With the rapid development of science and technology, the weight, size, and weight of steel ingots required in steel, energy, and petrochemical production have undergone significant changes and increased significantly. In order to prevent or reduce internal metallurgical defects and quality of steel ingots and hidden dangers, in the forging process of large forgings, it is necessary for us to choose a new process for analysis to ensure the smooth progress of the forging work. This article starts from the forging process of large forgings and makes a relevant technical analysis of its problems for the reference of relevant people.
1. Analysis of the forging process of large forgings
Large forgings are core components for the production of large-scale complete facilities such as metallurgy, electric power, chemical industry, petroleum, and transportation. They play a decisive role in the construction of the national economy and the development of modern society. However, when analyzing the forging and production processes of today’s large forgings, the problems faced are still quite prominent. For this reason, in today’s large forging production process, we need to analyze and summarize its forging process.
1). Overview of large forgings
Large forgings are indispensable basic components in the construction of major national scientific and technological equipment and major projects. Whether produced by domestic enterprises such as electric power, water conservancy, petrochemical industry, and military industry, or in private enterprises such as industrial and civil construction and mining, they play an important role. vital significance. It can be said that in today’s social and economic development, the production process of large forgings has become the key to measuring a country’s machinery production and manufacturing, and is also an important way to determine its scientific and technological level. Therefore, in today’s industrial production, the forging process of large forgings has attracted more and more attention.
2). Analysis of forging technology of large forgings
Among today’s large forging technologies, drawing and upsetting are some of the most common technologies. They are the main technical means and methods in the application process. Compared with the traditional rough blank deformation forging technology, there are It has the advantages of small size, large deformation, and strong defect control ability, and can effectively avoid other quality hazards caused by forging during the application process. An analysis of my country’s large-scale forging process shows that it has a history of half a century of application. In terms of application over the years, a large amount of money, manpower, and material resources have been invested in research every year, which has also resulted in various forging processes being developed. effective optimization and control.
2. Analysis of the forging process of large forgings
In the forging process of large forgings, in order to completely eliminate defects within the steel ingot and improve the structural quality, in addition to selecting reasonable supporting equipment during the forging process, we must also pay great attention and recognition to the forging process and forging technology. Drawing is one of the most popular techniques in the forging of large forgings. Its applications are as follows:
1). Analysis of the elongated forging process
In today’s large forging process, drawing is one of the main forging processes that determine the quality of large forgings. Most countries in the world use this technology to conduct experiments and research in the production of large forgings. Through a summary of relevant working examples, it can be concluded that the application of this technology can effectively eliminate quality hazards within forging, and obtain high forging hydrostatic pressure and deformation, thereby eliminating voids within the steel ingot, and improving the plasticity and forging of the structure. performance. Generally speaking, the application of the drawn forging process is mainly to optimize the internal quality defects of forgings by changing external conditions and external stress, which is to optimize the forging technology from top to bottom. In terms of the selection of the elongation forging process, it can be divided into upper and lower anvil and lower V-shaped anvil elongation from top to bottom. Later, by changing the elongation anvil shape and process conditions. After long-term exploration and research, forging workers have made remarkable achievements and made great contributions to improving the quality of large forgings. As the size of large forgings increases, the requirements for the quality of forgings are higher. Therefore, the forging ratio must be re-evaluated. Understand and conduct research on forging methods and technologies, microstructure simulation, and control of forging; establish a systematic simulation system to improve the forging process, and propose reasonable and effective forging methods based on the comparison of the advantages and disadvantages of existing forging methods to improve production Efficiency and quality of large forgings.
2). Key points for the application of the lengthening process
During the forging deformation process in a forging factory, due to the influence of friction and temperature gradient, there is always a large or small difficult deformation zone near the contact area between the tool and the forging blank. The size and shape of the refractory zone have an important influence on the deformation distribution and stress state inside the forging, thus affecting the quality of the forging. When drawing out, there is a difficult-to-deform area near the contact area between the anvil and the forging billet. Its pressing direction is perpendicular to the axis. Since the metallurgical defects of the steel ingot exist near the axis, during the drawing-out step, the area near the axis should be The formation of large deformation and good stress state is beneficial to the repair of metallurgical defects in steel ingots. The existence of a difficult-to-deform zone in the contact area between the forging blank and the anvil is exactly in line with the deformation characteristics of the elongation step. From the perspective of deformation, when there is a difficult-to-deformation zone in the contact area between the forging blank and the anvil, the core area will be deformed. The amount must be large; from the perspective of stress, during the elongation step, due to the existence of rigid end constraints, when the flow speed of the metal in the center is large, in order to maintain the continuity of the deformed body, the upper and lower dilemma deformation zones must block the metal near the axis through the rigid end. flow, causing large axial compressive stress in the center. Therefore, the existence of a refractory zone in the contact area between the forging blank and the anvil is beneficial to repairing metallurgical defects of the steel ingot, and the larger the refractory zone, the more obvious the effect. Based on the above analysis, the forging factory changed the bottom plane of the anvil to a slightly concave curved surface in the middle, which can increase the difficult-to-deform area at the bottom of the anvil. This kind of drawing process in which the bottom surface of the anvil is a concave curved surface is called concave anvil drawing. Studies have shown that concave anvil excavation is better than ordinary anvil excavation in terms of loosening compaction and cavity volume closing. Compared with other existing special forging methods, concave anvil elongation has the advantages of easy application and a wide application range.
3. Defect control of large forgings
Due to the particularity and complexity of large forging manufacturing technology, various defects that are different from small and medium-sized forgings are easily formed during the forging process. Therefore, it is necessary to study how to compact the defects in large forgings and successfully pass ultrasonic flaw detection. , which is of great significance to improving the manufacturing level of large forgings and the economic benefits of enterprises.
3.1. Non-metallic impurities
Non-metallic inclusions mainly refer to sulfide oxides and silicates brought by raw materials. The content distribution of these non-metallic inclusions is related to the smelting of steel ingots. Forging can only disperse them but cannot reduce the fundamental way to reduce inclusions. It is to minimize the source of inclusions during the smelting and pouring process. The inclusions that have been formed in the steel ingot should be made to float to the riser area as much as possible. During the deformation process, full anvil feeding and large reduction forging are used, which is beneficial to the center of the steel ingot. If inclusions are deformed and then pore welded, wide anvil forging may be used to form a compressive stress state that is conducive to forging defects. Choose an appropriate forging ratio and use a reasonable forging process to reduce coarse inclusions and disperse dense inclusions to reduce their harm.
3.2. Residual stress
This type of porosity defect destroys the continuity of the metal and forms stress concentration and crack sources, which is an impermissible defect. Countermeasures to prevent such defects include: strictly controlling the pouring temperature and speed to prevent low-temperature slow-speed ingot injection; using heating risers or insulated risers to improve feeding conditions and moving shrinkage holes upward to the riser area to prevent deep shrinkage holes. Go to the ingot body; control the cutting rate of the steel ingot riser during forging to fully cut out shrinkage and porosity defects; reasonably forge deformation and compact porosity defects.
3. Conclusion
The development and design of the forging process for large forgings is a key factor related to the success of large forging production. It is also one of the bottlenecks restricting the nuclear power industry in the equipment manufacturing industry. In recent decades, research on how to control internal crack damage of large forgings and improve forging quality has achieved many results, but there are still some unresolved problems.
