Method for centrifugal casting and articles so produced

Abstract

Tubular metal articles are produced by centrifugal casting in a rotary metal mold lined by centrifugally distributing a quantity of a dry finely particulate free flowing refractory material on the active mold surface with the quantity being in excess of that required for the lining, densifying the layer by rotating the mold at a rate such that the refractory layer is subjected to centrifugal force adequate to establish an equivalent specific gravity of at least 7.5, determined by multiplying the actual specific gravity of the refractory material by the number of gravities of centrifugal force, contouring the densified layer and removing the excess refractory material, rotating the mold at the casting rate and then introducing the molten metal for casting while continuing to rotate the mold at least that rate. Articles so cast have relatively smooth outer surfaces which require only finish machining. The invention employs no additives and thus eliminates the need for venting the metal mold, provides a relatively thick lining of predetermined insulating capability so as to control the grain structure of the cast metal, eliminates the usual end cores, and allows the refractory material to be recycled. The invention is particularly useful for casting articles, such as cylinder liner blanks, from grey iron, such articles having an outer enlargement, typically a transverse outer end flange. Cast according to the invention, such articles have Type A graphite throughout the entire inner surface and for at least a substantial portion of the thickness of the flange or other outer enlargement. .Iadd.

Claims

2. The method as defined in claim 1, and further comprising

recovering the cast article and said refractory material from the mold;

classifying the recovered refractory material to remove any debris;

and using the recovered refractory material for casting another article.

3. The method according to claim 1, wherein

said refractory material is zircon flour.

4. The method according to claim 1, wherein

the particles of said refractory material are predominantly smaller than 43 microns.

5. The method according to claim 1, wherein

the metal to be cast is iron; and

said refractory material is zircon flour the particles of which are predominantly smaller than 43 microns.

6. The method according to claim 5, wherein

after contouring of the densified layer, the rate of rotation of the mold is increased until a centrifugal force of at least 10 gravities is applied to the contoured layer preparatory to casting, such increased centrifugal force causing the contoured lining to be hardened.

7. The method according to claim 1, wherein

the metal to be cast is iron;

said refractory material is magnesium oxide; and

said step of densifying the layer of refractory material is carried out by rotating the mold at a rate such that the refractory material is subjected to a centrifugal force of at least 24 gravities.

8. The method according to claim 1, wherein

the metal to be cast is iron;

said refractory material is silica flour the particles of which are predominantly smaller than 45 microns; and

said step of densifying the layer of refractory material is carried out by rotating the mold at a rate such that the refractory material is subjected to a centrifugal force of at least 33 gravities.

9. The method according to claim 1, wherein

said quantity of particulate refractory material introduced into the mold is in excess of that required to form the completed mold lining;

the method further comprising recovering the excess refractory material concurrently with said contouring step.

10. The improvement according to claim 1 wherein

the article to be cast includes a transverse annular enlargement;

The contouring tool employed to accomplish said contouring step including a portion providing in the densified layer of refractory particulate material a transverse annular groove conforming to said transverse annular enlargement, the shape and orientation of the contouring tool being such that the portion of said layer at the bottom of said groove has a thickness equal to at least five times the maximum particle dimension of the predominant fraction of the particulate refractory material, other portions of the densified layer having a thickness substantially greater than the thickness of the portion of the layer at the bottom of said groove;

the metal to be cast is iron; and

the cast article is characterized by having AFA Type A graphite distributed throughout its inner surface and throughout at least a substantial portion of the thickness of the transverse annular enlargement.

12. The improvement defined in claim 11 and further comprising

recovering the excess refractory material concurrently with said contouring step.

13. The improvement defined in claim 11, wherein

said refractory material is zircon flour the particles of which are predominantly smaller than 43 microns.

15. The method defined in claim 14 wherein

said refractory material is zircon flour the particles of which are predominantly smaller than 43 microns.

17. The method defined in claim 16, wherein

said refractory material is zircon flour the particles of which are predominantly smaller than 43 microns..Iadd.

18. The method according to claim 1, wherein the particles of said refractory material are predominantly smaller than 74 microns..Iaddend..Iadd.19. An as-cast engine cylinder liner black cast from grey iron according to the method defined in claim 10, the outer surface of the as-cast blank formed by being cast directly against the mold lining being especially smooth and essentially free of embedded refractory particles;

all portions of the as-cast blank not cast against said groove being characterized by predominantly AFA Type A graphite at the inner surface and throughout the radial thickness of the as-cast blank;

that portion of the blank cast against said groove being characterized by predominantly AFA Type A graphite at the inner surface and throughout a major portion of the radial thickness of that portion..Iaddend..Iadd. 20. An as-cast engine cylinder liner blank cast from grey iron according to the method defined in claim 16, the outer surface of the as-cast blank formed by being cast directly against the mold lining being especially smooth and essentially free of embedded refractory particles;

all portions of the as-cast blank not cast against said groove being characterized by predominantly AFA Type A graphite at the inner surface and throughout the radial thickness of the piece;

that portion of the blank cast against said groove being characterized by predominantly AFA Type A graphite at the inner surface and for more than one-half of the radial thickness of a transverse annular enlargement formed by being cast against said groove..Iaddend..Iadd. 21. An as-cast tubular blank cast from grey iron according to the method defined in claim 1 to be converted into a completed article by a minimum amount of finish machining, the as-cast blank having a smooth outer surface formed by being cast directly against the mold lining and which is essentially free of embedded refractory particles;

the as-cast blank including a wall portion of uniform radial thickness and the cast iron of that wall portion being characterized by AFA Type A graphite not only at the inner surface but also throughout the radial thickness of the wall portion..Iaddend.