CN103469090A - Annealing method of ultrahigh-strength hot-forming steel - Google Patents
Annealing method of ultrahigh-strength hot-forming steel Download PDFInfo
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- CN103469090A CN103469090A CN2013104233345A CN201310423334A CN103469090A CN 103469090 A CN103469090 A CN 103469090A CN 2013104233345 A CN2013104233345 A CN 2013104233345A CN 201310423334 A CN201310423334 A CN 201310423334A CN 103469090 A CN103469090 A CN 103469090A
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Abstract
The invention discloses an annealing method of ultrahigh-strength hot-forming steel, belonging to the technical field of heat treatment on high-strength automobile steel. After hot rolling and cold rolling, the ultrahigh-strength hot-forming steel is subjected to annealing treatment to obtain a steel plate substrate before hot forming. The hot rolling process comprises the steps of heating a hot-rolled plate blank to 1,100-1,250 DEG C, and preserving heat for 0.5-1 hour, wherein the final rolling temperature is 800-900 DEG C, the coiling temperature is 600-700 DEG C, and the cold rolling reduction rate is 70-80%. The annealing process comprises the steps of slowly heating the cold-rolled steel plate to a two-phase region (alpha+gamma), namely a temperature above A1; preserving heat for 0.1-5 hours; cooling to a temperature below A1 at a cooling speed of 0.1-10 DEG C per second; preserving heat for 0.1-5 hours; finally, cooling to room temperature at a cooling speed of 0.1-10 DEG C per second. According to the ultrahigh-strength hot-forming steel prepared by the method disclosed by the invention, granular carbides are dispersed on a ferrite matrix of the microscopic structure of the steel plate before hot forming, the carbides are uniformly distributed, the reversion and re-crystallization of the ferrite are sufficient, and the sufficiency and uniformity of austenitizing in a hot forming heating stage are facilitated; compared with a traditional cover annealing process, the annealing time is short, and the production efficiency is high.
Description
Technical field
The invention belongs to high-strength vehicle and use steel heat treatment technics field, particularly relate to a kind of method for annealing of superelevation heat-flash forming steel.
Background technology
Along with the development of automotive industry, energy-saving and emission-reduction have become the common focus of paying close attention in the world today.Automotive light weight technology is the major measure of realizing this goal, and how advanced high-strength steel and super-high strength steel are widely used in body of a motor car.
Generally, tensile strength is greater than the superstrength automobile steel of 1000MPa because its intensity is high, the viscous deformation narrow range, and plasticity is bad, and required stamping press is large.At room temperature during Pressing Deformation, easy to crack, after being shaped the resilience of part serious, cause the size and dimension bad stability of part, the part punching of complicated shape is shaped more difficult.Therefore traditional cold stamping method is difficult to solve the problem that ultrahigh-strength steel plates runs in the body of a motor car manufacture.For this reason, the research that a large amount of energy is carried out ultrahigh-strength steel plates thermoforming technology is dropped in countries in the world.The heat forming technology technology is that plate (mostly being boron alloyed steel) is put into to soaking pit, insulation for some time after being heated to more than 900 ℃, after making its complete austenitizing, send into rapidly with carrying out Pressing Deformation in the mould of cooling system, after shaping, need pressurize for some time that the part shape size is tended towards stability, mould contact steel plate surface makes distortion and cooling generation simultaneously during this time, organize and undergo phase transition during the pressurize typing, become uniform martensitic stucture by austenitic transformation, thereby obtain the steel plate of superstrength, tensile strength can be brought up to more than 2.5 times of initial value.
The thermoforming steel is the high strength Special Alloy Steel that a kind of applied heat forming technology is produced, and is mainly the manganese boron steel.Microstructure before thermoforming is ferrite+pearlitic structure, tensile strength 400MPa～600MPa, and percentage of total elongation 20%～30%, show as hardness low, and plasticity is good, is easy to machining or cold working etc.; Microstructure after thermoforming is complete martensitic stucture, yield strength >=1000MPa, tensile strength >=1500MPa, percentage of total elongation >=5%, strong hardness and wear resistance are high, without cracking, without resilience, dimensional precision is high, can carry out complex parts processing, has made up to a certain extent the deficiency of super-high strength steel plate cold shaping.The thermoforming steel be most widely used on body of a motor car at present is the 22MnB5 steel, be mainly used in the parts that the forward and backward collision bumper of automobile, A/B/C post, roof framework, car bottom framework and inner plate of car door, side door beams etc. are had relatively high expectations to collision, and its usage quantity accounts for the ratio increasing year by year of body in white, part has substituted the use of high-strength TRIP steel and DP steel.In the following steel auto project of FSV, high tensile steel plate will account for 97% of material for integral body, these materials mainly comprise dual phase steel (DP), transformation induced plasticity steel (TRIP), twin crystal inducing plasticity steel (TWIP), Multiphase Steel (CP) and thermoforming steel (HS) etc., wherein the thermoforming steel will account for 11% left and right.
The report of the current production technology aspect about the thermoforming steel plate is less, and particularly for cold rolled annealed state thermoforming steel, what its annealing process major part may adopt is recrystallize bell-type annealing technique.Lower than A
1certain temperature at temperature, be incubated for a long time, make the ferrite in steel plate carry out sufficient recovery and recrystallization, the carbide disperse of trying one's best is distributed on ferrite matrix, and the tensile strength that makes final steel plate is 400-600MPa, and percentage of total elongation is 25-35%, show as intensity low, plasticity is good, has cold machining processibility preferably and plasticity, is conducive to the cutting of thermoforming front spring etc.Then, current recrystallize bell-type annealing technique, the production cycle is long, causes energy consumption very high.
Summary of the invention
Purpose of the present invention is exactly by changing annealing temperature and annealing way, reducing annealing time, also can access the granular carbide even dispersion and the tissue signature on axle columnar ferrite matrix such as be distributed in, and shortens the annealing cycle, enhances productivity.
A kind of superelevation heat-flash forming steel, the composition quality percentage composition is: C:0.1-0.5%, Si:1.0-2.0%, Mn:1.0-3.0%, Al:0.01-0.05%, Cr:0.50-1.50%, B:0.001-0.005%, Ti:0.01-0.05%, Nb:0.01-0.05%, P:<0.01%, S:<0.01%, N:<0.01%, and surplus is iron and inevitable impurity; The superelevation heat-flash forming steel of this composition through hot rolling and cold rolling after, carry out anneal, obtain the substrate steel sheet before thermoforming, the overall technology route of taking is:
(1) annealing temperature is controlled at two-phase region (α+γ), i.e. A
1above temperature, be 760-840 ℃, insulation 0.1-3h, and in this process, ferrite has carried out sufficient Recovery and recrystallization, and obtains the austenite structure of certain content, the uneven components in this part austenite, the not molten carbide particle of inner existence;
(2) speed of cooling with 0.1-5 ℃/s is chilled to A
1below a certain temperature, be 650-720 ℃, insulation 0.1-3h, making the part austenitic transformation is ferrite, and by isothermal process, carbide precipitate, avoided the pearlitic formation of sheet;
(3) finally with the speed of cooling of 0.1-5 ℃/s, be chilled to room temperature, make the austenite do not changed complete ferritic transformation, finally obtain waiting the distributing tissue signature of granular carbide of even dispersion on axle columnar ferrite matrix.
The yield strength of the superelevation heat-flash forming steel thermoforming front spring of producing by the present invention is 400-500MPa, and tensile strength is 500-600MPa, and percentage of total elongation is 30% left and right.
Superelevation heat-flash shaping steel plate of the present invention for through hot rolling and cold rolling after carry out again annealing process, it requires hot rolling finishing temperature is 800～900 ℃, 600～700 ℃ of coiling temperatures, the microstructure after hot rolling is for waiting axle columnar ferrite+sheet perlite; It requires cold rolling draft is 70-80%, usings this deformation energy storage produced as the motivating force with after annealing ferrite recovery and recrystallization, has determined the length of annealing time.
The mechanical property of superelevation heat-flash forming steel thermoforming front spring depends primarily on the disperse distributed degrees of ferritic recovery and recrystallization degree and carbide, also relevant with Heating temperature, soaking time, isothermal temperature, isothermal time and speed of cooling etc.
The difference of Heating temperature has directly affected austenitic content and homogeneity in two-phase region, too high austenite content increases, and easy homogenizing, make to be transformed into the sheet perlite in follow-up process of cooling, make the ferrite recrystallize insufficient too low within a short period of time, therefore, rationally controlling Heating temperature is the key that obtains desirable tissue.The soaking time major effect ferritic recovery and recrystallization degree and austenite interior element content and distributing homogeneity.A
1following isothermal temperature, isothermal time and the speed of cooling of point is mainly to control austenitic transmutation product and form.
The invention has the advantages that: with traditional recrystallize bell-type annealing, compare, the present invention can complete annealing process within the shorter time cycle, and reaches mechanical property and the microstructure of producing steel plate with traditional recrystallize bell-type annealing, has improved production efficiency, reduce energy consumption, cost-saving.
The accompanying drawing explanation
Fig. 1 rolling and annealing process schematic diagram
The displaing micro tissue topography of Fig. 2 embodiment of the present invention one
The displaing micro tissue topography of Fig. 3 embodiment of the present invention two
The displaing micro tissue topography of Fig. 4 embodiment of the present invention three
The displaing micro tissue topography of Fig. 5 embodiment of the present invention four
Embodiment
The embodiments of the invention chemical composition is as shown in table 1, and after smelting, strand is forged into that to be of a size of 40mm(thick) * 70mm(is wide) * 80mm(is long) blank.Blank, through 1200 ℃ of soaking 1 hour, is rolled into the 6.0mm Plate Steel through multi-pass, and controlling finishing temperature is 870 ℃, and water-cooled to 660 ℃ is put into furnace cooling after holding furnace insulation 1h, with the simulation coiling process.Hot-rolled sheet after pickling, after multi-pass is cold rolling, is rolled to 1.5mm, and cold rolling draft is 75%; Annealing process is: the rate of heating with 2 ℃/s is heated to 780 ℃, insulation 0.1-3h, then be chilled to 700 ℃ with the speed of cooling of 1 ℃/s, and insulation 1h, finally the speed of cooling with 1 ℃/s is chilled to room temperature, and concrete technology is as shown in Figure 1.
Embodiment mono-
Steel plate after cold rolling is heated to 780 ℃, insulation 10min, then be chilled to 700 ℃ with the speed of cooling of 1 ℃/s, and insulation 1h, finally the speed of cooling with 1 ℃/s is chilled to room temperature.Microstructure after annealing is ferrite+granular carbide, and the ferrite recrystallize is incomplete, still retains the fibrous tissue form of cold rolling state, the granular carbide skewness.
Embodiment bis-
Steel plate after cold rolling is heated to 780 ℃, insulation 0.5h, then be chilled to 700 ℃ with the speed of cooling of 1 ℃/s, and insulation 1h, finally the speed of cooling with 1 ℃/s is chilled to room temperature.Microstructure after annealing is ferrite+granular carbide, and the ferrite recrystallize completes substantially, and the granular carbide disperse is distributed on ferrite matrix.Embodiment tri-
Steel plate after cold rolling is heated to 780 ℃, insulation 1h, then be chilled to 700 ℃ with the speed of cooling of 1 ℃/s, and insulation 1h, finally the speed of cooling with 1 ℃/s is chilled to room temperature.Microstructure after annealing is ferrite+granular carbide, and the ferrite recrystallize completes, and the granular carbide disperse is distributed on ferrite matrix.
Embodiment tetra-
Steel plate after cold rolling is heated to 780 ℃, insulation 3h, then be chilled to 700 ℃ with the speed of cooling of 1 ℃/s, and insulation 1h, finally the speed of cooling with 1 ℃/s is chilled to room temperature.Microstructure after annealing is ferrite+granular carbide, and the ferrite recrystallize completes, and the granular carbide disperse is distributed on ferrite matrix.
The chemical composition of table 1 embodiment (massfraction/%)
Claims (1)
1. the method for annealing of a superelevation heat-flash forming steel, the composition quality percentage composition that it is characterized in that superelevation heat-flash forming steel is: C:0.1-0.5%, Si:1.0-2.0%, Mn:1.0-3.0%, Al:0.01-0.05%, Cr:0.50-1.50%, B:0.001-0.005%, Ti:0.01-0.05%, Nb:0.01-0.05%, P:<0.01%, S:<0.01%, N:<0.01%, and surplus is iron and inevitable impurity; The superelevation heat-flash forming steel of this composition through hot rolling and cold rolling after, carry out anneal, obtain the substrate steel sheet before thermoforming, the concrete technology step is as follows:
1) hot rolling and cold-rolling process: hot rolling slab is heated to 1100～1250 ℃, is incubated 0.5～1 hour, 800～900 ℃ of finishing temperatures, 600～700 ℃ of coiling temperatures; Cold rolling draft is 70-80%;
2) annealing process: cold-rolled steel sheet slowly is heated to two-phase region (α+γ), i.e. A
1above temperature, be 760-840 ℃, insulation 0.1-3h, and then the speed of cooling with 0.1-5 ℃/s is chilled to A
1below a certain temperature, be 650-720 ℃, the insulation 0.1-3h, finally the speed of cooling with 0.1-5 ℃/s is chilled to room temperature.
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Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104017952A (en) * | 2014-05-28 | 2014-09-03 | 攀枝花贝氏体耐磨管道有限公司 | Saving-type tempering-free strengthening toughening method for low-alloy high-strength steel products |
| CN106048174A (en) * | 2016-07-20 | 2016-10-26 | 柳州科尔特锻造机械有限公司 | Heat treatment method for high-strength alloy steel |
| CN106811689A (en) * | 2017-01-17 | 2017-06-09 | 北京科技大学 | A kind of preparation method of the hot forming steel of tensile strength >=2000MPa |
| CN106811681A (en) * | 2017-01-17 | 2017-06-09 | 北京科技大学 | A kind of preparation method without B hot forming steel |
| CN107923014A (en) * | 2015-08-19 | 2018-04-17 | 杰富意钢铁株式会社 | High-strength steel sheet and its manufacture method |
| CN107923013A (en) * | 2015-08-19 | 2018-04-17 | 杰富意钢铁株式会社 | High-strength steel sheet and its manufacture method |
| CN114622064A (en) * | 2022-02-23 | 2022-06-14 | 大冶特殊钢有限公司 | Spheroidizing annealing method of MnCr series low-carbon gear steel |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103261452A (en) * | 2010-10-22 | 2013-08-21 | 新日铁住金株式会社 | Method for manufacturing hot stamped body having vertical wall, and hot stamped body having vertical wall |
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2013
- 2013-09-17 CN CN2013104233345A patent/CN103469090A/en active Pending
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103261452A (en) * | 2010-10-22 | 2013-08-21 | 新日铁住金株式会社 | Method for manufacturing hot stamped body having vertical wall, and hot stamped body having vertical wall |
Cited By (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104017952A (en) * | 2014-05-28 | 2014-09-03 | 攀枝花贝氏体耐磨管道有限公司 | Saving-type tempering-free strengthening toughening method for low-alloy high-strength steel products |
| CN107923014A (en) * | 2015-08-19 | 2018-04-17 | 杰富意钢铁株式会社 | High-strength steel sheet and its manufacture method |
| CN107923013A (en) * | 2015-08-19 | 2018-04-17 | 杰富意钢铁株式会社 | High-strength steel sheet and its manufacture method |
| CN107923014B (en) * | 2015-08-19 | 2020-06-16 | 杰富意钢铁株式会社 | High-strength steel sheet and method for producing same |
| CN107923013B (en) * | 2015-08-19 | 2020-06-16 | 杰富意钢铁株式会社 | High-strength steel sheet and method for producing same |
| CN106048174A (en) * | 2016-07-20 | 2016-10-26 | 柳州科尔特锻造机械有限公司 | Heat treatment method for high-strength alloy steel |
| CN106811689A (en) * | 2017-01-17 | 2017-06-09 | 北京科技大学 | A kind of preparation method of the hot forming steel of tensile strength >=2000MPa |
| CN106811681A (en) * | 2017-01-17 | 2017-06-09 | 北京科技大学 | A kind of preparation method without B hot forming steel |
| CN106811689B (en) * | 2017-01-17 | 2018-02-09 | 北京科技大学 | A kind of preparation method of tensile strength >=2000MPa hot forming steel |
| CN106811681B (en) * | 2017-01-17 | 2018-03-30 | 北京科技大学 | A kind of preparation method of no B hot formings steel |
| CN114622064A (en) * | 2022-02-23 | 2022-06-14 | 大冶特殊钢有限公司 | Spheroidizing annealing method of MnCr series low-carbon gear steel |
| CN114622064B (en) * | 2022-02-23 | 2023-10-03 | 大冶特殊钢有限公司 | Spheroidizing annealing method of MnCr series low-carbon gear steel |
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Application publication date: 20131225 |