The effects of forging process on the microstructure and mechanical properties of forgings

In order to obtain good organizational performance of forging, in addition to the need to ensure the quality of good raw materials, also need to have reasonable forging process and heat treatment process. Forging process generally consists of the following processes including blanking, heating, forming, cooling after forging, pickling, Corrosion) And the heat treatment after forging. Including free forging forming process, die forging, trimming and correction; Free forging including upsetting, long pull, punching, bending and torsion; Die forging, including long pull, roll extrusion, forging, finish forging and heading, etc. From the above process, the effects of forging process on the microstructure and mechanical properties of forgings, ultimately boils down to the thermodynamic factors. The so-called thermodynamic factors is refers to the deformation temperature, deformation rate, cooling rate and stress state, and so on. Break the columnar crystal, improve macro segregation, the as-cast organization into forging state organization, and under the appropriate conditions of temperature and stress welded internal pore, improve the density of material; Ingot after forging, the formation of fibrous tissue, further by rolling, extrusion, forging, forging get reasonable distribution of fiber direction; Control of grain size and uniformity; Improve the interphase ( Such as alloy carbide in ledeburite steel) The distribution; Make the organization get deformation strengthening or deformation - Phase transformation strengthening, etc. Due to the improvement of the organization, the forging of plasticity, impact toughness, fatigue strength and the durable performance has been improved, and then the final heat treatment of the parts can get parts required hardness, strength and plasticity of good comprehensive performance and organization. The following specific discussion of thermodynamic factors affect the performance of forgings organization. 1. The influence of deformation temperature forging heating metal forging is not only to guarantee good plasticity and low deformation resistance, but also on the microstructure and mechanical properties of after forging has very big effect. For steel, due to the forging heating temperature is normally higher than parts of the final heat treatment temperature, so the heat of the grain size and subsequent organizational change will bring certain influence in the quality of forgings. Without proper heating temperature always create shortcomings to forgings. If the heating temperature and heating time is too long, causes decarburization, overheating, burnt ( Especially in high alloy steel and Si steel decarburization most easily) , such as: alloy structural steel superheat fracture, martensitic stainless steel in the delta ferrite, austenite ferritic stainless steel, 9 cr18 bearing steel carbide precipitation along the twin wire, heat resistant alloy appear coarse grains, titanium alloy appear coarsening, beta group. And forged carburizing steel overheating, it make thick martensite and carbide network after carburizing. That all kinds of tissue defects on the mechanical properties of the forgings especially toughness and fatigue performance. Forging heating temperature on the microstructure and mechanical properties of alpha + beta titanium alloy influence particularly evident. Forging temperature on alpha + beta titanium alloy beta, the influence of grain size and mechanical properties at room temperature, if the heating temperature is too low, not only easy cause uneven deformation, the heat resistant alloy and aluminum alloy after quenching heat easily appear coarse grain or grain weight