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THE BEGINNING

In 1837 Theodore Goldschmidt founded the Goldschmidt Company in Berlin to supply chemicals to the textile

industry, and established a research and development facility investigating processes for refining metals and

their oxides. In March 1895, Dr Hans Goldschmidt was granted German Patent #96317 for a "process to

manufacture metals and alloys" based upon the reduction of heavy metal oxides by a more reactive metal such

as aluminium.

THE THERMIT ® WELDING PROCESSES

When applied to the reduction of Iron oxides, the exothermic reaction generates sufficient energy to raise the

reaction product temperature to in excess of 3,000°C at which both the metal and aluminium oxide are both

liquid:

Iron Oxide + Aluminium > Aluminium Oxide + Iron + Heat

3FeO + 2Al > Al2O3 + 3Fe + 880 kJ

Fe2O3 + 2Al > Al2O3 + 2Fe + 850 kJ

The process was first used to provide the thermal energy for a method for forge welding rails in 1899, when a

number of welded joints were installed in the Essen Tramway. The process was first used in the UK to weld

tram rails installed in Leeds in 1904.

Further development leading to the addition of alloying elements to the basic Aluminothermic reaction produced

a steel with a compatible metallurgy to the parent rails, thus enabling a full fusion welding process to be

developed. While early welds were produced by casting the Thermit steel into hand produced moulds

encompassing the two rails to be joined together, subsequent development lead to the introduction of pre

formed refractory moulds designed to fit specific rail profiles.

While the basic Aluminothermic process still forms the heart of the Thermit welding processes, continuous

development coupled with modern production technology, statistical process control and quality assurance, has

resulted in processes which more than match the service demands of modern high speed, high axle load

railway systems.

Conventional "Flat bottom" or "Vignole" Rails

Special Section Railway rails

Grooved Tram Rails

Heavy Section Crane Rails

Electrical Conductor Rails

In addition, products are available to suit special types of track support, confines spaces, environmental

restrictions, and for joining rails of differing types or with differing degrees of wear.

THERMIT WELDING PROCESS

ESTABLISHED WORLDWIDE

TECHNICAL INFORMATION

LATEST NEWS

Brochures and Prices for SmartWeld

Control and Rail Setter now available

View full news list

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In each case, should products not be available from our own manufactured stock, we will either design and

manufacture the products to suit, or call on the extensive range available from within the Thermit Group.

THE PRINCIPLE OF THERMIT WELDING

Thermit welding is an effective, highly mobile, method of joining heavy section steel structures such as rails.

Essentially a casting process, the high heat input and metallurgical properties of the Thermit steel make the

process ideal for welding high strength, high hardness steels such as those used for modern rails.

Thermit Welding is a skilled welding process and must not be undertaken by anyone who has not been trained

and certificated to use it.

Detailed operating instructions are provided for each of our processes, but the welding methods all comprise of

6 main elements:

1.

A carefully prepared gap must be produced

between the two rails, which must then be

accurately aligned by means of straightedges

to ensure the finished joint is perfectly

straight and flat.

2.

Pre-formed refractory moulds which are

manufactured to accurately fit around the

specific rail profile are clamped around the

rail gap, and then sealed in position.

Equipment for locating the preheating burner,

and the Thermit container is then

assembled.

3.

The weld cavity formed inside the mould is

preheated using an oxy fuel gas burner withaccurately set gas pressures for a prescribed

time. The quality of the finished weld willdepend upon the precision of this preheating

process.

4.

The Thermit® Portion is manufactured to

produce a steel with a metallurgy compatiblewith the specific type of rail to be welded. On

completion of the preheating, the container isfitted to the top of the moulds, the portion is

ignited and the subsequent exothermicreaction produces the molten Thermit Steel.

The container incorporates an automatictapping system enabling the liquid steel -

which is at a temperature in excess of2,500°C - to discharge directly into the weld

cavity.

5.

The welded joint is allowed to cool for a

predetermined time before the excess steeland the mould material is removed from

around the top of the rail with the aid of ahydraulic trimming device.

6.

When cold the joint is cleaned of all debris,

and the rail running surfaces are precisionground the profile. The finished weld must

then be inspected before it is passed asready for service.

Once correctly installed, the finished weld is expected to last the life of therail, with no further maintenance.

It is estimated that over 100,000 Aluminothermic welds are manufactured in track each year, with a total

population in excess of 1.8 million. The processes are used throughout the year on site with no heavyequipment other than that which may be carried to site by the two man welding team. All the equipment, ancillary

tools such as lighting, gases and consumables can be transported to site by small commercial vehicles.

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WELD TYPES

SkV-E SkV-L SkS SrZ CRW

Joining of New andworn flat bottom rail

Replacement ofstandard welds,

removal of raildefects. Compositejoints between

different rail profiles

Joining of heavysection crane rails

Installation ofgrooved tram rails

and joining them toconventional rails

Joining of lowresistance electrical

conductor rails

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