the main aspects of precision forging

1、 ARCHIVES OF CIVIL AND MECHANICAL ENGINEERING Vol. VIII 2008 No.

2、 2The main aspects of precision forging Z. GRONOSTAJSKI, M. HAWRYLUK Wroc?aw University of Technology, Wybrze?e Wyspia?skiego 25, 50-370 Wroc?aw, Poland The article concerns the directions of development the forging and

3、 problems with precision forging like tool and preform temperature, slug geometry, press settings, process speed, lubrication and cooling, and tool shape and quality. It was introduced the present state of knowledge as

4、 well as crucial problems of the technology. Suggestions solving these problems as well as researches carried out in Metal Forming Processes Department of Wroclaw University of Technology were presented. Keywords: clos

5、ed die, precision forging, tool life 1. Introduction The main advantage of precision forging over conventional die forging is its lower (by as much as 60%) material consumption. This is owing to the lack of flash and to

6、 the fact that the end product has minimum machining allowances. The forgings gener- ally have very good service properties. Because of its advantages, precision forging is the most popular technology for producing car

7、 parts from relatively expensive materi- als. Connecting rods, skew and straight bevel gears, worm gears, tripods, turbines, al- ternators, constant-velocity joints and so on (Figure 1) are manufactured in this way [1–6

8、]. Fig. 1. Products manufactured by precision forging Besides its obvious advantages, precision forging has some drawbacks of which the most serious one is the too short life of the forming tools, mainly dies, punches (

9、Fig- ure 2). The tools used in precision forging wear out long before the end of their expect life. The main aspects of precision forging 41extrusion) was adopted to make preforms for precision forging. Extrusion forgi

10、ng has this advantage that the stress is mostly triaxial compression whereby large deforma- tions can be obtained without losing material cohesion. In addition, no die drafts are used in precision forming. The whole ma

11、nufacturing process is generally divided into stages. As an example, the process of manufacturing a low-carbon steel product is shown in Figure 3. Fig. 3. Flowchart of precision forging process Metal bundles are delive

12、red from a storeroom to a machine which cuts the rods into pieces with specified dimensions and weight. Then the pieces are heated up to a tem- perature of about 900 °C in an induction furnace. A constant process t

13、emperature must be maintained in order to ensure high quality of the forgings. Preforms heated up to a proper temperature are fed into a press where they are formed in 2–5 operations. The dies are preheated to a temp

14、erature close to the operating temperature to reduce the risk of die cracking as a result of thermal shock (Figure 4a). Fig. 4a. Dies are preheated Fig. 4b. Measurement and control of forged object temperatureThe forg