HU192114B - Releasable aluminium fastening member advantageously bolts of increased corrosion-resistance and mean tensile strength of 320-450 newton per square millimeter and their manufacturing process - Google Patents

Abstract

SUMMARY OF THE INVENTION The present invention relates to soluble aluminum fasteners, preferably screws or their alloys and manufacturing processes, having a high tensile strength of 320 to 450 N / mm 2. The essence of the invention is that it is expressed as a percentage by weight of 3.6-5.0% Zn, 0.7-1.8% Mg, 0.05-0.15% Zr, and maximum 0.57o Cu as needed. with a maximum of 0.45% MN or 0.35% Cr Alloy AIZnMg alloy molded homogenized ingot from extrusion and / or drawing or self-rolling and tempered at 420-480 ° C, preconditioning directly to forming operations 140-250 Reverse heat treatment at 0.5 ° C for 5 to 5 minutes is performed, and the screws formed by forming and / or cutting screw manufacturing operations are directly subjected to a multi-stage known aging heat treatment. -1-

Description

The present invention relates to a medium of 320-450 N / mn? soluble aluminum fasteners with high tensile strength, high corrosion resistance, preferably screws and their alloys and manufacturing processes.

Fastener bolts are usually manufactured with high productivity from wire, head gasket and tapping - or rolling - on automatic target machines, while nuts are made by cold-sealing, punching and tapping technology. The sealed cold-flow technology used in the manufacturing process requires a high degree of ductility from the raw materials used in the manufacture of fasteners. For example, in the head configuration, the compression ratio should be between s = 1 / d = 3 to 3.5, where 1 is the height of the cake and d is the diameter. However, excessive plasticity of the material is a disadvantage in threading and other operations (eg grooving).

AlMg non-heatable alloys or AlMgSi, AlCuMg, AIZnMg and sometimes AIZnMgCu alloys are generally used as starting materials for the production of aluminum screws.

For AlMg alloys, the strength of the product is provided by the semi-solid precursor and the forming hardness. Screws made of such an alloy have a final strength of 250-300 N / mm ³ . A disadvantage of the process starting from AlMg alloy material as the base material is that the strength created by the forming hardening is accompanied by a relatively low elongation value. As a result, the manufactured screws do not have a toughness reserve and are easily broken when tightened. It is also a disadvantage that the applied tensile force decreases over time as a result of creep relaxation, as a result of which the screws do not retain their bond strength after tightening.

In the case of AlMgSi and AIZnMg alloy screws, the final strength value is obtained during the hardening of the manufactured screws, i.e. during hardening, and at one or more stages of annealing. The strength values of 320-450 N / mm ³ produced during breeding are also accompanied by adequate elongation. The stretching ability then provides the screw with sufficient toughness, good grip and resistance to relaxation.

The AIZnMg alloys are known to become noble. When stirred at room temperature, i.e. 10-30 C, so-called Guinier-Preston Type I zones are formed which increase the strength of the alloy and reduce its malleability. This zone formation process is so fast that after 24 to 48 hours, the material can harden so much that it becomes unfit for die cutting in screw manufacturing. In practice, it takes considerably more time for the material cast in the semi-finished aluminum plant to be inserted into the automatic rack in a screw factory. To date, this has been eliminated by subjecting the base material to an excellent annealing at 350-400 ° C. However, precipitation annealing, on the one hand, damages the fabric structure of the material and, on the other hand, requires the heat treatment and hardening of the finished screws.

Post-production dissolution heat treatment and hardening of binders made of AIZnMg alloys have several disadvantages which make the process difficult to apply. Thus, for example, at 460-540 ° C, the threaded profile of the screws produced may be damaged, deformed, the resulting strengths reduced as a result of the recrystallization process at the hardening temperature, and, at the same time, the bonding susceptibility of the screw material increases. During breeding, with good toughness, the surface of the screw develops a medium hardness which increases the tendency of the screws to stick. Of particular concern is that the non-failure process is a very complex operation that can only be safely secured in aluminum semi-finished plants with specialized equipment and expertise. Last but not least, after finishing, and most importantly after hardening, the surface of the finished screws changes and therefore, for aesthetic reasons, the already finished finished screws require additional complicated surface finishing processes which further reduce the dimensional accuracy of the screws.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a medium and high corrosion resistant soluble aluminum fasteners, particularly screws, having a tensile strength of 320-450 N / mm ³ , by providing a process and alloy that avoids the disadvantages and difficulties of the prior art make the fastest manufacturing technology and equipment for fasteners in factories that have been rendered to manufacture other metal screwdrivers, so they only have automated special purpose screwmaking machines.

The present invention therefore relates to medium corrosion-resistant soluble aluminum fasteners with a high tensile strength of 320-450 N / mm ³ , preferably screws, which are known to be formed by extrusion (if necessary by drawing), (by rolling) or by tapping to produce soluble fasteners.

The essence of the invention is that, expressed in weight percent, 3.6 to 5.8% Zn, 0.7 to 1.8% Mg, 0.05 to 0.15% Zr, with a maximum of 0.5% Cu as required. , starting from a preformed die-cast homogenized ingot molded AIZnMg alloy containing up to 0,45% Mn or 0,35% Cr alloy, and pressed at 420 to 480 ° C, the live product is directly processed. Prior to forming operations, it is subjected to a reversible heat treatment at a temperature of 140-250 ° C for 0.5 to 5 minutes, and then the screws formed during the forming and / or screw manufacturing operations are directly heated in a multistage known heat treatment.

Unlike any similar process, the fastener manufacturing of the present invention is based on the surprising realization that hardening of manufactured screws, i.e. the most critical operation of heme transfer, can be omitted when starting from hardened precursor instead of the usual extruded and softened precursor. immediately prior to screw manufacturing operations, a heat treatment of 140 to 250 ° C for 0.5 to 5 minutes is carried out. The AIZnMg type alloy should be selected as the starting material for this process, since only this can be used to carry out the revolution heat treatment of the present invention, and only the non-curable aluminum alloys have the advantage of the thermomechanical treatment according to the invention.

The raw material is produced by extrusion or extrusion and drawing. The base material for screws with larger diameters is preferably produced by extrusion, while pressing from the extrusion temperature

-2192.114 training followed by a calibration pull to the original size of the screw manufacturer. For screws with smaller diameters, it is advisable to start with extruded material, mainly for productivity reasons. Pulling is completed within 24 hours after extrusion, in which case no intermediate softening is required. If pulling is not done within 24 hours, use softening according to standard technology before pulling. After pulling, the material is hardened in an oven. The training is preferably carried out in water at a temperature of 460-480 ° C for 0.5 to 1 hour. The size of the compression-drawing of the substrate is primarily an economic issue and, from a technical point of view, press-to-press hardening should be given priority, since pulling and separate hardening will damage the tissue structure, which may lead to slight deterioration of properties.

140-250 C between ^these dissolve in room temperature GP zones for 1 minute during the reversion heating treatment returns to approximately established over the solid solution hardening and to return better formability of the material. Reversible heat treatment can be carried out immediately before the head seal, preferably with a continuous heat treatment device built in front of the automat. The heat treated material is then fed directly into the machine where the head sealing can be performed. After the head is sealed, the mangrove or threading is carried out, the former of which must be completed within the laying time, which is 24 hours. (Today's state-of-the-art machines already perform head sealing and thread forming in a single closed manufacturing process.)

The finished screw is subjected to a three-step aging heat treatment consisting of 5-7 days at room temperature, 100 ° C for 8-24 hours, and 14 ° C for 8-24 hours.

This hardening, reversible heat treatment, screw shaping, aging sequence ensures that the screws do not deform due to the lack of post-hardening, the extruded-drawn fabric structure is maintained, which improves corrosion resistance, do not chew while the refined spindle body remains tough. At the same time, the heat treatment of the screws becomes simpler - and can be carried out in any screw manufacturing plant. Reversible heat treatment equipment is simple and does not require high precision. Finally, some of the user areas do not require subsequent surface treatment.

A great advantage of the fasteners made according to the invention is that they have a very good corrosion resistance, a medium soluble bond strength of 320-450 N / mm ³ and at the same time they are easy and economical to manufacture.

The construction of the fastener according to the invention will be described in detail in the following examples.

Example 1

MB screw spindle to be manufactured with tensile strength Rjn = 420-450 N / mm ³ , technical yield strength Rno 2 '370-390 N / mm ³ , elongation A _s = 12-15%.

During the manufacturing process 5.2% Zn, 1.6% Mg, 0.15% Zr, 0.45% Mn, 0.3% Cu, 0.05% Ti, 0.20% Si, AlZn Mg alloy containing 0.30% Fe alloy, molded in semi-continuous casting, homogenized at 480 ° C for 16 hours, pressed in rolls of 7.2 mm diameter and subsequently calibrated to a screw size of 7.05 mm h From the temperature, hardened wire is produced as a starting material.

After leaving the factory, the wire in the coil is threaded into the pre-blotting machine at the screw factory just before the machining operations. The threading is done by passing the wire unwound from the coil through a direct electrically heated rapid heat treatment device, which heats up to 250 ° C before entering the machine, for about 0.5 minutes. Reversible heat treatment of the raw material to be processed takes place in the heat treatment equipment. The cutting or head-sealing is carried out in a known manner on the automatic target machine, followed by known methods of rolling or rolling.

After forming, the formed screws are aged for 5 to 7 days at 10 to 30 ° C for aging. The screws are then kept at 100 ° C for 12 hours, followed by another 16 hour aging at 140 ° C.

Example 2

M4 cross-head screw to be manufactured, having a tensile strength R _m = 380-390 mm ³ , a technical yield point Rpo 2 = 330-350 N / mm ³ and an elongation As = 12-16%. '

As in Example 1, the starting material is AIZnMg aluminum alloy ingot molded by semi-continuous casting, homogenized at 480 ° C for 16 hours, and expressed as a percentage by weight of: 4.4% Zn, 1.1% Mg , 0.12% Zr, 0.15% Mn, 0.10% Cu, 0.05% Ti, 0.20% Si, 0.30% Fe. A 6 mm diameter wire is wound from the homogenized billet by a known method of extrusion. This wire is drawn in three steps to a diameter of 3.46 mm in 24 hours. The training is carried out in water at 460 ° C for 1 hour after exposure to heat. The substrate thus prepared is shipped to a screw machine and threaded into an automatic machine immediately prior to machining with a max. By passing it for 2 minutes, it is subjected to a reversible heat treatment.

After performing the subsequent forming operations of the already manufactured csavarorsókat laid down flat 10 to 30 ° C at room temperature for 5-7 days and then at 100 C for ⁶ to 12 hours and subsequently aged at 140 ° C for 16 hours.

Example 3

M12 screw spindle to be manufactured, of anodic quality with tensile strength R _m = 320-330 N / mm ³ , technical yield point Rpo 2 = 280-290 N / mm ³ , elongation A5 -14-17%,

In this embodiment, the starting material is a semi-continuous casting ingot having an AIZnMg aluminum alloy consisting of the following by weight alloys: 3.8% Zn, 0.8% Mg, 0.07% Zr, 0.2% Cu max. 0.05% Mn, 0.1% Si, 030% Fe, 0.05% Ti. After homogenization at 470 ° C for 12 hours, the wire is pressed in a known manner into a wire having a diameter of 12 mm, tempered with a wire press and pulled to a diameter of 11.68 mm by means of a calibration pull. After shipment, thread the entire roll from the 140 ° C oil bath, which is in the known manner, into the screw machine for 5 minutes.

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After the reversible heat treatment is completed in this way, the forming takes place in the machine. After completion of the screw spindles, the aging heat treatment is carried out as described in Example 2.

The product thus produced can be anodized in natural or other colors with the same color tone as the structure to be assembled.

Claims (3)

PATENT CLAIMS 1. Medium (320-450 N / mm ² ) corrosion-resistant soluble aluminum fasteners, particularly screws, characterized in that, by weight, 3.6 to 5.8% Zn, 0.7 to 1.8% Me. 05-0.15% Zr. are prepared from AIZnMg alloy containing a maximum of 0.5% Cu, a maximum of 0.4 5% Mn or 0.35% Cr as required. Process for the manufacture of fasteners made from the AIZnMg alloy of claim 1, characterized in that the precursor product of the molded-homogenized ingot is obtained directly by extrusion and / or drawing, directly from a temperature of 420-480 V. 10 is subjected to heat treatment for a period of 0.5 to 5 minutes at a temperature of 140-250 ° C prior to the forming operations, followed by a known stepwise heat treatment of the formed screws by performing the forming and / or cutting screw production operations.