| 摘要 |
<p>PURPOSE:To obtain a marking data processing method by which marked data can be securely read irrespective of contaminants or the like present on the surface of a marking material, by heating the surface of a steel material in an arbitrary pattern by a high energy density heat source, and then cooling the surface to vary the magnetic characteristics of the surface. CONSTITUTION:When a steel material is heated and then cooled or is melted and then solidified, a phase change or a hardness change occurs in the steel material, and the magnetic characteristics of the material are varied. Upon detection by a magnetic sensor 12, a great difference in level is found between parts A not irradiated with a laser beam 1 of the surface of the steel material 6 and parts B of data 7a irradiated with the laser beam 1. By reading the difference by the magnetic sensor 12, only the marking data can be detected. The method of reading the data 7a by a magnetic method using the magnetic sensor 12, unlike a method using an optical means or the like, is not affected by the surface condition such as the presence of contaminants in the marking areas, so that assured data can be obtained without misreading.</p> |
