Chapter 5 Material Codes & Coding Systems

I. Detailed Metal Coding System

A. Unified Numbering System(ASM International)

1. Letter – Indicates Main Metal or Alloy Group

2. Numeric – 5 digits indicate specific alloy

B. AISI –SAE Codes for Steels

1. 4 digit code

a. 1st digit indicates main alloy

b. last 2 digits indicates carbon content in wt %

c. 2nd digit indicates specific alloy group

C. Aluminum Association(AA) codes

1. 4 digit code plus temper or strain hardening code

2. 1st digit indicates main alloy

3. next 3 digits indicates specific alloy

4. temper or strain hardening is indicated by letter following 4 digits

5. following digits indicate specific heat treatment, strain level, or etc.

D. Other Codes

1. Structural Steels A-xxx

2. Stainless Steels, 2xx & 3xx(austenitic), 4xx (ferritic & martensitic)

II General Codes

A. General Classes for Steels

1. Carbon Steels

Low Carbon C < 0.30

Medium Carbon 0.30 <C < 0.60

High Carbon C > 0.60

2. Alloy Steels

Low Alloy Total Alloys < 10%

High Alloys Total Alloys > 10%

III General Cast Iron Codes

A. Structure Based

White Iron (no free graphite, martensite & carbide structure – very hard)

Gray Iron – Graphite flakes, ferrite or pearlite matrix

Compacted Iron – Vermicular(thick flakes), ferrite or pearlite matrix

Ductile(Nodular) Iron – Graphite Spheriods, ferrite, pearlite, bainite or martensite matrix

Malleable Iron – rosettes of graphite, ferrite or pearlite matrix

B. Codes related to Mechanical Properties

Gray Iron - Tensile Strength Class ASTM Class 20 = 20,000 psi tensile strength

Ductile Irons UTS – YS - %E 120-90-2 imples 120,000 psi UTS; 90,000 psi YS, and 2% elongation.

UNS Letter Prefix for Various Alloys ( See Table 5-1)

Letter Prefix Main Metal or Alloy

A Aluminum Alloys

C Copper Alloys

F Cast Irons

G AISI & SAE Steels

H Hardenable Steels, AISI & SAE H-steels

J Cast Steels

N Nickel Alloys

P Precious Metals

S Heat & Corrosion Resistant Stainless Steels

T Tool Steels

Table 5-2 AISI-SAE Main Alloy Groups - Steels

Code Main Alloy

1xxx Carbon(Plain Carbon)

2xxx Nickel

3xxx Nickel-Chromium

4xxx Molybdenum with Chromium and Nickel

5xxx Chromium

6xxx Chromium – Vanadium

8xxx Nickel-Chromium-Molybdenum(lower levels than 4xxx)

Table 5-5

Code Major Alloy Element Heat Treatable(ppt)

1xxx Aluminum(pure Al 99+%) No

2xxx Copper Yes

3xxx Manganese No

4xxx Silicon No

5xxx Magnesium No

6xxx Magnesium & Silicon Yes

7xxx Zinc Yes

8xxx Other Some

9xxx not used

Temper Codes C. Strain Hardened Codes

Code Condition Code Description

O Annealed H-12 Quarter Hard

H Strain Hardened(cold worked) H-14 Half Hard

F Temper as Fabricated H-18 Fully Hardened(75% Reduction

T Heat Treated