Questions and answers about welding equipment

1. What is welding power source? A: In the welding machine, the equipment that supplies the electricity needed for welding and has the electrical characteristics suitable for welding is called the welding power source. 2. Why are there special requirements for arc welding power sources? What are the requirements? Answer: In order to ensure the stable combustion of welding arc and meet the requirements of various welding processes, the arc welding power supply has the following special requirements: < 1 > The static characteristics of the arc welding power source (or external characteristics) — that is, the relationship between the steady-state output current and output voltage, has the characteristics of decline (constant current characteristics) and the characteristics of peace (constant voltage characteristics). A, electrode arc welding, TIG welding and carbon arc gouging power supply is the external characteristics of the decline (constant current) characteristics; B. The external characteristics of CO2/MAG/MIG arc welding power supply are flat characteristics (constant voltage characteristics). < 2 > Dynamic characteristics of arc welding power source — The relationship between output current and output voltage of arc welding power source and time when the load state changes instantaneously (such as short-circuit transition of droplet, particle transition, jet transition, etc.) is used to characterize the response ability to load transiants (namely, dynamic response ability), which is referred to as “dynamic characteristic”. < 3 > No-load voltage — voltage displayed by the power supply before starting the arc. < 4 > Adjusting characteristics — Changing 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: Determined by the external characteristics of the arc welding power source, the longer the arc, the higher the arc voltage; The shorter the arc, the lower the arc voltage. 4. Why does the current display value change when the length of the wire is changed during CO2 welding? Answer: the longer the length of the wire (i.e., the dry length), the greater the resistance of the wire, the greater the current consumed by the resistance heat, the smaller the welding current display value, and the smaller the actual welding current. So the length of the wire is generally set in the range of 12-20mm. 5. Why should the welding current and arc voltage be strictly matched in CO2/MAG/MIG welding? Answer: during CO2/MAG/MIG welding, adjust the welding current — that is, adjust the feeding speed of the welding wire; Adjust the arc voltage – that is, adjust the melting speed of the welding wire; Obviously, the welding wire melting speed and feed speed must be equal to ensure stable arc welding. < 1 > When the welding current is constant, adjust the arc voltage on the high side, the melting speed of the welding wire increases, the arc length increases, the droplet can not be normal transition, generally large particles fly out, more splashing. < 2 > When the welding current is constant, the adjusting arc voltage is low, the melting speed of the welding wire is reduced, the arc length is shorter, the welding wire is tied into the molten pool, the splash is large, and the weld is not well formed. < 3 > Best matching effect of welding current and arc voltage: high droplet transition frequency, minimum splash, beautiful weld formation. 6. What is arc stiffness? A: the degree to which the arc is straightened along the axial direction of the electrode under the effect of thermal shrinkage and magnetic shrinkage. 7. Why is the welding arc partially blown? A: During the welding process, the arc center deviates from the electrode axis due to the interference of the airflow, the action of the magnetic field or the influence of the eccentric electrode. 8. What is magnetic bias blowing? Answer: in dc arc welding, due to the action of the electromagnetic force in the welding circuit, the arc is blown. The influence of magnetic bias blowing can be weakened by changing the position of ground wire, reducing welding current and changing the Angle of electrode. 9. What is the self-regulating characteristic of CO2 power arc system? Why does CO2 welding use fine wire? Answer: In the constant speed wire feeding system, when the arc length changes, the current and melting speed change, so that the arc length recovery function becomes the self-regulation function of the power arc system. The finer the diameter of the welding wire, the stronger the self-regulating effect of the arc, the more stable the arc and the less splashing. This is the principle of fine wire for CO2 welding. Through the advanced control technology, the self – adjustment effect of arc is the best, the performance is the most stable. 10. What is the load duration of a welder? A: Load duration refers to the ability of the welding power source to work continuously under a certain current. National standard stipulated that the rated load duration of manual welding is 60%, automatic or semi-automatic is 60% and 100%. For example, the rated current of 500KR2 welder is 500A when the rated load duration rate is 60%, and the maximum welding current is less than or equal to 387A when the actual load duration rate is 100% (automatic welding). 11. What is the load duration of the torch? Answer: refers to the ability of the welding torch to work continuously under a certain current. < 1 > For example: 350KR welding torch in CO2 welding rated load sustained rate is 70%, rated current is 350A; When the actual load duration is 100% (automatic welding), the maximum welding current is less than or equal to 290A. In MAG welding, the rated load duration rate is 35%, and when the actual load duration rate is 100%, the maximum welding current is less than 207A. < 2 > For another example, the rated load duration rate of 500KR welding torch in CO2 welding is 70% and the rated current is 500A; When the actual load duration is 100% (automatic welding), the maximum welding current is less than or equal to 418A. In MAG welding, the rated load duration rate is 35%, and the maximum welding current is less than 296A when the actual load duration rate is 100%. 12. What is the correct connection? Answer: in dc arc welding, the welding part is connected to the positive electrode of the output end of the welding machine, and the welding gun (welding holder) is connected to the negative electrode of the output end, which is called the “positive connection method”, also known as the positive polarity. 13. What is antigrafting? Answer: in dc arc welding, the welding part is connected to the negative electrode of the output end of the welding machine, and the welding gun (welding holder) is connected to the positive electrode of the output end of the wiring method, which is called “reverse connection method”, also known as reverse polarity. Alkaline electrode (junction 507, etc.), carbon arc gouging, CO2 welding are used in reverse connection. 14. Why is dc TIG welding secondary output circuit connected to DC normal connection? Suitable for welding which metal materials? Answer: when dc is connected, tungsten is very negative, the cathode area emits electrons, the temperature is low, tungsten is very difficult to burn, can use a large welding current. Suitable for welding carbon steel, stainless steel, copper, titanium and refractory active metal molybdenum, niobium, tantalum, etc. 15. Why should AC TIG welding be used for welding aluminum, magnesium and their alloys? Answer: dc reverse connection, tungsten is very positive, produce a large kinetic energy of the cation, impact aluminum, magnesium and its alloy surface oxide film, has a cleaning effect; In the anode area of tungsten electrode, the temperature is very high, and the tungsten electrode is badly burned, so it is not possible to use large welding current for normal welding. The high quality welding of aluminum, magnesium and their alloys is realized by using alternating square wave power source, positive half wave heating workpiece and negative half wave cleaning oxide film. 16. What is the initial current? Answer: in the arc “have” state, press the welding torch switch arc current; Loosen the torch switch to transfer the welding current. < 1 > When TIG welding, the initial current is less than the welding current, used for preheating and guiding the arc and wire to the starting welding place, loosen the torch switch to normal welding. < 2 > MIG welding aluminum, the initial current is greater than the welding current 20-30A, reduce the unfusion at the beginning of the welding. < 3 > MIG welding stainless steel and steel, the starting current is equal to the welding current. 17. What is arc current? Answer: in the arc “have” state, the second press the current of the torch switch; Generally less than the welding current 40–60%, regardless of TIG/MIG/MAG/CO2 welding, are used to fill the arc pit at the end of the weld, reduce the arc pit defects (such as crater cracks). 18. What is time of rise? A: the transition time from the initial current to the welding current during TIG welding. The time from base current to pulse current during MIG welding. 19. What is descent time? A: the transition time from welding current to arc current during TIG welding. The time from pulse current to base current during MIG welding. 20. What is pulse welding current? A: peak current during TIG or MIG pulse welding. 21. What is the base welding current? A: the minimum current for TIG or MIG pulse welding (adjust welding current knob during TIG welding). 22. What is the lag stop time? Answer: that is, after the welding arc is extinguished, the protective gas delay is 0.3-5 seconds and then the time to stop the gas supply; In general, TIG welding aluminum, stainless steel, titanium and other metals, the lag stop time should be as long as 3-5 seconds. 23. What is arc spot welding? Answer: thin plate lap joint, using TIG/MIG/MAG/CO2 welding method, using a certain welding current, in the set time, the formation of surface fusion core, connecting the upper and lower plate welding method.铜焊丝,Copper Welding Rods,铝焊丝,aluminium welding wire,镍焊条,Nickel electrode,药皮焊条,Flux Coated Brazing Welding Rods