CN114318146A - High-toughness ferritic stainless steel and manufacturing method and application thereof - Google Patents
High-toughness ferritic stainless steel and manufacturing method and application thereof Download PDFInfo
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- CN114318146A CN114318146A CN202111596625.5A CN202111596625A CN114318146A CN 114318146 A CN114318146 A CN 114318146A CN 202111596625 A CN202111596625 A CN 202111596625A CN 114318146 A CN114318146 A CN 114318146A
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Abstract
The invention discloses a high-toughness ferritic stainless steel and a manufacturing method and application thereof, wherein the method comprises the following steps: c is more than 0.004 and less than 0.015; si is more than 0.10 and less than 0.80; mn is more than 0.45 and less than 1.40; p is less than 0.03; s is less than 0.005; cr is more than 10.5 and less than 12.0; ni is more than 0.01 and less than 1.0; al is more than 0.005 and less than 0.090; cu is more than 0.01 and less than 0.60; ti is more than 0.10 and less than 0.30; n is more than 0.004 and less than 0.015; the balance of Fe and inevitable impurities; 320 < FF-AF < 380, wherein: FF 69.6Si +261Al +35.1Cr +250 Ti; AF 1187C +816N +52.6Mn +82.0Ni +89.7 Cu. The ferritic stainless steel material is obtained through composition design, hot rolling and thermal annealing processes, and the automobile exhaust system flange is manufactured.
Description
Technical Field
The invention belongs to the technical field of stainless steel manufacturing, and particularly relates to high-toughness ferritic stainless steel and a manufacturing method and application thereof.
Background
The ferritic stainless steel is generally defined as a stainless steel material which is ferrite or has a ferrite-based structure from high temperature to room temperature, and the Cr content of the stainless steel material is more than 10.5%, wherein the low-chromium type ferritic stainless steel is taken as a main stream product in the ultra-low carbon nitrogen ferritic stainless steel and has been widely applied to important parts of low-temperature sections and the like of an automobile exhaust system, and particularly, a low-chromium type ferritic stainless steel hot rolling material is largely used for connecting piece flanges in the automobile exhaust system. At present, the component system of the low-chromium type ferrite stainless steel is matched with a hot rolling and hot annealing process, and ferrite hot rolled coil materials meeting the requirements of flange application can be produced. The low-chromium type ferritic stainless steel has the defects that the low-chromium type ferritic stainless steel is a ferritic structure from high temperature to low temperature, and a black skin coil after hot rolling obtains a ferritic structure with a coarse structure after hot annealing, so that the ductile-brittle transition temperature (DBTT) of the material is high, namely the material has poor impact resistance under the low-temperature condition and is easy to crack in the stamping process, particularly in winter or northern areas with low air temperature.
Disclosure of Invention
1. Technical problem to be solved
Aiming at the problems that in the prior art, low-chromium type ferritic stainless steel has a ferritic structure from high temperature to low temperature, and a black skin coil after hot rolling obtains a ferritic structure with a coarse structure after hot annealing, so that the ductile-brittle transition temperature (DBTT) of the material is high, namely poor impact resistance under low temperature and easy cracking in the process of stamping, the invention aims to provide high-toughness ferritic stainless steel and a manufacturing method and application thereof, through the composition design and the matching of proper hot rolling and thermal annealing processes, the hot rolled ferritic stainless steel material with excellent low-temperature toughness is obtained, the hot-rolled ferrite stainless steel material does not increase raw materials, equipment and manufacturing cost, has simple production process, can be used for manufacturing automobile exhaust system flanges, particularly, the flange processed by stamping avoids the stamping cracking of the processing environment in low temperature and northern areas, and can also be used in application occasions with high requirements on low-temperature toughness.
2. Technical scheme
In order to achieve the purpose and achieve the technical effect, the invention adopts the following technical scheme:
a high-toughness ferritic stainless steel is characterized by comprising the following chemical components in percentage by mass: c is more than 0.004 and less than 0.015; si is more than 0.10 and less than 0.80; mn is more than 0.45 and less than 1.40; p is less than 0.03; s is less than 0.005; cr is more than 10.5 and less than 12.0; ni is more than 0.01 and less than 1.0; al is more than 0.005 and less than 0.090; cu is more than 0.01 and less than 0.60; ti is more than 0.10 and less than 0.30; n is more than 0.004 and less than 0.015; the balance of Fe and inevitable impurities; the chemical components meet the following requirements: 320 < FF-AF < 380, wherein:
FF＝69.6Si+261Al+35.1Cr+250Ti；
AF＝1187C+816N+52.6Mn+82.0Ni+89.7Cu。
c and N are important elements affecting the toughness of the ferritic stainless steel, and generally, the C, N content is controlled to a low level in order to suppress the generation of brittle precipitates (Cr carbonitrides), but the ferritic stainless steel according to the present invention is a low-chromium type ferrite, and therefore, the C, N content is appropriately relaxed; on the other hand, coarse grain size is the most important factor for reducing toughness, and the definition of C, N range of the present invention considers grain refining effect, and the too low C, N content cannot combine with the production process to obtain fine-grained ferrite structure in the present invention. Based on the above, 0.004 < C < 0.015, 0.004 < N < 0.015 are set.
Si can improve certain high-temperature oxidation resistance, has a favorable effect on the high-temperature operation of an exhaust system, is a deoxidizing element, cannot be too low, and has a lower limit of 0.1; in addition, too high Si element inhibits the phase transformation refinement process of the material of the present invention, so the upper limit is set to 0.8.
The Mn element mainly plays a role in promoting the phase change of hot working, and the Mn element cannot play the role when the Mn element is too low; while too high Mn element causes an increase in ductile-brittle transition temperature, 0.45 < Mn < 1.40 is set.
Cr is an indispensable corrosion resistance element for stainless steel, and Cr is set to be more than 10.5 to ensure the basic corrosion resistance of the material, and Cr is set to be less than 12.0 to ensure the low chromium property of the material and avoid the formation of brittle precipitates due to high Cr content to reduce the workability of the material.
The Ni element can improve the toughness of the material, but the addition of Ni can obviously improve the product cost, so that the Ni is controlled below 1.0; meanwhile, Ni is set to be more than 0.1 in order to maintain the toughness-improving effect of the Ni element.
The Cu element inevitably has residue in the electric furnace steelmaking, and the lower limit of 0.01 is set to be considered in the characteristics of the electric furnace steelmaking; meanwhile, the Cu element is beneficial to reducing the ductile-brittle transition temperature of the material and improving the toughness of the material, so that under the condition of matching requirements of various components, Cu is used as an element which needs to be additionally added, but when the Cu exceeds 0.60, Cu dissolution-precipitation is easy to occur in the pickling process, so that the Cu adhesion color difference defect on the surface of the material is caused, and therefore, the Cu is set to be more than 0.01 and less than 0.60.
Ti is C, N stabilizing element, can combine with C, N to prevent C, N and Cr from combining to form brittle precipitate, and Ti is more than 0.10 for achieving the effect; however, as Ti element is increased, the nozzle blocking phenomenon already occurs in the steelmaking continuous casting process, so that the production is unstable, and Ti is set to be less than 0.30.
Al is mainly a deoxidizing element and is also a ferrite-forming element, the lower limit is set to ensure a certain deoxidizing ability, and the upper limit is set to suppress ferrite formation and promote austenite transformation, so 0.005 < Al < 0.090 is set.
The P and S elements are controlled as residual harmful elements, but cannot be completely avoided. Therefore, P < 0.03 is set; s is less than 0.005.
Further, the high-toughness ferritic stainless steel comprises the following chemical components in percentage by mass: c is more than 0.004 and less than 0.015; si is more than 0.10 and less than 0.50; mn is more than 0.55 and less than 1.00; p is less than 0.03; s is less than 0.005; cr is more than 10.5 and less than 12.0; ni is more than 0.01 and less than 1.0; al is more than 0.005 and less than 0.090; cu is more than 0.01 and less than 0.40; ti is more than 0.10 and less than 0.30; n is more than 0.004 and less than 0.015; the balance of Fe and inevitable impurities; the chemical components meet the following requirements: 320 < FF-AF < 380, wherein:
FF＝69.6Si+261Al+35.1Cr+250Ti；
AF＝1187C+816N+52.6Mn+82.0Ni+89.7Cu。
the invention also aims to provide a manufacturing method of the high-toughness ferritic stainless steel, which is characterized in that a continuous casting billet meeting the component requirements is obtained by steelmaking of raw materials, the continuous casting billet is heated and then is hot-rolled, the hot-rolling deformation temperature range is 950-1100 ℃, and the hot-rolled continuous casting billet is curled and air-cooled to obtain a black coil material; and annealing and pickling the black coil material to obtain a white coil material.
The invention also aims to provide application of the high-toughness ferritic stainless steel in stamping manufacture of components of low-temperature sections of flanges of automobile exhaust systems.
3. Advantageous effects
Compared with the prior art, the invention has the beneficial effects that: by designing the components and carrying out hot rolling processing in a proper temperature range, a high-toughness ferritic stainless steel hot rolled material is obtained, the material obtains a ferrite structure with the grain size of more than 6.0 (according to the ASTME112 rating), and the room-temperature impact toughness is 100J/cm2Above, the DBTT value is reduced to-20 ℃, the problem of punching cracking of the material is successfully avoided, and particularly, the advantage of high toughness is reflected when the material is used in winter or northern areas.
Drawings
To more clearly illustrate the significant improvements achieved by the present invention, the following figures compare the differences between the conventional materials and the inventive materials:
FIG. 1 is a microstructure comparison of stainless steel material prepared by the example of the present invention.
FIG. 2 is a microstructure comparison of a stainless steel material prepared in comparative example 1.
FIG. 3 is a comparison of ductile to brittle transition (DBTT) curves of a stainless steel material prepared in comparative example 1 and a stainless steel material prepared in examples.
Detailed Description
The technical solution of the present invention will be further described with reference to the preferred embodiments.
A high-toughness ferritic stainless steel comprises the following chemical components in percentage by mass: c is more than 0.004 and less than 0.015; si is more than 0.10 and less than 0.80; mn is more than 0.45 and less than 1.40; p is less than 0.03; s is less than 0.005; cr is more than 10.5 and less than 12.0; ni is more than 0.01 and less than 1.0; al is more than 0.005 and less than 0.090; cu is more than 0.01 and less than 0.60; ti is more than 0.10 and less than 0.30; n is more than 0.004 and less than 0.015; the balance of Fe and inevitable impurities; the chemical components meet the following requirements: 320 < FF-AF < 380, wherein:
FF＝69.6Si+261Al+35.1Cr+250Ti；
AF＝1187C+816N+52.6Mn+82.0Ni+89.7Cu。
carrying out electric furnace smelting and continuous casting according to target components to obtain a continuous casting blank; the continuous casting billet is heated to 900-1100 ℃ for hot rolling processing, curled and air-cooled to form a black coil, and the black coil is subjected to conventional annealing and acid cleaning to form a white coil, so that the finished product material is obtained. The chemical components, white coil grain size grade and room-temperature impact toughness of the material are shown in a table 1, the typical metallographic structure of the material is shown in a figure 1, and the typical DBTT curve of the material is shown in a figure 2.
Table 1 chemical composition (wt.%, C, N, P, Sinppm) of the examples and comparative examples
The above examples 1 to 9 and comparative examples 1 to 2 were subjected to room temperature impact toughness tests to obtain Table 2
TABLE 2 comparison of the properties of the examples with those of the comparative examples
As can be seen from Table 2, the stainless steel materials obtained with the compositions of examples 1-9, compared with the compositions of comparative examples 1 and 2, have a microstructure with a significantly finer grain size, which results in a significant increase in the impact toughness and a significant decrease in the ductile to brittle transition temperature (DBTT). The stainless steel materials of examples 1-9 were used in the press-fabrication of automobile exhaust system flanges without the problem of press-cracking.
The foregoing is a more detailed description of the present invention in connection with specific preferred embodiments thereof, and it is not intended that the invention be limited to the specific embodiments thereof. For those skilled in the art to which the present invention pertains, the framework system can be flexible and changeable without departing from the concept of the present invention, and can be derived into a series of products. But rather a number of simple derivations or substitutions are made which are to be considered as falling within the scope of the invention as defined by the appended claims.
Claims (4)
1. A high-toughness ferritic stainless steel is characterized by comprising the following chemical components in percentage by mass: c is more than 0.004 and less than 0.015; si is more than 0.10 and less than 0.80; mn is more than 0.45 and less than 1.40; p is less than 0.03; s is less than 0.005; cr is more than 10.5 and less than 12.0; ni is more than 0.01 and less than 1.0; al is more than 0.005 and less than 0.090; cu is more than 0.01 and less than 0.60; ti is more than 0.10 and less than 0.30; n is more than 0.004 and less than 0.015; the balance of Fe and inevitable impurities; the chemical components meet the following requirements: 320 < FF-AF < 380, wherein:
FF＝69.6Si+261Al+35.1Cr+250Ti；
AF＝1187C+816N+52.6Mn+82.0Ni+89.7Cu。
2. a high toughness ferritic stainless steel according to claim 1, characterized in that: the high-toughness ferritic stainless steel comprises the following chemical components in percentage by mass: c is more than 0.004 and less than 0.015; si is more than 0.10 and less than 0.50; mn is more than 0.55 and less than 1.00; p is less than 0.03; s is less than 0.005; cr is more than 10.5 and less than 12.0; ni is more than 0.01 and less than 1.0; al is more than 0.005 and less than 0.090; cu is more than 0.01 and less than 0.40; ti is more than 0.10 and less than 0.30; n is more than 0.004 and less than 0.015; the balance of Fe and inevitable impurities; the chemical components meet the following requirements: 320 < FF-AF < 380, wherein:
FF＝69.6Si+261Al+35.1Cr+250Ti；
AF＝1187C+816N+52.6Mn+82.0Ni+89.7Cu。
3. a manufacturing method of high-toughness ferritic stainless steel is characterized in that a continuous casting billet meeting the component requirements is obtained by steelmaking from the raw material of the high-toughness ferritic stainless steel of the claim 1 or 2, the continuous casting billet is heated and then is hot-rolled, the hot-rolling deformation temperature range is 950-1100 ℃, and the hot-rolled and curled materials are air-cooled to obtain a black coil material; and annealing and pickling the black coil material to obtain a white coil material.
4. Use of the high-toughness ferritic stainless steel prepared by the method for manufacturing high-toughness ferritic stainless steel according to claim 3 in stamping to manufacture parts of low-temperature sections of flanges of automobile exhaust systems.
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107541681A (en) * | 2016-06-23 | 2018-01-05 | Posco公司 | The ferrite-group stainless steel of the excellent in low temperature toughness of welding point |
| CN112739843A (en) * | 2018-09-19 | 2021-04-30 | 株式会社Posco | Hot-rolled unannealed ferritic stainless steel sheet having excellent impact toughness and method for manufacturing same |
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Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107541681A (en) * | 2016-06-23 | 2018-01-05 | Posco公司 | The ferrite-group stainless steel of the excellent in low temperature toughness of welding point |
| CN112739843A (en) * | 2018-09-19 | 2021-04-30 | 株式会社Posco | Hot-rolled unannealed ferritic stainless steel sheet having excellent impact toughness and method for manufacturing same |
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