Electric arc additive manufacturing method for assisting in titanium alloy grain refinement through coaxial ultrasound

Abstract

The invention discloses an electric arc additive manufacturing method for assisting in titanium alloy grain refinement through coaxial ultrasound. The method comprises the following steps that firstly, an ultrasonic gun is installed on a welding gun in the mode that the ultrasonic gun and a tungsten electrode are coaxial; 2, fully cleaning the surface of the titanium alloy substrate, clamping and fixing the titanium alloy substrate in a to-be-welded area, and adjusting the tip position of a tungsten electrode to the initial position of material increase; thirdly, welding shielding gas is introduced in advance, and after the electric arc is stable, layer-by-layer stacked additive manufacturing is carried out on the titanium alloy substrate through a coaxial ultrasonic auxiliary method; and fourthly, the titanium alloy component obtained after additive manufacturing is completed is cooled and then taken down from the clamp, and the additive manufacturing process is completed. According to the method, the ultrasonic waves are introduced into the electric arc and the molten pool, the electric arc form can be effectively controlled, the fluidity of the molten pool can be effectively improved, then grain size refinement and distribution uniformity of the titanium alloy additive manufacturing component are achieved, the titanium alloy additive manufacturing component is strengthened, the mechanical property of the titanium alloy additive manufacturing component is improved, and the method has very important significance on titanium alloy electric arc additive manufacturing.

Description

Technical Field

[0001] The present invention belongs to the technical field of titanium alloy arc additive manufacturing, and relates to a titanium alloy additive manufacturing method, and specifically to an arc additive manufacturing method through coaxial ultrasonic assisted titanium alloy grain refinement. Background Art

[0002] Titanium alloys have great application potential in the aerospace field because of their advantages such as high specific strength, corrosion resistance, high temperature resistance and good creep resistance. For example, structures such as aircraft engine casings, turbine blades, and compressor blades all use titanium alloys in large quantities to reduce weight and improve mechanical properties.

[0003] Additive manufacturing technology is a technology that produces three-dimensional structures by stacking materials layer by layer. Compared with traditional casting and forging technologies, additive manufacturing technology does not require complex molds, improves production efficiency and flexibility, reduces production costs, and has huge economic benefits.

[0004] In the additive manufacturing process of titanium alloys, it is easy to produce coarse columnar grains that grow continuously along the additive direction, resulting in uneven mechanical properties of additively manufactured components: the strength in the horizontal direction is better than that in the vertical direction. Therefore, how to control the uniformity of grain size and mechanical properties of additively manufactured titanium alloy components is an important issue in the field of additive manufacturing technology. Summary of the invention

[0005] In order to solve the technical problems of coarse grains and uneven mechanical properties of titanium alloy components in additive manufacturing, the present invention provides an arc additive manufacturing method through coaxial ultrasonic assisted titanium alloy grain refinement, which realizes grain size control of titanium alloy additive manufactured components.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] An arc additive manufacturing method for titanium alloy grain refinement assisted by coaxial ultrasound comprises the following steps:

[0008] Step 1: Install the ultrasonic gun on the welding gun in a coaxial manner with the tungsten electrode;

[0009] Step 2: Fully clean the surface of the titanium alloy substrate, place it on the welding positioner and clamp it in the area to be welded, and adjust the position of the tungsten electrode tip to the starting position of the additive material, wherein: the thickness of the titanium alloy substrate is 5 to 100 mm; the tungsten electrode tip is 2 to 10 mm (preferably 3 to 5 mm) away from the substrate surface; the angle between the welding wire and the titanium alloy substrate is 10 to 30°; the welding wire tip is directly below the tungsten electrode and in contact with the titanium alloy substrate;

[0010] Step 3, introduce welding shielding gas 1 to 30 seconds (preferably 5 to 10 seconds) in advance, wait for the arc to stabilize for 1 to 5 seconds (preferably 1 to 2 seconds), and use a coaxial ultrasonic assisted method to perform layer-by-layer additive manufacturing on the titanium alloy substrate cleaned in step 2 until the size of the titanium alloy component meets the use requirements, wherein: the operating frequency of the ultrasonic gun is 20kHZ, and the power is 50 to 200W; the welding mode of the welding machine is DC tungsten inert gas welding, and the working current is 100 to 200A; the wire feeding speed of the wire feeder is 1000 to 3000mm / min; the welding speed of the welding positioner is 120 to 200mm / min;

[0011] Step 4: Cool the titanium alloy component after the additive manufacturing in step 3, and then remove it from the fixture to complete the additive manufacturing process, wherein: the cooling method is natural cooling in the air.

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

[0013] Additive manufacturing uses an electric arc as a heat source, which mainly relies on the electric arc to melt the additive material and evenly spread it on the base material, and finally forms an additive manufacturing component by stacking layer by layer. In the additive manufacturing process, due to the large temperature difference between the electric arc and the base material, during the solidification of the additive material, coarse grains tend to grow along the direction of the temperature difference, resulting in directional grain growth, thereby reducing the mechanical properties of the additive manufacturing component. Therefore, it is necessary to control the growth of grains during the additive process. In the present invention, in the additive manufacturing process of titanium alloy, ultrasonic waves are introduced into the electric arc and the molten titanium alloy molten pool in a coaxial manner of an ultrasonic gun-tungsten pole. The ultrasonic wave can constrain the arc width, make the arc energy density more concentrated, promote the fluidity of the molten pool, and destroy the growth trend of the grains in the same direction. Therefore, using the additive manufacturing method of the present invention, it is possible to ensure that the grain size of the additive manufacturing component is small and uniform.

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

[0015] 1. Compared with the existing arc additive manufacturing method, the present invention can effectively control the arc morphology and improve the fluidity of the molten pool by introducing ultrasonic waves into the arc and the molten pool, thereby achieving the grain size refinement and distribution uniformity of titanium alloy additive manufacturing components, strengthening titanium alloy additive components, and having a very important significance for titanium alloy arc additive manufacturing.

[0016] 2. The coaxial ultrasonic equipment in the present invention has low cost, simple process method and is easy to implement, and is suitable for the arc additive manufacturing field of titanium alloys. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1This is a schematic diagram of the installation of the coaxial ultrasonic equipment, 1-ultrasonic power supply, 2-ultrasonic transducer, 3-ultrasonic horn, 4-ultrasonic transmitting end, 5-gas shielding nozzle, 6-tungsten electrode, 7-wire feeder switch, 8-welding power supply, 9-titanium alloy substrate, 10-welding positioner switch, 11-welding gun;

[0018] Figure 2 A comparison diagram of arc morphology between the method of the present invention and a common arc additive manufacturing method;

[0019] Figure 3 Comparison of the macro grain morphology of titanium alloy additive components prepared by the method of the present invention and the conventional arc additive manufacturing method, (a) macro grain morphology of the conventional method, (b) macro grain morphology of the method of the present invention, (c) grain size statistics of the conventional method, (d) grain size statistics of the method of the present invention;

[0020] Figure 4 EBSD grain size and orientation distribution diagram of titanium alloy additive components prepared by the method of the present invention and the conventional arc additive manufacturing method. DETAILED DESCRIPTION

[0021] The technical solution of the present invention is further described below in conjunction with the embodiments, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be included in the protection scope of the present invention.

[0022] Embodiment 1:

[0023] This embodiment provides an arc additive manufacturing method for titanium alloy grain refinement assisted by coaxial ultrasound, the method comprising the following steps:

[0024] Step 1: Figure 1 As shown, the ultrasonic gun and the tungsten electrode are installed on the welding gun 11, ensuring that the tungsten electrode 6 passes through the ultrasonic gun, so that the ultrasonic gun, the welding gun 11, and the tungsten electrode 6 are in a coaxial position relationship. The ultrasonic gun includes an ultrasonic power supply 1, an ultrasonic transducer 2, an ultrasonic horn 3, an ultrasonic transmitting end 4 and a gas protection nozzle 5.

[0025] Step 2: Thoroughly clean the surface of the titanium alloy substrate 9, place it on the welding positioner and clamp it in the area to be welded, adjust the position of the tungsten electrode tip to the starting position of the additive, wherein the thickness of the titanium alloy substrate is 10 mm, the tungsten electrode tip is 4 mm away from the surface of the titanium alloy substrate, the angle between the welding wire and the titanium alloy substrate is 30°, and the welding wire tip is directly below the tungsten electrode and in contact with the titanium alloy substrate.

[0026] Step 3: 5s in advance, introduce welding shielding gas into the gas shielding nozzle, then turn on the welding power supply 8, wait for 1s for the arc to stabilize, turn on the ultrasonic power supply, welding positioner switch 10 and wire feeder switch 7, and use the coaxial ultrasonic assisted method to perform layer-by-layer additive manufacturing on the titanium alloy substrate cleaned in step 2, and stop when the height of the additively manufactured titanium alloy component reaches 100mm. Among them: the operating frequency of the ultrasonic gun is 20kHZ, the power is 80W; the welding mode of the welding machine is DC tungsten inert gas arc welding, the working current is 100A; the wire feeding speed of the wire feeder is 2000mm / min; the welding speed of the welding positioner is 150mm / min.

[0027] Step 4: Cool the titanium alloy component manufactured in step 3 naturally in the air, then remove it from the fixture to complete the additive manufacturing process.

[0028] Figure 2 The arc morphology of conventional TIG and the method of the present invention is compared. Figure 2 It can be seen that after the application of ultrasound, the arc has an obvious shrinkage trend due to the ultrasonic radiation force, which is beneficial to the concentration of arc line energy and the increase of arc pressure. Figure 3 This is a comparison chart of the macroscopic morphology of titanium alloy additive manufacturing samples made by conventional TIG and the method of the present invention. Figure 3 It can be seen that the conventional single-filament additive sample (left) is a macroscopic coarse columnar grain that grows continuously from bottom to top, with an average grain size of 2.79 mm. 2 The sample (right picture) produced by the additive manufacturing method of the present invention is fine, uniform, equiaxed and short columnar crystals, with an average grain size of 0.35 mm. 2 . Figure 4 EBSD grain size and orientation distribution diagram of conventional TIG and titanium alloy additive manufacturing samples according to the present invention. Figure 4 It can be seen that after applying the ultrasonic radiation force, the grains of the titanium alloy additively manufactured component are significantly refined, and the orientation difference increases. The method of the present invention significantly improves the problem of coarse grains of the additively manufactured titanium alloy component, which is conducive to improving the performance of the titanium alloy additive component.

[0029] Embodiment 2:

[0030] This embodiment provides an arc additive manufacturing method for titanium alloy grain refinement assisted by coaxial ultrasound, the method comprising the following steps:

[0031] Step 1: Figure 1 As shown, the ultrasonic gun and the tungsten electrode are installed on the welding gun 11, ensuring that the tungsten electrode 6 passes through the ultrasonic gun, so that the ultrasonic gun, the welding gun 11, and the tungsten electrode 6 are in a coaxial position relationship. The ultrasonic gun includes an ultrasonic power supply 1, an ultrasonic transducer 2, an ultrasonic horn 3, an ultrasonic transmitting end 4 and a gas protection nozzle 5.

[0032] Step 2: Fully clean the surface of the titanium alloy substrate 9, place it on the welding positioner and clamp it in the area to be welded, and adjust the position of the tungsten electrode tip to the starting position of the material addition. The thickness of the titanium alloy substrate is 50mm, and the distance between the tungsten electrode tip and the surface of the titanium alloy substrate is controlled to be 5mm; the angle between the welding wire and the titanium alloy substrate is 20°, and the tip of the welding wire is directly below the tungsten electrode and in contact with the titanium alloy substrate.

[0033] Step 3: 10 seconds in advance, introduce welding shielding gas into the gas shielding nozzle, then turn on the welding power supply 8, wait for 2 seconds for the arc to stabilize, turn on the ultrasonic power supply, welding positioner switch 10 and wire feeder switch 7, and use the coaxial ultrasonic assisted method to perform layer-by-layer additive manufacturing on the titanium alloy substrate cleaned in step 2, and stop when the height of the additively manufactured titanium alloy component reaches 200mm. Among them, the operating frequency of the ultrasonic gun is 20kHZ and the power is 120W; the welding mode of the welding machine is DC tungsten inert gas arc welding, and the working current is 120A; the wire feeding speed of the wire feeder is 2200mm / min; the welding speed of the welding positioner is 180mm / min.

[0034] Step 4: Cool the titanium alloy component manufactured in step 3 naturally in the air, then remove it from the fixture to complete the additive manufacturing process.

Claims

1. An arc additive manufacturing method for titanium alloy grain refinement assisted by coaxial ultrasound, characterized in that The method comprises the following steps: Step 1: Install the ultrasonic gun on the welding gun in a coaxial manner with the tungsten electrode; Step 2: Fully clean the surface of the titanium alloy substrate, place it on the welding positioner and clamp it in the area to be welded, and adjust the position of the tungsten electrode tip to the starting position of the additive; Step 3: Introduce welding shielding gas 1 to 30 seconds in advance, wait for the arc to stabilize for 1 to 5 seconds, and then use a coaxial ultrasonic assisted method to perform additive manufacturing layer by layer on the titanium alloy substrate cleaned in step 2 until the size of the titanium alloy component meets the use requirements; 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.

2. The arc additive manufacturing method for titanium alloy grain refinement by coaxial ultrasonic assisted method according to claim 1, characterized in that In the step 2, the tip of the tungsten electrode is 2 to 10 mm away from the surface of the substrate.

3. The arc additive manufacturing method for titanium alloy grain refinement by coaxial ultrasonic assisted method according to claim 2, characterized in that The tungsten tip is 3 to 5 mm away from the substrate surface.

4. The arc additive manufacturing method for titanium alloy grain refinement by coaxial ultrasonic assisted method according to claim 1, 2 or 3, characterized in that The thickness of the tungsten titanium alloy substrate is 5 to 100 mm.

5. The arc additive manufacturing method for titanium alloy grain refinement assisted by coaxial ultrasound according to claim 1, characterized in that In the step 2, the angle between the welding wire and the titanium alloy substrate is 10-30 degrees, and the tip of the welding wire is directly below the tungsten electrode and contacts the titanium alloy substrate.

6. The arc additive manufacturing method for titanium alloy grain refinement assisted by coaxial ultrasound according to claim 1, characterized in that In the step 3, the welding shielding gas is introduced 5 to 10 seconds in advance.

7. The arc additive manufacturing method of titanium alloy grain refinement assisted by coaxial ultrasound according to claim 1, characterized in that In the step 3, the arc stabilization time is 1 to 2 seconds.

8. The arc additive manufacturing method for titanium alloy grain refinement assisted by coaxial ultrasound according to claim 1, characterized in that In the step three, the operating frequency of the ultrasonic gun is 20kHZ, and the power is 50-200W; the welding mode of the welding machine is DC tungsten inert gas arc welding, and the operating current is 100-200A; the wire feeding speed of the wire feeder is 1000-3000mm / min; and the welding speed of the welding positioner is 120-200mm / min.

9. The arc additive manufacturing method for titanium alloy grain refinement assisted by coaxial ultrasound according to claim 1, characterized in that In the step 4, the cooling method is natural cooling in the air.

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