Method for producing metal ingot, method for controlling liquid surface, and ultrafine copper alloy wire

A method for controlling liquid surface, which comprises the use of a liquid transfer apparatus, comprising:

• a liquid holding part in to which liquid is poured;
• an injection part for pouring liquid in to said liquid holding part;
• an opening adjustment part for adjusting an opening of said injection part;
• a camera for recording a surface of liquid within said liquid holding part;
• an analyzing part for analyzing a surface image recorded by said camera;
• a controlling part for adjusting the opening of said injection part, based on information analyzed by said analyzing part;
• wherein said analyzing part sets an analysis band along a direction of change of said surface on the surface image recorded by said camera, and said analysis band has a predetermined width and includes said surface, binarizes an image within said analysis band to a liquid part and a non liquid part, obtains a rate of change of binary data for a longitudinal direction of said analysis band, and identifies the lowest position among the positions where the peak of the calculated rate of change is equal to or above a predetermined standard value as a surface height;
• and
• wherein said controlling part adjusts the opening of said injection part by comparing said surface height with a standard surface height.