New process of manufacturing and repairing alloy steel corrugating rollers

Corrugated roller is the most expensive heart component in corrugated board production line. Its 楞 type rationality, manufacturing precision, wear resistance and pressure resistance, service life and running speed are the main technical indicators to measure its quality and economy. The import and domestic corrugated paperboard board production lines in the industry tend to be more and more wide in width, and the need for faster and faster operation is directly related to the product quality and economic benefits of the carton enterprises.
Corrugated paper in the high-speed continuous marching iron bending process, under the influence of online pressure and the corrugated roll dome relative displacement of the friction squeeze rolling, inclusions in the paper and mineral hard particles impact, so that the top of the crucible wear, From the arc to the flat head gradually, the height of the rake tooth is slowly lower than the standard lower limit. At the same time, some corrugating rollers with low hardness on the boring face will cause pits and depressions on the cul-de-sac surface. Due to the fact that the production line is often not full of paper, the surface of the corrugating roller is unevenly worn and the roller is concave. The low-hardness corrugating roller will collapse, tilt, twist, ellipticity and runout errors due to plastic deformation under continuous high-speed single-tooth meshing and directional operation conditions, which affects the service life and economy of the corrugating roller.
How to improve the sharp wear and deformation phenomenon in the above corrugating roller operation, prolong the service life of the corrugating roller in high speed operation, and improve the economical efficiency of the corrugating roller is an important issue that has been paid attention to by the corrugated paperboard carton industry in China for many years.
Using alloy steel precision forging materials with stable chemical composition, wear-resisting and pressure-resistance, advanced hardened layers of hardness HRC58 (HS80) are obtained with advanced heat treatment process, and computer-aided design of reasonable crucibles is realized by CNC grinding machines. Precisely grinding enamel-shaped and drum-shaped mid-height, surface-plated high-quality micro-crack wear-resistant hard chrome is the high-quality corrugating roller that has been painstakingly researched and repaired for years, and has been carefully researched and repaired with abrasion resistance, corrosion resistance, high precision and durability. New technological achievements achieved by the product.
First, the selection of materials China's current steel standards, the same chemical composition of a wide range of grades, its upper and lower limits are often connected with the adjacent brand (such as the domestic corrugated roller commonly used 35CrMo carbon content and other chemical composition cap In the middle and lower limits of 42CrMo), the chemical composition error of the same brand of steel is great, which brings great harm to the quality control of heat treatment.
We all know that the level of carbon content will directly affect the hardness of quenched martensite in the corrugated roll alloy steel roll body. For example, the carbon content of the alloy steel is 0.3%, and the martensite hardness is (HRC) 49-55. The carbon content is 0.4%, and its martensite hardness is (HRC) 54-60. The carbon content is 0.5%, and its martensite hardness is (HRC) 58-62.
Therefore, rigorous selection of materials, selection of high-quality 42CrMo and 50CrMo precision forgings, strict chemical composition of the good material off, the carbon, chromium, silicon, manganese, aluminum and other major components of the index is controlled within a certain range, for the subsequent preparation of heat treatment and Quenching quality and stability create the basic conditions.
Second, the advanced heat treatment process corrugating roller using alloy steel 42CrMo, 50CrMo precision forgings with good hardenability, but the special geometry and size of the roller surface to the heat treatment brings great difficulty and quality instability factors, it has been The major problems of domestic and foreign counterparts are devoted to research.
It is well known that corrugating rolls with excellent heat treatment quality should be sufficiently hardened to achieve the desired depth of hardened layer, uniform hardness without soft tape, and no cracking. The conditions of full and uniform hardenability and prevention of quench cracking, in addition to the stable composition of the material and adequate and reasonable preparation of heat treatment (such as quenching and tempering, repeated removal machining and welding stress), also require quenching in the cooling process, the temperature phase The cooling rate distribution must be in the quenching allowable cooling rate zone to realize the "water quenching and cooling" cooling rate distribution, that is, the high-medium temperature cooling stage has a water-like cooling rate to avoid the non-martensite structure. Change area. In the low-temperature stage, the cooling rate should be as low as possible, especially when the temperature is about 300°C, the cooling rate should be as slow as oil to avoid deformation and cracks.
The new process has undergone process reforms for traditional heat treatment methods. First, by adjusting the material, stabilizing and reducing the chemical composition range, adjusting the heating method and heating temperature to move the cooling rate allowable area. The second is to move the cooling curve by selecting a quench medium with superior performance and adjusting the cooling mode so that it enters the allowable cooling rate zone.
So far, domestic medium-frequency quenching of alloy steel generally uses polyvinyl alcohol solution as a quenching medium. Polyvinyl alcohol began to be used as an additive for water in the mid-1950s. It is currently used in China. Due to its fear of freezing in winter, it is susceptible to deterioration and odor in other seasons, and it is easy to block and inject pores during use, making maintenance and maintenance difficult. Effective service life is short. At the same time, it is difficult to accurately detect and control the concentration because the use of low levels (usually used in the range of about two to three-thousandths of a thousandth, and a one-thousandth of a change in its concentration can cause a large difference in performance), so most Only by the operator's experience to control (such as: see how much foam and feel the viscosity by hand, etc.), it can not guarantee a stable quenching quality. As it is not conducive to concentration management, it has been rarely used abroad.
The new process introduces SZ water-based quenching liquid and quenching process for the quenching of corrugating rollers and other alloy steels, effectively ensuring the stability of quenching quality. SZ water-based quenching liquid is Polyalklene Glycols quenching agent. It has insolubility and can be quenched and cooled faster than water by adjusting to a certain concentration. When the workpiece is quenched, the sprayed quenching liquid will adhere to the desolvable polymer film on the working surface. The film can effectively destroy the vapor film formed on the workpiece by the water, thus increasing the high temperature cooling rate of the water and making the workpiece different. The cooling rate of the part tends to be uniform, and the presence of this layer of polymer film also reduces the low temperature cooling rate of water, reducing the risk of quench deformation and cracking. At the same time, the concentration of quenching media is easy to detect and control, ensuring the stability of the process. Secondly, within a certain range, the temperature of the quenching medium is controlled by changing the stirring conditions to ensure that the cooling characteristic curve of the quenching medium falls within the permissible cold speed zone, so that the quenched workpiece achieves quenching with high hardness and uniformity, no cracking, and guarantees stability The hardened layer is deep. Because the layers in each process are strictly controlled, the amount of deformation of the quenched workpiece can be stably less than 0.15 mm.
Why some grooves in a pair of corrugating rollers (including the guide Plate slot, vacuum suction and suction slot) are easy to quench cracking and there are obvious soft bands, so the quenching tends to appear soft. This is because medium frequency induction quenching is an instant heating of the induction coil at a constant speed. With the upward movement of the induction coil during quenching, the lower end of the slot teeth are blocked by the slot to block the magnetic field and upward transfer of heat, and the power and heat are concentrated and the instantaneous overheating is easily quenched. Cracking teeth. At the same time, the upper end of the slot blocks the heat transfer from the lower part due to the slot, the temperature has not yet reached the phase change temperature but the induction coil has risen and the quenching is not hard, forming a distinct soft band. To reduce the risk of quench cracking, the quenching temperature is often reduced or a relatively low carbon content 35CrMo material is used at the expense of quenching hardness.
Corrugated roller similar to the following 2.5 module pinion, common frequency quenching frequency is generally between 2500 ~ 8000Hz. The corrugating roll with a large diameter is between 2500 and 4000 Hz. Therefore, there is a clear temperature difference between the tooth top and the tooth groove when quenching, which often results in hardened tooth tops and soft tooth grooves after quenching, and concentrates a large tensile stress near the tooth grooves, which can easily cause axial cracking.
The new process took targeted breakthroughs in heat treatment equipment, induction coil, water spray ring, distance between induction coil and water spray ring, clearance between two rings and workpiece, spray angle, heating method, and speed and method of induction coil movement. Improvements have been made to obtain a hardened layer with a depth of more than HRC58 and a depth of 6 to 7 mm, uniform hardness, and a soft groove with a grooved roller, thus ensuring the stability of heat treatment quality.
Third, the quality of the chrome-plated layer Hardened and fine-ground corrugated roll after plating more than 0.1 mm hard chrome plating, can reduce the friction surface friction coefficient, enhance the wear resistance of enamel teeth, extend the life of corrugating roller. At present, the traditional hard chrome plating process is applied in the country. Since the cathode current efficiency is low, it is generally 12% to 14%. The plating solution concentration and the plating temperature are controlled to be rough, and most of them are judged by the operator based on experience, so the coating quality is unstable. The performance is as follows: 1. The coating thickness is not easy to control. If a pair of corrugating rollers are not plated in pairs, the upper and lower corrugating roller plating thickness errors may even reach 50%. 2. Poor plating ability, especially grooved corrugating roller, flank teeth are often not coated with chromium or plating is very small, resulting in corrugated roller wear and tear during use. 3. The hardness is low and non-uniform. Since the corrugated roll plating is a deep well plating tank, if there is no agitation, the temperature difference between the upper and lower sides is large, resulting in the upper temperature high chromium layer is soft, and the lower temperature lower chromium layer is brittle, which seriously affects the quality of use.
The new process adopts the most advanced HBEF25 high-efficiency hard chrome plating process in the world currently in the functional chrome plating process. The advantages are: 1. Using a larger current density than the traditional electroplating hard chrome process, the cathodic current efficiency reaches 22-26%, twice as high as the conventional chrome plating process, and the deposition speed is 2 to 3 times that of the conventional chrome plating. Therefore, the plating ability is greatly improved. 2. The microhardness of the coating reaches HV900-1050, and the traditional process is HV700-800. 3. The wear of the hard chrome plating obtained by this process is nearly 25% less than that of the conventional plating. 4. The thickness of the coating is uniform due to the reduction of excessively high current and excessively thick deposits. 5. The coating is smooth and delicate. 6. Another major advantage of the HEEF-25 coating is the number of micro-cracks as many as 400 per cm. Microcracks represent a situation that is more susceptible to corrosion. Corrosion occurs along these microcracks. The smaller the number of microcracks, the deeper and longer the cracks, and the easier it is to corrode. The process generates many shallow and short micro-cracks, and the anti-corrosion capability is increased, so that the defects are less corroded.
Strict process management during electroplating, each roller set process parameters according to diameter, length and plating area, strict operation records, continuous circulating filtration of bath, strict control of plating temperature according to process requirements, strict detection and control of bath Concentration and various indicators. Ensure that hard chrome plating above 0.10mm is evenly plated on the top of the tooth most susceptible to wear and that a certain percentage of chromium plating is applied to the root and grate to obtain a harder, smoother, brighter, more wear-resistant than traditional hard chrome processes. Hard chrome plating.
Practice has proved that although the process cost is 3 times that of traditional process, it greatly improves the quality of the product, improves the wear resistance by 40%, prolongs the service life, and reduces maintenance costs.
Fourth, scientific design 楞 type Corrugated roller paper consumption for corrugated board manufacturing industry, is an important factor affecting the cost of production technology companies. Some foreign countries with relatively advanced packaging industry have attached great importance to the economic indicators of corrugated roller paper consumption. For example, Mitsubishi Japan has designed the same type of corrugated roller type as standard type and economic type separately. Therefore, although the height is the same, but the number of turns per 300 mm is different, the paper consumption rate (also known as buckling, shrinkage and corrugation, etc.) is completely different. Taking a three-layer corrugated paperboard production line with an annual output of 10 million square meters as an example, if the paper consumption rate is reduced by 1%, then more than 100,000 square meters of corrugated base paper can be saved, and the larger the output, the thicker the paperboard (such as five floors). Seventh floor), the more potential savings are. The paper consumption rate is the ratio of the length of a single tooth profile curve to the length of a single tooth. That is, the ratio of the length of the corrugated fiber to the length of the corrugated base paper after forming. Its rationality is an important economic indicator for directly measuring the quality of corrugating rollers.
The new process is computer-aided and scientifically designed. Users can directly participate in the design when repairing and making new corrugating rollers. The software can be used to evaluate and select the economy, rationality and quickness of various types of stencils.
With the rapid development of the carton industry, corrugating rollers tend to be wide and large in diameter.