Heat-resistant high-performance stainless steel applied to automobile turbocharger

Abstract

The invention relates to heat-resistant high-performance stainless steel applied to an automobile turbocharger. The heat-resistant high-performance stainless steel is prepared from the following components: 0.3 to 0.5 percent of carbon, 0.5 to 1.5 percent of silicon, 1.0 to 2.5 percent of manganese, 0.02 to 0.04 percent of phosphorus, 0.02 to 0.04 percent of sulfur, 0.3 to 0.5 percent of molybdenum, 18.0 to 23.0 percent of chromium, 2.0 to 7.8 percent of nickel, 0.5 to 1.5 percent of niobium, 0.2 to 0.5 percent of nitrogen and the balance of iron and indispensable impurities. Nickel in heat-resistant stainless steel can be replaced by adjusting nitrogen and manganese elements, the performance of the novel material at the normal temperature and the high temperature is superior to that of an existing material, the novel material can serve as a substitute of the existing material, and therefore the production cost is greatly reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heat-resistant stainless steel, in particular to a heat-resistant high-performance stainless steel applied to a turbocharger of an automobile. BACKGROUND

[0002] With the vigorous development and application of nickel-based heat-resistant alloy steel, and the increasing demand for stainless steel with the development of chemical industry, the supply and demand of nickel in the world has appeared contradictions, and the price of nickel has continued to rise. In order to save nickel, the research on heat-resistant stainless steel is carried out.

[0003] In the prior art, a ferrite heat-resistant stainless steel and a preparation method thereof are disclosed in a Chinese patent (application number: 201811452857.1, publication number: CN 109355571A). The ferrite heat-resistant stainless steel includes the following chemical components in percentage by weight: C: 0.06-0.11%, Si: 0.7-1.2%, Mn: 0.6-1.0%, Cr: 17.0-19.0%, Al: 0.7-1.2%, N: 0.005-0.015%, and the rest is Fe and inevitable impurities. The ferrite heat-resistant stainless steel contains Cr and Al, is applied to the manufacture of boiler connecting parts, has a narrow application range, has low strength, and cannot be applied to the manufacture of high-end equipment.

[0004] In the prior art, an austenitic heat-resistant stainless steel is disclosed in a Chinese patent (application number: 202211548897.2, publication number: CN 115927972B). The composition of the austenitic heat-resistant stainless steel is as follows: C: 0.05-0.2%, Al: 7-10%, Ni: 8-15%, Ti: 1-2%, Nb: 1-2%, Mn: 10-20%, B: 0.015-0.025%, and the rest is Fe and inevitable impurities. The content of nickel in the scheme is high, which increases the production cost. SUMMARY

[0005] In view of the deficiencies of the above prior art, the present application provides a heat-resistant high-performance stainless steel applied to a turbocharger of an automobile. The heat-resistant high-performance stainless steel is obtained by adjusting the proportions of nitrogen, manganese and other elements to replace nickel in the heat-resistant stainless steel, so that the performance of the new material at room temperature and high temperature is better than that of the existing material, and the new material can be used as a substitute for the existing material, thereby greatly reducing the production cost.

[0006] In order to achieve the above object and other related objects, the present application provides the following technical solutions: A heat-resistant high-performance stainless steel applied to a turbocharger of an automobile, which is composed of the following components: carbon 0.3-0.5%, silicon 0.5-1.5%, manganese 1.0-2.5%, phosphorus 0.02-0.04%, sulfur 0.02-0.04%, molybdenum 0.3-0.5%, chromium 18.0-23.0%, nickel 2.0-7.8%, niobium 0.5-1.5%, nitrogen 0.2-0.5%, and the rest is iron and the content of inevitable impurities.

[0007] Further, the heat-resistant high-performance stainless steel is composed of the following components: carbon 0.3-0.5%, silicon 1.0-1.5%, manganese 1.0-1.5%, phosphorus 0.02-0.04%, sulfur 0.02-0.04%, molybdenum 0.3-0.5%, chromium 18.0-20.0%, nickel 6.0-7.8%, niobium 0.5-0.8%, nitrogen 0.2-0.3%, and the rest is iron and the content of inevitable impurities.

[0008] Further, the heat-resistant high-performance stainless steel is composed of the following components: carbon 0.3-0.5%, silicon 1.0-1.5%, manganese 1.0-1.5%, phosphorus 0.02-0.04%, sulfur 0.02-0.04%, molybdenum 0.3-0.5%, chromium 18.0-20.0%, nickel 6.0-7.8%, niobium 0.5-0.8%, nitrogen 0.2-0.3%, and the rest is iron and the content of inevitable impurities.

[0009] Further, the heat-resistant high-performance stainless steel is composed of the following components: carbon 0.3-0.5%, silicon 1.0-1.5%, manganese 1.0-1.5%, phosphorus 0.02-0.04%, sulfur 0.02-0.04%, molybdenum 0.3-0.5%, chromium 18.0-20.0%, nickel 6.0-7.8%, niobium 0.5-0.8%, nitrogen 0.2-0.3%, and the rest is iron and the content of inevitable impurities.

[0010] Further, the heat-resistant high-performance stainless steel is composed of the following components: carbon 0.3-0.5%, silicon 1.0-1.5%, manganese 1.0-1.5%, phosphorus 0.02-0.04%, sulfur 0.02-0.04%, molybdenum 0.3-0.5%, chromium 18.0-20.0%, nickel 6.0-7.8%, niobium 0.5-0.8%, nitrogen 0.2-0.3%, and the rest is iron and the content of inevitable impurities.

[0011] Further, the heat-resistant high-performance stainless steel is composed of the following components: carbon 0.3-0.5%, silicon 1.0-1.5%, manganese 1.0-1.5%, phosphorus 0.02-0.04%, sulfur 0.02-0.04%, molybdenum 0.3-0.5%, chromium 18.0-20.0%, nickel 6.0-7.8%, niobium 0.5-0.8%, nitrogen 0.2-0.3%, and the rest is iron and the content of inevitable impurities.

[0012] Further, the heat-resistant high-performance stainless steel is composed of the following components: carbon 0.4%, silicon 0.75%, manganese 2.25%, phosphorus 0.03%, sulfur 0.03%, molybdenum 0.4%, chromium 22.5%, nickel 3.0%, niobium 1.25%, nitrogen 0.45%, and the rest is iron and the content of inevitable impurities.

[0013] The present application has the following positive effects: 1. The present application greatly reduces the amount of nickel in heat-resistant stainless steel by adjusting the elements such as nitrogen, manganese and nickel, abandoning the Al element, and through the most optimized ratio, the performance of the new material at room temperature and high temperature is better than that of the existing material, which can be used as a substitute for the existing material, thereby greatly reducing the production cost.

[0014] 2. The present application can not only improve the mechanical properties of the material at room temperature and high temperature, but also has low cost and is suitable for industrialized production application by using N-Mn-C elements to replace Ni elements to form stable austenite.

[0015] 3. Through material improvement, the present application represents the development direction of automobile lightweight and green manufacturing. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a high-temperature creep comparison chart of N8 and 1.4837 / 1.4848 / 1.4849 materials of the present application; Figure 2 is another high-temperature creep comparison chart of N8 and 1.4837 / 1.4848 / 1.4849 materials of the present application; Figure 3 is another high-temperature creep comparison chart of N8 and 1.4837 / 1.4848 / 1.4849 materials of the present application; Figure 4 is a high-temperature creep comparison chart of N5 and 1.4826 / 1.4837 materials of the present application; Figure 5 is another high-temperature creep comparison chart of N5 and 1.4826 / 1.4837 materials of the present application; Figure 6 is another high-temperature creep comparison chart of N5 and 1.4826 / 1.4837 materials of the present application; Figure 7 is a high-temperature creep comparison chart of N2 and 1.4826 / 1.4837 materials of the present application; Figure 8 is another high-temperature creep comparison chart of N2 and 1.4826 / 1.4837 materials of the present application; Figure 9 is another high-temperature creep comparison chart of N2 and 1.4826 / 1.4837 materials of the present application. Detailed Implementation

[0017] The exemplary embodiments of this disclosure are described below with reference to the accompanying drawings, including various details of the embodiments to aid understanding, and should be considered merely exemplary. Therefore, those skilled in the art will recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of this disclosure. Similarly, for clarity and brevity, descriptions of well-known functions and structures are omitted in the following description.

[0018] Example 1: A heat-resistant high-performance stainless steel for use in automotive turbochargers was produced. The trial production model was designated as N8. The stainless steel was composed of the following components: carbon 0.3%, silicon 1.0%, manganese 1.0%, phosphorus 0.02%, sulfur 0.02%, molybdenum 0.3%, chromium 18.1%, nickel 6.0%, niobium 0.5%, nitrogen 0.2%, with the remainder being iron and essential impurities.

[0019] Example 2: A heat-resistant high-performance stainless steel for use in automotive turbochargers was produced. The trial production model was designated as N8. The stainless steel was composed of the following components: 0.4% carbon, 1.25% silicon, 1.25% manganese, 0.03% phosphorus, 0.03% sulfur, 0.4% molybdenum, 19.0% chromium, 6.9% nickel, 0.65% niobium, 0.25% nitrogen, with the remainder being iron and essential impurities.

[0020] Example 3: A heat-resistant high-performance stainless steel for use in automotive turbochargers was produced. The trial production model was designated as N8. The stainless steel was composed of the following components: 0.5% carbon, 1.5% silicon, 1.5% manganese, 0.04% phosphorus, 0.04% sulfur, 0.5% molybdenum, 19.9% ​​chromium, 7.8% nickel, 0.8% niobium, 0.3% nitrogen, with the remainder being iron and essential impurities.

[0021] Comparative Example 1: A heat-resistant stainless steel, designated as 1.4826, which is composed of the following components: carbon 0.3-0.5%, silicon 0.8-1.5%, manganese 1.8-2.0%, phosphorus 0.03-0.04%, sulfur 0.03-0.04%, molybdenum 0.4-0.5%, chromium 18.0-23.0%, nickel 8.0-12.0%, niobium 1.3-1.7%, with the remainder being iron and essential impurities.

[0022] Comparative Example 2: A heat-resistant stainless steel, designated as 1.4837, which is composed of the following components: carbon 0.3-0.5%, silicon 1.0-2.5%, manganese 1.8-2.0%, phosphorus 0.03-0.04%, sulfur 0.03-0.04%, molybdenum 0.4-0.5%, chromium 24.0-27.0%, nickel 11.0-14.0%, niobium 0.5-1.5%, with the remainder being iron and essential impurities.

[0023] Comparative Example 3: A heat-resistant stainless steel, designated as 1.4848, which is composed of the following components: carbon 0.3-0.5%, silicon 1.0-2.5%, manganese 1.8-2.0%, phosphorus 0.03-0.04%, sulfur 0.03-0.04%, molybdenum 0.4-0.5%, chromium 23.0-27.0%, nickel 19.0-22.0%, niobium 1.3-1.6%, with the remainder being iron and essential impurities.

[0024] Comparative Example 4: A heat-resistant stainless steel, designated as 1.4849, which is composed of the following components: carbon 0.3-0.75%, silicon 1.0-2.5%, manganese 1.8-2.0%, phosphorus 0.03-0.04%, sulfur 0.03-0.04%, molybdenum 0.4-0.5%, chromium 17.0-21.0%, nickel 36.0-41.0%, niobium 1.2-1.8%, with the remainder being iron and essential impurities.

[0025] The composition of the heat-resistant stainless steels used in the comparative examples is shown in Table 1. Table 1

[0026] Table 2 shows a comparison of the mechanical properties of Examples 1, 2, and 3 with those of 1.4837 / 1.4848 / 1.4849. Table 2 I. Comparative Analysis of Chemical Composition:

[0027] 1. Nickel (Ni) content is significantly reduced: Examples 1, 2, and 3 (N8 series): Ni = 6.0-7.8%; Comparative examples: Ni starts at 8.0%, and reaches up to 41%; Since nickel is an austenite-stabilizing element, traditional heat-resistant stainless steels (such as 1.4848 / 1.4849) rely on high nickel content to maintain the austenitic structure, thereby achieving high-temperature toughness and oxidation resistance. The N8 series stabilizes austenite through other means (such as N, Cr, Nb systems), significantly reducing the Ni content, thereby greatly reducing costs (nickel is a precious metal) while maintaining performance.

[0028] 2. Introduction of nitrogen (N): Examples 1, 2, and 3 (N8 series): N = 0.2-0.3%; Comparative example: No additives or extremely low concentrations; Nitrogen is a strong austenite-forming element, and its solid solution strengthening effect is far greater than that of carbon. N can significantly improve strength (especially high-temperature strength), creep resistance, and pitting corrosion resistance. N and Nb can form fine and dispersed Nb(C,N) or NbN precipitates, which effectively hinder dislocation movement and grain boundary slip, thereby improving high-temperature strength and creep resistance.

[0029] This is one of the key reasons why N8 has better tensile strength and yield strength than the comparative ratio at high temperatures.

[0030] 3. The niobium (Nb) content is moderate, but it works synergistically with nitrogen: In Examples 1, 2, and 3 (N8 series), Nb = 0.5-0.8%, which is lower than the 1.3-1.7% of 1.4826 / 1.4848, but when used in conjunction with N, it forms a more effective precipitation strengthening. In the comparative examples, although Nb is high, the lack of N combination may result in coarse precipitates or low efficiency. The synergistic design of C+N+Nb in these examples achieves the precipitation of fine and dispersed carbonitrides (such as NbN) at grain boundaries and within grains, inhibiting grain growth, strengthening grain boundaries, and improving creep resistance. This represents an optimized combination of precipitation strengthening and solid solution strengthening.

[0031] 4. Moderate chromium (Cr) content, balancing antioxidant properties and cost: In Examples 1, 2, and 3 (N8), Cr = 18-20%, close to the upper limit of 1.4849, but lower than 1.4837 / 1.4848 (24-27%). Cr provides high-temperature antioxidant properties (forming a Cr2O3 protective film). The examples maintained excellent high-temperature performance even under slightly lower Cr conditions, indicating that the addition of N and Nb improved the antioxidant properties or compensated for the lack of Cr.

[0032] 5. Manganese (Mn) content is limited to 1.0-1.5%: In Examples 1, 2, and 3 (N8 series), the Mn:manganese content was 1.0-1.5%, which was much lower than the 1.8-2.0% in the comparative examples.

[0033] Mn is typically used for deoxidation and austenite stabilization, but excessive amounts can reduce hot strength and increase the tendency for hot cracking. N8 achieves a low-Mn design by replacing the austenite stabilizing effect of Mn with N, which is beneficial for improving purity and hot working performance.

[0034] 6. Carbon (C) levels are kept at a moderate level: In Examples 1, 2, and 3 (N8 series), C = 0.3-0.5%, which is comparable to the comparative examples. C can form carbides for strengthening, but too much C will reduce toughness and weldability. N8 achieves high strength through N+C composite strengthening without excessively increasing C.

[0035] II. Analysis of the mechanism of performance difference.

[0036] 1. Examples 1, 2, and 3 (N8 series) exhibit higher high-temperature strength (tensile strength and yield strength): This is mainly because: N atoms are small, and their solid solution in austenite produces strong lattice distortion, significantly improving strength. Fine Nb(C,N) precipitation strengthens the structure: N promotes the formation of finer, more stable precipitates, hindering dislocation movement. NbN precipitation inhibits high-temperature grain growth, resulting in finer grain strengthening. Therefore, at 800℃, 1000℃, and 1100℃, the strength of N8 is comprehensively superior to the comparative examples.

[0037] 2. Examples 1, 2, and 3 (N8 series) show higher elongation: Since elongation reflects the plasticity and toughness of a material, although N usually reduces plasticity, N8 still maintains a high elongation, indicating: good microstructure uniformity, no coarse precipitation or segregation; high austenite stability (synergistic effect of Ni, N, Cr, and appropriate Mn), avoiding harmful phase transformations at high temperatures. The present invention features strict impurity (P / S) control, clean grain boundaries, and reduced risk of brittle fracture.

[0038] 3. Examples 1, 2, and 3 (N8 series) exhibit excellent creep performance (especially at 800℃): Creep is a slow deformation under long-term stress at high temperatures and is a key indicator for turbocharger materials. The N8 of this invention exhibits better creep performance than the comparative examples at 800℃, and comparable performance at 1000℃ and 1100℃, indicating its significant advantage in the mid-temperature range.

[0039] This is because the N8 precipitate of this invention has high stability, and Nb(C,N) does not easily coarsen at 800℃, continuously pinning dislocations and grain boundaries. Simultaneously, the fine precipitate is distributed at the grain boundaries, inhibiting grain boundary slip. Furthermore, the strengthening effect of N is more significant in the mid-temperature region. Although high-nickel materials (such as 1.4849) have good high-temperature stability, their strengthening mechanism relies more on solid solution (Ni) than precipitation, and their mid-temperature creep resistance is actually inferior to that of N8.

[0040] In Examples 1, 2, and 3 (N8 series), stainless steel, through the innovative composition design of "low carbon, medium chromium, low nickel, nitrogen, and niobium", achieved a significant reduction in nickel content (reducing costs) while utilizing the solid solution strengthening of nitrogen and the fine precipitates formed by the synergistic effect of nitrogen and niobium, thus comprehensively improving the high-temperature strength, plasticity, and medium-temperature creep performance of the material.

[0041] In summary, as Figure 1 or Figure 2 or Figure 3As shown, compared with 1.4837 / 1.4848 / 1.4849 materials, Examples 1, 2, and 3 exhibit higher tensile strength, yield strength, and elongation at high temperatures of 800℃, 1000℃, and 1100℃. Furthermore, Examples 1, 2, and 3 show better creep performance than 1.4837 / 1.4848 / 1.4849 at 800℃; and comparable creep performance at 1000℃ / 1100℃. This material is particularly suitable for applications requiring high strength at medium to high temperatures, cost sensitivity, and lightweight construction, such as automotive turbochargers, and offers significant technical and economic advantages compared to traditional high-nickel heat-resistant stainless steels (such as 1.4837 / 1.4848 / 1.4849).

[0042] Example 4: A heat-resistant high-performance stainless steel for use in automotive turbochargers was produced. The trial production model was designated as N5. The stainless steel was composed of the following components: 0.3% carbon, 1.0% silicon, 1.5% manganese, 0.02% phosphorus, 0.02% sulfur, 0.3% molybdenum, 20.0% chromium, 4.0% nickel, 1.0% niobium, and 0.3% nitrogen.

[0043] Example 5: A heat-resistant high-performance stainless steel for use in automotive turbochargers was produced. The trial production model was designated as N5. The stainless steel was composed of the following components: 0.4% carbon, 1.25% silicon, 1.75% manganese, 0.03% phosphorus, 0.03% sulfur, 0.4% molybdenum, 20.5% chromium, 5.0% nickel, 1.25% niobium, and 0.35% nitrogen.

[0044] Example 6: A heat-resistant high-performance stainless steel for use in automotive turbochargers was produced. The trial production model was designated as N5. The stainless steel was composed of the following components: 0.5% carbon, 1.5% silicon, 2.0% manganese, 0.04% phosphorus, 0.04% sulfur, 0.5% molybdenum, 20.8% chromium, 6.0% nickel, 1.5% niobium, and 0.4% nitrogen.

[0045] In this embodiment, the mechanical properties of Examples 4, 5, and 6 are compared with those of 1.4826 / 1.4837 as shown in Table 3. Table 3 I. Comparative Analysis of Chemical Composition:

[0046] 1. In Examples 4-6 (N5 series), Ni = 4.0-6.0%, which is much lower than the levels of 1.4826: 8-12% and 1.4837: 11-14%, and even lower than 1.4848 / 1.4849 (19-41%).

[0047] Nickel is one of the most expensive alloying elements in stainless steel. Reducing the Ni content directly lowers material costs and is crucial for the large-scale application of automotive parts. In N5, Mn = 1.5-2.0%, lower than the 1.8-2.0% in the comparative example. This achieves an austenitic stabilization strategy of "replacing nickel with manganese."

[0048] 2. In the N5 series, N=0.3-0.4%, and its role is extremely crucial.

[0049] Nitrogen atoms have small atomic sizes, causing strong lattice distortion and significantly improving strength (especially high-temperature strength). It promotes precipitation strengthening, forming fine, dispersed Nb(C,N) or NbN precipitates with Nb, hindering dislocation movement. It enhances creep resistance: the precipitates are stable at high temperatures, inhibiting grain boundary slip and dislocation climb. It improves oxidation resistance: it helps form a dense oxide film. Mn and N have a synergistic effect; Mn increases the solubility of nitrogen in molten steel, preventing nitrogen precipitation; N is more stable in a high-Mn matrix, less prone to porosity; their combined action can effectively replace some of the austenite stabilizing function of Ni.

[0050] 3. In the N5 series, the niobium (Nb) content is moderate but the utilization is efficient.

[0051] In N5, Nb content is 1.0-1.5%, lower than the 1.3-1.7% in 1.4826 / 1.4848, but its synergistic effect with high N content is stronger. In a high N environment, Nb more readily forms fine, dispersed, and thermally stable carbonitrides (Nb(C,N)), resulting in higher strengthening efficiency. In contrast, even with high Nb content in the comparative example, the lack of N coordination may lead to coarse precipitates or a predominance of niobium-rich carbides, reducing the strengthening effect.

[0052] 4. In the N5 series, Cr=20.0-21.0%, which is within the range of good antioxidant properties.

[0053] In this embodiment, a stable CrO3 film can be formed with 20% or more of the total mass of Cr. Although this is lower than 1.4826 / 1.4837, the synergistic effect of N may improve the stability or self-healing ability of the oxide film, thereby maintaining good antioxidant properties without increasing Cr content.

[0054] II. Analysis of the mechanism of performance difference.

[0055] 1. Higher tensile strength and yield strength: In Examples 4-6 (N5 series), N atoms generate a strong stress field on the matrix, hindering dislocation movement. Fine Nb(C,N) precipitation strengthening: High N content promotes the formation of numerous nanoscale precipitates, significantly increasing yield strength. Solid solution strengthening contribution of Mn: Mn itself also has a strengthening effect. Despite lower Ni content, the strength of N5 comprehensively exceeds that of 1.4826 / 1.4837.

[0056] 2. The elongation rate remained basically the same: High nitrogen (N) content typically reduces plasticity, but Examples 4-6 (N5 series) still maintained elongation comparable to the comparative examples. This indicates that N5 exhibits good microstructure uniformity with no significant segregation or inclusion aggregation; high austenite stability, preventing deformation-induced martensitic transformation; fine grains (possibly due to NbN inhibiting grain growth); and strict control of phosphorus (P) and sulfur (≤0.04%), reducing grain boundary embrittlement. Therefore, this demonstrates that N5 maintains good plasticity while achieving high strength, exhibiting excellent overall mechanical properties.

[0057] 3. Creep performance is superior to the comparative example in all aspects: Examples 4-6 (N5 series) exhibit superior creep performance compared to 1.4826 / 1.4837 at various high temperatures, which is their most prominent advantage. This is because Nb(C,N) has a high precipitation temperature and slow coarsening rate in the 600-900℃ range, effectively pinning dislocations and grain boundaries during long-term service. Fine precipitates distributed at grain boundaries suppress grain boundary slip—one of the main mechanisms of creep fracture. The combined solid solution strengthening of N and Mn improves the matrix's resistance to deformation. While high-Ni materials (such as 1.4837) have good thermal stability, their strengthening mainly relies on solid solution, resulting in fewer or less stable precipitates, and their creep resistance at medium and high temperatures is inferior to N5.

[0058] The stainless steel materials in Examples 4-6 (N5 series) have achieved a significant reduction in nickel content (as low as 4%) by using the innovative composition design of "high manganese + high nitrogen + medium chromium + low nickel + niobium microalloying". This has enabled the materials to comprehensively improve high-temperature strength and creep resistance while maintaining good plasticity by utilizing the strong solid solution strengthening of nitrogen and the nitrogen-niobium synergistic precipitation mechanism.

[0059] In summary, such as Figure 4 or Figure 5 or Figure 6As shown, compared with 1.4826 / 1.4837 materials, Examples 4, 5, and 6 exhibit higher tensile strength and yield strength, while their elongation is essentially the same. Furthermore, Examples 4, 5, and 6 demonstrate superior creep performance compared to 1.4826 / 1.4837 materials at different high temperatures. This stainless steel material offers the following significant advantages over traditional heat-resistant stainless steels (such as 1.4826 and 1.4837): lower cost, higher high-temperature strength, and superior creep performance; it is particularly suitable for components such as turbocharger housings that require long-term exposure to medium- and high-temperature stresses.

[0060] Example 7: A heat-resistant high-performance stainless steel for use in automotive turbochargers was produced. The trial production model was designated as N2. The stainless steel was composed of the following components: 0.3% carbon, 0.5% silicon, 2.0% manganese, 0.02% phosphorus, 0.02% sulfur, 0.3% molybdenum, 21.0% chromium, 2.0% nickel, 1.0% niobium, 0.4% nitrogen, with the remainder being iron and essential impurities.

[0061] Example 8: A heat-resistant high-performance stainless steel for use in automotive turbochargers was produced. The trial production model was designated as N2. The stainless steel was composed of the following components: 0.4% carbon, 0.75% silicon, 2.25% manganese, 0.03% phosphorus, 0.03% sulfur, 0.4% molybdenum, 22.5% chromium, 3.0% nickel, 1.25% niobium, 0.45% nitrogen, with the remainder being iron and essential impurities.

[0062] Example 9: A heat-resistant high-performance stainless steel for use in automotive turbochargers was produced. The trial production model was designated as N2. The stainless steel was composed of the following components: 0.5% carbon, 1.0% silicon, 2.5% manganese, 0.04% phosphorus, 0.04% sulfur, 0.5% molybdenum, 23.0% chromium, 4.0% nickel, 1.5% niobium, 0.5% nitrogen, with the remainder being iron and essential impurities.

[0063] In this embodiment, the mechanical properties of Examples 7, 8, and 9 are compared with those of 1.4826 / 1.4837 as shown in Table 4. Table 4 I. Comparative Analysis of Chemical Composition:

[0064] In Examples 7-9 (N2 series), Mn is a strong austenite-forming element, and high Mn content can significantly expand the γ phase region.

[0065] At extremely low Ni contents (2.0-4.0%), Mn plays a major role in stabilizing austenite, preventing the precipitation of harmful phases such as δ-ferrite or σ-phase during high-temperature or cooling processes. Simultaneously, high Mn content helps increase the solubility of nitrogen in molten steel, providing a thermodynamic basis for subsequent high-nitrogen additions.

[0066] 2. In Examples 7-9 (N2 series), the extremely high nitrogen (N=0.4-0.5%) far exceeds that of conventional stainless steel (<0.1%).

[0067] Nitrogen atoms cause strong lattice distortion, significantly improving strength (tensile / yield strength); they form fine, dispersed, and thermally stable Nb(C,N) precipitates with Nb, which can enhance creep resistance, inhibit dislocation movement and grain boundary slip; improve oxidation resistance, and also help form a dense Cr2O3 film and enhance its adhesion.

[0068] 3. In Examples 7-9 (N2 series), the Ni content is only about 1 / 3 of that in 1.4826 and about 1 / 10 of that in 1.4849. This significantly reduces material costs, meeting the urgent needs of the automotive industry for low-cost, high-performance materials. The complete replacement of the austenitic stability brought by high Ni content with a "Mn+N+Cr" combination embodies an advanced nickel-saving stainless steel design concept.

[0069] 4. In Examples 7-9 (N2 series), Nb = 1.0-1.5%, which is lower than 1.4826 / 1.4848 (1.3-1.7%), but in a high N environment, the precipitation efficiency of Nb is higher and it is easier to form NbN or Nb(C,N).

[0070] Because the non-coarse NbC precipitates are finer and more dispersed, the strengthening effect is superior, the stability at high temperatures is good, and the resistance to coarsening is strong. This achieves "high-efficiency strengthening with low niobium" and avoids the decline in processing performance or brittleness caused by excessive Nb.

[0071] In Examples 7-9 (N2 series), the chromium (Cr) content (21.0-23.0%) meets the basic requirements for high-temperature oxidation resistance (≥20%, Cr can form a stable oxide film).

[0072] Although it is lower than 1.4837 / 1.4848 (24-27%), through the synergistic effect of N, it may improve the compactness and self-healing ability of the oxide film, avoiding the risk of σ phase precipitation and increased processing difficulty caused by excessive Cr.

[0073] II. Analysis of the mechanism of performance difference: 1. Significantly higher tensile strength and yield strength: The main reason is that the strong solid solution strengthening of nitrogen in Examples 7-9 (N2 series) leads to a strong stress field generated by N atoms on the matrix, which greatly hinders dislocation slip; fine Nb(C,N) precipitation strengthening: high N promotes the formation of a large number of nanoscale precipitates, which significantly improves the yield strength; solid solution strengthening contribution of Mn: Mn itself also has a certain strengthening effect, so despite the extremely low Ni content, the strength of N2 still surpasses all comparative materials.

[0074] 2. Elongation: Slightly lower at room temperature, consistent at high temperature: High nitrogen content leads to significant lattice distortion, increased resistance to dislocation movement, and a slight decrease in plasticity. However, this decrease remains within an acceptable range, indicating a uniform microstructure without significant defects. At high temperatures, dislocation activity is enhanced, plasticity is restored, the austenite structure is stable, there is no phase transformation embrittlement, and grain boundaries are clean (due to good P / S control), preventing high-temperature embrittlement. This demonstrates that N2 retains sufficient high-temperature plasticity under high strength conditions, making it suitable for complex forming and high-temperature service.

[0075] 3. Creep performance is superior to the comparative example in all aspects: This is because N(C,N) has a high precipitation temperature and slow coarsening rate in the 600-900℃ range, continuously pinning dislocations during long-term service; grain boundary strengthening: fine precipitates are distributed at grain boundaries, effectively suppressing grain boundary slip—the main cause of creep fracture; matrix strengthening: high N solid solution strengthening makes the matrix more difficult to deform; low Ni materials have obvious advantages: high Ni steel (such as 1.4837) relies on solid solution strengthening, has fewer precipitates, and its creep resistance at medium and high temperatures is not as good as N2.

[0076] The stainless steels in Examples 7-9 (N2 series) have achieved a comprehensive improvement in high-temperature strength and creep resistance while maintaining an acceptable level of plasticity by using the super solid solution strengthening of nitrogen and the nitrogen-niobium synergistic precipitation mechanism, through the innovative composition design of "ultra-high manganese + extremely high nitrogen + extremely low nickel + niobium microalloying". This is achieved by almost eliminating the expensive nickel element.

[0077] In summary, as Figure 7 or Figure 8 or Figure 9 As shown, compared with the 1.4826 / 1.4837 material, Examples 7, 8, and 9 exhibit higher tensile strength and yield strength, while their elongation is slightly lower at room temperature and similar at high temperature. Furthermore, Examples 7, 8, and 9 demonstrate superior creep performance compared to the 1.4826 / 1.4837 material at various high temperatures. This stainless steel material is more suitable for high-temperature, long-term service applications such as automotive turbochargers.

[0078] The specific embodiments described above do not constitute a limitation on the scope of protection of this disclosure. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this disclosure should be included within the scope of protection of this disclosure.

Claims

1. A heat-resistant, high-performance stainless steel for use in automotive turbochargers, characterized in that, It consists of the following components: carbon 0.3-0.5%, silicon 0.5-1.5%, manganese 1.0-2.5%, phosphorus 0.02-0.04%, sulfur 0.02-0.04%, molybdenum 0.3-0.5%, chromium 18.0-23.0%, nickel 2.0-7.8%, niobium 0.5-1.5%, nitrogen 0.2-0.5%, with the remainder being iron and essential impurities.

2. The heat-resistant high-performance stainless steel for use in automotive turbochargers according to claim 1, characterized in that, It consists of the following components: carbon 0.3-0.5%, silicon 1.0-1.5%, manganese 1.0-1.5%, phosphorus 0.02-0.04%, sulfur 0.02-0.04%, molybdenum 0.3-0.5%, chromium 18.0-20.0%, nickel 6.0-7.8%, niobium 0.5-0.8%, nitrogen 0.2-0.3%, with the remainder being iron and essential impurities.

3. The heat-resistant high-performance stainless steel for use in automotive turbochargers according to claim 1, characterized in that, It consists of the following components: carbon 0.3-0.5%, silicon 1.0-1.5%, manganese 1.5-2.0%, phosphorus 0.02-0.04%, sulfur 0.02-0.04%, molybdenum 0.3-0.5%, chromium 20.0-21.0%, nickel 4.0-6.0%, niobium 1.0-1.5%, nitrogen 0.3-0.4%, with the remainder being iron and essential impurities.

4. The heat-resistant high-performance stainless steel for use in automotive turbochargers according to claim 1, characterized in that, It consists of the following components: carbon 0.3-0.5%, silicon 0.5-1.0%, manganese 2.0-2.5%, phosphorus 0.02-0.04%, sulfur 0.02-0.04%, molybdenum 0.3-0.5%, chromium 21.0-23.0%, nickel 2.0-4.0%, niobium 1.0-1.5%, nitrogen 0.4-0.5%, with the remainder being iron and essential impurities.

5. The heat-resistant high-performance stainless steel for use in automotive turbochargers according to claim 2, characterized in that, It consists of the following components: 0.4% carbon, 1.25% silicon, 1.25% manganese, 0.03% phosphorus, 0.03% sulfur, 0.4% molybdenum, 19.0% chromium, 6.9% nickel, 0.65% niobium, 0.25% nitrogen, with the remainder being iron and essential impurities.

6. The heat-resistant high-performance stainless steel for use in automotive turbochargers according to claim 3, characterized in that, It is composed of the following components: carbon 0.4%, silicon 1.25%, manganese 1.75%, phosphorus 0.03%, sulfur 0.03%, molybdenum 0.4%, chromium 20.5%, nickel 5.0%, niobium 1.25%, and nitrogen 0.35%.

7. The heat-resistant high-performance stainless steel for use in automotive turbochargers according to claim 4, characterized in that, It consists of the following components: 0.4% carbon, 0.75% silicon, 2.25% manganese, 0.03% phosphorus, 0.03% sulfur, 0.4% molybdenum, 22.5% chromium, 3.0% nickel, 1.25% niobium, 0.45% nitrogen, with the remainder being iron and essential impurities.

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