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metals:transformation process - Coggle Diagram
metals:transformation process
Shaping Techniques
shaping
rolling
The unprocessed metal is passed through a series of rollers that compress it, reduce its thickness and increase its length. It's usually done when the metal is hot.
Uses: Sheets, plates, bars ...
extrusion
The heated metal is pushed through a hole by a piston, using compression.
Uses: Bars, tubes and other shapes.
forging
The metal piece is shaped by repeated and continuous compression forces using hammers, tongs and anvils.
Manual forging has been replaced by industrial or mechanical forging. The piece is placed on a platform that acts as an anvil. Using a pneumatic or hydraulic machine, the hammer rises and falls onto the piece again and again. Forging is usually carried out when the piece is hot.
Uses: Railings, bed headboards, horseshoes, keys, tools, nails, screws, rivets, engine pieces ...
press forging
The heated metal is placed between two dies, one fixed and the other mobile. The dies are the shape of the object we want to make. They are pressed together so that the piece takes the shape of the die.
Uses: Car body parts, radiators ...
punching
This is a cold forging process: a sheet of metal is hit with a punch to make the required shape in a mould.
Uses: Hollow pieces, such as bearings, from flat pieces.
bending
A metal sheet is subjected to force to make a curved shape with a specific curve radius.
Uses: Curved pieces or with angles.
wire drawing
A wire is pulled through a hole that has the required dimensions. A rotating drum is used to pull it through the hole to increase its length while reducing its diameter.
Uses: Metal strings and wires.
CASTING
Molten metal is poured into a container with a hollow space inside, which is the shape of the object we want to make.
The mould can be made from sand, steel or cast iron.
The metal is heated in a furnace.
The liquid metal is poured into the mould.
It is left to cool down.
The piece is removed from the mould.
Uses: Engine blocks, fire hydrants, small parts and alloys with low melting points, ornaments, jewellery, sculptures and dental implants.
Marking, cutting and finishing techniques
MARKING
Centre punch and scriber
The centre punch is used to mark lines and the scriber to mark points on sheets of metal.
How to mark a piece of metal:
Put the centre punch on the point you want to mark and hit the other end of the scriber hard once with a hammer.
Use the scriber to mark straight lines on the metal. You should use rulers and carpenter's rulers like the ones you can see in the pictures.
You can also use dividers to draw lines, circles and arcs, and to transfer measurements.
CUTTING
Cutter:Used to cut soft, flexible, thin sheets of metal. It can cut in straight, angled or curved lines.
Guillotine:Used to cut thin sheets of metal.
Punch press and die:Used to cut sheets of 5 mm or thinner.
It is used to cut simple pieces to the required shape by bringing the press down against the die.
Hacksaw:This has an arc-shaped metal frame, a plastic or metal handle and nuts or wing nuts that hold the blade in place.
It's used to cut metal in straight, accurate lines.
Power tools for cutting
Circular saw:Used to cut large metal sheets. It can cut along straight or sloping lines.
Grinder:This has a circular disc that can be used for many things. This tool can be used for cutting, sanding, polishing, planing, removing rough edges, etc. We use different types of discs depending on what we want to do.
Finishing
Sander:The motor moves the sandpaper, which is made from abrasive material, backwards and forwards rapidly. Sanding is quick and even.
grinder:This tool removes material to perfect surfaces. It is very precise and can remove as little as a hundreth of a milimeter of material.
TOOLS FOR CLEANING
Finishing
Finishing involves removing surface imperfections, polishing and protecting metals from water and corrosion.
Grinding
. A grinder is used to refine surfaces to precise, accurate dimensions and to remove any imperfections. We can use it on flat pieces or cylinders.
Lapping
. A lapping machine has a vertical handle and abrasive discs. This is usually used for finishing openings and conical surfaces, and is very accurate.
Polishing
. This technique produces a shine, using a polishing wheel with revolving, abrasive wheels or strips.
Buffing
. This technique also produces a shine. A mechanical buffing wheel is used with a steel disc or roll, which can be abrasive.
Coating
. This technique is used to protect the metal. The metal is coated in plastic or other metals, e.g. zinc, silver, gold, nickel or chrome. This technique is called galvanisation. Paints, varnishes and enamels can also be used.
Joining
PERMANENT JOINTS
Soft soldering:We use a tin-lead alloy. This is heated with an electric soldering iron, which reaches temperatures of 400°C.
Uses: Join tinplate, sheets of metal, brass and electronic and electrical components.
Hard soldering:Brass or copper is heated with a blowtorch to a temperature of 800°C.
Uses: Copper and brass; alloys of steel, bronze or cast iron.
Oxyacetylene welding:An oxyacetylene blowtorch is used which can reach temperatures of over 3000°C.
Uses: Sheets of steel in construction and in the shipbuilding and car industries.
TEMPORARY JOINTS
If you use temporary joints, they can be joined and separated again without breaking the joint or damaging the pieces.
Nuts and bolts The bolt is inserted through the pieces that need to be joined together. Washers are used so that the pieces don't break and to secure the joint.
Screws A screw joins one piece to another where there is a threaded hole. If the screw threads the hole as it is going in, we say it is a self-drilling screw.
Threaded stay bolts
This bolt has grooves at both ends, but the middle section is smooth.
Keyed joint With a piece of metal called a key, you can join two objects by putting the key in a groove.
Splined shafts The two pieces have grooves so that they fit together when joined together. The assembled pieces can rotate.
Sliding joints
Two objects that are joined together that can move or slide over each other.
