This invention relates to an improvement in or relating to an antipiping compound and to a process for the heat retaining of hot top surface during ingot making.
In ingot making, such a process has hitherto been carried out widely by fixing a moulding with exothermic or heat-insulating composition to the top end of the mold or to the top part of the inner surface of the mold, pouring molten steel into said mold, adding exothermic antipiping compound to the hot top immediately after the pouring has been completed, to retard the solidification of the top part of the molten steel in the mold, preventing the generation of shrinkage holes, and thereby a sound ingot is made to improve the yield at the time of blowing of rolling, and various compositions which are to be added to the hot top surface have also been suggested.
The antipiping compound and the process for heat retaining of the hot top surface in accordance with this invention aim at increasing the heat-retaining effect than those conventionally realized and providing an economical antipiping compound and heat-retaining process.
That is, the present invention is to provide an antipiping compound for use in ingot making, which is made by essentially containing more than 5 percent by weight of coffee grounds in components selected from the group consisting of easily oxidized metal powders, powdery metal oxide, carbonaceous materials, fibrous materials, fluorides, nitrates, nonporous and porous refractory materials and other effective materials.
Further, this invention is to provide process in which compositions selected from the group consisting of easily oxidized metal powders, powdery metal oxide ones, carbonaceous materials, fibrous materials, fluorides, nitrates, nonporous and porous refractory materials and other effective components are prepared, molten steel is poured into the mold provided with a heat-retaining moulding for hot top consisting of exothermic or heat-insulating compositions, the aforesaid compositions are added to the top of said molten metal immediately after the completion of said pouring, and the coffee rounds is added thereon to heat-retain the hot top during the ingot making.
Still, this invention is to provide the process in which molten steel is poured into the mold provided with an exothermic or heat-retaining moulding for hot top, and the coffee grounds is added to the top of the molten steel immediately after the completion of said pouring to heat-retain the hot top during the ingot-making.
The heat-retaining material and the process for heat retaining in accordance with this invention relate each to use, during ingot making, together with the mold, the top of which or inner portion of the upper portion of which is provided with an exothermic or heat-retaining moulding for hot top.
The coffee grounds used in this invention is one exhausted during the process for making taste drinks in which coffee beans is roasted to be ground, and the resulting grains are extracted with hot water at high pressure and temperature to take up an extract containing more than 30 percent of a solid matter. Although the components of the coffee grounds are different depending on kinds of coffee beans before roasting, roasting conditions and methods for and condition of extraction and filtration, the oil content (ether-extract) and the carbonaceous content are generally contained in amounts of about 20 percent and about 60 percent by weight, respectively, and thus they are materials having high calorie as compared with sawdust, having as high as approximately 6,300 cal/g. As they burn well, they are easily available in great amounts, and inexpensive, it is found that they are quite suitable material for antipiping compound.
The easily oxidized metal powder as the exothermic basic material used for the heat-retaining compound of exothermic composition is metallic aluminum powder and its fine grains, finely crushed metallic aluminum foil and its granular and scaly materials, magnalium powder, calcium-silicon powder, etc. The metal oxides as the oxidizing agents involve ferrous oxide, ferric oxide, ferrous-ferric oxide, manganese dioxide, etc. The carbonaceous materials as the easily inflammable agents include powdered or finely crushed coke, coal powder, fine grain carbonized matter of plants, etc. Organic matters such as sawdust, asbestos, rock wool, silicate cotton, fibrous matters processed by spraying refractory clay, etc. or inorganic matters are used as fibrous materials.
Fluorides such as sodium, sodium aluminum fluoride, etc. are used as exothermic reaction promoter.
Nitrates as ignition agent according to this invention include sodium, potassium and barium nitrates.
The nonporous refractory materials include aluminum oxide, aluminum residual ash, magnesium oxide, etc., and the porous oxides involve diatomaceous earth, pumice, heat-expansible or expanded vermiculite, obsidian, perlite, silex, shale, etc.
As for gas absorber or antiheating agent, calcium borate is sometimes used, and other materials are used which are effective for heat retaining hot top and not attack the ingredients of the molten steel.
This invention is characterized in that the coffee grounds are indispensably employed as component of the antipiping compound for ingot making by mixing it in the exothermic antipiping compound selected from the crude materials as above mentioned either by admixing it in the latter or by using it together or independently with the latter.
The following examples will explain this invention:
Table 1 illustrates several examples according to this invention:
Table 1 (Component) --------------------------------------------------------------------------- (% by weight)
Number No.1 No.2 No.3 No.4 No.5 Name of crude material __________________________________________________________________________ Metallic Powder 6 6 5 4 4 aluminum Fine grain 12 11 11 10 9 Ferrous oxide 12 12 11 12 11 Ferric oxide 8 7 8 7 8 Coke fine grain 3 3 3 3 3 Diatomous earth 4 4 4 4 4 Sodium fluoride 2 2 2 2 2 Sodium nitrate 3 3 3 2 2 Aluminum residual ash 45 45 41 40 36 Coffee grounds 5 7 12 16 21 __________________________________________________________________________
A 3t mold of which inner sectional shape is square and whose upper inner face is provided with a heat-retaining molding for a hot top of the same composition and shape with the top and made to 9.6 percent the hot top capacity is prepared by pouring molten steel therein, and comparison is made of the cases in which the heat-retaining materials having the compositions, No. 1-No. 5, shown in table 1 are added by 6 kg. each to the top surface of the molten steel immediately after the pouring completed, with those in which the antipiping compounds having the compositions same as those described in table 1 excepting that the coffee grounds are replaced by sawdust. The result as shown in table 2 are added by 6 kg. each.
Table 2 --------------------------------------------------------------------------- Comparison of Yield in Ingot Making (%)
No.1 Number No.2 No.3 No.4 No.5 Classification __________________________________________________________________________ Use of heat retaining material having the compositions shown in table 1 in accordance with this invention 86.8 87.2 87.1 86.9 86.4 __________________________________________________________________________ Use of those having same compositions as those shown in table 1 excepting that the coffee grounds are replaced by sawdust 86.1 86.3 85.9 86.0 85.3 __________________________________________________________________________
Table 2 shows a mean yield of 30 ingot makings in each number. The heat-retaining materials wherein coffee grounds are contained according to this invention improve the yields in ingot makings by 0.7-1.2 percent, i.e. 0.96 percent in mean value, as compared with those in which for example sawdust is used in place of coffee grounds are equal in amount.
A 6.5t mold of which inner sectional shape is square and whose upper inner face is provided with a heat-retaining molding for hot top of the same composition and shape with the top and made to 10.4 percent the hot top capacity is prepared by pouring molten steel therein, and comparison is made of the case in which 8 kg. of the exothermic antipiping compound is added to the top surface of the molten steel immediately after the pouring is completed and then the upper surface of said heat-retaining material is covered with 4 kg. of coffee grounds, the materials added being 12 kg. in total, with that in which 12 kg. of the exothermic antipiping compound is added in the same condition. The result obtained is as shown in table 3. ##SPC1##
Table 3 shows that the yields in ingot making are almost equal in both cases in which the heat-retaining material comprising 8 kg. conventional exothermic antipiping compound and 4 kg. coffee grounds are added and 12 kg. conventional antipiping compound added, and thus it is found that the antipiping effects in both cases are identical. Accordingly, it has been found that the process for heat retaining according to the present invention is economical and that said process makes possible reduction of the ingot making cost.
A 18t mold of which inner sectional shape is flat and has a ratio of the length to the width of 1:1.9 is provided with a heat-retaining moulding for hot top of the same composition and shape with the top and made to 12 percent the hot top capacity is prepared by pouring molten steel therein, and comparison is made of the case in which 40 kg. of coffee grounds are added by dividing it into 20 kg. each to the top surface of the molten steel immediately after the pouring is completed, with that in which 40 kg. of straw ash are added by dividing it into 20 kg. each in the same condition as above and that in which 40 kg. of chaff are added by dividing it into 20 kg. each. The result obtained is shown in table 4. ##SPC2##
The heat-retaining process for a hot top according to this invention, i.e. the addition of coffee grounds, improves the mean yields in ingot making by 0.35 percent and 0.53 percent as compared with the additions of straw ashes and chaff, respectively.
The coffee grounds which are to be admixed to the exothermic antipiping compound for use in steel ingot making according to this invention should be employed by more than 5 percent by weight. Although some effect may often be obtained by the addition of less than 5 percent by weight, apparent effect can be confirmed by the addition of more than 5 percent by weight.
The exothermic antipiping compound and the process for heat retaining according to this invention are characterized in that coffee grounds are employed either by being admixed or by being used together or independently. The coffee grounds exhibit superior heat-retaining effect than or equal to that conventionally attained either by admixing it to or by using it together with the heat-retaining material, and can reduce the cost for the heat-retaining material, being very economical. Moreover, whereas straw ashes and chaffs are particularly difficult to be collected and stored as well as to be handled, the coffee grounds are easily available and is put, for example, into a bag in a determined amount depending on these to be added. Therefore, the storage and handling are simple, and it is very convenient as it is durable to preserve for a long period, being extremely useful for steel ingot making.