Welding Essentials. William Galvery

arc and sparks by protective screens. Never view the welding being performed through the protective screens alone; the only way to safely view welding is through the proper shade lens and welding helmet or goggles.

      •Beware of hazards from gases and insure adequate ventilation; inert shielding gases may cause suffocation in confined areas.

      •Provide adequate ventilation from welding process smoke and the metal vapors, particularly heavy metals like zinc and cadmium that are toxic; keep your head out of the welding plume.

      •Leathers or specially treated canvas jackets must be worn when welding vertically or overhead to protect the welder from the falling hot metal, sparks and slag.

      •A welder’s hat will prevent both radiation burns to the head and hot sparks, falling slag and hot metal burns.

      •High-top boots can prevent hot sparks and slag from burning your feet.

      •Never weld with pant cuffs sparks falling into cuffs will burn pants.

      •Make sure your welding gloves are dry and have no holes.

      •Keep hands and body insulated from both the work and the metal electrode holder.

      •Do not change the polarity switch position while the machine is under welding current load.

      •Welding machines must be turned off when not attended.

      •Must not stand on a wet surface when welding to prevent electric shock.

      •Welding cables and electrode holders must be inspected for broken insulation regularly to prevent electric shock.

      •Welding power supplies on AC lines must be properly grounded and emergency shut-off switch location known and accessible.

      •Welding area must be dry and free of flammable materials.

      •Protect your ears from welding and grinding noise with ear plugs or ear protectors.

      •Any compressed gas cylinders must be properly secured and out of the spark stream.

      •Must avoid wrapping welding cable around their arms or bodies in case a vehicle snags the cables.

      •Never cut or weld on containers without taking precautions, see Chapter 1, Safety.

      •Shielded metal arc welding the welder must plan for disposal of electrode stubs: they are hot enough to cause burns and to start fires and must not be dropped from heights because of the hazard to others.

Chapter 5

       Shielded Metal Arc Welding

       I hear and I forget.I see and I remember.I do and I understand.

      Confucius

      Introduction

      Most accounts trace the history of electric welding to 1801 when Sir Humphrey Davy discovered an arc could be created with high-voltage electric current by bringing two terminals near each other. In 1881 Augustine de Mertines began experimenting with arc welding; these experiments were used to weld various parts of a lead battery plate using a carbon arc as the heat source. Carbon arc welding patents were issued to N. de Benardos, a Russian, May 17, 1887. Between 1889 and 1908 the N. G. Slavinoff system of arc welding, where the carbon electrode was replaced with a bare metal electrode was developed. American patents on this metal arc process were issued to Charles Coffin in 1889. Oscar Kjellberg, founder of ESAB of Sweden, applied a coating to the bare electrode between, 1907 and 1910, which began the development of coated metal arc welding electrodes.

      By 1912 Lincoln Electric, and three other well-established manufacturers, offered the first arc welding machines. It remains an important process for structural steel and pipe line welding. Decision makers in these critical industries use it because it is so reliable. Even with thousands of welds made in adverse conditions, on startup the trans-Alaska pipeline did not have a single weld failure. Arc welding is popular for industrial, automotive, and farm repair because its equipment is relatively inexpensive and can be made portable. More welders have learned this process than any other. Although it will be around for many years, and its annual filler metal poundage continues to grow, it is declining in importance as wire feed welding processes continue to gain popularity and market share. We will cover theory, equipment, electrode rod classification and selection, and safety.

      Process Names

       What is the AWS designation for welding with a flux coated electrode?

      Shielded metal arc welding (SMAW) is the AWS designation.

       What are other common names for SMAW?

      SMAW is also commonly called arc welding, stick welding, and stick electrode welding.

       What equipment makes up a SMAW setup?

      •Constant-current (CC) welding power supply

      •Electrode holder, lead, and its terminals

      •Ground clamp, lead, and its terminals

      •Welding electrodes. See Figure 5–1.

Figure 5–1Shielded metal arc welding machine

       What additional equipment may be found in an SMAW process welding station?

      •Booth walls or light shields

      •Jigs, fixtures, and positioning devices

      •Stool

      •Ventilation system

      •Workbench

      Process

       How does the SMAW process work?