| Summary: | 碩士 === 建國科技大學 === 自動化工程系暨機電光系統研究所 === 96 === Most conventional large impact tools are made of steel and other hard metal materials in a forging process. Forging tools have the characteristics of fast production speed and improvement on materials; therefore, they are widely used in the industry. Forging can be divided into cold forging, warm forging and hot forging, depending on the different temperatures of materials. Because of higher Deformation stress of the material, cold forging is applicable only to smaller parts. In hot forging, the Deformation stress of materials is smaller, but the surface is poorer. Thus the different forging processes have their strong points and weaknesses. Depending on die conditions, forging can be divided into free forging, semi-close, and close die forging. The large impact sleeves (socket wrench) is a typical hot forging part; its processing methods may differ because of different blank shapes. Some may involve drilling holes in rod materials before forging processes. Some may directly adopt the reverse extrusion die forging method. Some may directly heading processes with pipe shaped materials. Characteristics of finished products also differ because of different processing methods. According to the manufacturers, sleeves (socket wrench) produced by reverse extrusion die forging are stronger. This study has verified that statement through analysis.
In the reverse extrusion die forging, block shaped material is placed in the die, and a punch is then used to compress the materials in the middle, forcing the materials on the side to move in a direction reverse to the punching head, resulting in a hollow shape. However, when this method is adopted for sleeves (socket wrench) forming, the crystallized structure on the end side of the sleeves (socket wrench) is not satisfactory, resulting in a broken sleeves (socket wrench), and a reduced sleeves (socket wrench)strength. Therefore, there is much space for improvement in the forming processes of conventional reverse extrusion die forging.
This study has done analysis, using hot forging Deformation analyzing software (DEFORM 3D) targeting the existing production and die conditions of the sleeves (socket wrench), in order to observe the relations of stress changes and their flow conditions of materials during the production, and using the product of hydro static compressive stress multiplied by equivalent strain changes, to judge the strength of the elements. As indicated in the analysis result: the upper end surface of the sleeves (socket wrench) in conventional production processes has the least strength, and the end surface could easily be broken when used. This study tries to conduct analysis of formation of all types of sleeves (socket wrench) on the condition that no significant change is made to the production processes, but with slight changes of die measurements or the process order of production, to observe the value of hydro static compressive stress and equivalent strain change values of the material on the end surface of the sleeves (socket wrench), to serve as reference for judgment of strength, to find forging dies and forging methods that can enhance product strength, and to significantly upgrade product competitiveness.
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