RU2397271C2 - Rail steel - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention refers to ferrous metallurgy, particularly to steel used for fabrication of railroad rails designed for curvy sections of small radius of railroad under conditions of Siberia and the North. Steel contains carbon, manganese, silicon, aluminium, calcium, nitrogen, vanadium, strontium, copper, nickel, chromium, barium, zirconium, cerium, iron and impurities at the following ratio of elements, wt %: carbon 0.75 - 0.90, manganese 0.70 - 1.25, silicon 0.25 -0.55, aluminium not more 0.005, calcium 0.0001 - 0.005, nitrogen 0.006 - 0.015, vanadium 0.05 - 0.15, strontium 0.0001 - 0.001, copper 0.03 - 0.30, nickel 0.03 - 0.30, chromium 0.03 - 0.30, barium 0.0001 - 0.001, zirconium 0.0001 - 0.001, cerium 0.0001 - 0.001, iron and impurities - the rest. As impurities steel contains not more 0.020 wt % of sulphur and not more 0.025 wt % of phoshorus.

EFFECT: raised wear resistance at negative temperature and upgraded purity of steel by non-metallic inclusions.

3 tbl

Description

The invention relates to ferrous metallurgy, in particular to steel used for the manufacture of railway rails intended for movement in curved sections of small radius in the conditions of Siberia and the Far North.

Known rail steel [1], containing (in wt.%):

carbon 0.65-0.85 manganese 0.6-1.2 silicon 0.25-0.45 aluminum 0.005-0.012 calcium 0.002-0.020 nitrogen 0.006-0.015 vanadium 0.01-0.07 strontium 0.002-0.030 copper 0.05-0.80 barium 0.001-0.030 zirconium 0.005-0.020 iron rest

A significant drawback of this steel is the low operational stability of railway rails, due to insufficient wear resistance and purity of steel on non-metallic inclusions.

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

carbon 0.83-0.95 manganese 0.60-1.1 silicon 0.30-0.70 vanadium 0.008-0.15 aluminum no more than 0,005 nitrogen 0.012-0.020 calcium 0.0005-0.005 chromium 0.05-0.50 chromium no more than 0,15 molybdenum 0.11-0.3 nickel 0.05-0.30

one of the elements selected from the group comprising zirconium and rare-earth metals:

zirconium 0.0005-0.005 REM 0.0005-0.005 iron and impurities rest

The main disadvantage of this steel is the increased fragility of the rails in the area of the bolt holes due to the formation of a cementite mesh in the axial zone of the neck.

As the closest analogue, the authors adopted a prototype rail steel [3] containing carbon, manganese, silicon, aluminum, calcium, nitrogen, vanadium, strontium, copper, nickel, chromium, barium, iron and impurities in the following ratio of components, wt. %: containing carbon 0.71-0.82, manganese 0.75-1.1, silicon 0.4-0.6, aluminum no more than 0.005, calcium 0.0001-0.005, nitrogen 0.005-0.02, vanadium 0.05-0.15, strontium 0.0001-0.005, copper no more than 0.15, nickel 0.03-0.2, chromium 0.7-1.2, barium 0.0001-0.005, iron and impurities - the rest.

The desired technical result of the invention is to increase the purity of steel by non-metallic inclusions and the wear resistance of rails at low temperatures in relation to the conditions of Siberia and the Far North.

Rail steel containing carbon, manganese, silicon, aluminum, calcium, nitrogen, vanadium, strontium, copper, nickel, chromium, barium, iron and impurities, characterized in that it additionally contains zirconium and cerium in the following ratio of components (in wt. %):

carbon 0.75-0.90 manganese 0.70-1.25 silicon 0.25-0.55 aluminum no more than 0,005 calcium 0.0001-0.005 nitrogen 0.006-0.015 vanadium 0.05-0.15 strontium 0.0001-0.001 copper 0.03-0.30 nickel 0.03-0.30 chromium 0.03-0.30 barium 0.0001-0.001 zirconium 0.0001-0.001 cerium 0.0001-0.001 iron rest

however, as impurities, steel may contain sulfur not more than 0.020%, phosphorus not more than 0.025%.

The inventive chemical composition of the steel is selected based on the following premises:

The selected concentration limits of carbon provide an increase in the hardness and wear resistance of the rails, eliminating the possibility of the formation of a cementite mesh in the axial zone of the neck.

An increase in manganese to 1.25% increases the wear resistance and strength properties of rail steel. With a decrease in manganese below 0.70%, these parameters decrease.

The established concentration limits of silicon provide hardening of ferrite, thereby increasing the yield strength and strength of rail steel in a heat-strengthened state. With a decrease in silicon of less than 0.25%, a sharp decrease in these parameters is observed. An increase in the silicon concentration over 0.55% increases the likelihood of the formation of a needle microstructure from the surface of body-hardened rails.

The aluminum content is selected based on, on the one hand, the production of fine real grains, and on the other, the exclusion of unacceptable alumina non-metallic inclusions.

The introduction of nitrogen allows to obtain crushed austenite grain, which provides an increase in strength properties and an increase in the resistance of steel to brittle fracture. The presence of vanadium in this case allows us to achieve the necessary solubility of nitrogen in the compounds. In the presence of nitrogen less than 0.006%, grain grinding is impossible and, accordingly, the necessary hardening of steel is not provided, and more than 0.015% leads to the formation of insoluble nitrogen and the possible formation of unacceptable bubbles in steel. The selected content and ratio of nitrogen and vanadium provides the required impact strength (including at low temperatures) due to carbonitride hardening.

The limitation of the concentration of copper, chromium, nickel, phosphorus and sulfur is due to an improvement in the surface quality of the rails.

The combined introduction of strontium, cerium, calcium, and barium makes it possible to modify the sources of stress concentrators — nonmetallic inclusions, to exclude the formation of “dangerous” alumina inclusions, to increase the purity of steel by oxide and sulfide inclusions, to ensure the formation of globular inclusions, and to exclude the formation of line inclusions of aluminates. With the introduction of more than 0.001% calcium, barium, strontium and cerium into steel, it is possible to obtain coarse barium-calcium-strontium-cerium-containing non-metallic inclusions that pollute the steel, and as a result, the toughness of steel decreases. An additional introduction of strontium in steel provides an increase in the fluidity of slag, thereby contributing to the most efficient cleaning of metal from non-metallic inclusions.

A series of experimental swimming trunks with the claimed chemical composition was smelted in DSP-100I7 arc furnaces. The chemical composition is given in table 1. After casting the steel at the continuous casting machine, rolling of railway rails of type P65 was carried out. After rolling, the rails were heat treated by volume quenching in oil. The results of measuring the length of the line of brittle-broken non-metallic inclusions in the hot-rolled state in comparison with the standard steel rail steel [4], close to the prototype used, are shown in table 2. The mechanical properties of the rails in the heat-treated state compared to the standard steel rail E76F are given in the table 3. Thus, the claimed chemical composition provides an increase in the purity of steel for brittle fractured non-metallic inclusions, as well as an increase in ur vnya strength and hardness of the rails.

List of sources

1. RF patent №2161210 C1.

2. RF patent №2259416 C2.

3. RU 2291218 C1, C22C 38/24.

4. GOST R 51685-2000. Rails are railway. Technical conditions

Table 1 The chemical composition of steel Structure FROM Si Mn Cr V AI N Ca Ba Xie Sr Ni Zr S P Si Fe one 0.75 0.30 0.75 0.05 0.05 0.002 0.005 0.001 0.001 0.001 0.001 0,03 0.001 0.005 0.011 0.10 rest 2 0.85 0.28 0.70 0,03 0.09 0.005 0.010 0.0001 0.0001 0.0001 0.0001 0.14 0.0001 0.008 0.017 0.04 rest 3 0.80 0.40 0.89 0.06 0.12 0.003 0.014 0,0008 0,0002 0,0002 0,0008 0.30 0,0005 0.006 0.009 0.17 rest four 0.87 0.53 1.25 0.08 0.08 0.001 0.015 0,0009 0,0004 0,0008 0,0009 0.28 0,0004 0.005 0,020 0.10 rest 5 0.79 0.44 1.06 0.10 0.11 0.002 0.012 0.001 0,0009 0,0007 0,0006 0.15 0.0001 0.014 0.017 0.25 rest 6 0.90 0.55 1.15 0.05 0.14 0.004 0.010 0,0003 0.001 0,0002 0,0005 0.30 0,0004 0,025 0,021 0.30 rest E76F 0.71-0.82 0.25-0.60 0.75-1.15 n.b. 0,020 0.03-0.15 n.b. 0,020 - - - - - n.b. 0,020 - n.b. 0,025 n.b. 0,025 n.b. 0,020 rest

table 2 Stitch length of non-metallic inclusions Steel Maximum length of stitch inclusions, mm Alumina Silicate Cemented Alumina Titanium nitride Fractured Complex Oxides one 0 0 0 0.15 2 0 0 0 0 3 0 0 0 0.10 four 0 0 0 0 5 0 0 0 0.08 6 0 0 0 0 GOST R 51685 requirements for steel E76F category H - - - n.b.
2.0

Table 3 Mechanical properties of steel Structure Yield strength, N / mm ² Tensile strength, N / mm ² Relative extension, % Relative narrowing,% KCU impact strength, J / cm ² + 20 ° С -60 ° C one 1020 1330 eighteen 48 0.57 0.27 2 1000 1340 eighteen 45 0.48 0.30 3 1100 1390 twenty 40 0.48 0.28 four 1110 1460 22 48 0.32 0.38 5 1090 1440 33 48 0.53 0.29 6 1110 1430 thirty 48 0.57 0.31 E76F - N.M.
1180 N.M.
8 N.M.
25 N.M.
0.15 -

Claims (1)

Rail steel containing carbon, manganese, silicon, aluminum, calcium, nitrogen, vanadium, strontium, copper, nickel, chromium, barium, iron and impurities, characterized in that it additionally contains zirconium and cerium in the following ratio of components, wt.% :
carbon 0.75-0.90 manganese 0.70-1.25 silicon 0.25-0.55 aluminum no more than 0,005 calcium 0.0001-0.005 nitrogen 0.006-0.015 vanadium 0.05-0.15 strontium 0.0001-0.001 copper 0.03-0.30 nickel 0.03-0.30 chromium 0.03-0.30 barium 0.0001-0.001 zirconium 0.0001-0.001 cerium 0.0001-0.001 iron and impurities rest,
however, as impurities it contains not more than 0.020 wt.% sulfur and not more than 0.025 wt.% phosphorus.