A welding wire, flux, preparation method, and welding method for high-strength steel with high heat input for submerged arc welding (SAW) of 1000MPa grade.

Abstract

This invention discloses a welding wire, flux, and preparation and welding methods for high-heat submerged arc welding of 1000MPa grade high-strength steel, belonging to the technical field of welding materials and their preparation. This invention solves the problems of reduced low-temperature toughness, alloy element loss, arc instability, and high crack sensitivity associated with existing high-heat submerged arc welding of 1000MPa grade high-strength steel. By adjusting the composition of the welding wire and flux, this invention enables the welding of 1000MPa grade high-strength steel at high heat input. Tests show that the resulting weld metal has a beautiful shape and good straightness, with a tensile strength ≥950MPa, a yield strength ≥820MPa, and an impact absorption energy ≥54J in the Charpy pendulum test at -40℃ and ≥47J in the Charpy pendulum test at -60℃. No solidification cracks were observed, and no cracks were found in the side bending test, demonstrating excellent crack resistance and meeting the practical engineering application needs of 1000MPa grade high-strength steel.

Description

Technical Field

[0001] This invention relates to a welding wire, flux, preparation method, and welding method for high-strength steel with high heat input during submerged arc welding of 1000MPa grade high strength steel, belonging to the technical field of welding materials and their preparation. Background Technology

[0002] Submerged arc welding is widely used in the construction of hydropower equipment using 1000MPa high-strength steel. Hydropower equipment constructed with 1000MPa high-strength steel is generally thick, requiring high heat input to improve welding penetration and efficiency. However, high heat input welding also brings key technical problems such as reduced low-temperature toughness, loss of alloying elements, arc instability, and increased crack sensitivity.

[0003] Regarding the development of welding materials for low-alloy high-strength steel, existing patent CN112453662A discloses a submerged arc welding process and submerged arc welding wire composition suitable for 1000MPa grade high-strength steel. The mechanical properties of the weld metal meet the requirements for use with 1000MPa grade high-strength steel, requiring a welding heat input of 10–20 kJ / cm. Patent CN106825993A discloses a submerged arc welding flux for high-strength steel with a tensile strength of 900–1000MPa and its preparation method. The resulting weld metal has a tensile strength below 935MPa, and the welding heat input is 26–30 kJ / cm. A literature review on experimental research of submerged arc welding materials for 1000MPa hydropower high-strength steel proposes a 1000MPa grade high-strength steel submerged arc welding material. When the welding heat input is 25–30 kJ / cm, the mechanical properties of the weld metal meet the engineering application requirements, but when the welding heat input is above 35 kJ / cm, the tensile strength is below 930MPa.

[0004] In summary, the current field of welding materials for high heat input submerged arc welding of 1000MPa grade high-strength steel is still in its initial stage, and there are still problems such as reduced toughness at low temperatures, loss of alloying elements, arc instability, and high crack sensitivity. Summary of the Invention

[0005] To address the problems of reduced toughness at low temperatures, loss of alloying elements, arc instability, and high crack sensitivity in existing high-strength steel welding with high heat input, this invention provides a welding wire, flux, preparation method, and welding method for high-strength steel welding with high heat input.

[0006] The technical solution of this invention:

[0007] One objective of this invention is to provide a 1000MPa grade high-strength steel high-heat submerged arc welding wire. The chemical composition of this welding wire, by weight percentage, includes: C 0.1%–0.2%, Si 0.1%–0.4%, Mn 1.5%–3.0%, S≤0.005%, P≤0.007%, Cr 0.2%–0.7%, Ni 2%–4.0%, Mo 0.6%–1.6%, Ti 0.01%–0.05%, Cu 0.05%–0.30%, Al 0.01%–0.02%, Nb 0.01%–0.03%, O≤50ppm, N≤50ppm, with the balance being iron and unavoidable impurities.

[0008] Further specifying, the chemical composition of the welding wire by weight percentage includes: C 0.10%–0.15%, Si 0.15%–0.25%, Mn 1.5%–2.5%, S≤0.005%, P≤0.007%, Cr 0.3%–0.7%, Ni 2.5%–4.0%, Mo 0.8%–1.4%, Ti 0.01%–0.03%, Cu 0.15%–0.25%, Al 0.01%–0.02%, Nb 0.01%–0.02%, O≤50ppm, N≤50ppm, with the balance being iron and unavoidable impurities.

[0009] Further specifying, the chemical composition of the welding wire by weight percentage includes: C 0.10%, Si 0.20%, Mn 1.8%, S 0.005%, P 0.007%, Cr 0.5%, Ni 2.8%, Mo 0.8%, Ti 0.02%, Cu 0.15%, Al 0.01%, Nb 0.01%, O 50ppm, N 50ppm, with the balance being iron and unavoidable impurities.

[0010] Further specifying, the chemical composition of the welding wire by weight percentage includes: C 0.10%, Si 0.15%, Mn 2.0%, S 0.005%, P 0.007%, Cr 0.3%, Ni 3.2%, Mo 1.0%, Ti 0.01%, Cu 0.20%, Al 0.02%, Nb 0.02%, O 50ppm, N 50ppm, with the balance being iron and unavoidable impurities.

[0011] The second objective of this invention is to provide a method for preparing welding wire for high-strength steel with high heat input in submerged arc welding (SAW) at a pressure of 1000 MPa. This method includes the following steps:

[0012] S1, the welding wire raw material is smelted, refined, preheated and hot rolled into wire rod in sequence to obtain wire rod with a diameter of Ф5.5mm;

[0013] S2, after mechanical peeling and belt sanding, the wire rod is directly drawn into the roller die. The roller die drawing adopts an uncoated process and goes through 4 continuous drawing stages. The first three stages are roller dies and the fourth stage is eye dies, resulting in a finished product with a diameter of Ф3.2mm.

[0014] S3, the finished product is cleaned online, coated with an anti-rust coating, dried by a high-pressure air brush, wound by an I-beam reel, and then wound in layers using submerged arc welding wire to obtain welding wire.

[0015] Furthermore, the drawing speed of S2 is limited to no more than 300 m / min.

[0016] Further specifying, the diameter tolerance of the finished product obtained by S2 is -0.04mm to 0.01mm.

[0017] The second objective of this invention is to provide a flux that can be used in conjunction with the aforementioned 1000MPa grade high-strength steel high-heat submerged arc welding wire. The chemical composition of this flux, by weight percentage, includes: CaF2 20%–30%, SiO 25%–10%, MgO 15%–25%, TiO 25%–8%, Al2O3 16%–26%, CaO 16%–25%, nano-grade zirconium powder ≤1%, titanium-boron alloy ≤1%, aluminum-iron powder: 1%–5%, and silicon-manganese-iron alloy: 1%–5%.

[0018] Further specifying, the chemical composition of the flux, by weight percentage, includes: CaF2 20%–28%, SiO 25%–8%, MgO 18%–21%, TiO 25%–8%, Al2O3 16%–24%, CaO 16%–22%, nano-sized zirconium powder ≤1%, titanium-boron alloy ≤1%, aluminum-iron powder 2.5%–4.5%, and silicon-manganese-iron alloy 1%–4.5%.

[0019] Further specifying, the chemical composition of the flux, by weight percentage, includes: 23% CaF2, 8% SiO2, 20% MgO, 25% TiO2, 17% Al2O3, 22% CaO, 0.2% nano-zirconium powder, 0.2% titanium-boron alloy, 2.8% aluminum-iron powder, and 1.8% silicon-manganese-iron alloy.

[0020] Further specifying, the chemical composition of the flux, by weight percentage, includes: 23% CaF2, 25% SiO, 18% MgO, 27% TiO, 20% Al2O3, 18% CaO, 0.6% nano-sized zirconium powder, 0.4% titanium-boron alloy, 4.5% aluminum-iron powder, and 3.5% silicon-manganese-iron alloy.

[0021] Further specified, the titanium-boron alloy contains Ti ≥ 55 wt%, with the balance being B.

[0022] Further specified, the aluminum-iron powder contains ≥45wt% Al, with the balance being iron.

[0023] Further specified, the silicon-manganese-iron alloy contains Si ≥ 15wt%, Mn ≥ 50wt%, and the balance is iron.

[0024] The fourth objective of this invention is to provide a method for preparing the flux for high-strength steel with high heat input in submerged arc welding of the above-mentioned 1000MPa grade. The method involves using a continuous production line to produce the flux through processes such as powder mixing, stirring, granulation, low-temperature drying, sieving, high-temperature drying, sieving, and cooling.

[0025] Further specifying, the preparation method of the flux is as follows:

[0026] Step 1: Prepare the powder and pack it into cans according to the formula;

[0027] Step 2: Stirring. Load the mixture into a mixer and dry-stir for 5-10 minutes. Then add 10%-20% water glass and stir for another 5-10 minutes.

[0028] Step 3: Granulation. The wet mixture prepared in Step 2 is fed into a granulator for granulation. The granulator is a disc-type rotary granulator with a rotation speed of 200-300 rpm.

[0029] Step 4: Low-temperature drying. The granulated material from Step 3 is transferred to a low-temperature drying oven, which is a rotary continuous drying oven with a drying temperature of 200-300℃.

[0030] Step 5: Low-temperature screening. The powder dried at low temperature in step 4 is fed into a vibrating screen for screening. The particle size range of the low-temperature screening is 10 to 50 mesh.

[0031] Step 6: High-temperature sintering. The powder obtained in step 5 is transferred to a high-temperature drying furnace, which is a rotary continuous drying furnace with a drying temperature of 750-850℃.

[0032] Step 7: High-temperature sieving. The powder after high-temperature sintering in Step 6 is fed into a vibrating screen for further sieving and selection. The particle size range is 10-50 mesh.

[0033] Step 8: Cooling. The powder produced in step 7 is transferred to a cooling furnace, which is a rotary continuous cooling furnace, and the cooling method is external wall air cooling.

[0034] Step 9: Packaging. The cooled powder is packaged to obtain flux.

[0035] The fourth objective of this invention is to provide a high-energy submerged arc welding method for 1000MPa grade high-strength steel. The welding wire and flux used in this welding method are as described above. The welding method has an energy range of 40kJ / cm to 60kJ / cm. The base material is preheated to 100°C before welding.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] (1) This invention, by adjusting the composition of the welding wire and flux, enables the welding of 1000MPa grade high-strength steel at high heat inputs of 40kJ / cm to 60kJ / cm. Process tests show that the weld metal exhibits aesthetically pleasing and straight weld formation, with a tensile strength ≥950MPa, a yield strength ≥820MPa, and an impact absorption energy ≥54J in the Charpy pendulum test at -40℃ and ≥47J in the Charpy pendulum test at -60℃. No solidification cracks are observed, and no cracks are found in the side bending test, demonstrating excellent crack resistance. The welding material's properties meet the practical engineering application requirements of 1000MPa grade high-strength steel, effectively solving problems such as reduced low-temperature toughness, alloy element loss, arc instability, and high crack sensitivity during high heat input welding of 1000MPa grade high-strength steel.

[0038] (2) This invention improves the strength and toughness of weld metal by regulating the composition of welding wire and flux to form stable needle-shaped ferrite during the welding process, improves grain boundary strength by micro-alloying to avoid abnormal grain growth under high heat input, and reduces the tendency of weld metal to crack by deoxidizing and desulfurizing flux.

[0039] (3) The present invention has determined through oblique Y-shaped groove test that preheating the base material before welding can effectively reduce the tendency of cold cracking in the weld joint during high heat input welding.

[0040] (4) The welding wire preparation method provided by the present invention has excellent effect on reducing stress during the drawing process, and the flux preparation method provided by the present invention has significant effect on reducing O and N content, and improving the processability and toughness of weld metal.

[0041] (5) This invention addresses the problems of alloy element burn-off and arc instability in high heat input welding. Through experiments, the amount of alloy burn-off under different heat inputs was determined and replenished with flux. The combination of welding wire and flux improves arc stability and welding processability. Different flux compositions are controlled under different heat inputs to avoid abnormal grain growth under high heat inputs. Attached Figure Description

[0042] Figure 1 The mechanical properties of the weld metal at the corresponding welding line energy are shown for the welding wires and fluxes prepared in Examples 1-4.

[0043] Figure 2 The impact fracture morphology of weld metal prepared by welding wire and flux in Example 1 under conventional line energy is shown.

[0044] Figure 3 The impact fracture morphology of the weld metal prepared in Example 5 using welding wire and flux under high heat input is shown. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0046] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0047] Specific Implementation Method 1:

[0048] This invention provides a 1000MPa grade high-strength steel high-heat submerged arc welding wire. The chemical composition of the welding wire by weight percentage includes: C 0.1%~0.2%, Si 0.1%~0.4%, Mn 1.5%~3.0%, S≤0.005%, P≤0.007%, Cr 0.2%~0.7%, Ni 2%~4.0%, Mo 0.6%~1.6%, Ti 0.01%~0.05%, Cu 0.05%~0.30%, Al 0.01%~0.02%, Nb 0.01%~0.03%, O≤50ppm, N≤50ppm, with the balance being iron and unavoidable impurities.

[0049] The reasons for designing the composition range of the welding wire for high-strength steel with high heat input in this invention are as follows:

[0050] C: 0.1%–0.2%; when the C content is greater than 0.06%, it can significantly improve the strength and hardness of the weld metal, but when the C content is too high, it will promote the formation of high-carbon martensite and reduce the toughness of the material; high-C welding wire generates higher internal stress during drawing, and excessively high C will also lead to reduced corrosion resistance of the weld metal, and high C will worsen the welding processability during high heat input welding. In this invention, the C content is controlled at 0.1%–0.2%.

[0051] Si: 0.1%–0.4%; Si is an excellent deoxidizer, and an addition of 0.1% can achieve a good deoxidation effect. In addition, Si has the effect of solid solution strengthening, improving the strength of the weld metal. The presence of Si in the weld metal can improve its fluidity, but during high heat input welding, the molten pool reaction is violent, and excessive Si can lead to spatter. High Si content can also affect toughness. In this invention, the Si content is controlled at 0.1%–0.4%.

[0052] Mn content: 1.5%–3.0%; Mn can expand the austenite region, stabilize the formed austenite, inhibit the formation of proeutectoid ferrite, promote the formation of acicular ferrite, and improve the toughness and crack resistance of weld metal; Mn also has certain deoxidation, desulfurization, and solid solution strengthening effects; however, high Mn content can lead to segregation and Widmanstätten formation, which is detrimental to the low-temperature toughness of the material. In this invention, the Mn content is controlled at 1.5%–3.0%.

[0053] S≤0.005% and P≤0.007%; S reacts with alloy components to form low-melting-point compounds, and P reacts with alloy components to form brittle compounds. These are the main elements that reduce the ductility and toughness of weld metal. The content of S and P should be reduced as much as possible. However, the alloy composition inevitably contains a certain amount of S and P elements. In this invention, S≤0.005% and P≤0.007% are strictly controlled through welding wire refining.

[0054] Cr: 0.2%–0.7%; In high-strength steel weld metal, when the Cr content is greater than 0.2%, Cr has solid solution strengthening and grain refinement strengthening effects on the weld metal, significantly improving the weld metal strength; at the same time, Cr can inhibit the formation of proeutectoid ferrite and promote the formation of acicular ferrite, improving crack resistance; when Cr is high, it will improve hardenability and increase the brittle transition temperature. Experiments have shown that the combination of high Cr and high heat input promotes the formation of MA components and reduces the low-temperature toughness of the material. In this invention, the Cr content is controlled at 0.2%–0.7%.

[0055] Ni: 2.0%–4.0%; the solid solution formed by Ni can refine austenite grains, maintain austenite stability, promote the formation of acicular ferrite, lower the ductile-brittle transition temperature, reduce grain coarsening caused by high heat input, and improve material toughness; however, excessive Ni will increase weld hardenability and the tendency of weld metal to hot crack, which is detrimental to the material's ductility and toughness. In this invention, the Ni content is controlled at 2.0%–4.0%.

[0056] Mo: 0.6%–1.6%; Mo can lower the austenite transformation temperature, suppress proeutectoid ferrite, promote the intermediate-temperature transformation to form bainite, and increase strength and toughness. In weld metal, Mo forms solid solutions that segregate towards grain boundaries, preventing grain coarsening caused by high heat input and improving weld metal strength. However, excessive Mo can form substitutional solid solutions, causing crystal lattice deformation and reducing material toughness. In this invention, the Mo content is controlled at 0.6%–1.6%.

[0057] Ti: 0.01%–0.05%; Ti can suppress the precipitation of coarse carbides at grain boundaries, strengthen grain boundaries, and has a strong bonding force with O, reducing low-melting-point oxides caused by high heat input. The formed Ti oxides can act as nucleation sites for acicular ferrite, promoting its formation. However, excessive Ti will precipitate as coarse oxides, reducing the material's toughness. In this invention, the Ti content is controlled at 0.01%–0.05%.

[0058] Cu: 0.05%–0.30%; a certain amount of Cu in the welding wire provides excellent arc stabilization during high-heat welding; Cu in high-strength steel weld metal can refine grains and improve ductility and toughness; Cu in weld metal can improve corrosion resistance; however, excessive Cu content will increase the weld metal's tendency to hot crack. In this invention, the Cu content is controlled at 0.05%–0.30%.

[0059] Al: 0.01%–0.02%; Al can combine with O and N to form compounds, reducing the O and N content of the weld metal; Al can lower the austenitizing temperature of the weld metal and promote the formation of acicular ferrite; however, excessive Al content will reduce corrosion resistance. In this invention, the Al content is controlled at 0.01%–0.02%.

[0060] Nb: 0.01%~0.03%; Elemental Nb precipitates at austenite grain boundaries during high heat input welding, pinning the grain boundaries and inhibiting austenite growth. It improves the strength and toughness of the weld metal through grain refinement and dispersion effects. When Nb is high, it promotes martensite formation, which is not conducive to the strength of the weld metal. This invention controls the Nb content at 0.01%~0.03%.

[0061] O≤50ppm, N≤50ppm; During welding, some O and N will be introduced into the weld metal. Under the action of high heat input, they will combine with alloying elements to form oxides and nitrides, which are not conducive to the strength and toughness of the weld metal. This invention controls the O and N content to below 50ppm.

[0062] This invention provides a method for preparing the above-mentioned 1000MPa grade high-strength steel high-heat submerged arc welding wire, the method comprising the following steps:

[0063] Step 1: Prepare wire rods with a diameter of Ф5.5mm according to the above composition; after mechanical peeling and belt grinding, the Ф5.5mm wire rods are directly fed into the roller drawing production line for drawing. The drawing speed shall not exceed 300m / min.

[0064] Step 2: The roller drawing process adopts an uncoated process and goes through 4 continuous drawing passes. The first three passes are roller drawing, and the fourth pass is eye drawing. The finished product diameter is Ф3.2mm, and the diameter tolerance is -0.04mm to 0.01mm.

[0065] Step 3: The finished product is cleaned online, coated with an anti-rust coating, dried by a high-pressure air brush, and then wound up by an I-beam reel.

[0066] Step 4: Use a dense array of submerged arc welding wires to wind the wires to obtain the desired submerged arc welding wire.

[0067] This invention provides a flux for use with the aforementioned 1000MPa grade high-strength steel high-heat submerged arc welding wire. The chemical composition of the flux, by weight percentage, includes: CaF2 20%–30%, SiO 25%–10%, MgO 15%–25%, TiO 25%–8%, Al2O3 16%–26%, CaO 16%–25%, nano-grade zirconium powder ≤1%, titanium-boron alloy ≤1%, aluminum-iron powder: 1%–5%, and silicon-manganese-iron alloy: 1%–5%.

[0068] The reason for designing the composition range of the flux for high heat input submerged arc welding of 1000MPa grade high-strength steel in this invention is as follows:

[0069] CaF2: 20%–30%; CaF2 is an excellent slag-forming agent, improving the slag removal effect; CaF2 can optimize the fluidity of weld metal, facilitating better spreading of molten metal; CaF2 can lower the melting point of slag, reducing alloy loss caused by high heat input welding; CaF2 decomposes into F… - Ions and H + Ions combine to form HF, reducing the susceptibility of high-strength steel weld metal to hydrogen-induced cracking; however, excessively high levels of CaF2 in the flux are detrimental to arc stabilization during high heat input welding. In this invention, CaF2 is controlled at 20%–30%.

[0070] SiO2: 5%–10%; SiO2 is an acidic oxide that can adjust the pH of the slag system; SiO2 can improve the fluidity of the molten pool and promote slag removal; during high heat input welding, a certain amount of SiO2 has a good arc-stabilizing effect; however, excessive amounts will form silicate compounds, deteriorating the welding processability of high-strength steel and causing alloy molten metal splashing. In this invention, SiO2 is controlled at 5%–10%.

[0071] MgO: 15%–25%; MgO is a basic oxide that controls the H content in the weld metal by improving the alkalinity of the molten alloy; MgO has a good regulating effect on slag viscosity and melting point; an appropriate amount of MgO can improve slag removal and promote the formation of straight and smooth weld beads; however, during high heat input welding, a high MgO content can lead to molten alloy splashing. In this invention, MgO is controlled at 15%–25%.

[0072] TiO2: 5%–8%; TiO2 can improve the viscosity and interfacial tension of slag, promoting slag removal during welding; TiO2 has the effect of stabilizing the electric arc, reducing spattering of molten alloy during high heat input welding; however, excessive TiO2 will transfer some Ti into the weld metal, reducing the toughness of the weld metal. In this invention, TiO2 is controlled at 5%–8%.

[0073] Al2O3: 16%–26%; Al2O3 is a slag-forming agent, which is beneficial for slag removal and subsequent weld deslag removal. Al2O3 has a good regulating effect on the viscosity and melting point of the weld metal alloy, ensuring a stable reaction of the molten pool metal during high heat input welding, resulting in a smooth and flat weld bead. Excessive Al2O3 in the flux leads to severe spatter during high heat input welding. In this invention, Al2O3 is controlled at 16%–26%.

[0074] CaO: 16%–25%; CaO is a basic oxide that regulates the pH of molten slag; CaO has a certain arc-stabilizing effect and improves the welding processability at high heat input; at the same time, CaO has the effect of removing sulfur and phosphorus, reducing the sulfur and phosphorus content of the weld metal, and improving the crack resistance of the weld metal; however, excessive CaO will cause splashing of the molten alloy. In this invention, CaO is controlled at 16%–25%.

[0075] The content of nano-sized zirconium powder is ≤1%. When nano-sized zirconium powder is added to the flux, it transitions into the weld metal during high heat input welding, forming high-melting-point nano-sized zirconium oxide, which segregates at the austenite grain boundaries, reducing abnormal grain growth during high heat input welding. Simultaneously, nano-sized zirconium and zirconium oxide can promote grain slip during deformation, improving ductility and toughness. However, excessive zirconium content can lead to significant segregation at grain boundaries, negatively impacting material toughness. In this invention, the content of nano-sized zirconium powder is controlled below 1%.

[0076] The titanium-boron alloy content is ≤1%. During high-energy welding of low-alloy high-strength steel, proeutectoid ferrite often precipitates, which is detrimental to the material's low-temperature toughness. Adding trace amounts of boron can effectively suppress proeutectoid ferrite and promote the formation of acicular ferrite. In this invention, the titanium-boron alloy is added, utilizing the better bonding force between titanium and O / N than boron to prevent boron from being oxidized or nitrided under high heat input. In this invention, the titanium-boron alloy content is controlled to be below 1%.

[0077] Aluminum-iron powder: 1%–5%; Adding a certain amount of aluminum-iron powder to the flux can deoxidize, decarburize, and reduce the loss of other alloying elements. Simultaneously, Al can promote the formation of acicular ferrite in the weld metal and lower the temperature of the slag during high heat input welding. In this invention, the aluminum-iron powder content is controlled at 1%–5%.

[0078] Ferrosilicon alloy: 1%–5%; through combined silicon and manganese deoxidation, the oxidation effect of high heat input on the alloy melt is reduced, ensuring low oxygen and high toughness of the weld metal. Mn can promote the formation of acicular ferrite and improve the toughness of the weld metal. Therefore, during high heat input welding, the flux is used to replenish the Mn lost in the weld metal.

[0079] This invention provides a method for preparing the flux for high heat input submerged arc welding of 1000MPa grade high-strength steel, the method comprising the following steps:

[0080] Step 1: Mix the powder; mix the ingredients according to the above formula and pack into cans.

[0081] Step 2: Stirring; Put the powder prepared in Step 1 into the mixer, dry mix for 5 to 10 minutes, then add 10% to 20% water glass and stir for 5 to 10 minutes.

[0082] Step 3: Granulation; The wet mixture prepared in step 2 is fed into a granulator for granulation. The granulator is a disc-type rotary granulator with a rotation speed of 200-300 rpm.

[0083] Step 4: Low-temperature drying; The granulated material from Step 3 is transferred to a low-temperature drying oven, which is a rotary continuous drying oven with a drying temperature of 200-300℃.

[0084] Step 5: Low-temperature screening; The powder dried at low temperature in step 4 is fed into a vibrating screen for screening, and the particle size range of the low-temperature screening is 10 to 50 mesh.

[0085] Step 6: High-temperature sintering; The powder produced in step 5 is transferred to a high-temperature drying furnace, which is a rotary continuous drying furnace with a drying temperature of 750-850℃.

[0086] Step 7: High-temperature sieving; The powder after high-temperature sintering in step 6 is further sieved and selected by a vibrating screener, and the particle size range is 10-50 mesh.

[0087] Step 8: Cooling; The powder produced in step 7 is transferred to a cooling furnace, which is a rotary continuous cooling furnace, and the cooling method is external wall air cooling.

[0088] Step 9: Packaging; Package the cooled powder to obtain the required flux.

[0089] The following detailed description, in conjunction with embodiments, describes the welding wire and its preparation, flux and its preparation, welding materials and their applications for high-strength steel high-heat submerged arc welding of 1000MPa grade, provided by the present invention. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0090] The composition of the welding wires in Examples 1-4 and Comparative Examples 1-2 is shown in Table 1.

[0091] Table 1 Chemical composition of welding wire (by weight percentage)

[0092]

[0093] The preparation method of the above welding wire is as follows:

[0094] Step 1: Prepare wire rods with a diameter of Ф5.5mm according to the above composition; after mechanical peeling and belt grinding, the Ф5.5mm wire rods are directly fed into the roller drawing production line for drawing. The drawing speed shall not exceed 300m / min.

[0095] Step 2: The roller drawing process adopts an uncoated process and goes through 4 continuous drawing passes. The first three passes are roller drawing, and the fourth pass is eye drawing. The finished product diameter is Ф3.2mm, and the diameter tolerance is -0.04mm to 0.01mm.

[0096] Step 3: The finished product is cleaned online, coated with an anti-rust coating, dried by a high-pressure air brush, and then wound up by an I-beam reel.

[0097] Step 4: Use a dense array of submerged arc welding wires to wind the wires to obtain the desired submerged arc welding wire.

[0098] The composition of the flux in Examples 1-4 and Comparative Examples 1-2 is shown in Table 2.

[0099] Table 2 Chemical composition of flux (by weight percentage)

[0100]

[0101]

[0102] The preparation method of the above flux is as follows:

[0103] Step 1: Mix the powder; mix the ingredients according to the above formula and pack into cans.

[0104] Step 2: Stirring; Put the powder prepared in Step 1 into the mixer, dry mix for 5 to 10 minutes, then add 10% to 20% water glass and stir for 5 to 10 minutes.

[0105] Step 3: Granulation; The wet mixture prepared in step 2 is fed into a granulator for granulation. The granulator is a disc-type rotary granulator with a rotation speed of 200-300 rpm.

[0106] Step 4: Low-temperature drying; The granulated material from Step 3 is transferred to a low-temperature drying oven, which is a rotary continuous drying oven with a drying temperature of 200-300℃.

[0107] Step 5: Low-temperature screening; The powder dried at low temperature in step 4 is fed into a vibrating screen for screening, and the particle size range of the low-temperature screening is 10 to 50 mesh.

[0108] Step 6: High-temperature sintering; The powder produced in step 5 is transferred to a high-temperature drying furnace, which is a rotary continuous drying furnace with a drying temperature of 750-850℃.

[0109] Step 7: High-temperature sieving; The powder after high-temperature sintering in step 6 is further sieved and selected by a vibrating screener, and the particle size range is 10-50 mesh.

[0110] Step 8: Cooling; The powder produced in step 7 is transferred to a cooling furnace, which is a rotary continuous cooling furnace, and the cooling method is external wall air cooling.

[0111] Step 9: Packaging; Package the cooled powder to obtain the required flux.

[0112] After obtaining the welding wire and flux, the high-strength steel B950CF base material was welded based on the welding process in Table 3 below. The groove type was a 45° V-groove. The size of the welding test plate was 350mm×300mm×20mm.

[0113] Table 3 Welding Process

[0114]

[0115] The welds obtained in Examples 1-4 and Comparative Examples 1-2 were subjected to mechanical property tests, and the results are shown in Table 4 below:

[0116] Table 4 Mechanical properties of different weld metals

[0117]

[0118] As shown in Table 3, Examples 2-4 were welded under high heat input, while Example 1 was welded under conventional heat input. The mechanical properties of the weld metal obtained in all cases met the requirements for engineering applications. The impact fracture morphology of the weld metal obtained in Example 1 under conventional heat input is shown below. Figure 2 As shown, the impact fracture morphology of the weld metal obtained under high heat input in Example 4 is as follows. Figure 3 As shown, comparison Figure 2 and Figure 3 It is known that the impact fracture surface of the weld metal at high heat input has more precipitates in the dimples, which is beneficial to improving mechanical properties. Weld metals prepared by adjusting the composition of welding wire and flux during high heat input welding can still maintain a high strength and toughness match.

[0119] Comparative Examples 1, 2 and 4 used the same welding line energy. As can be seen from the comparison in Table 4, the Nb element in the welding wire and the nano-sized zirconium powder and titanium-boron alloy in the flux are beneficial to prevent abnormal grain growth in the weld metal. The aluminum-iron powder and silicon-manganese-iron alloy are beneficial to reduce the burn-off of alloy elements and ensure the high strength and toughness of the weld metal.

[0120] Figure 1 The mechanical properties of weld metal prepared in Examples 1-4 using welding wires and fluxes at different welding heat inputs are shown. The welding current is 500-590 A, the welding voltage is 32-34 V, the welding speed is 21-40 cm / min, the preheating temperature is 100 °C, and the interpass temperature is ≤150 °C. Figure 1 It can be seen that the mechanical properties of weld metals prepared by adjusting the corresponding welding material composition under different welding line energies all meet the technical indicators for engineering applications and the performance data are stable. The test proves that the designed welding material meets the performance requirements for welding under conventional line energy and high line energy.

[0121] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A large heat input submerged arc welding method for a 1000 MPa grade high-strength steel, characterized by, The welding method uses a welding wire chemical composition including, by weight percentage: C 0.1%-0.2%, Si 0.1%-0.4%, Mn 1.5%-3.0%, S≤0.005%, P≤0.007%, Cr 0.2%-0.7%, Ni 2%-4.0%, Mo 0.6%-1.6%, Ti 0.01%-0.05%, Cu 0.05%-0.30%, Al 0.01%-0.02%, Nb 0.01%-0.03%, O≤50ppm, N≤50ppm, the balance being iron and unavoidable impurities; and a flux chemical composition including, by weight percentage: CaF2 20%-30%, SiO2 5%-10%, MgO 15%-25%, TiO2 5%-8%, Al2O3 16%-26%, CaO 16%-25%, 0%< nanometer zirconium powder≤1%, 0%< titanium boron alloy≤1%, aluminum iron powder: 1%-5%, silicon manganese iron alloy: 1%-5%. The welding method has a linear energy range of 40-60 kJ / cm, and the welding base material is preheated to 100°C before welding.

2. The 1000 MPa grade high strength steel large heat input submerged arc welding method according to claim 1, characterized by, The welding wire chemical composition includes, by weight percentage: C 0.10%-0.15%, Si 0.15%-0.25%, Mn 1.5%-2.5%, S≤0.005%, P≤0.007%, Cr 0.3%-0.7%, Ni 2.5%-4.0%, Mo 0.8%-1.4%, Ti 0.01%-0.03%, Cu 0.15%-0.25%, Al 0.01%-0.02%, Nb 0.01%-0.02%, O≤50ppm, N≤50ppm, the balance being iron and unavoidable impurities.

3. The 1000 MPa grade high strength steel large heat input submerged arc welding method according to claim 1, characterized by, The welding wire preparation method includes: S1, the welding wire raw material is sequentially subjected to smelting, refining, preheating and hot rolling of a rod, to obtain a Ф5.5mm rod; S2, the rod is directly subjected to mechanical peeling, sand belt grinding and then roll die drawing, the roll die drawing adopts a coating-free process, and a total of 4 continuous drawing is performed, the first three passes are roll dies, and the fourth pass is an eye die, to obtain a finished product with a diameter of Ф3.2mm; S3, the finished product is subjected to online cleaning, surface coating of an anti-rust coating, high-pressure air brush drying, and H-shaped wheel take-up, and then is subjected to close-layer winding by an arc welding wire winding machine, to obtain the welding wire.

4. The 1000 MPa grade high strength steel large heat input submerged arc welding method according to claim 1, characterized by, The flux chemical composition includes, by weight percentage: CaF2 20%-28%, SiO2 5%-8%, MgO 18%-21%, TiO2 5%-8%, Al2O3 16%-24%, CaO 16%-22%, 0%< nanometer zirconium powder≤1%, 0%< titanium boron alloy≤1%, aluminum iron powder 2.5%-4.5%, silicon manganese iron alloy 1%-4.5%.

5. The 1000 MPa grade high strength steel large heat input submerged arc welding method according to claim 1, characterized in that, The titanium boron alloy in the flux has Ti≥55wt%, and the balance is B.

6. The 1000 MPa grade high strength steel large heat input submerged arc welding method according to claim 1, characterized by, The aluminum iron powder in the flux has Al≥45wt%, and the balance is iron.

7. The method of high strength 1000 MPa grade steel welding with large heat input submerged arc welding according to claim 1, characterized in that, The silicon manganese iron alloy in the flux has Si≥15wt%, Mn≥50wt%, and the balance is iron.

8. The 1000 MPa grade high strength steel large heat input submerged arc welding method according to claim 1, characterized by, The preparation method of the flux is as follows: adopting a continuous production line to prepare, stir, granulate, low-temperature drying, screening, high-temperature drying, screening and cooling processes.

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