440C is the representative steel of martensitic stainless steel, which can reach high hardness after heat treatment (the highest of all stainless steel and heat-resistant steel). It is usually used to manufacture bearings, cutting tools, or plastic molds requiring high load and high wear resistance under corrosive conditions.
There are four grades of 440 stainless steel in American Standard. The carbon content of 440A, 440b and 440C increased in turn; 440f (ASTM a582) is a free cutting steel by increasing the content of s on the basis of 440C.
Domestic corresponding brands include 9Cr18, 9Cr18Mo, etc.
Grade Comparison
USA | ASTM | 440A | 440B | 440C | 440F |
UNS | S44002 | S44003 | S44004 | S44020 | |
Japan | JIS | SUS 440A | SUS 440B | SUS 440C | SUS 440F |
Germany | DIN | 1.4109 | 1.4122 | 1.4125 | — |
China | GB | 7Cr17 | 8Cr17 | 11Cr17 9Cr18Mo | Y11Cr17 |
Composition specification
Grade | 440A | 440B | 440C | 440F | 9Cr18 | 9Cr18Mo |
C | 0.60 0.75 | 0.75 0.95 | 0.95 1.20 | 0.95 1.20 | 0.90 1.00 | 0.95 1.10 |
Si | ≤1.00 | ≤1.00 | ≤1.00 | ≤1.00 | ≤0.80 | ≤0.80 |
Mn | ≤1.00 | ≤1.00 | ≤1.00 | ≤1.25 | ≤0.80 | ≤0.80 |
P | ≤0.040 | ≤0.040 | ≤0.040 | ≤0.060 | ≤0.040 | ≤0.040 |
S | ≤0.030 | ≤0.030 | ≤0.030 | ≥0.150 | ≤0.030 | ≤0.030 |
Cr | 16.00 18.00 | 16.00 18.00 | 16.00 18.00 | 16.00 18.00 | 17.00 19.00 | 16.00 18.00 |
Mo | ≤0.75 | ≤0.75 | ≤0.75 | — | — | 0.40 0.70 |
Ni | (≤0.50) | (≤0.50) | (≤0.50) | (≤0.50) | (≤0.60) | (≤0.60) |
Cu | (≤0.50) | (≤0.50) | (≤0.50) | (≤0.60) | — | — |
Hardness
Grade | Hardness | |
Annealed state（HB） | After heat treatment（HRC） | |
440A | ≤255 | ≥54 |
440B | ≤255 | ≥56 |
440C | ≤269 | ≥58 |
440F | ≤269 | ≥58 |
