JPH01268841A - High-toughness sintered high alloy steel - Google Patents

Abstract

PURPOSE:To manufacture a high-toughness sintered high alloy steel improved in toughness and strength at the time of compaction by adding specific amounts of carbide powder, etc., to an atomized steel powder and further adding specific amounts of Co powder to the above. CONSTITUTION:One or >=2 kinds among carbide powder, nitride powder, and carbonitride powder are added by 1.0-50wt.% in total to an atomized steel powder, and then a Co powder is added to the resulting powder mixture by 3-20wt.%. Further, it is desirable that an atomized steel powder formed by means of gas atomizing or water atomizing is used as the above atomized steel powder and the steel powder has a composition consisting of, by weight, about 0.5-3% C, about 2-30% Cr, 0 or about 0.1-30% W, phi or about 0.1-20% Mo, about 0.5-7.5% V, phi or about 0.2-20% Co, and the balance Fe with inevi table impurities. Moreover, it is desirable that respective powders of the carbides, nitrides, and carbonitrides of the group IVb, Vb elements (Ti, V, Zr, Nb, Ta, etc.) of the periodic table are used as the above carbide powder, nitride powder, and carbonitride powder and they are added by about 1.0-50% based on the total amount of the atomized steel powder.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention can be used as a high-performance tool material for, for example, cutting tools, cold and hot molds, rolling rolls, impact-resistant parts, or wear-resistant parts. Regarding sintered high alloy steel, especially high hardness,
This invention relates to high-alloy steel powder that can improve toughness and strength of compacts while ensuring wear resistance.

[Conventional technology]

In recent years, high precision has been applied to processing metal materials.

As low costs are required and the workpiece material is also required to have high hardness, processing conditions are becoming more severe, and higher performance cutting tools, molds, and tool materials for rolling rolls are required. There is. In order to meet such requests,
For example, cutting tools are increasingly being replaced from high-speed steel (hereinafter referred to as high-speed steel) tools to cemented carbide. On the other hand, precision tools with high requirements for ease of machining and toughness are
It is thought that high-speed steel tools, which have superior toughness and workability compared to the cemented carbide mentioned above, will continue to be used in the future.

Conventionally, such high speed steel has high hardness (HRC65~
70) AISIM40 series. The M40 series is sometimes manufactured by adding 5% or more of Co to increase the amount of C to improve hardness and lowering the amount of v to prevent a decrease in toughness. However, since the above-mentioned M40 series is manufactured by a melting method, increasing the above-mentioned Co and C contents causes coarsening of carbides and
Segregation is likely to occur, and the toughness is significantly reduced, and heat treatment becomes intense, making hot working difficult. Further, if the v4 is lowered too much, there is a problem that the wear resistance decreases, and it is difficult to manufacture a sound tool material that can meet the above requirements.

For this reason, tool materials manufactured using the powder metallurgy method, which has higher reliability and higher hardness than the above-mentioned melting method, are being used. Examples of the high speed steel produced by this powder metallurgy method include those manufactured by the gas atomization HIP method. This high speed steel is made of Mo to improve wear resistance.

High-speed steel powder is produced by gas atomization from a highly alloyed molten metal with increased amounts of W, Co, C, N, etc. added, and this powder is sintered and formed by hot isostatic pressing (HIP). . However, the high speed steel manufactured by the above gas atomization method has a problem in that there is a limit to the adjustment of the amount of each component added, and if the amount added exceeds the limit, good atomization cannot be performed. When added, if the amount added exceeds 2%, even if vacuum melting is performed, bubbling occurs due to the Go reaction and the viscosity of the molten metal decreases, making atomization impossible. On the other hand, regarding the amount of ■, if 15% or more is added to improve wear resistance and dissolved in the atmosphere,
■ becomes oxidized and atomization becomes impossible. Also, the above v
When l is lowered to 7.5%, even though atomization is possible, the carbides in the powder become huge and the toughness decreases. Therefore, in order to prevent these problems, V
If the amount is decreased, sufficient hardness and wear resistance cannot be obtained.

Therefore, a method has been proposed that can improve the adjustment limit of the amount of each component added. This is a method of adding and mixing carbide powder and nitride powder to atomized steel powder and sintering the mixture. The manufacturing method of this mixed sintered high speed steel is as shown in Fig. 9.
The alloy powder 1 produced by atomization and the additive FA 2 consisting of one or more of carbide powder, nitride powder, and carbonitride powder are mixed and pulverized using a stirrer such as an attritor or a vibrating ball mill. 4. Forming the powder 3 Next, fill the mixed powder 3 with wax and knead it. After forming 5, dewaxing 6 is performed, which is reduced and sintered, and then HIP
Manufactured by processing 8. According to this manufacturing method, since the additive powder of each component is mixed and sintered into the atomized steel powder produced in advance, the content of each component can be adjusted relatively easily. As a result, the amount added can be increased, and hardness, wear resistance, and toughness can be ensured.

[Problem that the invention seeks to solve]

However, in order to meet the above-mentioned demands for improved toughness and workability, if the amount of carbide powder and nitride powder added to the atomized steel powder is further increased, the carbides and nitrides will be added when the two are mixed. There is a problem of agglomeration. As a result, there are problems in that the toughness is reduced and the strength of the molded product during molding is reduced, making cracks and the like more likely to occur.

Here, for example, it is conceivable to use an attritor or a vibrating ball mill to mix and stir both of the above materials and to disperse them by taking a long stirring time, but in reality, the dispersibility cannot be improved that much, and the stirring time Extending the stirring time is a waste of time, since the longer the stirring time, the more detrimental the problem is that it significantly impedes productivity and increases costs.

An object of the present invention is to provide a high-toughness sintered high-alloy steel that can improve toughness and strength during forming by solving the problem of agglomeration without using the above-mentioned mechanical means.

[Means for solving problems]

The inventors of the present invention have conducted extensive research in order to eliminate the agglomeration caused by increasing the amount of added charcoal, nitrides, etc., and found that it is possible to add CO silk powder when mixing atomized steel powder with charcoal, nitrides, etc. They discovered that the above-mentioned problems caused by agglomeration could be solved by adding a predetermined amount of this CO silk powder, and thus accomplished the present invention.

Therefore, the present invention provides atomized steel powder and carbide powder.

It is characterized in that Co powder within a range of 3 to 20% is added to a mixed powder of one or more of nitride powder and carbonitride powder.

Here, the reason why the above-mentioned amount of CO silk powder added was limited to the range of 3 to 20% will be explained.

According to experiments conducted by the present inventors, when the amount of Co powder added is 3% or less, carbides form when the matrix is worn out.

Since the nitrides easily fall off, the effects of improving wear resistance and transverse rupture strength cannot be obtained, and they also do not contribute to improving the strength of the compact. This is because the amount of Co powder added is too small, and the carbides and This is thought to be caused by the fact that the nitrides are aggregated and not dispersed. Furthermore, if the amount of Co powder added exceeds 20%, the wear resistance decreases, so the amount added is optimally within the above range of 3 to 20%.

In addition, as the above atomized steel powder, one generated by gas or water atomization can be used, and the composition range of this atomized steel powder depends on the target properties and the amount of charcoal, nitride powder, and Co powder added. Although it is not possible to determine immediately because the value changes depending on the situation, it is desirable to set it within the following range.

C: 0.5-3. Cr: 2-30. W:
O or 0.1-30. MO: O or 0.1-2
0. V: 0.5~? ,5. CO: 0 or 0.1~
20 (wt%), balance Fe and unavoidable impurities.Furthermore, the carbide powder and nitride powder are
It is preferable that the powder is a metal carbide, nitride, or carbonitride selected from group B and group VB (Ti, V, Zr, Nb, Ta, etc.), and the amount added above is based on the total amount of atomized steel powder. The range of 1.0 to 50% is good; if it is less than 1%, the wear resistance will decrease significantly, and if it is less than 50%
This is because if it exceeds this, the transverse rupture strength will drop significantly.

[Effect]

According to the high-toughness sintered high-alloy steel according to the present invention, since Co powder is added to the mixed powder of atomized steel powder, carbide powder, nitride powder, and carbonitride powder, the Co powder etc., and can prevent them from agglomerating.

As a result, the matrix of the high alloy steel itself has wear resistance, and the uniformity of carbides and nitrides improves toughness, making machining possible (n<not possible with cemented carbide) and improving grindability.

In addition, in the present invention, by adding Co powder, there is no unbalance in the composition distribution, so the strength of the molded product can be improved, which can prevent cracking during molding, which in turn makes it possible to mold irregular shapes. At the same time, the molding pressure can be lowered, making it possible to manufacture large-sized molded bodies.

〔Example〕

The present invention will be explained in detail below.

First, a method for manufacturing high-toughness sintered high-alloy steel of this example will be briefly described.

Carbide, nitride, and carbonitride powders are added to the atomized steel powder produced by atomization, and a predetermined amount of Co is added to this mixed powder.
Add powder Next, put this into a stirrer such as a ball mill or attritor and mix and grind (1 to 12 hours)
Next, a lubricant is added to this mixed powder, and after molding, dewaxing treatment is performed, and then vacuum sintering (1200
~1300°C) and, if necessary, subjected to IP treatment to obtain sintered steel.Finally, this sintered steel is annealed and machined to form a tool material.

Next, an experiment for confirming the effects of the present invention will be described.

Experiment 1 In this experiment, 6.5% VC powder as carbide powder and 10% TiN powder as nitride powder were added to water atomized steel powder (SKH57) consisting of the chemical components (%) shown in the first column of Table 1. 0 to 30% of Co powder was added to this mixed powder to produce a sintered alloy steel, and the transverse rupture strength, springback amount, hardness, and wear resistance of this sintered alloy steel were measured. . In addition,
An attritor is used for each of the above-mentioned stirring and mixing, and the mixed powder is stirred and mixed in alcohol for 5 hours by a wet method. Next, the above-mentioned mixed powder is molded into a molded body using a mold and CIP treatment, and this molded body is further vacuum sintered ( 1290°C for 2 hours) to obtain sintered steel. Then, this sintered steel was subjected to HIP treatment (1150℃
800 atm -2 hr), and then the sintered steel was annealed and machined to produce a tool material.

The above experimental results will be explained below. Figures 1 and 2 show the amount of Go added and the transverse rupture strength of the above-mentioned molded body, respectively.

It is a characteristic diagram showing the relationship with the amount of springback, and as is clear from the diagram, by adding Co powder,
It can be seen that the transverse rupture strength has improved and the amount of sbringing banks has decreased, indicating that a sound molded product has been obtained.

In addition, Figures 3 to 5 are characteristic diagrams showing the relationship between the CO addition color, transverse rupture strength, hardness, and specific wear amount of sintered steel, and as is clear from the figures, the transverse rupture strength is significantly improved when the amount of Co added exceeds 3%. Also, the hardness is 2
There is almost no decrease in hardness up to 0%, but beyond this the hardness decreases significantly. Furthermore, the specific wear amount decreases when it exceeds 3%, but on the contrary, it increases significantly when it exceeds 20%. From these, it is desirable that the amount of Co powder added is within the range of 3 to 20%.

Furthermore, FIGS. 6(a) to 6 (C1 is C1, respectively)
This is an enlarged view showing the structure of sintered steel when the OO loading is 0.3.10%, and as is clear from the same figure, the Co content is 0% (Figure 6 (a)). In contrast, agglomeration is observed in 3.10% (Figure 6, Mountain 1. (C1)), where it is seen that it is uniformly dispersed.

Experiment 2 In this experiment, 0 to 55% TiN powder was added and mixed by the same method as in Experiment 1 above to gas atomized steel powder (KHA7NH) consisting of the chemical components (%) shown in the second column of Table 1. However, if Co powder is not added to each of these mixed powders,
A sintered high alloy steel was produced from the 10% additive. At this time, differences in transverse rupture strength and abrasion resistance were investigated when changing the TiN powder. Note that in this experiment, the sintering temperature was 1200°C.

The results are shown in Figures 7 and 8. In the figures, ○ indicates the characteristics with no addition of Co powder, and . indicates the characteristics with 10% Co powder added. Figure 7 shows the relationship between the amount of TfN powder and the transverse rupture strength. As is clear from the figure, when the TiN powder content is 0%, the transverse rupture strength is large, and the above T
When iN powder is added, it decreases slightly, when the amount added exceeds 10%, it becomes almost stable, and when it approaches 50%, it decreases significantly, so from the point of view of improving transverse rupture strength, the less TiN powder is better. I can say that. However, it can be said from the characteristic diagram of TiN powder amount and specific wear amount in Figure 8 that by adding the above TiN powder, for example, from 0% to 1%, an improvement nearly double that amount is observed, and by 10%. It can be seen that it is stable when it exceeds. From this, it can be seen that in order to ensure both the above-mentioned transverse rupture strength and abrasion resistance, it is desirable to add TiN powder in a range of 1 to 50%. In addition, regarding the wear resistance mentioned above, both cases with no additives and those with additives show almost the same characteristics, but in terms of transverse rupture strength, the ones with additives are overall better, and we will continue to use Co powder in the future. It can be seen that the toughness can be improved by adding Cr.

〔Effect of the invention〕

As described above, according to the high-toughness sintered high-alloy steel according to the present invention, one or more of carbide powder, nitride powder, and carbonitride powder is added to the atomized steel powder, and Co powder is added to the atomized steel powder. By adding these additives, carbides and nitrides are uniformly dispersed, resulting in properties with excellent toughness and wear resistance, as well as improving the strength of the molded product, making it possible to mold irregular shapes and reducing molding pressure. This has the effect of making it possible to manufacture large molded bodies.

[Brief explanation of the drawing]

Figures 1 to 5, Figures 7 and 8 are characteristic diagrams for explaining the results of experiments conducted to confirm the effects of the present invention, respectively, and Figures 6 (fat to 6 fc) are Gold rfr of sintered high alloy steel produced according to this example, respectively.
% & 11 weave, and FIG. 9 is a process chart for explaining the manufacturing process of a general sintered high speed steel. Patent applicant: Chiaki Takami, Kobe Steel, Ltd.

Claims (1)

[Claims] (1) Add one or more of carbide powder, nitride powder, and carbonitride powder to the atomized steel powder in a total of 1.0 to 50% by weight.
(hereinafter simply referred to as %) Add 3% of Co powder to the added mixed powder.
High toughness sintered high alloy steel characterized by adding ~20%.