What do you know about common welding equipment?

1.What is welding power supply?

In the electric welding machine, the equipment which supplies the electric energy needed by welding and has the suitable welding electrical characteristics is called welding power supply.

2.When the arc length changes, the arc voltage will also change?

The longer the arc, the higher the arc voltage; the shorter the arc, the lower the arc voltage.

3.When the extension length of the welding wire is changed, the current display value will also change in the process of CO₂ welding?

The longer the extension length of welding wire (i.e. dry elongation length), the greater the resistance of welding wire, the greater the current consumed by resistance heat, the smaller the display 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 12-20 mm.

4. In the process of CO₂/ MAG / MIG welding, the welding current and arc voltage should be strictly matched?

CO₂/MAG/MIG When 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, if the arc voltage is too high, the melting speed and the arc length of the welding wire will increase, and the droplet can not transfer normally. Generally, large particles will fly out and spatter will increase.

(2) when the welding current is constant, the regulating arc voltage is low, the melting speed of welding wire is reduced, the arc length is shortened, the welding wire is penetrated into the molten pool, the spatter is large, and the weld is not formed well.

(3) the best matching effect of welding current and arc voltage: high frequency of droplet transfer, minimum spatter and beautiful weld appearance.

5. Special requirements for arc welding power source? What are the requirements?

Answer: in order to ensure the stable combustion of welding arc and adapt to various welding process requirements, arc welding power source has the following special requirements:

Static characteristics (or external characteristics) of arc welding power source, i.e. the relationship between steady-state output current and output voltage, has characteristics of descending (constant current) and (constant voltage).

A. The external characteristics of welding rod arc welding, TIG welding and carbon arc air gouging power supply are falling (constant current) characteristics;

B. The external characteristic of CO₂ / MAG / MIG arc welding power source is flat characteristic (constant voltage characteristic).

(2) dynamic characteristics of arc welding power source: when the load state changes instantaneously (such as droplet short-circuit transfer, particle transfer, jet transfer, etc.), the relationship between the output current and output voltage of the arc welding power source and time is used to characterize the reaction ability to the 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 arcing.

(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 shrinkage and magnetic contraction, the degree of arc straightening along the electrode axis.

7. What are the partial blowing phenomena of welding arc?

Answer: in the welding process, the arc center deviates from the electrode axis due to the interference of air flow, magnetic field or eccentric electrode.

8. What is a positive connection?

A: when DC arc welding, the welding parts are connected to the positive pole of the output end of the electric welding machine, and the welding gun (welding tongs) is connected to the negative pole of the output end, which is called "positive connection method", also known as positive polarity.

9. What is reverse connection?

A: in DC arc welding, the welding parts are connected to the negative pole of the output end of the welding machine, and the welding gun (welding tongs) is connected to the positive pole of the output end, which is called "reverse connection method", also known as reverse polarity. Alkaline electrode (J507, etc.), carbon arc gouging and CO Ψ welding are all used in reverse connection.

10. What is magnetic bias blowing?

Answer: during DC arc welding, the arc is blown by the electromagnetic force in the welding circuit. By changing the position of grounding wire or decreasing the welding current and changing the angle of electrode, the influence of magnetic bias blowing can be weakened.

11. What is the load duration of welding gun?

Answer: refers to the ability of welding gun to work continuously under a certain current.

(1) for example, the rated load duration rate of 350kr welding gun is 70% and the rated current is 350A; when the actual load duration rate is 100% (automatic welding), the maximum welding current is ≤ 290A. In MAG welding, the rated load duration is 35%, and the maximum welding current is less than 207A when the actual load duration is 100%.

(2) for example, when the 500kr welding torch is used for 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 the maximum welding current is ≤ 296A when the actual load duration is 100%.

12. Self regulation characteristics of arc system for CO₂ power supply? Why is the fine wire 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 arc length recovery becomes the self-regulation function of the power arc system. The smaller the diameter of the welding wire, the stronger the self regulating function of the arc, the more stable the arc and the less spatter. This is the principle of the fine wire used for CO₂ welding.

13. What is the load duration of welding machine?

A: load duration refers to the ability of welding power supply to work continuously under a certain current. According to the national standard, 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 rate is 60%, and the maximum welding current is ≤ 387a when the actual load duration rate is 100% (automatic welding).

14. What is arc spot welding?

Answer: for lap joint of thin plate, TIG / MIG / MAG / CO₂ welding method is used, and certain welding current is used to form surface nugget within the set time to connect the upper and lower plates.

15. What is the lag time?

Answer: that is, after the welding arc is extinguished, the shielding gas will be delayed for 0.3-5 seconds and then stop the gas supply; generally, the lag time for TIG welding aluminum, stainless steel, titanium and other metals will be as long as 3-5 seconds

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