CN105420632B - A kind of Q690CF hot rolled steel plates and preparation method thereof - Google Patents
A kind of Q690CF hot rolled steel plates and preparation method thereof Download PDFInfo
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Abstract
A kind of Q690CF hot rolled steel plates and preparation method thereof, hot rolled steel plate chemical composition is by mass percentage：C:0.05~0.08%, Si:0.22~0.30%, Mn:1.6~2.0%, Al:0.2~0.35%, Cr:0.10~0.35%, Mo:0.20~0.35%, Ni:0.1~0.4%, Cu:0.15~0.3%, Nb:0.025~0.045%, V:0.01~0.03%, Ti:0.005~0.03%, P≤0.010%, S≤0.008%, surplus are Fe and inevitable impurity.Preparation method：Melting；Pretreatment；Hot rolling：Multi-pass roughing and finish rolling；Quick cooling.Hot rolled steel plate of the present invention, with high intensity, good low-temperature toughness and welding performance realize that without preheating is welded；Preparation cost is low, and technique is simple.
Description
Technical field
The invention belongs to high-strength steel production technology development field, more particularly to a kind of Q690CF hot rolled steel plates and its preparation
Method.
Background technology
In recent years, structural steelwork develops to maximization, lightweight, high parameterization, such as Longspan Bridge, large-scale water power
Stand, heavy engineering machinery etc..This requires that structural steel has higher intensity, more preferable toughness, plasticity and welding performance.Heavy construction
Construction uses high-tensile structural steel, it is meant that cost of material, lightening material weight can be reduced while high-load condition is met.
But, high-tensile structural steel often brings the reduction of toughness.In addition, for high-strength hardened and tempered steel, a large amount of alloying elements
Addition can severe exacerbation its welding performance.Especially under low_input_power amount, high-strength steel welded joint easily forms welding cold cracking
Line and the structural intergrity for destroying Engineering System.In order to prevent the formation of welding cold cracking, it is necessary to carry out weld preheating to steel plate
Processing, and weld crack sensitivity means that several Pcm are bigger, preheating temperature is higher.However, the increase of preheating procedure not only have impact on life
Efficiency, increase energy consumption are produced, and welding operating mode can be caused to be deteriorated, property of welded joint is unstable, or even can influence structural member
Safe military service performance.Therefore, it is great society, economic effect to develop a kind of low-welding crack-sensitive high-strength steel without preheating
Benefit.
With the development of thermomechanical control technology (TMCP) and micro-alloying technology, all kinds of high-level steel grades are closed using micro-
Aurification technology reduces alloying element total content, and armor plate strength is further improved with precipitation strength mechanism, using TMCP technologies thin
Change austenite crystal, the high dislocation density of deformed austeaite is conducive to improving the intensity of phase-change product, with reference to On-line accelerated cooling
(ACC) technique accurately controls microscopic structure to match, and the thought of ' with water for alloy ' can reduce alloying element content, significantly drop
Low cost of material, while also ensure that low-welding crack-sensitive index, improves the solderability of steel plate.
Low welding crack sensitivity steel, also known as CF (Crack Free) steel, is that a class has low-carbon-equivalent in the world, low
Pcm values, the excellent steel grade of welding performance, it is considered that do not preheat or low preheating condition under weld and also occur without crackle；In order to
Its intensity is further improved, needs also exist for using TMCP and micro-alloying technology；The iron and steel industry professional standards of YB/T 4137 are also advised
Its fixed supply of material state has TMCP, TMCP+ to be tempered or modifier treatment.
At present, some patents of invention on low welding crack sensitivity steel plate are had, but in these patents of invention often
The relatively low steel grade of intensity rank (such as yield strength is in 550MPa or so) has been pertained only to, has been generally required using extra heat treatment work
Skill improves its toughness, and this mode of production not only increases production cost, and reduces production efficiency.Single invention patent
The manufacture of yield strength 690MPa level hot rolled steel plates is also related to, but needs to add more B element, ' boron is crisp ' in its composition
Phenomenon is very difficult to expect and control.Now published Patents are carried out as described below.
Patent CN101476080A, CN101812634A, CN104195429A are employed roll after offline hardening and tempering process (quench
Fire+tempering) prepare low-welding crack-sensitive high strength steel plate, complex manufacturing, low production efficiency.Such as latter two patents institute
State, (be more than 700MPa) when target tensile strength is higher, composition design also needs to add a certain amount of B to improve quenching for steel plate
Permeability, it is ensured that its tensile strength.
Patent CN1932063A, CN101096738A, CN102888571A, which are employed, rolls rear high tempering (600~650
DEG C) technique, and tempering time is longer.Obviously, the same energy consumption of this mode of production is big, is unfavorable for improving production efficiency.In addition, this
Target steel grade yield strength rank involved by three patents is far below 690MPa.
For patent CN101481774A, CN101353759A, although the two patents all use TMCP technique systems
Standby low welding crack sensitivity steel, but steel grade yield strength rank involved by it is only 500MPa and 550MPa ranks.Patent
CN101418418A " 690MPa grades of low-crackle sensitive steels of yield strength and its manufacture method " relate to yield strength and be more than
It is most of to employ higher Nb (0.06~0.08%), high V in 690MPa high strength construction steel, but example component system
(0.04~0.12%), and with the addition of 0.001~0.002%B.High microalloy element content, adds somewhat to
Cost；B element is a kind of element of easy segregation, the crisp phase Fe of boron23(CB)6Precipitation the impact flexibility of steel plate can be caused unstable,
The B content of welding base metal is higher simultaneously, improves the hardenability of heat affected area, increases the tendentiousness of welding cold cracking formation.
From upper analysis, rarely patent is related to the low-welding crack sensitivity that yield strength is 690MPa ranks at present
The exploitation of property steel plate；However, under the growth requirement of the structural steel for welding such as large-scale engineering machinery, it is ensured that high strength steel plate it is solderable
Property and the safe military service performance of welding product are particularly critical, therefore, it is necessary to develop a kind of low welding of high-intensity high-tenacity
Crack sensitive steel.In order to solve this problem, the present invention will provide a kind of new composition design, using TMCP+ rapid cooling works
Skill prepares the low-welding crack-sensitive hot rolled steel plate of high comprehensive performance.
The content of the invention
In view of the shortcomings of the prior art, the invention provides a kind of Q690CF hot rolled steel plates and preparation method thereof.Based on many
First micro-alloying technology, chemical constituent reasonable in design, by two-stage control rolling and On-line accelerated cooling technology, is prepared
The excellent hot rolled steel plate of comprehensive mechanical property.
Q690CF steel refers to that yield strength is superior to 690MPa and the class steel grade with low-welding crack-sensitive.
The Q690CF hot rolled steel plates of the present invention, chemical composition is by mass percentage：C：0.05~0.08%, Si：0.22
~0.30%, Mn：1.6~2.0%, Al：0.2~0.35%, Cr：0.10~0.35%, Mo：0.20~0.35%, Ni：0.1
~0.4%, Cu：0.15~0.3%, Nb：0.025~0.045%, V：0.01~0.03%, Ti：0.005~0.03%, P≤
0.010%, S≤0.008%, surplus is Fe and inevitable impurity.
The Q690CF hot rolled steel plates of the present invention, welding crack sensibility indices P cm values are not more than 0.20%.
The area percentage of bainite type ferrite and acicular ferrite in the Q690CF hot rolled steel plates of the present invention, microscopic structure
Content >=90%, bainite and ferritic width of sheet are distributed in 0.1~0.7 μm.
The Q690CF hot rolled steel plates of the present invention, mechanical property is：750MPa >=yield strength (Rp0.2) >=690MPa,
940MPa >=tensile strength (Rm) >=810MPa, 22.5% >=elongation percentage (A) >=17%, 250J >=-20 DEG C impact absorbing energy
(Akv) >=180J, yield tensile ratio (Rp0.2/Rm)≤0.93.
The Q690CF hot rolled steel plates of the present invention, the thickness range of hot-rolled finished product steel plate is 12~25mm.
In the Q690CF hot rolled steel plates of the present invention, make detailed narration to chemical composition proportion design：
C：Topmost solid solution element in mild steel, in addition can super saturated solid solution in the bainite matrix of high dislocation density
In, play a part of solution strengthening；In addition, also combining to form the tiny precipitated phase of disperse with strong carboritride formation element, rise
To the effect of precipitation strength；But the increase of carbon content can substantially deteriorate the welding performance of steel, also be unfavorable for impact flexibility, therefore
Carbon content control is 0.05~0.08% in the present invention.
Si：It is one of important element of deoxidation in steel-making, ferrite matrix can be solid-solution in steel, solution strengthening is played
Effect, while can also suppress cementite precipitation, but excessive add can deteriorate plasticity, improve ductile-brittle transition temperature, therefore
The control of its content is 0.22~0.30%.
Mn：It is stable austenite element, can effectively reduces Ar3 temperature, promote bainitic transformation, refinement microstructure carries
High intensity and toughness can be improved to a certain extent, especially under the conditions of low-carbon, Mn solution strengthening effect is more notable.But Mn
Too high levels can reduce the toughness of steel, and be unfavorable for the cold cracking performance of anti-welding of steel, consider, and Mn contents are scheduled on 1.6~
2.0%.
Al：Important deoxidant element when being equally steel-making, can also reduce steel grade N content, form AlN and prevent austenite crystal
Grain roughening, but Al is when adding excessive, can influence plate surface quality, therefore its content should be 0.2~0.35%.
Cr、Mo：The quenching degree of steel can be improved, its displacement is solid-solution in ferrite, the effect of alternative Mn elements, it is multiple
Close addition and optimize its invigoration effect effect, but Cr, Mo can improve Pcm values, can excessively cause deteriorated weldability, while also can
Increase cost, therefore its content should be controlled 0.10~0.35%, 0.20~0.35% respectively.
Ni、Cu：Ni can significantly improve the low-temperature flexibility of steel, but its is expensive；Cu can play the effect of precipitation strength,
But easily cause crystal boundary fire check, the grain-boundary crack that the two compound addition can be eliminated caused by Cu can be simultaneously reached Strengthening and Toughening
Effect, its content is respectively 0.1~0.4%, 0.15~0.3%
Nb、V、Ti：Strong carboritride formation element is belonged to, Nb can improve the recrystallization final temperature of austenite,
Fining austenite grains size；Ti and N formation TiN, can effectively organize the roughening of austenite crystal, while can also improve mother
The impact flexibility of material welding heat affected zone；VC or V (CN) disperse educt can be with efficient hardening phase-change product phases；Three's is micro
Compound addition can produce ' co precipitation strengthening effect ', while improving the obdurability of steel plate, if too high levels, can be roughened precipitation
Mutually obdurability is caused to reduce, therefore its content is controlled in Nb respectively：0.025~0.045%, V：0.01~0.03%, Ti：
0.005~0.03% is optimum.
P、S：Belong to impurity element, easy segregation damages obdurability in crystal boundary, P, S content control of the present invention for P≤
0.010%, S≤0.008%.
Pcm：Welding crack sensibility indices P cm is to assess the important finger of steel grade solderability based on Design of Chemical Composition
Mark, Pcm is smaller, and the solderability of steel is better, it is considered that, when Pcm is not more than 0.20%, steel grade can be under not preheating condition
Welding will not also produce welding cold cracking.Under the premise of herein, optimization chemical composition proportioning can improve obdurability.
' competition ' is combined between the compound addition of polynary, micro strong carbonitride-forming elements (Nb, V, Ti), different elements
C, N atom and form tiny and disperse precipitated phase, the composite carbon nitrogen compound such as based on Nb or V, tiny precipitated phase
' pinning ' effect effectively hinders dislocation motion by force, hot rolled steel plate is played ' co precipitation reinforcing effect '；And if only individually addition
A certain microalloy element, the increase of its content will certainly be roughened precipitated phase, improve unobvious to intensity, and can deteriorate toughness；
Meanwhile, strong carboritride element and other substitutional elements, the compound addition of such as Mn, Mo are conducive to improving the quenching degree of steel plate,
Collaboration promotes bainitic transformation.
The preparation method of the Q690CF hot rolled steel plates of the present invention, hot-rolled steel is directly prepared using the quick cooling techniques of TMCP+
Plate, comprises the following steps：
Step 1, melting：
By Q690CF hot rolled steel plate chemical compositions, electric furnace or converter smelting, smelting temperature are 1550~1670 DEG C, and are cast
Into steel ingot or strand；
Step 2, pre-process：
By steel ingot or heating strand to 1150~1200 DEG C, 60~120min of soaking time；
Step 3, hot rolling：
Rolled using two-stage control：
The start rolling temperature of roughing is 1050~1120 DEG C, multi- pass rolling, and it is 45~60%, finish to gauge to add up percentage pass reduction
Temperature is 1000~1080 DEG C, obtains workpiece thickness for 40~75mm；
The start rolling temperature of finish rolling is 810~860 DEG C, multi- pass rolling, and it is 60~80%, finish to gauge temperature to add up percentage pass reduction
Degree is not less than 780 DEG C, obtains steel plate thickness for 12~25mm；
Step 4, quick cooling：
The type of cooling being accelerated using laminar flow, steel plate begins to cool down temperature and is not less than 750 DEG C, cooling velocity is 15~30 DEG C/
S, final cooling temperature is controlled between 350~500 DEG C, is then air-cooled to room temperature, is obtained finished product Q690CF hot rolled steel plates.
In above-mentioned steps 3, the finishing temperature of finish rolling is not less than 780 DEG C, is because significantly increasing in austenite by machinery
Entanglement dislocation density produced by deformation, is unfavorable for improving toughness, in addition, finishing temperature is too low to form strain induced ferrite
Tissue, reduces intensity；In step 4, steel plate begins to cool down temperature and is not less than 750 DEG C, is cooling velocity when just entering water because of steel plate
It is uneven cause it is local there is grain boundary ferrite tissue, destroy the uniformity for rolling rear mechanical property of steel plate.
Compared with prior art, the beneficial effects of the present invention are：
(1) Q690CF hot rolled steel plates of the invention, without B element, it is easy to ensure the uniform of hot rolled steel plate mechanical property
Property, while using the cooperative effect between alloying element, addition noble element as few as possible reduces cost of material.
(2) Q690CF hot rolled steel plates of the invention, are the low-welding crack Q690CF hot rolled steel plates of high-strength tenacity matching, heat
The stable mechanical property at each position of rolled steel plate, with high intensity, without preheating weldering can be achieved in good low-temperature toughness and welding performance
Connect, fully meet the welding demand of heavy construction structure；The harsh operating mode of the service conditions such as low temperature, heavy duty is can be applied to, is such as made
The components such as standby large-scale low-temperature oil storage tank, pressure steel pipe of hydropower station, mining machinery.
(3) preparation method of Q690CF hot rolled steel plates of the invention, high tough hot-rolled steel is directly prepared using TMCP techniques
Plate, without any Technology for Heating Processing after rolling, simple production process significantly saves the energy, improves production efficiency and reduces system
Cause this.
Brief description of the drawings
Fig. 1 is the microstructure picture of the Q690CF hot rolled steel plates cross section of embodiment 2；
Fig. 2 is the fine battened construction photo of the Q690CF hot rolled steel plate microscopic structures of embodiment 2.
Embodiment
More full and accurate description is carried out to the specific embodiment of the present invention with reference to accompanying drawing, these embodiments are only to the present invention
Embodiment is described, and the scope of the present invention is not imposed any restrictions.
The mass percent of three kinds of chemical compositions of the embodiment of the present invention 1~7 of table 1
| C | Si | Mn | Al | Cr | Mo | Cu | Ni | Nb | V | Ti | S | P | * | |
| 1 | 0.063 | 0.25 | 1.83 | 0.03 | 0.10 | 0.21 | 0.22 | 0.3 | 0.04 | 0.01 | 0.02 | 0.004 | 0.008 | Surplus |
| 2 | 0.058 | 0.30 | 1.70 | 0.029 | 0.23 | 0.20 | 0.23 | 0.2 | 0.03 | 0.028 | 0.005 | 0.003 | 0.005 | Surplus |
| 3 | 0.07 | 0.22 | 1.68 | 0.034 | 0.20 | 0.22 | 0.18 | 0.18 | 0.04 | 0.022 | 0.028 | 0.003 | 0.007 | Surplus |
Note：* it is Fe and inevitable impurity.
The Pcm values of three kinds of chemical compositions of the embodiment of the present invention 1~7 of table 2
| Sequence number | 1 | 2 | 3 |
| Pcm | 0.199 | 0.195 | 0.200 |
Note：Pcm=C+Si/30+Mn/20+Cu/20+Cr/20+Ni/60+Mo/15+V/10+5B
Embodiment 1
The preparation method of the Q690CF hot rolled steel plates of the present invention, comprises the following steps：
Step 1, melting：
No. 1 Q690CF hot rolled steel plate chemical composition in table 1 is pressed, electric furnace smelting, smelting temperature is 1670 DEG C, is cast into thickness
For 110mm steel ingot；
Step 2, pre-process：
By Heating Steel Ingots to 1200 DEG C, soaking time 80min；
Step 3, hot rolling：
Rolled using two-stage control：
The start rolling temperature of roughing is 1080 DEG C, 3 passes, and it is 55% to add up percentage pass reduction, and finishing temperature is 1060
DEG C, workpiece thickness is obtained for 50mm；
After carrying out finish rolling after warm to 860 DEG C on roller-way, 7 passes, accumulative percentage pass reduction is 76%, finishing temperature
For 800 DEG C, steel plate thickness is obtained for 12mm；
Step 4, quick cooling：
The type of cooling is accelerated using laminar flow, steel plate begins to cool down temperature and is not less than 750 DEG C, and cooling velocity is 26 DEG C/s, eventually
Cold temperature control is 480 DEG C, is then air-cooled to room temperature, obtains finished product Q690CF hot rolled steel plates.
Embodiment 2
The preparation method of the Q690CF hot rolled steel plates of the present invention, comprises the following steps：
Step 1, melting：
No. 1 Q690CF hot rolled steel plate chemical composition in table 1 is pressed, converter smelting, smelting temperature is 1560 DEG C, is cast into
130mm strand；
Step 2, pre-process：
By heating strand to 1150 DEG C, soaking time 120min；
Step 3, hot rolling：
Rolled using two-stage control：
The start rolling temperature of roughing is 1100 DEG C, 3 passes, and it is 46% to add up percentage pass reduction, and finishing temperature is 1050
DEG C, workpiece thickness is obtained for 70mm；
After carrying out finish rolling after warm to 840 DEG C on roller-way, 6 passes, accumulative percentage pass reduction is 69%, finishing temperature
For 810 DEG C, steel plate thickness is obtained for 22mm；
Step 4, quick cooling：
The type of cooling is accelerated using laminar flow, steel plate begins to cool down temperature and is not less than 750 DEG C, and cooling velocity is 18 DEG C/s, eventually
Cold temperature control is 400 DEG C, is then air-cooled to room temperature, obtains finished product Q690CF hot rolled steel plates.
Embodiment 3
The preparation method of the Q690CF hot rolled steel plates of the present invention, comprises the following steps：
Step 1, melting：
No. 2 Q690CF hot rolled steel plate chemical compositions in table 1 are pressed, converter smelting, smelting temperature is 1600 DEG C, is cast into thickness
For 110mm strand,；
Step 2, pre-process：
By heating strand to 1180 DEG C, soaking time 60min；
Step 3, hot rolling：
Rolled using two-stage control：
The start rolling temperature of roughing is 1070 DEG C, 2 passes, and it is 45% to add up percentage pass reduction, and finishing temperature is 1000
DEG C, workpiece thickness is obtained for 60mm；
After carrying out finish rolling after warm to 830 DEG C on roller-way, 7 passes, accumulative percentage pass reduction is 77%, finishing temperature
For 790 DEG C, steel plate thickness is obtained for 14mm；
Step 4, quick cooling：
The type of cooling is accelerated using laminar flow, steel plate begins to cool down temperature and is not less than 750 DEG C, and cooling velocity is 20 DEG C/s, eventually
Cold temperature is 430 DEG C, is then air-cooled to room temperature, obtains finished product Q690CF hot rolled steel plates.
Embodiment 4
The preparation method of the Q690CF hot rolled steel plates of the present invention, comprises the following steps：
Step 1, melting：
No. 2 Q690CF hot rolled steel plate chemical compositions in table 1 are pressed, electric furnace smelting, smelting temperature is 1650 DEG C, is cast into thickness
For 130mm steel ingot,；
Step 2, pre-process：
By Heating Steel Ingots to 1150 DEG C, soaking time 120min；
Step 3, hot rolling：
Rolled using two-stage control：
The start rolling temperature of roughing is 1050 DEG C, 3 passes, and it is 48% to add up percentage pass reduction, and finishing temperature is 1000
DEG C, workpiece thickness is obtained for 68mm；
After carrying out finish rolling after warm to 850 DEG C on roller-way, 6 passes, accumulative percentage pass reduction is 71%, finishing temperature
For 800 DEG C, steel plate thickness is obtained for 20mm；
Step 4, quick cooling：
The type of cooling is accelerated using laminar flow, steel plate begins to cool down temperature and is not less than 750 DEG C, and cooling velocity is 15 DEG C/s, eventually
Cold temperature is 380 DEG C, is then air-cooled to room temperature, obtains finished product Q690CF hot rolled steel plates.
Embodiment 5
The preparation method of the Q690CF hot rolled steel plates of the present invention, comprises the following steps：
Step 1, melting：
No. 3 Q690CF hot rolled steel plate chemical compositions in table 1 are pressed, converter smelting, smelting temperature is 1600 DEG C, is cast into thickness
For 110mm strand,；
Step 2, pre-process：
By heating strand to 1200 DEG C, soaking time 60min；
Step 3, hot rolling：
Rolled using two-stage control：
The start rolling temperature of roughing is 1120 DEG C, 3 passes, and it is 55% to add up percentage pass reduction, and finishing temperature is 1080
DEG C, workpiece thickness is obtained for 50mm；
After carrying out finish rolling after warm to 860 DEG C on roller-way, 7 passes, accumulative percentage pass reduction is 76%, finishing temperature
For 810 DEG C, steel plate thickness is obtained for 12mm；
Step 4, quick cooling：
The type of cooling is accelerated using laminar flow, steel plate begins to cool down temperature and is not less than 780 DEG C, and cooling velocity is 30 DEG C/s, eventually
Cold temperature is 500 DEG C, is then air-cooled to room temperature, obtains finished product Q690CF hot rolled steel plates.
Embodiment 6
The preparation method of the Q690CF hot rolled steel plates of the present invention, comprises the following steps：
Step 1, melting：
No. 3 Q690CF hot rolled steel plate chemical compositions in table 1 are pressed, converter smelting, smelting temperature is 1580 DEG C, is cast into thickness
For 110mm strand,；
Step 2, pre-process：
By heating strand to 1200 DEG C, soaking time 60min；
Step 3, hot rolling：
Rolled using two-stage control：
The start rolling temperature of roughing is 1100 DEG C, 3 passes, and it is 45% to add up percentage pass reduction, and finishing temperature is 1080
DEG C, workpiece thickness is obtained for 60mm；
After carrying out finish rolling after warm to 820 DEG C on roller-way, 6 passes, accumulative percentage pass reduction is 73%, finishing temperature
For 790 DEG C, steel plate thickness is obtained for 16mm；
Step 4, quick cooling：
The type of cooling is accelerated using laminar flow, steel plate begins to cool down temperature and is not less than 780 DEG C, and cooling velocity is 24 DEG C/s, eventually
Cold temperature is 410 DEG C, is then air-cooled to room temperature, obtains finished product Q690CF hot rolled steel plates.
Embodiment 7
The preparation method of the Q690CF hot rolled steel plates of the present invention, comprises the following steps：
Step 1, melting：
No. 3 Q690CF hot rolled steel plate chemical compositions in table 1 are pressed, converter smelting, smelting temperature is 1630 DEG C, is cast into thickness
For 130mm strand,；
Step 2, pre-process：
By heating strand to 1200 DEG C, soaking time 80min；
Step 3, hot rolling：
Rolled using two-stage control：
The start rolling temperature of roughing is 1100 DEG C, 2 passes, and it is 46% that accumulative passage, which pushes rate, and finishing temperature is 1050
DEG C, workpiece thickness is obtained for 70mm；
After carrying out finish rolling after warm to 830 DEG C on roller-way, 6 passes, accumulative percentage pass reduction is 64%, finishing temperature
For 820 DEG C, steel plate thickness is obtained for 25mm；
Step 4, quick cooling：
The type of cooling is accelerated using laminar flow, steel plate begins to cool down temperature and is not less than 750 DEG C, and cooling velocity is 17 DEG C/s, eventually
Cold temperature is 400 DEG C, is then air-cooled to room temperature, obtains finished product Q690CF hot rolled steel plates.
The microsturcture of Q690CF hot rolled steel plates prepared by embodiment 2 is shown in Fig. 1, as seen from the figure, micro- group
Predominantly tiny bainite type ferrite and acicular ferrite are knitted, the fine battened construction of its microscopic structure is shown in Fig. 2, width of sheet
Average-size is 0.3 μm.
The mechanical property for the Q690CF hot rolled steel plates that each embodiment is obtained is shown in Table 3.
The mechanical property of the Q690CF hot rolled steel plates of the embodiment of the present invention 1~7 of table 3
| Embodiment | H(mm) | Rp0.2(MPa) | Rm(MPa) | A (%) | Rp0.2/Rm | Akv(-20℃/J) |
| 1 | 12 | 700 | 815 | 18.2 | 0.86 | 224,233,214 |
| 2 | 22 | 730 | 875 | 17.8 | 0.85 | 192,187,196 |
| 3 | 14 | 725 | 890 | 17.5 | 0.84 | 188,190,182 |
| 4 | 20 | 750 | 910 | 17.2 | 0.82 | 181,193,186 |
| 5 | 12 | 735 | 860 | 18 | 0.85 | 220,198,206 |
| 6 | 16 | 740 | 905 | 17.3 | 0.82 | 192,181,189 |
| 7 | 25 | 715 | 865 | 17.4 | 0.83 | 190,215,182 |
Note：H represents steel plate thickness；Rp0.2 represents yield strength；Rm represents tensile strength；A represents elongation percentage, Akv tables
Show -20 DEG C of impact absorbing energies.
It can be seen that from embodiments of the invention result and ensure that Pcm values are not more than 0.20% in example steel grade chemical composition
Condition, the hot rolled steel plate of high-intensity high-tenacity is directly prepared using TMCP techniques, it is big that mechanical property fully meets yield strength
In 690MPa, low-temperature impact absorbs work(and is more than 180J (- 20 DEG C), and each monodrome is highly stable.
The steel grade obtained to the embodiment of the present invention 3 carries out single pass plate welding experiment, and thermal weld stress is 1.08kJ/
Mm, room temperature be about 15 DEG C, without any preheating condition under weld, postwelding measures the Vickers hardness number of heat affected area, and its highest is hard
Spend for 310HV, less than easily there is the critical hardness value 350HV of welding cold cracking, show that the steel grade has preferable welding performance,
In room temperature, without implementing small heat input welding procedure under any preheating condition.
The steel grade obtained to the embodiment of the present invention 2 carries out small iron and grinds experiment, is about 15 DEG C, without any pre- equally in room temperature
Welded under heat condition, groove type uses oblique Y types groove, retain 2mm gaps, when using thermal weld stress amount for 1.30kJ/mm,
Welding cold cracking rate is 0；But when heat input is 0.9kJ/mm, there is a small amount of crackle in local heat affected area, shows the steel grade
The minimum heat input that can be used under without preheating, room temperature condition should be near 1kJ/mm.
Claims (3)
1. a kind of Q690CF hot rolled steel plates, it is characterised in that the chemical composition of described hot rolled steel plate is by mass percentage：C:
0.05~0.08%, Si:0.22~0.30%, Mn:1.6~2.0%, Al:0.2~0.35%, Cr:0.10~0.35%, Mo:
0.20~0.35%, Ni:0.1~0.18%, Cu:0.15~0.18%, Nb:0.025~0.045%, V:0.01~0.03%,
Ti:0.005~0.03%, P≤0.010%, S≤0.008%, surplus are Fe and inevitable impurity；Described hot-rolled steel
The welding crack sensibility indices P cm values of plate are not more than 0.20%；
Step is：
Step 1, melting：
By Q690CF hot rolled steel plate chemical compositions, electric furnace or converter smelting, smelting temperature are 1550~1670 DEG C, and are cast into steel
Ingot or strand；
Step 2, pre-process：
By steel ingot or heating strand to 1150~1200 DEG C, 60~120min of soaking time；
Step 3, hot rolling：
Rolled using two-stage control：
The start rolling temperature of roughing is 1050~1120 DEG C, multi- pass rolling, and it is 45~60%, finishing temperature to add up percentage pass reduction
For 1000~1080 DEG C, workpiece thickness is obtained for 40~75mm；
The start rolling temperature of finish rolling is 810~860 DEG C, multi- pass rolling, and it is 60~80% to add up percentage pass reduction, and finishing temperature is not
Less than 780 DEG C, steel plate thickness is obtained for 12~25mm；
Step 4, quick cooling：
The type of cooling is accelerated using laminar flow, steel plate begins to cool down temperature and is not less than 750 DEG C, and cooling velocity is 15~30 DEG C/s, eventually
Then cold temperature control is air-cooled to room temperature between 350~500 DEG C, obtains finished product Q690CF hot rolled steel plates.
2. Q690CF hot rolled steel plates according to claim 1, it is characterised in that in the microscopic structure of described hot rolled steel plate
Area percentage composition >=90% of bainite type ferrite and acicular ferrite, bainite and ferritic width of sheet are distributed
At 0.1~0.7 μm.
3. Q690CF hot rolled steel plates according to claim 1, it is characterised in that described hot rolled steel plate, mechanical property is：
750MPa >=yield strength >=690MPa, 940MPa >=tensile strength >=810MPa, 22.5% >=elongation percentage >=17%, 250J
>=-20 DEG C of impact absorbing energy >=180J, yield tensile ratio≤0.93.
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