JPS6043902B2 - weldable cemented carbide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a weldable cemented carbide based on tungsten carbide, and in particular selects the WC grain size and binder in the alloy to enhance thermal shock resistance and improve the meltability of the welding rod. There are some that make it easy to weld to the base metal by using.

Cemented carbide has high hardness, compressive strength, wear resistance, and corrosion resistance, so it has traditionally been used as cutting tools, wear-resistant tools,
It is applied to various aspects such as civil engineering and mining tools.

Moreover, 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, and the like. However, except for the throw-away type, the method of using it is to braze carbide tips to the necessary locations.

Therefore, due to the characteristics of the brazing filler metal, the bonding strength becomes weaker.
Further, peeling may occur due to breakage of the solder, which may cause problems. Furthermore, when these carbide tips become worn or broken during use, it is required that they can be easily replaced on site. However, brazing methods often cannot meet this requirement.
Therefore, the inventors believe that in order for cemented carbide to be used more widely in the above fields, a cemented carbide that can be easily welded by welding rods should be provided. I got to thinking.

As a result of various studies, it was found that a weldable cemented carbide could be provided by improving the thermal shock resistance by selecting the grain size of WC and the binder. The present invention
This was made based on the above knowledge, and in a tungsten carbide-based cemented carbide using nickel and cobalt as a binder, the grain size of tungsten carbide in the alloy is 4 to 8.
A weldable cemented carbide having a total content of nickel and cobalt of 15 to 3 nominal weight % and a part of the tungsten carbide based on titanium, tantalum, niobium, vanadium and chromium. Alternatively, the present invention provides a weldable cemented carbide in which 15% by volume or less is replaced with two or more types of carbides, nitrides, and carbonitrides.

Hereinafter, one embodiment of the weldable cemented carbide of the present invention will be described in detail.

The weldable cemented carbide of the present invention is based on tungsten carbide (hereinafter referred to as WC), with nickel (hereinafter referred to as TNi) as a base.
) and cobalt (hereinafter referred to as CO).

In this case, WC was used as the base because of its toughness, and N1+CO was used as the binder because it has better thermal shock resistance than a single material. Also, W.C.
(The composition range of 5Ni+CO is important, and N1
+CO is in the range of 15 to 3 saliva volume % (hereinafter simply referred to as %).

The lower limit should be determined mainly by the occurrence of weld cracks, and the upper limit should be determined by the presence or absence of deformation such as warping during sintering and wear resistance. Furthermore, regarding the particle size of WC, the particle size of the starting material does not matter, but the particle size after sintering is important. This is because the particle size can be adjusted by adjusting the sintering conditions. And W
The particle size range of C is 4 to 8 pm according to microscopic observation.

The above concept applies to these upper and lower limits. Furthermore, for weldable cemented carbide, if wear resistance and higher weldability (penetration of the cemented carbide) are required, a portion of the WC may be based on titanium, tantalum, niobium, vanadium and chromium. 1 type or more types of carbides, nitrides, and carbonitrides can be substituted by 1% or less by volume.

The reason why the upper limit is set at 15% by volume is that if it exceeds this, there is a risk of welding cracks occurring.

Example 1 Samples were prepared by changing the ratio (CO/Ni+CO) of WC with (Ni+CO) as a binder at 15% and 30%, respectively, as shown in Table 1, and at a sintering temperature of 1400°C. , 1450°C, and 1500°C.

If the amount of (Ni+CO) is 15%, WCl7OOg
7 to (Ni + CO) 300g 1 carbide ball 4k9
Then, 700 cc of acetone was added and mixed in a ball mill for 50 hours.

Then, while drying these combined powders, 40g of paraffin was added as a molding aid, and the mixture was heated at a pressure of 1t/Clt to 50g of paraffin.
A green compact of ×50×40T0L was formed and sintered in a vacuum/air furnace for 1 hour each.In this case, the blended amount (300g) of (Ni+CO) was 213 as the ratio of CO/Ni+CO.
,315,112,215,113,1110,113
I chose 0. In addition, when the amount of (Ni + CO) is 30%, (Ni + CO) is 600% for WCl4OOg.
g and sintered in the same manner as above.

In addition, for these samples, the grain size in the alloy was
It was adjusted to a range of μm.

The reason why it is adjustable is that during ball milling, WC is pulverized and becomes finer than the starting particle size, but during sintering, WC grows due to the phenomenon of dissolution and precipitation of WC into Ni and CO phases.
This tendency becomes more pronounced as the WC particle size becomes smaller, as the amount of Ni+CO increases, and as the sintering temperature increases. Next, after sandblasting the surfaces of these samples, 200×
One fillet weld was performed on a 300 x 10 size stainless steel base material (SUS3O4) using a Ni-Fe welding rod.

Therefore, the number of broken cards in Table 1 is per one loss. The results are shown in Table 1, and when the WC grain size in the alloy is 3 μm, 3 to 3 out of 10
Weld cracks appeared on 7 pieces.

In addition, the peel strength of the product of the present invention is 45 to 22k.
It showed a good score of 9/WOfL2. In addition, regarding the samples of WC-10%Ni and WC-10%CO prepared for comparison, 9 of the former and 1 of the latter (all samples) had weld cracks. From the results in Table 1, it was found that the lower limit of the WC grain size in the alloy was 4 μm, and the lower limit of the amount of Ni+CO was 15%.

Also, regarding the upper limit of Ni+CO amount and WC particle size,
The need for corrosion resistance, abrasion resistance, and manufacturing technology issues should be taken into consideration.
%, and the latter was found to be preferably 8 μm from the viewpoint of wear resistance as determined by a rotational wear test. In this rotational wear test, a sample was placed in a cylinder together with a cemented carbide ball, and the volumetric wear amount was measured. Regarding the component ratios of Ni and CO, the object of the present invention can be achieved even if either of them is large, but as a tendency, a larger amount of Ni is preferable. This is thought to be because Ni is less sensitive to heat than CO, and a similar tendency was observed in the thermal crack test using the spark discharge method. This spark discharge method uses copper electrodes to discharge at 300V and 340μF, and
%(Ni+CO) and the total length of thermal cracks for WC average grain size of 4 to 5 μm. As a result, as shown in Figure 1, the amount of Ni less than 112 and less than 215 was reduced to CO.
The effect increases in the order in which you do it. However, in consideration of weld cracking, it has been found that the entire range of CO/Ni+CO amounts excluding 0 and 1 is effective. This is because both Ni and CO are completely solid types. Example 2 Example 2 is an example in which a part of WC was replaced with another carbide.

In this case, based on WC-20% (Ni+CO), WC
3%, 5%, and 15% of the parts are TiC and Cr3C, respectively.
2. An alloy in which TaC was substituted was prepared and a welding test was conducted in the same manner as in Example 1. This is because adding other carbides to the WC-based cemented carbide can improve wear resistance, weldability due to penetration of the cemented carbide, and the like. These results are shown in Table 2,
In the case of adding TiC and Cr3C2, the tendency was almost the same as in Example 1. On the other hand, in the case of TaC, no weld cracks occurred even when 15% was added. However, two tests were conducted separately.
In the case of 0% addition, 10I9. There were cracks in the middle 3 pieces. These differences are not due to the thermal sensitivity of TiC, Cr3C2 and TaC, but are volume differences resulting from the difference in specific gravity.
In terms of volume ratio, the range where no thermal cracks occur is TiC
, Cr3C2 and TaC were found to be less than 1% by weight.

This led to the development of a weldable cemented carbide with improved corrosion resistance and wear resistance. In the case of double carbides, it has been confirmed that welding is possible if TiC-TaC, ■C-NbC, and TiC-TaC-Cr3C2 are added in a total amount of 15% or less.

This is the result shown in the second half of Table 2. Furthermore, as shown in Table 3, samples were also prepared and tested in cases where TiN and TiCN were added, and it was confirmed that fillet welding was possible and the peel strength was sufficient*. Also,
The same thing was confirmed for other nitrides and carbonitrides. The weldable cemented carbide of the present invention showed sufficient strength in the peel test. This peel test was conducted by the method shown in FIG. That is, various types of weldable cemented carbide 2 obtained in Examples 1 and 2 were welded to a stainless steel plate 1 of 55 x 130 x 10 T1rm, and this was statically pressurized with a punch 3 to peel it off. It is something. As mentioned above, the welding in this case is fillet welding on two sides, and its peel strength is 45
It showed ~55 kg/Mm2. This is a much stronger bond than 30 to 35 kg/Mm2 in the case of conventional brazing. As explained above, the present invention improves the thermal shock resistance of a WC-(Ni+CO) based cemented carbide by selecting the WC grain size and (Ni+CO) content in the alloy. Therefore, we have provided a weldable cemented carbide that can be used satisfactorily in welding, where extremely hot parts are heated at a higher temperature than brazing, so it can be used as corrosion-resistant and wear-resistant parts in the chemical industry, mechanical industry, etc. , which has the advantage of expanding its field of use.

[Brief explanation of drawings]

Figure 1 is a characteristic diagram showing the relationship between the amount of Ni+CO and thermal cracking obtained by the spark discharge method, and Figure 2 is a rough outline of the peel test of the weldable cemented carbide obtained by the present invention. FIG.

Claims (1)

[Scope of Claims] 1. A corrosion-resistant and wear-resistant cemented carbide made of tungsten carbide containing a binder made of nickel and cobalt, wherein the tungsten carbide has a grain size of 4 to 8 μm in the alloy. Welding, characterized in that the total content of nickel and cobalt (Ni+Co) is 15 to 30% by weight, and the content ratio of cobalt (Co/Ni-Co) is in a range excluding 0 and 1. Cemented carbide possible. 2 Corrosion-resistant and wear-resistant cemented carbide containing tungsten carbide as a main component and a binder made of nickel and cobalt, the tungsten carbide containing titanium, tantalum, niobium, vanadium, and chromium as a base. The alloy contains 15% by volume or less (not including 0) of one or more carbides, nitrides, and carbonitrides, and the grain size of tungsten carbide in the alloy is 4 to 8 μm.
and the total content of nickel and cobalt (Ni+Co) as the binder is 15 to 30% by weight, and the content ratio of cobalt (Co/Ni+Co) is in a range not including 0 and 1. A weldable cemented carbide characterized by: