GB1584037A

GB1584037A - Centrifugal casting dies

Info

Publication number: GB1584037A
Application number: GB5169777A
Authority: GB
Original assignee: SHEEPBRIDGE ENG Ltd
Current assignee: SHEEPBRIDGE ENG Ltd
Priority date: 1977-12-12
Filing date: 1977-12-12
Publication date: 1981-02-04
Also published as: DK557478A; ES240080U; FR2411048A1; ES240080Y; DE2853596A1

Description

(54) IMPROVEMENTS IN OR RELATING TO CENTRIFUGAL CASTING DIES (71) We, SHEEPBRIDGE ENGINEERING LIMITED, a British Company, of Sheepbridge Works Chesterfield. Derbyshire. S41 9QD do hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed to be particularly described in and by the following statement: This invention relates to centrifugal casting dies for casting cylinder liners.

Iron castings can be produced very economically by centrifugal casting in cast iron or steel dies and for the vast majority of applications these parts are fully satisfactory. Thus most cylinder liners used in diesel engines are produced by this process. However for some special applications the micro structures obtained may not be ideal.

Thus. the relatively slow cooling obtained in the bore of the casting results in a random distribution of graphite in the micro structure and this is accepted as giving good wear and scuff resistance. "Under cooled'' graphite tends to be obtained on the periphery or outer surface of the liner and this structure can result in impaired fatigue resistance. This can be an important disadvantage for some applications which involve particular liners: for example. if the liner is subjected to vibration or stresses in use.

This invention provides a centrifugal casting die for casting a cylinder liner. the die having a cvlindrical bore within which a liner mav be cast and defined by an encircling wall intended to be received in a socket in a casting apparatus. the wall having means disposed along at least a portion of its axial length to restrict radial heat flow through said portion of the wall to reduce the rate of cooling of the casting in the die in that portion of the die.

Bv reducing the rate of cooling over a portion of the casting. formation of undesirable under cooled graphite on the outer surface of that portion of the casting is minimised.

Preferablv the means to restrict radial heat flow through a portion of the axial length of the die is provided at at least one end portion of the die.

For example the die mav have. at one axial end thereof. a multiplicitv of blind holes extending into the die wall axiallv of the die at locations spaced around the die axis to provide cavities in the die wall to restrict the flow of heat through the die wall.

The open ends of the holes may be covered by an annular plate secured to the end of the die.

In an alternative arrangenent an annular recess mav be formed in the axial end of the die extending into the die wall to provide a restriction to flow heat through the die wall.

Preferablv the open end of the recess is covered by an annular plate secured to the end of the die wall.

In yet another further arrangement. the outer surface of the die wall may have an encircling groove or grooves around that portion of the die where the cooling rate is to be reduced. the groove or grooves forming an air gap with the encircling socket in which the die is mounted in use to restrict the heat flow from the die to the sockets.

More specifically. the die mav have an encircling head at one end thereof. the periphery of the head and the periphery of the die adjacent the head being formed with encircling grooves to restrict the heat flow to the wall of the socket which encircles the die in use.

The following is a description of some specific embodiments of the invention. reference being made to the accompanying drawings. in which: Figure 1 is a sectional view through a centrifugal casting die according to the invention for casting a cylinder liner: Figitre 2 is an end view of the die shown in Figure 1: Figure 3 is a similar view to Figure 1 showing a further arrangement; Figure 4 is an end view of the die shown in Figure 3; Figure 5 is a sectional view through a further die; and Figure 6 is and end view. of the die shown in Figure 5.

Referring y to Figures 1 and 2 of the drawings, there is shown a cast iron or steel die) 10 for use a centrifugal casting apparatus for the casting of cylinder lines for diesel engines. The die has a cylindrical wall 11 defining a central bore 12 within which the cylinder liner is cast. At one end of the wall 11 there is an out turned flange or head 13. The die 10 s mounted, in use, in a socket in a casting apparatus having a bore to receive the cylindi ical wall 11 with a recess at the open end of the bore within which the head or flange 13 fits.

In use the die 10 is rotated in the casting machine and molten iron is poured into the die and is deposited on the cylindrical wall 12 of the die by the rotation thereof The bore of the liner cast in the die cools relatively slowly and this results in'a random distribution of the graphite in the micro structure which gives a surface having good wear and scuff resistance.

To minimise or prevent an "under cooled graphite structure at the outer surface of the casting adjacent the end which is to be located adjacent the' end 6f th'e cylinder bore. in the engine. the flanged end of the die 1() is formed with a multiplicity of closely spaced blind bores 14 extending into the wall of the die parallel to the die axis. The open end of the bores are covered by an annular end plate 15 let into a recess 16 in the end of the die wall and secured by pins 17. The bores 14 can be empty or filled with a low conductivity refractory material such as sand or ceramic cement (to restore rigidity to the die if this is though to be necessary) and provide a resistance to heat flow outwardly from the inner surface of the die to the outer surface of the die. Thus the rate of flow of heat outwardlv from the inner surface of the die is reduced and. therefore. the rate of cooling of the surface of the casting in that part of the die is lowered. As a result the under cooled graphite structure referred to above is prevented or minimised.

Figure 3 shows a simllar arrangement to that of Figure 1 except that the multiplicity of bores 14 is replaced by a single annulat groove 18.

Figure 5 and Figure 6 show an alternatively arrangement in which the bores 14 are omitted and, instead. an annular groove 19 is formed around the outer periphery of the flange or head 13 or the die and a similar annular groove 20 is formed around the outer wall 11 of the die adjacent the flange 13. When the die is located in the socket in the casting apparatus, air gaps are formed between the bottom of the grooves 19,20 and the adjacent encircling wall of the socket. such air gaps restricting the flow of heat from the surface of the die to the socket and thereby lowering the rate of cooling in that portion of the die for the purpose stated above.

It is also possible for combinations of the various arrangements described above to be made. For example. the featurcs of the embodiment of Figures 5 and 6 which restrict heat flow could be used in the embodiments of Figures 1 and 2 or Figures 3 and 4. - A cylinder liner has been cast in a die as shown in Figures 1 and- 2 from an iron of the following composition: C Si Mn S P Ni Cr Mo Cu Wt% 3.35 2.50 0.7 0.06 0.054 0.8 0.47 0.28 0.19 The casting temperature was 1250 C and a conventional die dressing was used. The resulting cylindrical casting has an outside diameter of 127mm and a 20mm wall thickness.

It was found on subsequent microscopical examination that a marked improvement in graphite structure has been obtained. Thus, at a distance of 4mm from the cast outside diameter the graphite confirmed to ASTM-A247 type A sizes 5 to 6. Normally, when conventional, solid dies are used the graphite is of ASTM B size 7 with some D type size 7/8 and A type size 6/7.

Claims

WHAT WE CLAIM IS:

1. A centrifugal casting die for casting a cylinder liner, the die having a cylindrical bore within which a liner may be cast and defined by an encircling wall intended to be received in a socket in a casting apparatus, the wall having means disposed along at least a portion of its axial length to restriet radial heat flow through said portion of the wall to reduce the rate of cooling of the casting in the die in that portion of the die.

2. A die as cl-iimed in claim I wherein the means to- restrict radial heat flow through a portion of the axial length of the die is provided at at least one end portion of the die wall.

3. A die as claimed in cl-iim 2 blind hiving. at one axial end thereof. a multiplicity of blind holes extending into the die wall axially of the die at locations spaced around the die axis to provide cavities in the die wall to restrict the flow of heat through the die wall.

4. A die as claimed in claim 3 wherein the open ends of the holes are covered bv an annular plate secured to the end of the die.

5. A die as claimed in claim I or claim 2 wherein an annular recess is formed in an axial end of the die, the recess extending into the die wall to provide the restriction to flow of heat through the die wall.

6. A die as claimed in claim 5 wherein the open end of the recess is covered by an annular plate secured to the end of the die wall.

7. A die as claimed in claim 1 or claim 2 wherein the outer surface of the die has an encircling groove or grooves around that portion of the die where the cooling rate is to be reduced, the groove or grooves forming an air gap with the encircling socket in which the die is mounted in use to restrict the heat flow from the die to the socket.

8. A die as claimed in claim 7 and having an encircling head at one end thereof. the periphery of the head and the periphery of the die adjacent the head being formed with encircling grooves to restrict the heat flow to the wall of the socket which encircles the die in use.

9. A casting die for casting a cylinder liner substantially as described with reference to and as illustrated in Figures I and 2, Figures 3 and 4 or Figure 5 and 6 of the accompanying drawings.