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Method for controlling martensite structures in flash welded joints of R260 steel rails

A head martensite and rail technology, applied in the field of controlling R260 rail flash welded head martensite, can solve the problems of spot martensite, failure to pass welding type inspection, right shift, etc., and achieve simple and good control process Effect of Promoting App Foreground

Active Publication Date: 2020-02-07
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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  • Method for controlling martensite structures in flash welded joints of R260 steel rails
  • Method for controlling martensite structures in flash welded joints of R260 steel rails
  • Method for controlling martensite structures in flash welded joints of R260 steel rails

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Effect test

Embodiment 1

[0029] When controlling the content of Mn in the base material of R260 rail to be at the extremely low limit of 0.65%, and the content of C in other chemical components at the upper limit, and Si kept at ≤0.30%, it is necessary to add 0.30% Cr and 0.03% to the molten steel during the steelmaking process V, and increase the cooling air volume under the step-by-step cooling bed after the rail is hot-rolled, and increase the average cooling rate of the rail on the cooling bed above 500°C to 8.0°C / min, so as to meet the mechanical properties of the hot-rolled rail rolled by the universal line. Satisfy Rm≥880MPa, tread hardness ≥260HB, use rail mobile flash welding machine or fixed flash welding machine, adopt 3.5MJ small heat input after continuous flash welding, the actual welding upsetting amount is kept at 10.0mm, when the joint pushing is completed The back joint was air cooled to room temperature.

[0030] After testing, according to EN14587-2:2009 standard requirements of ra...

Embodiment 2

[0032] When controlling the content of Mn in the base material of R260 rail to be at the extremely low limit of 0.68%, and the content of C in other chemical components at the upper limit, and Si kept at ≤0.30%, it is necessary to add 0.28% Cr and 0.03% to the molten steel during the steelmaking process. V, and increase the cooling air volume under the step-by-step cooling bed after the rail is hot-rolled, and increase the average cooling rate of the rail at a temperature above 500°C on the cooling bed to 7.0°C / min, so as to meet the mechanical properties of the hot-rolled rail rolled by the universal line. Meet Rm≥880MPa, tread hardness ≥260HB, use rail mobile flash welder or fixed flash welder, after continuous flash welding with small heat input of 3.5MJ, the actual welding upsetting amount remains at 10.5mm, when the joint push is completed The back joint was air cooled to room temperature.

[0033]After testing, according to the requirements of EN14587-2:2009, the positio...

Embodiment 3

[0035] When controlling the content of Mn in the base material of R260 rail to be at the extremely low limit of 0.70%, and the content of C in other chemical components at the upper limit, and Si kept at ≤0.30%, it is necessary to add 0.25% Cr and 0.03% to the molten steel during the steelmaking process V, and increase the cooling air volume under the step-by-step cooling bed after the rail is hot-rolled, and increase the average cooling rate of the rail on the cooling bed above 500°C to 6.0°C / min, so as to meet the mechanical properties of the hot-rolled rail for normal production and rolling of the universal line Satisfy Rm≥880MPa, tread hardness ≥260HB, use the rail mobile flash welder or fixed flash welder, after continuous flash welding with a small heat input of 4.0MJ, the actual welding upsetting amount remains at 11.0mm, when the joint pushing is completed The back joint was air cooled to room temperature.

[0036] After testing, according to the requirements of EN1458...

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Abstract

The invention relates to a method for controlling martensite structures in flash welded joints of R260 steel rails and belongs to the technical field of welding of railway steel rails. The method solves the technical problem that martensite structures are likely to appear in air cooling after welding of flash welded joints of R260 steel rails. According to the technical scheme, the method for controlling the martensite structures in the flash welded joints of the R260 steel rails comprises the steps of controlling a hot rolling process, controlling a welding process and controlling cooling after welding, wherein the content of Mn in base materials of the R260 steel rails is controlled to be 0.65%-0.70%, the content of C is controlled to be at the middle and upper limit, the content of Si is controlled to be smaller than or equal to 0.30%, and 0.25%-0.30% of Cr and 0.03% of V are added in molten steel in the steel making process. By means of the method, it can be avoided that martensitestructures appear at specified inspection positions on the central faces in rail heads and rail bottom feet, various mechanical performance indicators of the joints are ensured, the technical requirement of EN14587-2:2009 is met, and the method has good application and popularization prospects.

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 R260 rail mechanical properties, tensile strength Rm ≥ 880MPa, elongation after fracture A ≥ 10%, and tread hardness 260-300HB. [...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22C38/24C22C38/04C22C38/02B21B37/00B23K9/23
CPCB21B37/00B23K9/23C22C38/02C22C38/04C22C38/24
Inventor 李大东陆鑫王若愚白威
Owner PANZHIHUA IRON & STEEL RES INST OF PANGANG GROUP
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