A wire rod steel for high alloy welding wire and its preparation method

Abstract

The present invention provides a wire rod steel for high-alloy welding wire and a preparation method thereof. The chemical components in the steel are as follows by weight percentage: C 0.06% - 0.10%, Si 0.65% - 0.85%, Mn 1.60% - 1.80%, P ≤ 0.020%, S ≤ 0.020%, Ni 0.70% - 0.95%, Cr 0.30% - 0.50%, Ti 0.04% - 0.09%, and the balance is iron and inevitable impurities. The production mode of "120t converter + LF furnace refining + small billet continuous casting + reheating furnace heating + controlled rolling and controlled cooling rolling + heat preservation channel" is adopted in the present invention to solve the problem of smooth casting in the continuous casting production of wire rod for high-alloy welding wire and prevent the "nodulation" of the tundish nozzle. At the same time, the present invention not only ensures the mechanical property requirements of the wire rod for high-alloy welding wire, but also has good drawing performance and welding performance.

Description

Technical Field

[0001] The present invention relates to the technical field of iron and steel metallurgy, and particularly relates to a wire rod steel for high-alloy welding wires and a preparation method thereof. Background Art

[0002] The wire rod for high-alloy welding wires produced by a certain steel plant is the main raw material for copper-plated gas shielded welding wires of low-carbon alloy structural steel. This wire rod for high-alloy welding wires has excellent welding process performance, with stable arc, less spatter, and good forming. The contents of impurities such as S and P are strictly restricted. The infiltration of a sufficient amount of nickel in the weld makes the weld metal have excellent comprehensive mechanical properties, and a small amount of titanium element in the welding wire prevents spark spatter during the welding process. It can be widely used in the welding of construction machinery, hoisting machinery, ships, bridges, pipelines, and pressure vessels, etc. This wire rod for high-alloy welding wires is one of the high-end and high-value-added branded steel grades of high-speed wire rod products.

[0003] The surface quality requirements for the wire rod for high-alloy welding wires are as follows: The non-water-pierced parts and defective parts at the head and tail of the wire rod should be cut off. There shall be no scabs, folds, fins, scratches, or cracks visible to the naked eye on the surface of the wire rod; indentations, local bumps, scratches, and pitted surfaces are allowed, but their depth or height (calculated from the actual size) shall not be greater than 0.10 mm.

[0004] Currently, there are the following problems in the production process of the wire rod steel for high-alloy welding wires: During the continuous casting of square billets, the problem of nodulation is likely to occur, resulting in the inability to pour steel smoothly. In addition, it is not easy to ensure the mechanical properties of the wire rod. Summary of the Invention

[0005] The purpose of the present invention is to provide a wire rod steel for high-alloy welding wires and a preparation method thereof. The present invention adopts a production mode of "120t converter + LF furnace refining + continuous casting of 150mm×150mm small square billets + heating in a heating furnace + controlled rolling and controlled cooling rolling + insulation channel" to solve the problem of smooth casting in the continuous casting production of the wire rod for high-alloy welding wires and prevent "nodulation" of the tundish nozzle. At the same time, the present invention not only ensures the mechanical property requirements of the wire rod for high-alloy welding wires, but also has good drawing performance and welding performance.

[0006] In order to achieve the above purpose, the present invention is realized by adopting the following technical solutions:

[0007] A wire rod steel for high-alloy welding wires, the chemical components in the steel are calculated by weight percentage as follows: C 0.06% - 0.10%, Si 0.65% - 0.85%, Mn 1.60% - 1.80%, P≤0.020%, S≤0.020%, Ni 0.70% - 0.95%, Cr 0.30% - 0.50%, Ti 0.04% - 0.09%, and the rest are iron and inevitable impurities.

[0008] The tensile strength of the wire rod is 760 - 818 MPa, the elongation is 18% - 26.5%, and the reduction of area is 62% - 70%; for non-metallic inclusions, A + C ≤ 1.5, and B + D ≤ 1.5.

[0009] The microstructure in the steel is ferrite + pearlite.

[0010] C is the most important strengthening element, but it will strongly deteriorate the plasticity, toughness and weldability. Research shows that when the Mn content is relatively high, the reduction of area and elongation of the steel decrease, and the cold working performance of the steel becomes poor, which is not conducive to drawing. In order to obtain good cold drawing performance, the C content is strictly controlled at 0.06 - 0.10%.

[0011] Si has a strong solid solution strengthening effect and greatly increases the work hardening rate at the same time. Excessive Si content leads to an increase in the deformation resistance during cold drawing and has a tendency to reduce plasticity and toughness. At the same time, the inclusions formed by Si oxidation will cause serious harm to the weld. Therefore, the addition amount of Si is controlled at 0.65 - 0.85%.

[0012] Mn improves the low-temperature impact toughness of the weld and has the functions of deoxidation and desulfurization. At the same time, the addition of Mn ensures the strength lost due to the decrease in strength caused by carbon reduction. Considering the basic strength of the steel, the Mn content is controlled at 1.60 - 1.80%.

[0013] S: It is a serious segregation element in the steel. Sulfides will deteriorate the properties of the steel, resulting in a decrease in toughness and a deterioration of the drawing performance; P: It will affect the plasticity and weldability of the steel. Try to reduce the contents of P and S, reduce the harmful effects of inclusions, and ensure the drawing elongation performance. The P content ≤ 0.020% and the S content ≤ 0.020%.

[0014] Ni helps to improve the toughness of the weld metal and reduce the ductile-brittle transition temperature. The Ni content in the present invention is 0.70 - 0.95%.

[0015] Increasing the content of Cr element is beneficial to improving the toughness of the weld. At the same time, it can form carbides with dispersed distribution with carbon and improve the strength of the weld; the Cr element is beneficial to increasing the content of acicular ferrite, reducing proeutectoid ferrite, and has the effect of refining the ferrite grains, improving the strength and toughness of the weld. Cr also helps to maintain the performance of the weld at a relatively high level after heat treatment. The Cr content is 0.30 - 0.50%.

[0016] During welding, Ti can combine with N and O to form TiN and TiO particles as crystal nuclei, prevent the growth of austenite grains during the welding heating process and refine the austenite grains of the weld. At the same time, it can also be used as a phase transformation core during the welding cooling process to form acicular ferrite with intragranular nucleation, improving the toughness of the weld. However, if Ti is excessive, a large number of TiC and TiN particles will be formed, reducing the toughness. The Ti content is 0.040% - 0.090%.

[0017] A preparation method of wire rod steel for high-alloy welding wire. In order to ensure the quality of the continuous casting billet, the following process mode is adopted: "120t converter + LF furnace refining + continuous casting of 150mm×150mm small square billets + heating in a heating furnace + controlled rolling and controlled cooling rolling + heat preservation channel". Effective measures such as molten steel superheat, casting speed, electromagnetic stirring in the continuous casting mold and electromagnetic stirring at the solidification end are used to control and improve the surface quality of the continuous casting billet, and reduce internal cracks and central defects. The specific method steps are as follows:

[0018] 1) Converter smelting: Scrap steel accounts for 10 - 15%, and hot metal accounts for 85 - 90%; 5.8 - 6.2 kg of nickel plates are added to the converter together with the scrap steel; Top and bottom combined blowing with oxygen, tapping temperature 1600 - 1630°C, tapping end point C is 0.045% - 0.050%, double slag smelting in the converter, target primary tapping P ≤ 0.008%, slagging is strictly prohibited. Auxiliary materials addition per ton of steel: 68 - 72 kg of active lime, 40 - 45 kg of dolomite, 13 - 15.5 kg of Australian ore; And 17 - 18 kg of return scrap, 18.4 - 18.8 kg of low-carbon ferromanganese, and 5.8 - 6.0 kg of low-carbon ferrochromium are added per ton of steel for alloying; Argon blowing time during tapping ≥ 5 min.

[0019] 2) Stationary argon blowing: Stationary argon blowing time ≥ 8 min, temperature before treatment 1570 - 1590°C, temperature after treatment 1560 - 1580°C, 1 - 1.2 kg / t·steel of pure calcium cored wire is fed after stationary argon blowing, wire feeding speed 2.8 - 3.2 m / s.

[0020] 3) LF furnace refining: White slag operation is required. Under the condition of ensuring slag fluidity, control the slag basicity and oxygen potential in the slag; Continuously detect the molten steel, and finely adjust the alloy to ensure that the molten steel composition meets the standard requirements; LF refining time 60 - 90 min, full analysis temperature 1580 - 1620°C; Auxiliary materials addition per ton of steel: 9.5 - 10.2 kg of active lime, 28 - 32 kg / ladle of calcium carbide slag, 30 - 34 kg / ladle of fluorite. In addition, 5.0 - 5.4 kg / t of low-aluminum ferrosilicon, 2.0 - 2.3 kg / t of ferrotitanium, and 100 kg / ladle of ferrosilicon powder are added per ton of steel, and the molten steel is continuously detected and the alloy is finely adjusted to ensure that the molten steel composition meets the standard requirements, soft blowing time ≥ 12 min.

[0021] 4) Continuous casting: Electromagnetic stirring current in the mold 220 - 260 A, frequency 4 - 6 Hz, forward and reverse rotation; Electromagnetic stirring current at the end 230 - 270 A, frequency 4 - 8 Hz, continuous rotation. Platform temperature 1610 - 1620°C, tundish temperature 1570 - 1585°C, superheat maintained at 25 - 35°C, casting speed 2.2 - 2.4 m / min; Protective casting throughout the process, and a special titanium-containing steel mold powder is used for the mold powder in the continuous casting mold; The continuous casting billet is cut by a combination of automatic and manual methods.

[0022] 5) Heating process: Heated in a walking beam reheating furnace, adopting a heating mode of "one blank and one empty space", that is, leaving an empty space between two adjacent billets. The preheating section is 860 - 900 °C, the heating section is 1080 - 1120 °C, the soaking section is 1120 - 1160 °C, and the heating time ≤ 2.5 h.

[0023] 6) Rolling process: Rough rolling temperature 980 - 1020 °C; Finishing mill entry temperature 900 - 940 °C; Spinning temperature 780 - 820 °C; Air-cooling roller table speed: Head roller table 0.09 - 0.12 m / s; Roller table speed increase setting 2 - 5%; All heat preservation covers are used.

[0024] Heat preservation channel: The heat preservation channel is effectively utilized to ensure the effective release of tissue stress and internal stress, thereby also ensuring the product performance and the requirements for the difference in product performance along the length.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] 1) Aiming at the problem that the tundish nozzle of small-section continuous casting billets is prone to "nodulation" and blockage due to high titanium content, the present invention uses a special protective slag for titanium-containing steel, and at the same time solves the problems that high titanium content is likely to cause large fluctuations in the mold liquid level and lead to steel slag entrainment in the mold.

[0027] 2) Adopting continuous casting mold electromagnetic stirring and final electromagnetic stirring to improve the surface quality of the cast billet and reduce defects such as central porosity.

[0028] 3) When heating in a walking beam reheating furnace, adopting a heating mode of "one blank and one empty space" to shorten the heating time, ensure uniform heating of the billets, and avoid the formation of difficult-to-remove FeSiO 4 .

[0029] 4) Through the controlled rolling and controlled cooling process of steel rolling and the slow cooling process, a metallographic structure composed of ferrite and pearlite is obtained.

[0030] 5) The thickness of the scale on the wire rod of the present invention (10 - 14 μm) is suitable for mechanical descaling. Description of the Drawings

[0031] Figure 1 It is the metallographic structure diagram of the product in Example 1. Detailed Embodiments

[0032] The following further describes the detailed embodiments of the present invention in conjunction with the examples.

[0033] The chemical components of the embodiments of the present invention are shown in Table 1; the manufacturing process parameters of the embodiments of the present invention are shown in Table 2; the addition amounts of smelting auxiliary materials in the embodiments of the present invention are shown in Table 3; the macrostructure defects of the continuous casting billets in the embodiments of the present invention are shown in Table 4; the mechanical properties of the products in the embodiments of the present invention are shown in Table 5; the microstructure and non-metallic inclusions of the products in the embodiments of the present invention are shown in Table 6.

[0034] Table 1 Chemical Components of Embodiments

[0035] Example C Si Mn P S Cr Ni Ti 1 0.06 0.75 1.62 0.013 0.009 0.38 0.86 0.083 2 0.07 0.66 1.64 0.015 0.007 0.40 0.73 0.055 3 0.065 0.76 1.71 0.009 0.005 0.35 0.85 0.086 4 0.062 0.81 1.72 0.005 0.007 0.44 0.94 0.088 5 0.062 0.84 1.67 0.01 0.008 0.37 0.81 0.066 6 0.075 0.77 1.69 0.015 0.007 0.34 0.75 0.055 7 0.066 0.74 1.66 0.009 0.009 0.32 0.82 0.087 8 0.08 0.70 1.72 0.005 0.007 0.41 0.8 0.046 9 0.09 0.73 1.76 0.01 0.008 0.47 0.89 0.085 10 0.092 0.68 1.78 0.01 0.008 0.45 0.92 0.080

[0036] Table 2 Manufacturing Process Parameters of Embodiments (I)

[0037]

[0038]

[0039] Table 2 Manufacturing Process Parameters of Embodiments (II)

[0040]

[0041] Table 3 Addition Amounts of Smelting Auxiliary Materials in Embodiments

[0042]

[0043] Table 4 Inspection Results of Macrostructure Defects of Continuous Casting Billets in Embodiments:

[0044]

[0045]

[0046] Table 5 Mechanical Properties of Products in Embodiments

[0047] Example Tensile strength / MPa Elongation after fracture / % Reduction of area / % 1 777 23.5 62 2 783 23.5 64 3 791 25 64 4 807 26.5 68 5 818 26.5 70 6 761 26.5 62 7 762 23.5 64 8 779 23.5 62 9 763 26.5 64 10 787 20 68

[0048] Table 6 Microstructure and Non-Metallic Inclusions of Products in Embodiments

[0049]

Claims

1. A wire rod steel for high alloy welding wire, characterized in that, the chemical components in the steel are by weight percentage: C 0.06% - 0.10%, Si 0.65% - 0.85%, Mn 1.60% - 1.80%, P ≤ 0.020%, S ≤ 0.020%, Ni 0.70% - 0.95%, Cr 0.32% - 0.50%, Ti 0.04% - 0.09%, and the rest is iron and inevitable impurities; A preparation method of the wire rod steel for high alloy welding wire, comprising the following steps: 1) Converter smelting: Scrap steel and hot metal are added; nickel plates are added to the converter together with the scrap steel, top and bottom combined blowing with oxygen, tapping temperature 1600 - 1630°C, tapping end point C is 0.045% - 0.050%, double slag smelting in the converter, target primary tapping P ≤ 0.008%; 2) Argon blowing: Argon blowing time ≥ 8 min, temperature before treatment 1570 - 1590°C, temperature after treatment 1560 - 1580°C; After argon blowing, 1 - 1.2 kg / t·steel of pure calcium cored wire is fed, wire feeding speed 2.8 - 3.2 m / s; 3) LF furnace refining: LF refining time 60 - 90 min, full analysis temperature 1580 - 1620°C; 4) Continuous casting: Platform temperature 1610 - 1620°C, tundish temperature 1570 - 1585°C, superheat maintained at 25 - 35°C, casting speed 2.2 - 2.4 m / min; Protecting casting throughout the process, using a special titanium-containing steel mold powder for the mold powder in the mold; The billet cutting adopts a combination of automatic and manual methods; 5) Heating process: Heating in a walking beam reheating furnace, adopting a heating method of "one interval and one empty position", preheating section 860 - 900°C, heating section 1080 - 1120°C, soaking section 1120 - 1160°C, heating time ≤ 2.5 h; 6) Rolling process: Rough rolling temperature 980 - 1020°C; Finishing mill inlet temperature 900 - 940°C; Spinning temperature 780 - 820°C; Air-cooling roller table speed: head roller table 0.09 - 0.12 m / s; Roller table speed increase set at 2 - 5%; All heat preservation covers are used; The tensile strength of the wire rod is 760 - 818 MPa, elongation after fracture is 18% - 26.5%, reduction of area is 62% - 70%; Non-metallic inclusions A + C ≤ 1.5, B + D ≤ 1.5; The structure in the steel is ferrite + pearlite.

2. A preparation method of the wire rod steel for high alloy welding wire as described in claim 1, characterized in that, it includes the following method steps: 1) Converter smelting: Scrap steel and hot metal are added; nickel plates are added to the converter together with the scrap steel, top and bottom combined blowing with oxygen, tapping temperature 1600 - 1630°C, tapping end point C is 0.045% - 0.050%, double slag smelting in the converter, target primary tapping P ≤ 0.008%; 2) Argon blowing: Argon blowing time ≥ 8 min, temperature before treatment 1570 - 1590°C, temperature after treatment 1560 - 1580°C; 3) LF furnace refining: LF refining time 60 - 90 min, full analysis temperature 1580 - 1620°C; 4) Continuous casting: Platform temperature 1610 - 1620 °C, tundish temperature 1570 - 1585 °C, superheat maintained at 25 - 35 °C, casting speed 2.2 - 2.4 m / min; 5) Heating process: Heated in a walking beam reheating furnace, adopting a heating method of "one space and one vacancy", preheating section 860 - 900 °C, heating section 1080 - 1120 °C, soaking section 1120 - 1160 °C, heating time ≤ 2.5 h; 6) Rolling process: Rough rolling temperature 980 - 1020 °C; Finishing mill entry temperature 900 - 940 °C; Spinning temperature 780 - 820 °C; Air-cooling roller table speed: Head roller table 0.09 - 0.12 m / s; Roller table speed increase set at 2 - 5%; All heat preservation covers are used.

3. A method for preparing wire rod steel for high-alloy welding wire according to claim 2, characterized in that in the converter smelting of the above step 1), the scrap steel accounts for 10 - 15%, and the hot metal accounts for 85 - 90%.

4. A method for preparing wire rod steel for high-alloy welding wire according to claim 2, characterized in that in the converter smelting of the above step 1), the addition amount of auxiliary materials per ton of steel is: 68 - 72 kg of active lime, 40 - 45 kg of dolomite, 13 - 15.5 kg of Australian ore; The argon blowing time during tapping ≥ 5 min.

5. A method for preparing wire rod steel for high-alloy welding wire according to claim 4, characterized in that after the above step 2) of static argon blowing, 1 - 1.2 kg / t·steel of pure calcium cored wire is fed, and the wire feeding speed is 2.8 - 3.2 m / s.

6. A method for preparing wire rod steel for high-alloy welding wire according to claim 2, characterized in that in the refining of the LF furnace in the above step 3), the addition amount of auxiliary materials: 9.5 - 10.2 kg / t·steel of active lime, 28 - 32 kg / furnace of calcium carbide slag, 30 - 34 kg / furnace of fluorite; The soft blowing time ≥ 12 min.

7. A method for preparing wire rod steel for high-alloy welding wire according to claim 2, characterized in that in the above step 4), the electromagnetic stirring current of the mold is 220 - 260 A, the frequency is 4 - 6 Hz, with forward and reverse rotation; The electromagnetic stirring current at the end is 230 - 270 A, the frequency is 4 - 8 Hz, with continuous rotation.

Images