In recent years, with the rapid improvement of science and technology level and the continuous promotion of industrial revolution, a large number of projects, especially basic projects, have sprung up like bamboo shoots after a spring shower.Nowadays, industry plays an indispensable role in promoting the development of our national economy.This leads to an increasing demand for geotechnical machinery.Under the background of industrial mass production, metal molds for geotechnical engineering machinery emerge as the times require.The emergence and wide application of dies have fully promoted the improvement of productivity and further met the demand of people for production.With the popularization and use of dies, their role in industry becomes more and more important, and dies have become the focus of attention.Die is a tool used to make moulded articles, which has strict requirements in wear resistance, corrosion resistance, strength and toughness, high temperature performance, fatigue fracture, cold and thermal fatigue resistance, etc.Die material plays a key role in die casting, and the quality of the material is related to all aspects of the performance of the die, so the selection of material is particularly stringent when casting the die.
Generally speaking, the materials used for metal dies of casting geotechnical engineering machinery can be roughly divided into four categories: carbon steel, high-speed steel, base steel and high-carbon and high-chromium steel.Carbon steel is widely used in the manufacturing field of our country because of its large output, high cost performance, strong plasticity, cutting and softening, which can well meet the needs of people to cast different dies.High-speed steel has good toughness, thermoplasticity and high quenching hardness.The ductility of high-speed steel is better at high temperature. At the same time, the ductility of molybdenum element itself is better because the high-speed steel is processed from molybdenum element. After processing, the ductility is greatly enhanced.Moreover, in the quenching process, the high-speed steel has a fast cooling speed, which can effectively reduce the occurrence of errors.Therefore, using this material as the manufacturing material of the mold can fully improve the controllability of the designer to the mold, so that the designer can shape the model according to the actual needs and the operation method is simple.
Base steel is processed on the basis of high-speed steel, so it also has some characteristics of high-speed steel, such as high hardness during quenching and short time for secondary hardening during quenching.In addition, the material also has its own characteristics. For high-speed steel, the toughness of the base steel is higher, but lower than that of super-hard high-speed steel, which is suitable for die casting with moderate toughness requirements.The hardness of the base steel is the same as that of the super-hard high-speed steel at a low cost, but it is much lower during machining than that of the super-hard high-speed steel. In other words, under certain conditions, the base steel can replace the role played by the super-hard high-speed steel in the machining process.High carbon high chromium steel has high hardness, strong wear resistance and hardening, but poor plasticity.
Chromium element in high-carbon and high-chromium steel is not less than 12%. When the content of chromium is between 12% and 15%, the hardness effect is the best and the corrosion resistance is strong. Therefore, high-carbon and high-chromium steel has strong hardness characteristics.Because of this, it is often difficult to leave scratches when subjected to external friction, which fully improves the aesthetics of the die.However, at the same time, due to its high hardness, it is difficult for the designer to shape such a mold.In addition to selecting the appropriate die material, the casting process is particularly important for a successful die.Geotechnical engineering is closely related to national livelihood, so it has strict requirements in die casting.Die design usually requires precise size, attractive surface, scientific structure, high productivity and high degree of automation.
In addition, it requires simple manufacturing process, scientific design, low cost and long service time.Therefore, metal molds of geotechnical engineering machinery also have corresponding requirements in casting technology.Common processing techniques in the process of casting mould are special processing, casting method and cutting processing.There are several machining methods under each process, and there are also some differences in the requirements of machining accuracy, machining technology and subsequent processing.For example, low melting point alloy casting in casting method has the same requirements as Shore casting method in machining accuracy and technology, but Shore casting method needs sequential processing, while low melting point alloy casting does not.
Therefore, the designer should master various casting processes, fully consider all factors such as the material selected by the die, the demand of the user for the die and so on when casting the die, and select the appropriate processing technology based on this, so as to achieve the best performance of all aspects of the die, at the same time effectively reduce the cost and maximize the benefits.In addition, the designer should also recognize that solid theoretical knowledge is required to do well in metal die casting of geotechnical engineering machinery, so it is imperative to learn this knowledge systematically.
The construction equipment composition, structural principle, technical performance and its application in pile foundation, underground continuous wall and non-excavation construction are analyzed emphatically.In addition, steel bar processing, concrete construction, circulation, water supply, lifting and other aspects are briefly outlined.The book takes geotechnical construction machinery as the center, and discusses from pile construction, underground continuous wall construction, non-excavation construction, foundation reinforcement treatment, reinforcement processing, concrete construction, etc.
Mold plays an important role in improving productivity and enterprise benefit. Good mold can not be separated from excellent materials and excellent casting process.Therefore, continuous research and optimization of die material selection and casting process can effectively improve the productivity and qualified rate of the die, at the same time, it can better meet the diversified demands of users on the die and promote win-win situation between enterprises and users.This research requires the researcher to have solid professional knowledge and to have a detailed understanding of the composition, principle and performance of various construction machinery and equipment in geotechnical engineering.