Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D27/00—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting
  • B22D27/18—Measures for using chemical processes for influencing the surface composition of castings, e.g. for increasing resistance to acid attack
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22C—FOUNDRY MOULDING
  • B22C9/00—Moulds or cores; Moulding processes
  • B22C9/12—Treating moulds or cores, e.g. drying, hardening
  • B22C9/123—Gas-hardening
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D27/00—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting
  • B22D27/20—Measures not previously mentioned for influencing the grain structure or texture; Selection of compositions therefor

Definitions

• the invention relates to a method for casting castings from a vermicular or a spheroidal graphite cast iron melt, in which the cast iron melt is poured into a casting mold comprising at least one casting part made of a molding material consisting of a sand-like base material and an organic binder is, molded and then with a sulfur-containing gas, in particular SÜ 2 gas, fumigated to cure the binder of the molding material, so that a dimensionally stable molded part has been obtained.
• a sulfur-containing gas in particular SÜ 2 gas
• mold parts of the above-mentioned type are in practice typically so-called "casting cores", with which cavities, such as channels, cavities, etc., or recesses with undercuts and comparable complex shapes are mapped to the casting to be cast.
• casting cores With which cavities, such as channels, cavities, etc., or recesses with undercuts and comparable complex shapes are mapped to the casting to be cast.
• the relevant mold parts are destroyed. They disintegrate into free-flowing individual parts, which can be conveyed mechanically, for example by shaking, or with the aid of a rinsing liquid from the casting.
• Casting cores of this type are used both in molds whose outer parts as solid permanent molds executed as well as in so-called "lost molds".
• lost molds are not only the cores, but also the outer, the casting outside bounding moldings made of molding material and are therefore also completely destroyed during demolding of the respective casting.
• a variant of the cold box method is the SC> 2 method.
• the molding material processed in each case is blended from a molding sand and a resin binder, which may be, for example, a furan-phenol or an epoxy resin binder.
• a resin binder which may be, for example, a furan-phenol or an epoxy resin binder.
• the respective resin binder hardens by reaction with the sulfuric acid, which is formed from sulfur dioxide, oxygen and water.
• the S ⁇ 2 ⁇ method is widely used in practice, since the moldable with sulfur dioxide moldings in the unconsolidated state have good flowability and, consequently, a particularly good mold filling capacity. Therefore, these mold materials are particularly suitable for the production of filigree shaped outer parts and cores for molds.
• the moldable with sulfur dioxide moldings are durable without special precautions and have a high dimensional stability after the gassing with the sulfur dioxide gas.
• cast iron can be subjected to a magnesium treatment immediately before it enters the casting mold or even in the casting mold itself.
• the magnesium supplied in this process forms with other constituents of the cast iron or with additionally additionally supplied elements compounds which serve as nuclei for the formation of the respectively desired graphite form.
• GJS Kugelgrafit
• GJV Vermiformgrafit
• Ballistic graphite cast iron has typical strengths of 350 MPa to 1000 MPa, while the strength of vermicular graphite cast iron is in the range of 350 MPa to 500 MPa.
• the particular advantage of Vermiculargrafit consists in a favorable combination of high strength and good thermal conductivity and good damping behavior.
• cast iron with lamellar graphite (“GJL”) has strengths in the range of 150 MPa to 350 MPa.
• the invention was based on the object of demonstrating possibilities with which casting molds which are produced according to the SÜ 2 method, the danger of the occurrence of local graphite and structural degenerations on the casting during casting of ball or Vermiculargrafit forming iron casting melt on let a minimum be reduced. This object has been achieved by the method specified in claim 1.
• the specified in the above claims variants of the invention is based on the idea, at least the surface of a mixed of a sand-like base material and an organic binder and by gassing with sulfur-containing gas, in particular S ⁇ 2 gas cured casting mold part, the casting of the metal casting melt in the mold using the molded part comes into contact with the cast metal melt to provide a coating containing a non-volatile sulfide former.
• the invention is based on the recognition that in the used in the prior art, hardened using SO 2 -GaS mold parts as a result of the associated with the pouring of the hot melt heating sulfur-containing vapors or gases escape from the mold parts and in the direction of urge the mold enclosed mold cavity. There they meet the casting metal filled in the mold cavity and react with the constituents contained in it.
• the sulfur-containing gas which is forced out of the casting mold part strikes the coating according to the invention and reacts with the sulfide former contained in it to form a sulfide. In this bound state, the sulfur is ineffective against the respectively poured molten metal.
• the invention uses in this way from DE-OS 24 08 344 already known way to coat a mold part on its surface with a mass that can bind or adsorb a flowing through the mold part acidic gas.
• the application of the coating has the purpose to bind gaseous, acidic catalysts contained in the respective molding, so as to avoid the escape of harmful or highly corrosive gases from the molded part, however, the invention sees the Using a on a specific problem, namely the formation of graphite degenerations in the casting, related coating ago.
• the coating provided according to the invention contains a sulfide former which prevents the magnesium contained in the molten metal according to the invention from forming a bond with the sulfur-containing gas which is emitted from the casting mold part.
• the coating applied in accordance with the invention to the respective casting mold part contains, as sulfide former, an alkali metal carbonate or alkaline earth metal carbonate.
• an alkali metal carbonate or alkaline earth metal carbonate contains, as sulfide former, an alkali metal carbonate or alkaline earth metal carbonate.
• CaCO ⁇ calcium carbonate
• the sulfides formed from the alkali metal or alkaline earth metal carbonates behave especially when as Cast iron metal is poured an iron casting melt, on the one hand neutral and on the other bind binding ausgasenden from the molding material in the direction of the mold cavity of the respective mold prevailing sulfur, so that it can no longer exert any influence on the constituents of each cast molten metal.
• the coating applied according to the invention as a sulfide former an alkali metal bicarbonate, z.
• sodium bicarbonate NaHCOs
• these substances also form sulfides, such as Na 2 S, with the sulfur emerging from the mold part and thus prevent the sulfur from reacting with a constituent of the casting metal cast in each case.
• the sulfide former contained in a coating according to the invention may be ammonium carbonate or ammonium bicarbonate. These substances form with sulfur amonium sulfides.
• the invention has a particularly advantageous effect when the casting mold part coated according to the invention is a casting core.
• such casting cores are substantially completely surrounded by the metal cast into the casting mold, so that the gas emerging from the core strongly penetrates the adjacent casting material.
• the invention is based on a
• FIG. 1 shows a mold in the unfilled state in a cross section.
• the casting mold 1 for casting a casting G from a magnesium-treated cast iron melt which is here a brake disk, has a lower outer molded part 2 and an upper, lying on the lower mold part 2 and this covering outer mold part 3.
• a mold cavity 4 is formed, which delimit the outer peripheral surfaces, the outer face of the pot and the outer face of the pot associated friction surface of the friction ring of the brake disc casting G to be produced.
• the other friction surface of the friction ring and the inner peripheral surfaces of the pot of the casting G are imaged by a casting core 5, which is inserted into the mold cavity 4.
• projections 6 which extend into the provided for the friction ring of casting casting G annular portion of the mold cavity 4 and with their free ends in correspondingly shaped, here in detail only hinted recordings of the lower mold part 2 sit.
• the projections 6 form in the casting G radially from the inside of the pot to the outer peripheral surface of the friction ring leading cooling channels.
• the outer mold parts 2, 3 and the casting core 5 with its integrally connected projections 6 are made of a molding material consisting of a sand-like molding base material and an organic resin binder mixing with the molding base material.
• this molding material has been filled and compacted in a manner known per se into a molding box (not shown here). Subsequently, the filled into the molding box molding material has been fumigated with SC> 2 gas. In this case, a chemical reaction has occurred between the resin binder and the sulfur dioxide gas, through which the resin binder has hardened.
• the dimensionally stable casting moldings (outer moldings 2, 3 and casting core 5 with its projections 6) thus obtained are in contact with their surfaces in contact with the melt (internal surfaces of the molds) Mold cavity 4, outer surfaces of the casting core 5 and its projections 6 and the mold cavity 4 covering portions of the lower mold part 2 associated surface of the upper outer mold part 3) has been coated with a coating applied in the form of a coating 7,8,9, as the sulfide formers calcium carbonate contained.
• the cast iron treated with magnesium immediately prior to entry into the casting mold 1 is poured into the casting mold 1 via the pond, not shown, and flows through channels, also not shown, into the molding cavity 4 until it is completely filled with cast iron.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Mold Materials And Core Materials (AREA)
• Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)

Priority Applications (6)

Applications Claiming Priority (2)

Publications (1)

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Citations (7)

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• 2007
  • 2007-07-05 DE DE102007031448A patent/DE102007031448A1/de not_active Withdrawn
• 2008
  • 2008-07-04 EP EP08774799A patent/EP2176018B1/de not_active Not-in-force
  • 2008-07-04 WO PCT/EP2008/058723 patent/WO2009004090A1/de not_active Ceased
  • 2008-07-04 US US12/529,683 patent/US8327909B2/en not_active Expired - Fee Related
  • 2008-07-04 DE DE502008003125T patent/DE502008003125D1/de active Active
  • 2008-07-04 ES ES08774799T patent/ES2361381T3/es active Active
  • 2008-07-04 AT AT08774799T patent/ATE504372T1/de active
  • 2008-07-04 MX MX2009007385A patent/MX2009007385A/es active IP Right Grant
  • 2008-07-04 BR BRPI0812881A patent/BRPI0812881B1/pt not_active IP Right Cessation

Patent Citations (7)

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