SU1747237A1 - Method of making hollow parts such as tubes from deformable aluminium alloys - Google Patents

Abstract

Usage: in the foundry and forging and stamping production. The essence of the invention: by casting with crystallization under pressure, a semi-finished product is obtained in the form of a disk with a blind hole with a diameter of 0.2-0.3 of its outer diameter and a depth of 0.65-0.8 of the thickness of the disk. The semi-finished product is subjected to vibration treatment with a frequency of 300-400 Hz for 15-25 minutes. Then from the semi-finished product cut down the workpiece and thermoablative. The final parts are extruded blanks. 1 tab. 6 Il.

Description

The invention relates to foundry and forging and stamping industries, in particular to the crystallization of castings under pressure and cold extrusion of products from them.

A known method of manufacturing tubes by cold extrusion is reverse, according to which a cylindrical billet is cut from an aluminum alloy strip and subjected to plastic deformation with a significant thinning of the product walls.

The disadvantages of this method are the intensive hardening of the metal during extrusion, the low resistance of the deforming tool and the increased defect in the breaks of the metal on the hollow part of the parts,

There is also known a method of manufacturing parts of the type of tubes, adopted as a prototype, in accordance with which an annular billet is made of a strip metal by cutting-punching. Then, it is annealed to soften the metal in the cutting zone and then back extruded.

The disadvantage of the method is the low utilization rate of the metal, due to its large losses during the cutting of cylindrical blanks from the strip.

The purpose of the invention is to increase the efficiency of production of hollow parts such as tubes through the use of waste.

This goal is achieved due to the fact that from a waste metal from a stamping production, by melting and crystallization under pressure, a semi-finished product is made in the form of a disk with a blind hole with a diameter equal to 0.2-0.3 of its outer diameter and a depth equal to 0.65-0.8 thickness a disk that is vibrated with a frequency of 300-400 Hz in

four

4 hO

3

15-25 minutes and makes cutting of blanks for the subsequent extrusion of tube-type parts.

The given quantitative intervals of the diameter and depth of the hole in the semi-finished product and the mode of vibro-processing of castings are due to the following data obtained in the process of conducting experimental work on the manufacture of pipes from aluminum alloys AO, AD and AD1.

It has been established that when a semi-finished product is made in the form of a thin-walled disc without a central hole, the crystallization process under pressure proceeds from the periphery to the center of the casting. The significant thermal stresses arising from this, due to the high rate of crystallization and distortion of the crystalline lattice of the alloy, lead to the formation of hot cracks with a length from 1/2 to 3/4 of the casting diameter. Making the central hole in the casting changes the direction of crystallization and the temperature field of the molding, which favorably reflects on their quality.

However, the production of castings with a hole with a diameter of less than 0.2 (for example, 0.18) of the outer diameter results in the appearance of hot cracks on some castings from the HELL 1 alloy. Casting a semi-finished product with a central hole of more than 0.3 (for example, 0.35) of its outer diameter ensures the production of high-quality castings. However, for cutting an economically feasible number of blanks for squeezing tubes out of a semi-finished product (16-18 pieces), it becomes necessary to increase the diameter of the casting and the press force, which reduces the economic indicators of production. Making a hole with a depth of less than 0.65 (for example, 0.6) of the thickness of the semi-finished product results in the formation of hot cracks with a length of 15-20 mm on the part. The manufacture of semi-finished products with holes deeper than 0.8 (for example, 0.9) of thickness is accompanied by intense heating of the protruding parts of the mold, their deformation after the manufacture of a small batch of castings and the difficulty of removing articles from the mold.

The study of the mechanical properties and quality of the cut blanks for extrusion of tubes makes it possible to draw the following (see table) conclusions. Vibration reduction of castings with a frequency of less than 300 Hz (for example, 250 Hz) leads to a slight increase in the strength characteristics of the alloys, practically without changing the ductility parameters. Therefore, on extrusion blanks, cut from semi-finished products,

vibro-treated with a marked hour, microcracks are preserved in the cut-off zone. The vibration treatment of semifinished products with a frequency of more than 400 Hz (for example, 450 Hz) is accompanied by a substantial hardening of the alloys and a slight decrease in the plastic characteristics as compared with the stated processing interval. As a result, the cutting punching force increases dramatically, and microcracks appear on the part of the cut blanks.

The application of vibrations to semi-finished products for less than 15 minutes (for example, 10 minutes) does not provide a significant effect on the structure of the material. Therefore, there is practically no change in the plastic characteristics of the alloys. Vibration treatment for a long time (more than 25 minutes) (for example, 30 minutes) leads to

0 embrittlement of aluminum alloys.

Thus, the casting with crystallization under pressure of semi-finished products in the form of discs with a hole equal to 0.2-0.3 of its outer diameter and depth equal to

5 0.65-0.8 heights of the workpiece, and the subsequent vibro-processing of castings with a frequency of 300-400 Hz for 15-25 minutes are optimal from the point of view of achieving the goal, as it provides

0 the possibility of using waste stamping production with minimal labor and energy costs.

FIG. 1 shows the waste stamping production after cutting blanks

5 for extruding tubular parts; in fig. 2 - melt prepared from waste stamping production; in fig. 3 - semi-finished product, made in the form of a thin-walled disk with a blind central hole, obtained by casting with crystallization under pressure; in fig 4

- casting after cutting blanks for extrusion; in fig. 5 blank for extrusion; in fig. b - extruded billet

5 tuba.

FIG. 1-6 marked; D is the outer diameter of the workpiece and the tube; B is the width of nchosy; Dn and dn are, respectively, the outer and inner diameters of the casting; h0 - thickness of casting; hn is the depth of the central version of the semifinished product; d is the diameter of the hole in the extrusion blank; H

- height of tuba; Hi is the height of the extruded thin-walled part of the tube.

5 A method of manufacturing tubes is implemented as follows.

Waste stamping production from alloys AO, AD and AD1 was melted in an induction furnace at 720-740 ° С, refined with Degazer and a measuring ladle

poured into a mold installed on a hydraulic press with a force of 4MN. The alloy pouring temperature was 710 ± 10 ° С, the crystallization pressure was 152 MPa. Castings with diameters of 183 mm, thickness of 4.4 mm with a hole with a diameter of 35 mm were subjected to vibro-processing on a WEDS 200 bench with a frequency of 350 Hz for 20 minutes. Then, from the obtained castings on the K2136B press with a force of 1000 kN, in one stroke, 16 pieces of blanks with a diameter of 30 mm and a hole with a diameter of 9.8 mm were cut. The resulting blanks were annealed at 350 ° C, subjected to tumbling and stamped on a cold-landing machine.

The method can be used in electronic, radio and other

0

industries that produce thin-walled hollow-tube products.

Claims (1)

The invention The method of manufacturing hollow parts such as tubes of wrought aluminum alloys, including cutting the semi-finished product, heat treatment and extrusion, which is also so that, in order to improve efficiency, the semi-finished product is obtained by casting with crystallization under pressure with a diameter of 0.2- 0.3 of its outer diameter, and a depth equal to 0.65-0.8 of the disk thickness, after which the semi-finished product is vibrated at a frequency of 300-400 Hz for 15-25 minutes. The test results of the mechanical properties of the alloy HELL; quality of semi-finished products with a diameter of 183 mm, a thickness of 4.4 mm, made by crystallization under pressure and blanks cut from them for pressure; 0.7 0.7 0.7 0.8 0.7 0.65 350 300 400 250 20 20 25 20 13 Rolling strip Note. During the experiment, at least 3 castings were made. 2 23 26 27 thirty 21 1740bryne cracks long 100-140 mm Cracks up to 40 them 1944 High-quality casting, microcracks on cut blanks 2456 Casting and cut blanks of high quality 2754-2952 The number of cut blanks decreased from 16 to II. 2042 High-quality casting, microcracks on the cut blanks Cracks in castings t5-20 mm long Nicotreshchiki on cut blanks 31 High quality blanks Cracks on the cut blanks 3678Quality blanks ФЗ) Г CnSKd oaohg - cLA phage. i Fig.Z Phie. Z G-LES  “No. Fig 5