CN109563589A - Austenite stainless steel - Google Patents
Austenite stainless steel Download PDFInfo
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- CN109563589A CN109563589A CN201780048557.4A CN201780048557A CN109563589A CN 109563589 A CN109563589 A CN 109563589A CN 201780048557 A CN201780048557 A CN 201780048557A CN 109563589 A CN109563589 A CN 109563589A
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Abstract
A kind of austenite stainless steel, it has: base material, with at least part of overlay film for being formed in surface possessed by base material, the chemical composition of base material is calculated as C:0.05% or less with quality %, Si:1.0% or less, Mn:2.0% or less, P:0.040% or less, S:0.010% or less, O:0.020% or less, N: less than 0.050%, Ni:12.0~27.0%, Cr:15.0% is more than and less than 20.0%, Cu: greater than 3.5% and be 8.0% or less, Mo: greater than 2.0% and be 5.0% or less, Co:0.05% or less, Sn:0.05% or less, V:0~0.5%, Nb:0~1.0%, Ti:0~0.5%, W:0~5.0%, Z R:0~1.0%, Al:0~0.5%, Ca:0~0.01%, B:0~0.01%, REM:0~0.01%, surplus: the chemical composition of Fe and impurity, the maximum Cr depth of overlay film meets [(Cr+Ni+Cu+Mo)/Fe >=1.0] in terms of at%.
Description
Technical field
The present invention relates to austenite stainless steels, more particularly to the austenite stainless steel that acid resistance is excellent.
As thermal power generation with or industry boiler oil and oil and coal for using etc so-called " fossil fires
Include in material " sulphur (S).Therefore, if fossil fuel burns, oxysulfide (SO can be generated in the offgasx).The temperature of exhaust gas
If reduced, SOxWith the reaction of moisture in gas as sulfuric acid, in the component surface for being in dew-point temperature low temperature below
Moisture condensation, generates corrosion of sulfuric acid at dew point as a result,.
It similarly, include SO in circulation even if in the flue gas desulfurization equipment used in various industriesxGas the case where
Under, if temperature reduces, it can also generate corrosion of sulfuric acid at dew point.It will include SO for the sake of easy in following this specificationxGas
Body is denoted as exhaust gas to be illustrated.
Since above-mentioned phenomenon can be generated, in heat exchanger used in waste gas system etc., in component surface sulfuric acid
Exhaust gas temperature is remained 150 DEG C or more of high temperature by the mode not condensed.
However, from the viewpoint of energy needs increase and energy effective use in recent years, in order to return as effectively as possible
Heat energy is received, for example, in the presence of the dew point trend below that the exhaust gas temperature from heat exchanger is reduced to sulfuric acid, gradually requirement pair
Sulfuric acid has indefatigable material.
In the case where exhaust gas temperature is not remained 150 DEG C or more, in 140 DEG C or so of temperature of the exhaust gas of general composition
It spends under domain, 80% or so high-concentration sulfuric acid can condense in component surface.Under such environment, so-called " low-alloy steel " gradually
It is used initially as various components with steel.This is because, for the sulfuric acid of foregoing high-temperature high concentration, low-alloy steel it is resistance to
Corrosivity is higher than general stainless steel.
On the other hand, as recorded in non-patent literature 1, in the area of low 20~60 DEG C of the temperature of dew point than sulfuric acid
In domain, the amount of the sulfuric acid of moisture condensation becomes at most, and therefore, corrosion caused by sulfuric acid becomes larger.Therefore, exhaust gas temperature is not remained
In the case where 150 DEG C or more, it is however generally that, become the region for most requiring corrosion resistance, herein, sulphur at the temperature near 100 DEG C
The concentration of acid becomes about 70%.However, in this region, not only general stainless steel, even the etching extent of low-alloy steel is also big,
It is not available.
So far, for the component in sulphuric acid environment, the side that specific resistant material can be used is proposed
A kind of resistant to sulfuric acid dew point corrosion stainless steel having superior hot workability is disclosed in case, such as patent document 1
In addition, disclosing a kind of austenite stainless steel in patent document 2, there is excellent patience for sulfuric acid corrosion
And processability is also excellent.
Existing technical literature
Patent document
Patent document 1: Japanese Unexamined Patent Publication 4-346638 bulletin
Patent document 2: Japanese Patent No. 3294282
Non-patent literature
Non-patent literature 1: Nagano win husband, " corrosion of sulfuric acid at dew point ", anticorrosion technique, 1977, volume 26, No. 12,
p.731-740
Summary of the invention
Problems to be solved by the invention
N (nitrogen) that the stainless steel recorded in patent document 1 contains 0.05 weight % or more attempts to ensure that austenite structure
Stabilisation and corrosion resistance.However, in the case where the N containing 0.05 weight % or more, compound Austria added with Cu, Cr and Mo
The corrosion resistance against sulfuric acid of family name's system stainless steel can reduce instead.In turn, in the case where N content is 0.05 weight % or more, such as
Fruit increases Cu content in order to improve corrosion resistance against sulfuric acid, then there is the reduction of the hot-workability in the temperature field less than 1000 DEG C
The problem of becoming apparent.
In addition, the austenite stainless steel recorded in patent document 2 has excellent corrosion resistance against sulfuric acid and processability.So
And about corrosion resistance against sulfuric acid, still there are further rooms for improvement.
The present invention solves the above problem, it is intended that providing in the environment of the condensation of the sulfuric acid of high concentration with excellent
Different acid proof austenite stainless steel.
It should be noted that " environment of the sulfuric acid condensation of high concentration " refers to the temperature at 50~100 DEG C in record below
Spend the environment that the sulfuric acid of lower concentration 40~70% can condense.
The solution to the problem
The present invention makes in order to solve the above problems, using following austenite stainless steels as purport.
(1) a kind of austenite stainless steel, has: base material and being formed in surface possessed by aforementioned base material at least
The overlay film of a part,
The chemical composition of aforementioned base material is calculated as with quality %
C:0.05% or less,
Si:1.0% or less,
Mn:2.0% or less,
P:0.040% or less,
S:0.010% or less,
O:0.020% or less,
N: less than 0.050%,
Ni:12.0~27.0%,
Cr:15.0% more than and less than 20.0%,
Cu: greater than 3.5% and for 8.0% or less,
Mo: greater than 2.0% and for 5.0% or less,
Co:0.05% or less,
Sn:0.05% or less,
V:0~0.5%,
Nb:0~1.0%,
Ti:0~0.5%,
W:0~5.0%,
Zr:0~1.0%,
Al:0~0.5%,
Ca:0~0.01%,
B:0~0.01%,
REM:0~0.01%,
Surplus: Fe and impurity,
The chemical composition that the Cr concentration of aforementioned overlay film becomes maximum maximum Cr depth meets following formula (i).
(Cr+Ni+Cu+Mo)/Fe≥1.0···(i)
Wherein, each element symbol in above-mentioned formula indicates the content (at%) of each element.
(2) austenite stainless steel according to above-mentioned (1), wherein the chemical composition of aforementioned base material is in terms of quality %
Containing being selected from
V:0.01~0.5%,
Nb:0.02~1.0%,
Ti:0.01~0.5%,
W:0.1~5.0%,
Zr:0.02~1.0%,
Al:0.01~0.5%,
Ca:0.0005~0.01%,
The and of B:0.0005~0.01%
REM:0.0005~0.01%
One or more of.
(3) austenite stainless steel according to above-mentioned (1) or (2), wherein the Cr concentration of aforementioned overlay film becomes minimum
Minimum Cr depth be present in than aforementioned maximum Cr depth closer to aforementioned base material side,
The chemical composition of aforementioned maximum Cr depth meets following formula (ii), and the chemical composition of aforementioned minimum Cr depth
Meet following formula (iii).
Cr/(Ni+Cu+Mo)≥1.0···(ii)
Cr/(Ni+Cu+Mo)<1.0···(iii)
Wherein, each element symbol in above-mentioned formula indicates the content (at%) of each element.
The effect of invention
According to the present invention it is possible to obtain that there is excellent acid proof austenite in the environment of the condensation of the sulfuric acid of high concentration
It is stainless steel.
Specific embodiment
Based on the inventors of the present invention's austenite stainless steel documented by the patent document 2, to further increasing resistance to sulfuric acid
Corrosive method has carried out in-depth study repeatedly, as a result obtains following opinion.
In terms of improve corrosion resistance against sulfuric acid, with the sulfuric acid contact of high concentration, be formed in the overlay film on base material surface
Composition becomes important.In overlay film, the total content of Cr, Ni, Cu and Mo relative to Fe by relativity are improved, can substantially be mentioned
Highly-acidproof.
In addition, it is found that implementing to be heat-treated under the defined conditions to steel, to form the oxidation based on Fe on surface
After overlay film, implements acid processing, melt Fe ingredient preferentially, it is possible thereby to be enriched with Cr, Ni, Cu and Mo in overlay film.
The present invention is made based on above-mentioned opinion.Hereinafter, each feature of the invention is described in detail.
1. constituting
Austenite stainless steel of the invention has: base material and being formed at least one of surface possessed by the base material
The overlay film divided.For base material and overlay film, it is described in detail individually below.
2. about base material
The chemical composition of base material is described in detail.The restriction reason of each element is as described below.It should be noted that with
Under explanation in about " % " of content refer to " quality % ".
C:0.05% or less
C is the element improve with intensity.But Cr carbide can be formed in conjunction with Cr and in crystal boundary, make
Resistance to grain boundary corrosion reduces.Therefore, C content is set as 0.05% or less.It should be noted that needing the case where improving intensity
Under, preferably contain more than 0.03%.On the other hand, in the case where preferentially ensuring corrosion resistance, C content is low to be advisable, and preferably sets
It is 0.03% or less.Lower limit is without especially setting, but said effect in order to obtain, C content are preferably set to 0.01% or more.
Si:1.0% or less
Si is the element with deoxidation.But content can then encourage the drop of hot-workability if it exceeds 1.0%
Low, the increase with Cu content interacts, so that being processed into product on an industrial scale becomes extremely difficult.Therefore, Si content is set
It is 1.0% or less.Si content preferably 0.6% or less.Si is without centainly containing, and therefore, lower limit is not arranged especially, but in order to obtain
Said effect, Si content are preferably set to 0.05% or more.In addition, extremely reducing Al for the purpose for improving hot-workability and containing
In the case where amount, it is preferred that containing 0.1% or more Si, carry out deoxidation sufficiently.
Mn:2.0% or less
Mn, which has, to be fixed S and improves hot-workability and make the stabilized effect of austenite phase.But even if containing super
The Mn of 2.0% amount is crossed, effect is also saturated, and only increases cost.Therefore, Mn content is set as 2.0% or less.Mn content is preferred
1.5% or less.Mn is without centainly containing, and therefore, lower limit is not arranged especially, but said effect in order to obtain, and Mn content is preferably set
It is 0.1% or more.
P:0.040% or less
P is contained in steel in the form of impurity, hot-workability and corrosion resistance can be made to deteriorate, therefore, content is preferably most
It measures low.Especially P content is if it exceeds 0.040%, then the deterioration of the corrosion resistance in the environment of the sulfuric acid condensation of high concentration is bright
It is aobvious.Therefore, P content is set as 0.040% or less.
S:0.010% or less
S is contained in steel in the form of impurity, deteriorates hot-workability, and therefore, content is preferably low as far as possible.Especially S
Content then will lead to the obvious deterioration of hot-workability if it exceeds 0.010%.Therefore, S content is set as 0.010% or less.
O:0.020% or less
O is contained in steel in the form of impurity, reduces hot-workability and ductility, content is preferably low as far as possible.Especially O
Content is if it exceeds 0.020%, then the reduction of hot-workability and ductility is obvious, and therefore, O content is set as 0.020% or less.
N: less than 0.050%
For N, previous N is for the stabilized purpose of austenite structure or raising to the part such as spot corrosion or crevice corrosion
The purpose of the patience of corrosion and energetically add.But in the environment of the condensation of the sulfuric acid of high concentration, the content of N becomes
When 0.050% or more, Austria containing the Cr of Cu, the Mo more than 2.0% and 15.0% more than and less than 20.0% for having more than 3.5%
The corrosion resistance of family name's system stainless steel can reduce instead.In turn, even if making the upper limit of the content of Cu and Mo be respectively 8.0% He
In the case where 5.0%, if the content of N becomes 0.050% or more, hot-workability can also be reduced.In order to austenite not
The steel that becomes rusty assigns the corrosion resistance and hot-workability in the environment of the sulfuric acid condensation of high concentration, and N content is set as less than 0.050%.It needs
It is noted that the lower N content the better, preferably 0.045% or less.
Ni:12.0~27.0%
Ni has the stabilized effect of austenite phase that makes, and also has resistance in the environment for the sulfuric acid condensation for improving high concentration
Corrosive effect.In order to substantially ensure such effect, the Ni of the amount containing 12.0% or more is needed.But even if contain
More than 27.0%, effect is also saturated.In turn, Ni is expensive element, and therefore, cost can become high, lacks economy.Cause
This, Ni content is set as 12.0~27.0%.It should be noted that in order to ensure in the environment that the sulfuric acid of high concentration condenses sufficiently
Corrosion resistance, preferably contain more than the Ni of 15.0% amount, be further preferably more than the Ni of 20.0% amount.
Cr:15.0% is more than and less than 20.0%
Cr is to the effective element of corrosion resistance for ensuring austenite stainless steel.N is especially limited to above-mentioned content
Austenite stainless steel in, if making the Cu and Mo of 15.0% or more Cr, preferably 16.0% or more Cr Yu aftermentioned amount
Contain together, then may insure good corrosion resistance in the environment of the condensation of the sulfuric acid of high concentration.But if excessively contain
There is Cr, even if then in the case where reducing N content and the compound austenite stainless steel added with Cu and Mo, in aforesaid environmental
Corrosion resistance can also deteriorate instead, and then can also generate the reduction of processability.If especially Cr content become 20.0% with
On, then the corrosion resistance deterioration of the austenite stainless steel in aforesaid environmental becomes apparent.In addition, by being less than Cr content
20.0%, so as to improve the hot-workability of the compound austenite stainless steel added with Cu and Mo, it is easy on an industrial scale
Fabricated product.Therefore, Cr content is set as 15.0% more than and less than 20.0%.
Cu: greater than 3.5% and be 8.0% or less
Cu is the necessary element for ensuring the corrosion resistance in sulphuric acid environment.By make be more than 3.5% Cu with before
The Cr for the amount stated and the Mo of aftermentioned amount contain together, thus in the environment of the condensation of the sulfuric acid of high concentration, it can be to making on N
The austenite stainless steel for stating content assigns good corrosion resistance.It is compound be added with Cu and Mo when Cu content it is more, then
Corrosion resistance improvement effect is bigger, therefore, Cu content be preferably set to be more than 4.0% amount.It should be noted that by increasing Cu
Content, although the corrosion resistance in aforesaid environmental improves, hot-workability can be reduced, especially Cu content if it exceeds 8.0%,
Even if then making the above-mentioned content of N, the obvious deterioration of hot-workability can be also generated.Therefore, Cu content is set as being greater than 3.5% and is
8.0% or less.
Mo: greater than 2.0% and be 5.0% or less
Mo is the effective element for the corrosion resistance for ensuring austenite stainless steel.If make be more than 2.0% amount
Mo contain together with the Cr of aforementioned quantities and Cu, then, can be to making the above-mentioned content of N in the environment of the condensation of the sulfuric acid of high concentration
Austenite stainless steel assign good corrosion resistance.But if excessively containing Mo, hot-workability is reduced, especially
It is Mo content if it exceeds 5.0%, even if then making the above-mentioned content of N, can also generates the obvious deterioration of hot-workability.Therefore, Mo
Content is set as greater than 2.0% and is 5.0% or less.It should be noted that in order to true in the environment that the sulfuric acid of high concentration condenses
Sufficient corrosion resistance is protected, the Mo of 3.0% amount is preferably contained more than.
Co:0.05% or less
Co is the element being contained in steel in the form of impurity.Co is the effective element for the toughness for improving steel, but
It is expensive element, it is therefore not necessary to energetically add.Therefore, Co content is set as 0.05% or less.
Sn:0.05% or less
Sn is contained in steel in the form of impurity, due to that hot-workability can be made to deteriorate, content is preferably low as far as possible.
Especially Sn content then will lead to the obvious deterioration of hot-workability if it exceeds 0.05%.Therefore, Sn content be set as 0.05% with
Under.
V:0.5% or less
V has the function of fixing and improving corrosion resistance, especially improve resistance to grain boundary corrosion C, therefore, can basis
It needs and contains.But content is if it exceeds 0.5%, even if then can also generate nitrogen in the case where making the above-mentioned content of N
Compound, corrosion resistance reduce instead, in turn, also result in the deterioration of hot-workability.Therefore, V content is set as 0.5% or less.For
Said effect is obtained, V content is preferably set to 0.01% or more.
Nb:0~1.0%
Nb has the function of fixing and improving corrosion resistance, especially improve resistance to grain boundary corrosion C, therefore, Ke Yigen
Contain according to needs.But content is if it exceeds 1.0%, even if then can also be generated in the case where making the above-mentioned content of N
Nitride, corrosion resistance reduce instead, in turn, also result in the deterioration of hot-workability.Therefore, Nb content is set as 1.0% or less.
Said effect in order to obtain, Nb content are preferably set to 0.02% or more.
Ti:0~0.5%
Ti has the function of fixing and improving corrosion resistance, especially improve resistance to grain boundary corrosion C in the same manner as Nb, because
This, can according to need and contain.But content is if it exceeds 0.5%, even if then in the case where making the above-mentioned content of N,
Also nitride can be generated, corrosion resistance reduces instead, in turn, also results in the deterioration of hot-workability.Therefore, Ti content is set as
0.5% or less.Said effect in order to obtain, Ti content are preferably set to 0.01% or more.
W:0~5.0%
W have the function of improve high concentration sulfuric acid condensation in the environment of corrosion resistance, therefore, can according to need and
Contain.But content if it exceeds 5.0%, then said effect is saturated, and only increases cost.Therefore, W content be set as 5.0% with
Under.Said effect in order to obtain, W content are preferably set to 0.1% or more.
Zr:0~1.0%
Zr has the function of therefore the corrosion resistance in the environment of the sulfuric acid condensation of raising high concentration can according to need
And contain.But content if it exceeds 1.0%, then said effect is saturated, and only increases cost.Therefore, Zr content is set as
1.0% or less.Said effect in order to obtain, Zr content are preferably set to 0.02% or more.
Al:0~0.5%
There is Al deoxidation therefore in the case where Si content is suppressed to extremely low, can also contain.But contain
Amount is if it exceeds 0.5%, even if being then the austenite stainless steel for making the above-mentioned content of N, hot-workability can also be reduced.Cause
This, Al content is set as 0.5% or less.The lower limit of Al content is not particularly limited, and can be the range of impurity.Wherein, by Si
Content be suppressed to it is extremely low in the case where, preferably energetically add and it made to contain 0.02% or more, make deoxidation fully into
Row.It should be noted that even if containing 0.05% or more Si, in order to give full play to deoxidation, it is also preferred that
Al content is set as 0.01% or more.
Ca:0~0.01%
Ca has the effect of that hot-workability is inhibited to reduce in conjunction with S, therefore, can according to need and contain.But
Content is if it exceeds 0.01%, then the cleannes of steel reduce, and can become the reason of generating defect when using the manufacture of heat.Cause
This, Ca content is set as 0.01% or less.Said effect in order to obtain, Ca content are preferably set to 0.0005% or more, more preferably set
It is 0.001% or more.
B:0~0.01%
B has the effect of therefore improving hot-workability can according to need and contain.But the excessive addition meeting of B
The precipitation for promoting the Cr-B compound in crystal boundary, leads to the deterioration of corrosion resistance.The especially content of B if it exceeds 0.01%,
The deterioration of apparent corrosion resistance can then be caused.Therefore, B content is set as 0.01% or less.Said effect in order to obtain, B content
It is preferably set to 0.0005% or more, is more preferably set as 0.001% or more.
REM:0~0.01%
REM (rare earth element) has the function of therefore improving hot-workability can according to need and contain.But contain
Amount is if it exceeds 0.01%, then the cleannes of steel reduce, and can become the reason of generating defect when using the manufacture of heat.Therefore,
REM content is set as 0.01% or less.Said effect in order to obtain, REM content are preferably set to 0.0005% or more.
Herein, REM refers to 17 kinds of elements of total of Sc, Y and lanthanide series, and the content of REM refers to always containing for these elements
Amount.
In the chemical composition of the base material of austenite stainless steel of the invention, surplus is Fe and impurity." impurity " herein
Refer to: when industrial manufacture steel by the raw materials such as ore, waste material, manufacturing process various factors and mixed ingredient, and for not
The ingredient allowed in the range of adverse effect is caused to the present invention.
3. about overlay film
As described above, overlay film is formed in at least part on surface possessed by base material.Moreover, in overlay film, relativity
Ground improves the total content of Cr, Ni, Cu and Mo relative to Fe, so as to so that acid resistance greatly improves.
In particular, it is desirable to which there are Cr concentration to become maximum maximum Cr depth in overlay film, and make maximum Cr depth
The chemical composition at place meets following formula (i).It, can be with it should be noted that the position of maximum Cr depth is not particularly limited
It is present in the most surface layer of overlay film.
(Cr+Ni+Cu+Mo)/Fe≥1.0···(i)
Wherein, each element symbol in above-mentioned formula indicates the content (at%) of each element at steel surface.
In addition, overlay film of the invention essentially becomes the opposite enrichments such as layer and the Ni of the surface layer side comprising the opposite enrichment of Cr
The structure of the layer of base material side.That is, that can have Cr concentration as the smallest minimum closer to base material side than above-mentioned maximum Cr depth
Cr depth.
Moreover, the chemical composition of maximum Cr depth preferably satisfies following formula (ii), the chemical composition of minimum Cr depth
Preferably satisfy following formula (iii).
Cr/(Ni+Cu+Mo)≥1.0···(ii)
Cr/(Ni+Cu+Mo)<1.0···(iii)
Wherein, each element symbol in above-mentioned formula indicates the content (at%) of each element.
For the thickness of overlay film, not especially setting limitation, such as the range of preferably 2~10nm.The thickness of overlay film is less than
When 2nm, there is the worry for being unable to fully obtain corrosion resistance against sulfuric acid.On the other hand, the thickness of overlay film is if it exceeds 10nm, then have change
The worry of the removing of the uneven and overlay film of overlay film composition must be easy to produce.
It should be noted that the chemical composition of overlay film is by utilizing X-ray photoelectron spectroscopy (XPS) in the present invention
Depth analysis measures.By above-mentioned depth analysis, with the shape of shared ratio (at%) in the ingredient in addition to O, C and N
The concentration curve of formula export each element.Then, it is determined that maximum Cr depth and minimum Cr depth, so as to find out each member of the depth
The concentration of element calculates above-mentioned formula (i)~(iii) by these values.
In addition, the thickness of overlay film is found out by the concentration curve of O (oxygen).Specifically, by 1/ as the maximum concentration of O
The position of 3 concentration is judged as the boundary portion of overlay film and base material, using the length until from overlay film surface to above-mentioned boundary portion as
The thickness of overlay film.The measurement of composition and thickness about overlay film, it is generally desirable to be carried out in many places, using its average value.
4. manufacturing method
It for the manufacturing condition of austenite stainless steel of the invention, is not particularly limited, for example, can be to above-mentioned
The steel blank of chemical composition implements heat treatment and acid processing under conditions of as shown below, to manufacture.
< heat treatment procedure >
For above-mentioned steel blank, firstly, implementing to keep within the temperature range of 1060~1140 DEG C at 60~600 seconds heat
Reason.The oxidation overlay film based on Fe is formed on steel blank surface as a result,.When heat treatment temperature is less than 1060 DEG C, Fe oxidation is covered
The formation of film becomes inadequate.On the other hand, heat treatment temperature is if it exceeds 1140 DEG C, then the grain coarsening of base material is big, Fe's
Diffusion tails off, and therefore, Fe oxidation overlay film becomes unevenly, and then becomes easy and generate overlay film removing.As a result, above-mentioned any feelings
Under condition, it is not likely to produce the enrichment of Cr, Ni, Cu and Mo.
< acid treatment process >
Then above-mentioned heat treatment implements acid processing to above-mentioned steel blank.In acid treatment process, melt Fe ingredient preferentially,
So as to so that Cr, Ni, Cu and Mo are enriched in steel surface.In order to melt Fe ingredient preferentially, preferably in 30~50 DEG C, 5~8 bodies
Product %HNO3, 5~8 volume %HF fluorine nitric acid in impregnate 1~5 hour.
Hereinafter, being more specifically illustrated according to embodiment to the present invention, but the present invention is not limited to these embodiments.
Embodiment
There is the steel (steel No.1~11) of chemical composition shown in table 1 with the VIM calciner melting of 3.5t, with common side
Method is hot-forged, hot extrusion and cold-drawn, the steel pipe base of production outer diameter 75mm, wall thickness 3mm.Later, for testing the He of No.1~17
19~28, implement heat treatment and acid processing under the conditions shown in Table 2, austenite stainless steel pipe is made.In addition, for test
No.18 grinds surface after implementing heat treatment and acid processing under the same conditions with test No.3.
[table 1]
[table 2]
Table 2
Then, pass through the chemical composition of overlay film that carries out being formed in each steel tube surface using XPS depth analysis and thickness
Measurement.Specifically, with the concentration of the form export each element of shared ratio (at%) in the ingredient in addition to O, C and N
Curve determines maximum Cr depth and minimum Cr depth, then finds out the concentration of each element of the depth.Then, by these values
Calculate above-mentioned formula (i)~(iii).It should be noted that in the present embodiment, in the example in addition to testing No.18, maximum Cr depth
It is present in the most surface layer of overlay film, in addition, in whole example, minimum Cr depth is present in than maximum Cr depth closer to base material side.
In addition, the thickness of overlay film is found out by the concentration curve of O (oxygen).Specifically, by 1/3 as the maximum concentration of O
The position of concentration be judged as the boundary portion of overlay film and base material, using the length until from overlay film surface to above-mentioned boundary portion as covering
The thickness of film.
In turn, in order to carry out the evaluation of corrosion resistance against sulfuric acid, the corrosion test in sulphuric acid environment is implemented.Corrosion test is logical
Crossing makes to carry out in the solution that each steel pipe is impregnated in 100 DEG C of temperature and sulfuric acid concentration is 70%.Then, measurement dipping 8 hours
Corrosion loss afterwards calculates the corrosion rate of per unit area.In the present invention, above-mentioned corrosion rate becomes 1.00g/ (m2·h)
When following, it is judged as that corrosion resistance against sulfuric acid is excellent.
These results are shown in table 3 together.
[table 3]
As shown in Table 3, the test No.18 of the unsuitable test No.1,2 and 14~17 of manufacturing condition and lapped face
In, do not generate the enrichment of Cr, Ni, Cu and Mo in overlay film, therefore, corrosion rate is high, becomes the result of corrosion resistance against sulfuric acid difference.
Similarly, the Cu content in base material is unable to get acidproof brought by Cu in the test No.28 except restriction of the invention
Property, and the enrichment of Cr, Ni, Cu and Mo in overlay film are insufficient, therefore, become the result of corrosion resistance against sulfuric acid difference.
In contrast, meet restriction of the invention and test No.3~13 that Cr, Ni, Cu and Mo are enriched in overlay film
In 19~27, corrosion rate becomes 1.00g/ (m2H) hereinafter, becoming the excellent result of corrosion resistance against sulfuric acid.
Industrial availability
According to the present invention it is possible to obtain that there is excellent acid proof austenite in the environment of the condensation of the sulfuric acid of high concentration
It is stainless steel.Therefore, austenite stainless steel of the invention can be used for heat exchange used in thermal power generation or industry boiler
In the equipment used under flue gas desulfurization equipment component used in device, flue and chimney and various industries or sulphuric acid environment
The various components such as the structural elements used.
Claims (3)
1. a kind of austenite stainless steel, has: base material and at least part for being formed in surface possessed by the base material
Overlay film,
The chemical composition of the base material is calculated as with quality %
C:0.05% or less,
Si:1.0% or less,
Mn:2.0% or less,
P:0.040% or less,
S:0.010% or less,
O:0.020% or less,
N: less than 0.050%,
Ni:12.0~27.0%,
Cr:15.0% more than and less than 20.0%,
Cu: greater than 3.5% and for 8.0% or less,
Mo: greater than 2.0% and for 5.0% or less,
Co:0.05% or less,
Sn:0.05% or less,
V:0~0.5%,
Nb:0~1.0%,
Ti:0~0.5%,
W:0~5.0%,
Zr:0~1.0%,
Al:0~0.5%,
Ca:0~0.01%,
B:0~0.01%,
REM:0~0.01%,
Surplus: Fe and impurity,
The chemical composition that the Cr concentration of the overlay film becomes maximum maximum Cr depth meets following formula (i),
(Cr+Ni+Cu+Mo)/Fe≥1.0···(i)
Wherein, each element symbol in the formula indicates the content of each element, unit at%.
2. austenite stainless steel according to claim 1, wherein the chemical composition of the base material is contained in terms of quality %
It is selected from
V:0.01~0.5%,
Nb:0.02~1.0%,
Ti:0.01~0.5%,
W:0.1~5.0%,
Zr:0.02~1.0%,
Al:0.01~0.5%,
Ca:0.0005~0.01%,
The and of B:0.0005~0.01%
REM:0.0005~0.01%
One or more of.
3. according to claim 1 or austenite stainless steel as claimed in claim 2, wherein the Cr concentration of the overlay film becomes
The smallest minimum Cr depth is present in than the maximum Cr depth closer to the base material side,
The chemical composition of the maximum Cr depth meets following formula (ii), and the chemical composition of the minimum Cr depth meets
Following formula (iii),
Cr/(Ni+Cu+Mo)≥1.0···(ii)
Cr/(Ni+Cu+Mo)<1.0···(iii)
Wherein, each element symbol in the formula indicates the content of each element, unit at%.
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US (1) | US20190177808A1 (en) |
EP (1) | EP3495526A4 (en) |
JP (1) | JP6724991B2 (en) |
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Citations (4)
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JPH1018004A (en) * | 1996-07-08 | 1998-01-20 | Sumitomo Metal Ind Ltd | Austenitic stainless steel excellent in sulfuric acid corrosion resistance |
EP0971045A1 (en) * | 1997-08-13 | 2000-01-12 | Sumitomo Metal Industries Limited | Austenitic stainless steel excellent in resistance to sulfuric acid corrosion and workability |
JP2003213379A (en) * | 2002-01-21 | 2003-07-30 | Sumitomo Metal Ind Ltd | Stainless steel having excellent corrosion resistance |
CN104736735A (en) * | 2012-10-30 | 2015-06-24 | 株式会社神户制钢所 | Austenitic stainless steel |
Family Cites Families (8)
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AU580758B2 (en) * | 1984-03-16 | 1989-02-02 | Inco Alloys International Inc. | High-strength alloy for industrial vessels |
JP2774709B2 (en) | 1991-05-22 | 1998-07-09 | 日本冶金工業 株式会社 | Sulfuric acid dew point corrosion resistant stainless steel with excellent hot workability |
JPH11158584A (en) * | 1997-11-27 | 1999-06-15 | Sumitomo Metal Ind Ltd | Austenitic stainless steel excellent in sulfuric acid corrosion resistance |
JPH11189848A (en) * | 1997-12-25 | 1999-07-13 | Sumitomo Metal Ind Ltd | Austenitic stainless steel excellent in sulfuric acid corrosion resistance |
JP3294282B2 (en) | 1998-08-10 | 2002-06-24 | 住友金属工業株式会社 | Austenitic stainless steel with excellent sulfuric acid corrosion resistance and workability |
JP2001107196A (en) * | 1999-10-07 | 2001-04-17 | Sumitomo Metal Ind Ltd | Austenitic steel welded joint excellent in weld cracking resistance and sulfuric acid corrosion resistance and the welding material |
JP3454216B2 (en) * | 1999-12-24 | 2003-10-06 | 住友金属工業株式会社 | Austenitic stainless steel |
JP2002121655A (en) * | 2000-10-18 | 2002-04-26 | Nippon Steel Corp | Stainless steel for crude phosphoric acid having excellent corrosion resistance |
-
2017
- 2017-08-02 EP EP17837044.1A patent/EP3495526A4/en not_active Withdrawn
- 2017-08-02 WO PCT/JP2017/028146 patent/WO2018025942A1/en unknown
- 2017-08-02 CA CA3032772A patent/CA3032772A1/en not_active Abandoned
- 2017-08-02 CN CN201780048557.4A patent/CN109563589B/en active Active
- 2017-08-02 JP JP2018531964A patent/JP6724991B2/en active Active
- 2017-08-02 KR KR1020197005733A patent/KR20190034286A/en not_active Application Discontinuation
- 2017-08-02 US US16/322,228 patent/US20190177808A1/en not_active Abandoned
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH1018004A (en) * | 1996-07-08 | 1998-01-20 | Sumitomo Metal Ind Ltd | Austenitic stainless steel excellent in sulfuric acid corrosion resistance |
EP0971045A1 (en) * | 1997-08-13 | 2000-01-12 | Sumitomo Metal Industries Limited | Austenitic stainless steel excellent in resistance to sulfuric acid corrosion and workability |
JP2003213379A (en) * | 2002-01-21 | 2003-07-30 | Sumitomo Metal Ind Ltd | Stainless steel having excellent corrosion resistance |
CN104736735A (en) * | 2012-10-30 | 2015-06-24 | 株式会社神户制钢所 | Austenitic stainless steel |
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EP3495526A1 (en) | 2019-06-12 |
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EP3495526A4 (en) | 2020-01-08 |
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JPWO2018025942A1 (en) | 2019-06-06 |
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