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Method for improving low-temperature toughness of medium carbon steel rail welding joint

A technology of welded joints and low temperature toughness, applied in the field of railway rail manufacturing, can solve problems such as brittle fracture, and achieve the effect of improving hardness and toughness

Active Publication Date: 2021-11-09
PANZHIHUA IRON & STEEL RES INST OF PANGANG GROUP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] Brittle fracture may occur when rails are served in low temperature environment for a long time

Method used

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  • Method for improving low-temperature toughness of medium carbon steel rail welding joint
  • Method for improving low-temperature toughness of medium carbon steel rail welding joint
  • Method for improving low-temperature toughness of medium carbon steel rail welding joint

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Experimental program
Comparison scheme
Effect test

Embodiment 1

[0037] The microstructure of the rail base metal is controlled to be 80% pearlite and 20% proeutectoid ferrite. The tensile strength of the rail parent material at room temperature (20-25°C) is 1080MPa, the elongation is 17%, and the U-shaped impact energy is 35J. Under the condition of -20℃, the U-shaped impact energy of the base metal of the rail is 29J. The chemical composition of the rail steel to obtain this microstructure needs to meet the following conditions: 0.50% content of C, 0.30% content of Si, 0.70% content of Mn, 0.1% content of Cr, 0.04% content of V, and the balance is Fe and unavoidable impurities. The heat treatment process of rail steel to obtain this microstructure needs to meet the following conditions: after the billet is heated and rolled into a rail with a single weight of 60kg / m, it is left to stand and cooled in the air. When the temperature at the center of the top surface of the rail head drops to 790°C Spray cooling medium to the top surface of ...

Embodiment 2

[0042] The microstructure of the control rail base metal is 88% pearlite and 12% proeutectoid ferrite. The tensile strength of the rail parent material at room temperature (20-25°C) is 1080MPa, the elongation is 17%, and the U-shaped impact energy is 32J. Under the condition of -20°C, the U-shaped impact energy of the base metal of the rail is 27J. The chemical composition of the rail steel to obtain this microstructure needs to meet the following conditions: 0.58% content of C, 0.45% content of Si, 0.90% content of Mn, 0.3% content of Cr, 0.045% content of V, and the balance is Fe and unavoidable impurities. The heat treatment process of rail steel to obtain this microstructure needs to meet the following conditions: after the steel billet is heated and rolled into a rail with a single weight of 60kg / m, it is left standing and cooled in the air. When the temperature at the center of the top surface of the rail head drops to 840°C Spray cooling medium to the top surface of t...

Embodiment 3

[0047] The microstructure of the rail base metal is controlled to be 90% pearlite and 10% proeutectoid ferrite. The tensile strength of the rail base material at room temperature (20-25°C) is 1100MPa, the elongation is 16%, and the U-shaped impact energy is 32J; at -20°C, the U-shaped impact energy of the rail base material is 28J. The chemical composition of the rail steel to obtain this microstructure needs to meet the following conditions: 0.58% content of C, 0.50% content of Si, 0.92% content of Mn, 0.35% content of Cr, 0.05% content of V, and the balance is Fe and unavoidable impurities. The heat treatment process of the rail steel to obtain this microstructure needs to meet the following conditions: the billet is heated and rolled into a rail with a single weight of 60kg / m, and then cooled in the air. When the temperature at the center of the top surface of the rail head drops to 800°C Spray a cooling medium with a cooling rate of 5.0°C / s to the top surface of the rail ...

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Abstract

The invention discloses a method for improving low-temperature toughness of a medium carbon steel rail welding joint. The method comprises the following steps that (1) medium carbon steel rail base metal is prepared, wherein the microstructure of the medium carbon steel rail base metal is controlled to comprise 80%-92% of pearlite and 8%-20% of pro-eutectoid ferrite; (2) a plurality of steel rails formed by rolling the medium carbon steel rail base metal in the step (1) are welded, wherein the welding operation comprises welding, upsetting and knot pushing; and (3) heat treatment is conducted on the welding joint obtained in the step (2), specifically, the heat treatment comprises the steps that after knot pushing is carried out on the welding joint, a cooling medium is blown to the welding joint, when the temperature reaches 350-420 DEG C, blowing of the cooling medium is stopped, the welding joint is heated to 500-650 DEG C, heat preservation is conducted for 20-35 minutes, and then the welded joint is naturally cooled to the room temperature in air.

Description

technical field [0001] The invention relates to the technical field of railway rail manufacturing, in particular to a method for improving the low-temperature toughness of welded joints of medium-carbon steel rails. Background technique [0002] The Sichuan-Tibet Railway is faced with complex service environments and terrains such as low temperature, humidity, wind, rain and snow, and fragile ecological areas. The extreme minimum temperature in winter is -32.2°C, the maximum temperature in summer is 40°C, and the maximum temperature difference between day and night can reach 35°C. The complex and changeable railway operating environment puts forward higher requirements on the service performance of rail base metal and welded joints. [0003] During the laying of rails, adjacent rails are usually joined together by welding. The welded joint of the rail is a transition area connecting different rails, and its mechanical properties have an important impact on the service safe...

Claims

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Application Information

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IPC IPC(8): C22C38/02C22C38/04C22C38/24C21D8/00C21D9/04C21D9/50E01B11/44
CPCC22C38/02C22C38/04C22C38/24C21D8/005C21D9/04C21D9/505C21D9/50E01B11/44C21D2211/009C21D2211/005
Inventor 白威李大东陆鑫徐飞翔
Owner PANZHIHUA IRON & STEEL RES INST OF PANGANG GROUP
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