CN101850408A - Vehicle axle steel continuous casting method - Google Patents
Vehicle axle steel continuous casting method Download PDFInfo
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- CN101850408A CN101850408A CN200910133326A CN200910133326A CN101850408A CN 101850408 A CN101850408 A CN 101850408A CN 200910133326 A CN200910133326 A CN 200910133326A CN 200910133326 A CN200910133326 A CN 200910133326A CN 101850408 A CN101850408 A CN 101850408A
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Abstract
The invention discloses a vehicle axle steel continuous casting method, wherein the method comprises the following steps: casting molten steel with the superheat temperature between 20 and 40 DEG C into a crystallizer for crystallization; forming an incompletely solidified vehicle axle steel casting blank; pulling out the incompletely solidified vehicle axle steel casting blank from the crystallizer to be sequentially sent into a secondary cooling region and an air cooling region to be cooled; reducing the surface temperature of the incompletely solidified vehicle axle steel casting blank to 800 to 850 DEG C; and then, down pressing 4 to 9 mm at the solidification terminal point of the incompletely solidified vehicle axle steel casting blank to obtain a completely solidified vehicle axle steel casting blank, wherein the secondary cooling region comprises the following conditions that a cooling agent adopts water with the temperature between 5 and 40 DEG C, in addition, the specific water capacity is 0.45 to 0.55 L/kg. When being adopted, the vehicle axle steel continuous casting method provided by the invention can improve the production efficiency and the metal yield, in addition, the ingredient segregation of the produced vehicle axle is small, the non-metallic inclusion content is low, the surface quality of the steel blank is good, in addition, the center segregation, the center looseness and the internal crack of the vehicle axle steel produced by the method are obviously reduced, and the invention completely conforms to the standard of the vehicle axle steel.
Description
Technical field
The present invention relates to a kind of axle steel continuous casting method.
Background technology
Axletree is the vitals of rail truck traveling, and its quality is directly connected to the bearing capacity and the transportation safety of vehicle.Along with railway develops to high speed and heavy loading direction, to the production technology and the higher requirement of quality proposition of axletree.Axle steel not only should have higher intensity, also should possess good plasticity, shock resistance and fatigue behaviour.
At present, the Rail vehicle axle steel of China all adopts die casting process production, for example, the existing railroad industry standard TB/T2945-1999 of China " rail truck with LZ50 steel axletree and steel billet technical conditions " has only stipulated that die casting process produces the content of Rail vehicle axle steel aspect.The labour intensity of die casting process is big and environmental pollution is big, and production efficiency is low and recovery rate of iron is low.And the component segregation of die casting process production Rail vehicle axle steel is big, nonmetal inclusion content height, and the surface quality of rolling steel billet is poor, has certain difficulty in the cleanliness factor control of steel.For example, " special steel " magazine (in November, 2005, the 26th the 6th phase of volume, P61-62) reach " this steel technology " magazine (2006 the 1st phases, P22-25) reported that Benxi iron and steel group company adopts converter → LF-IR → RH-TB → die casting → rolling of sectional iron explained hereafter LZ50 axle steel, the finished product chemical composition carbon content fluctuation of steel is at 0.47-0.55 weight %, the silicone content fluctuation is at 0.20-0.40 weight %, the fluctuation of manganese content is at 0.66-0.85 weight %, the macrostructure General Loosen of steel billet is the 0.5-2.5 level, center porosity is the 0.5-1.5 level, and segregation is the 0.5-2.0 level; Nonmetal inclusion category-A (sulfide) is the 0.5-2.5 level, and category-B (oxide) is the 0.5-2.0 level.
Therefore, press for a kind of new axle steel casting technique.
Continuous casting is one of steel casting technology that generally adopts at present, its technological process is generally the molten steel that refining is good and is poured in the tundish (can adorn tens tons of molten steel), and liquid molten steel vertically flows in the crystallizer that failure of oscillation does not move by the aperture under the tundish (immersion long nozzle).Crystallizer external application water under high pressure does not stop cooling, and molten steel forms the outside in crystallizer be that solid inner still is the liquid steel strand that does not solidify fully.Going out behind the crystallizer is the cooling roller bed of one section arc, and strand moves on this cooling roller bed, usually the strand that is solidified fully through two cold-zones and air cooling zone successively.Continuous casting can be produced continuously, enhances productivity; Can realize mechanization, reduce labour intensity; Except that a base and tail base of first stove of continuous pouring and last one heat steel,, therefore, can improve recovery rate of iron owing to do not need the two ends of steel billet are cut; In addition, in casting process,, can promote the come-up of field trash and bubble, thereby effectively reduce field trash and bubble in the molten steel, improve the quality of steel casting billet surface by the stirring of crystallizer electromagnetism.
Yet the steel strand that adopts continuous casting process to prepare is also deposited its intrinsic problem, as internal flaws such as center segregation, center porosities.
Summary of the invention
Production efficiency is low low with recovery rate of iron when producing the axletree strand for the die casting process that overcomes the prior art employing, the component segregation of the axle steel of producing is big, nonmetal inclusion content height, the defective of the surface quality difference of steel billet, provide a kind of production efficiency high and recovery rate of iron height, the component segregation of the axle steel of producing is little, nonmetal inclusion content is low, the axle steel continuous casting method that the surface quality of steel billet is good, and the center segregation of the axle steel of being produced by this method, center porosity etc. meet the standard of axle steel fully.
The present inventor finds, because axle steel belongs to medium carbon steel, in the process of setting of continuous casting, dendrite is relatively more flourishing, form dendrite " bridging " at the strand core easily, process of setting divides the effect of crystallization a large amount of low-melting solutes that made the interdendritic enrichment because of choosing, the residual liquid that the powerful suction force that produces in the solidification shrinkage of solidifying casting blank solidification terminal point solid-liquid two-phase region in latter stage causes enrichment impurity between dendrite to center flow and filling in wherein, thereby cause center segregation, internal flaws such as center porosity are particularly outstanding, thereby directly existing continuous casting technology being applied to prepare axle steel, the axle steel of preparation is difficult to satisfy the requirement of standard.
In continuous experimentation, the present inventor finds, the temperature of molten steel during by control cast simultaneously, the intensity of cooling of two cold-zones, and described strand solidify internal flaws such as center segregation that technological means that terminal point depresses can significantly improve the axle steel that adopts the continuous cast method preparation, center porosity, make the axle steel of preparation meet the standard of axle steel fully.
The invention provides a kind of axle steel continuous casting method, wherein, this method comprises with the degree of superheat being pouring molten steel crystallization to the crystallizer of 20-40 ℃, form the axle steel strand that does not solidify fully, this axle steel strand that does not solidify is fully pulled out from crystallizer, sending into two cold-zones and air cooling zone successively cools off, the surface temperature of the described axle steel strand that does not solidify fully is cooled to 800-850 ℃, depress the 4-9 millimeter at the terminal point that solidifies of the described axle steel strand that does not solidify fully then, the axle steel strand that acquisition is solidified fully, the condition of described two cold-zones comprises that cooling agent employing temperature is 5-40 ℃ a water, and the specific water is 0.45-0.55 liter/kilogram.
Adopt axle steel continuous casting method provided by the invention not only can enhance productivity and recovery rate of iron, and the component segregation of the axle steel of producing is little, nonmetal inclusion content is low, and the surface quality of steel billet is good; In addition, defectives such as the center segregation of the axle steel of being produced by this method, center porosity significantly reduce, and meet the standard of axle steel fully.
The specific embodiment
The invention provides a kind of axle steel continuous casting method, wherein, this method comprises with the degree of superheat being pouring molten steel crystallization to the crystallizer of 20-40 ℃, form the axle steel strand that does not solidify fully, this axle steel strand that does not solidify is fully pulled out from crystallizer, sending into two cold-zones and air cooling zone successively cools off, the surface temperature of the described axle steel strand that does not solidify fully is cooled to 800-850 ℃, depress the 4-9 millimeter at the terminal point that solidifies of the described axle steel strand that does not solidify fully then, the axle steel strand that acquisition is solidified fully, the condition of described two cold-zones comprises that cooling agent employing temperature is 5-40 ℃ a water, and the specific water is 0.45-0.55 liter/kilogram.
In the present invention, the molten steel of any trade mark that the molten steel that uses can be used always as casting vehicle axle steel is preferably LZ50, JZ35 and 35CrMo, most preferably is LZ50.LZ50 is a kind of medium carbon steel, and its carbon content is the 0.47-0.57 weight % of steel weight; LZ50 contains usually, is benchmark with the gross weight of described molten steel, in simple substance, and the C of 0.47-0.57 weight %, 0.17-0.4 the Si of weight %, the Mn of 0.6-0.9 weight %, the P of 0.01-0.02 weight %, 0.004-0.02 the S of weight %, the Als of 0.02-0.06 weight %, surplus is an iron.Molten steel used in the present invention is preferably the medium carbon steel water that has carried out micro-alloying when smelting, and described trace element can be metallic elements such as vanadium, chromium, nickel, calcium.Above-mentioned molten steel can obtain by the prior art smelting molten iron.
Among the present invention, the described degree of superheat is meant that the temperature of molten steel surpasses the number of degrees of this molten steel liquidus temperature.
Described air cooling zone is the common implication of this area, is meant at ambient temperature and carries out the nature cooled zones by the air in the atmosphere.
Described depressing can be realized by the conventional method of this area, for example adopts one or several frame to depress.So-called specific water is meant every kilogram of used water yield of axle steel strand of not solidifying fully of cooling in cooling section.
Because medium carbon steel is easy to generate dendrite, thereby form dendrite " bridging " at the strand core, process of setting divides the effect of crystallization a large amount of low-melting solutes that made the interdendritic enrichment because of choosing, the residual liquid that the powerful suction force that produces in the solidification shrinkage of solidifying casting blank solidification terminal point solid-liquid two-phase region in latter stage causes enrichment impurity between dendrite to center flow and filling in wherein, thereby cause center segregation, center porosity.The present inventor finds, the degree of superheat of molten steel is controlled to be 20-40 ℃, and in two cold-zones, be 5-40 ℃ water by adopting coolant temperature, and the specific water is cooled off the described axle steel strand that does not solidify fully for 0.45-0.55 liter/kilogram uniformly, and behind the described air cooling to the described axle steel strand that does not solidify fully when it solidifies terminal point and depresses the 4-9 millimeter, can significantly improve above-mentioned problem, the axle steel that adopts this method to prepare meets the standard of axle steel fully.
As preferred embodiment a kind of, described molten steel is that the trade mark is the molten steel of LZ50, JZ35 and 35CrMo, and therefore, the temperature of described molten steel can be 1505-1535 ℃.
Because conventional cooling means is to cause one of key factor that occurs dendrite, therefore, the present inventor by a large amount of experiments to improve cooling means, and be surprised to find that, when described two cold-zones comprise at least 3 cooling sections, and, when the temperature reduction value of the described axle steel strand that does not solidify fully in adjacent two cooling sections reduces successively, help to improve the problem that dendrite occurs according to the sequencing that the described axle steel strand that does not solidify fully passes through.In the present invention, described two cold-zones preferably include at least 3 cooling sections.Though the effect of the many more coolings of the number of cooling section is good more, yet, temperature reduction value in described each adjacent cooling section of the axle steel strand that does not solidify fully satisfies under the situation of above condition, when the number of described cooling section surpasses 5, the cooling effect of the described axle steel strand that does not solidify does not fully have significantly and improves, therefore, the number of described cooling section is preferably 3-5, most preferably is 5.
A kind of preferred embodiment in, surface temperature at the described axle steel strand that does not solidify fully in described crystallizer exit is 950-1050 ℃, described two cold-zones comprise 5 cooling sections, the described axle steel strand that does not solidify fully passes through described two cold-zones with identical speed Vc, according to the sequencing that the described axle steel strand that does not solidify fully passes through, the consumption of the water of each cooling section is respectively:
Wherein, S is the area of the described horizontal section of axle steel strand that does not solidify fully, and its unit is a square millimeter, and the unit of Vc is meter/minute, W
1, W
2, W
3, W
4And W
5The consumption of representing the water of first to the 5th cooling section respectively, unit are liter/minute.
When described cooling section was 3 or 4, according to the sequencing that the described axle steel strand that does not solidify fully passes through, the intensity of cooling of each spray cooling section was respectively to go forward 3 or preceding 4.When described cooling section is 5,, guarantee that the intensity of cooling of the first five cooling section is respectively above q according to the sequencing that the described axle steel strand that does not solidify fully passes through
1, q
2, q
3, q
4And q
5And the intensity of cooling of the 5th later cooling section reduces successively and gets final product.
The present invention does not limit especially for the spray mode of each cooling section, and under the preferable case, according to the sequencing that the described axle steel strand that does not solidify fully passes through, first cooling section adopts the water spray cooling, and all the other four cooling sections adopt the cooling of aerosol spray.Because first spray cooling section adopts water spray to force cooling, can increase intensity of cooling, guarantee that the thin solidified shell of crystallizer outlet obtains high-intensity cooling, prevent the axle steel casting billet surface backheat of not solidifying fully from the crystallizer outlet, help preventing the axle steel casting billet surface or the subcrack that do not solidify fully that cause because of thermal stress, simultaneously, by improving intensity of cooling, can increase thickness of solidified slab shell in secondary rapidly, help preventing approaching the bleed-out accident that bulge seriously causes because of crystallizer outlet base shell; And it is thicker at cooling section base shell subsequently, adopt the cooling of aerosol spray, can obviously reduce intensity of cooling and improve cooling uniformity, thereby can effectively reduce the internal-external temperature difference and the consequent thermal stress of solidified shell, reduce the danger that continuous casting billet produces underbead crack.Described aerosol can obtain after using atomizer with the aqueous water atomizing, and described atomizer can be to well known to a person skilled in the art various atomizers, and the diameter of atomizing back water droplet is 20-200 μ m, is preferably 50-100 μ m.
In the cooling means of the present invention, the speed of the described axle steel strand that does not solidify fully by each cooling section is not limited especially, yet, consider the intensity of the base shell of the described axle steel strand that does not solidify fully, the described axle steel strand that does not solidify fully is by the speed V of each cooling section
cCan for 0.3-0.8 rice/minute, be preferably 0.4-0.7 rice/minute.
After obtaining the described axle steel strand that solidifies fully, under the preferable case, method provided by the invention also comprises the step that steel billet is rolled, described rolling condition can be the rolling condition of routine, be preferably and earlier the described axle steel strand that solidifies fully be heated to 1250 ℃-1280 ℃, carry out laggard capable multi-pass pressure rolling in insulation under 1230 ℃-1250 ℃ after 1.5-2.0 hour then.Under the preferable case, after the described axle steel strand that solidifies is fully come out of the stove and before rolling, at first carry out de-scaling, to remove iron scale with water under high pressure.
In order to alleviate defectives such as center porosity as far as possible, of the present invention one preferred embodiment in, when rolling, the road number of times of described pressure rolling is 7-9 time, and is the 70-90 millimeter in the amount of the pressure rolling of 5-6 passage, the amount of the pressure rolling of all the other passages is the 15-60 millimeter.
In the present invention, described crystallization is meant that molten steel forms the process of the steel strand that does not solidify fully by cooling in crystallizer.Cooling means can be the method for this area routine, for example adopts water cooling.The speed of the routine that the speed of cooling can adopt for this area, the vibration frequency of crystallizer can be the conventional frequency that adopt this area.A kind of preferred embodiment in, the condition of described crystallization comprises that adopting frequency is that the agitator of 2-2.4 hertz stirs, stir current is 350-600A, adopt 5-40 ℃ water to cool off, the consumption of cooling water makes the surface temperature at the described axle steel strand that does not solidify fully in described crystallizer exit be 950-1050 ℃, for the LZ50 steel, the surface temperature of axle steel strand is preferably 980-1020 ℃.
Embodiment 1
Present embodiment is used to illustrate axle steel continuous casting method provided by the invention.
Continuous casting: the Ni, the molten steel that surplus is Fe of Cr, 0.04 weight % of Als (sour molten aluminium), 0.03 weight %Cu, 0.03 weight % of S, 0.02 weight % of P, 0.006 weight % of Mn, 0.012 weight % of Si, 0.82 weight % that will consist of C, the 0.35 weight % of 0.53 weight % is poured into the crystallizer from tundish.The temperature that the interior molten steel of tundish promptly advances the molten steel before the crystallizer is that (mean temperature is 1519 ℃ (measuring the mean value of temperature value several times) to 1507-1522, the liquidus temperature of LZ50 steel is 1485 ℃, the cast degree of superheat is 22-37 ℃, pouring into a mould the average degree of superheat is 34 ℃), crystallizer electromagnetic agitation electric current 600A, stirring frequency 2.4Hz.With 25 ℃ of cold water crystallizer is cooled off, the surface temperature that makes the axle steel strand that does not solidify fully in the crystallizer exit is 1020 ℃.With about 0.3 meter/minute pulling rate the described axle steel strand that does not solidify fully (laterally section be 360 millimeters * 450 millimeters) is pulled out during beginning and enter two cold-zones and cool off, two cold-zone specific waters are 0.54 liter/kilogram under this pulling rate.Then pulling rate progressively is stabilized in 0.50 meter/minute, two cold-zone specific waters are 0.447 liter/kilogram under this pulling rate.Described two cold-zones are divided into five cooling sections, first cooling section adopts the shower water cooling, all the other cooling sections adopt the aerosol cooling, wherein, the temperature of water is 18 ℃, and the temperature of aerosol is 20-30 ℃, when pulling rate is stabilized in 0.50 meter/minute, according to the sequencing of the described axle steel strand that does not solidify fully by cooling section, the water consumption of five cooling sections is respectively 40.82 liters/minute, 76.84 liters/minute, 49.54 liters/minute, 71.38 liters/minute and 26.48 liters/minute.It is 820 ℃ that axle steel strand that will not solidify fully by air cooling zone behind two cold-zones is cooled to its surface temperature, and carries out machinery and depress the axle steel strand that is solidified fully at the terminal point that solidifies of the axle steel strand that does not solidify fully.Described depressing adopts 7 frames to depress operation, and overall reduction is 4.2 millimeters.
Rolling: the axle steel strand that solidifies of above-mentioned acquisition is heated to 1260 ℃, comes out of the stove after 2.0 hours in insulation under 1230 ℃ of temperature then, be 3.8 hours total heat time heating time, and tapping temperature is 1150 ℃.Method routinely adopts then
Milling train begins pressure rolling axletree steel billet, and (250mm * 250mm), be total to pressure rolling 9 passages, wherein the amount of each road pressure rolling of 1-9 road is respectively 40 millimeters, 40 millimeters, 40 millimeters, 50 millimeters, 60 millimeters, 60 millimeters, 60 millimeters, 30 millimeters and 15 millimeters.Finishing temperature is 980 ℃.Axletree steel billet after rolling is concentrated the stacking cooling.Obtain LZ50 axletree continuous casting steel billet sample A1.
Comparative Examples 1
Continuous casting: the method according to embodiment 1 is carried out, different is that the temperature of molten steel is 1522-1541 ℃, and (mean temperature is 1536 ℃ (measuring the mean value of temperature value several times), and the liquidus temperature of LZ50 steel is 1485 ℃, the cast degree of superheat is 37-56 ℃, and pouring into a mould the average degree of superheat is 51 ℃); Specific water in whole two cold-zones is 0.38 liter/kilogram, the intensity of cooling of each section is compared to some extent with embodiment 1 and is weakened, and the water consumption of five cooling sections is respectively 40.82 liters/minute, 72.78 liters/minute, 45.60 liters/minute, 52.34 liters/minute and 24.64 liters/minute.To cool off by air cooling zone behind two cold-zones, making the axle steel strand that does not solidify fully be cooled to its surface temperature is 850 ℃, and does not carry out machinery and depress at the terminal point that solidifies of strand.
Rolling: the method according to embodiment 1 is carried out, and obtains LZ50 axletree continuous casting steel billet sample CA1.
Embodiment 2
Present embodiment is used to illustrate axle steel continuous casting method provided by the invention.
Continuous casting: the method according to embodiment 1 is carried out.
Rolling: the axle steel strand that solidifies of above-mentioned acquisition is heated to 1260 ℃, comes out of the stove after 2.0 hours in insulation under 1230 ℃ of temperature then, be 3.8 hours total heat time heating time, and tapping temperature is 1150 ℃.Method routinely adopts then
Milling train begins pressure rolling axletree steel billet, and (wherein the amount of each road pressure rolling of 1-9 road is respectively 40 millis, 40 millimeters, 40 millimeters, 50 millimeters, 70 millimeters, 85 millimeters, 35 millimeters, 20 millimeters and 15 millimeters for 250mm * 250mm), pressure rolling 9 passages altogether.Finishing temperature is 980 ℃.Axletree steel billet after rolling is concentrated the stacking cooling.Obtain LZ50 axletree continuous casting steel billet sample A2.
Embodiment 3
Present embodiment is used to illustrate axle steel continuous casting method provided by the invention.
Continuous casting: the molten steel of Ni of Cr, 0.04 weight % of Als (sour molten aluminium), 0.03 weight %Cu, 0.04 weight % of S, 0.03 weight % of P, 0.008 weight % of Mn, 0.009 weight % of Si, 0.82 weight % that will contain C, the 0.38 weight % of 0.54 weight % is poured into the crystallizer from tundish.The temperature of the molten steel of tundish is 1518-1525 ℃, and (mean temperature is 1523 ℃ (measuring the mean value of temperature value several times), the liquidus temperature of LZ50 steel is 1485 ℃, the cast degree of superheat is 33-40 ℃, pouring into a mould the average degree of superheat is 38 ℃), crystallizer electromagnetic agitation electric current 500A, stirring frequency 2.0Hz.With cold water crystallizer is cooled off, the surface temperature that makes the axle steel strand that does not solidify fully in the crystallizer exit is 1000 ℃.Being about 0.6 meter/minute with pulling rate pulls out the described axle steel strand that does not solidify fully (laterally section be 360 millimeters * 450 millimeters) and enters two cold-zones and cool off.Described two cold-zones are divided into five cooling sections, first cooling section adopts the shower water cooling, all the other cooling sections adopt the aerosol cooling, wherein, the temperature of water is 20-25 ℃, the temperature of aerosol is 25-30 ℃, and according to the sequencing of the described axle steel strand that does not solidify fully by cooling section, the water consumption of five cooling sections is respectively 43.82 liters/minute, 91.14 liters/minute, 59.24 liters/minute, 84.65 liters/minute and 31.36 liters/minute.Specific water in whole two cold-zones is 0.45 liter/minute.It is 810 ℃ that axle steel strand that will not solidify fully by air cooling zone behind two cold-zones is cooled to its surface temperature, and carries out machinery and depress the axle steel strand that is solidified fully at the terminal point that solidifies of the axle steel strand that does not solidify fully.Described depressing adopts 7 frames to depress operation, and overall reduction is 6.5 millimeters.
Rolling: the axle steel strand that solidifies of above-mentioned acquisition is heated to 1250 ℃, comes out of the stove after 2 hours in insulation under 1230 ℃ of temperature then, be 4.00 hours total heat time heating time, and tapping temperature is 1150 ℃.Method routinely adopts then
Milling train begins pressure rolling axletree steel billet, and (250mm * 250mm), be total to pressure rolling 9 passages, wherein the amount of each road pressure rolling of 1-9 road is respectively 40 millimeters, 40 millimeters, 40 millimeters, 50 millimeters, 75 millimeters, 85 millimeters, 40 millimeters, 20 millimeters and 15 millimeters.Finishing temperature is 980 ℃.Axletree steel billet after rolling is concentrated the stacking cooling.Obtain LZ50 axletree continuous casting steel billet sample A3.
Embodiment 4
Present embodiment is used to illustrate axle steel continuous casting method provided by the invention.
Continuous casting: the molten steel of Ni of Cr, 0.04 weight % of Als (sour molten aluminium), 0.03 weight %Cu, 0.04 weight % of S, 0.03 weight % of P, 0.007 weight % of Mn, 0.012 weight % of Si, 0.77 weight % that will contain C, the 0.31 weight % of 0.53 weight % is poured into the crystallizer from tundish.The temperature of the molten steel of tundish is 1505-1511 ℃, and (mean temperature is 1507 ℃ (measuring the mean value of temperature value several times), the liquidus temperature of LZ50 steel is 1485 ℃, the cast degree of superheat is 20-26 ℃, pouring into a mould the average degree of superheat is 22 ℃), crystallizer electromagnetic agitation electric current 350A, stirring frequency 2.0Hz.With cold water crystallizer is cooled off, the surface temperature that makes the axle steel strand that does not solidify fully in the crystallizer exit is 980 ℃.Being about 0.7 meter/minute with pulling rate pulls out the described axle steel strand that does not solidify fully (laterally section be 360 millimeters * 450 millimeters) and enters two cold-zones and cool off.Described two cold-zones are divided into five cooling sections, first cooling section adopts the shower water cooling, all the other cooling sections adopt the aerosol cooling, wherein, the temperature of water is 17-25 ℃, the temperature of aerosol is 20-30 ℃, and according to the sequencing of the described axle steel strand that does not solidify fully by cooling section, the water consumption of five cooling sections is respectively 54.5 liters/minute, 107.65 liters/minute, 70.92 liters/minute, 100.59 liters/minute and 37.25 liters/minute.Specific water in whole two cold-zones be 0.45 liter/kilogram will not solidify fully behind two cold-zones by air cooling zone the axle steel strand to be cooled to its surface temperature be 800 ℃, and carry out machinery and depress the axle steel strand that is solidified fully at the terminal point that solidifies of the axle steel strand that does not solidify fully.Described depressing adopts 7 frames to depress operation, and overall reduction is 8.8 millimeters.
Rolling: the axle steel strand that solidifies of above-mentioned acquisition is heated to 1280 ℃, comes out of the stove after 1.5 hours in insulation under 1250 ℃ of temperature then, be 3.5 hours total heat time heating time, and tapping temperature is 1200 ℃.Method routinely adopts then
Milling train begins pressure rolling axletree steel billet, and (250mm * 250mm), be total to pressure rolling 9 passages, wherein the amount of each road pressure rolling of 1-9 road is respectively 40 millimeters, 40 millimeters, 40 millimeters, 40 millimeters, 80 millimeters, 90 millimeters, 30 millimeters, 20 millimeters and 15 millimeters.Finishing temperature is 1020 ℃.Axletree steel billet after rolling is concentrated the stacking cooling.Obtain LZ50 axletree continuous casting steel billet sample A4.
Embodiment 5
Continuous casting: the Ni, the molten steel that surplus is Fe of Cr, 0.03 weight % of Als (sour molten aluminium), 0.03 weight %Cu, 0.10 weight % of S, 0.04 weight % of P, 0.005 weight % of Mn, 0.013 weight % of Si, 0.93 weight % that will consist of C, the 0.38 weight % of 0.35 weight % is poured into the crystallizer from tundish.The interior molten steel of tundish promptly advances 1518-1524 ℃ preceding molten steel of crystallizer, and (mean temperature is 1521 ℃ (measuring the mean value of temperature value several times), the liquidus temperature of JZ35 steel is 1496 ℃, the cast degree of superheat is 22-28 ℃, pouring into a mould the average degree of superheat is 25 ℃), crystallizer electromagnetic agitation electric current 600A, stirring frequency 2.4Hz.With cold water crystallizer is cooled off, the surface temperature that makes the axle steel strand that does not solidify fully in the crystallizer exit is 1050 ℃.With about 0.5 meter/minute pulling rate the described axle steel strand that does not solidify fully (laterally section be 360 millimeters * 450 millimeters) is pulled out and to enter two cold-zones and cool off, its two cold specific water is 0.45 liter/kilogram under this pulling rate.Described two cold-zones are divided into five cooling sections, first cooling section adopts the shower water cooling, all the other cooling sections adopt the aerosol cooling, wherein, the temperature of water is 20-25 ℃, and the temperature of aerosol is 25-30 ℃, when pulling rate is stabilized in 0.50 meter/minute, according to the sequencing of the described axle steel strand that does not solidify fully by cooling section, the water consumption of five cooling sections is respectively 40.82 liters/minute, 76.84 liters/minute, 49.54 liters/minute, 71.38 liters/minute and 26.48 liters/minute.It is 830 ℃ that axle steel strand that will not solidify fully by air cooling zone behind two cold-zones is cooled to its surface temperature, and carries out machinery and depress the axle steel strand that is solidified fully at the terminal point that solidifies of the axle steel strand that does not solidify fully.Described depressing adopts 7 frames to depress operation, and overall reduction is 7.5 millimeters.
Rolling: the axle steel strand that solidifies of above-mentioned acquisition is heated to 1270 ℃, comes out of the stove after 2.0 hours in insulation under 1240 ℃ of temperature then, be 3.8 hours total heat time heating time, and tapping temperature is 1170 ℃.Method routinely adopts then
Milling train begins pressure rolling axletree steel billet, and (250mm * 250mm), be total to pressure rolling 9 passages, wherein the amount of each road pressure rolling of 1-9 road is respectively 40 millimeters, 40 millimeters, 40 millimeters, 50 millimeters, 75 millimeters, 85 millimeters, 40 millimeters, 20 millimeters and 15 millimeters.。Finishing temperature is 1020 ℃.Axletree steel billet after rolling is concentrated the stacking cooling, obtains JZ35 axletree continuous casting steel billet sample A5.
Comparative Examples 2
Continuous casting: the method according to embodiment 5 is carried out, different is that the temperature of molten steel is 1531-1558 ℃, and (mean temperature is 1541 ℃ (measuring the mean value of temperature value several times), and the liquidus temperature of JZ35 steel is 1496 ℃, the cast degree of superheat is 35-62 ℃, and pouring into a mould the average degree of superheat is 45 ℃); Specific water in whole two cold-zones is 0.38 liter/kilogram, the intensity of cooling of each section is compared to some extent with embodiment 5 and is weakened, and the water consumption of five cooling sections is respectively 40.82 liters/minute, 72.78 liters/minute, 45.60 liters/minute, 52.34 liters/minute and 24.64 liters/minute.To cool off by air cooling zone behind two cold-zones, making the axle steel strand that does not solidify fully be cooled to its surface temperature is 850 ℃, and does not carry out machinery and depress at the terminal point that solidifies of strand.
Rolling: the method according to embodiment 5 is carried out, and obtains JZ35 axletree continuous casting steel billet sample CA2.
The detection method of each composition adopts carbon steel and middle-low alloy steel spark source Atomic Emission Spectral Analysis method respectively in the above-mentioned experiment, and national standard is GB/T4336.
The continuous casting steel billet performance test
Axletree is made in the steel billet A1-A5 and the CA1-2 forging of above-mentioned preparation, heat-treated the inspection by sampling performance then.Technology for Heating Processing: normalizing: 850-880 ℃ for the first time, normalizing: 800-820 ℃ for the second time, tempering: 500-540 ℃.Tensile property carries out according to GB/T228 metal material tensile test at room temperature method.According to GB/T226-1991 continuous casting and rolling steel billet are carried out the acidleach macroscopic examination, its face crack, rimhole, subsurface inclusion, underbead crack, center porosity and center segregation defective are detected and grade according to YB/T153-1999 and GB/T1979-2001, in its results list 1.
Table 1
| ??A1 | ??CA1 | ??A2 | ??A3 | ??A4 | ??A5 | ??CA2 | |
| Surface and subcrack (level) | Do not have | Do not have | Do not have | Do not have | Do not have | Do not have | Do not have |
| Rimhole (level) | Do not have | Do not have | Do not have | Do not have | Do not have | Do not have | Do not have |
| Subsurface inclusion (level) | Do not have | Do not have | Do not have | Do not have | Do not have | Do not have | Do not have |
| Underbead crack (level) | ??0 | ??1.5 | ??0 | ??0 | ??0 | ??0 | ??2.0 |
| Strand central pipe (level) | ??0 | ??1.0 | ??0 | ??0 | ??0 | ??0 | ??1.5 |
| Strand center segregation (level) | ??1.0 | ??1.5 | ??1.0 | ??0.5 | ??0.5 | ??1.5 | ??2.0 |
| Strand center porosity (level) before rolling | ??1.5 | ??2.0 | ??1.5 | ??0.5 | ??0.5 | ??1.5 | ??2.5 |
| Rolling back steel billet center porosity (level) | ??1.0 | ??1.5 | ??0.5 | ??0.5 | ??0.5 | ??1.0 | ??2.0 |
| Tensile strength (MPa) | ??745 | ??725 | ??745 | ??755 | ??720 | ??635 | ??635 |
| Yield strength (MPa) | ??420 | ??400 | ??420 | ??425 | ??410 | ??385 | ??380 |
| Percentage elongation (%) | ??21.5 | ??20.5 | ??21.5 | ??22 | ??20.5 | ??28 | ??28 |
| The contraction percentage of area (%) | ??41.5 | ??40.5 | ??42 | ??42 | ??40.5 | ??/ | ??/ |
| Ultrasonic flaw detection qualification rate (%) | ??98.0 | ??80.0 | ??100 | ??100 | ??100 | ??100 | ??85 |
As can be seen from Table 1, adopt the axletree steel billet of continuous cast method production provided by the invention not have surface and subcrack, defective such as also do not have rimhole, be mingled with.The axletree steel billet that adopts method provided by the invention to produce does not need to carry out the removing surface and the processing that strips off the skin; In addition, adopt the underbead crack of the axletree steel billet of method production provided by the invention, center porosity and center segregation are starkly lower than the underbead crack of the axletree steel billet that adopts conventional continuous cast method preparation, defectives such as center porosity and center segregation, thus obviously promoted the internal soundness of axletree steel billet.
Claims (8)
1. axle steel continuous casting method, it is characterized in that, this method comprises with the degree of superheat being pouring molten steel crystallization to the crystallizer of 20-40 ℃, form the axle steel strand that does not solidify fully, this axle steel strand that does not solidify is fully pulled out from crystallizer, sending into two cold-zones and air cooling zone successively cools off, the surface temperature of the described axle steel strand that does not solidify fully is cooled to 800-850 ℃, depress the 4-9 millimeter at the terminal point that solidifies of the described axle steel strand that does not solidify fully then, the axle steel strand that acquisition is solidified fully, the condition of described two cold-zones comprises that cooling agent employing temperature is 5-40 ℃ a water, and the specific water is 0.45-0.55 liter/kilogram.
2. method according to claim 1, wherein, the temperature of described molten steel is 1505-1535 ℃.
3. method according to claim 1, wherein, surface temperature at the described axle steel strand that does not solidify fully in described crystallizer exit is 950-1050 ℃, described two cold-zones comprise 5 cooling sections, the described axle steel strand that does not solidify fully passes through described two cold-zones with identical speed Vc, according to the sequencing that the described axle steel strand that does not solidify fully passes through, the consumption of the water of each cooling section is respectively:
Wherein, S is the area of the described horizontal section of axle steel strand that does not solidify fully, and its unit is a square millimeter, and the unit of Vc is meter/minute, W
1, W
2, W
3, W
4And W
5The consumption of representing the water of first to the 5th cooling section respectively, unit are liter/minute.
4. method according to claim 3, wherein, Vc be 0.4-0.7 rice/minute.
5. method according to claim 1, wherein, this method also comprises the described axle steel strand that solidifies fully is rolled.
6. method according to claim 5, wherein, with the described axle steel strand that fully solidify be heated to 1250-1280 ℃ earlier described rolling comprising, carries out the multi-pass pressure rolling in insulation under 1230-1250 ℃ after 1.5-2.0 hour then.
7. according to claim 1,5 or 6 described methods, wherein, the road number of times of described pressure rolling is 7-9 time, and is the 70-90 millimeter in the amount of the pressure rolling of 5-6 passage, and the amount of the pressure rolling of all the other passages is the 15-60 millimeter.
8. method according to claim 1, wherein, the condition of described crystallization comprises that adopting frequency is that the agitator of 2-2.4 hertz stirs, stir current is the 350-600 ampere; Adopt 5-40 ℃ water to carry out crystallisation by cooling, it is 950-1050 ℃ that the consumption of cooling water makes the surface temperature at the described axle steel strand that does not solidify fully in described crystallizer exit.
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Cited By (5)
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| CN102218516A (en) * | 2011-07-29 | 2011-10-19 | 攀钢集团有限公司 | Continuous casting method of high chrome steel |
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| CN102218516A (en) * | 2011-07-29 | 2011-10-19 | 攀钢集团有限公司 | Continuous casting method of high chrome steel |
| CN102218516B (en) * | 2011-07-29 | 2013-01-09 | 攀钢集团有限公司 | Continuous casting method of high chrome steel |
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