If there's other steel other than what was discussed I'm not aware of it.
I really shouldn't be reproducing these e-mails. He would rather answer people one on one but here's a e-mail:
For what little its worth I'm also listed under the contributors to the final WTC 7 report.
>>> -----Original Message-----
>>> From: Scott Sleeper [mailto:snssleep@pacbell.net]
>>> Sent: Tuesday, February 07, 2006 6:57 PM
>>> To: Barnett, Jonathan Ross
>>> Subject: Question about building 7 steel?
>>>
>>> Dear Mr. Barnett,
>>>
>>> I wanted to double check that these links were the
>> "partly evaporated"
>>> steel you referred to within your
>>> 2001 interview. Also what was your guestimate as
>> to the source of the
>>> sulfur within the samples.
>>>
>>> Thank you for your time.
>>>
>>> Scott Sleeper
>>>
>>>
>
http://www.tms.org/pubs/journals/JOM/0112/Biederman/Biederman-0112.html
>>>
http://www.me.wpi.edu/MTE/People/imsm.html
>>>
>>
> >"Barnett, Jonathan Ross" <jbarnett@WPI.EDU>
>> wrote:
>>
>>> These are the correct links. Possible sources of
>> enough sulfer:
>>>
>>> -Heating oil (extr high probability)
>>> -Construction materials such as gyp wallboard dust
>> (extr high
>>> probability) -environmental sources such as acid
>> rain (high)
>>>
>>> Hope this helps! Bottom line is that this is an
>> area that needs
>>> further study
>>>
>>> Dr. Jonathan R. Barnett, Professor, Fire
>> Protection Engineering, WPI
Last I saw here is what Sisson said in a public interview for BBC in 2008.
"I don't find it very mysterious at all, that if I have steel in this sort of a high temperature atmosphere that's rich in oxygen and sulphur this would be the kind of result I would expect."
Also see here: Start 48 minutes in. Barnett found the piece in a salvage yard.
http://video.google.com/videoplay?docid=9072062020229593250#