Tunsten wire, cathode heater, and filament for vibration service lamp

A tungsten wire containing 1 to 10% by mass of rhenium;

• said tungsten wire having a point which indicates a 5% elongation within a quadrangle formed by joining points with straight lines, where the values of x and y are point (20, 73), point (20, 83), point (90, 72), and point (90, 56), in this order, wherein the wire diameter of said tungsten wire is represented by x μm, and the elongation of the tungsten wire is 5% after electrically heating with an electrical current which is a ratio of y % to the fusion current (FC) at said wire diameter x μm, and wherein a semi-logarithmic system of coordinates is expressed by means of a horizontal axis using a logarithmic scale of said wire diameter x and a vertical axis using a normal scale of ratio y to said fusion current.

A tungsten wire containing more than 10% by mass but 30% by mass or less of rhenium;

• said tungsten wire having a point which indicates a 2% elongation within a quadrangle formed by joining points with straight lines, where the values of x and y are point (20, 55), point (20, 63), point (90, 51), and point (90, 39), in this order, wherein the wire diameter of said tungsten wire is represented by x μm, and the elongation of the tungsten wire is 2% after electrically heating with an electrical current which is a ratio of y % to the fusion current (FC) in said wire diameter x μm, and wherein a semi-logarithmic system of coordinates is expressed by means of a horizontal axis using a logarithmic scale of said wire diameter x and a vertical axis using a normal scale of ratio y to said fusion current.

A tungsten wire containing more than 10% by mass but 30% by mass or less of rhenium;

• said tungsten wire having a point which indicates a 5% elongation within a quadrangle formed by joining points with straight lines, where the values of x and y are point (20, 53), point (20, 60), point (90, 48), and point (90, 37), in that order, wherein the wire diameter of said tungsten wire is represented by x μm, and the elongation of the tungsten wire is 5% after electrically heating with an electrical current which is a ratio of y % to the fusion current (FC) at said wire diameter x μm, and wherein a semi-logarithmic system of coordinates is expressed by means of a horizontal axis using a logarithmic scale of said wire diameter x and a vertical axis using a normal scale of ratio y to said fusion current.