TC4 titanium alloy / GH4169 high-temperature alloy dissimilar metal rotary friction welding method for preheating before welding

Abstract

The invention discloses a TC4 titanium alloy / GH4169 high-temperature alloy dissimilar metal rotary friction welding method for preheating before welding, and relates to the technical field of friction welding. The method comprises the steps that GH4169 high-temperature alloy is preheated at the temperature of 970-990 DEG C, and after heat preservation is conducted for 5-10 minutes, friction welding is conducted on the GH4169 high-temperature alloy and TC4 titanium alloy; wherein during friction welding, the preheated GH4169 high-temperature alloy is placed at the feeding end of a friction welding machine, and the TC4 titanium alloy serves as the rotating end. According to the method, the GH4169 high-temperature alloy is preheated before welding at the temperature of 980 + / -10 DEG C, so that the GH4169 with high high-temperature hardness is softened, the problem of plastic deformation mismatch of an interface in the welding process is solved, and the welding strength of the GH4169 high-temperature alloy and the GH4169 high-temperature alloy can be remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of friction welding, and in particular to a TC4 titanium alloy / GH4169 high-temperature alloy dissimilar metal rotation friction welding method preheated before welding. Background Art

[0002] In recent years, the technology of joining dissimilar materials has gradually become one of the most critical and challenging technologies in the field of welding. It can not only effectively reduce the weight of the structure and reduce energy consumption, but also make full use of the advantages of different materials, so as to provide appropriate functions for specific applications. Titanium alloys represented by TC4 and high-temperature alloys represented by GH4169 are widely used in aerospace, medical equipment, automobile manufacturing and energy industries due to their good high-temperature performance, low density and excellent corrosion resistance. However, the welding of the two is very difficult, which seriously restricts the widespread application of titanium alloy / high-temperature alloy composite structures.

[0003] The poor weldability of the two is mainly reflected in the following aspects: (1) The physical properties of TC4 titanium alloy and GH4169 high-temperature alloy are very different: including density, melting point, thermal expansion coefficient, etc., which will make it difficult to fuse the welding interface during the welding process; (2) The two have the characteristics of chemical reaction: nickel and titanium can react at the welding temperature to produce a variety of brittle and hard intermetallic compounds, which will significantly reduce the mechanical properties of the joint. Therefore, the weldability of titanium alloy / high-temperature alloy is very poor, and welding the two has long been an engineering problem.

[0004] The existing welding technologies for TC4 titanium alloy / GH4169 high-temperature alloy dissimilar materials are mainly brazing, diffusion welding and friction welding. Among them, brazing mainly relies on the high-temperature melting of the brazing material, spreading and wetting on the joint of the welded parent material, and finally forming a joint that is connected as a whole. Brazing generally has the problem of low joint strength in the welding of TC4 titanium alloy / GH4169 high-temperature alloy. This is because the strength of the brazing material itself is relatively low, not as good as that of titanium alloy and high-temperature alloy. More importantly, during the high-temperature brazing process, the problem of brittle intermetallic compounds is still inevitable. For diffusion welding, due to the diffusion of elements at high temperature, a brittle and hard intermetallic compound layer is still formed at the interface, making the welding strength low (less than 200MPa) and lacking application value. Only the addition of an intermediate layer can improve it, but this will bring about the problems of high cost and low work efficiency. For friction welding, due to the large difference in the high-temperature strength of the two metals, "plastic deformation mismatch" will occur during the welding process, which is manifested in the presence of long cracks and unwelded joints along the interface direction after welding, which significantly affects the mechanical properties of the joint.

[0005] At present, the welding of titanium alloy / high temperature alloy is mainly brazing and diffusion welding or friction welding with an intermediate layer. However, these methods have limited improvement on joint performance, and the addition of an intermediate layer increases the instability of the joint, and the process is complicated and costly. Therefore, it is necessary to develop a low-cost and simple welding process to achieve the welding of TC4 titanium alloy and GH4169 high temperature alloy. Summary of the invention

[0006] In view of the deficiencies in the above-mentioned background technology, the present invention mainly solves the problem of "plastic deformation mismatch" in the friction welding process. The present invention provides a TC4 titanium alloy / GH4169 high-temperature alloy dissimilar metal rotation friction welding method with preheating before welding. The method preheats the GH4169 high-temperature alloy to 980±10℃ before welding to soften the GH4169 with high high-temperature hardness, thereby solving the problem of "plastic deformation mismatch" at the interface during the welding process, and can significantly improve the welding strength of the two.

[0007] The object of the present invention is to provide a TC4 titanium alloy / GH4169 high temperature alloy dissimilar metal rotation friction welding method preheated before welding, comprising the following steps: The GH4169 high temperature alloy was preheated at 970-990°C, kept warm for 5-10 minutes, and then friction welded with the TC4 titanium alloy. During friction welding, the preheated GH4169 high temperature alloy was placed at the feed end of the friction welding machine, and the TC4 titanium alloy was used as the rotating end.

[0008] Preferably, during friction welding, the rotation speed is set to ≦600 rpm, the welding pressure is set to ≧300 MPa, and the upset pressure is set to ≧300 MPa.

[0009] Preferably, during friction welding, an axial shortening control welding method is used, and the axial shortening of the welding is controlled to be 5 mm.

[0010] Preferably, the heating rate during preheating is 5-10°C / min.

[0011] Preferably, during the preheating process, the preheating temperature is monitored by a thermocouple or an infrared thermometer; when induction heating is selected for preheating, a thermocouple or an infrared thermometer is used for temperature monitoring; when a muffle furnace is selected for preheating, a thermocouple is used for temperature monitoring.

[0012] Preferably, when a thermocouple is used for temperature monitoring, the measuring end of the thermocouple should be close to the surface of the workpiece; when an infrared thermometer is used for temperature monitoring, the infrared emissivity of the material should be calibrated to avoid inaccurate temperature measurement.

[0013] Preferably, the preheating is carried out by using a muffle furnace or induction heating. Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a TC4 titanium alloy / GH4169 high-temperature alloy dissimilar metal rotation friction welding method with preheating before welding. The present invention preheats the GH4169 high-temperature alloy before welding to soften the GH4169 with high high-temperature hardness, thereby solving the "plastic deformation mismatch" problem at the interface during the welding process, and can significantly improve the welding strength of the two. At the same time, it has the advantages of simple process and low cost, and is suitable for industrial mass production.

[0014] The present invention can realize the welding of dissimilar metals of difficult-to-weld materials TC4 titanium alloy / GH4169 high-temperature alloy at low cost and high efficiency, and can realize industrialized mass production.

[0015] The joint welding strength obtained by the method provided by the present invention is high: compared with traditional brazing, diffusion welding without an intermediate layer and direct friction welding (the welding joint strength is less than 200 MPa), the welding joint strength of this preheating method can reach more than 500 MPa. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is the schematic diagram of friction welding machine; Figure 2 For the preheated friction welding specimen; Figure 3 is the cross-sectional morphology of the joint; Figure 4 This is the joint tensile test curve. DETAILED DESCRIPTION

[0017] In order to enable those skilled in the art to better understand and implement the technical solution of the present invention, the present invention is further described below in conjunction with specific embodiments and drawings, but the embodiments are not intended to limit the present invention.

[0018] The present invention is based on the advantages of friction welding itself, which has high welding efficiency and low cost, and can be suitable for industrial mass automated production. If the problem of "plastic deformation mismatch" in the friction welding process can be solved, the application scope of TC4 titanium alloy / GH4169 high-temperature alloy will be greatly increased. The present invention provides a TC4 titanium alloy / GH4169 high-temperature alloy dissimilar metal rotation friction welding method preheated before welding. The present invention preheats the GH4169 high-temperature alloy before welding to soften the GH4169 with high high-temperature hardness, thereby solving the "plastic deformation mismatch" problem at the interface of the welding process, and can significantly improve the welding strength of the two. At the same time, it has the advantages of simple process and low cost, and is suitable for industrial mass production.

[0019] In order to achieve the above object, the present invention provides a TC4 titanium alloy / GH4169 high temperature alloy dissimilar metal rotation friction welding method preheated before welding, comprising the following steps: The GH4169 high temperature alloy was preheated at 970-990°C, kept warm for 5-10 minutes, and then friction welded with the TC4 titanium alloy. During friction welding, the preheated GH4169 high temperature alloy was placed at the feed end of the friction welding machine, and the TC4 titanium alloy was used as the rotating end.

[0020] The present invention preheats the GH4169 high-temperature alloy before welding to soften the GH4169 with high high-temperature hardness, thereby solving the "plastic deformation mismatch" problem at the interface during the welding process and significantly improving the welding strength of the two.

[0021] When friction welding is performed, the rotation speed is set to ≤ 600 rpm, the welding pressure is set to ≥ 300 MPa, and the forging pressure is set to ≥ 300 MPa. When friction welding is performed, the axial shortening control welding method is used, and the axial shortening of the welding is controlled to be 5 mm.

[0022] The heating rate during preheating is 5~10℃ / min. Muffle furnace or induction heating is used for preheating.

[0023] During the preheating process, the preheating temperature is monitored by a thermocouple or an infrared thermometer; when induction heating is selected for preheating, a thermocouple or an infrared thermometer is used for temperature monitoring; when a muffle furnace is selected for preheating, a thermocouple is used for temperature monitoring.

[0024] When using a thermocouple for temperature monitoring, the measuring end of the thermocouple should be close to the surface of the workpiece; when using an infrared thermometer for temperature monitoring, the infrared emissivity of the material should be calibrated to avoid inaccurate temperature measurement.

[0025] Exemplarily, a TC4 titanium alloy / GH4169 high temperature alloy dissimilar metal rotation friction welding method with preheating before welding comprises: Step 1) Before welding, preheat the GH4169 high temperature alloy by using a muffle furnace or induction heating.

[0026] Among them, preheating before welding can use tools such as muffle furnaces to preheat the GH4169 high-temperature alloy parts as a whole; induction heating and other forms can also be used to preheat the joints of the GH4169 to be welded locally. When using a muffle furnace for preheating, in order to ensure that the welded parts can be heated through, the recommended heating rate is 5 to 10 ° C / min. When using induction heating for preheating, a faster heating rate can be used.

[0027] Step 2) Use a thermocouple or infrared temperature measuring device to monitor the preheating temperature in real time.

[0028] Among them, during the preheating process, the preheating temperature should be monitored by thermocouples or infrared thermometers. When induction heating is used to heat the workpiece, it is recommended to use thermocouples or infrared thermometers for temperature monitoring; when a muffle furnace is used to heat the workpiece, it is recommended to use thermocouples for temperature monitoring. When thermocouples are used for temperature monitoring, the measuring end of the thermocouple should be close to the surface of the workpiece; when an infrared thermometer is used for temperature monitoring, pay attention to calibrating the infrared emissivity of the material to avoid inaccurate temperature measurement.

[0029] Step 3) When the preheating temperature reaches 980±10℃, stop heating and keep it warm for 5 to 10 minutes before performing friction welding.

[0030] Among them, 980±10℃ is selected because it is the common solution temperature of GH4169. Using this temperature for preheating before welding is equivalent to a solution heat treatment of the material, which will not cause performance degradation of the material. When the welded part reaches 980±10℃, it is not suitable to weld immediately. It should be kept warm for 5 minutes to make the temperature uniform and the workpiece heated through.

[0031] Step 4) Select welding parameters with high friction pressure and low speed to complete the entire welding process.

[0032] Among them, the friction welding process after preheating should choose a low speed (low friction line speed) and high pressure welding process. For example, the speed is ≤ 600rpm, the welding pressure is ≥ 300 MPa, and the top forging pressure is ≥ 300 MPa. The welding method with axial shortening control is preferred, and the axial shortening of the welding is controlled to 5 mm.

[0033] GH4169 high temperature alloy is selected as the feed end of the friction welding machine, and TC4 titanium alloy is selected as the rotating end. After the preheated material is taken out of the muffle furnace, friction welding should be carried out quickly to avoid a significant drop in the interface temperature.

[0034] GH4169 is used as the feed end because, on the one hand, it is difficult to place the GH4169 in a red-hot state (980°C) at the feed end; on the other hand, the GH4169 at the rotating end will cause faster heat loss, lower the sample temperature, and the thermal intensity of GH4169 will increase rapidly, which will significantly reduce the preheating treatment effect.

[0035] It should be noted that the experimental methods used in the present invention are all conventional methods unless otherwise specified; the reagents and materials used are all commercially available unless otherwise specified.

[0036] Example 1 A TC4 titanium alloy / GH4169 high temperature alloy dissimilar metal rotation friction welding method preheated before welding, comprising the following steps: Step 1) Before welding, preheat the GH4169 high temperature alloy by using a muffle furnace or induction heating.

[0037] Among them, TC4 titanium alloy and GH4169 high-temperature alloy bars with a specification of φ25 mm and a length of 100 mm were selected as the base materials for welding. Before welding, the surface to be welded was processed by lathe to ensure the surface flatness and surface roughness. Alcohol was used to scrub the surface to remove oil stains.

[0038] Based on the laboratory conditions, a muffle furnace is used to preheat the GH4169 high-temperature alloy before welding. In order to ensure that the welded parts can be heated through, the heating speed is 10℃ / min.

[0039] Step 2) Use a thermocouple or infrared temperature measuring device to monitor the preheating temperature in real time.

[0040] Among them, during the preheating process, the preheating temperature is monitored by a thermocouple, and the measuring end of the thermocouple should be close to the surface of the GH4169 high-temperature alloy rod.

[0041] Step 3) When the preheating temperature reaches 980°C, stop heating, keep warm for 5 minutes, and then perform friction welding. When the heated GH4169 high temperature alloy reaches 980°C, stop heating, keep warm for 5 minutes, so that the temperature of the cylindrical test rod is uniform and heated through.

[0042] Step 4) Select welding parameters with high friction pressure and low speed to complete the entire welding process.

[0043] Among them, the friction welding process after preheating selects a low speed and high pressure welding process. In this embodiment, the speed is 400 rpm, the welding pressure is 300 MPa, and the top forging pressure is 360 MPa. The welding method of axial shortening control is selected, and the axial shortening of the welding is controlled to be 5 mm.

[0044] See also Figure 1 As shown in the figure, in the friction welding machine, GH4169 high temperature alloy is selected as the feed end of the friction welding machine, and TC4 titanium alloy is used as the rotating end. After the preheated material is taken out of the muffle furnace, friction welding should be carried out quickly to avoid a significant drop in the interface temperature.

[0045] After the welding process is completed, remove the workpiece, place it on a refractory floor, and allow it to cool naturally.

[0046] Example 2 The same as Example 1, except that the preheating temperature is set to 970°C.

[0047] Example 3 The same as Example 1, except that the preheating temperature is set to 990°C.

[0048] In order to illustrate a TC4 titanium alloy / GH4169 high-temperature alloy dissimilar metal rotation friction welding method with preheating before welding provided by the present invention, Example 1 is taken as an example and described in conjunction with the accompanying drawings.

[0049] The experimental materials used were TC4 titanium alloy / GH4169 high temperature alloy, and the welding test of the two was carried out using the welding method of preheating before welding. The test results (joint macromorphology, joint tensile test curve) and actual data are shown in Figure 1-3 .

[0050] Figure 2 For the preheated friction welding specimen, after preheating treatment, the GH4169 side of the friction welding joint produced obvious macroscopic plastic deformation.

[0051] Figure 3 Figure 2 is the cross-sectional morphology of the joint. Figure (a) is the macroscopic morphology of the joint after preheating treatment, and Figure (b) is the macroscopic morphology of the joint without preheating treatment. By observing the macroscopic morphology of the joint, after preheating treatment, the deformation on the TC4 parent material side is mainly concentrated near the weld interface. The deformation on the GH4169 parent material side changes in a gradient, and the deformation gradually decreases as it moves away from the weld interface. The GH4169 side does not deform after preheating treatment, and the deformation is mainly concentrated on the TC4 side.

[0052] See also Figure 4 As shown, the welded TC4 titanium alloy / GH4169 high-temperature alloy joint provided in Example 1 improves the "plastic deformation mismatch" problem, and the difficult-to-deform GH4169 high-temperature alloy undergoes obvious plastic deformation, making the deformation of the GH4169 high-temperature alloy and the TC4 titanium alloy more coordinated. This welding method significantly improves the welding strength, and the joint strength reaches the 500 MPa level.

[0053] It should be noted that after preheat treatment, the GH4169 side of the joint is significantly deformed, the forming quality of the joint is significantly improved, and the joint strength is about 150 MPa without heat treatment, while the joint strength can reach 500 MPa after preheat treatment.

[0054] The present invention describes preferred embodiments and their effects. However, those skilled in the art may make additional changes and modifications to these embodiments once they are aware of the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0055] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A TC4 titanium alloy / GH4169 high temperature alloy dissimilar metal rotation friction welding method with preheating before welding, characterized in that: The following steps are involved: The GH4169 high temperature alloy was preheated at 970-990°C, kept warm for 5-10 minutes, and then friction welded with the TC4 titanium alloy. During friction welding, the preheated GH4169 high temperature alloy was placed at the feed end of the friction welding machine, and the TC4 titanium alloy was used as the rotating end.

2. The TC4 titanium alloy / GH4169 high temperature alloy dissimilar metal rotation friction welding method with preheating before welding according to claim 1 is characterized in that: During friction welding, set the rotation speed ≤ 600 rpm, welding pressure ≥ 300 MPa, and upsetting pressure ≥ 300 MPa.

3. The TC4 titanium alloy / GH4169 high temperature alloy dissimilar metal rotation friction welding method with preheating before welding according to claim 1 is characterized in that: During friction welding, the axial shortening control welding method is used, and the axial shortening of the welding is controlled to be 5mm.

4. The TC4 titanium alloy / GH4169 high temperature alloy dissimilar metal rotation friction welding method with preheating before welding according to claim 1 is characterized in that: The heating rate during preheating is 5~10℃ / min.

5. The TC4 titanium alloy / GH4169 high temperature alloy dissimilar metal rotation friction welding method with preheating before welding according to claim 1 is characterized in that: During the preheating process, the preheating temperature is monitored by a thermocouple or an infrared thermometer; when induction heating is selected for preheating, a thermocouple or an infrared thermometer is used for temperature monitoring; when a muffle furnace is selected for preheating, a thermocouple is used for temperature monitoring.

6. The TC4 titanium alloy / GH4169 high temperature alloy dissimilar metal rotation friction welding method with preheating before welding according to claim 5 is characterized in that: When using a thermocouple for temperature monitoring, the thermocouple measuring end should be close to the workpiece surface; When using an infrared thermometer for temperature monitoring, the infrared emissivity of the material must be calibrated to avoid inaccurate temperature measurement.

7. The TC4 titanium alloy / GH4169 high temperature alloy dissimilar metal rotation friction welding method with preheating before welding according to claim 1 is characterized in that: The preheating method is a muffle furnace or induction heating.

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