WO1992000158A1 - METHOD OF POWDERMETALLURGICALLY MANUFACTURING FULLY DENSE BODIES FROM HIGH TEMPERATURE MARTENSITIC Cr STEEL - Google Patents

METHOD OF POWDERMETALLURGICALLY MANUFACTURING FULLY DENSE BODIES FROM HIGH TEMPERATURE MARTENSITIC Cr STEEL Download PDF

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Publication number
WO1992000158A1
WO1992000158A1 PCT/SE1991/000454 SE9100454W WO9200158A1 WO 1992000158 A1 WO1992000158 A1 WO 1992000158A1 SE 9100454 W SE9100454 W SE 9100454W WO 9200158 A1 WO9200158 A1 WO 9200158A1
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Prior art keywords
steel
powder
amounts
consolidated
isostatic pressing
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Application number
PCT/SE1991/000454
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French (fr)
Inventor
Ragnar Ekbom
Anders Salwen
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Abb Powdermet Ab
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Publication of WO1992000158A1 publication Critical patent/WO1992000158A1/en

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    • 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%

Definitions

  • the invention relates to a method manufacturing fully dense bodies of a high temperature martensitic Cr steel, a number of material properties, preferably properties at elevated temperatures, being improved through a well balanced composition and powdermetallurgical manufacture.
  • the steel is manufactured by gas atomization into a steel powder, which is consolidated into bodies of essentially full density by hot isostatic pressing or a combination of isostatic pressing and subsequent hot working.
  • martensitic 9-12% Cr steels which are attractive because of their high strength, low thermal expansion, good thermal conductivity, good ability to withstand stress corrosion and good damping properties .
  • Components of high temperature martensitic Cr steel with application within the energy field, for example in the generation of heat and electricity, are presently manufac ⁇ tured substantially with conventional ingot-based technique.
  • One condition for a steel component of the stated type to receive the desired properties primarily in connection with long-term use, that is, operating times of the order of magnitude of 100,000 hours or more in the temperature interval 550-630°C, is that the microstructure does not a ⁇ e too rapidly. This,- in turn, requires that the analysis is carefully balanced within certain intervals and that the material is given a good homogeneous composition.
  • Ta up to 0.5%, the balance being Fe and conventional impu ⁇ rities for this type of steel in conventional contents.
  • the 5 alloying elements included have been added based on the following.
  • Carbon is added in order for martensite to form in the matrix and in or ⁇ er to form, together with Cr, Mo, W, No and 0 V ana possibly Ti, Zr, Hf and Ta, carbides and/or carbo- nitrides .
  • Silicon is added as ⁇ eoxidan .
  • Manganese is added preferably to bind oxygen and sulphur formin ⁇ MnS and MnO. Chromium is added to obtain resistance to oxidation and wet corrosion and to form stable chromium carbides during tempe ⁇ ring.
  • Nickel is added to suppress the formation of deltaferrite .
  • Molybdenum and tungsten are added to increase the strength by solution hardening and to increase the stability of the chromium carbides. In addition, molybdenum and tungsten increase the corrosion resistance.
  • Vanadium is added to form a finely dispersed precipitation cf carbonitride .
  • Niobium is added to form a finely dispersed precipitaticn cf carbonitride .
  • Nitrogen is added to form stable carbonitride precipitations with vanadium and niobium.
  • Titanium, zirconium, -hafnium and tantalum are added as supplement to or to partially replace Nb and V, that is, tc form finely dispersed carbonitride precipitations.
  • an additional optimi ⁇ zation is required of the composition relating to important alloying elements such as carbon, chromium, molybdenum, tungsten, and boron, which according to the invention have been identified as key elements for which small changes in content are noticeably reflected in the properties of the material.
  • important alloying elements such as carbon, chromium, molybdenum, tungsten and boron are greatly prone to segregation, which in connection with the solidi ⁇ fication may result in the formation of residual melt regions, sometimes in the form of eutectics, with higher contents of the segregation-prone alloying materials, or in the occurrence of other serious defects such as residual porosity, residual ferrite, or cracks.
  • a steel powder s manufactured by gas atomization of the melt into a fine homogeneous and essen ⁇ tially segrega ion-free powder, which by subsequent hot- isostatic pressing or isostatic pressing followed by hot working is consolidated into an essentially dense body.
  • the tendency for crack ⁇ ing during a possible hot working which normally occurs in conventionally manufactured material of this type as a con ⁇ sequence of boron segregation providing variations in the boron content within the body, is eliminated.
  • a fully dense body is manufactured from a high temperature martensitic chrome steel by means of powdermetallurgical methods, whereby a steel melt with the following optimized composition (percen ⁇ tage by weight)
  • Ta up to 0.2% the balance being Fe, and conventional impurities for this type of steel in conventional contents, is atomized by means of gas atomization, into an essentially segregation-free steel powder with a powder particle size of at most 1 mm.
  • the contents of certain alloying elements included are adapted such that the molybdenum equivalent, 5 expressed as ( [%Mo] + 0.5 [%W]), amounts to between 1.1 and 1.9%, that the total carbon and nitrogen content, ([%C] + [%N]), amounts to between 0.12 and 0.22% and that the total content of titanium, niobium, tantalum and hafnium, expressed as ( [%Ti] + [%Nb] + 0.5 [%Ta] + 0.5 [%Hf]), C amounts to at most 0.15%.
  • the steel powder obtained is filled into a deformable container, which is evacuated and essentially gas-tightly sealed before the container containing the powder is consolidated into an essentially fully dense body by hot isostatic pressing or by a combination of isostatic pressing and subsequent hot - working .
  • the carbon content should be above 0.02% to provide the intended effect but below 0.18% in order for the carbide structure not to age too rapidly.
  • Nitrogen is added in contents exceeding 0.02% for the desired formation of carbonitrides but below 0.18% to avoid ageing by the growth of carbonitride precipitations.
  • the total carbon and nitrogen content ( [%C] + [%N] ) is adapted to between 0.12 and 0.22% to prevent carbonitrides and chromium carbides to coarsen too rapidly.
  • the total carbon and nitrogen content is adapted to be between 0.14 and 0.20%.
  • Silicon should be added i a content of at least 0.05% to provide the desired effect as deoxidant . However, the silicon content should net exceed 0.5% since silicon promotes the formation cf deitaferrite and Laves' phase.
  • the content of manganese should not be below 0.05% in order to bind oxygen and sulphur in the intended manner and not exceed 1.0% in order not to reduce the impact strength.
  • the chromium content should not be below 9.0% to provide the desired corrosion resistance, nor exceed 12.0% to avoid the formation of deltaferrite .
  • the nickel content should not be below 0.1% to suppress the formation of deltaferrite in the intended manner and not exceed 1.5% in order not to risk carbide coarsening, which is accelerated by nickel.
  • Molybdenum and tungsten are added in contents amounting tc at least 0.6% each to raise the strength of the matrix r>y solution hardening and to increase the stability of the chromium carbides.
  • molybdenum and tungsten contribute to an increase of the corrosion resistance.
  • the content of either is not allowed to exceed 1.4%, in order not to risk reduction of the creep strength and the ducti ⁇ lity during long periods.
  • the molybdenum equivalent, ( [%Mo]+0.5 [%W] ) is adapted within an interval of between 1.1% and 1.9% to obtain optimum creep properties at current temperatures.
  • the molybdenum equivalent is adapted to amount to between 1.3 and 1.7%.
  • the boron content is lower than 0.01% (100 ppm) . In one embodiment of the invention, the boron content is adapted to between 0.0005% (5 ppm) and 0.0100% (100 ppm) .
  • the vanadium content should not be below 0.1% to obtain the desired finely dispersed precipitation of carbonitrides and not exceed 0.3% in order not to provide too fast a coarse ⁇ ning of carbonitrides .
  • the niobium content should not be below 0.02% to obtain the desired finely dispersed precipitation of carbonitrides and not exceed 0.10% in order not to provide too fast a coarsening of carbonitrides .
  • titanium, zirconium, hafnium and tantalum which are added as supplements to or partially to replace niobium and vanadium, that is, to form finely dispersed carbonitride precipitations, are limited according to the below:
  • the content of Ti should not exceed 0.1%, the content of Zr should not exceed 0.1%, the content of Hf should not exceed 0.2%, and the content of Ta should not exceed 0.2%
  • the total content of titanium, niobium, tantalum and hafnium expressed as ( [%Ti) + [%Nb]+0.5[%Ta]+0.5 [%Hf] ) , is adapted to amount to at most 0.15%.
  • the fully dense body is manufactured by gas-atomizing a steel melt of the specified composition into a homogeneous, essentially segregation-free steel powder with a grain size of at most 1 mm.
  • This steel powder is filled into a deformable container which is evacuated and essentially gas-tightly sealed before it and its contents of steel powder are consolidated by means of hot isostatic pressing or a combination of isostatic pressing and subsequent hot working, such as forging or extrusion, intc an essentially fully dense body.
  • the container containing the powder is consolidated by hot isostatic pressing, at a temperature cf 1050-1200°C and a pressure of 75-150 MPa, into a density exceeding 99% of the theoretical density of the steel.
  • the container containing the powder is consolidated at a temperature of 1125-1175°C and a pressure of 90-110 MPa into a density exceeding 99.9% of the theoretical density of the steel.
  • the container containing the powder may be consolidated by cold isostatic pressing followed by hot working such as hot forging, hot extrusion or hot rolling into essentially full density.
  • the powder is preferably consolidated into components for use at elevated temperature within the energy region, such as turbine components, for example rotors, turbine discs, turbine blades and valves or components for steam and heat generation, for example pipes, pipe parts, tubes, valves, and steam collectors .
  • turbine components for example rotors, turbine discs, turbine blades and valves
  • components for steam and heat generation for example pipes, pipe parts, tubes, valves, and steam collectors .
  • the powder is rapidly solidified by means of gas atomization into a fine powder, the segregation problem is avoided and a homogeneous, essentially segregation-free steel powder is obtained.
  • nozzle parameters, atomizing gas and other process parameters during the gas atomization a powder with the desired grain size distribution is obtained.
  • Components manufactured according to the invention are primarily intended to be used for a long time at elevated temperatures, preferably within tne temperature interval 550-630°C. Therefore, after consolidation and any sub- sequent working, the steel is usually tempered at tempe ⁇ ratures within the interval 650-800°C.
  • the manufacture of fully dense bodies of a martensitic 9-12% Cr steel according to the invention also comprises conventional measures taken during powdermetallurgical manufacture to ensure or check the quality, adjust dimensions, etc., with regard to the powder, the semi-manufactures, and/or the finished product.

Abstract

A method of powdermetallurgically manufacturing a fully dense body of a high temperature martensitic chrome steel. A melt with an optimized composition (percentage by weight) of C 0.02 - 0.18 %; Si 0.05 - 0.5 %; Mn 0.05 - 1.0 %; Cr 9.0 - 12.0 %; Ni 0.1 - 1.5 %; Mo 0.6 - 1.4 %; W 0.6 - 1.4 %; V 0.1 - 0.3 %; Nb 0.02 - 0.10 %; N 0.02 - 0.18 %; B up to 0.01 %; Ti up to 0.1 %; Zr up to 0.1 %; Hf up to 0.2 %; Ta up to 0.2 %, the balance being Fe, and conventional impurities for this type of steel in conventional contents,is gas-atomized into a steel powder with a grain size of at most 1 mm. The contents of allowing elements included therein is adapted such that the molybdenum equivalent, expressed as ([%Mo]+0.5[%W]), amounts to between 1.1 and 1.9 %, the total carbon and nitrogen content, ([%C]+[%N]), amounts to between 0.12 and 0.22 % and the total content of titanium, niobium, tantalum and hafnium, expressed as ([%Ti]+[%Nb]+0.5[%Ta]+0.5[%Hf]), amounts to at most 0.15 %. The powder is filled into a deformable container which is evacuated and essentially gas-tightly sealed before the container with the contained powder is consolidated into an essentially fully dense body by hot isostatic pressing or a combination of isostatic pressing and subsequent hot working.

Description

Method of po dermetallurgically manufacturing fully dense bodies from high temperature martensltic Cr steel
TECHNICAL FIELD
The invention relates to a method manufacturing fully dense bodies of a high temperature martensitic Cr steel, a number of material properties, preferably properties at elevated temperatures, being improved through a well balanced composition and powdermetallurgical manufacture. The steel is manufactured by gas atomization into a steel powder, which is consolidated into bodies of essentially full density by hot isostatic pressing or a combination of isostatic pressing and subsequent hot working.
BACKGROUND ART
With rising oil prices considerable effort has been expended during the last few decades on achieving a more efficient energy utilization. A measure with great effect is to increase the temperature in the energy conversion processes . This, in turn, requires new materials with improved high temperature properties.
One important material group are martensitic 9-12% Cr steels, which are attractive because of their high strength, low thermal expansion, good thermal conductivity, good ability to withstand stress corrosion and good damping properties .
Components of high temperature martensitic Cr steel with application within the energy field, for example in the generation of heat and electricity, are presently manufac¬ tured substantially with conventional ingot-based technique. One condition for a steel component of the stated type to receive the desired properties, primarily in connection with long-term use, that is, operating times of the order of magnitude of 100,000 hours or more in the temperature interval 550-630°C, is that the microstructure does not aσe too rapidly. This,- in turn, requires that the analysis is carefully balanced within certain intervals and that the material is given a good homogeneous composition. These requirements cannot be met with conventional methods such as ϊ ingot casting, ESR re elting, etc, especially for the materials mentioned, which contains elements which are prone to segregation, such as , S , E, Mo and K. The diffi¬ culties increase with the dimension of the casting.
C Extensive development work has taken place, primarily withir. the scope of the conventional steel technique, to improve the alloying composition of this type of alloys. Alloys with compositions varying according to the following have been produced:
C 0.C5 - 0.25% Si 0.05 - 1.0%
Mn 0.05 - 2.0% Cr 8 - 15%
Ni 0.1 - 2.0% Mo 0.05 - 3.5%
W up to 2.5% V 0.1 - 0.5% 0 Nb up to 0.5% N 0.01 - 0.3%
B up to 0.01% Ti up to 0.1%
Zr up to 0.01% Hf up to 0.1%
Ta up to 0.5%, the balance being Fe and conventional impu¬ rities for this type of steel in conventional contents. The 5 alloying elements included have been added based on the following.
Carbon is added in order for martensite to form in the matrix and in orαer to form, together with Cr, Mo, W, No and 0 V ana possibly Ti, Zr, Hf and Ta, carbides and/or carbo- nitrides .
Silicon is added as αeoxidan .
"3 : Manganese is added preferably to bind oxygen and sulphur
Figure imgf000004_0001
forminσ MnS and MnO. Chromium is added to obtain resistance to oxidation and wet corrosion and to form stable chromium carbides during tempe¬ ring.
Nickel is added to suppress the formation of deltaferrite .
Molybdenum and tungsten are added to increase the strength by solution hardening and to increase the stability of the chromium carbides. In addition, molybdenum and tungsten increase the corrosion resistance.
Vanadium is added to form a finely dispersed precipitation cf carbonitride .
Niobium is added to form a finely dispersed precipitaticn cf carbonitride .
Nitrogen is added to form stable carbonitride precipitations with vanadium and niobium.
Boron is added to increase the creep rupture strength,
Titanium, zirconium, -hafnium and tantalum are added as supplement to or to partially replace Nb and V, that is, tc form finely dispersed carbonitride precipitations.
With the above materials, however, the desired improvements are not achieved, above all regarding properties such as impact strength, yield point, fatigue properties, creep properties in the temperature range 500-600°C as well as stress corrosion properties in steel manufactured with an analysis according to the above.
SUMMARY CF TEΞ INVENTION
According to the present invention, an additional optimi¬ zation is required of the composition relating to important alloying elements such as carbon, chromium, molybdenum, tungsten, and boron, which according to the invention have been identified as key elements for which small changes in content are noticeably reflected in the properties of the material. In addition, important alloying elements such as carbon, chromium, molybdenum, tungsten and boron are greatly prone to segregation, which in connection with the solidi¬ fication may result in the formation of residual melt regions, sometimes in the form of eutectics, with higher contents of the segregation-prone alloying materials, or in the occurrence of other serious defects such as residual porosity, residual ferrite, or cracks. Therefore, according to the invention, a steel powder s manufactured by gas atomization of the melt into a fine homogeneous and essen¬ tially segrega ion-free powder, which by subsequent hot- isostatic pressing or isostatic pressing followed by hot working is consolidated into an essentially dense body. In addition, by the careful inspection of the boron content and the avoidance of boron segregation, the tendency for crack¬ ing during a possible hot working, which normally occurs in conventionally manufactured material of this type as a con¬ sequence of boron segregation providing variations in the boron content within the body, is eliminated.
According to the invention, a fully dense body is manufactured from a high temperature martensitic chrome steel by means of powdermetallurgical methods, whereby a steel melt with the following optimized composition (percen¬ tage by weight)
C 0.02 - 0.18% Si 0.05 - 0.5%
Mn 0.05 - 1.0% Cr 9.0 - 12.0%
Ni 0.1 - 1.5% Mo 0.6 - 1.4%
W 0.6 - 1.4% V 0.1 - 0.3%
Nb 0.02 - 0.10% N 0.02 - 0.18% B up to 0.01% Ti up to 0.1%
Zr up to 0.1% Hf up to 0.2%
Ta up to 0.2%, the balance being Fe, and conventional impurities for this type of steel in conventional contents, is atomized by means of gas atomization, into an essentially segregation-free steel powder with a powder particle size of at most 1 mm. The contents of certain alloying elements included are adapted such that the molybdenum equivalent, 5 expressed as ( [%Mo] + 0.5 [%W]), amounts to between 1.1 and 1.9%, that the total carbon and nitrogen content, ([%C] + [%N]), amounts to between 0.12 and 0.22% and that the total content of titanium, niobium, tantalum and hafnium, expressed as ( [%Ti] + [%Nb] + 0.5 [%Ta] + 0.5 [%Hf]), C amounts to at most 0.15%. The steel powder obtained is filled into a deformable container, which is evacuated and essentially gas-tightly sealed before the container containing the powder is consolidated into an essentially fully dense body by hot isostatic pressing or by a combination of isostatic pressing and subsequent hot - working .
According to the optimization which the invention entails, the carbon content should be above 0.02% to provide the intended effect but below 0.18% in order for the carbide structure not to age too rapidly.
Nitrogen is added in contents exceeding 0.02% for the desired formation of carbonitrides but below 0.18% to avoid ageing by the growth of carbonitride precipitations.
According to the invention, the total carbon and nitrogen content, ( [%C] + [%N] ) , is adapted to between 0.12 and 0.22% to prevent carbonitrides and chromium carbides to coarsen too rapidly. In one embodiment of the invention, the total carbon and nitrogen content is adapted to be between 0.14 and 0.20%.
Silicon should be added i a content of at least 0.05% to provide the desired effect as deoxidant . However, the silicon content should net exceed 0.5% since silicon promotes the formation cf deitaferrite and Laves' phase. The content of manganese should not be below 0.05% in order to bind oxygen and sulphur in the intended manner and not exceed 1.0% in order not to reduce the impact strength.
The chromium content should not be below 9.0% to provide the desired corrosion resistance, nor exceed 12.0% to avoid the formation of deltaferrite .
The nickel content should not be below 0.1% to suppress the formation of deltaferrite in the intended manner and not exceed 1.5% in order not to risk carbide coarsening, which is accelerated by nickel.
Molybdenum and tungsten are added in contents amounting tc at least 0.6% each to raise the strength of the matrix r>y solution hardening and to increase the stability of the chromium carbides. In addition, molybdenum and tungsten contribute to an increase of the corrosion resistance. The content of either is not allowed to exceed 1.4%, in order not to risk reduction of the creep strength and the ducti¬ lity during long periods. According to the invention, the molybdenum equivalent, ( [%Mo]+0.5 [%W] ) , is adapted within an interval of between 1.1% and 1.9% to obtain optimum creep properties at current temperatures. According to one embodiment of the invention, the molybdenum equivalent is adapted to amount to between 1.3 and 1.7%.
Boron is added to provide the desired increase of the creep rupture strength. In order not to deteriorate the ductility at creep rupture or the weld properties, according to the invention the boron content is lower than 0.01% (100 ppm) . In one embodiment of the invention, the boron content is adapted to between 0.0005% (5 ppm) and 0.0100% (100 ppm) .
The vanadium content should not be below 0.1% to obtain the desired finely dispersed precipitation of carbonitrides and not exceed 0.3% in order not to provide too fast a coarse¬ ning of carbonitrides . The niobium content should not be below 0.02% to obtain the desired finely dispersed precipitation of carbonitrides and not exceed 0.10% in order not to provide too fast a coarsening of carbonitrides .
The contents of titanium, zirconium, hafnium and tantalum, which are added as supplements to or partially to replace niobium and vanadium, that is, to form finely dispersed carbonitride precipitations, are limited according to the below:
the content of Ti should not exceed 0.1%, the content of Zr should not exceed 0.1%, the content of Hf should not exceed 0.2%, and the content of Ta should not exceed 0.2%
in order not to bind too much carbon and nitrogen. In addition, according to the invention, the total content of titanium, niobium, tantalum and hafnium, expressed as ( [%Ti) + [%Nb]+0.5[%Ta]+0.5 [%Hf] ) , is adapted to amount to at most 0.15%.
One condition for achieving the desired properties and keeping the close analyses defined according to the invention is that the fully dense body is manufactured by gas-atomizing a steel melt of the specified composition into a homogeneous, essentially segregation-free steel powder with a grain size of at most 1 mm. This steel powder is filled into a deformable container which is evacuated and essentially gas-tightly sealed before it and its contents of steel powder are consolidated by means of hot isostatic pressing or a combination of isostatic pressing and subsequent hot working, such as forging or extrusion, intc an essentially fully dense body.
In one embodiment, the container containing the powder is consolidated by hot isostatic pressing, at a temperature cf 1050-1200°C and a pressure of 75-150 MPa, into a density exceeding 99% of the theoretical density of the steel. Preferably, the container containing the powder is consolidated at a temperature of 1125-1175°C and a pressure of 90-110 MPa into a density exceeding 99.9% of the theoretical density of the steel. Alternatively, the container containing the powder may be consolidated by cold isostatic pressing followed by hot working such as hot forging, hot extrusion or hot rolling into essentially full density.
The powder is preferably consolidated into components for use at elevated temperature within the energy region, such as turbine components, for example rotors, turbine discs, turbine blades and valves or components for steam and heat generation, for example pipes, pipe parts, tubes, valves, and steam collectors .
Since the powder, according to the invention, is rapidly solidified by means of gas atomization into a fine powder, the segregation problem is avoided and a homogeneous, essentially segregation-free steel powder is obtained. By adapting nozzle parameters, atomizing gas and other process parameters during the gas atomization, a powder with the desired grain size distribution is obtained. In the pro- duction of a segregation-free steel powder for manufacture of fully dense bodies by isostatic pressing, this means that the powder particle size is considerably below 1 mm.
By manufacturing the bodies by isostatic pressing, prefe- rably by not isostatic pressing, it is ensured that the residual porosity is very low, practically negligible, and that associated defects and deficiencies are essentially eliminated.
Components manufactured according to the invention are primarily intended to be used for a long time at elevated temperatures, preferably within tne temperature interval 550-630°C. Therefore, after consolidation and any sub- sequent working, the steel is usually tempered at tempe¬ ratures within the interval 650-800°C.
It is self-evident that the manufacture of fully dense bodies of a martensitic 9-12% Cr steel according to the invention also comprises conventional measures taken during powdermetallurgical manufacture to ensure or check the quality, adjust dimensions, etc., with regard to the powder, the semi-manufactures, and/or the finished product.

Claims

1. A method of powdermetallurgically manufacturing a fully dense body of a high temperature martensitic chrome steel, characterized in that a melt with an optimized composition (percentage by weight) of
C 0.02 - 0.18% Si 0.05 - 0.5%
Mn 0.05 - 1.0% Cr 9.0 - 12.0% Ni 0.1 - 1.5% Mo 0.6 - 1.4%
W 0.6 - 1.4% V 0.1 - 0.3%
Nb 0.02 - 0.10% K 0.02 - 0.18%
B up to 0.01% T up to 0.1%
Zr up to 0.1% Hf up to 0.2% Ta up to 0.2%, the balance being Fe, and conventional impurities for this type of steel in conventional contents, is gas-atomized into a steel powder with a grain size of at most 1 mm, wherein the contents of certain alloying elements included therein are adapted such that the molybdenum equi- valent, expressed as ([%Mo] + 0.5[%W]), amounts to between 1.1 and 1.9%, the total carbon and nitrogen content, ([%C]+[%N]), amounts to between 0.12 and 0.22%, and the total content of titanium, niobium, tantalum and hafnium, expressed as ( [%Ti]+ [%Nb] +0.5 [%Ta]+0.5 [%Hf] ) , amounts to at most 0.15%, whereupon said powder is filled into a defor- mable container which is evacuated and essentially gas- tightly sealed before the container with the contained powder is consolidated into an essentially fully dense body by hot isostatic pressing or a combination of isostatic pressing and subsequent hot working.
2. A method according to claim 1, characterized in that tne molybdenum equivalent is adapted to amount to between 1.3 and 1.7%.
3. A method according to claim 1 or claim 2, characterized in that the total carbon and nitrogen content is adapted to amount to between 0.14 and 0.20%.
4. A method according to claim 1, claim 2 or claim 3, characterized in that the boron content is adapted to amount to between 5 ppm and 100 ppm.
5. A method according to any of the preceding claims, characterized in that the container with the contained powder is consolidated into a body with a density exceeding 99% of the theoretical density of the steel by hot isostatic pressing, at a temperature of 1050-1200°C and a pressure of 75-150 MPa.
6. A method according to any of the preceding claims, characterized in that the powder is consolidated into turbine components, for example rotors, turbine discs, turbine blades and valves .
7. A method according to any of claim 1 to claim 5, characterized in that the powder is consolidated into components for steam and heat generation, for example pipes, pipe parts, tubes, valves and steam collectors.
PCT/SE1991/000454 1990-06-28 1991-06-25 METHOD OF POWDERMETALLURGICALLY MANUFACTURING FULLY DENSE BODIES FROM HIGH TEMPERATURE MARTENSITIC Cr STEEL WO1992000158A1 (en)

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EP0642877A1 (en) * 1993-03-10 1995-03-15 Nippon Steel Corporation Inert-gas arc welding wire for high-chromium ferritic heat-resisting steel
GB2368849A (en) * 2000-11-14 2002-05-15 Res Inst Ind Science & Tech Martensitic stainless steel
WO2002048418A1 (en) * 2000-12-11 2002-06-20 Uddeholm Tooling Aktiebolag Steel alloy, holders and holder details for plastic moulding tools, and tough hardened blanks for holders and holder details
US6793744B1 (en) 2000-11-15 2004-09-21 Research Institute Of Industrial Science & Technology Martenstic stainless steel having high mechanical strength and corrosion
US8808472B2 (en) 2000-12-11 2014-08-19 Uddeholms Ab Steel alloy, holders and holder details for plastic moulding tools, and tough hardened blanks for holders and holder details
WO2022083928A1 (en) * 2020-10-23 2022-04-28 Siemens Energy Global GmbH & Co. KG Martensitic steel with retarded z phase formation, powder and blank or component

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EP0118702A1 (en) * 1983-02-08 1984-09-19 Asea Ab Method of manufacturing a body from powdery material by isostatic pressing
EP0164678A1 (en) * 1984-06-05 1985-12-18 Alsthom Steel for the manufacture of large forgings and process for the treatment of this steel
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EP0118702A1 (en) * 1983-02-08 1984-09-19 Asea Ab Method of manufacturing a body from powdery material by isostatic pressing
EP0164678A1 (en) * 1984-06-05 1985-12-18 Alsthom Steel for the manufacture of large forgings and process for the treatment of this steel
EP0188995A1 (en) * 1984-10-17 1986-07-30 Mitsubishi Jukogyo Kabushiki Kaisha High chromium cast steel for high-temperature pressure container and method for the thermal treatment thereof

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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0642877A1 (en) * 1993-03-10 1995-03-15 Nippon Steel Corporation Inert-gas arc welding wire for high-chromium ferritic heat-resisting steel
EP0642877B1 (en) * 1993-03-10 2003-06-04 Nippon Steel Corporation Inert-gas arc welding wire for high-chromium ferritic heat-resisting steel
GB2368849A (en) * 2000-11-14 2002-05-15 Res Inst Ind Science & Tech Martensitic stainless steel
GB2368849B (en) * 2000-11-14 2005-01-05 Res Inst Ind Science & Tech Martensitic stainless steel having high mechanical strength and corrosion resistance
US6793744B1 (en) 2000-11-15 2004-09-21 Research Institute Of Industrial Science & Technology Martenstic stainless steel having high mechanical strength and corrosion
WO2002048418A1 (en) * 2000-12-11 2002-06-20 Uddeholm Tooling Aktiebolag Steel alloy, holders and holder details for plastic moulding tools, and tough hardened blanks for holders and holder details
US8808472B2 (en) 2000-12-11 2014-08-19 Uddeholms Ab Steel alloy, holders and holder details for plastic moulding tools, and tough hardened blanks for holders and holder details
WO2022083928A1 (en) * 2020-10-23 2022-04-28 Siemens Energy Global GmbH & Co. KG Martensitic steel with retarded z phase formation, powder and blank or component

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