Classifications

• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
  • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
  • C21C7/0056—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 using cored wires
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D1/00—Treatment of fused masses in the ladle or the supply runners before casting
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
  • C21C1/00—Refining of pig-iron; Cast iron
  • C21C1/10—Making spheroidal graphite cast-iron
  • C21C1/105—Nodularising additive agents
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C33/00—Making ferrous alloys
  • C22C33/08—Making cast-iron alloys
  • C22C33/10—Making cast-iron alloys including procedures for adding magnesium

Definitions

• the invention relates to an agent for treating cast iron melts based on a silicon alloy for the production of cast iron with spheroidal graphite, a method for producing this agent and its use.
• cast iron contains considerable amounts of dissolved carbon, which normally precipitates into lamellar form when the melt solidifies.
• the workpieces produced with such melts have insufficient mechanical strength values.
• ferrosilicon-magnesium alloys are the most commonly used alloys that are used to promote spheroidal graphite formation. Levels of cerium, rare earth metals and calcium control the reactivity of these alloys (Foundry Trade J. Int. (1987), 33 , 38 middle column, paragraph 1).
• any magnesium added to sulfur-containing cast iron melts has a desulfurizing effect.
• the higher the sulfur content of the cast iron melt the more magnesium is required to set the sulfur.
• it is therefore advisable to aim for a base iron with a low sulfur content but this is not always possible in practice. Therefore, in many cases it is necessary to presulfurize using the known presulfurization processes e.g. by introducing calcium carbide.
• Cast iron alloys solidify gray, white or mottled. These forms of solidification can also occur together in the casting.
• the cause is the microbial balance of the melt in interaction with the cooling conditions for the casting, the equilibrium temperature of the eutectic gray solidification falling below.
• the melt is inoculated, which means the addition of germ-active substances to the melt in order to specifically influence the solidification behavior or the microstructure formation in the casting.
• Vaccination can take place in the gutter, when filling the pan, in cast steel or in one or more stages.
• the invention has for its object to provide a treatment agent for cast iron melts, with which all previously necessary treatments can be carried out in a single operation.
• This task was solved by a means based on a silicon alloy with contents of magnesium, calcium, bismuth, rare earth metals, rest iron.
• An alloy is preferred which is composed as follows: Silicon 30 to 80% by weight magnesium 5 to 30% by weight Calcium 0.1 to 25% by weight bismuth 0.1 to 2% by weight Cerium mixed metal 0.1 to 5% by weight Iron as Rest.
• Bismuth in combination with the cerium mixed metal in the agent according to the invention has a high germination efficiency. This is particularly surprising, since bismuth, in addition to, for example, titanium, aluminum and lead, is one of the elements that tend to have a negative impact on spheroidal graphite formation in iron-carbon alloys. Due to the manufacturing process of the agent via a calcium silicon or ferrosilicon alloy, it is also possible that the agent still contains small amounts of aluminum due to the raw material.
• a product that has a desulfurizing, vaccinating and magnesium treatment and has the following composition has proven particularly useful: Silicon 40 to 60% by weight magnesium 15 to 25% by weight Calcium 5 to 20% by weight bismuth 0.3 to 1% by weight Cerium mixed metal 0.3 to 3% by weight Iron as Rest.
• the ratio of calcium, magnesium and silicon can be adapted to the requirements, with which one can control the desulfurization effect or the reactivity of the alloy and thus provide an optimally composed agent for each application.
• the preparation of the agent according to the invention can be carried out by first producing a calcium silicon or ferrosilicon melt in an electronic shaft furnace.
• the calcium content is expediently about 28 to 33% by weight, the silicon content about 60% by weight on tapping, while in the case of ferrosilicon the melt is said to contain about 60-75% by weight of silicon.
• the amount of magnesium, bismuth and cerium mixed metal is expediently added to the pan in metallic form by stirring.
• the melt which is about 1250 to 1450 ° C. hot, is tapped into a pan, the magnesium is alloyed, preferably as a pure metal, sets the desired calcium content of the alloy by adding metallic calcium or calcium silicon and finally stirs bismuth and the rare earth metal (cerium mixed metal).
• the calcium content can also be set directly in the base melt in the electronic shaft furnace using the appropriate composition of the mill, taking into account the raw materials used.
• the rare earth mineral in the form of bastnäsite, monazite or in the form of rare earth oxides can be added to the Möller.
• the rare earth metal is preferably metered into the base alloy in the form of cerium mixed metal, since in this way an exactly adjustable concentration in the alloy is obtained.
• the agent according to the invention is produced in the induction furnace from the metallic components.
• the procedure is completely analogous to the preparation of the agent according to the invention.
• the base melt temperatures required are between 1000 and 1250 ° C. Under these conditions, the required elements can be introduced and the finished product can be poured off after a short time.
• the agent can be used for the treatment of cast iron melts in the form of chunks or pieces as a pour-over or dip alloy.
• the agent is preferably metered into the pouring stream as fine-grained granules using a suitable device or, particularly preferably, brought into the form of a filled wire by covering it with a sheet metal jacket.
• the shape of the wire is particularly preferred because the transport of the agent as well as the targeted addition to a cast iron melt are thus completely problem-free.
• the agent according to the invention is obtained in an amount of 0.35 to 1.5% by weight applied to the weight of the cast iron.
• the winding speed of filled wires from 5 to 20 mm in diameter can be between 1 to 100 m / min. vary; 10 to 50 m / min are preferably set with a correspondingly selected wire thickness.
• the treatment of cast iron melts can be optimally simplified, since only a single treatment measure is necessary.
• the treatment can be carried out in a pan in a short time, while temperature losses remain very low.
• the combination of silicon-magnesium-calcium with bismuth and rare earth metal with sufficient deoxidation and desulphurization of the cast iron melt simultaneously creates a high nucleation capacity, which achieves a practically exclusive gray solidification of the cast iron with exclusive excretion of the carbon in spherulitic form. In this way, completely homogeneous material properties are achieved, even with different wall thicknesses of the castings.
• the alloy was broken, sieved to a grain size suitable for cored wire from 0.2 to 1.6 mm and packed in cored wire with a diameter of 13 mm.
• the wire produced in this way had the following characteristics: Wire type 13 mm Wire weight 350 g / m Filler weight 200 g / m Fill factor 57% Calcium content 40 g / m Magnesium content 47 g / m Silicon content 80 g / m Bismuth content 1 g / m Cerium mixed metal 1 g / m
• Base iron of the following chemical composition melted in a cold wind cupola furnace carbon 3.68% by weight Silicon 2.04% by weight manganese 0.14% by weight phosphorus 0.048% by weight sulfur 0.073% by weight is treated with cored wire of the above-mentioned characteristics, the wire being introduced into the cast iron melt using a winding device.
• the amount of iron treated varied between 630 and 650 kg.
• a typical covered nodular cast iron pan was used as the treatment vessel, the ratio of the height to the diameter being 2.4: 1.
• the sulfur reduction from 0.073% to ⁇ 0.01% was achieved with each of the 5 treatments.
• the graphite formation in the cast Y-2 samples (25 mm) was over 90% spherical.
• the number of spherulites with 100 - 200 balls / mm2 corresponded to the anticipated pre-vaccination effect of the treatment alloy.
• the alloy had the following composition: Silicon 50.2% by weight magnesium 24.3% by weight Calcium 5.1% by weight bismuth 0.5% by weight Cerium mixed metal 0.48% by weight iron Rest.
• the alloy was prepared as described in Example 1.
• the wire produced showed the following characteristics: Wire type 13 mm Wire weight 348 g / m Filler weight 198 g / m Fill factor 57% Calcium content 10 g / m Magnesium content 48 g / m Silicon content 99 g / m Bismuth content 1 g / m Cerium mixed metal 1 g / m

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Mechanical Engineering (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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Citations (3)

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• 1989
  • 1989-07-25 DE DE3924558A patent/DE3924558C1/de not_active Expired - Lifetime
• 1990
  • 1990-07-18 CA CA002021451A patent/CA2021451A1/fr not_active Abandoned
  • 1990-07-19 AU AU59164/90A patent/AU628197B2/en not_active Ceased
  • 1990-07-19 US US07/555,572 patent/US5087290A/en not_active Expired - Fee Related
  • 1990-07-23 EP EP90114104A patent/EP0410360A1/fr not_active Withdrawn
  • 1990-07-24 JP JP2194101A patent/JPH03122208A/ja active Pending

Patent Citations (3)

Non-Patent Citations (1)

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