Sintering Process for molybdenum rods

Molybdenum rod complete sintering process (powder metallurgy hydrogen high-temperature sintering)

Overall process flow Molybdenum powder batching and mixing → Isostatic pressing molding / Molded molding → Raw material decontamination and lubricant removal → High-temperature hydrogen sintering → Cooling and discharging → Finished sintered molybdenum rod

Sintered molybdenum rods density is 9.5 - 10.1 g/cm³. Porosity defects (the most distinctive):

Crystal boundaries are covered with numerous black dot-like / long strip-shaped holes, with interconnected air pores, relative density 92% - 98%, crystal boundaries are covered with tiny interconnected air pores.

Coarse equiaxed grains, grain size 45-60 μm, grain boundaries are straight and unoriented, without fiber streamlines;

Above refer picture is the longitudinal polishing surfaces of the edge and core of the sintered billet of molybdenum rod

Oxygen content: 40-60 ppm;

Performance origin: Holes cut through the matrix, poor thermal and electrical conductivity, high vacuum degassing for sintered blanks, high brittleness, easy penetration by molten medium, high vacuum degassing.

1. It can produce ultra-large-diameter and ultra-long molybdenum rods that cannot be processed by forging equipment and can only be sintered;

2. The process is short, energy consumption is lower than forging, and the production cost is low;

3. The equipment investment is simple and it is suitable for large-scale low-cost rough blanks.

Therefore, The cost is low, it can make large sizes, but it has micro-pores inside, poor toughness, and low strength. It is only suitable for light-load, intermittent high-temperature, no strong erosion, and short-term usage scenarios. It cannot be used for long-term bearing, glass main electrodes, or precision processing parts.

1. Internal holes cannot be completely eliminated, resulting in a density that is not fully dense;

2. Strength, toughness, and high-temperature creep resistance are far inferior to those of forged molybdenum;

3. Micro-pores are prone to trapping air, and the gas release volume is large in a vacuum environment; molten glass and metal liquid are easily able to penetrate the pores, and the electrode lifespan is short.

1.High-temperature sintering furnaces, hydrogen furnaces, vacuum furnaces, simple supporting components such as small support pins, partitions, base pads, sample holders, are not subject to high pressure and can be used intermittently.

2. The molybdenum heating strip is connected to the conductive rod, the simple lead-out electrode, and the low-power heating element's conductive connector. It is powered on for a short period of time, without the risk of molten liquid erosion.

3. The ceramic and hard alloy sintering tooling blanks are used as the holding rods and supports, not coming into contact with the molten metal/glass, and only bearing the solid raw materials.

1.Only used for auxiliary electrodes, small side electrodes, and short-term test electrodes; cannot be used as the main electrode for glass fiber drawing:

Auxiliary conductive rod for small glass melting kilns in the laboratory;

2. Intermittent small glass furnaces, temporary electrodes for test furnaces;
disadvantages: Micro-porous glass permeation, continuous production leads to rapid corrosion and short lifespan. For mass production, all use forged molybdenum rods.

1.Small conductive cathode and anode rods for rare earth electrolytic cells (for low current and shallow molten salt conditions)

2. Simple load-bearing rods for the sintering of tungsten, molybdenum and hard alloy preforms;

3. Internal positioning and limiting components of the metal reduction furnace.

1.Flame spraying and plasma spraying of molybdenum raw material rods (no strict requirements for density in the spraying process);

2. The original large-diameter sintered molybdenum rods before forging and rolling are used as raw material blanks for the forging factory. Then, they are forged at high temperatures into dense molybdenum rods, molybdenum wires, and molybdenum plates.

1. Simple heat insulation support columns and positioning rods for ordinary vacuum furnaces; not suitable for ultra-high vacuum in semiconductor and 
2. Simple molybdenum lead-in bases for small lamps and halogen lamps (for low current and light load).

1. For rough machining blanks with no requirements for strength and toughness, simply perform rough turning;

2. Low-speed, low-load wear-resistant bushings and pins (not subjected to impact or alternating loads); Do not process thin-walled parts, fine threads, or slender shafts, as they are prone to cracking and breaking.

1. Forging heating furnaces, salt bath furnaces, and the internal simple support rods and support bars for the equipment;

2. Titanium and nickel-based alloy heat treatment tooling positioning brackets, suitable for short-term high-temperature use.

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