Summary of the invention
The invention reside in to solve and adopt converter can't produce thickness greater than 114 millimeters, though adopt the forging mode to produce, cost is high, and inefficient deficiency, provides a kind of by adopting electric furnace
WithThe mode that esr combines produces not only that yield strength is at least 650MPa, and thickness is greater than 114 millimeters, and cost than the ocean platform of low 500~700 yuan/tons of steel of forging mode with tooth bar steel and production method thereof.
Realize the measure of above-mentioned purpose:
The ocean platform of a kind of thickness 〉=114mm tooth bar steel, its component and weight percent content are: C:0.14~0.192, Si:0.15~0.35, Mn:0.98~1.3, P :≤0.014, S :≤0.008, Cr:0.15~0.35, Ni:1.2~1.5, Mo:0.40~0.58, Cu:0.15~0.26, V:0.032~0.068, [O]≤0.0003, [N]≤0.007, Sn :≤0.003, As :≤0.003, Sb :≤0.002, and all the other are Fe and relict element; And should satisfy weld metal embrittlement sensitivity coefficient: X=(10P+5Sb+4Sn+As) * 1000≤16.
Produce the ocean platform of a kind of thickness 〉=114mm with the method for tooth bar steel, the steps include:
1) carry out electrosmelting, the control tapping temperature is at 1640-1660 ℃;
2) at the LF refining furnace, add quickened lime according to 7.1~10 kg/tonnes of steel;
3) vacuum metling in the VD stove, the control argon flow amount is at 80-90NL/min;
4) vacuumize in the VD stove and carry out pressurize, the control pumpdown time is no less than 30 minutes; When vacuum tightness is near when not being higher than 67Pa, the beginning pressurize, the control dwell time is not less than 20 minutes;
5) carry out soft blow in the VD stove, the soft blow argon time is not less than 10 minutes;
6) continuous casting, control starting pulling rate is at 1.6~1.8 m/mins;
7) carry out electric slag refusion and smelting: add pre-melted slag according to 5.7~8.6 kg/tonnes of steel; Toast under 1600~1700 ℃ temperature, storing time is 2.5~4.5 hours; Change slag after the oven dry; Change front 8 minutes of slag blowing out, in melt cinder, carrying out pre-deoxidation according to 1.0~2.0 kg/tonnes of steel adding aluminum shots; Add the Mn powder according to 0.5kg~1.5 kg/tonne steel before slagging tap, the molten steel temperature control is at 1650-1750 ℃ before the going out slag hearth; Adopt aluminum shot to carry out deoxidation, according to the speed adding aluminum shot of 30~40 gram/minute; Enter the remelting phase, the stripping speed control is in 8.0~8.5 mm/min, and burn-off rate is controlled at the 36-38.5 kg/minute; Cheat coldly, the time is not less than 48 hours;
8) the electroslag base is heated, Heating temperature is 1200 ℃~1240 ℃, and heating rate is 10~13min/cm, and the control tapping temperature is at 1180 ℃~1230 ℃;
9) segmentation is rolled: control roughing start rolling temperature is at 1100 ℃~1200 ℃, and the control draught per pass is 6.25~10.12%, and the steel plate thickness after roughing finishes is controlled at 190mm~240mm; Control finish rolling start rolling temperature is at 840 ℃~880 ℃, and finishing temperature is at 820 ℃~840 ℃, and the last three passage total reductions of control finish rolling are not less than 40%;
10) carry out air cooling, the control final cooling temperature is between 650 ℃~700 ℃;
11) heat-treat: adopt the quenching+tempering processing mode, control normalizing Heating temperature is at 920 ℃~950 ℃, and heat-up time was at 165~210 minutes; Control tempering Heating temperature is at 630 ℃~670 ℃, and heat-up time was at 195~240 minutes.
12) stand-by.
The function and mechanism of each element and main technique among the present invention:
C:C is one of element of the indispensable raising steel strength of steel grade, and every increase by 0.10% tensile strength of carbon content approximately improves 60MPa, and yield strength approximately improves 20~30MPa.Along with the increase of carbon content, Fe3C increases in the steel, and hardenability also increases, and the tensile strength of steel and yield strength can improve, and plasticity and toughness index can descend, the welding property variation.This steel grade is applicable to high strength and low-temperature flexibility, wherein with the C element to guarantee high strength as main, need simultaneously to guarantee certain toughness and welding property, so regulation C content is tending towards medium, lower be limited to 0.14%, on be limited to 0.192%.
Si:Si mainly improves steel strength with the solution strengthening form, also is the deoxidant element of steel grade.If but Si content is higher in the steel, can cause that then reduction of area descends, particularly impact toughness decreased is obvious, also unfavorable to the weldability of steel simultaneously, and the intensity rank of tooth bar steel is higher, and it is main needing certain Si content proof strength, therefore Si content is chosen in 0.15%~0.35%.
Mn: aspect the intensity of guaranteeing steel and toughness, Mn is indispensable element.And the intensity rank of tooth bar steel is higher, and it is main needing certain Mn content proof strength, and therefore the content with Mn is chosen in 0.98~1.30%.
P, S: control P≤0.014%, S≤.008%, this is owing to only having smelting Clean Steel, the over-all properties of guarantee steel of the present invention.
Cr: the content of Cr is chosen in 0.15~0.35%, is because Cr can improve steel plate hardening capacity, so that the ferritic phase apparition moves to right, the cooling rate of widening bainitic transformation is interval, promotes the formation of middle temperature transformation tissue, improves the steel plate yield strength.
Ni:Ni has strengthening effect, and the Ni of adding 1% can improve steel strength 20MPa.Ni can also improve the toughness, particularly low-temperature flexibility of steel significantly.Steel grade adds Ni, is that base material or simulation welded heat affecting zone have all improved low-temperature flexibility significantly. so steel grade of the present invention designed higher Ni content, is limited to 1.20% under selecting, on be limited to 1.50%.
The content of Mo:Mo is chosen in 0.40~0.58%, is because Mo can improve steel plate hardening capacity, so that the ferritic phase apparition moves to right, the cooling rate of widening bainitic transformation is interval, promotes the formation of middle temperature transformation tissue, improves the steel plate yield strength.And the heat treatment process that the invention steel grade need to quench, so the Mo of this scope is conducive to improve the hardening capacity of steel plate.
Cu:Cu is austenite former, has also promoted austenitic formation and stabilization when enlarging the austenite phase region in drawing process.The low-temperature flexibility that Ni improves steel simultaneously also improves the intensity of steel, but meeting is so that the hardening capacity of steel plate and hardenability increase when the Ni too high levels, so that steel plate HAZ toughness drop, the welding property of deterioration steel plate.The existence of a small amount of Cu can obviously improve the corrosion potential of steel, thereby improves the corrosion resistance nature of steel.Simultaneously when the content of Cu acquires a certain degree, but the precipitate of ε-Cu can improve the intensity of steel plate. and when the content of Cu is higher than 0.18%, can cause the hot-short phenomenon of steel, worsen plate surface quality.Therefore, be limited to 1.20% under selecting, on be limited to 1.50%.
The effect of V:V element crystal grain thinning is stronger, can improve intensity and the toughness of steel, reduces superheated susceptivity, improves thermostability, improves the temper resistance of M body.Reduced the alloy degree of sosoloid because V and C are combined to VC, so lower hardness, when quenching temperature is increased to (and longer soaking time is arranged) when a lot of above the AC3 point, then VC turns into sosoloid, so hardness can improve.V has adverse influence to hardening capacity in general, but toughness is better, has added V and has been difficult for hardening crack.Medium carbon steel of the present invention adds V can improve intensity, and while toughness is step-down not.Therefore be limited to 0.032% under selecting, on be limited to 0.068%.
Rare elements: Sn, As and Sb element are harmful element for this invention, and these three kinds of elements are very large for the temper brittleness impact of steel grade of the present invention, therefore carried out ceiling restriction for these three kinds of elements.
N :≤0.007%, steel grade N element is larger for the Toughness of steel plate, has therefore done the restriction of the upper limit.
The present invention compared with prior art, utilize traditional converter smelting-rolling pattern can't produce the above special thick ocean platform tooth bar steel of 114mm, not only cost is high but also efficient is extremely low with the tooth bar steel and adopt the mode that forges to produce the above special thick ocean platform of 114mm, the mode of the present invention by adopting electric furnace to combine with esr, producing not only, yield strength is at least 650MPa, thickness is at 114~152 millimeters, and cost is than low 500~700 yuan/tons of steel of forging mode, can manufacture, very favourable to the improving product competitive power.
Embodiment
The below is described in detail the present invention:
Table 1 is the value tabulation of various embodiments of the present invention and Comparative Examples;
Table 2 is the main technologic parameters tabulation of various embodiments of the present invention and Comparative Examples;
Table 3 is various embodiments of the present invention and the tabulation of Comparative Examples performance monitoring situation;
Various embodiments of the present invention are according to following steps production:
Its step:
1) carry out electrosmelting, the control tapping temperature is at 1640-1660 ℃;
2) at the LF refining furnace, add quickened lime according to 7.1~10 kg/tonnes of steel;
3) vacuum metling in the VD stove, the control argon flow amount is at 80-90NL/min;
4) vacuumize in the VD stove and carry out pressurize, the control pumpdown time is no less than 30 minutes; When vacuum tightness is near when not being higher than 67Pa, the beginning pressurize, the control dwell time is not less than 20 minutes;
5) carry out soft blow in the VD stove, the soft blow argon time is not less than 10 minutes;
6) continuous casting, control starting pulling rate is at 1.6~1.8 m/mins;
7) carry out electric slag refusion and smelting: add pre-melted slag according to 5.7~8.6 kg/tonnes of steel; Toast under 1600~1700 ℃ temperature, storing time is 2.5~4.5 hours; Change slag after the oven dry; Change front 8 minutes of slag blowing out, in melt cinder, carrying out pre-deoxidation according to 1.0~2.0 kg/tonnes of steel adding aluminum shots; Add the Mn powder according to 0.5kg~1.5 kg/tonne steel before slagging tap, the molten steel temperature control is at 1650-1750 ℃ before the going out slag hearth; Adopt aluminum shot to carry out deoxidation, according to the speed adding aluminum shot of 30~40 gram/minute; Enter the remelting phase, the stripping speed control is in 8.0~8.5 mm/min, and burn-off rate is controlled at the 36-38.5 kg/minute; Cheat coldly, the time is not less than 48 hours;
8) the electroslag base is heated, Heating temperature is 1200 ℃~1240 ℃, and heating rate is 10~13min/cm, and the control tapping temperature is at 1180 ℃~1230 ℃;
9) segmentation is rolled: control roughing start rolling temperature is at 1100 ℃~1200 ℃, and the control draught per pass is 6.25~10.12%, and the steel plate thickness after roughing finishes is controlled at 190mm~240mm; Control finish rolling start rolling temperature is at 840 ℃~880 ℃, and finishing temperature is at 820 ℃~840 ℃, and the last three passage total reductions of control finish rolling are not less than 40%;
10) carry out air cooling, the control final cooling temperature is between 650 ℃~700 ℃;
11) heat-treat: adopt the quenching+tempering processing mode, control normalizing Heating temperature is at 920 ℃~950 ℃, and heat-up time was at 165~210 minutes; Control tempering Heating temperature is at 630 ℃~670 ℃, and heat-up time was at 195~240 minutes.
12) stand-by.
The chemical composition value tabulation (one) of table 1 various embodiments of the present invention and Comparative Examples
The chemical composition value tabulation (two) of table 1 various embodiments of the present invention and Comparative Examples
The main technologic parameters tabulation (one) of table 2 various embodiments of the present invention and Comparative Examples
The main technologic parameters tabulation (two) of table 2 various embodiments of the present invention and Comparative Examples
The main technologic parameters tabulation (three) of table 2 various embodiments of the present invention and Comparative Examples
The main technologic parameters tabulation (four) of table 2 various embodiments of the present invention and Comparative Examples
The main technologic parameters tabulation (five) of table 2 various embodiments of the present invention and Comparative Examples
Table 3 is various embodiments of the present invention and Comparative Examples mechanical properties test the results list
Annotate: Comparative Examples 1 and 2 is for adopting the steel of converter smelting.
As everyone knows, steel plate thickness is larger, and then mechanical property more is difficult to guarantee.But as can be seen from Table 3, Comparative Examples 1 and 2 is compared with the present invention, although mechanical property is more or less the same, thickness differs widely, and the thicklyest reaches 152 millimeters.This is explanation just, and the present invention is guaranteeing that mechanical property satisfies under the prerequisite of the new market requirement, has satisfied again user's needs steel plate thickness greater than the new demand more than 114 millimeters.
Above-described embodiment only exemplifies for the best, and is not to be restriction to embodiments of the present invention.