CN115287539B - Stainless steel plate with good high-temperature strength for automobile exhaust system and preparation method thereof - Google Patents
Stainless steel plate with good high-temperature strength for automobile exhaust system and preparation method thereof Download PDFInfo
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- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
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- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
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Abstract
The invention relates to a stainless steel plate with good high-temperature strength for an automobile exhaust system, which comprises the following chemical components in percentage by weight: less than 0.02 percent of C, 0.8 to 1.0 percent of Si, 0.1 to 0.35 percent of Mn, less than 0.03 percent of S, less than 0.04 percent of P, 20 to 23 percent of Cr, 0.6 to 0.85 percent of Nb, less than 0.02 percent of N, 1.9 to 2.0 percent of Mo, 0.7 to 1.0 percent of Al, and the balance of Fe and unavoidable impurities. The beneficial effects of the invention are as follows: the steel for the high-temperature end of the automobile exhaust system, which can be used in a high-temperature environment of 950 ℃ or above, is designed to regulate and control the structure and the comprehensive performance of the ferrite stainless steel by reasonably designing the material components (adding Si, nb, cr and Al elements) and optimizing the hot rolling, hot rolling annealing, cold rolling and cold rolling annealing processes, and simultaneously improve the room temperature and high-temperature strength of the existing material.
Description
Technical Field
The invention relates to the technical field of ferrous metallurgy, in particular to an automobile exhaust system stainless steel plate with good high-temperature strength and a preparation method thereof.
Background
In recent years, global environmental problems have been increasingly emphasized, and there is a strong demand for improvement of the exhaust gas purification rate of automobiles in various countries. The european regulations and proposals of EU2000 and EU2005, etc. are put forward, and the five-stage emission standard of the european union is put forward in month 9 of 2009, and the automobile exhaust emission standard is also improved in recent years in the united states. In 2007, china publishes automobile exhaust emission standards equivalent to European III and European IV standards. With the improvement of the exhaust emission standard and the demand of the light weight of the automobile, the development and popularization of the turbocharging technology and the more sufficient fuel combustion, the result is that the service temperature of the hot end manifold of the automobile exhaust system is higher and higher, and the exhaust manifold is used as the nearest part of the exhaust system from the engine, and the working temperature of the exhaust manifold is highest and can reach 950-1050 ℃ or even higher. In addition, the exhaust manifold is required to have good formability due to its complicated shape.
The working temperature of the iron casting used for the early exhaust manifold is only below 800 ℃, and the service condition cannot be met. The austenitic stainless steel or the heat-resistant alloy brings great cost pressure, and meanwhile, the austenitic stainless steel has high thermal fatigue failure risk due to high thermal expansion coefficient. With the improvement of smelting technology, the ultra-low carbon nitrogen ferrite stainless steel becomes the first choice material of an automobile exhaust system. At present, home and abroad host factories are actively seeking ferrite stainless steel which can be used at 950 ℃ or above to meet the development of automobile technology.
Chen Liqing and the like of university of northeast study on steel for high temperature end of automobile exhaust system used in high temperature environment, and creates the invention of ' a ferrite stainless steel plate with good high temperature strength and forming property and a preparation method thereof (CN 109913758A) ' B444M2 ferrite stainless steel with improved high temperature oxidation resistance and a preparation method thereof (CN 109355478A) ', which mainly adds W element and rare earth element Ce on the basis of the traditional 444 ferrite stainless steel, thereby achieving the purpose of improving high temperature strength and forming property. Wherein W is a rare metal, which is a minor noble metal, and has a small reserveThe reserve volume ascertained all over the world is not more than 620 ten thousand tons, the exploitation capacity is only 290 ten thousand tons, and the cost is high; the oxidation resistance can be improved by adding proper rare earth elements, and the main viewpoints can be summarized as follows: enhancing the selective oxidation of Cr; altering Cr 2 O 3 The growth mode of the alloy and the adhesion between the oxide scale and the matrix are enhanced, but rare earth elements are easy to cause problems of blockage of a water gap of a continuous casting crystallizer in the smelting process, the smelting technical requirement is high, and the surface quality of the cold-rolled sheet is influenced by rare earth inclusions.
Disclosure of Invention
The invention provides a stainless steel plate with good high-temperature strength for an automobile exhaust system and a preparation method thereof, and aims to develop steel for the high-temperature end of the automobile exhaust system, which can be used in a high-temperature environment of 950 ℃ or above, and the structure and the comprehensive performance of ferrite stainless steel are regulated and controlled by reasonably designing material components (adding Si, nb, cr and Al elements) and optimizing hot rolling, hot rolling annealing, cold rolling and cold rolling annealing processes, and meanwhile, the room-temperature and high-temperature strength of the existing material is improved.
In order to achieve the above purpose, the invention is realized by adopting the following technical scheme:
the stainless steel plate with good high-temperature strength for the automobile exhaust system comprises the following chemical components in percentage by weight: less than 0.02 percent of C, 0.8 to 1.0 percent of Si, 0.1 to 0.35 percent of Mn, less than 0.03 percent of S, less than 0.04 percent of P, 20 to 23 percent of Cr, 0.6 to 0.85 percent of Nb, less than 0.02 percent of N, 1.9 to 2.0 percent of Mo, 0.7 to 1.0 percent of Al, and the balance of Fe and unavoidable impurities.
The effect of each alloy element is as follows:
nb as a strengthening element can remarkably improve the temperature and high-temperature strength when being added into stainless steel, and trace amount of Nb has good effect on high-temperature creep strength. And a great deal of research shows that niobium is an effective element for increasing high-temperature strength, and the content of solid solution niobium has a great influence on strength. Niobium is solid-dissolved in the matrix to improve the high-temperature strength, and the strength is improved as the solid-solution amount increases.
The alloying element Cr is the main element for providing the ferritic stainless steel with good corrosion resistance, and in the oxidizing medium, chromium can provide the stainless steel withCr is rapidly generated on the surface 2 O 3 Protective films, which can be repaired quickly even after they are destroyed. The alloy element Cr can improve the plastic strain ratio r value, and is mainly characterized in that the addition of the substitutional chromium atoms in the ferrite stainless steel makes some sliding systems in the body-centered cubic metal not easy to start, so that the plastic anisotropic deformation of the sheet is increased, and the r value is improved.
Al is an alloy element that is economical and can improve oxidation resistance of stainless steel. The stainless steel with certain Al content can form a layer of Al with good protection on the surface 2 O 3 Film having a protective effect on the matrix superior to Cr 2 O 3 And (3) a film.
Si has promotion effect on the oxidation performance of stainless steel, and especially has inhibition effect on destabilization oxidation. At a temperature of above 1000 ℃, siO formed by oxidation of Si element in stainless steel 2 Provides oxidation resistance and hot corrosion protection better than Cr 2 O 3 A layer. Due to the formation of continuous glassy SiO between the metal and oxide interfaces 2 The diffusion barrier layer thus improves high temperature oxidation resistance. At the same time, siO 2 Can be used as nucleation sites for protective chromium oxide layers.
Compared with the conventional 444 steel, the Cr content is increased, and the oxidation resistance and corrosion resistance are improved; si content is increased, and oxidation resistance is improved; the high Nb design improves the high temperature and high temperature strength through precipitation strengthening and improves the high temperature creep resistance, and in addition, nb can fix carbon and nitrogen, avoid precipitation of Cr and refine the recrystallization structure.
The addition of the alloy element Al improves the high-temperature oxidation resistance, improves the high-temperature strength, and simultaneously enhances the tissue stability at high temperature for a long time. For example, in the process of the invention, compared with the experimental steel without Al, the experimental steel with high Al content has the advantages that the high-temperature strength can be improved by 20-30MPa after long-time high-temperature aging, and the abnormal growth of grains does not occur.
The structure of the stainless steel plate is a ferrite structure with uniform equiaxed crystals; the structure after 100 hours aging treatment at 950 ℃ and 1000 ℃ is still a ferrite structure with uniform equiaxed crystals, and the grain size is smaller.
The yield strength of the stainless steel at room temperature is 380-400 MPa, the tensile strength is 560-570 MPa, and the elongation is 30% -32%.
The yield strength of the stainless steel plate after the time-efficient treatment at 1000 ℃ for 100 hours is 370-390 MPa, the tensile strength is 530-540 MPa, and the elongation is 29% -30%.
The tensile strength of the stainless steel plate at the high temperature of 950 ℃ is 34-36 MPa, and the yield strength is 24-28 MPa; the tensile strength is 24-26 MPa at the high temperature of 1000 ℃ and the yield strength is 20-22 MPa.
The preparation method of the stainless steel plate with good high-temperature strength for the automobile exhaust system comprises the following steps:
1) Smelting by adopting a vacuum induction furnace, slowly melting, and refining for 40-45 minutes at 1600-1620 ℃ after melting; filling argon 14500-15000 Pa after refining, and sequentially adding alloy at intervals of 5-7 minutes; stirring for 5-6 minutes after the alloy is added, regulating the temperature and tapping, wherein the tapping temperature is 1590-1600 ℃;
2) Alloy charging sequence: C. cr and Mo are added along with the furnace; adding Nb strips-silicon-manganese in sequence after refining is finished and argon is filled; the ingot is obtained and is skinned.
3) And (3) hot rolling: hot rolling the ingot to 25-30 mm from the first time, heating to 1170+/-5 ℃, and preserving the heat for 2-2.5 h; the second time of hot rolling from a 25 mm-30 mm intermediate blank to a 5 mm-6 mm thick hot rolled plate, the hot rolling temperature is 1050+/-5 ℃, the heat preservation time is 30-40 min, and the reduction rate of the second hot rolling pass is 20-50%; annealing the hot rolled plate at 1060+/-5 ℃ and preserving heat for 8-10 min; and (5) carrying out surface sand blasting after annealing is finished, and removing clean oxide scales.
4) Cold rolling: the hot rolled plate with the thickness of 5 mm-6 mm is cold rolled to 1.5 mm-2.0 mm, the single reduction rate is 20-25%, the final pass is not more than 10%, the cold rolled plate is annealed at 1060+/-5 ℃ and the temperature is kept for 5-8 min.
According to the invention, through the optimized matching of the forging temperature and the forging deformation, single-pass deformation ratio distribution and the like, the distribution uniformity of microstructure in steel is effectively controlled: in order to avoid the growth of high Wen Jingli, the initial rolling temperature is controlled to 1050 ℃ when the finished product is rolled, the pass reduction rate is controlled to 20% -50%, and water cooling is adopted after rolling, so that the generation of intermetallic phases is avoided to deteriorate the material performance.
In order to eliminate deformed structure after rolling, recrystallization is completed, and the grain size and the size and distribution of precipitated phases are controlled to obtain uniform structure. Finally, the hot rolled plate is annealed at 1060+/-5 ℃ and is kept for 10min. And (5) carrying out surface sand blasting after annealing is finished, and removing clean oxide scales.
The single rolling reduction rate of cold rolling is controlled to be 20%, and the final pass is not more than 10%. Annealing the cold-rolled plate at 1060+/-5 ℃ and preserving heat for 5min. The structure of the stainless steel after cold rolling and annealing is a ferrite structure with uniform equiaxed crystals.
The comparison of the optimized properties with the properties of the existing similar materials is shown in Table 1:
TABLE 1
Compared with the prior art, the invention has the beneficial effects that:
a stainless steel plate with good high-temperature strength for an automobile exhaust system and a preparation method thereof aim to develop steel for the high-temperature end of the automobile exhaust system, which can be used in a high-temperature environment of 950 ℃ or above, and the structure and the comprehensive performance of the ferrite stainless steel are regulated and controlled by reasonably designing material components (adding Si, nb, cr and Al elements) and optimizing hot rolling, hot rolling annealing, cold rolling and cold rolling annealing processes, and the room temperature and high-temperature strength of the existing materials are improved.
The yield strength of the ferrite stainless steel is 380-400 MPa, the tensile strength is 560-570 MPa, and the elongation is 30% -32%; the yield strength after the time-efficient treatment at 1000 ℃ for 100 hours is 370-390 MPa, the tensile strength is 530-540 MPa, and the elongation is 29% -30%; the tensile strength is 34-36 MPa at 950 ℃ and the yield strength is 24-28 MPa; the tensile strength is 24-26 MPa at the high temperature of 1000 ℃ and the yield strength is 20-22 MPa.
Drawings
FIG. 1 is a structure of a stainless steel after cold-rolled annealing at 1060℃in example 1;
FIG. 2 shows the structure (a) after 100h aging treatment at 950 ℃ in example 1;
FIG. 3 shows the structure (b) after 100h aging at 1000℃in example 1;
FIG. 4 is a structure of a stainless steel after cold-rolled annealing at 1060℃in example 2;
FIG. 5 is the structure (a) after 100h aging treatment at 950 ℃ in example 2;
FIG. 6 is the structure (b) after 100h aging at 1000℃in example 2;
FIG. 7 is a structure of stainless steel after cold rolling annealing at 1060℃in example 3;
FIG. 8 shows the structure (a) after 100h aging treatment at 950 ℃ in example 3;
FIG. 9 shows the structure (b) after 100h aging at 1000℃in example 3;
FIG. 10 is a structure of a stainless steel after cold rolling annealing at 1060℃according to comparative example 1;
FIG. 11 is a diagram showing the structure (a) after aging treatment at 950 ℃ for 100 hours in comparative example 1;
FIG. 12 is a diagram showing the structure (b) after aging treatment at 1000℃for 100 hours in comparative example 1;
FIG. 13 is a structure of a stainless steel after cold rolling annealing at 1060℃according to comparative example 2;
FIG. 14 is a diagram showing the structure (a) after aging treatment at 950 ℃ for 100 hours in comparative example 2;
FIG. 15 is a diagram showing the structure (b) after aging treatment at 1000℃for 100 hours in comparative example 2;
FIG. 16 is a structure (a) after annealing at 1030℃in comparative example 5;
FIG. 17 is a comparative example 5, cold rolled 1030℃annealed structure (b);
FIG. 18 is a diagram showing a structure (a) after heat rolling at 1080℃in comparative example 6;
FIG. 19 is a structure (b) after cold rolling 1080℃annealing in comparative example 6.
Detailed Description
The present invention will be described in more detail by way of examples, which are merely illustrative of the best modes of carrying out the invention, and do not limit the scope of the invention in any way.
The chemical composition of the steel of the example of the invention is shown in Table 2.
TABLE 2 chemical composition (wt%) of example steel
| Examples | C | Si | Mn | S | P | Cr | Nb | N | Mo | Al |
| 1 | 0.0046 | 0.91 | 0.215 | 0.0029 | 0.003 | 22.1 | 0.75 | 0.0019 | 1.94 | 0.86 |
| 2 | 0.0042 | 0.8 | 0.211 | 0.0031 | 0.003 | 22.2 | 0.74 | 0.0019 | 1.93 | 0.85 |
| 3 | 0.0041 | 0.99 | 0.214 | 0.0030 | 0.003 | 22.1 | 0.75 | 0.0019 | 1.94 | 0.84 |
| 4 | 0.0041 | 0.8 | 0.213 | 0.0031 | 0.003 | 20.2 | 0.74 | 0.0015 | 1.95 | 0.85 |
| 5 | 0.0040 | 0.79 | 0.212 | 0.0031 | 0.003 | 22.8 | 0.76 | 0.0016 | 1.93 | 0.85 |
| 6 | 0.0046 | 0.8 | 0.215 | 0.0029 | 0.003 | 22.1 | 0.63 | 0.0017 | 1.95 | 0.84 |
| 7 | 0.0046 | 0.8 | 0.215 | 0.0029 | 0.003 | 22.0 | 0.83 | 0.0016 | 1.94 | 0.86 |
| 8 | 0.0046 | 0.8 | 0.215 | 0.0029 | 0.003 | 22.1 | 0.75 | 0.0019 | 1.94 | 0.98 |
| 9 | 0.0046 | 0.8 | 0.215 | 0.0029 | 0.003 | 22.2 | 0.75 | 0.0019 | 1.94 | 0.71 |
The preparation method of the example steel is as follows:
1) Smelting by adopting a vacuum induction furnace, slowly melting, and carrying out heat preservation and refining for 40 minutes after melting, wherein the temperature is 1610 ℃; filling argon 15000 Pa after refining, sequentially adding alloy, and spacing for 5 minutes; stirring for 5 minutes after the alloy is added, regulating the temperature, tapping, and tapping at 1600 ℃. Alloy charging sequence: C. cr and Mo are added along with the furnace; and (5) charging argon after refining, and sequentially adding Nb strips-silicon-manganese. The ingot is obtained and is skinned.
3) And (3) hot rolling: hot rolling the ingot from the ingot casting to 25mm for the 1 st time, heating the ingot at 1170 ℃ and keeping the temperature for 2h; and hot rolling from a 25mm intermediate blank to a 5mm thick hot rolled plate for the 2 nd time, wherein the hot rolling temperature is 1050 ℃, the heat preservation time is 30min, and the pass reduction rates are respectively 50%, 30% and 20%. The hot rolled plate was annealed at 1060℃and incubated for 10min. And (5) carrying out sand blasting on the surface after annealing, and removing clean oxide scales.
4) Cold rolling: and (3) a hot rolled plate with the thickness of 5mm is cold rolled to 1.5mm, the single reduction rate is 20%, and the final pass is not more than 10%. The cold-rolled plate is annealed at 1060 ℃ and kept for 5min.
The mechanical properties of the steel plates of the examples are shown in Table 3.
Table 3 mechanical properties of the steel sheet of the example
The above embodiment, wherein: example 1 the structure of the stainless steel after cold-rolled annealing was a ferrite structure with uniform equiaxed grains (see fig. 1); after the cold-rolled sheet is subjected to aging treatment at 950 ℃ and 1000 ℃ for 100 hours, the structure is still a ferrite structure with uniform equiaxed crystals, and the grain size is smaller (see fig. 2 and 3). Example 2 the structure of the stainless steel after cold-rolled annealing was a ferrite structure with uniform equiaxed grains (see fig. 4); after the cold-rolled sheet is subjected to aging treatment at 950 ℃ and 1000 ℃ for 100 hours, the structure is still a ferrite structure with uniform equiaxed crystals, and the grain size is smaller (see fig. 5 and 6). Example 3 the structure of the stainless steel after cold-rolled annealing was a ferrite structure with uniform equiaxed grains (see fig. 7); after the cold-rolled sheet is subjected to aging treatment at 950 ℃ and 1000 ℃ for 100 hours, the structure is still a ferrite structure with uniform equiaxed crystals, and the grain size is smaller (see fig. 8 and 9).
Comparative example 1:
comparative example 1 the same procedure was used as in example 1 above except that the Nb element was 0.5% in the chemical composition. Comparative example 1 the structure of the stainless steel after cold-rolled annealing was a ferrite structure with uniform equiaxed grains, but the grains were larger (see fig. 10). After aging treatment for 100 hours at 950 ℃ and 1000 ℃, the cold-rolled sheet has coarse grains and serious mixed crystals (see fig. 11 and 12).
Comparative example 1 shows a decrease in strength at room temperature and high temperature through mechanical property test. The yield strength of the stainless steel at room temperature is 347MPa, the tensile strength is 493MPa, and the elongation is 28%; the yield strength after the time-efficient treatment at 1000 ℃ for 100 hours is 313MPa, the tensile strength is 468MPa, and the elongation is 29.5%; the tensile strength at 950 ℃ is 26MPa, and the yield strength is 20.2MPa; the tensile strength at 1000℃is 19.2MPa and the yield strength is 16.8MPa.
Comparative example 2:
comparative example 2 the same procedure was followed as in example 1 above except that the Nb element was 0.9% in the chemical composition. The structure of the stainless steel after cold rolling and annealing is a ferrite structure with uniform equiaxed crystals, and the crystal grains are larger (see fig. 13). After aging treatment for 100 hours at 950 ℃ and 1000 ℃, the cold-rolled sheet has coarse grains and serious mixed crystals (see fig. 14 and 15). The strength and the high-temperature strength are obviously reduced after long-time aging through mechanical property test. The yield strength of the stainless steel at room temperature is 355MPa, the tensile strength is 502MPa, and the elongation is 27%; the yield strength after the 100-hour time-effect treatment at 1000 ℃ is 308MPa, the tensile strength is 360MPa, and the elongation is 23.5%; the tensile strength at 950 ℃ is 24MPa, and the yield strength is 20MPa; the tensile strength at 1000℃is 19.6MPa and the yield strength is 15.8MPa.
Comparative example 3:
comparative example 3 the chemical composition and preparation method were the same as in example 1 above except that the Al element was 0.5%. The strength and the high-temperature strength are reduced after long-time aging through mechanical property test. The yield strength of the stainless steel at room temperature is 362MPa, the tensile strength is 532MPa, and the elongation is 28%; the yield strength after the time-efficient treatment at 1000 ℃ for 100 hours is 320MPa, the tensile strength is 441MPa, and the elongation is 23%; the tensile strength at 950 ℃ is 24.5MPa, and the yield strength is 21MPa; the tensile strength at 1000℃is 19MPa and the yield strength is 17.2MPa.
Comparative example 4:
comparative example 4 the chemical composition and preparation method were the same as in example 1 above except that the Al element was 1.1% in the chemical composition. Through mechanical property test, the strength and high-temperature strength of the product are reduced after long-time aging. The yield strength of the stainless steel at room temperature is 371MPa, the tensile strength is 562MPa, and the elongation is 29%; the yield strength after the time-efficient treatment at 1000 ℃ for 100 hours is 330MPa, the tensile strength is 445MPa, and the elongation is 22%; the tensile strength at 950 ℃ is 25.5MPa, and the yield strength is 21.5MPa; the tensile strength at 1000℃is 19.8MPa and the yield strength is 18MPa.
Comparative example 5:
comparative example 5 steel sheet the chemical composition was the same as in example 1 above; the procedure of example 1 was repeated except that the annealing temperature of the hot rolled sheet was 1030℃and the annealing temperature of the cold rolled sheet was 1030 ℃. Comparative example 5 the annealing temperature for hot rolling and cold rolling was lowered, and the deformed structure after annealing was not completely eliminated (fig. 16 and 17). The mechanical property test shows that the yield strength of the stainless steel at room temperature is 370MPa, the tensile strength is 544MPa, and the elongation is 28%; the yield strength after the 100-hour time-effect treatment at 1000 ℃ is 351MPa, the tensile strength is 496MPa, and the elongation is 25; the tensile strength at 950 ℃ is 31.93MPa, and the yield strength is 23.59MPa; the tensile strength at 1000℃is 23.07MPa and the yield strength is 16.84MPa.
Comparative example 6:
comparative example 6 steel sheet the chemical composition was the same as in example 1 above; the preparation method is the same as in example 1 except that the annealing temperature of the hot rolled sheet is 1080 ℃ and the annealing temperature of the cold rolled sheet is 1080 ℃. Comparative example 6 has high annealing temperatures for hot rolling and cold rolling, and the grains and the precipitated phases grow significantly after annealing (fig. 18 and 19). The mechanical property test shows that the yield strength of the stainless steel at room temperature is 362MPa, the tensile strength is 532MPa, and the elongation is 29%; the yield strength after the 100-hour time-effect treatment at 1000 ℃ is 325MPa, the tensile strength is 468MPa, and the elongation is 25.5; the tensile strength at 950 ℃ is 28.93MPa, and the yield strength is 22.59MPa; the tensile strength at 1000℃is 21.07MPa and the yield strength is 16.25MPa.
Claims (5)
1. The stainless steel plate with good high-temperature strength for the automobile exhaust system is characterized by comprising the following chemical components in percentage by weight: less than 0.02 percent of C, 0.8 to 1.0 percent of Si, 0.1 to 0.35 percent of Mn, less than 0.03 percent of S, less than 0.04 percent of P, 20 to 23 percent of Cr, 0.6 to 0.85 percent of Nb, less than 0.02 percent of N, 1.9 to 2.0 percent of Mo, 0.7 to 1.0 percent of Al and the balance of Fe and unavoidable impurities;
the preparation method of the stainless steel plate with good high-temperature strength for the automobile exhaust system comprises the following steps:
1) Smelting by adopting a vacuum induction furnace, and carrying out heat preservation and refining for 40-45 minutes after melting, wherein the temperature is 1600-1620 ℃; charging argon after refining, adding alloy, adjusting temperature, tapping, and tapping at 1590-1600 ℃;
2) Alloy charging sequence: C. cr and Mo are added along with the furnace; adding Nb strips-silicon-manganese in sequence after refining is finished and argon is filled;
3) And (3) hot rolling: hot rolling the ingot to 25-30 mm from the first time, heating to 1170+/-5 ℃, and preserving the heat for 2-2.5 h; the second time of hot rolling from a 25 mm-30 mm intermediate blank to a 5 mm-6 mm thick hot rolled plate, the hot rolling temperature is 1050+/-5 ℃, the heat preservation time is 30-40 min, and the reduction rate of the second hot rolling pass is 20-50%; annealing the hot rolled plate at 1060+/-5 ℃ and preserving heat for 8-10 min;
4) Cold rolling: the hot rolled plate with the thickness of 5 mm-6 mm is cold rolled to 1.5 mm-2.0 mm, the single reduction rate is 20-25%, the final pass is not more than 10%, the cold rolled plate is annealed at 1060+/-5 ℃ and the temperature is kept for 5-8 min.
2. The stainless steel sheet for an automotive exhaust system having excellent high-temperature strength according to claim 1, wherein the structure of the stainless steel sheet is a ferrite structure having uniform equiaxed grains; the structure after 100 hours aging treatment at 950 ℃ and 1000 ℃ is still a ferrite structure with uniform equiaxed crystals.
3. The stainless steel sheet for an exhaust system of an automobile having excellent high-temperature strength according to claim 1, wherein the stainless steel has a yield strength of 380 to 400MPa, a tensile strength of 560 to 570MPa, and an elongation of 30 to 32% at room temperature.
4. The stainless steel sheet for an exhaust system of an automobile having excellent high-temperature strength according to claim 1, wherein the stainless steel sheet has a yield strength of 370 to 390MPa, a tensile strength of 530 to 540MPa, and an elongation of 29 to 30% after being subjected to an aging treatment at 1000 ℃ for 100 hours.
5. The stainless steel sheet for an exhaust system of an automobile having excellent high-temperature strength according to claim 1, wherein the stainless steel sheet has a tensile strength of 34 to 36MPa and a yield strength of 24 to 28MPa at a high temperature of 950 ℃; the tensile strength is 24-26 MPa at the high temperature of 1000 ℃ and the yield strength is 20-22 MPa.
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| CA2085790A1 (en) * | 1991-12-19 | 1993-06-20 | Masao Koike | Steel for use in exhaust manifolds of automobiles |
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