Rail steel

FIELD: ferrous metallurgy.

SUBSTANCE: invention relates to steel used in making railways. Invention proposes steel comprising the following components, wt.-%: carbon, 0.71-0.82; manganese, 0.75-1.10; silicon, 0.40-0.60; chrome, 0.70-1.20; aluminum, 0.005, not above, vanadium, 0.05-0.15; calcium, 0.0001-0.005; nitrogen, 0.005-0.015; nickel, 0.03-0.20; barium, 0.0001-0.005; strontium, 0.0001-0.005, and iron, the balance. As impurities steel can comprise, %, sulfur, 0.02, not above; phosphorus, 0.025, not above, and copper, 0.15, not above. Invention provides enhancing complex of physical-mechanical properties and exploitation strength of steel.

EFFECT: improved and valuable properties of steel.

2 tbl

 

The invention relates to ferrous metallurgy, in particular to the steel used for the manufacture of rails.

Known selected as a prototype rail steel [1], containing (wt.%):

carbon0,62-0,84
manganeseof 0.8-1.3
silicon0,2-1,0
chrome0,6-1,5
aluminum0,02-0,05
vanadium0,03-0,12
calcium0,001-0,05
ironrest

A significant drawback of this steel is low maintenance durability due to reduced mechanical properties.

Also known rail steel AT [2], containing (wt.%):

carbon0,71-0,82
manganese0,75-1,05
silicon0,25-0,45
vanadium0,03-0,15
chromenot more than 0.15
Nickelnot more than 0.15
coppernot more than 0.15
ironrest

A significant drawback given the th steel is the low resistance of rails without heat treatment and the need for heat treatment of steel to improve performance properties.

Also known rail steel [3], containing carbon, silicon, manganese, chromium, tungsten, cerium, and iron, wherein, with the aim of increasing fatigue and brittle fracture, it further comprises aluminum, boron and lanthanum in the following ratio, wt.%:

carbon0,6-0,8
silicon0,5-1,3
manganese0,5-1,0
chrome0,5-1,0
Wolfram0,5-1,0
ceriumof 0.003 to 0.15
aluminum0,03-0,05
Bor0,002-0,007
lanthanum0,003-a 0.1
ironrest

A significant drawback of this steel is its high cost because of the content of tungsten and lanthanum, and (in connection with the cerium content) contamination of non-metallic inclusions so-called cerium regional heterogeneity.

Desired technical result of the invention is to improve the mechanical properties and service durability.

To achieve this rail steel containing carbon, manganese, silicon, chromium, aluminum, vanadium, calcium and iron, optionally contains nitrogen, ical, barium and strontium in the following ratio of components (wt.%):

carbon0,71-0,82
manganese0,75-1,10
silicon0,40-0,60
chrome0,70-1,20
aluminumnot more than 0.005
vanadium0,05-0,15
calcium0,0001-0,005
nitrogenof 0,005 0,020
Nickel0,03-0,20
barium0,0001-0,005
strontium0,0001-0,005
ironrest

at the same time as impurities, the steel may contain sulfur no more than 0,020%, phosphorus not more than 0,025%, copper not over 0.15%.

The inventive chemical composition of the steel is chosen based on the following assumptions:

The increase of silicon to 0.60% increases beyond the yield strength and durability, while reducing silicon less than 0.40% sharp decrease of these parameters.

The concentration of chromium is selected on the basis of ensuring high wear resistance and high strength properties, while reducing the concentration of chromium of less than 0,70% cannot provide the required resistance of rails in the track, and when the concentration of more than 1.20% significantly increases the price the steel at constant strength properties of steel.

The aluminium content is selected based on, on the one hand, getting smaller the actual grain, with the other exception getting invalid aluminous non-metallic inclusions.

Manganese concentration in the selected limits provide sufficient wear resistance of the rail.

The introduction of nitrogen allows you to get crushed grains of austenite, which provides improved strength properties and increased resistance to brittle fracture. The presence of vanadium thus allows to achieve the desired solubility of nitrogen compounds. In the presence of nitrogen of less than 0,005% impossible grinding grain and consequently does not provide the required hardening steel, and more 0,020% results of nerastvorimogo nitrogen and the possible formation invalid bubbles in steel. The selected content and the ratio of nitrogen and vanadium provides the required toughness (including at low temperatures) due to the density of hardening.

The concentration of Nickel more than 0.20% increases the probability of obtaining invalid microstructures, and the reduced concentration of less than 0.03% lowers the toughness of steel.

Additional introduction of barium and strontium allows you to modify the sources of stress concentrators - nonmetallic inclusions, to eliminate "dangerous is x" inclusions of alumina, to increase the purity of the steel oxide and sulfide inclusions to ensure formation of globular inclusions and exclude education strochechnyh inclusions aluminates. With the introduction of more than 0.005% barium and strontium in steel, you may receive the barium - and transesterify non-metallic inclusions, which reduces the mechanical properties of the steel.

Limiting concentrations of phosphorus, sulfur and copper due to improved surface quality of the finished product after rolling and improve its physical-mechanical properties.

A series of experimental heats were melted in an arc furnace EAF-I. Chemical composition shown in table 1. After casting of steel at continuous casting machine has been rolling rail type R65. After rolling rails heat treatment was not conducted. The test results of mechanical properties in hot rolled condition in comparison with steel-prototype, presented in table 2 show that the claimed chemical composition provides improved mechanical properties of rail steel, which in turn increases the operational stability of rails.

Sources of information

1. RF patent №819208, With 22 38/24.

2. GOST R 51685-2000 "railway Rails. General technical conditions".

3. RF patent №522265, With 22 38/22.

T the blitz 1

Chemical composition of steel
CompositionMnSiCrAlVCANNiVASrSPCuFe
10,710,750,410,700,0010,050,00010,0050,030,00010,00010,0080,0150,15OST
20,780,820,440,740,0030,080,0020,0150,160,00050,0030,0080,0080,05OST
30,730,920,490,820,0050,120,0030,0100,090,0030,0040,0030,0100,06OST
40,800,980,540,980,0020,100,0030,0150,200,0040,005 0,0050,0090,13OST
50,751,010,581,160,0050,150,0050,0180,150,0050,0040,0040,0180,06OST
60,821,100,601,200,0050,150,0050,0200,180,0050,0050,0070,0200,08OST
the placeholder0,62-0,84of 0.8-1.30,2-1,00,6-1,50,02-0,050,03-0,120,001-0,05----0,0200,0250,12OST
AF according to GOST R 5168520000,71-0,820,75-1,050,25-0,45≤0,15≤0,0200,03-0,15≤0,15≤0,030≤0,025≤0,15OST

Table 2
Mechanical properties of steel
CompositionYield strength,

N/mm2
Tensile strength,

N/mm2
Elongation, %Relative narrowing, %KCU impact strength, j/cm2
+20°-60°
11200157014320,380,38
21210168015350,470,34
31210155014340,430,36
41210175516360,480,36
51220170014330,460,39
61100150018350,400,37
the placeholder880-12001490-1720nd22-28is 0.16-0.27nd

Rail steel containing carbon, manganese, silicon, chromium, al is mine, vanadium, calcium and iron, characterized in that it further contains nitrogen, Nickel, barium and strontium in the following ratio, wt.%:

Carbon0,71-0,82
Manganese0,75-1,10
Silicon0,40-0,60
Chrome0,70-1,20
AluminumNot more than 0.005
Vanadium0,05-0,15
Calcium0,0001-0,005
Nitrogenof 0,005 0,020
Nickel0,03-0,20
Barium0,0001-0,005
Strontium0,0001-0,005
IronRest

at the same time as impurities, the steel may contain sulfur no more than 0,020%, phosphorus not more than 0,025%, copper not over 0.15%.



 

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2 tbl

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1 tbl, 1 ex

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