The safety of train traffic largely depends on the serviceable maintenance, quality, and durability of the railway track, in particular, its main element - rails. The problem of improving the performance of rails, despite the positive results achieved in ensuring the quality of steel, remains relevant. AT modern conditions exploitation railways during the movement of heavy transport, the load from the rolling stock on the axle can reach 35 tons, and the speed of movement of high-speed trains up to 250 km/h. It is necessary to determine the scientific and technical foundations for solving problems related to increasing the operational stability of rails. Along with scientific research, technical solutions are needed to improve the technology of domestic rail production, new ways and opportunities to improve the reliability of rails. The service life of railway rails is largely determined by the structure and mechanical properties of steel. In this regard, the role of research in the field of metal physics and metal science is increasing in the creation of more advanced steel grades that can provide long-term strength of products during operation.

For the conditions of use on the railways of Russia of a non-joining track, the quality of welded joints is subject to strict requirements, namely: they must have high strength, have a uniform structure and ensure the straightness of the lashes along the tread surface and the working side edge of the rail head. Metallurgical methods for improving the reliability of the welded joint of volumetrically hardened rails made of electric steel include: optimization of the chemical composition for the main elements and the total content of impurities; improving the ductility of rails by some reduction in hardness; purity of steel by non-metallic inclusions. The issues of improving the reliability of a welded joint are of particular relevance in connection with the creation of rails of several categories that differ in a set of mechanical properties.

The financial crisis has made adjustments to the timing and procedure for the reconstruction of domestic rail and beam shops for the production of 100-meter differentially hardened rails that meet the requirements of the new national standard on railroad tracks.

In recent years, competition has increased in the Russian railway rail market. The need for rails for high-speed traffic up to 250 km / h, caused by the need to organize such traffic on Russian railways as part of the implementation of the program "Strategy for the development of railway transport in Russian Federation until 2030” is satisfied by the supply of Japanese rails. It is planned to carry out certification of rails for high-speed traffic of Polish and Italian production. Russian enterprises do not yet participate in tenders for the supply of such rails due to the discrepancy between the technical level of the production base. Therefore, the issue of deadlines for the completion of the reconstruction of domestic rail and beam shops is becoming extremely relevant in order to maintain the volume of supplies of rails for Russian market. The volume of this market only for the high-speed traffic created in Russia with a total length of 13,190 km is 1 million 700 thousand tons of R65 type rails. Russian Railways has developed a Strategy for the Development of Railway Transport in the Russian Federation until 2030. The main activities of this strategy include the construction of lines with high-speed and high-speed traffic. With the development of such movement, the requirements for the elements of the superstructure of the track increase sharply, incl. and to the rails. The service life of the rails largely determines the turnaround time and, accordingly, the annual volume of repairs.

Much work has been done at the Novokuznetsk and Nizhny Tagil Iron and Steel Works to develop technology and equipment for the mass production of railway metal products. Many new technical solutions have been implemented in the field of production and operation of rails and rail fasteners related to the modernization process production capacity and new technologies in the field of railway transport, as a result, manufacturers and consumers of railway metal products have significantly reduced the costs of mastering the production of rail products with new consumer properties and, accordingly, the organization of high-speed and heavy traffic.

At the same time, the service life of the best samples of foreign rails is 1.5 times higher compared to this indicator for rails of domestic manufacturers, which is in the range of 700 million tons. gross. JSC "Russian Railways" supports the efforts of manufacturers aimed at radically improving the quality of rails.

Field testing of promising categories of rails made of hypereutectoid and microalloyed steels produced by NKMK has been successfully completed, which opens up opportunities for certification in the RS FZHT and subsequent delivery of domestic rails of increased wear resistance and cold resistance to Russian railways.

In connection with the organization of high-speed traffic on Russian railways, the activity of foreign manufacturers of railway rails has sharply increased, which makes the issue of accelerating the modernization of the Russian rail production base in terms of maintaining the supply volumes of rails for JSC Russian Railways extremely urgent.

Rails produced by the Novokuznetsk and Nizhny Tagil Iron and Steel Works during field tests at the EK VNIIZhT, incl. certification, show results approaching the results of the best world samples, which indicates that the network is currently supplied with domestic rails of high quality. Completion of the reconstruction of domestic rail and beam shops will make it possible to produce rails that are not inferior in comparable operating conditions in terms of track maintenance costs and turnaround time to rails of Japanese, French and Austrian production.

The study of the laws of steelmaking and metal forming helps to choose the most optimal modes technological processes, required main and auxiliary equipment. .

The main results of the industrial implementation of new technical solutions and operational improvements in the rail production process at OJSC NKMK

On the basis of numerous theoretical and experimental studies, it has been established that the resistance of rails to wear and damage by contact fatigue defects increases significantly as the structure is refined. In this direction, a large amount of research work and industrial experiments have been carried out, namely: a technology has been developed and patented for the production of rails of increased wear resistance from steel with a carbon content of up to 0.90% and microalloying additives of vanadium (0.07 - 0.08%) and nitrogen (0.012 - 0.017%). In the course of operational observations at the Irkutsk - Slyudyanka pass section of the East Siberian Railway, which differs a large number sections of small radius, revealed high wear resistance of rails made of steel of hypereutectoid composition - their specific lateral wear amounted to 0.076 - 0.072 mm per 1 million tons of gross cargo, while for standard rails it reaches 0.124 mm. A further increase in the carbon content is limited by the formation of structurally free cementite along the grain boundaries of pearlite colonies in the form of a grid, which leads to a sharp decrease in the impact strength of the steel and the dynamic strength of the rails.

Another important direction is the creation of low-temperature reliability rails. New technology The production of such rails made it possible to ensure traffic safety at temperatures of minus 40 ° C and below. According to the track services on roads located in areas with severe climatic conditions, single seizures due to defects are 2.0-2.5 times more in winter than in summer. Low temperatures have a particularly unfavorable effect on the development of fatigue cracks in the head of rails laid on a seamless track, as well as on ductility and toughness, resulting in possible brittle fracture of the rail. To improve the low-temperature reliability of the rail metal, it is necessary to ensure the formation of a fine-grained structure due to the formation of vanadium carbonitrides, which is possible with a sufficient amount of vanadium and nitrogen in the steel. It has been established that guaranteed obtaining of the required impact strength of rails of low-temperature reliability is provided with a nitrogen content of 0.010 - 0.020% and vanadium 0.07 - 0.08%.

Thanks to the optimization of the chemical composition of carbon rail electric steel and the use of carbonitride hardening technology, a significant increase in the service life of rails to the level of world standards was achieved, which ensured the production of more than 1 billion gross tons.

In recent years, a new direction has been outlined in the development of transport in Russia - the construction of high-speed railway lines. The need to create rails new category has become another incentive to search for promising technical solutions, as well as to improve existing technologies. In particular, the chemical composition and technology for the production of rails from low-alloy steel E76KhGF have been developed and patented. These rails in the hot-rolled state had a satisfactory quality in terms of non-metallic inclusions, macrostructure, pile strength, mechanical characteristics, decarburized layer and residual stresses. Ensuring the straightness of the rails required technical solutions aimed at improving the straightening mode, the use of bending machines and chilling the sole along the entire length of the rail before hardening, as well as optimizing the hardening and tempering modes. This made it possible to establish the production of rails for high-speed combined traffic.

As practice shows, during operation on rails, thermomechanical damage often occurs due to structural transformations in steel. Due to the slippage of the wheel on the rolling surface of the rail head in the contact zone, instant structural and phase changes occur, accompanied by the formation of a secondary structure (non-etching white zone), which is characterized by high hardness and brittleness. When modeling the process of impact loads on samples of steel with different contents of carbon and alloying elements, it was revealed that the formation of secondary structures depends on the chemical composition of the steel. It has been established that the resistance of rails to the formation of defects of thermomechanical origin increases with a decrease in the carbon content in steel. In this regard, another promising direction in the development of rail production has become the creation of a new generation of rails - with a bainitic structure. The formation of such a structure with a complex of high mechanical properties is achieved by rational concentration limits of alloying elements.

Conducted laboratory and industrial experiments made it possible to develop and patent the chemical compositions of bainitic rail steels. Of the series of heats, the most interesting was steel containing (mass fraction, %): 0.32 C; 1.48 MP; 1.21 Bc 1.0 Cr; 0.2 - 0.3 Mo; 0DZ V; 0.012 N. The experimental rails were distinguished by a complex of improved properties and satisfactory manufacturability, due to economical alloying they had a reduced cost and, no less important, they made it possible to abandon the environmentally harmful technology of volumetric oil quenching.

Due to the fact that the development of rail production in the direction of the use of new steels does not require significant capital investments and reconstruction, it can currently be recognized as a priority. In parallel, research is being carried out on the development of industrial production advanced technology of differentiated hardening of rails. This will ensure railway transport rails with great reliability and service life.

Thus, the following should be noted as the main directions for the development of rail production at OAO NKMK: the use of wear-resistant steel with an increased carbon content (up to 0.9%) and microalloying additives (0.070.8% V; 0.012 - 0.017% N); production of highly reliable rails for operation at low climatic temperatures from steel containing 0.01 - 0.02% N and 0.07 - 0.08% V); the use of bainitic steel, which has a balanced set of mechanical properties, as well as low-alloy electric steel for high-precision rails intended for high-speed highways.

The quality of the rails of OAO NKMK

At OAO NKMK, the rail production technology as a whole includes smelting in an electric furnace, out-of-furnace treatment, evacuation, casting on continuous casting machines, heating for rolling in PSHB furnaces, rolling, straightening in a roller straightener, heat treatment (quenching in oil with tempering) or its absence, editing in a roller straightening machine.

Rails of the following purpose and categories are produced:

1. Railway rails of the R65 type for general purposes are made of carbon steel (average carbon 0.75%) grade E76F, which are subdivided into categories H and T1 according to GOST R 51685-2000.

KCU+20 s = Yu J/cm) and hardness (285-331 HB). The specified level of mechanical properties is provided by the pearlite structure, which is formed over the rail cross section after rolling. Rails of this category are operated mainly on turnouts and subways.

Category T1 rails are characterized by higher strength (s = 1177-1373 N/mm2, ax = 800-1030 N/mm2), ductility (Ô = 8.0-17%, \|/ = 29-47%), shock l l viscosity (KSu + 20 s \u003d 25-60 J / cm) and hardness (341-401 HB). The specified level of mechanical properties is provided by a finely dispersed pearlite structure with small areas of ferrite, which is achieved by hardening heat treatment - bulk quenching in oil. Rails of this category are widely used on the vast majority of Russian railways.

2. Railway rails for special purposes are subdivided:

R65 type rails of low temperature reliability (NE) according to TU 0921-118-011243282003 are made of carbon steel (average carbon 0.75%) grade E76F, microalloyed with vanadium (0.07%) and nitrogen (0.012%). Rails of low-temperature reliability have a level of mechanical properties and hardness similar to category T1 rails and are distinguished by an increased level of impact strength at temperature

0 2 minus 600С (KSi.bo s = 25-60 J/cm). An increased level of low-temperature reliability, along with a sufficiently high level of strength, ductility and hardness of rails, is provided by a fine-grained finely dispersed pearlite structure with insignificant areas of ferrite, which is achieved by the combined influence of technologies - bulk quenching in oil and microalloying of steel with vanadium and nitrogen. Rails of low-temperature reliability have no analogues abroad and are intended for operation in regions with a cold climate (East Siberian, Trans-Baikal, Krasnoyarsk railways).

Rails of the R65 and R65K type of increased wear resistance and contact endurance (IE) according to TU 0921-125-01124328-2003 are made of high-carbon steel (average carbon 0.90%) grade E90AF, microalloyed with vanadium (0.08%) and nitrogen ( 0.014%). Due to the carbon content of more than 0.80% in steel, these rails are called hypereutectoid. Hypereutectoid rails or rails of increased wear resistance are characterized by an increased level of hardness (400-415 HB) and strength (ab = 1352-1400 N/mm2, at = 900-1111 N/mm2). At the same time, these rails retain enough high level plasticity (S = 11%, c/ = 37%), and impact strength at positive and negative temperatures (KCu + 2o ° c; -bo ° c = 25-27 J / cm2). The specified set of properties is provided by a homogeneous fine-grained finely dispersed perlite structure obtained as a result of volumetric quenching in oil due to an increased carbon content and microalloying of steel with vanadium and nitrogen. Rails with the specified complex of mechanical properties are characterized by high wear resistance and contact fatigue strength and have no analogues abroad. Such rails are operated in Russia on cargo-loaded sections, in curved sections of a small radius (600 mm or less) of the East Siberian and Transbaikal railways.

R65 type rails for high-speed combined traffic according to TU 0921-07601124328-2003, which are divided into CCI and CC2 versions.

Rails of CCI version are manufactured according to the technology similar to rails of the NE category with additional increased requirements for straightness.

CC2 version rails are manufactured according to the technology similar to the Tic category rails with additional increased straightness requirements.

Rails of CCI and CC2 versions are designed for operation on high-speed combined sections railway track respectively, in areas with a cold climate and the European part of Russia.

R65 type rails made of low-alloy chromium steel for high-speed traffic according to TU 0921-220-01124328-2006, which are subdivided according to the class of straightness and torsion into SP version that meets the requirements for category T1 rails and BC version with increased requirements.

Rails of execution SP and VS are made of low-alloyed chromium steel grade E76KhGF. SP and VS rails are characterized by a fairly high level of hardness (352 HB) comparable to the hardness of category T1 and NE rails. At the same time, the strength (av

About l 11 bON / mm, ox \u003d 740 N / mm), ductility (6 \u003d 10%, \| / \u003d 16%) and impact strength (KCU + 20 s \u003d 17 J / cm2) of the rails are somewhat superior to category H rails. The specified set of mechanical properties is provided by the pearlite structure, achieved without heat treatment by alloying the steel with chromium.

Low-alloy chromium steel rails are designed primarily for high-speed passenger traffic, where increased rail straightness and wear resistance are required.

High-strength R65 type rails made of bainitic steel according to TU 0921-167op-01124323-2003 are made from low-alloy steel grade 30KhG2SAFM. The rails are characterized by strength (ab = 1265 N/mm2, ot = 1040 N/mm2) and hardness (338 HB) comparable to category T1 rails. A distinctive feature of rails made of bainitic steel is their high level of ductility (ô = 14.5%, \j/ = 48.5%) and impact strength (KCU + 2o ° c = 73 J / cm2, KCU -bo ° s - 28 J/cm2). The specified set of mechanical properties is provided by a bainitic structure formed over the cross section of the rail in the hot-rolled state after tempering, due to the alloying of medium-carbon steel with chromium, manganese and silicon.

The scope of these rails is currently not defined and requires additional research and field tests.

3. Rails rail types R50 and R65 for the subway according to TU 0921-15401124328-2003 are made of E76F carbon steel using a technology similar to category H rails. The set of mechanical properties of rails for subways is low and typical of category H rails. reduced contact fatigue strength and wear resistance.

The rails are also made of low-alloyed chromium steel grade E78HSF, which is characterized by increased contact fatigue strength and wear resistance due to the increased content of carbon and chromium in the steel. The level of mechanical properties of these experimental rails is comparable to the level of properties of rails for high-speed movement made of steel grade E76KhGF. Chromium steel rails are currently under development.

4. Pointed rails OR50, OR65 according to GOST 9960 - 85 are made of carbon steel (average carbon 0.73%) grade E73V. According to the level of mechanical properties and structure, rails made of this steel are comparable to rails of category H.

Also, sharp rails are made of steel grade E76HSF according to TU 0921-03801124328-2007. In terms of mechanical properties and structure, these rails are comparable to rails for high-speed traffic made of E76KhGF steel and subway rails made of E78KhSF steel, but differ in a lower level of hardness, strength, and ductility.

Pointed rails are used for the manufacture of turnouts.

5. Tramway grooved rails according to TU 14-2R-320-96 are made of E76 grade carbon steel. In terms of mechanical properties and structure, tram rails correspond to rails of category H and have low strength values ​​(av = 940-1030 N/mm2, st = 540-620 N/mm2), ductility (8=6-9.5%, y= 11-17%) and hardness (285-321 HB).

6. Railway rails of the RP 50, RP65 type for industrial transport routes in accordance with GOST R 51045-97 and TU 14-2R-409-2006. The rails are made of carbon steel grades 76, 76F and E85F. Technical requirements for these rails in all characteristics are much lower than for rails of the above categories.

As a rule, general-purpose rails of categories T1 and H, as well as special-purpose rails of NE, IE, CCI, CC2 versions that do not satisfy technical requirements relevant standard and specifications.

In recent years, a lot of work has been done at the plant to modernize existing and commission new units, which made it possible to increase the overall technical level of production and created additional features to improve rail production technology. In chronological order, the implementation of the most significant events is as follows:

Launch of automatic transmission No. 1 - IV quarter. 2004

Reconstruction of chipboard No. 2 - I quarter. 2005

Transfer of furnaces of TOOZ RBC to natural gas - II quarter. 2005

Launch of ShPB RBC - I quarter. 2006

Launch of automatic transmission No. 2 - II quarter. 2006

Start-up of the air separation unit - Q1 2007

Completion of installation and start-up - II quarter. 2008

It should be noted that the implemented measures not only contributed to the creation of conditions for improving the quality of products, but are necessary condition the effectiveness of further work to improve the technology of rail production, starting from the first stage of the reconstruction of the RBC. The results of the production of R65 rails, as the most mass-produced type of product for Russian Railways, are presented in the table (Table 30), from which it follows that the production volume in 2007-2008. changed insignificantly, as did such qualitative indicators as the output of category H rails 25 m long and the output of heat-strengthened rails of category T1. It should be noted as a positive moment a noticeable increase in production in 2008. low-temperature reliability rails and rails for high-speed combined traffic. However, the data for 2009 show a significant decrease in rail production.

Conclusion

1. A comprehensive study was carried out to improve the technology of rolling rails in the roughing and finishing stands of a rail and beam mill, which ensures an increase in the quality, level consumer properties rails and mill performance, as well as the development and industrial testing of new grades of special-purpose rail steels.

2. Based on the analysis and generalization of experience in the production of high-quality metal products, a comprehensive methodology for operational improvements in the metallurgical process of rail production has been developed to improve the efficiency of technological modes and equipment parameters. It is shown that under the conditions of stable modern electric steel-smelting technology, the key process is rolling production, as the closing metallurgical stage, which provides the required profile, shape, straightness, length and quality of finished rails.

3. Based on mathematical model to determine the energy-power parameters and temperature in the “duo” reversing stand of a rail and beam mill, an analysis was made of the process of rolling rails at different temperatures and recommendations were made to reduce the deformation temperature in the “900” stand to 1070°C instead of 1200°C, while reducing the cycle of movement of the PSHB beam from 54 to 51 seconds and an increase in productivity by 100 thousand tons / year.

4. A method of hardening by electric arc hardening has been developed and calculated new form finishing gauge of the rail and beam mill, which allows to reduce the consumption of rolls by 0.2 kg / t, the stability of the size of the rail profile, its symmetry, and the reduction in the weight of a running meter of rail by 0.3 kg.

5. Technological regimes for smelting rail steel in electric furnaces have been developed that provide an increase in the complex of physical and mechanical properties of steel, a decrease in contamination with non-metallic inclusions and gases, a decrease in the mass fraction of residual elements, a decrease in metal rejection by surface defects by 0.7%, and an increase in casting seriality on average. for 0.5 heat. Developed and implemented automated system regulation of the metal level in the mold, providing an increase in the stability of the casting process and the exclusion of anomalies in the quality of the ingot.

6. A study of the structure, mechanical properties and fracture resistance was carried out, including when testing full-profile rail samples, rails made of HJI3 steel E76F, open-hearth steel and foreign-made rails. In terms of contamination with non-metallic inclusions, rails made of HJI3 electric steel are much cleaner than rails made of open-hearth steel, being at the level of the best foreign analogues. The mechanical properties of rails made of continuous casting of electric steel have a high uniformity of properties in the initial and final billets along the course of continuous casting and along the cross section of the rail.

7. Compositions have been developed and technologies for the production of new rail steels of increased operational stability have been mastered:

Hypereutectoid rail steel with a high carbon content of up to 0.90%, the hardness of rails from which reaches 400-415 HB, and wear resistance is 30% higher than standard rails; microalloyed with vanadium and nitrogen rail steel of increased low-temperature reliability, the cold resistance of which is 1.5-2.0 times higher than

O P of standard rails and is KSi = 25-60 J / cm at -60 C.

8. A complex technology for smelting, out-of-furnace processing, continuous casting and rolling of rails made of low-alloy steel of the E75KhGF type was developed and tested, and a study was made of the quality, level of mechanical properties and fracture resistance, including bench tests of full-profile rail samples in comparison with rails of other methods production. The level of strength and ductility of hot-rolled low-alloy steel rails is close to the properties of heat-treated carbon steel rails and meets the requirements of GOST R 51685 for body-hardened rails; cold resistance and crack resistance of low-alloy steel rails in the hot-rolled state is at the level of heat-treated carbon steel rails - the fracture toughness K1s for both rails is 73 MPa. The endurance limit in bench cyclic tests of full profile rails made of new steel is higher than for bulk hardened rails made of carbon steel.

The total economic effect from the introduction of developments amounted to more than 150 million rubles. rubles.

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Purpose:

- direct the wheels of the PS in motion;

Perceive elastically process and transfer loads from the wheels to the under-rail base;

In areas with a / b, serve as a conductor of signal current, and in case of electric traction - reverse power.

Classification:

Rails are divided into:

A) by types P50, P65, P65k, P75 (the type of rail is determined by the mass of one meter of the rail, the rounded value kt is substituted after the letter P).

R65k - rolled for laying in the outer threads of curves with R≤550 m.

B) by quality category: B-highest; T1 and T2 - heat-strengthened; H - non-heat-strengthened; (The category depends on the frequency of rail steel, its hardness, structure, straightness of rails during manufacture, etc.) ,SS - for combined high-speed traffic; NE - low-temperature reliability; IE - rails of increased wear resistance.

C) by the presence of bolt holes: with holes at both ends (2-3) or without holes.

D) according to the method of steel smelting: M - from open-hearth steel, K - from converter steel; E - from electric steel.

E) by type of initial blanks: from ingots; from continuously cast billets (CWB).

Requirements:

- Durability: have a sufficient moment of inertia (I cm 4) and a moment of resistance (W cm 3) so that the bending and torsion stresses arising in the rails do not exceed the permissible values.

-Durability: Rail steel must have high hardness, wear resistance, and toughness.

- High contact-fatigue endurance.

The mass of the rail, its outline (profile), the quality of rail steel and manufacturing features are closely related to each other and depend on the loads of wheelsets on the rail, speeds and load density.

Rail steel: The chemical composition is given in the table. In steel grades letters M, K, E- methods of steel smelting, figures - average mass fraction of carbon in hundredths of a%. Letters Ф,С,Х,Т- alloyed steels vanadium, silicon, chromium, titanium, respectively.

Chemical composition of rail steel:

98% iron; Carbon - increases the flexural strength of the rail; manganese - hardness, toughness, wear resistance; Silicon - hardness, wear resistance; Phosphorus - cold brittleness; sulfur - red brittleness.

The invention relates to ferrous metallurgy, in particular to the production of steel for railway rails of low temperature reliability. Proposed rail steel containing components in the following ratio, wt.%: carbon 0.69 - 0.82, manganese 0.60 - 1.05, silicon 0.18 - 0.45, vanadium 0.04 -0.10, nitrogen 0.008 - 0.020, aluminum 0.005 - 0.020, titanium 0.003 - 0.010, calcium 0.002 -0.010, magnesium 0.003 - 0.007, chromium 0.05 - 0.30, nickel 0.05 - 0.30, copper 0.05 - 0, 30, sulfur 0.005 - 0.010, phosphorus not more than 0.025, iron - the rest, while the total content of chromium, nickel and copper does not exceed 0.65 wt.%, and the ratio of calcium and sulfur is in the range of 0.4 - 2.0 . The technical result of the invention is the possibility of creating rails with increased impact strength and operational reliability at low temperatures down to -60 o C. 1 table.

The invention relates to the field of ferrous metallurgy, in particular, to the production of steel for railway rails of low temperature reliability. Known steel having the following chemical composition, wt.%; 1. 0.65 - 0.85 C; 0.18 - 0.40 Si; 0.60 - 120 Mn; 0.001 - 0.01 Zr; 0.005 - 0.040Al; 0.004 - 0.011 N; one element from the group containing Ca and Mg 0.0005 - 0.015; 0.004 - 0.040 Nb; 0.05 - 0.30 Cu; Fe - rest. 2. 0.65 - 0.89 C; 0.18 - 0.65 Si; 0.60 - 1.20 Mn; 0.004 - 0.030 N; 0.005 - 0.02 Al; 0.0004 - 0.005 Ca; 0.01 - 0.10V; 0.001 - 0.03 Ti; 0.05 - 0.40Cr; 0.003 - 0.10 Mo; vanadium carbonitrides 0.005 - 0.08, while calcium and aluminum are in the ratio 1: (4 - 13), Fe - rest. These steels are intended for the manufacture of rails, in particular, the second steel is for rails intended for operation on highways with increased traffic density. However, they do not provide the required performance of the rails under conditions of low climatic temperatures, typical for vast areas of Siberia. The closest in technical essence and the achieved result to the proposed one is steel having the following chemical composition, wt.%: 0.69 - 0.82 C; 0.45 - 0.65 Si; 0.60 - 0.90 Mn; 0.004 - 0.011 N; 0.005 - 0.009 Ti; 0.005 - 0.009 Al; 0.02 - 0.10V; 0.0005 - 0.004 Ca; 0.0005 - 0.005 Mg; 0.15 - 0.40 Cr; Fe -res. However, it is characterized by insufficiently dispersed microstructure, which cannot provide the required level of impact strength at low temperatures (-60 o C). In addition, the sulfur content of this steel can be as high as 0.035%. As a result, the rails contain a significant amount of lines of manganese sulfides, which reduces the impact strength of the rails both in the longitudinal and transverse directions. Due to the fact that impact strength correlates with fatigue strength, it can be assumed that its values ​​at low temperatures unambiguously correlate with low-temperature reliability, and rails made of this steel do not have a sufficient fatigue strength resource. The task was set to create rail steel, from which it is possible to produce rails with increased operational reliability at low temperatures, up to -60 o C. The task is achieved by the fact that rail steel containing carbon, manganese, silicon, vanadium, nitrogen, aluminum, titanium , calcium, magnesium and chromium, additionally contains nickel and copper in the following ratio of components, wt.%: Carbon - 0.69 - 0.82 Manganese - 0.60 - 1.05 Silicon - 0.18 - 0.45 Vanadium - 0.04 - 0.10 Nitrogen - 0.008 - 0.020 Aluminum - 0.005 - 0.020 Titanium - 0.003 - 0.010 Calcium - 0.002 - 0.010
Magnesium - 0.003 - 0.007
Chromium - 0.05 - 0.30
Nickel - 0.05 - 0.30
Copper - 0.05 - 0.30
Sulfur - 0.005 - 0.010
Phosphorus - Not more than 0.025
Iron - Rest
while the total content of chromium, nickel and copper does not exceed 0.65 wt. %, and the ratio of calcium and sulfur is in the range of 0.4 - 2.0
The introduction of nickel and copper into the steel significantly lowers the temperature of the onset of pearlite transformation when the rail steel is cooled from the austenitic state. As a result, there is a noticeable refinement of the structure, namely, the size of pearlite colonies, the interlamellar distance of pearlite and, consequently, the thickness of the cementite plates decrease. Since in steel with the structure of lamellar pearlite, the impact strength largely depends on the size of the pearlite colonies and the thickness of the cementite plates, their grinding leads to an increase in impact strength both at positive and negative temperatures up to -60 o C, and, consequently, to improving the low-temperature reliability of rails. When nickel and copper are introduced into steel in amounts less than 0.05%, they do not have a noticeable effect on the structure and impact strength of the rails. If the amount of nickel and copper exceeds 0.3% each or the total content of chromium, nickel and copper exceeds 0.65%, then in the steel, along with the pearlite structure, sections of the bainitic structure are formed. The impact strength of such a steel with a mixed structure is markedly reduced. The ratio of calcium and sulfur, equal to 0.4 - 2.0, provides the formation instead of strings of manganese sulfide long lines of short lines (Mn, Ca)S, globular calcium sulfides and shells of calcium sulfides on the surface of calcium aluminates. Globularization of sulfides increases impact strength in the longitudinal and transverse directions, reduces the anisotropy of impact strength. In this regard, the risk of crack development during the operation of rails is significantly reduced and their reliability is increased, especially at low temperatures. If the ratio of calcium to sulfur is less than 0.4, then there is no globularization of sulfides and no increase in the toughness of the steel. The ratio of calcium to sulfur content is greater than 2.0, it is difficult to provide with existing technologies for smelting, desulfurization of steel and the introduction of calcium into it
It should be noted that since the level of impact strength, especially at low temperatures, of rail steel is rather low, which is associated with the peculiarities of its chemical composition, only a joint simultaneous effect on the fineness of the microstructure and on the composition and shape of sulfides significantly increases the low-temperature reliability of rails. Significant differences between the proposed steel with the claimed ratio of components are: the introduction of nickel and copper into the steel with a total content of nickel, copper and chromium not higher than 0.65% and the ratio of calcium and sulfur in the range of 0.4 - 2.0. According to the information available in the scientific and technical literature, nickel and copper are usually introduced into steel, including rail steel, to increase its hardenability and obtain a fully martensitic structure, increase the strength and hardness of the steel. In the present invention, nickel and copper are introduced into steel to refine the microstructure and improve toughness. In the literature, we did not find data on the combined effect of nickel and copper and sulfide globularization on impact strength and low-temperature reliability. In view of the foregoing, the claimed technical solution meets the criterion of "novelty". Examples of a specific implementation of the invention are given in the table, which indicates the chemical composition of the steels and the properties of the rails obtained from these steels. From the proposed steel and prototype steel in the conditions of the Kuznetsk Iron and Steel Works, railway rails of the P65 type were rolled, which were heat-treated by bulk quenching in oil from 840 - 850 o C and tempering at 450 o C according to the technological instructions in force at the plant. The results shown in the table show that when nickel and copper are introduced into steel in such a ratio that the total amount of nickel, copper and chromium does not exceed 0.65%, and the ratio of calcium and sulfur is in the range of 0.4 - 2, 0, the impact strength of steel at a temperature of 20 o C in the longitudinal direction of the rail is 4.0 - 6.0 kgcm / cm 2, in the transverse direction - 3.6 - 5.7 kgcm / cm 2, anisotropy index n = 0.90 - 0.98. Under these conditions, the impact strength of steel on longitudinal samples at -60 o C is in the range of 2.0 - 2.7 kgcm/cm 2 . When the content of Nickel and copper, the total content of Nickel, copper and chromium, the ratio of calcium to sulfur below and above the specified limits, the values ​​of impact strength and its anisotropy do not differ markedly from the values ​​of these parameters for steel prototype. According to specifications TU 14-1-5233-93 rails with KCU-60 not less than 2.0 kgcm/cm 2 refer to low-temperature reliability rails. Thus, the smelting of the proposed steel will increase the production of rails of increased low-temperature reliability for regions with low climatic temperatures. Sources of information
1. Auth. St. USSR N 1435650 M. class. C 22 C 38/16, 1987. 2. Pat. RF N 1633008 M. class. C 22 C 38/16, 1989. 3. Auth. St. USSR N 1239164, M. class. C 22 C 38/28, 1984.

Claim

Rail steel containing carbon, manganese, silicon, vanadium, nitrogen, aluminum, titanium, calcium, magnesium and chromium, characterized in that it additionally contains nickel and copper in the following ratio, wt.%:
Carbon - 0.69 - 0.82
Manganese - 0.60 - 1.05
Silicon - 0.18 - 0.45
Vanadium - 0.04 - 0.10
Nitrogen - 0.008 - 0.020
Aluminum - 0.005 - 0.020
Titanium - 0.003 - 0.010
Calcium - 0.002 - 0.010
Magnesium - 0.003 - 0.007
Chromium - 0.05 - 0.30
Nickel - 0.05 - 0.30
Copper - 0.05 - 0.30
Sulfur - 0.005 - 0.010
Phosphorus - Not more than 0.025
Iron - Rest
while the total content of chromium, nickel and copper does not exceed 0.65 wt. %, and the ratio of calcium and sulfur is in the range of 0.4 - 2.0.

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Rail steel (~0.60–0.80% C), and cord steel, similar in composition, are smelted in oxygen converters and in arc furnaces. The most difficult task in the production of this steel is to obtain a sufficiently low phosphorus content during the oxidation of carbon to a given concentration in the steel. To solve this problem, special measures are taken according to the characteristics of melting in a converter or an arc furnace.

In an oxygen converter with top blowing or combined blowing from above and below, as shown above, dephosphorization begins from the first minutes of blowing. However, when the phosphorus content of the iron is high, the degree of dephosphorization is not sufficient to obtain an acceptable phosphorus content in the steel when stopping at a predetermined high carbon content. As with a carbon content of ∼0.6–0.9%, in the course of melting, the phosphorus content stabilizes or even begins to increase; the decrease in the phosphorus content occurs further at a much lower carbon content. This causes difficulty in dephosphorization in the production of high carbon steel. In the case of melting with a process stop at a given high carbon content in steel, it leads to the need for intermediate felling of the converter to change the slag by downloading it and introducing a new one. This complicates the process, causes a decrease in productivity, an increase in the consumption of slag-forming and cast iron.

The felling of the converter for changing slag is carried out at different plants with a carbon content of 1.2–2.5%. With a high phosphorus content in cast iron (0.20–0.30%), the slag is replaced twice at a carbon content of 2.5–3.0% and at 1.3–1.5%. After downloading the slag, a new one is made from freshly burnt lime. The content of FeO in the slag is maintained at the level of 12–18% by changing the level of the tuyere above the bath. In the course of melting, fluorspar is added to liquefy the slag - 5–10% of the mass of lime. As a result of dephosphorization, by the end of blowing to the carbon content specified in the finished steel, the phosphorus content in the metal is ≤ 0.010–0.020%. At the outlet into the ladle, the metal is deoxidized with ferrosilicon and aluminum additives. In this case, a very important operation is the cut-off of converter slag. If it enters the ladle, it causes rephosphorization during the deoxidation process and especially during out-of-furnace treatment with reducing slag for desulfurization.

The technology of smelting rail and cord steel in converters with blowing to a low carbon content (0.03-0.07%), followed by carburization in the ladle with specially prepared solid carburizers (petroleum coke, anthracite) has also gained some distribution. The final adjustment of the carbon content in steel is carried out in a vacuum treatment plant.

Purging the metal in the converter to a low carbon content provides deep dephosphorization. It is only necessary to ensure a reliable cut-off of slag at the outlet to prevent the possibility of it falling into the ladle and, as a result, rephosphorization.

The use of steel smelting technology in a converter with a blowdown to a low carbon content followed by carburizing in a ladle requires the use of carburizers that are clean in terms of the content of harmful impurities and gases, which necessitates their special preparation and sometimes creates significant difficulties. It is also difficult to obtain the desired carbon content within narrow limits. This limits the application of this technology.

The melting in the converter used at some plants, followed by carburizing with cast iron, previously poured into the ladle before the melt is released from the converter, has not found wide application. This requires cast iron that is sufficiently pure in terms of phosphorus content. The final carburization of the deoxidized metal, in order to reliably obtain the carbon content within the required limits, is carried out with solid carburizers in the process of vacuum processing.
In arc furnaces, rail and cord steel is smelted according to the usual technology described above, using measures to intensively remove phosphorus from the metal - additives iron ore into the filling and at the beginning of a short oxidation period, with continuous slag removal and its renewal with lime additives. It is also obligatory to prevent the ingress of slag into the steel-pouring ladle.

Due to the low oxygen content of high carbon rail steel high degree its purity in terms of oxide inclusions can be achieved without the use of a relatively complex out-of-furnace vacuum treatment or in a kosh-furnace. To achieve this goal, it is sufficient to purge the metal in the box with an inert gas. But at the same time, the furnace slag entering the ladle, in order to avoid secondary oxidation of the metal by it, should not be oxidizing. Therefore, before such out-of-furnace processing, the smelting of rail steel in an EAF is carried out with preliminary deoxidation of the metal in the furnace with silicon and manganese, which are added in the form of ferrosilicon and ferromanganese or silicomanganese. The slag is deoxidized with coke or electrode powder and granulated aluminum, and sometimes with ferrosilicon powder, before being tapped. However, it should be borne in mind that during the deoxidation of slag, especially with silicon, which causes the formation of SiO2, phosphorus is reduced. Therefore, such an operation is permissible only after a sufficiently deep dephosphorization with a change of slag and removal of phosphorus from the bath. The final deoxidation of steel with silicon and aluminum is carried out in a ladle during tapping. Then the metal in the ladle is blown with an inert gas to homogenize it and, mainly, to remove at least part of the accumulations (clusters) of Al2O3 inclusions that cause delamination in the working part of the rail heads during their operation. The consequence of this delamination may be the complete separation of the laminated plates on the rail head and its premature failure.

More effective way To prevent the formation of delaminations in rail steel, smelted both in converters and in arc furnaces, is the treatment of liquid metal in a ladle with calcium. As shown, this is done by introducing into the liquid metal a powder of silicocalcium clad in a wire or blown in a carrier gas flow.