Stainless Steel Grade UNS S31603 Properties and Applications

# Stainless Steel Grade UNS S31603 Properties and Applications

## Introduction to UNS S31603

UNS S31603 is a low-carbon variation of the popular 316 stainless steel alloy. This austenitic stainless steel is widely used in various industries due to its excellent corrosion resistance, good mechanical properties, and weldability. The “L” in 316L (its common name) stands for “low carbon,” which helps prevent carbide precipitation during welding.

## Chemical Composition

The chemical composition of UNS S31603 plays a crucial role in its performance:

• Chromium (Cr): 16-18%

• Nickel (Ni): 10-14%

• Molybdenum (Mo): 2-3%

• Manganese (Mn): ≤2%

• Silicon (Si): ≤1%

• Carbon (C): ≤0.03%

• Phosphorus (P): ≤0.045%

• Sulfur (S): ≤0.03%

• Iron (Fe): Balance

## Mechanical Properties

UNS S31603 offers excellent mechanical properties for various applications:

• Tensile Strength: 485 MPa (70 ksi) minimum

• Yield Strength: 170 MPa (25 ksi) minimum

• Elongation: 40% minimum in 50 mm

• Hardness: ≤95 HRB (Rockwell B scale)

• Density: 8.0 g/cm³

## Corrosion Resistance

One of the most significant advantages of UNS S31603 is its superior corrosion resistance:

• Excellent resistance to pitting and crevice corrosion in chloride environments

• Good resistance to organic acids

• Better performance than 304 stainless in many corrosive environments

• Resistant to intergranular corrosion due to low carbon content

## Heat Treatment

Proper heat treatment enhances the properties of UNS S31603:

• Solution Annealing: Typically performed at 1010-1120°C (1850-2050°F)

• Quenching: Rapid cooling in water or air after annealing

• Stress Relieving: Recommended for welded components at 400-450°C (750-850°F)

## Welding Characteristics

UNS S31603 is known for its excellent weldability:

• Can be welded by all standard fusion methods

• No post-weld heat treatment required for most applications

• Low carbon content minimizes carbide precipitation in heat-affected zones

• Recommended filler metals: 316L or 317L

## Common Applications

The unique properties of UNS S31603 make it suitable for numerous applications:

Chemical Processing

Used in tanks, piping, and valves for handling corrosive chemicals.

Pharmaceutical Industry

Ideal for equipment requiring high cleanliness and corrosion resistance.

Marine Environments

Excellent for boat fittings, marine hardware, and offshore applications.

Medical Devices

Commonly used for surgical instruments and implants due to biocompatibility.

Food Processing

Widely used in equipment that contacts food products.

## Comparison with Other Grades

UNS S31603 offers advantages over similar grades:

• Better corrosion resistance than 304/304L stainless steel

• More affordable than higher alloyed grades like 317L or 904L

• Better weldability than standard 316 due to lower carbon content

• More resistant to chloride attack than 316 stainless steel

## Fabrication Considerations

When working with UNS S