A method of controlling the martensitic structure of r260 rail flash welded joints

A technology of head martensite and rail, which is applied in the field of controlling the martensite structure of R260 rail flash welding head, can solve the problems of failing to pass the welding type inspection, appearing point-like martensite structure, and shifting to the right, and achieves good promotion and application prospects. Simple effect of control process

Active Publication Date: 2021-05-25
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

However, C and Mn are segregation elements. When the Mn content in the rail increases to the upper-middle range, the rail base metal with high Mn content will inevitably lead to Mn micro-segregation. The high content of chemical components in the segregation zone will seriously shift the CCT curve to the right. It is easy to cause spot martensitic structure in the air cooling process of the welded joint, which cannot pass the welding type inspection of the EN standard.

Method used

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  • A method of controlling the martensitic structure of r260 rail flash welded joints
  • A method of controlling the martensitic structure of r260 rail flash welded joints

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0025] When controlling the content of Mn in the parent metal composition of R260 rail at the lower limit of 0.75%, the content of C in other chemical components at the upper limit, and Si at ≤0.30%, it is necessary to add 0.25% Cr and 0.03% V to the molten steel during the steelmaking process. In order to meet the mechanical properties of the hot-rolled rails that are normally produced and rolled by the Universal Line, Rm≥880MPa, tread hardness≥260HB, use rail mobile flash welders or fixed flash welders, and use pulsation or preheating flash with a large heat input of 7.5MJ After welding, the actual welding upsetting amount is kept at 13.0mm, and the joint is air-cooled to room temperature after the joint pushing is completed.

[0026] After testing, according to EN14587-2:2009 standard requirements of rail head and rail foot specified position inspection confirmed no martensitic structure, the corresponding metallographic structure is as follows figure 2 As shown, and in th...

Embodiment 2

[0028] When controlling the content of Mn in the parent metal composition of R260 rail to be at the lower limit of 0.77%, the content of other chemical components C at the upper limit, and Si at ≤0.30%, it is necessary to add 0.25% Cr and 0.03% V to the molten steel during the steelmaking process. In order to meet the mechanical properties of the hot-rolled rails that are normally produced and rolled by the universal line, the mechanical properties of the hot-rolled rails should meet Rm≥880MPa, and the hardness of the tread surface should be ≥260HB. The rail mobile flash welder or fixed flash welder is used, and a large heat input of 8.0MJ is used. Pulse or preheating flash After welding, the actual welding upsetting amount is kept at 13.5mm, and the joint is air-cooled to room temperature after the joint pushing is completed.

[0029] After testing, according to the requirements of EN14587-2:2009 standard, it is confirmed that there is no martensitic structure in the specified...

Embodiment 3

[0031] When controlling the content of Mn in the parent material of R260 rail to be at the lower limit of 0.80%, the content of C in other chemical components at the upper limit, and Si at ≤0.30%, it is necessary to add 0.22% Cr and 0.03% V to the molten steel during the steelmaking process. In order to meet the mechanical properties of the hot-rolled rails that are normally produced and rolled by the universal line, Rm≥880MPa, tread hardness≥260HB, use the rail mobile flash welder or fixed flash welder, and use 8.5MJ large heat input pulsation or preheating flash After welding, the actual welding upsetting amount is kept at 14.0mm, and the joint is air-cooled to room temperature after the joint pushing is completed.

[0032] After testing, according to the requirements of EN14587-2:2009 standard, the position inspection of the rail head and rail foot has confirmed that there is no martensite structure, and the static bending load of five consecutive R260 rail joints in this em...

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Abstract

The invention relates to a method for controlling the martensitic structure of R260 rail flash welding joints, belonging to the technical field of railway rail welding. The technical problem solved by the invention is that the martensitic structure is easy to appear in the R260 rail flash welding joint after welding in air cooling. The technical solution of the present invention is a method for controlling the martensitic structure of R260 rail flash welded joints, including hot rolling process control, welding process control, and post-weld cooling control, wherein the Mn content of the R260 rail base material is controlled to be 0.75% to 0.80%, The C content is in the upper limit, Si≤0.30%, and 0.20%-0.25% Cr and 0.03% V are added to the molten steel during the steelmaking process. The invention can avoid martensitic structure at the specified inspection positions of the center surface of the rail head and the rail foot, ensures various mechanical performance indexes of the joint, meets the technical requirements of the EN14587‑2:2009 standard, and has good prospects for popularization and application.

Description

technical field [0001] The invention belongs to the technical field of railway rail welding, and in particular relates to a method for controlling the martensitic structure of R260 rail flash welding joints. Background technique [0002] EN R260 steel rail is one of the steel grades that Panzhihua Steel exports to Malaysia, Thailand and other Southeast Asian countries every year, with an annual export volume of about 20,000-40,000 tons. EN13674-1:2011 "Railway applications-Track-RailPart 1: Vignole railway rails 46kg / mand above" standard requires the chemical composition of R260 finished rails to be: 0.60%~0.82%C, 0.65%~1.25%Mn, 0.13 % ~ 0.60% Si, P, S≤0.030%, ≤0.15% Cr, ≤0.030% V, and the rest Mo, Ni, Cu, Sn, Pb, etc. are control elements, and the general content is required to be controlled at 0.02% ~ 0.15%. At the same time, the EN standard requires the mechanical properties of the R260 rail, the tensile strength Rm≥880MPa, the elongation after fracture A≥10%, and the tr...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C22C38/02C22C38/04C22C38/42C22C38/44C22C38/46C22C38/60B21B37/00B23K11/04
CPCB21B37/00B21B2201/06B23K11/04C22C38/002C22C38/008C22C38/02C22C38/04C22C38/42C22C38/44C22C38/46C22C38/60
Inventor 李大东陆鑫王若愚白威
Owner PANZHIHUA IRON & STEEL RES INST OF PANGANG GROUP
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