JP2006505694A - High temperature alloy - Google Patents

Abstract

An improved nickel-chromium-iron alloy is provided comprising up to about 5% by weight of hafnium-containing particles. In one embodiment, the improved creep resistant castable oxide dispersion strengthened nickel-chromium-iron alloy comprises up to about 5% by weight of hafnium, at least a portion of the hafnium being a finely dispersed oxidation. Present as particles. Another embodiment of the improved alloy can additionally include up to about 15 wt% aluminum. This alloy is particularly useful in the production of pipes and castings that require creep resistance, such as in the petrochemical market.

Description

  The present invention relates to high temperature alloys and, more particularly, to oxide dispersion strengthened alloys with improved high temperature creep and carburization resistance.

  For example, high temperature alloys used in the manufacture of alloy tubes for steam methane reforming often have the drawback of insufficient creep resistance. Other application areas for high temperature alloys, such as alloy tubes used in ethylene pyrolysis, have the disadvantage that the carburization resistance of the alloy is insufficient and, as a result, the creep resistance is insufficient.

  The petrochemical industry seeks improved materials and other technologies that can withstand more and more demanding process conditions to enable more efficient production and higher yields. continuing. In the case of steam methane reforming, these conditions include higher temperatures and higher gas pressures. In the case of ethylene pyrolysis, the conditions include increasingly severe pyrolysis / cracking conditions (higher temperatures, shorter residence times, and lower product partial pressures). Currently available alloys have special defects that cause failure relatively early under these process conditions. This is currently true for both cast alloy tubes and wrought alloy tubes.

  An example of a known alloy material is INCOLOY® alloy 803 (UNS S 35045), which is specifically designed for use in application fields in petrochemical processing, chemical processing, and heat treatment. It is an iron-nickel-chromium alloy. The composition of INCOLOY® alloy 803 is 25 wt% Cr, 35 wt% Ni, 1 wt% Mn, 0.6 wt% Ti, 0.5 wt% Al, 0.7 wt% Si, C 0. 07% by weight, and the remaining weight is Fe. Efforts to improve the properties of this alloy have not been so successful either by adding additional alloy components or by the cladding method.

  It has been known for about 30 years that the creep resistance of alloys can be significantly improved by adding a fine dispersion of oxide particles to a metal matrix, resulting in a so-called oxide dispersion strengthened (ODS) alloy. Such alloys exhibit a creep threshold. That is, the creep rate is very low below a certain stress. This behavior is generally explained by interfacial pinning of moving dislocations in oxide particles (see Non-Patent Document 1). Recently, it has been proposed to provide an oxide dispersion strengthened cladding tube based on INCOLOY® alloy 803, but to date, no fully successful product has been obtained (see Non-Patent Document 2). .

  Produced in the ethylene pyrolysis market to have good corrosion resistance and acceptable creep resistance, nickel-chromium-iron alloys have mainly developed oxide coating layers based on chromium oxide. (Sometimes with mixed silica). This layer under excessive carburizing conditions (high temperature, high carbon activity, low oxygen pressure) can become unstable and is therefore no longer a functional carbon diffusion barrier. Alumina is known to be a very stable oxide, and ideally it can produce an alumina layer on the surface of a nickel-chromium-iron alloy, for example by adding aluminum to the melt. It is considered desirable. However, aluminum has two very detrimental effects on the mechanical properties of such alloys, especially the creep resistance. First, the addition of aluminum to the melt can lead to a dispersion of alumina in the alloy, which can drastically reduce the creep resistance properties. Second, aluminum can form a brittle Ni—Al phase in the alloy.

Bartsch, M., A. Wasilkowska, A. Czyrska-Filemonowicz and U. Messerschmidt, Materials Science & Engineering A 272, 152-162 (1999) http://www.oit.doe.gov/imf/factsheets/mtu tubes

  It will be apparent that there is a need for new high temperature alloys with improved properties for various high temperature applications.

  The present invention provides a new class of improved nickel-chromium-iron alloys containing hafnium and methods for their production.

  In a first aspect, the present invention provides an improved creep resistant nickel-chromium-iron alloy comprising up to about 5% by weight of hafnium-containing particles.

  In a second aspect, the present invention provides an improved oxide dispersion strengthened nickel-chromium-iron containing up to about 5% by weight of hafnium, wherein at least a portion of the hafnium is present as finely divided oxide particles. Provide alloy.

  In a third aspect, the present invention provides a corrosion resistant nickel-chromium-compound comprising at most about 15 wt.%, Preferably at most about 10 wt.% Aluminum, and at most about 5 wt.% Hafnium-containing particles. An iron-aluminum alloy is provided.

  The alloys of the present invention can be cast and formed into tubes and coils.

In a further aspect, the present invention provides an oxide dispersion strengthened castable alloy comprising the following components:
Carbon 0.01-0.7% by weight
Silicon 0.1-3.0% by weight
Manganese 0-3.0% by weight
Nickel 15-90% by weight
Chromium 5-40% by weight
Molybdenum 0-3.0% by weight
Niobium 0-2.0% by weight
Tantalum 0-2.0% by weight
Titanium 0-2.0% by weight
Zirconium 0-2.0% by weight
Cobalt 0-2.0% by weight
Tungsten 0-4.0% by weight
Hafnium 0.01-4.5% by weight
Aluminum 0-15% by weight
0.001-0.5% by weight of nitrogen
Oxygen 0.001-0.7 wt%
Residual iron and incidental impurities provided that there is at least one carbide-forming element selected from niobium, titanium, tungsten, tantalum, and zirconium, the carbide of which is more stable than chromium carbide, and at least one of hafnium. The condition is that the part exists as finely divided oxide particles.

A preferred embodiment of the oxide dispersion strengthened nickel-chromium-iron castable alloy according to the present invention comprises the following components:
Carbon 0.01-0.5% by weight
Silicon 0.01-2.5% by weight
Manganese 0-2.5% by weight
Nickel 15-50% by weight
Chromium 20-40% by weight
Molybdenum 0-1.0% by weight
Niobium 0 to 1.7% by weight
Titanium 0-0.5 wt%
Zirconium 0-0.5 wt%
Cobalt 0-2.0% by weight
Tungsten 0-1.0% by weight
Hafnium 0.01-4.5% by weight
Aluminum 0-15% by weight
Residual iron and incidental impurities provided that at least one of niobium, titanium, and zirconium is present, provided that at least a portion of hafnium is present as finely divided oxide particles.

A preferred alloy composition according to the present invention comprises the following components:
Carbon 0.3-0.7 wt%
Silicon 0.1-2.5% by weight
Manganese up to 2.5% by weight
Nickel 30-40% by weight
Chromium 20-30% by weight
Molybdenum up to 3.0% by weight
Niobium up to 2.0% by weight
Hafnium 0.01-4.5% by weight
Titanium up to 0.5% by weight
Zirconium up to 0.5% by weight
Cobalt up to 2.0% by weight
Tungsten up to 1.0% by weight
0.001-0.5% by weight of nitrogen
Oxygen 0.001-0.7 wt%
Residual iron and incidental impurities.

Carbon 0.03-0.2% by weight
Silicon 0.1-0.25 wt%
Manganese up to 2.5% by weight
Nickel 30-40% by weight
Chromium 20-30% by weight
Molybdenum up to 3.0% by weight
Niobium up to 1.7% by weight
Hafnium 0.01-4.5% by weight
Titanium up to 0.5% by weight
Zirconium up to 0.5% by weight
Cobalt up to 2.05 wt%
Tungsten up to 1.0% by weight
Aluminum 0 to 15.0% by weight
0.001-0.5% by weight of nitrogen
Oxygen 0.001-0.7 wt%
Residual iron and incidental impurities.

Carbon 0.3-0.7 wt%
Silicon 0.01-2.5% by weight
Manganese up to 2.5% by weight
Nickel 40-60% by weight
Chromium 30-40% by weight
Molybdenum up to 3.0% by weight
Niobium up to 2.0% by weight
Hafnium 0.01-4.5% by weight
Titanium up to 1.0% by weight
Zirconium up to 1.0% by weight
Cobalt up to 2.0% by weight
Tungsten up to 1.0% by weight
Aluminum 0 to 15.0% by weight
0.001-0.5% by weight of nitrogen
Oxygen 0.001-0.7 wt%
Residual iron and incidental impurities.

Carbon 0.03-0.2% by weight
Silicon 0.1-2.5% by weight
Manganese up to 2.5% by weight
Nickel 40-50% by weight
Chromium 30-40% by weight
Molybdenum up to 3.0% by weight
Niobium up to 2.0% by weight
Hafnium 0.01-4.5% by weight
Titanium up to 0.5% by weight
Zirconium up to 0.5% by weight
Cobalt up to 2.0% by weight
Tungsten up to 1.0% by weight
Aluminum 0 to 15.0% by weight
0.001-0.5% by weight of nitrogen
Oxygen 0.001-0.7 wt%
Residual iron and incidental impurities.

Carbon 0.3-0.7 wt%
Silicon 0.01-2.5% by weight
Manganese up to 2.5% by weight
Nickel 19-22% by weight
Chromium 24-27% by weight
Molybdenum up to 3.0% by weight
Niobium up to 2.0% by weight
Hafnium 0.01-4.5% by weight
Cobalt up to 2.0% by weight
Tungsten up to 1.0% by weight
Aluminum 0 to 15.0% by weight
0.001-0.5% by weight of nitrogen
Oxygen 0.001-0.7 wt%
Residual iron and incidental impurities.

Carbon 0.03-0.2% by weight
Silicon 0.1-2.5% by weight
Manganese up to 2.5% by weight
Nickel 30-45% by weight
Chromium 19-22% by weight
Molybdenum up to 3.0% by weight
Niobium up to 2.0% by weight
Hafnium 0.01-4.5% by weight
Titanium up to 0.5% by weight
Zirconium up to 0.5% by weight
Cobalt up to 2.0% by weight
Tungsten up to 1.0% by weight
Aluminum 0 to 15.0% by weight
0.001-0.5% by weight of nitrogen
Oxygen 0.001-0.7 wt%
Residual iron and incidental impurities.

  Another preferred nickel-chromium-iron castable alloy according to the present invention comprises the following composition: All percentages are given by weight.

The balance is iron and accompanying impurities.

  The amount of hafnium in the alloy is preferably 0.05 to 3.0 wt%, more preferably 0.1 wt% to 1.0 wt% for high carbon alloys (0.3 to 0.6 wt% carbon). % By weight, most preferably 0.2 to 0.5% by weight, in the case of low carbon alloys (carbon 0.03-0.2% by weight), more than 1% by weight, preferably 1% to 4. 5% by weight. Preferably hafnium is present in the alloy in the form of finely divided oxide particles having an average particle size of 50 microns to 0.25 microns or less, more preferably 5 microns to 0.25 microns or less.

An example of a particularly preferred alloy composition according to the invention consists essentially of the following components:
Carbon 0.45% by weight
Silicon 1.3% by weight
Manganese 0.9% by weight
Nickel 33.8% by weight
25.7% by weight of chromium
Molybdenum 0.03% by weight
Niobium 0.85% by weight
Hafnium 0.25 wt%
Titanium 0.1% by weight
Zirconium 0.01 wt%
Cobalt 0.04% by weight
Tungsten 0.01% by weight
Nitrogen 0.1% by weight
Iron balance.

Carbon 0.07% by weight
Silicon 1.0% by weight
Manganese 0.98% by weight
Nickel 32.5% by weight
25.8% by weight of chromium
Molybdenum 0.20% by weight
Niobium 0.04% by weight
Hafnium 1.1% by weight
Titanium 0.12% by weight
Zirconium 0.01 wt%
Cobalt 0.04% by weight
Tungsten 0.08% by weight
Nitrogen 0.1% by weight
Iron balance.

Carbon 0.34% by weight
Silicon 1.68% by weight
Manganese 1.10% by weight
Nickel 32.0% by weight
21.3 wt% chromium
Molybdenum 0.01% by weight
Niobium 0.80% by weight
Hafnium 0.25 wt%
Titanium 0.12% by weight
Zirconium 0.01 wt%
Aluminum 3.28% by weight
Cobalt 0.04% by weight
Tungsten 0.01% by weight
Iron balance.

Carbon 0.42% by weight
Silicon 1.79% by weight
Manganese 1.17% by weight
Nickel 33.2% by weight
Chrome 23.3 wt%
Molybdenum 0.02% by weight
Niobium 0.77% by weight
Hafnium 0.24% by weight
Titanium 0.10% by weight
Zirconium 0.01 wt%
Aluminum 1.64% by weight
Cobalt 0.04% by weight
Tungsten 0.08% by weight
Iron balance.

  Incidental impurities in the alloys of the present invention can include, for example, phosphorus, sulfur, vanadium, zinc, arsenic, tin, lead, copper, and cerium in a total amount of up to about 1.0% by weight.

  In yet another aspect, the present invention is a method of making an oxide dispersion strengthened castable nickel-chromium-iron alloy comprising finely divided hafnium particles, at least a portion of the hafnium being a molten alloy. A method is provided that includes adding to the melt prior to casting under conditions such that it is converted to an oxide therein.

  In producing the alloys of the present invention, it is important to provide the melt with conditions that allow the oxidation of hafnium particles without the unintentional reaction of hafnium being incorporated into the slag (with or without aluminum). It is. The correct oxidation conditions are achieved by appropriate adjustment or addition of components such as silicon and / or manganese, and by ensuring that undesirable contaminants are not present or minimized. be able to. If the slag can react with the hafnium oxide particles, this slag naturally removes these particles from the melt, of course. The level of oxygen in the melt can be varied, for example by the addition of one or more of silicon, niobium, titanium, zirconium, chromium, manganese, calcium, and the optimal free oxygen required to react with the hafnium particles The level can be easily found by routine experimentation.

  In the production of the castable nickel-chromium-iron alloy of the present invention, it is often desirable to introduce minor additions of certain components in order to obtain the desired alloy properties. Such components may be more reactive to oxygen, but are generally less reactive than hafnium. The formation of oxides by these minor additions should be avoided, and preferably the added component should form carbides, carbonitrides, nitrides or be present in solid solution. Any such minor additions are preferably made after adding hafnium. For example, after the reaction of hafnium particles with free oxygen, alloying amounts of titanium and / or zirconium can be added in each case up to the limit specified at 0.5% by weight. Substantial removal of available free oxygen from the melt causes a harmful reaction with the hafnium particles by any addition of such titanium and / or zirconium, and titanium, zirconium, And helps to ensure that no oxides are formed that would reduce the yield of hafnium.

  It is important to add hafnium to the melt as finely divided particles and to oxidize in situ.

  The inventors have discovered that adding hafnium in a non-granular form to a nickel / chromium alloy does not disperse or reacts only with the existing carbon / nitrogen resulting in a decrease in alloy properties. Attempts to add large hafnium fragments to nickel / chromium microalloys have revealed that hafnium does not disperse and settles to the bottom of the alloy melt and is therefore not present in the final casting. Surprisingly, the inventors have found that the desired dispersion strengthening is not achieved when hafnia (hafnium oxide) particles are added directly to the melt. Hafnia added in this way only enters the slag. According to the present invention, it has been found that the hafnium particles need to be oxidized in the melt to obtain the desired improvement.

  The composition of the feed should be unused feed (pure metal), a mixture of unused feed and revert, a mixture of unused feed and ingot, or a mixture of unused feed and revert and ingot Can do. The ingot can be made from an argon / oxygen decarburization (AOD) revert alloy process or from an in-house revert process, for example by argon purging. In each case, the chemical composition of the melt should be carefully monitored to avoid the formation of contaminants and undesirable slag.

  Special care should be taken to remove slag from the bath, and it is preferable to remove the maximum amount of slag from the surface of the bath. By using neutral deslagging powder, it is possible to improve slag removal. If desired, the melt can be maintained in an argon atmosphere, but this is not essential.

  The melting temperature is preferably in the range of 1500 ° C. to 1700 ° C., preferably 1610 ° C. to 1670 ° C. for nickel-chromium-iron and 1630 ° C. to 1690 ° C. for nickel-chromium-iron-aluminum. is there.

  The hafnium particles are preferably added to the melt immediately before casting the molten alloy into the mold. When using a ladle, it is preferred to add hafnium to the ladle. In order to improve the dispersion of hafnium, it is preferable to stir before casting the molten alloy.

  Any type of hafnium can be used, but electrolytic hafnium is preferred. The hafnium particles are preferably reduced in size as much as possible, for example, by pulverizing them into a fine powder in an appropriate mill. The hafnium particles preferably have a particle size of less than 5 mm, preferably less than 4 mm, with an average particle size of 1 to 2 mm. When dispersed in the melt, the size of the hafnium particles is further reduced.

  The high carbon alloy of the present invention (carbon 0.3 to 0.6% by weight) has the same primary carbide network structure as the corresponding alloy having no oxide dispersion. Primary carbides are mainly composed of chromium and / or iron carbonitrides, and optionally niobium, titanium, and / or zirconium carbonitrides. The present invention also provides the possibility of obtaining a dispersion of secondary carbides after the alloy is hot. These secondary carbides are mainly carbonitrides of chromium (or other elements such as iron) and optionally carbonitrides of niobium, titanium (and / or zirconium).

  The low carbon alloy of the present invention (carbon 0.03-0.2% by weight) is a carbide, carbonitride, or nitride such as titanium nitride, titanium carbonitride, niobium carbide, niobium carbonitride, niobium nitride, zirconium nitride. , Zirconium carbonitride, zirconium carbide, tantalum carbide, tantalum carbonitride, tantalum nitride, tungsten carbide, tungsten nitride, and / or a dispersion of tungsten carbonitride.

In addition to these precipitates, the present invention provides for the formation of hafnia / hafnium oxide dispersions (hafnium can be oxidized to form HfO ₂ , but oxide HfO _x where x is a variable. Some can also be expected to form). Furthermore, in alloys containing niobium and titanium that are not insignificant, such as high carbon nickel-chromium-iron alloys, hafnium / niobium / titanium carbonitrides and (rarely) oxide mixtures (the amount of niobium and titanium is Can be predicted as well as the amount of nitrogen and oxygen. A larger number of nitrided (and / or carbonized) titanium dispersions can also be obtained in the alloy, some of which may contain hafnia particles. Some hafnium carbonitride can also be formed.

  According to another aspect of the present invention, there is provided an oxide dispersion strengthened nickel-chromium-iron alloy comprising up to about 5 wt% hafnium, wherein at least a portion of the hafnium is present as finely dispersed oxide particles. The carbon content of the alloy is 0.3 wt% to 0.5 wt%, and the high temperature creep resistance is improved, and as a result, an alloy having an improved service life expectancy is provided. Without being bound by any particular theory, it is believed that the creep resistance of high carbon alloys that are substantially free of aluminum is obtained by the ability of the particle dispersion to retard dislocation behavior in the alloy lattice. It is done. In the case of microalloys that do not contain oxide dispersions, the dislocation behavior can be delayed by the presence of carbide (and / or nitride) precipitates, but the presence of oxide dispersions unexpectedly exceeds expectations. There is a considerable improvement. An example of a high carbon oxide dispersion strengthened alloy is Alloy A in Table 1 (no aluminum present).

  In yet another aspect, the present invention is an oxide dispersion strengthened nickel-chromium-iron alloy comprising up to about 5% hafnium, wherein at least a portion of the hafnium is present as finely dispersed oxide particles, The alloy has a carbon content of 0.03% to 0.2%, preferably 0.03% to 0.1%, more preferably 0.03% to 0.08%, such as about 0.05% to 0.00. This provides an alloy that has a significantly increased service temperature, preferably higher than 1150 ° C. Without being bound by any particular theory, the improved high temperature performance of the new low carbon alloy in this further aspect of the present invention is that instead of a reinforced carbide dispersion, a hafnia dispersion that is more stable than carbide at high temperatures. This is considered to be caused by the use of. An example of a low carbon oxide dispersion strengthened alloy is Alloy B in Table 1 (no aluminum present).

  When the nickel-chromium-iron alloy of the present invention also contains aluminum, the aluminum is preferably 0.1 wt% to 10 wt%, more preferably 0.5 wt% to 6 wt%, most preferably 1.0 wt%. % To 5% by weight.

  In yet another aspect of the present invention, a method of producing a carburized nickel-chromium-iron alloy comprising sequentially adding finely divided hafnium particles and aluminum to a melt of the alloy, followed by casting. Is provided.

  Aluminum is preferably added to the melt immediately before casting the molten alloy into the mold.

  Without being bound to any particular theory, the addition of hafnium limits the amount of oxygen available in the alloy that can react with aluminum and minimizes the formation of harmful dispersions of alumina particles. Suppressed or eliminated.

  The alloy of the present invention can be formed into a tube, for example, by rotational molding, and a tube molded by such rotation is another aspect of the present invention. The rotational molding process can result in a non-uniform particle distribution on the tube wall, increasing the concentration of particles toward the outer surface of the tube wall, which is advantageous in some cases. For certain applications, such as machining the inner wall of the tube to remove 4-5 mm of material, this concentration gradient ensures that the hafnium / hafnia reinforcement is maintained in the useful portion of the tube. Other components that can be made from the new alloy include fixtures, fully fabricated ethylene furnace assemblies, reformer tubes, and manifolds.

  In the case of alloys with high chromium content (greater than 10%), another advantage of hafnium addition is that it tends to improve the adhesion of the oxide layer on the alloy tube surface. For example, when a nickel-chromium-iron alloy is used in an ethylene furnace, the alloy can have an oxide layer on its surface that protects the alloy from carburizing corrosion. The protective oxide layer is ideally formed from chromium / manganese / silicon oxide, but can also include iron and nickel oxides. The oxide layer tends to flake off during the useful life of the tube (due to differences in expansion coefficient from the alloy, compressive stress in the oxide, etc.). Stripping renders the alloy vulnerable to corrosion by the gaseous and particulate reactants of the ethylene cracking process. Surprisingly, it has been found that the addition of hafnium described herein tends to delay the exfoliation of the protective oxide layer.

  Embodiments of the alloy according to the invention are shown by way of example only in the accompanying drawings.

  The invention is illustrated by the following examples, in which all percentages are given by weight.

The following molten composition is produced in a clean furnace:
Nickel 35% by weight
25% by weight of chromium
Carbon 0.4% by weight
Niobium 0.8-0.9% by weight
1.6-1.8% by weight of silicon
Manganese 1.1-1.3 wt%
Iron balance.

  The melt temperature is increased from 1640 ° C. to 1650 ° C. tap temperature and the silicon content is checked to ensure correct oxidation conditions. The furnace is then de-slagged to remove as much slag as possible. Next, 100 kg of the alloy is poured out into the ladle, and 0.35% of hafnium particles having a maximum particle size of 5 mm and an average of 1 to 2 mm are added to the pouring stream. After adding hafnium, 0.18% titanium is added to the ladle in the form of FeTi.

  Stir the alloy in the ladle and immediately cast it into the mold of the tube.

  The creep resistance properties of the alloys thus produced were compared to those of commercial alloys that were similar except that no hafnium was present.

  The stress-rupture properties of commercial alloys, derived from regression analysis of numerous creep tests, were plotted on a Larson Miller diagram and showed a typical figure of 16.7 MPa at a temperature of 1100 ° C. (FIG. 7). Commercial alloys are expected to fail after a minimum of 100 hours with an average failure value of 275 hours. The alloy according to the present invention has a shortest failure time to break of 370 hours and an average failure value of 430 hours. A comparison of creep strength is shown in FIG.

  Table 3 shows the results of a 100,000 hour creep rupture stress test on the alloy of Example 1.

  The procedure of Example 1 is repeated using the same molten composition except that the addition of titanium is omitted.

  The creep resistance properties of the alloys thus produced were compared to the creep resistance properties of commercial alloys that were similar except that the addition of hafnium was omitted.

  The stress-rupture properties of commercial alloys derived from regression analysis of numerous creep tests were plotted on a Larson Miller diagram, yielding a typical figure of 16.2 MPa at a temperature of 1100 ° C. Commercial alloys are expected to fail after a minimum of 100 hours, with an average failure value of 202 hours. The alloy according to the present invention has a minimum failure time to break of 396 hours, an average failure value of 430 hours, and a maximum failure time to break of 629 hours.

  The results of Examples 1 and 2 show the dramatic improvement in creep properties that can be obtained using the alloys and methods of the present invention.

  This example describes the production of a low carbon oxide dispersion strengthened alloy according to the present invention.

The following molten composition is produced in a clean furnace:
Nickel 33-35% by weight
Chromium 24-26% by weight
Carbon 0.04-0.08% by weight
Silicon 1.0-1.2% by weight
Manganese 1.0-1.2% by weight
Molybdenum 0.14-0.3 wt%
Iron balance.

  The melt temperature is increased from 1640 ° C. to a tapping temperature of 1650 ° C. and the silicon content is checked. The furnace is then de-slagged to remove as much slag as possible. Next, 100 kg of the alloy is poured out into the ladle and 0.75% by weight of hafnium particles having a maximum particle size of 5 mm and an average of 1 to 2 mm is added to the pouring stream. After adding hafnium, 0.25% titanium is added to the ladle in the form of FeTi.

  Stir the alloy in the ladle and immediately cast it into the mold of the tube. The chemical composition of the tube alloy by spectroscopic analysis is as follows.

  A micrograph of the alloy is shown in FIG. The dispersed oxide particles can be clearly seen.

  The procedure of Example 3 is repeated using a similar molten composition except that the hafnium addition is 0.5 wt%. The chemical composition of the tube alloy by spectroscopic analysis is as follows.

  A micrograph of the alloy is shown in FIG. The dispersed oxide particles can be clearly seen.

  Examples 3 and 4 show a higher solid phase curve than the high carbon alloys of Examples 1 and 2, and indeed this solid phase curve is 1344 ° C. instead of 1260 ° C. for the high carbon alloy.

  This example describes the production of an oxide dispersion strengthened nickel-chromium-iron alloy according to the present invention containing both hafnium and aluminum.

A nickel-chromium-iron alloy melt having the following constituents by weight is formed in a clean furnace and brought to the hot water temperature.
Nickel 35% by weight
25% by weight of chromium
Carbon 0.4% by weight
Niobium 0.8-0.9% by weight
1.6-1.8% by weight of silicon
Manganese 1.1-1.3 wt%
Iron balance.

  When suitable oxidation conditions are obtained, 100 kg of the melt is poured into the ladle and at the same time hafnium particles are added to the pour stream to reduce the hafnium level in the alloy from 0.15% to 0.30% by weight. To. Just prior to casting, aluminum is added to the melt to bring the aluminum level from 1.5% to 1.8%.

  The alloy of Example 5 was tested to confirm that aluminum can improve the carburization resistance of the hafnium-containing alloy of the present invention. A very severe pack-carburization test was performed and the results are shown in FIG. It has been found that the creep resistance of this alloy is sufficiently maintained compared to similar alloys without the addition of hafnia and aluminum. Certainly, it was observed that creep resistance was reduced by up to 20% compared to similar alloys without the addition of hafnium and aluminum, whereas similar alloys with the addition of aluminum but no hafnium had a resistance to creep. The reduction was shown to be 80%.

  The reader's interest is directed to all papers and documents filed with or prior to this specification in connection with the present application and made available to the public handbook along with this specification. The contents of these papers and documents are incorporated herein by reference.

  All of the features disclosed herein (including any of the appended claims, abstracts, and drawings) and / or all of the steps of any method or process so disclosed are These can be combined in any combination, except that at least some of the features and / or steps are incompatible with each other.

  Instead of each feature disclosed in this specification (including any of the appended claims, abstract, and drawings), unless otherwise specified, serves the same, equivalent, or similar purpose Alternative features can be used. Thus, unless expressly specified otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

  The present invention is not limited to any of the details of the foregoing embodiments. The invention extends to any novel one or any novel combination of features disclosed in the specification (including any of the appended claims, abstract and drawings), or Extends to any novel one or any novel combination of any method or process steps disclosed.

It is the figure which showed the micrograph of the 1st alloy by this invention, and the composition by weight. It is the figure which showed the microscope picture of the 2nd alloy by this invention, and the composition by weight. It is the figure which showed the micrograph of the 3rd alloy by this invention, and the composition by weight. It is the figure which showed the micrograph of the 4th alloy by this invention, and the composition by weight. It is a microscope picture of the 5th alloy by the present invention. It is a microscope picture of the 6th alloy by this invention. It is a Larson mirror curve of Example 1 by this invention. It is the creep strength of Example 1 by this invention. It is a pack-carburization test result of Example 5 by this invention.

Claims (52)

An oxide dispersion strengthened nickel-chromium-iron alloy,
0.01 to 0.7% by weight of carbon,
0.1-3.0% by weight of silicon,
Manganese 0-2.5% by weight,
Nickel 15-90% by weight,
5-40 wt% chromium,
0 to 3.0% by weight of molybdenum,
0 to 2.0% by weight of niobium,
0 to 2.0% by weight of tantalum,
Titanium 0-2.0% by weight,
Zirconium 0-2.0 wt%,
Cobalt 0-2.0% by weight,
0 to 4.0% by weight of tungsten,
Hafnium 0.01-4.5% by weight,
0-15% by weight of aluminum,
0.001-0.5 wt% nitrogen,
0.001 to 0.7% by weight of oxygen,
Residue iron and incidental impurities,
Provided that there is at least one carbide-forming element selected from niobium, titanium, tungsten, tantalum, and zirconium, the carbide of which is more stable than chromium carbide, and at least a portion of hafnium. An alloy provided that is present as finely divided oxide particles. An oxide dispersion strengthened nickel-chromium-iron alloy,
0.01 to 0.5% by weight of carbon,
0.01 to 2.5% by weight of silicon,
Manganese 0-2.5% by weight,
Nickel 15-50% by weight,
20-40% by weight of chromium,
0 to 1.0% by weight of molybdenum,
0 to 1.7% by weight of niobium,
Titanium 0-0.5 wt%,
Zirconium 0-0.5 wt%,
Cobalt 0-2.0% by weight,
0 to 1.0% by weight of tungsten,
Hafnium 0.01-4.5% by weight,
Residue iron and incidental impurities,
An alloy that contains at least one of niobium, titanium, and zirconium, and is provided that at least a part of hafnium is present as finely divided oxide particles. The following composition,
Carbon 0.3-0.7 wt%,
Silicon 0.1-2.5% by weight,
Manganese up to 2.5% by weight,
Nickel 30-40% by weight,
20-30% by weight of chromium,
Molybdenum up to 3.0% by weight,
Niobium up to 2.0% by weight,
Hafnium 0.01-4.5% by weight,
Titanium up to 0.5% by weight,
Zirconium up to 0.5% by weight,
Cobalt up to 2.0% by weight,
Tungsten up to 1.0% by weight,
0.001-0.5 wt% nitrogen,
0.001 to 0.7% by weight of oxygen,
Residue iron and incidental impurities,
The alloy according to claim 1, comprising: The following composition,
0.03-0.2 wt% carbon,
Silicon 0.1-0.25 wt%,
Manganese up to 2.5% by weight,
Nickel 30-40% by weight,
20-30% by weight of chromium,
Molybdenum up to 3.0% by weight,
Up to 1.7% by weight of niobium,
Hafnium 0.01-4.5% by weight,
Titanium up to 0.5% by weight,
Zirconium up to 0.5% by weight,
Cobalt up to 2.05% by weight,
Tungsten up to 1.0% by weight,
0-15.0% by weight of aluminum,
0.001-0.5 wt% nitrogen,
0.001 to 0.7% by weight of oxygen,
Residue iron and incidental impurities,
The alloy according to claim 1, comprising: The following composition,
Carbon 0.3-0.7 wt%,
0.01 to 2.5% by weight of silicon,
Manganese up to 2.5% by weight,
40-60% by weight of nickel,
30-40% by weight of chromium,
Molybdenum up to 3.0% by weight,
Niobium up to 2.0% by weight,
Hafnium 0.01-4.5% by weight,
Titanium up to 1.0% by weight,
Zirconium up to 1.0% by weight,
Cobalt up to 2.0% by weight,
Tungsten up to 1.0% by weight,
0-15.0% by weight of aluminum,
0.001-0.5 wt% nitrogen,
0.001 to 0.7% by weight of oxygen,
Residue iron and incidental impurities,
The alloy according to claim 1, comprising: The following composition,
0.03-0.2 wt% carbon,
Silicon 0.1-2.5% by weight,
Manganese up to 2.5% by weight,
Nickel 40-50% by weight,
30-40% by weight of chromium,
Molybdenum up to 3.0% by weight,
Niobium up to 2.0% by weight,
Hafnium 0.01-4.5% by weight,
Titanium up to 0.5% by weight,
Zirconium up to 0.5% by weight,
Cobalt up to 2.0% by weight,
Tungsten up to 1.0% by weight,
0-15.0% by weight of aluminum,
0.001-0.5 wt% nitrogen,
0.001 to 0.7% by weight of oxygen,
Residue iron and incidental impurities,
The alloy according to claim 1, comprising: The following composition,
Carbon 0.3-0.7 wt%,
0.01 to 2.5% by weight of silicon,
Manganese up to 2.5% by weight,
Nickel 19-22% by weight,
24-27% by weight of chromium,
Molybdenum up to 3.0% by weight,
Niobium up to 2.0% by weight,
Hafnium 0.01-4.5% by weight,
Cobalt up to 2.0% by weight,
Tungsten up to 1.0% by weight,
0-15.0% by weight of aluminum,
0.001-0.5 wt% nitrogen,
0.001 to 0.7% by weight of oxygen,
Residue iron and incidental impurities,
The alloy according to claim 1, comprising: The following composition,
0.03-0.2 wt% carbon,
Silicon 0.1-2.5% by weight,
Manganese up to 2.5% by weight,
30-45% nickel by weight,
19-22% by weight of chromium,
Molybdenum up to 3.0% by weight,
Niobium up to 2.0% by weight,
Hafnium 0.01-4.5% by weight,
Titanium up to 0.5% by weight,
Zirconium up to 0.5% by weight,
Cobalt up to 2.0% by weight,
Tungsten up to 1.0% by weight,
0-15.0% by weight of aluminum,
0.001-0.5 wt% nitrogen,
0.001 to 0.7% by weight of oxygen,
Residue iron and incidental impurities,
The alloy according to claim 1, comprising:   8. An alloy according to any one of claims 1, 2, 3, 5 or 7, characterized in that it has a carbon content of 0.3 to 0.5% by weight.   Alloy according to claim 1 or 2, characterized in that it has a carbon content of 0.03 to 0.2% by weight.   The amount of carbon in the alloy is 0.3 to 0.6 wt%, and the amount of hafnium in the alloy is 0.01 to 3.0 wt%. alloy.   The amount of carbon in the alloy is 0.3 to 0.6 wt%, and the amount of hafnium in the alloy is 0.1 wt% to 1.0 wt%. The described alloy.   13. The amount of carbon in the alloy is 0.3 to 0.6% by weight, and the amount of hafnium in the alloy is 0.2 to 0.5% by weight. The described alloy.   The amount of carbon in the alloy is from 0.03 to 0.2% by weight, and the amount of hafnium in the alloy is from 1 to 4.5% by weight. Alloys described in 1.   9. The amount of aluminum in the alloy is from 0.1% to 10% by weight and the amount of hafnium is from 0.01% to 4.5% by weight. The alloy according to any one of the above.   16. The alloy of claim 15, wherein the amount of aluminum in the alloy is 0.1% to 6% by weight and the amount of hafnium is 0.1% to 1.0% by weight.   The amount of aluminum in the alloy is 0.1 wt% to 4.5 wt%, and the amount of hafnium is 0.2 wt% to 0.5 wt%. The described alloy.   The method of any one of the preceding claims, wherein the hafnium is present in the alloy in the form of finely divided oxide particles having an average particle size of 50 microns to 0.25 microns or less. The described alloy.   The method of any one of the preceding claims, wherein the hafnium is present in the alloy in the form of finely divided oxide particles having an average particle size of 5 microns to 0.25 microns or less. The described alloy. The following composition:
0.45% carbon by weight,
1.3% by weight of silicon,
Manganese 0.9% by weight,
33.8% by weight nickel,
25.7% by weight of chromium,
0.03% by weight of molybdenum,
Niobium 0.85% by weight,
0.25 wt% hafnium,
Titanium 0.1% by weight,
0.01% by weight of zirconium,
0.04% by weight of cobalt,
0.01% by weight of tungsten,
0.1% by weight of nitrogen,
Iron balance;

Carbon 0.07% by weight,
1.0% by weight of silicon,
0.98% by weight manganese,
32.5% nickel by weight,
25.8% by weight of chromium,
0.20% by weight molybdenum,
Niobium 0.04% by weight,
1.1% by weight of hafnium,
Titanium 0.12% by weight,
0.01% by weight of zirconium,
0.04% by weight of cobalt,
0.08 wt% tungsten,
0.1% by weight of nitrogen,
Iron balance;

Carbon 0.34% by weight,
1.68% by weight of silicon,
Manganese 1.10% by weight,
32.0% nickel by weight,
21.3 wt% chromium,
0.01% by weight of molybdenum,
Niobium 0.80% by weight,
0.25 wt% hafnium,
Titanium 0.12% by weight,
0.01% by weight of zirconium,
3.28% by weight of aluminum,
0.04% by weight of cobalt,
0.01% by weight of tungsten,
Iron balance;

0.42% carbon by weight,
1.79% by weight of silicon,
1.17% by weight manganese,
33.2% by weight of nickel,
23.3 wt% chromium,
0.02% by weight molybdenum,
Niobium 0.77% by weight,
0.24% by weight of hafnium,
0.10% by weight of titanium,
0.01% by weight of zirconium,
1.64% by weight of aluminum,
0.04% by weight of cobalt,
0.08 wt% tungsten,
Iron balance;
An alloy having any one of the following.   5. An alloy according to any one of the preceding claims substantially as described in Examples 1 to 4.   6. An alloy according to any one of the preceding claims substantially as described in Example 5.   A nickel-chromium-iron alloy comprising up to about 5% by weight of hafnium-containing particles.   An oxide dispersion strengthened nickel-chromium-iron alloy comprising up to about 5% by weight of hafnium, wherein at least a portion of the hafnium is present as finely divided oxide particles.   A corrosion resistant nickel-chromium-iron-aluminum alloy comprising up to about 15 wt% aluminum, preferably up to about 10 wt% and up to about 5 wt% hafnium-containing particles.   Oxidation comprising adding finely divided hafnium particles to the alloy melt prior to casting under conditions such that at least a portion of the hafnium is converted to oxide in the melt A method for producing a material dispersion strengthened nickel-chromium-iron alloy.   27. The method of claim 26, wherein the alloy is an alloy according to any of claims 1-25.   28. A method according to claim 26 or 27, wherein the hafnium particles have a particle size of less than 50 microns.   29. A process according to any one of claims 26 to 28, characterized in that the amount of hafnium added to the melt is 0.01 to 3.0% by weight.   30. A method according to any one of claims 26 to 29, wherein the hafnium particles are added to the melt immediately before casting the molten alloy into the mold.   31. The method of claim 30, wherein the hafnium particles are added to a molten alloy in a ladle.   32. A method according to any of claims 26 to 31 wherein the hafnium is electrolytic hafnium.   33. A method according to any one of claims 26 to 32, wherein the level of oxygen in the melt varies with the addition of one or more of niobium, titanium and zirconium.   34. The method of claim 33, wherein the titanium is added in the form of TiFe after the addition of hafnium.   33. A method according to any one of claims 22 to 32, wherein the melting temperature is in the range of 1500 <0> C to 1700 <0> C.   A method of producing a corrosion-resistant nickel-chromium-iron, comprising sequentially adding finely divided hafnium particles and aluminum to an alloy melt and then casting.   37. The method of claim 36, wherein the aluminium is added to the melt just prior to casting the molten alloy into the mold.   38. A method according to any one of claims 26 to 37, wherein the alloy is formed into a tube by rotational molding.   39. A method according to any one of claims 26 to 38, substantially as described in Examples 1 to 4.   40. A method according to any one of claims 26 to 39, substantially as described in Example 5.   A method of producing a nickel-chromium-iron alloy comprising casting finely divided hafnium particles after adding them to a melt.   A creep resistant alloy tube formed from a nickel-chromium-iron alloy characterized by containing up to about 5% by weight of hafnium-containing particles.   43. The tube of claim 42, comprising an oxide dispersion strengthened nickel-chromium-iron alloy containing up to about 5% by weight of hafnium.   A nickel-chromium-iron alloy tube comprising up to about 5% by weight of hafnium-containing particles substantially as described above.   A tube formed from the alloy according to any one of claims 1 to 25 by rotational molding.   A nickel-chromium-iron alloy having a structure and composition substantially as described and illustrated in any one of Figures 1 to 4 of the accompanying drawings, wherein the table represents weight percentages of the alloy components Alloy.   Nickel-chromium-iron alloy having the structure substantially described and illustrated in FIG. 5 or 6 of the accompanying drawings.   A corrosion-resistant alloy tube formed from a nickel-chromium-iron alloy characterized by containing up to about 15% by weight aluminum and up to about 4.5% by weight hafnium-containing particles.   49. The tube of claim 48, comprising an oxide dispersion strengthened nickel-chromium-iron alloy containing up to about 5% by weight of hafnium.   A nickel-chromium-iron alloy tube comprising up to about 5% by weight of hafnium-containing particles substantially as described above.   26. A tube formed from an alloy according to any one of claims 1 to 25, wherein the tube is formed by rotational molding. 48. An alloy according to any one of claims 1 to 25, 46 and 47, produced by the method according to any one of claims 26 to 41.

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