EP0149210B1 - Verfahren zum Herstellen hochfester, duktiler Körper aus Kohlenstoffreichen Eisenbasislegierungen - Google Patents

Verfahren zum Herstellen hochfester, duktiler Körper aus Kohlenstoffreichen Eisenbasislegierungen Download PDF

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Publication number
EP0149210B1
EP0149210B1 EP84116080A EP84116080A EP0149210B1 EP 0149210 B1 EP0149210 B1 EP 0149210B1 EP 84116080 A EP84116080 A EP 84116080A EP 84116080 A EP84116080 A EP 84116080A EP 0149210 B1 EP0149210 B1 EP 0149210B1
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EP
European Patent Office
Prior art keywords
iron
carbon
powder
process step
less
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP84116080A
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German (de)
English (en)
French (fr)
Other versions
EP0149210A2 (de
EP0149210A3 (en
Inventor
Barry Leslie Prof. Dr. Mordike
Hans Wilhelm Dr.-Ing. Bergmann
Georg Prof. Dr. Frommeyer
Karl-Ulrich Dr. Kainer
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
ROBERT ZAPP WERKSTOFFTECHNIK GmbH and CO KG
Original Assignee
ROBERT ZAPP WERKSTOFFTECHNIK GmbH and CO KG
Robert Zapp Werkstofftechnik & Co KG GmbH
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Publication of EP0149210A2 publication Critical patent/EP0149210A2/de
Publication of EP0149210A3 publication Critical patent/EP0149210A3/de
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    • 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
    • B22F9/10—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 using centrifugal force
    • 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

Definitions

  • the invention relates to a method for producing high-strength, ductile bodies from carbon-rich iron-based alloys, in which a molten iron-based alloy is quenched, atomized and thermomechanically compressed.
  • end products are desired that have a high strength on the one hand, on the other hand, they are also characterized by favorable ductility parameters.
  • the heat treatment of the steel or iron or the workpieces made from it i.e. the thermal treatment of the metal in the solid state.
  • a grain refinement is achieved by annealing at approx. 800 - 950 ° C and then quenching, which requires a significant increase in strength, but at the same time also increases the brittleness of the workpiece. Subsequent quenching and tempering (for example by so-called tempering) will then cause the workpiece to lose some strength again, but favorable ductility and homogeneity properties can be achieved.
  • thermomechanical treatment processes particularly for micro-alloyed structural steels, have recently come to the fore.
  • These metals dissolve and, on the other hand, they can be eliminated again specifically, allows the effects of very fine carbonitride particles on the structure and the mechanical properties of the rolled products to be exploited.
  • the carbonitrides When the carbonitrides are precipitated in austenite in a relatively fine form during the subsequent austenite transformation, they act as germs and act as a brake against the migration of the phase and grain boundaries.
  • thermomechanical technologies as described, for example, by Kaspar et. al. in “Stahl und Eisen” 101 (1981), 721 "Metallurgical processes during preheating and pre-rolling of microalloyed structural steels" all refer to weldable, i.e. low-carbon steels or iron alloys.
  • unalloyed and alloyed cast iron ie iron with a carbon content of more than 1.7% by weight
  • the plastic deformability of carbon-rich cast iron alloys is only 1 - 2%. The reason for this is in particular the relatively high volume fraction of carbides (V carbide ⁇ 33%) or the amount, shape and distribution of the carbon separated out as graphite.
  • a two-stage powder metallurgical process is also known from British Patent Application 2 116 207, in which a melt is atomized at a high cooling rate and the powder is then thermomechanically treated, that is to say hot consolidated.
  • a melt or powder comes with it for use, which contains 0.1 to 1.5% boron. Boron improves supercooling and promotes the formation of a homogeneous and metastable crystallized structure when the melt is atomized with a high cooling rate.
  • the melt or alloy contains in principle neither manganese, nor silicon and nickel, which can at best be considered impurities.
  • the invention has for its object to apply the aforementioned method to another alloy powder and to show a way of producing workpieces from carbon-rich iron-based alloys which have both a particularly high strength and particularly advantageous ductile properties.
  • This object is achieved by a method of the type mentioned in the introduction, in which, according to the invention, an alloy with over 1.7% carbon, over 3.0% nickel and / or manganese, up to 15% chromium and / or cobalt and individually or side by side to 1 % Boron, tellurium, bismuth, selenium, antimony, titanium, niobium, magnesium and phosphorus as well as optionally 2 to 4% silicon, the rest iron is atomized to an average particle diameter of less than 30 ⁇ m and then thermomechanically compressed.
  • thermomechanical compression either temperatures below 720 ° C., preferably 650 ° C., are to be regarded as particularly advantageous in the sense of the invention, or the thermomechanical treatment can also be carried out at normal annealing temperatures of 850 to 1000 ° C.
  • the first stage of the process the quenching and atomization of the molten metal in such a way that powder particles with a diameter of less than 30 ⁇ m are formed, has the effect that the structure structures obtained by normal solidification conditions, such as coarse dendrites and / or acicular carbides, are changed in favor of a fine crystalline structure.
  • This process section is preferably carried out according to the so-called "rapid solidification technology", a temperature gradient of, for example, 104 - 104 K / s being selected. With such a quenching rate, extremely high germination rates can be achieved, however, to keep the germ growth very low due to the short crystallization time until the solid phase is reached.
  • the quenching rate should be chosen depending on the alloy and the particular process so that particles with an average diameter that is smaller than 30 microns are available for the second process stage and the phases of the structure that forms in the particles unite Have a diameter that is less than 0.1 microns.
  • the quenching according to an exemplary embodiment of the invention is particularly advantageous if additives such as tellurium, bismuth, selenium or antimony, in amounts of up to 1% by weight, achieve a higher supercooling of the melt.
  • the rapid cooling from the homogeneous melting phase has the further consequence that the crystals formed do not precipitate out in the total weight composition, since the short diffusion times available are not sufficient to bring about complete segregation.
  • a preferred method for carrying out the first method step according to the teaching of the invention is the so-called “melt spinning” method known for low-carbon steels.
  • the melt which is saturated with carbon due to its high solubility at high temperatures, is atomized and at the same time extremely quenched, which causes the small particles formed to freeze due to the short diffusion times.
  • the carbon dissolved in the melt cannot separate out in the form of graphite, but on the other hand, precipitation in carbide form is only fine-grained possible or even completely excluded if suitable additional alloying elements are added.
  • a preferred embodiment of the invention provides that after the completion of the first process stage and before the start of the thermomechanical treatment, the powders are pre-compacted in an intermediate stage to form a blank and / or are encased in a metal container. It can also be provided that the powders are sifted to a grain size of less than 30 microns after atomization. Furthermore, it can be provided that the powders are subjected to a reducing annealing before they are compacted, optionally with deoxidizing additives being added.
  • the invention teaches in a first embodiment to work in a temperature range below the A 1 temperature.
  • the metastable ⁇ phase and the martensite phase in finely disperse cementite with a grain size can be obtained by hot isostatic pressing, forging or extrusion at temperatures between 600 ° C and 720 ° C, preferably in the range around 650 ° C below 0.5 ⁇ m and fine-grained ferrite with a particle size below 2 ⁇ m can be converted.
  • the dendritic microstructure is simultaneously molded into a finely crystalline, equiaxial structure made of spherodized, dispersed carbides in the ferrite.
  • the volume fraction of the Carbide particles for example, is over 50% and thus forms the matrix of these high-carbon iron-based alloys.
  • this iron-based alloy is adjusted by adding up to 1% by weight of boron to the iron-based alloy in such a way that the powders produced therefrom by the first process step according to the invention also at temperatures between 850 ° C. - 1000 ° C, ie at "normal" processing temperatures, can be treated thermomechanically, since the addition of boron reduces the carbon solubility of the austenite. Materials of ferrite and carbide are then produced in such a process.
  • the alloy can also be adjusted by adding nickel and / or manganese, in an order of magnitude greater than 3% by weight, so that iron-based materials with a purely austenitic structure are formed. Also leave these iron base materials treat themselves thermomechanically at normal processing temperatures.
  • iron-based alloy is that silicon is added in an order of magnitude of 2-4% by weight to the melt, so that a material with a bainitic matrix and carbides is produced, which is also found in the previous examples mentioned temperatures can be treated.
  • superplasticity can be achieved in the temperature range between 600 ° C and 720 ° C with deformation values of up to 1,300% with high strength at the same time.
  • the structure, structure, hardness and ductility were tested in the strips obtained.
  • the samples were produced according to the so-called "melt spinning” process.
  • the fracture appearance of tempered samples is different from that of the as-quenched sample.
  • the samples with a content of 6% by weight of chromium and 3% by weight of carbon have different properties after an annealing treatment in that the fracture no longer runs along the former dendrite grain boundaries.
  • the samples were produced by the powder atomization method, which allows large quantities of rapidly quenched material to be produced, so that further processing by means of powder metallurgical techniques is possible.
  • Creep properties in the temperature range between 500 and 720 ° C were investigated on rapidly quenched strips of Fe-Cr-C alloys. This leads to changes during heating in the form of changes in length, which are due to the residual austenite transformation, precipitations, etc. (1st-3rd tempering stage). Such falsifying effects can be eliminated by heating once at 10 K / min.
  • the change in length depending on the temperature in the temperature range of 500 - 600 ° C indicates a normal dislocation creep. In the temperature range of 600 to 650 ° C, however, the creep speed drops. This is due on the coagulation of cementite. Above 650 ° C, up to around 720 ° C, effects are obtained which indicate superplasticity.
  • the compacting and compacting of the extremely rapidly quenched Fe-C-Cr powder by a combination of powder metallurgical and thermomechanical process techniques, namely hot isostatic pressing and rolling just below the A 1 transformation temperature, causes profound structural changes in the structure. These consist in the transformation of the metastable ⁇ phase and the martensite into finely disperse cementite with a grain size of less than 0.5 ⁇ m and fine-grained ferrite with a grain size of less than 2 ⁇ m.
  • the dendritic microstructure is molded into a finely crystalline, equiaxial structure made of spherodized, dispersed carbides in the ferrite.
  • FIG. 2 shows a scanning electron microscope micrograph of the equiaxial microstructure of the compacted and thermomechanically treated high-carbide iron alloys.
  • the volume fraction of the carbide particles is approximately 56 vol .-% and thus represents the matrix phase of this high-carbon iron-based alloy.
  • the yield stresses and compressive strengths of the two alloys produced according to the invention are different from one another.
  • the higher strength values of the chromium-rich alloy are due to the structurally more stable, fine-crystalline structure after the thermomechanical treatment.
  • the predominant content of chromium is dissolved in the cementite, stabilizes the carbides and prevents undesired carbide growth.
  • a strength-increasing contribution due to the solid solution hardening of the ferrite by the chromium dissolved in the ⁇ -iron can be assumed.
  • the optimal superplastic deformation temperature is about 650 ° C.
  • the diffusion-controlled accommodation mechanisms of grain boundary sliding are sufficiently thermally activated, and at this temperature the microstructure is stable against a stress or strain-induced grain growth of the cementite and ferrite phase. This applies in particular to the chromium-containing alloy.
  • Superplastic materials are generally characterized by high amounts of uniform expansion. In the fracture zone, however, local constrictions can often be found, which are caused by the plastomechanical instabilities due to local hardening processes.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Powder Metallurgy (AREA)
EP84116080A 1983-12-21 1984-12-21 Verfahren zum Herstellen hochfester, duktiler Körper aus Kohlenstoffreichen Eisenbasislegierungen Expired - Lifetime EP0149210B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19833346089 DE3346089A1 (de) 1983-12-21 1983-12-21 Verfahren zum herstellen hochfester, duktiler koerper aus kohlenstoffreichen eisenbasislegierungen
DE3346089 1983-12-21

Publications (3)

Publication Number Publication Date
EP0149210A2 EP0149210A2 (de) 1985-07-24
EP0149210A3 EP0149210A3 (en) 1987-07-29
EP0149210B1 true EP0149210B1 (de) 1992-04-29

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EP84116080A Expired - Lifetime EP0149210B1 (de) 1983-12-21 1984-12-21 Verfahren zum Herstellen hochfester, duktiler Körper aus Kohlenstoffreichen Eisenbasislegierungen

Country Status (2)

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EP (1) EP0149210B1 (enrdf_load_stackoverflow)
DE (2) DE3346089A1 (enrdf_load_stackoverflow)

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6033343A (ja) * 1983-08-03 1985-02-20 Nippon Piston Ring Co Ltd 耐摩耗性焼結合金
JPH0610321B2 (ja) * 1985-06-17 1994-02-09 日本ピストンリング株式会社 耐摩耗性焼結合金
DE3544759A1 (de) * 1985-12-18 1987-06-19 Zapp Robert Werkstofftech Verfahren zum herstellen von werkzeugen
JP3077410B2 (ja) * 1992-07-29 2000-08-14 アイシン精機株式会社 ターボチャージャのタービンハウジング
EP0808681A4 (en) * 1995-10-18 1999-12-29 Kawasaki Steel Co IRON POWDER FOR POWDER METALLURGY, METHOD FOR THE PRODUCTION THEREOF, AND IRON-BASED POWDER MIXTURE FOR POWDER METALLURGY
JP3694732B2 (ja) * 2000-05-16 2005-09-14 独立行政法人産業技術総合研究所 高硬度高クロム鋳鉄粉末合金の製造方法

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE317522B (enrdf_load_stackoverflow) * 1968-04-16 1969-11-17 Hoeganaes Ab
JPS599615B2 (ja) * 1974-09-25 1984-03-03 株式会社リケン 超塑性を有する強靭球状黒鉛鋳鉄及び熱処理方法
US3951697A (en) * 1975-02-24 1976-04-20 The Board Of Trustees Of Leland Stanford Junior University Superplastic ultra high carbon steel
SE7612279L (sv) * 1976-11-05 1978-05-05 British Steel Corp Finfordelat glodgat stalpulver, samt sett att framstella detta.
US4331478A (en) * 1979-02-09 1982-05-25 Scm Corporation Corrosion-resistant stainless steel powder and compacts made therefrom
BR8200106A (pt) * 1982-01-11 1983-09-13 Metal Leve Sa Processo para fabricacao de porta-aneis por metalurgia do po,a partir de ligas ferrosas austeniticas
GB2116207A (en) * 1982-03-02 1983-09-21 Marko Materials Inc Improved tool steels which contain boron and have been processed using a rapid solidification process and method

Also Published As

Publication number Publication date
DE3346089A1 (de) 1985-07-18
DE3346089C2 (enrdf_load_stackoverflow) 1988-01-14
EP0149210A2 (de) 1985-07-24
EP0149210A3 (en) 1987-07-29
DE3485689D1 (de) 1992-06-04

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