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Chapter 5. Weldings and Soldering

Arc Welding

Outline of Arc Welding

The arc welding makes arcs between a material and a welding rod. And it is a well used welding method. In the arc welding, we use a torch with a welding rod as shown in Figure 1. And both of the material and the welding rod are ment in the arc. The arc welding is very high speed, and if the welding is very well, the strength is very high. But the arc is very light, then we cannot see the welding processes. A beginner may be often failed the welding.

All weldings, including the arc welding, need higher technique than cutting processings, because we do not have the same conditions.

Fig.1, Hand Torch for Arc Welding

Actual Arc Welding

As shown in Figure 2, An arc welding machine is connected to electric cables to the electric source, the torch and the material (earth). After switch on the machine, the welding rod is touched to the material, and the arc occures. The basic handling of the arc welding is in follows.

Fig.2, Arc Welding System

Angle of Welding Rod

In the arc welding, it is important to set the angle of a welding rod (coated electrode).

As the most fundamental welding, the case where two griddles (mother material) are welded in the shape of [ of a transverse direction ] a straight line is considered. It welds laying down about 45 degrees of wedding rods in the direction of the right (in the case of a right-handed person) from the left, as shown in Fig. 3 (a). And it is the foundations which are maintained at the same angle (90 degrees) to two griddles.


As shown in Fig. 3 (b), when a wedding rod is leaned, a material opposite to the leaned side becomes easy to melt. Welding is advanced checking that both of material melts uniformly using this.


Fig.3, Angle of Welding Rod

Distance between the Welding Rod and Material

You have to keep constant the interval of a wedding rod tip and mother material during welding. As a standard, the distance is about 3-5mm. If an interval approaches too much and a wedding rod and mother material contact, an arc stops occurring and a wedding rod and mother material will adhere depending on the case. Moreover, if an interval separates too much, an arc will be distributed and suitable welding cannot be performed. Since a wedding rod becomes short as it advances welding, it warns to keep the interval of a wedding rod and mother material suitable.


Fig.4, Distance between the Welding Rod and Material

Movements of Welding Rod

What is necessary is generally, just not to necessarily move a wedding rod straightly. The wedding rod is buried in the meantime, checking that two mother material has melted firmly. The rhythm which leans (1) wedding rod and melts the material of one side as an image and which melts (2) another material of pushing in (3) wedding rod will be repeated.


Fig.5, Imagine of Arc Welding

Adjustment of Electric Current

In the arc welding, the adjustment of an electric current is very important. If the electric current is too low, the materials are not melted enough. Also the arc does not often birth, and the welding rod fixes to the material easily. Oppositely, if the electric current is too high, the materials are melted excessively, and a hole is often made at the welding point.
Examples of Arc Welding

When an equipment is made by constructed channel materials, we can make it with bolts and nuts. However if we can handle the arc welding, the processing has more shorter time and easy building. Figure 6 shows an example of the experimental equipment using the arc welding.

(a) Cutting of the materials

(b) Completed Waving Table
Fig.6, Waving Table for Model Wheelchairs

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