Stainless Steel Grades
There are 150 plus stainless steel grades have been discovreed and expanded to use in various applications, each grade exhibits unique chemical composition澳门凯发娱乐 and mechanical property, knowing characteristics of these grades is necessary lesson to select a right grade to your use.
There are so many stainless steel grades, and equivalents defined by different organizations, it is hard to say which one is the best, just the most suitable grade depends on properties and applications.
Five Types of Stainless Steel
There are five types of stainless steel depending on their metallurgical microstructure, each group possesses special alloying elements and composition that will affect stainless steel properties and uses.
- Austenitic stainless steels
- Martensitic stainless steels
- Ferritic stainless steels
- Duplex (ferritic-austenitic) stainless steels
- Precipitation-Hardening (PH) stainless steels
Austenitic Stainless Steel
These grades are the most widely used stainless stee due to their excellent properties to resist corrosion, Austenitic Stainless Steel grades contain high Chromium and Nickel content, they cannot be hardened through heat treatment, but can be hardened through cold-working, the most common austenitic alloys are iron-chromium-nickel steels and are widely known as the 300 series providing fine mechanical properties
Typical grades are given as following:
- 304, standard 18/8 grade, the most commonly used stainless steel grade
- 316, contains 16% to 18% chromium and 11% to 14% nickel. It also has molybdenum added to the nickel and chrome of the 304.
- 316L, it is low carbon of 316 grade, addition of molybdenum alloy improve corrosion resistance, particular in chloride environments
- 321, Titanium addition of at least five times the carbon content, lower risk of weld decay
- 904L, high Chromium content increase general corrosion, pitting and stress corrosion cracking resistance
Martensitic stainless steels
This group contains 10。5% minimum Chromium, and without nickel, Martensitic Stainless Steels also have a moderate resistance to corrosion but again this resistance isn’t as strong as the Austenitic stainless steels, they can be harden by heat treated, grades are mainly used where hardness, strength, are required。
- 410, standard martensitic grade for slight corrosion applications
- 416, good machinability
- 420, Higher hardness martensitic grade, contains increased carbon to improve mechanical properties.
- 431, best corrosion resistance properties of all the martensitic grades. It has excellent tensile and torque strength, and good toughness
Ferritic stainless steels
These grades contain Chromium alloy with the absence of Nickel, moderate corrosion resistance, they cannot be hardened using heat treatment, cost saving grades, but not as good for welding.
- 409, decreased chromium content, Automotive exhaust grade
- 430, A basic Ferritic grade, used for mildly corrosive environments, ike nitric acid, sulfur gases, and many organic and food acids
- 436, columbium added for corrosion and heat resistance
- 446, higher chromium content improve corrosion and scaling resistance at high temperatures
Duplex (ferritic-austenitic) stainless steels
Duplex grades are a combination of austenitic and ferritic material, having very high strength, and better toughness and ductility than the ferritic grades.
- 2205, the most widely used duplex grade, high resistance to pitting and stress corrosion
- 2507, super duplex grade, the high chromium, molybdenum, and nitrogen levels provide excellent resistance to pitting, crevice, and general corrosion.
Stainless steel grades can be also grouped into
- 200 Series
- 300 Series
- 400 Series
- 500 Series
- 600 Series
Stainless Steel Grades and Equivalents
There are several stainless steel grade systems in the world, each standard has unique No. or name, in many cases, these grades can be equivalent, due to their the same or similar chemical composition and properties.
- ASTM, American Society for Testing and Materials
- EN, European Standard
- DIN, German Standard
- JIS, Japanese Industrial Standards
- GB, Chinese Standard
- BS, British Standards
|EN Designation||Alternative Designations|
|Steel name||Steel number||AISI||UNS||GB||BS||Generic/Brand|
|Ferritic stainless steels|
|Austenitic stainless steels|
|Austenitic stainless steels – heat resisting Grades|
|Austenitic-ferritic stainless steels|