Molybdenum is a refractory metal with the symbol Mo and atomic number 42. It is most commonly used as a high temperature, corrosion resistant metal alloy in steel, cast iron and super alloys for the military and defense industry, semiconductor industry and specialty machine shops.
Molybdenum metal products are available in plate, sheet, strip & foil, bar, rod, tube, wire and customized parts. The metal is silvery white, very hard transition metal, but is softer and more ductile than tungsten. It is easier to be rolled in to thinner sheets and have a wider dimension limits than tungsten. It is also easier to machine molybdenum into complex parts than tungsten, that means molybdenum can be made into more precise & smaller parts. Even though, the machining process is similar.
Here we will introduce the machining process for molybdenum rod
and bar roughly.
After sintering, the molybdenum blank will be forged, to make it with higher density and better mechanical properties.
for molybdenum rod from blank: Spin forging and drawing
several times a suitable ingot, repeated annealing is necessary during the
several times of drawing. Mold is engaged in the process in order to draw to
desired diameter. Remove the oxide surface, graphite is used as lubricant, this
step will also remove it from the surface of rod. Regular surface treatment is
grinding or finish turning.
Process for molybdenum rectangular bar or square bar: 1. Forging, annealing and mold are engaged in this process. 2.Remove the oxide and grinding the surface. The narrow faces can only be turning instead of grinding. The other way to produce molybdenum bar is cut form plate, next article we will talk about process for rolling molybdenum products. The method depends on the specific dimensions of the bar. If it is thin and narrow, it will be from molybdenum plate.
Process of molybdenum tube: Small tubes (roughly with diameter <100mm) are drilled from rods, larger tubes is made by sintering directly. Will need to make mold first if the tubes are large, you can choose a more economical way to make a molybdenum tube with a critical outer diameter. Drilling from rods will waster some materials, while sintering needs a tool. We now have the capacity of providing moly tubing with length up to 2.7m.
If the complex parts are made from bar, and rod and other machining processes such as: laser cut, water jet cut, drilling, turning, wire cutting, etc. will be chosen according to drawing and process technology.
As you can see, the processes are similar with tungsten machining, but requires different tools, feed speed, and annealing process. The accuracy of the work-pieces presented is also different.
Pure molybdenum has better ductility than tungsten, while tungsten alloys (WNiFe, WNiCu) have better machining performance than molybdenum alloys (Mo-La alloy, TZM Alloy, especially TZM alloy). We will introduce this in future articles.