CN112375979A - Process for hot rolling thin steel plate with 800 MPa-level tensile strength, high plasticity and low cost - Google Patents
Process for hot rolling thin steel plate with 800 MPa-level tensile strength, high plasticity and low cost Download PDFInfo
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- CN112375979A CN112375979A CN202011198538.XA CN202011198538A CN112375979A CN 112375979 A CN112375979 A CN 112375979A CN 202011198538 A CN202011198538 A CN 202011198538A CN 112375979 A CN112375979 A CN 112375979A
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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
- C21D8/02—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
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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
- C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
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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
- C22C38/04—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
- 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
- C21D2211/001—Austenite
-
- 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
- C21D2211/002—Bainite
-
- 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
Abstract
The invention discloses a process for hot rolling a thin steel plate with 800 MPa-level tensile strength, high plasticity and low cost, belonging to the field of hot rolling high-strength steel, and the process is characterized in that: the chemical components by weight percentage are as follows: 0.10 to 0.20%, Si: 1.0-1.6%, Mn: 1.0-1.7%, P: 0.015-0.25%, S is less than or equal to 0.005%, Als: 0.020 to 0.050%, Re: 0.003-0.006% of Fe and the balance of unavoidable impurities. Compared with the prior art, the invention has good comprehensive mechanical property and welding property and does not contain toxic element Cr.
Description
Technical Field
The invention relates to the field of hot-rolled high-strength steel, in particular to a high-strength high-plasticity low-cost hot-rolled thin steel plate with 800 MPa-level tensile strength and a manufacturing process thereof.
Background
In recent years, with the continuous improvement of national emission standards for energy conservation and environmental protection in the automobile field, the automobile industry puts forward comprehensive characteristic requirements of higher strength, better plasticity, higher surface quality, thinner thickness specification and the like on hot rolled steel plates so as to achieve the purposes of high strength and thinning, energy conservation and emission reduction and cost reduction.
Generally, for hot-rolled high-strength steel with the tensile strength of more than 800MPa, microalloy or alloy elements such as Nb-Ti-Cr and the like are mostly required to be added for improving the hardenability of a steel plate in the hot rolling process, so that the hot-rolled steel plate has higher strength and higher production cost; meanwhile, along with the increase of the strength, the plasticity is also obviously reduced, the rolling load is also obviously increased, the subsequent acid rolling production is not facilitated, the difficulty is brought to the production of the steel plate with a thinner specification (less than 3.0 mm), and the requirements of high strength and thinning, forming processing and cost control cannot be met. And the surface Cr is seriously harmful to the health of people in a +6 valence state, has huge toxicity and is not beneficial to implementing large heat input welding on the steel plate.
In order to solve the technical problem, the Chinese invention applies for a super-high-strength and plasticity cold-rolled Mn-Al series TRIP steel plate and a rapid annealing preparation method thereof (CN201810967333.X), wherein the steel plate comprises 0.18-0.22% of C, 0.30-0.70% of Si, 6.0-7.5% of Mn, 2.0-3.0% of Al, 0.08-0.12% of V, less than or equal to 0.005% of P, less than or equal to 0.005% of S, less than or equal to 0.006% of N, less than or equal to 0.003% of O, and the balance of Fe and inevitable impurity elements; the components of the alloy are 'Al replaces Si' and V is added to realize no Nb-Ti-Cr component, but the core of the formula lies in Mn-Al series medium manganese TRIP steel, the preparation is limited to medium manganese steel, and in the field of low manganese steel, too high Al deteriorates the mechanical property of the steel and correspondingly reduces the wear resistance.
Similarly, the Chinese patent (publication No. CN103695765A) discloses a high-strength high-plasticity cold-rolled medium manganese steel and a preparation method thereof, which all adopt Al: 3-4% to realize no Cr addition.
In other studies, alloy elements such as Mo are used for replacing Cr, and although Cr has no potential toxicity, Mo is a ferrite forming element, so that when Mo is used for replacing Cr, the content of Mn must be increased to form austenite in order to obtain austenite, or when Mo content is high, a ferrite δ phase or other brittle phases are likely to occur to reduce toughness, which causes inconvenience in steel making and rolling.
Disclosure of Invention
The technical task of the invention is to provide a high-strength high-plasticity low-cost hot-rolled thin steel plate with the tensile strength of 800MPa and a manufacturing process thereof aiming at the defects of the prior art, and the hot-rolled thin steel plate has good comprehensive mechanical property and welding property and does not contain toxic element Cr.
The technical scheme for solving the technical problem is as follows: a high-strength high-plasticity low-cost hot-rolled thin steel plate with 800 MPa-level tensile strength is characterized in that: the chemical components by weight percentage are as follows: 0.10 to 0.20%, Si: 1.0-1.6%, Mn: 1.0-1.7%, P: 0.015-0.25%, S is less than or equal to 0.005%, Als: 0.020 to 0.050%, Re: 0.003-0.006% of Fe and the balance of unavoidable impurities.
The Si/Re is between 200 and 350.
The P/Re is between 35 and 55.
Compared with the prior art, the invention has the following outstanding beneficial effects:
1. the invention adopts the low-cost component design of C-Si-Mn and the inclusion and segregation control of rare earth elements, avoids the addition of alloy elements such as Nb, Ti, Cr, Mo and the like, improves the plasticity of thin steel plates (less than 3.0 mm) on the basis of ensuring the tensile strength to be more than 800MPa, and is beneficial to later welding;
2. through controlled rolling and controlled cooling, a ferrite, bainite and residual austenite organizational structure which is beneficial to strength increase and plasticity improvement is obtained, and residual austenite in steel is converted into martensite under the action of external force, so that the strength can be obviously improved; the residual austenite absorbs external stress, so that crack initiation in steel can be relieved, and good plasticity is obtained;
3. the lubricating rolling process can effectively reduce the rolling load and is beneficial to rolling with thin specification (the thickness is below 3.0 mm);
4. the low-cost component design and the low-temperature heating of the plate blank enable the product to be low in cost, the high-strength thin plate is used for high-strength thin reduction of parts such as commercial vehicles and load-carrying vehicles, the light weight popularization and application potential is large, and the economic benefit is obvious.
Detailed Description
The present invention will be further described with reference to the following embodiments.
The invention relates to a high-strength high-plasticity low-cost hot-rolled thin steel plate with the tensile strength of 800 MPa.
The chemical components are designed as follows (wt%):
c: 0.10 to 0.20%, Si: 1.0-1.6%, Mn: 1.0-1.7%, P: 0.015-0.25%, S is less than or equal to 0.005%, Als: 0.020 to 0.050%, Re: 0.003-0.006% of Fe and the balance of unavoidable impurities. No Nb, Ti, Cr and other elements are added, and the production cost is low.
Elements with high lattice such as Nb, Ti and Cr are not added into the steel, and solid solution strengthening and fine grain strengthening are mainly carried out through conventional C, Si and Mn elements; carrying out structure strengthening and plasticity improvement through retained austenite phase transformation; meanwhile, Re element is adopted to improve plasticity. The principle of the specific elements and contents is as follows:
c: can obviously improve the strength and has the function of interstitial solid solution strengthening. However, the C content should not be too high to ensure the weldability and formability. The C content of the invention is not more than 0.20%.
Si: the strength can be improved through solid solution strengthening, the segregation of manganese and phosphorus can be inhibited, the carbon content in austenite can be increased, the residual austenite is favorably obtained, but the plasticity of the steel is influenced by too high Si content. However, in the present invention, the silicon content is 1.0 to 1.6%.
Mn: strength can be improved by solid solution strengthening; the phase transformation temperature of the steel can be reduced, and the crystal grains can be refined; and the stability of austenite can be increased, which is beneficial to obtaining residual austenite. However, too high Mn content increases the cost and also increases the band structure in the steel. The Mn content of the invention is 1.0-1.7%.
And Als: the aluminum element can increase the plasticity of the material. However, when the aluminum is added into the low-carbon steel in an excessive amount, the graphitization of the steel is promoted, the carbon dissolution concentration in an alloy phase is reduced, and the strength is affected. And coarsening the crystal grains of the steel, deteriorating the mechanical properties of the steel, and the cleavage of the crystal is very weak, affecting the hot workability, weldability, and machinability of the steel. The present application defines Als: 0.020-0.050%.
P: phosphorus improves the strength of steel, but easily forms segregation in steel, easily causes high-temperature cracks, easily increases low-temperature crack sensitivity, and reduces the plasticity of the material. The content of P in the invention is 0.15-0.25%.
S: sulfide inclusions are generated in the steel, and the mechanical properties of the steel are seriously influenced. The present invention requires that the S content is 0.005% or less.
Re: re can form a compound with a melting point of about 1800 ℃ with harmful impurity elements with low melting points such as phosphorus and the like, and the compound is mainly positioned in austenite crystals, so that the number of phosphorus eutectic crystals on the boundaries of the austenite crystals can be reduced, the mechanical property of steel can be improved, and the segregation included on the boundaries can be inhibited, thereby improving the plasticity of the material and antagonizing the plasticity negative effect brought by Si and P in the formula. The Re content of the invention is 0.003-0.006%. Ensure that Si/Re is less than or equal to 400 and P/Re is less than or equal to 60, and the negative effects of inhibition cannot be antagonized if the range is exceeded. In the optimization scheme, the Si/Re is 200-350, and the P/Re is 35-55.
The mechanical property indexes of the high-strength high-plasticity low-cost hot-rolled thin steel plate with the tensile strength of 800MPa can meet the following requirements: yield strength ReLNot less than 700MPa, tensile strength RmThe strength is more than or equal to 800MPa, the elongation A after fracture is more than or equal to 23 percent, compared with the material in the prior art, the strength is higher, the plasticity is better, the high-strength thinning and the processing forming of parts are facilitated, and the application range is wide.
In order to achieve the performance indexes, reduce the cost and improve the surface quality, the production method adopted by the invention comprises the following steps: the method comprises the following steps of converter smelting, LF refining, slab continuous casting, slab heating, high-pressure water descaling, lubrication rolling, controlled cooling and low-temperature coiling, and comprises the following specific process steps:
(1) smelting:
molten iron → converter smelting → LF refining → continuous casting → plate blank;
(2) a heating process:
and (3) charging the plate blank into a furnace by adopting a cold blank, wherein the heating temperature is 1100-1180 ℃, and the heating time is 160-210 min.
In the prior art, the solid solution and precipitation requirements of Nb are required to be met, so that the heating temperature of a plate blank is 1200-1300 ℃, the energy consumption is increased, and the components are improved, and the energy is saved.
In addition, cold charging can increase the amount of retained austenite, which can be transformed into martensite under the subsequent compressive and tensile stresses.
In the optimization scheme, a three-section heating mode and a one-section soaking mode are adopted, wherein the three-section heating temperatures are respectively as follows: 840-1060 ℃, 1110-1250 ℃, 1220-1290 ℃ and soaking temperature is 1100-1180 ℃.
(3) The rolling process comprises the following steps:
the high-pressure water descaling pressure before rough rolling is 28MPa to remove surface scale.
The rough rolling is reversible rolling in 5 passes, and the thickness of the intermediate blank is 32-40 mm.
The finish rolling is 7-pass continuous rolling, and the finish rolling temperature is 810-850 ℃; lubricating and rolling are adopted between frames of the F2-F7 finishing mill: in order to avoid the difficulty of natural biting during the rolling of the strip steel caused by the lubricating liquid, in 7 frame rolling mills, for the 800 MPa-grade high-strength steel, the flow of the lubricating liquid input into the first frame is 20 percent of the maximum flow, and the flow of the lubricating liquid input into other frames is 70 to 80 percent. The saponification value of the rolling oil can be 30 (mgKOH. g)-1)。
(4) And (3) a cooling process:
and (3) adopting full-section cooling, wherein the cooling rate is 28-50 ℃/s.
(5) And (3) a coiling process:
and (3) carrying out full-section cooling and low-temperature coiling at 350-450 ℃, so that a certain amount of retained austenite can be obtained.
To better compare the formulations of the present application with the prior art, comparative tests were performed.
The chemical composition (wt%) of the steels in the specific examples and comparative examples is shown in the following table:
| C | Si | Mn | Ats | P | S | Re | |
| example 1 | 0.192 | 1.59 | 1.2 | 0.0288 | 0.208 | 0.003 | 0.006 |
| Example 2 | 0.176 | 1.04 | 1.4 | 0.0352 | 0.251 | 0.004 | 0.005 |
| Example 3 | 0.136 | 1.36 | 1.7 | 0.022 | 0.192 | 0.005 | 0.004 |
| Example 4 | 0.102 | 1.02 | 1.0 | 0.049 | 0.152 | 0.003 | 0.003 |
| Comparative example 1 | 0.168 | 1.2 | 1.4 | 0.0352 | 0.224 | 0.004 | 0.002 |
| Comparative example 2 | 0.136 | 1.36 | 1.4 | 0.024 | 0.192 | 0.005 | - |
The manufacturing process parameters of the steels in the various examples and comparative examples of the invention are shown in the following table:
the tensile properties of the steels in the examples and comparative examples of the present invention are shown in the following table (the product performance is tested by the national standard of "Metal Material tensile test method at Room temperature GB/T228"):
as can be seen from the above table, the low-carbon hot-rolled sheet strips produced by the components and the process in the examples 1-4 have excellent mechanical properties and surface quality (yield strength Rel: 735-740 MPa, tensile strength Rm: 830-855 MPa, and elongation A after fracture is more than or equal to 25.5-27%). The production process is less, the common cold rolling and annealing process is saved, and the energy consumption and the cost are low.
While the components of the comparative example 1 do not control the Si/Re and P/Re ratios, the components of the comparative example 2 do not add Re, and although the rolling and cooling control are the same in the later period, the negative effect of the corresponding plasticity caused by high Si and P cannot be inhibited in an antagonistic manner, the mechanical property is deteriorated, and the wear resistance is poor.
It should be noted that while the invention has been described in detail with respect to specific embodiments thereof, it will be apparent to those skilled in the art that various obvious changes can be made therein without departing from the spirit and scope of the invention.
Claims (3)
1. A high-strength high-plasticity low-cost hot-rolled thin steel plate with 800 MPa-level tensile strength is characterized in that: the chemical components by weight percentage are as follows: 0.10 to 0.20%, Si: 1.0-1.6%, Mn: 1.0-1.7%, P: 0.015-0.25%, S is less than or equal to 0.005%, Als: 0.020 to 0.050%, Re: 0.003-0.006% of Fe and the balance of unavoidable impurities.
2. The high-strength high-ductility low-cost hot-rolled steel sheet as claimed in claim 1, having a tensile strength of 800MPa grade, characterized in that: the Si/Re is between 200 and 350.
3. The high-strength high-ductility low-cost hot-rolled steel sheet as claimed in claim 1, having a tensile strength of 800MPa grade, characterized in that: the P/Re is between 35 and 55.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202011198538.XA CN112375979A (en) | 2020-10-31 | 2020-10-31 | Process for hot rolling thin steel plate with 800 MPa-level tensile strength, high plasticity and low cost |
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| CN202011198538.XA CN112375979A (en) | 2020-10-31 | 2020-10-31 | Process for hot rolling thin steel plate with 800 MPa-level tensile strength, high plasticity and low cost |
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Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20030003322A1 (en) * | 2001-04-16 | 2003-01-02 | Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd) | Galvannealed steel sheet superior in workability |
| EP1391526A2 (en) * | 2002-08-20 | 2004-02-25 | Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.) | Dual phase steel sheet with good bake-hardening properties |
| US20050133124A1 (en) * | 2003-12-18 | 2005-06-23 | Osamu Kawano | Multi-phase steel sheet excellent in hole expandability and method of producing the same |
| CN101717886A (en) * | 2009-11-20 | 2010-06-02 | 江苏省沙钢钢铁研究院有限公司 | Hot rolled dual phase steel plate with 650MPa of tensile strength and manufacturing method thereof |
| CN102650017A (en) * | 2012-05-25 | 2012-08-29 | 宝山钢铁股份有限公司 | Hot-rolled steel plate and manufacturing method thereof |
| CN106167875A (en) * | 2016-09-29 | 2016-11-30 | 马钢(集团)控股有限公司 | A kind of strength and ductility product economical high strength cold-rolled TRIP steel more than 20GPa % and preparation method thereof |
| CN110343961A (en) * | 2019-07-26 | 2019-10-18 | 马鞍山钢铁股份有限公司 | A kind of tensile strength 800MPa grades of hot rolling Multiphase Steels and its production method |
| CN110747391A (en) * | 2019-08-30 | 2020-02-04 | 武汉钢铁有限公司 | Cold-rolled ultrahigh-strength steel with excellent elongation and preparation method thereof |
-
2020
- 2020-10-31 CN CN202011198538.XA patent/CN112375979A/en active Pending
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20030003322A1 (en) * | 2001-04-16 | 2003-01-02 | Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd) | Galvannealed steel sheet superior in workability |
| EP1391526A2 (en) * | 2002-08-20 | 2004-02-25 | Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.) | Dual phase steel sheet with good bake-hardening properties |
| US20050133124A1 (en) * | 2003-12-18 | 2005-06-23 | Osamu Kawano | Multi-phase steel sheet excellent in hole expandability and method of producing the same |
| CN101717886A (en) * | 2009-11-20 | 2010-06-02 | 江苏省沙钢钢铁研究院有限公司 | Hot rolled dual phase steel plate with 650MPa of tensile strength and manufacturing method thereof |
| CN102650017A (en) * | 2012-05-25 | 2012-08-29 | 宝山钢铁股份有限公司 | Hot-rolled steel plate and manufacturing method thereof |
| CN106167875A (en) * | 2016-09-29 | 2016-11-30 | 马钢(集团)控股有限公司 | A kind of strength and ductility product economical high strength cold-rolled TRIP steel more than 20GPa % and preparation method thereof |
| CN110343961A (en) * | 2019-07-26 | 2019-10-18 | 马鞍山钢铁股份有限公司 | A kind of tensile strength 800MPa grades of hot rolling Multiphase Steels and its production method |
| CN110747391A (en) * | 2019-08-30 | 2020-02-04 | 武汉钢铁有限公司 | Cold-rolled ultrahigh-strength steel with excellent elongation and preparation method thereof |
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Application publication date: 20210219 |