CN102644024B - Low-alloy low-yield-ratio steel for oceaneering structure and production method thereof - Google Patents
Low-alloy low-yield-ratio steel for oceaneering structure and production method thereof Download PDFInfo
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Abstract
Provided are a low-alloy low-yield-ratio steel for an oceaneering structure and a production method thereof. The steel contains the following chemical components by mass: 0.09-0.13% of C, 0.15-0.40% of Si, 0.80-1.50% of Mn, 0.01-0.04% of Alt, 0.02-0.04% of Nb, 0.008-0.018% of Ti, less than 0.015% of P, less than 0.005% of S and the balance, Fe and unavoidable impurities. The production method includes that thick plate slabs of 250-400mm are heated before being rolled with heating temperature as 1180-1260 DEG C, rolling is divided into two stages, start rolling temperature at an austenite recrystallization area is 1000-1100 DEG C, start rolling temperature at an austenite non-recrystallization area is 850-950 DEG C, finishing rolling temperature is 790-820 DEG C, the thick plate slabs enter a water cooling area after being rolled with cooling speed as 9-12 DEG C/s and fishing cooling temperature as 450-500 DEG C, and steel plates are cooled in heap for more than 12 hours after being taped out. The steel has the advantages of good strength, low yield ratio, good toughness and good lamellar tearing resistant performance, thereby being capable of being used in oceaneering structure construction under severe conditions.
Description
Technical field
The invention belongs to oceanographic engineering work technical field, particularly relate to a kind of low-alloy low yield strength ratio offshore engineering structure steel and production method thereof.
Background technology
Offshore engineering structure is the important ultra-large type welded steel structure of ocean platform, be applied in the severe ocean Working environment such as wave, tide, storm and cold floating ice, support platform and drilling outfit that gross weight surpasses hundreds of tons, stand again the test of the abominable natural disaster such as earthquake, tsunami simultaneously.These use characteristic have determined that offshore engineering structure must have the performances such as high strength, high tenacity, low yield strength ratio and anti-lamellar tearing with steel.
Yet due to the character of described steel, the low-temperature flexibility of steel plate can reduce along with the increase of armor plate strength usually.The increase of armor plate strength simultaneously also can cause the increase of yield tensile ratio.The offshore engineering structure of producing at present generally adopts with steel and adds a large amount of alloying elements, takes to roll rear tempering or modifier treatment on technique, has not only increased production cost but also can not guarantee the performance of steel plate low yield strength ratio.
Publication number is that a kind of yield strength of CN101613828A patent of invention proposition is 460MPa level super-thick steel plate for low yield ratio buildings and manufacture method, it need to add the V alloy element, adding of V element has disadvantageous effect to welding property, and employing hardening and tempering process, production cost is high, complex procedures, the production cycle is long.The observed value that does not relate to the ballistic work below-20 ℃.
Publication number is that the CN101358320A patent of invention proposes steel for controlled rolling and controlled cooling platform and production method thereof, needs to add V and higher than 0.03% Nb, but its tensile strength is lower than 610MPa, does not relate to yield tensile ratio and steel plate heart section low-temperature impact work observed value.
Publication number is that the CN101906591A patent of invention adopts controlled rolling and controlled cooling+tempering process to produce 460MPa level offshore engineering structure steel, but it needs subsequent heat treatment, the alloying elements such as Ni, Cr, Cu, Mo have been added, when increasing cost, welding property there is disadvantageous effect, to the not elaboration of heart section's low-temperature flexibility, yield tensile ratio is high.
Publication number is that the CN101868560A patent of invention proposes a kind of the have high strength of good low-temperature flexibility and the production method of low yield strength ratio structural steel, it need to add the precious alloy elements such as Cr, Mo, Ni, Cu, V, its complex manufacturing is controlled window narrows and is unfavorable for industrialized production, does not relate to research and description to heart section's low-temperature flexibility and anti-lamellar tearing ability.
Publication number is the production method that contains the niobium steel that the CN101255528A patent of invention proposes a kind of ultralow-temperature flexibility excellence, its C content is extremely low, control difficulty during smelting large, Nb content is 0.04-0.10%, content is higher, its tensile strength can not be stablized and reaches 610MPa, and steel plate thickness is at 20-30mm, does not relate to the description to steel plate heart section low-temperature impact toughness.
At present temporarily without adopting low-alloy to produce low yield strength ratio, high strength, high tenacity offshore engineering structure with the precedent of steel.
Summary of the invention
The object of the present invention is to provide a kind of low-alloy low yield strength ratio offshore engineering structure steel and production method thereof, low-alloy composition (only adding Nb, the Ti alloy of trace), rationally and be convenient to rolling, the water-cooled of suitability for industrialized production, produce the offshore engineering structure steel of low yield strength ratio, high strength, high tenacity.
A kind of low-alloy low yield strength ratio offshore engineering structure provided by the invention with the chemical composition of steel by mass percent is: C 0.09-0.13%, Si 0.15-0.40%, Mn 0.80-1.50%, Alt 0.01-0.04%, Nb 0.02-0.04%, Ti 0.008-0.018%, P≤0.010%, S≤0.005%, its amount is Fe and inevitable impurity.
C content of the present invention is controlled at 0.09-0.13%, because C is one of the most cheap strengthening element, for guaranteeing the intensity of steel plate, is limited to 0.09% under C content.But will produce adverse influence to steel plate toughness and welding property during the C too high levels, thus C content on be limited to 0.13%.
Si content of the present invention is controlled at 0.15-0.40%, adds Si as reductive agent and reductor in steelmaking process, so killed steel contains the silicon of 0.15-0.40%, and Si can improve the intensity of steel plate by the solution strengthening mode.But the Si too high levels has disadvantageous effect to toughness and welding property, thereby the upper limit must be set.
Mn content of the present invention is controlled at 0.80-1.50%, and in steelmaking process, Mn is good reductor and sweetening agent, and Mn is also the principal element that improves hardness of steel.But all unfavorable to toughness and welding property during the Mn too high levels.
Nb content of the present invention is controlled at 0.02-0.04%, adds appropriate Nb in steel, and purpose is to be convenient to carry out the non-recrystallization controlled rolling.Nb also can stop growing up of austenite crystal, crystal grain thinning.Niobium is a kind of carbide in addition, the second-phase particles such as the NbC that forms in steel, Nb (CN), intensity and the low-temperature flexibility of raising steel.Add a large amount of Nb and not only do not have better reinforcement and thin brilliant effect, easily produce on the contrary intergranular crack, the upper limit is set to 0.04%.
Ti content of the present invention is controlled at 0.008-0.018%, titanium is a kind of strong carbide and nitride forming element, the not molten carbonitride of Ti can stop growing up of austenite crystal when steel heats, TiN, the TiC that separates out when the high temperature austenite roughing be inhibiting grain growth effectively, improves simultaneously the solid solubility of Nb in austenite.When welding, the TiN in steel, TiC particle can significantly stop the heat affected zone grain growth, thereby improve welding property.But the Ti too high levels generates the TiC carbide, and low-temperature flexibility is reduced.
Al content of the present invention is controlled at 0.01-0.04%, and Al is the main deoxidant element in steel, is conducive to crystal grain thinning, all adds a certain amount of Al in general steel.
P and S are inevitable harmful element in steel, and be unfavorable to plasticity and the toughness of steel, answers reduce P and S content, improves the cleanliness factor of steel.But consider and reduce P, difficulty and the cost increase of S content to smelting, in steel of the present invention, P controls≤0.010%, S and controls≤0.005%.
The production method that the present invention relates to comprise desulfurizing iron skim → 100t converter smelting → ladle deoxidation alloying → LF stove refining → RH vacuum-treat → conventional slab caster cast → heating of plate blank → controlled rolling → control is cooling → the steel plate cooling in heap that rolls off the production line.It is characterized in that: adopt carbon containing 0.09～0.13% carbon steel smelting process for production; Add micro-Nb, Ti alloy; Carry out vacuum-treat after ladle furnace refining; The permanent pulling rate of slab and light soft reduction process guarantee slab quality; Carry out two-stage control rolling on wide and heavy plate mill; Roll rear control cooling system, final cooling temperature 450-500 ℃, 9～12 ℃/S of speed of cooling.Plate property: yield strength 〉=460MPa, tensile strength 〉=610MPa, yield tensile ratio≤0.80, unit elongation 〉=20%, the Charpy-V impact power average 〉=100J of heart section-60 ℃, the Z-direction relative reduction in area surpasses 35%.
Technical scheme of the present invention comprises the following steps:
(1) smelting system: according to C 0.09-0.13%, Si 0.15-0.40%, Mn 0.80-1.50%, Alt 0.01-0.04%, Nb 0.02-0.04%, Ti 0.008-0.018%, P≤0.010%, S≤0.005%, the low-alloy composition smelt;
(2) after (2) converter smelting, continuous casting is the 250-400mm heavy slab, reheats before rolling, and Heating temperature is 1180-1260 ℃;
(3)) controlled rolling and controlled cooling; In two stages rolling, namely rolling the and non-recrystallization in recrystallization zone district is rolling, 1000～1100 ℃ of austenite recrystallization district start rolling temperatures; 850～950 ℃ of austenite non-recrystallization district start rolling temperatures, 790～820 ℃ of finishing temperatures, steel plate rolls the rear rapid cooling zone territory of entering rapidly, and cold but temperature is 450～500 ℃ eventually, 9～12 ℃/s of speed of cooling;
(5) cooling in heap system: the steel plate laggard windrow that rolls off the production line is cold, and cooling in heap begins temperature 350-450 ℃, and the cooling in heap time is no less than 12 hours.
Preferably, step (3) is at austenite recrystallization single pass minimal deformation rate 〉=8%, and deformation rate 〉=20% passage is not less than 2 passages, accumulative total deformation rate 〉=60%.
The invention has the advantages that:
(1) alloy designs is simple, and cost is low: only add a small amount of Nb, Ti microalloy, do not add the alloying elements such as V, Ni.
(2) rational process system: by the Clean Steel technology, reduce P, S content, control inclusion and center segregation, guarantee Inner Quality of Billet, for steel plate heart section impelling strength provides good guarantee; Guarantee large draught and the large cooling rate of water cooling stage of controlled rolling stage, the performance of intensity, center toughness and low yield strength ratio by controlled rolling and controlled cooling institutional guarantee steel plate.
(the high comprehensive performance of 3 steel of the present invention, yield strength can be stablized and reaches 〉=460MPa, tensile strength 〉=610MPa, yield tensile ratio≤0.80, heart section-60 equal the value stabilization of ℃ low-temperature impact work reaches 〉=100J, the Z-direction relative reduction in area is greater than 35%, can satisfy offshore engineering structure with steel to intensity, heart section low-temperature flexibility, low yield strength ratio and anti-lamellar tearing performance requriements.Good intensity, low yield strength ratio, toughness and anti-lamellar tearing performance; Can be used for mal-condition Ocean engineering structure builds.Open up a kind of low-alloy and produced the method that high-intensity high-tenacity low yield strength ratio offshore engineering structure is used steel.
Description of drawings
Fig. 1 is the reduction schedule of 40mm Plate Steel.
Fig. 2 is the surface microhardness in 40mm Plate Steel transverse section.
Fig. 3 is the heart section microstructure in 40mm Plate Steel transverse section.
Concrete embodiment
Hereinafter will be described in detail exemplary of the present invention.It should be understood that the explanation that proposes just only is used for illustrating the embodiment of purpose, is not intended to limit scope of the present invention herein.
Table 1 composition weight/%
| Numbering | C | Si | Mn | P | S | Alt | Nb | Ti |
| A | 0.11 | 0.34 | 1.37 | 0.012 | 0.0018 | 0.034 | 0.028 | 0.012 |
| B | 0.13 | 0.35 | 1.40 | 0.011 | 0.0013 | 0.036 | 0.028 | 0.013 |
| C | 0.10 | 0.37 | 1.39 | 0.012 | 0.0015 | 0.032 | 0.029 | 0.013 |
| D | 0.09 | 0.34 | 1.38 | 0.011 | 0.0017 | 0.031 | 0.028 | 0.013 |
The thick steel billet of 250mm with the listed composition of table 1 and content preparation thereof is rolled with cooling with the listed condition of table 2.
Table 2 technique
Table 3 performance
Claims (2)
1. a low-alloy low yield strength ratio offshore engineering structure is with the preparation method of steel, comprise desulfurizing iron skim → 100t converter smelting → ladle deoxidation alloying → LF stove refining → RH vacuum-treat → conventional slab caster cast → heating of plate blank → controlled rolling → control is cooling → the steel plate cooling in heap that rolls off the production line; It is characterized in that: the technical parameter of controlling in technique is:
(1) smelt: according to C 0.09-0.13%, Si 0.15-0.40%, Mn 0.80-1.50%, Alt 0.01-0.04%, Nb 0.02-0.04%, Ti 0.008-0.018%, P≤0.010%, the low-alloy composition of S≤0.005% is smelted;
(2) after converter smelting, continuous casting is the 250-400mm heavy slab, reheats before rolling, and Heating temperature is 1180-1260 ℃;
(3) controlled rolling and controlled cooling; In two stages rolling, namely rolling the and non-recrystallization in recrystallization zone district is rolling, 1000～1100 ℃ of austenite recrystallization district start rolling temperatures; 850～950 ℃ of austenite non-recrystallization district start rolling temperatures, 790～820 ℃ of finishing temperatures, steel plate rolls the rear rapid cooling zone territory of entering rapidly, and cold but temperature is 450～500 ℃ eventually, 9～12 ℃/s of speed of cooling;
(4) cooling in heap: cooling in heap begins temperature 350-450 ℃, and the cooling in heap time is no less than 12 hours;
Described low-alloy low yield strength ratio offshore engineering structure with the chemical composition of steel is by mass percentage: C 0.09-0.13%, Si 0.15-0.40%, Mn 0.80-1.50%, Alt 0.01-0.04%, Nb 0.02-0.04%, Ti 0.008-0.018%, P≤0.015%, S≤0.005%, surplus are Fe and inevitable impurity;
The performance of this steel is: yield strength 〉=460MPa, and tensile strength 〉=610MPa, yield tensile ratio≤0.80, unit elongation 〉=20%, the Charpy-V impact power average 〉=100J of heart section-60 ℃, the Z-direction relative reduction in area surpasses 35%.
2. method according to claim 1, is characterized in that, step (3) is at austenite recrystallization single pass minimal deformation rate 〉=8%, and deformation rate 〉=20% passage is not less than 2 passages, accumulative total deformation rate 〉=60%.
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| CN103469106B (en) * | 2013-09-17 | 2016-08-17 | 江阴兴澄特种钢铁有限公司 | Directly produce big thickness rack steel plate and manufacture method thereof with continuous casting billet |
| CN103451534B (en) * | 2013-09-18 | 2017-06-23 | 济钢集团有限公司 | A kind of excellent offshore platform steel plate of 60mm thickness directional properties and its production method |
| CN103667909B (en) * | 2013-12-13 | 2016-02-03 | 武汉钢铁(集团)公司 | A kind of mobile ocean Platform Steel of yield tensile ratio≤0.65 and production method |
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| CN102011050A (en) * | 2010-07-15 | 2011-04-13 | 秦皇岛首秦金属材料有限公司 | Steel for 36kg-grade ocean platform and production method thereof |
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Address after: 100041 Shijingshan Road, Shijingshan District, Shijingshan District, Beijing Patentee after: Shougang Group Co. Ltd. Address before: 100041 Shijingshan Road, Shijingshan District, Shijingshan District, Beijing Patentee before: Capital Iron & Steel General Company |
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