JP6635664B2 - Hard powder for Fe-based sintering and Fe-based sintered body using the same and having excellent wear resistance - Google Patents

Description

  The present invention relates to a hard powder for Fe-based sintering, which is used for a sintered valve seat which is press-fitted into a cylinder head of an internal combustion engine and prevents abrasion of the cylinder head due to opening / closing of a valve, and Fe having excellent wear resistance using the same. It relates to a base sintered body.

  2. Description of the Related Art Conventionally, for valve seats of internal combustion engines, sintered alloys based on Fe-based powder and mixed with hard particles containing a large amount of rare metals such as Mo and Ni and Co have been used. Mo added to the hard particles mainly forms a hard carbide to improve wear resistance, and has a function of suppressing solidification by providing solid lubricity because oxides are easily generated. Ni and Co are added with the intention of turning the matrix of the hard particles into austenite and increasing the amount of Mo dissolved in the hard particles of Mo, which improves wear resistance and adhesion.

  For example, as disclosed in Japanese Patent Application Laid-Open No. 2001-181807 (Patent Document 1), by mass%, Mo: 20 to 60%, C: 0.2 to 3%, Ni: 5 to 40%, Mn : Hard particles containing 1 to 15% and Cr: 0.1 to 10% with the balance being inevitable impurities and Fe have been proposed. Further, as disclosed in Japanese Patent Application Laid-Open No. 2011-190526 (Patent Document 2), by mass%, Mo: 20 to 40%, C: 0.5 to 1.0%, Ni: 5 to 30% , Mn: 1 to 10%, Cr: 1 to 10%, Co: 5 to 30%, Y: 0.05 to 2%, with the balance being hard particles for blending a sintered alloy comprising unavoidable impurities and Fe. I have.

JP 2001-181807 A JP 2011-190526 A

  As disclosed in Patent Literature 1 and Patent Literature 2 described above, these hard particles are manufactured by a general-purpose method such as a casting and pulverizing method, a water atomizing method, and a gas atomizing method as conventionally proposed. . On the other hand, since rare metals such as Ni and Co have high raw material costs and large price fluctuations, stabilizing prices and supply has been one of the issues in the industry. However, when the amount of Ni or Co added to the hard particles is reduced, the matrix of the hard particles becomes ferritic, and the amount of wear increases.

  In order to solve the above-mentioned problems, the present inventors have conducted intensive studies on hard powders having sufficient wear resistance without excessively adding Co and Mo, and as a result, they have been replaced with Cr, Ni, and C. As a result, it has been found that sufficient performance can be obtained, and the present invention has been achieved.

The gist of the invention is that
(1) In mass%, C: 2.5 to 6%, Si: 1% or less, Mn: 10% or less, Mo: less than 20%, Cr: 10 to 30%, Ni: 3 to 30%, W + V + Nb: Hard powder for Fe-based sintering, characterized in that 5% or less, the balance being Fe and unavoidable impurities.

(2) Fe having excellent wear resistance, which is obtained by mixing and sintering the hard powder for Fe-based sintering described in (1) and an Fe-based powder as a base of a sintered body. Base sintered body.
(3) A hardened powder obtained by mixing 1 to 50% by mass of the hard powder for Fe-based sintering described in (1) with an Fe-based powder serving as a base of a sintered body and sintering the mixture. It is an Fe-based sintered body having excellent wear properties.

  As described above, according to the present invention, a hard powder for Fe-based sintering which is excellent in economical efficiency while maintaining wear resistance and workability of a conventional material and Fe which has excellent wear resistance, which is used for a valve seat of an internal combustion engine, is used. A base sintered body can be provided.

FIG. 1 is a view schematically showing a valve seat wear tester.

Hereinafter, the present invention will be described in detail.
The greatest feature of the present invention is that precipitation of Cr carbides prevents adhesion wear with a valve as a partner material, while stabilizing an austenite phase by Fe, Ni, and C forming a hard powder matrix. Thus, wear resistance in a high-temperature region is ensured, and high economic efficiency is realized by reducing the amount of expensive elements such as Co and Mo. .

  The hard powder according to the present invention may contain one, two or more of W, V, and Nb as needed. As a manufacturing method, a conventional method such as a general casting and pulverizing method, a water atomizing method, and a gas atomizing method can be applied. The hard powder according to the present invention is mixed with various powders such as Fe powder and, if necessary, graphite powder or other pure metal or alloy powder, and sintered, as conventionally proposed. , Can be used as a valve seat. Further, the addition amount of the hard powder is set to 1 to 50%. Preferably, it is 5 to 40%.

Hereinafter, the reasons for limiting the hard powder according to the present invention will be described.
C: 2.5-6%
In the alloy of the present invention, C is an essential element for forming a Cr-based carbide in the hard powder to prevent cohesive wear and for austenitizing the matrix together with Ni. However, if added in excess of 6%, the melting point decreases and melting occurs during sintering. If the addition is less than 2.5%, the sinterability deteriorates, so that the adhesion to the matrix deteriorates and the wear resistance deteriorates remarkably.

Si: 1% or less In the alloy of the present invention, Si is an element having an effect of improving heat resistance, and can be added as necessary. However, if added in excess of 1%, the brittleness increases and the wear resistance deteriorates.

Mn: 10% or less In the alloy of the present invention, Mn is an element having an effect of improving the adhesion between the hard powder and the matrix at the time of sintering, and can be added as needed. Diffusion into the matrix becomes so large that the shape of the hard powder cannot be maintained, but rather the adhesion is reduced and the workability is deteriorated.

Mo: less than 20% In the present invention, Mo is not an essential element, but is an element that facilitates formation of an oxide film. Since addition of Mo improves wear resistance, it may be added to less than 20% as necessary. Can be. However, since it is an expensive element, the cost increases with the addition amount. Preferably it is 1 to 15%, more preferably 2 to 12%.

Cr: 10 to 30%
In the alloy of the present invention, Cr is an essential element for forming Cr-based carbides in the hard powder together with C to improve wear resistance. If it is less than 10%, the amount of carbide is small and the wear resistance is not sufficient. If it exceeds 30%, the amount of carbide increases, the hardness of the hard powder increases, and the workability deteriorates.

Ni: 3 to 30%
In the alloy of the present invention, Ni is an element necessary for stabilizing the austenite phase of the matrix of the hard powder together with C. If it is less than 3%, it is not sufficient and melting occurs during sintering. If it exceeds 30%, ductility is increased and workability is remarkably deteriorated.

W + V + Nb: 5% or less In the alloy of the present invention, W, V, and Nb are elements forming a hard carbide, and one or more of them can be added as necessary. However, if the total amount exceeds 5%, the carbide consumes a large amount of C, and as a result, the formation of Cr-based carbide is inhibited. Therefore, the total amount of W, V and Nb is preferably more than 0.1% and less than 3%, more preferably more than 0.5% and less than 2%.

Hard powder addition amount: 1-50%
Basically, as the added amount of the hard powder increases, the abrasion resistance improves. If it is less than 1%, the effect of addition is small, and if it exceeds 50%, the shape is not stable when filled in a mold and pressed.

  Further, Fe in the hard powder of the present invention is the remainder and is not particularly limited, but has a lower cost and a lower melting point than Cr, which is the most added in the hard powder of the present invention. Therefore, considering the raw material cost and the solubility at the time of production, the content is preferably more than 35% and less than 60%, more preferably more than 45% and less than 55%. Further, although there is no particular limitation on Co in the present invention, it is preferable to make Co less than 5%, which does not affect the properties, and more preferably, it is not added because it increases the cost.

Hereinafter, the present invention will be specifically described with reference to examples.
(Preparation of hard powder)
Using the raw materials weighed so as to have the component compositions shown in Tables 1 and 2, hard powder was produced by a gas atomizing method, and the hard powder was classified into 210 μm or less and used as hard powder.

(Preparation of sintered body)
After mixing the hard powder, the C powder (graphite), and the Fe powder under the conditions shown in Tables 1 and 2 above, filling the mixed powder in a mold, press-molding, sintering, and sintering the test piece. Was prepared.

(Evaluation of wear resistance)
The wear resistance of the sintered alloy was evaluated using the valve seat wear tester shown in FIG. In this tester, a propane gas burner 1 is used as a heating source, and a sliding portion between a ring-shaped valve seat 2 which is a test piece made of a sintered alloy prepared as described above and a valve face 4 of a valve 3 is propane-coated. A gas combustion atmosphere was used. The valve face 4 is made of SUH35 material. The temperature of the valve seat face 5 is controlled to 300 ° C., a load of 245 N is applied when the valve seat face 5 and the valve face 4 are contacted by the spring 6, and the valve seat face 5 is contacted at a rate of 3250 times / minute, and the wear test is performed for 8 hours. Was done. The test results are shown in Tables 1 and 2.

(Evaluation of workability)
A machinability test was performed using an NC lathe under the following conditions to evaluate the workability of the produced sintered body, and the wear amount of the cutting tool was measured. The test results are shown in Tables 1 and 2.
Direction: Traverse test specimen shape: outer diameter 30mm, inner diameter 22mm, total length 9mm
Number of revolutions: 970 rpm
Feeding speed: 0.08mm / rev
Cutting depth: 0.3mm
Cutting distance: 320m
Cutting tool: Carbide coated with titanium aluminum nitride

  Table 1 shows that the addition amount of the hard powder composed of various components was fixed at 15%, the influence of the hard powder composition was evaluated, and the hard powder composition range having excellent characteristics was clarified. Further, Table 2 was evaluated by changing the addition amount of the hard powder having the components inside and outside the claim 1 to clarify the addition amount range in which the hard powder in the claim 1 shows excellent characteristics. Things. No. shown in Table 1. Nos. 1 to 20 and Nos. Nos. 31 to 35 are examples of the present invention. Nos. 21 to 30 and Table 2 Reference numerals 36 and 37 to 42 are comparative examples.

  As shown in Table 1, Comparative Example No. Sample No. 21 is inferior in wear resistance and workability due to low contents of C and Cr which are the component compositions of the hard powder. In addition, the cost is high because the contents of Mo and Co are high. Comparative Example No. Sample No. 22 has high values of C and Cr, which are the component compositions of the hard powder, so that a large amount of Cr carbide is precipitated and the hardness is increased, thereby deteriorating the workability. Comparative Example No. Sample No. 23 has poor wear resistance due to low Cr content, which is a component composition of the hard powder.

  Comparative Example No. No. 24 has a low C content, which is a component composition of the hard powder, so that the adhesion to the matrix deteriorates and the workability deteriorates. Comparative Example No. No. 25 has a high content of C, which is a component composition of the hard powder, so that its melting point is lowered and melting occurs during sintering. Comparative Example No. No. 26 does not contain Ni, which is the component composition of the hard powder, and Similar to 25, melting occurs during sintering. Comparative Example No. No. 27 has a high content of Ni, which is a component composition of the hard powder, and therefore has high ductility and deteriorates workability.

  Comparative Example No. No. 28 has a high brittleness due to a high Si content, which is a component composition of the hard powder, and has poor wear resistance and workability. Comparative Example No. No. 29 has a high content of Mn, which is a component composition of the hard powder, so that the diffusion into the matrix becomes too large to keep the shape of the hard powder, the adhesion is reduced, and the workability is deteriorated. Comparative Example No. In No. 30, since the value of W + V + Nb is high, the formation of Cr-based carbide is inhibited, and the workability is deteriorated. On the other hand, in Example No. Since all of Nos. 1 to 20 are hard powders satisfying the conditions of the present invention, it is understood that they are excellent in wear resistance and workability.

  Next, from Table 2, Comparative Example Nos. In Nos. 37 to 41, the mixing amount of the hard powder was changed to 1, 5, 30, 40, and 50%. On the other hand, in the present invention example No. When comparing the mixing amount of the hard powder according to 31 to 35 with the mixing amount of the same hard powder as 1, 5, 30, 40, and 50, the comparative example satisfies the conditions of the present invention. It can be seen that the wear amount ratio and the cutting tool wear ratio are significantly worse than those of the present invention examples. Furthermore, in Comparative Examples 36 and 42 in which the mixing amount of the hard powder is 60%, it can be seen that the shape after processing and shaping becomes unstable and the test is impossible regardless of the composition of the hard powder.

  As described above, the feature of the present invention is that precipitation of Cr carbides prevents adhesion wear with a valve as a mating material, while Fe, Ni, and C form a hard powder matrix to form an austenitic phase. Stabilizes the wear resistance in a high temperature region, and realizes high economic efficiency by reducing the amount of expensive elements such as Co and Mo.

1 Propane gas burner 2 Valve seat 3 Valve 4 Valve face 5 Valve seat face 6 Spring


Applicant Sanyo Special Steel Co., Ltd. 1
Attorney Patent Attorney Shiina Jin

Claims (2)

In mass%,
C: 2.5-6%,
Si: 1% or less,
Mn: 10% or less,
Mo: less than 20%,
Cr: 10 to 30%,
Ni: 3 to 30%,
W + V + Nb: 5% or less,
A hard powder for Fe-based sintering, the balance being Fe and unavoidable impurities;
Mix with the Fe-based powder that is the base of the sintered body,
An Fe-based sintered body having excellent wear resistance characterized by being sintered. In mass%,
C: 2.5-6%,
Si: 1% or less,
Mn: 10% or less,
Mo: less than 20%,
Cr: 10 to 30%,
Ni: 3 to 30%,
W + V + Nb: 5% or less,
Mixing 1 to 50% by mass of a hard powder for Fe-based sintering characterized by the balance consisting of Fe and unavoidable impurities and an Fe-based powder serving as a base of a sintered body,
An Fe-based sintered body having excellent wear resistance characterized by being sintered.

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