JPS613870A - Wear resistant parts and its production - Google Patents

Abstract

PURPOSE:To produce parts having excellent wear resistance by cooling ultraquickly the melt of an alloy steel contg. >=1 kind among Cr, Mo and W and a specific amt. of V and C to a pulverous powder state and solidifying and molding the powder by a hot hydrostatic press, sintering, etc. CONSTITUTION:The melt of the high-carbon alloy steel contg. by atomic%, about 2%<C<about 25%, about 5%<V+Nb<about 25% and contg. 0<=Cr+ Mo+W<=20% is ultraquickly cooled at a cooling rate of >=10<3> deg.C/sec to produce the powder in which VC having high hardness and <=2mum average grain size is uniformly dispersed and incorporated and which contains the hard carbide of Cr, Mo and W. The non-equil. phase appears markedly in the structure and the powder having the higher hardness is obtainable if the powder is produced at >=10<5> deg.C/sec ultraquick cooling rate. Such high-hardness alloy steel powder is molded and solidified by a hot hydrostatic method and sintering method, by which the production of the parts having the extremely large wear resistance is made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a manufacturing method for manufacturing a high vanadium alloy steel containing about 5% (at% basis, the same applies hereinafter) or more of V by a powder metallurgy method.

Conventionally, methods suitable for producing alloy powder include (1) spraying method, (2) pulverization method, and (2) reduction method.

The spray method (2) is a method in which a molten metal containing alloying elements is rapidly cooled by spraying using water or an inert gas as a spray medium. VC is distributed in the range of several 10 μm to several 100 μm, and is coarse and the quenching rate is slow, so the maximum cooling rate is 102°C/seag degree. minute V due to
It has the disadvantage that it is not possible to obtain a high vanadium alloy powder in which C is uniformly dispersed. An example is shown in Figure 3.

The pulverization method (2) involves creating an alloy ingot from a molten metal containing alloying elements and mechanically pulverizing it.In high-vanadium alloy steel, segregation of coarse carbides is inevitable during the casting process of alloy steel. Even if this is crushed, good quality alloy powder cannot be obtained.

The reduction method (2) is industrially applicable to the production of alloy powders that are relatively easy to reduce; 5
It is extremely difficult to produce metal powder containing more than %.

The present invention is based on iron, which is easy to compact and has excellent sinterability, and which is difficult to produce with conventional alloy powder manufacturing methods.
, W, and about 5 at% or more of V and about 5 to about 25 at% of C. Flakes, powders, etc. that are ultra-quenched from the corresponding molten metal.
The objective is to obtain wear-resistant parts using filaments.

This part has high hardness and toughness, and by selecting the composition, it is possible to give it a hardness comparable to that of carbide, and it has better wear resistance than powdered high-speed tool steel produced by conventional spraying methods. . On the other hand, Ca, which is expensive compared to cemented carbide,
It is economical as it does not contain a large amount of WC.

For V-containing alloy steels manufactured by conventional spraying or crushing methods, high speed steel JIB 5KB-, 10
5.2% of the seed showed the highest V content, and this was thought to be the upper limit for a V-containing alloy steel that could be cast with a normal structure. On the other hand, alloy tool steel (SKB-11, 5
Ko-ei, 5KT-5) and high speed steel are the main ones,
These alloy steels have different contents, but Or,
Contains at least one component element such as Mo, W, etc.

The effects of each of these constituent elements are as follows.

Cr: Reacts with C and precipitates as a carbide in the matrix, helping to improve the wear resistance of the alloy.

It reacts with MO and W:C to form carbides, which improves the wear resistance of the alloy, and also partially dissolves in the matrix to improve the strength of the alloy.

Therefore, at least one of these constituent elements should be included in the steel composition in order to provide the properties (=l) required for steel, and in the present invention, Cr, MO,
It was decided to include at least one type of W.

Further, C is necessary for each component in the alloy steel to form carbides. By setting ① to about 5.0% or more, about 5% C is required to form carbide with this V. On the other hand, regarding the upper limit, considering the melting temperature, the maximum amount of ■ is considered to be 25%, so the maximum value of
%, the upper limit was set at 25%, which is the amount of C required.

That is, the Fe-based alloy powder according to the present invention contains (1) Cr
, MO, W, and (2)■ about 5
．． 0% or more and (3) c 5. ~25%, and is characterized by being obtained by rapid cooling from a molten metal at a cooling rate of 10''°C/sec or more.

The reason for adopting the ultra-quenching method is as follows.

(2) When the cooling rate is 101°C/'sea or more, the coarsening of VC is suppressed and it becomes finely dispersed throughout the base.

■The resulting flakes and filaments are easily crushed into powder.

■Ultra-quenching allows VC to be finely dispersed, resulting in high hardness.

(2) When Cr, Mo, and W are added, a non-equilibrium phase is generated during rapid cooling, and the structure of the final product is densified.

In this way, by adopting the ultra-quenching method, advantages not available with conventional methods can be obtained.

Furthermore, if the cooling rate exceeds 105° C./See, a non-equilibrium phase will appear significantly, and an amorphous phase may occur.

When the non-equilibrium phase is formed, the hardness increases, and a finer carbide structure can be obtained by performing the sintering treatment.

Example 1 Molten metal was spouted from a round hole nozzle onto a Cu roll with a diameter of 300φ to produce flakes having the composition shown in Table 1, and then crushed using a vibration mill to obtain a flat powder of 100 meshes or less. . This was cold-molded and then hot-pressed at 1000°C to obtain a sample. Thereafter, the hardness was adjusted by quenching and tempering.

The hardness after heat treatment is also shown in Table 1. The flakes used as the material are approximately 15 μm thick, and the cold fly speed is 105'C/
sec or more.

No segregation was observed in the molded sample, and fine carbides were dispersed. FIG. 1 shows the microscopic structure, and the carbide size is fine, about 1 μm or less.

Example 2 The alloys shown in Table 2, which were atomized by dropping the molten metal onto a disk rotating at high speed, were classified, and those with 100 mesh or less were cold molded and hot pressed at 1000°C to obtain samples. . Thereafter, the hardness was adjusted by quenching and tempering. The hardness after heat treatment is also shown in Table 2. The cooling rate in this example is estimated to be ~103°C/sec.

Although the carbides are slightly larger than those in Example 1, no segregation is observed in the molded sample, and fine carbides are dispersed.

Figure 2 shows the microscopic structure.

From the above examples, it has become clear that hardness increases with increasing amounts of v and C, and that addition of Or and MO brings about a significant increase in hardness. In addition, the cooling rate is 103℃/
It was found that at temperatures above SeC, there were no coarse carbides or segregation in the obtained sample, and at temperatures above 105° C./'sea, the carbide size decreased and the hardness, bending horns, and deflection increased.

In Examples 1 and 2, the l1G2 acid elements are not particularly used, but AI, Si, Mn, and Ca are commonly used to prevent oxidation during melting.

Adding one or more deoxidizing elements such as Sr facilitates dissolution.

In addition, F
It can be used in place of e without detracting from the spirit of the present invention. Example 3 shows an example.

Example 3 The results of manufacturing samples having the compositions shown in Table 3 using the method of Example 1 are shown below.

It was done.

As described above, the present invention has low segregation, high hardness, and excellent mechanical strength, and has good properties as a wear-resistant component. In particular, as a tool, it has both wear resistance and fire resistance, making it ideal for end mill tools, rolling rolls, etc.

In addition, the hardness of this sample is comparable to that of expensive cemented carbide (WC; +COj), making it an economical and wear-resistant tool.

Figure 3 shows the same composition as No. 7, and the migration to normal gas 71.
1Q only

Claims (1)

[Claims] 1. Composition in at%: about 2%<C<about 25%, about 5%<V
+Nb<approximately 25% alloy containing 0≦Cr+Mg+W
≦20, the balance being Fe and unavoidable impurities, and a molten metal deoxidizer, and the material is rapidly cooled from a molten state at 10^3°C/sec or more. 2. The wear-resistant part according to claim 1, wherein not more than 1/4 of the element contained in ordinary tool steel is replaced with Fe. 3. The wear-resistant part according to claim 1, wherein the final product has an average particle size of fine carbides of 2 μm or less and is free from segregation. 4, at%: approx. 2%<C<approx. 25%, approx. 5%<V+Nb
<Alloy containing about 25%, 0≦Cr+Mo+W≦20
A molten metal containing unavoidable residual impurities and a molten metal deoxidizer is cooled at a cooling rate of 10^3°C/sec or more to create flakes, filaments, ribbons, powders, etc. Hot press, extrude the raw materials,
A method for manufacturing wear-resistant parts characterized by solidification by hot isostatic pressing, sintering, etc. 5. The method for manufacturing wear-resistant parts according to claim 4, wherein the cooling rate is 10^5°C/sec or more.