10XX = Plain Carbon Steels (Non-Alloyed)
11XX = Free-Cutting Steels (Automatic Steels)
13XX = Manganese Steels
2XXX = Nickel Steels
3XXX = Chromium-Nickel Alloy Steels
303XX = Heat and Corrosion Resistant Steels
4XXX = Molybdenum Alloy Steels
41XX = Molybdenum-Chromium Alloy Steels
43XX = Molybdenum-Chromium-Nickel Alloy Steels
46XX = Molybdenum-Nickel Alloy Steels
5XXX = Chromium Alloy Steels
514XX = Heat and Corrosion Resistant Steels
515XX = Heat and Corrosion Resistant Steels
6XXX = Chromium-Vanadium Alloy Steels
7XXX = Chromium-Tungsten Alloy Steels
8XXX = Nickel-Chromium-Molybdenum Alloy Steels
92XX = Silicon and Manganese Alloy Steels

Note: 1. If C >1, the representation will be five digits, and the last three digits represent the carbon content.

Example: SAE 1040
Plain Carbon Steel with an average of 0.40% carbon
%C: 0.37-0.44
%Mn: 0.60-0.90
%S: 0.03
%P: 0.05

Example: SAE 4140
Molybdenum-Chromium Alloy Steel with an average of 0.40% carbon
%C: 0.38-0.43
%Mn: 0.75-1.00
%Cr: 0.80-1.10
%Mo: 0.15-0.25
%S: 0.03
%P: 0.04

Steel Standards Notation:
X.YYZZ
X:
• 0 indicates pig iron, ferro alloys, and iron-based cast materials.
• 1 indicates steel and steel cast materials.
• 2 indicates non-ferrous heavy metals and alloys.
• 3 indicates light metals and alloys.
• 4-8 indicates non-metallic materials.

YY meanings are as follows:

General Grades:
00: Commercial and basic qualities
01-02: General structural steels
03-07: Non-alloy quality steels
08-09: Alloy quality steels

Special Grades:
90: Commercial and basic qualities
91-99: Other grades

Non-Alloy Prime Steels:
10: Steels with special physical properties
11-12: Structural steels
15-18: Non-alloy quality steels based on their grades (15-W1, 16-W2, etc.)

Alloy Prime Steels:
22-28: Tool steels
32-33: High-speed steels
34: Wear-resistant steels
35: Bearing steels
36-39: Special physical property-based iron-based materials
40-41-43-44-45: Stainless steels
47-48: Heat-resistant steels
49: High-temperature materials
50-59: Structural steels
60-69: Structural steels
70-79: Structural steels
80-84: Structural steels
85: Nitriding steels
88: Hard alloys

Chemical Composition Notation According to DIN/EN Standards:

Non-Alloy Steels Notation:
In the notation of non-alloy steels, the carbon content is multiplied by 100, and the resulting number is written as the identifier.

Example: Average 0.45% carbon non-alloy steel is denoted as C45. After the letter "C," some additional letters indicate special properties:

K (Ck): Low phosphorus and sulfur content
F (Cf): Flame hardenable surface
Q (Cq): Cold-formable
M (Cm): Low phosphorus, very low sulfur content
Low-Alloy Steels Notation:
For these steels, the carbon content is written first, multiplied by 100. Then, the alloying elements are listed, starting with the highest content element. The alloying elements are indicated either individually or in combination. After the alloy elements are listed, numbers follow that represent the sequence of elements and their corresponding factor multipliers.