CN102921914B - Heavy reduction technology for improving center segregation and center porosity of super-thick slabs - Google Patents
Heavy reduction technology for improving center segregation and center porosity of super-thick slabs Download PDFInfo
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Abstract
The invention discloses a heavy reduction technology for improving center segregation and center porosity of super-thick slabs. The heavy reduction technology is characterized in that the oil cylinder pressure of hydraulic cylinders on three sectorial sections of solidification tail ends of the continuous casting slabs ranges from 1800KN to 2500KN; and according to the solidification characteristics of steel types, the superheat degree of molten steel is controlled between 10-35 DEG C, the casting speed of a casting machine is controlled between 0.6 meter/minute and 1.0 meter/minute, the specific water flow of a secondary cooling zone is controlled between 0.4 and 0.6 liter/kilogram, large pressure is applied to one sectorial section to achieve the reduction of 5.0-12.0 millimeters, and the other two sectorial sections are slightly pressed to achieve reductions of 2-3 millimeters. The heavy reduction technology can be implemented to improve the quality of the super-thick slabs which further can be used for substituting for static ingots to produce super-thick steel plates with the thickness of 100millimeters and more, and the heavy reduction technology can achieve the high production efficiency and is environment-friendly.
Description
Technical field
The present invention relates to a kind of continuous casting steel billet Reduction Technology, relate in particular to a kind of large reduction method of improving thickness 300～420mm extra-thick plate blank center segregation and center porosity.
Background technology
Since entering the new century, due to scientific and technological progress and expanding economy, super-thick steel plate demand more than 100mm is increasing both at home and abroad.Some iron companies successively build or plan to build super-thick steel plate and produce equipment.The main equipment that super-thick steel plate is produced comprises smelting equipment, continuous casting installation for casting and Wide and Heavy Plates rolling equipment.Rolling special heavy plate material blank used is static ingot or continuous casting steel billet, China at present can steady production continuous casting steel billet thickness be all below 300mm substantially, be subject to some steel grade requirement compression ratios to be more than or equal to the restriction of 3:1, produce the super-thick steel plate of the above thickness of 100mm, need special thick strand as raw material rolling, because center segregation and the center porosity of the thick strand of spy are restive, generally do not adopt continuous casting steel billet as blank, but adopt static ingot to produce.Die casting process energy consumption is high, recovery rate of iron is low, environmental pollution is large, is not suitable with the social orientation of current energy-saving and emission-reduction and environmental protection.
Patent documentation application number 201010119734.3 mentions that the online doctor roll formula of a kind of conticaster depresses greatly liquid core rolling method, to increase a set of rolling equipment of depressing greatly at solidification end, by target setting thickness, Real-time Feedback one-tenth-value thickness 1/10 and detect oil pressure, whether conversion roll-force transfinites, if roll-force does not transfinite, stable rolling to rolling finishes; If roll-force transfinites, adjust and rejudge roll-force.Utility model patent 201020642804.9 discloses a kind of liquid-core high reduction rolling equipment for continuous casting machines, is arranged on slab caster level and solidifies the liquid core rolling district of holding latter end.These two patents only relate to conticaster and implement equipment and the liquid core rolling method depressed greatly, need increase a set of rolling equipment of depressing greatly at solidification end, investment is large, the not mentioned concrete technology of depressing greatly simultaneously, to how improving center segregation of casting blank and center porosity does not illustrate, especially there is not pertinent literature report to how solving thickness at 300～420mm extra-thick plate blank center segregation and center porosity problem.
Center segregation and center porosity defect more and more become one of principal element affecting steel product quality.Strand only possesses good internal soundness, and the center segregation of strand and center porosity are slighter, and the steel plate of the above thickness of rolling 100mm is better in aspect performances such as Z-direction performance, heart portion low temperature (≤-40 DEG C) impacts, and flaw detection qualification rate is high.Therefore, in the special heavy plate technological process of production, the steady production of high-quality extra-thick plate blank is core link, urgently obtains and breaks through technically.Processing and the use to steel of the center segregation of continuous casting billet and center porosity all can have a negative impact.For example, for natural gas transmission pipeline steel, segregation or loose place that the hydrogen in conveying gas can be diffused into tube wall crack and expand, and finally cause steel pipe to break; The structural steel of using for drilling at the sea platform, center segregation or loose meeting reduce its welding performance, cause steel plate to be difficult for welding, even postwelding cracking, thus greatly shortened the service life of steel.For this reason, start the nineties in 20th century, on slab caster, develop light Reduction Technology (referring to that drafts is 1.0～1.5mm/m), drafts 2～the 4mm(of common single fan-shaped section exceed 5mm the present invention be defined as greatly depress), its objective is near liquid core of continuous casting billet end and exerted pressure in continuous casting billet surface, make continuous casting billet produce certain drafts to compensate the solidification shrinkage amount of strand, can eliminate or reduce like this strand the contraction internal voids forming and the solute element that prevents intergranular enrichment to strand center flow, thereby play the effect that improves center segregation of casting blank and center porosity.But along with the continuous increase of slab thickness, the control difficulty of center segregation and center porosity is increasing, the requirement of slab caster gently being depressed to fan-shaped section hydraulic test is also more and more higher.Center segregation and the center porosity of resolving extra-thick plate blank are production high-quality super-thick steel plate and the key link that realizes target for energy-saving and emission-reduction, the super super-thick steel plate of research and development high-quality not only can improve China's device fabrication level, but also can greatly promote development and the breed structure readjustment thereof in the fields such as China's chemical industry, oil, machinery, power, metallurgy, nuclear energy, Aeronautics and Astronautics, ocean, have important practical significance and good economy and social benefit.
Summary of the invention
The object of the present invention is to provide the control technology of a kind of extra-thick plate blank (thickness 300～420mm) center segregation and center porosity, by controlling molten steel overheat and casting machine pulling rate, implement dynamically to depress greatly at Slab Solidification end, and in conjunction with the strong cold control jointly realizing extra-thick plate blank center segregation and center porosity of secondary cooling water.
The present invention realizes by following technical proposal: a kind of large reduction method of improving extra-thick plate blank center segregation and center porosity, it is characterized in that: slab thickness is 300～420mm, the oil cylinder working-pressure of 3 fan-shaped section hydraulic cylinders of Slab Solidification end is 1800～2500KN; According to steel grade coagulating property, control molten steel overheat 10～35, DEG C casting machine pulling rate is between 0.6m/min～1.0m/min, controlling two cold-zone specific waters is 0.4～0.6L/kg, a fan-shaped section is implemented to depress greatly therein, drafts is 5.0～12.0mm, and other two fan-shaped section are implemented gently to depress, drafts 2～3mm.
Determine the terminal that solidifies of different casting blank thickness by method of powder actuated shot.Method of powder actuated shot is that the steel nail taking sulphur as tracer is impacted into strand, analyze at the corresponding position sample of strand, be melted owing to being driven into after the steel nail of strand runs into liquid phase molten steel, solid phase area at strand is different with liquid phase region pattern, start to occur alligatoring place as boundary taking nailing, measure thickness of solidified slab shell in secondary by means such as macroscopic examination, sufur printing analyses, calculate the composite solidification coefficient of strand under various working conditions and solidify terminal according to shell thickness, calculate the liquid core length of strand, determine the fan-shaped section that needs enforcement to depress greatly.According to solidifying end point determination result, determine the best fan-shaped section of depressing greatly of different-thickness strand enforcement.
The present invention has following advantages and effect:
(1) by increasing the oil cylinder working-pressure of 3 fan-shaped section hydraulic cylinders of Slab Solidification end, drafts is increased, compensate the amount of contraction that special thick casting blank solidification end produces because of solidification shrinkage, simultaneously in conjunction with the cooling amount of contraction of bringing of secondary cooling water, can effectively control the center porosity of special thick strand.
(2), without increasing a set of rolling equipment of depressing greatly, by controlling molten steel overheat and casting machine pulling rate, a fan-shaped section is implemented to depress greatly therein, can control easily and effectively the center segregation of extra-thick plate blank (thickness 300～420mm), simple and easy to do.
(3) the invention process has been improved extra-thick plate blank quality, can replace the special heavy plate of the above thickness of static ingot production 100mm.
Brief description of the drawings
Fig. 1 is for implementing extra-thick slab casting machine frock schematic diagram of the present invention
Fig. 2 is that Slab Solidification end fan-shaped section roller is implemented the inner liquid core of strand compression variation schematic diagram time of the present invention.
Fig. 3 is that steel grade Q345D implements macrograph of the present invention.
Fig. 4 is that steel grade Q345R implements macrograph of the present invention.
Fig. 5 is that steel grade EH36 implements macrograph of the present invention.
In Fig. 1: 1-crystallizer; 2-0～8 fan-shaped section; 3-the 9th fan-shaped section; 4-the 10th fan-shaped section; 5-the 11st fan-shaped section; 6-12～16 fan-shaped section.
Detailed description of the invention
Referring to Fig. 1, implement extra-thick slab casting machine of the present invention, formed by 0 to 16 fan-shaped section, each fan-shaped section has 7 pair of rollers and four hydraulic jacks, and oil cylinder is exerted pressure, and 7 pair of rollers directly act on casting billet surface.Wherein the oil cylinder working-pressure of 3 fan-shaped section hydraulic cylinders of the 9th fan-shaped section the 3, the 10th fan-shaped section 4 of Slab Solidification end, the 11st fan-shaped section 5 is 1800～2500KN; Molten steel is through the cooling crust of 0 fan-shaped section of crystallizer 1 end opening, further cooling to the strand of solidified shell in 1～8 fan-shaped section secondary cooling zone, control molten steel overheat 10～35, DEG C casting machine pulling rate is between 0.6m/min～1.0m/min, controlling two cold-zone specific waters is 0.4～0.6L/kg, according to steel grade coagulating property, strand is implemented to depress greatly in the 9th fan-shaped section 3 or the 10th fan-shaped section 4 or the 11st fan-shaped section 5 one of them fan-shaped section, drafts is 5.0～12.0mm, other two fan-shaped section are implemented gently to depress, drafts 2～3mm.By continuous casting billet surface being applied to the solidification shrinkage amount of depressing greatly to compensate strand near liquid core of continuous casting billet end, the drafts acting on continuous casting billet is 9.0～18.0mm, can eliminate or reduce like this strand the contraction internal voids forming and the solute element that prevents intergranular enrichment to strand center flow, thereby play the effect that improves center segregation of casting blank and center porosity.Further cooling in 12～16 fan-shaped section 6 subsequently, obtain high-quality extra-thick plate blank.
Referring to Fig. 2, by continuous casting billet surface being applied to depressing greatly of 5.0～12.0mm near liquid core of continuous casting billet end, add gently depressing of other adjacent fan-shaped section, the heavy reduction that makes continuous casting billet produce 9.0～18.0mm compensates the solidification shrinkage amount of strand, eliminate or reduce strand the contraction internal voids forming and the solute element that prevents intergranular enrichment to strand center flow, thereby play the effect that improves center segregation of casting blank and center porosity.
Embodiment 1: steel grade Q345D, slab thickness 300mm, width 2270mm, detects 35 DEG C of the degrees of superheat, pulling rate 1.0m/min, two cold-zone specific waters are 0.4L/kg.Implementing to depress is greatly the 9th fan-shaped section 3, and drafts is 5.0mm, and the 10th fan-shaped section 4 and the 11st fan-shaped section 5 drafts are 3mm, and the 9th fan-shaped section 3 oil cylinder working-pressures are 1800KN.
Implementation result: strand detects through low power, center segregation is C1.0, center porosity is C1.0, occurs without middle crack.Fig. 3 is shown in by macrograph.
Embodiment 2: steel grade Q345R, slab thickness 360mm, width 2070mm, detects the degree of superheat 25, DEG C pulling rate 0.8m/min, two cold-zone specific waters are 0.5L/kg.Implementing to depress is greatly the 11st fan-shaped section 5, and drafts is 9mm, and the 9th fan-shaped section and the 10th fan-shaped section drafts are 2.5mm, and the 11st fan-shaped section oil cylinder working-pressure is 2000KN.
Implementation result: strand detects through low power, center segregation is C0.5, center porosity is C0.5, occurs without middle crack.Fig. 4 is shown in by macrograph.
Embodiment 3: steel grade EH36, slab thickness 420mm, width 2070mm, detects 10 DEG C of the degrees of superheat, pulling rate 0.6m/min, two cold-zone specific waters are 0.6L/kg.Implementing to depress is greatly the 10th fan-shaped section 4, and drafts is 12mm, and the 9th fan-shaped section 3 and the 11st fan-shaped section 5 drafts are 2mm, and the 10th fan-shaped section 4 pressure are 2500KN.
Implementation result: strand detects through low power, center segregation is C0.5, center porosity is C0.5, occurs without middle crack.Fig. 5 is shown in by macrograph.
Claims (1)
1. a large reduction method of improving extra-thick plate blank center segregation and center porosity, is characterized in that: slab thickness is 300～420mm, and the oil cylinder working-pressure of 3 fan-shaped section hydraulic cylinders of Slab Solidification end is 1800～2500KN; According to steel grade coagulating property, control molten steel overheat 10～35, DEG C casting machine pulling rate is between 0.6m/min～1.0m/min, controlling two cold-zone specific waters is 0.4～0.6L/kg, a fan-shaped section is implemented to depress greatly therein, drafts is 5.0～12.0mm, and other two fan-shaped section are implemented gently to depress, drafts 2～3mm.
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| JP5779978B2 (en) * | 2010-05-31 | 2015-09-16 | Ｊｆｅスチール株式会社 | Light reduction method of slab in continuous casting |
| CN101934357B (en) * | 2010-08-23 | 2012-05-30 | 首钢总公司 | Process for effectively controlling central segregation of continuous cast slab |
| CN102601331B (en) * | 2011-12-09 | 2014-01-29 | 秦皇岛首秦金属材料有限公司 | Method for improving center segregation of extra thick slab with thickness of 400mm |
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Effective date of registration: 20160708 Address after: 338001 Xinyu metallurgy Road, Jiangxi, No. 1 Patentee after: Xinyu Iron & Steel Co., Ltd. Address before: 338001 Xinyu metallurgy Road, Jiangxi, No. 1 Patentee before: Xinyu Iron & Steel Co., Ltd. |
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Correction item: Patentee|Address Correct: Xinyu Iron & Steel Co., Ltd.|338001 Xinyu metallurgy Road, Jiangxi, No. 1 False: Xinyu Iron & Steel Co., Ltd.|338001 Xinyu metallurgy Road, Jiangxi, No. 1 Number: 23 Volume: 30 |
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Effective date of registration: 20160802 Address after: 338001 Xinyu metallurgy Road, Jiangxi, No. 1 Patentee after: Xinyu Iron & Steel Co., Ltd. Address before: 338001 Xinyu metallurgy Road, Jiangxi, No. 1 Patentee before: Xinyu Iron & Steel Co., Ltd. |