The raw materials for forging are ingots, rolled materials, extruded materials, and forging billets. The rolled material, extruded material, and forging billet are respectively semi-finished products formed by rolling, extrusion, and forging of ingots. For cast ingots, the composition of the charge, the smelting method, and the forging process are important links that determine its quality. The rolling, extrusion, and forging process is another link that determines the quality of the corresponding semi-finished products.
Before the raw materials enter the forging process, they need to be inspected for size, surface quality, chemical composition, macrostructure, and mechanical properties and can be put into production after they meet the technical requirements.
The chemical composition, high magnification structure, low magnification structure, and mechanical properties of the raw materials are the basis for ensuring the structure and performance of the forgings, and the size and surface quality of the raw materials directly affect the process plasticity and forming of the forgings. In addition, the enforceability of raw materials and their recrystallization characteristics are the basis for determining the forging process parameters.
Therefore, the good quality of raw materials is a prerequisite to ensure the quality of large forgings. However, the quality inspection of raw materials has certain limitations (such as missed inspection and sampling is not representative, etc.). The inspection methods specified by the technical conditions of the raw materials cannot expose all the internal quality problems of the steel, such as Internal composition and segregation, etc. Various defects in raw materials will inevitably affect the forming process of large forgings and the final quality of forgings.
The influence of raw materials on the structure and performance of large forgings mainly includes the following aspects:
1. The influence of chemical composition and impurity elements;
2. The influence of internal defects of raw materials;
3. The influence of surface defects of raw materials;
4. The influence of raw material flowlines.