US2937424A

US2937424A - Ingot mould made of spheroidal graphite cast iron

Info

Publication number: US2937424A
Application number: US668401A
Authority: US
Inventors: Guenzi Eraldo
Original assignee: Pont a Mousson SA
Current assignee: Pont a Mousson SA
Priority date: 1956-06-28
Filing date: 1957-06-27
Publication date: 1960-05-24
Anticipated expiration: 1977-05-24

Description

May 24, 1960 E. GUENZI 2,937,424

meow MOULD MADE OF SPHEROIDAL GRAPHITE CAST IRON Filed June 27, 1957 United States Patent INGOT MOULD MADE OF SPHEROIDAL GRAPHITE CAST IRON Eraldo Guenzi, Pont-a-Mousson, France, assignor to Compagnie ode Pont-a-Mousson, Pont-a-Mousson, France, a French body corporate Filed June 27, 1957, Ser. No. 668,401 Claims priority, application France June 28, 1956 2 Claims. (Cl. 22-139) The present invention relates to cast iron ingot moulds for casting steel ingots or ingots of other ferrous alloy. It is known that ingot moulds are used in the casting of solid blocks usually of steel. On account of the high temperature of the steel during the casting operation, the moulds undergo a great thermal shock which is repeated for each casting. An ingot mould is put out of condition due in particular to the appearance of small superficial cracks in its inner surface and/or splits or cracks in the wall. Usually these defects appear after a great number of casting operations. In some cases, the cracking occurs as soon as the first casting operations have been performed and the mould is said to have undergone a premature cracking and is of course thenceforth useless.

It is usual to estimate the output of an ingot mould by the number of tons of steel cast with the same mould until it is rendered useless. There results a particular conception of mould quality which is the consumption of ingot moulds per ton of steel, this consumption being obtained in dividing the weight of the ingot mould in kilograms by the total number of tons of steel cast; the lower this consumption the better is the output of the mould.

Another conception known to steel workers is the ratio between the weight of the mould and that of the ingot, or P/p, where P is the weight of the mould and p the weight of the ingot. This ratio may be expressed as a function of the volume V of the metal of which the mould is formed and of the inner volume V of the mold in which the steel is cast.

Thus:

where d is the density of the cast iron, which is on average 7.15, and

where d is the density of the molten steel;

K is the coefficient of filling of the mould; usually ingot moulds are filled up to 9/10 of their volume, so that K=0.9.

If the density of the molten steel is 7:

p: V 7 0.9=6.3V

the ratio P/ p is therefore written:

The ratio V V therefore permits calculating the mean thickness of the wall of the mould.

A general investigation relating to cast iron ingot moulds used in steelworks, carried out by the Institut de Recherches Sidrurgiques (IRSID) and published in September 1954, reveals that the ratio P/p is generally greater than 1. This corresponds to usual conditions of use of ingot moulds having have of occurring rapidly.

In other words an ingot mould is heavier than the ingot it is intended to cast.

Experience has furthermore shown that, as concerns cooling of the steel, the mould acts as a heat accumulator. Temperature readings taken on the outer surface of the moulds in current use, show that the wall remains during the whole period of solidification at a relatively low temperature, which rises slowly, after the steel has remained a relatively long period in the mould, to a value of around 500 to 600 C. During the whole of the main phase of the solidification, the heat evacuated by the steel or other ferrous alloy accumulates therefore in the walls of the mould, and calculation shows that the quantity of heat evacuated by radiation is hardly 5% of' that stored in the walls of the mould.

The investigations carried out by I RSID had, moreover, for purpose to ascertain the variations in the output or consumption of an ingot mould as a function of the ratio P/ p. The results of the investigations confirm the known fact that the percentage of crack appearance due to successive thermal shocks increases with the ratio P/ p the heavier the mould the more tendency the cracks In a general way, the ratio P/ p rarely exceeds 1.5

(namely ;=1.32)

Further, it has been established that the appearance of cracking increases with decrease in the ratio P/ p; the smaller this ratio the more cracking there is at the end of a restricted number of casting operations. Briefly, heavy ingot moulds, namely those in which the ratio P/ p is between 1.2 and 1.5 (so that 2 is between 1.14 and 1.32), eventually become useless owing to small cracks which occur in the inner surface of the moulds. The light ingot moulds, whose ratio P/ p is between 1 and 1.2 (so that 2 is between 0.88 and 1.14) become useless more frequently on account of cracking due to excessive inner stresses, and tests carried out show that decreasing still more this ratio increases the speed at which the ingot moulds are put out of use due to cracking.

If the variations in the consumption of ingot moulds per ton of steel cast as a function of the ratio P/p are studied from the results provided by the American Iron and Steel Institute in February 1948, it is found that if it is attempted to reduce the ratio P/ p below 1, the consumption of ingot moulds passes through a minimum, if P/ p is about 0.9

1 (so that 0.79 the consumption once more rising when this ratio is less than 0.9.

Applicant has discovered that the use of spheroidal graphite cast iron in the construction of ingot moulds permits obtaining moulds of reduced thickness Whose ratio 1 2 is less than 0.79 (so that P/p 0.9), and this results in the mould lasting longer than conventional ingot moulds and having a notably more restricted consumption.

The object of the invention is to provide an ingot mould characterized in that it is composed of spheroidal which is less than 0.79 is obtained.

In the accompanying drawing:

Fig. 1 is a side elevation, and

Fig. 2 a top plan view of one example of ingot mould in accordance with the invention.

As shown in the drawing, the ingot mould may be of truncated shape with substantially square cross-section having rounded corners. The overall heightis 205 cm. The larger base has an internal dimension of 63 cm. and a wall thickness of 11 cm., while the smaller base or apex an internal dimension of 55 cm. and a wall thickness of 7 cm. The mould is provided with the customary outstanding lifting hooks or lugs for engagement with an elevating or tipping device.

When made of spheroidal graphite as herein described and with dimensions substantially as illustrated, the ingot mould falls within the ranges of material-volume to internal-volume ratio and mould-weight to ingot-weight ratio as defined in the appended claims.

Tests carried out on an ingot mould embodying the invention demonstrate that this mould no longer acts in the manner of a heat accumulator but as a heat dissipator, which is the more efiicient as the thickness is less.

There will now be given some results obtained from comparative tests of ingot moulds of cast iron used in casting Thomas steel ingots of about four tons. These ingot moulds were of four types:

(1) Conventional ingot moulds (L composed of a lamellar graphite grey iron having a ratio The analysis of this cast iron was the following by weight, in addition to the iron:

Percent Carbon 3.58 Silicon 1.82 Manganese 0.86 Phosphorus 0.10 Sulphur 0.05

(2) Ingot moulds (L composed of spheroidal graphite cast iron having a ratio (3) Ingot moulds (L composed of spheroidal graphite cast iron having a ratio (4) Ingot moulds (L composed of spheroidal graphite cast iron having a ratio Apart from their thicknesses, the moulds L L L had shapes similar to that of the conventional moulds L The spheroidal graphite cast iron of which the moulds L L L, were composed had the following approximate analysis by weight, in addition to the iron:

Moreover, this cast iron had a pearlitic-ferritic structureobtained, in the known manner, either directly upon casting or following on a heat treatment by annealing in the known manner.

The tests were carried out on six ingot moulds of each type, used under the same conditions. The results were as follows:

The results of these tests demonstrate that ingot moulds composed of spheroidal graphite cast iron have a ratio less than 0.79 and have a consumption which decreases with decrease in this ratio, contrary to what occurs in that case of grey cast iron ingot moulds. This consumption is two to three times less than that of the lightest conventional ingot moulds (L having a ratio -088 that is a ratio Preferably, the ratio is between 0.7 and 0.4

Applicant believes that these particularly favorable results can be explained owing to observations during the tests.

In the course of a first phase, which lasts about 5 of the total time during which the metal rests in the mould, starting from the pouring of the liquid steel, the mean temperature of the light ingot moulds is higher than that of the heavy ingot moulds. Owing to the characteristics of spheroidal graphite cast iron in the hot state being superior to those of grey cast iron, a premature cracking is avoided, which cracking would render the mould useless and is frequent in the case of grey cast iron moulds as soon as the ratios 5 and P drop below 1 and 0.88 respectively.

In the course of cooling, the temperatures of the inner and outer faces of the ingot moulds continue to rise and it is observed that the outer temperature is the higher as the mould is thinner.- As, when removing the ingot from the mould, the problem is to dissipate from the steel cast a certain amount of heat, resulting from the weight of the ingot and the temperature drop it is neces' sary to obtain in the metal, this dissipation of heat is the quicker as the thickness of the ingot mould is thinner, since dissipation of heat by radiation which is, as is known, proportional to the fourth power of the temperature, is the greater as the temperature of the outer face of the ingot mould is higher. Thus, with thin ingot moulds there results a more rapid dissipation of heat due to the more intense radiation from the mould, which then performs the function of a heat dissipato'r. Thus the inside temperature reached by the ingot mould is the lower as the mould is thinner, which decreases the rate at which small cracks appear and thus increases the life of the ingot mould.

Although a specific embodiment of the invention has been described, many modifications and changes may be made therein without departing from the scope of the invention as defined in the appended claims.

Having now described my invention what I claim as new and desire to secure by Letters Patent is:

1. Ingot mould for steel ingots and other ferrous alloy ingots, characterized by said mould being composed of spheroidal graphite cast iron and by a ratio between the volume V of the mould side walls and the volume V of the mould cavity between 0.79 and 0.4.

2. Ingot mould wherein the ratio spheroidal graphite cast iron which has the following analysis by weight, in addition to the iron:

Percent Carbon 3.4 to 3.7 Silicon 1.8 to 2.4 Manganese 0.25 to 0.5 Phosphorus 0.03 to 0.10 Sulphur 0.005 to 0.01 Magnesium 0.05 to 0.08

References Cited in the file of this patent UNITED STATES PATENTS 1,158,318 Sheldon Oct. 26, 1915 1,336,459 Woodward Apr. 13, 1920 1,672,479 Williams June 5, 1928 2,071,906 Stevens Feb. 23, 1937 2,485,760 Millis et al. Oct. 25, 1949 OTHER REFERENCES Bacon: Journal of the Iron and Steel Institute, vol. 158, 1948, No. 1, pages 81-95. Published by the Institute, London, England. 7

Bauer et al.: Fonderie, vol. 133, February 1957, pages 64-79. Published by Editions Techniques des Industries de la Fonderie, Paris, France.

Gagnebin et al.: Iron Age, vol. 163, No. 7, Feb. 17, 1949, pages 77-84. Published by the Chilton Co., Inc., Philadelphia, Pa.

Ristow: Stahl and Eisen, vol. 60, No. 19, May 9, 1940, pages 401-404 and 427-433. Published by Verl-ag Stahleisen M.B.H., Dusseldorf, Germany.