Best of material Aotumotive

Aluminum alloy products particularly for automotive applications, e.g. panel members, may be produced from a body of aluminum base alloy consisting essentially of, by weight, 0.5 to 0.85% Si, 0.25 to 0.48% Mg, 0.05 to 0.4% Fe, 0.75 to 1.1% Cu, 0.1 to 0.5 wt. % Mn, the balance essentially aluminum and incidental elements and impurities. The alloy body may be homogenized at a temperature in the range 900° to 1100° F. and thereafter worked into a wrought product such as sheet which may be continuously solution heat treated and quenched and aged to a T4 condition prior to forming into vehicular panel members, for example.

The improved sheet and other wrought products produced as herein described have a range of yield strength of from around 12 to 30 ksi, typically 15 to 25 ksi, for sheet in the naturally aged condition following proper solution and quench treatments as described herein. The naturally aged condition is achieved without any added treatment and occurs naturally with the passage of time. There are two aspects of natural aging in the practice which make such particularly suited to use in automotive or vehicular body applications. One aspect is that a stable property level is reached relatively quickly, after about only 1 or 2 weeks, or perhaps a month at room temperature, wherein the strength levels off and remains substantially at or near a relatively constant level for many months, or even years. Another aspect is that this stable level of properties is characterized by strength and formability qualities particularly suited to automotive or vehicular body applications. The condition of naturally aged stable properties is termed the T4 temper.

Aluminum wrought products produced in accordance with the foregoing practice provide material having the strength and forming characteristics required to serve as automotive or vehicular body sheet. One test of formability is a bend test which relates formability, especially with respect to the hemming or seaming which is sometimes employed to join inner and outer automotive panels in a dual panel structure such as a door or hood. It will be noted that the bend can be 180° and the radius of curvature can be equivalent to half the thickness (1/2 T) of the metal. For example, the bend radius would be 0.02 inch for 0.04 inch thick sheet. Automotive body sheet should be capable of withstanding such 180°-1/2 T bends without cracking, crazing or other signs of failure or incipient failure. The cracking in the hemming operation not only weakens the structure comprising the outer panel and support panel, but is also generally considered unacceptable aesthetically and can necessitate additional work to fill in and finish the hem area.

Sheet or other wrought products produced in accordance herewith are relatively readily formed into shaped or contoured automotive panels or structural members. Such forming typically includes pressing or stamping between opposite mating dies. In the case of a bumper, an extrusion or relatively thick sheet is stamped to provide the longitudinal curvature. A wheel is formed by first forming a welded hoop from a sheet, further forming the hoop to provide the desired contour and the welding or riveting to the inside of the hoop of the radial spider member which is typically stamped from sheet. These forming operations are typically carried out at room temperature but can be effected at slightly elevated temperatures of up to around 200° or at the so-called warm forming temperatures of up to around 400° F. or perhaps 450° F. However, it is preferred in some instances to perform the forming at substantially room temperature meaning not over 150° or 200° F. in order to avoid inducing uncontrolled precipitation effects in the alloy member.