Helium-free argon arc welding method and welding gun electrode used by same

Abstract

The invention belongs to the technical field of argon arc welding production, and particularly relates to an argon arc welding helium-free welding method and a welding gun electrode used by the argon arc welding helium-free welding method. The method comprises the steps that (1) a non-consumable electrode metal argon arc welding system is built, argon serves as protective gas, and a cerium tungsten electrode serves as a welding gun electrode; (2) welding parameters are set based on the argon arc welding system built in the step (1); and (3) cleaning a welded junction of the metal welding material, and introducing protective gas to weld the welding material through an argon arc welding system. The helium-free welding technology for welding the corrugated aluminum sheath through argon arc welding can meet the requirement for high-quality welding seams on the aluminum sheath of a high-voltage cable, can also be used for welding thin pieces and small pieces and is suitable for single-face welding, double-face forming and all-position welding.

Description

Technical Field

[0001] The invention belongs to the technical field of argon arc welding production, and in particular relates to an argon arc welding helium-free welding method and a welding gun electrode used therefor. Background Art

[0002] In the high-voltage cable production line, argon arc welding is a key process in the production process of high-voltage cables, which is directly related to the quality of cable products. The main task of this process is to use a argon arc welding machine to weld the annular aluminum strip longitudinally to form a closed aluminum cylinder to prevent the insulation core from being damaged by foreign objects and signal interference. Argon arc welding (also known as argon gas shielded welding) technology is based on the principle of ordinary arc welding. It uses argon gas to protect metal welding materials. Argon shielding gas is passed around the arc welding. Through high current, the welding material is melted into liquid on the welded substrate to form a molten pool, so that the welded metal and the welding material can achieve metallurgical bonding. Because argon gas is continuously supplied during high-temperature molten welding, the welding material cannot come into contact with oxygen in the air, thereby preventing the oxidation of the welding material (stainless steel, iron hardware metals, etc.).

[0003] There are two types of welding: consumable electrode argon arc welding and non-consumable electrode argon arc welding (also known as tungsten electrode argon arc welding). In non-consumable electrode argon arc welding, an arc burns between a non-consumable electrode (usually a tungsten electrode) and a workpiece. An inert gas (usually argon) that does not chemically react with metals passes around the welding arc to form a protective gas hood, which prevents the tungsten electrode tip, arc, molten pool, and metal at a high temperature from contacting the air, preventing oxidation and absorption of harmful gases, thereby forming a dense weld joint. The resulting weld joint has very good mechanical properties.

[0004] However, the welding current used in tungsten inert gas welding is limited by the current carrying capacity of the tungsten electrode, the arc power is small, the arc penetration is small, the melting depth is shallow, and the welding speed is low. Tungsten inert gas welding is easy to deform after working for a long time, and the welding effect of large lengths is poor. The tungsten electrode needs to be replaced frequently during the welding process. Moreover, DC welding of aluminum is difficult to achieve, and the welding speed is slower than that of AC welding with the same current. In addition, the current welding process often uses argon and helium mixed gas as a shielding gas. The content of helium in the air is very small, accounting for only 0.0005% by volume, and the density is about 1 / 10 of argon. In order to obtain a good protection effect, the flow rate must be increased, but the cost of helium extraction is expensive, and the procurement cost is more expensive than argon. The average purchase price of helium is 3,500 yuan, and the average purchase price of argon is 130 yuan. Using pure argon welding can greatly reduce production costs. However, the heat conduction effect and arc current must be adjusted, which reduces production efficiency and has a great impact on the service life of the tungsten electrode.

[0005] Therefore, improving the existing argon arc welding system and the non-melting tungsten electrode used therein is an important direction to achieve technical optimization and reduce energy and material losses. Summary of the invention

[0006] Based on the above content, in order to solve a series of problems of argon arc welding such as high gas cost, poor weld quality, short tungsten electrode life and high production cost, the present invention proposes a argon arc welding helium-free welding method and a new welding gun electrode required for use in the new method.

[0007] The objects of the present invention are:

[0008] 1. Reduce the welding cost of argon arc welding and improve the welding quality of corrugated sheath welds;

[0009] 2. Extend the service life and use effect of welding gun electrode and make it suitable for helium-free system welding.

[0010] To achieve the above objectives, the present invention adopts the following technical solutions.

[0011] A argon arc welding helium-free welding method,

[0012] The method comprises:

[0013] 1) Build a non-melting electrode metal argon arc welding system, use argon as the shielding gas, and use cerium tungsten as the welding gun electrode;

[0014] 2) Based on the argon arc welding system constructed in step 1), setting welding parameters;

[0015] 3) Clean the weld of the metal welding material, introduce protective gas and weld the welding material with argon arc welding system.

[0016] As a preference,

[0017] Step 2) The welding parameters include:

[0018] The argon gas flow rate is controlled to be 12-24 L / km of metal welding material, the arc striking current is 50-80 A, the base current is 45-69.3 A, the welding current is 45-73 A / m of metal welding material, and the welding rate is 3.5-6.0 m / min.

[0019] As a preference,

[0020] In the protective gas of step 1) and step 3), the helium concentration is ≤0.01%VOL, the oxygen concentration is ≤0.0015%VOL, the hydrogen concentration is ≤0.0005%VOL, the carbon content is ≤0.001wt%, and the water content is ≤30mg / m 2 , the balance is argon.

[0021] A welding gun electrode,

[0022] The welding gun electrode is a cerium tungsten electrode.

[0023] As a preference,

[0024] The preparation method of the cerium tungsten electrode is:

[0025] Tungsten powder is used as raw material, rare earth oxide is added into the raw material, and cerium tungsten electrode is obtained after pressing and sintering in sequence.

[0026] As a preference,

[0027] The rare earth oxide is cerium oxide, and its usage is 0.01-0.03 g / g raw material.

[0028] As a preference,

[0029] The pressing is performed by cold isostatic pressing at 200-250 MPa.

[0030] As a preference,

[0031] The sintering is carried out in a reducing atmosphere at a constant temperature of 2200-2300° C. for 2-3 hours.

[0032] In order to improve the purity of weld metal, reduce welding defects, and reduce production costs, based on argon arc welding technology, the present invention provides a helium-free welding technology, which uses a cerium tungsten electrode non-melting welding gun electrode and high-purity argon gas for argon arc welding. Compared with the traditional argon-helium mixture as a shielding gas, the use of high-purity argon gas has the characteristics of low cost, but as mentioned above, pure argon gas has a certain adverse effect on tungsten. Because the thermal conductivity of argon gas is poorer than that of helium and argon-helium mixture, the tungsten electrode is heated unevenly, which can easily lead to local overheating and melting loss, and even easily cause tungsten to be clamped in the weld, resulting in problems such as reduced welding quality. However, the traditional tungsten electrode has always been unable to overcome this problem. Even if the argon gas flow rate, temperature and welding current are adjusted, it cannot be completely avoided. Therefore, the most effective way is to improve the tungsten electrode, such as the common thorium tungsten electrode, but the cerium tungsten electrode provided by the present invention is completely different as a welding gun electrode.

[0033] The cerium tungsten non-melting electrode of the present invention has the following advantages: compared with the thorium tungsten electrode, the cerium tungsten electrode does not contain radioactive elements and is safer and more environmentally friendly; the cerium tungsten electrode has excellent arc starting performance under low current conditions and is suitable for fine welding; the cerium tungsten electrode has a low melting rate and a long service life, which is conducive to maintaining the shape of the end, thereby reducing costs and improving production efficiency; compared with the thorium tungsten electrode, the cerium tungsten electrode has higher chemical stability, a small cathode spot, a low voltage drop, less burnout, and a strong thermal electron emission ability, which makes the arc stable and the heat concentrated, which is conducive to improving the stability of the welding process, thereby improving the quality of the weld.

[0034] The amount of cerium oxide used will have a great impact on the performance of the cerium tungsten electrode. Due to the relative particularity of the welding system of the present invention, the performance of the cerium tungsten electrode is also greatly affected by factors such as welding materials and environment. The present invention is mainly for the optimization of welding technology for aluminum sheath welding of high-voltage cables (such as 110kV high-voltage cables and 220kV high-voltage cables, etc.), and therefore the research is mainly conducted on aluminum. Based on the composition, melting point, vapor pressure and other characteristics of the aluminum strip, the present invention adds cerium oxide. After a series of experiments and characterizations, it was found that a small amount of cerium oxide will cause the arc starting and stability of the cerium tungsten electrode to be insufficient, resulting in premature burning of the electrode or low welding performance. With the increase in the amount of cerium oxide used, the work function of the cerium tungsten electrode is reduced, the arc starting and stability are significantly improved, the service life of the electrode is extended, and the burnout rate of the cerium tungsten electrode is significantly reduced. However, since the thermal expansion coefficient of cerium oxide is different from that of tungsten, under high temperature operation, a large amount of cerium oxide will cause the grain size and structure of the cerium tungsten electrode to change, increase the stress inside the electrode, and reduce its mechanical strength, thereby causing the electrode to degrade prematurely. In addition, since the system of the present invention changes the atmosphere environment, and the pure argon atmosphere environment also increases the temperature non-uniformity, it is easy to produce local overheating and the like, so the amount of cerium also needs to be relatively strictly controlled. In addition, in certain acidic or alkaline environments, the cerium tungsten electrode to which a large amount of cerium oxide is added is more susceptible to corrosion. In addition, a large amount of cerium oxide enters the welding area, which not only affects the purity and welding performance of the weld, but also causes pollution problems during the welding process. Therefore, in order to ensure the excellent performance of the cerium tungsten electrode during the welding process, the present invention controls the relative addition amount of cerium oxide.

[0035] After cold isostatic pressing, the powder is compacted evenly, which is beneficial to improve the density and uniformity of the cerium tungsten electrode. Cold isostatic pressing is an isotropic pressure, and the material can be compacted without external force, which reduces the stress concentration inside the cerium tungsten electrode, is beneficial to the preparation of a specific shape of cerium tungsten electrode, and improves the toughness and fatigue resistance of the cerium tungsten electrode. At the same time, cold isostatic pressing is carried out at a lower temperature, which is beneficial for the powder to maintain its original microstructure.

[0036] The cerium tungsten electrode is sintered at a relatively high temperature, which is conducive to the full diffusion of atoms. The high temperature provides a driving force to overcome the potential energy barrier between particles and promotes the close bonding of particles, which is beneficial to the density of the cerium tungsten electrode. At the same time, it grows during the sintering process, the interface between grains is reduced, and its mechanical properties are improved. Moreover, high-temperature sintering is conducive to the rapid completion of the phase change process. As the sintering temperature continues to increase, grain growth occurs inside the material. Excessive grain growth leads to insufficient toughness of the cerium tungsten electrode and the formation of coarse grains, resulting in uneven microstructure of the material and decreased mechanical properties of the material. In order to take into account both the density of the material and good mechanical properties, the present invention regulates the grain size by sintering temperature. The cerium tungsten electrode is prepared by cold isostatic pressing and sintering, such as Figure 1 Showing the detailed dimensions of the cerium tungsten electrode.

[0037] On the other hand, the larger the diameter of the welding material, the more current passes through, and the volume of the weld increases accordingly. Under the conditions of high-speed welding or insufficient parameters such as welding current, the heat is not enough to fully fuse the welding material and the electrode, and the expected weld size cannot be obtained using welding materials with larger diameters; if the welding speed is too slow or the welding current is too large, it may cause excessive fusion of the weld and even welding defects. The thickness of the welding material determines the welding current, welding speed and energy distribution during the welding process. To ensure the integrity and performance of the weld, welding materials of different thicknesses need to adjust the current size and welding speed. Moreover, according to the thickness of the aluminum strip, in order to ensure the welding quality, the present invention accurately sets the arc starting current. Based on the settings of current and welding speed, the present invention adjusts the specifications of the welding material, welding speed, and argon gas usage. When welding in a horizontal position, a higher welding speed can usually be used because the molten pool cools faster, which helps metal flow and weld formation. When welding at a vertical or elevation angle, the welding speed needs to be reduced to avoid weld defects such as pores and lack of fusion caused by too fast cooling. Based on welding speed and economic benefits, in order to maintain the stability of the arc and ensure the continuous flow of the shielding gas, the present invention limits the amount of argon used. If the amount of argon used is insufficient, the quality of the weld will be significantly reduced.

[0038] The beneficial effects of the present invention are as follows:

[0039] (1) The weld quality of the aluminum sheath after welding by the method of the present invention is good, the appearance has no obvious damage, and the mechanical properties of the weld meet the requirements of the welding process;

[0040] (2) The equipment adopts positive grounding of welding power supply, that is, cerium tungsten electrode non-melting electrode argon arc welding is adopted. The cerium tungsten electrode is not easy to deform after long-term work, which prolongs the service life and ensures the possibility of long-length welding;

[0041] (3) Taking advantage of the easy ionization of argon gas, argon ions are used to bombard the oxide layer on the metal surface, making DC welding of aluminum, which is generally not possible, possible. Compared with AC welding of the same current, argon arc welding is faster;

[0042] (4) The helium-free argon arc welding technology for welding corrugated aluminum sheaths provided by the present invention can meet the requirements of high-quality welds on high-voltage cable aluminum sheaths, and can also be used for welding thin and small parts, and is suitable for single-sided welding, double-sided forming and all-position welding. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 A schematic diagram of a welding device used in an embodiment of the present invention;

[0044] Figure 2 Schematic diagram of standard dimensions of welding electrodes used in embodiments of the present invention. DETAILED DESCRIPTION

[0045] The present invention is further described in detail below in conjunction with specific embodiments and the accompanying drawings. A person of ordinary skill in the art will be able to implement the present invention based on these descriptions. In addition, the embodiments of the present invention involved in the following description are generally only embodiments of a part of the present invention, rather than all embodiments. Therefore, based on the embodiments of the present invention, all other embodiments obtained by a person of ordinary skill in the art without making creative work should fall within the scope of protection of the present invention.

[0046] If there is no special explanation, the welding equipment system used in the present invention is the existing Figure 1 The metal argon arc welding machine (DAG60 / 180 metal argon arc welding machine - equipped with S7-200 series PLC and MP-270 human-machine interface) shown in the figure is improved. The improvement is that the protective gas cylinder is replaced with a high-purity argon gas cylinder, and the welding gun electrode is replaced with a specific cerium tungsten electrode used in the present invention (some comparative examples still use tungsten electrodes or thorium tungsten electrodes, etc.), and the welding electrodes are as follows Figure 2 The standard size is shown. The metal argon arc welding pipe machine used in the present invention integrates automated functions such as crawler precision cutting, argon arc welding, and aluminum corrugation. It can control the welding equipment, enable the speed to automatically track the welding current, and realize the welding of metal pipes of any length.

[0047] Unless otherwise specified, the raw materials used in the examples of the present invention are all commercially available or available to those skilled in the art; unless otherwise specified, the methods used in the examples of the present invention are all methods known to those skilled in the art.

[0048] Unless otherwise specified, the purity of the tungsten powder used in the embodiments of the present invention is 99.95 wt %.

[0049] Unless otherwise specified, the grade of the aluminum strip used in the embodiments of the present invention is 1060.

[0050] Unless otherwise specified, the argon gas used in the embodiments of the present invention is bottled high-purity argon for welding (in accordance with GB / T 4842-2006), the filling cylinder has a capacity of 40L, and its filling pressure is 15MPa at room temperature. The cylinder is painted gray and marked with the word "argon gas".

[0051] Example 1

[0052] A argon arc welding helium-free welding method, the method comprising:

[0053] 1) Tungsten powder was used as raw material, 0.01 g of cerium oxide was added per gram of tungsten powder, and cold isostatic pressing was performed at 200 MPa. 2 In the atmosphere, sintering was carried out at 2300℃ for 2h to obtain the cerium tungsten electrode;

[0054] 2) Select the positive pole of the DC power supply to be grounded, use a high-voltage pulse arc starting and arc stabilization device, take aluminum strip as the metal welding material, use argon as the shielding gas, and use cerium tungsten as the welding gun electrode. Based on this non-melting electrode metal argon arc welding system, control the argon flow rate to 12L / km of metal welding material, the arc starting current to 50A, the base current to 45A, the welding current to 45A / m of metal welding material, and the welding speed to 6.0m / min;

[0055] The protective gas has a helium concentration of ≤0.01%VOL, an oxygen concentration of ≤0.0015%VOL, a hydrogen concentration of ≤0.0005%VOL, a carbon content of ≤0.001wt%, and a water content of ≤30mg / m 2 , the balance is argon

[0056] 3) Clean the aluminum strip weld, introduce protective gas and weld the welding material using argon arc welding system;

[0057] The protective gas has a helium concentration of ≤0.01%VOL, an oxygen concentration of ≤0.0015%VOL, a hydrogen concentration of ≤0.0005%VOL, a carbon content of ≤0.001wt%, and a water content of ≤30mg / m 2 , the balance is argon.

[0058] The welding products in this example are characterized and tested, and the specific methods are as follows.

[0059] 1. Non-destructive testing:

[0060] The morphology of the weld is analyzed by scanning electron microscope; ultrasonic wave is used to detect whether there are defects such as pores and slag inclusions inside the weld; water pressure resistance method is used to detect whether there are surface crack defects in the weld; high-pressure water is used to impact the weld to observe whether there is leakage or visible deformation on the weld surface. If there is no defect, the product is recorded as "○", if there is a defect, the product is recorded as "×".

[0061] 2. Destructive testing:

[0062] According to GB / T 228.1-2021 "Tensile Test of Metallic Materials", take the cap weld part of the weld cladding metal, set the experimental parameters, and the tensile strain rate is 0.00025s -1 , determine the tensile strength of the weld; according to GB / T 229-2020 “Charpy Pendulum Impact Test Method for Metallic Materials”, take a 55mm×10mm×10mm welding product sample with the weld located in the center of the sample and the notch perpendicular to the sample, and carry out a Charpy V-notch impact test at 0℃ and room temperature to determine the impact absorption energy of the weld.

[0063] 3. Corrosion resistance test:

[0064] A 3.5wt% NaCl aqueous solution was used to simulate the marine environment, and the weld products were immersed in the solution. The Versa STAT3F electrochemical workstation was used, with a saturated calomel electrode as the reference electrode and a platinum electrode as the auxiliary electrode. The scanning speed was 0.167mV / s, and electrochemical corrosion was carried out at room temperature. After 2000s, the experiment was stopped, and the defects inside or on the surface of the weld were detected by water pressure resistance, ultrasonic testing and other methods. The corrosion resistance was evaluated based on the results. If there was no visible deformation on the weld surface, the product was recorded as a qualified product, otherwise it was recorded as an unqualified product.

[0065] The results are as follows.

[0066]

[0067] According to observation, it can be seen that the surface of the weld is continuous fish scale-like, without obvious unevenness. According to the characterization of the weld, it can be known that the weld is well formed, and there are no obvious impurities, pores, cracks and other defects inside. When in a low temperature environment, the weld undergoes a ductile-brittle transition. After many experiments and analyses, it was found that the average temperature of the ductile-brittle transition of the weld is -5.3°C, that is, in an environment below the ductile-brittle transition temperature, the weld will undergo brittle fracture. When stretched at room temperature, its tensile properties far exceed the regulations for domestic welding materials. After stretching, the fracture occurs at a non-weld position, and the fracture shows a typical ductile fracture, indicating that the material has good toughness and can effectively resist plastic deformation. Welds at different sampling positions have excellent impact resistance, with a small difference. Under electrochemical accelerated corrosion, there is a certain amount of pitting on the weld surface, but there is no obvious deformation. Products prepared by the welding method provided by the present invention, such as ships, can work in the sea for a long time.

[0068] In addition to the above tests, the present invention also conducted a cupping test, and the weld cracking position was perpendicular to the weld direction, meeting the welding requirements.

[0069] Example 2

[0070] A argon arc welding helium-free welding method, the method comprising:

[0071] 1) Tungsten powder was used as raw material, 0.02g cerium oxide was added per gram of tungsten powder, and cold isostatic pressing was performed at 200MPa. 2 In the atmosphere, sintering was carried out at 2300℃ for 2h to obtain the cerium tungsten electrode;

[0072] 2) Select the positive pole of the DC power supply to be grounded, use a high-voltage pulse arc starting and arc stabilization device, take aluminum strip as the metal welding material, use argon as the shielding gas, and use cerium tungsten as the welding gun electrode. Based on this non-melting electrode metal argon arc welding system, control the argon flow rate to 12L / km of metal welding material, the arc starting current to 50A, the base current to 45A, the welding current to 45A / m of metal welding material, and the welding speed to 6.0m / min;

[0073] The protective gas has a helium concentration of ≤0.01%VOL, an oxygen concentration of ≤0.0015%VOL, a hydrogen concentration of ≤0.0005%VOL, a carbon content of ≤0.001wt%, and a water content of ≤30mg / m 2 , the balance is argon

[0074] 3) Clean the aluminum strip weld, introduce protective gas and weld the welding material using argon arc welding system;

[0075] The protective gas has a helium concentration of ≤0.01%VOL, an oxygen concentration of ≤0.0015%VOL, a hydrogen concentration of ≤0.0005%VOL, a carbon content of ≤0.001wt%, and a water content of ≤30mg / m 2 , the balance is argon.

[0076] The welding product of this example was characterized and tested in the same manner as in Example 1, and the results are as follows.

[0077]

[0078] During the research, it was found that adding an appropriate amount of cerium oxide to tungsten powder during the preparation of cerium tungsten electrode can improve the stability of cerium tungsten electrode, thereby improving the quality of weld. Cerium oxide has a cubic structure similar to fluorite. Ce atoms and O 2- Ionic coordination, the surface of cerium oxide has a large number of oxygen vacancies. Tungsten atoms and cerium atoms are chemically bonded, and the electronic structure around the cerium atoms is coordinated to form a "bonding phase" in the system to regulate the extreme density of cerium tungsten. With the increase of cerium oxide dosage, the work function of the cerium tungsten electrode is reduced, and the arc starting performance and stability are significantly improved, avoiding premature burning of the electrode or low welding performance. Stable cerium tungsten electrode can reduce the generation of welding defects such as pores, impurities, cracks, etc.; it can ensure the stability of welding speed, thereby obtaining high-quality welds; it helps to maintain a continuous and stable arc, reduce welding defects, and improve welding quality. According to the results in the table, the tensile strength and impact resistance of the weld are improved.

[0079] Example 3

[0080] A argon arc welding helium-free welding method, the method comprising:

[0081] 1) Tungsten powder was used as raw material, 0.03g cerium oxide was added per gram of tungsten powder, and cold isostatic pressing was performed at 200MPa. 2 In the atmosphere, sintering was carried out at 2300℃ for 2h to obtain the cerium tungsten electrode;

[0082] 2) Select the positive pole of the DC power supply to be grounded, use a high-voltage pulse arc starting and arc stabilization device, take aluminum strip as the metal welding material, use argon as the shielding gas, and use cerium tungsten as the welding gun electrode. Based on this non-melting electrode metal argon arc welding system, control the argon flow rate to 12L / km of metal welding material, the arc starting current to 50A, the base current to 45A, the welding current to 45A / m of metal welding material, and the welding speed to 6.0m / min;

[0083] The protective gas has a helium concentration of ≤0.01%VOL, an oxygen concentration of ≤0.0015%VOL, a hydrogen concentration of ≤0.0005%VOL, a carbon content of ≤0.001wt%, and a water content of ≤30mg / m 2 , the balance is argon

[0084] 3) Clean the aluminum strip weld, introduce protective gas and weld the welding material using argon arc welding system;

[0085] The protective gas has a helium concentration of ≤0.01%VOL, an oxygen concentration of ≤0.0015%VOL, a hydrogen concentration of ≤0.0005%VOL, a carbon content of ≤0.001wt%, and a water content of ≤30mg / m 2 , the balance is argon.

[0086] The welding product of this example was characterized and tested in the same manner as in Example 1, and the results are as follows.

[0087]

[0088] Cerium oxide and tungsten powder have different thermal expansion coefficients, so under high temperature operation, a large amount of cerium oxide will cause the grain size of the cerium tungsten electrode to increase significantly, increase the stress inside the electrode, crack the grains, reduce its mechanical strength, and thus cause premature degradation of the electrode. In addition, the uniformity of the weld deteriorates, and the metal on both sides of the weld deforms unevenly during heat treatment and cooling, resulting in a small angle deviation at the weld, and its impact resistance decreases.

[0089] Comparative Example 1

[0090] A argon arc welding helium-free welding method, the method comprising:

[0091] 1) Tungsten powder was used as the raw material, 0.02 g of thorium oxide was added per gram of tungsten powder, and cold isostatic pressing was performed at 200 MPa. 2 In the atmosphere, sintering was carried out at 2300℃ for 2h to obtain the thoriated tungsten electrode;

[0092] 2) Select the positive pole of the DC power supply to be grounded, use a high-voltage pulse arc starting and arc stabilization device, take aluminum strip as the metal welding material, use argon as the shielding gas, and use a thorium tungsten electrode as the welding gun electrode. Based on this non-melting electrode metal argon arc welding system, control the argon flow rate to 12L / km of metal welding material, the arc starting current to 50A, the base current to 45A, the welding current to 45A / m of metal welding material, and the welding speed to 6.0m / min;

[0093] The protective gas has a helium concentration of ≤0.01%VOL, an oxygen concentration of ≤0.0015%VOL, a hydrogen concentration of ≤0.0005%VOL, a carbon content of ≤0.001wt%, and a water content of ≤30mg / m 2 , the balance is argon

[0094] 3) Clean the aluminum strip weld, introduce protective gas and weld the welding material using argon arc welding system;

[0095] The protective gas has a helium concentration of ≤0.01%VOL, an oxygen concentration of ≤0.0015%VOL, a hydrogen concentration of ≤0.0005%VOL, a carbon content of ≤0.001wt%, and a water content of ≤30mg / m 2 , the balance is argon.

[0096] The welding product of this example was characterized and tested in the same manner as in Example 1, and the results are as follows.

[0097]

[0098] The burnout amount of the tungsten-based electrode in Example 2 and this example was calculated, and the results are as follows.

[0099] Burning loss of cerium tungsten electrode (%) Thorium tungsten electrode burnout (%) 0.04 0.06

[0100] In this example, thoriated tungsten electrodes and pure argon gas are used for argon arc welding. According to the research of technicians in this field, the electron work function of cerium and cerium tungsten in cerium tungsten electrodes is smaller than that of thoriated tungsten electrodes. Under the condition of direct current, high-frequency arc initiation is carried out, and it is observed that the cerium tungsten electrode can completely establish a stable arc, while the probability of establishing a stable arc after the thoriated tungsten electrode in this example is less than 80%. The welding head is unstable during the welding process, which significantly affects the quality of the weld. In the early stage of welding, the arc jitters, the cathode voltage of the thoriated tungsten electrode decreases, the cathode spot temperature decreases insufficiently, the electrode is difficult to cool, the end loss increases, and the allowable welding current density is small. When the welding current is higher than the allowable welding current density of the electrode, the electrode generates strong heat, the end melts into a spherical shape, generates a large amount of metal vapor, burns rapidly, the end consumes quickly, the shape of the end cannot be maintained, a molten drop is formed, and the arc splashes into the welding pool, resulting in an uneven weld.

[0101] According to the results in the table, it can be seen that the tensile and impact resistance of the welded product has decreased. The most important thing is that the thoriated tungsten electrode contains radioactive elements, which is a threat to the environment, has low market acceptance, and has a high preparation cost, so it is generally not used in this field.

[0102] Comparative Example 2

[0103] A argon arc welding helium-free welding method, the method comprising:

[0104] 1) Tungsten powder was used as raw material, 0.02g cerium oxide was added per gram of tungsten powder, and cold isostatic pressing was performed at 200MPa. 2 In the atmosphere, sintering was carried out at 2300℃ for 2h to obtain the cerium tungsten electrode;

[0105] 2) Select the positive pole of the DC power supply to be grounded, use a high-voltage pulse arc starting and arc stabilization device, take aluminum strip as the metal welding material, use argon as the shielding gas, and use cerium tungsten as the welding gun electrode. Based on this non-melting electrode metal argon arc welding system, control the argon flow rate to 12L / km of metal welding material, the arc starting current to 50A, the base current to 45A, the welding current to 45A / m of metal welding material, and the welding speed to 6.0m / min;

[0106] The protective gas has a helium concentration of ≤0.01%VOL, an oxygen concentration of ≤0.0015%VOL, a hydrogen concentration of ≤0.0005%VOL, a carbon content of ≤0.001wt%, and a water content of ≤30mg / m 2 , the balance is argon

[0107] 3) Clean the aluminum strip weld, introduce protective gas and weld the welding material using argon arc welding system;

[0108] The protective gas has a helium concentration of ≤0.01%VOL, an oxygen concentration of ≤0.0015%VOL, a hydrogen concentration of ≤0.0005%VOL, a carbon content of ≤0.001wt%, and a water content of ≤30mg / m 2 , the balance is argon.

[0109] The welding product of this example was characterized and tested in the same manner as in Example 1, and the results are as follows.

[0110]

[0111] The cerium tungsten electrode in this case has coarse grains and many pores between the grains. During the sintering process, due to the displacement of tungsten powder particles, the cerium tungsten electrode has certain initial fine lines, and its stability is reduced. After welding, the weld is obviously irregular, with obvious pore defects, and the continuity and uniformity of the weld are deteriorated, resulting in reduced mechanical properties and poor corrosion resistance.

[0112] Comparative Example 3

[0113] A argon arc welding helium-free welding method, the method comprising:

[0114] 1) Tungsten powder was used as raw material, 0.02g cerium oxide was added per gram of tungsten powder, and cold isostatic pressing was performed at 200MPa. 2 In the atmosphere, sintering was carried out at 2400℃ for 2h to obtain the cerium tungsten electrode;

[0115] 2) Select the positive pole of the DC power supply to be grounded, use a high-voltage pulse arc starting and arc stabilization device, take aluminum strip as the metal welding material, use argon as the shielding gas, and use cerium tungsten as the welding gun electrode. Based on this non-melting electrode metal argon arc welding system, control the argon flow rate to 12L / km of metal welding material, the arc starting current to 50A, the base current to 45A, the welding current to 45A / m of metal welding material, and the welding speed to 6.0m / min;

[0116] The protective gas has a helium concentration of ≤0.01%VOL, an oxygen concentration of ≤0.0015%VOL, a hydrogen concentration of ≤0.0005%VOL, a carbon content of ≤0.001wt%, and a water content of ≤30mg / m 2 , the balance is argon

[0117] 3) Clean the aluminum strip weld, introduce protective gas and weld the welding material using argon arc welding system;

[0118] The protective gas has a helium concentration of ≤0.01%VOL, an oxygen concentration of ≤0.0015%VOL, a hydrogen concentration of ≤0.0005%VOL, a carbon content of ≤0.001wt%, and a water content of ≤30mg / m 2 , the balance is argon.

[0119] The welding product of this example was characterized and tested in the same manner as in Example 1, and the results are as follows.

[0120]

[0121] Excessively high sintering temperature causes grain growth inside the cerium tungsten electrode. Grain growth leads to insufficient toughness of the cerium tungsten electrode and the formation of coarse grains, which leads to uneven microstructure of the cerium tungsten electrode and reduced mechanical properties of the cerium tungsten electrode. After welding, the weld has a high porosity and uneven pore distribution. Due to defects such as pores and cracks, the corrosion resistance of the welded product is reduced.

[0122] Combining Example 3 and Comparative Examples 1 to 3, it is found that the cerium tungsten electrode is not stable enough, and will swing or jump during welding, resulting in uneven welding speed, thus affecting the continuity and uniformity of the weld. It will also cause the arc to be frequently extinguished and reignited, and the unstable arc will cause defects such as pores and impurities in the weld.

[0123] Comparative Example 4

[0124] A argon arc welding helium-free welding method, the method comprising:

[0125] 1) Tungsten powder was used as raw material, 0.02g cerium oxide was added per gram of tungsten powder, and cold isostatic pressing was performed at 200MPa. 2 In the atmosphere, sintering was carried out at 2300℃ for 2h to obtain the cerium tungsten electrode;

[0126] 2) Select the positive pole of the DC power supply to be grounded, use a high-voltage pulse arc starting and arc stabilization device, take aluminum strip as the metal welding material, use argon as the shielding gas, and use cerium tungsten as the welding gun electrode. Based on this non-melting electrode metal argon arc welding system, control the argon flow rate to 12L / km of metal welding material, the arc starting current to 50A, the base current to 45A, the welding current to 45A / m of metal welding material, and the welding speed to 6.0m / min;

[0127] The protective gas has a helium concentration of ≤30.00%VOL, an oxygen concentration of ≤0.0015%VOL, a hydrogen concentration of ≤0.0005%VOL, a carbon content of ≤0.001wt%, and a water content of ≤30mg / m 2 , the balance is argon

[0128] 3) Clean the aluminum strip weld, introduce protective gas and weld the welding material using argon arc welding system;

[0129] The protective gas has a helium concentration of ≤30.00%VOL, an oxygen concentration of ≤0.0015%VOL, a hydrogen concentration of ≤0.0005%VOL, a carbon content of ≤0.001wt%, and a water content of ≤30mg / m 2 , the balance is argon.

[0130] The welding product of this example was characterized and tested in the same manner as in Example 1, and the results are as follows.

[0131]

[0132] The content of helium in the air is small, and its volume and density are small. In order to obtain a good protective effect, the flow rate must be increased. However, the cost of helium extraction is expensive, and the procurement cost is expensive. Based on this, the production cost of this welding technology is high and it is not suitable for widespread application. Moreover, when welding under this mixed gas, the thermal conductivity increases, and the heat transfer to the outside increases, resulting in the loss of heat in the arc, which makes the welding arc burning unstable, and finally causes irregular small cracks in the weld, resulting in reduced mechanical properties of the welded product.

[0133] Comparative Example 5

[0134] A argon arc welding helium-free welding method, the method comprising:

[0135] 1) Tungsten powder was used as raw material, 0.02g cerium oxide was added per gram of tungsten powder, and cold isostatic pressing was performed at 200MPa. 2 In the atmosphere, sintering was carried out at 2300℃ for 2h to obtain the cerium tungsten electrode;

[0136] 2) Select the positive pole of the DC power supply to be grounded, use a high-voltage pulse arc starting and arc stabilization device, take aluminum strip as the metal welding material, use argon as the shielding gas, and use cerium tungsten as the welding gun electrode. Based on this non-melting electrode metal argon arc welding system, control the argon flow rate to 12L / km of metal welding material, the arc starting current to 50A, the base current to 45A, the welding current to 45A / m of metal welding material, and the welding rate to 3.0m / min;

[0137] The protective gas has a helium concentration of ≤0.01%VOL, an oxygen concentration of ≤0.0015%VOL, a hydrogen concentration of ≤0.0005%VOL, a carbon content of ≤0.001wt%, and a water content of ≤30mg / m 2 , the balance is argon

[0138] 3) Clean the aluminum strip weld, introduce protective gas and weld the welding material using argon arc welding system;

[0139] The protective gas has a helium concentration of ≤0.01%VOL, an oxygen concentration of ≤0.0015%VOL, a hydrogen concentration of ≤0.0005%VOL, a carbon content of ≤0.001wt%, and a water content of ≤30mg / m 2 , the balance is argon.

[0140] The welding product of this example was characterized and tested in the same manner as in Example 1, and the results are as follows.

[0141]

[0142] In this case, the cerium tungsten electrode was overheated and worn seriously due to the low welding speed. The vibration and deviation of the cerium tungsten electrode caused humps and depressions at the bottom of the weld, and the cooling rates of different parts of the weld were uneven. The weld quality was poor. After knocking the product, it can be observed that the weld appearance was obviously damaged and the mechanical strength was significantly reduced.

[0143] Comparative Example 6

[0144] A argon arc welding helium-free welding method, the method comprising:

[0145] 1) Tungsten powder was used as raw material, 0.02g cerium oxide was added per gram of tungsten powder, and cold isostatic pressing was performed at 200MPa. 2 In the atmosphere, sintering was carried out at 2300℃ for 2h to obtain the cerium tungsten electrode;

[0146] 2) Select an AC power source, use a high-voltage pulse arc starting and arc stabilization device, take aluminum strip as the metal welding material, use argon as the shielding gas, and use a cerium tungsten electrode as the welding gun electrode. Based on this non-melting electrode metal argon arc welding system, control the argon flow rate to 12L / km of metal welding material, the arc starting current to 50A, the base current to 45A, the welding current to 45A / m of metal welding material, and the welding speed to 6.0m / min;

[0147] The protective gas has a helium concentration of ≤0.01%VOL, an oxygen concentration of ≤0.0015%VOL, a hydrogen concentration of ≤0.0005%VOL, a carbon content of ≤0.001wt%, and a water content of ≤30mg / m 2 , the balance is argon

[0148] 3) Clean the aluminum strip weld, introduce protective gas and weld the welding material using argon arc welding system;

[0149] The protective gas has a helium concentration of ≤0.01%VOL, an oxygen concentration of ≤0.0015%VOL, a hydrogen concentration of ≤0.0005%VOL, a carbon content of ≤0.001wt%, and a water content of ≤30mg / m 2 , the balance is argon.

[0150] The welding product of this example was characterized and tested in the same manner as in Example 1, and the burnout amount of the cerium tungsten electrode was tested. The results are as follows.

[0151]

[0152] Compared with Example 2, the welding speed of AC welding in this example is fast, but the electrode in this example is impacted by high-speed electrons, and the cerium tungsten electrode quickly generates a large amount of heat. Due to the violent evaporation, the cerium content decreases rapidly, resulting in a decrease in the electron emission ability of the cerium tungsten electrode, thereby causing the arc stability to decrease. Not only does it cause the cerium tungsten electrode to burn more, but it also causes the allowable welding current density to decrease. When the welding current is higher than the allowable welding current density of the electrode, the cerium tungsten electrode tip is severely burned, and the molten droplet is ejected, resulting in an uneven weld.

Claims

1. A method for argon arc welding without helium, characterized in that: The method comprises: 1) Build a non-melting electrode metal argon arc welding system, use argon as the shielding gas, and use cerium tungsten as the welding gun electrode; 2) Based on the argon arc welding system constructed in step 1), setting welding parameters; 3) Clean the weld of the metal welding material, introduce protective gas and weld the welding material using the argon arc welding system.

2. The argon arc welding helium-free welding method according to claim 1, characterized in that: Step 2) The welding parameters include: The argon gas flow rate is controlled to be 12-24 L / km of metal welding material, the arc striking current is 50-80 A, the base current is 45-69.3 A, the welding current is 45-73 A / m of metal welding material, and the welding rate is 3.5-6.0 m / min.

3. A argon arc welding helium-free welding method according to claim 1 or 2, characterized in that: In the protective gas of step 1) and step 3), the helium concentration is ≤0.01%VOL, the oxygen concentration is ≤0.0015%VOL, the hydrogen concentration is ≤0.0005%VOL, the carbon content is ≤0.001wt%, and the water content is ≤30mg / m 2 , the balance is argon.

4. A welding gun electrode, characterized in that: The welding gun electrode is a cerium tungsten electrode.

5. A welding gun electrode according to claim 4, characterized in that: The preparation method of the cerium tungsten electrode is: Tungsten powder is used as raw material, rare earth oxide is added into the raw material, and cerium tungsten electrode is obtained after pressing and sintering in sequence.

6. A welding gun electrode according to claim 5, characterized in that: The rare earth oxide is cerium oxide, and its usage is 0.01-0.03 g / g raw material.

7. A welding gun electrode according to claim 5, characterized in that: The pressing is performed by cold isostatic pressing at 200-250 MPa.

8. A welding gun electrode according to claim 5 or 6, characterized in that: The sintering is carried out in a reducing atmosphere at a constant temperature of 2200-2300° C. for 2-3 hours.

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