Unlike some other uses of iron and steel, railway rails are subject to very high stresses and have to be made of very high quality steel. It took many decades to improve the quality of the materials, including the change from iron to steel. Minor flaws in the steel that pose no problems in reinforcing rods for buildings, can, however, lead to broken rails and dangerous derailments when used on railway tracks.
By and large, the heavier the rails and the rest of the trackwork, the heavier and faster the trains these tracks can carry.
The rails represent a substantial fraction of the cost of a railway line. Only a small number of rail sizes are made by the steelworks at the one time, so a railway must choose the nearest suitable size. Worn, heavy rail from a mainline is often reclaimed and downgraded for re-use on a branchline, siding or yard.
Pound is a railroad term that indicates the weight of rail per yard. For example one yard of "132 pound rail" weighs 132 pounds. Depending on the use of imperial or metric units, rail sizes are usually expressed in terms of pounds per yard or kilograms per metre. Coincidentally, the pounds-per-yard figure is almost exactly double the kilograms-per-metre figure, making rough conversions easy. Rails in Canada, the United Kingdom, and United States are still described using imperial units. However, in Australia they are now described in metric units and always have been on mainland Europe.
In the countries of former USSR rails are common. Thermally hardened rails also have been used on heavy-duty railroads like Baikal-Amur Mainline, but have proven themselves deficient in operation and were mainly rejected in favor of rails.
The American Society of Civil Engineers (or ASCE) specified rail profiles in 1893 for increments from . ASCE tee-rail profiles specified fixed proportions—height of rail equaled width of foot and proportion of weight in head, web and foot were 42%, 21% and 37%, respectively. ASCE profile was adequate; but heavier weights were less satisfactory. In 1909 the American Railway Association (or ARA) specified standard profiles for increments from . The American Railway Engineering Association (or AREA) specified standard profiles for 100, 110 and 120 pound rails in 1919, for 130 and 140 pound rails in 1920, and for 150 pound rails in 1924. The trend was to increase rail height/foot-width ratio and strengthen the web. Disadvantages of the narrower foot were overcome through use of tie-plates. AREA recommendations reduced the relative weight of rail head down to 36%, while alternative profiles reduced head weight to 33% in heavier weight rails. Attention was also focused on improved fillet radii to reduce stress concentration at the web junction with the head. AREA recommended the ARA 90 pound profile. Old ASCE rails of lighter weight remained in use, and satisfied the limited demand for light rail for a few decades. AREA merged into the American Railway Engineering and Maintenance-of-Way Association in 1997. By the mid-20th century, most rail production was medium heavy (112 to 119 pound) and heavy (127 to 140 pound.) Sizes under 100 pound rail are usually for lighter duty freight, low use trackage, or light rail. Track using 100 to 120 pound rail is for lower speed freight branch lines or rapid transit (for example, most of the New York City Subway system track is constructed with 100 pound rail). Main line track is usually built with 130 pound rail or heavier. Some common North American rail sizes include:
Some common North American crane rail sizes include:
Early rails were used on horse drawn wagonways, initially using strap-iron rails, which consisted of thin strips of iron strapped onto wooden rails. These rails were too fragile to carry heavy loads, but because the initial construction cost was less, this method was sometimes used to quickly build an inexpensive rail line. Strap rails sometimes separated from the wooden base and speared into the floor of the carriages above, creating what was referred to as a "snake head." However, the long-term expense involved in frequent maintenance outweighed any savings.
These were superseded by cast iron rails which were flanged (i.e 'L' shaped) with the wagon wheels being flat, an early exponent being Benjamin Outram. His partner William Jessop had pioneered the use of "edge rails" in 1789 where the wheels were flanged and, over time it was realised that these worked better.
The earliest of these in general use were the so-called cast iron fishbelly rails from their shape. Rails made from cast iron were brittle and broke easily. They could only be made in short lengths which would soon become uneven. By 1840, wrought iron in longer lengths replaced cast iron as rolling techniques improved. The cross-section varied widely from one line to another, but were of three basic types as shown in the diagram. The parallel cross-section which developed in later years was referred to as Bullhead.
Meanwhile, in May 1831, the first flanged T rail (also called T-section) arrived in America from Britain and was laid into the Pennsylvania Railroad by Camden and Amboy Railroad. They were also used by Charles Vignoles in Britain.
The first steel rails were made in 1857 by Robert Forester Mushet, who laid them at Derby station in England. Steel is a much stronger material, which steadily replaced iron for use on railway rail and allowed much longer lengths of rails to be rolled.
The American Railway Engineering Association (AREA) and the American Society for Testing Materials (ASTM) specified carbon, manganese, silicon and phosphorus content for steel rails. Tensile strength increases with carbon content, while ductility decreases. AREA and ASTM specified 0.55 to 0.77 percent carbon in 70 to 90 pound rail, 0.67 to 0.80 percent in rail weights from 90 to 120 pounds, and 0.69 to 0.82 percent for heavier rails. Manganese increases strength and resistance to abrasion. AREA and ASTM specified 0.6 to 0.9 percent manganese in 70 to 90 pound rail and 0.7 to 1 percent in heavier rails. Silicon improves steel by increasing density. AREA and ASTM specified 0.1 to 0.23 percent silicon. Phosphorus and sulfur are impurities causing brittle rail with reduced impact-resistance. AREA and ASTM specified maximum phosphorus concentration of 0.04 percent.
The use of welded rather than jointed track began in around the 1940s and had become widespread by the 1960s.
Rail weights are very important in determining axleloads and speeds.
These limits are so low that sharp curves hardly impose any extra speed limits.
In late 1830s England, railway lines had a vast range of different patterns. One of the earliest lines to use double-headed rail was the London and Birmingham Railway, which had offered a prize for the best design. If it were true that the rail could be turned over when the running surface became worn, the argument lost its validity as it evolved into the bullhead rail, with a heavier profile to the top edge. The lower edge also wore in patches where it was borne on the chairs. Although it became the standard for the British railway system until the mid-20th century, there seems to be nothing in the literature about any other advantages it may have had.
Flat bottomed rail was first introduced in America by R.L.Stevens in 1830. There were no steel mills in America capable of rolling long lengths, so it was manufactured in Britain. Charles Vignoles observed that wear was occurring with steel rails and steel chairs upon stone blocks, the normal system at that time. In 1836 he recommended flat-bottomed rail to the London and Croydon Railway for which he was consulting engineer.
His original rail had a smaller cross-section to the Stevens rail, with a wider base than modern rail, fastened with screws through the base. Other lines which adopted it were the Hull and Selby, the Newcastle and North Shields, and the Manchester, Bolton and Bury Canal Navigation and Railway Company.
When it became possible to preserve wooden sleepers with mercuric chloride (a process called Kyanising) and creosote, they gave a much quieter ride than stone blocks and it was possible to fasten the rails directly using clips or rail spikes. Their use spread world-wide and acquired Vignoles' name.
Iron-strapped wooden rails were used on all American railways until 1831. Col. Robert L. Stevens, the President of the Camden and Amboy Railroad, conceived the idea that an all-iron rail would be better suited for building a railroad. He sailed to England which was the only place where his flanged T rail (also called T-section) could be rolled. Railways in England had been using rolled rail of other cross-sections which the ironmasters had produced.
In May, 1831, the first 500 rails, each 15 feet (4.57 m) long and weighing 36 pounds per yard (18 kg/m), reached Philadelphia and were placed in the track, marking the first use of the flanged T rail. Afterwards, the flanged T rail became employed by all railroads in the United States. Col. Stevens also invented the hooked spike for attaching the rail to the crosstie (or sleeper). At the present time, the screw spike is being used widely in place of the hooked spike, perhaps because it is possible to install the screw spike by using a labor-saving machine that replaces salaried workers.
At the present time, crossties or sleepers constructed of concrete are in use in some places. The use of creosote as a treatment for wooden crossties has been declared to be detrimental to the health of people and plants. The crossties or sleepers are embedded in ballast in order to provide stability and drainage.
The joint where two rails are connected is the weakest part of a rail line. The earliest iron rails were joined by a simple fishplate or bar of metal bolted through the web of the rail. Stronger methods of joining two rails together have been developed. When sufficient metal is put into the rail joint, the joint is almost as strong as the rest of the rail length. The noise generated by trains passing over the rail joints, described as "the clickity clack of the railroad track", can be eliminated by welding the rail sections together forming a continuous rail. One kind of welding is the Thermite welding process.
Development of improved switch point rail profiles for heavy-haul operations: TTCI researchers investigate what role switch-point rail-profile design plays in the formation of RCF on switch points.(TTCI R&D)
Jul 01, 2010; Transportation Technology Center, Inc., has designed two new switch-point rail profiles for AREMA No. 20 style (1) switches based...
WIPO PUBLISHES PATENT OF SITECH SITZTECHNIK FOR "RAIL PROFILE WITH DELIBERATELY ESTABLISHED LASER-STRENGTHENED ZONES" (GERMAN INVENTORS)
May 04, 2012; GENEVA, May 2 -- Publication No. WO/2012/052105 was published on April 26. Title of the invention: "RAIL PROFILE WITH...