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Stainless steel, also known as INOX, CRES (corrosion-resistant steel) or rust-free steel, is an iron alloy that is rust- and corrosion-resistant. It contains at least 10.5% chromium, often nickel, and may contain other elements such as carbon to achieve the desired properties. Stainless steel's corrosion resistance comes from chromium, which forms a passive film that protects the material and repairs itself in the presence of oxygen.
This alloy material has properties such as luster and corrosion resistance, and is very common in many applications. Stainless steel can be made into sheets, plates, instruments, building materials, industrial equipment, etc. It is also widely used in commercial kitchens, usually including stainless steel worktops, refrigerators, ovens, cookware, knives, etc.
Stainless steel's excellent biological cleanliness is comparable to that of glass, and its cleanliness, strength and corrosion resistance make it an excellent choice for pharmaceutical and food processing plants.
Stainless steel is not completely immune to rust, but it only affects a few outer layers of atoms, and its chromium content protects the deeper atoms from oxidation. Different stainless steel grades have different chromium and molybdenum contents to adapt to different environments.
The strength of stainless steel is very high, about 3 times that of ordinary steel, so it is more durable and has a longer service life.
Stainless steel is essentially a type of steel, so its melting point is close to that of ordinary steel and much higher than that of metals such as aluminum and copper.
Like steel, stainless steel is a relatively poor conductor of electricity, with its conductivity significantly lower than that of copper, so it is not typically used as an electrical conductor.
Ferritic stainless steels, martensitic stainless steels, duplex stainless steels and precipitation hardened stainless steels are magnetic, while austenitic stainless steels are generally not magnetic. The magnetism of ferritic steel is due to its body-centered cubic crystal structure - the iron atoms inside are arranged in a cube, with an iron atom in the center. This central iron atom is why steel is magnetic.
Austenitic steels are generally nonmagnetic, but can be made slightly magnetic after work hardening.
Alloys are classified into different series based on specific properties and the proportions of various metals in the alloy are given. Stainless steel can be divided into five different series:
This series is the most widely used and popular material. They have an austenitic microstructure, a face-centered cubic crystal structure. This microstructure is achieved by adding sufficient amounts of nickel, manganese and nitrogen to the steel so that it maintains this structure at temperatures from the cryogenic zone to the melting point. It usually contains chromium, nickel, aluminum, copper, manganese, molybdenum and other metal elements.
Austenitic stainless steel is nonmagnetic when solid solution annealed, but it becomes magnetic after being cold worked. Thermal quenching does not work on this type of steel, so it is ideal for kitchens where heat is high.
They have excellent corrosion and creep resistance, making them ideal for welding. Commonly used austenitic stainless steels include 303, 304, 316, 310 and 321 grades.
This steel has the same ferritic microstructure as carbon steel, that is, a body-centered cubic crystal structure. It contains very little or no nickel, but has higher contents of chromium, molybdenum, niobium and titanium. Its chromium content is 10.5%-27% to improve toughness and creep resistance.
Due to the addition of chromium, this microstructure is present at all temperatures and therefore cannot be hardened by heat treatment, nor can it be strengthened by cold working like austenitic stainless steels. The addition of niobium (Nb), titanium (Ti) and zirconium (Zr) to Type 430 stainless steel gives it good weldability. Since they contain virtually no nickel, they are less expensive than austenitic steels, can be used in many products, and are popular in indoor applications or inconspicuous applications.
Common ferritic stainless steels include grades 409 and 430.
Martensitic stainless steel has a body-centered cubic crystal structure, which is transformed from austenite through quenching. Quenched martensite is very hard but too brittle for most applications. The martensite is tempered and heated to 500°C, kept warm, and then air cooled. Higher tempering temperatures can reduce the yield strength and ultimate tensile strength, but also increase its elongation and impact resistance.
The range's stainless steel interior contains many of the latest proprietary alloys. Many duplex stainless steels also have characteristics of both austenitic and ferritic stainless steels, and their structure is a mixed microstructure of the two. The ideal mix ratio is 50:50, but commercial alloys may have a ratio of 40:60. The chromium content of dual-phase steel is 19%-32%, the molybdenum content is up to 5%, and the nickel content is low.
The properties of stainless steel generally depend on the type of alloy they are made of. Because many alloys are created to solve specific industrial problems, such as weight, toughness, corrosion resistance and higher tensile strength. And compared to other steels, most duplex steels have good weldability and formability.
Common duplex steel alloys include 318L, LDX2101, LDX2304, 2507 and 4501 grades.
Although this steel is less common, it is still popular in applications where a refined hard edge is required.
Since it has added carbon, it can undergo tempering and hardening processes, making it the most suitable material for making knives, scissors, razors, and some medical tools.
This stainless steel also has moderate to good corrosion resistance and remains very magnetic after hardening.
Common martensitic steels and precipitation hardening steels are 410 and 420 grades.
|
Alloy Type |
Austenitic |
Ferrite |
Martensitic |
Duplex |
Precipitation Hardened |
|
Magnetic Reaction |
Normally None |
Yes |
Yes |
Yes |
Yes |
|
Work Hardening Rate |
Very High |
Medium |
Medium |
Medium |
Medium |
|
Corrosion Resistance |
High |
Medium |
Medium |
Very High |
Medium |
|
Hardenability |
Cold Worked |
None |
Quenched and Tempered |
None |
Age Hardening |
|
Toughness |
Very High |
Medium |
Low |
Medium |
Medium |
|
High Temperature Resistance |
Very High |
High |
Low |
Low |
Low |
|
Low Temperature Resistance |
Very High |
Low |
Low |
Medium |
Low |
|
Weldability |
Very High |
Low |
Low |
High |
High |
Stainless steel is widely used in our daily lives, such as the construction industry, aerospace industry, etc., and it is most commonly used in the catering industry. Stainless steel applications are often seen in commercial kitchens, such as stainless steel refrigerators, stainless steel knives, stainless steel worktops, etc. As you can see, it’s really worth our investment!
