Introduction to Stainless Steel Angle Steel Structure and Identification Methods

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I. Introduction to Stainless Steel Angle Irons

Stainless steel angle irons are long strips of steel with a standard "L" shape cross-section. The two sides are either of equal length or unequal length, forming a 90-degree right angle. They are the most commonly used type of stainless steel profiles. 

1. Main features: 

Corrosion resistance: Core advantage, especially suitable for humid and highly corrosive environments (such as kitchens, coastal areas, and chemical plants). 

High strength: Possesses excellent structural support capability. 

Aesthetics: The surface is smooth and shiny, presenting a modern appearance and is often suitable for decorative purposes on exposed structures. 

Durability: Long service life, with minimal maintenance required. 

2. Common Materials (This is the key to differentiation): 

201 stainless steel: Contains a high amount of manganese and a low amount of nickel. It has average corrosion resistance and is prone to rusting in humid environments. It is inexpensive and is commonly used in dry environments or in situations where there is no strict requirement for rust prevention. 

304 Stainless Steel: The most common food-grade and construction-grade steel. It has a high content of chromium and nickel, and has excellent corrosion resistance. It is the mainstream choice in the market. Formula: 18-8 (18% chromium, 8% nickel). 

304L stainless steel: It is the ultra-low-carbon version of 304, with better resistance to intergranular corrosion. It is suitable for components that cannot undergo heat treatment after welding. 

316 Stainless Steel: This type of steel is an upgraded version of 304, containing molybdenum as an element. It has extremely strong corrosion resistance, especially capable of resisting corrosion from chloride compounds (such as seawater and deicing salts). It is expensive and is commonly used in high-demand environments such as marine and chemical industries. 

316L stainless steel: It is the ultra-low-carbon version of 316. 

3. Main production processes: 

Hot rolling: Steel billets are heated and then rolled to form the product. The surface has an oxide layer, is relatively rough, has slightly lower dimensional accuracy, but has good mechanical properties and is used for heavy-duty structures. 

Cold rolling / cold drawing:  It is rolled or drawn at room temperature. The surface is smooth and shiny, the dimensions are precise, the appearance is beautiful, but the thickness is usually thinner and is used in fields such as decoration and furniture where high surface requirements are needed. 

4. Representation Method: 

It is expressed as "side width × side width × side thickness". 

Equilateral angle steel: 50×50×5mm (Both sides have a width of 50mm and the thickness is 5mm) 

Unequal-sided angle steel: 100×63×8mm (long side 100mm, short side 63mm, thickness 8mm)

Chemical reagent identification method (fast, accurate, low cost)

This is the most effective and economical way to distinguish 201 from 304. 

Stainless steel identification solution (manganese element detection solution): 

Principle: 201 contains a high amount of manganese (around 5.5%), while 304 contains a low amount of manganese (< 2%). 

Operation:  Polish the surface of the angle steel until it is shiny. Drop a drop of the identification liquid and wait for a few minutes to observe the color change. 

Result:

Quickly turning deep purple-red → 201 stainless steel (with high manganese content). 

No color change or light red color → 304 stainless steel (with low manganese content). 

Purchase: Searching online for "stainless steel testing solution" and "manganese element detection liquid", the prices are very reasonable (ranging from a few yuan to over ten yuan per bottle). 

Copper element detection solution: 

It is specifically designed for detecting 304 (containing about 8% nickel), while 201 basically does not contain nickel. After dripping the reagent, when electricity is applied, a chemical reaction occurs, and if a pink substance is produced, it indicates 304. The operation is a bit more complicated, but it is more accurate. 

Professional institution inspection (the most authoritative and costly)

When it comes to major engineering projects or legal disputes, the most authoritative proof is required. 

Spectral analysis: By aiming the spectrometer at the angle steel, the content of all chemical elements can be accurately analyzed within a few seconds, and the results are completely accurate. This is the most scientific method.

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