CN113061701B - Low-compression-ratio super-thick fine grain structure steel plate and preparation method thereof - Google Patents
Low-compression-ratio super-thick fine grain structure steel plate and preparation method thereof Download PDFInfo
- Publication number
- CN113061701B CN113061701B CN202110302979.8A CN202110302979A CN113061701B CN 113061701 B CN113061701 B CN 113061701B CN 202110302979 A CN202110302979 A CN 202110302979A CN 113061701 B CN113061701 B CN 113061701B
- Authority
- CN
- China
- Prior art keywords
- rolling
- percent
- steel plate
- less
- equal
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Classifications
-
- 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
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
-
- 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
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/005—Heat treatment of ferrous alloys containing Mn
-
- 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
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/008—Heat treatment of ferrous alloys containing Si
-
- 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
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
-
- 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
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
-
- 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
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
-
- 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
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
-
- 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
- C22C38/008—Ferrous alloys, e.g. steel alloys containing tin
-
- 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
-
- 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
- C22C38/12—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
-
- 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
Abstract
A steel plate with a low compression ratio and super-thick fine grain structure and a preparation method thereof belong to the technical field of metallurgical manufacturing. The preparation method comprises the following steps: s1, heating a casting blank. S2, rolling: firstly, rough rolling is carried out in the range of an austenite recrystallization zone, the single pass rolling reduction of the first three passes of rough rolling is more than 12%, the single pass rolling reduction of the rest passes is more than 10%, the accumulated rolling reduction of the rough rolling passes is more than 55%, and when the thickness of a rolled intermediate blank is as follows: y=21.932 log e And (5) heating at the temperature of x+39.953, wherein x is the thickness of a finished product of the steel plate with the low compression ratio and a thin grain structure, y is the thickness of an intermediate blank at the temperature, and performing finish rolling in an austenite non-recrystallization region to obtain a finish rolled plate. S3, cooling. According to the preparation method, on the premise that the thickness of the finished steel plate reaches 120mm and the compression ratio is low, the effects of rough rolling in an austenite recrystallization region and finish rolling in an unrecrystallized region can be fully exerted, and the ultra-thick steel plate with the low compression ratio and the fine grain structure, which has good performance and can be widely applied to engineering machinery structures, is obtained.
Description
Technical Field
The application relates to the technical field of metallurgical manufacturing, in particular to a steel plate with a low compression ratio and a super-thick fine grain structure and a preparation method thereof.
Background
The typical strength level of the high-strength steel sheet for engineering construction is 355 to 460MPa, and it is required that the thickness is 1/4 th of the thickness, even the core has good low-temperature impact toughness. The steel plate with the yield strength of 460MPa is widely applied to large-span bridge structures, high-rise building ocean platforms and subway steel structural members in low-temperature environments. Because of the severe use environment, the steel sheet is required to have high strength and a certain thickness, and thus, the demand for ultra-thick structural steel sheets is increasing.
Because these steel structures or devices need to bear larger impact load and are often used in lower temperature environments, the steel plates are required to have good low-temperature impact toughness, but the thicker the steel plates are, the more difficult to ensure each property, and more alloy elements are required to be added or more strict steelmaking process or steel rolling process is required to ensure the steel plates to have better mechanical properties and technological properties. In addition, the steel plate is often divided into a certain size according to design requirements in the use process and then spliced, so that the welding performance of the steel plate is very important.
In view of this, the present application is hereby presented.
Disclosure of Invention
The present application provides a low compression ratio super-thick fine grain structure steel sheet and a method for manufacturing the same, which can solve at least one of the above-mentioned technical problems.
Embodiments of the present application are implemented as follows:
in a first aspect, the present examples provide a method for preparing a low compression ratio, super-thick fine grain structure steel sheet, comprising the steps of:
s1, heating a casting blank.
Heating the casting blank to the solid solution of Nb element, wherein the heating temperature is 1220-1280 ℃ and the heating time is 270-300 min.
S2, rolling: firstly, rough rolling is carried out in the range of an austenite recrystallization zone, the single pass rolling reduction rate of the first three passes of rough rolling is more than 12%, the single pass rolling reduction rate of the rest passes is more than 10%, the accumulated rolling reduction rate of rough rolling passes is more than 55%, and when the thickness of a rolled intermediate blank is as follows: y=21.932 log e And (5) heating at the temperature of x+39.953, wherein x is the thickness of a finished steel plate with a low compression ratio and a thin grain structure, y is the thickness of an intermediate blank at the temperature, and then finish rolling is carried out in an austenite non-recrystallization region to obtain a finish rolling plate.
Since the thickness of the intermediate billet is larger in the optional range when the thickness of the finished steel plate is thinner in the actual rough rolling process and the thickness of the intermediate billet is larger in the optional range when the thickness of the finished steel plate is thicker, the influence on the strength and impact energy performance of the finished steel plate is larger if the optional range of the thickness of the intermediate billet is also larger in the thick finished steel plate, so that the formula y=21.932 is utilized for log e And x+39.953, selecting the optimal intermediate blank to be Wen Houdu according to the thickness of the finished product of the steel plate with the low compression ratio and the ultra-thick fine grain structure, obtaining the mechanical property of the finished product, and ensuring the strength and the low-temperature impact toughness of the finished product of the steel plate.
By matching the strict limitation of the intermediate blank to-be-heated target thickness in the rolling stage with the single-pass rolling reduction requirement and the accumulated rolling reduction requirement, the dynamic recrystallization is more facilitated to occur by strengthening the single-pass rolling reduction in the rough rolling stage on the premise of ensuring the small total number of passes in the rough rolling stage, and the internal defect energy of the steel plate is improved by dislocation accumulated by rough rolling deformation, so that the dynamic recrystallization and static recrystallization of the steel plate occur. Through repeated recrystallization process, austenite grains are effectively refined, and the rough rolling effect of the austenite recrystallization region is fully exerted. The austenite grain is deformed by finish rolling in an austenite non-recrystallization zone to generate a deformation zone, the nucleation and growth rate of recrystallization are improved, the formed structure is uniform and tiny, the dislocation density is improved, meanwhile, the rolling effect of the austenite recrystallization zone and the non-recrystallization zone is fully exerted by reasonably selecting the thickness of an intermediate blank to be warmed, the austenite grain is crushed by the single-pass reduction rate of rough rolling pass strengthening, the accumulated reduction rate of finish rolling pass strengthening, and the phase transformation is promoted. The steel plate manufactured by the method has better performance even under the conditions of thicker finished steel plate and smaller compression ratio.
S3, cooling.
And (3) rapidly feeding the finish rolled plate into ultra-fast cooling equipment for water cooling for 30-50 s, and cooling to 500-550 ℃.
In a second aspect, the present examples provide a low compression ratio, super-thick fine grain structure steel sheet produced by the production method provided in the first aspect of the present application.
Wherein, the low compression ratio and super-thick fine grain structure steel plate comprises the following chemical components by mass percent: c:0.03 to 0.09 percent of Si:0.20 to 0.30 percent of Mn:1.50 to 1.64 percent of Nb:0.040 to 0.050 percent, mo:0.09 to 0.16 percent of Ti:0.008 to 0.020 percent, als:0.015 to 0.040%, P.ltoreq.0.020%, S.ltoreq.0.005%, as.ltoreq.0.04%, sn.ltoreq.0.03%, N.ltoreq.0.005%, O.ltoreq.0.003%, H.ltoreq.0.0002% and M, the balance Fe and unavoidable impurities, the carbon equivalent CEV being determined by the formula CEV (%) = C+Mn/6+ (Cr+Mo+V)/5+ (Ni+Cu)/15.
Wherein the carbon equivalent CEV is less than or equal to 0.42%, M is Cr accounting for 0.20-0.29% of the steel plate, and the mass percent of the steel plate is less than or equal to 0.30% (Cr/5+Mn/6) and less than or equal to 0.33%, and the mass percent of the steel plate is less than or equal to 0.18% and less than or equal to 0.25%; or M is V with the mass percent of 0.02-0.029% in the steel plate, and C+Mo is more than or equal to 0.18% and less than or equal to 0.25% in mass percent.
Through the composition design of the low-C high-Mn and Mo, the structure composition of the steel plate with the low-compression ratio and super-thick fine grain structure obtained through the preparation method can be ensured to contain acicular ferrite, bainite and pearlite, the acicular ferrite is mainly distributed at the position of 1/4 of the thickness of the steel plate, and the low-temperature impact toughness of the steel plate can be obviously improved by utilizing the acicular ferrite. By limiting the (Cr/5+Mn/6) content to 0.30% or less and within this range, the selectable ranges of the Cr and Mn contents are further limited, and a decrease in the strength of the super-thick steel sheet can be further avoided, and a low compression ratio can be advantageously achieved. Although low carbon is a precondition for obtaining ferrite, the higher the addition amount of C, the higher the strength of the corresponding steel sheet, and the more expensive Mo, therefore, 0.18% or more C+Mo is 0.25% or less, the strength of the steel sheet is improved as much as possible on the premise of forming ferrite, and the cost is reduced.
Further, log is calculated using the formula y=21.932 e And x+39.953, wherein x is the thickness of the finished steel plate with the low compression ratio and the ultra-thick fine grain structure, y is the temperature waiting thickness of the intermediate blank, the rolling effect of an austenite recrystallization region and a non-recrystallization region is fully exerted through reasonable selection of the temperature waiting thickness of the intermediate blank, the single-pass rolling reduction rate is enhanced by rough rolling, the austenite grains are crushed, the accumulated rolling reduction rate is enhanced by finish rolling, and the phase transformation is promoted. The mechanical property of the finished steel plate is better even under the conditions of thicker finished steel plate and smaller compression ratio, and the strength and low-temperature impact toughness of the finished steel plate are ensured.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered limiting the scope, and that other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a structure morphology of a low compression ratio thick fine grain structure steel sheet provided in example 3.
Detailed Description
Embodiments of the present application will be described in detail below with reference to examples, but it will be understood by those skilled in the art that the following examples are only for illustration of the present application and should not be construed as limiting the scope of the present application. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.
The following specifically describes a low compression ratio, super-thick fine grain structural steel sheet and a method for manufacturing the same according to the embodiments of the present application:
the thickness of the low compression ratio super-thick fine grain structure steel plate in the embodiment of the present application is 100 to 120mm.
The application provides a preparation method of a low-compression-ratio super-thick fine grain structure steel plate, which comprises the following steps:
s1, heating a casting blank.
The higher the temperature of the casting blank is, the smaller the deformation resistance of the casting blank is, so that the heating temperature of the casting blank is properly increased under the condition that the casting blank does not generate overheat and overburning, the load of a rolling mill for rough rolling in the subsequent step S2 is reduced, the capacity of the rolling mill is fully exerted, and meanwhile, the plasticity of a steel plate is also improved. However, when the heating temperature of the cast slab is too high, the cast slab may have coarse grains, even overheating and overburning, which affect the final steel sheet properties, and the heating temperature is too high, which may also increase energy consumption.
Therefore, the heating temperature is 1220-1280 ℃, and the heating time is 270-300 min.
Alternatively, the maximum thickness of the cast slab is 270mm, and the thickness of the steel plate with the low-compression ratio super-thick fine grain structure is 100-120 mm, namely the super-thick steel plate is rolled by adopting the medium-thin slab in practice.
Wherein the composition of the casting blank is the same as that of the finally obtained low-compression-ratio super-thick fine grain structure steel plate, and the chemical composition of the low-compression-ratio super-thick fine grain structure steel plate comprises the following components in percentage by mass: c:0.03 to 0.09 percent of Si:0.20 to 0.30 percent of Mn:1.50 to 1.64 percent of Nb:0.040 to 0.050 percent, mo:0.09 to 0.16 percent of Ti:0.008 to 0.020 percent, als:0.015 to 0.040 percent, less than or equal to 0.020 percent of P, less than or equal to 0.005 percent of S, less than or equal to 0.04 percent of As, less than or equal to 0.03 percent of Sn, less than or equal to 0.005 percent of N, less than or equal to 0.003 percent of O, less than or equal to 0.0002 percent of H, M and the balance of Fe and unavoidable impurities.
Wherein the carbon equivalent CEV is less than or equal to 0.42%, M is Cr accounting for 0.20-0.29% of the steel plate, and the mass percent of the steel plate is less than or equal to 0.30% (Cr/5+Mn/6) and less than or equal to 0.33%, and the mass percent of the steel plate is less than or equal to 0.18% and less than or equal to 0.25%; or M is V with the mass percent of 0.02-0.029% in the steel plate, and C+Mo is more than or equal to 0.18% and less than or equal to 0.25% in mass percent.
In the above implementation, the carbon equivalent CEV (%) =c+mn/6+ (cr+mo+v)/5+ (ni+cu)/15. In the actual calculation, in the carbon equivalent calculation formula and the above-mentioned (Cr/5+mn/6) and c+mo content limitation formulas, each element symbol refers to the value of the mass percentage thereof in the low compression ratio thick fine grain structure steel sheet.
Specifically, C is a strengthening element in steel, the high carbon content can obviously improve the strength of the steel, but can reduce the plasticity and impact property of the steel, and can increase the carbon equivalent and welding crack sensitivity index, so as to deteriorate the welding performance of the steel, but the low carbon content can reduce the NbC generation amount, influence the rolling control effect, and can increase the decarburization cost in the steelmaking process and increase the smelting control difficulty, so that the mass percentage of C in the steel plate with a low compression ratio thick fine grain structure is controlled to be 0.03% -0.09%.
Si mainly plays a role of solid solution strengthening, and is an indispensable reducing agent and deoxidizing agent in the steelmaking process; the increase in Si content increases the strength of the steel, but decreases the plasticity and toughness of the steel, so that the mass percentage of Si in the low-compression-ratio thick fine grain structural steel sheet is controlled to be 0.20 to 0.30%.
Mn mainly plays a role in solid solution strengthening, has the functions of refining a structure and improving the strength of steel, and has no deterioration of toughness, so Mn is an indispensable element, but too high Mn content can cause casting blank segregation, so that the strip structure of the steel plate is serious, the anisotropy of the steel plate is enhanced, and the mass percentage of Mn in the steel plate with a low compression ratio and a super-thick fine grain structure is controlled to be 1.50-1.64% comprehensively.
S is easy to combine with Mn to generate MnS inclusion, and the elongation and low-temperature impact toughness of the steel plate are affected; p is an element which is easy to cause segregation in the steel plate, the low-temperature impact toughness of the steel is obviously reduced, the ductile-brittle transition temperature is improved, the room-temperature plasticity of the steel is easy to be rapidly reduced and becomes brittle, and the phenomenon of cold embrittlement is caused, therefore, P, S element is removed as much as possible to meet the use requirement of a product, but the dephosphorization and desulfurization cost of a steelmaking process is also increased along with the reduction of P, S content, so that the mass percentage of P in the steel plate with a low-compression-ratio thick fine grain structure is controlled to be less than or equal to 0.020%, and the mass percentage of S in the steel plate with a low-compression-ratio thick fine grain structure is controlled to be less than or equal to 0.005%.
As and Sn are extremely easy to gather at the grain boundary, the grain boundary cohesion is reduced, the impact on the macroscopic properties is obviously reduced, therefore, the content of As should be particularly properly controlled, namely, the mass percent of As in the steel plate with the low-compression-ratio and super-thick fine grain structure is controlled to be less than or equal to 0.04 percent, and the mass percent of Sn in the steel plate with the low-compression-ratio and super-thick fine grain structure is controlled to be less than or equal to 0.03 percent.
Niobium in steel can be dissolved in austenite after being heated to above 1200 ℃ for a period of soaking, the solid-solution niobium can inhibit the single-phase diffusion motion interface of austenite in the heating process, prevent austenite grains from growing, precipitate niobium carbo/nitride on dislocation, subgrain boundary and grain boundary in rolling, delay or prevent austenite from dynamically recrystallizing through a solute drag mechanism and a precipitation pinning mechanism, refine austenite grains, precipitate nano-scale second particles Nb (C, N) in the cooling process, that is, the solid-solution effect of Nb is obvious, and the strength and toughness of the steel plate can be obviously improved, so that the mass percentage of Nb in the steel plate with a low compression ratio ultra-thick fine grain structure is controlled to be 0.040-0.050%.
Ti and N, O, C have extremely strong affinity and are effective elements for deoxidizing and fixing N and C well. The micro Ti is used for fixing N in the steel, and free nitrogen in the steel is eliminated due to the formation of indissolvable TiN, so that the toughness of the steel is improved, the TiN has the effect of preventing the growth of crystal grains, and the strength of the steel is further improved. However, since TiC, which is disadvantageous in toughness, is formed by excessively large addition amount of Ti, the mass percentage of Ti in the low-compression-ratio thick fine grain structure steel sheet is controlled to be 0.008 to 0.020% and N is not more than 0.005%.
Mo is carbide forming element, mo exists in solid solution phase and carbide phase, so that the molybdenum-containing steel has the functions of solid solution strengthening and carbide dispersion strengthening, and in the steel with low C and high Mn and Mo component system, the solid solution strengthening and dispersion strengthening functions of Mo can be fully exerted, grains of the steel are thinned, and the strength and toughness of the steel, especially the low-temperature impact toughness, are improved. The mass percentage of the steel plate with the low compression ratio and the super-thick fine grain structure is controlled to be 0.09-0.16 percent.
Al forms fine and dispersed AlN precipitation with N in steel at a higher temperature, so that the growth of grains is inhibited, the purposes of refining the grains and improving the toughness of the steel at a low temperature are achieved, and therefore, the Al with the mass percentage of 0.015-0.04% in the steel plate with the low-compression-ratio super-thick fine grain structure is added, the grains can be refined, the toughness of the steel plate is improved, and the welding performance of the steel plate is ensured.
O is Al 2 O 3 SiO 2 The inclusion forms exist in steel, H can cause hydrogen embrittlement, the toughness of the steel plate is affected, and the residual H in the steel can also affect the internal quality of the steel plate, so that the control is required, wherein in the application, O is less than or equal to 0.003% and H is less than or equal to 0.0002% by mass percent.
Cr is a carbide forming element, and Cr is dissolved in steel to form fine carbides such as (Fe, ce) 3 C、(Fe，Cr) 7 C 3 And the like, the strength of the steel plate is obviously improved, but the elongation of the steel is reduced due to the excessively high Cr content. The Cr and Nb are used in combination, so that the strength and toughness of the steel plate can be obviously improved under the condition of not reducing the elongation. Therefore, when Cr is added to the steel, the mass percentage of Cr in the steel sheet having a low compression ratio and a super-thick fine grain structure is controlled to be 0.20 to 0.29%.
V has extremely strong affinity with carbon, nitrogen and oxygen, and V is dissolved in steel to form fine second phase particles such as V (C, N) and the like, and has precipitation strengthening effect, but the effect is not obvious, and generally has great contribution to strength in normalized steel. Generally, V has a smaller strengthening effect than Nb but is stronger than Cr at the same content. Therefore, when the content of Nb reaches the upper limit, it can be used in place of Cr and Nb. Therefore, when V is added to the steel instead of Cr, the mass percentage of V in the steel sheet having a low compression ratio and a super-thick fine grain structure is controlled to be 0.02 to 0.029%.
It should be noted that only one of Cr and V is added.
S2, rolling, which comprises the following steps:
s2.1, rough rolling in the range of an austenite recrystallization zone, wherein when the thickness of the intermediate blank is rolled to be: y=21.932 log e And (5) heating at x+39.953, wherein x is the thickness of a finished product of the steel plate with the low compression ratio and the thickness of an intermediate blank to be heated.
When the intermediate blank temperature-waiting thickness of the formula is reached, the rough rolling stage is ended, and temperature waiting is carried out, wherein the intermediate blank temperature-waiting thickness is actually the target thickness of the rough rolling stage.
The inventor finds that in the course of rough rolling, with the increase of the deformation quantity of single pass and the increase of the accumulated deformation quantity, the quantity of recrystallized nucleation and the growth rate thereof can be obviously improved, the deformation quantity of single pass can be limited by the reduction rate of single pass, and the accumulated deformation quantity can be limited by the reduction rate of single pass and the target thickness of rough rolling stage.
Thus, alternatively, the first three passes of rough rolling have a single pass reduction of greater than 12% and the remaining passes have a single pass reduction of greater than 10%, when rolled to a thickness of the intermediate billet of: y=21.932 log e And ending the rough rolling stage at the time of x+39.953, wherein the accumulated reduction rate of rough rolling passes is more than 55%.
Through the combination of the strict limitation of the target thickness (the thickness y of the intermediate billet to be heated) in the rolling stage and the single-pass reduction rate requirement and the accumulated reduction rate requirement of rough rolling, the total number of passes in the rough rolling stage can be limited to be kept in a smaller range, the internal defect energy of the steel plate is improved through dislocation accumulated in the rough rolling reduction, the steel plate is subjected to dynamic recrystallization and static recrystallization, and the number of recrystallized nucleation and the growth rate of the recrystallized nucleation are obviously improved, so that refined and dense austenite grains are obtained.
Alternatively, the total rolling pass of the rough rolling is 5 passes.
Optionally, the rolling temperature of rough rolling is 1020-1095 ℃, namely, the initial rolling temperature of the rough rolling stage and the final rolling temperature of the rough rolling stage are all in the range, the characteristic of small deformation resistance of a casting blank at high temperature is utilized, the load of a rolling mill is reduced, the capacity of the rolling mill is fully exerted, and meanwhile, the plasticity of a steel plate can be improved.
Since the intermediate blank temperature waiting thickness calculated according to the above formula is an accurate value, but the rigidity of the rolling mill body equipment is certain, that is, after the last pass rolling in the rough rolling stage is completed, the thickness of the steel plate, that is, the actual intermediate blank temperature waiting thickness, has a deviation from the intermediate blank temperature waiting thickness calculated according to the formula, and when the thickness of the finished steel plate is thicker, the fluctuation of the selected range value of the intermediate blank temperature waiting thickness is larger, the influence on the performance, particularly the yield strength, of the finished steel plate is larger.
Thus, optionally, the accuracy of y is controlled to + -1 mm.
S2.2, performing finish rolling in an austenite non-recrystallized region to obtain a finish rolled steel plate.
Since the finished steel sheet is an extra thick steel sheet having a thickness of 100 to 120mm, the intermediate blank is thick, which makes it difficult to cool, and the temperature gradient from the surface to the core temperature of the intermediate blank is large, so that, optionally, the initial rolling temperature of finish rolling is not more than 850 ℃, the temperature gradient of the blank is reduced and the strength of the steel sheet is improved by reducing the initial rolling temperature of finish rolling.
Optionally, the finish rolling temperature of finish rolling is 800-840 ℃, the single-pass rolling reduction rate of finish rolling is 0.5-10%, the accumulated rolling reduction rate of finish rolling is 18-35%, austenite grains are deformed by the arrangement, deformation zones are generated, phase transformation is facilitated to be formed, the formed tissue is uniform and fine, dislocation density is improved, carbonitride is strained and separated out at dislocation positions, and movement of pinning dislocation is ready for the next cooling.
Optionally, the total rolling pass of the finish rolling is more than 5 passes, for example, the finish rolling passes adopt 7 or 8 passes, that is, the finish rolling adopts the effect of multi-pass small reduction rate, so that the dislocation density is further improved, meanwhile, the unevenness of the finish rolling plate is convenient to control, preparation for subsequent cooling is carried out, and the precision of the thickness tolerance of the steel plate is effectively controlled through the three-pass reduction rate after the finish rolling.
S3, cooling.
Optionally, the finish rolled steel plate is rapidly fed into ultra-fast cooling equipment to be cooled for 30-50 s, cooled to 500-550 ℃, and cooled to obtain the plate after water outlet.
The composition design, the rolling step and the cooling step are matched, so that the obtained low-compression-ratio super-thick fine grain structural steel plate has the following structure: the thickness 1/4 of the steel plate is mainly made of acicular ferrite and contains pearlite which is dispersed and distributed, the bainite is mainly distributed on the surface layer, meanwhile, the acicular ferrite has the characteristics of large-angle grain boundary, high-density dislocation distribution and the like, and acicular ferrite laths are arranged in a 'hybrid' way of different phases, so that the crack growth can be effectively inhibited, and the low-temperature toughness of the steel plate is improved.
The application also provides a low-compression ratio super-thick fine grain structure steel plate, which is prepared by the preparation method.
Alternatively, the thickness of the steel plate is 100 to 120mm.
Compared with the original medium-thickness structural steel plate and the production line thereof, the low-compression-ratio super-thick fine grain structural steel plate is rolled by casting blanks with the thickness of 270mm, and the thickness range of the finished steel plate is expanded from less than or equal to 90mm to less than or equal to 120mm of the original medium-thickness structural steel plate, namely the low-compression-ratio super-thick fine grain structural steel plate provided by the application effectively reduces the compression ratio from 3 times of the original medium-thickness structural steel plate to 2.25-2.7 times, and meanwhile, the comprehensive performance of the low-compression-ratio super-thick fine grain structural steel plate is guaranteed to be excellent.
Specifically, the yield strength of the steel plate with the low compression ratio and super-thick fine grain structure is more than or equal to 435MPa, the tensile strength is more than or equal to 550MPa, the elongation is more than or equal to 22 percent, and the longitudinal impact energy Akv at the position of 1/4 of the steel plate thickness at minus 60 ℃ is more than or equal to 200J. Wherein Akv refers to the impact absorption work of the V-notch sample. That is, the low-compression-ratio ultra-thick fine grain structural steel sheet can be used as a high-strength sheet for an engineering machine structure in a large-span bridge structure, a high-rise building ocean platform, a subway steel structure and the like in a low-temperature environment.
Optionally, the low compression ratio, super-thick fine grain structure steel sheet comprises, in volume percent: 27-38% of acicular ferrite, 51-60% of bainite and 10-14% of pearlite; enabling better performance through specific tissue components.
Alternatively, acicular ferrite has large angle grain boundaries > 15 ° and high density dislocation distribution characteristics, and acicular ferrite laths are arranged in a "hybrid" of different phases, effectively suppressing crack propagation, thereby effectively improving low temperature toughness thereof.
A low compression ratio, super-thick fine grain structural steel sheet and a method for manufacturing the same according to the present application will be described in further detail with reference to examples.
Examples 1 to 12 and comparative examples 1 to 2
Examples 1 to 12 are low compression ratio, super-thick fine grain structural steel sheets provided herein, respectively, having chemical compositions shown in table 1 in mass percent, and the balance being iron. Comparative examples 1 and 2 are examples 1 and 3 of patent No. CN 109943771A.
Table 1 chemical compositions of examples 1 to 12 and comparative examples 1 and 2
Wherein, the preparation methods of the embodiments 1-7 are similar, the converter smelting, LF+RH refining, dephosphorization, desulfurization and continuous casting are carried out in the same mode, the casting blank with the thickness of 270mm is obtained, then the heating treatment is carried out at the same heating temperature and time, and then the rolling and cooling process steps are adopted to obtain the product; examples 8 to 12 differ from examples 1 to 7 mainly in the rough rolling pass and the thickness of the intermediate billet to be warmed. Comparative examples 1 and 2 are examples 1 and 3 of patent No. CN 109943771A. The rolling and cooling processes of examples 1 to 12 and comparative examples 1 and 2 are shown in table 2.
Table 2 rolling and cooling process parameters for examples 1 to 12 and comparative examples 1 and 2
The tensile and impact properties of the low compression ratio, super-thick fine grain structural steel sheets obtained in examples 1 to 12 were measured according to the requirements of the standards GB/T228.1 and GB/T229, and the results are shown in Table 3.
Table 3 mechanical properties test results for examples 1 to 12 and comparative examples 1 and 2
As can be seen from the combination of tables 1, 2 and 3, the steel sheets obtained in examples 1 to 7 by using the components and processes of the present invention have good combination of strength and toughness, and the thickness of the steel sheets is 100 to 120mm. Wherein, the Cr element is added without V in examples 1-5, the V element is added without Cr in examples 6 and 7, the rolling and cooling processes of examples 1-7 are close, the yield strength is between 440 and 489MPa, the low-temperature impact energy Akv at 0 to minus 60 ℃ is relatively close, and the average value is more than or equal to 200J.
As can be seen from the results of Table 3 in combination with tables 1 and 2, the steel sheet properties obtained in examples 1 to 7 using the composition and process of the present invention are superior to those obtained in examples 8 to 12. The composition systems of examples 8 to 12 were designed by the composition of the present invention, wherein Cr element was added without adding V in examples 8, 10 and 11, and V element was added without adding Cr in examples 9 and 12.
The rolling and cooling processes of examples 8 to 12 are different from those of examples 1 to 7.
The rough rolling passes of examples 8, 9 were 7 passes, the intermediate blank to be warmed was according to the invention y=21.932 log e The x+39.953 is 142mm, the single pass reduction rate of the first three passes is less than 12% according to a rolling procedure calculation algorithm, the austenite recrystallization of the rough rolling pass is insufficient due to the small single pass reduction rate, the grain refinement effect is not obvious, the yield strength of the steel plate is only 395-402 MPa, and the low-temperature impact toughness is slightly deteriorated compared with that of the steel plate in the embodiment 2.
The intermediate blanks of examples 10, 11, 12 were not as thick as required herein. In example 10, the thickness of the steel plate finished product is 110mm, the thickness of the intermediate blank to be heated is 165mm, under the condition that the rough rolling pass is 5 passes, according to a rolling rule calculation algorithm, the single pass rolling reduction of the first three passes is less than 12%, the rough rolling accumulated rolling reduction is less than 55%, the austenite recrystallization of the rough rolling pass is insufficient due to the excessively small single pass rolling reduction and accumulated rolling reduction, the grain refinement effect is not obvious, the yield strength of the steel plate is only 396MPa, and the low-temperature impact toughness is slightly deteriorated compared with example 3.
In example 11, the thickness of the steel plate finished product is 110mm, the thickness of the intermediate blank to be warmed is 165mm, under the condition that the rough rolling pass is 4 passes, according to a rolling rule calculation algorithm, the single pass reduction rate of the first three passes is possibly more than 12%, but the 4 th pass reduction rate is less than 10%, although the rough rolling pass is reduced, the single pass reduction rate requirement can be met, but obviously the cumulative reduction rate of the rough rolling pass is less than 55%, which leads to insufficient austenite recrystallization of the rough rolling pass and insignificant grain refinement effect; in addition, example 11 ended the rough rolling pass at a higher temperature, and the finish rolling start temperature was within the scope of the present invention, so that the period of time between the end of rough rolling and the start of finish rolling was relatively long, austenite grains had a sufficient time to grow, and even if grains were refined by the finish rolling pass, the effect was not as good as in example 3.
In the embodiment 12, the thickness of the steel plate finished product is 110mm, the thickness of the intermediate blank to be heated is 128mm, and the rough rolling can be completed by adopting 6 times according to a rolling procedure calculation algorithm, so that under the condition that the three single-pass reduction rate before the rough rolling is more than 12%, the cumulative reduction rate of the rough rolling is also more than 55%, but the finish rolling is completed by only 4 times, the yield strength of the steel plate is influenced, and the yield strength is only 425MPa; on the other hand, the thickness of the intermediate blank to be heated is close to the thickness of the steel plate finished product, so that the finish rolling passes are too few, the rolling reduction is insufficient, the plasticity of the steel plate is poor, and the elongation is only 17.5%. Meanwhile, the low-temperature impact toughness was slightly deteriorated as compared with example 3.
The steel sheets of examples 1 to 7 were observed under a metallographic microscope, and FIG. 1 shows the structure morphology of a steel sheet having a low compression ratio and a very thick fine grain structure as provided in example 3.
The metallographic structure of the cross section of the low-compression-ratio, super-thick, fine-grain-structured steel sheet obtained in examples 1 to 7 was analyzed, wherein the structure components of the low-compression-ratio, super-thick, fine-grain-structured steel sheet were: 27-38% of acicular ferrite, 51-60% of bainite and 10-14% of pearlite, wherein the steel plate is mainly acicular ferrite at 1/4 of the thickness and has pearlite with certain dispersion distribution, the steel plate has higher toughness on the premise of effectively ensuring higher yield strength, and the steel plate also has higher strength due to the arrangement of surface bainite.
In summary, the preparation method of the low-compression-ratio thick fine grain structural steel plate provided by the application makes full use of the rough rolling and finish rolling effects of the non-recrystallized regions of the austenite to obtain the low-compression-ratio thick fine grain structural steel plate with better performance and capable of being applied to engineering structures on the premise that the thickness of the low-compression-ratio thick fine grain structural steel plate reaches 120mm and the low compression ratio is low.
The foregoing is merely a specific embodiment of the present application and is not intended to limit the application, and various modifications and variations may be made to the present application by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.
Claims (11)
1. A method for producing a steel sheet having a low compression ratio and a very thick fine grain structure, comprising the steps of:
s1, heating a casting blank;
s2, rolling: firstly, rough rolling is carried out in an austenite recrystallization region, the single pass reduction rate of the first three passes of rough rolling is more than 12%, the single pass reduction rate of the rest passes is more than 10%, the accumulated reduction rate of the rough rolling passes is more than 55%, and when the thickness of a middle blank is rolled:heating, wherein x is the thickness of a finished product of the low-compression-ratio super-thick fine grain structural steel plate and is in mm, y is the thickness of the intermediate blank to be heated and is in mm, and then finish rolling is carried out in an austenite non-recrystallization region to obtain a finish rolling plate;
s3, cooling to obtain the low-compression-ratio super-thick fine grain structure steel plate;
in the step S2, the casting blank is subjected to compression ratio of 2.25-2.7 times to prepare the finish rolling plate;
the thickness of the finished product of the steel plate is 100-120 mm;
wherein the low compression ratio ultra-thick fine grain structure steel sheet comprises the following chemical components in mass percent: c:0.03 to 0.09 percent of Si:0.20 to 0.30 percent of Mn:1.50 to 1.64 percent of Nb:0.040 to 0.050 percent, mo:0.09 to 0.16 percent of Ti:0.008 to 0.020 percent, als:0.015 to 0.040 percent, less than or equal to 0.020 percent of P, less than or equal to 0.005 percent of S, less than or equal to 0.04 percent of As, less than or equal to 0.03 percent of Sn, less than or equal to 0.005 percent of N, less than or equal to 0.003 percent of O, less than or equal to 0.0002 percent of H, M and the balance of Fe and unavoidable impurities; the carbon equivalent CEV is determined by the formula CEV (%) =c+mn/6+ (cr+mo+v)/5+ (ni+cu)/15;
wherein the carbon equivalent CEV is less than or equal to 0.42%, the M is Cr with the mass percentage of 0.20-0.29% in the steel plate, and the mass percentage is less than or equal to 0.30% (Cr/5+Mn/6) and less than or equal to 0.33%, and the mass percentage is less than or equal to 0.18% and less than or equal to 0.25%; or, M is V with the mass percent of 0.02-0.029% in the steel plate, and C+Mo is more than or equal to 0.18% and less than or equal to 0.25% in terms of mass percent;
in the carbon equivalent calculation formula and the above-mentioned (Cr/5+mn/6) and c+mo content limitation formulas, each element symbol refers to a value of its mass percentage in the low-compression-ratio, super-thick fine grain structure steel sheet.
2. The method of claim 1, wherein the accuracy of y is controlled to ±1mm.
3. The method according to claim 1, wherein in step S2, the rough rolling is performed at a rolling temperature of 1020 to 1095 ℃.
4. A method of manufacture according to claim 3, wherein the total rolling pass of the rough rolling is 5 passes.
5. The method according to any one of claims 1 to 4, wherein in the step S2, the initial rolling temperature of the finish rolling is equal to or less than 850 ℃, the finish rolling temperature of the finish rolling is 800 to 840 ℃, the single pass rolling reduction of the finish rolling is 0.5 to 10%, and the cumulative rolling reduction of the finish rolling is 18 to 35%.
6. The method according to claim 5, wherein the total rolling pass of the finish rolling is greater than 5 passes.
7. The method according to any one of claims 1 to 4, wherein in step S3, the finish rolled sheet is rapidly fed into an ultra-fast cooling apparatus to be cooled by water for 30 to 50 seconds to a temperature of 500 to 550 ℃.
8. A low compression ratio super-thick fine grain structure steel sheet, characterized by being produced by the production method as claimed in any one of claims 1 to 7.
9. The low compression ratio, super-thick fine grain structure steel sheet as set forth in claim 8, wherein the structural components of the low compression ratio, super-thick fine grain structure steel sheet include, in volume percent: 27-38% of acicular ferrite, 51-60% of bainite and 10-14% of pearlite.
10. The low compression ratio, super thick fine grain structure steel sheet as claimed in claim 9, wherein said acicular ferrite has a large angle grain boundary of > 15 °.
11. The low-compression-ratio, super-thick fine grain structural steel sheet according to claim 8, wherein the yield strength of the low-compression-ratio, super-thick fine grain structural steel sheet is not less than 435MPa, the tensile strength is not less than 550MPa, the elongation is not less than 22%, and the longitudinal impact energy Akv at 1/4 of the thickness of the steel sheet at-60 ℃ is not less than 200J.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110302979.8A CN113061701B (en) | 2021-03-22 | 2021-03-22 | Low-compression-ratio super-thick fine grain structure steel plate and preparation method thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110302979.8A CN113061701B (en) | 2021-03-22 | 2021-03-22 | Low-compression-ratio super-thick fine grain structure steel plate and preparation method thereof |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN113061701A CN113061701A (en) | 2021-07-02 |
| CN113061701B true CN113061701B (en) | 2023-08-01 |
Family
ID=76563204
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202110302979.8A Active CN113061701B (en) | 2021-03-22 | 2021-03-22 | Low-compression-ratio super-thick fine grain structure steel plate and preparation method thereof |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN113061701B (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114101344B (en) * | 2021-11-24 | 2024-01-09 | 广东韶钢松山股份有限公司 | Intermediate blank temperature waiting thickness adjusting method for rolling thick-specification steel plate |
| CN115323265B (en) * | 2022-07-15 | 2024-03-19 | 南京钢铁股份有限公司 | Superfine crystal steel plate and preparation method thereof |
| CN115418548B (en) * | 2022-08-27 | 2023-06-09 | 昆明理工大学 | Multi-pass compression preparation method of Mn-substituted Ni-type duplex stainless steel |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104561771A (en) * | 2014-12-26 | 2015-04-29 | 南阳汉冶特钢有限公司 | Boron charging thick plate with low compression ratio, low alloy content and high strength and production method of boron charging thick plate |
| CN106319380A (en) * | 2015-06-16 | 2017-01-11 | 鞍钢股份有限公司 | Low compression ratio 690MPa grade extra thick steel plate and production method thereof |
| CN109943771B (en) * | 2017-12-21 | 2021-04-02 | 广东韶钢松山股份有限公司 | High-toughness weldable steel plate with fine grain structure and production method thereof |
-
2021
- 2021-03-22 CN CN202110302979.8A patent/CN113061701B/en active Active
Also Published As
| Publication number | Publication date |
|---|---|
| CN113061701A (en) | 2021-07-02 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN113061701B (en) | Low-compression-ratio super-thick fine grain structure steel plate and preparation method thereof | |
| EP1444373A1 (en) | STEEL PLATE HAVING SUPERIOR TOUGHNESS IN WELD HEAT−AFFECTED ZONE AND METHOD FOR MANUFACTURING THE SAME, WELDING FABRIC USING THE SAME | |
| KR101417231B1 (en) | Ultra heavy steel plate for pressure vessel with excellent low-temperature toughness and tensile property and manufacturing method of the same | |
| WO1995013405A1 (en) | High-strength high-ductility two-phase stainless steel and process for producing the same | |
| KR20210002621A (en) | High-strength double-sided stainless steel clad sheet and its manufacturing method | |
| WO2013073136A1 (en) | Thin steel sheet and process for producing same | |
| CN111356781B (en) | High-strength hot-rolled steel sheet having excellent bendability and low-temperature toughness, and method for producing same | |
| KR102379443B1 (en) | Steel material for hot press forming, hot pressed member and manufacturing method theerof | |
| EP1337678A1 (en) | Steel plate to be precipitating tin+mns for welded structures, method for manufacturing the same and welding fabric using the same | |
| JP5701483B2 (en) | Extremely thick steel plate for welded structure with excellent strength and toughness at the center of thickness and little material deviation, and method for manufacturing the same | |
| JP4514150B2 (en) | High strength steel plate and manufacturing method thereof | |
| JP3922805B2 (en) | Manufacturing method of high-tensile steel with excellent low-temperature toughness | |
| JPH03257124A (en) | Production of cold rolled steel sheet for deep drawing having baking hardenability | |
| WO2006118423A1 (en) | Cold rolled steel sheet having superior formability , process for producing the same | |
| JP7197699B2 (en) | Steel material for pressure vessel excellent in resistance to hydrogen-induced cracking and its manufacturing method | |
| JP7265008B2 (en) | Steel material for pressure vessel excellent in resistance to hydrogen-induced cracking and its manufacturing method | |
| KR20020048199A (en) | Method of manufacturing high strength steel plate to be precipitating TiO and TiN by nitriding treatment for welded structures | |
| KR20060066745A (en) | High strength thin steel sheet excellent in hole expansibility and ductility | |
| KR20010060759A (en) | High strength steel having low yield ratio and method for manufacturing it | |
| KR100325714B1 (en) | A bainitic steel with good low temperature toughness and a method of manufacturing thereof | |
| JP2007186789A (en) | High-strength steel sheet excellent in strength-ductility balance and deep drawability, and its manufacturing method | |
| KR100435446B1 (en) | Method for manufacturing steel in which toughness at low temperature required in ultra-cold area is greatly improved while maintaining 60 kgf/mm¬2 or more tensile strength by means of controlling alloy composition, hot rolling and cooling conditions of steel properly | |
| KR100240999B1 (en) | The manufacturing method for high strength steel sheet with low temperature shocking toughness property | |
| KR100256357B1 (en) | The manufacturing method for high strength steel sheet with cu precipitation hardening type | |
| KR101069995B1 (en) | High Strength Steel Sheet for Line-pipe and Manufacturing Method Thereof |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |