About Arc Welding
Shielded metal – arc welding, sometimes referred to as Metallic-arc welding, or just arc welding, is widely used in the construction many products. Examples include ships, tanks, trains, vehicles and everyday household products like appliances. The process of ark welding not only simplifies the maintenance and manufacture of goods and machines, but it permits the skilled operator to perform all operations quickly and easily.
When an electrical current moves through a wire, heat is generated by the resistance of the wire to the flow of electricity. The greater the current flow the greater the resistance and the more intense the heat.
The heat generated for welding comes from an arc which develops when electricity jumps across an air gap between the end of an electrode and the base metal. The air gap produces a high resistance to the flow of current and this resistance generates an intense arc heat which may be anywhere from 6,000°F to to 10,000°F.
Welding current is provided by an AC or DC machine. The primary current (input) to a welding machine is either two hundred twenty or four hundred forty volts. Since voltage of this magnitude is always dangerous, extreme care must be taken to ensure that the motor and frame are well grounded.
The actual voltage used to provide welding current is low (eighteen to thirty-six) whereas high amperage is necessary to produce the heat required for welding. However, low voltage and high amperage for welding are not particularly dangerous if there is adequate branding and proper insulation. Although they need not be feared, both should be treated with care to avoid any electrical accident.
When an electrical current moves through a wire, heat is generated by the resistance of the wire to the flow of electricity. The greater the current flow the greater the resistance and the more intense the heat.
The heat generated for welding comes from an arc which develops when electricity jumps across an air gap between the end of an electrode and the base metal. The air gap produces a high resistance to the flow of current and this resistance generates an intense arc heat which may be anywhere from 6,000°F to to 10,000°F.
Welding current is provided by an AC or DC machine. The primary current (input) to a welding machine is either two hundred twenty or four hundred forty volts. Since voltage of this magnitude is always dangerous, extreme care must be taken to ensure that the motor and frame are well grounded.
The actual voltage used to provide welding current is low (eighteen to thirty-six) whereas high amperage is necessary to produce the heat required for welding. However, low voltage and high amperage for welding are not particularly dangerous if there is adequate branding and proper insulation. Although they need not be feared, both should be treated with care to avoid any electrical accident.
Types of Arc Welding Machines
To supply the current for welding, three types of power sources are available: transformers, motor generators, and rectifiers.
Sizes of welding machines are rated according to their approximate amperage capacity at 60% duty cycle, such as 150, 200, 250, 300, 400, 500 or 600. This amperage is the rated current output at the working terminal. Thus, a machine rated at 150 amperes can be adjusted to produce a range of power up to 150 amperes.
The Duty cycle for most welding machines is based on a 10-minute period of time. Every welding machine is rated at a certain amperage output and voltage output for a given period of time.
The size of the welding machine to be use is governed largely by the kind of welding that is to be done.
Sizes of welding machines are rated according to their approximate amperage capacity at 60% duty cycle, such as 150, 200, 250, 300, 400, 500 or 600. This amperage is the rated current output at the working terminal. Thus, a machine rated at 150 amperes can be adjusted to produce a range of power up to 150 amperes.
The Duty cycle for most welding machines is based on a 10-minute period of time. Every welding machine is rated at a certain amperage output and voltage output for a given period of time.
The size of the welding machine to be use is governed largely by the kind of welding that is to be done.
Trasformers
The Transformer type of welding machine produces AC current and is considered to be the least expensive, lightest, and smallest machine. It takes power directly from a power supply line and transforms it to the voltage required for welding.
One outstanding advantage of the AC will there is the freedom from magnetic Art blow which often occurs when welding with DC machines. Art flow is a condition that causes the art to wonder while welding in corners on heavy metal or if using large electrodes.
Another feature of the AC welder is it low operating and maintenance costs, its high overall electrical efficiency, and noiseless operation.
Transformer types of welding machines are particularly adaptable for metallic arc, or “stick” welding. However, they do not, as a rule, have as much flexibility as the dual control generator to meet different welding requirements.
One outstanding advantage of the AC will there is the freedom from magnetic Art blow which often occurs when welding with DC machines. Art flow is a condition that causes the art to wonder while welding in corners on heavy metal or if using large electrodes.
Another feature of the AC welder is it low operating and maintenance costs, its high overall electrical efficiency, and noiseless operation.
Transformer types of welding machines are particularly adaptable for metallic arc, or “stick” welding. However, they do not, as a rule, have as much flexibility as the dual control generator to meet different welding requirements.
Motor Generators
Motor generators are designed to produce DC current in either straits or reverse polarity. The polarity selected for welding depends on the kind of electro views and the material to be welded.
A switch on the machine can be turned first-rate or reverse polarity.
Present day motor generators are usually of the constant current, dual control type. Constant current simply means that a steady supply of current is produced over a wide range of welding voltages. Without a steady flow of current, it would be virtually impossible to produce consistently uniformed welds with proper penetration.
The conventional DC motor generator has its widest usage in metallic arc “stick” welding.
A switch on the machine can be turned first-rate or reverse polarity.
Present day motor generators are usually of the constant current, dual control type. Constant current simply means that a steady supply of current is produced over a wide range of welding voltages. Without a steady flow of current, it would be virtually impossible to produce consistently uniformed welds with proper penetration.
The conventional DC motor generator has its widest usage in metallic arc “stick” welding.
Rectifiers
Rectifiers are essentially transformers containing an electrical device which changes alternating current into direct current. Some types are designed to provide a choice of low voltage for metal inert gas welding and submerged arc welding, or a high open circuit with drooping voltage characteristics for tungsten inert gas welding and metallic arc (stick) electrode welding.
Rectifier welding machines are also available to produce both DC as well as AC current. By simply turning a switch, you output terminals can be changed to either AC or DC current.
The transformer rectifier is usually considered more efficient electrically than the generator and provides quiet operation.
Rectifier welding machines are also available to produce both DC as well as AC current. By simply turning a switch, you output terminals can be changed to either AC or DC current.
The transformer rectifier is usually considered more efficient electrically than the generator and provides quiet operation.
Constant Potential (voltage) Welding Machine
This type of welding machine is either a rectifier or motor generator designed especially for MIG welding. It provides practically a constant voltage to the ark regardless of the arc length. Since in MIG welding a continuous wire electrode is fed into the arc, any variation and arc length will automatically bring about an adjustment in the arc voltage. Thus this type of machine is inherently self-regulating.
Welding Equipment
Hand Shield or Helmet
Electric arc welding not only produces a brilliant light, but it also gives us invisible ultraviolet an infrared rays which are extremely dangerous to the eyes and skin. Because of this, a person should never look directly at an arc with their eyes alone, From closer than 50 feet away. To protect themselves from these harmful rays, a person must use either a hand shield or a helmet.
The hand shield provides protection similar to a helmet, except that it is held in position by a persons hand using a handle. This type of protective shield is very often used by an observer of the welding, or by a person who may only be welding for a short period of time. Shields are equipped with special colored lenses that reduced the brilliancy of the light and screen out the infrared and ultraviolet rays. Lenses come in a variety of shades, and the type used depends on the kind of welding being performed.
Helmets, as can be expected, fit over the head as a full form of head protection. They have a pivoting face guard that maybe swing upward when not welding. The greatest advantage of using a helmet over a shield is that it leaves both hands free, making it possible to hold the work and weld at the same time.
Goggles
In arc welding, a thin crust forms on the deposited bead. This crust is known as slag, and must be removed. For a welding technician who is removing slag from a weld, goggles offer a form of protection that keep particles and other debris from getting into the welder’s eyes. Without proper eye protection, these particles may cause serious eye injury.
Gloves
It is also important to protect your hands when arc welding. Because of this, you must wear gloves to protect your hands from ultraviolet ultraviolet rays and the spattering hot metal that is produced.
There are a variety of glove types available. Generally, the leather gauntlet type gloves provide the best protection. Regardless of the type used, they should be flexible enough to permit proper hand movement yet not so thin as to allow the heat to penetrate easily.
Aprons
It is wise to wear an apron when performing work as an arc welder. The apron protects from the spattering metal that might otherwise ruin your clothing. The spattering medal particles are very hot, so any leather apron is the best form of protection against this. Most experience welders stop worrying apron on the job after a wild, except in situations where there maybe an excessive amount of metal spatter due to a strange or unconventional welding position. Instead of an apron, experience welders may choose to wear coveralls.
Electric arc welding not only produces a brilliant light, but it also gives us invisible ultraviolet an infrared rays which are extremely dangerous to the eyes and skin. Because of this, a person should never look directly at an arc with their eyes alone, From closer than 50 feet away. To protect themselves from these harmful rays, a person must use either a hand shield or a helmet.
The hand shield provides protection similar to a helmet, except that it is held in position by a persons hand using a handle. This type of protective shield is very often used by an observer of the welding, or by a person who may only be welding for a short period of time. Shields are equipped with special colored lenses that reduced the brilliancy of the light and screen out the infrared and ultraviolet rays. Lenses come in a variety of shades, and the type used depends on the kind of welding being performed.
Helmets, as can be expected, fit over the head as a full form of head protection. They have a pivoting face guard that maybe swing upward when not welding. The greatest advantage of using a helmet over a shield is that it leaves both hands free, making it possible to hold the work and weld at the same time.
Goggles
In arc welding, a thin crust forms on the deposited bead. This crust is known as slag, and must be removed. For a welding technician who is removing slag from a weld, goggles offer a form of protection that keep particles and other debris from getting into the welder’s eyes. Without proper eye protection, these particles may cause serious eye injury.
Gloves
It is also important to protect your hands when arc welding. Because of this, you must wear gloves to protect your hands from ultraviolet ultraviolet rays and the spattering hot metal that is produced.
There are a variety of glove types available. Generally, the leather gauntlet type gloves provide the best protection. Regardless of the type used, they should be flexible enough to permit proper hand movement yet not so thin as to allow the heat to penetrate easily.
Aprons
It is wise to wear an apron when performing work as an arc welder. The apron protects from the spattering metal that might otherwise ruin your clothing. The spattering medal particles are very hot, so any leather apron is the best form of protection against this. Most experience welders stop worrying apron on the job after a wild, except in situations where there maybe an excessive amount of metal spatter due to a strange or unconventional welding position. Instead of an apron, experience welders may choose to wear coveralls.
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