An Introduction To Stick Welding
The Welding Circuit
The welding circuit consists of a power source, electrode holder, electrode and earth clamp.
1. Power Source
The power source feeds the electric arc with a current sufficient to keep the arc ignited. Electrode welding is based on the constant current principle; the current delivered by the power source should not vary when the operator moves the electrode towards the piece. The purpose of the power source is therefore to keep the current unchanged in the presence of variations in arc length. The more constant the current, the more stable the arc and the simpler the operator's work.
The power source usually contains a current adjustment device, of a mechanical (e.g a shunt) or electronic (e.g inverter) type. Power sources can be differentiated by their output current:
a) alternating current (AC)
The output current forms a sine wave, which changes polarity at regular intervals, with a frequency of 50 or 60 cycles per second (Hz). A transformer converts the mains current into a suitable current for welding.
b) direct current (DC)
The output current has a continuous wave form, which is obtained by a 'rectifier', which converts alternating current to direct current. This output is typical of electronic & inverter power sources. DC power sources can be classified by polarity:
i) straight polarity connection
The electrode holder cable is connected to the negative socket (-) and the earth clamp cable to the positive (+). The arc concentrates the heat produced and melts the piece. As the electrode melts, it is deposited and penetrates into the welding joint.
ii) reverse polarity connection
The electrode holder cable is connected to the positive socket (+) and the earth clamp cable to the negative (-). The heat of the arc is concentrated at the tip of the electrode. Each type of electrode requires a specific current type (AC or DC) and, in DC, a specific polarity: the electrode choice can depend on the type of power source. Incorrect use causes arc instability & weld quality problems.
Arc force, hot start and anti stick devices
Welding power sources may contain special devices to aid their use. An arc force device eases the transfer of melted drops from the electrode to the base material, preventing the arc from extinguishing when the drops cause a short circuit between the electrode and the weld pool. The hot start device helps strike the arc, by supplying an over-current every time welding restarts. The anti-stick device switches off the power source if the electrode sticks to the material, allowing it to be removed.
2. electrode holder
The primary function of the electrode holder is to support the electrode, guaranteeing a good electrical contact for current passage; it should also guarantee sufficient electrical insulation for the operator.
3. coated electrode
The electrode has a core and a coating which have different, complementary functions: the core acts mainly as a conductor for the arc power and as supplier of the material that fills the joint; the coating has the function to protect the weld pool and stabilise the arc.
4. earth clamp and cables
The earth clamp, via the earth cable, ensures the circuit is closed between the power source and the piece to be welded. Choice of cable diameter should be based on welding current.
The Welding Circuit
The welding circuit consists of a power source, electrode holder, electrode and earth clamp.
1. Power Source
The power source feeds the electric arc with a current sufficient to keep the arc ignited. Electrode welding is based on the constant current principle; the current delivered by the power source should not vary when the operator moves the electrode towards the piece. The purpose of the power source is therefore to keep the current unchanged in the presence of variations in arc length. The more constant the current, the more stable the arc and the simpler the operator's work.
The power source usually contains a current adjustment device, of a mechanical (e.g a shunt) or electronic (e.g inverter) type. Power sources can be differentiated by their output current:
a) alternating current (AC)
The output current forms a sine wave, which changes polarity at regular intervals, with a frequency of 50 or 60 cycles per second (Hz). A transformer converts the mains current into a suitable current for welding.
b) direct current (DC)
The output current has a continuous wave form, which is obtained by a 'rectifier', which converts alternating current to direct current. This output is typical of electronic & inverter power sources. DC power sources can be classified by polarity:
i) straight polarity connection
The electrode holder cable is connected to the negative socket (-) and the earth clamp cable to the positive (+). The arc concentrates the heat produced and melts the piece. As the electrode melts, it is deposited and penetrates into the welding joint.
ii) reverse polarity connection
The electrode holder cable is connected to the positive socket (+) and the earth clamp cable to the negative (-). The heat of the arc is concentrated at the tip of the electrode. Each type of electrode requires a specific current type (AC or DC) and, in DC, a specific polarity: the electrode choice can depend on the type of power source. Incorrect use causes arc instability & weld quality problems.
Arc force, hot start and anti stick devices
Welding power sources may contain special devices to aid their use. An arc force device eases the transfer of melted drops from the electrode to the base material, preventing the arc from extinguishing when the drops cause a short circuit between the electrode and the weld pool. The hot start device helps strike the arc, by supplying an over-current every time welding restarts. The anti-stick device switches off the power source if the electrode sticks to the material, allowing it to be removed.
2. electrode holder
The primary function of the electrode holder is to support the electrode, guaranteeing a good electrical contact for current passage; it should also guarantee sufficient electrical insulation for the operator.
3. coated electrode
The electrode has a core and a coating which have different, complementary functions: the core acts mainly as a conductor for the arc power and as supplier of the material that fills the joint; the coating has the function to protect the weld pool and stabilise the arc.
4. earth clamp and cables
The earth clamp, via the earth cable, ensures the circuit is closed between the power source and the piece to be welded. Choice of cable diameter should be based on welding current.