WO2007139417A1

WO2007139417A1 - Rail steel

Info

Publication number: WO2007139417A1
Application number: PCT/RU2006/000269
Authority: WO
Inventors: Larissa Victorovna Korneeva; Saul Samuilovich Tchernyak; Valeriy Petrovich Dementyev; Nikolay Anatolyevich Kozyryev; Valeriy Alexandrovich Rudenkov; Andrey Pavlovich Khomenko; Mikhail Vladimirovich Klokov
Original assignee: STATE EDUCATIONAL INSTITUTION OF HIGHER PROFESSIONAL TRAINING
Current assignee: STATE EDUCATIONAL INSTITUTION OF HIGHER PROFESSIONAL TRAINING
Priority date: 2006-05-26
Filing date: 2006-05-26
Publication date: 2007-12-06
Anticipated expiration: 2008-11-26

Abstract

The rail steel is claimed. The technical result consists in the improving of the complex of its physical and mechanical characteristics and of its operational proof strength. The rail steel contains the following components (weight %) : carbon 0,71-0,82, manganese 0,75-1,10, silicon 0,40-0,60, chromium 0,70-120, aluminium less then 0,005, vanadium 0,05-0,17, calcium 0,0001-0,005, azote 0,005-0,020, nickel 0,03-0,20, barium 0,0001-0,005, strontium 0,0001-0,005, iron -the rest. The rail steel thereby can contain sulphur less then 0,020 wt.%, phosphorus less then 0,025 wt.% and copper less then 0,15 wt.% as additives.

Description

Rail Steel

The invention to be patented refers to ferrous metallurgy and in particular to steel used for making rails. The known kind of rail steel chosen as a prototype [1] contains (weight per

cent, %)

carbon 0.62 - 0.84

manganese 0.8 - 1.3

silicon 0.2 - 1.0

chromium 0.6 - 1.5

aluminium 0.02 - 0.05

vanadium 0.03 - 0.12

calcium 0.001 - 0.05

iron the rest

This kind of steel essential disadvantage is its low operational stability caused by the poor complex of its physical and mechanical properties.

There is also a known kind of E76F rail steel [2] having (weight per cent, %) carbon 0.71 - 0.82 manganese 0.75 - 1.05 silicon 0.25 - 0.45 vanadium 0.03 - 0.15 chromium not more than 0.15 nickel not more than 0.15 copper not more than 0.15 iron the rest This kind of steel essential disadvantage is the low endurance of rails without thermal treatment as well as the need for steel thermal pretreatment in order to improve its operational characteristics.

There also exists a known kind of rail steel [3] containing carbon, silicon, manganese, chromium, wolfram, cerium and iron which features additional components as aluminium, boron, lanthanum to improve fatigue and short metal strength. The components proportion is the following (weight per cent,

%) carbon 0.6 - 0.8 silicon 0.5 - 1.3 manganese 0.5 - 1.0 chromium 0.5 - 1.0 wolfram 0.5 - 1.0 cerium 0.003 - 0.15 aluminium 0.03 - 0.05 boron 0.002 - 0.007 lanthanum 0.003 - 0.1 iron the rest

This steel main disadvantage is its high cost because of the wolfram and lanthanum content as well as its contamination by non-metal inclusions caused by cerium presence, so called cerium edge non-uniformity.

The intended technical effect of the invention is improving of the complex of its physical and mechanical characteristics and of its operational strength.

To achieve this purpose the rail steel containing carbon, manganese, silicon, chromium, aluminium, vanadium, calcium and iron, contains in addition azote, nickel, barium and strontium. The components ratio is the following (weight, per cent %) carbon 0.71 - 0.82

manganese 0.75 - 1.10

silicon 0.40 - 0.60

chromium 0.70 - 1.20

aluminium less than 0.005

vanadium 0.05 - 0.15

calcium 0.0001 - 0.005

azote 0.005 - 0.020

nickel 0.03 - 0.20

barium 0.0001 - 0.005

strontium 0.0001 - 0.005

iron the rest

And the steel can also contain sulphur (less than 0.020%), phosphorus (less than 0.025%), copper (less than 0.15%) as additives.

The requested rail steel chemical composition was chosen on the base of the following considerations.

Increasing of silicon weight per cent up to 0.60% improves the rail steel yield and strength. At decreasing silicon addition to less than 0.40% dramatic reduction of these parameters is observe*!

The determined amount of chromium addition is supposed to provide high resistance to wear and strength properties of the steel. Decreasing the chromium content to 0.70% does not provide the required track rails durability and if the chromium percentage increases to more than 1.20% the steel cost grows significantly while its strength properties are the same. The aluminium content was calculated, on one hand, after getting of available fine grain and, on the other hand, after the elimination of inadmissible aluminous non-metallic inclusions.

The manganese amount in determined limits provides required rails resistance to wear.

Azote addition makes it possible to get austenite fine grain to provide increase of the rail steel strength and resistance to fragility.

Vanadium presence helps thereby to get required azote solubility in its compounds. If azote content is less than 0.005% grain bucking is impossible and, thereby, required steel hardness cannot be reached. And if azote content is more than 0.020% it causes azote not to be dissolved and inadmissible nipples to appear in steel.

The determined azote and vanadium content and ratio ensure required steel impact strength (even at temperature below zero) because of carbonic nitrite setting.

Nickel content being more than 0.20% the possibility of getting inadmissible microscopic structures increases. Nickel addition being reduced to less than 0.03% makes the steel impact strength lower.

Barium and strontium addition makes it possible to modify such tensions concentrators sources as non-metal inclusions, to prevent creation of so called "dangerous" alumina inclusions, to increase the steel purity from oxide and sulphide ones, to provide globe inclusions formation and to eliminate backstitch aluminates inclusions formation. In case of adding more than 0.005% barium and strontium weight per cent to the steel, there is a danger to get barium and strontium non-metal inclusions worsening steel physical properties.

Phosphorus, sulphur and copper content limitation causes the improvement of the surface quality of the ready steel rolled and advance in its physical and mechanical properties. A series of tentative smelts was made in arc steel furnaces DSP- 10017.

The rail steel chemical composition is shown in the Table 1 (fig. 1).

The steel having been poured at MNLZ the rolling of R65 type rails was made. Having been rolled the rails were not processed with thermal treatment. The tests results of their mechanical properties in hot rolled state in comparison with the prototype steel kind shown in the Table 2 (fig. 2) reflect that the requested rail steel chemical composition provides improvement upon the mechanical properties of the steel. And this improvement, in its turn, increases the operational proof strength of track rails.

References

1. ITaTeHT PΦ JVb 819208, C. 22 C 38/24.

2. FOOT P 51685-2000 "PejiBcti jκejie3Hθ,a;opo)KHE>ie. O6πine TexHHHecKHe ycjioBHa".

3. IIaτeHT PΦ Jfe 522265, C. 22 C 38/22.

Table 1

The Rail Steel Chemical Composition

Table 2

The Mechanical Properties of the Rail Steel

Claims

The Summary of the Invention

The rail steel containing carbon, manganese, silicon, chromium, aluminium, vanadium, calcium and iron, differs in additions of azote, nickel, barium and strontium. The components proportion is the following (weight per cent, %) carbon 0.71 - 0.82

manganese 0.75 - 1.10

silicon 0.40 - 0.60

chromium 0.70 - 1.20

aluminium less than 0.005

vanadium 0.05 - 0.15

calcium 0.0001 - 0.005

azote 0.005 - 0.020

nickel 0.03 - 0.20

barium 0.0001 - 0.005

strontium 0.0001 - 0.005

iron the rest

The rail steel thereby can contain sulphur (less than 0.020%), phosphorus (less than 0.025%), copper (less than 0.15%) as additives.