CN115433873B - E-grade flat bulb steel with economy and excellent strength and toughness and production method thereof - Google Patents
E-grade flat bulb steel with economy and excellent strength and toughness and production method thereof Download PDFInfo
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- CN115433873B CN115433873B CN202211051954.6A CN202211051954A CN115433873B CN 115433873 B CN115433873 B CN 115433873B CN 202211051954 A CN202211051954 A CN 202211051954A CN 115433873 B CN115433873 B CN 115433873B
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 60
- 239000010959 steel Substances 0.000 title claims abstract description 60
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 18
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 29
- 238000000034 method Methods 0.000 claims abstract description 22
- 230000008569 process Effects 0.000 claims abstract description 20
- 238000005496 tempering Methods 0.000 claims abstract description 16
- 229910052742 iron Inorganic materials 0.000 claims abstract description 12
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 11
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 11
- 239000000126 substance Substances 0.000 claims abstract description 10
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 10
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 9
- 239000012535 impurity Substances 0.000 claims abstract description 8
- 229910052758 niobium Inorganic materials 0.000 claims abstract description 8
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 8
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 7
- 238000001816 cooling Methods 0.000 claims description 32
- 238000005096 rolling process Methods 0.000 claims description 20
- 238000010438 heat treatment Methods 0.000 claims description 18
- 238000009749 continuous casting Methods 0.000 claims description 15
- 239000011575 calcium Substances 0.000 claims description 11
- 229910000859 α-Fe Inorganic materials 0.000 claims description 11
- 238000003723 Smelting Methods 0.000 claims description 10
- 229910001566 austenite Inorganic materials 0.000 claims description 10
- 238000007670 refining Methods 0.000 claims description 9
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 8
- 238000007664 blowing Methods 0.000 claims description 8
- 238000011282 treatment Methods 0.000 claims description 8
- 229910052791 calcium Inorganic materials 0.000 claims description 7
- 238000005266 casting Methods 0.000 claims description 6
- 239000000498 cooling water Substances 0.000 claims description 6
- 229910000734 martensite Inorganic materials 0.000 claims description 6
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims description 4
- FBPFZTCFMRRESA-JGWLITMVSA-N D-glucitol Chemical compound OC[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO FBPFZTCFMRRESA-JGWLITMVSA-N 0.000 claims description 4
- 229910052786 argon Inorganic materials 0.000 claims description 4
- 238000006477 desulfuration reaction Methods 0.000 claims description 4
- 230000023556 desulfurization Effects 0.000 claims description 4
- 238000004321 preservation Methods 0.000 claims description 3
- 229910045601 alloy Inorganic materials 0.000 abstract description 19
- 239000000956 alloy Substances 0.000 abstract description 19
- 238000013461 design Methods 0.000 abstract description 11
- 229910020012 Nb—Ti Inorganic materials 0.000 abstract description 3
- 238000005265 energy consumption Methods 0.000 abstract description 2
- 238000004886 process control Methods 0.000 abstract description 2
- 239000000047 product Substances 0.000 description 18
- 239000011572 manganese Substances 0.000 description 15
- 238000005728 strengthening Methods 0.000 description 10
- 238000009628 steelmaking Methods 0.000 description 6
- 229910052802 copper Inorganic materials 0.000 description 5
- 238000003466 welding Methods 0.000 description 5
- 229910052804 chromium Inorganic materials 0.000 description 4
- 239000006104 solid solution Substances 0.000 description 4
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 3
- 230000008901 benefit Effects 0.000 description 3
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- 238000005260 corrosion Methods 0.000 description 3
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- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 229910000746 Structural steel Inorganic materials 0.000 description 2
- 229910052787 antimony Inorganic materials 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 239000003638 chemical reducing agent Substances 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
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- 238000003303 reheating Methods 0.000 description 2
- 229910052718 tin Inorganic materials 0.000 description 2
- 230000009466 transformation Effects 0.000 description 2
- 229910052720 vanadium Inorganic materials 0.000 description 2
- 229910000975 Carbon steel Inorganic materials 0.000 description 1
- 229910000742 Microalloyed steel Inorganic materials 0.000 description 1
- 229910000990 Ni alloy Inorganic materials 0.000 description 1
- 229910008455 Si—Ca Inorganic materials 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052785 arsenic Inorganic materials 0.000 description 1
- 239000010962 carbon steel Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
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- 238000005516 engineering process Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 230000006870 function Effects 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
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- 239000004615 ingredient Substances 0.000 description 1
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- 230000007246 mechanism Effects 0.000 description 1
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- 150000004767 nitrides Chemical class 0.000 description 1
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- 238000004804 winding Methods 0.000 description 1
Classifications
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
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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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- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
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- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Heat Treatment Of Steel (AREA)
Abstract
The invention relates to E-grade flat bulb steel with economy and excellent strength and toughness, which comprises the following chemical components in percentage by weight ：C：0.05％～0.07％、Si：0.15％～0.25％、Mn：1.50％～1.90％、Nb：0.04％～0.06％、Ti：0.022％～0.032％、Ni：0.6％～1.4％、Als：0.015％～0.045％、P≤0.015％、S≤0.015％、N≤0.005％, and the balance of iron and unavoidable impurities. The invention adopts the design of C-Mn-Ni-Nb-Ti series alloy, ni is added to improve the low temperature toughness, the design of the product alloy is economical and reasonable, the process route is simple, the execution is easy, and the process control stability is strong. By only tempering at high temperature, the energy consumption is saved, the production efficiency is improved, the tempering can homogenize the alloy components, and the structural stress is reduced, so that the toughness index is improved, and the product has excellent toughness matching.
Description
Technical Field
The invention relates to the technical field of marine structural steel, in particular to E-grade flat bulb steel with economy and excellent strength and toughness and a production method thereof.
Background
The flat bulb steel is special structural steel for ships, is welded with a ship body steel plate or connected in other modes to form various structures, is used for strengthening and preventing winding, and plays a vital role in the ship body structure. Currently, the development trend of the world shipbuilding industry is large, high-speed and automatic, the large-scale use specification of the flat-bulb steel is initiated, higher requirements are put forward on the performance of the flat-bulb steel, particularly, the flat-bulb steel is well matched with high strength and high toughness, D-grade flat-bulb steel is mainly used at present, the low-temperature toughness is improved by adopting a V-N microalloying technology and a subsequent heat treatment process of normalizing and high-temperature tempering in the prior art, and in addition, few published materials related to the development of E-grade flat-bulb steel are also provided.
(1) A hot rolled flat bulb steel for large-size high-strength D40 ship and a production process thereof, application number CN201110449456.2, wherein C 0.08％～0.15％、Si 0.10％～0.50％、Mn 1.15％～1.75％、S、P≤0.020％、V0.08％～0.15％、Ni 0.10％～0.50％、Ti 0.01％～0.03％、Mg 0.001％～0.01％、Ca 0.001％～0.01％、O 0.001％～0.01、N 0.016％～0.025％、 of the patent components contains Mn/C more than or equal to 14.0, ni/Mn more than or equal to 0.15, (Mg+Ca)/O more than or equal to 1.0, and the balance of Fe and unavoidable impurities. The patent adopts V-N microalloying, has higher Ni content, has special requirements on the use of Mg and Ca and the proportion of the Mg and Ca to other elements, has higher alloy cost and has higher steelmaking difficulty.
(2) A high-strength flat-bulb steel with uniform interface performance and a production process thereof are disclosed in application number CN201611096842.7, and the high-strength flat-bulb steel with uniform interface performance and the production process thereof are disclosed, wherein the components are (weight percentage )：C:0.07％～0.12％,Si:0.30％～0.50％,Mn:1.00％～1.50％,P≤0.015％,S≤0.010％,Ni:0.50％～1.00％,V:0.05％～0.12％,Ti:0.005％～0.012％,N:0.014％～0.024％,, C/N is less than or equal to 5.5, ti/V is less than or equal to 0.15, mn/Ni is less than or equal to 2.0, and the balance is Fe and unavoidable impurities.
(3) The patent application No. CN202110101385.0 of high-toughness heat-resistant marine flat-bulb steel and a preparation method thereof discloses high-toughness heat-resistant marine flat-bulb steel and a preparation method thereof, wherein the weight percent of chemical components is ：C:0.02～0.059％,Si:0.51～0.82％,Mn:0.1～0.29％,P≤0.006％,S≤0.002％,Ni：4.21～4.62％,Nb：0.25～0.45％,Ti:0.28～0.36％,, and the balance is Fe and unavoidable impurities. The noble metals Ni and Nb in the patent are extremely high in content, and the higher toughness index is an advantage effect brought by extremely high alloy cost, and the alloy has no batch use potential.
(4) A high-strength corrosion-resistant flat-bulb steel and a production method thereof, application number CN201911023062.3, a high-strength corrosion-resistant flat-bulb steel and a production method thereof, wherein the chemical components are C 0.050％～0.100％,Si 0.10％～0.50％,Mn 1.10％～1.60％,P 0.010％～0.030％,S≤0.005％,Cu 0.30％～0.50％,Ni 0.40％～0.90％,Cr 0.40％～0.80％,Nb 0.010％～0.050％,V 0.010％～0.060％,Ti 0.007％～0.030％,Sb 0.03％～0.08％,N 0.0080％～0.0120％,Als 0.015％～0.030％,, and the balance of Fe and unavoidable impurities. The invention has lower S content and higher steelmaking cost, and a large amount of Cr, ni and Cu elements and Sb elements are added to ensure the product; mechanical properties and corrosion resistance.
(5) A high-strength low-temperature-resistant flat-bulb steel and a production process thereof are disclosed in the application number CN201910061374.7, wherein the high-strength low-temperature-resistant flat-bulb steel comprises the chemical components of ：C0.08～0.11％,Si0.40～0.60％,Cr0.3～0.7％,Mo0.11～0.29％,Cu≤0.04％,Al0.03～0.07％,O≤0.0011％,H≤0.00013％,Ca0.001～0.006％,Sb0.0001～0.0004％,Sn≤0.001％,As≤0.006％,B≤0.009％,Nb≤0.04％,Mn1.00～1.60％,P≤0.013％,S≤0.011％,Ni0.60～1.00％,V0.06～0.12％,Ti0.006～0.013％,N0.015～0.023％, mass percent and the balance of Fe. In the invention, in addition to Cr, ni and Cu, mo, sn and Sb are added, so that the alloy cost is high and the component system is complex.
(6) Xue Dongmei, chen Xuehui et al, in the publication of heat treatment Process for high-strength flat-bulb steels at 440MPa, volume 41, 3 of journal of continuous casting, year 2016. The chemical components are as follows: 0.096% of C, 0.51% of Si, 1.09% of Mn, less than or equal to 0.011% of P, less than or equal to 0.005% of S, 0.059% of V and 0.019% of Ti, and meanwhile, mo, cr and Ni are contained. The S content is lower, and the steelmaking cost is higher; in addition, noble metal is added, the alloy cost is higher, and the alloy system and the alloy design thought are obviously different from those of the invention.
The flat-bulb steel disclosed in the above documents is mostly V-N microalloyed in alloy design; also, a large amount of noble metals (Cr, mo.Ni and Cu) are added in part of the invention, so that the alloy cost is high; part of patents control lower S content, resulting in higher steelmaking cost; part of the data adopts a heat treatment mode of normalizing and high-temperature tempering to improve the toughness. The research and achievement of the published data are focused on D-grade flat bulb steel.
Disclosure of Invention
The invention aims to solve the technical problem of providing E-grade flat bulb steel with economy and excellent strength and toughness and a production method thereof.
In order to achieve the above purpose, the invention adopts the following technical scheme:
An E-grade flat bulb steel with economy and excellent strength and toughness comprises the chemical components of ：C：0.05％～0.07％、Si：0.15％～0.25％、Mn：1.50％～1.90％、Nb：0.04％～0.06％、Ti：0.022％～0.032％、Ni：0.6％～1.4％、Als：0.015％～0.045％、P≤0.015％、S≤0.015％、N≤0.005％, weight percent and the balance of iron and unavoidable impurities.
E-grade flat-bulb steel performance index: the yield strength is more than or equal to 420MPa, the tensile strength is more than or equal to 543MPa, the elongation is more than or equal to 21.8%, the impact energy KV2 is more than or equal to 94J at minus 40 ℃ and the impact energy KV2 is more than or equal to 58J at minus 60 ℃.
The components of the E-grade flat-bulb steel adopt the design of C-Mn-Ni-Nb-Ti series alloy, the alloy cost is lower, the fine original structure and fine hot rolled flat-bulb steel is obtained through an accurate rolling and cooling control process, the toughness index is improved through high-temperature tempering, the excellent proportion of the E-grade flat-bulb steel toughness is achieved, and the main elements have the following functions and selection reasons:
c: the steel is the most important element next to iron in the steel, the strength, plasticity, toughness, welding performance and the like of the steel are directly affected, the strength of the steel is obviously improved by solid solution strengthening and precipitation strengthening, but the toughness and the welding performance of the steel are gradually deteriorated along with the improvement of the content of C, and the low-carbon design is the basic guarantee for ensuring that the flat-bulb steel has excellent toughness and good welding performance because the flat-bulb steel is an important component of a ship body structure. Therefore, the invention controls the content of C to be 0.05-0.07%.
Si: is an important reducing agent and deoxidizer in the steelmaking process, and for many materials in carbon steel, si is contained below 0.5%, and is generally carried in as the reducing agent and deoxidizer in the steelmaking process, and Si can be dissolved in ferrite and austenite to improve the strength of the steel, but the plasticity and toughness are lost at the same time. Therefore, the Si content of the present invention is controlled to be 0.15% to 0.25%.
Mn: manganese has the solid solution strengthening effect, can reduce the gamma-alpha transformation temperature, further refine ferrite grains, and is the most main and economical strengthening element for compensating the strength loss caused by the reduction of the C content in steel. However, too high a manganese content may cause serious segregation, and loss of toughness. Therefore, the manganese content is controlled to be 1.50-1.90 percent.
Nb: is the most main element for controlling rolling in modern microalloyed steel, nbC strain-induced precipitation prevents recovery and recrystallization of deformed austenite, reduces the phase transformation temperature, and plays a role in refining grains. Nb can also improve the performance of steel through a plurality of strengthening mechanisms such as precipitation strengthening, phase change strengthening and the like, but Nb is a noble element and the strengthening effect is not obvious after the Nb is added to a certain amount. Therefore, the Nb content is controlled to be 0.04-0.06%.
Ti: the alloy is an extremely strong nitride forming element, the stoichiometric ratio of Ti/N is 3.42, 50ppm of N in the alloy can be completely fixed only by about 0.017% of Ti, and the tiny TiN particles stable at high temperature can effectively prevent the growth of austenite in the reheating process of a casting blank on one hand and improve the impact toughness of a welding heat affected zone on the other hand; in addition, the invention utilizes the characteristic that the binding capacity of Ti and S is far greater than that of Mn, so that Ti can 'deprive' S from MnS, thereby reducing the toughness loss caused by splitting the matrix by the MnS. Therefore, the Ti content of the invention is 0.022 to 0.032 percent.
Ni: is an austenite stabilizing element, so Ni can prevent the growth of crystal grains at high temperature, can still keep a fine grain structure, and is beneficial to ensuring fine original austenite crystal grains of products; ni can promote the cross sliding of dislocation, so that the impact toughness of the product can be effectively improved; in addition, ni can play a certain solid solution strengthening role and provide a certain contribution to the strength index of the product, but Ni alloy has higher cost and is not suitable for excessive addition, so that the economical efficiency of the product is affected. Therefore, the Ni content of the invention is 0.6% -1.4%.
Als: deoxidizing element, adding proper amount of aluminum can form fine and dispersed AlN particles, which is favorable for refining grains and improving the toughness of steel; when the content of solid-solution Al exceeds 0.015%, a fine austenite grain structure is obtained from the steel during welding and reheating, and weldability is improved. Therefore, the Als content of the invention is 0.015 to 0.045 percent.
P: the steel is extremely easy to highly segregate during molten steel solidification, a banded F-P structure can be formed, P can greatly reduce the benefit brought by low-carbon design, the toughness of the steel is lost, and the steel is used as a harmful element in flat-bulb steel as much as possible, but the cost is increased due to the excessively low requirement. Therefore, the P content of the present invention is controlled to be 0.015% or less.
S: the S content is controlled widely, and Ti 4C2S2 is added to reduce the harmful effect of long-strip MnS on the mechanical property, especially toughness of the steel. Therefore, S is less than or equal to 0.015 percent.
N: the increase of nitrogen content can obviously improve the strength of steel, but the plasticity, particularly toughness, is obviously reduced, the weldability is poor, and the cold brittleness is aggravated. Therefore, N is less than or equal to 0.005 percent.
An E-grade flat bulb steel production method with economy and excellent strength and toughness comprises the following production process steps: molten iron pretreatment, converter smelting, external refining LF+calcium treatment, continuous casting, rolling, multi-form cooling and subsequent heat treatment; the method comprises the following specific steps:
1) Smelting continuous casting process: molten iron pretreatment, and converter smelting adopts top blowing or top-bottom combined blowing; the external refining adopts LF furnace desulfurization treatment, si-Ca wire is fed to control inclusion, the average speed is not less than 2m/t, and the wire feeding speed is 3.5 m/s-5 m/s; the continuous casting adopts long nozzle argon seal protection casting, and the final finished product is mixed with class A0.5 to 1.5, class B0 to 0.5, class C0 to 0.5 and class D0 to 0.5;
2) The rolling process comprises the following steps: heating the continuous casting slab to 1115-1150 ℃, and performing laminar cooling, ultra-fast cooling and air cooling processes at the final rolling temperature ranging from 840 to 890 ℃, wherein the laminar cooling is 750-780 ℃, the cooling water quantity at the ball head is 1.5-1.7 times that at the web plate, and the ultra-fast cooling is performed to 300-330 ℃ to obtain uniform martensitic structure and residual austenitic structure; the residual austenite accounts for less than 10 percent;
3) The heat treatment process comprises the following steps: only a high-temperature tempering process is adopted, the specific tempering temperature is 620-650 ℃, the heat preservation time is 2.5-3 hours, and sorbite and ferrite are obtained, wherein the ferrite accounts for 25% -30%.
Compared with the prior art, the invention has the beneficial effects that:
(1) The Ti-modified sulfide inclusion is used for 'depriving' S in MnS to form Ti 4C2S2, and spherical Ti 4C2S2 which is not easy to deform in the rolling process is used for completely replacing MnS which is easy to deform and is elongated in the rolling process, so that the structural uniformity of the product can be remarkably improved, and the obdurability index of the product can be remarkably improved.
(2) The invention adopts the design of C-Mn-Ni-Nb-Ti series alloy to improve the low temperature toughness, controls the inclusion through the matching of the alloy, reduces the influence of the inclusion on the product performance, and has the advantages of economical and reasonable design, simple process route, easy execution and strong process control stability.
(3) The grain growth and fine grains are further inhibited through a controlled rolling process, the product is subjected to crystallization and further refined structure for multiple times through recrystallization rolling, fine and uniform structure morphology is provided for subsequent heat treatment, the finishing rolling temperature is 840-890 ℃, the low-temperature steel is matched with low-temperature steel burning, the grain size of the product is refined by 0.5-1 grain size compared with the prior austenite grains, and basic conditions are provided for subsequent obtaining of narrower martensite laths.
(4) The cooling control process is matched, so that a fine and uniform martensitic structure is obtained, the defect that the bulb structure is thicker than the web plate due to the special shape of the flat-bulb steel is overcome, the purpose of uniform product structure is achieved by increasing the cooling water quantity of the bulb, and the product is ensured to obtain uniform and fine martensite without cracking through the cooperation of laminar cooling and ultra-fast cooling, the residual austenite content is reduced by 4% -7%, and the stability of the product performance is improved while the product performance is improved. Air cooling is started to room temperature at 300-330 ℃, so that energy is saved and cost is reduced under the condition that the product organization is not affected.
(5) Only through high-temperature tempering, through reasonable ingredient design and process design in the early stage, multiple tempering or normalizing and tempering are not needed in the heat treatment link, so that the energy consumption can be saved and the production efficiency can be improved. Tempering can homogenize alloy components to obtain sorbite and ferrite, and the ferrite accounts for 30% -35% to reduce the structural stress so as to improve the toughness index, so that the product has excellent toughness matching.
(6) The yield strength of the final product is more than or equal to 420MPa, the tensile strength is more than or equal to 543MPa, the elongation is more than or equal to 21.8%, the impact power (KV 2) at-40 ℃ is more than or equal to 94J, the impact power (KV 2) at-60 ℃ is more than or equal to 58J, and even the standard requirement of F-level flat-bulb steel is met.
Drawings
FIG. 1 is an optical microstructure-sorbite+ferrite graph of example 1.
Detailed Description
The technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without making any inventive effort, are intended to fall within the scope of the present invention.
An E-grade flat bulb steel with economy and excellent strength and toughness comprises the chemical components of ：C：0.05％～0.07％、Si：0.15％～0.25％、Mn：1.50％～1.90％、Nb：0.04％～0.06％、Ti：0.022％～0.032％、Ni：0.6％～1.4％、Als：0.015％～0.045％、P≤0.015％、S≤0.015％、N≤0.005％, weight percent and the balance of iron and unavoidable impurities.
An E-grade flat bulb steel production method with economy and excellent strength and toughness comprises the following production process steps: molten iron pretreatment, converter smelting, external refining LF+calcium treatment, continuous casting, rolling, multi-form cooling and subsequent heat treatment; the method comprises the following specific steps:
1) Smelting continuous casting process: molten iron pretreatment, and converter smelting adopts top blowing or top-bottom combined blowing; the external refining adopts LF furnace desulfurization treatment, calcium treatment is adopted to control the quantity of inclusions, si-Ca wire is fed to control inclusions, the average wire feeding speed is not less than 2m/t, and the wire feeding speed is 3.5 m/s-5 m/s; the continuous casting adopts long nozzle argon seal protection casting, prevents secondary oxidation of molten steel, ensures the surface quality and the internal quality of casting blanks, and finally the finished product is mixed with class A0.5 to 1.5, class B0 to 1, class C0 to 1 and class D0 to 1;
2) The rolling process comprises the following steps: and heating the continuous casting slab to 1115-1150 ℃ and the final rolling temperature range of 840-890 ℃, and then carrying out laminar cooling, ultra-fast cooling and air cooling processes. Laminar cooling is carried out at 750-780 ℃, the cooling water quantity at the ball head is 1.5-1.7 times of the cooling water quantity at the web plate, ultra-fast cooling is carried out to 300-330 ℃, and then air cooling is carried out, thus obtaining a more uniform martensitic structure and a small amount of residual austenitic structure;
3) The heat treatment process comprises the following steps: only a high-temperature tempering process is adopted, the specific tempering temperature is 620-650 ℃, the heat preservation time is 2.5-3 hours, and the fine sorbite and ferrite are obtained, wherein the ferrite accounts for 25% -30%.
The chemical composition of the steel examples of the present invention is shown in table 1.
Table 1 example chemical composition (wt.%)
| Examples | C | Si | Mn | P | S | Nb | Ti | Ni | Als | N |
| 1 | 0.052 | 0.16 | 1.50 | 0.014 | 0.015 | 0.058 | 0.032 | 1.39 | 0.028 | 0.005 |
| 2 | 0.050 | 0.20 | 1.72 | 0.013 | 0.014 | 0.060 | 0.031 | 1.26 | 0.033 | 0.005 |
| 3 | 0.057 | 0.17 | 1.56 | 0.014 | 0.013 | 0.046 | 0.022 | 0.73 | 0.045 | 0.004 |
| 4 | 0.065 | 0.15 | 1.67 | 0.012 | 0.014 | 0.053 | 0.028 | 0.60 | 0.022 | 0.004 |
| 5 | 0.060 | 0.25 | 1.83 | 0.011 | 0.015 | 0.060 | 0.030 | 0.89 | 0.015 | 0.005 |
| 6 | 0.070 | 0.22 | 1.61 | 0.015 | 0.014 | 0.040 | 0.027 | 0.96 | 0.020 | 0.004 |
| 7 | 0.063 | 0.18 | 1.89 | 0.012 | 0.0013 | 0.043 | 0.030 | 1.4 | 0.042 | 0.005 |
| 8 | 0.055 | 0.24 | 1.90 | 0.015 | 0.0014 | 0.055 | 0.027 | 0.61 | 0.038 | 0.005 |
The production process flow of the embodiment comprises the following steps:
Molten iron pretreatment, and converter smelting adopts top blowing or top-bottom combined blowing; the external refining adopts LF furnace desulfurization treatment, the Si-Ca wire feeding speed is not less than 2m per ton of steel, the wire feeding speed is not less than 3.5m/s, and continuous casting adopts long nozzle argon seal protection casting; and rolling the continuous casting slab after heating, performing laminar cooling, ultra-fast cooling and air cooling after rolling, performing laminar cooling to 750-780 ℃, performing ultra-fast cooling to 300-330 ℃, then performing air cooling, and performing tempering heat treatment.
The rolling process schedule and the heat treatment schedule of the examples are shown in Table 2.
Table 2: example Rolling Process System and Heat treatment System
The mechanical properties of the examples are shown in Table 3.
Table 3: examples major mechanical Properties
Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (2)
1. The E-grade flat bulb steel with economy and excellent strength and toughness is characterized in that the weight percentage of chemical components is ：C：0.052%～0.063%、Si：0.15%～0.25%、Mn：1.61%～1.90%、Nb：0.053%～0.060%、Ti：0.022%～0.028%、Ni：0.96%～1.40%、Als：0.015%～0.045%、P≤0.015%、S≤0.015%、N≤0.005%,, and the balance is iron and unavoidable impurities, and the production process flow is as follows: molten iron pretreatment, converter smelting, external refining LF+calcium treatment, continuous casting, rolling, multi-form cooling and subsequent heat treatment, and the specific steps comprise:
1) Smelting continuous casting process: molten iron pretreatment, and converter smelting adopts top blowing or top-bottom combined blowing; the external refining adopts LF furnace desulfurization treatment, si-Ca wire is fed to control inclusion, the average speed is not less than 2m/t, and the wire feeding speed is 3.5 m/s-5 m/s; the continuous casting adopts long nozzle argon seal protection casting, and the final finished product is mixed with class A0.5-1.5, class B0-1, class C0-1 and class D0-1;
2) And (3) rolling and cooling: heating a continuous casting slab to 1115-1148 ℃, finishing the rolling temperature range of 840-872 ℃, then performing laminar cooling, ultra-fast cooling and air cooling processes, wherein the laminar cooling is 750-780 ℃, the cooling water quantity at the ball head is 1.5-1.7 times of the cooling water quantity at the web plate, ultra-fast cooling to 300-330 ℃, and then air cooling to obtain a uniform martensitic structure and a residual austenitic structure; the residual austenite accounts for 4% -7%;
3) The heat treatment process comprises the following steps: only a high-temperature tempering process is adopted, the specific tempering temperature is 620-650 ℃, the heat preservation time is 2.5-3 hours, and sorbite and ferrite are obtained, wherein the ferrite accounts for 30-35 percent.
2. The economical, high strength and toughness grade E flat bulb steel of claim 1, wherein the performance index is: the yield strength is more than or equal to 420MPa, the tensile strength is more than or equal to 543MPa, the elongation is more than or equal to 21.8%, the impact energy KV2 is more than or equal to 94J at minus 40 ℃ and the impact energy KV2 is more than or equal to 58J at minus 60 ℃.
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