TR201815694T4 - Process for obtaining a part made of low silicon aluminum alloy. - Google Patents

Abstract

The part made of low silicon aluminum alloy includes silicon, magnesium, copper, manganese, titanium and strontium. Said part is obtained by a process, wherein: - said alloy is poured into a mold to obtain the part, - after casting, the part forming a pre-mold which is still hot, is then removed from the mold, followed by 470 ° C and 550 ° C. C, said preform is cooled between two shells of a matrix defining a cavity which is substantially equal but less than the size of the mold; The two shells are pressed together strongly to apply a combined effect for surface pressing and kneading.

Description

DESCRIPTION HAND A PIECE MADE OF LOW SILICONE ALUMINUM ALLOY PROCESS FOR The invention includes the use of aluminum parts in the automobile, aerospace, and more generally in all types of industries. It is related to the casting sector for the manufacture of After treatment (Rpog has high mechanical characteristics.

These are combined in the 6000 series of the classification of aluminum alloys (Al-Mg-Si). available with ingredients similar to forged alloys, among them, for example, EP 0 987 The specified alloys are suitable for high deformation rates (> 50%) in hot or cold semi-finished products (iron iron bars or ingots for forging or rolling) developed. As the geometry of these semi-finished products becomes simpler (bar, rod or nugget), which is a minimum requirement using processes with high solidification rates of these alloys. allows them to be solidified with error. These geometries and these processes are nowadays according to the techniques used, it leads to half-finished products devoid of faults, among which these may be specified: shrinkage voids, cracks, macro-segregations, macro-precipitates (highly prevents the formation of coarse precipitates, >100 nm).

Based on this state of the art, the problem that the invention aims to solve is high quality and parts that meet safety standards and can have complex forms is realizable.

To solve this problem, the object of the invention is 6000 type, low silicon aluminum relates to a process for manufacturing a part made of alloy.

More specifically, the invention contains silicon in a proportion of between 0.5 and 3%, and between 0.65% and 1%. magnesium, 0.20% to 0.40% copper, 0.15% to 0.15% 0.25 percent anganane, 0.10 to 0.20 titan and low silicon aluminum containing 0 to 120 ppm of strontium It relates to a process for obtaining a part made of alloy, accordingly: . the alloy in question to obtain the part is poured into a mold, . after casting, the part forming a still hot preform is removed from the mold, . said preform is cooled, then a temperature between 470 °C and 550 °C It is subjected to an operation that can reheat it at the same temperature. 0 the part in question has dimensions that are substantially equal, but less than that of the die. positioned between two shells of a matrix that defines a space with . superficial pressing on the part arranged between said shells and two shells to exert a combined effect for kneading pressed together.

The object of the present invention is also to: Application of the above process in 0 automobile field and aviation field; - a part obtained by the above-mentioned process, in the automobile field use of; and . is the use of the alloy in the above-mentioned process in the aviation field.

In one embodiment of the process, after the preform has cooled, the preform is placed in a tunnel kiln. arranged and reheated, As a result of these characteristics, forging in a pre-die step followed by casting operation, the same temperature parameters as the processes of the prior art, solidification It does not have speed, deformation rate, forging temperature.

The alloy specified in the claims corresponds to these limitations and in particular their safety must meet its obligations (floor attachment = safety parts) In case of case, it allows to obtain parts with satisfactory quality.

Among these limitations, the following elements are indicated by way of example: o Unlike bars or ingots, the geometry of the preform is designed to ensure that the part It contains a rough outline of functional regions and thus isolates the liquid metal. It has a complex geometry that includes cross-section beams and variables that give rise to masses of may have. By increasing the silicon ratio to these isolated masses, « tolerance can be displayed » (type AS7GO3, standard cast alloy). At this rate, a falling alloy during solidification, it makes it more sensitive and produces a larger number of volume shrinkage leads to gaps errors.

- defined by the difference between the liquefaction temperature of the alloy and the eutectic temperature solidification range is considered. A strontium-modified alloy of the AS7G03 type For this purpose, this range is approximately 50 oC (. 6000 type low for a silicon alloy, this is a precipitate of macroscopic MgZSi (or silicon) with pseudo-eutectic eclipse, it is at 90 °C (. Genis a solidification gap, which is classically and almost natural with an AS7G03 alloy Orientation of the solidification corner to reduce errors as done a paste-like structure that extends further into the piece, making it more difficult. leads to the area. 0 AS7G03, cracks appearing during treatment during solidification an almost zero due to the large amount of eutectic points that can fill has sensitivity. This leads to a strong susceptibility to cracking and adapt the composition and manage thermal solidification gradients. valid for a low silicon alloy containing very few eutectic points that require is not.

At the same time, with the parameters of the chemical composition, casting, forging, thermal treatment. to achieve the best match between the desired mechanical characteristics in the final parts. adjustment is required. To this end, each of the following alloy elements The contents and the effects that lead to keeping these values are explained in detail: Silicon content is between 0.5 and 3%. A silicon content of less than 1% may impair elastic nerves. and leads to the highest elongations. However, the alloy for this is the most crack-proof. It is mentioned that it is sensitive and has the weakest fluidity. Thus, silicon It is necessary to adapt the ratio according to the geometry of the part. complex geometries, will require a fairly high rate to reduce this sensitivity to cracking. Despite the fact that production with The magnesium content is between 0.65% and 1%. This ratio is Mgzsi in the aluminum matrix. It allows optimizing the density of the precipitates. Silicon ratio dissolution or dissolution during thermal treatment, which is damaging and stabilizes it by having minimal macroscopic MgZSi precipitates that need to be converted. If the precipitates are quite numerous or quite large, thermal treatment may only be used. have a weak effect due to critical dissolution size overshoot for their dissolution will be.

The copper rate is between 0.20% and 0.40%. This ratio is equal to the A12Cu precipitates in the matrix. allows the formation and total absence of macroscopic A12Cu precipitates. This The absence of macroscopic precipitates allows maintaining high forging temperatures and thus minimizing the effort of forging (performed in a single step) Allows. Basic precipitates formed in the presence of copper, at 490 °C and 525 °C, respectively. melted AlgCu and AlMgSiCu, the presence of which makes the parts unusable. will prevent forging at very high temperatures without the risk of burns. This The degradation is similar to the destruction of alloy. At the same time, a fairly high virgin rate, low mechanical stresses applied on the part for these at temperatures ( due to the fact that a point of eutectic remains to solidify increases the alloy's susceptibility to cracking.

Manganese content is between 0.15 and 0.25%. This ratio is in the ß form (highly damaging sheet) prevents the formation of AlFeSi precipitates and is more in a form (less damaging Chinese script) allows the formation of AlFeMnSi precipitates. In this case, Cobapress allowing to maximize the elongation on the final part resulting from the it provides. This effect is more often used with larger amounts of manganese and iron, these two The elemental alloy gives a strong hardening, but at the same time becomes larger during solidification. leads to precipitates. These coarse precipitates are disadvantageous for a good alloy. With this, The alloy according to the invention is intended for the Cobapress process as indicated, accordingly, the iron with large deformations encountered in forging, rolling, or demoulding Iron is forged in a single step that does not exist. These large deformations caused these large sediments to detach and retain their hardening effect, making them considerably less damaging. allows it to be made. In the case of the alloy according to the invention, the mechanical characteristics minimizing the impact of iron-based precipitates on it, as in pouring suitable. Their morphology will only be modified, forging in one step, does not deform the part sufficiently to change their morphology. Finally, this the manganese content is adapted to the cooling rates obtained during continuous casting, According to these speeds, (in the form 1) AlFeMnSi facilitates the formation of precipitates.

Titan ratio is between 0.10% and 0.20%. This ratio means that the particles are effectively have a significant effect on the germination and mechanical characteristics of these alloys. required for a fine particle size.

Strontium content is between 0 and 120 ppm. This ratio is the ratio of the weak eutectic amounts formed. It is necessary for solidification in fibrous form. This is usually more than 1.5% silicon. occurs for rates.

The weak deformation of the composition of this alloy during the Cobapress process allow the mechanical characteristics to be maximized, despite the It has been seen that it has been adapted to cause a solidification that will provide

However, solidification defects, branching and interparticle solidification of localized shrinkage in particle bonds with diffuse morphology. degradation continues.

The Cobapress iron casting operation uses this with a control in the design of the rate of deformation. allows errors to be closed and resolved. temperature/deformation couple allows for resolution. The table below shows the T6 thermal conductivity of low silicon alloy. mechanically applied to the cast and parts according to the Cobapress process. shows the characteristics. Improvement in break at break (Rm) and elongation at break can be specified: Cast AlMgSiCu + T6 300 315 1,3 cobapressTM AlMgSiCu + T6 300 340 8 Rp = Elastic nerve Rm = Mechanical resistance Finally, this composition is the result of the usual thermal infusions for Al-Mg-Si-Cu type alloys. It allows to reduce complexity. Silicon ratio, solidification rates and particle reduction is that its size and inorphology facilitate dissolution during thermal treatment. Mggsi leads to macroscopic precipitates.

In order to show the importance of manganese and copper ratios, metal parts of a piece Reference is made to the figures of the attached drawings showing the microscope. Figure 1, without manganese, « needle-like » precipitated, ß-type cast microstructure, figure 2, with manganese Figures 3, 4 and 5 show the elimination of AlgCu virgin precipitates.

In Figures 3 and 43, the copper content is more than 0.40%, which leads to the presence of AlgCu Precipitates. opens. Figure 4 shows AlFeMnSi and MgZSi precipitates surrounded by A12Cu precipitates. indicates an observable pattern.

Figure 5 shows an absence of AlgCu precipitates between 0.20% and 0.40% according to the invention. indicates a virgin ingredient found.

Claims (3)

REQUESTS 1. Process for obtaining a part made from a low silicon aluminum alloy, characterized in that it contains: - 0.5% to 3% silicon, - 0.65% to 1% magnesium, - 0% 20 to 0.40% copper, - 0.15 to 0.25% manganese, - 0.10 to 0.20% titanium, and - 0 to 120 ppm strontium, the remainder of the alloy, is formed from aluminum and optional impurities, according to which: - said alloy for obtaining the part is poured into a mold, - after casting, the part forming a still hot preform is removed from the mold, - said preform it is cooled, then subjected to an operation capable of reheating it at a temperature between 470 °C and 550 °C - the part is placed between two shells of a matrix that defines a cavity with substantially equal but smaller dimensions than that of the mold The two shells are pressed together vigorously to exert a combined effect of superficial pressing and kneading on the piece arranged between said shells. 2. It is the use of a part obtained by process according to claim 17, its feature is that it is in the automobile field. 3. According to claim 1, it is the use of the alloy in the process and its feature is that it is in the aviation field.