Vacuum electron beam welding method for platinum-iridium alloy

Abstract

The invention relates to a vacuum electron beam welding method for platinum-iridium alloy, which comprises the following steps: S1, pre-treating a platinum-iridium alloy plate to be welded, S2, fixing the pre-treated platinum-iridium alloy plate, and enabling a to-be-welded area to be tightly connected and to be positioned in an electron beam welding working area; s3, electron beam butt joint parameters and welding parameters are set, vacuumizing is conducted, the platinum-iridium alloy plate to be welded is preheated, and welding is conducted; and S4, after welding is completed, a weldment is cooled. According to the welding method, the technical defects existing in platinum-iridium alloy welding are overcome, the machinable range is wide, after welding, a platinum-iridium alloy plate and a welding area are not oxidized, impurity elements are not introduced, the volatilization loss of platinum-iridium precious metal is extremely small, and the uniformity of molten metal components and structures of a weld joint is guaranteed. And after welding, the connection strength is reliable, welding defects such as cracks and air holes do not exist, the mechanical property is close to that of a platinum-iridium alloy welding joint, the welding quality is excellent, and a new optional thought is provided for the platinum-iridium alloy machining technology.

Description

Technical Field

[0001] The invention belongs to the field of platinum-iridium alloy processing, and in particular relates to a vacuum electron beam welding method for platinum-iridium alloy. Background Art

[0002] Platinum-iridium alloy (Pt-Ir) refers to a platinum-based binary alloy containing iridium. It has the characteristics of high hardness, high melting point, high corrosion resistance and low contact resistance, and has excellent conductivity and biocompatibility. It is widely used in electrical contact and microelectronics, aerospace, biomedical equipment and other fields. Platinum-iridium alloy has a high elastic modulus and Poisson's ratio, high mechanical strength, difficult processing and high work hardening rate; platinum-iridium alloy also has the characteristic that the processing performance decreases with the increase of iridium content, and belongs to the type of alloy with greater processing difficulty. At present, platinum-iridium alloy rough blanks are usually formed by investment casting, which has a short casting cycle and low cost, but is prone to defects such as segregation, shrinkage, and holes. Therefore, it can only be formed in the simplest square or cylindrical shape. After casting, post-processing methods such as hot rolling can only be used for simple shaping, and it is difficult to obtain workpieces with diverse structures. Therefore, the welding technology of platinum-iridium alloy is of great practical significance for obtaining workpieces with diverse shapes and expanding the engineering application of platinum-iridium alloy.

[0003] Electron beam welding technology has unique and excellent characteristics such as small molten pool, large aspect ratio, low joint stress, and small workpiece deformation; its weld structure is good, thermal residual stress is low, and this welding method does not introduce other elements. The alloy composition of the weld is controllable, which theoretically meets the welding requirements of platinum-iridium alloy workpieces. However, the existing literature has not conducted relevant research on electron beam welding of platinum-iridium alloys, and whether electron beam welding is suitable for platinum-iridium alloy welding remains to be experimentally demonstrated.

[0004] Through extensive reference to literature related to platinum-iridium alloy processing, it is known that at present, the preparation of platinum-iridium alloy workpieces almost all adopts the mode of casting, extrusion, hot rolling, cold rolling, cold drawing or lathe processing. Patent text CN118003084A discloses a method of suction casting, extrusion, and cold drawing of platinum-iridium alloy into tubes; patent text CN115418724A discloses a method of smelting platinum-iridium alloy combined with directional solidification into rods; patent text CN116623034A discloses a method of directional solidification of platinum-iridium alloy into tubes and isothermal drawing into microtubes. The above methods can only obtain platinum-iridium alloy workpieces with simple structure and single morphology. Patent text CN112872090A discloses a method of extruding platinum-iridium ingots into rods and turning + grinding them into thin-walled tubes; in the processing method disclosed in patent text CN118003045A, laser cutting is selected to process the micropores of platinum-iridium thin plates. Both methods involve subtractive manufacturing of platinum-iridium workpieces, which will result in a large loss of platinum-iridium precious metals and extremely high costs.

[0005] Welding is an effective method for connecting platinum-iridium alloy parts and obtaining complex structural elements. Welding connections have begun to be used in the processing of some platinum-iridium alloy products. In terms of welding, patent text CN118003045A discloses a method for welding platinum-iridium microtubes and platinum-iridium thin plates using laser welding, but laser welding has problems such as low heat input, small penetration depth, and difficulty in welding alloys with high reflectivity. The thickness of the workpiece sheet welded in this method is only 0.05-0.01mm. In the method disclosed in patent text CN101456100A, laser welding is also used to connect platinum-iridium ultrafine wires and platinum alloy rings. This method has the advantages of slight processing weld spots, high welding speed, little thermal damage to the rest of the workpiece, and no pollution to the weld point, but this method only performs single-point welding, and the overall structural strength of the platinum-iridium alloy parts does not need to be considered after welding. Patent text CN106677905A discloses a welding method of thread fastening plus laser welding, but the main function of welding in this method is to ensure that the thread does not loosen, and the platinum-iridium ignition nozzle electrode does not bear stress, and the main fastening effect is generated by the thread. In summary, the existing platinum-iridium alloy laser welding is used in simple cases with small thickness, low required penetration depth, and required welding strength. Patent text CN105886826A provides a platinum-iridium-zirconium-tungsten-thorium alloy solder for welding connections required for complex iridium alloy parts, filling the gap of alloy solders with similar strength of welds and iridium alloys at high temperatures of 1000-1800℃, acid and alkali corrosion resistance and high temperature oxidation. When the solder is used for fusion welding or brazing, the strength of the weld after forming is close to the strength of the original workpiece, but when this welding method is processed, most areas or the entire workpiece need to be heated to above 1820℃. This heating temperature is close to the melting point of the platinum-iridium alloy of common components (1750-1850℃), which will have a more serious and unacceptable thermal impact on the heated workpiece. At the same time, this processing method introduces a variety of additive elements, which is obviously not suitable for processing situations where the workpiece composition needs to be kept clean or highly biocompatible. Similarly, patent document CN110449681A discloses the use of pure copper solder T-3 to weld platinum-iridium alloys to low-carbon steel, but it is not suitable for welding between platinum-iridium alloys.

[0006] Therefore, it is necessary to develop a new welding method to expand the processing methods of platinum-iridium alloys. Summary of the invention

[0007] In view of the shortcomings of the existing processing technology of the above-mentioned platinum-iridium alloy, the inventors conducted in-depth research on various welding processes of platinum-iridium alloy in production practice, and finally determined to provide a vacuum electron beam welding method for platinum-iridium alloy.

[0008] The specific technical scheme of the present invention is as follows:

[0009] A vacuum electron beam welding method for platinum-iridium alloy comprises the following steps:

[0010] S1 Pretreatment of platinum-iridium alloy plates to be welded.

[0011] S2 fixes the pretreated platinum-iridium alloy plate so that the areas to be welded are closely connected and located in the electron beam welding working area;

[0012] S3 sets the electron beam seam alignment parameters and welding parameters, evacuates the vacuum, preheats the platinum-iridium alloy plate to be welded, and performs welding;

[0013] S4 After welding is completed, the weldment is cooled.

[0014] Furthermore, according to the percentage of elements, the composition range of the platinum-iridium alloy is platinum:iridium=95%:5% to 70%:30%.

[0015] Furthermore, in step S1, the pretreatment includes at least one of grinding, ultrasonic cleaning, and acid boiling. Grinding is mainly used to remove processing burrs, adhered pollutants, etc. Ultrasonic cleaning can clean the surface and remove surface oil, dust, etc., and alcohol ultrasonic cleaning or water ultrasonic cleaning can be used as needed. Acid boiling is mainly carried out by cleaning with dilute acid to remove possible impurity metals. The above pretreatment means can be selected and used as needed, and the main purpose is to make the welding surface clean and pollution-free through pretreatment.

[0016] Further, in step S3, the electron beam alignment parameters are as follows: acceleration voltage 20-40KV; focusing current 300-500mA; bias voltage 500V; alignment beam current 0.5-2.5mA; alignment speed 500-700mm / min; scanning frequency 10-40Hz; X-axis and Y-axis scanning range 50-350;

[0017] The welding vacuum degree is 1×10 -4 Pa~6×10 -2 Pa, welding parameters are as follows: acceleration voltage 50~70KV; focusing current 500~900mA; bias voltage 1000~1500V; welding beam 5~15mA; welding speed 400~900mm / min; scanning frequency 40~110Hz; X, Y axis scanning range 100~550.

[0018] Furthermore, when the iridium content in the platinum-iridium alloy is 20wt% to 30wt%, the welding vacuum degree is 1×10 -3 Pa~6×10 -2Pa; welding parameters are: acceleration voltage 50~60KV; focusing current 700~900mA; bias voltage 1000~1500V; welding beam 5~8mA; welding speed 600~800mm / min; scanning frequency 70~110Hz; X, Y axis scanning range 100~300, the volatilization weight loss of precious metals is less, and the welding quality and efficiency are better.

[0019] Furthermore, if the unconnected gap span in the area to be welded after fixing in step S2 is less than or equal to 0.5 mm, there is no need to fill solder; during welding, the electron beam alignment parameters are as follows: acceleration voltage 20~40KV; focusing current 400~500mA; bias 500V; alignment beam current 0.5~2mA; alignment speed 500-700mm / min; scanning frequency 10~30Hz; X, Y axis scanning range 50~300; electron beam welding parameters are as follows: acceleration voltage 50~70KV; focusing current 500~700mA; bias 1000~1500V; welding beam current 5~10mA; welding speed 400~700mm / min; scanning frequency 40~100Hz; X, Y axis scanning range 200~500.

[0020] Furthermore, if there is an unconnected gap in the area to be welded after fixing in step S2, and the gap span is greater than 0.5 mm but less than 2 mm, the gap is filled and fixed with solder, and the solder is a platinum-iridium alloy bar of similar shape and same composition. By controlling the size of the welding gap and filling it with solder of the same composition, the introduction of new impurity elements is avoided. At the same time, adjust the relevant welding parameters. The electron beam seam parameters are as follows: acceleration voltage 20~40KV; focusing current 300~500mA; bias voltage 500V; seam beam current 1.5~2.5mA; seam speed 500~700mm / min; scanning frequency 10~40Hz; X, Y axis scanning range 250~350; electron beam welding parameters are as follows: acceleration voltage 60~70KV; focusing current 500~800mA; bias voltage 1000~1500V; welding beam current 7~13mA; welding speed 700~900mm / min; scanning frequency 40~100Hz; X, Y axis scanning range 250~550.

[0021] Furthermore, in step S3, the platinum-iridium alloy weldment filled with solder is preheated by a reciprocating seam scanning secondary preheating method to ensure the molten pool formed by the electron beam during welding.

[0022] Furthermore, step S3 also includes shaping of the welding area, and the electron beam welding parameters of the shaping are as follows: welding beam current 2 to 4 mA; X, Y axis scanning range 200 to 500. Through shaping, the surface morphology of the weldment can be made more regular to meet the subsequent processing requirements.

[0023] Further, in step S4, after welding is completed, the workpiece is cooled by slow cooling with the furnace; or, 1 to 3 minutes after welding is completed, the welding chamber is inflated, and the weldment is quickly taken out for water cooling to further improve the weld strength. 1 to 3 minutes after welding is completed, the welding chamber is inflated, and the weldment is quickly taken out for water cooling (normal temperature) to avoid high-temperature solid phase decomposition of the platinum-iridium alloy during the cooling process; it can also avoid welding defects and thermal cracks at the weld, reduce the influence of welding stress, and improve the microstructure and performance of the platinum-iridium alloy at the weld.

[0024] The beneficial effects of the present invention are:

[0025] The platinum-iridium alloy vacuum electron beam welding method provided by the present invention breaks through the technical defects existing in platinum-iridium alloy welding, has a wide processing range, and after welding, the platinum-iridium alloy plate and the welding area are not oxidized, no impurity elements are introduced, and the volatilization loss of platinum-iridium precious metal is extremely small, thereby ensuring the uniformity of the molten metal composition and structure of the weld. The connection strength after welding is reliable, without welding defects such as cracks and pores, the mechanical properties are close to those of the platinum-iridium alloy welding joint, the welding quality is excellent, and a new optional idea is provided for the platinum-iridium alloy processing technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is the metallographic structure photograph of the platinum-iridium alloy weld obtained by welding. DETAILED DESCRIPTION

[0027] The present invention provides a vacuum electron beam welding method for platinum-iridium alloy, comprising the following steps:

[0028] S1 is the pretreatment of platinum-iridium alloy plates to be welded.

[0029] Pretreatment includes grinding, ultrasonic cleaning, acid boiling and other methods.

[0030] Grinding mainly involves removing machining burrs, adherent pollutants, etc. by using water-resistant sandpaper.

[0031] Ultrasonic cleaning can clean the surface and remove oil, dust, etc. Alcohol ultrasonic cleaning or water ultrasonic cleaning can be used as needed. After cleaning, use a hot air gun or box drying equipment to dry the cleaned workpiece.

[0032] Acid boiling mainly uses dilute acid to clean and remove possible impurity metals. The dilute acid can be 5% to 10% dilute sulfuric acid. During acid boiling, the reaction phenomenon in the solution stops, and the workpiece is taken out and the surface of the workpiece is rinsed with a large amount of clean water; then use an ultrasonic cleaner equipped with deionized water to ultrasonically clean the workpiece at a frequency of 28kHz for 15 to 60 minutes to ensure that the surface of the platinum-iridium alloy workpiece to be welded is clean and free of pollution. Finally, use a hot air gun or box-type drying equipment to dry the cleaned workpiece.

[0033] The above-mentioned pretreatment means can be selected and used as needed. The main purpose is to make the welding surface clean and pollution-free through pretreatment without damaging the weldment.

[0034] For example, if the surface of the workpiece to be welded is seriously contaminated with oil, a high-purity alcohol ultrasonic cleaning step can be added. Use an ultrasonic cleaning machine filled with high-purity alcohol to clean for 3 to 8 minutes at a frequency of 28 Hz; after cleaning, rinse the surface of the workpiece with clean alcohol and directly put it into a box dryer for drying.

[0035] If the workpiece to be welded already has relatively fragile preliminary processing results, such as wires that have been welded in, the acid boiling step can be omitted and ultrasonic cleaning can be performed at a frequency of 28 Hz during the deionized water cleaning stage.

[0036] S2 fixes the pre-treated platinum-iridium alloy plate so that the areas to be welded are closely connected and located in the electron beam welding working area.

[0037] This step is mainly to fix the platinum-iridium alloy plates to be welded to ensure that the areas to be welded are closely connected. Generally, they are fixed by clamps. The clamping position of the clamps is adjusted to avoid the areas to be welded. The clamps are placed on the working platform of the electron beam welder, the movement limit of the platform is tested, and the position of the clamps is adjusted to ensure that the areas to be welded are located within the electron beam welding working area.

[0038] If there is an unconnected gap in the area to be welded after fixing, and the gap span is greater than 0.5mm but less than 2mm, the gap is filled and fixed with solder, which can be a platinum-iridium alloy bar of similar shape and same composition. The platinum-iridium alloy bar can be obtained by rolling or cutting, and filled and fixed by extrusion or laser welding. By filling with solder of the same composition, the introduction of new impurity elements can be avoided.

[0039] If the gap is less than or equal to 0.5mm after fixing, it can be directly welded. If the gap span is ≥2mm, further adjust the fixation. When the gap width meets the range, fill with solder to fix.

[0040] S3 sets the electron beam seam alignment parameters and welding parameters, evacuates the space, preheats the platinum-iridium alloy sheet to be welded, and performs welding.

[0041] In specific operation, the electron beam welder can be started first, the electron beam alignment parameters can be set, and then the vacuum system can be started to draw the electron beam welding device cavity to the welding working vacuum degree. While waiting for the vacuum to be drawn, the electron beam welding parameters can be set. Then the electron beam emission structure can be preheated, and then the electron beam alignment system can be started to test the electron beam focusing to determine the movement of the electron beam welding point, and the platinum-iridium alloy plate can be preheated at the same time; then the welding program can be started to weld the platinum-iridium alloy plate.

[0042] The electron beam alignment parameters can range from: acceleration voltage 20 to 40KV; focusing current 300 to 500mA; bias voltage 500V; alignment beam current 0.5 to 2.5mA; alignment speed 50-7000mm / min; scanning frequency 10 to 40Hz; X and Y axis scanning range 50 to 350; welding vacuum range can be 1×10 -4 Pa~6×10 -2 Pa, the welding parameter range can be: acceleration voltage 50~70KV; focusing current 500~900mA; bias voltage 1000~1500V; welding beam 5~15mA; welding speed 400~900mm / min; scanning frequency 40~110Hz; X, Y axis scanning range 100~550.

[0043] For conventional welding plates, that is, the connection is tight, the unconnected gap after fixation is less than or equal to 0.5mm, and no solder filling is required to obtain the weldment, the electron beam seam parameter range is: acceleration voltage 20~40KV; focusing current 400~500mA; bias voltage 500V; seam beam current 0.5~2mA; seam speed 500~700mm / min; scanning frequency 10~30Hz; X, Y axis scanning range 50~300; welding parameter range is: acceleration voltage 50~70KV; focusing current 500~700mA; bias voltage 1000~1500V; welding beam current 5~10mA; welding speed 400~700mm / min; scanning frequency 40~100Hz; X, Y axis scanning range 200~500, and the welding quality is good.

[0044] For the above-mentioned weldments that need to be filled with solder, the electron beam alignment parameter range is: acceleration voltage 30~40KV; focusing current 300~500mA; bias voltage 500V; alignment beam current 1.5~2.5mA; alignment speed 500~700mm / min; scanning frequency 10~40Hz; X, Y axis scanning range 250~350; electron beam welding parameters are as follows: acceleration voltage 60~70KV; focusing current 500~800mA; bias voltage 1000~1500V; welding beam current 7~13mA; welding speed 700~900mm / min; scanning frequency 40~100Hz; X, Y axis scanning range 250~550, and the welding quality is good.

[0045] Furthermore, for weldments filled with solder, preferably, a method of reciprocating seam scanning for secondary preheating is used for preheating and temperature raising to ensure the molten pool formed by the electron beam during welding has a deep molten pool.

[0046] In addition, as the concentration of iridium and the heating temperature of platinum-iridium alloy increase, the volatilization weight loss increases, which leads to the loss of precious metal materials. Especially when the content of metal iridium in the platinum-iridium alloy to be welded is high (20% to 30%), it is usually necessary to increase the vacuum degree of the welding work area and adjust the welding speed to reduce the thermal volatilization of the alloy. The welding vacuum degree range is generally set to 1×10 - 4 Pa~1×10 -3 Pa. However, increasing the vacuum degree will greatly prolong the system vacuum pumping time. Preferably, when the iridium content in the platinum-iridium alloy is 20wt% to 30wt%, the welding vacuum degree is 1×10 -3 Pa~6×10 -2 Pa, welding parameters are: acceleration voltage 50~60KV; focusing current 700~900mA; bias voltage 1000~1500V; welding beam 5~8mA; welding speed 600~800mm / min; scanning frequency 70~110Hz; X, Y axis scanning range 100~300, the volatilization weight loss of precious metals is less, and it can well balance the welding quality and welding efficiency.

[0047] If the platinum-iridium alloy workpiece has subsequent processing requirements or surface morphology requirements including the welding area, the welding seam can be reheated for modification by reducing the welding beam current and increasing the scanning area. The adjusted modification electron beam welding parameters are as follows: welding beam current 2~4mA; X, Y axis scanning range 200~500, and the welding quality is better within the range again.

[0048] S4 After welding is completed, the weldment is cooled.

[0049] Usually, for ordinary welding workpieces, there is no special requirement for the strength of the welding seams. After welding, the workpiece can be cooled by slow cooling in the furnace; that is, the welding workpiece is placed in a vacuum furnace body and waits for 10-30 minutes to allow the workpiece to cool slowly.

[0050] If the weld strength requirement is high, the weld performance can be improved by rapid water cooling. Specifically, the welding chamber can be inflated 1 to 3 minutes after the welding is completed, and the weldment can be quickly taken out for water cooling. When the platinum-iridium alloy is cooled from high temperature to around 900°C, a very slow solid phase decomposition will occur. If the platinum-iridium alloy weldment requires higher metal strength in the process, the welding chamber can be inflated 1 to 3 minutes after the welding is completed, and the weldment can be quickly taken out for water cooling to avoid the occurrence of solid phase decomposition. It can also avoid welding defects and thermal cracks at the weld, reduce the impact of welding stress, and improve the microstructure and performance of the platinum-iridium alloy at the weld.

[0051] The vacuum electron beam welding method of platinum-iridium alloy provided by the present invention is applicable to platinum-iridium alloys having a composition range of platinum:iridium=95%:5% to 70%:30% (element percentage content).

[0052] The present invention is further described below in conjunction with specific examples, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art. Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0053] Example 1 A high vacuum electron beam welding method for platinum-iridium 25 alloy

[0054] The workpieces to be welded are two identical platinum-iridium 25 rectangular plates with a thickness of 3 mm and smooth edges; the composition is as follows: In terms of element percentage, the platinum-iridium alloy plates to be processed are composed of the following elements: Pt content 75%, Ir content 25%.

[0055] The specific welding method includes the following steps:

[0056] S1. Use brown corundum water-resistant sandpaper to grind the long edge of the platinum-iridium alloy plate, then put the polished plate into a 5% dilute sulfuric acid solution for acid boiling. After the acid boiling reaction stops, take out the plate and rinse it with a large amount of clean water; then put it into an ultrasonic cleaner and use deionized water to clean it for 20 minutes at a frequency of 28kHz. After cleaning, put the workpiece into a box dryer and dry it at 70℃ for 15 minutes.

[0057] S2. Fixing: Fix the long sides of two cleaned platinum-iridium 25 plates on the welding fixture respectively, connect the long sides to form the position to be welded, move the position to be welded to the protection area of ​​the fixture and lock the fixture. Place the entire set of platinum-iridium 25 plates and fixtures in the electron beam welding work area to ensure that the weld movement trajectory is within the working range of the work platform.

[0058] S3. Welding.

[0059] S31 turns on the electron beam welding machine, sets the seam parameters and starts the vacuum system. The seam parameters are as follows: vacuum degree 6×10 -2 Pa; accelerating voltage 40KV; focusing current 500mA; bias voltage 500V; slit beam current 2mA; slit speed 700mm / min; scanning frequency 30Hz; X, Y axis scanning range 150;

[0060] While waiting for the vacuum system to work, S32 sets the electron beam welding parameters, which are as follows: acceleration voltage 60KV; focusing current 900mA; bias voltage 1500V; welding beam current 7mA; welding speed 600mm / min; scanning frequency 70Hz; X and Y axis scanning range 100.

[0061] S33 preheats the electron beam emission system, starts the electron beam seam alignment program and preheats once, and confirms that the electron beam seam alignment program and welding trajectory are running correctly.

[0062] S34 starts the electron beam welding program to perform welding.

[0063] After S35 welding, it was observed that the weld surface had a slight bulge. In order to reduce post-processing losses, the weld surface modification was started. The modification parameters were as follows: acceleration voltage 60KV; focusing current 900mA; bias voltage 1500V; welding beam 2mA; welding speed 700mm / min; scanning frequency 70Hz; X and Y axis scanning range 200.

[0064] S4 Cooling

[0065] After the shaping is completed, the welding surface morphology is observed to be correct, and the electron beam welding machine cavity inflation program is started after 1 minute. After the inflation is completed, the cavity cover is opened, and the fixture and the plate are taken out for water cooling.

[0066] The mechanical properties test and metallographic structure observation were performed on the platinum-iridium 25 alloy sample obtained by electron beam welding in Example 1. The mechanical properties test results of the welded sample are shown in Table 1, and the metallographic structure is shown in Table 1. Figure 1 As shown in Table 1, the mechanical properties of the Pt-I 25 alloy welded specimens are lower than those of the processed plates, but are close to those of the annealed plates. Figure 1 According to the metallographic structure analysis, the reason may be that the original plate of the welding sample is in the processed state, with fine grains and more grain boundaries blocking the movement of dislocations, so the tensile strength is large but the elongation is reduced; while the metal at the weld is obviously heated, the grain size is large, and there is a certain amount of metal iridium segregation on the surface, so the mechanical properties of the welding sample are somewhat different from those of the processed sample, and are close to the annealed sample. However, there is almost no dislocation or deformation at the interface of the platinum-iridium alloy plate on both sides of the weld, and the structure distribution in the weld is uniform, without obvious welding defects such as pores and shrinkage. This shows that the welding quality of this method is excellent.

[0067] Table 1 Mechanical properties test of welding specimens

[0068]

[0069] The technical features of the above-mentioned embodiments can be combined arbitrarily. To make the description concise, all possible combinations of the technical features in the above-mentioned embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification. It should be pointed out that for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the attached claims.

Claims

1. A vacuum electron beam welding method for platinum-iridium alloy, characterized in that: The following steps are included: S1 Pretreatment of platinum-iridium alloy plates to be welded. S2 fixes the pretreated platinum-iridium alloy plate so that the areas to be welded are closely connected and located in the electron beam welding working area; S3 sets the electron beam seam alignment parameters and welding parameters, evacuates the vacuum, preheats the platinum-iridium alloy plate to be welded, and performs welding; S4 After welding is completed, the weldment is cooled.

2. The vacuum electron beam welding method of platinum-iridium alloy according to claim 1, characterized in that: According to the percentage of elements, the composition range of the platinum-iridium alloy is platinum:iridium=95%:5% to 70%:30%.

3. The vacuum electron beam welding method of platinum-iridium alloy according to claim 1, characterized in that: In step S1, the pretreatment includes at least one of grinding, ultrasonic cleaning, and acid boiling.

4. The vacuum electron beam welding method of platinum-iridium alloy according to claim 1, characterized in that: In step S3, the electron beam alignment parameters are as follows: acceleration voltage 20-40KV; focusing current 300-500mA; bias voltage 500V; alignment beam current 0.5-2.5mA; alignment speed 500-700mm / min; scanning frequency 10-40Hz; X-axis and Y-axis scanning range 50-350; The welding vacuum degree is 1×10 -4 Pa~6×10 -2 Pa, The welding parameters are as follows: acceleration voltage 50~70KV; focusing current 500~900mA; bias voltage 1000~1500V; welding beam 5~15mA; welding speed 400~900mm / min; scanning frequency 40~110Hz; X, Y axis scanning range 100~550.

5. The vacuum electron beam welding method of platinum-iridium alloy according to claim 4, characterized in that: When the content of iridium in the platinum-iridium alloy is 20wt% to 30wt%, Welding vacuum degree 1×10 -3 Pa~6×10 -2 Pa; Welding parameters are: acceleration voltage 50~60KV; Focusing current 700~900mA; bias voltage 1000~1500V; welding beam 5~8mA; welding speed 600~800mm / min; scanning frequency 70~110Hz; X, Y axis scanning range 100~300.

6. The vacuum electron beam welding method of platinum-iridium alloy according to claim 4, characterized in that: If the unconnected gap span in the area to be welded after fixing in step S2 is less than or equal to 0.5 mm, no solder filling is required; during welding, The electron beam alignment parameters are as follows: acceleration voltage 20-40KV; focusing current 400-500mA; bias voltage 500V; alignment beam current 0.5-2mA; alignment speed 500-700mm / min; scanning frequency 10-30Hz; X-axis and Y-axis scanning range 50-300; The electron beam welding parameters are as follows: acceleration voltage 50~70KV; focusing current 500~700mA; bias voltage 1000~1500V; welding beam current 5~10mA; welding speed 400~700mm / min; scanning frequency 40~100Hz; X, Y axis scanning range 200~500.

7. The vacuum electron beam welding method of platinum-iridium alloy according to claim 4, characterized in that: If there is an unconnected gap in the area to be welded after fixing in step S2, and the span of the gap is greater than 0.5 mm but less than 2 mm, the gap is filled and fixed with solder, and the solder is a platinum-iridium alloy bar of similar shape and same composition; during welding, The electron beam alignment parameters are as follows: acceleration voltage 30-40KV; focusing current 300-500mA; bias voltage 500V; alignment beam current 1.5-2.5mA; alignment speed 500-700mm / min; scanning frequency 10-40Hz; X-axis and Y-axis scanning range 250-350; The electron beam welding parameters are as follows: acceleration voltage 60~70KV; focusing current 500~800mA; bias voltage 1000~1500V; welding beam current 7~13mA; welding speed 700~900mm / min; scanning frequency 40~100Hz; X, Y axis scanning range 250~550.

8. The vacuum electron beam welding method of platinum-iridium alloy according to claim 7, characterized in that: In step S3, preheating and heating are performed by reciprocating slit scanning and secondary preheating.

9. The vacuum electron beam welding method of platinum-iridium alloy according to claim 1, characterized in that: Step S3 also includes shaping the welding area, and the electron beam welding parameters of the shaping are as follows: welding beam current 2-4 mA; X-axis and Y-axis scanning range 200-500.

10. The vacuum electron beam welding method of platinum-iridium alloy according to claim 1, characterized in that: In step S4, after welding is completed, the workpiece is cooled by a furnace slow cooling method; Alternatively, 1 to 3 minutes after welding is completed, the welding chamber is inflated and the weldment is quickly removed for water cooling.

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