US3695865A

US3695865A - Process for the production of cylindrical hollow bodies in the centrifugal casting process

Info

Publication number: US3695865A
Application number: US13181A
Authority: US
Inventors: Karl Wolker
Original assignee: Pleuco-G mbH
Current assignee: Pleuco-G mbH
Priority date: 1969-02-21
Filing date: 1970-02-20
Publication date: 1972-10-03
Anticipated expiration: 1989-10-03
Also published as: DE1908856C3; FR2031578A1; GB1269014A; DE1908856A1; FR2031578B1; DE1908856B2

Abstract

PROCESS FOR THE PRODUCTION OF CYLINDRICAL HOLLOW BODIES WITH A PEARLITIC STRUCTURE FROM CAST IRON MATERIAL BY SUPERHEATING A EUTECTIC OR HYPEREUTECTIC MELT AFTER ADDING ALLOYING ELEMENTS SO THAT IN SUBSEQUENT CASTING A MIXTURE SUPERSATURATED WITH CARBON RESULTS, AND THE PRODUCTS THEREOF.

Description

United States Patent Office 3,695,865 Patented Oct. 3, 1972 US. Cl. 75-430 R 8 Claims ABSTRACT OF THE DISCLOSURE Process for the production of cylindrical hollow bodies with a pearlitic structure from cast iron material by superheating a eutectic or hyperentectic melt after adding alloying elements so that in subsequent casting a mixture supersaturated with carbon results, and the products thereof.

The invention relates to a process for the production of cylindrical hollow bodies, especially cylinder liners, in the centrifugal casting process from cast iron material with at least 3% by weight of graphite and 3.7% by weight of total carbon content. I

The production of cylindrical hollow bod1es, for example cylinder liners, with a pearlitic structure and a total carbon content of up to about 3.7% by weight in the centrifugal casting process is already known. Whilst the pearlitic structure favourably influences the wear properties, the graphite serves the purpose of creating anti-friction properties (Notlaufeigenschaften) which are necessary in the case of insufficient separate lubrication. In these known cylindrical hollow bodies the graphite content in the structure amounts to a maximum of 2.8%, since up to 1% of carbon in pearlite is bound as cementite.

Until now, it has not been possible in the centrifugal casting process to treat a pearlitic cast iron with graphite content of more than 2.8% by weight, since the structure such high carbon content in relation to the silicon content is either ferrite or carbide.

The problem underlying the invention resides in the creation of a process, according to which cylindrical hollow bodies, for example cylinder liners, axials and bearing rings, can be produced which are distinguished particularly by improved anti-friction characteristics and by a higher corrosion resistance against acid combustion products and cooling water.

The process according to the invention for the production of cylindrical hollow bodies, more especially cylinder liners, is characterised in that a eutectic or hypereutectic melt, after the addition of such alloying elements which are required for the formation of a pearlitic structure, is superheated in a melting furnace and so far carburised, that in the subsequent tapping and casting, limited through temperature drop and inoculation, a mixture supersaturated with carbon results, which under controlled rotation conditions is cast in such a way, that the so produced cylindrical hollow body has at its bearing surface at least 3% by weight of graphite in a pure pearlitic structure.

This has essentially the advantage, that in the so produced cylindrical hollow bodies, which are stressed by friction and the separate lubrication of which is not unconditionally assured, the bearing surface has significant surface portions of graphite, so that adequate resulting properties are thus assured with high stress. Thereby, the bearing surface of these liners contains about 19% graphite. This signifies in contrast to the usual pearlite casting in which only about 12% of the surface consists of graphite, a relative increase of the graphite surface of about 50%.

Suitably a eutectic to hypereutectic cast iron with the following analysis is used:

Percent Carbon 23.7 Silicon (max.) 1.5 Manganese (max) 1.0 Phosphorus (max.) 1.0 Chromium (max.) 0.9 Molybdenum (max.) 0.9 Nickel (max) 2.5 Copper (max.) 1.5 Tin (max.) 1.2 Sulphur (max.) 0.12

Thereby a heterogeneous mixture of liquid cast iron and containing solid graphite can be teemed into the centrifugal mould.

The carbon supersaturation and graphite separation can also be initiated through mould inoculation only in the centrifugal mould. Advantageously the peripheral speed of the centrifugal mould amounts to a maximum of 5 metres per second.

This has essentially the advantage that on the one hand zone formation is avoided or reduced and on the other hand a coarser graphite is obtained and a fine eutectic graphite is avoided.

If desired and a fine eutectic graphite formation is to be obtained, the peripheral speed can amount to over 5 metres per second.

For production of cylindrical hollow bodies with variable graphite content in the bore, the melt is suitably cast to liners with diiferent external diameters of constant bore. Accordingly, there then results high machining allowances or high wall thicknesses respectively of high graphite content in the bore and visa versa.

Further advantages are shown from the following explanation of embodiments of the invention:

A hypereutectic cast iron is used, which is melted and superheated in an electric furnace and is highly carburised. In the filling in the casting ladle through inoculation and assisted through temperature drop a heterogeneous mixture, supersaturated with carbon, from liquid cast iron and graphite results. By flotation the graphite is enriched in the direction of the bore and there is then obtained according to this process, for example at the bearing surface of the cylinder liner, not only absolute high graphite content, but increased graphite content in relation to the external surface of the liner. The graphite content attainable in the bore increases, with equal chemical analysis of the melt, with increasing wall thickness of the unfinished piece in consequence of the flotation process taking place.

Example Raw material 116 X X70 96 X70 Wall thickness, millimeters- 23 18 13 C (furnace), percent 4. 6 4. 6 4. 6 Graphite, percent 3. 9 3. 4 3. 18 (Bearing surface), combined carbon, percent 1. 0 0. 86 0. 96 Silicon (furnace), percent. 1. 05 1.05 1. O5 Silicon (ladle), percent.-. 1. 26 1. 30 1. 26 Mn, percent. 0. 29 0. 47 0. 29 P, percent 0. 12 0. 34 0. 12 8, percent. 0. 038 0. 04 0. 038 Or, percent.. 0.07 0. 30 0. 07 N 1, percent Traces 0.27 Traces Mo, percent Traces O. 25 Traces Sn, percent 0. 5

The cylinder liners produced according to the process of the invention have, even with small wall thicknesses of for example, 10 to 25 mm., still have several zones of variable structure. In the processing of the bearing surface guided difierent zones are chamfered the graphite contents of which differ up to 1%. The number of these zones can, in accordance with the invention, be reduced to a maximum of two and in particular a graphite-rich inner zone and a graphite-poor outer zone. It is possible even to attain a continuous graphite enrichment in the direction of the axis of rotation. In order to avoid more than two different zones the peripheral speed of the rotating liners is adjusted in relation to the central diameter of a blank to a maximum of 5 metres per second. This permits the use both of a eutectic and hypereutectic melt with at least 3.7% carbon which for the rest has the Supplementary inoculants The carbon supersaturation accordingly occurs during the solidification of the melt. The graphite present after the casting then floats in the direction of the bore up to completion of the solidification so that the latter is thus enriched with graphite. An exclusive as well as additional graphite separation can be obtained through mould inoculation.

The liners produced in accordance with the invention have in the pure pearlitic structure a microhardness of 220 to 290 HV. The selected regulation of the peripheral speed influences both the formation of the individual zones and the graphite formation. Accordingly, lower peripheral speeds of a maximum of 5 metres per second yield coarse graphite and higher peripheral speeds of more than 5 metres per second fine to punctiform graphite of dendritic formation.

I claim:

1. Process for the production of cylindrical hollow bodies, particularly cylinder liners in the centrifugal casting process from a cast iron material with at least 3.7% by Weight total carbon content, which comprises superheating from a eutectic to a hypereutectic highly carburised melt in the furnace after the addition of the alloying elements required for the formation of a pearlitic structure, so that subsequently in the casting ladle through inoculation and through a temperature drop a mixture supersaturated with carbon results, which mixture under controlled rotation conditions is cast in such a way, that the so produced cylindrical hollow body has at its bearing surface at least 3% by weight of graphite in a pure pearlitic structure.

2. Process according to claim 1, wherein eutectic to hypereutectic melt is cast iron with the following analysis is used:

3. Process according to claim 1, wherein a heterogeneous mixture from liquid cast iron containing solid graphite is teemed into a centrifugal mould.

4. Process according to claim 1, wherein the carbon supersaturation and graphite separation is initiated by mould inoculation in the centrifugal mould.

5. Process according to claim 1, wherein the peripheral speed of the centrifugal mould amounts to a maximum of 5 metres per second.

6. Process according to claim 1, wherein the peripheral speed of the centrifugal mould amounts to more than 5 metres per second.

7. Process according to claim 1, wherein the melt is cast to liners with different external diameters of constant bore.

8. The process of claim 1, wherein said melt is a hypereutectic highly carburised cast iron.

References Cited UNITED STATES PATENTS 1,280,418 10/1918 DeLavaud 148-35 X 1,614,863 1/ 1927 Beatty 14 8-35 1,702,128 2/1929 Niedringhaus 148-35 1,871,544 8/ 1932 McCarroll 148-35 X 1,953,180 4/ 1934 Langenberg 148--35 X 1,971,385 8/1934 Russell 148-35 X 2,689,990 9/1954 Samuels 148-35 X 3,559,775 2/1971 Miller 148-35 X 1,793,268 2/ 1931 Williams -58 2,731,690 1/1956 Coupland, Jr., et al. 1641 14 X 3,415,307 12/1968 Schuh et al 164-114- 3,563,300 2/1971 Honda et al. 164-414 X L. DEWAYNE RUTLEDGE, Primary Examiner J. E. LEGRU, Assistant Examiner US. Cl. X.R.

75-l23 C-B; 14835; 164-114