High-temperature oxidation resistant 409ti flux-cored wire for additive manufacturing of automobile exhaust system and preparation method thereof

Abstract

The application discloses a high-temperature oxidation resistant 409Ti flux-cored wire for additive manufacturing of an automobile exhaust system and a preparation method thereof. The outer skin is made of low-carbon steel strips, and the core is composed of the following components with mass percentages: C 0.05%-0.1%, Si 0.5%-1.0%, Mo 0.1%-0.5%, Cu 2.0%-3.0%, Al 1.5%-6.0%, Cr 11.0%-14.0%, Mn 7.0%-10.0%, Ni 0.5%-1.0%, Nb 0.2%-1.0%, Ti 0.1%-0.5%, Ce 0.05%-0.1%, W 0.5%-2.0%, and the balance is iron powder. The core powder is filled into a U-shaped groove rolled by a low-carbon steel strip, and then closed and drawn to form the flux-cored wire. When the flux-cored wire is used for welding of a 409 type ferrite stainless steel pipeline of an automobile exhaust system, the high-temperature oxidation rate is reduced by nearly 90%, and the weld performance meets the requirements of the automobile welding quality standard.

Description

Technical Field

[0001] This invention belongs to the field of welding materials, specifically relating to a high-temperature resistant oxidized 409Ti flux-cored welding wire for additive manufacturing of automotive exhaust systems and its preparation method. Background Technology

[0002] The automotive exhaust system mainly consists of the exhaust manifold, front pipe, catalytic converter, muffler, middle pipe, and tailpipe. In recent years, with the implementation of the Euro VI standard in Europe from January 1, 2013, my country has also fully implemented the corresponding emission standards. As exhaust emission standards continue to rise, exhaust temperatures are also increasing, sometimes reaching 950-1050℃. The 409 and 439 types of ferritic stainless steel, developed in recent years, have become the preferred material for exhaust systems due to their low cost, low coefficient of linear expansion, high strength, good thermal conductivity, and high corrosion resistance. This is especially true for the manifold and front pipe, which are located at high temperatures, as these components are directly connected to the engine and require high performance in high-temperature environments such as high-temperature fatigue, thermal fatigue, and high-temperature oxidation. The catalytic converter in the automotive exhaust system plays a crucial role in three-way catalysis, and its effective catalytic action occurs at temperatures exceeding 1000℃. Therefore, the materials used for the catalytic converter housing and welds also require excellent resistance to high-temperature oxidation. Meanwhile, because the catalytic converter is located in a place where it is easily exposed to the outside world, especially in cars used in coastal areas and snow-melting areas, the outer shell of the catalytic converter is also susceptible to high-temperature salt corrosion, making the high-temperature salt corrosion resistance of the weld metal particularly important.

[0003] Currently, the welding of automotive exhaust systems, especially the welding of 409 ferritic stainless steel, which accounts for the majority of automotive exhaust system materials, mainly focuses on improving the plasticity and toughness of the joints and controlling welding costs. However, there is very little research on the high-temperature oxidation resistance of welded joints in high-temperature environments (above 950°C) such as automotive exhaust system manifolds, front pipes, and catalytic converters, and there is no practical and corresponding flux-cored welding wire. Summary of the Invention

[0004] To address the aforementioned problems, the main objective of this invention is to provide a high-temperature oxidation-resistant 409Ti flux-cored welding wire for additive manufacturing of automotive exhaust systems, which nearly doubles the high-temperature oxidation resistance, corrosion resistance, and thermal fatigue performance of welded joints in automotive exhaust systems under high-temperature environments (above 950°C).

[0005] Another objective of this invention is to provide a method for preparing the high-temperature resistant oxidized 409Ti flux-cored welding wire for additive manufacturing of automotive exhaust systems, which has a simple process.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] The first aspect of this invention provides a high-temperature resistant oxidized 409Ti flux-cored welding wire for additive manufacturing of automotive exhaust systems, comprising an outer sheath and a flux core. The outer sheath is made of low-carbon steel strip, and the flux core is composed of the following components in weight percentage: C: 0.05%-0.1%, Si: 0.5%-1.0%, Mo: 0.1%-0.5%, Cu: 2.0%-3.0%, Al: 1.5%-6.0%, Cr: 11.0%-14.0%, Mn: 7.0%-10.0%, Ni: 0.5%-1.0%, Nb: 0.2%-1.0%, Ti: 0.1%-0.5%, Ce: 0.05%-0.1%, W: 0.5%-2.0%, with the balance being iron powder.

[0008] Preferably, the outer skin is made of low-carbon steel strip with a width of 10-12mm and a thickness of 0.4-0.8mm.

[0009] Preferably, the low-carbon steel strip used for the outer skin has the following composition and mass percentage: C: 0.01%-0.1%, Si: 0.05%-0.2%, Mn: 0.1%-0.5%, P≤0.01%, S≤0.01%, N≤0.005%, Nb: 0.01%-0.2%, Ti: 0.005%-0.1%, Mo: 0.1%-1.0%, with the balance being Fe and unavoidable impurities.

[0010] Preferably, the filling rate of the core is controlled at 20%-22.5%.

[0011] Preferably, the composition of the core material satisfies the following conditions: when the content of W is 0.5%-2.0%, the content of Ce is 0.05%-0.1%, and the W / Ce ratio is 20:1. Under this ratio, the welded joint has excellent resistance to high-temperature oxidation and thermal fatigue.

[0012] Preferably, Cr and W are added in metallic form, Mn is added in the form of electrolytic manganese, Ti is added in the form of ferrotitanium, C is added in the form of graphite, and Ce is added in the form of cerium oxide powder.

[0013] Preferably, the particle size of the components in the core is 80-200 mesh.

[0014] Preferably, the component content of the core material satisfies the following condition: the content of impurity elements S and P is less than 0.03%.

[0015] Preferably, the component content of the core material satisfies: Ti / Nb = 1:2.

[0016] Preferably, the composition content of the low-carbon steel strip satisfies: Ti / Nb = 1:2.

[0017] Preferably, the component content of the core material satisfies the following ratio: Cu / Al = 1:2.

[0018] The high-temperature oxidation-resistant 409Ti flux-cored welding wire used in the additive manufacturing of automotive exhaust systems of this invention exhibits a nearly 90% reduction in oxidation rate after welding in an air environment at 1000℃. Its weld metal has excellent high-temperature oxidation resistance, and the welding process and mechanical properties are also excellent. The bonding strength between the substrate and the weld meets the requirements of dynamic and static load applications in high-temperature environments. It also allows for multi-layer, multi-pass welding to accommodate different weld thicknesses. During multi-layer welding, the interpass temperature is controlled below 100℃ to reduce weld joint embrittlement. The design concept is as follows: In the flux core, a very small amount of carbon can improve weld strength; Si and Mn act as deoxidizers and compensate for low Cr content in the weld; Mo improves the strength, hardness, and corrosion resistance of the weld metal; Cu improves the corrosion resistance and plasticity of the weld metal; Al improves the oxidation resistance of the weld metal at room temperature and high temperatures; Cr improves the corrosion resistance of the weld; Ni improves the toughness of the weld; Nb and Ti improve the resistance to intergranular corrosion; and W and Ce are added in a coordinated manner to refine the grains, improving the weld's high-temperature oxidation resistance, corrosion resistance, and toughness. The functions of each component are as follows:

[0019] C: It can react with other alloying elements to form carbides, which can play a solid solution strengthening role in weld metal.

[0020] Si has an arc-stabilizing effect, and when its content is less than 1%, it also has a deoxidizing effect and can compensate for the low Cr content in terms of antioxidant properties.

[0021] Mn: A layer of MnCr2O4 is formed between the matrix and the outer oxide layer to improve the weld's resistance to cyclic oxidation, inhibit abnormal oxidation, enhance the strength of the weld oxide layer, and prevent oxide layer peeling.

[0022] Mo: Increases the stability of the passivation film on the weld surface, improving the vehicle's resistance to chloride stress corrosion in high-temperature salt corrosion environments.

[0023] Cu: Inhibits anodic dissolution in welds and improves the corrosion resistance of welds.

[0024] Al: gives the weld excellent oxidation resistance at high temperatures.

[0025] Cr: helps form a stable oxide film in the weld and reduces the weld's susceptibility to intergranular corrosion.

[0026] Ni: Improves the plasticity and toughness of the weld and enhances its corrosion resistance in corrosive media.

[0027] Nb combines with excess carbon in the weld to form a stable compound NbC, preventing the formation of chromium-depleted zones in the weld and improving the weld's resistance to intergranular corrosion.

[0028] Ti combines with excess nitrogen in the weld to form a stable compound TiN, preventing the formation of chromium-depleted zones in the weld and improving the weld's resistance to intergranular corrosion.

[0029] W: It has a strong grain-refining effect and can effectively improve the heat resistance, high-temperature strength and oxidation resistance of welds at high temperatures for a long time.

[0030] Ce: Promotes the transformation of columnar crystals to equiaxed crystals in the heat-affected zone of the weld, refines the grains, reduces the sensitization effect in the chromium-depleted zone of the weld, and improves the corrosion resistance and toughness of the weld.

[0031] A second aspect of the present invention also provides a method for preparing the above-mentioned high-temperature oxidized 409Ti flux-cored welding wire for additive manufacturing of automotive exhaust systems, comprising the following steps:

[0032] Step 1: Weigh each component of the core according to the above proportions and mix them evenly. Dry the core powder in a dryer at 250-300℃ for 1 hour.

[0033] Step 2: The low-carbon steel strip is placed on the feeding machine of the welding wire forming machine. The low-carbon steel strip is rolled into a U-shaped groove by the pressing groove of the forming machine. The flux core powder obtained in Step 1 is filled into the U-shaped groove. The U-shaped groove is closed by the forming machine. Then it is drawn to a diameter of 1.0-1.2mm. The oil and moisture on the surface of the welding wire are removed by a degreasing machine and a dryer.

[0034] The third aspect of the present invention also provides the application of the high-temperature resistant oxidation-resistant 409Ti flux-cored welding wire for additive manufacturing of automotive exhaust systems in the welding of 409 type ferritic stainless steel pipes in automotive exhaust systems, with a welding current of 90-120A, an arc voltage of 14-16V, and a welding speed of 25-30cm / min.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] I. The high-temperature oxidation-resistant 409Ti flux-cored welding wire for additive manufacturing of automotive exhaust systems of this invention exhibits excellent arc stability, minimal welding spatter, aesthetically pleasing weld formation, high deposition rate, and all-position welding capability. The weld metal possesses excellent high-temperature oxidation resistance and relatively high joint toughness. When applied to welding 409 ferritic stainless steel pipes in automotive exhaust systems, the average oxidation rate of the weld in an air environment at 1000℃ is 0.022 / cm². 2 The high-temperature oxidation rate is reduced by nearly 90%, and the tensile strength is also significantly improved. The weld performance meets the requirements of the automotive welding quality standard GB / T18344-2016.

[0037] II. The present invention relates to a high-temperature oxidation-resistant 409Ti flux-cored welding wire for additive manufacturing of automotive exhaust systems, in which W and rare earth element Ce are added in a coordinated manner. The addition of W can form a Laves phase (Fe,Cr)₂(Nb,W) in ferritic stainless steel. This phase has a high melting point and hardness, is very stable at high temperatures, neither dissolving nor easily growing, thus maintaining the unbalanced microstructure at high temperatures at higher temperatures, thereby improving the high-temperature oxidation resistance and heat resistance of the weld. However, since the Laves phase reduces the plasticity and toughness of the weld, it is necessary to add an appropriate amount of rare earth element Ce to form a dispersed and fine Laves phase, thereby refining the grains and inhibiting grain growth, thus improving the weld toughness. Detailed Implementation

[0038] The present invention will be further described in detail below with reference to the embodiments, but the scope of protection of the present invention is not limited to the following embodiments.

[0039] The following embodiment provides a high-temperature resistant oxidized 409Ti flux-cored wire for additive manufacturing of automotive exhaust systems, comprising an outer sheath and a flux core. The outer sheath is made of low-carbon steel strip with a width of 10-12 mm and a thickness of 0.4-0.8 mm, and the composition and its mass percentage are as follows: C: 0.01%-0.1%, Si: 0.05%-0.2%, Mn: 0.1%-0.5%, P≤0.01%, S≤0.01%, N≤0.005%, Nb: 0.01%-0.2%, Ti: 0.005%-0.1%, Mo: 0.1%-1.0%, with the balance being Fe and unavoidable impurities.

[0040] Example 1

[0041] This embodiment provides a high-temperature oxidation-resistant 409Ti flux-cored wire for additive manufacturing of automotive exhaust systems. The flux-cored wire composition and its mass percentage are as follows: C: 0.05%, Si: 0.5%, Mo: 0.5%, Cu: 2.0%, Al: 4.0%, Cr: 12.0%, Mn: 7.0%, Ni: 0.5%, Nb: 0.2%, Ti: 0.1%, Ce: 0.05%, W: 1.0%, with the remainder being iron powder.

[0042] The flux-cored welding wire is prepared by the following method: weigh each component according to the above proportion and mix them evenly. Dry the mixture in a drying oven at 300℃ for 1 hour to obtain flux-cored powder. Place the low-carbon steel strip on the feeding machine of the welding wire forming machine. Roll the low-carbon steel strip into a U-shaped groove through the pressing groove of the forming machine. The filling rate is 20%. After the U-shaped groove is closed by the forming machine, it is drawn to a diameter of 1.0 mm. Finally, use a degreasing machine and a dryer to remove oil and moisture from the surface of the welding wire to obtain the final product.

[0043] Example 2

[0044] This embodiment provides a high-temperature resistant oxidized 409Ti flux-cored wire for additive manufacturing of automotive exhaust systems. The flux composition and its mass percentage are as follows: C: 0.05%, Si: 0.6%, Mo: 0.3%, Cu: 2.5%, Al: 5.0%, Cr: 13.0%, Mn: 8.0%, Ni: 0.6%, Nb: 0.4%, Ti: 0.2%, Ce: 0.05%, W: 2.0%, with the remainder being iron powder.

[0045] The flux-cored welding wire is prepared by the following method: weigh each component according to the above proportion and mix them evenly. Dry the mixture in a drying oven at 300℃ for 1 hour to obtain flux-cored powder. Place the low-carbon steel strip on the feeding machine of the welding wire forming machine. Roll the low-carbon steel strip into a U-shaped groove through the pressing groove of the forming machine. The filling rate is 20%. After the U-shaped groove is closed by the forming machine, it is drawn to a diameter of 1.2 mm. Finally, use a degreasing machine and a dryer to remove oil and moisture from the surface of the welding wire to obtain the final product.

[0046] Example 3

[0047] This embodiment provides a high-temperature resistant oxidized 409Ti flux-cored wire for additive manufacturing of automotive exhaust systems. The flux composition and its mass percentage are as follows: C: 0.05%, Si: 0.7%, Mo: 0.3%, Cu: 2.0%, Al: 4.0%, Cr: 13.0%, Mn: 8.0%, Ni: 0.7%, Nb: 0.6%, Ti: 0.3%, Ce: 0.1%, W: 2.0%, with the remainder being iron powder.

[0048] The flux-cored welding wire is prepared by the following method: weigh each component according to the above proportion and mix them evenly. Dry the mixture in a drying oven at 300℃ for 1 hour to obtain flux-cored powder. Place the low-carbon steel strip on the feeding machine of the welding wire forming machine. Roll the low-carbon steel strip into a U-shaped groove through the pressing groove of the forming machine. The filling rate is 20%. After the U-shaped groove is closed by the forming machine, it is drawn to a diameter of 1.2 mm. Finally, use a degreasing machine and a dryer to remove oil and moisture from the surface of the welding wire to obtain the final product.

[0049] Example 4

[0050] This embodiment provides a high-temperature resistant oxidized 409Ti flux-cored wire for additive manufacturing of automotive exhaust systems. The flux composition and its mass percentage are as follows: C: 0.05%, Si: 0.8%, Mo: 0.5%, Cu: 2.5%, Al: 5.0%, Cr: 14.0%, Mn: 8.0%, Ni: 0.8%, Nb: 0.8%, Ti: 0.4%, Ce: 0.1%, W: 1.0%, with the remainder being iron powder.

[0051] The flux-cored welding wire is prepared by the following method: weigh each component according to the above proportion and mix them evenly. Dry the mixture in a drying oven at 300℃ for 1 hour to obtain flux-cored powder. Place the low-carbon steel strip on the feeding machine of the welding wire forming machine. Roll the low-carbon steel strip into a U-shaped groove through the pressing groove of the forming machine. The filling rate is 20%. After the U-shaped groove is closed by the forming machine, it is drawn to a diameter of 1.0 mm. Finally, use a degreasing machine and a dryer to remove oil and moisture from the surface of the welding wire to obtain the final product.

[0052] Example 5

[0053] This embodiment provides a high-temperature resistant oxidized 409Ti flux-cored wire for additive manufacturing of automotive exhaust systems. The flux composition and its mass percentage are as follows: C: 0.05%, Si: 0.9%, Mo: 0.5%, Cu: 3.0%, Al: 6.0%, Cr: 13.0%, Mn: 10.0%, Ni: 0.9%, Nb: 1.0%, Ti: 0.5%, Ce: 0.05%, W: 0.5%, with the remainder being iron powder.

[0054] The flux-cored welding wire is prepared by the following method: weigh each component according to the above proportion and mix them evenly. Dry the mixture in a drying oven at 300℃ for 1 hour to obtain flux-cored powder. Place the low-carbon steel strip on the feeding machine of the welding wire forming machine. Roll the low-carbon steel strip into a U-shaped groove through the pressing groove of the forming machine. The filling rate is 20%. After the U-shaped groove is closed by the forming machine, it is drawn to a diameter of 1.0 mm. Finally, use a degreasing machine and a dryer to remove oil and moisture from the surface of the welding wire to obtain the final product.

[0055] Example 6

[0056] This embodiment provides a high-temperature resistant oxidized 409Ti flux-cored wire for additive manufacturing of automotive exhaust systems. The flux composition and its mass percentage are as follows: C: 0.05%, Si: 1.0%, Mo: 0.5%, Cu: 3.0%, Al: 6.0%, Cr: 14.0%, Mn: 10.0%, Ni: 1.0%, Nb: 1.0%, Ti: 0.5%, Ce: 0.1%, W: 0.5%, with the remainder being iron powder.

[0057] The flux-cored welding wire is prepared by the following method: weigh each component according to the above proportion and mix them evenly. Dry the mixture in a drying oven at 300℃ for 1 hour to obtain flux-cored powder. Place the low-carbon steel strip on the feeding machine of the welding wire forming machine. Roll the low-carbon steel strip into a U-shaped groove through the pressing groove of the forming machine. The filling rate is 20%. After the U-shaped groove is closed by the forming machine, it is drawn to a diameter of 1.0 mm. Finally, use a degreasing machine and a dryer to remove oil and moisture from the surface of the welding wire to obtain the final product.

[0058] Welding experiments were conducted on the flux-cored welding wires prepared in Examples 1-6 and conventional commercially available flux-cored welding wires used for welding 409 type ferritic stainless steel (Comparative Example 1 and Comparative Example 2). Tungsten inert gas (TIG) welding was used, with a shielding gas of 98% Ar + 2% O2, DC positive polarity, a tungsten electrode diameter of 2 mm, and a 20° cone head. After welding, the mechanical properties of the welds were tested, including the crucial oxidation kinetic analysis. The eight samples were placed in an air environment at 1000°C, and their oxidation rates were calculated by plotting oxidation weight gain curves to determine their resistance to high-temperature oxidation. The mechanical properties of the weld metal are shown in Tables 1 and 2 below.

[0059] Table 1: Mechanical properties of weld metal at room temperature (25℃)

[0060]

[0061] Table 2: Mechanical properties of weld metal at 1000℃

[0062]

[0063] As can be seen from Tables 1 and 2, the mechanical properties and oxidation rate at high temperature (1000℃) of Examples 1-6 are superior to those of Comparative Examples 1 and 2. The high-temperature oxidation 409Ti flux-cored welding wire used for additive manufacturing of automotive exhaust systems exhibits a tensile strength ≥23MPa, yield strength ≥15MPa, elongation after fracture ≥40%, hardness ≥177HV, and oxidation rate ≤0.025mg / cm at 1000℃. 2 The weldability of this material is significantly improved compared to existing flux-cored welding wires for 409 type ferritic stainless steel. Specifically, it features a more stable arc, less welding spatter, more aesthetically pleasing weld formation, higher deposition rate, and the ability to perform all-position welding. The weld metal exhibits excellent high-temperature oxidation resistance, as well as relatively high joint toughness and corrosion resistance, with a high-temperature oxidation rate reduced by nearly 90%.

[0064] The above description of the embodiments is intended to enable those skilled in the art to understand and use the present invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the principles of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A high-temperature resistant 409Ti flux-cored welding wire for additive manufacturing of automotive exhaust systems, characterized in that, Including the outer casing and the drug core; The outer sheath is made of low-carbon steel strip; The core is composed of the following components in weight percentage: C: 0.05%-0.1%, Si: 0.5%-1.0%, Mo: 0.1%-0.5%, Cu: 2.0%-3.0%, Al: 1.5%-6.0%, Cr: 11.0%-14.0%, Mn: 7.0%-10.0%, Ni: 0.5%-1.0%, Nb: 0.2%-1.0%, Ti: 0.1%-0.5%, Ce: 0.05%-0.1%, W: 0.5%-2.0%, with the balance being iron powder; The component content of the core meets the following conditions: when the content of W is 0.5%-2.0%, the content of Ce is 0.05%-0.1%, and the W / Ce ratio is 20:

1. The component content of the core material satisfies: Cu / Al = 1:2; The outer sheath uses a low-carbon steel strip with a width of 10-12 mm and a thickness of 0.4-0.8 mm. The composition and mass percentage of the low-carbon steel strip are as follows: C: 0.01%-0.1%, Si: 0.05%-0.2%, Mn: 0.1%-0.5%, P≤0.01%, S≤0.01%, N≤0.005%, Nb: 0.01%-0.2%, Ti: 0.005%-0.1%, Mo: 0.1%-1.0%, with the balance being Fe and unavoidable impurities. The preparation method of the high-temperature resistant oxidized 409Ti flux-cored welding wire for additive manufacturing of automotive exhaust systems includes the following steps: Step 1: Weigh the components according to the composition of the core and mix them evenly. Dry them in a dryer at 250-300℃ for 1 hour to obtain the core powder. Step 2: The low-carbon steel strip is placed on the feeding machine of the welding wire forming machine. The low-carbon steel strip is rolled into a U-shaped groove by the pressing groove of the forming machine. The flux core powder obtained in Step 1 is filled into the U-shaped groove. The U-shaped groove is closed by the forming machine. Then it is drawn to a diameter of 1.0-1.2mm. The oil and moisture on the surface of the welding wire are removed by a degreasing machine and a dryer to obtain the final product. The component content of the core material satisfies: Ti / Nb = 1:2; The composition content of the low-carbon steel strip satisfies: Ti / Nb = 1:

2.

2. The high-temperature resistant 409Ti flux-cored welding wire for additive manufacturing of automotive exhaust systems according to claim 1, characterized in that, The filling rate of the core is controlled at 20%-22.5%.

3. The high-temperature resistant 409Ti flux-cored welding wire for additive manufacturing of automotive exhaust systems according to claim 1, characterized in that, The core has a particle size of 80-200 mesh, wherein Cr and W are added in the form of metal, Mn is added in the form of electrolytic manganese, Ti is added in the form of ferrotitanium, C is added in the form of graphite, Ce is added in the form of cerium oxide powder, and the content of impurity elements S and P is less than 0.03%.

4. The application of the high-temperature resistant oxidation-resistant 409Ti flux-cored welding wire for additive manufacturing of automotive exhaust systems as described in any one of claims 1 to 3 in the welding of 409 type ferritic stainless steel pipes in automotive exhaust systems, wherein the welding current is 90-120A, the arc voltage is 14-16V, and the welding speed is 25-30cm / min.

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