Extrusion Profile Features

1 - General Features:

Metals play a crucial role in the development of civilization. In this process, only a few metals, such as aluminum, have played as important a role. Aluminum, with its unique properties, has gained significance since ancient times and today is used in greater quantities than all other non-ferrous metals such as wood, copper, iron, and steel. Despite being a very young metal industrially produced since the second half of the 19th century, copper and its alloys are used in larger quantities than all non-ferrous metals such as lead, tin, and zinc combined.

The general features of aluminum are summarized below:

♦ Aluminum is lightweight. It weighs only about one-third of the weight of an equal volume of steel material. ♦ Aluminum is resistant to weather conditions, food substances, and many liquids and gases used in daily life. ♦ Aluminum has high reflectivity. Along with the contribution of silver to its white color, it has an attractive appearance for both interior and exterior architecture. The beautiful appearance of aluminum can be preserved for a long time through applications such as anodic oxidation (anodizing), lacquers, etc. In many applications, even the natural oxide layer is sufficient. ♦ The strength of various aluminum alloys is equivalent to or higher than the strength of normal structural steel. ♦ Aluminum is an elastic material, making it resistant to sudden impacts. Additionally, its durability does not decrease at low temperatures. (The strength of steels decreases against sudden impacts at low temperatures.) ♦ Aluminum is an easy-to-process metal. It can be transformed into foil or wire with a thickness of less than 1/100 mm. ♦ Aluminum conducts heat and electricity as well as copper. ♦ All methods such as casting, forging, rolling, pressing, extrusion, and drawing can be applied to shape aluminum.

2 - Aluminum Extrusion Profile:

A "profile" is defined as shaped material with a specific cross-sectional shape (the shape of this section can be flat or variably shaped according to the purpose) and a small cross-section/length ratio, meaning its length is much greater than its width.

Like many metals, aluminum is processed for profile production through rolling (drawing) or extrusion. However, for profiles with complex shapes, "extrusion" is the most commonly used method. (See: Aluminum Extrusion Press and Aluminum Extrusion Plant)

The areas of application for aluminum profiles produced by extrusion include:

♦ Transportation vehicles (automobile, ship, train, subway, aircraft, and spacecraft), ♦ Architectural applications and the construction industry (building facade systems, windows, doors, various constructions), ♦ Electrical industry, ♦ Machinery and equipment manufacturing, ♦ Chemical and food industry.
 

3 - Classification of Aluminum Alloys According to Chemical Structure:

To impart various properties to aluminum, various metals are mixed. Classification is made according to the added metals. An alloy is defined with a notation consisting of 4 digits. The first digit indicates the main metal added to aluminum. According to U.S. standards:         1XXX: Unalloyed aluminum         2XXX: Aluminum alloy with copper         3XXX: Aluminum alloy with manganese         4XXX: Aluminum alloy with silicon         5XXX: Aluminum alloy with magnesium         6XXX: Aluminum alloy with silicon and magnesium         7XXX: Aluminum alloy with zinc         8XXX: Aluminum alloy with iron and silicon         9XXX: Newly discovered alloys (Example: Lithium-containing alloys)

4 - Classification of Aluminum Alloys According to Heat Treatment Condition:

After the production of aluminum semi-finished or finished products, they undergo certain processes to have specific physical properties. Generally, aluminum alloys are divided into two groups:

1 - Alloys that can undergo heat treatment

2 - Alloys that cannot undergo heat treatment

For both groups, notations are used to describe the applied processes.
 

5 - Profiles Produced for Architectural Applications

Worldwide, profiles produced for architectural purposes are typically made from 6XXX alloys using the extrusion method and are coated with anodized oxidation (anodizing), either colored or colorless, to preserve their appearance for years. Among these alloys, the most commonly used are the 6063, 6060, or AlMgSi0.5 alloys, which have similar chemical composition and physical properties.

5.1. General Properties of 6xxx Series Aluminum Alloys

Alloys of the 6XXX series contain magnesium (Mg) and silicon (Si). The varying values of these elements and other impurities (such as Fe, Cu, Mn, Zn, etc.) within specific limits allow for the production of profiles with different properties depending on the intended use of the alloys. In 6XXX series alloys where the iron (Fe) content is 0.20% or less, a polished profile yields a shiny surface. If the iron content exceeds this value, the color of the profile starts to gray, and the brightness dulls. To achieve a matte surface, the iron content should be at least 0.18%. As the iron content increases, a comfortable and attractive matte surface is obtained. An iron content exceeding 0.30% not only leads to a dull appearance after anodizing but also complicates the extrusion process. The quantities of Mg and Si are crucial for the hardness of the profile after the artificial aging (thermal) treatment. However, for the maximum post-heat treatment hardness, these elements need to be at the upper limits, requiring slow production since the aluminum billet used is equally hard. In conclusion, it is beneficial to produce profiles with a suitable alloy as much as possible, depending on the intended use of the profiles. Sacrificing one property for another may be necessary, considering the desired characteristics of the profile.

The most commonly used alloys in the architectural construction sector within the 6XXX series (AlMgSi) are 6060 and 6063 (in the EN and new TS notation) and AlMgSi0.5 (in the DIN and old TS notation). Their chemical compositions are generally the same but show nuances in differences between lower and upper limits. EN AW/AA 6005, 6005A, and 6082 aluminum alloys are preferred for engineering applications where higher mechanical properties are required.

 

Rm: Tensile Strength Rp0.2: Yield Strength kg/mm2 = 10 MPa

The tempers and mechanical properties of aluminum profiles and sheets can be easily and practically understood using the Webster Hardness Measurement Calipers. To see the values of yield and tensile strength, a Tensile Test should be conducted as specified in the standards by preparing the samples accordingly.

5.2. Production of Aluminum Profiles by Extrusion Method

The production of aluminum profiles by the extrusion method requires three main components.

a - Aluminum Billet (Billet, Blank) b - Extrusion Press c - Extrusion Mold

In general, extrusion can be defined as the process where the aluminum blank, with the large force provided by the press, is passed through the mold to obtain the profile in the shape of the mold. Aluminum extrusion is done hot; billets are heated to 420-470 ºC, molds must be heated to 450 ºC, and the temperature of the profile exiting the press is above 500 ºC. Extrusion is also a cross-sectional reduction process. The section of the aluminum billet is transformed into the section of the aluminum profile. Therefore, the process becomes easier the closer the section of the billet used is to the surface measurement of the profile to be produced. This fact brings forth many technical alternatives, such as the design of profile molds and the selection of the production press (force, die diameter). Consequently, for the production of thin and small section profiles, a small amount of billet and hence a correspondingly sized press is required. For large profiles, large molds, billets, and presses are required. When attempting to produce small profiles in large presses with large billets, it leads to time and energy losses, and a decrease in efficiency. On the contrary, large section profiles often cannot be produced in small presses with small billets. The profile exiting the extrusion press is cooled, subjected to a cold stretching process, and cut to the desired length. Subsequently, heat treatments (according to order specifications), detailed below, are applied. (Those marked with the T are used.) It is recommended to use a hardness measuring caliper for aluminum profiles to ensure that the surface of the aluminum profile does not get damaged after leaving the press, and to avoid black/gray cooling spots after anodizing, special heat-resistant textile products should be used on the conveyors of the extrusion press instead of wood or graphite. The extent to which profiles will have shape and dimension tolerances is specified in various standards. Producing dimensions outside the standards depends on the agreement between the customer and the manufacturer. However, it should be remembered that producing profiles with much narrower tolerances than the standards is always more costly than normal.

 

5.3. Anodic Oxidation of Aluminum Profiles (Anodized)

Architecturally produced aluminum profiles are preferred to be visually appealing. It is desired that their appearance and color remain unchanged for many years at the usage site. In reality, the naturally occurring oxide layer of aluminum protects it from corrosion for years without the need for any treatment. However, by increasing the thickness of this layer (which is 12 microns) to 10-25 microns, the appearance is guaranteed to be preserved. This process is known as "Anodic Oxidation" (Anodizing, Anodic Oxidation) in English or "Eloxal" in German. In this text, both expressions are used in the same way.

Anodic Oxidation is carried out electrolytically, and there are many methods for it. In principle, aluminum profiles are immersed as an anode in an acidic electrolyte. A certain voltage (direct current) is applied between the anode and cathode. The electrolyte dissolves, and an oxide layer forms on the surface of the profile. This layer is transparent like glass. Aluminum is protected from corrosion by this layer. Among the many methods of Anodic Oxidation, the "Direct Current Method with Sulfuric Acid" is the most widely used worldwide. Aluminum anodizing plant (Anodic Oxidation)

5.3.1. Pre-treatment of Profiles Before Anodic Oxidation:

Since the Anodic Oxide layer is transparent, it reveals the surface of the profile. If the surface is desired to be matte or shiny, these pre-treatments should be carried out before Anodic Oxidation.
 

5.3.1.1. Polishing Process:

To polish the surfaces of the profiles, brushes made from special fabrics are used to apply polish to the surface. If there are excessive scratches on the surface that polishing brushes cannot remove, scratches are eliminated before polishing through a special sisal brush or sanding process, and then polishing is performed.

5.3.1.2. Sanding Process (Feltting):

There can be two purposes for the sanding process:

• To remove scratches on the surface before polishing,
• By using different types of sandpaper, create patterned lines on the surface.

5.3.1.3. Satinizing Process:

The satinizing process is used to give the surface a matte appearance by equipping it with numerous lines, typically done with stainless steel wire circular brushes or special circular Scotchbrush brushes. (The machines for both types of brushes are separate.) Depending on the characteristics of the brushes used, the surface appearance can vary.
 

5.3.1.4. Industrial Anodizing:

For this surface appearance, no mechanical (physical) process is carried out before anodizing. The profile goes directly to the anodizing facility and is only treated by soaking in a caustic bath for a specific period to provide a matte finish. This achieved matte finish is often sufficient to eliminate surface lines. Due to its low cost, this is the preferred surface type in most Western countries.

5.3.2. Anodic Oxidation Process:

Profiles undergo a series of chemical processes before being immersed in the electrolyte of anodic oxidation and subjected to current. These processes include: a) Degreasing: For cleaning the surface of the profiles. b) Caustic Cleaning: To remove dirt and oils that cannot be cleaned by the degreasing process and, if necessary, to provide a matte effect on the surface. c) Neutralization: Removes the sludge generated during the caustic process. d) Anodic Oxidation (Anodizing): A protective oxide layer is applied to the surface according to the process described in section 5.3. To ensure the longevity of the oxide layer, a "sealing process" is performed. e) Sealing Process: Profiles are left in a hot water bath with an adjusted pH or in a special impregnation bath with a specific chemical composition for a specified time. This volumetrically enlarges the pores of the anodized layer, increasing resistance to both physical and chemical effects. Among all the processes outlined above, thorough rinsing ensures the quality of the process and prevents the mixing of chemicals.

 

5.4. Coloring of Aluminum Profiles

In addition to the silver-white color of aluminum, profiles are prepared in various colors for architectural and decorative purposes. Generally, coloring is done with two alternative methods.

♦ Painting ♦ Coloring for anodized aluminum

5.4.1. Painting:

The painting process is similar to painting wood, steel, and other materials. However, for aluminum profiles, a chemical conversion (chromating or chromate equivalent coating) process is performed, and then the profiles are painted in the desired colors using one of the "powder coating" methods. A recent innovation in this regard is the application of wood-like patterns on aluminum. For applying wood patterns on aluminum profiles, the aluminum profile is first painted with a powder coating in the base color of the pattern to be applied. Subsequently, the profile is covered with a special plastic film or paper on which the wood pattern is transferred to the painted aluminum surface through vacuum transfer printing. For details of the painting process, refer to the Qualicoat Specifications prepared by QUALICOAT. Electrostatic Powder Coating Plant Wood pattern coating plant Wood pattern coating films.
 

5.4.2. Coloring of Anodized Aluminum:

Coloring of anodized aluminum is the most common method. This is because the anodized layer is currently the best and most durable among all known methods of protecting aluminum. Coloring of aluminum profiles with anodizing can also be done with two alternative methods: ♦ Single-Stage Coloring, ♦ Two-Stage Coloring

5.4.2.1. Single-Stage Coloring:

This method is known as "Integral Colour Anodizing" and is mainly used in the USA. The anodizing bath simultaneously serves as the coloring bath. The electrolyte of this bath is different from the normal anodizing bath solution and also consumes much more energy because it operates at a higher voltage. Additionally, it works under limited conditions since the achievable coloration depends on the alloy profile. For all these reasons, U.S. companies are also transitioning to the two-stage coloring method.
 

5.4.2.2. Two-Stage Coloring:

As the name suggests, two separate baths are used for anodic oxidation and coloring. It is a prerequisite that the profile undergoes anodic oxidation first. Then the profile is washed and enters the coloring bath to apply the desired color. This coloring method is divided into: ♦ Immersion Painting ♦ Electrolytic Coloring

5.4.2.2.1. Immersion Painting:

The coloring bath (Painting Bath) is an aqueous solution of a specially formulated paint marketed by various companies. In this painting method, colorant pigments are absorbed between the pores of the anodized layer and penetrate from the surface of the layer to some extent below it. After being taken out of the paint bath, the profile undergoes a sealing process after washing.

5.4.2.2.2. Electrolytic Coloring:

In this method, the coloring bath is an aqueous solution of some metal salts and has electrodes because coloring is done through electrolysis. The profile is placed in the bath, and alternating current is passed between the profile and the electrodes. The metal ions in the solution are set in motion and penetrate the anodized layer. Since, in this method, electrical power is used instead of absorption, the colorant pigments reach the deepest boundary of the layer, the boundary between the profile surface and the anodized layer. Thus, the colors obtained with the electrolytic method are much more resistant to physical and chemical effects compared to those obtained with the immersion method. There are many commercial chemicals available for electrolytic coloring. The oldest of these is the ANOLOK method, which is made under license from Alcan Aluminium and uses Cobalt (Co) metal salt.
 

6. Quality

The quality of an aluminum profile intended for architectural purposes is determined by the following factors:

6.1. External Appearance

This inspection is done visually. There should be no undesirable elements such as deep grooves, wounds, notches, or dents on the profile surface.

6.2. Profile Dimensions

The aluminum profile, after production, must conform to the drawing dimensions and tolerances agreed upon with the customer. These checks are performed using tools such as calipers, micrometers, and scales.

6.3. Physical Properties of the Profile

The hardness value (60-75 BHN) of aluminum profiles used for architectural purposes is generally a good indicator in terms of other physical properties (tensile strength, elongation, etc.). Hardness can practically be measured using a Webster Penetrator. Material control tests for different alloys used in the manufacturing industry, such as series 2xxx, 7xxx, 5xxx, are more critical, and specialized equipment is used for these tests.

6.4. Anodizing/Painting Quality of the Profile

Especially for aluminum profiles intended for architectural purposes, post-anodizing color and surface quality are crucial. Whether the profile is white or colored, it should match its sample. The surface's brightness or matte condition is equally important. Although this check is currently done visually, the newly introduced "reflectometer device" provides good results and convenience.

6.5. Anodic Oxidation Layer Thickness and Detection Quality Control

The thickness and detection quality of anodic oxidation are crucial because these two factors determine the durability of the profile's appearance, whether colorless or colored.

6.5.1. Determination of Anodizing Thickness

Firstly, the anodizing thickness should not fall below the thickness requested by the customer. In Western countries, profiles used indoors require a minimum of 10 micrometers, and profiles used outdoors require a minimum of 15 micrometers of anodizing thickness. However, these thicknesses may vary more or less depending on the customer. Some countries' standards are binding in this regard. There are various methods to measure anodizing thickness. The most common and practical method today utilizes the insulating nature of the anodized layer. In this method, an electronic device called PERMASCOPE is used to take measurements. The most widely accepted anodizing specification in Europe is QUALANOD. Click here for QUALANOD specifications.

6.5.2. Determination of Detection Quality

Even if the anodizing thickness complies with standards, if the detection quality is inadequate, the lifespan of the anodized layer is short. Therefore, the last and most critical quality factor is the detection quality.

Various methods are available for determining detection quality. These methods and their general application areas are summarized below:
 

Temperature (heat treatment/condition) indicators for aluminum alloys are typically defined by adding one or more letters, indicating the heat treatment condition of aluminum and aluminum alloys obtained through casting or shaping.

Essentially, four types of heat treatment indicators are used: (O) annealed; (F) "as-fabricated" condition; (H) indicating an increase in hardness and strength due to plastic deformation below the recrystallization temperature; and (T) indicating the heat treatment condition. (W) represents the non-permanent structure after solution heat treatment, and if a time is specified, it signifies a specific heat treatment.

Descriptions of the characteristics of various heat treatments are provided below.

• F: "As-fabricated" condition (as manufactured) This condition indicates the physical structure after manufacturing without any additional treatment, with no guarantee of the mechanical properties of shaped aluminum alloys. For the cast state, for example, the designation 43F is used.

• O: Annealed, recrystallized state It is the softest state of formable aluminum alloys.

• H: Generally used for flat products (sheet/plate). It represents an increase in strength and hardness obtained in formable aluminum alloys, whether additional heat treatment is performed to achieve partial softening after cold forming (plastic deformation) below the recrystallization temperature.

After (H), there are usually two or more digits. The first digit represents the basic treatment, and subsequent digits indicate the final physical properties within the limits of plastic forming.

The characteristics represented by these digits are specified as follows:

• H1: Only shaping within the plastic forming limits. The second digit represents the performed cold working. For example, the digit 8 represents the maximum hardness achievable. Thus, (H18) indicates this result. Medium hardness between the hardest and softest is expressed as (H14). Similarly, one-quarter hardness is indicated as (H12).

The third digit is usually used to specify additional properties. For instance, (H141) has the same minimum properties as (H14), but maximum values are closer to standard values. The third digit, whether present or not, does not represent significantly different values from (H14) and is not sufficient to replace (H13) or (H15). Very hard properties are indicated by using the digit (9) as the second digit, whether or not there is a third digit. The designation (H112) signifies "controlled" as it guarantees the mechanical properties of the fabricated condition.

• H2: Represents the partially annealed state after plastic forming. After achieving a certain strength and hardness through plastic shaping, it is partially annealed to bring these values within the desired limits. This condition is indicated by writing the first digit as 2. The desired permanent strength and hardness are specified, as in (H1). For example, H28 indicates fully hardened, and H24 indicates half-hard. The H2 state for alloys that achieve age softening at room temperature is equal to the physical properties of H3. In other alloys, the H2 state is approximately equal to the physical properties of H1, although the elongation ratio is slightly higher.

• H3: Represents the state after plastic shaping and subsequent stabilization. Aluminum alloys containing magnesium are stabilized by heating at low temperatures, reducing their strength slightly while increasing their formability. If this process is not performed, the mentioned changes occur very slowly at room temperature.

This process is indicated by the third digit after (H). Plastic forming is also expressed by the two or first digit after (H).

• W: Indicates the non-permanent structure after solution heat treatment. This state is indicated due to natural aging, specified by the aging time. For example, 2024 W (1/2 hour), 7075 W (2 months), etc.

• I: Apart from the F, O, H states, it indicates heat treatments applied to achieve structural stabilization, whether plastic forming is performed or not, to stabilize the structure. After the T, digits from 2 to 9 can be added. These digits indicate specific treatments to be applied.

When the alloy code 6061-T6 is taken, additional designations are made to this base code when different properties are desired by applying separate treatments, such as in the case of 6061T62.

Natural aging at room temperature can be applied during or after the main heat treatments. The duration is controlled if it is metallurgically significant, but otherwise, it is not specified.

• T: The T notation indicates the tempers obtained by heat treatment. Different types of heat treatments are expressed with the following letter and number indicators.

Aluminum Heat Treatment Furnace:

• T1: Cooled after hot working and stabilized by natural aging.
• T2: Cooled after hot working, cold worked, and stabilized by natural aging.
• T3: Solution heat treatment applied, cold worked, and stabilized by natural aging.
• T4: Solution heat-treated, stabilized by natural aging.
• T5: Cooled after hot working and artificially aged to harden (Thermal heat treatment).
• T6: Solution heat-treated and artificially aged to harden (Thermal heat treatment).
• T7: Solution heat-treated and artificially over-aged (Thermal heat treatment).
• T8: Solution heat-treated, cold worked, and artificially aged (Thermal heat treatment).
• T9: Solution heat-treated, artificially aged (thermal heat treatment), and cold worked.
• T10: Cooled after hot working, cold worked, and artificially aged (Thermal heat treatment).

Please note that this translation is a lengthy one and may not be suitable for certain contexts. If you have specific sections or sentences you would like to focus on, feel free to ask for a more targeted translation.

Notes:

Solution Heat Treatment: Thermal process of bringing an aluminum alloy to a temperature of 520 degrees Celsius or above for a specific duration, followed by rapid cooling to dissolve alloying elements within the material. In some aluminum alloys (e.g., 6060/6063/AlMgSi0.5), quenching the material with air or water after a hot process like extrusion results in the solution heat treatment effect.

Natural Aging: The increase in material hardness through the mechanism of "precipitation hardening" by allowing an aluminum alloy to sit at room temperature, causing alloying elements to separate from the solid solution and precipitate.

Artificial Aging: Achieving hardness values not attainable through natural aging by subjecting the material to specific temperature and duration in a heat treatment furnace. (Example: 180 degrees Celsius for 5 hours for 6060/6063/AlMgSi0.5 alloy). Thermal Heat Treatment Furnace.

Thermal: The term used in the Turkish extrusion industry for "artificial aging heat treatment" of aluminum.