Studies on the potential risk of liquid metal assisted cracking (LMAC) in normal‐temperature and high‐temperature hot‐dip galvanizing of high strength bolts of dimensions greater M24

Liquid metal assisted cracking (LMAC) mainly occurs due to an unfavorable interaction of three factors: a susceptible material condition, presence of a liquid metal and sufficient tensile stress. Hot‐dip galvanizing of high‐strength bolts induces high thermal loads in bolts made of tempered steel in the presence of a zinc melt and thus, provides the boundary conditions for the above mentioned critical factors to interact. The focus of this study is on investigating thermally‐induced stresses in large diameter bolts and their impact on the formation of liquid metal assisted cracking (LMAC). In order to calculate the thermal loads in hot‐dip galvanizing, simulations were carried out regarding the thermo‐mechanical behavior of bolts during the hot‐dip galvanizing process. The simulations illustrate that cracks are most likely to occur in the first thread turn. This prediction is confirmed by experimental observations.     

Development of the heating and forming strategy in compound forging of hybrid steel‐aluminum parts

In times of increasing energy costs automotive light weight construction is gaining more importance. The production of hybrid compounds by forging is a promising method for manufacturing functional parts by applying resource‐saving process steps. The mechanical properties of these parts can be specifically adapted to the requirements. In compound forging of steel‐aluminum parts the two materials need to be heated to different forming temperatures. In this paper, the challenges and their methods for the development of a heating and forming strategy based on different material characteristics are presented.     

Verbundschmieden hybrider Stahl‐Aluminium Bauteile

Compound forging of hybrid steel aluminium components Due to a major increase of energy prices the importance of lightweight construction has increased. The production of hybrid compounds by forging is a promising method to successfully manufacture functional parts by few process steps. The heating of hybrid material work pieces made of steel and aluminum is a great challenge. Steel is forged at a temperature of at least 900 °C, while aluminum should not exceed a temperature of 500 °C. For this inhomogenous temperature distribution warming up possibilities are presented.