Several main surface treatment processes for stainless steel pipelines-Zhejiang Benji Stainless Steel Co., Ltd

There are several specific methods for processing and treating the inner and outer surfaces of stainless steel pipes:

1. AP (Acid Pickling) pickling treatment

AP refers to acid pickling treatment, which uses acidic solutions such as nitric acid and fluoric acid to remove the oxide layer of steel pipes. Cheap and fast, but easy to cause grain boundary corrosion, and the inner and outer surfaces are rough and prone to suspended impurities adhering. The corrosion resistance of stainless steel mainly comes from the chemical reaction between the chromium element inside and oxygen, which forms a dense oxide film on its surface. The function of the pickling process is to cause this reaction to occur in advance, in order to improve the corrosion resistance of stainless steel pipes.

2. BA (Bright Annealing) Bright Annealing

During high-temperature heat treatment under hydrogenation or vacuum conditions, on the one hand, internal stress is eliminated, and on the other hand, a passivation film is formed on the surface of stainless steel pipes to improve morphology and reduce energy levels, but it will not increase surface roughness. Steel pipes will definitely require oil during the extraction process. Grease lubrication can also cause deformation of grains due to processing. To avoid this grease residue in the steel pipe. In addition to cleaning the steel pipe, argon gas can also be used to eliminate deformation during high-temperature annealing. The atmosphere inside the furnace is further cleaned by the combustion of argon combined with carbon and oxygen on the surface of the steel pipe.

The method of using pure argon gas annealing for heating and rapid cooling to brighten the smooth surface is called brilliant annealing, although using this method to brighten the surface can ensure that the steel pipe is fully clean and free of any external pollution. However, if the brightness of this surface is compared to other polishing methods such as mechanical, chemical, and electrolytic methods, it will have a fogging effect. Of course, its effect is also related to the content of argon and the number of heating times.

3. MP (Mechanical Polishing) Mechanical Polishing

Improving surface roughness through precision grinding can improve surface texture, but it will not improve morphology, energy level, and number of intermediate layers.

4. PD: Mechanical Drawing (Plug Draw)

Commonly known as wire drawing, precise cold drawing of plugs is used to improve surface roughness, which can improve surface structure but does not improve morphology, energy level, and number of intermediate layers. As the most basic surface treatment process, the roughness of mechanical drawing lays the foundation for other surface treatment processes.

5. EP (Electro Polishing) Electropolishing

Electropolishing is a method of Anodizing. According to the principle of electrochemistry, properly adjusting the voltage, current, acid composition, and polishing time can not only make the surface bright, smooth, and clean, but also enhance the corrosion resistance of the surface. Therefore, it is a good way to brighten the surface. Of course, its cost and technology will also be improved.

6. BP (Buffed Polished) feather fabric shine

It is commonly used in the decorative stainless steel industry to improve the surface brightness. Although the Ra value may be very good, many cracks can be observed under the electron microscope, the actual surface area is expanded, and there are separated ferrite and Martensite structures locally. The surface is mixed with many impurities, such as grinding particles. Due to the use of polishing sound, a lot of energy is stored in the original depression, resulting in an increase in the number of media. This type of stainless steel pipeline is generally not allowed to be used in sensitive and corrosive media of microelectronics, optoelectronics, and biopharmaceuticals. Stainless steel pipes, after pickling or passivation, will not improve surface roughness, but can remove residual particles on the surface, reduce energy levels, but will not reduce the number of intermediate layers.

Zhejiang Benji Stainless Steel Co., Ltd.,