EP2097550A1 - Plate of a plate heat exchanger, a plate heat exchanger made of these plates and use of this plate heat exchanger - Google Patents

Plate of a plate heat exchanger, a plate heat exchanger made of these plates and use of this plate heat exchanger

Info

Publication number
EP2097550A1
EP2097550A1 EP07852257A EP07852257A EP2097550A1 EP 2097550 A1 EP2097550 A1 EP 2097550A1 EP 07852257 A EP07852257 A EP 07852257A EP 07852257 A EP07852257 A EP 07852257A EP 2097550 A1 EP2097550 A1 EP 2097550A1
Authority
EP
European Patent Office
Prior art keywords
alloy
plate
heat exchanger
weight
content
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP07852257A
Other languages
German (de)
French (fr)
Inventor
Ulf KIVISÄKK
Kenneth GÖRANSSON
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sandvik Intellectual Property AB
Original Assignee
Sandvik Intellectual Property AB
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sandvik Intellectual Property AB filed Critical Sandvik Intellectual Property AB
Publication of EP2097550A1 publication Critical patent/EP2097550A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D9/00—Heat-exchange apparatus having stationary plate-like or laminated conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall
    • F28D9/0031—Heat-exchange apparatus having stationary plate-like or laminated conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the conduits for one heat-exchange medium being formed by paired plates touching each other
    • F28D9/0043—Heat-exchange apparatus having stationary plate-like or laminated conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the conduits for one heat-exchange medium being formed by paired plates touching each other the plates having openings therein for circulation of at least one heat-exchange medium from one conduit to another
    • F28D9/005—Heat-exchange apparatus having stationary plate-like or laminated conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the conduits for one heat-exchange medium being formed by paired plates touching each other the plates having openings therein for circulation of at least one heat-exchange medium from one conduit to another the plates having openings therein for both heat-exchange media
    • 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
    • C22C38/001—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
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F19/00—Preventing the formation of deposits or corrosion, e.g. by using filters or scrapers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F21/00—Constructions of heat-exchange apparatus characterised by the selection of particular materials
    • F28F21/08—Constructions of heat-exchange apparatus characterised by the selection of particular materials of metal
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F21/00—Constructions of heat-exchange apparatus characterised by the selection of particular materials
    • F28F21/08—Constructions of heat-exchange apparatus characterised by the selection of particular materials of metal
    • F28F21/081—Heat exchange elements made from metals or metal alloys
    • F28F21/082—Heat exchange elements made from metals or metal alloys from steel or ferrous alloys

Definitions

  • the present invention relates to a plate of a plate heat exchanger, said plate comprising a material which constitutes a part of said plate with a surface made of this material positioned to be in direct contact with a chloride-containing cooling liquid, such as sea water, and a plate heat exchanger adapted to utilize a chloride-containing liquid, such as sea water, as cooling medium.
  • a chloride-containing cooling liquid such as sea water
  • a plate heat exchanger adapted to utilize a chloride-containing liquid, such as sea water, as cooling medium.
  • crevice corrosion phenomena constitutes the main problem in plate heat exchangers utilizing sea water as cooling liquid, since it may not be avoided that connecting interfaces between adjacent plates of the heat exchanger are located so that the sea water will reach the crevices or joint thus formed between adjacent plates, and they have also to be located where the cooling liquid has a comparatively high temperature, which is also critical (see below).
  • This problem is much smaller for tube heat exchangers, where such crevices or joints are less severe and may be located where the risk of crevice corrosion is much lower.
  • the problems of crevice corrosion in plate heat exchangers may be reduced by welding the plates to each other and connect them to each other by sealings, but the problem will by that not disappear.
  • Fig 1 schematically shows a plate heat exchanger PHE of this type having a number of plates P joined to each other in a stack for the flow of a cooling medium in the form of sea water SW in channels formed in every second gap between adjacent plates P 1 , P 2 and a medium to be cooled in adjacent channels in every second gap between such plates.
  • the crevice or joint sensitive to crevice corrosion is indicated at C.
  • Crevice corrosion destroying the material is temperature dependent, and when the material for a given cooling liquid, in this case sea water, has a temperature below a critical crevice temperature (CCT) substantially nothing will happen, but when the temperature of the material is raised above this temperature the corrosion of the material at said crevice will be very strong and in a short time destroy the connection, so that temperatures above said critical crevice temperature may not be accepted.
  • This crevice corrosion temperature should in a plate heat ex- changer using a chloride-containing cooling liquid, such as sea water, as cooling medium be at least 50 0 C, preferably at least 60°, for providing an acceptable cooling capacity of the heat exchanger. Sea water used in plate heat exchangers may be chlorinated for the purpose of killing micro organisms.
  • chloride-containing cooling liquid such as sea water
  • cooling medium for use at higher temperatures have for that sake so far almost exclusively been provided with plates made of titanium, which has a critical crevice temperature above 8O 0 C in sea water.
  • titanium is a very expensive material and it is also not easy available, so that it may sometimes be impossible to avoid waiting times for deliveries thereof in the order of a year or more irrespectively of the financial resources of the buyer.
  • the object of the present invention is to provide a plate of a plate heat exchanger being less costly and easier available than such plates of titanium while still having sufficiently high corrosion resistance for making it attractive to be used in a plate heat exchanger using a chloride-containing cooling liquid, such as sea water, as cooling medium.
  • a chloride-containing cooling liquid such as sea water
  • This object is according to the invention obtained by providing such a plate in which said plate material is a duplex stainless steel alloy containing in weight %: C max 0.06%, Si max 1.5%, Mn 0-3.0%, Cr 23.0-32.0%, Ni 4.9-10.0%, Mo 3.0-8.0%, N 0.15- 0.5%, B 0.-0.010%, S max 0.030%, Co 0-3.5%, W 0-3.0%, Cu 0- 2.0%, Ru 0-0.3%, Al 0-0.2%, Ca 0-0.010% balance Fe and normal occurring impurities, wherein the ferrite content is 35-70 volume-%.
  • said plate material is a duplex stainless steel alloy containing in weight %: C max 0.06%, Si max 1.5%, Mn 0-3.0%, Cr 23.0-32.0%, Ni 4.9-10.0%, Mo 3.0-8.0%, N 0.15- 0.5%, B 0.-0.010%, S max 0.030%, Co 0-3.5%, W 0-3.0%, Cu 0- 2.0%, Ru 0-0.
  • impurities from the manufacturing process are Al and Mg.
  • the content of impurities are preferably kept at such a level that the properties of the produced material is substantially unaffected thereof.
  • the inventors have realized that for materials used for plate heat exchanger using a chloride-containing cooling liquid as cooling medium the critical crevice temperature is the main issue and that the composition of the material may be determined with the aim to raise this temperature to a level acceptable for a plate heat exchanger without spending any particular efforts on other resistance properties of the material.
  • duplex stainless steel alloys with a composition within these ranges has a critical crevice temperature in sea water well ex- ceeding 50 0 C and in fact exceeding 60 0 C.
  • the PRE-value also containing a factor of 16%N, decides the crevice corrosion behaviour of the duplex stainless steel alloy, but it is the content of Cr and Mo, that is the determining factor for the critical crevice temperature of the material.
  • such a Eq1 -value above 40.5 has turned out to result in a critical crevice temperature of the steel alloy exceeding 60 0 C.
  • the critical crevice temperature may even be raised to the region of 80 0 C.
  • this material will constitute an attractive substitution to titanium in a plate heat exchanger.
  • the cost thereof will be only a small fraction of the cost for titanium, such as about 10-20% thereof, and it will be manufactured at any time avoiding the long waiting times that may occur for titanium.
  • said average Eq1 -value of the two phases of the alloy is higher than 41 , preferably higher than 42. It has been found that such high levels of the Eq1 -value are influencing the critical crevice temperature of the material in chloride-containing environment towards higher levels.
  • the Eq1 -value for both the ferrite and the austenite phase is higher than 35, preferably higher than 36, which in combination with an average Eq1 -value exceeding 40.5 is preferred for keeping the critical crevice temperature of the material at a required high level.
  • Mo and Cr will primarily choose the ferrite phase, so that the Eq1- vaule of the austenite phase may be close to 35, although said average Eq1 -value is above 40.5.
  • the content of Mo is 4.5-6.5 weight-%. It has turned out that for a given value of Eq 1 it is preferred to have a content of Mo being high, namely within this range, since the content of Mo has turned out to be the most important factor for the critical crevice tempera- ture of the material. For obtaining a given Eq 1 -value it is also preferred to increase the content of Mo rather than that of Cr, even though an increased content of Cr increases the workability of the material when producing the plate, but it increases at the same time the risk of formation of CrN. According to another embodiment of the invention the content of Mo is 4.5-5.5 weight- %.
  • the content of Cr is 23.0-30.0 weight-%. It has been found that a content of Cr within this range is suitable for obtaining a crevice corrosion behaviour of the alloy in a chloride-containing environment aimed at.
  • the content of Al is 0-0.1 weight-%.
  • the invention also relates to a plate heat exchanger adapted to utilize the chloride-containing liquid, such as sea water, as cooling medium, which is characterized in that it is made of plates according to the invention.
  • the advantageous features and advantages of such a plate heat exchanger appear clearly from the above discussion of the plate according to the invention.
  • the invention also relates to use of a plate heat exchanger according to the invention for cooling a medium to be cooled by a chloride-containing cooling liquid, such as sea water, and such a use in which the temperature of said cooling liquid is allowed to reach a temperature of at least 5O 0 C, preferably at least 60 0 C.
  • the medium to be cooled by the heat exchanger may be of any type, and it may be a gas or gas mixture, such as air, just as well as for example a liquid.
  • Fig 1 is a very simplified view showing the general structure of a plate heat exchanger with a portion thereof enlarged for explaining the problems to be solved by the present invention
  • Fig 2 is a graph of critical crevice temperatures versus PRENW- value for alloys according to the invention and reference alloys,
  • Fig 3 is a graph of critical crevice temperatures versus Eq1- value for alloys according to the invention and reference alloys,
  • Fig 4 is a simplified view illustrating how a material test has been carried out for alloys according to the invention and reference alloys, and
  • Fig 5 is a graph corresponding to the graph of Fig 3 based on another testing method.
  • a high critical crevice temperature in chloride-containing environment is obtained by the combination of elements in a duplex stainless steel alloy according to the invention.
  • the alloy according to the invention contains (in weight-%):
  • Carbon (C) has limited solubility in both ferrite and austenite.
  • the limited solubility implies a risk of precipitation of chromium carbides and the content should therefore not exceed 0.06 weight- %, preferably not exceed 0.02 weight-%.
  • Si Silicon (Si) is utilized as desoxidation agent in the steel production and it increases the flowability during production and welding.
  • too high contents of Si lead to precipitation of un- wanted intermetallic phase, and the content thereof is limited to 1.5 weight-%.
  • Manganese (Mn) is added in order to increase the N-solubility in the material.
  • Mn only has a limited influence on the N-solubility in the type of alloy in question. Instead there are found other elements with higher influence on the solubility.
  • Mn in combination with high contents of sulfur can give rise to formation of manganese sulfides, which act as initiation-points for pitting corrosion.
  • the content of Mn should therefore be limited to between 0-3.0 weight-%.
  • S Sulfur influences the corrosion resistance negatively by forming soluble sulfides. Furthermore, the hotworkability deteriorates, for what reason the content of sulfur is limited to max 0.030 weight-%, preferably max 0.010 weight-%.
  • Chromium (Cr) is an active element in order to improve the crevice corrosion resistance. Furthermore, a high content of chromium implies that one gets a very good N-solubility in the material. Thus, it is desirable to keep the Cr-content as high as possible in order to improve the corrosion resistance. For good crevice corrosion resistance the content of chromium should be at least 23 weight-%. However, high contents of Cr increase the risk for intermetallic precipitations and the formation of CrN, for what reason the content of chromium should not exceed 32 weight-%, preferably not 30 weight-%.
  • Nickel (Ni) is used as austenite stabilizing element and is added in suitable contents in order to obtain the desired content of fer- rite.
  • an addition of 4.9-10.0 weight-% nickel is required.
  • Molybdenum (Mo) is an active element which improves the crevice corrosion resistance in chloride environments.
  • the Mo-content in the present invention should lie in the range of 0-8.0 weight-%, preferably above 4.5 weight-%.
  • the content of Mo in combination with the content of Cr is the determining factors for obtaining a high critical crevice temperature of the alloy.
  • Tungsten increases mainly the resistance to pitting corro- sion. But the addition of too high contents of tungsten in combination with that the Cr-contents as well as Mo-contents are high, means that the risk for intermetallic precipitations increases.
  • the W-content in the present invention should lie in the range of 0- 3.0 weight-%.
  • Copper (Cu) may be added in order to improve the general corrosion resistance in acid environments such as sulfuric acid. At the same time Cu influences the structural stability. However, thigh contents of Cu imply that the solid solubility will be exceeded . Therefore the Cu-content should be limited to max 2.0 weight-%.
  • Co Co has properties that are intermediate between those of iron and nickel. Therefore, a minor replacement of these elements with Co, or the use of Co-containing raw materials (Ni scrap metal usually contains some Co, in some cases in quanti- ties greater than 10%) will not result in any major change in properties.
  • Co can be used to replace some Ni as an austenite- stabilizing element. Co is a relatively expensive element, so the addition of Co is limited to be within the range of 0-3.5 weight-%.
  • Al Aluminium (Al) and Calcium (Ca) are used as desoxidation agents at the steel production.
  • the content of Al should be limited to max 0.2 weight-%, preferably max 0.1 weight-%, in order to limit the forming of nitrides.
  • Ca has a favourable effect on the hotductility.
  • the Ca-content should be limited to max 0.010 weight-% in order to avoid an unwanted amount of slag.
  • Boron (B) may be added in order to increase the hotworkability of the material. At a too high content of Boron the weldability as well as the corrosion resistance could deteriorate. Therefore, the content of boron should be limited to max 0.010 weight-%.
  • N Nitrogen
  • N is a very active element, which increases the corrosion resistance, the structural stability as well as the strength of the material. Furthermore, a high N-content improves the recovering of the austenite after welding, which gives good properties within the welded joint. In order to obtain a good effect of N, at least 0.15 weight-% N should be added. At high contents of N the risk for precipitation of chromium nitrides increases, especially when simultaneously the chromium content is high. Furthermore, a high N-content implies that the risk for porosity in- creases because of the exceeded solubility of N in the smelt. For these reasons the N-content should be limited to max 0.50 weight-%.
  • the content of ferrite is important in order to obtain good me- chanical properties and corrosion properties as well as good weldability. From a corrosion point of view and a point of view of weldability a content of ferrite between 35-70% is desirable in order to obtain good properties.
  • Table 1 below shows the composition of alloys 1-25 according to the invention and reference alloys being not according to the invention as well as results of a testing, Testing 1.
  • the crevice corrosion resistance of 25 alloys according to the invention and 7 reference alloys was tested according to MTI-2.
  • the critical crevice temperature (CCT) was determined for all the 32 alloys for two different samples.
  • the average value of CCT for each alloy is indicated in Table 1.
  • Alloy 17 90 50,5 41 ,6 28,5 7,0 4,0 1 0,45
  • Fig 2 shows the relationship between PRENW and CCT and Fig 3 the relationship between Eq1 and CCT for Testing 1.
  • Fig 2 shows that the CCT is for all the alloys according to the invention above 60 0 C, whereas it is not above 50 0 C for any of the reference alloys in spite of high PRENW-values thereof. It is shown that the PRENW-value as long as it is in a region above 46 has no real influence upon the critical crevice temperature of the alloy.
  • Fig 3 shows that Eq1 should be higher than 40.5 for obtaining a CCT above 60 0 C.
  • the test was carried out for four different constant potentials: 0, +200, +400 and +700 mV SCE .
  • the start temperature was 2O 0 C, and the temperature increased during the experiment 1 0 C per minute.
  • the CCT for each sample has been defined as the temperature resulting in a corrosion current density of at least 0, 1 mA/cm 2 in 60 seconds.
  • CCT was determined for 4-6 samples per material and potential. Table 2 below shows the compositions and the results in the form of min values of CCT for all potentials over 0 mV versus SCE. The variations in CCT between different potentials were small. In most cases no crevice corrosion was noted at 0 mV.
  • Fig 5 shows the relation between Eq1 and CCT according to this modified ASTM G-150. Some of the alloys are present both in Testing 1 and Testing 2. The two different testing methods give somewhat different values of CCT, which is considered to be normal as a consequence of the differences of the methods. However, the relationship between the composition and the CCT- value is mainly the same in the two Testings.
  • This Testing 2 measures primarily the tendency to initiate crevice corrosion, while the Testing 1 primarily measures the tendency to propagation of crevice corrosion. This means that the CCT-val- ues will in the Testing 2 be somewhat higher than in the testing
  • This testing was an electrochemical testing with constant poten- tial and temperature in 24 hours.
  • the same type of crevice former and the same crevice pressure as in the Testing 2 were used.
  • New samples were used for each temperature-/potential-combi- nation.
  • the potential was: +200 mV versus SCE.
  • the CCT-value for each sample was defined as the temperature resulted in a corrosion current density of at least 0,01 mA/cm 2 in 60 s.
  • This testing is extremely tough, since the material is tested in an active state, whereas it in the preceding testings was passivated before testing, when the temperature was low.
  • the ability of the material to form a passivating oxide layer at certain temperature was measured in this Testing 3.
  • the passivating temperature is for most of the materials considerably lower than the CCT.
  • a comparison of the alloy 26 and 27 in the testing 2 shows that the alloy 26 was not passivated at 45 0 C, whereas the alloy 27 was passivated at 45 0 C as well as at 55 0 C. However, it may not be passivated at 65°. This means that if a corrosion attack has been started as a consequence of for example an over temperature, the alloy 27 will be able to be passivated already when the temperature falls down below 55 0 C, which remarkably reduces the risk for propagating attacks upon disturbances in the operation of the plate heat exchanger.
  • the alloy 27 having a higher content of Mo has a better ability to be passivated than the alloy 26 in spite of the fact that the alloy 26 has a higher Eq1-value.
  • the conclusion is that the Eq1-value well describes the initiation and the propagation of crevice corrosion, while passivation against crevice corrosion is mainly controlled by the material content of Mo.
  • An alloy according to another embodiment of the invention has the following approximate composition: C 0.017%, Si 0.2%, Mn 0.5%, P 0.005%, S 0.006%, Cr 26%, Ni 7%, Mo 5.2%, W ⁇ 0.01 %, Cu ⁇ 0.01 %, Co ⁇ 0.010%, Ti ⁇ 0.005%, Al 0.004%, B 24ppm, Ca 22ppm, N 0.41 %. Testing of critical crevice temperature (CCT) according to MTI-2 for two samples resulted in 65 0 C and 7O 0 C.
  • CCT critical crevice temperature

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Heat Treatment Of Sheet Steel (AREA)
  • Heat Treatment Of Steel (AREA)
  • Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)

Abstract

The present invention relates to a plate of a plate heat exchanger, said plate comprising a material which constitutes a part of said plate with a surface made of this material positioned to be in direct contact with a chloride-containing cooling liquid, such as sea water, in which the material is a duplex stainless steel alloy containing in weight-%: C max 0.06%, Si max 1.5%, Mn 0-3.0%, Cr 23.0-32.0%, Ni 4.9-10.0%, Mo 3.0-8.0%, N 0.15- 0.5%, B 0.-0.010%, S max 0.030%, Co 0-3.5%, W 0-3.0%, Cu 0- 2.0%, Ru 0-0.3%, Al 0-0.2%, Ca 0-0.010% balance Fe and normal occurring impurities, wherein the ferrite content is 35-70 volume-%.

Description

A plate
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a plate of a plate heat exchanger, said plate comprising a material which constitutes a part of said plate with a surface made of this material positioned to be in direct contact with a chloride-containing cooling liquid, such as sea water, and a plate heat exchanger adapted to utilize a chloride-containing liquid, such as sea water, as cooling medium.
BACKGROUND OF THE INVENTION AND PRIOR ART
In different plants, such as different types of machines, electric converter stations and the like, located close to the sea or on off-shore platforms it is necessary to use chloride-containing liquid in the form of sea water as cooling medium in heat ex- changers used for cooling purposes in these plants. The use of sea water in these heat exchangers puts high demands on the material used due to the tough high corrosive environment created by the sea water.
The crevice corrosion phenomena constitutes the main problem in plate heat exchangers utilizing sea water as cooling liquid, since it may not be avoided that connecting interfaces between adjacent plates of the heat exchanger are located so that the sea water will reach the crevices or joint thus formed between adjacent plates, and they have also to be located where the cooling liquid has a comparatively high temperature, which is also critical (see below). This problem is much smaller for tube heat exchangers, where such crevices or joints are less severe and may be located where the risk of crevice corrosion is much lower. The problems of crevice corrosion in plate heat exchangers may be reduced by welding the plates to each other and connect them to each other by sealings, but the problem will by that not disappear. Appended Fig 1 schematically shows a plate heat exchanger PHE of this type having a number of plates P joined to each other in a stack for the flow of a cooling medium in the form of sea water SW in channels formed in every second gap between adjacent plates P1 , P2 and a medium to be cooled in adjacent channels in every second gap between such plates. The crevice or joint sensitive to crevice corrosion is indicated at C.
Crevice corrosion destroying the material is temperature dependent, and when the material for a given cooling liquid, in this case sea water, has a temperature below a critical crevice temperature (CCT) substantially nothing will happen, but when the temperature of the material is raised above this temperature the corrosion of the material at said crevice will be very strong and in a short time destroy the connection, so that temperatures above said critical crevice temperature may not be accepted. This crevice corrosion temperature should in a plate heat ex- changer using a chloride-containing cooling liquid, such as sea water, as cooling medium be at least 500C, preferably at least 60°, for providing an acceptable cooling capacity of the heat exchanger. Sea water used in plate heat exchangers may be chlorinated for the purpose of killing micro organisms. If these microorganisms are not killed by e.g. chlorination, their presence will cause an increase in the corrosivity of the environment. At low temperatures, i.e. below approximately 4O0C, the chlorination in itself does not result in any increased corrosivity towards e.g. stainless steels. At temperatures above 4O0C, the increase in redox potential caused by the chlorination severely increases the corrosivity of the water with respect to pitting and crevice corrosion, thus limiting the choice of available construction materials for heat exchangers. Plate heat exchangers of the type defined in the introduction, i.e. utilizing chloride-containing cooling liquid, such as sea water, as cooling medium, for use at higher temperatures have for that sake so far almost exclusively been provided with plates made of titanium, which has a critical crevice temperature above 8O0C in sea water. However, titanium is a very expensive material and it is also not easy available, so that it may sometimes be impossible to avoid waiting times for deliveries thereof in the order of a year or more irrespectively of the financial resources of the buyer.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a plate of a plate heat exchanger being less costly and easier available than such plates of titanium while still having sufficiently high corrosion resistance for making it attractive to be used in a plate heat exchanger using a chloride-containing cooling liquid, such as sea water, as cooling medium.
This object is according to the invention obtained by providing such a plate in which said plate material is a duplex stainless steel alloy containing in weight %: C max 0.06%, Si max 1.5%, Mn 0-3.0%, Cr 23.0-32.0%, Ni 4.9-10.0%, Mo 3.0-8.0%, N 0.15- 0.5%, B 0.-0.010%, S max 0.030%, Co 0-3.5%, W 0-3.0%, Cu 0- 2.0%, Ru 0-0.3%, Al 0-0.2%, Ca 0-0.010% balance Fe and normal occurring impurities, wherein the ferrite content is 35-70 volume-%. The steel may also contain impurities resulting from the raw material used and/or the manufacturing process, and the average Eq 1 -value of the two phases of the alloy exceeds 40.5, whereby Eq1 = %Cr + 3.3%Mo, wherein % is weight-%. Examples of impurities from the manufacturing process are Al and Mg. However, the content of impurities are preferably kept at such a level that the properties of the produced material is substantially unaffected thereof. The inventors have realized that for materials used for plate heat exchanger using a chloride-containing cooling liquid as cooling medium the critical crevice temperature is the main issue and that the composition of the material may be determined with the aim to raise this temperature to a level acceptable for a plate heat exchanger without spending any particular efforts on other resistance properties of the material. It has been found that duplex stainless steel alloys with a composition within these ranges has a critical crevice temperature in sea water well ex- ceeding 500C and in fact exceeding 600C. Thus, it has been found that not the PRE-value, also containing a factor of 16%N, decides the crevice corrosion behaviour of the duplex stainless steel alloy, but it is the content of Cr and Mo, that is the determining factor for the critical crevice temperature of the material. Furthermore, such a Eq1 -value above 40.5 has turned out to result in a critical crevice temperature of the steel alloy exceeding 600C. For some compositions within these ranges the critical crevice temperature may even be raised to the region of 800C. This means that this material will constitute an attractive substitution to titanium in a plate heat exchanger. The cost thereof will be only a small fraction of the cost for titanium, such as about 10-20% thereof, and it will be manufactured at any time avoiding the long waiting times that may occur for titanium.
According to another embodiment of the invention said average Eq1 -value of the two phases of the alloy is higher than 41 , preferably higher than 42. It has been found that such high levels of the Eq1 -value are influencing the critical crevice temperature of the material in chloride-containing environment towards higher levels.
According to another embodiment of the invention the Eq1 -value for both the ferrite and the austenite phase is higher than 35, preferably higher than 36, which in combination with an average Eq1 -value exceeding 40.5 is preferred for keeping the critical crevice temperature of the material at a required high level. Mo and Cr will primarily choose the ferrite phase, so that the Eq1- vaule of the austenite phase may be close to 35, although said average Eq1 -value is above 40.5.
According to another embodiment of the invention, the content of Mo is 4.5-6.5 weight-%. It has turned out that for a given value of Eq 1 it is preferred to have a content of Mo being high, namely within this range, since the content of Mo has turned out to be the most important factor for the critical crevice tempera- ture of the material. For obtaining a given Eq 1 -value it is also preferred to increase the content of Mo rather than that of Cr, even though an increased content of Cr increases the workability of the material when producing the plate, but it increases at the same time the risk of formation of CrN. According to another embodiment of the invention the content of Mo is 4.5-5.5 weight- %.
According to another embodiment of the invention the content of Cr is 23.0-30.0 weight-%. It has been found that a content of Cr within this range is suitable for obtaining a crevice corrosion behaviour of the alloy in a chloride-containing environment aimed at.
According to another embodiment of the invention the average PRE-value of the two phases of the alloy is higher than 46, preferably higher than 47, whereby PRE = %Cr + 3.3%Mo + 16%N, wherein % is weight-%. It has turned out to be advantageous to have such a high PRE-value of the material, although the Eq1 - value is more important for the crevice corrosion resistance of the material.
According to another embodiment of the invention the content of Al is 0-0.1 weight-%.
The invention also relates to a plate heat exchanger adapted to utilize the chloride-containing liquid, such as sea water, as cooling medium, which is characterized in that it is made of plates according to the invention. The advantageous features and advantages of such a plate heat exchanger appear clearly from the above discussion of the plate according to the invention. The invention also relates to use of a plate heat exchanger according to the invention for cooling a medium to be cooled by a chloride-containing cooling liquid, such as sea water, and such a use in which the temperature of said cooling liquid is allowed to reach a temperature of at least 5O0C, preferably at least 600C. It is pointed out that the medium to be cooled by the heat exchanger may be of any type, and it may be a gas or gas mixture, such as air, just as well as for example a liquid.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig 1 is a very simplified view showing the general structure of a plate heat exchanger with a portion thereof enlarged for explaining the problems to be solved by the present invention,
Fig 2 is a graph of critical crevice temperatures versus PRENW- value for alloys according to the invention and reference alloys,
Fig 3 is a graph of critical crevice temperatures versus Eq1- value for alloys according to the invention and reference alloys,
Fig 4 is a simplified view illustrating how a material test has been carried out for alloys according to the invention and reference alloys, and
Fig 5 is a graph corresponding to the graph of Fig 3 based on another testing method.
DETAILED DESCRIPTION OF THE INVENTION
A high critical crevice temperature in chloride-containing environment is obtained by the combination of elements in a duplex stainless steel alloy according to the invention. The alloy according to the invention contains (in weight-%):
C max 0.06%
Si max 1.5%
Mn 0-3.0%
Cr 23.0-32.0%
Ni 4.9-10.0%
Mo 3.0-8.0%
N 0.15-0.5%
B 0.-0.010%
S max 0.030%
Co 0-3.5%
W 0-3.0%
Cu 0-2.0%
Ru 0-0.3%
Al 0-0.2%
Ca 0-0.010% balance Fe and normal occurring impurities, wherein the ferrite content is 35-70 volume-%.
Carbon (C) has limited solubility in both ferrite and austenite. The limited solubility implies a risk of precipitation of chromium carbides and the content should therefore not exceed 0.06 weight- %, preferably not exceed 0.02 weight-%.
Silicon (Si) is utilized as desoxidation agent in the steel production and it increases the flowability during production and welding. However, too high contents of Si lead to precipitation of un- wanted intermetallic phase, and the content thereof is limited to 1.5 weight-%.
Manganese (Mn) is added in order to increase the N-solubility in the material. However, it has shown that Mn only has a limited influence on the N-solubility in the type of alloy in question. Instead there are found other elements with higher influence on the solubility. Besides, Mn in combination with high contents of sulfur can give rise to formation of manganese sulfides, which act as initiation-points for pitting corrosion. The content of Mn should therefore be limited to between 0-3.0 weight-%.
Sulfur (S) influences the corrosion resistance negatively by forming soluble sulfides. Furthermore, the hotworkability deteriorates, for what reason the content of sulfur is limited to max 0.030 weight-%, preferably max 0.010 weight-%.
Chromium (Cr) is an active element in order to improve the crevice corrosion resistance. Furthermore, a high content of chromium implies that one gets a very good N-solubility in the material. Thus, it is desirable to keep the Cr-content as high as possible in order to improve the corrosion resistance. For good crevice corrosion resistance the content of chromium should be at least 23 weight-%. However, high contents of Cr increase the risk for intermetallic precipitations and the formation of CrN, for what reason the content of chromium should not exceed 32 weight-%, preferably not 30 weight-%.
Nickel (Ni) is used as austenite stabilizing element and is added in suitable contents in order to obtain the desired content of fer- rite. In order to obtain the desired relationship between the aus- tenitic and the ferritic phase with between 40-65 volume-% fer- rite, an addition of 4.9-10.0 weight-% nickel is required.
Molybdenum (Mo) is an active element which improves the crevice corrosion resistance in chloride environments. The Mo-content in the present invention should lie in the range of 0-8.0 weight-%, preferably above 4.5 weight-%. The content of Mo in combination with the content of Cr is the determining factors for obtaining a high critical crevice temperature of the alloy.
Tungsten (W) increases mainly the resistance to pitting corro- sion. But the addition of too high contents of tungsten in combination with that the Cr-contents as well as Mo-contents are high, means that the risk for intermetallic precipitations increases. The W-content in the present invention should lie in the range of 0- 3.0 weight-%.
Copper (Cu) may be added in order to improve the general corrosion resistance in acid environments such as sulfuric acid. At the same time Cu influences the structural stability. However, thigh contents of Cu imply that the solid solubility will be exceeded . Therefore the Cu-content should be limited to max 2.0 weight-%.
Cobalt (Co) has properties that are intermediate between those of iron and nickel. Therefore, a minor replacement of these elements with Co, or the use of Co-containing raw materials (Ni scrap metal usually contains some Co, in some cases in quanti- ties greater than 10%) will not result in any major change in properties. Co can be used to replace some Ni as an austenite- stabilizing element. Co is a relatively expensive element, so the addition of Co is limited to be within the range of 0-3.5 weight-%.
Aluminium (Al) and Calcium (Ca) are used as desoxidation agents at the steel production. The content of Al should be limited to max 0.2 weight-%, preferably max 0.1 weight-%, in order to limit the forming of nitrides. Ca has a favourable effect on the hotductility. However, the Ca-content should be limited to max 0.010 weight-% in order to avoid an unwanted amount of slag.
Boron (B) may be added in order to increase the hotworkability of the material. At a too high content of Boron the weldability as well as the corrosion resistance could deteriorate. Therefore, the content of boron should be limited to max 0.010 weight-%.
Nitrogen (N) is a very active element, which increases the corrosion resistance, the structural stability as well as the strength of the material. Furthermore, a high N-content improves the recovering of the austenite after welding, which gives good properties within the welded joint. In order to obtain a good effect of N, at least 0.15 weight-% N should be added. At high contents of N the risk for precipitation of chromium nitrides increases, especially when simultaneously the chromium content is high. Furthermore, a high N-content implies that the risk for porosity in- creases because of the exceeded solubility of N in the smelt. For these reasons the N-content should be limited to max 0.50 weight-%.
The content of ferrite is important in order to obtain good me- chanical properties and corrosion properties as well as good weldability. From a corrosion point of view and a point of view of weldability a content of ferrite between 35-70% is desirable in order to obtain good properties.
DESCRIPTION OF PREFERRED EMBODIMENTS
Table 1 below shows the composition of alloys 1-25 according to the invention and reference alloys being not according to the invention as well as results of a testing, Testing 1.
Testing 1
The crevice corrosion resistance of 25 alloys according to the invention and 7 reference alloys was tested according to MTI-2. The critical crevice temperature (CCT) was determined for all the 32 alloys for two different samples. The average value of CCT for each alloy is indicated in Table 1. Furthermore, the conventional expression for "pitting resistance equivalent" in the alloys is given in Table 1 (PRENW = %Cr + 3.3%Mo + 0.5%W) + 16%N, as well as the Eq1-value defined as Eq1 = %Cr + 3.3%Mo.
All the alloys were produced by melting, hot working and annealing followed by water quenching. 1
Table 1
CdV0C PRENW %Cr+ Si Mn Cu Co
3,3%Mo
Alloy 1 77,5 49,9 42,8 0,015 0,16 0,86 0,01 1.5 Alloy 2 65 49,0 42,7 0,017 0,18 1,06 0,01 1 ,5 Alloy 3 77,5 50,5 42,8 0,017 0,23 0,99 0,01 1 ,5 Alloy 4 82,5 50,8 42,8 0,019 0,23 1,12 0,03 0,6 Alloy 5 65 48,2 42,1 0,017 0,22 1,01 0,03 1 ,5 Alloy 6 70 48,2 42,3 0,018 0,2 1 ,1 0,03 0,5 Alloy 7 75 48,4 42,5 0,012 0,15 1,04 0,01 1 ,4 Alloy 8 80 50,4 42,7 0,016 0,2 1,07 0,03 1 ,0 Alloy 9 65 46,9 41 ,9 0,017 0,21 1,02 0,04 3 Alloy 10 67,5 50,3 43,0 0,02 0,25 1 ,1 0,14 1 ,5 Alloy 11 85 50,2 43,0 0,02 0,23 1,1 0,14 0,6 Alloy 12 70 48,5 41 ,4 0,018 0,25 1 ,1 0,13 1 ,5 Alloy 13 77,5 48,6 41,7 0,019 0,23 1 0,13 0,6 Alloy 14 82,5 47,9 40,5 0,017 0,21 2,7 0,12 1 Alloy 15 75 50,0 41 ,9 0,018 0,2 1 0,13 1 Alloy 16 77,5 49,3 43,3 0,02 0,25 1,1 0,14 <0,1 Alloy 17 90 50,5 41,6 0,019 0,25 1 0,18 1 Alloy 18 85 49,9 41,4 0,02 0,28 1,1 1 1 Alloy 19 80 49,2 42,7 0,021 0,24 1 0,14 1 ,5 Alloy 20 72,5 49,3 43,3 0,019 0,23 1,1 1 ,5 <0,1 Alloy 21 65 47,8 41,4 0,019 0,22 0,5 0,02 <0,1 Alloy 22 62,5 49,8 43,1 0,019 0,62 0,47 0,02 <0,1 Alloy 23 67,5 49,8 43,2 0,017 0,21 0,49 <0,01 <0,1 Alloy 24 62,5 49,3 43,2 0,021 0,61 0,48 0,01 1.0 Alloy 25 62,5 48,6 42,0 0,019 0,24 0,51 <0,01 1.0 Ref 1 50 50,1 38,3 0,034 0,42 0,86 1 ,0 1 ,0 Ref 2 35 47,4 34,2 0,055 0,89 0,93 2,0 <0,1 Ref 3 45 50,3 38,0 0,035 0,48 0,93 1 ,0 1.0 Ref 4 40 49,4 36,5 0,007 0,12 0,9 2,0 0,1 Ref 5 30 49,9 34,5 0,006 0,12 0,95 2,0 2,0 Ref 6 35 51,9 36,8 0,06 0,11 1,09 <0,01 <0,1 Ref 7 40 47,3 40,3 0,008 0,14 1 ,07 <0,01 <0,1 CCT/°C PRENW %Cr+ Cr Ni Mo W N
3,3%Mo
Alloy 1 77,5 49,9 42,8 28,9 6,6 4,2 0,01 0,44
Alloy 2 65 49,0 42,7 28,8 6,5 4,2 0,01 0,39
Alloy 3 77,5 50,5 42,8 28,8 7,0 4,2 1 0,38
Alloy 4 82,5 50,8 42,8 28,8 7,6 4,2 0,99 0,4
Alloy 5 65 48,2 42,1 28,1 6,5 4,2 0,01 0,38
Alloy 6 70 48,2 42,3 28,4 6,9 4,2 <0,01 0,37
Alloy 7 75 48,4 42,5 28,8 7,0 4,2 <0,01 0,37
Alloy 8 80 50,4 42,7 26,9 6,5 4,8 1 ,01 0,38
Alloy 9 65 46,9 41 ,9 28,6 6,5 4,0 0,01 0,31
Alloy 10 67,5 50,3 43,0 29,0 6,5 4,2 <0,01 0,46
Alloy 11 85 50,2 43,0 29,0 6,8 4,2 <0,01 0,45
Alloy 12 70 48,5 41 ,4 27,5 5,9 4,2 <0,01 0,44
Alloy 13 77,5 48,6 41,7 27,8 6,1 4,2 <0,01 0,43
Alloy 14 82,5 47,9 40,5 27,6 6,9 3,9 1 0,36
Alloy 15 75 50,0 41,9 28,7 6,6 4,0 1 0,4
Alloy 16 77,5 49,3 43,3 30,0 7,1 4,0 <0,01 0,38
Alloy 17 90 50,5 41 ,6 28,5 7,0 4,0 1 0,45
Alloy 18 85 49,9 41,4 28,2 6,6 4,0 1 0,43
Alloy 19 80 49,2 42,7 28,8 7,0 4,2 <0,01 0,41
Alloy 20 72,5 49,3 43,3 29,3 6,5 4,2 <0,01 0,38
Alloy 21 65 47,8 41 ,4 25,8 7,1 4,7 <0,01 0,4
Alloy 22 62,5 49,8 43,1 26,1 7,0 5,2 <0,01 0,42
Alloy 23 67,5 49,8 43,2 26,1 7,1 5,2 <0,01 0,41
Alloy 24 62,5 49,3 43,2 26,3 7,0 5,1 <0,01 0,38
Alloy 25 62,5 48,6 42,0 26,2 6,5 4,8 <0,01 0,41
Reference 1 50 50,1 38,3 30,8 7,5 2,2 2,7 0,46
Reference 2 35 47,4 34,2 29,2 7,6 1 ,5 3,72 0,44
Reference 3 45 50,3 38,0 30,6 7,7 2,2 2,88 0,47
Reference 4 40 49,4 36,5 31 ,6 9,4 1 ,5 3,86 0,41
Reference 5 30 49,9 34,5 29,3 6,2 1 ,6 3,94 0,56
Reference 6 35 51,9 36,8 31 ,9 6,3 1 ,5 3,85 0,55
Reference 7 40 47,3 40,3 28,7 7,4 3,5 <0,01 0,44 Appended Fig 2 shows the relationship between PRENW and CCT and Fig 3 the relationship between Eq1 and CCT for Testing 1. Fig 2 shows that the CCT is for all the alloys according to the invention above 600C, whereas it is not above 500C for any of the reference alloys in spite of high PRENW-values thereof. It is shown that the PRENW-value as long as it is in a region above 46 has no real influence upon the critical crevice temperature of the alloy. Fig 3 shows that Eq1 should be higher than 40.5 for obtaining a CCT above 600C. It should be noted that the experimental spread in determining the CCT-value is great (about +100C), and that it is not only the total value of Eq1 that is determining but also how it is distributed between the two phases of the material (ferrite and austenite).
Testing 2
An electrochemical test according to a modified version of ASTM G-150, modified in the way that the samples examined were pro- vided with a crevice former in PVDF mounted in approximately the same way as in MTI-2 in Testing 1. A constant tightening moment of 3 Nm was used for mounting crevice formers. A constant crevice pressure was maintained by means of four spring washers 1 mounted according to Fig 4, in which 2 shows the sample and 3 and 4 the crevice formers.
The test was carried out for four different constant potentials: 0, +200, +400 and +700 mVSCE. The start temperature was 2O0C, and the temperature increased during the experiment 10C per minute. The CCT for each sample has been defined as the temperature resulting in a corrosion current density of at least 0, 1 mA/cm2 in 60 seconds.
CCT was determined for 4-6 samples per material and potential. Table 2 below shows the compositions and the results in the form of min values of CCT for all potentials over 0 mV versus SCE. The variations in CCT between different potentials were small. In most cases no crevice corrosion was noted at 0 mV.
Table 2 Alloy Cr Ni Mo W N PRENW EqI CCT Alloy 26 31 ,71 7 3,45 <0,01 0,50 51,095 43,1 82, 7 Alloy 27 26,62 7 4,73 <0,01 0,38 48,309 42,2 86, 7 Alloy 28 26,02 9 5,06 <0,01 0,4 49,118 42,7 87,1
31,9 Reference 6 6 1,47 3,85 0,55 51,9035 36,8 67,1
28,71 Reference 7 7 3,51 <0,01 0,44 47,333 40,3 76,3 Reference 8 29,88 7 1,5 1,98 0,44 45,137 34,8 58,4 Reference 9 29,36 8 2,51 2,1 0,44 48,148 37,6 73,1 Reference 10 25 7 4,00 <0,01 0,28 42,68 38.2 70.6 Reference 1 1 29,21 7 2,32 <0,01 0.37 42,786 36,9 72,3
Fig 5 shows the relation between Eq1 and CCT according to this modified ASTM G-150. Some of the alloys are present both in Testing 1 and Testing 2. The two different testing methods give somewhat different values of CCT, which is considered to be normal as a consequence of the differences of the methods. However, the relationship between the composition and the CCT- value is mainly the same in the two Testings.
This Testing 2 measures primarily the tendency to initiate crevice corrosion, while the Testing 1 primarily measures the tendency to propagation of crevice corrosion. This means that the CCT-val- ues will in the Testing 2 be somewhat higher than in the testing
1. This is the reason while the lowest CCT-value allowed for use in a plate heat exchanger according to the Testing 2 should be set to 8O0C.
Testing 3
This testing was an electrochemical testing with constant poten- tial and temperature in 24 hours. The same type of crevice former and the same crevice pressure as in the Testing 2 were used. New samples were used for each temperature-/potential-combi- nation. The potential was: +200 mV versus SCE. The CCT-value for each sample was defined as the temperature resulted in a corrosion current density of at least 0,01 mA/cm2 in 60 s. This testing is extremely tough, since the material is tested in an active state, whereas it in the preceding testings was passivated before testing, when the temperature was low. The ability of the material to form a passivating oxide layer at certain temperature was measured in this Testing 3. The passivating temperature is for most of the materials considerably lower than the CCT.
A comparison of the alloy 26 and 27 in the testing 2 shows that the alloy 26 was not passivated at 450C, whereas the alloy 27 was passivated at 450C as well as at 550C. However, it may not be passivated at 65°. This means that if a corrosion attack has been started as a consequence of for example an over temperature, the alloy 27 will be able to be passivated already when the temperature falls down below 550C, which remarkably reduces the risk for propagating attacks upon disturbances in the operation of the plate heat exchanger.
Thus, the alloy 27 having a higher content of Mo has a better ability to be passivated than the alloy 26 in spite of the fact that the alloy 26 has a higher Eq1-value. The conclusion is that the Eq1-value well describes the initiation and the propagation of crevice corrosion, while passivation against crevice corrosion is mainly controlled by the material content of Mo.
An alloy according to another embodiment of the invention has the following approximate composition: C 0.017%, Si 0.2%, Mn 0.5%, P 0.005%, S 0.006%, Cr 26%, Ni 7%, Mo 5.2%, W <0.01 %, Cu <0.01 %, Co <0.010%, Ti <0.005%, Al 0.004%, B 24ppm, Ca 22ppm, N 0.41 %. Testing of critical crevice temperature (CCT) according to MTI-2 for two samples resulted in 650C and 7O0C.

Claims

Claims
Plate of a plate heat exchanger, said plate comprising a material which constitutes a part of said plate with a surface made of this material positioned to be in direct contact with a chloride-containing cooling liquid, such as sea water, characterized in that said plate material is a duplex stainless steel alloy containing in weight-%:
C max 0.06%
Si max 1 .5%
Mn 0-3.0%
Cr 23.0-32.0%
Ni 4.9-10.0%
Mo 3.0-8.0%
N 0.15-0.5%
B 0.-0.010%
S max 0.030%
Co 0-3.5%
W 0-3.0%
Cu 0-2.0%
Ru 0-0.3%
Al 0-0.2%
Ca 0-0.010% balance Fe and normal occurring impurities, wherein the ferrite content is 35-70 volume-%, and that the average
Eq1 -value of the two phases of the alloy exceeds 40.5, whereby Eq 1 = %Cr + 3.3%Mo, wherein % is weight-%.
2. A plate according to claim 1 , characterized in that said average Eq1 -value of the two phases of the alloy is higher than 41 , preferably higher than 42.
3. A plate according to claim 1 or 2, characterized in that the Eq1 -value for both the ferrite and the austenite phase is higher than 35, preferably higher than 36.
4. A plate according to any of the preceding claims, characterized in that the content of Mo is 4.5-6.5 weight-%.
5. A plate according to claim 4, characterized in that the con- tent of Mo is 4.5-5.5 weight-%.
6. A plate according to any of the preceding claims, characterized in that the content of Cr is 23.0-30.0 weight-%.
7. A plate according to any of the preceding claims, characterized in that the average PRE-value of the two phases of the alloy is higher than 46, preferably higher than 47, whereby PRE = %Cr + 3.3%Mo + 16%N, wherein % is weight-%.
8. A plate according to any of the preceding claims, characterized in that the content of Al is 0-0.1 weight-%.
9. Plate heat exchanger adapted to utilise a chloride-contain- ing liquid, such as sea water, as cooling medium, characterized in that it is made of plates according to any of claims 1-8.
10. Plate heat exchanger according to claim 9, characterized in that said plates are joined to each other in a stack for forming channels between adjacent plates (P) and that said channels formed in every second gap between adjacent plates are configured to have a chloride-containing cooling liquid (SW) flowing therein and said channels formed in every second gap between adjacent plates are configured to have a medium to be cooled flowing therein.
1 1. Use of a plate heat exchanger according to claim 9 or 10 for cooling a medium to be cooled by a chloride-containing cooling liquid, such as sea water.
12. Use according to claim 1 1 , in which the temperature of said cooling liquid is allowed to reach a temperature of at least 5O0C1 preferably at least 6O0C.
EP07852257A 2006-12-14 2007-12-13 Plate of a plate heat exchanger, a plate heat exchanger made of these plates and use of this plate heat exchanger Withdrawn EP2097550A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE0602697A SE530847C2 (en) 2006-12-14 2006-12-14 Plate for plate heat exchangers, plate heat exchangers made up of such plates and use of this plate heat exchanger
PCT/SE2007/050986 WO2008073047A1 (en) 2006-12-14 2007-12-13 Plate of a plate heat exchanger, a plate heat exchanger made of these plates and use of this plate heat exchanger

Publications (1)

Publication Number Publication Date
EP2097550A1 true EP2097550A1 (en) 2009-09-09

Family

ID=39511973

Family Applications (1)

Application Number Title Priority Date Filing Date
EP07852257A Withdrawn EP2097550A1 (en) 2006-12-14 2007-12-13 Plate of a plate heat exchanger, a plate heat exchanger made of these plates and use of this plate heat exchanger

Country Status (7)

Country Link
US (1) US20100084121A1 (en)
EP (1) EP2097550A1 (en)
JP (1) JP2010513708A (en)
CN (1) CN101558181A (en)
BR (1) BRPI0720285A2 (en)
SE (1) SE530847C2 (en)
WO (1) WO2008073047A1 (en)

Families Citing this family (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE533067C2 (en) 2008-10-03 2010-06-22 Alfa Laval Corp Ab plate heat exchangers
CN102041455B (en) * 2009-10-23 2013-03-27 宝山钢铁股份有限公司 Stainless steel for heat exchanger welded pipe and manufacturing method thereof
JP2012107804A (en) * 2010-11-17 2012-06-07 Mitsubishi Heavy Ind Ltd Laminated heat exchanger, and heat medium heating apparatus and in-vehicle air-conditioning apparatus using the laminated heat exchanger
WO2012121232A1 (en) * 2011-03-10 2012-09-13 住友金属工業株式会社 Duplex stainless steel sheet
WO2017013181A1 (en) * 2015-07-20 2017-01-26 Sandvik Intellectual Property Ab New use of a duplex stainless steel
KR20240042679A (en) 2015-07-20 2024-04-02 산드빅 인터렉츄얼 프로퍼티 에이비 Duplex stainless steel and formed object thereof
JP7277484B2 (en) * 2018-06-15 2023-05-19 エービー サンドビック マテリアルズ テクノロジー Duplex stainless steel strip and method for manufacturing same
CN110565012B (en) * 2019-07-19 2021-08-10 浙江青山钢铁有限公司 Continuous casting manufacturing method of ultra-high chromium ferrite stainless steel
DE102020203339A1 (en) * 2020-03-16 2021-09-16 Mahle International Gmbh Heat exchanger
CN115948698B (en) * 2022-12-30 2024-12-03 广东省科学院新材料研究所 A duplex stainless steel material and its application in preparing seawater heat exchanger

Family Cites Families (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DD156057A3 (en) * 1980-10-14 1982-07-28 Dieter Boehm plate heat exchanger
US4915752A (en) * 1988-09-13 1990-04-10 Carondelet Foundry Company Corrosion resistant alloy
US4942922A (en) * 1988-10-18 1990-07-24 Crucible Materials Corporation Welded corrosion-resistant ferritic stainless steel tubing having high resistance to hydrogen embrittlement and a cathodically protected heat exchanger containing the same
JP3227734B2 (en) * 1991-09-30 2001-11-12 住友金属工業株式会社 High corrosion resistant duplex stainless steel and its manufacturing method
JP3166798B2 (en) * 1992-10-06 2001-05-14 住友金属工業株式会社 Duplex stainless steel with excellent corrosion resistance and phase stability
JP3446294B2 (en) * 1994-04-05 2003-09-16 住友金属工業株式会社 Duplex stainless steel
ATE195559T1 (en) * 1994-05-21 2000-09-15 Park Yong S DUPLEX STAINLESS STEEL WITH GOOD CORROSION RESISTANCE
JPH1060598A (en) * 1996-08-19 1998-03-03 Nkk Corp Precipitation strengthened duplex stainless steel for seawater resistance
SE514044C2 (en) * 1998-10-23 2000-12-18 Sandvik Ab Steel for seawater applications
JP4703831B2 (en) * 2000-09-29 2011-06-15 株式会社日阪製作所 Plate heat exchanger
JP4849731B2 (en) * 2001-04-25 2012-01-11 日新製鋼株式会社 Mo-containing high Cr high Ni austenitic stainless steel sheet excellent in ductility and manufacturing method
SE524951C2 (en) * 2001-09-02 2004-10-26 Sandvik Ab Use of a duplex stainless steel alloy
BRPI0412092A (en) * 2003-06-30 2006-09-05 Sumitomo Metal Ind duplex stainless steel

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO2008073047A1 *

Also Published As

Publication number Publication date
CN101558181A (en) 2009-10-14
WO2008073047A1 (en) 2008-06-19
BRPI0720285A2 (en) 2014-02-25
SE0602697L (en) 2008-06-15
JP2010513708A (en) 2010-04-30
SE530847C2 (en) 2008-09-30
US20100084121A1 (en) 2010-04-08

Similar Documents

Publication Publication Date Title
WO2008073047A1 (en) Plate of a plate heat exchanger, a plate heat exchanger made of these plates and use of this plate heat exchanger
EP0708845B1 (en) Ferritic-austenitic stainless steel and use of the steel
EP2246454B1 (en) Carburization-resistant metal material
US6220306B1 (en) Low carbon martensite stainless steel plate
EP2725112B1 (en) Carburization-resistant metal material and uses of the carburization-resistant metal material
US6749697B2 (en) Duplex stainless steel
KR20090078813A (en) Duplex Stainless Steel Alloys and Their Uses
US20090081069A1 (en) Austenitic stainless steel
CN101421429A (en) Stainless steel weld overlay with enhanced wear resistance
US5945064A (en) Welding material for low chromium (Cr) ferritic steel having high toughness
WO2003020995A1 (en) Use of a duplex stainless steel alloy
AU2002329144A1 (en) Use of a duplex stainless steel alloy
EP1599612A1 (en) Duplex stainless steel alloy for use in seawater applications
JP5324149B2 (en) Corrosion resistant austenitic stainless steel
EP0368487A1 (en) Welded corrosion-resistant ferritic stainless steel tubing and a cathodically protected heat exchanger containing the same
EP1263999B1 (en) Corrosion resistant austenitic alloy
US4808371A (en) Exterior protective member made of austenitic stainless steel for a sheathing heater element
JPS6358214B2 (en)
JP3848463B2 (en) High strength austenitic heat resistant steel with excellent weldability and method for producing the same
JP2001113388A (en) Welding materials for ferritic and austenitic duplex stainless steels
EP0320548B1 (en) Method of making a duplex stainless steel and a duplex stainless steel product with improved mechanical properties
JP3525843B2 (en) High strength low alloy heat resistant steel
JP3565155B2 (en) High strength low alloy heat resistant steel
KR20010061570A (en) a super ferritic stainless steel with improved dissimilar materials crevice corrosion resistance
JPS6325053B2 (en)

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

17P Request for examination filed

Effective date: 20090529

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IS IT LI LT LU LV MC MT NL PL PT RO SE SI SK TR

RIN1 Information on inventor provided before grant (corrected)

Inventor name: GOERANSSON, KENNETH

Inventor name: KIVISAEKK, ULF

RIN1 Information on inventor provided before grant (corrected)

Inventor name: KIVISAEKK, ULF

Inventor name: GOERANSSON, KENNETH

DAX Request for extension of the european patent (deleted)
STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION HAS BEEN WITHDRAWN

18W Application withdrawn

Effective date: 20140307