Bill,
I agree with John and Joseph, this sounds very interesting.
I remember very well a lecture of Prof. Bill Lucas (TWI - The Welding Institute - Great Britain) presented on the Intermediate Meeting of IIW-Commission XII (Arc welding processes and production systems) in 2005. The paper dealt with an investigation directly comparable with what you have described in your post. The presentation was entitled: "The Cause Of Variations In Charpy Energy Levels - Electrode Approvals at Five Test Houses". Mentioned by the way, it is available by the International Institute of Welding (IIW Doc. XII-1851-05).
It explaines the normal practice of consumable manufacturers, to determine and ensure data for metal composition and mechanical properties of their filler materials. And further, that users are going to carry out independent batch controls to find out if they meet the requirements and to compare with the data been provided by the consumable manufacturer.
The initial for the investigations was such a "normal" batch control been ordered from the british Ministry of Defence (MoD) and been carried out by five different test houses in GB. Well what they could find out was, although all the test houses received the same batch of electrodes they had significant discrepancies in Charpy impact energy values! Therefore the MoD instigated an investigation into the cause of the variations in the impact test levels. Before they started the investigation they collected the following potential reasons for causing the discrepancies:
- Differences in the test house procedures and practices
- The effect of using different welders to produce the batch control test plates.
- Differences in the Charpy notch profile, and
- The effect of the quality of broaching.
I ask for your understanding for not treating the entire details of mechanical procedures and tests herein but what I would like to tell you is, the results they could determine for being the reasons of variations were tremendous. They have shown extraordinary differences between the different test houses who carried out the tests under using the same batch of electrodes and same welding procedures. Similar this is comparable for me with Joseph's posted predication, "...had the best testing lab in the world,... which resulted in better properties..." which is showing in the same direction the TWI could find out.
For me one of the most important predications made by Prof. Luacs and his brilliant team, I would like to cite here:
"The lack of agreement between the test houses as to the Charpy energy level for the same test weld, in particular, calls into question the suitability of this test in its present form for assessing the toughness of the weld metal."
I guess this says more than a thousand words. I can only recommend to get and read the mentioned IIW-paper since it contains a lot of fantastic information for you, certainly replying a great share of your inquiry in an appropriate way.
Regards from Germany
Stephan