JPS60204860A - Manufacture of sintered high-speed steel containing dispersed titanium compound - Google Patents

Abstract

PURPOSE:To disperse more uniformly a titanium compound in a sintered body and to simplify the manufacture by combining a stage for mixing the titanium compound with a stage for blending it so as to finish mixing at a time. CONSTITUTION:Iron oxide powder, metallic oxide powder, metallic powder, alloy powder, carbon powder, titanium nitride powder and titanium carbonitride powder are prepd. as powdery starting materials. Among the materials the necessary materials including the iron oxide powder are reduced, and the materials are blended and mixed so as to provide the composition of high-speed contg. a prescribed titanium compound. The powdery mixture is reduced under heating in vacuum or an inert or reducing atmosphere to form reduced powder having the composition of high-speed steel contg. titanium nitride and/or titanium carbonitride. The reduced powder is press-molded to form a green compact, and sintered high-speed steel contg. a dispersed titanium compound is obtd. by sintering the green compact.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a titanium compound dispersed sintered high-speed steel that exhibits excellent cutting performance and tool performance when used as a wear-resistant tool for cutting and other types of plants. It is something.

Previously, the same applicant filed Japanese Patent Application No. 58-140731 (Japanese Unexamined Patent Publication No. 140731) on a sintered high-speed steel that exhibits excellent cutting performance and tool performance when used for cutting and various other tools. proposed a manufacturing method.

This advanced sintered high-speed steel manufacturing method added a titanium compound addition and mixing process to the conventional sintered high-speed steel manufacturing method in order to improve the cutting performance and tool performance of sintered high-speed steel. However, it has the following characteristics: (a) Iron oxide fine powder as the main raw material is supplemented with soba-→◆44. (b) A blending step of blending gold-stripe fluoride fine powder and carbon fine powder to have a predetermined high-speed steel composition after reduction; (b) subjecting this blended powder to a heating reduction treatment in a vacuum or a hydrogen atmosphere; (e) a reduction step of making a reduced powder and then pulverizing it to make a high-speed steel fine powder;
a mixing step of blending fine powder consisting of one or more of titanium carbides, nitrides, and carbonitrides with this high-speed steel fine powder; (d) a compacted powder of this mixed powder; (e) a sintering step of sintering this green compact in a vacuum or a reducing gas atmosphere;
The main point is a series of steps (a) to (e). Therefore, this manufacturing method requires two mixing steps (al, (cl), which complicates the manufacturing process as a whole, and two separate mixing steps add titanium compounds into the sintered high-speed steel. This is disadvantageous for completely uniform dispersion.

In other words, in the reduction step (b) above, the alloy components are not sufficiently diffused into each other to form a complete alloy, and the individual powder particles are weakly bonded to form secondary particles. Since a reduced powder is obtained, it can be easily ground into a very fine powder with an average particle size of less than 10 μm, thus forming a fine powder phase in which each component is homogeneously mixed. In the above manufacturing method, since the 551J atane compound is physically mixed in the step (C), it is possible to obtain a high speed steel raw material powder in which the titanium compound is uniformly dispersed to the same degree as each component of the reduced powder. As a result, the structure of the resulting sintered high-speed steel tends to be non-uniform. This invention provides an improved method for the above manufacturing method.
In the above manufacturing method, if the mixing step of the titanium compound in (c) is combined with the blending step in (a), and the two mixing steps of (a) and (e) are completed once, the sintered body is made of titanium This was done based on the knowledge that the compound can be obtained in a more uniformly dispersed state, and at the same time, the manufacturing method itself can be simplified.

Therefore, this invention provides a method for producing titanium compound dispersed sintered high-speed steel, which uses iron oxide powder and metal oxide powder as raw material powder.

Metal powder 9 alloy powder, carbon powder, VCG titanium titanium oxide powder, titanium carbonitride powder are prepared, and after reducing the required raw material powders with iron oxide powder as the main raw material, a predetermined titanium compound-containing powder is prepared. After blending and mixing to have a high-speed steel composition, this mixed powder is subjected to a heat reduction treatment in a vacuum, an inert atmosphere, or a reducing atmosphere to reduce the amount of titanium nitride and titanium carbonitride. A reduced powder having a composition of high-speed steel containing one or more of the above-mentioned pulverized powder is then press-molded into a green compact and sintered.

Next, the method for manufacturing sintered high-speed steel of this invention will be described in detail.
It consists of the following steps (al to (cl). That is, (at
First, the main raw materials are iron oxide powder, Co, V, and Cr.

One or more of oxide powders such as W and Mo, one or more of the metal powders of the above components as necessary, and further two of the above components as necessary One or more of the alloy powders configured above, carbon powder, and one or more of titanium nitride powder and titanium carbonitride are prepared, and these raw material powders are reduced to Co:] 55% by weight or less Veer,
Total amount of Mo, W = 10 to 40% by weight, TiN and /
or T1CN: 1 to 15% by weight, C: 0.5 to 2.5
The above powders are blended and wet-mixed to obtain a sintered high-speed steel having a composition of TiN, Fe, and the remainder: unavoidable impurities. After drying, the mixed powder is placed in a hydrogen atmosphere or other reducing atmosphere. A reduced powder having a high speed steel composition containing a titanium compound is produced by performing a heating reduction treatment in an inert atmosphere or in a vacuum.

fbl A very fine powder with an average particle size of 10 μm or less obtained by pulverizing the reduced powder produced in the above fat is molded into a green compact. In this case, although the reduced powder after pulverization is extremely fine, it has extremely good compression moldability and can be easily press-molded.

(cl) The above green compact is sintered by heating to a temperature of 1100 to 1300°C in a vacuum, an inert atmosphere, or a reducing atmosphere. The resulting sintered body has a theoretical density ratio of 95 cm or more, and has a homogeneous microstructure in which the alloying elements are completely diffused. Therefore, even if the sintered body is heated in the atmosphere, the inside of the sintered body will not be oxidized or decarburized through the pores. It is possible to perform hot plastic working such as rolling and forging directly in the atmosphere.In addition, in this invention in particular, titanium compounds are mixed with other high-speed steel raw material powders and then they are simultaneously heated and reduced. Because of this treatment, a sintered body with a structure in which the titanium compound is more uniformly dispersed together with other alloy components can be obtained. Therefore, during the hot plastic working described above, large-scale machining is required to uniformly and finely disperse the titanium compound. There is no need to take a high speed steel.This invention is based on the above (at~(cl) process, and the manufacturing process is simplified compared to the above-mentioned high-speed steel manufacturing method that has already been proposed. In addition to having advantages, the thermal reduction treatment of the present invention can be applied to various metal oxides with different degrees of difficulty in carbonization and reduction, such as Fe and Go, which are most easily reduced, and W and Mo, which are moderately easy to reduce and carbonize. Because powders such as Cr and V, which are the most difficult to reduce, coexist, metal oxide powder, metal carbide powder, or both, and titanium compound powder are always present between the metal powders during the reduction process. As a result, a reduced powder composed of loosely bonded metal powder, metal carbide powder, and titanium compound powder is produced.Therefore, the above-mentioned reduced powder Titanium is easily ground into extremely fine powder of 10 μm or less by a small external force, forming a homogeneous powder phase in which each component is evenly dispersed. The compound is also uniformly dispersed like other components, and after producing the above-mentioned reduced powder, the titanium compound powder is added and mixed later.2.
Compared to the manufacturing method described in III which adopts a step-by-step mixing process, this invention can form a more homogeneous high-speed steel raw material powder, and as a result, a more homogeneous sintered high-speed steel can be manufactured (・5
be effective.

Furthermore, according to the previously proposed manufacturing method including the two-step mixing process, a problem arises in that the density of the core of a sintered body, especially a large sintered body such as a roll, becomes low. In the former case, the additional effect of obtaining a sintered body whose density does not decrease all the way to the center is one of the reasons for this difference. In contrast, in the case of the present invention, a large amount of oxygen is mixed in the reduced powder, and the oxygen generates CO gas during the sintering process, forming pores in the structure. This is thought to be because only a small amount of is mixed in.

Further, in order to further increase the density and bonding strength of the sintered body after sintering, that is, to increase the toughness, it is also effective to perform HIP treatment in the same manner as the above-mentioned hot plastic working.

As mentioned above, it is possible to produce a sintered body that is more homogeneous in both the distribution of constituent components and the distribution of density.
The effects of this invention are ultimately closely linked to the ability to produce a sintered high-speed steel with excellent cutting performance and tool performance, and such effects are illustrated by the following examples. .

Example 1 Iron oxide (with an average particle size of 0.15 μm) was used as a raw material powder.
Fe203) powder, 0.1 pm of Cr@ oxide powder, 0.2 μm of W oxide powder, 0.2 μm of ■ oxide powder, 0.2 μm of M. Oxide powder, 0.4μm
co powder, 0.1 μm carbon powder, 0.7 μm TiN powder, and 0.7 μm TiC (L5 NO
, s powders were prepared, and these raw material powders were blended so as to obtain a reduced powder having the composition shown in Table 1 after reduction, mixed in a ball mill for 72 hours, and the mixed powder was heated in hydrogen at a temperature of 1100°C. High speed steel yA raw powder (a source powder) was produced by subjecting it to heat reduction treatment for 3 hours.
When this high-speed steel raw material powder was pulverized, the average particle size was 0.
．． It was possible to obtain extremely fine powder with a diameter of 5 μm. This powder was compressed at a pressure of 5 tons/C- to form a green compact, and the green compact was further processed to form a predetermined shape of a cutting test piece. Subsequently, the green compact is placed in a vacuum at a temperature of:
The sintered high-speed steels 1 to 5 of the present invention having almost no pores and having a theoretical density ratio of 99.81 were sintered by holding at 1230° C. for 1 hour. Invention sintered high speed steel 1~5V
C was subjected to HIP treatment at a temperature of 1,200°C and a pressure of 1,000 atm, followed by a tempering heat treatment of holding at a temperature of 1,220°C for 2 minutes, quenching, and then holding at a temperature of 540°C for 1 hour, repeated twice. After measuring the Rockwell hardness (HRC), work material: JIS-8NCM8
(Hardness HB: 240), depth of cut: 5 points, feed = 0.4 ■/tooth, cutting speed: 50 m/'', Continuous cutting test was conducted under the following conditions, and the flank wear of the cutting edge was 0.1- The cutting durability time until reaching the point was measured.The test results are shown in Table 1.

Example 2 Using the same reduced powder that was ground into extremely fine powder as used in Example 1 to produce the sintered high-speed steel 1 of the present invention, it was compressed at a pressure of 2 tons/cd to a diameter of 360 mm.
A green compact with a thickness of 120+w+ was formed, and the green compact was further processed to have an outer diameter of 320m.

It was molded into a roll shape with an inner diameter of 200 mm and a thickness of 100 m+. Subsequently, the green compact was heated in vacuum at a temperature of 1235
Sintered by holding at ℃ for 2 hours, theoretical density ratio:
A sintered high speed steel roll of the present invention was produced which was virtually void free and had a porosity of 99.7%.

Next, this sintered high-speed steel roll of the present invention was subjected to HIP treatment and heat treatment under the same conditions as those used in Example 1. As a result, the Rockwell hardness (C scale) = 6
7 was shown. Subsequently, when this sintered high-speed steel roll of the present invention was used for rolling steel wire under normal conditions, it exhibited a lifespan 10 times longer than that of a cast roll.

The above results were obtained by the method of this invention! ! ! The results show that the produced sintered high-speed steel has high hardness, excellent wear resistance, and high toughness, so it can exhibit remarkable durability even when formed into large tools. Such excellent performance confirms that the production method of the present invention can produce sintered high-speed steel having an extremely homogeneous structure containing almost no pores.

As mentioned above, according to the method of the present invention, it is possible to produce a sintered high-speed steel having high hardness and high toughness and exhibiting excellent wear resistance. When used in the production of cutting tools and other various types of wear-resistant tools, which are particularly required, they exhibit excellent performance over an extremely long period of time.

Applicant Mitsubishi Metals Co., Ltd. Agent: Tomi 1) Kazuo and 1 other person Patent Application No. 1981-61945, April 20, 1980, Title of Invention: Process for producing titanium compound dispersed sintered high-speed steel 3, Amendment Relationship with the case involving a person who does

Claims (1)

[Claims] Iron oxide powder and metal oxide powder are used as raw material powder. Metal powder 1 Alloy powder, carbon powder, VCN titanium powder, and titanium carbonitride powder are prepared, and required raw material powders from these raw powders are reduced using iron oxide powder as the main raw material, and then reduced to contain a predetermined titanium compound. After blending and mixing to have a high-speed steel composition of A titanium compound-dispersed sintered high-speed steel, characterized in that the reduced powder has a high-speed steel composition containing 181 or more of manufacturing method,