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Die in Aluminum Forging

For closed-die forging of aluminum components, die or mold is critical element in the overall aluminum forging process, because the dies are a major element of the final cost of such forgings. Further, forging process parameters are affected by die design, and the dimensional integrity of the finished forging is in large part controlled by the die cavity. Therefore, the forging of aluminum alloys requires the use of dies specifically designed for aluminum because:
  • The deformation behavior of aluminum alloys differs from that of other materials; therefore, the intermediate and final cavity die designs must optimize metal flow under given forging process conditions and provide for the fabrication of defect-free final parts.
  • Allowances for shrinkage in aluminum alloys are typically greater than those for steels and other materials.
  • Temperature control of the dies used to forge aluminum alloys is critical; therefore, the methods used for die preheating and maintaining die temperatures during forging must be considered in the design.

The die materials used in drop forging aluminum components are identical to those employed in forging steel alloys except that, because of the higher forces applied in aluminum alloy forging and the design sophistication of the aluminum parts produced, the die materials are typically used at lower hardness levels in order to improve their fracture toughness.

Commercially available die materials were primarily designed for the forging of steels and are not necessarily optimized for the demands of aluminum alloy forging processes. However, with advanced steelmaking technology, such as argon oxygen decarburization refining, vacuum degassing, and ladle metallurgy, the transverse ductility and fracture toughness of available standard and proprietary die steel grades have been improved dramatically. As a result, the performance of these grades in the forging of aluminum alloys has also improved dramatically. Although die wear is less significant with aluminum alloy forging than with steel and other high-temperature materials, high-volume aluminum forgings can present die wear problems in cases in which die blocks have reduced hardness in order to provide improved toughness. Therefore, higher hardness die inserts and/or cavity surface treatments comparable to those used for steel forging dies are often used to improve wear characteristics in order to maintain die cavity integrity for aluminum forging dies. The surface treatments employed include carburizing, nitriding, carbonitriding, and surface alloying using a variety of state-of-the-art techniques. Beyond die wear, the most common cause of die failure in aluminum forging dies is associated with die checking or die cracking, which, if left unheeded, can lead to catastrophic loss of the die. Such die checking usually occurs at stress risers inherent in the die cavity features from the design of the forging being produced. Improved toughness die steels, improved die-sinking techniques, improved die design, and lower hardness die blocks serve to reduce the incidence of die checking in dies for forging of aluminum alloys. Numerical modeling of the dies, using state-of-the-art finite element methods (FEM) techniques, is widely used for analysis of die stress, die strain, and thermal conditions as a function of the die design and forging process conditions. With these analytical models, optimization of the die design and/or forging process conditions can be fully evaluated prior to actual die sinking and shop floor use, dramatically increasing die life. Further, aluminum alloy forging dies with die checking or cracking are routinely repair welded using metal inert gas, tungsten inert gas, or other welding techniques. With weld repair and numerical models of the dies, it is possible, through weld rod composition selection, to modify the performance capabilities of critical areas of the die cavity that models have shown to have high stresses or unavoidably severe stress risers.

CFS Drop Forge
has individual die manufacturing shop in house directly, our die making capability including selecting superier die material and mature die machining technology enable us to forge aluminum components in larger quantity and better control of size accuracy.

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