The protesters are demanding a 40 percent pay raise. They are also want improved safety conditions where they work.
Most of the demonstrators gathered in front of their employer's office building in the town of Temirtau, in Karaganda Oblast.
MORE: Coverage in Kazakh from RFE/RL's Kazakh Service.
For years, workers have been saying that Arcelor Mittal -- the world's largest steel producer -- has done little to improve labor and safety conditions since taking over Kazakhstan's largest metal factory more than 10 years ago.
The protests started after 41 miners were killed earlier this month in a methane-gas explosion at a mine operated by the company.