Sulfur-containing cored wire for vacuum induction furnace and use method

Abstract

The invention relates to the technical field of metallurgical materials, in particular to a sulfur-containing cored wire for a vacuum induction furnace and a using method.The diameter specification of the cored wire ranges from phi 3.0 mm to phi 5.0 mm, the cored wire comprises a steel belt shell and powder, the steel belt shell is formed by rolling a steel belt, the steel belt shell is filled with the powder, and the powder is filled with the sulfur-containing cored wire. The powder comprises industrial pure iron powder, manganese oxide powder, ferrotitanium powder containing 30% of titanium and ferrous sulfide powder, and the powder is prepared by blending and mixing industrial pure iron powder, manganese oxide powder, ferrotitanium powder containing 30% of titanium and ferrous sulfide powder according to the mass ratio of (65-75): (7-10): (15-18): 1. The sulfur-containing cored wire has the beneficial effects that after the sulfur-containing cored wire is added into molten steel to be solidified, a large number of submicron-level particles containing Ti, S, Mn and O are obtained, the strength of the steel is improved, and the service life of the steel is prolonged; and the toughness of the steel grade is improved, and the toughness of the hot-rolled or normalizing-rolled steel grade and the toughness of a heat affected zone during high heat input welding of the steel grade are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of metallurgical materials, and particularly relates to a sulfur-containing cored wire for a vacuum induction furnace and a using method thereof. Background Art

[0002] Steel materials play an important role in the mechanical engineering manufacturing industry due to their high strength and good low-temperature impact toughness. After entering the 21st century, mechanical engineering structures have developed towards the direction of gigantism and high parameters. Such as ultra-large ships and offshore platforms, long-span bridges, long-distance oil and gas pipelines, etc. These large mechanical engineering structures have put forward higher and higher requirements for the performance of steel materials, requiring that the strength and toughness of steel materials be doubled on the premise of not increasing or minimizing the content of alloying elements as much as possible. Many research results show that grain refinement is the most effective method to double the strength and toughness of steel materials. Oxide metallurgy is a new method and technology used in recent years to refine the grains of steel materials and improve strength and toughness. It has been successfully used in the development of non-quenched and tempered steels, microalloyed low-carbon steels, and natural gas pipeline steels. In addition to refining the grain size, the oxide metallurgy method can induce the formation of acicular ferrite (Acicular Ferrite, abbreviated as AF) or intragranular ferrite (Intragranular Ferrite, abbreviated as IGF). Based on the objective facts that non-metallic inclusions induce intragranular ferrite nucleation, refine grains, and improve strength and toughness, a large number of studies on oxide metallurgy have been carried out.

[0003] At present, most of the cored wires used for oxide metallurgy are mainly aimed at converter steelmaking. Since the smelting process of converter steelmaking is significantly different from the metallurgical process of vacuum induction furnaces, directly applying the cored wire used in converter oxide metallurgy to a vacuum induction furnace often fails to achieve the corresponding effect. The strength of the obtained steel grade is not high, the toughness of the steel grade after hot rolling or normalizing rolling is low, the toughness of the heat-affected zone during welding is low, and the quality of the steel grade is poor.

[0004] Patent CN112301186B "An alloy cored wire and its application in oxide metallurgy", this patent adopts a coating layer and a core wrapped in the coating layer. The core includes rare earth metals and titanium metals, which can improve the effect of oxide inclusions in the alloy cored wire, effectively remove the free oxygen in the molten steel, reduce the content of sulfur and oxygen in the molten steel, and improve the mechanical properties of the steel. However, this alloy cored wire is mostly used in the process of rough molten steel, and the effect of refining the grains of molten steel in a vacuum induction furnace is not good, the strength of the steel grade is not high, and the welding toughness is also not good.

[0005] Patent CN112195308A, "A perovskite alloy cored wire and its application in oxide metallurgy". This patent uses a cladding layer and a core wrapped inside the cladding layer. The core is a perovskite alloy. When applied to oxide metallurgy, on the one hand, due to the limited deoxidation ability of titanium metal in the perovskite alloy cored wire, while calcium metal has a strong affinity for sulfur and oxygen and can react with free oxygen and sulfur in the molten steel to form calcium oxide and calcium sulfide respectively, and most of them float up and can be removed, thereby reducing the sulfur and oxygen content in the molten steel and not causing the problem that the desulfurization of weakly deoxidized molten steel is difficult, resulting in the sulfur content in the molten steel exceeding the standard. Excessive sulfur content easily causes hot brittleness in steel and reduces the performance of steel; it can reduce the sulfur and oxygen content in the molten steel and improve the mechanical properties of steel. However, this method is applied to the molten steel in rough steelmaking and is not applicable to the molten steel smelting process in a vacuum induction furnace, and it cannot achieve the improvement of the strength of the steel grade. The toughness of the steel grade after hot rolling or normalizing rolling is relatively reduced, affecting the tensile strength and impact work of the steel plate under extreme conditions, and the welding performance is not good. Summary of the Invention

[0006] In order to overcome the deficiencies of the prior art, the present invention provides a sulfur-containing cored wire for a vacuum induction furnace and a usage method. Powders are filled inside the cored wire shell formed by winding a steel strip to make a cored wire that improves the material properties through oxide metallurgy. During the steelmaking process in a vacuum induction furnace, adding this cored wire to the molten steel by an appropriate process can obtain a large number of submicron-sized particles containing Ti, S, Mn, and O distributed in the solidified steel grade, improving the strength of the steel grade, improving the toughness of the steel grade after hot rolling or normalizing rolling, and the toughness of the heat-affected zone during high heat input welding of the steel grade.

[0007] To achieve the above object, the present invention is implemented by adopting the following technical solutions:

[0008] A sulfur-containing cored wire for a vacuum induction furnace, the diameter specification of the cored wire is Φ3.0mm - Φ5.0mm, including a steel strip shell and powders. The steel strip shell is formed by winding a steel strip, and powders are filled inside the steel strip shell. The powders include industrial pure iron powder, manganese oxide powder, titanium iron powder containing 30% titanium, and ferrous sulfide powder, and are proportioned and mixed according to the mass ratio of 65 - 75:7 - 10:15 - 18:1.

[0009] Further, the particle size of the industrial pure iron powder is 44 - 150μm, the particle size of the manganese oxide powder is 160 - 250 mesh, the particle size of the titanium iron powder containing 30% titanium is 44 - 150μm, and the particle size of the ferrous sulfide powder is 170 - 280 mesh.

[0010] Further, the thickness of the steel strip is 1.8mm - 2.2mm.

[0011] Further, the filling rate of the cored wire is 16% - 20%.

[0012] The usage method of the sulfur-containing cored wire for a vacuum induction furnace is specifically as follows:

[0013] S1. Add the sulfur-containing cored wire into the molten steel 10 - 15 minutes before the end of steelmaking in the vacuum induction furnace;

[0014] S2. The superheat of the molten steel in the vacuum induction furnace is 40 - 100 °C; the Als content in the molten steel should be below 0.03 wt%; the oxygen content in the molten steel is below 20 ppm;

[0015] S3. The addition amount of the cored wire per ton of molten steel is 7 - 11 kg. The cored wire is put into the vacuum induction furnace, and under the action of stirring in the vacuum induction furnace, the sub-micron-sized second-phase particles generated by the diffusion reaction of each component in the cored wire in the molten steel are uniformly distributed in the steel;

[0016] S4. After the fed cored wire is completely melted, casting is completed within 40 minutes, and then the cast ingot is used for rolling.

[0017] Further, in step S3, the cored wire is put into the vacuum induction furnace at one time.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] 1) When the sulfur-containing cored wire is added into the molten steel, S reacts chemically with Mn, Ti, etc. in the cored wire in the molten steel, and sub-micron-sized sulfur-containing second-phase particles with a dispersed distribution are generated under the stirring action of the induction furnace, which play roles such as pinning grain boundaries and nucleation cores during the rolling and welding processes of the steel plate. After solidification, the steel grade obtains a large number of uniformly distributed sub-micron-sized particles containing Ti, S, Mn, and O, improving the strength and toughness of the steel grade.

[0020] 2) The tensile strength of the steel plate rolled from the ingot cast by this method is increased by more than 20 MPa; the impact energy of the steel plate at -40 °C is not less than 150 J; the impact energy of the large heat input welding thermal simulation specimen at -40 °C is not less than 70 J; the tensile strength is high, the toughness of the steel plate is high, the comprehensive performance of the steel plate is improved, the impact resistance of the steel plate under the working condition of -40 °C is increased, and the toughness of the hot-rolled or normalized rolled steel grade and the toughness of the heat-affected zone during the welding of the steel grade with a large heat input are improved. Specific Embodiments

[0021] The specific embodiments of the present invention will be further described below:

[0022] The composition of the sulfur-containing cored wire for a vacuum induction furnace is as follows in the table:

[0023]

[0024] Specific usage conditions of the sulfur-containing cored wire in the above embodiments for steelmaking in a vacuum induction furnace:

[0025] Superheat of molten steel Als content Oxygen content of molten steel Addition amount of wire per ton of ladle Example 1 80℃ 0.020wt% 15ppm 8kg Example 2 50℃ 0.025wt% 18ppm 10kg Example 3 90℃ 0.015wt% 17ppm 9kg

[0026] Specific usage method of the sulfur-containing cored wire in the above embodiments for steelmaking in a vacuum induction furnace: Add the sulfur-containing cored wire into the molten steel 10 - 15 minutes before the end of steelmaking in the vacuum induction furnace; the cored wire is put into the vacuum induction furnace at one time, and under the action of stirring in the vacuum induction furnace, the sub-micron second-phase particles generated by the diffusion reaction of each component in the cored wire in the molten steel are evenly distributed in the steel; casting is completed within 40 minutes after the fed cored wire is melted, and then the cast steel ingot is used for rolling.

[0027] Using the above usage method, a comparative test of steelmaking without adding the cored wire and steelmaking in the above embodiments was carried out using the hot-rolled Q345 steel grade, and rolling and welding thermal simulation tests were also carried out. The peak temperature of the thermal simulation was 1300 °C, the residence time at the peak temperature was 0.5 s, and the T8 / 5 time was 350 s. The performance test results are shown in the following table:

[0028]

[0029] As mentioned above, the above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and its concept of the present invention, makes equivalent substitutions or changes, and all should be covered within the protection scope of the present invention.

Claims

1. A sulfur-containing cored wire for a vacuum induction furnace, wherein the cored wire has a diameter of Φ3.0 mm to Φ5.0 mm, and comprises a steel strip shell and powder, wherein: The steel belt shell is made of rolled steel belt, and the steel belt shell is filled with powder. The powder includes industrial pure iron powder, manganese oxide powder, ferrotitanium powder containing 30% titanium and ferrous sulfide powder, which are mixed in a mass ratio of 65-75:7-10:15-18:

1.

2. The sulfur-containing cored wire for vacuum induction furnace according to claim 1, characterized in that: The particle size of the industrial pure iron powder is 44-150 μm, the particle size of the manganese oxide powder is 160-250 meshes, the particle size of the ferrotitanium powder containing 30% titanium is 44-150 μm, and the particle size of the ferrous sulfide powder is 170-280 meshes.

3. The sulfur-containing cored wire for vacuum induction furnace according to claim 1, characterized in that: The thickness of the steel strip is 1.8 mm to 2.2 mm.

4. The sulfur-containing cored wire for vacuum induction furnace according to claim 1, characterized in that: The core-spun wire filling rate is 16% to 20%.

5. A method for using the sulfur-containing cored wire for a vacuum induction furnace according to claim 1, characterized in that: The specific steps of the method of use are as follows: S1. Add sulfur-containing cored wire into the molten steel 10-15 minutes before the end of steelmaking in the vacuum induction furnace; S2. The superheat of molten steel in the vacuum induction furnace is 40-100℃; the Als content in the molten steel should be below 0.03wt%; the oxygen content in the molten steel is below 20ppm; S3. The amount of cored wire added per ton of molten steel is 7-11 kg. The cored wire is put into a vacuum induction furnace. Under the stirring action of the vacuum induction furnace, the submicron second phase particles generated by the diffusion reaction of each component in the cored wire in the molten steel are evenly distributed in the steel. S4. After the cored wire to be fed is cleaned, the casting is completed within 40 minutes, and then the cast steel ingot is used for rolling.

6. The method for using the sulfur-containing cored wire for a vacuum induction furnace according to claim 4, characterized in that: In step S3, the cored wire is put into the vacuum induction furnace at one time.

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