Type 303Se (UNS S30323/JIS SUS303Se)

  • Excellent cryogenic resistivity
  • Good ductility.
  • Superb corrosion and rust resistance features.
  • Abrasive in appearance.
  • Won’t harden with heat treatment.
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Grade 303Se (UNS S30323/JIS SUS303Se)

The 303Se stainless steel is very close in chemical and physical properties to Type 303. It has some ductility and comes with good strength. The 303Se is a great choice for machining, but it is also not very simple to weld either. Therefore, just like the 303 types you can mod it or create different machinery shapes using this type of stainless steel.

Hence, this metal alloy is better to be used for components and parts. It is not as great as the type 304 stainless steel in terms of rust and corrosion, but it still does a pretty fair job. You can’t harden the type with heat treatment, but you can do that by cold working.

Common Names:

303Se Stainless Steel is also known as AISI 303Se.

Executive Standards:

Inventory Standards

  • ASTM A 895
  • UNS S30300
  • AMS 5640 Chem Only

Chemical Properties:

The 303 stainless steel is made of 17% to 19% of chromium along with 8% to 10% nickel.  0.15% of carbon is there, while manganese is 2%. 1% silicon is there in the mix, and instead of molybdenum, nitrogen, or aluminum, the 303Se has 0.15% Selenium.

Mechanical Properties:

The 303Se type won’t harden with a heat treatment just like type 303, but you can use cold working on it. The annealed form is frequently used, and the only useful mechanical property of this alloy is its hardness, which tops off at 202 (HBN).

Physical Properties:

Here are some of the physical properties of this type of stainless steel,

Density0.290 lb/in (7.89 g/cm)
Thermal conductivity @ 212°F16.2W/m-°K (112 BTU/hr/ft²/ft/°F)
Melting point2552°F
Electric resistivityAt 68°C, 28.3 Microhm-in (at 20°C, 72.0 Microhm-cm)

Key Features:

The 303Se closes down the gap between the 303 and 304 types. It has a lot of resemblance to its predecessor but also matches a lot with its successor. 303Se is better than 303 in machining. With additional sulfur and selenium, the performance of the cutting tool improves significantly. It is slightly better than 303 in terms of welding as well.

Product Forms Available:

The 303Se stainless steel comes in annealed form along with a cold working state.


  • Pump and valve components.
  • Various medical devices.
  • Bolts and nuts
  • Aircraft Parts.
  • Screwing machines.
  • Different architectural applications.

Frequently Asked Questions:

  • Does 303Se rust easily?

No, it doesn’t rusty easily. It is slightly better than type 303 but still lags behind type 304 in this aspect.

  • Is 303Se magnetic?

No, it is non-magnetic, but in an annealed state, it develops slight magnetic properties.

  • How does Type 303Se handle heat treatment?

It won’t harden with heat treatment, but you can do cold working and annealing.

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