DE1210138B - Void-resistant mixtures - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. CL:

B22d

German class: 31c-14

Number: 1210138 K $ U

File number: K 51844 VI a / 31 c

Filing date: January 16, 1964

Opening day: February 3, 1966

The present invention relates to a heat » supplying mixture that is used »to cast iron or steel in lost heads, memories, To keep funnels, risers and the like liquid as long as possible during and after the end of the pouring process and thus prevent the formation of voids in the casting.

Such mixtures are known and have been in various compositions for a long time used. These heat-giving mixtures keep the cast iron or steel fluid by adding z. B. when sprinkling on the surface of the melt due to an exothermic chemical reaction Develop considerable amounts of heat. In principle, they are structured like the well-known thermite mixtures and consist of at least one substance that provides heat when burned, e.g. Aluminum, as well as at least one substance that supplies the oxygen necessary for combustion, e.g. B. an iron oxide. In addition, they usually contain varying amounts of loosening agents and fluxes, Coal or coke dust and other additives that promote or delay combustion.

The technical development, especially in the casting of steel blocks, has recently gone by, To use mixtures that release the highest possible amount of heat. With such mixtures it is possible to keep the lost heads on steel blocks or slabs very small and thus increasing the yield of steel. A disadvantage of the known and suitable for this purpose Mixtures, insofar as they are made on a pure aluminum basis, is, however, extraordinarily high Price.

It is also known to use void-preventing mixtures in whole or in part with ferrosilicon as a heat-releasing agent To produce substance, however, such mixtures have hitherto had the disadvantage that their ignitability and their burning rate was very slow. It is also used by the incineration The silica produced by ferrous silicon greatly lowers the solidification point of the slag. Through this the castings or the slag from the combustion of the anti-void agent must be used Let them cool down for a long time before they can be treated any further *. This so far with wholly or partially Ferrosilicon as a heat-releasing substance produced masses are accordingly for use as so-called highly exothermic powder, in which there is the development of a high amount of heat within a relatively short period of time and rapid solidification of the slag arrives, unsuitable.

Void-preventing mixtures

Applicant:

Knapsack Aktiengesellschaft, Huerth-Knapsack

Named as inventor:
Dipl.-Chem. Dr. Hellmut Gabler,
Knapsack near Cologne;
Dipl.-Chem. Dr. Joachim Kandier,
Hans-Dieter Thiel, Brühl

The known highly exothermic mixtures thus have considerable disadvantages. The aluminum-containing compounds are extremely expensive, while the ferrosilicon-containing mixtures burn off too slowly and produce a slag that is too low in smear.

The method according to the invention also relates to a mixture partially produced with ferrosilicon as the heat-releasing substance, but which, on the other hand, does not have the above-mentioned disadvantages. It is an object of the invention that the mixture contains a bauxite as a loosening agent, the silica content of which is as low as possible. In general, bauxite contains 55 to 75% Al ₂ O ₃ , 0 to 30% Fe ₂ O ₃ , 2 to 35% SiOj and small amounts of TiO ₂ .

If a bauxite with less than 5% SiO ₂ is used, a slag is obtained after the incineration, the silica content of which is not higher than that of a slag obtained by burning off an aluminum and conventional loosening agents such as fireclay (about 42 to 45% Al ₂ O ₃ ; 50 to 54 ⁰ Z ₀ SiO ₂ ) containing mixture is formed. Surprisingly, it has also been found that the ignition and burn-off speed of such a mixture can be increased by adding small amounts of magnesium so that the amount of heat released in the unit of time is greatly increased. As a result, high peak temperatures are reached. If such a powder z. B. sprinkled on lost heads of steel ingots, a completely smooth surface of the solidified steel ingot is obtained even _five if comparable in quite some time since filling the dome with steel

609 503/321

■ - ■■ 'Γ 210 138 -' ^!

3 4

is streaked and is already standing high on the edge.A mixture with:
Have formed steel edges. So these powders have

even the effect, such frozen edges or weight percent

To melt wreaths again. '' Ferrosilicon (about 75 weight

The use of 5 ^r '■ · "percent Si) ·. \, 7. to 15

Magnesium described in highly exothermic masses,,. Bauxite _ (<5 percent by weight SiO ₂ ) '.10 "to 20.

however, in amounts that the corresponding mixture contains oxygen-supplying substances (hematite,

practically transform into a flash powder. At . Magnetite, manganese dioxide) 40 to 60

the aluminum evaporates larger amounts of magnesium. 8 to 18

Magnesium and burns ineffectively: over the upper ίο _Λ,. new- ι

area of the void-preventing mixture. Magnesium 0.5 to 1

The advantage of the mixture according to the invention is calcium fluoride about 2

precisely because with very small amounts of alkali _{nitrate (KNO 3} , NaNO ₃ ) about 2

Magnesium igniting and burning off the ex- - -

othermen mixture achieved to the desired extent 15 The constituents of the mixture according to the invention can. The released amount of heat can be finely divided in the following parts the desired time compressed, small sizes are available: ■

so that the corresponding heating or melting ferrosilicon. ' <1 mm, preferably

effect occurs. Thus, these additives make it possible. "^ q η jL ™ '

of magnesium, the highly exothermic mixture in the 20th '- ■ -. '-

Add amounts of bauxite necessary to obtain a · bauxite <2 mm

sufficient content of Al ₂ O ₃ in the slag and oxygen-supplying substances .. <1 mm

thus a high solidification point required aluminum <5 mm, preferably

are. The method according to the invention thus comprises ^: <2mm

the addition of small amounts of magnesium to a magnesium <3 mm, preferably

highly exothermic mixture containing considerable amounts <lmm

of ferrosilicon in combination with silicic acid ■ .- ■; ■

mem contains bauxite. The following examples show how the

The ferrosilicon is generally a fine addition according to the invention of small amounts of divided ferrosilicon with an Si content of more than 45%. 3 ° Magnesium, the ignition and burn-off speed is preferably over 60%. In particular, raises heavily. It is also shown that a ferrosilicon is used, which has the commercial substitute for common loosening agents such as chamotte called "ferrosilicon 75% Si". It is well known that low-silica bauxite causes the solidification of the Si content of such ferrosilicon to be increased in some cases at the rate of the slag, and in some cases its melt is slightly lower, and in some cases slightly higher than 75%. It is raised 35 point. The percentages can also be commercial, about 90% ferrous- are in percent by weight,
silicon as well as pure silicon with about 98% or '■ ■.:. . ^:
more percent Si can be used. As an example of magnesium
can be pure magnesium chips or waste chips . ■ ■
of any kind. The aluminum is in 40 It was used an experimental apparatus, the form of grit or chips mixed. Next r of an iron plate with an established Thermo Can mixtures of the invention to the element was. On the iron plate, a ring made of an insulating material was optimally placed under various practical conditions. In the ring fitted ^ZÜ: be, small amounts of fluxes or · 5 kg of highly exothermic combustion mass below demanding or -blocking agents; 45 Composition filled. ■ The ignition took place like calcium fluoride, cryolite, alkali nitrate or -chlo- ·. from the ground with HiKe of an ignition mixture, Als rat, marble powder, barite or the like. . : Time was measured as a measure of ignitability

In particular, the invention relates to a heat + that after igniting the cherry to the general

dispensing mixture to keep steel igniting liquid - recognizable by the mixture by one

and cast iron smelting in lost heads, violent flame development over the whole area.

like or funnels, which is characterized by - area - passed away. This time is hereinafter referred to as

denotes a content of: ignition time! After igniting the

• Mass, there was an even burning, of which

Weight percent duration is referred to as the burn time. The crowd had

55 following composition:

. Ferrosilicon (45 to about 90 wt.%

Weight percent Si) ... 5 to 30 aluminum. 14%

Bauxite (<5 percent by weight SiO ₂ ) ■ 5 to 25. Ferrosilicon 75% Si, 12%

Oxygen-thinning substances (iron - potassium nitrate ...: ...... 2%

oxides and / or manganese oxides) 40 to 70 60 _{Mixed hematite (Fe2} o _{3) 58} o _{/ o}

. Atammmm 5 to 20 _{"construction;;}

Magnesium ... 0.2 to 3 _ .. ^v ' ^ιο ., ^Λ _o ' ^v

Flux (CaF ₂ , Na ₂ F ₂ , Na ₃ AlF ₆ ) 0 to 5. Calcium fluoride 2% ■

Verbrennungsf promoting substances. . . ₆₅ ignition time,., ...., .., 112 seconds

(Alkali nitrates, alkali chlorates) ... 0 "to 5, ..-- '■ Burning time 113 seconds

Fillers (marble powder, coke, ■■■.:. Maximum temperature at

Charcoal or the like) .. .-, .. · ..,., .. · 0 to 20 ^.: \ Thermocouple .. .... 1520 ° C

1

The slag could be easily knocked off after just 30 minutes. After this time she was already brittle and did not pull strings. The surface of the iron regulator fused to the base plate was exposed of slag.

Example 2

The procedure was as in Example 1, but the mixture had the following composition:

Aluminum 14%

Ferrosilicon 75% Si 12%

Potassium nitrate 2%

Ground hematite 57.5%

Bauxite (2.7 ο /. Si) 12%

Magnesium powder 0.5%

Calcium fluoride 2%

Ignition time 95 seconds

Burn time 90 seconds

Maximum temperature on ^ao

Thermocouple 1600 ° C

Behavior of the slag after 30 minutes as in example 1.

Example 3

The procedure was as in Examples 1 and 2, but the mixture had the following composition:

Aluminum 14%

Ferrosilicon 75% Si 12%

Potassium nitrate 2%

Ground hematite 57%

Bauxite (2.7% Si) 12%

Magnesium powder 1%

Calcium fluoride 2%

Ignition time 55 seconds

Burn time 80 seconds

Maximum temperature at
Thermocouple 1630 ° C

Behavior of the slag after 30 minutes as in example 1.

Example 4

45

The procedure was as in Examples 1 to 3, but the following mixture was used:

Aluminum 14%

Ferrosilicon 75% Si 12%

Potassium nitrate 2%

Ground hematite 58%

Chamotte 12%

Calcium fluoride 2%

Ignition time 108 seconds

Burn time 120 seconds

Maximum temperature at

Thermocouple 1515 ⁰ C

When the slag was detached from the iron regulator after minutes, a layer of slag remained on the Glue regulus. The slag pulled strong threads.

Claims (3)

Patent claims: 1. Heat-giving mixture for keeping molten steel and cast iron in liquid lost heads, risers, or hoppers, characterized by a content of: Weight percent Ferrosilicon (45 to about 90 weight percent Si) 5 to 30 Bauxite (<5 percent by weight SiO ₂ ) 5 to 25 Oxygen-supplying substances (iron oxides and / or manganese oxides) 40 to 70 Aluminum 5 to 20 Magnesium 0.2 to 3 Flux (CaF ₂ , Na ₂ F ₂ ,
Na ₃ AlF ₆ ) 0 to 5 Substances that promote combustion (alkali nitrates, alkali chlorates) 0 to 5 Fillers (marble powder, coke, charcoal or the like) 0 to 20 2. Mixture according to claim 1, characterized by a content of: Weight percent Ferrosilicon (about 75 percent by weight Si) 7 to 15 Bauxite (<5 percent by weight SiO ₂ ) 10 to 20 Oxygen-supplying substances
(Hematite, magnetite, manganese dioxide) 40 to 60 Aluminum 8 to 18 Magnesium 0.5 to 1.0 Calcium fluoride about 2 Alkaline nitrate (KNO _{3 , NaNO 3} ) ... about 2 3. Mixture according to claim 1 or 2, characterized in that the components in finely divided Form in the following particle sizes: Ferrosilicon <1 mm, preferably <0.3 mm Bauxite <2 mm Oxygen supplying substances <1 mm Aluminum <5 mm, preferably <2mm Magnesium <3 mm, preferably <lmm 609 503/321 1.66 © Bundesdruckerei Berlin