CN104907657B - A kind of TiAl/TC4 electron beam melt-brazing methods for adding alloy interlayer - Google Patents

Abstract

The invention relates to a TiAl/TC4 electron beam melting and brazing method adding an alloy intermediate layer, by presetting an intermediate metal layer composed of Ni and Nb at the position of the TiAl/TC4 electron beam welding seam, and by selecting a reasonable intermediate layer composition , the arrangement of the middle layer, the thickness of the middle layer and the parameters of the electron beam welding process to obtain a high-strength, crack-free TiAl/TC4 electron beam welded joint. In addition, the welding process of the present invention is less, simple to operate, easy to implement, and has strong practicality. sex.

Description

A TiAl/TC4 Electron Beam Melting and Brazing Method Adding an Alloy Intermediate Layer

technical field

The invention relates to a TiAl/TC4 electron beam melting and brazing method with an alloy intermediate layer added, belonging to the field of brittle material welding.

Background technique

In the aerospace industry, the structural service conditions are harsh, and they often work in harsh environments such as high temperature, heat resistance, corrosion, and low temperature, so there are high requirements for the performance of materials. In addition, strict restrictions on the weight of the structure put forward higher requirements for the lightweight of materials. Therefore, TiAl, a new material with light weight, high strength, high specific modulus, and high specific strength, has been widely used in the aerospace field. Cracks occur, which greatly limits its popularization and application.

The electron beam welding process carried out in a vacuum environment eliminates the harm of harmful impurities in the air to the weld and purifies the weld, which is a method to obtain high-quality welds. At the same time, the energy density of the electron beam current is high, and it has a high penetration ability to the material. A single welding can obtain a large penetration depth, reduce the number of welding times, and improve the production efficiency of the welding process. Moreover, due to the concentration of the electron beam current, the heat-affected zone caused by the electron beam heat source is obviously prior to the size of the heat-affected zone of other welding methods. The concentration of the thermal process has a great advantage in controlling the deformation of the structure, so Electron beam welding of structures is often used as a final processing step. In addition, since the electron beam welding process can precisely control the beam spot, the welding of precise welds can be realized, and because the working distance of the beam current of the electron beam can be adjusted, electron beam welding can also be used for positions that are difficult to reach by conventional welding methods. Can be done easily. Therefore, electron beam welding is a welding method with great industrial application prospects. However, due to the metallurgical characteristics of the electron beam welding process, during the remelting process of the weld seam, the rapid cooling process of the weld seam makes the microstructure change of the weld joint position undergo a complete unsteady transition, and the microstructure characteristics of the weld seam area have obvious changes. Variety. Especially for the brittle material TiAl, after the welding melting-solidification process, the microstructure in the weld changes from a microstructure with good plasticity to a brittle supersaturated _Ti3Al phase. Large brittleness greatly reduces the plasticity of the joint and increases the tendency of cracking. In addition, during the welding process, due to the concentration of electron beam welding energy, the cooling rate is significantly higher than other welding methods. The increase in cooling rate will increase the residual tensile stress at the weld position. In the welding process of brittle materials, the residual stress The increase of will cause the material to crack and form cracks. Therefore, in the process of electron beam welding of brittle materials, how to eliminate cracks is a problem that must be studied.

Contents of the invention

The purpose of the present invention is to overcome the above-mentioned defects of the prior art, and to provide a TiAl/TC4 electron beam melting and brazing method that adds an alloy interlayer. The preparation method, as well as the electron beam welding process parameters, obtain high-strength, crack-free TiAl/TC4 electron beam welded joints.

Above-mentioned purpose of the present invention is mainly achieved through the following technical solutions:

A kind of TiAl/TC4 electron beam fusion brazing method that adds alloy intermediate layer, comprises the steps:

(1) After stacking and arranging 1-3 layers of Nb foils and 1-3 layers of Ni foils in sequence, they are positioned by spot welding to form an intermediate layer. The thickness of each layer of Nb foils is 80-120 μm. The thickness of the layer Ni foil is 80-120 μm;

(2) Spot weld the intermediate layer to the welding surface of the TC4 base metal or the TiAl base metal, and make the intermediate layer between the TC4 base metal and the TiAl base metal, and make the TC4 base metal and the TiAl base metal tightly docked by the clamp And fixed to form the workpiece to be welded;

(3) Put the workpiece to be welded into the vacuum chamber of the electron beam welding machine and start vacuuming. When the vacuum degree reaches 4×10 ^-2 Pa～7×10 ^-2 Pa, adjust the parameters of the electron beam welding process, first A small beam is used to fuse the metal in the middle layer. The parameters of the electron beam welding process are: accelerating voltage 50-60kV, focusing current 1500-1700mA, welding beam current 5-20mA, and welding speed 500-1500mm/min;

(4), then adjust the electron beam welding process parameters, and carry out electron beam welding on the workpiece to be welded;

(5) After the welding is completed, keep warm in the vacuum chamber for 3 to 8 minutes, then deflate, and take out the workpiece.

In the TiAl/TC4 electron beam melting and brazing method with the addition of an alloy intermediate layer, in step (1), there is one layer of Ni foil, and one to two layers of Nb foil.

In the above-mentioned TiAl/TC4 electron beam melting and brazing method with an alloy intermediate layer added, the width of the Ni foil and the Nb foil is the thickness of the weld, and the preparation of the foil is cut by wire cutting.

In the above-mentioned TiAl/TC4 electron beam melting and brazing method with an alloy intermediate layer added, in step (2), the Nb foil is placed on the side close to the TiAl base material, and the Ni foil is placed on the side close to the TC4 base material.

In the above-mentioned TiAl/TC4 electron beam melting and brazing method with an alloy intermediate layer added, the TC4 base material and the TiAl base material are plates or rings, the thickness of the weld seam of the plate is 1 mm to 5 mm, and the thickness of the weld seam of the ring is 1 mm to 5 mm.

In the above-mentioned TiAl/TC4 electron beam melting and brazing method with an alloy interlayer added, the thicknesses of the Ni foil and the Nb foil are both 100 μm.

In the above-mentioned TiAl/TC4 electron beam melting and brazing method with an alloy intermediate layer added, the process parameters for electron beam welding of the workpiece to be welded in step (4) are: accelerating voltage 50-60kV, focusing current 1500-1700mA, welding beam current 5~50mA, welding speed is 500~1500mm/min.

In the above-mentioned TiAl/TC4 electron beam melting and brazing method that adds an alloy intermediate layer, when the workpiece to be welded is electron beam welded in step (4), the electron beam spot shifts to the TC4 side, and the deviation from the weld center The distance is 0.2-0.5 mm.

Compared with the prior art, the present invention has the following beneficial effects:

(1), the present invention is aimed at the joint crackle of traditional TiAl/TC4 welding is big, and the defect of welding strength is low, for the first time at TiAl/TC4 electron beam welding weld seam position, the middle metal layer of Ni and Nb composition is preset, by selecting reasonable The composition of the intermediate layer, the arrangement of the intermediate layer, the thickness of the intermediate layer and the parameters of the electron beam welding process are used to obtain high-strength, crack-free TiAl/TC4 electron beam welded joints;

(2) The present invention adopts the method of stacking metal foils to prepare the middle layer. The basic elements of the middle layer are Ni and Nb, and the 100μm Ni foil and Nb foil are superimposed in a specified ratio. Taking advantage of the fusible characteristics of the foil, it can be fully fused with the molten base metal during the welding process to optimize the mechanics of the weld Performance, improve joint crack resistance;

(3), the present invention at first adopts small electron beam current to carry out fusion to intermediate layer, guarantees the fixing of intermediate layer in the welding process position, then carries out electron beam welding, the present invention is to the welding of small electron beam current welding and electron beam current The technological parameters of the invention have been optimized, which can effectively control the generation of cracks in the TiAl/TC4 electron beam welding process and improve the joint strength. The test shows that the strength of the welded joint of the present invention can reach 80% of the TiAl base material at the highest, and the joint has no cracks;

(4), when the present invention carries out electron beam welding to the workpiece to be welded, the electron beam spot shifts to the TC4 side, and the offset distance with the weld seam center is 0～0.5mm, preferably 0.2～0.5mm, and the test shows that it moves towards TC4 One side offset can increase the melting amount of TC4, promote the fusion of the middle layer metal and the weld, and improve the bonding strength;

(5), the welding process flow of the present invention is few, and operation is simple, is easy to realize.

Description of drawings

Fig. 1 is TiAl/TC4 welding seam appearance figure among the embodiment 1 of the present invention;

Fig. 2 is a SEM photo of TiAl/TC4 weld seam in Example 2 of the present invention.

detailed description

Below in conjunction with accompanying drawing and specific embodiment the present invention is described in further detail:

The present invention adds the TiAl/TC4 electron beam fusion brazing method of alloy intermediate layer, specifically comprises the following steps:

(1) Clean the TC4 base metal and TiAl base metal before welding, and remove the oil stain and oxide layer on the surface of the material by physical and chemical methods;

(2), prepare the intermediate layer alloy according to the requirements, the alloy elements of the intermediate layer are Nb, Ni, select the appropriate number of Nb foil and Ni foil layers according to the design, the present invention combines 1-3 layers of Nb foil and 1-3 layers After the Ni foils are stacked and arranged in sequence (when the Nb foil and the Ni foil are both multi-layered, the multi-layered Nb foils are stacked first, and then stacked with the multi-layered Ni foils), the spot welding machine is used for welding. Spot welding and positioning to form an intermediate layer. The thickness of each layer of Nb foil is 80-120 μm, and the thickness of each layer of Ni foil is 80-120 μm. Preferably, there is 1 layer of Ni foil and 1-2 layers of Nb foil. The width of the Ni foil and the Nb foil is the thickness of the welding seam, and the preparation of the foil is cut by wire cutting.

(3), spot weld the middle layer to the TC4 base metal welding surface or the TiAl base metal welding surface, and make the middle layer between the TC4 base metal and the TiAl base metal, and fix it by the clamp so that the TC4 base metal and the TiAl base metal The materials are tightly butted to form the workpiece to be welded. Among them, the Nb foil is placed on the side close to the TiAl base material, and the Ni foil is placed on the side close to the TC4 base material.

(4) Put the workpiece to be welded into the vacuum chamber of the electron beam welding machine and start vacuuming. When the vacuum degree reaches 4×10 ^-2 Pa～7×10 ^-2 Pa, adjust the parameters of the electron beam welding process, first A small beam is used to fuse the metal in the middle layer. The parameters of the electron beam welding process are: accelerating voltage 50-60kV, focusing current 1500-1700mA, welding beam current 5-20mA, welding speed 500-1500mm/min;

(5), then adjust the electron beam welding process parameters, and carry out electron beam welding on the workpiece to be welded; the process parameters of electron beam welding are: accelerating voltage 50 ~ 60kV, focusing current 1500 ~ 1700mA, welding beam current 5 ~ 50mA, welding speed is 500～1500mm/min. When performing electron beam welding on the workpiece to be welded, the electron beam spot can be aligned with the center of the weld seam, or it can be offset to the side of TC4. 0.2 ~ 0.5mm.

(6) After the welding is completed, keep warm in the vacuum chamber for 3 to 8 minutes, then deflate, and take out the workpiece.

The above-mentioned TC4 base material and TiAl base material are plates or ring parts, the thickness of the welding seam of the plate is 1mm-5mm, and the thickness of the weld seam of the ring part is 1mm-5mm.

For the preparation of the composite interlayer alloy, it is necessary to ensure that the interlayer alloy has an effective structure improvement effect and has good process applicability. In the present invention, the middle layer is prepared by stacking metal foils. The basic elements of the middle layer are Ni and Nb, and 100 μm Ni foil and Nb foil are superimposed in a specified ratio. The advantage of using foil is that the foil is fusible and can fully fuse with the molten base metal during the welding process. Before the actual welding, the metal foil is cut to the required thickness, and the multi-layer foil is spot-welded with a capacitor energy storage spot welder to form a composite intermediate layer alloy. Then, use a spot welding machine to spot weld the middle layer on the welding surface of the TC4 base material, and then use a clamp to ensure the butt joint between TC4 and TiAl. The process is less, the operation is simple, and the strength of the spot welding can effectively ensure the combination of the composite middle layer.

Example 1

(1) The base metal to be welded is cleaned before welding, and the oil stain and oxide layer on the surface of the material are removed by physical and chemical methods. The base metal is TiAl and TC4 plate, and the thickness of the plate is 1.5mm.

(2), prepare the intermediate layer alloy by wire cutting, the intermediate layer alloy elements Nb, Ni, the Nb foil is 1 layer, and the Ni foil is 1 layer. The foil is spot welded and positioned by a spot welding machine, and then the intermediate layer Spot welding to the welding surface of TC4 base metal; the thickness of each layer of Nb foil is 100 μm, and the thickness of each layer of Ni foil is 100 μm.

(3) Fix the workpiece with a fixture to ensure the tight connection between TC4 and TiAl;

(4) Put the workpiece into the vacuum chamber of the electron beam welding machine and start vacuuming;

(5) When the vacuum reaches 5×10 ^-2 Pa, adjust the electron beam welding process parameters to prepare for welding. First, use a small beam to fuse the metal in the middle layer, and align the electron beam spot to the middle layer. The electron beam welding process parameters are acceleration voltage 50kV, focusing current 1650mA, welding beam current 8mA, and welding speed 700mm/min. Then electron beam welding is carried out on the weld seam, and the electron beam spot is aligned with the center of the weld seam. The electron beam welding process parameters are acceleration voltage 50kV, focusing current 1650mA, welding beam current 20mA, and welding speed 1000mm/min.

(6) After the welding is completed, keep the heat in the vacuum chamber for 5 minutes and then deflate, and take out the workpiece. The weld seam thickness of the obtained sheet is 1.5mm.

As shown in Figure 1 is the appearance of the weld seam in Example 1 of the present invention; it can be seen from the figure that the weld seam is well formed and there is no crack on the surface. The strength of the welded joint can reach 65% of the strength of the TiAl base metal.

Example 2

(1) The base metal to be welded is cleaned before welding, and the oil stain and oxide layer on the surface of the material are removed by physical and chemical methods. The base metal is TiAl and TC4 plate, and the thickness of the plate is 1.5mm.

(2) Prepare the intermediate layer alloy by wire cutting, the intermediate layer alloy elements Nb, Ni, the Nb foil is 2 layers, and the Ni foil is 1 layer. Use a spot welding machine to spot weld the foil and then spot weld the intermediate layer To the welding surface of TC4 base metal; the thickness of each layer of Nb foil is 100 μm, and the thickness of each layer of Ni foil is 100 μm.

(3) Fix the workpiece with a fixture to ensure the tight connection between TC4 and TiAl;

(4) Put the workpiece into the vacuum chamber of the electron beam welding machine and start vacuuming;

(5) When the vacuum reaches 5×10 ^-2 Pa, adjust the electron beam welding process parameters to prepare for welding. First, use a small beam to fuse the metal in the middle layer, and align the electron beam spot to the middle layer. The electron beam welding process parameters are acceleration voltage 50kV, focusing current 1650mA, welding beam current 8mA, and welding speed 700mm/min. Then carry out electron beam welding on the weld seam, the electron beam spot is biased to the TC4 side, and the offset distance from the center of the weld seam is 0.5mm, the electron beam welding process parameters are acceleration voltage 50kV, focusing current 1680mA, welding beam current 20mA, welding The speed is 1000mm/min

(6) After the welding is completed, keep the heat in the vacuum chamber for 5 minutes and then deflate, and take out the workpiece. The weld seam thickness of the obtained sheet is 1.5 mm.

As shown in Figure 2 is the SEM photograph of the weld seam in Example 2 of the present invention; it can be seen from the figure that there is no crack inside the weld seam. The strength of the welded joint can reach 75% of the strength of the TiAl base metal.

Example 3

(1) The base material to be welded is cleaned before welding, and the oil stain and oxide layer on the surface of the material are removed by physical and chemical methods. The base material is TiAl and TC4 ring, with a thickness of 2mm.

(2) Prepare the intermediate layer alloy by wire cutting, the intermediate layer alloy elements Nb, Ni, the Nb foil is 2 layers, and the Ni foil is 1 layer. Use a spot welding machine to spot weld the foil and then spot weld the intermediate layer To the welding surface of TC4 base metal; the thickness of each layer of Nb foil is 100 μm, and the thickness of each layer of Ni foil is 100 μm.

(3) Fix the workpiece with a fixture to ensure the tight connection between TC4 and TiAl;

(4) Put the workpiece into the vacuum chamber of the electron beam welding machine and start vacuuming;

(5) When the vacuum reaches 5×10 ^-2 Pa, adjust the electron beam welding process parameters to prepare for welding. First, use a small beam to fuse the metal in the middle layer, and align the electron beam spot to the middle layer. The electron beam welding process parameters are acceleration voltage 50kV, focusing current 1650mA, welding beam current 8mA, and welding speed 700mm/min. Then carry out electron beam welding on the weld seam, the electron beam spot is biased to the TC4 side, and the offset distance from the center of the weld seam is 0.4mm, the electron beam welding process parameters are acceleration voltage 50kV, focusing current 1690mA, welding beam current 25mA, The speed is 900mm/min.

(6) After the welding is completed, keep the heat in the vacuum chamber for 5 minutes and then deflate, and take out the workpiece. The thickness of the weld seam of the obtained annular member was 2 mm.

Tests show that the strength of the welded joint reaches 80% of the strength of the TiAl base metal.

The above description is only the best specific implementation mode of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of changes or modifications within the technical scope disclosed in the present invention. Replacement should be covered within the protection scope of the present invention.

The content that is not described in detail in the specification of the present invention belongs to the well-known technology of those skilled in the art.

Claims (8)

1. a kind of add alloy interlayer TiAl/TC4 electron beam melt-brazing methods, it is characterised in that：Comprise the steps：

(1), 1～3 layer of Nb paillon foil and 1～3 layer of Ni paillon foil are stacked after arrangement successively, is positioned by spot welding, is formed intermediate layer, institute The thickness for stating every layer of Nb paillon foil is 80～120 μm, and the thickness of every layer of Ni paillon foil is 80～120 μm；Wherein when Nb paillon foils and Ni paper tinsels When piece is multilayer, after first stack multilayer Nb paillon foil, then stack with multilayer Ni paillon foil；

(2), intermediate layer is spot welded on TC4 mother metals solder side or TiAl mother metal solders side, and make intermediate layer be located at TC4 mother metals with Between TiAl mother metals, make TC4 mother metals with the closed butt joint of TiAl mother metals and fixed by fixture, form workpiece to be welded；

(3), workpiece to be welded is put in the vacuum chamber of electron-beam welder, starts to vacuumize, when vacuum reaches 4 × 10^-2Pa ～7 × 10^-2During Pa, electro-beam welding process parameter is adjusted, is fused initially with little line centering interbed metal, the electricity Beamlet welding condition is：50～60kV of accelerating potential, 1500～1700mA of focus current, weld 5～20mA of line, welding Speed is 500～1500mm/min；

(4) electro-beam welding process parameter is adjusted afterwards, and treating welding workpiece carries out electron beam welding；

(5), after the completion of, welding, deflate after 3～8min of insulation in a vacuum chamber, take out workpiece.

2. according to claim 1 a kind of add alloy interlayer TiAl/TC4 electron beam melt-brazing methods, its feature It is：In step (1), Ni paillon foils are 1 layer, and Nb paillon foils are 1～2 layer.

3. a kind of TiAl/TC4 electron beam melt-brazing methods for adding alloy interlayer according to claim 1 and 2, which is special Levy and be：Thickness of the width of the Ni paillon foils and Nb paillon foils for weld seam, the preparation of paillon foil are cut using wire cutting mode.

4. a kind of TiAl/TC4 electron beam melt-brazing methods for adding alloy interlayer according to claim 1 and 2, which is special Levy and be：In step (2), Nb paillon foils are disposed close to TiAl mother metals side, and Ni paillon foils are disposed close to TC4 mother metals side.

5. a kind of TiAl/TC4 electron beam melt-brazing methods for adding alloy interlayer according to claim 1 and 2, which is special Levy and be：The TC4 mother metals and TiAl mother metals are sheet material or annular element, and sheet material throat depth is 1mm～5mm, annular element weld seam Thickness is 1mm～5mm.

6. a kind of TiAl/TC4 electron beam melt-brazing methods for adding alloy interlayer according to claim 1 and 2, which is special Levy and be：The thickness of the Ni paillon foils and Nb paillon foils is 100 μm.

7. a kind of TiAl/TC4 electron beam melt-brazing methods for adding alloy interlayer according to claim 1 and 2, which is special Levy and be：Welding workpiece is treated in step (4) carry out the technological parameter of electron beam welding be：50～60kV of accelerating potential, 1500～1700mA of focus current, welds 5～50mA of line, and speed of welding is 500～1500mm/min.

8. a kind of TiAl/TC4 electron beam melt-brazing methods for adding alloy interlayer according to claim 1 and 2, which is special Levy and be：When treating welding workpiece in step (4) and carrying out electron beam welding, electron beam spot is offset to TC4 sides, with weldering The offset distance at seam center is 0.2～0.5mm.