US1988911A - Chill cast iron alloy - Google Patents

Description

Patented Jan. 22, 1935 v UNITED STATES CHILL CAST IRON ALLOY Paul D. Merica, New York, N. Y., and James S. Vanick, Elizabeth, and Thomas H. Wickenden, Roselle, N. L, asslgnors, by mesne assignments, to The International Nickel Company, Inc., New York, N. Y., a corporation of Delaware No Drawing. Application October 21, 1926, Se-

rial No. 143,293., Renewed June 13, 1934 3 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 Percent 24 .25-2

Carbon Silicon Manganese .25-2 Nickel 2 -10 Chromium Up to 4 25 Phosphorus 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, 9 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

(Cl. I5-1) it states in the lower part of that page and in respect to the above sulphur contentIn 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 mustbe 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 or cupola.

Casting compositions lying within these ranges are particularly desirable in that good adjustment of nickel, chromium, silicon and carbon contents is secured to nicely regulate thedepth 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 that the amount of chill may be nicely controlled by suitably adjusting the various elements according to the rough rule that 1 part carbon equals 3 silicon, 1 part silicon equals 2 parts nickel, 1 partchromium 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 thanthat mentioned above, the increased chilling tendency accompanying the lowered'silicon and carbon contents being counteracted by the higher nickel content.

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

Percent Carbon 3.0 Manganese .6 Silicon 1.0 Nickel 4.5 Chromium 1,5

Phosphorus and sulphur 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 of 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 square inch in comparison with 20,- 000 to 25,000 psi for high carbon iron ordinarily used for chill work.

Our composition has the further advantage that it is subject to heat treatment and the hardness and toughness may be so modified, if desired.

The composition is not only extremely hard in the chilled condition, but it is strong and tough both in-the chilled condition and in the gray condition. 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 e1- i'ect 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 strong. By properly proportioning the alloying elements, we have produced an 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 giving a Brinell hardness 01' 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 of 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 iumace.

.We claim:

1. A chilled iron casting containing carbon 2-4%, silicon .5-l.25%, nickel 3.5-6% and chromium .5-2% the nickel content being greater than the chromium content.

2. A chilled iron casting containing carbon 2.5-3.3%, silicon .5-1.25%, nickel 3.545% and chromium 5-2%. r

3. An iron roll containing carbon about 2% to 3.75%, nickel about 3% to 8%, chromium about 1% to 3%,. sulphur not over about .10%. phosphorus not over about .40%, and manganese less than 1.5%.

PAUL D. MERICA. JAMES S. VANICK. THOMAS H. WICKENDEN.