JPS5921580A - Machining tool for iron and iron alloy - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a stainless processing tool used for drawing, wire drawing, wire rolling, extrusion, or die casting of iron and iron-based alloys.

Conventionally, cemented carbide and die steel high speed steel have been used as plastic working tools for iron and iron alloys.

However, the manufacturing conditions for mass-produced products such as wire-drawing rolls have become stricter year by year due to higher precision and economic demands, and as a result, plastic working tools have also become more demanding in terms of heat resistance, abrasion resistance, thermal shock resistance, etc. Improvement is required.

In order to satisfy these demands, new materials are being developed day and night in the fields of cemented carbide, die steel, high speed steel, etc., but no material with the above-mentioned performance has yet been found.

As mentioned above, steel such as tool steel or cemented carbide is generally used as a metal plastic working tool material, and even when looking at the movement toward new plastic working tool materials, there have been only slight changes.

On the other hand, ceramics have recently attracted attention as a material for plastic working tools, but their properties such as thermal shock resistance, impact resistance, and brittleness are inferior to those of the materials mentioned above. Among them, it is only gradually beginning to be used in the field of guide rolls, etc., which have low stress, and at present, there is almost no idea of using it for rolling rolls.

The present inventors have arrived at this invention after many years of studying the possibility of using ceramic materials as plastic working tool materials.

That is, the present invention is a new plastic working tool made of a silicon nitride ceramic, in particular a sintered body having 10% or less of pores, and obtained by hot pressing or pressureless sintering.

This brings about a revolutionary change that breaks the conventional concept of various plastic working tools.

Silicon nitride is also a type of ceramic material, and although it has the weaknesses as a ceramic material as described above, it is superior to the metal materials in terms of wear resistance, especially at high temperatures. In terms of abrasion resistance, those 10~
The value reaches 100 times. Therefore, among plastic working tools, it is particularly effective in the field of hot rolling rolls and the like that are used at high temperatures.

The general concept for conventional jigs and tools is that they reach the end of their service life after a short period of use, so processes and equipment have been designed accordingly.

However, the plastic working tool of this invention has a lifespan of 10 to 100 times longer than conventional tools, and these jigs and tools have come to be considered part of the equipment.
For example, it becomes possible to add this to the regular maintenance items for the installation itself, and there will be no unproductive situations such as having to stop equipment to replace the jigs and tools themselves during that time.

As a result, not only does the operating rate of the equipment improve, but the stock that is generated during the process is reduced, and there is no need to carry a large number of jigs and tools on hand, which has a very large effect.

That is, the present invention provides a raw material composition for plastic working tools for iron and iron alloys, in which 50% by weight or more of Si3N4 contains MgO and A.
l2O3, ZrO2, TiO2, Nb2O5, SiO2
, BeO, Ta2O3, CeO2, Y2O3, HfO2
, Mg3N2, AlN, ZrN, NbN, TiN, Ta
N, YN, Be3N2, Mo2C, SiC, WC, Al
1 of oxides, nitrides, carbides, or metals such as
It is characterized by being made of a Si3N4 sintered body containing 0.1 to 50% by weight of one or more species and having 10% or less of pores.

Hereinafter, the present invention will be explained in detail. First, it is important that the tool be made of a material that causes the welding phenomenon to be minimized.

However, ceramics have low weldability to metals.

Among them, the most common alumina-based ceramic has low strength and high stress, so it cannot withstand use due to reliability problems in plastic processing where it is subjected to impact.

In addition, various improvements have been made to the thermal shock resistance of alumina, but it is still not sufficient.
It only has a thermal shock resistance of ℃.

So I tried testing with various ceramic tools and found that S
It was discovered that a ceramic mainly composed of i3N4 exhibits superior performance as a plastic working tool for iron and iron alloys than conventionally used cemented carbide and die steel.

As for the manufacturing method of Si3N4 used as the main material in this invention, the reaction sintering method in which a compact of SI metal powder is nitrided, or the method of adding additives to Si3N4 and then connecting it under normal pressure or hot pressing are used. It is being

However, in the former reaction sintering method, more than 10% of pores remain.
It is unsuitable for the purpose of this invention.

Therefore, Si3 used as the main material in this invention
The reason for setting N4 to 0.1 to 50% by weight is that if it is less than 0.1% by weight, the strength will be insufficient and a sintered body with sufficient density will not be obtained.
Moreover, if it exceeds 50% by weight, the characteristics of Si3N4 are lost.

The additives added to Si3N4 are as described above, but among them (1) Al203, MgO, Mg3N2, BeO, Be
3N2, CaO, Ca3N2, FeO, WC or M
A Si3N4 sintered body containing 0.1 to 20% by weight of one or more of O2C is used for plastic working tools used at temperatures below 1000°C. 1-25% by weight
and S containing 0.1 to 25% by weight of oxides, carbides, nitrides, borides, and silicides of Group B elements such as Ce and Y.
The i3N4 sintered body is suitable as a plastic working tool used in the region below 1200°C.

In general, hot plastic working tools are subjected to impact and thermal impact, so they must have properties that can withstand these impacts, but for this purpose, it is first necessary to control the porosity to 10% or less.

The present invention will be explained in detail below with reference to Examples.

Example 1 Commercially available Si3N485% by weight, Al2O37% by weight, Y
Weigh out 38% by weight of 2O, mix thoroughly in a ball mill, press mold at a pressure of 1 t/cm2, and then press under a nitrogen pressure of 1
A die for hot extrusion of iron was prepared by sintering at 1800° C. for 1 hour under atmospheric pressure.

When the obtained die was compared with a commercially available cemented carbide die, the commercially available cemented carbide die reached its lifespan after 500 tons of use, whereas the die of the present invention did not reach any lifespan even after 1500 tons of use.

Example 2 Various auxiliary agents were mixed with commercially available Si3N4 in the proportions shown in Table 1, and steel rolling rolls were prepared under the same conditions as in Example 1.

In this case, it is the final stage roll of a block mill, the processing rate is 18%, the rolling speed is 25 m/sec, and the temperature is approximately 850.
It was ℃.

The amount of processing and the cause of the lifespan of each roll are the first.
Shown in the table.

Example 3 Commercially available Si3N4 30% by weight, SiC 10% by weight, Y2
A guide roller for steel was prepared in the same manner as in Example 1 by mixing 35% by weight of MgO and 5% by weight of MgO. The sintering temperature at this time was 1700°C.

When the guide roller of this example was compared with commercially available guide rollers made of cemented carbide and alumina ceramic in terms of service life, the results shown in Table 2 were obtained. It has been proven to be excellent.

The plate material was processed at a speed of 1.5 m/sec and at a temperature of 900°C.
Met.

Claims (2)

[Claims] (1) Contains 50% by weight or more of SN3N4 and has 10 pores.
% or less of Si3N4 sintered body. (2) MgO, Al2O3, ZrO for Si3N4
2, TiO2, Nb2O5, SiO2, BeO, Ta2
O3, CeO2, Y2O3, HfO2, Mg3N2, A
lN, ZrN, NbN, TiN, TaN, YN, Be3
The plastic working tool for iron and iron alloys according to claim 1, which contains 0.5 to 50% by weight of one or more of N2, Mo2C, SiC, WC, Al, etc. .