Method for manufacturing steel bar with intermittent smooth surface and patterned relief segments, and mine roof bolt product

摘要

A method is disclosed for manufacturing steel bar (10) with intermittent smooth surface segments (11) and patterned relief segments (12). The method includes the steps of heating the bar (10) to a semiplastic state, rolling the semiplastic metal bar between rollers (30) having segments of patterned relief (33) around their respective circumferences separated by intermittent smooth segments (34). The rollers (30) rotate in registration with each other thereby imparting a corresponding intermittent pattern to the surface of the bar (10) along its length. The metal bar is then cooled to a solid state with the intermittent pattern intact on the surface of the bar. The metal bar (10) has intermittent segments of patterned relief (12) separated by intermittent smooth segments (11), the intermittent segments of patterned relief (12) being rolled onto the surface of the bar by passing the bar in a semiplastic state between rollers (30) having corresponding patterned relief (33) around their respective circumferences. The metal bar (10) has particular application as mine roof bolts when cut to an appropriate length and threads (14) are formed on one end of the bar to receive a threaded nut (15).