Pig Iron, Cast Iron, Rolled Steel, What Are the Materials of Railroad Tracks?

Tracks are not only made for supporting trains, they are high quality and well-made technical products. Do you know which material is used in railway track? YONGYANG introduces you to the production process of raw materials for railways, which are mostly made of steel and have a specific composition with different components to make them durable.

In the early days of railroads, rails were made of cast iron, which could lead to breakage and other damage. Technology has now improved the material of the rails. The track provides the surface on which the railroad cars run. At the bottom of the track, the track legs transfer the load and distribute the load to a larger surface. Great forces can be applied to all dimensions, whether in freight transport with high axle loads or in high-speed train transport with very dynamic loads.

Wear resistance and long life of the rails are very important, as the rails must neither break nor be too soft. Despite the relatively small contact area of the wheels on the running surface of the rail, the frictional connection must be obtained without leaving any marks on the structure and surface. It must be possible to grind, plane grind or to allow reconditioning several times, also the running surface accumulation of welds should be provided as appropriate.

Pig iron

To make steel rails, pig iron must first be made. For this purpose, iron ore containing lime and coke is heated to over 1,500 °C with a constant supply of fresh air in the blast furnace. The result is the product pig iron and slag. Pig iron is not suitable as a building material but as a raw material for the production of steel. It must still be desulfurized.

Steel

Steel is produced in a second step by a so-called oxy-fuel refining process. The carbon content is reduced from about 4% to a maximum of 1.5%. Other additives determine the subsequent material properties. The alloys made in this way from rail steel are composed of a complex mixture of various chemical elements. Some are added, and other substances - especially those that make it more brittle - are safely removed by the refining process.

Some of the useless iron products were deposited as slag. The "oxygen blowing process", which is common today, was introduced in 1949 and is a very economical way to make high-quality, low-contamination steel. It is also common to add large amounts of scrap metal to the steel melt. The entire production process ensures a pure, homogeneous material with precisely defined properties.

Forming

Static steel is poured into a mold to be moved for further processing. For rails from the hot rolling process, this may include up to 20 rolling operations until the desired profile is achieved. The rail steel can be rolled at a temperature of about 1,250 °C. This temperature must be maintained during the rolling process in order to obtain a uniform structure.

After rolling, the finished rails must be cooled in a controlled manner to avoid damaging the internal stresses and the rough structure. One uses a roll straightener at approx. 50 °C for alignment. In addition, ultrasonic testing is recommended to detect any production errors; otherwise, voids and cavities in the material may have unforeseen consequences if the rails fail later.

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