The cut wire certification list an upper limit on hardness. Hardened cut wire shot is more expensive than regular hardness. Why is there an upper limit on high hardness material. (ex VDFI 8001 on 0.9 the upper limit is HV 700)
knife
I'm not real familiar with VDFI 8001, but have a copy of an old revision. This revision has ranges stated, similar to AMS 2431/8b. The AMS 2431/8b hardness for all sizes is 90% 55/62 HRC, which would be approximately 90% 595-746 HV. What is the revision level of the VDFI 8001 you are quoting?
Could it be that the upper limit of hardness is included in order to limit the tendency to fracture?
We are using VDFI edition May 2009 supersedes VDFI 8001 October 1994
It is a interesting specification for hardness. There are three different hardness values (spec?) listed. 1 Nominal Value. 2. Mean valve of 20 particles. 3. limit values of the 20 individual particles. Each size of shot has three Nominal hardness values, with each having a range of hardness values for 2 and 3 above. The three nominal values correspond to three types of rod used to make the cut wire shot.
After all of that, I can not tell you why they have done this other than they must have data to support differences in work created by these slight changes in hardness.
Or, this is the resulting hardness of drawing the wire to the correct size.
I look forward to hearing if someone who is involved in the "Association of German Spring Industries" that controls this document has some information to share.
I know of one Aerospace prime that deviates from the AMS 2431 documents by stating the hardness of conditioned cut wire shall be 45HRC minimum. While on one hand it gives the shot peener a wider range of material to choose from, this could lead to problems. The hardness range selected for the machine/process should be frozen. Example: If you add harder media to your machine that was using a softer media it will cause havoc with your ability to repeat the process from your originally developed saturation curves.
The upfront cost of high hardness conditioned cut wire is true. One should consider the potential energy savings long term. A high hardness media will achieve the same intensity value with less air pressure / wheel speed.