332 Prakt. Met. Sonderband 38 (2006) 
2. INTERNAL THREAD MOLDING PROCESS Sp: 
enc 
Thread molding is dominated by multiaxial material flow, mainly radial and axial to the feed wa: 
direction, but also partly tangential referred to the rotating direction (Fig. 1). The thread 
length is approximately 17 mm and is molded in the industrial process every 2.5 seconds. 
The molding tool material correspond to the high speed steel grade HS 6-5-2-5 C and 3.1 
carries a titanium nitride (TiN) coating (Fig. 2). The thread tube is designed after the sheet 
metal strip (1.4509) has passed through 28 molding stations (Fig. 3). At the thread The 
molding station the forming oil is applied to the former with four micro spry nozzles. 10. 
foul 
feed dircection dar 
The 
on 
sur 
are 
infl 
molding tool 
Fig. 1: principle of internal thread molding [1] 
Fig. 2: molding tool Fig. 3: thread tube 
3. INVESTIGATION 
The results of the investigation on internal M12-thread molding tools in different stadia of 
service life are presented here. The failure investigation was structured in 
» visual investigation 
SEM (Scanning Electron Microscope) investigation 
metallographic investigation 
The visual investigation was done with the naked eye and by stereomicroscopy and gave 
information about the macrostructure of the surface. The SEM investigation revealed the 
microstructure of the surface and offers the possibility of chemical analyses by an EDAX- 
system and of element information in the BSE-modus (Back Scatter Electron-modus). The 
metallographic investigation of the cross-section specimen provided material information 
beyond the surface, both of the titanium-nitride (TiN) coating and of the substrate material.