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Q&A on Basic Welding Knowledge (compiled and uploaded on December 24, 2006) I. Basic Knowledge 1. What is welding? Answer: Welding is a process in which two or more materials (of the same type or different types) are combined together through heating, pressing, or both methods, thereby achieving atomic bonding and forming a permanent connection. 2. What is an arc? Answer: It is powered by a welding power supply, and it generates a strong and sustained gas discharge between the two electrodes—a phenomenon known as an arc. <1>Based on the type of current, it can be classified into alternating current arcs, direct current arcs, and pulse arcs. <2>According to the state of the arc, it can be divided into free arcs and compressed arcs (such as plasma arcs). <3>Based on the electrode material, it can be categorized as melting electrode arcs and non-melting electrode arcs. 3. What is the base metal? Answer: The metal that is being welded is called the base material. 4. What is a droplet? Answer: When the tip of the welding wire is heated and melts, the liquid metal droplet that transitions into the molten pool is called a weld droplet. 5. What is a molten pool? Answer: The liquid metal portion with a specific geometric shape that forms on the workpiece during fusion welding is called the weld pool. 6. What is a weld? Answer: The joint formed in the welded piece after welding. 7. What is weld metal? Answer: The part of metal that is formed after the melting base material and filler metal (welding wire, electrodes, etc.) solidify. 8. What is a shielding gas? Answer: The gas used in welding to protect the metal droplets and the molten pool from harmful external gases (hydrogen, oxygen, nitrogen) is the shielding gas. 9. What is welding technology? Answer: The general term for various welding methods, welding materials, welding processes, welding equipment, and their underlying theories is welding technology. 10. What is a welding process? What does it contain? Answer: The entire set of process procedures and technical specifications during the welding process. The content includes: welding methods, pre-welding preparation and processing, assembly, welding materials, welding equipment, welding sequence, welding operations, welding process parameters, and post-welding treatment. 11. What is CO2 welding? Answer: Melt-core gas shielded welding using CO2 with a purity of > 99.98% as the shielding gas is called CO2 welding. 12. What is MAG welding? Answer: Metal arc gas welding using a shielding gas composed of 75–95% Ar + 25–5% CO2 (the standard ratio is 80% Ar + 20% CO2) is known as MAG welding. 13. What is MIG welding? Answer: <1>Gas metal arc welding of non-ferrous metals such as aluminum and its alloys, as well as copper and its alloys, using high-purity argon (Ar ≥ 99.99%) as the shielding gas is known as TIG welding. <2>The process of gas metal arc welding using solid stainless steel wire, with a shielding gas of 98% Ar + 2% O2 or 95% Ar + 5% CO2, is called MIG welding. <3>Gas metal arc welding that uses an inert mixture of helium and argon as a shielding gas. 14. What is TIG (tungsten inert gas) welding? Answer: TIG welding is inert gas shielded arc welding that uses pure tungsten or activated tungsten (thorium-tungsten, cerium-tungsten, zirconium-tungsten, lanthanum-tungsten) as the non-melting electrode. 15. What is SMAW (stick arc welding)? Answer: An arc welding method in which the weld rod is manually manipulated for welding. 16. What is carbon arc gas gouging? Answer: A surface treatment method that uses carbon rods as electrodes to generate an arc with the workpiece, and then uses compressed air (at a pressure of 0.5–0.7 Mpa) to blow away the molten metal. It is commonly used for root cleaning of welds, groove preparation, and repairing defects. 17. Why is CO2 welding more efficient than shielded metal arc welding? Answer: <1>CO2 welding has a melting speed and melting rate 1-3 times higher than those of shielded metal arc welding ； 〈2〉The groove cross-section is 50% smaller than that of the electrode, resulting in a reduction of the deposited metal amount by 1/2 ； 〈3〉The auxiliary time is 50% of that in shielded metal arc welding. Total of the three items: The work efficiency of CO2 welding is 2.02–3.88 times higher compared to that of shielded metal arc welding. 18. Why are the welds produced by CO2 welding of higher quality than those produced by shielded metal arc welding? Answer: CO2 welding results in a small heat-affected zone and minimal welding deformation ； CO2 welds have a low hydrogen content (≤1.6 ML/100g), with little tendency to form pores or cracks ； CO2 welding produces good weld profiles with few surface and internal defects, resulting in a higher defect detection pass rate compared to shielded metal arc welding. 19. Why is the overall cost of CO2 welding lower than that of shielded metal arc welding? Answer: <1> The cross-sectional area of the groove is reduced by 36-54%, resulting in less filler metal being required ； 〈2〉Reduce power consumption by 65.4% ； 〈3〉The cost per machine shift for this method is 67-80% lower than that of shielded metal arc welding, resulting in a cost reduction of 20-40% ； 〈4〉Reduce labor costs and working hours, cutting costs by 10-16% ； 〈5〉Save auxiliary labor time, consumable material usage, and costs associated with correcting deformities ； Taking all five factors into account, CO2 welding can reduce the total welding cost by 39.6–78.7%, with an average reduction of 59%. 20. What is a low-frequency pulse? Which ones apply? Answer in this article: Pulse arc with a pulse frequency of 0.5–30 Hz is called low-frequency pulse welding. It is mainly used for TIG welding of non-ferrous metals such as stainless steel, steel, and titanium. 21. What is an intermediate-frequency pulse? Which welds are applicable? Answer: Pulse arc welding with a pulse frequency of 30–500 Hz is called medium-frequency pulse welding. Due to the arc compression effect, the arc is concentrated and the stiffness is high; it is mainly used for TIG welding of thin stainless steel, steel, and non-ferrous metals such as titanium, as well as for MIG welding of stainless steel, aluminum, and aluminum alloys. 22. Why is there spatter in CO2 welding? Answer: The droplet at the end of the welding wire makes short-circuit contact with the molten pool (short-circuit transition), and due to intense overheating and magnetic contraction, the droplet breaks apart, resulting in spatter. The output reactor and waveform control of the CO2 welder can minimize spatter. 23. Why can jet transition and no spatter be achieved only in MIG/MAG welding with high current? Answer: During MIG/MAG welding, all metals have a critical current value at which the short-circuit transition changes to a jet transition (for example, for φ1.2 carbon steel and stainless steel wires, the current I should be ≥260–280 A); at this point the arc is in a jet transition state, enabling splatter-free welding. 24. Why is a pulsed power supply required for low-current MIG/MAG welding in order to achieve a jet transition with no spatter? Answer: In MIG/MAG welding, when the welding current is below the critical value, a pulsed power supply is used; the pulse current in this case is higher than the critical value, allowing the arc to be in a jet transition state and thus enabling splatter-free welding. (For example, with Panasonic AG2/GE2 pulsed MIG/MAG welders, welding of φ1.2 carbon steel, stainless steel, aluminum, and aluminum alloys can achieve pulse droplet transition at a current of I≥80A, with the pulse current Ip≥350A.) II. Welding Materials 1. What are welding materials? What is included? Answer: Welding materials include electrodes, welding wires, fluxes, gases, electrodes, backing pads, etc. 2. What is a welding wire? Answer: The metal wire used as filler material during welding and also for conducting electricity is called welding wire. It is divided into solid wire and flux-cored wire. Common solid wire grades: ER50-6 (grade: H08Mn2SiA). 3. Why do MAG welded joints have higher impact toughness than CO2 welded joints? Answer: During MAG welding, the active gas makes up only 20%; the transition coefficient of the alloying elements in the wire is high, resulting in high impact toughness of the weld. The active gas for CO2 welding is 100%; manganese and silicon, which are alloying elements in the wire, work together to remove oxygen from the metal. The transition coefficient of these alloying elements is slightly lower, resulting in welds that have lower impact toughness compared to those produced by MAG welding. For example, the Tangshan Shinko MG-51T welding wire (equivalent to ER50-6) has the following impact toughness value at room temperature: MAG: 160J ； CO2: 110J. 4. What is flux-cored wire? Answer: It is a type of welding wire that is made by coiling thin steel strips into circular steel tubes and then filling them with powder of a specific composition, followed by drawing. 5. Why is CO2 gas used for shielding flux-cored wires? Answer: Based on the protection method, flux-cored wires are divided into two types: flux-cored gas-shielded welding wires and flux-cored self-shielded welding wires. Flux-cored gas shielded welding wires generally use CO2 gas for protection, belonging to the combined gas-slag shielding method; they yield welds with good shape and high overall mechanical properties. 6. Why do dentations and pores appear on the surface of wire rod welds? Answer: Since flux-cored wire is a tubular wire made by rolling thin steel strips, it belongs to seamed wire ； Moisture in the air can penetrate into the core through gaps, causing the welding flux to become damp (unable to be dried), which results in indentations and pores in the weld. 7. Why are there technical requirements for the purity of CO2 gas? Answer: Generally, CO2 gas is a by-product of chemical manufacturing, with a purity of only around 99.6%; it contains trace amounts of impurities and moisture, which can cause defects such as pores in the welds. When welding important products, it is essential to use gas with a CO2 purity of ≥99.8% – this results in fewer weld pores, a lower hydrogen content, and better crack resistance. 8. Why are there high technical requirements for argon purity? Answer: There are currently three types of argon available on the market: ordinary argon (with a purity of around 99.6%), pure argon (with a purity of around 99.9%), and high-purity argon (with a purity of 99.99%). The first two types can be used for welding carbon steel and stainless steel ； When welding non-ferrous metals such as aluminum and aluminum alloys, as well as titanium and titanium alloys, high-purity argon must be used ； Prevent the welds and heat-affected zones from oxidizing, which could prevent welding. 9. Why are there various sizes of TIG welding nozzles? Answer: There are 4–8 different sizes of nozzles available. For welding carbon steel, nozzles of size 4–5 can be used, while for welding stainless steel, aluminum, and aluminum alloys, larger nozzles of size 6–7 should be employed to enhance the coverage of the weld seam and the heat-affected zone. When welding non-ferrous metals such as titanium and titanium alloys, a nozzle with a size of 7–8# or larger should be used to prevent oxidation of the weld seam and heat-affected zone. 10. What is an acidic welding electrode? Answer: Welding electrodes whose flux contains large amounts of acidic oxides, such as Jie 422 (E4303) and Jie 502 (E5003), which are suitable for both AC and DC welding. 11. What is an alkaline welding electrode? Answer: Welding electrodes whose flux contains large amounts of basic oxides as well as fluorides, such as Jie 507 (E5015) and Jie 506 (E5016) and other similar welding electrodes. 12. What is a cellulose-type electrode (specific for vertical down welding)? Answer: Welding rods with a flux coating containing large amounts of organic substances, designed specifically for vertical welding in pipeline and thin plate structures. 〈1〉 Like E6010 (equivalent to E4310, J425G), it is suitable for root welding, heat welding, and fill welding. 〈2〉 E8010 (equivalent to E5511, J555) is suitable for hot welding, filler welding, and surfacing layers. Generally, low-hydrogen downward welding electrodes are used for the overlay weld ； The weld shape of E7048 (equivalent to J506X) is neat and aesthetically pleasing. 13. Why must welding rods be dried thoroughly before welding? Answer: Welding electrodes often experience a deterioration in their performance due to moisture absorption, which leads to an unstable arc, increased spatter, and an increased likelihood of defects such as pores and cracks. Therefore, the welding rod must be thoroughly dried before use. Generally, the drying temperature for acidic welding electrodes is 150–200°C, with a duration of 1 hour ； The drying temperature for alkaline welding electrodes is 350–400°C, with a drying time of 1–2 hours. After drying, they should be stored in an insulated box at 100–150°C, and retrieved as needed. III. Welding Equipment 1. What is a welding power source? Answer: In a welding machine, the device that supplies the electrical energy required for welding and possesses electrical characteristics suitable for welding is called a welding power source. 2. Why are there special requirements for arc welding power supplies? What are the requirements? Answer: To ensure the stable combustion of the welding arc and to meet the requirements of various welding processes, arc welding power sources have the following special requirements: <1> The static characteristics (or external characteristics) of an arc welding power source – that is, the relationship between the steady-state output current and the output voltage – include a drooping characteristic (constant current characteristic) and a flat characteristic (constant voltage characteristic). A. The external characteristics of welding electrode arc welding, TIG welding, and carbon arc gas gouging power supplies are descending (constant current) characteristics ； B. The external characteristic of CO2/MAG/MIG arc welding power sources is a flat characteristic (constant voltage characteristic). 〈2〉Dynamic characteristics of the arc welding power supply – When there are instantaneous changes in the load condition (such as short-circuit transfer, granular transfer, jet transfer, etc.), it refers to the relationship between the output current and output voltage of the arc welding power supply over time; this is used to indicate the ability to respond to such load variations (i.e., the dynamic response capability), commonly referred to as “dynamic characteristics”. 〈3〉No-load voltage — the voltage displayed by the power supply before arc initiation. 〈4〉Regulation characteristics – Adjusting the external characteristics of the power supply to meet the requirements of welding specifications. 3. Why does the arc voltage change when the arc length changes? Answer: It is determined by the external characteristics of the arc welding power supply; the longer the arc, the higher the arc voltage ； The shorter the arc, the lower the arc voltage. 4. Why does the current reading change when the length of the welding wire protruding changes during CO2 welding? Answer: The longer the length of the wire that extends outside (i.e., the dry extension length), the greater the resistance of the wire. This results in more current being consumed due to resistive heating, leading to a lower displayed welding current value; the actual welding current also decreases as a result. Therefore, the protrusion length of the welding wire is generally set within the range of 12–20 mm. 5. Why must the welding current and arc voltage be precisely matched during CO2/MAG/MIG welding? Answer: When welding with CO2/MAG/MIG, adjust the welding current—that is, adjust the wire feeding speed ； Adjusting the arc voltage – that is, adjusting the melting speed of the welding wire ； Obviously, the melting speed of the welding wire and its feeding speed must be equal in order to ensure stable arc welding. 〈1〉When the welding current remains constant, increasing the arc voltage causes the melting rate of the wire to rise as well as the arc length to increase; as a result, the molten droplets cannot transfer properly and tend to emerge in large particles, leading to increased spatter. 〈2〉When the welding current remains constant, lowering the arc voltage reduces the melting speed of the wire, shortens the arc length, causes the wire to penetrate deeper into the molten pool, increases spatter, and results in poor weld formation. 〈3〉Optimal matching of welding current and arc voltage: high droplet transfer frequency, minimal spatter, and aesthetically pleasing weld shape. 6. What is arc stiffness? Answer: The degree to which the arc becomes straight along the axis of the electrode, under the effects of effects such as thermal contraction and magnetic contraction. 7. Why does the welding arc exhibit deflection? Answer: During welding, the phenomenon in which the arc center deviates from the electrode axis due to air current interference, the effect of a magnetic field, or electrode eccentricity. 8. What is magnetic deflection blowing? Answer: During DC arc welding, arc deflection occurs due to the electromagnetic forces acting in the welding circuit. The effect of magnetic deflection can be reduced by changing the position of the ground wire, reducing the welding current, or altering the angle of the electrode. 9. What are the self-regulation characteristics of a CO2 power arc system? Why is a fine wire used for CO2 welding? Answer: In a constant-speed wire feeding system, changes in arc length cause variations in current and melting speed; the mechanism that restores the arc length is the self-regulation mechanism of the power supply arc system. The finer the diameter of the welding wire used, the stronger the self-regulating effect of the arc, the more stable the arc becomes, and the less spatter there is. This is the principle behind the fine welding wire used for CO2 welding. Tangshan Panasonic CO2 welders feature advanced control technology, enabling the best self-regulation of the arc and thus the most stable performance. 10. What is the duty cycle of a welding machine? Answer: The duty cycle refers to the ability of a welding power supply to operate continuously at a certain current level. National standards specify that the rated load continuity rate for manual welding is 60%, while it is 60% and 100% for automatic or semi-automatic welding. For example, the rated current of the 500KR2 welder at a rated load duty cycle of 60% is 500A; at an actual load duty cycle of 100% (automatic welding), its maximum welding current is ≤387A. 11. What is the duty cycle of a welding torch? Answer: It refers to the ability of the welding gun to operate continuously at a certain current level. 〈1〉For example: The rated load continuity rate of a 350KR welding torch during CO2 welding is 70%, and its rated current is 350A ； At a real load duty cycle of 100% (automatic welding), its maximum welding current is ≤290A. In MAG welding, the rated load duty cycle is 35%, and at an actual load duty cycle of 100%, the maximum welding current is ≤207A. 〈2〉For example, the rated load continuity rate of a 500KR welding torch during CO2 welding is 70%, and its rated current is 500A ； At a real load duty cycle of 100% (automatic welding), its maximum welding current is ≤418A. In MAG welding, the rated load duty cycle is 35%, and at an actual load duty cycle of 100%, the maximum welding current is ≤296A. 12. What is the direct connection method? Answer: In DC arc welding, the wiring method in which the workpiece is connected to the positive terminal of the welder’s output, and the welding torch is connected to the negative terminal, is called the \"direct current positive connection\" method, or positive polarity. 13. What is reverse connection? Answer: In DC arc welding, the wiring method in which the workpiece is connected to the negative terminal of the welder’s output, and the welding torch is connected to the positive terminal, is called the \"reverse polarity\" method. Reverse polarity is used for alkaline electrodes (such as Jie 507), carbon arc gouging, and CO2 welding. 14. Why is the secondary output circuit of DC TIG welding connected in direct current positive polarity? Which metal materials are suitable for welding? Answer: When connected in direct current with the positive polarity, the tungsten electrode acts as the negative pole; electrons are emitted from the cathode area. At low temperatures, the tungsten electrode is less likely to be damaged, allowing for the use of higher welding currents. It is suitable for welding carbon steel, stainless steel, copper, titanium, as well as refractory reactive metals such as molybdenum, niobium, and tantalum. 15. Why is AC TIG welding used for welding aluminum, magnesium, and their alloys? Answer: When connected in reverse polarity for DC, the tungsten electrode acts as the positive pole, generating cations with high kinetic energy that strike the oxide films on the surfaces of aluminum, magnesium, and their alloys, thereby serving a cleaning function ； The tungsten electrode is in the anode area where the temperature is very high; as a result, the tungsten electrode suffers severe wear, making it impossible to use high welding currents for normal welding. By using an alternating square-wave power supply, the workpiece is heated during the positive half-cycle, while the oxide film is removed during the negative half-cycle, thereby enabling high-quality welding of aluminum, magnesium, and their alloys. 16. What is starting current (initial current)? Answer: With the arc-closing function enabled, press the welding torch switch to apply the starting current ； Release the welder switch to activate the welding current. 〈1〉During TIG welding, the starting current is lower than the welding current; it is used to preheat and guide the arc as well as the weld wire to the starting point, after which the welding gun switch is released to proceed with normal welding. 〈2〉For MIG welding of aluminum, the starting current should be 20–30A higher than the welding current, in order to reduce lack of fusion at the start of welding. 〈3〉For MIG welding of stainless steel and steel, the starting current is equal to the welding current. 17. What is arc-closing current? Answer: The current when the welding torch switch is pressed a second time with the arc termination set to “on” ； It is generally less than 40–60% of the welding current, and is used in TIG/MIG/MAG/CO2 welding to fill the crater at the end of the weld, thereby reducing crater-related defects such as crack at the weld tip. 18. What is rise time? Answer: <1>During TIG welding, it is the transition time from the starting current to the welding current. <2>During MIG welding, it is the time from the base current to the pulsed current. 19. What is the drop time? Answer: <1>During TIG welding, it is the transition time from the welding current to the current at the end of welding. <2>During MIG welding, it is the time from the pulsed current to the base current. 20. What is pulsed welding current? Answer: The peak current during TIG or MIG pulsed welding. 21. What is the base welding current? Answer: The minimum current for pulsed TIG or MIG welding (adjust the welding current knob for TIG welding). 22. What is the lag time for gas shutdown? Answer: That is, the time during which the shielding gas continues to be supplied 0.3–5 seconds after the welding arc goes out ； Generally, when TIG welding metals such as aluminum, stainless steel, and titanium, the delay before stopping the gas supply should be 3–5 seconds. 23. What is arc spot welding? Answer: A thin plate lap joint is a welding method in which TIG/MIG/MAG/CO2 welding techniques are used, with a certain welding current applied to form a molten pool on the surface within a set time, thereby joining the upper and lower plates together. IV. Welding Process 1. What are welding conditions? What does it contain? Answer: The conditions surrounding the welding process include: the material of the base metal, plate thickness, groove shape, type of joint, degree of restraint, ambient temperature and humidity, level of cleanliness; as well as the type and diameter of wire (or electrode) determined based on these factors, welding current, voltage, welding speed, welding sequence, deposition method, and the method of moving the welding tool (or electrode), etc. 2. What is a welding joint? How many basic forms are there? Answer: A joint connected by welding. A welded joint consists of three parts: the weld seam, the fusion zone, and the heat-affected zone. The basic forms of joints include butt joint, corner joint, lap joint, and T-joint, etc. 3. What is penetration depth? Answer: The depth to which the base material is melted in the cross-section of the welded joint. 4. What is the welding position? How many forms are there? Answer: During fusion welding, it refers to the spatial position of the joint between the welded parts. There are forms such as flat welding, vertical welding, horizontal welding, and overhead welding. 5. What are vertical down welding and vertical up welding? Answer: <1>When welding in the vertical position, the arc moves from top to bottom – this is called vertical down welding. For example: cellulose electrode for vertical down welding ； CO2 vertical down welding, etc. 〈2〉When welding in the vertical position, the arc moves from bottom to top – this is called upward vertical welding. 6. What is a welded structure? Answer: A steel structure connected by welding is called a welded structure. 7. Why are bevels required for welded joints? Answer: Groove – A groove formed by shaping the part of the weldment to be welded into a specific geometric shape according to design or process requirements, after assembly. To achieve full penetration of the weld joint cross-section and reduce the fusion ratio ； Common groove shapes include: I, V, Y, X, U, K, J, etc. 8. Why is preheating necessary for certain materials before welding? Answer: To slow down the cooling rate of the welded joint after welding and prevent the formation of cold cracks. 9. Why is heat treatment required for certain welded components after welding? Answer: To eliminate welding residual stresses and improve the microstructure and properties of the welded joint. 10. Why is it necessary to develop a welding procedure specification before welding? Answer: Ensuring welding quality relies on five key control aspects: people, machinery, materials, methods, and environment. Man – the operator’s skills and experience; Machine – the high performance and stability of welding equipment; Material – the high quality of welding materials; Method – the correct welding procedures and standardized operations; Environment – a favorable welding environment. The welding procedures established based on welding tests and welding procedure qualifications prior to welding are considered \"regulations\" and represent an important factor in ensuring welding quality. 11. Why is surface treatment required for the base material before welding? Answer: If there are impurities such as oil (paint), water, or rust on the groove and surface of the weldment, they will dissolve into the weld, causing defects such as pores, inclusions, slag inclusions, and cracks, which pose risks and hazards to the welded joint. 12. What is the melting coefficient of welding wire? Answer: The melting coefficient of welding wire refers to the amount of welding wire that melts per unit time under a unit current. (g/Ah) The finer the welding wire, the greater its melting coefficient, which means higher efficiency. 13. What are welding process parameters? Answer: During welding, it refers to the collective term for various physical parameters selected to ensure welding quality (such as welding current, arc voltage, welding speed, wire energy, etc.). 14. What is welding current? Answer: During welding, the current flowing through the welding circuit is generally expressed in amps (A). 15. What is arc voltage? Answer: The voltage drop between the two ends of an arc (the two electrodes) is generally expressed in volts (V). 16. What is welding speed? Answer: The length of weld completed per unit of time is generally expressed in centimeters per minute (cm/min). 17. What is the dry elongation? Answer: During welding, it is the distance between the end of the welding wire and the tip of the electrode tip. 18. What is welding line energy? Answer: In fusion welding, it refers to the energy supplied per unit length of weld by the welding heat source, also known as “heat input”. It is generally expressed in joules per centimeter (J/cm). 19. What is the fusion ratio of weld metal? Answer: During fusion welding, it is the proportion of the melted base material in the weld metal. 20. What is the weld shape coefficient? Answer: In fusion welding, it is the ratio of the weld width to the weld thickness in the cross-section of a single weld. 21. What is leftward welding? Answer: In fusion welding, it is a welding method in which the welding torch moves from the right end to the left end of the joint between the workpieces. It provides excellent gas protection and results in aesthetically pleasing welds. For both CO2 and TIG welding, the left-hand welding method is used ； MIG welding of aluminum must be done using the left-hand welding method. 22. What is right-hand welding? Answer: In fusion welding, it is a welding method in which the welding torch moves from the left end to the right end of the joint between the workpieces. 23. Why is the welded joint considered the weak link in welded structures? Answer: This is because welding joints exhibit heterogeneity in their structure and properties, and they often contain various welding defects, as well as high residual tensile stresses ； Therefore, the weld joint is the weak link in welded structures. 24. Why is it said that high-quality welded joints can be obtained through appropriate processing methods? Answer: To improve the quality of welded joints, the following approaches can be adopted: selecting appropriate welding materials, using reasonable welding processes, controlling the fusion ratio, adjusting the characteristics of the welding heat cycle, employing proper operation techniques and groove designs, along with measures such as preheating, interpass insulation and controlled cooling, post-weld heating, or post-weld heat treatment, to obtain high-quality welded joints