JPH02209449A - Sintered hard alloy containing composite area - Google Patents

Abstract

PURPOSE:To combinedly provide the sintered hard alloy with excellent toughness and wear resistance, in a sintered hard alloy constituted of a hard dispersed phase contg. WC and a bonding phase of iron-group metal, by forming the area with changed quantity of the bonding phase on the alloy surface as compared to that of the inner part into the specified thickness. CONSTITUTION:The sintered hard alloy is constituted of a hard dispersed phase contg. WC and a boding phase of iron-group metal; the alloy surface contains the area having reduced quantity of the bonding phase as compared to that of the inside; and ts/td, i.e., the ratio of the thickness td in this area to the thickness ts in the area of the quantity of the average bonding phase is regulated to 1.0 to 1000. The sintered hard alloy contains the area having reduced quantity of the bonding phase of Co, etc., on the surface, by which wear resistance on the alloy surface can be maintained or improved. At the same time, the bonding phase of Co, etc., and relatively be increased inside of the alloy which does not contribute to the wear resistance, so that high toughness can be imparted as a whole. When the ratio ts/td is <1.0, the lowering of the toughness is high and, conversively, in the case of >1000, wear resistance can not be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a cemented carbide having both excellent toughness and wear resistance.

[Conventional technology]

BACKGROUND ART Conventionally, cemented carbide consisting of a hard dispersed phase containing WC, Tie, etc., and a binder phase of iron group metals such as Fe, Ni, and Co has been used as an alloy for tools. We-C! is especially suitable for forged tools such as punches and headers that require wear resistance and impact resistance. .

Cemented carbides are mainly used.

In order to improve the performance of these cemented carbides as tools, efforts have been made to improve wear resistance and toughness by adjusting the Co content and making the WC finer.

However, since wear resistance and toughness are contradictory properties,
It was difficult to improve both at the same time. For example, WC! -C! In o-based cemented carbide, when increasing the amount of Co to impart high toughness, wear resistance inevitably decreases.
Conversely, if the amount of Co is reduced, the wear resistance will improve, but the toughness will decrease.

Due to these circumstances, the use of cemented carbide as wear-resistant and impact-resistant tools has been limited compared to high speed steel.

[Problem to be solved by the invention]

In view of such conventional circumstances, an object of the present invention is to provide a cemented carbide that has both excellent toughness and wear resistance and is suitable as a wear-resistant and impact-resistant tool.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a cemented carbide comprising a hard dispersed phase containing WC and a binder phase of iron group metal, which has a region on the alloy surface with a reduced amount of binder phase than the inside of the alloy, It is characterized in that the ratio ts/td of the thickness td of this region with reduced binder phase amount to the thickness ts/ of the average binder phase amount region other than this region is 1.0 to 1000.

As a means of forming a region on the surface of a cemented carbide with a reduced amount of binder phase than the inside of the alloy, a press forming mold is filled with powder having a predetermined amount of binder phase (average amount of binder phase), and the surface and There is a method in which a powder with a reduced amount of binder phase is filled into a portion where the binder phase is reduced, which is then press-formed and then sintered. In addition, after press forming using only powder with a predetermined amount of binder phase, the binder phase on the surface is segregated inside the alloy by repeating carburization and decarburization in the sintering process, and as a result, the amount of binder phase on the surface is increased. There is also a method of forming a region with reduced .

[Function] Since the cemented carbide of the present invention has a region in which the amount of binder phase such as Co is reduced on the alloy surface, wear resistance on the alloy surface is maintained or improved. At the same time, it is possible to relatively increase the amount of a binder phase such as Co within the alloy that does not contribute to wear resistance, so it is possible to provide high toughness as a whole.

The ratio ts/td of the thickness t(l) of the region with reduced binder phase amount to the thickness ts of the average binder phase amount region other than this region is 1.0
~1000. If this ratio ts/td is less than 1.0, the region with reduced binder phase content is too thick, resulting in a large decrease in toughness at the surface, while if it exceeds 1000, the reduced binder phase region is too thin and wear resistance is not improved.

〔Example〕

Example 1 Further G was added to the outer periphery of WC-15wt% co powder which was press-molded into a cylindrical shape with an outer diameter of 20 nm and an inner diameter of 10 nm using a mold.
This We-7 wt% CO powder was press-molded to a thickness Q of 5 ms to form a multilayer structure, and sintered at 1400C. The ratio ts/td of the thickness td of the region with reduced binder phase amount on the alloy surface (outer periphery) of the obtained alloy to the thickness ts/ of the average binder phase amount region other than this region was 10.

The obtained alloy sample was used as a punch for forward extrusion, and 5O
A life test was conducted on R21 at a cross-sectional area reduction rate of 58% and an extrusion length of 10 cycles. For comparison, regular WC! -7wt%
CO alloy (sample A) and WC! A punch made of -15 wt% CO alloy (Sample B) was also tested in the same manner. As a result, 120,000 shots were possible with the alloy of the present invention. However, in Comparative Example A, cracks occurred after 60,000 pieces and reached the end of its life, and in Comparative Example B, the wear was so severe that it became unusable after 40,000 pieces.

Example 2 Same as Example 1, but the ratio ta/ls was 1 (Sample C)
, 10 (sample D) and 20 (sample E) were made, and using these alloys, 8150 with an initial shape of 32 mm in diameter and length/diameter 1.5 was forged (forward extruded) to form a cab blank. processed. The life of the punches at this time was 40,000, 120,000, and 100,000 for samples OSD and E, respectively.

However, for comparison, the normal "l-7wt%C
O alloy (sample A) and WC! In a similar test using a -15wt% CO alloy (sample B), sample A developed cracks and reached the end of its life after 20,000 pieces, and sample B was so worn that it became unusable after 3000 pieces.

Example 3 Only WO-15wt% CO powder was press-molded into a predetermined shape. After sintering the compact at 1400 tr, it was cooled to 1300 t: at 2 C/min in a co atmosphere and then heated from 13ooC to 1350C at 27:/min in a 30 ton(r) OH atmosphere. and held at 1350C for 1 hour. This treatment reduces the amount of Co on the alloy surface by about 30%, and the OO on the alloy surface decreases by about 30%.
The ratio ts/td between the thickness tel of the iO-poor region and the average thickness of the CO-poor region other than this region, 70, was 500.

When the obtained alloy was subjected to the same life test as in Example 1, it was found that up to 130,000 pieces could be used.

〔Effect of the invention〕

According to the present invention, it is possible to provide a cemented carbide having both excellent toughness and wear resistance by forming regions with different amounts of binder phase on the surface and inside the alloy.

Therefore, this cemented carbide is suitable as a wear-resistant and impact-resistant tool used in forging and the like.

Claims (1)

[Claims] (1) In a cemented carbide consisting of a hard dispersed phase containing WC and a binder phase of iron group metal, the alloy surface has a region where the amount of binder phase is reduced compared to the inside of the alloy, and the thickness of this region where the amount of binder phase is reduced is s td and the thickness ts of the average binder phase amount region other than the region
A cemented carbide having a ratio ts/td of 1.0 to 1000.