What’s The Difference Of 440A、440B、440C、440F?

Martensitic stainless steel is a kind of chromium stainless steel which maintains martensitic microstructure at room temperature, whose properties can be adjusted by heat treatment (quenching and tempering). Generally speaking, it is a kind of hardenable stainless steel. After quenching, tempering and annealing process, The hardness of the 440 stainless steel has been greatly improved than that of other stainless and heat resistant steels. It is commonly used in the manufacture of bearing, cutting tools, or plastic molds that require high loads and wear resistance under corrosive conditions. American standard 440 series stainless steel including: 440A, 440B, 440C, 440F. The carbon content of 440A, 440B and 440C increased successively. 440F (ASTM A582) is a type of free cutting steel with S content added on the basis of 440C.


Equivalent grades of 440 SS

American

ASTM

440A

440B

440C

440F

UNS

S44002

S44003

S44004

S44020


Japanese

JIS

SUS 440A

SUS 440B

SUS 440C

SUS 440F

German

DIN

1.4109

1.4122

1.4125

/

China

GB

7Cr17

8Cr17

11Cr17

9Cr18Mo

Y11Cr17


Chemical composition of 440 SS

Grades

C

Si

Mn

P

S

Cr

Mo

Cu

Ni

440A

0.6-0.75

≤1.00

≤1.00

≤0.04

≤0.03

16.0-18.0

≤0.75

(≤0.5)

(≤0.5)

440B

0.75-0.95

≤1.00

≤1.00

≤0.04

≤0.03

16.0-18.0

≤0.75

(≤0.5)

(≤0.5)

440C

0.95-1.2

≤1.00

≤1.00

≤0.04

≤0.03

16.0-18.0

≤0.75

(≤0.5)

(≤0.5)

440F

0.95-1.2

≤1.00

≤1.25

≤0.06

≥0.15

16.0-18.0

/

(≤0.6)

(≤0.5)

Note: the values in brackets are allowed and not mandatory.


Hardness of 440 SS

Grades
Hardness, Annealing(HB)
Heat treatment(HRC)
440A
≤255
≥54
440B
≤255
≥56
440C
≤269
≥58
440F
≤269
≥58



Similar to ordinary alloy steel, 440 series Martensite stainless steel has the characteristics of hardening through quenching, and can obtain a wide range of mechanical properties through different heat treatment. In general, 440A has excellent hardening performance and high hardness, and its toughness is higher than that of 440B and 440C. 440B has a higher hardness and toughness than 440A and 440C for cutting tools, measuring tools, bearings and valves. The 440C has the highest hardness of all stainless steel and heat resistant steel for high quality cutting tools, nozzles and bearings. 440F is a free-cutting steel and mainly used in automatic lathes.