For any type of corrugating roller, it has the same basic function and wear mechanism. Corrugated paper is subjected to high-speed, continuous-punching, ironing and bending processes. Under the action of the online pressure, relative displacement of the corrugating roll dome is continuously performed and friction-squeezing rolling occurs, which is impacted by the inclusions and the hard particles of the mineral hard particles in the base paper. Causes the corrugating roll to wear violently at the top of the crucible, gradually becomes irregular shape from the circular arc, continuous high-speed operation, and the height of the crucible slowly becomes lower, so that the produced cardboard gradually tends to the lower limit of the standard. Some corrugating rollers with low surface hardness will also cause dimples and depressions in the dome's surface, exacerbating the wear process.
Due to the fact that the production line is often not full of paper, the uneven wear of the corrugating roller surface causes the corrugating roller to be concave, resulting in defoaming of the cardboard. The low-hardness corrugating roller will continue to fall down, tilt, twist, increase ellipticity and runout error due to plastic deformation under the continuous high-speed single-tooth meshing and directional operation, and accelerate the service life and economic performance of the corrugating roller.
From the working principle and wear mechanism of the above corrugating roller, it can be seen that the use process of the corrugating roller is a process that is constantly being worn out. The forms of damage are summarized as:
Normal wear, wear parts are domes;
· pits and depressions caused by soft roll surface, thinned reinforcement layer and poor paper quality;
·Inflation caused by improper management;
· The base body is soft, and the roll is poor in manufacturing quality due to falling, tilting, and twisting.
How to extend the life of corrugating rollers
For any grade of corrugated board production line, corrugated rollers are always one of the most expensive and vulnerable components. Its economic performance and service life have always been an important issue for the corrugated box industry. Raising the wear resistance of the corrugating roller and prolonging the service life of the corrugating roller is an effective method to reduce the production cost of the corrugated board. At present, there are light industrial standards in China, and there are also corrugated roller manufacturers' enterprise standards that effectively control the quality of corrugating rollers.
The requirements for surface hardness and depth of hardened layer are shown in the following table. The thickness of the coating that is completed under different heat treatment processes determines the hardness of the corrugation, and is an effective parameter of the corrugating roll.
Corrugated roller manufacturer's corporate standard
At present, most manufacturers use composite processing, intermediate frequency quenching after nitriding or chrome plating, nitride layer thickness of 0.5 ~ 0.6mm, chromium plating layer thickness of 0.10 ~ 0.15mm, the mainstream of the process for the quenching after chrome plating. In order to meet this requirement, the materials of various manufacturers now use 42CrMo and 48CrMo forgings to meet their hardenability and hardenability. The service life of the composite processing roller is 800 to 9 million meters. In order to win the leading position in the market, manufacturers have tried new steel grades in terms of materials, adopting new technologies in the process, and forming the competition in the three main processes of medium-frequency quenching, chrome plating, medium-frequency quenching and tungsten carbide spraying, and chromium plating after laser quenching. For the choice of carton manufacturers to provide a variety of programs. The demand of the market will eventually become the dominant direction of which process, and the market will make a choice based on quality and cost.
The three processes after the process
(1) → grinding teeth → medium frequency quenching → stress removal → sandblasting → chrome plating (thickness 0.10-0.15mm) — lifespan 800-900 million metre;
(2) → grinding teeth → (medium frequency quenching) → sandblasting → preheating → bottoming → spraying tungsten carbide (thickness of 0.05 ~ 0.06mm) → polishing - life of 2000 to 50 million meters;
(3) → grinding teeth → laser quenching → sandblasting → chrome plating (thickness 0.05 ~ 0.10mm) - life 1300 ~ 15000000 runm.
Corrugated Roller Condition Under Three Mainstream Processes
Medium frequency quenching corrugating roller
Medium-frequency quenching after chrome plating is medium-frequency quenching and chrome plating is a long history of technology, the process is mature, but due to medium frequency quenching is bare heating, it is inevitable oxidation, decarburization; medium frequency quenching using water-based quenching liquid, quenching the object is high hardenability The CrMo steel inevitably generates cracks and soft spots. Intermediate frequency quenching has the advantage of thicker layers, but the medium frequency quenched corrugating rollers lower rollers have problems such as large deformation after quenching, but the greatest advantage of chrome-plated corrugating rollers after medium frequency quenching is lower cost.
Tungsten carbide corrugating roller
Qualified tungsten carbide corrugating roller is a high-end technology product in the corrugating roller manufacturing industry. Its excellent wear resistance is undeniable, but the application of tungsten carbide corrugating roller also has many difficulties. Firstly, its manufacturing cost is relatively high; secondly, the use environment is strict, and it cannot withstand sand gravel rolling; pitting and dents are more likely to occur under poor paper quality; the third is that quality control is difficult and must be very high. The temperature of the processing, otherwise poor wear resistance, low life. Such as cobalt-based tungsten carbide, available 2100 ~ 2200 °C heating temperature, its wear resistance is the lower limit of the life of tungsten carbide corrugating roller family, only about 20 million meters long.
Laser Quenching After Chrome Plating
Laser Enhanced Technology Principle
The laser surface enhancement technology is based on the high energy density heating of the laser beam and the self-cooling of the workpiece. Laser surface hardening is a technology that rapidly strengthens the surface of metal materials and parts. It can improve the surface hardness, strength, and wear resistance, and at the same time, it still maintains a good comprehensive mechanical performance of the heart. Corrugated roll surface hardening is a phase transformation of the laser surface.
Laser Enhanced Technology Features
• Laser surface hardening has little dependence on the hardenability of the material. Laser-strengthening triggers the possibility of lower-grade materials instead of engaging in graded materials.
· Dispersion strengthening. The austenite grains formed in the rapid heating and rapid cooling process environment do not give birth opportunities for growth. The dispersed austenite grains form a dispersed martensite or shell-like phase, making martensite or shellfish. The body has lattice strengthening and has a dispersion strengthening effect.
·Without oxidative decarburization and quenching, in the traditional heat treatment, if there is no protective measure in the heating process of the steel, oxidation and decarburization will occur, which will reduce the hardness, wear resistance, service performance and service life of the steel. Laser phase-enhancement due to the use of the light-absorbing coating can form a gas-protecting atmosphere around the spot to protect the treated surface from oxidation and to protect the surface of the workpiece.
· Anti-fatigue problem, the laser treated workpiece surface is in a compressive stress state, this performance makes the gear more resistant to fatigue, so that fatigue phenomena such as cracks, furrows, adhesion and delay appear, extending service life.
·Strong working layer, conventional heat treatment, including intermediate frequency quenching, from the table and its hardness value has a significant drop gradient, the laser-strengthened workpiece, the hardness of the entire strengthening layer is almost the same. The strong working layer such as the laser strengthener avoids the phenomenon that the conventional heat-treating parts are once worn on the surface and the wear rate is accelerated.
• Non-deformed quenching, due to the containment of the matrix, the stress of the laser-strengthened surface layer is insufficient to deform the workpiece.
• No pollution.
The improvement of corrugating roller life guarantees the longest running time of the production line, reduces the shutdown and roll change time, greatly improves the production efficiency of the manufacturers, and reduces the number of paper breaks in the shutdown compared with the past, which reduces the waste of the core paper. The improvement of the abrasion resistance of the corrugating roller makes the selection of the core paper more extensive, so that the corrugated board manufacturer can effectively reduce the cost. The emergence of laser corrugating rollers provides corrugated paper manufacturers with a cost-effective corrugating roller, which saves a large number of direct costs for corrugating roller manufacturers.
At present, in the application of corrugating rollers, mid-frequency corrugating rolls are used in medium and low speed production lines; the application of tungsten carbide corrugating rolls is concentrated in high-speed production lines, but it is difficult to enter the middle and low-speed corrugating roll markets due to high cost. The application of laser corrugating roller is relatively wide. Compared with middle frequency corrugating roller, it has higher and more stable quality and longer service life in the middle and low speed production lines. In the high-speed production line, the laser corrugating roller needs only minimal deformation. After grinding, you can meet the requirements of high-speed production lines. Taken together, laser corrugating rolls and tungsten carbide corrugating rolls are high-tech products. Among the three major roll making processes, laser corrugating rolls have the best performance-cost ratio.
Reprinted from: Jingtao Paper Tube
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