JPS61124548A - Ultrafine particle sintered hard alloy - Google Patents

Abstract

PURPOSE:To obtain the titled hard alloy having superior toughness and improved resistances for wear, pitching, by adding a specified quantity of Hf to sintered hard alloy in which hard phase composed mainly of WC and Fe group, Cr group elements are joined at a specified ratio. CONSTITUTION:By weight ratio, 75-90% hard phase (having <=0.8mu average grain size of WC) composed mainly of WC is bonded with 10-25% element of >=one kind among Fe, Cr groups (excluding Mo) to manufacture sintered hard alloy. To said alloy, 0.3-3.2% Hf or Hf carbide is added. By substituting <=about 5% WC by 0.1-5% one or 2 kinds among TaC, NbC, suppressing effect of grain growth can be promoted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ultrafine particle cemented carbide used in various applications as solid end mills and drills.

[1. American technology] WC-based hard alloys are widely used as alloy materials for cutting tools and wear-resistant tools. Rotary tools such as end mills and drills use ultrafine-grain cemented carbide, which has increased strength by dispersion strengthening by refining WC grains.

When cutting steel with a rotating engineer, cutting at low speed will generate a built-up cutting edge on the tool cutting edge. If cutting continues further, the built-up cutting edge will fall off from the tool cutting edge. By continuing cutting while repeating the attachment and detachment of the built-up cutting edge, the cutting edge of the tool is repeatedly subjected to stress, which eventually leads to chipping.

[Problem 3 to be solved by the invention Tool materials that can withstand the above phenomena are
A material with low reactivity is desirable.

Therefore, the requirements for materials used in rotating tools are (
Two points are achieved: 1) A cutting edge that is strong and resistant to repeated stress can be obtained, and (2) a single-component cutting edge is less likely to occur due to welding of the work material.

[Means for solving problems]

The present invention is characterized by ultrafine particles consisting of 75 to 90% of a hard phase mainly composed of WC, and 10 to 25% of a binder phase of one or more of the iron group and the Or group (excluding MO). Add 0.1 to 3.2% Hf or Hf carbide to hard alloy
It is characterized by the addition of

In the present invention, when the above-mentioned WC has a large particle size, the binder layer becomes thicker and easily falls off from that part, causing chipping. Therefore, the average particle size is preferably 0.8μ or less. By adding a small amount of Hf or Hf carbide, the dispersion strengthening of the alloy becomes remarkable and the wear resistance improves, while the mechanical strength of Hf itself is higher than other additives, so the toughness of the alloy is improved. Almost never deteriorates.

The amount of Hf or Hf carbide added is 0.1 to 3.2% by weight.
The reason why 1 is limited to less than 0.1% by weight is that no effect is observed when added, and when added in excess of 3.2% by weight 1, sinterability and room temperature strength begin to deteriorate.

Furthermore, in the present invention, W which is the main component of the hard phase
5% or less of C is added for the purpose of promoting the effect of suppressing grain growth, etc.
Even if TaC and NbCt'ft are exchanged, there is no effect on the practical effects (grain growth suppression, !It toughness, absorbed energy, etc.) of adding a small amount of Hf or Hf carbide of the present invention.

However, if the amount of substitution exceeds 5%, the strength decreases, causing a practical problem. In addition, in ultrafine particle cemented carbide,
The combined use of V, which is usually added to suppress grains, is also effective in the present invention in order to obtain effects such as grain suppression and toughness.

〔Example〕

Next, the ultrafine grain cemented carbide of the present invention will be described with reference to Examples.

Example 1゜ 85% by weight WC with an average particle size of 0.7μ, C.

0.7% by weight of H in a composition of 111% by weight and 4% by weight of Ni.
f After mixing the carbide-added material in a wet ball mill for 96 hours, adding 2% paraffin dissolved in toluene and molding the dried powder into an end mill (8φ, 2 blades), vacuum sintering at 1350°C. and processed.

End mill of the present invention (A') produced as above
We analyzed the components and measured the hardness and fracture toughness values for the following four materials: Toichi 11j High I degree @ S K H9 type (B), and commercially available fine particle hard alloys (C) and CD). Shown in Table 1.

Furthermore, a life test was conducted under the following cutting conditions.

Work material 545C (Hc28-32> Cutting speed 26.5 m/win Feed rate 0.0311a/blade depth of cut 8-1 mid-cut 4-all Cutting oil Oil-based cutting method Single cut Cutting under the above conditions resulted in 5KH9 Nene (B) has a cutting length of 2.5-mm, and the commercially available ultra-fine grained cemented carbide (C) has a 5th grade, and the commercially available ultrafine-grained cemented carbide (D) has a 7-mm diameter. All of them reached the end of their service life due to chipping. However, the finished surface of Alloy A of the present invention became rough due to abrasion during 35-mm cutting, and the service life finally ended.

Example 2 Commercially available WC powder (average particle size 0.7#s), Mo powder (average particle size 1μs), Hf powder (average particle size 1μs), Co powder (average particle size 1.3
μ-), mixed with the composition shown in Table 2, molded,
Sintering was performed at 350°C for 1 hour.

The hardness, transverse rupture strength, and fracture toughness value (Klc) of the obtained alloy were measured.

Table 2 shows the results.

Furthermore, an end mill (8φ, 2 blades) was manufactured and cut under the same conditions as in Example 1! II length was 5-, and a life test was conducted.

Table 3 shows the state of wear of the cutting edge.

V S 3 Table Note: Comparative Alloy 7 was damaged at cutting length 3-.

Wear values are shown at 3Ia.

From Table 3, it can be seen that the addition of a small amount of HfC improves the wear resistance.

Further, although the chipping resistance of the end mill cutting edge was improved by adding a small amount of HfC, chipping occurred in the initial stage of HfC4,5 (comparative alloy 7). However, 0
．． It was confirmed that the alloys to which 1 to 3.2 weight % of HfC were added (invention alloys 2 to 6) had low occurrence of chipping (and wear preceded).

Example 3 Table 4 shows the hardness, transverse rupture strength, and K+c measurement results of alloys of the present invention in Table 2 of Example 2 in which the basic composition was replaced with WCeTaC and/or NbC.

Furthermore, an end mill (8φ, 2-flute) was manufactured, and a trial edge cutting with a cutting length of 20 m was conducted under the following conditions. 1. ! Table 5 shows the wear condition of the J blade.

For comparison, the high speed steel 5KH9 used in Example 1
Seed (B), commercially available ultrafine particle cemented carbide (C), and (p) were used.

Cutting material FCD45 Cutting speed 28
．． 9m/in feed 0.13m+s/cutting depth 8-cutting width 41 Cutting oil Oil-based cutting method Single cutting From Table 4.5, the addition of TaC and/or NbC increases the hardness and the chipping resistance slightly increases. It can be seen that there is an effect of improving wear resistance, although it decreases.

Table 5 Note: Comparative alloy B has a lifespan due to chatter.

Wear is the value when chatter occurs.

〔Effect of the invention〕

As described above, by adding a small amount of Hr or Hf carbide to the alloy of the present invention, wear resistance and chipping resistance are improved, and a tool with excellent toughness and long life can be obtained.

Claims (2)

[Claims] (1) Hard phase mainly composed of WC 75 to 90 in weight ratio
% combined with 10 to 25% of one or more elements of the Fe group and Cr group (excluding Mo), in which 0.1 to 3.2% of Hf or Hf carbide is added. Ultrafine particle cemented carbide characterized by: (2) In the alloy according to claim 1, a part of the hard phase is replaced with 0.1 to 5% of one or two of TaC and NbC. Hard metal.