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Ultra-high strength bainite rail steel and manufacturing method thereof

An ultra-high-strength, manufacturing method technology, applied in the field of ultra-high-strength steel, can solve problems such as complex process, complex processing process, and complex production process, and achieve the effect of simple chemical composition, simple process, and low cost

Inactive Publication Date: 2011-09-07
WUHAN UNIV OF SCI & TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] (2) For pearlitic rail steel, the service life of the rail is still unsatisfactory, especially the rails on the curve and the rails on the heavy-duty line are damaged by abrasion and peeling, and there are also problems of brittleness and low fracture toughness
[0005] (3) For austenitic rail steel, the rail can show very high wear resistance under work hardening conditions, which is 5 times that of pearlitic rail steel, but the processing process is complicated, the plastic toughness is not good, and the brittleness is large. Rail steel is only used to make turnouts, crossings, etc.
[0006] (4) For martensitic rail steel, the strength and hardness are very high, but the plasticity and toughness are very poor, and the process is complicated
[0007] (5) For the air-cooled bainite rail steel without heat treatment or less heat treatment, the structure is bainite / martensite multiphase structure, the fracture toughness is lower than that of tempered martensite at the same yield strength, and the strength is not special. High, toughness is not particularly good
[0008] (6) For general (ultra) low-carbon bainitic rail steel, the carbon content is not high, the main alloy elements Si, Mn, Cr, and Mo are small, and the bainite transformation temperature is high. In this technology, the alloy Al content Little or no, the bainite transformation time is very long, the production process is complicated, there are many links, and the production cost is high; the toughness and plasticity are good, but the strength generally does not exceed 1500MPa
[0010] All kinds of rail steels are high-strength grades, and ultra-high-strength grades are not involved; various rail steels use precious alloy elements such as Ni or Ti, and the alloy cost is high; the strength, toughness and elongation of various rail steels are difficult to be synchronized Matching; the manufacturing and processing of various rail steels are complex

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0021] A method for manufacturing steel for ultra-high strength bainitic rails. The chemical composition and content of the slab are: C is 0.35-0.50wt%, Si is 1.40-1.70wt%, Mn is 1.60-2.00wt%, Cr is 1.30-1.60wt%, Mo is 0.30-0.60wt%, Al is 0.05-0.60wt%, P<0.015wt%, S<0.010wt%, and the rest is Fe and unavoidable impurities. Wherein: the sum of the contents of Si, Mn, Cr, Mo and Al in the slab is less than 5.00wt%.

[0022] After molten iron is made and refined, die casting, hot rolling and heat treatment are carried out. The process of hot rolling and heat treatment is as follows: First, soak the billet at 1200-1250°C for 2.0-3.0 hours, hot-roll, and cool naturally; then austenitize the cooled steel plate at 850-950°C for 0.4 ~0.6 hours; then keep warm for 4.0~6.0 hours under the conditions of nitrogen atmosphere and 300~450℃, and cool to room temperature with the furnace.

[0023] The steel for ultra-high-strength bainite rail produced in this embodiment: the tensile strengt...

Embodiment 2

[0025] A method for manufacturing steel for ultra-high strength bainitic rails. The chemical composition and content of the slab are: C is 0.35-0.50wt%, Si is 1.40-1.70wt%, Mn is 1.60-2.00wt%, Cr is 1.30-1.60wt%, Mo is 0.30-0.60wt%, Al is 0.60-1.20wt%, P<0.015wt%, S<0.010wt%, and the rest is Fe and unavoidable impurities. The sum of the contents of Si, Mn, Cr, Mo and Al in the slab is less than 5.00wt%.

[0026] After steelmaking and refining, scrap steel is subjected to continuous casting, hot rolling and heat treatment. The process of hot rolling and heat treatment is as follows: First, soak the billet at 1200-1250°C for 2.0-3.0 hours, hot-roll, and cool naturally; then austenitize the cooled steel plate at 850-950°C for 0.4 ~0.6 hours; then keep warm at 300~450°C, nitrogen atmosphere and 10~12T strong magnetic field for 0.5 hours~1.0 hours, and cool to room temperature with the furnace.

[0027]The steel for ultra-high-strength bainitic rail produced in this embodiment: ...

Embodiment 3

[0029] A method for manufacturing steel for ultra-high strength bainitic rails. The chemical composition and content of the slab are: C is 0.20-0.35wt%, Si is 1.10-1.40wt%, Mn is 2.00-2.40wt%, Cr is 1.00-1.30wt%, Mo is 0.10-0.30wt%, Al is 0.05-0.60wt%, P<0.015wt%, S<0.010wt%, and the rest is Fe and unavoidable impurities. The sum of the contents of Si, Mn, Cr, Mo and Al in the slab is less than 5.00wt%.

[0030] After molten iron and scrap steel are made and refined, continuous casting, hot rolling and heat treatment are carried out. The process of hot rolling and heat treatment is: first soak the billet at 1150-1200°C for 2.0-3.0 hours, hot-roll, and cool naturally; then austenitize the cooled steel plate at 950-1050°C for 0.2 ~0.4 hours; then keep warm for 2.0~4.0 hours under the conditions of nitrogen atmosphere and 450~600℃, and cool to room temperature with the furnace.

[0031] The steel for ultra-high-strength bainite rail produced in this embodiment: the tensile str...

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Abstract

The invention relates to ultra-high strength bainite rail steel and a manufacturing method thereof. The technical proposal is as follows: the casting billet comprises the following chemical components: 0.20-0.50wt% of C, 1.10-1.70wt% of Si, 1.60-2.40wt% of Mn, 1.00-1.60wt% of Cr, 0.10-0.60wt% of Mo, 0.05-1.20wt% of Al, P less than 0.015wt%, S less than 0.010wt% and the balance Fe and inevitable impurities. The method is characterized by carrying out die casting or continuous casting after steel making and refining; soaking the casting billet at the temperature of 1150-1250 DEG C for 2.0-3.0h,hot rolling and cooling the casting billet; austenitizing the casting billet at the temperature of 850-1050 DEG C for 0.2-0.6h; then insulating the casting billet at the temperature of 300-600 DEG C in the nitrogen atmosphere for 2.0-6.0h, or insulating the casting billet at the temperature of 300-600 DEG C in the nitrogen atmosphere and in the strong magnetic field of 8-12T for 0.2-1.0h. The invention has the characteristics of low cost and simple process, and the manufactured steel plates have good properties.

Description

technical field [0001] The invention belongs to the technical field of ultra-high strength steel. In particular, it relates to a steel for ultra-high strength bainitic rails and a manufacturing method thereof. Background technique [0002] The currently researched rail steels include ferritic rail steel, pearlitic rail steel, sorbite rail steel, austenitic rail steel and bainitic rail steel. There is a great development trend to continue to improve the internal and surface quality of rails and improve the strength and toughness of rails to meet the requirements of heavy-duty high-speed railways. The strength, hardness, notched impact toughness and ballistic limit of rail steel have been greatly improved, but there are also the following problems: [0003] (1) For ferritic rail steel, the carbon content is low, the carbon content of rail steel is lower than the eutectoid composition, but its manganese content is much higher than that of carbon steel, and its metallographic ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C22C38/38C21D8/02C21D1/74C21D10/00
Inventor 吴开明胡锋
Owner WUHAN UNIV OF SCI & TECH