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| periodic table: click image to enlarge |
Elements
4 Be Berylium - ingredient in bronze
6 C Carbon - essential ingredient in steel 0.05% to 1.5%
12 Mg Magnesium
- alloyed with aluminum or used by itself
- small shavings can burn without oxygen
13 Al Aluminum
- melts at 1,217 deg. F
- in nature, found in dirt like substance called bauxite; can be extracted with electric current
- ingredient in bronze
- second most common base metal in welding after steel
- high thermal conductivity
- becomes weaker when heated; HAZ weaker than base metal by as much as 40%
- T designates heat treated; H designates cold worked
- series for 1000, 2000, 3000, 4000, 5000, 6000, and 7000
14 Si Silicon - alloyed with aluminum
15 P Phosphorus
16 S Sulfur - inclusion makes steel brittle but also easier to drill
23 V Vanadium
24 Cr Chromium - alloy in stainless steel or aluminum
25 Mn Manganese - alloyed with aluminum
26 Fe Iron (a.k.a. Ferrite) - main ingredient in steel
28 Ni Nickel
- alloy in some stainless steel
- soft and ductile
- high resistance to corrosion and oxidation
- easily welded
- nickel alloys frequently include 75% nickel, 20% chromium, 5% iron
29 Cu Copper
- melts at 1,980 deg. F
- exists in nature in pure form
- main ingredient in brass and bronze; also alloyed with aluminum
- high thermal conductivity means high heat dissipation and a lot of heat required to maintain high heat at weld and therefore higher amperages
- becomes very soft during welding
- can use GTAW, but more frequently joined using brazing or soldering
30 Zn Zinc - alloyed with aluminum; alloyed with copper to make brass
42 Mo Molybdenum - used for 4130 steel in cars and planes with high strength to weight ratio
47 Ag Silver
50 Sn Tin - ingredient in bronze
74 W Tungsten
79 Au Gold
Steel = Iron alloyed with 0.05% to 1.50% Carbon
Low-carbon steel = 0.05% to 0.14% Carbon (highest melting point 2,786 degrees F)
Mild Steel = 0.15% to 0.29% Carbon, melts at 2,700 deg. F, tensile strength 33-40 ksi, includes A36
Medium-carbon steel = 0.30% to 0.59% Carbon
High-carbon steel = 0.60% to 0.75% Carbon
Very high-carbon steel = 0.76% to 1.50% Carbon (lowest melting point 2,464 degrees F)
More carbon results in:
- lower melting point
- more ease in hardening by heat treatment
- more difficulty in welding
Alloy Steels
Low-alloy steel (a.k.a. high strength steel, 90 ksi or higher): total alloy content including Carbon is 1.5% to 9%
4130 (normalized condition) molybdenum steel: uses chromium and molybdenum in addition to 0.30% Carbon; main applications are race cars and aircraft frames
Tool steel (a.k.a. quenched and tempered steel): main application is cutting tools, many of which are in the mining industry. Easy to harden. Difficult to weld.
Stainless Steels
- alloys of chromium and nickel increase resistance to corrosion.
- distort more when heated; expand 50% faster than regular steel.
- lower thermal conductivity
- designation "L" stands for low carbon and reduced the tendency for carbide precipitation, chromium's bonding to carbon instead of iron, resulting in formation of chromium carbide. Rapid cooling also helps prevent carbide precipitation by not giving chromium and carbon the chance to bond. Carbide precipitation changes the color of the stainless steel from straw or copper to blue or black, and reduces corrosion resistance.
Austenitic Stainless Steel (200 and 300 series)
- melts at 2500 deg F, 200 deg lower than mild steel
- 304, 308 for restaurant equipment; 316 for structural and marine applications and have higher corrosion resistance
- easily welded with some care
- have iron, chromium and nickel, but little to no carbon
- cannot be hardened by heat treatment, but can be by cold (room temperature) work
Ferritic Stainless Steel (400 series)
- alloyed mainly with 11% or more chromium; contains little to no carbon
- non-heat-treatable
- soft
- applications: building trim, pots & pans
Martensitic Stainless Steel (400 and 500 series)
- alloyed mainly with chromium and has relatively high carbon content (~1%)
- heat-treatable
- 440C not weldable; 430 is magnetic and comes in a No. 8 mirrored finish
- applications: knives
Sulfur Steel
- Sulfur is normally considered a contaminant in steel that makes it brittle, but some steels contain up to 0.33% sulfur to make them easier to drill and machine in a mill.
- Sulfur in excess of 0.55% will result in welds that are too brittle.
- not advisable to weld sulfur steels unless using an E7016 or E7018 electrode
Wrought Iron
- under 0.05% carbon
- "alloyed" with impurities such as iron silicate (glass), up to 3%
- ductile, but becomes brittle at extreme temperatures
Cast Iron
- 2.5% to 4.5% carbon
- "grey" (porous surface with graphite flakes distributed throughout) is the most common and easiest to machine
- types grey, malleable, alloy and nodular can be welded
- "white" is hard and brittle and cannot be welded
- often cracks at 1400 deg. F and above - requires heat management when welding
- commonly used electrodes include Ni-55 and Ni-98, respectively 55% and 98% Nickel, classified by AWS as "Ni-Cl," where "Cl" designates electrodes for use on cast iron.
Cast Steel
Steel up to 0.5% carbon and stainless steel can both be cast.
Forged Steel
- hammered into shape with an industrial forging press
- very tough
- high resistance to fatigue
- high resistance to cracking
Pot Metal
- made from melting down a lot of stuff in a big pot
- large variation in composition
- may have better luck brazing than welding
Brass
- copper + zinc (20% to 40%)
- melts at 1,652-1,724 deg. F
- applications: bullet jackets, cartridge cases, musical instruments, ornamental work
- can be joined by welding, brazing or soldering
Bronze
- copper + tin + aluminum + beryllium
- melts at 1,566-1,832 deg. F
- applications: bullet jackets, cartridge cases, musical instruments, ornamental work
- can be joined by welding, brazing or soldering
