The approval rate stems largely from the success of two companies. Mandel has won 400 aluminum exclusions — nearly half of all the exemptions granted to companies seeking relief from the aluminum levies through early November. Those exclusions allow Mandel to import six times the amount of metal it sells every year, and company officials say they will not come close to using all of that allowance.

Greenfield Industries, a South Carolina maker of saw blades and other cutting tools, has won 1,000 exclusions from the steel tariffs. Greenfield is owned by China’s Top-Eastern Group.

The exclusions stem from the Commerce Department’s process for determining whether companies can win tariff relief for imported metals. The requests are generally granted as long as no American producer formally objects and says it can provide the metals.

Both supporters and opponents of the tariffs have criticized the process as haphazard and ineffective. Aluminum trade groups — including some that have criticized the tariffs — say the fact that Mandel received approval to import more metal, including aluminum from China, than it can use highlights the program’s flaws. Others have criticized the process for giving large domestic producers, like Nucor and Century Aluminum, outsize power to block exemptions by claiming they can provide the metals.

“Generally, it seems the department is not evaluating whether there is actually demand in the market for these large volumes and has granted the requests based simply on the absence of any objections,” Heidi Brock, the president of the Aluminum Association, wrote in a letter to the Commerce Department this month. She cited Mandel and another set of exclusions, to Ta Chen International, for potentially one billion pounds of imports from China.