CN102400040B - Production method of low-carbon bainite steel hot-rolled strip used in low-temperature - Google Patents
Production method of low-carbon bainite steel hot-rolled strip used in low-temperature Download PDFInfo
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- CN102400040B CN102400040B CN201010276431.2A CN201010276431A CN102400040B CN 102400040 B CN102400040 B CN 102400040B CN 201010276431 A CN201010276431 A CN 201010276431A CN 102400040 B CN102400040 B CN 102400040B
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Abstract
The invention provides a low-carbon bainite steel hot-rolled strip used in low-temperature, and a production method thereof. The bainite steel hot-rolled strip comprises elements of: 0.03%-0.07% of C, 0.10%-0.30% of Si, 1.50%-1.90% of Mn, no higher than 0.015% of P, no higher than 0.003% of S, 0.06%-0.08% of Nb, 0.005%-0.018% of Ti, 0%-0.30% of Mo, 0%-0.20% of Ni, 0%-0.24 of Cu, and 0.015%-0.040% of Alsoul. The production method comprises steps of: medium thin slab casting, low-temperature feeding and heating, rough rolling, soaking, fine rolling, laminar cooling, reeling, and air-cooling. The feeding temperature is 300 to 700 DEG C. The heating temperature is 1150 to 1180 DEG C. The slab is roughly rolled into an intermediate slab with a thickness of 55-60mm through 3-5 times of rough rolling, and are soaked to 950 to 900 DEG C. The intermediate slab is then finely rolled into a hot-rolled plate with a thickness of 11-19mm. The hot-rolled plate is cooled to 450 to 550 DEG C with a speed of 10-25 DEG C/s, and is reeled. According to the invention, a small amount or no Mo, Ni, or Cu element is added, the cost is low, and the production period is short. The yield strength of the hot-rolled strip is above 500MPa, and the impact power of the hot-rolled strip is above 260J under a temperature of -60 DEG C.
Description
Technical field
The invention belongs to metallic substance technical field, relate in particular to a kind of low-temperature-used low carbon bainite steel hot-rolled coil and production method thereof.
Background technology
Low-carbon bainite steel becomes new steel grade in recent decades with its high strength, high tenacity and excellent weldability, also be referred to as environment-friendly steel grade, be widely used in the fields such as long-distance transport pipes, engineering machinery, bridge, pressurized vessel, naval vessel, freight container.Low-carbon bainite steel has adopted low-carbon (LC), the compound Composition Design that adds alloy and microalloy element, and by two-stage control rolling, roll rear cooling, lower final cooling temperature or low temperature fast and batch, obtain tiny, uniform bainite structure, guaranteed the matched well of its intensity and toughness.Its strengthening mechanism comprises solution strengthening, refined crystalline strengthening, dislocations strengthening, precipitation strength etc.
Along with the fast development of world economy, low-carbon bainite steel is widely used.Meanwhile, various industrial circles also improve constantly the requirement of low-carbon bainite steel.Iron and steel enterprise has developed some high strength low carbon bainibic steel hot-rolled sheets both at home and abroad, and produce to reduce production costs by new technologies such as thin slab continuous rolling process, such as publication number is the Chinese patent disclosed " producing the method for low-carbon bainite high-strength steel based on bar strip continuous casting and rolling flow path " of CN101254527A (comparative example 1), its content relates to and has high strength low carbon bainibic steel, be characterized in: 1. by CSP, produce hot-rolled coil, energy consumption is less; 2. product thickness only has 3～12mm, belongs to thinner low-carbon bainite roll bending; 3. intensity is higher, reach 650MPa (the thick roll bending of 4.8mm), but its low temperature impact properties is not mentioned.
Guaranteeing that under the prerequisite of higher-strength, low-carbon bainite steel hot-rolled sheet also should have good low-temperature flexibility, to adapt to military service needs of low temperature environment, as cold zone military service pipeline, bridge, pressurized vessel etc.For this reason, a lot of iron and steel enterprises have carried out high strength and have had the development of the low-carbon bainite steel of good low-temperature toughness.For example publication number is the Chinese patent disclosed " a kind of high strength low-temperature-used low carbon bainite steel and production technique thereof " of CN101338400A (comparative example 2), its content relates to the low-carbon bainite steel with high strength and good low-temperature toughness, be characterized in: the flat board that the thickness of 1. producing by plate mill is 12～30mm, continuous casting steel billet reheats after need rolling off the production line, and energy consumption is larger; 2. after rolling, need tempering, process cost is higher; 3. the following dull and stereotyped the highest mean value of ballistic work at-40 ℃ of 16mm is 250J (258J, 256J, 238J).
Summary of the invention
The object of the invention is to reach compared with the problem that the temperature drift of HI high impact merit, production process are long, process costs is higher for prior art is existing, a kind of low-carbon bainite steel hot-rolled coil and production method thereof with good low-temperature toughness that adopts medium thin slab continuous casting and rolling explained hereafter is provided
The present invention realizes like this, the chemical composition of this low-temperature-used low carbon bainite steel hot-rolled coil (weight percent) is as follows: C:0.03%～0.07%, Si:0.10%～0.30%, Mn:1.50%～1.90%, P≤0.015%, S≤0.003%, Nb:0.06%～0.08%, Ti:0.005%～0.018%, Mo:0%～0.30%, Ni:0%～0.20%, Cu:0%～0.24%, Al
soul: 0.015%～0.040%.
In the present invention, the design of main chemical elements be the reasons are as follows:
C: be strengthening element the most basic in steel, can produce strong solution strengthening and certain precipitation strength effect in steel.But carbon content is too high, can have a negative impact to low-temperature flexibility and welding property.Therefore the carbon content in the present invention is 0.03～0.07%, to guarantee that low-carbon bainite steel has good low-temperature flexibility and welding property.
Mn: there is strong solution strengthening effect, also, because reducing the ferrite crystal grain after γ-α transformation temperature refinement phase transformation, also can compensate C simultaneously and reduce the loss of strength causing.But Mn too high levels, also can cause component segregation and microstructure segregation, thereby low-temperature flexibility is had a negative impact, so the Mn content in the present invention is 1.50～1.90%.
Nb: be the topmost micro alloying element adding in modern high strength microalloy steel.Stop when reheating and in Austenite Grain Growth, deformation process, suppress recrystallize and reduce transformation temperature to produce obvious Grain Refinement Effect.In addition, also can produce certain precipitation strength, phase transformation strengthening.Nb content in the present invention is 0.06～0.08%.
Ti: the Ti in steel and N have very strong avidity, is easy to form nitride.While adding 0.005～0.020% Ti in steel, can be when continuous casting in slab is inner, form stable and tiny TiN, stop slab reheat with welding process in the growing up of austenite crystal, be conducive to improve the low-temperature flexibility of steel.Ti content in the present invention is 0.005～0.018%.
Mo: the hardening capacity that can effectively improve steel.Suppress consumingly the formation of proeutectoid ferrite, promote the formation of acicular ferrite.But Mo is expensive, in the present invention, only in the low-carbon bainite hot-rolled coil of thick specification, add, the low-carbon bainite hot-rolled coil of producing thin specification makes up the deficiency of hardening capacity by improving speed of cooling.Therefore the Mo content in the present invention is 0～0.30%.
Cu and Ni:Cu and Ni play certain solution strengthening effect in steel, also can improve the hardening capacity of steel.In addition, Cu has certain anti-corrosion effect after adding in steel.The red brittleness easily causing in steel for improving Cu, generally adds in the steel of Cu and adds certain Ni.The price of Cu and Ni is also more expensive, therefore the present invention only adds when producing thick specification low-carbon bainite hot-rolled coil.Cu content of the present invention is that 0～0.24%, Ni content is 0～0.20%.
The composition contrast of the present invention and prior art is in Table 1.
The composition contrast (wt%) of table 1 the present invention and prior art
The production method of low-temperature-used low carbon bainite steel hot-rolled coil of the present invention, it is characterized in that comprising the thick medium thin slab → low temperature of following processing step: medium and thin slab continuous caster → 130～170mm pack into process furnace → roughing mill → treat temperature → finishing mill → laminar flow cooling → batch → air cooling, slab charging temperature is 300～700 ℃, Heating temperature is 1150～1180 ℃, slab becomes the intermediate blank of 55～60mm through 5 passage roughing, intermediate blank is after temperature is to 950～900 ℃, entering finishing mill carries out 6 passages and is rolled into the hot-rolled sheet that 11～19mm is thick, and entering fast laminar flow cooling zone, with the speed of cooling of 10～25 ℃/s, to carry out laminar flow cooling, being cooled to 450～550 ℃ batches.
The present invention adopt medium thin slab continuous casting and rolling production technique to produce to have good low-temperature toughness low-carbon bainite steel hot-rolled coil according to being: low-carbon (LC) is designed with and is beneficial to low-temperature flexibility, reaches tissue and the performance of expectation by alloying/micro alloying element and technology controlling and process simultaneously.130～170mm continuous casting steel billet enters and reheats with the temperature of 300～700 ℃, has both been conducive to save energy, can utilize again austenitic twice phase transformation to obtain tiny austenite.By control, reheat temperature (1150～1180 ℃), can make most of Nb solid solution, also can obtain the relatively tiny austenite (≤150 μ m) that reheats.In rough rolling process, reheat austenite by recrystallization softening, after temperature, below non-recrystallization temperature, enter finish rolling rolling, in the austenite of recrystallization softening, produce Strain Accumulation, for tissue after obtaining tiny phase transformation provides favourable condition.Roll the middle temperature transformation tissue that rear cooling, lower coiling temperature fast and solid solution Nb (with the Ni and the Cu that add in larger thickness of slab situation) are conducive to obtain tiny, uniform high bit dislocation density, the yield strength of final hot-rolled coil is more than 500MPa, and the ballistic work of-60 ℃ is more than 260J.
The alloy designs of the present invention by optimizing, meticulously control crystal grain in whole TMCP technological process (austenite and ferrite), finally obtain tiny, take acicular ferrite uniformly as main microstructure.This alloy designs and technique are to adopt low-carbon (LC) and Nb-Ti microalloy to design, by refined crystalline strengthening and appropriate dislocations strengthening, obtain higher intensity and good low-temperature flexibility.By contrast, the low-carbon bainite steel that some produce on plate mill is dull and stereotyped, and the technique of rear tempering is rolled in some employings.This technique can be by the further raising yield strength of separating out of micro alloying element, but precipitation strength is unfavorable for low-temperature flexibility.
Low-temperature-used low carbon bainite steel hot-rolled coil of the present invention is according to a small amount of interpolation of final thickness or do not add Mo, Ni, Cu alloying element, by production control technique, can obtain tiny, uniform final tissue,-60 ℃ of ballistic works make more than the yield strength of hot-rolled coil reaches 500MPa, more than can reach 260J.Adopt medium thin slab continuous casting and rolling technique, can produce the low-carbon bainite steel thicker than CSP, by 300～700 ℃ of low temperature shove charges, not only can save mass energy, reduce the production cycle, also can obtain tiny austenite the same as conventional hot continuous rolling machine, be conducive to the refinement of final tissue and the low-temperature flexibility of product.
Accompanying drawing explanation
Fig. 1～Fig. 4 is respectively the metallographic structure of the embodiment of the present invention 1～4.
Embodiment
The present invention is further described by the following embodiment.
The embodiment of the present invention is utilized medium thin slab, by hot charging, roughing, treat temperature, finish rolling, laminar flow is cooling and coiling technique is produced the low-carbon bainite steel hot-rolled coil of 11.4mm, 13.7mm, 14.3mm and tetra-kinds of specifications of 17.5mm, is also embodiment 1～4.The chemical composition of the embodiment of the present invention is in Table 2, and main technologic parameters is in Table 3, and final mechanical property is in Table 4.
The chemical composition of table 2 embodiment of the present invention (%)
The main technologic parameters of table 3 embodiment of the present invention
The mechanical property of table 4 embodiment of the present invention
Claims (2)
1. the production method of a low-temperature-used low carbon bainite steel hot-rolled coil, the chemical component weight per-cent that it is characterized in that this roll bending is: C0.03%～0.07%, Si0.10%～0.30%, Mn1.50%～1.90%, P≤0.015%, S≤0.003%, Nb0.06%～0.08%, Ti0.005%～0.018%, Mo0%～0.30%, Ni0%～0.20%, Cu0%～0.24%, Al
s0.015%～0.040%, surplus is Fe and inevitable impurity; Comprise following processing step: continuous casting of middle-thin slabs, low temperature shove charge heating, roughing, treat that temperature, finish rolling, laminar flow are cooling, batch, air cooling, described slab charging temperature is 300～700 ℃, Heating temperature is 1150～1180 ℃, slab becomes the intermediate blank of 55～60mm through 3～5 passage roughing, after temperature is to 950～900 ℃, finish rolling becomes the hot-rolled sheet that 11～19mm is thick, and it is cooling with the speed of cooling of 10～25 ℃/s, to carry out laminar flow, and coiling temperature is 450～550 ℃.
2. the production method of low-temperature-used low carbon bainite steel hot-rolled coil according to claim 1, the thickness that it is characterized in that described medium thin slab is 130～170mm.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102899562B (en) * | 2012-10-29 | 2014-08-27 | 首钢总公司 | Complex phase-type high-strength low-carbon bainitic medium and heavy steel plate and production method thereof |
| CN108330399A (en) * | 2018-01-09 | 2018-07-27 | 唐山钢铁集团有限责任公司 | A kind of low-cost and high-performance bridge steel and its production method |
| CN108486473B (en) * | 2018-05-14 | 2020-01-14 | 武汉钢铁有限公司 | Low-yield-ratio sulfide stress corrosion resistant 345 MPa-grade steel plate for low-temperature pressure container and preparation method thereof |
| CN109234613A (en) * | 2018-08-24 | 2019-01-18 | 包头钢铁（集团）有限责任公司 | The production method of hot-rolled coil and hot-rolled coil |
| CN111057954A (en) * | 2020-01-02 | 2020-04-24 | 鞍钢股份有限公司 | High-strength pipeline rolled plate for large thick wall acidity and manufacturing method thereof |
| CN116043112A (en) * | 2023-01-10 | 2023-05-02 | 安阳钢铁股份有限公司 | 500 MPa-grade bridge steel suitable for earthquake resistance in extremely cold areas and preparation process thereof |
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| CN101130846A (en) * | 2006-08-24 | 2008-02-27 | 鞍钢股份有限公司 | Phase-change induced plastic steel plate by continuous casting and rolling middle bar strip and manufacturing method thereof |
| CN101161847A (en) * | 2006-10-13 | 2008-04-16 | 鞍钢股份有限公司 | High-ductility steel for hot-bending bends and production method for hot rolled plates thereof |
| CN101254527A (en) * | 2008-02-01 | 2008-09-03 | 湖南华菱涟源钢铁有限公司 | Method for producing low carbon bainite high-strength steel based on sheet bar continuous casting and rolling process flow |
| CN101338400A (en) * | 2008-08-18 | 2009-01-07 | 南京钢铁股份有限公司 | High strength low-temperature-used low carbon bainite steel and production process thereof |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101130846A (en) * | 2006-08-24 | 2008-02-27 | 鞍钢股份有限公司 | Phase-change induced plastic steel plate by continuous casting and rolling middle bar strip and manufacturing method thereof |
| CN101161847A (en) * | 2006-10-13 | 2008-04-16 | 鞍钢股份有限公司 | High-ductility steel for hot-bending bends and production method for hot rolled plates thereof |
| CN101254527A (en) * | 2008-02-01 | 2008-09-03 | 湖南华菱涟源钢铁有限公司 | Method for producing low carbon bainite high-strength steel based on sheet bar continuous casting and rolling process flow |
| CN101338400A (en) * | 2008-08-18 | 2009-01-07 | 南京钢铁股份有限公司 | High strength low-temperature-used low carbon bainite steel and production process thereof |
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