JP3396800B2 - Composite sintered alloy for non-ferrous metal melt and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal-ceramic composite sintered body which is useful as a material for forming an injection part of a die casting machine which is in contact with a non-ferrous metal melt such as aluminum and which has excellent corrosion corrosion resistance and wear resistance. Regarding bond gold.

[0002]

2. Description of the Related Art A die casting machine is capable of casting aluminum, zinc, copper, lead, tin, or non-ferrous metal products mainly containing these at high speed and with high precision, and is used in various products such as automobiles, industrial machines, and home appliances. It occupies an important position as a manufacturing method for components. Alloy tool steel for hot molds conventionally represented by SKD61 (JIS G4404) as a material for parts such as a plunger sleeve, a piston, a tip, and a sprue sleeve that constitute an injection part of a die casting machine.
Has been used. However, the corrosive erosion resistance to molten metal is not sufficient, and in the plunger sleeve, corrosive erosion and the wear action due to the sliding of the piston are superimposed, and the wear damage is likely to proceed, resulting in great cost and labor for maintenance. I need. Surface damage such as corrosion and wear of members contaminates the cast metal melt and adversely affects the quality of die cast products. As a countermeasure against this, it has been proposed to apply engineering ceramics products such as dense silicon nitride or metal-ceramics composite sintered products produced by sintering a mixture of titanium alloy powder and ceramics powder. (JP-A-2-280953, JP-A-5-140692, JP-B-7-84601, etc.).

[0003]

Ceramic sintered products such as silicon nitride have excellent corrosion resistance against molten aluminum and the like, and are excellent in wear resistance, but poor in toughness, and plunger sleeves and the like. It is difficult to achieve stable use with members that have a large mechanical shock load such as. The composite sintered alloy composed of titanium alloy and ceramics is intended to improve the corrosion and corrosion resistance, the wear resistance and the like while avoiding the drawbacks of the ceramics single material as a composite effect of two kinds of materials. The present invention has been made for the purpose of improving and stabilizing the material properties of a composite sintered alloy used as a member for molten non-ferrous metal.

[0004]

The composite sintered alloy of the present invention is produced by sintering a powder mixture consisting of 20 to 40% by weight of tungsten carbide and the balance of titanium, Ti.
It is characterized by being a sintered body having a composite structure in which titanium carbide particles or titanium carbide particles and tungsten particles are dispersed in a matrix made of a -W alloy.

The composite sintered alloy of the present invention has a structure in which titanium carbide particles or titanium carbide particles and tungsten particles are dispersed in a Ti-W alloy matrix. This composite structure is formed by the following reactions occurring during the sintering process: Ti + WC → TiC + W ... [1]. That is, the entire amount of the tungsten carbide in the sintering raw material is consumed in the reaction with titanium, and the titanium carbide precipitated as a reaction product becomes the dispersed phase particles of the product sintered body. In addition, the generated tungsten forms a Ti-W alloy matrix by forming a solid solution with titanium. When producing a relatively large amount of tungsten that exceeds the solid solubility limit for titanium, the excess tungsten remains Ti-W as fine particles.
It remains in the alloy matrix and becomes part of the dispersed phase.

The matrix of the Ti-W alloy has excellent corrosion resistance due to titanium and high wear resistance due to the solid solution effect of tungsten, and the titanium carbide particles (and the tungsten particles) have a dispersion effect as the hardness of the sintered alloy.・ To further improve wear resistance. The Ti-W alloy matrix has a tungsten content of about 20-30% by weight. The amount of dispersed phase particles in the composite structure is about 6.5 to 16.8 parts by weight for titanium carbide particles based on 100 parts by weight of the matrix metal. Tungsten particles (dispersion in the case where tagstene exceeding the solid solubility limit in titanium is generated) The maximum amount ratio of phase tungsten particles) is about 22 parts by weight.

The titanium carbide produced by the above reaction is dispersed and precipitated as ultrafine particles in the matrix, and when a part of tungsten remains without being solid-solved in titanium, the dispersion of the tungsten particles is extremely fine and uniform. This multiphase structure is finer and more uniform than the conventional composite sintered alloy in which the particles of the ceramic powder in the sintering raw material are the dispersed phase particles of the product sintered body. The formation of a fine and uniform multiphase structure is effective in suppressing the deterioration of the ductility and toughness associated with the increase in hardness and wear resistance of the composite sintered alloy and maintaining the suitability as a structural member.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The reason why the content of tungsten carbide in the sintering raw material is 20% by weight or more is that when the content is smaller than that, titanium carbide which becomes a dispersed phase of the product sintered body,
Also, the amount of tungsten required for forming the matrix alloy (Ti-W alloy) is insufficient, and the effect of improving the hardness and wear resistance of the product sintered body is insufficient. With the increase in the amount of tungsten carbide powder, the amount of titanium carbide and tungsten produced increases, and when the content is about 30 wt% or more, tungsten exceeding the solid solubility limit of titanium is produced, and excess tungsten is dispersed. It becomes a phase particle. The upper limit of the compounding amount is set to 40% by weight, because if it exceeds that amount, excessive production of tungsten and titanium carbide weakens the product sintered body and impairs its suitability as a material for the structure portion.

Sintering of the powder mixture of tungsten carbide and titanium is carried out by heat treatment under pressure. As the sintering method, hot isostatic pressing treatment (HIP treatment) is suitable. According to the HIP treatment, it is possible to obtain a highly dense composite sintered body regardless of the shape and size of the product sintered body under the uniform action of a high pressing force. The HIP process is performed at a temperature of about 1000 to 1200 ° C and a pressing force of 80 to 12
The above reaction can be efficiently achieved under the condition of 0 MPa.

[0010]

EXAMPLE A mixture of titanium powder (particle size: 350 mesh under) and tungsten carbide (average particle size: 3 μm) is filled in a metal capsule, degassed and hermetically sealed, and subjected to HIP treatment (temperature: 110).
0 ° C, pressure: 100 MPa, processing time: 2 hours). A test piece is taken from the obtained sintered body to measure the mechanical properties and corrosion resistance.

[Measurement of Bending Strength] Three-point bending test (JIS R
1601). Specimen size: 3 x 4 x 50 (mm) Span distance: 30 mm Test temperature: Room temperature

[Abrasion resistance test] A specific wear amount (x10 ^-8 mm ³ / kg ・ mm) of the friction surface after a certain period of time when the test piece was pressed against the mating material (rotary ring) by a RIKEN-Okoshi rapid wear tester ) Measure. Specimen size: 40 × 20 × 10 (mm) Counterpart material: SUJ steel ring Friction speed: 1.93 m / sec Friction distance: 600 m Final load: 6.2 kgf

[Corrosion resistance test] After immersing the test piece in an aluminum alloy molten bath for a predetermined time, the thickness (mm) of the erosion layer on the surface of the test piece is measured, and the erosion layer thickness of the SKD61 alloy tool steel is set to 1. Calculate the ratio. Specimen size: 40 x 17 x 5.5 (mm) Bath composition: Al-9.5Si-3.0Cu (JIS H 5202 AC 4B) Bath temperature: 750 ° C Immersion time: 24 Hr

Table 1 shows the raw material composition of the test material, the composition of the product sintered body and the test results. Inventive Examples Nos. 1 to 3 have excellent corrosion resistance and wear resistance to a non-ferrous metal melt, as compared with the alloy tool steel (No. 7) which is a conventional typical non-ferrous metal melt material. There is. Comparative Examples No. 4 to No. 6 are composite sintered alloys obtained by using the mixed powder of tungsten carbide and titanium and carrying out the reaction [1] in the sintering process as in the case of the invention examples. However, No. 4 is insufficient in the amount of tungsten carbide compounded in the raw material, so the effect of improving the hardness and wear resistance of the product sintered body is insufficient, and No. 5 and No. 6 have an excessive amount of compounded amount. Therefore, the toughness is poor, and none of them is equal to the invention examples.

[0015]

[Table 1]

[0016]

The composite sintered alloy of the present invention has a composite structure composed of a Ti-W alloy matrix formed by the reaction of the sintering process and titanium carbide particles (and tungsten particles) which are fine precipitation products. As a result, it has high corrosion resistance and wear resistance to molten non-ferrous metal, which is required as a material for the injection part of die casting machines, and has an improved service life / reduction of maintenance, efficient casting operation, It contributes to reduction of pollution and improvement of casting quality.

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Claims (2)

(57) [Claims] 1. A sintered body produced by sintering a powder mixture comprising 20 to 40% by weight of tungsten carbide (WC) and the balance of titanium, which has the following formula in the sintering process: Ti + WC → TiC + W As shown, T formed by the solid solution of tungsten formed by the reaction between the total amount of tungsten carbide and titanium
a matrix consisting of i-W alloy, the reaction titanium carbide particles child generated in or, if the amount of tungsten produced in the above reaction exceeds the solid solubility limit with respect to titanium, the excess tungsten particles and the response above the solubility limit in non-ferrous metal composite sintered alloy for molten metal, wherein the resulting titanium carbide particles are sintered body made of distributed composite tissue. 2. A powder mixture comprising 20 to 40% by weight of tungsten carbide (WC) and the balance titanium as a sintering raw material,
In the sintering process, a matrix of Ti-W alloy represented by the following formula: Ti + WC → TiC + W, in which the tungsten produced in the above reaction is solid-dissolved in titanium by causing the reaction of the total amount of tungsten carbide with titanium. a titanium carbide particle Komata produced in the above reaction
When the amount of tungsten produced in the above reaction exceeds the solid solubility limit for titanium, it is composed of a composite structure in which excess tungsten particles exceeding the solid solubility limit and titanium carbide particles produced in the above reaction are dispersed. A method for producing a composite sintered alloy for molten non-ferrous metal, which comprises forming a sintered body.