Welding device for preventing oxidation of titanium alloy welding area and method and application thereof

Abstract

The invention belongs to the technical field of titanium alloy welding, and particularly discloses a welding device for preventing oxidation of a titanium alloy welding area and a method and application thereof.The device comprises a carrying table and a welding machine, a welding seam protection plate is arranged on the carrying table and located on a bottom welding seam of a titanium alloy workpiece, and a welding seam protection cover is arranged on a top welding seam; the welding seam protection cover is arranged in a matched mode according to the shape of the workpiece, gas conveying pipelines are arranged among the workpiece, the welding gun protection cover for fixing the welding gun of the welding machine, the welding seam protection plate, the welding seam protection cover and the argon bottle, and a servo adjusting valve is arranged on each pipeline. And a temperature measuring instrument and an oxygen sensor which are arranged on the workpiece and a gas distributor on the argon bottle are connected with each servo regulating valve through a PLC (Programmable Logic Controller) control system and are used for dynamically regulating the argon flow in a welding area. According to the method, a welding area can be effectively prevented from being in contact with oxygen, the welding quality is greatly improved, and the strict requirements of the high-end field on titanium alloy welding products (such as jackets used for hot isostatic pressing) are met.

Description

Technical Field

[0001] The present invention belongs to the technical field of titanium alloy welding, and particularly relates to a welding device, method and application for preventing oxidation in the welding area (weld seam and heat affected zone) of titanium alloy. Background Art

[0002] Titanium alloy is widely used in the fields of aerospace, ocean engineering, medical devices, etc. due to its low density (4.5 g / cm 3 ~4.8 g / cm 3 , about 40% lighter than steel), high specific strength, excellent corrosion resistance and biocompatibility. However, during the welding process of titanium alloy, due to the extremely high chemical activity of titanium element, the weld seam and heat affected zone are extremely easy to react with oxygen in the air at high temperature to form a titanium oxide layer, resulting in a decrease in weld strength, a reduction in toughness (increasing the risk of brittle fracture), and a deterioration in corrosion resistance, seriously affecting the service life of the workpiece. For example, in the preparation of the cladding of metal powder hot isostatic pressing precision parts, oxidation in the welding area will cause the failure of the cladding sealing performance, leading to metal powder pollution in the high-pressure inert gas environment, and finally resulting in defects such as excessive porosity and poor interface bonding in the hot isostatic pressing products, significantly reducing the material density and the stability of mechanical properties.

[0003] To address the above challenges, the existing technologies mainly adopt two methods when welding titanium alloy: local argon protection or vacuum welding. Local argon protection attempts to form an inert gas protection environment around the weld seam by delivering argon to the welding area. However, this method has the problem of uneven gas coverage, making it difficult to ensure that the entire welding area can be effectively protected, resulting in unstable protection effect, large gas consumption and high production cost. Vacuum welding, on the other hand, places the welding process in a vacuum environment to fundamentally eliminate the contact with oxygen. However, this method requires complex vacuum equipment, not only with high equipment purchase cost, but also high operation and maintenance costs, and it is difficult to meet the welding requirements of large-size workpieces, restricting its application in actual production.

[0004] In addition, the existing welding devices generally lack the ability to monitor and dynamically control the temperature and oxygen concentration in real time. During the welding process, operators can only rely on manual experience to adjust welding parameters, making it difficult to accurately control according to the actual situation, resulting in the protection effect depending on the manual skill level and insufficient reliability. Moreover, in the design of the weld protection device in the existing technology, there is a lack of adaptability to different weld forms and complex working conditions, making it difficult to meet the diverse production requirements.

[0005] In summary, there are many deficiencies in the existing titanium alloy welding technologies in preventing oxidation in the weld seam and heat affected zone. There is an urgent need for an efficient, economical and intelligent solution to improve the welding quality and production efficiency of titanium alloy and promote its wider application in high-end fields.

[0006] In view of this, the present invention is hereby proposed. Summary of the Invention

[0007] The object of the present invention is to overcome the above-mentioned disadvantages of the prior art, and provide a welding device, method and application for preventing oxidation of the welding area of titanium alloy. The present invention is mainly used to solve the problem of oxidation in the weld and heat affected zone during the welding process of titanium alloy, so as to achieve the purpose of improving the welding quality and efficiency of titanium alloy.

[0008] The object of the present invention is solved by the following technical solutions:

[0009] In the first aspect, the present invention provides a welding device for preventing oxidation of the welding area of titanium alloy, including a stage for carrying the titanium alloy workpiece to be welded, and a welding machine for welding the titanium alloy workpiece. A weld protection plate is provided on the stage and at the bottom welding area of the titanium alloy workpiece, and a weld protection cover is provided at the top welding area of the titanium alloy workpiece, and the weld protection cover is arranged in a matching manner according to the shape of the titanium alloy workpiece;

[0010] Among them, the first gas connection pipe arranged on the titanium alloy workpiece is connected to an argon gas cylinder through a first gas transmission pipeline; the welding torch of the welding machine is installed on the welding torch protection cover, and the second gas connection pipe on the welding torch protection cover is connected to the argon gas cylinder through a second gas transmission pipeline; a plurality of first air outlet holes are evenly opened on the top surface of the weld protection plate, and the third gas connection pipe arranged on the weld protection plate is connected to the argon gas cylinder through a third gas transmission pipeline; a plurality of second air outlet holes are evenly opened on the surface of the weld protection cover facing the welding area, and the fourth gas connection pipe arranged on the weld protection cover is connected to the argon gas cylinder through a fourth gas transmission pipeline;

[0011] The argon gas cylinder supplies gas to the welding area through four gas transmission pipelines, and a servo regulating valve is installed on each pipeline. The temperature measuring instrument and oxygen sensor arranged on the titanium alloy workpiece, and the gas distributor arranged on the argon gas cylinder are connected to each servo regulating valve through a PLC control system for dynamically adjusting the argon gas flow in the welding area.

[0012] Further, the welding torch protection cover includes a main housing, the upper part of the main housing is respectively provided with a second gas connection pipe and a clamp, and the lower edge is provided with a sealing strip that fits with both sides of the weld when welding the titanium alloy workpiece;

[0013] Among them, the second gas connection pipe is connected to the welding machine and the argon gas cylinder through a second gas transmission pipeline, and the clamp is used for fixedly installing the welding torch of the welding machine.

[0014] Further, the servo regulating valve installed on the second gas transmission pipeline is located between the welding machine and the argon gas cylinder.

[0015] Further, the sealing strip is made of an elastic material.

[0016] Further, the weld protection plate, the weld protection cover and the main housing are respectively made of a metal composite material resistant to temperatures above 1500 °C, and spiral mesh argon gas delivery pipes are evenly distributed inside the weld protection plate and the weld protection cover.

[0017] Further, the carrier table is a rotating carrier table, and a plurality of sliders are provided at the bottom of the rotating carrier table, and the plurality of sliders are movably installed on a horizontally arranged slide rail.

[0018] Further, a pressure gauge is installed on the argon gas cylinder.

[0019] In a second aspect, the present invention provides a welding method for preventing oxidation of a titanium alloy welding area. The welding method is based on the above-mentioned welding device and includes the following steps:

[0020] Step 1: Pretreatment of titanium alloy workpieces

[0021] Adopt a combination of wiping with an organic solvent and ultrasonic cleaning to remove impurities on the surface of the titanium alloy workpiece, and use it after drying.

[0022] Step 2: Welding preparation

[0023] Place the titanium alloy workpiece pretreated in Step 1 on the carrier table, and according to the welding area, a weld protection plate is provided on the carrier table and at the bottom welding area of the titanium alloy workpiece, or a weld protection cover is provided at the top welding area of the titanium alloy workpiece, and a temperature measuring instrument and an oxygen sensor are arranged on the titanium alloy workpiece. At the same time, connect the four pipes according to the connection relationship between each pipeline and the corresponding component, and install the welding torch of the welding machine on the welding torch protection cover; then open the first gas delivery pipeline, and the third gas delivery pipeline or the fourth gas delivery pipeline to deliver argon to the welding area;

[0024] Step 3: Welding operation

[0025] Adopt the MIG welding method for welding. Open the second gas delivery pipeline and the welding machine, and make the welding torch move along the weld under the protection of the welding torch protection cover for welding. During the welding process, change the position of the titanium alloy workpiece through the carrier table to assist welding until the welding is completed; if during the welding process, the temperature measuring instrument monitors that the temperature of the welding area exceeds the set threshold, and / or the oxygen sensor monitors that the oxygen content in the welding area exceeds the set threshold, the PLC control system controls the gas distributor and each servo regulating valve to adjust and increase the argon gas flow rate in the welding area; otherwise, reduce the argon gas flow rate in the welding area;

[0026] Step 4: Two-stage cooling

[0027] The first stage: within the first 30 s, control the argon gas flow rate in the welding area at 18 L / min to 22 L / min, and use forced convection for cooling;

[0028] The second stage: from 30 s to 120 s, control the argon gas flow rate in the welding area at 8 L / min to 12 L / min, and at the same time cooperate with a water-cooled copper backing to inhibit the growth of the oxide layer in the welding area.

[0029] Furthermore, in step 3, the MIG welding method includes root pass welding, filler pass welding, and capping welding;

[0030] Among them, the welding parameters for the root pass welding are: welding current 110 A to 140 A, welding voltage 10 V to 11 V, welding speed 10 cm / min to 15 cm / min, and gas flow rate 25 L / min to 30 L / min;

[0031] The welding parameters for the filler pass welding are: welding current 120 A to 145 A, welding voltage 20 V to 30 V, welding speed 60 cm / min to 65 cm / min, and gas flow rate 35 L / min to 40 L / min;

[0032] The welding parameters for the capping welding are: welding current 120 A to 145 A, welding voltage 20 V to 30 V, welding speed 60 cm / min to 65 cm / min, and gas flow rate 30 L / min to 35 L / min.

[0033] In a third aspect, the present invention also provides an application based on the above-mentioned welding device. The welding device is used for welding a titanium alloy sheath, and the titanium alloy sheath includes a cylindrical sheath, an annular sheath, and other shaped titanium alloy sheaths;

[0034] When the titanium alloy sheath is a cylindrical sheath, the weld protection cover is an annular shell structure, the second air outlet is opened on the inner wall of the annular shell structure, and the weld protection cover is sleeved outside the cylindrical sheath during welding;

[0035] When the titanium alloy sheath is an annular sheath, the weld protection cover is a cylindrical shell structure, the second air outlet is opened on the outer wall of the cylindrical shell structure, and the weld protection cover is sleeved inside the annular sheath during welding.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] Through the organic integration of multi-channel gas collaborative protection, dynamic closed-loop control, adaptive structure design, and gradient cooling technology, the present invention systematically solves the oxidation problem in the welding area (weld and heat-affected zone) of titanium alloys from four dimensions: gas coverage, real-time regulation, structural adaptation, and post-treatment. Meanwhile, it improves the welding quality and performance of titanium alloy workpieces, meeting the strict requirements for titanium alloy welded products (such as the jackets used in hot isostatic pressing) in high-end fields. Specifically, the present invention has the following characteristics:

[0038] Firstly, multi-dimensional argon collaborative protection to enhance the coverage effect of inert gas: The present invention designs four gas delivery pipelines to provide comprehensive argon protection for the welding area. Specifically, the gas connection pipes of the workpiece, welding torch protection cover, weld protection plate, and weld protection cover are all connected to the argon gas cylinder through independent pipelines. Combining the design of the spiral mesh argon gas delivery pipelines inside the weld protection plate and the weld protection cover, it can achieve three-dimensional and comprehensive protection for different welding areas.

[0039] Secondly, dynamic closed-loop regulation to achieve precise protection: The present invention arranges temperature sensors and oxygen sensors on the titanium alloy workpiece and connects them to the gas distributor and servo control valve through the PLC control system. It can monitor the temperature and oxygen concentration in the welding area in real time. When the welding heat input causes the temperature to rise or the local oxygen content is abnormal, it can automatically and precisely adjust the argon gas flow according to the actual situation, getting rid of the dependence on manual experience, improving the reliability and stability of the welding process, and ensuring the consistency of welding quality.

[0040] Thirdly, strong adaptability: The weld protection cover of the present invention can be set according to the shape of the titanium alloy workpiece, and can meet the welding requirements of workpieces with different shapes and sizes (such as jackets of cylindrical, annular and other shapes) according to actual requirements.

[0041] Fourthly, gradient cooling control to inhibit the formation of oxide layer: The two-stage cooling process of the present invention, in the first stage (0 - 30s), high-flow argon gas forced convection is used to quickly reduce the temperature of the welding area and shorten the high-temperature exposure time; in the second stage (30s - 120s), low-flow argon gas is combined with a water-cooled copper gasket to control the cooling rate, effectively inhibiting the growth of the oxide layer in the welding area and further improving the welding quality. Description of the Drawings

[0042] The drawings here are incorporated into the specification and form a part of this specification, and are used together with the specification to explain the principles of the present invention.

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0044] Figure 1 It is a schematic connection diagram of the welding device for preventing oxidation of the titanium alloy welding area in the present invention;

[0045] Figure 2 It is a schematic structural diagram of the welding torch protective cover in the welding device of the present invention;

[0046] Figure 3 It is a structural diagram of the cylindrical sleeve welded in Example 1 of the present invention (the bold part is the weld seam);

[0047] Figure 4 It is a schematic diagram of the welding device when welding the cylindrical sleeve in Example 1 of the present invention;

[0048] Figure 5 It is a structural diagram of the circular ring-shaped sleeve welded in Example 2 of the present invention (the bold part is the weld seam);

[0049] Figure 6 It is a schematic structural diagram of the welding device when welding the circular ring-shaped sleeve in Example 2 of the present invention;

[0050] Figure 7 It is a half-sectional schematic structural diagram of the welding device when welding the circular ring-shaped sleeve in Example 2 of the present invention.

[0051] Wherein: 1 is a stage; 2 is a welding machine; 3 is a weld protection plate; 4 is a weld protection cover; 5 is a first gas delivery pipeline; 6 is an argon gas cylinder; 7 is a welding torch protective cover; 8 is a second gas delivery pipeline; 9 is a third gas delivery pipeline; 10 is a fourth gas delivery pipeline; 11 is a servo regulating valve; 12 is a temperature measuring instrument; 13 is an oxygen sensor; 1-1 is a slider; 2-1 is a welding torch; 3-1 is a first air outlet; 3-2 is a third gas connecting pipe; 4-1 is a second air outlet; 4-2 is a fourth gas connecting pipe; 6-1 is a gas distributor; 6-2 is a pressure gauge; 7-1 is a second gas connecting pipe; 7-2 is a main housing; 7-3 is a clamp; 7-4 is a sealing strip; A is a titanium alloy workpiece; A1 is a first gas connecting pipe. Specific Embodiments

[0052] Here, the exemplary embodiments will be described in detail, and the examples are shown in the drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. On the contrary, they are merely examples of the devices consistent with some aspects of the present invention detailed in the appended claims.

[0053] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the drawings and embodiments.

[0054] AsFigure 1 As shown in the figure, a welding device for preventing oxidation of the welding area of a titanium alloy provided by the present invention includes a stage 1 for carrying the titanium alloy workpiece A to be welded and a welding machine 2 for welding the titanium alloy workpiece A. A weld protection plate 3 is provided on the stage 1 and at the bottom welding area of the titanium alloy workpiece A, and a weld protection cover 4 is provided at the top welding area of the titanium alloy workpiece A. It should be specially noted that the weld protection cover 4 is precisely matched and designed according to the specific shape of the titanium alloy workpiece A, and its purpose is to ensure that the top welding area is within the protection range of the weld protection cover 4.

[0055] Preferably, the stage 1 adopted in the present invention is a rotating stage. The rotating stage mainly consists of an upper and a lower support plate and a rotating bearing located between the upper and lower support plates. The driving form of the rotating stage is flexible. It can be driven manually or automatically. The present invention does not make specific restrictions on this, as long as it can ensure that the upper support plate can rotate freely by 360° to facilitate the welding operation of the rotary workpiece. In addition, to further improve the convenience of the welding operation, a plurality of sliders 1-1 are evenly arranged at the bottom of the lower support plate of the rotating stage. These sliders 1-1 are movably installed on the horizontally arranged slide rails. In this way, the entire rotating stage can move linearly along the slide rails. This design is extremely beneficial for the welding operation of longer workpieces and greatly expands the applicability of the welding device in terms of different workpiece sizes and shapes.

[0056] Further, a first gas connection pipe A1 communicating with the inside thereof is provided on the titanium alloy workpiece A, and it is connected to the argon gas cylinder 6 through the first gas transmission pipeline 5; the welding torch 2-1 of the welding machine 2 is installed on the welding torch protection cover 7, and the second gas connection pipe 7-1 on the welding torch protection cover 7 is connected to the argon gas cylinder 6 through the second gas transmission pipeline 8; a plurality of first air holes 3-1 are evenly formed on the top surface of the weld protection plate 3, and the size of the air holes can be set according to actual conditions. For example, in the present invention, the diameter is set to 0.8 mm and the spacing is 6 mm. The third gas connection pipe 3-2 provided on the weld protection plate 3 is connected to the argon gas cylinder 6 through the third gas transmission pipeline 9; a plurality of second air holes 4-1 are evenly formed on the surface of the weld protection cover 4 facing the welding area, and the fourth gas connection pipe 4-2 provided on the weld protection cover 4 is connected to the argon gas cylinder 6 through the fourth gas transmission pipeline 10. The argon gas cylinder 6 supplies argon gas to the welding area through four gas transmission pipelines (5, 8, 9, 10), and a servo regulating valve 11 (a flow regulating valve driven by a servo motor) is installed on each pipeline; a thermometer 12 and an oxygen sensor 13 are reasonably arranged on the titanium alloy workpiece A, and the thermometer 12, the oxygen sensor 13 and the gas distributor 6-1 provided on the argon gas cylinder 6 are connected to each servo regulating valve 11 through a PLC control system so as to dynamically adjust the argon gas flow in the welding area according to actual conditions. In this way, when welding the titanium alloy workpiece A, the oxidation phenomenon in the welding area (including the weld and the heat affected zone) can be effectively prevented, thereby meeting the strict requirements for the high quality of titanium alloy welded products (such as the jackets used in hot isostatic pressing) in high-end fields.

[0057] Specifically, the structure of the welding torch protection cover 7 provided by the present invention is as Figure 2As shown in the figure, it mainly includes a main housing 7-2. A second gas connection pipe 7-1 and a clamp 7-3 are respectively arranged on the upper part of the main housing 7-2, and a sealing strip 7-4 is arranged on the lower edge. When welding a titanium alloy workpiece A, the sealing strip 7-4 can be closely attached to both sides of the weld seam. Among them, the second gas connection pipe 7-1 is connected to a welding machine 2 and an argon gas cylinder 6 through a second gas transmission pipeline 8; the main housing 7-2, a weld protection plate 3 and a weld protection cover 4 are all made of a metal composite material with a temperature resistance of over 1500°C. For example, it is made by compounding a high-temperature resistant metal alloy (such as Inconel 625) with ceramic fibers. This material has a temperature resistance of ≥1600°C. Further, since the welding torch protection cover 7 accompanies the entire welding process, in order to further improve the temperature resistance performance, an antioxidant coating is sprayed on the inner wall of the main housing 7-2. The coating composition is Al2O3-20% Y2O3, with a thickness of 50μm - 100μm, making its temperature resistance ≥1800°C. Additionally, a plurality of evenly distributed air holes are opened on the inner wall of the main housing 7-2 for the protective gas introduced by the second gas connection pipe 7-1 to be evenly ejected; the clamp 7-3 is used to fixedly install the welding torch 2-1 of the welding machine 2, and a servo regulating valve 11 installed on the second gas transmission pipeline 8 is located between the welding machine 2 and the argon gas cylinder 6; the sealing strip 7-4 is made of an elastic high-temperature resistant material, such as high-temperature resistant composite silicone, so that during welding, the sealing strip 7-4 can be closely attached to the surfaces on both sides of the weld seam of the titanium alloy workpiece A to form a relatively closed space. During welding, the protective gas argon is introduced into this space through the second gas connection pipe 7-1, thereby effectively preventing external air from infiltrating into the welding area. In addition, the shape of the welding torch protection cover 7 can be set as rectangular or circular. The rectangular cover is suitable for butt welds, and its size is preferably adjustable, with a coverage range not less than the weld width plus 20mm; the annular cover is used for circumferential welds, and its inner diameter tolerance is controlled within ±0.5mm.

[0058] To ensure the uniformity of the argon gas flow rate in the welding area, in the present invention, spiral mesh argon gas transmission pipelines (as Figure 7 shown) are evenly distributed in the cavities inside the weld protection plate 3 and the weld protection cover 4, and the spiral mesh argon gas transmission pipelines are connected to the corresponding gas connection pipes. Generally, the transmission pipes are made of copper pipes. Considering that the area of the weld protection plate 3 is relatively large, in order to enable the argon gas entering it to quickly and evenly discharge through the first air holes 3-1 to protect the welding area, a third gas connection pipe 3-2 is respectively arranged on the left and right sides of the weld protection plate 3 to further ensure the even spraying of argon gas.

[0059] Preferably, a pressure gauge 6-2 is installed on the argon gas cylinder 6 of the present invention to keep track of the remaining amount of argon gas at any time, replenish the argon gas in a timely manner, ensure the stability of the argon gas supply during the welding process, and thus better maintain the protection effect on the welding area. In addition, it should be noted that the argon gas used in the present invention is high-purity argon gas, and its purity requirement is greater than or equal to 99.999%. Further preferably, the pressure gauge 6-2 can be connected to the warning device through the PLC control system. Once the remaining amount of argon gas is lower than the preset safety threshold, the pressure gauge 6-2 detects the pressure change and transmits the signal to the PLC control system. The PLC control system then responds and triggers the connected warning device to timely remind the operator in a way such as sound and light alarm. This automated warning mechanism greatly improves the timeliness and accuracy of the monitoring of the remaining amount of argon gas, further ensures the smooth progress of the welding process, and effectively avoids adverse effects on the welding quality caused by the failure of manual negligence to detect the insufficient argon gas in a timely manner.

[0060] In addition, based on the above welding device, the present invention also provides a welding method for preventing oxidation of the titanium alloy welding area, which specifically includes the following steps:

[0061] Step 1. Pretreatment of the titanium alloy workpiece A

[0062] Adopt a combination of wiping with organic solvents and ultrasonic cleaning to remove impurities (including oil stains, oxides, etc.) on the surface of the titanium alloy workpiece A. After drying, detect the surface cleanliness by laser scanning. After ensuring that it meets the welding process requirements, it is ready for use.

[0063] Step 2. Welding preparation

[0064] Place the titanium alloy workpiece A pretreated in Step 1 on the stage 1, and according to the welding area, a weld protection plate 3 is provided on the stage 1 and at the bottom welding area of the titanium alloy workpiece A, or a weld protection cover 4 is provided at the top welding area of the titanium alloy workpiece A. At the same time, a thermometer 12 and an oxygen sensor 13 are arranged on the titanium alloy workpiece A. Then, connect the four gas delivery pipelines (5, 8, 9, 10) according to the connection relationship between each pipeline and the corresponding component, and install the welding torch 2-1 of the welding machine 2 on the welding torch protection cover 7; then turn on the first gas delivery pipeline 5, and the third gas delivery pipeline 9 or the fourth gas delivery pipeline 10 to deliver argon gas to the welding area; make the welding area of the titanium alloy workpiece A in a pure argon gas protection state.

[0065] Step 3. Welding operation

[0066] Weld using the MIG welding method. Turn on the second gas delivery pipeline 8 and the welding machine 2, and move the welding torch 2-1 along the weld under the protection of the welding torch protective cover 7 for welding. During the welding process, change the position of the titanium alloy workpiece A through the carrier table 1 to assist welding until the welding is completed. If during the welding process, the thermometer 12 monitors that the temperature in the welding area exceeds the set threshold (such as the temperature exceeds 650 °C), and / or the oxygen sensor 13 monitors that the oxygen content in the welding area exceeds the set threshold (such as the oxygen concentration is greater than 0.01%), the PLC control system controls the gas distributor 6-1 and each servo regulating valve 11 to adjust and increase the argon gas flow rate in the welding area (such as increasing the argon gas flow rate to 40 L / min) to quickly replace the contaminated gas to ensure the welding quality; otherwise, reduce the argon gas flow rate in the welding area to the lower limit of 20 L / min to reduce gas consumption and at the same time ensure that the oxygen concentration and temperature are within a reasonable range.

[0067] Step 4: Two-stage cooling

[0068] First stage: Within the first 30 s, control the argon gas flow rate in the welding area at 18 L / min to 22 L / min for forced convection cooling;

[0069] Second stage: From 30 s to 120 s, control the argon gas flow rate in the welding area at 8 L / min to 12 L / min, and at the same time cooperate with the water-cooled copper backing to inhibit the growth of the oxide layer in the welding area.

[0070] Specifically, in step 3, the MIG welding method includes root pass welding, fill pass welding, and cap pass welding. Among them, the welding parameters for root pass welding are: welding current 110 A to 140 A, welding voltage 10 V to 11 V, welding speed 10 cm / min to 15 cm / min, gas flow rate 25 L / min to 30 L / min; the welding parameters for fill pass welding are: welding current 120 A to 145 A, welding voltage 20 V to 30 V, welding speed 60 cm / min to 65 cm / min, gas flow rate 35 L / min to 40 L / min; the welding parameters for cap pass welding are: welding current 120 A to 145 A, welding voltage 20 V to 30 V, welding speed 60 cm / min to 65 cm / min, gas flow rate 30 L / min to 35 L / min. During actual welding, according to the specifications of the titanium alloy workpiece A to be welded (such as the thickness of the welding object, etc.), refer to Table 1 below and select one or at least two combination methods for welding to meet the welding requirements of different titanium alloy workpiece A welds.

[0071] Table 1 Welding parameters for root pass welding, fill pass welding, and cap pass welding

[0072]

[0073] To further verify the efficacy of the welding device of the present invention, the inventor of the present invention conducted the following specific tests:

[0074] Example 1

[0075] As Figure 3 shown, in this embodiment, a TC4 titanium alloy cylindrical jacket with a thickness of 6 mm needs to be welded. Since the jacket is cylindrical, the weld protection cover 4 adapted thereto is a ring-shaped shell structure. The second air outlet 4-1 is opened on the inner wall of the ring-shaped shell structure, and the height of the ring-shaped shell structure is slightly higher than that of the jacket. When welding the annular weld (black thickened part) at the top of the jacket, the weld protection cover 4 of the ring-shaped shell structure is sleeved outside the cylindrical jacket, and its structure is as Figure 4 shown. The specific welding process is as follows:

[0076] 1) Remove the impurities on the surface of the TC4 titanium alloy cylindrical jacket by a combination of wiping with organic solvents and ultrasonic cleaning, and dry it for later use;

[0077] 2) Place the TC4 titanium alloy cylindrical jacket pretreated in step 1) on the stage 1, and a weld protection plate 3 is provided on the stage 1 and at the welding area at the bottom of the jacket according to the welding area, or a weld protection cover 4 of a ring-shaped shell structure is provided outside the jacket, and a thermometer 12 and an oxygen sensor 13 are arranged on the jacket. At the same time, connect the four gas transmission pipelines (5, 8, 9, 10) according to the connection relationship between each pipeline and the corresponding component, and install the welding torch 2-1 of the welding machine 2 on the welding torch protection cover 7; when welding the annular weld at the top of the jacket, open the first gas transmission pipeline 5 and the fourth gas transmission pipeline 10 to convey argon to the top welding area; if welding the weld at the bottom of the jacket, remove the weld protection cover 4, and open the first gas transmission pipeline 5 and the third gas transmission pipeline 9 to convey argon to the bottom welding area; the initial argon flow rate is 30 L / min to 35 L / min to form a positive pressure protection environment;

[0078] 3) Weld by MIG welding method (in this embodiment, the top annular weld is taken as an example). Open the second gas transmission pipeline 8 and the welding machine 2, and make the welding torch 2-1 move along the top annular weld under the protection of the welding torch protection cover 7 for welding, and change the position of the titanium alloy workpiece A by rotating the stage 1 during the welding process to assist welding until the welding is completed; if during the welding process, the thermometer 12 monitors that the temperature of the welding area rises to 650 °C, the PLC control system automatically increases the argon flow rate in the welding area, that is, dynamically adjusts the argon flow rate (20 L / min to 40 L / min) through the PID algorithm to ensure that the oxygen concentration during the whole welding process is ≤ 0.01%. The welding parameters in the actual welding process are specifically selected according to Table 1;

[0079] 4) After the welding of the circumferential weld at the top of the shroud is completed, it is cooled in two stages. The first stage: within the first 30 s, control the argon flow rate in the welding area at 20 L / min for forced convection cooling; the second stage: from 30 s to 120 s, control the argon flow rate in the welding area at 10 L / min, and at the same time cooperate with a water-cooled copper backing (temperature ≤ 100 °C) to inhibit the growth of the oxide layer in the welding area. After inspection, the surface of the weld is silver-white without oxidation color. The measured thickness of the weld oxide layer is 1.8 μm, and the width of the heat-affected zone is 1.3 mm, which is 60% lower than that of the traditional process. Moreover, the tensile strength of the weld is 11% higher than that of the traditional process.

[0080] Example 2

[0081] As Figure 5 shown, in this example, a circular shroud made of TC4 titanium alloy with a thickness of 10 mm needs to be welded. Since the shroud is circular, the weld protection cover 4 adapted to it is a cylindrical shell structure. The second air outlet 4-1 is opened on the outer wall of the cylindrical shell structure, and the height of the cylindrical shell structure is slightly higher than that of the shroud. When welding the circumferential weld at the top of the shroud, the cylindrical weld protection cover 4 of the shell structure is arranged inside the circular shroud of TC4 titanium alloy, and the structure is as Figure 6 、 7 shown. The specific welding process is the same as that of Example 1. The welding parameters can be selected from Table 1 according to the actual situation. Finally, after welding and two-stage cooling are completed and inspected, the surface of the weld is silver-white without oxidation color. The measured thickness of the weld oxide layer is 1.6 μm, and the width of the heat-affected zone is 1.2 mm, which is 65% lower than that of the traditional process. The tensile strength of the weld reaches 980 MPa, and its strength is 12% higher than that of the traditional process.

[0082] In summary, when the present invention welds titanium alloy workpieces, a weld protection plate is provided at the bottom of the welding area according to the welding area, or a weld protection cover is provided in the welding area at the top of the titanium alloy workpiece, and the weld protection cover is matched according to the shape of the titanium alloy workpiece. Before welding operation, high-purity protective gas argon is introduced into the inner cavity of the titanium alloy workpiece and the weld protection plate or the weld protection cover in advance according to different welding positions, and in this way, the air around the welding area is effectively replaced, creating a low-oxygen environmental condition for the welding work. In addition, during welding, the welding torch is in the effective protection of the welding torch protection cover. The bottom of the welding torch protection cover is closely attached to both sides of the weld through a sealing strip, and a protective gas is continuously introduced into the welding torch protection cover during the welding process. This design greatly reduces the contact opportunity between the welding part and the air.

[0083] Through the above settings, the present invention avoids the oxidation phenomenon of the titanium alloy welding area (weld seam and heat affected zone) during the welding process. It not only significantly improves the forming effect of the weld seam, making the appearance of the weld seam smoother and more beautiful, but also effectively guarantees the welding quality of the weld seam, meeting the strict quality requirements for titanium alloy welded products in high-end fields. In addition, the present invention is also reasonably provided with a temperature measuring instrument and an oxygen sensor connected to the PLC control system on the titanium alloy workpiece, which can obtain the temperature and oxygen content data of the welding area in real time and accurately, and then dynamically adjust the argon flow rate in the welding area through the PLC control system, realizing the intelligent and precise control of the welding process.

[0084] The above are only specific embodiments of the present invention, enabling those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention.

[0085] It should be understood that the present invention is not limited to the above-described content and can be variously modified and changed without departing from its scope. The scope of the present invention is only limited by the appended claims.

Claims

1. A welding device for preventing oxidation of the welding area of titanium alloy, characterized in that, It includes a stage (1) for carrying the titanium alloy workpiece (A) to be welded, and a welding machine (2) for welding the titanium alloy workpiece (A). A weld protection plate (3) is provided on the stage (1) and at the bottom welding area of the titanium alloy workpiece (A), and a weld protection cover (4) is provided at the top welding area of the titanium alloy workpiece (A), and the weld protection cover (4) is arranged in a matching manner according to the shape of the titanium alloy workpiece (A); Among them, the first gas connection pipe (A1) provided on the titanium alloy workpiece (A) is connected to an argon gas cylinder (6) through a first gas transmission pipeline (5); the welding torch (2-1) of the welding machine (2) is installed on a welding torch protection cover (7), and the second gas connection pipe (7-1) on the welding torch protection cover (7) is connected to the argon gas cylinder (6) through a second gas transmission pipeline (8); a plurality of first air outlet holes (3-1) are evenly opened on the top surface of the weld protection plate (3), and the third gas connection pipe (3-2) provided on the weld protection plate (3) is connected to the argon gas cylinder (6) through a third gas transmission pipeline (9); a plurality of second air outlet holes (4-1) are evenly opened on the surface of the weld protection cover (4) facing the welding area, and the fourth gas connection pipe (4-2) provided on the weld protection cover (4) is connected to the argon gas cylinder (6) through a fourth gas transmission pipeline (10); The argon gas cylinder (6) supplies gas to the welding area through four gas transmission pipelines (5, 8, 9, 10), and a servo regulating valve (11) is installed on each pipeline. The temperature measuring instrument (12) and oxygen sensor (13) arranged on the titanium alloy workpiece (A), and the gas distributor (6-1) provided on the argon gas cylinder (6) are connected to each servo regulating valve (11) through a PLC control system for dynamically adjusting the argon gas flow in the welding area.

2. The welding device for preventing oxidation of the titanium alloy welding area according to claim 1, characterized in that, The welding torch protection cover (7) includes a main housing (7-2). The upper part of the main housing (7-2) is respectively provided with a second gas connection pipe (7-1) and a clamp (7-3), and the lower edge is provided with a sealing strip (7-4) that fits against both sides of the weld when welding the titanium alloy workpiece (A); Among them, the second gas connection pipe (7-1) is connected to the welding machine (2) and the argon gas cylinder (6) through a second gas transmission pipeline (8), and the clamp (7-3) is used for fixedly installing the welding torch (2-1) of the welding machine (2).

3. The welding device for preventing oxidation of the titanium alloy welding area according to claim 2, characterized in that, The servo regulating valve (11) installed on the second gas transmission pipeline (8) is located between the welding machine (2) and the argon gas cylinder (6).

4. The welding device for preventing oxidation of the titanium alloy welding area according to claim 2, characterized in that, The sealing strip (7-4) is made of an elastic material.

5. The welding device for preventing oxidation of the titanium alloy welding area according to claim 2, wherein, The weld protection plate (3), weld protection cover (4) and main housing (7-2) are respectively made of metal composite materials with a temperature resistance of more than 1500 °C, and spiral mesh argon gas transmission pipelines are evenly distributed inside the weld protection plate (3) and weld protection cover (4), and the spiral mesh argon gas transmission pipelines are connected to the corresponding gas connection pipes.

6. The welding device for preventing oxidation of the titanium alloy welding area according to claim 1, characterized in that, The stage (1) is a rotating stage, and a plurality of sliders (1-1) are provided at the bottom of the rotating stage, and the plurality of sliders (1-1) are movably installed on a horizontally arranged slide rail.

7. The welding device for preventing oxidation of the titanium alloy welding area according to claim 1, characterized in that, A pressure gauge (6-2) is installed on the argon gas cylinder (6).

8. A welding method for preventing oxidation of the welding area of titanium alloy, characterized in that, The welding method is based on the welding device described in any one of claims 1 to 7, and includes the following steps: Step 1. Pretreatment of the titanium alloy workpiece (A) Remove the impurities on the surface of the titanium alloy workpiece (A) by combining wiping with organic solvent and ultrasonic cleaning, and dry it for later use. Step 2. Welding preparation Place the titanium alloy workpiece (A) pretreated in Step 1 on the stage (1), and according to the welding area, a weld protection plate (3) is provided on the stage (1) and at the bottom welding area of the titanium alloy workpiece (A), or a weld protection cover (4) is provided at the top welding area of the titanium alloy workpiece (A), and a thermometer (12) and an oxygen sensor (13) are arranged on the titanium alloy workpiece (A). At the same time, connect the four gas delivery pipelines (5, 8, 9, 10) according to the connection relationship between each pipeline and the corresponding component, and install the welding torch (2-1) of the welding machine (2) on the welding torch protection cover (7); then open the first gas delivery pipeline (5), and the third gas delivery pipeline (9) or the fourth gas delivery pipeline (10) to deliver argon to the welding area; Step 3. Welding operation Weld by MIG welding method. Open the second gas delivery pipeline (8) and the welding machine (2), and make the welding torch (2-1) move along the weld under the protection of the welding torch protection cover (7) for welding. During the welding process, change the position of the titanium alloy workpiece (A) through the stage (1) to assist welding until the welding is completed; if during the welding process, the thermometer (12) monitors that the temperature of the welding area exceeds the set threshold, and / or the oxygen sensor (13) monitors that the oxygen content in the welding area exceeds the set threshold, the PLC control system controls the gas distributor (6-1) and each servo regulating valve (11) to adjust and increase the argon gas flow rate in the welding area; otherwise, reduce the argon gas flow rate in the welding area; Step 4. Two-stage cooling The first stage: within the first 30 s, control the argon gas flow rate in the welding area at 18 L / min to 22 L / min, and cool down by forced convection; The second stage: from 30 s to 120 s, control the argon gas flow rate in the welding area at 8 L / min to 12 L / min, and at the same time cooperate with the water-cooled copper gasket to inhibit the growth of the oxide layer in the welding area.

9. The welding method for preventing oxidation of the titanium alloy welding area according to claim 8, wherein, In Step 3, the MIG welding method includes root pass welding, filler pass welding and capping welding; Among them, the welding parameters for the root pass welding are: welding current 110 A to 140 A, welding voltage 10 V to 11 V, welding speed 10 cm / min to 15 cm / min, gas flow rate 25 L / min to 30 L / min; The welding parameters for the filler pass welding are: welding current 120 A to 145 A, welding voltage 20 V to 30 V, welding speed 60 cm / min to 65 cm / min, gas flow rate 35 L / min to 40 L / min; The welding parameters for the capping welding are: welding current 120 A to 145 A, welding voltage 20 V to 30 V, welding speed 60 cm / min to 65 cm / min, gas flow rate 30 L / min to 35 L / min.

10. Application of a welding device for preventing oxidation of a titanium alloy welding area according to any one of claims 1 to 7, characterized in that, The welding device is used for welding a titanium alloy sheath, and the titanium alloy sheath includes a cylindrical sheath and an annular sheath; When the titanium alloy sheath is a cylindrical sheath, the weld protection cover (4) is an annular shell structure, the second air outlet hole (4-1) is opened on the inner wall of the annular shell structure, and during welding, the weld protection cover (4) is sleeved outside the cylindrical sheath; When the titanium alloy sheath is an annular sheath, the weld protection cover (4) is a cylindrical shell structure, the second air outlet hole (4-1) is opened on the outer wall of the cylindrical shell structure, and during welding, the weld protection cover (4) is sleeved inside the annular sheath.

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