Metal treatment – Process of modifying or maintaining internal physical... – Heating or cooling of solid metal
Reexamination Certificate
1998-06-18
2001-02-27
Jenkins, Daniel J. (Department: 1742)
Metal treatment
Process of modifying or maintaining internal physical...
Heating or cooling of solid metal
Reexamination Certificate
active
06193822
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention concerns a method of manufacturing diesel engine valves for both intake and exhaust having good corrosion resistance and strength.
In general, intake and exhaust valves for diesel engines are made of strong precipitation-hardening Ni-base heat resistant alloys represented by Nimonic 80A. It is a permanent problem to elongate valve lives, and there has been demand for further improvement in corrosion resistance and strength thereof. A typical process for manufacturing the valves conventionally practiced comprises hot forging at a temperature above 900° C. to form valve blanks, and solution treatment followed by age-hardening.
It is, however, inevitable that the steps for improving corrosion resistance and strength of the valve materials results in lowering processability and increase of manufacturing costs, and therefore, the improvement has been effected to only the face parts which require better properties. For example, the assignee developed and disclosed (Japanese Patent Publication No. 64-8099) a valve for marine diesel engines made by using a strong precipitation-hardening heat resistant alloy as the material, forming valve cone parts by forging at a temperature in the range of 700-900° C. under a forging degree of 20% or higher, and subjecting the forged products to age-hardening. It is also known to manufacture valves by forging at a temperature of 700-900° C., and solution treatment followed by partial cold processing.
In the practice of the above technology proposed by the assignee, because of a relatively low forging temperature of 700-900° C., cracking of materials at processing often occurs when the material is of low hot processability. Therefore, it is difficult to carry out forming with a high forging degree and to realize partial hardening to a desired high extent. In the other technology, in which partial cold processing follows solution treatment and age-hardening, the cold processing is the only way to increase strength, and unless strong processing is done at this stage, sufficient strength can not be obtained. However, limitation is posed on the forging degree at the cold processing to the valve blanks, which are already hardened to some extent by age-hardening, and thus, limitation is posed also on increase in the strength.
For the purpose of elongating valve lives not only strength but also corrosion resistance is an important factor. However, it is difficult to unite the strength and the corrosion resistance in the engine valves, because materials of high corrosion resistance generally have lower strength. Thus, it is concluded that, if partial strengthening of materials having good corrosion resistance could be made, this problem would be automatically solved.
SUMMARY OF THE INVENTION
The object of the present invention is to break through the above limit inherent in the conventional technology of manufacturing diesel engine valves and to provide an improved method of manufacturing which gives diesel engine valves having both higher strength and better corrosion resistance, and therefore, of longer lives.
The method of manufacturing diesel engine valves according to the present invention comprises: using a strong precipitation-hardening heat resistant alloy as the material, hot forging the material to prepare blank forms of the diesel engine valves, cold processing the face parts of the blanks, and age-treating the cold processed parts to enhance hardness thereof.
REFERENCES:
patent: 4019900 (1977-04-01), Raghavan et al.
patent: 4547229 (1985-10-01), Larson et al.
patent: 4652315 (1987-03-01), Igarashi et al.
patent: 4741080 (1988-05-01), Larson et al.
patent: 4798632 (1989-01-01), Yonezawa et al.
patent: 5087305 (1992-02-01), Chang
patent: 5225009 (1993-07-01), Orikasa et al.
patent: 5413752 (1995-05-01), Kissinger et al.
patent: 5547523 (1996-08-01), Blankenship, Jr. et al.
ASM Handbook, Tenth Edition, vol. 1, pp. 950-962, 983-985, 1990.
Nagashima Tomotaka
Noda Toshiharu
Okabe Michio
Daido Steel Co. Ltd.
Jenkins Daniel J.
Varndell & Varndell PLLC
LandOfFree
Method of manufacturing diesel engine valves does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of manufacturing diesel engine valves, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of manufacturing diesel engine valves will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2571733