AISI SS 440 Stainless Steel 440C 440A 440B Material Properties Composition Hardness

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SS 440 Stainless Steel

SS 440A, 440B and 440C stainless steel are AISI and ASTM standard high carbon high chromium martensitic stainless steel, SS440 has high strength, good hardness, corrosion resistance, wear resistance and high temperature dimensional stability. For AISI 440 stainless steel datasheet, heat treatment and equivalent chart, please see the tables below.

Datasheet & Specification

ASTM AISI 440 stainless steel data sheet and specification are summarized in the following tables, including chemical composition and properties.

SS440 Steel Chemical Composition

The following table shows the chemical composition of AISI 440 stainless steel.

440 Stainless Steel Chemical Composition, %
ASTMSteelAISI (UNS)CSi (≤)Mn (≤)P (≤)S (≤)CrMo (≤)
ASTM A276/A276M440 Steel440A (S44002)0.60-0.751.001.000.0400.03016.0-18.00.75
440B (S44003)0.75-0.951.001.000.0400.03016.0-18.00.75
440C (S44004)0.95-

440 Stainless Steel Properties

SS 440 stainless steel properties (physical properties, mechanical properties, magnetic properties) are given in the lists below.

Physical Properties

SS440 Physical Properties
Density (g/cm3)7.8
Melting point (℃)1370-1480
Specific heat capacity, J/(Kg·K)460 (0-100 ℃)
Electrical resistivity (μΩ·m)0.6 (20 ℃)
Elastic modulus (GPa)200
Thermal conductivity (W/m·K)24.2 (100 ℃)
Coefficient of thermal expansion10.2 (0-100 ℃)

Mechanical Properties

Mechanical Properties
Grade (UNS)Tensile Strength (MPa) ≥Yield Strength, 0.2%, ≥ (MPa)Elongation in 50 mm (%) ≥Reduction in area (%)HardnessProduct & Condition
440A (S44002)7254152095 HRBAnnealed bar
1790165052051 HRCBars tempered at 315 °C
≤ 965Annealed wire, cold finished
440B (S44003)7404251896 HRBAnnealed bar
1930186031555 HRCBars tempered at 315 °C
≤ 965Annealed wire, cold finished
440C (S44004)7604501497 HRBAnnealed bar
1970190021057 HRCBars tempered at 315 °C
≤ 965Annealed wire, cold finished

SS440 Heat Resistance

AISI 440 has good oxidation resistance in intermittent use below 815 °C and continuous use up to 760 °C in air.

Heat Treatment of SS440

SS440 heat treatment including annealing, quenching, tempering and stress relieving, etc.


Subcritical annealing temperature range: 675-760 ℃ (1250-1400 ℉)

Full annealing: insulation from 845-900 °C (1550-1650 ℉) to completely soaking, then furnace cooling to 790 °C, continue cooling to 595 ° C at a cooling rate of 15-25 °C/h, then air cool to room temperature.

Isothermal Annealing: heat treat to 845-900 °C, kept at 690 °C for 4 hours.

SS440 Quenching

Heat to 1010-1065 °C and quench in air or oil. To ensure maximum dimensional stability, cold treatment should be performed immediately after cooling to room temperature.

Tempering & Hardness

For 440A and 440B stainless steel, 150 °C – 370 °C, and can get the HRC hardness 49-57 for 440A, 53-59 for 440B steel.

For 440C stainless steel, tempering temperature and corresponding HRC hardness, as follows

  • Max 160 °C, ≥ 60 HRC
  • Max 190 °C, ≥ 58 HRC
  • Max 230 °C, ≥ 57 HRC
  • Max 355 °C, 52-56 HRC


Typical forging temperature range for 440A, 440B and 440C stainless steel.

  • 440A: 925-1200 ℃
  • 440B: 925-1175 ℃
  • 440C: 925-1150 ℃


440 stainless steel can be hardened and tempered in the same manner as alloy steel.


440 steel, especially 440C, is difficult to process due to its high annealing hardness and abrasive chromium carbide.


440 steel welding is not recommended because of high carbon content, extremely easy to crack and metal fillers are not easily available.

Applicatioins of AISI 440 Steel

AISI 440 steel is used to manufacture bearing parts working in corrosive environment, and can also be used to manufacture high quality tools (medical scalpels, scissors and blades, surgical and dental instruments), molds and dies, springs, cutlery, valves and valve components, cams, gears, shafts, ball bearings, nozzles and measuring tools.

Equivalent Grade

AISI 440 steel equivalent to US ASTM AISI, European EN (Germany DIN, Britain BS, France NF…), ISO, Asian Japanese JIS, and China GB standard. (For reference)

ASTM 440C stainless steel equivalent grades
USEuropean UnionGermanyUKFranceISOJapanChina
StandardGradeStandardSteel Name (Steel Number)StandardGradeStandardGradeStandardGradeStandardGradeStandardGradeStandardGrade
ASTM A276/A276M
440CEN 10088-3X105CrMo17
DIN EN 10088-3X105CrMo17
BS EN 10088-3X105CrMo17
NF EN 10088-3X105CrMo17
ISO 683-17X108CrMo17JIS G4303SUS 440CGB/T 12209Cr18Mo

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