WO2025081933A1 - 一种含镁氧化物的易焊接海洋工程用钢板及其制备方法 - Google Patents

一种含镁氧化物的易焊接海洋工程用钢板及其制备方法 Download PDF

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WO2025081933A1
WO2025081933A1 PCT/CN2024/106171 CN2024106171W WO2025081933A1 WO 2025081933 A1 WO2025081933 A1 WO 2025081933A1 CN 2024106171 W CN2024106171 W CN 2024106171W WO 2025081933 A1 WO2025081933 A1 WO 2025081933A1
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steel plate
controlled
steel
marine engineering
passes
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PCT/CN2024/106171
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English (en)
French (fr)
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王中学
麻衡
何康
张佩
王腾飞
张庆普
孙正旭
霍孝新
陈爱娇
吴群
王月香
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山东钢铁股份有限公司
莱芜钢铁集团银山型钢有限公司
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Publication of WO2025081933A1 publication Critical patent/WO2025081933A1/zh

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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/001—Continuous casting of metals, i.e. casting in indefinite lengths of specific alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • C21C5/28—Manufacture of steel in the converter
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/0006—Adding metallic additives
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/0075—Treating in a ladle furnace, e.g. up-/reheating of molten steel within the ladle
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/06—Deoxidising, e.g. killing
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/10—Handling in a vacuum
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D11/00—Process control or regulation for heat treatments
    • C21D11/005—Process control or regulation for heat treatments for cooling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/005—Heat treatment of ferrous alloys containing Mn
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/008—Heat treatment of ferrous alloys containing Si
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/04—Making ferrous alloys by melting
    • C22C33/06—Making ferrous alloys by melting using master alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/002—Bainite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/009—Pearlite
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Definitions

  • the invention belongs to the field of iron and steel metallurgy, and relates to an easy-to-weld marine engineering steel plate containing magnesium oxide and a preparation method thereof.
  • Marine engineering steel is mainly high-strength low-alloy steel, which is required to have high strength and toughness, fatigue resistance, lamellar tearing resistance, and good weldability.
  • high-energy line welding is often used to improve production efficiency.
  • the low-temperature impact toughness of the welding heat affected zone Heat Affected Zone, HAZ
  • HAZ welding heat affected zone
  • low-temperature impact toughness is one of the important properties of marine engineering steel, it is a key factor that must be considered in the design of marine engineering equipment. Therefore, improving the low-temperature impact toughness of the HAZ of high-energy line welded steel plates is a technical problem that high-strength and thick-gauge marine engineering steels must overcome.
  • Chinese patent application CN 110004358 A discloses "a low Pcm value, thick and easy-to-weld marine steel plate and its production method".
  • the patent is based on a low-carbon component system and combines Nb, V, Ti, Ni, Mo and other alloys to develop a low Pcm value marine steel plate.
  • the method disclosed in the patent reduces the Pcm value of the steel plate through a variety of precious alloys, with a high overall cost, and is limited to obtaining a lower Pcm value, without fundamentally improving the performance of the heat-affected zone of the steel plate welding.
  • Chinese patent application CN 110791702 A discloses "a low yield ratio marine steel plate with good welding performance and its manufacturing method".
  • the patent adopts low carbon micro-niobium technology and adds Cu, Ni and Mo to improve the strength and low temperature impact performance of the steel plate to achieve low yield ratio control.
  • the overall Ceq and Pcm content of the method described in the invention is still at a high level, and the improvement of welding performance is limited.
  • Chinese patent application CN 115323253 A discloses a "method for producing S355NL low-temperature impact thick plates by rolling at low compression ratio".
  • This patent uses oxide metallurgy in the steelmaking process and Ti-Mg nano-precipitate control technology to promote the online generation of intragranular ferrite induced by fine second phase particles, which can achieve the production of 355MPa grade medium and thick plates under low compression ratio rolling conditions.
  • the method described in this patent adopts a low-carbon high-alloy design, which has low comprehensive strength and high CEV, and poor welding performance under large-scale conditions.
  • the steel plate has high strength and toughness.
  • the yield strength of the base material of the 60mm thick marine engineering steel plate produced by the present invention is ⁇ 420MPa, the tensile strength is ⁇ 550MPa, A is ⁇ 45%, and the transverse and longitudinal impact energies near the surface, 1/4 and the core at -60°C are all ⁇ 200J, and the mechanical properties are excellent;
  • the Pcm designed by the present invention is ⁇ 0.18, and the weldability is good.
  • the Mg oxide in the steel can greatly improve the mechanical properties of the welding heat affected zone. After welding under the condition of 300kJ/cm heat input, the tensile strength at the steel plate joint is still ⁇ 550MPa, and the impact energy at -60°C in the thickness direction is ⁇ 150J.
  • the present invention provides a magnesium oxide-containing easy-to-weld marine engineering steel plate and a preparation method thereof.
  • the production method can be used to prepare a low-cost, high-strength and toughness steel plate suitable for the field of shipbuilding and marine engineering, which is easy to weld with high line energy, and its mechanical properties and 300kJ/cm heat input welding performance meet the application requirements, and form a set of specific magnesium oxide-containing easy-to-weld marine engineering steel components and corresponding production processes.
  • the present invention adopts the following technical scheme:
  • the invention discloses an easy-to-weld marine engineering steel plate containing magnesium oxide, wherein the chemical composition by mass percentage is C: 0.05-0.09%, Si: 0.15-0.30%, Mn: 1.10-1.50%, P ⁇ 0.010%, S ⁇ 0.003%, Nb: 0.008-0.020%, Ti: 0.005-0.015%, Al: 0.0050-0.010%, Mg: 0.0010-0.0025%, and the remaining components are Fe and unavoidable impurities.
  • Interstitial solid solution strengthening of C atoms is the most economical and effective strengthening method in steel materials.
  • C atoms enter the crystal lattice of the body, causing the crystal lattice to distort, thereby generating forward interaction and greatly improving the body strength.
  • the C content in this steel is controlled to 0.05-0.09%.
  • the Si element can be dissolved in the steel and cause lattice distortion, resulting in a solid solution strengthening effect and improving the strength of the steel plate.
  • too high a Si content can deteriorate the welding performance, so the Si content in this steel is controlled to be 0.15-0.30%.
  • Mn can reduce the ⁇ - ⁇ phase transformation temperature of steel, refine the grains and change the microstructure after phase transformation. Mn can also refine the pearlite lamellae and improve the pearlite strength in low carbon steel without significantly reducing ductility. Therefore, the Mn content in this steel is controlled to 1.10-1.50%.
  • Nb can refine the grains and increase the grain coarsening temperature.
  • Nb in the steel combines with C and N to form nano-sized Nb (C, N), which can produce a significant strengthening effect.
  • Nb can improve the mechanical properties of the welding heat-affected zone.
  • the price of Nb alloy is relatively high, so the addition amount in this steel is 0.008-0.020%.
  • Ti plays a significant role in preventing austenite grain growth, delaying austenite recrystallization, fine grain strengthening, and precipitation strengthening, and is beneficial to the strength and toughness of steel plates. Ti can also significantly improve the tensile strength of weld metal, which is beneficial to improving plasticity and toughness. However, the Ti content must be controlled within a reasonable range. Too little strengthening effect is weak, and too much will lead to a significant decrease in weld toughness. Therefore, the Ti content in this steel is controlled to 0.005-0.015%.
  • Al is a strong deoxidizing element, which can significantly reduce the oxygen content in steel, reduce the number of oxide inclusions in steel, and improve the comprehensive performance of steel. If the Al content in steel is too high, it will hinder the production of Mg-containing oxides in steel, which is not conducive to oxide metallurgical control. Based on this, the Al content in this steel is controlled to 0.005-0.010%
  • Mg is a strong deoxidizing element, and its ability to bind to [O] in molten steel is stronger than that of deoxidizing elements such as Al and Ti. After entering the molten steel, Mg can either directly react with [O] in the molten steel to generate MgO, or reduce the Al and Ti deoxidation products generated in the molten steel to replace the deoxidizing elements therein. In addition, Mg has a significant modifying effect on oxide inclusions. As the Mg content in the steel increases, the incremental refinement and precipitation of nano-scale TiN particles in the steel is promoted, the pinning effect is enhanced, and it is beneficial to inhibit the growth of austenite grains in the high temperature stage of the welding thermal cycle. Based on this, the Mg content in this steel is controlled to be 0.0010-0.0025%
  • Sulfur is easy to combine with manganese to form MnS inclusions, and deform during rolling, seriously affecting the low-temperature impact toughness of steel.
  • sulfur will increase the hot brittleness of weld metal, easily causing hot cracks and pores in the weld, and its content should not be higher than 0.003%.
  • Phosphorus is an element that easily segregates in steel, making it prone to cold brittleness.
  • phosphorus plays a similar role in welds as in steel, and is prone to weld cracks. To ensure that the weld metal has sufficient toughness, the phosphorus content should not be higher than 0.013%.
  • a method for preparing an easily weldable marine engineering steel plate containing magnesium oxide comprising the following steps:
  • LF refining argon is blown and stirred at the bottom throughout the whole process, and lime is added for slag making.
  • Ferrosilicon powder is used to adjust the free oxygen content, and sampling is performed after the top slag is yellow and white.
  • the top slag must be yellow and white slag or white slag before leaving the station.
  • the retention time of yellow and white slag or white slag is ⁇ 8 minutes, and the final slag basicity is ⁇ 2.3; oxygen is determined during the refining process, and when the free oxygen content is between 30-60ppm, wire feeding and alloy fine-tuning are performed: 1 Ti wire is fed, the wire feeding speed is 1.5-2.5m/s, and the length is 80-100m; 2 After the Ti wire is fed, the Mg wire is fed, the wire feeding speed is 1.0-3.0m/s, and the length is 1200-1400m; 3 Alloying is performed while feeding the wire, and the composition is adjusted to the control range. After feeding the wire, argon is blown and stirred for 3-5min, oxygen is determined, and steel samples are taken; the refining process time is controlled to be ⁇ 45min, and the soft blowing time is ⁇ 5min.
  • Mg wire diameter Wire weight ratio 330g/m
  • Ti wire diameter Line weight ratio 596g/m
  • RH refining During the RH refining process, the vacuum degree is between 40-133Pa, the holding time is ⁇ 15 minutes, and the pure degassing time is greater than 5 minutes; after the RH treatment, calcium treatment cannot be carried out, the soft blowing time is maintained at ⁇ 8min, and the entire RH smelting cycle is controlled within 40-60 minutes.
  • the pulling speed and superheat are crucial to the core quality of the easily welded marine engineering steel plate.
  • the pulling speed of the 250 section is controlled to be: 1.0-1.3m/min, and the pulling speed of the 300 section is: 0.7-0.9m/min;
  • the crystallizer uses peritectic steel protection slag; argon blowing is used to protect the pouring throughout the process; the slow cooling time after the billet is off the line is ⁇ 72 hours to completely eliminate the influence of H in the steel.
  • the slab is heated by cold charging. Since this steel grade is designed with low alloy and low Pcm, low temperature steel burning is required to prevent coarse grains.
  • the temperature of the heating furnace soaking section is controlled to be 1130-1200°C, the steel tapping temperature is 1130-1170°C, and the heating rate is ⁇ (9-11) min/cm. When heating thick cold billets (h ⁇ 300mm), the minimum heating rate is 9-10min/cm. This heating rate and temperature can homogenize the original austenite structure in the billet, fully dissolve the alloy elements such as Ti and Nb in the steel, and at the same time do not destroy the oxide metallurgical effect.
  • the steel plate is rolled by controlled rolling and controlled cold rolling, and MULPIC water cooling is used after finishing rolling.
  • the specific process is shown in Table 2.
  • the rough rolling stage is completed in 5-7 passes according to the target steel plate thickness, and the reduction rate of each pass is controlled to gradually increase.
  • the reduction rate of the first pass is ⁇ 7%, and the reduction of the last two passes should be ⁇ 20%.
  • the temperature of this steel grade is still in the recrystallization zone during the rough rolling stage.
  • the gradually increasing reduction rate can fully crush the austenite grains, promote the complete recrystallization process, and then refine the austenite grains.
  • the preferred rough rolling pass for this steel grade is 5 passes, the first pass reduction rate is 7.5%, and the last two passes reductions are 20% and 21% respectively.
  • the finishing rolling stage is in the non-recrystallization zone, and the rolling method still adopts the method of increasing the reduction in each pass.
  • the specific operation is as follows: the finishing rolling passes are controlled to be 7-9 according to the thickness of the finished product, the reduction rate of the first pass is ⁇ 8%, the reduction rate is increased in each pass, and the temperature is controlled to be 760-790°C for at least 3 passes, and the cumulative deformation is ⁇ 25%.
  • Increasing the deformation rate in each pass in the finishing rolling stage can ensure the penetration effect of the core rolling, refine the grain size of the core structure, and improve the uniformity.
  • the second phase nanoparticles such as NbC and TiC precipitated during the finishing rolling process form Coriolis gas masses to pin the austenite grain boundaries, hinder the recrystallization process, and inhibit the abnormal growth of austenite grains.
  • this steel grade is preferably finished with 9 passes, and the comprehensive reduction rate of 3 passes between 760-780°C is 27%.
  • the steel plate After rolling, the steel plate quickly enters the MULPIC water cooler for controlled cooling.
  • the temperature of the steel plate entering the water cooler is 760-780°C.
  • the cooling rate is controlled at 12-26°C/s according to the thickness of the steel plate, so that the austenite is completely transformed into a mixed structure of ferrite, pearlite and bainite, so that the steel plate has higher strength and toughness.
  • the preferred cooling process for this steel grade adopts the centerline control in Table 2.
  • the 60mm thick marine engineering steel plate produced by the present invention has a base material yield strength of ⁇ 420MPa, a tensile strength of ⁇ 550MPa, A ⁇ 45%, and transverse and longitudinal impact energies near the surface, 1/4, and the core at -60°C are all ⁇ 200J, with excellent mechanical properties.
  • Steel plates can be welded under high-wire input conditions of ⁇ 300kJ/cm, and the steel plates do not need to be preheated before welding.
  • the welding process adopts double-wire submerged arc welding, single-sided V-shaped groove, welding interlayer temperature control ⁇ 200°C, and welding passes are determined according to the thickness of the steel plate. After the steel plate is welded, the tensile strength at the joint is ⁇ 540MPa, and the -60°C impact energy of the weld fusion metal area near the surface, 1/4 of the thickness, and the core is ⁇ 120J.
  • Mg fed into the steel is a strong deoxidizing element
  • its ability to combine with [O] in the molten steel is stronger than that of deoxidizing elements such as Al and Ti.
  • Mg can either directly react with [O] in the molten steel to generate MgO, or reduce the Al and Ti deoxidizing products generated in the molten steel, replacing the deoxidizing elements therein to form Mg-containing inclusions. Since there is no excess oxygen in the steel to combine with Ti to form Ti-containing oxides, large-sized TiN particles that affect the toughness of the welding heat affected zone (HAZ) cannot be formed.
  • Mg has a strong modifying effect on oxide inclusions.
  • the addition of Mg to the steel can modify the Al 2 O 3 inclusions in the steel into magnesium-aluminum spinel inclusions, and can also promote the incremental refinement and precipitation of nano-scale TiN particles in the steel, enhancing the pinning effect.
  • the HAZ structure retains a complete original austenite grain boundary (PAGB), and the intracrystalline structure is a high-strength, low-toughness lath-shaped bainite (LB), and the LB lath structure is a small MA island.
  • the morphology of MA islands significantly affects the toughness of HAZ: small point-shaped MA islands are harmless to toughness; slender MA islands will deteriorate the toughness of HAZ.
  • the oxides formed by the addition of Mg to the steel will greatly promote the formation of nano-sized TiN particles, thereby pinning the boundaries and inhibiting the growth of the original austenite grain boundaries (PAGB), thereby promoting the formation of point-shaped MA islands and improving the toughness of HAZ.
  • PAGB original austenite grain boundaries
  • the magnesium oxide-containing easy-to-weld marine engineering steel plate of the present invention adds microalloying elements such as Nb and Ti to refine the grains and produce obvious fine grain strengthening and precipitation strengthening effects.
  • microalloying elements such as Nb and Ti
  • the dislocation density in the steel plate can be greatly improved, and the strength and toughness of the steel can be improved.
  • the Mg element added to the steel can inhibit the precipitation of large-sized TiN, and at the same time has a strong modifying effect on inclusions.
  • the Mg element can also promote the refinement of the original austenite grain boundary (PAGB), and improve the strength and toughness of the weld as a whole.
  • the yield strength of the base material of the 60mm thick magnesium oxide-containing easy-to-weld marine engineering steel plate is ⁇ 420MPa
  • the tensile strength is ⁇ 550MPa
  • a ⁇ 45% the transverse and longitudinal impact energy at -60°C near the surface, 1/4
  • the core is greater than 200J
  • CEV ⁇ 0.38 and Pcm ⁇ 0.18 are controlled
  • after welding with a line input of ⁇ 300kJ/cm the tensile strength at the joint is ⁇ 540MPa, and the impact energy at -60°C in the thickness direction is ⁇ 150J, which fully meets the requirements of large line energy welding.
  • the easy-to-weld marine engineering steel produced by the magnesium oxide metallurgical technology disclosed in the invention has excellent comprehensive mechanical properties, low alloy cost, strong production line adaptability, and has broad promotion prospects.
  • FIG1 is a metallographic structure (near the surface) of an easily weldable marine engineering steel plate containing magnesium oxide according to Example 1 of the present invention
  • FIG2 is a metallographic structure (1/4 thickness) of an easily weldable marine engineering steel plate containing magnesium oxide according to Example 1 of the present invention
  • FIG3 is a metallographic structure (1/2 thickness) of an easily weldable marine engineering steel plate containing magnesium oxide according to Example 1 of the present invention
  • FIG. 4 is a macroscopic metallographic view of the welding area of the easily weldable marine engineering steel plate containing magnesium oxide according to Example 1 of the present invention.
  • Embodiment 1 is a diagrammatic representation of Embodiment 1:
  • a 60mm thick magnesium oxide-containing easy-to-weld marine engineering steel plate comprising the following chemical components C: 0.07%, Si: 0.25%, Mn: 1.20%, P: 0.007%, S: 0.003%, Nb: 0.015%, Ti: 0.010%, Al: 0.006%, Mg: 0.0015%, and the remaining components are Fe and unavoidable impurities.
  • the steel plate base material yield strength is 433MPa
  • tensile strength is 572MPa
  • A is 48%
  • the average transverse and longitudinal impact energy values near the surface, 1/4, and the core at -60°C are 313J, 287J, and 267J respectively
  • the manufacturing method comprises the following steps: the molten iron is continuously cast after converter smelting, LF refining, and RH degassing refining, and a 250mm or 300mm thick continuous casting billet is selected, and the billet needs to be slowly cooled after continuous casting.
  • the wire is fed and the alloy is fine-tuned: 1 Ti wire is fed, the wire feeding speed is 2m/s, and the length is 85m; 2 After the Ti wire is fed, the Mg wire is fed, the wire feeding speed is 2.0m/s, and the length is 1273m; 3 The wire is fed and alloyed at the same time, and the composition is adjusted to the control range.
  • the continuous casting process implements a 300mm billet drawing speed.
  • the steel plate for marine engineering is obtained by heating, rolling and MULPIC water cooling to 510°C.
  • the temperature of the steel plate in the soaking section is 1160°C
  • the steel tapping temperature is 1150°C
  • the heating rate is 10/min/cm.
  • the rough rolling stage of the steel plate is completed in 5 passes, and the reduction rate of each pass is gradually increased.
  • the first pass reduction rate is 7.5%
  • the last two passes are 100°C.
  • the first pass reduction rate is 8.2%, and the reduction rate increases gradually.
  • the last three rolling temperatures are 787°C, 767°C, and 760°C, respectively, and the cumulative deformation is 26%.
  • Figures 1 to 3 reflect the changes in the structure of the steel plate in the thickness direction. It can be seen from the figure that the structure of the steel plate produced by the embodiment of the present invention is ferrite/pearlite, the core contains part of bainite, the thickness direction has good structure uniformity, and there is no grain coarsening phenomenon, indicating that the smelting composition and rolling process are properly controlled.
  • the steel plate adopts a single-sided V-shaped groove. After double-wire submerged arc welding, the tensile strength at the weld joint is 570MPa.
  • the average values of the -60°C impact energy of the weld fusion metal area near the surface, 1/4 of the thickness, the core, and the lower surface are 209J, 192J, 178J, and 202J respectively, and the comprehensive mechanical properties of the weld are excellent.
  • the welding process and mechanical properties are shown in Tables 3 and 4.
  • An 80mm thick magnesium oxide-containing easy-to-weld marine engineering steel plate comprises the following chemical components: C: 0.09%, Si: 0.26%, Mn: 1.49%, P: 0.006%, S: 0.003%, Nb: 0.020%, Ti: 0.013%, Al: 0.008%, Mg: 0.0023%, and the remaining components are Fe and unavoidable impurities.
  • the yield strength of the steel plate base material is 417MPa
  • the tensile strength is 568MPa
  • A is 45%
  • the average transverse and longitudinal impact energy values at -60°C near the surface, 1/4, and the core are 271J, 235J, and 217J respectively, CEV: 0.34, and Pcm: 0.17.
  • the manufacturing method comprises the following steps: the molten iron is continuously cast after converter smelting, LF refining, and RH degassing refining, and a 300mm thick continuous casting billet is selected, and the billet needs to be slowly cooled after continuous casting.
  • the wire is fed and the alloy is fine-tuned: 1 Ti wire is fed, the wire feeding speed is 2m/s, and the length is 106m; 2 After the Ti wire is fed, the Mg wire is fed, the wire feeding speed is 2.0m/s, and the length is 1854m; 3
  • the wire is fed and alloyed at the same time, and the composition is adjusted to the control range.
  • the continuous casting process implements the 300mm billet drawing speed, and the drawing speed is 0.95m/min.
  • the steel billet is heated, rolled, and cooled to 450°C by MULPIC water cooling to obtain the above-mentioned marine engineering steel plate.
  • the temperature of the steel billet soaking section is 1160°C
  • the steel tapping temperature is 1150°C
  • the heating rate is 9-10/min/cm
  • the rough rolling stage of the steel plate is completed in 5 passes, and the reduction rate of each pass is controlled to gradually increase.
  • the reduction rate of the first pass is 5.2%
  • the reductions of the last 2 passes are 17.2% and 24.20% respectively.
  • the finishing rolling stage requires 8+1 rolling passes, and the rolling method still adopts the method of increasing the reduction amount pass by pass.
  • the reduction rate of the first pass is 3.5%, and the reduction rate increases pass by pass, and finally the belt is pressed down.
  • the three rolling temperatures were 763°C, 755°C and 748°C respectively, and the cumulative deformation was 18%.
  • the steel plate adopts a single-sided V-shaped groove, and after double-wire submerged arc welding, the weld has good toughness.
  • the welding process is similar to that of the embodiment, and the mechanical properties of the steel plate of embodiment 2 after welding are shown in Table 5.

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Abstract

本发明公开了一种含镁氧化物的易焊接海洋工程用钢板及其制备方法，其化学成分质量百分比为C：0.05-0.09％，Si：0.15-0.30％，Mn：1.10-1.50％，P≤0.010％，S≤0.003％，Nb：0.008-0.020％，Ti：0.005-0.015％，Al：0.005-0.010％，Mg：0.0010-0.0025％，其余成分为Fe及不可避免杂质。所述易焊接海洋工程钢板母材屈服强度≥420MPa，抗拉强度≥550MPa，A≥45％，-60℃近表面、1/4处、心部的横纵向冲击功≥200J，控制CEV≤0.34、Pcm≤0.18；经≥300kJ/cm线输入焊接后，接头处抗拉强度≥540MPa，厚度方向-60℃冲击功≥150J，完全满足大线能量焊接需要。该发明公开的含镁氧化物冶金技术生产的易焊接海洋工程钢综合力学性能优秀，合金成本低廉，产线适应性强，具有广阔的推广前景。

Description

一种含镁氧化物的易焊接海洋工程用钢板及其制备方法
相关申请
本申请要求名称为“一种含镁氧化物的易焊接海洋工程用钢板及其制备方法”、于2023年10月19日提交的中国专利申请2023113541781的优先权，在此通过引用包括该件申请。
技术领域
本发明属于钢铁冶金领域，涉及一种含镁氧化物的易焊接海洋工程用钢板及其制备方法。
背景技术
海洋工程用钢以高强低合金钢为主，要求具备高强度韧、抗疲劳、抗层状撕裂、以及良好的焊接性等性能。现阶段船舶及海工装备向大型化、高效化方向发展，在建造过程中多采用大线能量焊接以提高生产效率。但各类海洋工程钢板在采用大线能量焊接时易出现焊接热影响区(Heat Affected Zone，HAZ)低温冲击韧性严重下降的问题，严重制约其应用。由于低温冲击韧性是海洋工程用钢的重要性能之一，是海洋工程装备设计时必须考虑的关键因素。因此，提高大线能量焊接钢板HAZ的低温冲击韧性是高强度、厚规格海洋工程用钢要突破的技术难题。
虽然目前关于易焊接海洋工程用钢板的专利较多，但是此类专利所用合金较多，成本较高。以下简要介绍几个相似的专利：
中国专利申请CN 110004358 A公布了“一种低Pcm值大厚度易焊接海工钢板及其生产方法”，该专利基于低碳成分体系，并配合Nb、V、Ti、Ni、Mo等合金开发出低Pcm值海工钢板。该专利公布的方法通过多种贵重合金降低钢板Pcm值，综合成本较高，且仅局限于获得较低Pcm值，未从根本上改善钢板焊接热影响区性能。
中国专利申请CN 110791702 A公布了“一种焊接性能良好的低屈强比海工钢板及其制造方法”，该专利采用低碳微铌技术，同时添加Cu、Ni、Mo以提高钢板强度和低温冲击性能，实现低屈强比控制。但该发明阐述方法的总体Ceq、Pcm含量仍处于较高水平，对焊接性能改善程度有限。
中国专利申请CN 115323253 A公布了“一种低压缩比轧制S355NL低温冲击厚板的生产方法”，该专利采用炼钢过程氧化物冶金工艺和Ti-Mg纳米级析出物控制技术促成微细第二相粒子诱导晶内铁素体在线生成，可实现低圧缩比轧制条件下生产355MPa级别中厚板。但该专利阐述的方法采用低碳高合金设计，综合强度较低，且CEV较高，大输条件下焊接性能较差。
本发明优势主要表现在：(1)钢板具有高强韧特点，本发明生产的60mm厚海洋工程钢板母材屈服强度≥420MPa，抗拉强度≥550MPa，A≥45％，-60℃近表面、1/4处、心部的横纵向冲击功均≥200J，力学性能优异；(2)本发明设计的Pcm≤0.18，可焊性良好，同时钢中的Mg氧化物可大幅改善焊接热影响区力学性能，经300kJ/cm热输入量条件下焊接后，钢板接头处抗拉强度仍≥550MPa，厚度方向-60℃冲击功≥150J。
发明内容
为克服现有技术不足，本发明提供一种含镁氧化物的易焊接海洋工程用钢板及其制备方法。采用此生产方法可制备出一种适用于船舶海洋工程领域的易于大线能量焊接的低成本、高强韧性钢板，其力学性能、300kJ/cm热输入量焊接性能均满足应用需求，并形成一套特定的含镁氧化物的易焊接海洋工程用钢成分及相应的生产工艺。
为达到上述目的，本发明采用如下技术方案：
一种含镁氧化物的易焊接海洋工程钢板，其化学成分质量百分比为C：0.05-0.09％，Si：0.15-0.30％，Mn：1.10-1.50％，P≤0.010％，S≤0.003％，Nb：0.008-0.020％，Ti：0.005-0.015％，Al：0.0050-0.010％，Mg：0.0010-0.0025％，其余成分为Fe及不可避免杂质。
成分设计及冶炼
本发明中，添加的化学元素、及作用机理如下：
(a)碳
C原子的间隙固溶强化是钢铁材料中最经济、最有效的强化方式。C原子进入机体晶体点阵中，使得晶体点阵发生畸变，从而产生前行相互作用，大幅提高机体强度。但随着C含量增加，机体的韧性、延伸率等性能大幅下降，同时焊接性能急剧恶化，因此本钢中C含量控制为0.05-0.09％。
(b)硅
Si元素可固溶于钢中并引起晶格畸变，产生固溶强化效果，提高钢板强度。但Si含量过高可恶化焊接性能，因此本钢中Si含量控制为0.15-0.30％。
(c)锰
Mn能降低钢的γ－α相变温度，使晶粒细化并改变相变后的微观组织。Mn还可细化珠光体片层，提高低碳钢中珠光体强度，同时不大幅降低延展性，因此本钢中Mn含量控制为1.10-1.50％。
(d)铌
Nb可以细化晶粒，提高晶粒粗化温度，同时钢中Nb与C、N结合形成纳米尺寸Nb(C、N)，可产生显著的强化效果，同时Nb可改善焊接热影响区力学性能。但Nb合金价格较高，因此本钢中加入量为0.008-0.020％。
(e)钛
Ti在阻止奥氏体晶粒长大、延迟奥氏体再结晶、细晶强化、析出强化方面均显著作用，而且有利于钢板的强韧性。Ti也能显著地提高焊缝金属的抗拉强度，对改善塑性和韧性有利。但Ti含量必须控制在合理范围，过少强化作用微弱，过多反而导致焊缝韧性大幅度下降。因此本钢中Ti含量控制为0.005-0.015％％。
(f)铝
Al为强脱氧元素，可大幅度减低钢中氧含量，减少钢中氧化物夹杂物数量，提高钢的综合性能。若钢中Al含量过高时可阻碍钢中含Mg氧化物生产，不利于氧化物冶金控制。基于此，本钢中Al含量控制为0.005-0.010％
(g)镁
Mg是一种强脱氧元素，与钢液中[O]的结合能力强于Al、Ti等脱氧元素。Mg进入钢液之后既可通过直接与钢水中的[O]反应生成MgO，也可将钢液中生成的Al、Ti脱氧产物还原，置换其中的脱氧元素。此外Mg对氧化物夹杂的改性作用明显。随着钢中Mg含量升高，促进钢中纳米级TiN粒子增量细化析出，增强钉扎作用，有利于抑制焊接热循环高温阶段奥氏体晶粒长大，基于此本钢中Mg含量控制为0.0010-0.0025％
(h)有害元素
硫易与锰结合生成MnS夹杂物，并在轧制过程中变形，严重影响钢的低温冲击韧性性。另外，硫会增加焊缝金属的热脆性，易使焊缝产生热裂纹和气孔，其含量不应高于0.003％。
磷：磷在钢中是一种易偏析元素，使钢易发生冷脆。另外，磷在焊缝中与在钢中起相似作用，易产生焊接裂纹。为保证焊缝金属具有足够的韧性，磷含量不应高于0.013％。
一种含镁氧化物的易焊接海洋工程钢板的制备方法，所述制备方法包括以下步骤：
1)冶炼生产
转炉冶炼：入炉铁水须计量称重，控制废钢加入比例≤20％；冶炼过程中渣料于终点前3分钟加完，采用一次拉碳及单渣深脱磷工艺冶炼，终渣碱度控制在R＝3.5-4.5；放钢时采用硅铁等脱氧，并分批加入金属锰、硅铁、铌铁合金，顺钢流加入500kg顶石灰、200kg预熔渣，为保证脱氧效果及合金充分熔融，控制放钢流程时间≥3min。
LF精炼：全程底吹氩搅拌，并加入石灰进行造渣，采用硅铁粉调整自由氧含量，顶渣黄白渣后取样。出站前顶渣必须为黄白渣或白渣，黄白渣或白渣保持时间≥8分钟，终渣碱度≥2.3；精炼过程中定氧，自由氧含量介于30-60ppm时喂线并合金微调：①喂Ti线，喂线速度1.5-2.5m/s，长度80-100m；②Ti线喂完后喂入Mg线，喂线速度1.0-3.0m/s，长度1200-1400m，③喂线同时进行合金化，调整成分到控制范围，喂线后吹氩搅拌3-5min，定氧、取钢样；控制精炼流程时间≥45min，软吹时间≥5min。
表1 Ti线和Mg线化学成分
注：Mg线：直径线重比330g/m；Ti线：直径线重比596g/m
RH精炼：RH精炼处理过程中真空度介于40-133Pa之间，保持时间≥15分钟，纯脱气时间大于5分钟；RH处理结束后，不可进行钙处理，保持软吹时间≥8min，控制整个RH冶炼周期在40-60分钟。
连铸：拉速及过热度对易焊接海洋工程用钢板的心部质量至关重要，实际生产中控制250断面拉速为：1.0-1.3m/min，300断面拉速为：0.7-0.9m/min；结晶器均采用包晶钢保护渣；全程吹氩保护浇注；铸坯下线后缓冷时间≥72小时，以彻底消除钢中H影响。
2)轧制
板坯加热制度
板坯采用冷装坯加热，由于本钢种采用低合金、低Pcm设计，为防止晶粒粗大需低温烧钢，控制加热炉均热段温度为1130-1200℃，出钢温度1130-1170℃，加热速率≥(9-11)min/cm。厚规格冷坯(h≥300mm)加热时，加热速度最低按9-10min/cm执行。此加热速度和温度可使钢坯中原始奥氏体组织均匀化，钢中Ti、Nb等合金元素充分固溶，同时又不破坏氧化物冶金效果。本钢种优选的板坯加热制度：均热段温度为1160℃，出钢温度1160℃，加热速率10min/cm。
轧制工艺
钢板采用控轧控冷轧制，精轧后采用MULPIC水冷，具体工艺如表2所示。其中，粗轧阶段依据目标钢板厚度分5-7道次完成，控制道次压下率逐渐上升，首道次压下率≥7％，最后2道次压下量均应≥20％。本钢种粗轧阶段温度仍处于再结晶区，逐步递增的压下率能充分破碎奥氏体晶粒，促进完全再结晶过程，进而细化奥氏体晶粒。采用300mm厚板坯型生产60mm钢板时，本钢种优选的粗轧制道次为5道次，首道次压下率为7.5％，最后2道次压下量分别为20％、21％。
精轧阶段处于未再结晶区，轧制方式仍采用压下量逐道次提升方式，具体操作如下：根据成品厚度控制精轧道次为7-9道，首道次压下率≥8％，压下率逐道次递升，待温控制至少3道次轧制温度为760-790℃，且累计变形量≥25％。精轧阶段逐到道次提高变形率可保证心部轧制的渗透效果，细化心部组织晶粒度，提高均匀性。同时精轧过程中析出的NbC、TiC等第二相纳米粒子形成柯氏气团钉扎奥氏体晶界，阻碍再结晶过程，抑制奥氏体晶粒异常长大。采用300mm厚板坯生产60mm钢板时，本钢种优选9道次精轧，在760-780℃间3道次综合压下率为27％。
轧后钢板快速进入MULPIC水冷机进行控冷，钢板进去水冷机温度为760-780℃，根据钢板厚度控制冷速为12-26℃/s不等，使奥氏体完全转变为铁素体、珠光体和贝氏体混合组织，使钢板在具有较高的强度和韧性。本钢种优选的冷却工艺采用表2中线控制。
表2轧制及水冷工艺

运用本发明生产的60mm厚海洋工程钢板母材屈服强度≥420MPa，抗拉强度≥550MPa，A≥45％，-60℃条件下近表面、1/4处、心部的横纵向冲击功均≥200J，力学性能优异。
钢板可实现≥300kJ/cm高线输入条件下焊接，且钢板无需焊前预热，焊接工艺采用双丝埋弧焊接，采用单边V型坡口，焊接层间温度控制≤200℃，焊接道次依据钢板厚度确定。钢板焊后，接头处抗拉强度≥540MPa，焊缝熔合金属区域近表面、厚度1/4处、心部的-60℃冲击功均≥120J。
针对大线能量焊接方面，由于钢中喂入的Mg是一种强脱氧元素，与钢液中[O]的结合能力强于Al、Ti等脱氧元素，Mg进入钢液之后既可通过直接与钢水中的[O]反应生成MgO，也可将钢液中生成的Al、Ti脱氧产物还原，置换其中的脱氧元素形成含Mg夹杂物，由于钢中没有富余的氧与Ti结合形成含Ti氧化物，所以无法形成影响焊接热影响区(HAZ)强韧性的大尺寸TiN粒子。此外Mg对氧化物夹杂具有很强的改性作用，钢中添加的Mg可将钢中Al2O3夹杂改性为镁铝尖晶石类夹杂物，还可促进钢中纳米级TiN粒子增量细化析出，增强钉扎作用。HAZ组织中保留完整的原奥氏体晶界(PAGB)，晶内组织均为高强度、低韧性板条状贝氏体(LB)，LB板条结构中为细小M-A岛。M-A岛形貌显著影响HAZ韧性：尺寸细小的点状M-A岛对韧性无害；细长状M-A岛会恶化HAZ韧性。由于PAG尺寸直接影响M-A尺寸，进而影响HAZ韧性，所以钢中添加的Mg形成的氧化物会大大促进纳米级TiN等粒子形成，进而钉扎境界，抑制原奥氏体晶界(PAGB)长大，进而促进点状M-A岛形成，提高HAZ韧性。
本发明所述含镁氧化物的易焊接海洋工程用钢板中添加Nb、Ti等微合金元素以细化晶粒，并产生明显的细晶强化和沉淀强化效果。结合粗轧阶段的逐道次压下率提升轧制模式及精轧阶段760-790℃区间内道次累加变形控制，可大幅提升钢板中位错密度，提升钢材强韧性。钢中添加的Mg元素可抑制大尺寸TiN析出，同时对夹杂物有较强的改性作用，此外Mg元素还可以促进原奥氏体晶界(PAGB)细化，整体提升焊缝处强韧性。给予以上关键技术实施所述60mm厚的含镁氧化物的易焊接海洋工程钢板母材屈服强度≥420MPa，抗拉强度≥550MPa，A≥45％，-60℃近表面、1/4处、心部的横纵向冲击功均大于200J，控制CEV≤0.38、Pcm≤0.18；经≥300kJ/cm线输入焊接后，接头处抗拉强度≥540MPa，厚度方向-60℃冲击功≥150J，完全满足大线能量焊接 需要。该发明公开的含镁氧化物冶金技术生产的易焊接海洋工程钢综合力学性能优秀，合金成本低廉，产线适应性强，具有广阔的推广前景。
附图说明
图1为本发明实施例1含镁氧化物的易焊接海洋工程用钢板的金相组织(近表面)；
图2为本发明实施例1含镁氧化物的易焊接海洋工程用钢板的金相组织(1/4厚度)；
图3为本发明实施例1含镁氧化物的易焊接海洋工程用钢板的金相组织(1/2厚度)；
图4为本发明实施例1含镁氧化物的易焊接海洋工程用钢板的焊接区域宏观金相。
具体实施方式
下面结合附图和实施例对本发明的技术方案进行详细的说明。
实施例1：
一种60mm厚含镁氧化物的易焊接海洋工程用钢板，包括以下化学成分C：0.07％，Si：0.25％，Mn：1.20％，P：0.007％，S：0.003％，Nb：0.015％，Ti：0.010％，Al：0.006％，Mg：0.0015％，其余成分为Fe及不可避免杂质。其中所述钢板母材屈服强度为433MPa，抗拉强度为572MPa，A为48％，-60℃近表面、1/4处、心部的横纵向冲击功均值分别为313J、287J、267J，CEV：0.27，Pcm：0.14。
其制造方法包括以下步骤：铁水经转炉冶炼、LF精炼、RH脱气精炼后进行连铸，选用250mm或300mm厚连铸拉坯，钢坯连铸完成后需缓冷处理。所述冶炼过程中，精炼自由氧含量位45ppm时喂线并合金微调：①喂Ti线，喂线速度2m/s，长度85m；②Ti线喂完后喂入Mg线，喂线速度2.0m/s，长度1273m，③喂线同时进行合金化，调整成分到控制范围，喂线后吹氩搅拌5min，软吹时间≥9min；RH精炼处理过程中真空度位≤70Pa，保持时间15分钟，纯脱气时间10分钟；连铸工艺执行300mm坯型拉速。
钢坯经加热、轧制、MULPIC水冷控冷至510℃，获得上述海洋工程用钢板。加热过程中钢坯均热段温度为1160℃，出钢温度1150℃，加热速率10/min/cm；钢板粗轧阶段分5道次完成，控制道次压下率逐渐上升，首道次压下率为7.5％，最后2道 次压下量分别为20％、21％。精轧阶段需7道次轧制，轧制方式仍采用压下量逐道次提升方式，首道次压下率为8.2％，压下率逐道次递升，最后三道轧制温度分别为787℃、767℃、760℃，累计变形量为26％。
图1-图3反映了钢板厚度方向组织变化情况，由图可知，本发明实施例生产钢板组织为铁素体/珠光体，心部含有部分贝氏体，厚度方向组织均匀性良好，并未出现晶粒粗化现象，说明冶炼成分及轧制工艺控制得当。所述钢板采用单边V型坡口，经双丝埋弧焊接后，焊接接头处抗拉强度为570MPa，焊缝熔合金属区域近表面、厚度1/4处、心部、下表面的-60℃冲击功均值分别为209J、192J、178J、202J，焊缝处综合力学性能优异。焊接工艺、力学性能如表3、表4所示。
表3实施例1钢板双丝埋弧焊接

表4实施例1钢板焊后力学性能
实施例2
一种80mm厚含镁氧化物的易焊接海洋工程用钢板，包括以下化学成分C：0.09％，Si：0.26％，Mn：1.49％，P：0.006％，S：0.003％，Nb：0.020％，Ti：0.013％，Al：0.008％，Mg：0.0023％，其余成分为Fe及不可避免杂质。其中所述钢板母材屈服强度为417MPa，抗拉强度为568MPa，A为45％，-60℃近表面、1/4处、心部的横纵向冲击功均值分别为271J、235J、217J，CEV：0.34，Pcm：0.17。
其制造方法包括以下步骤：铁水经转炉冶炼、LF精炼、RH脱气精炼后进行连铸，选用厚度300mm连铸拉坯，钢坯连铸完成后需缓冷处理。所述冶炼过程中，精炼自由氧含量位50ppm时喂线并合金微调：①喂Ti线，喂线速度2m/s，长度106m；②Ti线喂完后喂入Mg线，喂线速度2.0m/s，长度1854m，③喂线同时进行合金化，调整成分到控制范围，喂线后吹氩搅拌5min，软吹时间12min；RH精炼处理过程中真空度位≤60Pa，保持时间15分钟，纯脱气时间10分钟；连铸工艺执行300mm坯型拉速,拉速为0.95m/min。
钢坯经加热、轧制、MULPIC水冷控冷至450℃，获得上述海洋工程用钢板。加热过程中钢坯均热段温度为1160℃，出钢温度1150℃，加热速率9-10/min/cm；钢板粗轧阶段分5道次完成，控制道次压下率逐渐上升，首道次压下率为5.2％，最后2道次压下量分别为17.2％、24.20％。精轧阶段需8+1道次轧制，轧制方式仍采用压下量逐道次提升方式，首道次压下率为3.5％，压下率逐道次递升，最后带圧下 量的三道轧制温度分别为763℃、755℃、748℃，累计变形量为18％。
所述钢板采用单边V型坡口，经双丝埋弧焊接后，焊缝处强韧性良好。焊接工艺与实施例去相似，实施例2钢板焊后力学性能表5所示。
表5实施例2钢板焊后力学性能
本发明的工艺参数(如轧制变形量、保温时间等)区间上下限取值以及区间值都能实现本法，在此不一一列举实施例。
本发明未详细说明的内容均可采用本领域的常规技术知识。
最后所应说明的是，以上实施例仅用以说明本发明的技术方案而非限制。尽管参照实施例对本发明进行了详细说明，本领域的普通技术人员应该理解，对本发明的技术方案进行修改或者等同替换，都不脱离本发明技术方案的精神和范围，其均应涵盖在本发明的权利要求范围当中。

Claims (10)

  1. 一种含镁氧化物的易焊接海洋工程用钢板，其特征在于，所述易焊接海洋工程用钢板的化学成分质量百分比为C：0.05-0.09％，Si：0.15-0.30％，Mn：1.10-1.50％，P≤0.010％，S≤0.003％，Nb：0.008-0.020％，Ti：0.005-0.015％，Al：0.005-0.010％，Mg：0.0010-0.0025％，其余成分为Fe及不可避免杂质。
  2. 根据权利要求1所述的一种含镁氧化物的易焊接海洋工程用钢板，其特征在于，所述易焊接海洋工程用钢板的母材屈服强度≥420MPa，抗拉强度≥550MPa，A≥45％，-60℃近表面、1/4处、心部的横纵向冲击功≥200J，控制CEV≤0.34、Pcm≤0.18；经≥300kJ/cm线输入焊接后，接头处抗拉强度≥540MPa，厚度方向-60℃冲击功≥150J。
  3. 根据权利要求1所述的一种含镁氧化物的易焊接海洋工程用钢板，其特征在于，所述易焊接海洋工程用钢板的厚度为40-60mm。
  4. 一种含镁氧化物的易焊接海洋工程用钢板的制备方法，所述制备方法包括以下步骤：
    1)冶炼生产
    转炉冶炼：入炉铁水计量称重，控制废钢加入比例≤20％；冶炼过程中渣料于终点前3分钟加完，采用一次拉碳及单渣深脱磷工艺冶炼，终渣碱度控制在R＝3.5-4.5；放钢时采用硅铁脱氧，并分批加入金属锰、硅铁、铌铁合金，顺钢流加入石灰和预熔渣，为保证脱氧效果及合金充分熔融，控制放钢流程时间≥3min；
    LF精炼：全程底吹氩搅拌，并加入石灰进行造渣，采用硅铁粉调整自由氧含量，顶渣黄白渣后取样；出站前顶渣必须为黄白渣或白渣，黄白渣或白渣保持时间≥8分钟，终渣碱度≥2.3；精炼过程中定氧，自由氧含量介于30-60ppm时喂线并合金微调：喂Ti线，喂线速度1.5-2.5m/s，长度80-100m；Ti线喂完后喂入Mg线，喂线速度1.0-3.0m/s，长度1200-1400m；喂线同时进行合金化，调整成分到控制范围，喂线后吹氩搅拌3-5min，定氧、取钢样；控制精炼流程时间≥45min，软吹时间≥5min；
    RH精炼：RH精炼处理过程中真空度介于40-133Pa之间，保持时间≥15分钟，纯脱气时间大于5分钟；RH处理结束后，不可进行钙处理，保持软吹时间≥8min，控制整个RH冶炼周期在40-60分钟；
    连铸：控制断面拉速为：7.0-1.3m/min；结晶器均采用包晶钢保护渣；全程吹氩 保护浇注；铸坯下线后缓冷时间≥72小时；
    2)轧制
    板坯加热制度
    板坯采用冷装坯加热，控制加热炉均热段温度为1130-1200℃，出钢温度1130-1170℃，加热速率9-11min/cm；
    钢板采用控轧控冷轧制，其中，精轧阶段处于未再结晶区，轧制方式仍采用压下量逐道次提升方式；
    轧后钢板快速进入MULPIC水冷机进行控冷，钢板进去水冷机温度为760-780℃，根据钢板厚度控制冷速为12-26℃/s不等，使奥氏体完全转变为铁素体、珠光体和贝氏体混合组织。
  5. 根据权利要求4所述的制备方法，其特征在于，连铸过程中，控制250断面拉速为：1.0-1.3m/min，300断面拉速为：0.7-0.9m/min。
  6. 根据权利要求4所述的制备方法，其特征在于，均热段温度为1160℃，出钢温度1160℃，加热速率10min/cm。
  7. 根据权利要求4所述的制备方法，其特征在于，粗轧阶段依据目标钢板厚度分5-7道次完成，控制道次压下率逐渐上升，首道次压下率≥7％，最后2道次压下量均应≥20％。
  8. 根据权利要求7所述的制备方法，其特征在于，采用300mm厚板坯型生产60mm钢板时，粗轧制道次为5道次，首道次压下率为7.5％，最后2道次压下量分别为20％、21％。
  9. 根据权利要求4所述的制备方法，其特征在于，压下量逐道次提升方式具体操作为：根据成品厚度控制精轧道次为7-9道，首道次压下率≥8％，压下率逐道次递升，待温控制至少3道次轧制温度为760-790℃，且累计变形量≥25％。
  10. 根据权利要求9所述的制备方法，其特征在于，采用300mm厚板坯型生产60mm钢板时，采用9道次精轧，在760-780℃间3道次综合压下率为27％。
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