Active Atom

Active Atom Materials - Steel Group

Steel and Steel Alloys

Simply put mix iron with carbon from 0.002% to 2.14% by weight and you get the base product of steel.
Higher carbon percentages above 2.14% produces cast iron.
Controlling the alloying chemical and physical makeup and amount of carbon added and how these are added during smelt at the foundry and at what temperatures creates steel with qualities such as quenching behavior, tempering behavior, hardness, annealing, yield strength and tensile strength.

Heat treatment of steel through annealing, tempering, quenching.
Steel strengthen can only benefit if the carbon content in the iron is greater then 0.8% otherwise heat treatment achieves no benefit.

Steels we precision machine at Active Atom:

  • Carbon Steel
  • Alloyed Steel
  • Stainless Steel
  • Tool Steel

US Standards

SAE (Society of Automotive Engineers) and the AISI (American Iron & Steel Institute).
The organizations created a numerical index that identifies the chemical composition of structural steels.
Four numeral series is applied to designate the plain carbon and alloy steels.
Five numerals are used to designate certain types of alloy steels.
First digit indicates the type of steel, that second digit provides the major alloy element in that steel and the last two and or three digits indicate the middle carbon quantity range for that steel type.

The SAE numerical index offers numbers 1 through 9 this first digit shares the type of steel it is.
Example 4130 Steel
The 4 indicates it is a molybdenum Mo steel, the second digit is the concentration of the major element, in this example the 1 equals 1% chromium Cr and the last two digits is the carbon C and is 30% hence 4130 steel.

Major Classifications of Steel

  • 1xxx Carbon Steels low, mild carbon content steels.
  • 2xxx Nickel Steels
  • 3xxx Nickel Chromium Steels
  • 4xxx Molybdenum Steels
  • 5xxx Chromium Steels
  • 6xxx Chromium Vanadium Steels
  • 7xxx Tungsten Steels
  • 8xxx Nickel Chromium Molybdenum Steels
  • 9xxx Silicon Manganese Steels

*Boron is added under some steel types under 4xxx 5xxx 8xxx.

  • Mild Carbon Steels
    are made up of 0.05% to 0.25% Carbon C, and contains up to 0.4% Manganese Mnd
  • Medium Carbon Steels
    are made up of 0.29% to 0.54% Carbon C, and 0.60% to 1.65% Manganese Mn
  • High Carbon Steels
    are made up of 0.55% to .095% Carbon C, 0.30% to 0.90% Manganese Mn
  • Very High Carbon Steels
    are made up of 0.96% to 2.1% Carbon C

Detail of the above Major Steel Classifications

Carbon Steels

  • 100xx
    Nonsulphurized carbon steels Manganese Mn 1.00% maximum
  • 11xx
    Resulphurised carbon steels (free machining)
  • 12xx
    Rephosphorized and resulphurised carbon steels (free machining)
  • 15xx
    Carbon C 1.00% to 1.65% maximum

Manganese Steels

13xx Manganese Mn 1.75% maximum

Nickel Steels

23xx Nickel Ni 3.50%
25xx Nickel Ni 5.00%

Nickel Chromium Steels

31xx Nickel Ni 1.25%, Chromium Cr 0.65%
32xx Nickel Ni 3.50% chromium Cr 1.07%
33xx Nickel Ni 3.50%, Chromium Cr 1.55%
34xx Nickel Ni 3.00$ chromium 0.77%

Molybdenum Steels

40xx Molybdenum Mo 0.20% or 0.25%
44xx Molybdenum Mo 0.40% or 0.52%

Chromium Molybdenum (chromoly) Steel

41xx Chromium Cr 0.50% or 0.95% molybdenum Mo 0.12% or 0.20%

Nickel Chromium Molybdenum Steels

43xx Nickel Ni 1.80% chromium Cr 0.50% or 0.80% molybdenum Mo 0.25%
43BVxx Nickel Ni 1.82% chromium Cr 0.50% molybdenum Mo 0.12% or 0.35% Vanadium V 0.03% minimum
47xx Nickel Ni 1.05% chromium Cr 0.45% molybdenum Mo 0.20% or 0.35%
81xx Nickel Ni 0.30chromium Cr 0.40% molybdenum Mo 0.12%
81Bxx Nickel Ni 0.30% chromium 0.45% molybdenum 0.12% and added boron B
86xx Nickel Ni 0.55% chromium Cr 0.50% molybdenum 0.20%
87xx Nickel Ni 0.55% chromium Cr 0.05% molybdenum Mo 0.25%
88xx Nickel Ni 0.55% chromium Cr 0.05% molybdenum Mo 0.35%
93xx Nickel Ni 3.25% chromium Cr 1.20% molybdenum Mo 0.12%
94xx Nickel Ni 0.45% chromium Cr 0.40% molybdenum Mo 0.12%
94Bxx Nickel 0.45% Chromium Cr 0.40% molybdenum Mo 0.12% and added boron B
97xx Nickel Ni 0.55% chromium Cr 0.20% molybdenum Mo 0.20%
98xx Nickel Ni 1.00% chromium Cr 0.80% molybdenum Mo 0.25%

Nickel Molybdenum Steels

46xx Nickel Ni 0.85% or 1.82% chromium Cr
48xx Nickel Ni 3.50% molybdenum Mo 0.25%

Chromium Steels

50xx Chromium Cr 0.25% or 0.40% or 0.50%
50xxx Carbon C 1.00% chromium Cr 0.50%
50Bxx Chromium Cr 0.28% or 0.50% and added boron B
51xx Chromium Cr 0.80% - 0.90% - 0.95% or 1.00%
51xxx Carbon C 1.00% chromium Cr 1.05%
51Bxx Chromium Cr 0.80% and added boron B
52xxx Carbon C 1.00% chromium Cr 1.45%

Chromium Vanadium Steel

61xx Chromium Cr 0.60% - 0.80% - 0.90% vanadium V 0.12%, 0.10% minimum., or 0.15% minimum

Tungsten Chromium Steel

72xx Tungsten W 1.75% chromium Cr 0.75%

Silicon Manganese Steel

92xx Manganese Mn 0.65% 0.82% or 0.85% silicon Si 1.40% or 2.00% chromium Cr 0 or 0.65%

Here are some steels from the above list of basic alloyed steel makeup

4130 Chromoly Steel

Weldable strong light weight. Carbon C .28% to .33%, Manganese Mn .40% to 60%, Phosphorus P .035%, Sulfur S .04%, Silicon Si .15% to .35%, Chromium Cr .80% to 1.10%, Molybdenum Mo .15% to .25% Hardness Rockwell HRC 19
(before heat treat in workable state)

4140 Steel

Tough machining without leaded alloy grades.
Carbon C .38% to .43%, Manganese Mn .75% to 1.00%, Phosphorus P .035%, Sulfur S .04%, Silicon Si .15% to .35%, Chromium Cr .80% to 1,10%, Molybdenum Mo .15% to .25% Hardness Rockwell HRC 15
(before heat treat in workable state)

4340 Steel

Tough deeper hardened high strength non distortion steel.
Carbon C .38% to .43%, Manganese Mn .60% to ,90%, Phosphorus P .035%, Sulfur S .04%, Silicon Si .15% to .35%, Chromium Cr .70% to .90%, Molybdenum Mo .20% to .30%, Nickel Ni 1.65% to 2.00% Hardness Rockwell HRC 14
(before heat treat in workable state)

6150 Steel

Commercial quality high strength and hardness steel.
Carbon C .48% to .53%, Manganese Mn .70% to .90%, Phosphorus P .035%, Sulfur S .04%, Silicon Si .15% to .35%, Chromium Cr .80% to 1.10%, Vanadium V .15% Hardness Rockwell as rolled HRC 28
Hardness Rockwell annealed HRC 14

8620 Steel

Tough externally, increase hardness for strong tough core great wearability.
Carbon C .18% to .23%, Manganese Mn .70% to .90%, Phosphorus P .035%, Sulfur S .04%, Silicon Si .15% to .35%, Chromium Cr .40% to .60%, Molybdenum Mo .15% to .25%, Nickel Ni .40% to .70%
Hardness Rockwell as rolled HRC 15
Hardness Rockwell annealed HRC 2