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%
  • 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
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium

Definitions

• the composition is formed by employing titanium and carbon together in the combined form as primary grains of titanium carbide as an alloying ingredient together with a steel matrix which reacts with the carbide to a certain extent in producing the desired composition.
• the steel employed in forming the matrix contains at least about 60 percent iron by weight of the steel matrix composition.
• Powder metallurgy is employed as the preferred method in producing the desired composition which comprises broadly mixing powdered steel-forming ingredients and forming a compact by pressing the mixture in a mold, followed by subjecting the compact to liquid phase sintering under non-oxidizing conditions, such as in vacuum.
• a steel matrix found particularly useful in combination with titanium carbide is one containing about 0.5 percent carbon, about 3 percent chromium, about 3 percent molybdenum and the balance iron.
• TiC titanium carbide tool steel composition
• a titanium carbide tool steel composition containing for example 33 percent by weight of TiC (approximately 45 volume percent) and substantially the balance the aforementioned steel matrix
• about 500 grams of powdered TiC (of about 5 to 7 microns in average size) are mixed with about 1,000 grams of steel-forming ingredients in a mill half filled with stainless steel balls.
• To the powder ingredients is added one gram of paraffin wax for 100 grams of mix. The milling is conducted for about 40 hours using hexane as a vehicle.
• the mix is removed and dried and compacts of a desired shape pressed at about 15 t.s.i. and the compacts then subjected to liquid phase sintering in vacuum at a temperature of about 2,640F (1,450C) for about one-half hour at a vacuum corresponding to 20 microns of mercury or better.
• the compacts are cooled and then annealed by heating to 900C for 2 hours followed by cooling at a rate of about 60F (33C or 35C) per hour to about 1,000F (538C) and thereafter furnace cooled to room temperature to produce an annealed structure containing spheroidite.
• the annealed hardness is in the neighborhood of about 45 R and the high carbon tool steel is capable of being machined and/or ground into a desired tool shape or machine part prior to hardening.
• the hardening treatment employed comprises heating the machined piece to an austenitizing temperature of about l,750F (about 955C) for about one-quarter hour followed by quenching in oil to produce a hardness in the neighborhood of about R THE PROBLEM CONFRONTING THE ART
• the aforementioned titanium carbide tool steel containing by volume about 45 percent titanium carbide and the balance a low chromium-molybdenum steel containing by weight of about 0.3 to 0.8 percent C, 1 to 6 percent Cr, 0.3 to 6 percent Mo and the balance essentially iron has been found very useful in the manufacture of tools, dies and many wear parts; particularly for use under generally normal environmental conditions.
• the foregoing composition presents certain problems, insofar as tool life and overall tool efficiency are concerned.
• the tool is a pair of seaming rolls or hammers employed in the manufacture of cans involving the use of chloride soldering fluxes (for example, a mixture of ammonium and zinc chlorides)
• the tool does not exhibit adequate corrosion resistance to the fluxes, whereby the steel matrix relative to the titanium carbide grains is selectively corroded.
• titanium carbide grains are dislodged due to the lack of support in the matrix. This leads to an accelerated wearing of the seaming rolls, which results in a loss in tool life and tool efficiency.
• the acid media which normally prevail in the canning of foods such as, by way of example, citric acid, carbonic acid and the like, will generally have a corrosive effect on the tool or wear part and, as described hereinabove, adversely affect the life of the tool or wear resistant part.
• Another object is to provide a hardened sintered corrosion and wear resistant tool element formed of a high chromium refractory carbide alloy.
• the invention is directed to a powder metallurgy sintered corrosion and wear resistant high chromium containing refractory carbide alloy comprising primary grains of at least one refractory carbide selected from the group consisting of TiC, CbC, VC and TaC dispersed or distributed through a high chromium alloy matrix consisting essentially by weight of about 14 to 24 percent chromium, about 0.4 to 1.2
• the high chromium ferrous matrix may contain other elements, such as small amounts of one or more of the elements silicon, manganese, vanadium, molybdenum, and the like.
• a composition range which is particularly advantageous is one in which the refractory carbide ranges by volume from about 30 to 75 percent, with the balance substantially the aforementioned high chromium matrix alloy.
• a more advantageous composition is one in which the refractory carbide (e.g. TiC) ranges by volume from about 35 to 55 percent, and wherein the matrix alloy making up substantially the balance consists essentially by weight of about 16 to 20 percent chromium, about 0.5 to 0.9 percent carbon, and thebalance essentially iron.
• the refractory carbide e.g. TiC
• the matrix alloy making up substantially the balance consists essentially by weight of about 16 to 20 percent chromium, about 0.5 to 0.9 percent carbon, and thebalance essentially iron.
• the foregoing composite refractory carbide alloy is capable of being annealed to a hardness as low as 50 R and hardened to as high as 69 R, to provide markedly improved resistance to wear and corrosion.
• a substantially martensitic matrix is assured by heat treatment, including a dispersion in the matrix of a secondary carbide containing chromium, probably an iron-chromium carbide.
• the secondary carbide together with the primary carbide provides improved wear resistance while the chromium dissolved in the matrix assures resistance to corrosion.
• the matrix metal had the following nominal composition by weight:
• the balance iron may include the presence of amounts of other ingfiedients which do not adversely affect the basic characteristics of the a y.
• the mix After completion of the milling, the mix is removed and vacuum dried. A proportion of the mixed product is compressed in a die at tons/sq. inch to the desired shape.
• the shape is liquid phase sintered at a temperature of about 1,3 50C for one-half hour (after reaching the temperature) at a vacuum corresponding to microns or better.
• the shape After completion of sintering, the shape is cooled and then annealed by heating to 900C for 2 hours followed by cooling at a rate of about C/hour to about 550C and thereafter furnace cooled to room temperature to produce an annealed microstructure containing mainly sphereoidite, the hardness being about 50 R
• the sintered shape is then machined into a tool element, e.g., seaming rolls or hammers for the canning industry, and thereafter hardened by heating to an austenitizing temperature of about 1,875F (about 1,025C) for about one-quarter hour at temperature and then air or oil quenched to form a hard microstructure consisting essentially of martensite.
• a tool element e.g., seaming rolls or hammers for the canning industry
• the tool element is tempered at a temperature within the range of about 400F (205C) to 800F (427C) for about 1 to 2 hours and thereafter cooled in air.
• the final hardness is in the neighborhood of about 68 R Following hardening, the
• the nominal composition of the matrix by weight is as follows:
• the nominal composition of the matrix by weight is as follows:
• the nominal composition by weight of the matrix is as follows:
• the nominal composition of the matrix by weight is a as follows;
• the nominal composition of the matrix by weight is as follows:
• the appropriate amount of steelforming ingredients is mixed with an appropriate amount of primary carbide in a ball mill.
• the mixture may be shaped a variety of ways. It is preferred to press the mixture to a density of at least about 50 percent of true density by pressing over the range of about 10 t.s.i. to 75 t.s.i., preferably t.s.i. to 50 t.s.i., followed by sintering under substantially inert conditions, e.g., in a vacuum or an inert atmosphere.
• the temperature employed is above the melting point of the chromium steel matrix, for example, at a temperature up to about 100C above the melting point for a time sufficient for the primary carbide and the matrix to reach equilibrium and to obtain substantially complete densification, for example, for about one minute to six hours.
• the product is allowed to furnace cool to room temperature. If necessary, the as-sintered product is subjected to mechanical cleaning. If the as-sintered product requires annealing, it is heated to a temperature of about 1,550F (845C) to 1,700F (926C) for about 2 to 5 hours and then slowly cooled at a rate not exceeding 25C/hour.
• the austenitizing temperature may range from about 1,700F (926C) to 2,000F (1,093C) for about 30 minutes to 2 hours followed by air cooling. Thereafter, the hardened composition may be tempered at a temperature ranging from about 400F (205C) to 800F (427C) for about 1 to 2 hours.
• the hardness after tempering may range from about 65 R,
• alloy compositions of the invention exhibit good resistance to corrosion in such acid media as concentrated nitric acid and dilute (about 10 vol. percent) sulfuric acid.
• a powder metallurgy sintered corrosion and wear resistant high chromium refractory carbide alloy comprising about 30 to 75 percent by volume of primary grains of at least one refractory carbide selected from the group consisting of TiC, CbC, VC and TaC dispersed through a high chromium alloy matrix making up the balance, said alloy matrix consisting essentially by weight of about 14 to 24 percent chromium, about 0.4 to 1.2 percent carbon, up to about 3 percent nickel, up to about 5 percent molybdenum, and the balance essentially iron.
• a hardened sintered corrosion and wear resistant tool element formed of a high chromium refractory carbide alloy comprising about 30 to 75 percent by volume of primary grains of at least one refractory carbide selected from the group consisting of TiC, CbC, VC and TaC dispersed through a high chromium alloy matrix consisting essentially by weight of about 14 to 24 percent chromium, up to about 3 percent nickel, up to about 5 percent molybdenum, about 0.4 to 1.2 percent carbon and the balance essentially iron, the metallographic structure of the alloy matrix consisting essentially of martensite.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Powder Metallurgy (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=22173451

Family Applications (1)

Country Status (6)

Cited By (5)

Families Citing this family (1)

Citations (12)

Family Cites Families (1)

• 1970
  • 1970-10-21 US US00082787A patent/US3715792A/en not_active Expired - Lifetime
• 1971
  • 1971-09-09 CA CA122,477A patent/CA944976A/en not_active Expired
  • 1971-10-06 GB GB4649271A patent/GB1324050A/en not_active Expired
  • 1971-10-20 FR FR7137607A patent/FR2111571A5/fr not_active Expired
  • 1971-10-21 JP JP8291471A patent/JPS5537587B1/ja active Pending
• 1972
  • 1972-04-13 DE DE19722061986 patent/DE2061986B2/de not_active Ceased

Patent Citations (13)

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events