DE9218007U1 - Rail steel - Google Patents

Description

The invention relates to steels for rails, wheel guides and rolling railway equipment such as wheel disks, wheel tires and solid wheels.

Such steels are known with different compositions; they are essentially described in Werkstoffkunde Stahl (1985) Volume 2, D 27 "Stähle für den Eisenbahnsuperbau", p. 594/601, Springer Verlag/Verlag Stahleisen and in Draft European Rails Standard, Part 1: Issue Dec. 1991. Their service life is essentially determined by their wear resistance and the wear volume present in the rail head of newly rolled rails under the same mechanical stress. All other conditions being equal, the wear resistance of rails increases with higher strength. However, the strengths that can be achieved today, for example 1100 or 1200 N/mm ^2, come at the expense of toughness, weldability and fracture resistance, according to R. Schweitzer et al. "Zur bewertet des Britödbruchverhaltens von Schienen", AET (39), 1984, pages 55 to 60.

The invention is therefore based on the object of creating a steel with improved wear resistance without impairing its toughness, weldability and fracture resistance.

The solution to this problem is to alloy a common steel with up to 0.004% tellurium.

As tests have shown, tellurium increases the hot strength of the sulfides, which therefore do not stretch during hot forming, but essentially retain their spherical-elliptical shape. Accordingly, these sulfides have a much lower stress concentration than the usual sulfides, which stretch in the rolling direction during hot rolling. The result of this is not only better wear behavior, but also an improvement in the mechanical transverse properties without affecting the weldability.

The effect of tellurium is evident in all known rail qualities, regardless of whether their structure is ferritic-pearlitic, pearlitic, fine-pearlitic, tempered or bainitic.

The steel according to the invention preferably contains less than 0.0015% oxygen and/or less than 0.007% sulphur. A particularly favourable wear behaviour is obtained if the sulphur/tellurium ratio is approximately 0.1 to 0.6.

Particularly suitable are steels with 0.55 to 0.75% carbon, 0.10 to 0.50% silicon, 1.30 to 1.70% manganese and a maximum of 0.05% phosphorus, the remainder being iron including impurities resulting from the melting process.

Also suitable are steels with 0.60 to 0.80% carbon, 0.60 to 1.20% silicon, 0.80 to 1.30% manganese, maximum 0.030% phosphorus and 0.70 to 1.20% chromium, the remainder being iron including impurities resulting from the melting process.

Furthermore, steels with 0.70 to 0.80% carbon, 0.80 to 1.20% silicon, 0.80 to 1.30% manganese, a maximum of 0.030% phosphorus, 0.80 to 1.20% chromium, up to 0.25% titanium and/or vanadium, the remainder iron including impurities caused by the melting process, are also suitable for alloying with tellurium according to the invention. However, the steels are preferably titanium-free, since the cubic titanium carbides and carbonitides impair the fatigue behavior.

Finally, steels with 0.53 to 0.62% carbon, 0.65 to 1.1% manganese, 0.8 to 1.3% chromium, 0.1 to 0.6% silicon, 0.05 to 0.11% molybdenum, 0.05 to 0.11% vanadium and less than 0.02% phosphorus, the remainder being iron including impurities resulting from the melting process, are also suitable as rail materials containing tellurium.

The rail steels specified above with their analysis may also contain 0.01 to 0.025% aluminium, preferably up to 0.004% aluminium.

Comparative tests with a conventional rail steel have shown that the wear resistance can be increased by 50% and more with the help of the tellurium additive according to the invention. For example, the specific surface wear on a track curve with a curve radius of 350 m per 100 x 10 ⁶ t load was 200 mm ² for the conventional rail steel 900A, but only 120 mm ² for a tellurium-containing steel according to the invention.

A significantly better wear behavior is also achieved when the steel 900 A is tellurium-free, but only contains 0.003% sulfur. In this respect, the object underlying the invention can also be achieved by limiting the sulfur content to less than 0.007%,

-A-

although not to the same extent as in the case of a steel according to the invention with up to 0.004% tellurium.

The following table shows how the mechanical properties can be improved by limiting the sulphur content and adding just 0.002% tellurium. This is particularly evident in the transverse properties as well as the elongation and reduction in area at break, which are particularly important given the relatively high tensile strength.

In addition to tellurium, the steel according to the invention can also contain other sulfur-affine elements such as zirconium, calcium, magnesium and rare earth metals.

steel sulfur
salary
(*) tensile strenght
(N/mm2) across Tensile stress
(N/nun2) across Elongation at break
(96) across Fractional
lacing
(*) across along 815 along 87o along 8th along 12 UCI700 o,o25 82o 82o 12oo 1o4o 2o 14.5 4o 25 UCI700 o,oo3 823 822 124o 117o 19.5 18.5 38 32 UCI700 *) o,oo3 + Te 824 975 125o I12o 2o 7 39 1o UCI900A o,o24 98o 977 135o 121o 13 9 25 18 UCI900A o,oo3 978 975 1348 1315 13.5 12 29 24 UCI900A *) o,oo3 + Te 976 1345 14 29

) Tellurium addition of o.oo2 %

Accordingly, the steel according to the invention is particularly suitable as a material for rails, wheel guides and rolling railway equipment.

Claims (12)

1. Steel for rails, check rails and railway rolling stock with a composition in particular according to Draft European Rails Standard, Part 1: Edition December 1991, characterized by a tellurium content of less than 0.004 %. 2. Steel according to claim 1, characterized by an oxygen content below 0.0015%. 3. Steel according to claim 1 and 2, characterized by a sulfur content of up to 0.007%. 4. Steel according to one of claims 1 to 3, characterized in _that the tellurium/sulphur ratio is 0.1 to 0.6. 5. Steel according to one of claims 1 to 3, characterized by 0.6 to 0.8% carbon, 0.10 to 0.50% silicon, 0.80 to 1.30% manganese and at most 0.05% phosphorus, the remainder being iron including impurities resulting from the melting process. 6. Steel according to one of claims 1 to 4, characterized by 0.5 to 0.75% carbon, 0.10 to 0.50% silicon, 1.30 to 1.70% manganese and at most 0.05% phosphorus, the remainder iron including impurities resulting from the melting process. 7. Steel according to one of claims 1 to 4, characterized by 0.60 to 0.80% carbon, 0.60 to 1.20% silicon, 0.80 to 1.30% manganese, at most 0.030% phosphorus and 0.70 to 1.20% chromium, the remainder iron including impurities resulting from the melting process. 8. Steel according to one of claims 1 to 4, characterized by 0.70 to 0.80% carbon, 0.80 to 1.20% silicon, 0.80 to 1.30% manganese, at most 0.030% phosphorus, 0.80 to 1.20% chromium, up to 0.25% titanium and/or vanadium, the remainder iron including impurities resulting from the melting process. 9. Steel according to one of claims 1 to 4, characterized by 0.53 to 0.62% carbon, 0.65 to 1.1% manganese, 0.8 to 1.3% chromium, 0.1 to 0.6% silicon, 0.05 to 0.11% each molybdenum and vanadium and less than 0.02% phosphorus, the remainder iron including impurities resulting from the melting process. 10. Steel according to one of claims 1 to 9, characterized by 0.01 to 0.25% aluminum. 11. Steel according to one of claims 1 to 9, characterized by less than 0.004% aluminum. 12. Use of a steel according to one of claims 1 to 11 as a material for rails, wheel guides and rolling railway equipment. br