CN103184386A - Method for improving mechanical property of low-carbon silicomanganese series cold rolling dual-phase steel - Google Patents
Method for improving mechanical property of low-carbon silicomanganese series cold rolling dual-phase steel Download PDFInfo
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Abstract
The invention belongs to the technical field of roll steel and relates to a method for improving the mechanical property of low-carbon silicomanganese series cold rolling dual-phase steel. The method comprises the following steps of: smelting and forging the low-carbon silicomanganese series cold rolling dual-phase steel to manufacture a plate blank, heating to 1100-1250 DEG C, carrying out heat preservation, carrying out rough rolling and finish rolling at 820-1100 DEG C, wherein the hot rolling and finish rolling temperature is (Ar3+30) DEG C-(Ar3+100) DEG C, then carrying out laminar cooling to (Ar3-50) DEG C-(Ar3-100) DEG C at cooling rate of 20 DEG C, and carrying out air cooling to room temperature; pickling, heating to (Ac3-50 DEG C)-(Ac3+100 DEG C) after cold rolling by adopting higher than or equal to 80% of rolling reduction, carrying out annealing treatment for 10-20s, carrying out slow cooling to 600-720 DEG C at rate of 5-8 DEG C/s, cooling to 250-300 DEG C at rate of higher than or equal to 30 DEG C/s for isothermal treatment, and carrying out air cooling and water-cooling or naturally cooling to room temperature. A cold rolling dual-phase steel plate with excellent mechanical property can be obtained by adopting the preparation method; the strength, the total percentage elongation after fracture and the work-hardening index of the cold rolling dual-phase steel plate are improved; and the strength of the cold rolling dual-phase steel plate is obviously improved.
Description
Technical field
The invention belongs to technical field of steel rolling, particularly a kind of method that improves the system cold-rolled dual phase steel mechanical property of low-carbon (LC) silicomanganese.
Background technology
In recent years, problem such as climate change, energy shortage was producing day by day development of modern industry and daily life and was seriously influencing.Energy-saving and emission-reduction, low-carbon environment-friendly have been countries nowadays industrial development institute problem demanding prompt solutions.Automotive industry as the sign of modern industry and symbol is the mainstay industry of the pulling national economic development, also be high flow rate, maximum discharge, cause the key industry of environmental pollution, its a series of environment negative impacts that produce have constituted the automotive industry Sustainable development and have faced the matter of utmost importance that will solve.
Safe, comfortable, energy-saving and environmental protection are new demands that people propose Hyundai Motor.Studies show that: under the constant situation of other condition, car mass whenever alleviates 10%, and then oil consumption can descend 8～10%.Therefore, guaranteeing to realize lightweight under the prerequisite of vehicle performance, becoming the target of each automobile enterprise research and development product innovation, and realizing that light-weighted main means are the application to structure Design optimization and novel material, novel process.Iron and steel is the main raw of automobile making, but the huge consumption that Iron And Steel Industry has also been brought the energy when increasing, and is all increasing year by year as the microalloy element that produces steel needed coal charcoal ﹑ electric power and add in the various uses steel.Reducing the usage quantity of microalloy element, transform by process system reasonable in design and produce other steel of ad eundem, reduce the cost that contains the alloying element steel, realize Jie Neng ﹑ environmental protection, is that the world today realizes the huge challenge that Sustainable development faces.
CN102943205A discloses a kind of dual phase steel, its alloy designs composition is simple, only require and add an amount of C ﹑ Si ﹑ Mn ﹑ Ti, but in the TMCP process control procedure, requirement to the cold temperature parameter of two secondary controls after the finish rolling is too strict, and can only prepare the dual phase steel product of tensile strength 580MPa level.
CN101802233A discloses flat product of a kind of dual phase steel preparation and preparation method thereof, and this dual phase steel has the good deformable performance of the strong degree ﹑ of 950MPa at least and has certain surface smoothness.But require to add precious metal chromium 0.20%～0.80% in its design of alloy, titanium 0.02%～0.08%, and also unit elongation only is about 10%.
CN102703815A discloses the semi-endless rolled technology of a kind of application, can solve problems such as the vertical performance of rolling thin rule lattice ﹑ band is even, can not only have considerable economic benefits, can fall consumption ﹑ with the time and reduce CO
2Quantity discharged is the environmentally friendly new technology of the Yue Xing ﹑ of a kind of Jie.But this invention is had relatively high expectations to capacity of equipment, must add precious metal chromium 0.5%～0.7% on design of alloy, and tensile strength is the highest can only reach about 650MPa.
Summary of the invention
At the problems referred to above, the invention provides a kind of method that improves the system cold-rolled dual phase steel mechanical property of low-carbon (LC) silicomanganese, purpose is on the basis of the existing system cold-rolled dual phase steel chemical composition design of low-cost low-carbon (LC) silicomanganese, adopt novel process of the present invention, improve its mechanical property, this will provide new approaches for the production technique that further improves the system cold-rolled dual phase steel over-all properties of low-carbon (LC) silicomanganese and develop the system cold-rolled dual phase steel of high-strength low-carbon (LC) silicomanganese.
Dual phase steel is made up of ferrite and martensite, based on phase transformation strengthening, has low yield strength ratio, high initial manufacture hardening rate, characteristics such as good intensity and ductility cooperation.The production process of cold-rolled biphase steel comprises technologies such as smelting, hot rolling, pickling, cold rolling, continuous annealing.Reasonable component design, the hot rolling microstructure that is fit to have material impact to the performance of cold-rolled biphase steel, and annealing parameter has most important influence to final tissue topography and the mechanical property of dual phase steel.
The invention provides the system cold-rolled dual phase steel of a kind of low-carbon (LC) silicomanganese, constituted by the martensite of 19.0～26.0% volume ratios, the ferrite of 74.0～81.0% volume ratios, and its chemical constitution is C:0.06%～0.20% by mass percentage, Si:0.1%～0.8%, Mn:1.0%～2.0%, Nb≤0.05%, V≤0.05%, P≤0.035%, S≤0.035%, surplus is Fe.
Preferably, the system cold-rolled dual phase steel of described low-carbon (LC) silicomanganese is because chemical ingredients addition and the variation of processing parameter in claimed range, make yield strength 290～438/MPa, tensile strength 540～826/MPa, yield tensile ratio 0.46～0.58, unit elongation 24.7～30.1%.
The measuring method of mechanical property (Qu clothes Qiang Du ﹑ Kang La Qiang Du ﹑ Qu Qiang is Bi ﹑ unit elongation) adopts State Standard of the People's Republic of China GB/T 228-2002.
The preparation method that the system cold-rolled dual phase steel of described low-carbon (LC) silicomanganese also is provided of the present invention comprises the following steps:
(1) choose the system cold-rolled dual phase steel of low-carbon (LC) silicomanganese, make slab through smelting and forging, be heated to 1100～1250 ℃ of insulations, carry out hot rolling under 820～1100 ℃ of conditions, hot rolling finishing temperature is (A
R3+ 30) ℃～(A
R3+ 100) ℃, and the cooling rate laminar flow with 10～30 ℃/s is cooled to (A after hot rolling finish to gauge
R3-50) ℃～(A
R3-100) ℃, air cooling to room temperature obtains hot rolling steel billet then;
(2) the above-mentioned hot rolling steel billet of pickling obtains the cold-rolled steel plate, to remove oxide compound, obtains the cold-rolled steel plate;
(3) it is cold rolling the cold-rolled steel plate to be adopted 〉=80% draught carry out, and being beneficial to significantly increases dislocation desity in deformation phases, store more distortional strain energy;
(4) cold rolled strip is heated to (A with the heating rate of at least 80 ℃/s
C3-50 ℃)～(A
C3+ 10 ℃), with speed slow cooling to 600～720 of 5～8 ℃/s ℃, the speed with 〉=30 ℃/s is cooled to 250～300 ℃ then behind anneal 10～20s, isothermal processes 120～300s, last Kong Leng ﹑ water-cooled or naturally cool to room temperature.
Described A
R3For ferrite transformation begins temperature, described A
C1For ferrite in the annealing heat-processed begins temperature to austenitic transformation, A
C3For annealing heat-processed in ferrite to the austenitic transformation end temp.Because the composition difference of steel (as the variation) ﹑ changes in process parameters (as heating rate) of Tan Han Liang ﹑ silicone content etc., A
C1﹑ A
C3﹑ can change thereupon.Steel of the present invention records its A by the thermal expansion curve
C1And A
C3And Hua learns into Fen ﹑ rolling technological parameter etc. to A
R3Remarkably influenced is arranged.
Preferably, the soaking time of step 1) is 1～2 hour.
Preferred, the described hot rolling of step 1) comprises roughing and finish rolling, and the roughing process is 3～5 passages, and the roughing start rolling temperature is 1000～1150 ℃, and obtaining thickness is the intermediate blank of 15～25mm; The finish rolling process is 4～6 passages, and the finish rolling start rolling temperature is 950～1050 ℃, and the finish rolling finishing temperature is 820～950 ℃, and the thickness of hot-rolled sheet is 4～8mm after the finish rolling.
Preferred, the described roughing of step 1) and finish rolling, the roughing process is 4 passages, and the roughing start rolling temperature is 1050～1100 ℃, and obtaining thickness is the intermediate blank of 20mm; The finish rolling process is 5 passages, and the finish rolling start rolling temperature is 980～1000 ℃, and the finish rolling finishing temperature is 840～880 ℃, and the thickness of hot-rolled sheet is 6mm after the finish rolling.
Preferably, the hot rolling finishing temperature of step 1) is (A
R3+ 30) ℃～(A
R3+ 60) ℃.
Preferably, the cooling rate of step 1) is 15～25 ℃/s; The cooling rate of preferred step 1) is 18～22 ℃/s; Most preferred, the cooling rate of step 1) is 20 ℃/s.
Preferably, step 2) described pickling is for using iron scale (FeO, the Fe on sulfuric acid or the hydrochloric acid flush away steel surface
3O
4, Fe
2O
3), the concentration of the acid of use and using method all can adopt prior art.
Preferably, the heating rate of step 4) is 80～150 ℃/s; The rate of cooling of step 4) is 〉=30 ℃/s.
Characteristics of the present invention and beneficial effect are:
Adopt preparation method of the present invention can obtain the cold-rolled biphase steel of mechanical property excellence, have no progeny percentage of total elongation and work hardening exponent of its Qiang Du ﹑ is improved, and especially intensity significantly increases.
Principle of the present invention is:
At first, preparation is during hot rolling slab, changed when common process prepares after hot rolling finish to gauge Direct Air-Cooled to room temperature roll the back type of cooling, but the cooling rate laminar flow with～20 ℃/s is cooled to (A after hot rolling finish to gauge
R3-50) ℃～(A
R3-100) ℃, air cooling to room temperature obtains hot rolling steel billet then, and this will make average grain size of the initial tissue of hot rolling significantly be decreased to＜6 μ m.Reduce the grain-size of the initial tissue of hot rolling, can increase grain boundary area, interfacial energy raises simultaneously, thereby increases the motivating force that austenite is grown up; In addition when annealing insulation is handled, the grow up diffusion length of required carbon and manganese of austenite is relative shorter in fine grained texture.When these factors cause hot rolling initially to organize grain-size to reduce, austenite in initial fine grained texture forming core and grow up relatively easy, thereby the austenite volume fraction behind the annealing isothermal is more, and the martensite in the two-phase steel organization is to be come by the austenitic transformation of two-phase region generation, thereby the Ovshinsky scale of construction of two-phase region formation has directly determined the martensite volume fraction in the final finished steel, so the martensite volume fraction that obtains under the same annealing process is higher, thereby improve its intensity.In addition, the average grain size of the initial tissue of hot rolling significantly reduces, and causes finished product dual phase steel ferrite crystal grain to reduce simultaneously, as everyone knows, crystal grain thinning is onlyly can improve intensity, increases the effective measure of its plastic property simultaneously again, thereby the intensity of finished product dual phase steel and plasticity increase synchronously.
Secondly, increase cold roling reduction (〉=80%), this will directly influence the size of dual phase steel austenite recrystallization crystal grain in continuous annealing heat-processed.There is a critical strain amount in the cold-rolled process, when cold roling reduction reaches this deflection, can makes steel plate obtain thick recrystal grain; Greater than this deflection, then along with the increase of deformation extent, its annealing grains is more little; Otherwise, be lower than this critical strain amount, then almost there is not the recrystallize phenomenon, namely steel plate still keeps its original grain after annealing.The phenomenon of the crystal grain thinning that the increase cold rolling reduction has says that simply because a large amount of distortion causes the fragmentation of steel plate tissue, the equally distributed nucleus that produces when making recrystallize is caused exactly.And the direct refinement of refinement of recrystallize austenite crystal annealing dual phase steel grain structure, thereby cause comprehensive mechanical property significantly to increase.
Moreover, under its capacity of equipment enabled condition, increase the heating rate in the annealing process.Rapid heating makes the recrystallize in the continuous annealing heat-processed begin temperature and raises, the recrystallization temperature range extension, and final recrystallization crystal particle dimension reduces.The control that reduces to be subjected to nucleation rate and the rate of growing up of recrystallization crystal particle dimension, during rapid heating, there is not time enough to reply at the forming core initial stage, thereby reply before the recrystallize deformation energy storage consume when low with respect to heating rate seldom, recrystallization temperature is postponed to high relatively temperature simultaneously, and this also is that the annealing temperature laid down by is (A
C3-50 ℃)～(A
C3+ 10 ℃), want high cause with respect to conventional dual phase steel annealing temperature.During rapid heating because will in the limited time, require the forming core amount that reaches considerable, so under higher recrystallization temperature, increased nucleation rate, the result makes grain-size more tiny, and crystal grain thinning is the only intensity that can improve, increase simultaneously the effective measure of its plastic property again, thereby the intensity of finished product dual phase steel and plasticity increase synchronously.
Description of drawings
Fig. 1 is the hot rolling slab metallographic structure of the system cold-rolled dual phase steel of low-carbon (LC) silicomanganese in the embodiment of the invention 1;
Wherein (a): obtain the metallographic structure of hot rolling steel billet after the technology 1-I hot rolling finish to gauge according to preparation method's Direct Air-Cooled to the room temperature of routine, (b): the cooling rate laminar flow with～20 ℃/s after the technology 1-II hot rolling finish to gauge is cooled to～and 620 ℃, air cooling to room temperature obtains the metallographic structure of hot rolling steel billet then.
Fig. 2 corrodes the observed metallographic structure in back for the system cold-rolled dual phase steel finished product of the low-carbon (LC) silicomanganese sheet material of new invention prepared among the embodiment of the invention 2-II through Lepera reagent.
Embodiment
The chemical constitution of the system cold-rolled dual phase steel of low-carbon (LC) silicomanganese that adopts in the invention process example is C:0.06%～0.20%, Si:0.1%～0.8%, Mn:1.0%～2.0% by mass percentage, Nb≤0.05%, V≤0.05%, P≤0.035%, S≤0.035%, surplus are Fe.
Slab is heated to 1100～1250 ℃ in the invention process example when hot rolling, carries out roughing and finish rolling under 820～1100 ℃ of conditions, and hot rolling finishing temperature is (A
R3+ 30) ℃～(A
R3+ 100) ℃, and the cooling rate laminar flow with～20 ℃/s is cooled to (A after hot rolling finish to gauge
R3-50) ℃～(A
R3-100) ℃, air cooling to room temperature obtains hot rolling steel billet then.
The draught of cold-rolled steel plate employing 〉=80% carries out cold rolling in the invention process example.
Steel plate after cold rolling in the invention process example when anneal, heating rate 〉=80 ℃/s; Annealing temperature is at (A
C3-50 ℃)～(A
C3+ 10 ℃) scope, anneal 10～20s; Then with speed slow cooling to 600～720 of 5～8 ℃/s ℃, be cooled to 250～300 ℃ with the speed of 〉=30 ℃/s, isothermal processes 120～300s, last Kong Leng ﹑ water-cooled or naturally cool to room temperature.
Cut out metallographic specimen from the annealed sheet steel for preparing in the invention process example, behind Yan Mo ﹑ light, adopt 4% nital and Lepera reagent (1%Na
2S
2O
5The picral of the aqueous solution and massfraction 4% 1:1 by volume mixes) corrode, what be white in color in Lepera reagent caustic solution can dividing tissue is organized as martensite, the grizzly ferrite that is organized as.
Analyze the grain-size of martensite volume fraction and tissue in the invention process example from the annealed sheet steel sampling for preparing; The martensite volume fraction is used the Leica image analysis software and is calculated; Grain-size adopts secant method to measure.
Make tension specimen from the annealed sheet steel sampling for preparing by standard in the invention process example, effectively gauge length is 50 * 15mm, draw speed 5mm/min.
Below the specific embodiment of the present invention is described in further detail, but embodiments of the present invention are not limited thereto.
Embodiment 1
The chemical constitution of the system cold-rolled dual phase steel of low-carbon (LC) silicomanganese that adopts is C:0.06% by mass percentage, Si:0.25%, and Mn:1.71%, P:0.003%, S:0.016%, surplus is Fe.Record its A by the thermal expansion curve
C1And A
C3Be respectively 759 and 890 ℃.
Adopting above-mentioned low-carbon (LC) silicomanganese is dual phase steel, through smelting and forging and make the thick slab of 70mm, is heated to 1100 ℃, and insulation 1h carries out roughing, and the roughing process is 4 passages, and the roughing start rolling temperature is 1050 ℃, and obtaining thickness is the intermediate blank of 20mm.
Intermediate blank is carried out finish rolling, and the finish rolling process is 5 passages, and the finish rolling start rolling temperature is 980 ℃, and the finish rolling finishing temperature is 840 ℃, and the thickness of hot-rolled sheet is 6mm after the finish rolling.
To room temperature, the hot rolling slab metallographic structure is shown in Fig. 1 (a) according to preparation method's Direct Air-Cooled of routine for technology 1-I after the hot rolling finish to gauge, and the average grain size of the initial tissue of hot rolling is～17.8 μ m; 1-II～1-IX then with the cooling rate laminar flow of～20 ℃/s be cooled to～620 ℃, air cooling to room temperature obtains hot rolling steel billet then, the hot rolling slab metallographic structure of technology 1-II is shown in Fig. 1 (b), the average grain size of the initial tissue of hot rolling significantly is decreased to～5.5 μ m.
The above-mentioned hot rolling steel billet of pickling to remove oxide compound, obtains the cold-rolled steel plate.
It is cold rolling to adopt different cold roling reductions to carry out respectively the cold-rolled steel plate, and concrete cold rolling and parameter and annealing sees Table 1.1-I is the cold-rolled biphase steel of common process technology preparation, and cold roling reduction is 58.3%, and heating rate is 10 ℃/s; The cold-rolled biphase steel of 1-II～1-IX for adopting preparation method of the present invention to obtain, cold roling reduction is 81.2～83.2%, and heating rate is 80～150 ℃/s, and annealing temperature is at (A
C3-50 ℃)～(A
C3+ 10 ℃) scope, anneal 10～20s; After the anneal with speed slow cooling to 670～720 of 5～8 ℃/s ℃ (being called for short this temperature in the watch is that the fast cold beginning is warm), be cooled to 250～290 ℃ (are called for short this temperature in the table be overaging temperature /) with the speed of 〉=30 ℃/s then, isothermal processes 150～300s, last water-cooled is to room temperature.
Cold rolling and the parameter and annealing of table 1 embodiment 1
The mechanical property of cold-rolled biphase steel sees Table 2.Compare with the cold-rolled biphase steel that the common process technology prepares, adopt in the microstructure of the cold-rolled biphase steel that preparation method of the present invention obtains, the martensite mark has increased by 3.7～8.0%, and mechanical property significantly improves, wherein yield strength has increased by 29～78MPa, tensile strength has increased by 35～127MPa, and unit elongation has improved 0.9～3.9%.As seen, adopt preparation method of the present invention can obtain the cold-rolled biphase steel of mechanical property excellence, have no progeny percentage of total elongation and work hardening exponent of its Qiang Du ﹑ is improved, and especially intensity significantly increases.
The mechanical property of table 2 embodiment 1 and tissue volume mark
Embodiment 2
The chemical constitution of the system cold-rolled dual phase steel of low-carbon (LC) silicomanganese that adopts is C:0.11% by mass percentage, Si:0.14%, and Mn:1.81%, P:0.015%, S:0.01%, surplus is Fe.Record its A by the thermal expansion curve
C1And A
C3Be respectively 746 and 854 ℃.
Adopting above-mentioned low-carbon (LC) silicomanganese is dual phase steel, through smelting and forging and make the thick slab of 60mm, is heated to 1200 ℃, and insulation 1h carries out roughing, and the roughing process is 4 passages, and the roughing start rolling temperature is 1100 ℃, and obtaining thickness is the intermediate blank of 20mm.
Intermediate blank is carried out finish rolling, and the finish rolling process is 5 passages, and the finish rolling start rolling temperature is 1000 ℃, and the finish rolling finishing temperature is 880 ℃, and the thickness of hot-rolled sheet is 6mm after the finish rolling.
To room temperature, the average grain size of the initial tissue of hot rolling is～19.1 μ m to technology 2-I according to preparation method's Direct Air-Cooled of routine after the hot rolling finish to gauge; 2-II～2-VI then with the cooling rate laminar flow of～20 ℃/s be cooled to～645 ℃, air cooling to room temperature obtains hot rolling steel billet then, the average grain size of the initial tissue of hot rolling significantly is decreased to～5.7 μ m.
The above-mentioned hot rolling steel billet of pickling to remove oxide compound, obtains the cold-rolled steel plate.
It is cold rolling to adopt different cold roling reductions to carry out respectively the cold-rolled steel plate; Concrete cold rolling and parameter and annealing sees Table 3.2-I is the cold-rolled biphase steel of common process technology preparation, and cold roling reduction is 69.8%, and heating rate is 10 ℃/s; The cold-rolled biphase steel of 2-II～2-VI for adopting preparation method of the present invention to obtain, cold roling reduction is 83.0～83.7%, and heating rate is 80～150 ℃/s, and annealing temperature is at (A
C3-44 ℃)～(A
C3+ 6 ℃) scope, anneal 15～20s; With speed slow cooling to 650～710 ℃ (being called for short this temperature in the watch is fast cold beginning temperature) of 5～8 ℃/s, the speed with 〉=30 ℃/s is cooled to 250～280 ℃ then after the anneal, isothermal processes 120～200s, and last water-cooled is to room temperature.Fig. 2 corrodes the observed metallographic structure in back for the system cold-rolled dual phase steel finished product of the low-carbon (LC) silicomanganese sheet material of new invention prepared among the embodiment of the invention 2-II through Lepera reagent, and as seen, martensite all is distributed in the tissue to even ﹑ disperse.
Cold rolling and the parameter and annealing of table 3 embodiment 2
The mechanical property of cold-rolled biphase steel sees Table 4.Compare with the cold-rolled biphase steel that the common process technology prepares, adopt in the microstructure of the cold-rolled biphase steel that preparation method of the present invention obtains, the martensite mark has increased by 3.0～5.2%, and mechanical property significantly improves, wherein yield strength has increased by 10～37MPa, tensile strength has increased by 29～84MPa, and unit elongation has improved 0.4～3.7%.As seen, adopt preparation method of the present invention can obtain the cold-rolled biphase steel of mechanical property excellence, have no progeny percentage of total elongation and work hardening exponent of its Qiang Du ﹑ is improved, and especially intensity significantly increases.
The mechanical property of table 4 embodiment 2 and tissue volume mark
Embodiment 3
The chemical constitution of the system cold-rolled dual phase steel of low-carbon (LC) silicomanganese that adopts is C:0.16% by mass percentage, Si:0.5%, and Mn:1.54%, V:0.05%, P:0.019%, S:0.016%, surplus is Fe.Record its A by the thermal expansion curve
C1And A
C3Be respectively 728 and 865 ℃.
Adopting above-mentioned low-carbon (LC) silicomanganese is dual phase steel, through smelting and forging and make the thick slab of 60mm, is heated to 1200 ℃, and insulation 1h carries out roughing, and the roughing process is 4 passages, and the roughing start rolling temperature is 1100 ℃, and obtaining thickness is the intermediate blank of 20mm.
Intermediate blank is carried out finish rolling, and the finish rolling process is 5 passages, and the finish rolling start rolling temperature is 990 ℃, and the finish rolling finishing temperature is 876 ℃, and the thickness of hot-rolled sheet is 6mm after the finish rolling.
To room temperature, the average grain size of the initial tissue of hot rolling is～17.4 μ m to technology 3-I according to preparation method's Direct Air-Cooled of routine after the hot rolling finish to gauge; 3-II～3-VII then with the cooling rate laminar flow of～20 ℃/s be cooled to～670 ℃, air cooling to room temperature obtains hot rolling steel billet then, the average grain size of the initial tissue of hot rolling significantly is decreased to～5.4 μ m.
The above-mentioned hot rolling steel billet of pickling to remove oxide compound, obtains the cold-rolled steel plate.
It is cold rolling to adopt different cold roling reductions to carry out respectively the cold-rolled steel plate, and concrete cold rolling and parameter and annealing sees Table 5.3-I is the cold-rolled biphase steel of common process technology preparation, and cold roling reduction is 69.0%, and heating rate is 10 ℃/s; The cold-rolled biphase steel of 3-II～3-VII for adopting preparation method of the present invention to obtain, cold roling reduction is 83.2～83.8%, and heating rate is 80～150 ℃/s, and annealing temperature is at (A
C3-25 ℃)～(A
C3+ 10 ℃) scope, anneal 10～20s; With speed slow cooling to 660～700 ℃ (being called for short this temperature in the watch is fast cold beginning temperature) of 5～8 ℃/s, the speed with 〉=30 ℃/s is cooled to 255～295 ℃ then after the anneal, isothermal processes 120～200s, and last water-cooled is to room temperature.
Cold rolling and the parameter and annealing of table 5 embodiment 3
The mechanical property of cold-rolled biphase steel sees Table 6.Compare with the cold-rolled biphase steel that the common process technology prepares, adopt in the microstructure of the cold-rolled biphase steel that preparation method of the present invention obtains, the martensite mark has increased by 5.3～7.6%, and mechanical property significantly improves, wherein yield strength has increased by 1～24MPa, tensile strength has increased by 28～107MPa, and unit elongation has improved 3.4～4.9%.As seen, adopt preparation method of the present invention can obtain the cold-rolled biphase steel of mechanical property excellence, have no progeny percentage of total elongation and work hardening exponent of its Qiang Du ﹑ is improved, and especially intensity significantly increases.
The mechanical property of table 6 embodiment 3 and tissue volume mark
Embodiment 4
The chemical constitution of the system cold-rolled dual phase steel of low-carbon (LC) silicomanganese that adopts is C:0.20% by mass percentage, Si:0.81%, and Mn:1.90%, Nb:0.04%, P:0.006%, S:0.024%, surplus is Fe.Record its A by the thermal expansion curve
C1And A
C3Be respectively 705 and 882 ℃.
Adopting above-mentioned low-carbon (LC) silicomanganese is dual phase steel, through smelting and forging and make the thick slab of 60mm, is heated to 1200 ℃, and insulation 1h carries out roughing, and the roughing process is 4 passages, and the roughing start rolling temperature is 1050 ℃, and obtaining thickness is the intermediate blank of 20mm.
Intermediate blank is carried out finish rolling, and the finish rolling process is 5 passages, and the finish rolling start rolling temperature is 980 ℃, and the finish rolling finishing temperature is 865 ℃, and the thickness of hot-rolled sheet is 6mm after the finish rolling.
To room temperature, the hot rolling slab metallographic structure is shown in Fig. 1 (a) according to preparation method's Direct Air-Cooled of routine for technology 4-I after the hot rolling finish to gauge, and the average grain size of the initial tissue of hot rolling is～18.0 μ m; 4-II～4-VII then with the cooling rate laminar flow of～20 ℃/s be cooled to～680 ℃, air cooling to room temperature obtains hot rolling steel billet then, the average grain size of the initial tissue of hot rolling significantly is decreased to～5.6 μ m.
The above-mentioned hot rolling steel billet of pickling to remove oxide compound, obtains the cold-rolled steel plate.
It is cold rolling to adopt different cold roling reductions to carry out respectively the cold-rolled steel plate, and concrete cold rolling and parameter and annealing sees Table 7.4-I is the cold-rolled biphase steel of common process technology preparation, and cold roling reduction is 68.3%, and heating rate is 10 ℃/s; The cold-rolled biphase steel of 3-II～3-VII for adopting preparation method of the present invention to obtain, cold roling reduction is 81.5～83.8%, and heating rate is 80～150 ℃/s, and annealing temperature is at (A
C3-47 ℃)～(A
C3+ 8 ℃) scope, anneal 10～15s; With speed slow cooling to 690～720 ℃ (being called for short this temperature in the watch is fast cold beginning temperature) of 5～8 ℃/s, the speed with 〉=30 ℃/s is cooled to 250～300 ℃ then after the anneal, isothermal processes 120～200s, and last water-cooled is to room temperature.
Cold rolling and the parameter and annealing of table 7 embodiment 4
The mechanical property of cold-rolled biphase steel sees Table 8.Compare with the cold-rolled biphase steel that the common process technology prepares, adopt in the microstructure of the cold-rolled biphase steel that preparation method of the present invention obtains, the martensite mark has increased by 3.5～5.8%, and mechanical property significantly improves, wherein yield strength has increased by 21～72MPa, tensile strength has increased by 55～136MPa, and unit elongation has improved 1.6～4.1%.As seen, adopt preparation method of the present invention can obtain the cold-rolled biphase steel of mechanical property excellence, have no progeny percentage of total elongation and work hardening exponent of its Qiang Du ﹑ is improved, and especially intensity significantly increases.
The mechanical property of table 8 embodiment 4 and tissue volume mark
Claims (10)
1. system cold-rolled dual phase steel of low-carbon (LC) silicomanganese, constituted by the martensite of 19.0～26.0% volume ratios, the ferrite of 74.0～81.0% volume ratios, and its chemical constitution is C:0.06%～0.20% by mass percentage, Si:0.1%～0.8%, Mn:1.0%～2.0%, Nb≤0.05%, V≤0.05%, P≤0.035%, S≤0.035%, surplus is Fe.
2. the system cold-rolled dual phase steel of low-carbon (LC) silicomanganese as claimed in claim 1 is characterized in that, the system cold-rolled dual phase steel yield strength of described low-carbon (LC) silicomanganese 290～438/MPa, tensile strength 540～826/MPa, yield tensile ratio 0.46～0.58, unit elongation 24.7～30.1%.
3. the preparation method of the system cold-rolled dual phase steel of low-carbon (LC) silicomanganese as claimed in claim 1 comprises the following steps:
(1) choose the system cold-rolled dual phase steel of low-carbon (LC) silicomanganese, make slab through smelting and forging, be heated to 1100～1250 ℃ of insulations, carry out hot rolling under 820～1100 ℃ of conditions, hot rolling finishing temperature is (A
R3+ 30) ℃～(A
R3+ 100) ℃, and the cooling rate laminar flow with 10～30 ℃/s is cooled to (A after hot rolling finish to gauge
R3-50) ℃～(A
R3-100) ℃, air cooling to room temperature obtains hot rolling steel billet then;
(2) the above-mentioned hot rolling steel billet of pickling obtains the cold-rolled steel plate, to remove oxide compound, obtains the cold-rolled steel plate;
(3) it is cold rolling the cold-rolled steel plate to be adopted 〉=80% draught carry out, and being beneficial to significantly increases dislocation desity in deformation phases, store more distortional strain energy;
(4) cold rolled strip is heated to (A with the heating rate of at least 80 ℃/s
C3-50 ℃)～(A
C3+ 10 ℃), with speed slow cooling to 600～720 of 5～8 ℃/s ℃, the speed with 〉=30 ℃/s is cooled to 250～300 ℃ then behind anneal 10～20s, isothermal processes 120～300s, last Kong Leng ﹑ water-cooled or naturally cool to room temperature.
4. the preparation method of the system cold-rolled dual phase steel of low-carbon (LC) silicomanganese as claimed in claim 3 is characterized in that, the soaking time of step 1) is 1～2 hour.
5. the preparation method of the system cold-rolled dual phase steel of low-carbon (LC) silicomanganese as claimed in claim 3, it is characterized in that the described hot rolling of step 1) comprises roughing and finish rolling, the roughing process is 3～5 passages, the roughing start rolling temperature is 1000～1150 ℃, and obtaining thickness is the intermediate blank of 15～25mm; The finish rolling process is 4～6 passages, and the finish rolling start rolling temperature is 950～1050 ℃, and the finish rolling finishing temperature is 820～950 ℃, and the thickness of hot-rolled sheet is 4～8mm after the finish rolling.
6. the preparation method of the system cold-rolled dual phase steel of low-carbon (LC) silicomanganese as claimed in claim 4 is characterized in that, the described roughing of step 1) and finish rolling, and the roughing process is 4 passages, and the roughing start rolling temperature is 1050～1100 ℃, and obtaining thickness is the intermediate blank of 20mm; The finish rolling process is 5 passages, and the finish rolling start rolling temperature is 980～1000 ℃, and the finish rolling finishing temperature is 840～880 ℃, and the thickness of hot-rolled sheet is 6mm after the finish rolling.
7. the preparation method of the system cold-rolled dual phase steel of low-carbon (LC) silicomanganese as claimed in claim 3 is characterized in that, the hot rolling finishing temperature of step 1) is (A
R3+ 30) ℃～(A
R3+ 60) ℃.
8. the preparation method of the system cold-rolled dual phase steel of low-carbon (LC) silicomanganese as claimed in claim 3 is characterized in that, the cooling rate of step 1) is 15～25 ℃/s.
9. the preparation method of the system cold-rolled dual phase steel of low-carbon (LC) silicomanganese as claimed in claim 8 is characterized in that, the cooling rate of step 1) is 18～22 ℃/s; Most preferred, the cooling rate of step 1) is 20 ℃/s.
10. the preparation method of the system cold-rolled dual phase steel of low-carbon (LC) silicomanganese as claimed in claim 3 is characterized in that, the heating rate of step 4) is 80～150 ℃/s; The rate of cooling of step 4) is 〉=30 ℃/s.
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| CN103411815A (en) * | 2013-07-31 | 2013-11-27 | 攀钢集团攀枝花钢铁研究院有限公司 | Method for measuring martensite content in heat rolling dual-phase steel |
| CN103627950A (en) * | 2013-12-13 | 2014-03-12 | 安徽工业大学 | Hot rolled spoke steel with yield ratio of 0.45-0.49 and tensile strength of 630-670 MPa and manufacturing method thereof |
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| CN103411815A (en) * | 2013-07-31 | 2013-11-27 | 攀钢集团攀枝花钢铁研究院有限公司 | Method for measuring martensite content in heat rolling dual-phase steel |
| CN103627950A (en) * | 2013-12-13 | 2014-03-12 | 安徽工业大学 | Hot rolled spoke steel with yield ratio of 0.45-0.49 and tensile strength of 630-670 MPa and manufacturing method thereof |
| CN103866181A (en) * | 2014-03-14 | 2014-06-18 | 莱芜钢铁集团有限公司 | Method for manufacturing low-cost ultrafine grain dual-phase steel seamless tube on line |
| CN103866181B (en) * | 2014-03-14 | 2015-12-09 | 莱芜钢铁集团有限公司 | A kind of preparation method of online manufacture low cost superfine crystal particle dual phase steel seamless pipe |
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| CN107794444A (en) * | 2017-10-16 | 2018-03-13 | 首钢京唐钢铁联合有限责任公司 | Strong cold-rolled biphase steel of carbon silicomanganese system superelevation and preparation method thereof |
| CN108517468A (en) * | 2018-05-24 | 2018-09-11 | 山东钢铁集团日照有限公司 | A kind of economical cold-rolled biphase steel and its production method of steel multistage |
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| US11873538B2 (en) * | 2019-04-18 | 2024-01-16 | Sms Group Gmbh | Cooling device for seamless steel pipes |
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