CN102260824A - Hot-rolled steel plate with yield strength of 550 MPa for hot forming and manufacturing method thereof - Google Patents
Hot-rolled steel plate with yield strength of 550 MPa for hot forming and manufacturing method thereof Download PDFInfo
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Abstract
The invention relates to a hot-rolled steel plate with yield strength of 550 MPa for hot forming, which comprises the following ingredients in percentage by mass: 0.13-0.20 of C, 0.30-0.60 of Si, 1.4-2.0 of Mn, 0.05-0.1 of V, 0.01-0.10 of Ti, less than or equal to 0.03 of Nb, less than or equal to 0.50 of Cr, less than or equal to 0.025 of P, less than or equal to 0.01 of S, 0.0005-0.005 of Ca, 0.03-0.10 of Al, more than 0.10 of V and Ti and the rest of Fe and unavoidable impurities. The hot-rolled high-strength steel plate is not subjected to heat-treatment, thus the manufacturing cost is low; after the steel plate is hot-rolled, no complicated-control cooling technique is needed and cooling can be realized by using a common laminar cooling process, thus the steel plate is easy to produce; and in addition, the steel plate has high strength and toughness before/after hot processing.
Description
Technical field
The invention belongs to metal material field, relate to the ferrous alloy that contains C, Si, Mn, V, Nb, Ti etc., particularly a kind of behind the high temperature process air cooling material yield intensity still can reach hot-rolled steel sheet and manufacture method thereof more than the 550MPa.
Background technology
Along with the development of Domestic Automotive Industry, the trend of vehicle loss of weight makes automobile vendor propose new demand to more high-intensity product in recent years.Its key problem is the raising of intensity and guarantees the stable of other use propertieies.
From manufacturing experience for many years, microalloying is studied by each steel production enterprise as the main method that improves this type of product strength.Generally adopt Nb, Ti microalloying to produce high-strength automobile steel abroad, progressively replaced traditional C-Mn steel.But adopt the automobile steel of microalloy Nb, Ti also to have some problems, particularly for the hot-work trolley part, its manufacturing process generally is the pattern of air cooling after the high temperature process, and this technology has weakened the precipitating reinforcing effect of microalloy things such as Nb, Ti greatly, makes that the strength of materials after the hot-work reduces greatly.
In order to improve the intensity of steel plate, provide multielement micro-alloyed air cooled bainite/ferritic steels such as a kind of Mn, Si, B in the patent of publication number for CN1288971, belong to low-carbon micro steel-alloy.Promptly obtain bainite structure by optimizing components such as adding Mn, Si, B under air cooling condition after the hot-work and improve intensity, its yield strength under controlled rolling air cooling condition is more than the 520MPa.Applied heat processing back air cooling is without the part of modifier treatment.As High Strength Steel Bar, low-alloy abrasion-proof spare etc.Yet this steel formability poor performance is not suitable for the complex structural member of making automobile.
In addition, publication number is that the application of CN 101275200A obtains martensitic stucture and improves intensity by adding optimizing components such as C, Mn, B under air cooling condition after the hot-work, and its tensile strength under the thermoforming treatment condition can reach more than the 1000MPa.Same, this class steel plate is only applicable to the thin specification automobile stiffener of quench treatment after the hot-work, and is not suitable for the complex structural member of making air cooling after the thermoforming.
Therefore, need badly and a kind ofly behind the thermoforming air cooling, have higher-strength and toughness, and possess the steel of favorable forming property, be used to make truck heat and dash parts such as weldering axle housing.
Summary of the invention
The object of the present invention is to provide a kind of low-carbon micro steel-alloy and manufacture method thereof, need not modifier treatment, guarantee to reach higher intensity behind the hot-work air cooling, and have preferable combination of strength and toughness.
For achieving the above object, steel provided by the present invention, its composition quality degree is:
C:0.13～0.20, Si:0.30～0.60, Mn:1.4～2.0, V:0.05～0.1, Ti:0.01～0.10, Nb :≤0.03, Cr :≤0.50, P :≤0.025, S :≤0.01, Ca:0.0005～0.005, Al:0.03～0.10, V+Ti:＞0.10, all the other are Fe and unavoidable impurities.
In addition, the present invention also provides a kind of manufacture method of above-mentioned steel, comprises smelting, casting, hot rolling successively, cools off, batches.
Preferably, described smelting is that top-blown oxygen converter is smelted.
Preferably, described hot rolling comprises heating, roughing, finish rolling step successively.
Preferably, described cooling 1-2 after described hot rolling carried out in second, adopted the laminar flow cooling, and described speed of cooling is greater than 20 ℃/s.
Preferably, described coiling temperature is 580-660 ℃.
Further preferably, the tapping temperature of described heating is 1150-1250 ℃.
Preferably, described roughing temperature is 1000-1100 ℃.
More preferably, described finish rolling temperature in is 920-980 ℃, and the finish rolling finishing temperature is 820-880 ℃, and rolling reduction is greater than 80%.
To further specify the present invention below.
The present invention controls content and the ratio of key element such as C, V, V+Ti, and control element S and P etc.Elements such as control C, Mn increase solid solution strengthening effect and improve the solubleness of V, Nb, Ti, elements such as control V, Ti make it to form V/Ti (C, N) precipitation strength, guarantee that steel has good comprehensive mechanical performance, particularly higher intensity and toughness in the Direct Air-Cooled of elevated temperature heat processing back.
Below the design of composition of steel of the present invention is described:
C: be used to form enough solid solution carbon with mutually carbide reinforced, to guarantee the intensity rank of steel, C too low strength does not reach requirement, and C is too high unfavorable to welding property and forming property.So carbon content is 0.13～0.20%.
Si: play the solution strengthening effect in steel, and can improve purity of steel and deoxidation, Si can suppress separating out of carbide, improves toughness.The too high surface of steel plate that makes easily of content produces surface imperfection such as red iron sheet.
Mn: the adding of manganese can improve the intensity and the toughness of steel, and it is long-pending to improve V, Nb, the Ti solid solubility in austenite, strengthens its precipitating reinforcing effect.Manganese content is too high not only can to make the plasticity decline of steel also can produce strong segregation, causes composition of steel and performance inequality, increases manufacture difficulty, and its component content should be not more than 2.0%.
V: vanadium mainly plays the precipitation strength effect in steel, because its carbide solvent temperature is low than Nb, Ti, also can carbide precipitate in the air cooling after the hot-work of lesser temps, and reach strengthening effect, the intensity behind the increase air cooling.
Cr: be carbide forming element, can improve the intensity and the toughness of steel.But too high Cr amount can increase the formation of bainite, reduces toughness.Content should be less than 0.6% in the micro-alloyed steel.
Al: be the deoxidant element in the steel, reduce oxide inclusion, pure steel in the steel, help improving the forming property of steel plate.Yet, if the too high levels of Al can raise the cost; If content is low excessively, its deoxidizing capacity reduces.
Nb, Ti: be effective crystal grain thinning, improve intensity and flexible element, be present in the steel with the form of carbide and carbonitride, it is little that add-on is lower than 0.01% strengthening effect.For thermoforming air cooling spare, Ti has significant effect to the control grain size, and thinner initial crystal grain can make the tissue behind the thermoforming air cooling keep tiny, helps improving intensity and toughness.
Ca: can change the form of sulfide in the steel, improve the plasticity and the toughness of steel plate.
P, S: be the impurity element in the steel, content should be low more good more.
V+Ti: elements such as control V, Ti make it to form V/Ti (C, N) precipitation strength, and V+Ti＞0.10% has good comprehensive mechanical performance, particularly higher intensity and toughness to guarantee steel in the Direct Air-Cooled of elevated temperature heat processing back.
Simultaneously, the present invention controls the fabrication process condition of steel plate:
The tapping temperature of heating is 1150-1250 ℃, if Heating temperature is lower than 1150 ℃, the microalloy element dissolving is insufficient, fails to make full use of the effect of microalloy element, and intensity reduces; If it is be higher than 1250 ℃ of easy alligatoring of crystal grain, unfavorable to improving steel plate toughness.
The tapping temperature of heating is 1150-1250 ℃, if the roughing temperature is lower than 1000 ℃, then slab can not carry out roughing in the crystal boundary area again at austenite.
The finish rolling finishing temperature is controlled at 820～880 ℃ in austenite non-recrystallization district, rolling deformation by the austenite cold zone, the carbonitride precipitation that makes the austenite crystal intragranular form deformation bands and bring out microalloy element in response to change, the phase-change product of refine austenite, the toughness of raising steel plate.The deflection of steel plate is more than 80%.
Because steel of the present invention has tangible grain growth after rolling, must control by finish to gauge to the time that begins to cool down in 2 seconds.Steel plate is cooled to 580～660 ℃ with the above speed of cooling of 20 ℃/s and batches after the finish to gauge.Be lower than 580 ℃ if batch, there is bainite structure in steel plate, is unfavorable for improving toughness.Batch the back air cooling to room temperature.
Compare with steel plate with existing hot rolling thermoforming, the present invention has following beneficial effect:
1, hot-rolled high-strength steel plate of the present invention, without thermal treatment, so low cost of manufacture;
2, need not complicated controlled cooling technology after the hot rolling, just can realize, be easy to produce with general laminar flow cooling technology;
3, steel plate of the present invention all has higher intensity and toughness before and after hot-work.
Description of drawings
The metallographic structure photo figure (amplifying 500 times) that Fig. 1 is embodiment of the invention F1 after simulation thermoforming (920 ℃ insulation after 10 minutes air cooling to room temperature).Wherein ferritic volumn concentration is about 90%, and all the other are perlite.
Embodiment
According to the chemical ingredients requirement of steel grade of the present invention, through smelting, forging, rolling to make the steel sample of different size.Table 1 is the chemical ingredients of embodiment steel, and technology controlling and process and gained thickness were the mechanical property of the steel plate of 12mm when table 2 was rolling.The test of mechanical property is undertaken by the GB6397-86 standard, and ballistic work test is the shock test of v-notch sample-20 ℃.
The chemical ingredients of table 1 embodiment (wt%)
The technology controlling and process and the mechanical property of table 2 embodiment steel
| Embodiment | Finishing temperature (℃) | Coiling temperature (℃) | Yield strength (MPa) | Tensile strength (MPa) | Unit elongation (A5%) | Ballistic work a (J) |
| A1 | 830 | 655 | 605 | 690 | 25 | 139 |
| A2 | 853 | 601 | 615 | 730 | 23 | 117 |
| B1 | 850 | 605 | 610 | 725 | 22 | 165 |
| B2 | 870 | 638 | 595 | 700 | 24 | 141 |
| C1 | 885 | 628 | 625 | 760 | 23 | 95 |
| C2 | 878 | 585 | 640 | 735 | 22 | 88 |
| D1 | 835 | 625 | 625 | 730 | 24 | 82 |
| D2 | 825 | 601 | 635 | 745 | 23 | 80 |
| E1 | 832 | 630 | 610 | 720 | 25 | 116 |
| E2 | 840 | 598 | 630 | 750 | 22 | 109 |
| F1 | 870 | 620 | 645 | 760 | 22 | 97 |
| F2 | 833 | 631 | 635 | 785 | 23 | 133 |
Mechanical property mean value after the embodiment A 1～F2 simulation thermoforming (920 ℃ of insulations, after 10 minutes air cooling to room temperature) is: yield strength: 555MPa; Tensile strength: 690MPa; Unit elongation: 24%;-20 ℃ of ballistic work: 110J.
Claims (9)
1. a yield strength is a 550MPa level hot rolling thermoforming steel plate, and its composition quality degree is:
C：0.13～0.20
Si：0.30～0.60
Mn：1.4～2.0
V：0.05～0.1
Ti：0.01～0.10
Nb：≤0.03
Cr：≤0.50
P：≤0.025
S：≤0.01
Ca：0.0005～0.005
Al：0.03～0.10
V+Ti：＞0.10
All the other are Fe and unavoidable impurities.
2. make the method for steel plate as claimed in claim 1, it is characterized in that, described method comprises smelting, casting, hot rolling successively, cools off, batches.
3. method as claimed in claim 2 is characterized in that, described smelting is that top-blown oxygen converter is smelted.
4. method as claimed in claim 2 is characterized in that, described hot rolling comprises heating, roughing, finish rolling step successively.
5. method as claimed in claim 2 is characterized in that, described cooling 1-2 after described hot rolling carried out in second, adopts the laminar flow cooling, and described speed of cooling is greater than 20 ℃/s.
6. method as claimed in claim 2 is characterized in that, described coiling temperature is 580-660 ℃.
7. method as claimed in claim 4 is characterized in that, the tapping temperature of described heating is 1150-1250 ℃.
8. method as claimed in claim 4 is characterized in that, described roughing temperature is 1000-1100 ℃.
9. method as claimed in claim 4 is characterized in that, described finish rolling temperature in is 920-980 ℃, and the finish rolling finishing temperature is 820-880 ℃, and rolling reduction is greater than 80%.
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Cited By (7)
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|---|---|---|---|---|
| CN103422020A (en) * | 2013-09-05 | 2013-12-04 | 济钢集团有限公司 | Steel plate for punching-welding axle housing and manufacturing method thereof |
| CN104561791A (en) * | 2015-01-28 | 2015-04-29 | 河北钢铁股份有限公司承德分公司 | 800MPa grade automobile box steel and production method thereof |
| CN105239013A (en) * | 2015-08-11 | 2016-01-13 | 首钢总公司 | Axle housing steel for cold-machining formation and manufacturing method of axle housing steel |
| CN106636890A (en) * | 2016-11-11 | 2017-05-10 | 武汉钢铁股份有限公司 | Thin hot-rolled sheet steel for direct thermal forming and manufacturing method of thin hot-rolled sheet steel |
| CN108754318A (en) * | 2018-06-04 | 2018-11-06 | 包头钢铁（集团）有限责任公司 | The manufacturing method of 550MPa level steel plates and 550MPa level steel plates |
| CN111235460A (en) * | 2020-02-12 | 2020-06-05 | 首钢集团有限公司 | Axle housing steel suitable for induction heating and production method thereof |
| CN113416902A (en) * | 2021-06-30 | 2021-09-21 | 宝武集团鄂城钢铁有限公司 | Low-cost thermal-forming axle housing steel plate with yield strength of 460MPa and preparation method thereof |
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Cited By (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103422020A (en) * | 2013-09-05 | 2013-12-04 | 济钢集团有限公司 | Steel plate for punching-welding axle housing and manufacturing method thereof |
| CN103422020B (en) * | 2013-09-05 | 2015-05-20 | 济钢集团有限公司 | Steel plate for punching-welding axle housing and manufacturing method thereof |
| CN104561791A (en) * | 2015-01-28 | 2015-04-29 | 河北钢铁股份有限公司承德分公司 | 800MPa grade automobile box steel and production method thereof |
| CN105239013A (en) * | 2015-08-11 | 2016-01-13 | 首钢总公司 | Axle housing steel for cold-machining formation and manufacturing method of axle housing steel |
| CN105239013B (en) * | 2015-08-11 | 2017-07-18 | 首钢总公司 | A kind of cold machine-shaping axle housing steel and its manufacture method |
| CN106636890A (en) * | 2016-11-11 | 2017-05-10 | 武汉钢铁股份有限公司 | Thin hot-rolled sheet steel for direct thermal forming and manufacturing method of thin hot-rolled sheet steel |
| CN108754318A (en) * | 2018-06-04 | 2018-11-06 | 包头钢铁（集团）有限责任公司 | The manufacturing method of 550MPa level steel plates and 550MPa level steel plates |
| CN108754318B (en) * | 2018-06-04 | 2020-06-02 | 包头钢铁（集团）有限责任公司 | 550 MPa-grade steel plate and manufacturing method of 550 MPa-grade steel plate |
| CN111235460A (en) * | 2020-02-12 | 2020-06-05 | 首钢集团有限公司 | Axle housing steel suitable for induction heating and production method thereof |
| CN111235460B (en) * | 2020-02-12 | 2021-08-17 | 首钢集团有限公司 | Axle housing steel suitable for induction heating and production method thereof |
| CN113416902A (en) * | 2021-06-30 | 2021-09-21 | 宝武集团鄂城钢铁有限公司 | Low-cost thermal-forming axle housing steel plate with yield strength of 460MPa and preparation method thereof |
| CN113416902B (en) * | 2021-06-30 | 2022-06-14 | 宝武集团鄂城钢铁有限公司 | Low-cost thermal-forming axle housing steel plate with yield strength of 460MPa and preparation method thereof |
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Application publication date: 20111130 |