Here is a report on how to handle, extract, and troubleshoot this file: Technical Overview Part 2 of a Multi-volume RAR Archive.
Based on your request, is a segment of a multi-part RAR archive. This is a common file format used to split large data sets into smaller, manageable chunks, likely requiring the corresponding B1.part1.rar (and potentially others) to be present for successful extraction. B1.part2.rar
Use The Unarchiver or B1 Free Archiver to handle split .rar files. Troubleshooting Here is a report on how to handle,
Ensure B1.part1.rar and B1.part2.rar are in the same folder. B1.part2.rar
Requires B1.part1.rar to be in the same folder to function. How to Extract/Open