Steel for submerged arc welding wire, wire rod, submerged arc welding wire and its manufacturing method

Abstract

A method for producing steel for high-Ti pipeline submerged arc welding wire, comprising converter smelting, LF refining, continuous casting, rolling, and cooling, in which the composition of the refined slag in the LF refining is (CaO+CaF2) 40%-50% by weight, Al2O3 30%-40% by weight, SiO2 5% or less by weight, and MnO 10%-20% by weight, and in the LF refining process, a pure calcium wire is supplied before tapping. A steel for submerged arc welding wire and a method for producing the same, a wire rod for submerged arc welding wire, a submerged arc welding wire, and a method for producing the same. The steel for submerged arc welding wire and the method for producing the submerged arc welding wire solve the defects of submerged arc welding wire, such as high cost and easy clogging. Continuous pouring of 10 or more furnaces is possible for producing the steel for submerged arc welding wire.

Description

[Technical field]

[0001] This application claims priority to a Chinese patent application bearing application number 202211276565.3 and entitled "Steel for submerged arc welding wire, wire rod, submerged arc welding wire, and manufacturing method thereof" filed with the China Patent Office on October 19, 2022, the entire contents of which are incorporated herein by reference.

[0002] The present application belongs to the field of steel smelting technology, and specifically relates to steel for submerged arc welding wire, wire rod, submerged arc welding wire, and a manufacturing method thereof. [Background technology]

[0003] Submerged arc welding has higher production efficiency and higher automation than gas shielded welding. Titanium-containing welding wire steel is widely used in welding pipeline steel. Adding Ti element to alloy welding wire can refine the grain and improve the low temperature impact toughness and tensile strength of the deposited metal. However, titanium-containing pipeline submerged arc welding wire steel faces smelting problems during production. (1) Nozzle clogging is formed in the pouring process, and the plug rod in the pouring process appears as a rise. (2) The Ti yield in the smelting process is low, less than 40%. Considering the difficulty of continuous pouring in steelmaking, many steel enterprises control the mass% of Ti in the welding wire to less than 0.07% and add expensive Mo to meet the requirements of the mechanical properties of the deposited metal. Some steel enterprises choose large billet production. No matter which method is chosen, the cost will increase significantly.

[0004] Patent document CN201110242037.1 discloses a wire rod for producing pipeline submerged arc welding wire, the chemical composition of the wire rod is: C0.04-0.11% by weight, Si0.10-0.40% by weight, Mn1.40-1.90% by weight, Ni0.40-0.60% by weight, Mo0.20-0.40% by weight, Ti0.03-0.10% by weight, B0.004-0.007% by weight, Al0.010-0.030% by weight, S0.003% by weight or less, P0.008% by weight or less, O0.0015% by weight or less, N0.0040% by weight or less, the balance being Fe and unavoidable impurities. Considering the difficulty of steelmaking, the Ti content is only 0.03-0.10%, and the addition of alloying elements such as Mo, Ni, and B to meet the mechanical properties of the welds will significantly increase the cost.

[0005] Patent document CN112011718A provides a low aluminum high titanium welding wire steel and a smelting method thereof, which includes: deoxidation and alloying at the time of tapping from converter: when the converter is tapped, high silicon silicomanganese and high purity ferrosilicon are added in sequence to deoxidize and alloy, and then lime and fluorspar are added in sequence in step S1; LF smelting: according to the fluidity of the smelting slag, lime and fluorspar are added to the LF furnace in step S2; and carbide and ferrosilicon powder are added at the time of the first current supply for smelting. Add in batches, deoxidize the slag surface, apply current for a certain period of time, sample and test, add high purity ferrosilicon and manganese metal according to the test results to adjust the composition to the target value, add ferrosilicon powder to maintain the reducibility of the slag after the alloy is added until the end of smelting, add ferrotitanium wire at once to make the titanium content the target value, replenish sulfur wire according to the sulfur content according to the test results, soft blow, and feed to the continuous casting machine. In this way, the composition of low aluminum high titanium welding wire steel is stably controlled, while the continuous pouring performance of low aluminum high titanium welding wire steel is greatly improved and production costs are reduced. This patent can realize the stable control of the composition of low aluminum high titanium welding wire steel, but it can only be applied to welding wire steel that does not contain Al, but in the case of Al-containing welding wire steel, secondary oxidation of Al2O3 occurs during pouring. Summary of the Invention Means for solving the invention

[0006] Therefore, the technical problem to be solved by the present application is to provide a steel for submerged arc welding wire, a wire rod, a submerged arc welding wire, and a manufacturing method thereof, in order to solve the defects of the conventional submerged arc welding wire, such as high cost and susceptibility to clogging. [Means for solving the problem]

[0007] To this end, the present application provides the following technical solutions:

[0008] In a first aspect, the present application provides a method for producing a steel for high Ti pipeline submerged arc welding wire, the method comprising converter smelting, LF refining, continuous casting, rolling, and cooling; In the LF refining, the composition of the refining slag is 40 to 50% by weight of CaO + CaF2, 30% to 40% by weight of Al2O3, 5% by weight or less of SiO2, and 10% to 20% by weight of MnO; In the LF refining process, a pure calcium wire is provided before tapping.

[0009] Optionally, supplying a pure calcium wire before tapping comprises supplying a pure calcium wire (250-400 m / t) having a diameter of 5-10 mm 15-18 minutes before tapping.

[0010] Optionally, the continuous casting process includes placing a layer of refractory material around an upper edge of the tundish before pouring, then covering the tundish with a tundish cover, and blowing argon gas into the tundish to displace the air in the tundish; The superheat degree of the tundish is 30-50°C, the withdrawal speed is 2.5±0.1 m / s, the temperature difference between the inlet and outlet water of the crystallizer is 10°C or less, the inlet water temperature of the secondary cooling and crystallizer is 30°C or more, and when the depth of the molten steel in the tundish becomes greater than the height of the upper hole of the slag retaining wall, the plug rod is opened to start pouring the molten steel.

[0011] Optionally, argon gas is blown into the tundish using an argon gas blowing tube, the height of the argon gas blowing tube is consistent with the depth of the tundish, and the argon gas blowing time is 5-6 minutes.

[0012] Optionally, in the rolling process, 870°C≦finish rolling entrance temperature≦900°C, and 90m / s≦rolling speed≦100m / s; In the cooling process, the wire is cooled while controlling the temperature in a Stelmor cooling line, with the wire discharge temperature being set to 880 to 900° C. and the cooling speed being set to 6 m / s or less.

[0013] In a second aspect, there is provided a steel for high Ti pipeline submerged arc welding wire produced by the above method.

[0014] Optionally, the chemical composition of the above-mentioned steel for high Ti pipeline submerged arc welding wire includes 0.07-0.10 mass% C, 0.15-0.25 mass% Si, 1.50-1.80 mass% Mn, 0.25-0.35 mass% Ti, 0.02-0.03 mass% Al, 0.0020 mass%≦Ca≦0.0040 mass%, O≦0.004 mass%, the balance being Fe and unavoidable impurities.

[0015] In a third aspect, there is provided a high-Ti wire rod for pipeline submerged arc welding wire, having a tensile strength of 600 MPa or less and an area reduction rate of 75% or more.

[0016] In a fourth aspect, there is provided a high Ti pipeline submerged arc welding wire produced using the above-mentioned wire rod for high Ti pipeline submerged arc welding wire.

[0017] In a fifth aspect, there is provided a method for producing a high Ti pipeline submerged arc welding wire, which does not require annealing and involves directly drawing the wire at a drawing speed of 15 m / s or less.

[0018] In this application, the continuous casting is a small billet continuous casting with a cross-sectional area of ​​140mm*140mm. Effect of the Invention

[0019] The technical solution of the present application has the following advantages:

[0020] 1. According to the manufacturing method of steel for high Ti pipeline submerged arc welding wire according to the present application, in the LF smelting, pure calcium wire is supplied before tapping. The supplied calcium wire absorbs oxygen in the molten steel, forms calcium oxide with oxygen in the steel, reduces the oxide content in the steel, and floats to the surface of the slag by stirring. After the oxygen is reduced, the amount of titanium oxide and aluminum oxide produced is reduced, and the size of the composite inclusions is reduced. In addition, in the smelting process, the oxygen content of the steel is effectively controlled to 0.004% or less by blending the slag, which can fundamentally solve the problem of nozzle clogging in continuous casting. Supplying calcium wire not only solves the problem of clogging caused by secondary oxidation of TiO2 at the start of pouring and the problem of pouring stop, but also improves the yield of Ti and solves the problem of clogging of molten steel with high Al content. There is no need to add expensive Mo to replace part of Ti, and the alloy cost is low, so if a small billet is selected, continuous casting can be performed in more than 10 furnaces, and there is no phenomenon such as nozzle clogging.

[0021] 2. The chemical composition of the high Ti steel for pipeline submerged arc welding wire according to the present application includes 0.07 to 0.10 mass% C, 0.15 to 0.25 mass% Si, 1.50 to 1.80 mass% Mn, 0.25 to 0.35 mass% Ti, 0.0020 mass%≦Ca≦0.0040 mass%, 0.004 mass% or less O, and the balance being Fe and unavoidable impurities. In this application, it has a high Ti content of 0.25-0.35%, which can improve the strength and toughness of the weld metal, and there is no need to add other alloy elements to improve the mechanical properties of the weld, so the cost of the steel is reduced. The high Si design allows Si to be used for deoxidation during steelmaking, which further reduces the Ti oxide inclusions in the molten steel and helps solve the problem of nozzle clogging during continuous casting. In the present invention, the addition of Ca element can reduce the oxide content in the steel, the amount of titanium and aluminum oxides produced, and the size of the composite inclusions (Ti and Al oxide inclusions are prone to agglomerate during pouring and block the nozzle), fundamentally solving the problem of nozzle clogging during continuous casting, and also improving the Ti yield. The addition of calcium element to carbon steels can also form dispersed, thermally stable, second-phase calcium-containing oxide particles in the steel, which can block the migration of austenite grain boundaries in the coarse-grained heat-affected zone (CGHAZ) during the welding thermal cycle, limit the growth of austenite grains, and obtain finer weld CGHAZ grain sizes, thus improving the strength of the CGHAZ from the weldment of micro-calcium steels.

[0022] 3. In the present application, the wire rod has a tensile strength of 600 MPa or less and a cross-sectional reduction rate of 75% or more. Since annealing is not required during the manufacture of the submerged arc welding wire, production costs are reduced. When the submerged arc welding wire of the present application is used in a deposited metal test, the tensile strength of the weld is 560 MPa or more and the low-temperature impact toughness at -40°C is 150 J or more. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The following examples are provided for a better understanding of the present application, and are not intended to limit the content and scope of protection of the present application, and the present application is not limited to the above-mentioned best embodiment. Any products that are the same or similar to the present application obtained under the teachings of the present application or by combining the features of the present application with other prior art are within the scope of protection of the present application.

[0024] If no specific experimental steps or conditions are specified in the examples, they can be carried out according to conventional experimental steps or conditions described in the literature in the field. If the manufacturers of the reagents and instruments used are not indicated, they are all conventional reagent products that are commercially available.

[0025] Examples 1 to 4 The method for producing a submerged arc welding wire includes the following steps.

[0026] (1) Converter smelting

[0027] (2) LF refining: A pure calcium wire with a diameter of 8 mm was added 18 minutes before the steel was discharged, and argon gas was blown in for more than 10 minutes while stirring.

[0028] [Table 1]

[0029] [Table 2]

[0030] (3) Continuous casting of small billets Before pouring, a thick refractory cotton was placed around the upper edge of the tundish, then the tundish cover was placed on it, and argon gas was blown into the tundish using three argon gas blowing tubes to replace the air in the tundish. The height of the argon gas blowing tubes was set to match the depth inside the tundish, and the argon gas blowing time was 5 to 6 minutes. The superheat degree was 40°C, the withdrawal speed was 2.5 m / s, the inlet and outlet water temperature difference was 10°C, and the inlet water temperature of the secondary cooling and crystallization equipment was 35°C. When the depth of the molten steel in the tundish became greater than the height of the upper hole of the slag retaining wall, the plug rod was opened and pouring began.

[0031] (4) Rolling Small billets were heated in a heating furnace and then continuously rolled. In Examples 1 to 4, the finish rolling entrance temperatures were 870°C, 900°C, 880°C, and 900°C, respectively, and the rolling speeds were 90 m / s, 100 m / s, 92 m / s, and 98 m / s, respectively.

[0032] (5) Cooling The wire is discharged into the Stelmor cooling line for controlled cooling. The wire discharge temperatures are 880°C, 900°C, 900°C, and 890°C in sequence. All fans and hoods are closed. The roller speed of the Stelmor cooling line is 0.15m / s, and the cooling speeds in the hood are 6m / s, 6m / s, 5m / s, and 5m / s in sequence.

[0033] (6) Wire drawing and copper plating The wire produced in step (5) was directly drawn at a drawing speed of 15 m / s without annealing, and then copper plated into a coil. Comparative Example 1

[0034] Comparative Example 1 was almost the same as Example 1, except that no calcium wire was added. Comparative Example 2

[0035] The refining slag was a low alkalinity slag system, the components of which were 30 wt% "CaO+CaF2", 10 wt% Al2O3, 42 wt% SiO2, and 18 wt% MnO. Except for the composition of the slag system described in this application, Comparative Example 2 was almost the same as Example 1. Test Example

[0036] (1) The maximum number of continuous steelmaking furnaces was recorded, and the composition of the wire rod was tested by ICP and CS equipment. The chemical composition is shown in Table 3 in weight percentage.

[0037] [Table 3]

[0038] (2) Testing of tensile strength and cross-sectional shrinkage of wire The wire was cut into 30 cm pieces and tested for tensile strength and area reduction using a 250 kN tensile tester (Instron 5585). The test results are shown in Table 4.

[0039] [Table 4]

[0040] (3) Mechanical property test of welded joints The weld metal test is carried out with reference to standard GBT 8110-2008, and then the mechanical property test is carried out, and the test results are shown in Table 5.

[0041] [Table 5]

[0042] The weld formed using the submerged arc welding wire of the present invention had a tensile strength of 560 MPa or more and a low-temperature impact toughness of -40°C of 150 J or more.

[0043] From the above, it was found that, compared with Example 1, the wire rod described in Comparative Example 1 had insufficient Ca content in the components, so that the strength and toughness of the welded part were reduced. In addition, in Comparative Example 1, since calcium wire was not added, clogging occurred, and the number of continuous pouring furnaces was only three. In the case of the wire rod described in Comparative Example 2, in the steelmaking process, the composition of the smelting slag did not meet the technical requirements, so the O content was too high, and the number of continuous pouring furnaces was only five.

[0044] Of course, the above examples are merely examples for clear explanation and are not intended to limit the embodiments. Those skilled in the art can make other changes or modifications based on the above description. It is not necessary and impossible to cover all the embodiments here. Any obvious changes or modifications derived therefrom are still within the scope of protection of the present application.

Claims

1. A method for producing a steel for high Ti pipeline submerged arc welding wire, comprising: The process includes converter smelting, LF refining, continuous casting, rolling, and cooling. In the LF refining, the composition of the refining slag is (CaO + CaF ２ ): 40-50% by weight, Al ２ O ３ :30% to 40% by weight, SiO ２ ≦5 wt.%, MnO: 10% to 20 wt.%, In the LF refining process, a pure calcium wire is supplied before tapping, The manufacturing method is characterized in that the chemical components of the produced high Ti pipeline submerged arc welding wire steel include C: 0.07 to 0.10 mass%, Si: 0.15 to 0.25 mass%, Mn: 1.50 to 1.80 mass%, Ti: 0.25 to 0.35 mass%, Al: 0.02 to 0.03 mass%, 0.0020 mass%≦Ca≦0.0040 mass%, O≦0.004 mass%, and the balance being Fe and unavoidable impurities.

2. 2. The method for producing a steel for high Ti pipeline submerged arc welding wire according to claim 1, characterized in that the supply of the pure calcium wire before tapping comprises supplying a pure calcium wire (250 to 400 m / t) having a diameter of 5 to 10 mm 15 to 18 minutes before tapping.

3. In the continuous casting process, before pouring, a layer of refractory material is placed around the upper edge of the tundish, then the tundish cover is placed over it, and argon gas is blown into the tundish to replace the air in the tundish; The method for producing steel for high Ti pipeline submerged arc welding wire according to claim 1, characterized in that the tundish has a superheat of 30 to 50°C, a drawing speed of 2.5±0.1 m / s, a temperature difference between the inlet and outlet water of the crystallizer is 10°C or less, the inlet water temperature of the secondary cooling and crystallizer is 30°C or more, and when the depth of the molten steel in the tundish becomes greater than the height of the upper hole of the slag retaining wall, the plug rod is opened to start pouring.

4. The manufacturing method of steel for high Ti pipeline submerged arc welding wire according to claim 3, characterized in that argon gas is injected into the tundish using an argon gas injection tube, the height of the argon gas injection tube is made to coincide with the depth of the tundish, and the argon gas injection time is 5 to 6 minutes.

5. In the rolling process, 870° C.≦finish rolling entrance temperature≦900° C., and 90 m / s≦rolling speed≦100 m / s; The method for producing steel for high Ti pipeline submerged arc welding wire according to claim 1, characterized in that, in the cooling process, cooling is performed while controlling the temperature in a Stelmor cooling line, the wire discharge temperature is set to 880 to 900°C, and the cooling rate is set to 6 m / s or less.

6. A steel for high Ti pipeline submerged arc welding wire, produced by the production method according to any one of claims 1 to 5.

7. A wire rod for high Ti pipeline submerged arc welding wire using steel manufactured by the manufacturing method according to any one of claims 1 to 5, characterized in that the wire rod has a tensile strength of 600 MPa or less and an area reduction rate of 75% or more.

8. A high Ti pipeline submerged arc welding wire, which is manufactured using the wire rod for high Ti pipeline submerged arc welding wire according to claim 7.

9. The method of claim 8, wherein the wire is directly drawn at a drawing speed of 15 m / s or less without requiring annealing.

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