Thorium (Th) | Korea Tungsten Co., Ltd.

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Thorium

Thorium is an actinide metal whose oxide has the highest melting point of any known oxide. It is used as a special material in thoriated tungsten electrodes, high-temperature refractories and optical glass, and as a radioactive material it is handled under license in accordance with the applicable regulations.

Radioactive material, licensed handling

232.038

1750Melting point °C

11.7Density g/cm³

54Thermal conductivity W/m·K

11.0Thermal expansion µm/m·K

INTRODUCTION

Thorium

A small addition to tungsten greatly improves electron emission. It is used as an additive in welding electrodes and electron tube filaments.

ThO₂-doped tungsten (W-Th)

INTRODUCTION

Thorium

A small addition to tungsten greatly improves electron emission. It is used as an additive in welding electrodes and electron tube filaments.

ThO₂-doped tungsten (W-Th)

WHY THORIUM

An additive that emits electrons readily

01

It lowers the work function

A small addition of ThO₂ to tungsten emits far more electrons at the same temperature.

02

The arc stabilizes

Used in TIG welding electrodes it starts easily and the arc does not wander.

03

Electrode life lengthens

Wear falls and the replacement interval extends.

KEY PROPERTIES

Key Properties

1750 °C

Melting point

Rarely used alone

11.7

Density g/cm³

Medium-high density

Thermal conductivity W/m·K

Moderate

11.0

Thermal expansion µm/m·K

At room temperature

Additive

Form of use

Added to tungsten as ThO₂

1 grade

Supply grade

W-Th electrodes

Figures are representative values. The thermal expansion coefficient is taken from published literature and needs review before release; actual delivery specifications follow the per-lot test report.

WHY THORIUM

An additive that emits electrons readily

01

It lowers the work function

A small addition of ThO₂ to tungsten emits far more electrons at the same temperature.

02

The arc stabilizes

Used in TIG welding electrodes it starts easily and the arc does not wander.

03

Electrode life lengthens

Wear falls and the replacement interval extends.

KEY PROPERTIES

Key Properties

1750 °C

Melting point

Rarely used alone

11.7

Density g/cm³

Medium-high density

Thermal conductivity W/m·K

Moderate

11.0

Thermal expansion µm/m·K

At room temperature

Additive

Form of use

Added to tungsten as ThO₂

1 grade

Supply grade

W-Th electrodes

Figures are representative values. The thermal expansion coefficient is taken from published literature and needs review before release; actual delivery specifications follow the per-lot test report.

WHY THORIUM

An additive that emits electrons readily

01

It lowers the work function

A small addition of ThO₂ to tungsten emits far more electrons at the same temperature.

02

The arc stabilizes

Used in TIG welding electrodes it starts easily and the arc does not wander.

03

Electrode life lengthens

Wear falls and the replacement interval extends.

KEY PROPERTIES

Key Properties

1750 °C

Melting point

Rarely used alone

11.7

Density g/cm³

Medium-high density

Thermal conductivity W/m·K

Moderate

11.0

Thermal expansion µm/m·K

At room temperature

Additive

Form of use

Added to tungsten as ThO₂

1 grade

Supply grade

W-Th electrodes

Figures are representative values. The thermal expansion coefficient is taken from published literature and needs review before release; actual delivery specifications follow the per-lot test report.

Comparison

High-temperature refractory materials compared

Properties

Aluminum oxide (Al₂O₃)

Zirconium oxide (ZrO₂)

Thorium oxide (ThO₂)

Melting point (°C)

2,072

2,715

3,390 (the highest of any oxide)

Density (g/cm³)

3.95