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
  • C22C33/08—Making cast-iron alloys
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
  • B22F1/05—Metallic powder characterised by the size or surface area of the particles
• • 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

Definitions

• the invention relates to a treatment agent for the production of cast iron with spheroidal graphite or vermicular graphite and a method for its production.
• magnesium-containing treatment agents for the production of cast iron with spheroidal graphite or vermicular graphite.
• the addition of magnesium improves the strength properties of cast iron through its property of converting the graphite into the spherical or compact graphite form.
• Treatment agents are known from DE-OS 17 58 768, which have a coating of refractory masses, with the aim of alleviating the severity of the reaction and controlling the treatment.
• DE-OS 21 57 395 it is proposed in DE-OS 21 57 395 to coat the fine-grained magnesium-containing ferrosilicon alloys with pulverulent, binder-containing treatment materials made from graphite, sulfur or metals, with condensation resins, starch or cellulose derivatives or inorganic substances such as e.g. B. water glass can be used.
• the disadvantages of all these known means are to be seen in the fact that they have to be provided with any coatings in additional processes and that z. T. unwanted accompanying substances are introduced into the melt.
• the present invention was therefore based on the object of developing a treatment agent for cast iron melts based on ferrosilicon magnesium with a silicon content of 40 to 80% and a magnesium content of 1 to 15%, which does not have the disadvantages mentioned and that without the aid of any coatings enables an even and bumpless reaction.
• a ferrosilicon magnesium of the above composition in the form of granules with a specific surface area of 0.2 to 0.8 m2 / g .
• the agent according to the invention with its specific surface area, has an extremely uniform and calm reaction with the iron melt. Furthermore the cast iron pieces produced with the treatment agent according to the invention have low slag and surface defects, which was likewise not foreseeable.
• the treatment agents according to the invention are ferrosilicon magnesium granules and, in addition to a BET specific surface area of between 0.2 to 0.8 m 2 / g, advantageously have a grain size of 0.1 to 20 mm, preferably 1 to 3 mm. Their specific surface is therefore much larger than that of normal, broken ferrosilicon magnesium particles of the same grain size. This large specific surface is due to the porous and jagged surface structure of the granules, which is due to the manufacturing process.
• the agent according to the invention also contains 2 to 50 wt .-% fluorides of alkaline earth metals such.
• ferrosilicon magnesium granules of the invention can also contain 0.1 to 5% by weight of rare earths, based on the weight of the treatment agent, the rare earths preferably consisting of 40 to 100%, in particular 40 to 50% cerium or 100 % Lanthanum exist. These additives further improve the spheroidal graphite formation of the cast iron.
• This structure of the granules is obtained according to the invention by directing a melt jet of a ferrosilicon-magnesium alloy onto a baffle plate made of refractory material and allowing the melt drops thrown back from the baffle plate to solidify in a liquid-filled collecting container.
• the basic principle of this granulation method is known for the production of granules with a smooth surface and can e.g. B. be carried out with a device according to DE-AS 10 24 315.
• the ferrosilicon-magnesium melt surprisingly, however, the usual granules with a smooth surface are not obtained, but rather jagged grains with a porous surface structure and a large specific surface.
• the height of the melt jet is preferably about 0.1 to 1.0 m.
• the desired grain size range from 0.1 to 20 mm, preferably from 1 to 3 mm, is thus obtained. Since the grain size also depends on the flow rate of the melt, it is advisable to use the molten ferrosilicon magnesium alloy in an amount of 50 to 500 kg / per minute. It is also possible to work with other quantities and drop heights, but the parameters given above have proven to be particularly advantageous.
• the type of liquid in the collecting container has little or no influence on the surface quality and the specific surface. Only chemically inert behavior towards the liquid ferrosilicon magnesium alloy is necessary. An aqueous liquid is preferred for economic reasons.
• the ferrosilicon magnesium treatment agent according to the invention which has a silicon content of 40 to 80% and a magnesium content of 0.5 to 15%, is preferably used in an amount of 0.1 to 4% by weight for the production of cast iron with spheroidal graphite or vermicular graphite. , based on the weight of the molten iron.
• the treatment can be carried out according to the usual methods such. B. overflow process (sandwich method) or inmold process take place, with the overflow process because of the extremely quiet and uniform reaction even a covering of the ferrosilicon magnesium granules with steel chips or iron shavings can be dispensed with, without the yield of magnesium falling significantly as a result of burn-off losses.
• the smooth and shock-free reaction not only achieves high magnesium yields, but also prevents material losses due to ejection.
• the treatment agent according to the invention has a higher tendency to ferritization than comparable magnesium-containing agents, whereby the toughness values of the castings are decisively improved.
• the castings have fewer slag and surface defects, so that this quality of the castings is also increased.
• a ferrosilicon magnesium alloy with the following composition is melted in the induction furnace and poured into a graphite crucible using a transport pan, which acts as a tundish and has an outlet cross section of 20 mm.
• the molten alloy with a temperature of 1450 ° C leaves the tundish at a flow rate of 80 kg per minute and hits in the form of a pouring jet on a baffle plate made of refractory material, which is located 0.64 m below the outlet opening.
• the liquid material is thrown back from this baffle plate in the form of small droplets and collected in a container filled with water, which is located 4.5 m below the baffle plate.
• the particles obtained in the form of granules have the following grain size distribution: Their specific surface area is on average 0.35 m 2 / g.
• This iron melt is treated in a showering process with ferrosilicon magnesium granules with a grain size of 0.5 to 6 mm and a specific surface area of 0.3 m 2 / g and the following composition:
• the magnesium yield is 57% despite the lack of coverage.
• the subsequent vaccination with 0.25% with FeSi 75 is carried out as a ladle vaccination when pouring into the ladle.
• the metallographic examination of the cast castings with a wall thickness between 8 and 35 mm shows in all cross sections a formation of at least 90% spheroidal graphite with 80 to 90% ferrite and 10 to 20% pearlite as structural components. Cementite is not observed in any of the samples examined. In addition, the castings are free of reaction products and influences of slag.
• wall thickness samples with wall thicknesses of 2.5, 5, 7.5 and 10 mm are cast and examined metallographically. Depending on the wall thickness, the ferrite content drops from 70% to 10 mm wall thickness to 40%, with 2.5 mm wall thickness. All samples are free of cementite.
• the base iron is melted in a casting furnace with plug discharge, the temperature of the melt being 1445 ° C. and the iron having the following composition:
• the ferrosilicon magnesium treatment agent has a specific surface area of 0.45 m 2 / g and is composed as follows:
• the casting of the casting mold takes place in 9 seconds, whereby the reaction during the casting process is very calm and uniform and no post-reaction is observed after the end of the casting.
• ferrosilicon magnesium granules are poured into the bottom pocket of a graphite crucible and poured over with the base iron, which has a temperature of 1500 ° C.
• the treatment agent used has a specific surface area of 0.3 m 2 / g and has the following analysis:
• the melt Before casting the melt into a U-test according to DIN 1693, the melt is ew with 0.3 G .-% ferrosilicon by stirring, seeded at a temperature from 1405 ° C three minutes after the treatment with ferrosilicon magnesium granules encapsulated with the following Set analysis values:
• the metallographic examination carried out on sections of the tear rod shows approximately 90% vermicular graphite with approximately 10% spheroidal graphite with a predominantly ferritic matrix and with a residual pearlite content of approximately 25%.

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• 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)
• Manufacture Of Iron (AREA)

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• 1984
  • 1984-02-09 DE DE19843404607 patent/DE3404607A1/de not_active Withdrawn
  • 1984-06-20 AU AU29547/84A patent/AU546120B2/en not_active Withdrawn - After Issue
  • 1984-06-26 NO NO842574A patent/NO842574L/no unknown
  • 1984-07-02 US US06/626,634 patent/US4540436A/en not_active Expired - Fee Related
  • 1984-07-02 BR BR8403262A patent/BR8403262A/pt unknown
  • 1984-07-04 ES ES534019A patent/ES534019A0/es active Granted
  • 1984-07-05 EP EP84107888A patent/EP0131271A1/fr not_active Withdrawn

Patent Citations (6)

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