High nitrogen and high elongation stainless steel flux-cored wire and method of making same

Abstract

The present application relates to the technical field of flux-cored wire, and discloses a high-nitrogen high-elongation stainless steel flux-cored wire and a preparation method thereof.The flux-cored wire adopts a 316L stainless steel strip as an outer skin, and the optimized components of the flux-cored wire include 0.1%-0.2% nitrogen and 7%-8% nickel, and are matched with a special formula of core powder.The core powder contains 30%-40% chromium powder, 4%-12% molybdenum powder, 2%-6% metal nitride, zirconium-iron alloy and other components, and through the synergistic nitrogen supply mechanism of the steel strip and the core powder, the nitrogen content of the weld is 0.20-0.30%.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 the titanium-iron alloy is combined to refine the grains.The argon-rich gas protection welding is adopted to effectively inhibit the nitrogen loss and oxide inclusions.The obtained weld has a nickel content of 7.5-10% and an elongation of greater than or equal to 30%, and through nitrogen strengthening and microstructure regulation, the weld has high strength and plasticity while reducing the amount of nickel.

Description

TECHNICAL FIELD

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

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

[0003] Nitrogen is a strong austenite-forming element that can promote the formation of austenite phase and inhibit the excessive growth of ferrite at high temperatures, thereby maintaining the ideal proportion of austenite (γ) and ferrite (α) two-phase medium. This is particularly important for the balance of the microstructure after welding or hot working, avoiding the performance degradation caused by single-phase ferrite. The solid solution of nitrogen in austenite and ferrite can improve the mechanical properties of the material, especially the yield strength and tensile strength, while maintaining good toughness. By refining the 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 of welding materials are also increasing. Especially in terms of high strength, high toughness and corrosion resistance, traditional stainless steel wires cannot meet the needs of modern engineering in some specific applications. Although existing stainless steel flux-cored wires have good fluidity and formability during welding, their nitrogen content is generally low, which leads to insufficient strength and elongation of the weld, and problems such as weld brittleness and cracking, affecting the overall performance and service life of the welded structure.

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

[0006] Therefore, developing a stainless steel flux-cored wire with high nitrogen content and good ductility has become a technical problem to be solved in the field of welding materials. The present application aims to provide a high-nitrogen high-ductility stainless steel flux-cored wire, which significantly improves the nitrogen content and ductility of the weld by optimizing the composition and preparation process of the wire, thereby solving the problem of insufficient weld performance in the prior art and meeting the higher requirements of modern industry for welding materials. SUMMARY

[0007] The problem existing in the prior art is that the nickel powder in the core powder is expensive, and reducing the addition amount of nickel element while increasing the nitrogen element, but it is difficult to add nitrogen element in the weld cladding metal to reach the standard required weight percentage range, while also ensuring the standard required mechanical properties.

[0008] In view of the above problems, the present application provides a stainless steel flux-cored wire for preparing a high-nitrogen high-ductility weld and a preparation method and application thereof, comprising a shell and a core powder, the thickness of the shell is 0.4mm, the core powder is uniformly filled and fills the cylindrical cavity formed by the shell, the filling rate of the core powder is 23-28%, and the shell is a 316L stainless steel strip;

[0009] The 316L stainless steel strip contains the following components by weight percentage: 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.

[0010] The core powder contains the following components by weight percentage: rutile powder 10-20%; mixed oxide powder 10-20%; fluoride powder 2-4%; metal elemental powder 10-30%; titanium-iron alloy powder 1-4%; zirconium-iron alloy powder 1-2%; nickel powder 1-4%; chromium powder 30-40%; molybdenum powder 4-12%; bismuth oxide powder 0.2-0.4%; arc stabilizer 2-6%; metal nitride powder 2-6%; rare earth fluoride powder 0.2-1%; and the balance is iron powder.

[0011] 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;

[0012] 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;

[0013] The weight ratio of titanium element to iron element in the titanium-iron alloy powder is 7.2:2.5, and the balance is inevitable impurity elements; the weight percentage of zirconium element in the zirconium-iron alloy powder is 80%.

[0014] The arc stabilizing agent comprises one or a combination of more than two of potassium titanate, lithium titanate, sodium titanate, potassium chloride and sodium chloride.

[0015] The metal nitride powder comprises at least one of manganese-iron nitride powder and chromium-iron nitride powder.

[0016] The rare earth fluoride powder is at least one of lanthanum fluoride, cerium fluoride and yttrium fluoride.

[0017] The weight ratio of the titanium-iron alloy to the zirconium-iron alloy is 2:1.

[0018] The weight ratio of the chromium powder to the metal nitride powder is greater than or equal to 10:1.

[0019] The preparation method of the high-nitrogen and high-elongation stainless steel flux-cored wire comprises the following steps:

[0020] (1) rolling 316L stainless steel strip into a U-shaped form, and adding a formula amount of flux powder into the U-shaped groove;

[0021] (2) rolling the U-shaped groove into an O-shaped steel tube, and controlling the filling rate of the flux powder to be 23-28%;

[0022] (3) performing roller die rolling, sizing die drawing, 800 DEG C bright annealing and surface cleaning treatment on the O-shaped steel tube to obtain a Φ2.0 mm welding wire;

[0023] (4) performing drawing reduction on the Φ2.0 mm welding wire, and performing 800 DEG C bright annealing and surface cleaning treatment again to obtain a Φ1.2 mm welding wire.

[0024] Further, in step (3), 5 groups of 30 roller dies are adopted for rolling, and 1 sizing die is adopted for drawing; and in step (4), 10 drawing reduction dies are adopted.

[0025] The stainless steel flux-cored wire is applied in a high-nitrogen and high-elongation weld, the weight percentage of nitrogen element in the weld cladding metal of the stainless steel base material welded by using argon-rich gas is 0.20-0.30%, the weight percentage of nickel element is 7.5-10%, and the elongation is greater than or equal to 30%.

[0026] Further, the argon-rich gas is 80% Ar+20% CO2 or 95% Ar+5% CO2.

[0027] Compared with the prior art, the present application has the following beneficial effects:

[0028] (1) The nitrogen element in the stainless steel strip is the main source of the nitrogen element in the weld cladding metal, and cooperates with the metal nitride powder added in the cored powder. In order to prevent the nitrogen element in the metal nitride powder added in the cored powder from being too low, resulting in the nitrogen element in the weld cladding metal still not meeting the standard, compared with the case that the metal nitride in the cored powder is the main source of the nitrogen element, the production cost of the nitrogen element in the strip is relatively low. And the strip and the cored powder cooperate to supply nitrogen, effectively improving the tensile strength and other properties of the weld.

[0029] (2) In view of the need for a large amount of ferrite element in the E2209 stainless steel cored powder to maintain the ferrite content in the weld, the present application improves the traditional 316L stainless steel strip: reduces the addition amount of nickel element (controlled at 11-12%), and at the same time, increases the addition amount of manganese (Mn) and nitrogen (N) elements, so as to optimize the microstructure of the weld and improve the elongation.

[0030] (3) The application increases the addition amount of zirconium (Zr) element in the cored powder, so that the free nitrogen element combines with Zr to form stable nitride ZrN. In addition, copper (Cu) element is added to improve the solid solubility of nitrogen element and promote the cold working shaping of the cored wire, so as to ensure the formation of austenite in the welding cladding process, balance the proportion and stability of austenite and ferrite in the weld cladding metal. The plastic deformation ability of the material after welding is enhanced, so as to improve the elongation.

[0031] (4) The Ti and Zr elements in the cored powder are added in an appropriate amount, so that Ti and Zr combine with N element to form stable compounds TiN and ZrN during the welding high-temperature cladding process, inhibit the grain growth of the weld metal, refine the microstructure, and improve the strength and toughness of the weld. At the same time, Zr can purify the molten pool, react with O in the molten pool to form low-density inclusions and float to the slag as a deoxidizer, and improve the purity of the weld.

[0032] (5) In order to avoid the precipitation of N element during the welding high-temperature cladding process, the stainless steel cored wire obtained by the application is welded using argon-rich gas (80% Ar+20% CO2 or 95% Ar+5 CO2), so as to avoid the excessive mixing of CO2 in the weld, and form ZrO2 inclusions to affect the toughness of the weld. DETAILED DESCRIPTION

[0033] The application will be described in detail below in conjunction with the embodiments. However, it should be understood that the following embodiments are only exemplary descriptions of the embodiments of the application, and are not limitations on the scope of the application.

[0034] The rutile (TiO2) used in the following examples of the application has a purity of 97%;

[0035] The mixed oxide powder used in the following examples of the present application is composed of silicon dioxide, titanium dioxide, aluminum oxide, and triiron tetroxide in a mass ratio of 4:1:2:2. The fluoride used in the following examples of the present application 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 examples of the present application is 99.9%.

[0036] Example 1: A stainless steel flux-cored wire for preparing a high-nitrogen high-elongation weld, with a diameter Φ = 1.2 mm, composed of a sheath and a core powder, the thickness of the sheath being 0.4 mm, the core powder uniformly filling and filling the cylindrical cavity formed by the sheath, the filling rate of the core powder being 25%, the sheath being a 316L stainless steel strip;

[0037] The core powder, in terms of weight percentage, is composed of: rutile powder 10%; mixed oxide powder 10%; fluoride powder 2%; elemental metal 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 stabilizer 2%; metal nitride powder 2%; rare earth fluoride powder 0.2%; iron powder in the balance;

[0038] The elemental metal powder is composed of manganese powder, copper powder, and aluminum powder in a mass ratio of 4:1:1; the ferrotitanium alloy powder has a weight ratio of titanium to iron of 7.2:2.5, with the balance being unavoidable impurity elements; the arc stabilizer is composed of potassium titanate, sodium titanate, and sodium chloride in a mass ratio of 3:2:1; the metal nitride powder is chromium-iron nitride powder; the rare earth fluoride powder is composed of lanthanum fluoride and cerium fluoride in a mass ratio of 2:1;

[0039] The 316L stainless steel strip, in terms of weight percentage, is composed of: carbon 0.01%; silicon 0.02%; manganese 0.5%;

[0040] 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%; and the balance being iron.

[0041] A high-nitrogen high-elongation stainless steel flux-cored wire, the preparation method steps being as follows:

[0042] (1) A 316L stainless steel strip is rolled into a U shape by 6 groups of 24 rollers, and the formula amount of core powder is added to the U-shaped groove;

[0043] (2) The U-shaped groove is closed by 5 groups of 20 rollers to form an O-shaped steel pipe, and the filling rate of the core powder in the O-shaped steel pipe is 25%;

[0044] (3) The O-shaped steel pipe is rolled by 5 sets of 30 rollers, drawn by 1 sizing die, bright annealed at 800℃ by the welding wire annealing machine, and cleaned to produce Φ2.0mm stainless steel flux-cored welding wire;

[0045] (4) The obtained Φ2.0mm welding wire is then subjected to 10 drawing and diameter reduction grinding processes, bright annealing at 800℃ in a welding wire annealing machine, and surface cleaning treatment to produce Φ1.2mm stainless steel flux-cored welding wire.

[0046] Example 2: A high-nitrogen, high-elongation stainless steel flux-cored welding wire with a diameter of Φ=1.2mm, composed of iron sheet and flux powder. The thickness of the iron sheet is 0.4mm. The flux powder uniformly fills and saturates the cylindrical cavity formed by the iron sheet. The filling rate of the flux powder is 23%. The iron sheet is 316L stainless steel strip.

[0047] The core powder, by weight percentage, comprises the following: 12% rutile powder; 12% mixed oxide powder; 3% fluoride powder; 12% elemental metal powder; 2% ferrotitanium alloy powder; and 2% ferrizirconium alloy powder.

[0048] Nickel powder 2%; Chromium powder 36%; Molybdenum powder 10%; Bismuth oxide powder 0.2%; Arc stabilizer 2%; Metal nitride powder 3%; Rare earth fluoride powder 0.4%; Iron powder balance;

[0049] The metal element powder is composed of manganese powder, copper powder, and aluminum powder in a mass ratio of 3:3:1; the titanium-iron alloy powder has a titanium to iron element weight ratio of 7.2:2.5, with the remainder being unavoidable impurity elements; the arc stabilizer is composed of potassium titanate and sodium titanate in a mass ratio of 1:1; the metal nitride powder is chromium nitride powder; and the rare earth fluoride powder is lanthanum fluoride.

[0050] The 316L stainless steel strip has the following composition by weight percentage: 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%; balance iron.

[0051] A high-nitrogen, high-elongation stainless steel flux-cored welding wire, the preparation method of which includes the following steps:

[0052] (1) Roll the 316L stainless steel strip into a U-shape using 6 sets of 24 rolls, and add the prescribed amount of core powder into the U-shaped groove;

[0053] (2) The U-shaped groove is rolled into an O-shaped steel pipe by 5 sets of 20 rolls, and the filling rate of the core powder in the O-shaped steel pipe is 25%;

[0054] (3) The O-shaped steel tube is drawn by 5 groups of 30 roller dies, 1 sizing die, 800℃ bright annealing by the wire annealing machine, and surface cleaning treatment to produce Φ2.0mm stainless steel flux-cored wire;

[0055] (4) The obtained Φ2.0mm wire is further drawn by 10 drawing reducing dies, 800℃ bright annealing by the wire annealing machine again, and surface cleaning treatment to produce Φ1.2mm stainless steel flux-cored wire.

[0056] Example 3: A high-nitrogen and high-elongation stainless steel flux-cored wire with a diameter of Φ=1.2mm, which is composed of a shell and a core powder, the thickness of the shell is 0.4mm, the core powder uniformly fills and fills the cylindrical cavity formed by the shell, the filling rate of the core powder is 27%, and the shell is a 316L stainless steel strip;

[0057] The core powder, in terms of weight percentage, has the following components: 10% rutile powder; 10% mixed oxide powder; 2% fluoride powder; 15% elemental metal powder; 1% titanium-iron alloy powder; 1% zirconium-iron alloy powder; 1% nickel powder; 34% chromium powder; 5% molybdenum powder; 0.2% bismuth oxide powder; 2% arc stabilizer; 2.5% metal nitride powder; 0.5% rare earth fluoride powder; and the balance is iron powder.

[0058] The elemental metal powder is composed of manganese powder and copper powder in a mass ratio of 5:4; the titanium-iron alloy powder has a titanium to iron weight ratio of 7.2:2.5, with the balance being unavoidable impurity elements; the arc stabilizer is composed of potassium titanate and sodium titanate in a mass ratio of 1:2; the metal nitride powder is chromium-iron nitride powder; and the rare earth fluoride powder is cerium fluoride;

[0059] The 316L stainless steel strip, in terms of weight percentage, has the following components: 0.014% carbon; 0.03% silicon; 0.5% manganese; 0.008% sulfur; 0.011% phosphorus; 7.6% nickel; 20% chromium; 3.0% molybdenum; 0.03% aluminum; 0.07% titanium; 0.14% copper; 0.1% nitrogen; and the balance is iron.

[0060] A high-nitrogen and high-elongation stainless steel flux-cored wire, and the preparation method steps are as follows:

[0061] (1) The 316L stainless steel strip is rolled into a U shape by 6 groups of 24 roller dies, and the formula amount of core powder is added to the U-shaped groove;

[0062] (2) The U-shaped groove is closed by 5 groups of 20 roller dies to form an O-shaped steel tube, and the filling rate of the core powder in the O-shaped steel tube is 25%;

[0063] (3) The O-shaped steel tube is drawn by 5 groups of 30 roller dies, 1 sizing die, 800℃ bright annealing by the wire annealing machine, and surface cleaning treatment to produce Φ2.0mm stainless steel flux-cored wire;

[0064] (4) The obtained Φ2.0mm wire is further drawn by 10 drawing reducing dies, 800℃ bright annealing by the wire annealing machine again, and surface cleaning treatment to produce Φ1.2mm stainless steel flux-cored wire.

[0065] Example 4: A high-nitrogen and high-elongation stainless steel flux-cored wire with a diameter of Φ=1.2mm, which is composed of a shell and a core powder, the thickness of the shell is 0.4mm, the core powder uniformly fills and fills the cylindrical cavity formed by the shell, the filling rate of the core powder is 26%, and the shell is a 316L stainless steel strip;

[0066] The core powder, in terms of weight percentage, has the following composition: 10% rutile powder; 16% mixed oxide powder; 2% fluoride powder; 15% elemental metal powder; 1% titanium-iron alloy powder; 1% zirconium-iron alloy powder; 2% nickel powder; 40% chromium powder; 10% molybdenum powder; 0.2% bismuth oxide powder; 2% arc stabilizer; 4% metal nitride powder; 0.2% rare earth fluoride powder; and the balance is iron powder.

[0067] 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; the titanium-iron alloy powder has a weight ratio of titanium to iron of 7.2:2.5, and the balance is unavoidable impurity elements; the arc stabilizer is composed of potassium titanate, sodium titanate, and potassium chloride in a mass ratio of 1:1:1; the metal nitride powder is chromium-iron nitride powder; and the rare earth fluoride powder is cerium fluoride;

[0068] The 316L stainless steel strip has the following composition in terms of weight percentage: 0.02% carbon; 0.028% silicon; 1% manganese; 0.004% sulfur; 0.010% phosphorus; 7.2% nickel; 18% chromium; 2.3% molybdenum; 0.016% aluminum; 0.1% titanium; 0.2% copper; 0.1% nitrogen; and the balance is iron.

[0069] A high-nitrogen and high-elongation stainless steel flux-cored wire, and the preparation method steps are as follows:

[0070] (1) The 316L stainless steel strip is rolled into a U-shaped tube by 6 groups of 24 roller dies, and the formula amount of core powder is added to the U-shaped groove;

[0071] (2) The U-shaped groove is closed by 5 groups of 20 roller dies to form an O-shaped steel tube, and the filling rate of the core powder in the O-shaped steel tube is 25%;

[0072] (3) The O-shaped steel tube is drawn by 5 groups of 30 roller dies, 1 sizing die, 800°C bright annealing by a welding wire annealing machine, and surface cleaning treatment to produce a Φ2.0 mm stainless steel flux-cored wire;

[0073] (4) The obtained Φ2.0 mm welding wire is further drawn by 10 drawing reducing dies, 800°C bright annealing by a welding wire annealing machine, and surface cleaning treatment to produce a Φ1.2 mm stainless steel flux-cored wire.

[0074] Comparative Example 1: Comparative Example 1 is the same as Example 1 except that no metal nitride powder is added in Comparative Example 1.

[0075] Comparative Example 2: Comparative Example 2 is the same as Example 1 except that the stainless steel strip contains no nitrogen element or the nitrogen element content is ≤0.01%, and the metal nitride content in the flux powder is 10% in Comparative Example 2. Other operations are the same as those in Example 1.

[0076] Comparative Example 3: Comparative Example 3 is the same as Example 1 except that the nickel element content in the stainless steel strip is 13% in Comparative Example 3. Other operations are the same as those in Example 1.

[0077] Comparative Example 4: Comparative Example 4 is the same as Example 1 except that no zirconium-iron alloy powder is added in Comparative Example 4. Other operations are the same as those in Example 1.

[0078] Comparative Example 5: Comparative Example 5 is the same as Example 1 except that the weight ratio of titanium-iron alloy to zirconium-iron alloy is 1:2 in Comparative Example 5. Other operations are the same as those in Example 1.

[0079] Comparative Example 6: Comparative Example 6 is the same as Example 1 except that the welding protective gas used in Comparative Example 6 is 20% Ar + 80% CO2. Other operations are the same as those in Example 1.

[0080] Comparative Example 7: Comparative Example 7 is the same as Example 1 except that the composition of the stainless steel strip used in Comparative Example 7 is, by weight percentage: 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%; and the balance is iron.

[0081] Performance Test

[0082] The core wire obtained in each of the embodiments 1-4 and the comparative examples 1-7 is used to bevel weld a UNS31803 duplex stainless steel base material using different argon-rich gases, and the weld overlay metal obtained is tested for relevant performance, 10 times of parallel experiment testing are performed for each group, and the average value is taken, and the specific test results are shown in Tables 1 and 2. After the core wire obtained in each of the embodiments 1-4 and the comparative examples 1-7 is welded under 80% Ar+20% CO2 and 95% Ar+5% CO2 protective gas, the composition of the weld overlay metal obtained is shown in Table 3.

[0083] Weld overlay metal, tensile strength: the test standard is GB / T 228.1-2021.

[0084] Weld overlay metal, elongation at break: the test standard is GB / T 228.1-2021.

[0085] Weld overlay metal, impact energy: the test standard is GB / T 229-2020, the test temperature is-20℃, and the notch type is U type.

[0086] Table 1

[0087]

[0088] Table 2

[0089]

[0090] Table 3

[0091]

[0092] In the comparative example 1, no metal nitride powder is added, the nitrogen element in the weld overlay metal is excessive or supplemented by the nitrogen element in the air during welding, the nitrogen element content in the weld overlay metal is not up to standard, and the strength and toughness of the weld are reduced;

[0093] In the comparative example 2, the amount of metal nitride powder added is excessive, and the weight percentage ratio of Cr / N in the core powder is less than 10:1, which causes the coarse-grained nitride Cr2N to precipitate in the weld, and the strength and toughness of the weld are reduced;

[0094] In the comparative example 3, the nickel content in the stainless steel strip is excessive, the nickel content in the weld overlay metal is excessive, the balance of the synergistic effect of Ni, Cr and Mo in the duplex stainless steel is destroyed, and the strength and toughness of the weld are reduced;

[0095] In the comparative example 4, no zirconium-iron alloy powder is added, the C and N elements in the weld combine with the Ti element to form stable compounds TiC and TiN, and the Ti element has a stronger combination ability than the Zr element, which has no obvious effect on the strength and toughness of the weld;

[0096] In the comparative example 5, the mass ratio of zirconium-iron alloy and titanium-iron alloy is increased, the N-fixing capacity of Zr element is relatively low, N element is precipitated in the weld, the content of nitrogen element in the cladding metal is reduced; and excessive Zr element generates coarse compound ZrC or ZrN, which becomes a crack source to reduce the toughness;

[0097] In the comparative example 6, the protective gas is changed to 20% Ar+80% CO2, the inert gas is insufficient to protect N element, the heat cycle of multi-layer and multi-pass welding changes the distribution of nitrogen element in the weld, and the diffusion loss or excessive precipitation of nitrogen element is aggravated;

[0098] In the comparative example 7, the content of Mo, Cu, Ti and N elements in the stainless steel strip is obviously increased, on the one hand, the solid solubility of N element in the weld is increased, the content of N element in the weld is increased; on the other hand, the Cr / N ratio in the weld is reduced, the coarse grain nitride Cr2N is precipitated, and the strength and toughness of the weld are affected.

[0099] Based on the above ideal embodiments according to the present application, through the above description, relevant personnel can make various changes and modifications without deviating from the technical idea of the present application. The technical scope of the present application is not limited to the contents in the specification, and must be determined according to the scope of claims.

Claims

1. Use of a high nitrogen high ductility stainless steel flux cored wire, characterized in that, The flux-cored wire is used for beveling welding of stainless steel base material with argon-rich gas, the weld bead cladding metal of the wire has 0.20-0.30% of nitrogen and 7.5-10% of nickel, and the elongation is greater than or equal to 30%; the argon-rich gas is 80% Ar+20% CO2 or 95% Ar+5% CO2; The high-nitrogen and high-elongation stainless steel flux-cored wire comprises a sheath and a core powder, the sheath is a 316L stainless steel strip, and the core powder filling rate is 23-28%; The 316L stainless steel strip comprises, in percentage by weight, 0.01-0.02% of carbon, 0.02-0.04% of silicon, 0.5-1% of manganese, less than 0.03% of sulfur, less than 0.04% of phosphorus, 7-8% of nickel, 16-20% of chromium, 2.0-3.0% of molybdenum, 0.01-0.03% of aluminum, 0.05-0.1% of titanium, 0.05-0.2% of copper, and 0.1-0.2% of nitrogen, and the balance is iron; the copper element is used to improve the solid solubility of nitrogen; The core powder comprises, in percentage by weight, 10-20% of rutile powder, 10-20% of mixed oxide powder, 2-4% of fluoride powder, 10-30% of metal element powder, 1-4% of titanium-iron alloy powder, 1-2% of zirconium-iron alloy powder, 1-4% of nickel powder, 30-40% of chromium powder, 4-12% of molybdenum powder, 0.2-0.4% of bismuth oxide powder, 2-6% of arc stabilizing agent, 2-6% of metal nitride powder, 0.2-1% of rare earth fluoride powder, and the balance is iron powder; the weight ratio of the titanium-iron alloy to the zirconium-iron alloy is 2:1; the Ti and Zr elements in the core powder combine with N element to form stable compounds TiN and ZrN in the welding high-temperature cladding process.

2. Use of the high nitrogen high ductility stainless steel flux cored wire according to claim 1, characterized in that, The mixed oxide powder is composed of at least one of silicon dioxide, titanium dioxide, aluminum oxide and iron oxide; The metal element 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. Use of the high nitrogen high ductility stainless steel flux cored wire according to claim 1, characterized in that, The weight ratio of titanium element to iron element in the titanium-iron alloy powder is 7.2:2.5, and the balance is inevitable impurity elements; the weight percentage of zirconium element in the zirconium-iron alloy powder is 80%.

4. Use of the high nitrogen high ductility stainless steel flux cored wire according to claim 1, characterized in that, The arc stabilizing agent comprises 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 chromium-iron nitride.

5. Use of the high nitrogen high ductility stainless steel flux cored wire according to claim 1, characterized in that, The rare earth fluoride powder is at least one of lanthanum fluoride, cerium fluoride and yttrium fluoride.

6. Use of the high nitrogen high stretch stainless steel flux cored wire according to claim 1, characterized in that, The weight ratio of the chromium powder to the metal nitride powder is greater than or equal to 10:

1.

7. Use of the high-nitrogen high-ductility stainless steel flux-cored wire according to any one of claims 1-6, characterized in that, The preparation method of the high-nitrogen and high-elongation stainless steel flux-cored wire comprises the following steps: (1) rolling the 316L stainless steel strip into a U shape through multiple groups of rollers, and filling the core powder into the U-shaped groove; (2) rolling the U-shaped groove into an O-shaped steel pipe, and controlling the core powder filling rate to be 23-28%; (3) rolling the O-shaped steel pipe through a roll die, drawing through a sizing die, bright annealing and surface cleaning treatment to prepare a Φ2.0 mm wire; (4) reducing the diameter of the Φ2.0 mm wire through drawing, bright annealing again and surface cleaning treatment to prepare a Φ1.2 mm wire.

Images