Analysis of temperature fields in the tools during forging of axially symmetrical parts

An evaluation of the temperature distribution in tools during forging of axially symmetrical parts was performed. The finite element method was employed both for the material flow and temperature field computations. Heat generation due to plastic work and friction on the workpiece - tools contact surfaces was accounted for. Heat losses to the dies and environment were computed leading to tools temperature increase. Then, tolls cooling was modelled. The heat transfer from tools to the atmosphere, lubricant, cooling water and water sprays was accounted for. The results of the finite element modelling have demonstrated that during the forging operations the die surface temperature rises locally up to 618-630 degreesC at the end of plastic deformation and drops to approximately 400 degreesC after cooling. The punch surface temperature rises to 570-585 degreesC at the end of the plastic deformation and drops to 370 degreesC after cooling. The workpiece temperature resulting from thermal-mechanical modelling of the first operation was employed as the initial preform temperature at the second operation. The finite element modelling of the following forging operations have shown that the die temperature stabilises after 16 minutes of forging. Based on the results of computation it has been demonstrated that the water spray cooling of the punch is sufficient at the press rate of 15rpm. Further, finite element modelling of forging operations indicate that water spray cooling on the die face and water cooling on the outer die surface is needed in order to stabilise the die temperature at the values below 630 degreesC. Temperature variation due too heating and cooling cycles take place in surface layer of the tools. The thickness of the layer ranges from 2 to 3 mm.