JPS60169504A - Manufacture of pipe by powder metallurgical process - 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 method of making pie f by powder metallurgy, in which metal and/or metal alloy powder is filled into a thin-walled casing having an inner wall, an outer wall and a bottom, and then Place an annular cover on the far side, close the casing, apply cold isostatic pressure, and as a result, all the powder inside the casing is compressed and formed into a hard or dimensional-change-free pipe material. An Ide compact (hereinafter referred to as Zoino material) is made, and then hot processing such as heating extrusion is performed.

Such methods are generally known. However, thermal stress often occurs mainly in the inner side walls and the inner side walls, especially at the bottom of the casing and at both ends of the casing near the cover, and therefore cracks are likely to occur. Due to the intensity of thermal stress, the crack propagates over the entire circumference or part of the inner wall of the inner pipe.

It is known that the formation of such ranks is due to non-uniform heating during hot working. Such non-uniform heating occurs particularly when relatively large pipes are made in large furnaces.

For example, stretching, especially inner pipe or inner via'' walls,
It is known that thermal stress occurs when stretching 5 to 1q6.

The entire purpose of this invention is to prevent cracks that occur when the tube material is fully heated during hot working.

This objective can be achieved very simply by the claimed engineering molding method, the young fruits of which are large.

In this invention, by forming one or more overhangs (parzos) at the locations where the maximum thermal stress is applied, that is, preferably at both ends of the inner wall or the inner wall, Total stress can be reduced or relaxed.

The dimensions of this overhang depend on the dimensions of the pipe material as well as the hot working temperature. The overhang must be dimensioned so that the inner pipe or inner wall is substantially completely smooth when the pipe material is heated to hot working temperatures.

The inner pipe is expanded or stretched due to the temperature difference, and this amount is calculated based on the following equation.

ΔT (°C) XL (return) × α (L) °C However, ΔT: Temperature difference (°C) L: Length of pipe material α: Coefficient of thermal expansion Here, the overhang part is the male type and female type. Preferably, the rollers or rolls are formed so as to extend in a radially outward direction.

The overhang should also have a gently curved shape, especially in the transition region between the overhang and the inner tube or inner pipe wall. Therefore, the cross section of the overhanging part has no valley shape, and the radius of curvature of the changing part is within the range of the radius of the inner pipe wall. Bends should never be formed in the overhang.

As mentioned above, when the pipe material is heated to the hot working temperature, the overhanging portion of the present invention forms an inner pie! or allow for expansion and distraction of the medial 2ig wall. As a result, the inner wall becomes smooth.

Particularly in the case of large pipe materials, it is appropriate to anneal the inner side and both ends of the tube before forming the overhang, and then perform a complete treatment to remove the oxide layer formed thereby.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. The drawing is a cross-sectional view of the pipe material before hot working. In the drawing, 10 is the NoR Ino material, 11 is the outer wall of the casing, and 12 is the inside of the casing concentric with the outer wall of the casing. γ, 13 is an annular casing bottom, and 14 is an annular casing cover.

Both ends of the inner pipe or inner pipe wall 120 are each formed with a radially outwardly extending bulge 15,16. This overhang allows the inner pipe to extend when the tubular casing Nofino material 10 is heated to a hot working temperature, resulting in a smooth inner pipe wall 12. If the pipe material 10, which is a tubular casing, is long and large in size, a plurality of overhangs are installed at both ends of the overhang 15 and 16 depending on the size of the overhang. 'It may be formed in the circumferential direction of the inner or inner wall. As shown in the figure, the overhanging portions 1.5 and 16 have a relatively large radius of curvature at the changing portion, and have a relatively gentle cross-sectional shape within the radius of the inner wall 120.

- The rib material 10 is heated to the hot working temperature, and the inner rib wall 12 becomes smooth. Then, extrusion processing is performed according to conventional methods to form the final pieno.

Depth of overhanging part and radius of changing part r11r2+ri
l depends on the dimensions of the pipe material 100, the powder material used, the materials of the inner sleeve wall 12 and the outer pipe wall 11, and the hot working temperature. Radius of curvature r2 of the bottom of the overhang
The overhang and the inside! It is preferable that the radii of curvature r1 and r3 in the changing region between the curved surface and the curved surface are twice as large as the radius of curvature r1 and r3.

[Brief explanation of the drawing]

The drawing is a sectional view of a pipe material for explaining an example of the method of the present invention. lO...Pipe material (Pipe material or Pig compact)
, 11... Casing outer wall, 12... Casing inner wall, 13... Annular casing bottom, I4...
Annular casing cover, 15.16... overhang (bulk). Applicant's representative Patent attorney Takehiko Suzue Engraving of the drawings (L with no changes to the content) Supplementary writing style) % formula % ■, Indication of the incident % Kugai Sho 59-220293 No. 2, Invention of famous pak powder How to produce noise using metallurgical methods, 3. Relation to the amended Nagisa incident, q'Jmu 1, h person Nibi Utsudeporum Powder Nibi 4, agent January 29, 1985.

Claims (5)

[Claims] (1) A method of making pipes by powder metallurgy, in which a thin-walled casing with an inner pipe wall, an outer pipe wall and a bottom is filled with powder of a metal, alloy, or a mixture thereof, and the end of the pipe is then separated from the bottom. In a method of closing the casing by placing an annular cover on it, applying cold isostatic pressure to produce a solid or dimensionally stable pipe material, and then subjecting it to hot processing such as hot extrusion, A method for manufacturing an arm igu by a powder metallurgy method, characterized in that at least one circumferential overhang is formed on at least one end of the inner igu before the process. (2) The radially outwardly extending overhang rollers the end of the inner pipe or inner wall. A method for producing a mother ino by a powder metallurgy method according to claim 1, characterized in that it is formed by a roll or the like. (3) A pipe manufactured by a powder metallurgy method according to claim 1 or 2, characterized in that both ends of the inner pipe wall are each formed with an overhanging part of at least one circumference. Production method. (4) A patent claim characterized in that before forming the one or more overhangs, at least the portion of the pipe material where the overhangs are to be formed is annealed, and then the oxide layer formed during annealing is removed. A method for manufacturing a pipe by the powder metallurgy method according to item 1, 2, or 3. (5) The overhang part changes with a relatively large radius of curvature, especially the changing area between the overhang part and the inner wall or inner wall changes with a large radius of curvature, and the overhang part changes with a relatively gentle radius of curvature. A method for manufacturing a pipe by powder metallurgy according to any one of claims 1 to 4, characterized in that the pipe has a cross-sectional shape.