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Pealite like thermal treating steel rail and producing method thereof

A production method and pearlite technology, applied in heat treatment furnaces, heat treatment equipment, furnace types, etc., can solve problems such as difficult operation, fatigue cracking, and high carbon equivalent, and achieve broad application prospects, good wear resistance, and excellent weldability Effect

Active Publication Date: 2006-06-28
PANZHIHUA IRON AND STEEL
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

In the above-mentioned patent application, hypereutectoid carbon steel (C: 0.85-1.40%) is used to generate fine pearlite structure to increase the cementite density in the pearlite structure sheet to improve wear resistance, but the above-mentioned method exists Many disadvantages, (1) Due to the much higher carbon content than the current eutectoid steel, the plasticity is reduced, the rail is easy to break, and a segregation zone enriched in carbon and alloy elements is easy to form in the center of the slab, and is formed along the segregation zone Proeutectoid cementite, which becomes the origin of fatigue cracks and brittle fractures during use
(2) The temperature is uneven in the length direction and cross section of the rail, resulting in differences in the performance of various parts of the rail, especially the connection between the bottom of the rail, the rail bottom, and the rail waist, which is prone to generate fatigue cracks and brittle cracks. Analysis of cementite structure
(3) In order to suppress the occurrence of secondary proeutectoid cementite on the rail waist and rail bottom, different cooling devices are added to the rail head, rail waist and rail bottom according to the cooling rate, the production process is complicated and the operation is difficult
(4) It cannot be guaranteed that there is no pro-eutectoid cementite in the structure of the rail head depth outside 20mm
(5) The welding carbon equivalent of hypereutectoid steel is high, and the welding performance of the rail is poor

Method used

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  • Pealite like thermal treating steel rail and producing method thereof
  • Pealite like thermal treating steel rail and producing method thereof

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Experimental program
Comparison scheme
Effect test

Embodiment 1

[0034] The weight percentage of the chemical composition of the rail steel is: C: 0.76%, Si: 0.61%, Mn: 0.81%, V: 0.06%, Cr: 0.68%, P: 0.014%, S: 0.012%, the rest is iron, others Trace elements and impurities, of which Mn+2Cr+5Mo+3Nb=2.17%.

[0035] After the rail is rolled, the temperature of the residual heat is 840°C, and the rail head is spray-cooled at a cooling rate of 4.0°C / s for 110 seconds. When the temperature is 450°C, the cooling is stopped, and it is left naturally. After heat treatment, a fine pearlite structure is obtained. The mechanical properties are: tensile strength Rm is 1360MPa, yield strength Rp0.2 is 940MPa, elongation A is 13%, Brinell hardness of rail head tread is 390HB, Rockwell hardness of rail head section 3mm from the surface is 41.5HRC, The Rockwell hardness at 21mm on the surface is 39.0HRC, and the depth of the hardened layer is 39mm.

[0036] figure 1 It is a schematic diagram of the obtained steel rail's full-section hardness. In the figure, t...

Embodiment 2

[0050] The weight percentage of the chemical composition of the rail steel is: C: 0.70%, Si: 0.55%, Mn: 0.96%, V: 0.08%, Cr: 0.46%, P: 0.022%, S: 0.011%, Ti: 0.01%, The rest is iron, other trace elements and impurities, of which Mn+2Cr+5Mo+3Nb=1.88%

[0051] After the rail is rolled, the temperature of the residual heat is 785°C, and the rail head is spray-cooled at a cold rate of 5.0°C / s for 70 seconds. When the temperature is 438°C, the cooling stops and it is left naturally. After heat treatment, a fine pearlite structure is obtained. The mechanical properties are: tensile strength Rm is 1330MPa, yield strength Rp0.2 is 905MPa, elongation A is 12%, Brinell hardness of rail head tread is 380HB, Rockwell hardness of rail head section 3mm from the surface is 39.5HRC, The Rockwell hardness at 21mm on the surface is 38.5HRC, and the depth of the hardened layer is 35mm.

[0052] After the wear test, the wear rate is 29% of the U71Mn hot-rolled rail, that is, the wear resistance is 3....

Embodiment 3

[0054] The weight percentage of the chemical composition of rail steel is: C: 0.85%, Si: 0.73%, Mn: 0.75%, V: 0.11%, Cr: 0.38%, P: 0.019%, S: 0.010%, Nb: 0.03%, Cu: 0.30%. The rest is iron, other trace elements and impurities, of which Mn+2Cr+5Mo+3Nb=1.60%.

[0055] After the rail is rolled, the temperature of the residual heat is 682°C, and the rail head is cooled with compressed air at a cooling rate of 2.5°C / s for 100 seconds. When the temperature is 437°C, the cooling stops and it is left naturally. After heat treatment, a fine pearlite structure is obtained. The mechanical properties are: tensile strength Rm is 1390MPa, yield strength Rp0.2 is 1040MPa, elongation A is 11%, rail head tread Brinell hardness is 401HB, rail head section 3mm from the surface, Rockwell hardness is 41.5HRC, The Rockwell hardness at 21mm on the surface is 40.0HRC, and the depth of the hardened layer is 35mm. According to the neutral salt spray accelerated corrosion comparison test, the corrosion rate...

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Abstract

The invention relates to pearly heat-treated steel rail and its manufacturing method. Its chemical composition percentage by weight includes: C:0.70%-0.95%, Si:0.20%-1.10%, Mn:0.50%-1.50%, V:0.01%-0.20%, Cr:0.15%-1.20%, P: not less than 0.035%, S:not less than 0.035%, and Al: not less than 0.005%. The method includes the following steps: smelting; casting; rolling; cooling from 650-880 centigrade degree to 400-500 centigrade degree or room temperature with 1-10 centigrade degree per second; heating to 850-1100 centigrade degree; natural cooling to 650-880 centigrade degree; cooling to 400-500 centigrade degree with 1-10 centigrade degree per second than stop cooling; and natural laying. The formed steel rail has good wear resistance.

Description

Technical field [0001] The invention relates to a steel rail and a production method thereof, in particular to a pearlite heat-treated steel rail and a production method thereof. Background technique [0002] The heavy load of railway freight requires steel rails to have higher strength, and the tissues that can be used in a large number of rails are mainly pearlite, tempered martensite or bainite. Among them, pearlite has the most wear resistance and the most production technology. Simple, the lowest production cost and the most stable performance are one of the directions for continuous improvement and development of rail materials in the future. Generally, the strengthening methods of pearlite rails include alloying, heat treatment, and alloying + heat treatment. From the perspective of development, alloying + heat treatment is an ideal method, which has the advantages of high strength, good toughness and plasticity, and low cost. [0003] CN1012906B discloses a wear-resistant...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/24C21D1/34C21D9/04C22C38/50
Inventor 邹明梅东生周一平张昆吾徐权周伟
Owner PANZHIHUA IRON AND STEEL
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