Good collection of articles about the influencing factors and control methods of the surface quality of copper rows
Copper busbar (also called copper busbar) products are mainly used in power, electronics, communications, heat dissipation, mold and other industries. With the development of the national economy and increasingly fierce market competition, users have higher and higher requirements for the surface quality of copper bar products. In the current national standards, the macro description of the surface quality of copper bar products can no longer fully cover the market's requirements for the surface quality of copper bar products. quality requirements [1]. Through statistical analysis of copper row quality complaint information, surface quality complaints (referring to defects such as spots, pits, scratches, color differences, and defects) accounted for 30.92% of the number of complaints. Surface quality is not only the aesthetic requirement of the user's first sense, but also the requirement of downstream users for product production technology and quality. It is necessary to optimize and improve the factors affecting surface quality during the production process of copper bars to reduce or avoid surface defects of copper bars.
1. Surface quality standards of copper bars
The standard used for copper busbars is GB/T5585.1-2005 "Copper, Aluminum and Their Alloy Busbars for Electrical Use Part 1: Copper and Copper Alloy Busbars". The surface quality requirements are "The surface of the copper busbars should be smooth and flat, and should not be There should be no defects that are not commensurate with good industrial products. There should be no flash, burrs and cracks in the rounded corners and rounded edges of the copper bars. "Due to factors such as technology, equipment, management and operation, we still mainly rely on the production process. Inspection by experienced personnel and manual visual inspection. Although product standards are relatively precise and testing methods are relatively flexible, their operability is poor and they cannot fully cover the user market's product quality requirements.
2. Surface quality index of copper busbar
The surface quality of copper strips can be divided into three main aspects: surface smoothness, surface smoothness and surface defects. It is inseparable from copper properties, production technology, production management and production environment [2].
2.1 Factors affecting the surface smoothness of copper bar blanks
Copper row blanks are currently mainly produced by continuous extrusion, and the surface of the blank is cooled by coolant + alcohol. Adding a small amount of alcohol to the coolant can reduce oxides and obtain the required surface [3]. During the continuous extrusion cooling process, alcohol will volatilize more as the coolant temperature increases, causing oxidation on the surface of the billet, directly affecting the surface quality of the copper bar, resulting in an increase in production costs.
2.2 Lubrication of drawing mold
During the metal drawing process, relative motion occurs between the tool and the workpiece surface, resulting in friction. Proper lubrication must be carried out. This lubrication is also called process lubrication [4]. At present, traditional stretching oils are mainly used when stretching copper rows. Traditional stretching oils mainly include mineral oil, volatile oil, boronized soap-based compounds, etc. Among them, mineral oil is difficult to mix, contains harmful and flammable components, and is difficult to clean and directly weld. Volatile oil is flammable and toxic, has little protective effect on tools, increases the content of volatile organic compounds (VOC) in the workshop, and seriously reduces environmental quality.
2.3 Surface defects caused by improper protection during production, storage and transportation
During the production process, the product was improperly protected and the product was in direct contact with iron or sharp objects, resulting in bump defects on the surface of the copper bar. The production process planning is unreasonable, the products are transferred frequently, and the products are constantly swinging or moving, causing the surfaces of adjacent copper bars to constantly rub against each other, resulting in scratches and abrasions on the surface of the copper bars.
2.4 Packaging quality
Ordinary copper busbars (including bulk copper busbars) are not tightly packed, causing friction between the copper busbars during loading, unloading, lifting, and product transportation, resulting in bumps and scratches on the product surface, especially during transportation. Static electricity injury (black spot burn).
3. Process control of copper bar surface quality
Surface quality control is the entire process control from copper bar production to product packaging. It is a systematic project with fine management and careful operation. Each process is the key to controlling the surface quality of the product.
3.1 Ensure that the cooling system of the continuous extruder is normal
Lubricant additive liquid + water is used for billet cooling. Whether the cooling system of the continuous extruder is normal has a great impact on the quality of the billet surface. The first is to transform the cooling water circuit of the continuous extruder to ensure that the cooling water temperature is in an ideal state; the second is to combine the actual production and use a reasonable ratio of lubricant additive liquid + water to cool the surface of the blank. Through the transformation of the cooling water circuit of the continuous extruder and the combined use of lubricant additives, the surface quality of the billet has been significantly improved. The surface of the billet is smooth, bright and free of oxidation. .
3.2 Use water-based lubricant to lubricate the stretching mold
Use water-based lubricant to lubricate the stretching mold. This lubricant is a water-soluble stretching oil. Water-soluble stretching oil has extremely high lubrication effect and continuously provides a perfect lubrication and anti-friction film during plastic deformation, which can effectively improve the surface quality of the product and effectively reduce the occurrence of scratches, scratches and other phenomena. It has super extreme pressure and anti-wear properties, which is beneficial to protect the mold and extend the life of the mold. The cooling performance is good, and the stretching oil is completely dissolved in water, which greatly saves the overall cost of use. Easy-to-clean product, economical, safe, stable, and clean workshop environment. It has extremely high wettability and can effectively improve the roughness and precision of the product. Excellent anti-rust performance, will not corrode sensitive metals. An environmentally friendly product, the additives do not contain sulfur and phosphorus, comply with environmental protection requirements, and have no impact on the skin. Since the lubricant contains a large amount of water and is prone to deterioration, care should be taken during maintenance and monitoring, and it should be replaced regularly as required. Through the use of water-based lubricant, the surface color of the copper busbar is smooth, uniform and uniform, and the surface quality has been significantly improved. The comparison of surface quality before and after switching to drawing die lubricant is shown in Figure 3.
3.3 Optimize production processes and process routes to reduce lifting
In order to avoid scratches, bruises, and abrasions on the surface of the copper bars during the production processes of stretching, straightening, sawing, packaging, etc. or during transportation, it is necessary to reasonably arrange the production process, select the most appropriate process route, and reduce hanging costs. operation times to reduce secondary damage to the surface of the copper bar. All areas in direct contact with the product should be wrapped with soft glue or cloth to avoid bumps, bruises and scratches on the surface of the copper bar. The surface of each layer of copper busbars is separated by a non-woven fabric to ensure that the surface of the copper busbars is not scratched.
3.4 Optimize packaging methods
Standardized packaging is implemented, using the copper bar with a length of 6000 mm as the standard, and adopting the method of wrapping 5 equidistant textile tapes and PVT tapes for each hoisting, which is to change the previous method of bulk packaging or simply wrapping the copper bar with film. Copper busbars of other lengths should be wrapped with 3 to 5 equidistant textile tapes and PVT tapes for fastening. At least 3 locations should be used. Through the optimization of the packaging method, bumps, scratches or rubs on the surface of the copper busbars can be avoided. Injuries, especially electrostatic shocks (burns and black spots) generated during transportation are avoided. The comparison before and after the optimization of packaging methods is shown in Figure 4 and Figure 5.
4. Copper bar surface quality inspection
At present, the detection of copper strip surface quality relies on visual observation and judgment by operators and inspectors, lacking unified standards and quantitative concepts. Although the requirements for the surface quality of copper bars are getting higher and higher, due to the influence of factors such as technology, equipment, management and operations during the processing, the controllability of the surface quality of the copper bars and the accuracy of the test results are still not ideal. With users' quantitative requirements for the surface quality of copper bars and the need for modern production management, inspection methods that rely on operators and inspectors to visually observe and judge the surface quality of copper bars will eventually be eliminated, with machine vision as the core. The surface defect detection technology of plates and strips has become the focus of current research [5] and will be further promoted and used in the industry.
5 Conclusion
(1) As the market competition becomes increasingly fierce and the requirements for the surface quality of copper busbars become higher and higher, high surface quality has become an important indicator to measure the quality of copper busbars.
(2) The control and improvement of the surface quality of copper rows is a comprehensive project, involving many factors such as production technology, equipment level, production environment and personnel quality. Only all aspects and links must cooperate closely to avoid the occurrence of various adverse factors. , in order to obtain better surface quality of the copper bus. The surface smoothness of the blank, stretch lubrication, protection of each process in the production process, and packaging methods are the main factors that affect the surface quality of the copper bar. Through process optimization and improvement of the production process, fine management, and careful operation, the surface quality of the copper bar is better than before. Process optimization has significantly improved compared to before improvement, and the number of surface defect complaints dropped from the original 30.92% to 17.54%.
(3) Online surface defect automatic detection technology is an ideal equipment for surface quality detection in copper bar production. It realizes the quantification of copper bar surface defects, provides a basis for product surface quality determination and process optimization, and greatly improves product quality. Quality reputation. The use of online surface defect automatic detection technology instead of visual inspection methods will be further promoted and used in the industry.
