JPS6169941A - Wear-resistant sintered hard alloy - Google Patents

Abstract

PURPOSE:To obtain the titled sintered hard alloy composed of the WC-base sintered hard alloy contg., in a proper ratio, a binding phase having a specified composition consisting of Ni, Co, Mo and Cr, which has superior properties such as resistance to heat, impact and thermal shock as well as wear resistance at high temps. CONSTITUTION:The binding phase of a WC-base sintered hard alloy consists of Ni, Co, Mo and Cr, and the composition thereof is as follows: Mo/(Ni+Co+ Mo+Cr)=1/50-1/10, Cr/(Ni+Co+Mo+Cr)=1/20-1/5, Co/Ni=9/1-1/9; Ni+Co+ Mo+Cr=10-30wt%. Hereby a sintered hard alloy having excellent properties under the conditions in which thermal shock and thermal fatigue resistance as well as wear resistance at high temp. are required can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tungsten carbide-based cemented carbide.

Tungsten carbide-Co cemented carbide is widely used in cutting tools, machine guns, etc. In particular, for wear resistance, the binder phase ranges from CO alone to Co-NitNi-Or.

Co--Ni--Cr, etc., have been improved in corrosion resistance, thermal shock resistance, thermal fatigue resistance, etc. However, under conditions that require severe high-speed characteristics, conventional W C-+ (Co or Ni) alloys may suffer from defects, have a short lifespan, and do not exhibit sufficient characteristics. In addition, in systems containing Cr, Cr is dissolved in Co or Ni to improve oxidation resistance, thermal shock resistance, thermal fatigue resistance, etc., but Cr also suppresses the solid solution of WC. It is also an element that inhibits solid solution strengthening by W in the binder phase.

An object of the present invention is to provide a heat-resistant cemented carbide having high heat resistance, impact resistance, hot wear resistance, and heat fatigue resistance.

The present invention provides a WCC cemented carbide whose binder phase is Ni.
, Co, Mo, Cr, Mo/(Ni+C
o + Cr + Mo) = 1 / 50 - 1 / 10
, Cr/(N i + Co 1 Mo 10 r) = 1 /20
~115,G.

/ Ni −9/ 1 to 1 / 9, and Ni
+c.

This is a wear-resistant cemented carbide characterized by 10Mo10r=10 to 30% by weight.

The cemented carbide of the present invention has a W solid solution strengthening effect on Co and Ni and V
In addition to providing excellent heat resistance and jft 8 a-tropism due to Cr, W solid solution is suppressed due to the addition of Cr.
Further, MO is added to greatly increase the solid solution of Mo and W, thereby imparting excellent high-temperature strength and thermal shock resistance.

Therefore, it exhibits excellent performance as wear-resistant tools such as hot rolling rolls and hot rolling guide rollers that require hot wear resistance and high-temperature properties.

Next, the effects of each component in the cemented carbide of the present invention and the reason for limiting the range of the components will be explained.

When Mo is used as an additive element, it improves sinterability and has the effect of suppressing WC grains. Furthermore, it dissolves in solid solution in the binder phase and has the effect of greatly improving the plastic deformability of the binder phase. However, if the limit of solid solution in the bonded phase is increased by 9, then M
Since it exists as 92C and deteriorates thermal performance, its content is reduced to Mo/(Ni+Go+Cr+Mo)=1/1.
It was set to 0 or less. Also Mo/(Ni+Co+Cr+Mo)
= less than 1150, substantially (N i +G o+
It is no different from the bonded phase of Cr). Therefore, the content of MO is Mo/(Ni + Co 〇r〇Mo) = 1150-1
/10.

Cr/(Ni-HC) improves the thermal properties of C1r.
If the ratio (o+Mo+Cr) is less than 1/20, there will be almost no effect, and if it exceeds 115, the strength will deteriorate significantly.

When Co and Ni coexist, Co and N
Solid solution strengthening with i and solid solution strengthening with W and Mo on Co and Ni suppresses strength loss at high temperatures, and has significant effects on thermal fatigue and thermal shock. Co/in alloy
When the N i ratio is less than 1/9:i or more than 9/1, there is almost no effect.

If the sum of (Co+Ni+Cr+Mo) in the binder phase is less than 10%, the toughness will be insufficient, and if it exceeds 30%, the thermal properties will deteriorate severely.

In the cemented carbide of the present invention, the effect remains the same even if Mo is added in the form of Mo carbide or metallic.

The present invention will be largely explained by examples.

Example 1 Commercially available WC powder (average particle size 6 μm), Mo powder (average particle size 1 μm)
m), Co powder (1.3 μm), Ni powder (1.3 μm)
μm), f shown in Table 11 using Cr powder (2 μm)
Mix and mold at 1350-1400'C
Carry out sintering at a temperature of 1 hour.

The obtained alloy was analyzed for its hardness, transverse rupture strength, and composition of the binder phase, and the results shown in Table 2 were obtained.

Furthermore, high temperature creep and thermal shock resistance were tested, and the results shown in Table 3 were obtained.

Table 1 (Unit = m view%) High temperature creep test pieces are JIS test pieces (4X8X24ffiI
11) was subjected to a three-point bending creep test (span distance 20 mm) at 900°C in an inert gas atmosphere with an applied stress of 50 ky/m.
The unsatisfactory rupture time was investigated in m2. Thermal shock resistance was determined by placing a sample in a furnace with an inert bath atmosphere (900°C), holding it for 10 minutes, then quenching it in water at about 20°C, and checking the number of times until thermal cracks occurred.

Table 2! As shown in Table 3, the performance of the alloy of the present invention at room temperature is equivalent to or slightly superior to that of the comparative example. However, when the MO2C phase appears, the strength decreases.

Furthermore, the performance at high temperatures is improved by solid solution strengthening of the binder phase. Furthermore, since it has a high plastic deformability, it can effectively absorb thermal shock and improve toughness.

Example 2 Using Sample 3 used in Example 1 and Comparative Example, a 6'' rolling roll (154 mm φ x 87 mm φ x 70 mmH) was manufactured and hot rolled.

The operating conditions are a combination of two rolls, wire passing speed 35 III/sea, and IIA material temperature 900°.
C1 cooling method Water cooling, i.e. 900℃ on one side of the roll
It was used in a section where a wire rod passes through and one side is cooled with water, which repeats heating and cooling.

As a result, the conventionally used (Co -N i -C
The roll of the binder phase r) had a rolling amount of 2500 t and a grinding allowance of 1.3 m+o, whereas the roll of the alloy of the present invention had a rolling amount of 3000 t and a grinding allowance of 0.8 mm''C.

In other words, the rolls made of the alloy of the present invention have fewer thermal cracks even though the rolling weight is large, and the thermal cracks can be removed by a smaller amount of grinding.

As described above, the cemented carbide of the present invention combines the various effects of Ni-Co-Cr and Mo, so that it can withstand conditions that require thermal shock resistance, thermal fatigue resistance, and hot wear resistance. It has excellent performance.

Claims (1)

[Claims] In tungsten carbide-based cemented carbide, the binder phase is composed of Ni, Co, Mo, and Cr, and Mo/(Ni+Co
+Cr+Mo)=1/50~1/10, Cr/(Ni+
Co+Mo+Cr)=1/20~1/5, Co/Ni=
9/1 to 1/9, and Ni+Co+Mo+Cr=
A wear-resistant cemented carbide having a content of 10 to 30% by weight.