Since 1998, Sumitomo Japan united with Magnequench Company launched the US 337 investigation in conjunction. Finally, the US International Trade Commission issued a "General exclusion order", that is, unless the permission of Sumitomo (Hitachi Metal after 2003) or Magnequench is obtained, any violation of the corresponding Sinter NdFeB products of national patent can not be sold to the United States.

Hitachi Metal acquired Sumitomo Corporation of Japan in 2003 and acquired more than 600 patented Sinter NdFeB technologies worldwide, the patent still continually updating.

On September 18, 2012, the U.S. International Trade Commission initiated a "337 investigation" on Hitachi's suit against 29 enterprises for infringement of their patent rights on Sinter NdFeB magnet products. In May 2013, Ningbo Jinji and Hitachi reached a settlement agreement and obtained Sinter NdFeB patent authorization.