Application of Nylon Brush Roll & Non-woven Mill Roll for the Production of Aluminum Sheets & Strips

0 Preface

With the rapid development of industrial technology, the use of aluminum sheet and strip as the basic material of modern industry has become more and more extensive, and its surface requirements have also become higher and higher. In recent years, nylon brush rolls have been widely used in the cleaning, degreasing, roll cleaning, polishing and other processes of aluminum strips. Non-woven rolls are used for degreasing and dewatering processes to make the surface quality of the strips have a qualitative leap. This article introduces and discusses the working principle, classification and characteristics of nylon brush roll and non-woven mill roll, as well as their application in the production of aluminum sheet and strip and related issues, for reference by sheet and strip manufacturers and related equipment manufacturers.

1 Characteristics & Classification of Nylon Brush Rolls

1.1 Features of Nylon Brush Roll

The chemical name of nylon is also known as polyamide (PA). Because it is a crystalline polymer and has high crystallinity, its tensile strength, hardness, elasticity and wear resistance are higher than other plastics. At the same time, nylon has good chemical resistance. In particular, it has excellent oil resistance and can withstand weak acids, weak alkalis and general solvents. Therefore, it is the first choice in the production of aluminum strips among many engineering plastic brush filaments, which has certain rationality and inevitability.

1.2 Classification & Characteristics of Nylon Filament

1.21 Nylon 66 Filament

At present, the brush filaments used in industrial brush making mainly include nylon 6, nylon 66, nylon 610, nylon 1010, nylon 612 and other nylon materials. During the cold rolling process of aluminum plate and strip, due to the friction and rolling between the roll and the surface of the strip, the surface will produce micro-oxidized powder shedding and adsorption, and the rolling oil and its attached suspended components will remain on the surface of the strip. If it is not cleaned up in time, it will adhere to the roll surface of the stretch-bending leveler, causing the roll surface to wear and cause the surface of the strip to be damaged. For this reason, the high-temperature hot water scrubbing process is indispensable. However, among many nylon brush filaments, most of the nylon materials have a melting point of about 210°C, which will degrade and deform when used for a long time at a water temperature above 80°C, while nylon 66 has a melting point of 250°C and will not deform when used in hot water above 80°C. Therefore, nylon 66 brush filaments are mostly used for cleaning aluminum strips. But the fatal flaw of nylon 6 is that the water absorption is too high (1.5%). Brushing in water will soften the brush filaments and reduce the rigidity, resulting in unclean degreasing. In addition, nylon itself is not resistant to strong alkalis, and the life of the brush roll will also be reduced.

1.2.2 DT-Belon Filament

According to the problems of the above brush filaments, some foreign companies have added nano-montmorillonite and other materials on the basis of nylon 66, and developed DT-Bellon brush filaments, which have much lower water absorption than nylon 66, alkali resistance and tensile strength Significantly improved, completely solved the problem of aluminum strip brushing. After testing, its polishing effect is doubled compared to nylon 66, and the life of the brush roll is increased by 3-5 times.

1.23 Containing Abrasive Wire

Abrasive brush filaments are abrasive brush filaments of different thicknesses made by adding about 30% silicon carbide and other abrasives to nylon resin materials through mixing, extrusion, wire drawing and other processes. Nylon 612 is the first choice among nylon materials. In addition to the characteristics of PA, nylon 612 also has the advantages of relatively small width, low water absorption (0.1%), good density and dimensional stability, and high tensile strength. Nylon 610 is also used as the drawing material, but the cost performance is low. According to the different materials used, there are mainly the following types of brush filaments at present:

(1) Silicon carbide abrasive filaments are drawn by adding silicon carbide powder to nylon. Due to the polygonal shape of the silicon carbide structure, the products thrown out are of bright light type, and the strip industry mainly uses 180#~800#.

(2) Alumina powder is added to alumina abrasive filaments and nylon filaments. Because of their multi-prismatic structure, the thrown products are of matte type, mainly 180#~800#.

(3) Diamond brush wire is made of nylon with diamond powder. Due to its unique sharpness and hardness, it is mainly used for mirror polishing and other processes in the production of aluminum strips, and 320#~3000# is mainly used.

(4) High temperature resistant special abrasive wire
The high temperature resistant abrasive wire is mainly made of synthetic resin PPS or PEEK and abrasive wire drawing. Because its melting point is as high as 300℃ and 355℃, it is mainly used in the cleaning process of dry polishing or hot roll. Under the same high-speed dry polishing conditions, the general abrasive filaments have been melted and deformed, but the high-temperature resistant filaments can still be used normally.

(5) Multi-strand brush wire
Although finer brush filaments are often used in the brushing of precision aluminum strips, since the brush filaments are still single, scratches will still be left on the surface of the board after careful observation. For this reason, Germany, Japan, and South Korea have successively introduced multi-strand brush filaments, that is, there are countless fine fiber filaments in the 0.5-Imm brush filaments. The thread becomes a brush surface, which solves this problem very well.

1.3 Selection of Brush Rolls for the Production of Aluminum Sheet & Strip

(1) Stretch-bending and leveling cleaning machine: Stretch-bending and leveling cleaning machine is generally the last process of aluminum sheet production. The requirements for the board surface are extremely strict. Therefore, the internal spray brush roll is selected for the structure of the brush roll. The brush wire is a multi-strand brush wire from Germany Haar Company or Japanese Hotan Company, or nylon brush wire below 0.15mm. 0.3-05mm nylon wire can be used for cleaning of aluminum thick plate strip.

(2) Hot-rolling mill roll cleaning brush: The purpose of the hot-rolling mill roll cleaning brush is to use wire brushes in the overall process. Due to the brittleness of the steel wire, it is easy to break and scratches on the surface of the roll. At present, the most effective is the internal spray type abrasive brush. Generally, 180# nylon abrasive filament is used, and the density of the brush filament should not be less than 50%. Due to the low melting point of nylon, burning of brush filaments may occur occasionally when the amount of water is insufficient. Many manufacturers have begun to use high temperature resistant abrasive filaments, but the price is relatively higher.

(3) Cold rolling mill roll cleaning brush: In recent years, the roll cleaning of cold rolling mill rolls has begun to attract the attention of many manufacturers. In addition to removing dirt on the surface of the roll, the cleaning roll of cold rolling mill cannot scratch the surface of the roll body. Mingtai Aluminum has conducted many years of cooperative experimentation, choosing abrasive filaments below 05mm, controlling the length of the brush filaments within a certain range, keeping the density of the brush filaments above 60%, and performing multiple polishing from coarse to fine is the best way.

(4) Mirror panel polishing: Due to the stickiness and easy oxidation defects of the aluminum sheet and strip, the mirror panel polishing of the aluminum sheet and strip has long been a problem that has plagued aluminum sheet and strip manufacturers for a long time. For this reason, after years of cooperative testing with Henan Mingmingtai Aluminum, it was found that 320#-3000# diamond brush roll is a good solution.

(5) Roll mirror polishing brush: The mirror polishing of the roll is a major problem in the aluminum strip industry. At present, most manufacturers still use the abrasive belt polishing solution, which is time-consuming and laborious. The roll mirror polishing refreshing plan is to use PEEK as the material to add 5000# abrasive to make a disk brush, and equipped with special equipment for polishing. It originally took 5 days of polishing time, but now it only takes 2 hours to achieve a mirror effect of 0.001.

1.4 Reshaping the Brush Roll

After the brush roll is used for a long time, the surface will appear two large dumbbells (or commonly known as dog bones). The following methods can be used for trimming at the right time:

(1) Whether pure nylon or abrasive filaments can be cut with a special tool, the tool holder is simple and easy to install on a lathe;

(2) The abrasive filament brush roll can be installed on a cylindrical grinder or a lathe. The grinding wheel is re-ground, and the grinding wheel can be 46# silicon carbide grinding wheel.

2 Features & Applications of Non-woven Multi-purpose Mill Rolls

The non-woven multi-purpose roll is a non-woven mill roll made by sintering a special non-woven mill into a cylindrical structure by a special process, and then pressing it on a steel shaft, which is different from the traditional rubber and steel rolls. The biggest feature of this mill roll is the use of a special non-woven mill with a net-like internal organization, which can absorb oil, water and infiltrate the residual powder on the surface of the sheet, and has a high friction coefficient.

2.1 Squeeze Water in the Washing Line

In the last process of the cleaning production line, there is nothing more than adding a rubber squeezing roll. Due to the defect that the rubber roll itself cannot absorb water, a large amount of water needs to be dried in the subsequent drying tunnel, which consumes a lot of energy. Any carelessness will leave water stains on the surface of the plate and strip, which will directly affect the external quality of the aluminum plate and strip. According to calculations, a large part of the cost of the cleaning line will be spent on the subsequent drying of the plate and strip. Generally speaking, every 1% increase in dryness is equivalent to 5% less water evaporated in the drying tunnel, which means that power consumption increases by about 5%. What is more serious is the fouling phenomenon of using old rolls, and the residue is not squeezed cleanly, which makes the surface form an extra linear structure, and the surface reflectivity is only about 30%.

The water squeezing effect of the non-woven roll is increased by more than 5 times, which greatly saves energy. The surface of the sheet is very clean and bright, and the reflectivity is above 90%. In the past, the rubber roll had to be replaced once a month. The output of aluminum plate and strip is up to 1200t. Now it produces 4000t for grinding once. The roll life is more than 2 years, which greatly saves costs.

2.2 Improvement of Degreasing Technology for Checkered Plate

Degreasing of pattern plate is a difficult problem in strip production. After many developments, a vacuum squeeze roll for pattern plate has been developed on the basis of non-woven rolls. The basic principle is to cover the vacuum roll shaft with elastic materials of different hardness to adapt to the uneven surface of the pattern plate, and suck the oil into the roll body to achieve the purpose of degreasing. At present, it has been well received by many manufacturers such as Mingtai Aluminum, filling the gap in this field in China (see Figure 4).

Figure 4 Pattern plate vacuum squeezing roll

2.3 Improvement of the Function of the Guide Driving Roll

In the traditional process, most of the guide rolls and S rolls in the production of aluminum sheets and strips are made of polyurethane rubber rolls, but due to their insufficient friction coefficient, the strips slip and deviate from time to time. Non-woven mill multi-purpose roll because of its fiber-wrapped characteristics, its high friction coefficient ensures that it has a stable drive and guidance control, see Table 1.

It can be seen from Table 1 that the friction coefficient of the non-woven roll is 20-40 times higher than that of the steel roll and rubber roll. This high friction coefficient ensures that the tension is increased by 20-40 times at the same time, ensuring the smooth operation of the tension roll. , To avoid the undesirable phenomena such as the sagging of the coil during operation.

Due to the excellent characteristics of the non-woven roll itself, in addition to the above applications, it has also been widely used in aluminum strips, foil ironing, and slitting machines. The life of the roll is 8-10 times that of the rubber roll, which greatly saves the cost and the time required to change the roll for the user, and improves the production efficiency.

At present, DT non-woven mill rolls have occupied a large part of the market in the production of domestic copper strips and aluminum strips, and steel strip manufacturers have also begun to use them. The products have gradually matured and formed a certain scale to replace imports. Tested by the internationally renowned rolling mill manufacturer Italy MINO, the technical indicators and cost performance of DT non-woven rolls have surpassed the imported similar products.
DT non-woven rolls are highly praised by users for their high cost performance, short delivery cycle and convenient maintenance, and have broad promotion value.

3 Vacuum Squeezing Machine

The vacuum squeezing machine is a new type of vacuum squeezing machine modified on the basis of the original non-woven multi-purpose roll. The principle is to change the solid core roll body of the original non-woven multi-purpose roll into a vacuum roll with corresponding rows of holes on the surface. During operation, the liquid on the plate and strip is squeezed into the inside of the roll body, and then the circulating pump of the machine vacuum system is used to pump it away. The liquid is filtered through the gas-water separation system and can be reused. The working principle is shown in Figure 5.

This machine is often used and rigorously tested by many manufacturers such as Aluminum Co., Ltd., Mingtai Aluminum, and Sanfeng Copper. Compared with the original non-woven roll, the drying rate of the vacuum squeezer is increased by more than 30%. Practice has proved that the use of vacuum squeezer is the most effective means of removing liquid in the production of plate and strip. The project has obtained the national utility model patent and passed the expert appraisal organized by the Xianyang Science and Technology Bureau of Shaanxi Province. It is unanimously agreed that the project has reached the domestic advanced level and is an achievement worthy of vigorous promotion.

4 Summary

In the production process of aluminum sheet and strip, cleaning, degreasing, cleaning roll, squeezing water, polishing and other processes are one of the key process measures to ensure its high surface quality. Nylon brush rolls and non-woven multi-purpose rolls have a series of excellent characteristics. It plays an important role in improving the surface quality of aluminum sheet and strip, and it is worthy of vigorous promotion and application.