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440B Stainless Steel

440B Stainless Steel (UNS S44003) is a high-carbon, martensitic stainless steel with high hardness and moderate corrosion resistance. With slightly lower carbon content than 440C, it offers slightly less hardness but better corrosion resistance. Common applications include surgical tools, knife blades, valve components, and ball bearings, where wear resistance and edge retention are essential. Its excellent hardness (up to 58 HRC) makes it ideal for high-wear applications.

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Chemical Composition of 440B Stainless Steel

Element	Composition (%)
Carbon (C)	0.85 – 0.95
Chromium (Cr)	17.0 – 19.0
Molybdenum (Mo)	0.90 – 1.30
Vanadium (V)	0.07 – 0.12
Manganese (Mn)	≤ 1.00
Silicon (Si)	≤ 1.00
Phosphorus (P)	≤ 0.040
Sulfur (S)	≤ 0.030
Iron (Fe)	Balance

Technical Specifications of 440B Stainless Steel

Physical Properties

Property	Metric	Imperial
Density	7.70 g/cm³	0.278 lb/in³
Elastic Modulus	200 GPa	29.0 x 10⁶ psi
Thermal Conductivity (at 100°C)	24.2 W/m·K	14 BTU/hr·ft·°F
Coefficient of Thermal Expansion	10.1 µm/m°C	5.6 x 10⁻⁶ in/in°F
Specific Heat	460 J/kg·K	0.11 BTU/lb·°F
Electrical Resistivity	600 nΩ·m	23.6 µΩ·in
Melting Point	1370 – 1480°C	2500 – 2700°F

Mechanical Properties

Tempering Temperature (°C)	Tensile Strength (MPa)	Yield Strength (MPa)	Elongation (%)	Hardness (HRC)
Annealed	750	450	20	95
Hardened	1725	1448	5	57
Tempered (204°C)	1900	1630	4	58
Tempered (316°C)	1860	1740	4	57
Tempered (593°C)	1035	810	18	35

Thermal Properties

Property	Metric	Imperial
Thermal Conductivity (at 100°C)	24.2 W/m·K	14 BTU/hr·ft·°F
Coefficient of Thermal Expansion	10.1 µm/m°C	5.6 x 10⁻⁶ in/in°F
Melting Point	1370 – 1480°C	2500 – 2700°F

Electrical Properties

Property	Metric	Imperial
Electrical Resistivity	600 nΩ·m	23.6 µΩ·in

Product Specifications by Solitaire Steel & Engineering LLP

Product Type	Standards	Sizes	Types	Applications
Sheets & Plates	ASTM A240	Thickness: 1.5mm – 50mm	Hot Rolled, Cold Rolled	Knife blades, precision instruments
Pipes & Tubes	ASTM A268, A249	Diameter: 6mm – 1200mm	Seamless, Welded	Medical instruments, food processing
Bars	ASTM A276	Diameter: up to 100mm	Round, Square, Hex	Fasteners, bushings, wear-resistant parts
Angles, Channels, Beams	ASTM A484	Custom sizes available	L-Angles, U-Channels, I-Beams	Structural and load-bearing applications
Fittings	ASTM A403	Size: 1/2″ – 72″	Buttweld, Socket Weld	Industrial, marine applications

Processing and Fabrication Properties of 440B Stainless Steel

Forming: Limited ductility; recommended for moderate cold forming applications.
Welding: Welding can be performed with preheating to 250°C and post-weld heat treatment. Grade 309 or 310 filler rods are recommended for more ductile welds.
Heat Treatment:
- Annealing: Heat to 850-900°C, followed by slow furnace cooling.
- Hardening: Heat to 1010-1065°C, then quench in air or oil. Oil quenching is advised for heavier sections.
- Tempering: Temper between 150-370°C for high hardness. Avoid tempering between 425-565°C to prevent decreased impact resistance.
Heat Resistance: Performs well up to 650°C but is not suitable for use above the tempering temperature to avoid reducing hardness.
Machinability: Machining in the annealed condition is comparable to high-speed steel, though machining when hardened is challenging.

Applications of 440B Stainless Steel

The high hardness and moderate corrosion resistance of 440B Stainless Steel make it ideal for applications such as:

Cutlery: Suitable for knife blades and cutting tools.
Medical Instruments: Commonly used in surgical tools due to biocompatibility.
Industrial Tools: Ideal for shear blades, dies, and chisels due to hardness.
Marine Applications: Works well in marine fittings due to mild corrosion resistance.