In bridge steel field, with the raising of steel grade intensity rank, the organization type of steel gradually from ferrite+pearlite to
ULCB changes.ULCB tissue belongs to a kind of middle temperature transformation tissue, with intensity height, good toughness, easily welds
The features such as connecing, gradually promotes in bridge steel field.In some sciences of bridge building, it is desirable to adopt Ultra-low carbon shellfish on bridge U-rib
Family name's body steel, and the thickness of U rib steel plates is generally 6mm or 8mm.ULCB sheet metal is generally rolled using hot continuous rolling process
System, but the technique includes coiling machine rolling process, carries out again winding off flat technique in follow-up use, and the technique is accumulated aborning
Substantial amounts of residual stress is tired out, residual stress can discharge in the operation such as slitting, milling side, bending, welding in the manufacture of U ribs, cause
Steel plate produces side sway, distortion etc. affects the problem of scantling precision.If produced using heavy and medium plate mill, due to aborning
Equality operation is not crimped and opened, thus residual stress is less, scantling precision is easily guaranteed that in processing and manufacturing, but this
Plant technique and there is very big production difficulty, wherein most distinct issues are exactly the control of temperature and plate shape when producing.
In a kind of Chinese invention patent " 6mm steel plate rolling techniques " of Publication No. CN101259482A, application is disclosed
A kind of 6mm steel plate rolling techniques, the technique light plate are not quickly cooled down after rolling, and can only produce ferrite+pearlite group
The steel plate of type is knitted, control difficulty is relatively low, but its intensity is relatively low.
The Chinese invention patent of Publication No. CN103469066A is " a kind of to produce high-mouldability energy steel using heavy and medium plate mill
In the method for plate and its obtained steel plate ", the steel plate that embodiment is enumerated is required to cooling control after rolling, can only also produce ferrite+pearl
The steel plate of body of light organization type.
Chinese invention patent " the 2800mm Stand Mill heavy and medium plate mill Limit specifications steel of Publication No. CN 102688884A
In plate rolling mill practice ", for Ultra-thin steel plate, cooling control after rolling is not required, its illustration enumerated is also ferrite+pearlite
The Q345B steel of organization type.
A kind of Chinese invention patent " system of rolled Thin Specs high intensity bridge plate of 104264062 A of Publication No. CN
Make method " in, application discloses a kind of method of rolling thin specification steel plate, and the illustration in embodiment is 8mm thickness steel plates,
The tissue of its steel plate is not ferrite+pearlite type, but acicular ferrite+granular bainite, but its content requirement to P
It is relatively tight, P content≤0.013% is controlled, and requires the V element of addition 0.02～0.04%, it is clear that increased smelting cost.Separately
Outward, the patent is indefinite to rolled blank gauge lattice, but in embodiment, sotck thinkness is 220mm, in rolling 8mm thickness
During steel plate, finished steel plate length can be caused in more than 30m so that steel plate temperature homogeneity in the longitudinal direction it is difficult to ensure that,
And then affect the uniformity of mechanical property of steel plate.
A kind of Chinese invention patent " Stand Mill heavy and medium plate mill Thin Specs pipe line steel of Publication No. CN 102671941A
Production technology " in, claims do not have the organization type of clear and definite steel plate, but are X70 pipe line steels in embodiment, this steel
Although organization type be not ferrite+pearlite, in claim 1 thickness of clear and definite slab be 180mm, this causes steel
Production limited by slab thickness.And the technology is produced by the way of thick steel billet is once rolled down to bottom, can also be caused
The length of finished steel plate is oversize and cause difficult shifting of temperature homogeneity to ensure, and then affect mechanical property of steel plate and plate shape.
Therefore it provides it is a kind of with good mechanical property, excellent welding performance and cold machine-shaping, product not
The little heavy and medium plate mill rolling ULCB class thin specification steel plate of Pingdu and its production method have important practical significance.
The content of the invention
It is an object of the invention to overcome above-mentioned the deficiencies in the prior art, there is provided a kind of heavy and medium plate mill rolls Ultra-low carbon shellfish
Family name's body class thin specification steel plate and its production method.
For achieving the above object, the technical solution used in the present invention is：A kind of heavy and medium plate mill rolls ULCB
Class thin specification steel plate, the chemical composition of steel plate and its percentage by weight it is as follows：C：0.02～0.08%, Si：0.10～0.40%,
Mn：0.90～2.00%, P≤0.018%, S≤0.005%, Cu≤0.40%, B≤0.0003%, Ni：0.10～0.55%,
Mo：0.10～0.40%, Cr：0.12～0.60%, V：0.030～0.090%, Nb：0.010～0.035%, Ti：0.005～
0.035%, Als≤0.060%, remaining is Fe and inevitable impurity；And while meet：V/Nb=2.0～2.7, carbon equivalent
CEV=C+Mn/6+ (Cr+Mo+V)/5+ (Ni+Cu)/15≤0.475%, welding crack sensibility indices P cm=C+Si/30+
Further, the chemical composition of steel plate and its percentage by weight are as follows：C：0.02～0.08%, Si：0.10～
0.40%, Mn：1.20～1.70%, P≤0.018%, S≤0.005%, Cu≤0.40%, B≤0.0003%, Ni：0.15～
0.50%, Mo：0.10～0.30%, Cr：0.15～0.60%, V：0.040～0.080%, Nb：0.015～0.030%, Ti：
0.008～0.030%, Als≤0.060%, remaining is Fe and inevitable impurity.
Further, the chemical composition of steel plate and its percentage by weight are as follows：C：0.05%, Si：0.25%, Mn：
1.55%, P：0.012%, S：0.002%, Cu：0.20%, B：0.00012%, Ni：0.20%, Mo：0.15%, Cr：
0.18%, V：0.050%, Nb：0.022%, Ti：0.010%, Als：0.030%, remaining is Fe and inevitable impurity.
In the heavy and medium plate mill rolling ULCB class thin specification steel plate of the present invention, each composition effect is as follows：
Carbon (C)：Carbon is the effective element for improving hardness of steel, and when content is more than 0.08%, after rolling, rate of cooling is larger
When, M/A islands are easily formed, and easily Assembled distribution is taken in segregation bar, cause mechanical property of steel plate to present significantly vertically and horizontally poor
It is different；When its content is relatively low, such as less than 0.02%, armor plate strength can be made not enough, while difficulty when can also increase smelting.Cause
This, controlling carbon content scope is：0.02～0.08%.
Silicon (Si)：Silicon is conventional deoxidizer, and having, and is conducive to improving its combination property, but Si contents
When higher, reduce toughness, plasticity and the ductility of steel, be easily caused it is cold short be unfavorable for welding.Therefore, it is of the invention by the content of Si
Desired value is controlled 0.10～0.40%.
Manganese (Mn)：Manganese is important Strengthening and Toughening element, can increase the stability of austenite, expands γ phase region austenites, is promoted
Enter the middle temperature structural transformation of steel.The too high toughness that steel billet center segregation is adversely affected, steel plate is impaired of Mn contents, and
Easily crack during welding, Mn contents are too low, middle temperature structural transformation can not be effectively facilitated, the intensity of steel is easily reduced.Therefore
Controlling Mn content ranges is：0.90～2.00%.
Phosphorus (P)：Phosphorus is harmful element in steel, and its content strictly will be controlled, and high P content can increase the cold short of steel and incline
To, and P is easily in the center portion segregation of steel billet, due to the high strong segregated zone of this P content it is more crisp so that easily produce after steel rolling
Raw latent defect.The phosphorus content of the present invention is controlled to P≤0.018%.
Sulfur (S)：Sulfur is harmful element in steel, and high S contents can not only make steel plate, and vertically and horizontally performance produces notable difference,
Also its low-temperature flexibility and Z-direction performance are reduced simultaneously.Sulfur content of the present invention is S≤0.005%.
Copper (Cu)：Copper can improve its quenching degree in steel, act primarily as solid solution and precipitation enhancement, in addition with beneficial to obtaining
Low-temperature flexibility well is obtained, increases its fatigue crack extended capability；But when its addition is more than 0.40%, the sweating heat of steel plate
Zone of influence toughness can be reduced, and steel billet is also easy to produce check crack in heating process.The copper content control of the present invention is Cu≤0.40%.
Boron (B)：Boron can improve the quenching degree of steel, but content increases and can increase crack sensitivity to Grain Boundary Segregation.The present invention
The middle content for controlling boron is B≤0.0003%.
Nickel (Ni)：Nickel can improve quenching degree, with certain invigoration effect, can significantly improve its low-temperature flexibility, make base material
Increase substantially with Low Temperature Impact Toughness of Heat-affected Zone, while Ni can also effectively prevent the hot-short check crack for causing of Cu.When itself plus
Enter amount less than 0.10%, then Ni does not have effect, but too high levels easily cause steel-plate iron oxide scale and are difficult to come off and increase steel
Cost.Ni contents of the present invention are：0.10～0.55%.
Molybdenum (Mo)：Molybdenum can make ferrite separate out and increase the stability of austenite, the formation to pearlite from austenite
With strong inhibition, but Mo belongs to noble element, and excessive Mo will improve the cost of steel；Simultaneously too high Mo contents
The low-temperature flexibility of steel can be made significantly to deteriorate, martensite is formed in welding, cause welding point fragility to increase.Therefore in control steel
Mo content ranges are：0.10～0.40%.
Chromium (Cr)：Chromium can improve the intensity and hardness of steel, but its too high levels then easily increases welding difficulty, and content mistake
It is low, can not effectively play its effect.In the present invention, the content of Cr is controlled to 0.12～0.60%.
Vanadium (V) and niobium (Nb)：In ultra-low-carbon bainite steel, only add substantial amounts of Nb, be remarkably improved intensity, due to which
Substantially, it is higher to also result in yield tensile ratio for grain refinement effect, therefore, Nb contents are limited in into reduced levels in the present invention, which is strong
The loss of degree is then by adding suitable V ensureing.In the present invention, the content of V is 0.030～0.090%.Niobium is strong carbon nitridation
Compound formation element, can improve the austenite recrystallization temperature of steel, and austenite can be rolled under higher rolling temperature.
In addition precipitation strength effects of the Nb in controlled rolling continuous cooling process, can by the strain induced precipitate of the carbonitride of Nb
With pinning austenite crystal, crystal grain thinning simultaneously improves intensity and low-temperature flexibility.But when Nb contents are more than 0.035%, crystal grain thinning
Improve the effect of intensity clearly, but also cause its yield tensile ratio too high；When its content is less than 0.010%, controlled rolling is not played
Effect.Therefore controlling Nb content ranges is：0.010-0.035%.
Titanium (Ti)：Titanium is carbide, can form trickle TiC granules, and crystal grain thinning can prevent crystalline substance
Between corrosion phenomenon, improving welding property.Ti content of the present invention is：0.005～0.035%.
Aluminum (Als)：Aluminum is the main deoxidant element in steel, and the oxide for causing Als is mingled with increasing during Als too high levels
Plus, the degree of purity of steel is reduced, is unfavorable for the toughness of steel.The fusing point of Als is higher, and aborning, Als can be used to prevent crystal grain long
Greatly.Ti content is controlled in the present invention for Als≤0.060%.
Further, the mechanical property of steel plate of the invention is：Yield strength ReLFor 500～630MPa, yield tensile ratio ReL/
Rm≤0.83, -40 DEG C of impact absorbing energy KV2>=120J, steel plate unevenness are less than 3 ‰, with excellent welding performance and cold rnning
Above-mentioned heavy and medium plate mill rolls the production method of ULCB class thin specification steel plate, comprises the steps：Smelting
Refining, casting, continuous casting billet heating, continuous casting billet milling, intermediate wood cutting, intermediate wood heating, intermediate wood roughing, intermediate wood finish rolling and steel
Plate control is cold.In continuous casting billet heating stepses, thickness of strand is 150～300mm, and heating-up temperature is 1210～1250 DEG C；Continuous casting billet
In milling step, it is the intermediate wood that thickness is 60～80mm by continuous casting billet milling, rolls end temp >=1000 DEG C；Intermediate wood adds
In hot step, heating-up temperature is 1210～1250 DEG C；In intermediate wood roughing step, according to finished steel plate thickness, it is divided into 3～4 roads
Secondary, wherein 1～2 passage of broadening, rolling terminate rear intermediate wood thickness for 20～40mm, and this temperature losses of the process is controlled to 10～15 DEG C；
In intermediate wood finish rolling step, according to finished steel plate thickness, it is divided into 6～8 passages, this temperature losses of the process is controlled to 150～200 DEG C；Steel
In the cold step of plate control, temperature is begun to cool down for 720～760 DEG C, be cooled to 520～580 DEG C with the cooldown rate of 6～9 DEG C/S, so
After naturally cool to room temperature.
Further, in the intermediate wood roughing step, rolling started temperature be >=1070 DEG C, rolling end temp for >=
Further, in the intermediate wood finish rolling step, rolling started temperature is≤1020 DEG C, and rolling end temp is
770～840 DEG C.
Compared with prior art, the present invention has advantages below：
(1) present invention is reduced by way of reheating rolling after rolling thinning and cutting to initial continuous casting steel billet
The length of final rolled plate, it is ensured that steel plate along the temperature homogeneity rolled upwards, while by control intermediate wood roughing, in
Between material finish rolling, steel plate control cooling stage temperature drop, it is ensured that steel plate is being controlled opening for cooling into acceleration cooling system
Beginning temperature, is conducive to obtaining the microstructure based on ULCB, so as to ensure that the mechanical property requirements of steel plate.
(2) above-mentioned production technology is adopted, without the need for special transformation being carried out to equipment, you can roll out thickness using heavy and medium plate mill
The ULCB bridge steel for 6～8mm is spent, the mechanical property of steel plate is：Yield strength ReL：500～630MPa, yield tensile ratio
ReL/ Rm≤0.83, -40 DEG C of impact absorbing energy KV2>=120J, with excellent welding performance and cold machine-shaping, steel plate is not
Pingdu is less than 3 ‰.