Summary of the invention
It is an object of the invention to provide a kind of high-strength tenacity pearlite steel rail, gained pearlite steel rail intensity and toughness are equal
More excellent.
Technical scheme:
The present invention provides a kind of high-strength tenacity pearlite steel rail,
The satisfied following requirement of this rail chemical composition: C:0.75%-0.84%, Si:0.30%-0.80%, Mn:
0.50%-1.50%, V:0.04%-0.12%, Ti:0.004%-0.02%, and meet 0.10%≤V+10Ti≤0.25%,
[N]≤30ppm, P≤0.020%, S≤0.008%, surplus is Fe and inevitable impurity;
Further, the following process conditions in its rolling process are controlled when preparing described high-strength tenacity pearlite steel rail: steel
Rail starts rolling temperature 1120-1180 DEG C, finishing temperature 840-880 DEG C, rolls the rail profile minification of last two passages
6%-12%, after finish to gauge, rail is cooled to less than 600 DEG C with the cooling rate of≤2.0 DEG C/s, is further continued for air cooling to room temperature.
After finish to gauge, rail is cooled to less than 600 DEG C employing compressed airs as cooling medium using the cooling rate of≤2.0 DEG C/s.
After finish to gauge, rail is cooled to less than 600 DEG C with the cooling rate of≤2.0 DEG C/s in cold bed standing.
The section of described rail is 50-75kg/m.
Inventor finds in research process, if the rail reaching fining austenite grains final excellent produces
Product, need to be to the chemical composition of steel billet, heating and holding temperature, start rolling temperature, finishing temperature, last two passage amounts of rolling and remaining
Hot rail carries out being uniformly coordinated control at cold bed process air cooler, could finally realize the production of high quality rail.
First, the restriction reason of essential element content in rail of the present invention is described in detail.
C is that pearlite steel rail improves strong hardness, promotes the element that perlitic transformation is most important, the most cheap, when C content <
When 0.75%, under production technology of the present invention, intensity, hardness number are too low, it is impossible to ensure the abrasion resistance properties needed for rail;Work as C
During content > 0.84%, even if using the acceleration cooling of≤2.0 DEG C/s after finish to gauge, trace secondary carburizing will be separated out at grain boundaries
Body, deteriorates the toughness plasticity of rail;Therefore, C content is limited to 0.75%-0.84%.
Si is present in the intensity improving tissue in ferrite and austenite as the solution strengthening element in steel.When Si content
During < 0.30%, solid solution capacity is on the low side to be caused strengthening DeGrain;As Si content > 0.80%, mould reducing the tough of rail
Property, deteriorate the lateral performance of rail, be unfavorable for the use safety of rail.Therefore, Si content is limited to 0.30%-0.80%.
Mn can form solid solution with Fe, improves ferrite and the intensity of austenite.Meanwhile, Mn is again that carbide forms unit
Element, can partly substitute Fe atom after entering cementite, increase the hardness of carbide, the final hardness increasing steel.As Mn content <
When 0.50%, strengthening effect is not notable, is only capable of making the performance of steel slightly improve by solution strengthening;As Mn content > 1.50%
Time, carbide much higher hard in steel, toughness plasticity substantially reduces;Meanwhile, Mn is notable on Carbon diffusion impact at steel, though air cooling bar
Under part, Mn segregation zones still may produce the abnormal structures such as B, M.Therefore, Mn content is limited between 0.50%-1.50%.
When V is under room temperature condition, the dissolubility in steel is the lowest, and is the most such as present in austenite grain boundary
Or other region, separate out with the vanadium carbonitride form of micronized particles shape, or precipitation compound with the Ti in steel, suppress austenite crystal
The growth of grain, thus reach crystal grain thinning and put forward high performance purpose.When V content is less than 0.04%, the Carbonitride Precipitation containing V has
Limit, it is difficult to play strengthening effect;As V content > 0.12%, it is easily formed thick carbonitride, deteriorates the toughness plasticity of rail.
Therefore, V content is limited to 0.04%-0.12%.
Ti Main Function in steel is refinement heating, austenite crystal when rolling and cool down, and final increases prolonging of rail
Stretch rate and rigidity, be one of important addition element of the present invention.As Ti content < 0.004%, the carbonization formed in rail
Thing quantity is extremely limited;As Ti content > 0.02%, one side is strong carbonitride-forming elements due to Ti, the TiC of generation
On the high side will make rail much higher hard;On the other hand, TiC is on the high side forms thick carbide by segregation enrichment, not only reduces toughness plasticity,
Rail contact surface under impact loading is also made to be prone to cracking and cause fracture.Therefore, Ti content is limited to 0.004%-
Between 0.02%.
V, Ti constituent content sum is explained in detail below and meets the reason of 0.10%≤V+10Ti≤0.25%: V, Ti in steel with
The affinitys such as C, N and the quantity of formation carbide and form are clearly distinguished from, but form carbonitride fining austenite grains
Effect be similar.As a example by V, in the steel that N content is relatively low, it is solid-solution in the V content of ferrite matrix more than 50%, and N contains
Measuring in higher steel, the V being solid-solution in steel is about 20%, and the form of residue 70% vanadium carbonitride the most separates out.In the present invention
In, individually add V or Ti the most notable to the improvement of performance, as add 0.10% V while without Ti rail strength still
Can reach 1000MPa but elongation percentage is generally below 12%, and individually add Ti microalloying, the intensity of rail is unable to reach
1000MPa requirement, by repeatedly screening, it is believed that V, Ti content sum can reach when meeting 0.10%≤V+10Ti≤0.25%
Purpose of the present invention.
Within N content is limited to 30ppm in the present invention, primarily to suppress the thick nitride containing V, Ti thick
Change, thus reach to be formed the purpose of the carbide suppression Austenite Grain Growth of small and dispersed.
S mainly forms the difference of fragility and the vertically and horizontally performance causing steel in steel with MnS field trash, when S content≤
When 0.008%, purity of steel is higher, can be prevented effectively under wheel stress effect and be formed at the cavity of field trash and formation thereof
Defect, and then affect the military service performance of rail.
Beneficial effects of the present invention:
The rail pearlitic grain using the method manufacture significantly refines, tensile strength >=1000MPa, and elongation percentage >=
14%, there is good tough combination property.
Detailed description of the invention
The satisfied following requirement of rail chemical composition of the present invention: C:0.75%-0.84%, Si:0.30%-0.80%, Mn:
0.50%-1.50%, V:0.04%-0.12%, Ti:0.004%-0.02%, and meet 0.1%≤V+10Ti≤0.25%,
[N]≤30ppm, P≤0.020%, S≤0.015%, surplus is Fe and inevitable impurity.Use converter or electric furnace smelting
Containing the molten steel of mentioned component, al-free deoxidation, reduce after LF refine after S content in steel, RH application of vacuum or VD process and carry out
Molten steel continuous casting in target zone, is that cooling enters after 250mm × 250mm-450mm × 450mm section steel billet by trimming
Heating furnace heats.Billet heating temperature >=1200 DEG C, insulation guarantees to go out after steel billet section blank temperature is uniformly to less than 3h
Stove, removes iron scale through water under high pressure, and rail carries out the start rolling temperature of the first passage and is 1120-1180 DEG C, selects above-mentioned heating
And thicker V, Ti precipitate that the reason of rolling temperature mainly solves to be formed in casting process dissolves or big portion again
Dividing and dissolve, separate out tiny V, Ti carbonitride during steel rail rolling, pinning is in the austenite grain boundary of austenite phase field,
Fining austenite grains, to reach the effect of the present invention.Finishing temperature 840-880 DEG C after five frames or seven frames roll, rolls
Making rail profile minification 6%-12% of last two passages, after finish to gauge, rail stands cold with the cooling rate of≤2.0 DEG C/s at cold bed
But to continuing air cooling when less than 600 DEG C to room temperature.Finishing temperature control is to ensure that have certain particle size the reason of 840-880 DEG C
Precipitate stable, uniformly separate out;When temperature is higher than 880 DEG C, precipitate has the trend of roughening, has relied on the effect separated out
Weaken;When temperature is less than 840 DEG C, precipitate is the most tiny, it is impossible to continue to play the effect of pinning austenite grain boundary;It addition,
In the range of 840-880 DEG C, finishing temperature is the lowest, and in steel, the precipitation effect of V, Ti carbonitride is the most notable.Equally, rail is last
Two passage deformation amount controlling are also the better performances being experimentally verified that at 6%-12%, and being simultaneously in mill load can bear
Deflection scope.Rail completes to continue to continue cool to 600 DEG C with the cooling rate less than 2.0 DEG C/s after rolling arrives cold bed
Main purpose is the formation of thick austenite structure before being still to ensure that pearlitic structrure phase transformation, jointly reaches the present invention with abovementioned steps
Purpose.When rail temperature is less than 600 DEG C, continues to naturally cool to suitable temperature in atmosphere and complete to align, detect a flaw, add
The operations such as work, final acquisition finished product rail.
Hereinafter, a kind of high-strength tenacity pearlite steel rail and production method thereof will be specifically described in conjunction with the embodiments.
Embodiment and corresponding comparative example all select following six groups of rail chemical compositions of the present invention.
Six groups of embodiments of table 1 present invention and comparative example chemical composition
Steel billet containing mentioned component is all rolled into 60kg/m rail, cool down technique after rolling and finish to gauge as shown in table 2;
Comparative example uses existing routine techniques, as shown in table 3.
Six groups of embodiment rollings and roller repairing technological parameter in table 2 present invention
Six groups of comparative example rollings and roller repairing technological parameter in table 3 present invention
By the above-mentioned rail air cooling completing to process to room temperature, carry out rail head tension impact and microscopic structure test, knot respectively
Fruit is shown in Table 4, and wherein, Rm represents tensile strength, and A is elongation after fracture, and wherein tension impact performance test is entered according to GB/T 228
Row test.
Six groups of embodiments of table 4 present invention and comparative example Some Mechanical Properties and microscopic structure
The present invention have chosen has identical chemical composition, different rolling and six groups of embodiments of roller repairing technique and corresponding
Comparative example contrast, all rail tissues are pearlite.In an embodiment, the technique of employing is side of the present invention
Method, separates out uniform, tiny carbonitride particle pinning austenite grain boundary in steel by V, Ti, significantly improves the tough of rail
Plasticity particularly elongation percentage, six groups of rail strengths in the range of 1020MPa-1100MPa while elongation percentage reach 14.5%-
16.0%, there is more excellent obdurability coupling.By contrast, existing maturation process is used the most not to steel rail rolling and to roll rear high temperature
Quite but elongation percentage is significantly lower than embodiment for the comparative example intensity level that section air cooling is controlled and embodiment, and higher plasticity is not only
Ensure that the traffic safety of train, additionally aid the raising of rail contact fatigue.
Although specifically described a kind of controlled rolling pearlite steel rail and production method thereof, but the technology of this area
Personnel it should be understood that without departing from the spirit and scope of the present invention, and the present invention can make various forms of changing
Become.