Current status and development of material thermal processing technology

At present, metal materials are still the most widely used mechanical engineering materials. Material thermal processing (including casting, forging, welding, heat treatment, etc.) is an important processing procedure in the mechanical manufacturing industry, and it is also the intersection and interface technology of the two major industries of materials and manufacturing . The material can only become a part or a blank after hot processing. It not only makes the material obtain a certain shape and size, but more importantly, it gives the material its final composition, organization and performance. Since thermal processing has both functions of forming and modification, compared with cold processing and systematic material preparation, its process quality control is more difficult. Therefore, it is more urgent to simulate the process of material thermal processing and optimize the process design. In the past two decades, material thermal processing technology simulation technology has developed rapidly and has become the most active research hotspot and technological frontier in this field.
0 Preface

0.1 Make the thermal processing of metal materials from “technique” to “science”, completely change the backward appearance of thermal processing

The thermal processing of metal materials is an extremely complex high-temperature, dynamic, and instantaneous process, which is difficult to observe directly. In this process, the material undergoes a series of complex physical, chemical, and metallurgical changes such as various microstructure changes such as liquid flow filling, solidification crystallization, solid flow deformation, phase transition, recrystallization and recrystallization, and the generation and disappearance of defects. And finally it becomes a blank or component. We must control this process so that the composition, organization, and performance of the material are in the best state, and defects must be minimized or driven to the least harmful place. But none of this can be directly observed, and indirect testing is also very difficult.

For a long time, the theoretical knowledge of basic disciplines has been difficult to quantitatively guide the material processing process, and the design of material thermal processing technology can only be based on “experience”. In recent years, with the development of experimental technology and computer technology and the deepening of material forming theory, the process design method of material forming process is undergoing qualitative changes. Material thermal processing technology simulation technology is to dynamically simulate the material thermal processing process in the laboratory through numerical simulation and physical simulation under the guidance of material thermal processing theory, predict the final structure, performance and quality of the material under actual process conditions, and then realize the thermal Optimized design of processing technology. It will make the thermal processing of materials move from “technique” to “science” in this direction, and take the first step to realize virtual manufacturing and make a qualitative leap in the technical level of machinery manufacturing.

0.2 is an advanced method to predict and ensure the quality of the thermal processing of materials, especially to ensure the success of the first-time manufacturing of key large parts, and has significant application background and benefits

One of the difficulties in the development and production of major electromechanical equipment in my country is the manufacture of large parts; the key to the manufacture of large parts is thermal processing. Before 2015 in my country, major electromechanical equipment such as hydropower, thermal power, nuclear power, metallurgy, mining, petrochemicals, etc. all had an urgent need for the manufacture of key large parts. Taking the Three Gorges hydropower unit as an example, the single unit has a capacity of 700,000 kilowatts, and the weight and size of the five major components (rotor, volute, main shaft, seat ring, and top cover) rank first in the world. The runner has a diameter of 9.8 meters and a weight of 500 tons. The cast-welded structure is very difficult to manufacture.

Due to the large shape and weight, many varieties, small batches, long production cycle and high cost, it is urgently required to “manufacture once successfully”. Once it is scrapped, it will suffer heavy economic and time losses and cannot be recovered. Because the traditional thermal processing technology design can only rely on experience and adopts the test and error method (Test and Error Method), it is unable to ideally control the evolution of the internal macro and micro structure of the material, so there have been many tragic accidents of large-scale scrapping and put into use It is also difficult to eliminate defects such as shrinkage cavity, shrinkage porosity, inclusions, segregation, hot cracking, cold cracking, mixed crystal, etc., and many large pieces run with damage. Thermal processing technology design based on process simulation and optimization can eliminate “hidden dangers” in repeated comparisons of computer simulation processing, thereby ensuring that key large parts are successfully manufactured at one time. This has been confirmed by many application examples at home and abroad. 0.3 is the technical foundation for rapid design and manufacturing, virtual design and manufacturing, and distributed design and manufacturing

Thermal processing is an important process in the manufacturing industry. The development of the manufacturing industry and the transformation of manufacturing models are inseparable from the technological progress of thermal processing. The National Science Foundation (NSF) uses the chart “The impact of different development stages of knowledge/automation on manufacturing” (see Figure 1) to illustrate the dependence of design and manufacturing technology on knowledge and automation [1]. From the perspective of knowledge, human beings have gone through the process of skill→manual guidance→expert system. To reach a more complete level, process/process simulation must be carried out. Because only through simulation can people understand the essence of the process, predict and optimize the results of the process, and quickly make design and process changes to the rapidly changing market changes; in addition, only through process simulation can design and manufacturing be integrated. It is the knowledge (technical) basis for rapid design, manufacturing, virtual design, manufacturing, and distributed design and manufacturing. 0.4 This field is the intersection of multiple disciplines, which is of great significance to the application of high-tech to transform traditional disciplines and to develop emerging engineering and technology disciplines

This research field involves thermal processing disciplines such as casting, forging, welding, and heat treatment of metallic materials; physical chemistry, computational mathematics, graphics, material forming theory, heat transfer, mass transfer, fluid mechanics, solid mechanics, metal science, metal Basic technical disciplines such as physics; high-tech disciplines such as computer application, testing technology, network technology, and new materials. The academic value of this research lies in: using modern computers and testing technology as means to build a bridge between basic technical disciplines and thermal processing of metal materials, so that the theories of basic disciplines can directly and quantitatively guide the process of thermal processing of materials, reflecting basic disciplines, The cross and organic combination of high-tech and material thermal processing disciplines. It turns the subject of thermal processing of materials from a “technique” into a “science”, and it will promote the theory of thermal processing of materials, computer graphics, computer metallography, computer stereology, computational heat transfer, computational fluid dynamics, concurrent engineering, etc. The formation and development of emerging interdisciplinary subjects.