DE889838C - Process for the extrusion of aluminum alloys - Google Patents

Description

Method of Extrusion of Aluminum Alloys The Invention refers to -ein used for extrusion and cold processing of aluminum alloys Serving process that creates a state in the works that makes it possible makes them to anneal at a low temperature, being the extruded and cold worked product has the same property.

The extrusion process for forming metal is very widely used in the metal-working equipment for many years in use and is in the manufacture of articles made of aluminum and aluminum alloys tall. When this process is used in the manufacture of aluminum articles, it is generally used. the metal to be pressed is heated so high that the metal flows easily, the casting metal -introduced into a heated cylinder and. the metal is pressed from an extrusion die located at one end of the cylinder. In the extrusion of commercial grade aluminum and those aluminum alloys that do not undergo precipitation treatment to increase their strength, it is. Usually the metal bodies, usually ingots, to a temperature within. a range of 40o to 54.o ° C before the blocks are introduced into the cylinder of the extrusion press. The pressure exerted during extrusion: often causes a. Heating the metal so that only a slight cooling of the metal body takes place during the extrusion process, such cooling is carried out if at all. The temperature to which the metal is heated prior to extrusion is therefore considered to be the desired or normal temperature of the metal during the extrusion process and is referred to as the extrusion temperature. The extrusion of aluminum and aluminum alloys within the temperature range of 40o to 5409 C is called hot working, in contrast to. working, for example, at room temperature, the one; Hardening of the structure. The extruded product is cooled to room temperature in the usual way before it is subjected to a further production process.

In many cases the extruded article will have the one desired Shape so that no further processing is required. However, it is often beneficial a semi-finished product. Making extrusion: and the manufacturing process to end by cold deformation, for example cold drawing. The fiber-forming effect of the extrusion process also consists of the cold-formed product and gives directional properties :, which cannot be found in rolled or forged objects. If the semi-finished pressing is cold-formed, the strength and hardness are increased. We then. Instead of a product that has become hard as a result of the deformation, a soft one If the product is desired, the cold-worked object must be annealed. Will the finished object is annealed, this treatment is referred to as final annealing, while there is talk of intermediate annealing as soon as further processing takes place.

The effect of the annealing treatment, as mentioned above, is that the Reduce strength and hardness of the processed object to a minimum. As a result, tensile specimens can be used to monitor the progress of softening - and as soon as the strength value, the elongation value and the hardness value reach an essentially constant minimum value, the material will regarded as fully annealed. With regard to the internal structure of the annealed. Metal, this treatment has done that by working the metal The resulting microstructure forms new crystals that are free from deformation stresses. As soon as tensile tests show that a noticeable decrease in tensile strength and a As the elongation increases, the formation of new crystals has begun.

The temperature at which new crystals form is called the Umkri.stallisierung temperature called. This temperature is not the same for all types of aluminum and all Aluminum alloys. The main factors influencing the recrystallization temperature are the composition of the metal, the length of time selected for annealing and the amount of cold deformation that the object immediately prior to annealing. is subject. For practical purposes both manufacturing operations have been found that a temperature between 338 and 354 ° C is sufficient to recrystallize cold worked aluminum and aluminum alloys within reasonable times to obtain or carry out.

In the manufacture of certain items, it is very desirable to have a very low recrystallization temperature. For example, is an aluminum cable jacket cold drawn onto an insulated telephone or power cord, so it is necessary to annealing the cable jacket to achieve the desired flexibility in the cable. The usual annealing temperature would destroy the insulation provided on cables. Therefore, in order to soften the protective cover without damaging the insulation., Is a Annealing required at a much lower temperature.

The recrystallization of cold worked aluminum can be found as became smaller by regulating the ratio of iron to silicon and by adding it Amounts of at least one of the metals beryllium and nickel are decreased. For the sake of simplicity, these metals and others will have the same effect Metals here as alloy additives to reduce the recrystallization temperature designated. It has now been found that these advantages are more fully exploited and the effect of beryllium and nickel in the manufacture of extruded and cold worked items increased through the stages described below can be. A general object of the invention is therefore a method for Manufacture of objects that have a low recrystallization temperature. A particular aim is to have this property in certain articles made of aluminum alloy to increase.

The invention is based on the discovery that the recrystallization temperature in. Articles made of extruded and cold-worked aluminum alloys, that of an element that lowers the recrystallization temperature, for example o; oo5 to o; 25% beryllium and 0.04 to i ° / o nickel, in total o, oi to 0.8% iron and silicon as impurities, the ratio of iron to silicon being four Not exceeding one third of the silicon content and preferably only three quarters of the silicon content, the remainder being aluminum, consist of a pretreatment the mass to be extruded can be reduced by a relatively low. Temperature an extrusion takes place and at a Vera relativi, g If the temperature is low, an intermediate anneal is carried out before cold working annealing is required. each of these stages affects those in the following Machining process obtained results, and therefore can only be achieved through strict observance the limits of each stage the end product can be obtained that. the desired low Has recrystallization temperature. The individual stages of the process are now described in more detail below.

The mass of metal that has the shape of an ingot or a rolled one or forged billet and has the correct chemical composition, is first a heat treatment that so-called preheating, subjected, which is followed by controlled cooling to a medium temperature range, whereupon the metal mass is at this temperature range for a while before extrusion held. will:. The treatment consists in: that the metal mass to a temperature heated between 454 and 51o ° C and: within this temperature range is held for a period of r to 12 hours. The temperature and the length the treatment time varies with the alloy composition and size the treated load.

After completing the preheating or the first heat treatment - the alloy mass to a controlled extent, and not above 25 ° C per hour; - cooled to a temperature within the range of 26o to 343 ° C and the metal mass for a period of 1 to 12 hours within this temperature range held. For simplicity, this can be viewed as an intermediate equalization treatment denotes values. The hot metal mass is then cooled to room temperature or can be fed to a strand press if the temperature of the mass is so is that extrusion is possible within the range given below is. The effect of the two heat treatments has not been established, however Both heat treatments are necessary to achieve that required in the finished product low recrystallization: inherently good to maintain.

When the mass has cooled to room temperature or to a temperature which is below the temperature at which the mass is to be extruded, the mass is heated to a temperature between 2o5 and 288 ° C, in the heated Transferred cylinders to an extrusion press and extruded them. It is believed that the temperature of the metal during the extrusion process. within: this area remain. In any case, the lowest possible extrusion temperature should be used The selected temperature is generally determined by the pressure of the press is determined and more pressure is required; once the extrusion temperature decreases. Extrusion temperatures in excess of 288 ° C are used as are usual are used in the extrusion of aluminum, the desired recrystallization property becomes not preserved in the finished product. The resulting semi-finished extruded The product is usually referred to as a bloom. Depending on the mold used it can have a full or a hollow shape. The combination of preheating, Intermediate leveling treatment and extrusion taking place at low temperature results in a condition and internal structure in the bloom that is essential for achieving this a low recrystallization temperature in the subsequently cold-formed Subject is.

The extruded billet is then subjected to further processing subjected to a much lower temperature, which is usually the chewing temperature is or something above it. The deformation can consist of rolling, pulling, Pressing, or similar operations that involve a reduction in the thickness of the Cause object. In the manufacture of tubular products, a Machine used; known as a pipe puller. Editing can in one stage or in several stages: and, in one operation or in several successive operations are carried out. When the final product is to be produced at this stage, d. H. reduced to final shape and final thickness the reduction should be at least 40% and must be for best results go exceed% if the advantages of a low recrystallization temperature should be preserved.

If the previous working process is not a final processing step, the: Cold-worked product can be treated by intermediate annealing within the temperature range of 205 to 316 ° C for 1 to 12 hours. It has been found that such a relatively low temperature range for the intermediate anneal is necessary in order to ensure a low recrystallization temperature in the final article.

After the intermediate anneal, the object undergoes further cold working subjected.,. which is a reduction in the thickness of the article by at least 40% and preferably by more than 20% brings about the advantages of recrystallization to achieve at a reduced temperature. This deformation can have two or more stages of processing include. In the case of pipe formation, for example, these work stages can consist of pulling and reduce exist. Since reducing or pulling in the wall thickness is only slightly changes, in this case the main part of the required cold deformation is carried out the pulling can be carried out.

The object that the above cold deformation and the correct Has undergone heat treatment has the ability to work at a lower temperature to be recrystallized as-: the, same object, made according to the usual procedures is made. In general, the recrystallization temperature is below -316 "C and in many cases is less than 232 ° C.

The invention finds application in the manufacture of seamless Cable jackets for an insulated telephone cable. The effects of preheating and of extrusion temperatures on the tensile properties of a cable jacket are in reproduced in the following experiments.

The manufacturing plan for the cable jackets was the same, except for changes. when performing preheating and reheating necessary for extrusion. The. constant factors were the size of the ingot, the extrusion speed, the cold drawing of the extruded Vorb: locks. with a reduction of about 61%, the annealing at 238 to 24g ° C for 12 hours and further that Cold drawing of a tube with an outside diameter of 12 mm and a wall thickness of 1.27 mm with a reduction of 95019. The finished cold-drawn cable jacket was then annealed at Igo ° C for 1/2 hour to mimic the treatment, those at an isolated. Cable could be applied. The tensile properties of the finished annealed product were noted to allow comparison with the others: to enable annealed products and the effects of the change preheating and extrusion temperature. The alloy used consisted of 0.07% beryllium, 0.03% iron and 0.04% silicon, the remainder aluminum. The tubular ingots had an outside diameter of 227 mm and an inside diameter of 45 mm.

In the first tests, through which the effect of the preheating and the intermediate equalization of the ingot was to be determined, a. Ingot not preheated, but. only heated to the extrusion temperature of 266 ° C, while the other ingot heated for 2 hours from 471 to 482 ° C, slowly to 305 to 35 ° C, and less than 25 ° C per hour, cooled and at this temperature during Was held for 4 hours. The tensile properties of the cold-drawn and annealed protective sleeves are given in: the table below. Table I. Effect of preheating on properties des- cable jacket Ingot Tensile Strength Yield Strength Elongation state kg / cm2 kg / em2 0/0 not preheated 1181 = o68 7 preheated 717 414 17 It is quite evident that the preheating and the intermediate leveling treatment have a very marked effect on the tensile properties. The low values obtained by the cable jackets made from the preheated ingots indicate that recrystallization has occurred.

The influence of the extrusion temperature on the tensile properties of annealed cable jackets has been determined in tests in which two ingots were subjected to the above-mentioned preheating and intermediate leveling treatment. One ingot was extruded at 485 ° C., which is in the temperature range normally used in the extrusion of commercial grade aluminum, while the other ingot was heated to 266 ° C. and extruded. The tensile properties of the finished products are shown in Table 2. The addition property values for the cable jacket, which is extruded from a bloom at a low temperature, shows that recrystallization has taken place, while this recrystallization has not taken place in the other cable jacket.

Although the full benefit of the invention does not arise until the extruded article is cold worked more than 40%, it has been found that the tensile properties of blooms made from preheated and equilibrated ingots differ significantly from those obtained . Distinguish properties from billets extruded from ingots which have not undergone these treatments. This is shown in Table 3. the strength values and elongation values of the tubular bloom from which the casing heated in Table I was made and; which had an outer diameter of 65 mm and a wall thickness of zo mm. These test results and other results have shown that the preheating, the intermediate equalization treatment and a low extrusion temperature have a certain good effect on the billets and that the billets therefore have distinctive properties which are not present in the usual extruded product.

Claims (7)

PATENT CLAIMS: I. Procedure. for production of; extruded Aluminum metal, which has low annealing temperatures in the cold-worked state, characterized by the following stages: A metal body made of an alloy from together 0.05 to 0.8% iron and silicon as impurities, the amount of iron being four Does not exceed one third of the amount of silicon, an element capable of the recrystallization temperature of the metal body. after its cold working to belittle Remainder aluminum, is at a temperature between 454 and 51o ° C, heated to this temperature for a period of 1 to Held for 12 hours, then at a temperature between 26o and 343 ° C at a Control that does not exceed 25 ° C per hour is cooled down within this. Temperature range maintained for a period of time from i to 12 hours and finally extruded at a temperature between 205 and 288 ° C. 2. The method according to claim i, characterized in that an alloy is used which contains 0.005 to 0.251 / o beryllium and / or 0.04 to i% nickel to reduce the recrystallization temperature. 3. The method according to claim i or 2, characterized in that the metal body is cooled to room temperature and then heated again to the extrusion temperature lying between 205 and 288 ° C. 4. Procedure according to claims i to 3, characterized in that the extruded metal body is cold worked by at least 40% after extrusion. 5. The method according to any one of claims i to 3, characterized in that the object is cold-formed after extrusion, then annealed at a temperature between 205 and 316 ° C for a period of 1 to 12 hours and finally by at least 40% and if desired is cold deformed by 9o%. 6. The method according to claim 5 for production of cable sheaths with low annealing temperatures, characterized in that the metal body having the shape of an ingot to form the cable jackets extruded to the shape of a tubular bloom, this bloom cold drawn, annealed and then cold-drawn again to at least 90%. 7. Procedure. after claims i to 6, characterized in that an alloy is used, in which the amount of iron does not exceed three quarters of the silicon content. B. According to the method of claims 1 to 7 extruded bloom or extruded cold-formed object or cable jacket.