Welding Arcs

Welding arcs are used as a concentrated source of high-temperature heat that can be moved and manipulated to melt the base metal and filler metal to produce welds. Types of Welding Arcs There are two basic types of welding arcs. One uses the non-consumable electrode and the other uses the consumable electrode. The non-consumable electrode does … Read more

Backhand Welding

a. Backhand welding, also known as drag angle, is illustrated in figure 6-41. The drag angle points backward from the direction of travel.  b. In this method, the torch precedes the welding rod, as shown in figure 6-41. The torch is held at an angle approximately 30 degrees from the vertical, away from the direction of welding, with … Read more

Pipe Welding

Pipe welding involves the welding of pipe for the handling of oil, gases, water, and other substances, the operating conditions of which range from high vacuum to pressure of several thousand pounds per square inch. Mechanical joints are not satisfactory for many of these services. Electric arc or oxyacetylene welding provides effective joints in these services … Read more

Surface Cleaning

It is most important to properly prepare the surface to be welded because a satisfactory weld cannot be made over thick paint, rust, or marine growth. The initiation of an arc may be impossible or, at best, very difficult when the surface has not been made ready for welding. Even a slightly rusty surface will … Read more

Arc Welding Machines: Direct Current

The direct current welding machine has a heavy-duty direct current generator (fig. 5-17). The generators are made in six standardized ratings for general purposes as described below:  Arc welding machines rated at 150 and 200 amperes, 30 volts, are used for light shielded metal-arc welding and for gas metal-arc welding. They are also used for general-purpose job … Read more

Forehand Welding

Forehand welding describes the travel angle or direction of travel. Work angle is the angle that the electrode, or centerline of the welding gun, makes with the referenced plane or surface of the base metal in a plane perpendicular to the axis of a weld. Figure 6-38 shows the working angle for a fillet weld and a groove … Read more

Pipe Welding Positions

Pipe welding positions are dictated by the job. Pipe welds are made under many different requirements and in different welding situations.  In general, the position is fixed, but in some cases can be rolled for flat-position work. Positions and procedures for welding pipes are outlined below. Horizontal pipe rolled Weld(1) Align the joint and tack weld or … Read more

Welding Positions

Welding is often done on structures in the position in which they are found. Techniques have been developed to allow welding in any position. Some welding processes have all-position capabilities, while others may be used in only one or two positions. All welding can be classified according to the position of the workpiece or the … Read more

Arc Welding With Constant Voltage

The second type of power source is the constant voltage (CV) machine or the constant potential (CP) machine. It has a relatively flat volt-ampere characteristic curve. a. The static output characteristic curve produced by both the CV and CC machine is shown in figure 10-1 above. The characteristic curve of a welding machine is obtained by measuring … Read more

Welding with DC Straight and Reverse Polarity

To understand welding with DC straight and reverse polarity, it is important to understand the*** electrical arc welding circuit,*** which is the same as any electrical circuit. In the simplest electrical circuits, there are three factors: current, or the flow of electricity; pressure, or the force required to cause the current to flow; and resistance, or the force … Read more