CN115679202A - Super-thick steel plate without heat treatment and with excellent Z-directional performance and production method thereof - Google Patents
Super-thick steel plate without heat treatment and with excellent Z-directional performance and production method thereof Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 87
- 239000010959 steel Substances 0.000 title claims abstract description 87
- 238000010438 heat treatment Methods 0.000 title claims abstract description 29
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 25
- 238000005096 rolling process Methods 0.000 claims abstract description 44
- 238000005266 casting Methods 0.000 claims abstract description 34
- 238000001816 cooling Methods 0.000 claims abstract description 22
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 20
- 238000000034 method Methods 0.000 claims abstract description 20
- 238000010583 slow cooling Methods 0.000 claims abstract description 20
- 239000011575 calcium Substances 0.000 claims abstract description 14
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims abstract description 11
- 229910052791 calcium Inorganic materials 0.000 claims abstract description 11
- 239000002131 composite material Substances 0.000 claims abstract description 9
- 238000009749 continuous casting Methods 0.000 claims abstract description 8
- 229910052742 iron Inorganic materials 0.000 claims abstract description 8
- 238000004321 preservation Methods 0.000 claims abstract description 8
- 238000009489 vacuum treatment Methods 0.000 claims abstract description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 8
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 7
- 238000006477 desulfuration reaction Methods 0.000 claims abstract description 6
- 230000023556 desulfurization Effects 0.000 claims abstract description 6
- 238000007670 refining Methods 0.000 claims abstract description 6
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 5
- 238000003723 Smelting Methods 0.000 claims abstract description 4
- 239000012535 impurity Substances 0.000 claims abstract description 4
- 229910052739 hydrogen Inorganic materials 0.000 claims description 6
- 239000001257 hydrogen Substances 0.000 claims description 6
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 5
- WNQQFQRHFNVNSP-UHFFFAOYSA-N [Ca].[Fe] Chemical compound [Ca].[Fe] WNQQFQRHFNVNSP-UHFFFAOYSA-N 0.000 claims description 4
- 238000007664 blowing Methods 0.000 claims description 4
- 238000002791 soaking Methods 0.000 claims description 3
- 230000000052 comparative effect Effects 0.000 description 8
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 7
- 238000003466 welding Methods 0.000 description 7
- 239000010955 niobium Substances 0.000 description 6
- 239000000047 product Substances 0.000 description 6
- 239000010936 titanium Substances 0.000 description 6
- 238000005728 strengthening Methods 0.000 description 5
- 230000008901 benefit Effects 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 229910052782 aluminium Inorganic materials 0.000 description 3
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical group [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 3
- 229910001566 austenite Inorganic materials 0.000 description 3
- 238000013461 design Methods 0.000 description 3
- 229910052758 niobium Inorganic materials 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
- 230000035945 sensitivity Effects 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- 238000009628 steelmaking Methods 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 229910052719 titanium Inorganic materials 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 2
- 229910000746 Structural steel Inorganic materials 0.000 description 2
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 2
- 230000032683 aging Effects 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 2
- 239000011574 phosphorus Substances 0.000 description 2
- 238000004886 process control Methods 0.000 description 2
- 239000002893 slag Substances 0.000 description 2
- 239000002436 steel type Substances 0.000 description 2
- 238000005496 tempering Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 229910052720 vanadium Inorganic materials 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- 229910001209 Low-carbon steel Inorganic materials 0.000 description 1
- 229910001257 Nb alloy Inorganic materials 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 239000005864 Sulphur Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- XFWJKVMFIVXPKK-UHFFFAOYSA-N calcium;oxido(oxo)alumane Chemical compound [Ca+2].[O-][Al]=O.[O-][Al]=O XFWJKVMFIVXPKK-UHFFFAOYSA-N 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
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- 238000001514 detection method Methods 0.000 description 1
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- 238000004512 die casting Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
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- 239000007789 gas Substances 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 229910000734 martensite Inorganic materials 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
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- 239000007769 metal material Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
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- 238000001556 precipitation Methods 0.000 description 1
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- 239000012629 purifying agent Substances 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 150000003568 thioethers Chemical class 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 description 1
Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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Abstract
The invention relates to an ultra-thick steel plate without heat treatment and with excellent Z-direction performance and a production method thereof, wherein the steel plate consists of the following elements in percentage by mass: c:0.12 to 0.20%, si:0.15 to 0.45%, mn:1.00 to 1.80%, ti:0.018 to 0.025%, nb:0.030 to 0.055%, als: 0.010-0.028%, P is less than or equal to 0.012%, S is less than or equal to 0.004%, ca:0.0008 to 0.0045 percent, and the balance of Fe and inevitable impurities, and simultaneously satisfies the following conditions: mn/S is more than 220; the production method comprises the following steps: the method comprises the following steps of iron water deep desulfurization → converter top and bottom composite smelting → inclusion calcium treatment → LF furnace refining → vacuum treatment → continuous casting → heat preservation pit slow cooling → casting blank heating → rolling mill rolling → steel plate stack cooling → finishing, the thickness of the steel plate finished product prepared by the method is 50-100mm: 55-68%, yield strength: 462 to 489MPa, tensile strength: 638 to 671MPa, yield ratio is less than or equal to 0.73, impact at-20 ℃:215 to 247J; the invention does not need large single-weight and large-thickness plate blanks, and the casting blank can meet the thickness of 300mm, thereby having general popularization significance.
Description
Technical Field
The invention relates to the technical field of metal material manufacturing, in particular to an ultra-thick steel plate which does not need heat treatment and has excellent Z-direction performance and a production method thereof.
Background
With the rapid development of modern industry in China, higher and higher requirements are put on the thickness and the mechanical property of the steel plate, and particularly, the production of the large-thickness steel plate is required more and more in the fields of high-rise buildings, bridges, engineering machinery, molds and the like. Because of the structural load bearing requirements, thick plate welded structures are often employed. During welding, the thick plate is liable to be torn in layers due to the quality of the steel material and the welding configuration, which is extremely disadvantageous to a joint pulled in the thickness direction. Therefore, the Z-directional performance of the steel plate is significant. At present, steel plants in China produce the super-thick steel plates with Z-direction performance, super-large specification steel nails or continuous casting blanks (the thickness is more than 400 mm) are generally adopted, even composite welding is adopted to prepare a mother blank, a large amount of Nb, V or Cu is selectively added to the components, and the steel plates are prepared by adopting an off-line normalizing heat treatment or even tempering mode after rolling. The methods have long process flow, need to invest huge equipment cost, and have high cost and low efficiency of producing ton steel. Therefore, under the existing equipment conditions, a slab with the common casting blank thickness (less than or equal to 300 mm) is developed, and an ultra-thick steel plate which does not need post-rolling heat treatment and has excellent Z-directional performance is obtained through a certain process control measure, so that the ultra-thick steel plate has great social benefit and economic benefit.
In China, the production of super-thick steel plates by casting blanks is mostly reported and also patented. The application number CN200910048139.2 discloses a super-thick steel plate with excellent Z-directional performance for buildings and a production method thereof, the application number CN201711310106.1 discloses a 160 mm-thick super-thick plate produced under the condition of low compression ratio and a production method thereof, the application number CN 102732674A discloses the production of a large-thickness large-piece-weight low-alloy high-strength structural steel plate and the like, the above patents all adopt continuous casting billets or die castings with the thickness of more than 300mm, and simultaneously adopt the process flow of rolling-normalizing heat treatment, namely after the rolling forming is completed, the steel plate needs to be additionally heated in a furnace for heat treatment, and the invention does not need heat treatment to obtain the design idea of the super-thick plate with excellent mechanical performance.
Based on the above situation, the demand for designing and producing the steel plate with extra-thick and better thickness directional performance by adopting the short-flow process and the green and economic components on the basis of not increasing the investment becomes the next problem to be solved urgently, and the great significance is brought to the production of the extra-thick plate.
Disclosure of Invention
The invention aims to provide an ultra-thick steel plate which does not need heat treatment and has excellent Z-direction performance and a production method thereof, aiming at the defects in the prior art, the method adopts a casting blank with the thickness of less than or equal to 300mm, and obtains the steel plate with the thickness of 50-100mm, the Z-direction performance of 55-68%, the yield strength of 462-489 MPa, the tensile strength of 638-671 MPa, the yield ratio of less than or equal to 0.73 and the impact of 215-247J at-20 ℃ without normalizing and other heat treatment modes under the condition of not modifying equipment.
The invention discloses an ultra-thick steel plate which does not need heat treatment and has excellent Z-direction performance, and the steel plate consists of the following elements in percentage by mass: c:0.12 to 0.20%, si:0.15 to 0.45%, mn:1.00 to 1.80%, ti:0.018 to 0.025%, nb:0.030 to 0.055%, als: 0.010-0.028%, P is less than or equal to 0.012%, S is less than or equal to 0.004%, ca:0.0008 to 0.0045 percent, and the balance of Fe and inevitable impurities, and simultaneously satisfies the following conditions: mn/S is more than 220.
The thickness of the finished product of the steel plate prepared by the invention is 50-100mm, and the Z-direction performance is as follows: 55-68%, yield strength: 462-489 MPa, tensile strength: 638 to 671MPa, yield ratio is less than or equal to 0.73, impact at-20 ℃:215 to 247J.
The invention discloses a method for producing an ultra-thick steel plate without heat treatment and with excellent Z-direction performance, which comprises the following steps: the method comprises the following steps of iron water deep desulphurization → converter top and bottom composite smelting → inclusion calcium treatment → LF furnace refining → vacuum treatment → continuous casting → heat preservation pit slow cooling → casting blank heating → rolling mill rolling → steel plate cooling by stacking → finishing, wherein:
(1) Deep desulfurization of molten iron, composite blowing at the top and bottom of a converter, RH vacuum treatment, calcium treatment by feeding calcium iron wires, controlling the hydrogen content to be less than 1.0ppm, P to be less than or equal to 0.007 percent, S to be less than or equal to 0.002 percent, controlling the pulling speed to be 0.60-0.70 m/min, continuously casting into a casting blank with the thickness of 250-300 mm, controlling the superheat degree to be within the range of 10-25 ℃, and simultaneously strictly limiting: mn/S is more than 220;
(2) After the casting blank is off-line at 400-500 ℃, the casting blank enters a heat preservation pit for slow cooling, and the slow cooling time is as follows: h is less than or equal to 250mm, and the slow cooling time is more than or equal to 50 hours; h is more than or equal to 300mm and more than 250mm, the slow cooling time is more than or equal to 75 hours, H is the thickness of a casting blank, and the casting blank is cleaned, checked and then delivered;
(3) The heating time of the casting blank is 1800-1230 ℃, and the soaking rate is controlled according to the speed of more than or equal to 1.4 min/cm;
(4) The rolling of the rolling mill adopts two-stage controlled rolling, the initial rolling temperature of one stage is controlled to be 1050-1080 ℃, the widening pass is controlled to be 2-3 passes, the initial rolling temperature of the two stages is controlled to be 880-960 ℃, the roller speed is controlled to be 0.6-0.8 m/s, and the load temperature of the final rolling is 840-860 ℃;
(5) Cooling by water after rolling, wherein the starting cooling temperature is controlled to be 760-820 ℃, the cooling speed is controlled to be 25-30 ℃/S, and the temperature of red return is controlled to be 600-650 ℃;
(6) The steel plate is subjected to stack cooling from the lower line of the cooling bed, and the stack cooling time is as follows: (32h + 40)/60 hours, wherein h is the thickness of the finished product.
The reasons for limiting the main chemical components in the steel of the present invention are as follows:
c: carbon is one of indispensable elements for improving the strength of steel, and when the content of C is less than 0.12%, the above-mentioned strengthening effect of C is weakened, so that the strength of the inventive steel is insufficient; when the content of C is more than 0.20%, the welding cold crack sensitivity coefficient is improved, the low-temperature toughness of the base material and a welding heat affected zone is reduced strongly, and the cold and hot processing performance is influenced, so that the content is controlled to be 0.12-0.20%.
Si: silicon has a strong solid solution strengthening effect and is also a deoxidizing element in steel. Si reduces the solubility of C in austenite, promotes C to be dropped and precipitates as carbide, but if the Si content in the steel is too high, the reduction in area ratio is caused, and the weldability of the steel is also impaired, so that the content is controlled to 0.15 to 0.45%.
Mn: the Mn content is not too high, otherwise, the reduction of the martensite transformation point is influenced, and further, the residual austenite amount at room temperature is increased, so that the steel strength is controlled to be 1.00-1.80%.
Ti: titanium is a strong deoxidizer in steel, can make the internal structure of steel compact, refine crystal grains, reduce aging sensitivity and cold brittleness, improve welding performance, and can reduce the difference of longitudinal and transverse performances by adding a certain amount of Ti. In addition, compared with the strengthening elements such as niobium, vanadium and the like, titanium has larger resource and cost advantages, the price is less than one tenth of the price, so the Ti content is designed as follows: ti:0.018 to 0.025 percent.
Ca: calcium is a good molten steel purifying agent, and can be used for deep deoxidation and deep desulfurization. Can be mixed with Al in steel 2 O 3 The reaction takes place. Calcium in these Al 2 O 3 The mixed particles are diffused to ensure that calcium continuously enters the position of aluminum, the replaced aluminum enters molten steel, and Al is diffused along with Ca 2 O 3 The CaO content on the inclusion surface is increased when CaO>When 25 percent of the slag is in a liquid state, most of the liquid calcium aluminate inclusion with high CaO content floats out of the molten steel and enters a slag layer, and a small part of non-floating inclusion particles are remained in the steel in a small spherical shape, so that the deoxidation problem is solved, and Al in the steel is greatly reduced 2 O 3 And the inclusion can also make the microstructure of the billet tend to be uniform, improve the fluidity of molten steel, and reduce the problems of water gap blockage and the like in the pouring process. Ca is controlled to be 0.0008 to 0.0045 percent.
Nb: the metal niobium is a strong carbide forming element and has strong grain refining and precipitation strengthening effects, and fine carbonitride particles formed by Nb can effectively inhibit austenite grains from growing in the rolling process and have a strong refining effect on the final structure of a product, so that the strength, the low-temperature toughness and the elongation property are improved. Nb is controlled to be 0.030 to 0.055 percent.
And Als: aluminum is used as a nitrogen deoxidizing and fixing agent in steel making, crystal grains are refined, the aging of low-carbon steel is inhibited, the toughness of the steel at low temperature is improved, and the oxidation resistance of the steel can be improved, when Als is more than 0.030%, the grade of sulfide inclusion exceeds 1.5, and when Als is 0.003%, II-type sulfide inclusion exists in the steel. Controlling Als at 0.010-0.028%. ( The sulfides are classified into three groups according to their morphology and distribution in steel. The I type is spherical and randomly distributed, and the inclusions are single-phase or two-phase; the 1I type is distributed along the grain boundary or in a fan shape; the III groups are blocky and are distributed randomly. )
P: the biggest harm of phosphorus is to cause serious segregation and influence the performance in the thickness direction and the flaw detection result, and meanwhile, the phosphorus element increases the tempering brittleness and the cold brittleness sensitivity, so that the welding performance of steel is deteriorated, the plasticity is reduced, but the cost is increased due to the over-low requirement of the P content, and the production difficulty is improved, so the P content is designed to be less than or equal to 0.012 percent.
S: sulphur is also a harmful element in normal conditions, and is generally present in steel in the form of FeS, which is poor in plasticity and low in melting point. FeS is distributed around the grain boundary when the molten steel is crystallized. Heating and rolling at 800-1200 ℃ can lead to cracking through grain boundaries. In addition, S often forms strip-like MnS inclusions with Mn in molten steel, and it has been found that when the MnS content in steel is high, the lower the diffusion coefficient of hydrogen in steel is, the lower the mechanical properties and internal quality are. Therefore, the S content is designed to be less than or equal to 0.004 percent.
And meanwhile, strictly defining Mn/S to be more than 220, and verifying by a large amount of data, when Mn/S is more than 220, the sulfide inclusion can be ensured to be within 1 grade, and the grade of the sulfide inclusion is reduced along with the increase of the ratio of [ Mn ]/[ S ]. On the one hand, along with the increase of [ Mn ], the capacity of the molten steel to [ S ] is increased, and the precipitated sulfide is more dispersed and finer, so that the grade of the sulfide is reduced.
The main process and process parameter setting reasons of the steel of the invention are as follows:
deep desulfurization of molten iron, composite blowing at the top and bottom of a converter, RH vacuum treatment, calcium treatment by feeding calcium iron wires, continuous casting into a casting blank with the thickness of 250-300 mm, controlling the superheat degree within the range of 10-25 ℃, reducing the internal gas content of the casting blank by the control parameters, reducing the generation of defects such as inclusion, shrinkage cavity and the like, and laying a foundation for producing a steel plate with good internal quality, wherein the hydrogen content is less than 1.0ppm, the P is less than or equal to 0.007%, the S is less than or equal to 0.002%, the pulling speed is controlled within the range of 0.60-0.70 m/min; and at the same time strictly limiting: mn/S is more than 220;
after the casting blank is off-line at 400-500 ℃, the casting blank enters a heat preservation pit for slow cooling and hydrogen diffusion treatment;
the slow cooling time is as follows: h is less than or equal to 250mm, and the slow cooling time is more than or equal to 50 hours; h is more than 250mm when the thickness is more than or equal to 300mm, and the slow cooling time is more than or equal to 75 hours; (H is the thickness of the casting blank)
Two-stage rolling is adopted in the rolling process, the initial rolling temperature of one stage is strictly controlled, the number of widening passes is controlled, the initial rolling temperature of the two stages is properly increased, sulfide inclusions are prevented from being further elongated, the lamellar tearing resistance is reduced, the Z-direction section shrinkage rate is reduced, and the final rolling load temperature is 840-860 ℃;
the technical scheme provided by the invention adopts medium-low carbon on the components of the steel grade, uses cheap Ti, mn and trace Nb alloy as main strengthening alloy elements, limits the addition ratio of Mn/S, strictly controls the contents of harmful elements P and S, and is in rolling.
The thickness specification of the steel plate is 50-100 mm, the Z-direction performance is 55-68%, the yield strength is 462-489 MPa, the tensile strength is 638-671 MPa, the yield ratio is not more than 0.73, and the impact is 215-247J at-20 ℃.
The method for producing the super-thick steel plate with excellent Z-direction performance without heat treatment has the following beneficial effects:
(1) By adopting a short-flow process, the process design of the heat treatment after rolling required for producing the ultra-thick steel by steel mills at home and abroad by more than 90 percent is broken through, the production period is greatly shortened, the delivery efficiency of production and contract is improved, and the win-win situation between the steel mills and users is realized;
(2) The green and economic component design is adopted, and the clean and high-quality blank is obtained by strictly limiting the type and the quantity of the inclusions;
(3) The method has the advantages that large sheet weight and large thickness of the plate blank are not needed, the casting blank can be 300mm thick, more than 95% of domestic medium plate production line production is met, the method has general popularization significance, belongs to high value-added products, and has great popularization significance.
Detailed Description
In order to better explain the technical solution of the present invention, the technical solution of the present invention is further described below with reference to specific examples, which are only exemplary to illustrate the technical solution of the present invention and do not limit the present invention in any way.
In practical applications, according to different production specifications and batches of steel plates, different component contents in a control range, specific process control conditions and corresponding mechanical property indexes are provided, and in order to better illustrate and explain the invention, the components, process conditions and mechanical properties of the examples (steel types related to the invention) and the comparative examples (existing steel types) of the invention are listed and compared in tables 1 to 3.
The following table 1 is a list of main control parameters and values of chemical components (wt%) in a steelmaking process of steel sheets according to each example and comparative example of the present invention;
the following table 2 is a list of values of main process parameters for rolling steel plates according to the examples and comparative examples of the present invention;
table 3 below is a table showing the results of the main mechanical property tests of the steel sheets of the examples and comparative examples of the present invention.
The super-thick steel plate without heat treatment and with excellent Z-direction performance provided by the embodiments of the invention comprises the following elements in percentage by mass: c:0.12 to 0.20%, si:0.15 to 0.45%, mn:1.00 to 1.80%, ti:0.018 to 0.025%, nb:0.030 to 0.055%, als: 0.010-0.028%, P is less than or equal to 0.012%, S is less than or equal to 0.004%, ca:0.0008 to 0.0045 percent, and the balance of Fe and inevitable impurities, and simultaneously satisfies the following conditions: mn/S is more than 220.
The thickness of the finished product of the prepared steel plate is 50-100mm, and the Z-direction performance is as follows: 55-68%, yield strength: 462 to 489MPa, tensile strength: 638 to 671MPa, yield ratio is less than or equal to 0.73, impact at-20 ℃:215 to 247J.
The method for producing the super-thick steel plate which does not need heat treatment and has excellent Z-direction performance comprises the following steps: the method comprises the following steps of iron water deep desulphurization → converter top and bottom composite smelting → inclusion calcium treatment → LF furnace refining → vacuum treatment → continuous casting → heat preservation pit slow cooling → casting blank heating → rolling mill rolling → steel plate cooling by stacking → finishing, wherein:
(1) Deep desulfurization of molten iron, composite blowing at the top and bottom of a converter, RH vacuum treatment, calcium treatment by feeding calcium iron wires, controlling the hydrogen content to be less than 1.0ppm, P to be less than or equal to 0.007 percent, S to be less than or equal to 0.002 percent, controlling the pulling speed to be 0.60-0.70 m/min, continuously casting into a casting blank with the thickness of 250-300 mm, controlling the superheat degree to be within the range of 10-25 ℃ and strictly limiting the following steps: mn/S is more than 220;
(2) After being off-line at 400-500 ℃, the casting blank enters a heat preservation pit for slow cooling, wherein the slow cooling time is as follows: h is less than or equal to 250mm, and the slow cooling time is more than or equal to 50 hours; h is more than or equal to 300mm and more than 250mm, the slow cooling time is more than or equal to 75 hours, H is the thickness of a casting blank, and the casting blank is cleaned, checked and then delivered;
(3) The heating time of the casting blank is 1800-1230 ℃, and the soaking rate is controlled according to the speed of more than or equal to 1.4 min/cm;
(4) The rolling of the rolling mill adopts two-stage controlled rolling, the initial rolling temperature of one stage is controlled to be 1050-1080 ℃, the widening pass is controlled to be 2-3 passes, the initial rolling temperature of the two stages is controlled to be 880-960 ℃, the roller speed is controlled to be 0.6-0.8 m/s, and the load temperature of the final rolling is 840-860 ℃;
(5) Cooling by water after rolling, wherein the starting cooling temperature is controlled to be 760-820 ℃, the cooling speed is controlled to be 25-30 ℃/S, and the temperature of red return is controlled to be 600-650 ℃;
(6) The steel plate is cooled in a piling way from the lower line of the cooling bed, and the piling cooling time is as follows: (32h + 40)/60 hours, wherein h is the thickness of the finished product.
TABLE 1 Steel-making Process and chemical composition (wt%) value List of Steel sheets according to examples and comparative examples of the present invention
TABLE 2 tabulation of values of main process parameters for rolling steel plates of each example of the invention and comparative example
TABLE 3 test result list of mechanical properties of steel sheets of each example and comparative example of the present invention
As can be seen from Table 3, the Z-directional performance of the steel plates with thickness of 50 to 100mm produced by the components and the production process designed by the invention is within 55 to 68 percent, the yield strength is 462 to 489MPa, the tensile strength is 638 to 671MPa, the yield ratio is less than or equal to 0.73, and the impact at minus 20 ℃ is 215 to 247J.
In contrast to comparative examples 1 and 2, the performance in the thickness direction is only 11 to 24 percent, the requirement of the lowest Z15 cannot be met, and the strength of a steel plate with the thickness of 100mm only marginally meets the level of 420 MPa.
The data in tables 1 to 3 show that the steel plates produced by the production method without post-rolling heat treatment have excellent Z-directional performance, and the steel plates can actually obtain structural steel with the thickness of 50 to 100mm by using a continuous casting billet with the thickness of 250 to 300mm, the thickness-directional performance of 55 to 68 percent and the yield strength of more than or equal to 460 MPa.
The embodiments described above are merely specific examples of the present invention exemplified for explaining the present invention, and do not limit the present invention in any way, and any insubstantial changes from the above-described contents and forms without departing from the scope of the present invention are considered to fall within the scope of the present invention as claimed.
Claims (3)
1. The super-thick steel plate which does not need heat treatment and has excellent Z-direction performance is characterized by comprising the following elements in percentage by mass: c:0.12 to 0.20%, si:0.15 to 0.45%, mn: 1.00-1.80%, ti:0.018 to 0.025%, nb:0.030 to 0.055%, als: 0.010-0.028%, P is less than or equal to 0.012%, S is less than or equal to 0.004%, ca:0.0008 to 0.0045 percent, and the balance of Fe and inevitable impurities, and simultaneously satisfies the following conditions: mn/S is more than 220.
2. The super thick steel plate having excellent Z-directional properties without heat treatment according to claim 1, wherein: the thickness of a finished product of the steel plate is 50-100mm, and the Z-direction performance is as follows: 55-68%, yield strength: 462 to 489MPa, tensile strength: 638 to 671MPa, yield ratio less than or equal to 0.73, impact at-20 deg.C: 215 to 247J.
3. The method for producing the super thick steel plate having excellent Z-directional properties without heat treatment according to claim 1 or 2, comprising the steps of: the method comprises the following steps of iron water deep desulphurization → converter top and bottom composite smelting → inclusion calcium treatment → LF furnace refining → vacuum treatment → continuous casting → heat preservation pit slow cooling → casting blank heating → rolling mill rolling → steel plate cooling by stacking → finishing, and is characterized in that:
(1) Deep desulfurization of molten iron, composite blowing at the top and bottom of a converter, RH vacuum treatment, calcium treatment by feeding calcium iron wires, controlling the hydrogen content to be less than 1.0ppm, P to be less than or equal to 0.007 percent, S to be less than or equal to 0.002 percent, controlling the pulling speed to be 0.60-0.70 m/min, continuously casting into a casting blank with the thickness of 250-300 mm, controlling the superheat degree to be within the range of 10-25 ℃ and strictly limiting the following steps: mn/S is more than 220;
(2) After the casting blank is off-line at 400-500 ℃, the casting blank enters a heat preservation pit for slow cooling, and the slow cooling time is as follows: h is less than or equal to 250mm, and the slow cooling time is more than or equal to 50 hours; h is more than or equal to 300mm and more than 250mm, the slow cooling time is more than or equal to 75 hours, H is the thickness of a casting blank, and the casting blank is cleaned, checked and then delivered;
(3) The heating time of the casting blank is 1800-1230 ℃, and the soaking rate is controlled according to the speed of more than or equal to 1.4 min/cm;
(4) The rolling of the rolling mill adopts two-stage controlled rolling, the initial rolling temperature of one stage is controlled to be 1050-1080 ℃, the widening pass is controlled to be 2-3 passes, the initial rolling temperature of the two stages is controlled to be 880-960 ℃, the roller speed is controlled to be 0.6-0.8 m/s, and the load temperature of the final rolling is 840-860 ℃;
(5) The cooling is water cooling after rolling, the starting cooling temperature is controlled to be 760-820 ℃, the cooling speed is controlled according to 25-30 ℃/S, and the temperature of the red returning is controlled according to 600-650 ℃; the steel plate is subjected to stack cooling from the lower line of the cooling bed, and the stack cooling time is as follows: (32h + 40)/60 hours, wherein h is the thickness of the finished product.
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