JP2005330576A - Aluminum alloy for cast joint member of automotive space frame, and method for manufacturing cast joint member utilizing it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aluminum alloy for a cast joint member of an automotive space frame, which is sand-cast from the aluminum alloy, and to provide a method for manufacturing the cast joint member using it. <P>SOLUTION: The aluminum alloy for the cast joint member of the automotive space frame includes aluminum as a main material, 0.4-0.5 wt.% copper (Cu), 2.5-3.0 wt.% silicon (Si), 0.1 wt.% or less magnesium (Mg), 0.1 wt.% or less iron (Fe) and 0.20 wt.% or less titanium (Ti). The method for manufacturing the cast joint member using the alloy comprises: casting the aluminum alloy; solution-treating it; and heat-treating it at 150 to 160°C for 4 to 5 hours. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an aluminum alloy for cast connection members of automobile space frames, and a method for producing a cast connection member using the same (Aluminum alloy for cast node of method for manufacturing casting node using the same). In more detail, a product having a high elongation characteristic can be manufactured by appropriately adjusting the addition range of each component of the aluminum alloy and presenting optimum heat treatment conditions thereby. The present invention relates to an aluminum alloy for a cast connecting member and a method for producing a cast connecting member using the same

  In recent years, the application range of aluminum materials has been widely expanded mainly in the automobile industry to reduce the weight of automobiles in response to demands for improving fuel efficiency, and in particular, the design and manufacture of automobile bodies using aluminum materials. Technology is being developed in various ways.

  Among them, as shown in FIG. 1, an aluminum space frame (ASF) is made of an aluminum extruded material, and a cast connecting member for connecting the extruded materials. (Cast node) is applied, and an ultralight vehicle body structure in which an inner plate and an outer plate are formed of an aluminum alloy plate material.

  Thus, the aluminum space frame has a structure in which the extruded material frame and the cast connecting member bear all loads applied to the vehicle.

  On the other hand, in the case of a vehicle, it is most important to ensure collision safety. However, particularly when a vehicle collides, the vehicle body must appropriately absorb the collision energy while being deformed at a certain portion, and the passengers must be safely protected.

  Accordingly, the aluminum space frame body must also have characteristics that allow the frame and the cast connecting member to absorb the collision energy while being appropriately deformed without being easily fractured.

  That is, the frame and the cast connecting member must maintain a high elongation rate in terms of material safety in terms of ensuring safety by absorbing collision energy.

However, in the case of an aluminum casting product, the elongation is generally low, and in the case of a sand casting product, it has an elongation of 3% inside and outside, and in the case of a die casting product, it has an elongation of 6-7%. It is not suitable for vehicle body parts that require a high elongation such as a connecting member.
For example, Patent Literature 1 discloses a technique of an aluminum alloy die-cast casting used for a space frame joint or the like.

  As a result, in the case of aluminum space frame vehicles (Germany Audi A2, A3) of some automobile manufacturers, a newly developed alloy (Aural: Al-10% Si-Mg, Mn, Fe) and this new alloy were used. A high-speed metal mold casting (die casting) method is used to produce a thin, high-elongation cast connecting member having a thickness of 2 to 3 mm for mass production.

  The cast connecting member made of such a material has physical properties of a tensile strength of 200 MPa, a yield strength of 130 MPa, and an elongation rate of 14 to 18%, and particularly ensures a sufficient elongation rate as a vehicle body part.

  However, when the high vacuum die casting method is applied, the equipment itself is expensive and die casting, so the investment cost such as equipment cost and die cost becomes excessive, and the product quantity is small, or the test product In the case of manufacturing, there is a problem that enormous cost burden and development cost are required.

  Compared to this, sand casting has the advantage that it is suitable for low-volume production because the product is manufactured by injecting molten metal into the sand mold at the time of casting. Mainly applied).

However, in the case of an aluminum sand mold casting, the physical properties of the product, particularly the elongation rate (3% inside and outside), is low compared to the mold casting, so it is difficult to apply to car body parts. In fact, there is an urgent need for a method capable of producing a cast connecting member having an elongation rate.
JP 11-293375 A

  The present invention has been made to solve the above problems, and by appropriately adjusting the addition range for each component of the aluminum alloy and presenting optimum heat treatment conditions therefor, sand casting An aluminum alloy for a cast connecting member of an automobile space frame and a method of manufacturing a cast connecting member using the same, which can manufacture a product having a high elongation characteristic equivalent to that of a product manufactured through a high vacuum die casting method. The purpose is to provide.

  The aluminum alloy for a cast connecting member of an automobile space frame according to the present invention has aluminum as a main material, 0.4 to 0.5% by weight of copper (Cu), and 2.5 to 3.0% by weight of silicon. (Si), 0.1 wt% or less of magnesium (Mg), 0.1 wt% or less of iron (Fe) and 0.20 wt% or less of titanium (Ti) are contained.

  Moreover, the manufacturing method of the cast connecting member for an automobile space frame according to the present invention includes aluminum as a main material, 0.4 to 0.5% by weight of copper (Cu), 2.5 to 3.0% by weight. Cast aluminum alloy containing silicon (Si), 0.1 wt% or less magnesium (Mg), 0.1 wt% or less iron (Fe) and 0.20 wt% or less titanium (Ti) After the solution treatment, the heat treatment is performed at a temperature of 150 to 160 ° C. for 4 to 5 hours.

  According to the present invention, the alloy for the cast connecting member of the automobile space frame and the method for manufacturing the cast connecting member using the same, the range of addition of the alloy components (copper, silicon, magnesium, iron) is appropriately adjusted, and the optimum thereby By presenting the heat treatment conditions, it is possible to produce a product having a level equivalent to that of a high-vacuum die-cast product in terms of tensile strength, yield strength, and elongation even when using a sand casting method.

  That is, even if the high vacuum die casting method is not applied, an aluminum body part having an equivalent level of physical properties can be manufactured by using an inexpensive sand casting method, so that development costs and cost savings can be obtained.

  Hereinafter, the present invention will be described in detail with reference to the drawings and tables.

  In order to manufacture a cast connecting member used for connecting the frame extruded materials as a part of the aluminum space frame, a method capable of ensuring a high elongation rate is required.

  In the present invention, so as to enable production as a complex car body part, a sand casting alloy that is excellent in castability and can secure a high elongation rate from the viewpoint of ensuring safety by absorbing collision energy, The optimum heat treatment conditions for ensuring sufficient physical properties even in the production method adapted to this, especially in the production process, are presented.

  The aluminum alloy to be developed in the present invention is used for manufacturing a large-sized part having a thin wall thickness and a large rib structure due to the characteristics of the car body part, and thus has high castability. Elongation must be secured.

  For this reason, the aluminum alloy for cast connecting members according to the present invention is an aluminum-copper-silicon alloy, and mainly contains aluminum as a main material, and 0.4 to 0.5% by weight of copper (Cu), 2.5-3.0 wt% silicon (Si), 0.1 wt% or less magnesium (Mg), 0.1 wt% or less iron (Fe) and 0.20 wt% or less titanium (Ti) It is characterized by containing.

  At present, alloys used for sand casting or gravity casting are mainly AC4C (A356) series alloys and contain about 6.5 to 7.5% of Si (KS D 6008). Table 1 below shows the contents of the high elongation sand mold casting aluminum alloy and the AC4C aluminum alloy according to the invention with respect to the respective components.

  In the composition and content range of the present invention shown in Table 1, copper (Cu) has the functions of solid solution strengthening and precipitation strengthening, but if it is too much, there is a possibility that the corrosion resistance may be lowered. Limited to ~ 0.5 wt%.

  In addition, silicon (Si) is an element that is often added to improve the castability because it improves fluidity when added to an aluminum alloy. Was limited to 2.5-3.0 wt%.

  Magnesium (Mg) has a precipitation strengthening effect, but if excessive precipitates are produced during heat treatment, the elongation is adversely affected. Therefore, the content range is limited to 0.1% by weight or less.

  Further, the iron (Fe) element forms a compound with aluminum, silicon and the like to reduce the elongation rate, so the addition amount is limited to 0.1% by weight or less.

  On the other hand, in a method for producing a cast connecting member of an automobile space frame using an aluminum alloy having the above composition, the present invention is a process in which a solution treatment is performed after casting a product, and then an artificial aging treatment is performed. The heat treatment condition for artificial aging is characterized by heat treatment (artificial aging) at a temperature of 150 to 160 ° C. for 4 to 5 hours.

  FIG. 2 shows a heat treatment curve of the production method according to the present invention.

  FIG. 2 shows a preferred embodiment of the present invention, which shows an example in which a solution treatment is performed at a temperature of 538 ° C. for 8 hours and then an artificial aging treatment is performed at a temperature of 155 ° C. for 4 hours.

  In the production method of the present invention, when the heat treatment temperature is less than 150 ° C., there is a problem that the aging does not occur properly and the strength is not secured, and when it is higher than 160 ° C., the elongation rate is lowered due to overaging. This is not preferable.

  In addition, if the heat treatment time is less than 4 hours in the above temperature range, there is a problem that aging does not occur properly and the strength is insufficient, and this is not preferable. It is not preferable.

  In this way, after an aluminum alloy having the above composition and content is used and a product is cast by the sand casting method, after solution treatment, artificial aging treatment is performed under the heat treatment conditions presented in the present invention, an automobile space frame is obtained. It is possible to ensure sufficient physical properties required as a cast connecting member.

  Hereinafter, the present invention will be described in more detail through examples.

  As an example of the present invention, an aluminum alloy having the composition and content presented in the present invention was used, a cast product was manufactured by a normal sand casting method, and this was subjected to solution treatment at 538 ° C. for 8 hours. Heat treatment was performed at 4 ° C. for 4 hours.

  The tensile strength, yield strength, and elongation were measured using the specimens produced by the above method, and the results are shown in Table 2 together with the physical properties of the AC4C alloy widely used for sand casting.

  As can be seen from Table 2, the yield strength is inferior to that of existing materials, but the elongation is 18.3%. According to the present invention, a product with a high elongation that cannot be obtained from a general cast product is obtained. Can be confirmed, and physical property values similar to those obtained by the high vacuum die casting (die casting) method can be secured (in the case of products applied to German Audi A2, A3 vehicles, The tensile strength is 200 MPa, the yield strength is 130 MPa, and the elongation is 14 to 18%).

  On the other hand, using the aluminum alloy of the same composition and content presented in the present invention, after performing sand casting and solution treatment under the same conditions, each specimen manufactured through a heat treatment process at different temperatures and times. The results of evaluating the physical properties are shown in Tables 3 and 4 below.

  Table 3 shows a comparison of the physical properties of each specimen according to the heat treatment temperature, and Table 4 shows a comparison of the physical properties of each specimen according to the heat treatment time.

  In the comparison of Table 3, the heat treatment time was all 4 hours, and in the comparison of Table 4, the heat treatment temperatures were all 155 ° C.

  Looking at the measurement results in Table 3 and Table 4, in the case of Example 1 and Example 2, it is possible to obtain preferable physical property values as a casting connecting member such as a high elongation rate. It can be seen that the presented temperature and time heat treatment conditions are optimal.

  This embodiment is for explaining the present invention more specifically, and it is obvious to those skilled in the art to which the present invention belongs that the technical scope of the present invention is not limited thereto. Will.

It is the schematic which showed the normal motor vehicle space frame. It is the figure which showed the heat processing curve of the manufacturing method by this invention.

Claims (2)

In aluminum alloy for cast connecting member of automobile space frame,
With aluminum as the main material, 0.4 to 0.5 wt% copper (Cu), 2.5 to 3.0 wt% silicon (Si), 0.1 wt% or less magnesium (Mg), An aluminum alloy for a cast connecting member of an automobile space frame, characterized by containing 0.1% by weight or less of iron (Fe) and 0.20% by weight or less of titanium (Ti). In the method of manufacturing a cast connecting member for an automobile space frame,
With aluminum as the main material, 0.4 to 0.5 wt% copper (Cu), 2.5 to 3.0 wt% silicon (Si), 0.1 wt% or less magnesium (Mg), After casting and solution treatment of an aluminum alloy containing 0.1 wt% or less of iron (Fe) and 0.20 wt% or less of titanium (Ti), the temperature is 150 to 160 ° C. for 4 to 5 hours. A method for producing a cast connecting member for an automobile space frame, characterized by performing heat treatment.