Composite ferrous castings

Cast iron selected from the group consisting of white iron, compacted graphite iron, malleable iron, gray iron, and ductile iron is cast in a mold in which steel or metal, such as a tube defines a portion of the mold form.

FIELD OF THE INVENTION 
This invention relates to methods of using and producing ferrous castings 
with forged or sheet materials used as part of the mold form and thereby 
integrated into the cast product. 
BACKGROUND OF THE INVENTION 
Ferrous castings are used in the manufacture of various parts for machines, 
engines and the like. For example, a crankshaft or steering gear may be a 
ferrous casting. In the manufacture of a crankshaft, it is often necessary 
to provide a series of connected non-linear passages through the ferrous 
casting to carry lubricants. These connected passages are most often 
conventionally provided into the casting by a gun drilling method. The 
drilled passages typically require counterboring, tapping, and plugging in 
order to provide a generally smooth, continuous, winding passage through 
the casting. This method of providing a continuous passage is relatively 
expensive and time consuming. In some cases, the drilling operation cannot 
provide the optimum design from the standpoint of crankshaft 
functionality, and the crankshaft has to be designed around the 
limitations of the drilling operation. Thus, there has been a need to 
provide an improved means for manufacture of such a casting. 
Additionally, there exist many applications where ferrous castings possess 
the requisite mechanical strength properties, but where ferrous castings 
are presently considered undesirable or unacceptable due to the inherent 
limitations of other metallurgical properties associated with the 
castings. For example, crankshaft crankpins inherently provide a rotating 
mass, and therefore need a counterweight to balance the mass. Large 
dimension crankpins conventionally give rise to larger counterweights 
which therefore require a larger crankcase and related engine components. 
There exists a need to be able to reduce the size of the crankcase and the 
counterweight independently of the design considerations of the crankpins. 
As another example, many applications exist where advantageously part but 
not all of a ferrous casting is forged and metallurgically bonded to a 
casting. However, it may be impractical or impossible to provide such a 
product because of the inability to metallurgically bond forged metal to 
cast metal. For example, currently automotive and light truck drive line 
U-joints are welded to the drive shaft tube. Heavy truck torque arms are 
currently produced by welding a relatively expensive forged eye to the end 
of a section of heavy walled alloy steel tubing. Both could advantageously 
be fabricated in part from a casting. However, the U-joint or eye cannot 
be made in commercial practice by ferrous casting because the casting 
cannot be easily bonded by welding to the forged tubing. 
The art of ferrous castings is well developed. For example, various prior 
art patents depict processes for the manufacture of castings having 
complex shapes and forms. Walker in U.S. Pat. No. 1,729,848 discloses a 
method of manufacture for white iron castings wherein copper plated steel 
rods are utilized as reinforcements in the casting. Such white iron 
castings are typically utilized as grates inasmuch as the white iron is 
not heat treated and is therefore very brittle, yet hard. 
Dobovan in U.S. Pat. No. 3,170,452 discloses that a cylinder head of cast 
iron maybe cast with a wear and corrosion resistant steel metal insert in 
the shape of a valve seat coated with a suitable brazing alloy. Typically, 
the insert, which is steel, is coated with a layer of a nickel base 
brazing alloy. The valve seat is thus cast in place with the gray cast 
iron. 
Vishnevsky, et al. in U.S. Pat. No. 4,008,052 discloses a bimetallic 
casting wherein a boron containing alloy is provided intermediate the 
materials being cast. The materials involved are generally known as super 
alloys. 
Spalding in U.S. Pat. No. 4,209,058 discloses yet another die casting 
operation and, in particular, a casting process whereby a section of steel 
tubing is die cast in combination with an alloy of magnesium or aluminum. 
There has remained, however, a need to provide ferrous castings and methods 
for making such castings which can be used in a wider variety of 
applications, as noted above. 
SUMMARY OF THE INVENTION 
In a principal aspect, the present invention is an improved method for 
using and producing various cast irons as a composite article in 
combination with various metal or steel forms. The metal or steel forms 
may serve as part of the mold form for the cast iron material, which 
preferably includes cast iron selected from the group consisting of white 
iron, compacted graphite iron, malleable iron, gray iron, and ductile 
iron. 
In one preferred embodiment the metal form component consists of tubular or 
other hollow conduit forms of steel or other alloys compatible with cast 
iron. For example, the invention may comprise a shaped ferrous casting 
having a multi-sectioned, non-linear passageway therethrough. By 
"multi-sectioned, non-linear passageway" is meant a passage that has at 
least two, and most preferably more than two non-linear sections defining 
a tortuous pathway through the casting. 
The casting of this preferred embodiment is provided by initially bending a 
steel or other metal tube or conduit into a predetermined, 
multi-sectioned, non-linear shape, and then positioning the conduit in a 
mold form such that the ends of the steel conduit will extend through the 
wall of the product to be cast. The mold form is then completed to define 
the remainder of the shape of the product to be cast. Thereafter, the mold 
form is filled with iron thereby enveloping the conduit, at least in part. 
The iron is then hardened, leaving a multi-sectioned, non-linear passage 
of any desired shape through the ferrous casting, without the necessity 
for any drilling operation. 
In another preferred embodiment, the ferrous casting will include tubular 
inserts as a method to control the casting weight and weight distribution. 
By inserting a tubular element into the ferrous casting during the casting 
operation as previously described, it is possible to reduce the weight of 
the casting or to alter the center of mass of the casting independently of 
the physical size or configuration of the casting. In some applications, 
i.e., the crankpins previously mentioned, this embodiment can be used in a 
more complex manner to (i) reduce the principal rotating mass without 
affecting the dimensions thereof and (ii) thereby reduce both the size and 
weight of the counterweight of the principal rotating mass. 
The invention may also be used as a method to produce multi-component 
elements in which a forged steel or metal form defines a part of the 
outside surface of the composite steel or metal and cast product with the 
cast iron metallurgically bonded to metal form component. By way of 
example, in this method a steel tube or conduit is positioned in the mold 
form such that a portion of the exterior surface of the tube will define a 
predetermined portion of the exterior surface of the product to be cast. 
The predetermined portion of the product to be cast is chosen to define 
the location at which the composite cast product may be metallurgically 
bonded by welding, for example. The mold form is then completed to define 
the remainder of the product to be cast, and the completed mold form is 
filled with iron which is cooled to provide the final product. This cast 
component may then be metallurgically bonded to another part, i.e., by 
welding, thus producing an integral multi-component element comprising 
both cast and non-cast components, metallurgically bonded throughout. 
One further embodiment of the invention comprises a method of forming 
chills in a casting to thereby reduce the tendency of iron, particularly 
malleable iron, to crack and tear from internal stresses during 
solidification. This embodiment involves inserting a chill form insert 
into the mold in the area where cracking is likely to occur. The insert 
promotes rapid freezing of the iron in the area of the insert. As a 
result, the iron in this area forms a skin or surface layer which has 
increased tensile strength, sufficient to resist the build-up of stresses 
during the complete solidification of the casting. 
The method further contemplates that the tubular metal conduit surface 
which interfaces with the cast iron may or may not be coated. In a 
preferred embodiment, the conduit is coated with copper metal to enhance 
the metallurgical bond between the cast iron and steel. 
As an article of manufacture, the cast product includes the metal conduit 
metallurgically bonded to a selected cast iron from the group consisting 
of white iron, compacted graphite iron, malleable iron, gray iron and 
ductile iron in the shape of a useful article, such as a crankshaft. 
Thus, it is an object of the invention to provide an improved ferrous cast 
product and the method of manufacture thereof. 
A further object of the invention is to provide an improved cast product 
and method of manufacture wherein a steel tube form is utilized as part of 
the mold for the casting. 
Yet a further object of the invention is to provide a cast iron product and 
method of manufacture thereof wherein a tubular steel form is incorporated 
into the article to define a multi-sectioned, non-linear fluid flow 
passage through the article without drilling and other metal working 
operations. 
Yet another object of the invention is to provide a method for adjusting 
either the weight or the center of mass of a cast product independently of 
adjusting the exterior design or dimensions of the cast product. 
Yet still another object of the invention is to provide a method of 
producing a multi-component object wherein some of the components are 
ferrous cast components and some of the components are non-cast 
components, yet all of the components are metallurgically bonded so as to 
form a single integral object. 
Still one further object of the invention is to provide a method of 
reducing shrinking and stress in malleable iron castings due to internal 
stress build-up during solidification. 
Yet another object of the invention is to provide an inexpensive and highly 
efficient method for manufacturing cast articles having steel tubular 
passages therethrough. 
These and other objects, advantages and features of the invention will be 
set forth in the detailed description which follows.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 1A which represents a particular example and embodiment 
of the practice of the present invention, any desired configuration and 
cross sectional shape of a tubular steel conduit 10 is incorporated into a 
mold 12 for a cast iron article. The steel tube 10 thus may define a 
passage through a casting by connecting through at least two points on the 
surface of the casting defined by the mold. In preferred form, the tube 10 
defines a multi-sectioned and non-linear passage. Arcuate passages are 
also contemplated. Also, the tube 10 may have a constant or non-constant 
diameter or cross sectional shape. 
The mold is comprised typically of a cope 13 and drag 14. As in FIG. 1A, 
the cope 13 and drag 14 define a form for a crankshaft. The tube 10, for 
example, defines a continuous channel through the interior of the mold 
form for the crankshaft 16 and connects a bearing surface 18 of the 
crankshaft with an oil or lubricant supply surface 20 as depicted in FIG. 
1A. 
In practicing the method of the invention, the tube 10 is first restrained 
in the mold. Cast iron is then introduced through a sprue 20 until the 
mold is filled as detected at gates 22, 24. The molded article (crankshaft 
16 in FIG. 1B) may then be removed from the mold and machined or finished 
in normal fashion. A drilling operation to define a lubricant passage is 
not necessary because of the presence of tube 10. Tube 10 eliminates the 
need for drilling, plugging, and finishing operations normally required to 
define a flow passage in the crankshaft 16 after casting, regardless of 
the shape of the passage. 
In the practice of the invention it is preferred to utilize low carbon 
steels for the tube 10. For example, 1018 to 1026 carbon steels have been 
found to be particularly useful. Stainless steel is not preferred. 
However, any commercially available steel alloy that will form a 
metallurgical bond with the ferrous casting and having strength properties 
comparable to those of either the casting or the tube is useful in the 
practice of the invention. 
In a preferred embodiment of the invention, the surface of steel tubing 
which interfaces with the cast iron is coated or plated before the casting 
operation. Preferably the coating material is copper metal having a 
thickness in the range of 0.0002 to 0.0005 inches. However, various copper 
or tin based alloys may be utilized as a coating. The copper is 
electroplated on the tubing surface which will interface with the cast 
iron. Techniques other than electroplating may be utilized to apply the 
coating. For example, techniques such as metal spraying, plasma coating 
and others known to those skilled in the art may be used. 
The cast material is a ferrous material selected from the group consisting 
of ductile iron, malleable iron, gray iron, and compacted graphite iron 
excluding white iron. It is possible, but not preferred, to utilize white 
iron in the practice of the invention. White iron is extremely hard and 
brittle and for that reason is not considered to be especially useful in 
the practice of the invention. 
As a further embodiment of the invention, a steel tube or form may be 
utilized to define at least a part of an outside surface of the metal 
casting at a predetermined location. In that event the tube or form again 
may be copper plated to enhance the metallurgical bond between the cast 
material and the tubing. The materials and process utilized for this 
embodiment are essentially the same as those utilized for this embodiment 
are is practiced to define a passage through the casting, except that a 
tube is positioned in the mold so as to define a part of the external 
surface of the casting at the predetermined location. After the casting 
has solidified, the tube may be metallurgically bonded to another 
component at the predetermined location. 
The purpose and utility of this second embodiment, as previously noted, is 
to provide an external steel surface which may be easily welded or 
otherwise worked yet which simultaneously is metallurgically bonded to a 
cast article. In the practice of this embodiment, the steel tube or form 
26 will simultaneously define a portion of the inside surface of the mold 
and the outside surface of the cast articles, for example as shown by a 
steel ring 38 in FIG. 3. 
In review, in the first step to practice the invention, steel or other 
metal tubing 10 is properly positioned in a mold 12 as described 
previously. The tubing 10 may be any one of various grades of steel tubing 
or alloys as also previously described. Single and double wall, welded 
seamless, and drawn tubing may be utilized. Tube and bar weldments, 
stamped, drawn and spun shapes as well as sheet steel inserts of various 
gauges and configurations may also be used. 
Preferably the metal tubing 10 or inserts are copper plated or sprayed 
either by electroplating or plasma spraying on the surface which is to 
engage and metallurgically combine with cast iron material. A thickness of 
0.0002 to 0.00003 inches of copper metal is preferred. No fluxing or 
protective coatings are require for the copper plated, steel insert and, 
in fact, such coatings or fluxing are not recommended in the practice of 
the process. Coatings such as chromium oxide adversely affect the casting 
operation and also impact adversely on the heat treatment response of some 
cast irons. For example, since most fluxing agents contain some type of 
boron, which is a very powerful carbide stabilizer, it is speculated that 
this can cause formation of iron carbides adjacent to the insert that 
cannot be subsequently removed by heat treatment. Heavy carbide formations 
are extremely abrasive to machine tools and are generally considered 
non-machinable. For these reasons, flux materials are preferably avoided. 
The thickness of the tube or insert as well as the mass is an important 
consideration in the practice of the invention. An insert or tube wall 
that is too heavy or defines an area without sufficient flow of iron 
during the casting operation will not transfer heat properly and thus will 
not metallurgically fuse with the cast iron. On the other hand, a tube 
wall that is too thin or in an excessively hot or turbulent area of the 
ferrous material will erode and eventually fail. Balancing these 
considerations can be done empirically. 
After the steel tube or insert is properly positioned within a mold form, 
clean, essentially slag-free iron is then poured into the mold. The iron 
forms a metallurgical bond with the steel. It is noted that a properly 
sized insert or tube will become molten at its surface when brought into 
contact with the molten ferrous stream. Since copper plating is highly 
reactive with ferrous metals, formation of an alloy of the iron and steel 
at the interface is promoted over a rather broad fusion zone. This occurs 
during solidification with the various types of irons set forth and can be 
enhanced by subsequent heat treatment operations particularly high 
temperature extended life heat treatment cycles. However, the heat 
treatment will not cause bonding of components where no previous bond 
existed and cannot therefore be used to salvage an improperly fabricated 
part. The design and parameters of the insert, in order to cause 
metallurgical bonding, are therefore quite important though they are 
derived empirically. 
The position and configuration of gating and forming risers are also more 
important than in conventionally poured castings. Generally castings that 
have a tube running through or along a center line of a part must be 
sufficiently gated to reduce as much as possible the turbulence inside the 
mold cavity and to avoid a high velocity iron stream directly on a section 
of the tube. With a long thin castings, such as a crankshaft, this 
generally means bottom filling on a vertically parted mold and multiple 
gates on a horizontally parted one. Such methods reduce dirt and slag 
defects. 
With the invention, certain classes of castings can achieve higher than 
normal yield figures. These castings utilize very heavy tubes which 
displace considerable iron and form a chill in what previously was 
considered an isolated, heavy section of the casting. The chilling of the 
iron promotes directional solidification, and the elimination of the 
isolated heavy section considerably reduces metal feed requirements. 
Machinability and utilization of such a casting thus is significantly 
improved. 
FIG. 2 illustrates further the article made by the method of FIGS. 1A and 
1B; namely, a crankshaft with a cast in place multi-sectional, non-linear 
oil supply passage. The method eliminates the expensive prior art series 
of drilling operations as well as counterboring, tapping, and plugging 
necessary to seal the open ends of several drilled passages that 
interconnect to form an extended passage. The tube 10 which is formed of 
steel is positioned within a mold. Cast iron flows about and solidifies 
over the tube 10. The tube 10 is preferably coated with copper metal. Upon 
removal from the mold form, the tube 10 defines a passage 33 through the 
casting 16. The ends 35, 37 of the tube 10 may then be easily tapped or 
machined. 
FIG. 3 represents a component part 36 of a power steering assembly. The 
mold form for the part 36 included a tubular section 38 which is a 
cylindrical tubular steel section which metallurgically bonds to the cast 
iron. The inside surface 37 of the steel tubular section portion 38 is 
preferably copper plated. Ductile iron is then cast over the steel section 
38. The outside surface 39 of the steel tubular section 38 may be welded, 
machined, or otherwise worked in the manner of a normal steel tube. In 
preferred form, the casting 36 is metallurgically bonded to a non-cast 
steel component at the point of the outside surface of the steel tubing, 
thereby forming a multi-component device of cast and non-cast components 
which are metallurgically bonded together. The casting 36 is otherwise the 
same as prior castings except for the portion wherein the steel tubing 38 
is provided. 
FIG. 4 is a microphotograph depicting the metallurgical bond between steel 
tubing and cast iron. Ductile iron 44 is cast about a steel insert 46. 
Carbon has migrated into the insert from the casting forming a carbide 
network and causing the formation of grains that cross the fusion zone. 
This enhances the engagement or interlocking of the steel tube and the 
cast iron. 
The process of the present invention may be utilized to make products such 
as crankshafts, drive clutch controls for air compressors, bearing caps 
for engines, fertilizer applicator knives requiring a passage, butterfly 
valve stems, the internal pump cavity for a power steering pump, and many 
other parts. As a particular example, in a hydraulic pump, the internal 
surface of the pump may be formed by a closed, steel tubular member. The 
tubing does not have to be cylindrical but can be any particular size and 
shape. The cast iron body may be metallurgically attached to the tubing by 
casting about the tubing. 
Another example of the invention is the use of steel inserts in the casting 
in the form of a solid insert, i.e. form chills that reinforce an area 
which is prone to crack in a malleable casting. The chill effect can be 
used to control a tendency of malleable iron to crack and tear from 
internal stresses during solidification. By contrast, current practice is 
to form a cooling fin or crack strip in the mold or pattern that fills 
with iron and dissipates heat into the mold during solidification. The 
cooling fin remains as part of the casting and must be removed with a 
separate operation. However, if a steel metal insert is provided in the 
mold in a area where cracking is likely to occur, the insert can act as a 
chill and, of course, perform some minor reinforcing. However, the primary 
benefit is rapid chilling and freezing in the cast part thus forming a 
part with a skin having enough tensile strength to resist the build-up of 
stresses during final solidification. This eliminates the need for a crack 
strip and subsequent operations to remove it. 
In sum, by use of steel tubing in the described cast iron articles, it is 
possible to reduce the weight for the article which is being cast or to 
alter the center of mass of the article without modifying the external 
design of the casting. The tubing may also be used as a wear surface or 
for forming a bearing surface or as a passage. 
Following are tables setting forth parameters of malleable iron and ductile 
iron which have so far been used in combination with steel tubing, as 
previously described, in the manufacture of articles using the process 
described: 
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MALLEABLE IRON - CHEMISTRY RANGES 
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Carbon Operating range: 2.45-2.55% 
Mark iron under 2.35 or over 2.60% 
Silicon Operating range: 1.40-1.50% 
Mark iron under 1.35 or over 1.60% 
Manganese 
Operating range: 0.40-0.47% 
Mark iron over 0.50% 
Chromium Operating range: .060% Max. 
Mark iron if 
% Chromium 
% Silicon Si is over 
0.060-0.070 
1.45-1.55% 1.60% 
over 0.070 
1.50-1.60% 1.60% 
Sulfur Operating range: 0.060-0.080% 
Sulfur may require adjustment to compensate for 
high manganese. 
Sulfur and manganese should stay within the 
relationship. % Mn = 6.25 (% S) 
Aluminum 0.0125% maximum in final iron. 
.008% minimum in final iron. 
Boron Operating range: 
0.0014-0.0022 in furnace iron 
0.0022-0.0030 in final iron 
Quantovac boron analysis must be adjusted for 
sulfur content. 
Titanium .015% maximum in final iron. 
.012% maximum in base iron 
Liquidus Operating range: 2350-2370.degree. F. 
Temperature 
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DUCTILE IRON - CHEMISTRY RANGES 
Ladle Analysis: Final Iron 
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Carbon Normal Range: 3.55-3.75% 
Silicon Normal Range: 2.60-2.80% 
Minimum: 2.40%-Maximum: 3.00% 
(3.10 Wet Analysis) 
Manganese 0.20% Minimum-Maximum 0.45% 
Chromium 0.060% Maximum 
Aluminum 0.040% Maximum 
Boron 0.0018% Maximum 
Sulfur 0.015% Maximum 
Phosphorus 0.035% Maximum 
Copper Ferritic - 0.20% Maximum 
Pearlitic - 0.80% Maximum (depending on 
hardness) 
Nickel 0.05% Maximum 
Titanium 0.03% Maximum 
Tin 0.010% Maximum 
Molybdenum 0.015% Maximum 
Magnesium Normal Range: 0.045-0.055% 
Minimum 0.040%-Maximum 0.058% 
Vanadium 0.02% Maximum 
Cerium 0.02% Maximum 
Lead 0.004% Maximum 
Zinc 0.05% Maximum 
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These cast iron compositions have been utilized for the manufacture of 
articles in accord with the described invention though it is possible to 
vary the cast iron compositions considerably. Thus, while there has been 
set forth a series of preferred embodiments of the invention, it is to be 
understood that the invention is to be limited only by the following 
claims and their equivalents.