What role for Large-diameter Molybdenum Tube?

For many enterprises doing vacuum heat treatment, one of the most easily overlooked details when upgrading equipment is the material selection of large-size structural parts in the furnace. Improper material selection for key parts such as furnace tanks, heating screens, and airflow pipes will not only affect the uniformity of the temperature field, but also directly reduce the overall life of the equipment. At this time, large-diameter molybdenum tubes can often play an unexpected role.

Why are large bore molybdenum tubes particularly suitable for vacuum furnaces? The key lies in its dimensional stability under high temperature vacuum and low vapor pressure. The thermal coefficient of molybdenum itself is very low (about 5.0 × 10 °C/°C), and the deformation of large-diameter molybdenum pipes that have been processed reasonably is extremely small when repeatedly heated and cooled in the range of 1200-1800 °C. This means that the support structure in the furnace will not be loosened or offset due to thermal expansion and contraction, and the temperature uniformity is easier to control.

Compared with graphite materials, large-diameter molybdenum tubes do not produce carbon pollution, and are particularly friendly to some high-cleanliness heat treatment processes (such as vacuum quenching of blades and die steel). Graphite will slowly sublimate at high temperature for a long time, while the vapor pressure of high-purity molybdenum tubes is extremely low, and the volatilization loss is negligible. This directly prolongs the maintenance cycle of the furnace and stops cleaning.

In actual cases, after many users use large-diameter molybdenum pipes with a diameter of 150-300mm as the liner or shunt ring of vacuum furnaces, the most obvious changes in feedback are:
-The heating rate is faster, and the temperature fluctuation is smaller during the heat preservation stage;
-The volume utilization rate of the effective heating zone in the furnace is improved;
-The single maintenance interval has been extended from the original 6-8 months to more than 18 months.

Of course, large-diameter molybdenum tubes are not omnipotent. It requires surface protection under oxidation (such as silicide coating), and it is heavier than graphite, which should be considered when designing furnace support. However, in vacuum heat treatment scenarios that really require high stability and cleanliness, its overall performance is often more dominant.

With the growing demand for new energy vehicles, high-end molds and parts heat treatment, more and more equipment manufacturers have begun to take large-diameter molybdenum tubes as a priority for vacuum furnace upgrades. Although its initial investment is slightly higher, the stability and process yield improvement it brings can usually recover the cost within one year.

If you are planning a new vacuum furnace or the transformation of old equipment, you may wish to focus on whether the large-size structural parts in the furnace can be optimized with large-diameter molybdenum tubes. The choice of different specifications, wall thickness and purity will directly affect the final heat treatment effect.

If you have specific furnace type parameters or process temperature requirements, please leave a message or contact us, and we can help you analyze the most molybdenum tube configuration scheme.