With this guide, you will learn everything about 321 SS, its advantages, disadvantages, its properties, fabricating and machining properties, its unique forms, and more.
Read more for accurate details.
What is 321 Stainless Steel?
321 is also called or known as UNS S32100. It is a non-magnetic and stabilized austenitic alloy or SS.
Other identifiable names of 321 SS include:
- AMS5510
- AMS5645
Advantages of 321 Stainless Steel?
- It is non-magnetic.
- 321 SS provides you with the best resistance to stress corrosion cracking.
- Great weldability due to its intergranular corrosion resisting attributes.
- Has high tensile and yield strength levels.
- Formability features are the best.
- Can withstand marine environments to a higher level.
- Doesnt get hardened through heat treatment.
Disadvantages of 321 Grade Stainless Steel
- Requires cold working to achieved some level of magnetism.
- Machining isn’t easy.
321 Stainless Steel Properties
When evaluating 321 SS properties, you should consider chemical, physical and mechanical attributes.
Chemical Properties
- Formability – has the finest formability features.
- Welding – welding is perfected with fusion and resistance welding procedures.
- Can withstand the stress of different acidic environments.
- Due to the right methods of welding joints, cracking is avoided as well as corrosion.
- 321 resists corrosion to perfection.
The different elements that make the chemical properties of 321 alloy include:
- Carbon 0.08%
- Nickel 9.0-12.0%
- Chromium 17.0-19.0%
- Manganese 2.00%
- Nitrogen 0.10%
- Silicon 0.75%
- Phosphorus 0.045%
- Titanium 0.70 maximum
- Sulfur 0.030%
Physical Properties
- It is able to withstand higher temperatures, up to 870°C. This makes it perfect for Inconel sheet uses such as fire protection, heating, including insulation.
- This alloy is not a magnetic stainless steel.
- For upsetting, forging, and other hot working procedures, 1149-1260°C working temperatures are ideal. It should not be worked below 1700°F or 927°C.
- It has a decent level of strength and ductility and can be stamped, spun, blanked, and drawn effortlessly.
- 321 SS doesn’t harden through heat treating.
- Electrical resistivity 720 nΩ.m
- 193 GPa Elastic Modulus
Annealing leads to increased ductility in the stainless steel.
Mechanical Properties
- 515Mpa minimum tensile strength.
- 205 mpa yield strength proof
- 40% elongation
- 95 Hardness Rockwell B.
- 217 Brinell
What is 321 Stainless Steel Equivalent?
321 SS is equivalent to 304 SS. It is considered equivalent to 304 due to the similarities in their makeup elements or chemical composition.
321 SS has titanium elements while 304 doesn’t.
Difference between 321 vs 316 Stainless Steel
Corrosion resisting
321 SS takes the lead where corrosion resistance is concerned when compared to 316.
Titanium in 321 gives its surface a protective oxide film. So, when exposed to water or even other chloride or sulfuric acid filled compounds, it stands tall.
Crevice and Pitting Corrosion
316 has better crevice and pitting corrosion than 321.
Inter-granular Corrosion
321 has the best inter-granular corrosion compared to 316 due to its high carbon content.
Strength levels
The level of strength is almost similar with both stainless steels.
Machining
Machining 316 is far easier than machining 321.
Designations of 321 Stainless Steel
When buying this stainless steel grade, you may encounter other names such as:
- UNSS32100
- Nr.1.4541
- AWS 133
321 Fabricating and Machining Properties
Cold bending
321 cold bending is very simple. Mild magnetic features should be expected after cold working process.
Hot bending
Hot bends needs to be done at a minimum of 950°C and a maximum of 1100°C.
Annealing must always come next after this procedure to restore higher corrosion resistance.
Forging
Forging shouldn’t be done below 900°C.
Also, forgings completed need to be air cooled.
Annealing forgings will increase the level of corrosion resistance in 321 SS.
Machining
Machining 321 can be quite complex. This is due to its titanium elements.
To make the most of 321SS where machining is concerned, it is best to use powerful and unbending machining.
Do not forget to include the best lubricants with your tools being very sharp always.
When machining, do not create a lot of interruptions. This can lead to work hardening that could’ve been prevented.
Heat treatment
321 SS will not get hardened from heat treating method.
Welding
321 should be welded with a lot of care and the right methods which are resistance and fusion welding. These methods when used to produce weld joints leads to these benefits:
- Ensures resistance to corrosion is well preserved.
- Avoids cracking.
Different Forms of 321 Stainless Steel
You will find 321 SS in different forms such as flats, square, coil, foil, round bar, sheets, hex bar, and more.
Different Applications of 321 Stainless Steel
- Joint expansions
- Exhaust stacks and piston engine manifolds for aircraft.
- Food storage and processing equipment.
- Equipment for high temperature chemical processings
- Equipment for refinery
- Thermal oxidizers, etc.
Conclusion
Versatility is one thing that 321 SS represents. So, if you need an alloy with the finest versatility features, the best strength levels, and resistance to corrosion when used right, 321 is the SS to use.
It is time to save cash using this SS to achieve the right outcomes with applications.
More Resources:
Stainless Steel – Source: Science Direct
Stainless Steel Grade 321 – Source: AZO Materials
Stainless Steel Composition – Source: Tuolian
Stainless Steel Classification – Source: Engineering Toolbox