Stainless steel is widely used in many fields such as modern industry, construction, home and medical treatment. With its excellent corrosion resistance, strength and good machinability, it has become the "universal metal" in people's minds. However, stainless steel is not a single material, but an alloy series that includes hundreds of different types. From 304, 316, to 201, 430, to the more advanced 904L, 2205 duplex stainless steel, different types of stainless steel have different performances due to their different alloy compositions and smelting processes.
So, what type of stainless steel is the best? This is not a general question, but depends on many factors such as the use environment, performance requirements and cost budget. This article will describe in detail the characteristics, advantages and disadvantages and usage scenarios of different types of stainless steel to help you choose the right stainless steel.
What Is Stainless Steel?
Stainless steel is a steel with iron as the main component, chromium (Cr), nickel (Ni) and other alloy elements added, which has corrosion resistance and high temperature resistance. Its core characteristic is the chromium oxide layer (Cr₂O₃) formed on the surface. This dense protective film can effectively prevent further erosion by oxygen and moisture, thus giving stainless steel excellent corrosion resistance. In addition to corrosion resistance, stainless steel also has the following characteristics:
- High strength: Some types of stainless steel have high tensile strength.
- Aesthetics: The surface of stainless steel is smooth and easy to clean.
- Machinability: Stainless steel can be processed by welding, cutting, forming, etc. to meet various manufacturing needs.
- High temperature resistance: Some models can still maintain structural stability in high temperature environments.
Basic Classification Of Stainless Steel:
Stainless steel is a type of steel with a chromium content of not less than 10.5%. It mainly resists corrosion by forming a stable passivation film on the surface of chromium. According to its metallographic structure, stainless steel can be divided into the following categories:
Austenitic Stainless Steel：
This type of stainless steel has a typical ratio of 18% chromium and 8% nickel (such as 304), and has excellent corrosion resistance, good plasticity and toughness. Common models: 304, 304L, 316, 316L, 321, 310, 310s, 904L, etc.
Ferritic Stainless Steel：
Ferritic stainless steel does not contain nickel, has low cost, has good corrosion resistance and resistance to stress corrosion cracking, and is magnetic. Common models: 409, 410s, 430, 434, 446, etc.
Martensitic Stainless Steel：
Martensitic stainless steel has the characteristics of high strength and high hardness. It can be heat treated to enhance hardness, but its corrosion resistance is low. Common models: 410, 420, 431, 440A, 440B, 440C, etc.
Duplex Stainless Steel：
Duplex stainless steel combines the advantages of austenite and ferrite, and has excellent strength and corrosion resistance, especially resistance to chlorine pitting. Common models: 2205, 2507, 2101, 2304, etc.
Precipitation Hardening Stainless Steel：
This type of stainless steel obtains high strength through precipitation hardening heat treatment while taking into account good corrosion resistance. Common models: 17-4PH, 15-5PH, 13-8Mo, etc.
Introduction To Common Stainless Steel Models:
304 Stainless Steel
304 stainless steel is the most widely used austenitic stainless steel, with an alloy ratio of 18% chromium and 8% nickel, and has excellent corrosion resistance, processability and weldability. It is suitable for most household, industrial and food fields, such as sinks, kitchen utensils, storage tanks, etc. Its advantage is a good balance of performance, and its disadvantage is that it is sensitive to chloride ions (such as seawater) and prone to pitting.
316 Stainless Steel
316 stainless steel adds 2%-3% molybdenum to 304, making it more corrosion-resistant in high-chlorine environments (such as seaside, swimming pools, chemical pipelines). 316 is an important material for food grade, medical grade, and marine grade applications, and its price is about 20%-30% higher than 304. In highly corrosive environments, 316 is a better choice.
201 Stainless Steel
201 stainless steel has low nickel content, high manganese content, and low cost. It is often used in decoration industries that are price-sensitive but have low requirements for corrosion resistance (such as elevator decoration, guardrails, door and window frames, etc.). Although its mechanical properties are acceptable, it is easy to rust in acidic or chlorine-containing environments. It is a model with high cost performance but limited performance.
430 Stainless Steel
430 is a ferritic stainless steel with good oxidation resistance and certain corrosion resistance, but its weldability and plasticity are not as good as 304. Because of its lower cost, it is widely used in home appliance back panels, kitchen equipment, washing machine inner barrels and other occasions. It has strong magnetism, so it is not suitable for non-magnetic occasions.
410/420 Stainless Steel
410 and 420 are martensitic stainless steels with good mechanical properties and quenching hardness. They are widely used in the manufacture of knives, scissors, and shaft parts. However, its corrosion resistance is far inferior to that of 304 or 316, and it is more suitable for dry environments.
904L is a high-alloy austenitic stainless steel, containing high chromium and high nickel, and copper is added to improve corrosion resistance in sulfuric acid environments. It is expensive and is often used in special industries such as chemical, pharmaceutical, and metallurgy.
2205 Duplex Stainless Steel
2205 has the characteristics of both austenitic and ferritic stainless steels, has a higher yield strength than 304/316, and has much better pitting resistance than 316. It is suitable for extreme environments such as chemical plants, seawater treatment facilities, and oil platforms.
Selection Of Stainless Steel Models In Different Application Fields
- Home Kitchenware And Tableware
In the home kitchen, acid and alkali environments are involved, and choosing 304 is safe and economical enough. If used for containers that are in long-term contact with salt or vinegar, the 316 model can be considered. It is more appropriate to use 420 for parts that require hardness, such as table knives.
- Medical Equipment
The medical industry requires high cleanliness and high corrosion resistance materials. 316L (low carbon version of 316) is the first choice due to its better welding performance and rust resistance. Surgical tools can use 420 type to improve sharpness.
- Construction And Decoration Industry
Indoor stainless steel decoration mostly uses 201 or 430, which is economical and practical. If it is exposed outdoors, it is recommended to use 304 or higher grade materials to prevent rust.
- Petrochemical And Marine Engineering
This type of environment is extremely corrosive, and high corrosion resistant profiles such as 2205 or 904L are generally recommended. They can resist corrosion from chlorides, water vapor, acids and alkalis for a long time.
- Automobile Industry
Automobile exhaust systems mostly use 409 or 430, and 304 materials are also used in chassis structures. In high-end models, there are also cases of using 316 or duplex stainless steel.
- Food Industry
304 is the first choice for food-grade stainless steel, with good cleaning performance and neutral corrosion resistance. 316 is used in more demanding environments such as dairy products, soy sauce, and brewing equipment.
5 Factors To Consider When Choosing Stainless Steel Models
Use Environment
When choosing a stainless steel model, the first thing to consider is the environment, such as humidity, pH, contact with salt water, temperature changes, etc. For example, 201 or 304 should not be used in a seaside environment, and 316 or higher grade stainless steel should be used.
Cost Budget
The price difference between different models is large. For example, the price of 201 is about 50%-60% of 304, while the price of 316 is 20%-30% higher than 304, and the price of 904L or 2205 is even higher. It should be weighed according to the project budget.
Strength Requirements
For load-bearing structures or high mechanical strength requirements, duplex stainless steel 2205 or martensitic 420 should be used to ensure sufficient yield strength and impact resistance.
Weldability And Formability
For high welding performance requirements, low-carbon models such as 304L or 316L should be preferred. When forming requirements are high, austenitic materials perform best.
Whether It Needs To Be Non-Magnetic
For fields that are sensitive to magnetism, such as electronic instruments and magnetic resonance rooms, austenitic stainless steels such as 304 and 316 should be used. These materials are naturally non-magnetic
"What type of stainless steel is the best?" There is no unified answer, because the best model depends on specific needs. Through the analysis of this article, readers can choose the most suitable stainless steel model according to actual needs.
