CN117660830A - 100 kg-level cold-rolled low-alloy annealed dual-phase steel and manufacturing method thereof - Google Patents
100 kg-level cold-rolled low-alloy annealed dual-phase steel and manufacturing method thereof Download PDFInfo
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- 229910000885 Dual-phase steel Inorganic materials 0.000 title claims abstract description 85
- 229910045601 alloy Inorganic materials 0.000 title claims abstract description 75
- 239000000956 alloy Substances 0.000 title claims abstract description 75
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 28
- 229910000734 martensite Inorganic materials 0.000 claims abstract description 21
- 238000005452 bending Methods 0.000 claims abstract description 18
- 229910052729 chemical element Inorganic materials 0.000 claims abstract description 16
- 229910000859 α-Fe Inorganic materials 0.000 claims abstract description 15
- 239000012535 impurity Substances 0.000 claims abstract description 12
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 8
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract description 8
- 238000000137 annealing Methods 0.000 claims description 22
- 238000000034 method Methods 0.000 claims description 21
- 238000001816 cooling Methods 0.000 claims description 19
- 238000005496 tempering Methods 0.000 claims description 11
- 238000005096 rolling process Methods 0.000 claims description 9
- 238000005097 cold rolling Methods 0.000 claims description 8
- 230000009467 reduction Effects 0.000 claims description 8
- 238000002791 soaking Methods 0.000 claims description 8
- 238000005098 hot rolling Methods 0.000 claims description 7
- 229910052758 niobium Inorganic materials 0.000 claims description 5
- 229910052717 sulfur Inorganic materials 0.000 claims description 5
- 238000003723 Smelting Methods 0.000 claims description 4
- 238000009749 continuous casting Methods 0.000 claims description 4
- 238000005266 casting Methods 0.000 claims description 3
- 238000010438 heat treatment Methods 0.000 claims description 3
- 229910052748 manganese Inorganic materials 0.000 claims description 3
- 229910000831 Steel Inorganic materials 0.000 description 77
- 239000010959 steel Substances 0.000 description 77
- 230000000052 comparative effect Effects 0.000 description 43
- 238000013461 design Methods 0.000 description 19
- 239000000126 substance Substances 0.000 description 15
- 230000009286 beneficial effect Effects 0.000 description 10
- 230000009977 dual effect Effects 0.000 description 10
- 229910052799 carbon Inorganic materials 0.000 description 9
- 230000008569 process Effects 0.000 description 9
- 230000000694 effects Effects 0.000 description 8
- 239000000203 mixture Substances 0.000 description 8
- 238000012360 testing method Methods 0.000 description 8
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 7
- 229910001566 austenite Inorganic materials 0.000 description 5
- 229910052757 nitrogen Inorganic materials 0.000 description 5
- 238000011161 development Methods 0.000 description 4
- 229910052698 phosphorus Inorganic materials 0.000 description 4
- 238000007670 refining Methods 0.000 description 4
- 239000002245 particle Substances 0.000 description 3
- 238000009864 tensile test Methods 0.000 description 3
- 229910000851 Alloy steel Inorganic materials 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- 230000009471 action Effects 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 230000002401 inhibitory effect Effects 0.000 description 2
- 239000007769 metal material Substances 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 229910000521 B alloy Inorganic materials 0.000 description 1
- 229910000742 Microalloyed steel Inorganic materials 0.000 description 1
- 229910000676 Si alloy Inorganic materials 0.000 description 1
- 229910006639 Si—Mn Inorganic materials 0.000 description 1
- 229910000797 Ultra-high-strength steel Inorganic materials 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000013329 compounding Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000005121 nitriding Methods 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- 230000006911 nucleation Effects 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 238000011112 process operation Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 238000001953 recrystallisation Methods 0.000 description 1
- 238000005482 strain hardening Methods 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 239000013585 weight reducing agent Substances 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
Classifications
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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
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/26—Methods of annealing
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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
-
- 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
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Heat Treatment Of Sheet Steel (AREA)
Abstract
The invention discloses a 100 kg-level cold-rolled low-alloy annealed dual-phase steel, which contains Fe and unavoidable impurity elements and also contains the following chemical elements in percentage by mass: c is more than 0.1 percent and less than or equal to 0.13, si:0.5 to 0.8 percent, mn:1.6 to 1.8 percent of Al:0.01% -0.03%, nb:0.01 to 0.03 percent of Ti:0.01 to 0.03 percent, B:0.0020 to 0.0030 percent; the chemical elements do not contain Mo and Cr; the microstructure of the 100 kg-level cold-rolled low-alloy annealed dual-phase steel is martensite and ferrite. Correspondingly, the invention also discloses a manufacturing method of the 100 kg-level cold-rolled low-alloy annealed dual-phase steel. The cold-rolled low-alloy annealed dual-phase steel with the 100 kg level obtained by adopting the manufacturing method not only has good economy, but also has high strength and excellent elongation and bending property.
Description
Technical Field
The invention relates to a metal material and a manufacturing method thereof, in particular to a 100 kg-level cold-rolled low-alloy annealed dual-phase steel and a manufacturing method thereof.
Background
In recent years, with the increase of global energy crisis and environmental problems, energy saving and safety have become main development directions of automobile manufacturing, wherein the reduction of vehicle weight is one of energy saving and emission reduction measures. In the practical application process, the high-strength dual-phase steel has good mechanical property and service performance, so that the high-strength dual-phase steel can be effectively applied to the production and manufacture of vehicle structural members.
Currently, with the development of ultra-high strength steel and the change of the current market, the market and users generally expect the high strength steel to have economical and better performance. Currently 980 MPa-grade low alloy steel is still the mainstream application steel, accounting for 20% of the total amount of the whole low alloy steel, and is widely applied to various types of structural parts and safety parts. Along with the continuous development of the trend of weight reduction and energy saving in the automobile industry, the level of steel factories at home and abroad, especially at home and abroad, is rapidly improved, and the development of future dual-phase steel is inevitably mainly based on the combination of low cost and high performance.
In the current prior art, for 980 MPa-grade dual-phase steel, a great deal of research has been carried out by current researchers, and a certain research result has been achieved.
For example: chinese patent document with publication number CN109280854a, publication date 2019, 1 month and 29 days, named "980MPa low-carbon cold-rolled dual-phase steel and preparation method thereof", discloses 980MPa low-carbon cold-rolled dual-phase steel. The technical scheme aims to solve the technical problems of high production cost and high production difficulty of the existing 980MPa cold-rolled dual-phase steel, and comprises the following chemical components in percentage by mass: c:0.05 to 0.10 percent, si:0.30 to 0.70 percent, mn:2.00 to 2.50 percent, cr:0.40 to 0.80 percent of Al:0.01 to 0.06 percent, controlling the content of molten iron V in a converter, and then obtaining 980MPa low-carbon cold-rolled dual-phase steel through hot rolling, acid rolling and annealing processes. The dual-phase steel prepared by adopting the technical scheme has excellent mechanical property and forming property and obvious cost advantage. However, the technical proposal adopts noble alloy Cr in the design of steel, and contains higher content of Mn, which not only leads to the rise of alloy cost, but also causes serious banded structure, thereby causing the non-uniformity of mechanical properties.
Also for example: the Chinese patent literature with publication number of CN111455285A and publication date of 2020, 7 months and 28 days, named as low-cost and easy-to-produce cold-rolled dual-phase steel with tensile strength of 980MPa and production method thereof, discloses cold-rolled dual-phase steel with tensile strength of 980MPa and production method thereof, and the chemical components of the cold-rolled dual-phase steel are as follows: 0.080 to 0.095 percent of C, 0.4 to 0.6 percent of Si, 2.1 to 2.3 percent of Mn, 0.06 to 0.08 percent of Als, 0.2 to 0.4 percent of Cr, 0.03 to 0.05 percent of Nb, 0.01 to 0.02 percent of Ti, 0.0015 to 0.0040 percent of Ca, less than or equal to 0.012 percent of P, less than or equal to 0.005 percent of S, less than or equal to 0.005 percent of N, and the balance of Fe and unavoidable impurities.
For another example: the Chinese patent literature with publication number of CN107043888A and publication date of 2017, 8 month and 15 days, named as 980MPa grade cold-rolled dual-phase steel plate with excellent cold bending performance and a preparation method thereof, discloses 980MPa grade cold-rolled dual-phase steel plate, which comprises the following chemical components in percentage by weight: c0.10-0.12%; si 0.45-0.65%; mn 2.4-2.6%; cr 0.35-0.45%; nb is 0.05-0.075; 0.06 to 0.10 percent of Ti; 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 is Fe and unavoidable impurities. The dual-phase steel plate prepared by the technical scheme has excellent mechanical properties, but the content of Cr, nb and Ti elements which are designed and added in the steel is higher.
Therefore, the 1000Mpa dual-phase steel patent technology designed in the prior art has better forming performance, but the technical proposal adopts high C content and high Si content or contains more Cr, nb, ti and other alloy contents, which is not beneficial to the weldability, the surface quality and the phosphating performance of the steel, and can also cause the increase of cost. In addition, some steels with high Si content have high hole expansion ratio and good bending property, but have high yield ratio and reduced press performance.
Therefore, in order to meet the current market demand, the invention is expected to develop the 100 kg-level cold-rolled low-alloy annealed dual-phase steel with economical efficiency and excellent mechanical property.
Disclosure of Invention
One of the purposes of the invention is to provide a 100 kg-grade cold-rolled low-alloy annealed dual-phase steel, which has economical efficiency and excellent mechanical properties, and still has high strength, excellent elongation and bending properties on the premise of not adding Mo and Cr elements, and the yield strength is more than or equal to 550MPa; the tensile strength is more than or equal to 1000MPa; a is that 50 The elongation at break of the gauge length is more than or equal to 12%; the 90-degree bending performance R/t is less than or equal to 1.0, and has very good popularization prospect and application value.
In order to achieve the above purpose, the invention provides a 100 kg grade cold-rolled low alloy annealed dual-phase steel, which contains Fe and unavoidable impurity elements, and also contains the following chemical elements in percentage by mass:
0.1％＜C≤0.13，Si：0.5％～0.8％，Mn：1.6％～1.8％，Al：0.01％～0.03％，Nb：0.01～0.03％，Ti：0.01～0.03％，B：0.0020～0.0030％；
the chemical elements do not contain Mo and Cr;
the microstructure of the 100 kg-level cold-rolled low-alloy annealed dual-phase steel is martensite and ferrite.
Further, in the 100 kg-level cold-rolled low-alloy annealed dual-phase steel, the mass percentage of each chemical element is as follows:
c is more than 0.1 percent and less than or equal to 0.13, si:0.5 to 0.8 percent, mn:1.6 to 1.8 percent of Al:0.01% -0.03%, nb:0.01 to 0.03 percent of Ti:0.01 to 0.03 percent, B:0.0020 to 0.0030 percent, and the balance of Fe and other unavoidable impurities.
In the invention, the inventor adopts a component system which takes C-Si-Mn as a main component to ensure that the obtained cold-rolled low-alloy annealed dual-phase steel can reach 1000 MPa-level strength. In the design of chemical components, the dual-phase steel is free from adding noble alloy elements such as Mo, cr and the like, and can effectively ensure economy; in addition, the invention also adds and utilizes trace high hardenability element B in the design of chemical components so as to further reduce Mn content; in addition, a trace amount of Nb and Ti are added into the steel to achieve the effect of inhibiting the growth of austenite grains, thereby effectively refining the grains.
In the 100 kg-level cold-rolled low-alloy annealed dual-phase steel, the design principle of each chemical element is specifically as follows:
c: in the 100 kg-level cold-rolled low-alloy annealed dual-phase steel, the strength of the steel can be improved by adding the element C, and the hardness of martensite can be improved. If the mass percentage of C in the steel is less than 0.1%, the strength of the steel plate is affected and the formation amount and stability of austenite are not facilitated; when the mass percentage of the C element in the steel is higher than 0.13%, the martensite hardness is too high, the grain size is coarse, the formability of the steel plate is not facilitated, and meanwhile, the carbon equivalent is too high, so that the welding is not facilitated. Therefore, in order to ensure the performance of the steel, the mass percent of C element in the 100 kg-grade cold-rolled low-alloy annealed dual-phase steel is specifically controlled to be less than or equal to 0.13 and more than 0.1 percent.
Si: in the 100 kg-level cold-rolled low-alloy annealed dual-phase steel, the quenching property of the steel can be improved by adding Si element into the steel, and the interaction of dislocation can be influenced by Si dissolved in the steel, so that the work hardening rate is increased, the elongation of the dual-phase steel can be properly improved, and the better formability is beneficial to being obtained. However, it should be noted that the Si element content in the steel is not too high, and when the Si element content in the steel is too high, the control of the surface quality of the steel sheet is not facilitated. Therefore, in order to exert the beneficial effect of Si element, the mass percent of Si element is controlled between 0.5% and 0.8% in the 100 kg-grade cold-rolled low-alloy annealed dual-phase steel.
Mn: in the 100 kg-level cold-rolled low-alloy annealed dual-phase steel, mn element is added, so that the hardenability of the steel is improved, and the strength of the steel plate can be effectively improved. When the mass percentage of Mn element in the steel is lower than 1.6%, the strength of the steel plate is insufficient; when the mass percentage of Mn element in the steel is more than 1.8%, the strength of the steel sheet is excessively high, which may deteriorate the formability. Therefore, considering the beneficial effect of Mn element, in the 100 kg-level cold-rolled low alloy annealed dual-phase steel, the mass percentage of Mn element is controlled between 1.6% and 1.8%.
Al: in the 100 kg-level cold-rolled low-alloy annealed dual-phase steel, the addition of the Al element can play a role in deoxidizing and refining grains. On the other hand, the lower the content of Al element in the steel, the more favorable the castability of smelting. Therefore, in order to exert the beneficial effect of the Al element, the mass percentage of the Al element is controlled to be between 0.01 and 0.03 percent in the invention.
Nb: in the 100 kg-level cold-rolled low-alloy annealed dual-phase steel, nb element is an important element for refining grains, after a small amount of strong carbide forming element Nb is added into the micro-alloy steel, the recrystallization temperature of deformed austenite can be obviously reduced by strain induced precipitated phases through the actions of particle pinning and subgrain boundaries in the rolling control process, and nucleation particles are provided, which have obvious effect on refining grains; in addition, during the austenitizing process of continuous annealing, the points of the soaking undissolved carbon and nitriding substances prevent coarsening of soaking austenite grains through a particle pinning grain boundary mechanism, so that the grains are effectively refined. Based on the above, in order to exert the beneficial effect of Nb, in the 100 kg-level cold-rolled low-alloy annealed dual-phase steel, the mass percentage of Nb is controlled to be between 0.01 and 0.03 percent.
Of course, in some preferred embodiments, to achieve a better implementation effect, it may be further preferable to control the mass percentage of Nb element to be between 0.015 and 0.025%.
Ti: in the 100 kg-level cold-rolled low-alloy annealed dual-phase steel, the added strong carbide forming element Ti also shows a strong effect of inhibiting the growth of austenite grains at high temperature, and meanwhile, the addition of the Ti element is also beneficial to grain refinement. Therefore, in the present invention, the content of Ti element is specifically controlled to be 0.01 to 0.03% by mass in order to exert the beneficial effect of Ti element.
Of course, in some preferred embodiments, in order to achieve a more preferable implementation effect, the content of Ti element may be further preferably controlled to be between 0.015 and 0.025% by mass.
B: in the 100 kg-level cold-rolled low-alloy annealed dual-phase steel, the B element is added, so that the hardenability of the steel is improved, and the strength of the steel plate can be effectively improved. When the mass percentage of B element in steel is less than 0.0020%, it also causes insufficient strength of the steel sheet; when the content of B element in steel is more than 0.0030% by mass, the strength of the steel sheet is too high, and the formability is lowered. Therefore, in the 100 kg-level cold-rolled low-alloy annealed dual-phase steel, the mass percentage of the B element is controlled to be between 0.0020 and 0.0030 percent.
In the composition design, the dual-phase steel designed by the invention is not added with noble alloy elements such as Mo, cr and the like, and has excellent economical efficiency. Meanwhile, in order to ensure that the dual-phase steel can obtain 1000 MPa-level tensile strength at the normal continuous annealing gas cooling speed of 40-100 ℃/s, the alloy addition content of C, mn and B needs to be ensured in the chemical composition design so as to provide enough hardenability. However, the contents of the C, mn, B alloy elements in the dual phase steel also need to be controlled with an upper limit to ensure excellent weldability and formability and to avoid exceeding the upper limit of strength.
Further, in the 100 kg-level cold-rolled low-alloy annealed dual-phase steel, among unavoidable impurities, P is less than or equal to 0.012%, S is less than or equal to 0.0025%, and N is less than or equal to 0.005%.
In the 100 kg-level cold-rolled low-alloy annealed dual-phase steel, the P element, the S element and the N element are all impurity elements in the steel, and the lower the content of P, N and the S element in the steel is, the better the implementation effect is. Specifically, mnS formed by the combination of the S element seriously affects the formability of the steel, and N element easily causes cracks or bubbles on the surface of the slab. Therefore, in order to obtain a steel with better performance and better quality, the content of impurity elements in the steel should be reduced as much as possible, and the P, S, N elements in the steel should be specifically controlled to satisfy: p is less than or equal to 0.012 percent, S is less than or equal to 0.0025 percent, and N is less than or equal to 0.005 percent.
Further, in the 100 kg-level cold-rolled low-alloy annealed dual-phase steel, the mass percentage of each chemical element of the dual-phase steel meets at least one of the following components:
Nb：0.015～0.025％，
Ti：0.015～0.025％。
further, in the 100 kg-level cold-rolled low-alloy annealed dual-phase steel, the volume percentage content of martensite is more than or equal to 60%.
Further, in the 100 kg-level cold-rolled low-alloy annealed dual-phase steel, the hardenability factor Y of the dual-phase steel Q The method meets the following conditions: y is more than or equal to 2.0 Q Not more than 2.4, wherein Y Q Each chemical element in the formula is substituted into the numerical value before the mass percentage number =mn+200×b.
In the 100 kg-level cold-rolled low-alloy annealed dual-phase steel designed by the invention, the composite action of the B element and the Mn element can lead the steel to achieve better strength effect. In order to ensure that the final strength of the steel meets the requirement, the invention can further control Y which is less than or equal to 2.0 while controlling the mass percent of single chemical element Q Not more than 2.4, wherein Y Q ＝Mn+200×B。
However, it should be noted that in the alloy design, the Mn content is the maximum equivalent affecting the overall cost, so the invention can further reduce the alloy design amount of Mn by adding an appropriate amount of B by utilizing the comprehensive hardenability of Mn-B, thereby being beneficial to reducing the cost and improving the manufacturability of on-site production.
Further, in the 100 kg-grade cold-rolled low alloy annealed dual-phase steel of the present invention, both the grain size of martensite and ferrite are not more than 5 μm.
Further, in the 100 kg-grade cold-rolled low alloy annealed dual-phase steel, the microhardness difference DeltaHV of martensite and ferrite is less than or equal to 150.
Further, in the 100 kg cold rolling low alloy annealing method of the inventionIn the dual-phase steel, the yield strength is more than or equal to 550MPa, the tensile strength is more than or equal to 1000MPa, A 50 The elongation at break of the gauge length is more than or equal to 12 percent, and the bending performance R/t at 90 degrees is less than or equal to 1.0.
Accordingly, still another object of the present invention is to provide a method for manufacturing the above-mentioned cold rolled low alloy annealed dual phase steel of 100 kg grade, which is convenient and simple to implement, and the cold rolled low alloy annealed dual phase steel of 100 kg grade manufactured by the manufacturing method has high strength and excellent elongation and bending property, the yield strength is not less than 550MPa, the tensile strength is not less than 1000MPa, A 50 The elongation at break of the gauge length is more than or equal to 12 percent, and the bending performance R/t at 90 degrees is less than or equal to 1.0.
In order to achieve the above object, the present invention provides a method for manufacturing the cold rolled low alloy annealed dual phase steel of 100 kg grade, comprising the steps of:
(1) Smelting and casting;
(2) And (3) hot rolling: heating the continuous casting blank to 1160-1190 ℃, preserving heat for more than 150min, then carrying out hot rolling and finish rolling at 850-890 ℃, and rapidly cooling at a speed of 30-80 ℃/s after rolling; then coiling, wherein the coiling temperature is 500-540 ℃, and air cooling is performed after coiling;
(3) Cold rolling;
(4) Annealing: the annealing soaking temperature is 825-855 ℃, the annealing time is 40-200 s, then the annealing temperature is cooled to the rapid cooling starting temperature at the speed of 3-5 ℃/s, then the annealing temperature is rapidly cooled at the speed of 40-100 ℃/s, wherein the rapid cooling starting temperature is 735-760 ℃, and the rapid cooling ending temperature is 265-290 ℃;
(5) Tempering;
(6) Leveling.
Further, in the manufacturing method according to the present invention, in the step (4), the annealing soaking temperature is 830 to 840 ℃.
In the technical scheme designed by the invention, in order to obtain better implementation effect, the obtained crystal grain size is finer, the mechanical property of the obtained steel is moderate, the forming property is better, and the annealing soaking temperature can be further preferably controlled between 830 ℃ and 840 ℃.
Further, in the production method of the present invention, in the step (3), the cold rolling reduction is controlled to be 50 to 70%.
Further, in the manufacturing method of the present invention, in the step (5), the tempering temperature is controlled to be 265 to 290 ℃ and the tempering time is controlled to be 100 to 400 seconds.
Further, in the manufacturing method of the present invention, in the step (6), the flat rolling reduction is controlled to be 0.3% or less.
Compared with the prior art, the 100 kg-level cold-rolled low-alloy annealed dual-phase steel and the manufacturing method thereof have the following advantages and beneficial effects:
the invention develops a novel 100 kg-level cold-rolled low-alloy annealed dual-phase steel, which can obtain a martensite and ferrite dual-phase structure steel plate reaching 1000 MPa-level strength on the premise of not adding Mo and Cr silicon alloy elements through reasonable chemical component design and matching with an optimized manufacturing process; the fine and uniform martensite and ferrite dual-phase structure can further ensure that the steel has excellent elongation and bending performance and good formability.
Therefore, the 100 kg-level cold-rolled low-alloy annealed dual-phase steel prepared by adopting the design of the invention not only has good economical efficiency, but also has high strength, excellent elongation and bending property, the yield strength is more than or equal to 550MPa, the tensile strength is more than or equal to 1000MPa, and A 50 The elongation at break of the gauge length is more than or equal to 12 percent, and the bending performance R/t at 90 degrees is less than or equal to 1.0. The 100 kg-level cold-rolled low-alloy annealed dual-phase steel is simple to produce and prepare, has very good popularization prospect and application value, and can effectively meet the demands of markets and users.
Detailed Description
The 100 kg-level cold rolled low alloy annealed dual-phase steel and the manufacturing method thereof according to the present invention will be further explained and illustrated with reference to specific examples, but the explanation and illustration do not unduly limit the technical scheme of the present invention.
Examples 1 to 6 and comparative examples 1 to 14
Table 1-1 shows the mass percentages of the chemical elements designed for the 100 kg grade cold rolled low alloy annealed dual phase steels of examples 1-6 and the comparative steels of comparative examples 1-14.
Table 1-1 (wt.%), the balance being Fe and unavoidable impurities other than P, S and N
Tables 1-2 list the hardenability factor Y for 100 kg cold rolled low alloy annealed dual phase steels of examples 1-6 and comparative steels of comparative examples 1-14 Q Is a value of (2).
Tables 1-2.
| Numbering device | Hardenability factor Y Q |
| Example 1 | 2.11 |
| Example 2 | 2.12 |
| Example 3 | 2.19 |
| Example 4 | 2.26 |
| Example 5 | 2.23 |
| Example 6 | 2.20 |
| Comparative example 1 | 2.20 |
| Comparative example 2 | 2.15 |
| Comparative example 3 | 2.08 |
| Comparative example 4 | 2.42 |
| Comparative example 5 | 2.01 |
| Comparative example 6 | 2.25 |
| Comparative examples 7 to 14 | 2.19 |
Note that: in the above tables 1-2, Y Q Each chemical element in the formula is substituted into the numerical value before the mass percentage number =mn+200×b.
The 100 kg-level cold-rolled low-alloy annealed dual-phase steels of the examples 1 to 6 and the comparative steels of the comparative examples 1 to 14 are prepared by the following steps:
(1) Smelting and casting were performed according to the chemical composition designs shown in tables 1-1 and 1-2 to obtain continuous casting billets.
(2) And (3) hot rolling: heating the continuous casting blank to 1160-1190 ℃, preserving heat for more than 150min, then carrying out hot rolling and finish rolling at 850-890 ℃, and rapidly cooling at a speed of 30-80 ℃/s after rolling; and then coiling, controlling the coiling temperature to be 500-540 ℃, and performing air cooling after coiling.
(3) Cold rolling: cold rolling the steel coil, and controlling the cold rolling reduction to be 50-70%.
(4) Annealing: the annealing soaking temperature is 825-855 ℃, the annealing time can be controlled between 830-840 ℃ preferably, the annealing time is controlled between 40-200 s, the annealing temperature is cooled to the rapid cooling starting temperature at the speed of 3-5 ℃/s, and then the rapid cooling is performed at the speed of 40-100 ℃/s, wherein the rapid cooling starting temperature is 735-760 ℃, and the rapid cooling ending temperature is 265-290 ℃.
(5) Tempering: the tempering temperature is controlled to be 265-290 ℃ and the tempering time is controlled to be 100-400 s.
(6) Leveling: the flattening reduction rate is controlled to be less than or equal to 0.3 percent so as to obtain the finished dual-phase steel.
In the technical scheme designed by the invention, the chemical composition design and the related process of the 100 kg-level cold-rolled low-alloy annealed dual-phase steel of the prepared embodiments 1-6 meet the design specification requirements of the invention.
Correspondingly, the comparative steels of comparative examples 1 to 14 were prepared by adopting the compounding schemes of tables 1 to 1 and tables 1 to 2 in combination with the above-mentioned process flows, but in order to highlight the superiority of the technical scheme of the present invention, the comparative steels of comparative examples 1 to 14 were designed to have parameters which did not satisfy the design requirements of the present invention in the chemical composition and/or the related manufacturing process.
Specifically, the comparative steels of comparative examples 1 to 6 have parameters in chemical compositions that fail to satisfy the requirements of the design of the present invention; while the chemical components of the steel grades corresponding to comparative examples 7-14 meet the design requirements of the present invention, the relevant process parameters all have parameters that fail to meet the design specifications of the present invention.
Tables 2-1 and 2-2 set forth specific process parameters in the above process steps (1) - (6) for the 100 kg grade cold rolled low alloy annealed dual phase steels of examples 1-6 and the comparative steels of comparative examples 1-14.
Table 2-1.
Table 2-2.
In table 2-2, the rapid cooling end temperature of each example and comparative example was the same as the tempering temperature because the tempering operation was performed after the rapid cooling operation was completed during the actual process operation.
Accordingly, after completing the above manufacturing process, the inventors sampled the dual phase steels of each example and comparative example separately for the prepared finished dual phase steels of examples 1 to 6 and comparative examples 1 to 14 to obtain corresponding sample steel plates, and observed and analyzed the microstructures of the sample steel plates of each example and comparative example, and observed that the microstructures of the 100 kg grade cold rolled low alloy annealed dual phase steels of examples 1 to 6 and the comparative steel plates of comparative examples 1 to 14 were martensite+ferrite.
For this reason, the inventors further analyzed the microstructures of the respective example and comparative example steel sheets to obtain test results of martensite phase ratio, martensite grain size, ferrite grain size and microhardness difference Δhv of martensite and ferrite in the microstructures of the example 1 to 6 and comparative example 1 to 14, and the relevant test results are specifically listed in the following table 3.
Table 3.
As can be seen from the above Table 3, in the present invention, the microstructure of the 100 kg grade cold rolled low alloy annealed dual phase steel prepared in examples 1 to 6 is martensite + ferrite, and the volume percentage content of martensite (comparative example) is between 62 to 82%, the grain size of martensite is between 3.9 to 4.7 μm, the grain size of ferrite is between 4.0 to 4.6 μm, and the microhardness difference DeltaHV between martensite and ferrite is between 95 to 115.
Accordingly, after the above observation and analysis were completed, in order to verify the properties of each of the example and comparative example steels, samples were taken for the produced 100 kg grade cold rolled low alloy annealed dual phase steels of examples 1 to 6 and comparative example steels of comparative examples 1 to 14, and respective sample steel plates were obtained. And mechanical property tests were conducted on the obtained sample steel sheets of examples 1 to 6 and comparative examples 1 to 14 to obtain mechanical property data of the steels of examples 1 to 6 and comparative examples 1 to 14, and the test results of the related tests are listed in the following table 4.
The related mechanical property testing method is as follows:
tensile test: the test was conducted by using the GB/T228-2010 tensile test method at room temperature to examine the yield strength, tensile strength and A of the steels of examples 1-6 and comparative examples 1-14 obtained 50 Gauge length elongation at break. Wherein, the A50 gauge elongation at break represents: tensile test specimen parallel length x width is 50mm x 25mm elongation at break.
Bending performance test: the GB/T232-2010 metallic material bending test method was adopted to examine the 90-degree bending properties R/T of the steels of examples 1-6 and comparative examples 1-14.
Table 4 shows the results of mechanical property tests of the cold rolled low alloy annealed dual phase steels of 100 kg of examples 1 to 6 and the comparative steels of comparative examples 1 to 14.
Table 4.
Note that: kilogram force, i.e. kilo-gram force, is a common unit of force, and the international unit of force is newton; 1 kg force refers to the weight force (i.e., 9.8N) to which 1 kg of the object is subjected, so 1 kg force=9.8 newtons.
As can be seen from Table 4, in the present invention, the 100 kg cold-rolled low alloy annealed dual phase steels of examples 1 to 6 prepared by the technical scheme of the present invention have quite excellent mechanical properties, the yield strength is between 585 and 655MPa, the tensile strength is between 1002 and 1054MPa, and A is 50 The elongation at break of the gauge length is between 12.7 and 15.5 percent, and the 90-degree bending performance R/t is between 0.6 and 1.0. The dual-phase steel of each embodiment obtains the tensile strength of more than 1000MPa on the premise that noble alloy elements such as Mo, cr and the like are not added, and the dual-phase steel is 100 kg-level cold-rolled low-alloy annealed dual-phase steel and has better elongation and bending property.
The comparative steels of comparative examples 1 to 14 were significantly inferior in combination properties to the 100 kg grade cold rolled low alloy annealed dual phase steels of examples 1 to 6 because they had parameters in the chemical composition design and/or the related manufacturing process to satisfy the requirements of the present invention.
From the above, it can be seen that, in the invention, through reasonable chemical composition design and combination with optimization process, the dual-phase steel with low cost and excellent mechanical property is obtained, and the tensile strength of more than 1000MPa is obtained, and meanwhile, the dual-phase steel has better elongation and bending characteristics.
It should be noted that the combination of the technical features in the present invention is not limited to the combination described in the claims or the combination described in the specific embodiments, and all the technical features described in the present invention may be freely combined or combined in any manner unless contradiction occurs between them.
It should also be noted that the above-recited embodiments are merely specific examples of the present invention. It is apparent that the present invention is not limited to the above embodiments, and similar changes or modifications will be apparent to those skilled in the art from the present disclosure, and it is intended to be within the scope of the present invention.
Claims (14)
1. The cold-rolled low-alloy annealed dual-phase steel with the level of 100 kg contains Fe and unavoidable impurity elements, and is characterized by also containing the following chemical elements in percentage by mass:
0.1％＜C≤0.13，Si：0.5％～0.8％，Mn：1.6％～1.8％，Al：0.01％～0.03％，Nb：0.01～0.03％，Ti：0.01～0.03％，B：0.0020～0.0030％；
the chemical elements do not contain Mo and Cr;
the microstructure of the 100 kg-level cold-rolled low-alloy annealed dual-phase steel is martensite and ferrite.
2. The cold-rolled low alloy annealed dual-phase steel with the level of 100 kg according to claim 1, wherein the mass percentage of each chemical element is as follows:
c is more than 0.1 percent and less than or equal to 0.13, si:0.5 to 0.8 percent, mn:1.6 to 1.8 percent of Al:0.01% -0.03%, nb:0.01 to 0.03 percent of Ti:0.01 to 0.03 percent, B:0.0020 to 0.0030 percent, and the balance of Fe and other unavoidable impurities.
3. The cold rolled low alloy annealed dual phase steel of 100 kg grade according to claim 1 or 2, wherein among unavoidable impurities, P is 0.012% or less, S is 0.0025% or less, and N is 0.005% or less.
4. The cold rolled low alloy annealed dual phase steel of 100 kg grade according to claim 1 or 2, characterized in that the mass percentage of each chemical element satisfies at least one of the following:
Nb：0.015～0.025％，
Ti：0.015～0.025％。
5. the cold rolled low alloy annealed dual phase steel of 100 kg grade according to claim 1 or 2, wherein the volume percentage of martensite is more than or equal to 60%.
6. Cold rolled low alloy annealed dual phase steel of 100 kg grade according to claim 1 or 2, characterized by the hardenability factor Y Q The method meets the following conditions: y is more than or equal to 2.0 Q Not more than 2.4, wherein Y Q Each chemical element in the formula is substituted into the numerical value before the mass percentage number =mn+200×b.
7. The cold rolled low alloy annealed dual phase steel of 100 kg grade according to claim 1 or 2, wherein the grain size of both martensite and ferrite is not more than 5 μm.
8. The cold rolled low alloy annealed dual phase steel of 100 kg grade according to claim 1 or 2, wherein the microhardness difference avv of martensite and ferrite is equal to or less than 150.
9. The cold rolled low alloy annealed dual phase steel of 100 kg grade according to claim 1 or 2, wherein the yield strength is not less than 550MPa, the tensile strength is not less than 1000MPa, a 50 The elongation at break of the gauge length is more than or equal to 12 percent, and the bending performance R/t at 90 degrees is less than or equal to 1.0.
10. Method for manufacturing a cold rolled low alloy annealed dual phase steel of 100 kg grade according to any of the claims 1-9, characterized in that it comprises the steps of:
(1) Smelting and casting;
(2) And (3) hot rolling: heating the continuous casting blank to 1160-1190 ℃, preserving heat for more than 150min, then carrying out hot rolling and finish rolling at 850-890 ℃, and rapidly cooling at a speed of 30-80 ℃/s after rolling; then coiling, wherein the coiling temperature is 500-540 ℃, and air cooling is performed after coiling;
(3) Cold rolling;
(4) Annealing: the annealing soaking temperature is 825-855 ℃, the annealing time is 40-200 s, then the annealing temperature is cooled to the rapid cooling starting temperature at the speed of 3-5 ℃/s, then the annealing temperature is rapidly cooled at the speed of 40-100 ℃/s, wherein the rapid cooling starting temperature is 735-760 ℃, and the rapid cooling ending temperature is 265-290 ℃;
(5) Tempering;
(6) Leveling.
11. The method according to claim 10, wherein in the step (4), the annealing soaking temperature is 830 to 840 ℃.
12. The method according to claim 10, wherein in the step (3), the cold rolling reduction is controlled to be 50 to 70%.
13. The method according to claim 10, wherein in the step (5), the tempering temperature is controlled to be 265 to 290 ℃ and the tempering time is controlled to be 100 to 400 seconds.
14. The method according to claim 10, wherein in the step (6), the flat reduction is controlled to be 0.3% or less.
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