JPH04131385A - Method for reinforcing aluminum parts - Google Patents

Abstract

PURPOSE:To provide the aluminum parts which are decreased in the amt. of the intermetallic compds. to be formed, are improved in mechanical properties, such as brittleness and hardness, and have the toughness to thermal cracking by increasing the Vf value of a reinforcing material to aluminum and preventing the segregation of the reinforcing material to the aluminum. CONSTITUTION:The free control to increase or decrease the Vf value of the reinforcing material 7 as compared with the Vf value of the conventional materials is possible if the reinforcing material 7 which does not react with the aluminum, for example, the oxide, nitride and carbide, such as, for example, Al2O3, Si3N4 and SiC, are coated with aluminum powder 9 and this coated powder is used as a sintering raw material. The amt. of the metallic compds. to be formed at the boundary between the 1st layer 5 and the 2nd layer 12 is decreased by specifying the VF value of the 1st layer 5 to >=30%. The reinforcing material 7 is dispersed without segregation and the stable 1st layer 5 is formed if the 1st layer 5 is formed by remelting this sintered material 4 with a high-density energy beam. Then, the thermal cracking of the reinforcing part 2 is prevented by effectively utilizing the buffer effect of the 1st layer 5 to the 2nd layer 12 and the thermal cracking of the aluminum parts 1 is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for strengthening aluminum parts such as cylinder heads and pistons.

[Prior art] Aluminum is lighter and has better cooling properties than general materials such as steel, so it is widely used as a material for general mechanical parts and structural members, and is also used for cylinder heads and pistons in internal combustion engines. . However, in order to handle areas with severe thermal and mechanical loads, as well as to respond to the recent trend toward higher output and turbos, aluminum parts are required to have higher durability. Research on strengthening methods is underway. In cylinder heads and pistons that are directly exposed to combustion gas energy and heated to high temperatures, there is a particular need to improve thermal cracks that occur on the combustion surfaces. Thermal cracks occur intensively in areas where the cross section is small in response to thermal stress, that is, in areas where the wall thickness is thin. For example, thermal cracks in cylinder heads tend to occur in the partition between the intake and exhaust boats and between each of the intake and exhaust boats and the hot plug mounting hole or fuel injection nozzle mounting hole.
For pistons, local strengthening methods that tend to occur on the squish lip that borders the upper part of the cavity include:
Fe,
By remelting and alloying one or more of Ni, Co, ■, Zr, and Ce using high-density energy, specific parts of the aluminum alloy can be remelted and alloyed using high-density energy, without impairing the characteristics of aluminum alloy castings such as light weight and excellent thermal conductivity. Proposal to strengthen the
No. 786).

However, the proposed strengthening method involves directly remelting and alloying the heat-resistant metal into the aluminum base material, which is brittle (
There is a problem in that a large amount of metal open compounds with properties such as extremely low elongation) and hardness (reduced rigidity) are likely to be generated. A method of uniformly dispersing intermetallic compounds at the same time as alloying is also being researched, but it is technically difficult to control the amount of intermetallic compounds precipitated, but this method has not been put to practical use.

Therefore, the applicant first applied A1□0. After remelting and integrating the composite material, Co, Ni
, Ti, Mo, Zr, and other heat-resistant metals are re-melted and built-up welded singly or in combination to reduce the amount of intermetallic compounds produced, and at the same time actively utilize AJ 203 as a buffer material to reduce brittleness. We have proposed a ``Method for Strengthening Internal Combustion Engine Parts'' (Japanese Patent Application No. 1-221558) that improves mechanical properties such as strength and hardness.

[Problem to be solved by the invention] By the way, l□0. The composite material is obtained by sintering a mixture of Al2O and aluminum powder,
Since it is difficult to uniformly disperse AlxOs in the blending stage, there is a problem in that during remelting, AJ20m segregates in some areas, resulting in variations in crack resistance against heat shrinkage. In particular, the Vf value (volume ratio) of AjxOs
Even if it is desired to increase the Vf value, if the Vf value exceeds 30%, segregation will be too large and it can no longer be used.

[Means for Solving the Problems] In order to solve the above problems, the present invention forms a sintered material by coating the surface of a reinforcing material that does not react with aluminum with aluminum powder, and forms a sintered material. A first layer is formed by fusion welding the metal to the surface of an aluminum component, and then a second layer is formed by fusion welding a heat-resistant metal to the surface of the first layer.

[Operation] In the present invention, reinforcing materials that do not react with aluminum, such as AN 20v, Si3N4.

An oxide, nitride, or carbide such as SiC is coated with aluminum powder, and this coated powder is used as a sintering raw material. That is, in the present invention, the volume ratio of aluminum and reinforcing material is adjusted in the raw material stage before sintering, and a sintered material is obtained in which the reinforcing material is uniformly dispersed in the aluminum. Then, this sintered material is fused to the surface of the reinforced portion of the aluminum component without segregation to form a first layer. Furthermore, even if a second layer is formed on the surface of the first layer, the amount of intermetallic compounds generated will decrease due to an increase in the volume ratio of the reinforcing material, and the buffering effect of the first layer will be effectively used to reduce the heat generated during fusion welding. It is possible to prevent thermal cracks from occurring due to shrinkage.

Embodiment] Hereinafter, an embodiment of the present invention will be described in detail based on the accompanying drawings.

In Fig. 1, 1 is an aluminum part such as a cylinder or a piston, and in order to locally strengthen the high-load parts or parts that receive mechanical load, the first step is to strengthen the specified reinforcement parts of the aluminum part 1. In the example, the sintered material 4 is placed on the recess 3 formed in the reinforced region 2 of the aluminum component 1! This is then remelted using high-density energy such as a laser, an electron beam, or TIG to form the first layer 5 in the recess 3 of the aluminum component. The sintered material 4 is formed by sintering capsule powder by current sintering or normal atmosphere sintering.
This is a sintering method in which at least one of the lower molds is provided movably in the pressing direction, xi having different polarities are attached to these molds, and sintering is performed by applying electricity. As shown in FIG. 3 or 4, the capsule powder is made of reinforcing material 7 that does not react with aluminum, such as AJ 20x, Six Ni,
It is formed by coating hard powder 7a of oxide, nitride, or carbide such as SiC, or long fibers (or short fibers) 8 made of this hard material with aluminum powder 9 in a capsule shape. Powder 7a is AJ 20j, Sis N
i, SiC, etc., and the aluminum powder 9 is aluminum (AC2B).

They are formed by using AC8, etc. (JIS) as the pulverizing raw materials and pulverizing them with a fine powder pulverizer.

Hereinafter, the first reinforcing material 7 will be specifically explained as Aj2os.

Aj 20. Up to a particle size of 50 to 100 μm, aluminum is approximately 1/1/2 of the A1□03 powder 7a.
Grind to a particle size of about 1 to 10 μm.

After this, according to the Vf value of AJ x O3 powder 7a,
i 205 powder 7a and aluminum powder 9 are mixed and stirred to adhere aluminum powder 9 to the surface of AfJ20y powder 7a by electrostatic adhesion to form capsule powder 1.
form 0. After this, using a stirrer, AJ20
．． Aluminum powder 9 is fixed on the surface of powder 7a. As the stirrer, a stirrer is used that has rotary blades inside the housing and is configured to centrifugally transfer the capsule powder 10 along the inner surface of the housing (for example, a hybridization device, manufactured by Nara Kikai). That is, by centrifugally transferring the capsule powder 10 in the range of 1000 to 7000 rpm using a stirrer, moderate frictional heat is generated at the joint surface of the A j 203 powder 7a and the aluminum powder 9, and at the same time, the impact force , aluminum powder 9 is AJ
A1□0. The aluminum powder 9 is stretched and fixed on the surface of the powder 7a to obtain a capsule powder 10 in a perfect form as a sintered material.

The encapsulation of the AJ 20s long fibers (or short edges 1ii) 8 is also formed using a stirrer, similar to the encapsulation of the AJ 203 powder 7a. This sintered material 4 is filled into the recess 3 formed in the aluminum part 1 in advance, and fused by irradiating it with high-density energy to form a first layer 5 on the aluminum part 1.
form. As a second step, as shown in FIG. 2, heat-resistant metals 11 such as Co, Ni, Ti, Mo, and Zr are re-melted and built up on the first layer 5, either alone or in combination, to form a second layer. . Incidentally, the heat-resistant metal 11 is made of powder or solid material. This hot metal 11 is filled into the recess formed on the first layer 5, and re-melted overlay using high-density energy such as PTA (plasma tungsten arc), laser, electron beam, or TIG. (filling) to form the second layer 12.

Reinforcement material 7 that does not react with aluminum in this way
, eg AJ 20s, Sii N4.

By coating an oxide, nitride, or carbide such as SiC with aluminum powder 9 and using this coated powder as a sintering raw material, the Vf value of the reinforcing material 7 can be increased or decreased more freely than before.
By setting the vf value of the first layer 5 to 30% or more, it is possible to reduce the amount of metal compounds generated at the interface between the first layer 5 and the second layer 12, and this sintered material 4 is remelted with a high-density energy beam. By forming the first layer 5 in this manner, a stable first layer 5 in which the reinforcing material 7 is dispersed without segregation in aluminum can be formed. Therefore, it is possible to effectively utilize the buffering effect of the first layer 5 against the second layer 12 to prevent thermal cracking of the reinforced portion 2, thereby preventing thermal cracking of the aluminum component 1.

According to this embodiment, the following effects are achieved.

(2) A reinforcing material 7 (powder, short fibers, or long fibers) that does not react with aluminum can be coated with aluminum powder 9 to provide the sintered material 4.

(2) Adjustment of the volume ratio of the aluminum powder 9 and the reinforcing material 7 can be completed at the raw material stage of the sintered material 4.

(2) The reinforcing material 7 can be uniformly dispersed in the first layer 5 to prevent its segregation.

■When the vf value of the first layer 5 is 3o% or more, the first layer 5 and the second layer
The amount of metal compounds produced at the interface with layer 12 can be reduced.

■The second layer 12 effectively utilizes the brim impact effect and the first layer 5
can prevent the occurrence of thermal cracks.

[Effects of the Invention] In summary, according to the present invention, it is possible to increase the Vf value of the reinforcing material with respect to aluminum, and to prevent segregation of the reinforcing material with respect to aluminum, thereby reducing the amount of intermetallic compounds produced and improving the strength of brittle and hard machines. This has the excellent effect of providing aluminum parts with improved thermal properties and prevention of thermal cracking.

[Brief explanation of drawings]

FIGS. 1 and 2 are cross-sectional views showing the reinforcing process of aluminum parts of the present invention, and FIGS. 3 and 4 are views showing capsule powder. In the figure, 1 is an aluminum part, 4 is a sintered material, 5 is a first layer, 7 is a reinforcing material, 9 is an aluminum powder, 11 is a heat-resistant metal, and 12 is a second layer. Patent Applicant: Isuzo Jidosha Co., Ltd. Representative Patent Attorney: Nobuo Kinutani Figure 2

Claims (1)

[Claims] 1. A sintered material is formed by coating the surface of a reinforcing material that does not react with aluminum with aluminum powder, and the sintered material is fused to the surface of an aluminum component to form a first layer.
A method for strengthening aluminum parts, characterized in that a second layer is formed by fusion welding a heat-resistant metal to the surface of the layer.