AISI/SAE Steel - numbering system

I spend a decent amount of my summer talking to industry folks. Sometimes they're materials engineers, sometimes metallurgists, sometimes polymer engineers, forgers, welders, failure engineers.

No matter what they're titles, they're typically far more knowledgeable about industrial materials than I am. They throw around all sorts of acronyms that I have to take note of and look up later.

Sometimes I save reference materials here just so I can look them up later.

Today's reference material is about the AISI (American Iron and Steel Institute) / SAE (Society of Automotive Engineers) steel numbering system. See, the wikipedia article - while thorough - is a little too thorough for me.

Instead, I like the simplicity of the Engineering Toolbox's reference chart...

10XX	Carbon steels	Plain carbon, Mn 1.00% max
11XX		Resulfurized free machining
12XX		Resulfurized / rephosphorized free machining
15XX		Plain carbon, Mn 1.00-1.65%
13XX	Manganese steel	Mn 1.75%
23XX	Nickel steels	Ni 3.50%
25XX		Ni 5.00%
31XX	Nickel-chromium steels	Ni 1.25%, Cr 0.65-0.80%
32XX		Ni 1.75%, Cr 1.07%
33XX		Ni 3.50%, Cr 1.50-1.57%
34XX		Ni 3.00%, Cr 0.77%
40XX	Molybdenum steels	Mo 0.20-0.25%
44XX		Mo 0.40-0.52%
41XX	Chromium-molybdenum steels	Cr 0.50-0.95%, Mo 0.12-0.30%
43XX	Nickel-chromium-molybdenum steels	Ni 1.82%, Cr 0.50-0.80%, Mo 0.25%
47XX		Ni 1.05%, Cr 0.45%, Mo 0.20-0.35%
46XX	Nickel-molybdenum steels	Ni 0.85-1.82%, Mo 0.20-0.25%
48XX		Ni 3.50%, Mo 0.25%
50XX	Chromium steels	Cr 0.27-0.65%
51XX		Cr 0.80-1.05%
50XXX		Cr 0.50%, C 1.00% min
51XXX		Cr 1.02%, C 1.00% min
52XXX		Cr 1.45%, C 1.00% min
61XX	Chromium-vanadium steels	Cr 0.60-0.95%, V 0.10-0.15%
72XX	Tungsten-chromium steels	W 1.75%, Cr 0.75%
81XX	Nickel-chromium-molybdenum steels	Ni .30%, Cr 0.40%, Mo 0.12%
86XX		Ni .55%, Cr 0.50%, Mo 0.20%
87XX		Ni .55%, Cr 0.50%, Mo 0.25%
88XX		Ni .55%, Cr 0.50%, Mo 0.35%
92XX	Silicon-manganese steels	Si 1.40-2.00%, Mn 0.65-0.85%, Cr 0-0.65%
93XX	Nickel-chromium-molybdenum steels	Ni 3.25%, Cr 1.20%, Mo 0.12%
94XX		Ni 0.45%, Cr 0.40%, Mo 0.12%
97XX		Ni 0.55%, Cr 0.20%, Mo 0.20%
98XX		Ni 1.00%, Cr 0.80%, Mo 0.25%

...with its couple of examples:

Example AISI/SAE No. 1020

• the first digit indicates that this is plain carbon steel.
• the second digit indicates there are no alloying elements
• the last two digits indicates that the steel contains approximately 0.20 percent carbon
   

Example AISI/SAE No. 4340

• the first two digits indicates a Nickel-Chromium-Molybdenum alloy steel
• the last two digits indicates carbon content roughly 0.4 percent