Methods for manufacturing tubes filled with powdery and granular substances

A method for manufacturing tubes filled with powdery and/or granular substances comprising the steps of:

• forming a metal strip into a tube;
• feeding powdery and/or granular substances into the tube being formed as a core, the powdery and/or granular substances consisting of ferromagnetic and paramagnetic substances mixed to a basic formulation, with a first portion consisting of the ferromagnetic and paramagnetic substances of the basic formulation forming the bottom layer of the core and a second portion consisting of only the paramagnetic substances of the basic formulation forming the top layer of the core;
• joining together the edges of the tube filled with the core of the powdery and/or granular substances by high-frequency welding;
• and
• reducing the diameter of the welded tube filled with the core of the powdery and/or granular substances.

A method for manufacturing tubes filled with powdery and/or granular substances comprising the steps of:

• forming a metal strip into a tube;
• feeding powdery and/or granular substances into the tube being formed as a core;
• joining together the edges of the tube filled with the core of the powdery and/or granular substances by high-frequency welding;
• reducing the diameter of the welded tube filled with the core of the powdery and/or granular substances;
• and
• removing magnetic particles contained in the core in the tube by magnetic attraction before the edges of the tube are welded together.

A method for manufacturing tubes filled with powdery and/or granular substances comprising the steps of:

• forming a metal strip into a tube;
• feeding powdery and/or granular substances into the tube being formed as a core;
• joining together the edges of the tube filled with the core of the powdery and/or granular substances by high-frequency butt-welding, the butt-welding being performed on the edges of the tube having a wall thickness of not more than 5 mm and an outside diameter of not more than 50 mm, the edges forming a groove flaring upward and downward from the center of the wall thickness;
• and
• reducing the diameter of the welded tube filled with the core of the powdery and/or granular substances.