Investigation And Device Development For Measuring Heat Transfer Coefficient On The Contact Surface Of Hot Forgings

Hot forging is one of the most important processing methods To obtain good mechanical properties of the workpieces in the industry. Heavy forgings are especially the key parts and products of major technology and equipment in the industry, such as nuclear power and electric power. To a great degree, its manufacturing capacity represent a country’s level of economic development. Due to the large size,small batch and long production cycle of the large forgings, the numerical simulation technology plays an important role in the field. And the simulation of temperature field is an crucial part of the numerical simulation in forging process. Meanwhile, the temperature distribution is highly influenced by the contact heat transfer coefficient(CHTC). To provide basic parameters for simulation, it is necessary for us to find the method to obtain the available CHTC.Based on the Energy Conservation Law and the analysis of the temperature field of die in forging process, a new method to measure the CHTC under high temperature and plastic deforming is presented. A test device which can measure the CHTC of all metal materials under the different contact conditions is designed and manufactured. At the same time, the supporting software to achieve the real-time measuring, displaying, storing the temperature data is developed successfully. The CHTC also can be calculated by the supporting software rapidly.The transient contact heat transfer under different initial temperature and contact pressure between the H13 and SA508-3,45,Q235 steel was investigated by a set of self-developed test apparatus. The test results indicate that the CHTC increases with the increase of contact pressure and initial temperature. The relationship between the CHTC and contact pressure follows the power-law correlation, and the exponent is generally in the range of 0.7 to 0.99. The effect of initial contact temperature on the exponent of x was also analyzed,which reflect the effect of temperature on the CHTC. The results show that the contact pressure influences the CHTC greater than temperature under the conditions of high temperature deformation.Finally, in order to validate the reliability of the test apparatus and method, the measured temperature on the typical point was compared with the simulated temperature. The results indicated that the measured temperature agrees well with the simulated value, and the test apparatus are reliable and have the practical value in the industry.