CN110438327A - Hypo eutectoid steel rail weld joint heat treatment method - Google Patents
Hypo eutectoid steel rail weld joint heat treatment method Download PDFInfo
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- CN110438327A CN110438327A CN201910848022.6A CN201910848022A CN110438327A CN 110438327 A CN110438327 A CN 110438327A CN 201910848022 A CN201910848022 A CN 201910848022A CN 110438327 A CN110438327 A CN 110438327A
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- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
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Abstract
The invention discloses a kind of hypo eutectoid steel rail weld joint heat treatment methods, are related to railway track manufacturing technology field, provide it is a kind of cost is relatively low and after handling welding point satisfactory mechanical property hypo eutectoid steel rail weld joint heat treatment method.Method includes the following steps: the welding point that A, the temperature for forming two hypo eutectoid rail weldings are 1100~1400 DEG C carries out first stage cooling, welding point surface temperature is set to be reduced to 730~820 DEG C, the stage is cooled to natural cooling in air, and cooling velocity is 4.5~7.0 DEG C/s；B, welding point is subjected to second stage cooling, welding point surface temperature is made to be reduced to 200~280 DEG C, which is cooled to the cooling carried out using imitative type cooling device, and cooling velocity is 1.2~3.2 DEG C/s；C, welding point is subjected to phase III cooling, welding point surface temperature is made to be reduced to 10~40 DEG C, which is cooled to the cooling carried out using imitative type cooling device, and cooling velocity is 0.02~0.40 DEG C/s.
Description
Technical field
The present invention relates to railway track manufacturing technology field more particularly to a kind of hypo eutectoid steel rail weld joint heat treatment sides
Method.
Background technique
At this stage, heavy haul railway, high-speed railway and passenger-cargo mixed fortune railway three types are mainly covered in the global railway system.Weight
It is great (axis weight 25t~40t) to carry railway train axle, the carbon content of rail used is typically larger than 0.75%, and tensile strength exists
1200MPa or more has full pearlitic structrure or based on pearlite, comprising micro secondary cementite, have it is high-intensitive,
Guarantee wearability while high rigidity.Since passenger-cargo mixed fortune railway should undertake passenger traffic, guarantee cargo transport again, thus requires
Rail will also have good anti-fatigue performance while with certain abrasion resistance properties.Therefore, used in passenger-cargo mixed fortune railway
The carbon content of rail is usually 0.70%~0.80%, and tensile strength is organized between 900MPa~1100MPa generally with pearly-lustre
Based on body, part rail tissue includes micro ferrite.And for high-speed railway (axis weight 11t~14t) and quasi high-speed highway,
Since the two is required to rail with certain anti-fatigue performance, thus it is now widely used be carbon content 0.65%~
Between 0.76%, the U71Mn hot rolled rail of tensile strength 900MPa.
However, route investigation shows that abrasion during operation between wheel track is smaller, leads since bullet train axis weight is lighter
Cause has resulted from rail head of rail surface or the crackle of side is difficult to grind off, and through wheel track contact forces reciprocating, can aggravate instead
Crack propagation considerably increases the fracture tendency of rail, seriously jeopardizes railway operation safety.In addition, if only by reduction
Rail strength and hardness improve rail wear rate, so that rail surface layer is generated plastic flow, cause rail profile ruler
Very little deviation will also make rail abrasion too fast, shorten the working life.Therefore, in high speed and quasi high-speed highway, with pearlitic structrure
Based on hot rolled rail be difficult to achieve the purpose that take into account it is wear-resistant with resistance to rolling contact fatigue performance.To improve rail in high speed railway
Anti- rolling contact fatigue performance, developed in recent years one kind based on bainite structure, include micro martensite and remnants
The rail of austenite.The patent of the patent No. " CN1074058C " discloses a kind of bainitic steel rail that weld part zygosity is excellent
And its manufacturing method.However, such rail needs to add in process of production a large amount of noble element (such as Nb, Mo, V), lead
Cause manufacturing cost has reached twice of common pearlite steel rail.In addition, rail process control and manufacturing technique requirent strictly etc. because
Element causes such rail to be difficult in high volume promote the use of.In this case, for carbon content between 0.55%~0.65%, tension is strong
Degree comes into being in 900MPa hypo eutectoid heat-treated rail below.Such rail tissue contains trace iron based on pearlite
Ferritic.Compared with traditional U71Mn hot rolling pearlite steel rail, hypo eutectoid rail has low production cost, good wear-resistant
Performance and anti-fatigue performance are expected to become the rail product of new generation of substitution U71Mn, for high speed and quasi high-speed highway.Asia is altogether
The chemical component for analysing rail is general are as follows: 0.40~0.64 weight %, Si content of C content, 0.10~1.00 weight %, Mn content
0.30~1.50 weight %, less than the P for being equal to 0.025 weight %, less than the S for being equal to 0.025 weight %, less than equal to 0.005
The Al of weight %, greater than 0 less than the rare earth element equal to 0.05 weight %, total amount is greater than 0 and less than or equal to 0.20 weight %'s
V, at least one of Cr and Ti and the Fe and inevitable impurity of surplus.Hypo eutectoid rail rail based on mentioned component
The metallographic structure of head position at room temperature is pearlite and 15%~50% ferritic uniform line and staff control.
At this stage, the mobile flash welding of rail has become the online welding technique of mainstream rail at domestic and international construction of railways scene,
And for two kinds of rail that strength grade and material are all different, the difference between base material performance brings huge choose to its welding
War.Meanwhile after rail is acted on by Thermal Cycle, the quench-hardened case disappearance of welding region is simultaneously biggish in weld seam two sides formation width
Soft area causes the hardness of weld dimensions lower than rail base material.During route is on active service, Yi Youxian is being welded rail
The rail head tyre tread of connector forms " saddle " abrasion, not only increases wheel-rail impact, also seriously affects rail service life, very
To jeopardizing traffic safety.Thus, how to restore before the mechanical property that rail is reduced by welding just is able to apply at rail
It mentions.
Application No. is 201410135909.8, a kind of entitled " post weld heat treatment of bainite rail welding point
The patent of method " discloses a kind of bainite rail postwelding connector heat-treating methods, this method include will weld obtain to
Cooling bainite rail welding point carries out being cooled to the first temperature not higher than 450 DEG C for the first time, then cooling by first
Welding point afterwards is heated to second temperature, then carry out again it is second cooling, the second temperature be higher than first temperature and
Not higher than 510 DEG C.The post weld heat treatment technique that this method is carried out primarily directed to bainite rail welding point, wherein the shellfish
The cooling initial temperature of family name's body rail is 1300~1380 DEG C, and the second cooling termination temperature after cooling is room temperature.However, it is necessary to
Illustrate, the bainite rail that foregoing invention patent is related to has different ingredients from hypo eutectoid rail according to the present invention
System has completely different metallographic structure and Mechanical Characteristics.In addition, foregoing invention is also relating to the postwelding of rail just
Burning hot treatment process needs to implement local heating and cooling to steel rail weld joint using Post-Welding Heattreatment of Rail equipment, not only
Operation is complicated with implementation process, and high expensive.
Summary of the invention
The technical problem to be solved by the present invention is providing, a kind of cost is relatively low and welding point satisfactory mechanical property after handling
Hypo eutectoid steel rail weld joint heat treatment method.
In order to solve the above problem the technical solution adopted is that: hypo eutectoid steel rail weld joint heat treatment method include successively into
Capable following steps:
A, the welding point that the temperature for forming two hypo eutectoid rail weldings is 1100~1400 DEG C carries out the first stage
It is cooling, so that welding point surface temperature is reduced to 730~820 DEG C, the first stage is cooled to natural cooling in air, cooling velocity
For 4.5~7.0 DEG C/s；
B, that welding point is carried out second stage is cooling, and welding point surface temperature is made to be reduced to 200~280 DEG C, and second
Stage is cooled to the cooling carried out using imitative type cooling device, and cooling medium is compressed air or water mist gaseous mixture, cooling velocity
For 1.2~3.2 DEG C/s；
C, welding point is subjected to phase III cooling, so that welding point surface temperature is reduced to 10~40 DEG C, third rank
Section is cooled to the cooling carried out using imitative type cooling device, and cooling medium is compressed air or water mist gaseous mixture, cooling velocity are
0.02~0.40 DEG C/s.
Further, imitating type cooling device apart from 20~40mm of rail head of rail tyre tread in step B；Imitative type cooling device
The pressure of the compressed air or water mist gaseous mixture that eject is 0.25~0.65MPa.
Further, imitating type cooling device apart from 20~40mm of rail head of rail tyre tread in step C；Imitative type cooling device
The pressure of the compressed air or water mist gaseous mixture that eject is 0.01~0.20MPa.
Further, welding point welds to be formed by the mobile flash welder of rail.
The beneficial effects of the present invention are: (1) present invention is heat-treated using the welding waste heat of welding point, it is heat treated
It does not need to reheat in journey, therefore simplifies heat treatment process, and reduce cost.
(2) the invention can ensure that away from corresponding to the rail joint longitudinal direction hardness satisfaction in the region Weld pipe mill ± 10mm
Hypo eutectoid rail base material average hardness ± 30HV range (do not include the axis of a weld of decarburization: being influenced by rail welding high temperature,
Weld pipe mill decarburization simultaneously generates melting loss of elements, leads to lower hardness), and the softening sector width of joint welding two sides no more than
10mm.Meanwhile, it is capable to control the martensitic structure percentage composition being likely to occur in steel rail weld joint metallographic structure≤2%
In range, so as to improve rail route military service during because of welding region lower hardness caused by rail joint " saddle
Type " abrasion help to ensure that railway operation safety.
Detailed description of the invention
Fig. 1 is the hypo eutectoid steel rail weld joint under the conditions of the post weld heat treatment obtained using the method in embodiment 1
Longitudinal stiffening effect figure of the position 3~5mm below rail head tyre tread.
Fig. 2 is using the hypo eutectoid steel rail weld joint under the conditions of the obtained post weld heat treatment of method in embodiment 2
Rail head tyre tread below the position 3~5mm longitudinal stiffening effect figure.
Fig. 3 is the hypo eutectoid steel rail weld joint using the obtained postwelding of method in comparative example 1 under the conditions of air-cooled
Longitudinal stiffening effect figure of the position 3~5mm below rail head tyre tread.
Fig. 4 is using the hypo eutectoid steel rail weld joint under the conditions of the obtained post weld heat treatment of method in comparative example 2
Rail head tyre tread below the position 3~5mm longitudinal stiffening effect figure.
Fig. 5 is using the hypo eutectoid steel rail weld joint under the conditions of the obtained post weld heat treatment of method in comparative example 3
Rail head tyre tread below the position 3~5mm longitudinal stiffening effect figure.
Fig. 6 is longitudinal hardness determination point position of the rail head tyre tread of steel rail weld joint of the invention or less the position 3~5mm
Schematic diagram.
Fig. 7 is the rail head tyre tread metallographic specimen sample position schematic diagram of steel rail weld joint of the invention.
Fig. 8 is that rail head of rail used in the present invention imitates type cooling device schematic diagram.
Fig. 9 is that rail head of rail used in the present invention imitates type cooling device bottom schematic view.
In the figure, it is marked as medium channel A1, top jet nozzle 2, medium channel B3, side nozzle 4.
Specific embodiment
With reference to embodiment, the present invention is further described for embodiment and comparative example.Rail welding of the present invention
The rail head tyre tread metallographic specimen sample position of connector is as shown in Figure 7.In embodiment and comparative example, the rail head of steel rail weld joint is stepped on
Longitudinal hardness determination point position of 3~5mm position below face is as shown in Figure 6.A is recrystallization zone in figure, and b is rail head tyre tread, and c is
Weld seam, d are that metallographic test examines face.
Inventor has found the critical of the martensite transfor mation during the continuous cooling transformation of sub-eutectoid steel rail steel in early-stage study
About 0.5~0.9 DEG C/s of cooling velocity, about 250~320 DEG C of Ms temperature (start temperature that martensitic structure is formed).Usually keep away
Exempt from steel rail weld joint and the abnormal structures such as martensite, bainite occur, is carried out at postwelding heat when to hypo eutectoid steel rail weld joint
When reason, the final cooling temperature during need to being quickly cooled down Post-Welding Heattreatment of Rail is controlled more than rail Ms temperature.Meanwhile rail
Cooling velocity in PWHT procedures must be limited with the Critical cooling speed of martensite transfor mation, and otherwise connector will be due to largely quenching
Hard martensitic structure and cause premature fatigue to be broken.Therefore, rail welding standard such as Australia rail welding standard
It is provided in AS1085.20-2012: for the rail of certain high grades, high carbon content and high alloy content, in metallography microscope
Under the observation multiplying power of mirror 100x, for the most serious region that martensite in steel rail weld joint occurs, the percentage of martensitic structure
Content must not be higher than 5%, and otherwise connector will cause premature fatigue to be broken due to the martensitic structure largely hardened, serious shadow
Ring railway operation safety.Therefore, stable operation of the martensite content in strict control rail welding tissue for rail track
For it is most important.Based on above-mentioned discovery, inventor completes the present invention.
Hypo eutectoid steel rail weld joint heat treatment method includes the following steps successively carried out: A, by two hypo eutectoid rail
The welding point that the temperature that welding is formed is 1100~1400 DEG C carries out first stage cooling, makes the reduction of welding point surface temperature
To 730~820 DEG C, the first stage is cooled to natural cooling in air, and cooling velocity is 4.5~7.0 DEG C/s；B, by welding point
It is cooling to carry out second stage, so that welding point surface temperature is reduced to 200~280 DEG C, second stage is cooled to cold using imitative type
But the cooling that device carries out, cooling medium are compressed air or water mist gaseous mixture, and cooling velocity is 1.2~3.2 DEG C/s；It C, will weldering
Connector carries out phase III cooling, so that welding point surface temperature is reduced to 10~40 DEG C, the phase III is cooled to using imitative
The cooling that type cooling device carries out, cooling medium are compressed air or water mist gaseous mixture, and cooling velocity is 0.02~0.40 DEG C/s.
Wherein in step B, preferably imitative type cooling device is apart from 20~40mm of rail head of rail tyre tread；Imitative type cooling device injection
The pressure of compressed air or water mist gaseous mixture out is 0.25~0.65MPa.In step C, preferably imitative type cooling device distance steel
20~40mm of rail rail head tyre tread；The pressure of compressed air or water mist gaseous mixture that imitative type cooling device ejects is 0.01~
0.20MPa.Welding point welds to be formed by the mobile flash welder of rail.
Imitative type cooling device in step B and step C is as shown in Figure 8 and Figure 9, including medium channel A1, medium channel B3,
Top jet nozzle 2 and side nozzle 4, medium channel A1 are connect with top jet nozzle 2, and medium channel B3 is connect with side nozzle 4.
The higher rail joint of the residual temperature that the present invention is obtained for welding implements postwelding and accelerates cooling, to reduce connector rail head
From austenite to the phase transition temperature of perlitic transformation, the hardness in austenite recrystallization area is improved.Based on Principles of Metallography, rail is connect
Head, there are certain dynamic degree of supercooling, causes under nonequilibrium condition austenite to pearlite under postwelding high temperature condition of fast cooling
The phase transition temperature of transformation moves down, and with the increase of degree of supercooling, phase transition temperature is gradually decreased.Therefore, even if opening cold temperature phase
Cooling to lower second stage, connector rail head remains to occur the structural transformation from austenite to pearlite.It is described in the present invention
First is cooled to the natural cooling carried out in air, can be by adjusting test ambient temperature (such as using central air-conditioner temperature control)
Realize control to first stage cooling velocity, and can be by adjusting welding machine setting or manual operation for steel rail weld joint the
One cooling final cooling temperature is controlled at 730~820 DEG C.Described second cooling cold temperature of opening is 730~820 DEG C.In the present invention,
Described second cooling final cooling temperature is slightly below the Ms (martensite start) point (Ms temperature) of sub-eutectoid steel rail steel, in the present invention
Second cooling final cooling temperature is 200~280 DEG C.When carrying out phase III cooling to rail joint, to avoid connector from occurring
The martensitic structure largely hardened, present invention selection is with the cooling velocity lower than sub-eutectoid steel rail steel martensite transfor mation Critical cooling speed
0.02~0.40 DEG C/s butt joint implementation cools down at a slow speed.
In Principles of Metallography, the martensitic structure of steel is steel more than austenitizing temperature, to face higher than martensite transfor mation
The cooling velocity of boundary's cooling rate is cooled to (start temperature that martensitic structure is formed) Ms temperature product below.It is to keep away in the present invention
Exempt to generate a large amount of brittle martensites in rail joint, when carrying out post weld heat treatment to rail joint, in the second cooling stage
Final cooling temperature during post weld heat treatment is quickly cooled down controls below the Ms temperature of slightly below rail steel.When cold second
But when the stage uses the cooling velocity butt joint for being higher than rail steel martensite formation Critical cooling speed to implement heat treatment, due to the stage
Final cooling temperature be slightly below the Ms temperature of rail steel and the cooling velocity of third cooling stage formed in rail steel martensite it is critical
Cooling rate will not cause to significantly affect hereinafter, therefore can only generate micro martensitic structure to rail joint fatigue life.Together
When, in second and third cooling stage, since the cooling velocity in the two stages is all relatively large, biggish degree of supercooling facilitates
The promotion of joint toughness, therefore rail joint fatigue life is higher in the present invention.
Embodiment 1:
Specification connects for the upset during the mobile Flash Butt Welding of rail completion of 60kg/m and after pushing away tumor to what welding obtained
Head carries out post weld heat treatment.Firstly, the residual temperature that welding is obtained is cooling fast with the first of 7.0 DEG C/s in 1100 DEG C of rail joint
Degree carries out first stage cooling so that the rail head skin temperature of rail joint is down to 750 DEG C, then makes rail joint with 2.0 DEG C/s
The second cooling velocity to carry out second stage cooling the rail head skin temperature of rail joint is down to 270 DEG C, finally make rail
Connector carries out phase III cooling with the third cooling velocity of 0.30 DEG C/s the rail head skin temperature of rail joint is down to 25
DEG C room temperature, to obtain the steel rail weld joint of the invention through post weld heat treatment.In PWHT procedures, first is cooling
For the natural cooling carried out in air；Rail head of rail is used to imitate type cooling device to press in second cooling and third cooling procedure
Contracting air cools down the rail head tyre tread of rail joint and rail head side as cooling medium, and cooling device is apart from rail head of rail
Tyre tread 40mm；In second cooling procedure, the gas pressure of the compressed air of cooling device injection is 0.40MPa；Third is cooled
Cheng Zhong, the gas pressure of the compressed air of cooling device injection are 0.15MPa.Rail head of rail tyre tread is monitored using infrared radiation thermometer
Temperature.
The rail joint through post weld heat treatment that the present embodiment is obtained is machined to longitudinal hardness specimens.It is hard using cloth dimension
Degree meter position 4mm below rail head of rail tyre tread (Laizhou, Shandong city testing machine head factory, model HBV-30A), using 2mm between measuring point
Away from longitudinal Vickers hardness detection is carried out to hardness specimens, two sides are symmetrically arranged measuring point to the left and right centered on weld seam.Vickers hardness
The method of inspection is carried out referring to GB/T 4340.1-2009 " Vickers Hardness Test part 1: test method ", is marked using HV
Ruler.Hardness Surveillance data are shown in Table 1, and the distributed effect of connector longitudinal direction hardness is as shown in Figure 1.
Table 1:
By table 1 and Fig. 1 it is found that for steel rail weld joint processed by the invention, away from the region Weld pipe mill ± 10mm
± 30HV the range that interior rail joint longitudinal direction hardness meets corresponding rail base material average hardness respectively (does not include decarburization
Axis of a weld: being influenced by rail welding high temperature, and Weld pipe mill decarburization simultaneously generates melting loss of elements, leads to lower hardness).Connector weldering
The softening sector width in seam left side is 10.0mm, and the softening sector width on the right side of joint welding is 9.0mm, the softening of joint welding two sides
Sector width is no more than 10.0mm.
Referring to sampling method shown in Fig. 7 by GB/T13298-2015 " the metal microstructure method of inspection " to rail joint
Metallographic specimen carries out microstructure examination, carries out etch to rail joint metallographic specimen using 3% nital, using moral
State comes card MeF3 optical microscopy and observes rail joint metallographic structure.The result shows that connector metallographic is martensite-free, bayesian
Ti Deng abnormal structure.
Embodiment 2:
Specification connects for the upset during the mobile Flash Butt Welding of rail completion of 68kg/m and after pushing away tumor to what welding obtained
Head carries out post weld heat treatment.Firstly, the residual temperature that welding is obtained is cooling fast with the first of 6.5 DEG C/s in 1200 DEG C of rail joint
Degree carries out first stage cooling so that the rail head skin temperature of rail joint is down to 730 DEG C, then makes rail joint with 2.5 DEG C/s
The second cooling velocity to carry out second stage cooling the rail head skin temperature of rail joint is down to 220 DEG C, finally make rail
Connector carries out phase III cooling with the third cooling velocity of 0.20 DEG C/s the rail head skin temperature of rail joint is down to 25
DEG C room temperature, to obtain the steel rail weld joint of the invention through post weld heat treatment.In PWHT procedures, first is cooling
For the natural cooling carried out in air；Second is cooling and third cooling procedure in, use rail head of rail imitate type cooling device with
Water mist gaseous mixture cools down the rail head tyre tread of rail joint and rail head side as cooling medium, and cooling device is apart from rail
Rail head tyre tread 40mm；In second cooling procedure, the gas pressure of the water mist gaseous mixture of cooling device injection is 0.50MPa；Third
In cooling procedure, the gas pressure of the water mist gaseous mixture of cooling device injection is 0.10MPa.Rail is monitored using infrared radiation thermometer
Rail head wheel tread temperature.
The rail joint through post weld heat treatment that the present embodiment is obtained is machined to longitudinal hardness specimens.It is hard using cloth dimension
Degree meter position 4mm below rail head of rail tyre tread (Laizhou, Shandong city testing machine head factory, model HBV-30A), using 2mm between measuring point
Away from longitudinal Vickers hardness detection is carried out to hardness specimens, two sides are symmetrically arranged measuring point to the left and right centered on weld seam.Vickers hardness
The method of inspection is carried out referring to GB/T 4340.1-2009 " Vickers Hardness Test part 1: test method ", is marked using HV
Ruler.Hardness Surveillance data are shown in Table 2, and the distributed effect of connector longitudinal direction hardness is as shown in Figure 2.
Table 2:
By table 2 and Fig. 2 it is found that for steel rail weld joint processed by the invention, away from the region Weld pipe mill ± 10mm
± 30HV the range that interior rail joint longitudinal direction hardness meets corresponding rail base material average hardness respectively (does not include the weldering of decarburization
Seam center line: it is influenced by rail welding high temperature, Weld pipe mill decarburization simultaneously generates melting loss of elements, leads to lower hardness).On the left of connector
Softening sector width be 9.0mm, the softening sector width on right side is 8.0mm, the softening sector widths of joint welding two sides no more than
10.0mm。
Rail is connect by GB/T 13298-2015 " the metal microstructure method of inspection " referring to sampling method shown in Fig. 7
Head metallographic specimen carries out microstructure examination, carries out etch to rail joint metallographic specimen using 3% nital, uses
Leca MeF3 optical microscopy observes rail joint metallographic structure.Metal lographic examination shows to observe multiplying power in 100X
Under, for the region for the most serious that martensitic structure occurs, the percentage composition of martensitic structure is lower than≤1%, helps to protect
Demonstrate,prove railway operation safety.
Comparative example 1:
Specification is for the upset during the mobile Flash Butt Welding of rail completion of 68kg/m and after pushing away tumor, by residual temperature at 1100 DEG C
Rail joint Direct Air-Cooled to room temperature (about 25 DEG C), to obtain the steel rail weld joint under the conditions of air-cooled (natural cooling).
Rail joint under the conditions of the postwelding for taking this comparative example to obtain is air-cooled is processed into longitudinal hardness specimens.It is hard using cloth dimension
Degree meter position 5mm below rail head of rail tyre tread (Laizhou, Shandong city testing machine head factory, model HBV-30A), using 2mm between measuring point
Away from longitudinal Vickers hardness detection is carried out to hardness specimens, two sides are symmetrically arranged measuring point to the left and right centered on weld seam.Vickers hardness
The method of inspection is carried out referring to GB/T 4340.1-2009 " Vickers Hardness Test part 1: test method ", is marked using HV
Ruler.Hardness Surveillance data are shown in Table 3, and the distributed effect of connector longitudinal direction hardness is as shown in Figure 3.
Table 3:
By table 3 and Fig. 3 it is found that for not connect using the rail welding of post weld heat treatment method provided by the invention processing
Head, compared with the rail base material hardness of weld seam two sides, entire welding region is rendered as soft state.Away from Weld pipe mill ± 10mm
± 30HV the range that rail joint longitudinal direction hardness in region is not able to satisfy corresponding rail base material average hardness (do not include
The axis of a weld of decarburization: being influenced by rail welding high temperature, and Weld pipe mill decarburization simultaneously generates melting loss of elements, leads to lower hardness).
Softening sector width on the left of joint welding is 17.0mm, and the softening sector width on the right side of joint welding is 16.0mm.By the comparative example
For obtained welding point during route is on active service, Yi Youxian forms that rail head of rail tyre tread is low collapses in welding joint softened area, causes " saddle
Type " abrasion, influence Track regularity and traffic safety.
Referring to sampling method shown in Fig. 7 by GB/T13298-2015 " the metal microstructure method of inspection " to rail joint
Metallographic specimen carries out microstructure examination, carries out etch to rail joint metallographic specimen using 3% nital, using moral
State comes card MeF3 optical microscopy and observes rail joint metallographic structure.The result shows that connector metallographic structure is normal, no horse
The abnormal structures such as family name's body, bainite.
Comparative example 2:
Specification connects for the upset during the mobile Flash Butt Welding of rail completion of 75kg/m and after pushing away tumor to what welding obtained
Head carries out post weld heat treatment.Firstly, the residual temperature that welding is obtained is cooling fast with the first of 6.0 DEG C/s in 1250 DEG C of rail joint
Degree carries out first stage cooling so that the rail head skin temperature of rail joint is down to 780 DEG C, then makes rail joint with 3.0 DEG C/s
The second cooling velocity to carry out second stage cooling the rail head skin temperature of rail joint is down to 180 DEG C, finally make rail
Connector carries out phase III cooling with the third cooling velocity of 0.20 DEG C/s the rail head skin temperature of rail joint is down to 30
DEG C room temperature, to obtain the steel rail weld joint of the invention through post weld heat treatment.In PWHT procedures, first is cooling
For the natural cooling carried out in air；Second is cooling and third cooling procedure in, use rail head of rail imitate type cooling device with
Compressed air cools down the rail head tyre tread of rail joint and rail head side as cooling medium, and cooling device is apart from rail rail
Head tyre tread 38mm；In second cooling procedure, the gas pressure of the compressed air of cooling device injection is 0.60MPa；Third is cooling
In the process, the gas pressure of the compressed air of cooling device injection is 0.10MPa.It is stepped on using infrared radiation thermometer monitoring rail head of rail
Face temperature.
Rail joint under the conditions of the postwelding for taking this comparative example to obtain is air-cooled is processed into longitudinal hardness specimens.It is hard using cloth dimension
Degree meter position 4mm below rail head of rail tyre tread (Laizhou, Shandong city testing machine head factory, model HBV-30A), using 2mm between measuring point
Away from longitudinal Vickers hardness detection is carried out to hardness specimens, two sides are symmetrically arranged measuring point to the left and right centered on weld seam.Vickers hardness
The method of inspection is carried out referring to GB/T 4340.1-2009 " Vickers Hardness Test part 1: test method ", is marked using HV
Ruler.Hardness Surveillance data are shown in Table 4, and the distributed effect of connector longitudinal direction hardness is as shown in Figure 4.
Table 4:
By table 4 and Fig. 4 it is found that for not connect using the rail welding of post weld heat treatment method provided by the invention processing
Head, the softening sector width on the left of obtained connector are 9.0mm, and the softening sector width on right side is 9.0mm.Joint welding or so two
Side, the hardness away from the position Weld pipe mill 2mm, 4mm exceed rail base material average hardness 30HV or more.
Rail is connect by GB/T 13298-2015 " the metal microstructure method of inspection " referring to sampling method shown in Fig. 7
Head metallographic specimen carries out microstructure examination, carries out etch to rail joint metallographic specimen using 3% nital, uses
Leca MeF3 optical microscopy observes rail joint metallographic structure.Metal lographic examination shows joint welding or so two
Occurs the martensitic structure largely hardened in the heat affected area of side.In the case where 100X observes multiplying power, martensitic structure is gone out
The percentage composition in the region of existing most serious, martensitic structure has reached 8%, is unfavorable for railway operation safety.
Comparative example 3:
Specification connects for the upset during the mobile Flash Butt Welding of rail completion of 75kg/m and after pushing away tumor to what welding obtained
Head carries out post weld heat treatment.Firstly, the residual temperature that welding is obtained is cooling fast with the first of 7.0 DEG C/s in 1300 DEG C of rail joint
Degree carries out first stage cooling so that the rail head skin temperature of rail joint is down to 730 DEG C, then makes rail joint with 2.2 DEG C/s
The second cooling velocity to carry out second stage cooling the rail head skin temperature of rail joint is down to 350 DEG C, finally make rail
Connector carries out phase III cooling with the third cooling velocity of 2.5 DEG C/s the rail head skin temperature of rail joint is down to 25 DEG C
Room temperature, to obtain the steel rail weld joint of the invention through post weld heat treatment.In PWHT procedures, first is cooled to
The natural cooling carried out in air；Second is cooling in third cooling procedure, and rail head of rail is used to imitate type cooling device to press
Contracting air cools down the rail head tyre tread of rail joint and rail head side as cooling medium, and cooling device is apart from rail head of rail
Tyre tread 35mm；In second cooling procedure, the gas pressure of the compressed air of cooling device injection is 0.50MPa；Third is cooled
Cheng Zhong, the gas pressure of the compressed air of cooling device injection are 0.55MPa.Rail head of rail tyre tread is monitored using infrared radiation thermometer
Temperature.
Rail joint under the conditions of the postwelding for taking this comparative example to obtain is air-cooled is processed into longitudinal hardness specimens.It is hard using cloth dimension
Degree meter position 4mm below rail head of rail tyre tread (Laizhou, Shandong city testing machine head factory, model HBV-30A), using 2mm between measuring point
Away from longitudinal Vickers hardness detection is carried out to hardness specimens, two sides are symmetrically arranged measuring point to the left and right centered on weld seam.Vickers hardness
The method of inspection is carried out referring to GB/T4340.1-2009 " Vickers Hardness Test part 1: test method ", using HV scale.
Hardness Surveillance data are shown in Table 5, and the distributed effect of connector longitudinal direction hardness is as shown in Figure 5.
Table 5:
By table 5 and Fig. 5 it is found that for not connect using the rail welding of post weld heat treatment method provided by the invention processing
Head, the softening sector width on the left of obtained joint welding are 9.0mm, and the softening sector width on the left of joint welding is 9.0mm.It connects
At left and right sides of head weld seam, the hardness away from the position Weld pipe mill 2mm, 4mm, 6mm exceeds rail base material average hardness 30HV or more.
Rail is connect by GB/T 13298-2015 " the metal microstructure method of inspection " referring to sampling method shown in Fig. 7
Head metallographic specimen carries out microstructure examination, carries out etch to rail joint metallographic specimen using 3% nital, uses
Leca MeF3 optical microscopy observes rail joint metallographic structure.Metal lographic examination shows joint welding or so two
Occurs the martensitic structure largely hardened in the heat affected area of side.In the case where 100X observes multiplying power, martensitic structure is gone out
The percentage composition in the region of existing most serious, martensitic structure has reached 10%, is unfavorable for railway operation safety.
By welding point rail head tyre tread longitudinal direction hardness of the comparison diagram 1 into Fig. 5 and welding joint softened sector width it can be seen that
Post weld heat treatment is implemented for hypo eutectoid rail joint using post weld heat treatment method provided by the invention, can be made in away from weld seam
Rail joint longitudinal direction hardness in the region the heart ± 10mm meets the ± 30HV range of corresponding rail base material average hardness respectively
(does not include the axis of a weld of decarburization: being influenced by rail welding high temperature, Weld pipe mill decarburization simultaneously generates melting loss of elements, causes hard
Spend relatively low), and the softening sector width of joint welding two sides is no more than 10.0mm.Meanwhile, it is capable to by steel rail weld joint gold
The martensitic structure percentage composition being likely to occur in phase constitution controls in≤2% range, helps to ensure that railway operation safety.
Claims (4)
1. hypo eutectoid steel rail weld joint heat treatment method, it is characterised in that: including the following steps successively carried out:
A, the welding point that the temperature for forming two hypo eutectoid rail weldings is 1100~1400 DEG C carries out first stage cooling,
Welding point surface temperature is set to be reduced to 730~820 DEG C, the first stage is cooled to natural cooling in air, cooling velocity 4.5
~7.0 DEG C/s；
B, welding point is subjected to second stage cooling, so that welding point surface temperature is reduced to 200~280 DEG C, second stage
It is cooled to the cooling carried out using imitative type cooling device, cooling medium is compressed air or water mist gaseous mixture, cooling velocity 1.2
~3.2 DEG C/s；
C, welding point is subjected to phase III cooling, so that welding point surface temperature is reduced to 10~40 DEG C, the phase III is cold
It but is the cooling carried out using imitative type cooling device, cooling medium is compressed air or water mist gaseous mixture, cooling velocity 0.02
~0.40 DEG C/s.
2. hypo eutectoid steel rail weld joint heat treatment method according to claim 1, it is characterised in that: in step B, imitate type
Cooling device is apart from 20~40mm of rail head of rail tyre tread；The pressure of compressed air or water mist gaseous mixture that imitative type cooling device ejects
Power is 0.25~0.65MPa.
3. hypo eutectoid steel rail weld joint heat treatment method according to claim 1, it is characterised in that: in step C, imitate type
Cooling device is apart from 20~40mm of rail head of rail tyre tread；The pressure of compressed air or water mist gaseous mixture that imitative type cooling device ejects
Power is 0.01~0.20MPa.
4. hypo eutectoid steel rail weld joint heat treatment method according to claim 1, it is characterised in that: welding point passes through
The mobile flash welder of rail welds to be formed.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112063826A (en) * | 2020-08-28 | 2020-12-11 | 攀钢集团攀枝花钢铁研究院有限公司 | 1300 MPa-level low-alloy heat treatment steel rail postweld heat treatment method |
| CN112063825A (en) * | 2020-08-28 | 2020-12-11 | 攀钢集团攀枝花钢铁研究院有限公司 | Postweld heat treatment method for 1100 MPa-level low-alloy heat-treated steel rail |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN108950158A (en) * | 2018-08-20 | 2018-12-07 | 攀钢集团攀枝花钢铁研究院有限公司 | Eutectoid rail and hypereutectoid steel rail weld joint heat treatment method |
| CN109022750A (en) * | 2018-10-26 | 2018-12-18 | 攀钢集团攀枝花钢铁研究院有限公司 | The post weld heat treatment method of rail |
| CN109355482A (en) * | 2018-10-26 | 2019-02-19 | 攀钢集团攀枝花钢铁研究院有限公司 | The post weld heat treatment method of hypo eutectoid rail |
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2019
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108950158A (en) * | 2018-08-20 | 2018-12-07 | 攀钢集团攀枝花钢铁研究院有限公司 | Eutectoid rail and hypereutectoid steel rail weld joint heat treatment method |
| CN109022750A (en) * | 2018-10-26 | 2018-12-18 | 攀钢集团攀枝花钢铁研究院有限公司 | The post weld heat treatment method of rail |
| CN109355482A (en) * | 2018-10-26 | 2019-02-19 | 攀钢集团攀枝花钢铁研究院有限公司 | The post weld heat treatment method of hypo eutectoid rail |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112063826A (en) * | 2020-08-28 | 2020-12-11 | 攀钢集团攀枝花钢铁研究院有限公司 | 1300 MPa-level low-alloy heat treatment steel rail postweld heat treatment method |
| CN112063825A (en) * | 2020-08-28 | 2020-12-11 | 攀钢集团攀枝花钢铁研究院有限公司 | Postweld heat treatment method for 1100 MPa-level low-alloy heat-treated steel rail |
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