US1564284A - Gray cast iron and the process for its production - Google Patents

Description

Patented Dec, 8, 1925.

UNITED STATES 1,564,284 PATENT OFFICE.

KARL srrr, or

MANNHEIM, GERMANY, ASSIGNOR TO THE EIRM HEINRICH LANZ, OI

MANNHEIM, BADEN, GERMANY, A COPARTNERSHIP.

GRAY CAST IRON AND THE PROCESS FOR ITS PRODUCTION.

No Drawing.

1 all whom it may concern:

Be it known that I, KARL SIPP, a citizen of Germany, and a resident of Mannheim, Baden, Germany, have invented certain new and useful Improvements in Gray Cast Iron and the Process for its Production, of which the following is a specification. Y

My present invention relates to the production of gray cast iron, and has for its 1 object the further improvement of the physical and mechanical properties thereof.

In cast iron silicon acts as a precipitant of the carbon, driving it out of combination and into graphite form. In fact, the lower the carbon content of the composition the more silicon is required, although the amount of silicon that can be added is practically limited by various considerations. Thus, for example, a silicon content of much above 1 per cent influences deleteriously the structural stability of the cast iron under high temperatures and hence should not be used for castings of machine parts which are subjected to a high degree of heat, such as cylinders and pistons of internal combustion engines, for fire-exposed parts, etc.; and, again, while increases of the silicon content up to about 3.5 per cent increase the amount of gra hite precipitate, in higher percentages its influence is reversed and it-then produces a precipitation, not of graphite, but of various combined carbons.

Gray cast iron with a carbon content below 3 per cent and a silicon content of less than 1 per cent has never heretofore been produced, at least on any practical commercial scale. I have discovered however, as the result of recent investigations, not only that nickel also acts, and in the same way as silicon, as a precipitant of graphite, but, further, that if the silicon heretofore required for the purpose is partially or wholly replaced by a substantially equal amount of nickel I am able to cut down the total carbon content of gray cast iron to approximately 1.7 per cent. Because of the impossibility, in normal practice, of effecting a precipitation of carbon as graphite in iron-carbon compositions in which the carbonoontent lies between 1.7 and 2.2 per cent, compositions with such carbon content have always been regarded as belonging to the steel groups. In steel, however, it is the rule to keep the carbon content below 1.7 per cent, and hence compositions Application filed May 15, 1924. Serial No. 713,605.

with carbon content between the limits mentioned have never been practically used. On the other hand, it is known that the lower the carbon content of cast iron the higher ,will be its physical and mechanical properties.

My invention accordingly comprises both a new process and a new product.

The process consists, first, in adjusting the composition to a carbon content below the limit heretofore considered permissible for gray cast iron and which may be reduced to approximately 1.7 per cent, and then in effecting the required precipitation of graphite by the addition of nickel instead of an increase in the percentage of silicon. For example, in a mixture with a low carbon content which would ordinarily call for 1.7 per cent of silicon I replace about half of the silicon with an equal amount of nickel, using 0.9 per cent only of silicon and 0.8 per cent of nickel.

The gray cast iron thus roduced, containing as it does a total car on content of less than 3 per cent and less than 1 per cent of silicon is, ascompared with all previously known forms of gray cast iron, characterized by a very high stability, both structural and as regards volume, under high temperatures and, moreover, by its great strength, due to the small carbon content and to the nickel-iron alloy.

Furthermore, by so governing the casting operation in the practice of my new process, according to the now known pearlite casting method, that the nickel, either alone or in conjunction with any silicon present in the composition,- will precipitate the.

graphite required under cooling conditions suitable for the production of the pearlite structure I obtain a pearlite nickel cast iron with a minimum of graphite veinings, and consequently a product which is produced like cast iron and is to be considered as cast iron but which exhibits the properties of an alloy steel. Thus, in a bar of 80 millimeters diameter, for example, a very good pearlite structure is obtained from a mixture containing 2.12 per cent carbon +0.56 per cent silicon +1.07 per cent nickel +0.15'per cent phosphorus +0.08 per cent sulphur +0.8 per cent manganese when cast in a sand mould preheatedlto' about 210 centigrade.

by Letters Patent, is-

1. Thep'rocess of producing gray cast iron which comprises preparing acasting mix: ture and introducing thereinnickel m an amount suficient to eflect, in conjunction from a mixture having a content of carbon and of silicon-less than 3 and 1 per centrespectively in which the precipitation of the graphite required is efi'ecte'd by-the addition of nickel to the mixture.

4. The processof producing gray cast iron having a total carbon content of from about 3 to about 1 per cent and a. silicon content of not much 1f any over 1 per cent which comprises adding to the casting mixture nickel in amount suificient, in conjunction with the silicon present, to effect the precipitation of the graphite required.

,5. Gray cast iron whlch is characterized by a relatively low total carbon content and in'which the usual silicon content is replaced in whole or in part by avsubstantially equal amount of nickel. with the silicon present therein, the precipi- 6. Gray cast' iron having a total carbon content of between 3 per cent and 1.7 per cent approximately, a silicon content of not sub stantially more than 1 per cent, and a nickel content suflicient in amount to effect the precipitation of the graphite required.

7 Gray cast iron which has a total carbon content of from 3 to 1.7 per cent and a silicon content of less than 1 per cent and contains nickel, and which is characterized by great strength and a very high stability, both structural and as regards volume, under high temperatures.

Gray pearlite cast iron which contains nickel and has a total carbon content between 3 and 1.7 per cent, approximately, of which substantially 0.85- per cent is chemically combined with the iron-nickel elements andthe remainder is in the form of finely divided graphite.

KARL srPr.