Sep 29, 2017
Steel rail, we also called rails, tracks, is an important element of the rail system. The steel rail is used with rail joint and railway fasteners like rail clip, railraod tie plate, turnouts to make the train run fast and steady without steering.
As we know, the rail system is composed of the two parallel rails and sleepers. The steel rails are fixed on the sleepers, and under the rail sleeper, is the railway track ballast. The steel rail can bear much more weight compared with other material rails. Due to the enormous pressure, the steel rail needs high-quality steel to make.
Nowadays, we would like to make the section of the steel rail as a Chinese character “工”. And the steel rails have their own destiny according to the use. Some steel rails are used for coming into contact with the wheels, which called railhead. Some steel rails at the middle of the track, which called rail web, and some steel rails at the bottom, which called the rail flanges. Different ways have different requirements for the intensity, stability and abrasion resistance of the steel rail. So there are many steel rails standards.
The types of railway track are expressed in kilometer per meter. The heavier the steel rail per meter, the greater weight the rail can bear.
As for the rail track sizes, there are some differences among countries. The common standards in Europe are 40kg/m, 50kg/m, and 60kg/m. And the common rails standards in China are 43kg, 50kg, 60kg, and 75kg. Generally, the most common rails standards are 43kg, 60kg/m and 75kg/m. The United States prefers to the heavier rails. For example, the coal line applied to the 75kg/m rails at the United States. Of course, these rails mentioned, which are belong to the heavy steel rail category. Where can buy railroad rail? If you want to find the light railroad track manufacturers, you can choose the AGICO Rail.
The process of steel rail manufacturing is simple. The most important is rolling the steel. After choosing the suitable steel billet, then the next step is rolling the steel.
Adopt the continuous casting bloom to improve the macrostructure of the billet steel. Besides, adopt the vacuum degassing and secondary refining technology to ensure the inner quality of the billet steel. This technology can control the Residual element and gas content and ensure the purity of the steel.
As we know, the steel billet through rolling, cooling, and straightening can be made to the rails. During the process, the vital part is rolling. There are two methods to rolling: groove rolling and universal rolling.
Groove rolling is simpler than the universal rolling. The metal deformation is steady. The groove rolling is suited for roughing deformation because of the simple control system. But the hole pattern adopts the asymmetry design, so the symmetry of the steel rail section is not very well. Besides, the control accuracy is not rigid, so the surface quality cannot be controlled well.
Universal rolling is popular among the world, which is the best technology to produce the steel rail. The universal rolling system is fond of a pair of the active horizontal roll and a pair of the passive horizontal roll. These four rolls are working on the same level. The flat roll processes the rail web. The vertical roll and the flat roll processes the railhead and rail flanges together. The rolling mill guide beam is mounted directly on the bearing seat, which can move as a whole system and the rolling process is complete automation.
Heating is better for improving the mechanical property drastically. The most popular heating technology is Quenching and tempering heat treatment and slow quenching. Meanwhile, adopt the walking beam furnace to heat the billet steel that can control the gas fractionation and prevent the decarburization and uneven temperature.
We would like to adopt the long rod to rolling, cooling and straightening. This technology is better for increasing the yield, reducing the residue stress and lengthening the service life of the steel rail.
Through the online quality inspect center, adopt the ultrasound wave, eddy, and laser to inspect the steel inner quality, the rail surface quality and the railroad track dimension.
It is common that adopt the carbide machine to drill and process the rail head so that can get the high accuracy.
With the development of the society, the high-speed railway, heavy load railway and the railway automatic control systems are becoming mainstreams. From the 1980s, China has studied this part and now takes new technology.
Except for the advanced production technology, AGICO RAIL provides various standards railroad tracks and many different railroad track dimensions. As a railway component manufacturer, we also provide customization service for joint bar, rail clip, railroad spike, etc.
Not all rails are created equal. In previous #rail101 articles I've talked about some of the different shapes of rail and how they are used, but the steel they are made from often differs too.
Why?
Not all rails need to withstand the same loads and traffic and often the optimum life for a rail is a balancing act between different types of degradation competing to limit the rails useful life. I wrote a little bit recently about which rail is best which discusses this further.
There are literally thousands of types of steel out there filling different needs. Your steel rule has different properties from your can of soft drink for example.
Most rail standards around the world contain multiple options for rail steels to try to address the differing needs of traffic they are trying to support. For a list of the common steel grades and their compositions along with their typical applications you can find a handy reference table here.
The type of steel can have dramatic effects on the track performance and maintenance. For example some rail steels wear 10 times faster than others - so picking the right one(s) can make huge differences to networks bottom lines.
The European rail standard (EN) for rails is the one I'm most familiar with, (indeed I've had a little input into what is in it), so I'll discuss the types in this first. There are of course many other standards around the globe and I'll not be able to include them all in this article without boring all my readers to tears - so apologies in advance if I miss yours out. Feel free to leave some comments on the key differences that people should know about.
The European rail standard has two distinct groups of steels. Those which are heat treated, and those which are not. Heat treatment is used to alter the properties of the steel - essentially to make it harder and hopefully more wear resistant. Here is a link to more detail on heat treating rail.
Their name reflects the minimum hardness that the surface of the rail should be (in Brinell) and is often used as a proxy for wear resistance. That isn't quite true but that is an explanation for another day/article. All are prefixed by the letter "R" for some reason which I don't know. If you know why then let me know in the comments.
R200 has a minimum hardness of 200 Brinell. Other as-rolled grades are R220, R260, R260Mn, and R320Cr. The numbers indicating the minimum hardness and the suffix letters indicate alloy additions to alter the properties of the rail. In many countries, (but certainly not all) R260 is often the "standard" grade that is used for the majority of the mainline track.
At this point I will mention that progress in standards to reflect the real world happens at a seemingly glacial rate. The UK has used a harder as rolled grade (we call it HP335) since 2010 yet as of 2019 it still does not appear in the European rail standard. *rolls eyes*
Then there are the Heat treated grades which all carry a suffix "HT"
R350HT / R350LHT / R370CrHT / R400HT
These grades are used typically in areas experiencing heavier wear or plastic flow. There are very good reasons why you don't use the most wear resistant rail everywhere - but that is for a separate article.
All of the rails so far are pearlitic rails. Pearlitic refers to the structure within the steel. I don't want to baffle many of my audience by trying to turn this into a metallurgy article, but steel exists in different phases as well as different compositions and heat treatments. Common steel phases are Ferrite, Pearlite, Bainite, and Martensite. The vast majority of rails are pearlite, however British Steel has pioneered Bainitic rails which have some very interesting anti-fatigue properties to avoid the need for rail grinding. Indeed SNCF mandate it's use in parts of their rail infrastructure and Eurotunnel used it for over 1 billion tonnes of traffic without grinding needed in the channel tunnel. If you want more in-depth articles on rail steel metallurgy then let me know in the comments.
Where the European standard (EN) names their rails by the minimum hardness, other specifications such as the UIC and Indian rail specification use the tensile strength of the steel instead.
The UIC rail grades of 700, 900A or B, and 1100 require minimum strengths of 680, 880 and 1080MPa respectively. I'm not sure why the grade numbers are different - perhaps someone can comment below to explain?
The Indian rail specification (IRS) more sensibly aligns the numbers for grade and strength, i.e. 880 grade needs a tensile strength of 880MPa. The Indian specification again uses suffix letters to indicate alloy element additions or heat treatment, e.g., 1080HH is head hardened.
There is quite close agreement between these specifications on some grades, e.g.,
There may be significant differences in the standards but the steel can be the same.
The American (AREMA) specification is the one I find hardest to explain. Whilst it sensibly focuses on the properties the rail has to achieve (via a hardness specification), the grades names aren't quite as intuitive - to me at least. There are two main categories, Carbon Rail Steel and Low Alloy Rail Steel which vary by the composition of the steel. Then both of these categories are sub divided into Standard, Intermediate and High strength sub-categories. The standard and high strengths use minimum harness requirements of 310 and 370 Brinell respectively. The intermediate strength category however has different levels depending on which steel composition is used, (350 for Carbon rail, and 325 for Low Alloy rail). Whether heat treatment is used to achieve the properties is indicated in the brand (or a metal plate), which leads to quite a potential number of different permutations.
Lastly I'll mention the BS11 standard. One of the first rail standards out there (first issued in 1905 last revised in 2015 its 10th edition), it has a long history but is now largely superseded by the Euro Norm (EN13674) rail standard. However BS11 remains current to identify the dimensions and tolerances of various rails produced which are still used around the globe including bullhead rail.
Thanks for reading, please like, comment and share if you think it could help people in your network. If you need rail or rail info then drop me a line and check out some of my other #rail101 articles.