80-100 mm 1000 MPa grade steel and welding method thereof

Abstract

The invention discloses 1000 MPa grade steel with the thickness of 80-100 mm and a welding method of the 1000 MPa grade steel, and belongs to the technical field of welding. The 1000 MPa grade steel provided by the invention comprises the following components in percentage by weight: 0.06 to 0.14 percent of C, 0.05 to 0.30 percent of Si, 0.65 to 1.20 percent of Mn, 1.6 to 2.5 percent of Ni, 0.02 to 0.06 percent of Alt, 0.02 to 0.08 percent of V, 0.004 to 0.016 percent of B, 0.30 to 0.70 percent of Cr, 0.15 to 0.42 percent of Cu, 0.25 to 0.70 percent of Mo, 0.010 to 0.030 percent of Nb, 0.008 to 0.020 percent of Ti and the balance of Fe. The tensile strength is 1000-1180 MPa, the impact absorbing energy at the temperature of-60 DEG C is larger than or equal to 150 J, and a flat and crack-free welding joint with good mechanical performance can be obtained after welding.

Description

Technical Field

[0001] The invention belongs to the technical field of welding, and in particular relates to a 1000MPa grade steel material with a thickness of 80-100mm and a welding method thereof. Background Art

[0002] Against the backdrop of rapid development of my country's energy and infrastructure construction, the development and utilization of clean energy has reached an unprecedented level, becoming a key force in promoting energy structure optimization and sustainable development. With the continuous expansion of the scale of related projects and the increasing complexity of the operating environment, the performance requirements for key structural materials have become increasingly stringent and diversified. As one of the core engineering materials, steel not only has to withstand huge mechanical stress, but also needs to have good corrosion resistance to resist long-term erosion in harsh environments such as humidity and acid-base substances. At the same time, under extreme temperature conditions such as low temperature and high temperature, stable mechanical properties and structural integrity must still be maintained to ensure the safety and durability of the project.

[0003] For the current thicker steel billets, traditional welding methods have exposed many drawbacks. Since welding grooves need to be opened, their width is often large, which not only makes the difficulty of weld formation increase dramatically, but also easily causes large welding deformation, and the subsequent cleaning of the weld is also extremely difficult. In addition, traditional welding methods are inefficient and the welding quality is difficult to guarantee. There are huge challenges in preparing thick steel billets and ensuring their excellent performance. In the welding process of traditional welding technology, due to the large groove width, the heat input is not easy to accurately control during welding, which can easily lead to uneven crystallization of weld metal, and then produce defects such as pores and slag inclusions, which seriously affect the density and strength of the weld. Moreover, large welding deformation may cause the dimensional accuracy of the steel billet to exceed the design requirements. The subsequent correction work is not only complicated, but may also introduce new residual stresses, reducing the fatigue life and overall performance of the steel billet.

[0004] Chinese patent CN112453662A discloses a submerged arc welding process suitable for 1000MPa high-strength steel. The chemical composition and mass percentage of 1000MPa high-strength steel are as follows: C: 0.08% to 0.16%, Si: 0.15% to 0.45%, Mn: 0.80% to 1.85%, Ni≤3.0%, Mo≤0.50%, Cr≤0.50%, P≤0.012%, S≤0.004%, the remainder is Fe and unavoidable impurities; the thickness of the welding plate is 16 to 38mm, the impact energy of the weld seam and heat-affected zone at -60℃ is ≥47J, and the tensile strength is ≥980MPa. However, the thickness of the 1000MPa high-strength steel in the patent is less than 80mm, which cannot meet the requirements of some large-scale engineering equipment for high-strength steel with a thickness of more than 80mm, and the low-temperature impact toughness is low. Summary of the invention

[0005] In order to solve the above technical problems, the present invention proposes a 1000MPa grade steel material with a thickness of 80-100mm and a welding method thereof. The steel material provided by the present invention has a thickness of 80-100mm, a tensile strength of 1000-1180MPa, and an impact absorption energy of ≥150J at -60°C. It has the advantages of high strength and high low-temperature impact toughness, and after welding, a flat, crack-free welded joint with good mechanical properties can be obtained. At the same time, the welding method provided by the present invention significantly shortens the process of traditional welding technology, greatly improves work efficiency, and effectively reduces welding defects.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] The invention provides a 1000MPa grade steel material with a thickness of 80-100mm, comprising the following components in weight percentage: C: 0.06-0.14%, Si: 0.05-0.30%, Mn: 0.65-1.20%, Ni: 1.6-2.5%, Alt: 0.02-0.06%, V: 0.02-0.08%, B: 0.004-0.016%, Cr: 0.30-0.70%, Cu: 0.15-0.42%, Mo: 0.25-0.70%, Nb: 0.010-0.030%, Ti: 0.008-0.020%, and the balance is Fe and other inevitable impurities.

[0008] Furthermore, the yield strength of the 80-100 mm 1000 MPa grade steel is ≥920 MPa, the tensile strength is 1000-1180 MPa, the elongation after fracture is ≥17%, the strength-ductility product is ≥20 GPa·%, and the impact absorption energy at -60°C is ≥150 J.

[0009] The role of each component in the present invention:

[0010] C: Carbon can effectively improve the strength of steel, but it will reduce the weldability of steel, so excessive carbon should be avoided during welding to avoid generating more hard and brittle phases. Taking all factors into consideration, the present invention controls the carbon content within the range of 0.06-0.14%.

[0011] Si: Silicon is used as a deoxidizer in steel. When aluminum is used for deoxidation, adding a certain amount of silicon can effectively improve the deoxidation ability of aluminum and reduce the oxygen content in steel, thereby reducing the formation of pores and inclusions. Silicon has limited effect on the strength and plasticity of steel, but it helps to improve the corrosion resistance of steel. Too much silicon is prone to quenching cracks, and the tendency to crack under ultra-fast cooling is greater, which will directly reduce the welding performance of steel. At the same time, low-melting-point silicates are easily generated during welding, which increases the fluidity of the molten metal and affects the quality of the weld. Therefore, the silicon content needs to be controlled at 0.05-0.30%.

[0012] Mn: Manganese can improve the performance of steel through phase transformation strengthening and solid solution strengthening, but too high manganese will cause component segregation and destroy the low-temperature toughness of the product. Therefore, the present invention controls the manganese content to 0.65-1.20%.

[0013] Ni: Nickel can promote the formation of acicular ferrite, improve weld toughness, and inhibit side plate strip ferrite. A certain amount of nickel can refine the columnar crystal structure, while an excessive amount will cause coarsening. Therefore, the present invention controls the nickel content to 1.6-2.5%.

[0014] Alt: Aluminum plays a major role in deoxidation and grain size control in steel. Aluminum is used to refine the intrinsic grains of steel and increase the temperature at which steel grains coarsen. However, too much aluminum will change the physical properties of steel, making it difficult to weld, and will also cause the plasticity, toughness and high temperature resistance of the steel to deteriorate. Therefore, the present invention controls the Alt content to 0.02-0.06%.

[0015] V: Vanadium is the preferred precipitation strengthening element. If the vanadium content is too low, it may not fully exert its strengthening effect, while if the vanadium content is too high, it may reduce the toughness of the material, especially in a high strain environment, and increase the cost of the material, affecting the economic efficiency of the steel. Therefore, the present invention controls the vanadium content to 0.02-0.08%.

[0016] Vanadium has a strong affinity for carbon in steel and forms relatively stable fine carbides, such as VC, at high welding temperatures. During the welding process, as the temperature changes, these vanadium carbides will dissolve and precipitate. When the temperature of the heat-affected zone of welding rises, part of the carbides dissolve, allowing the vanadium element to enter the matrix of the steel, playing a role in solid solution strengthening. During the cooling process of welding, due to the decrease in solubility, vanadium carbides will re-precipitate, and the precipitated phases are extremely small. When dislocations encounter these precipitated phases, they require greater external force to continue to slip, so the strength and hardness of steel welded joints can be significantly improved.

[0017] In addition, vanadium can refine the grains and effectively prevent excessive grain growth in the heat-affected zone of welding, making the structure more uniform and dense, thereby improving the strength and toughness of the welded joints and improving the fatigue resistance of the welded joints to a certain extent, which helps the steel welded structure to operate stably for a long time in a complex working environment.

[0018] B: Boron can not only improve the hardenability, wear resistance, strength and hardness of steel, but also improve the welding quality of steel. The addition of boron can reduce the hardening tendency of the heat-affected zone during welding, thereby reducing the risk of welding defects, cracks and pores. Therefore, the boron content in the present invention should be controlled within the range of 0.004-0.016%.

[0019] Cr: A proper amount of chromium can induce the formation of acicular ferrite and inhibit proeutectoid ferrite, but excessive chromium will cause acicular ferrite to be replaced by bainite and martensite, reducing processability and weldability. In addition, the addition of chromium can also improve the corrosion resistance of steel, because chromium can promote the formation of a dense passivation film on the steel surface to protect the matrix. Therefore, the present invention controls the chromium content to 0.30-0.70%.

[0020] Cu: Copper can refine the grains, improve the strength and toughness of steel, and adding an appropriate amount of copper helps to reduce the hardness of the heat-affected zone of welding. In addition, copper is also a key element for improving the atmospheric corrosion resistance of steel. Therefore, the present invention controls the copper content within the range of 0.15-0.42%.

[0021] Mo: Molybdenum can refine grains, improve the strength and toughness of steel, especially at high temperatures, and can also increase the corrosion resistance of steel. Molybdenum forms molybdenum oxides in steel. When steel contains 0.4-0.5% molybdenum, the corrosion rate of steel in atmospheric corrosion environments can be greatly reduced. However, excessive molybdenum will damage the processing and welding properties, and the price of molybdenum is relatively expensive. Large-scale use will increase production costs. Considering all factors, the molybdenum content should be controlled within the range of 0.25-0.70%.

[0022] Nb: Niobium can not only inhibit the growth of austenite grains in steel, but also prevent grain boundary migration during hot working processes such as heating and rolling, so that the grains remain small and uniform. Fine grains not only increase the strength of steel, but also improve its toughness, plasticity and fatigue properties. After grain refinement, the grain boundary area increases, and crack propagation consumes more energy, making the material less likely to break when subjected to external forces. In addition, niobium can also reduce the brittleness tendency of the heat affected zone of welding, and can adjust the phase change process of the heat affected zone of welding, promote the formation of a structure that is more conducive to performance, thereby improving the organizational properties of the heat affected zone of welding.

[0023] Ti: The addition of titanium can refine the grain structure, inhibit grain coarsening, form a favorable microstructure, and improve the strength and toughness of steel. At the same time, titanium can reduce the welding deformation and crack tendency of steel, which is of great significance for the manufacture and maintenance of steel structures. Therefore, the content of titanium in the present invention should be controlled within the range of 0.008-0.020%.

[0024] The present invention provides a method for preparing the 1000MPa grade steel material with a thickness of 80 to 100 mm described in the above technical solution, comprising the following steps:

[0025] Molten steel is prepared according to the component ratio of 80-100mm 1000MPa grade steel, and then cast and forged to obtain a steel billet; the obtained steel billet is heated to 1100-1200°C and kept warm for 3h, and then rough rolled and finish rolled to obtain a steel plate, which is then water-cooled to a surface temperature of 540-650°C, and then air-cooled to room temperature to obtain the 80-100mm 1000MPa grade steel.

[0026] The present invention also provides a welding method for 80-100 mm 1000 MPa grade steel described in the above technical solution, comprising the following steps:

[0027] Taking 80-100mm 1000MPa grade steel as the substrate, an asymmetric X-shaped groove is opened on the substrate, and then preheating treatment is carried out. After that, base welding, filling welding, cover welding and heat treatment are performed to achieve welding of 80-100mm 1000MPa grade steel.

[0028] Furthermore, the asymmetric X-shaped groove has a large groove surface angle of 55 to 65 degrees, a small groove surface angle of 40 to 50 degrees, a blunt edge of 4 to 8 mm, and a butt welding assembly gap of 2 to 4 mm.

[0029] Furthermore, the welding current of the base welding is 250-350A, the welding voltage is 25-35V, the welding speed is 350-450mm / min, and the welding heat input is controlled at 15-30kJ / cm.

[0030] Furthermore, the interlayer temperature of the filling weld is controlled at 100-150°C, the welding current of the first and second passes is 450-550A, the welding voltage is 28-30V, and the welding speed is 350-400cm / min. The welding current of the remaining passes is 600-700A, the welding voltage is 30-38V, and the welding speed is 350-400cm / min.

[0031] Furthermore, the interlayer temperature of the cap welding is controlled at 80-150° C., the welding current is 600-700A, the welding voltage is 30-38V, and the welding speed is 350-400cm / min.

[0032] Furthermore, the welding wires used for the base welding, the filling welding and the cap welding are all submerged arc welding wires;

[0033] The submerged arc welding wire comprises the following components in weight percentage: C: 0.02-0.13%, Mn: 1.4-3.2%, Si: 0.26-0.54%, S: ≤0.03%, P: ≤0.02%, Ni: 2.2-5.2%, Cr: 0.26-0.64%, Mo: 0.53-0.78%, V: ≤0.03%, and the balance is Fe and other inevitable impurities.

[0034] Furthermore, the combination form of the base body is (80-100)+(80-100) mm two-plate docking, and the size of the single-side base plate is 200×150×(80-100) mm.

[0035] Furthermore, the temperature of the preheating treatment is 110-160°C.

[0036] Furthermore, the heat treatment temperature is 320-420° C., and the heat treatment time is 2.5-3.5 hours.

[0037] Compared with the prior art, the present invention has the following advantages and technical effects:

[0038] (1) The 1000MPa grade steel with a thickness of 80 to 100 mm provided by the present invention has a low carbon content, so the hardening tendency is small, and the probability of generating welding defects such as pores and slag inclusions is relatively low. In addition, during the welding thermal cycle, it is not easy to generate quenched structure, which effectively reduces the possibility of cold cracks in the welded joint.

[0039] (2) In the welding method of the present invention, both the base weld and the filling weld are matched with corresponding submerged arc welding wires, which can enable the welded joint to exhibit excellent performance. The obtained welded joint not only has sufficient margin in terms of plasticity and toughness, effectively improving the reliability and durability of the joint under complex working conditions, but also in the entire preparation process, the welded joint does not have defects such as deformation and cracks, ensuring the stability and consistency of the welding quality.

[0040] The welding method adopted by the present invention significantly shortens the process of traditional welding technology, greatly improves the work efficiency of the factory, and realizes the simplification, efficiency and economy of the welding process by simplifying the operating steps, while achieving the environmental protection goal of reducing carbon emissions.

[0041] By adopting the welding method of the present invention to weld 1000MPa grade steel with a thickness of 80-100mm, a weld joint without internal cracks can be obtained, the joint part is flat, and the weld joint has good low-temperature impact toughness. The X-notch low-temperature impact energy of the weld zone at a test temperature of -40°C is ≥140J, the impact energy of the coarse grain zone at -60°C is ≥90J, the impact energy of the fine grain zone at -40°C is ≥105J, the microhardness of the weld zone is ≥210HV, the microhardness of the coarse grain zone is ≥230HV, the microhardness of the fine grain zone is ≥250HV, the yield strength of the weld joint is ≥620MPa, the tensile strength is ≥780MPa, and the elongation is 17.5-19.1%.

[0042] (3) The 1000MPa grade steel of 80-100mm of the present invention is used for welding. The coarse grain area of ​​the weld joint is closely connected with the molten pool. The VC phase is precipitated in the austenite in the coarse grain area during the high temperature cooling process, which effectively promotes the significant nucleation of intracrystalline ferrite, increases the phase transformation rate of acicular ferrite, and refines the laths of acicular ferrite, so that the microstructure of the weld metal is mainly composed of a large number of criss-crossed acicular ferrite and polygonal proeutectoid ferrite. This specific organizational morphology gives the weld metal excellent mechanical properties. Among them, the network structure formed by the acicular ferrite interlaced with each other and the reasonable distribution of proeutectoid ferrite can effectively prevent the generation and expansion of cracks. In a low temperature environment, the weld exhibits excellent impact toughness and can withstand impact loads under low temperature conditions without brittle fracture. In addition, the weld joint as a whole also has excellent crack resistance, can effectively resist the generation of cracks under complex stress conditions, and exhibits good weather resistance.

[0043] (4) The submerged arc welding method adopted by the present invention is double-wire submerged arc welding. This method has a large penetration depth. The synergistic effect of the two welding wires can effectively ensure sufficient penetration of the thick plate. The welding efficiency is quite high. Compared with single-wire submerged arc welding, the welding time can be greatly shortened, thereby effectively reducing labor costs. This method is relatively simple to operate. The welding process is mainly carried out under the coverage of flux, which is less affected by the external environment and has a low overall use cost. In addition, this welding method performs well in controlling welding deformation. Through reasonable welding parameter settings and welding sequence arrangements, the thermal stress distribution can be more balanced, the deformation is smaller, and the precision quality requirements for the workpiece group are relatively less stringent. It is easier to obtain good welding quality, reduce the risk of subsequent maintenance and reshaping due to welding defects, and effectively guarantee the stability and reliability of the extra-thick steel welding structure.

[0044] (5) The submerged arc welding method for 80-100 mm 1000 MPa grade steel proposed in the present invention significantly reduces welding costs, effectively reduces welding defects by precisely controlling welding parameters, and reduces rework and repair costs. The welding method of the present invention achieves cost savings in terms of material costs, energy costs, labor costs, and equipment costs, providing an economical and efficient welding solution for enterprises.

[0045] In addition, the welding method of the present invention achieves a balance between high strength and good toughness by optimizing the chemical composition of the steel, while reducing the use of expensive alloy elements, further reducing material costs. The high efficiency and high quality welded joints of this method mean longer service life and lower maintenance costs, which can bring long-term economic benefits to the enterprise. The welding method of the present invention has obvious advantages in reducing welding costs by simplifying the process, improving welding efficiency and quality, and reducing material and equipment costs, which helps to improve the market competitiveness of enterprises. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0047] Figure 1 Schematic diagram of the X-shaped groove in the present invention;

[0048] Figure 2 A process flow chart of a welding method for 80-100 mm 1000 MPa grade steel provided by the present invention;

[0049] Figure 3 This is a schematic flow chart of a method for preparing a 1000MPa grade steel material having a thickness of 80 to 100 mm in Examples 1-3 of the present invention;

[0050] Figure 4 The overall metallographic structure diagram of the welded joint obtained by the welding method of Example 1;

[0051] Figure 5 The metallographic structure diagram of the weld zone of the welded joint obtained by the welding method of Example 1;

[0052] Figure 6 The metallographic structure diagram of the coarse grain area of ​​the welded joint obtained by the welding method of Example 1;

[0053] Figure 7 This is an impact fracture morphology of the weld zone of a welded joint obtained by the welding method of Example 1;

[0054] Figure 8 This is the impact fracture morphology of the coarse grain area of ​​the welded joint obtained by the welding method of Example 1. DETAILED DESCRIPTION

[0055] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0056] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0057] The embodiment of the present invention provides a 1000MPa grade steel material with a thickness of 80 to 100 mm, comprising the following components in weight percentage: C: 0.06 to 0.14%, Si: 0.05 to 0.30%, Mn: 0.65 to 1.20%, Ni: 1.6 to 2.5%, Alt: 0.02 to 0.06%, V: 0.02 to 0.08%, B: 0.004 to 0.016%, Cr: 0.30 to 0.70%, Cu: 0.15 to 0.42%, Mo: 0.25 to 0.70%, Nb: 0.010 to 0.030%, Ti: 0.008 to 0.020%, and the balance is Fe and other inevitable impurities. The present invention achieves a balance between high strength and good toughness by optimizing the chemical composition of the steel material, while reducing the use of expensive alloy elements, further reducing material costs.

[0058] In a preferred embodiment, the yield strength of the 80-100 mm 1000 MPa grade steel is ≥920 MPa, the tensile strength is 1000-1180 MPa, the elongation after fracture is ≥17%, the strength-ductility product is ≥20 GPa·%, and the -60°C impact absorption energy is ≥150 J.

[0059] The present invention provides a method for preparing the 1000MPa grade steel material with a thickness of 80 to 100 mm described in the above technical solution, comprising the following steps:

[0060] Molten steel is prepared according to the component ratio of 80-100mm 1000MPa grade steel, and then cast and forged to obtain a steel billet; the obtained steel billet is heated to 1100-1200°C and kept warm for 3h, and then rough rolled and finish rolled to obtain a steel plate, which is then water-cooled to a surface temperature of 540-650°C, and then air-cooled to room temperature to obtain the 80-100mm 1000MPa grade steel.

[0061] The preparation method of 80-100 mm 1000 MPa grade steel provided by the present invention can produce steel with excellent strength and toughness through rough rolling and finish rolling, avoiding the problems of increased production complexity and cost investment in the prior art that relies on low-temperature rolling (i.e. cold rolling), and easily leading to uneven organizational properties and difficulty in ensuring product quality stability.

[0062] In a preferred embodiment, the starting rolling temperature of the rough rolling is 1100-1150°C, the final rolling temperature is 950-1000°C, the total reduction rate is 60%-70%, the reduction rate of each pass is 15%-25%, and the number of rolling times is 6-8 times.

[0063] In a preferred embodiment, the start rolling temperature of the finish rolling is 850-900°C, the final rolling temperature is 750-800°C, the total reduction rate is 30%-40%, the reduction rate of each pass is 10%-15%, and the rolling times are 4-6 times.

[0064] In a preferred embodiment, the cooling rate of the water cooling is 10-25° C. / s.

[0065] The embodiment of the present invention further provides a welding method for 80-100 mm 1000 MPa grade steel described in the above technical solution, comprising the following steps:

[0066] Taking 80-100mm 1000MPa grade steel as the substrate, an asymmetric X-shaped groove is opened on the substrate, and then preheating treatment is carried out. After that, base welding, filling welding, cover welding and heat treatment are performed to achieve welding of 80-100mm 1000MPa grade steel.

[0067] In a preferred embodiment, the welding method provided by the present invention is double-wire submerged arc welding. Double-wire submerged arc welding has a greater penetration depth, and the synergistic effect of the two welding wires can effectively ensure sufficient penetration of the thick plate, and the welding efficiency is quite high. Compared with single-wire submerged arc welding, the welding time can be greatly shortened, thereby effectively reducing labor costs.

[0068] In a preferred embodiment, the large groove surface angle of the asymmetric X-shaped groove is 55-65°, the small groove surface angle is 40-50°, the blunt edge is 4-8mm, and the butt welding assembly gap is 2-4mm; preferably, the large groove surface angle of the asymmetric X-shaped groove is 60-65°, the small groove surface angle is 45-50°, the blunt edge is 4-8mm, and the butt welding assembly gap is 3-4mm.

[0069] In a preferred embodiment, before welding, the asymmetric X-shaped groove and the steel on both sides thereof are pre-treated; the pre-treatment is specifically: using a wire brush or a grinding wheel to clean the surface of the asymmetric X-shaped groove and the surfaces on both sides thereof to remove oil stains, and then using acetone to clean the welding part to remove rust and impurities until the metallic luster is exposed; further, the grinding wheel cleaning is: grinding the surfaces of the asymmetric X-shaped groove and the surfaces on both sides thereof to 1 mm or 0.5 mm. The present invention ensures the welding quality by pre-treating the asymmetric X-shaped groove and the steel on both sides thereof.

[0070] In a preferred embodiment, the temperature of the preheating treatment is 110-160° C., preferably 110-135° C. The present invention reduces the risk of cracks by preheating the substrate before welding.

[0071] In a preferred embodiment, the base welding, filling welding and capping welding are all performed under flux coverage. After welding, heat treatment is performed under flux coverage to maintain the integrity and stability of the weld. After the heat treatment is completed, the flux is cleaned, which is conducive to ensuring welding quality and overall construction efficiency.

[0072] In a preferred embodiment, the welding current of the base welding is 250-350A, the welding voltage is 25-35V, the welding speed is 350-450mm / min, and the welding heat input is controlled at 15-30kJ / cm; preferably, the welding current of the base welding is 250-280A, the welding voltage is 25-31V, the welding speed is 350-410mm / min, and the welding heat input is controlled at 15-22kJ / cm. Further, the base welding is electrode base welding. The present invention adopts electrode welding for base welding, which is conducive to forming good penetration and root shape.

[0073] In a preferred embodiment, the filling weld is a multi-layer and multi-pass welding, and the interlayer temperature of the filling weld is controlled at 100-150°C, the welding current of the first and second passes is 450-550A, the welding voltage is 28-30V, and the welding speed is 350-400cm / min, and the welding current of the remaining passes is 600-700A, the welding voltage is 30-38V, and the welding speed is 350-400cm / min; preferably, the interlayer temperature is controlled at 124-150°C, the welding current of the first and second passes is 450-480A, the welding voltage is 28-29V, and the welding speed is 350-380cm / min, and the welding current of the remaining passes is 600-660A, the welding voltage is 30-35V, and the welding speed is 380-400cm / min. In order to prevent the weld from overheating and avoid welding defects such as coarse grains, while ensuring a reasonable cooling process for the weld so that the weld metal and heat-affected zone have good performance, the interlayer temperature of the filling weld should be controlled at 100-150°C.

[0074] In a preferred embodiment, the interlayer temperature of the cap welding is controlled at 80-150°C, the welding current is 600-700A, the welding voltage is 30-38V, and the welding speed is 350-400cm / min; preferably, the interlayer temperature of the cap welding is controlled at 80-150°C, the welding current is 600-660A, the welding voltage is 30-35V, and the welding speed is 380-400cm / min. The present invention forms the final weld surface by cap welding.

[0075] In a preferred embodiment, the total number of welding passes is 11 to 17, wherein the number of welding passes for base welding is 1 to 2, the number of welding passes for filling welding is 8 to 12, and the number of welding passes for cap welding is 2 to 3.

[0076] In a preferred embodiment, the welding wires used for the base welding, the filling welding and the cap welding are all submerged arc welding wires. The submerged arc welding wires used in the welding process of the present invention are all 1000MPa submerged arc welding wires.

[0077] In a preferred embodiment, the 1000MPa submerged arc welding wire comprises the following components in weight percentage: C: 0.02-0.13%, Mn: 1.4-3.2%, Si: 0.26-0.54%, S: ≤0.03%, P: ≤0.02%, Ni: 2.2-5.2%, Cr: 0.26-0.64%, Mo: 0.53-0.78%, V: ≤0.03%, and the balance is Fe and other inevitable impurities. The present invention helps to improve the strength and toughness of the weld metal by regulating the chemical composition and proportion of the submerged arc welding wire.

[0078] In a preferred embodiment, the combination form of the base body is (80-100)+(80-100) mm two-plate docking, and the size of a single-side base plate is 200×150×(80-100) mm.

[0079] In a preferred embodiment, the temperature of the heat treatment is 320-420° C., preferably 320-370° C.; the time of the heat treatment is 2.5-3.5 h, preferably 2.5-3.1 h.

[0080] The welding process of the present invention is continuous welding without stopping.

[0081] The room temperature in the embodiments of the present invention refers to "25±2°C".

[0082] Unless otherwise specified, the raw materials in the examples of the present invention were purchased from commercial sources.

[0083] Example 1

[0084] A submerged arc welding method for 80-100mm 1000MPa grade steel, the process flow is shown in Figure 2 , the specific steps are as follows:

[0085] (1) Welding equipment and welding materials:

[0086] The welding equipment used is MZ-1000 automatic submerged arc welding machine.

[0087] Submerged arc welding uses 1000MPa submerged arc welding wire with a diameter of 4mm. Impurities such as oil and rust on the surface of the welding wire are removed before welding; the 1000MPa submerged arc welding wire is composed of the following components in weight percentage: C: 0.07%, Mn: 2.6%, Si: 0.54%, S: 0.03%, P: 0.015%, Ni: 3.62%, Cr: 0.26, Mo: 0.61%, V: 0.015%, and the balance is Fe and other inevitable impurities, and the impurity content is ≤0.025%.

[0088] The base is 80mm 1000MPa grade steel, the size of the single-side base plate is 200×150×80mm, and the base plate combination is 80mm+80mm two plates butt-jointed.

[0089] 80mm 1000MPa grade steel, composed of the following components in weight percentage: C: 0.14%, Si: 0.30%, Mn: 0.84%, Ni: 1.9%, Alt: 0.02%, V: 0.04%, B: 0.012%, Cr: 0.30%, Cu: 0.15%, Mo: 0.43%, Nb: 0.010%, Ti: 0.008%, the balance is Fe and other unavoidable impurities, the impurity content is ≤ 0.008%.

[0090] The yield strength of 80mm 1000MPa grade steel is 940MPa, the tensile strength is 1050MPa, the elongation after fracture is 17%, the strength-ductility product is 20.4GPa·%, the impact absorption energy at -40℃ is 203J, and the impact energy at -60℃ is 154J.

[0091] The preparation method of 80mm 1000MPa grade steel, the process diagram is shown in Figure 3 Specifically, molten steel is prepared according to the component ratio of the above-mentioned 80mm 1000MPa grade steel, and then cast and forged to obtain a steel billet; the obtained steel billet is heated to 1200℃ and kept warm for 3h, and then rough rolling and finish rolling are carried out, the starting rolling temperature of the rough rolling is 1100℃, the final rolling temperature is 980℃, the total reduction rate is 63%, the reduction rate of each pass is 18%, and the number of rolling times is 8 times; the starting rolling temperature of the finish rolling is 850℃, the final rolling temperature is 770℃, the total reduction rate is 36%, the reduction rate of each pass is 12%, the number of rolling times is 5 times, and a steel plate is obtained, which is then water-cooled to a surface temperature of 540℃ for the steel plate, and the cooling rate of water cooling is 25℃ / s, and then air-cooled to room temperature to obtain an 80mm 1000MPa grade steel.

[0092] (2) Preparation before welding

[0093] An asymmetric X-shaped groove is opened at the double butt joint of the substrate. The large groove surface angle of the asymmetric X-shaped groove is 60°, the small groove surface angle is 45°, the blunt edge is 4mm, and the butt welding assembly gap is controlled at 3mm;

[0094] Use a grinding wheel to clean the surface of the X-shaped groove and the steel on both sides to remove oil stains, and then use acetone to clean it to remove rust and impurities until the metallic luster is exposed to ensure the quality of the welded joint.

[0095] Before welding, the steel to be welded (i.e., the substrate) is preheated at a temperature of 110°C.

[0096] (3) Welding (under flux coverage)

[0097] A. Use electrode welding for base welding at a room temperature not lower than 20℃. The welding current of base welding is 280A, the welding voltage is 25V, the welding speed is 450mm / min, the welding heat input is 15kJ / cm, and the welding passes are 2 times.

[0098] B. After the base welding, the filling welding is carried out, with multiple layers and multiple passes continuous welding, 8 passes, no pause in the middle, the interlayer temperature is 124℃, the welding current of the first and second passes of the filling welding is 480A, the welding voltage is 28V, the welding speed is 400cm / min, and the welding current of the remaining passes is 660A, the voltage is 30V, and the speed is 400cm / min.

[0099] C. After the filling welding, the cap welding is performed, with 2 passes, the interlayer temperature is 80℃, the welding current is 660A, the voltage is 30V, and the speed is 400cm / min to form the final weld surface. After the cap welding is completed, the post-weld heat treatment is performed at a temperature of 320℃ for 3.5h to complete the welding.

[0100] Mechanical properties of the welded joint obtained by the welding method of this embodiment were tested, and the yield strength of the welded joint was 870MPa, the tensile strength was 985MPa, the elongation was 17.8%, the impact energy at -40°C at 1 / 4 of the weld zone of the welded joint was 145J, the impact energy at -60°C in the coarse grain zone was 115J, and the impact energy at -40°C in the fine grain zone was 115J, and the impact performance of the welded joint was good. The microhardness of the weld zone of the welded joint was 245HV, the microhardness of the coarse grain zone was 254HV, and the microhardness of the fine grain zone was 275HV, which can meet the performance requirements.

[0101] The overall metallographic structure diagram of the welded joint obtained by the welding method of Example 1 is shown in Figure 4 .from Figure 4 It can be seen that no welding defects such as pores and undercuts occur in the welding joint during the welding process, indicating that the welding method of the present invention is reasonably designed.

[0102] The metallographic structure diagram of the weld zone of the welded joint obtained by the welding method of Example 1 is shown in Figure 5 .from Figure 5 It can be seen that the weld structure is mainly composed of a large number of criss-crossing acicular ferrite and polygonal proeutectoid ferrite. This interwoven large-angle grain boundary can hinder the expansion of cracks and effectively improve the low-temperature impact toughness of the weld.

[0103] The coarse grain metallographic structure diagram of the welded joint obtained by the welding method of Example 1 is shown in Figure 6 .from Figure 6 It can be seen that the original austenite grains in the coarse-grained area have grown seriously, and the interior of the grains is mainly composed of lath-shaped bainite, granular bainite, acicular ferrite and polygonal ferrite. While ensuring that the welding coarse-grained area has a certain hardness and tensile strength, it also ensures good low-temperature impact toughness of the coarse-grained area of ​​the welded joint.

[0104] The impact fracture morphology of the weld zone of the welded joint obtained by the welding method of Example 1 is shown in FIG. Figure 7 .from Figure 7 It can be seen that the weld fractured ductilely, and there are a large number of small equiaxed dimples on the fracture surface. The dimples are caused by shear stress failure. When the material is subjected to external pressure, the shear stress will promote crystal slip to produce dimples, presenting a complex network structure. The presence of small dimples will enable the steel to absorb more energy when fracture occurs, effectively reducing the expansion of cracks and improving the strength and toughness of the material.

[0105] The impact fracture morphology of the coarse grain zone of the welded joint obtained by the welding method of Example 1 is shown in FIG. Figure 8 .from Figure 8 It can be seen that the uneven thermal cycle during welding will cause grain coarsening in some areas. The coarse-grained area has ductile fracture. The fracture morphology is mainly composed of large dimples and small dimples. The size of large dimples is about 20-30μm, and the size of small dimples is about 1-3μm. Some large dimples are elongated and even parabolic. The bending direction of the dimple represents the shear stress on the matrix on one side of the weld joint.

[0106] Example 2

[0107] A submerged arc welding method for 80-100mm 1000MPa grade steel, the process flow is shown in Figure 2 , the specific steps are as follows:

[0108] (1) Welding equipment and welding materials:

[0109] The welding equipment used is MZ-1000 automatic submerged arc welding machine.

[0110] Submerged arc welding uses 1000MPa submerged arc welding wire with a diameter of 4mm. Impurities such as oil and rust on the surface of the welding wire are removed before welding; the 1000MPa submerged arc welding wire is composed of the following components in weight percentage: C: 0.13%, Mn: 1.4%, Si: 0.34%, S: 0.01%, P: 0.017%, Ni: 3.8%, Cr: 0.37%, Mo: 0.78%, V: ≤0.009%, the balance is Fe and other inevitable impurities, and the impurity content is ≤0.025%.

[0111] The base is 90mm thick 1000MPa grade steel, the size of a single side base plate is 200×150×90mm, and the base plate combination is 90mm+90mm two plates butt-jointed.

[0112] 90mm thick 1000MPa grade steel, composed of the following components in weight percentage: C: 0.10%, Si: 0.18%, Mn: 0.65%, Ni: 2.5%, Alt: 0.06%, V: 0.08%, B: 0.004%, Cr: 0.70%, Cu: 0.42%, Mo: 0.70%, Nb: 0.022%, Ti: 0.014%, the balance is Fe and other unavoidable impurities, the impurity content is ≤ 0.008%.

[0113] The service strength of 90mm thick 1000MPa grade steel is 980MPa, the tensile strength is 1180MPa, the elongation after fracture is 17.5%, the strength-ductility product is 22.1GPa·%, the impact absorption energy at -40℃ is 212J, and the impact energy at -60℃ is 164J.

[0114] The preparation method of 90mm 1000MPa grade steel, the process diagram is shown in Figure 3 Specifically, molten steel is prepared according to the component ratio of the above-mentioned 90mm 1000MPa grade steel, and then cast and forged to obtain a steel billet; the obtained steel billet is heated to 1200℃ and kept warm for 3h, and then rough rolling and finish rolling are carried out, the starting rolling temperature of rough rolling is 1150℃, the final rolling temperature is 1000℃, the total reduction rate is 70%, the reduction rate of each pass is 25%, and the number of rolling times is 6 times; the starting rolling temperature of finish rolling is 870℃, the final rolling temperature is 750℃, the total reduction rate is 30%, the reduction rate of each pass is 10%, and the number of rolling times is 6 times to obtain a steel plate, which is then water-cooled to a surface temperature of 540℃ for the steel plate, and the cooling rate of water cooling is 25℃ / s, and then air-cooled to room temperature to obtain a 90mm 1000MPa grade steel.

[0115] (2) Preparation before welding

[0116] An asymmetric X-shaped groove is opened at the double butt joint of the substrate. The large groove surface angle of the asymmetric X-shaped groove is 65°, the small groove surface angle is 50°, the blunt edge is 8mm, and the butt welding assembly gap is controlled at 4mm;

[0117] Use a grinding wheel to clean the surface of the X-shaped groove and the steel on both sides to remove oil stains, and then use acetone to clean it to remove rust and impurities until the metallic luster is exposed to ensure the quality of the welded joint.

[0118] Before welding, the steel to be welded (i.e., the substrate) is preheated at a temperature of 135°C.

[0119] (3) Welding (under flux coverage)

[0120] A. Use electrode welding for base welding at a room temperature not lower than 20℃. The welding current of base welding is 250A, the welding voltage is 31V, the welding speed is 410mm / min, the welding heat input is 22kJ / cm, and the welding passes are 2 times.

[0121] B. After the base welding, the filling welding is carried out, with multiple layers and multiple passes continuous welding, 8 passes, no pause in the middle, the interlayer temperature is 150℃, the welding current of the first and second passes of the filling welding is 450A, the welding voltage is 29V, the welding speed is 380cm / min, and the welding current of the remaining passes is 600A, the voltage is 35V, and the speed is 380cm / min.

[0122] C. After the filling welding, the cap welding is performed, with 2 passes, the interlayer temperature is 150℃, the welding current is 600A, the voltage is 35V, and the speed is 380cm / min to form the final weld surface. After the cap welding is completed, the post-weld heat treatment is performed at a temperature of 370℃ for 3.1h to complete the welding.

[0123] Mechanical properties of the welded joint obtained by the welding method of this embodiment were tested, and the yield strength of the welded joint was 910MPa, the tensile strength was 1040MPa, the elongation was 17.5%, the impact energy at -40°C at 1 / 4 of the weld zone of the welded joint was 155J, the impact energy at -60°C in the coarse grain zone was 109J, and the impact energy at -40°C in the fine grain zone was 110J, and the impact performance of the welded joint was good. The microhardness of the weld zone of the welded joint was 232HV, the microhardness of the coarse grain zone was 241HV, and the microhardness of the fine grain zone was 264HV, which can meet the performance requirements.

[0124] Example 3

[0125] A submerged arc welding method for 80-100mm 1000MPa grade steel, the process flow is shown in Figure 2 , the specific steps are as follows:

[0126] (1) Welding equipment and welding materials:

[0127] The welding equipment used is MZ-1000 automatic submerged arc welding machine.

[0128] Submerged arc welding uses 1000MPa submerged arc welding wire with a diameter of 4mm. Impurities such as oil and rust on the surface of the welding wire are removed before welding; the 1000MPa submerged arc welding wire is composed of the following components in weight percentage: C: 0.02%, Mn: 3.2%, Si: 0.26%, S: 0.027%, P: 0.014%, Ni: 5.2%, Cr: 0.64%, Mo: 0.53%, V: 0.021%, and the balance is Fe and other inevitable impurities, and the impurity content is ≤0.025%.

[0129] The substrate is 100mm thick 1000MPa grade steel, the size of a single side substrate is 200×150×100mm, and the substrate combination is 100mm+100mm two plates butt-jointed.

[0130] 100mm thick 1000MPa grade steel is composed of the following components in weight percentage: C: 0.06%, Si: 0.05%, Mn: 1.20%, Ni: 1.6%, Alt: 0.03%, V: 0.02%, B: 0.016%, Cr: 0.44%, Cu: 0.32%, Mo: 0.25%, Nb: 0.030%, Ti: 0.020%, the balance is Fe and other unavoidable impurities, the impurity content is ≤ 0.008%.

[0131] The yield strength of 1000MPa grade steel with a thickness of 100mm is 965MPa, the tensile strength is 1000MPa, the elongation after fracture is 17.3%, the strength-ductility product is 21GPa·%, the impact absorption energy at -40℃ is 207J, and the impact energy at -60℃ is 169J.

[0132] The preparation method of 100mm 1000MPa grade steel, the process diagram is shown in Figure 3 Specifically, molten steel is prepared according to the component ratio of the above-mentioned 100mm 1000MPa grade steel, and then a steel billet is obtained by casting and forging; the obtained steel billet is heated to 1200℃ and kept warm for 3h, and then rough rolling and finish rolling are carried out, the starting rolling temperature of the rough rolling is 1130℃, the final rolling temperature is 950℃, the total reduction rate is 60%, the reduction rate of each pass is 15%, and the number of rolling times is 7 times; the starting rolling temperature of the finish rolling is 900℃, the final rolling temperature is 800℃, the total reduction rate is 40%, the reduction rate of each pass is 15%, and the number of rolling times is 4 times to obtain a steel plate, which is then water-cooled to a surface temperature of 540℃ for the steel plate, and the cooling rate of water cooling is 25℃ / s, and then air-cooled to room temperature to obtain a 100mm 1000MPa grade steel.

[0133] (2) Preparation before welding

[0134] An asymmetric X-shaped groove is opened at the double butt joint of the substrate. The large groove surface angle of the asymmetric X-shaped groove is 55°, the small groove surface angle is 40°, the blunt edge is 5mm, and the butt welding assembly gap is controlled at 2mm;

[0135] Use a grinding wheel to clean the surface of the X-shaped groove and the steel on both sides to remove oil stains, and then use acetone to clean it to remove rust and impurities until the metallic luster is exposed to ensure the quality of the welded joint.

[0136] Before welding, the steel to be welded (i.e., the substrate) is preheated at a temperature of 160°C.

[0137] (3) Welding (under flux coverage)

[0138] A. Use electrode welding for base welding at a room temperature not lower than 20℃. The welding current of base welding is 350A, the welding voltage is 31V, the welding speed is 350mm / min, the welding heat input is 30kJ / cm, and the welding passes are 2 times.

[0139] B. After the base welding, the filling welding is carried out, with multiple layers and multiple passes continuous welding, 10 passes, no pause in the middle, the interlayer temperature is 100℃, the welding current of the first and second passes of the filling welding is 550A, the welding voltage is 30V, the welding speed is 350cm / min, and the welding current of the remaining passes is 700A, the voltage is 38V, and the speed is 350cm / min.

[0140] C. After the filling welding, the cap welding is performed, the welding passes are 3 times, the interlayer temperature is 102℃, the welding current is 700A, the voltage is 38V, and the speed is 350cm / min to form the final weld surface. After the cap welding is completed, the post-weld heat treatment is performed at a temperature of 420℃ for 2.5h to complete the welding.

[0141] Mechanical properties of the welded joint obtained by the welding method of this embodiment were tested, and the yield strength of the welded joint was 855MPa, the tensile strength was 945MPa, the elongation was 19.1%, the impact energy at -40°C at 1 / 4 of the weld zone of the welded joint was 146J, the impact energy at -60°C in the coarse grain zone was 94J, and the impact energy at -40°C in the fine grain zone was 117J, and the impact performance of the welded joint was good. The microhardness of the weld zone of the welded joint was 232HV, the microhardness of the coarse grain zone was 236HV, and the microhardness of the fine grain zone was 257HV, which can meet the performance requirements.

[0142] Comparative Example 1

[0143] The only difference from Example 1 is that the 80 mm 1000 MPa grade steel is composed of the following components in weight percentage: C: 0.14%, Si: 0.30%, Mn: 0.84%, Ni: 1.9%, Alt: 0.02%, V: 0.04%, B: 0.012%, Cr: 0.30%, Cu: 0.15%, Mo: 0.43%, Nb: 0.040%, Ti: 0.008%, and the balance is Fe and other unavoidable impurities, and the impurity content is ≤0.0075%. Others are the same as Example 1.

[0144] The mechanical properties of the welded joint obtained by the welding method of Comparative Example 1 were tested and found to have a yield strength of 740 MPa, a tensile strength of 820 MPa, an elongation of 15.4%, an impact energy of 121 J at -40°C in the 1 / 4 of the weld zone of the welded joint, 72 J at -60°C in the coarse grain zone, and 91 J at -40°C in the fine grain zone. The microhardness of the weld zone of the welded joint was 192 HV, the microhardness of the coarse grain zone was 195 HV, and the microhardness of the fine grain zone was 208 HV, which could not meet the performance requirements.

[0145] Comparative Example 2

[0146] The only difference from Example 1 is that the 80 mm 1000 MPa grade steel is composed of the following components in weight percentage: C: 0.14%, Si: 0.30%, Mn: 0.84%, Ni: 1.4%, Alt: 0.02%, V: 0.04%, B: 0.012%, Cr: 0.30%, Cu: 0.15%, Mo: 0.43%, Nb: 0.040%, Ti: 0.008%, and the balance is Fe and other unavoidable impurities, and the impurity content is ≤0.0075%. Others are the same as Example 1.

[0147] The mechanical properties of the welded joint obtained by the welding method of Comparative Example 2 were tested and found to have a yield strength of 736 MPa, a tensile strength of 825 MPa, an elongation of 15.2%, an impact energy of 117 J at -40°C at 1 / 4 of the weld zone of the welded joint, 74 J at -60°C in the coarse grain zone, and 87 J at -40°C in the fine grain zone. The microhardness of the weld zone of the welded joint was 194 HV, the microhardness of the coarse grain zone was 197 HV, and the microhardness of the fine grain zone was 211 HV, which could not meet the performance requirements.

[0148] Comparative Example 3

[0149] The only difference from Example 1 is that the 80 mm 1000 MPa grade steel is composed of the following components in weight percentage: C: 0.14%, Si: 0.30%, Mn: 0.84%, Ni: 1.9%, Alt: 0.02%, V: 0.04%, B: 0.003%, Cr: 0.30%, Cu: 0.15%, Mo: 0.43%, Nb: 0.040%, Ti: 0.008%, and the balance is Fe and other inevitable impurities, and the impurity content is ≤0.0075%. Others are the same as Example 1.

[0150] The mechanical properties of the welded joint obtained by the welding method of Comparative Example 3 were tested and found to have a yield strength of 733 MPa, a tensile strength of 811 MPa, an elongation of 15.2%, an impact energy of 110 J at -40 ° C in the weld zone of the welded joint, 67 J at -60 ° C in the coarse grain zone, and 88 J at -40 ° C in the fine grain zone. The microhardness of the weld zone of the welded joint was 183 HV, the microhardness of the coarse grain zone was 187 HV, and the microhardness of the fine grain zone was 206 HV, which could not meet the performance requirements.

[0151] Comparative Example 4

[0152] The only difference from Example 1 is that the 80 mm 1000 MPa grade steel is composed of the following components in weight percentage: C: 0.14%, Si: 0.30%, Mn: 1.4%, Ni: 1.9%, Alt: 0.02%, V: 0.04%, B: 0.012%, Cr: 0.30%, Cu: 0.15%, Mo: 0.43%, Nb: 0.040%, Ti: 0.008%, and the balance is Fe and other inevitable impurities, and the impurity content is ≤0.0075%. Others are the same as Example 1.

[0153] The mechanical properties of the welded joint obtained by the welding method of Comparative Example 4 were tested and found to have a yield strength of 732 MPa, a tensile strength of 814 MPa, an elongation of 14.9%, an impact energy of 114 J at -40 ° C in the weld zone of the welded joint, 68 J at -60 ° C in the coarse grain zone, and 85 J at -40 ° C in the fine grain zone. The microhardness of the weld zone of the welded joint was 187 HV, the microhardness of the coarse grain zone was 191 HV, and the microhardness of the fine grain zone was 204 HV, which could not meet the performance requirements.

[0154] Comparative Example 5

[0155] The only difference from Example 1 is that the 1000MPa submerged arc welding wire is composed of the following components in weight percentage: C: 0.12%, Mn: 2.5%, Si: 0.38%, S: ≤0.03%, P: ≤0.02%, Ni: 6.3%, Cr: 0.53%, V: ≤0.03%, the balance is Fe and other inevitable impurities, and the impurity content is ≤0.0075%. Others are the same as Example 1.

[0156] The mechanical properties of the welded joint obtained by the welding method of Comparative Example 5 were tested and found to have a yield strength of 742 MPa, a tensile strength of 834 MPa, an elongation of 15.1%, an impact energy of 116 J at -40°C in the weld zone of the welded joint, 71 J at -60°C in the coarse grain zone, and 87 J at -40°C in the fine grain zone. The microhardness of the weld zone of the welded joint was 182 HV, the microhardness of the coarse grain zone was 189 HV, and the microhardness of the fine grain zone was 207 HV, which could not meet the performance requirements.

[0157] The above are only preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A 1000MPa grade steel material with a thickness of 80 to 100 mm, characterized in that: The invention comprises the following components in weight percentage: C: 0.06-0.14%, Si: 0.05-0.30%, Mn: 0.65-1.20%, Ni: 1.6-2.5%, Alt: 0.02-0.06%, V: 0.02-0.08%, B: 0.004-0.016%, Cr: 0.30-0.70%, Cu: 0.15-0.42%, Mo: 0.25-0.70%, Nb: 0.010-0.030%, Ti: 0.008-0.020%, and the balance is Fe and other inevitable impurities.

2. The 1000MPa grade steel material with a thickness of 80-100mm according to claim 1, characterized in that: The yield strength of the 80-100 mm 1000 MPa grade steel is ≥920 MPa, the tensile strength is 1000-1180 MPa, the elongation after fracture is ≥17%, the strength-ductility product is ≥20 GPa·%, and the -60°C impact absorption energy is ≥150 J.

3. A method for preparing a 1000 MPa grade steel material with a thickness of 80 to 100 mm as claimed in any one of claims 1 to 2, characterized in that: The following steps are involved: Molten steel is prepared according to the component ratio of 80-100mm 1000MPa grade steel, and then cast and forged to obtain a steel billet; the obtained steel billet is heated to 1100-1200°C and kept warm for 3h, and then rough rolled and finish rolled to obtain a steel plate, which is then water-cooled to a surface temperature of 540-650°C, and then air-cooled to room temperature to obtain the 80-100mm 1000MPa grade steel.

4. A method for welding a 1000 MPa grade steel material with a thickness of 80 to 100 mm as claimed in any one of claims 1 to 2, characterized in that: The following steps are involved: Taking 80-100mm 1000MPa grade steel as the substrate, an asymmetric X-shaped groove is opened on the substrate, and then preheating treatment is carried out. After that, base welding, filling welding, cover welding and heat treatment are performed to achieve welding of 80-100mm 1000MPa grade steel.

5. The welding method of 80-100 mm 1000 MPa grade steel material according to claim 4, characterized in that: The asymmetric X-shaped groove has a large groove surface angle of 55-65 degrees, a small groove surface angle of 40-50 degrees, a blunt edge of 4-8 mm, and a butt welding assembly gap of 2-4 mm.

6. The welding method of 80-100 mm 1000 MPa grade steel material according to claim 4, characterized in that: The welding current of the base welding is 250-350A, the welding voltage is 25-35V, the welding speed is 350-450mm / min, and the welding heat input is controlled at 15-30kJ / cm.

7. The welding method of 80-100 mm 1000 MPa grade steel material according to claim 4, characterized in that: The interlayer temperature of the filling weld is controlled at 100-150°C, the welding current of the first and second passes is 450-550A, the welding voltage is 28-30V, and the welding speed is 350-400cm / min. The welding current of the remaining passes is 600-700A, the welding voltage is 30-38V, and the welding speed is 350-400cm / min.

8. The welding method of 80-100 mm 1000 MPa grade steel material according to claim 4, characterized in that: The interlayer temperature of the cap welding is controlled at 80-150° C., the welding current is 600-700A, the welding voltage is 30-38V, and the welding speed is 350-400cm / min.

9. The welding method of 80-100 mm 1000 MPa grade steel material according to claim 4, characterized in that: The welding wires used for the base welding, filling welding and cap welding are all submerged arc welding wires; The submerged arc welding wire comprises the following components in weight percentage: C: 0.02-0.13%, Mn: 1.4-3.2%, Si: 0.26-0.54%, S: ≤0.03%, P: ≤0.02%, Ni: 2.2-5.2%, Cr: 0.26-0.64%, Mo: 0.53-0.78%, V: ≤0.03%, and the balance is Fe and other inevitable impurities.

10. The welding method of 80-100 mm 1000 MPa grade steel material according to claim 4, characterized in that: The temperature of the preheat treatment is 110-160° C.; the temperature of the heat treatment is 320-420° C., and the time of the heat treatment is 2.5-3.5 hours.

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