CN103468871B - Method for preventing Q345B directly-loaded slabs from having cold-bending cracks - Google Patents
Method for preventing Q345B directly-loaded slabs from having cold-bending cracks Download PDFInfo
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- CN103468871B CN103468871B CN201310401455.XA CN201310401455A CN103468871B CN 103468871 B CN103468871 B CN 103468871B CN 201310401455 A CN201310401455 A CN 201310401455A CN 103468871 B CN103468871 B CN 103468871B
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Abstract
The invention provides a method for preventing Q345B directly-loaded slabs from having cold-bending cracks, and the method comprises the following steps: after LF (Ladle Furnace) refining and complete deoxidation alloying are performed, adding a rare earth alloy at an adding amount of 0.38-0.54 kg/t; controlling that in an LF evacuated liquid steel, the content of S is less than and equal to 0.005%, the content of Ti is greater than or equal to 0.01%, and [Nb]*[C] is greater than or equal to 0.004%; under the conditions that the argon-blowing flow of an argon station is 30-50 nm<3>/min and the argon blowing time is 3-5 min, carrying out argon-blowing and killing on the obtained object, and then placing the obtained product into a casting machine. The method disclosed by the invention is simple in process and operating conditions, and easy to implement; cold-bending cracks of Q345B directly-loaded slabs caused by slag inclusion defects can be effectively prevented, thereby improving the internal quality of slabs; problems existing in a direct loading process for micro alloyed steel are solved, and the production cost can be reduced.
Description
Technical field
The invention belongs to smelting technology technical field, particularly a kind of processing method for preventing Q345B from directly filling slab Cold Bending Crack.
Background technology
It is point out that the hot base of casting machine is with comparatively high temps (A that continuously cast bloom directly fills technique
1~ A
3) directly load process furnace, rolling after heating.Find in straight process of assembling, roll plate cold-bending property and do not conform to, occur crackle after Q345B steel grade directly fills, the Cold Bending Crack how solving straight dress stocking becomes the key realizing straight dress technique.
In document " Q345B rolled Strip Steel Cold Bending cracking Analysis ", the factor of analyzing influence cold-bending property, thinks in literary composition that more inclusion, serious banded structure are the major causes causing cold bend cracking.The impact of sulfide inclusion on cold-bending property is analyzed in document " sulfide inclusion in steel plate and the impact on cold-bending property thereof ", think in literary composition that size is comparatively large and the sulfide inclusion of integrated distribution can be used as formation of crack, directly cause plate of moderate thickness cold bend cracking, therefore, the cold-bending property that improve plate of moderate thickness must improve form and the distribution of sizes of sulfide.Document " analysis of Q345 steel plate cold bending crackle Producing reason ", hot-rolled steel sheet Q345 being produced to Cold Bending Crack has carried out system check, thinks that unrelieved stress, banded structure and the large-sized calcium-aluminate inclusion in steel plate is the reason causing Cold Bending Crack.
Through furtheing investigate straight dress defect stocking, find that crackle comes from MnS and is mingled with the junction with matrix, and launch along crystal boundary, this is because MnS is as different in the coefficient of expansion from the physical properties of steel matrix, easily form a kind of pre-destruction region in straight process of assembling, the emergence and development of crackle is played a decisive role, in addition, the gap also easy housing hydrogen of MnS and steel matrix, becomes hydrogen trap; Therefore, the generation directly filling slab Cold Bending Crack be avoided, deeply must carry out the research that in strand, inclusion MnS controls.
Document " Calcium treatment is analyzed nonmetallic inclusionsin steel degenerative effects ", by VD Calcium treatment, finds that friable alumina and harmful manganese sulfide have different sex change.Document " is fed CaSi line (Calcium treatment) to the analysis and research of steel inclusion sex change " and is mentioned, by control Ca/S than the form that can control sulfide.The document control of inclusion " in the RE-treated non orientating silicon steel " is mentioned, after RE-treated, be mainly mingled with from size relatively little, irregular AlN, MnS duplex impurity changes that size is comparatively large into, the rare earth class of almost spherical or elliposoidal is mingled with.
Although mention the modification technology of MnS in prior art, the concrete form of modification MnS, inclusion type, distribution are not all specifically studied.The simultaneously modification MnS for how, the needs making it to adapt to directly fill technique also lack research.Especially for precipitation process and the control method of NdC, existing document lacks correlative study especially.
Summary of the invention
The object of the invention is to the difficult point directly filling technique for micro-alloyed steel, provide a kind of simple, can production cost be reduced, effectively avoid Q345B directly to fill the method for slab Cold Bending Crack.
For this reason, the solution that the present invention takes is:
Prevent Q345B from directly filling a method for slab Cold Bending Crack, its concrete grammar is:
1, after the complete deoxidation alloying of LF refining, add rare earth alloy according to the add-on of steel 0.38 ~ 0.54kg per ton, carry out the process of inclusion remodeling, to change the existence form that MnS is mingled with, strand is not occurred, and independent MnS is mingled with.
2, control LF takes out of mass percent in molten steel: S≤0.005%, Ti >=0.01%, and [Nb] × [C] >=0.004%, thus improve the solid solubility temperature of NbC.Because under existing smelting technology condition, because molten steel component is different, therefore the solid solubility temperature constant interval of NdC is 900 DEG C-1200 DEG C, and only has when [Nb] × [C]≤0.004%, solid solubility temperature≤1100 DEG C of guarantee NbC.
3, argon station argon blowing rate is 30 ~ 50Nm
3/ min, argon blowing time 3 ~ 5 min, ensure that rare earth alloy fully dissolves and is evenly distributed, Argon calmness goes up casting machine afterwards.
La+Ce=26% ~ 70% in described rare earth alloy composition quality percentage composition.
Beneficial effect of the present invention is:
1, present invention process and operational condition simply, easily realize;
2, effectively can prevent the Q345B caused due to inclusion defects from directly filling the Cold Bending Crack of slab, improve the inner quality of slab;
3, solve the difficult point that micro-alloyed steel directly fills technique, and can production cost be reduced.
Embodiment
Embodiment steel mill smelts and slab continuous casting installation for casting is support, and Q345B smelts route and is: add rare earth alloy after BOF-RH – LF, LF deoxidation alloying, control LF takes out of sulphur content, and adjustment carbon, niobium, titanium content are to specified requirement.Get LF and take out of sample survey sulphur content, get middle ladle sample and carry out rare earth, niobium, carbon, titanium composition analysis, after getting the sample preparation of strand sample, carry out inclusion analysis, slab cold-bending property after tracking rolling simultaneously.Involved by embodiment, chemical composition is mass percentage.
Embodiment 1:
LF takes out of molten steel [S]: 0.005%, rare earth adding quantity: 140kg.
Argon station argon blowing rate: 30Nm
3/ min, the time: 5min.
Bag chemical composition in table 1 embodiment 1
| Re % | Nb % | C % | Ti % |
| 0.002 | 0.025 | 0.16 | 0.01 |
Have no grey large size sulfide inclusion under metallographic, can not see simple MnS under scanning electron microscope and be mingled with,
Crackle is had no after slab clod wash after rolling.
Embodiment 2:
LF takes out of molten steel [S]: 0.0035%, rare earth adding quantity: 120kg.
Argon station argon blowing rate: 40Nm
3/ min, time 4min.
Bag chemical composition in table 2 embodiment 2
| Re % | Nb % | [ C % | [ Ti % |
| 0.0015 | 0.026 | 0.17 | 0.012 |
Have no grey large size sulfide inclusion under metallographic, can not see simple MnS under scanning electron microscope and be mingled with; Crackle is had no after slab clod wash after rolling.
Embodiment 3:
LF takes out of molten steel [S]: 0.0026%, rare earth adding quantity 100kg.
Argon station argon blowing rate: 50Nm
3/ min, time 3min.
Bag chemical composition in table 3 embodiment 3
| Re % | Nb % | C % | Ti % |
| 0.0012 | 0.03 | 0.18 | 0.015 |
Have no grey large size sulfide inclusion under metallographic, can not see simple MnS under scanning electron microscope and be mingled with; Crackle is had no after slab clod wash after rolling.
Claims (2)
1. prevent Q345B from directly filling a method for slab Cold Bending Crack, it is characterized in that, concrete grammar is:
(1), after the complete deoxidation alloying of LF refining, rare earth alloy is added according to the add-on of steel 0.38 ~ 0.54kg per ton, to change the existence form that MnS is mingled with;
(2), control LF takes out of mass percent in molten steel: S≤0.005%, Ti >=0.01%, and [Nb] × [C] >=0.004%;
(3), argon station argon blowing rate is 30 ~ 50Nm
3/ min, argon blowing time 3 ~ 5min, Argon calmness goes up casting machine afterwards.
2. the Q345B of preventing according to claim 1 directly fills the method for slab Cold Bending Crack, it is characterized in that, La+Ce=26% ~ 70% in described rare earth alloy composition quality percentage composition.
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| CN201310401455.XA CN103468871B (en) | 2013-09-06 | 2013-09-06 | Method for preventing Q345B directly-loaded slabs from having cold-bending cracks |
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| CN103468871B true CN103468871B (en) | 2015-07-08 |
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| CN105195700A (en) * | 2014-06-23 | 2015-12-30 | 鞍钢股份有限公司 | Method for preventing surface cracks of thick plates in direct hot charge rolling |
Citations (6)
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| CN101871083A (en) * | 2010-06-14 | 2010-10-27 | 南阳汉冶特钢有限公司 | Ultra-thick low-alloy high-strength Q345-series steel plate and production method thereof |
| CN102041431A (en) * | 2010-12-21 | 2011-05-04 | 南阳汉冶特钢有限公司 | Q345B protected flaw detection steel plate and production method thereof |
| CN102560243A (en) * | 2011-12-02 | 2012-07-11 | 内蒙古包钢钢联股份有限公司 | Rolling method for Q345 steel plate with thickness of 50-100mm |
| CN102747277A (en) * | 2012-06-07 | 2012-10-24 | 河北钢铁股份有限公司 | Method for producing Q345 heat rolling plate rolls with excellent performance by low silicon low manganese |
| CN102828115A (en) * | 2012-09-25 | 2012-12-19 | 鞍钢股份有限公司 | Medium plate Q345B and production method of same |
| CN103031489A (en) * | 2012-06-03 | 2013-04-10 | 宝钢集团新疆八一钢铁有限公司 | Production method of Q345B steel plate |
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Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101871083A (en) * | 2010-06-14 | 2010-10-27 | 南阳汉冶特钢有限公司 | Ultra-thick low-alloy high-strength Q345-series steel plate and production method thereof |
| CN102041431A (en) * | 2010-12-21 | 2011-05-04 | 南阳汉冶特钢有限公司 | Q345B protected flaw detection steel plate and production method thereof |
| CN102560243A (en) * | 2011-12-02 | 2012-07-11 | 内蒙古包钢钢联股份有限公司 | Rolling method for Q345 steel plate with thickness of 50-100mm |
| CN103031489A (en) * | 2012-06-03 | 2013-04-10 | 宝钢集团新疆八一钢铁有限公司 | Production method of Q345B steel plate |
| CN102747277A (en) * | 2012-06-07 | 2012-10-24 | 河北钢铁股份有限公司 | Method for producing Q345 heat rolling plate rolls with excellent performance by low silicon low manganese |
| CN102828115A (en) * | 2012-09-25 | 2012-12-19 | 鞍钢股份有限公司 | Medium plate Q345B and production method of same |
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