6063 Aluminum Profile Extrusion Core Standards

In the aluminum alloy extrusion profile market, 6063 alloy is considered a "star material." Statistics show that 6000 series alloys account for over 70% of the global aluminum alloy extrusion market share, with 6063 alloy, due to its excellent processing performance and surface treatment characteristics, becoming the preferred material in construction, transportation, electronics, and other fields. Mastering standard extrusion processes is crucial for manufacturing high-quality 6063 Aluminum Profiles. This article will comprehensively analyze the technical key points of the 6063 Aluminum Profile extrusion process from the perspectives of material standards, process flow, process parameters, and quality control.

Ⅰ Material Standards for 6063 Aluminum Alloy

1. Chemical Composition

6063 Aluminum Alloy belongs to the Al-Mg-Si system of heat-treatable wrought Aluminum Alloys, with Mg₂Si as its main strengthening phase. According to the national standard GB/T 3190-2020 "Chemical Composition of Wrought Aluminum and Aluminum Alloys", the chemical composition range of 6063 Aluminum Alloy is shown in the table below:

Among them, Mg and Si are the core strengthening elements of 6063 alloy. The ideal Mg/Si mass ratio is approximately 1.73, at which point the Mg₂Si strengthening phase ratio is the highest. Although Fe is an impurity element, too low a content can easily lead to hot cracking during extrusion. An appropriate amount of Fe (0.15%-0.25%) is beneficial to the extrusion process.

2. Product Standards

Currently, the main product standards implemented for 6063 Aluminum Profiles in China are GB/T 5237 series (for building profiles) and GB/T 6892 (for general industrial profiles). The GB/T 5237 standard is divided into six parts, covering substrate, anodized profiles, electrophoretic coated profiles, powder coated profiles, fluorocarbon coated profiles, and thermally insulated profiles.

According to GB/T 5237.1-2023, the mechanical properties of the 6063-T5 substrate are: tensile strength ≥200MPa, yield strength ≥160MPa, and elongation after fracture ≥8%. Regarding dimensional tolerances, the profile wall thickness deviation ≤±0.15mm, plane gap ≤0.3mm/m, and angular deviation ≤±1°.

Ⅱ Ingot Heating and Extrusion Preparation

The core of pre-extrusion treatment lies in the selection and heating of the ingot. A common practice is to prioritize the use of ingots that have undergone homogenization treatment. The standard homogenization annealing process is 560±20℃, held for 4-6 hours, and cooled by forced air cooling or rapid water spraying after removal from the furnace. After homogenization, the ingot extrusion speed can be significantly increased, while simultaneously optimizing mechanical properties and surface gloss.

In the heating stage, controlling the ingot heating temperature is crucial. Generally, the following settings can be used: unhomogenized ingots are heated to 460-520℃, and homogenized ingots to 430-480℃. The extrusion temperature needs to be flexibly adjusted according to different product cross-sections, extrusion ratios, and die types. The extrusion barrel temperature is generally controlled at 380-450℃, and the die temperature at 450-500℃.

Ⅲ Extrusion Process Parameter Control

1. Extrusion Temperature

Extrusion temperature is the most fundamental and critical process factor. To ensure sufficient solid solution of the strengthening phase Mg₂Si in the aluminum rod during extrusion, the temperature of the 6063 Aluminum Alloy rod before extrusion should typically be maintained at 460-510℃. The process temperatures vary depending on the heat treatment state and die type.

Studies show that extrusion temperature significantly affects the mechanical properties of profiles. As the extrusion temperature increases from 460℃ to 540℃, the tensile strength and yield strength of the profile change significantly. Furthermore, excessively low extrusion temperatures can lead to inconsistent grain size during dynamic recrystallization, affecting the uniformity of the microstructure. Therefore, in actual production, the extrusion temperature must be rationally determined for different cross-sectional shapes to ensure that the profile temperature remains within the range required for solution heat treatment.

2. Extrusion Speed

Extrusion speed has a significant impact on the deformation heat effect, deformation uniformity, recrystallization and solution treatment processes, the mechanical properties of the product, and surface quality. Excessive extrusion speed can result in defects such as pitting and cracks on the product surface, and also increases the non-uniformity of metal deformation.

Specifically, when the extrusion speed exceeds 12 m/min, structural striation defects begin to worsen; at 17 m/min, these defects become even more pronounced. In summary, the suitable extrusion speed for 6063 profiles is generally in the range of 10-30 m/min, but in actual production, it needs to be determined based on the complexity of the profile cross-section, wall thickness, and product application.

3. Influence of Extrusion Ratio on Mechanical Properties

The extrusion ratio (extrusion coefficient) is a quantitative indicator of the degree of cross-sectional reduction of the alloy in the die, and its magnitude directly affects the mechanical properties of the product and the uniformity of metal flow. Changes in extrusion temperature, extrusion speed, and extrusion ratio have a significant impact on the tensile strength and yield strength of industriaL Profiles such as radiators, while the impact on elongation after fracture is relatively weak. The selection of the extrusion ratio needs to comprehensively consider factors such as the product cross-sectional area, die design, and extruder capacity.

Ⅳ Key Points of Die Design

The mainstream structure of 6063 aluminum profile extrusion dies is a flow-dividing die, whose main components include the flow-dividing orifice, die core, welding chamber, and working zone. The working zone is a critical component determining the profile dimensions and surface quality. Generally, negative tolerances are used to ensure the aluminum material meets tolerance standards and to extend mold life as much as possible. An excessively short working zone length leads to unstable product dimensions, easily causing defects such as ripples, ovality, and indentations, and also easily causes premature mold wear.

The working zone surface should undergo nitriding or other surface heat treatment, with a surface roughness requirement of not less than Ra0.8~0.4. The size of the manifold orifice should be directly proportional to the profile area. The size design of the manifold orifice should be optimized as much as possible without affecting mold strength and profile surface quality.

Ⅴ Online Quenching Process

1. Cooling Method Selection

6063 aluminum alloy has low sensitivity to quenching cooling rate and possesses "self-quenching" properties, allowing for quenching using air cooling. However, the cooling rate still has a significant impact on the final mechanical properties of the product: to ensure the formation of a supersaturated solid solution and vacancies in the aluminum profile, and to achieve the standard-specified mechanical properties after aging, the cooling rate needs to be sufficiently high. The minimum cooling rate for strengthening 6063 alloy is 38℃/min.

For profiles with a wall thickness greater than 5.0mm, if air cooling equipment cannot meet the requirements, water mist spraying should be added to the outlet cooling zone to accelerate the cooling rate. For thinner profiles, air cooling is sufficient, and the thermal stress generated by air cooling is smaller, making it less likely to cause longitudinal bending, twisting, and cross-sectional distortion of the profile. In the spray cooling process, the vapor film layer can be quickly broken through mechanical action, resulting in more uniform cooling and effectively preventing bending and twisting deformation of complex-shaped profiles during quenching.

2. Quenching Temperature and Time Requirements To achieve online quenching, the following conditions must be met: the temperature of the extruded product before flowing out of the die must reach the solution heat treatment temperature range of the alloy; the time from when the product flows out of the die to when it enters the cooling device should not exceed the quenching transfer time; the temperature of the hot-extruded product after passing through the cooling device should be lower than the specified temperature of the alloy.

After passing through the outlet cooling zone and the storage platform cooling zone, the temperature of the aluminum profile should drop below 50℃ to ensure that the profile is sufficiently cooled before tension straightening. To achieve this goal, the distance from the quenching and cooling device to the extruder outlet should be as short as possible, generally not exceeding 1 meter.

Ⅵ Tension Straightening After the profile exits the die, a traction machine is typically used for synchronous traction. The traction machine applies a certain tension to the extruded product while moving synchronously with the product's outflow speed. This aims to reduce uneven lengths and scratches during multi-line extrusion, and to prevent twisting and bending of the profile after exiting the die. Tension straightening not only eliminates longitudinal irregularities in the profile's shape but also reduces residual stress, improves strength characteristics, and maintains good surface quality. The tensile rate is generally controlled within 1%.

Ⅶ Artificial Aging Process

1. Difference between T5 and T6 6063 aluminum profiles are mainly supplied in two states: T5 and T6. T5 involves air-cooling and quenching after extrusion followed by incomplete artificial aging, achieving a certain strength while maintaining good plasticity. T6 involves water-cooling and quenching after extrusion followed by complete artificial aging, achieving maximum strength and hardness. The prices of the two differ significantly, and their selection should be based on a comprehensive consideration of actual mechanical performance requirements.

2. Aging Parameters

The aging process mainly includes two key parameters: holding temperature and holding time. A typical artificial aging process parameter for 6063 alloy, as defined by an aluminum profile manufacturer, is as follows:

Supply Status | Aging Temperature | Holding Time

T5 | 200±5℃ | 120-140 minutes

T6 | 190±5℃ | 160-180 minutes

If the aging temperature is too high or too low, or the holding time is too long or too short, it will lead to over-aging or under-aging of the aging microstructure, causing the mechanical properties to fail to meet standard requirements. Aging treatment requires uniform temperature, with a temperature difference generally not exceeding ±3-5℃.

For thick-walled profiles with a wall thickness ≥2.5mm, the time to reach the holding temperature is 25-30 minutes later than for thin-walled profiles. Therefore, the holding time needs to be extended accordingly in actual production. The pre-aging framing process is also crucial. Profiles within the same frame should maintain a certain spacing to avoid interlocking stacking, ensuring smooth air circulation within the aging furnace and preventing temperature differences at any point from exceeding 5℃.

Ⅷ Finished Product Inspection According to national standards, finished 6063 aluminum profiles require multiple performance tests. Mechanical properties are tested through tensile testing for tensile strength, specified non-proportional elongation, and elongation after fracture. Surface properties include anodized film thickness and coating adhesion. Dimensional properties are measured using calipers, projectors, and other tools to ensure compliance with GB/T 14846 "Dimensional Tolerances for Aluminum Profiles". All test reports must be CMA/CNAS accredited and serve as essential documents for profile delivery and project acceptance.

Ⅸ Conclusion The extrusion process for 6063 aluminum profiles is a complete system involving material selection, ingot heating, temperature and speed control, die design, quenching and cooling, tensile straightening, aging treatment, and finished product inspection. Each step has corresponding national standards and process parameters as specifications and guidelines.