1. Structural Steel Designations
Most structural steel grades in ASTM standards follow the SAE system, with minor deviations. Refer to ASTM A29/A29M for details.
Carbon steel bars: Grades range from 1005 to 1095 (49 grades). The prefix “10” indicates plain carbon steel. Example: 1020 steel contains ~0.20% carbon.
High-manganese carbon steels: Grades 1513 to 1572 (16 grades). The “15” prefix indicates higher Mn content for improved strength and toughness (e.g., 1524 steel).
Free-cutting steels: Grades 1108–1151, 1211–1215, and 12L13–12L15 (23 grades). “11” = sulfur-based free-machining steels (enhanced machinability). “12” = sulfur-phosphorus alloyed grades (further improved cutting performance). “12L” = leaded grades for reduced cutting forces and better surface finish.
Alloy structural steels: Grades range from 1330 to E9310, plus boron steels from 50B44 to 94B30 (90 grades). First two digits indicate alloy type (e.g., 4140 is a Cr-Mo steel used for high-strength parts).
Spring steels: 1050 = carbon spring steel, 5160 = alloy spring steel, 51B60 = boron spring steel. Known for high elasticity and fatigue strength.
H steels (Hardenability steels): Carbon types: 1038H–15B62H. Alloy types: 1330H–94B30H (total: 86 grades). The suffix “H” indicates guaranteed hardenability with adjusted chemistry.
High-carbon chromium bearing steels: Defined in ASTM A295, includes 52100, 5195, K19526, 1070M, 5160, with non-sequential numbering.
Low-alloy high-strength steels: Covered by 17 ASTM standards (e.g., A572, A588, A656, etc.) with 49 grades such as Type I, Gr42, GrA, Gr II, 65, and 80. Some grades are composition-based only, without specific grade numbers.
2. Stainless and Heat-Resistant Steels
Classified by metallurgical structure:
Austenitic (including high-N)
Ferritic
Austenitic (standard)
Martensitic
Precipitation-hardening
Grade formats include: Three-digit (e.g., 304), XM-series (e.g., XM-16), Triple number codes (e.g., 26-3-3). Total: 125 grades (81 + 28 + 16), as per ASTM A484.
Example: 304 stainless steel, an austenitic grade, is widely used for its corrosion resistance and workability in applications like kitchenware and architectural trim.
3. Tool Steel Designations
Category | Grade Range | Quantity | |
Carbon Tool Steel ASTM A686 | W1-A～W5 | 5 | |
Alloy Tool Steel ASTM A680 | Hot Work Tool Steel | W1-A～W5 | 5 |
Air-Hardening Cold Work Tool Steel | H10～H43 | 15 | |
High-Carbon High-Chromium Cold Work Tool Steel | A2～A10 | 9 | |
Oil-Hardening Cold Work Tool Steel | D2～D7 | 5 | |
Shock-Resisting Tool Steel | O1～O7 | 4 | |
Low-Carbon Tool Steel | S1～S7 | 6 | |
Carbon-Tungsten Alloy Tool Steel | P1～P21 | 8 | |
Special Purpose Tool Steel | F1、F2 | 2 | |
Other Tool Steels | L2～L6 | 3 | |
High-Speed Tool Steel ASTM A600 | Tungsten-Type High-Speed Tool Steel | 6G～6F6 | 6 |
Molybdenum-Type High-Speed Tool Steel | T1～T15 | 7 | |
Intermediate-Type High-Speed Tool Steel | M1～M62 | 20 | |
4. Cast Steel Grade Designations
High-Strength Cast Steel – ASTM A148
Designations are based on minimum tensile strength (MPa) and yield strength (MPa), in the format: Grade XXX-XXX.
Example: Grade 550-345 (≥550 MPa tensile, ≥345 MPa yield).
Total: 15 grades.
General-Purpose and Structural Cast Steel – ASTM A27
Two designation formats:
① Mechanical property-based: e.g., Grade 415-205 (≥415 MPa tensile, ≥205 MPa yield).
② Alphanumeric: e.g., Grade N-1 (special-purpose grade).
Total: 7 grades.
Corrosion-Resistant and Stainless Cast Steel – ASTM A743/A743M
Designation system:
Prefix C = corrosion-resistant (for environments < 650°C)
Prefix H = heat-resistant (≥ 650°C)
Letter/number suffixes indicate alloy content (e.g., Cr, Ni).
Examples: CF8 (19Cr-9Ni), CA15 (12Cr)
Total: 34 grades.
Heat-Resistant Cast Steel – ASTM A297
Grades begin with H, followed by a two-letter combination representing the alloy series.
Examples: HF, HH, HP, etc.
Total: 14 grades for various high-temperature applications.
High-Manganese Cast Steel – ASTM A128
Grades are categorized by composition and application:
A series: standard austenitic manganese steel
B series (B-1 to B-4): wear-resistant grades with increasing carbon content
C, D, E1/E2, F: special modified grades
Total: 10 grades.
5. Cast Iron Grade Designations
Gray Cast Iron: ASTM A48
Grade designation method: Grades are composed of letters and numbers in the format: No.XX (A, B, C, S).
Example grades: No.20A, No.60B, etc., indicate minimum tensile strengths of 20 ksi and 60 ksi, respectively. The letters A, B, C, and S represent different casting processes or wall thickness ranges (A for thin wall, B for medium wall thickness, C for thick wall, and S for special requirements).
Ductile (Nodular) Cast Iron:
Grades consist of three groups of numbers. The first number is a code, the second number represents the minimum tensile strength (MPa), and the third number indicates the minimum elongation (%).
Malleable Cast Iron:
According to ASTM A47M standard, grades of ferritic malleable cast iron are represented by numerical combinations; examples include 22010 and 32510 grades. In ASTM A220M, grades of pearlitic malleable cast iron are represented by a combination of numbers and letters; examples include 280M10, 620M1, among eight grades. The number 280 represents minimum tensile strength (MPa), and 10 represents minimum elongation (%).
Wear-Resistant White Cast Iron:
The grade designation system for wear-resistant white cast iron is more complex and different from other cast irons. It includes numeric levels I, II, III, categories A, B, C, D, and alloy element symbols with their content. For example, ASTM A532 includes grades such as II B15%Cr-Mo.
Austenitic Cast Iron:
There are two types: austenitic gray cast iron and austenitic ductile cast iron. Austenitic gray cast iron grades are designated from Type 1 to Type 6; ASTM A436 includes 8 grades. Austenitic ductile cast iron grades are designated as D2 to D5S; ASTM A439 includes 10 grades.