Aluminum alloy sheet strip rolling process lubrication technology and challenges
所属分类:Industry information
With the development of modern industrial technology, the quality requirements for aluminum alloy sheet strips are getting higher and higher. Under the “new normal” of China's economic devel..........
With the development of modern industrial technology, the quality requirements for aluminum alloy sheet strips are getting higher and higher. Under the “new normal” of China's economic development, the high value-added, high-tech aluminum alloy sheet has great market potential, especially for aluminum panels for automotive lightweighting, aluminum alloy sheets for aerospace, aluminum sheets for food and beverage cans, and consumption. Aluminum strips for the electronics and construction sectors, PS-based aluminum strips, etc. The aluminum alloy sheet strips meet the requirements of size, performance and surface quality by hot and cold rolling, and can be summarized as “good dimensional shape and high surface smoothness performance” [2]. To effectively meet these requirements, The rolling process lubrication technology puts forward higher requirements, and it is necessary to select a suitable rolling process lubricant. At the same time, the process lubricant should be properly maintained and managed, so that the function of the lubricant can be effectively and stably exerted.

In this paper, the characteristics of some aluminum alloy sheet strip rolling are briefly discussed. The related process lubrication technology is also briefly discussed. At the same time, the challenges faced by the aluminum sheet strip rolling process lubrication technology are also briefly explained.

1. Aluminum alloy sheet strip rolling products, characteristics and quality requirements

Aluminum alloy sheet aluminum is the main product in aluminum sheet, mainly used in cans, automotive aviation, PS plate base, building curtain wall and so on. Among them, the aluminum can body is an alloy such as 3104, 3004, and the can material is an alloy such as 5083, 5182. Aluminum can material requirements are very strict, requiring intrinsic quality, deep drawing performance, and good surface quality, high hot rolling finishing temperature, basically above 320 ° C, cold rolling finishing thickness 0.28 - 0.32 mm, thickness tolerance High requirements such as plate type. PS plate is usually made of 1050 aluminum alloy for electrolytic grinding plate, and 3103 aluminum alloy is often used for brush grinding plate at home and abroad. The PS version has high requirements on the quality of the aluminum plate base. The apparent quality, flatness and thickness difference of the aluminum plate base will affect the quality index of the PS plate. The quality of the PS plate is very high, especially for high-end color printing. It is not allowed to have a slight defect in the printing plate. To ensure the quality of the printing plate, the apparent quality of the aluminum plate for the PS plate is the most important. Aluminum alloy sheets for automobiles, especially automobile outer panels, are the top products in the production of aluminum alloy sheets. At present, there are two series of aluminum alloy automobile sheets, 5xxx and 6xxx series, and 5xxx series aluminum alloys have medium strength and good processing performance. 6xxx series aluminum alloy has the characteristics of good formability and high strength. In its research and development, it focuses on 7-point performance requirements such as formability, surface smear uniformity and surface treatment. Alumina sheet is widely used in ceilings, electrical panels, furniture panels, etc. Alumina sheets have strong decorative properties, moderate hardness, no need for complicated surface treatment, and 1xxx, 5xxx, 6xxx series alloys in alumina sheets. More, 1xxx alloy has good characteristics in bright and protective oxidation, 6xxx can be anodized and colored, suitable for building decoration materials.

In addition to the high requirements for performance, aluminum alloy sheet strips place high demands on the surface quality of the strip, such as sticking, scratching, imprinting, pine branching, metal and non-metal pressing, oil staining. , annealing oil spots, color difference, bright strips, orange peel, etc. have clear requirements and regulations, which puts higher requirements on process lubrication technology.

Second, aluminum alloy sheet with rolling process lubrication technology

Aluminum alloy sheet with rolling process lubrication technology mainly has three major categories, water-based lubrication technology, oil-based lubrication technology, oil and water application two-phase lubrication technology.

1. Water-based lubrication technology

Water-based lubrication technology is divided into emulsion technology, dispersion technology and synthetic liquid technology.

The emulsion technology is to introduce an emulsifier, the emulsifier is a surface active substance, and the lipophilic part is concentrated in the oil, and the hydrophilic end face is in the water to form a protective barrier between the oil beads, which greatly reduces the accumulation of the oil beads. The rate reduces the free energy of the oil bead surface, prevents the accumulation of oil beads, and maintains the dynamic balance of the emulsion, as shown in Figure 1.

Aluminum rolling emulsions often use anionic and nonionic emulsification techniques. Among them, the anionic emulsification technology is more mature and stable in aluminum rolling, and it is a widely used technology. Since the surface of the aluminum plate is often positively charged during the rolling process, the anion technology is used to assist the lubrication component adsorption, and the weak alkaline condition. It also contributes to better cleaning, rust and antibacterial functions.

Houghton has done a lot of research and development and application 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. Good use. In addition to the lubrication, cooling and cleaning properties that lubricants must provide, they are also unique in terms of self-cleaning, controllability and stability.

Dispersion technology is one of the emulsion technologies that use cationic emulsifiers. In addition to the bacteriostatic action, the cationic emulsifier has a large size and a uniform distribution of oil beads in a certain pH range, as shown in FIG. 2 . This distribution of oil particles not only greatly improves the lubricating ability of the dispersion liquid (because the oil is precipitated from the emulsion is the premise of lubrication), but also improves the lubrication uniformity and the wetting ability of the oil beads on the surface of the aluminum plate, which helps To improve the surface quality after rolling.

Dispersion technology is less used in aluminum rolling, mainly due to poor stability of emulsion technology, difficult control of lubrication and emulsion, and high maintenance and management pressure. However, Houghton's dispersion technology has been used extensively in steel cold rolling.

Synthetic fluid technology and emulsion technology are different, as shown in Figure 3. The synthetic liquid is a single-phase product, which is very stable, clear and transparent, and has good detergency, but the surface tension of the synthetic liquid is low and the corrosion is strong. Water-soluble polymers are often dissolved in water by forming hydrogen bonds, hydrogen bonds disappear at elevated temperatures, and polymer precipitation promotes lubrication, which is different from the lubrication mechanism of emulsions in the bite zone. There is basically no application in rolling.

2. Oil-based lubrication technology

Oil-based aluminum cold-rolled oils are usually solvent-based oils with additives (alcohols, esters and acids) and are the most important process lubrication applications for aluminum cold rolling. Oil-based rolling oil technology is mature, basic oil and additive selection, cooling system setting, maintenance management and related equipment process parameters such as rolling speed, reduction, tension setting, etc. have rich experience and mature cases. Learn from.

Most of the current aluminum cold rolling additive technology basically maintains the use of C12-C18 alcohols, esters or acids. Alcohols and esters are mixed and used in a certain proportion. Sometimes the rolling process assists in adding a small amount of acid to achieve surface brightening or to improve lubrication. The key to the design and selection of additives is to balance the carbon chain length of the alcoholic acid. 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 there are many residues, as shown in Fig. 4. The rolling speed of modern aluminum cold rolling mills is getting higher and higher, which requires higher cooling and lubricating ability of rolling oil. At the same time, it puts forward higher requirements on surface residual and annealing oil spots, how to ensure lubrication and cooling, and ensure the surface. Depth is an important issue.

In solving the contradiction between lubrication and decontamination, Houghton 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 to ensure cleanability, enhanced lubrication and so on. Houghton cold rolling additive technology is widely used all over the world. In China, Cindol 9xxx series additive products have been well applied in many aluminum cold rolling mills, in high-speed rolling of aluminum cold rolling, high reduction, high surface requirements, There is a good performance in reducing the consumption of additives.

3, oil and water application two-phase technology

Combining the advantages of water-based and oil-based technologies, and avoiding corresponding deficiencies as much as possible, a two-phase application technique of water and oil was developed. The oil phase and the water phase were respectively applied to the rolls, the water was cooled, and the oil phase provided lubrication. Figure 5 is a schematic diagram of the supply of two-phase medium [11], red for oil supply, at the inlet, blue for water, and both inlet and outlet. The outstanding advantage of this technology is that the lubrication can be adjusted by changing the amount and pressure of the oil phase as needed, or by adjusting the amount of water supply. Tests show that this kind of control method can better optimize lubrication, increase rolling speed, and make shape control easier.

Houghton has this technology, especially in the rolling of steel strips.

Third, the challenge of aluminum alloy sheet metal strip rolling process lubrication technology

1. How to choose the right process lubrication technology and products

The production of aluminum alloy sheet strips requires hot rolling and cold rolling, and both hot rolling and cold rolling are generally lubricated by the process to lubricate the rolled and rolled surfaces. Rolling mills, process and process lubrication are the three most important factors in ensuring production and quality. Mills and process parameters are more constrained, and process lubricants as a dynamic variable need to be managed to match mill and process parameters. How to choose the right process lubrication technology and products is very important. Faced with challenges, the following aspects need to be considered

Consider the role of process lubrication, lubrication, cooling, cleaning, surface quality improvement, load bearing, etc.

Considering the key points of rolling, hot rolling and cold rolling have different focuses, which are to reduce the internal resistance (the deformation resistance of the strip itself) and to reduce the external resistance (to reduce the resistance of the external friction to metal deformation) [12]. Among them, the surface condition of hot rolling rolls and rolled parts, rolling temperature, process lubricants, etc., cold rolling roll diameter, tension, lubricating fluid, etc. need to be considered.

Considering the difficulty of rolling, hot rolling includes surface defects, high temperature rolling, finish rolling temperature, aluminum powder removal, etc. Cold rolling includes surface cleaning, speed and temperature, reduction ratio, plate type, safety, etc.

Consider different alloys and processes, such as 1xxx alloy with low strength, high reduction ratio, easy to stick aluminum, 3xxx alloy is not high strength, high temperature, easy to produce coarse grains, high strength magnesium plate in 5xxx alloy, high rolling Difficulties, low magnesium content of the board is low [5], the final rolling temperature range is wide, etc., 6xxx alloy medium strength, high requirements for annealing performance should also be fully considered.

Considering the matching of rolling mill, process and lubrication, each rolling mill, rolling process and process lubrication system are different. The alloy type, production quality, operating condition of the process lubricating fluid, management and maintenance conditions, and demand are all different.

2. How to solve some problems and challenges in the application (listed below)

How to improve surface cleanliness: The use of water-based and oil-based products has the potential to cause residual and annealed oil spots. For example, using a water-based product, there is a vapor barrier film between the water-based medium and the plate surface as shown in Fig. 6. When the temperature is low, the vapor film cannot be maintained, and the water-based medium directly wets the surface of the plate to bond with the surface of the plate. It is one of the challenges that it is very easy to bring in residues and bring great difficulties to the purge.

How to improve the self-purification and anti-pollution ability: there are equipment oil leakage, oxidative deterioration, aluminum powder production, aluminum powder and other solid pollution, metal soap base other pollution, water-based emulsified state, fungus breeding, etc. It is also one of the challenges.

Cold-rolled water-based lubricating fluid: aluminum cold-rolled oil has low flash point, fire hazard and poor safety. If water-based products can make up for the shortage of oil base, eliminate the fire hazard and improve the cooling capacity, the water-based cold rolling liquid The use is not extensive, there are some shortcomings or risks, such as 1) more surface residue, 2) microbial breeding risk, 3) risk of discoloration of aluminum plate, 4) lubrication and cooling uniformity is not as good as oil, 5) maintenance management is difficult, the above risks are Common shortcomings of water-based products [13] and the challenges they face.

In the face of challenges, Houghton Company fully considers and understands various factors, chooses the most suitable process lubrication products (to tailor the body), combined with good service and problem-solving ability, rich product and application experience, etc. Satisfactory production and quality needs, and many users of Houghton are a good illustration.

Fourth, summary

1. The aluminum alloy sheet has its own characteristics in terms of performance, but it has high requirements on the surface quality, which also puts forward higher requirements for the process lubrication technology.

2. At present, the lubrication technology of aluminum alloy sheet strip rolling process mainly includes water-based lubrication technology (emulsion, dispersion liquid, synthetic liquid), oil-based lubrication technology, oil-water two-phase application technology, etc., each has its own characteristics, according to needs .

3, Houghton has done a lot of research and development and application work in the field of process lubrication, among which water-based Tandemol technology (Tandemol 6xxx, 5xxx series products) and oil-based Cindol technology (Cindol 9xxx series additive products) and other ancillary products in 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 excellent and unique performance in terms of self-purification, controllability and stability, high reduction, high surface quality, and reduced consumption.

4, aluminum alloy sheet with rolling process lubrication technology faces many challenges, how to choose the right process lubrication technology and products, how to solve the problems in the application, etc. are very important, Houghton through process lubrication technology and product selection, application, process Control, problem solving, service and other aspects make efforts to meet the user's satisfactory results in production and quality.

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