CN105803151A - Center porosity control method for 35CrMo round blooms with cross section diameter being 280 mm - Google Patents
Center porosity control method for 35CrMo round blooms with cross section diameter being 280 mm Download PDFInfo
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- CN105803151A CN105803151A CN201610172942.7A CN201610172942A CN105803151A CN 105803151 A CN105803151 A CN 105803151A CN 201610172942 A CN201610172942 A CN 201610172942A CN 105803151 A CN105803151 A CN 105803151A
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- molten steel
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- controls
- argon
- 35crmo
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
- C21C5/28—Manufacture of steel in the converter
- C21C5/30—Regulating or controlling the blowing
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/10—Supplying or treating molten metal
- B22D11/11—Treating the molten metal
- B22D11/114—Treating the molten metal by using agitating or vibrating means
- B22D11/115—Treating the molten metal by using agitating or vibrating means by using magnetic fields
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/16—Controlling or regulating processes or operations
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/16—Controlling or regulating processes or operations
- B22D11/18—Controlling or regulating processes or operations for pouring
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/16—Controlling or regulating processes or operations
- B22D11/22—Controlling or regulating processes or operations for cooling cast stock or mould
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/16—Controlling or regulating processes or operations
- B22D11/22—Controlling or regulating processes or operations for cooling cast stock or mould
- B22D11/225—Controlling or regulating processes or operations for cooling cast stock or mould for secondary cooling
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/072—Treatment with gases
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/10—Handling in a vacuum
Abstract
The invention discloses a center porosity control method for 35CrMo round steel casting blooms with cross section diameter being 280 mm. The method comprises the following steps: converter smelting, LF molten steel refining, RH refining and continuous casting of molten steel, and is characterized in that crystallizer electromagnetic stirring and solidification end electromagnetic stirring are combined in the continuous casting step. The method has the benefits that first, in the molten steel smelting step, control is carried out according to reasonable parameters, so as to improve the impurity of molten steel and ensure that the discharging conditions of the molten steel are optimal; and then, in the molten steel casting step, crystallizer electromagnetic stirring and solidification end electromagnetic stirring are combined to ensure that molten steel ingredients and temperature are homogenized, a blank shell grows uniformly, and columnar crystal structures are consistently scoured and fused in the stirring process, so that the areas of center porosity in the casting blooms are reduced, and the density is improved.
Description
Technical field
The present invention relates to field of steel metallurgy, particularly relate to a kind of center porosity control method producing the 35CrMo pipe steel strand that section is φ 280mm.
Background technology
The steel for oil well pipes that 35CrMo tube blank steel uses mainly for the production of oil-gas mining, transport, chemical constituent is by weight percentage: C:0.27%～0.32%, Si:0.20%～0.35%, Mn:0.45%～0.65%, P≤0.020%, S≤0.010%, V≤0.015%, Cr::0.85%～1.05%, Mo:0.17%～0.24%, Cu≤0.15%, Ni≤0.20%, Alt:0.020%～0.040%, residual elements require: Nb≤0.010%, Ti≤0.010%, B≤0.005%, and V+Nb+Ti+B+Zr≤0.15%；As≤0.015%, Sn≤0.010%Sb≤0.010%, Pb≤0.008%, Bi≤0.010%, and As+Sn+Sb+Pb+Bi≤0.045%, surplus is Fe.In use under the combined effect of applied stress and hydrogen sulfide gas, often there is suddenly brittle failure (being called H 2 S stress corrosion) when stress is far below itself yield strength, easily cause the problems such as raw leakage, production and environmental protection are adversely affected.Along with socioeconomic development, oil gas transport efficiency requirements is higher, exploit the development trends such as difficulty increase constantly proposes harsher requirement to slab quality.Especially such as defects such as strand center porosities, strand is rolled poling processing and end product quality has a negative impact.
For 35CrMo tube blank steel, it is relatively big that the Gao Ge in steel grades, molybdenum content itself determine strand column crystal prosperity trend, furthermore, due to casting blank section is relatively large and for circle base, its specific surface area less strand heat transfer efficiency is lower, and slowly, the control of crystalline structure is more difficult in solidification cooling.In continuous casting production process, strand column crystal is flourishing, often lead to column crystal interdendritic and occur bonding, form confined space, molten steel continues cooled and solidified, volume contraction, and outside molten steel cannot feeding in time and form the defects such as loose, these defects can not all effectively eliminate in subsequent rolling process process, affects product quality.
Summary of the invention
For overcoming the 35CrMo pipe steel strand of existing relatively big cross section size the deficiencies such as center porosity phenomenon easily occur, the technical problem to be solved is: provide a kind of center porosity control method for the 35CrMo pipe steel strand that section is φ 280mm.
The technical solution adopted for the present invention to solve the technical problems is:
Produce the center porosity control method of the 35CrMo pipe steel strand that section is φ 280mm, comprise the following steps:
I, converter smelting: converter terminal is controlled according to following mass percent and temperature index, aim carbon 0.05%～0.15%, terminal phosphorus≤0.010%, outlet temperature >=1670 DEG C, pushing off the slag of tapping, control slag thick within 60mm；
II, the molten steel obtained in step I is carried out LF stove refine, refine whole process Argon stirs, LF sets off target [S]≤0.008% by mass percentage, and [P]+[S]≤0.023% is controlled, departures Als is controlled according to mass percent 0.020%～0.040%, refine continues Argon at least 5min after terminating, and out-station temperature presses 1590～1620 DEG C of controls；
III, the molten steel obtained in step II is carried out RH refine, RH refine requires that argon flow amount controls by 1100～1350NL/min, vacuum < 3mbar, process time >=10min, application of vacuum continues Argon at least 5min after terminating, RH goes out to stand firm hydrogen thermometric, controls according to concentration [H]≤2.0ppm, and out-station temperature controls at 1540～1565 DEG C；
IV, continuous casting steel: continuous casting link adopts the mode that M-EMS combines with solidification end electromagnetic agitation, and wherein, the parameter of M-EMS is: stir current 380～450A, 3～5Hz；Solidification end stirring parameter is: stir current 300～400A, frequency 7.0～9.0Hz.
Further, in step II and step III refining process adopt in the stirring of intensity Argon, occur without with molten steel surface and turn over greatly boiling and be as the criterion；Refine adopts soft argon blowing stirring after terminating, make molten steel have faint stirring.
It is further, also need in step IV carries out molten steel cast control following parameter: the degree of superheat controls at 25～40 DEG C, casting speed control is at 0.75～1.00m/min, and crystallizer cooling controls at 2450～2650L/min, and two cold specific waters control at 0.25～0.35l/kgSteel。
The invention has the beneficial effects as follows: first in the smelting molten steel stage according to rational state modulator, improve the degree of purity of molten steel and make its condition of setting off reach the best, subsequently in the process of pouring molten steel, adopt the mode that M-EMS combines with solidification end electromagnetic agitation, making molten steel component and equalizing temperature, green shell homoepitaxial, fusing is constantly washed away in whipping process by columanar structure, thus causing that strand center porosity region area reduces, consistency is improved.
Detailed description of the invention
Below by way of detailed description of the invention, the invention will be further described, but should not be understood as the restriction of the present invention.Those of ordinary skill in the art are according to such scheme, it is also possible to make various forms of amendment, replacement, change.Every amendment, replacement and change made based on above-mentioned technological thought broadly falls into the scope of the present invention.
Produce the center porosity control method of the 35CrMo pipe steel strand that section is φ 280mm, comprise the following steps:
I, converter smelting: converter terminal is controlled according to following mass percent and temperature index, aim carbon 0.05%～0.15%, terminal phosphorus≤0.010%, outlet temperature >=1670 DEG C, pushing off the slag of tapping, control slag thick within 60mm；
II, the molten steel obtained in step I is carried out LF stove refine, refine whole process Argon stirs, LF sets off target [S]≤0.008% by mass percentage, and [P]+[S]≤0.023% is controlled, departures Als is controlled according to mass percent 0.020%～0.040%, refine continues Argon at least 5min after terminating, and out-station temperature presses 1590～1620 DEG C of controls；
III, the molten steel obtained in step II is carried out RH refine, RH refine requires that argon flow amount controls by 1100～1350NL/min, vacuum < 3mbar, process time >=10min, application of vacuum continues Argon at least 5min after terminating, RH goes out to stand firm hydrogen thermometric, controls according to concentration [H]≤2.0ppm, and out-station temperature controls at 1540～1565 DEG C；
IV, continuous casting steel: continuous casting link adopts the mode that M-EMS combines with solidification end electromagnetic agitation, and wherein, the parameter of M-EMS is: stir current 380～450A, 3～5Hz；Solidification end stirring parameter is: stir current 300～400A, frequency 7.0～9.0Hz.
Step I, II, III mainly the smelting of molten steel is controlled, it is ensured that molten steel has stable characteristic, uniform composition and suitable pouring temperature before cast.Wherein, the content of carbon and phosphorus is controlled by converter steelmaking process to be to ensure that and the internal soundness of molten steel improve its stability；LF stove refine is to make molten steel fully react, and remove unnecessary impurity, owing to the mechanical performance of steel is had adverse effect by S and P, so needing the strict content controlling two kinds of elements, wherein Als is acid aluminum content, the control of Als is conducive to making the uniform small grains of steel, its hardenability and quenching degree and plasticity and toughness can be improved simultaneously；RH refine is the degree of purity in order to improve molten steel further, and makes the composition stable and uniform more of molten steel, is conducive to forming good isometry crystalline region during follow-up continuous casting, and the concentration controlling hydrogen is to prevent from hydrogen induced cracking occur in follow-up casting process.
The present invention it is critical only that the continuous casting steel stage in step IV, it is generally the case that in continuous casting process, casting blank solidification tissue presents the crystallizer tissue regions in chill fine grained region, columnar zone, Center Equiaxial Crystal district successively from casting billet surface to center.Tissue looseness and steel ingot centre that when center porosity Producing reason is solidification of molten steel, volume contraction causes are gathered caused by field trash gathering comparatively seriously because final set makes gas analyse.For improving slab quality, it is to avoid center porosity occurs in strand, and existing mode typically just reduces impurity or slows down rate of cooling etc..The present invention thes improvement is that, employing is the mode that combines with solidification end electromagnetic agitation of M-EMS.The mechanism of action of this technology is: M-EMS produces electromagnetic torque by magnetic field, change crystallizer internal flow field of molten steel, thermo parameters method situation, promote Mold composition, equalizing temperature, weaken the directivity of solidification and heat transfer, promote green shell homoepitaxial；Further, fusing, by forcing to drive the flowing of mushy zone molten steel, is washed away by solidification end electromagnetic agitation by columanar structure, improves equiax crystal nucleation rate, finally realizes the uniform cooled and solidified in strand center, it is achieved the control to center porosity.
LF stove refined molten steel and RH refining process all adopt Argon to be stirred, intensity Argon stirring in being generally adopted in refining process, occur without with molten steel surface and turn over greatly boiling and be as the criterion；Refine adopts soft argon blowing stirring after terminating, make molten steel have faint stirring.Argon stirring is primarily to and enables molten steel fully to react, and makes the composition mix homogeneously in molten steel, it is simple to follow-up can form stable solidified structure in pouring molten steel process.
Further, when carrying out the continuous casting steel stage, if solidification end electromagnetic agitation intensity controls bad, easily cause dentrite tip and wash away seriously, the low solute concentration molten steel causing the strong mobility of low melting point is assembled ringwise, form white band, it is thus desirable to its stirring intensity is accurately controlled, in addition in order to ensure last quality of becoming a useful person, also need to control following parameter when carrying out molten steel cast: the degree of superheat controls at 25～40 DEG C, casting speed control is at 0.75～1.00m/min, crystallizer cooling controls at 2650～2650L/min, two cold specific waters control at 0.25～0.35l/kgSteel.The rational degree of superheat, pulling rate match control and intensity of secondary cooling formulate the key being casting blank solidification heat transfer is controlled, and desirably prevent the appearance of center porosity.
Embodiment:
Certain steel mill adopts 120t converter smelting → LF stove refine → RH refine → six machine six to flow casting machine φ 280mm section continuous casting and produces 35CrMo circular pipe blank.When bessemerizing end, aim carbon is 0.15% be controlled, and terminal phosphorus is 0.009%, and outlet temperature controls at 1675 DEG C, and ladle slag thickness controls as 56mm.
Molten steel arrives LF refining furnace place, carry out Argon molten steel slightly to fluctuate, there is not turning over greatly phenomenon, departures Als mass percent controls to be 0.041%, and molten steel is carried out soft blow argon after terminating by refine, and argon blowing time is 6.5min, after LF process terminates, constant temperature is 1611 DEG C, and LF departures [S] is 0.006%, and [S]+[P] is 0.020%.
After molten steel arrives at a station, RH refine Argon argon flow amount is 1350NL/min control, the process time 11.6min of vacuum < 3mbar, RH departures Als is 0.033%, application of vacuum terminates rear Argon 5.3min, and the hydrogen that goes out to stand firm is 1.2ppm, and out-station temperature controls at 1551 DEG C.
RH application of vacuum is allocated and transported after terminating and is flowed casting machine φ 280mm section to six machines six and carry out molten steel casting, and actual control of the critical technical parameter relevant to application claims is: M-EMS: stir current 450A, stirring frequency 4.0Hz；Solidification end electromagnetic agitation: stir current 340A, stirring frequency 7.5Hz；The actual casting process degree of superheat of molten steel controls at 20～27 DEG C；Pulling rate is 0.85m/min；Crystallizer cooling controls at 2450L/min；Two cold specific waters control at 0.35/kgSteel。
After above-mentioned technological invention is stably used, slab quality is well controlled, and the loose low power testing result of strand is: strand sedimentation 0.5～1.0 grade, non-densified regions area ratio 25.2%, strand in-situ metal analyzes consistency detection, and central area is 0.81.
Claims (3)
1. the 35CrMo circular pipe blank center porosity control method of φ 280mm, it is characterised in that comprise the following steps:
I, converter smelting: converter terminal is controlled according to following mass percent and temperature index, aim carbon 0.05%～0.15%, terminal phosphorus≤0.010%, outlet temperature >=1670 DEG C, pushing off the slag of tapping, control slag thick within 60mm；
II, the molten steel obtained in step I is carried out LF stove refine, refine whole process Argon stirs, LF sets off target [S]≤0.008% by mass percentage, and [P]+[S]≤0.023% is controlled, departures Als is controlled according to mass percent 0.020%～0.040%, refine continues Argon at least 5min after terminating, and out-station temperature presses 1590～1620 DEG C of controls；
III, the molten steel obtained in step II is carried out RH refine, RH refine requires that argon flow amount controls by 1100～1350NL/min, vacuum < 3mbar, process time >=10min, application of vacuum continues Argon at least 5min after terminating, RH goes out to stand firm hydrogen thermometric, controls according to concentration [H]≤2.0ppm, and out-station temperature controls at 1540～1565 DEG C；
IV, continuous casting steel: continuous casting link adopts the mode that M-EMS combines with solidification end electromagnetic agitation, and wherein, the parameter of M-EMS is: stir current 380～450A, 3～5Hz；Solidification end stirring parameter is: stir current 300～400A, frequency 7.0～9.0Hz.
2. the 35CrMo circular pipe blank center porosity control method of φ 280mm as claimed in claim 1, is characterized in that: in step II and step III refining process adopt in the stirring of intensity Argon, occur without with molten steel surface and turn over greatly boiling and be as the criterion；Refine adopts soft argon blowing stirring after terminating, make molten steel have faint stirring.
3. the 35CrMo circular pipe blank center porosity control method of φ 280mm as claimed in claim 1, it is characterized in that: also need to when carrying out molten steel cast in step IV control following parameter: the degree of superheat controls at 25～40 DEG C, casting speed control is at 0.75～1.00m/min, crystallizer cooling controls at 2450～2650L/min, and two cold specific waters control at 0.25～0.35l/kgSteel。
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114086081A (en) * | 2021-11-19 | 2022-02-25 | 中天钢铁集团有限公司 | Method for controlling center loosening in cold forging steel production by small-section casting blank |
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2016
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114086081A (en) * | 2021-11-19 | 2022-02-25 | 中天钢铁集团有限公司 | Method for controlling center loosening in cold forging steel production by small-section casting blank |
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