Stainless Steel Grade 431: Properties, Composition & Applications
Metallurgy science advances the knowledge of stainless steel applications in various industries. Well, known different grades are available worldwide. Stainless steel can be recycled infinitely, remarkably strong, and substantial.
Stainless steel is the simplest name used for a large variety of ferrous amalgamation which is resistant to corrosion. Chromium makes a protective layer on the surface of stainless steel that protects it from different surrounding mediums.
There are several grades of stainless steel and each grade has different compositions of iron, carbon, and chromium. Also constitutes other alloying agents like nickel, molybdenum, manganese, sulfur, etc. Resisting corrosion makes it an ideal selection for numerous applications.
Ferritic stainless steel is a low carbon, chromium stainless steel with 11- 18% chromium. It may also contain molybdenum in small traces. Ferritic stainless steel has a body-centered cubic (BCC) crystal structure; due to its structure, it is magnetic. It offers good corrosion resistance, depends upon the level of chromium.
In comparison to other stainless steel, it has low carbon content and results in relatively low strength. Ferritic stainless steel shows poor weldability and lowers corrosion resistance
Ferritic stainless steels are ideal for applications runs at elevated temperatures. Mostly used in petrochemical, exhaust systems, heat exchangers, furnaces applications, hot water tanks, etc
Grade 431 Stainless Steel
SS 431 stainless steel (UNS S43100 / AISI 431 / DIN 1.4057) is a martensitic stainless steel known for its exceptional combination of high hardness, tensile strength, and superior corrosion resistance among the 400-series grades. With 15–17% chromium and 1.5–2.5% nickel, Grade 431 achieves hardness up to 40 HRC through heat treatment — making it the preferred choice for marine shafts, aircraft fasteners, pump components, and valve parts.
Ambica Steels supplies SS 431 bars (round, flat, hexagonal, and square) from our facility in Wazirpur Industrial Area, New Delhi, India, serving clients across aerospace, marine, and petrochemical industries globally.
SS 431 Chemical Composition (UNS S43100)
| Element | Composition (%) | Notes |
|---|---|---|
| Chromium (Cr) | 15 – 17 | Provides corrosion resistance |
| Nickel (Ni) | 1.5 – 2.5 | Improves toughness and ductility |
| Silicon (Si) | Small amount | Enhances oxidation resistance |
| Manganese (Mn) | Small amount | Improves strength and hardness |
| Phosphorus (P) | Trace amount | Usually controlled to low levels |
| Sulfur (S) | Trace amount | Improves machinability |
SS 431 Physical & Thermal Properties
| Property | Value | Unit |
|---|---|---|
| Density | 7.8 | g/cm³ |
| Modulus of Elasticity | 200 | GPa |
| Electrical Resistivity | 720 | nΩ·m |
| Melting Point Range | ~1482 | °C |
| Property | Value | Unit | Temperature Range |
|---|---|---|---|
| Thermal Expansion Coefficient | 10.2 | µm/m·°C | 1–100°C |
| Thermal Conductivity | 20.2 | W/m·K | At 100°C |
Mechanical Properties
| Property | Value | Unit |
|---|---|---|
| Tensile Strength | 862 | MPa |
| Yield Strength | 655 | MPa |
| Hardness | 285 | HB |
| Elongation | 20 | % in 50 mm |
Heat Treatment
Annealing
| Process | Details |
|---|---|
| Annealing Type | Full annealing is not possible |
| Reason | Material becomes hard during slow cooling |
| Process Annealing Temperature | 620–660°C |
| Cooling Method | Air cooling |
Hardening
| Process | Details |
|---|---|
| Heating Temperature | 980–1065°C |
| Holding Time | Approximately 30 minutes |
| Cooling Method | Oil quenching |
Tempering
| Process | Details |
|---|---|
| Tempering Temperature | 600–800°C |
| Purpose | Improves mechanical properties |
| Precaution | Avoid tempering between 425–600°C |
Properties - Corrosion Resistance
| Property | Description |
|---|---|
| General Resistance | Highest corrosion resistance among ferritic stainless steels |
| Resistant To | Saltwater, industrial atmosphere, organic materials, nitric acid, and petroleum products |
| Best Performance Condition | Smooth surface in hardened and tempered condition |
| Limitation | Not suitable for warm tropical water |
| Comparison | Less corrosion resistant than austenitic stainless steels |
Heat Resistance
| Property | Description |
|---|---|
| Intermittent Scaling Resistance | Up to 925°C |
| Continuous Service Temperature | Up to 870°C |
| Limitation | Should not be exposed above tempering temperature |
Welding
Grade SS 431shows poor weldability. It is difficult to weld Grade 431 stainless steel due to the incidence of cracking. Welding can be done by preheating the material to 200 to 300 °C. Then re-hardening and annealing are done at 650°C.
Alloy 410 low hydrogen electrodes are appropriate for welding if needed.
Stainless steel 410 is type which comes under stainless steel 400 series
Machinability
Grade SS 431 can be machined easily in an annealed state. It is difficult to machine the material if hardened above 30HRC.
SS 431 Applications & Industries
Grade 431 stainless steel is intended to use for applications requiring high tensile strength and toughness coupled with good corrosion properties.
It is used extensively for the following:
- Aircraft parts
- Marine components
- Pump and propellers shafts
- Nuts and bolts
- Laboratory equipment
- Studs
- Valve parts
Ambica steels offer superior fine quality grades 431 bars. Bars are available in round, square, flat, hexagonal, and customized shapes. Inquiry and orders are welcome.