JPH11270320A - Manufacture of valve for internal combustion engine and valve formed manufactured thereby - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low speed internal combustion engine valve excellent in abrasion resistance and high temperature corrosion resistance and available at low cost and top provide a method for manufacturing such low speed internal combustion engine valve allowing reliable production of such valves and providing high productive efficiency. SOLUTION: A precipitation hardening type Ni base alloy material 6 performed in a specific shape is pressurized by pressing an upper mold 7 forming the face side of a shade 3a against a downward stationary lower mold 8b and only the shade 3a is formed by forging a neck round part towards the rear of an upper mold 7b. A method for manufacturing a low speed internal combustion engine valve integrally friction welding the shade 3a to a shaft 4 separately formed and a valve formed under such manufacturing method is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a valve for an internal combustion engine and a valve formed by the method. More specifically, the present invention relates to a valve for a large low- and medium-speed internal combustion engine used in ships and power plants. The present invention relates to a method for producing a valve for an internal combustion engine having excellent wear resistance and high-temperature corrosion resistance, and a valve formed by the method.

[0002]

2. Description of the Related Art Hitherto, a valve for an internal combustion engine has been forged and formed from a heat-resistant alloy. However, especially in low-medium-speed internal combustion engines such as marine diesel engines and power plants, in addition to the use of low-quality fuel, and because they are operated at high temperatures, valves
Higher abrasion resistance and high temperature corrosion resistance are required.

[0003] In particular, the durability of the umbrella face, which is repeatedly exposed to the valve seat and exposed to a severe temperature change,
High standards are required.

Therefore, conventionally, as a material for forging a valve for a low-to-medium-speed internal combustion engine, a precipitation-hardening Ni-based alloy (JIS standard, NCF80) having excellent heat resistance and high-temperature corrosion resistance has been used.
A, NCF 75l). In addition, forging techniques for further improving the durability of the umbrella face have been devised.

However, in the prior art, a method of integrally forging and molding an umbrella portion (especially a face portion) that requires higher durability and a shaft portion that does not need durability as hard as the umbrella portion is required. Has been adopted.

[0006] More specifically, FIG.
As shown in the figure, first, a precipitation hardening type N preliminarily formed into a predetermined shape so as to conform to a desired size and shape of a valve.
The i-based alloy material 26 is installed in a hammer facility composed of upper and lower molds.

Then, the upper mold 24 for molding the lower surface of the umbrella portion is placed from above (from the direction of arrow X), and the lower fixed lower mold 25 for molding the neck radius portion and the shaft portion of the umbrella portion.
To form a shaft while deforming the alloy material 26 further below (in the direction of arrow Y) the lower mold 25 (hereinafter referred to as “forward extrusion”). Method ").

As a technique for improving the wear resistance and high-temperature corrosion resistance of a valve, there can be mentioned the techniques disclosed in Japanese Patent Publication Nos. 60-34607 and 64-8699.

In the former, a precipitation hardening type Ni-base alloy having a specific composition ratio is used as a material, and the material is subjected to hot working at a final hot working end temperature of 700 to 900 ° C. and a working rate of 25 to 75%. Subsequently, the present invention relates to a technique relating to a method of manufacturing a valve body made of a Ni-based alloy, which is heat-treated at 650 to 825 ° C.

The latter is a technique relating to a valve of a marine diesel engine in which an umbrella portion is formed by forging with a working ratio of 20% or more in a temperature range of 700 to 900 ° C. using a strong precipitation hardening type heat-resistant alloy and subjected to aging treatment. .

[0011]

However, the above-mentioned prior art has the following technical problems. First, in the forging method by the above-mentioned “front extrusion method”, an upper mold for molding the lower surface of the umbrella portion is hit on the alloy material, and the shaft is formed while deforming the alloy material further below the lower mold. Since the method is adopted, there is a technical problem that the force is dispersed, the alloy material is hardly stretched, and the shaft portion is hardly formed.

In addition, since the conventional method is based on the premise that the umbrella portion and the shaft portion are integrally formed, in order to secure high hardness of the umbrella portion face portion, a high-cost precipitation hardening type Ni-based alloy material is used for the valve. The problem is that the cost of the valve is increased because it has to be used for the whole.

Further, in the technique disclosed in the above publication, although the wear resistance and the high-temperature corrosion resistance are improved, the average hardness is only about Vickers hardness 420. Such a hardness is insufficient for a valve for a low-speed internal combustion engine, and the reliability of operation of a marine diesel engine, a power plant, or the like cannot be ensured.

That is, if the hardness is about HV420, there is a problem that the combustion residue easily bites into the umbrella face and indentation is generated relatively early. In this valve, it is necessary to increase the hardness of the face portion to improve the wear resistance and the high-temperature corrosion resistance.

Regarding the above technical problem, in order to increase the thermal strength of the face portion, there may be a case in which stellite is applied to the face portion. However, with this means, pinholes are easily generated and the reliability is poor. In addition, since the processing required for the stellite filling is troublesome, a new problem that the production efficiency of the valve is deteriorated occurs.

Accordingly, the present invention has been made in view of the above technical problems, and an object of the present invention is to provide a valve which is suitable for a large low-medium-speed internal combustion engine particularly used for ships and power plants. It is an object of the present invention to provide a method for producing a valve for a low-speed internal combustion engine which can be provided and has high production efficiency, and a low-cost valve for an internal combustion engine which is produced by the production method and has excellent wear resistance and high-temperature corrosion resistance.

[0017]

In order to achieve the above object, the present invention employs the following means.

According to the first aspect of the present invention, the pre-formed member is formed in a predetermined shape.
The upper mold for forming the umbrella face is pressed against the lower fixed lower mold against the precipitation hardening Ni-based alloy material placed between the upper mold and the lower mold, and the neck is moved rearward of the upper mold. By the configuration for forging the round part, only the umbrella part is formed, and the umbrella part is
Friction welding is performed on the separately formed stem portion to integrate it (hereinafter, referred to as “rear extrusion method”). The precipitation hardening type Ni-based alloy material used ensures the heat resistance and high-temperature corrosion resistance of the valve and fixes the upper mold for molding the umbrella face (forming the neck radius) downward (the umbrella). Press on the lower mold (for lower surface molding), behind the upper mold,
The means for forging the rounded neck portion upward facilitates the forming of the rounded neck portion. In particular,
When a precipitation hardening type Ni-based alloy material held at a high temperature of 1000 ° C. or more at the start of beating is installed in a lower mold, the alloy material rapidly transfers heat from a lower temperature (about 200 ° C.) contact portion with the lower mold. Therefore, the workability of the lower side of the alloy material is lower than that of the upper side. In addition, the lower side of the alloy material installed in the lower mold is in contact with the lower mold, so the friction coefficient is large and it is difficult to deform, but since the upper side of the alloy material is open, the friction coefficient is small. Easy to deform. Therefore, when processing the alloy material, it is maintained at a high temperature,
In addition, the upper die is struck from the upper side with less friction, and the neck radius portion requiring a larger processing amount than the bottom surface side of the umbrella portion is formed, whereby forging of the umbrella portion is facilitated. In addition, by forming only the head portion and frictionally welding the head portion to a separately formed shaft portion and integrating the same, a high-cost precipitation-hardening Ni-based alloy material is used for the head portion that requires the most durability. Can be used only, which is advantageous in terms of cost.

According to a second aspect of the present invention, the upper mold is provided with a gas vent hole for releasing air pushed between the precipitation hardening type Ni-based alloy material and the upper mold. By this means, when the upper die is driven from above to form the round neck portion on the alloy material, air trapped between the alloy material and the upper die is released to facilitate the forging of the umbrella portion.

According to a third aspect of the present invention, after performing the forging step using the first hammer according to the first or second aspect, the trimming step and the second forging step using the second hammer are performed, and then the aging treatment is performed. , Forming the umbrella. While separating the first hammer for forging and the second hammer that performs the trimming step and the secondary forging step, by performing the secondary forging after the primary hammer is formed by the primary forging, it is possible to improve productivity, If the primary forging and the secondary forging are performed successively, no reheating treatment for the secondary forging is required. In addition, since reheating for secondary forging is not required, variation in temperature due to a difference in residence time in the furnace can be suppressed, and the secondary forging temperature can be kept constant. Further, the optimum temperature required for the secondary forging can be selected by utilizing the time difference from the forming by the primary forging to the secondary forging.

According to a fourth aspect of the present invention, the processing rate of the umbrella face at the time of primary forging is 5 to 15% on the face inner diameter side and 10% on the face outer diameter side by the method for manufacturing a valve for an internal combustion engine according to the third aspect. Secure ~ 30%. If this processing rate is secured, in the secondary forging, when the upper die of the second hammer is hit against the coining allowance, the coining allowance slides into the umbrella outer diameter side and is pushed into the face. As a result, a uniform fiber flow can be formed in the face portion. Also, no cracking occurs in the secondary forging.

In a fifth aspect, the secondary forging step according to the fourth aspect is performed at an umbrella face temperature of 500 to 700 ° C.,
The aging treatment according to claim 2, wherein the umbrella face temperature is 720 to 7
Perform for 2-7 hours at 50 ° C. By this means, it is possible to sufficiently secure the hardness of the umbrella face portion required for a valve for a low-speed internal combustion engine. The secondary forging process is performed at an umbrella face temperature of 500 to 700 ° C, and the aging treatment is performed at an umbrella face temperature of 720 to 750 ° C for 2 to 7 hours.
Over time, the umbrella face can be formed to a hardness that is particularly suitable for low to medium speed internal combustion engines.

According to a sixth aspect of the present invention, the hardness of the umbrella face formed by the method for manufacturing a valve for an internal combustion engine according to the fifth aspect is H.
V420-480. Face hardness is HV4
The valve held in the range of 20 to 480 can effectively prevent the combustion residue from being caught, and no indentation is generated on the face portion. In addition, since the hardness is not excessive, there is a tendency for plastic deformation, and there is no fear that cracks occur during operation of the internal combustion engine.

According to a seventh aspect, a fine flow is formed in the macrostructure of the umbrella portion formed by the method for manufacturing a valve for an internal combustion engine according to the fifth aspect, and the microstructure has a crystal grain size of 7 or more. This is a minutely formed valve for a low-speed internal combustion engine. A fine flow is observed in the macrostructure of the valve made of the solid solution alloy. That is, the so-called fiber flow (also referred to as "slip band") generated by the slip plastic deformation is made uniform, the force at the time of forging is uniformly spread, the metal structure is adjusted, and the subsequent plastic deformation is performed. Resistance and the strength is secured. In the microstructure, there are no large crystal grains, no mixed grains, etc., and the microstructure is adjusted to very fine crystal grains, and the metal structure is made uniform.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described based on preferred embodiments with reference to the accompanying drawings. First, FIG. 1 is a view showing a general shape of a valve which is a final product formed by a method for manufacturing a valve for a low-speed internal combustion engine according to the present invention, and FIG. 2 is a relation between temperature and time in a manufacturing process of the method. FIG.

FIG. 3 is a schematic view showing the shape and configuration of a hammer die used in the primary forging and secondary forging steps of the same manufacturing method. FIG. 3 (A) shows a precipitation hardening type Ni-based alloy material in a first hammer. Fig. 3 (B) as viewed from right beside the state in which is installed.
Is linked to or continuous with the first hammer,
FIG. 3 (C) is a view showing a state where a primary forged umbrella section is installed, FIG. 3 (C) is a view showing a state where a deburred umbrella section is installed on a second hammer, and FIG. It is a figure which shows half of the umbrella part cross section seen.

First, as shown in FIG. 1, a valve 1 for an internal combustion engine is a portion from a face 2 in contact with a valve seat (not shown) to a shaft portion 4, and has a shape like a foot of a mountain. An umbrella portion 3 having a neck radius portion 9 having a substantially flat lower surface 5 facing a cylinder (not shown);
A rod-shaped shaft portion 4 integrally formed with the umbrella portion 3 and connected to the neck radius portion 19 and formed above the umbrella portion 3.
(Also referred to as a “stem”).

The face 2 of the umbrella portion 3 which is in contact with a valve seat (not shown) is most durable,
That is, since it is a part where wear resistance and high-temperature corrosion resistance are required, it is a part where high hardness is required.

For this reason, a precipitation hardening type Ni-based alloy material has conventionally been generally used for the valve 1 because:
This material ensures a durable face 2
This is because it is the most suitable material.

The present invention particularly provides a method for molding a valve for a low-medium-speed internal combustion engine and a valve molded by the method, and has a face 2 which is most required to have durability. One major feature of the present invention resides in that only the umbrella portion 3 is formed separately from the shaft portion 4.

That is, according to the present invention, since the cost of the precipitation hardening type Ni-based alloy material is high, if the use amount of the material increases,
While directly affecting the cost of the valve 1, the shaft portion 4 is made of a precipitation hardening type Ni-based alloy material based on the fact that the high temperature durability is not required as much as the umbrella portion 3 (particularly the face portion 2). It can be said that it is a technical idea born by focusing on the fact that there is no necessity to use it.

By molding only the umbrella portion 3 separately from the shaft portion 4, the molding conditions of the umbrella portion 3 are set intensively.
Since it can be improved, various effects derived from the present invention can be expected in future technical development.

Hereinafter, an outline of the entire process of the method for manufacturing a valve for an internal combustion engine according to the present invention will be described mainly with reference to FIGS. 2 and 3 mainly focusing on temperature conditions. First, the horizontal axis shown in FIG. 2, which is a schematic diagram showing the relationship between temperature and time in the manufacturing process of the same manufacturing method, indicates “time” and the vertical axis indicates “temperature”.

Prior to the primary forging step (A in FIG. 2) using the first hammer 17 (see FIG. 3), the furnace temperature of the precipitation hardening type Ni-based alloy material (hereinafter simply referred to as “alloy material”) 6 is set. The temperature is raised to about 1150 ° C. or more to form a solid solution.

The primary forging (step A shown in FIG. 2) performed by hitting the first hammer 17 against the alloy material 6 is started at about 1000 ° C. to 1200 ° C.
The impact is terminated at a temperature in the range of 880 ° C to 950 ° C.

Subsequently, the umbrella part 3a, which is an intermediate part that has been primarily forged and formed into a substantially umbrella part shape, is set by moving it to the second hammer 18 that is linked to or continuous with the first hammer 17, and the temperature is set to 500. To 700 ° C. (step B1 shown in FIG. 2).

Thereafter, the second hammer 18 is used to strike the coining margin (also referred to as a processing margin or crush margin) 12 of the umbrella part face 2 portion, and secondary forging is performed (step B2 shown in FIG. 2). I do.

After the completion of the secondary forging, the valve is air-cooled (step C shown in FIG. 2), subjected to natural aging, and then raised to a temperature of 720 to 750 ° C. again, followed by high-temperature aging for 2 to 7 hours. Process to cause hardening of the alloy.

Next, the contents of each of the above-described steps will be described in detail mainly with reference to FIGS. FIG. 3A shows a state in which a precipitation hardening type Ni-based alloy material is installed on the first hammer 17. In order to form a desired valve in advance at the center of the lower die 8 a fixed below. A columnar alloy material 6 having a required size and shape is provided.

For this alloy material 6, an upper die 7a (a part of a driving device installed further above the upper die 7a, which is omitted in the drawing) is disposed just above the lower die 8a. When the material was hit in the direction of arrow 8a (arrow X direction) and pressurized, the upper end portion of the alloy material 6 that had been solid-solutioned under high temperature conditions was formed to penetrate vertically in the center region in the diameter direction of the upper mold 7a. It enters into the shaft portion forming hole 20a while being deformed, and the neck radius portion 19 is formed.

At this time, the alloy material 6 in the shaft portion forming hole 20a is
If the air pushed between the upper die 7a and the upper die 7a is left as it is inside the upper die 7a, it will hinder the forging operation.

Therefore, while being fitted into the shaft portion forming hole 20a of the upper die 7a, a device is devised so that the volume of the space (above) on the shaft side of the shaft portion forming hole 20a can be adjusted. The gap of about 0.2 mm between the fitting member 21 and the inner peripheral surface of the shaft portion forming hole 20a, that is, the gas vent hole 22, is provided so that the vertical length of the shaft 3 can be finely adjusted.
To form Since the compressed air escapes from the gas vent hole 22, forging of the umbrella portion 3 becomes easier.

On the other hand, the lower end of the alloy material 6 is
Is pressed against the lower mold 8a to form the substantially flat lower surface 5 of the umbrella. In addition, the solid line part shown by the code | symbol 15 shown in FIG. 4 has shown the shape of the umbrella part 3 immediately after the primary forging by the said method.

Here, the upper mold 7a for molding the umbrella part face side (for molding the neck radius part 19) is pressed against a lower mold 8a (for molding the lower surface of the umbrella part) which is fixed downward, and pressurized. The means for forging the rounded neck portion 19 toward the rear (that is, the upper side) of the mold 7a is employed for the following reason.

First, when the alloy material 6 held at a high temperature of 1000 ° C. or higher at the start of the punching is placed in the lower mold, the high-temperature alloy material 6 is used in the lower mold 8a at a lower temperature (about 200 ° C.).
Because the lower mold 8a rapidly removes heat from the contact area with
This is because the lower side of the alloy material 6 has lower workability than the upper side.

Second, since the lower side of the alloy material 8a provided on the lower mold 8a is in contact with the lower mold 8a, the coefficient of friction is large and it is difficult to deform, but the upper side of the alloy material 6 is The reason for this is that since it is open, the coefficient of friction is small and processing is easy.

Therefore, when processing the alloy material 6, the upper die 7a is hit from the upper side which is maintained at a high temperature and has little friction, so that a larger processing amount is required than the bottom side of the umbrella portion 3. The forging of the umbrella 3 is facilitated by forming the rounded neck 19.

The umbrella portion 3a formed by the above primary forging
The processing rate of the face inner diameter side calculated by (H1-h1) / h1 in FIG. 4 is 5 to 15%, and the processing rate of (H0-h0) /
Face outer diameter side processing rate required by H0 is 10 to 30%
It is.

The method of calculating the processing rate will be described in detail. The intersection P of the lower extension line L1 from the inclined surface of the coining allowance 12 and the upper extension line L2 from the outermost surface of the valve will be described.
The length between the horizontal line L3 passing through the line 1 and the horizontal line L4 extending from the lower surface 5 is defined as H0.

The length between the horizontal line L5 passing through the point P2 on the outermost diameter side of the coining margin 12 and the line L4 is defined as h0. In this case, the face outer diameter side processing rate is
It is determined by (H0−h0) / H0.

On the other hand, the length between the horizontal line L6 passing through the inclination start point (also referred to as the bearing inner diameter point) P3 on the inner diameter side of the coining allowance 12 and the above L4 is H1, and the vertical line L7 passing through the inclination start point P3. From the intersection P4 of the secondary forging shape line 14 with the lower surface 5
The length until is h1. In this case, the face inner diameter side processing rate is obtained by (H1-h1) / h1.

The above-mentioned numerical values ensured that the face inner diameter and outer diameter side processing rates obtained by the above calculation method were as follows.
In the secondary forging, when the upper die 7b of the second hammer is hit against the coining allowance 12 part, the coining allowance 12 part slides and deforms on the outer diameter side of the umbrella, and the face 2
Face 2 for uniform fiber flow
This is because it can be formed in

Also, cracks that can occur from the face 2 to the lower surface 5 in secondary forging can be prevented.

Next, FIG. 3B shows a state in which the umbrella portion 3a primary forged by the first hammer 17 is moved to the second hammer 18 interlocking with or continuous with the first hammer 17 and installed. Is shown. At this stage, the burrs 11 are formed on the outer diameter portion of the umbrella portion 3a.

The reason why the burrs 11 are formed is that, in order to minimize the turning margin in the turning stage of the final finish and obtain high dimensional accuracy, the shape of the final product (FIG. 4) (The shape of the dotted line portion indicated by reference numeral 16 shown in FIG.
This is because the molding is performed up to the level of the shape extremely similar to the following.

Therefore, before the second forging by the second hammer 18 is started, the trimming upper die 9 for removing the burrs inserted between the upper die 7b and the lower die 8b of the second hammer 18 is trimmed. An operation of removing the burr 11 is performed by hitting the mold 10. After the burrs 11 are removed, a coining allowance 12 is formed by swelling the face 2 of the umbrella portion 3a.
Re-forging of the part, that is, secondary forging is performed.

The solid line indicated by reference numeral 14 in FIG. 4 represents a secondary forging shape. The coining in which the hatched area in FIG. 4 is pushed in by the secondary forging while slidingly deforming in the outer diameter direction of the umbrella portion. 12 is shown.

The region indicated by reference numeral 23 in FIG. 4 indicates a "relief" portion formed between the rounded neck portion after the primary forging and the upper die 7b for secondary forging. That is, by forming the relief 23, the load on the coining allowance 12 can be intensively applied, and the secondary forging can be performed efficiently.

After the completion of the secondary forging, air cooling is performed and natural aging is performed. Then, the temperature of the umbrella portion 3b is raised again to 720 to 750 ° C., and a high temperature aging treatment is performed for 2 to 7 hours to obtain a supersaturated solution. Excess solute atoms of the resulting alloy are precipitated, causing strain in the crystal lattice and further hardening the alloy material.

The hardness of the face 2 portion of the umbrella portion 3 formed through the above steps is Vickers hardness HV420-480.
, And a valve 1 having durability particularly suitable for a low-to-medium-speed internal combustion engine can be provided.

Hereinafter, a hardness test was performed based on the above method, and the results will be described with reference to FIGS. First, FIG. 6 is a diagram (table) showing the conditions of primary forging and secondary forging of the sample used for the hardness test, and FIG.
It is the figure (table) which put together the aging processing conditions of the same sample, and the hardness measurement result near the umbrella part face part under the conditions.

FIG. 8 is a diagram showing the measurement results of the hardness distribution near the umbrella face of the sample before and after the aging treatment at 720 ° C. for 5 hours. FIG. 8 (A) shows the results before the aging treatment. Hardness distribution, FIG. 8B is a diagram showing a hardness distribution after the aging treatment.

FIG. 9 is a diagram showing the hardness distribution near the umbrella face of the sample before and after the aging treatment at 750 ° C. for 5 hours. The meaning of the diagrams shown in FIGS. 8
The same is true.

The hardness test was performed under the conditions shown in FIG. 6 using a precipitation hardening type Ni-base alloy conforming to JIS NCF80A.
As a result of aging treatment at 0 ° C. for 5 hours, a hardness near the face 2 as shown in FIG. 7 was obtained.

That is, under any aging treatment conditions, a hardness of HV420 or more can be ensured, which is good. Near the center of the face 2 portion, an appropriate hardness of about HV435 is obtained, and a high hardness of about 480 is secured on the outer diameter side.

Although not particularly shown, according to the test conducted at the same time, the difference in the secondary forging temperature and the number of impacts of the secondary forging did not significantly affect the hardness.

Referring to FIGS. 8 and 9, the hardness (A) before the aging treatment and the hardness (B) after the aging treatment are compared, and the face hardness after the aging treatment ranges from about HV10 to about 50. , Indicating that the hardening of the aging treatment is remarkably exhibited. 8 and 9 shows a region where a hardness of HV420 or more is obtained near the face 2.

Subsequently, in this test, a microscopic photograph of the test sample was taken, and the state of the macro metal structure and the micro structure around the face portion will be described with reference to FIGS.

FIG. 10 is a drawing substitute photograph showing the macro metal structure around the umbrella face portion of the sample, and FIG. 11 is a view showing a photographed portion of a microscopic photograph showing the micro metal structure around the umbrella face portion. 12 is a drawing substitute photograph showing the micro metal structure of the umbrella face surface portion of the sample shown in FIG. 11, and FIG. 13 is a drawing substitute photograph showing the micro metal structure of the sample inside the umbrella face part shown in FIG. ,.

First, as shown in the substitute photograph of FIG. 10, the macrostructure of the umbrella portion 3 formed by the method for manufacturing a valve for an internal combustion engine according to the present invention has a fine fiber flow.

That is, after the primary forging and the secondary forging, a so-called “slip band (fiber flow)” generated by the sliding plastic deformation is formed uniformly, and the force at the time of forging is uniformly spread. It can be seen that, by adjusting the metal structure, the resistance to subsequent plastic deformation increases, and the strength is secured.

Further, as shown in the substitute photographs in FIGS. 12 and 13, the microstructure is fine at any of the photographing locations shown in FIG. 11, and the crystal grain size of 7 or more can be ensured.

That is, in the microstructure, there are no large crystal grains, mixed grains, etc., and the microstructure is adjusted to very fine crystal grains, and the metal structure is made uniform.

[0074]

The effects of the invention disclosed by the present application will be described below.

(1) By forging the alloy material by the "rearward extrusion method" described in claim 1, the upper die is driven from above with little friction while keeping the alloy material at a high temperature. By forming a rounded neck portion that requires a larger processing amount than the umbrella bottom surface side, the umbrella portion can be easily forged and formed. In this case, it is possible to solve a large problem that the material is not easily stretched and it is difficult to form the shaft portion.

(2) By this “rearward extrusion method”, only the umbrella portion is formed without performing the conventional upsetting,
The means of friction welding and integrating the umbrella part with the separately formed stem part enables high-cost precipitation-hardening Ni-based alloy material to be used only in the umbrella part requiring the most durability. Thus, the cost of the valve can be reduced.

(3) In addition, by adopting means for forming only the umbrella portion by the "rear extrusion method", the amount of deformation can be increased from a small-diameter material, and furthermore, a mold having a shape very close to the product shape. Since high-precision molding is performed by using, high dimensional accuracy can be obtained.

(4) In the second aspect, the upper die is provided with a gas vent hole for releasing air pushed in between the precipitation hardening type Ni-based alloy material and the forging upper die, so that the upper die is formed from the upper side. At the time of hitting and forming the alloy material, the air compressed between the alloy material and the upper mold can be released to the outside, so that forging of the umbrella portion is facilitated and the productivity is improved.

(5) In claim 3, the first hammer for the primary forging and the second hammer for performing the trimming step and the secondary forging step are separated, and the secondary hammer is continuously formed after the primary forging by the first hammer. If forging is performed, reheating treatment for secondary forging is not required at all, and production efficiency can be improved.

(6) As a result of eliminating the need for reheating for secondary forging, temperature variations due to differences in residence time in the furnace can be suppressed, a constant secondary forging temperature can be secured, and valve quality can be maintained. In addition to stabilizing the temperature, the optimal temperature required for secondary forging can be selected by using the time difference between primary forging and secondary forging, making it very convenient for adjusting production conditions, etc. It is.

(7) By performing trimming and coining with a single hammer (second hammer) to remove burrs generated in the primary forging, the productivity of the hammer is not hindered and the production efficiency is high.

(8) According to the fourth aspect, according to the method for manufacturing an internal combustion engine valve according to the third aspect, the processing rate of the umbrella face when primary forged is 5 to 15% on the face inner diameter side and the face outer diameter. By securing 10% to 30% on the side, in secondary forging, when the upper die of the second hammer is hit against the coining allowance portion, the coining allowance portion slides and deforms on the umbrella outer diameter side, Since it can be pushed into the face portion, a uniform fiber flow can be reliably formed on the face portion. In addition, since cracks do not occur during secondary forging, loss of material can be eliminated.

(9) In claim 5, the secondary forging is performed at an umbrella face temperature of 500 to 700 ° C., and the aging treatment is performed at an umbrella face temperature of 720 to 750 ° C. for 2 to 7 hours. A so-called "slip band" generated by slip plastic deformation in the first forging and the second forging can be uniformly formed in the metal structure. In other words, the force at the time of forging can be spread evenly, the metal structure can be made uniform, the resistance to subsequent plastic deformation can be increased, and high hardness can be secured.

(10) In the sixth aspect, a valve for a low-speed internal combustion engine in which the hardness of the umbrella face formed by the method for producing an internal combustion engine valve according to the fifth aspect is maintained at HV420 to 480 is obtained. The wear resistance and high-temperature corrosion resistance of the umbrella part, particularly the face part, can be greatly improved.

More specifically, since abrasion due to the combustion residue deposited between the valve and the valve seat and the bite of the residue can be prevented, no indentation is generated on the face portion, and the low-medium-speed internal combustion engine is used. However, operation can be performed reliably and stably.

(11) A valve provided with a face portion having a hardness of HV420 to 480 is not excessively hard, and therefore has a risk of plastic deformation and may cause cracks during operation of the internal combustion engine. There is no.

(12) For a low-speed internal combustion engine according to claim 7, a fine flow is formed in the macrostructure of the formed umbrella portion, and the microstructure is formed extremely fine with a crystal grain size of 7 or more. You can get a valve.

That is, the so-called “slip band” generated by the slip plastic deformation in the forging process is formed uniformly, and the microstructure is adjusted to very fine crystal grains without large crystal grains and mixed grains. Since the metal structure can be made uniform, a valve having high resistance to plastic deformation can be provided.

[0089]

[Brief description of the drawings]

FIG. 1 is a view showing a general shape of a valve which is a final product formed by a method for manufacturing a valve for a low-speed internal combustion engine according to the present invention.

FIG. 2 is a schematic diagram showing a relationship between temperature and time in a manufacturing process of the manufacturing method.

FIG. 3A is a side view of a state in which a precipitation hardening type Ni-based alloy material is installed on a first hammer. FIG. 3B is an umbrella that is primarily forged on a second hammer that is linked to or continuous with the first hammer. (C) Diagram showing the umbrella portion from which the burrs have been removed being installed on the second hammer

FIG. 4 is a view showing a cross section of an umbrella half after primary forging viewed from a lateral direction.

FIG. 5 is a partially enlarged view of the vicinity of an umbrella face after primary forging.

FIG. 6 is a table summarizing conditions for forging and secondary forging of a sample used in a hardness test (table).

FIG. 7 is a table summarizing the aging treatment conditions of the same sample and the results of hardness measurement near the umbrella face under the aging treatment conditions (table).

8A is a diagram showing a hardness distribution near the umbrella face portion of the sample before the aging treatment at 720 ° C. for 5 hours. FIG. 8B is a diagram showing the hardness distribution of the sample after the aging treatment at 720 ° C. for 5 hours. Diagram showing hardness distribution in the vicinity

9A is a diagram showing a hardness distribution in the vicinity of an umbrella face portion of a sample before aging treatment at 750 ° C. for 5 hours. FIG. 9B is a diagram showing an umbrella face portion of a sample after aging treatment at 750 ° C. for 5 hours. Diagram showing hardness distribution in the vicinity

FIG. 10 is a drawing substitute photograph showing a macro metal structure around the umbrella face of the sample.

FIG. 11 is a view showing a photographed portion of a microscopic photograph showing a micro metal structure around an umbrella face;

FIG. 12 is a drawing substitute photograph showing the micrometal structure of the surface of the umbrella face shown in FIG. 11 of the sample.

FIG. 13 is a drawing substitute photograph showing the micro metal structure of the sample inside the umbrella face shown in FIG. 11;

FIG. 14 is a diagram schematically showing a conventional forging technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Valve 2 Face 3 (3a, 3b) umbrella part 4 Shaft part 6 Precipitation hardening type Ni base alloy material 7 (7a, 7b) Upper die 8 (8a, 8b) Lower die 9 Trimming upper die 10 Trimming lower die 17 First Hammer 18 Second hammer 22 Gas vent hole A Primary forging process with first hammer B Secondary forging process with second hammer D Aging treatment process

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Keinori Yamakawa 3-2 Hie-cho, Kosai-cho, Koga-gun, Shiga Prefecture Inside Yamazaki Machinery Works Co., Ltd. (72) Suehiro Shimotani 3-2, Hie-cho, Kosai-cho, Koga-gun, Shiga Prefecture Yamazaki Machinery Works, Ltd.

Claims (7)

[Claims] 1. An upper mold for molding an umbrella face side to a lower fixed lower mold for a precipitation hardening type Ni-based alloy material previously formed in a predetermined shape and installed between an upper mold and a lower mold. Pressurize,
By forging the rounded portion of the neck toward the rear of the upper mold, only the umbrella portion is formed, and the umbrella portion is integrated by friction welding with a separately formed shaft portion. Manufacturing method of a valve for an internal combustion engine. 2. An internal combustion engine according to claim 1, wherein said upper mold is provided with a gas vent hole for letting out air forced between said precipitation hardening type Ni-based alloy material and said upper mold. Manufacturing method for valves. 3. After primary forging is performed by a first hammer including the upper mold and the lower mold, a second hammer is used.
3. The method for manufacturing an internal combustion engine valve according to claim 1, wherein the umbrella portion is formed by performing trimming and secondary forging, and thereafter performing aging treatment. 4. The processing rate of an umbrella face when primary forged by the method for manufacturing a valve for an internal combustion engine according to claim 3 is 5 to 15% on the face inner diameter side and 10 to 3 on the face outer diameter side.
A method for producing a valve for an internal combustion engine, wherein the valve is secured at 0%. 5. The valve, which is primarily forged at the working ratio, is subjected to secondary forging at an umbrella face temperature in the range of 500 to 700 ° C., and then subjected to an aging treatment at an umbrella face temperature of 720 to 750 ° C.
5. The method for producing a valve for an internal combustion engine according to claim 4, wherein the treatment is performed for 2 to 7 hours in the range described above. 6. The umbrella face formed by the method for manufacturing a valve for an internal combustion engine according to claim 5 has a hardness of HV420 to HV4.
80. An internal combustion engine valve held at 80. 7. A macro-structure of an umbrella formed by the method for manufacturing a valve for an internal combustion engine according to claim 5, wherein a fine flow is formed and the micro-structure is formed extremely fine with a crystal grain size of 7 or more. A valve for an internal combustion engine, characterized in that: