[China Aluminum Network] Lubrication Technology and Challenges of Aluminum Alloy Thin Strip Rolling Process
With the development of modern industrial technology, the quality requirements for aluminum alloy sheet strips are getting higher and higher. As China's economic development enters the â€œnew normalâ€, the market potential for high value-added and high-tech aluminum alloy sheet metal strips is huge, especially for aluminum plates for light weight automobiles, aluminum alloy sheets for aerospace, and aluminum strips for food and beverage cans. In the electronics and construction field, aluminum strips , PS plate aluminum strips, etc. The aluminum alloy sheet strips can meet the requirements of the corresponding size specifications, performance and surface quality through hot rolling and cold rolling. It can be summarized as â€œgood dimensional accuracy, good surface finish, high performanceâ€ . To effectively meet these requirements, Rolling process lubrication technology puts forward higher requirements. It is necessary to select suitable rolling process lubricants. At the same time, it is necessary to perform reasonable maintenance and management of the process lubricant so that the function of the lubricant can be effectively and stably exerted.
This article briefly discusses the characteristics of some aluminum alloy thin-plate strip rolling and related process lubrication technology. At the same time, it also briefly explains the challenges faced by aluminum thin-plate strip rolling process lubrication technology.
First, aluminum alloy sheet rolling products, features and quality requirements
Aluminum alloy sheet aluminum is the main product in the aluminum strip, mainly used in cans, automotive aviation, PS base, building curtain wall and so on. Among them, aluminum cans are alloys such as 3104, 3004, and cans are alloys such as 5083 and 5182. Aluminum cans require very strict requirements, intrinsic quality, deep drawing performance, good surface quality at the same time, hot rolling finishing temperature is high, basically above 320 Â°C, cold rolling final rolling thickness 0.28 - 0.32mm, thickness tolerance And plate type and other high requirements . The electroplating mill of PS plate is commonly used in 1050 aluminum alloys. The domestic and international brush grinding plates often use 3103 aluminum alloy. PS version has high requirements on the quality of aluminum bases. The apparent quality, flatness, and thickness difference of aluminum bases will affect the quality indicators such as the state of the sand plate of the PS plate. The quality of the PS plates is very high, especially high-end color printing. The printing plate is not allowed to have a bit of ills. To ensure the quality of the printing plate, the apparent quality of the aluminum plate for the PS plate is more important . Aluminum alloy plates for automobiles, especially automobile outer plates, are products in the production of aluminum alloy plates. At present, there are two series of aluminum alloy automobile plates, 5xxx and 6xxx series , and 5xxx series aluminum alloys have medium strength and good processing performance. Etc., 6xxx series aluminum alloy with good formability, high strength and other characteristics, in its research and development to focus on its formability, surface brightness uniformity, surface treatment and other seven performance requirements . Alumina sheet is widely used for ceilings, curtain wall panels, electrical panels, furniture panels, etc. Alumina sheets are highly decorative, moderate in hardness, and do not require complex surface treatments, etc., alumina sheet 1xxx, 5xxx, 6xxx series alloys are more, 1xxx alloy has good characteristics in light and protective oxidation, 6xxx can be anodized and colored, suitable for building decoration materials.
In addition to the high requirements for performance and other aspects, aluminum alloy sheet strips have imposed high requirements on the surface quality of strips, such as surface defects such as sticking, scratches, imprints, pine-tree patterns, metal and non-metal indentation, and oil contamination. , Annealed oil spots, color difference, bright strips, orange peels, etc. have clear requirements and regulations , which put forward higher requirements for process lubrication technology.
Second, aluminum alloy sheet rolling process lubrication technology
There are three main types of lubrication technology for aluminum alloy sheet rolling process, water-based lubrication technology, oil-based lubrication technology, and oil-water application two-phase lubrication technology.
1, water-based lubrication technology
Water-based lubrication technology is divided into emulsion technology, dispersion fluid technology and synthetic fluid technology.
Emulsion technology is the introduction of emulsifiers. The emulsifier is a surface active material. The lipophilic part is concentrated in the oil, while the hydrophilic end face is in the water, forming a protective barrier between the oil beads, which greatly reduces the accumulation of oil beads. The rate reduces the free energy on the surface of the oil droplet and prevents the aggregation between the oil beads. This maintains the dynamic balance of the emulsion , as shown in Figure 1.
Aluminum rolling emulsions often use anionic and nonionic emulsification techniques. Among them, anion emulsification technology is more mature and stable in aluminum rolling, and it is a widely used technology. Since the aluminum plate is always positively charged during rolling, anion technology is used to facilitate the adsorption of lubricating components, and weak alkaline conditions It also helps in better cleaning, rust prevention and antibacterial functions.
Houghton developed a lot of R&D and application work in the field of water-based process lubrication. Among them, Tandemol technology is widely used. Tandemol 62xx, 63xx, 68xx, 67xx, 69xx, 5xxx series products are compared in aluminum hot rolling and cold rolling respectively. Good use. In addition to the lubrication, cooling, and cleaning features that lubricants must provide, there are also unique areas for self-purification, controllability, and stability.
Dispersion technology is a type of emulsion technology that uses a cationic emulsifier. In addition to the bacteriostatic effect of cationic emulsifiers, the oil droplets are large in size and evenly distributed over a range of pH, as shown in Figure 2. This distribution of oil particles not only greatly improves the lubricating ability of the dispersion (because the precipitation of oil from the emulsion is a prerequisite for lubrication), but also improves the lubrication uniformity and the wetting ability of the oil droplets on the surface of the aluminum sheet. To improve the surface quality after rolling.
Dispersion technology is less applied in aluminum rolling, mainly due to poor emulsion stability of cationic technology, difficulty in controlling lubrication and emulsion, and maintenance and management pressure. However, Houghton's dispersion fluid technology has been used extensively in steel cold rolling.
Synthetic fluid technology and emulsion technology are different, as shown in Figure 3. Synthetic solution is a single-phase product, it is very stable, clear and transparent, good detergency, but the synthesis of low surface tension, corrosion is strong. Water-soluble polymers are often dissolved in water by forming hydrogen bonds through hydrogen bonding. Hydrogen bonds disappear when the temperature rises. The polymer precipitates and promotes lubrication. This is different from the lubrication mechanism of the emulsion in the nip region . The technology has almost no application in aluminum rolling.
2. Oil-based lubrication technology
Oil-based aluminum cold-rolled oils are usually solvent-based oils, and are supplemented with additives (alcohols, esters, and acids). They are the main process lubrication products for aluminum cold rolling. Oil-based rolling oil technology is mature, base oil and additive selection, cooling system setting, maintenance management, and related equipment process parameters such as rolling speed, pressure reduction, tension setting, etc., have rich experience and mature cases. Reference.
Most current aluminum cold rolling additive technology basically maintains the use of C12-C18 alcohols, esters or acids. Alcohols and esters are used after being mixed in a certain proportion. Sometimes the rolling process assists in the addition of a small amount of acid in order to obtain a bright surface or improve lubrication. The key to the design and selection of additives is to determine the carbon chain length of the alcohol esters. The carbon chain is short, the cleaning performance is good, but the lubrication performance is poor, the carbon chain is long, the lubrication performance is good, but the residual is much, as shown in FIG. 4 . The rolling speed of modern aluminum cold rolling mills is getting higher and higher, and the requirements for cooling and lubricating capacity of rolling oil are higher. At the same time, higher demands are made on the surface residue and anneal oil spots, how to ensure lubrication and cooling, and the surface is guaranteed at the same time Cleanliness is an important issue.
In solving the contradiction between lubrication and cleanliness, Houghton Company has done a lot of exploration work and achieved good results. For example, the introduction of carrier technology, the use of long-chain alcohol esters does not deteriorate the surface cleanliness, the introduction of anti-wear agents, the use of short-chain alcohol esters under the guarantee of cleanliness, enhanced lubrication capabilities. Houghton cold rolling additive technology is widely used around the world. China's Cindol 9xxx series of additive products have been used in many aluminum cold rolling mills for high speed rolling, high rolling reduction, high surface requirements, Reducing additive consumption and other aspects have a good performance.
3, oil and water two-phase technology
Integrating the advantages of water-based and oil-based technologies, and avoiding corresponding deficiencies as far as possible, the technology of water-oil two-phase separation was developed. The oil phase and the water phase were applied to the rollers respectively, and the water was cooled and the oil phase was provided with lubrication. Figure 5 is a schematic diagram of liquid supply for a two-phase medium . Red represents oil supply, which is supplied at the inlet, blue represents water, and both inlet and outlet supply. The outstanding advantage of this technology is that lubrication can be adjusted as needed by changing the amount and pressure of the oil phase, or cooling can be changed by adjusting the amount of water supplied. The test shows that this control method can achieve better lubrication optimization, increase rolling speed, and make it easier to control the shape of the plate.
Houghton owns this technology, especially in steel strip rolling applications.
III. Challenges of Lubrication Technology of Aluminum Alloy Thin Strip Rolling Process
1, how to choose the right process lubrication technology and products
The production of aluminum alloy sheet strips requires hot rolling and cold rolling. The hot rolling and cold rolling generally use process lubrication to lubricate the rolling stock and roll surfaces. Rolling mill, process and process lubrication are three factors that ensure production and quality are more important. There are many factors that limit the rolling mill and process parameters, and as a dynamic variable, process lubricants need to be matched with the mill and process parameters. How to choose the right process lubrication technology and product is very important. Faced with challenges, the following aspects need to be considered
Considering the role of process lubrication, lubrication, cooling, cleaning, improving surface quality, and carrying loads.
Considering the key points of rolling, hot rolling and cold rolling have different focuses, which are to reduce the internal resistance (deformation resistance of the strip itself) and reduce the external resistance (reduce the resistance of external friction to metal deformation) . Among them, the hot rolling roll and rolling surface conditions, rolling temperature, process lubricants, etc., cold roll diameter, tension, lubricating fluid, etc. need to be considered.
Consider rolling difficulties, hot rolling including surface defects, high temperature rolling, finishing temperature, aluminum powder removal, etc. Cold rolling including surface cleaning, speed and temperature, reduction rate, plate type, safety, etc. need to be considered.
Consider different alloys and processes, such as 1xxx alloy with low strength, high reduction rate, easy to stick aluminum, 3xxx alloy strength is not high, high temperature, easy to produce coarse grains, 5xxx alloy high magnesium content plate high strength, rolling Difficulties, lower strength of the plate with lower magnesium content , wider finish rolling temperature range, moderate strength of the 6xxx alloy, and high requirements for annealing performance also need to be fully considered.
Considering the matching of rolling mill, process and lubrication, each rolling mill, rolling process and process lubrication system are different, alloy types, production quality, operating conditions of the process lubricant, management and maintenance conditions, and requirements are all different.
2. How to solve some problems and challenges in application (enumerated below)
How to improve the surface cleanliness: The use of water-based and oil-based products can have problems with residual and anneal oil spots. For example, when using a water-based product, there is a layer of steam barrier film between the water-based medium and the board surface. As shown in Fig. 6, when the temperature is low, the steam film cannot be maintained, and the water-based medium will directly wet the board surface and combine with the board surface. Large increase, it is easy to bring residue, but also bring great difficulties to purge, which is one of the challenges.
How to improve the self-purification and anti-pollution ability: There are equipment oil leakage, oxidation deterioration, aluminum powder production, solid aluminum powder pollution, other metal soap base pollution, water-based emulsification, and bacteria breeding. It is also one of the challenges faced.
Cold-rolled water-based lubricating fluid: Aluminium cold-rolled oil has a low flash point, which has a fire hazard and poor safety. If water-based products are used to compensate for the lack of oil base, fire hazards are eliminated and cooling capacity is improved, but water-based cold-rolled liquids The use is not yet widespread, there are some drawbacks or risks, such as 1) more surface residues, 2) the risk of microbial breeding, 3) the risk of aluminum plate discoloration, 4) lubrication and cooling uniformity is not as good as oil, 5) maintenance management is difficult, the above risks are The common inadequacies of water-based products  and the challenges they face.
In the face of challenges, Houghton Company fully considered and understood various factors, selected more suitable process lubrication products (to be tailor-made), coupled with good service and problem-solving capabilities, and rich product and application experience, allowing users to achieve Satisfying the production and quality needs, Houghton's numerous users are a good illustration.
1. Aluminum alloy sheet strips have their own characteristics in terms of performance and other aspects, but they all impose high requirements on the surface quality, which also raises higher requirements for process lubrication technology.
2. At present, aluminum alloy sheet rolling process lubrication technology mainly includes water-based lubrication technology (emulsion, dispersion, synthetic fluid), oil-based lubrication technology, oil-water two-phase separation technology, etc. They have their own characteristics, according to the need to choose .
3ã€Huffuton has done a lot of R&D and application work in the field of process lubrication, including water-based Tandemol 6xxx (5xxx series) and oil-based Cindol (Cindol 9xxx series of additive products) and other ancillary products in the aluminum heat Both rolling and cold rolling have been widely and better applied. In addition to providing good lubrication, cooling and cleaning performance, it has a superior and unique performance in terms of self-purification, controllability and stability, high reduction, high surface quality, and reduced consumption.
4, aluminum alloy sheet rolling process lubrication technology faces many challenges, how to choose the right process lubrication technology and products, how to solve the application of the issues are very important, Houghton through the process of lubrication technology and product selection, application, process Efforts have been made in control, problem solving, services, etc. to meet the users' satisfactory results in production and quality.
(The author is a good futon (Shanghai) Advanced Industrial Media Co., Ltd. Wang Jianing)
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