Mixed gas welding stainless steel flux-cored wire and welding process thereof

Abstract

The invention belongs to the technical field of stainless steel flux-cored wires, and relates to a mixed gas welding stainless steel flux-cored wire and a welding process thereof. The flux core powder is composed of, by weight, 10-18 parts of metal nickel powder, 18-25 parts of metal chromium powder, 5-10 parts of electrolytic manganese powder, 1-1.5 parts of silicon iron, 1-3 parts of ferrotitanium, 15-25 parts of 95 rutile, 1-4 parts of fluorite, 6-10 parts of zircon sand, 3-6 parts of magnesia, 3-8 parts of feldspar, 1-3 parts of aluminum oxide, 2-4 parts of potassium silicate, less than 1 part (not 0) of lithium carbonate and 5-40 parts of atomized iron powder. According to the method, the stability of the electric arc can be improved, the spraying transition current is reduced, the wettability and welding bead forming are improved, air holes are completely eradicated, meanwhile, splashing is less, the deposition efficiency is high, and the welding cost is reduced. Mixed gas shielded welding is more suitable for flat welding, vertical position welding, horizontal position welding and overhead position welding, and large-current all-position welding can be achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of stainless steel flux-cored wires, and relates to a stainless steel flux-cored wire for mixed gas welding and its welding process. Background Art

[0002] In recent years, with the wide application of stainless steel, stainless steel flux-cored wires have also been popularized. In many industries and fields, stainless steel flux-cored wires have gradually replaced solid stainless steel wires and electrodes. All stainless steel flux-cored wires on the domestic market use 100% carbon dioxide as the shielding gas. Stainless steel flux-cored wires using carbon dioxide as the shielding gas have the following main problems: The welding position is limited. The arc rigidity is too strong, resulting in difficult control of the molten pool. In overhead welding / vertical welding, the molten pool is prone to sag. Therefore, it can only be used for flat (fillet) welding and horizontal welding; The spatter rate is as high as 15 - 25%, and the welding torch needs to be cleaned frequently; CO2 decomposes at high temperatures to produce O, resulting in the burning loss of alloying elements such as Cr and Mn (loss rate > 8%), reducing the corrosion resistance of the weld. At the same time, the hydrogen content in the deposited metal is high, and cracks are easily generated; There are a large number of pores when directly changing the wire with a 100% carbon dioxide shielding gas formula to mixed gas shielded welding. Summary of the Invention

[0003] The present invention proposes a new type of stainless steel flux-cored wire for mixed gas welding and its welding process in view of the problems existing in the process of using pure carbon dioxide as the shielding gas in traditional stainless steel flux-cored wires.

[0004] To achieve the above object, the present invention is realized by the following technical solutions: A flux-cored stainless steel wire for mixed gas welding, comprising a steel strip and flux powder. The flux powder is composed of the following substances in parts by weight: 10-18 parts of metallic nickel powder, 18-25 parts of metallic chromium powder, 5-10 parts of electrolytic manganese powder, 1-1.5 parts of ferrosilicon, 1-3 parts of ferrotitanium, 15-25 parts of 95 rutile (main component TiO2), 1-4 parts of fluorite (main component CaF2), 6-10 parts of zircon sand, 3-6 parts of magnesia, 3-8 parts of feldspar, 1-3 parts of alumina, 2-4 parts of potassium silicate, <1 part and not 0 of lithium carbonate, and 5-40 parts of atomized iron powder; The steel strip preferably has a yield strength ≥ 210 N / mm², a tensile strength ≥ 520 N / mm², and an elongation rate ≥ 42%. The mass fractions of various elements contained in the 304L steel strip are controlled as follows: C: ≤ 0.03%, Si: ≤ 1%, Mn: ≤ 2%, Cr: 18%-20%, Ni: 8%-12%, S: ≤ 0.03%, P: ≤ 0.035%. The steel strip is preferably a stainless steel strip 00Cr19Ni10 (304L) or 00Cr16Ni14Mo2 (316L) with a thickness of 0.3-0.5 mm and a width of 10-14 mm, wrapped with flux powder and processed according to a filling ratio of 20-25%, and the final wire diameter is 0.8-1.6 mm. It has been verified that zircon sand, magnesia, and alumina in the above flux powder can all improve the slag, shorten the slag solidification time, and prevent the loss of molten iron, thus realizing the function of vertical welding. However, using only one or two of them has no obvious effect. All three must be combined, and the ratio is within the above range.

[0005] Preferably, the wire contains the following elements in parts by weight: Cr: 18-25 parts, Ni: 10-18 parts, Ti: 1-3%, C: ≤ 0.03 parts, Si: ≤ 1 part, Mn: 1-2 parts, S: ≤ 0.025 parts, P: ≤ 0.04 parts, Mo ≤ 0.75 parts.

[0006] Preferably, the steel strip is a stainless steel strip 00Cr19Ni10 or 00Cr16Ni14Mo2 with a thickness of 0.3-0.5 mm and a width of 10-14 mm.

[0007] Preferably, the wire diameter is 0.8-1.6 mm.

[0008] Preferably, the welding atmosphere is a mixture of argon and nitrogen dioxide, where the volume fraction of argon is 75-85% and the volume fraction of carbon dioxide is 15-25%.

[0009] The present invention constructs an oxidation and burn - loss resistant alloy system by strictly controlling the ratio of Cr, Ni, and Ti. The three metals play the following roles in the wire welding process: Low burn - loss under Ar protection: In an inert atmosphere with Ar ≥ 75%, the oxidation and burn - loss rate of Cr decreases from 12% in pure CO2 to ≤ 5%, ensuring that the Cr equivalent (Creq = Cr + 1.5Mo) in the austenite matrix of the weld seam is stable at 22 - 24, meeting the corrosion resistance requirement of PREN ≥ 38. Ni compensates for carbon activity: By controlling the Ni content, the carbon increment (ΔC ≤ 0.03%) in the molten pool caused by the decomposition of CO2 is offset, avoiding the intergranular corrosion caused by the formation of Cr 23 C6 carbides. Ti oxidation protection: Ti preferentially combines with the active O decomposed from CO2 to form Ti2O3 (with high melting point and thermal stability), forming a dense oxide film on the surface of the molten pool, reducing the generation amount of FeO to < 0.5%, and inhibiting the initiation of pitting corrosion.

[0010] In addition, the present invention replaces the commonly used NaF2 in traditional welding wires with fluorite mainly composed of CaF2. CaF2 has the following functions in the formula process of the present invention. Low - temperature eutectic effect: CaF2 forms a eutectic slag with a melting point of 1150 °C with TiO2, enabling the molten slag to quickly solidify into a shell in the vertical welding position and restricting the shape of the molten pool. Deoxidation strengthening: CaF2 promotes the formation of the SiO2 - MnO slag system, and the oxygen content in the molten pool is stable at 180 - 220 ppm (300 - 400 ppm for traditional welding wires). Rutile TiO2 dominates slag formation and controls the viscosity and surface tension of the molten slag. Specifically, control of the molten slag viscosity gradient: When the TiO2 content > 15%, the viscosity of the molten slag decreases to 0.8 - 1.2 Pa·s at 1400 °C (2 - 3 Pa·s for the traditional CaO - SiO2 slag system), increasing the spreadability of the molten slag by 40% during flat welding and accelerating the solidification rate by 50% during overhead welding, preventing the molten pool from sagging. Surface tension adjustment: TiO2 reduces the surface tension of the molten pool to 1.1 - 1.3 N / m (1.6 - 1.8 N / m for pure CO2 welding), improving the wettability of the molten pool to the groove and eliminating bead - edge undercut during horizontal welding.

[0011] Furthermore, the present invention also realizes the collaborative control of arc-droplet transfer through the cooperation of three materials, namely Mn, Si, and K2SiO3, including a dynamic deoxidation reaction: Mn reacts with O decomposed from CO2 to form MnO (ΔG° = -320 kJ / mol), and Si further reduces the residual FeO, reducing the oxygen activity of the molten pool to ≤0.02% and the porosity to <0.3%; droplet refinement: Mn / Si oxides serve as heterogeneous nucleation sites, reducing the droplet diameter from 1.2 mm in pure CO2 welding to 0.3 - 0.5 mm, achieving jet transfer. Arc stability against CO2 interference: K⁺ has a low ionization potential (4.3 eV) and can still maintain arc conductivity in a CO2 atmosphere, resulting in an arc length fluctuation of <1 mm (3 - 4 mm for traditional Na2SiO3); slag system modification: K2O generated during welding reacts with TiO2 to form K2Ti2O5, reducing the slag resistivity to 0.1 - 0.3 Ω·cm (conventional slag systems >0.5 Ω·cm) and enhancing arc penetration.

[0012] Compared with the prior art, the advantages and positive effects of the present invention are as follows: 1. The present invention can improve the stability of the arc, reduce the spray transfer current, improve wettability and bead formation, eliminate the generation of pores, and at the same time reduce spatter, have a high deposition efficiency, and reduce welding costs.

[0013] 2. Improve welding quality: Gas mixture shielded welding can effectively refine the droplets, with less alloying element burn-off, low hydrogen content in the weld, good crack resistance, deeper weld bead penetration, which helps to improve the strength and impact toughness of the weld, thus significantly improving welding quality.

[0014] 3. Gas mixture shielded welding is more suitable for flat welding, vertical welding, horizontal welding, and overhead welding, and can achieve all-position welding with large currents. Specific Embodiments

[0015] In order to more clearly understand the above objects, features, and advantages of the present invention, the following specific embodiments are used to further illustrate the present invention. It should be noted that, without conflict, the embodiments of the present application and the features in the embodiments can be combined with each other.

[0016] In the following description, many specific details are set forth to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described herein. Therefore, the present invention is not limited by the specific embodiments disclosed in the following specification.

[0017] Example 1 The following examples and the flux-cored powder used in the following examples are all commercially available materials commonly used in the welding wire industry. A commercially available 304L steel strip with a size of 0.4×10mm (from Jinan Farina Welding Equipment Co., Ltd.) is selected, meeting the requirements of C:≤0.03%, Si:≤1%, Mn:≤2%, Cr: 18%-20%, Ni: 8%-12%, S:≤0.03%, P:≤0.035%. The mechanical properties of 304L stainless steel are: yield strength ≥210N / mm², tensile strength ≥520N / mm², elongation ≥42%.

[0018] By weight percentage, the flux core accounts for 20% of the weight of the welding wire. The weight percentage of the flux core components is as follows: 16 parts of metallic nickel powder, 20 parts of metallic chromium powder, 7 parts of electrolytic manganese, 20 parts of 95 rutile, 7 parts of zircon sand, 5 parts of magnesia, 6 parts of feldspar, 1.5 parts of alumina, 1 part of fluorite, 4 parts of potassium silicate, 1 part of ferrosilicon, 2 parts of ferrotitanium, 0.5 part of lithium carbonate. The total amount of the flux-cored powder is 100 parts, and it is supplemented with atomized iron powder.

[0019] According to a filling ratio of 20%, the powder is placed in a steel strip rolled into a U-shape by rollers. After multiple rollings, the U-shaped groove is changed into an O-shape, and then after multiple drawings, and finally through surface cleaning, a welding wire with a diameter of 1.2mm is made.

[0020] Verification: Using a mixed gas shielded welding of 80%Ar + 20%CO2, the chemical composition (by weight percentage) of the deposited metal of the obtained finished welding wire is: C 0.02%, Mn 1.35, Si 0.47, S 0.002%, P 0.013, Cr 18.8, Ni 9.6, and the balance is Fe. The mechanical properties of the deposited metal are: tensile strength is 670MPa, elongation is 47%, there are no pores after welding, the slag coverage is uniform, and slag removal is easy. The vertical welding voltage is 26 - 30V, the current is 180 - 220A, and the vertical welding effect is good.

[0021] Example 2 A 304L steel strip with a size of 0.4×10mm is selected. By weight percentage, the flux core accounts for 20% of the weight of the welding wire. The weight parts of the flux core components are as follows: 16 parts of metallic nickel powder, 22 parts of metallic chromium powder, 8 parts of electrolytic manganese powder, 18 parts of 95 rutile, 7 parts of zircon sand, 5 parts of magnesia, 7 parts of feldspar, 1 part of alumina, 1 part of fluorite, 2 parts of potassium silicate, 1 part of ferrosilicon, 1.6 parts of ferrotitanium, 0.4 part of lithium carbonate. The total amount of the flux-cored powder is 100 parts, and it is supplemented with atomized iron powder.

[0022] After rolling and drawing, a welding wire with a diameter of 1.2mm is made.

[0023] Verification: Using shielded metal arc welding with a mixed gas of 80% Ar + 20% CO2, the chemical composition of the deposited metal of the finished welding wire (calculated by weight percentage) is: C 0.019%, Mn 1.27, Si 0.42, S 0.003%, P 0.012, Cr 19.2, Ni 9.8, and the balance is Fe. The mechanical properties of the deposited metal are: tensile strength of 664 MPa, elongation of 49%, no porosity after welding, uniform slag coverage, and easy slag removal. Vertical welding voltage is 26 - 30 V, current is 180 - 220 A, and the vertical welding effect is good.

[0024] Example 3 Select a 304L steel strip with a size of 0.4×10 mm. By weight percentage, the flux-cored part accounts for 22% of the weight of the welding wire. The weight parts of the flux-cored composition are: 18 parts of metallic nickel powder, 22 parts of metallic chromium powder, 7 parts of electrolytic manganese powder, 21 parts of 95 rutile, 9 parts of zircon sand, 4 parts of magnesia, 8 parts of feldspar, 1.5 parts of alumina, 2.4 parts of fluorite, 3 parts of potassium silicate, 0.6 parts of lithium carbonate, 1.3 parts of ferrosilicon, and 2.2 parts of ferrotitanium. After rolling and drawing, a welding wire with a diameter of 1.2 mm is made.

[0025] Verification: Using shielded metal arc welding with a mixed gas of 80% Ar + 20% CO2, the chemical composition of the deposited metal of the finished welding wire (calculated by weight percentage) is: C 0.019%, Mn 1.30, Si 0.41, S 0.004%, P 0.011, Cr 19.6, Ni 9.9, and the balance is Fe. The mechanical properties of the deposited metal are: tensile strength of 657 MPa, elongation of 52%, no porosity after welding, uniform slag coverage, and easy slag removal. Vertical welding voltage is 27 - 29 V, current is 180 - 200 A, and the vertical welding effect is good.

[0026] Example 4 Select a 304L steel strip with a size of 0.4×10 mm. By weight percentage, the flux-cored part accounts for 22% of the weight of the welding wire. The weight parts of the flux-cored composition are: 15 parts of metallic nickel powder, 24 parts of metallic chromium powder, 9 parts of electrolytic manganese powder, 20 parts of 95 rutile, 6 parts of zircon sand, 5 parts of magnesia, 8 parts of feldspar, 2 parts of alumina, 3 parts of fluorite, 3 parts of potassium silicate, 3 parts of lithium carbonate, 1 part of ferrosilicon, 1 part of ferrotitanium, and 5 parts of atomized iron powder. After rolling and drawing, a welding wire with a diameter of 1.2 mm is made.

[0027] Verification: Using shielded metal arc welding with a mixed gas of 80% Ar + 20% CO2, the chemical composition of the deposited metal of the finished welding wire (calculated by weight percentage) is: C 0.021%, Mn 1.22, Si 0.43, S 0.003%, P 0.013, Cr 19.7, Ni 10.2, and the balance is Fe. The mechanical properties of the deposited metal are: tensile strength of 673 MPa, elongation of 52%, no porosity after welding, uniform slag coverage, and easy slag removal. Vertical welding voltage is 26 - 30 V, current is 180 - 220 A, and the vertical welding effect is good.

[0028] Example 5 Select a 304L steel strip with a size of 0.4×10 mm. By weight percentage, the flux-cored part accounts for 24% of the weight of the welding wire. The weight parts of the flux-cored composition are: 15 parts of metallic nickel powder, 21 parts of metallic chromium powder, 6.5 parts of electrolytic manganese powder, 23 parts of 95 rutile, 7 parts of zircon sand, 3.5 parts of magnesia, 5 parts of feldspar, 3 parts of alumina, 1.5 parts of fluorite, 3 parts of potassium silicate, 2.5 parts of lithium carbonate, 1.5 parts of ferrosilicon, 3 parts of ferrotitanium, and 8 parts of atomized iron powder. After rolling and drawing, a welding wire with a diameter of 1.2 mm is made.

[0029] Verification: Using shielded metal arc welding with a mixed gas of 80% Ar + 20% CO2, the chemical composition of the deposited metal of the finished welding wire (calculated by weight percentage) is: C 0.022%, Mn 1.25, Si 0.37, S 0.004%, P 0.010, Cr 19.7, Ni 10.6, and the balance is Fe. The mechanical properties of the deposited metal are: tensile strength of 663 MPa, elongation of 51%, no porosity after welding, uniform slag coverage, and easy slag removal. Vertical welding voltage is 26 - 30 V, current is 180 - 220 A, and the vertical welding effect is good.

[0030] Example 6 Select a 304L steel strip with a size of 0.4×10 mm. By weight percentage, the flux-cored part accounts for 24% of the weight of the welding wire. The weight parts of the flux-cored composition are: 13 parts of metallic nickel powder, 21 parts of metallic chromium powder, 6 parts of electrolytic manganese powder, 23 parts of 95 rutile, 8 parts of zircon sand, 6 parts of magnesia, 5 parts of feldspar, 3 parts of alumina, 3 parts of fluorite, 2 parts of potassium silicate, 1 part of lithium carbonate, 1 part of ferrosilicon, 2 parts of ferrotitanium, and 10 parts of atomized iron powder. After rolling and drawing, a welding wire with a diameter of 1.2 mm is made.

[0031] Verification: Using shielded metal arc welding with a mixed gas of 80% Ar + 20% CO2, the chemical composition of the deposited metal of the finished welding wire (calculated by weight percentage) is: C 0.021%, Mn 1.23, Si 0.35, S 0.002%, P 0.011, Cr 19.8, Ni 10.7, and the balance is Fe.

[0032] The mechanical properties of the deposited metal are as follows: the tensile strength is 677 MPa, the elongation is 53%, there are no pores after welding, the slag coverage is uniform, and slag removal is easy. The vertical welding voltage is 26 - 30 V, the current is 180 - 220 A, and the vertical welding effect is good.

[0033] The welding wire prepared in Example 1 was used for experimental comparison under the pure CO2 atmosphere with the same welding process conditions. After testing, the results are shown in Table 1 below.

[0034] Table 1 Test Results of the Process Effect of the Mixed Gas As can be seen from Table 1 above, under the mixed atmosphere of the present invention, the four performance indicators of the spatter rate, arc stability, Cr element burn - out rate, and droplet transfer mode are all greatly improved compared with the pure carbon dioxide atmosphere.

[0035] The above - mentioned are only the preferred embodiments of the present invention, and it is not intended to limit the present invention in other forms. Any person skilled in the art may use the disclosed technical content to make changes or modifications into equivalent embodiments with equivalent changes and apply them to other fields. However, any simple modification, equivalent change, and modification made to the above - mentioned embodiments based on the technical essence of the present invention without departing from the technical solution content of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A flux-cored wire for gas-shielded arc welding of stainless steel, comprising a steel strip and flux powder, characterized in that, The flux-cored powder consists of the following substances in parts by weight: 10-18 parts of metallic nickel powder, 18-25 parts of metallic chromium powder, 5-10 parts of electrolytic manganese powder, 1-1.5 parts of ferrosilicon, 1-3 parts of ferrotitanium, 15-25 parts of 95 rutile, 1-4 parts of fluorite, 6-10 parts of zircon sand, 3-6 parts of magnesia, 3-8 parts of feldspar, 1-3 parts of alumina, 2-4 parts of potassium silicate, <1 part and not 0 of lithium carbonate, and 5-40 parts of atomized iron powder; the yield strength of the steel strip is ≥210 N / mm², the tensile strength is ≥520 N / mm², and the elongation is ≥42%.

2. The stainless steel flux cored wire for mixed gas welding according to claim 1, wherein The welding wire contains the following elements in parts by weight: Cr: 18-25 parts, Ni: 10-18 parts, Ti: 1-3%, C: ≤0.03 parts, Si: ≤1 part, Mn: 1-2 parts, S: ≤0.025 parts, P: ≤0.04 parts, Mo ≤0.75 parts.

3. The stainless steel flux-cored wire for mixed gas welding according to claim 1, wherein, The steel strip is a stainless steel strip 00Cr19Ni10 or 00Cr16Ni14Mo2 with a thickness of 0.3-0.5 mm and a width of 10-14 mm.

4. The stainless steel flux cored wire for mixed gas welding according to claim 1, wherein, The diameter of the welding wire is 0.8-1.6 mm.

5. The welding process of the stainless steel flux-cored wire prepared by the method according to any one of claims 1-4, characterized in that, The welding atmosphere is a mixture of argon and nitrogen dioxide, where the volume fraction of argon is 75-85% and the volume fraction of carbon dioxide is 15-25%.

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