Como identificar aço falsificado e de qualidade inferior?

How to identify counterfeit and inferior steel?

1. Low-quality steel often has bending. Bending refers to multiple fold lines formed on the surface of the steel, a defect that often runs longitudinally throughout the product. This is caused by manufacturers of counterfeit products who seek high efficiency, apply excessive reduction, and create ears that bend during the next lamination process. Once bent, the product will crack when bent, significantly reducing the strength of the steel.

2. The surface of the lower steel often has a marked appearance. This irregularity is due to severe wear of the groove, causing an uneven surface. Because counterfeit steel manufacturers prioritize profit, they often roll beyond standard slot capacity.

3. Steel bottom surfaces are prone to scarring. This is due to two reasons: a) the material of counterfeit steel is irregular and contains many impurities; b) the protective equipment used by counterfeit manufacturers is rudimentary, causing the steel to adhere and resulting scars after being bitten by the roller.

4. Inferior materials are susceptible to surface cracking. This is because its billets are made from blocks of earth, which have many pores. During cooling, these earth plates crack under thermal stress and persist after rolling.

5. Counterfeit steel is easily scratched due to the rudimentary equipment of counterfeit manufacturers, which can create burrs that scratch the surface of the steel. Deep scratches reduce the strength of the steel.

6. Counterfeit steel has no metallic luster and appears light red or similar to the color of raw iron. This is due to two reasons: a) the billet is raw earth; b) manufacturers of counterfeit products do not comply with standard lamination temperatures. They visually estimate the temperature of the steel, which prevents proper rolling of the austenitic region, naturally leading to lower steel performance.

7. The ribs of counterfeit steel are thin and low, often with insufficient filling. This is because manufacturers, aiming for a large negative tolerance, apply excessive reduction during the initial stages of production, resulting in smaller iron profiles and poorly filled hole shapes.

8. The cross section of counterfeit steel is elliptical. This is due to manufacturers trying to save material and applying excessive shrinkage during the initial stages of rolling. This significantly reduces the strength of this rebar and does not meet the standard size for rebar profiles.

9. High-quality steel has a uniform composition, and the cold shearing machine has high tonnage, resulting in a smooth and tidy cutting end face. However, due to its inferior material, the cut end face of counterfeit steel often has a fleshing phenomenon, that is, it is uneven and lacks metallic luster. In addition, because manufacturers of counterfeit products cut fewer product ends, there will be large ears on the head and tail.

10. Inferior steel materials contain many impurities, resulting in low density and significant dimensional deviations. Therefore, in the absence of a caliper, weight checking can be carried out. For example, for rebar 20, the national standard stipulates a maximum negative tolerance of 5%. When the specified length is 9M, the theoretical weight of a single piece is 120 kilograms. Its minimum weight should be: 120 X (1－5%) = 114 kilograms. If the actual weight of a single piece is less than 114 kilograms, it is considered inferior steel as its negative tolerance exceeds 5%. Generally, a comprehensive weighing process produces better results, mainly due to cumulative errors and probability theory issues.

11. The inner diameter of the bottom steel varies significantly due to unstable steel temperatures, uneven composition, and the use of rudimentary equipment, leading to low foundation strength and significant mill bounce. This results in significant changes in internal diameter within the same week, making the steel susceptible to uneven stresses and potential fracturing.

12. High-quality materials have standardized trademarks and printing.

13. For large threaded steel bars with a diameter of 16 or more, the distance between two marks is always greater than 1M.

14. The longitudinal ribs of rebar made of lower quality steel often form a wave shape.

15. Manufacturers of lower quality steel materials typically do not use overhead cranes, resulting in loosely packed bundles that appear elliptical when viewed from the side.

Recommended for you:

  • The Ultimate Guide to Stainless Steel Materials
  • The definitive guide to steel
  • Special Foundry: Everything you need to know
  • Steel classification and types: the definitive guide
  • Different Types of Structural Steel Profiles: Comprehensive Guide
  • What is steel plate?

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