CN100507047C - Cr-Mo alloyed steel round billet produced by arc continuous casting machine and technique thereof - Google Patents
Cr-Mo alloyed steel round billet produced by arc continuous casting machine and technique thereof Download PDFInfo
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- CN100507047C CN100507047C CNB2006100307246A CN200610030724A CN100507047C CN 100507047 C CN100507047 C CN 100507047C CN B2006100307246 A CNB2006100307246 A CN B2006100307246A CN 200610030724 A CN200610030724 A CN 200610030724A CN 100507047 C CN100507047 C CN 100507047C
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Abstract
The present invention relates to one kind of round Cr-Mo alloy steel billet produced in a bow-type continuous casting machine and its production process. The molten steel for the round Cr-Mo alloy steel billet contains P not more than 0.012 wt% and S not more than 0.002 wt%, and has Mn/S weight ratio not smaller than 200. The present invention features that the continuous casting process has the second cooling with specific cooling water amount of 0.47-0.53, the first region cooling water amount accounting for 35-45 %, the second region cooling water amount accounting for 22-32 %, the third region cooling water amount accounting for 14-24 %, the fourth region cooling water amount accounting for 9-19 %, and Mn/S content ratio in steel not smaller than 200. The present invention can produce continuously cast round low carbon alloy steel billet without crack, shrinkage hole and other defects.
Description
Technical field
The present invention relates to a kind of steel alloy and processing method thereof, relate in particular to Cr-Mo alloyed steel round billet and processing method thereof that a kind of curved type continuous caster is produced.
Background technology
The Baosteel electric furnace was gone into operation from December, 96 because do not introduce corresponding smelting, the consistent Technology of casting, main carbon steel, manganese steel and the low alloy steel produced in preceding 7 years that go into operation.Be that 2.5～5.5% Cr-Mo series alloy steel is also manufactured experimently to alloy content during this period, but owing to fail to grasp the relevant key process technology of smelting, cast of steel alloy, causing cast alloys steel continuous cast round billets to produce bleed-out, subsurface defect, mainly is centre burst, shrinkage cavity severe overweight.Because the Baosteel electric furnace continuous casting is produced
178mm garden base mainly is that direct-furnish Baosteel steel pipe branch office wroughtsteel pipe uses.The every mechanical property of Baosteel steel pipe, tolerance of dimension control take the lead and the product of going together both at home and abroad, and along with the steel pipe market development, present numerous users place high hopes to the Baosteel steel pipe, are mainly reflected in product innovation and expand, on particularly the Medium Alloy Steel kind is expanded.Because Baosteel electric furnace product mix mainly is to produce straight carbon steel, therefore the steel alloy aspect lacks correlation technique aborning, the process trial initial stage for grope centre burst, shrinkage cavity exceed standard strand to steel pipe rolling after in the table quality influence also try to roll, the steel pipe inboard wall of tube body produces a large amount of fragmentations and sticks up skin as a result; The pipe finished product rate only is 48.9%.Above situation restricts seriously that steel pipe product innovation class promotes and the development of Baosteel electrosmelting, casting technique.
The Cr-Mo alloyed steel round billet processing method of existing curved type continuous caster production makes [S] in the steel alloy steel reach 0.00435% and since in the steel sulphur when high in process of setting easily with iron formation FeS and FeS
2Two kinds of sulfide, the former is more common in steel, its fusing point lower (1190 ℃), and form the eutectic of fusing point lower (988 ℃) with iron; The temperature range of solid and liquid phase coexistence is wide to reach hundreds of degree; The solubleness of sulphur in δ iron and γ iron is very little, and with solidifying of molten steel, sulphur will cause the sulfide segregation to make crystal boundary have very strong red brittleness to the liquid portion enrichment of ot-yet-hardened, causes in the inner centre burst that forms easily of steel alloy.
Prior art does not have strict demand to [Mn] in the steel/[S], causes [Mn] in the steel/[S] fluctuation big (50～600), because [Mn]/[S] is low in the steel, just impel low-melting dendritic FeS to form, (Fe, Mn) S+FeS complex chemical compound increase crystal boundary fragility in crystal boundary formation in process of setting to make sulphur.
Prior art makes [P] in the steel alloy steel reach 0.011523%, can obtain from the Fe-P equilibrium phase diagram, phosphorus adds the distance that has enlarged solidus curve and liquidus line in the iron, so the phosphorated iron compound from liquid state to the temperature province of solid-state need by broad, the higher iron liquid (fusing point is lower) of phosphorus concentration is filled in the crack of the dendrite that has solidified and forms the iron phosphide film at crystal boundary like this, thereby the high temperature toughness of steel is reduced.With increasing of phosphorus content, the A4 of ferrophosphor(us) point descends gradually, and the A3 point constantly rises simultaneously, and the γ that forms sealing at last encloses mutually.Former technology causes phosphorus obvious more at grain boundary segregation owing to [P] in the steel is higher, and crystal boundary is also fragile more, so the susceptibility of the middle crack of strand, shrinkage cavity strengthens greatly.
In the prior art because the viscosity of steel alloy own is dead in order to prevent casting cycle knot greatly, so disconnected water actual molten steel overheat and be controlled at 30 ± 5 ℃ and be equipped with the 2.3m/min pulling rate simultaneously, this technology causes casting billet surface chill thickness to reduce, the casting billet surface radiating rate increases, thereby solidified shell can not evenly be grown, cause the central cylindrical crystalline region to strengthen and cause that strand goes out the crystallization rear surface and rises again bigger, solidify the generation thermal stresses at columnar zone, and column crystal exists owing to impurity is built up hot strength and the lower plane of weakness of plasticity that forms, so easily form the column crystal intergranular crack.Can bring out column crystal easily transcrystalline " bridgings " at first in the inner indivedual positions of strand when serious, cause the condensation contraction of the raffinate partial closure space in to can not get replenishing formation center porosity and shrinkage cavity.
Continuous casting secondary cooling purpose is by supply with the water spray of q.s to the band liquid core base shell of pulling out from crystallizer, directly cooling continuously, short its quick and complete solidifying, secondary cooling system must be arranged to reduce the strand temperature equably, to avoid casting blank surface temperature sharply to change, prior art adopts the 0.35L/kg specific water to cause liquid core length long easily, cause band liquid heart aligning, be easy to generate defectives such as crackle, prior art four districts adopt " flighting schedule " water distribution in addition, cause strand temperature difference between fan-shaped section very big, make strand in process of setting, easily produce " backheat ", can cause localized heat stress to make strand produce defective.
Summary of the invention
Main purpose of the present invention provides Cr-Mo alloyed steel round billet and the processing method thereof that a kind of curved type continuous caster is produced, by controlling best steel-making, continuous casting two cold processing parameter and suitable pouring temperature, pulling rate coupling, avoid cast alloys steel continuous cast round billets to produce bleed-out, subsurface defect, produce satisfactory low-carbon alloy steel continuous cast round billets.
The object of the present invention is achieved like this: (except that special instruction was arranged, all per-cents, ratio and ratio herein all was by weight)
The low-carbon (LC) Cr-Mo series alloy steel that the present invention relates to is meant in the steel and contains≤0.35% carbon, and contains chromium, molybdenum, one or more elements of nickel, and above constituent content is at 2.5%-5.5%, is cast into specifications section by curved type continuous caster and is
The continuously cast bloom of 178mm.
It is as follows that its Production Flow Chart and present technique are implemented point:
EAF smelting (30-45% molten iron+70-55% steel scrap) control tapping [P] content-eccentric bottom tapping-LF ladle external refining (adjusting [Mn], [S] and liquid steel temperature in the steel)-VD vacuum outgas (fine setting [Mn]/[S] ratio, liquid steel temperature)-6 stream arcs
178mm continuous caster (control molten steel casting superheating temperature and pulling rate rational Match, two cold specific waters and four district's water yield optimum distribution)-strand finishing.
In the present invention relates to, the principle of low-carbon (LC) Cr-Mo series alloy steel round blank manufacture method is: by optimizing the design of steel grade composition, control steel grade [Mn]/[S] ratio, secondly by optimum matching between control molten steel casting superheating temperature and the pulling rate, adopt best caster two cold specific water and continuous casting two cold four district's optimum waters to distribute simultaneously, can avoid molten steel in the cooled and solidified process, to produce the generation of defectives such as strand centre burst, shrinkage cavity because of Quench.Key manufacturing technology of the present invention is as follows:
The control of table one composition
Table two superheating temperature and pulling rate control
Table three two cold specific waters and four district's water distributions
The Cr-Mo alloyed steel round billet that a kind of curved type continuous caster is produced is characterized in that, in the molten steel composition: P≤0.012%, S≤0.002%, Mn/S 〉=200 contain chromium, molybdenum, one or more elements of nickel, and above constituent content are at 2.5%-5.5%.
Above-mentioned curved type continuous caster is produced the processing method of Cr-Mo alloyed steel round billet, it is characterized in that: the continuous casting two cold specific water is 0.47～0.53, one district's water yield per-cent is 35%～45%, two district's water yield per-cents are 22%～32%, three district's water yield per-cents are 14%～24%, four district's water yield per-cents are 9%～19%, Mn/S 〉=200 in the control steel.Wherein, weight percent content≤0.012% of P in the control steel, weight percent content≤0.002% of S in the control steel, molten steel overheat is 1.9m/min～2.3m/min at 20 ± 5 ℃ of corresponding coupling pulling rates of scope, reduce 0.2m/min control if molten steel overheat is high by 8 ± 5 ℃ of corresponding pulling rates of every rising, improve 0.2m/min control if temperature is on the low side by 8 ± 5 ℃ of corresponding pulling rates of every reduction, guarantee in time when temperature is on the low side that plasma gun comes into operation.In this process, need the control charge composition, guarantee hot metal ratio in 30～45% scopes, go into the stove steel scrap and adopt low-phosphorous, low-sulfur steel scrap; Control T.Fe controls slag basicity 3.0～3.2 simultaneously in 30～40% scopes in converting process; Eccentric bottom tapping is adopted in tapping, controls the interior surplus steel amount of stove simultaneously at 15 tons～30 tons, controls ladle refining slag system basicity R=3.5～4.0 simultaneously.
The present invention makes it compared with prior art owing to adopted above-mentioned technical scheme, has following advantage and positively effect:
1, because the present invention effectively controls [S] in the steel, thereby can effectively avoid molten steel in process of setting, to form low-melting-point eutectic, strand centre burst incidence is obviously reduced;
2, because the present invention is by guaranteeing that [Mn]/[S] was greater than 200 o'clock in the steel, because [Mn]] with the avidity of [S] greater than [Fe] avidity with [S], thereby make molten steel when solidifying, most of [S] combines with [Mn], form and stablize MnS, crystal boundary fragility is reduced, greatly reduce the inner probability that forms centre burst of steel alloy;
3, adopt the present invention effectively to control [P] in the steel alloy steel, thereby avoid the segregation of phosphorus between crystal boundary, so the susceptibility of the middle crack of strand, shrinkage cavity has also reduced greatly thereupon;
4, adopt the present invention can make strand Homogeneouslly-radiating in process of setting effectively avoid steel alloy centre burst, shrinkage cavity to take place, can make strand slow cooling step by step in four district's process of cooling, evenly cooling, thereby alleviate the centre burst incidence.
Embodiment
The present invention further specifies in conjunction with following embodiment:
The composition of table four low-carbon (LC) Cr-Mo steel alloy
Critical technical parameter control actual achievement in table five statistics annual A in 2005, the B steel
Table six two cold specific waters and four districts water distribution control actual achievement
Table seven shrinkage cavity contrast actual achievement
Table eight centre burst contrast actual achievement
As can be seen from the above table, make by the art of this patent in, low-carbon (LC) Cr-Mo series alloy steel round blank centre burst, shrinkage cavity descends 39.886%, 36.916% respectively more than or equal to 3 grades of exceeding standard rate.
Table quality and finished product rate in table nine steel pipe rolling
Because contain more alloying element in the steel grade compositions such as alloy high temperature steel, cracking tube, high pressure boiler tube, these elements are improving steel grade performance (mechanical property, high temperature resistant, corrosion-resistant) simultaneously, increase many difficulties also for steel-making, continuous casting, Rolling Production.As alloying element [Cr] commonly used the hardening capacity that improves steel, the wear resistance that increases steel are had remarkable effect, but easily produce fragility when content is higher, this just causes being easy to generate centre burst, shrinkage cavity on continuous-cast blank.So must strictly control the alloy inner quality, thereby guarantee table quality in the steel pipe.The process trial initial stage for grope centre burst, shrinkage cavity exceed standard strand to steel pipe rolling after in the table quality influence also try to roll, the steel pipe inboard wall of tube body produces a large amount of fragmentations and sticks up skin as a result; The pipe finished product rate only is 48.9%, well below normal continuously cast bloom finished product rate 82% left and right horizontal.Implement by this technical patent, reduced centre burst, the shrinkage cavity ratio that exceeds standard, therefore make Medium Alloy Steel steel pipe finished product rate reach 83.42%, rise about 27%.The present invention can adopt curved type continuous caster to produce in the light section, be applicable in the low-carbon (LC) Cr-Mo steel in relevant steel mill.
Claims (5)
1. curved type continuous caster is produced the processing method of Cr-Mo alloyed steel round billet, it is characterized in that:
1) control charge composition guarantees hot metal ratio in 30～45% scopes, goes into the stove steel scrap and adopts low-phosphorous, low-sulfur steel scrap;
2) control ladle furnace basicity of slag R=3.5～4.0;
3) the control molten steel overheat is 1.9m/min～2.3m/min at 20 ± 5 ℃ of corresponding coupling pulling rates of scope, reduce 0.2m/min control if molten steel overheat is high by 8 ± 5 ℃ of corresponding pulling rates of every rising, improve 0.2m/min control by 8 ± 5 ℃ of corresponding pulling rates of every reduction if temperature is on the low side;
4) the continuous casting two cold specific water is that 0.47～0.53, one district's water yield per-cent is that 35%～45%, two district's water yield per-cents are that 22%～32%, three district's water yield per-cents are that 14%～24%, four district's water yield per-cents are 9%～19%, Mn/S 〉=200 in the control steel.
2. curved type continuous caster as claimed in claim 1 is produced the processing method of Cr-Mo alloyed steel round billet, it is characterized in that: weight percent content≤0.012% of P in the control steel.
3. curved type continuous caster as claimed in claim 1 or 2 is produced the processing method of Cr-Mo alloyed steel round billet, it is characterized in that: weight percent content≤0.002% of S in the control steel.
4. curved type continuous caster as claimed in claim 3 is produced the processing method of Cr-Mo alloyed steel round billet, it is characterized in that: guarantee in time when temperature is on the low side that plasma gun comes into operation.
5. curved type continuous caster as claimed in claim 1 is produced the processing method of Cr-Mo alloyed steel round billet, it is characterized in that:
1) control T.Fe controls slag basicity 3.0～3.2 simultaneously in 30～40% scopes in converting process;
2) eccentric bottom tapping is adopted in tapping, controls the interior surplus steel amount of stove simultaneously at 15 tons～30 tons.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102019389B (en) * | 2010-11-30 | 2013-02-13 | 攀钢集团钢铁钒钛股份有限公司 | P91 steel round billet continuous casting method |
| CN104975233B (en) * | 2015-06-11 | 2016-11-09 | 攀钢集团成都钢钒有限公司 | The production method of ultra-high-strength/tenacity structural alloy steel continuous cast round billets |
| CN105598407B (en) * | 2016-03-04 | 2018-01-26 | 攀钢集团攀枝花钢铁研究院有限公司 | The method for improving strand central dense degree |
| CN106216624B (en) * | 2016-08-25 | 2018-07-06 | 江苏省沙钢钢铁研究院有限公司 | A kind of low-carbon high-chromium ferrite corrosion-resisting steel continuous small-billet casting manufacturing method |
| CN107552753B (en) * | 2017-08-31 | 2020-04-17 | 山东莱钢永锋钢铁有限公司 | Water distribution process of secondary cooling chamber in molten steel continuous casting process |
| CN112522567B (en) * | 2019-09-19 | 2022-06-24 | 宝山钢铁股份有限公司 | High-strength thin-specification high-corrosion-resistance steel and manufacturing method thereof |
| CN110576163B (en) * | 2019-09-28 | 2021-07-20 | 江苏联峰能源装备有限公司 | Method for producing high-carbon manganese-chromium steel by large-section continuous casting round billet |
| CN111014607B (en) * | 2019-12-13 | 2021-07-09 | 河钢乐亭钢铁有限公司 | Continuous casting high-quality accurate secondary cooling process |
| CN114799100A (en) * | 2022-05-05 | 2022-07-29 | 芜湖新兴铸管有限责任公司 | Continuous casting large round billet casting method |
| CN115041654B (en) * | 2022-05-27 | 2023-06-20 | 昆明理工大学 | Control method for center segregation of casting blank |
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