AISI 431 / S43100/ 1.4057 SS 431 STAINLESS STEEL BARS

440 Stainless Steel, Stainless Steel 440b Round Bar431 is a high chromium-low nickel high hardenability Martensitic stainless steel with high strength and good corrosion resistance, as generally supplied hardened and tempered in the tensile range 850 - 1000 Mpa (condition T) Brinell range 248 - 302. Characterised by very good corrosion resistance in general atmospheric corrosive environments, good resistance to mild marine and industrial atmospheres, resistant to many organic materials, nitric acid and petroleum products coupled with high tensile and high yield strength plus excellent toughness in the hardened and tempered condition.

431 due to its excellent hardenability is capable of being through hardened up to Rc44, depending upon carbon content and section size. Small sections can be air cooled and larger sections oil quenched for maximum through hardness. Pre hardened and tempered 431 will also respond readily to nitriding achieving a typical surface hardness of over Rc65. The nitriding process however reduces the corrosion resistance and is therefore not generally recommended except for critical applications where the benefit outweighs all other considerations. Used extensively for parts requiring a combination of high tensile strength, good toughness and good corrosion resistant properties.

This heat treatable martensitic, nickel-bearing grade has the best corrosion resistance properties of all the martensitic grades. It has excellent tensile and torque strength, and good toughness, making it ideally suited to shafting and bolt applications. It can be hardened to approximately 40HRC. Because of its high yield strength, this grade is not readily cold worked and is therefore not recommended for use in operations such as cold heading, bending, deep drawing or spinning. Martensitic stainless steels are optimised for high hardness, and other properties are to some degree compromised. Fabrication must be by methods that allow for poor weldability and usually also allow for a final harden and temper heat treatment. Corrosion resistance is generally lower than the common austenitic grades, and their useful operating temperature range is limited by their loss of ductility at sub-zero temperatures and loss of strength by over-tempering at elevated temperatures.

Corrosion Resisting Alloy 4S80 / 5S80 / 6S80 7S80

Specification

• AISI 431
• T431 SS
• UNS S43100 AMS2303
• AMS-5628 HI SHEAR #115 (CHEM ONLY)
• AMS-S-18732
• ASTM-A-276
• DMS-1565 EXC. SONIC
• MIL-S-18732
• QQS-763 EXC HARDNESS & IZOD

Heat Treatment of Stainless 431

Process anneal at 1150° to 1225°F (621° to 663°C) before air cooling

Harden by heating to 1800° to 1950°F (982° to 1066°C) for 30 minutes, then oil quench

Temper by heating to 400° to 1200°F (204° to 649°C), then air cool

Heat to 800° to 1700°F (427° to 927°C) to help eliminate stress corrosion cracking.

Avoid intergranular corrosion by performing stress relief from 450° to 750°F (232° to 399°C)

Applications of Stainless 431

• Marine components
• Aircraft Parts and Components
• Bolts and Nuts
• Fasteners
• Pump Shafts
• Propeller Shafts
• Studs
• Valve Parts etc.

Machinability of Stainless 431

• Carbide tools recommended
• Machine with carbide tools at higher speeds than high-speed tools

Workability of Stainless 431

• Forge and hot form from 1500° to 2150°F (816° to 1177°C)
• Easy to cold work sheet and small bars
• Extreme flanging and bending of heavy pieces at 1350° to 1550°F (732° to 843°C)

431 S43100 431S29 1.4057 X17CrNi16-2 2321 SUS 431

These comparisons are approximate only. The list is intended as a comparison of functionally similar materials not as a schedule of contractual equivalents. If exact equivalents are needed original specifications must be consulted.

Table 1. Composition ranges for 440 grade stainless steels.

Mechanical Properties

Table 2. Mechanical properties of 440C grade stainless steels.

Physical Properties

Table 3. Typical physical properties for 440 grade stainless steels.

Grade Specification Comparison

Table 4. Grade specifications for 440 grade stainless steels.

Possible Alternative Grades

Table 5. Possible alternative grades to 440 stainless steel.