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A method for improving low temperature toughness of medium carbon steel rail welded joint

A technology of welding joints and low-temperature toughness, which is 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: 2022-08-05
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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  • A method for improving low temperature toughness of medium carbon steel rail welded joint
  • A method for improving low temperature toughness of medium carbon steel rail welded joint
  • A method for improving low temperature toughness of medium carbon steel rail welded joint

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0037] The microstructure of the control rail base metal is 80% pearlite and 20% proeutectoid ferrite. The tensile strength of the rail base metal 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 rail base metal is 29J. The chemical composition of the rail steel to obtain this microstructure must meet the following conditions: 0.50% C, 0.30% Si, 0.70% Mn, 0.1% Cr, 0.04% V, and the balance Fe and inevitable impurities. The heat treatment process of the rail steel with this microstructure must meet the following conditions: the billet is heated and rolled into a rail with a single weight of 60kg / m, and then left to stand and cooled in the air, when the temperature of the center of the top surface of the rail head drops to 790℃ The cooling medium is sprayed on the top surface of the rail head, the two sides of the rail head and the lower jaws on both sides of th...

Embodiment 2

[0042] The control rail base metal microstructure is 88% pearlite and 12% proeutectoid ferrite. The tensile strength of the rail base metal 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℃, the U-shaped impact energy of the rail base metal is 27J. The chemical composition of the rail steel with this microstructure must meet the following conditions: 0.58% C, 0.45% Si, 0.90% Mn, 0.3% Cr, 0.045% V, and the balance Fe and inevitable impurities. The heat treatment process of the rail steel with this microstructure must meet the following conditions: the billet is heated and rolled into a rail with a single weight of 60kg / m, then it is left to stand and cooled in the air, when the temperature of the center of the top surface of the rail head drops to 840℃ The cooling medium is sprayed on the top surface of the rail head, the two sides of the rail head and the lower jaws on both sides of the rail he...

Embodiment 3

[0047] The microstructure of the control rail base metal is 90% pearlite and 10% proeutectoid ferrite. The tensile strength of the rail base metal 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 metal is 28J. The chemical composition of the rail steel to obtain this microstructure must meet the following conditions: 0.58% C, 0.50% Si, 0.92% Mn, 0.35% Cr, 0.05% V, and the balance Fe and inevitable impurities. The heat treatment process of the rail steel with this microstructure should meet the following conditions: after the billet is heated and rolled into a 60kg / m single weight rail, it is left to cool in the air. Spray a cooling medium with a cooling rate of 5.0°C / s to the top surface of the rail head, both sides of the rail head and the lower jaws on both sides of the rail head to 380°C, then stop the accelerated cooling and continue to air-cool to room temperature...

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Abstract

The invention discloses a method for improving the low temperature toughness of a medium carbon steel rail welded joint. The method includes the following steps: Step 1): preparing the medium carbon steel rail base material, wherein the medium carbon steel rail base material microstructure is controlled to include 80-92% of pearlite and 8-20% of pro-copolymer ferrite; step 2): welding a plurality of rails rolled from the medium carbon steel rail base material of step 1), and the welding operation includes welding, upset forging and push-out; step 3): to The welded joint obtained in step 2) is subjected to heat treatment, the heat treatment includes spraying a cooling medium to the welded joint after the bump is pushed out of the welded joint, and when the temperature reaches 350-420°C, the spraying of the cooling medium is stopped, and the welded joint is heated to 500‑650°C, hold for 20‑35 minutes, and then naturally cool to 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 a medium carbon steel rail welded joint. Background technique [0002] The Sichuan-Tibet Railway faces complex service environments and topography 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 for the service performance of rail base materials and welded joints. [0003] During the laying of rails, adjacent rails are usually welded together. As the transition area connecting different rails, the mechanical properties of the welded joint of the rail have an important impact on the service safety of the e...

Claims

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Application Information

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Patent Type & Authority Patents(China)
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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