Background technology
Adjustment with China's energy resource structure and the reinforcement of environmental conservation dynamics, using petroleum gas Substitute coal as master
Want the inexorable trend that the energy is 21 century development.In addition, with the rapid growth of domestic consumption amount, China also plans from Russia
Inlet part oil and natural gas.
To consider from China's production of hydrocarbons and consumption structure and strategy to develop western regions, distance, heavy caliber, height
Pressure is the inexorable trend of China's oil and gas pipes development, and this just puts forward higher requirement to the intensity and toughness of pipe line steel.First
First require to improve the grade of steel of pipe line steel.Often improve a grade of steel, construction cost 7% about can be saved.In recent years, in world wide
Interior conduit engineering is all so that, based on x70 pipe line steel, also batch is used in pipeline construction x80, and x100 and more Hi-grade steel
Pipe line steel also in exploitation with probation promote.Secondly, while stepping up to develop senior pipe line steel, raising steel to be focused on tough
Property, take into account high intensity and the high tenacity of material.
But up to the present, for pipe line steel steel plate thickness most of less than 30 millimeters, as 34 millimeters will be thickened
More than, or then prior art complex process, that is, will be through Overheating Treatment, or being difficult to make the properties of steel plate be satisfied by wanting
Ask.
Through retrieval: China Patent Publication No. is the patent documentation of cn101684539a, it discloses a kind of component and weight
Percentage ratio be c:0.03~0.06%, mn:1.55~1.75%, si:0.15~0.25%, s≤0.003%, p≤0.012~
0.020%th, cu:0.20~0.35%, cr:0.20~0.35%, nb:0.06~0.08%, t:0.01~0.02%, als≤
0.05%th, mo:0.20~0.30%, remaining be ferrum and inevitable impurity, but its obtain be thickness >=14mm x70 heat
Rolled steel coils, not hot rolled steel plate.
China Patent Publication No. is the patent documentation of cn101992213a, and it discloses a kind of component and percentage by weight is
C:0.04~0.07%, mn:1.50~1.68%, si:0.10~0.20%, s≤0.003%, p≤0.015%,
Nb:0.04~0.08%, ti:0.006~0.018%, mo:0.05~0.30%, als≤0.05%, n≤
0.006%th, ni≤0.20%, cu≤0.25%.Its pipe line steel for top layer compact grained x65 and x70 rank finally giving
Hot-rolled coil, its thickness specification is 13~20mm, is similarly roll bending.
China Patent Publication No. is the patent documentation of cn102172619a, and it discloses one kind and can improve Hi-grade steel think gauge
The hot rolling technology of pipe line steel fracture toughness, the steel grade that it is related to is x70 and x80 hot-rolled coil, and thickness range is >=15mm, real
The thickness specification that example is related to is 15.9mm, 17.5mm and 18.4mm.
Content of the invention
Present invention aim at providing a kind of steel plate thickness to be more than 34 millimeters, its mechanical property is: yield strength >=
555mpa, tensile strength >=630mpa, a50>=35.0%, -20 DEG C of kv2>=350j, -15 DEG C of sa% >=80% that drop hammer, metallographic group
It is woven to bainite, engineering steel and its production method of heat treatment need not be carried out.
For reaching above-mentioned purpose, as follows using technical scheme:
A kind of think gauge high-strength tenacity bainite engineering steel, its component and weight percent content are: c:0.03~
0.05%, si:0.10~0.30%, mn:1.60~1.80%, nb:0.04~0.06%, ti:0.01~0.020%, mo:
0.10~0.20%, ni:0.10~0.40%, cr:0.10~0.30%, cu≤0.20%, p≤0.010%, s≤
0.0015%, as≤0.012% remaining be ferrum and inevitable impurity;Its yield strength >=555mpa, tensile strength >=
630mpa, a50>=40%, -20 DEG C of kv2>=350j, -15 DEG C of sa% >=80% that drop hammer.
A kind of think gauge high-strength tenacity bainite engineering steel, its component and weight percent content are: c:0.035~
0.045%, si:0.18~0.26%, mn:1.65~1.75%, nb:0.043~0.056%, ti:0.013~0.018%,
Mo:0.12~0.18%, ni:0.20~0.30%, cr:0.18~0.25%, cu≤0.20%, p≤0.010%, s≤
0.0015%, as≤0.012% remaining be ferrum and inevitable impurity;Its yield strength >=555mpa, tensile strength >=
630mpa, a50>=40%, -20 DEG C of kv2>=350j, -15 DEG C of sa% >=80% that drop hammer.
A kind of think gauge high-strength tenacity bainite engineering steel, its component and weight percent content are: c:0.048%,
Si:0.18%, mn:1.65%, nb:0.06%, ti:0.010%, mo:0.1%, ni:0.18%, cr:0.18%, cu≤
0.20%, p≤0.010%, s≤0.0015%, as≤0.012% remaining be ferrum and inevitable impurity;Its yield strength
>=555mpa, tensile strength >=630mpa, a50>=40%, -20 DEG C of kv2>=350j, -15 DEG C of sa% >=80% that drop hammer.
The production method of above-mentioned think gauge high-strength tenacity bainite engineering steel, comprises the following steps:
1) converter smelting be casting continuously to form the slab of thickness 290-400mm;
2) by heating strand to 1150~1200 DEG C;
3) segmentation rolling: in roughing section, control 1080~1140 DEG C of roughing start rolling temperature, control the pressure of last two passages
Rate is not less than 20%, and the reduction ratio of remaining rolling pass is not less than 15%, and ensures that the total reduction of roughing section is not less than 60%;
In the finish rolling stage, control 850~900 DEG C of finish rolling start rolling temperature, and control last twice to have the reduction ratio carrying passage to be respectively not less than
15%;Finishing temperature control is at 820~850 DEG C;
4) cool down: steel plate open cold temperature at 760~800 DEG C, and be cooled to 200 with 30~40 DEG C/sec of rate of cooling~
350℃;Control the steel plate after cooling to obtain thickness and be more than 34mm high-strength tenacity bainite engineering steel.
A kind of preparation method of think gauge high-strength tenacity bainite engineering steel, its component and weight percent content are:
C:0.048%, si:0.18%, mn:1.65%, nb:0.06%, ti:0.010%, mo:0.1%, ni:0.18%, cr:
0.18%, cu≤0.20%, p≤0.010%, s≤0.0015%, as≤0.012% remaining be ferrum and inevitable impurity;
1) converter smelting be casting continuously to form the slab of thickness 400mm;
2) by heating strand to 1158 DEG C;
3) segmentation rolling: in roughing section, control 1080 DEG C of roughing start rolling temperature, control the reduction ratio of last two passages
24%, the reduction ratio of remaining rolling pass is not less than 15%, and ensures that the total reduction of roughing section is not less than 60%;In finish rolling rank
Section, controls 890 DEG C of finish rolling start rolling temperature, and controls last twice to have the reduction ratio 16% carrying passage;Finishing temperature control is 840
℃;
4) cool down: steel plate open cold temperature at 792 DEG C, and be cooled to 200~350 DEG C with 36 DEG C/sec of rate of cooling;Control
Steel plate after cooling obtains thickness and is more than 34mm high-strength tenacity bainite engineering steel.
In the present invention effect of each component and main technique and control the reasons why:
C: carbon is most economical, most basic intensified element in steel, and solution strengthening and precipitation strength are to the intensity improving steel plate
There is an obvious effect, but improve carbon and have negative impact to the ductility of steel, toughness and weldability, therefore, the evolution of pipe line steel
It is the process constantly reducing carbon content.The carbon content control of the present invention is 0.03~0.05%.The impact higher to ensure steel plate
The block hammer performance of performance requirement and superelevation requires.
Mn: reduce the lower change point of steel, increase the degree of supercooling of austenite cooling, refine pearlitic structrure, and improve it
Mechanical property, can significantly improve the quenching degree of steel, but have the unfavorable trend increasing grain size roughening and temper brittleness.Manganese element can
To improve the intensity of steel, but when content is high, the low-temperature flexibility of steel will be reduced.
Nb: niobium is one of topmost element in microalloying pipe line steel, and the effect to crystal grain refinement is fairly obvious.Niobium can
To significantly improve the austenite recrystallization temperature of steel, expand Unhydrated cement scope, facilitate implementation high temperature rolling.Niobium can also press down
Austenite Grain Growth processed, has significantly refined crystalline strengthening and precipitation strength effect.But in high strength bainite steel, add
Excessive niobium can promote the formation on m-a island, reduces the toughness of welding heat affected zone.
Ti: titanium is strong n element, austenite crystal grain length when tiny tin particle can effectively stop slab from heating again
Greatly, it is favorably improved solid solubility in austenite for the nb, the impact flexibility of welding heat affected zone can also be improved simultaneously.
Mo: molybdenum significantly postpones austenite to ferritic transformation, suppresses the formation of ferrite and pearlite, promotes there is height
The formation of the bainite/acicular ferrite of density dislocation substructure.Make steel in the rear wider rate of cooling scope of rolling
Interior energy accesses bainite/acicular ferrite structure.But, excessive molybdenum can lead to the low-temperature flexibility of steel to deteriorate, and molybdenum belongs to
Precious metal, addition increase can significantly improve the manufacturing cost of steel.
Ni: nickel can effectively improve the quenching degree of steel, has certain solution strengthening effect moreover it is possible to significantly improve the low of steel
Warm toughness, as long as the addition of ni improves the red brittleness that cu easily causes in steel grade and favourable to toughness, in think gauge pipe line steel
Can also compensate for the intensity that causes because of the increase of thickness decline, but, it is difficult that too high nickel content easily causes steel-plate iron oxide scale
To remove, lead to plate surface quality problem, and nickel belongs to precious metal, addition increase can significantly improve being manufactured into of steel
This.
Cu: the intensity of steel can be improved by solution strengthening effect, meanwhile, copper improves the corrosion resistance of steel, but, copper is to welding
Performance is unfavorable.
Cr: chromium passes through solution strengthening and crystal grain refinement improves intensity.
P: P elements increase temper brittleness and cold short sensitivity.
S: element sulphur increases the red brittleness of steel, when sulfur content is high, unfavorable to welding performance.
As: arsenic is the harmful element in steel, is inevitable element in steel, and belongs to and cannot be removed by steel-making means
Impurity, when content is more than 0.015%, so that the toughness of steel is drastically declined.Therefore, high-quality ore deposit need to be selected when joining ore deposit.
Generally speaking the feature of chemical composition be low-carbon (LC), Gao Meng, containing microalloy elements such as micro nb, ti, a small amount of
The alloying elements such as mo, ni, cr are it is necessary to strictly control impurity content it is ensured that the degree of purity of molten steel.
In the present invention, following technique is controlled:
Why control 1080~1140 DEG C of roughing start rolling temperature, be to ensure that big pressure carried out at high temperature by steel plate,
Make crystal grain fully broken.
The reduction ratio why controlling last two passages of rough rolling step is not less than 20%, is in order to steel plate is not tied close again
It is ensured that austenite crystal is fully broken during brilliant temperature, suppress excessively growing up of crystal grain simultaneously;
Why control 850~900 DEG C of the finish rolling start rolling temperature of steel plate, be to ensure that the finishing temperature of steel plate and open cold
Temperature.
The reduction ratio controlling last two passages of finish rolling is not less than 13% respectively, is to ensure that steel plate before undergoing phase transition
Crystal grain fully refines.
Control steel plate to open cold temperature and be 760~800 DEG C, be in order to avoid partial austenitic is changed into pro-eutectoid ferrum in steel plate
Ferritic is it is ensured that obtain the tissue of full bainite.Ensure high intensity and the high tenacity of steel plate.
Compared with prior art, steel plate thickness is thicker >=34mm for the present invention.Pipe line steel, due to there being block hammer performance requirement, exists
Tubulation process, therefore, typically all in below 30mm, steel plate is thicker, and tubulation process is more difficult, and block hammer performance is more difficult to for the thickness of steel plate
To meet requirement.The present invention breaks through thickness and limits, alloy formula simple (such as nb, mo content is relatively low, and cu can plus can be not added with), fall
Low production cost, simultaneously with low-carbon (LC) as feature, on the premise of ensureing armor plate strength, improves impact flexibility, fracture toughness
With good welding performance.In the hot rolling technology that the present invention provides compared with prior art, prior art is all to set two benches
Total reduction, the present invention especially sets finish rolling and the reduction ratio of last two passages of roughing, do not increase operation, and for thickness
The steel plate of specification, increasing reduction ratio does not affect on steel-plate shape, easily operates, and productivity ratio is high, the product yield strength of acquisition
>=555mpa, tensile strength >=630mpa, a50>=35.0%, -20 DEG C of kv2>=350j, -15 DEG C of sa% >=80% that drop hammer, need not
Carrying out heat treatment thus simplifying production process, improve yield, and reduce production cost.Feed-line can be significantly reduced simultaneously
Construction cost.