JPS60174804A - Production of pipe - Google Patents

Abstract

PURPOSE:To make easy mass production of a pipe consisting of a shape memory alloy by subjecting a sintered body obtd. by extrusion molding and sintering of the kneaded material of shape memory alloy powder to a pipe shape to plstic working at an adequate processing ratio. CONSTITUTION:A binder such as rosin, plasticizer such as polyethylene glycol, dispersant such as glycerol, ethylene glycol, solvent such as toluene, lubricating agent such as sodium laurate, etc. are suitably added as desired to shape memory alloy powder of Ti-Ni alloy, etc. and further a prescribed amt. of water is added thereto to prepare the kneaded material. the kneaded material is then extrusion-molded to a pipe shape by using an extrusion molding device. The molding is subjected further to machining or degreasing according to need and is sintered. The sintered body obtd. in such a way is subjected to plastic working at 10-50% processing ratio to increase the density of the sintered body, by which the pipe having an improved shape memory effect is obtd. The sintered body is further subjected to a heating treatment at >=200 deg.C and the recrystallization temp. or below after the above-mentioned plastic working by which a good superelastic effect is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a pipe made of a shape memory alloy.

Pipes made of this type of shape memory alloy can be used, for example, to make pipe fittings by taking advantage of its property of increasing the pipe diameter at temperatures above the transformation point, or if it is shaped like a pipe, it can be heated and cooled to below or above the transformation point. The heating medium and refrigerant can be passed through the inside of the pipe itself, which has the advantage of faster response and no need to provide surrounding heating and cooling means.

Shape memory alloys are highly work hardened, and during annealing after plastic working, the shape returns slightly due to the shape memory effect, making it difficult to manufacture pipes through plastic working. had no choice but to manufacture pipes. However, machinability is not necessarily good due to large work hardening caused by cutting, and such poor machinability has been a major hindrance to the practical application of pipes made of shape memory alloys, which have the advantages mentioned above. It is.

The object of the present invention is to solve the above-mentioned conventional problems and easily mass-produce pipes made of shape memory alloys.

Therefore, the present invention consists of the following three or four steps.

Step 1 of extruding the shape memory alloy powder mixture into a pipe shape Step 2 of sintering the molded product obtained in Step 1 Processing rate of 10 to 50% for the sintered body obtained in Step 2 Step 3 of adding plasticity and if desired Step 3. 200°C for the resultant
Step 4: Heat treatment is performed within a range that does not cause recrystallization. The present invention will be described in detail below in the order of the steps.

In step 1, first, a kneaded product of shape memory alloy powder is prepared. As is well known, a shape memory alloy is an alloy whose elasticity changes greatly above and below the transformation point, such as titanium-nickel alloy, or alloys such as aluminum, aluminum, etc.
Zirconium, cobalt.

Chromium, tantalum, vanadium, molybdenum, niobium,
Alloys containing one or more third components such as palladium, platinum, manganese, iron, etc., gold-cadmium alloys, silver-cadmium alloys, gold-silver-cadmium alloys, copper-aluminum-nickel alloys, copper- It includes all types of alloys such as zinc alloys. The above examples are not intended to limit the invention. The above alloys are used in powder form, and two or more types of alloy powders may be mixed together. Its composition is determined by a predetermined transformation point. If desired, the alloy powder or alloy mixture powder may further contain rosin, modified rosin, polyvinyl alcohol, sodium alginate,
Poxymethylcellome, methylcellulose, ethylcellulose, ethoxycellulose, ethoxycellulose, cellulose acetate.

Casein, gluten, gum arabic, m powder, modified starch °1, acrylic resin, styrene resin, vinyl acetate resin, styrene-butadiene copolymer, polyvinyl butyral, pheno-μ resin, urea resin, melamine resin, urethane One or more types of binders for resins, one or more types of plasticizers such as polyethylene glycol μ, polypropisone glycol, diethyl oxalic acid, pomegranate acetate, glycerin ethylene glycol, propylene glycol, triglyceride, etc. Glyceryl stearate, oleic acid.

One or more dispersants such as stearic acid, toluene, xylene, ethyl acetate, TiDe-y''.

Acetone, methyl ethyl ketone, methyl isobutyl ketone, methano-μ, ethanol)butano-)v.

One or more solvents such as dichloroethylene, tricloethylene, and dichloroethylene, and sodium laurate.

A mixed material is prepared by mixing one or more lubricants such as zinc stearate, calcium stearate, and silicone oil, and adding a predetermined amount of water.

The composition of the above mixer depends on the alloy powder characteristics and extrusion conditions.

Determine as appropriate, taking into consideration extrusion dimensions, etc. The apparatus for extruding the kneaded product is equipped with extrusion means of a plunger type or a set of screws, and the extrusion is carried out through a die having an orifice of a predetermined size and shape.

In step 2, the molded product obtained in step 11 is sintered.1. Cut if desired prior to sintering.

Machining such as cutting and polishing, or processing such as degreasing may be performed. Sintering conditions such as sintering temperature, sintering time, and sintering atmosphere are determined in consideration of the desired density of the final product. Further, the above-mentioned mechanical processing may be performed once in the semi-sintered state during sintering, and then final sintering may be performed.

In step 3, the sintered body obtained in step 2 is subjected to plastic working at a processing rate of 10 to 50%. The plastic working Fi is a force normal to the circumferential surface of the sintered body (1) as shown by the arrow in FIG. This is generally done by applying a force in the axial direction. A processing rate of 10 to 50% means, for example, in the case of Figure 1, if the area of the end face of the sintered body (1) is 100, the area after processing will be 90 to 50. means that if the length of the sintered body (1) is 100, it will be 110-150 or 90-50 after processing. Depending on the type of alloy, work hardening is significant and plastic working is difficult, so plastic working is temporarily interrupted, softening annealing is performed, and then plastic working is continued.

When softening annealing is performed, the plastic working rate should be maintained at 10% or more. The plastic working increases the density of the sintered body and improves the shape memory effect of the final product. This shape memory effect is caused by the introduction of phase dislocations in the sintered body. For this purpose, the above plastic working should be performed in a latent or warm state.

The pipe of the present invention is obtained by the above-mentioned steps 1 and 2.3, but if the pipe of the present invention utilizes a superelastic effect other than the shape memory effect, step 4 is performed.

In step 4, the resultant product of step 3 is subjected to heat treatment at 200°C or higher. However, the heat treatment described above prevents recrystallization from occurring in the resulting product. For this purpose, it is necessary to perform the heat treatment at a temperature (and/or a time during which no recrystallization occurs) at which recrystallization does not occur, for example, in the case of titanium-nickel alloys, at a temperature of 600° C. or lower.

When recrystallization occurs, the pseudoelastic region becomes narrower and the superelastic effect decreases.

Examples for explaining the present invention more specifically will be described below.

Example: An alloy consisting of 51 atomic percent of nickel/l' and 49 at. Add twice the amount and knead thoroughly using a kneader. Then, extrude the mixed wire obtained by using a plunge or type extruder to obtain a product with an outer diameter of 12 mm, an inner diameter of 9 mm, and a length of 30 mm.
The main pipe was molded (Step 1).

The molded product obtained in step 1 above was degreased by heat treatment at 500°C for 1 hour, and then heated to 110°C in an argon gas atmosphere.
Sintering is performed at 0°C for 2 hours (Step 2).

The sintered body (1) obtained in step 2 above is shown in Figures 1 and 2.
A swaging process was performed by applying force in the direction of the arrow as shown in the figure to create a pipe with an outer diameter of 10 rin and an inner diameter of 8 rin (Step 3).
. In this way, a pipe made of a shape memory alloy with a transformation point of -40°C is obtained.

For comparison, a pipe having the same dimensions as the above example was manufactured by cutting from a hot-rolled bar with a diameter of 11mm. Cutting requires a lot of effort and creates a cutting layer, resulting in poor material efficiency.

15 pipes manufactured according to the above examples and comparative examples.
Cooled to 0°C (transformation point -40°C or less), outer diameter 10n,
Inner diameter 8! ! A pipe made of Stepless Steel 1V of FF was inserted and bonded inside, returned to room temperature, and the bonding strength was measured. As a result, the bonding strength of the example and the comparative example was exactly the same.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are explanatory diagrams of step 3. In the figure, (1)... Sintered body Patent applicant: Daido Steel Co., Ltd. Talent 1 diagram ″Figure 22

Claims (2)

[Claims] (1) Step 1 of extruding the shape memory alloy powder kneaded material into a pipe shape. Step 2 of sintering the molded product obtained in step 1. Processing rate of 10 to 10 for the sintered body obtained in step 2. A method for manufacturing a pipe consisting of steps 1 and 2.3 of 50% plastic working of 3 degrees or more (2) Step 1 of extruding the shape memory alloy powder mixture into a pipe shape; Step 2 of sintering the molded product obtained in Step 1; Processing rate of 10 to 10 for the sintered body obtained in Step 2. A method for manufacturing a pipe consisting of steps 1, 2, and 3.4: step 3 of applying plastic working of 5096; step of heat-treating the resultant of step 3 at a temperature of 200° C. or more in a range that does not recrystallize; 4° or more;