The content of alloying elements, harmful impurity elements, gases and residual elements in the chemical composition materials shall conform to the technical standards and relevant technical conditions or technical agreements of raw materials for aviation use. The content of harmful elements, gases and residual elements in materials should be controlled as far as possible under production conditions. The uniformity of alloying element distribution is required.
High strength steel, titanium alloy and superalloy are produced by vacuum consumable remelting process. Titanium alloy and high alloy require no less than two vacuum consumable remelting processes. Alloy structural steel and stainless and hot steel are produced by electric arc furnace, electric arc furnace and electroslag remelting process or other better smelting methods. Aluminum alloy is usually smelted by flame furnace, resistance furnace and induction furnace, and a series of technological measures are taken to strictly control the impurity content and diversify the heat treatment status of high quality aluminum alloy.
According to the production process and quality requirements of forgings, the material specifications are ingot, bar (rolled, forged, extruded), billet, flat, cake (ring) and so on. When forgings have strict streamline distribution requirements, we should pay attention to the choice of raw material streamline direction to make it and forgings specified streamline distribution coordination. Surface defects of raw materials, such as cracks, folding, scarring, heavy skin and other easy to cause defects on the surface of forging, so should be limited. The dimensional tolerance of raw materials has an important effect on forging precision forming.
The forging ratio of the material should ensure that the material has enough deformation degree, that is, the size of the forging ratio should be specified in the range of meet, in order to ensure sufficient deformation of the material, reduce or eliminate the casting channel structure in the material. For aviation large forgings, it is generally required that the forging ratio of raw materials is greater than 6~8.
Mechanical properties The mechanical properties of raw materials include mechanical properties at room temperature and high temperature, such as strength index, plastic index, impact toughness, hardness, fracture toughness, endurance strength, creep limit, fatigue properties. Stress corrosion resistance, etc., shall be specified according to the different forgings and their uses, and shall be specified in the technical requirements for raw materials.