The authenticity of stainless steel flanges can be identified through a comprehensive judgment of various methods. The following is the specific operation and principle analysis:

I. Chemical Reagent Detection Method (Quick Preliminary Judgment)

1. Nitric acid point test

Principle: Stainless steel is resistant to concentrated nitric acid and dilute nitric acid, while ordinary carbon steel or low alloy steel is subject to corrosion.

Operation: Dip a cotton swab in concentrated nitric acid (or dilute it to an appropriate concentration) and drop it onto the surface of the faran. If there are no obvious signs of corrosion, it is stainless steel. If it turns black or bubbles rapidly, it may be a counterfeit product.

Note: Operate in a well-ventilated area and avoid skin contact.

2. Copper sulfate spot test

Principle: Copper sulfate solution (concentration 5%-10%) can react with common carbon steel to form a purple-red copper deposit, while stainless steel does not have this reaction.

Operation: Remove the oxide layer on the surface of the flange, drop a drop of copper sulfate solution, and observe the color change. If it doesn't change color, it might be stainless steel; if it turns purplish red, it could be carbon steel or low alloy steel.

3. Stainless steel testing solution

Principle: The solution reacts with different materials to present specific colors (for example, 304 stainless steel appears colorless or light yellow, and 201 appears dark red).

Operation: Clean the surface of the flange, drop a drop of the detection solution, and after 2-3 minutes, compare the color change. Refer to the manual to determine the material.

Ii. Physical Property Testing Method (Simple and Non-destructive)

1. Magnetic experiment

Principle: Austenitic stainless steel (such as 304 and 316) is non-magnetic in the annealed state, but may become weakly magnetic after cold working. Ferritic stainless steel or low alloy steel has strong magnetism.

Operation: Bring a magnet close to the flange. If it is strongly attracted, it may be ferritic steel or a counterfeit product. If there is slight adsorption or no reaction, it may be austenitic stainless steel.

Limitation: High manganese steel with a relatively high manganese content is non-magnetic and needs to be verified in combination with other methods.

2. Surface observation

Principle: The surface of genuine stainless steel is smooth, with uniform color, free of rust or obvious scratches.

Operation: Visually inspect the surface of the flange. If rust spots, roughness or coating peeling are found, be alert to material issues.

Iii. Advanced Detection Method (Professional Equipment)

1. Spectral detection

Principle: The composition and content of metal elements are detected through a spark direct reading spectrometer or an X-ray fluorescence analyzer.

Operation: Professional institutions use equipment to conduct non-destructive testing on flanges, which can accurately determine whether the material meets the standards (for example, 304 stainless steel contains 18% chromium and 8% nickel).

Advantages: The results are accurate and reliable, suitable for batch testing or high-value products.

2. Spark identification method

Principle: When different materials are ground on a grinding wheel machine, the number, shape and color of sparks vary.

Operation: Gently grind the edge of the flange with a grinding wheel machine and observe the sparks.

High manganese steel with a relatively high manganese content: The sparks are streamlined and have many knots.

Chromium steel or chromium-nickel stainless steel: Sparse sparks, no knots.

Note: It requires experienced personnel to operate and is suitable for on-site quick judgment.

Iv. Comprehensive Identification Suggestions

1. Preliminary screening: Prioritize magnetic tests and surface observations to quickly eliminate obviously counterfeit products.

2. Chemical verification: Conduct nitric acid spot tests or copper sulfate spot tests on the suspected products to further confirm the material.

3. Precise detection: If it is necessary to determine the specific grade (such as 304, 316), it is recommended to use spectral detection or stainless steel detection solution.

4. Purchasing channels: Choose regular manufacturers or brands to avoid "three-no" products and reduce purchasing risks.

Common Misconceptions Reminder

Magnetism does not equal authenticity: Austenitic stainless steel may have weak magnetism after cold working and cannot be judged solely by its magnetism.

Color ≠ material: The surface coating or oxide layer may mask the true material and needs to be removed before testing.

Low-price trap: If the price is significantly lower than the market average, be cautious of material adulteration (such as passing off 201 as 304).