1. Properties of Metals
In order to weld, you must have a basic knowledge of metals.

2. All of the problems of metal casting are present in fusion welding
expansion
contraction
shrinkage
cracks
hardening
brittleness

3. Welding effects any metal.
Some effects are slight, but they can be harmful if certain rules are not followed.

4. Metal Numbering Systems
Several organizations have numbering systems for the designation of metals.

5. Society of Automotive Engineers (SAE)
American Society for Testing and Materials (ASTM)
American Iron and Steel Institute (AISI)
American National Standards Institute (ANSI)
American Society of Mechanical Engineers (ASME)
Aluminum Association (AA)

6. Unified Numbering System
UNS
The Society of Automotive Engineers and American Society for Testing and Materials developed the Unified Numbering System as a means for correlating the different numbers for some of the common metals and alloys.
In many instances, the UNS numbers contain the same number sequence given by the original organization.

7. For example, a AISI 1080 steel would be given a G10180 in the Unified Numbering System (UNS)
A UNS designation number begins with a letter followed by a 5-digit number.

8. Nonferrous Metals and Alloys
Letter Metal
A Aluminum and aluminum alloys
C Copper and copper alloys
E Rare earth and rare earth-like metals and alloys
L Low melting metals and alloys
M Miscellaneous nonferrous metals and alloys

9. P Precious metals and alloys
R Reactive and refractor metals and alloys
Z Zinc and zinc alloys

10. Ferrous Metals and Alloys
Letter Metal
D Specified mechanical property steels
F Cast irons
G AISI and SAE carbon and alloy steels
H AISI H-steels
except tool steels

11. K Miscellaneous steels and ferrous alloys
S Heat and corrosion resistant (stainless) steels
T Tool steels

12. AA System for Aluminum
The Aluminum Association uses a four-digit numbering system for designating wrought (rolled or extruded shapes) and cast aluminum alloys.
Examples would be XXXX for wrought alloys and XXX.X for cast alloys.
Letters may follow the numbers series which may indicate annealing, hardening, heat-treated or tempered.

13. Annealing
Softening metal by heat treatment.
Relieves metal of internal stress caused by the expansion and contraction during welding.

14. Hardening
The rapid cooling of hot metal.

15. Heat-treating
The process of heating and cooling metals in order to obtain desired properties.

16. Tempering
The heating of a quenched steel in a furnace to a specified temperature below the critical temperature and then allowing it to cool at any desired rate.

17. Example of structural aluminum
The “T-6” means the aluminum has been solution heat-treated and then artificially aged to obtain a desired hardness (temper).

18. Major Groups of Metals Ferrous Metals
metals containing iron and its alloys such as steel
Examples
cast iron
wrought iron
steel

19. Nonferrous Metals metals containing little or no iron Examples copper
brass
zinc
bronze
lead
aluminum

20. Metal Melting Points Material Degrees Fahrenheit Aluminum 1218
Brass
Copper
Cast iron
Wrought iron
Stainless steel
Mild Steel

21. Physical Properties of Metals
A characteristic of a metal which be observed or measured

22. Tensile strength
the ability of a metal to resist being pulled apart.
Ductility
the ability of a metal to be stretched.
Hardness
the quality which allows a metal to resist penetration.

23. Brittleness
means a metal will fracture easily if bent sharply or struck with a sharp blow.
Compression
strength of a metal measured by how much squeezing force it can stand before it fails.
Yield strength
the force in psi at which a weld specimen starts to pull apart.

24. Elongation
how much a metal will stretch before it breaks.
Malleability
the tendency of a metal to be hammered into shape.

25. Toughness
can withstand repeated twisting or bending.
Grain size
examination of the grain size under a microscope gives a good idea of brittleness, tensile strength, heat treatment and ductility.

26. Physical properties of steel are effected by:
Carbon content
carbon combines with iron to form iron carbide, a very hard, brittle substance.
this means as the carbon content of the steel increases, the hardness also increases.

27. Impurities
Two harmful impurities are phosphorous and sulphur
during welding, sulphur and phosphorous tend to form gas pockets in the molten metal, resulting in gas pockets in the weld.
brittleness also increase because of sulphites and phosphates.
dirt and slag are other impurities.

28. Addition of various alloying metals
Nickel
Chromium
manganese
Vanadium
Other alloys may be added to steel to improve physical properties.

29. Heat treatment
Enable steel to retain the strength of its higher carbon content, yet not have the extreme brittleness usually found with high carbon steels.

30. Alloy Metals An alloy metal is a mixture of two or more metals.
Any ferrous or nonferrous metal may be alloyed to form an alloy metal with new and desirable characteristics.
Steel is an alloy of iron and controlled amounts of carbon.
Alloy steels are created by adding other metals to plain carbon steel.

31. How To Identify Iron and Steel
The most common tests for shop use are:
Spark test
File test
Fracture test
Color test
Density test
Ring or sound of metal
Magnetic test
Chip test

32. Spark test
Can be used to separate ferrous from nonferrous metals
Lightly touch metal to grinding wheel
The type of spark produced will identify the metal
Nonferrous metals will not produce sparks.

34. Wrought Iron
large stream volume
straw colored stream
white colored streaks
very few spurts
forked spurts

35. Mild Steel
large stream volume
white colored stream
white colored streaks
few spurts
forked spurts

36. Carbon tool steel
moderately large stream volume
white colored stream
white colored streaks
very many spurts
fine, repeating spurts

37. Gray cast iron
small stream volume
red colored stream
straw colored streaks
many spurts
fine, repeating spurts

38. White cast iron
Very small stream volume
red colored stream
straw colored streaks
few spurts
fine, repeating spurts

39. Stainless steel
moderate stream volume
straw colored stream
white colored streaks
moderate spurts
forked spurts

40. Copper, Brass and Aluminum
no sparks

41. File test
comparison of filings of the “white metals”
magnesium
float like a feather
zinc die cast
fall like a rock
aluminum
in between

42. A file test can be used to check the relative hardness of a piece of ferrous metal or to see if it is heat treated.
Strike an arc with a GTAW torch on the edge of the material and see if a file will cut the area melted by the arc.
if the file will not cut the arc area, the metal is heat treated.
If the arc area is not noticeably affected (hardened) by the the arc strike, normal weld procedures and filler can be used.

43. Fracture test
breaking a portion of the metal in two.
check the grains
large grains mean the metal is brittle and weak.
small grains mean the metal is usually hard and brittle, or soft and ductile
fractures also show the color of the metal, which is a good way to tell one metal from another.

44. Color test
irons and steels
gray-white color
nonferrous metals
yellow or white color
aluminum, white metal, aluminum alloys, zinc and the likes
silver-gray color

45. Density test
basically the weight of the metal
example is lead and aluminum
basically the color is somewhat the same, yet lead is more dense than aluminum
in other words, lead is somewhat heavier than aluminum

46. Magnetic test
used to identify ferrous from nonferrous metals
all steels are affected by magnetism
nonferrous metals are not affected by magnetism
however, some stainless steels are not magnetic

47. Chip test
cutting action with a chisel indicates the structure and heat treatment
cast iron breaks off in small particles
mild steel tends to curl and cling to the base piece