President Chavez has nationalised a number of foreign-owned companies
President Hugo Chavez has signed a decree to nationalise Venezuela's biggest steelmaker, Ternium-Sidor.
Argentina's Techint, which owns 60% of it, has been given until the end of June to hand it over.
In the past two years the Venezuelan state has taken over foreign-controlled companies including cement, telecoms, oil, gas and electricity firms.
President Chavez threatened to nationalise the steelmaker after trade union talks broke down last month.
The workers wanted better pay and benefits.
Talks between the government and Techint broke down earlier this month when a price for the controlling stake could not be agreed.
Rodolfo Sanz, minister of basic industries and mining, has been appointed as the new president of Ternium-Sidor.
The government already owned 20% of the shares and had first threatened to take control of the company last year unless its owners agreed to sell more of its steel in Venezuela.