JP2996408B2 - Manufacturing method of wear-resistant iron-based sintered alloy - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to a method for producing a wear-resistant iron-based sintered alloy.
And a method for producing an iron-based sintered alloy containing

(Prior Art) Conventionally, it has been known to use a Ni-containing iron-based sintered alloy as a wear-resistant material obtained by sintering using a Ni source and one or more powders other than Ni. The applicant has also filed a patent application in which the following sintered alloy is mainly used for a valve seat of an automobile internal combustion engine, and the main points in the production method are as follows.

JP-A-63-149353: 6-14% Ni, C = (0.84-0.056xNi
(%)) To (1.4-0.067xNi (%)), with the balance being Fe. This alloy has a structure in which bainite having excellent wear resistance, toughness and strength, a Ni-rich portion having excellent wear resistance and heat resistance, and pearlite having excellent workability are mixed. It is assumed that one third of the total Ni gathers in the Ni enrichment department. The raw material is a commercially available Ni powder (in the examples, carbonyl Ni powder)
It is preferable to use C powder as fine as possible.

JP-A-63-235447: Ni = 6 to 14%, C = 0.8 to 1.
An alloy having a composition of 2%, with the balance being Fe, in which hard particles are dispersed in a matrix in which a high alloy phase, bainite and pearlite are mixed.
The main points in the production method are the same as in the above-mentioned published gazette.

JP-A-64-39349: Mo = 3-14%, Ni = 3-14
%, C = 0.3 to 1.5%, the balance being Fe, and most of Mo is dissolved in an iron matrix. The point of the production method is to use iron powder in which Mo is dissolved.

JP-A-64-15349: Mo = 3-14%, Ni = 3-14
%, C = 0.5-2.0%, alloy in which hard particles are dispersed in a base structure composed of the balance of Fe. High Mo or high Ni iron powder, pure
Use raw materials in which Ni, pure Mo powder, iron powder, hard particle powder, etc. are mixed.

In the above prior art, Ni diffuses into the iron matrix and controls the structure of pearlite, bainite, martensite, and the like, and Ni that does not diffuse into the iron matrix forms a high alloy phase. , For the purpose of improving heat resistance and the like.

(Problems to be Solved by the Invention) However, since the high alloy phase generated by the latter action is lower in hardness than the hardened iron matrix or hard particles, sliding or hardening in parts having a high sliding surface pressure is performed. In the case of sliding in which foreign matter particles are present on the sliding surface, it becomes a starting point of wear and promotes wear of the sintered material itself.In addition, hard particles etc. fall off from the sintered alloy and wear of the valve, which is the mating material, etc. It turned out that there was a problem of promoting. As a countermeasure for this problem, it is conceivable to use a raw material powder in which Ni prealloyed iron-based alloy is atomized and Ni is uniformly diffused and dissolved. The reality was that it was not feasible to manufacture Ni-containing sintered bodies.

Accordingly, an object of the present invention is to provide a manufacturing method capable of improving the wear resistance of an iron-based sintered alloy containing high concentration of Ni.

(Means for Solving the Problems) The method of the present invention relates to a method for producing an abrasion-resistant iron-based sintered alloy containing 3% or more of Ni. Alloy powder and Ni containing carbon
Producing a sintered alloy having a structure in which the special carbide is dispersed in the Ni-based alloy powder by using at least one powder other than the above-mentioned powder. Secondly, by using a Ni-based alloy powder in which a special carbide is dispersed and one or more kinds of powders other than Ni, a structure in which the special carbide is dispersed in the Ni-based alloy powder is obtained. A method for producing a wear-resistant iron-based sintered alloy, characterized by producing a sintered alloy having the same.

 Hereinafter, the configuration of the present invention will be described.

In the present invention, the production target is limited to the iron-based sintered alloy containing 3% or more of Ni because the problem with the Ni-enriched portion becomes significant at the Ni content of 3% or more. The Ni content of the preferred sintered alloy to which the method of the present invention is applied is 3 to
20%.

According to the method of the present invention, as disclosed in JP-A-63-149353, the amount of C in the iron matrix and the amount of Ni are adjusted in relation to each other (see FIG. 6 of the same publication), and a sintered alloy which forms a Ni-rich phase It is also applied to the manufacturing method.

The method of the present invention is also applied to a method for producing a sintered alloy in which a Ni-enriched phase is actively generated and Ni is diffused from the Ni-enriched phase to an iron matrix to improve heat resistance.

Further, in the present invention, the limitation of the iron-based sintered alloy to the alloy in which the special carbide is dispersed is indispensable for eliminating the defect of the Ni-rich portion as described below because the special carbide has a high hardness. Because there is. Special carbides are carbides of transition elements other than iron carbide, especially Cr, W, Mo, Ti, N
It is a carbide of one or more transition metals such as b, Ta, and V.

The amount of these carbide forming elements is preferably 20 to 50 parts by weight based on 100 parts by weight of Ni in the Ni source. this
If the amount is less than 20 parts by weight, it is difficult to exhibit the effect of including the special carbide in the Ni source, while if the amount is more than 50 parts by weight, Ni is excessively diluted by the carbide-forming element and its inherent heat resistance, etc. Becomes unavailable. In this case, the balance between the carbide-forming element added to the iron base and the carbide-forming element added to the Ni source is lost, and the amount of the former is insufficient, and it becomes difficult to secure the required amount of carbide in the iron base. Insufficient wear resistance of the iron base is caused. The content of the special carbide in the entire sintered alloy is not particularly limited, and is determined exclusively by the intended use.

The Ni source in the present invention is roughly classified into two types: a Ni-based alloy powder containing a special carbide forming element such as Cr, and a powder containing a Ni-based alloy powder in which a special carbide is dispersed as a Ni addition source. The former is intended to improve the wear resistance of the Ni-enriched portion remaining in the sintered body after sintering by diffusing carbon from the iron matrix into the Ni source powder during sintering to form carbide. The latter is to improve the wear resistance of the Ni-rich phase by dispersing the special carbide in the Ni powder particles in advance. Of course, these two types of powders may be used simultaneously. Free Cr even in the latter carbide dispersion powder
Is present in addition to Cr carbide, and the effect of the present invention is achieved even if free Cr and C react as in the case of the former powder, so the Ni source of the present invention contains a special carbide forming element. And / or a Ni-based alloy powder in which a special carbide is dispersed.

As the special carbide-forming element-containing powder, a powder mainly containing Ni and containing 5 to 25% of Cr, W, Mo, Ti, Nb, Ta, V, or the like is used. In addition to these elements, the inclusion of some impurities such as Fe, Co, and Si is allowed. In addition, special carbide-containing powders such as Cr ₂₃ C ₆ , Cr ₂ C ₃ , WC, TiC, Nb
By preparing the fine powder of C, TaC, and VC together with Ni powder by mechanical alloying method, it is possible to use carbide as a powder uniformly dispersed in Ni or integrally with Ni matrix. In addition, an alloy whose composition is adjusted so that carbides are precipitated is adjusted by a melting method, and the alloy is atomized, thereby similarly obtaining an alloy powder in which carbides are dispersed in Ni.

Although the use of pure Ni powder is not preferred, Ni
When the content increases and the amount of the Ni source powder of the present invention increases, the effect of the present invention is not impaired even if it is slightly used.

As the components other than those described above, one or more of the following hard particles can be used as a mixture in a sintering raw material.

a) Cr: 50-57%, Mo: 18-22%, Co: 8-12%, C-0.1-1.
4%, Si 0.8-1.3% balance Fe and impurities b) Cr: 27-33%, W: 22-28%, Co: 8-12%, C-1.0-2.0
%, Balance Fe and impurities c) Mo: 55 to 70%, CO: 0.1% or less, balance Fe and impurities (effect) In the present invention, Ni of the Ni source is not completely diffused, and the Ni content in the sintered alloy is not increased. When the chemical phase is generated, the raw material powder is adjusted so that carbides are dispersed in the Ni-rich phase. For this purpose, the Ni source contains carbide forming elements and / or
Or disperse carbides.

FIG. 1 (magnification: 100 times) shows the structure of the alloy of No. 2 in Table 1 described below manufactured by the manufacturing method of the present invention.
FIG. 2 shows an alloy of Comparative Example (also No. 1) using i-powder. In FIG. 1, it is clear that the black carbide is finely dispersed in the white Ni-rich phase. Thus, the iron-based sintered alloy obtained by the production method of the present invention has a novel structure in which carbides are finely dispersed in the Ni-rich phase, and the wear resistance is further improved.

Hereinafter, the present invention will be described in detail with reference to examples.

An iron powder that uniformly dissolves 5 wt% molybdenum powder having a peak at a particle size of 150 to 200 mesh was prepared by an atomizing method. To this Fe-Mo iron powder, 5% of metallic Mo powder and 15% of Fe-63% Mo powder as a hard phase were added, and 17% Cr-6% Mo containing special carbide forming elements W, Cr, Mo = 10% W-balance N
Add Ni alloy powder and graphite powder of 150 mesh under, consisting of i, so that the final Ni and C composition will be Ni: 10% and C: 1.3%. The mixed powder to which 0.6% of zinc acid was added was pressed by 6.5
After molding at a molding pressure of t / cm ² and dewaxing at 650 ° C for 1 hour,
Sintered at 1130 ° C for 1 hour in a vacuum furnace. After sintering in liquid nitrogen
Sub-zero treatment was performed by immersion for 10 minutes, and tempering was further performed at 400 ° C. for 1 hour.

A Ni powder in which fine Cr ₂ C ₃ with a particle size of 10 to 20 μm is dispersed by 20% is prepared by a mechanical alloying method, and a sintered alloy is prepared in the same manner as above except that the Ni powder sieved to 150 mesh under is used. Manufactured. For comparison, pure Ni was replaced with Ni.
A sintered alloy was produced in the same manner as described above except that it was used as a source.

 The composition of each sintered alloy is shown in the following table.

After processing each sintered alloy sample to a predetermined size, the performance as a valve seat material was evaluated by a single wear tester simulating a water-cooled automobile engine. The test conditions were as follows.

Valve material: Stellite # 12 filling Valve surface temperature: 450-650 ℃ Surface temperature per valve seat: 250-350 ℃ Rotation speed: 3000rpm Test time: 5 hours Valve heating: LPG flame Cylinder head cooling: water Test in the following table The results are shown.

(Effects of the Invention) From the above description, the use of the Ni source of the present invention reduces both the wear of the wear-resistant sintered alloy itself such as a valve seat and the wear of the mating material such as a valve particularly in a high temperature range. You can see that. Therefore, the sintered alloy of the present invention
The Ni-rich part has both wear resistance and heat resistance, and greatly contributes to the improvement of the performance of sliding materials for internal combustion engines.

[Brief description of the drawings]

FIG. 1 is a micrograph of an iron-based sintered alloy manufactured by the method of the present invention, and FIG. 2 is a micrograph of an iron-based sintered alloy manufactured by a conventional method.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C22C 33/02

Claims (3)

(57) [Claims] 1. A method for producing a wear-resistant iron-based sintered alloy containing 3% or more of Ni, comprising: a Ni-based alloy powder containing a special carbide-forming element; By using a powder containing the element of the above, by causing the Ni-based alloy powder and the powder containing the carbon and containing one or more elements other than Ni to react, the special carbide is converted into the Ni-based alloy powder. A method for producing a wear-resistant iron-sintered base alloy, comprising producing a sintered alloy having a dispersed structure. 2. A method for producing a wear-resistant iron-based sintered alloy containing 3% or more of Ni, comprising the steps of:
Abrasion-resistant iron, characterized in that a sintered alloy having a structure in which the special carbide is dispersed in the Ni-based alloy powder is produced by using a base alloy powder and at least one powder other than Ni. Manufacturing method of base sintered base alloy. 3. The method for producing a wear-resistant iron-based sintered alloy according to claim 1, wherein the at least one powder other than Ni contains hard particles.