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
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D6/00—Heat treatment of ferrous alloys
• • 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 powder-metallurgically produced high-speed steel for wearing parts, in particular tools, containing C, Cr, V, W and / or Mo, optionally containing Co and / or Mn and / or Si and / or Al and containing iron companions, e.g. P, S, O as well as iron and impurities as the rest.
• tools containing C, Cr, V, W and / or Mo, optionally containing Co and / or Mn and / or Si and / or Al and containing iron companions, e.g. P, S, O as well as iron and impurities as the rest.
• Such high-speed steels are used, among other things. for the production of tools for the machining of workpieces, e.g. Milling cutters, drills, reamers, but also for tools for non-cutting shaping such as Drawing nozzles, extrusion dies etc. used.
• niobium carbides from TYp MC occur in the melt metallurgical production of niobium alloyed high-speed steels, which can have a grain size of more than 100 ⁇ m and impair the toughness and cutting edge durability of wear parts made from these high-speed steels. Since niobium also has only a very low solubility in the base alloy, only high-speed steels alloyed with niobium generally have no pronounced secondary hardness behavior.
• the alloy element vanadium also forms carbides of the type MC, which, however, have a lower thermal stability than niobium carbides. For this reason, when using high hardness or Austenitizing temperatures, as are necessary in particular in the production of cutting tools, in order to achieve the required performance properties, namely hardness, to coarsen the austenite grain and the carbides precipitated with a reduction in toughness.
• JP-PA 144456/1983 has disclosed a powder metallurgical process for producing high-speed steel, an Nb concentration in the steel being limited to 0.1 to 1.5% by weight and high tungsten and / or molybdenum contents improving hardness values should provide after the heat treatment.
• the aim of the invention is to produce high-speed steels which, in addition to having sufficient wear resistance and hardness, also have great thermal stability.
• the steels should have a uniformly fine carbide distribution in order to obtain appropriate toughness properties, especially on fine cutting edges. Hardness values of up to 7o HRC should also be achievable.
• a powder metallurgically manufactured high-speed steel of the type mentioned at the outset in that the steel has an Nb content of from 2% by weight to 15% by weight, preferably from 3% by weight to 10% by weight, in particular of more than 4% by weight to 10% by weight and a vanadium content of 1 to 4% by weight, preferably 1.5 to 2.5% by weight, that the steel has 10 to 30% by volume.
• a process for the powder metallurgical production of Wear parts in particular tools, made of high-speed steels containing C, Cr, V, W and / or Mo, optionally containing Co and / or Mn and / or Si and / or Al, and containing iron companions, for example P, S, O and iron and impurities the remainder, the alloying constituents being melted and the melt atomizing into powder, in particular gas atomizing, whereupon the powder is shaped into a shaped body in the course of consolidation under the application of temperature and optionally pressure, in particular in a sintering process, which shaped body optionally after annealing and / or hot forging is subjected to a soft annealing process and is formed into a wearing part by means of machining or non-cutting machining, whereupon the wearing part is heated above its austenitizing temperature or subjected to high-speed steel hardening, from which temperature the wearing part is cooled, in particular quenched, and at least two tempering or Is subject
• the indicated niobium content and vanadium content as well as the amount of metal carbides formed in the steel due to the regulation of the carbon content create a high-speed steel which has the desired advantageous properties. Because the superheated melt of the alloy components is powder atomized, a powder is obtained in which the niobium carbides which form during solidification are in finely divided form. These very finely divided niobium carbides hinder the grain growth at the high austenitizing temperatures provided according to the invention.
• a powder-metallurgically manufactured wear part in particular a tool, consists of a high-speed steel containing C, Cr, W, V and / or Mo, optionally containing Co and / or Mn and / or Si and / or Al, and containing iron companions, for example P, S.
• the carbon values given in the formulas for C min and C max result from the interaction of the carbide-forming elements in high-speed steel, which means that the metal carbides can have different carbon concentrations.
• the factors in the formulas result from the fact that NbC can bind 0.10 to 0.15% carbon and VC o, 20 to 0.24% carbon.
• the summands o, 45 and 1.0 in the formulas take into account the carbon content to form the basic hardness of the matrix and the Nb and V-free carbides.
• the MIN and MAX values are finally determined by the Cr, Mo, W contents.
• the production of the powder metallurgical high-speed steel is carried out as follows:
• the individual alloy components are melted together and the melt is overheated by approximately 100 to 6000 ° C., preferably 300 ° C., as a result of which the alloy components niobium and carbon are distributed in the melt.
• the melt is atomized into a powder under protective gas (in principle, water atomization is also possible). Due to the rapid cooling, small, well-distributed niobium carbides separate out. Shaped bodies are then produced from these powders using temperature and optionally pressure.
• the powders are filled into steel containers made of alloyed or unalloyed steel, sealed gas-tight and consolidated using pressure and temperature, for example by hipen, extrusion or forging.
• Consolidation temperatures are approximately 1o50 to 1,100 ° C, at a pressure of 1000 bar or if working without pressure, approximately 1,200 to 1,250 ° C.
• the consolidation can be followed by a glow.
• the strength can e.g. the bending strength of the molded body can be increased.
• the hot shaping which is carried out if necessary is followed by soft annealing at a temperature of approximately 700 to 85 ° C., preferably 80 ° C.
• the annealed workpiece is then formed into the desired wear part or tool by machining or non-machining.
• the workpiece is hardened at an austenitizing temperature of vis to 1,350 ° C. During this hardening process, the niobium carbide inhibits grain growth and the undissolved vanadium carbide contributes to the formation of a very fine grain before quenching in air, water or oil.
• the higher austenitizing temperature provided according to the invention enables a larger amount of the carbides present to disintegrate or to dissolve at this temperature, so that a fine and hard grain structure is achieved in the matrix when cooling thereon.
• a first tempering takes place at a temperature of around 5oo to 600 ° C, at which fine metal carbides (e.g. vanadium mixed carbide of type MC) are precipitated.
• fine metal carbides e.g. vanadium mixed carbide of type MC
• the higher austenitizing temperature can be used without the occurrence of toughness-reducing phenomena or grain coarsening, melting and other disadvantageous processes. Because chrome is the excretion Influenced by carbides, the chromium content is limited to a range of 2 to 5% by weight. Any cobalt present should be in the range of 0-10% by weight.
• the metal carbides have a size of less than 6 ⁇ m.
• a further reduction in the grain size of the metal carbides can be achieved by increasing the melt temperature or the rate of solidification in the course of the production of the metal powder.
• the powder consolidation was carried out at 1,150 ° C and a pressure of 1,070 bar.
• hardening or austenitization was carried out at a temperature of 1,290 ° C. without coarsening of the grain or melting at the grain boundaries.
• This austenitizing temperature which is about 50 ° C above the conventional hardening temperature, enabled higher carbide or carbon contents to be dissolved in the matrix and thus the hardness and wear resistance to be improved in the outlet processes.
• the hardness measurement was 68.8 HRC.
• the milling cutters produced according to the invention showed an increase in output of approximately 30 to 50% in the machining of St52 and tempering steel of the type X38CrMoV51, compared to milling cutters of the alloy S6-5-2-5.
• the block was gas atomized at a temperature exceeding the liquidus temperature by 35 ° C.
• the powder was used in a sintering process to produce a shaving wheel, such as is used for the fine machining of gear wheels in the automotive industry.
• the hardening took place at an austenitizing temperature of 1,300 ° C, which was followed by a double tempering at 580 ° C. After double tempering, the shaving wheel was finished by grinding. The hardness measurement in the working area of the tool gave a value of 69.5 HRC.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Powder Metallurgy (AREA)
• Manufacture Of Metal Powder And Suspensions Thereof (AREA)

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• 1987
  • 1987-12-23 AT AT0340187A patent/AT391324B/de not_active IP Right Cessation
• 1988
  • 1988-11-22 EP EP88890293A patent/EP0322397B1/fr not_active Expired - Lifetime
  • 1988-11-22 DE DE8888890293T patent/DE3868038D1/de not_active Expired - Lifetime
  • 1988-12-22 JP JP63322288A patent/JPH01212736A/ja active Pending
• 1990
  • 1990-02-07 US US07/476,138 patent/US5021085A/en not_active Expired - Fee Related

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