What is arc welding and how to make arc

What is arc welding and how to make arc

Date 06/05/2019

What is arc welding?

When the tip of the welding rod contact with the surface of the welding material, it will produce short-circuit phenomenon and at the contact point will be very high temperature. Then, when most rods are welded out of the weld at a certain distance, that air becomes conducive and produces electricity that produces heat and strong light.

Arc is a stable discharge in the gas environment, between negative and positive electrodes. The arc consists of large heat sources, strong lighting and focus.

For the arc to appear, the following conditions are required:

- Between the ends of the electrodes (welding rod and solder), voltage must be applied. The minimum voltage to maintain the fire curve is 40 ÷ 80V.

- Between the two electrodes there must be a gap to appear neutral electrons.

- The process of occurring arc occurs in very short time but can be described into 4 stages later





- Due to the surface of the welding rod and the non-planar welding material, the arc will appear at the higher point of the welding object. (Picture A)

Because the arc only appears locally, it generates a huge heat that causes the metal to melt and fill the space between the two electrodes. At this time molten metal acts as a conductor between the solder and the solder (Figure b).

- As the electrodes are pulled out of the weld at a certain distance, the electric field causes the metal line to stretch and the cross section is reduced and the current density increases (Figure c).

- At the ligation site, molten metal rapidly reaches boiling and evaporating temperatures. When the liquid metal line is broken and transferred to the tank, the arc is formed (Figure d).

Structure and distribution of heat on the arc tube:

Structure:

The entire arc column space is divided into three regions:



+ Cathode (also known as cathode) and anode (also called anode). The energy from the anode is higher than the cathode (about 500 ÷ 600 degrees Celsius).

+ Arc Column: cylindrical cylinder driven from cathode to anode. Electric conduction in the arc is caused by the presence of electrons and charges.

Characteristics of the heat distribution on the arc tube:

When burned, the arc will have a very high temperature. The heat concentration is uneven, usually the highest in the middle and decreasing outwards.

The temperature of the arc depends on:

- Materials of electrodes and welding methods. In manual arc welding, the hand-held arc temperature is about 4200 ÷ 5700 degrees Celsius. When soldered under Tig or Tig welding, the arc temperature is 6200 ÷ 7800 C. In the Mig / Mag welding, the arc temperature Can reach 10000 degrees C.

Not all heat generated is transferred to the weld, but a portion of the heat is used to heat the surrounding air, protect the protective gas, and coat the weld.

Welding current magnitude factors:

The welding current intensity has a great influence on the temperature of the arc. Variability of the arc temperature is proportional to the change in electric current. The arc temperature increases as the current increases.



The properties of the arc:

High brightness, high temperature and focus are two of the most important properties of human-applied arcs in industry, especially welding. When welding, to achieve the weld quality should:

- Maintain stable arc whether the current is large or small.

- It is possible to control arc direction to any position that need welding, arc welding with long and short arc.

How to make an arc:

There are two methods of arcing: friction and straightening:

Causing the arc by friction:



The arc can be generated when the rod is tipped onto the welding object in the arc direction. After the arc appears, maintain the distance from the welding rod to the welding material from 2 ÷ 4mm to ensure a stable arc.

This method is relatively easy to implement but easy to damage the surface of the weld, especially for small surface welding.

Arc welding with direct method



Place the tip of contact rods perpendicular to the surface of the weld and then quickly lift the welding rod. After the arc arises near the electrodes, the surface of the weld and the distance between 2 ÷ 4mm to maintain the arc.

This method is relatively difficult to implement because the arc is easily turned off or the solder tip is prone to sticking to the solder. When the arc is unlucked if the tip of the solder is stuck to the solder, just shake it to the right and then to the left several times to remove the solder. If the welding rod still stick tight, then open the pliers solder and  take the welding rod from the weld material.

Note that the operation when the tip of the rod contacts with the surface of the welding, material should be done quickly and when lifting the rod beyond far from the welding material is made slower.

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