High-nitrogen high-elongation stainless steel flux-cored wire and preparation method thereof

Abstract

The invention relates to the technical field of flux-cored wires, and discloses a high-nitrogen high-elongation stainless steel flux-cored wire and a preparation method thereof. According to the welding wire, a 316L stainless steel strip is adopted as an outer skin, the optimal components of the 316L stainless steel strip comprise 0.1%-0.2% of nitrogen and 7%-8% of nickel, and the 316L stainless steel strip is matched with flux core powder of a specific formula. The flux core comprises 30%-40% of chromium powder, 4%-12% of molybdenum powder, 2%-6% of metal nitride, ferrozirconium and the like, and the nitrogen content of a welding seam ranges from 0.20% to 0.30% through the synergistic nitrogen supply mechanism of the steel strip and the flux core. The zirconium element is introduced to form a stable ZrN compound with nitrogen, the copper element is added to improve the nitrogen solid solubility, and grains are refined in combination with the ferrotitanium alloy. And argon-rich gas is adopted for shielded welding, so that nitrogen escape and oxide inclusion are effectively inhibited. The nickel content of the obtained weld joint is 7.5-10%, the ductility is larger than or equal to 30%, and the high strength and plasticity are achieved through nitrogen strengthening and microstructure regulation and control while the nickel consumption is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of flux-cored wires, and relates to a high-nitrogen and high-elongation stainless steel flux-cored wire and a preparation method thereof. Background Art

[0002] Compared with austenitic stainless steel and ferritic stainless steel, duplex stainless steel has excellent comprehensive properties and is widely used in fields such as offshore engineering, chemical equipment, and nuclear power equipment. Among them, the nitrogen element plays a crucial role. The nitrogen element regulates the microstructure of duplex stainless steel to strengthen its mechanical properties and improve its corrosion resistance.

[0003] Nitrogen is a strong austenite-forming element, which can promote the formation of austenite phase and inhibit the excessive growth of ferrite at high temperatures, thereby maintaining an ideal ratio of two-phase media of austenite (γ) and ferrite (α). This is particularly important for the tissue balance after welding or hot working, avoiding the deterioration of properties caused by single-phase ferrite. The solid solution of nitrogen in austenite and ferrite can improve the mechanical properties of materials, especially contributing significantly to the yield strength and tensile strength, while maintaining good toughness. By refining grains and inhibiting brittle phases, nitrogen helps to improve the impact toughness at low temperatures.

[0004] With the continuous progress of industrial technology, the performance requirements for welding materials are also increasing day by day. Especially in terms of high strength, high toughness, and corrosion resistance, traditional stainless steel welding wires cannot meet the needs of modern engineering in certain specific applications. Although the existing stainless steel flux-cored wires have good fluidity and formability during the welding process, their nitrogen content is generally low, resulting in insufficient strength and elongation of the weld seam, and problems such as weld brittleness and cracks are likely to occur, affecting the overall performance and service life of the welded structure.

[0005] According to the standard regulations, for ordinary E2209 duplex stainless steel flux-cored wires, the weight percentage of nickel element in the undiluted weld metal is 7.5 - 10%, and the weight percentage of nitrogen element is 0.08 - 0.20%. As a precious metal, the price of nickel element fluctuates greatly affected by the market. At the same time, the addition of nitrogen element needs to be strictly matched with process control to avoid precipitation phases and processing difficulties and ensure excellent mechanical properties of the material. However, at the high temperature of the welding pool, the solubility of nitrogen element in liquid metal is relatively high, but as the temperature decreases, the solubility drops sharply, and the undissolved nitrogen tends to escape in the form of gas (N2), resulting in a low retention rate of nitrogen. At the same time, although nitrogen element as an interstitial atom can improve the strength and hardness of the weld seam, excessive addition will significantly reduce plasticity and toughness, resulting in embrittlement.

[0006] Therefore, the development of a stainless steel flux-cored wire with high nitrogen content and good elongation has become a technical problem that urgently needs to be solved in the field of welding materials. The present invention aims to provide a stainless steel flux-cored wire with high nitrogen and high elongation. By optimizing the composition and preparation process of the wire, the nitrogen content and elongation of the weld seam are significantly improved, thereby solving the problem of insufficient weld seam performance in the prior art and meeting the higher requirements of modern industry for welding materials. Summary of the Invention

[0007] Problems existing in the prior art are as follows: Nickel powder in the flux powder is expensive. While reducing the addition amount of nickel element and increasing the nitrogen element, it is difficult to add nitrogen element in the weld cladding metal to reach the weight percentage range required by the standard, and at the same time, the mechanical properties required by the standard should be ensured.

[0008] In view of the above problems, the present invention provides a stainless steel flux-cored wire for preparing a weld seam with high nitrogen and high elongation, its preparation method and application, including iron skin and flux powder. The thickness of the iron skin is 0.4 mm. The flux powder is evenly filled and fills the cylindrical accommodating cavity formed by the iron skin. The filling rate of the flux powder is 23%-28%. The iron skin is a 316L stainless steel strip; The 316L stainless steel strip, in terms of weight percentage, has the following components: carbon 0.01%-0.02%; silicon 0.02%-0.04%; manganese 0.5%-1%; sulfur <0.03%; phosphorus <0.04%; nickel 7%-8%; chromium 16%-20%; molybdenum 2.0%-3.0%; aluminum 0.01%-0.03%; titanium 0.05%-0.1%; copper 0.05-0.2%; nitrogen 0.1%-0.2%; the balance is iron.

[0009] The flux powder, in terms of weight percentage, has the following components: rutile powder 10-20%; mixed oxide powder 10-20%; fluoride powder 2-4%; metal elemental powder 10-30%; ferro-titanium alloy powder 1-4%; ferro-zirconium alloy powder 1-2%; nickel powder 1-4%; chromium powder 30-40%; molybdenum powder 4-12%; bismuth oxide powder 0.2-0.4%; arc stabilizing agent 2-6%; metal nitride powder 2-6%; rare earth fluoride powder 0.2-1%; the balance is iron powder; The mixed oxide powder is composed of one or a mixture of two or more of silicon dioxide, titanium dioxide, aluminum oxide, and iron oxide; The metal elemental powder is composed of one or a mixture of two or more of manganese powder, iron powder, aluminum powder, magnesium powder, and copper powder; In the ferro-titanium alloy powder, the weight ratio of titanium element to iron element is 7.2:2.5, and the balance is inevitable impurity elements; in the ferro-zirconium alloy powder, the weight percentage of zirconium element is 80%.

[0010] The arc stabilizing agent includes one or more compositions of potassium titanate, lithium titanate, sodium titanate, potassium chloride, and sodium chloride; The metal nitride powder includes at least one of ferromanganese nitride powder and ferrochromium nitride powder; The rare earth fluoride powder is at least one of lanthanum fluoride, cerium fluoride, and yttrium fluoride; The weight ratio of the ferro titanium alloy to the ferro zirconium alloy is 2:1; The weight ratio of the chromium powder to the metal nitride powder is ≥10:1; The preparation method of the high nitrogen and high elongation stainless steel flux cored wire includes the following steps: (1) Roll the 316L stainless steel strip into a U shape, and add the formula amount of flux cored powder into the U-shaped groove; (2) Close the U-shaped groove and roll it into an O-shaped steel pipe, and control the flux cored powder filling rate to be 23-28%; (3) The O-shaped steel pipe is subjected to roll die rolling, sizing die drawing, bright annealing at 800°C and surface cleaning treatment to make a Φ2.0mm wire; (4) The Φ2.0mm wire is subjected to drawing and diameter reduction, bright annealing at 800°C again and surface cleaning treatment to make a Φ1.2mm wire.

[0011] Further, in step (3), 5 groups of 30 passes of roll die rolling and 1 pass of sizing die drawing are adopted; in step (4), 10 passes of drawing and diameter reduction dies are adopted.

[0012] Application of the stainless steel flux cored wire in a high nitrogen and high elongation weld. When the flux cored wire uses an argon-rich gas for groove welding of the stainless steel base material, the nitrogen element weight percentage content in the weld cladding metal of the wire is 0.20-0.30%, the nickel element weight percentage content is 7.5-10%, and the elongation rate ≥30%.

[0013] Further, the argon-rich gas is: 80% Ar + 20% CO2 or 95% Ar + 5% CO2.

[0014] Compared with the prior art, the beneficial effects of the present invention are: (1) The nitrogen element in the stainless steel strip is the main source of the nitrogen element in the weld cladding metal. It acts synergistically with the metal nitride powder added in the flux cored powder. In order to prevent the situation that the nitrogen element in the metal nitride powder added in the flux cored powder has a relatively low over coefficient, resulting in the nitrogen element in the weld cladding metal still not meeting the standard. At the same time, compared with the situation where the metal nitride in the flux cored powder is the main source of the nitrogen element, the production cost of the strip containing nitrogen element is relatively low. And the strip and the flux core supply nitrogen synergistically, effectively improving the properties such as the tensile strength of the weld.

[0015] (2) In response to the requirement that a large amount of ferrite elements are needed in the E2209 stainless steel flux-cored powder to maintain the ferrite content in the weld, the present invention has made improvements on the basis of traditional 316L stainless steel strips: reducing the addition amount of nickel element (controlled at 11-12%), and at the same time increasing the addition amounts of manganese (Mn) and nitrogen (N) elements to optimize the microstructure of the weld, thereby improving the elongation.

[0016] (3) The invention increases the addition amount of zirconium (Zr) element in the flux-cored powder, so that the free nitrogen element combines with Zr to form a stable nitride ZrN. In addition, copper (Cu) element is added to improve the solubility of nitrogen element and promote the cold working plasticity of the flux-cored wire, thereby ensuring the formation of austenite during the welding cladding process and balancing the proportion and stability of austenite and ferrite in the weld cladding metal. The plastic deformation ability of the welded material is enhanced, thereby improving the elongation.

[0017] (4) Appropriate amounts of Ti and Zr elements are added to the flux-cored powder, so that Ti and Zr combine with N element to form stable compounds TiN and ZrN during the high-temperature welding cladding process, inhibiting the growth of weld metal grains, refining the microstructure, and enhancing the strength and toughness of the weld. At the same time, Zr can purify the molten pool, react with O in the molten pool as a deoxidizer to form low-density inclusions and float up to the slag, improving the weld purity.

[0018] (5) To avoid the precipitation of N element during the high-temperature welding cladding process, the stainless steel flux-cored wire obtained by the present invention is welded using an argon-rich gas (80% Ar + 20% CO2 or 95% Ar + 5% CO2), avoiding the excessive mixing of CO2 into the weld and forming ZrO2 inclusions that affect the weld toughness. Specific Embodiments

[0019] The present invention will be described in detail below with reference to embodiments. However, it should be understood that the following embodiments are only illustrative examples of the implementation modes of the present invention, rather than limiting the scope of the present invention.

[0020] The purity of rutile (TiO2) used in the following embodiments of the present invention is 97%; The mixed oxide powder used in the following embodiments of the present invention is composed of silica, titanium dioxide, alumina, and iron tetroxide in a mass ratio of 4:1:2:2. The fluoride used in the following embodiments of the present invention is composed of sodium fluoride and calcium fluoride in a mass ratio of 2:1. The purity of the manganese powder, aluminum powder, magnesium powder, copper powder, and iron powder used in the following embodiments of the present invention is 99.9%.

[0021] Example 1: A stainless steel flux-cored wire for preparing a high-nitrogen and high-elongation weld seam, with a diameter of Φ = 1.2 mm, consisting of a steel strip and flux-cored powder. The thickness of the steel strip is 0.4 mm, and the flux-cored powder is evenly filled and fills the cylindrical accommodating cavity formed by the steel strip. The filling rate of the flux-cored powder is 25%. The steel strip is a 316L stainless steel strip; The flux-cored powder, by weight percentage, has the following composition: rutile powder 10%; mixed oxide powder 10%; fluoride powder 2%; metal elemental powder 10%; ferrotitanium alloy powder 1%; ferrozirconium alloy powder 1%; nickel powder 2%; chromium powder 34%; molybdenum powder 8%; bismuth oxide powder 0.2%; arc stabilizing agent 2%; metal nitride powder 2%; rare earth fluoride powder 0.2%; the balance is iron powder; Among them, the metal elemental powder is composed of manganese powder, copper powder, and aluminum powder in a mass ratio of 4:1:1; in the ferrotitanium alloy powder, the weight ratio of titanium element to iron element is 7.2:2.5, and the balance is inevitable impurity elements; the arc stabilizing agent is composed of potassium titanate, sodium titanate, and sodium chloride in a mass ratio of 3:2:1; the metal nitride powder is ferrochromium nitride powder; the rare earth fluoride powder is composed of lanthanum fluoride and cerium fluoride in a mass ratio of 2:1; The 316L stainless steel strip, by weight percentage, has the following composition: carbon 0.01%; silicon 0.02%; manganese 0.5%; sulfur 0.012%; phosphorus 0.008%; nickel 7%; chromium 16%; molybdenum 2.0%; aluminum 0.01%; titanium 0.05%; copper 0.05%; nitrogen 0.2%; the balance is iron.

[0022] A high-nitrogen and high-elongation stainless steel flux-cored wire, and its preparation method steps are as follows: (1) Roll the 316L stainless steel strip into a U shape through 6 groups of 24 rolling mills, and add the formula amount of flux-cored powder into the U-shaped groove; (2) Close the U-shaped groove and roll it into an O-shaped steel pipe through 5 groups of 20 rolling mills. The filling rate of the flux-cored powder in the O-shaped steel pipe is 25%; (3) Roll the O-shaped steel pipe through 5 groups of 30 roll dies, draw it through 1 sizing die, anneal it brightly at 800 °C with a wire annealing machine, and perform surface cleaning treatment to make a Φ2.0 mm stainless steel flux-cored wire; (4) The obtained Φ2.0 mm wire is further drawn through 10 drawing and reducing dies, annealed brightly again at 800 °C with a wire annealing machine, and surface cleaned to make a Φ1.2 mm stainless steel flux-cored wire.

[0023] Example 2: A high-nitrogen and high-elongation stainless steel flux-cored wire with a diameter of Φ = 1.2 mm, which is composed of iron skin and flux-cored powder. The thickness of the iron skin is 0.4 mm. The flux-cored powder is evenly filled and fills the cylindrical accommodating cavity formed by the iron skin. The filling rate of the flux-cored powder is 23%. The iron skin is a 316L stainless steel strip; The flux-cored powder, by weight percentage, has the following composition: rutile powder 12%; mixed oxide powder 12%; fluoride powder 3%; metal elemental powder 12%; ferro-titanium alloy powder 2%; ferro-zirconium alloy powder 2%; nickel powder 2%; chromium powder 36%; molybdenum powder 10%; bismuth oxide powder 0.2%; arc stabilizing agent 2%; metal nitride powder 3%; rare earth fluoride powder 0.4%; iron powder as the balance; Among them, the metal elemental powder is composed of manganese powder, copper powder, and aluminum powder according to a mass ratio of 3:3:1; in the ferro-titanium alloy powder, the weight ratio of titanium element to iron element is 7.2:2.5, and the balance is inevitable impurity elements; the arc stabilizing agent is composed of potassium titanate and sodium titanate according to a mass ratio of 1:1; the metal nitride powder is ferro-chromium nitride powder; the rare earth fluoride powder is lanthanum fluoride; The 316L stainless steel strip, by weight percentage, has the following composition: carbon 0.012%; silicon 0.02%; manganese 0.8%; sulfur 0.014%; phosphorus 0.008%; nickel 8%; chromium 18%; molybdenum 2.4%; aluminum 0.02%; titanium 0.05%; copper 0.1%; nitrogen 0.15%; the balance is iron.

[0024] A high-nitrogen and high-elongation stainless steel flux-cored wire, and its preparation method comprises the following steps: (1) Roll the 316L stainless steel strip into a U shape through 6 groups of 24 rolling mills, and add the formula amount of flux-cored powder into the U-shaped groove; (2) Close the U-shaped groove and roll it into an O-shaped steel pipe through 5 groups of 20 rolling mills. The filling rate of the flux-cored powder in the O-shaped steel pipe is 25%; (3) Roll the O-shaped steel pipe through 5 groups of 30 roller dies, draw it through 1 sizing die, anneal it brightly at 800 °C with a wire annealing machine, and perform surface cleaning treatment to make a Φ2.0 mm stainless steel flux-cored wire; (4) The obtained Φ2.0 mm wire is further drawn through 10 drawing and reducing die drawing processes, annealed brightly again at 800 °C with a wire annealing machine, and surface cleaned to make a Φ1.2 mm stainless steel flux-cored wire.

[0025] Example 3: A high-nitrogen and high-elongation stainless steel flux-cored wire with a diameter of Φ = 1.2 mm, which is composed of iron skin and flux-cored powder. The thickness of the iron skin is 0.4 mm. The flux-cored powder is evenly filled and fills the cylindrical accommodating cavity formed by the iron skin. The filling rate of the flux-cored powder is 27%. The iron skin is a 316L stainless steel strip; The said flux-cored powder, by weight percentage, has the following composition: rutile powder 10%; mixed oxide powder 10%; fluoride powder 2%; metal elemental powder 15%; ferro-titanium alloy powder 1%; ferro-zirconium alloy powder 1%; nickel powder 1%; chromium powder 34%; molybdenum powder 5%; bismuth oxide powder 0.2%; arc stabilizing agent 2%; metal nitride powder 2.5%; rare earth fluoride powder 0.5%; iron powder as the balance; Among them, the metal elemental powder is composed of manganese powder and copper powder in a mass ratio of 5:4; in the ferro-titanium alloy powder, the weight ratio of titanium element to iron element is 7.2:2.5, and the balance is inevitable impurity elements; the arc stabilizing agent is composed of potassium titanate and sodium titanate in a mass ratio of 1:2; the metal nitride powder is ferro-chromium nitride powder; the rare earth fluoride powder is cerium fluoride; The said 316L stainless steel strip, by weight percentage, has the following composition: carbon 0.014%; silicon 0.03%; manganese 0.5%; sulfur 0.008%; phosphorus 0.011%; nickel 7.6%; chromium 20%; molybdenum 3.0%; aluminum 0.03%; titanium 0.07%; copper 0.14%; nitrogen 0.1%; the balance is iron.

[0026] A high-nitrogen and high-elongation stainless steel flux-cored wire, its preparation method steps are as follows: (1) Roll the 316L stainless steel strip into a U shape through 6 groups of 24 rolling mills, and add the formula amount of flux-cored powder into the U-shaped groove; (2) Close the U-shaped groove and roll it into an O-shaped steel pipe through 5 groups of 20 rolling mills. The filling rate of the flux-cored powder in the O-shaped steel pipe is 25%; (3) Roll the O-shaped steel pipe through 5 groups of 30 roller dies, draw it through 1 sizing die, anneal the wire at 800°C in a bright annealing furnace, and perform surface cleaning treatment to make a Φ2.0mm stainless steel flux-cored wire; (4) The obtained Φ2.0mm wire is further drawn through 10 drawing and reducing dies, annealed again at 800°C in a bright annealing furnace for the wire, and surface cleaning treatment is performed to make a Φ1.2mm stainless steel flux-cored wire.

[0027] Example 4: A high-nitrogen and high-elongation stainless steel flux-cored wire with a diameter of Φ = 1.2mm, which is composed of iron skin and flux-cored powder. The thickness of the iron skin is 0.4mm. The flux-cored powder is evenly filled and fills the cylindrical accommodating cavity formed by the iron skin. The filling rate of the flux-cored powder is 26%. The said iron skin is 316L stainless steel strip; The said flux-cored powder, by weight percentage, has the following composition: rutile powder 10%; mixed oxide powder 16%; fluoride powder 2%; metal elemental powder 15%; ferro-titanium alloy powder 1%; ferro-zirconium alloy powder 1%; nickel powder 2%; chromium powder 40%; molybdenum powder 10%; bismuth oxide powder 0.2%; arc stabilizing agent 2%; metal nitride powder 4%; rare earth fluoride powder 0.2%; iron powder as the balance; Among them, the elemental metal powder is composed of manganese powder, copper powder, magnesium powder, and aluminum powder in a mass ratio of 4:3:1:2; in the ferro-titanium alloy powder, the weight ratio of titanium element to iron element is 7.2:2.5, and the balance is inevitable impurity elements; the arc stabilizing agent is composed of potassium titanate, sodium titanate, and potassium chloride in a mass ratio of 1:1:1; the metal nitride powder is ferrochromium nitride powder; the rare earth fluoride powder is cerium fluoride; For the 316L stainless steel strip by weight percentage, the composition is as follows: carbon 0.02%; silicon 0.028%; manganese 1%; sulfur 0.004%; phosphorus 0.010%; nickel 7.2%; chromium 18%; molybdenum 2.3%; aluminum 0.016%; titanium 0.1%; copper 0.2%; nitrogen 0.1%; the balance is iron.

[0028] A high-nitrogen and high-elongation stainless steel flux-cored wire, and its preparation method steps are as follows: (1) Roll the 316L stainless steel strip into a U shape through 6 groups of 24 rolling mills, and add the formulated flux powder into the U-shaped groove; (2) Close the U-shaped groove and roll it into an O-shaped steel pipe through 5 groups of 20 rolling mills. The filling rate of the flux powder in the O-shaped steel pipe is 25%; (3) Roll the O-shaped steel pipe through 5 groups of 30 roller dies, draw it through 1 sizing die, anneal it brightly at 800°C with a wire annealing machine, and perform surface cleaning treatment to make a Φ2.0mm stainless steel flux-cored wire; (4) The obtained Φ2.0mm wire is further drawn through 10 drawing and reducing dies, annealed brightly again at 800°C with a wire annealing machine, and surface cleaned to make a Φ1.2mm stainless steel flux-cored wire.

[0029] Comparative Example 1: Compared with Example 1, the difference in Comparative Example 1 is only that no metal nitride powder is added in Comparative Example 1; other operations are the same as in Example 1.

[0030] Comparative Example 2: Compared with Example 1, the difference in Comparative Example 2 is only that the stainless steel strip in Comparative Example 2 does not contain nitrogen element or the nitrogen element content ≤ 0.01%, and the metal nitride content in the flux powder is 10%. Other operations are the same as in Example 1.

[0031] Comparative Example 3: Compared with Example 1, the difference in Comparative Example 3 is only that the nickel element content in the stainless steel strip in Comparative Example 3 is 13%; other operations are the same as in Example 1.

[0032] Comparative Example 4: Compared with Example 1, the difference in Comparative Example 4 is only that no zirconium ferroalloy powder is added in Comparative Example 4; other operations are the same as in Example 1.

[0033] Comparative Example 5: Compared with Example 1, the only difference is that in Comparative Example 5, the weight ratio of ferrotitanium alloy to ferrozirconium alloy is 1:2; other operations are the same as those in Example 1.

[0034] Comparative Example 6: Compared with Example 1, the only difference is that in Comparative Example 6, the welding shielding gas used is 20% Ar + 80% CO2; other operations are the same as those in Example 1.

[0035] Comparative Example 7: Compared with Example 1, the only difference is that in Comparative Example 7, the composition of the stainless steel strip used, by weight percentage, is: carbon 0.01%; silicon 0.028%; manganese 1%; sulfur 0.005%; phosphorus 0.010%; nickel 8%; chromium 20%; molybdenum 4%; aluminum 0.016%; titanium 0.1%; copper 0.4%; nitrogen 0.4%; the balance is iron.

[0036] Performance Test The flux-cored wires obtained in Examples 1-4 of the present invention and Comparative Examples 1-7 were used to perform groove welding on the base metal of UNS31803 duplex stainless steel with different argon-rich gases, and relevant performance tests were carried out on the weld cladding metals obtained respectively. Each group of parallel experiments was tested 10 times, and the average value was taken. The specific test results are shown in Tables 1 and 2. After the flux-cored wires obtained in Examples 1-4 of the present invention and Comparative Examples 1-7 were welded under the protection gases of 80% Ar + 20% CO2 and 95% Ar + 5% CO2, the compositions of the weld cladding metals obtained are shown in Table 3.

[0037] Weld deposit metal, tensile strength: The test standard is GB / T 228.1-2021.

[0038] Weld deposit metal, elongation at fracture: The test standard is GB / T 228.1-2021.

[0039] Weld deposit metal, impact energy: The test standard is GB / T 229-2020, the test temperature is -20 °C, and the notch type is U-shaped.

[0040] Table 1

[0041] Table 2

[0042] Table 3

[0043] In Comparative Example 1, the metal nitride powder was not added, and the nitrogen element in the weld cladding metal was supplemented by the excess of the stainless steel strip or the nitrogen element in the air during the welding process. The nitrogen element content in the cladding metal did not meet the standard, resulting in a decrease in the strength and toughness of the weld. In Comparative Example 2, an excessive amount of metal nitride powder was added, and the weight percentage ratio of Cr / N in the flux-cored powder was less than 10:1, resulting in the precipitation of coarse-grained nitride Cr2N in the weld, leading to a decrease in the strength and toughness of the weld. In Comparative Example 3, the nickel content in the stainless steel strip exceeded the standard, and the nickel content in the weld cladding metal was excessive. The synergistic balance of Ni, Cr, and Mo in the duplex stainless steel was damaged, resulting in a decrease in the strength and toughness of the weld. In Comparative Example 4, no ferrozirconium alloy powder was added. The C and N elements in the weld combined with the Ti element to form stable compounds TiC and TiN, and the binding ability of the Ti element was stronger than that of the Zr element, having no obvious effect on the strength and toughness of the weld. In Comparative Example 5, the mass ratio of ferrozirconium alloy and ferrotitanium alloy was increased. The nitrogen-fixing ability of the Zr element was relatively low, and the N element precipitated in the weld, resulting in a decrease in the nitrogen element content in the cladding metal. Moreover, excessive Zr elements formed coarse compounds ZrC or ZrN, becoming crack sources and reducing toughness. In Comparative Example 6, the shielding gas was changed to 20% Ar + 80% CO2. The inert gas provided insufficient protection for the N element. The thermal cycle of multi-layer multi-pass welding changed the distribution of nitrogen elements in the weld, exacerbating the diffusion loss or excessive precipitation of nitrogen elements. In Comparative Example 7, the contents of Mo, Cu, Ti, and N elements in the stainless steel strip increased significantly. On the one hand, it increased the solubility of the N element in the weld, resulting in an increase in the N element content in the weld. On the other hand, it decreased the Cr / N ratio in the weld, enhancing the precipitation of coarse-grained nitride Cr2N and affecting the strength and toughness of the weld.

[0044] Inspired by the ideal embodiments of the present invention described above, through the above description, relevant staff can make various changes and modifications without departing from the technical idea of this invention. The technical scope of this invention is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A high-nitrogen and high-elongation stainless steel flux-cored wire, characterized in that, It includes iron skin and flux-cored powder. The iron skin is 316L stainless steel strip, and the filling rate of the flux-cored powder is 23 - 28%; The 316L stainless steel strip, by weight percentage, has the following components: carbon 0.01% - 0.02%, silicon 0.02% - 0.04%, manganese 0.5% - 1%, sulfur < 0.03%, phosphorus < 0.04%, nickel 7% - 8%, chromium 16% - 20%, molybdenum 2.0% - 3.0%, aluminum 0.01% - 0.03%, titanium 0.05% - 0.1%, copper 0.05 - 0.2%, nitrogen 0.1% - 0.2%, and the balance is iron; The flux-cored powder, by weight percentage, has the following components: rutile powder 10 - 20%, mixed oxide powder 10 - 20%, fluoride powder 2 - 4%, metal elemental powder 10 - 30%, ferro-titanium alloy powder 1 - 4%, ferro-zirconium alloy powder 1 - 2%, nickel powder 1 - 4%, chromium powder 30 - 40%, molybdenum powder 4 - 12%, bismuth oxide powder 0.2 - 0.4%, arc stabilizing agent 2 - 6%, metal nitride powder 2 - 6%, rare earth fluoride powder 0.2 - 1%, and the balance is iron powder.

2. The high-nitrogen and high-elongation stainless steel flux-cored wire according to claim 1, wherein The mixed oxide powder is composed of at least one of silicon dioxide, titanium dioxide, aluminum oxide, and iron oxide; The metal elemental powder is composed of one or a mixture of two or more of manganese powder, iron powder, aluminum powder, magnesium powder, and copper powder.

3. The high-nitrogen and high-elongation stainless steel flux-cored wire according to claim 1, wherein, In the ferro-titanium alloy powder, the weight ratio of titanium element to iron element is 7.2:2.5, and the balance is inevitable impurity elements; in the ferro-zirconium alloy powder, the weight percentage of zirconium element is 80%.

4. The high-nitrogen and high-elongation stainless steel flux-cored wire according to claim 1, wherein The arc stabilizing agent includes at least one of potassium titanate, lithium titanate, sodium titanate, potassium chloride, and sodium chloride; The metal nitride powder is at least one of manganese nitride and ferro-chromium nitride.

5. The high-nitrogen and high-elongation stainless steel flux-cored wire according to claim 1, wherein The rare earth fluoride powder is at least one of lanthanum fluoride, cerium fluoride, and yttrium fluoride.

6. The high-nitrogen and high-elongation stainless steel flux-cored wire according to claim 1, wherein The weight ratio of the ferro-titanium alloy powder to the ferro-zirconium alloy powder is 2:1; the weight ratio of the chromium powder to the metal nitride powder ≥ 10:

1.

7. The preparation method of the high-nitrogen and high-elongation stainless steel flux-cored wire according to any one of claims 1-6, characterized in that, It includes the following steps: (1) Roll the 316L stainless steel strip into a U shape through multiple groups of rollers, and fill the U-shaped groove with flux-cored powder; (2) Close the U-shaped groove and roll it into an O-shaped steel pipe, and control the filling rate of the flux-cored powder to be 23 - 28%; (3) Subject the O-shaped steel pipe to roll die rolling, sizing die drawing, bright annealing, and surface cleaning treatment to make a Φ2.0mm welding wire; (4) Subject the Φ2.0mm welding wire to drawing and diameter reduction, secondary bright annealing, and surface cleaning treatment to make a Φ1.2mm welding wire.

8. Use of the high-nitrogen and high-elongation stainless steel flux-cored wire according to any one of claims 1-6, characterized in that: When using the flux-cored welding wire for groove welding of stainless steel base metal with argon-rich gas, the weight percentage of nitrogen element in the weld cladding metal is 0.20 - 0.30%, the weight percentage of nickel element is 7.5 - 10%, and the elongation ≥ 30%.

9. The application according to claim 8, wherein: The argon-rich gas is: 80% Ar + 20% CO2 or 95% Ar + 5% CO2.

Images