Method and apparatus for adding solid alloying ingredients to molten metal stream

In a process wherein molten metal descends in a vertical stream from an upper container to a lower container, a method for adding solid particles of an alloying ingredient to said stream, said method comprising the steps of:

• directing said descending stream initially through an elongated, vertically disposed conduit having a lower end;
• forming a bath of said molten metal in said lower container;
• positioning the lower end of said conduit above the top of said bath;
• enclosing said conduit and said descending stream within elongated, vertically disposed solid, tubular shroud means having walls laterally spaced from the conduit and the descending stream to define an unfilled, annular space between (a) the shroud means and (b) the conduit and descending stream;
• the cross-sectional area of the interior of said shroud means being greater than the cross-sectional area of the conduit's interior;
• protecting the interior of said shroud means and the contents thereof from the outside atmosphere surrounding said shroud means;
• creating within said shroud means, by the flow of said stream descending from the conduit into the shroud means, a low pressure region having a pressure less than the pressure of the outside atmosphere surrounding said shroud means;
• said low pressure region extending between the lower end of the conduit and the top of said bath;
• providing a mixture containing a transport gas and solid particles of an alloying ingredient;
• and directing said mixture into said shroud means and into the interior of said descending stream, at a stream location below the lower end of the conduit and above the top of the bath, in said low pressure region.