RU2457272C1 - Rail steel - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: rail steel contains carbon, manganese, silicon, aluminium, nitrogen, vanadium, chrome, nickel, oxygen, iron and sulphur, phosphorus and copper as impurities at the following component ratio, wt %: carbon 0.71 - 0.90, manganese 0.85 - 1.20, silicon 0.20 - 0.40, aluminium not more than 0.004, nitrogen 0.010 - 0.018, vanadium 0.05 - 0.15, chrome 0.40 - 0.80, nickel 0.03 - 0.20, oxygen of not more than 0.0020, iron and impurities are the rest; at that, impurities are contained in the following amounts: sulphur - not more than 0.020, phosphorus - not more than 0.020, and copper - not more than 0.20.

EFFECT: improving steel purity as per nonmetallic inclusions to improve the reliability and contact fatigue strength of rails.

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Description

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

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

carbon 0.71-0.82 manganese 0.75-1.05 silicon 0.30-0.60 aluminum no more than 0,005 nitrogen 0.005-0.015 vanadium 0.05-0.15 chromium 0.40-0.80 nickel 0.03-0.30 calcium 0.0001-0.005 barium 0.0001-0.005 iron rest,

while the impurities are contained in the following amounts: sulfur - not more than 0.020%, phosphorus - not more than 0.025%, copper not more than 0.20%.

A significant drawback of this steel is the presence in the structure of non-deformable and brittle-fractured non-metallic inclusions due to the modification of steel with calcium.

Known selected as a prototype rail steel [2], containing (in wt.%):

carbon 0.71-0.82 manganese 0.75-1.05 silicon 0.45-0.80 aluminum 0.005-0.015 nitrogen 0.0005-0.015 vanadium 0.03-0.09 chromium 0.35-0.70 nickel 0.03-0.20 iron rest

A significant disadvantage of this steel is its low operational stability, due to a reduced set of physical and mechanical properties.

The desired technical result of the invention is to increase the purity of steel on non-metallic inclusions to ensure reliability and contact fatigue strength of rails.

To achieve this, rail steel containing carbon, manganese, silicon, aluminum, nitrogen, vanadium, chromium, nickel, iron, and sulfur, phosphorus and copper as impurities, characterized in that it has an additional oxygen content in the following ratio of components (in wt.%):

carbon 0.71-0.90 manganese 0.85-1.20 silicon 0.20-0.40 aluminum no more than 0,004 nitrogen 0.010-0.018 vanadium 0.05-0.15 chromium 0.40-0.80 nickel 0.03-0.20 oxygen no more than 0,0020 iron rest,

while the impurities are contained in the following amounts: sulfur - not more than 0.020%, phosphorus - not more than 0.020%, copper not more than 0.20%.

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

The selected carbon content with the established ratio of manganese, silicon and chromium provides an increase in impact strength, ductility while maintaining the hardness and strength of steel. The increase in carbon content compared with the prototype will further increase the contact-fatigue strength of the rails. The upper limit of the carbon content is set based on the fact that with an increase of more than 0.90% there is a sharp decrease in ductility and toughness of rail steel.

The silicon concentration was established to ensure a balanced level of the mechanical properties of the rails, while a decrease in its concentration of less than 0.20% does not provide the required level of properties, with an increase of 0.40%, the likelihood of formation of an unfavorable structure increases.

The chromium concentration is selected on the basis of ensuring high wear resistance and high strength properties, while a decrease in chromium concentration of less than 0.40% does not allow to provide the required resistance of rails in the way, and with an increase in concentration of more than 0.80%, the cost of steel increases significantly with constant strength properties become.

A decrease in the aluminum content to 0.004% and oxygen less than 0.0020% provides an increase in the purity of the metal for non-metallic inclusions, leading to a decrease in their size and quantity. An aluminum content of more than 0.004% and oxygen of more than 0.0018% leads to steel contamination with lines of non-metallic inclusions of large sizes.

The concentration of manganese in the selected range provides sufficient wear resistance of the rails. Manganese increases the stability of supercooled austenite and at a content of at least 0.85% provides the formation of dispersed thin-plate perlite having a good combination of strength, ductility and viscosity. Since manganese shifts the phase transition point to lower temperatures, a further increase in its concentration of more than 1.20% in steel with a high carbon content leads to brittleness of rails.

The introduction of nitrogen from 0.010 to 0.018 can also improve the strength properties of rails and increase resistance 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 0.010%, it is impossible to provide the necessary hardening of steel, and with a nitrogen content of more than 0.018%, insoluble nitrogen is obtained and possible formation of unacceptable bubbles in the steel. The selected content and ratio of nitrogen and vanadium provides the desired toughness.

The limitation of the concentration of nickel to 0.20% is associated with the possibility of the formation of structurally free ferrite having low wear resistance.

The limitation of the concentration of phosphorus, sulfur and copper is due to an improvement in the surface quality of the finished product after rolling and an increase in its physical and mechanical properties.

A series of experimental swimming trunks with the claimed chemical composition was smelted in DSP-100I7 arc furnaces. The chemical composition is shown in table 1. After casting the steel at the continuous casting machine, railway rails of the P65 type were rolled. After rolling the rails, heat treatment was not carried out. The test results of the mechanical properties in the hot-rolled state in comparison with the prototype rail steel (after bulk quenching in oil and tempering) are given in table 2. Thus, the claimed chemical composition with a limited oxygen content provides an increase in the purity of steel by non-metallic inclusions while ensuring a sufficiently high level mechanical properties of rails in a non-heat-strengthened state, comparable with the level of mechanical properties of steel-prototype in a heat-strengthened state.

Information sources

1. RU 2292221 C1, C22C 38/46

2. RF patent No. 2131946, C22C 38/46.

Table 1 The chemical composition of steel Structure FROM Si Mn Cr V AI N Ni S P Cu Fe one 0.90 0.20 0.85 0.80 0.08 0.001 0.010 0,03 0.007 0.016 0.06 ost 2 0.77 0.40 0.88 0.40 0.09 0.004 0.012 0.10 0.008 0.019 0.08 ost 3 0.71 0.34 0.86 0.47 0.11 0.004 0.011 0.20 0.006 0.009 0.01 ost four 0.80 0.23 0.89 0.55 0,07 0.001 0.012 0.12 0.005 0.015 0.15 ost 5 0.77 0.36 1.20 0.69 0.11 0.003 0.018 0.14 0.012 0.018 0.20 ost 6 0.81 0.40 1.10 0.50 0.15 0.004 0.012 0.18 0,020 0,020 0.16 ost proto
type of 0.71-0.82 0.45-0.80 0.75-1.05 0.35-0.70 0.03-0.09 0.005-0.015 0.0005-0.015 0.03-0.20 ≤0.020 ≤0.020 ≤0.20 ost

table 2 Mechanical properties of steel and evaluation results of non-metallic inclusions Structure Yield strength, N / mm ² Tensile strength, N / mm ² Relative
elongation,% Relative narrowing,% KCU impact strength, J / cm ² Non-metallic inclusions, mm + 20 ° С non-deforming
sya brittle
ny one 1100 1190 10 twenty twenty 0 0 2 900 1180 12 21 21 0.001 0 3 800 1190 12 28 25 0 0.01 four 889 1170 13 27 24 0 0 5 1000 1150 eleven 22 26 0 0 6 900 1170 10 21 23 0 0 Proto
type (temper
ka and vacation) 880-1200 1350-1550 10-17 30-34 33-44 - -

Claims (1)

Rail steel containing carbon, manganese, silicon, aluminum, nitrogen, vanadium, chromium, nickel, iron and sulfur, phosphorus and copper as impurities, characterized in that it additionally contains oxygen in the following ratio, wt.%:
carbon 0.71-0.90 manganese 0.85-1.20 silicon 0.20-0.40 aluminum no more than 0,004 nitrogen 0.010-0.018 vanadium 0.05-0.15 chromium 0.40-0.80 nickel 0.03-0.20 oxygen no more than 0,0020 iron and impurities rest,
the impurities are contained in the following amounts,%: sulfur, not more than 0.020, phosphorus, not more than 0.020, copper, not more than 0.20.