1. What is welding?
A: WELDING IS A PROCESS IN WHICH TWO OR MORE MATERIALS (OF THE SAME OR DIFFERENT SPECIES), BY HEATING OR pressurIZING OR BOTH, JOIN ATOMS TOGETHER TO FORM A PERMANENT CONNECTION.
2. What is welding process? What does it contain?
A: A complete set of technological procedures and technical requirements in the welding process. The contents include: welding method, pre-welding preparation and processing, assembly, welding materials, welding equipment, welding sequence, welding operation, welding process parameters and post-welding treatment, etc.
3. What is welding technology?
Answer: ALL kinds of welding methods, welding materials, welding technology and welding equipment and their basic theory of the general name - called welding technology.
4. What are the welding methods of electric welding (manual welding)?
A: Manual welding is manual arc welding, which is a manual welding method that uses arc as a heat source to melt the electrode and the base metal to form a weld. According to the technological standard of manual arc welding, it mainly includes flat welding, vertical welding, horizontal welding and vertical welding.
5. What is CO2 welding?
A: MIG WELDING WITH CO2 > 99.98% PURITY AS THE shielding GAS is called CO2 welding.
6. What is welding power supply?
A: IN THE WELDING machine, THE EQUIPMENT THAT PROVIDES THE electric energy required for welding and has the electrical characteristics suitable for welding is called welding power supply.
7. Why are there special requirements for arc welding power supply? What are the requirements?
A: In order to ensure the stable combustion of welding arc and adapt to various welding process requirements, arc welding power supply has the following special requirements:
< 1 > Static characteristics (or external characteristics) of arc welding power supply -- that is, the relationship between the steady-state output current and the output voltage, there is a downward characteristic (constant current characteristic) and a constant voltage characteristic (constant voltage characteristic).
A. The external characteristics of electrode arc welding, TIG welding and carbon arc air gouging power supply are falling (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 supply -- The relationship between the output current and output voltage of arc welding power supply and time when the load state changes instantaneously (such as short-circuit transition of molten droplet, particle transition, jet transition, etc.) is used to characterize the response ability to load transients (dynamic response ability), referred to as "dynamic.
Characteristics ".
< 3 > No-load voltage -- the voltage displayed by the power supply before arc ignition.
< 4 > Regulating characteristics -- changing the external characteristics of the power supply to meet the requirements of the welding code.
8. What is an arc?
Answer: BY the welding power supply, produce strong and lasting gas discharge phenomenon between the two poles - called arc.
< 1 > According to the type of current, it can be divided into AC arc, DC arc and pulse arc.
< 2 > According to the state of the arc can be divided into: free arc and compressed arc (such as plasma arc).
< 3 > According to the electrode material, it can be divided into molten arc and non-molten arc.
9. Why does the arc voltage change when the arc length changes?
A: Determined by the external characteristics of arc welding power supply, the longer the arc, the higher the arc voltage; The shorter the arc, the lower the arc voltage.
10. What is arc stiffness?
A: The degree to which the arc is straightened along the axis of the electrode under the effect of thermal contraction and magnetic contraction.
11. What is arc spot welding?
A: The thin plate lap joint is welded by TIG/MIG/MAG/CO2 welding method, using a certain welding current to form a surface fusion core within a set time, and connecting the upper and lower plates.
12. What is the base material?
A: The metal being welded is called the base metal.
13. What is a melt drop?
A: When the tip of the wire is heated, it melts and passes into the pool of liquid metal - called a droplet.
14. What is a molten pool?
A: During fusion welding, the liquid metal part with a certain geometric shape formed on the weldment is called molten pool.
15. What is a weld?
Answer: The joint part formed in the weldment after welding.
16. What is weld metal?
A: THE PORTION OF METAL FORMED BY the SOLIDIFICATION OF the MELTED BASE METAL AND the filler metal (wire, electrode, etc.).
17. What is a protective gas?
A: THE GAS USED IN WELDING TO PROTECT THE metal DROPLETS and molten pool from the invasion of harmful gases (hydrogen, oxygen, nitrogen).
18. What is MAG welding?
A: Use gas mixture 75--95% AR + 25-- 5% CO2, (standard ratio: 80% AR + 20% CO2) as the protective gas of the melting electrode welding - called MAG welding.
19. What is MIG welding?
Answer: < 1 > Use high-purity argon AR ≥99.99% as the protection gas for welding aluminum and aluminum alloy, copper and copper alloy and other non-ferrous metals; < 2 > process for welding solid stainless steel wire with 98% ar + 2%o2 or 95%ar + 5%co2 as the guard gas - called mig welding. < 3 > MIG welding with an inert mixture of helium and argon.
20. What is TIG (argon tungsten arc welding) welding?
A: Inert gas shielded arc welding using pure tungsten or activated tungsten (thorium tungsten, cerium tungsten, zirconium tungsten, lanthanum tungsten) as a non-melting electrode, referred to as TIG welding.
21. What is SMAW (electrode arc welding) welding?
A: A method of arc welding with manually operated electrodes.
22. What is carbon arc gouging?
A: The use of carbon rod as the electrode, and the workpiece between the arc, with compressed air (pressure 0.5-0.7mpa) will melt metal blown out of a surface processing method. It is commonly used for root cleaning of weld seams, groove planing, repairing defects, etc.
23. Why is CO2 welding more efficient than electrode arc welding?
A: < 1 > CO2 welding is 1-3 times higher than the melting speed and melting coefficient of electrode arc welding;
< 2 > the groove section is reduced by 50% compared with the electrode, and the amount of molten metal is reduced by 1/2;
< 3 > The auxiliary time is 50% of the electrode arc welding.
Three total: the efficiency of CO2 welding is 2.02-3.88 times higher than that of electrode arc welding
24. Why are co2 welded joints of better quality than rod arc welded joints?
A: The heat-affected zone of CO2 weld is small, and the welding deformation is small; The hydrogen content of CO2 weld is low (≤1.6ml/100g), and the porosity and crack tendency are small; The co2 weld is well formed, the surface and internal defects are less, and the pass rate of flaw detection is higher than that of electrode arc welding.
25. Why is the combined cost of CO2 welding lower than that of electrode arc welding?
Answer: < 1 > The cross-sectional area of the groove is reduced by 36-54%, saving the amount of filling metal;
< 2 > reduce power consumption by 65.4%;
< 3 > The equipment cost is 67-80% lower than that of electrode arc welding, and the cost is 20-40% lower;
< 4 > Reduce labor costs and hourly costs, reducing costs by 10-16%;
< 5 > Save auxiliary hours, auxiliary materials consumption and deformation correction cost;
Considering the five items, CO2 welding can reduce the total welding cost by 39.6-78.7%, with an average reduction of 59%.
26. What is a low-frequency pulse? Which welds are applicable?
Answer: Pulse frequency in 0.5-30Hz pulse arc is called low-frequency pulse welding. It is mainly used for TIG welding of stainless steel, steel and titanium and other non-ferrous metals.
27. What is an intermediate frequency pulse? Which welds are applicable?
A: Pulse arc with a pulse frequency of 30-500Hz is called intermediate frequency pulse welding. Due to the arc compression effect, arc concentration, good stiffness, mainly used for thin stainless steel, steel and titanium and other non-ferrous metal TIG welding and stainless steel and aluminum and aluminum alloy MIG welding.
28. Why do CO2 welds spatter?
Answer: The molten drop at the end of the welding wire is in contact with the molten pool short circuit (short circuit transition). Due to strong overheating and magnetic contraction, the molten drop is broken and splashes are generated. The output reactor and waveform control of the co2 welder minimize spatter.
29. Why can MIG/MAG high-current welding achieve jet transition without spatter?
Answer: During MIG/MAG welding, all kinds of metals have the critical current value of short circuit transition to jet transition (such as: φ1.2 carbon steel, stainless steel welding wire, current I ≥ 260-280A), at this time, the arc is jet transition state, to achieve no splash welding.
30. Why does MIG/MAG low-current welding need pulsed power supply to achieve jet transition without splash?
Answer: For MIG/MAG welding, when the welding current is lower than the critical current value, the power supply with pulse is used, and the pulse current is greater than the critical current value. The arc can also be in the jet transition state to achieve spill-free welding (e.g. Using Panasonic AG2 / GE2 pulse MIG/MAG welding machine, φ1.2 carbon steel, stainless steel, aluminum and aluminum alloy welding wire has achieved pulse injection drop transition when current I ≥ 80A, its pulse current IP ≥ 350A).
31. Why does the current display value change when the wire extension length changes during CO2 welding?
Answer: THE LONGER THE WIRE EXTENSION LENGTH (i.e., THE LONGER THE DRY EXTENSION length), THE greater THE resistance of the wire, the greater the current consumed by the resistance, the smaller the welding current display value, and the smaller the actual welding current. So the wire extension length is generally set in the range of 12- 20mm.
32. Why should welding current and arc voltage be strictly matched in CO2/MAG/MIG welding?
Answer: When CO2/MAG/MIG welding, adjust the welding current -- that is, adjust the wire feeding speed; Adjust the arc voltage, that is, adjust the melting speed of the welding wire; Obviously, the melting speed and feed speed of the wire must be equal to ensure stable arc welding.
< 1 > When the welding current is fixed, the regulated arc voltage is high, the melting speed of the welding wire increases, the arc length increases, the droplet can not transition normally, generally large particles fly out, and the splashing increases.
< 2 > When the welding current is fixed, adjust the arc voltage is low, the melting speed of the welding wire decreases, the arc length becomes short, the welding wire is stuck into the welding pool, the splash is large, and the weld is poorly formed.
< 3 > Best matching effect of welding current and arc voltage: high droplet transition frequency, minimum spatter, beautiful weld shape.
33. Why does welding arc blow off course?
Answer: IN THE welding process, because of the interference of airflow, the effect of magnetic field or the influence of electrode eccentricity, the arc center deviates from the electrode axis phenomenon.
34. What is magnetic deflection?
Answer: DC arc welding, due to the effect of the electromagnetic force in the welding circuit and the arc deflection. By changing the position of the ground wire or reducing the welding current and changing the electrode Angle, the influence of magnetic deflection can be reduced.
35. What are the self-regulating characteristics of CO2 power arc systems? Why use fine wire for CO2 welding?
Answer: UNDER THE constant speed wire feeding system, when the arc length changes, the current and melting speed will change, so that the arc length recovery function becomes the self-regulation function of the power arc system. The thinner the diameter of the welding wire used, the stronger the self-regulation effect of the arc, the more stable the arc, the less splashing. This is the principle of fine wire for CO2 welding. Through the advanced control technology, the arc has the best self-regulation effect and the most stable performance.
36. What is the load persistence rate of the welder?
A: Load persistence rate refers to the ability of welding power supply to work continuously under a certain current. The rated load duration is 60% for manual welding and 60% and 100% for automatic or semi-automatic welding. For example, the rated current of 500KR2 welder is 500A when the rated load persistence rate is 60%, and the maximum welding current of 500KR2 welder is less than 387A when the actual load persistence rate is 100%(automatic welding).
37. What is the load persistence rate of the welding torch?
Answer: It refers to the ability of welding torch to work continuously under a certain current.
< 1 > such as: 350KR welding gun in CO2 welding rated load duration of 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 persistence rate is 35%. When the actual load persistence rate is 100%, the maximum welding current is less than 207A.
< 2 > Again, for example, the rated load persistence rate of 500KR welding gun in CO2 welding is 70%, and the rated current is 500A; When the actual load persistence rate is 100%(automatic welding), the maximum welding current is less than 418A. In MAG welding, the rated load persistence rate is 35%. When the actual load persistence rate is 100%, the maximum welding current is less than 296A.
38. What is correct connection?
A: In DC arc welding, the welding piece 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 of the wiring method, which is called "positive connection method", also known as positive polarity.
39. What is reverse connection?
A: In DC arc welding, the welding piece 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 all used in reverse connection.
40. What is the lag stop time?
Answer: that is, after the welding arc is extinguished, the time for the protection gas to delay 0, 3-5 seconds and then stop the air supply; General TIG welding aluminum, stainless steel, titanium and other metals lag stop time to 3-5 seconds.
