WO2011067979A1 - 耐応力腐食割れ性と加工性に優れた微細粒オーステナイト系ステンレス鋼板 - Google Patents
耐応力腐食割れ性と加工性に優れた微細粒オーステナイト系ステンレス鋼板 Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/34—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of silicon
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/001—Austenite
Definitions
- the present invention relates to an austenitic stainless steel sheet having a fine grain structure (structure consisting of fine crystal grains) having an average crystal grain size of 10 ⁇ m or less and excellent in stress corrosion cracking resistance and workability.
- Non-Patent Documents 1 and 2 disclose refinement of crystal grains using phase transformation from work-induced martensite to austenite in SUS304 defined in JIS G4305. By such a method, a fine grain structure having a crystal grain size of 1 to 5 ⁇ m is formed. As an effect of refinement, Non Patent Literature 1 reports an increase in yield strength (0.2% yield strength). Patent Document 2 reports the development of superplasticity at 650 to 750 ° C.
- Patent Document 1 discloses a metal gasket, its material, and a manufacturing method thereof as a technique using the effect of crystal grain refinement.
- This Patent Document 1 uses SUS301L defined in JIS G4305 to form a fine grain structure having a crystal grain size of 5 ⁇ m or less by utilizing the above-described phase transformation from processing-induced martensite to austenite and precipitation of chromium nitride. Yes. By combining the formation of this fine grain structure and temper rolling, the strength of Hv500 or higher is increased.
- the crystal grain size is adjusted to 1 to 5 ⁇ m, thereby increasing the 0.2% proof stress and increasing the strength. Is oriented.
- Non-Patent Document 3 describes that as a countermeasure, the change to ferritic stainless steel not containing Ni is certain.
- ferritic stainless steel when it is difficult to use ferritic stainless steel from the viewpoint of workability and weldability, it is a high austenite (SUSXM15J1) with high Ni content (11.5-15%) and high Si content and Cu content. It is also described that stainless steel is effective.
- Patent Document 2 discloses an austenitic stainless steel excellent in stress corrosion cracking resistance and pitting corrosion resistance containing about 9% Ni, 1.5% to less than 2.5% Cu, and a small amount of Mo and N. It is disclosed.
- Patent Document 3 includes Cr: 18 to 35%, Ni: 25 to 50%, Mo: 8% or less, Mn: 6% or less, N: 0.5% or less, C: 0.03% or less, An austenitic alloy excellent in stress corrosion cracking resistance characterized by a large amount of Cr and Ni is disclosed.
- Patent Document 4 C: 0.08% or less, Si: 0.1 to 3%, Cr: 18 to 23%, Ni: 8.5 to 12%, Mo: 0.2 to 2%, Cu: 0 .2 to 3.5%, N: 0.03 to 0.25%, the contents of Mn and S are adjusted, Cu and N are added together, and a small amount of Co , W, V, and Nb are added, and an austenitic stainless steel excellent in weather resistance, crevice corrosion resistance, and stress corrosion cracking resistance is disclosed.
- Patent Documents 5 to 7 disclose improvement of grain boundary type stress corrosion cracking.
- Patent Document 5 discloses an austenitic stainless steel excellent in intergranular corrosion resistance and intergranular stress corrosion cracking characteristics, characterized by containing either or both of Mo and Nb.
- Patent Documents 6 and 7 the amount of carbide is reduced by restricting the C amount to 0.03% or less, containing N at 0.15% or less, and adjusting the heating temperature and time of the steel slab.
- An austenitic stainless steel excellent in intergranular stress corrosion cracking resistance and a method for producing the same are disclosed, which is characterized by reducing the Cr deficiency in the vicinity of the grain boundary.
- All of the austenitic stainless steels disclosed in Non-Patent Document 3 and Patent Documents 2 to 7 described above contain more than 8% Ni, and Cu, Mo, Si, and Nb, Co, W as trace elements. , V and the like are added to improve the stress corrosion cracking resistance.
- the annealing temperature in industrial production is known in Non-Patent Documents 3 and 4.
- the crystal grain size is known in Non-Patent Document 5.
- austenitic stainless steel is annealed at 1000 to 1100 ° C., and even if the components are adjusted, the limit of refining is the grain size no. It is described that it is less than 10, that is, the crystal grain size is larger than 10 ⁇ m.
- Patent Documents 2 to 7 do not specifically describe the production method (annealing temperature) and the crystal grain size. Therefore, the steel disclosed in Patent Documents 2 to 7 can be easily estimated that the grain size of the steel is larger than 10 ⁇ m, similarly to Non-Patent Document 3, unless a special production method different from usual is disclosed. it can.
- the present invention overcomes stress corrosion cracking, which is a defect of austenitic stainless steel, by refining crystal grains, and does not rely on the addition of expensive Mo with Ni content of 8% or less,
- An object is to provide an austenitic stainless steel sheet having a fine grain structure with an average crystal grain size of 10 ⁇ m or less that is compatible with workability.
- the fine-grained austenitic stainless steel sheet excellent in stress corrosion cracking resistance and workability is C: 0.05% or less, Cr: 14-19%, Si: 2% in mass%.
- Mn 4% or less, Ni: 5-8%, Cu: 4% or less, and N: 0.1% or less, with the balance being Fe and inevitable impurities, and the following Md is ⁇ 20 to It has a steel component in the range of 40, the average crystal grain size is 10 ⁇ m or less, and the ratio of the large tilt grain boundaries of 15 ° or more is more than 80%.
- Md 551-462 (C + N) -9.2Si-8.1Mn-13.7Cr-29 (Ni + Cu) -18.2Mo
- the steel component is further in mass%, Mo: 1% or less, V: 1% or less, B : 0.010% or less, Nb: 0.5% or less, Ti: 0.5% or less, Rare earth elements: 0.5% or less, Al: 0.5% or less, Mg: 0.005% or less, and Ca : You may contain 1 type, or 2 or more types selected from 0.005% or less.
- the fine-grained austenitic stainless steel sheet excellent in stress corrosion cracking resistance and workability according to one aspect of the present invention is manufactured by cylindrical deep drawing of a steel sheet in a drawing ratio of 1.5 to 2.0.
- the fine-grained austenitic stainless steel sheet excellent in stress corrosion cracking resistance and workability has a 0.2% proof stress of less than 400 MPa and a uniform elongation of more than 30%, as determined by a tensile test.
- the amount of Ni is 8% or less, and without depending on the addition of expensive Mo, stress corrosion which is a disadvantage of the austenitic stainless steel It is possible to overcome cracking and achieve both stress corrosion cracking resistance and workability.
- the present inventors have targeted an austenitic stainless steel with an Ni content of 8% or less, an optimum component balance for forming a fine grain structure, and an effect of improving stress corrosion cracking by refinement.
- the present invention was completed by earnestly studying the compatibility between the process and workability. The typical experimental results will be described below.
- the fine grain structure means that the average crystal grain size is 10 ⁇ m or less.
- the austenitic stainless steel which shows a steel component in Table 1 was melted, and it hot-rolled, and manufactured the hot rolled sheet of thickness 3.0mm.
- Hot-rolled sheet annealing was performed at 1150 ° C., pickled and cold-rolled to produce a 0.5 mm thick cold-rolled sheet.
- cold-rolled sheet annealing was performed. In the cold rolling, the plate temperature was kept at 10 ° C. while cooling with water, and processing heat generation was suppressed. This promoted the formation of processing-induced martensite.
- final annealing In cold-rolled sheet annealing (final annealing), the temperature is adjusted in the range of 600 to 1050 ° C and the holding time is 1 minute in order to form a fine grain structure by utilizing the phase transformation from work-induced martensite to austenite. Adjustment was made in the range of ⁇ 24 hours.
- the steel sheet obtained by final annealing after cold rolling was pickled, and then subjected to measurement of the average crystal grain size, measurement of the ratio of the large-angle grain boundary, and measurement of crack generation time.
- the steel sheet cross section was embedded in a resin and polished, and nitric acid electrolytic etching was performed.
- the average crystal grain size was determined by a steel-grain size microscopic test method specified in JIS G 0551.
- the ratio of the large tilt grain boundaries was measured by the grain boundary map display of the EBSP method.
- a low-angle grain boundary of less than 15 ° and a large-angle grain boundary of 15 ° or more can be identified by displaying the grain boundary map, and the ratio of the large-angle grain boundary in all the crystal grain boundaries can be calculated.
- Non-Patent Document 6 it is reported that the measurement result of 3000 or more crystal grains statistically reflects the bulk properties. For this reason, the measurement magnification was adjusted to include 3000 or more crystal grains.
- FIG. 1 shows the relationship between the average crystal grain size and the component balance (Md) of a steel sheet obtained by performing cold-rolled sheet annealing at 800 ° C. for 4 hours.
- Md is a value defined by the following formula (1).
- the element symbol in a formula shows content (mass%) of the element.
- the average crystal grain size decreases with increasing Md.
- the Md increases, the amount of work-induced martensite generated by cold rolling increases. Therefore, it is considered that the increase in Md promoted the refinement utilizing the phase transformation from work-induced martensite to austenite in the annealing after cold rolling as described in Non-Patent Documents 1 and 2 described above. From this study, it is effective to set Md to ⁇ 20 or more for the target refinement to an average crystal grain size of 10 ⁇ m or less.
- the steel component (steel D) in which the Cr content and the Ni content are reduced and Cu is added is better. It was confirmed that it was effective for miniaturization.
- FIG. 2 shows the appearance of the molded product after immersion.
- FIG. 3 shows a photograph of the microstructure of steel B (i), (ii) subjected to the test of FIG.
- the average crystal grain size was refined to 3 ⁇ m as compared with steel (FIG. 2 (ii)) having an average crystal grain size of 28 ⁇ m manufactured by normal annealing (held at 1050 ° C. for 1 minute).
- steel (FIG. 2 (i)) cracks are not generated in a test result in which a molded product (cylindrical deep drawn material) is immersed in a boiling 42% magnesium chloride aqueous solution.
- SUS316L (17Cr-12Ni-2Mo) (FIG. 2 (iii)) contains Ni and Mo at a high content, and is more expensive than the general-purpose SUS304 (18Cr-8Ni) in terms of stress corrosion cracking resistance.
- FIG. 4 shows the relationship between crack generation time, average crystal grain size and Md in the boiling 42% magnesium chloride aqueous solution.
- the upward arrow ( ⁇ ) in FIG. 4 indicates that the crack occurrence time is longer than the value at the plotted point.
- miniaturization shown in FIG. 4 is the final annealing of the cold rolled sheet after cold rolling at 800 degreeC for 4 hours or It was manufactured under the condition of heating for 24 hours.
- the final annealing of the cold-rolled sheet after cold rolling is performed at 900 ° C. to 1050 ° C. for 1 minute to 4 hours. It was manufactured under the conditions of heating.
- a steel plate having a crack generation time of less than 4 hours and an average crystal grain size of 10 ⁇ m or less is manufactured by performing final annealing of the cold-rolled sheet after cold rolling at 800 ° C. for 4 hours.
- FIG. 5 is a graph showing the relationship between the crack generation time and the ratio of the large-angle grain boundaries of 15 ° or more in the steel sheet having the steel component of Steel B. Note that the up arrow ( ⁇ ) in FIG. 5 indicates that the crack occurrence time is longer than the value at the plotted point.
- the items (b) and (c) The stress corrosion cracking resistance described in 1 is significantly improved. The reason is considered as follows.
- the fine-grained material is produced by a method of generating as much work-induced martensite as possible by cold rolling and then utilizing reverse transformation from work-induced martensite to austenite by annealing at a lower temperature than usual. Since the accumulation of strain in cold rolling is large and low temperature annealing is performed, residual strain after annealing tends to increase. When a steel sheet is manufactured under such conditions, recrystallization of austenite grains is in progress, and there are many small-angle boundaries of less than 15 ° that are not recognized as large-angle boundaries. Therefore, a decrease in the ratio of the large-angle grain boundaries means that the residual strain of the steel is large, and it is presumed that the residual strain of the steel hinders the stress corrosion cracking resistance.
- the steel plate having the steel component of Steel B shown in FIG. 5 is manufactured by performing final annealing of the cold-rolled sheet after cold rolling at 800 ° C. for 10 minutes to 24 hours. By adjusting the heating time of the final annealing, steel plates having different ratios of large tilt grain boundaries were produced.
- the steel sheet having a large tilt grain boundary ratio of more than 80% shown in FIG. 5 is manufactured by performing the final annealing of the cold-rolled sheet after cold rolling at 800 ° C. for more than 1 hour. .
- the refinement of crystal grains is affected by manufacturing conditions in addition to steel components.
- it is effective to promote the work-induced martensite transformation in cold rolling.
- it is preferable to increase the rolling reduction and suppress the processing heat generation by cold rolling.
- the final annealing performed after cold rolling should be performed under the condition that the temperature is kept as low as possible for a long time. Is preferred. Specifically, it is effective to carry out the final annealing under the condition of heating at 700 to 900 ° C. for more than 1 hour.
- increasing the ratio of the large tilt grain boundaries of 15 ° or more is effective in reducing the 0.2% proof stress and increasing the elongation, and contributes to the improvement of workability.
- Patent Document 8 describes “aging cracking” after deep drawing, that is, “stress corrosion cracking” improved in this embodiment for the purpose of improving delayed fracture of a material, that is, a phenomenon involving corrosion and dissolution of a material. It is a technology related to different technical issues.
- the ratio of the large-angle grain boundaries of 15 ° or more that affect the stress corrosion cracking described above is not studied at all.
- the final annealing time is substantially 1 hour or less.
- the upper limit of the C content is set to 0.05%. This upper limit is preferably 0.03%.
- the lower limit of the C content is preferably 0.005% from the viewpoint of manufacturability.
- the lower limit of the Cr content is 14%.
- This lower limit is preferably 15%, more preferably 16%.
- the upper limit of the Cr content is 19%. This upper limit is preferably 18%.
- Si is effective as a powerful deoxidizer. However, when Si is added in a large amount, it hardens and manufacturability is impaired. For this reason, the upper limit of Si content is made 2%. This upper limit is preferably 1.5%. On the other hand, Si has an effect of improving the stress corrosion cracking resistance aimed at by this embodiment. In order to obtain these actions, it is preferable to contain 0.5% or more of Si.
- the lower limit of the Si content is preferably 0.1% from the viewpoint of manufacturability.
- Mn is an austenite-forming element and is added for the purpose of ensuring austenite stability and improving workability.
- MnS is formed and the corrosion resistance is lowered.
- the target stress corrosion cracking resistance of the present embodiment is hindered. Therefore, the upper limit of the Mn content is 4%. This upper limit is preferably 3%.
- the lower limit of the Mn content is preferably 0.5%.
- Ni is an indispensable element for austenitic stainless steel, and the lower limit of Ni content is 5% from the viewpoint of ensuring the stability and workability of austenite. This lower limit is preferably 6%.
- Ni is an expensive and rare element, and also has an effect of inhibiting the refinement of crystal grains intended by the present embodiment. For this reason, the upper limit of Ni content is 8%. This upper limit is preferably 7.5% or less.
- Cu is added for the purpose of ensuring the stability and softening of austenite, like Ni. Furthermore, it is a preferable element for reducing the Ni content, and improving the stress corrosion cracking resistance and promoting the refinement of crystal grains.
- the upper limit of Cu content is 4%. This upper limit is preferably 3%. In order to acquire the said effect, it is preferable that the minimum of Cu content is 1%, More preferably, it is 1.5%.
- N is an austenite-forming element like C, and is added for the purpose of ensuring the stability of austenite.
- the upper limit of N content is 0.1%. This upper limit is preferably 0.06% or less.
- the lower limit of the N content is preferably 0.005%, more preferably 0.01% from the viewpoint of manufacturability.
- Mo is not an essential element in the present embodiment, but may be added in a timely manner in order to improve the corrosion resistance and the stress corrosion cracking resistance targeted by the present embodiment.
- the upper limit of the Mo content is set to 1%. This upper limit is preferably 0.5%. In order to acquire the said effect, it is preferable to make the minimum of content of Mo into 0.1%.
- V is not an essential element in the present embodiment, but may be added in a timely manner in order to improve the corrosion resistance and the stress corrosion cracking resistance targeted by the present embodiment, even if it does not reach Mo.
- V is an expensive element and is a solid solution strengthening element, which impairs workability. Therefore, when adding, the upper limit of V content shall be 1%. This upper limit is preferably 0.5%. In order to acquire the said effect, it is preferable to make the minimum of V content into 0.1%.
- B and rare earth elements may be added in a timely manner in order to improve hot workability.
- the productivity and corrosion resistance may be significantly impaired. Therefore, when adding, the upper limit of B content is made 0.010%. This upper limit is preferably 0.005%.
- the lower limit of the B content is preferably 0.0005%.
- the upper limit of the rare earth element content is preferably 0.5%. This upper limit is more preferably 0.2%.
- the lower limit of the rare earth element content is preferably 0.005%.
- the rare earth element (REM) is one or more selected from Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. It is.
- Nb and Ti suppress the formation of Cr carbide by forming carbonitride. Thereby, it contributes to the improvement of stress corrosion cracking resistance. For this reason, you may add timely.
- the upper limit of each content of Nb and Ti is set to 0.5%.
- the upper limit of each content of Nb and Ti is preferably 0.3%.
- the lower limit of each content of Nb and Ti is preferably 0.005%, more preferably 0.01%.
- Al is an element effective as a deoxidizing element, it may be added as appropriate. However, if an excessive amount of Al is added, workability and weldability are reduced, so the upper limit of Al content is 0.5%. This upper limit is preferably 0.3%, more preferably 0.1%. When added, the lower limit of the Al content is preferably 0.01%.
- Mg and Ca form oxides with Al in molten steel and act as a deoxidizer, so they may be added as appropriate.
- Ca has an action of fixing S and improving hot workability.
- adding excessive amounts of Mg and Ca leads to a decrease in corrosion resistance and weldability, so the upper limit of the content of each of Mg and Ca is set to 0.005%.
- the upper limit of each content of Mg and Ca is preferably 0.002%.
- the minimum of each content of Mg and Ca is 0.0001%, More preferably, it is 0.0003%.
- the austenitic stainless steel of this embodiment may contain P and S in the following ranges as a part of inevitable impurities in addition to the above components.
- P and S are elements harmful to hot workability and corrosion resistance.
- the P content is preferably 0.1% or less.
- the P content is more preferably 0.05% or less.
- the S content is preferably 0.01% or less.
- the S content is more preferably 0.005% or less.
- an optimal component balance for the formation of a fine grain structure is defined by Md shown in Equation (1).
- Md 551-462 (C + N) -9.2Si-8.1Mn-13.7Cr-29 (Ni + Cu) -18.2Mo (1)
- Metastable austenitic stainless steel undergoes martensitic transformation by plastic working even at temperatures above the Ms point (martensitic transformation start temperature).
- the upper limit temperature that causes transformation by processing is called the Md point. That is, the Md point is an index indicating the stability of austenite.
- (B) The manufacturing method of the steel plate of this embodiment is demonstrated below.
- the steel component described in the item (A) is included, the average crystal grain size is 10 ⁇ m or less, and the proportion of the large-angle grain boundaries of 15 ° or more is occupied. Is more than 80%, and the following production conditions are preferable in order to effectively develop the stress corrosion cracking resistance.
- the manufacturing method of the steel plate of the present embodiment includes a step of hot rolling a slab having the steel component of the item (A) to form a hot rolled plate, a step of annealing the hot rolled plate (hot rolled plate annealing), It has the process of cold-rolling the annealed hot-rolled sheet to make a cold-rolled sheet, and the process of annealing the cold-rolled sheet (also referred to as cold-rolled sheet annealing or final annealing).
- the manufacturing method up to hot rolling is not particularly limited, and known conditions are applied.
- it is effective to promote the work-induced martensitic transformation by cold rolling as described in item (g) above.
- the volume ratio of processing-induced martensite is more than 60%.
- the final annealing conditions after cold rolling are adjusted so that the crystal grains are refined and the ratio of the large-angle grain boundaries of 15 ° or more is increased. It is preferable that the cold rolling conditions are also adjusted, and it is more preferable that hot-rolled sheet annealing is also adjusted. The conditions for each step will be described below.
- the austenite grains used for cold rolling are coarsened to 20 ⁇ m or more by hot rolling, and the temperature of hot rolling is 1050 to 1200 ° C. It is preferable to be in the range.
- the temperature of hot-rolled sheet annealing is less than 1050 ° C.
- the austenite grain size may be less than 20 ⁇ m.
- the temperature of hot-rolled sheet annealing is higher than 1200 ° C., pickling properties after annealing are lowered, and surface quality may be hindered.
- annealing above 1200 ° C. has a large load on the equipment.
- the temperature of hot-rolled sheet annealing is more preferably in the range of 1080 to 1180 ° C.
- the rolling reduction is 70% or more and the rolling temperature is 50 ° C. or less in order to promote the work-induced martensitic transformation.
- the rolling reduction is less than 70%, the volume ratio of the processing-induced martensite is less than 50%, and it becomes difficult to form a fine grain structure as described above.
- the rolling reduction is more preferably 80% or more.
- the upper limit of the rolling reduction is not particularly specified, but is preferably 90% or less in consideration of hot-rolled sheet production and cold-rolling equipment capacity.
- the rolling temperature is higher than 50 ° C., the work-induced martensite volume ratio is less than 50%, and it becomes difficult to form a fine grain structure as described above.
- the lower limit of the rolling temperature is not particularly specified, but industrially, a temperature of 10 ° C. or higher that is reached by water cooling is preferable.
- the rolling temperature is not limited to 10 ° C. or higher, and may be a low temperature (for example, ⁇ 200 ° C.) reached by cooling with liquid nitrogen or the like.
- the final annealing temperature is set in the range of 700 to 1050 ° C. in order to make the average crystal grain size 10 ⁇ m or less and the ratio of the large-angle grain boundaries to more than 80%.
- the final annealing temperature is less than 700 ° C., the strain in cold rolling is accumulated, the recrystallization of austenite grains becomes insufficient, and the workability is remarkably lowered. Further, the ratio of the large tilt grain boundaries of 15 ° or more is small, and the target stress corrosion cracking resistance of the present embodiment is hindered.
- the lower limit of the final annealing temperature is preferably 750 ° C. or higher.
- the final annealing temperature exceeds 1050 ° C., austenite crystal grain growth proceeds, and the average crystal grain size exceeds 10 ⁇ m.
- the final annealing temperature is preferably 900 ° C. or lower. In order to realize a fine grain structure in which the ratio of the large-angle grain boundary targeted in the present embodiment is more than 80%, it is more preferable that the final annealing temperature is in the range of 750 to 850 ° C.
- the annealing time of the final annealing is longer than 1 hour in order to promote the recrystallization of austenite and increase the ratio of the large tilt grain boundaries of 15 ° or more.
- the annealing time of the final annealing is more preferably 2 hours or more.
- the upper limit of the annealing time (holding time) of the final annealing is not limited, it is preferably 24 hours or less, assuming box annealing that is industrially known for chromium-based stainless steel.
- the annealing time of the final annealing is in the range of 4 to 24 hours.
- the annealing time for final annealing is not limited to 24 hours or less, and may exceed 24 hours.
- the final annealing temperature is more than 900 ° C. to 1050 ° C., it is preferable to set the annealing time to 10 minutes or less (holding for a short time) in consideration of crystal grain growth. More preferably, the annealing time (holding time) of the final annealing may be 1 minute or less.
- the average crystal grain size is 10 ⁇ m or less, and the ratio of large tilt grain boundaries of 15 ° or more is more than 80%.
- This metal structure is obtained by using the slab having the steel component of the item (A) and carrying out the preferable production conditions of the item (B).
- the average crystal grain size is more than 10 ⁇ m, it is difficult to develop excellent stress corrosion cracking resistance due to the refinement aimed at by this embodiment.
- the average crystal grain size is 10 ⁇ m or less, when the ratio of the large-angle grain boundaries of 15 ° or more is less than 80%, as described in the above item (f), the stress corrosion resistance due to refinement Improvement in crackability is hindered.
- the average crystal grain size is 5 ⁇ m or less and the ratio of the large tilt grain boundaries of 15 ° or more is more than 85%. .
- the lower limit of the average crystal grain size is not particularly specified, but it is difficult to make the average crystal grain size less than 1 ⁇ m also from Non-Patent Documents 1 and 2 and Patent Document 1. Therefore, in consideration of practical use, the average crystal grain size is preferably in the range of 1 to 5 ⁇ m.
- the ratio of the large tilt grain boundaries of 15 ° or more is more than 80%, preferably more than 85%.
- Increasing the ratio of the large-angle grain boundaries is effective in reducing 0.2% proof stress and increasing elongation in a fine-grained material (steel plate with fine crystal grains), and contributes to improving workability.
- the target workability of this embodiment is preferably close to that of ferritic stainless steel and close to that of austenitic stainless steel represented by SUS304 and the like. Therefore, it is preferable that the 0.2% proof stress is less than 400 MPa and the uniform elongation is more than 30%.
- the ratio of the large-angle grain boundaries of 15 ° or more is preferably more than 85%, more preferably more than 90%.
- the mechanical properties of 0.2% proof stress and uniform elongation are evaluated by a JIS No. 13 B tensile test.
- An austenitic stainless steel slab having the steel components shown in Table 2 was melted and hot-rolled to obtain a hot-rolled sheet having a thickness of 4 mm.
- Steel No. 1 to 23 satisfy the conditions of the steel components defined in this embodiment.
- Steel No. Nos. 24-28 are outside the steel component conditions defined in this embodiment.
- the hot rolled sheet was annealed, followed by cold rolling and final annealing.
- Cold rolling and final annealing were performed under the preferable conditions of this embodiment and other conditions.
- cold rolling is performed under conditions in which the rolling temperature is less than 30 ° C. while cooling with water at room temperature ( ⁇ 30 ° C.), and conditions in which the rolling temperature exceeds 50 ° C. during cold rolling due to processing heat generation without performing water cooling (> 50 ° C.).
- the steel sheet produced by cold rolling and final annealing is pickled, then the average grain size is measured, the ratio of large-angle grain boundaries of 15 ° or more by the EBSP method, the stress corrosion cracking resistance (cracking) Generation time) and mechanical properties (0.2% yield strength, uniform elongation) were measured.
- the average crystal grain size was determined by a steel-grain size microscopic test method specified in JIS G 0551.
- the measurement magnification was adjusted so that 3000 or more crystal grains were included, and the grain boundary map of the microstructure of the steel sheet was measured by the EBSP method.
- the grain boundary map display discriminates the small tilt grain boundary of less than 15 ° and the large tilt grain boundary of 15 ° or more, and calculates the ratio of the large tilt grain boundary in the total crystal grain boundary.
- the drawing ratio (value obtained by dividing the blank diameter by the punch diameter) under the conditions of a blank diameter of 67.5 mm ⁇ , a punch diameter of 35 mm ⁇ , a die diameter of 37 mm ⁇ , and a wrinkle holding pressure of 1 ton as in the measurement method described above.
- the cylindrical deep drawing of 1.9 was performed on the steel sheet.
- the obtained molded product was left for 48 hours to confirm that no aging cracks occurred.
- the molded article was immersed in a boiling 42% magnesium chloride aqueous solution specified in JIS G 0576, and the time when a crack (stress corrosion cracking) occurred was measured. The presence or absence of cracks was determined visually. Mechanical properties were evaluated by JIS No. 13 B tensile test.
- Table 3 shows the relationship between manufacturing conditions and characteristics.
- HA indicates hot-rolled sheet annealing
- FA indicates final annealing.
- Gram size represents the average crystal grain size
- large tilt ratio represents the ratio (%) of the large angle grain boundary.
- SCC occurrence time indicates the time at which stress corrosion cracking occurred. In “SCC occurrence time”, “ ⁇ ” means that it exceeds the value described on the left side. Further, the symbol * indicates that it is out of the essential conditions and preferred conditions defined in the present embodiment.
- Test No. 1, 3, 8 to 29 have the steel components of the present embodiment and were manufactured under the preferable manufacturing conditions of the present embodiment. These steel sheets have an average crystal grain size of 10 ⁇ m or less, and a ratio of a large-angle grain boundary of 15 ° or more exceeds 80%, and the stress corrosion crack occurrence time greatly exceeds the target of 4 hours or more. Obtained. Furthermore, these steel sheets have mechanical properties with a 0.2% yield strength of less than 400 MPa and a uniform elongation of more than 30%. For this reason, preferable workability is achieved together with excellent stress corrosion cracking resistance.
- the annealing time of the last annealing was as short as 1 hour. For this reason, recrystallization of austenite is not sufficiently promoted, and the ratio of the large-angle grain boundaries of 15 ° or more is 75%, which is less than 80%. For this reason, although the average crystal grain size was as small as 6 ⁇ m, the stress corrosion cracking time was 3 hr, and the target stress corrosion cracking resistance was not obtained.
- Test No. 6 has the steel component of this embodiment, it was manufactured on the conditions which deviated from the preferable manufacturing conditions of this embodiment. Since the final annealing temperature is lower than 700 ° C., the strain in cold rolling is accumulated, the austenite grains are insufficiently recrystallized, and the ratio of large-angle grain boundaries of 15 ° or more is 80%. Less than Moreover, although the average crystal grain size was as small as 1 ⁇ m, the stress corrosion cracking resistance was not improved due to residual strain during cold rolling, and the stress corrosion cracking time was 0.5 hr. Further, the 0.2% proof stress was 400 MPa or more, the steel plate was hardened, and the workability was also lowered.
- Test No. 7 has the steel component of this embodiment, but was manufactured at a known annealing temperature, and the final annealing temperature was higher than 1050 ° C. For this reason, the average crystal grain size was 30 ⁇ m. The ratio of the large-angle grain boundaries of 15 ° or more is 98%, but the stress corrosion cracking time is 3 hours, and the improvement of the stress corrosion cracking resistance due to the refinement of crystal grains was not observed.
- Test No. 30, 32, 34, 35, and 37 have steel components that deviate from the conditions of this embodiment, but were manufactured under the preferable manufacturing conditions of this embodiment.
- Test No. In 30, 32, and 37 the crystal grains were refined, and the average crystal grain size was 10 ⁇ m or less. However, the stress corrosion cracking occurrence time was less than 4 hr, and the improvement of the stress corrosion cracking resistance targeted by this embodiment was not observed.
- test no. In No. 37 since Md exceeds 40, it is considered that the development of stress corrosion cracking resistance is inhibited.
- Test No. In 34 and 35 since Md was less than ⁇ 20, it was difficult to form a fine grain structure, and the average crystal grain size was larger than 10 ⁇ m. For this reason, the stress corrosion cracking occurrence time was less than 4 hr, and the improvement of the stress corrosion cracking resistance targeted by this embodiment was not observed.
- Test No. 31, 33, and 36 have steel components that deviate from the conditions of this embodiment, and were manufactured under conditions that deviate from the preferred production conditions of this embodiment. These steel sheets had an average crystal grain size of 28 ⁇ m or 30 ⁇ m, and did not reach the target stress corrosion cracking resistance of the present embodiment as expected from the conventionally known components.
- the stress corrosion cracking which is a defect of the austenitic stainless steel, is overcome by refining the crystal grains without relying on the addition of Mo with an amount of Ni of 8% or less and expensive stress resistance.
- An austenitic stainless steel sheet that achieves both corrosion cracking and workability is obtained.
- the austenitic steel plate of this embodiment is applied suitably for the member etc. which are used in the corrosive environment containing a chloride ion.
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Abstract
Description
本願は、2009年12月1日に、日本に出願された特願2009-273868号に基づき優先権を主張し、その内容をここに援用する。
工業生産における焼鈍温度は、非特許文献3,4で公知である。また、結晶粒径については、非特許文献5で公知である。通常、オーステナイト系ステンレス鋼は、1000~1100℃で焼鈍され、成分を調整しても、細粒化の限度は、結晶粒度No.10に満たない、すなわち結晶粒径は10μmより大きくなると説明されている。
また、上述したように、通常、オーステナイト系ステンレス鋼は、1000~1100℃で焼鈍され、成分を調整しても、結晶粒径は10μmより大きくなると説明されている。特許文献2~7には、製造方法(焼鈍温度)と結晶粒径に関して特に記載されていない。従って、特許文献2~7に開示された鋼も、通常と異なる特別な製造方法を開示していない限りにおいて、その結晶粒径は、非特許文献3と同様に10μmより大きいことが容易に推定できる。
Md=551-462(C+N)-9.2Si-8.1Mn-13.7Cr-29(Ni+Cu)-18.2Mo
本発明の一態様に係る耐応力腐食割れ性と加工性に優れた微細粒オーステナイト系ステンレス鋼板は、鋼板を絞り比1.5~2.0の範囲で円筒深絞り加工して成形品を作製し、前記成形品を沸騰42%塩化マグネシウム水溶液中に4hr浸漬し、前記成形品の割れの発生を確認する応力割れ試験において、割れが発生しないことを特徴とする。
なお、前記絞り比は、ブランク径をポンチ径で割った値とする。
本発明の一態様に係る耐応力腐食割れ性と加工性に優れた微細粒オーステナイト系ステンレス鋼板は、引張試験によって求められる0.2%耐力が400MPa未満、均一伸びが30%超である。
なお、本実施形態において、微細粒組織とは、平均結晶粒径が10μm以下であることを意味する。
冷間圧延では、水冷しながら板温を10℃に保ち、加工発熱を抑制した。これにより、加工誘起マルテンサイトの生成を促進した。
冷延板焼鈍(最終焼鈍)では、加工誘起マルテンサイトからオーステナイトへの相変態を活用して微細粒組織を形成させるために、温度を600~1050℃の範囲で調整し、保持時間を1分~24時間の範囲で調整した。
冷間圧延後に最終焼鈍して得られた鋼板を酸洗し、次いで平均結晶粒径の測定、大傾角粒界の占める比率の測定、割れ発生時間の測定に供した。
大傾角粒界の占める比率は、EBSP法の粒界マップ表示により測定した。EBSP法では、粒界マップ表示によって15°未満の小傾角粒界と15°以上の大傾角粒界を識別して、全結晶粒界に占める大傾角粒界の比率を算出できる。ここで、非特許文献6において、結晶粒数3000個以上の測定結果が統計的にバルクの性質を反映すると報告されている。このため、結晶粒数3000個以上含むように測定倍率を調整した。
Mdは、下記(1)式で定義される値である。なお、式中の元素記号は、その元素の含有量(質量%)を示す。
また、Mdがほぼ同等のSUS304(図1中の菱形の符号)と鋼Dの結果を比較すると、Cr量及びNi量が低減され、かつCuが添加された鋼成分(鋼D)の方が、微細化に対して有効であることが確認された。
SUS316L(17Cr-12Ni-2Mo)(図2(iii))は、高い含有量でNiかつMoを含有し、汎用のSUS304(18Cr-8Ni)と比較して耐応力腐食割れにも優れた高価なオーステナイト系ステンレス鋼である。しかしながら、図2(iii)に示されたように、成形品の開口端部において、複数の割れが発生した。
この結果から、耐応力腐食割れ性(割れ発生の有無)は、結晶粒の微細化により飛躍的に向上する新規な知見を見出した。
Md=29.5の鋼成分(鋼B)を有する鋼板では、結晶粒の微細化(平均結晶粒径10μm以下)による効果によって、割れ発生時間は飛躍的に上昇することが分かる。この理由は、必ずしも明らかでないが、以下のように推定される。応力腐食割れは基本的に粒内割れである。結晶粒の微細化によって、割れの起点となる粒内面積率が大幅に減少する。さらに、鉄鋼材料における破壊靭性は、結晶粒の微細化によって格段に向上することが知られている。これら要因が、耐応力腐食割れ性に対して少なからず効果を発揮したためであると思われる。
比較としたSUS316Lでは、同じ試験条件において2~3hrの浸漬で割れが発生した。本実施形態では、この試験条件において4時間(hr)浸漬して割れが発生しないことを目標特性とした。この目標特性は、割れ発生時間が4時間超となることを意味し、SUS316Lの耐応力腐食割れ性(割れ発生時間)を明らかに凌駕する。
また、図4に示す割れ発生時間が4時間未満であり、平均結晶粒径が10μm超の鋼板は、冷間圧延後の冷延板の最終焼鈍を900℃~1050℃で1分~4時間加熱する条件で実施して製造されたものである。割れ発生時間が4時間未満で平均結晶粒径が10μm以下の鋼板は、冷間圧延後の冷延板の最終焼鈍を800℃で4時間加熱する条件で実施して製造されたものである。
図4において、Md=43の鋼成分(鋼A)を有する鋼板では、結晶粒が微細化しても、割れ発生時間は大きく上昇していない。この理由は、以下のように推定される。微細化によって材料そのものが硬質化したと考えられる。これにより、円筒深絞りにおいて多量の加工誘起マルテンサイトが生成し、カップ側壁での残留応力の上昇によって応力腐食割れの抑止効果が発現しなかったと推定される。この検討から、応力腐食割れを抑制する微細化による効果の発現には、Md:40以下が有効である。
本実施形態では、特許文献8で提案した微細粒鋼において、耐応力腐食割れ性を向上させるために、その影響因子である15°以上の大傾角粒界の比率の必須範囲を見出した。また、最終の焼鈍時間を1時間超にコントロールすることが極めて有効であること知見した。
以下、本実施形態の各要件について詳しく説明する。なお、各元素の含有量の「%」表示は「質量%」を意味する。
本実施形態では、平均結晶粒径10μm以下の微細粒組織を形成して、この微細化による効果によって、耐応力腐食割れ性を向上させる。このために、本実施形態のオーステナイト系ステンレス鋼板では、成分および成分バランス(Md)が規定されている。
一方、希土類元素の含有量が0.5%を超えると、製造性および経済性を損なう場合がある。そのため、希土類元素の含有量の上限を0.5%とすることが好ましい。この上限は、より好ましくは、0.2%である。添加する場合、希土類元素の含有量の下限は0.005%が好ましい。
なお、希土類元素(REM)は、Sc,Y,La,Ce,Pr,Nd,Pm,Sm,Eu,Gd,Tb,Dy,Ho,Er,Tm,Yb,及びLuから選択される1種以上である。
Md=551-462(C+N)-9.2Si-8.1Mn-13.7Cr-29(Ni+Cu)-18.2Mo ・・・(1)
(1)式に示すMdが-20~40の範囲となるように成分調整することにより、本実施形態の目的とする微細粒組織の形成と微細化による耐応力腐食割れ性の向上作用が得られる。Mdが-20未満の場合、上記の項目(d),(e)で述べたように、微細粒組織の形成及び耐応力腐食割れ性の発現が困難である。一方、Mdが40を越える場合、上記の項目(d),(e)で述べたように、微細粒組織の形成には有効であるが、耐応力腐食割れ性の発現が阻害される。好ましいMdの範囲は-5~35である。
本実施形態の微細粒オーステナイト系ステンレス鋼板を製造する際には、(A)項に述べた鋼成分を有し、平均結晶粒径10μm以下とし、かつ15°以上の大傾角粒界の占める比率を80%超とし、耐応力腐食割れ性を効果的に発現させるために、以下の製造条件とすることが好ましい。
本実施形態の鋼板の製造方法は、(A)項の鋼成分を有する鋳片を熱間圧延して熱延板とする工程と、熱延板を焼鈍する工程(熱延板焼鈍)と、焼鈍された熱延板を冷間圧延して冷延板とする工程と、冷延板を焼鈍する工程(冷延板焼鈍又は最終焼鈍とも言う)を有する。
冷間圧延後の最終焼鈍により、微細粒組織を形成するためには、上記の項目(g)に記載したように、冷間圧延で加工誘起マルテンサイト変態を促進させることが有効である。本実施形態の目的とする平均結晶粒径10μm以下とするためには、冷間圧延後に加工誘起マルテンサイトの体積率を50%以上とすることが効果的である。好ましくは、加工誘起マルテンサイトの体積率を60%超とする。冷間圧延後の最終焼鈍条件は、結晶粒を微細化し、かつ15°以上の大傾角粒界の比率を上昇させるように調整される。冷間圧延条件も調整されることが好ましく、さらに、熱延板焼鈍も調整されることがより好ましい。
各工程の条件について以下に説明する。
圧下率が70%未満の場合、加工誘起マルテンサイトの体積率は50%未満となり、上述したように微細粒組織を形成することが困難となる。圧下率は、80%以上がより好ましい。圧下率の上限は、特に規定するものではないが、熱延板製造と冷延設備能力を考慮して90%以下が好ましい。
圧延温度が50℃超の場合、加工誘起マルテンサイト体積率は50%未満となり、前記したように微細粒組織の形成が困難となる。圧延温度の下限は、特に規定するものではないが、工業的には水冷で到達する温度10℃以上が好ましい。小規模の圧延設備で製造する場合、圧延温度は、10℃以上に限定されず、液体窒素等の冷却で到達する低温(例えば、-200℃)でも構わない。
最終焼鈍の温度が900℃超~1050℃の場合、結晶粒成長を考慮して、焼鈍時間を10分以下とすること(短時間保持)が好ましい。より好ましくは、最終焼鈍の焼鈍時間(保持時間)を1分以下としても構わない。
本実施形態の微細粒オーステナイト系ステンレス鋼板では、平均結晶粒径が10μm以下であり、かつ15°以上の大傾角粒界の比率が80%超である。この金属組織は、(A)項の鋼成分を有する鋳片を用い、(B)項の好ましい製造条件を実施して得られる。
本実施形態の目的とする耐応力腐食割れ性を有効に発現させるには、平均結晶粒径が5μm以下であり、かつ15°以上の大傾角粒界の比率が85%超であることが好ましい。平均結晶粒径の下限は、特に規定するものではないが、非特許文献1,2や特許文献1からも、平均結晶粒径を1μm未満とすることは困難である。従って、実用面を考慮して、平均結晶粒径は1~5μmの範囲とすることが好ましい。
本実施形態の目標とする加工性は、上述した背景から、フェライト系ステンレス鋼を凌駕してSUS304等に代表されるオーステナイト系ステンレス鋼に近いことが好ましい。そのため、0.2%耐力が400MPa未満であり、かつ均一伸びが30%超であることが好ましい。
耐応力腐食割れ性とこれら加工性を両立するために、15°以上の大傾角粒界の比率は、好ましくは85%超であり、より好ましくは90%超である。
なお、本実施形態においては、機械的性質である0.2%耐力及び均一伸びは、JIS13号B引張試験により評価される。
表2に示された鋼成分を有するオーステナイト系ステンレス鋳片を溶製し、熱間圧延を行い板厚4mmの熱延板とした。鋼No.1~23は、本実施形態で規定する鋼成分の条件を満たす。鋼No.24~28は、本実施形態で規定する鋼成分の条件から外れる。
冷間圧延と最終焼鈍を行って製造された鋼板を酸洗し、次いで、平均結晶粒径の測定、EBSP法による15°以上の大傾角粒界の比率の測定、耐応力腐食割れ性(割れ発生時間)の測定、機械的性質(0.2%耐力、均一伸び)の測定を行った。
具体的には、平均結晶粒径の測定では、鋼板断面を樹脂に埋め込み研磨して硝酸電解エッチングした。次いで、JISG 0551に規定する鋼-結晶粒度の顕微鏡試験方法により平均結晶粒径を求めた。
大傾角粒界の比率の測定では、3000個以上の結晶粒が含まれるように測定倍率を調整し、EBSP法により鋼板のミクロ組織の粒界マップを測定した。粒界マップ表示によって15°未満の小傾角粒界と15°以上の大傾角粒界を識別して、全結晶粒界に占める大傾角粒界の比率を算出した。
割れ発生時間の測定では、上述した測定方法と同様に、ブランク径67.5mmφ,ポンチ径35mmφ,ダイス径37mmφ,しわ押さえ圧1トンの条件で絞り比(ブランク径をポンチ径で割った値)1.9の円筒深絞り加工を鋼板に対して行った。得られた成形品を48hr放置して時効割れの発生しないことを確認した。そして、成形品をJIS G 0576に規定する沸騰42%塩化マグネシウム水溶液中に浸漬して、割れ(応力腐食割れ)が発生した時間を測定した。割れの有無は、目視により判定した。
機械的性質は、JIS13号B引張試験により評価した。
なお、表3中の『HA』は、熱延板焼鈍を示し、『FA』は、最終焼鈍を示す。『粒径』は、平均結晶粒径を示し、『大傾角比率』は、大傾角粒界(large angle grain boundary)の占める比率(%)(ratio of large angle grain boundary)を示す。『SCC発生時間』は、応力腐食割れが発生した時間を示す。『SCC発生時間』において、『↑』は、その左側に記載の数値を上回ることを意味する。また、符号*は、本実施形態にて規定された必須条件や好ましい条件から外れていることを示す。
Claims (4)
- 質量%にて、C:0.05%以下、Cr:14~19%、Si:2%以下、Mn:4%以下、Ni:5~8%,Cu:4%以下,及びN:0.1%以下を含み、残部がFeおよび不可避的不純物からなり、かつ下記のMdが-20~40の範囲にある鋼成分を有し、
平均結晶粒径が10μm以下であり、かつ15°以上の大傾角粒界の占める比率が80%超であることを特徴とする耐応力腐食割れ性と加工性に優れた微細粒オーステナイト系ステンレス鋼板。
Md=551-462(C+N)-9.2Si-8.1Mn-13.7Cr-29(Ni+Cu)-18.2Mo - 前記鋼成分が、さらに質量%にて、Mo:1%以下、V:1%以下,B:0.010%以下,Nb:0.5%以下,Ti:0.5%以下,希土類元素:0.5%以下,Al:0.5%以下,Mg:0.005%以下,及びCa:0.005%以下から選択される1種または2種以上を含有していることを特徴とする請求項1に記載の耐応力腐食割れ性と加工性に優れた微細粒オーステナイト系ステンレス鋼板。
- 鋼板を絞り比1.5~2.0の範囲で円筒深絞り加工して成形品を作製し、前記成形品を沸騰42%塩化マグネシウム水溶液中に4hr浸漬し、前記成形品の割れの発生を確認する応力割れ試験において、割れが発生しないことを特徴とする請求項1または請求項2に記載の耐応力腐食割れ性と加工性に優れた微細粒オーステナイト系ステンレス鋼板。
- 引張試験によって求められる0.2%耐力が400MPa未満,均一伸びが30%超であることを特徴とする請求項1から3のいずれかに記載の耐応力腐食割れ性と加工性に優れた微細粒オーステナイト系ステンレス鋼板。
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EP10834432.6A EP2508639B1 (en) | 2009-12-01 | 2010-09-29 | Fine grained austenitic stainless steel sheet exhibiting excellent stress corrosion cracking resistance and processability |
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ES10834432.6T ES2546412T3 (es) | 2009-12-01 | 2010-09-29 | Chapa de acero inoxidable austenítico, de grano fino, que exhibe una excelente resistencia al agrietamiento por corrosión bajo tensión y capacidad de tratamiento |
KR1020127014003A KR101411703B1 (ko) | 2009-12-01 | 2010-09-29 | 내응력 부식 균열성과 가공성이 우수한 미세립 오스테나이트계 스테인리스 강판 |
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Citations (13)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS619557A (ja) | 1984-06-25 | 1986-01-17 | Kawasaki Steel Corp | 耐応力腐食割れ性および耐孔食性に優れたオ−ステナイト系ステンレス鋼 |
JPS62180037A (ja) | 1986-02-03 | 1987-08-07 | Daido Steel Co Ltd | 耐応力腐食割れ性に優れたオ−ステナイト系合金 |
JPS62247048A (ja) | 1986-04-18 | 1987-10-28 | Nisshin Steel Co Ltd | 耐候性、耐隙間腐食性および耐応力腐食割れ性に優れたオ−ステナイト系ステンレス鋼 |
JPS62287051A (ja) | 1986-06-03 | 1987-12-12 | Kobe Steel Ltd | 耐粒界腐食性並びに耐粒界応力腐食割れ性の優れたオ−ステナイト系ステンレス鋼 |
JPH04214841A (ja) * | 1990-12-14 | 1992-08-05 | Nisshin Steel Co Ltd | 成形加工性に優れたエンジンガスケット用ステンレス鋼およびその製造方法 |
JPH08269550A (ja) | 1995-03-31 | 1996-10-15 | Nippon Steel Corp | 耐粒界応力腐食割れ性に優れたオーステナイト系ステンレス鋼の製造方法 |
JPH10317104A (ja) | 1997-05-16 | 1998-12-02 | Nippon Steel Corp | 耐粒界応力腐食割れ性に優れたオーステナイト系ステンレス鋼およびその製造方法 |
JP2000079405A (ja) * | 1998-09-07 | 2000-03-21 | Sumitomo Metal Ind Ltd | 表面性状の良好なオーステナイト系ステンレス薄鋼板の製造方法 |
WO2002088410A1 (fr) | 2001-04-27 | 2002-11-07 | Sumitomo Metal Industries, Ltd. | Garniture metallique, materiau brut et procedes de production |
JP2005105412A (ja) * | 2003-09-10 | 2005-04-21 | Nippon Steel & Sumikin Stainless Steel Corp | ステンレス鋼板及びその製造方法 |
JP2008157717A (ja) | 2006-12-22 | 2008-07-10 | Toshiba Corp | 放射線検出器およびその製造方法 |
JP2009273868A (ja) | 2008-04-15 | 2009-11-26 | Kao Corp | 吸収性物品 |
JP2009299171A (ja) | 2008-06-17 | 2009-12-24 | Nippon Steel & Sumikin Stainless Steel Corp | 微細粒組織を有するプレス成形用オーステナイト系ステンレス鋼板およびその製造方法 |
Family Cites Families (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP4578296B2 (ja) * | 2005-03-18 | 2010-11-10 | 日新製鋼株式会社 | エアコン四方弁のバルブシート用鋼板 |
JP4503483B2 (ja) * | 2005-04-14 | 2010-07-14 | 日立Geニュークリア・エナジー株式会社 | 被溶接材とそれを用いた溶接構造物及び高耐食性オーステナイト系ステンレス鋼 |
EP2172574B1 (en) * | 2007-08-02 | 2019-01-23 | Nippon Steel & Sumikin Stainless Steel Corporation | Ferritic-austenitic stainless steel excellent in corrosion resistance and workability and process for manufacturing the same |
JP5500960B2 (ja) * | 2009-12-01 | 2014-05-21 | 新日鐵住金ステンレス株式会社 | 耐応力腐食割れ性と加工性に優れた微細粒オーステナイト系ステンレス鋼板 |
-
2009
- 2009-12-01 JP JP2009273868A patent/JP5500960B2/ja active Active
-
2010
- 2010-09-29 CN CN201080054359.7A patent/CN102753717B/zh active Active
- 2010-09-29 WO PCT/JP2010/066968 patent/WO2011067979A1/ja active Application Filing
- 2010-09-29 KR KR1020127014003A patent/KR101411703B1/ko active IP Right Grant
- 2010-09-29 EP EP10834432.6A patent/EP2508639B1/en active Active
- 2010-09-29 ES ES10834432.6T patent/ES2546412T3/es active Active
Patent Citations (13)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS619557A (ja) | 1984-06-25 | 1986-01-17 | Kawasaki Steel Corp | 耐応力腐食割れ性および耐孔食性に優れたオ−ステナイト系ステンレス鋼 |
JPS62180037A (ja) | 1986-02-03 | 1987-08-07 | Daido Steel Co Ltd | 耐応力腐食割れ性に優れたオ−ステナイト系合金 |
JPS62247048A (ja) | 1986-04-18 | 1987-10-28 | Nisshin Steel Co Ltd | 耐候性、耐隙間腐食性および耐応力腐食割れ性に優れたオ−ステナイト系ステンレス鋼 |
JPS62287051A (ja) | 1986-06-03 | 1987-12-12 | Kobe Steel Ltd | 耐粒界腐食性並びに耐粒界応力腐食割れ性の優れたオ−ステナイト系ステンレス鋼 |
JPH04214841A (ja) * | 1990-12-14 | 1992-08-05 | Nisshin Steel Co Ltd | 成形加工性に優れたエンジンガスケット用ステンレス鋼およびその製造方法 |
JPH08269550A (ja) | 1995-03-31 | 1996-10-15 | Nippon Steel Corp | 耐粒界応力腐食割れ性に優れたオーステナイト系ステンレス鋼の製造方法 |
JPH10317104A (ja) | 1997-05-16 | 1998-12-02 | Nippon Steel Corp | 耐粒界応力腐食割れ性に優れたオーステナイト系ステンレス鋼およびその製造方法 |
JP2000079405A (ja) * | 1998-09-07 | 2000-03-21 | Sumitomo Metal Ind Ltd | 表面性状の良好なオーステナイト系ステンレス薄鋼板の製造方法 |
WO2002088410A1 (fr) | 2001-04-27 | 2002-11-07 | Sumitomo Metal Industries, Ltd. | Garniture metallique, materiau brut et procedes de production |
JP2005105412A (ja) * | 2003-09-10 | 2005-04-21 | Nippon Steel & Sumikin Stainless Steel Corp | ステンレス鋼板及びその製造方法 |
JP2008157717A (ja) | 2006-12-22 | 2008-07-10 | Toshiba Corp | 放射線検出器およびその製造方法 |
JP2009273868A (ja) | 2008-04-15 | 2009-11-26 | Kao Corp | 吸収性物品 |
JP2009299171A (ja) | 2008-06-17 | 2009-12-24 | Nippon Steel & Sumikin Stainless Steel Corp | 微細粒組織を有するプレス成形用オーステナイト系ステンレス鋼板およびその製造方法 |
Non-Patent Citations (7)
Title |
---|
"Nishiyama Memorial Technology Course", vol. 115, IRON AND STEEL INST. OF JAPAN, article "Recent Advances in Technology of Producing of Stainless Steel" |
"Stainless Steel Handbook", pages: 560 |
IRON AND STEEL, vol. 78, 1992, pages 141 - 148 |
IRON AND STEEL, vol. 80, 1994, pages 249 - 253 |
NIPPON KOKAN TECHNICAL REPORT, 1980, pages 51 - 60 |
See also references of EP2508639A4 * |
YOICHI TOKUNAGA: "Austenitic stainless steels having ultra-fine crystal grains", THE JAPAN SOCIETY FOR HEARTTREATMENT KOEN TAIKAI KOEN GAIYOSHU, vol. 26, May 1988 (1988-05-01), pages 71 - 74, XP008160338 * |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2011117024A (ja) * | 2009-12-01 | 2011-06-16 | Nippon Steel & Sumikin Stainless Steel Corp | 耐応力腐食割れ性と加工性に優れた微細粒オーステナイト系ステンレス鋼板 |
TWI628296B (zh) * | 2012-09-27 | 2018-07-01 | 奧托昆布公司 | 沃斯田鐵系不鏽鋼 |
US11597982B2 (en) | 2018-09-28 | 2023-03-07 | Japan Atomic Energy Agency | Production process of fine-grained austenitic stainless steel |
JP2020084288A (ja) * | 2018-11-29 | 2020-06-04 | 株式会社特殊金属エクセル | ステンレス鋼帯またはステンレス鋼箔及びその製造方法 |
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