The Performance of Hot Stamping Die’s Cooling System

The forming process of ultra-strength steel is a typical thermal-mechanical coupling process, which is affected by both plastic mechanics and thermodynamics. Therefore, it is of great importance to control the temperature field of formed parts and die accurately. Designing stamping dies sensibly can improve the efficiency of the cooling system, which has an influence on the quenching process of formed parts and further affects their mechanical properties. During the high-temperature forming process, the cooling and quenching processes occur simultaneously, because of the different heat transfer conditions between various positions of formed parts and die. Thus, to control the homogeneity of hot stamping parts during the cooling process, the optimization design of the die’s cooling system is essential.

The optimization design of the die’s cooling system is a key point of hot stamping technology, which can determine the quality of formed parts. The formed parts are quenched by die surface fast in the synchronous quenching process, and the phase transitions of austenite into martensite can strengthen them. In addition, by controlling the water velocity in each insert, the homogeneity of martensitic phase transitions can be improved. The hot forming mold system is composed of a die, blank holder, punch, and cooling system. Especially, in order to cool the piece quickly, the die and punch are made by some insert blocks.

After the hot stamping process (without the cooling process), the temperature distribution of part surface. The heat of the blank was lost through heat conduction and heat radiation during the hot stamping Process and the temperature of the formed part decreased as a whole. The heat loss of the central section was more difficult than that of the edge section. In addition, the temperature distribution had a strong relationship with the order and amount of deformation, while they are relatively uniform and within the best temperature range for deformation. From Figure 3, we can see that the cooling channels should be mainly arranged on the top of the punch and the water velocity in each insert block should be controlled to increase the cooling efficiency of high-temperature positions.

The cooling system of the hot stamping die usually consisted of two parts: the external water circulation system and the power system; the internal cooling channels. Meanwhile, the water circulation system is made up of pipes, and the cooling channels are usually got by boring within the die.

To realize the quenching process of formed parts after forming, the e?ciency of the cooling system should be enhanced and the temperature distribution of the die surface should be as uniform as possible. The layout of cooling channels, the size of insert blocks, and the metal ?ow of blank should be taken into consideration when designing the insert die structure. The design of cooling channels includes the number, diameter, and position of the channels, which has a crucial in?uence on the cooling e?ect and cooling homogeneity of dies surface.

Parameter Setting:

The hot stamping is a complex process along with temperature variation and phase transformation, and in this process, stress and strain a?ect each other. Therefore, in order to improve the accuracy of the numerical simulation of the hot stamping process, the accuracy of data on the thermal properties of water and materials, thermal conductivity, and other essential data are required.

Although the overall temperature of die is a little higher than that of the punch, the temperature distribution of die is similar to that of punch, and die corners witnessed the highest temperature. Therefore, moving the two cooling channels inwards and increasing their diameter. By simulating the temperature distribution of the formed part, the cooling channels should be arranged at the top of the punch and the water velocity of each insert block should be rationally designed to control the uniformity of martensitic phase transitions.