JPS6167759A - Sintered iron alloy for valve seat - Google Patents

Abstract

PURPOSE:To obtain the titled sintered Fe alloy inhibiting the wear of an unfilled valve and having superior wear resistance by uniformly dispersing a proper amount of alloy steel particles having a specified composition consisting of Cr, Ni and Fe in an Fe alloy contg. a proper amount of C as a matrix. CONSTITUTION:Alloy steel particles having a composition consisting of 10-40wt% Cr, 10-40wt% Ni and the balance Fe are uniformly dispersed by 10-30wt% in an Fe alloy contg. 0.5-2.0wt% C or further contg. 0.2-3wt% one or more among CaF2, BaF2 and MnS as a matrix, and 1-20wt% Pb is infiltrated into the alloy as required to obtain a sintered Fe alloy for a valve seat for an internal-combustion engine. This alloy has superior wear and corrosion resistances and high machinability and hardly attacks a non-built-up valve.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a sintered alloy for valve seats of internal combustion engines.

[Conventional technology]

Valve seats for internal combustion engines, especially valve seats for automobiles.
The engine valve, which is a mating member, is coated with Stellate or the like to prevent wear caused by sliding with the valve seat.

[Problem that the invention seeks to solve]

In recent years, consideration has been given to abolishing valve linings. However, two conventional valve seats are not made for valves without ferrules, so if the ferrules of the valve are discarded and a conventional valve seat is used, a problem arises in that the valve wears out.

An object of the present invention is to provide a valve seat member that suppresses valve wear and has wear resistance.

[Means for solving problems]

The sintered alloy for valve seats of the present invention has a C weight ratio of 0.
Cr1 in weight ratio in iron-based alloy matrix containing 5 to 2.0%
It is characterized in that alloy steel particles consisting of 0 to 40% Ni, 10 to 40% Ni, and the balance Fe are uniformly dispersed in a total weight ratio of 10 to 30%.

The present invention also provides a valve seat river iron-based sintered alloy, characterized in that the sintered body is further infiltrated with 1 to 20 parts by weight of Pb, and the sintered body is further provided with a base component. The present invention provides a valve seat river iron-based sintered alloy characterized in that 0.2 to 3% by weight of one or two selected from the group consisting of CaF2, BaF2 and MnS is added.

In this specification, % indicates heavy % unless otherwise specified.

The reasons for limiting the ingredients will be explained below.

C (carbon) dissolves and diffuses into the iron-based matrix during sintering,
It has the effect of accelerating sintering and improving the strength of the iron-based substrate, but if the amount of C added is less than 0.5%, this effect cannot be obtained, and if it exceeds 2%, the substrate will become separated from M as graphite. The content was limited to 0.5 to 2% because the amount remaining in the interior would be too large and the strength of the base would deteriorate.

BaF2 (barium fluoride), CaF, (calcium fluoride), and MnS (manganese sulfide) are effective in improving machinability, but they have no effect at less than 0.2%, and at more than 3% 0.
It was set at 2 to 3%.

Cr (chromium) reacts with C (carbon) to form Cr carbide, which improves the strength of alloy steel particles, and also partially dissolves into the sintered iron-based matrix, improving corrosion resistance and heat resistance. However, if less than 10% of Cr is added to alloy steel, this effect will be small, and if it exceeds 40%, the amount of carbides will increase too much and wear out the mating material. The addition was limited to 10-40%.

Ni (nickel) is dissolved in the alloy steel matrix to improve the strength of the alloy steel particles, and a portion diffuses into the sintered iron-based matrix to improve the strength and heat resistance of the matrix. However, if less than 10% Ni is added to the alloy steel, the effect will be small, and if it exceeds 40%, the alloy steel will weaken. The addition of Ni to the steel was limited to 10-40%.

The alloy steel particles have a particle size of 20 to 150 Ij, m and have the effect of improving the wear resistance of the valve seat, but if the amount of alloy steel added is less than 10%, this effect will not be apparent, and if it exceeds 30%, Since the aggressiveness towards the mating material increases and the valve wears out, it is limited to 10 to 30%.

Pb (lead) is present on the sliding surfaces of the valve and valve seat,
The oxide layer has the effect of improving mutual wear resistance, but if it is less than 1% infiltrated, it is not effective, and if it exceeds 20%, the base material becomes weaker and wear increases.

[Effect]

C dissolves and diffuses into the iron-based alloy matrix during sintering, promotes sintering, and improves the strength of the iron-based alloy matrix.
CaF2 and MnS improve machinability.

Cr reacts with C to form Cr carbide, which improves the strength of the alloy steel particles, and a portion of which is solidly dissolved in the sintered iron-based alloy matrix to improve corrosion resistance and heat resistance.Ni improves the corrosion resistance and heat resistance of the alloy steel matrix. In addition to improving the strength of the alloy steel particles by solid solution in the sintered iron-based alloy base, the alloy also diffuses into the sintered iron-based alloy base and improves the strength and heat resistance of the base. The steel particles improve bonding with the substrate, and the alloy steel particles improve the wear resistance of the valve seat.

Pb is present on the sliding surfaces of the pulp and the valve seat, and its oxide layer improves their mutual wear resistance.

〔Example〕

The present invention will be explained by examples.

Example 1 15% alloy steel powder consisting of 1.5% Cr, 35% Ni and balance Fe, 0.8% graphite powder (-325 mesh),
Zinc stearate 08 is added to 100 parts by weight of a powder made by blending 0.2% S powder and the balance Fe powder (-100 mesh).
parts by weight were added and thoroughly mixed. This mixed powder was molded using a molding pressure cuff t/Cm' to obtain a molded body. Next, the molded body was sintered for 60 minutes at 1120° C. in an ammonia decomposition gas atmosphere to obtain a sintered body (sintered alloy).

This sintered body was then processed into a help sheet and used as an intake valve seat for the aluminum alloy cylinder head of a 1600 cc four-cylinder gasoline engine. Processed by three people. Next, use leaded gasoline to increase the rotation speed to 660 Orp.
A durability test was carried out for 200 hours under full load. The other pulp used was a pulp with no deposits. After the test was completed, the increase in the contact surface width of the valve seat and the amount of valve seat wear were measured.

Regarding the sintered alloy, its hardness (Vickers hardness) and density were measured in advance.

However, sintered alloys of Examples 2 to 5 having different sintered alloy compositions and Comparative Examples 1 to 3 outside the scope of the present invention were obtained in the same manner as in Example 1 using the blending ratios shown in the table. In addition, P
The infiltration of b was carried out by bringing Pb into contact with the sintered body and heating it at a temperature of 1100° C. for 30 minutes in an ammonia decomposition gas atmosphere.

These sintered bodies were then subjected to hardness and density measurements and wear tests in the same manner as described above. These results are also shown in the table above.

As can be seen from these results, all of Examples 1 to 5 of the present invention have an increased width per valve seat, a small amount of valve wear, and excellent wear resistance, and are superior to the other valves without fillers, which are the mating materials. M wear was also suppressed, and aggressiveness was small.

Comparative Example 1 has a Cr content of over 40% and an alloy steel of 30%.
The attack on the other material increased as the amount exceeded the limit. Comparative Example 2 contains less than 0.5% C, more than 0.5% S, and 40% Ni.
and Pb exceeded 20%, which weakened the substrate and increased valve seat wear. Comparative example 3 has 2% C
Since the BaF2 content exceeded 3%, the base material became brittle, and since the alloy steel powder width was less than 105, wear resistance was low and valve seat wear increased.

〔Effect of the invention〕

Since the sintered alloy for valve seats of the present invention has alloy steel dispersed therein, it has excellent wear resistance and is less aggressive to valves without a metal filler, reducing valve wear. This is a sintered alloy for valve seats that is also ideal as a mating material for valves. Furthermore, the corrosion resistance is also good. Furthermore, a sintered alloy with good machinability can also be obtained.

Patent Issuer - Person Toyota Motor Corporation (and 1 other person)

Claims (4)

[Claims] (1) 10-40% Cr and 10-40% Ni by weight in an iron-based alloy matrix containing 0.5-2.0% C by weight
and the balance is Fe, the weight ratio of alloy steel particles is 10 to 30.
An iron-based sintered alloy for valve seats that is characterized by uniform dispersion. (2) 10-40% Cr and 10-40% Ni by weight in an iron-based alloy matrix containing 0.5-2.0% C by weight
and the balance is Fe, the total weight ratio of alloy steel particles is 10 to 3.
0% Pb is uniformly dispersed in a sintered body containing 1 to 20% by weight of Pb.
A ferrous sintered alloy for valve seats, characterized by being infiltrated. (3) 0.5 to 2.0% C and CaF_2 by weight ratio
, BaF_2, and MnS, the base is an iron-based alloy containing 0.2 to 3% of one or more selected from the group consisting of BaF_2 and MnS, and the alloy consists of 10 to 40% Cr, 10 to 40% Ni, and the balance Fe by weight ratio. An iron-based sintered alloy for a valve seat, characterized in that steel particles are uniformly dispersed in a sintered alloy base at a total weight ratio of 10 to 30%. (4) 0.5 to 2.0% C and CaF_2 by weight ratio
, BaF_2, and MnS, the base is an iron-based alloy containing 0.2 to 3% of one or more selected from the group consisting of BaF_2 and MnS, and the alloy consists of 10 to 40% Cr, 10 to 40% Ni, and the balance Fe by weight ratio. An iron system for valve seats, characterized in that a sintered body in which steel particles are uniformly dispersed in a sintered alloy matrix with a total weight ratio of 10 to 30% is infiltrated with 1 to 20% by weight of Pb. Sintered alloy.