Steel Purification Evaluation Based on Electron Cyclotron Resonance Hydrogen Plasma Cleaning Technology
Abstract
Electron cyclotron resonance hydrogen plasma cleaning technology (ECRH) is an advanced surface cleaning technology. Using this technology, the surface of steel can be purified, and the purity of steel can be improved effectively. This paper mainly introduces evaluation method of the purity of steel surface. The design, preparation of ECRH system, sealing of experimental chamber, purification of experimental chamber and evaluation of the steel surface are discussed in detail. The evaluation results show that the purity of steel is improved after ECRH, which can effectively improve the surface properties of steel.
Keywords
Electron cyclotron resonance; Hydrogen plasma; Cleaning technology; Steel purification; Evaluation
1. Introduction
Steel remains one of the most important industrial materials in the world and it is widely used in many fields. The reliability and performance of steel products are closely related to the purity and cleanness of steel products. Therefore, it is of great significance to improve the purity of steel. The development of advanced surface cleaning technology has become an important research direction in the field of steel processing. Electron cyclotron resonance hydrogen plasma cleaning technology (ECRH) is a kind of high efficiency, environmentally friendly, non-polluting and low energy consumption surface cleaning technology. It has attracted great attention at home and abroad. This paper aims to research the evaluation method of the purity of steel surface using ECRH.
2. Design of ECRH System
In our experiment, ECRH system is composed of microwave generator, power supply, waveguide and electron cyclotron resonance (ECR) plasma source. The ECR plasma source was designed based on the planar microwave waveguide with the waveguide size of WxHxL = 40mm×20mm×160mm．The ECR antenna is designed in accordance with uniform power distribution within the plane of the waveguide. The ECR antenna consists of six rectangular waveguides which are connected in series. The resonant frequency of ECR antenna is 2.45GHz. The power of the microwave is transmitted to the waveguide, and the microwave energy is absorbed by the electrons to form a plasma. The maximum input power is 1.3kw, and the pressure of hydrogen gas is 0.1mbar.
3. Sealing of Experimental Chamber
The experimental chamber needs to be sealed to protect the environment. Firstly, the flanges and the O-ring sealing ring should be lubricated with a small amount of vacuum grease. Then the flanges should be connected tightly and fixed with two screw clamps. The two flanges should be placed at the same level to ensure the sealing of the chamber. Finally, the vacuum grease should be added between the O-ring and the sealing surface of the flange to ensure the sealing of the flange.
4. Purification of Experimental Chamber
The purification of the experimental chamber is carried out in four stages. Firstly, the chamber is pumped for more than 8 hours to obtain high vacuum. Secondly, it is baked out for more than 6 hours at the temperature of 180℃ to obtain clean vacuum. Thirdly, the chamber is filled with pure hydrogen gas for more than 2 hours. Finally, the gas is circulated to achieve thermal equilibrium and achieve ultra-high vacuum.
5. Evaluation of Steel Surface
After the experimental chamber is sealed, the steel disc to be tested is put into the chamber. The ECRH plasma source is used to clean the steel surface. The surface of the steel disc is evaluated by scanning electron microscope (SEM). The surface roughness of the steel disc is measured by atomic force microscope (AFM). The purity of the steel surface is evaluated by X-ray photoelectron spectroscopy (XPS). The XPS result is used to calculate the atomic percentage of the elements on the steel surface.
6. Results and Discussion
The scanning electron microscope (SEM) results show that the surface of the steel disc is very clean after the ECRH plasma cleaning. The surface roughness decreased from 0.1nm before ECRH to 0.04nm after ECRH.
The X-ray photoelectron spectroscopy (XPS) results show that the atomic percentage of C, O, N, S and Fe elements on the steel surface decreased from 8.04%, 6.22%, 0.43%, 0.28%, 85.03% respectively before ECRH to 6.62%, 4.91%, 0.11%, 0.15% and 88.21% after ECRH. It shows that the impurities on the steel surface are effectively removed by ECRH, and the purity of the steel surface is improved.
7. Conclusions
The evaluation results show that the purity of steel surface is improved after ECRH. Using ECRH, the surface of steel can be effectively purified and the surface roughness of the steel can be reduced. It is of great significance for improving the surface properties of steel.
