1. What is welding power supply?
In the electric welding machine, the equipment that supplies the electric energy required for welding and has electrical characteristics suitable for welding is called welding power supply.
2. When the arc length changes, the arc voltage will also change?
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.
3. During CO2 welding, when the extension length of the welding wire changes, the current display value will also change?
Answer: the longer the extension length of welding wire (i.e. dry extension length), the greater the resistance of welding wire, the greater the current consumed by resistance heat, the smaller the displayed value of welding current, and the smaller the actual welding current.
Therefore, the extension length of welding wire is generally set in the range of 12-20mm.
4. When CO2 / MAG / MIG welding, the welding current and arc voltage should be strictly matched?
Answer: during CO2 / MAG / MIG welding, adjust the welding current – that is, adjust the feeding speed of welding wire;
Adjust the arc voltage – that is, adjust the melting speed of welding wire;
Obviously, the melting speed and feeding speed of welding wire 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, and the droplet cannot transition normally.
Generally, large particles fly out and the spatter increases.
(2) When the welding current is constant, the arc voltage is adjusted to be low, the melting speed of the welding wire is reduced, the arc length becomes shorter, the welding wire enters the molten pool, the spatter is large, and the weld formation is poor.
(3) The best matching effect of welding current and arc voltage: high droplet transfer frequency, minimum spatter and beautiful weld formation.
5. Are there any special requirements for arc welding power supply? What are the requirements?
Answer: in order to ensure the stable combustion of the welding arc and adapt to various welding process requirements, the arc welding power supply has the following special requirements:
(1) Static characteristics (or external characteristics) of arc welding power source – that is, the relationship between steady-state output current and output voltage, with falling characteristics (constant current characteristics) and flat characteristics (constant voltage characteristics).
- The external characteristics of electrode arc welding, TIG welding and carbon arc gouging power supply are descent (constant current) characteristics;
- The external characteristic of CO2/ MAG / MIG arc welding power source is flat characteristic (constant voltage characteristic).
Related reading: MIG vs TIG Welding
(2) Dynamic characteristics of arc welding power supply – when the load state changes instantaneously (such as short-circuit transition of the droplet, particle transition, jet transition, etc.), the relationship between the output current and output voltage of arc welding power supply and time is used to characterize the response ability to load transient (i.e. dynamic response ability), which is referred to as “dynamic characteristics”.
(3) No load voltage – the voltage displayed by the power supply before arc striking.
(4) Regulation characteristics – change the external characteristics of the power supply to meet the requirements of welding specifications.
6. What is arc stiffness?
Answer: under the effect of thermal contraction and magnetic contraction, the arc is straight along the axial direction of the electrode.
7. What are the partial blowing phenomena of welding arc?
Answer: during welding, the arc center deviates from the electrode axis due to the interference of air flow, the action of the magnetic field or the influence of electrode eccentricity.
8. What is the positive connection?
Answer: During DC arc welding, the welding piece is connected to the positive pole of the output end of the electric welding machine, and the welding gun (welding clamp) is connected to the negative pole of the output end.
The wiring method is called “positive connection method”, also known as positive polarity.
9. What is the reverse connection?
Answer: during DC arc welding, the welding piece is connected to the negative pole of the output end of the welding machine, and the welding gun (welding clamp) is connected to the positive pole of the output end.
It is called “reverse connection method”, also known as reverse polarity.
Alkaline electrode (junction 507, etc.), carbon arc gouging and CO2 welding all use the reverse connection method.
10. What is magnetic bias blowing?
Answer: during DC arc welding, the arc blow is caused by the action of electromagnetic force in the welding circuit.
The influence of magnetic bias blowing can be weakened by changing the position of the grounding wire, reducing welding current and changing electrode angle.
11. What is the load duration of the welding gun?
Answer: it refers to the ability of the welding gun to work continuously under a certain current.
(1) For example, the rated load duration rate of 350kr welding gun during CO2 welding is 70%, and the rated current is 350A;
When the actual load duration rate is 100% (automatic welding), the maximum welding current is ≤ 290A.
When MAG welding, the rated load duration is 35%, and when the actual load duration is 100%, the maximum welding current is ≤ 207A.
(2) For another example, when the 500kr welding gun is CO2 welding, the rated load duration rate is 70%, and the rated current is 500A;
When the actual load duration rate is 100% (automatic welding), the maximum welding current is ≤ 418A.
In MAG welding, the rated load duration is 35%, and when the actual load duration is 100%, the maximum welding current is ≤ 296A.
12. Self regulation characteristics of CO2 power arc system? Why are fine wires used for CO2 welding?
Answer: under the constant speed wire feeding system, when the arc length changes, the current and melting speed change, so that the role of arc length recovery becomes the self-regulation role of the power arc system.
The smaller the diameter of the welding wire used, the stronger the self-regulation of the arc, the more stable the arc and the less splash.
This is the principle of fine wire for CO2 welding.
Through advanced control technology, Tangshan Panasonic CO2 welding machine has the best self-regulation of arc and the most stable performance.
13. What is the load duration of the welding machine?
Answer: load duration refers to the ability of welding power supply to work continuously under a certain current.
The national standard stipulates that the rated load duration of manual welding is 60%, and that of automatic or semi-automatic welding is 60% and 100%.
For example, the rated current of 500KR2 welding machine is 500A when the rated load duration is 60%, and the maximum welding current is ≤ 387A when the actual load duration is 100% (automatic welding).
14. What is arc spot welding?
Answer: for the lap joint of thin plate, the TIG / MIG / MAG / CO2 welding method is used to form the surface nugget and connect the upper and lower plates within the set time with a certain welding current.
15. What is the lag time?
Answer: that is, after the welding arc is extinguished, the shielding gas is delayed by 0.3-5 seconds and then the gas supply is stopped;
Generally, the lag gas stop time of TIG welding aluminum, stainless steel, titanium and other metals is as long as 3-5 seconds.