JPH01224131A - Die for forging at constant temperature - Google Patents

Abstract

PURPOSE:To extend the life of a die by forming a die in a compound structure by a metal and ceramics, making the R of the corner part of a ceramics part at more than specified value if necessary, and forming it by a conductive ceramics. CONSTITUTION:The outermost die 7 and bottom die 8 of the die for forging at constant temp. are formed by metal and inner die 4, intermediate die 5 and outer die 6 are made in the structure composed of the ceramics of a conductive sialon, etc. If necessary, the R of the corner part of the ceramics part is taken in the shape in >=0.3mm. The part brought into contact directly with a forging material is taken of ceramics, the outermost die 7 and bottom die 8 of metal material and they are taken as fitting parts, hence the strength of the die is improved and the generation of a crack of the ceramics parts 4, 5, 6 is prevented. The stress concentration is eased due to the R of the ceramics part being set in >=0.3mm. The life of the die is thus extended.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a die used in isothermal forging for forming difficult-to-work materials such as nickel-based alloys or intermetallic compounds.

[Conventional technology]

In isothermal forging of nickel-based alloys, superplastic materials with extremely fine crystal grains are used at high temperatures (1000 to 1100°C).
Further, processing is performed in a region of low strain rate (104 to 10'S-'). At this time, the major issues are the selection of a mold material that can be heated and maintained at high temperatures, and the selection of a lubricant that prevents bonding between the mold and the workpiece and obtains good fluidity (Ohmukai et al.; Mechanical Research Institute Report. , 37-6 (1983), 1)
. Conventional mold material is molybdenum-based alloy.

Tungsten-based alloys, nickel-based alloys, etc. are used. There has also been a study on the use of ceramics (Ohmukai et al., Abstracts of the 1985 Spring Lecture of the Japan Society for Plasticity Processing, 339).

[Problem to be solved by the invention]

Among the above-mentioned mold materials, in the method of using high melting point metal molds such as molybdenum-based alloys and tungsten-based alloys, it is necessary to perform processing in a vacuum or in a non-oxidizing atmosphere to prevent oxidation. Not only does this require a large amount of equipment such as a chamber, but it also becomes difficult to apply lubricant, load and unload workpieces, etc.

Further, when a nickel-based alloy is used, it is possible to mold the mold in the atmosphere without any problem, but the mold is slightly oxidized and it is extremely difficult to remove the lubricant from the mold.

In order to solve the above problems, Ohmukai et al. have been investigating ceramic molds, and the results have shown that a SiAlON mold that can be electrically discharged makes it possible to perform isothermal forging in the atmosphere, making it practically useful. I am getting . However, in the case of ceramic molds, it is difficult to make large molds, and considering the brittleness of ceramics, it is necessary to have a different shape and design than traditional metal molds. .

An object of the present invention is to provide a mold for isothermal forging using ceramics having the above-mentioned advantages, and a mold that solves the structural shape and design problems therefor.

[Means to solve the problem]

The present invention is a constant temperature forging die characterized by being a composite of metal and ceramics.

The structure is preferably made of ceramic for the part that comes into direct contact with the forging material, and for the outer periphery to be made of metal.If the entire outer periphery is made of ceramic, if the dimensions of the mold are large, it is preferable to use ceramic and dense ceramics. This is because it is difficult to make a mold with sufficient strength. Furthermore, when considering attachment to a forging machine, it is preferable to fix the ceramic with metal and attach the metal to the machine from the viewpoint of preventing cracking of the ceramic. Although it is structurally possible to attach ceramics directly to a forging machine, the difference in thermal expansion coefficients causes tensile stress to act on the ceramics, causing breakage or creating gaps and causing play.

In addition, in order to prevent destruction due to stress concentration in the ceramic part, it is also possible to divide the ceramic part at the part where the maximum tensile stress is applied due to stress concentration, such as the corner part of a concave part, so that it is composed of two or more parts. It is an effective method.

Furthermore, it is a desirable method when using ceramics as part of a constant temperature forging die to reduce stress concentration and prevent chipping by adding radii to the convex or concave corners of the ceramic part. In this case, the size of R is preferably RO63 or more, more preferably RO15 or more.

The material is 5iC1Si3N, which has high strength even at high temperatures.
Sialon, etc., which are tough, can be considered, but SL, N, which has high toughness
Sialon-based materials are preferred.

Furthermore, by using conductive sialon or the like, electrical discharge machining becomes possible, and molds with complex shapes can be easily produced.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.

The isothermal forging molds shown in FIGS. 1 to 3 were manufactured using SiAlON, which has electrical conductivity, for the ceramic portion and Ni-based super super heat-resistant alloy INloo) for the metal portion.

The outer diameter is approximately 300 mm and the thickness is approximately 100 mm. For each shape, two types were produced, one in which the corner radius of the ceramic was 0.2 m and one in which the radius was 0.5.

Using the upper and lower molds shown in each figure, make Ni-based alloy lN-100.
We carried out constant temperature forging. The results are shown in Table 1.

As shown in Table 1, the lifespan is improved when ceramics and metals are combined. In addition, by dividing the mold at the stress concentration part, the R of the ceramic part can be reduced from 0.2 to 0.
．． It can be seen that the life span is significantly improved by setting the value to 5■.

〔Effect of the invention〕

According to the present invention, it is possible to further increase the effectiveness of the use of ceramics in molds for isothermal forging as shown by Daikyu et al. In other words, the life of isothermal forging dies using ceramics can be further improved by combining them with metals, dividing the dies to relieve stress concentration, and changing the corner radius shape. This is a very effective means for practical application to processing difficult-to-process materials such as base alloys.

[Brief explanation of the drawing]

FIG. 1 shows a composite type of metal and ceramics according to the present invention, FIG. 2 shows a type in which the ceramic portion is further divided to relieve stress concentration, and FIG. 3 shows a conventional integrated ceramic type. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. A mold for constant temperature forging characterized by a composite of metal and ceramics. 2. The mold for isothermal forging according to claim 1, wherein the ceramic is composed of two or more parts. 3. The mold for isothermal forging according to any one of claims 1 and 2, characterized in that the radius of the corner portion of the ceramic component is 0.3 mm or more. 4. The mold for isothermal forging according to any one of claims 1 to 3, wherein the ceramic is a silicon nitride-based or sialon-based material. 5. The mold for isothermal forging according to any one of claims 1 to 3, wherein the ceramic is a conductive ceramic. 6. The mold for isothermal forging according to any one of claims 1 to 3, wherein the ceramic is a conductive silicon nitride ceramic or a sialon ceramic.