CN110016546A - Construction method for the heat treatment of bainite rail postwelding connector - Google Patents
Construction method for the heat treatment of bainite rail postwelding connector Download PDFInfo
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- CN110016546A CN110016546A CN201910453521.5A CN201910453521A CN110016546A CN 110016546 A CN110016546 A CN 110016546A CN 201910453521 A CN201910453521 A CN 201910453521A CN 110016546 A CN110016546 A CN 110016546A
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- rail
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- heat treatment
- bainite
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/04—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for rails
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/50—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for welded joints
- C21D9/505—Cooling thereof
Abstract
The invention discloses a kind of construction methods, especially disclose a kind of construction method for the heat treatment of bainite rail postwelding connector, belong to steel rail rolling technical field of producing.A kind of construction method for being used for the heat treatment of bainite rail postwelding connector that can be controlled the tyre tread hardness of bainite rail welding point in the reasonable scope is provided.The construction method is based on bainite rail welding point of the temperature not less than 1100 DEG C for welding acquisition, the cooling post weld heat treatment for completing the bainite rail welding point of the sequence successively to be slowed down gradually respectively by cooling velocity three times works, wherein, two cold final cooling temperatures are 150~210 DEG C, which is also three cold cold temperature.
Description
Technical field
The present invention relates to a kind of construction methods, more particularly, to a kind of applying for the heat treatment of bainite rail postwelding connector
Work method belongs to steel rail rolling technical field of producing.
Background technique
Bainite rail is the research hotspot of recent decades countries in the world, because its obdurability is high, wear-resisting undermines service life
The characteristics such as long and be expected to replace conventional pearlitic rail, be widely used in the sharp radius curve of railway switch component and heavy-haul line
Section.At this stage, rail seamless process has become inexorable trend.As one of important procedure in rail seamless process link, rail weldering
The quality connect is directly related to rail track service life or even traffic safety.During rail is on active service, by welding quality and line
The influence of road actual operation complicated condition so that the fracture of welding long rail string mostly occurs on welding point, thus is welded
Connector becomes the weak link of gapless track.
It is influenced by fusion process and high temperature, rail welding overheated zone austenite grain is coarse, causes the hardness in the region bright
It is aobvious to be lower than base material.For steel rail weld joint after softening during military service, Yi Youxian forms " saddle at connector rail head tyre tread position
Type " abrasion, increase wheel-rail impact, influence rail service life, or even jeopardize traffic safety.Therefore, domestic current railway row
Industry standard TB/T1632.2-2014 " rail welding part 2: Flash Butt Welding " and TB/T1632.4-2014 " rail welding the 4th
Part: air pressure welding " regulation, for heat-treated rail, the average hardness of welding region must not be lower than rail base material average hardness
90%, and should not have the adverse tissues such as martensite or bainite in the microstructure of Seam and heat effected zone.Above-mentioned two steel
Object involved in rail welding standard is pearlite steel rail, and there is no the welding mark suitable for bainite rail both at home and abroad at present
It is quasi-.Thus, it is commented completely in accordance with mechanical property of the domestic current rail welding technique standard to bainite rail welding point
It is inappropriate for estimating, and excessively high welding point rail head tyre tread longitudinal direction hardness (higher than the 90% of rail base material average hardness) will
Cause joint fatigue performance to decline, early fracture occurs.
The chemical component of bainite rail is general are as follows: C content 0.20-0.30 weight %, Si content 0.8-1.8 weight %,
Mn content 1.5-2.5 weight %, Cr content 0.50-1.60 weight %, Mo content 0.20-0.50 weight %.Using heat treatment work
Skill technology, after being acted on based on the bainite rail that refined crystalline strengthening principle is manufactured by Thermal Cycle, welded seam area hardens
Floor disappears and a wider soft area occurs, causes the hardness of weld dimensions far below rail base material, thus to shellfish
Family name's body steel rail weld joint carries out post weld heat treatment just into the most effective means for restoring rail welding zone hardness.
Currently, being generally compliant with TB/T1632.2-2014 " rail welding part 2: flash welding after the completion of domestic rail welding
Connect " and TB/T1632.4-2014 " the 4th part of rail welding: air pressure welding " standard progress postwelding normalizing heat treatment, with intermediate frequency sense
After answering electric heating or oxyacetylene torch heating that steel rail weld joint is heated to austenitizing temperature temperatures above as heat source, adopt
Air-cooled or air-cooled technique is taken further to promote the tyre tread hardness in rail welding region.
Application No. is 201210394058.X, the existing patent skill of denomination of invention " heat treatment method of bainite rail "
Art, discloses a kind of heat treatment method of bainite rail, and this method includes by the rail natural cooling after finish to gauge, so that rail
Rail head skin temperature is down to 460-490 DEG C；Rail is forced into cooling with the cooling velocity of 2.0-4.0 DEG C/s, so that rail head of rail
Skin temperature is down to 250-290 DEG C；Rail temperature is set to go up naturally until rail head of rail skin temperature reaches 300 DEG C or more；It will
Rail is placed in tempering 2-6h in the heating furnace that fire box temperature is 300-350 DEG C；Rail is air-cooled to room temperature.The mesh of the invention
Be to belong to Rail Production heat treatment process to obtain the good bainite rail of comprehensive mechanical property, pass is not suitable for
The post weld heat treatment process of non-bainite rail welding point.
Application No. is 201810480790.6, denomination of invention " heat treatment type bainite rail welding point post weld heat treatment
The existing patented technology of method " discloses a kind of bainite weld connector post weld heat treatment method, and this method is specially will welding
Obtained connector tread surface temperature to be cooled is cooled to the railhead part progress of butt joint after 850~500 DEG C of temperature range
It is air-cooled, terminate after tread surface temperature is cooled to 270~210 DEG C air-cooled, allows connector cooled to room temperature.The invention be
Directly butt joint implementation is air-cooled after bainite rail completes welding, and rail postwelding remains to be discussed without heating process, thermal effectiveness.
The master thesis of China Academy of Railways Sciences State of Zhao " grind by bainite rail Microstructure of Joint and hurt
Study carefully " involved in bainite rail from the present invention in bainite rail belong to different component systems.By the visible two kinds of shellfishes of following table
Si, Ni, Cr and Mo content in family name's body rail base material composition is significantly different.For the rail of heterogeneity system, corresponding weldering
Heat treatment process is also just completely different afterwards.
Table bainite rail chemical component compares (mass fraction %)
| Classification | C | Si | Mn | Ni | Cr | Mo | V | Al | P、S |
| Documents | 0.1~0.3 | 0.5~0.9 | 1.0~2.3 | 0.30~0.75 | 0.6~1.3 | 0.2~0.7 | / | 0.004 | ≤0.015 |
| Rail of the present invention | 0.15~0.30 | 1.0~1.8 | 1.5~2.5 | / | 0.2~0.6 | 0.05~0.10 | / | ≤0.005 | ≤0.010 |
Annotation: "/" is without this kind of element.
In conclusion railway engineering field need it is a kind of by the way that the control of the tyre tread hardness of bainite rail welding point exists
Mode in zone of reasonableness reaches the post weld heat treatment method and process for guaranteeing steel rail weld joint service life, to guarantee bainite
Military service performance and the railway operation safety of steel rail weld joint.
Summary of the invention
The technical problems to be solved by the present invention are: provide it is a kind of can be by the tyre tread hardness control of bainite rail welding point
The construction method for the heat treatment of bainite rail postwelding connector of system in the reasonable scope.
Used technical solution is to solve above-mentioned technical problem: one kind is heat-treated for bainite rail postwelding connector
Construction method, the construction method is to weld the bainite rail welding point of the temperature of acquisition not less than 1100 DEG C as base
Plinth, the cooling postwelding for completing the bainite rail welding point of the sequence successively to be slowed down gradually respectively by cooling velocity three times
Work is heat-treated,
Wherein, two cold final cooling temperatures are 150~210 DEG C, which is also three cold cold temperature.
Further, a cold whole cooling temperature is 550~750 DEG C, which is also two cold cold temperature.
The preferred mode of the above solution is that primary and three cold uses is the natural cooling carried out in air.
Further, the two cold rapid coolings using cooling medium.
The preferred mode of the above solution is that the cooling medium is compressed air or water mist gaseous mixture.
It is quickly sprayed further, the compressed air or water mist gaseous mixture imitate type cooling device by rail head of rail
It being mapped to welding point surface, sprays pressure between 0.40~0.80MPa, distance of the nozzle away from rail head tyre tread be 20~
50mm。
The preferred mode of the above solution is that a cold cooling velocity is 3.0~5.0 DEG C/s, two cold cooling velocities are 1.5
~2.5 DEG C/s, three cold cooling velocities are 0.05~0.50 DEG C/s.
Further, the primary cold temperature that rises is 1100~1400 DEG C, three cold final cooling temperatures be but speed be 10~
30℃。
The preferred mode of the above solution is that the cold temperature and final cooling temperature are to adopt in each cooling stage
With the temperature for the rail head of rail tyre tread that infrared radiation thermometer acquires.
Further, the welding point of the bainite rail is flash welded tool joint or air pressure welding point, rail type
For the heavy rail of 60~75kg/m.
The beneficial effects of the present invention are: technical solution provided by the present application is due to during heat treatment using three times
The sequence that cooling velocity slows down gradually is cooling to be not less than 1100 DEG C of bainite weld rail to soldered postwelding temperature
Welding point is heat-treated, so as to it is effective by bainite rail welding point away from the region Weld pipe mill ± 25mm
Interior rail joint longitudinal direction hardness controls the 85-90% in rail base material average hardness, and the softened zone of joint welding two sides is wide
Degree is below 20.0mm；And the object fatigue service life that can control the bainite rail welding point is not less than 2,200,000 times, is higher than
2,000,000 times as defined in TB/T1632.2-2014 and TB/T1632.4-2014 standard, and bainite rail welding point is golden
The martensitic structure percentage composition being likely to occur in phase constitution is controlled≤8%.Due to being applied by the post weld heat treatment of the application
The hardness of work method treated bainite rail welding point and its neighbouring tyre tread is the 85-90% of rail base material average hardness
Between, and the softening sector width of joint welding two sides is controlled lower than 20.0mm, effectively rail can also be avoided to exist
Occur " saddle-shape " abrasion in long-term use process, and then eliminate the disperse accumulation factor for seriously affecting rail service life, reaches and prolong
Gapless line service life and the purpose for guaranteeing railway operation safety.
Detailed description of the invention
Fig. 1 is the rail head using the steel rail weld joint under the conditions of the obtained post weld heat treatment of method in embodiment 1
Longitudinal stiffening effect figure of 5mm position below tyre tread；
Fig. 2 is the rail head using the steel rail weld joint under the conditions of the obtained post weld heat treatment of method in embodiment 2
Longitudinal stiffening effect figure of 5mm position below tyre tread；
Fig. 3 is the bainite rail welding point using the obtained postwelding of method in comparative example 1 under the conditions of air-cooled
Longitudinal stiffening effect figure of the position 5mm under rail head tyre tread；
Fig. 4 is using the bainite rail welding point under the conditions of the obtained post weld heat treatment of method in comparative example 2
Rail head tyre tread under the position 5mm longitudinal stiffening effect figure；
Fig. 5 illustrates for longitudinal hardness determination of the position 5mm under the rail head tyre tread of bainite rail welding point of the invention
Figure；
Fig. 6 is the rail head tyre tread metallographic specimen sample position schematic diagram of steel rail weld joint of the invention.
Fig. 7 be the present invention relates to rail head of rail imitate the schematic diagram that uses of type cooling device and three dimensional structure diagram.
The device only implements cooling to rail head of rail tyre tread and rail head side, and aperture can be designed processing according to actual needs, from
And realize different intensities of cooling.Flow through compressed air or water mist mixed gas passage one and compressed air or water mist mixed gas passage
Two gas pressure can be monitored by related pressure detection device, and flow through compressed air or water mist mixed gas passage one and compression
The gas pressure of air or water mist mixed gas passage two is adjusted according to actual needs.Wherein left side is that the imitative type of rail head of rail is cold
But the schematic diagram that device uses, right side are the three dimensional structure diagram that rail head of rail imitates type cooling device.
Specific embodiment
It is provided by the invention a kind of bainite rail to be welded in order to solve above-mentioned technical problem of the existing technology
The construction method for the heat treatment of bainite rail postwelding connector of the tyre tread hardness control of connector in the reasonable scope.Described
Construction method successively passes through three based on bainite rail welding point of the temperature not less than 1100 DEG C for welding acquisition respectively
The cooling post weld heat treatment work for completing the bainite rail welding point of the sequence that secondary cooling velocity slows down gradually,
Wherein, two cold final cooling temperatures are 150~210 DEG C, which is also three cold cold temperature.It is provided by the present application
Technical solution completes welding since the sequence to slow down gradually during heat treatment using cooling velocity three times is cooling
Postwelding temperature be heat-treated not less than 1100 DEG C of bainite weld steel rail weld joint, so as to effective by shellfish
Family name's body steel rail weld joint is average in rail base material away from the rail joint longitudinal direction hardness control in the region Weld pipe mill ± 25mm
The 85-90% of hardness, and the softening sector width of joint welding two sides is below 20.0mm；And it can control bainite rail welding
The object fatigue service life of connector is not less than 2,200,000 times, is higher than TB/T1632.2-2014 and TB/T1632.4-2014 standard and provides
2,000,000 times, and by the martensitic structure percentage composition being likely to occur in bainite rail welding point metallographic structure control
≤ 8%.Due to the hardness by the construction method of the application treated bainite rail welding point and its neighbouring tyre tread
Between 85-90% for rail base material average hardness, and the softening sector width of joint welding two sides controlled to be lower than
20.0mm can also effectively avoid rail from occurring " saddle-shape " abrasion in the long-term use, and then eliminate and seriously affect
The negative factor of rail service life.
It is micro- based on steel rail welding line specified in Chinese railroad industry rail welding standard TB1632-2014 and heat affected area
There should not be the requirement of the adverse tissues such as martensite or bainite in tissue.And Rails In Foreign Countries welding standard, as Australia rail welds
It connects in standard AS1085.20-2012 and provides: for the rail of certain high grades, high carbon content and high alloy content, in gold
Phase microscope 100x is observed under multiplying power, and for the most serious region that rail welding martensite occurs, martensite percentage composition is not
Be higher than 5%, otherwise connector will cause premature fatigue to be broken due to the martensite that largely hardens, influence railway operation safety
Regulation.Therefore, strict control rail welding martensite content is most important for the stable operation of rail track.It needs
, it is noted that above-mentioned standard is directed to conventional pearlitic rail.It is different from pearlite steel rail tissue, bainite rail base material group
Knit the heterogeneous structure being usually made of bainite, martensite, this resulted in bainite rail weld it is quick heat and
Martensite is inevitably formed during being quickly cooled down.In addition, for conventional pearlitic rail, brittle martensitic structure
It is harmful to rail military service performance, but influence of the martensite to bainite rail military service performance there is no final conclusion.Therefore, usually pass through tune
Whole rail welding and post weld heat treatment technique come reduce brittle martensitic structure as far as possible may be to bainite rail military service performance
Caused by negatively affect.Based on above-mentioned discovery, applicant completes the above-mentioned technical solution of the application.
In above embodiment, for more accurate control heat treatment process, thermal effectiveness is improved, while facilitating again
Operation, the welding point based on the bainite rail are flash welded tool joint or air pressure welding point, and rail type is 60~75kg/
The characteristics of heavy rail of m, the specific requirement in each work step of the application is as follows, and a cold whole cooling temperature is 550~750
DEG C, which is also two cold cold temperature.Primary and three cold uses is the natural cooling carried out in air.Two cold adopt
It is the rapid cooling of cooling medium.The cooling medium is compressed air or water mist gaseous mixture.The compressed air
Or water mist gaseous mixture imitates type cooling device by rail head and is quickly ejected into welding point surface, injection pressure 0.40~
Between 0.80MPa, distance of the nozzle away from rail head tyre tread is 20~50mm.One cold cooling velocity is 3.0~5.0 DEG C/s, and two is cold
Cooling velocity be 1.5~2.5 DEG C/s, three cold cooling velocities be 0.05~0.50 DEG C/s.The primary cold temperature that rises is 1100
~1400 DEG C, three cold final cooling temperatures are that but speed is 10~30 DEG C.In each cooling stage, described plays cold temperature and end
Cold temperature is the temperature using the rail head of rail tyre tread of infrared radiation thermometer acquisition.
In conclusion the welding point for handling bainite rail using the construction method of the application can be by rationally controlling
The mode of welding point rail head tyre tread longitudinal direction processed hardness achievees the purpose that guarantee steel rail weld joint fatigue life.To facilitate
Improve railway operation during because rail welding zone hardness it is relatively low caused by " saddle-shape " abrasion and wheel-rail impact, extend steel
Rail service life and guarantee railway operation safety.The rail head tyre tread of bainite rail welding point through post weld heat treatment is longitudinally hard
Zone of reasonableness of the degree control between the 85-90% of rail base material average hardness.It can control bainite rail welding point
The object fatigue service life is not less than 2,200,000 times, much higher than 200 as defined in TB/T1632.2-2014 and TB/T1632.4-2014 standard
Ten thousand times, make the martensitic structure percentage composition being likely to occur in welding point metallographic structure control in the range of≤8%.
Embodiment
According to conventional means, there are welding region tyre tread lower hardness, poor toughness etc. for heat treatment type bainite rail postwelding
Phenomenon, it usually needs carry out normalizing heat treatment to improve joint performance.But after normalizing welding point occur again hardness it is low collapse,
Softened zone broadens, and " shape of a saddle " is worn away during be easy to causeing welding point to be on active service, and leads to military service degradation.Work of the invention
It is based on this, finds and devises a kind of post weld heat treatment method of heat treatment type bainite rail, ensure that connector
While tyre tread hardness, rail joint service life ensure that.
Detailed description of the preferred embodiments below.It should be understood that described herein specific
Embodiment is merely to illustrate and explain the present invention, and is not intended to restrict the invention.
In the present invention, in the absence of explanation to the contrary, " steel rail weld joint " be it is welded obtain include
Length including weld seam and/or heat affected area is the region of 70~100mm range, and the center in the region is the weld seam of rail.This
In invention, " room temperature " is the temperature of 10~30 DEG C of ranges.
The present invention provides a kind of bainite rail post weld heat treatment methods, this method comprises: the temperature that welding is obtained
1100 DEG C or more of rail joints carried out under the first cooling velocity the first stage it is cooling so that rail joint rail head surface layer
Temperature is down to 570~750 DEG C, and rail joint is then made to carry out second stage cooling under the second cooling velocity so that rail joint
Rail head skin temperature be down to 150~210 DEG C, finally make rail joint carried out under third cooling velocity the phase III it is cooling with
The rail head skin temperature of rail joint is set to be down to 10~30 DEG C of room temperature；Wherein, first cooling velocity be 3.0~5.0 DEG C/
S, second cooling velocity are 1.5~2.5 DEG C/s, and the third cooling velocity is 0.05~0.50 DEG C/s.
It is an object of the present invention to provide a kind of bainite rail post weld heat treatment methods, this method comprises: welding is obtained
Temperature 1100 DEG C or more of rail joint carried out under the first cooling velocity the first stage it is cooling so that rail joint rail
Head skin temperature is down to 550~750 DEG C, and rail joint is then made to carry out second stage cooling under the second cooling velocity so that steel
The rail head skin temperature of rail connector is down to 150~210 DEG C, and rail joint is finally made to carry out the phase III under third cooling velocity
Cooling is so that the rail head skin temperature of rail joint is down to 10~30 DEG C of room temperature.Wherein, the first stage is cooling and third is cooling
Mode be aerial natural cooling.Second is cooled to imitate type cooling device using rail head of rail as shown in Figure 7, with pressure
The cooling that contracting air or water mist gaseous mixture carry out the rail head tyre tread of rail joint and rail head side as cooling medium.
In the present invention, described first type of cooling cooling and that third is cooling is the natural cooling carried out in air, institute
It states second to be cooled to imitate type cooling device using rail head of rail, using compressed air or water mist gaseous mixture as cooling medium to rail
The rail head tyre tread of connector and rail head side are cooled down, and cooling device is 20~50mm apart from rail head of rail tyre tread；Cooling device
The gas pressure of the compressed air or water mist gaseous mixture that are ejected is 0.05~0.5MPa.
In the present invention, using the temperature signal of infrared radiation thermometer acquisition rail head of rail tyre tread, the rail head of rail tyre tread is
The contact portion of wheel and rail.
It should be noted that hardness number corresponding to softened zone width measurement line in the hardness curve of rail joint longitudinal direction
(0.9Hp) is the 90% of rail base material average hardness Hp.Softening sector width in hardness curve is that hardness curve and softened zone are wide
The intercept of degree measurement line.
In the present invention, bainite rail rail type having the same for welding, the specially specification of 60~75kg/m, institute
Stating steel rail weld joint is the welding point being welded using same welding procedure by the mobile flash welder of rail.
It below will the present invention will be described in detail by specific embodiment.In following embodiment, bainite rail be
Line heat treatment type, is all produced by Pan Gang group.
In a kind of bainite rail post weld heat treatment method of the present invention, it is cooling and third cooling cold to carry out first
But mode is directly to place bainite rail welding point to carry out the air-cooled of natural cooling in air.
In a kind of bainite rail post weld heat treatment method of the present invention, carry out the second cooling type of cooling be with
Spray the rapid cooling of compressed air or water mist gaseous mixture as cooling medium.
The present invention realizes the PWHT procedures of rail using the welding waste heat of rail, for the obtained residual temperature of welding compared with
High rail joint implements postwelding and accelerates cooling, to reduce connector rail head region phase transition temperature, improves austenite recrystallization area
Hardness.Based on Principles of Metallography, rail joint, there are certain dynamic degree of supercooling, causes under postwelding high temperature condition of fast cooling
The phase transition temperature that austenite changes under nonequilibrium condition moves down and with the increase of degree of supercooling, and phase transition temperature gradually decreases.Therefore,
Even if the relatively low second stage of cold temperature is cooling opening, connector rail head remains to that structural transformation occurs.
In the present invention, described first is cooled to the natural cooling carried out in air, can be by adjusting test ambient temperature
(such as use central air-conditioner temperature control) realizes the control to first stage cooling velocity, and can be by adjusting welding machine setting or artificial
Operation controls the cooling final cooling temperature of steel rail weld joint first at 550~750 DEG C, and cold temperature is opened in second cooling
It is 550~750 DEG C.In the present invention, the described second martensite transfor mation of the cooling final cooling temperature lower than bainite rail steel starts temperature
It spends (Ms temperature), the second cooling final cooling temperature is 150~210 DEG C in the present invention.
Under preferable case, in a kind of bainite rail post weld heat treatment method of the present invention, the described first cooling, institute
At least one of cooling means such as air-cooled and air-cooled can be used by stating the second cooling and described second cooling cooling means, but
In order to which the tyre tread longitudinal direction hardness of welding point is controlled in the reasonable scope, the first cooling and third cooling cooling in the present invention
Mode preferably uses air-cooled, and the second cooling type of cooling preferably uses air-cooled.
What the welding that a kind of bainite rail post weld heat treatment method of the present invention can be used for various temperature obtained
Bainite rail welding point, the preferably described initial temperature for welding obtained bainite rail welding point of the present invention are
1100-1400℃。
It below will the present invention will be described in detail by specific embodiment.In following embodiment, the type of bainite rail
Number be PB2 burning optimization on line type bainite rail, originate from Pan Gang group.
The post weld heat treatment process of a kind of bainite rail welding point of the present invention, referring to TB/
T1632.2-2014 " rail welding part 2: Flash Butt Welding " and " the 4th part of rail welding: air pressure TB/T1632.4-2014
Welding " steel rail weld joint is machined to vertical section hardness specimens by standard, and the position 5mm Welded Joints carry out under tyre tread
The detection of vertical section Rockwell hardness, two sides are symmetrically arranged measuring point to the left and right centered on weld seam, measuring point spacing 5mm, Rockwell hardness
Method is provided to carry out by GB/T230.1-2009, using HRC scale, with HpIndicate the hardness average value of rail base material, HjExpression connects
The hardness average value of head, connector hardness are lower than 0.9HpPosition indicate softened region.
Three-point bending fatigue test is carried out to steel rail weld joint material object using MTS-FT310 type fatigue tester, is used
Pulsation repeated bend test mode.Load frequency 7Hz, load ratio 0.2, welding point maximum fatigue stress is 300MPa, to follow
It is test objective that fatigue fracture, which does not occur, for welding point when ring load loads 3,000,000 times.
Embodiment one
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 4.5 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 700 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 200 DEG C, finally make rail
Connector carries out phase III cooling with the third cooling velocity of 0.4 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.Wherein, the first cooling and third are cooled to
The natural cooling carried out in air, second is cooled to that rail head of rail is used to imitate type cooling device with compressed air or water mist gaseous mixture
As the cooling that cooling medium carries out the rail head tyre tread of rail joint and rail head side, cooling device is apart from rail head of rail tyre tread
40mm.In second cooling procedure, the compressed air of cooling device injection or the gas pressure of water mist gaseous mixture are 0.30MPa.It adopts
Rail head of rail wheel tread temperature is monitored with infrared radiation thermometer.
The bainite rail connector that the present embodiment obtains is machined to longitudinal hardness specimens, and the position 5mm under tyre tread
Welded Joints carry out longitudinal Rockwell hardness detection, and two sides are symmetrically arranged measuring point to the left and right centered on weld seam, and measuring point spacing is
5mm.The Rockwell hardness method of inspection is provided to carry out by GB/T 230.1-2009, using HRC scale.The rail head tyre tread of welding point
Longitudinal hardness data of the position lower 5mm is shown in Table 1, and the distributed effect of longitudinal hardness is as shown in Figure 1.
Table 1
By table 1 and Fig. 1 it is found that for bainite rail welding point processed by the invention, away from Weld pipe mill ±
Rail joint longitudinal direction hardness in the region 25mm has reached the 88% of rail base material average hardness.The softened zone of joint welding two sides
Width is 18.0mm, and the softening sector width of joint welding two sides is below 20.0mm.
Rail is connect by GB/T 13298-2015 " the metal microstructure method of inspection " referring to sampling method shown in fig. 6
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.Inspection result shows: rail joint weld seam two
Occurs a small amount of martensitic structure in the heat affected area of side.In the case where the 100x of metallographic microscope observes multiplying power, for geneva
The most serious region that body tissue occurs, through counting, the percentage composition of martensitic structure is 6%.
By table 1 and Fig. 1 it is found that handling what flash welding welded using post weld heat treatment process provided by the invention
For temperature in the welding point of 1500 DEG C of bainite rail, gained rail joint is hard in the region Weld pipe mill ± 25mm
Degree average value is 38.2HRC, has reached the 88% of rail base material average hardness.The softening sector width of joint welding two sides is
The softening sector width of 18.0mm, joint welding two sides are below 20.0mm.It is connect by the bainite rail that the present embodiment obtains
The fatigue test that head sample can be 2,600,000 times by cycle-index, is higher than specified in TB/T1632.2-2014 2,000,000 times.
Embodiment two
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 4.5 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 650 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 180 DEG C, finally make rail
Connector carries out phase III cooling with the third cooling velocity of 0.10 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.Wherein, the first cooling and third are cooled to
The natural cooling carried out in air, second is cooled to that rail head of rail is used to imitate type cooling device with compressed air or water mist mixing
The cooling that gas carries out the rail head tyre tread of rail joint and rail head side as cooling medium, cooling device are stepped on apart from rail head of rail
Face 40mm.In second cooling procedure, the gas pressure of the water mist gaseous mixture of cooling device injection is 0.60MPa.Using infrared survey
Warm instrument monitors rail head of rail wheel tread temperature.
The bainite rail welding point that the present embodiment obtains is machined to longitudinal hardness specimens, and the 5mm under tyre tread
Position Welded Joints carry out longitudinal Rockwell hardness detection, and two sides are symmetrically arranged measuring point to the left and right centered on weld seam, between measuring point
Away from for 5mm.The Rockwell hardness method of inspection is provided to carry out by GB/T 230.1-2009, using HRC scale.The rail head of welding point
Longitudinal hardness data of the position 5mm is shown in Table 2 under tyre tread, and the distributed effect of longitudinal hardness is as shown in Figure 2.
Table 2
By table 2 and Fig. 2 it is found that for bainite rail welding point processed by the invention, away from Weld pipe mill ±
Rail joint longitudinal direction hardness in the region 25mm has reached the 90% of rail base material average hardness.The softened zone of joint welding two sides
It is 15mm on the left of width, the softening sector width of right side 17.0mm, joint welding two sides are below 20.0mm.
Referring to sampling method shown in fig. 6 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.Inspection result shows: rail joint weld seam two sides
Heat affected area in there is a small amount of martensitic structure.In the case where the 100x of metallographic microscope observes multiplying power, for martensite
The most serious region occurred is organized, through counting, the percentage composition of martensitic structure is 8%.The bainite obtained by the present embodiment
The fatigue test that steel rail weld joint sample can be 2,300,000 times by cycle-index.
By table 2 and Fig. 2 it is found that handling what flash welding welded using post weld heat treatment process provided by the invention
For temperature in the welding point of 1500 DEG C of bainite rail, gained rail joint is hard in the region Weld pipe mill ± 25mm
Degree average value is 39.0HRC, has reached the 90% of rail base material average hardness.It is on the left of the softening sector width of joint welding two sides
The softening sector width of 15mm, right side 17.0mm, joint welding two sides are below 20.0mm.The bainite obtained by the present embodiment
The fatigue test that steel rail weld joint sample can be 2,300,000 times by cycle-index, is higher than specified in TB/T1632.2-2014
2000000 times.
Comparative example one
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 1200 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, and under tyre tread
The position 5mm Welded Joints carry out longitudinal Rockwell hardness detection, and two sides are symmetrically arranged measuring point to the left and right centered on weld seam, measuring point
Spacing is 5mm.The Rockwell hardness method of inspection is provided to carry out by GB/T 230.1-2009, using HRC scale.The rail of welding point
Longitudinal hardness data of the position 5mm is shown in Table 3 under head tyre tread, and the distributed effect of longitudinal 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.Gained rail joint distance weldering
Hardness average value in the region ± 25mm of seam center is 35.8HRC, has reached the 83% of rail base material average hardness, is lower than rail
The 85-90% range of base material average hardness, the softening sector width at left and right sides of joint welding is 25.0mm.It is obtained by the comparative example
For the welding point arrived during route is on active service, Yi Youxian is low in the softened zone of steel rail weld joint formation rail head of rail tyre tread
It collapses, influences Track regularity and traffic safety.
Referring to Fig. 5, sampling method shown in fig. 6 by GB/T 13298-2015 " the metal microstructure method of inspection " to steel
Rail connector metallographic specimen carries out microstructure examination, carries out etch to rail joint metallographic specimen using 3% nital,
Rail joint metallographic structure is observed using Leca MeF3 optical microscopy.The result shows that welding point metallographic group
Knit normal, the abnormal structures such as martensite-free, bainite.Thus the bainite rail weld joint samples that comparative example obtains are recycling
When being 1,700,000 times fatigue test occurs for number.
Comparative example two
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 4.0 DEG C/s in 1150 DEG C of rail joint
Degree carries out first stage cooling so that the rail head skin temperature of rail joint is down to 620 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 130 DEG C, finally make rail
Connector carries out phase III cooling with the third cooling velocity of 0.10 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
The natural cooling carried out in air is cooled to third；Second is cooled to that rail head of rail is used to imitate type cooling device to compress sky
The cooling that gas carries out the rail head tyre tread of rail joint and rail head side as cooling medium, cooling device are stepped on apart from rail head of rail
Face 40mm；In second cooling procedure, the gas pressure of the compressed air of cooling device injection is 0.60MPa.Using infrared measurement of temperature
Instrument monitors rail head of rail wheel tread 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, and under tyre tread
The position 5mm Welded Joints carry out longitudinal Rockwell hardness detection, and two sides are symmetrically arranged measuring point to the left and right centered on weld seam, measuring point
Spacing is 5mm.The Rockwell hardness method of inspection is provided to carry out by GB/T 230.1-2009, using HRC scale.The rail of welding point
Longitudinal hardness data of the position 5mm is shown in Table 4 under head tyre tread, and the distributed effect of longitudinal 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, hardness average value of the gained rail joint in the region Weld pipe mill ± 25mm are 40.6HRC, and it is flat to have reached rail base material
The 94% of equal hardness, the 85-90% range beyond rail base material average hardness, the joint welding left and right sides is without obvious softened zone.
Referring to Fig. 5, sampling method shown in fig. 6 by GB/T 13298-2015 " the metal microstructure method of inspection " to steel
Rail connector metallographic specimen carries out microstructure examination, carries out etch to rail joint metallographic specimen using 3% nital,
Rail joint metallographic structure is observed using Leca MeF3 optical microscopy.The result shows that rail welding heat affecting
Occurs different degrees of martensitic structure in area.In the case where the 100x of metallographic microscope observes multiplying power, for geneva in connector
The most serious region that body tissue occurs, through counting, martensitic structure percentage composition is 10%.Thus the bainite that comparative example obtains
When cycle-index is 1,200,000 times fatigue fracture occurs for steel rail weld joint sample.
It is distributed by the welding point rail head tyre tread longitudinal direction hardness in comparison Fig. 1 to Fig. 4 it can be seen that being mentioned using the present invention
The martensitic structure percentage composition control that the process of confession can will be likely to occur in bainite rail welding point metallographic structure
System will be controlled away from the rail joint longitudinal direction hardness in the region Weld pipe mill ± 25mm in rail base material average hardness≤8%
The 85-90% and softening sector width of joint welding two sides is below 20.0mm helps to improve rail during route is on active service
Because steel rail weld joint " saddle " is worn away caused by welding region lower hardness.Meanwhile bainite rail joint fatigue can be made
Service life is maintained at 2,200,000 times or more, has reached guarantee connector compared with high fatigue life while guaranteeing that connector has higher hardness
Purpose.
The preferred embodiment of the present invention has been described above in detail, although describing with reference to specific embodiment according to this hair
The post weld heat treatment process of bright bainite rail, it will be recognized to those skilled in the art that of the invention not departing from
In the case where thought and range, various modifications and combinations can be made to the present invention herein.
Claims (10)
1. it is a kind of for bainite rail postwelding connector heat treatment construction method, it is characterised in that: the construction method with
Based on bainite rail welding point of the temperature that welding obtains not less than 1100 DEG C, successively pass through cooling velocity three times respectively
The cooling post weld heat treatment work for completing the bainite rail welding point of the sequence to slow down gradually,
Wherein, two cold final cooling temperatures are 150~210 DEG C, which is also three cold cold temperature.
2. the construction method according to claim 1 for the heat treatment of bainite rail postwelding connector, it is characterised in that: one
Cold whole cooling temperature is 550~750 DEG C, which is also two cold cold temperature.
3. the construction method according to claim 1 or 2 for the heat treatment of bainite rail postwelding connector, feature exist
In: primary and three cold uses is the natural cooling carried out in air.
4. the construction method according to claim 3 for the heat treatment of bainite rail postwelding connector, it is characterised in that: two
The cold rapid cooling using cooling medium.
5. the construction method according to claim 4 for the heat treatment of bainite rail postwelding connector, it is characterised in that: institute
The cooling medium stated is compressed air or water mist gaseous mixture.
6. the construction method according to claim 5 for the heat treatment of bainite rail postwelding connector, it is characterised in that: institute
The compressed air or water mist gaseous mixture stated imitate type cooling device by rail head of rail and are quickly ejected into welding point surface, spray
For injection pressure between 0.40~0.80MPa, distance of the nozzle away from rail head tyre tread is 20~50mm.
7. the construction method according to claim 1 or 2 for the heat treatment of bainite rail postwelding connector, feature exist
In: a cold cooling velocity is 3.0~5.0 DEG C/s, and two cold cooling velocities are 1.5~2.5 DEG C/s, and three cold cooling velocities are
0.05~0.50 DEG C/s.
8. the construction method according to claim 7 for the heat treatment of bainite rail postwelding connector, it is characterised in that: one
The secondary cold temperature that rises is 1100~1400 DEG C, and three cold final cooling temperatures are that but speed is 10~30 DEG C.
9. the construction method according to claim 1 for the heat treatment of bainite rail postwelding connector, it is characterised in that:
In each cooling stage, the cold temperature and final cooling temperature are the rail head of rail tyre tread acquired using infrared radiation thermometer
Temperature.
10. the construction method according to claim 9 for the heat treatment of bainite rail postwelding connector, it is characterised in that:
The welding point of the bainite rail is flash welded tool joint or air pressure welding point, and rail type is the heavy-duty steel of 60~75kg/m
Rail.
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| CN110480141B (en) * | 2019-08-26 | 2021-07-13 | 攀钢集团攀枝花钢铁研究院有限公司 | Process for controlling flash welding joint structure of steel rail with middle and lower limit Mn content R350HT |
| CN110480140B (en) * | 2019-08-26 | 2021-07-13 | 攀钢集团攀枝花钢铁研究院有限公司 | Process for controlling flash welding joint structure of steel rail with upper limit Mn content R350HT |
| CN110480144B (en) * | 2019-08-26 | 2021-07-13 | 攀钢集团攀枝花钢铁研究院有限公司 | Process for controlling flash welding joint structure of medium-limit Mn content R350HT steel rail |
| CN110480142B (en) * | 2019-08-26 | 2021-07-13 | 攀钢集团攀枝花钢铁研究院有限公司 | Process for controlling flash welding joint structure of steel rail with middle and upper limit Mn content R350HT |
| CN110480143B (en) * | 2019-08-26 | 2021-07-13 | 攀钢集团攀枝花钢铁研究院有限公司 | Process for controlling flash welding joint structure of steel rail with lower limit Mn content R350HT |
| CN110480139B (en) * | 2019-08-26 | 2022-08-05 | 攀钢集团攀枝花钢铁研究院有限公司 | Process for controlling flash welding joint structure of steel rail with lower limit Mn content R350HT |
| CN110480138B (en) * | 2019-08-26 | 2022-08-09 | 攀钢集团攀枝花钢铁研究院有限公司 | Process for controlling upper limit Mn content R350HT steel rail flash welding joint structure |
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Application publication date: 20190716 |