CN110331274A - Bainite rail post weld heat treatment method - Google Patents
Bainite rail post weld heat treatment method Download PDFInfo
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- CN110331274A CN110331274A CN201910768908.XA CN201910768908A CN110331274A CN 110331274 A CN110331274 A CN 110331274A CN 201910768908 A CN201910768908 A CN 201910768908A CN 110331274 A CN110331274 A CN 110331274A
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- rail
- cooling
- bainite
- heat treatment
- welding
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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
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
- C21D1/19—Hardening; Quenching with or without subsequent tempering by interrupted quenching
-
- 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 bainite rail post weld heat treatment methods, belong to rail welding technique field.The purpose of the invention is to make up the deficiency of existing Post-Welding Heattreatment of Rail technology, a kind of bainite rail post weld heat treatment method is provided: 1100~1300 DEG C of bainite rail welding points being carried out first and are cooled to 260~350 DEG C, then the first cooling gained welding point is heated to 780~870 DEG C, when then progress second is cooled to 450~510 DEG C, the room temperature that third is cooled to 10~40 DEG C is carried out immediately.The method of the present invention passes through rational bainite rail post weld heat treatment technique, make martensite-free in rail joint metallographic structure, it is simultaneously rail base material 80~85% away from the average hardness in the region Weld pipe mill ± 70mm, and the fatigue life of bainite rail connector reaches 4,000,000 times or more.
Description
Technical field
The invention belongs to rail welding technique fields, and in particular to a kind of bainite rail post weld heat treatment method.
Background technique
Bainite rail is the research hotspot of recent decades countries in the world, because obdurability is high, wear-resisting undermines long service life
Etc. characteristics 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.
CN201410135909.8 discloses a kind of post weld heat treatment method of bainite rail connector, and this method includes will
It welds obtained bainite rail welding point to be cooled to carry out being cooled to the first temperature not higher than 450 DEG C for the first time, so
The first welding point after cooling is heated to second temperature afterwards, then carries out second cooling, the second temperature is higher than described the
One temperature and be not higher than 510 DEG C, wherein the cooling initial temperature of bainite rail be 1300-1380 DEG C, second is after cooling cold
But final temperature is room temperature.This method can significantly reduce martensitic structure content and raising in bainite rail welding point
The impact flexibility of welding point, but the connector hardness that bainite rail is reduced by welding can not be restored.
CN201210394058.X discloses a kind of heat treatment method of bainite rail, and this method includes will be after finish to gauge
Rail natural cooling, so that rail head of rail skin temperature is down to 460-490 DEG C；By rail with the cooling velocity of 2.0-4.0 DEG C/s
Cooling is forced, 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 surface layer
Temperature reaches 300 DEG C or more；Rail is placed in tempering 2-6h in the heating furnace that fire box temperature is 300-350 DEG C；By rail
It is air-cooled to room temperature.This method belongs to Rail Production heat treatment process to obtain the good bainite rail of comprehensive mechanical property,
It is not particularly suited for the post weld heat treatment of bainite rail welding point.
CN201810480790.6 discloses a kind of bainite weld connector post weld heat treatment method, and this method is specially will
The connector tread surface temperature to be cooled that welding obtains is cooled to the railhead part of butt joint after 850~500 DEG C of temperature range
It carries out air-cooled, terminates after tread surface temperature is cooled to 270~210 DEG C air-cooled, allow connector cooled to room temperature.This method
What is solved is impact, hardness and the anti-hammer performance of bainite rail connector, but due to being heat-treated without normalizing, joint toughness compared with
Difference does not solve the Fatigue Life Problems of bainite rail connector.
CN201710666513.X discloses a kind of post weld heat treatment method of bainite rail welding point, this method packet
It includes: 1500~1600 DEG C of the steel rail weld joint that welding obtains being carried out first and is cooled to 150~250 DEG C, then by first
Steel rail weld joint after cooling is heated to 880-960 DEG C, then carries out the second wheel tread temperature for being cooled to steel rail weld joint
It is 180-250 DEG C, finally carries out third and be cooled to room temperature.In this method, though the hardness of bainite rail connector can reach rail
The 85~90% of base material average hardness, but its rail joint fatigue life is only capable of reaching 3,000,000 times, and its bainite rail is real
Apply that thermal weld stress is high, normalizing initial temperature is relatively low, normalizing temperature is higher, energy consumption is big.
CN201610909362.1 discloses the method that a kind of pair of steel rail weld joint carries out post weld heat treatment.This method packet
It includes: the steel rail weld joint to be cooled that welding obtains being carried out first and is cooled to 400 DEG C hereinafter, then after cooling by first
Steel rail weld joint is heated to 860-930 DEG C, and then carrying out the wheel tread temperature that second is cooled to steel rail weld joint is 410-450
℃.It should be noted that this method is using the two stages type of cooling, it is therefore an objective to improve 75kg/m hypereutectoid rail and pearly-lustre
The mechanical property of body steel rail weld joint is not particularly suited for bainite rail welding point.
In conclusion railway engineering field need it is a kind of by by the metallographic structure and hardness of bainite rail welding point
The mode of control in the reasonable scope reaches the Post-Welding Heattreatment of Rail method and process for guaranteeing steel rail weld joint service life, with
Guarantee the military service performance and railway operation safety of bainite rail welding point.
Summary of the invention
The purpose of the invention is to make up in existing Post-Welding Heattreatment of Rail technology through postwelding is air-cooled or post weld heat treatment
The problem of existing rail joint rail head tyre tread longitudinal direction lower hardness and fatigue life deficiency afterwards provides a kind of bainite rail weldering
Heat treatment method afterwards, this method can control the metallographic structure of bainite rail connector and longitudinal hardness in the reasonable scope,
To help to improve during rail is on active service because of " saddle-shape " abrasion caused by welding region lower hardness and guarantee wear-resisting
Performance extends rail service life and guarantees railway operation safety.
To achieve the goals above, the present invention provides a kind of bainite rail post weld heat treatment methods, including following step
It is rapid: the temperature that welding obtains is cooled to 260~350 in 1100~1300 DEG C of bainite rail welding point progress first
DEG C, the welding point that the first cooling condition obtains then is heated to 780~870 DEG C, then carry out it is second cooling, when being cooled to
Stop the second cooling at 450~510 DEG C, carries out the ambient temperature that third is cooled to 10~40 DEG C immediately.
Wherein, in bainite rail post weld heat treatment method described above, the described first cooling type of cooling is sky
Cold, described second type of cooling cooling and that third is cooling is the acceleration cooling carried out using cooling medium.
Wherein, in bainite rail post weld heat treatment method described above, first cooling velocity is 5.0~8.0
℃/s。
Wherein, in bainite rail post weld heat treatment method described above, the second stage is cooling to use rail rail
Imitative type cooling device, using compressed air or water mist gaseous mixture as cooling medium to the rail head tyre tread and rail of steel rail weld joint
Head side is cooled down, and cooling device is 25~35mm apart from rail head of rail tyre tread；The compressed air that cooling device is ejected
Or the gas pressure of water mist gaseous mixture is 0.50~1.00MPa.
Wherein, in bainite rail post weld heat treatment method described above, the described second cooling cooling velocity is 2.0
~4.0 DEG C/s.
Wherein, in bainite rail post weld heat treatment method described above, the phase III is cooling using rail rail
Imitative type cooling device, using compressed air or water mist gaseous mixture as cooling medium to the rail head tyre tread and rail of steel rail weld joint
Head side is cooled down, and cooling device is 25~35mm apart from rail head of rail tyre tread；The compressed air that cooling device is ejected
Or the gas pressure of water mist gaseous mixture is 0.10~0.30MPa.
Wherein, in bainite rail post weld heat treatment method described above, the cooling cooling velocity of the third is
0.40~0.80 DEG C/s.
Wherein, in bainite rail post weld heat treatment method described above, the cooling cold temperature of opening of control second is weldering
Connector is by 260~350 DEG C of 780 DEG C or more be heated to after 780~870 DEG C of stoppings.
Wherein, described to be heated in 780~870 DEG C of uses in bainite rail post weld heat treatment method described above
Frequency incudes imitative type electric heating coil and/or oxy-acetylene flame imitates the heating of type heater.
It is further, described when being heated to 780~870 DEG C in bainite rail post weld heat treatment method described above,
To being about that steel rail weld joint whole cross section within the scope of 70~100mm carries out tunneling boring heating comprising the length including weld seam.
Preferably, in bainite rail post weld heat treatment method described above, the welding method of bainite rail connector
It is welded for Flash Butt Welding or air pressure.
Wherein, in bainite rail post weld heat treatment method described above, the bainite rail weldering through post weld heat treatment
Martensite-free tissue in the metallographic structure of connector, while being rail base material away from the average hardness in the region Weld pipe mill ± 70mm
The 80~85% of average hardness, and the fatigue life of bainite rail connector reaches 4,000,000 times or more.
Beneficial effects of the present invention:
The method of the present invention is by rational bainite rail post weld heat treatment technique, the bainitic steel through post weld heat treatment
Martensite-free tissue in the metallographic structure of rail welding point, while being rail away from the average hardness in the region Weld pipe mill ± 70mm
The 80~85% of base material average hardness, so as to improve during railway operation because rail welding zone hardness it is relatively low caused by
" saddle-shape " abrasion and wear-resisting property, improve toughness, ensure that steel rail weld joint military service performance, weld bainite rail
The fatigue life of connector is maintained at 4,000,000 times or more, has achieved the purpose that guarantee that connector compared with high fatigue life, while ensure that and connect
Head has higher hardness, guarantees railway operation safety.Further, since without brittle geneva in bainite rail welding microstructure
Body, this also contributes to bainite rail joint fatigue life-time dilatation.
Detailed description of the invention
Fig. 1 is to be connect using bainite rail of the obtained postwelding normalizing of method in embodiment 1 under the conditions of air-cooled
Longitudinal stiffening effect figure of the position 5mm under the rail head tyre tread of head.
Fig. 2 is to be connect using bainite rail of the obtained postwelding normalizing of method in embodiment 2 under the conditions of air-cooled
Longitudinal stiffening effect figure of the position 5mm under the rail head tyre tread of head.
Fig. 3 is to be connect using bainite rail of the obtained postwelding normalizing of method in comparative example 1 under the conditions of air-cooled
Longitudinal stiffening effect figure of the position 5mm under the rail head tyre tread of head.
Fig. 4 is the bainite rail welding point using the obtained postwelding of method in comparative example 2 under the conditions of air-cooled
Longitudinal stiffening effect figure of the position 5mm under rail head tyre tread.
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.
Specific embodiment
Specifically, bainite rail post weld heat treatment method, comprising the following steps: by the obtained temperature of welding 1100~
1300 DEG C of bainite rail welding point carries out first and is cooled to 260~350 DEG C, the weldering for then obtaining the first cooling condition
Connector is heated to 780~870 DEG C.Second cooling, the second cooling of stopping when being cooled to 450~510 DEG C is then carried out, immediately
Carry out the ambient temperature that third is cooled to 10~40 DEG C.
The critical cooling rate of martensite transfor mation during bainitic steel rail steel continuous cooling transformation is about 1.0~2.0
DEG C/s, about 390~450 DEG C of Ms temperature (start temperature that martensitic structure is formed).After first cooling stage, inside connector
Though be likely to form martensite, due to the first cooling stage after rail joint be reheated to 780~870 DEG C, temperature
Reach austenitizing temperature, make first it is cooling it is stepped at martensite disappear.To avoid steel rail weld joint in subsequent heat treatment
There are a large amount of martensites, the present invention is in the second cooling procedure using slightly above bainitic steel rail steel martensite transfor mation Critical cooling speed
Cooling velocity butt joint implement to accelerate cooling, and control the second cooling final cooling temperature more than Ms temperature, and control third
Cooling cooling velocity is lower than bainitic steel rail steel martensite transfor mation Critical cooling speed, makes in bainite rail welding point without geneva
Body tissue generates.Based on above-mentioned discovery, inventor completes the present invention.
In the present invention, the first cold stage is but the natural cooling (carrying out at room temperature) carried out in air, cooling speed
Degree is 5.0~8.0 DEG C/s, can be realized by adjusting test ambient temperature (as used central air-conditioner temperature control) cooling to the first stage
The control of speed, and can be controlled the welding temperature of rail joint at 1100~1300 DEG C by adjusting welding machine setting；This hair
The cooling velocity of second cooling stage described in bright is 2.0~4.0 DEG C/s, and final cooling temperature is 450~510 DEG C；It is connect when to rail
When head carries out phase III cooling, for the martensite for avoiding connector from occurring largely hardening, present invention selection is to be lower than bainitic steel
Cooling velocity 0.40~0.80 DEG C/s butt joint implementation of rail steel martensite transfor mation Critical cooling speed cools down at a slow speed, and is cooled to room temperature
(10~40 DEG C)；The present invention limits the cold of different cooling stages by using the cooling type of cooling with normalizing heat treatment of three steps
But speed and cooling temperature and normalizing temperature can reach and promote steel rail weld joint hardness and toughness, guarantee steel rail weld joint
The purpose organized and connector is made to be kept for higher fatigue life.Further, since without brittle in bainite rail welding microstructure
Martensite, this also contributes to bainite rail joint fatigue life-time dilatation.
In the method for the present invention, the second stage is cooling and phase III cooling uses rail head of rail to imitate type cooling device,
The rail head tyre tread of steel rail weld joint and rail head side are cooled down using compressed air or water mist gaseous mixture as cooling medium,
Cooling device is 25~35mm apart from rail head of rail tyre tread；The compressed air or water that the second stage cooling device is ejected
The gas pressure of mist gaseous mixture is 0.50~1.00MPa, the compressed air or water that the phase III cooling device is ejected
The gas pressure of mist gaseous mixture is 0.10~0.30MPa.
The postwelding normalizing heat treatment of steel rail weld joint is different from the heat treatment process that usual small size workpiece uses, because of steel
Specimen length may be up to hundreds of meters after rail welding, this just determines that the normalizing heat treatment of steel rail weld joint can not reach mesh
Long-time heat preservation (temperature more than austenitizing temperature) is carried out after marking temperature.Thus, the present invention imitates type electricity using Medium frequency induction
Heating coil and/or oxy-acetylene flame imitate type heater and carry out local heating to rail welding region, by steel rail weld joint plus
Heat after making its abundant austenitizing, is used using compressed air or water mist gaseous mixture as medium to target temperature (780~870 DEG C)
Type of cooling butt joint carry out acceleration cooling, by " slack quenching " reach promoted bainite rail connector hardness and improve it is tough
The purpose of plasticity facilitates extending connector fatigue life.
Second cooling cold temperature of opening may be selected 780 DEG C or more, and the welding point after normalizing is heat-treated is cooling by second
To 450~510 DEG C, cooled region further includes the rail rail outside heating zone within the scope of two side length 80mm in addition to normalizing heating zone
Head tyre tread and side.
In the method for the present invention, mode that the welding point that first obtains after cooling is heated can there are many, this hair
It is bright preferably to be heated using the imitative type electric heating coil of Medium frequency induction and/or the imitative type heater of oxy-acetylene flame.
It is further, described when being heated to 780~870 DEG C in bainite rail post weld heat treatment method described above,
To being about that steel rail weld joint whole cross section within the scope of 70~100mm carries out tunneling boring heating comprising the length including weld seam,
Help to make welding region abundant austenitizing in normalizing heating process using tunneling boring heating, and then accelerate it is cooled
The mechanical property of welding region is set to be significantly improved in journey.
The method of the present invention can be used for the bainite rail welding point that the welding of various temperature obtains, preferably described to weld
The initial temperature of the bainite rail welding point arrived is 1100~1300 DEG C, using lower thermal weld stress, and control compared with
The first high cooling rate outlet temperature is conducive to normalizing heating, significantly reduces energy consumption；The method of the present invention can be used for using various welderings
Connect method acquisition welding after bainite rail welding point of the temperature at 1100~1300 DEG C, be preferred for using include flash of light
Welding and gas pressure welding at least one of connect the higher bainite rail welding of the residual temperature after the welding that welding method obtains
Connector.
The method of the present invention is by rational bainite rail post weld heat treatment technique, the bainitic steel through post weld heat treatment
Martensite-free tissue in the metallographic structure of rail welding point is rail base material away from the average hardness in the region Weld pipe mill ± 70mm
The 80~85% of average hardness ensure that steel rail weld joint military service performance, make the fatigue life of bainite rail welding point
It is maintained at 4,000,000 times or more.
Below by embodiment, invention is further described in detail, but does not therefore limit the scope of the present invention
Among the embodiment described range.
In embodiment and comparative example, the model PB2 of bainite rail is heat-treated bainite rail.
In embodiment and comparative example, referring to TB/T1632.2-2014 " rail welding part 2: Flash Butt Welding " and TB/
Steel rail weld joint is machined to the examination of vertical section hardness by T1632.4-2014 " the 4th part of rail welding: air pressure welding " standard
Sample, and the position 5mm Welded Joints carry out the detection of vertical section Rockwell hardness, measuring point centered on weld seam to the left and right two under tyre tread
Side is symmetrically arranged, measuring point spacing 5mm, and Rockwell hardness method is by GB/T230.1-2009 regulation progress, using HRC scale, with
Hp indicates that the hardness average value of rail base material, Hj indicate the hardness average value of connector, and position of the connector hardness lower than 0.9Hp indicates
Softened region.Three-point bending fatigue test is carried out to steel rail weld joint using MTS-FT310 type fatigue tester, is carried with recycling
It is test objective that fatigue fracture, which does not occur, for welding point when lotus loads 4,000,000 times.
Embodiment 1
The temperature welded using flash welding is cold in 1300 DEG C of bainite rail welding point progress first stage
But, first stage cooling is carried out so that the rail head skin temperature of rail joint is cooled to 280 with the first cooling velocity of 6.0 DEG C/s
DEG C when carry out it is air-cooled.Then, type electric heating coil is imitated using Medium frequency induction and tunneling boring heating is carried out to steel rail weld joint region.
Stop heating when the wheel tread temperature of rail reaches 850 DEG C, it is cold then to carry out second stage with the second cooling velocity of 3.0 DEG C/s
But rail joint is cooled to 480 DEG C, it is cooling with by rail that the phase III is finally carried out with the third cooling velocity of 0.6 DEG C/s
The rail head skin temperature of connector is down to room temperature (25 DEG C), to obtain the bainite rail welding of the invention through post weld heat treatment
Connector.
In PWHT procedures, first is cooled to the natural cooling carried out in air；Second cooling and third cooling
Rail head of rail is used to imitate type cooling device using compressed air as cooling medium to the rail head tyre tread and rail of rail joint in the process
Head side is cooled down, and cooling device is apart from rail head of rail tyre tread 30mm；In second cooling procedure, the compression of cooling device injection
The gas pressure of air is 0.80MPa；In third cooling procedure, the gas pressure of the compressed air of cooling device injection is
0.20MPa.Rail head of rail wheel tread temperature is monitored using infrared radiation thermometer.
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 1 under tyre tread, and the distributed effect of longitudinal hardness is as shown in Figure 1.
1 embodiment of table, 1 welding point longitudinal direction hardness data
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 1300 DEG C of bainite rail, gained rail joint is hard in the region Weld pipe mill ± 70mm
Degree average value is 35.3HRC, has reached the 82% of rail base material average hardness, in the 80-85% model of rail base material average hardness
In enclosing.The fatigue test that the bainite rail weld joint samples obtained by the present embodiment can be 4,300,000 times by cycle-index,
Higher than 2,000,000 times specified in TB/T1632.2-2014.
Sampling method referring to Figure 5 connects rail by GB/T 13298-2015 " the metal microstructure method of inspection "
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: seeing in metallographic microscope
It examines down, does not occur martensitic structure in the heat affected area of rail joint weld seam two sides, help to ensure that railway operation safety.
Embodiment 2
The temperature welded using gas pressure welding is cold in 1150 DEG C of bainite rail welding point progress first stage
But, first stage cooling is carried out so that the rail head skin temperature of rail joint is cooled to 330 with the first cooling velocity of 7.0 DEG C/s
℃.Then, type heater is imitated using oxy-acetylene flame and tunneling boring heating is carried out to steel rail weld joint region.When stepping on for rail
Face temperature stops heating when reaching 830 DEG C, and water mist gaseous mixture is then used to carry out second-order with the second cooling velocity of 3.5 DEG C/s
Section is cooling rail joint is cooled to 500 DEG C, finally with the third cooling velocity of 0.40 DEG C/s carry out the phase III it is cooling with
The rail head skin temperature of rail joint is down to room temperature (25 DEG C), to obtain the bainitic steel of the invention through post weld heat treatment
Rail welding point.
In PWHT procedures, first is cooled to the natural cooling carried out in air；Second cooling and third cooling
Rail head of rail is used to imitate type cooling device using compressed air as cooling medium to the rail head tyre tread and rail of rail joint in the process
Head side is cooled down, and cooling device is apart from rail head of rail tyre tread 30mm；In second cooling procedure, the compression of cooling device injection
The gas pressure of air is 0.90MPa；In third cooling procedure, the gas pressure of the compressed air of cooling device injection is
0.10MPa.Rail head of rail wheel tread temperature is monitored using infrared radiation thermometer.
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.
2 embodiment of table, 2 welding point longitudinal direction hardness data
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 1400 DEG C of bainite rail, gained rail joint is hard in the region Weld pipe mill ± 70mm
Degree average value is 35.4HRC, has reached the 82% of rail base material average hardness, in the 80-85% model of rail base material average hardness
In enclosing.The fatigue test that the bainite rail weld joint samples obtained by the present embodiment can be 4,100,000 times by cycle-index,
Higher than 2,000,000 times specified in TB/T1632.2-2014.
Sampling method referring to Figure 5 connects rail by GB/T 13298-2015 " the metal microstructure method of inspection "
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: metallography microscope sem observation
Under, do not occur martensitic structure in the heat affected area of rail joint weld seam two sides.
Comparative example 1
The temperature welded using flash welding is cold in 1200 DEG C of bainite rail welding point progress first stage
But, first stage cooling is carried out so that the rail head skin temperature of rail joint is cooled to 300 with the first cooling velocity of 6.0 DEG C/s
DEG C when.Then, type electric heating coil is imitated using Medium frequency induction and tunneling boring heating is carried out to steel rail weld joint region, when rail
Stop heating when wheel tread temperature reaches 870 DEG C, it is cooling with by steel then to carry out second stage with the second cooling velocity of 7.0 DEG C/s
Rail connector is cooled to 150 DEG C, and it is cooling with by the rail of rail joint finally to carry out the phase III with the third cooling velocity of 0.6 DEG C/s
Head skin temperature is down to room temperature (25 DEG C), to obtain connecing using the bainite rail through post weld heat treatment of the comparative example
Head.
In PWHT procedures, first is cooled to the natural cooling carried out in air；Second cooling and third cooling
Rail head of rail is used to imitate type cooling device using compressed air as cooling medium to the rail head tyre tread and rail of rail joint in the process
Head side is cooled down, and cooling device is apart from rail head of rail tyre tread 30mm；In second cooling procedure, the compression of cooling device injection
The gas pressure of air is 0.90MPa；In third cooling procedure, the gas pressure of the compressed air of cooling device injection is
0.20MPa.Rail head of rail wheel tread temperature is monitored using infrared radiation thermometer.
The longitudinal hardness specimens for the bainite rail welding point for taking this comparative example to obtain, the 5mm under rail head of rail tyre tread
Position carries 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 5mm.Lip river
Family name's Hardness Surveillance method is provided to carry out by GB/T 230.1-2009, using HRC scale.5mm under the rail head tyre tread of welding point
The longitudinal hardness data set is shown in Table 3, and the distributed effect of longitudinal hardness is as shown in Figure 3.
3 comparative example of table, 1 welding point longitudinal direction hardness data
By table 3 and Fig. 3 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 1200 DEG C of bainite rail, gained rail joint is hard in the region Weld pipe mill ± 70mm
Degree average value is 40.4HRC, has reached the 94% of rail base material average hardness, the 80-85% beyond rail base material average hardness
Range.Fatigue occurs when object fatigue is carried out to 1,800,000 times for the bainite rail weld joint samples obtained by this comparative example
Fracture.
Sampling method referring to Figure 5 connects rail by GB/T 13298-2015 " the metal microstructure method of inspection "
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
Occur a large amount of martensitic structures in the heat affected area of side.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 10%.
Comparative example 2
The temperature welded using gas pressure welding is directly air-cooled in 1300 DEG C of bainite rail welding point
Room temperature (25 DEG C), to obtain the bainite rail welding point under the conditions of air-cooled (natural cooling).
The longitudinal hardness specimens for the bainite rail welding point for taking this comparative example to obtain, the 5mm under rail head of rail tyre tread
Position carries 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 5mm.Lip river
Family name's Hardness Surveillance method is provided to carry out by GB/T 230.1-2009, using HRC scale.5mm under the rail head tyre tread of welding point
The longitudinal hardness data set is shown in Table 3, and the distributed effect of longitudinal hardness is as shown in Figure 4.
4 comparative example of table, 2 welding point longitudinal direction hardness data
By table 4 and Fig. 4 it is found that for not welding obtained residual temperature using post weld heat treatment method provided by the invention processing
Higher bainite rail welding point, hardness average value of the gained rail joint in the region Weld pipe mill ± 70mm are
32.8HRC has reached the 77% of rail base material average hardness, lower than the 80-85% of rail base material average hardness.With rail base material
Hardness is compared, the lower hardness of entire welding region, and hardness is in " W-shaped " distribution trend.Thus the welding point that comparative example obtains
It easily causes the connector rail head shape of a saddle to wear away during route is on active service, influences Track regularity and traffic safety.Thus comparative example
When object fatigue is carried out to 1,900,000 times fatigue fracture occurs for obtained bainite rail weld joint samples, is lower than TB/
2,000,000 times specified in T1632.2-2014.
Sampling method referring to Figure 5 connects rail by GB/T 13298-2015 " the metal microstructure method of inspection "
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
Do not occur martensitic structure in the heat affected area of side.
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 rail head tyre tread longitudinal direction hardness of bainite rail welding point can be controlled and be put down in 80-85% rail base material by the process of confession
In equal hardness range；Post-Welding Heattreatment of Rail process provided by the invention can make the fatigue of bainite rail welding point
Service life is maintained at 4,000,000 times or more, the technical requirements much higher than 2,000,000 times specified in TB1632, has reached guarantee rail clothes
Use as a servant the purpose in service life.
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. bainite rail post weld heat treatment method, it is characterised in that: shellfish of the temperature for obtaining welding at 1100~1300 DEG C
Family name's body steel rail weld joint carries out first and is cooled to 260~350 DEG C, and the welding point for then obtaining the first cooling condition heats
To 780~870 DEG C, the second cooling is then carried out, stops the second cooling when being cooled to 450~510 DEG C, it is cold to carry out third immediately
But to 10~40 DEG C of room temperature.
2. bainite rail post weld heat treatment method according to claim 1, it is characterised in that: described first is cooling cold
But mode is air-cooled, and described second type of cooling cooling and that third is cooling is cooling for the acceleration carried out using cooling medium.
3. bainite rail post weld heat treatment method according to claim 1, it is characterised in that: first cooling velocity
For 5.0~8.0 DEG C/s.
4. bainite rail post weld heat treatment method according to claim 1 or 2, it is characterised in that: the second stage
It is cooling that type cooling device is imitated using rail head of rail, using compressed air or water mist gaseous mixture as cooling medium to steel rail weld joint
Rail head tyre tread and rail head side cooled down, cooling device apart from rail head of rail tyre tread be 25~35mm；Cooling device is sprayed
The compressed air of injection or the gas pressure of water mist gaseous mixture are 0.50~1.00MPa.
5. bainite rail post weld heat treatment method according to claim 4, it is characterised in that: described second is cooling cold
But speed is 2.0~4.0 DEG C/s.
6. bainite rail post weld heat treatment method according to claim 1 or 2, it is characterised in that: the phase III
It is cooling that type cooling device is imitated using rail head of rail, using compressed air or water mist gaseous mixture as cooling medium to steel rail weld joint
Rail head tyre tread and rail head side cooled down, cooling device apart from rail head of rail tyre tread be 25~35mm；Cooling device is sprayed
The compressed air of injection or the gas pressure of water mist gaseous mixture are 0.10~0.30MPa.
7. bainite rail post weld heat treatment method according to claim 6, it is characterised in that: the third cools down cold
But speed is 0.40~0.80 DEG C/s.
8. bainite rail post weld heat treatment method according to claim 1, it is characterised in that: control second is cooling to open
Cold temperature is welding point by 260~350 DEG C of 780 DEG C or more be heated to after 780~870 DEG C of stoppings.
9. bainite rail post weld heat treatment method according to claim 1, it is characterised in that: at least meet following one
:
It is described to be heated to 780~870 DEG C using the imitative type electric heating coil of Medium frequency induction and/or the imitative type heater of oxy-acetylene flame
Heating；
It is described when being heated to 780~870 DEG C, to being about rail welding within the scope of 70~100mm comprising the length including weld seam
Connector whole cross section carries out tunneling boring heating.
10. bainite rail post weld heat treatment method described according to claim 1~any one of 9, it is characterised in that: through welding
Martensite-free tissue in the metallographic structure for the bainite rail welding point being heat-treated afterwards, while away from the region Weld pipe mill ± 70mm
Interior average hardness is the 80~85% of rail base material average hardness, and the fatigue life of bainite rail connector reaches 4,000,000
More than secondary.
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| CN112251587A (en) * | 2020-10-23 | 2021-01-22 | 攀钢集团攀枝花钢铁研究院有限公司 | Heat treatment method for welded joint of bainite steel rail and eutectoid pearlite steel rail |
| CN112251592A (en) * | 2020-10-23 | 2021-01-22 | 攀钢集团攀枝花钢铁研究院有限公司 | Construction method for heat treatment of dissimilar steel rail flash welded joint |
| CN112359179A (en) * | 2020-10-23 | 2021-02-12 | 攀钢集团攀枝花钢铁研究院有限公司 | Steel rail postweld heat treatment construction method |
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| CN110042218A (en) * | 2019-05-28 | 2019-07-23 | 攀钢集团攀枝花钢铁研究院有限公司 | Construction method for the heat treatment of bainite rail postwelding connector |
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| CN112251592A (en) * | 2020-10-23 | 2021-01-22 | 攀钢集团攀枝花钢铁研究院有限公司 | Construction method for heat treatment of dissimilar steel rail flash welded joint |
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| CN112251592B (en) * | 2020-10-23 | 2022-03-22 | 攀钢集团攀枝花钢铁研究院有限公司 | Construction method for heat treatment of dissimilar steel rail flash welded joint |
| CN112251587B (en) * | 2020-10-23 | 2022-03-22 | 攀钢集团攀枝花钢铁研究院有限公司 | Heat treatment method for welded joint of bainite steel rail and eutectoid pearlite steel rail |
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