JPH0754736A - Valve element or valve seat for fuel injection valve - Google Patents

Abstract

PURPOSE:To provide a valve element or valve seat for a fuel injection valve which is free from troubles related to heat resistance or wear resistance even when this injection valve is used at a high temperature as an in-cylinder-injecting fuel injection valve for a gasoline-fuel engine. CONSTITUTION:A valve element 1 or a valve seat 2 is manufactured from martensite stainless steel containing in weight percentage C: 0.6 to 1.5%, Si: 2.0% or less, Mn: 1.0% or less, Cr: 10 to 18%, Mo and/or W: 1 to 6% (as calculated in terms of Mo+1/2W) or/plus V and/or Nb: 2% or less (as calculated in terms of V+1/2Nb), Co: 6% or less, Cu: 3.5% or less. It suitably contains one or two or more kinds of free-cutting elements among Pb, S, and Se. The remainders consist of Fe and inevitable impurities. With this constitution, durability can be enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a valve body or valve seat for a fuel injection valve for a so-called in-cylinder injection gasoline engine, in which fuel is injected into a combustion chamber or a preliminary combustion chamber,
In particular, it relates to the material.

[0002]

2. Description of the Related Art As the characteristics of a valve body and a valve seat material for a fuel injection valve for a gasoline engine, abrasion resistance of a sliding portion, corrosion resistance to a small amount of water in fuel, and the like are particularly important points. . Since the current mass production type fuel injection valve has an operating environment temperature of 150 ° C. or lower, as the valve body and valve seat material, JIS-SUS440C is generally used after quenching and then low-temperature tempering at 200 ° C. or lower. ing.

On the other hand, in recent years, studies on lean-burn engines have been actively conducted in order to deal with environmental problems.
One of them relates to an in-cylinder injection engine that directly injects fuel into a combustion chamber or a preliminary combustion chamber. In this type of engine, a part of the fuel injection valve is exposed in the combustion chamber, and its heat resistance becomes a problem. That is, in the case of in-cylinder injection, the ambient temperature becomes 300 ° C. or higher, so that if the above-mentioned conventional low temperature tempering material is used, it will be tempered in the state of normal use. For this reason, it is necessary to carry out tempering at a high temperature of 400 ° C. or higher in order to prevent a decrease in hardness and a dimensional change.

[0004]

However, when high temperature tempering is performed on the above conventional JIS-SUS440C,
The following problems occur. (1) Deterioration of corrosion resistance due to precipitation of secondary Cr / Fe composite carbide. (2) Softening due to tempering and hardness reduction due to high temperature use,
Deteriorated wear resistance.

The present invention has been devised in order to eliminate such disadvantages of the prior art, and its main purpose is to:
As a fuel injection valve for in-cylinder injection used in a gasoline fuel engine, it is to provide a valve body or a valve seat of a fuel injection valve that does not cause a problem in corrosion resistance and wear resistance even when used in a high temperature state. .

[0006]

According to the present invention, such an object is achieved by the following: C: 0.6 to 1.5% by weight, Si:
2.0% or less, Mn: 1.0% or less, Cr: 10-18
%, 1 type or 2 types of Mo and W is 1 with Mo + 1 / 2W
~ 6%, or 1 or 2 kinds of V and Nb in addition to V
+ 1 / 2Nb: 2% or less, Co: 6% or less, Cu: 3.
5% or less, and specific amounts of free-cutting elements Pb, S, S
It is achieved by manufacturing a valve body or a valve seat of a fuel injection valve from a martensitic stainless steel material that appropriately contains one or two or more groups of e, and the balance is Fe and inevitable impurities. . Further, as in the valve body or valve seat of the present invention, when high-C, high-Cr steel contains Mo, W, V, etc., M ₇ C ₃ , M ₂₃ containing Cr as the primary carbide is the main component. C ₆ becomes a composite carbide in which Mo, W, V and the like are solid-solved. If this compound carbide is huge, the high speed at the portion of the fuel injection valve that contacts the valve seat and the valve seat,
It was found that a high frequency of impact causes cracking, resulting in deterioration of sealing performance. Further, this phenomenon can be almost eliminated by setting the average grain size of the primary carbides to 15 μm or less, and within the range of the components of the present invention, this condition is satisfied by rapid cooling during agglomeration and hot working. It turned out that it is possible under high pressure.

[0007]

According to this, when martensitic stainless steel in which C, Si, Mn, Cr, Mo, etc. are appropriately alloyed is quenched and then tempered at a high temperature of 450 to 550 ° C., secondary carbides are precipitated. Harden. Using this secondary curing, the hardness (Vickers hardness) at 300 ° C. is Hv580.
As described above, desirably, by setting the Hv to 610 or more, the wear resistance as the valve body or the valve seat of the in-cylinder fuel injection valve used in the gasoline fuel engine can be improved. Moreover, with the above-described composition, the corrosion resistance and wear resistance (high temperature hardness, temper secondary hardening, creep resistance, temper softening resistance) of the in-cylinder fuel injection valve are improved.

The grounds for limiting the chemical components of the material of the present invention will be described below.

C forms a solid solution in Fe, converts the matrix into martensite when quenched, and also contains Cr, Mo, V, Nb,
Since they form carbides with Al and W, they are essential elements for improving hardness and wear resistance.

In order to obtain the hardness required for the fuel injection valve to which the present invention is applied, it is necessary to add at least 0.6%, and in order to form carbides in order to improve wear resistance, it is more preferable. However, if added excessively, the hot workability deteriorates, so the content was made 0.6% to 1.5%.

Si is added as a deoxidizer for steel,
It has the effects of strengthening the base, increasing high temperature strength, and improving wear resistance. However, excessive addition causes deterioration of hot workability, so the content was made 2.0% or less.

Mn is an element used for refining steel and has an effect of improving hardenability. However, since this is an austenite-forming element, if it is added in excess, the amount of retained austenite during quenching becomes excessive, which makes it difficult to obtain hardness, and there is a concern that dimensional changes may occur over time. Therefore, it is set to 1.0% or less.

[0013] Cr has the effect of passivating the steel and improving the corrosion resistance. Further, it is an essential element for improving temper softening resistance, hardenability, and creep strength, and for forming M ₇ C ₃ and M ₂₃ C ₆ type carbides to improve wear resistance. Further, Cr is effective in improving the oxidation resistance of the material. To maintain a good surface condition when exposed to a temperature of 300 ° C or higher as in a cylinder fuel injection valve, 10
% Or more must be contained. Especially for improving the corrosion resistance of steel,
It is necessary to add 10% or more, preferably 12% or more, but if added excessively, the hardness of the matrix decreases and the hot workability deteriorates, so the range was made 10% to 18%.

Mo and W have the effects of strengthening the matrix and improving corrosion resistance and temper softening resistance. Further, high temperature tempering causes precipitation of composite carbides and carbides with Cr,
It has an effect of improving the secondary curability and the high temperature hardness. Therefore, in order to improve the corrosion resistance and wear resistance, both elements are essential elements in the present invention, but they are both expensive elements. Therefore, from the balance of performance / cost, Mo + 1 / 2W is set to a range of 1% to 6%.

V and Nb have the functions of precipitating secondary carbides, improving the secondary hardenability, improving the high temperature strength, and refining the crystal. In addition, since the tendency of carbide formation is higher than that of Cr and Mo, as a result, Cr and Mo in the base are
Increase the amount to indirectly improve the corrosion resistance. Both V and Nb have similar effects, but since Nb has an atomic weight about twice that of V, it is preferable to specify V + 1 / 2Nb. Further, both elements are expensive, and if added in excess, hard carbides are generated and the grindability deteriorates.
% Or less (V + 1 / 2Nb ≦ 2%). If Nb alone or a small amount of V, Nb can be added up to about 4%.

Co has the effects of strengthening the base to increase the high temperature strength of the base and improving toughness and creep resistance. In addition to strengthening the retention of carbides and improving wear resistance, it is also effective in corrosion resistance. Since this is also an expensive element, it is set to 6% or less from the viewpoint of performance / cost balance.

Cu improves the corrosion resistance of the matrix and at the same time precipitates a Cu solid solution, thereby improving machinability. However, addition of 4% or more significantly deteriorates the hot workability of steel, so the content was made 3.5% or less.

S, Pb, and Se are elements that improve machinability, but if added in excess, wear resistance deteriorates. Moreover, since corrosion resistance is deteriorated by the excessive addition of S and Pb, S
Was 0.05% or less and Pb was 0.2% or less. Further, although Se is effective for improving the corrosion resistance, it deteriorates the wear resistance, so the content is made 0.1% or less.

Next, hardness will be described. The present inventors
The material subjected to high temperature tempering or the valve body and the valve seat were subjected to a simple wear test described later, and it was found that there is a strong correlation between the result and the hardness at 300 ° C. As described above, the operating temperature of the in-cylinder injection valve is 300 ° C. or higher. That is, the JIS-SUS in the fuel injection valve in the conventional intake manifold
It has been found that the hardness needs to be Hv580 or more, and preferably Hv610 or more, in order to obtain the same wear condition as the low temperature tempered material of 440C.

[0020]

EXAMPLES Specific examples of the present invention will be described in detail below.

Table 1 shows the chemical composition of each material used in the test. In Table 1, No. 1 to 14 are materials of the present invention which are effective as materials for valve bodies and valve seats. And No. No. 15 is a conventional general gasoline injection valve material. 16, 17
Is a material for a diesel engine injection valve, and is all specified by JIS.

[0022]

[Table 1]

Various tests were carried out on the materials having the respective compositions. The test items are a room temperature Vickers hardness after quenching and high temperature tempering, a high temperature Vickers hardness test at 300 ° C., a single wear test, an assembly durability test, a corrosion resistance test and a machinability test. Also, for some materials,
The average particle size of the primary carbide was measured. The results are summarized in Table 2.

[0024]

[Table 2]

The conditions of the above tests and the heat treatment conditions are shown below. (1) Single-body wear test Test format: Chip-on-disk Mating material: Same material (However, for No. 16 and 17, assuming an actual diesel nozzle, No. 16 was used as a tip and No. 17 was used as a disk. The test was conducted.) Surface pressure: 100 kgf / cm ² Sliding speed: 1 m / sec Environmental temperature: 250 ° C Lubrication: None Test time: 20 min Judgment standard: JIS-SUS440C tempered at 180 ° C (hardness HRC59) Environment Temperature 150
The above-mentioned test was carried out at 0 ° C, and based on the abrasion state, those equal to or higher than were evaluated as ◯, those of the same degree were evaluated as Δ, and those inferior were evaluated as ×.

(2) Assembly endurance test An operation endurance test was carried out in a state where an actually assembled injection valve was heated to 300 ° C. After 300 million operations, the oscilloscope was used to check for variations in lift characteristics for evaluation.

(3) Corrosion resistance test Test format: Immersion test Solution: Ethanol + (1% NaCl water) 1% Temperature: Normal temperature Judgment criteria: Based on JIS-SUS440C tempered at 480 ° C, red rust occurrence time is 5 More than double
2 times or more was marked with Δ, and 2 times or less was marked with x.

(4) Machinability test Test format: Comparison of surface roughness after drilling Tool used: Spiral drill Cutting feed: 32 mm / min Specimen condition: Annealing Judgment condition: What is better than JIS-SUS440C ◎ The same grade is indicated by ○ and the slightly worse one is indicated by △
And the inferior one was marked as x.

(5) Heat treatment conditions No. 1 to 15; Quenching: After holding in a vacuum of 1050 to 1100 ° C. (changed depending on the composition of the test material) for 2 hours, cooling with N ₂ gas Subzero: Holding at −75 ° C. for 30 minutes Tempering: 480 to 520 After holding for 1.5 hours in vacuum at ℃ (varied depending on the composition of the sample material), cooling with N ₂ gas No. 16; Quenching: 1250 ° C Tempering: 2 times at 540 ° C No. 17; quenching after tempering, tempering, effective carburizing depth 0.
5 to 0.8 mm

FIG. 1 shows a main part of a fuel injection valve manufactured from the above material. In the figure, 1 indicates a needle valve element and 2 indicates a valve seat.

The following can be judged from Table 2.

The valve body or valve seat of the present invention has a red rust generation time which is more than twice as long as that of SUS440C tempered material at 480 ° C., depending on the proper chemical composition. It can be seen that by setting the hardness at Hv 610 or higher, a sufficiently high abrasion resistance can be obtained in all cases. Further, it can be seen that by setting the hardness to Hv580 or higher, the same wear condition as the JIS-SUS400C in the conventional fuel injection in the intake manifold (see the judgment standard of the single wear test) can be obtained.

No. In No. 7, the high temperature hardness was Hv580, which was the lowest in the examples, and the evaluation of the single wear test was Δ. However, since the durability test result was good, high temperature hardness and From the single wear test results,
It can be estimated that good endurance test results can be obtained.

On the other hand, No. 15 has a high temperature hardness of H
As low as v565, the results of the single wear test and the durability test are also poor, and the corrosion resistance is also poor. Furthermore N
o. In No. 15, the average particle size of primary carbides was as large as 16.4 μm, and a drop-out trace of carbide was observed on the seat surface after the durability test and the portion in contact with the seat surface of the valve seat. In addition, No. 1
Since Nos. 6 and 17 are for diesel, both have low Cu content and Mo content and are absolutely inferior in corrosion resistance. The unit wear test is No. Since the high temperature hardness of 17 is as low as Hv545,
The result was poor.

Summarizing the above results, the valve body or valve seat of the present invention provides high temperature hardness and high corrosion resistance after high temperature tempering due to its proper chemical composition, so that it is in-cylinder-injected as compared with existing materials. It turns out that it is excellent for use.

[0035]

As described above, according to the present invention, as is clear from Table 2, both wear and corrosion after the operation test are significantly reduced. Therefore, the valve element of the fuel injection valve for the cylinder injection engine and Excellent properties can be obtained as a valve seat material.
Therefore, an extremely large effect can be achieved in improving the durability of the fuel injection valve.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a main part of a fuel injection valve to which the present invention is applied.

[Explanation of symbols]

 1 Needle valve body 2 Valve seat

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Noriaki Fukushima 2107-2 Yasugi-cho, Yasugi-shi, Shimane 2 Hitachi Metals Co., Ltd. Yasugi factory

Claims (10)

[Claims] 1. A valve body or a valve seat of a fuel injection valve for a cylinder injection gasoline engine, which is made of martensitic stainless steel, wherein C: 0.6 to 1.5% by weight, Si: 2. 0% or less, Mn: 1.0% or less, Cr: 10 to 18%, Mo or 1 to 6% of W or Mo + 1 / 2W, and the balance Fe and unavoidable impurities. Disc or valve seat. 2. A valve body or a valve seat of a fuel injection valve for a cylinder injection gasoline engine, which is made of martensitic stainless steel, wherein C: 0.6 to 1.5%, Si: 2. 0% or less, Mn: 1.0% or less, Cr: 10 to 18%, Mo or further W is 1 to 6% with Mo + 1 / 2W, and one or two kinds of V and Nb is 2% with V + 1 / 2Nb. Below, balance Fe
And a valve element or valve seat of a fuel injection valve, which is composed of unavoidable impurities. 3. A valve body or a valve seat of a fuel injection valve for a cylinder injection gasoline engine, which is made of martensitic stainless steel, wherein C: 0.6 to 1.5%, Si: 2. 0% or less, Mn: 1.0% or less, Cr: 10 to 18%, Mo or further W is 1 to 6% when Mo + 1 / 2W, Co: 6% or less, balance Fe and inevitable impurities. The valve body or valve seat of the fuel injection valve. 4. A valve body or a valve seat of a fuel injection valve for a cylinder injection gasoline engine, which is made of martensitic stainless steel, wherein C: 0.6 to 1.5% by weight, Si: 2. 0% or less, Mn: 1.0% or less, Cr: 10 to 18%, Mo or further W is Mo + 1 / 2W and 1 to 6%, Cu: 3.5.
% Or less, the balance being Fe and unavoidable impurities, and a valve body or valve seat of the fuel injection valve. 5. A valve body or a valve seat of a fuel injection valve for a cylinder injection gasoline engine, which is made of martensitic stainless steel, wherein C: 0.6 to 1.5% by weight, Si: 2. 0% or less, Mn: 1.0% or less, Cr: 10 to 18%, Mo or further W is 1 to 6% with Mo + 1 / 2W, and one or two kinds of V and Nb is 2% with V + 1 / 2Nb. Below, Co: 6
% Or less, the balance being Fe and unavoidable impurities, and a valve body or valve seat of the fuel injection valve. 6. A valve body or a valve seat of a fuel injection valve for a cylinder injection gasoline engine, which is made of martensitic stainless steel, in which C: 0.6 to 1.5% by weight, Si: 2. 0% or less, Mn: 1.0% or less, Cr: 10 to 18%, Mo or further W is 1 to 6% with Mo + 1 / 2W, and one or two kinds of V and Nb is 2% with V + 1 / 2Nb. Below, Cu:
A valve body or a valve seat of a fuel injection valve, which is composed of 3.5% or less and the balance Fe and inevitable impurities. 7. A valve body or a valve seat of a fuel injection valve for a cylinder injection gasoline engine, which is made of martensitic stainless steel, wherein C: 0.6 to 1.5%, Si: 2. 0% or less, Mn: 1.0% or less, Cr: 10 to 18%, Mo or further W is Mo + 1 / 2W and 1 to 6%, Co: 6% or less, Cu: 3.5% or less, balance Fe and A valve body or valve seat of a fuel injection valve, which is composed of inevitable impurities. 8. A valve body or a valve seat of a fuel injection valve for a cylinder injection gasoline engine, which is made of martensitic stainless steel, wherein C: 0.6 to 1.5% by weight, Si: 2. 0% or less, Mn: 1.0% or less, Cr: 10 to 18%, Mo or further W is 1 to 6% with Mo + 1 / 2W, and one or two kinds of V and Nb is 2% with V + 1 / 2Nb. Below, Co: 6
% Or less, Cu: 3.5% or less, balance Fe and inevitable impurities, and a valve body or valve seat of the fuel injection valve. 9. A valve body or a valve seat of a fuel injection valve for a cylinder injection gasoline engine, which is made of martensitic stainless steel, and in addition to the additive element according to any one of claims 1 to 8, % By weight, Pb: 0.2% or less, S: 0.05%
A valve element or a valve seat of a fuel injection valve, which includes one or more of the following and Se: 0.1% or less. 10. The valve body or valve seat of a fuel injection valve according to claim 1, wherein the average particle size of the primary carbide is 15 μm or less.