Elkem Technology A/s

Yngve Strom

Eiolf Vikhagen

Jan Nilsen

Jan T Malmo

Karl O Bjornestol

Heljar Hovland

Continuously cast metal billets are continuously passed by a symmetric light source comprising a plurality of single light sources arranged in a circle or in another way such that the light falls substantially symmetrically on the part of the surface of the metal billet which is to be detected in such a way that the surface of the metal billet which faces the light source is illuminated except for pinholes. Reflected light from the surface of the billet is detected by a linescan camera arranged centrally in relation to the light source, which camera has a scanning direction normal to the direction of movement of the metal billet, whereby pinholes are detected by registration of reflected light intensity below a preset threshold value.

Method for detecting pinholes in continuously cast billets

The present invention relates to a method for detecting flaws and surface defects in metallic workpieces, particularly in non-magnetic steel workpieces. The surface of the workpiece is heated by passing the workpiece in its longitudinal direction through an induction coil, scanning the surface of the workpiece with an infrared camera transversely across the surface of the moving workpiece immediately after induction heating and recording a streaked pattern temperature profile in which the streaked pattern repeats itself where there are flaws in the surface. It is used an induction coil with a current frequency which gives a penetration depth of the induced current in the workpiece which is greater than the depth of the flaws which are to be detected. The flaws and surface defects are detected by recording a lower surface temperature than the rest of the surface of the workpiece by scanning the temperature profile immediately after induction heating.

Growing community of inventors

Osto, Norway

Yngve Strom