Title of Invention

A DOUBLE LAYER EXHAUST POWDER METALLURGY VALVE SEATS AND PROCESS FOR MANUFACTURE THEREOF

Abstract

The present invention relates to a Double Layer Exhaust Powder Metallurgy Valve Seats for gasoline engines of automotive having uniform distribution of metal carbides, said valve seats comprising; a. a valve side composition having Cu 0.9-1.4% + C 1-1.5% + W 0.75-1.25% + Mo 0.7-1.2% + Cr 0.5-1% + V 2.5-3.5% + Co 0.2- 2.5% (HSS alloy) + Fe 7586% + 2% of other metals having a high wear resistance; and b. a Cylinder side composition having Cu 0.7-1.3% + C 0.6-1.2% + Cr 0.6-1.2% + Fe 91-96% + I % of other metals having high creep resistance. The Valve seats having applications in gasoline engine automotive that require a high surface resistance and high temperature tolerance and the present invention also relates to a process for the manufacture of the said parts using Powder Metallurgy technology with a novel composition of metals.

Full Text

FIELD OF THE INVENTION The present invention relates to a Double Layer Exhaust Powder Metallurgy Valve Seats having uniform distribution of metal carbides useful in two/four stroke gasoline engine driven vehicles. This invention also relates to a process of manufacturing double layer powder metallurgy exhaust valve seats. BACK GROUND AND PRIOR ART REFERENCES Using the casting route conventionally produced valve seats. However, Powder Metallurgy (PM) Route has become more popular as the PM process produces large volume of products at a low cost. 1 he production is faster and the products thus obtained are near to net shape. Further, the chemistry of the valve seat can be designed by way of blending various ingredients to form the part. Hence, each ingredient may be chosen to meet a specific property or requirement. Exhaust valve seats require room temperature properties such as hardness, and crushing strength, both required for handling are due to and for not failing during fitment. Further, these properties are essential for performance during the initial few operating cycles during which time the seat would not have heated to the operating temperature. The operating temperature of exhaust valve seat is 350-450°C and in that condition, retention of hardness and resistance to wear is very critical. Commonly used PM alloys use Fe as the base material with addition of carbide forming elements such as Mo, Cr, Nb, V and W to form stable carbides that provide the above properties. In general materials containing Cobalt, Cr, Ni, and Mo are commonly added for valve seat production. Generally, in the valve seat, only the valve side of the part is subjected to severe working conditions as compared to the cylinder side material. Due to this, as a part of cost reduction, some of the manufacturers started using double layer valve seats with rich mix containing Iron, Co, Cr, Mo and C in the valve side and cylinder side containing Iron with Mo and Carbon additions. The disadvantages Co base materials addition is that it is a strategic material and is expensive. It also requires higher sintering temperature in the range of 1180-1220°C which makes the processor cost also to increase. The commercially available High-speed steel powder along with Iron Powder addition is an attractive alternative to reduce cost and commercially these types of valve seats are available. High-speed steel is still an expensive material. The cost of HSS powder M3/2 , which is the popular powder, used for valve seat is expensive. This type of high wear resistance, high temperature strength required only on the side where the valve comes in contact with the valve and on the Cylinder side good creep resistance is sufficient. OBJECTS OF THE PRESENT INVENTION The main object of the present invention is to provide a double layer powder metallurgy exhaust valve seat with HSS containing alloy on the valve side and Fe-Cr-C on the cylinder side. Another object of the present invention is to provide a double layer exhaust valve seats having a low cost raw material for use in two & four-wheelers using PM Technology. Yet another object of the present invention is to minimize the cost of the raw material, by using a blend of commercially available alloy and Fe powder using PM Technology. Another object of the present invention is to provide double layer exhaust valve seats with good diffusion of alloying elements. Still, yet another object of the present invention is to provide double layer exhaust valve seats that can retain the hardness and resistance both at room temperature and high temperatures ranging 350-450°C. Further, another object of the present invention is to provide for a process for manufacturing double layer exhaust valve seats using Powder Metallurgy. STATEMENT OF THE INVENTION The present invention relates to a Double Layer Exhaust Powder Metallurgy Valve Seats for gasoline engines of automotive having uniform distribution of metal carbides, said valve seats comprising; (a) a valve side composition having Cu 0.9-1.4% + C 1-1.5% + W 0.75-1.25%» + Mo 0,7-1.2% + Cr 0.5-1% + V 2.5-3.5% + Co 0.2- 2.5% (HSS alloy) + Fe 75-86% + 2% of other metals having wear resistance; (b) a Cylinder side composition having Cu 0.7-1.3% + C 0.6-1.2% + Cr 0.6-1.2% + Fe 91-96% + 1 % of other metals having creep resistance; and also A process for manufacture of Double Layer Exhaust Powder Metallurgy Valve Seats for gasoline engines of automotive having imiform distribution of metal carbides, said process comprising steps of: (a) producing a powder by mixing Cu 0.9-1.4% + C l-1.5%o + W 0.75-1.25% + Mo 0.7-1.2% + Cr 0.5-1% + V 2.5-3.5% + Co 0.2- 2.5% (HSS alloy) + Fe 75-86% + 2% of other metals having wear resistance for the valve side; (b) producing a powder by mixing Cu 0.7-1.3% + C 0.6-1,2% + Cr 0.6-1.2%> + Fe 91-96% +1% of other metals having creep resistance for the cylinder side (c) mixing the powders of step(a) and step (b) with a lubricant; (d) blending the mixed powders in a double cone blender for about 20 minutes; (e) compacting blended mixture in a specific press to a green density in the range of6.80-6.90g/cc; (f) sintering the compacted material in a belt furnace at a minimum temperature of 1120°C using N2-H2 atmosphere for about 20 minutes; and (g) infiltrating the sintered material with Copper to obtain exhaust valve seats. BRIEF DESCRIPTION OF THE ACCOMPANIED DIAGRAMS Figure 1 shows the microstructure of SFL valve seat at the interface between the valve side and cylinder side showing good bonding between the two materials. Figure 2 shows microstructures of Cylinder side material with uniform distribution of alloy carbides Figure 3 shows microstructures of Valve side material with uniform distribution of alloy carbides. Figure 4 depicts softening resistance of valve side material. Figure 5 depicts softening resistance of cylinder side material. DETAILED DESCRIPTION OF THE PRESENT INVENTION Accordingly, the present invention provides for a Double Layer Exhaust Powder Metallurgy Valve Seats for gasoline engines of automotive having uniform distribution of metal carbides, said valve seats comprising; a. a valve side composition having Cu 0.9-1.4% + C 1-1.5% + W 0.75-1.25% + Mo 0.7-1.2% + Cr 0.5-1% + V 2.5-3.5% + Co 0.2- 2.5% (HSS alloy) + Fe 75-86% + 2% of other metals having a high wear resistance; and b. a Cylinder side composition having Cu 0.7-1.3% + C 0.6-1.2% + Cr 0.6-1.2% + Fe 91-96%) + 1%) of other metals having high creep resistance. In an embodiment of the present invention, the valve side of said seats of Two wheeler engines, consists of 10-25% of said High Speed Steel composition along with the remaining composition of Fe. In another embodiment of the present invention, the valve side of said seats of four wheeler engines having capacity of 1500 CC, consists of about 25% of said High Speed Steel composition (High Speed Steel), along with the remaining composition of Fe. In yet another embodiment of the present invention, valve side of said seats of heavy engines, consisting of about 40% of said High Speed Steel composition, along with the remaining composition of Fe. In still another embodiment of the present invention, Cr carbide contributes maximum to the strength by causing good diffusion. In still another embodiment of the present invention, the valve side consists of high temperature strength and the cylinder side having a good creep resistance sufficient for normal working conditions. Further, in an embodiment of the present invention, said valve seats having a good wear and tear resistance at a temperature range of 350°C - 450 C. In another embodiment of the present invention, said seats consisting of a cylinder side with hardness 340-HVlO. In yet another embodiment of the present invention, said seats consisting of a valve side with hardness 368-HVlO. In still another embodiment of the present invention, said seats having a better thermal conductivity of about 40W/mK. In yet another embodiment of the present invention, the pores contained in the valve seats are filled with 12-20% Cu due to capillary reaction. In still another embodiment of the present invention, said part can be used for both leaded and unleaded gasoline engines. The present invention also provides for a process for manufacture of Double Layer Exhaust Powder Metallurgy Valve Seats for gasoline engines of automotive having uniform distribution of metal carbides and high thermal conductivity due to low porosity, said process comprising steps of: a. producing a powder by mixing Cu 0.9-1.4% + C 1-1.5% + W 0.75-1.25% + Mo 07-1.2% + Cr 0.5-1% + V 2.5-3.5% + Co 0.2- 2.5% (HSS alloy) + Fe 75-86% + 2% of other metals having a high wear resistance for the valve side; b. producing a powder by mixing Cu 0.7-1.3% + C 0.6-1.2% + Cr 0.6-1.2% + Fe 91-96% + 1% of other metals having high creep resistance for the cylinder side c. mixing the powders of step(a) and step (b) with a lubricant; d. blending the mixed powders (Figure 1) in a double cone blender for about 20 minutes; e. compacting blended mixture in a specific press to a green density in the range of6.80-6.90g/cc; f sintering the compacted material in a belt furnace at a minimum temperature of 1120°C using N2-H2 atmosphere for about 20 minutes; and g. infiltrating the sintered material with Copper to obtain exhaust valve seats. In an embodiment of the present invention, the lubricant is selected for the group consisting of Zinc stearate and H wax. In another embodiment of the present invention, a specific press having a top punch is used to compact both the powders of the valve side and the cylinder side to produce a two layer exhaust valve seats with valve side and cylinder side components. Further, in an embodiment of the present invention, said part is compacted to a green density in the range of 6.80-6.90 g/cc to obtain valve seats. In yet another embodiment of the present invention, Nitrogen-Hydrogen atmosphere having a gas ratio of 70:30. In another embodiment of the present invention, the pores contained in the valve seats are filled with 12-20% Cu due to capillary reaction. The invention is further explained in the form of following preferred embodiments To determine that the performance of this valve seat will be as good as the bench mark combination at higher temperatures, softening resistance trials are conducted. The present invention is to provide a double layer valve seats for automotive comprising a valve side component having a high temperature and friction resistance and a cylinder side component with a good creep resistance. The present invention also provides for a process of manufacturing double layer exhaust valve seats for automotive. In this test the samples are held at various high temperatures for 30 minutes and the samples cooled to room temperature to measure the hardness. The softening resistance of the benchmark valve side alloy and cylinder side alloy is compared with SFL materials in Figs.4 and 5 respectively. The softening resistance is obviously as good for SFL material as that of the bench mark. Further, as the SFL material will have better thermal conductivity due to low porosity and presence of Cu, the valve seat will be cooler during operation than the bench mark valve seat making the SFL valve seat performance superior. The benchmark alloys used for determining the efficacy of SFL valve seat are in the composition of Fe + Co 6-8% + Cr 3-5% + Mo 3-4% + Ni 1-2% + C 1.2-1.5% and the compositon of the Cylinder side is in the range of Fe + Mo 0.5-0.8 + Cu 3-5% + C 1.2-1.5% are blended and valve seats obtained as per the said process and the comparitive hardness of SFL Material vis-a-vis Benchmark Material is tabulated in Table 1 & Table 2 indicating good diffusion of the alloying elements.. ADVANTAGES OF THE PRESENT INVENTION 1. The cost of HSS is high. Hence, it is used only on the valve side where it requires high wear resistance and high temperature strength thereby reducing the cost of the product considerably. 2. PM Technology is used to meet the specific property of the alloy material to attain the desired product having net shape. REFERENCES: 1. Material and Design aspects of modem valve seat inserts - D. Dolley, T. Trudeau, D. Bancroft, L.E. Jones company. 2. A review of valve seat insert material properties required for success - G. Strong, X. Liang, Winsert, Inc., Marinette. 3. Sintered valve seat inserts and valve guides: factors affecting design, performance & machinability - H. Rodrigues, Engineered sintered components. 4. Development and performance of Infiltrated and non-infiltrated valve seat insert materials and their performance - G. Greetham, Powder Metallurgy 1990, vol.33, No.2. 5. Double-Layer valve seat inserts for Passenger Car Diesel Engines - N. Motooka, N. Kuroishi & M. Moritani of Sumitomo Electric Industries Ltd. and A. Manabe, K. Kazuoka & T. Syganuma of Toyota Motor Co. Ltd. WE CLAIM 1. A Double Layer Exhaust Powder Metallurgy Valve Seats for gasoline engines of automotive having uniform distribution of metal carbides, said valve seats comprising; (a) a valve side composition having Cu 0.9-L4% + C 1-L5% + W 0.75-L25% + Mo 0.7-1.2% + Cr 0.5-1% + V 2.5-3.5% + Co 0.2- 2.5% (HSS alloy) + Fe 75-86% + 2% of other metals having wear resistance; and (b) a Cylinder side composition having Cu 0.7-1.3% + C 0.6-1.2% + Cr 0.6-1.2% + Fe 91-96% + 1% of other metals having creep resistance. 2. The Exhaust valve seats as claimed in claim 1, wherein the valve side of said seats of two wheeler engines consists of 10-25% of said High Speed Steel composition along with the remaining composition of Fe. 3. The Exhaust valve seats as claimed in claim 1, wherein the valve side of said seats of four wheeler engines having capacity of 1500 CC consists of about 25% of said High Speed Steel composition (HSS) along with the remaining composition of Fe. 4. The Exhaust valve seats as claimed in claim 1, wherein the valve side of said seats of heavy engines consisting of about 40% of said High Speed Steel composition along with the remaining composition of Fe. 5. The Exhaust valve seats as claimed in claim 1, wherein said valve seats having high wear and tear resistance at a temperature range of 350°C - 450°C. 6. The Exhaust valve seats as claimed in claim 1, wherein said seats consisting of a cylinder side with hardness 340-HVl0. 7. The Exhaust valve seats as claimed in claim 1, wherein said seats consisting of a valve side with hardness 368-HVlO. 8. The Exhaust valve seats as claimed in claim 1, wherein said seats having thermal conductivity of about 40W/m0K. 9. The Exhaust valve seats as claimed in claim 1, wherein the pores contained in the valve seats are filled with 12-20% Cu due to capillary reaction. 10. The Exhaust valve seats as claimed in claim 1, wherein said compositions can be used for both leaded and unleaded gasoline engines. 11. A process for manufacture of Double Layer Exhaust Powder Metallurgy Valve Seats for gasoline engines of automotive having uniform distribution of metal carbides, said process comprising steps of: (a) producing a powder by mixing Cu 0.9-1.4% + C 1-1.5% + W 0.75-1.25% + Mo 0.7-1.2% + Cr 0.5-1% + V 2.5-3.5% + Co 0.2- 2.5% (HSS alloy) + Fe 75-86% + 2% of other metals having wear resistance for the valve side; (b) producing a powder by mixing Cu 0.7-1.3% + C 0.6-1.2% + Cr 0.6-1.2% + Fe 91-96% + 1% of other metals having creep resistance for the cylinder side; (c) mixing the powders of step(a) and step (b) with a lubricant; (d) blending the mixed powders in a double cone blender for about 20 minutes; (e) compacting blended mixture in a specific press to a green density in the range of6.80-6.90g/cc; (f) sintering the compacted material in a belt furnace at a minimum temperature of 1120°C using N2-H2 atmosphere for about 20 minutes; and (g) infiltrating the sintered material with Copper to obtain exhaust valve seats. 12. The process as claimed in claim 11, wherein the lubricant is selected for the group consisting of Zinc stearate and H wax. 13. The process as claimed in claim 11, wherein a specific press having a top punch is used to compact both the powders of the valve side and the cylinder side to produce a two layer exhaust valve seats with valve side and cylinder side components. 14. The process as claimed in claim 11, wherein said blended powder is compacted to a green density in the range of 6.80-6.90 g/cc to obtain valve seats. 15. The process as claimed in claim 11, wherein said Nitrogen-Hydrogen atmosphere having a gas ratio of 70:30. 16. The process as claimed in claim 11, wherein the pores contained in the valve seats are filled with 12-20% Cu due to capillary reaction. 17. The Double Layer Exhaust Powder Metallurgy Valve Seats substantially herein described with reference to the accompanying drawings.. 18. The process for the manufacture of Double Layer Powder Metallurgy Exhaust Valve substantially herein described with reference to the accompanying drawings..

Documents:

0079-mas-2001 claims duplicate.pdf

0079-mas-2001 description(complete) duplicate.pdf

0079-mas-2001 abstract duplicate.pdf

0079-mas-2001 drawings duplicate.pdf

079-mas-2001-abstract.pdf

079-mas-2001-claims .pdf

079-mas-2001-correspondence others.pdf

079-mas-2001-correspondence po.pdf

079-mas-2001-description complete .pdf

079-mas-2001-description provisinol.pdf

079-mas-2001-drawings.pdf

079-mas-2001-form 1.pdf

079-mas-2001-form 26.pdf

079-mas-2001-form 3.pdf

079-mas-2001-form 5.pdf

079-mas-2001-other documents.pdf