ASTM 440B Stainless Steel

 

Core Chemical Composition (wt%)

The chemical composition is precisely proportioned to ensure its mechanical and corrosion-resistant properties, with the following typical ranges:

Element	Content Range
Carbon (C)	0.75–0.95
Chromium (Cr)	16.00–18.00
Manganese (Mn)	≤1.00
Silicon (Si)	≤1.00
Molybdenum (Mo)	≤0.75
Nickel (Ni)	≤0.60 (allowed content)
Phosphorus (P)	≤0.040
Sulfur (S)	≤0.030
Iron (Fe)	Balance

Key Performance and Processing Characteristics

Balanced hardness and toughness: After proper quenching and tempering, its hardness can reach 55–58 HRC. Compared with 440A, it has higher hardness and better wear resistance; compared with 440C, it has stronger toughness and is less likely to crack under impact, which solves the problem that 440C is brittle in high-hardness states. In the annealed state, its hardness is no more than 255 HB, which is convenient for preliminary processing.

Moderate corrosion resistance: The high chromium content endows it with good resistance to atmospheric corrosion and fresh water erosion. However, its corrosion resistance is inferior to austenitic stainless steels such as 304 and 316. It is not suitable for long-term use in harsh corrosive environments like high-chloride seawater or strong acid/alkali media.

Strict heat treatment requirements: Annealing is usually carried out at 800–920°C followed by slow cooling; quenching is done at 1010–1070°C with oil cooling; tempering is performed at 100–180°C with rapid air cooling. This process effectively enhances its hardness and wear resistance while avoiding brittleness.

Special machining properties: It tends to be sticky and heats up quickly during grinding, but it is easier to grind than carbon steel and can be easily cut with a handsaw. Machining is best done in the annealed state, and ceramic or cemented carbide tools are recommended for better results. Welding is generally not advisable as it hardens easily in air; if welding is necessary, post-weld heat treatment at 732–760°C for 6 hours and slow furnace cooling are required to prevent cracking.