JPH09209092A - Secondary combustion chamber mouthpiece for diesel engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary combustion chamber mouthpiece for diesel engine, excellent in high temp. strength, thermal fatigue resistance, and high temp. deformation resistance. SOLUTION: This mouthpiece is composed of a heat resistant stainless steel which has a composition consisting of 15-27% Cr, 1-8% Ni, 0.1-2.0% Mn, 0.1-2.0% Si, 0.3-2.5% Nb, 0.1-2.5% W, 0.002-0.1% Zr, 0.002-0.1% B, 0.06-0.2% C, 0.01-0.15% N, and the balance Fe with inevitable impurities and containing, if necessary, at least one kind among the following (a), (b), (c): (a) 0.01-2.0% of one or >=2 elements among Ta, Ti, and V; (b) 0.01-2.0% of one or >=2 elements among Mo, Co, and Cu; (c) either or both of 0.01-2.0% Al and 0.001-0.05% rare earth elements including Y. Further, this stainless steel has a three-phase structure consisting of, by volume, 20-80% of ferritic phase, 0.3-7% of carbonitride phase, and the balance austenitic phase.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary combustion chamber mouthpiece for a diesel engine, which is excellent in high temperature strength, heat fatigue resistance and high temperature deformation resistance.

[0002]

2. Description of the Related Art Generally, a sub-combustion chamber of a diesel engine is provided with a die 1 as shown in a partial sectional view of FIG. 1. The die 1 has high-temperature strength, thermal fatigue resistance and high temperature deformation resistance. Is required. In FIG. 1, 2 is an injection nozzle, 3 is a glow plug, 4 is a cylinder block, and 5 is a piston. As a sub-combustion chamber mouthpiece of this diesel engine, in weight%, Cr: 16
-20%, Mn: 0.1-2.0%, Si: 0.1
2.0%, Mo: 1.1 to 2.4%, Nb: 0.3 to
2.1%, Ta: 0.1 to 2.2%, Co: 0.2 to
2.5%, C: 0.1 to 0.2%, N: 0.05 to 0.
15%, and if necessary, Ni: 0.2
~ 2.5%, W: 0.2-2.5%, balance F
Fe-Cr having a composition of e and inevitable impurities
A sub-combustion chamber base for a diesel engine, which is composed of a system alloy casting, is known (see Japanese Patent Laid-Open No. 7-228952).

[0003]

However, as the performance of the diesel engine becomes higher, the die attached to the auxiliary combustion chamber is required to have further high temperature strength, heat fatigue resistance and high temperature deformation resistance. The conventional auxiliary combustion chamber die for a diesel engine, which is made of a Fe—Cr alloy casting, has not been able to sufficiently meet such a requirement.

[0004]

Therefore, as a result of earnest research, the present inventors have found that in addition to the conventional Fe--Cr alloy, Zr:
0.002-0.1% and B: 0.002-0.1%
Fe-C having a composition with addition of
After the r-based alloy is melted, a heat treatment at 900 to 1050 ° C. for isothermal holding is performed to obtain a ferrite phase in a volume percentage of 20 to 80%,
Carbonitride phase: 0.3 to 7%, balance: Austenite phase has a three-phase structure, the auxiliary combustion chamber mouthpiece for diesel engines made of heat-resistant stainless steel having this three-phase structure has higher high temperature strength than conventional. That is, they have found that they are excellent in high temperature oxidation resistance and heat fatigue resistance.

The present invention has been made on the basis of such findings, and in weight%, Cr: 15 to 27%, N
i: 1-8%, Mn: 0.1-2.0%, Si: 0.1
~ 2.0%, Nb: 0.3-2.5%, W: 0.1
2.5%, Zr: 0.002-0.1%, B: 0.00
2 to 0.1%, C: 0.06 to 0.2%, N: 0.01
.About.0.15%, and if necessary, one or more of (a) Ta, Ti, and V: 0.
01-2.0%, (b) one or more of Mo, Co and Cu:
0.01-2.0%, (c) Al: 0.01-2.0% and R: 0.001
To 0.05%, at least one of (a) to (c), and the balance being Fe and inevitable impurities, and a ferrite phase of 20 to 80% by volume. %, Carbonitride phase: 0.3
~ 7%, balance: Characteristic of the auxiliary combustion chamber mouthpiece for diesel engines made of heat-resistant stainless steel having a three-phase structure consisting of austenite phase.

The reason for limiting the alloy composition and structure of the heat-resistant stainless steel sub-combustion chamber mouthpiece for diesel engines of the present invention as described above will be described in detail below. A, Component composition Cr: The Cr component has a function of significantly improving the high temperature oxidation resistance of the auxiliary combustion chamber mouthpiece for diesel engines made of heat-resistant stainless steel by forming a solid solution in the austenite phase and the ferrite phase, but its content If it is less than 15%, its effect is small. On the other hand, if it exceeds 27%, the σ phase, which is a harmful phase, precipitates and becomes brittle, and the toughness sharply decreases, which is not preferable. Therefore, the Cr content contained in the heat-resistant stainless steel for producing the sub-combustion chamber mouthpiece for a diesel engine of the present invention is set to 15 to 27%. The more preferable range of Cr content is 16 to 21.5%.

Ni: Ni component has the effect of improving high temperature oxidation resistance and toughness in the presence of Cr, but if its content is less than 1.0%, its effect is insufficient. If it is contained in excess of%, it becomes difficult to secure the thermal fatigue resistance, which is not preferable. Therefore, the Ni content in the heat-resistant stainless steel for producing the auxiliary combustion chamber die for a diesel engine of the present invention is 1.0 to
8%. A more preferable range of the Ni content is 2 to
7%.

Mn: Mn is a component effective in deoxidizing upon dissolution, but if its content is less than 0.1%, the desired effect cannot be obtained, while if it is more than 2.0%. If added too much, the oxidation resistance will be impaired. Therefore, the Mn content contained in the heat-resistant stainless steel constituting the sub-combustion chamber mouthpiece for a diesel engine of the present invention is set to 0.1 to 2.0%. M
A more preferable range of the n content is 0.3 to 1.5%.

Si: Si has a deoxidizing effect at the time of melting and an effect of increasing castability, but if its content is less than 0.1%, it is insufficient, while on the other hand, it exceeds 2.0%. If added too much, the oxidation resistance due to the precipitation of harmful phases is impaired. Therefore, the Si content contained in the heat-resistant stainless steel constituting the sub-combustion chamber mouthpiece for a diesel engine of the present invention is set to 0.1 to 2.0%. A more preferable range of Si content is 0.3 to 1.5%.

Nb: Nb mainly forms an M (CN) type carbonitride and further acts as a solid solution in the matrix to increase the high temperature strength and the thermal fatigue resistance, but its amount is 0.3. If the amount is less than 2.5%, the effect is insufficient. On the other hand, if the amount exceeds 2.5% and is excessively added, the amount exceeding the carbonitride formation and the solid solution in the matrix leads to the precipitation of harmful phase and the toughness. Not desirable because it inhibits. Therefore, the Nb content contained in the heat-resistant stainless steel forming the auxiliary combustion chamber die for the diesel engine of the present invention is set to 0.3 to 2.5%. Nb
The more preferable range of the content is 1.1 to 2.0%.

W: W has a function of increasing the high temperature strength, the heat fatigue resistance and the high temperature deformation resistance as a solid solution in the matrix and suppressing the precipitation of the σ phase, but its content is 0.1%.
If it is less than 2.5%, the desired effect cannot be obtained. On the other hand, if it exceeds 2.5%, the toughness and ductility are significantly deteriorated, which is not preferable. Therefore, the W content contained in the heat-resistant stainless steel constituting the sub-combustion chamber mouthpiece for a diesel engine of the present invention is set to 0.1 to 2.5%.

Zr: Zr has the effect of strengthening grain boundaries and refining carbonitrides to improve high temperature strength, heat fatigue resistance and high temperature deformation resistance, but the content thereof is 0.
If it is less than 002%, the desired effect cannot be obtained.
If it is contained in excess of%, a harmful phase is precipitated and toughness and ductility are significantly deteriorated, which is not preferable. Therefore,
The Zr content of the heat-resistant stainless steel forming the auxiliary combustion chamber mouthpiece for diesel engines of the present invention is 0.002.
˜0.1%.

B: B has the effect of strengthening the crystal grain boundaries and improving the high temperature strength, and at the same time improving the toughness by refining the carbides, but if the content is less than 0.002%, the desired effect is also obtained. On the other hand, if it exceeds 0.1%, a harmful phase is precipitated and the toughness and high temperature strength are deteriorated. Therefore, the B content contained in the heat-resistant stainless steel constituting the sub-combustion chamber cap for the diesel engine of the present invention is set to 0.002 to 0.1%.

C: C forms a carbonitride together with Nb to improve high temperature strength, high temperature oxidation resistance and thermal fatigue resistance, but is desirable even if its content is less than 0.06%. Is not obtained. On the other hand, if over 0.2% is added too much, carbonitride becomes excessive and the toughness deteriorates, which is not preferable. Therefore, C contained in the heat-resistant stainless steel forming the sub-combustion chamber mouthpiece for the diesel engine of the present invention is set to 0.06 to 0.2%. The more preferable range of the C content is 0.07 to 0.16%.

N N forms a carbonitride mainly with Nb in the presence of C and acts as a solid solution in the matrix (mainly austenite phase) to improve high temperature strength, heat fatigue resistance and high temperature deformation resistance. However, if its content is less than 0.01%, the desired effect cannot be obtained, while if it is added in excess of 0.15%, carbonitride precipitation becomes excessive and obstructs toughness. Therefore, the N content contained in the heat-resistant stainless steel forming the sub-combustion chamber mouthpiece for a diesel engine of the present invention is set to 0.01 to 0.15%.

Ta, Ti, V: These components form carbonitrides and have a function of improving the high temperature strength, the heat fatigue resistance and the high temperature deformation resistance by forming a solid solution in the matrix, and are added if necessary. However, its content is 0.01%
If it is less than 2.0%, the desired effect cannot be obtained. On the other hand, if it is added in excess of 2.0%, the amount exceeding the carbonitride formation and solid solution in the matrix leads to precipitation of harmful phases and impairs toughness. Not preferred because of Therefore, the content of one or more of Ta, Ti, and V contained in the heat-resistant stainless steel constituting the sub-combustion chamber mouthpiece for a diesel engine of the present invention is set to 0.01 to 2.0%. It was A more preferable range of the content of one or more of Ta, Ti, and V is 0.04 to 1.5%.

Mo, Co, Cu: These components form a solid solution in the austenite phase and the ferrite phase, and have high temperature strength,
Since it has the effect of improving heat fatigue resistance and high temperature deformation resistance, it is added as necessary, but its content is 0.
If it is less than 01%, the desired effect cannot be obtained, while on the other hand, it is 2.0%.
If it is added in an excessively large amount, the toughness is impaired by the precipitation of harmful phases, which is not preferable. Therefore, the content of one or more of Mo, Co, and Cu contained in the heat-resistant stainless steel forming the sub-combustion chamber mouthpiece for a diesel engine of the present invention is set to 0.01 to 2.0%. It was Mo, C
A more preferable range of the content of one or more of o and Cu is 0.04 to 1.5%.

Al, R: These components are added as necessary because they have the effect of improving the adhesion of the oxide film and the high temperature oxidation resistance, but the content is Al: 0.0.
If less than 1% and R: less than 0.001%, the desired effect cannot be obtained. On the other hand, if Al is more than 2.0% and R: more than 0.05%, toughness and ductility are impaired. Absent. Therefore, Al contained in the heat-resistant stainless steel constituting the sub-combustion chamber mouthpiece for the diesel engine of the present invention,
At least one of R is Al: 0.01-
2.0% (more preferably 0.04 to 1.5%),
R: 0.001 to 0.05% (more preferably 0.0
04-0.03%).

B, Structure Ferrite phase: The ferrite phase is a phase having a small coefficient of thermal expansion and excellent thermal fatigue resistance.
If it is present in an amount of less than 20%, the austenite phase increases, the coefficient of thermal expansion increases, and the thermal fatigue resistance becomes too low, which is not preferable. On the other hand, if the ferrite phase exceeds 80% in the matrix, the high temperature strength decreases. It is not preferable. Therefore, the ferrite phase existing in the matrix is set to 20 to 80% by volume.

Carbonitride phase: 0.3% by volume of carbonitride phase
If it is present in an amount of less than 7%, the high temperature strength and heat fatigue resistance will be deteriorated, and if it is in excess of 7%, the ductility and toughness will be deteriorated. Therefore, the carbonitride phase present in the austenite matrix and the ferrite phase in a uniformly dispersed state is 0.3 to 7% by volume.
%.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Heat-resistant stainless steel having the composition shown in Tables 1 to 5 is melted in the air, and the resulting molten metal is cast into a mold by the lost wax precision casting method, and the outer diameter of the upper end portion is 35 mm. Upper end inner diameter: 30 mm, height: 25 mm
Of the shape of the auxiliary combustion chamber for a diesel engine of the shape shown in 1 of FIG. 1 and a test piece having dimensions of parallel part diameter: 6 mm and parallel part length: 30 mm are prepared. 6 to Table 10, heat treatment under the conditions shown in Tables 1 to 5 and composition of Tables 1 to 5 and structures shown in Tables 6 to 10 of the present invention. ) 1
42, Subcombustion chamber base for comparative diesel engine (hereinafter,
The same components as the comparative caps 1 to 8 and the conventional diesel engine auxiliary combustion chamber caps (hereinafter referred to as the conventional caps) 1 to 2, and the present invention caps 1 to 42, the comparative caps 1 to 8 and the conventional caps 1 and 2. A test piece having a composition and a structure was prepared.

[0022]

[Table 1]

[0023]

[Table 2]

[0024]

[Table 3]

[0025]

[Table 4]

[0026]

[Table 5]

[0027]

[Table 6]

[0028]

[Table 7]

[0029]

[Table 8]

[0030]

[Table 9]

[0031]

[Table 10]

These inventive bases 1 to 42 and comparative bases 1 to
8 and conventional mouthpieces 1-2 and test pieces were used to perform the following engine test to evaluate heat fatigue resistance and high temperature deformation resistance, and further high temperature tensile test at 900 ° C. to measure high temperature strength. The test results are shown in Table 11 to Table 15.
It was shown to.

Engine test: Displacements of the present invention mouthpieces 1 to 42, the comparative mouthpieces 1 to 8 and the conventional mouthpieces 1 and 2, respectively: 2
Installed in a 500cc diesel engine, run the engine for 3 minutes at a rotation speed of 4000 rpm, and then stop for 4 minutes as one cycle. Conduct this test for 5000 cycles. Perform the actual machine test, take out the mouthpiece after the test, and in the bottom nozzle of the mouthpiece. The maximum crack length and the maximum deformation amount were measured to evaluate the thermal fatigue resistance and the thermal fatigue resistance.

[0034]

[Table 11]

[0035]

[Table 12]

[0036]

[Table 13]

[0037]

[Table 14]

[0038]

[Table 15]

[0039]

From the results shown in Tables 1 to 15, the mouthpieces 1 to 42 of the present invention are superior in high temperature strength, heat fatigue resistance and high temperature deformation resistance to the conventional mouthpieces 1 and 2. Recognize. However, the comparative spinnerets having a component composition deviating from the conditions of the present invention (indicated by an asterisk for the component compositions deviating from the conditions of the present invention) 1 to 8 are
It can be seen that either the heat fatigue resistance or the high temperature deformation resistance is deteriorated.

As described above, the heat-resistant stainless steel sub-combustion chamber mouthpiece for diesel engines of the present invention is excellent not only in high temperature strength but also in heat fatigue resistance and high temperature deformation characteristics, and is useful for improving the performance of diesel engines. It can make a great contribution.

[Brief description of drawings]

FIG. 1 is a cross-sectional explanatory view showing a state in which a mouthpiece is attached to a sub combustion chamber of a diesel engine.

[Explanation of symbols]

 1 mouthpiece 2 injection nozzle 3 glow plug 4 cylinder block 5 piston

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Saburo Wakita 1-297 Kitabukuro-cho, Omiya-shi, Saitama Inside Mitsubishi Materialial Co., Ltd. Industrial Co., Ltd. (72) Inventor Susumu Kawamoto 1 Uzumasa Tatsumicho, Ukyo-ku, Kyoto City Kyoto Prefecture Mitsubishi Motors Corporation

Claims (8)

[Claims] 1. By weight%, Cr: 15 to 27%, Ni: 1 to 8%, Mn: 0.1 to 2.0%, Si: 0.1 to 2.0%, Nb: 0.3. -2.5%, W: 0.1-2.5%, Zr: 0.002-0.1%, B: 0.002-0.1%, C: 0.06-0.2%, N: 0.01 to 0.15%, with the balance being Fe and inevitable impurities, and in volume%, ferrite phase: 20 to 80%, carbonitride phase: 0.3 to 7%, balance : A sub-combustion chamber cap for a diesel engine, which is composed of heat-resistant stainless steel having a three-phase structure composed of an austenite phase. 2. By weight%, Cr: 15 to 27%, Ni: 1 to 8%, Mn: 0.1 to 2.0%, Si: 0.1 to 2.0%, Nb: 0.3. -2.5%, W: 0.1-2.5%, Zr: 0.002-0.1%, B: 0.002-0.1%, C: 0.06-0.2%, N: 0.01 to 0.15%, and one or more of Ta, Ti, and V: 0.01 to
2.0%, with the balance being Fe and unavoidable impurities, and ferrite phase in volume%: 20-80
%, Carbonitride phase: 0.3 to 7%, balance: a heat-resistant stainless steel having a three-phase structure consisting of an austenite phase. 3. By weight%, Cr: 15 to 27%, Ni: 1 to 8%, Mn: 0.1 to 2.0%, Si: 0.1 to 2.0%, Nb: 0.3. -2.5%, W: 0.1-2.5%, Zr: 0.002-0.1%, B: 0.002-0.1%, C: 0.06-0.2%, N: 0.01 to 0.15%, and one or more of Mo, Co, and Cu: 0.01
˜2.0%, with the balance being Fe and unavoidable impurities, and ferrite phase in volume%: 20-8
A sub-combustion chamber mouthpiece for a diesel engine, which is made of heat-resistant stainless steel having a three-phase structure of 0%, carbonitride phase: 0.3 to 7%, balance: austenite phase. 4. By weight%, Cr: 15 to 27%, Ni: 1 to 8%, Mn: 0.1 to 2.0%, Si: 0.1 to 2.0%, Nb: 0.3. -2.5%, W: 0.1-2.5%, Zr: 0.002-0.1%, B: 0.002-0.1%, C: 0.06-0.2%, N: 0.01 to 0.15%, and further, Al: 0.01 to 2.0% and a rare earth element including Y (hereinafter, referred to as R): 0.001 to 0.05%. Of at least one of the above and the balance being Fe and inevitable impurities, and the ferrite phase in volume%: 20
-80%, carbonitride phase: 0.3-7%, balance: a heat-resistant stainless steel having a three-phase structure consisting of an austenite phase. 5. By weight%, Cr: 15 to 27%, Ni: 1 to 8%, Mn: 0.1 to 2.0%, Si: 0.1 to 2.0%, Nb: 0.3. -2.5%, W: 0.1-2.5%, Zr: 0.002-0.1%, B: 0.002-0.1%, C: 0.06-0.2%, N: 0.01 to 0.15%, and one or more of Ta, Ti, and V: 0.01 to
2.0%, and one or more of Mo, Co and Cu: 0.01
˜2.0%, with the balance being Fe and unavoidable impurities, and ferrite phase in volume%: 20-8
A sub-combustion chamber mouthpiece for a diesel engine, which is made of heat-resistant stainless steel having a three-phase structure of 0%, carbonitride phase: 0.3 to 7%, balance: austenite phase. 6. By weight%, Cr: 15 to 27%, Ni: 1 to 8%, Mn: 0.1 to 2.0%, Si: 0.1 to 2.0%, Nb: 0.3. -2.5%, W: 0.1-2.5%, Zr: 0.002-0.1%, B: 0.002-0.1%, C: 0.06-0.2%, N: 0.01 to 0.15%, and one or more of Ta, Ti, and V: 0.01 to
2.0%, and further, Al: 0.01 to 2.0% and R: 0.001 to 0.
A composition containing at least one of 05% and the balance being Fe and unavoidable impurities, and, in volume%, ferrite phase: 20 to 80%, carbonitride phase: 0.3 to 7%, balance: austenite. A sub-combustion chamber mouthpiece for a diesel engine, which is made of heat-resistant stainless steel having a three-phase structure consisting of phases. 7. By weight%, Cr: 15 to 27%, Ni: 1 to 8%, Mn: 0.1 to 2.0%, Si: 0.1 to 2.0%, Nb: 0.3. -2.5%, W: 0.1-2.5%, Zr: 0.002-0.1%, B: 0.002-0.1%, C: 0.06-0.2%, N: 0.01 to 0.15%, and one or more of Mo, Co, and Cu: 0.01
To 2.0%, and further, Al: 0.01 to 2.0% and R: 0.001 to 0.
A composition containing at least one of 05%, the balance being Fe and unavoidable impurities, and, in volume%, ferrite phase: 20 to 80%, carbonitride phase: 0.3 to 7%, balance: austenite. A sub-combustion chamber mouthpiece for a diesel engine, which is made of heat-resistant stainless steel having a three-phase structure consisting of phases. 8. By weight%, Cr: 15 to 27%, Ni: 1 to 8%, Mn: 0.1 to 2.0%, Si: 0.1 to 2.0%, Nb: 0.3. -2.5%, W: 0.1-2.5%, Zr: 0.002-0.1%, B: 0.002-0.1%, C: 0.06-0.2%, N: 0.01 to 0.15%, and one or more of Ta, Ti, and V: 0.01 to
2.0%, and one or more of Mo, Co and Cu: 0.01
To 2.0%, and further, Al: 0.01 to 2.0% and R: 0.001 to 0.
A composition containing at least one of 05% and the balance being Fe and unavoidable impurities, and, in volume%, ferrite phase: 20 to 80%, carbonitride phase: 0.3 to 7%, balance: austenite. A sub-combustion chamber mouthpiece for a diesel engine, which is made of heat-resistant stainless steel having a three-phase structure consisting of phases.