Shares of Vale SA (ADR) ( VALE -0.71% ), Gerdau SA ( GGB -1.30% ), Companhia Siderurgica Nacional ( SID -2.52% ), Usinas Siderurgicas de Minas Gerais SA (ADR) ( USNZY -2.88% ), and ArcelorMittal SA (ADR) ( MT -2.67% ) all fell sharply on Sept. 13: