Do you mean something like this? http://matrix-eps.com/features/welding-quality-control-software.html
Here's a job opening for a document control clerk @ Spitzer Industries in Houston, TX: http://www.spitzerind.com/careers/document-control-clerk
If you notice in the job description under General/Minimum Responsibilities, you'll read the following:
"Create weld matrix (structural and piping) from weld maps obtained from QC.
Updates matrixes with revised weld numbers from revised weld maps, enter reports.
Issue out weld/map matrix to Shop and Client inspectors using Weld Map Issued Log."
So a weld matrix used for welding management is basically a set weld maps which include, weld #'s, WPS's, Code references & reports and all sorts of welding and inspection related data usually put together in spreadsheet form unless custom software is used in aiding their creation... And in case you're wondering what a weld map is - otherwise known as weld mapping, here's a brief description:
Weld mapping is the process of assigning information to a weld joint to enable easy identification of its design (WPS), production (welders, their qualifications, date welded), quality (visual inspection, NDT) and traceability (heat numbers of materials joined & welding consumables)...Weld mapping should also incorporate a pictorial identification to represent the weld number on the fabrication drawing, in case the designer does not nominate a weld number.