Figure 2 The retraction 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 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, and the distance between the plasma welding gun 2 and the sample surface is adjusted to 5-6 mm to ensure uniform heat input and stable molten pool formation.

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

[0036] The arc groove protects the powder from being blown away by the arc. Its design rules are determined according to the arc temperature. The temperature at the center of the plasma arc is the highest, corresponding to the thick wall part of the arc groove, while the temperature at the edge of the plasma arc is lower, corresponding to the thin wall part of the arc groove. Compared with the straight wall, it can ensure that the heat is melted evenly on the powder, avoiding the collapse of the molten pool caused by excessive local heat and the blowing away of the powder.

[0037] After the preliminary preparations are completed, the plasma arc welding machine is operated. Turn on the plasma welding machine 8 and start the flow of the protective gas argon with a gas flow rate of 10 to 15 L / min. Start the tungsten arc so that it contacts the butt interface 11, and adjust the current to 150 to 180 A and the voltage to 22 to 25 V. The arc generated by the tungsten electrode quickly heats the titanium-steel interface area, so that the pre-filled powder in the groove melts to form a molten pool, and at the same time, metallurgical reactions occur with the titanium plate and the steel plate. The wire feeder feeds the welding wire into the molten pool at a speed synchronized with the arc (1.5 to 2.5 m / min), and the welding wire forms an alloyed weld with the powder in the molten pool. Most of the heat in the entire welding process is used to melt the powder and the steel plate, and only a small amount of the titanium alloy is melted, so the molten pool will not form Fe-Ti brittle intermetallic compounds, and the joint strength is effectively improved.

[0038] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A titanium / steel plasma arc welding method with pre-filled powder, characterized in that: A welding groove is processed at the junction of titanium and steel in a titanium-steel dissimilar metal workpiece, and multi-element alloy powder is pre-filled in the welding groove; during the welding process, the pre-filled multi-element alloy powder forms an alloy transition layer with the titanium-steel interface; the welding wire fills the weld after melting, and together with the pre-filled powder, it constitutes the weld area, and the welding groove maintains the stability of the multi-element alloy powder to prevent it from being blown away by the airflow.

2. The titanium / steel plasma arc welding method with prefilled powder according to claim 1, characterized in that: The welding groove 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, the semi-U-shaped groove straight wall height h2: 0.86a≤h2≤0.94a.

3. The titanium / steel plasma arc welding method with prefilled powder according to claim 1, characterized in that: The multi-component powder is a copper-titanium-iron-nickel-niobium alloy powder, which includes, by mass percentage: Cu: 35-45wt%, Ti: 15-20wt%, Fe: 15-20wt%, Ni: 15-20wt%, and Nb: 3-5wt%.

4. The titanium / steel plasma arc welding method with prefilled powder according to claim 3, characterized in that: Cu powder, Ti powder, Fe powder, Ni powder and Nb powder are mixed and ground in a ball mill under argon protection, with a grinding speed of 150-250 rpm and a grinding time of 7-9 hours; during the grinding process, a 10-minute pause is performed every 1 hour, and the ground and mixed powders are 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.

5. The titanium / steel plasma arc welding method with prefilled powder according to claim 1, characterized in that: The multi-component powder occupies 80% to 90% of the area of ​​the groove.

6. The titanium / steel plasma arc welding method with prefilled powder according to claim 1, characterized in that: The distance between the tungsten pole of the plasma welding gun and the steel-titanium interface is 1.5-2 mm.

7. The titanium / steel plasma arc welding method with prefilled powder according to claim 1, characterized in that: The welding process adopts coaxial wire feeding or side-axis wire feeding, the welding wire is Cu-(20-30)Zn welding wire, and the good fluidity of Zn is used to achieve uniform melting and mixing of powder elements.

8. The titanium / steel plasma arc welding method with prefilled powder according to claim 1, characterized in that: The welding current is 150-180A, the voltage is 22-25V, the wire feeding speed is 1.5-2.5m / min, and the shielding gas flow rate is 10-15L / min.

9. The titanium / steel plasma arc welding method with prefilled powder according to claim 1, characterized in that: The titanium steel dissimilar metal workpiece is placed on an aluminum alloy plate.

10. The titanium / steel plasma arc welding method with prefilled powder 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 quickly heats the titanium steel weld area, and the multi-component powder in the semi-U-shaped groove melts to form a molten pool, while metallurgical reactions occur with the titanium plate and the steel plate.

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