Welding material for submerged arc welding, submerged arc welding method and welding wire production method

Abstract

The invention provides a welding material for submerged-arc welding, a submerged-arc welding method and a welding wire production method, the welding material for submerged-arc welding comprises a welding wire and a welding flux, and the welding wire comprises the following chemical components in percentage by weight: 0.05-0.2% of C, 0.1-0.5% of Si, 1.5-3.0% of Mn, 3-5% of Ni, 1-2% of Cr + Mo, 0.05-0.15% of B + Ti and the balance of iron and inevitable impurities; the flux comprises the following chemical components in percentage by weight: 45 to 55 percent of CaF2 + MgO, 5 to 10 percent of SiO2, 6 to 12 percent of Al2O3, 8 to 12 percent of CaO, 3 to 5 percent of K2O + Na2O, 2 to 6 percent of Re and the balance of inevitable impurities. By adopting the design scheme of Ni + B + Re, the low-temperature toughness of a welding seam is improved, and meanwhile, the forming performance of the welding seam and the deslagging performance of the welding flux can be improved.

Description

Technical Field

[0001] This application relates to the technical field of metal welding, and particularly to a welding material for submerged arc welding, a submerged arc welding method, and a production method of welding wire. Background Art

[0002] The corresponding materials applied to hydropower station projects are constantly being updated. High-strength steel of 800 MPa grade has been widely used in the hydropower industry, and the various benefits brought by high-strength steel are also obvious. Currently, new materials of 1000 MPa will also be gradually promoted and used.

[0003] When using 1000 MPa high-strength steel materials in hydropower station projects, the wall thickness of devices can be effectively reduced, the mass of components can be reduced, the construction difficulty can be lowered, and production costs can be saved. The 1000 MPa steel plates used in important components such as large hydropower stations and pumped-storage power stations have the advantages of high plastic toughness and ultra-low welding crack sensitivity. The submerged arc welding materials suitable for 1000 MPa hydropower stations need to have corresponding strength, and while ensuring high strength, it is also necessary to reduce their crack sensitivity and achieve a certain low-temperature toughness. However, the current welding wires and fluxes are difficult to achieve high strength, high and low-temperature toughness, and low crack sensitivity. Summary of the Invention

[0004] The purpose of this application is to provide a welding material for submerged arc welding, which solves the problem that it is difficult to optimize the welding strength, low-temperature toughness, and crack sensitivity of 1000 MPa grade hydropower steel simultaneously in the prior art.

[0005] In order to achieve one of the above-mentioned invention purposes, an embodiment of this application provides a welding material for submerged arc welding, including a welding wire and a flux. The chemical composition of the welding wire by weight percentage includes: C: 0.05 - 0.2%, Si: 0.1 - 0.5%, Mn: 1.5 - 3.0%, Ni: 3 - 5%, Cr + Mo: 1 - 2%, B + Ti: 0.05 - 0.15%, and the balance is iron and unavoidable impurities; The chemical composition of the flux by weight percentage includes: CaF2 + MgO: 45 - 55%, SiO2: 5 - 10%, Al2O3: 6 - 12%, CaO: 8 - 12%, K2O + Na2O: 3 - 5%, Re: 2 - 6%, and the rest are unavoidable impurities.

[0006] In one embodiment of this application, the B content in the welding wire is 0.003 - 0.01%.

[0007] In one embodiment of this application, the basicity of the flux ≥ 3.0.

[0008] One embodiment of the present application also provides a submerged arc welding method, in which the welding material as described above is placed at the position to be welded, and welding is carried out under the conditions of a welding current of 600 - 700 A, an arc voltage of 35 - 40 V, and a welding speed of 300 - 350 mm / min.

[0009] In one embodiment of the present application, the oxygen content of the welded metal formed at the welding position is 0.01 - 0.03%, the nitrogen content ≤ 0.005%, the sulfur content ≤ 0.005%, and the phosphorus content ≤ 0.008%.

[0010] In one embodiment of the present application, before welding, the workpiece to be welded is preheated to 80 - 100 °C.

[0011] In one embodiment of the present application, the interpass temperature of welding is controlled to be 80 - 200 °C.

[0012] In one embodiment of the present application, the tensile strength of the welded metal formed at the welding position ≥ 1000 MPa, the yield strength ≥ 900 MPa, the elongation ≥ 15%, the impact absorption energy in the -60 °C Charpy pendulum test ≥ 80 J, there is no solidification crack, and there is no crack in the side bend test.

[0013] One embodiment of the present application also provides a production method of a welding wire. The chemical composition of the welding wire by weight percentage includes: C: 0.05 - 0.2%, Si: 0.1 - 0.5%, Mn: 1.5 - 3.0%, Ni: 3 - 5%, Cr + Mo: 1 - 2%, B + Ti: 0.05 - 0.15%, and the balance is iron and inevitable impurities; The production method includes making the wire rod obtained by sequentially carrying out converter smelting, LF refining, continuous casting, rolling, and cooling processes through drawing, where, In the rolling process, first heat the billet obtained from the continuous casting process to 1050 - 1090 °C, then roll the billet into a wire rod, control the entry temperature of the finishing mill to be 850 - 900 °C, and control the laying temperature to be 800 - 850 °C; In the cooling process, after laying, control the wire rod to cool to 750 - 800 °C at a cooling rate of 3 - 5 °C / s, and then cool to 550 - 580 °C at a cooling rate of ≤ 1 °C / s.

[0014] In one embodiment of the present application, in the converter smelting process, control the basicity of the final slag to be 3.2 - 3.8, and control the MgO content in the final slag to be 8 - 10%; In the LF refining process, after the ladle arrives at the station, start bottom blowing argon, and the molten steel shall not be exposed during the whole refining process.

[0015] In one embodiment of the present application, in the continuous casting process, the tundish temperature is controlled at 1500 - 1550 °C, and the continuous casting speed is controlled at 2.6 - 2.8 m / min.

[0016] One or more technical solutions provided by the present application have at least the following technical effects or advantages: In the welding consumables for submerged arc welding provided by the present application, a design scheme of Ni + B + Re is adopted. Among them, Ni can improve the low-temperature toughness of the matrix microstructure of the weld seam; on the one hand, B refines the weld seam structure and improves the low-temperature toughness, and at the same time, it can also diffuse to the welding heat-affected zone near the fusion line; Re is transferred to the weld metal after welding through the welding flux to regulate the oxygen content in the weld seam, as well as the types and contents of oxides, thereby improving the low-temperature toughness of the weld seam. At the same time, it can also improve the forming performance of the weld seam and the slag removal performance of the welding flux. Specific embodiments

[0017] The technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0018] The embodiments of the present application provide a welding consumable for submerged arc welding, including a welding wire and a welding flux. The chemical composition of the welding wire by weight percentage includes: C: 0.05 - 0.2%, Si: 0.1 - 0.5%, Mn: 1.5 - 3.0%, Ni: 3 - 5%, Cr + Mo: 1 - 2%, B + Ti: 0.05 - 0.15%, and the balance is iron and unavoidable impurities.

[0019] The chemical composition of the welding flux by weight percentage includes: CaF2 + MgO: 45 - 55%, SiO2: 5 - 10%, Al2O3: 6 - 12%, CaO: 8 - 12%, K2O + Na2O: 3 - 5%, Re: 2 - 6%, and the rest are unavoidable impurities.

[0020] The wire composition of the present application adopts a strategy of low carbon, high nickel, and microalloying (Ti and B), effectively balancing strength and toughness, optimizing the deoxidation performance of the welding flux, and further improving the purity and low-temperature impact toughness of the weld seam.

[0021] And the design scheme of Ni + B + Re is adopted, where Ni can improve the low-temperature toughness of the matrix microstructure of the weld seam; on the one hand, B can refine the weld seam structure and improve the low-temperature toughness, and at the same time, it can also diffuse to the welding heat-affected zone near the fusion line; Re is transitioned into the weld metal through the welding flux after welding, which is used to regulate the oxygen content in the weld seam, as well as the type and content of oxides, so as to improve the low-temperature toughness of the weld seam. At the same time, it can also improve the forming performance of the weld seam and the slag removal performance of the welding flux.

[0022] The functions and dosage selection of the components contained in the present invention are specifically described as follows: Carbon (C): Carbon is a key element affecting the strength and toughness of the weld seam. An appropriate amount of carbon can improve the strength and hardness of the weld seam, but too high a carbon content will lead to a decrease in the toughness of the weld seam and an increase in brittleness.

[0023] Silicon (Si): Silicon is a commonly used deoxidizing element, which can prevent iron from combining with oxygen and reduce FeO in the molten pool. However, when using silicon for deoxidation alone, the generated SiO2 has a high melting point and is difficult to float out, which is likely to cause inclusions.

[0024] Manganese (Mn): Manganese is an important alloying element, which has the functions of deoxidation and desulfurization, and can reduce the tendency of hot cracks caused by sulfur. In addition, manganese can also improve the strength and toughness of the weld seam.

[0025] Nickel (Ni): Nickel can significantly improve the toughness of the weld metal, especially the low-temperature impact toughness, and reduce the brittle transition temperature. Nickel can also expand the austenite region and improve the tensile strength and hardness of the weld seam.

[0026] Boron (B): Boron is a trace alloying element, which can significantly improve the hardenability of steel, refine the grains, and thus improve the strength and toughness of the weld seam.

[0027] Chromium (Cr): Chromium can significantly improve the strength and hardness of the weld seam. At the same time, chromium can also improve the oxidation resistance and corrosion resistance of the weld seam.

[0028] Molybdenum (Mo): Molybdenum can significantly improve the strength and hardness of the weld seam. At the same time, it can refine the grains and improve the toughness of the weld seam.

[0029] Titanium (Ti): Al and Ti are strong deoxidizers, which can refine the grains, improve the toughness and crack resistance of the weld seam. Nb can also refine the grains and improve the crack resistance of the grain boundary.

[0030] In addition, CaF2 + MgO in the welding flux will also be transitioned into the weld metal to regulate the alloying components in the molten pool. SiO2 and Al2O3 supplement the burned Si and Al in the welding wire to prevent the Si and Al elements in the molten pool from forming slag and being stripped, so that the Si and Al contents in the weld metal cannot reach the target contents.

[0031] CaO, K2O, and Na2O can regulate the viscosity and thermal conductivity of the slag in the molten pool, enabling the slag to be easily peeled off after welding. K2O and Na2O can also enhance the moisture resistance of the welding flux and shorten the drying time before using the welding flux.

[0032] In an embodiment of the present application, the B content in the welding wire is 0.003 - 0.01%. B has a strong affinity with O and N, and it is easy to generate non-metallic inclusions, which will affect the welding quality. Therefore, the B content needs to be kept at a low value.

[0033] In an embodiment of the present application, the basicity of the welding flux ≥ 3.0, which can remove oxygen in the molten pool, making the oxygen content in the formed weld metal relatively low, and being beneficial to the low-temperature toughness of the weld metal.

[0034] In an embodiment of the present application, the P content in the welding flux ≤ 0.0006%, and the S content ≤ 0.0006%. By controlling P and S at extremely low values, adverse effects on the cold cracking and low-temperature toughness of the welded metal can be avoided.

[0035] The embodiment of the present application also provides a submerged arc welding method, which uses the welding wire and welding flux in the aforementioned welding materials. The welding wire and welding flux are placed at the location to be welded, and welding is carried out under the conditions that the welding current is 600 - 700 A, the arc voltage is 35 - 40 V, and the welding speed is 300 - 350 mm / min.

[0036] Before welding, remove rust, oil, and moisture on the surface of the workpiece to be welded to ensure the welding quality. During the welding process, reasonably control the heat input to ensure the temperature at the weld and the cooling rate after welding, so as to ensure that the weld metal after cooling has high strength and high plasticity, meeting the strength requirements of 1000 MPa grade hydroelectric steel for the weld; and the welding is efficient.

[0037] During the welding process, keep the arc stable to avoid arc blow and welding defects. After welding, clean the welding slag in time. The surface of the weld should be smooth and flat, without defects such as undercut, porosity, and slag inclusion.

[0038] Two workpieces to be welded adopt a V-shaped groove, with the groove angle being 45 - 65°, the root face thickness being 1.5 - 4 mm, and the assembly gap being 2 - 3 mm.

[0039] In an embodiment of the present application, the oxygen content of the welded metal formed after welding is 0.01 - 0.03%, the nitrogen content ≤ 0.005%, the sulfur content ≤ 0.005%, and the phosphorus content ≤ 0.008%.

[0040] In an embodiment of the present application, before welding, preheat the workpiece to be welded to 80 - 100 °C, which can effectively reduce the generation of welding cold cracks.

[0041] In an embodiment of the present application, the interpass temperature for welding is controlled to be 80 - 200 °C, which can keep the workpiece to be welded in a preheated state all the time and avoid the welding temperature of the next pass being too high and the cooling rate being too low, thereby affecting the strength of the welded metal.

[0042] In an embodiment of the present application, the tensile strength of the welded metal formed after welding is ≥1000 MPa, the yield strength is ≥900 MPa, the elongation is ≥15%, the impact absorption energy in the Charpy pendulum test at -60 °C is ≥80 J, there is no solidification crack, and there is no crack in the side bend test. This strength and toughness can meet the actual engineering application requirements of 1000 MPa grade hydroelectric steel.

[0043] The embodiment of the present application also provides a production method of a welding wire. The chemical composition of the welding wire by weight percentage includes: C: 0.05 - 0.2%, Si: 0.1 - 0.5%, Mn: 1.5 - 3.0%, Ni: 3 - 5%, Cr + Mo: 1 - 2%, B + Ti: 0.05 - 0.15%, and the balance is iron and inevitable impurities; It is made by drawing the wire rod obtained through the converter smelting, LF refining, continuous casting, rolling, and cooling processes in sequence. Among them, In the rolling process, first heat the slab obtained from the continuous casting process to 1050 - 1090 °C, then roll the slab into a wire rod, control the finishing mill inlet temperature to be 850 - 900 °C, and control the laying head temperature to be 800 - 850 °C; In the cooling process, after laying head, control the wire rod to cool to 750 - 800 °C at a cooling rate of 3 - 5 °C / s, and then cool to 550 - 580 °C at a cooling rate of ≤1 °C / s.

[0044] Through the lower heating temperature and rolling temperature, combined with the slower cooling rate, the obtained wire rod has good drawing performance, providing a good basis for subsequent drawing into a welding wire.

[0045] After the slab is heated, high-pressure water descaling with a water pressure ≥14 MPa is used to remove the oxide layer on the surface of the steel billet, ensuring the surface quality of the wire rod and avoiding the increase of the oxygen content in the welding wire.

[0046] In an embodiment of the present application, the rolling speed is controlled at 95 - 100 m / s to ensure the high efficiency of welding wire production.

[0047] In an embodiment of the present application, in the converter smelting process, control the basicity of the final slag to be 3.2 - 3.8, and control the MgO content in the final slag to be 8 - 10%; in the LF refining process, after the ladle arrives at the station, turn on the bottom blowing argon, and the molten steel shall not be exposed during the whole refining process.

[0048] In the converter smelting process, the final basicity of the slag is controlled to be relatively high to improve the deoxidation ability of the molten steel, reduce the oxygen content in the molten steel, purify the molten steel, and prevent oxygen from affecting the strength of the welded metal after welding is completed.

[0049] The ratio of the hot metal amount to the clean scrap in converter smelting is 5 - 6:1 to avoid introducing too much carbon element, and the hot metal temperature is controlled at 1350 - 1450 °C. The tapping temperature is 1600 - 1650 °C. When tapping from the converter, argon bottom blowing in the ladle is started, and the argon gas pressure is 0.5 - 0.7 MPa.

[0050] During the LF refining process, the molten steel is not exposed to prevent secondary oxidation of the molten steel and keep the molten steel pure. After the ladle arrives at the station, the argon gas pressure is 1.5 - 1.8 MPa; alloying is carried out in the LF refining process. During the alloy addition stage, the argon gas flow rate is controlled at 190 - 210 L / min; then the argon gas flow rate is controlled at 160 - 180 L / min for strong stirring for 2 - 3 min; during the inclusion removal and homogenization stage, the argon gas flow rate is controlled at 45 - 60 L / min.

[0051] In an embodiment of the present application, during the continuous casting process, the tundish temperature is controlled at 1500 - 1550 °C, and the continuous casting drawing speed is controlled at 2.6 - 2.8 m / min.

[0052] For continuous casting, a long nozzle for the tundish and argon sealing, as well as a covering agent for the low-carbon steel tundish, are used for protected casting. Before starting casting, argon is blown into the tundish for 3 - 5 min to remove the solidified molten steel or slag residues on the inner wall of the tundish. The water flow rate of the mold is 1800 ± 25 L / min, and the temperature difference between the inlet and outlet water of the mold is < 10 °C.

[0053] After the wire rod is cooled, the scale is removed by mechanical descaling and / or pickling, and then it is drawn by a continuous drawing test machine, electroplated with copper online, and wound in layers to make welding wires with a diameter of 0.9 - 4.0 mm.

[0054] The technical solutions of the present application will be further described below in conjunction with some specific embodiments.

[0055] Table 1 and Table 2 show the chemical compositions and contents of the welding wire and the welding flux respectively. Table 3 shows the welding consumables formed by the combination of the welding wire in Table 1 and the welding flux in Table 2, as well as the welding process parameters. Table 4 shows the production processes of the welding wires in Table 1. Table 5 shows the contents of impurity elements in the welded metal and the mechanical properties of the welded metal. Among them, the mechanical properties in Table 5 are obtained by testing the welds according to the standards GB / T228.1 "Metallic materials - Tensile testing - Part 1: Method of test at room temperature", GB / T229 "Metallic materials - Charpy pendulum impact test method", and GB / T232 "Metallic materials - Bend test method".

[0056] Table 1 Chemical composition of welding wire (wt.%)

[0057] Table 2 Flux Composition (wt.%)

[0058] Table 3 Combinations of Welding Wire + Flux and Welding Processes

[0059] Table 4 Welding Wire Production Process

[0060] Table 5 Impurity Content and Mechanical Properties of Weld Metal

[0061] It should be understood that although this specification is described in terms of embodiments, not every embodiment contains only one independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0062] The series of detailed descriptions listed above are only specific descriptions of the feasible embodiments of this application, and they are not intended to limit the protection scope of this application. Any equivalent embodiments or changes made without departing from the technical spirit of this application should be included within the protection scope of this application.

Claims

1. A welding consumable for submerged arc welding, characterized in that, It includes a welding wire and a welding flux. The chemical composition of the welding wire by weight percentage includes: C: 0.05 - 0.2%, Si: 0.1 - 0.5%, Mn: 1.5 - 3.0%, Ni: 3 - 5%, Cr + Mo: 1 - 2%, B + Ti: 0.05 - 0.15%, and the balance is iron and inevitable impurities; The chemical composition of the welding flux by weight percentage includes: CaF2 + MgO: 45 - 55%, SiO2: 5 - 10%, Al2O3: 6 - 12%, CaO: 8 - 12%, K2O + Na2O: 3 - 5%, Re: 2 - 6%, and the rest are inevitable impurities.

2. The welding consumable for submerged arc welding according to claim 1, wherein The B content in the welding wire is 0.003 - 0.01%.

3. The welding consumable for submerged arc welding according to claim 1, characterized in that, The basicity of the welding flux ≥ 3.

0.

4. A submerged arc welding method, characterized in that, Use the welding materials described in any one of claims 1 - 3 and place them at the welding position, and weld under the conditions of a welding current of 600 - 700 A, an arc voltage of 35 - 40 V, and a welding speed of 300 - 350 mm / min.

5. The submerged arc welding method according to claim 4, wherein The oxygen content of the weld metal formed at the welding position is 0.01 - 0.03%, the nitrogen content ≤ 0.005%, the sulfur content ≤ 0.005%, and the phosphorus content ≤ 0.008%.

6. The submerged arc welding method according to claim 4, characterized in that, Before welding, preheat the workpiece to be welded to 80 - 100 °C.

7. The submerged arc welding method according to claim 6, characterized in that, Control the interpass temperature of welding to be 80 - 200 °C.

8. The submerged arc welding method according to any one of claims 4 to 7, characterized in that, The tensile strength of the weld metal formed at the welding position ≥ 1000 MPa, the yield strength ≥ 900 MPa, the elongation ≥ 15%, the impact absorption energy in the -60 °C Charpy pendulum test ≥ 80 J, there is no solidification crack, and there is no crack in the side bend test.

9. A production method of a welding wire, characterized in that, The chemical composition of the welding wire by weight percentage includes: C: 0.05 - 0.2%, Si: 0.1 - 0.5%, Mn: 1.5 - 3.0%, Ni: 3 - 5%, Cr + Mo: 1 - 2%, B + Ti: 0.05 - 0.15%, and the balance is iron and inevitable impurities; The production method includes making the wire rod obtained by sequentially performing converter smelting, LF refining, continuous casting, rolling, and cooling processes through drawing, where, In the rolling process, first heat the slab obtained from the continuous casting process to 1050 - 1090 °C, then roll the slab into a wire rod, control the finishing mill inlet temperature to be 850 - 900 °C, and control the laying head temperature to be 800 - 850 °C; In the cooling process, after laying head, control the wire rod to cool at a cooling rate of 3 - 5 °C / s to 750 - 800 °C, and then cool at a cooling rate of ≤ 1 °C / s to 550 - 580 °C.

10. The production method of the welding wire according to claim 9, characterized in that, In the converter smelting process, control the basicity of the final slag to be 3.2 - 3.8, and control the MgO content in the final slag to be 8 - 10%; In the LF refining process, after the ladle arrives at the station, start bottom blowing argon, and the molten steel shall not be exposed during the whole refining process.

11. The production method of the welding wire according to claim 10, characterized in that, In the continuous casting process, control the tundish temperature to be 1500 - 1550 °C, and control the continuous casting drawing speed to be 2.6 - 2.8 m / min.

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