The magnetism of stainless steel is directly related to its material type, and not all stainless steel is non-magnetic. When choosing, it is necessary to make a comprehensive judgment based on actual requirements (such as corrosion resistance, strength, magnetism requirements).
Specifically, it can be divided into the following categories:
1、Austenitic stainless steel (non-magnetic or weakly magnetic)
Its representative models: 304,316,201,302, etc.
Its characteristics: austenitic structure itself is not magnetic.
Cold working may result in slight magnetism, but can be restored to non-magnetic after heating.
Common use: tableware, kitchen utensils, medical equipment, building decoration and other scenes with high requirements for non-magnetic.
2、Ferritic stainless steel (magnetic)
Its representative models: 430,403,434, etc.
Its characteristics: ferrite structure naturally has magnetic properties.
The corrosion resistance is weak, but the cost is low, suitable for normal temperature environment.
Common use: adding point shell, automobile exhaust system, valves, etc.
3、Martensitic stainless steel (strong magnetism)
Its representative models are 410,420,440C, etc.
Its characteristics: can be hardened by heat treatment, with strong magnetism.
High strength, but poor corrosion resistance.
Common use: tools, bearings, valves and other scenarios that require high hardness.
4、Duplex stainless steel (weak magnetic)
Its representative models: 2205,2207, etc.
Its characteristics: both austenite and ferrite structure, magnetic strength is weak.
High strength and corrosion resistance are better than ordinary austenitic steel.
Common use: chemical equipment, Marine equipment, oil equipment, underground engineering and other harsh environment.
How to determine whether stainless steel is magnetic?
1、Simple test: use a magnet close to it, and the adsorption may be ferritic or martensitic stainless steel.
2、Pay attention to the processing state: cold worked austenitic stainless steel may show weak magnetism, which needs to be combined with the model to determine.
How to choose the model of stainless steel?
1、Non-magnetic: Preferentially austenitic stainless steel (such as 304,316)
2、Acceptable magnetic: ferritic or martensitic stainless steel is more economical (e.g., 430,410)
3、In harsh environments requiring strong magnetism or corrosion: preferentially use duplex stainless steel (such as 2205).
5. Comparison between austenitic 304 stainless steel and 316 stainless steel
1. Component comparison
element | 304 stainless steel | 316 stainless steel |
chromium (Cr) | 18% | 16% |
nickel (Ni) | 8% | 10% |
molybdenum (Mo) | not have | 2%~3% |
carbon (C) | ≤0.08% | ≤0.08% |
Difference: 316 stainless steel contains molybdenum (Mo), which significantly improves the ability to resist chloride ion corrosion; 304 stainless steel does not contain molybdenum (Mo), which is cheaper.
2. Corrosion resistance comparison
environment | 304 stainless steel | 316 stainless steel |
Normal air/water | Good corrosion resistance | Better corrosion resistance (molybdenum (Mo enhancement)) |
Chlorine-containing environment (sea water, salt water) | Easy to corrosion, crevice corrosion | Strong resistance to chloride ion corrosion |
Acidic environment (weak acid) | Acid resistance is generally good | Molybdenum (Mo) element improves acid resistance |
High temperature oxidation environment | Performance was good | Better oxidation resistance at high temperature |
Use environment scenario:
304 stainless steel: tableware, cabinets, interior decoration, etc.
316 stainless steel: medical devices, Marine equipment, chemical pipelines, etc.
3、Price and economy
metric | 304 stainless steel | 316 stainless steel |
prime cost | Lower (about 70 to 80 percent of 316) | Higher (molybdenum and nickel are more expensive) |
cost performance | It applies to common scenarios | More economical in harsh environments (longer life) |
4、Physical and processing properties
characteristic | 304 stainless steel | 316 stainless steel |
magnetism | Weak magnetism after cold working | Weak magnetism after cold working |
ductility | Better, easy to stamp and weld | Slightly below 304, but still processable |
hardness | lower | Slightly higher (due to molybdenum reinforcement) |
5、application scenarios
scene | 304 stainless steel | 316 stainless steel |
kitchenware | Knives, pots and pans, sinks | High-end medical machinery and surgical instruments |
architectural ornament | Railing, curtain wall, door and window | Ocean engineering, coastal construction |
commercial installation | Food processing machinery, storage tanks | Chemical pipeline, pharmaceutical equipment |
marine environment | Not applicable (easily corroded) | Ship parts, seawater desalination equipment |
6、How to choose
Select 304 stainless steel: daily use, limited budget and no strong corrosive environment.
Selected 316 stainless steel: contact with salt water, chemicals or high temperature acidic environment, medical, Marine, chemical and other high requirements fields.
7、sum up
316 stainless steel is an upgraded version of 304 stainless steel, which greatly improves corrosion resistance and high temperature oxidation by adding molybdenum.
6. Will 304 stainless steel rust?
It is not easy to rust in ordinary environment, but long-term contact with salt water, high humidity or chemical pollution may cause local corrosion.
7. What is stainless steel used for in industry?
Various types of stainless steel pipe, stainless steel plate, stainless steel coil, stainless steel rod, stainless steel wire, stainless steel profile and various stainless steel accessories.
What are the benefits of stainless steel?
Stainless steel's corrosion resistance, high strength and durability, hygiene and safety, aesthetics, environmental friendliness and recyclability, low-cost maintenance, quick processing, and flexibility for various environments. Although stainless steel pipes have a higher initial cost, their overall performance is excellent, with low long-term maintenance costs, making them particularly suitable for scenarios that require durability, safety, and aesthetics.