Causes of Black Spots on Steel Strip Surfaces
Release Date:
2022-06-23
Author:
Hengyuan Industry and Trade
The primary cause of black spots on the surface of cold‑rolled strip steel is insufficient removal of the emulsion, which leads to the formation of black spots after annealing.
Causes of Black Spots on Steel Strip Surfaces
1. Strip surface roughness: If the surface roughness is pronounced, the gap between the layers of the steel coil is larger, which facilitates the evaporation of the emulsion.
2. Annealed substrate–cold‑rolled coil type: During the annealing heating process, the evaporation of the emulsion can severely compromise the quality of the cold‑rolled coil; moreover, if the strip exhibits waviness, this can also exert a certain influence on the volatilization of the interlayer emulsion.
3. Residual chloride ions on the strip surface: If rinsing is insufficient, chloride ions will remain on the strip surface, leading to electrochemical corrosion and the formation of black Fe₃O₄.
4. Emulsion volatility: High-quality emulsions with low volatility can help reduce the occurrence of black spots on cold-rolled coils.
5. Coiling tension of the rolled product: Reducing the coiling tension decreases the inter‑layer gaps, promotes flow between layers, and ensures thorough emulsion evaporation.
Previous page:
Next page:
Related News
News
2022/06/23
Two categories of heat-treated steel strips
As the pace of modern industrialization accelerates, mechanical equipment is becoming increasingly prevalent in daily life, and the rhythm of people’s lives is quickening. Consequently, demand for dairy products, beverages, and fast‑food items is steadily rising, driving growth in the heat‑treated steel strip industry. Heat‑treated steel strips are widely used across numerous applications, enriching the market with a broader range of products and generating substantial profits for many manufacturers. These strips are suitable for die‑cutting blades, etching dies, corrosion dies, substrates for large circular saw blades, machine tool guideways, railway joint plates, and military‑grade components. At present, large‑size, high‑strength heat‑treated steel strips are entirely imported and subject to stringent export restrictions imposed by the supplying countries.
2022/06/23
Causes of Black Spots on Steel Strip Surfaces
The primary cause of black spots on the surface of cold‑rolled strip steel is insufficient removal of emulsion, which leads to the formation of such defects after annealing.
2022/06/23
Quality Characteristics of Stainless Steel
In general, the required material thickness tolerances vary depending on the type of stainless steel product. For example, Class II tableware and insulated cups typically demand tighter tolerances, around –3% to +5%, whereas Class I tableware usually calls for a tolerance of –5%, and steel pipes require –10%. For materials used in hotel refrigeration cabinets, the thickness tolerance is specified at –8%.
Telephone
Mobile phone
Email box
Address
No. 28, Chunhui Middle Road, Yong’an Industrial Zone, Xianju County, Zhejiang Province