US1988912A - Chill cast iron alloy - Google Patents

Description

Patented Jan. 22, 1935 UNITED STATES PATENT OFFICE emu. cas'r IRON ALLOY poration of Delaware No Drawing. Original application October 21,

1926, Sfl'lal No. 143,293. Divided and one application June 6, 1934, Serial No. 129,290

Claims.

This invention relates to alloys and more especially to chill cast nickel bearing iron alloys.

The invention relates particularly to castings formed.- by casting nickel bearing iron compositions against chills to form castings having extreme hardness in the chilled portion and improved toughness and strength in. the chilled portion and in the gray iron adjacent the chilled portion. This material is well adapted for chilled iron wearing parts which require strength and toughness, for example, hot or cold rolls for glass and metal working, cams, gears,. dies, stamps and like parts subjected to impact or heavy pressure. Our improved composition is characterized by its strength, hardness and toughnessqualities desirable in wearing parts.

We have obtained good results in practice with compositions within the following general ranges:

Percent Carbon 2-4 Silicon .25-2 'Manganesen, .25 -2 Nickel 2 -10 Chrommium Up to4 Phosphorous and sulphur may be present within the ranges usually found in cast iron, as for instance, phosphorus .03 to 1.15% and sulphur .03 to 25%. See any edition of Kents handbook, 1900 and later; Moldenke, Principles of Iron Founding, edition of 1917, page 198; Hatfield, Cast Iron in the Light of Recent Research; and others. In respect to the ranges of phosphorus and sulphur in chilled, white and gray iron castings such as for rolls, cams, brake shoes, gears, plow points, etc., phosphorus ranges from, under .10 to 1.0% and sulphur .04 to 25%. See particularly pages 196, 182, 183, 199 and 198 in their order of Moldenkes Principles of Iron Founding, 1917, where both the phosphorus and sulphur for chilled rolls must be, under .3 and 08% respectively, and for chilled castings in general. As indicated on page 183, the phosphorus and sulphur shall be, below .20 and .06% respectively. On page 199, it is shown Again, the sulphur and phosphorus percentages givenexcept where wanted high, can be anything below the figures. In addition, page 198, there is a statement as to the percentages in the tables on the pages noted that The tables of analyses given in the above classification of castings must, as was said at the outset, be considered only as typical. Again, in Kents Mechanical Engineers Handbook, edition printed in 1923, attention is called to page 434, wherein sulphur is recited from .05 to .20% and it states in the lower part of that page and in respect to the above sulphur content-In this composition phosphorus is supposed to be well below .10%. It is also to be noted that the ranges of analyses of American, as well as foreign, pig irons, are good indications of castings produced from pig irons as very often a definite and consistent type of pig iron must be used. Such ranges are to be found in Appendix II of Hatflelds Cast Iron in the Light of Recent Research, second edition 1918 and third edition 1928.

- The composition may be varied somewhat, if desired, by the addition of other alloying materials, such as molybdenum, tungsten, titanium, copper, etc. The carbon content is within the general range usual for cast iron, from either air furnace orcupola.

Casting compositions l ing within those ranges are particularly desirable in that good adjustment of nickel, chromium, silicon and carbon contents is secured to nicely regulate the depth of chill.

We find that the amount of chill in the chill cast iron may be maintained sensibly constant if nickel and chromium are added as alloying materials in about the ratio of 2 or 3 to 1, say about 2 to 1. We also find thatthe amount of chill may be nicely controlled by suitably adjusting the various elements according to the rough rule that 1 part carbon equals 3 parts silicon, 1 part silicon equals 2 parts nickel, 1 part chromium equals 2 parts nickel, and 1 part sulphur equals 10 parts silicon; increasing the silicon, carbon and nickel acts to decrease the chill, whereas, increasing the chromium and sulphur acts to increase the chill. The silicon and carbon contents may be lowered, if desired, by using a higher ratio of nickel to chromium than that mentioned above, the increased chilling tendency accompanying the lowered' silicon and carbon contents being counteracted by the higher nickel content. It is to be noted that the foregoing is to be taken into consideration in connection with the statement and expression used herein that the nickel is present in the proportion of 2 or 3 to 1 of chromium.

For ordinary work, however, we have obtained good results with a composition containing about the following percentages:

Phosphorus and sulphur may be present within the ranges usually found in cast iron, as indicated above.

Such a composition, ii chill cast, will give a white iron having'a Brinell hardness of 550, as compared with the 400-500 of ordinary chilled iron. The chilled metal under tension has a transverse strength oi 8000 pounds for 1 inch square bars tested on 12 inch centers in comparison with about 6000 pounds for ordinary high carbon chilled iron. Gray iron having ,this composition. has a tensile strength of about 35,000 pounds per' dition. These characteristics render the composition desirable for chilled castings to be subjected to heavy pressure or impact, since such castings are less liable to breakage than ordinary chilled iron castings.

We are aware that nickel has been proposed as an addition material to reduce the chilling effect in iron alloys, and that chromium has been proposed as a hardener. We have found, however, that a proper proportion should be maintained between the nickel and chromium with respect to the silicon and carbon if the composition is to be rendered hard, and yet tough and v strong. By properly proportioning the alloying elements, we have produced and improved iron alloy adapted to be chill cast to form an exceedingly hard and tough white iron with a strong, tough gray iron adjacent thereto.

We have found that the hardness of chilled cast iron castings made under our invention is due to the fact that the matrix portion of the iron is changed from the softer pearlite of ordinary chilled iron castings into the harder martensite or troostite. Martensite is often associated with austenite and hence by martensite, we mean martensite or austenite or both in association. Hence the resulting hardness is between that of the very hard iron carbide grains and the martensite having a Brinell hardness of from 550 up to about 750 where the carbon is about 3.50%. This hardness may be regulated somewhat by proportions of the alloy or the use of equivalents.

A further important advantage of our invention resides in the provision of an improved chill casting alloy wherein the depth of chill may be nicely controlled by suitable adjustment of the.

addition elements. Cast iron 01 our composition may be made either in the air furnace or cupola, and we intend to cover such composition of; cast iron made in either type of furnace.

The present application is a divisional case of.

our co-pending application,'Serial No. 143,293, filed October 21, 1926. We claim:

1. A cast iron alloy containingirom about 2 to about 2.5% carbon, about 2% nickel, from about .25 to about 2% chromium and wherein the nickel content bears a relation of approximately three to one of the chromium content.

2. A chilled iron casting containing from about 2 to about 2.5% carbon, about 2% nickel, from about;. 25 to about 2% chromium and wherein the nickel content bears a relation 01 approximately three to one of the chromium content.

.3. An iron roll containing from about 2 to about 25% carbon, about 2% nickel, from about .25 to about 2% chromium and wherein the nickel content bears a-- relation of approximately three to one of the chromium content.

4. A'cast iron alloy containing from about 2 to about 2.5% carbon, about 2% nickel, from about .25 to about 2% chromium, and a small but effective amount of molybdenum, and wherein the nickel content bearsa relation of approximately three to one of the chromium content.

5. A chilled iron casting containing from about 2 to about 2.5% carbon, about 2% nickel, from about .25 to about 2% chromium, and a small but effective amount of molybdenum, and wherein thenickelcontent bears a relation of approximately three to one of the chromium content 6. An iron roll containing from about 2 to about 2.5% carbon, about 2% nickel, from about .25 to about 2% chromium, and a small but eilective amount of molybdenum, and wherein the nickel icontent bears a relation of approximately three ,to one of the chromium content.

7. A cast iron alloy containing from about 2 to about 2.5% carbon, about 2% nickel, from about .25 to about 2% chromium and a small but eifective amount up to about 2% of silicon and a small but eifective amount up to about 2% of manganese, and wherein the nickel content bears a relation of approximately three to one of the chromium content.

8. 'Acast iron. alloy containing from about 2 to about 2.5% carbon, about 2%.nickel, from about .25 to about 2% chromium, about 0.25% to about 2% of silicon, about 0.25% to about 2% of manganese, and a small but effective amount of molybdenum, and wherein the nickel content bears a relation of approximately 3 to 1 of the the nickel content bears a relation of approxi-' mately 3 to 1 of the chromium content.

PAULD. MERICA.

JAMES S. VANICK.

THOMAS H. WICKENDEN.