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
  • C21D5/04—Heat treatments of cast-iron of white cast-iron
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C37/00—Cast-iron alloys
  • C22C37/06—Cast-iron alloys containing chromium

Definitions

• the invention relates to cast parts with high impact strength and wear resistance made of white, at least predominantly austenitic chromium cast iron, which contains alloy components of 2.2 - 3.6% C, 8 - 30% Cr, O - 3% Mo, 0 - 6% Ni, O - 2% Mn, O - 3% Cu and O - 1.5% V.
• the chemical analysis of the alloys mentioned in these sheets is usually within the following limits, with all percentages, as in the introduction, being percentages by weight:
• the base consists of austenite and martensite with 10 to 50% pearlite.
• the matrix Due to the presence of pearlite or secondary carbides, the matrix is brittle and the long-term impact strength and wear resistance are low.
• the base material is converted into martensite by tempering and the properties are improved according to the application.
• heat treated i.e. After hardening and single or multiple tempering and relaxation with the aim of reducing the residual austenite content, the hardness is increased and the permanent impact resistance is improved.
• the latter is still only a fraction of that which e.g. is known from high manganese steel, and therefore the wear parts occasionally fail during operation.
• the operational breaks of the wearing parts not only lead to a breakdown of the crusher, for example, but sometimes to damage to the machine itself.
• such castings are characterized in that the structure is free of pearlite and secondary carbide precipitates.
• the content of the casting mold which in this case is formed from a metallic permanent mold, is formed by suitable cooling after casting to give a predominantly austenitic or pearlite or secondary carbide-free structure.
• the casting process takes place at a temperature of about 1400 ° C, the unpacking takes place at a temperature of over 900 ° C, predominantly above 1000 ° C, in any case above the AC3 temperature, which is called the ⁇ - ⁇ transition temperature.
• the cooling rate must be controlled in such a way that no secondary carbide precipitations and thus destabilization of the austenite and no pearlite formation can take place.
• the cross section of the cast parts can vary widely, so that the cooling rate also changes.
• the ability to influence the cooling rate has certain limits (thermal conductivity, stress build-up, risk of cracking and others), so that it may be necessary to work with a lower cooling rate than would be necessary to prevent pearlite formation or secondary carbide deposits.
• an alloy must be produced by changing the chemical composition, the time-temperature conversion curve of which allows a lower cooling rate without getting into the pearlite conversion range.
• the castings can be relaxed afterwards up to temperatures which cannot cause any changes in the austenite, i.e. that there is no destabilization by secondary carbide precipitations, preferably at 200 - 300 ° C.

Landscapes

• 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)
• Heat Treatment Of Articles (AREA)
• Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)

Applications Claiming Priority (2)

Publications (1)

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Cited By (6)

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Citations (7)

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• 1979
  • 1979-11-19 CH CH10291/79A patent/CH648353A5/de not_active IP Right Cessation
• 1980
  • 1980-11-08 EP EP80106898A patent/EP0029539A1/fr not_active Ceased
  • 1980-11-12 BR BR8007383A patent/BR8007383A/pt unknown
  • 1980-11-18 US US06/207,997 patent/US4382828A/en not_active Expired - Lifetime
  • 1980-11-18 JP JP16149580A patent/JPS5687651A/ja active Pending
  • 1980-11-19 AU AU64496/80A patent/AU537793B2/en not_active Ceased

Patent Citations (7)

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