Flashcards
1 of 20
Welding | Definitions
Welding
Welding refers to a group of joining processes that involve the fusing together of metal parts.
Oxidation
If welding is carried out in the air, i.e. gas and arc welding, oxides are created which make a weak weld. Oxides create undesirable compounds and gas bubbles in the metal, creating porosity and weakness. Oxides occur naturally on the surface of the metals and should be cleaned off before welding. However, heat from the welding process creates new oxides and these and other impurities can get brought into the molten metals.
Flux
Flux is a mixture of chemical compounds that prevent oxidation and help the welding process. Fluxes can be applied in paste or powder form before welding or can be applied using flux-coated filler rods.
Dissolved Acetylene
If acetylene is compressed into a cylinder, it would explode under high pressure. Acetylene cylinders are packed with a porous material that is filled with acetone which can absorb 25 times its volume of acetylene.
Slag Inclusions
Foreign matter becomes entrapped in the weld. This can be caused by welding on dirty surfaces or contamination from the atmosphere.
Porosity
Usually caused by the presence of moisture in the weld, the presence of paint, oil/grease or if the cylinder is out of gas.
Multi-Run Welds
Multi-run welding means welding the same joint more than once. This leads to a better and tougher joint as each new weld re-heats the previous run, annealing the metals so they are less hard and brittle. Multi-runs are superior to single-run welds due to a post-heating effect occurring after each weld run. This refines the material’s structure and strengthens the weld.
Flashback Arrestor
Prevents the flame from returning through the hoses to the cylinders in oxy-acetylene welding.
Neutral Flame
The flame used in oxy-acetylene welding which has a balanced proportion (1:1) of oxygen and acetylene with a working temperature of up to 3,300°C.
Carburising Flame
The flame used in oxy-acetylene welding which contains excess acetylene. The ratio is 10:9 (10 parts acetylene to 9 parts oxygen) with a working temperature of up to 3,150°C. The flame is larger, with the distinctive acetylene feather.
Oxidising Flame
The flame used in oxy-acetylene welding that contains excess oxygen. The ratio is 1.5:1 (1.5 parts oxygen to 1 part acetylene) with a working temperature of up to 3,500°C. The flame appears smaller.
Step-Down Transformer
Used to change the mains voltage from 220V to a suitable level (80-100V) for welding, which will provide the high current needed for welding. This type has more turns on the primary coil than the secondary coil and will induce alternating current (AC) at a lower voltage.
Rectifier
The rectifier changes alternating current (AC) to direct current (DC). It consists of four diodes which allows two of the diodes to conduct on each half-cycle of the AC supply.
Bridge Rectifier
Converts AC (alternating current) to DC (direct current) and consists of 4 diodes. A diode can only conduct electricity in one direction. In the positive voltage half of the AC cycle, D1 and D3 diodes conduct. In the negative half of the AC cycle, D2 and D4 diodes conduct. This 'unreverses' the reverse direction of the current and creates a current flowing in the forward direction only. This current charges the capacitor.
Capacitor
Used to provide a smooth supply of low voltage DC.
Earth Clamp
The earth clamp is a clip/clamp that attaches to the piece being welded to complete the electric circuit. An earth clamp is essential on the workpiece to route the arc current back safely to the power supply and not through the person.
Resistance Welding
Resistance welding passes a large electric current through the material to melt and fuse the parts together. No shielding flux or gas is needed because the join is internal and not exposed to the air.
Metal Machinability
Refers to the ease with which a metal can be machined to an acceptable surface finish.
Permanent Joint
A permanent joint can’t be dismantled without causing damage to the joint. It can withstand high pressure and vibrations.
Temporary Joint
A temporary joint can be dismantled with little effort. It can withhold moderate pressure and vibrations and is often used for parts that may need to be disassembled for maintenance or replacement.
Deck complete
You’ve reviewed 20 terms. Keep up the good work!
tap to flip
Print
Welding | Definitions
Welding
Welding refers to a group of joining processes that involve the fusing together of metal parts.
Oxidation
If welding is carried out in the air, i.e. gas and arc welding, oxides are created which make a weak weld. Oxides create undesirable compounds and gas bubbles in the metal, creating porosity and weakness. Oxides occur naturally on the surface of the metals and should be cleaned off before welding. However, heat from the welding process creates new oxides and these and other impurities can get brought into the molten metals.
Flux
Flux is a mixture of chemical compounds that prevent oxidation and help the welding process. Fluxes can be applied in paste or powder form before welding or can be applied using flux-coated filler rods.
Dissolved Acetylene
If acetylene is compressed into a cylinder, it would explode under high pressure. Acetylene cylinders are packed with a porous material that is filled with acetone which can absorb 25 times its volume of acetylene.
Slag Inclusions
Foreign matter becomes entrapped in the weld. This can be caused by welding on dirty surfaces or contamination from the atmosphere.
Porosity
Usually caused by the presence of moisture in the weld, the presence of paint, oil/grease or if the cylinder is out of gas.
Multi-Run Welds
Multi-run welding means welding the same joint more than once. This leads to a better and tougher joint as each new weld re-heats the previous run, annealing the metals so they are less hard and brittle. Multi-runs are superior to single-run welds due to a post-heating effect occurring after each weld run. This refines the material’s structure and strengthens the weld.
Flashback Arrestor
Prevents the flame from returning through the hoses to the cylinders in oxy-acetylene welding.
Neutral Flame
The flame used in oxy-acetylene welding which has a balanced proportion (1:1) of oxygen and acetylene with a working temperature of up to 3,300°C.
Carburising Flame
The flame used in oxy-acetylene welding which contains excess acetylene. The ratio is 10:9 (10 parts acetylene to 9 parts oxygen) with a working temperature of up to 3,150°C. The flame is larger, with the distinctive acetylene feather.
Oxidising Flame
The flame used in oxy-acetylene welding that contains excess oxygen. The ratio is 1.5:1 (1.5 parts oxygen to 1 part acetylene) with a working temperature of up to 3,500°C. The flame appears smaller.
Step-Down Transformer
Used to change the mains voltage from 220V to a suitable level (80-100V) for welding, which will provide the high current needed for welding. This type has more turns on the primary coil than the secondary coil and will induce alternating current (AC) at a lower voltage.
Rectifier
The rectifier changes alternating current (AC) to direct current (DC). It consists of four diodes which allows two of the diodes to conduct on each half-cycle of the AC supply.
Bridge Rectifier
Converts AC (alternating current) to DC (direct current) and consists of 4 diodes. A diode can only conduct electricity in one direction. In the positive voltage half of the AC cycle, D1 and D3 diodes conduct. In the negative half of the AC cycle, D2 and D4 diodes conduct. This 'unreverses' the reverse direction of the current and creates a current flowing in the forward direction only. This current charges the capacitor.
Capacitor
Used to provide a smooth supply of low voltage DC.
Earth Clamp
The earth clamp is a clip/clamp that attaches to the piece being welded to complete the electric circuit. An earth clamp is essential on the workpiece to route the arc current back safely to the power supply and not through the person.
Resistance Welding
Resistance welding passes a large electric current through the material to melt and fuse the parts together. No shielding flux or gas is needed because the join is internal and not exposed to the air.
Metal Machinability
Refers to the ease with which a metal can be machined to an acceptable surface finish.
Permanent Joint
A permanent joint can’t be dismantled without causing damage to the joint. It can withstand high pressure and vibrations.
Temporary Joint
A temporary joint can be dismantled with little effort. It can withhold moderate pressure and vibrations and is often used for parts that may need to be disassembled for maintenance or replacement.
Cut dotted horizontal lines. Fold vertical line.

Welding
Welding refers to a group of joining processes that involve the fusing together of metal parts.
Oxidation
If welding is carried out in the air, i.e. gas and arc welding, oxides are created which make a weak weld. Oxides create undesirable compounds and gas bubbles in the metal, creating porosity and weakness. Oxides occur naturally on the surface of the metals and should be cleaned off before welding. However, heat from the welding process creates new oxides and these and other impurities can get brought into the molten metals.
Flux
Flux is a mixture of chemical compounds that prevent oxidation and help the welding process. Fluxes can be applied in paste or powder form before welding or can be applied using flux-coated filler rods.
Dissolved Acetylene
If acetylene is compressed into a cylinder, it would explode under high pressure. Acetylene cylinders are packed with a porous material that is filled with acetone which can absorb 25 times its volume of acetylene.
Slag Inclusions
Foreign matter becomes entrapped in the weld. This can be caused by welding on dirty surfaces or contamination from the atmosphere.
Porosity
Usually caused by the presence of moisture in the weld, the presence of paint, oil/grease or if the cylinder is out of gas.
Multi-Run Welds
Multi-run welding means welding the same joint more than once. This leads to a better and tougher joint as each new weld re-heats the previous run, annealing the metals so they are less hard and brittle. Multi-runs are superior to single-run welds due to a post-heating effect occurring after each weld run. This refines the material’s structure and strengthens the weld.
Flashback Arrestor
Prevents the flame from returning through the hoses to the cylinders in oxy-acetylene welding.
Neutral Flame
The flame used in oxy-acetylene welding which has a balanced proportion (1:1) of oxygen and acetylene with a working temperature of up to 3,300°C.
Carburising Flame
The flame used in oxy-acetylene welding which contains excess acetylene. The ratio is 10:9 (10 parts acetylene to 9 parts oxygen) with a working temperature of up to 3,150°C. The flame is larger, with the distinctive acetylene feather.
Oxidising Flame
The flame used in oxy-acetylene welding that contains excess oxygen. The ratio is 1.5:1 (1.5 parts oxygen to 1 part acetylene) with a working temperature of up to 3,500°C. The flame appears smaller.
Step-Down Transformer
Used to change the mains voltage from 220V to a suitable level (80-100V) for welding, which will provide the high current needed for welding. This type has more turns on the primary coil than the secondary coil and will induce alternating current (AC) at a lower voltage.
Rectifier
The rectifier changes alternating current (AC) to direct current (DC). It consists of four diodes which allows two of the diodes to conduct on each half-cycle of the AC supply.
Bridge Rectifier
Converts AC (alternating current) to DC (direct current) and consists of 4 diodes. A diode can only conduct electricity in one direction. In the positive voltage half of the AC cycle, D1 and D3 diodes conduct. In the negative half of the AC cycle, D2 and D4 diodes conduct. This 'unreverses' the reverse direction of the current and creates a current flowing in the forward direction only. This current charges the capacitor.
Capacitor
Used to provide a smooth supply of low voltage DC.
Earth Clamp
The earth clamp is a clip/clamp that attaches to the piece being welded to complete the electric circuit. An earth clamp is essential on the workpiece to route the arc current back safely to the power supply and not through the person.
Resistance Welding
Resistance welding passes a large electric current through the material to melt and fuse the parts together. No shielding flux or gas is needed because the join is internal and not exposed to the air.
Metal Machinability
Refers to the ease with which a metal can be machined to an acceptable surface finish.
Permanent Joint
A permanent joint can’t be dismantled without causing damage to the joint. It can withstand high pressure and vibrations.
Temporary Joint
A temporary joint can be dismantled with little effort. It can withhold moderate pressure and vibrations and is often used for parts that may need to be disassembled for maintenance or replacement.
Related subjects & topics
Ordinary Engineering
Ordinary Engineering
Welding & Soldering
Explore similar posts in our community