US3793873A

US3793873A - Method of hot forming of hollow mushroom type metallic parts

Info

Publication number: US3793873A
Application number: US00258854A
Authority: US
Inventors: T Iwata; M Miwa; N Hojyo; T Ando
Original assignee: Mitsubishi Motors Corp; Mitsubishi Heavy Industries Ltd
Current assignee: Mitsubishi Motors Corp; Mitsubishi Heavy Industries Ltd
Priority date: 1971-06-10
Filing date: 1972-06-01
Publication date: 1974-02-26
Anticipated expiration: 1991-02-26

Abstract

This invention relates to a method of hot forming from a blank pipe hollow mushroom type metallic parts having a hollow stem and a cap portion whose outer diameter is far larger than that of the blank pipe. By using a thin-walled pipe whose size corresponds to that of the hollow stem processing of the hollow stem can be omitted or minimized. More particularly, it relates to a method of hot forming hollow valves for engines or parts having a cap portion and hollow stem, the outer diameter of said cap portion being more than two or three times as large as that of the stem portion, by using a thin-walled pipe having a ratio between its outer diameter and its wall thickness of more than 3.5.

Description

United States Patent [191 Iwata et al.

[ METHOD OF HOT FORMING OF HOLLOW MUSHROOM TYPE METALLIC PARTS Inventors: Tokushige lwata; Nobuyoshi Hojyo;

Tokushi Ando; Masao Miwa, all of Kyoto, Japan Filed: June 1, 1972 Appl. No.: 258,854

[30] Foreign Application Priority Data June 10, 1971 Japan 46-49548 References Cited UNITED STATES PATENTS 6/1930 Thompson et al. 29/156.7 11/1948 Bartlett et a1 29/156.7

[ Feb. 26, 1974 1,991,199 2/1935 Eisele 72/368 2,053,975 9/1936 Spatta 72/367 FOREIGN PATENTS OR APPLICATIONS 679,331 2/1964 Canada 72/377 4,511,421 4/1970 Japan 72/342 Primary ExaminerLowell A. Larson Attorney, Agent, or Firm-Toren & McGeady [5 7] ABSTRACT This invention relates to a method of hot forming from a blank pipe hollow mushroom type metallic parts having a hollow stem and a cap portion whose outer diameter is far larger than that of the blank pipe. By using a thin-walled pipe whose size corresponds to that of the hollow stem processing of the hollow stem can be omitted or minimized. More particularly, it relates to a method of hot forming hollow valves for engines or parts having a cap portion and hollow stem, the outer diameter of said cap portion being more than two or three times as large as that of the stem portion, by using a thin-walled pipe having a ratio between its outer diameter and its wall thickness of more than 3.5.

8 Claims, 9 Drawing Figures PATENTEDFEBZGW 3.793.873

' sum a 052 'F|G.'4 FIG.5

PRESSURE (.Kg/cm (OIL PRESSURE v o 01 METHOD OF HOT FORMING OF HOLLOW MUSHROOM TYPE METALLIC PARTS This invention relates to a method of forming hollow parts of a thin walled configuration such as hollow valves for engines. More particularly, it relates to a method of forming hollow mushroom type metallic parts having a projected cap portion whose outer diameter is larger than that of the stem.

Conventional hot forming methods for forming hollow mushroom type metallic parts are accomplished by means of an upsetting press or extruding press by utilizing solid steel bars. The solid bars are hollowed out before hand or are made hollow simultaneously with extrusion pressing.

The former method is disadvantageous in that the life of the cutting tool used is short and the required number of man hours is great. The latter method has disadvantages that the wall thickness of the hollow portion or the accuracy of the size of the bent portion is not uniform and the life of the dies is short. In the case of hollow valves, hot draw forging or the hot forming method according to the specification of US. Pat. No. 3,358,350 has been conventionally used. These methods are considered uneconomical because of the increased number of man hours involved in the process.

The object of this invention is to eliminate the abovementioned drawbacks and to provide a hot forming method which is applicable to the production not only of entirely hollow valves but also of hollow body valves for engines, and the invention can easily and economically be used to manufacture hollow mushroom type metallic parts wherein having the stem is of a shape similar to that of a thin-walled pipe material used in forming the valve. In order to achieve this object, the method embodying this invention for hot upset forging of hollow mushroom type metallic parts from thinwalled pipe material resides in the combination of an upsetting process to be accomplished after the pipe end to be upset is bent outwardly to be buckled before the upsetting process or alternatively, at the early stage of said process by bringing said end portion into contact with an upsetting anvil, and includes a subsequent pressing process in which press dies provided with allowances for removing excess metal of said buckled portion of pipe at least at the place corresponding to the top of the cap portion of the mushroom type parts are utilized.

Other objects and advantages of this invention will be apparent from the following description which should be read in conjunction with the accompanying drawings.

In the accompanying drawings:

FIGS. la-b illustrates an embodiment of the forming method of hollow mushroom type metallic parts according to this invention in which the process of upsetting a hollow valve from a pipe material is shown;

FIGS. 2a-b and 3a-b are cross-sectional views of forming conditions of a hollow valve;

FIG. 4 shows an example of an electrode anvil provided with a projection which can be used at the time of upsetting according to the method embodying this invention;

FIG. 5 shows an example of an upper die provided with a projection which can be used at the time of press forging according to the method embodying this invention; and

FIG. 6 is a graph illustrating the processing condition in a case where the pipe shown in FIG. I is to be upset after the pipe end is bent to be buckled at the early stage of upsetting process so that said end is brought into contact with an upsetting anvil.

FIG. 1(a) illustrates the set-up condition of a blank material 1 in a case where a direct current electric upsetter is employed. A pipe material 1 is located between a fixed electrode anvil 2 and a pusher 4. The pipe material I placed between a clamped electrode 3 and the electrode anvil 2 is subjected to resistance heating. The pipe material 1 is upset while the clamped electrode 3 is being caused to slide by means of the pusher 4. Thus, upsetting is accomplished in the same manner as in upsetting by means of conventional upsetters.

According to the method of this invention, first of all the pipe is outwardly bent to cause buckling at the end y thereof to be brought into contact with the electrode anvil 2 before the start of upsetting or after the start of upsetting as shown by the dotted line (diameter Do) in FIG. 1, or the pipe is bent especially by the pressure exerted at the early stage of upsetting while gradually increasing the pressure application of the speed of pusher 4 as shown, for example, in FIG. 6 so that the pipe is upset while it is being buckled. After that, the pipe 1 is processed by increasing the pressure gradually at the later stage of the upsetting process. In this way, upsetting sufficient to insure subsequent projection of a cap portion of mushroom shape can be obtained as shown in FIG. 1(b).

The buckling diameter D0 of the pipe end effected by bending is determined by considering several parameters including the setting of the interelectrode space, the upsetting speed under pressure, pipe heating temperature and pipe material. In the case of steel pipe, the diameter Do should be preferably about 1.5 2 times the outer diameter d of the pipe.

Referring now to FIG. 1(b), if the pipe outer diameter 11 is 8 10 mm and the wall thickness 1 is in the range of 1.5 2.5 mm, an upsetting thickness T which is about 5 6 times the wall thickness t can be easily obtained.

When a pipe having a think wall is upset as it is according to the conventional upsetting process without performing the operation embodying this invention, the outer and inner circumferences of the pipe will be deformed in the so-called snake shape, and therefore mushroom type parts of required configuration cannot be obtained. Even if the ratio d/t is less than about 3.5, the method according to this invention is preferable for obtaining a greater upsetting amount. When the ratio d/t exceeds 3.5 4.0, flawless mushroom type parts of satisfactory configuration can be obtained according to the method embodying this invention.

After the upsetting process as illustrated in FIG. 1(b) is completed, die forging (by means of a press) as shown in FIGS. 2(a), (b) or 3(a), (b) is carried out. In this case, the bent portion shown in FIG. 1(b) remains as a striking mark e as shown in FIG. 2 or 4. Allowances should be made in the size of dies (upper or lower die) so that said striking mark e can be removed at the time of completion.

FIGS. 2(a) and (b) illustrate a hollow mushroom type part having a hollow cap. FIG. 2(a) shows an example in which allowances for removal of striking mark e are made in the lower dies of the press. FIG. 2(b) shows an example in which allowances for removal of striking mark e are made in the upper die. The striking mark e is removed along the removal line 1: at the time of completion.

FIGS. 3(a) and (b) illustrate examples in which the cap portion is made solid by increasing the upsetting amount shown in FIG. 1(b) than in the examples of FIGS. 2(a) and (b). These are embodiments for producing the so-called hollow body valve.

The parts shown in FIGS. 3(a) and (b) are produced by the same process as in FIGS. 2(a) and (b) which correspond to FIGS. 3(a) and (b), respectively. In the parts shown in FIGS. 3(a) and (b), the axially joined portion remains in the center of the cap portion. This is a mechanically joined condition remaining as a narrow line along the center line as a result of compression of the pipe wall toward the axis at the time of forging. Depending on the purpose of use, such parts can be used as they are. If the pipe inner surface is subjected to highly fusible metal plating or has applied thereto a flux such as borax as appropriate, it is possible to strengthen adhesion of the axially joined portion c.

Accordingly, in case of producing, for example, hollow suction valves in which reduction in weight is the aim, it is not necessary to enclose, for example, sodium after the above-mentioned processes are completed. The valves having the axially joined portion c in the mechanically joined condition can be used as they are.

When a high degree of adhesion is required by admitting high pressure gas, fluid or the like into the hollow portion, the axially joined portion 0 may be welded by, for example, electron-beam welding, laser welding or the like as appropriate.

In order to ensure reliable forming of the lateral side of said hollow portion in forming parts with a hollow cap portion as shown in FIG. 2, upsetting according to the method of this invention may be accomplished by using the electrode anvil 2 having an appropriately tapered projection f which can be inserted to extend well into the pipe material. Or, a similar projection g may be provided on the press upper die which is used at the time of the pressing process as shown in FIG. 5.

In case of parts having either a hollow cap or a hollow stem, the length of the heating time shown in, for example, FIG. 1 and the forging ratio T/t should be appropriately selected in accordance with the required shape.

The above-described embodiments utilize a direct current electric heating method. However, other rapid heating methods such as high-frequency induction, plasma or flame heating may be employed. It is needless to say that the forgings obtained by the forming method as shown in FIG. 2 or 3 are processed into finished products through subsequent heat treatment or grinding of the inner and outer surfaces.

We claim:

1. A method for manufacturing hollow-mushroomshaped engine valves from hollow blanks of thin walled pipe material utilizing hot upset forging techniques to form said valves with a mushroom shaped top portion and a lower stem portion, comprising the steps of initially buckling one end of said pipe material to effect bending of the wall of said pipe material at said buckled end outwardly from the hollow interior thereof, upsetting said buckled end by bringing said end into contact with an upsetting anvil thereby to form said end into a mushroom shaped cap portion, and pressing said metallic parts in press dies and removing therefrom during said pressing step excess material formations caused by said buckling step at portions of said metallic parts along the top of said mushroom-shaped cap portion.

2. The method according to claim 1 wherein the outer diameter of said pipe is 3.5-4.0 times the wall thickness of the pipe.

3. The method according to claim 1 wherein said hollow engine valves are heated by electrical resistance heating.

4. The method according to claim 1 wherein said buckling step is performed in the initial stages of said upsetting step as part of said upsetting step.

5. The method according to claim 4 wherein said upsetting step is performed by abutting said pipe material blank against an upsetting anvil and applying pressure thereto, with a lower pressure being applied in the early stages of said upsetting step to perform said buckling step and with said pressure application being subsequently increased during the latter stages to complete said upsetting step.

6. The method according to claim I wherein striking marks are formed in said buckled end during said buckling step, and wherein said striking marks are removed during said pressing step with the removal of said excess material formations.

7. The method according to claim 1 wherein said metalic parts are formed with a hollow stem and a closed solid mushroom shaped cap portion by increasing the amount of material which is upset in said upsetting step thereby to form said cap portion as a closed solid mushroom shape.

8. The method according to claim I wherein an appropriately shaped die projection is provided for insertion extending well into said pipe blank.

Claims

1. A method for manufacturing hollow-mushroom-shaped engine valves from hollow blanks of thin walled pipe material utilizing hot upset forging techniques to form said valves with a mushroom shaped top portion and a lower stem portion, comprising the steps of initially buckling one end of said pipe material to effect bending of the wall of said pipe material at said buckled end outwardly from the hollow interior thereof, upsetting said buckled end by bringing said end into contact with an upsetting anvil thereby to form said end into a mushroom shaped cap portion, and pressing said metallic parts in press dies and removing therefrom During said pressing step excess material formations caused by said buckling step at portions of said metallic parts along the top of said mushroom-shaped cap portion.

6. The method according to claim 1 wherein striking marks are formed in said buckled end during said buckling step, and wherein said striking marks are removed during said pressing step with the removal of said excess material formations.

8. The method according to claim 1 wherein an appropriately shaped die projection is provided for insertion extending well into said pipe blank.