Lincoln Electric 100S manual Making a Weld, Figure b.5

b-3 OPERATION b-3

This figure closely resembles what is actually seen during welding. The “arc stream’’ is seen in the middle of the figure. This is the electric arc created by the electric current flowing through the space between the end of the electrode and the work.

The temperature of this arc is about 6000°F (3315°C), which is more than enough to melt metal. The arc is very bright, as well as hot, and cannot be looked at with the naked eye without risking painful injury. A very dark lens, specifically designed for arc welding, must be used with a hand or face shield whenever viewing the arc. The arc melts the base metal and actually digs into it, much as water through a nozzle on a gar- den hose digs into the earth. The molten metal forms a pool or crater and tends to flow away from the arc. As it moves away from the arc, it cools and solidifies. A slag forms on top of the weld to protect it during cooling.

The function of the covered electrode is much more than simply to carry current to the arc. The electrode is composed of a core rod of metal with an extruded chemical covering. The core rod melts in the arc and tiny droplets of molten metal shoot across the arc into the molten pool. The electrode provides additional filler metal for the joint to fill the groove or gap between the two pieces of the base metal. The cover- ing also melts or burns in the arc. It has several func- tions. It makes the arc steadier, provides a shield of smoke-like gas around the arc to keep oxygen and nitrogen in the air away from the molten metal, and provides a flux for the molten pool. The flux picks up impurities and forms the protective slag.

MAKING A WELD

Insert the bare part of the electrode into the electrode holder jaws and connect the work clamp to the weld- ing piece. Make sure to have good electrical contact.

1.Turn the welder on.

2.Lower your welding helmet to protect your face and eyes.

3.Strike the electrode at the work point on the work- piece as if striking a match. Do not hit the electrode on the workpiece, which will damage the stick elec- trode and make striking an arc difficult. Scratch the electrode slowly over the metal and you will see sparks. While scratching, lift the electrode 1/8" (3.2mm) and the arc will establish.

NOTE: If you stop moving the electrode while scratch- ing, the electrode will stick.

NOTE: Most beginners try to strike the arc by a fast jabbing motion down on the plate. Result: They either stick or their motion is so fast that they break the arc immediately.

4.Immediately after striking the arc try to maintain a distance from the workpiece that is equivalent to the diameter of the electrode used. Maintain this distance as constantly as possible during the weld. Whenever possible, weld from left to right (if right- handed). Hold the electrode at a slight angle as shown. (See Figure B.5)

FIGURE b.5

5.As the electrode burns off the electrode must be fed to the work to maintain correct arc length. The easi- est way to tell whether the arc has the correct length is by listening to its sound. A nice, short arc has a distinctive, “crackling” sound, very much like eggs frying in a pan. The incorrect, long arc has a hollow, blowing or hissing sound.

6.The important thing to watch while welding is the puddle of molten metal right behind the arc. Do NOT watch the arc itself. It is the appearance of the puddle and the ridge where the molten puddle solidifies that indicate correct welding speed. The ridge should be approximately 3/8" (9.5mm) behind the electrode. (See Figure B.6)

FIGURE b.6

Most beginners tend to weld too fast, resulting in a thin, uneven, “wormy” looking bead. They are not watching the molten metal.

IMPORTANT: For general welding it is not necessary to weave the arc; neither forwards and backwards nor sideways. Weld along at a steady pace. You will find it easier. NOTE: When welding on thin plate, you will find that you will have to increase the welding speed, whereas when welding on heavy plate, it is necessary to go more slowly in order to get good penetration.

INVERTEC® 100S