The forging of wheel forgings mainly undergoes heating, deformation and cooling processes. Wheel forgings show different organizational states due to the material composition and the size of the wheel forgings. In summary, there are mainly the following two points.
1. Organizational status of large wheel forgings
This type of wheel forgings are generally formed by direct forging of steel ingots. Due to the high number of heating (6 fires or more) during forging, uneven deformation, large cross-section differences, and high degree of material alloying, the most prominent feature of the structure of large wheel forgings is the high residual hydrogen content and the serious unevenness of the structure. Existence (mixed crystal phenomenon), which is an important factor affecting the performance of large wheel forgings, so it is also a problem that needs to be addressed in the heat treatment process design of large wheel forgings.
2. Organizational status of small and medium-sized wheel forgings
This type of wheel forgings are mainly formed by die forging of rolled profiles. For hypoeutectoid steels (medium carbon steel, medium carbon low alloy structural steel), after the final forging, when air-cooled to room temperature, coarse and massive ferrite and Lamellar pearlite structure; for hypereutectoid steels, especially high-carbon and high-alloy steels, slow cooling after final forging can generally obtain a coarser annealed structure. In addition, due to the difference in the shape and cross section of the wheel forgings and the uncontrollable cooling, the structure is often uneven. At the same time, due to the effects of temperature stress (also called thermal stress) and structural stress, residual internal stresses will be generated in the wheel forgings, so heat treatment must be used to treat them. Improve and eliminate.
The heat treatment of wheel forgings is based on the type of wheel forgings and the raw materials used to reasonably formulate heat treatment process parameters. Mainly heating temperature, holding time and cooling rate, and through fully coordinating heating technology and cooling technology, namely heating equipment, heating speed, heating atmosphere and cooling device, cooling medium, to obtain the metallographic structure, mechanical properties and mechanical properties of wheel forgings. Use performance. Give full play to the potential of the material, and avoid heat treatment defects (deformation, decarburization, cracks and abnormal structures, etc.), so heat treatment is a very important and indispensable processing procedure for the formation of wheel forgings.
Almost all cold, warm and hot wheel forgings must pass heat treatment to become qualified parts. The level of heat treatment technology plays a decisive role in ensuring and improving the performance, accuracy, stability and service life of the parts. At the same time, the raw materials, heating, The forging process and cooling also affect the heat treatment quality of wheel forgings. The two are closely related and inseparable.
Post time: Jun-18-2021