Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/02—Compacting only
  • B22F3/04—Compacting only by applying fluid pressure, e.g. by cold isostatic pressing [CIP]
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/12—Both compacting and sintering
  • B22F3/14—Both compacting and sintering simultaneously
  • B22F3/15—Hot isostatic pressing
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/20—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces by extruding
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F5/00—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product
  • B22F5/10—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product of articles with cavities or holes, not otherwise provided for in the preceding subgroups
  • B22F5/106—Tube or ring forms
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D7/00—Modifying the physical properties of iron or steel by deformation
  • C21D7/02—Modifying the physical properties of iron or steel by deformation by cold working
  • C21D7/10—Modifying the physical properties of iron or steel by deformation by cold working of the whole cross-section, e.g. of concrete reinforcing bars
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/08—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for tubular bodies or pipes
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C33/00—Making ferrous alloys
  • C22C33/02—Making ferrous alloys by powder metallurgy
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C33/00—Making ferrous alloys
  • C22C33/02—Making ferrous alloys by powder metallurgy
  • C22C33/0257—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements
  • C22C33/0278—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements with at least one alloying element having a minimum content above 5%
  • C22C33/0285—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements with at least one alloying element having a minimum content above 5% with Cr, Co, or Ni having a minimum content higher than 5%
• • 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
  • C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
• • 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
  • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
• • 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
  • C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F9/00—Making metallic powder or suspensions thereof
  • B22F9/02—Making metallic powder or suspensions thereof using physical processes
  • B22F9/06—Making metallic powder or suspensions thereof using physical processes starting from liquid material
  • B22F9/08—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying
  • B22F9/082—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying atomising using a fluid
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/10—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies

Definitions

• the present disclosure relates to a tube of a Fe—Cr—Al alloy. More specifically, the present disclosure relates to a tube which has been manufactured from a specific Fe—Cr—Al powder composition.
• Fe—Cr—Al tubes provide excellent heat resistance up to approximately 1450° C. while at the same time providing an extraordinarily good form stability as well as resistance against corrosion. High temperature applications of such Fe—Cr—Al tubes range from oxidizing, sulphidation to carbonaceous environments. Fe—Cr—Al tubes offer several advantages to other tube materials, such as chromia forming tube materials in these demanding environments. This is mostly due to the capability of the Fe—Cr—Al tubes to form a dense and adherent alumina layer that protects the tube against corrosion and atmospheric attack.
• CN110004367 discloses that Fe—Cr—Al tubes with the composition (in percentage by weight, wt %) of 14-22 wt % of Cr, 3-5 wt % of Al, 0.15-0.5 wt % of Y and the balance of Fe can be manufactured by preparing a powder, hot isostatic pressing the powder to a billet, forging, heat treatment, piercing and followed by reducing the diameter and/or the wall thickness of the tube by cold working steps at room temperature with sequential heat treatment steps.
• the Fe—Cr—Al tubes mentioned therein have problems with crack formation during operation.
• the present disclosure aims at solving or at least reducing the above-mentioned problem.
• the present disclosure therefore provides a tube of an iron-chromium-aluminum (Fe—Cr—Al) alloy which has been made from a specific a powder composition which powder composition has been optimized for providing a less brittle tube at room temperature and thus can be cold worked.
• Fe—Cr—Al iron-chromium-aluminum
• the Fe—Cr—Al tube is characterized in that the tube comprises a powder with the following composition (in weight %)
• TiN is present as inoculant.
• TiN is present as an inoculant in the Fe—Cr—Al powder. It has been shown that the inoculant will provide advantages for the tube and during the manufacturing process of the tube. In particular, the TiN inoculants will introduce grain refinement. A tube made from the powder as defined hereinabove or hereinafter will not crack easily when being cold worked or when being exposed to stresses or thermal shock.
• the present disclosure relates to a Fe—Cr—Al tube is characterized in that the tube comprises a powder with the following composition (in weight %)
• TiN is present as inoculant.
• weight % and “wt %” are used interchangeably. Also, the list of properties or contributions mentioned for a specific element should not be considered exhaustive.
• the main function for iron in the Fe—Cr—Al powder is to balance the powder composition or the composition of alloying elements of the tube.
• Chromium is an important element since it will improve the corrosion resistance of the obtained tube and increase its tensile and yield strength. Further, chromium facilitates the formation of the Al 2 O 3 layer on the final tube through the so-called third element effect, i.e. by formation of chromium oxide in the transient oxidation stage. Too low amount of chromium will result in loss of corrosion resistance. Thus, chromium shall be present an amount of at least 12.0 wt %, such as at least 15.0 wt %, such as at least 20.0 wt %. Too much chromium will enable ⁇ to ⁇ ′decomposition and 475° C. embrittlement and will also lead to an increased solid solutioning hardening effect on the ferritic structure.
• the maximum content of chromium is set to 25.0 wt %, such as maximum 24.0 wt %, such as maximum 23.50 wt %, such as maximum 23.0 wt %, such as maximum 22.50 wt %, such as maximum 22.0 wt %, such as maximum 21.50 wt %.
• the content of chromium is from 12.0 to 25.0 wt %, such as from 18.0 0 to 24.0 wt %, such as from 20.0 to 23.50 wt %.
• Aluminum is an important element since aluminum, when exposed to oxygen at high temperatures, will form a dense and thin Al 2 O 3 layer on the surface of the manufactured tube, which will protect the underlying surface from further oxidation. Further, aluminum increases the electrical resistivity. At too low amounts of aluminum, there will be a loss of the ability for the formation of the Al 2 O 3 layer and thereby will the electrical resistivity be reduced. Thus, aluminum shall be present in an amount of at least 3.50 wt %, such as at least 4.00 wt %, such as at least 4.50 wt %, such as at least 4.80 wt %. Too high content of aluminum will cause brittleness at low temperatures and will also enhance the formation of unwanted brittle aluminides.
• the maximum aluminum is set to 6.50 wt %, such as maximum 6.00 wt %, such as maximum 5.50 wt %, such as maximum 5.40 wt %, such as maximum 5.30 wt %, such as maximum 5.20 wt %.
• the content of aluminum is from 3.50 to 6.50 wt %, such as from 4.00 to 5.50 wt %, such as from 4.50 to 5.50 w1%.
• Titanium is an important element since titanium will together with nitrogen form TiN. According to an embodiment, due to the molar weights of Ti and N, the ratio of Ti/N in weight-% should be at least 3.3, such as at least 4.5.
• titanium may also reduce the activity of carbon by the formation of TiC and may furthermore improve high temperature creep strength.
• a too low amount of Ti will result in that not enough TiN inoculates is present in the present powder for nucleation of ferrite crystals during solidification in the additive manufacturing process.
• titanium shall be present in an amount of at least 0.20 wt %, such as at least 0.25 wt %, such as at least 0.30 wt %.
• a too high content of titanium may have a negative effect on the formation of Al 2 O 3 as TiO 2 may be formed.
• the maximum content of Ti is set to 1.10 wt %, such as maximum 1.00 wt %, such as maximum 0.90 wt %, such as maximum 0.8 wt %.
• the content of Ti is from 0.20 to 0.80 wt % such as from 0.20 to 0.70 wt %, such as from 0.24 to 0.60 wt %.
• Nitrogen is also an important element as it will enable precipitation of other metallic nitrides, such as ZrN. ZrN will improve the high temperature creep resistance. However, too low amounts of nitrides will be formed if the nitrogen content is too low. Accordingly, the nitrogen shall be present in an amount of at least 0.06 wt %, such as at least 0.07 wt %, such as at least 0.08 wt %, such as at least 0.09 wt %. Further, if the nitrogen content is too high in relation to the titanium content, there may be a risk that AlN will be formed, which will have a negative impact on the oxidation resistance.
• the maximum content of N is set to 0.20 wt %, such as maximum 0.15 wt %, such as maximum 0.10 wt %.
• the content of N is from 0.060 to 0.20 wt % such as from 0.07 to 0.15 wt % such as from 0.07 to 0.12 wt %.
• the tube comprising the Fe—Cr—Al alloy made from the powder as as defined hereinabove or hereinafter will have homogenously distributed TiN inoculants.
• TiN is a desired inoculant which will introduce grain refinement in the tube.
• the resulting grain structure of the obtained tube has a significantly reduced average grain size compared to a typical conventional Fe-Cr- Al tubes without these TiN inoculants.
• the homogenous and finely dispersed TiN inoculants in the present Fe—Cr—Al powder will provide for a tube which will have a more fine-grained Fe—Cr—Al alloy. This will provide for reduced cracking behavior during and/or after cold working of present tube. This will also provide that the presentl tube will be more resistant to strain.
• Zirconium is an important element in the present powder composition as zirconium will reduce the activity of C and N by the formation of ZrC or ZrN precipitates. Zirconium can also improve the high temperature creep strength of a manufactured tube. Too low amount of Zr will increase the risk of the formation of unwanted chromium carbides and/or aluminum nitrides. Accordingly, zirconium shall be present in an amount of at least 0.05 wt %, such as at least 0.07 wt %, such as at least 0.10 wt %. On the other hand, a too high content of zirconium may have a negative impact on the formation of Al 2 O 3 .
• the maximum content of zirconium is set to 0.20 wt %, such as maximum 0.15 wt %.
• the content of zirconium is from 0.05 to 0.20 wt %, such as from 0.07 to 0.20 wt %, such as from 0.070 to 0.10 wt %.
• yttrium improves the oxidation resistance of a manufactured tube. Too little amount of added yttrium will result in reduced oxidation resistance. For this reason, yttrium must be added in the amount of at least 0.01 wt %, such as at least 0.02 wt %, such as at least 0.04 wt %, such as 0.05 wt %, such as 0.06 wt %. However, if too much yttrium is added, this will cause hot embrittlement. As a result, the maximum content of yttrium content is set to 0.15 wt %, such as 0.10 wt %, such as 0.08 wt %.
• Carbon is an element which is not added on purpose but is an unavoidable element due to powder handling. This element may cause reduction in hot ductility and formation of metallic carbides. Thus, in order to limit the presence of too many metallic carbide precipitates, the carbon content must be ⁇ 0.050 wt %, such as ⁇ 0.040 wt %, such as ⁇ 0.030 wt %.
• Silicon may be present in levels of up to 0.50 wt % in order to increase electrical resistivity and to increase hot corrosion resistance. However, above this level, the hardness will increase and also there will be brittleness at low temperatures.
• Tantalum may optionally be added and if added, tantalum will improves the high temperature creep strength. Tantalum may also reduce the carbon activity by the formation of TaC precipitates and therefore the maximum tantalum content is set to 0.30 wt %.
• Hafnium may optionally be added.
• the addition of hafnium will improve the high temperature creep strength.
• hafnium may reduce the carbon activity by the formation of HfC precipitates. Therefore, the maximum hafnium content is set to ⁇ 0.30 wt %.
• Manganese may be present as an impurity. Manganese may disturb the formation of the Al2O3 layer and thus have a negative impact on the oxidation resistance. Thus, the maximum content of manganese is ⁇ 0.40 wt %, such as ⁇ 0.20 wt %.
• Nickel may be present as an impurity. Nickel may however increase the hardness and brittleness at low temperatures. Thus, the maximum content of nickel is therefore ⁇ 0.60 wt %, such as ⁇ 0.5 wt %.
• Oxygen may be present in the form of oxides.
• the maximum content allowed i is ⁇ 600 ppm.
• the powder may also include minor fractions of one or more of the following impurity elements such as but not limited to: Magnesium (Mg), Cerium (Ce), Calcium (Ca), Phosphorus (P), Tungsten (W), Cobalt (Co), Sulphur(S), Molybdenum (Mo), Niobium (Nb), Vanadium (V) and Copper (Cu) and in an amount up to 0.2 wt %.
• impurity elements such as but not limited to: Magnesium (Mg), Cerium (Ce), Calcium (Ca), Phosphorus (P), Tungsten (W), Cobalt (Co), Sulphur(S), Molybdenum (Mo), Niobium (Nb), Vanadium (V) and Copper (Cu) and in an amount up to 0.2 wt %.
• the Fe—Cr—Al powder as defined hereinabove or hereinafter may comprise the alloying elements mentioned herein in any of the ranges mentioned herein.
• the present tube of Fe—Cr—Al consists of all the alloying elements mentioned herein, in any of the ranges mentioned herein.
• Fe—Cr—Al powder as defined hereinabove or hereinafter may be manufactured through different methods. For example, but not limiting to:
• the tube of an Fe—Cr—Al alloy as defined hereinabove or hereinafter may be manufactured by a method comprising the following steps:
• the tube of the Fe—Cr—Al alloy as defined hereinabove or hereinafter may be manufactured by a method comprising the following steps:
• the tube of the Fe—Cr—Al alloy as defined hereinabove or hereinafter may be manufactured by a method comprising the following steps:
• the tube of the Fe—Cr—Al alloy as defined hereinabove or hereinafter may be more easily welded without addition of filler material. This is a result of the grain refining effect caused by the present TiN inoculants.
• the tube of the Fe—Cr—Al alloy as defined hereinabove or hereinafter will operate well in temperatures up to 1350° C. Furthermore, the present tube of the Fe—Cr—Al alloy will have a significant high-temperature corrosion resistance and a high resistance against oxidation, sulphidation and carburization. Additionally, the present tube will have significant high- temperature creep strength, form stability and high electrical resistivity.
• the present tube is especially useful as an electrical heating element or as a component in high temperature applications (in applications operating between 400 to 1350° C.).
• the present tube is also especially useful as a component in electrical heating applications.
• the present tube may also be used for protecting another tube against high temperature wear and corrosion such as thermocouple protection tubes. Hence, the present tube may be used in both electrical heating and high temperature applications. Further, the present tube can be used as nuclear cladding tube.
• the present tube can also be used as gas tubes in heat exchangers or as gas lance tubes.
• Powder 1 and 2 are comparative example and Powder 3* and 4* are inventive powders.
• the powders were produced by induction melting and subsequent gas atomization. A metallic melt with the specified composition is poured through a small melt nozzle into an atomizing chamber filled with inert atmosphere. With a system of high velocity gas nozzles, the melt stream was disintegrated into very fine droplets which were cooled down and then transferred to solidified particles in-flight a fraction of a second. The particles were collected and cooled to ambient temperature within the inert atmosphere. The powders were sieved to ⁇ 45 ⁇ m.
• the grain refining effect through the introduction of TiN inoculants can be obtained and visually perceived already in the solidification microstructure of the as-atomized powders.
• the degree of mono-crystallinity vis-à-vis polycrystallinity can be visually perceived through the “grain contrast imaging technique” or “electron channeling contrast imaging technique”, briefly described as follows.
• the Fe—Cr—Al powder is mixed with electrically conductive Bakelite powder and molded into a solid cylindrical puck. One of the flat surfaces of the puck is ground to sufficient depth and then polished to very high surface finish. Thereby, polished sections of a number of powder particles will be visible on this polished puck surface when analyzed by scanning electron microscope (SEM).
• the depth to which incoming SEM electrons penetrate the studied crystalline metal material and thereby also the number of back-scattered electrons that are reflected back depend on the crystal orientation of the studied crystals in the sample.
• grains of different crystal orientation vis-a-vis the direction of the incoming electrons will result in different amounts of reflected back-scatter electrons and thus ultimately to a difference in contrast between these studied grains. Consequently, this effect is best perceived with the back-scatter electron detector.

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• 2022
  • 2022-11-10 WO PCT/SE2022/051051 patent/WO2023086005A1/en not_active Ceased
  • 2022-11-10 JP JP2024527705A patent/JP2024543067A/ja active Pending
  • 2022-11-10 KR KR1020247015653A patent/KR20240075923A/ko not_active Ceased
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