EP0467857B1 - Pulvermetallurgische Werkzeugstähle - Google Patents

Pulvermetallurgische Werkzeugstähle Download PDF

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Publication number
EP0467857B1
EP0467857B1 EP91830235A EP91830235A EP0467857B1 EP 0467857 B1 EP0467857 B1 EP 0467857B1 EP 91830235 A EP91830235 A EP 91830235A EP 91830235 A EP91830235 A EP 91830235A EP 0467857 B1 EP0467857 B1 EP 0467857B1
Authority
EP
European Patent Office
Prior art keywords
steel
powder
temperature
bath
salt
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
EP91830235A
Other languages
English (en)
French (fr)
Other versions
EP0467857A1 (de
Inventor
Fabio Guglielmi
Giovanni Barcaro
Paolo Sommovigo
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.)
Centro Sviluppo Materiali SpA
Original Assignee
Centro Sviluppo Materiali SpA
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Filing date
Publication date
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Publication of EP0467857A1 publication Critical patent/EP0467857A1/de
Application granted granted Critical
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Anticipated expiration legal-status Critical
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Classifications

    • 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%
    • 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%
    • C22C33/0292—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 more than 5% preformed carbides, nitrides or borides

Definitions

  • the present invention concerns PM. More precisely it concerns a composition designed specifically for Hot Isostatic Pressing (HIP) capable of furnishing finished products with very good service behaviour.
  • HIP Hot Isostatic Pressing
  • Metal cutting tools are subject to very difficult working conditions so they require very good hardness, wear resistance, cutting capacity, thermal shock resistance, toughness, etc,; some of these qualities are actually in contrast with one another and are not easily attained.
  • the main functions of the alloy elements are to increase hardenability, form hard wear-resistant carbides, and maintain hardness during tempering or anyway during heating to high temperatures.
  • Solidification, cooling and more generally treatment conditions help produce the desired characteristics in the steel by exerting an influence on carbide type and size, morphology and extent of segregation, and microstructure.
  • the object of the present invention is to provide a better quality PM tool steel which ensures a considerably longer tool life.
  • Another object is to improve the productivity of the machines on which the ensuing tools are used.
  • a further object of the invention is to eliminate or at least limit the use of costly, strategic elements, thus lowering the price of the tools made from the steel concerned.
  • a molten steel having the following composition (%wt): C from 1,50 to 1.85%, Mn from 0.20 to 0.55%, Si from 0,35 to 0.70%, W from 1.50 to 3.00%, Mo from 8.00 to 9.50%, V from 5.50 to 6.50%, Cr from 4.00 to 5,00%, the remainder being iron and impurities.
  • composition %wt: C from 1,50 to 1.85%, Mn from 0.20 to 0.55%, Si from 0,35 to 0.70%, W from 1.50 to 3.00%, Mo from 8.00 to 9.50%, V from 5.50 to 6.50%, Cr from 4.00 to 5,00%, the remainder being iron and impurities.
  • Preferred embodiments are disclosed in the dependent claims 2 to 4.
  • the powder cooling rate is between 1000 and 10000°C/s. This results in a powder of excellent chemical uniformity, containing very fine carbide precipitates, which are useful during subsequent treatments, as will be explained below.
  • the powders thus obtained are subjected to Hot Isostatic Pressing to obtain semis such as round bars or more complex shapes which, in turn, can be worked to obtain the desired finished product.
  • the latter is then heated in a salt-bath at a temperature between 1160 and 1200°C for 3 to 10 minutes, hardened in a salt-bath in the usual way at a temperature between 450 and 600°C and then cooled to ambient temperature.
  • the product is tempered three times in succession at temperatures between 530 and 560°C, then 540 and 570°C and again between 530 and 560°C; each of these treatment lasts for between one and two hours.
  • the purpose of these thermal treatments is to solubilize and reprecipitate the carbides in the best possible way as regards composition, quantity and dimensions for the purpose of the invention. Since the carbides are already in very fine form in the atomized powders, they can be solubilized at relatively low temperatures in the 1160 to 1200°C range without there being any excessive grain growth.
  • the carbides thus obtained are of the M2C-MC type; their maximum diameter is less than 3.5 um, typically being between 0.5 and 2.5 um, and they are present with a volume fraction between 13 and 18%.
  • the characteristics imparted to the tools by that treatment are usually in line with the highest values encountered in the best known tool steels used, even as regards properties that are antithetic or difficult to combine, such as hardness and toughness. It is precisely this general line-up at high values which renders the quality of these tool far superior to any yet known.
  • CSM1, CSM2 and CSM3 Three steels, CSM1, CSM2 and CSM3, have been prepared as per the present invention. Their compositions and those of three comparable steels already on the market, RIF1, RIF2 and RIF3, are compared in Table 1.
  • RIF1 and RIF2 represent the best tungsten and molybdenum ingot steels respectively, while RIF3 is the most widely used powder steel.
  • RIF2 1.12 nd nd 1.60 9.72 1.15 3.70 7.87
  • the heat-cracking factor indicates the ability of the material to support rapid thermal cycles, as well as the rate at wich thermal fatigue cracks develop and propagate in said material. This factor is measured in the laboratory by means of a test designed by the proprietor of this invention, the method being as follows:
  • a test disc of the material concerned is made to rotate and heated by induction so that part of its surface on the maximum circumference is heated to about 800°C. At the same time, half of said circumference is cooled by water sprays so that during every revolution of the test specimen its surface is subjected to a thermal cycle between the heating temperature indicated and about 100°C.
  • test specimens of the same material are tested for 500, 1000, 2000 and 4000 revolutions. They are then ground and examined under the microscope to measure the number, length and penetration of the cracks formed during the test.
  • the steel according to the invention is in line - characteristic by characteristic - with the best products on the market, and it is the only one which maintains all its properties consistently high compared therewith. Precisely because of this singular feature of possessing excellent values simultaneously for all relevent characteristics, the steel as per this invention is found to be of an exceptionally high quality in practical applications that is not encountered in any other steel for the same applications.
  • Envelope-cutting hobs produced according to the present invention and tested over long periods on high-speed gear-making operations have increased line productivity by 400 to 500%.
  • hobs with CSM1, CSM2 and CSM3 compositions have repeatedly resulted in the production of up to 12000 very hard quenched and tempered steel gears without requiring sharpening, while the average for RIF3 powder steel hobs is 4000 pieces, which is in itself better than the performance of conventional ingot steel hobs.
  • productivity is improved not only through an increase in the number of pieces produced with the same tool, but even more so through avoidance of tool-change stoppages, which are extremely costly in modern high-speed machining operations.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Powder Metallurgy (AREA)
  • Dental Tools And Instruments Or Auxiliary Dental Instruments (AREA)
  • Hand Tools For Fitting Together And Separating, Or Other Hand Tools (AREA)

Claims (4)

  1. Pulvermetallurgischer Werkzeugstahl, dadurch gekennzeichnet, daß seine Zusammensetzung ist (% im Gewicht): C (1,50-1,85), Mn (0,20-0,55), Si (0,35-0,70), W (1,50-3,00), Mo (8,00-9,50), V (5,50-6,50) und Cr (3,00-5,00), wobei das Übrige Eisen und kleinere Unreinheiten ist.
  2. Werkzeugstahl nach Anspruch 1, dadurch gekennzeichnet, daß das Pulver durch Zerstäubung in einem Gas erhalten wird, das Stickstoff oder Argon sein kann, wobei die herauskommenden Teilchen kugelförmig sind und 80% von denen kleiner als 500 µm sind.
  3. Werkzeugstahl nach Anspruch 2, dadurch gekennzeichnet, daß er nach dem folgenden Zyclus:
    - Abkühlung während der Pulvererstarrung mit einer Geschwindigkeit von 1000-10000°C/s;
    - Warme isostatische Verdichtung um ein halbfertiges Stück zu erhalten;
    - Umwandlung des halbfertigen Stückes in das gewünschte Produkt;
    - Erhitzung des Produktes in einem Salzbad mit einer Temperatur von 1160-1200°C für 3-10 Minuten;
    - Verhärtung in einem Salzbad mit einer Temperatur von 450-600°C und folgende Abkühlung bis zur Raumtemperatur;
    - Serie von drei Anlassen nacheinander, mit Temperaturen von 530- 560°C, 540-570°C und dann wieder 530-560°C, jedes von denen für 1-2 Stunden;
    niedergeschlagene Karbiden vom M2C-MC Typ enthält, die weniger als 3,5 µm messen und einen Inhaltsbruchteil von 13-18% darstellen.
  4. Werkzeugstahl nach Anspruch 3, dadurch gekennzeichnet, daß die maximale Größe der Karbiden 0,5-2,5 µm ist.
EP91830235A 1990-07-17 1991-05-30 Pulvermetallurgische Werkzeugstähle Expired - Lifetime EP0467857B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IT48150A IT1241490B (it) 1990-07-17 1990-07-17 Acciaio rapido da polveri.
IT4815090 1990-07-17

Publications (2)

Publication Number Publication Date
EP0467857A1 EP0467857A1 (de) 1992-01-22
EP0467857B1 true EP0467857B1 (de) 1996-03-06

Family

ID=11264854

Family Applications (1)

Application Number Title Priority Date Filing Date
EP91830235A Expired - Lifetime EP0467857B1 (de) 1990-07-17 1991-05-30 Pulvermetallurgische Werkzeugstähle

Country Status (7)

Country Link
EP (1) EP0467857B1 (de)
AT (1) ATE135056T1 (de)
DE (1) DE69117605T2 (de)
DK (1) DK0467857T3 (de)
ES (1) ES2085457T3 (de)
GR (1) GR3019999T3 (de)
IT (1) IT1241490B (de)

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE500008C2 (sv) * 1991-08-07 1994-03-21 Erasteel Kloster Ab Snabbstål med god varmhårdhet och slitstyrka framställt av pulver
AU2430192A (en) * 1991-08-07 1993-03-02 Kloster Speedsteel Aktiebolag High-speed steel manufactured by powder metallurgy
AU2430092A (en) * 1991-08-07 1993-03-02 Kloster Speedsteel Aktiebolag High-speed steel manufactured by powder metallurgy
ATE223975T1 (de) * 1996-06-17 2002-09-15 Hau Hanspeter Pm-warmarbeitsstahl und verfahren zu dessen herstellung
AT411580B (de) * 2001-04-11 2004-03-25 Boehler Edelstahl Verfahren zur pulvermetallurgischen herstellung von gegenständen
EP2570507A1 (de) * 2011-09-19 2013-03-20 Sandvik Intellectual Property AB Verfahren zur Herstellung von Schnelldrehstahl
EP2933345A1 (de) * 2014-04-14 2015-10-21 Uddeholms AB Kaltverarbeiteter Werkzeugstahl

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3117863A (en) * 1960-11-14 1964-01-14 Vanadium Alloys Steel Co Alloy steels
US4249945A (en) * 1978-09-20 1981-02-10 Crucible Inc. Powder-metallurgy steel article with high vanadium-carbide content
US4276087A (en) * 1979-05-03 1981-06-30 Crucible Inc. Powder-metallurgy vanadium-containing tungsten-type high-speed steel
JPS57181367A (en) * 1981-04-08 1982-11-08 Furukawa Electric Co Ltd:The Sintered high-v high-speed steel and its production
US4880461A (en) * 1985-08-18 1989-11-14 Hitachi Metals, Ltd. Super hard high-speed tool steel

Also Published As

Publication number Publication date
ES2085457T3 (es) 1996-06-01
DK0467857T3 (da) 1996-05-20
IT9048150A0 (it) 1990-07-17
EP0467857A1 (de) 1992-01-22
DE69117605D1 (de) 1996-04-11
IT1241490B (it) 1994-01-17
ATE135056T1 (de) 1996-03-15
DE69117605T2 (de) 1996-09-26
GR3019999T3 (en) 1996-08-31
IT9048150A1 (it) 1992-01-17

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