CN104195429B - Low yield strength ratio low-crackle sensitive Q550CF quenched and tempered steel and production method - Google Patents
Low yield strength ratio low-crackle sensitive Q550CF quenched and tempered steel and production method Download PDFInfo
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Abstract
A kind of low yield strength ratio low-crackle sensitive Q550CF quenched and tempered steel and production method, belong to steel material technical field.Chemical composition is, C:0.07% ~ 0.09%; Si:0.10% ~ 0.40%; Mn:1.60% ~ 1.80%; Nb:0.04% ~ 0.06%; V:0.040% ~ 0.06%; Ti:0.010% ~ 0.030%; Alt:0.015% ~ 0.035%; B:0.0010% ~ 0.0020%; P :≤0.015%; S :≤0.010%; Carbon equivalent Ceq (%) scope: 0.34 ~ 0.40; Welding crack sensibility refers to Pcm (%) scope: 0.16 ~ 0.20; All the other are Fe and inevitable impurity.Technique comprises: blast-melted → molten iron pre-desulfurization → converter smelting → LF+RH refining → sheet billet continuous casting → heating of plate blank → 4300 mill milling → ACC cools → cooling in heap → quenching → tempering → sampling, inspection → warehouse-in, shipping fast.Advantage is, stable mechanical property, has good intensity, plasticity, toughness, excellent welding property, meets Low Crack Sensitivity Steel design requirements completely; Meanwhile, this Q550CF steel has lower and stable yield tensile ratio 0.68≤yield tensile ratio≤0.78.
Description
Technical field
The invention belongs to steel material technical field, particularly relate to a kind of low yield strength ratio low-crackle sensitive Q550CF quenched and tempered steel and production method, be applicable to steel for engineering machinery field.
Background technology
At present, along with the fast development of national economy, the state of the art of the Infrastructure such as engineering machinery, bridge, building improves constantly, and its intensity to structural steel, toughness, plasticity and welding property etc. require more and more higher.But along with intensity rank improves, the danger of structure generation brittle failure increases.
Generally, the yield strength of material and tensile strength present positively related relation (yield tensile ratio is yield strength and tensile strength ratio).Dependency structure steel standards and design, while constantly revising strength of materials rank, also carries out strict restriction to Ductility Indexes such as toughness, plasticity and yield tensile ratios.Experimental study and engineering practice all show, yield tensile ratio is an important mechanical performance index of relational structure security.Yield tensile ratio is higher, namely yield strength and tensile strength spacing too small, material deforms shortly can rupture.But the material that yield tensile ratio is low, easily produces viscous deformation under external broach effect, because its tensile strength is high, material can not rupture easily.Therefore viscous deformation can as the sign of fracture, the time arriving fracture is longer, and the security of material is higher.For ensureing the security of structure design, requiring that material has enough viscous deformation before breaking, namely requiring that material has low yield tensile ratio.
Low welding crack sensibility high-strength steel welds when not preheating or low preheating and does not occur crackle, is called CF (CrackFree) steel in the world.The principal feature of this type of steel has low Pcm value, low-carbon-equivalent, excellent welding property, has the features such as low carbon content, high strength, high tenacity simultaneously; Its main production process generally has TMCP, TMCP+ tempering or modified (quenching+tempering).
TMCP or " TMCP+ tempering " high strength CF steel, organization type is acicular ferrite or ferrite bainite, yield tensile ratio higher (generally between 0.88 ~ 0.93).As yield tensile ratio will be reduced, the cooling rate after steel plate controlled rolling need be reduced to obtain the granular bainite of some amount, but its intensity and low-temperature flexibility there is the trend of reduction.Modified high strength CF steel, the organization type after tempering is tempered sorbite, and yield tensile ratio is higher (generally between 0.90 ~ 0.95) also; Meanwhile, in order to ensure quenched and tempered steel hardening capacity, under the prerequisite suitably improving C content, generally need to add the alloying elements such as Ni, Cr, Mo, Cu, the raising of C content and the interpolation of alloying element, increase Pcm index and carbon equivalent Ceq value, have a negative impact to the welding property of material.
Documents 1, the Chinese invention patent " high-strength steel of low-carbon low-welding crack-sensitive, steel plate and manufacture method thereof " that application number is " 200910046442.9 " discloses a kind of yield strength and reaches 700Mpa to 800Mpa maximum ga(u)ge specification 60mm low welding crack sensitivity steel, 0.10% ~ 0.40% precious alloy Mo is added in its Composition Design, add the alloying element such as Ni, Cr, Cu that other content does not wait simultaneously, adopt hardening and tempering process (quench hot+high tempering), manufacturing cost is obviously higher; Meanwhile, 20mm ~ 60mm specification Low Crack Sensitivity Steel yield tensile ratio manufactured in the example is generally between " 0.90 ~ 0.97 ", and yield tensile ratio is higher, greatly reduces materials'use security.
Documents 2, application number is that the Chinese invention patent " a kind of low-welding crack-sensitive quenched and tempered high tensile strength plate and manufacture method thereof " of " 200810224730.4 " discloses a kind of tensile strength 610Mpa water-power steel, the same with patent 1, the precious alloy such as 0.10% ~ 0.20%Mo and 0.30% ~ 0.50%Ni is still added in its Composition Design, adopt normal hardening and tempering process, cost is also obviously higher; And the yield tensile ratio of 12mm specification steel plate involved in the example is more than 0.85, and tensile strength rank is only 610MPa rank.
Documents 3, application number discloses a kind of manufacture method of tensile strength 780Mpa level low yield strength ratio steel plate for the Chinese invention patent of " 200710042357.6 " " has low yield ratio HT 780 steel plate and the manufacture method thereof of superior weldability ", the precious alloys such as more Cr, Ni, Mo, Cu are added in its component system, take strict restriction to " Mn/C " ratio, " Ti/N " ratio, " Ni/Cu " ratio etc., Composition Design is complicated; Adopt " normalizing+tempering " explained hereafter, operation is also more.Alloy is many, operation is many, causes its manufacturing cost high, not easily promotes and guiding actual production.
Documents 4, application number is the manufacture method that the Chinese invention patent " a kind of high strength low yield ratio welding structure steel and production method " of " 200910061106.1 " discloses a kind of tensile strength 550Mpa ~ 700Mpa level low yield strength ratio steel plate, the alloys such as more Mn, Si, Cr, Ni, Mo, Cu are added in its component system, and alloy composition " [Mn%]+[Cr%]=2.20% ~ 2.80% " limits, and low-crackle sensitive indices P cm higher (the highest to 0.30%), require also very strict to the operation of rolling; In process of cooling, adopt and cool stage by stage; Finally carry out stress-removal tempering, production process more complicated, cost is not low yet.
Documents 5, the Chinese invention patent " yield strength 460MPa level super-thick steel plate for low yield ratio buildings and manufacture method " that application number is " 200910089346.2 " provides a kind of 80mm and above specification super-thick steel plate manufacture method thereof, the carbon of 0.16% is added in alloy system, do not belonged to low-crackle sensitive CF steel category, its carbon equivalent Ceq is greater than 0.40%; Meanwhile, its yield strength is only 440Mpa, and belongs to construction(al)steel field.
The present invention is in conjunction with Qinhuangdao Shou Qin metallic substance company (hereinafter referred to as " Shou Qin company ") existing tooling device advantage and strict technical process control, appropriate design modified CF composition of steel system, under the prerequisite of not adding any precious alloy Ni, Mo, Cr, Cu, adopt low C, high Mn, suitable interpolation microalloy element Nb, V, Ti and micro-B, by two-stage control rolling, roll the ultrafast cold quick cooling of rear use UFC and subsequent heat treatment operation, successfully produce the modified CF steel of low yield strength ratio low-welding crack-sensitive.
Summary of the invention
The object of the present invention is to provide a kind of low yield strength ratio low-crackle sensitive Q550CF quenched and tempered steel and production method.
The chemical composition of steel of the present invention is (weight percent), C:0.07% ~ 0.09%; Si:0.10% ~ 0.40%; Mn:1.60% ~ 1.80%; Nb:0.04% ~ 0.06%; V:0.040% ~ 0.06%; Ti:0.010% ~ 0.030%; Alt:0.015% ~ 0.035%; B:0.0010% ~ 0.0020%; P :≤0.015%; S :≤0.010%; Carbon equivalent Ceq (%)=C+Mn/6+ (Cr+Mo+V)/5+ (Ni/+Cu)/15, and Ceq (%) scope: 0.34 ~ 0.40; Welding crack sensibility refers to Pcm (%)=C+Si/30+Mn/20+Cu/20+Cr/20+Ni/60+Mo/15+V/10+5B, and Pcm (%) scope: 0.16 ~ 0.20; All the other are Fe and inevitable impurity.
Q550CF of the present invention modified engineering machinery steel production method is as follows:
Adopt conventional smelting and slab production method, its operation is as follows: desulfurizing iron is skimmed → converter smelting → LF stove refining → RH vacuum-treat → slab casting; In smelting process, strictly control C, P, S composition ensure that carbon equivalent Ceq and welding crack sensibility refer to that Pcm is in span of control; In slab casting cycle, control casting billet surface and internal soundness, for follow-up steel plate rolling creates conditions.
Heating of plate blank: adopt walking beam heating furnace by heating of plate blank to design temperature (between 1160 DEG C ~ 1220 DEG C), and conservative control and slab time inside furnace (between 220min ~ 400min), to ensure the abundant austenitizing of slab.
Steel plate rolling and cooling: in the operation of rolling, adopt controlled rolling (two-phase control rolling-recrystallization zone and the rolling of non-recrystallization zone) and controlled cooling model (UFC is ultrafast cold); Rolling end temp in recrystallization zone is between " 950 DEG C ~ 1000 DEG C "; Steel plate treats that temperature thickness sets by " 2 ~ 4 times of finished steel plate thickness "; The rolling of non-recrystallization zone starts temperature between " 860 DEG C ~ 900 DEG C ", and its end temp is between " 810 DEG C ~ 830 DEG C ".Enter the ultrafast cold radiator cooler of UFC after steel plate rolling fast to cool; Steel plate enters water temp and controls by " 800 DEG C ~ 770 DEG C ", and final cooling temperature controls by " 0 DEG C ~ 100 DEG C ", and cooling rate sets by " 25 DEG C/S ~ 40 DEG C/S ".Utilize the ultrafast cool equipment advantage of Shou Qin company UFC, carry out " large cooling rate, comparatively low temperature " cooling, steel plate is as cold as lower temperature, under the prerequisite obtaining required microtexture (ferrite bainite) and performance, improves the cooling uniformity of steel plate transverse and longitudinal further.
Heat treatment step: carry out quenching and tempering process at the modified line of Shou Qin company 4300mm Wide and Thick Slab; In heat treatment process, reasonable set quenching temperature (between 800 DEG C ~ 880 DEG C) and soaking time (between 10min ~ 30min); After steel plate quenching process, carry out temper, tempering temperature and soaking time are respectively " 400 DEG C ~ 500 DEG C " and " 5min ~ 50min ".
By above technical process, the modified steel for engineering machinery stable mechanical property of low yield strength ratio low-crackle sensitive Q550CF produced, there is good intensity, plasticity, toughness, and there is excellent welding property, while meeting modified Q550CF rigidity mechanical property requirements, also meet Low Crack Sensitivity Steel design requirements completely.Meanwhile, the yield tensile ratio of modified rear steel plate is lower, and materials'use safety coefficient is high.Its every mechanical performance index: 565MPa≤Rp0.2 (yield strength)≤620MPa, 750MPa≤Rm (tensile strength)≤830MPa, 18.0%≤A (elongation after fracture)≤22.5%, 165J≤-20 DEG C-AKv (-20 DEG C of impact values)≤255J, 110J≤-40 DEG C-AKv (-40 DEG C of impact values)≤180J; 0.68≤yield tensile ratio≤0.78.
Accompanying drawing explanation
Fig. 1 is that embodiment 20mm specification steel plate rolls state metallographic structure.
Fig. 2 is that embodiment 25mm specification steel plate rolls state metallographic structure.
Fig. 3 is the metallographic structure of embodiment 20mm specification steel plate quenching state.
Fig. 4 is the metallographic structure of embodiment 20mm specification steel plate tempering state.
Fig. 5 is the metallographic structure of embodiment 25mm specification steel plate quenching state.
Fig. 6 is the metallographic structure of embodiment 25mm specification steel plate tempering state.
Embodiment
According to the chemical composition ranges requirement of the present invention's " modified engineering machinery steel of a kind of low yield strength ratio low-crackle sensitive Q550CF ", steel billet smelting, slab casting (slab specification-thickness * width * length: 250mm × 2000mm ~ 2400mm × 2700mm ~ 4100mm) and steel plate rolling (rolling specs-thickness * width * length: 20mm/25mm*2500mm*24000mm, 2 scale rollings), quenching and tempering process is completed in Shou Qin company " 4300mm Heavy Plate Rolling Line ".
In this example, the actual chemical composition of Q550CF steel is as shown in table 1:
Table 1 chemical composition (wt%)
| Numbering | C | Si | Mn | P | S | Alt | V | Nb | Ti | B | Ceq | Pcm |
| 1# | 0.07 | 0.30 | 1.65 | 0.011 | 0.005 | 0.028 | 0.051 | 0.048 | 0.017 | 0.0015 | 0.36 | 0.18 |
| 2# | 0.09 | 0.32 | 1.78 | 0.009 | 0.006 | 0.031 | 0.045 | 0.056 | 0.015 | 0.0017 | 0.40 | 0.20 |
This example rolling technological parameter arranges in table 2:
Table 2 rolling technological parameter is arranged
Note: thickness unit-mm; Temperature unit-DEG C; Speed of cooling-DEG C/S
This example quenching technology is as shown in table 3:
Table 3 quenching temperature and soaking time
| Steel plate thickness/mm | Quenching temperature/DEG C | Soaking time/min |
| 20 | 850 | 8 |
| 25 | 830 | 12 |
This example tempering process is as shown in table 4:
Table 4 tempering Heating temperature and soaking time
| Steel plate thickness/mm | Tempering temperature/DEG C | Soaking time/min |
| 20 | 450 | 20 |
| 25 | 400 | 25 |
The every mechanical property of this example steel plate and yield tensile ratio as shown in table 5:
The every mechanical property of table 5 steel plate and yield tensile ratio
Claims (2)
1. a low yield strength ratio low-crackle sensitive Q550CF quenched and tempered steel, is characterized in that, chemical component weight percentage ratio is, C:0.07% ~ 0.09%; Si:0.10% ~ 0.40%; Mn:1.60% ~ 1.80%; Nb:0.04% ~ 0.06%; V:0.040% ~ 0.06%; Ti:0.010% ~ 0.030%; Alt:0.015% ~ 0.035%; B:0.0010% ~ 0.0020%; P :≤0.015%; S :≤0.010%; Carbon equivalent Ceq% scope: 0.34 ~ 0.40; Welding crack sensibility refers to Pcm% scope: 0.16 ~ 0.20; All the other are Fe and inevitable impurity;
The mechanical property of this steel is: 565MPa≤Rp0.2≤620MPa, 750MPa≤Rm≤830MPa, 18.0%≤A≤22.5%, 165J≤-20 DEG C-AKv≤255J, 110J≤-40 DEG C-AKv≤180J, 0.68≤yield tensile ratio≤0.78.
2. a production method for low yield strength ratio low-crackle sensitive Q550CF quenched and tempered steel described in claim 1, technique comprises desulfurizing iron skims → converter smelting → LF stove refining → RH vacuum-treat → slab casting; It is characterized in that, the technical parameter controlled in technique is as follows:
In smelting process, strictly control C, P, S composition ensure carbon equivalent Ceq (%) scope: 0.34 ~ 0.40; Welding crack sensibility refers to Pcm (%) scope: 0.16 ~ 0.20;
Heating of plate blank: adopt walking beam heating furnace by heating of plate blank to 1160 DEG C ~ 1220 DEG C, and control between slab time inside furnace 220min ~ 400min, ensure slab austenitizing;
Steel plate rolling and cooling: in the operation of rolling, adopt controlled rolling: two-phase control rolling-recrystallization zone and the rolling of non-recrystallization zone, controlled cooling model: UFC is ultrafast cold; Rolling end temp in recrystallization zone is between 950 DEG C ~ 1000 DEG C; Steel plate treats that temperature thickness sets by 2 ~ 4 times of finished steel plate thickness; The rolling of non-recrystallization zone starts temperature between 860 DEG C ~ 900 DEG C, and its end temp is between 810 DEG C ~ 830 DEG C; Enter the ultrafast cold radiator cooler of UFC after steel plate rolling to cool; Steel plate enters water temp by 800 DEG C ~ 770 DEG C controls, and final cooling temperature is by 0 DEG C ~ 100 DEG C controls, and cooling rate is undertaken by 25 DEG C/S ~ 40 DEG C/S; Obtain required microtexture ferrite bainite;
Heat treatment step: carry out quenching and tempering process at the modified line of 4300mm Wide and Thick Slab; In heat treatment process, between quenching temperature 800 DEG C ~ 880 DEG C, between soaking time 10min ~ 30min; After steel plate quenching process, carry out temper, tempering temperature is: 400 DEG C ~ 500 DEG C, and soaking time is 5min ~ 50min.
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| CN109136747A (en) * | 2018-08-01 | 2019-01-04 | 舞阳钢铁有限责任公司 | The quenched thin plate of 8mm thickness Q690 intensity rank low yield strength ratio and production method |
| CN108941494B (en) * | 2018-09-25 | 2020-07-07 | 湖南华菱湘潭钢铁有限公司 | Hot-feeding and hot-charging process for medium-thickness plate continuous casting billet |
| CN112210649B (en) * | 2020-09-25 | 2022-06-28 | 邯郸钢铁集团有限责任公司 | Flexible control method for yield ratio of high-strength steel |
| CN114182165A (en) * | 2021-10-29 | 2022-03-15 | 南京钢铁股份有限公司 | Low-yield-ratio high-toughness Q500qE bridge steel and production method thereof |
| CN115433873B (en) * | 2022-08-31 | 2024-04-19 | 鞍钢股份有限公司 | E-grade flat bulb steel with economy and excellent strength and toughness and production method thereof |
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Address after: 066326 Du Zhuang Township, Funing County, Qinhuangdao, Hebei Co-patentee after: Shougang Group Co. Ltd. Patentee after: Qinhuangdao Shouqin Metal Material Co., Ltd. Address before: 066326 Du Zhuang Township, Funing County, Qinhuangdao, Hebei Co-patentee before: Capital Iron & Steel General Company Patentee before: Qinhuangdao Shouqin Metal Material Co., Ltd. |
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Effective date of registration: 20190528 Address after: 100041 Shijingshan Road, Shijingshan District, Shijingshan District, Beijing Patentee after: Shougang Group Co. Ltd. Address before: 066326 Du Zhuang Township, Funing County, Qinhuangdao, Hebei Co-patentee before: Shougang Group Co. Ltd. Patentee before: Qinhuangdao Shouqin Metal Material Co., Ltd. |