JPH0625391B2 - Method for producing wear-resistant iron-based alloy - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing an alloy having excellent wear resistance, and particularly has a structure in which hard crystals mainly containing boride are finely and uniformly distributed. It relates to a wear resistant alloy.

[Conventional technology]

In recent years, as the performance of mechanical parts and internal combustion engines has improved, the demand for alloys with excellent wear resistance has increased. In particular, in a valve rocker of an internal combustion engine, wear tends to be severe with increasing speed.

Conventionally, as a countermeasure against this, a chill cast product is brazed to a heavily worn part, high-speed steel is used, or carburization is performed.
It has been used after being subjected to nitriding treatment and further hard chrome plating.

However, even when it is used in normal rotation without any particular problem, it does not exhibit satisfactory wear resistance at high speed and high load. In such a case, stellite is typically used by plating. However, although stellite is almost satisfactory in wear resistance, it has a drawback that it is expensive because it mainly contains W and Co.

[Problems to be Solved by the Present Invention]

The present invention has variously studied the problems of the prior art, and variously studied wear-resistant alloys capable of withstanding high speed and high load.
The present invention has been completed by paying attention to rB-based alloys, conducting various studies on the composition range, additional elements and cooling rates to rapidly solidify the Fe-Cr-B alloy.

[Means for solving problems]

That is, the present invention is (1) Cr 8 to 20 wt%, B 6 to 20 wt%
And wear-resistant iron characterized in that an alloy containing 0.05 to 2.5% by weight of C or Al and the balance being essentially Fe was rapidly solidified from the melt at a cooling rate of 10 ³ ° C / sec or more. Base alloy manufacturing method. And (2) Cr 8-20% by weight, B 6-20% by weight
And C or Al 0.05 to 2.5 wt%, and Ni, Co, Nb, W, Mo
One or more of Ni + Co = 1-5% by weight, Nb + W + Mo
= 1 to 5% by weight, the balance of which is composed essentially of Fe, was rapidly solidified from the melt at a cooling rate of 10 ³ ° C / sec or more to produce a wear-resistant iron-based alloy. Is the way.

[Action]

According to the present invention, an Fe-Cr-B alloy is rapidly solidified from a melt at a cooling rate of 10 ³ ° C / sec or more to form fine iron boride and chromium boride,
The uniform distribution makes it possible to exhibit a high degree of wear resistance.

Generally, a boride of an alloy containing boron obtained by casting has a crystal length of about 70 μm. Although such a boride has high hardness, it lacks in toughness, so when it is applied to a part under a high load, a part of the crystal is chipped and falls off, which causes the phenomenon that other parts are dropped. May increase wear.

In the present invention, in order to solve this drawback, an alloy is prepared from the melt by 10 ³
It is rapidly solidified at a cooling rate of ℃ / sec or more, and the maximum length of boride crystals is 20 μm or less.

The reason for defining the alloy structure of the present invention as described above is as follows.

(a) Cr The Cr component combines with B to form hard borides Cr ₂ B, CrB and improves wear resistance. It also reacts with C to strengthen the alloy matrix and improve wear resistance. Further, since it is a solid solution with Fe, it has the effect of improving heat resistance. If the Cr content is 8% or less, the above effect cannot be obtained.
%, The content of Cr is set to 8 to 20%.

(b) BB component forms borides with Cr, Fe, Ni and Co to improve wear resistance. When the B content is 6% or less, the precipitation amount of Fe and Cr borides is insufficient, and the above effects cannot be obtained.
Even if the content exceeds the above range, the amount of precipitation is too large and the strength is lowered, so the content was set to 6 to 20%.

(c) C or Al Both C and Al improve the wear resistance of the alloy. In particular
C forms a solid solution with Fe to strengthen the alloy matrix, and Cr and N
It has the action of forming a carbide by combining with b and W.

Al solid-dissolves in Fe to strengthen the alloy matrix, which also increases hardness and improves wear resistance.

The above effect cannot be obtained with C or Al at 0.05% or less,
If the content is 2.5% or more, the hardness becomes high, which causes the alloy to become brittle and the strength to decrease, so it was set to 0.05 to 2.5%.

(d) Ni, Co, Nb, W, Mo Ni, Co, Nb, W and Mo both have the function of increasing the wear resistance of the alloy of the present invention, whether they are contained alone or in a combination of two or more.

Ni and Co form a solid solution with Fe and form an intermetallic compound with boron to improve the wear resistance of the alloy, but if the Ni + Co content is 1% or less, the above effect does not occur and the content exceeds 5%. Even if it is carried out, no further improvement in wear resistance is recognized, so the content thereof is set to 1 to 5% in consideration of economic efficiency.

Nb, W, Mo have a strong affinity with C contained in the alloy of the present invention,
Form carbide and strengthen the bond with the alloy base,
It has the function of further improving the wear resistance, and has its effect particularly when used under a high load. If the content of Nb + W + Mo is 1% or less, the above effect is not obtained, and even if it exceeds 5%, further improvement in wear resistance is not recognized, and in consideration of economical efficiency,
It was set to ~ 5%.

In producing the alloy of the present invention, it is necessary to cool at a cooling rate of 10 ³ ° C / sec or more, and such a cooling rate can be easily obtained by a usual method for producing a quenched alloy,
As a method industrially suitable for mass production, a method of obtaining powder by a water atomizing method is preferable.

The alloy of the present invention solidified at a high cooling rate of 10 ³ ° C./sec or more has an irregular or spherical powder, or a flake or ribbon-like shape. When applying this to wear-resistant members, it is possible to stick it to the base material by brazing etc. in the shape of a ribbon.In the case of powder, shape it into the required shape or put the powder in a refractory container. Sinter with emphasis. It is also possible to consider a method in which it is placed on a necessary member or adhered by an appropriate method, and then it is locally redissolved by a laser beam or the like and adhered to a base material. Further, when it is in the form of powder or ribbon, it is solidified at a relatively slow cooling rate of 10 ³ ° C / sec or less, and applied to wear-resistant members even when the length of boride crystal grains is 20 µm or more. In this case, when the molten metal is cooled at a cooling rate of 10 ³ ° C / sec or more, the abrasion resistance intended by the present invention is not deteriorated at all. For example, when the molten metal of the alloy of the present invention is pulverized by a normal gas atomization method, even if the powder cooled at a cooling rate of 10 ³ ° C / sec or less is mixed, the powder is sprayed to an abrasion resistant member or the like. The object of the present invention can be achieved by setting the conditions such that the metal is remelted with a laser beam or the like after being plated and the cooling rate is 10 ³ ° C / sec or more when it is solidified.

Hereinafter, typical examples and comparative examples of the present invention will be described.

〔Example〕

Example (1) A molten alloy prepared to have the composition shown in Table 1
An alloy powder was manufactured by a water spray method in which a molten metal flow of 10 mmφ was dropped and 0.5 m ³ / min of water was sprayed onto the molten metal flow. The obtained powder was classified with a 149 μm sieve to collect −149 μm powder. To 100 g of this powder, 1 g of zinc stearate as a lubricant and 0.3 g of polyvinyl chloride as a binder
Addition, mixing and molding of 11 × 30 × 3 mm at molding pressure of 8 t / cm ² A body was prepared and was sintered in hydrogen at 1180 ° C for 1 hour. The obtained sintered body was an alloy having a density of 6.9 g / cm ³ and a uniform structure of boride.

A microstructure photograph of No. 3 alloy of the present invention alloy is shown in FIG.

A special alloy chill casting, surface hardness Hv 600, rotating piece (outer diameter 30 mmφ, width 5 mm) was pressed against the alloy obtained as above in 70 ° C. motor oil at a pressure of 40 kg, and the rotation speed was 3370 rpm. A wear test was carried out to measure the wear loss and wear amount of the alloy. The results are shown in Table 2.

Example (2) The alloy powder having the composition No. 6 of the alloy of the present invention shown in Table 1 was used as the material moving distance of 200c by the plasma jet at the argon gas flow rate of 30 / min, the spraying material feeding rate of 30g / min and the spraying distance of 60cm.
The surface of the steel was sprayed with a single pass at a coating thickness of 0.1 mm at m / min. As a melting process after thermal spraying, a carbon dioxide laser beam is irradiated with a laser beam having a wavelength of 10.6 μm to melt it locally, without damaging the base, and the sprayed surface can be rapidly solidified to obtain an alloy with a uniform structure. Was given. After thermal spraying, the melt-processed alloy was cut into 11 × 30 × 3 mm test pieces, and a wear test was conducted in the same manner as in Example (1) to measure the wear loss and wear amount of the alloy. As a result, wear loss after 50 hours 3.1 mg,
The amount of wear was 6.5 μm.

[Comparative example]

As for the alloy of Comparative Example No. 1, powder of a melt of the alloy compounded so as to have the structure shown in Table 1 was produced by a normal water atomizing method, and a powder of −149 μm was obtained by a sieve. The powder obtained
After adding 0.5 g of zinc stearate as a lubricant to 100 g, mix and mix to make a compact of 11 × 30 × 3 mm at a molding pressure of 7 t / cm ² , and vacuum sinter at 1240 ° C. for 10 minutes (1 × 10 ^-4 torr). Next, the sintered body was quenched at 1150 ° C and tempered at 550 ° C. The sintered body density is 8.1 g / cm ³ .

The alloy of Comparative Example No. 2 was made of an alloy tool steel material (SKD11), quenched at 1000 ° C, tempered at 200 ° C and treated to prepare a test piece.

The alloy of Comparative Example No. 3 was made of alloy steel for machine structure (SNCM420) as a raw material, held at 950 ° C. for 5 hours with a solid carburizing agent, and then cooled in a furnace to prepare a test piece.

The alloy of Comparative Example No. 4 was made of alloy steel material for machine structure (S15C) as a raw material, and hard chromium plating by electrolysis was applied to a thickness of 10 μm to prepare a test piece.

The test pieces of Comparative Examples No. 1 to No. 4 were subjected to an abrasion test in the same manner as in Example (1), and the results are shown in Table 2.

〔effect〕

As described above in Examples (1) and (2), the alloy produced by suddenly solidifying the Fe-Cr-B alloy from the melt at the cooling rate of 10 ³ ° C / sec or more by the method of the present invention is Industrially useful effects can be obtained as a material that has excellent wear resistance and exerts remarkably excellent performance when applied to highly worn members such as machine parts and internal combustion engines.

[Brief description of drawings]

FIG. 1 is a microstructure photograph of the alloy of the present invention, Example No. 3 (1).

Claims (2)

[Claims] 1. An alloy having a composition containing 8 to 20% by weight of Cr, 6 to 20% by weight of B, and 0.05 to 2.5% by weight of C or Al, and the balance being substantially Fe at 10 ³ ° C. from the melt. A method for producing a wear-resistant iron-based alloy, characterized by being rapidly solidified at a cooling rate of not less than / sec. 2. Cr 8 to 20% by weight, B 6 to 20% by weight, C or Al 0.05 to 2.5% by weight, and one or more of Ni, Co, Nb, W and Mo Ni +. Co = 1-5% by weight, Nb + W + Mo = 1-5% by weight
A method for producing a wear-resistant iron-based alloy, characterized in that an alloy having a composition substantially containing Fe as a balance is rapidly solidified from a melt at a cooling rate of 10 ³ ° C / sec or more.