Die casting dies corrosion - Tool steel defects

Die casting dies corrosion - Tool steel defects

Figure 1: Insert for a die casting die having corrosion induced cracks from cooling channels to working surface. Left: general view of the insert; right: view onto the inner cooling channels after slitting and cleaning the part.

Figure 2: Water leakage from a cooling channel of a hot-stamping tool.

Figure 3: Section through a hot-stamping tool (right); corroded cooling channels and corrosion induced crack from a cooling channel to the working surface (right).

Defect name: Corrosion
Record No.: 3237
Type of defect (Internal/Surface): Surface
Defect classification: Corrosion defects, tool steel defects
Steel name: Tool steel
Steel composition in weight %: No data.
Note: In hot-work tools like die casting dies corrosion has not been a reason of tool failure for very many years. During the last 3 – 5 years the number of corrosion induced tool failures has become more apparent. Cracks spread out from cooling channels or spot coolings leading to total failure of these tool components (figures 1 - 2). Water leakage in a die casting die not only reduces the functionability of the tool it also bears the great risk of explosion during the casting process.

Hot-stamping tools for the production of hardened automotive sheet components are intensively cooled tools. More and operators of these production facilities intend to optimize their tools and production cycles by using the tool steels at their maximum hardness and locating the cooling channels only 5 – 6 mm from the working surface. Water leaking from the cooling channels (figure 3) has often been observed as the main cause of premature tool failure.

Figure 3 displays a section through a defect hot-stamping tool. The corroded surface of the cooling channel is clearly visible. The detailed view shows a crack which has propagated from a corrosion pit through the remaining wall between cooling channel and surface. Several similar tool failures were the motivation for a more detailed study of the corrosion behaviour of hot-work tool steels. Only little information on this topic can be found in the literature. To gain a more profound knowledge on this important topic Kind & Co and Institut für Werkstoffsystemtechnik Thurgau an der Hochschule Konstanz conducted this investigation on some frequently used hot-work tool steels in aqueous solutions.
Reference: Not shown in this demonstration version.