Metal Processes

Question 1

What are the metal processes grouped into ?
And what does each of this mean ?

Answer 1

Re-distribution, wasting and addition process

Re-distribution = deforming or reforming materials

Wasting = removal of material

Addition = joining materials together

Question 2

What are metal re-distribution processes ?

Answer 2

• Press forming
• Spinning
• Cupping
• Deep drawing
• Forging
• Drop forging
• Bending
• Rolling
• Casting: sand casting, die casting, investment casting, low temperature casting (pewter).

Question 3

What are the addition processes ?

Answer 3

● Metal inert gas (MIG) welding
● Tungsten inert gas (TIG) welding
● Spot welding
● Oxy-acetylene welding
● Soldering (soft and hard)
● Brazing
● Riveting
● Temporary Joining methods and fasteners:
- self tapping screws
- machine screws
- nuts and bolts.

Question 4

What are the wasting processes ?

Answer 4

● Milling
● Turning
● Flame cutting
● Plasma cutting
● Laser cutting
● Punching/stamping

Question 5

Explain MIG welding

Answer 5

It works by forming an electrical arc between a metal wire electrode and the parts that you are welding to locally heat it to a very high temperature - this melts the base metal allowing it to join together - and the wire ( which is usually a similar material to the metal that is being joined ) is fed out of the MIG gun by an electric motor and pushed into the weld puddle to reinforce the weld as the wire melts in the arc and fills the gap between the 2 pieces being joined - gas flows out of the nozzle to protect the molten metal from contamination ( the weld puddle ) by the air - the gas is also important for the arc to work correctly

The contaminating oxygen could oxidise and would prevent the weld from forming properly

Question 6

What metals is MIG welding used for ?

Answer 6

It is suitable for thin gauge metals - because the heat generated by the electrical arc is localised to a small area and will not burn through the metal or distort the surrounding metal

Question 7

What products is MIg welding used to produce ?

Answer 7

It is often used to join tubular steel products such as climbing frames, bike frames and vehicle exhausts

Question 8

What is TIG welding ?

Answer 8

TIG welding is very similar to MIG welding - the differences are that the metal wire electrode is made from tungsten and does not melt in the process to fill in the gaps of the 2 joining metals - instead a separate filler rod is used to do this - a gas shield of argon or helium is used released from the nozzle and used to protect the weld pool from contamination from oxygen and from oxidisation

Question 9

Where might TIG welding be used ?

Answer 9

Fabricating stainless steel ladders for boats or swimming pools

Question 10

What metals are usually used in TIG welding ?

Answer 10

Stainless steel, as well as non-ferrous metals such as aluminium and copper or magnesium

Question 11

Explain the process of Oxy-acetylene welding

Answer 11

Oxy-acetylene welding is basically welding with fire - you use a mixture of 2 high pressure gases - oxygen and acetylene to form an internet flame that can burn at high temps

The 2 metal pieces are prepared by grinding an angle on the edges of the 2 pieces to form a ‘v’ shape - this is to ensure that the weld runs through the entire thickness of the metal

Then the joint area is heated to form a melt pool and at the same time a steel filler rod is introduced to the joint area - the melt pool is extended along the length of the joint and a continuous seam is formed

At first you start with both ends of the joint and then the melt pool is extended throughout the rest of the joint ( the middle ) so that a continuous seem is formed as you kind of move the melt pool ( molten metal pool ) along the joint

Question 12

What is Oxy-acetylene welding used for ?

Answer 12

Used to weld low carbon steel sheet, tube or plate

And used where arc welding processes like MIG are not available for e.g. where there is no electricity supply

Question 13

Explain brazing

Answer 13

The material that you are joining first has to be cleansed and degreased - then the 2 pieces are clamped together and a flux is applied to prevent the joint from oxidising

The joint heated using an oxy-acetylene or gas torch to around 850 degrees - then the brazing filler rod ( made of brass ) is applied to the joint area - the filler rod melts and you can make the ‘spelter’ to follow the joint line by manipulating the torch

Question 14

What is brazing used for ?

Answer 14

Suitable for joining together thinner gauge low carbon steel tube or bar as uses a lower temperature than welding - the joint is not as strong as welding but is ideal for general fabrication

Brazing can be used to join dissimilar metals

Question 15

What is brazing also known as ?

Answer 15

Hard soldering

Question 16

Explain the process of soldering

Answer 16

A soldering iron is used to melt the solder over the joint ( the solder is usually made mostly of tin which also contains flux ). The solder flows along the joint using capillary action and cools and hardens into place

The solder has a lower melting point that the metal being joined

Question 17

What is soldering used for ?

Answer 17

it is used for lightweight applications - for e.g. joining precious metals like on jewellery

Question 18

How does cold riveting work?

Answer 18

the 2 metal pieces that you want to join are overlapped and drilled

The rivet shaft is placed into the hole - the head of the rivet is dome shaped and a set tool is placed over this - the end of the shaft is then hammered over to squeeze the 2 pieces together

Question 19

How do self-tapping screws work ?

Answer 19

A pilot hole needs to be drilled through the metal parts - the screw has a coarse thread which is made from hardened steel; - when it is screwed into the pilot hole - it cuts its own thread which hold the screw in place

Question 20

What are self tapping screws used for ?

Answer 20

They are used for polymer products where battery components need to be secured with screws

Used in computers