Welding method and welding protection device for titanium alloy heat exchange tube and tube plate

Abstract

The invention relates to the technical field of welding of a titanium alloy or titanium heat exchange tube and a tube plate, and discloses a welding method and a welding protection device for the titanium alloy heat exchange tube and the tube plate. 2, positioning and mounting the positioning shaft head; step 3, mounting and adjusting a main air tap; step 4, mounting and adjusting the auxiliary air tap; 5, welding the tube plate and the heat exchange tube; a welding protection device for welding a titanium alloy heat exchange tube and a tube plate mainly comprises a positioning shaft head, a main air tap, a tungsten electrode and an auxiliary air tap. The device has the beneficial effects that all-directional argon isolation air protection near a welding seam, a heat affected zone and a welding zone in the welding process of the tube plate and the heat exchange tube is achieved, and the protection range of argon in the welding process is enlarged; and the uniformity, compactness and strength of the welding seam are improved, the forming quality of the welding seam is improved on the whole, and a silver welding joint is obtained.

Description

Technical Field

[0001] The invention relates to the technical field of welding of titanium alloy heat exchange tubes or titanium heat exchange tubes and tube sheets, and in particular to a welding method and a welding protection device for titanium alloy heat exchange tubes and tube sheets. Background Art

[0002] The welding of titanium or titanium alloy must be carried out under vacuum or inert gas protection. Due to the limited size of the vacuum chamber and the complex welding process, the welding operator has high welding skills. Therefore, inert gas protection is often used to weld in an atmospheric environment. Due to the active chemical properties of titanium or titanium alloys, they have a strong affinity with oxygen, and an oxide film will quickly form on the surface at room temperature. Below 400°C, the oxide film formed is dense, firmly attached, not easy to fall off, and has a protective effect; above 400°C, titanium will gradually absorb harmful impurities such as hydrogen, oxygen, and nitrogen. As the temperature rises, the color of the oxide film generated gradually deepens and the thickness thickens, causing the plasticity and toughness of titanium to drop sharply, seriously affecting the quality of the weld. Due to different temperatures, the oxidation of the titanium surface forms titanium oxide with different valences, and the color of the oxide film is also different. Below 200℃, it is silvery white, 300℃ is light yellow, 400℃ is golden yellow, 500℃ is blue, 600℃ is purple, 700℃~800℃ is reddish gray, and 800℃~900℃ is gray. In the prior art, the argon protection effect can be tested by the surface color of the weld. If the weld joint is silvery white or light yellow, it means that the inert gas protection is good in the area above 400℃.

[0003] At present, the welding of titanium or titanium alloy heat exchange tubes and tube sheets is mainly to avoid oxidation of the welding area at a temperature above 400°C. The main technical difficulties are as follows: 1. Titanium has a high melting point, poor thermal conductivity, small heat capacity, and large resistivity. Therefore, compared with the welding of steel, aluminum, copper, etc., the titanium welding molten pool accumulates more heat, is large in size, has a long high-temperature residence time, and a slow cooling rate. Under normal welding technology, the area of ​​the weld that has just been welded that exceeds 600°C in the length direction is 1.5 times larger than stainless steel, 2.3 times larger than carbon steel, 16 times larger than aluminum, and 23 times larger than copper (that is, the hot melt area and heat-affected area are relatively large). Titanium welds and heat-affected zones with temperatures above 400°C should be placed in argon protection. Therefore, when welding titanium, not only the molten pool should be protected, but also the welded joints that are cooling after welding, and the areas near the welded joints with temperatures above 400°C should also be protected. 2. During the welding process, the temperature of the molten pool is around 1700°C, and can reach up to 2900°C. The temperature of the area near the molten pool decreases step by step with the distance. Since the wall of the heat exchange tube is thin, the temperature of the welded joint just after welding is much higher than 400°C. Also, because the welding gun rotates at a fast speed and the argon protection range is small, the joint leaves the argon protection zone before it has time to cool down. Therefore, it is very difficult to achieve a silvery-white welded joint when welding titanium or titanium alloy heat exchange tubes. Based on the above-mentioned defects in the prior art, the inventor has developed a welding method and welding protection device for titanium alloy heat exchange tubes and tube sheets, which can well solve the technical problems existing in the prior art. Summary of the invention

[0004] In order to solve the above-mentioned problems in the prior art, the present invention provides a welding method and a welding protection device for titanium alloy heat exchange tubes and tube sheets. The present invention solves the technical problems in the prior art that the argon protection range of the welding between the tube sheet and the heat exchange tube is small, the protection is not comprehensive, and it is difficult to obtain a silvery white welded joint.

[0005] The present invention relates to the explanation of nouns: Fusion welding: the end of the heat exchange tube melts, and the end of the tube protrudes from the tube sheet by 0mm~1mm. Extension welding: the end of the heat exchange tube does not melt, and the end of the tube protrudes from the tube sheet by 4mm~6mm. Welding temperature: the actual temperature of the workpiece before welding. Welding heat input / welding line energy: during welding, the heat source moves at a certain speed. Generally, welding heat input / welding line energy is used to measure the thermal effect of the heat source, which is defined as the energy input from the moving heat source per unit length of the weld; the expression of welding heat input is E=UI / v, U is the welding voltage, I is the welding current, and v is the welding speed. Post-weld gas supply time: after welding is completed, the arc is extinguished, and the gas nozzle continues to supply gas for a period of time. Welding pool: during melting welding, under the action of the heat source, the liquid metal part with a certain shape formed on the weldment is called the welding pool. Welded joint: refers to the joint where two or more parts are connected by welding, including the weld, fusion zone and heat-affected zone.

[0006] The present invention provides a welding protection device for welding a titanium alloy heat exchange tube and a tube sheet, comprising a tube sheet and a heat exchange tube, the tube sheet being square in shape, the heat exchange tube being inserted into the tube sheet, the front end of the heat exchange tube extending to the outside of the front side surface of the tube sheet; the positioning shaft head comprising a cooling cavity, the cooling cavity being hollow and circular in shape, the chamfer being arranged at the rear end surface of the positioning shaft head, the recessed step being arranged at the middle of the positioning shaft head close to the front side position, and the fixed countersunk hole being arranged at the front end portion of the positioning shaft head; the front end of the main gas nozzle being fixedly mounted on the welding gun head, the rear end of the main gas nozzle being inclined close to the front end surface of the heat exchange tube; the tungsten electrode being fixedly mounted at the center position of the welding gun head, the tungsten electrode being arranged at the center position of the main gas nozzle, the rear end of the tungsten electrode being close to the contact edge between the heat exchange tube and the front side surface of the tube sheet; the auxiliary gas nozzle being tilted and fixedly arranged at the right side position of the main gas nozzle, the rear end of the auxiliary gas nozzle being close to the circumferential edge of the outer diameter of the heat exchange tube, the auxiliary gas nozzle being fixed on the rotating spindle of the welding machine through a fixing frame, and the front end of the auxiliary gas nozzle being fixedly connected to an argon gas bottle through a gas pipe.

[0007] The tube sheet comprises a tube sheet body, a through hole is formed in the center of the tube sheet body; the heat exchange tube is inserted into and installed in the through hole and fixed by micro-connection through spot welding.

[0008] The chamfer diameter of the positioning shaft head is 0.3mm~0.5mm smaller than the inner diameter of the heat exchange tube; the rear end vertex of the cooling chamber is 3mm away from the rear end face of the positioning shaft head; the length of the rear end of the positioning shaft head penetrating into the interior of the heat exchange tube is greater than or equal to 20mm; the positioning shaft head is made of copper.

[0009] The angle between the main air nozzle axis and the positioning shaft head axis is 0° to 25°, the distance between the rear end of the main air nozzle and the tube plate is less than or equal to 4 mm; the inner diameter of the rear end of the main air nozzle is greater than or equal to 12 mm, and the main air nozzle is made of ceramic material.

[0010] The length of the tungsten electrode extending from the rear end face of the main gas nozzle is less than or equal to 6 mm, and the tungsten electrode and the main gas nozzle are coaxially and concentrically arranged.

[0011] The axis angle between the auxiliary gas nozzle and the main gas nozzle is 25° to 35°, the axis angle between the auxiliary gas nozzle and the positioning shaft head is 25° to 45°, and the distance between the rear end of the auxiliary gas nozzle and the front side of the tube plate is less than or equal to 4 mm.

[0012] The inner diameter of the main air nozzle is greater than or equal to 12 mm, and the inner diameter of the auxiliary air nozzle is greater than or equal to 18 mm.

[0013] A water inlet and a water outlet are provided on the welding spindle. The water inlet is connected to the water outlet of the circulating water pump, and the water outlet is connected to the water inlet of the radiator. After the circulating water is cooled by the radiator, the water outlet of the radiator is connected to the water inlet of the circulating water pump to form a circulating cooling system.

[0014] The present invention provides a method for welding a titanium alloy heat exchange tube and a tube sheet: Step 1: Coordinated installation of tube sheet and heat exchange tube: insert the heat exchange tube into the through hole of the tube sheet, and the front end of the heat exchange tube extends out of the front side of the tube sheet by 0mm~1mm or 4mm~6mm; at the same time, evenly spot weld and fix the contact edge between the heat exchange tube and the front side of the tube sheet and the contact edge between the heat exchange tube and the rear side of the tube sheet; Step 2: Positioning and installation of the positioning shaft head: install the rear chamfer of the positioning shaft head inside the front end of the heat exchange tube, and then fix the front end fixing countersunk hole of the positioning shaft head to the main shaft of the welding machine; Step 3. Installation and adjustment of the main gas nozzle: fix the front end of the main gas nozzle to the outer surface of the welding gun, so that the axis of the tungsten electrode on the welding gun coincides with the axis of the main gas nozzle, and the welding gun is fixedly connected to the welding power source; the angle between the axis of the main gas nozzle and the axis of the positioning shaft head is 0°~25°, the distance between the rear end of the main gas nozzle and the tube sheet is less than or equal to 4mm, and the length of the tungsten electrode extending from the rear end face of the main gas nozzle is less than or equal to 6mm; Step 4. Installation and adjustment of the auxiliary gas nozzle: Fix the auxiliary gas nozzle on the fixed bracket on the rotating spindle of the welding machine, so that the axis angle between the auxiliary gas nozzle and the main gas nozzle is 25°~35°, the axis angle between the auxiliary gas nozzle and the positioning shaft head is 25°~45°, and the distance between the rear end of the auxiliary gas nozzle and the front side of the tube sheet is less than or equal to 4mm; Step 5. Welding of tube sheet and heat exchange tube: the welding temperature is controlled at less than or equal to 40℃; start the welding gun and tungsten electrode to ignite the arc, control the heat input (welding line energy) to be less than or equal to 8J / cm, control the gas flow in the gas nozzle to be greater than or equal to 25L / min, and control the argon purity to be greater than or equal to 99.999%; start the welding spindle to rotate it, and the rotation of the spindle drives the positioning shaft head, main gas nozzle, tungsten electrode and auxiliary gas nozzle to rotate synchronously, and the rear end tip of the tungsten electrode rotates evenly along the circumference of the front end of the heat exchange tube, while starting the arc and feeding the wire to weld. After the spindle rotates one circle, the welding operation of the tube sheet and the heat exchange tube is completed; after the welding is completed, the main gas nozzle and the auxiliary gas nozzle continue to supply gas for a time greater than or equal to 9s.

[0015] In step 2, the depth of the rear end of the positioning shaft head is controlled to be greater than or equal to 20 mm.

[0016] In step 1, the heat exchange tube is inserted into the through hole of the tube sheet, and the front end of the heat exchange tube extends out of the front side of the tube sheet by 0mm~1mm or 4mm~6mm; at the same time, the contact edge between the heat exchange tube and the front side of the tube sheet and the contact edge between the heat exchange tube and the rear side of the tube sheet are evenly spot welded and fixed. The main purpose of this is: on the one hand, it plays a supporting role for the positioning shaft head; on the other hand, during the rotation process, the positioning shaft head is tightened with the inner wall of the heat exchange tube by using the chamfer, so that the positioning shaft head uses the inner wall of the heat exchange tube as the rotation fulcrum, thereby realizing the rotation of the positioning shaft head driven by the rotation of the welding machine main shaft.

[0017] In step 2, the rear chamfer of the positioning shaft head is installed inside the front end of the heat exchange tube, and the depth of the rear end of the positioning shaft head is controlled to be greater than or equal to 20mm, and then the front end of the positioning shaft head is fixed to the main shaft of the welding machine. The main purpose of doing this is: on the one hand, it plays a role in aligning the main gas nozzle and the tungsten electrode to the center of the heat exchange tube; on the other hand, it allows the circulating cooling water to penetrate into the inner wall of the heat exchange tube, which has the effect of cooling the inner wall of the heat exchange tube.

[0018] Among them, in step three, when the angle between the axis of the main gas nozzle and the axis of the positioning shaft head is 0°~25°, and the distance between the rear end of the main gas nozzle and the tube sheet is less than or equal to 4㎜; the main purpose of doing this is: on the one hand, to ensure the protection width of the argon gas blown by the main gas nozzle, completely covering the weld at the junction of the tube sheet and the heat exchange tube; on the other hand, to enable the argon gas blown by the main gas nozzle to be partially blown into the recessed step of the positioning shaft head, thereby forming a cooling cavity for cooling the end and inner wall of the heat exchange tube.

[0019] In step 3, the length of the tungsten electrode extending from the rear end face of the main gas nozzle is less than or equal to 6 mm. The main purpose of this is: on the one hand, it plays a role in quickly melting the heat exchange tube head and welding wire; on the other hand, it is conducive to forming a uniformly molten welding pool, thereby improving the quality of the weld.

[0020] In step 4, the auxiliary gas nozzle is fixedly mounted on the fixed frame on the rotating main shaft of the welding machine, so that the axis angle between the auxiliary gas nozzle and the main gas nozzle is 25°~35°, the axis angle between the auxiliary gas nozzle and the positioning shaft head is 25°~45°, and the distance between the rear end of the auxiliary gas nozzle and the front side of the tube sheet is less than or equal to 4㎜. The main purpose of doing this is: on the one hand, it improves the consistency of the angle and spacing between the auxiliary gas nozzle and the main gas nozzle, improves the matching degree between the auxiliary gas nozzle and the main gas nozzle, and enhances the argon protective atmosphere between the tube sheet and the heat exchange tube, so that the gas nozzle can better protect the tube end and the inner wall of the heat exchange tube; on the other hand, with the argon gas blown out by the main gas nozzle, a cooling area with good cooling effect can be formed in the recessed step of the positioning shaft head, which improves the cooling effect on the tube end and the inner wall of the heat exchange tube.

[0021] In step 5, the welding temperature is controlled at less than or equal to 40°C; the welding gun is started, the tungsten electrode is ignited and the heat input (welding line energy) is controlled to be less than or equal to 8J / cm; the main purpose of doing this is: under the conditions of welding temperature less than or equal to 40°C and heat input less than or equal to 8J / cm, the melting temperature of the tube head of the heat exchange tube 2 and the welding wire can be guaranteed, thereby ensuring the melting speed of the weld molten pool and obtaining a fully molten weld molten pool.

[0022] In step five, the gas flow rate in the nozzle is controlled to be greater than or equal to 25L / min, and the purity of the argon gas is controlled to be greater than or equal to 99.999%. The main purpose of doing this is: when the gas flow rate in the nozzle is controlled to be greater than or equal to 25L / min, combined with high-purity argon gas, the effect of isolating the air and preventing oxidation can be achieved, and sufficient argon flow can ensure sufficient argon protection range for the weld, heat-affected zone, and welding area.

[0023] In step five, the welding spindle is started to rotate. The rotation of the spindle drives the positioning shaft head, the main gas nozzle, the tungsten electrode and the auxiliary gas nozzle to rotate synchronously. The rear end tip of the tungsten electrode rotates evenly along the circumference of the front end of the heat exchange tube. The arc is started and the wire is fed while welding. After the spindle rotates one circle, the welding operation of the tube sheet and the heat exchange tube is completed. The main purpose of doing this is: as the positioning shaft head rotates, the main gas nozzle, the tungsten electrode and the auxiliary gas nozzle are driven to rotate synchronously, which improves the uniformity of the welding molten pool, thereby improving the uniformity of the weld.

[0024] In step 5, after welding is completed, the main gas nozzle and the auxiliary gas nozzle continue to supply gas for a time greater than or equal to 9 seconds. The main purpose of this is to isolate the weld, fusion area and heat-affected zone from the air during the cooling process with argon gas; on the one hand, it isolates the air and prevents oxidation, and on the other hand, it continuously and rapidly cools the weld, fusion area and heat-affected zone during the cooling process, thereby obtaining a silver-white weld joint.

[0025] The beneficial effects of the present invention are as follows: by arranging the positioning shaft head, the main gas nozzle and the auxiliary gas nozzle, and driven by the uniform rotation of the main shaft of the welding machine, the positioning shaft head, the main gas nozzle and the auxiliary gas nozzle can rotate along with the uniform rotation of the main shaft; all-round argon gas-insulated air protection is achieved near the weld, the heat-affected zone and the welding zone during the welding of the tube sheet and the heat exchange tube, and the protection range of the argon gas during the welding process is increased; the uniformity, density and strength of the weld are improved, the molding quality of the weld is improved as a whole, and a silver-white welded joint is obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the structure of the tube sheet and the heat exchange tube when being welded externally; Figure 2 It is a cross-sectional view of the tube sheet and the heat exchange tube when being welded externally; Figure 3 It is a cross-sectional view of the positioning shaft head of the present invention; Figure 4 It is a structural schematic diagram of the tube sheet and the heat exchange tube during fusion welding of the present invention; Figure 5 It is a cross-sectional view of the tube sheet and the heat exchange tube during fusion welding of the present invention; Figure 6A comparison diagram of welding effects before and after the method and device of the present invention are used; Markings in the figure: 1. tube sheet, 11. tube sheet body, 12. through hole, 2. heat exchange tube, 3. positioning shaft head, 31. cooling chamber, 32. chamfer, 33. recessed step, 34. fixed countersunk hole, 4. main gas nozzle, 5. tungsten electrode, 6. auxiliary gas nozzle. DETAILED DESCRIPTION

[0027] The present invention is further described below in conjunction with specific examples. These examples are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0028] The present invention provides a welding method and a welding protection device for titanium alloy heat exchange tubes and tube sheets: like Figure 1 , 2 As shown in Figures 4 and 5, the tube sheet 1 is square in shape, the heat exchange tube 2 is inserted into the tube sheet 1, and the front end of the heat exchange tube 2 extends to the outside of the front side of the tube sheet 1; the tube sheet 1 includes a tube sheet body 11, and a through hole 12 is opened through the center of the tube sheet body 11; the heat exchange tube 2 is inserted and installed in the through hole 12 and fixed by micro-connection through spot welding.

[0029] The above-mentioned spot welding micro-connection at the intersection of the front and rear sides of the heat exchange tube 2 and the tube sheet 1 improves the firmness between the heat exchange tube 2 and the tube sheet 1. On the one hand, it plays a supporting role for fixing the positioning shaft head 3. On the other hand, during the rotation process, the positioning shaft head 3 is tightened against the inner wall of the heat exchange tube 2 by using the chamfer 32, so that the positioning shaft head 3 uses the inner wall of the heat exchange tube 2 as the rotation fulcrum, thereby realizing the rotation of the positioning shaft head 3 driven by the rotation of the welding machine main shaft.

[0030] like Figure 3 As shown, the positioning shaft head 3 includes a cooling cavity 31, which is a hollow circular shape, a chamfer 32 is opened on the rear end face of the positioning shaft head 3, a recessed step 33 is opened in the middle of the positioning shaft head 3 near the front side, and a fixed countersunk hole 34 is opened at the front end of the positioning shaft head 3; the diameter of the chamfer 32 of the positioning shaft head 3 is 0.3㎜~0.5㎜ smaller than the inner diameter of the heat exchange tube 2; the rear end vertex of the cooling cavity 31 is 3㎜ away from the rear end face of the positioning shaft head 3; the length of the rear end of the positioning shaft head 3 penetrating into the interior of the heat exchange tube 2 is greater than or equal to 20㎜; the positioning shaft head 3 is made of copper.

[0031] The above-mentioned setting of the cooling chamber 31 and the distance between the rear end vertex of the cooling chamber 31 and the rear end face of the positioning shaft head 3 is 3 mm can effectively extend the depth of the cooling chamber 31. On the one hand, more cooling water can be circulated and stored, thereby improving the cooling effect of the heat-affected area of ​​the inner wall of the heat exchange tube 2; on the other hand, the heat exchange area of ​​the circulating cooling water in the cooling chamber 31 is increased, thereby improving the heat exchange effect of the cooling water.

[0032] The chamfer 32 is provided on the rear end face of the positioning shaft head 3, and the diameter of the chamfer 32 of the positioning shaft head 3 is 0.3 mm to 0.5 mm smaller than the inner diameter of the heat exchange tube 2. This improves the fit between the chamfer 32 and the inner diameter of the heat exchange tube 2. On the one hand, the positioning of the axis of the heat exchange tube 2 by the positioning shaft head 3 is achieved. On the other hand, when the main shaft rotates, the chamfer 32 is in tight contact with the inner wall of the heat exchange tube 2, forming a rotating fulcrum for the positioning shaft head 3 to rotate.

[0033] The above-mentioned setting of the recessed step 33, on the one hand, provides a movable space for the angle adjustment of the main gas nozzle 4 and the tungsten electrode 5, making the angle adjustment of the main gas nozzle 4 and the tungsten electrode 5 more flexible; on the other hand, when the main gas nozzle 4 blows out argon gas, a cooling cavity is provided for the inner wall (heat affected zone) of the heat exchange tube 2, so that the argon gas blown out by the main gas nozzle 4 is directly blown into the inner wall of the heat exchange tube 2, playing a role in cooling the inner wall of the front end of the heat exchange tube 2.

[0034] The positioning shaft head 3 is made of copper, and the high thermal conductivity and good heat dissipation of copper are utilized to improve the heat dissipation effect of the positioning shaft head 3. At the same time, the temperature of the positioning shaft head 3 itself is reduced under the coordinated cooling of the cooling circulating water and argon gas cooling medium.

[0035] like Figure 1 , 2 As shown in Figures 4 and 5, the front end of the main gas nozzle 4 is fixedly mounted on the welding gun head, and the rear end of the main gas nozzle 4 is inclined close to the front end face of the heat exchange tube 2; the angle between the axis of the main gas nozzle 4 and the axis of the positioning shaft head 3 is 0° to 25°, and the distance between the rear end of the main gas nozzle 4 and the tube sheet 1 is less than or equal to 4 mm; the inner diameter of the rear end of the main gas nozzle 4 is greater than or equal to 12 mm, and the main gas nozzle 4 is made of ceramic material. Through the above-mentioned setting of the main gas nozzle 4, on the one hand, the protection width of the weld by argon gas is increased during the welding process, and the welding quality of the weld between the heat exchange tube 2 and the tube sheet 1 is improved; on the other hand, it plays a role in protecting the tungsten electrode 5 to prevent the tungsten electrode 5 from oxidation during the welding process, thereby reducing the performance of the tungsten electrode 5; on the other hand, the argon gas blown from the main gas nozzle 4 is used to cool the fusion zone at the weld of the heat exchange tube 2 and the tube sheet 1, thereby improving the cooling rate of the weld fusion zone.

[0036] like Figure 2 As shown in or 5, the tungsten electrode 5 is fixedly installed at the center position of the welding gun head, and the tungsten electrode 5 is arranged at the center position of the main gas nozzle 4, and the rear end of the tungsten electrode 5 is close to the contact edge of the heat exchange tube 2 and the front side of the tube sheet 1; the length of the tungsten electrode 5 extending from the rear end face of the main gas nozzle 4 is less than or equal to 6 mm, and the tungsten electrode 5 and the main gas nozzle 4 are coaxial and concentric.

[0037] The rear end of the tungsten electrode 5 is close to the contact edge between the heat exchange tube 2 and the front side of the tube sheet 1, which can increase the arc starting temperature at the junction of the heat exchange tube 2 and the tube sheet 1. On the one hand, it plays a role in quickly melting the tube head and welding wire of the heat exchange tube 2; on the other hand, it is conducive to forming a welding molten pool with uniform fusibility, thereby improving the quality of the weld.

[0038] like Figure 1 As shown in or 2, the auxiliary gas nozzle 6 is tilted and fixedly arranged at the right side of the main gas nozzle 4, the rear end of the auxiliary gas nozzle 6 is close to the circumferential edge of the outer diameter of the heat exchange tube 2, and the auxiliary gas nozzle 6 is fixed on the rotating spindle of the welding machine through a fixing bracket; the axial angle between the auxiliary gas nozzle 6 and the main gas nozzle 4 is 25°~35°, the axial angle between the auxiliary gas nozzle 6 and the positioning shaft head 3 is 25°~45°, and the distance between the rear end of the auxiliary gas nozzle 6 and the front side surface of the tube sheet 1 is less than or equal to 4㎜.

[0039] The above-mentioned setting of the auxiliary gas nozzle 6, on the one hand, plays a role in argon gas protection of the weld heat affected zone of the heat exchange tube 2 and the tube sheet 1, thereby increasing the argon gas protection width of the weld; on the other hand, plays a role in rapid cooling of the heat affected zone of the weld, thereby increasing the cooling effect of the heat affected zone of the weld.

[0040] The axis angle between the auxiliary gas nozzle 6 and the main gas nozzle 4 is 25°~35°, the axis angle between the auxiliary gas nozzle 6 and the positioning shaft head 3 is 25°~45°, and the distance between the rear end of the auxiliary gas nozzle 6 and the front side surface of the tube sheet 1 is less than or equal to 4㎜; the main purpose of such arrangement is: through the setting of the angle and distance position of the auxiliary gas nozzle 6, on the one hand, the consistency of the angle and spacing between the auxiliary gas nozzle 6 and the main gas nozzle 4 is improved, the matching degree between the auxiliary gas nozzle 6 and the main gas nozzle 4 is improved, and the argon protective atmosphere between the tube sheet 1 and the heat exchange tube 2 is enhanced, so that the gas nozzle can better protect the tube end and the inner wall of the heat exchange tube 2; on the other hand, in cooperation with the argon gas blown by the main gas nozzle 4, a cooling area with good cooling effect can be formed in the recessed step 33 of the positioning shaft head 3, thereby improving the cooling effect on the tube end and the inner wall of the heat exchange tube 2.

[0041] like Figure 1 , 2 As shown in , 4 and 5, the inner diameter of the main gas nozzle 4 is greater than or equal to 12 mm, and the inner diameter of the auxiliary gas nozzle 6 is greater than or equal to 18 mm. The main purpose of the above arrangement is: on the one hand, to increase the gas output of the protective gas argon; on the other hand, to increase the protection width of the argon gas on the inner wall of the heat exchange tube 2, the tube end and the weld.

[0042] like Figure 1-5 As shown, a specific embodiment of the method for welding a titanium alloy heat exchange tube to a tube sheet is as follows: Heat exchange tube and tube sheet extension welding: The heat exchange tube end does not melt, and the tube end extends out of the tube sheet by 4mm~6mm. Specific implementation example: Embodiment 1:

[0043] Step 1: Coordinated installation of the tube sheet and the heat exchange tube: insert the heat exchange tube 2 into the through hole 12 of the tube sheet 1, and the front end of the heat exchange tube 2 extends 4 mm beyond the front side of the tube sheet 1; at the same time, evenly spot weld the contact edge between the heat exchange tube 2 and the front side of the tube sheet 1 and the contact edge between the heat exchange tube 2 and the rear side of the tube sheet 1; Step 2: Positioning and installing the positioning shaft head: install the rear end chamfer 32 of the positioning shaft head 3 inside the front end of the heat exchange tube 2, control the depth of the rear end of the positioning shaft head 3 to be greater than 20 mm, and then fix the front end fixing countersunk hole 34 of the positioning shaft head 3 to the main shaft of the welding machine; Step 3, installation and adjustment of the main gas nozzle: fix the front end of the main gas nozzle 4 to the outer surface of the welding gun, so that the axis of the tungsten electrode 5 on the welding gun coincides with the axis of the main gas nozzle 4, and the welding gun is fixedly connected to the welding power source; the angle between the axis of the main gas nozzle 4 and the axis of the positioning shaft head 3 is 0°, the distance between the rear end of the main gas nozzle 4 and the tube sheet 1 is less than 4mm, and the length of the tungsten electrode 5 extending from the rear end face of the main gas nozzle 4 is less than 6mm; Step 4, installation and adjustment of the auxiliary gas nozzle: fix the auxiliary gas nozzle 6 on the fixing bracket on the rotating main shaft of the welding machine, so that the axis angle between the auxiliary gas nozzle 6 and the main gas nozzle 4 is 25°, the axis angle between the auxiliary gas nozzle 6 and the positioning shaft head 3 is 25°, and the distance between the rear end of the auxiliary gas nozzle 6 and the front side of the tube sheet 1 is less than or equal to 4mm; Step 5. Welding of tube sheet and heat exchange tube: the welding temperature is controlled at less than 40°C; start the welding gun and tungsten electrode to ignite the arc, control the heat input (welding line energy) to be less than or equal to 8J / cm, control the gas flow in the gas nozzle to be greater than or equal to 25L / min, and control the argon purity to be greater than or equal to 99.999%; start the welding spindle to rotate it, and the rotation of the spindle drives the positioning shaft head 3, the main gas nozzle 4, the tungsten electrode 5 and the auxiliary gas nozzle 6 to rotate synchronously, and the rear end tip of the tungsten electrode 5 rotates evenly along the circumference of the front end of the heat exchange tube 2, while starting the arc and feeding the wire to weld. After the spindle rotates one circle, the welding operation of the tube sheet 1 and the heat exchange tube 2 is completed; after the welding is completed, the main gas nozzle 4 and the auxiliary gas nozzle 6 continue to supply gas for more than 9s.

[0044] Embodiment 2:

[0045] Step 1: Coordinated installation of the tube sheet and the heat exchange tube: insert the heat exchange tube 2 into the through hole 12 of the tube sheet 1, and the front end of the heat exchange tube 2 extends 6mm beyond the front side of the tube sheet 1; at the same time, evenly spot weld the contact edge between the heat exchange tube 2 and the front side of the tube sheet 1 and the contact edge between the heat exchange tube 2 and the rear side of the tube sheet 1; Step 2: Positioning and installing the positioning shaft head: install the rear end chamfer 32 of the positioning shaft head 3 inside the front end of the heat exchange tube 2, control the depth of the rear end of the positioning shaft head 3 to be equal to 20 mm, and then fix the front end fixing countersunk hole 34 of the positioning shaft head 3 to the main shaft of the welding machine; Step 3, installation and adjustment of the main gas nozzle: fix the front end of the main gas nozzle 4 to the outer surface of the welding gun, so that the axis of the tungsten electrode 5 on the welding gun coincides with the axis of the main gas nozzle 4, and the welding gun is fixedly connected to the welding power source; the angle between the axis of the main gas nozzle 4 and the axis of the positioning shaft head 3 is 25°, the distance between the rear end of the main gas nozzle 4 and the tube sheet 1 is equal to 4mm, and the length of the tungsten electrode 5 extending from the rear end face of the main gas nozzle 4 is equal to 6mm; Step 4, installation and adjustment of the auxiliary gas nozzle: fix the auxiliary gas nozzle 6 on the fixing bracket on the rotating main shaft of the welding machine, so that the axis angle between the auxiliary gas nozzle 6 and the main gas nozzle 4 is 35°, the axis angle between the auxiliary gas nozzle 6 and the positioning shaft head 3 is 45°, and the distance between the rear end of the auxiliary gas nozzle 6 and the front side of the tube sheet 1 is equal to 4mm; Step 5. Welding of tube sheet and heat exchange tube: the welding temperature is controlled at 40°C; start the welding gun and tungsten electrode to ignite the arc, control the heat input (welding line energy) to be less than or equal to 8J / cm, control the gas flow in the gas nozzle to be greater than or equal to 25L / min, and control the purity of argon gas to be greater than or equal to 99.999%; start the welding spindle to rotate it, and the rotation of the spindle drives the positioning shaft head 3, the main gas nozzle 4, the tungsten electrode 5 and the auxiliary gas nozzle 6 to rotate synchronously, and the rear end tip of the tungsten electrode 5 rotates evenly along the circumference of the front end of the heat exchange tube 2, while starting the arc and feeding the wire to weld. After the spindle rotates one circle, the welding operation of the tube sheet 1 and the heat exchange tube 2 is completed; after the welding is completed, the main gas nozzle 4 and the auxiliary gas nozzle 6 continue to supply gas for 9s.

[0046] Fusion welding of tube sheet 1 and heat exchange tube 2: the end of heat exchange tube 2 is melted, and the end of the tube protrudes from the tube sheet by 0mm~1mm. Specific implementation example: Embodiment 1:

[0047] Step 1: Coordinated installation of the tube sheet and the heat exchange tube: insert the heat exchange tube 2 into the through hole 12 of the tube sheet 1, and the front end of the heat exchange tube 2 extends 0mm out of the front side of the tube sheet 1; at the same time, evenly spot weld and fix the contact edge between the heat exchange tube 2 and the front side of the tube sheet 1 and the contact edge between the heat exchange tube 2 and the rear side of the tube sheet 1; Step 2: Positioning and installing the positioning shaft head: install the rear end chamfer 32 of the positioning shaft head 3 inside the front end of the heat exchange tube 2, control the depth of the rear end of the positioning shaft head 3 to be greater than 20 mm, and then fix the front end fixing countersunk hole 34 of the positioning shaft head 3 to the main shaft of the welding machine; Step 3, installation and adjustment of the main gas nozzle: fix the front end of the main gas nozzle 4 to the outer surface of the welding gun, so that the axis of the tungsten electrode 5 on the welding gun coincides with the axis of the main gas nozzle 4, and the welding gun is fixedly connected to the welding power source; the angle between the axis of the main gas nozzle 4 and the axis of the positioning shaft head 3 is 0° to 25°, the distance between the rear end of the main gas nozzle 4 and the tube sheet 1 is less than 4mm, and the length of the tungsten electrode 5 extending from the rear end face of the main gas nozzle 4 is less than 6mm; Step 4. Welding of tube sheet and heat exchange tube: the welding temperature is controlled at less than 40°C; start the welding gun and tungsten electrode to ignite the arc, control the heat input (welding line energy) to be less than or equal to 8J / cm, control the gas flow in the gas nozzle to be greater than or equal to 25L / min, and control the argon purity to be greater than or equal to 99.999%; start the welding spindle to rotate it, and the rotation of the spindle drives the positioning shaft head 3, the main gas nozzle 4, the tungsten electrode 5 and the auxiliary gas nozzle 6 to rotate synchronously, and the rear end tip of the tungsten electrode 5 rotates evenly along the circumference of the front end of the heat exchange tube 2, while starting the arc and feeding the wire to weld. After the spindle rotates one circle, the welding operation of the tube sheet 1 and the heat exchange tube 2 is completed; after the welding is completed, the main gas nozzle 4 continues to supply gas for more than 9s.

[0048] Embodiment 2:

[0049] Step 1: Coordinated installation of the tube sheet and the heat exchange tube: insert the heat exchange tube 2 into the through hole 12 of the tube sheet 1, and the front end of the heat exchange tube 2 extends 1 mm beyond the front side of the tube sheet 1; at the same time, evenly spot weld the contact edge between the heat exchange tube 2 and the front side of the tube sheet 1 and the contact edge between the heat exchange tube 2 and the rear side of the tube sheet 1; Step 2: Positioning and installing the positioning shaft head: install the rear end chamfer 32 of the positioning shaft head 3 inside the front end of the heat exchange tube 2, control the depth of the rear end of the positioning shaft head 3 to be equal to 20 mm, and then fix the front end fixing countersunk hole 34 of the positioning shaft head 3 to the main shaft of the welding machine; Step 3, installation and adjustment of the main gas nozzle: fix the front end of the main gas nozzle 4 to the outer surface of the welding gun, so that the axis of the tungsten electrode 5 on the welding gun coincides with the axis of the main gas nozzle 4, and the welding gun is fixedly connected to the welding power source; the angle between the axis of the main gas nozzle 4 and the axis of the positioning shaft head 3 is 25°, the distance between the rear end of the main gas nozzle 4 and the tube sheet 1 is less than or equal to 4mm, and the length of the tungsten electrode 5 extending from the rear end face of the main gas nozzle 4 is equal to 6mm; Step 4. Welding of tube sheet and heat exchange tube: the welding temperature is controlled at 40°C; start the welding gun and tungsten electrode to ignite the arc, control the heat input (welding line energy) to be less than or equal to 8J / cm, control the gas flow in the gas nozzle to be greater than or equal to 25L / min, and control the argon purity to be greater than or equal to 99.999%; start the welding spindle to rotate it, and the rotation of the spindle drives the positioning shaft head 3, the main gas nozzle 4, the tungsten electrode 5 and the auxiliary gas nozzle 6 to rotate synchronously, and the rear end tip of the tungsten electrode 5 rotates evenly along the circumference of the front end of the heat exchange tube 2, while starting the arc and feeding the wire to weld. After the spindle rotates one circle, the welding operation of the tube sheet 1 and the heat exchange tube 2 is completed; after the welding is completed, the main gas nozzle 4 continues to supply gas for 9s.

[0050] like Figure 6As shown, in the figure, A is a welding effect diagram before the titanium alloy heat exchange tube and tube sheet welding method and welding protection device of the present invention are adopted; in the figure, B is a welding effect diagram of the fusion head welding of tube sheet 1 and heat exchange tube 2 after the titanium alloy heat exchange tube and tube sheet welding method and welding protection device of the present invention are adopted; in the figure, C is a welding effect diagram of the extension welding of heat exchange tube 2 and tube sheet 1 after the titanium alloy heat exchange tube and tube sheet welding method and welding protection device of the present invention are adopted. From the comparison of the above actual welding effect diagrams, it can be seen that the weld between the heat exchange tube 2 and the tube sheet 1 in figure A is uneven and uneven, and the color of the weld is blue, purple and yellow; the weld between the heat exchange tube and the tube sheet in figure B is uniform and dense, and the weld is white, and the fusion head of the heat exchange tube 2 is completely melted; the weld between the heat exchange tube 2 and the tube sheet 1 in figure C is uniform and dense, and the weld is white.

[0051] Various modifications to the above embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will be adapted to the widest range consistent with the principles and novel features disclosed herein.

Claims

1. A welding method for titanium alloy heat exchange tubes and tube sheets, characterized in that: Step 1: Coordinated installation of the tube sheet and the heat exchange tube: insert the heat exchange tube (2) into the through hole (12) of the tube sheet (1), with the front end of the heat exchange tube (2) extending out of the front side of the tube sheet (1) by 0 mm to 1 mm or 4 mm to 6 mm; at the same time, evenly spot weld the contact edge between the heat exchange tube (2) and the front side of the tube sheet (1) and the contact edge between the heat exchange tube (2) and the rear side of the tube sheet (1); Step 2: Positioning and installing the positioning shaft head: install the rear end chamfer (32) of the positioning shaft head (3) inside the front end of the heat exchange tube (2), and then fix the front end fixing countersunk hole (34) of the positioning shaft head (3) to the main shaft of the welding machine; Step 3, installation and adjustment of the main gas nozzle: fix the front end of the main gas nozzle (4) to the outer surface of the welding gun, so that the axis of the tungsten electrode (5) on the welding gun coincides with the axis of the main gas nozzle (4), and the welding gun is fixedly connected to the welding power source; the angle between the axis of the main gas nozzle (4) and the axis of the positioning shaft head (3) is 0° to 25°, the distance between the rear end of the main gas nozzle (4) and the tube plate (1) is less than or equal to 4 mm, and the length of the tungsten electrode (5) extending from the rear end face of the main gas nozzle (4) is less than or equal to 6 mm; Step 4: Installation and adjustment of the auxiliary gas nozzle: The auxiliary gas nozzle (6) is fixedly mounted on the fixing bracket on the rotating main shaft of the welding machine, so that the axis angle between the auxiliary gas nozzle (6) and the main gas nozzle (4) is 25° to 35°, the axis angle between the auxiliary gas nozzle (6) and the positioning shaft head (3) is 25° to 45°, and the distance between the rear end of the auxiliary gas nozzle (6) and the front side surface of the tube plate (1) is less than or equal to 4 mm; Step 5. Welding of tube sheet and heat exchange tube: the welding temperature is controlled at less than or equal to 40℃; start the welding gun, ignite the tungsten electrode, control the heat input to be less than or equal to 8J / cm, control the gas flow in the nozzle to be greater than or equal to 25L / min, and control the purity of argon gas to be greater than or equal to 99.999%; The welding spindle is started to rotate. The rotation of the spindle drives the positioning shaft head (3), the main gas nozzle (4), the tungsten electrode (5) and the auxiliary gas nozzle (6) to rotate synchronously. The tip of the rear end of the tungsten electrode (5) rotates evenly along the circumference of the front end of the heat exchange tube (2). The arc is started and the wire is fed while welding. After the spindle rotates one circle, the welding operation of the tube sheet (1) and the heat exchange tube (2) is completed. After the welding is completed, the main gas nozzle (4) and the auxiliary gas nozzle (6) continue to feed gas for a time greater than or equal to 9 seconds.

2. A method for welding a titanium alloy heat exchange tube and a tube sheet according to claim 1, characterized in that: In step 2, the depth of the rear end of the positioning shaft head (3) is controlled to be greater than or equal to 20 mm.

3. A welding protection device for welding titanium alloy heat exchange tubes and tube sheets, characterized in that: The invention comprises a tube sheet (1) and a heat exchange tube (2), wherein the tube sheet (1) is square in shape, the heat exchange tube (2) is inserted into the tube sheet (1), and the front end of the heat exchange tube (2) extends to the outside of the front side surface of the tube sheet (1); the positioning shaft head (3) comprises a cooling cavity (31), the cooling cavity (31) is hollow and circular in shape, a chamfer (32) is provided on the rear end surface of the positioning shaft head (3), a recessed step (33) is provided in the middle of the positioning shaft head (3) near the front side, and a fixed countersunk hole (34) is provided on the front end of the positioning shaft head (3); the front end of the main gas nozzle (4) is fixedly mounted on the welding gun head, and the main gas nozzle (4) is provided on the front end of the welding gun head. The rear end of the nozzle (4) is tilted and close to the front end surface of the heat exchange tube (2); the tungsten electrode (5) is fixedly installed at the center position of the welding gun head, the tungsten electrode (5) is arranged at the center position of the main gas nozzle (4), and the rear end of the tungsten electrode (5) is close to the contact edge between the heat exchange tube (2) and the front side surface of the tube sheet (1); the auxiliary gas nozzle (6) is tilted and fixedly arranged at the right position of the main gas nozzle (4), the rear end of the auxiliary gas nozzle (6) is close to the outer diameter circumferential edge of the heat exchange tube (2), the auxiliary gas nozzle (6) is fixed to the rotating main shaft of the welding machine through a fixing frame, and the front end of the auxiliary gas nozzle (6) is fixedly connected to the argon gas bottle through a gas pipe.

4. A welding protection device for welding a titanium alloy heat exchange tube to a tube sheet according to claim 3, characterized in that: The tube sheet (1) comprises a tube sheet body (11), a through hole (12) being provided through the center of the tube sheet body (11); the heat exchange tube (2) is inserted and installed in the through hole (12) and fixed by micro-connection through spot welding.

5. The welding protection device for welding a titanium alloy heat exchange tube to a tube sheet according to claim 3, characterized in that: The diameter of the chamfer (32) of the positioning shaft head (3) is 0.3 mm to 0.5 mm smaller than the inner diameter of the heat exchange tube (2); the distance between the rear end vertex of the cooling cavity (31) and the rear end surface of the positioning shaft head (3) is 3 mm; the length of the rear end of the positioning shaft head (3) penetrating into the interior of the heat exchange tube (2) is greater than or equal to 20 mm; and the positioning shaft head (3) is made of copper.

6. The welding protection device for welding a titanium alloy heat exchange tube to a tube sheet according to claim 3, characterized in that: The angle between the axis of the main gas nozzle (4) and the axis of the positioning shaft head (3) is 0° to 25°, the distance between the rear end of the main gas nozzle (4) and the tube plate (1) is less than or equal to 4 mm; the inner diameter of the rear end of the main gas nozzle (4) is greater than or equal to 12 mm, and the main gas nozzle (4) is made of ceramic material.

7. The welding protection device for welding a titanium alloy heat exchange tube to a tube sheet according to claim 3, characterized in that: The length of the tungsten pole (5) extending from the rear end face of the main gas nozzle (4) is less than or equal to 6 mm, and the tungsten pole (5) and the main gas nozzle (4) are coaxially and concentrically arranged.

8. The welding protection device for welding a titanium alloy heat exchange tube to a tube sheet according to claim 3, characterized in that: The axis angle between the auxiliary gas nozzle (6) and the main gas nozzle (4) is 25° to 35°, the axis angle between the auxiliary gas nozzle (6) and the positioning shaft head (3) is 25° to 45°, and the distance between the rear end of the auxiliary gas nozzle (6) and the front side surface of the tube plate (1) is less than or equal to 4 mm.

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