US3795511A

US3795511A - Method of combining iron-base sintered alloys and copper-base sintered alloys

Info

Publication number: US3795511A
Application number: US00191606A
Authority: US
Inventors: S Mitani; K Imanishi; K Ushitani; Y Serino; I Niimi; K Hashimoto
Original assignee: Toyota Motor Corp
Current assignee: Toyota Motor Corp
Priority date: 1971-04-27
Filing date: 1971-10-22
Publication date: 1974-03-05
Anticipated expiration: 1991-03-05
Also published as: GB1312024A; DE2154107B2; DE2154107A1; DE2154107C3; JPS4948060B1

Abstract

METHOD OF COMBINING IRON-BASE SINTERED ALLOYS AND COPPER-BASE SINTERED ALLOYS COMPRISES STEPS OF THINLY COATING MIXED POWDER OF COPPER AND NICKEL ONTO JOINT SURFACE OR IRON-BASE POWDER OR SINTERED MASS THEREOF, AND SUBJECTING THE COATING TO SINTERING PROCESS USING TEMPERATURE APPLOCABLE TO IRON-BASE POWDER. JOINT SURFACE OF COPPER-NICKEL IN THEN ABUTTED WITH FORMED MASS OD COPPERBASE POWDER AND AGAIN SUBJECTED TO SINTERING PROCESS USING TEMPERATURE APPLICABLE TO COPPER-BASE POWDER. IN TEGRAL PIECE IS THEREBY OBTAINED MOST SUITABLE FOR FABRICATING VALVE SEATS OF INTERNAL COMBUSTION ENGINES.

Description

March 5, 1974 lTARu N||M| ETAL 3,795,511

METHOD OF COMBINING IRON-BASE SINTERED ALLOYS AND COPPER-BASE SINTERED ALLOYS Filed Oct. 22, 1971 Z7 1 W *HHIHW @2111 HI! l nun 2 United States Patent Japan Filed Oct. 22, 1971, Ser. No. 191,606 Claims priority, application Japan, Apr. 27, 1971, 46/331,680 Int. Cl. B21k J/24; B22f 7/00 US. Cl. 75-208 1 Claim ABSTRACT OF THE DISCLOSURE Method of combining iron-base sintered alloys and copper-base sintered alloys comprises steps of thinly coating mixed powder of copper and nickel onto joint surface of iron-base powder or sintered mass thereof, and subjecting the coating to sintering process using temperature applicable to iron-base powder. Joint surface of copper-nickel is then abutted with formed mass of copperbase powder and again subjected to sintering process using temperature applicable to copper-base powder. Integral piece is thereby obtained most suitable for fabricating valve seats of internal combustion engines.

BACKGROUND OF THE INVENTION The present invention relates to a method of combining iron-base sintered alloys and copper-base sintered alloys to produce an integral and solid alloy. These alloys have excellent adaptability for use as valve seats in internal combustion engines.

When the head of an engine is made of cast iron and the valve seat is entirely made of a copper-base alloy, the copper-base material yields during use due to the difference in the coefficient of thermal expansion between the two materials. Also, the valve seat tends to move away from the engine head when the engine is cooled. This problem may be solved by applying copper-base sintered material to the part of the valve seat that engages the face of the valve. Copper-base sintered material is a highly suitable valve seat material. The remaining portion of the valve seat is fabricated of ironbase sintered material which has a high heat resistance and coefiicient of thermal expansion very close to that of cast iron.

The above selected materials fully satisfy the requirements necessary for valve seat materials. However, when iron-base sintered material and copper-base sintered mateiral are combined into an integral sintered mass, the conventional practice is not easily applicable since the iron and copper materials have different melting points. Conventional practice, namely, utilization of changes in size appeared during the sintering process, hot forging, brazing with copper or copper-tin compositions, or combinations of the above are not suitable for the purpose of combining iron-base and copper-base sintered alloys into an integral mass.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a method of combining iron-base and copperbase sintered alloys into a unitary alloy useful for the fabrication of components subjected to high temperature.

In accordance with the present invention a method is provided for combining iron-base sintered alloys and copper-base sintered alloys wherein a mixed powder of copper and nickel is thinly coated onto the joint surface of a formed mass of iron-base powder or the sintered mass thereof. The coating is subjected to a sintering process utilizing the temperature applicable to iron-base powder. The joint surface of copper-nickel is then abutted with a formed mass of copper-base powder and again subjected to a sintering process utilizing the temperature applicable to copper-base powder. A unitary composite material is thereby obtained, the material being most suitable for fabricating valve seats as used in internal combustion engines.

BRIEF DESCRIPTION OF THE DRAWING Novel features and advantages of the present invention in addition to those mentioned above will become apparent to those skilled in the art from a reading of the following detailed description in conjunction with the accompanying drawing wherein:

'FIG. 1 is a top plan view of a valve seat fabricated of material processed in accordance with the present invention;

FIGS. 2 and 3 are cross sectional views of the valve seat of FIG. 1 illustrating the procedure of the present invention for combining different alloys into a unitary composite alloy materials; and

FIG. 4 is a fragmental sectional view of the valve seat of FIGS. 1-3 in an internal combustion engine.

DETAILED DESCRIPTION OF THE INVENTION Referring in more particularity to the drawings, the individual figures illustrate an annulus of copper-base material 1 associated with an annulus of iron-base material 2. The interface between the annuli 1 and 2 comprises joint material 3. The copper-base 1, iron-base 2 and joint 3 material are formed into a sintered mass 5 in the shape of a valve seat. As shown best in FIG. 4, the valve seat or sintered mass 5 cooperates with a head 4 of an internal combustion engine.

According to the method of the present invention, ironbase sintered material and copper-base sintered material are combined together into an intensified unitary sintered material. The material thus combined is particularly adaptable for fabricating those parts and components of machines for which anti-friction qualities and wear resistance are indispensable, such as valve seats for automobile engines.

As previously explained above, copper and nickel mixed powder is selected as the joint material 3. This mixture is composed of electrolytic copper powder of under mesh and carbonyl nickel powder having a particle size of about 414.. An iron-base formed mass or sintered mass thereof is thinly coated with a uniform layer of the joint material 3. Alternatively, the copper-nickel powder mixture may be uniformly coated onto an iron-base mixed powder after which the material is sintered at a temperature agreeable to iron-base sintered material. By this heat treating copper melts and permeates into iron-base sintered material, but by the existence of nickel, copper remains near the combined surface, and nickel rich material remained on the surface thereof. On the other hand, the surface of remained nickel (includes copper) becomes a rugged or rough. The sintered mass is then placed in a mold and copper-base powder is filled in on top of it. Pressing the copper-base mixed powder causes entangling engagement between the powder and the rugged or rough surface of the iron-base sintered material which is rich with nickel. After this mass is sintered, nickel diffuses into the copperbase material to provide a very intense joint surface and excellent bond.

Concerning other joint materials, in the case of a 100% nickel the diffusion of nickel into the iron-base material is insufficient and the resultant surface after the first sintering process is lacking in ruggedness or roughness.

As a result, when the copper-base mixed powder is formed on the nickel joint material the resultant joint or bond is most unsatisfactory since the copper-base material lacks entangling engagement with the nickel joint material. Also, joint materials of 100% copper or substances having a melting point less than copper, for example coppertin alloys, are equally unsatisfactory since each of these joint materials diffuses in an excessive amount into the iron-base material. Additionally, when using such joint materials, very little remains on the surface after the first sintering process which is carried out at a temperature agreeable to the iron-base material. In the event some of the joint material remains, the surface thereof after sintering is quite smooth and almost the equivalent of the 100% nickel joint material. Moreover, since coppertin alloys have melting points close to the copper-base mixed powder the sintering conditions are difiicult to select and maintain.

As is clear from the above, copper-nickel mixed powder should be utilized as the joint material in the present invention. The advantageous result of the present invention is obtained by appropriately choosing the mixing ratio of copper and nickel by taking into consideration the constituents of the iron-base and copper-base materials to be combined. The required joint strength is also important.

A preferred embodiment of the present invention is described below with reference to the present drawing.

EXAMPLE Mixed powder composed of 96% iron, 3% moly'bdenum and 1% graphite was filled into a metal mold. A mixed powder of 50% copper and 50% nickel was then thinly and uniformly applied to the annulus 2, and then formed under a pressure of 6 t./cn1. into an annulus 2 and 3, as best illustrated in FIG. 2, which may also be sintered under the sintering conditions agreeable to the iron-base material as specified hereinafter. The thickness of the uniform layer was 0.5 to 1.0 mm. The mixed joint material powder 3 of 50% copper and 50% nickel was also coated onto a powder of 96% iron, 3% molybdenum and 1% carbon. The latter iron-base powder was formed in a metal mold under a pressure of 6 t./cm. Each of the above masses was then sintered at a temperature of 1150 to 1180 C. for 60 minutes in an ammonia cracked gas which met the sintering conditions for the iron-base material. Each sintered mass thus obtained was put into a metal mold and covered with a copper-base mixed powder composed of 80% copper, 8% tin and 12% chromium. After pressing the copper-base material under a pressure of 6 t/cm. the copper-base material had a shape similar to the annulus 1 shown in the drawing. Next, the material was sintered at a temperature of 900 to 950 C. for minutes in a nitrogen gas under conditions agreeable to the copper-base material. The twice sintered mass was again pressed under 6 t./cm. to provide an accurately sized unitary composite material 5 composed of an annulus 2 of iron-base sintered material 1, an annulus 1 of copper-base sintered material 1 and a joint material layer 3, as shown best in FIG. 3.

For the purpose of evaluation, the sintered mass 5 was inserted into the cast iron head 4 of an internal combustion engine (see FIG. 4). The copper-base material of the mass 5 engaged the face of the valve. The internal combustion engine was run at 5,200 r.p.m. for two hours under a full load after which it was cooled. This cycle was repeated and the iron-copper sintered material of the present invention was perfect even after 50 cycles. A copper-base sintered material of copper alloy (fusion material) fell away from the cast iron engine head after several cycles.

What is claimed is:

1. A method of combining an iron-base sintered alloy and a copper-base sintered alloy comprising coating a mixed copper and nickel powder as a bonding agent onto the joint surface of an iron-base mass, sintering the copper and nickel powder at a temperature agreeable to the iron-base mass to thereby diffuse and permeate part of the copper and nickel of the bonding agent into the ironbase mass and thereby form a rough nickel rich surface on the joint surface of the iron-base mass, abutting a formed mass of copper-base powder at the surface of the copper-nickel coating on the iron-base mass, and finally sintering the abutted masses at a temperature agreeable to the formed mass of copper-base powder to thereby diffuse part of the nickel of the copper and nickel coating of the iron-base mass into the copper-base mass whereby the masses are intensely combined together.

References Cited UNITED STATES PATENTS 2,753,859 7/1956 Bartlett 29-1822 X 3,359,623 12/ 1967 Gwyn -208 R X 2,251,410 8/1941 Koehring et a1. 75-208 R X BENJAMIN R. PADGE'I'I, Primary Examiner R. E. SCHAFER, Assistant Examiner US. Cl. X.R.