profiles 

Aluminum profiles: limiting dimensions

Press, technology and alloy

Maximum dimensions aluminum profiles - their cross-section and total length - depend on:

  • technical parameters of extrusion press,
  • applied pressing technology,
  • type of heat treatment of profiles, and
  • type aluminum alloy.

Maximum length of aluminum profiles

For aluminum alloy profiles, which are hardened not directly at the exit from the press, and from separate heating, such as high-strength alloys of the 2xxx and 7xxx series, the maximum length is determined by the dimensions of the heating furnace for hardening, dimensions of the quenching vessel and dimensions of the aging furnace. With the vertical arrangement of the furnace and quenching vessel, this length is about 6 m, and with horizontal - about 10 m.

For aluminum profiles from 6xxx series alloys, which are subject to artificial aging, the maximum length is limited by the length of the aging oven.

Aluminum profiles of the 6xxx series alloys, which naturally age, as well as from alloys, which are not subjected to thermal hardening (1xxx, 3xxx and 5xxx), the maximum length of the profiles is limited only by the possibilities of in-shop movement and transportation of the profiles.

The same transport restrictions apply to aluminum profiles from some 7xxx series alloys.. These are alloys, which do not contain much copper, have the minimum strength for this series and weld well. To such alloys, first of all, alloy applies 7005 (1915), which is usually press hardened by moderate air cooling and then naturally aged.

The maximum length of very massive aluminum profiles is limited by the amount of metal in the original blank. The most commonly used workpieces with a diameter (traditionally in inches): 6, 7 and 8 inches, less often - 5, 9, 10 inches and more. The optimal length of the workpiece is usually considered its four diameters..

Maximum width of the aluminum profile

The width of regular profiles is limited to about 0,8 press container diameters. On matrices of special design, so-called matrices with expander, profiles with a width of 15 % wider, than container diameter.

Profiles up to 300 mm are pretty commonplace, as there are quite a few extrusion presses in the world with large enough containers. There are profiles - panels - width 600 mm or even more, but only a few presses around the world are capable of this. Such huge profiles apply, eg:

  • in aircraft construction;
  • in carriage building;
  • in the bodies of trucks (figures 1 and 2);
  • on platforms of offshore oil rigs (figure 2).

shassi-avtomobilyaFigure 1 – Two designs of truck chassis elements using special aluminum profiles: (a) – for welding, (b) – under the adhesive connection.

Pay attention to the slots for the screw heads, which are used to connect with cross members. Made to improve fatigue strength.

profili-kuzovFigure 2 - Some typical large width aluminum profiles:

a – for the deck of an offshore oil rig;
b, c, d - profiles for truck bodies

The minimum thickness of the aluminum profile wall

For reasons of economy, the designer usually strives to make a cross-section of an aluminum profile with as thin walls as possible.. Minimum aluminum profile wall thickness depends on profile design and alloy type, as well as from the need to control the warpage of the profile during pressing and hardening.

The minimum possible wall thickness of an aluminum profile depends on the dimensions of the cross-section of the profile. Very rude, minimum "practical" thickness of the solid profile of "soft" alloys of the 6xxx series, such as 6060 and 6063, simultaneously meets the following two conditions:

  • no less 1,2 mm;
  • no less 1 % profile cross section size.

Figure 3 – Recommendations for the minimum wall thickness
for profiles of varying complexity made of alloy 6063 [2]

Figure 4 – Minimum wall thickness for extrusion presses by force 10-80 MN [3]

I must emphasize, that these are very rough estimates. Sometimes the smallest possible profile thickness is thicker, sometimes thinner.

See. See also: Discussion on Minimum thickness of aluminum profiles

The second condition (1 %) refers rather to the overall profile thickness, for example, than such details, like short ribs. It is more realistic to successfully extrude a profile with such a thickness., if the state T5 is set for it with air cooling. With more intensive cooling, the risk of excessive warping of the profiles and a large percentage of rejections for this defect increase sharply.

For hollow profiles, the value of the minimum possible wall thickness increases in comparison with solid profiles by percent 25.

For more "hard" alloys of the 6xxx series, such as 6061 and 6082, minimum thickness, naturally, increases slightly. For aluminum alloys at the beginning of the strength series of the 7xxx series, such as, alloy 7005, the minimum thickness is already increasing more significantly. For alloys of the 2xxx series, harder 7xxx series alloys and 5xxx series alloys, especially with a magnesium content of more 2,5 %, this minimum practical value rises even more.

Sources:

  1. John Dwight, Aluminium Design and Construction, Taylor & Francis e-Library, 2002
  2. TALAT 1302
  3. TALAT 2202