TCM 1 1218-(R) – Blanc Aero Industries – LISI – La Glèbe, La Rouquette, (FR) PQ426

4 Replies to “TCM 1 1218-(R) – Blanc Aero Industries – LISI – La Glèbe, La Rouquette, (FR) PQ426”

1. Bolt head macrographic examination: we can see a “wave” between head and shank flow lines.
   Shall it be considered as breaks in flowlines?
   How can we explain this phenomenon?
   When has this macro examination been carried out? Before heat treatment or after?
   Hopefully, fatigue test results are in line with ISO9154.

   Many thanks in advance,
   Best regards.

   Reply

2. Hi Julian,

   The image you are referring to is labelled “Macro sur piece finie / macro on a finished part” and therefore the macro is taken after heat treatment.

   ISO9154 Figure 2 clearly shows a standard protruding head and a countersunk head. There is no image for a 12 point head in ISO9154 that we can compare like for like. However, If you look at the the images in ISO9154 figure 2, the flowlines follow the contour of the head.

   For me the there is no break in flowlines. What the specification calls for is that flowlines do not break out onto the surface especially in the area of the underhead radius as that is where maximum tensile stress is applied in service and hence a fatigue test is required as a referee. As you can see from from the macro image it doesn’t break out.

   The certificate of conformity shows all samples to have successfully reached 130000 cycles without failure.

   Any further questions, please don’t hesitate to ask.

   Thanks

   Marko

   Reply

   1. Thanks Marko.

      This phenomenon is inherent to the hot forging process and is completely normal. We commonly call this “la croix du forgeron” and it is representative of the material’s temperature gradient during the die forging process. It has no impact on mechanical caracteristics.

      Reply

3. Dear Edith, dear Marko,

   Many thanks for your replies!
   This is clear for me now, so, approved from my side.
   Have a nice day,
   Best regards.
   Julien

   Reply