Abstract
Steel sheet is an important material for forming finished products in the industrial production process, and its quality directly affects the quality of the finished product. There are many factors that can cause defects in the surface of a steel slab, such as poor lubricating oil, process control conditions, improper blank polishing or grinding, etc. This paper analyzes and determines the main factors that cause surface defects of steel slabs according to the relevant literature and combed out the general principles of surface defects prevention of steel slabs.
Keywords: steel slab, surface defects, factors, prevention
1. Introduction
The steel sheet is an important material for forming finished products in the industrial production process, which directly affects the quality of the finished products, and the surface defects of steel sheet is one of the important factors that directly affect the quality of the finished product. Therefore, it is necessary to study the causes and prevention of the surface defects of steel sheet. At present, the research on the surface defects of steel sheet has been paid more and more attention, and the research on various factors that may cause surface defects of steel sheet has made considerable progress, but there are still many aspects that need further research.
2. Factors that Cause Surface Defects of Steel Slabs
At present, researchers have studied the influence of various factors on the surface defects of steel slabs through experiments and research, and the factors can be divided into three major categories: material factors, process factors and control factors.
2.1 Material factors
Material factors refer to some factors related to raw materials, such as the chemistry composition, hardness, thickness and surface texture of the slab. If the composition of raw materials is not appropriate, it would easily cause cracks in the surface of steel slab, and a certain kind of alloying elements may increase the probability of surface defects. And improper choice of steel grades can also cause surface defects. The hardness of the slab will also largely inflect the surface defects of steel slabs, too low hardness will lead to surface defects, like cracks, folding and mesa defects. In addition, the thickness and surface texture of the slab will also influence the surface defects.
2.2 Process factors
Process factors refer to the design of the processing process and the technological parameters, such as the rolling gap, the technological parameters of rolling, the inner and outer diameter of the roller sleeve, the lubricating system and the mold and gas pressure, etc.
2.2.1 Rolling Gap: If the rolling gap is too large, it will lead to deformation and surface defect of the steel plates.
2.2.2 Technological parameters of rolling: The rolling parameters will also affect the surface defects and the evenness of steel slabs. Improper selection of rolling parameters will lead to the unequal force distribution in the roll surface, which may cause surface defects. If the speed is too fast, it would affect the quality of surface.
2.2.3 Inner and Outer Diameter of the Roller Sleeve: If the inner and outer diameter of the roller sleeve is too large or too small, it will cause columnar defects, scratches and surface defects in the slab.
2.2.4 Lubrication System: The lubrication system should be regularly guaranteed because the high-temperature environment in the rolling process will cause the lubricating oil to volatilize and combust easily, which will decrease the coefficient of friction between the slab and the roller and form rolled-in scale in the surface of slab.
2.2.5 Mold and Gas Pressure: If the mold pressure is too high, it will easily cause surface defects, such as folding and surface crack. The gas pressure should be evenly distributed over the entire width of the slab to avoid causing local surface defects.
2.3 Control Factors
Control factors refer to the management and control of the rolling process, the set limit parameters, the measurement method of parameter control value.
2.3.1 Operators: The qualification and skill of operators is also an influencing factor of the surface defects of steel slabs, and it is related to the operation during the rolling process. If the operator does not follow the process requirements and does not pay attention to the process control, it may cause the surface defects.
2.3.2 Set parameters: The set parameters should be appropriate in order to ensure that the surface defects of the steel slab are within the acceptable range.
2.3.3 Control method: It is necessary to select an appropriate control method, such as on-line shielding, digital control and so on, to make the rolling data parameters in the process of steel slab rolls digital, so as to ensure the accuracy and stability of the slab surface quality.
3. Conclusion
In order to avoid the surface defects of steel slabs in the production process, it is necessary to control each step of the slitting process, understand and eliminate the factors that cause these defects. The relevant factors that cause surface defects of steel slabs mainly include material factors, process factors and control factors. Material factors include steel grades, thickness, surface texture and other factors; process factors include rolling gap, lubrication system, roller sleeve, mold and gas pressure and so on; control factors mainly include operators, set parameters and control methods.
4. References
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