Niobium (UNS R04210)

Topics Covered

Introduction
Physical Properties
Mechanical Properties
Thermal Properties
Other Designations
Fabrication and Heat Treatment
     Machinability
     Forming
     Welding
     Forging
     Cold Working
     Annealing
Applications

Introduction

Niobium is a soft and light weight metal, and is sometimes also referred to as columbium. It forms a bluish cast when it is exposed to air for a long period of time. Alloys used in aerospace, electronics, and medical industries are produced by adding niobium to nickel or iron. It has high malleability, corrosion resistance and ductility. It is not naturally found in a free state. The chemical and physical properties of niobium are very similar to that of tantalum.

The following datasheet gives more details about niobium.

Physical Properties

The physical properties of niobium are highlighted in the following table.

Properties Metric Imperial
Density 8.57 g/cm³ 0.310 lb/in³
Melting point 2415°C 4380°F

Mechanical Properties

The mechanical properties of niobium are outlined in the following table.

Properties Metric Imperial
Tensile strength 275 - 585 MPa 39900 - 84800 psi
Yield strength (@ strain 0.200%) 207 MPa 30000 psi
Modulus of elasticity 103 GPa 14900 ksi
Elongation at break 5-30% 5-30%
Hardness, Vickers 80 - 120 80 - 120

Thermal Properties

The thermal properties of niobium are displayed in the following table.

Thermal Properties Metric Imperial
Thermal conductivity 52.3 W/mK 363 BTU in/hr. ft².°F

Other Designations

Other designations that are equivalent to niobium are:

  • ASTM B391
  • ASTM B392
  • ASTM B393
  • ASTM B394

Fabrication and Heat Treatment

Machinability

Niobium can be machined using high speed tooling with good lubrication. It can be modified similar to lead or soft copper. It has high gall tendency.

Forming

Niobium can be easily formed, stamped and spun due to its low work hardening rate.

Welding

Niobium can be welded using TIG welding method with small modifications. Inert gas is used for covering a weld pool on back and a face of the weld area.

Forging

At room temperature, niobium is cold forged from ingot.

Cold Working

Niobium has good cold working characteristics.

Annealing

Niobium is annealed by heating at 1200°C (2192°F) in vacuum or inert gas. It can be stress relieved at 800°C (1472°F).

Applications

Niobium finds applications in the following areas:

  • Nuclear power industry
  • Jet engine components
  • Optics
  • Electronics
  • Advanced air frame systems
  • Numismatics
  • Jewellery

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