Molybdenum rods, forged products

Rods of the following grades are produced:

1. Mo-PM molybdenum rods and forged products;
2. Mo99.95-PM super-thin molybdenum rods.

Application

Mo-PM and Mo99.95-PM rods and forged products are used to make components of high-temperature vacuum and hydrogen furnaces, hot zones of sapphire smelting units, components of gas turbines, heat exchangers, electrodes for smelting glass and basalt, etc. The thermionic properties of molybdenum are as follows: electronic work function of 4.29 eV, low vacuum evaporation speed and vapor pressure at 1000 - 2000 ºC, allowing the metal to be used widely in various structures of electrovacuum devices and as thermoelectric energy converters. Pure unalloyed molybdenum prepared using the method of PM-Mo powder metallurgy (POLEMA analogues include Mo-PM, Mo99.95-PM) is marked by good plastic characteristics after annealing for internal stress removal (ISR). The fraility threshold of Tx is in a temperature range well below room temperature. The σ_B PM tensile strength of ISR molybdenum in the range of high temperatures drops monotonically: 95-100 Mpa at T=1200 ⁰C, 75-80 MPa at T=1400 ⁰C, and approximately 50-40 Mpa at T=1600 -1800 ⁰C. The useful life of molybdenum products is affected by the metal's creep and vaporization in a vacuum. The speed of molybdenum's vaporization is 2.07x10^-9 g/cm²xsec at T=1727 ⁰C; 7.3x10^-8 g/cm²xsec at T=1927 ⁰C; 5.03x10^-6 g/cm²xsec at T=2227 ⁰C. Nevertheless, in structures operating in static conditions (screens of vacuum furnaces) - sheets and rods made of molybdenum M-MP and M99.95MP that are used, for example, to outfit hot zones for growing sapphire single crystals, function under working temperatures of 2000 -2100 ⁰C.

The temperatures of recrystallization of molybdenum are as follows: initiation at 900 ⁰C, with full recrystallization commencing at 1100 ⁰C (annealing within 1 hr). Once recrystallized, molybdenum is fragile at room temperature. In open air, molydbenum begins to oxidize at T=400 ⁰C, while the speed of oxidation accelerates significantly at T > 600 ⁰C.   
These properties of pure unalloyed molybdenum determine the sphere of its application as a heat-resistant material.

1. Mo-PM molybdenum rods and forged products

Chemical composition

Current powder metallurgy methods ensure a high level of purity of molybdenum in terms of metallic interstitial impurities (C, N, O, H), the necessary microstructure for use as a heat-resistant construction material in electronics and other devices functioning at extremely high temperatures. The chemical composition of rods and forged products is ensured to meet or surpass the norms set for the initial molybdenum powder. Since 2002, the company has primarily used Mo powder 99.95 in its products.

By virtue of its low content of interstitial and metallic impurities, as well as its small-grain structure, finished products are distinguished by outstanding plastic characteristics.

Guaranteed chemical composition of  Mo powder 99.95

*The weight percentage of Mo in Mo powder 99.95 is determined by subtracting the sum of all metallic impurities controlled for using mass-spectrometry with ICP-MS inductively coupled plasma.

The gas-forming impurities C, O, N, H, S, F, and Cl are not included when calculating the share of molybdenum.

** ∑Me – total metallic impurities.

Dimensions of Mo-PM rods and forged products

Hot-rolled rods are produced with diameters from 10 to 40 mm, and forged products (forged rods, cylinders, cubes, parallelipeds and sheets) with a diameter of rectangular edge from 30-300 mm to 1500 mm in length with a surface cleansed from oxides or tooled.

Annealing

At the client's request, products are manufactured with annealing for internal stress removal.

Tooling

At the client's request, rods and forged products are delivered with ground, turned or milled (for flat forged products) surfaces, whose dimensions and tolerances are determined by the consumer's drawings or order.

Microstructure

Microstructure is controlled in rods with a diameter of 30 mm or less. A full recrystallization structure is not permitted, unless otherwise requested by the client.

Guaranteed mechanical properties of  hot-rolled rods  Mo-PM

Upon agreement with the client, rods are delivered without any set mechanical properties with a guarantee that they meet the parameters established by the standard.

2. High precision Mo99.95-PM molybdenum rods

Guaranteed chemical composition

* The weight percentage of Mo is determined by subtracting from 100% the total content of metallic impurities (without including gas-forming elements)

The share of molybdenum and the total content of metallic impurities is guaranteed and set according to the client's request.

Sample chemical composition of 20 mm diameter rods*

* The full analysis of the chemical composition is determined using inductively coupled plasma mass spectrometry (ICP-MS).

Deformation method

Hot rolling, extrusion, forging or cobbing.

Shapes of rods and forged products

Round, rectangular, or of other section types.

Surface finish

Rods are produced chemically cleansed of oxides or machined: tooled or ground. Local defects (with the exception of cracks, backfins and blemishes) on the surface of oxide-cleansed rods that do not cause the rods to exceed the maximum dimensions are permitted.

Roughness requirements for tooled rods are set based on the client's requests. Unless otherwise requested, the roughness of tooled rods is set at Ra 2.5 maximum and the roughness of ground rods at Ra 1.25 maximum.

Dimensions and tolerances for dimensions of round  Mo99.95-PM rods

* Maximum dimensions of turned rods with a diameter of more than 80 mm are determined based on agreement with the client.

Dimension intervals and maximum deviations of rod dimensions are set in accordance with the ASTM B 387 standard

Rod length is established in accordance with the client's request.

Length tolerances are < ± 6.35 mm.

Curvature < 1.27 mm for 305 mm of length.

Acceptable deviations for rod dimensions of rectangular or other sections other than round ones are established based on client request.

Guaranteed mechanical properties of Mo99.95-PM rods

Norms of mechanical properties are set for material following annealing at 900 ⁰C over the course of 0.5 hrs.

Thermal treatment and microstructure

Rods are thermally treated, with annealing for internal stress removal, unless otherwise requested by the client.

In the microstructure of rods with a diameter of 40 mm or less, full recrystallization structure is not permitted, unless otherwise requested by the client, and special requests regarding recrystallization annealing or structure parameters are agreed to.

Sample structures and mechanical properties of Mo99.95-PM rods with a 20 mm diameter

Microstructure in longitudinal and transverse direction x200
After annealing (for internal stress removal)
Average grain size is 20-30 microns.

Hardness HV10 230 kgf/mm²
Short-term strength at room temperature σ_B 690 N/mm²
Relative elongation δ 33%.
Tensile strength  at 1800 ^oC  σ_B40 N/mm², relative elongation δ 17%

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