Pearlitic rail and method for manufacturing pearlitic rail

Patent metadata

Field	Value
Publication number	US-10253397-B2
Application number	US-201414779755-A
Country	US
Kind code	B2
Filing date	Mar 25, 2014
Priority date	Mar 27, 2013
Publication date	Apr 9, 2019
Grant date	Apr 9, 2019

Abstract

A pearlitic rail includes a composition including in % by mass: 0.70% to 0.90% of C; 0.1% to 1.5% of Si; 0.01% to 1.5% of Mn; 0.001% to 0.035% of P; 0.0005% to 0.030% of S; 0.1% to 2.0% of Cr, remainder of the composition consisting of Fe and inevitable impurities. Surface hardness of a rail top is not less than HB 430, and hardness at a depth of 25 mm from a surface of the rail top is not less than HB 410.

First claim

The invention claimed is:

1. A method of manufacturing a pearlitic rail, the method comprising:
hot rolling a billet having a composition including in % by mass: 0.70% to 0.90% of C; 0.1% to 1.5% of Si; 0.01% to 1.5% of Mn; 0.001% to 0.035% of P; 0.0005% to 0.030% of S; 0.1% to 2.0% of Cr, remainder of the composition consisting of Fe and inevitable impurities, so as to achieve a finishing rolling temperature of not lower than 900° C. to form a rail material; and
cooling the rail material in an accelerated manner at a cooling rate of 2° C./s to 30° C./s from a temperature of 770° C. to 500° C., reheating the rail material or subjecting the rail material to secondary heating to a temperature within a range of 530° C. to 580° C., holding the rail material within the range of 530° C. to 580° C. for 20 s to 100 s, and cooling the rail material in an accelerated manner at a cooling rate of 2° C./s to 10° C./s to a temperature within a range of not higher than 450° C.

2. The method of manufacturing a pearlitic rail according to claim 1 , further comprising terminating the accelerated cooling performed at a cooling rate of 2° C./s to 10° C./s, at a temperature within a range of 350° C. to 450° C., and then slowly cooling the rail material at a cooling rate of not more than 0.5° C./s.

3. The method of manufacturing a pearlitic rail according to claim 1 , wherein the composition of the billet further includes in % by mass one or both of: not more than 0.010% of Ca; and not more than 0.1% of REM.

4. The method of manufacturing a pearlitic rail according to claim 3 , further comprising terminating the accelerated cooling performed at a cooling rate of 2° C./s to 10° C./s, at a temperature within a range of 350° C. to 450° C., and then slowly cooling the rail material at a cooling rate of not more than 0.5° C./s.

5. The method of manufacturing a pearlitic rail according to claim 1 , wherein the composition of the billet further includes in % by mass at least one of: not more than 0.15% of V; not more than 0.030% of Nb; not more than 1.0% of Cu; not more than 0.5% of Ni; and not more than 0.5% of Mo.

6. The method of manufacturing a pearlitic rail according to claim 5 , further comprising terminating the accelerated cooling performed at a cooling rate of 2° C./s to 10° C./s, at a temperature within a range of 350° C. to 450° C., and then slowly cooling the rail material at a cooling rate of not more than 0.5° C./s.

7. The method of manufacturing a pearlitic rail according to claim 5 , wherein the composition of the billet further includes in % by mass one or both of: not more than 0.010% of Ca; and not more than 0.1% of REM.

8. The method of manufacturing a pearlitic rail according to claim 7 , further comprising terminating the accelerated cooling performed at a cooling rate of 2° C./s to 10° C./s, at a temperature within a range of 350° C. to 450° C., and then slowly cooling the rail material at a cooling rate of not more than 0.5° C./s.

Assignees

• Jfe Steel Corp

Inventors

• Kimura Tatsumi
• Uwai Kiyoshi
• Endo Shigeru
• Yamaguchi Moriyasu

Classifications

• C21D8/00

  Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment (hardening articles or materials formed by forging or rolling with no further heating beyond that required for the formation C21D1/02) · CPC title

• C22C38/14

  containing titanium or zirconium · CPC title

• C22C38/005

  containing rare earths, i.e. Sc, Y, Lanthanides · CPC title

• C22C38/001

  containing N · CPC title

• C22C38/02

  containing silicon · CPC title