Non-gas tungsten arc welding method for grain refinement of titanium alloy by double wire synchronous feeding

Abstract

The application discloses a non-melted electrode arc additive manufacturing method for titanium alloy grain refinement through double-wire synchronous feeding, and the method is as follows: 1, the surface of a titanium alloy substrate is cleaned thoroughly, and the titanium alloy substrate is clamped and fixed at a welding area, and the position of a tungsten electrode tip is adjusted to an additive starting position; 2, the tip of a welding wire is adjusted to be in contact with the titanium alloy substrate directly below the tungsten electrode; 3, welding protection gas is fed in advance, and after the arc is stable, the double-wire synchronous feeding method is adopted to perform layer-by-layer additive manufacturing on the titanium alloy substrate; 4, the titanium alloy component after the additive manufacturing is completed is cooled, and then is taken off from the clamp, and the arc additive manufacturing is completed. Through the double-wire synchronous feeding, the welding process stability under a relatively large wire feeding speed can be effectively controlled, the unit wire line energy is reduced, the molten pool flow is promoted, and then the grain size refinement and the uniform distribution of the titanium alloy additive manufacturing component are realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of titanium alloy electric arc additive manufacturing, and relates to a titanium alloy additive manufacturing method, in particular to a non-gas tungsten arc welding (GTAW) additive manufacturing method for titanium alloy grain refinement through double-wire synchronous feeding. BACKGROUND

[0002] Titanium alloy has great application potential in the field of aerospace due to its high specific strength, corrosion resistance, high temperature resistance and good creep resistance, such as the structures of aero-engine casing, turbine blade and compressor blade, which all use titanium alloy to reduce weight and improve mechanical properties.

[0003] Additive manufacturing technology is a technology for producing three-dimensional structures by layer-by-layer stacking of materials. Compared with traditional casting and forging technologies, additive manufacturing technology does not require complex molds, improves production efficiency and flexibility, and reduces production cost, thereby having great economic benefits.

[0004] In the additive manufacturing process of titanium alloy, coarse columnar grains grow continuously along the additive direction, thereby causing the mechanical properties of the additive manufacturing component to be non-uniform, i.e., the strength in the horizontal direction is better than that in the vertical direction. Therefore, how to control the grain size and the uniformity of the mechanical properties of the additive manufacturing titanium alloy component is an important problem in the field of additive manufacturing technology. SUMMARY

[0005] In order to solve the technical problems of coarse grains and non-uniform mechanical properties of the additive manufacturing titanium alloy component, the application provides a non-gas tungsten arc welding (GTAW) additive manufacturing method for titanium alloy grain refinement through double-wire synchronous feeding, which realizes the control of the grain size and the improvement of the mechanical properties of the additive manufacturing titanium alloy component.

[0006] The purpose of the application is achieved by the following technical solutions:

[0007] A non-gas tungsten arc welding (GTAW) additive manufacturing method for titanium alloy grain refinement through double-wire synchronous feeding, as shown in Figure 2 , comprises the following steps:

[0008] Step 1: The surface of the titanium alloy substrate is cleaned thoroughly, the titanium alloy substrate is placed on a welding displacement machine and clamped and fixed in the welding area, and the position of the tungsten electrode tip is adjusted to the starting position of the additive manufacturing, wherein the thickness of the titanium alloy substrate is 5-100 mm, and the distance between the tungsten electrode tip and the surface of the substrate is 2-10 mm (preferably 3-5 mm);

[0009] Step 2: As shown in Figure 3 , the double-wire synchronous feeding clamp is adjusted so that the included angle between the two welding wires is 30-60°, the included angle between the welding wire and the titanium alloy substrate is 10-30°, and the tip of the welding wire is in contact with the titanium alloy substrate directly below the tungsten electrode;

[0010] Step three, 1-10s (preferably 5-10s) before the welding protective cover is introduced into the welding protection gas, then the welding power is turned on, after the arc is stable for 1-5s (preferably 1-2s), the double-wire synchronous feeding method is used to carry out layer-by-layer additive manufacturing on the titanium alloy substrate cleaned in step one, until the size of the titanium alloy component meets the use requirement, wherein: the welding mode of the welding machine is direct current tungsten electrode argon arc welding, the working current is 100-200A; the wire feeding speed of the wire feeder is 1000-3000mm / min; the welding speed of the welding positioner is 120-200mm / min;

[0011] Step four, the titanium alloy component after additive manufacturing in step three is cooled, then taken off from the clamp, and the additive manufacturing process is completed, wherein: the cooling method is natural cooling in air.

[0012] The manufacturing mechanism of the present application is as follows:

[0013] The additive manufacturing using arc as heat source mainly relies on the arc to melt the additive material and uniformly spread on the base material, and through layer-by-layer stacking, finally forms the additive manufacturing component. In the additive manufacturing process, due to the large temperature difference between the arc and the base material, during the solidification process of the additive material, it tends to grow along the direction of the temperature difference, resulting in the directionality of grain growth, thereby reducing the mechanical properties of the additive manufacturing component. Therefore, the grain growth process needs to be controlled during the additive process. In the present application, under the condition of constant total heat input, by introducing more to-be-melted welding wire into the base plate melting area through double-wire synchronous feeding method, the line energy per unit time acting on the welding wire can be reduced, the excess unmelted welding wire enters the molten pool, which can promote the molten pool flow and heat and mass transfer, at the same time, the insufficiently melted welding wire plays a role in promoting heterogeneous nucleation of grains during the solidification process, thereby destroying the growth trend of grains along the same direction. Therefore, using the additive manufacturing method of the present application can ensure that the grain size of the additive manufacturing component is small and uniform.

[0014] Compared with the prior art, the present application has the following advantages:

[0015] 1. Compared with the existing arc additive manufacturing method, the present application can effectively control the stability of the welding process under a large wire feeding speed, reduce the unit wire line energy, promote the molten pool flow, and thereby realize the grain size refinement and uniform distribution of the titanium alloy additive manufacturing component, and strengthen the titanium alloy additive component, which has very important significance for titanium alloy arc additive manufacturing.

[0016] 2. The coaxial ultrasonic device in the present application has low cost, simple process method and easy implementation, and is suitable for the field of arc additive manufacturing of titanium alloy. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 A schematic diagram of dual-wire synchronous feeding of titanium alloy in arc additive manufacturing: 1-Tungsten electrode, 2-First wire feeder, 3-First welding wire, 4-Second wire feeder, 5-Second welding wire, 6-Welding power source, 7-Titanium alloy substrate, 8-Welding positioner switch, 9-Gas protective cover.

[0018] Figure 2 Flowchart of the dual-wire synchronous feeding titanium alloy arc additive manufacturing process;

[0019] Figure 3 This is a schematic diagram of simultaneous feeding of two wires;

[0020] Figure 4 This is a comparison diagram of the macroscopic grain morphology of titanium alloy additive components prepared by the method of this invention and the conventional electric arc additive manufacturing method. Detailed Implementation

[0021] The technical solution of the present invention will be further described below with reference to the embodiments, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0022] Example 1:

[0023] This embodiment provides a non-consumable electrode arc additive manufacturing method for refining titanium alloy grains by simultaneously feeding two wires into the material. The method includes the following steps:

[0024] Step 1: Thoroughly clean the surface of the titanium alloy substrate, such as... Figure 1 As shown, the titanium alloy substrate is placed on the welding positioner and clamped and fixed in the area to be welded. The position of the tungsten electrode tip is adjusted to the additive manufacturing start position. The titanium alloy substrate is 10 mm thick and the tungsten electrode tip is 5 mm away from the surface of the titanium alloy substrate.

[0025] Step 2: Adjust the dual-wire synchronous feeding fixture so that the angle between the two welding wires is 45° and the angle between the welding wire and the titanium alloy substrate is 15°, with the tip of the welding wire directly below the tungsten electrode and in contact with the titanium alloy substrate.

[0026] Step 3: Introduce welding shielding gas into the gas-shielded hood 5 seconds in advance, then turn on the welding power supply. After the arc stabilizes for 1 second, simultaneously turn on the switches of both wire feeders and the welding positioner. Use a dual-wire synchronous feeding method to perform additive manufacturing by stacking layers on the titanium alloy substrate cleaned in Step 2. Stop the additive manufacturing sample when it reaches a height of 100mm. The welding mode of the welding machine is DC tungsten inert gas welding, with a working current of 120A; the wire feeder speed is 2000mm / min; and the welding positioner speed is 180mm / min.

[0027] Step 4: Cool the titanium alloy component after the additive manufacturing in Step 3, and then remove it from the fixture to complete the arc additive manufacturing. The cooling method is natural cooling in the air.

[0028] Figure 4 This is a comparison image of the macroscopic morphology of additive samples produced by conventional single-wire titanium alloy additive manufacturing methods and those produced by the method of this invention. Figure 4 As can be seen, the conventional monofilament additive manufacturing sample (left figure) macroscopically consists of coarse columnar grains that grow continuously from bottom to top, with an average grain size of 4.65 mm. 2 The additive sample produced by the method of this invention (right figure) macroscopically consists of fine, uniform equiaxed crystals and short columnar crystals, with an average grain size of 0.59 mm. 2 The method of this invention significantly improves the problem of coarse grains in additively manufactured titanium alloy components, which is beneficial to the improvement of the performance of titanium alloy additive components.

[0029] Example 2:

[0030] This embodiment provides a non-consumable electrode arc additive manufacturing method for refining titanium alloy grains by simultaneously feeding two wires into the material. The method includes the following steps:

[0031] Step 1: Thoroughly clean the surface of the titanium alloy substrate, such as... Figure 1 As shown, the titanium alloy substrate is placed on the welding positioner and clamped and fixed in the area to be welded. The position of the tungsten electrode tip is adjusted to the additive manufacturing start position. The titanium alloy substrate is 50 mm thick and the tungsten electrode tip is 3 mm away from the surface of the titanium alloy substrate.

[0032] Step 2: Adjust the dual-wire synchronous feeding fixture so that the angle between the two welding wires is 60° and the angle between the welding wire and the titanium alloy substrate is 20°, with the tip of the welding wire directly below the tungsten electrode and in contact with the titanium alloy substrate.

[0033] Step 3: 8 seconds beforehand, introduce welding shielding gas into the gas-protected hood. Then, turn on the welding power supply and wait 2 seconds for the arc to stabilize. Simultaneously turn on the switches of both wire feeders and the welding positioner. Use a dual-wire synchronous feeding method to perform additive manufacturing by stacking layers on the titanium alloy substrate cleaned in Step 2. Stop when the height of the additively manufactured component reaches 50mm. The welding mode of the welding machine is DC tungsten inert gas welding, with a working current of 150A; the wire feeder speed is 3000mm / min; and the welding positioner speed is 150mm / min.

[0034] Step 4: Cool the titanium alloy component after the additive manufacturing in Step 3, and then remove it from the fixture to complete the arc additive manufacturing. The cooling method is natural cooling in the air.

Claims

1. A non-gas tungsten arc welding method of titanium alloy grain refinement by twin wire simultaneous feed, characterized by The method comprises the following steps: Step one, clean the surface of the titanium alloy substrate thoroughly, place it on the welding positioner, clamp and fix it in the welding area, and adjust the position of the tungsten tip to the additive starting position; Step two, adjust the double-wire synchronous feeding clamp so that the included angle between the two welding wires is 30-60°, the included angle between the welding wire and the titanium alloy substrate is 10-30°, and the tip of the welding wire is directly below the tungsten electrode and in contact with the titanium alloy substrate; Step three, introduce the welding protective gas into the gas protection cover 1-10 seconds in advance, then turn on the welding power supply, and after the arc is stable for 1-5 seconds, use the double-wire synchronous feeding method to perform layer-by-layer additive manufacturing on the titanium alloy substrate cleaned in step one until the size of the titanium alloy component meets the use requirements, the welding mode of the welding machine is direct current tungsten argon arc welding, the working current is 100-200 A, the wire feeding speed of the wire feeder is 1000-3000 mm / min, and the welding speed of the welding positioner is 120-200 mm / min; Step four, cool the titanium alloy component after additive manufacturing in step three, then take it off from the clamp, and complete the additive manufacturing process, wherein: the cooling method is natural cooling in air; In the process of titanium alloy additive manufacturing, under the condition that the total heat input is constant, more welding wires to be melted are introduced into the substrate melting area by the double-wire synchronous feeding method, the line energy acting on the welding wire per unit time is reduced, the excess unmelted welding wire enters the molten pool, promotes the flow and heat transfer and mass transfer of the molten pool, and at the same time, the welding wire that is not fully melted plays a role in promoting heterogeneous nucleation of grains during the solidification process, thereby destroying the growth trend of grains in the same direction.

2. The non-gas tungsten arc welding method of claim 1, wherein In step one, the distance between the tip of the tungsten electrode and the surface of the substrate is 2-10 mm.

3. The non-gas tungsten arc welding method of claim 2, wherein The distance between the tip of the tungsten electrode and the surface of the substrate is 3-5 mm.

4. The non-gas tungsten arc welding method of titanium alloy grain refinement by twin wire synchronized feed of claim 1, 2 or 3, wherein The thickness of the titanium alloy substrate is 5-100 mm.

5. The non-gas tungsten arc welding method of titanium alloy grain refinement by twin wire synchronized feed of claim 1, wherein In step three, the welding protective gas is introduced 5-10 seconds in advance.

6. The non-gas tungsten arc welding method of titanium alloy grain refinement by twin wire synchronized feed of claim 1, wherein In step three, the arc is stable for 1-2 seconds.

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