JPH1161319A - Composite sintered alloy for molten nonferrous metal, and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metal-ceramics composite sintered alloy useful as a component material for a nonferrous metal caster such as a die casting machine and excellent in wear resistance, corrosion resistance, etc. SOLUTION: This sintered alloy is produced by sintering a powder mixture having a composition consisting of, by weight, 20-40% tungsten carbide and the balance titanium and has a composite structure where titanium carbide grains (or titanium carbide grains and tungsten grains) are finely and uniformly dispersed in a Ti-W alloy matrix. This composite structure is formed by causing, in the course of sintering, a reaction between tungsten carbide and titanium [Ti+WC→TiC+W]. It is preferable to perform sintering treatment by means of hot isostatic pressing at about 1000 to 1200 deg.C under about 80 to 120 MPa pressurizing force.

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 sintering excellent in corrosion-erosion resistance, abrasion resistance, etc. useful as a material for forming an injection portion of a die casting machine which comes into contact with a molten non-ferrous metal such as aluminum. Concerning bond money.

[0002]

2. Description of the Related Art Die casting machines are capable of casting aluminum, zinc, copper, lead, tin, or non-ferrous metal products based on these materials at high speed and high precision. It occupies an important position as a method of manufacturing components. Alloy tool steel for hot dies (JIS G4404) conventionally represented by SKD61 as a component material for a plunger sleeve, a piston, a tip, a sprue sleeve, etc. constituting an injection portion of a die casting machine.
Has been used. However, corrosion and corrosion resistance to molten metal is not sufficient, and in the plunger sleeve, corrosion and corrosion are superimposed on the wear effect due to the sliding of the piston, and wear damage is likely to progress. I need. Surface damage such as corrosion and abrasion of the member contaminates the molten cast metal and adversely affects the quality of the die cast product. As a countermeasure, it has been proposed to apply engineering ceramic products such as dense silicon nitride, or a metal-ceramic composite sintered product manufactured by sintering a mixture of a titanium alloy powder and a ceramic powder. (JP-A-2-80953, JP-A-5-140692, JP-B-7-84601, etc.).

[0003]

A ceramic sintered product such as silicon nitride has excellent corrosion resistance to molten aluminum and the like, and is excellent in wear resistance, but has poor toughness and has a plunger sleeve and the like. It is difficult to ensure stable use of a member having a large mechanical impact load as described above. A composite sintered alloy composed of a titanium alloy and a ceramic is intended to improve the corrosion erosion resistance, abrasion resistance, and the like as a composite effect of the two materials while avoiding the drawbacks of the ceramic single material. An object of the present invention is to improve and stabilize the material properties of a composite sintered alloy used as a member for a non-ferrous metal melt.

[0004]

The composite sintered alloy of the present invention is manufactured by sintering a powder mixture comprising 20 to 40% by weight of tungsten carbide and the balance of titanium.
The sintered body has 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.

[0005] 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 matrix of a Ti-W alloy. This composite structure is formed by the following reaction occurring during the sintering process: Ti + WC → TiC + W (1) That is, the entire amount of tungsten carbide in the sintering raw material is consumed by the reaction with titanium, and the titanium carbide precipitated as a reaction product becomes dispersed phase particles of the sintered product. In addition, the generated tungsten forms a solid solution in titanium to form a matrix of a Ti-W alloy. If a relatively large amount of tungsten exceeding the solid solubility limit for titanium is to be produced, the excess tungsten will remain as fine particles in Ti-W
It remains in the alloy matrix and becomes part of the dispersed phase.

[0006] The matrix of the Ti-W alloy has excellent corrosion resistance due to titanium and high wear resistance due to the effect of solid solution of tungsten.・ Further enhance wear resistance. The tungsten content of the Ti-W alloy matrix is 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 of titanium carbide particles with respect to 100 parts by weight of matrix metal. The maximum amount ratio of tungsten particles to be a phase) is about 22 parts by weight.

[0007] The titanium carbide produced by the above reaction is dispersed and precipitated as very fine particles in the matrix, and when a part of tungsten remains without being dissolved in titanium, the dispersion of tungsten particles is extremely fine and uniform. This mixed phase structure is finer and more uniform than a conventional composite sintered alloy in which ceramic powder particles in a sintering raw material are dispersed phase particles of a product sintered body. The formation of a fine and uniform mixed phase structure is effective in suppressing a decrease in ductility accompanying the increase in hardness and wear resistance of the composite sintered alloy, and maintaining the suitability as a structural member.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The reason why the blending amount of tungsten carbide in a sintering raw material is set to 20% by weight or more is that if the blending amount is smaller than that, titanium carbide, which is a dispersed phase of a product sintered body,
In addition, 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 sintered product is insufficient. When the amount of titanium carbide and tungsten increases with the increase in the amount of tungsten carbide powder, and when the blending amount is about 30% by weight or more, tungsten exceeding the solid solubility limit of titanium is generated, and excess tungsten is dispersed. It becomes phase particles. The reason why the upper limit of the compounding amount is set to 40% by weight is that if it exceeds that, excessive production of tungsten and titanium carbide weakens the product sintered body and impairs its suitability as a structural part material.

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

[0010]

EXAMPLE A metal capsule was filled with a mixture of titanium powder (particle size 350 mesh under) and tungsten carbide (average particle size 3 μm), degassed and sealed, and HIPed (temperature: 110).
0 ° C, pressure: 100MPa, treatment time: 2Hr). A test piece is collected from the obtained sintered body, and the mechanical properties and corrosion resistance are measured.

[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: normal temperature

[Abrasion resistance test] The specific wear amount of the friction surface after a certain period of time (x10 ^-8 mm ³ / kg · mm) by pressing the test piece against the counterpart material (rotating wheel) using a RIKEN-Ogoshi rapid wear tester ) Measured. Specimen size: 40 × 20 × 10 (mm) Material: SUJ steel ring Friction speed: 1.93 m / s Friction distance: 600 m Final load: 6.2 kgf

[Corrosion Resistance Test] After immersing a test piece in an aluminum alloy bath for a predetermined time, the erosion layer thickness (mm) on the test piece surface is measured, and the erosion layer thickness of the SKD61 alloy tool steel is set to 1. Calculate the ratio. Specimen size: 40 × 17 × 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 sintered product, and the test results. Invention Examples Nos. 1 to 3 have outstanding corrosion resistance and wear resistance to nonferrous metal melts compared to alloy tool steel (No. 7), which is a conventional representative nonferrous metal material. I have. Comparative Examples No. 4 to No. 6 are composite sintered alloys obtained by performing the above reaction [1] in the sintering process using a mixed powder of tungsten carbide and titanium, similarly to the invention examples. However, No. 4 lacks the effect of improving the hardness and wear resistance of the sintered product due to the lack of the amount of tungsten carbide in the raw material, and the amounts of No. 5 and No. 6 are excessive. 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 a reaction in the sintering process and titanium carbide particles (and tungsten particles) as fine precipitation products. As a result, it has high corrosion resistance and abrasion resistance to the non-ferrous metal melt required as a constituent material of the injection part of the die casting machine, etc., improving the service life of the member, reducing maintenance, improving the efficiency of casting operation, It contributes to the reduction of contamination and improvement of casting quality.

Continued on the front page (51) Int.Cl. ⁶ Identification code FI C22C 14/00 B22F 3/10 G

Claims (2)

[Claims] 1. A titanium carbide particle or a mixture of titanium carbide particles and tungsten particles dispersed in a matrix made of a Ti—W alloy, which is produced by sintering a powder mixture consisting of 20 to 40% by weight of tungsten carbide and the balance titanium. A composite sintered alloy for a non-ferrous metal melt, characterized in that it is a sintered body having a composite structure. 2. A matrix composed of a Ti-W alloy by using a powder mixture of 20 to 40% by weight of tungsten carbide and a balance of titanium as a sintering material and performing a reaction of the following formula in the sintering process: Ti + WC → TiC + W. A method for producing a composite sintered alloy for molten non-ferrous metal, wherein a sintered body having titanium carbide particles or a composite structure in which titanium carbide particles and tungsten particles are dispersed is formed.