Embodiment
The demand for development rail of high speed and quasi high-speed highway has the excellent comprehensive performance, with security and the longevityization that guarantees high-speed railway.Train is run at high speed along rail, except that the outward appearance that requires rail has high straightness, high geometric accuracy and do not have any defective, also requires rail to have good toughness plasticity and rolling contact fatigue performance.For present stage at a high speed and the rail that uses of quasi high-speed highway, guarantee that it has the long lifetime, need to reduce as far as possible because the wheel track contact friction causes the wearing and tearing on rail surface; Simultaneously, for guaranteeing that the tiny crack that has resulted from the rail surface inwardly can in time ground off before the expansion, also need guarantee certain wear rate, this has just formed and has improved rail work-ing life is the contradiction of cost to improve wear rate, can't fundamentally solve and reduce wearing and tearing and the problem of improving the rolling contact fatigue performance.
Therefore, in the present invention, by reducing the C constituent content in the rail, cooperate the mode of rolling the back controlled chilling, else improve the toughness plasticity and the yield strength of rail simultaneously at the intensity, the durometer level that keep existing rail in high speed railway, raising is formed at the tired microcrack initiation on rail top layer and expands required Energy value, thereby can improve the rolling contact fatigue performance of rail under the same conditions, finally improves the work-ing life and the Transport Safety of rail.
Specifically, the invention provides a kind of being used at a high speed and the rail of quasi high-speed highway, the chemical ingredients that this rail comprises is by weight: 0.40%~0.64% C, 0.10%~1.00% Si, 0.30%~1.50% Mn, be less than and equal 0.025% P, be less than and equal 0.025% S, be less than and equal 0.005% Al, greater than 0 and be less than and equal 0.05% Re, total amount is greater than 0 and at least a smaller or equal among 0.20% V, Cr and the Ti, and the Fe of surplus and unavoidable impurities.Preferably, the chemical ingredients that the rail that is used for high speed and quasi high-speed highway according to the present invention comprises is by weight: 0.45%~0.60%C, 0.15%~0.50%Si, 0.50%~1.20%Mn is less than and equals 0.025%P, is less than to equal 0.025%S, be less than and equal 0.005%Al, greater than 0 and be less than and equal 0.05% rare earth element, total amount is greater than 0 and at least a smaller or equal among 0.20% V, Cr and the Ti, and the Fe of surplus and unavoidable impurities.In the following description, except as otherwise noted, otherwise the content of the material of being mentioned all by weight percentage.
The rail that is used for high speed and quasi high-speed highway according to the present invention at room temperature is organized as the uniform mixing tissue of perlite and 15%~50% ferrite (being preferably perlite and 15%~30% ferrite), elongation after fracture 〉=15%, yield strength (R
El) 〉=550MPa, the fracture toughness property K in the time of-20 ℃
IC〉=40MPam
1/2
Below, illustrate that at first chemical ingredients according to rail of the present invention is limited to the reason in the above-mentioned scope.
C is that to make rail obtain a kind of most important of suitable intensity, hardness and wear resisting property also be the most cheap element.In rail according to the present invention, when C%<0.40% (wt),, below the rail head of rail tread, be difficult to assemble because the carbide quantity in the tissue is few, reduce polishing machine, cause rail to reduce work-ing life because of rapid wear; Simultaneously, because the reduction of hardness makes rail tread form the plastic flow district, and be easy to produce defective such as overlap, the traffic safety that jeopardizes bullet train.In rail according to the present invention, when C%>0.64% (wt),, will make rail strength, hardness too high by the subsequent heat treatment operation, expand owing to the crackle that has produced can't in time wear away on the one hand, thereby make the proneness enhancing of rail transverse breakage; On the other hand, the too high wheel wear speed that makes of rail hardness is accelerated the work-ing life of seriously reducing train.In addition, under the same conditions, the raising of rail strength will be followed the reduction of toughness plasticity, can't satisfy security requirement equally.Therefore, in the present invention, C content is limited between 0.40%~0.64%, can satisfy the required rigidity of rail better, simultaneously, makes the wheel track Hardness Match and improves the security that rail uses.Preferably, C content is limited between 0.45%~0.60%.
Si is present in the intensity that improves tissue in ferrite and the austenite with the solid solution form usually as the main adding elements of steel.In rail according to the present invention, when Si% in the rail<0.10% (wt), solid solution capacity is on the low side will to cause strengthening effect not obvious; When Si%>1.00% (wt), the toughness plasticity of steel and ductility will be reduced.In addition, the serious lateral performance that reduces steel was unfavorable for the security that rail uses when the Si content in the steel was higher.Therefore, in the present invention, Si content is limited between 0.10%~1.00%, and when 0.15wt%<Si%<0.50wt%, effect is remarkable especially.
Mn can form sosoloid with Fe, improves ferrite and austenitic intensity.Simultaneously, Mn is again a carbide forming element, can partly substitute the Fe atom after entering cementite, increases the hardness of carbide, finally increases the hardness of steel.In rail according to the present invention, when Mn% in the rail<0.50% (wt), strengthening effect is undesirable, only by the solid solution effect performance of steel is improved slightly; When Mn%>1.20% (wt), the hardness of carbide is too high in the steel, make rail can't obtain the ideal combination of strength and toughness, the more important thing is, because Mn has the effect that pulls solute atoms, the cold stage of control in making the rail process, because rate of cooling is very fast, C atom under the austenitic state can't fully spread owing to the effect of Mn, saturated or the hypersaturated state of final formation, be easy to produce abnormal structures such as bainite and martensite, then both forbid occurring in the perlite series rail.Therefore, in the present invention, Mn content is limited between 0.30%~1.50%, and particularly when 0.50wt%<Mn%<1.20wt%, effect is remarkable.
Al easily combines with oxygen in steel, forms Al
2O
3Or other complex oxide, as fail fully to float, will retain in the steel, this inclusion is as the heterogeneous continuity that will destroy matrix mutually when rail uses, under the effect of pulsating stress, form the fatigue cracking source, further expanding to increase the trend of the horizontal brittle failure of rail.Therefore, be to improve the purity of rail, guarantee safe in utilizationly, the content regulation of Al is no more than 0.005%.
The effect of RE (rare earth element) in steel is to promote form modification of nonmetallic inclusion, improves purity of steel simultaneously.In addition, RE reduces the harm of impurity such as S, As to steel performance in addition, improves the fatigue property of rail steel.Yet, when RE%>0.05%, easily promote thick inclusion to generate the severe exacerbation steel performance.For high speed or quasi high-speed highway rail, improve purity of steel, it is very important to the destruction of steel substrate to reduce non-metallic inclusion.Therefore, in the present invention, the scope of adding RE is defined as and is less than or equal to 0.05%, and when 0.010wt%<Re%<0.020wt%, effect is remarkable especially.
In the present invention, the V+Cr+Ti total amount requires≤0.20%, reason is as follows: C is as the main strengthening element of steel, and its content height is the microstructure and property of decision rail directly, with the reduction of C content, ferritic ratio progressively enlarges in the tissue, the perlite ratio reduces, and ferrite is difficult to bear wheel and wears away repeatedly as the soft phase in the steel, even it is by thermal treatment, also very limited to the raising of ferrite matrix intensity.Therefore, need to add and come the reinforced ferrite matrix, thereby when improving polishing machine, improve the toughness plasticity of rail as alloying elements such as V, Cr and/or Ti.Below specify the adding purpose and the scope of above-mentioned three kinds of alloying elements.
V in the steel at room temperature solubleness is very low, usually with steel in C and N form V (C, N), crystal grain thinning improve toughness plasticity when strengthening matrix, be one of strengthening element of using always in the present carbon steel.In rail according to the present invention, when V%<0.15%, this effect is comparatively obvious; When further raising V content, intensity will further improve and toughness particularly impact property significantly descend, promptly rail is resisted ballistic ability and is weakened, the required high security of this and used for high-speed railway rail is not inconsistent; If V%<0.01%, because the V limited amount of separating out is difficult to bring into play strengthening effect, so separately during interpolation V, V content is limited to 0.01%~0.15%, particularly when 0.02%≤V%≤0.08%, effect is more remarkable.
Cr and Fe can form continuous solid solution and form multiple carbide with C, also are one of main strengthening elements in the steel.In addition, the evenly distribution of carbide in the steel of Cr improves the polishing machine of steel.Compare with V, the advantage of Cr maximum is an economy.Yet, will bring disadvantageous effect to welding property when Cr content is higher.In the present invention, because the reduction of C content, make that ratio of ferrite enlarges in the steel, need to add the solution strengthening element to improve ferritic intensity, guarantee the polishing machine in the rail use, simultaneously, because high speed or quasi high speed train axle heavy and light wear away limited, therefore, Cr content is limited to 0.02%~0.20%, and particularly when 0.10%≤Cr%≤0.15%, effect is more remarkable.
Austenitic crystal grain when the main effect of Ti in steel is refinement heating, rolling and cooling, final toughness plasticity and the rigidity that increases tissue.In rail according to the present invention, when Ti%>0.05%, because Ti is strong carbonitride forming element, the TiC of the generation rail hardness that will make on the high side is too high on the one hand; On the other hand, TiC is on the high side will to be gathered enrichment partially and form thick carbide, not only reduce toughness plasticity, also make rail contact surface under impact loading be easy to cracking and cause fracture.In rail according to the present invention, when Ti%<0.01%, the carbonitride thing limited amount of formation is difficult to play a role, so in the present invention, Ti content is limited to 0.01%~0.05%.
Because high speed or quasi high-speed highway rail strength are lower, solution strengthening, the precipitation strength effect of elements such as required V, Cr and Ti are limited; Simultaneously, because the reduction of carbon content among the present invention, toughness plasticity significantly improves, and only relies on above-mentioned alloying element to improve the polishing machine of rail.Therefore, limit 0<V+Cr+Ti≤0.20% among the present invention.
Below, be used at a high speed and the manufacture method of the rail of quasi high-speed highway describing in detail according to of the present invention.
According to the present invention, the method for making the rail that is used for high speed and quasi high-speed highway may further comprise the steps:
(1) molten steel is smelted and casting
At first, adopt converter, electric furnace or open hearth that the molten steel that comprises following composition is smelted: 0.40%~0.64%C, 0.10%~1.00%Si, 0.30%~1.50%Mn is less than and equals 0.025% P, is less than to equal 0.025% S, be less than and equal 0.005% Al, greater than 0 and be less than and equal 0.05% Re, total amount is greater than 0 and at least a smaller or equal among 0.20% V, Cr and the Ti, and the Fe of surplus and unavoidable impurities.Then, carry out LF (Ladle Furnace) stove refining (being external refining), vacuum-treat, be square billet or slab postcooling with molten steel casting or directly delivering to the process furnace intensification.
(2) steel rail rolling
The continuously cast bloom that will be warming up to certain temperature (being preferably 1200 ℃~1300 ℃) and be incubated 0.5~2h is sent into milling train, with rolling be the rail of required section.
(3) roll the back controlled chilling
After the finish to gauge, rail remains on the temperature more than 800 ℃ usually, and can make rail obtain different performance by control rail head of rail rate of cooling this moment.For the rail that still has surplus heat after rolling, because the rolling characteristics of milling train, common rail is with a siding track bottom comer and rail head contacts side surfaces roller-way, and the actual rail that uses has only the rail head position.In the present invention, the process of controlled chilling is as follows: at first rail is stood on roller-way, rotate the drive rail by roller-way and enter the thermal treatment unit.Before this, the thermal treatment unit is used to cool off rail head of rail end face and two lateral nozzles to have begun winding-up and has had suitable pressure and flow, is generally the heat-eliminating medium of 2kPa~15KPa under the atmospheric environment.When passing through the nozzle of arranging continuously under the drive of rail at roller-way, rate of cooling with 1 ℃/s~4 ℃/s is evenly cooled off the rail head position of rail, when the infrared temperature means of detection that is positioned at thermal treatment unit top is found out rail head end face skin temperature and is reduced to 350 ℃~550 ℃, cooling stops, and finishes the controlled chilling of rail head of rail.
That in the present invention, quickens that heat-eliminating medium can be in pressurized air, gas-vapor mix and the gas-oil mixture is at least a.Under guidance of the present invention, those skilled in the art can determine the acceleration heat-eliminating medium that adopted according to actual needs.Specifically, adopt pressurized air and gas-vapor mix as the situation of quickening heat-eliminating medium under, can select to determine ratio between the two according to routine.
(4) air cooling is placed
After the rail head of rail temperature reaches termination among the present invention and quickens the cooling temperature scope, rail is placed the air naturally cooling, and carry out subsequent handling and handle.
In addition, in above-mentioned steps (3), employing be online thermal treatment process.Yet,, also can adopt the off-line thermal treatment process for the present invention.Off-line thermal treatment is that rail rolls the first air cooling in back to room temperature, is heated to austenite phase region temperature by induction heating device again, is generally 900 ℃~1100 ℃, again the refrigerative process is quickened at the rail head position.Specifically, after billet rolling being become rail by abovementioned steps, rail is naturally cooled to the temperature that is lower than the austenite phase region, and then rail is reheated technology to austenite phase region or the temperature more than 800 ℃ and take steps (3), can obtain the product among the present invention equally.In the present invention, when becoming rail to be cooled to billet rolling to be lower than the temperature of austenite phase region, rail is heated to 800 ℃~1000 ℃ temperature range with 1 ℃/s~20 ℃/speed of s, the technology of repeating step (3) then, promptly, stop cooling when evenly cooling off rail's end portion to 350 ℃~550 ℃, in air, naturally cool to room temperature thereafter with the rate of cooling of 1 ℃/s~4 ℃/s.Here, it should be noted that, when reheating the rail of naturally cooling to austenite phase region temperature, can adopt different heating rate according to concrete factors such as appointed condition, for example, can rail slowly be heated to the temperature of austenite phase region with 1 ℃/s, also can rail be heated to rapidly the temperature of austenite phase region with 20 ℃/s.
Except the step of rolling the back controlled chilling, basic identical according to the method for the manufacturing rail of the method for manufacturing rail of the present invention and prior art, therefore, identical content is not described in detail at this.In the present invention, after finish to gauge, evenly cool off with the rate of cooling of the 1 ℃/s~4 ℃/s head to rail, the temperature for the treatment of rail's end portion stops cooling when reducing to 350 ℃~550 ℃.Because the selection of process for cooling will determine the performance of the finished product, therefore, in the present invention, employing contains the rail of mentioned component, when 1 ℃/s of rate of cooling less than, can't reach and at a high speed existing or the equal intensity of quasi high-speed highway rail by ferrite in the thinning microstructure and pearlitic grain, the vertical load that the ferrite matrix undercapacity is difficult to bear train in may causing using, made the rail head end face because of plastic flow when producing quick-wearing, size generation deviation, not only reduce the work-ing life of rail, also jeopardize traffic safety simultaneously; On the other hand, when rate of cooling surpassed 4 ℃/s, the rate of diffusion of carbide in steel reduced, and increases the proneness that produces as bainite, martensitic stucture, and then two kinds of tissues are clearly to forbid in the pearlitic rail occurring.In addition, rate of cooling is too high will significantly to improve the intensity of rail, although improved the energy of crack initiation and expansion simultaneously, can't remove by wheel-rail wear for the crackle that has produced simultaneously, be unfavorable for traffic safety equally.
In the present invention, quickening the refrigerative final temperature is 350 ℃~550 ℃, and reason is: adopt the rail that comprises mentioned component to quicken cooling from the austenite phase region, in the time of about 550 ℃ rail surface and surface down at least in the 15mm scope transformation finished; At this moment, the heat that rail head inside has will outwards transmit, and as stopping quickening cooling, may make established thinning microstructure roughening because thermal conduction causes skin temperature to raise, be unfavorable for that the rail head interior tissue finishes transformation under bigger condensate depression, can't give full play to heat treated effect.Be lower than 350 ℃ if quicken cooling temperature, then entered the bainite transformation district, be unfavorable for obtaining stable perlite, ferritic structure, increase the proneness that abnormal structure produces.
Only rail's end portion is quickened cooling in the present invention and the web of the rail and flange of rail position are as follows to the reason of room temperature with natural air cooling: the rail web of the rail is as the linker of head and bottom, bear weight indirectly from train, need certain rigidity, also bear the normal force that train turns to generation simultaneously; The flange of rail directly acts on sleeper, determines the train operation track, and load finally is passed to railway roadbed.For at a high speed and quasi high-speed highway, the train axle is heavy, and (11t~14t) is lower than passenger-cargo mixed transport line road or heavy-haul line, and (25t~40t) and route curve radius are big, and (usually>1000m), the web of the rail and the flange of rail are subjected to vertical power and normal force limited.In addition, quicken cooling and compare with air cooling, limited to the influence of toughness plasticity index, the security that rail is used does not make significant difference.
Adopt the method for manufacturing rail of the present invention, can obtain the rail head position is the rail of the thin ferrite mixed structure of nodular troostite+(15%~50%), this rail strength reach existing at a high speed or quasi high-speed highway else significantly improved the toughness plasticity and the yield strength of rail simultaneously with the equality strength level of rail, when improving rail top layer crack initiation and expansion energy, improved the ability of rail opposing shock load, finally improve the rolling contact fatigue performance of rail, guarantee railway safety.Simultaneously, need not in process of production the existing installation transformation, production technique is simple, and is easy and simple to handle, flexible.
Below, will come to describe in more detail the present invention in conjunction with specific embodiments.These examples are for illustrational purpose, and are not intended to limit the scope of the invention.
Example 1
Listed steel in the table 2 that the employing converter smelting is composed as follows, carry out the refining of LF stove, vacuum stripping, billet continuous casting, billet heating furnace heating, steel rail rolling then, finishing temperature is 903 ℃, after placing 40s, the rail head top surface temperature is reduced to 800 ℃ and is begun the pressurized air of jetting, rate of cooling with 3.1 ℃/s is evenly cooled off rail's end portion, the rail head of rail top surface temperature was 520 ℃ after winding-up finished, the web of the rail and flange of rail temperature are greater than 600 ℃, place air to naturally cool to room temperature rail then, obtain sample 1.
Example 2
Except the step of rolling the back controlled chilling, adopt the method identical to make rail with the method for example 1.Specifically, in this example, finishing temperature is 910 ℃, after placing 45s, the rail head top surface temperature is reduced to 780 ℃ of begin to jet pressurized air and gas-oil mixtures, evenly cools off rail's end portion with the rate of cooling of 2.9 ℃/s, the rail head of rail top surface temperature was 514 ℃ after winding-up finished, the web of the rail and flange of rail temperature place air to naturally cool to room temperature rail greater than 600 ℃ then, obtain sample 2.
Example 3
Except the step of rolling the back controlled chilling, adopt the method identical to make rail with the method for example 1.Specifically, in this example, finishing temperature is 900 ℃, after placing 42s, the rail head top surface temperature is reduced to 770 ℃ and is begun the gas-oil mixture of jetting, and evenly cools off rail's end portion with the rate of cooling of 2.7 ℃/s, the rail head of rail top surface temperature was 530 ℃ after winding-up finished, the web of the rail and flange of rail temperature place air to naturally cool to room temperature rail greater than 600 ℃ then, obtain sample 3.
Example 4
Except the step of rolling the back controlled chilling, adopt the method identical to make rail with the method for example 1.Specifically, in this example, finishing temperature is 890 ℃, after placing 35s, the rail head top surface temperature is reduced to 790 ℃ of begin to jet gas-vapor mix and gas-oil mixtures, evenly cools off rail's end portion with the rate of cooling of 3.0 ℃/s, the rail head of rail top surface temperature was 495 ℃ after winding-up finished, the web of the rail and flange of rail temperature place air to naturally cool to room temperature rail greater than 550 ℃ then, obtain sample 4.
Example 5
Except the step of rolling the back controlled chilling, adopt the method identical to make rail with the method for example 1.Specifically, in this example, finishing temperature is 915 ℃, after placing 50s, the rail head top surface temperature is reduced to 780 ℃ and is begun the pressurized air of jetting, and evenly cools off rail's end portion with the rate of cooling of 2.8 ℃/s, the rail head of rail top surface temperature was 528 ℃ after winding-up finished, the web of the rail and flange of rail temperature place air to naturally cool to room temperature rail greater than 600 ℃ then, obtain sample 5.
Example 6
Except the step of rolling the back controlled chilling, adopt the method identical to make rail with the method for example 1.Specifically, in this example, finishing temperature is 922 ℃, after placing 53s, the rail head top surface temperature is reduced to 795 ℃ and is begun the pressurized air of jetting, and evenly cools off rail's end portion with the rate of cooling of 2.1 ℃/s, the rail head of rail top surface temperature was 519 ℃ after winding-up finished, the web of the rail and flange of rail temperature place air to naturally cool to room temperature rail greater than 600 ℃ then, obtain sample 6.
Example 7
Except the step of rolling the back controlled chilling, adopt the method identical to make rail with the method for example 1.Specifically, in this example, finishing temperature is 918 ℃, after placing 49s, the rail head top surface temperature is reduced to 800 ℃ and is begun the pressurized air of jetting, and evenly cools off rail's end portion with the rate of cooling of 2.2 ℃/s, the rail head of rail top surface temperature was 531 ℃ after winding-up finished, the web of the rail and flange of rail temperature place air to naturally cool to room temperature rail greater than 600 ℃ then, obtain sample 7.
Example 8
Except the step of rolling the back controlled chilling, adopt the method identical to make rail with the method for example 1.Specifically, in this example, finishing temperature is 907 ℃, after placing 48s, the rail head top surface temperature is reduced to 785 ℃ of begin to jet pressurized air and gas-vapor mix, evenly cools off rail's end portion with the rate of cooling of 2.3 ℃/s, the rail head of rail top surface temperature was 526 ℃ after winding-up finished, the web of the rail and flange of rail temperature place air to naturally cool to room temperature rail greater than 600 ℃ then, obtain sample 8.
Example 9
Except the step of rolling the back controlled chilling, adopt the method identical to make rail with the method for example 1.Specifically, in this example, finishing temperature is 895 ℃, at first air cooling is to room temperature, adopt the line-frequency induction heating unit rail's end portion to be reheated to 900 ℃ then with the speed of 5 ℃/s, when rail's end portion natural air cooling to 760 ℃, winding-up gas-vapor mix and pressurized air, rate of cooling with 2.2 ℃/s is evenly cooled off rail's end portion, the rail head of rail top surface temperature was 510 ℃ after winding-up finished, the web of the rail and flange of rail temperature place air to naturally cool to room temperature rail greater than 600 ℃ then, obtain sample 9.
Comparative Examples 1
Except the step of rolling the back controlled chilling, adopt the method identical to make rail with the method for example 1.Obtain directly placing air to be cooled to room temperature it behind the required section rail, obtain at a high speed existing or quasi high-speed highway rail, promptly Comparative Examples 1.
The chemical constitution of the rail of table 2 rail of the present invention and Comparative Examples
Experimental example 1
Mechanical property according to the rail of rail of the present invention and prior art has been shown in the following table 3.
The mechanical property of the rail of table 3 rail of the present invention and Comparative Examples
By top table 3 as can be seen, be in same rank according to the intensity of the rail of the rail of example according to the present invention 1 and example 3 and Comparative Examples 1, but unit elongation improves about 50%.Tensile strength (R according to example 2 according to the present invention and example 8 rail
m) a little less than the rail of Comparative Examples 1, but yield strength (R
El) higher, equal conditions will effectively stop rail to use the germinating of mesexine fatigue cracking down; Simultaneously, rail in high speed railway is in use because wheel Rail Contact Stresses is low at present, and it is slight to wear and tear, and can satisfy the abrasion requirement.In addition, it is about 75% to exceed the rail of Comparative Examples 1 according to the rail elongation after fracture of example 2 of the present invention, and safety in utilization is improved.With respect to Comparative Examples 1, example 4, example 6, example 7 and the intensity of example 8, also obviously improvement of plasticity when hardness improves among the present invention, over-all properties is promoted.For the example 9 that adopts second-heating, because ferrite crystal grain obtains refinement, performance satisfies at a high speed or quasi high-speed highway rail requirement equally.
Fig. 2 is the metallograph according to the rail head tissue of the rail of example 1 of the present invention.Fig. 3 is the metallograph according to the rail head tissue of the rail of Comparative Examples 1.By Fig. 2 and Fig. 3 as can be seen, with compare according to the rail of Comparative Examples 1, it is the tissue that perlite and ferrite mix arrangement that the rail that makes according to method of the present invention has, therefore, in rail of the present invention, can improve the polishing machine of rail by the cementite in the perlite, can improve the toughness and the fatigue property of rail simultaneously by the ferrite of having strengthened, so, for at a high speed and quasi high-speed highway for rail, rail according to the present invention has wearability and the antifatigue contact that rail than prior art will be good.
Experimental example 2
Gone out the ballistic work (Ak under differing temps in the following table 4 according to the rail of rail of the present invention and prior art
u).
The ballistic work of the rail of table 4 the present invention and Comparative Examples under differing temps
By top table 4 as can be seen, compare with the rail of prior art manufacturing, rail made according to the method for the present invention impelling strength under normal temperature and low temperature obviously improves, owing to adopt low carbon content and microalloying to handle, toughness improves one times nearly to example 2 with example 8.The example 4 and the example 6 of and alloy-freeization higher for carbon content, impelling strength has also improved 25%.This shows that the controlled chilling mode was comparatively favourable to the toughness of raising rail after employing reduction carbon content and cooperation were rolled.The safety in utilization of train provided more effective guarantee when therefore, rail made according to the method for the present invention will cause wheel-rail impact because of irregularity or other reason for the cold district high-speed railway.
Experimental example 3
Polishing machine according to the rail of rail of the present invention and prior art has been shown in the following table 5.
Mode by the skid wearing and tearing contrasts rail polishing machine under the same conditions, is the rail of Comparative Examples 1 to grind away.Concrete test conditions and parameter are as follows:
Trier title: MM-200 type;
Specimen size: thickness 10mm, internal diameter 10mm, external diameter 36mm;
Test load: 980N;
Slippage: 10%;
Testing circumstance: normal temperature, air-cooled;
Rotating speed: 200r/min;
To grinding total revolution: 200,000;
Experiment quantity: 3 to (getting its arithmetical av ecbatic)
Wearing test the results are shown in Table 5, and the wearing and tearing synoptic diagram is seen Fig. 1.
The polishing machine of the rail of table 5 part embodiment of the present invention and Comparative Examples
By top table 5 as can be seen, the polishing machine of 8 rail of the example among the present invention is a little less than the rail of Comparative Examples 1.Because the bullet train axle is heavy lighter, rail wear speed is lower, helps the fatigue cracking of rail head of rail surface germinating is removed by abrasion, and is very favourable to improving the rolling contact fatigue performance.For example 5 and example 6, its polishing machine is suitable with Comparative Examples 1, is equally applicable at a high speed or the quasi high-speed highway application.
Experimental example 4
Fatigue crack growth rate according to the rail of rail of the present invention and prior art has been shown in the following table 6.Adopting model is the crack growth rate trier of ISTRON 8801, and research crack length (or degree of depth) is along the rule perpendicular to the stress direction spreading rate.Crack growth rate is slow more, helps stoping crack propagation under the same terms more.
The crack growth rate of the rail of table 6 the present invention and Comparative Examples
By top table 6 as can be seen, by comparing with the rail of Comparative Examples 1, the crack growth rate of rail made according to the method for the present invention is lower, thereby helps stoping crack propagation more under the same terms.
Experimental example 5
Below table 7 in illustrated according to the rail of rail of the present invention and the prior art fracture toughness property (K when low temperature (20 ℃) and the normal temperature (20 ℃)
IC).The employing model is the fracture toughness property that the fracture toughness test machine of ISTRON 8801 has been measured rail.Fracture toughness property K
ICIt is the mechanical performance index of weighing material opposing crack propagation ability.K
ICBe worth highly more, show that the ability of rail opposing crack propagation is strong more, help traffic safety more.
The fracture toughness property of table 7 the present invention and Comparative Examples rail
By top table 7 as can be seen, under the same conditions, the fracture toughness property of rail made according to the method for the present invention no matter normal temperature or low temperature all is higher than the rail of Comparative Examples 1.By finding that relatively along with the reduction of carbon content in the steel, fracture toughness property significantly improves.Therefore, the higher fracture toughness property of the favourable acquisition of carbon content in the reduction rail.
Experimental example 6
Axial fatigue performance comparison according to the rail of rail of the present invention and Comparative Examples 1 has been shown in the following table 8.Adopt model to measure the axial fatigue limit of rail for the PQ-6 fatigue-bending machine adopts the stress amplitude lifting and lowering method, test conditions: when the overall strain width of cloth was 1350 μ ε, the fatigue lifetime of every group of sample was all greater than 5 * 10
6Requirement.
The axial fatigue limit of the rail of table 8 the present invention and Comparative Examples
By top table 8 as can be seen, rail made according to the method for the present invention and all satisfy standard-required according to the rail of prior art manufacturing, and to be higher than the safe range of stress of the rail of making according to prior art according to the safe range of stress of rail of the present invention.
Use in the rail in existing high speed and quasi high-speed highway, the head of rail is a large amount of perlite and less than 5% ferritic tissue, and be used at a high speed and the rail of quasi high-speed highway according to provided by the invention, by the reduction carbon content in the rail, cooperate the mode of rolling the back controlled chilling, can make the head of rail at room temperature be the ferritic uniform mixing tissue of perlite+15%~50%.Ferrite ratio in tissue is increased to 15%~50% advantage and is in the used for high-speed railway rail: tissue is based on perlite in (1) existing rail in high speed railway, comprise and be less than 5% ferritic structure, find through after the operation of certain hour, bullet train and interorbital wearing and tearing take place hardly, cause the pearlitic structure that is celebrated with good polishing machine to be difficult to play a role, on the contrary, owing to there are not wearing and tearing, the tiny crack that results from rail head top layer running surface of wheeltrack will be difficult to remove, reciprocating through wheel, to make crackle to the rail internal extended, finally form crackle, fall rolling contact fatigues such as piece, continue the danger that development will have disconnected rail.After the ratio of ferritic structure improves, because ferrite belongs to the soft phase in the steel, its polishing machine will make rail in use produce certain wearing and tearing not as perlite, can in time be ground off with the crackle of guaranteeing the rail top layer.Yet,, will influence the work-ing life of rail equally owing to rapid wear if the C content in the steel of demoting merely obtains a certain proportion of ferrite.Have only by the reinforced ferrite matrix and achieve the goal, and improve three kinds nothing more than of the methods of matrix strength, be alloying element solid solution, precipitation strength and thermal treatment refined crystalline strengthening, and rely on thermal treatment process merely, to when improving ferrite matrix intensity, the strengthening effect of cementite strengthen on year-on-year basis, and can make intensity too high, therefore, add the part micro alloying element based on the reinforced ferrite matrix, can also improve toughness plasticity slightly simultaneously.In addition,, will make the perlite ratio reduce, can't guarantee certain polishing machine, can't be applied to high-speed line equally if ratio of ferrite surpasses 50%.(2) raising of ratio of ferrite means tough moulding significantly lifting in the rail, and higher unit elongation and impelling strength will make the probability of rail disconnected rail under the condition that is subjected to uniform impingement load significantly reduce, and will be very favourable to guaranteeing traffic safety.
In sum, by metallographic structure to rail of the present invention and existing used for high-speed railway rail, conventional mechanical property and the contrast of special mechanical property under different condition are as can be seen, in the present invention, by reducing the carbon element content in the rail, cooperate the mode of rolling the back controlled chilling, the intensity that has kept existing rail in high speed railway, the hardness rank, meanwhile, the toughness plasticity and the yield strength of rail are significantly increased, promptly improve and be formed at the tired microcrack initiation on rail top layer and expand required Energy value, thereby can improve the rolling contact fatigue performance of rail under the same conditions, finally improve the work-ing life and the Transport Safety of rail.
The invention is not restricted to the foregoing description, without departing from the present invention, can carry out various changes and modifications.