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The composition of stainless steel

The composition of stainless steel

2024-03-26

Welcome to the realm of stainless steel composition, where science meets artistry to create a functional and beautiful material.

Stainless steel is a corrosion-resistant alloy of iron and chromium, a staple in modern construction and design. Each component contributes unique characteristics to the final product, from chromium and nickel to molybdenum and titanium.

In a natural environment, stainless steel is neutral and inert, which can meet sustainable construction needs. In addition, when in contact with an element such as water, it does not produce compounds that may change its composition. When using it in architecture, it is completely and infinitely recyclable. 

Not only that, stainless steel is also aesthetically appealing, extremely hygienic, easy to maintain, highly durable, and offers various aspects. It plays a prominent role in multiple industries, including energy, transportation, building, research, medicine, food, and logistics.

Stainless Steel Composition

Stainless steel is the abbreviation for stainless acid-resistant steel, which is resistant to air, steam, water, and other weak corrosive media. It takes chromium as the main element and contains a small amount of carbon and other alloy elements, requiring chromium content greater than 10.5% and carbon content not more than 1.2%.

Stainless steel has excellent corrosion resistance because the chromium element will oxidize to form a passive layer on the stainless steel surface, preventing rusting. This passive layer also has the unique ability to repair itself.

Based on this, for different applications, stainless steel's corrosion resistance and mechanical properties can be further improved by adding other elements, such as nickel, molybdenum, titanium, niobium, manganese, etc.

Different grades of stainless steel exist in the market based on their chemical composition and intended use. Each grade offers unique characteristics tailored for specific applications ranging from household appliances to industrial equipment.

Just-produced stainless steel is not recommended for direct use. To ensure optimal durability and appearance, stainless steel often undergoes surface treatments like pickling or passivation. These processes remove impurities from the surface and improve the overall look and functionality of the material.

Specialized stainless steel alloys have been developed to meet the demands of specific industries such as aerospace or medical devices. These alloys contain additional elements like titanium or copper to enhance their performance in extreme conditions.

Grades of Stainless Steel and Their Chemical Composition

Stainless steel comes in various grades, each with its unique chemical composition. Five categories of stainless steels are available, each differentiated by the alloying elements added to iron, carbon, and chromium.

Austenitic or 300 series

Austenitic or 300 series is the most used type, which contains 0.015 to 0.10% carbon, 16 to 21% chromium, 6 to 26% nickel, and 0 to 7% molybdenum. This steel has good plasticity, toughness, weldability, and corrosion resistance, especially non-magnetic or weak magnetic. It has good corrosion resistance in oxidizing and reducing media.

301 stainless steel composition (%): C: ≤0.15, Si: ≤1.0, Mn: ≤2.0, Cr: 16.0 ~ 18.0, Ni: 6.0-8.0, S: ≤0.03, P: ≤0.045. It is prone to work hardening during deformation and is used in places requiring higher strength. However, its corrosion resistance in chemical media is poor and not recommended for a corrosion environment.

304 stainless steel composition (%): C: ≤0.08, Si: ≤1.0, Mn: ≤2.0, Cr: 18.0~20.0, Ni: 8.0~10.0, S: ≤0.03, P: ≤0.045. It is widely used to produce equipment and parts requiring comprehensive performance (corrosion resistance and formability).

316 stainless steel composition (%): C: ≤0.08, Si: ≤1.0, Mn: ≤2.0, Cr: 16.0~18.0, Ni: 10.0~14.0, S: ≤0.03, P: ≤0.045, Mo: ≤2.0-3.0. It can withstand 1200-1300 degrees and is suitable for harsh conditions. It is often used in construction and equipment in coastal areas, as well as chemical, dye, paper, oxalic acid, fertilizer, and other production equipment.

Austenitic with Mn

These are chromium manganese steels with a low nickel content (always below 5%). This series of steels is commonly used in asphalt tankers, tubes, food containers, silos, conveyor chains, safety soles, etc.

201 stainless steel composition: C: ≤0.15, Cr: 16 - 18, Ni: 3.50 - 5.5, Mn: 5.50-7.5, P: ≤0.060, S: ≤0.030, Si: ≤1.00, N: ≤0.25. It is mainly used for decorative, industrial, and shallow stretching products.

202 stainless steel composition: C: ≤0.15, Cr: 17 - 19, Ni: 4 - 6, Mn: 7.5-10, P: ≤0.060, S: ≤0.030, Si: ≤1.00, N: ≤0.25. It is widely used in architectural decoration and public facilities, such as municipal engineering, highway guardrails, hotel facilities, shopping malls, and glass handrails.

Ferritic or 400 series

Ferritic stainless steel is commonly developed for envelope and structural products, such as car exhaust systems, conveyor chains, cooking utensils, boilers, domestic appliances, trim, dishware, heating, hot water tanks, tubes, etc.


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