What are the differences between BA grade and EP grade stainless steel pipe fittings

Stainless steel pipe fittings classification: AP, MP, BA, EP AP < MP < BA < EP

AP: Acid Pickling: Uses acidic solutions such as nitric acid and fluorine to remove the oxide layer from the steel pipe. Inexpensive and fast, but prone to causing intergranular corrosion and resulting in a rougher inner and outer surface that is more susceptible to suspended impurities.

MP: Mechanical Polishing: Commonly used for removing oxide layers, pores, and scratches from the surface of steel pipes. Its brightness and effect depend on the type of processing method. While mechanical polishing results in a more aesthetically pleasing appearance, it also reduces corrosion resistance, so passivation treatment is necessary when used in corrosive environments. Furthermore, polishing material residue often remains on the steel pipe surface.

BA: Bright Annealing: During the drawing process, steel pipes require grease lubrication, and the grains are deformed due to processing. To prevent grease residue from remaining in the steel pipe, in addition to cleaning the pipe, high-temperature annealing can be used to eliminate deformation. Argon gas is used as the furnace atmosphere, and the argon combines with the carbon and oxygen on the steel pipe surface to burn, further cleaning the surface and producing a bright finish. Therefore, this method of using pure argon gas for annealing, followed by rapid cooling to brighten the surface, is called gloss annealing. While this method ensures the steel pipe is thoroughly clean and free of external contaminants, the brightness of this surface, compared to other polishing methods such as mechanical, chemical, and electrolytic polishing, may appear somewhat matte. Of course, the effect is also related to the argon gas content and the number of heating cycles.