Friction and characteristics of plastic forming of wheel forgings

2019-03-19 15:54:46 8

Preparations for forging wheel forgings include raw material selection, material calculation, blanking, heating, calculation of deformation force, selection of equipment, and design of molds. Lubrication methods and lubricants must be selected before forging the forgings of the wheel.


Forging materials are very wide. It is well known that the quality of products is closely related to the quality of raw materials. Therefore, for forging workers, it is necessary to have the necessary material knowledge, and be good at selecting the most suitable materials according to the process requirements.


Calculating and unloading is one of the important links to improve material utilization and achieve blank refinement. Excessive materials not only cause waste, but also exacerbate mold wear and energy consumption. If the blank is not left blank, it will increase the difficulty of process adjustment and increase the scrap rate. In addition, the quality of the blanking end face also has an impact on the quality of the process and wheel forgings.


The purpose of heating is to reduce the forging deformation force and to improve the metal plasticity. But heating also brings a series of problems, such as oxidation, decarburization, overheating and overburning. Accurate control of the initial forging and final forging temperatures has a major impact on product organization and performance.


The furnace heating has the advantages of low cost and strong applicability, but the heating time is long, the oxidation and decarburization are easy to occur, and the working conditions also need to be continuously improved. Electric induction heating has the advantages of rapid heating and less oxidation, but has poor adaptability to changes in product shape and material.


Forging shape is generated under the action of external force. Therefore, correct calculation of deformation force is the basis for selecting equipment and performing mold calibration. Stress and strain analysis inside the deformed body is also indispensable for optimizing the process and controlling the structural properties of the wheel forgings.


The friction in the plastic forming of the wheel forging can be divided into internal friction and external friction. The so-called internal friction is the interaction between the individual mass points of the entire deformed body. This effect occurs at the grain boundary or the actual slip surface within the crystal and impedes the slip deformation of the deformed metal; the external friction appears as an interaction of the forces of the two objects on the contact surface that impede their relative movement. The internal friction in metal plastic forming occurs in the process of intragranular deformation and intergranular deformation, which is directly related to the plastic deformation process of the polycrystal, and the external friction occurs in the portion where the deformed metal is in contact with the tool.


Friction is generally divided into: dry friction, boundary friction, fluid friction and mixed friction.


Dry friction: Unlubricated and moisture-free friction is called dry friction. There is actually no absolute dry friction, so the dry friction usually refers to friction without lubrication.


Boundary friction: There is a very thin film of lubricant between the two contact surfaces. The friction does not depend on the viscosity of the lubricant, but on both surface properties and lubricant properties.


Fluid Friction: Friction between the surfaces of two objects separated by a continuous fluid layer.


Mixed friction: Mixed friction is a mixture of dry and fluid friction or boundary friction and fluid friction.