Patent Publication Number: US-2019185968-A1

Title: Al casting alloy

Description:
The invention relates to an aluminum casting alloy. 
     From DE 10 2015 111 020 A1, an Al casting alloy is known that contains the alloy components 
     Si: &lt;3.8 to 5.8 wt.-%, 
     Mg: 0.1 to 0.6 wt.-%, 
     Cr: 0.05 to 1.3 wt.-%, 
     Fe: &lt;0.18 wt.-%, 
     Mn: &lt;0.06 wt.-%, 
     Ti: &lt;0.2 wt.-%, 
     Cu: ≤0.03 wt.-%, 
     Sr: &lt;0.010 to 0.030, 
     Zr: &lt;0.006 wt.-%, 
     Zn: &lt;0.006 wt.-%, 
     Contaminants: &lt;0.1 wt.-%, 
     and is supplemented to 100 wt.-% with Al, in each instance. 
     Proceeding from this prior art, which discloses an Al casting alloy with optimized mechanical properties, and thereby advantageously leads to material savings when used for the production of cast components, in particular in the chassis sector of motor vehicles, and in the case of more complex geometries of the cast components to be cast, it has been shown, however, that in the case of some geometries of the cast components to be cast, problems can occur in connection with their castability. 
    
    
     The invention is therefore based on the task of further improving such an Al casting alloy with regard to its castability, without its mechanical properties being excessively influenced in negative manner. 
     This is achieved, according to the invention, by means of an Al casting alloy that contains the alloy components listed below 
     Si: &gt;3.8 to 5.8 wt.-%, 
     Mg: 0.45 to 0.55 wt.-%, 
     Cr: 0.05 to 0.5 wt.-%, 
     Sr: 0.010 to 0.030, 
     Contaminants: &lt;0.1 wt.-%, 
     and is supplemented to 100 wt.-% with Al, in each instance. 
     The selection of alloy components according to the invention on the order stated leads to an improvement in castability, without the mechanical properties being negatively influenced. 
     The alloys according to the invention can contain production-related contaminants. It can be advantageous if the permissible admixture of P amounts to maximally 10 ppm. It can be advantageous if the permissible admixture of Ca amounts to maximally 20 ppm. It can be advantageous if the permissible admixture of Sb amounts to maximally 40 ppm. It can be advantageous if the permissible admixture of Cd amounts to maximally 75 ppm. It can be advantageous if the permissible admixture of Na amounts to maximally 15 ppm. It can be advantageous if the permissible admixture of Na amounts to maximally 15 ppm. It can be advantageous if permissible admixtures of other alloy components individually amount to maximally 0.03 wt.-%, but in total, as has already been mentioned, amount to maximally 0.10 wt.-%. 
     For optimization of the castability without a negative influence on mechanical characteristic values of the cast component to be cast, it can be advantageous if Si is contained with a content of more than 4.0 wt.-%, preferably of at least 4.5 wt.-%, particularly preferably of at least 4.7 wt.-%, very particularly preferably of at least 4.9 wt.-%. For optimization of the castability without a negative influence on mechanical characteristic values of the cast component to be cast, it can be advantageous if Si is contained with a content of maximally 5.5 wt.-%, preferably of maximally 5.3 wt.-%, particularly preferably of maximally 5.1 wt.-%. 
     For optimization of the castability without a negative influence on mechanical characteristic values of the cast component to be cast, it can be advantageous if Mg is contained with a content of more than 0.45 wt.-%, preferably of at least 0.47 wt.-%, particularly preferably of 0.49 wt.-%. For optimization of the castability without a negative influence on mechanical characteristic values of the cast component to be cast, it can be advantageous if Mg is contained with a content of less than 0.55 wt.-%, preferably of maximally 0.53 wt.-%, particularly preferably of maximally 0.51 wt.-%. 
     For optimization of the castability without a negative influence on mechanical characteristic values of the cast component to be cast, it can be advantageous if Cr is contained with a content of more than 0.05 wt.-%, preferably of at least 0.07 wt.-%, particularly preferably of at least 0.09 wt.-%, particularly preferably of at least 0.11 wt.-%. For optimization of the castability without a negative influence on mechanical characteristic values of the cast component to be cast, it can be advantageous if Cr is contained with a content of less than 0.250 wt.-%, preferably of less than 0.20 wt.-%, particularly preferably of less than 0.18 wt.-%, very particularly preferably of less than 0.15 wt.-%, very very particularly preferably of less than 0.13 wt.-%. 
     For optimization of the castability without a negative influence on mechanical characteristic values of the cast component to be cast, it can be advantageous if Fe is contained with a content of less than 0.18 wt.-%, preferably of up to 0.15 wt.-%, particularly preferably with a content of up to 0.12 wt.-%. For optimization of the castability without a negative influence on mechanical characteristic values of the cast component to be cast, it can be advantageous if Fe is contained with a content with a content of at least 0.01 wt.-%. 
     For optimization of the castability without a negative influence on mechanical characteristic values of the cast component to be cast, it can be advantageous if Mn is contained with a content with a content of up to 0.06 wt.-%, preferably of up to 0.05 wt.-%, particularly preferably of up to 0.03 wt.-%. For optimization of the castability without a negative influence on mechanical characteristic values of the cast component to be cast, it can be advantageous if Mn is contained with a content of at least 0.01 wt.-%. 
     For optimization of the castability without a negative influence on mechanical characteristic values of the cast component to be cast, it can be advantageous if Ti is contained with a content of less than 0.2 wt.-%, preferably of up to 0.03 wt.-%. For optimization of the castability without a negative influence on mechanical characteristic values of the cast component to be cast, it can be advantageous if Ti is contained with a content of at least 0.005 wt.-%, preferably of at least 0.010 wt.-%, particularly preferably of more than 0.015 wt.-%. For optimization of the castability without a negative influence on mechanical characteristic values of the cast component to be cast, it can be advantageous, for some applications, if Ti is contained with a content of at least 0.05 wt.-%, preferably of at least 0.10 wt.-%, particularly preferably of more than 0.15 wt.-%. 
     For optimization of the castability without a negative influence on mechanical characteristic values of the cast component to be cast, it can be advantageous if Cu is contained with a content of up to 0.03 wt.-%, preferably of up to 0.015 wt.-%, preferably of up to 0.01 wt.-%, particularly preferably of up to 0.0075 wt.-%. For optimization of the castability without a negative influence on mechanical characteristic values of the cast component to be cast, it can be advantageous if Cu is contained with a content of at least 0.001 wt.-%, preferably of at least 0.0025 wt.-%, particularly preferably of at least 0.005 wt.-%. 
     For optimization of the castability without a negative influence on mechanical characteristic values of the cast component to be cast, it can be advantageous if Sr is contained with a content of at least 0.015 wt.-%, preferably of at least 0.019 wt.-%. For optimization of the castability without a negative influence on mechanical characteristic values of the cast component to be cast, it can be advantageous if Sr is contained with a content of up to 0.025 wt.-%, preferably of up to 0.024 wt.-%. 
     For optimization of the castability without a negative influence on mechanical characteristic values of the cast component to be cast, it can be advantageous if Zr is contained with a content of less than 0.006 wt.-%, preferably of 0.001 to 0.005 wt.-%. 
     For optimization of the castability without a negative influence on mechanical characteristic values of the cast component to be cast, it can be advantageous if Zn is contained with a content of less than 0.006 wt.-%, preferably of 0.001 to 0.005 wt.-%. 
     For numerous applications, it can be advantageous if contaminants are contained, in sum, at a content of &lt;0.05 wt.-%. For diverse applications, it can also be advantageous if contaminants are individually contained at a content of &lt;0.005 wt.-%. 
     For specific cast components, it has proven to be advantageous if the Al casting alloy according to the invention is a low-pressure Al casting alloy. 
     Accordingly, the invention also relates to a method for the production of a cast component from an Al casting alloy according to one of claims  1  to  22 , in which the low-pressure casting method is used. 
     For specific cast components, it has proven to be advantageous if the Al casting alloy according to the invention is a counter-pressure (CPC) Al casting alloy. 
     Accordingly, the invention also relates to a method for the production of a cast component from an Al casting alloy according to one of claims  1  to  22 , in which the low-pressure/counter-pressure casting method is used. 
     Fundamentally, various permanent mold casting methods are suitable as production methods for cast components, particularly as chassis parts, preferably as wheel-guiding parts, very preferably as damper stilts, wheel mounts or pivot bearings of motor vehicles, composed of the casting alloy according to the invention. Because of the very good mechanical properties in the case of wheel-guiding parts of motor vehicles subjected to great stress, however, low-pressure chill casting and the low-pressure/counter-pressure casting method (CPC method), which is also called the counter-pressure chill casting method, are particularly suitable as production methods. 
     Squeeze casting, gravity chill casting or die-casting, particularly thixo, rheo, or low-pressure sand-casting, can be used as production methods for cast components, particularly as chassis parts, preferably as wheel-guiding parts, very preferably as damper stilts, wheel mounts or pivot bearings of motor vehicles, composed of the casting alloy according to the invention. 
     In order to achieve the advantages mentioned above or to develop them even further, it is advantageous if the cast components are subjected to two-stage heat treatment, namely solution annealing and subsequent heat aging. It can be advantageous if the cast component is quenched in air or preferably water between the heat treatment stages. 
     It can be practical if the cast component, after the casting process, is solution-annealed between 530° C. and 550° C. for 6 to 10 h, preferably between 540° C. and 550° C. for 7 to 9 h, particularly for 8 to 9 h, very particularly preferably between more than 540° C. and 550° C. for 7 to 9 h, particularly for 8 to 9 h. 
     It can be practical if the cast component, after the casting process, is tempered between 180° C. and 210° C. for 1 to 8 h, particularly for 1 to 6.5 h, preferably between 180° C. and 190° C. for 1 to 6.5 h, particularly for 4 to 6.5 h, particularly preferably between 180° C. and less than 190° C. for 4 to 6.5 h, particularly for 5 to 6.5 h. 
     The invention furthermore provides for the use of an Al casting alloy according to one of the claims or of a particularly heat-treated component according to one of the claims, for chassis parts of motor vehicles, preferably for wheel-guiding components of motor vehicles, very particularly preferably for damper stilts, wheel mounts, pivot bearings or, in particular, transverse control arms of motor vehicles. 
     The Al casting alloy according to the invention is preferably intended for a transverse control arm as disclosed in the German patent application DE 10 2015 122 859.9. The content of DE 10 2015 122 859.9 is properly incorporated into the disclosure content of the present application, by means of explicit reference, as belonging to the object of the present application. 
     The invention furthermore provides for use of an Al casting alloy according to one of the claims or of a cast component, in particular a heat-treated component, according to one of the claims, for wheel rims of motor vehicles. 
     Cast components according to the invention, which are produced from an Al casting alloy according to one of the claims and/or according to a method according to one of the claims are characterized in that in spite of the improved castability, no excessively negative influence on their mechanical characteristic values obtained after heat treatment takes place, in particular of the tensile yield strength R p 0.2 of 300 to 325 MPa, preferably of 305 to 310 MPa, and/or of the elongation to rupture A5 of 4 to 10%, preferably of 7 to 9%, and/or of the tensile strength R m  of 350-375 MPa, preferably of 350-360 MPa.