Molybdenum threaded rod

Molybdenum threaded rods, also called molybdenum bolts, screws or studs, are high-temperature fasteners turned, thread-rolled or thread-milled from molybdenum rod and used with molybdenum nuts and washers. Steel fasteners soften noticeably above 1100 °C in long service, whereas molybdenum retains strength higher up the temperature range. Common sizes cover M3–M30 with hex, socket, slotted, T-head, square and countersunk heads, and coarse, fine or extra-fine threads. Fine threads engage more turns and resist loosening better, suited to parts with frequent thermal cycling; thin-wall parts also often use fine threads.

Assembly is where molybdenum fasteners most often fail. At room temperature molybdenum has limited elongation and tensile strength, so tightening torque should be 60–70% of that for a steel fastener of the same size, and extended levers must not be used. High-temperature threads can gall; apply molybdenum disulfide or boron nitride anti-seize and keep bolt, nut and washer in the same material. Threaded rods are often used in the same hot zone as electrodes and crucibles, so material and surface can be reviewed together.

In high-temperature melting and thermal-field systems this part is often used alongside electrodes elsewhere in the line. We recommend selecting them together against furnace structure, assembly method and working temperature to reduce thermal-expansion mismatch between different materials.