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The role of tungsten and molybdenum in high-speed steel rolls

The role of tungsten and molybdenum in high-speed steel rolls

The role of tungsten and molybdenum in high-speed steel rolls Tungsten and molybdenum are the main alloying elements in ordinary high-speed steel rolls. The chemical properties of tungsten and molybdenum are similar, and their effects on the microstructure transformation and properties of high-speed steel rolls are almost the same. The difference is that molybdenum causes a lower temperature of the structural transition. The main reason for using high-speed steel to manufacture rolls is to use the excellent red hardness of high-speed steel to improve the high-temperature wear resistance of rolls. The excellent red hardness of high-speed steel rolls is firstly attributed to the strong aggregation resistance of M2C and MC. A large amount of retained austenite can also be obtained in the quenched structure of ordinary carbon steel and low alloy steel. Decomposition of this retained austenite at high temperatures rarely increases the hardness. The austenite in these steels usually decomposes at a lower temperature, while the precipitated Fe3C type carbides rapidly aggregate at a slightly higher temperature, and the aggregation of carbides is the direct cause of softening. In high-speed steel, the precipitation of carbides into very fine particles and the decomposition of residual austenite jointly cause secondary hardening, and the carbides always maintain their fine size, so high-speed steel has good red hardness. In high-speed steels, the elements that influence this phenomenon are tungsten and molybdenum. The atomic size of tungsten and molybdenum in high-speed steel is much larger than that of any other element, and the diffusion rate is slower. In order for carbides to continue to accumulate, not only chromium is needed.

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What is the role of chromium in high speed steel rolls?

What is the role of chromium in high speed steel rolls?

What is the role of chromium in high-speed steel rolls? Chromium in high-speed steel is partially present in M6C type carbides and can also form M23C6 type carbides. M23C6 can be completely dissolved at a lower quenching temperature, so that the solid solution can reach carbon chromium saturation without affecting the grain size. Chromium can also promote the complete dissolution of M6C in austenite, thereby improving the hardenability and red hardness of high-speed steel. In addition, when high-speed steel is tempered at 450-525°C, a part of chromium precipitates from martensite, which promotes dispersion hardening; another part of chromium remains in solid solution a to prevent softening when heated to higher temperatures. Adding 3%-4% chromium can obtain three times slightly higher hardness. Chromium can also significantly reduce oxidation in high speed steels. However, if the chromium content is too high, the excess chromium will participate in the formation of carbides precipitated during tempering. Such chromium-containing carbides tend to precipitate at lower temperatures, reducing the thermal stability of high-speed steels. If the chromium content is too high, the unevenness of the carbides also increases. Since chromium increases the amount of M7C3 carbides in high-speed steel rolls and reduces the amount of MC carbides, and the hardness of M7C3 carbides is lower than that of MC carbides, which is detrimental to wear resistance. However, for rolls with low chromium content

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Development and production status of high speed steel roll

Development and production status of high speed steel roll

Development and production of high-speed steel roll High-speed steel roll is a hot roll material with short history, rapid development and wide application prospect. High-speed steel, also known as wind steel or pointed steel, means that it can harden even if it is cooled in air during the quenching process and is very sharp. It is a complex composition of alloy steel, containing tungsten, molybdenum, chromium, vanadium and other carbide forming elements. The total amount of alloying elements is about 10% to 25%. The application of high-speed steel roll is an important part of the development of modern steel rolling production. This is another major change in the development of the iron and steel industry after microalloying, controlled rolling and cooling technology. In Japan, high-speed steel rolls have been widely used in the production of steel rolling of plates, profiles, bars and wires, not only for work rolls, but also for support rolls. The good wear resistance of high-speed steel rolls is closely related to their different characteristics from traditional rolls. The unit price of high-speed steel rolls is indeed higher than that of high-boron and high-nickel-chromium rolls. However, due to material characteristics, the steel passing capacity of high-speed steel rolls is much higher than that of high-boron and high-nickel-chromium rolls. For example, the passing capacity of 12 1/4-cut rebar and high-speed steel K1 single-slot steel is 350 tons, 150 tons of high-boron and 100 tons of high-nickel.

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Introduction of Roller Development

Introduction of Roller Development

Introduction to the development of the main working parts and tools for the continuous plastic deformation of metals on the rolling mill. The roll is mainly composed of three parts: roll body, roll neck and shaft head. The roll body is the middle part of the roll, which actually involves rolling metal. It has a smooth cylindrical or grooved surface. The roller neck is installed in the bearing, and the roller force is transmitted to the frame through the bearing seat and the pressing device. The shaft head at the transmission end is connected with the gear seat through the connecting shaft, and the rotating torque of the motor is transmitted to the roller. The rolls can be arranged in a two-roll, three-roll, four-roll or multi-roll arrangement in the roll stand. With the development of metallurgical technology and the development of rolling equipment, the variety and manufacturing process of rolls are also developing. In the Middle Ages, low-strength gray cast iron rolls were used to roll soft non-ferrous metals. In the middle of the 18th century, Britain mastered the technology of producing cold cast iron rolls for rolling steel plates. In the second half of the 19th century, the progress of European steelmaking technology required the rolling of large tonnage ingots, whether gray cast iron rolls or chilled cast iron rolls, their strength could not meet the requirements. The birth of the carbon content of 0.4% ~ 0.6% of the ordinary cast steel roll. The emergence of large-scale forging equipment has further improved the strength and toughness of the forging roller of this composition. In the early 20th century, the use of alloying elements

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The role of rolls in the rolling mill production line!

The role of rolls in the rolling mill production line!

The role of rolls in the rolling mill production line! The roll includes the main equipment, auxiliary equipment, lifting and transportation equipment and auxiliary equipment, each of which is very important and indispensable. A roll is a machine that rolls steel between rotating rolls. Rolling mills are said to have appeared in Europe in the 14th century. Continuity, automation, specialization, high quality and low consumption are the development trends of modern rolling mills. The working frame of the rolling mill is used to install the frame and is fixed on the foundation, also known as the floor. To bear the dead weight and dumping moment of the work frame, while ensuring the accuracy of the installation size of the work frame. So, what does the work of the rolling mill include? The main equipment of the rolling mill is the work frame and the transmission device. The machine base is composed of roll, roll bearing, frame, guide rail seat, roll adjusting device, upper roll balancing device and roll changing device. The roll is an important part of the roll in the rolling mill. It uses the pressure generated by a pair or set of rolls to roll steel. It mainly bears the influence of rolling brake, static load, wear and temperature change. Roll is divided into hot roll and cold roll. The role of the roll in the rolling mill production line is crushing. For example, a 3mm thick steel plate is rolled to a thickness of 0.5mm by a rolling mill. Different working conditions of the roller material is very different. Generally speaking, it uses materials with high hardness, high strength and small deformation. In

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Classification of rolls

Classification of rolls

Classification of rolls There are many classification methods for rolls, mainly including:(1) according to product types, they are divided into strip steel rolls, special-shaped steel rolls, wire rod rolls, etc. (2) according to the position of the rolls in the rolling mill series, there are open rolls, rough rolls, fine rolls, etc. (3) according to the roll function, it is divided into scale breaking rolls, perforated rolls, leveling rolls, etc. (4) according to the material of the rolls, there are steel rolls, cast iron rolls, carbide rolls, ceramic rolls, etc.;(5) according to the manufacturing method is divided into casting rolls, forging rolls, surfacing rolls, inlaid rolls, etc.;(6) according to the state of rolled steel is divided into hot rolls and cold rolls. Various categories can be combined accordingly, so that the roll has a clearer meaning, such as centrifugal casting of high chromium cast iron work rolls for hot strip steel. Common drum materials and uses are shown in the table. The performance and quality of a roll generally depends on its chemical composition and manufacturing method, and can be evaluated by its microstructure, physical and mechanical properties, and the type of residual stress inside the roll (see roll inspection). The effect of the roll on the rolling mill depends not only on the material and metallurgical quality of the roll, but also on the conditions of use of the roll, roll design, operation and maintenance. The rolling conditions vary greatly for different types of mills. The factors contributing to the difference are:(1) mill conditions. such as mill type, rolling

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Precautions for installation and use of roll ring

Precautions for installation and use of roll ring

Precautions for installation and use of 1. roller rings The following points should be paid attention to in the installation of carbide roller rings: 1. The roller ring machine should strictly check the size of the roller ring according to the process design requirements. In order to ensure the same batch of roller rings, it is more suitable for the same batch of attack with the same brand of roller rings, matching roller ring material. The performance and density should be consistent. If there is a difference, it will affect the dynamic balance and the use effect of the roller ring. 2. Roller ring installation and roller ring. The matching surface between the roller shaft and the roller cone sleeve and the sleeve should be kept clean, and the matching place should be kept clean and reasonable. The assembly should not be too tight or too loose. If the assembly is too tight, the rolling temperature will increase. At this time, the roller ring is in a state of large tensile stress, once the rolling force is shaken, it will cause the roller ring to crack radially, so that the roller ring is cracked and scrapped. If the combination is too loose, the roller ring and the roller shaft will slide relative to each other, resulting in frictional heat, resulting in thermal stress and cracks in the roller ring. In severe cases, the roller ring and the roller shaft taper sleeve can be discarded. Therefore, the installation pressure of the roller ring should be strictly controlled. 3. Roll ring is a brittle material. It is heavy and easily damaged. Therefore, collision is strictly prohibited during the installation, transportation and handling of the roller ring. Wait. 2. reasonably determine the rolling volume roll ring single groove rolling to a certain time. When the rolling groove produces a

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