Ways to improve the performance of the welding process.
use of electrodes with a diameter exceeding 8 mm usually allows to increase the productivity of the process, as increasing the weight of the electrode and the holder (in conjunction with an increase in welding current) leads to a rapid exhaustion of the welder. The same is observed in manual arc welding of three-phase arc. These methods may find limited use in the bathroom welding rebar reinforced concrete structures. However, here is preferable to use a single electrode.
When welding bath melt the base metal by the arc, and partly due to the heat transferred by product superheated molten metal weld pool (Figure 21). Therefore, welding pro-Figure 21 assembly by welding lead bath at higher effect of horizontal reinforcement bars: current. Joint rods are collected
with a gap in the forms of the remaining steel (a metal band) or copper removable, reusable or disposable graphite.
Welding start at the bottom of the form, arc melting the lower edges of the joint. Until the end of the weld metal at the top of the weld pool are trying to maintain a molten state to the greatest possible depth and width required for all cuts and shapes. The seam overlay slightly above the surface of the rods. The process is carried out manually, although there were attempts to create systems for mechanized welding in which the melting of the electrode occurred automatically, and their replacement was performed manually. However, the installation proved to be difficult to use and low productivity.
Improved process performance is also achieved using electrodes containing iron powder in the coating (see Chap. III). With the use of these electrodes, welding is possible only in the lower position, as by welding at other spatial positions of the increased size of the weld pool leads to leakage of molten metal out of it. Technique of welding joints in the lower position is also complicated for this reason, but not fundamentally different from conventional welding electrodes.
When welding with deep penetration (other names: leaning electrode submerged arc, etc.) increase the productivity of welding is achieved by a deeper penetration of the base metal. Welding is performed by special electrode giving during their high melting peak size, and based on which the electrode (see Fig. 70). Welder holding the electrode at an angle of 70-85 ° to the surface of the product, move it along the welded edges without bending vibrations. Use the maximum allowable current. Released during the melting of the electrode gases, pushing the molten metal weld pool from the arc, increasing the depth of penetration, which is regulated by varying the angle of inclination of the electrode and the speed of its movement. Welding is performed in the lower position of butt and fillet welds.
When welding methods and the bed-oblique electrodes are also used special electrodes, which melt coating, forming a canopy of a certain size, prevents short-circuiting of the arc. Increased productivity is achieved by the fact that a welder at the same time serves several arcs. Bed-electrode (Fig. 22a) butt weld and lap and fillet welds connecting steel to a thickness of 0.5-6 mm. Use electrodes with a diameter 2,5-8 mm and a length of 2000 mm. The electrode is placed on the joint to be welded and is covered from top to massive copper bars, insulated from the paper products, to prevent possible breakage of the arc due to the deformation of the electrode when it is
melting. Doug lit end of the closure of the working electrode, a carbon rod or a metal electrode and move as far as the melting of the electrode.
For welding in this way is more convenient to use special tools. This method of welding can be used for welding equipment, welding seam is, in different spatial positions. For directions to the root of the arc and the weld metal transfer control of the electrode in the weld pool, as well as to hold the molten metal weld pool from leaking in different spatial positions created by the use of external solenoids specially designed magnetic field.
The method of welding electrode is inclined (Fig. 22b) has been developed in the USSR in the mid 30s. At the present time it is used abroad under the name of gravity welding. When welding electrode is fixed to the tripod, placed at the surface of the product through an insulating pad, as it is melting it down with a clip under the weight. Current supply is carried out directly to the electrode or the holder. The depth of penetration and weld width adjusted by varying the angle of inclination of the electrode alfa.
In practice, a small amount of installation are used for mechanized arc welding of metal electrodes coated with (MMA). They maintain the arc and its movement along the 'welded edges automatically. The electrodes are replaced by manually moving the machine or stop without stopping. Increased productivity of the welding process is achieved through the maintenance welder two units or more.
See also:
Manual Arc Welding
Introduction to Arc Welding
Creating and maintaining an arc
Ways to improve performance
Technique of upper and horizontal joints
Technique of the lower seam
Pipe Welding Technique
The Method
Arc Welding in Protective Gases
Electrodes for Manual Arc Welding
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