US1511142A - Cast-iron alloy - Google Patents

Description

Patented (lot. 7, 1924.

UNITED s'rrEs TEN oFFIcE.

HIROSHI SHIOKAWA. 0F KOBE, JEAN.

CAST-IRON ALLOY.

No Drawing.

To all whom i t may concern.

Be it known that I, HIROSHI SHIOKAWA, a subject of the Emperor of Japan, and resident of 18 Nichome, Dainichidori, at the city of Kobe, in the Prefecture of Hyogo and Empire of Japan, have invented a new and useful Cast-Iron Alloy, of which the following is a specification.

' My present invention relates to an immanganese from 0.30 to 1.50 per cent, silicon from 0.30 to 4.00 per cent, chromium from 0.05 to 0.50 percent, titanium from 0.05 to 0.80 per cent, and iron in requisite proportion in each case, and has for its primary object a more economical production of an improved cast-iron alloy suitable as material v for making cylinders, rolls, piston-rings,

pipes, propellers for ships, valves, machine parts, steel-ingot cases and other casting molds, and other articles which call for iron having a dense and fine structure, high in hardness and strength, highly resistant to wear and tear, heat and chemical actions, and extremely durable.

Other objects and advantages to be de rived from the use of this invention will appear in the following description and claims:

To produce a'cast-iron alloy, in accordance with this invention, I prefer to fuse various materials or ingredients mixed in the re- 'quired predetermined proportions in a suittable melting furnace, a-cupola furnace for instance, and such mixture is made withln r the range of: the following proportions:

Generally it is more advisable to make the desired products, such as cylinders, rolls, and

Application filed April 5, 1923. Serial No. 630,156.

the like, by casting the resulting alloy, while it is yet in a molten state, in suitable molds, but it is possible, of course, to cast the alloy into ingots of suitable dimensions to facilitate transportation, and then to make such products at any time and place, by remelting it, just in the same manner as stated above.

These constituents or ingredients can be conveniently incorporated into the alloy by using each or some of them as ferro-alloy or in the form of ore in such a way that the required proportions can be arrived at. As in the case of producing ordinary cast-iron, it is necessary to reduce the amount of impurities, such as copper, sulphur, and the like, as far as possible. 'This rule holds good with phosphorus also, but its presence can be tolerated in some cases as much as 0.50 per cent, at the maximum, since its harmful effect can be mitigated by virtues of titanium and. chromium.

This invention can be carried out in various ways, but I shall set forth one specific instance so that one skilled in the ant to which it appertains may understand it easily, thus;

When the coke thrown into the bottom or base of a suitable pig-melting furnace, such as a cupola furnace, has been White-heated and the pig-melting preparation completed, alternate layers of coke, pig iron and mixture of the ingredients are charged into the furnace, titanium-bearing material placed under the uppermost layer, until the charge reaches the lower end of the charging port or entrance (when the charge is replenished, the titanium-beaming material 1S to be charged in layer alternate with the others), and the proportions for materials to be charged are, per 100 kilograms of iron, as follows:

Kllograms. Coke 9. Ferromanganese (75%)- 1. Ferrosilicon (75%) 0.5 Ferrochromium 0.3 Or chromium ore (40%) 1.0 Titanium ore (12%) 5.0 Limestone 1.8

When the charge has thus been piled up to the charging port, air-blast or forced draught is introduced into the furnace to aid combustion, and as soon as white-heated molten iron begins to run out of the discharging port, a clay stopper is applied to said. port to clog it up, and after! lapse of about one hour the several ingredients are melted and run down and collect in the receptacle disposed at the bottom of the furnace. And when this molten metal has reached a suitable amount, it'is taken out and cast into desired products in the usual It is a well-known fact that ox gen has a strong aflinity for carbon, that al elements increase in chemical functions according as they become pure, a dthat-all chemical reactions arepromow under high heat. That the temperature within the meltin furnace is very high is so evident as tone no explanation, and so I shall briefly describe about the relation between these two definite rules and this invention, thus:

When the materials or constituents charged in the furnace have melted and run down, oxide of titanium becomes mixed with slag. Since the slag floats among pieces of coke at the upper portion of the molten metal,

the oxide. of titanium comes into contact With the coke, and at this time the oxygen present in said oxide combines itself with the carbon in the coke, for which it has a greater aflinity, and in consequence the titaa mg.

And the slag which is melted and runs down in turn causes continuous chemical reactlons by floating about the layer of coke, and the molten iron compound passes down through said layer of slag and collects in the receptacle. 7

While the molten iron is passing down through the layer of slag containing the oxide of titanium in the above-mentioned manner, the impurities, such as nitrogen, oxygen, sulphur, copper and the like, incorporated in said molten iron, form compounds by combining themselves with the titanium and are taken out by the slag. And at the same time, part of the reduced titanium sinks down .into the molten iron and combines itself with the remnant of impurities in the metal, and the resulting compounds float up and become incorporated in the slag.

The cast-iron alloy, refined by said react1on s of titanium, has the greatest part of its impurities precipitated or removed, and analysis of such refined cast-iron shows that in this way the harmful sulphur has been reduced most remarkably, andthat there remams a trace of copper. And it is quite It is advisable to have a small amount ofreduced titanium remain in the refined metal at the end of the above-mentioned refining process, in order to remove impuritles from the molten metal as much as possible. In other words, best results can be had by adding to the original charge such proportion of titanium ore or some other titaniumbearing material as to leave small amount of pure titanium in the refined alloy when the refining process has been completed.

Various ingredients present in the molten metal come to possess strong chemical functions or capacities by being refined by titanium, and the presence of chromium not only improves their functions, but also harmonizes the temperature, and lowers the eutectic point on solidification, with the conse quence that part of the carbon microscopically constitutes pearlite and covers the entire area. And the graphite (free carbon) is distributed uniformly by describing chrysanthemum-like curves, that is, irregular and regular overlapping curved lines somewhat corresponding to the curyes of the petals of a chrysanthemum- It is particularly to be noted in this connection that the cast-iron alloy, in accordance with this invention is sufficiently hard and strong for the reason that pearlite and ferrite are well'propor tioned and associatedharmoniously, and that graphite is evenly distributed so as to form the product of uniform strength-which is not the case with the ordinary cast-iron of this class. And from metallurgical point of view, it. may be readily inferred that the alloy has the highest elongation expectable from metals ,of this sort, since the structure is orientated, that is, pearli'te and ferrite are disposed in an orderly manner and evenly distributed.

In making cast-iron for cylinders, rolls,

piston-rings, propellers for ships, valves,

steel-ingot cases, and the like, it has been the general practice to produce it by using v and iron as chief ingredients, and to impart 4 carbon, manganese, silicon (or phosphorus softness to the product, carbon has been freed or graphitized, and to .obtain desired strength various grades of high-priced pig iron were selected and used. These ingredients were fused in the cupola furnace, which furnace was used for the sole purpose of melting, and had the defect of adding more gases, though not traceable by usual methods of analysis, do muchharm to the product oxygen and nitrogen to the product. These by causing roughness of structure with con- 7 se uent brittleness and lack of elongation.

n the contrary, the same cupola furnace serves the double purpose of a melting furnace'and refining furnace when used in connection with this invention, and a brief contflast of these two methods will be given, t us:

(A). Cast-iron, produced hitherto, rich in free carbon (carbon which was freed from cementite and graphi-tized) is very porous, and is apt to absorboxygen in the air, under water or under heat through those pores and promote oxidation; it is liable to wear and tear on account of being soft; and, as it is rough in structure and brittle in physical property and 'is subject to deformation and deterioration, and is apt to cause unexpected disasters by increasing chilling effect, that is, unequality of temperature of a product, when attacked by sudden change of temperature. In short, cast-iron of this class hitherto in use requires high-priced materials with consequent high cost of production, and has various defects such as referred to hereinabove, and it is quite evident that there is an ample room for improvement.

(B). On the contrary, with my present invention various titanium-bearing materials, very cheap in cost yet extremely eflicient as refining agent, such as slag conrtaining from 5.0 to 20.0 per cent of oxide of titanium, titanium ore or iron-sand (it is well known that iron-sand contains titanium), can be utilized in the cupola furnace so as to remove impurities in the pig iron, and so it. is possible as well as practicable to obtain superior grade of cast-iron by using pig iron, bearing comparatively arge amount of impurities and very low in price, with consequent remarkable reduction in cost of production. Furthermore, through combined use of chromium and titanium, graphite becomes evenly distributed by describing chrysanthemum-like curves, that is, irregular and regular curved lines overlapping one another and somewhat corresponding to the curves of the petals of a chrysanthemum, and not thick radial lines usually found in cast iron of this class hitherto in existence, and which produces a very dense, somewhat uniform structure calculated to prevent oxidation. And by virtue of chromium, cohesion between grains or particles is greatly increased with resulting superior quality from the viewpoint of strength of materials and consequent increase in resistance to blows, hammering, shocks, and the like. As it is, the cast-iron alloy in accordance with this invention may be said to have thoroughly eliminated various defects incident to this class of cast-iron hitherto in use.

Widening of the range of carbon contents attributable to the combined use of titanium and chromium in the proportions named, attended by the greater easiness and economy with which to produce cast-iron having a degree of hardness within reasonable limits, is another feature of this invention.

Various products made from the cast iron alloy, as described, have various features from industrial viewpoint, some of which will be cited hereinafter as examples:

1) Cylinders are highly resistant to high pressure, both internal and external, do not suffer from wear and tear, and are free from oxidation, deterioration and deformation; (2) rolls sufl'er least from wear and tear on account of suitable hardness possessed, are free from various defects attributable to stresses exerted on, and are least prone to breakage, owing to the toughness; as to chilled rolls, it is possible to determine degree chilling on account of smallness of content of impurities in the material and special properties of chromium, and to remove any possibility of suffering breakage attributable to internal stresses which would be caused on transformation, since the structure is chiefly composed of fine-grained pearlite and very small amount of cementite is incorporated in said pearlite, and they can bear excessive overload, owing to the hardness and strength possessed; (3) piston-rings are not only least liable to wear and tear, but also free from deformation attributable to thermal energies, on account of the structure being uniform; i) pipes can bear high pressure, both internal and external, and are impervious to oxidizing influence of oxygen; (5) propellers for ships are least prone to damages due to obstacles, on account of the great toughness possessed, and least subject to oxidation, deterioration and corrosion, besides being highly resistant to breakage; (6) valves are not only resistant to high pressure, both internal and external, but also free from wear fluences and chemicalactions, least liable to transformation or deterioration, and extremely durable, besides being free from oxidation attributable to molten metals.

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

A cast iron alloy consisting of carbon to the extent of from 2.00 to 4.50 per cent, manganese from 0.30 to 1.50 per cent, silicon from 0.30 to 4.00 per cent, chromium from 0.05 to 0.50 per cent, titanium from 0.05 to 0.80 per cent, and iron from 97.30 to 88.70%.

In testimony whereof I afiix my signature hereunto.

' HIRO-SHI SHIOKAWA.