Classifications

• • 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
  • C21D5/00—Heat treatments of cast-iron
• • 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
  • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
  • C21D1/06—Surface hardening
  • C21D1/09—Surface hardening by direct application of electrical or wave energy; by particle radiation
• • 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
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/40—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for rings; for bearing races
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16J—PISTONS; CYLINDERS; SEALINGS
  • F16J10/00—Engine or like cylinders; Features of hollow, e.g. cylindrical, bodies in general
  • F16J10/02—Cylinders designed to receive moving pistons or plungers
  • F16J10/04—Running faces; Liners
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05C—INDEXING SCHEME RELATING TO MATERIALS, MATERIAL PROPERTIES OR MATERIAL CHARACTERISTICS FOR MACHINES, ENGINES OR PUMPS OTHER THAN NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES
  • F05C2203/00—Non-metallic inorganic materials
  • F05C2203/04—Phosphor
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05C—INDEXING SCHEME RELATING TO MATERIALS, MATERIAL PROPERTIES OR MATERIAL CHARACTERISTICS FOR MACHINES, ENGINES OR PUMPS OTHER THAN NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES
  • F05C2203/00—Non-metallic inorganic materials
  • F05C2203/08—Ceramics; Oxides
  • F05C2203/0865—Oxide ceramics
  • F05C2203/0882—Carbon, e.g. graphite

Definitions

• the invention relates to a part having a tread in the combustion chamber of a piston internal combustion engine, which part consists of cast iron with lamellar, vermicular and / or spherical graphite and has a minimum diameter of 200 mm and a minimum wall thickness of 5 mm, and a method for its manufacture.
• the part having a tread is in particular a piston ring or a cylinder liner.
• Piston rings and cylinder liners made of the cast iron mentioned have the advantages of higher tensile strength and greater toughness, as well as better machinability and better thermal conductivity, than those made of chilled cast iron.
• the wear on these parts is increasing, e.g. the quality of the fuel, particularly with regard to the sulfur content and abrasive residues after combustion, has deteriorated over time. Not only does the abrasion increase, but also, due to the formation of sulfuric acid in the combustion chamber, e.g. if the operating temperature is too low, the corrosion attack.
• the object of the present invention is therefore the abrasion resistance and the corrosion resistance
• the tread consists of a carbide structure with a depth of at least 0.5 mm and at most 8 mm.
• a method for producing such a tread in a cylinder liner is characterized in that the cylinder liner includes a preheating rate of a maximum of 100 C / h to a temperature between 450 and 600 C, that the preheated tread is gradually melted locally in the intended depth and progressively by rapid heating to above the liquidus temperature of the material immediately following rapid cooling below the Ar .. point of the iron-carbon diagram with the carbide structure is solidified again, and that finally the cylinder liner is cooled to ambient temperature with a maximum cooling rate of 50 ° C / h. It was surprisingly shown that the cylinder liner includes a preheating rate of a maximum of 100 C / h to a temperature between 450 and 600 C, that the preheated tread is gradually melted locally in the intended depth and progressively by rapid heating to above the liquidus temperature of the material immediately following rapid cooling below the Ar .. point of the
• the invention is limited to parts with a diameter of 200 mm and larger for parts that serve as cylinder liners.
• the radial wall thickness must be at least 5 mm, since otherwise a sufficiently rapid cooling and solidification rate the melted depth range is not guaranteed.
• the minimum depth of the melted and carbidically solidified surface area for example in the case of cylinder liners and piston rings, must be at least 0.5 mm.
• the upper limit of 8 mm is primarily determined by the susceptibility to cracking or the prevailing cooling conditions; it also proves to be useful for economic reasons.
• Cast iron with lamellar, spherical and / or vermicular graphite has proven to be an advantageous base material for a part, the composition of which (in% by weight) comprises the following ranges:
• the degree of saturation of the cast iron being 0.7 to 1.1, the lower degrees of saturation of 0.7-0.95 for cylinder liners and the higher values of 0.8-1.1 for piston rings being maintained.
• the degree of saturation is calculated in a known manner according to the relationship
• a cast iron of the composition (in% by weight) has proven particularly useful for parts according to the invention which are cylinder liners:
• Preheating - for example in an oven, inductively or with the help of a number of preheating burners - before melting and cooling - advantageously in an oven - after carbide solidification of the melted layer are necessary in the prescribed manner to prevent cracks, especially in the transition area between the base material and the carbide tread.
• Electric arcs are particularly suitable as the energy source for the melting, with welding torches - especially those with a tungsten electrode - with energy
• the melting is advantageously carried out under a protective gas atmosphere
• the energy source used is preferably, for example, TIG welding torch.
• OMPI IPO To achieve a structure, it is furthermore expedient to mechanically remove the cast skin from the parts before the treatment according to the invention. After the treatment, the tread is mechanically finished in the customary manner, with carbide treads then being between, for example, 0.2 to 5 mm.
• O ⁇ FI 2 shows the same diagram for a piston ring according to Example II.
• a TIG (tungsten inert gas) welding torch with a tungsten electrode with a diameter of 3.2 mm is permanently installed inside.
• the melting area of the burner arc is held in a protective gas atmosphere by means of a helium diameter of 7 1 / min which emerges from the burner.
• the cylinder liner is placed in an oven preheated to 500 ° C. and slowly cooled at a maximum cooling rate of 50 ° C./h.
• a remelting depth of about 6 mm is achieved in this way.
• the microhardness has been measured for various distances a (in mm) from the tread surface by a conventional method and has been plotted against this distance a.
• the hardnesses measured are given in micro-Vickers (MV), the measuring load being 200 g.
• Microhardness is still about half that of the carbide structure.
• the part to be provided with a hardened running surface is a piston ring with an outside diameter of 400 mm and a wall thickness of 20 mm made of spheroidal graphite cast iron with the following chemical composition (in% by weight) C 3.4; P 0.04; S 0.005; Si 2.3; Mn 0.15; Ni 0.5; Mg 0.05; Cu 1.03 and balance Fe, which has a degree of saturation of 0.96; it is slowly preheated evenly by two gas burners with a heating rate of at most 100 C / h uniformly everywhere to a preheating temperature of about 500 C.
• the protective gas atmosphere and the cooling conditions both when cooling the melted area under the point Ar of the iron-carbon diagram and the entire piston ring after the remelting treatment has been completed in accordance with that of Example I.
• a remelting depth of approximately 4 mm is achieved in this way.
• the high hardness values of the carbide structure are again given at 0-4 mm depth from the tread (area 1); Area 2, about 4 - 8 mm deep, is the heat-affected zone with a tempering structure and decreasing microhardness, while this zone finally closes into the pearlitic basic structure of the next 2 - 3 mm. Material passes over, the microhardness of which is still about half that of the carbide structure.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Materials Engineering (AREA)
• Crystallography & Structural Chemistry (AREA)
• Thermal Sciences (AREA)
• Physics & Mathematics (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• General Engineering & Computer Science (AREA)
• Combustion & Propulsion (AREA)
• Heat Treatment Of Articles (AREA)
• Pistons, Piston Rings, And Cylinders (AREA)

Applications Claiming Priority (2)

Publications (1)

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• 1982
  • 1982-03-11 CH CH1494/82A patent/CH659300A5/de not_active IP Right Cessation
• 1983
  • 1983-02-16 EP EP83900551A patent/EP0102963A1/de not_active Withdrawn
  • 1983-02-16 WO PCT/CH1983/000016 patent/WO1983003261A1/en unknown
  • 1983-03-08 IT IT19944/83A patent/IT1160512B/it active
  • 1983-03-10 PL PL24096683A patent/PL240966A1/xx unknown

Non-Patent Citations (1)

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