High-heat-resistant, light-weight, and heat-insulating three-way catalyst housing material for passenger cars and method for manufacturing the same

Abstract

The application discloses a high-heat-resistance heat-insulation light-weight three-way catalytic shell material for passenger cars and a preparation method thereof, and belongs to the technical field of automobile exhaust purification and vehicle light-weight. The shell material comprises, from inside to outside, an inner heat-resistant stainless steel layer, an intermediate metal-ceramic porous heat-insulation layer and an outer high-strength austenitic stainless steel layer; the thickness of the inner heat-resistant stainless steel layer is 0.15-0.35 mm; the thickness of the intermediate metal-ceramic porous heat-insulation layer is 0.10-0.40 mm, and the porosity is 40wt%-75wt%; and the thickness of the outer high-strength austenitic stainless steel layer is 0.20-0.40 mm. Under the premise of meeting or being superior to the high-temperature strength and vibration fatigue life of an existing shell, the shell material obviously reduces the shell plate thickness and the area density, significantly reduces the outer surface temperature of the shell, and maintains good stamping formability and welding performance.

Description

Technical Field

[0001] This invention relates to the field of automotive exhaust purification and vehicle lightweighting technology, specifically to a high heat-resistant, heat-insulating, lightweight three-way catalytic converter shell material for passenger vehicles and its preparation method. Background Technology

[0002] With the increasing demand for vehicle weight reduction, passenger car three-way catalytic converters are gradually developing towards closer proximity to the engine, miniaturization, and modularization. The three-way catalytic converter shell typically uses a single layer of 1.2–1.5 mm thick austenitic or ferritic stainless steel sheet, formed through stamping, rolling, and welding. In existing technologies, single-layer stainless steel shells suffer from problems such as large shell mass, high external surface temperature, insufficient thermal insulation, and susceptibility to thermal fatigue and deformation under frequent thermal cycling. To meet requirements for high-temperature strength, vibration fatigue, and corrosion resistance, a larger sheet thickness is usually necessary, resulting in a larger overall mass of the three-way catalytic converter, hindering vehicle lightweighting. Furthermore, under close-to-engine conditions, the internal surface temperature of the shell can reach 800–900℃. The high thermal conductivity of a single-layer metal sheet and the excessively high external surface temperature are detrimental to engine compartment thermal management and the reliability of surrounding components, often requiring additional, heavy external insulation materials. Existing metal sandwich panels and thermal insulation structures are mostly used in low- and medium-temperature areas such as vehicle bodies and floor components, making them difficult to apply directly to exhaust gas casing environments that continuously operate above 800°C. Furthermore, high-temperature insulation materials are typically brittle ceramics or bulky fiber cotton, posing challenges for stamping and welding assembly. Therefore, there is an urgent need to develop a lightweight casing material that possesses good high-temperature strength, significant thermal insulation performance, and is stampable and weldable under 800–900°C conditions. This material-level support would enable the lightweighting and thermal management optimization of three-way catalytic converters and related aftertreatment devices. Summary of the Invention

[0003] In order to overcome the above-mentioned shortcomings of the existing technology, the purpose of this invention is to provide a high heat-resistant, heat-insulating, lightweight three-way catalytic converter shell material for passenger vehicles and its preparation method. The shell material significantly reduces the shell plate thickness and areal density, significantly reduces the outer surface temperature of the shell, and maintains good stamping formability and welding performance while meeting or exceeding the high temperature strength and vibration fatigue life of existing shells.

[0004] The technical solution of this invention to solve the above-mentioned technical problems is as follows: A high-heat-resistant, heat-insulating, lightweight three-way catalytic converter shell material for passenger vehicles is provided. This shell material has a metal-heat-insulating composite plate structure, comprising, from the inside out: an inner heat-resistant stainless steel layer, a middle metal-ceramic porous heat-insulating layer, and an outer high-strength austenitic stainless steel layer; the thickness of the inner heat-resistant stainless steel layer is 0.15–0.35 mm; the thickness of the middle metal-ceramic porous heat-insulating layer is 0.10–0.40 mm, with a porosity of 40%–75%; and the thickness of the outer high-strength austenitic stainless steel layer is 0.20–0.40 mm.

[0005] Based on the above technical solution, the present invention can be further improved as follows:

[0006] Furthermore, the inner heat-resistant stainless steel layer has a thickness of 0.20 mm; the middle metal-ceramic porous insulation layer has a thickness of 0.30 mm and a porosity of 70%; and the outer high-strength austenitic stainless steel layer has a thickness of 0.25 mm.

[0007] Furthermore, the inner heat-resistant stainless steel layer comprises the following components by mass percentage: C ≤ 0.03%, Cr 17%~22%, Al 0.3%~1.0%, Nb 0.2%~0.4%, Ti 0.1%~0.2%, with the balance being Fe and unavoidable impurities; preferably, the inner heat-resistant stainless steel layer comprises the following components by mass percentage: C 0.02%, Cr 19%, Al 0.6%, Nb 0.3%, Ti 0.1%, with the balance being Fe and unavoidable impurities.

[0008] Furthermore, the intermediate metal-ceramic porous insulation layer comprises Fe-Cr-Al alloy fibers and an Al2O3-SiO2 ceramic phase; the Fe-Cr-Al alloy fibers contain 15wt%~25wt% Cr and 3wt%~6wt% Al, with the balance being Fe and unavoidable impurities; the Al2O3-SiO2 ceramic phase contains 60wt%~90wt% Al2O3 and 10wt%~40wt% SiO2; preferably, the Fe-Cr-Al alloy fibers contain 22wt% Cr and 5wt% Al, with the balance being Fe and unavoidable impurities; the Al2O3-SiO2 ceramic phase contains 75wt% Al2O3 and 25wt% SiO2.

[0009] Furthermore, the outer high-strength austenitic stainless steel layer comprises the following components by mass percentage: C ≤ 0.08%, Cr 17%–21%, Ni 6%–10%, Mn 1%–2%, with the balance being Fe and unavoidable impurities; preferably, the outer high-strength austenitic stainless steel layer comprises the following components by mass percentage: C 0.05%, Cr 18%, Ni 8%, Mn 1.5%, with the balance being Fe and unavoidable impurities.

[0010] Furthermore, the total thickness of the shell material is 0.60–1.15 mm, and the areal density is 4.5–6.0 kg / m³. 2 The preferred shell material has a total thickness of 0.75 mm and a surface density of 4.7 kg / m³. 2 .

[0011] Furthermore, the shell material exhibits a tensile strength ≥250 MPa at 700℃ and a weight gain ≤1.5 mg / cm³ after 100 h of oxidation at 900℃. 2 .

[0012] The preparation method of the above-mentioned high heat-resistant, heat-insulating, lightweight three-way catalytic converter shell material for passenger vehicles includes the following steps:

[0013] (1) Stainless steel strip and austenitic stainless steel strip are respectively pressed into an inner heat-resistant stainless steel layer and an outer high-strength austenitic stainless steel layer;

[0014] (2) Preparation of intermediate layer metal fiber felt: Fe-Cr-Al alloy is made into alloy fibers, and metal fiber felt is prepared by web laying and needle punching process;

[0015] (3) Prepare an aluminum-silicon composite sol with a solid content of 10%~30%, impregnate the metal fiber felt in it and dry it, and sinter it at 600~900℃ for 0.5~3 h to form an alloy fiber-metal-ceramic porous heat insulation layer, namely the intermediate metal-ceramic porous heat insulation layer.

[0016] (4) The inner heat-resistant stainless steel layer, the middle metal-ceramic porous heat insulation layer and the outer high-strength austenitic stainless steel layer are stacked together, and after being sealed and fixed, they are kept at 900~1150℃. At the same time, rolling composite or hot isostatic pressing is carried out to make the three layers form a metallurgical bond or diffusion bond interface to obtain a composite plate.

[0017] (5) Heat treatment and straightening and leveling of the composite board.

[0018] Furthermore, in step (2), the Fe-Cr-Al alloy fibers have a diameter of 5~30 μm and a length of 0.5~5 μm, and the density of the metal fiber felt is 0.25~0.5 g / m³. 3 The preferred Fe-Cr-Al alloy fibers have a diameter of 10 μm and a length of 3 μm, and the metal fiber felt has a density of 0.30 g / m³. 3 .

[0019] Furthermore, in step (3), the mass ratio of aluminum sol to silica sol in the aluminum-silicon composite sol is 1:1 to 4:1.

[0020] Furthermore, in step (3), sintering is carried out at 800°C in air for 1 h.

[0021] Furthermore, in step (4), the temperature is maintained at 900~1150℃ for 0.5~1 h; preferably, it is maintained at 1050℃ for 0.5 h.

[0022] Further, step (5) specifically involves annealing and straightening the composite plate obtained in step (4) at 700~900℃ to obtain a high heat-resistant, heat-insulating, lightweight three-way catalytic converter shell material for passenger vehicles.

[0023] Furthermore, in step (5), the composite board is annealed at 700~900℃ for 0.5~1.5 h; preferably annealed at 800℃ for 1 h.

[0024] The present invention has the following beneficial effects:

[0025] (1) Significant weight reduction: Through the three-layer composite design of inner and outer thin plates plus middle porous heat insulation, the total thickness of the shell is reduced from the traditional 1.2-1.5 mm to 0.60-1.15 mm while ensuring high strength and vibration fatigue life. The surface density can be reduced by 20%-40%, achieving significant weight reduction of the three-way catalytic shell.

[0026] (2) Excellent high-temperature thermal insulation performance: The porous structure of the intermediate metal-ceramic layer significantly reduces thermal conductivity and heat flux, making the outer surface temperature of the shell 30-80°C lower than that of a single-layer austenitic stainless steel shell under typical exhaust gas conditions of 800-900°C, reducing heat radiation in the engine compartment, reducing the thickness of external thermal insulation cotton or eliminating local thermal insulation.

[0027] (3) Balancing strength and formability: The inner layer of ferritic heat-resistant stainless steel provides high-temperature strength and oxidation resistance, the outer layer of austenitic stainless steel maintains good room-temperature formability and weldability, and the middle layer of metal fiber skeleton improves overall toughness. The composite material can adapt to conventional three-dimensional stamping and rolling processes, avoiding the problem of traditional brittle ceramic insulation layers being difficult to form.

[0028] (4) Improved thermal fatigue and durability: The porous middle layer has a certain compressive deformation capacity and thermal stress buffering capacity, which effectively weakens the stress concentration caused by the expansion mismatch between the inner and outer layers, reduces the probability of shell bulging and cracking, and improves the reliability under long-term thermal cycling conditions.

[0029] (5) Good process adaptability: The Fe-Cr-Al alloy fiber, aluminum-silica sol and stainless steel substrate used in this invention are all mature industrial materials. The preparation route can be realized on the existing stainless steel composite plate or metal carrier production line by appropriate modification, and has good prospects for engineering scale-up and industrialization.

[0030] (6) The shell material obtained by the present invention can be used in exhaust gas aftertreatment shell structures such as three-way catalytic converters, integrated GPF / TWC devices, and DOC / DPF shells. Attached Figure Description

[0031] Figure 1 A process roadmap for the preparation of high heat-resistant, heat-insulating, and lightweight three-way catalytic converter shell materials for passenger vehicles. Detailed Implementation

[0032] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer should be followed. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0033] Example 1:

[0034] A high heat-resistant, heat-insulating, and lightweight three-way catalytic converter shell material for passenger vehicles. The shell material is a metal-heat-insulating composite plate structure, comprising, from the inside out: an inner heat-resistant stainless steel layer, a middle metal-ceramic porous heat-insulating layer, and an outer high-strength austenitic stainless steel layer; the inner layer thickness is 0.25 mm, the middle layer thickness is 0.25 mm, the outer layer thickness is 0.30 mm, and the total thickness of the shell material is 0.80 mm.

[0035] The inner heat-resistant stainless steel layer comprises the following components by mass percentage: C 0.02%, Cr 19%, Al 0.6%, Nb 0.3%, Ti 0.1%, with the balance being Fe and unavoidable impurities;

[0036] The intermediate metal-ceramic porous insulation layer comprises Fe-Cr-Al alloy fibers and Al2O3-SiO2 ceramic phase; the Fe-Cr-Al alloy fibers contain 22wt% Cr and 5wt% Al, with the remainder being Fe and unavoidable impurities; the Al2O3-SiO2 ceramic phase contains 75wt% Al2O3 and 25wt% SiO2.

[0037] The outer high-strength austenitic stainless steel layer comprises the following components by mass percentage: C 0.05%, Cr 18%, Ni 8%, Mn 1.5%, with the balance being Fe and unavoidable impurities.

[0038] The preparation method of the above-mentioned high heat-resistant, heat-insulating, lightweight three-way catalytic converter shell material for passenger vehicles includes the following steps:

[0039] (1) The selected ferritic heat-resistant stainless steel strip is rolled to a thickness of 0.25 mm and used as the inner layer;

[0040] (2) The selected austenitic stainless steel strip is rolled to a thickness of 0.30 mm as the outer layer;

[0041] (3) Fe-Cr-Al alloy wire was drawn to a diameter of 15 μm and a length of 3 μm, and then processed by air web laying and needle punching to obtain metal fiber felt with a density of 0.35 g / m³. 3 ;

[0042] (4) Aluminum sol and silica sol were mixed at a mass ratio of 3:1 to obtain a composite sol with a solid content of 20%. Metal fiber felt was impregnated in the composite sol, and excess sol was removed by roller pressing. The sol was dried at 100°C for 2 h. The sol was sintered at 800°C in air for 1 h to obtain a metal-ceramic porous heat insulation layer coated with Al2O3-SiO2 ceramic phase. The thickness of the layer was 0.25 mm and the porosity was 60%.

[0043] (5) The inner heat-resistant stainless steel, the middle metal-ceramic porous heat insulation layer and the outer high-strength austenitic stainless steel plate are stacked in the order of inner-middle-outer, and the edges are sealed by spot welding around the perimeter. Then, the plate is heated to 1050℃ in a vacuum furnace and kept at that temperature for 0.5h. At the same time, hot rolling is carried out to make the three layers form a diffusion bond, thus obtaining a composite plate.

[0044] (6) After the composite plate obtained in step (5) is cooled, it is annealed at 800℃ for 1 hour and straightened and leveled to obtain a high heat-resistant, heat-insulating, lightweight three-way catalytic converter shell material for passenger cars with a total thickness of 0.80 mm.

[0045] The high heat-resistant, heat-insulating, lightweight three-way catalytic converter shell material for passenger vehicles prepared in Example 1 was tested as follows:

[0046] ① The areal density of the shell material obtained in Example 1 is 5.2 kg / m³. 2 It uses 1.2 mm thick single-layer austenitic stainless steel sheet (area density approximately 7.5 kg / m³), which is standard in the industry and meets basic performance requirements. 2 Compared to the benchmark, the material of this invention is about 30% lighter.

[0047] ② The shell material of this invention was heated to 700℃±5℃ and held at this temperature for 20 minutes to reach thermal equilibrium. Then, it was stretched at an initial strain rate of 1 mm / min until fracture. The high-temperature tensile strength of the material was measured to be 260 MPa, and the elongation after fracture was 14%.

[0048] ③ A sample measuring 30 mm × 15 mm was obtained by wire cutting from the shell material of this invention. After cleaning and drying with acetone, the initial mass (m0) was recorded using an analytical balance with an accuracy of 0.1 mg. The sample was then placed horizontally in a box-type resistance furnace preheated to 900℃ ± 10℃ and continuously oxidized in a static air atmosphere for 100 hours. After cooling to room temperature, it was weighed again (m1). The oxidation weight gain ΔW was calculated using the formula ΔW = (m1 - m0) / S, where S is the initial total surface area of ​​the sample, and the measured result was 1.2 mg / cm². 2 .

[0049] ④ The shell material obtained in Example 1 was used to make a cylindrical specimen. A K-type thermocouple was placed at the central axis of the inner cavity to monitor and control the inner surface temperature to be stable at 850℃±10℃. Another K-type thermocouple was fixed at the geometric center of the outer wall of the specimen to measure the outer surface temperature. Data were recorded after the thermal state stabilized (about 30 minutes). The results show that the outer surface temperature of the specimen of the present invention is 50℃ lower than that of the cylindrical specimens made of a single layer of 1.2 mm thick austenitic stainless steel plate commonly used in the industry.

[0050] Example 2:

[0051] The difference between Example 2 and Example 1 is that the inner layer thickness is adjusted to 0.20 mm, the middle layer thickness is adjusted to 0.30 mm, the outer layer thickness is adjusted to 0.25 mm, and the total thickness of the shell material is 0.75 mm; the diameter of the metal fibers in the middle metal-ceramic porous insulation layer is 10 μm, and the density of the metal fiber felt is 0.30 g / m³. 3 The porosity of the intermediate metal-ceramic porous insulation layer is 70%.

[0052] The high heat-resistant, heat-insulating, lightweight three-way catalytic converter shell material for passenger vehicles prepared in Example 2 was tested (the testing procedure was the same as in Example 1), and the surface density of the obtained material was 4.7 kg / m³. 2 The tensile strength at 700℃ is 265 MPa, the elongation after fracture is 13%, and the weight gain after oxidation at 900℃ for 100 h is 1.1 mg / cm³. 2 The outer surface temperature is reduced by 55°C, making it more suitable for near-machine three-way catalytic converter housing applications where lightweighting and heat insulation requirements are higher.

[0053] Example 3:

[0054] The difference between Example 3 and Example 1 is that the alloy composition of the inner heat-resistant stainless steel was adjusted, specifically: C 0.01%, Cr 20%, Al 0.4%, Nb 0.25%, Ti 0.15%, with the balance being Fe and unavoidable impurities.

[0055] The high heat-resistant, heat-insulating, lightweight three-way catalytic converter shell material for passenger vehicles prepared in Example 3 was tested (the testing procedure was the same as in Example 1), and the surface density of the obtained material was 5.5 kg / m³. 2 The tensile strength at 700℃ is 255 MPa, and the elongation after fracture is 14%. The weight gain after oxidation at 900℃ for 100 h is 1.3 mg / cm³. 2 Using the same method, the outer surface temperature decreased by 45°C. This example demonstrates that, with a high Cr content in the inner layer and appropriate amounts of Nb and Ti, the material can still maintain good high-temperature strength and oxidation resistance even when the Al content is at the lower limit of the range.

[0056] Example 4:

[0057] The difference between Example 4 and Example 1 is that the Fe-Cr-Al alloy fiber contains 18wt% Cr and 4wt% Al, with the balance being Fe and unavoidable impurities. The Al2O3-SiO2 ceramic phase contains 65wt% Al2O3 and 35wt% SiO2.

[0058] The high heat-resistant, heat-insulating, lightweight three-way catalytic converter shell material for passenger vehicles prepared in Example 4 was tested (the testing procedure was the same as in Example 1), and the surface density of the obtained material was 5.0 kg / m³. 2 The tensile strength at 700℃ is 250 MPa, and the elongation is 15%. The weight gain after oxidation at 900℃ for 100 h is 1.4 mg / cm³. 2 The outer surface temperature decreased by 40°C. This embodiment shows that using a ceramic phase with a high SiO2 content and alloy fibers with a medium Cr content in the intermediate layer can potentially reduce material costs or adjust the coefficient of thermal expansion while ensuring thermal insulation and mechanical properties.

[0059] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high heat-resistant, heat-insulating, lightweight three-way catalytic converter shell material for passenger vehicles, characterized in that, The shell material, from the inside out, comprises: a heat-resistant stainless steel layer, a metal-ceramic porous insulation layer, and a high-strength austenitic stainless steel layer; the thickness of the heat-resistant stainless steel layer is 0.15–0.35 mm; the thickness of the metal-ceramic porous insulation layer is 0.10–0.40 mm, and the porosity is 40%–75%; the thickness of the high-strength austenitic stainless steel layer is 0.20–0.40 mm. The heat-resistant stainless steel layer comprises the following components by mass percentage: C≤0.03%, Cr 17%~22%, Al 0.3%~1.0%, Nb 0.2%~0.4%, Ti 0.1%~0.2%, with the balance being Fe and unavoidable impurities; The metal-ceramic porous insulation layer comprises Fe-Cr-Al alloy fibers and an Al2O3-SiO2 ceramic phase; the Fe-Cr-Al alloy fibers contain 15wt%~25wt% Cr and 3wt%~6wt% Al, with the balance being Fe and unavoidable impurities; the Al2O3-SiO2 ceramic phase contains 60wt%~90wt% Al2O3 and 10wt%~40wt% SiO2. The high-strength austenitic stainless steel layer comprises the following components by mass percentage: C ≤ 0.08%, Cr 17%~21%, Ni 6%~10%, Mn 1%~2%, with the balance being Fe and unavoidable impurities.

2. The high heat-resistant, heat-insulating, lightweight three-way catalytic converter housing material for passenger vehicles according to claim 1, characterized in that, The total thickness of the shell material is 0.60–1.15 mm, and the areal density is 4.5–6.0 kg / m³. 2 The tensile strength at 700℃ is ≥250MPa, and the weight gain after oxidation at 900℃ for 100 h is ≤1.5 mg / cm³. 2 .

3. The method for preparing the high heat-resistant, heat-insulating, lightweight three-way catalytic converter shell material for passenger vehicles according to any one of claims 1 to 2, characterized in that, Includes the following steps: (1) Stainless steel strip and austenitic stainless steel strip are respectively pressed into heat-resistant stainless steel layer and high-strength austenitic stainless steel layer; (2) Preparation of metal fiber felt: Fe-Cr-Al alloy is made into alloy fibers, and metal fiber felt is prepared by web laying and needle punching process; (3) Prepare an aluminum-silicon composite sol with a solid content of 10%~30%, impregnate the metal fiber felt in it and dry it, and sinter it at 600~900℃ for 0.5~3 h to form a metal-ceramic porous heat insulation layer; (4) The heat-resistant stainless steel layer, the metal-ceramic porous heat insulation layer and the high-strength austenitic stainless steel layer are stacked together, and after being sealed and fixed, they are kept at 900~1150℃. At the same time, rolling composite or hot isostatic pressing is carried out to make the three layers form a metallurgical bond or diffusion bond interface to obtain a composite plate. (5) Heat treatment and straightening and leveling of the composite board.

4. The preparation method according to claim 3, characterized in that, In step (3), the mass ratio of aluminum sol to silica sol in the aluminum-silicon composite sol is 1:1 to 4:

1.

5. The preparation method according to claim 3, characterized in that, In step (4), the temperature is maintained at 900~1150℃ for 0.5~1 h.

6. The preparation method according to claim 3, characterized in that, Step (5) specifically involves annealing and straightening the composite plate obtained in step (4) at 700~900℃ to obtain a high heat-resistant, heat-insulating, lightweight three-way catalytic converter shell material for passenger vehicles.

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