Steel for submerged arc welding wire, wire drawing, submerged arc welding wire and method of manufacturing the same

Abstract

The steel for submerged arc welding wire, the wire drawing, the submerged arc welding wire, and the method for manufacturing the same belong to the field of steel smelting technology and overcome the drawbacks of conventional technology, such as high cost and easy nodule formation. The method for manufacturing the steel for high-Ti pipeline submerged arc welding wire of the present application comprises converter smelting, LF refining, continuous casting, rolling, and cooling; in the LF refining, the composition of the refining slag is (CaO+CaF2) 40-50% by weight percentage, Al2O3 30%-40%, SiO2≤5%, and MnO 10%-20%; and in the LF refining process, pure calcium wire is fed before tapping. The steel for high-Ti pipeline submerged arc welding wire of the present application can be continuously cast in 10 or more furnaces during manufacturing.

Description

Technology Field

[0001] This application was filed with the Chinese Intellectual Property Office on October 19, 2022, and claims priority to a Chinese patent application with application number 202211276565.3 and invention titled "Steel for submerged arc welding wire, wire drawing, submerged arc welding wire and method for manufacturing the same," and incorporates all of the contents of the same by reference into this application.

[0002] This application relates to the field of steel smelting technology, specifically to steel for submerged arc welding wire, wire drawing, submerged arc welding wire, and a method for manufacturing the same. Background Technology

[0003] Compared to gas shield welding, submerged arc welding has higher production efficiency and a higher level of automation. Titanium-containing welding wire steel is widely used for welding pipeline steel. Adding the element Ti to alloy welding wire can finer the grain size while simultaneously improving the low-temperature impact toughness and tensile strength of the metal cladding. However, titanium-containing pipeline submerged arc welding wire steel faces smelting problems during production, such as (1) nodulation forming in the nozzle during the casting process and the stopper rod rising during the casting process; and (2) a low Ti yield of less than 40% during the refining process. Considering the difficulties of continuous steelmaking casting, many steel companies control the mass percentage of Ti content in the welding wire to less than 0.07% and add expensive Mo to meet the requirements of the metal cladding for mechanical performance, while some steel companies choose to produce large square billets, but regardless of which method is chosen, costs increase significantly.

[0004] Patent document CN201110242037.1 discloses the production of a wired material for pipeline submerged arc welding wire, and the chemical composition of the wired material is, in weight percent, C 0.04 - 0.11%, Si 0.10 - 0.40%, Mn 1.40 - 1.90%, Ni 0.40 - 0.60%, Mo 0.20 - 0.40%, Ti 0.03 - 0.10%, B 0.004 - 0.007%, Al 0.010 - 0.030%, S ≤ 0.003%, P ≤ 0.008%, O ≤ 0.0015%, N ≤ 0.0040%, excess Fe and unavoidable impurities. Considering the difficulties of steelmaking, the Ti content is only 0.03 - 0.10%, and other alloying elements such as Mo, Ni, and B are added to meet the mechanical performance requirements of the welded joint, but this significantly increases the cost.

[0005] Patent document CN112011718A provides a low-aluminum high-titanium welded steel and a method for smelting the same, comprising: a deoxidation alloying step S1 of sequentially adding high-silicon manganese and high-purity ferrosilicon to perform deoxidation alloying upon tapping from the converter, followed by sequentially adding lime and fluorite; adding lime and fluorite according to the fluidity of the refining slag in the LF furnace; performing slag surface deoxidation by adding calcium carbide and ferrosilicon powder in multiple batches during the first energization of refining; conducting chemical experiments by sampling after energizing for a certain period of time, and adjusting the composition to a target value by adding high-purity ferrosilicon and metallic manganese according to the results of the chemical experiments; and adding ferrosilicon powder to maintain the reducing properties of the refining slag from the time of alloy addition until the completion of refining. In the later stages of refining, the LF refining step of step S2 is included, in which the ferro-titanium line is fed in one go to ensure the titanium content reaches the target value, the sulfur line is replenished according to the sulfur content of the chemical experiment results, soft blowing is performed, and then loading is performed for continuous casting. This achieves stable control of the components of low-aluminum high-titanium welded steel, while significantly improving the continuous casting performance of low-aluminum high-titanium welded steel and reducing production costs. Although this patent can achieve stable control of the components of low-aluminum high-titanium welded steel, it is applicable only to welded steel that does not contain aluminum, and in the case of welded steel containing aluminum, it may cause secondary oxidation of Al2O3 during casting.

[0006] Accordingly, the technical problem that the present application aims to solve is to overcome the defects of the prior art submerged arc welding wire, such as high cost and easy nodule formation, and to provide steel for submerged arc welding wire, a wire drawing material, a submerged arc welding wire, and a method for manufacturing the same.

[0007] Accordingly, the present application provides the following technical solution.

[0008] In a first aspect, the present application provides a method for manufacturing steel for high-Ti pipeline submerged arc welding wire, comprising converter smelting, LF refining, continuous casting, rolling, and cooling;

[0009] In the above LF refining, the composition of the refining slag is (CaO+CaF2) 40-50% by weight percentage, Al2O3 30%-40%, SiO2≤5%, MnO 10%-20%;

[0010] In the above LF refining process, pure calcium wire is fed before tapping.

[0011] Optionally, in the step of feeding pure calcium wire before tapping, 250 to 400 meters / ton of pure calcium wire with a diameter of 5 to 10 mm is fed 15 to 18 minutes before tapping.

[0012] Optionally, in the above continuous casting process, a layer of refractory material is supported around the top of the tundish prior to casting, the tundish is covered, and argon gas is blown into the tundish to replace the air inside the tundish;

[0013] When the superheating degree of the tundish is 30 - 50 ℃, the casting speed is 2.5 ± 0.1 m / s, the temperature difference between the crystallizer inflow and outflow water is 10 ℃ or less, the temperature of the second grade and crystallizer inflow water is 30 ℃ or more, and the depth of the molten steel in the tundish is higher than the height of the upper hole of the slag retaining wall, the stopper rod is opened and casting is performed.

[0014] Optionally, argon gas is blown into the tundish using an argon blowing pipe, the height of the argon blowing pipe is maintained to match the depth inside the tundish, and the argon blowing time is 5 to 6 minutes.

[0015] Optionally, in the above rolling process, 870 ℃ ≤ finish rolling inlet temperature ≤ 900 ℃, and 90 m / s ≤ rolling speed ≤ 100 m / s;

[0016] In the above cooling process, temperature-controlled cooling is performed in the Stelmor cooling line, the spinning temperature is 880 - 900 ℃, and the cooling speed is 6 m / s or less.

[0017] In a second embodiment, a steel for high-Ti pipeline submerged arc welding wire manufactured through the method described above is provided.

[0018] Optionally, the chemical composition of the steel for the high-Ti pipeline submerged arc welding wire described above comprises, in mass percentage, C 0.07 - 0.10%, Si 0.15 - 0.25%, Mn 1.50 - 1.80%, Ti 0.25 - 0.35%, Al 0.02 - 0.03%, 0.0020% ≤ Ca ≤ 0.0040%, O ≤ 0.004%, excess Fe and unavoidable impurities.

[0019] In a third embodiment, a wire drawing for high Ti pipeline submerged arc welding wire is provided, said wire drawing has a tensile strength of 600 MPa or less and a cross-sectional shrinkage rate of 75% or more.

[0020] In a fourth embodiment, a high-ti pipeline submerged arc welding wire is provided and manufactured using the above-described high-ti pipeline submerged arc welding wire wire.

[0021] In the fifth embodiment, a method for manufacturing a high-Ti pipeline submerged arc welding wire is provided, wherein wire drawing is performed directly on the wire drawing material, annealing is not required, and the wire drawing speed is 15 m / s or less.

[0022] In this application, the continuous casting is a continuous casting of a small square billet with a cross-sectional area of ​​140 mm * 140 mm.

[0023] The technical solution of the present application has the following advantages.

[0024] 1. In the method for manufacturing steel for high-Ti pipeline submerged arc welding wire provided in this application, in the LF refining process, a pure calcium wire is fed before tapping. By feeding the calcium wire, oxygen in the molten steel is absorbed, and oxides of oxygen and calcium are formed in the steel, thereby reducing the oxide content in the steel. While stirring, the oxides rise to the surface of the slag, and after the reduction of oxygen, the quantity of titanium and aluminum oxides formed is reduced, and the size of the composite inclusion is reduced. Furthermore, by mixing the refining slag during the refining process, the oxygen content in the steel can be effectively controlled to 0.004% or less, thereby fundamentally solving the problem of nodules forming in the nozzle during the continuous casting process. Calcium wire feeding can not only solve the problem of stopping casting due to nodules formed by the secondary oxidation of TiO2 during the casting process, but also improve the yield of Ti. Additionally, the problem of nodules forming in molten steel with a high aluminum content can also be solved.

[0025] Without the need to replace some Ti by adding expensive Mo, the alloy cost is low, and even if small square billets are selected in continuous steelmaking casting, more than 10 can be continuously cast, and no problems such as nodule formation in the nozzle occur.

[0026] 2. In the steel for high-Ti pipeline submerged arc welding wire provided in this application, the chemical composition comprises, in mass percentage, C 0.07 - 0.10%, Si 0.15 - 0.25%, Mn 1.50 - 1.80%, Ti 0.25 - 0.35%, 0.0020%≤Ca≤0.0040%, O≤0.004%, excess Fe and unavoidable impurities.

[0027] The present application has a high Ti content of 0.25 - 0.35%, which can improve the toughness of the weld joint metal, improve the mechanical performance of the weld joint without the need to add other alloying elements, and reduce the cost of the steel. Through the high-Si design, deoxidation can be performed using Si during the steelmaking process, which can further reduce the oxide inclusions of Ti in the molten steel and is advantageous for solving the problem of nodule formation in the nozzle during the continuous casting process.

[0028] In this application, by adding the element Ca, the oxide content in the steel is reduced, and the quantity of titanium and aluminum oxides and the size of the composite inclusions (Ti and Al oxide inclusions are prone to agglomeration during the casting process, causing nozzle clogging) can be reduced, thereby fundamentally solving the problem of nodule formation in the nozzle during the continuous casting process while simultaneously improving the yield of Ti.

[0029] By adding calcium elements to carbon steel, thermally stable second-phase calcium-containing oxide particles dispersed within the steel can be produced. During the welding heat cycle, the movement of austenite grain boundaries in the coarse grain heat affected zone (CGHAZ) can be peened, limiting the growth of austenite grains and obtaining a fine weld CGHAZ grain size, thereby improving the toughness of the weld CGHAZ in fine calcium steel.

[0030] 3. The tensile strength of the wire of the present application is 600 MPa or less, and the cross-sectional shrinkage rate is 75% or more. Since there is no need to perform annealing when manufacturing the submerged arc welding wire, manufacturing costs are reduced. When a metal cladding test is performed using the submerged arc welding wire of the present application, the tensile strength of the weld joint is 560 MPa or more, and the impact toughness at -40 ℃ is 150 J or more. Specific details for implementing the invention

[0031] To further understand the present application in more detail, the following examples are provided, but are not limited to the most preferred embodiments above and do not limit the content and scope of protection of the present application. Any product identical or similar to the present application obtained by combining the features of the present application or other prior art with the present application falls within the scope of protection of the present application.

[0032] Specific experimental steps or conditions not specified in the examples may be carried out according to the operations or conditions of conventional experimental steps described in the literature of the art. Unless the manufacturer is specified, the prototypes or equipment used are all general prototype products available on the market.

[0033] The method for manufacturing a submerged arc welding wire according to Examples 1-4 comprises the following steps.

[0034] (1) Converter smelting.

[0035] (2) LF Refining: 18 minutes before tapping the refined steel, a pure calcium wire with a diameter of 8 mm is fed, and argon is blown in and stirred, and the argon blowing stirring time is 10 minutes or more.

[0036] Table 1 LF Refining Parameters

[0037] Length of pure calcium wire being fed Argon blowing stirring time Example 1 250 meters / ton 10 min Example 2 300 meters / ton 12 min Example 3 350 meters / ton 15 min Example 4 400 meters / ton 13 min

[0038] Table 2 Refining Slag Composition (wt%)

[0039] CaO + CaF2 Al2O3 SiO2 MnO Example 1 50 30 2 18 Example 2 40 37 3 20 Example 3 45 35 4 16 Example 4 48 37 5 10

[0040] (3) Continuous casting of small square billets:

[0041] Before casting, a layer of thick refractory wool is placed around the top of the tundish, the tundish cover is placed, and argon gas is blown into the tundish using three argon blowing pipes to replace the air inside the tundish, the height of the argon blowing pipes is maintained at the same depth as the inside of the tundish, and the argon blowing time is 5 to 6 minutes.

[0042] When the superheating degree is 40 ℃, the casting speed is 2.5 m / s, the inflow and outflow water temperature difference is 10 ℃, the inflow water temperature of the second grade and crystallizer is 35 ℃, and the depth of the molten steel in the tundish is higher than the height of the upper hole of the slag retaining wall, the stopper rod is opened and casting is performed.

[0043] (4) Rolling

[0044] After heating a small square billet in a heating furnace, it is continuously rolled, and the finish rolling inlet temperatures of Examples 1-4 are 870 ℃, 900 ℃, 880 ℃, and 900 ℃ in order, and the rolling speeds are 90 m / s, 100 m / s, 92 m / s, and 98 m / s in order.

[0045] (5) Cooling

[0046] When spinning and entering the Stelmore cooling line, temperature-controlled cooling is performed, where the spinning temperatures are 880 ℃, 900 ℃, 900 ℃, and 890 ℃ in order, the fan and insulation cover are both closed, the roller speed of the Stelmore cooling line is 0.15 m / s, and the cooling speed inside the insulation cover is 6 m / s, 6 m / s, 5 m / s, and 5 m / s in order.

[0047] (6) Wire drawing copper plating

[0048] The fresh material produced in step (5) is wire drawn directly without undergoing annealing treatment, and the wire drawing speed is 15 m / s, and then copper plating is performed and coiled.

[0049] Comparative Example 1

[0050] Comparative Example 1 and Example 1 are almost identical, the difference being that calcium wire was not added in Comparative Example 1.

[0051] Comparative Example 2

[0052] Comparative Example 2 and Example 1 are almost identical, the difference being that the refining slag is a low-alkali slag system, and the composition is "CaO+CaF2" 30%, Al2O3 10%, SiO2 42%, MnO 18% by weight percentage, which does not correspond to the slag system combination described in the present application.

[0053] Test example

[0054] (1) The number of maximum continuous casting furnaces for steelmaking is recorded, and the composition of the drawn steel is tested using ICP and CS instruments, and the chemical composition is listed in Table 3 as a weight percentage.

[0055] Table 3 Fresh Ingredients

[0056] C Si Mn Ti Ca O Ai Continuous casting number (ro) Example 1 0.10 0.15 1.75 0.25 0.0020 0.004 0.02 17 Example 2 0.07 0.25 1.50 0.29 0.0025 0.003 0.02 17 Example 3 0.08 0.25 1.55 0.32 0.0029 0.003 0.03 16 Example 4 0.09 0.20 1.80 0.35 0.0040 0.004 0.02 18 Comparative Example 1 0.10 0.16 1.76 0.25 0.0003 0.004 0.03 3 Comparative Example 2 0.09 0.17 1.75 0.24 0.0022 0.008 0.03 5

[0057] (2) Test of tensile strength and cross-sectional shrinkage of fresh material

[0058] The wire was cut to a length of 30 cm, and the wire tensile strength and cross-sectional shrinkage were tested using a 250 kN tensile testing machine (Instron 5585). The test results are listed in Table 4.

[0059] Table 4 Tensile Strength and Area Shrinkage

[0060] Tensile strength / MPa Cross-sectional shrinkage rate % Example 1 544 81 Example 2 521 78 Example 3 553 76 Example 4 600 75

[0061] (3) Mechanical performance test of welded joints

[0062] After conducting a metal cladding test in reference to standard GBT 8110 - 2008, a mechanical performance detection test was conducted, and the test results are listed in Table 5.

[0063] Table 5 Cladding weld seams

[0064] Tensile strength / MPa - 40℃ Impact Value / J Example 1 630 178 / 195 / 184 Example 2 570 192 / 186 / 164 Example 3 610 174 / 185 / 192 Example 4 620 152 / 164 / 171 Comparative Example 1 600 92 / 84 / 111

[0065] The tensile strength of the weld joint formed using the submerged arc welding wire of the present application is 560 MPa or more, and the impact toughness at -40 ℃ is 150 J or more.

[0066] As can be seen from the above, compared to Example 1, the wire described in Comparative Example 1 has a low Ca content in its composition, resulting in a slight decrease in both the strength and toughness of the weld joint. Additionally, since calcium wire was not added in Comparative Example 1, nodule formation occurred, and the number of continuous casting furnaces was only 3. In the wire described in Comparative Example 2, the O content was too high because the refining slag system components did not meet the requirements of the present technology during the steelmaking process, and the number of continuous casting furnaces was only 5.

[0067] Of course, the embodiments described above are merely examples for clear explanation and are not intended to limit the embodiments. Those skilled in the art may further implement various forms of changes and variations based on the descriptions above. It is not possible to list all embodiments infinitely, nor is it necessary to do so. Obvious changes or variations derived thereby are still within the scope of the claims of this application.

Claims

Claim 1 A method for manufacturing steel for high-ti pipeline submerged arc welding wire comprises converter smelting, LF refining, continuous casting, rolling, and cooling; in the LF refining, the composition of the refining slag produced from the LF refining is, in weight percentage, 40-50% (CaO+CaF2), 30-40% Al2O3, ≤5% SiO2, and 10-20% MnO; in the LF refining process, calcium wire is fed before tapping; and the chemical composition of the high-ti pipeline submerged arc welding wire obtained by manufacturing is, in mass percentage, C 0.07-0.10%, Si 0.15-0.25%, Mn 1.50-1.80%, Ti 0.25-0.35%, and Al 0.02-0.03%. A method for manufacturing steel for high-Ti pipeline submerged arc welding wire, characterized by containing 0.0020%≤Ca≤0.0040%, O≤0.004%, excess Fe, and unavoidable impurities. Claim 2 A method for manufacturing steel for high-Ti pipeline submerged arc welding wire, characterized in that, in the step of feeding calcium wire before tapping, 250 to 400 meters / ton (Moulton steel) of calcium wire with a diameter of 5 to 10 mm is fed 15 to 18 minutes before tapping. Claim 3 A method for manufacturing steel for high-Ti pipeline submerged arc welding wire according to claim 1, wherein, in the continuous casting process, a layer of refractory material is supported around the top of the tundish before casting, a tundish cover is placed, and argon gas is blown into the tundish to replace the air inside the tundish; wherein the superheating degree of the tundish is 30 - 50 ℃, the casting speed is 2.5 ± 0.1 m / s, the temperature difference between the crystallizer inlet and outlet water is 10 ℃ or less, and the secondary cooling and crystallizer inlet water temperature is 30 ℃ or more. Claim 4 A method for manufacturing steel for high-Ti pipeline submerged arc welding wire, characterized in that, in claim 3, argon gas is blown into a tundish using an argon blowing pipe, and the argon blowing time is 5 to 6 minutes. Claim 5 A method for manufacturing steel for high-Ti pipeline submerged arc welding wire according to claim 1, wherein in the rolling process, 870 ℃ ≤ finishing rolling inlet temperature ≤ 900 ℃ and the rolling speed at the finishing inlet is 90 m / s ≤ rolling speed ≤ 100 m / s; and in the cooling process, temperature-controlled cooling is performed in a Stelmor cooling line, wherein the cooling speed is 6 ℃ / s or less. Claim 6 Steel for high-ti pipeline submerged arc welding wire manufactured by a manufacturing method according to any one of claims 1 to 5. Claim 7 A high-ti pipeline submerged arc welding wire wire drawing material using steel manufactured by a manufacturing method according to any one of claims 1 to 5, wherein the tensile strength of the drawing material is 600 MPa or less and the cross-sectional shrinkage rate is 75% or more. Claim 8 A high Ti pipeline submerged arc welding wire characterized by being manufactured using a fresh material for a high Ti pipeline submerged arc welding wire according to claim 7. Claim 9 A high-Ti pipeline submerged arc welding wire according to claim 8, characterized in that wire drawing is performed directly on the fresh material, annealing is not performed, and the wire drawing speed is 15 m / s or less.

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