RAIL STEEL

In the USSR, heavy type rails (R75, R65 and R50, 25 m long) are made of high-carbon steel with a high manganese content (Table 36.1). This carbon content is typical for rail steel in the USA and Canada. In other countries it is slightly lower, for example in England 0.50-0.60%, in Japan 0.60-0.75%, in Germany 0.40-0.60% with an increased manganese content (up to 1.2- 1.3%). Abroad, rail steel is smelted in open-hearth furnaces (USA, Canada), oxygen converters (Japan, Germany, England), electric furnaces (Germany), and Thomas converters (France). When smelting rail steel in converters, the quality of the rails decreases due to the increased content of harmful impurities (up to 0.07% P and 0.06% S).

Over the years, the improvement of the chemical composition of rail steel has been carried out in the following main directions:

1. Reducing the content of harmful impurities (sulfur, phosphorus, oxygen, hydrogen) in rail steel in order to increase its purity and metallurgical quality.

2.Increasing the carbon content in steel to eliminate the soft component in its structure - ferrite and increase the amount of solid particles of the second phase - cementite, which is part of thin-plate pearlite. With an increase in the content of rail steel from 0.5 to 0.8% C, its strength, wear and crush resistance increased significantly.

Table 36.1

3. Alloying of rail steel, i.e. increasing its content to more than 1.0% Mn, more than 0.4% Si and introducing into its composition such elements as Cr, Ni, Mo, V, Nb, Ti, etc. This also includes attempts to improve the complex properties of rail steel through modification and microalloying, which amounts to adding small amounts of elements such as Mg, B, Ce and rare earth elements.

The carbon content in rail steel is currently brought to the eutectoid level, above which structurally free cementite is formed. One of the promising directions for modifying rail steel aims to increase the upper permissible limit of carbon content in rail steel to 0.85-0.87% without the release of structurally free cementite.

The best options for non-heat-treated rails made of low-alloy steel made it possible to increase their operational durability on domestic railways by no more than 25%.

In the hot-rolled state (end rolling temperature 1000-1050°C), the grain size in rail steel corresponds to 2-3 points according to GOST 5639-65, after hardening (heating temperature 830-850 °C) it corresponds to 7-8 points. The structure of rail steel in the hot-rolled state is a sorbite-like fine-plate pearlite, sometimes with individual thin ferrite deposits. The hardenability of rail steel is low: when determined by the end hardening method (GOST 5657-69), it is 4-6 mm.

In the USSR, rail steel is mainly smelted in heavy-duty open-hearth furnaces with a capacity of 380-450 tons at the Kuznetsk Metallurgical Plant (KMK), Nizhny Tagil Metallurgical Plant (NTMK) and the Azovstal plant. It is partially smelted in Bessemer converters at the Dnieper Metallurgical Plant named after. Dzerzhinsky (DMZ). A diagram of the technological process of rail production at four domestic rail rolling plants is shown in Fig. 36.3. It shows that in the production of railway rails three types of heat treatment are used: anti-floc heat treatment; thermal hardening of ends; thermal hardening along the entire length.

Long-term and trouble-free operation of VSP elements is possible only when they are made of suitable material. And today we will look at what steel railway rails are made of, why this particular metal was chosen, and what properties it has. The information will help you choose the right rolled products for the actual construction of the track.

It is important to take into account the specifics of modern times. Over almost 100 years, the carrying capacity of railway transport has increased 8-10 times, and the speed of its movement along the roadway has increased 5 times. It turns out that the supporting structures experience completely different loads. Therefore, it is necessary that they are stronger, harder and more wear-resistant than they were a century ago.

Rail steel

It combines several types of similar metals, similar in method of application - used for the manufacture of elements of the VSP (superstructure of the track). Fine-needle perlite forms the basis of the phase structure for all variants smelted in converter or arc furnaces. After heat treatment, it becomes as homogeneous as possible, acquiring viscosity, sufficient hardness and high wear resistance.

According to deoxidizers, it is divided into 2 main groups:

I – harmful impurities are removed using ferromanganese or ferrosilicon;

II – aluminum inclusions are used to remove oxygen (considered more preferable due to their nature).

Basic materials for making rails

Much depends on the area in which the rental products will be used. VSP elements are made from converter steel, laid into the railway track and forming a wide or narrow gauge. But crane support metal structures need to withstand completely different loads, so factories use high-carbon alloys to produce them.

A completely different case is the so-called contact ones, installed to create a subway track. They do not accept huge voltages, but they must effectively remove current, so they are made of relatively soft metals.

Chemical composition and its advantages

For the main steel grades of railway rails, it is regulated by GOST R 554 97-2013. This interstate standard establishes that the main component is iron, but in addition to it, the alloy must include a number of other elements - in the following mass fractions:

• Carbon (carbon) – from 0.71 to 0.82%, increases the mechanical properties by approximately half. Its particles bind ferromolecules, turning them into carbides, which are much stronger and larger. And high-temperature effects become less critical.
• Manganese – from 0.25 to 1.05%, improves impact strength (by a quarter to a third), as well as wear resistance and hardness. Moreover, the ductility does not deteriorate, which has a very positive effect on the manufacturability of the finished rolled product.
• Silicon - from 0.18 to 0.4%, is required to remove oxygen impurities, and therefore to optimize the internal crystalline structure of the material. With this additive, the likelihood of segregation stains appearing is significantly reduced, and durability increases by approximately 1.4 times.
• Vanadium - from 0.012 to 0.08%, depending on the specific grade of steel for the manufacture of rails. Important for ensuring sufficient contact strength. In combination with carbon, it forms carbides that increase the endurance limit (namely, its lower threshold).

Undesirable or even harmful impurities deserve special consideration, but it is not yet possible to completely isolate them with the help of modern technologies. This:

• Nitrogen - from 0.03 to 0.07%, is bad because it neutralizes the alloying effect. Because of this, nitrides are formed in the thickness of the profile, which are not amenable to heat strengthening, and therefore reduce the mechanical properties of the finished VSP elements.
• Sulfur – up to 0.045%. Its inclusions prevent the alloy from being malleable during hot processing under pressure. As a result, after rolling, you may end up with a product that is prone to cracking and will have to be immediately rejected.
• Phosphorus – up to 0.035. It also increases the fragility of the metal structure. Fatigue quickly accumulates with it, which leads to rapid delamination and fractures.

For the sake of maximum clarity, we present the chemical composition of popular grades of steel for railway rails in the following summary table:

steel grade	Mass fraction of elements %
	Carbon	Manganese	Silicon	Vanadium	Titanium	Chromium	Phosphorus	Sulfur	Aluminum
							No more
K78HSF	0,76-0,82	0,75-1,05	0,40-0,80	0,05-0,15		0,040-0,60	0,025	0,025	0,005
E78HSF
M76F	0,71-0,82		0,25-0,45	0,03-0,15			0,035	0,040	0,020
K76F							0,030	0,035
E76F							0,025	0,030
M76T					0,007-0,025		0,035	0,040
K76T							0,030	0,035
E76T							0,025	0,030
M76							0,035	0,040	0,025
K76							0,030	0,035
E76							0,025	0,030
Notes: In steel grades, the letters M, K, E - indicate the method of steel smelting, the numbers - the average mass fraction of carbon, the Letters F, S, X, T - alloying of steel with vanadium, silicon, chromium and titanium, respectively. The allowed mass fraction of residual elements is chromium (in rails of categories T1, T2, H), nickel and copper no more than 0.15% each, with a total mass fraction of no more than 0.40%. The chemical composition for P65K must correspond to that specified, with the exception of the mass fraction of carbon, which should be 0.83 - 0.87%. In this case, the numbers in the steel grade are replaced by 85.

As you can see, two more components are additionally indicated - titanium and chromium. We did not describe them in detail above, since they are not always present, but the first of them is a useful admixture, whose positive effect is reduced to increasing strength, and the second is a residual element. It is also worth paying attention to the presence of aluminum, which helps reduce weight without compromising other quality indicators.

Mechanical properties

• Impact resistance - the hardness of the material alloyed with additives after volumetric hardening reaches 60 HRC on the Rockwell scale, viscosity - 2.5 kg/cm2. Thanks to this, it is difficult to accidentally damage already laid metal structures.
• Resistance to cyclic loads - rolled metal products are made from steel, because its tensile strength reaches up to 1000 MPa. In the climatic conditions of our latitudes, they do not deform for decades (especially with proper care).
• Moderate ductility - a hot-rolled product during production can be heated to a temperature of 1000 degrees Celsius. The indicator of its relative narrowing will not go beyond 25%. The result is a profile without voids and minor defects, which during operation could quickly turn into serious flaws.

The combination of such practical properties also determines the constant popularity and widespread use of I-beam guides made specifically from the alloy in question.

Applications and grades of rail steel

The main area of ​​use of the metal (as is clear from its name) is the production of rolled products for laying VSP.

Now let's look at the most popular variations of alloys:

• 76 is the most popular. Profiles of the P50 and P65 series are made from it, constituting 3/4 of all supporting structures of wide-gauge railway tracks.
• 76F – already reinforced with vanadium, with an increased resource. Therefore, it is used for the production of rolled products, which will later be laid in lines for high-speed movement of locomotives and other fast transport.
• K63 – alloyed with nickel (up to 0.3%), has impressive hardness and better corrosion resistance. Crane rails are made from it; the grade of steel allows it to withstand loads that in other cases become critical.
• K63F – with tungsten additives, which means even higher cyclic strength.
• M54 – enriched with manganese and due to this has good viscosity. It has found its application in the production of linings for joints and turnouts.
• M68 – relevant for the production of specific elements of the superstructure of the track.

The need for mechanical properties in various combinations determined such a variety of options. Add here the relatively low weight and low cost, and you get a very practical design for the construction of transport lines and interchange nodes.

The type of rail steel is indicated on the marking, which can be either permanent or temporary. In the first case it is applied by branding, in the second - by paint. Other designations include compliance of the rolled product with GOST, as well as its additional features (shortened length, grade, location of technical holes, etc.).

The profiles can be used until the expiration of the service life specified by the manufacturer and calculated by the tonnage passed. Premature failure of VSP elements caused by the appearance of defects is also possible. Then they need to be replaced or repaired. You can read about different types of defects in.

So, we found out that for railway tracks the steel grade is 76 and 76F, with a high carbon content and with vanadium additives (in the second case). It is smelted in converter and arc furnaces, with deoxidation with ferrosilicon and aluminum, followed by dephosphorization and slag renewal, with vacuum and heat treatment. With this approach, the finished rolled products are distinguished by a high degree of purity and a low tendency to develop defects.

In a similar way, manufacturing plants produce not only structures for forming the fabric, but also other important elements used at railway facilities. Let's take a closer look at them.

Wheel steels – for railway wheels

The rims of moving parts of transport simply must be wear-resistant (otherwise all the strength advantages of the superstructure of the track will be reduced to zero). Therefore, they are produced from those types of metal we are considering that are enriched with carbides. Then they fail less often, which means they provoke less emergency situations, and in the long term they also reduce the cost of operating locomotives and cars.

Carbon in wheel steels

Analyzing the chemical composition, we concluded that carbon inclusions increase the metal’s resistance to wear, but they also increase susceptibility to critical temperatures. In the case of rims, it is especially important to make them resistant to thermal damage. It must be remembered that premature wear (especially with careless maintenance) can lead to vehicles moving at an impressive speed going off the road.

Therefore, there is no point in focusing exclusively on high-carbon alloys - their strength in this case can be quite detrimental. Conventional rail steel may not be suitable for the production of wheels; the grade for their manufacture must meet the following standards:

• AAR M-107/M-208 – American;
• EN 13262 – European;
• JIS E 5402-1 – Japanese;
• GOST 10791-2011 – intersectoral.

The design solutions of the Land of the Rising Sun deserve special attention. The railway service there is quite well developed and today is at that modern level, which is worth emulating not only in the CIS countries. The locomotives there are advanced and move at impressive speeds. How do the moving parts of this transport withstand the most severe loads? Let's try to figure it out.

Japanese wheel steels

About 90 years ago, local engineers and builders were faced with a global problem: experts discovered that the wheels of their vehicles were wearing out prematurely, although the service life was calculated for years to come.

An explanation was found and turned out to be simple: the alloy for the production of metal elements, made using borrowed European technologies, contained only 0.5% carbon. This mass fraction was clearly insufficient to provide the required wear resistance.

Scientists from Japan understood that increasing the percentage of carbon in the thickness of the profile could also lead to negative consequences (in particular, a tendency to thermal damage). Therefore, large-scale research was launched, the goal of which was to find the optimal concentration of the additive while maintaining all the beneficial properties. As a result, we settled on the level of 0.6-0.75%, which corresponds to the JIS E 5402-1 standard.

Higher carbon in the wheels - less wear on the rails

The search allowed us to draw another important conclusion: with a balance of impurities and the base metal, not only the moving parts of the transport, but also those elements of the VSP on which they travel last longer.

An explanation for this effect was also found: the smallest particles break off from the wheels, settle at the point of contact and have an abrasive effect on the rolling surface. As a result, scratches appear on the head, and over time, cracks.

These results prompted engineers to experimentally increase the carbon content - up to the level that the steel grade currently boasts for JIS E 5402-1 (that is, up to 0.75%).

Japanese wheels on a German railway

There was a problem in the German railway traffic: the moving parts of local trains (ICE) quickly deformed, which led to their failure, loss of traction quality, and the occurrence of emergency situations. When Deutsche Bann specialists learned that the locomotives of the Shinkan-sen company from the Land of the Rising Sun do not experience such difficulties even when moving at the maximum permissible speeds, they wanted to conduct comparative tests.

The German trains were equipped with both European wheels made of ER7 alloy (with a mass fraction of carbon up to 0.52%) and Japanese wheels made according to the JIS E 5402-1 standard. After 6 years of independent testing, from 2003 to 2009, the second option showed that it resists wear 1.5 times more effectively.

At the same time, metal structures laid in the track were also regularly checked. It turned out that they also erase more slowly - exactly 1.5 times. Fewer abrasive particles remain on the contact surface. Enriching the material with carbon gives a good increase in service life - thanks to the Japanese for this discovery.

Advantages of railway rails

Modern varieties of them have the following advantages (and a material such as rail steel helps to emphasize these practical advantages):

• distribute the tested loads evenly along the entire length of the web;
• provide a reliable surface for the wheels of vehicles, helping them develop and maintain high speeds of movement;
• have a significant service life (over 50 years), during which they can withstand severe stress and effectively resist wear.

Thus, they help to cope with the main task - they are the key to fast and safe transportation of passengers and cargo.

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Now that you know what kind of material there is for the production of railway metal, its characteristics, chemical composition, as well as mechanical properties, it will be easier to choose a specific brand that is optimally suitable for arranging a railway facility. And the PromPutSnabzhenie company will always help you quickly obtain the required volume of metal structures at an attractive price - contact us to order.

Recently, work has been actively carried out to modernize railway tracks. Outdated rails and sleepers are replaced with new elements that meet international standards.

A large assortment of railway rails is presented on the website www.rails.com.ua/relsy.html. All products have quality reports, certificates and passports.

Areas of use

Railway tracks are necessary not only for communication between populated areas. They are often laid at industrial enterprises to provide access for loading or unloading. Heavy construction equipment, such as cranes and forklifts, moves on rails.

All components of the railway track have special markings, by which you can understand where these rails will be used. There are the following options for using rails:

• laying narrow-gauge tracks for railway transport, for transporting goods in mines or quarries, at various industrial facilities;
• laying broad gauge railway tracks at large factories and other enterprises;
• arrangement of subways;
• laying tracks for railway transport.

Classification and production of rails

The rails by which the locomotive and carriages move are marked with the Latin letter “P”. Then there are some numbers. This is a designation for the weight of one meter of a given rail. Based on this indicator, one can judge the load that the railway track will withstand during operation.

All rails for railway tracks are made of open hearth steel. To increase strength, various additives and processing methods are used:

• mild steel from an open-hearth furnace is deoxidized with special additives; aluminum is not included in this complex. Rails made from this alloy are marked blue;
• Rails made of manganese-aluminum alloy are produced with white markings. It is produced by deoxidizing open hearth steel with aluminum;
• High-carbon steel is additionally subjected to thermal hardening in oil; such rails are particularly durable.

The strongest rails are those that are used for laying railway tracks for high-speed trains and for moving freight trains. As a rule, they are made of open hearth and converter steel.

Where there is less load on the track, carbon steel is used.

[Article] Rail steel and rail markings

Rail steel and rail markings

Rail steel

The material for the rails is rail steel. Rails are made of two groups: Group I - from mild open-hearth steel, deoxidized in a ladle with complex deoxidizers without the use of aluminum or other deoxidizers that form harmful streaked non-metallic inclusions in the steel; Group II - from mild open-hearth steel, deoxidized with aluminum or manganese-aluminum alloy.

The quality of steel is determined by its chemical composition (Table 1.2).

With an increase in carbon C in steel, the overall bending strength of the rails, hardness and wear resistance increase. Manganese Mn increases the hardness, wear resistance and toughness of rail steel, and silicon Si increases hardness and wear resistance. Phosphorus P and sulfur S are harmful impurities. At low temperatures, rails with a high phosphorus content become brittle, and sulfur - red-brittle (cracks form when the rails are rolled). Vanadium, titanium and zirconium are micro-alloying and modifying additives that improve the structure and quality of steel.

The macrostructure of modern carbon rail steel is lamellar pearlite with small ferrite veins at the boundaries of pearlite grains. Significant hardness, wear resistance and toughness of carbon steels are achieved by giving them a homogeneous sorbitol structure (using special heat treatment).

The mechanical properties of steel for rails of groups I and II during tensile tests must correspond to the data given in table. 1.3.

These data correspond to rails made of open hearth steel, not hardened along the entire length.

Steel for rails must have a clean, uniform, dense, fine-grained structure (macrostructure).

The rail manufacturing technology must guarantee the absence of flakes in them, as well as local non-metallic inclusions (alumina, titanium carbides and nitrides or alumina cemented with silicates), extended along the rolling direction in the form of tracks - lines.

The surface of the rail head at its ends is subjected to hardening by rolling or induction heating with high frequency currents.

To ensure greater wear resistance and durability, the rails are made of open-hearth high-carbon steel (types P75, P65, P50), subjecting them to hermetic treatment along the entire length by volumetric hardening in oil followed by furnace tempering (GOST 18267-82). The macrostructure of the quenched rail head metal is sorbitol quenching. The Brinell hardness on the rolling surface of the head of hardened rails should be in the range of 341-388 HB, the neck and sole - no more than 388 HB.

The mechanical properties of volume-hardened rails must be characterized by values ​​not less than those indicated below:

Rails that fully meet technical requirements and standards are classified as 1st grade. Rails that have deviations in the chemical composition and mechanical properties are classified as 2nd grade.

Volume-hardened rails have a service life 1.3-1.5 times higher than conventional ones.

The operating conditions of rails on the roads of Siberia and the Far East are almost twice as difficult as in the European part of Russia. Therefore, rails of low-temperature reliability P65, volume-hardened of group I, manufactured from vanadium-niobium-boron-containing steel using nitrided ferroalloys for alloying have been created. These rails use electric steel, which is welded in arc furnaces.

At a temperature of minus 60 °C, electric steel rails can withstand shock loads twice as high as open-hearth steel rails.

Currently, Russian rails are among the best in the world. However, Japanese, French, Swedish and Canadian rails have significantly lower levels of self-stress and greater purity of the rail steel, as well as straightness. That is why their purchase has now begun for high-speed sections of Russian railways.

Marking, service life of rails and measures to extend them

Rails are marked to ensure their correct placement on the track and to determine the place and time of manufacture of each individual rail. It is divided into the main (permanent) one, performed during rolling by stamping in a hot and cold state (Fig. 1.2) and additional or temporary, performed with paint. The main factory marking indicates the conformity of the rails

requirements of the standards, and an additional one notes the features of each rail (shortening, grade, etc.).

The plant that produces the rails guarantees the proper service of the rails along the way during the operating period, calculated in millions of tons of gross tonnage T. Rails are removed from the track either due to head wear or defects. As a rule, vertical wear of the head does not reach the limit values ​​at the operating rate T, at which the rails are continuously replaced due to their maximum yield for single defects.

Currently, the accepted classification of rail defects is given in Table. 1.4.

The intensity of a single output of rails depends on their operating time (the tonnage passed along them), the track design, loads on the rails from wheel pairs of circulating rolling stock, the layout and profile of the track, the type of rails, the quality of steel and other factors. In Fig. Figure 1.3 shows the growth curves averaged for the network of the former USSR for a single withdrawal of non-heat-treated rails on straight and flat curves, depending on the skipped tonnage during a link track on wooden sleepers.

Bulk-hardened rails have a significantly lower output, which can be seen, for example, in the graph in Fig. 1.4 for the line St. Petersburg - Moscow.

The largest single removal of defective rails is made due to insufficient contact fatigue strength of the metal, due to excessive lateral wear of the head in curves and due to corrosion of the rail base and corrosion fatigue cracks (defects 44, 17, 21, 14, 11 , 69 - see table 1.4).

Extending the service life of rails is currently being done through the use of resource-saving technologies; in particular, a good means of restoring the service properties of rails is their periodic grinding along the way or sharpening of old rails at rail welding enterprises. Rail grinding mechanisms and rail grinding trains with abrasive wheels are used for grinding rails.

Improving the quality of rails is carried out in three main areas: increasing the purity of rail steel; increasing the hardness of rail metal and improving its structure; increasing the straightness of rails during manufacturing. The R65sh rail is also being developed, which will have a head height reserve (6...7 mm) for subsequent grinding.

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Rails are iron profiled rolled products in the form of strips, fastened with beams and intended for the movement of rolling stock of railways and subways, trams, trains and trolleys of mining transport and monorails and in general any mobile, turning and rotating structures.

Rails are parts of the upper structure of the road, laid on supports and fastened to them and to each other to form a rail track. The rails directly take the pressure of the wheels of the rolling stock.

We present railway rails produced by the Novokuznetsk Metallurgical Plant of the following types:

Railway rails - rails intended for sectional and continuous railway tracks and for the manufacture of turnouts, are produced in accordance with GOST R 51685-2000.

Rails are divided into types: P50, P65 (for external threads of curved sections of the road, GOST 8161-75) and P75.

Railway rails are produced from steel grades K78ХSF, E76, E78ХSF, М76Ф, К76Ф, E76Ф, К76Т, М76Т, E76Т, М76, К76.

Rail designation scheme: rail type, quality group, steel grade, rail length, presence of bolt holes, designation of this standard.

Rails for industrial railway tracks - wide gauge rails intended for railway tracks and switches of industrial enterprises are produced in accordance with GOST R 51045-97 and are divided into 3 types: PP50, PP65 and RP75.

This type of rail is made from carbon steel grade 76 and special carbon microalloy steel grades 76T, 76F and 76Ts.

Rail designation scheme: rail type, rail length, bolt grooves (2 - on both ends, 0 - without holes), rail hardening (T - heat-strengthened, H - non-heat-strengthened), steel grade, standard designation.

Broad gauge railway rails made of open hearth steel - broad gauge railway rails of types P75, P65 and P50 made of open hearth steel are manufactured in accordance with GOST 24182-80. The design and dimensions of the rails are calculated according to GOST 7174-75, GOST 8161-75 and GOST 16210-77.

Rails are manufactured in 2 accuracy groups:

Group 1: rails are made of mild open-hearth steel, deoxidized with complex deoxidizers without the use of aluminum. Such rails are marked blue.

Rails R75, R65 are made from steel M76V, M76T, M76VT, M76Ts;

Rails P50 - made of steel M74T, M74Ts.

Group 2: rails are made from mild open-hearth steel, deoxidized with aluminum or, as it is often called, manganese-aluminum alloy. Such rails are indicated by white markings.

For the manufacture of rails R75, R65, M76 steel is used;

For P50 rails, M74 steel is used.

The length of the rails is 24.92; 24.84; 12.42; 12.46 meters.

Railway rails, heat-treated by volumetric hardening in oil - rails P50, P65, P75 made of open-hearth high-carbon steel. Such rails are subjected to heat treatment in accordance with GOST 18267-82 along the entire length using the method of volumetric hardening in oil followed by furnace tempering. The range and chemical composition of such rails is specified in GOST 24182-80.

Hardened rails are divided into first and second grade. Rails of the 1st grade are divided into rails of the first group of classes 1 and 2 and the second group of classes 1 and 2. Rails are sorted into groups and grades according to GOST 24182-80.

Based on materials from the site http://www.corunamet.ru/produkcia/relsi/