JPH0372148B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a cemented carbide that can be suitably used as a wear-resistant member and a method for producing the same. [Technical background] Conventionally, cemented carbide mainly made of WC was WC-Co.
Co-based materials are mainly used, but the binding material is Co
Therefore, the wear resistance is insufficient. In order to improve this wear resistance, it is possible to use an iron alloy as a binder, but Fe causes solid solution of C in WC, which causes a decarburization effect on the WC itself.
It embrittles the alloy, and the embrittled parts are likely to fall off and wear out. In addition, as another means of improving wear resistance, attempts have been made to add around 1% of carbides such as VC, TaC, _{and Cr3C2} to prevent grain growth during sintering and increase hardness. However, the current situation is that dramatic improvements cannot be expected. [Object of the Invention] The object of the present invention is to improve wear resistance by using a high-hardness iron alloy that does not cause decarburization of WC during sintering as a binder instead of conventional Co. The object of the present invention is to provide a cemented carbide and a manufacturing method thereof. [Structure of the Invention] The present invention consists of 70 to 90% by weight of tungsten carbide and the balance is a binder alloy, and the binder alloy consists of 25 to 30% by weight of chromium, 2 to 5% by weight of carbon, and the balance is iron. This purpose was achieved by being an iron alloy and having trichromium dicarbide dispersed in the binder alloy. In manufacturing, WC as well as WC
Fe alloy powder containing 25 to 30% by weight of chromium and 2 to 5% by weight of carbon without causing decarburization is used. When the WC content of cemented carbide exceeds 90wt%, the wear resistance decreases due to the shedding of WC particles, which is caused by the decrease in mechanical strength.
If it is less than %, the amount of WC, which is a hard phase, will be too small and the wear resistance will decrease. Therefore, the amount of WC is 70
~90wt% is desirable. Cr forms a solid solution in Fe together with C to strengthen the base, and also partially combines with C to produce Cr ₃ C ₂ which is precipitated and dispersed in the base to increase wear resistance. For this purpose, it is necessary that it be present in the binder in an amount of 25% by weight. However, if it exceeds 30% by weight, Cr ₃ C ₂
Since the amount of precipitation increases and makes the base brittle, it is necessary to keep it below this amount. Further, in addition to the solid solution in Fe and the formation of Cr ₃ C ₂ described above, C is added to prevent decarburization of WC. A minimum of 2% by weight is required for this purpose, but 5%
If it exceeds % by weight, sinterability will deteriorate, so it is necessary to keep it below that range. In order to disperse Cr ₃ C ₂ throughout the bonded metal phase, individual components such as Cr, C, and Fe can be added in powder form, but alloys of these, Cr ₃ It is better to optionally add compounds such as _C2 , high chromium cast iron, etc. to the specified composition.
The tungsten carbide-iron cemented carbide of the present invention has a uniform and fine structure, which has a significant effect of improving wear resistance. When adding Cr in the form of Cr ₃ C ₂ , the amount of C added is
Reduce the amount of C in Cr ₃ C ₂ . By setting the sintering temperature to 1300-1600°C, uniform dispersion of the trichromium dicarbide fine particles in the bond metal is achieved. If the sintering temperature is lower than 1300℃, the sintered density will be low and it will be difficult to uniformly disperse trichromium dicarbide.If the sintering temperature is higher than 1600℃, the binder alloy will seep out and the trichromium dicarbide will This is not preferable because the aggregation becomes significant. As a result, during sintering, there is no decarburization from the WC, and chromium carbide precipitates in the binder phase, improving wear resistance and improving the wear resistance of the cemented carbide as a whole. can do. [Example] Example 1 Tungsten carbide powder 85 with an average particle size of 1.32 μm
chromium powder, iron powder, carbon powder for alloy formation with 4.05 wt% each,
10.62% by weight, 0.33% by weight (Cr as binder composition)
27% by weight, 70.8% by weight of Fe, 2.2% by weight of C) and 2% by weight of cetyl alcohol were added to these powders and thoroughly mixed in a ball mill. Next, using a hydraulic press machine, press at a pressure of 2.4t/ ^cm2.
A green compact of 10 x 30 x 5 mm was produced. This compacted powder
After holding at 800°C for 10 minutes in a vacuum of 10 ^-4 Torr,
It was sintered at 1500°C for 1 hour. The density of the obtained sintered body was 13.10, the hardness was 1780 on the Bitkers hardness, WC was 85% by weight, Co
It has excellent wear resistance and is far superior to the Bitkers hardness of 1200, which is the standard cemented carbide made of 15% by weight. Example 2 Tungsten carbide powder having an average particle size of 1.32 μm, chromium carbide powder having an average particle size of 3.5 μm, iron powder, and carbon powder were blended in the proportions shown in Table 1, and 2% by weight of cetyl alcohol was added to this. and mixed in a Bobor mill for 5 hours. After this, a compact of 10 x 30 x 5 mm was produced with a press pressure of 2.4 t/cm ² and sintered in a vacuum of 10 ^-4 Torr at the temperature listed in the same table for 1 hour. The characteristics shown in the figure were obtained. Example 3 Chromium cast iron powder with a grain size of -320 mesh containing 27% by weight of chromium was blended with tungsten carbide powder having an average particle size of 1.32 μm in the proportions shown in Table 2, and this was mixed under the same conditions as in Example 2. The powder compact was mixed and shaped, and the green compact was sintered in a vacuum of 10 ^-4 Torr at the temperature shown in the table. The properties after sintering are shown in the same table.

【table】

〔Effect of the invention〕

The sintered body obtained in Example 3 above was subjected to an abrasion test under the following conditions, and the results shown in the attached drawings were obtained. Abrasion tester: Suga flat abrasion tester Load: 3Kg Abrasive paper: Carbon random paper #320 Number of abrasion (back and forth): 2400 times In the same figure, curves A and B are shown in Table 2 obtained by Example 3 ( The cases of sintered bodies according to 3) and (4) are shown, and curves C and D respectively show the case of the conventional WC-Co sintered body which is bonded by 15 wt% Co and the same which is bonded by 18 wt% Co. The results of the wear test of the WC-Co based sintered body are shown below. This figure shows that the sintered body according to the present invention has extremely excellent wear resistance, which is more than twice as high as that of tungsten carbide-based cemented carbide containing cobalt as a binder.

[Brief explanation of drawings]

The attached figure shows the wear resistance properties of the sintered body of the present invention.

Claims (1)

[Claims] 1. Consisting of 70 to 90% by weight of tungsten carbide and the balance being a binder alloy, the binder alloy containing 25 to 30% by weight of chromium.
A tungsten carbide-iron cemented carbide, which is an iron alloy consisting of 2 to 5% by weight of carbon and the balance iron, and is characterized in that trichromium dicarbide is dispersed in the binder alloy. . 2 Chromium carbide powder, carbon powder and iron powder or high-carbon powder to form a binder alloy consisting of iron alloy containing 70 to 90% by weight of tungsten carbide powder, the balance being 25 to 30% by weight of chromium and 2 to 5% by weight of carbon. After mixing and compression molding the same compound with chrome cast iron powder, it is heated to 1300 ~
A method for producing a tungsten carbide-iron cemented carbide, which is characterized by sintering at 1600°C to form and uniformly disperse trichromium dicarbide in a binder alloy.