FI56980C - NODULISERINGSKOMPOSITION FOER ANVAENDNING VID FRAMSTAELLNING AV SEGJAERN - Google Patents

Description

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Patent · och registerttyrelaan 'Aniekan utiagd och uti. * Krifun pubik.nd 31.01.80 (32) (33) (31) Requested Muoikus »Begird prloritet 15.10.71 ~ USA (US) 189670 (71) United States Pipe and Foundry Company, 3300 First Avenue, North _ Birmingham, Alabama, USA (72) Andrew Batisto Malizio, Delran, NJ, Martin Albert Rice, Florence, NJ, Harry Fisher Brooks, Levittovn, Penn., USA (US) ( FIELD OF THE INVENTION Such a mixture is of interest in cast iron metallurgy, the end products of which are malleable cast iron products which are produced, for example, by the molding or sand casting process.

For many years, the main commercial method in the production of wrought iron has been the addition of magnesium in the form of magnesium-containing alloys or elemental, whereby magnesium causes graphite to solidify as spheroids. The formation of graphite in this form results in excellent strength and forgeability of the material.

The use of magnesium or magnesium-containing alloys has many well-known drawbacks, the most important of which is that the reaction from the addition of magnesium to molten iron is usually quite violent and causes the formation of thick, white clouds containing magnesium oxide particles. The reaction is also accompanied by a dazzling white flame which is impaired in sight. Other disadvantages are that the high reactivity present makes it difficult to achieve high utilization of added magnesium, so that the efficiency of the process is poor. In addition to the generally achievable poor utilization, the magnesium content of the melt decreases with time, 56980 because magnesium is lost through evaporation, oxidation, and association with any sulfur in the melt. This loss of magnesium is commonly referred to in this art as "fading".

Some of the aforementioned drawbacks can be partially avoided depending on the manner in which magnesium or magnesium alloy is added to the molten metal bath. For example, the eyes can be protected from glare by using a protective cover. Somewhat better efficiencies can also be achieved by adding magnesium to the bath under pressure rather than pouring molten metal over the magnesium alloy. From an economic and process point of view, these methods are generally poor in that they require additional equipment either to close the area where the magnesium additions are made or to put pressure on the vessel in which the additions are made. These methods, especially pressurization, also increase the duration and cost of the process.

On the other hand, it is already known that cerium is also a nodulating element and less reactive when added to molten cast iron, thus overcoming glare and smoke difficulties and also giving better utilization rates. However, despite better utilization rates and lower reactivity, serum exhibits a detrimental "fading" rate. In addition, cerium is generally effective only in hyper-eutectic cast irons, is a strong carbide former, and in our experience it has formed graphite particles that are not as perfect in shape as those obtained by the magnesium process.

The object of the invention has been to develop a method for producing malleable cast iron which would solve some of the problems encountered in the prior art. It is an object of our invention to reduce the amount of nodulating agent required to provide nodulated graphite in light.

It is a further object of the invention to reduce the smoke and glare associated with the addition of a nodulating agent.

It is a further object of the invention to reduce the rate of "fading" of the nodulating effect in a treated bath.

It is a further object of the invention to provide a method for minimizing the slag content of wrought iron.

It is also an object of the invention to provide a method in which it is possible to carry out a selection from different nodulating agents and different amounts of nodulating agents.

These objects are achieved by the process according to the invention, which is characterized in that magnesium and each other element in the mixture are present in an amount of 1 to 3% by weight and that the total amount of nodulating elements in the mixture does not exceed 12% by weight. that it contains at least 45% by weight of silicon and that the amount of magnesium possibly used in the form of an alloy in the alloy is 1 to 3% by weight. In this case, the amounts of the individual elements are selected so that the amount of each individual nodulating element alone is not sufficient to form a spheroidal graphite, but the total amount of nodulating agents is sufficient to provide said spheroidal graphite.

According to a preferred embodiment of the invention, two or more nodulants are added to the silicon-iron alloy or mixture of ferrous alloys so that the alloy or mixture of alloys does not contain more than 3 # of each individual nodulant and that the combination of nodulants in the alloy or alloys does not. The advantages according to the invention are the following: a) a strong reduction in smoke and glare when the alloy is added to the bath, b) a large reduction in the fading effect, c) a reduction in the total amount of nodulant required for a given light, d) a reduction in the slag content of the lights.

Figure 1 is a schematic representation of a conventional forging process for forging iron castings and is therefore not part of the present invention.

Figure 2 is a graph showing the residual amount of effective nodu warp elements in a molten iron bath as a function of time and comparing the addition of one nodulating element (as is known in the art) to the addition of more than one nodulating element according to the present invention.

Figure 3 is a photomicrograph of the graphite structure of a tube light to which five nodulating elements have been added in accordance with the present invention after prolonged storage of the melt.

Figure 4 is a graph comparing the percentages of initial additions in a cast iron bath as a function of shelf life and the addition of one nodulating element (as is known in the art) to the addition of more than one nodulating element according to the present invention.

Figure 5 is a graphical representation of the amount of two nodulating elements remaining in a tube made under production conditions as a function of the time elapsed after addition in accordance with the present invention.

4,55980

Figure 1 schematically shows a conventional forging iron light manufacturing process. This invention relates to a nodulation step, the steps preceding which are known to those skilled in the art. The ratio of the nodulating agents used, their mode of use and the nodulating power are the basis of the invention.

The present invention is based on the finding that the total amount of nodulating agents required to produce forging iron can be reduced by adding more than one nodulating element in appropriate amounts. This makes it possible to reduce the concentration of the nodulating element in the bath, which in turn improves the efficiency, gives a longer effective duration, i.e. reduces' 'fading *', minimizes glare and smoke, and minimizes the tendency of iron to form slag.

The following results, shown in Tables I and II, were obtained by nodulating individual batches of molten low-sulfur cast iron as indicated in the tables:

Table I

Added Added start- total- Remaining in the melt after time had elapsed:

Test substances amount 1 5 10 15 minutes A Mg 0.05% 0.022 0.016 0.011 0.008 B Ce 0.055? 0.037 0.019 0.011 0.003 C Mg + Ce 0.055? 0.04l 0.037 0.030 0.027

(0.025 Mg + (0.020) (0.017) (0.015) (0.013) Mg-X

0.025 Ce) (0.021) (0.020) (0.015) (0.014) Ce D Mg 0.055? 0.034 0.029 0.025 0.022 + Ce (0.015? Kuta- (0.008 0.007 0.006 0.005) Mg + La kin 5 ai- (0.008 0.006 0.005 0.004) Ce + Nd material) (0.0085 0.006 0.0025 0.00l) La + Y (0.005 0.005 0.0065 0.010) Nd

(0.005 0.005 0.005 0.002) Y

The numbers in parentheses represent the amounts of private elements.

Table II _% of the original total amount remaining in the melt when Added initial- Added total time had elapsed Test substances amount 1 5 10 15 minutes A Mg, 0.055 alone? 44 26.5 22 16 B Ce, just 0.055? 74 38 22 6 C Mg + Ce $ 0.05 80 64 60 52 D Mg + Ce + LA + Nd + Y $ 0.05 69 58 50 44

In all the experiments listed in the previous tables, the AB low-sulfur molten cast iron bath before the nodulation step contained the following elements within the following limits: total carbon $ 3.5 - $ 3.6 silicon 1.9 - $ 2.1 manganese 0.25 - $ 0.30 5,56980 sulfur 0.005 - 0.012? phosphorus 0.04 - 0.06%

In Experiment A, 0.05 wt.% Of magnesium? the addition of iron was made as a commercial, serum-free magnesium iron with a magnesium content of 6.17% · In Experiment B, 0.05% by weight of? clean cerium metal chips for the bath. In Experiment C, magnesium and cerium additions were made as an alloy containing 3> 0? magnesium plus 3.0? serium, 45? silicon and the rest iron. The total addition of 0.05% by weight of nodulating agent consisted of 0.025? Of magnesium plus 0.025? Of serum. In Experiment D, the total addition of nodulating agent was again 0.05% by weight. In this case, the addition of the nodulating agent consisted of 0.01? Each of the following five elements: magnesium, cerium, lanthanum, neodymium, and yttrium. Magnesium and cerium were added as a silicon-iron alloy containing 3? magnesium and 3? cerium.

Lanthanum and neodyn were added as metals: neodymium contained 74% neodymium and 14% praseodymium. Yttrium was added as a pie iron containing 20? of yttrium.

The results listed in Tables I and II are also shown graphically in Figure 2, where in each experiment A-D, the amount of nodulant remaining in the molten cast iron bath is plotted as a function of time compared to the amount of nodulant originally added to the bath.

It can be seen from Figure 2 that the magnesium and cerium concentrations “fade” to lower and lower values over time, so that at some point the concentration is insufficient to develop a proper spheroidal graphite structure.In centrifugal casting of pipes in metal molds we have found that when cast iron with an sulfur content of? the minimum range of magnesium content required to obtain a graphite structure in 15 cm diameter tubes with approximately 90? graphite as well-formed spheroids is 0.012-0.014? magnesium.In the case of serum, the required residual concentration has been found to be about 0.016?. after the residence time, neither magnesium nor cerium, when added alone, as shown by curves A and B in Figure 2, are either present in sufficient amounts in the melt to ensure the desired graphite structure, i.e., both are below the "critical level".

In contrast to the behavior of magnesium and cerium when added alone, 0.05% smaller amounts (0.025?) Of magnesium and cerium together or 0.01? the addition of each of the five nodulating elements results in a more efficient utilization of the nodulating agent both in terms of higher initial recovery and longer duration of action. Thus, curves C and D show that the residual nodulant concentration in the bath is greater than 0.02? another 15 minutes after the addition.

6 56980

We have further found that the nodulation ability of different nodulating elements is different when added to cast iron melts; however, it appears that the sum of the percentages of nodulating elements remaining in the melt can be used to evaluate their nodulating ability in the melt.

To illustrate this point, Table I shows the residual concentration of the five nodulating elements in the cast iron melt up to 15 minutes from 0.01? each element was added. A 15 cm diameter tube (Experiment D) was cast from this melt 18 minutes after the addition of these five elements.

This tube had a valid nodular graphite structure as shown in Figure 3. Since the remaining amounts of private nodulating elements are as small as shown in Table I, the structure of Figure 3 can only be due to the combined nodulating ability of all the elements present. Table I also shows that the total amount of residual nodulants required to provide a valid graphite structure in the tube is of the same order of magnitude as the (remaining) amount of magnesium alone or cerium alone (which would be required to provide a valid graphite structure as mentioned above).

The curves in Figure 2 were determined by adding either a single nodule element or combinations of these elements to molten cast iron baths containing the following elements within the following ranges as a percentage of the final mixture:

Total carbon 3.4 - 3.6%

Silicon 2.7 - 2.9%

Manganese 0.25 - 0.30%

Sulfur 0.004 - 0.008%

Phosphorus 0.04 - 0.06%

The contents of Table II, derived from Table I, are shown graphically in Figure 4, where the higher utilization rate of the modulating agents used according to the invention is again apparent from the prior art.

In production trials, magnesium plus serum was added to six-ton iron batches in a ladle. The analysis of iron was as follows before the addition of magnesium plus cerium.

Total carbon 3.4 - 3.6%

Silicon 1.9 - 2.1%

Manganese 0.25 - 0.30%

Sulfur 0.005 - 0.012%

Phosphorus 0.04 - 0.06% The results of these production experiments are shown in Table III.

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The additions consisted of magnesium iron (containing 5¾ magnesium) plus serum iron (containing 10¾ serum). The amounts added were 0.025¾ magnesium plus 0.025¾ serum, so that the total addition of nodulant was 0.05¾. The experiments showed that a tube with a good spheroidal graphite structure could sometimes be cast as long as 34 minutes after the addition was made. The results shown in Table III are shown graphically in Figure 5. · The curves in Figure 5 show that the tubes cast 34 minutes after the addition of magnesium plus serum were found to contain 0.013¾ magnesium plus 0.010¾ serum. A striking feature of these results is that neither element is present in sufficient amount to ensure a good spheroidal graphite structure alone, but the total amount of nodulating elements (0.023¾) is sufficient to provide the desired graphite structure. This also illustrates the efficacy and longer effective duration achieved with small additions of nodulating elements, as the residual concentration of magnesium plus serum (0.023¾) represents 46¾ retention of the original total nodulating addition 34 minutes after the addition. The results of strength tests, which indicate the quality of the structures obtained in the pipe, are also included in Table III. These tubes met the stringent requirements of commercial specifications for both the notched impact strength test and the tensile strength.

A second series of experiments were performed under production conditions to determine whether or not the results obtained by adding two separate alloys (magnesium iron plus cerium iron) can be obtained by adding one alloy containing both magnesium and cerium. In these experiments, an alloy containing 2.5¾ magnesium plus 2.4¾ serum was added to six-ton cast iron batches. In one experiment, 0.83 weights of this alloy were added. This meant a 0.021¾ increase in magnesium plus a 0.020¾ increase in cerium, so that the total addition of nodulants was 0.041¾.

In this experiment, a 20 cm diameter tube cast 31 minutes after the addition of the nodulating agent contained 0.011¾ magnesium plus 0.012¾ cerium, i.e. a total of 0.023¾ (magnesium plus serum). The total weight of the nodulating elements in the molten cast iron bath was about 0.03-0.12 weights based on the weight of the bath. This represents a 56¾ survival of the original amount, and proves that these high retention amounts and longer effective durations of nodulating elements can be achieved either by simultaneously adding different alloys, 9 56960 each containing one nodulating agent, or by adding one alloy containing more than one nodulating agent. In these factory experiments where this 2.5? magnesium plus 2.4¾ serum-containing alloy, glare and smoke evolution, usually associated with the addition of magnesium-containing alloys, were virtually eliminated.

It follows from the above that an alloy or alloy mixture containing up to 3? the addition of small amounts of each of the two or more noduizers ensures that sufficient noduizers are present for longer than when the same total amount of one nodulant is added, and eliminates the violent reaction associated with the addition. This phenomenon is quite surprising and has not been fully elucidated.

In experiments using 2.5? magnesium plus 2.41? cerium-containing alloy for making sandlights, it was found that valid graphite structures could be developed using nodulating element additions of 20? smaller than the usual 5? when using magnesium iron was necessary. As a result of this reduction, less alloy needs to be added, which in turn reduces the amount of slag formed.

Although a preferred embodiment of the invention has been described above, it is to be understood that the description is intended to cover all changes and modifications to this embodiment selected for purposes of illustration which do not depart from the spirit and scope of the invention.

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Claims (2)

10 56980 1. A composite composition for the preparation of a mixture comprising a magnesium and an acetic acid in the form of a cerium, yttrium, lanthanum, neodymium and / or praseodymium, which comprises a magnesium and a shielding element to give the element 1 to the composition vikt- # och att totalmängden av noduliseringselement inte överstiger 12 vikt- #, var-vid kiseljärnets andel i kompositionen är sddan att däri ingär minst 45 vikt- # kisel, och att den eventuellt i forma av en legering använda magnesiumen föreligger i en mängd av 1-3 vikt- # av legeringen. A nodulating composition for the production of spheroidal graphite cast iron, which mixture contains magnesium and at least one other nodulating element in the form of cerium, yttrium, lanthanum, neodymium and / or praseodymium, characterized in that magnesium and each other element are included in the mixture. # and that the total number of nodulating elements in the alloy does not exceed 12% by weight, the proportion of iron silicon in the alloy being such that it contains at least 45% by weight of silicon, and that the amount of magnesium possibly used in the alloy is 1-3% by weight. Mixture according to Claim 1, characterized in that the nodulating elements are present in the mixture in the form of at least one iron-silicon alloy. Alloy according to Claim 1 or 2, characterized in that the nodulating elements consist of substantially equal amounts of magnesium and cerium. Mixture according to one of the preceding claims, characterized in that it contains at least two alloys, one of which contains magnesium in amounts of 1 to 3% by weight and that the other contains at least one nodulating element in a muddium of cerium, yttrium, lanthanum, neodymium and / or praseodyme, which each present in an amount of 1 to 3 by weight in the # alloy. Mixture according to one of Claims 1 to 4, characterized in that the alloy contains the individual nodulating elements in substantially equal amounts, 3% by weight, based on the alloy. 2. A composition according to claim 1, which comprises, as a nodule element, a composition according to the invention in the form of a mineral and ferrocellular alloy.