CN102581555B - P91 seamless steel pipe and method for manufacturing same - Google Patents
P91 seamless steel pipe and method for manufacturing same Download PDFInfo
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- CN102581555B CN102581555B CN201210039842.9A CN201210039842A CN102581555B CN 102581555 B CN102581555 B CN 102581555B CN 201210039842 A CN201210039842 A CN 201210039842A CN 102581555 B CN102581555 B CN 102581555B
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Abstract
The invention provides a P91 seamless steel pipe and a method for manufacturing the P91 seamless steel pipe. The method comprises the following steps: smelting a blank: performing smelting, refining, vacuum degassing and round-blank continuous casting on raw materials to obtain the blank; annealing: performing high-temperature diffusion annealing and low-temperature isothermal annealing on the blank; rolling the blank periodically: heating the annealed blank uniformly, hot rolling, perforating, sizing and cooling; and carrying out thermal treatment: heating the blank rolled periodically to 1,040-1,080 DEG C, normalizing, preserving heat, cooling, heating to 750-800 DEG C, performing tempering, preserving heat and cooling to obtain the P91 seamless steel pipe. The content of P in the raw materials is less than or equal to 0.015%, and the content of S content is less than 0.007%. and the diameter phi of the seamless steel pipe is 325-720mm. The P91 seamless steel pipe manufactured by adopting the method is compact in internal structure and excellent in performance. The metal yielding rate and the steel pipe forming yield are improved, the production cost is reduced, and resources are saved.
Description
Technical field
The present invention relates to the manufacture field of seamless steel pipe, in particular to a kind of P91 seamless steel pipe and preparation method thereof.
Background technology
P91 steel is at 9Cr-1Mo(P9) on the basis of steel, by adding a small amount of Nb, V micro alloying element and controlling a kind of novel ferrite type heat resisting steel of the content exploitation of N element.This steel heat resistance is good, reached the level of Austenitic heat resisting steel creep rupture strength, comprehensive mechanical property is excellent, thermal conductance is high, linear expansion coefficient is low, there is good quenching degree and solderability, be widely used in manufacturing the parts such as high temperature superheater, high temperature reheater pipeline and main steam line of super (super-) critical thermal power generation unit.
At present, along with the development of China's thermal power generation unit to high parameter, large capacity, environment-friendly type direction, to the demand of P91 steel pipe, by being the trend rising year by year, particularly to the demand of heavy caliber P91 seamless steel pipe, will increasingly increase.Since China carries out the production production domesticization of T/P91 seamless steel pipe the nineties in 20th century, the domestic technological process that also has many trial-production and production large aperture P91 seamless steel pipe, as the steel ingot punching+pipe pushing technology of Wuhan 471 factories, forging pipe+Pilger pipe mill tube-rolling technique of PanGang Group Chengdu Steel and Iron Co.,Ltd Chengdu 65 factories, forging pipe+460PQF continuous rolling process of Tianjin Steel Tube Group Co., Ltd, oblique milling tube-making process of forging pipe+bis-roller of Yangzhou Chengde Steel Tube Co., Ltd., the steel ingot of Inner Mongol north heavy industry group company and HeBei HongRun Heavy Manufacturing Group Co., Ltd is forged into rod+boring process etc.The hot extrusion technique that 3.5 ten thousand tons of vertical extruders of main flow production technology Shi Yi U.S. Wyman Gordon company of external heavy caliber P91 seamless steel pipe are representative.
But the production technology of above-mentioned technology not only long flow path, metal consumption is high, and unstable product quality.The demand of facing P91 steel pipe will be the trend rising year by year, and we need a kind of new manufacture method of exploitation badly, to shorten the technological process of production, and the high-quality P91 seamless steel pipe that reduces costs and obtain.
Summary of the invention
The present invention aims to provide a kind of preparation method of P91 seamless steel pipe, and to solve, in prior art, the technological process of production is long, metal consumption is high, unstable product quality problem.
The preparation method who the invention provides a kind of P91 seamless steel pipe, comprises the following steps: blank is smelted, and raw material, through smelting-refining-vacuum outgas-continuous casting circular tube blank technique, is made to blank; Annealing in process, carries out high temperature diffusion annealing or low temperature isothermal annealing by blank; Pilger mill, by the blank soaking of annealed processing, soaking temperature is 1230～1270 ℃, soaking temperature deviation ± 10 ℃ keep 1.5～3h; Blank after soaking is carried out to hot-puncturing process, and the temperature of hot-puncturing process is 1100～1200 ℃; Then carry out pepriodic rolling, the temperature of pepriodic rolling is 950～1100 ℃, carries out sizing and cooling processing; And heat treatment, the steel pipe through pilger mill is heated to 1040～1080 ℃, carry out normalizing, cooling after insulation, be then heated to 750～800 ℃, carry out tempering, cooling after insulation, make P91 seamless steel pipe; Wherein, in raw material, P content is less than or equal to 0.015%, S content and is less than 0.007%, and the bore of seamless steel pipe is Φ 325～720mm.
Further, in above-mentioned raw materials, the quality percentage composition of each chemical composition is: C0.08～0.12%, Si0.20～0.45%, Mn0.35～0.55%, P≤0.015%, S < 0.007%, Cu≤0.15%, Ni≤0.20%, Cr8.10～9.30%, Mo0.85～1.05%, V0.18～0.23%, Nb0.06～0.10%, N0.030～0.070%, Al≤0.020%, Ti≤0.010%, Zr≤0.010%, surplus is Fe and impurity.
Further, after above-mentioned heat treatment step, steel pipe is carried out to Surface Machining step.
Further, above-mentioned continuous casting circular tube blank technique comprises: molten steel is injected in the crystallizer of circular-arc type continuous casting machine, employing mold liquid level automated watch-keeping facility is monitored the temperature of molten steel and controlled the degree of superheat of molten steel, according to molten steel overheat, regulates in real time casting speed; Molten steel is frozen into and take the base shell that molten steel is the liquid heart along the tube wall of crystallizer copper pipe, adopts two way alternate rotating excitation field to stir the solidification end of strand, adopts the end molten steel applied thrust of electromagnetism accelerator to strand; When strand enters after the arcuate guide section of circular-arc type continuous casting machine, by two cold-zones of arcuate guide section leading portion periphery, divide three sections strand to be carried out cooling, comprise that water ring water spray in Zu Gun district is cooling, active segment top aerosol is cooling and active segment bottom aerosol is cooling; Strand is carried out to continuous straightening; And strand cutting, slow cooling after aligning are obtained to continuous casting circular tube blank.
Further, the temperature of above-mentioned high temperature diffusion annealing is 950～1100 ℃; The isothermal annealed temperature of low temperature is 600～800 ℃.
Further, before above-mentioned blank is carried out to equal heat treatment, to the blank heat treated that heats up, successively through heat-recovery section, preheating section, heating I section, heating II section, heating III section and six sections of heating IV section, target temperature≤800 ℃ of heat-recovery section, 900 ± 10 ℃ of the target temperatures of preheating section, 1000 ± 10 ℃ of the target temperatures of heating I section, 1150 ± 10 ℃ of the target temperatures of heating II section, 1230 ± 10 ℃ of the target temperatures of heating III section, 1260 ± 10 ℃ of the target temperatures of heating IV section.
Further, the sizing reduction of above-mentioned hot-puncturing process is controlled between 70～160mm, and wall thickness reducing amount is controlled between 15～60mm.
Further, in above-mentioned heat treatment step, the temperature retention time >=40min of normalizing, the temperature retention time >=120min of tempering.
Further, in above-mentioned heat treatment step, normalizing is cooling according to the difference of thickness of steel pipe, adopts air cooling, air-cooled, mist is cold or spraying cooling, as the wall thickness < of steel pipe 30mm, adopts air cooling to process; When the wall thickness range of steel pipe is 30mm-60mm, adopt spraying cooling processing; And the wall thickness >60mm that works as steel pipe, adopt spraying cooling to process.
Further, in above-mentioned heat treatment step, the cooling employing air cooling of tempering is processed.
It is a kind of by the prepared P91 seamless steel pipe of preparation method of the present invention that the present invention also provides.
The technique effect that the present invention reaches: preparation in accordance with the present invention, produce P91 seamless steel pipe, steel duct dense structure, function admirable, can meet main steam line, reheaing steam pipe and the header of super (super-) critical fired power generating unit and the requirement of identical service condition pipeline completely, and this technique not only production procedure is short, recovery rate of iron and the Tube yield of heavy caliber P91 seamless steel pipe have been improved simultaneously, reduced production cost, saved resource, thereby a kind of technological process of producing the seamless steel pipe of heavy caliber, high alloy content is provided.
Except object described above, feature and advantage, the present invention also has other object, feature and advantage.Below with reference to figure and the specific embodiment the present invention is further detailed explanation.
Accompanying drawing explanation
Figure of description is used to provide a further understanding of the present invention, forms a part of the present invention, and schematic description and description of the present invention is used for explaining the present invention, does not form inappropriate limitation of the present invention.In the accompanying drawings:
Fig. 1 shows the flow chart of the preparation method of P91 seamless steel pipe according to the present invention;
Fig. 2 shows according to the microstructure of the P91 seamless steel pipe of first embodiment of the invention.
The specific embodiment
Below in conjunction with the accompanying drawing in the embodiment of the present invention, technical scheme in embodiments of the invention is described in detail, but following embodiment and accompanying drawing are only to understand the present invention, and can not limit the present invention, the multitude of different ways that the present invention can be defined by the claims and cover is implemented.
In a kind of typical embodiment of the present invention, a kind of preparation method of P91 seamless steel pipe is provided, as shown in Figure 1, comprise the following steps: blank is smelted, raw material, through smelting-refining-vacuum outgas-continuous casting circular tube blank technique, is made to blank; Annealing in process, carries out high temperature diffusion annealing or low temperature isothermal annealing by blank; Pilger mill, by the blank soaking of annealed processing, soaking temperature is 1230～1270 ℃, soaking temperature deviation ± 10 ℃ keep 1.5～3h; Blank after soaking is carried out to hot-puncturing process, and the temperature of hot-puncturing process is 1100～1200 ℃; Then carry out pepriodic rolling, the temperature of pepriodic rolling is 950～1100 ℃, carries out sizing and cooling processing; And heat treatment, the steel pipe through pilger mill is heated to 1040～1080 ℃, carry out normalizing, cooling after insulation, be then heated to 750～800 ℃, carry out tempering, cooling after insulation, make P91 seamless steel pipe; Wherein, in raw material, P content is less than or equal to 0.015%, S content and is less than 0.007%, and the bore of seamless steel pipe is Φ 325～720mm.
The present invention adopts continuous casting process to obtain blank, has avoided as much as possible the generation of slab surface crack, middle crack and aligning crackle, has improved the centre burst of strand; To the blank processing of annealing, reduced continuous casting billet internal stress, reduced blank hardness, be conducive to sawing; Pilger mill technique is because it is forged, rolls, squeezes the mode of texturing combining, and deflection is large, is applicable to very much producing heavy caliber seamless steel pipe; Adopt Technology for Heating Processing, guaranteed the uniformity of steel pipe austenitizing, improve the high-temperature behavior of steel pipe; And the content of P, S in control raw material, avoided P, S to reduce the toughness of steel pipe.The method according to this invention is produced P91 seamless steel pipe, bore can be between Φ 325～720mm, steel duct dense structure, function admirable, can meet main steam line, reheaing steam pipe and the header of super (super-) critical fired power generating unit and the requirement of identical service condition pipeline completely, and this technique not only production procedure is short, recovery rate of iron and the Tube yield of heavy caliber P91 seamless steel pipe have been improved simultaneously, reduced production cost, saved resource, thereby a kind of technological process of producing the seamless steel pipe of heavy caliber, high alloy content is provided.
During the present invention is raw materials used, the quality percentage composition of each chemical composition is: C0.08～0.12%, Si0.20～0.45%, Mn0.35～0.55%, P≤0.015%, S < 0.007%, Cu≤0.15%, Ni≤0.20%, Cr8.10～9.30%, Mo0.85～1.05%, V0.18～0.23%, Nb0.06～0.10%, N0.030～0.070%, Al≤0.020%, Ti≤0.010%, Zr≤0.010%, surplus is Fe and impurity.
The present invention adopts and first the chemical composition in raw material is optimized, avoid some harmful components as elements such as P, S, toughness and plasticity with steel pipe can have a negative impact, and the circular pipe blank performance of using the raw material after optimizing to produce is more stable, meets the instructions for use as seamless steel pipe raw material.
The present invention, after heat treatment step, carries out Surface Machining step to steel pipe.After aligning and Surface Machining, the surface property of steel pipe is better, the requirement of the more realistic application of product obtaining.
Continuous casting circular tube blank technique of the present invention comprises: molten steel is injected in the crystallizer of circular-arc type continuous casting machine, employing mold liquid level automated watch-keeping facility is monitored the temperature of molten steel and controlled the degree of superheat of molten steel, according to molten steel overheat, regulates in real time casting speed; Molten steel is frozen into and take the base shell that molten steel is the liquid heart along the tube wall of crystallizer copper pipe, adopts two way alternate rotating excitation field to stir the solidification end of strand, adopts the end molten steel applied thrust of electromagnetism accelerator to strand; When strand enters after the arcuate guide section of circular-arc type continuous casting machine, by two cold-zones of arcuate guide section leading portion periphery, divide three sections strand to be carried out cooling, comprise that water ring water spray in Zu Gun district is cooling, active segment top aerosol is cooling and active segment bottom aerosol is cooling; Strand is carried out to continuous straightening; And strand cutting, slow cooling after aligning are obtained to continuous casting circular tube blank.
Adopt continuous temperature control device to monitor in real time liquid steel temperature, controlling molten steel overheat is 25～40 ℃, so that regulate in real time casting speed according to actual temperature, has avoided monitoring temperature to cause not in time product defects; Adopt crystallizer and solidification end combination electromagnetic agitation, make solidification end under electromagnetic stirring in dynamically, when solidifying, solidify gap that state and non-contact of solidifying between state closely avoided producing and cause the generation of face crack and middle crack in process of setting, and use electromagnetism to accelerate, make molten steel towards the accelerated motion of the base shell direction of motion, the space producing while supplementing molten steel solidification in time, under the acting in conjunction of magnetic stirrer and electromagnetism accelerator, avoid the generation of slab surface crack and middle crack, improved the centre burst of strand; Two three sections of cold-zones employings are cooling, for the different curdled appearance of molten steel, regulate cooling means, controlled strand thermograde, avoided base shell surface temperature sharply to change and caused strand to crack defect; Adopt continuous straightening, be different from single-point or multipoint straightening and becoming the larger aligning strain peak value of radius point place generation, avoided the generation of strand aligning crackle, said process has been avoided the generation of slab surface crack, middle crack and aligning crackle as much as possible, has improved the centre burst of strand.
High temperature diffusion annealing temperature of the present invention is 950～1100 ℃; Low temperature isothermal annealing temperature is 600～800 ℃.By high temperature diffusion annealing, low temperature isothermal annealing, reduced continuous casting billet internal stress, reduced blank hardness, be conducive to sawing.
The present invention is before carrying out equal heat treatment to blank, to the blank heat treated that heats up, successively through heat-recovery section, preheating section, heating I section, heating II section, heating III section and six sections of heating IV section, target temperature≤800 ℃ of heat-recovery section, 900 ± 10 ℃ of the target temperatures of preheating section, 1000 ± 10 ℃ of the target temperatures of heating I section, 1150 ± 10 ℃ of the target temperatures of heating II section, 1230 ± 10 ℃ of the target temperatures of heating III section, 1260 ± 10 ℃ of the target temperatures of heating IV section.By heat stepwise, make pipe progressively be elevated to soaking temperature, avoided the too fast problem that causes crackle to produce of programming rate.
The sizing reduction of perforation of the present invention is controlled between 70～160mm, and wall thickness reducing amount is controlled between 15～60mm.According to the difference of P91 blank diameter, suitably adjust perforation parameter, strictly control capillary outer diameter and internal diameter, obtain the seamless steel pipe of uniform diameter.
The present invention in heat treatment step, the temperature retention time >=40min of normalizing, the temperature retention time >=120min of tempering.Normalizing temperature retention time >=40min has guaranteed the uniformity of steel pipe austenitizing, meanwhile, makes alloying element fully be dissolved in austenite; Tempering insulation time >=120min fully separates out alloying element from oversaturated solid solution, obtains the carbide of disperse and makes the tissue trend after tempering stable, thereby improve the high-temperature behavior of steel pipe.
The present invention is in heat treatment step, and normalizing is cooling according to the difference of thickness of steel pipe, adopts air cooling, air-cooled, mist is cold or spraying cooling, as the wall thickness < of steel pipe 30mm, adopts air cooling to process; When the wall thickness range of steel pipe is 30mm-60mm, adopt spraying cooling processing; And the wall thickness >60mm that works as steel pipe, adopt spraying cooling to process.Adopt the above-mentioned type of cooling by controlling the cooling velocity of steel pipe, guaranteed the tissue of steel pipe and the uniformity of performance and stability.
The present invention is in heat treatment step, and the cooling employing air cooling of tempering is processed.After tempering, adopt air cooling to process, reduced steel pipe internal stress, improve plasticity and the toughness of steel pipe, simultaneously, make alloying element reasonable distribution between solid solution and the tiny carbide of separating out in steel pipe, improve the stability of tissue, the interaction energy of alloying element is accessed and fully play.
In the another kind of typical embodiment of the present invention, a kind of P91 seamless steel pipe is also provided, by preparation method of the present invention, obtain.
Below with reference to embodiment and comparative example, further illustrate and adopt beneficial effect of the present invention.Embodiment 1 is only for illustrating, and it can not limit protection scope of the present invention, and to those skilled in the art, under enlightenment of the present invention and instruction, choose reasonable is produced equipment and the parameter of seamless steel pipe.
Embodiment 1
Adopt preparation method of the present invention to produce the seamless steel pipe of Φ 711 * 63mmP91.
1) P91 steel chemical composition is optimized
According to ASME SA335 standard, the chemical composition of P91 steel is optimized, the chemical composition of the P91 steel after optimization following (mass fraction, %): C0.08～0.12%, Si0.20～0.45%, Mn0.35～0.55%, P≤0.015%, S < 0.007%, Cu≤0.15%, Ni≤0.20%, Cr8.10～9.30%, Mo0.85～1.05%, V0.18～0.23%, Nb0.06～0.10%, N0.030～0.070%, Al≤0.020%, Ti≤0.010%, Zr≤0.010%, surplus is Fe and inevitable impurity;
2) smelting of blank
Adopting high-quality molten iron and steel scrap is that raw material carries out the smelting of blank through 45 tons of electric furnace smeltings, 45 tons of refining furnace refinings, 45 tons of vacuum degassing furnaces and round base circular-arc type continuous casting machine continuous casting process, the strict chemical composition of controlling P91 steel in smelting process, make it meet the requirement of the chemical composition of optimizing, circle base circular-arc type continuous casting machine continuous casting, controls refining furnace ladle bull ladle liquid steel temperature=liquidus temperature+(90～120) ± 10 ℃; Casting speed is controlled at 0.20～0.50m/min; The vibration frequency adjusting range 200opm of crystallizer, amplitude adjusting range ± 2～4mm, side-play amount adjusting range 10～30%; Crystallizer cooling water inflow is controlled: 4000～5000L/min,
P91 continuous casting billet is cut after scale, carried out slow cooling.In blank, the content of each chemical composition is in Table 1.
3) preparation of blank
Blank after slow cooling is carried out to low temperature isothermal annealing, and the annealing process of pipe is for being heated to 600～650 ℃, and temperature retention time is 100min; Then be warmed up to 780 ± 10 ℃, temperature retention time is 160min; Then with stove, be cooled to 600 ± 10 ℃, temperature retention time is 100min, the air cooling of finally coming out of the stove.
4) pilger mill
P91 continuous casting material heating cycle according to table 2 in annular furnace is heated.
While preparing the seamless steel pipe of Φ 711 * 63mmP91, piercing temperature is 1183 ℃, and the dimensions after perforation is Φ 820 * 80mm, and the specification after pilger mill is Φ 718 * 63mm, and sizing reduction during pilger mill is 102mm, and wall thickness reducing amount is 17mm.
Pilger mill pass is Φ 718mm,, adjustment cycle Rolling mill parameter then,
Diameter of mandrel: 595mm; Feed quantity: 35mm; Roll rotational speed: 28rpm; Roll spacing: 84mm; Blast: 5.6bar; Brake chamber: 5.6mm.Guarantee the dimensional accuracy of hot finished steel pipe.During pilger mill, start rolling temperature is 1078 ℃, and finishing temperature is 974 ℃.
5) heat treatment of steel pipe
Normalizing: 1050 ± 10 ℃, temperature retention time: 160min, normalizing is cooling: S (wall thickness) >60mm, adopts normalizing spraying cooling to process; Tempering: 780 ± 10 ℃, temperature retention time: 230min, tempering is cooling: adopt tempering air cooling to process.
6) Surface Machining of steel pipe
According to the instructions for use of heavy caliber P91 seamless steel pipe, adopt inside and outside grinding technique to remove the iron scale of steel pipe surfaces externally and internally, guarantee surface quality and the dimensional accuracy of steel pipe.Steel pipe through inside and outside grinding does not exist height or the degree of depth to be greater than the screw thread of 0.3mm.
Steel pipe, after Surface Machining is processed, then carries out desk checking, sprays mark, japanning after nondestructive inspection is qualified, packing warehouse-in.
Measure every mechanical property of the P91 seamless steel pipe of the present embodiment, wherein, tensile property in Table 3, steel pipe hardness from the inner surface to outer surface in Table 4, impact property is in Table 5.
Table 1
| Element | C | Si | Mn | P | S | Cu | Ni | Cr | Mo |
| Content (wt%) | 0.08 | 0.36 | 0.40 | 0.013 | 0.002 | 0.04 | 0.06 | 8.69 | 0.89 |
| Element | V | Al | Sn | As | Pb | Sb | Bi | Nb | N |
| Content (wt%) | 0.22 | 0.019 | 0.006 | 0.013 | 0.001 | 0.005 | 0.006 | 0.06 | 0.058 |
Table 2
Table 3
| RP0.2（MPa） | Rm（MPa） | A（%） |
| 587 | 712 | 21 |
| 582 | 716 | 22 |
Table 4
| Hardness (HBW) |
| 224，227，224，223，225，227 |
Table 5
| Temperature | Akv（J） |
| Room temperature | 212，216，226 |
| 0 | 202，184，222 |
| -20 | 160，162，146 |
Data in table 3, table 4 and table 5 can find out, stretching, hardness, impact all show good performance.
As shown in Figure 2, the microscopic structure of the seamless steel pipe of the present embodiment, determines that this is organized as single tempered martensite after testing, and grain size is 8 grades.
The non-metallic inclusion of Φ 711 * 63mmP91 seamless steel pipe of the present embodiment is: A0.5; B1.0; C0.5; D0.5; Ds0.5, and macroscopic examination and bend test all qualified.
The foregoing is only the preferred embodiments of the present invention, be not limited to the present invention, for a person skilled in the art, the present invention can have various modifications and variations.Within the spirit and principles in the present invention all, any modification of doing, be equal to replacement, improvement etc., within all should being included in protection scope of the present invention.
Claims (9)
1. a preparation method for P91 seamless steel pipe, is characterized in that, described preparation method comprises the following steps:
Blank is smelted, and raw material, through smelting-refining-vacuum outgas-continuous casting circular tube blank technique, is made to described blank;
Annealing in process, carries out high temperature diffusion annealing or low temperature isothermal annealing by described blank;
Pilger mill, by the blank soaking through described annealing in process, carries out hot-puncturing process to described blank after soaking, the temperature of described hot-puncturing process is 1100～1200 ℃, then carry out pepriodic rolling, the temperature of described pepriodic rolling is 950～1100 ℃, carries out sizing and cooling processing; And
Heat treatment, is heated to 1040～1080 ℃ by the steel pipe through described pilger mill, carries out normalizing, cooling after insulation, is then heated to 750～800 ℃, carries out tempering, cooling after insulation, makes described P91 seamless steel pipe;
Wherein, in described raw material, P content is less than or equal to 0.015%, S content and is less than 0.007%, and the bore of described seamless steel pipe is Φ 325～720mm,
Described continuous casting circular tube blank technique comprises:
Molten steel is injected in the crystallizer of circular-arc type continuous casting machine, employing mold liquid level automated watch-keeping facility is monitored the temperature of described molten steel and is controlled the degree of superheat of described molten steel, according to described molten steel overheat, regulates in real time casting speed;
Molten steel is frozen into and take the base shell that molten steel is the liquid heart along the tube wall of described crystallizer copper pipe, adopts two way alternate rotating excitation field to stir the solidification end of strand, adopts the end molten steel applied thrust of electromagnetism accelerator to described strand;
When described strand enters after the arcuate guide section of described circular-arc type continuous casting machine, by two cold-zones of described arcuate guide section leading portion periphery, divide three sections described strand to be carried out cooling, comprise that water ring water spray in Zu Gun district is cooling, active segment top aerosol is cooling and active segment bottom aerosol is cooling;
Described strand is carried out to continuous straightening; And
Strand cutting, slow cooling after aligning are obtained to described continuous casting circular tube blank.
2. preparation method according to claim 1, is characterized in that, in described raw material, the quality percentage composition of each chemical composition is: C0.08～0.12%, Si0.20～0.45%, Mn0.35～0.55%, P≤0.015%, S < 0.007%, Cu≤0.15%, Ni≤0.20%, Cr8.10～9.30%, Mo0.85～1.05%, V0.18～0.23%, Nb0.06～0.10%, N0.030～0.070%, Al≤0.020%, Ti≤0.010%, Zr≤0.010%, surplus is Fe and impurity.
3. preparation method according to claim 1, is characterized in that, after described heat treatment step, described steel pipe is carried out to Surface Machining step.
4. preparation method according to claim 1, is characterized in that, the temperature of described high temperature diffusion annealing is 950～1100 ℃; The isothermal annealed temperature of described low temperature is 600～800 ℃.
5. preparation method according to claim 1, it is characterized in that, described soaking temperature is 1230～1270 ℃, described soaking temperature deviation ± 10 ℃, keep 1.5～3h, before described blank is carried out to equal heat treatment, to the described blank heat treated that heats up, pass through successively heat-recovery section, preheating section, heating I section, heating II section, heating III section and six sections of heating IV section, target temperature≤800 ℃ of described heat-recovery section, 900 ± 10 ℃ of the target temperatures of described preheating section, 1000 ± 10 ℃ of the target temperatures of described heating I section, 1150 ± 10 ℃ of the target temperatures of described heating II section, 1230 ± 10 ℃ of the target temperatures of described heating III section, 1260 ± 10 ℃ of the target temperatures of described heating IV section.
6. preparation method according to claim 1, is characterized in that, the sizing reduction of described hot-puncturing process is controlled between 70～160mm, and wall thickness reducing amount is controlled between 15～60mm.
7. preparation method according to claim 1, is characterized in that, in described heat treatment step, and the temperature retention time >=40min of described normalizing, the temperature retention time >=120min of described tempering.
8. preparation method according to claim 1, is characterized in that, in described heat treatment step, described normalizing is cooling according to the difference of thickness of steel pipe, adopts air cooling, air-cooled, mist is cold or spraying cooling,
As the wall thickness < of described steel pipe 30mm, adopt air cooling to process;
When the wall thickness range of described steel pipe is 30mm-60mm, adopt spraying cooling processing; And
As the wall thickness >60mm of described steel pipe, adopt spraying cooling to process.
9. preparation method according to claim 1, is characterized in that, in described heat treatment step, the cooling employing air cooling of described tempering is processed.
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