JPH074245A - Auxiliary combustion chamber nozzle for diesel engine and manufacture thereof - Google Patents

Abstract

PURPOSE:To prevent generation of crack caused by heat shock in an injection port acute angle part and in the vicinity thereof. CONSTITUTION:An electron beam or a laser beam is radiated on the injection port acute angle part 3 of an auxiliary combustion chamber nozzle 1 for a diesel engine formed by means of normal lost wax precision casting method and in the vicinity thereof, so that the part and its vicinity may be melted and congealed 5 so as to form a fine structure whose average crystal diameter is 2mum or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diesel engine auxiliary combustion chamber mouthpiece in which cracks due to thermal shock do not occur at an acute angle portion of a nozzle and its vicinity, and a method for producing the same.

[0002]

2. Description of the Related Art In general, a sub-combustion chamber of a diesel engine is equipped with a mouthpiece having a muzzle having an acute angle portion. Martensitic heat-resistant steel is produced by the lost wax casting method, cutting method, hot or cold forging method, or the like.

The nozzle of the die attached to the auxiliary combustion chamber is heated to a high temperature because high-temperature and high-pressure gas passes at a high speed, and is rapidly cooled when the diesel engine is stopped to generate a thermal shock. Nozzle 2 as shown in the figure
In particular, cracks 4 were generated in the acute-angled portion 3, the acute-angled portion 3 was missing and deformed, and there was a problem that the output of the diesel engine was affected.

In order to solve such a problem, more expensive high alloy super heat resistant steel may be used. However, use of such high alloy super heat resistant steel undesirably increases the cost of the diesel engine.

Therefore, as shown in the sectional view of FIG.
A sub-combustion chamber composite mouthpiece for a diesel engine, in which the main body of the mouthpiece 1 is made of inexpensive ordinary heat-resistant steel, and the acute-angled portion of the mouthpiece 2 and the vicinity thereof are composed of the high-alloy superheat-resistant steel layer 4 has also been proposed. (See JP-A-63-47346).

[0006]

However, the conventional auxiliary combustion chamber composite spinneret for a diesel engine, which has the high alloy superheat resistant steel layer 4 only at the acute angle portion of the injection port 2 and in the vicinity thereof, is costly for welding. In addition to this, there is a problem that cracks are still unavoidable at the acute-angled portions of the nozzles when used for a long period of time.

[0007]

Therefore, the present inventors have
As a result of research to obtain a secondary combustion chamber mouthpiece for diesel engines that is less likely to crack than before even when used for a long period of time, the surface of the acute angle part of the auxiliary combustion chamber mouthpiece for a diesel engine and its vicinity When only the surface layer is melted and solidified by irradiating the surface layer with an electron beam or a laser beam, the average crystal grain size of the sharp edge portion of the mouth of the die and the surface layer portion in the vicinity is refined to about 2 μm or less. This is the result of the research that the thermal shock resistance is improved and the occurrence of cracks is extremely reduced.

The present invention has been made on the basis of the results of such research, and the melting is performed by irradiating an electron beam or a laser beam on the surface of the mouth of a sub-combustion chamber for a conventional diesel engine and the vicinity thereof.・ Coagulate,
It is characterized by a diesel engine auxiliary combustion chamber having a fine crystal structure with an average crystal grain size of 2 μm or less and a manufacturing method thereof.

A depth of 20 μm from the surface of the injection nozzle acute angle portion of the auxiliary combustion chamber mouth for a normal diesel engine and the vicinity thereof.
Average grain size: 2μ when irradiated with electron beam or laser beam with melting power to melt and solidify
A fine crystal structure of m or less is obtained, and this fine crystal structure is most effective when formed in a normal sub-combustion chamber die for a diesel engine obtained by a precision casting method.

It is sufficient that the fine crystal structure having an average crystal grain size of 2 μm or less is distributed within a range of a width of 0.1 mm or more from the tip ridgeline of the acute angle portion. However, the portion where cracking occurs due to thermal fatigue is 3 mm from the tip ridgeline of the sharp corner
Since it is within the range, it is sufficient that the fine crystal structure is within 3 mm from the ridgeline of the tip of the acute angle portion, and even if the fine crystal structure is formed wider than that, time and energy are consumed unnecessarily and cost is not preferable. . Therefore, a fine crystal structure having an average grain size of 2 μm or less was determined within the range of 0.1 to 3 mm from the ridgeline at the tip of the sharp edge of the mouth.

Even if an electron beam or a laser beam is irradiated to form a fine crystal structure region having an average crystal grain size of 2 μm or less, if the depth of the fine crystal structure region is less than 20 μm from the surface, a crack generation preventing effect is obtained. Is not enough. Therefore, the depth of the fine crystal structure region having an average crystal grain size of 2 μm or less was determined to be 20 μm or more.

[0012]

EXAMPLES By weight%, Ni-20% Cr-2.4% Ti
-1.2% Al-0.12% C with a composition of Ni
The base heat-resistant alloy is vacuum melted, and the resulting molten metal is cast into a mold by the lost wax precision casting method, and has the shape shown in the sectional view of FIG. 1 and the plan view of FIG. 2, diameter: 30 mm, thickness: A base 1 having a size of 20 mm was produced. The average crystal grain size of the acute angle portion 3 of the mouth 2 of the die 1 obtained by precision casting of the lost wax and the vicinity thereof was 300 μm.

By irradiating the acute angle portion 3 of the nozzle 2 of the die 1 and its vicinity with a CO ₂ laser beam having an output of 1 kW and a beam diameter of 50 μm, a melting and solidifying region having the width and depth shown in Table 1 is obtained. No. 5 and having the average crystal grain size shown in Table 1 for the present invention diesel engine auxiliary combustion chamber caps (hereinafter referred to as the present invention caps) 1 to 10, comparative diesel engine auxiliary combustion chamber caps (hereinafter referred to as comparative caps) 1 to 3 and a conventional diesel engine auxiliary combustion chamber mouthpiece without laser beam irradiation (hereinafter referred to as a conventional mouthpiece)
Was produced.

These inventive bases 1 to 10 and the comparative bases 1 to
No. 3 and the conventional spinneret were each heated by a propane gas burner for 1 minute and then water-cooled as one thermal shock treatment, and this thermal shock treatment was repeatedly applied until a crack was generated in the acute angle portion 3 of the injection port 2. Table 1 shows the number of thermal shock treatments at the time of occurrence of.

[0015]

[Table 1]

[0016]

From the results shown in Table 1, the present invention base 1
It can be seen that Nos. 10 to 10 are excellent in thermal shock resistance since the number of thermal shocks until crack initiation is remarkably higher than that of the conventional die without beam irradiation.

However, it can be seen that the comparative bases 1 to 3 which are out of the conditions of the present invention have a low thermal shock resistance because the number of thermal shocks until the cracking is reduced.

As described above, according to the present invention, it is possible to provide a sub-combustion chamber mouthpiece for a diesel engine, which is superior in thermal shock resistance to conventional ones, by performing a relatively simple treatment, which is an excellent industrial effect. Will bring about.

[Brief description of drawings]

FIG. 1 is a sectional view of a sub-combustion chamber cap for a diesel engine of the present invention.

FIG. 2 is a plan view of a sub-combustion chamber cap for a diesel engine of the present invention.

FIG. 3 is an explanatory plan view showing a crack that occurs in a conventional diesel engine auxiliary combustion chamber cap.

FIG. 4 is a cross-sectional view of a conventional diesel engine auxiliary combustion chamber cap.

[Explanation of symbols] 1 mouthpiece 2 nozzle 3 sharp corner 4 crack 5 melting / solidification zone

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Keiji Wada 1-297 Kitabukuro-cho, Omiya-shi, Saitama Prefecture Central Research Laboratory, Mitsubishi Materials Co., Ltd. (72) Hideo Inohara 5-3-8, Shiba 5-chome, Minato-ku, Tokyo Mitsubishi Automotive Industry Co., Ltd.

Claims (2)

[Claims] 1. A sub-combustion chamber mouthpiece for a diesel engine, wherein crystal grains in an acute angle portion of the sub-combustion chamber mouthpiece and in the vicinity thereof have a fine crystal structure with an average grain size of 2 μm or less. 2. A sub-combustion chamber mouthpiece for a diesel engine, characterized by irradiating an electron beam or a laser beam to the acute-angled portion of the mouth of the sub-combustion chamber mouthpiece for a conventional diesel engine and the surface in the vicinity thereof to melt and solidify. Manufacturing method.