CN109913763B - Low-cost cold-rolled dual-phase steel with good 1000 MPa-level cold processing performance and manufacturing method thereof - Google Patents
Low-cost cold-rolled dual-phase steel with good 1000 MPa-level cold processing performance and manufacturing method thereof Download PDFInfo
- Publication number
- CN109913763B CN109913763B CN201910229042.5A CN201910229042A CN109913763B CN 109913763 B CN109913763 B CN 109913763B CN 201910229042 A CN201910229042 A CN 201910229042A CN 109913763 B CN109913763 B CN 109913763B
- Authority
- CN
- China
- Prior art keywords
- equal
- less
- cold
- rolling
- cooling
- 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
Landscapes
- Heat Treatment Of Sheet Steel (AREA)
Abstract
The invention discloses low-cost cold-rolled dual-phase steel with good 1000 MPa-level cold processing performance and a manufacturing method thereof, belonging to the technical field of steel smelting. The composite material comprises the following chemical components in percentage by mass: c: 0.13 to 0.22, Mn: 1.20 to 1.70, Si: 0.20 to 0.50, Als: 0.30-0.80, P is less than or equal to 0.015, S is less than or equal to 0.0010, N is less than or equal to 0.004, and Cr: 0.20 to 0.50, Nb: 0.010-0.05, Ca: 0.0005-0.0025, less than or equal to 0.002 of T [ O ], and the balance of Fe and inevitable impurities; and Si + Als is more than or equal to 0.50 and less than or equal to 1.00. And undergoes the processes of steel making, LF refining, RH refining, continuous casting, hot rolling, cooling, coiling, acid washing, cold rolling, annealing and leveling; according to the method, on the basis of selecting a design with lower alloy element content, rolling and cooling processes are combined, so that the prepared product has low requirements on a production line of a production process on the basis of higher strength and cold bending property.
Description
Technical Field
The invention relates to cold-rolled dual-phase steel, belongs to the technical field of steel smelting, and particularly relates to low-cost cold-rolled dual-phase steel with good 1000 MPa-level cold workability and a manufacturing method thereof.
Background
In recent years, in order to reduce energy consumption in the using process of automobiles, CO is reduced2In the discharge, automobile steel is developing towards high strength and high toughness, ultra-high strength steel of 1000MPa grade and above is one of the main development directions, and dual-phase steel has high work hardening rate and forming performance, so that the ultra-high strength dual-phase steel of 1000MPa grade and above is widely applied.
For example, the Chinese invention patent application (application publication No. CN105803321A, application publication No. 2016-07-27) discloses 980MPa grade vanadium-containing ultra-fine grain cold-rolled dual-phase steel and a preparation method thereof, wherein the steel comprises the following components in percentage by weight: c: 0.10 to 0.20%, Si: 0.30 to 1.00%, Mn: 1.50-2.50%, Cr: 0.20-0.80%, Al: 0.01-0.06%, V: 0.05-0.15%, P is less than or equal to 0.020%, S is less than or equal to 0.015%, and N is less than or equal to 0.006%; the balance being Fe and unavoidable impurities. The invention refines ferrite and martensite crystal grains by using micro V, simultaneously VC is dispersed and separated out to play a role of precipitation strengthening, and the production cost is obviously reduced.
For another example, the Chinese invention patent application (application publication No. CN107058869A, application publication No. 2017-08-18) discloses a 980 MPa-grade cold-rolled dual-phase steel with an ultralow yield ratio and a manufacturing method thereof, wherein the chemical components in percentage by weight are as follows: c: 0.13 to 0.18%, Si: 0.3-0.6%, Mn: 1.7-2.4%, Als: 0.03-0.06%, Nb: 0-0.05%, Cr: 0.3-0.5%, and the balance of Fe and other inevitable impurities. The cold-rolled dual-phase steel plate can be used as an automobile anti-collision part, a structural part and an inner plate material by mainly adopting phase change strengthening and combining a composite strengthening mode of solid solution strengthening, fine grain strengthening, phase change strengthening and precipitation strengthening during component design. The DP980 has the characteristics of ultralow yield ratio, good elongation, higher n value, small mechanical property fluctuation range, low process sensitivity and the like, can reduce the rebound after stamping, and is favorable for the subsequent deep processing of the automobile industry. The above 2 applications do not have requirements for performance indexes such as cold bending and hole expansion rate, and therefore, for some parts with higher requirements for forming performance, the products cannot meet the requirements.
For another example, the Chinese invention patent application (application publication No. CN107043888A, application publication No. 2017-08-15) discloses a 980 MPa-grade cold-rolled dual-phase steel plate with excellent cold bending performance and a preparation method thereof, wherein the steel plate comprises the following chemical components in percentage by weight: c: 0.10-0.12%; si: 0.45-0.65%; mn: 2.4-2.6%; cr: 0.35-0.45%; nb: 0.05-0.075%; ti: 0.06-0.10%; and Als: 0.055-0.075%; p is less than or equal to 0.008 percent; s is less than or equal to 0.002%; n is less than or equal to 0.003 percent, and the balance of Fe and inevitable impurities. The dual-phase steel plate with the martensite and ferrite structure is obtained through the working procedures of smelting, LF refining, RH refining, hot continuous rolling, acid pickling and cold rolling and continuous annealing, the grain size grade of the dual-phase steel plate can reach more than 12 grades, the dual-phase steel plate has excellent mechanical property, the yield strength is 810-850 MPa, the tensile strength is 980MPa or more, the elongation is 10-20%, the 180-degree cold bending property is less than or equal to 2a, a is the plate thickness, and the dual-phase steel plate has the characteristics of relatively low cost and good product application performance. Although the performance indexes of the application comprise indexes such as cold bending and hole expansion rate, the plasticity and cold bending performance of parts with higher drawing and bending performance can not meet the requirements, and higher alloy elements such as Si, Mn, Nb, Ti and the like are added in the component design, so that the alloy cost is higher, and on the other hand, in the production process, the continuous casting and rolling difficulty is high, and the production needs to be carried out on a special high-strength steel production line.
In a word, when the prior art adopts high carbon content to produce 1000MPa grade dual-phase steel, the addition of alloy elements is relatively less, the tensile strength can reach over 1000MPa, but better performances such as cold bending and hole expanding rate cannot be obtained at the same time, and the products cannot meet the part requirement with higher requirement on the forming performance.
Disclosure of Invention
In order to solve the technical problems, the invention provides the low-cost cold-rolled dual-phase steel with good 1000 MPa-level cold processing performance and the manufacturing method thereof. On the basis of selecting a design with lower alloy element content, rolling and cooling processes are combined, so that the prepared product has low requirements on a production line of a production process on the basis of better strength and cold bending property.
In order to achieve the aim, the invention discloses low-cost cold-rolled dual-phase steel with good cold workability at 1000MPa level, which comprises the following chemical components in percentage by mass:
c: 0.13 to 0.22, Mn: 1.20 to 1.70, Si: 0.20 to 0.50, Als: 0.30-0.80, P is less than or equal to 0.015, S is less than or equal to 0.0010, N is less than or equal to 0.004, and Cr: 0.20 to 0.50, Nb: 0.010-0.05, Ca: 0.0005-0.0025, less than or equal to 0.002 of T [ O ], and the balance of Fe and inevitable impurities;
and Si + Als is more than or equal to 0.50 and less than or equal to 1.00.
Further, the paint comprises the following chemical components in percentage by mass:
c: 0.15 to 0.20, Mn: 1.20 to 1.70, Si: 0.20 to 0.50, Als: 0.40-0.80, P is more than or equal to 0.005 and less than or equal to 0.015, S is more than or equal to 0.0001 and less than or equal to 0.0010, N is more than or equal to 0.001 and less than or equal to 0.004, and Cr: 0.20 to 0.50, Nb: 0.010-0.05, Ca: 0.0005-0.0025, less than or equal to 0.002 of T [ O ], and the balance of Fe and inevitable impurities;
and Si + Als is more than or equal to 0.50 and less than or equal to 0.80.
Further, the paint comprises the following chemical components in percentage by mass:
c: 0.15 to 0.20, Mn: 1.20 to 1.70, Si: 0.20 to 0.50, Als: 0.40-0.80, P is more than or equal to 0.005 and less than or equal to 0.015, S is more than or equal to 0.0001 and less than or equal to 0.0010, N is more than or equal to 0.001 and less than or equal to 0.004, and Cr: 0.20 to 0.50, Nb: 0.010-0.05, Ca: 0.0005-0.0025, more than or equal to 0.001 and less than or equal to 0.002 of T [ O ], and the balance of Fe and inevitable impurities;
and Si + Als is more than or equal to 0.60 and less than or equal to 0.80.
Preferably, the paint comprises the following chemical components in percentage by mass:
c: 0.131, Mn: 1.50, Si: 0.30, Als: 0.50, P: 0.008, S: 0.0008, N: 0.003, Cr: 0.38, Nb: 0.030, Ca: 0.0008, T [ O ]: 0.0012, and the balance of Fe and inevitable impurities;
and, Si + Als: 0.80.
preferably, the paint comprises the following chemical components in percentage by mass:
c: 0.18, Mn: 1.60, Si: 0.30, Als: 0.30, P: 0.012, S: 0.0005, N: 0.0035, Cr: 0.50, Nb: 0.012, Ca: 0.0012, T [ O ]: 0.0013, and the balance of Fe and inevitable impurities;
and, Si + Als: 0.55.
preferably, the paint comprises the following chemical components in percentage by mass:
c: 0.14, Mn: 1.65, Si: 0.45, Als: 0.42, P: 0.010, S: 0.0003, N: 0.004, Cr: 0.30, Nb: 0.042, Ca: 0.0009, T [ O ]: 0.0015, and the balance of Fe and inevitable impurities;
and, Si + Als: 0.87.
preferably, the paint comprises the following chemical components in percentage by mass:
c: 0.19, Mn: 1.30, Si: 0.21, Als: 0.70, P: 0.008, S: 0.0005, N: 0.003, Cr: 0.35, Nb: 0.016, Ca: 0.0015, T [ O ]: 0.0017, and the balance of Fe and inevitable impurities;
and, Si + Als: 0.91.
preferably, the paint comprises the following chemical components in percentage by mass:
c: 0.21, Mn: 1.55, Si: 0.26, Als: 0.60, P: 0.0056, S: 0.0007, N: 0.0035, Cr: 0.46, Nb: 0.015, Ca: 0.0013, T [ O ]: 0.0010, and the balance of Fe and inevitable impurities;
and, Si + Als: 0.72.
preferably, the paint comprises the following chemical components in percentage by mass:
c: 0.20, Mn: 1.21, Si: 0.22, Als: 0.78, P: 0.006, S: 0.0004, N: 0.0025, Cr: 0.48, Nb: 0.012, Ca: 0.0018, T [ O ]: 0.0016, and the balance of Fe and inevitable impurities;
and, Si + Als: 0.70.
preferably, the paint comprises the following chemical components in percentage by mass:
c: 0.16, Mn: 1.35, Si: 0.40, Als: 0.35, P: 0.013, S: 0.0005, N: 0.0025, Cr: 0.42, Nb: 0.030, Ca: 0.0016, T [ O ]: 0.0018, and the balance of Fe and inevitable impurities;
and, Si + Als: 0.75.
preferably, the paint comprises the following chemical components in percentage by mass:
c: 0.15, Mn: 1.40, Si: 0.36, Als: 0.64, P: 0.008, S: 0.0002, N: 0.0035, Cr: 0.32, Nb: 0.015, Ca: 0.0020, T [ O ]: 0.0014, and the balance of Fe and inevitable impurities;
and, Si + Als: 1.00.
preferably, the paint comprises the following chemical components in percentage by mass:
c: 0.17, Mn: 1.45, Si: 0.49, Als: 0.51, P: 0.014, S: 0.0003, N: 0.0032, Cr: 0.36, Nb: 0.030, Ca: 0.0002, T [ O ]: 0.0012, and the balance of Fe and inevitable impurities;
and, Si + Als: 1.00.
furthermore, the microstructure of the cold-rolled dual-phase steel consists of an upper layer, a middle layer and a lower layer in the thickness direction, wherein the ferrite accounts for more than or equal to 95% in the tissues of the upper layer and the lower layer, and the thicknesses of the upper layer and the lower layer are respectively 1-50 mu m; the middle layer structure is composed of 40-80% of ferrite and 20-60% of martensite. Wherein, the ferrite content is controlled in a proper range, which is more beneficial to the final cold bending property;
preferably, the microstructure of the cold-rolled dual-phase steel consists of an upper layer, a middle layer and a lower layer in the thickness direction, wherein in the tissues of the upper layer and the lower layer, the proportion of ferrite is more than or equal to 95 percent and less than or equal to 98 percent, and the thicknesses of the ferrite and the lower layer are respectively 5-35 mu m; the middle layer structure is composed of 50-70% of ferrite and 30-50% of martensite.
Preferably, the grain size of the ferrite structure is less than 3 um.
Preferably, the grain size of the ferrite structure is less than 3um and greater than 1 um.
Furthermore, the tensile strength of the cold-rolled dual-phase steel obtained by the invention reaches more than 1000 MPa.
Preferably, the tensile strength of the cold-rolled dual-phase steel is greater than or equal to 1000MPa and less than or equal to 1200 MPa.
Furthermore, the cold-rolled dual-phase yield strength obtained by the method is 550-750 MPa.
Preferably, the cold rolling dual-phase yield strength obtained by the method is 550-700 MPa.
Furthermore, the elongation A80 of the cold-rolled dual-phase steel obtained by the method is more than or equal to 16 percent;
preferably, the elongation percentage of the cold-rolled dual-phase steel obtained by the invention is more than or equal to 16.0 percent and less than or equal to A80 and less than or equal to 25.0 percent.
Furthermore, the cold-rolled dual-phase steel obtained by the invention has the hole expansion rate of 20-70%.
Preferably, the cold-rolled dual-phase steel obtained by the invention has the hole expansion rate of 40-50%.
Furthermore, the cold-rolled dual-phase steel obtained by the invention has the cold bending strength of 0.3 a-1.5 a at 180 ℃.
Preferably, the cold-rolled dual-phase steel obtained by the invention has the cold bending strength of 0.5a at 180 degrees.
Preferably, the cold-rolled dual-phase steel obtained by the invention has the cold bending strength of 1.0a at 180 degrees.
In order to better realize the technical purpose of the invention, the invention also discloses a preparation method of the low-cost cold-rolled dual-phase steel with good cold processing performance at 1000MPa level, which comprises the processes of steelmaking, LF refining, RH refining, continuous casting, hot rolling, cooling, coiling, acid washing, cold rolling, annealing and leveling; the LF refining can effectively reduce the S content in the steel, reduce the sulfide content in the steel and improve the toughness of the product; the RH vacuum is adopted, so that the content of harmful elements such as N, H in the steel can be reduced, the content of nitride and gas in the steel can be reduced, and the toughness of the product can be improved;
1) hot rolling: the method comprises the steps of rough rolling and finish rolling, wherein the rough rolling temperature is more than or equal to 950 ℃, and the rough rolling reduction rate is more than or equal to 80%; the precision rolling temperature is 800-900 ℃, the precision rolling reduction rate is more than or equal to 95%, and the thickness of the obtained hot rolled product is 1.0-2.5 mm;
2) and (3) cooling: the method comprises slow cooling, isothermal cooling and quick cooling, wherein the slow cooling rate is less than or equal to 20 ℃/s, the isothermal temperature is 680-750 ℃, the isothermal time is 5-20 s, and the quick cooling speed is more than or equal to 50 ℃/s;
3) coiling: the coiling temperature is 100-300 ℃;
4) cold rolling: the cold rolling reduction rate is 30-60%, and the thickness of the obtained cold rolled product is 0.5-1.5 mm;
5) annealing: the method comprises the steps of strip steel heating, soaking, slow cooling, fast cooling and overaging treatment, wherein the soaking temperature is 760-830 ℃, and the soaking time is 30-200 s; the slow cooling termination temperature is 620-700 ℃, the slow cooling rate is less than or equal to 15 ℃/s, and the fast cooling rate is more than or equal to 50 ℃/s; the overaging temperature is 200-300 ℃;
6) leveling: and (3) adopting polishing, wherein the reduction rate of the polishing is 0.3-1.0%, the dew point in the annealing furnace is controlled to be-20 to-50 ℃, the content of hydrogen in the furnace is 1-20%, and the residual oxygen is 1-30 ppm.
Furthermore, in the hot rolling process, the rough rolling temperature is more than or equal to 950 ℃ and less than or equal to 1000 ℃, and the rough rolling reduction rate is more than or equal to 80% and less than or equal to 95%; the precision rolling temperature is 830-880 ℃, and the precision rolling reduction rate is more than or equal to 95% and less than or equal to 98%.
This is because, if the rough rolling temperature is too low, the rolling load of the rolling equipment increases, and the quality of the steel sheet shape deteriorates; meanwhile, the rough rolling reduction rate cannot be controlled too low, otherwise, the grain refinement is not facilitated, the structure is coarse, and the strength and the toughness of the product are reduced. If the finishing temperature is too low in the finish rolling process, uneven structures are easily formed in steel, the ferrite content in the upper surface layer structure and the lower surface layer structure is reduced, the final cold bending performance is not favorable, and hot rolling is difficult, thick grain structures are easily formed if the finishing temperature is too high, the ferrite content in the upper surface layer structure and the lower surface layer structure is increased, the strength of the product is not favorably improved, the finish rolling reduction rate is too low, grain refinement is not favorably realized, the thick grain structures are easily formed, the hot rolling finish rolling reduction rate is too low, the hot rolled product is too thick, the cold rolling reduction rate is increased, the rolling in a cold rolling process is difficult, and the product is not easy. Therefore, the rough rolling temperature is preferably between 950 ℃ and 1000 ℃, and the rough rolling reduction rate is preferably between 80% and 95%; the precision rolling temperature is 830-880 ℃, and the precision rolling reduction rate is more than or equal to 95% and less than or equal to 98%.
Further, in the cooling process, the slow cooling rate is less than or equal to 20 ℃/s and less than or equal to 10 ℃/s, the isothermal temperature is 700-730 ℃, the isothermal time is 8-15 s, and the fast cooling speed is less than or equal to 50 ℃/s and less than or equal to 75 ℃/s.
The cooling process adopts three sections of slow cooling, isothermal section and quick cooling, wherein the temperature setting of the slow cooling section and the isothermal section can enable a certain amount of ferrite to be generated in the hot rolled product structure, and the rolling in the acid rolling process is facilitated. The cooling of the quick cooling section can avoid the generation of coarse pearlite and bainite structures in the steel, and is beneficial to refining the continuous annealing structure. Therefore, the slow cooling rate is preferably less than or equal to 10 ℃/s and less than or equal to 20 ℃/s, the isothermal temperature is 700-730 ℃, the isothermal time is 8-15 s, and the fast cooling rate is preferably less than or equal to 50 ℃/s and less than or equal to 75 ℃/s.
In the coiling process, the coiling temperature is too high, so that coarse structures and carbides are easily formed, and the refining of the crystal grains of the steel is not facilitated. The coiling temperature is too low, the structure of the steel can not be recovered, so that the raw material is too hard and is not beneficial to acid rolling.
In the acid rolling process, the cold rolling reduction rate is too low to fully refine the structure in the steel, and too high cold rolling reduction rate causes difficulty in rolling and the strip is easy to crack at the edge part, so that the cold rolling reduction rate is preferably 30-60%, and the thickness of the obtained cold rolled product is 0.5-1.5 mm.
Further, in the annealing process, the soaking temperature is 780-820 ℃, the slow cooling termination temperature is 650-680 ℃, the slow cooling rate is less than or equal to 15 ℃/s and the fast cooling rate is less than or equal to 70 ℃/s and is less than or equal to 10 ℃/s.
The soaking temperature of the invention is too high, the ferrite thickness in the upper layer structure and the lower layer structure is increased, the strength of the steel is reduced, the temperature is too low, the ferrite content in the upper layer structure and the lower layer structure is lower, and the cold bending performance of the material is reduced. Therefore, the soaking temperature is preferably 780-820 ℃.
In order to enable the ratio of ferrite to martensite in the steel product structure to meet the requirements of the invention, the slow cooling termination temperature is preferably 650-680 ℃, the slow cooling rate is more than or equal to 10 ℃/s and less than or equal to 15 ℃/s, and the fast cooling rate is more than or equal to 50 ℃/s and less than or equal to 70 ℃/s.
Further, in the leveling process, the polishing reduction rate is 0.5-0.8%, the dew point in the annealing furnace is controlled to be-20 to-40 ℃, the hydrogen content in the annealing furnace is controlled to be 5-15%, and the residual oxygen is 1-20 ppm.
The invention needs to control the dew point in the annealing furnace, the hydrogen content in the furnace and the like, because the too high dew point in the annealing furnace easily causes the too thick thickness of the ferrite on the upper surface layer and the lower surface layer, and reduces the strength; and if the dew point is too low, the ferrite content in the upper and lower layer structures is insufficient, thereby reducing the hole expansibility, cold bending property and extensibility of the product. Too low hydrogen content easily causes too thick ferrite on the upper and lower surface layers and reduces strength, while H2If the content is too high, the ferrite content in the upper and lower layer structures is insufficient, thereby reducing the hole expansibility, cold bending property and elongation property of the product. Too high residual oxygen content easily causes the thickness of ferrite on the upper and lower surface layers to be too thick, thus reducing the strength, while too low residual oxygen content causes the ferrite content in the upper and lower layer tissues to be insufficient, thereby reducing the hole expansion ratio, cold bending property and elongation property of the product.
The selection principle of the alloy elements and the contents is as follows:
carbon (C): the carbon-containing steel is the most effective and cheap additive element for improving the strength of steel, the tensile strength and the yield strength of the steel are improved along with the increase of the carbon content, but the elongation and the impact toughness are reduced, the corrosion resistance is also reduced, and the welding heat affected zone of the steel can be hardened to cause the generation of welding cold cracks. The carbon content is too low, so that in order to ensure the strength of the steel, alloy elements such as Mn, Si, Cr, Nb, Ti and the like in the steel need to be increased, so that the alloy cost is increased, the carbon content is too high, the martensite content of the surface layer of the steel is easy to increase, the surface is hardened, the local plasticity is reduced, and surface microcracks are easy to generate during cold bending, so that the cold bending performance of the steel is reduced, therefore, the C content is preferably 0.15-0.20%.
Silicon (Si): the Si can also improve the corrosion resistance of the steel, and is often added into stainless steel, low alloy steel and corrosion resistant alloy to improve the corrosion resistance of the alloy, so that the alloy has the performances of resisting chloride stress corrosion cracking, pitting corrosion, hot concentrated nitric acid corrosion, oxidation, seawater corrosion and the like. Si can also improve the corrosion resistance of a splash zone of the low alloy steel in seawater, but the Si content is too high, so that the ferrite strength of the upper surface and the lower surface is too high, and the cold bending performance is reduced, therefore, the Si content is preferably 0.20-0.50%.
Manganese (Mn): the Mn content is preferably 1.20-1.70%, the steel strength is obviously increased, the impact transformation temperature is hardly changed, the tensile strength can be improved by about 100MPa by 1% of Mn, meanwhile, the Mn slightly improves the corrosion resistance of the steel, but the alloy cost of the steel is obviously increased by the high Mn content, the Mn also promotes the formation of more hard phase martensite in the surface layer structure and serious segregation in the center to cause cold bending cracking, and the Mn also easily forms complex carbide of FeMnCr in the steel to generate adverse effect on the hole expansion performance of the steel.
Phosphorus (P) and sulfur (S) are impurity elements in steel, P has a certain effect of improving corrosion resistance, but P is an element easy to segregate, severe segregation is generated in the local part of the steel, plasticity and toughness are reduced, the low-temperature toughness is extremely harmful, S is easy to segregate and enrich in the steel and is an element harmful to corrosion resistance, and S can be controlled to be less than 0.001 by controlling the contents of Si and Al in the steel and a steelmaking process, so that P is controlled to be less than or equal to 0.015% and S is controlled to be less than or equal to 0.0001% to 0.0010%.
Nitrogen (N): n is an impurity element in steel, Al, Nb, Ti and the like in the steel are easy to form nitrides, on one hand, the strength can be improved by proper amount of nitrides, on the other hand, coarse nitrides are easy to form by too high content of nitrogen, so that the hole expanding rate and the cold bending performance of the steel are reduced, and therefore, the content is reduced as much as possible, and N is controlled to be more than or equal to 0.001% and less than or equal to 0.004%.
And Als: al is beneficial to promoting the formation of a ferrite structure on the surface of steel, and can play a role in reducing the content of S in steel and reducing sulfide inclusions in the steel, so that the toughness of the steel is improved, but the Al content is too high, the thicknesses of the ferrite on the upper surface layer and the lower surface layer are too thick, so that the strength is reduced, in addition, the Al is easy to form coarse nitride/sulfide and oxide inclusion particles with nitrogen, sulfur and oxygen in the steel, and the cold bending and hole expanding performance of the steel is reduced, so the Al content is 0.40-0.80%.
Niobium (Nb) is two strong carbide and nitride forming elements, has a strong affinity with nitrogen and carbon, and can form an extremely stable carbonitride therewith. The distribution of the dispersed Nb carbonitride second phase particles along the austenite grain boundary can greatly improve the coarsening temperature of original austenite grains, the Nb carbonitride precipitate can be used as the nucleation core of the austenite grains in the austenite recrystallization temperature region in the rolling process, and the dispersed Nb carbonitride precipitate can effectively pin the austenite grain boundary in the non-recrystallization temperature range to prevent the austenite grains from further growing up, thereby refining ferrite grains and achieving the purpose of improving the strength and the impact toughness; therefore, the steel sheet can obtain excellent toughness by the fine grain strengthening and precipitation strengthening action of the Nb microalloy element. The invention controls Nb: 0.010-0.050%.
Chromium (Cr): the invention comprehensively considers the corrosion resistance, impact toughness and alloy cost of the steel, but the Cr content is too high, and the Cr content is easy to generate complex FeMnCr carbide with Fe, Mn and C in the steel, and has adverse effect on the hole expansion performance of the steel, so the invention controls the Cr: 0.20 to 0.50 percent.
Calcium (Ca): ca can lower the melting point of the inclusions in the steel, so that the inclusions can be removed in the steelmaking stage, the shape of the inclusions can be changed, and the formation of pointed inclusions can be reduced, but the content of Ca is too high, so that the amount of the inclusions in the steel can be increased, and therefore, the content of Ca in the invention is 0.0005-0.0025%.
T [ O ]: the content of TiO in the steel is less than 0.002% and is easy to form oxide inclusion.
Si + Als: si + Als is more than or equal to 0.50% and less than or equal to 0.80%, and according to test results, the control of Si + Als in the range of the invention is beneficial to reducing the S content in steel and obtaining the microstructure of the product of the invention.
The beneficial effects of the invention are mainly embodied in the following aspects:
1. the tensile strength of the cold-rolled dual-phase steel prepared by the method is more than or equal to 1000MPa, and the yield strength is 550-750 MPa; meanwhile, the elongation A80 is more than or equal to 16 percent, and the hole expansion rate is 20-70 percent; the cold bending strength at 180 ℃ is 0.3 a-1.5 a; therefore, the dual-phase steel prepared by the method has better mechanical property, plasticity and cold bending property, and meanwhile, the product has good surface quality and good welding property.
2. The dual-phase steel with the good performance, which is prepared by the invention, has the advantages of low alloy content, low reduction rate under the acid rolling process, easy manufacture and suitability for a production line with low rolling equipment capacity.
Detailed Description
In order to better explain the invention, the following further illustrate the main content of the invention in connection with specific examples, but the content of the invention is not limited to the following examples.
The invention discloses a preparation method of low-cost cold-rolled dual-phase steel with good 1000 MPa-level cold processing performance, wherein alloy elements designed in a table 1 are adopted for smelting;
TABLE 1 Main ingredient list of inventive and comparative examples
In Table 1 above, 10 and 11 are the components of comparative example, C, Si, Als, (Si + Als), Mn, and T [ O ] of comparative example 10 are out of the range of the present invention, and Si, Als, (Si + Als), Mn, Nb, S, Ca, and T [ O ] of comparative example 11 are out of the range of the present invention.
The cold-rolled dual-phase steel comprises steel making, LF refining, RH refining, continuous casting, hot rolling, cooling, coiling, acid cleaning, cold rolling, annealing and leveling processes; wherein the main process parameters are shown in tables 2 and 3;
TABLE 2 list of process parameters
In Table 2, the finish rolling temperature, the laminar cooling isothermal time, and the rapid cooling rate and the coiling temperature of comparative examples 3-2 were out of the range of the present invention, the hot rolling finish rolling reduction, the slow cooling rate, and the laminar cooling isothermal temperature of comparative examples 3-3 and 3-4 were out of the range of the present invention, and the cold rolling reduction of 3-4 was too high. 3-3 and 3-4 are both difficult to manufacture due to cold rolling cracking caused by unreasonable control of hot rolling and cold rolling process parameters. Other embodiments of the manufacturing process parameters are within the scope of the invention.
TABLE 3 Process parameter List (II)
In table 3, the above comparative examples and examples employ continuous annealing, the soaking temperature of the continuous annealing of comparative examples 1 to 2 is higher than that of the inventive examples, the soaking temperature of comparative examples 1 to 3 is too low, the slow cooling termination temperature is too low, the soaking time of comparative examples 1 to 4 is too long, and the dew point, residual oxygen content, and the like are too high.
The cold-rolled dual-phase steels obtained in the above examples and comparative examples were subjected to the property test to obtain the table shown in table 4.
TABLE 4 Dual-phase Steel Properties List
As can be seen from the above list, the comparative examples 1-2, 1-3 and 1-4 have lower ferrite proportion or thicker thickness and larger ferrite grains in the upper and lower layer structures of the product due to the fact that the continuous annealing process parameters are out of the range of the present invention, resulting in lower final strength, lower elongation and hole expansibility and poor cold bending property. In the comparative example 3-2, the hot rolling process parameters are out of the range of the invention, so that ferrite grains of the product are coarse, and the product strength, hole expansion and cold bending properties are low. Comparative example 10 has a lower Si + Als content than the present invention and a higher Mn content than the present invention, so ferrite in the upper and lower layer structures is lower than the present invention, and has a lower Si and Al content and a higher S content, resulting in a lower hole expansibility and cold bending formability, comparative example 11 has a higher Mn content, resulting in a lower ferrite content in the surface layer structure, which adversely affects the cold bending formability, and has a higher S content and a higher T [ O ] content, and has no Ca content, resulting in a higher number of inclusions and a lower hole expansibility.
The above examples are merely preferred examples and are not intended to limit the embodiments of the present invention. In addition to the above embodiments, the present invention has other embodiments. All technical solutions formed by adopting equivalent substitutions or equivalent transformations fall within the protection scope of the claims of the present invention.
Claims (7)
1. The low-cost cold-rolled dual-phase steel with good cold workability at 1000MPa level comprises the following chemical components in percentage by mass:
c: 0.15 to 0.20, Mn: 1.20 to 1.70, Si: 0.20 to 0.50, Als: 0.40-0.80, P is more than or equal to 0.005 and less than or equal to 0.015, S is more than or equal to 0.0001 and less than or equal to 0.0010, N is more than or equal to 0.001 and less than or equal to 0.004, and Cr: 0.32 to 0.50, Nb: 0.010-0.05, Ca: 0.0005-0.0025, less than or equal to 0.002 of T [ O ], and the balance of Fe and inevitable impurities;
and Si + Als is more than or equal to 0.50 and less than or equal to 0.80;
the dual-phase steel is prepared by the following preparation method, which comprises the processes of steel making, LF refining, RH refining, continuous casting, hot rolling, cooling, coiling, acid cleaning, cold rolling, annealing and flattening;
1) hot rolling: comprises rough rolling and finish rolling, wherein the rough rolling temperature is more than or equal to 950 ℃ and less than or equal to 1000 ℃, and the rough rolling reduction rate is more than or equal to 80% and less than or equal to 95%; the finish rolling temperature is 830-880 ℃, the finish rolling reduction rate is more than or equal to 95% and less than or equal to 98%, and the thickness of the obtained hot rolled product is 1.0-2.5 mm;
2) and (3) cooling: the method comprises slow cooling, isothermal cooling and quick cooling, wherein the slow cooling rate is less than or equal to 20 ℃/s, the isothermal temperature is 680-750 ℃, the isothermal time is 5-20 s, and the quick cooling speed is more than or equal to 50 ℃/s;
3) coiling: the coiling temperature is 100-300 ℃;
4) cold rolling: the cold rolling reduction rate is 30-60%, and the thickness of the obtained cold rolled product is 0.5-1.5 mm;
5) annealing: the method comprises the steps of strip steel heating, soaking, slow cooling, fast cooling and overaging treatment, wherein the soaking temperature is 760-830 ℃, and the soaking time is 30-200 s; the slow cooling termination temperature is 620-700 ℃, the slow cooling rate is less than or equal to 15 ℃/s, and the fast cooling rate is more than or equal to 50 ℃/s; the overaging temperature is 200-300 ℃;
6) leveling: and (3) adopting polishing, wherein the polishing reduction rate is 0.3-1.0%, the dew point in the annealing furnace is controlled to be-20 to-50 ℃, the hydrogen content in the furnace is 1-20%, and the residual oxygen is 1-30 ppm.
2. The low-cost cold-rolled dual-phase steel with good cold workability at 1000MPa level according to claim 1, characterized in that: the composite material comprises the following chemical components in percentage by mass:
c: 0.15 to 0.20, Mn: 1.20 to 1.70, Si: 0.20 to 0.50, Als: 0.40-0.80, P is more than or equal to 0.005 and less than or equal to 0.015, S is more than or equal to 0.0001 and less than or equal to 0.0010, N is more than or equal to 0.001 and less than or equal to 0.004, and Cr: 0.32 to 0.50, Nb: 0.010-0.05, Ca: 0.0005-0.0025, more than or equal to 0.001 and less than or equal to 0.002 of T [ O ], and the balance of Fe and inevitable impurities;
and Si + Als is more than or equal to 0.60 and less than or equal to 0.80.
3. The low-cost cold-rolled dual-phase steel with good cold workability at 1000MPa level according to claim 1 or 2, characterized in that: the microstructure of the cold-rolled dual-phase steel consists of an upper layer, a middle layer and a lower layer in the thickness direction, wherein in the structure of the upper layer and the structure of the lower layer, the ferrite proportion is more than or equal to 95%, and the thicknesses of the upper layer and the lower layer are respectively 1-50 mu m; the middle layer structure is composed of 40-80% of ferrite and 20-60% of martensite.
4. A method for preparing the low-cost cold-rolled dual-phase steel with good 1000MPa cold processing performance as claimed in claim 1, which comprises the processes of steel making, LF refining, RH refining, continuous casting, hot rolling, cooling, coiling, acid pickling, cold rolling, annealing and flattening;
1) hot rolling: comprises rough rolling and finish rolling, wherein the rough rolling temperature is more than or equal to 950 ℃ and less than or equal to 1000 ℃, and the rough rolling reduction rate is more than or equal to 80% and less than or equal to 95%; the finish rolling temperature is 830-880 ℃, the finish rolling reduction rate is more than or equal to 95% and less than or equal to 98%, and the thickness of the obtained hot rolled product is 1.0-2.5 mm;
2) and (3) cooling: the method comprises slow cooling, isothermal cooling and quick cooling, wherein the slow cooling rate is less than or equal to 20 ℃/s, the isothermal temperature is 680-750 ℃, the isothermal time is 5-20 s, and the quick cooling speed is more than or equal to 50 ℃/s;
3) coiling: the coiling temperature is 100-300 ℃;
4) cold rolling: the cold rolling reduction rate is 30-60%, and the thickness of the obtained cold rolled product is 0.5-1.5 mm;
5) annealing: the method comprises the steps of strip steel heating, soaking, slow cooling, fast cooling and overaging treatment, wherein the soaking temperature is 760-830 ℃, and the soaking time is 30-200 s; the slow cooling termination temperature is 620-700 ℃, the slow cooling rate is less than or equal to 15 ℃/s, and the fast cooling rate is more than or equal to 50 ℃/s; the overaging temperature is 200-300 ℃;
6) leveling: and (3) adopting polishing, wherein the polishing reduction rate is 0.3-1.0%, the dew point in the annealing furnace is controlled to be-20 to-50 ℃, the hydrogen content in the furnace is 1-20%, and the residual oxygen is 1-30 ppm.
5. The method for preparing the low-cost cold-rolled dual-phase steel with good cold workability at 1000MPa according to claim 4, wherein the method comprises the following steps: in the cooling process, the slow cooling rate is less than or equal to 20 ℃/s and less than or equal to 10 ℃/s, the isothermal temperature is 700-730 ℃, the isothermal time is 8-15 s, and the fast cooling speed is less than or equal to 50 ℃/s and less than or equal to 75 ℃/s.
6. Method for producing a low cost cold rolled dual phase steel with good cold workability at 1000MPa level according to claim 4 or 5, characterized in that: in the annealing process, the soaking temperature is 780-820 ℃, the slow cooling termination temperature is 650-680 ℃, the slow cooling rate is less than or equal to 15 ℃/s and the fast cooling rate is less than or equal to 70 ℃/s and is less than or equal to 10 ℃/s.
7. Method for producing a low cost cold rolled dual phase steel with good cold workability at 1000MPa level according to claim 4 or 5, characterized in that: in the leveling process, the rolling reduction rate of the leveling is 0.5-0.8%, the dew point in an annealing furnace is controlled to be-20 to-40 ℃, the hydrogen content in the furnace is 5-15%, and the residual oxygen is 1-20 ppm.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910229042.5A CN109913763B (en) | 2019-03-25 | 2019-03-25 | Low-cost cold-rolled dual-phase steel with good 1000 MPa-level cold processing performance and manufacturing method thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910229042.5A CN109913763B (en) | 2019-03-25 | 2019-03-25 | Low-cost cold-rolled dual-phase steel with good 1000 MPa-level cold processing performance and manufacturing method thereof |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN109913763A CN109913763A (en) | 2019-06-21 |
| CN109913763B true CN109913763B (en) | 2020-07-03 |
Family
ID=66966641
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201910229042.5A Active CN109913763B (en) | 2019-03-25 | 2019-03-25 | Low-cost cold-rolled dual-phase steel with good 1000 MPa-level cold processing performance and manufacturing method thereof |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN109913763B (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110747405B (en) * | 2019-10-24 | 2021-09-14 | 邯郸钢铁集团有限责任公司 | One-thousand-megapascal-grade cold-rolled bainite steel plate suitable for rolling and preparation method thereof |
| CN111500935B (en) * | 2020-06-09 | 2021-10-26 | 首钢集团有限公司 | 1000 MPa-grade high-strength steel and preparation method and application thereof |
| CN112281062A (en) * | 2020-10-22 | 2021-01-29 | 本钢板材股份有限公司 | 1000 MPa-grade low-cost hot-galvanized dual-phase steel and preparation method thereof |
| CN113308649B (en) * | 2021-05-14 | 2022-10-18 | 唐山钢铁集团有限责任公司 | Low-yield-ratio 1000 MPa-grade cold-rolled dual-phase strip steel and production method thereof |
| CN113684427A (en) * | 2021-08-13 | 2021-11-23 | 北京首钢冷轧薄板有限公司 | 800 MPa-grade dual-phase steel with excellent bulging capacity and preparation method thereof |
| CN115522131B (en) * | 2022-10-13 | 2023-12-05 | 武汉科技大学 | 1000 MPa-grade hot-rolled dual-phase steel and preparation method and application thereof |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102828119A (en) * | 2011-06-14 | 2012-12-19 | 鞍钢股份有限公司 | High-bending 980 MPa-grade cold-rolled dual-phase steel and preparation process thereof |
| WO2014093744A1 (en) * | 2012-12-13 | 2014-06-19 | Thyssenkrupp Steel Usa, Llc | Process for making cold-rolled dual phase steel sheet |
| CN107619993A (en) * | 2016-07-13 | 2018-01-23 | 上海梅山钢铁股份有限公司 | Yield strength 750MPa level cold rolling martensite steel plates and its manufacture method |
| CN108913991A (en) * | 2018-06-20 | 2018-11-30 | 武汉钢铁有限公司 | With good 980MPa grades of cold rolling Multiphase Steels of reaming performance and preparation method thereof |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7959747B2 (en) * | 2004-11-24 | 2011-06-14 | Nucor Corporation | Method of making cold rolled dual phase steel sheet |
-
2019
- 2019-03-25 CN CN201910229042.5A patent/CN109913763B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102828119A (en) * | 2011-06-14 | 2012-12-19 | 鞍钢股份有限公司 | High-bending 980 MPa-grade cold-rolled dual-phase steel and preparation process thereof |
| WO2014093744A1 (en) * | 2012-12-13 | 2014-06-19 | Thyssenkrupp Steel Usa, Llc | Process for making cold-rolled dual phase steel sheet |
| CN107619993A (en) * | 2016-07-13 | 2018-01-23 | 上海梅山钢铁股份有限公司 | Yield strength 750MPa level cold rolling martensite steel plates and its manufacture method |
| CN108913991A (en) * | 2018-06-20 | 2018-11-30 | 武汉钢铁有限公司 | With good 980MPa grades of cold rolling Multiphase Steels of reaming performance and preparation method thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| CN109913763A (en) | 2019-06-21 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN109913763B (en) | Low-cost cold-rolled dual-phase steel with good 1000 MPa-level cold processing performance and manufacturing method thereof | |
| CN112048681B (en) | 980 MPa-grade high-formability cold-rolled DH steel and preparation method thereof | |
| CN108796375B (en) | Hot-galvanized high-strength steel with tensile strength of 1000MPa and reduction production method thereof | |
| CN108823507B (en) | Tensile strength 800 MPa-grade hot-galvanized high-strength steel and reduction production method thereof | |
| CN111979489B (en) | 780 MPa-grade high-plasticity cold-rolled DH steel and preparation method thereof | |
| US10889873B2 (en) | Complex-phase steel sheet having excellent formability and method of manufacturing the same | |
| CN111441000A (en) | 690 MPa-yield-strength low-yield-ratio high-strength steel plate and manufacturing method thereof | |
| CN113234995B (en) | Ultra-thick hot-rolled H-shaped steel with yield strength of 600MPa and production method thereof | |
| CN113388779B (en) | 1.5 GPa-grade ultrahigh-strength high-plasticity high-hole-expansion DH steel plate and preparation method thereof | |
| CN109207849B (en) | High-strength high-plasticity 1000 MPa-grade hot rolled steel plate and preparation method thereof | |
| CN105925912B (en) | Tensile strength 780MPa levels cold-rolled biphase steel containing vanadium and preparation method thereof | |
| KR20200075991A (en) | Cold rolled steel sheet with excellent formability, galvanized steel sheet, and manufacturing method thereof | |
| CN111455269A (en) | Yield strength 960MPa grade very high strength marine steel plate and manufacturing method thereof | |
| CN102925814B (en) | Steel for hydrogen sulfide stress corrosion resisting pressure container and production method of steel | |
| CN113416889B (en) | Ultrahigh-strength hot-galvanized DH1470 steel with good welding performance and preparation method thereof | |
| CN111979490A (en) | High-ductility and high-formability cold-rolled DH590 steel and production method thereof | |
| CN106282831A (en) | A kind of high-strength container weather resisting steel and manufacture method thereof | |
| JP2013181208A (en) | High strength hot-rolled steel sheet having excellent elongation, hole expansibility and fatigue characteristics, and method for producing the same | |
| CN112226673A (en) | Hot rolled steel plate with 650 MPa-grade tensile strength and manufacturing method thereof | |
| CN114107789A (en) | 780 MPa-grade high-surface high-performance high-stability ultrahigh-hole-expansion steel and manufacturing method thereof | |
| CN114134388B (en) | Thin-specification ultrahigh-strength steel plate with 1300 MPa-level tensile strength and manufacturing method thereof | |
| JP2023554449A (en) | High-strength steel plate with excellent workability and its manufacturing method | |
| KR20220073762A (en) | Composite steel with high hole expandability and manufacturing method therefor | |
| CN115572901B (en) | 630 MPa-grade high-tempering-stability low-carbon low-alloy steel plate and manufacturing method thereof | |
| CN114134387B (en) | 1300 MPa-tensile-strength thick-specification ultrahigh-strength steel plate 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 |