Stainless steel Grade 440A (UNS S44002)

Topics Covered

Introduction
Chemical Composition
Mechanical Properties
Other Designations
Manufacturing Process
Applications

Introduction

Stainless steel grade 440A is a high carbon martensitic stainless steel that possesses good strength, moderate corrosion resistance, and excellent hardness and wear resistance.

The following datasheet provides an overview of stainless steel grade 440A.

Chemical Composition

The chemical composition of grade 440A stainless steel is outlined in the following table.

Element Content (%)
Iron, Fe Balance
Chromium, Cr 16-18
Manganese, Mn 1
Silicon, Si 1
Molybdenum, Mo 0.75
Carbon, C 0.60-0.75
Sulfur, S 0.03
Phosphorous, P 0.04

Mechanical Properties

The mechanical properties of grade 440A stainless steel are displayed in the following table.

Properties Metric Imperial
Tensile strength 725-1790 MPa 105000 - 260000 psi
Yield strength (@strain 0.200 %) 415-1650 MPa 60200 - 239000 psi
Modulus of elasticity 204 - 215 GPa 29600 - 31200 ksi
Elongation at break (in 50 mm) 5- 20% 5- 20%
Hardness, Rockwell B 95 95

Other Designations

Equivalent materials to grade 440A stainless steel are given below.

AISI 440A AMS 5631 AMS 5632 ASTM A276 ASTM A314
ASTM A473 ASTM A511 ASTM A580 QQ S763 SAE 51440A
FED QQ-S-763 MIL SPEC MIL-S-862 SAE J405 (51440A)    

Manufacturing Process

Stainless steel grade 440A can be easily machined in the annealed condition. Carbide or ceramic tooling is recommended for performing machining. Chip breakers enable easy handling of tough stringy chips. As this steel has the tendency to air harden, welding is not performed; however if it is required, the steel should be preheated to 260°C (500°F) and post-weld treated at 732-760°C (1350-1400°F) for 6 h. This is followed by a slow furnace cooling to avoid cracking.

Grade 440A stainless steel is annealed at 843-871°C (1550-1600°F), followed by very slow furnace cooling. For performing hot working, the materials needs to be preheated to 760°C (1400°F) and then slowly increased to 1038-1204°C (1900-2200°F) before proceeding. The material should then be cooled slowly after working and once again cooled at room temperature. Finally it must be annealed fully. This material should not be heated below 927°C (1700°F).

For performing tempering, grade 440A should be soaked at 148°C (300°F). Similarly for hardening, the material should be heated slowly to 760°C (1400°F), then soaked at 1010°C (1850°F), finally air or oil cooled.

Applications

Grade 440A stainless steel is widely used in the following applications:

  • Cutlery
  • Bearings
  • Gage blocks
  • Molds and dies
  • Valve components
  • Turbine components
  • Medical instruments
  • Aircraft structural parts
  • Knives and measuring instruments

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