Electric Slag Welding by Paton B

Author:Paton,B.
Language: eng
Format: epub
Tags: TECHNOLOGY, Engineering. Technology in general, Electrical engineering
Publisher: Foreign Languages Publishing House.

Fig. 146. Type A-306 single-electrode single-motor trackless automatic welder.

Fig. 147. Type A-340 single-electrode trackless automatic welder.

Fig. 148. Type A-350 three-electrode trackless automatic welder.

fore, on heavy sections it has a higher production rate than the A-340. On thicknesses up to 180 mm its welding speed is anywhere from 1 to 3 m/hr. The circuitry, including the automatic control of the weld pool level, three-phase power supply and control, is similar to that of the A-372 set.

4. Walking Magnet Welding Sets

These are the lightest and most portable of ail electric slag welding sets. They are best suited for erection work on construction sites and for bulky jobs in hard-to-reach locations, where the heavy A-372 and A-350 sets cannot be operated so conveniently (for example, for press bedframes with walls up to 100 mm thick).

As a rule, walking magnet welding sets are of the single- or double-electrode type, without wire-feed and weaving-motion mechanisms, which fact reduces their weight and enhances their portability. Electrode wire is usually fed by an external feed mechanism through a metal hose.

Walking magnet welding sets are held on the workpiece and mo^ ed across it by electromagnets. Their motion across the work resembles walking—hence their name. As has been established experimentally, this walking in small steps (up to 5 mm) does not affect the stability of welding and the quality of the weld. The operation of the walking mechanism is schematically shown in Fig. 149. One complete cycle consists of four stages (1 through IV). The mechanism consists of two electromagnets 1 and 2 which are always energised and coupled by a crankshaft or an eccentric with an eccentricity e. Each centre of the crankshaft is hinged on to the appropriate electromagnet. As the crankshaft rotates, the magnets break

away in turn from the work and move a certain distance in the direction of welding. The two magnets make one step each during a complete revolution of the crankshaft; the pitch being twice the eccentricity of theshaft (h=2e). The hinges connecting the eccentric to the magnets are found in the head portion of the magnets. Therefore, only the head portion of each magnet breaks away from the work-piece in the forward movement, and the magnets can easily overcome what small obstacles may come their way.

An advantage of the walking magnet system just described is that the breaking action of one magnet is imparted to the other mag-

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