303 Steel

As with other austenitic stainless steels, 303 has good toughness and is non-magnetic. The added sulphur makes the steel better machinable but affects the corrosion resistance in comparison to for example 304, and lowers the toughness of the steel slightly.

Applications

Applications for this tool steel include: shafts, springs bushings, nuts and bolts, valves.

Corrosion resistance

Sulphur makes this steel grade vulnerable to pitting corrosion, therefore should be avoided for environments over 140°F (60°C) containing chloride. This steel grade is better suited in mild environments, when exposed to moist environments, like a marine environment, pitting as well as a film of rust will form.

Heat resistance

303 stainless steel has good oxidation resistance when the material is sporadically exposed to temperatures of 1400°F (760°C) as well as continuous service at 1598°F (870°C). The latter is not recommended, as this steel grade is sensitive to carbide precipitation with continuous use at a temperature range of 797-1580°F (425-860°C).

Heat treatment

303 is not hardenable by heat treatment. Cold working this steel grade can increase hardness and tensile strength.

Annealing

Heat the material to 1850°F (1010°C) following with a quenching in water or cool rapidly by other means. To prevent embrittlement and loss of corrosion resistance, temperatures between 800-1500°F (427-816°C) should be avoided for prolonged exposure.

Hardening

This steel grade cannot be hardened by heat treatment. This steel grade can be cold work hardened for improved strength and hardness.

Cold working

303 cannot be readily be cold worked, some cold work is possible but sharp bending should not be applied. As an alternative 304 can be used for cold working.

Hot working

Uniformly heat the material to 2100-2300°F (1149-1260°C) for hot working, when finished, rapidly cool the work piece to ensure the maximum corrosion resistance.

Machinability

To avoid excess work hardening keep the cutting edges sharp. Lubricants and coolants should be used liberally to avoid the heat concentration at the cutting edges. Chip breakers should be employed to keep the work piece clear.

Weldability

It is not recommended to weld this steel grade.

Forging

This steel grade is not easily forged due to the risk of overheating with the high forging temperatures needed. Forging is usually performed at a temperature range of 2102-1742°F (1150-950°C) with subsequent cooling in air. To minimizing the risk of hot cracking low forging temperatures are preferred.

Fabrication

To avoid cross contamination while fabricating, only tools dedicated to stainless steel materials should be used to avoid surface discoloration of the fabricated products. Clean all tooling and work surfaces thoroughly against cross contamination as well.