CN113396238A - Stainless steel plate - Google Patents
Stainless steel plate Download PDFInfo
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- CN113396238A CN113396238A CN202080012767.XA CN202080012767A CN113396238A CN 113396238 A CN113396238 A CN 113396238A CN 202080012767 A CN202080012767 A CN 202080012767A CN 113396238 A CN113396238 A CN 113396238A
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- 229910001220 stainless steel Inorganic materials 0.000 title claims description 30
- 239000010935 stainless steel Substances 0.000 title claims description 30
- 238000001556 precipitation Methods 0.000 claims description 22
- 239000012535 impurity Substances 0.000 claims description 9
- 229910052760 oxygen Inorganic materials 0.000 claims description 4
- 229910052698 phosphorus Inorganic materials 0.000 claims description 3
- 229910052717 sulfur Inorganic materials 0.000 claims description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 2
- 229910052799 carbon Inorganic materials 0.000 claims description 2
- 229910052751 metal Inorganic materials 0.000 claims description 2
- 239000002184 metal Substances 0.000 claims description 2
- 230000007797 corrosion Effects 0.000 abstract description 50
- 238000005260 corrosion Methods 0.000 abstract description 50
- 229910000831 Steel Inorganic materials 0.000 abstract description 46
- 239000010959 steel Substances 0.000 abstract description 46
- 239000000126 substance Substances 0.000 abstract description 13
- 229910052804 chromium Inorganic materials 0.000 abstract description 12
- 238000010438 heat treatment Methods 0.000 abstract description 12
- 229910001039 duplex stainless steel Inorganic materials 0.000 abstract description 9
- 229910052750 molybdenum Inorganic materials 0.000 abstract description 9
- 229910052757 nitrogen Inorganic materials 0.000 abstract description 5
- 229910052759 nickel Inorganic materials 0.000 abstract description 4
- 229910052748 manganese Inorganic materials 0.000 abstract description 3
- 238000001816 cooling Methods 0.000 description 16
- 230000000694 effects Effects 0.000 description 15
- 238000005098 hot rolling Methods 0.000 description 15
- 150000004767 nitrides Chemical class 0.000 description 13
- 239000000243 solution Substances 0.000 description 12
- 238000012360 testing method Methods 0.000 description 11
- 239000002244 precipitate Substances 0.000 description 9
- 229910052761 rare earth metal Inorganic materials 0.000 description 9
- 229910001566 austenite Inorganic materials 0.000 description 5
- 238000005096 rolling process Methods 0.000 description 5
- 239000002253 acid Substances 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 3
- 229910000963 austenitic stainless steel Inorganic materials 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 229910052791 calcium Inorganic materials 0.000 description 3
- 230000008021 deposition Effects 0.000 description 3
- 229910052735 hafnium Inorganic materials 0.000 description 3
- 230000001771 impaired effect Effects 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- 238000000034 method Methods 0.000 description 3
- 229910052758 niobium Inorganic materials 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- 229910052715 tantalum Inorganic materials 0.000 description 3
- 229910052719 titanium Inorganic materials 0.000 description 3
- 229910052721 tungsten Inorganic materials 0.000 description 3
- 229910052720 vanadium Inorganic materials 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- 229910052726 zirconium Inorganic materials 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 2
- 150000007513 acids Chemical class 0.000 description 2
- 238000005275 alloying Methods 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 238000000605 extraction Methods 0.000 description 2
- 230000003993 interaction Effects 0.000 description 2
- 229910000765 intermetallic Inorganic materials 0.000 description 2
- 229910052747 lanthanoid Inorganic materials 0.000 description 2
- 150000002602 lanthanoids Chemical class 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 150000001247 metal acetylides Chemical class 0.000 description 2
- 230000001629 suppression Effects 0.000 description 2
- 239000002344 surface layer Substances 0.000 description 2
- 229910052684 Cerium Inorganic materials 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
- 239000000460 chlorine Substances 0.000 description 1
- 229910052801 chlorine Inorganic materials 0.000 description 1
- -1 chlorine ions Chemical class 0.000 description 1
- GTKRFUAGOKINCA-UHFFFAOYSA-M chlorosilver;silver Chemical compound [Ag].[Ag]Cl GTKRFUAGOKINCA-UHFFFAOYSA-M 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 238000005242 forging Methods 0.000 description 1
- 230000005764 inhibitory process Effects 0.000 description 1
- 229910052746 lanthanum Inorganic materials 0.000 description 1
- 238000003754 machining Methods 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000013535 sea water Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000002436 steel type Substances 0.000 description 1
Classifications
-
- 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
-
- 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
-
- 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
-
- 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
-
- 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
-
- 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
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
-
- 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
- C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
-
- 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
- C22C38/52—Ferrous alloys, e.g. steel alloys containing chromium with nickel with cobalt
-
- 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
- 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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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Heat Treatment Of Steel (AREA)
- Heat Treatment Of Sheet Steel (AREA)
Abstract
通过一种双相不锈钢板，能够得到即使省略固溶热处理，也在适用于水工建筑物、工业机械、化学工业罐等构造物时兼具充分的耐蚀性和SUS304N2‑X的同等以上的强度及韧性的钢板，该钢板含有C：0.001～0.03％、Si：0.05～1.5％、Mn：0.10～3.00％、Cr：22.00～27.00％、Ni：4.00～7.00％、Mo：0.50～2.50％、W：0～1.50％和N：0.10～0.25％，且满足式1和式2。PREW＝Cr+3.3(Mo+0.5W)+16N(式1)TS(℃)＝4Cr+25Ni+11(Mo+W)×(Mo+W)+41(Mo+W)+5Si‑6Mn‑30N+550(式2)。Even if solution heat treatment is omitted, a duplex stainless steel sheet can be obtained that has sufficient corrosion resistance and is equal to or higher than SUS304N2-X when applied to structures such as hydraulic structures, industrial machinery, and chemical industrial tanks. Strength and toughness steel sheet containing C: 0.001 to 0.03%, Si: 0.05 to 1.5%, Mn: 0.10 to 3.00%, Cr: 22.00 to 27.00%, Ni: 4.00 to 7.00%, Mo: 0.50 to 2.50% , W: 0 to 1.50% and N: 0.10 to 0.25%, and the formulas 1 and 2 are satisfied. PREW=Cr+3.3(Mo+0.5W)+16N(Formula 1)TS(℃)=4Cr+25Ni+11(Mo+W)×(Mo+W)+41(Mo+W)+5Si‑6Mn‑ 30N+550 (Formula 2).
Description
Technical Field
The present invention relates to stainless steel. For example, SUS304N2-X as austenitic stainless steel and SUS329J4L as duplex stainless steel may be substituted.
Background
Stainless steel is used as a measure against corrosion in hydraulic structures, industrial machines, chemical industrial tanks, and the like. When stainless steel is used as a structural member, an austenitic stainless steel SUS304N2-X containing N in SUS304 and omitting solution heat treatment may be used because a material having high strength is required for reducing the weight by thinning and the like.
However, SUS304N2-X is inferior in corrosion resistance to SUS316L, and therefore may not be suitable in view of corrosion. Cr and Mo are known as elements for improving corrosion resistance, but in order to form an austenite phase single phase, the content of Ni as an austenite phase forming element must be increased in addition to these elements, which leads to a significant increase in cost.
Duplex stainless steel has a low content of expensive Ni and high strength as compared with austenitic stainless steel. However, the duplex stainless steel subjected to the solution heat treatment did not have such a strength as SUS304N 2-X. In addition, SUS329J4L, which is a representative steel type of duplex stainless steel, is unavoidable in precipitation of the σ phase during hot rolling, so when solution heat treatment is omitted to obtain strength, the σ phase remains in the product, and corrosion resistance and toughness are greatly deteriorated.
As a duplex stainless steel having improved strength by omitting solution heat treatment, a stainless steel disclosed in patent document 1 has been proposed. The steel saves Mo and further focuses on the precipitation suppression of Cr nitride.
Documents of the prior art
Patent document 1: japanese laid-open patent publication No. 2012-153953
Disclosure of Invention
Hydraulic structures, industrial machinery, chemical industry tanks, and the like sometimes become a harsh corrosive environment due to the chloride ions and/or acids in the fluids they contact. In such a place, SUS304N2-X containing a small amount of Cr and no Mo cannot ensure the intended corrosion resistance.
In the hot-rolled steel sheet disclosed in patent document 1, the suppression of the precipitation of Cr nitrides is focused, but in duplex stainless steel having a large Cr and Mo content, the σ phase precipitation has a great influence on the toughness and corrosion resistance. Cr nitrides are compounds that precipitate by the interaction between Cr and N, and it is effective for the inhibition of Cr nitride precipitation to reduce N and the content of austenite phase-forming elements (e.g., Ni, Mn). On the other hand, the σ phase is an intermetallic compound precipitated by the interaction of Cr and Mo, and Ni accelerates the precipitation of the σ phase. In addition, Mn is an element effective in suppressing Cr nitride precipitation but deteriorating corrosion resistance. Therefore, in duplex stainless steel having a large content of Cr and Mo, the influence of the content elements such as Ni and Mn on the formation of precipitates and intermetallic compounds and the corrosion resistance is greatly different. That is, the hot-rolled steel sheet disclosed in patent document 1 has limited corrosion resistance because it does not consider deterioration of toughness and deterioration of corrosion resistance due to σ phase precipitation, and further requires a steel sheet having toughness and enhanced corrosion resistance.
Under such a background, the present inventors have made an object to obtain a stainless steel sheet having sufficient corrosion resistance when applied to structures such as hydraulic structures, industrial machines, and chemical industrial tanks, and having strength and toughness equal to or higher than those of SUS304N 2-X.
The present inventors have considered that, in order to solve the above problems, by designing a composition capable of avoiding the precipitation of the σ phase during hot rolling while ensuring corrosion resistance, a stainless steel sheet having high strength even if solution heat treatment is omitted and excellent in corrosion resistance and toughness can be obtained. That is, an estimated expression is newly found for the σ phase precipitation temperature TS, and according to this expression, a steel material having a different TS is used, and the entry side temperature TF of the final pass of hot rolling and the cooling rate in the range from 800 ℃ to 600 ℃ after the end of hot rolling are changed, and the strength, impact property, and corrosion resistance of the obtained hot-rolled steel sheet are evaluated.
Through the above experiments, it was clarified that the stainless hot rolled steel sheet was omitted from the solution heat treatment, and the present invention was finally completed.
That is, the gist of the present invention is as follows.
[1] A stainless steel sheet characterized by containing, in mass%, (ii) a metal
C：0.001～0.030％、
Si：0.05～1.50％、
Mn：0.10～3.00％、
Cr：22.00～27.00％、
Ni：4.00～7.00％、
Mo：0.50～2.50％、
W：0～1.50％、
N：0.10～0.25％、
Co：0～1.00％、
Cu：0～3.00％、
V：0～1.00％、
Nb：0～0.200％、
Ta：0～0.200％、
Ti：0～0.030％、
Zr：0～0.050％、
Hf：0～0.100％、
B：0～0.0050％、
Al：0～0.050％、
Ca：0～0.0050％、
Mg：0～0.0050％、
REM: 0 to 0.100%, and
Sn：0～0.100％，
the balance being Fe and unavoidable impurities,
limiting O, P and S as impurities to
O: less than 0.006 percent,
P: less than 0.05 percent of,
S: the content of the active carbon is less than 0.003 percent,
PREW determined by the formula 1 is 25.0 to 36.0 inclusive,
the sigma phase precipitation temperature estimated formula TS (DEG C) obtained from the formula 2 is 800 ℃ to 950 ℃,
0.2% yield strength of 450MPa or more,
the Charpy impact value at-20 ℃ is 70J/cm2In the above-mentioned manner,
the pitting potential measured at 50 ℃ is 0.40V or more based on SSE,
PREW ═ Cr +3.3(Mo +0.5W) +16N (formula 1)
TS(℃)＝4Cr+25Ni-11(Mo+W)×(Mo+W)+100(Mo+W)+5Si-6Mn-30N+550
(formula 2)
In the formulae 1 and 2, the symbol of each element indicates the content (mass%) of the element, and 0 may be substituted when not included.
[2] The stainless steel sheet according to [1], wherein the stainless steel sheet contains 1 or 2 or more of the following components in mass%,
Cr：0.01～1.00％、
Cu：0.01～3.00％、
V：0.01～1.00％、
Nb：0.005～0.200％、
Ta：0.005～0.200％、
Ti：0.001～0.030％、
Zr：0.001～0.050％、
Hf：0.001～0.100％、
B：0.0001～0.0050％、
Al：0.003～0.050％、
Ca：0.0005～0.0050％
Mg：0.0001～0.0050％、
REM: 0.005 to 0.100%, and
Sn：0.005～0.100％。
the stainless steel sheet obtained according to the present invention has strength equal to or higher than that of SUS304N2-X, sufficient toughness as a structural material, and further has corrosion resistance exceeding SUS304N 2-X. On the other hand, the cost of the alloy is also reasonable, and therefore, the economical efficiency is also good. As a result, the stainless hot-rolled steel sheet according to the present invention is used in hydraulic structures, industrial machines, chemical industrial tanks, and the like, and is improved in terms of both performance and cost, and contributes greatly to the industrial aspect and the environmental aspect.
Detailed Description
The reasons for limiting the composition of the stainless steel of the present invention will be explained. In the present specification, unless otherwise specified, the% relating to a component means mass%.
In order to ensure corrosion resistance of stainless steel, the content of C is limited to 0.030% or less. If the content exceeds 0.030%, Cr carbide is formed during hot rolling, and the corrosion resistance and toughness deteriorate. On the other hand, from the viewpoint of cost reduction of the C content of stainless steel, 0.001% is set as the lower limit.
Si is contained in an amount of 0.05% or more for deoxidation. Preferably 0.20% or more. On the other hand, if it exceeds 1.50%, the toughness deteriorates. Therefore, it is set to 1.50% or less. Preferably 1.00% or less.
Mn has an effect of increasing the austenite phase and lowering the σ phase precipitation temperature, and therefore may be contained in 0.10% or more. On the other hand, Mn is an element that lowers the corrosion resistance of stainless steel, and therefore Mn may be 3.0% or less. Preferably 2.50% or less, 2.00% or less, 1.50% or less, 1.00% or less, 0.50% or less, 0.45% or less, 0.40% or less, or 0.35% or less.
In order to ensure the basic corrosion resistance, Cr is contained at 22.00% or more. Preferably 23.00% or more, 24.00% or more, 25.00% or more, 25.10% or more, 25.20% or more, 25.30% or more, 25.40% or more, or 25.50% or more. On the other hand, since Cr is an element that promotes the precipitation of the σ phase, the content is limited to 27.00% or less. Preferably 26.90% or less, 26.80% or less, 26.70% or less, 26.60% or less, or 26.50% or less.
Ni is an element that promotes the formation of an austenite structure, has an effect of suppressing the formation of Cr nitrides, and has an effect of improving corrosion resistance to various acids. Therefore, it may be contained in an amount of 4.00% or more. Preferably, the content is 4.50% or more, 5.00% or more, 5.10% or more, 5.20% or more, 5.30% or more, 5.40% or more, or 5.50% or more. On the other hand, Ni is an element that promotes the σ phase precipitation, and if the σ phase precipitates, Cr is formed as a deficient phase, and local corrosion resistance deteriorates, so that it may be contained by 7.00% or less. Preferably 6.90% or less, 6.80% or less, 6.70% or less, 6.60% or less, or 6.50% or less.
Mo is a very effective element for improving the corrosion resistance of stainless steel, and may be contained in an amount of 0.50% or more for imparting the corrosion resistance of 304N2-X or more. Preferably 1.00% or more, 1.30% or more, 1.35% or more, 1.40% or more, 1.45% or more, 1.50% or more, 1.55% or more, 1.60% or more, 1.65% or more, or 1.70% or more. On the other hand, Mo is an element that promotes the precipitation of the σ phase, and is locally deteriorated in corrosion resistance, so that Mo may be contained in an amount of 2.50% or less. Preferably 2.40% or less, 2.30% or less, 2.10% or less, and 2.00% or less.
W has the effect of improving the corrosion resistance of stainless steel, as with Mo. The steel of the present invention may contain 1.50% as an upper limit for the purpose of improving corrosion resistance. On the other hand, it is also a high-priced element and therefore, it may not be particularly contained. The preferable content may be 0.02% or more.
N (nitrogen) is an effective element for improving the strength and corrosion resistance of stainless steel, and therefore may be contained in an amount of 0.10% or more. Preferably 0.15% or more. On the other hand, since N forms Cr nitride to inhibit corrosion resistance, the content thereof may be 0.25% or less. Preferably 0.20% or less.
The balance being Fe and unavoidable impurities. The inevitable impurities refer to elements contained in the raw materials, elements unintentionally contained in the production, and the like. O, P, S among the impurities is limited for the following reasons.
O (oxygen) is an element that is inevitably mixed in, and is an element that hinders hot workability, toughness, and corrosion resistance of stainless steel, and therefore it is preferable to reduce it as much as possible. Therefore, the O content may be 0.006% or less.
P is an element inevitably mixed from the raw material and deteriorates hot workability and toughness, and therefore, it is preferably as small as possible and limited to 0.05% or less. Preferably 0.03% or less.
S is an element inevitably mixed from the raw material, and deteriorates hot workability, toughness, and corrosion resistance, so that S is preferably as small as possible, and the upper limit may be 0.003% or less.
Further, instead of Fe, 1 or 2 or more of the following elements (Co, Cu, V, Nb, Ta, Ti, Zr, Hf, B, Al, Ca, Mg, REM, Sn) may be contained. These elements may not be contained, and therefore, the content range also includes 0%.
Co is an element effective for improving the corrosion resistance of steel, and may be contained. Since Co is an expensive element, it is not effective to achieve the effect commensurate with the cost even if it is contained in excess of 1.00%, and therefore it may be contained in an amount of 1.00% or less. Preferably, the content is 0.50% or less. In order to obtain this effect, the content may be 0.01% or more, preferably 0.03% or more.
Cu is an element that additionally improves the corrosion resistance of stainless steel against acid, and therefore may be contained. When the content of Cu exceeds 3.0% or more, since epsilon-Cu is precipitated by exceeding the solid solubility at the time of cooling after hot rolling to cause embrittlement, 3.00% or less may be contained. Preferably, the content is 2.00% or less. When Cu is contained, the content may be 0.01% or more, preferably 0.20% or more, in order to obtain the effect.
V, Nb, and Ta form carbides and nitrides in steel and are elements that additionally improve corrosion resistance, and therefore may be contained. On the other hand, if it is contained in a large amount, the toughness is impaired by the excessively formed carbide and nitride, and therefore the contents of V, Nb, and Ta may be 1.00% or less, 0.200% or less, and 0.200% or less, respectively. When these elements are contained, they may be contained in an amount of 0.01% or more, 0.005% or more, or 0.005% or more, respectively, in order to obtain the effects.
Ti, Zr, and Hf are elements that form carbides and nitrides in steel to refine crystal grains, and therefore may be contained. On the other hand, if it is contained in a large amount, the toughness is impaired by excessively formed carbide and nitride, so that the contents of Ti, Zr, and Hf may be 0.030% or less, 0.050% or less, and 0.100% or less, respectively. When these elements are contained, they may be contained in an amount of 0.001% or more, or 0.001% or more, respectively, in order to obtain the effects.
B is an element for improving hot workability of steel, and may be contained. On the other hand, if it is contained in a large amount, B nitrides precipitate, and the toughness is hindered. Therefore, the content thereof may be 0.0050% or less. When B is contained, the content may be 0.0001% or more, preferably 0.0005% or more, in order to obtain the effect.
Al is an element used for deoxidation of steel, and may be contained. On the other hand, if the content is too large, Al nitrides are generated, which hinders toughness. Therefore, the content thereof may be 0.050% or less. Preferably 0.030% or less. When Al is contained, the content may be 0.003% or more, preferably 0.005% or more, in order to obtain the effect.
Ca and Mg may be contained for the purpose of improving hot workability. On the other hand, if it is contained excessively, the hot workability is rather inhibited, and therefore, the contents of Ca and Mg may be 0.0050% or less and 0.0050% or less, respectively. When these elements are contained, they may be set to 0.0005% or more and 0.0001% or more, respectively, in order to obtain the effects.
REM is an element that improves hot workability of steel, and therefore may be contained. On the other hand, since excessive content rather reduces hot workability and toughness, the content may be 0.100% or less when REM is contained. In the case of containing REM, 0.005% or more may be contained in order to obtain the effect. Here, the REM content is the sum of the contents of lanthanoid rare earth elements such as La and Ce.
Sn is an element that improves the corrosion resistance of steel against acid, and therefore, may be contained. On the other hand, if it is contained excessively, hot workability is impaired. Therefore, when Sn is contained, it may be 0.100% or less. When Sn is contained, the content may be 0.005% or more in order to obtain the effect.
PREW is an index of pitting corrosion resistance of stainless steel, and is calculated from formula 1 using the contents (%) of the alloying elements Cr, Mo, W, and N. If the PREW of the stainless steel is less than 25.0, corrosion resistance in a brackish water/seawater environment or a chlorine ion environment such as a chemical industrial tank cannot be exhibited. The upper limit is not particularly limited, but if the content exceeds 36.0 and the alloying element is contained, the cost increases, and therefore the PREW may be in the range of 25.0 to 36.0.
PREW ═ Cr +3.3(Mo +0.5W) +16N (formula 1)
In formula 1, each element symbol represents the content (mass%) of the element, and 0 may be substituted when not contained.
In hydraulic structures, industrial machinery, chemical industrial tanks, and the like, chlorine ions are a main cause of corrosion, and corrosion occurs. In order to ensure sufficient corrosion resistance in this environment, the PREW may be set to a value of 25.0 or more by including Cr, Mo, N, and W. From the viewpoint of ensuring corrosion resistance, the lower limit of PREW may be 26.0, 27.0, 28.0, 29.0, 29.5, 30.0, 30.5, or 31.0. On the other hand, if the content of Cr and Mo is too large in order to improve PREW, the σ phase precipitates as described above, and if the content of N is too large, the toughness deteriorates, and the like, which has an adverse effect. In consideration of the influence on these characteristics, the upper limit of PREW may be 36.0.
In general stainless steel sheets (particularly duplex stainless steel sheets), even when the σ phase precipitates during hot rolling, the σ phase disappears in the subsequent solution heat treatment. However, since the strength is lowered by the solution treatment, the solution treatment can be omitted in order to secure the strength, and the strain introduced into the steel during hot rolling remains in the final product.
The precipitation temperature of the sigma phase is determined by the chemical composition of the steel, and the temperature range in which the sigma phase can be precipitated in a chemical equilibrium state can be estimated based on thermodynamic calculations. For example, the calculation can be performed using software known as thermocalc (registered trademark) and a thermodynamic database (FE-DATA version6 or the like) which are commercially available. The present inventors obtained expression 2 for estimating the upper limit value of the σ phase deposition temperature range (hereinafter referred to as σ phase deposition temperature, denoted by TS) using the software and the database. Further, in order to obtain desired characteristics by suppressing the precipitation of the σ phase, TS may be 950 ℃ or lower. TS is preferably 930 ℃ or lower or 910 ℃ or lower. The lower TS, the more difficult the sigma phase precipitates, but the less Cr, Mo and W, the less corrosion resistance. Therefore, the lower limit of TS can be set to 800 ℃. Preferably 820 ℃ or higher, 830 ℃ or higher, or 840 ℃ or higher.
TS(℃)＝4Cr+25Ni-11(Mo+W)×(Mo+W)+100(Mo+W)+5Si-6Mn-30N+550
(formula 2)
In formula 2, each element symbol represents the content (mass%) of the element, and 0 may be substituted when not contained.
The following formula 2' may be used as the expression for estimating the σ phase deposition temperature TS. Within the scope of the present invention, both formula 2' and formula 2 are equivalent.
TS(℃)＝4Cr+25Ni+71(Mo+W)-11.4(Mo-1.3)×(Mo-1.3)+5Si-6Mn-30N+569
(formula 2')
The hot rolling step will be explained below.
The heating temperature of the cast slab before the start of rolling may be appropriately determined, and may be, for example, in the range of 1150 to 1250 ℃.
Next, regarding the rolling schedule, if the finishing temperature TF (the temperature of the surface of the steel at the entrance of the final pass of hot rolling) is too high and approaches the solution heat treatment temperature, the hot-rolled steel sheet does not retain sufficient strain and the desired hardness cannot be obtained. On the other hand, if TF is too low, the precipitation of the σ phase cannot be avoided. Here, TS is an estimated value of the σ phase precipitation temperature when the steel sheet is maintained in a chemical equilibrium state, that is, for an infinite time, and therefore, since actual hot rolling is completed for a finite time, TF does not need to exceed TS. The component ranges specified in the present invention may satisfy formula 3. The conditions other than the finishing temperature are not particularly limited, and the rolling reduction in each pass may be determined according to the capacity of the rolling mill, for example.
TF-TS ≧ -100 (formula 3)
After hot rolling, the steel sheet is cooled at a cooling rate of 1 ℃/s or more in the range of 800 to 600 ℃ in the range of the components specified in the present invention, in order to suppress the sigma phase precipitation during cooling. The cooling method is not particularly limited, and water cooling, air cooling, or the like may be used depending on the thickness of the plate. As described above, the hot-rolled steel sheet thus obtained may not be subjected to solution heat treatment.
The strength may be equal to or higher than that of SUS304N2-X, that is, 0.2% yield strength of 450MPa or higher. Preferably 480MPa or more.
Stainless steel is used outdoors as a hydraulic structure and in chemical equipment together with cooling equipment, and is thus sometimes exposed to temperatures lower than normal temperatures. For use as a structural member in such an environment, toughness at low temperatures is required, and specifically, the Charpy impact value of a hot-rolled steel sheet at-20 ℃ may be 70J/cm2The above.
In the above applications, sufficient corrosion resistance is required for chloride ions which cause corrosion, and specifically, the pitting potential of the hot-rolled steel sheet at 50 ℃ may be 0.40V or more based on SSE. Here, the potential based on the silver-silver chloride reference electrode using a saturated KCl aqueous solution at 25 ℃ as an electrolyte is shown based on SSE.
Among the σ phases that precipitate, what affects the corrosion resistance is a component that precipitates during hot rolling and subsequent cooling. Therefore, the influence of precipitation during hot rolling and cooling thereafter is quantified by the difference Δ Cr between the Cr extraction residue amount of the hot-rolled steel sheet and the Cr extraction residue amount of the steel sheet obtained by subjecting the hot-rolled steel sheet to solution heat treatment at 1000 to 1100 ℃ and then water-cooling. As a result, when Δ Cr exceeds 0.010% in terms of Cr content in the steel sheet, the corrosion resistance of the hot-rolled steel sheet tends to decrease. Therefore, Δ Cr is preferably 0.010% or less.
Examples
The following examples are provided. Table 1 shows the chemical compositions, PREW and TS of the steel samples. Among the components of the steel, components not shown in table 1 are Fe and inevitable impurity elements. These steels were obtained using a vacuum melting furnace. The components shown in table 1 were not described in the content, and the content was an inevitable impurity level. REM refers to the lanthanide rare earth elements, and the content indicates the sum of these elements. These vacuum-melted cast pieces were heated at 1200 ℃ for 2 hours, and then hot forged to obtain a steel ingot having a predetermined shape. In the shape of the steel ingot, the thickness after finish rolling is 20mm or less, 110mm width × 150mm length × 60mm thickness, and more than 20mm, 110mm width × 150mm length × 100mm thickness.
Table 2 shows the conditions of hot rolling performed to form a steel slab into a steel sheet and the cooling rate thereafter, and the values of 0.2% proof stress, charpy absorption energy, and pitting potential of the obtained hot-rolled steel sheet. In the production of a hot-rolled steel sheet, first, the steel slab obtained by the above-described forging is soaked at 1200 ℃ for 60 minutes. Then, the pressure was reduced so that TF reached the temperature shown in table 2, and cooling was performed so that the cooling rate in the range of 800 to 600 ℃ reached the value shown in the table. The cooling method is water cooling.
The method for measuring 0.2% yield strength is described. From the hot-rolled steel sheet, JIS Z2241: 2011 of test specimen No. 4. The measurement method was carried out in accordance with JIS Z2241: 2011 in implementation.
A method for measuring Charpy absorption energy is described. From the hot-rolled steel sheet, JIS Z2242: 2018 or a test piece. The notch is in the shape of a V-notch. When the steel sheet had an insufficient thickness and no standard test piece could be obtained, small-sized test pieces were obtained as shown in Table 2. The measurement was carried out according to JIS Z2242: 2018. Wherein the test temperature is-20 ℃.
A method for measuring pitting potential is described. A sample having a width of 15mm, a length of 30mm and a thickness of 2mm was cut from the surface layer of the hot-rolled steel sheet by machining, and 0.5mm was ground from the surface layer to prepare a test piece having a measurement surface subjected to #600 wet polishing finish. A resin was applied to the test piece leaving a 10mm X10 mm portion of the test surface. Using this test piece, the test piece was measured according to JIS G0577: 2014. Among them, in JIS G0577: 2014, the site with the test temperature of 30 ℃ is set to 50 ℃. The measurement was conducted until the anode current density reached 1mA/cm2Until the pitting potential is that the current density exceeds 100 muA/cm2The potential at the time point of (a).
As is apparent from the above examples, according to the present invention, a stainless hot-rolled steel sheet having strength and toughness suitable for structural members and excellent corrosion resistance, and exhibiting good economy, can be obtained.
TABLE 2
Industrial applicability
The stainless steel sheet of the present invention has strength equal to or higher than that of conventional stainless steel (SUS304N2-X and SUS329J4L), has toughness and corrosion resistance suitable for structural members, and is excellent in economical efficiency, and therefore, can be applied to all industrial machines and structures for hydraulic buildings, chemical plants, and the like.
Claims (2)
1. A stainless steel sheet characterized by containing, in mass%, (ii) a metal
C：0.001～0.030％、
Si：0.05～1.50％、
Mn：0.10～3.00％、
Cr：22.00～27.00％、
Ni：4.00～7.00％、
Mo：0.50～2.50％、
W：0～1.50％、
N：0.10～0.25％、
Co：0～1.00％、
Cu：0～3.00％、
V：0～1.00％、
Nb：0～0.200％、
Ta：0～0.200％、
Ti：0～0.030％、
Zr：0～0.050％、
Hf：0～0.100％、
B：0～0.0050％、
Al：0～0.050％、
Ca：0～0.0050％、
Mg：0～0.0050％、
REM: 0 to 0.100%, and
Sn：0～0.100％，
the balance being Fe and unavoidable impurities,
limiting O, P and S as impurities to
O: less than 0.006 percent,
P: less than 0.05 percent of,
S: the content of the active carbon is less than 0.003 percent,
PREW determined by the formula 1 is 25.0 to 36.0 inclusive,
the sigma phase precipitation temperature estimated by the equation (2) is 800 ℃ to 950 ℃,
0.2% yield strength of 450MPa or more,
the Charpy impact value at-20 ℃ is 70J/cm2In the above-mentioned manner,
the pitting potential measured at 50 ℃ is 0.40V or more based on SSE,
PREW ═ Cr +3.3(Mo +0.5W) +16N (formula 1)
TS 4Cr +25Ni-11(Mo + W) × (Mo + W) +100(Mo + W) +5Si-6Mn-30N +550 (formula 2)
Wherein, the symbol of each element in formula 1 and formula 2 represents the content of the element in mass%, and 0 is substituted when not contained, and the unit of TS is ° C.
2. The stainless steel plate according to claim 1, wherein the stainless steel plate contains 1 or 2 or more of the following components in mass%,
Co：0.01～1.00％、
Cu：0.01～3.00％、
V：0.01～1.00％、
Nb：0.005～0.200％、
Ta：0.005～0.200％、
Ti：0.001～0.030％、
Zr：0.001～0.050％、
Hf：0.001～0.100％、
B：0.0001～0.0050％、
Al：0.003～0.050％、
Ca：0.0005～0.0050％
Mg：0.0001～0.0050％、
REM: 0.005 to 0.100%, and
Sn：0.005～0.100％。
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| CN103298965A (en) * | 2011-01-27 | 2013-09-11 | 新日铁住金不锈钢株式会社 | Alloying element-saving hot rolled duplex stainless steel material, clad steel sheet having duplex stainless steel as mating material therefor, and production method for same |
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| CN103298965A (en) * | 2011-01-27 | 2013-09-11 | 新日铁住金不锈钢株式会社 | Alloying element-saving hot rolled duplex stainless steel material, clad steel sheet having duplex stainless steel as mating material therefor, and production method for same |
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