JPS5924173B2 - weldable cemented carbide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a weldable cemented carbide, and particularly to a weldable cemented carbide that can be easily welded to a base metal by melting a welding rod.

Cemented carbide has high hardness, compressive strength, wear resistance, and corrosion resistance, and is used in various fields such as cutting tools, wear-resistant tools, and civil engineering and mining tools.

Recently, there has been a strong tendency for them to be used as corrosion-resistant and wear-resistant members in the chemical industry, mechanical industry, etc.

However, since cemented carbide is more expensive and has a higher specific gravity than structural steel, stainless steel, etc., efforts have been made to reduce the amount of cemented carbide used and increase its effectiveness. , the cemented carbide is brazed onto other base metals.

However, due to the characteristics of the brazing material, brazing has a low bonding strength, and the bonded portion often peels off during use due to breakage of the brazing material, which often causes problems.

More importantly, if these cemented carbide parts wear out or break during use, ideally they can be easily replaced on the spot, and brazing is prohibited by law. Demands are often not met.

For these reasons, the inventors have developed a cemented carbide that can be used more widely in the above-mentioned fields and that can be easily welded by melting a welding rod. I came to think that it is necessary.

As a result of various studies, the inventors found that it is possible to provide a weldable cemented carbide by improving thermal shock resistance by selecting the grain size of tungsten carbide and the amount of binder.

The present invention has been made based on the above findings, and provides a tungsten carbide-based cemented carbide using cobalt or nickel as a binder. A part of the weldable cemented carbide having a cobalt or nickel content of 15 to 30% by weight and the tungsten carbide is replaced by titanium, tanker,
The present invention provides a weldable cemented carbide in which up to 15% by volume of one or more carbides, nitrides and carbonitrides based on niobium, vanadium and chromium are substituted.

Hereinafter, the weldable cemented carbide of the present invention will be described in detail based on Examples.

[Example 1] *The samples contained tungsten carbide (WC) and cobalt (hereinafter referred to as Co) as a binder.
5% by weight (hereinafter simply %), created to be 30% 1
child.

In the case of WC-15%Co, C for WC1700P
o300P, carbide ball 4 kg-B Yobi T seton 7
00 cc was added and mixed in a ball mill for 50 hours, and then, while drying the powder, 40 g of paraffin was added as a molding aid and molded into a 50 x 50 x 4 mm O powder compact at a pressure of 1 tΔ. This was sintered in a vacuum furnace. It is something.

In this case, the starting average particle size of WC is 3 μm x 5 μm
, 7μm, respectively at 1400°C and 1450°C.
'C, sintered at 1500°C for 1 hour each.

WC-30%Co is for WC1400P,
Co600P was added and sintered in the same manner as above.

Table 1 shows the results of measuring the particle size of WC in the sintered alloy using a microscope for these samples.

° In this case, when WC and CO are mixed, Wc becomes finer than the starting particle size when pulverized, but during sintering, the WC
WC grows by the phenomenon of dissolution precipitation into the O phase, and the tendency is that the smaller the WC particle size and the more Co there is,
Also, the higher the sintering temperature, the more pronounced it is.

Therefore, the average particle size of WC in the sintered alloy can be easily adjusted.

Next, the surfaces of these samples were subjected to side blast treatment, and then a stainless steel base material (SU
S304) Weld 10 pieces each on f.

As for the welding rod, use a Ni-Fe type one.

Table 2 shows the degree of weld cracking as a result of welding the alloys in Table 4.

In this case, normal cemented carbide tends to generate thermal stress because the expansion coefficients of its constituent phases are greatly different1, and in particular, brazing in a short period of time is difficult to achieve during welding, where extremely local parts are heated above the temperature. If cracks occur.

The numbers in the table indicate the number of samples with cracks after the 10-piece welding test.

For example, in the case of WC-15%Co, 3 μm, and 1400° C., cracks appeared in 7 out of 10 sheets, and no cracks appeared in the remaining 3 sheets.

From Table 1, We-15%Co and WC-3
It can be seen that with 0% Co, weld cracks did not occur in alloys with a WC grain size of 4tlJn or more.

This showed the same tendency as the preliminary evaluation of thermal shock properties by the spark discharge method.

In this test, copper electrodes were used to test cemented carbide at 300cm and 340cm.
μF.

The occurrence of thermal cracks was measured by discharging the battery.

As can be seen in Figure 1, this evaluation of thermal shock resistance shows that the larger the WC grain size in the alloy, the greater the Co content, the better the thermal shock resistance. In the following cases, there shall be no cracks due to welding as described above.
It turns out that the lower limit of the amount is 15%.

On the other hand, the cemented carbide that can be welded according to the present invention needs to have high corrosion resistance and wear resistance due to its use8, and due to manufacturing technology issues, the upper limit of the UCo amount should be set based on the WC6 grain size. It is.

For this setting, a rotational abrasion test was conducted to find the upper limit of the WCC particle size and the amount of Co.

The results of the rotational wear test are shown in Figure 2, which is
15 mm ψ x 10 mm sample (A-D) K total weight 45 kg
The ball was charged into the cylinder at the same time as the carbide ball, and the volumetric wear amount was measured.

In this case, the amount of Co is 30% for A-C and 3% for D.
5%, iy && in that alloy, A is 3
μm, B is μm, and C8 and D are 7 μm.

For comparison, sample E was prepared by spraying a commercially available thermal spraying material onto gold and gold and polishing it into the same shape.

As shown in Figure 2, the wear resistance of cemented carbide is WC
The smaller the particle size and the smaller the amount of Co, the better.

The wear resistance of the sample is 1. This is about twice that of sample E, and the advantage of using an expensive cemented carbide diminishes.At the same time, when the Co content reaches 35 cycles, warpage and other deformations occur during sintering, making it impossible to obtain the specified size and shape. You won't be able to get it.

Therefore, it was found that the upper limit of the Co content was 30% and the upper limit of the WC grain size in the alloy was 8 μm.

[Example 2] Example 2 is the same as Example 1 using N1 powder instead of Co.
A welding test was conducted on a cemented carbide with a Ni binder made using the same WCf as in Example 1 and using the same method as in Example 1.

The degree of cracking in the cemented carbide with the Ni binder was somewhat lower than that with the Co binder, but the WC0 in the alloy
When the particle size was μm and the amount of N1 was 15%, the force was insufficient to the extent that no cracks were formed.

The WC grain size in the alloy by microscopic observation shows that even in the case of Ni, C
Although there was no big difference in the case of o, the NiO
The fact that there are fewer thermal cracks suggests that the alloy using Ni is less sensitive to heat.

[Example 3] Example 3 is a cell in which a part of WC is replaced with another carbide.

In this case, based on WC-20%Ni, 5
%, 10%, and 15% of Tic, Cr5(J5
In the case of TaC, replace by 10%, 20% f
This alloy was made and a welding test was conducted in the same manner as in Example 1.This shows that adding other carbides to cemented carbide improves wear resistance, weldability (melting of the cemented carbide), etc. Because it can be done.

As a result, in the case of addition of TiC and Cr3C, Example 1
The same trend was observed, with no weld cracks occurring when 5% was added, and weld cracks appearing when 10% and 15% were added.

On the other hand, in the case of TaC, there were almost no weld cracks even with 15% addition, and cracks appeared in 3 out of 10 sheets with 20% addition.

These differences are TiC, Cr3, Cr3 C2 and TaC
The difference in volume is not due to the thermal sensitivity of the material, but is due to the difference in specific gravity.When converted to a volume ratio, the range in which thermal cracks do not occur is approximately 15% by volume in the case of T t C1Cr 3C2,3 and TaC. I understand.

As a result, a weldable cemented carbide with improved corrosion resistance and wear resistance has been developed.

8. TiC and TaC, VC and NbC, or TiC
It was confirmed that welding was possible even when TaC, Cr3C2, etc. were added at the same time in a total amount of 15 volume or less.

Furthermore, it can be easily assumed that similar characteristics will be exhibited even if ZrC, HfC, etc. other than the above-mentioned carbides, or nitrides and carbonitrides such as TiN, T1CN, etc. are added.

The weldable cemented carbide of the present invention constructed in this manner showed sufficient strength even in the peel test.

This was done by the method shown in Fig. 3, in which a stainless steel plate 1 measuring 55 x 130 x 10 mm was welded with various types of weldable cemented carbide 2, such as those obtained in Examples 1 to 3. , which was statically pressed with a punch 3 and peeled off.

The welding in this case is fillet welding on two sides,
Its peel strength was 45-55 kg/n4, which is 9/vt compared to 30-35 when brazing! t
However, it is much more strongly bonded.

[Example 4] Example 4 is an example in which a part of WC is replaced with TiN.

That is, based on WC-20 Ni, 1 of the WC part
%, 4%, 7%, and 10% were replaced with TiN to prepare a single alloy, and a welding test was conducted in the same manner as in Example 1.

This is expected because when nitrides such as TiN are added to WC-based cemented carbide, improvements in wear resistance, oxidation resistance, etc. are generally observed.

The sintering temperature in this case was 1450° C., and the WC particles in each sample were adjusted so that the average particle diameters after sintering were 3 μm, 5 μm, and 17 μm, respectively.

The results are shown in Table 3, and the numbers in the table indicate the number of cracks in one case when 10 pieces were welded.

As can be seen from Table 3, when the average particle size of WC is 3 μm, cracks occur in all pores, indicating that the particle size has a large effect.

On the other hand, when the average particle size of WC was 5 μms to 7 μm, cracks did not occur when the amount of TiN added was 1% and 4%, but cracks occurred when the width increased to 7 μm.

Similar to Example 3, this is not due to the thermal sensitivity of TiN, but is thought to be due to a volume difference resulting from a difference in specific gravity.

Therefore, it was found that the range in which thermal cracks do not occur is 15% by volume or less when converted to a volume ratio.

Also, for TaN, NbNE and VN, similar to the case of TiN, alloys are made based on WC-20%Ni, with 1%, 4%, 7 width and 10% of the WC portion replaced with the above nitrides. A welding test was conducted in the same manner as in Example 1.

As a result, even with nitrides other than TiN, the grain size of WC is 4 to 8 μm, and the force 1 is 1 in the WC portion, similar to TiN.
It was confirmed that if the amount of nitride substitution is 5% by volume or less, it can be used as a weldable cemented carbide.

[Example 5] Example 5 is an example in which a part of WC is replaced with TlCN"ii?, and like Example 4, WC-20%Ni
f group, and the substitution amount is also 1%, 4%, 7
%, with a width of 10.

As a result, it was confirmed that the range in which thermal cracks do not occur due to welding is 15% by volume or less in terms of volume ratio.

It has also been found that for carbonitrides other than T1CN, such as TaCN and NbCN, it is preferable to replace the WC portion with an amount of 15% by volume or less.

Furthermore, the weldable cemented carbide obtained in Examples 48 and 5 was subjected to a fillet weld peel test as shown in FIG.
As explained above, the present invention provides a WC-Co-based material with a separation strength of 55 kg/In.
Regarding C-Ni-based cemented carbide, the WC grain size and Co or Ni content in the alloy are selected to improve thermal shock resistance, so it can be used at higher temperatures than brazing. Since the product provides a weldable cemented carbide that can be used even in welding where extremely hot parts are heated in has advantages.

[Brief explanation of the drawing]

Figure 1 is a characteristic diagram showing the relationship between the amount of Co and thermal cracking obtained by the spark discharge method, and Figure 2 is a characteristic diagram showing the relationship between the wear time and volumetric wear amount obtained by the rotational wear test. , FIG. 3 is a diagram conceptually showing a peel test of the weldable cemented carbide obtained according to the present invention.

Claims (1)

[Scope of Claims] 1. Corrosion-resistant and wear-resistant cemented carbide made by containing cobalt or nickel as a binder in tungsten carbide; 8μ
A weldable cemented carbide, characterized in that the content of cobalt or nickel is 15 to 30% by weight, and is welded to the base metal as the welding rod melts. . 2 Corrosion-resistant and wear-resistant cemented carbide containing tungsten carbide as a main component and cobalt or nickel as a binder. and chromium-based type 1 or 2
The grain size of tungsten carbide in the alloy contains up to 15% by volume of one or more carbides, carbonitrides, or one or more nitrides based on titanium, tantalum, niobium-8, and vanadium. is 4 to 8 μm, and the cobalt or nickel content is 15 to 30% by weight,
A weldable cemented carbide, characterized in that it is welded to a base metal as a welding rod melts.