CN107075639B - Two phase stainless steel and its manufacturing method - Google Patents
Two phase stainless steel and its manufacturing method Download PDFInfo
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Abstract
A kind of two phase stainless steel, wherein, chemical composition is in terms of quality %, C:0.03% or less, Si:1.0% or less, Mn:1.0% or less, P:0.04% or less, S:0.01% or less, Cu:0.1~1.0%, Ni:5.0~7.5%, Cr:22.0~26.0%, W:6.0~12.0%, N:0.20~0.32%, Mo:0.01% or less, surplus: Fe and impurity, metallographic structure is calculated with the area ratio, α phase is 0.40~0.60, and surplus is γ phase and 0.01 other phases below.
Description
Technical field
The present invention relates to two phase stainless steel and its manufacturing methods.
Background technique
Chemical industrial field etc., in high-temperature high concentration chloride in the environment of there are etching problem use on the way, seek
The stainless steel for having excellent corrosion resistance.
With using SUS304 or SUS316L as the common stainless steel of representative compared with, the two phase stainless steel (first containing a large amount of Cr
For two phase stainless steel: SUS329J4L etc.) show excellent corrosion resistance.But in recent years, the application environment of stainless steel becomes
Extremely harsh, previous two phase stainless steel can not show gratifying corrosion resistance.
Patent document 1, patent document 2 and patent document 3 disclose a kind of two phase stainless steel (second generation two phase stainless steel),
It meets the corrosion proof index of expression as two phase stainless steel and resistance to spot corrosion that is known, being indicated with following formula (1) and formula (2)
Index (PRE, PREW) is improved corrosion resistance by using Mo and N with harshization of application environment.But even if
It is these second generation two phase stainless steels, the corrosion resistance under briny environment is also insufficient.
PRE=Cr+3.3Mo+16N (1)
PREW=Cr+3.3 (Mo+0.5W)+16N (2)
Patent document 4, patent document 5, patent document 6, non-patent literature 1 and non-patent literature 2 disclose double containing W
Phase stainless steel (third generation two phase stainless steel).Third generation two phase stainless steel corrosion resistance compared with previous second generation two phase stainless steel
It is excellent, it is widely used under briny environment.
Existing technical literature
Patent document
Patent document 1: Japanese Unexamined Patent Application 62-180043 bulletin
Patent document 2: Japanese Unexamined Patent Publication 2-258956 bulletin
Patent document 3: Japanese Unexamined Patent Publication 5-132741 bulletin
Patent document 4: Japanese Unexamined Patent Application 62-56556 bulletin
Patent document 5: Japanese Unexamined Patent Publication 5-132741 bulletin
Patent document 6: Japanese Unexamined Patent Publication 8-170153 bulletin
Non-patent literature
Non-patent literature 1:Anthony Comer, Lisa Looney, Corrosion and fatigue
characteristics of positively polarised Zeron 100base&weld metal in synthetic
seawater,International Journal of Fatigue,Vol 28,826-834.
Non-patent literature 2: corrosion centers news " corrosion セ ン タ ー ニ ュ ー ス " No.059 (2012)
Summary of the invention
Problems to be solved by the invention
Even third generation two phase stainless steel, in the high-temperature high concentration that chemical industrial field etc. is harsher compared with seawater
Corrosion resistance in the environment of chloride is also insufficient.
The object of the present invention is to provide the corrosion resistances by improving third generation two phase stainless steel to be able to solve in chemistry
The two phase stainless steel and its manufacturing method of etching problem in the environment of the high temperature high concentration chloride such as industrial circle.
The solution to the problem
Think that W is influenced for caused by corrosion resistance and its mechanism of action and Mo are identical mechanism in the past.But it is of the invention
People etc. are studied in detail for the corrosion proof mechanism of action of intervention of Mo and W, as a result, it has been found that: under harsh environment, with
There are mistakes for past opinion.
Fig. 1 shows the polarization curve of pure W and pure Mo in corrosive environment.As shown in Figure 1, even if being dissolved out in Mo
Region in, W is also hardly dissolved out.Thus can be predicted: Mo and W influences significantly different caused by improving on corrosion resistance.
Thus, based on the chemical composition of third generation two phase stainless steel, for not adding Mo but largely double containing W
The corrosion resistance of phase stainless steel is studied in detail.Its result obtains following opinions.
If (a) suitably adjusting chemical composition and manufacturing method, two phase constitution of α+γ that σ phase or χ phase is not precipitated is made, then
In high temperature, there are also have excellent corrosion resistance in the environment of high concentration chloride.Corrosion resistance at this time is more than the pass by PREW
It is the predictable corrosion resistance of formula.
If (b) suitably adjusting chemical composition and manufacturing method, in low pH, high temperature, there are the rings of high concentration chloride
The passivation epithelium formed under border can be rich in W.Corrosion resistance of the passivation epithelium under above-mentioned environment rich in W improves tremendously.
The present invention is carried out based on above-mentioned opinion, using following two phase stainless steels and its manufacturing method as purport.
(1) a kind of two phase stainless steel, wherein chemical composition in terms of quality %,
C:0.03% or less,
Si:1.0% or less,
Mn:1.0% or less,
P:0.04% or less,
S:0.01% or less,
Cu:0.1~1.0%,
Ni:5.0~7.5%,
Cr:22.0~26.0%,
W:6.0~12.0%,
N:0.20~0.32%,
Mo:0.01% or less,
Surplus: Fe and impurity,
In terms of the area ratio, α phase is 0.40~0.60 for metallographic structure, and surplus is γ phase and 0.01 other phases below.
(2) two phase stainless steel according to above-mentioned (1), wherein in the NaCl aqueous solution for remaining 90 DEG C of 250g/L
When middle dipping, correspond to 100 μ A/cm2Pitting potential be 600mV (vs.SCE) more than.
(3) two phase stainless steel according to above-mentioned (1) or (2), wherein impregnated 24 hours in the experimental liquid of pH=1
The chemical composition of the outmost surface of passivation epithelium afterwards meets following formula (i).
W/(Fe+Cr)≥0.09…(i)
Wherein, each element symbol in above-mentioned formula indicates the content (at%) of each element of the outmost surface of passivation epithelium.
(4) a kind of manufacturing method of two phase stainless steel, wherein real for the steel with chemical composition described in above-mentioned (1)
Apply following heat treatments: until being heated to 1150~1300 DEG C of temperature field, after keeping under the temperature field, with more than water cooling cold
But speed is cooled down.
It should be noted that α phase refers to ferritic phase in the present invention, γ phase refers to austenite phase.
The effect of invention
In accordance with the invention it is possible to obtain the two phase stainless steel with excellent corrosion resistance.The two phase stainless steel is applicable to
There are chemical industrial fields of etching problem etc. in the environment of high-temperature high concentration chloride.
Detailed description of the invention
Fig. 1 is the schematic diagram of the polarization curve of pure W and pure Mo in corrosive environment.
Fig. 2 is showing for the value of the W/ (Fe+Cr) of the outmost surface of the passivation epithelium in embodiment and the relationship of pitting potential
It is intended to.
Specific embodiment
Hereinafter, embodiments of the present invention will be described for needle.In the following description, for the content of each element, " % "
Refer to " quality % ".
1. the chemical composition of base material
C:0.03% or less
C is austenite forming element, is effective for making austenite phase become to stablize.But the present invention that
In the high Cr stainless steel of sample, when content is more than 0.03%, it is possible to Cr carbide be precipitated, corrosion resistance is deteriorated.Therefore, C content
It is set as 0.03% or less.Preferably 0.01% or less.Even C is micro, there is said effect, therefore lower limit as long as comprising C
It is not particularly limited.Wherein, in order to sufficiently obtain said effect, 0.003% or more C is preferably comprised.
Si:1.0% or less
Si is effective as the deoxidation ingredient of steel, but when its content is excessive, it is possible to promote the precipitation of σ phase and χ phase.Cause
This, Si content is set as 1.0% or less.Preferably 0.5% or less.When carrying out deoxidation using other elements, Si content substantially may be used
Think zero, but in order to sufficiently obtain said effect, preferably comprises 0.2% or more Si.
Mn:1.0% or less
Mn is austenite forming element, facilitates the stabilisation of austenite.But content it is excessive when, become and corrode
The MnS of point is possible to can crystallization or precipitation.Therefore, Mn content is set as 1.0% or less.Preferably 0.5% or less.Even if Mn is micro-
Amount has said effect as long as containing Mn, therefore lower limit is not particularly limited.Wherein, excellent in order to sufficiently obtain said effect
Select the Mn containing 0.1% or more.
P:0.04% or less
P is inevitable impurity element during manufacturing, and when content is excessive, processability is likely to decrease.Therefore, P contains
Amount is set as 0.04% or less.Preferably 0.01% or less.
S:0.01% or less
S is inevitable impurity element during manufacturing, and when content is excessive, processability is likely to decrease.In addition, worrying
MnS as corrosion starting point can crystallization or precipitation.Therefore, S content is set as 0.01% or less.Preferably 0.004% or less.
Cu:0.1~1.0%
Cu is austenite forming element, for improve it is resistance to it is sulfuric acid be effective.Promote largely to include W in addition, also having
Passivation epithelium formation effect.Specifically, having the passivation epithelium for promoting cathode reaction, quickening formation largely to include W
Effect.Therefore, content is set as 0.1% or more.But content it is excessive when, formability is possible to be deteriorated.Therefore, Cu contains
Amount is set as 0.1~1.0% or less.Lower limit is preferably 0.4%, and the upper limit is preferably 0.6%.
Ni:5.0~7.5%
Ni is austenite forming element.There is expectation in terms of with the relationship of the ferrite generating elements such as Cr, W in order to obtain
Two phase constitution of α+γ of balance needs to contain Ni in the range of 5.0~7.5%.Lower limit is preferably 6.0%, and the upper limit is preferably
6.8%.
Cr:22.0~26.0%
Cr is ferrite generating elements, in addition, being the effective basic element for improving corrosion resistance.Cr content is very few
When or it is excessive when, the temperature field that can steadily obtain two phase constitution of α+γ becomes narrow.Therefore, Cr content be set as 22.0~
26.0%.Lower limit is preferably 23.0%, and the upper limit is preferably 25.5%.
W:6.0~12.0%
W is ferrite generating elements, in addition, being important element for showing excellent corrosion resistance.W content mistake
When few or excessive, two phase constitution of α+γ can not be steadily obtained.Therefore, W content is limited to 6.0~12.0%.Lower limit is preferred
It is 8.0%, the upper limit is preferably 11.0%.
N:0.20~0.32%
N is austenite forming element, is effective member for the thermal stability for improving two phase stainless steel and corrosion resistance
Element.In order to obtain two phase constitution of α+γ in terms of with the relationship of the ferrite generating elements such as Cr, W with expectation balance, need
Contain 0.20% or more N.But content is when being more than 0.32%, it is possible to lead to the toughness, resistance to of steel because generating nitride
Corrosion is significantly deteriorated.Therefore, N content is set as 0.20~0.32%.Lower limit is preferably 0.24%, and the upper limit is preferably 0.28%.
Mo:0.01% or less
Mo and Cr and W are similarly ferrite generating elements.But when containing Mo, the solid solubility of W can be made to reduce, therefore needed
Its content is reduced as far as possible.Therefore, the content of Mo is set as 0.01% or less.Preferably 0.008% or less.
The chemical composition of two phase stainless steel of the invention includes above-mentioned each element in the range of respective regulation, surplus by
Fe and impurity composition.It is mixed due to the raw materials such as ore, waste material and other factors when impurity refers to industrially manufacture steel
Ingredient.
2. the metallographic structure of base material
It is 0.40~0.60 that base material, which has the area ratio of α phase, the α+γ two that surplus is γ phase and 0.01 other phases below
Phase constitution.In phase other than α phase and γ phase, especially σ phase and χ phase are formed around it lacks Cr layers, and corrosion resistance is caused to become
Difference it is therefore preferable that making their gross area rate zero, but allows to be 0.01 or less.It should be noted that when the ratio of γ phase is big, it is resistance to
Corrosion is deteriorated sometimes, and therefore, the area ratio of γ phase is preferably set to 0.58 or less.
3. being passivated epithelium
It, can will be if having the two phase stainless steel of above-mentioned chemical composition and metallographic structure using condition appropriate manufacture
There are the passivation epitheliums formed in the environment of high concentration chloride, and the product rich in W is made for low pH, high temperature.In low ph conditions
Under, be passivated epithelium in Fe and Cr can corrode, but include mass efficient contribute to corrosion proof W passivation epithelium it is resistance to
Corrosion is excellent.
Also, the chemical composition of the outmost surface of the passivation epithelium after impregnating 24 hours in the experimental liquid of pH=1 meets
When following formula (i), the corrosion resistance of two phase stainless steel can be made to improve tremendously.The left side value of following formula (i) is more preferably set as
0.10% or more.
W/(Fe+Cr)≥0.09…(i)
Wherein, each element symbol in above-mentioned formula indicates the content (at%) of each element of the outmost surface of passivation epithelium.
4. the manufacturing method of two phase stainless steel
Product is made by implementing following heat treatments in two phase stainless steel of the invention: under the manufacturing condition generallyd use
Melting is carried out, the necessary processing such as hot-working, cold working are implemented, until being finally heated to 1150~1300 DEG C of temperature field,
After being kept in the temperature field, cooled down with cooling velocity more than water cooling.
This is because: the precipitation of σ phase or χ phase is difficult to avoid that if above-mentioned heat treatment temperature is lower than 1150 DEG C, in addition, super
When crossing 1300 DEG C, it is possible to cannot get α phase the area ratio be 0.4~0.6, surplus be essentially γ phase two phase constitution of α+γ.
Therefore, heat treatment carries out under 1150~1300 DEG C of temperature field.Retention time different, Ke Yi due to thickness of two phase stainless steel
It is suitably selected in the range of 1~120min.
If the cooling velocity after being kept in above-mentioned temperature field is excessively slow, it is possible to that σ phase is precipitated in cooling procedure
Or χ phase, therefore cooled down with cooling velocity more than water cooling.Specifically, being carried out with the cooling velocity of 40 DEG C/s or more cold
But.
Hereinafter, further illustrating the present invention by embodiment, but the present invention is not limited to these embodiments.
Embodiment 1
Using the vacuum melting furnace of 17kg, melting is carried out to the steel ingot with chemical composition shown in table 1, is hot-rolled down to 4~8mm's
Until thickness.It should be noted that being directed to arbitrary steel, the resistance to spot corrosion indices P REW that equal following formula defines reaches 43~44 or so side
Formula is adjusted.
PREW=Cr+3.3 (Mo+0.5W)+16N
Wherein, each element symbol in above-mentioned formula indicates the content (quality %) of each element in steel.
Thereafter, it after being heated to temperature shown in table 1 and being kept, carries out water cooling and obtains material to be tested.In addition, conduct
Material to be tested has been also prepared for the commercially available stainless steel with chemical composition shown in table 2.For these materials to be tested, base material is carried out
The observation of metallographic structure, corrosion proof measurement and the constituent analysis for being passivated epithelium.
[table 1]
[table 2]
<observation of the metallographic structure of base material>
It for each section for test material, is observed using optical microscopy with 500 times of multiplying power, measures α phase and γ phase
The area ratio.It further confirms that the presence or absence of σ phase and χ phase, is denoted as "○" when σ phase and χ phase not being precipitated, observe at least precipitation one
Shi Jizuo "×", and measure their gross area rate.
<corrosion proof measurement>
The discoid test film that diameter is 15mm, plate thickness is 2mm is cut out from each material to be tested, by surface wet lapping essence
It is machined to #600.Test is based on JIS G 0577 (2014), and measurement corresponds to 100 μ A/cm2Pitting potential V ' C100.It should
Illustrate, due to contemplating environment of the high temperature there are high concentration chloride, aqueous solution, which has used, remains 90 DEG C
The NaCl aqueous solution of 250g/L.
<constituent analysis of passivation epithelium>
For a part of material to be tested, after impregnating 24 hours in the experimental liquid of pH=1, pass through x-ray photoelectron spectroscopy
Method is passivated the measurement of each main metal element in epithelium, calculates the value of the W/ (Fe+Cr) of the outmost surface of passivation epithelium.
Their result summary is shown in table 3.
[table 3]
Table 3
*It indicates to deviate regulation of the invention.
W/(Fe+Cr)≥0.09...(i)
As shown in table 3 like that, chemical composition and metallographic structure meet present invention provide that test No.1~6 pitting potential
For 600mV or more, good corrosion resistance is shown.
In contrast, at least chemical composition deviate present invention provide that range test No.16~21,25~27 and 29~
32 and at least metallographic structure deviation present invention provide that range test No.7~15,22~24 and 28 present corrosion resistance difference
As a result.
As shown in Figure 2, it is passivated between the value and pitting potential of the W/ (Fe+Cr) of the outmost surface of epithelium and exists centainly
Correlation can make pitting potential 600mV or more when the value of W/ (Fe+Cr) is 0.09 or more.
Industrial availability
In accordance with the invention it is possible to obtain the two phase stainless steel with excellent corrosion resistance.The two phase stainless steel is applicable to
There are chemical industrial fields of etching problem etc. in the environment of high-temperature high concentration chloride.
Claims (4)
1. a kind of two phase stainless steel, wherein chemical composition in terms of quality %,
C:0.03% or less,
Si:1.0% or less,
Mn:1.0% or less,
P:0.04% or less,
S:0.01% or less,
Cu:0.1~1.0%,
Ni:5.0~7.5%,
Cr:22.0~26.0%,
W:6.0~12.0%,
N:0.20~0.32%,
Mo:0.01% or less,
Surplus: Fe and impurity,
In terms of the area ratio, α phase is 0.40~0.60 for metallographic structure, and surplus is γ phase and 0.01 other phases below.
2. two phase stainless steel according to claim 1, wherein soaked in the NaCl aqueous solution for remaining 90 DEG C of 250g/L
When stain, correspond to 100 μ A/cm2The pitting potential relative to SCE be 600mV or more.
3. according to claim 1 or two phase stainless steel as claimed in claim 2, wherein it is small to impregnate 24 in the experimental liquid of pH=1
When after the chemical composition of outmost surface of passivation epithelium meet following formula (i):
W/(Fe+Cr)≥0.09…(i)
Wherein, each element symbol in above-mentioned formula indicates the content of each element of the outmost surface of passivation epithelium, the unit of content
For at%.
4. a kind of manufacturing method of two phase stainless steel, wherein for the steel with chemical composition described in claim 1, in reality
After applying necessary processing, implement following heat treatments: until being heated to 1150~1300 DEG C of temperature field, being protected under the temperature field
After holding, cooled down with cooling velocity more than water cooling,
The necessary processing includes hot-working and/or cold working.
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| JP2014-217632 | 2014-10-24 | ||
| JP2014217632 | 2014-10-24 | ||
| PCT/JP2015/079962 WO2016063974A1 (en) | 2014-10-24 | 2015-10-23 | Two-phase stainless steel and production method therefor |
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| CN107075639B true CN107075639B (en) | 2019-09-27 |
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| US (1) | US20170327915A1 (en) |
| EP (1) | EP3211107A4 (en) |
| JP (1) | JP5962878B1 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN1070930C (en) * | 1995-06-05 | 2001-09-12 | 浦项综合制铁株式会社 | Duplex stainless steel, and its manufacturing method |
| CN1816640A (en) * | 2003-06-30 | 2006-08-09 | 住友金属工业株式会社 | Duplex stainless steel |
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| JPS56119721A (en) * | 1980-02-25 | 1981-09-19 | Sumitomo Metal Ind Ltd | Solid solution treatment of two-phase stainless steel |
| JP2500162B2 (en) * | 1991-11-11 | 1996-05-29 | 住友金属工業株式会社 | High strength duplex stainless steel with excellent corrosion resistance |
| JPH08170153A (en) * | 1994-12-19 | 1996-07-02 | Sumitomo Metal Ind Ltd | Highly corrosion resistant two phase stainless steel |
| JPH1060598A (en) * | 1996-08-19 | 1998-03-03 | Nkk Corp | Seawater resistant precipitation strengthening type duplex stainless steel |
| JPH1060526A (en) * | 1996-08-19 | 1998-03-03 | Nkk Corp | Production of seawater resistant precipitation strengthening type duplex stainless steel |
| CN1201028C (en) * | 2001-04-27 | 2005-05-11 | 浦项产业科学研究院 | High manganese deplex stainless steel having superior hot workabilities and method for manufacturing thereof |
| JP4967398B2 (en) * | 2006-03-22 | 2012-07-04 | Ｊｆｅスチール株式会社 | Stainless steel suitable for polymer electrolyte fuel cell and its separator |
| JP5211841B2 (en) * | 2007-07-20 | 2013-06-12 | 新日鐵住金株式会社 | Manufacturing method of duplex stainless steel pipe |
| ES2708945T3 (en) * | 2009-01-19 | 2019-04-12 | Nippon Steel & Sumitomo Metal Corp | Procedure to produce a duplex stainless steel pipe |
| JP5511208B2 (en) * | 2009-03-25 | 2014-06-04 | 新日鐵住金ステンレス株式会社 | Alloy-saving duplex stainless steel material with good corrosion resistance and its manufacturing method |
| WO2012121232A1 (en) * | 2011-03-10 | 2012-09-13 | 住友金属工業株式会社 | Duplex stainless steel sheet |
| WO2013115524A1 (en) * | 2012-01-31 | 2013-08-08 | 한국기계연구원 | High-performance high-nitrogen duplex stainless steels excellent in pitting corrosion resistance |
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- 2015-10-23 CN CN201580057001.2A patent/CN107075639B/en active Active
- 2015-10-23 EP EP15852926.3A patent/EP3211107A4/en not_active Withdrawn
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| CN1070930C (en) * | 1995-06-05 | 2001-09-12 | 浦项综合制铁株式会社 | Duplex stainless steel, and its manufacturing method |
| CN1816640A (en) * | 2003-06-30 | 2006-08-09 | 住友金属工业株式会社 | Duplex stainless steel |
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| US20170327915A1 (en) | 2017-11-16 |
| EP3211107A4 (en) | 2018-05-09 |
| CN107075639A (en) | 2017-08-18 |
| EP3211107A1 (en) | 2017-08-30 |
| JPWO2016063974A1 (en) | 2017-04-27 |
| WO2016063974A1 (en) | 2016-04-28 |
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