JPH02200744A - Manufacture of tungsten carbide-base sintered hard alloy for cutting tools having less dimension in void defect - Google Patents

Abstract

PURPOSE:To obtain the sintered hard alloy for cutting tools having less defect caused by the segregation of cobalt by using coated power of which the surface of hard carbide material powder is coated with Co as a raw material. CONSTITUTION:The surface of respective hard material powder constituted of (A) WC, (B) the solid solution carbide and solid solution nitride of W and Ti and (C) the solid solution carbide and solid solution nitride of W and Ti with one or more kinds among the transition metals in the groups IVa, Va and VIa (except W and Ti) is coated with Co as a bonding phase. The coated powder is added with a forming auxiliary, which is subjected to press forming and sintering to obtain the WC-base sintered hard alloy for cutting tools. The coating of Co is executed by electroless plating, a deposition method or the like. In this way, dimension in void defection caused by aggregated Co is re duced, by which the effect of showing excellent capacity when used to tools for intermittent cutting applied with impact loads can be obtd.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to the production of tools for interrupted cutting under impact loads, and is particularly concerned with the production of tools with small defect sizes caused by cobalt segregation and with fracture-resistant properties. The present invention relates to a method for producing an excellent tungsten carbide-based cemented carbide for cutting tools.

(Prior Art) Conventional cemented carbide for cutting tools uses, for example, tungsten carbide powder and Co powder, or tungsten carbide powder, solid solution carbide powder, and Co powder as raw material powders, and these raw material powders are It is manufactured by blending into a predetermined composition, crushing, mixing, press molding 2, and finally sintering.

(Problem to be solved by the invention) By the way, in these conventional manufacturing processes, during pulverization and mixing, coagulation and coagulation of several micrometers to several tens of micrometers mixed in the Co raw material powder occur.
Since the aggregated Co particles cannot be made sufficiently fine, these aggregated Co particles exist dispersed between the carbide particles, and during sintering, they are melted and sucked up between the carbide particles, resulting in the formation of pores. Ru. The diameter of the pores is several J1m-several 1-μm, and the pores are the starting point for fracture of tungsten carbide/base cemented carbide; when used in applications that carry impact loads of ft. It was short.

As a countermeasure, pressure sintering or hot isostatic pressing (HIP) after sintering is known, but commercially available cemented carbide contains void defects up to several tens of diameters deep. However, sufficient effects have not been obtained.

In addition, a manufacturing method using a composite coated powder in which the surfaces of solid solution carbides and solid solution carbonitrides are coated with iron-based metals, WC powder, and powder of one or more types of iron-group metals is disclosed in JP-A-60 Although this method can prevent agglomeration of solid solution powders during sintering, there are agglomerated single Co particles in the Co raw material, which causes pores as described above. This is not sufficient as a countermeasure against pores.

(Means for Solving the Problems) Therefore, the present inventors conducted research to produce a cemented carbide with excellent fracture resistance, and found that the surface of the WC raw material powder and the solid solution raw material powder was coated with Co. When powder is used as a raw material powder and Co powder is not used as a raw material powder, Co aggregates observed in existing manufacturing methods will not be generated, and after sintering, the cemented carbide will contain particles with a maximum diameter of about 10-odd micrometers. It was discovered that only vacancies remained.

(Function) The present invention is based on the above knowledge, and the typical composition of the target WCC cemented carbide is A as a hard substance.
) WC, B) (WTi) carbides and carbonitrides as solid solution components, C) (W, Ti, M) carbides and carbonitrides (
However, M is Zr+tlf+V, Ta.

Only A) of (representing one or more types of Nl+),
Contains A) and B) or A) and C) to the same extent as commercially available cemented carbide tools, that is, 85 to 96% by weight, and the balance is 4 to 15% by weight.
is Co which becomes the bonding phase.

A tool manufactured by coating A) with Co is a tool with particular emphasis on mechanical damage resistance, and a tool manufactured with A) and C) coated with Co places particular emphasis on thermal damage resistance. The tool produced by coating A) and B) with Co is a tool that exhibits intermediate performance between A) or A) and C) described above.

Co as a binder phase is added in the form of coating a hard compound by the following method so that the content in the cemented carbide is 4 to 15% by weight. If it is less than 4%, the transverse rupture strength will be insufficient and if an impact load is applied to the tool, it will easily break, so 4% or more is required. If it exceeds 15%, the impact resistance properties will improve, but the abrasion resistance will deteriorate, so it is necessary to keep it below 15%. Co
Addition is done by electroless plating, chemical vapor deposition method (thermal CVD, plasma CVD), physical vapor deposition method (vacuum deposition method, sputtering method)
This is done by coating carbide or carbonitride with co@ by a method such as . The reason why these methods were selected is that a pattern with a relatively uniform thickness can be formed. mixture,
After press forming, the cutting tool is manufactured by sintering and grinding.

Next, the present invention will be specifically explained using examples.

Example 1 Coated powder in which the surface of -C powder with an average particle size of 1.5 μm was coated with Co to an average thickness of 0.2 pm by electroless plating method (WC: Co 90:10 in weight ratio) Add an appropriate amount of molding aid and mix in a ball mill to make 1.5 L/
After press molding at a pressure of c+fl, the temperature was 1380″C.
Sintering was carried out under conditions of a holding time of 90 ml and a pressure of 0.5 torr. A bending test piece and a cutting tool were cut out from this sintered body by grinding and finished to predetermined dimensions. Comparative materials were -C powder with an average particle size of 1.5 μm and -C powder with an average particle size of 1.5 μm. O)t
m of Co powder was crushed and mixed at a weight ratio of 90:10, and a solvent and a lubricant were added to form granules, which were then sintered under the same conditions as above to cut out bending test pieces and cutting tools. It was made by

As a result of observing the fracture origin on the fracture surface after the bending test using an electron microscope, in the case of the comparative material, pores with a diameter of 60 pm caused by agglomerated Co were detected. On the other hand, in the case of the present invention material, a 5 pti defect was detected at the starting point of fracture, and there was a c.
No segregation of o was observed.

Next, the cutting evaluation test results will be described.

The material of the work material is JIS 555C, and the shape is a round steel with a diameter of 55ffII11 and a length of 350 am, with five grooves of 10 mm width machined at equal intervals in the direction parallel to the rolling direction on the surface layer. The cutting conditions are V = 160 m/lll1n, d
=2.0++ua, f =0.25M/rev. Comparing the tool life based on the number of collisions with the groove, the comparison material was 2.
．． Both Ts were deleted in 5×10” cycles.

With the material of the present invention, tool breakage did not occur even after 5×10' cycles. However, the wear progressed at 2 and the tool life reached the end at 7. It is clear that reducing the hole defect size significantly improves tool chipping 11.

Example 2 Partial powder with average particle size i,, 5/1111 and (W,
Ti, Ta) Raw material powder coated with Co on the surface of C powder 7 with an average film thickness of 0°2 μm by vacuum evaporation method (weight ratio: WC:TiC:TaC:Co=80:5:
5: Add an appropriate amount of molding aid to 10), mix in a ball mill, press mold at a pressure of 1.5 t/cd, then heat at 1380°C, hold time 90ml, pressure 0,5
It was sintered under conditions of torr. A bending test piece and a cutting tool are cut out from this sintered body by grinding, and a predetermined
1" method. Comparative materials are tag powder with an average particle size of 1.5, (W, Ti, Ta) C and an average particle size of 1.0-
C.

Powder (weight ratio: WC:TiC:TaC; Co=80:5
:5:10) was crushed and mixed, and a solvent and a lubricant were added to form granules, which were then sintered under the same conditions as above, and bending test pieces and cutting tools were cut out.

As a result of observing the fracture origin of the fracture surface -L after the bending test using an electron microscope, in the case of the comparative material, pores with a diameter of 504 due to ia-aggregated Co were detected. On the other hand, in the case of Invention H, a defect of 8 μI was detected at the starting point of fracture, and there was a C
No segregation of o was observed.

Next, the cutting evaluation test results will be described.

The material of the work material is INS 555C, and the shape is a round steel with a diameter of 55 mm and a length of 350 mm, with 5 grooves of width 1.0111 mm (O) machined at equal intervals on the surface layer in the direction parallel to the rolling force direction. The cutting conditions are V = 160 +n/n1r
i, d -2°0ff1111. f-〇. 25 marks/r
It is ev. Comparing the tool life based on the number of collisions with the groove, the comparison material had 1.2 x 102 collisions, with only one member missing. With the present invention material, tool breakage did not occur even when 3×106 was used.

However, wear has progressed]: The tool life has been reached. It is clear that reducing the hole defect size significantly improves tool chipping.

(Effects of the Invention) As can be seen from the two series of examples, according to the present invention, which uses a coated powder in which the surface of a hard carbide raw material powder is coated with Co as a raw material, cutting with fewer defects caused by cobalt segregation can be achieved. It is possible to produce tungsten carbide-based cemented carbide for tools, and when it is used in tools for interrupted cutting that are subject to shock loads, it exhibits excellent performance. 2. The industrial effects are extremely remarkable. .

Claims (1)

[Claims] Hard substances include A) tungsten carbide, B) solid solution carbide and solid solution carbonitride of W and Ti, and C) W and Ti.
Of the solid solution carbides and solid solution carbonitrides of W and Ti and one or more of the transition metals of Groups 4a, 5a, and 6a of the periodic table excluding B), or when producing a tungsten carbide-based cemented carbide containing A) and C) above and further containing Co as a binder phase, Co is added to the surface of the hard substance powder.
A method for producing a tungsten carbide-based cemented carbide for cutting tools with small pore defect sizes caused by cobalt segregation, characterized by using only coated powder coated with as a raw material.