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Fabrication in metal
Fabrication in metal
Metal is a versatile material that can be 'worked' hot or cold making it suitable for nearly all types of production, and the fabrication of metal is a common process. There are no commonly used metal joints and metal is either fused / welded together or joined using fixings such as screws, rivets and bolts.
Crimping (P)
Crimping (P)
is a method used in thin sheet metal to join two sheets together.
The edge of one sheet is folded over, then the edge of the other sheet is placed in the fold before rollers press the fold down (known as crimping).
It provides a tight fit and can be further reinforced by welding if necessary.
Soldering, Brazing and Welding (which are similar processes)
Soldering, Brazing and Welding (which are similar processes)
Soldering
Soldering
Heating of the work pieces is not required.
brazing
brazing
Work pieces are heated but below their melting point.
welding
welding
Work pieces need to be heated up to their melting point.
Soldering
Soldering
Two or more metal items are joined together by melting and flowing solder (an alloy of Tin and Lead) into the joint, the solder has a lower melting point (180 C) than the two metals that are being joined.
Soldering differs from welding in that it does not involve melting the work pieces.
It is particularly suitable for intricate work such as soldering electronic components onto a circuit board.
Silver Soldering
Silver Soldering
This is used to join precious and semi-precious metals such as Gold, Silver, Brass, and Copper.
The solder is usually referred to as easy, medium, or hard. This refers to its melting temperature, not the strength of the joint. Extra-easy solder contains 56% Silver and has a melting point of 1,145 °F (618 °C).
Extra-hard solder has 80% Silver and melts at 1,370 °F (740 °C).
If multiple joints are needed, then the jeweler will start with hard or extra-hard solder and switch to lower-temperature solders for later joints.
With Silver soldering, small pieces of solder wire are placed onto the metal prior to heating. A flux is used to keep the metal and solder clean and to prevent the solder from moving before it melts. Silver solder is absorbed by the surrounding metal, resulting in a joint that is actually stronger than the metal being joined. The metal being joined must be perfectly flush, as silver solder cannot normally be used as a filler and any gaps will remain.
Before we continue...
Before we continue...
... we must understand Flux
... we must understand Flux
Flux is a mixture of various minerals, chemicals, and alloying materials that primarily protect a molten weld metal from contamination by oxygen, nitrogen, other contaminants in the atmosphere. You apply it during the welding process.
Brazing
Brazing
Brazing is a metal-joining process where a filler metal is heated above its' melting point and distributed between two or more close-fitting parts. The filler metal is brought slightly above its melting temperature while protected by a suitable atmosphere, usually a flux.
It is used for more decorative work as the soft (Brass) brazing rod is easier to file to shape.
Welding
Welding
Welding is a fabrication or sculptural process that joins materials, usually metals (there is plastic welding), by melting the work pieces and adding a filler material to form a pool of molten material (the weld pool). That cools to become a strong joint, with pressure sometimes used in conjunction with heat, or by itself, to produce the weld.
This is in contrast with Soldering and Brazing, which involve introducing a lower-melting-point material between the work pieces to form a bond between them, without melting the actual work pieces.
There are several types of welding commonly used depending on the job and the material.
Gas welding, Arc welding, MIG welding, TIG welding and Spot welding.
Gas welding
Gas welding
Sometimes referred to as Oxy-Acetylene Welding because it uses Oxygen and Acetylene gases. It uses a filler material like Brazing, but with a much higher temperature.
The metal to be joined needs to be heated until white hot at which point the welding rod is introduced to the joint.
It can be a slower process but can result in a neater finish and requires inexpensive equipment which does not need an electrical supply.
Arc Welding
Arc Welding
Sometimes referred to as 'electric' or 'stick' welding, Arc is a type of welding that uses a welding power supply to create an electric arc between an electrode and the base material to melt the metals at the welding point.
The welding region is usually protected by some type of shielding gas, vapour, or slag.
Arc welding processes were first developed in the late part of the 19th century, and arc welding became commercially important in shipbuilding during the Second World War.
Today it remains an important process for the fabrication of steel structures and vehicles.
MIG Welding (P)
MIG Welding (P)
MIG (Metal Inert Gas) welding is a type of welding process that uses an electric arc to generate heat to fuse metal together. The process uses a wire that is continuously fed through a welding gun and onto the workpiece. An inert gas, such as argon or helium, is used to shield the weld from contaminants in the air.
MIG welding is a popular choice for many types of welding projects because
It is relatively easy to learn and use,
It can be used to weld a variety of metals, including steel, aluminum, and stainless steel.
It is also a fast process, making it efficient for many types of production work.
TIG Welding (P)
TIG Welding (P)
Also known as Tungsten Inert Gas welding, is an arc welding process that uses a non-consumable tungsten electrode to produce the weld. The weld area is protected from atmospheric contamination by an inert shielding gas such as Argon, and a filler metal is normally used.
TIG is most commonly used to weld thin sections of Stainless Steel and non-ferrous metals such as Aluminium, Magnesium, and Copper alloys.
The process grants the operator greater control over the weld than other types of welding, allowing for stronger, higher quality welds.
TIG is a skilled process that is difficult to master, and it is significantly slower than most other welding techniques.
Spot Welding
Spot Welding
Is a process in which contacting metal surfaces are joined by the heat obtained from resistance to electric current.
The process uses two shaped copper alloy electrodes to concentrate a welding electrical current into a small ‘spot’ and to simultaneously clamp the metal sheet together.
Forcing a large current through the spot will melt the metal and form the weld. A lot of energy can be delivered to the spot in milliseconds and avoids excessive heating of the remainder of the sheet.
Metal Glues
Metal Glues
Metal is a non-porous material therefore, it is much harder to join using adhesives.
There is one commonly used metal adhesive called Epoxy Resin.
In its commercial form this adhesive can be stronger than a welded joint!
A domestic version is commonly sold in hardware stores and is known by the brand name Araldite. It is a two part glue consisting of resin and a hardener. Neither part is of use without the other and they are mixed in equal parts to create the adhesive.
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