6063 aluminum alloy profiles are widely used due to their many advantages such as good plasticity, moderate heat treatment strength, good welding performance, and gorgeous color after anodizing. However, in the production process, some defects often occur, resulting in low product quality, reduced product yields, increased production costs, and reduced efficiency. As a result, the company’s market competitiveness has decreased. Therefore, from the root cause to solve the 6063 aluminum extrusion profile defects is an important aspect of improving their own competitiveness. According to many years of aluminum production practice, the author summarized the common defects of 6063 aluminum alloy extrusions and their solutions, and communicated with many colleagues in order to promote each other.
1 Scratching, rubbing, bruising, scratching, and bumping are surface damages that result when the profile exits the die hole and comes into contact with tools, equipment, etc. in subsequent processes.
1.1 Main cause 1 Ingot surface has foreign matter or segregation of ingot components. When a large amount of segregated precipitates are present on the surface of the ingot and the ingot is not homogenized or homogenized, the ingot has a certain amount of hard metal particles, and the metal flows through the working belt during the extrusion process. , These segregated precipitates or hard metal particles adhere to the surface of the working belt or cause damage to the working belt, resulting in scratches on the surface of the profile; 2 Mold cavity or work belt with debris, mold work with low hardness , The work belt surface is injured in the extrusion and scratches the profile; 3 The exposed metal or graphite bar in the discharge track or oscillating bed has hard inclusions, which cause scratches on the surface of the profile when it comes into contact with the profile; 4 In the fork material bar, when the profile is sent from the discharge track to the swing bed, the profile is damaged due to excessive speed; 5 In the swing bed, the profile is dragged by human; 6 The friction between the profiles during the transportation process or Extrusion causes damage.
1.2 Solution 1 Strengthen the control of the quality of the ingot; 2 Improve the quality of mold repair, mold nitriding and strictly enforce the nitriding process; 3 Use soft felt to isolate the profile and the auxiliary tool to minimize the profile and the auxiliary tool. Contact damage; 4 Handle with care in production, try to avoid arbitrarily dragging or turning the profiles; 5 Reasonably place the profiles in the material Frame, try to avoid mutual friction.
2 Failed mechanical performance
2.1 The main cause 1 The extrusion temperature is too low, the extrusion speed is too slow, the profile extrusion temperature in the extruder can not reach the solution temperature, will not achieve solid solution strengthening; 2 profile outlet fan less air volume Not enough, resulting in slow cooling, can not make the profile in a short period of time down to below 200 °C, so that premature precipitation of coarse Mg2Si, so that the solid solution phase decreases, affecting the mechanical properties of the profile after heat treatment; 3 ingot composition Failed, the content of Mg and Si in the ingot did not meet the standard requirements; 4 The ingot was not homogenized, so that the Mg2Si phase precipitated in the ingot structure could not be re-dissolved in the extrusion for a short time, resulting in solid solution Insufficient and affect the product performance; 5 Aging process is not properly, the hot air circulation is not smooth or the thermocouple installation position is not correct, resulting in insufficient aging or over-ageing.
2.2 Solution 1 Reasonably control the extrusion temperature and extrusion speed to keep the profile at the outlet temperature of the extruder at a lower solution temperature; 2 Strengthen the air-cooling conditions, and the conditional factory can install the atomization cooling device. , in order to achieve the lower requirements of 6063 alloy cooling gradient; 3 strengthen the quality management of the ingot; 4 homogenization of the ingot; 5 reasonable determination of aging process, the correct installation of thermocouples, properly placed profiles to ensure smooth circulation of hot air.
3 geometrical tolerance
3.1 The main reasons 1 due to the unreasonable mold design or manufacturing errors, improper extrusion process, the mold and the squeeze tube is not centered, unreasonable lubrication, etc., resulting in metal flow in each point of the flow rate difference is too large, resulting in internal stress caused Profile deformation; 2 Due to excessive traction force or excessive amount of tension and straightening, the size of the profile is extremely poor.
3.2 Solution 1 Reasonably design the mold to ensure the accuracy of the mold; 2 Correctly execute the extrusion process, reasonably set the extrusion temperature and extrusion speed; 3 Ensure the neutrality of the equipment; 4 Adopt moderate traction and strictly control the profile Stretch straightening amount.
4 Extrusion Ripple Extrusion Ripple refers to the appearance of water ripples on the surface of extruded profiles. Generally, it does not have a feeling of hand. It is obvious under the effect of light.
4.1 Main Causes 1 The tractor periodically oscillates up and down to cause partial bending on the surface of the profile. 2 The design of the die is irrational, and the work belt flutters under the action of the extrusion force, which causes the profile to ripple. 4.2 Solution 1 Ensure stable operation of the tractor; 2 Reasonably design the mold structure.
5 Mamian pockmark refers to the appearance of uneven density on the surface of the profile, with trailing, very small nodules, feel is obvious, there is a spiked feeling.
5.1 The main reason is that due to inclusions in the ingot or mold work belt with metal or debris, in the extrusion when the high temperature and high pressure aluminum with the off, in the profile surface hemp surface.
5.2 Solution 1 Appropriately reduce the extrusion speed, use reasonable extrusion temperature and mold temperature; 2 Strictly control the quality of the ingot, reduce the content of inclusions in the ingot, and homogenize the ingot; 3 Strengthen mold repair Quality Control.
6 After the anodizing of the black-stained profile, an approximately round black-gray spot appears locally and is distributed equidistantly across the surface of the profile in a longitudinally oscillating bed.
6.1 The main reason is that due to the insufficient air cooling at the outlet of the extruder, the aluminum material contacts the swing bed at a relatively high temperature. The cooling rate at the contact location is different at other locations, and a coarse Mg2Si phase precipitates after the anodizing treatment. This part turns dark gray.
6.2 Solution 1 Strengthen the air-cooling strength to avoid the air-cooled temperature gradient being too small on the swing bed profile; 2 Conditional factories should use the method of atomized water-cooling combined with air-cooling to completely eliminate dark spots. .
7 There are many types of streak defects in streaked extrusion profiles, and the formation factors are also more complicated. Here, the causes and solutions of some common striations are discussed.
7.1 Friction pattern Each time the light mold is pressed on the machine, the lines cannot be matched one by one, and they are light and heavy.
7.1.1 The main reason is that during the extrusion process, the profile exits the die hole immediately and closely with the working belt to form a pair of hot dry friction pair, and the working belt is divided into two zones - Adhesion zone and sliding zone. In the adhesive zone, the metallic dots are subjected to forces from at least two aspects: friction and shear. When the friction force of the metal point in the adhesion zone is greater than the shear force, the metal dot will adhere to the surface of the work zone in the adhesion zone, and the surface of the profile will be scratched to form a friction pattern.
7.1.2 Solution 1 Adjust the working angle of the die with the exit angle α so that it is in the range of -1° to -3°. This can reduce the height of the work zone with the adhesion zone, reduce the friction in the zone, and increase the sliding zone. 2 High-efficiency mold nitriding treatment to keep the hardness of the mold surface above HV900; the surface sulfur permeability of the working belt can reduce the friction in the adhesive area and reduce the friction pattern.
7.2 Tissue Striping
7.2.1 Main reasons The cast structure of the ingot is uneven, segregation of components, serious defects under the surface of the ingot, insufficient uniformity of ingot processing, etc., resulting in uneven surface composition of the profile during the subsequent extrusion process. , so that the coloring ability of the profile after oxidation is not the same, forming a tissue stripe.
7.2.2 Solution 1 Reasonably carry out the casting process to eliminate or reduce the segregation of the tissue; 2 Ingot surface wagons; 3 Intensify the ingot homogenization.
7.3 Metallic bright lines appear bright in an oxide white material. In most cases, they are straight strips and have an indeterminate width. In the oxidized coloring material, the stripes are light-colored stripes.
7.3.1 Main Causes Due to friction or deformation of the metal flow, the local temperature of the metal will rise very high. In addition, the uneven metal flow will cause the grains to be severely broken, and then recrystallization will occur. Changes, in the subsequent oxidation process leads to vertical bright streak on the surface of the profile, the coloring process causes the profile to not color or appear light-colored stripes.
7.3.2 Solution 1 Reasonably design the mold structure; 2 The mold processing should pay attention to the transition of the working belt to prevent the work from having a drop; 3 Ensure that the mold bridge is drop-shaped and eliminates corners.
7.4 Welded Stripes Welded strips, also known as welds, are straight, long and have a slightly grayish appearance in the oxide white material.
7.4.1 Main reason 1 Die diversion hole design is too small; 2 Weld chamber depth is not enough, can not guarantee that there is enough pressure; 3 In the extrusion welding, the supply of aluminum material in the welding room is insufficient; 4 The extrusion process is irrational, lubrication improper.
7.4.2 Solution 1 Reasonably design the mold structure; 2 Pay attention to the coordination of extrusion temperature and extrusion speed; 3 Minimize lubrication or no lubrication.
8 When the crack is extruded, the profile is subjected to tensile stress and forms a different degree of transverse tear in the surface of the metal.
8.1 The main cause 1 The metal surface is subjected to additional tensile stress due to friction. When the additional tensile stress is greater than the tensile strength of the surface metal, cracks will occur. 2 Excessive extrusion temperature is too high, and the tensile strength of the metal surface decreases. , Under the action of friction, cracks occur; 3 When the extrusion speed is too fast, the additional tensile stress on the surface of the metal increases, causing the profile to crack.
8.2 Solution The extrusion process parameters are strictly controlled to ensure a reasonable outlet speed and outlet temperature.
9 Waves, twists, bends, twists, and bends are defects in the profile due to uneven metal flow.
9.1 The main cause 1 The mold design is unreasonable and the metal flow is not uniform due to unreasonable design. 2 Excessively high extrusion speed or high extrusion temperature results in uneven metal flow. 3 Inconsistent metal flow due to irrational mold hole layout. The guide is not suitable or the guide is not installed. 5 Lubrication is not suitable. 9.2 Solution 1 Trim mold work belt to make the metal flow evenly; 2 Use reasonable extrusion process, try to use low-temperature extrusion under the premise of ensuring the outlet temperature; 3 Reasonably design the mold structure; 4 Configure the appropriate guide path; Reasonable lubrication; 6 using traction traction.
10 Partially continuous or intermittent separation of the surface layer metal and matrix metal of the bubble profile, which appears as a round or partially continuous bulge.
10.1 Main Cause 1 Due to the oversized size of the extrusion cylinder after long-term use, the gas in the cylinder is not removed during extrusion, and the surface of the deformed metal flows out along the elastic zone at the front end to cause air bubbles; 2 The surface of the ingot has grooves or ingot structure There are pores, the ingots are filled with gas when the piers are thick, and the gas enters the metal surface during extrusion; 3 When the extrusion is carried out, the ingots or molds contain moisture and oil, and the water and oily pollutants are evaporated into gas at high temperatures. High-pressure metal flows into the surface of the profile to form gas; 4 equipment exhaust device is not working properly; 5 metal filling is too fast, causing extrusion exhaust is not good.
10.2 Solution 1 Reasonably select and equip extrusion tools for timely inspection and replacement; 2 Strengthen the quality management of ingots and strictly control the surface quality and gas content of ingots; 3 Ensure that the exhaust system of the equipment works properly; 4 Scissors , squeeze barrels and molds should be as little as possible with or without oil; 5 reasonable control of extrusion speed, exhaust as required.
11 The graphite is pressed into the semi-depressed porosity along the longitudinal surface of the profile, a few millimeters short and a few centimetres or more in length. The main component of the pores is graphite.
11.1 Main reasons 1 Due to the high proportion of graphite in the graphite lubricant or the graphite is not completely stirred evenly, there are particles or chunks of graphite present; 2 Graphite lubricant applied too close to the shunt or hole, these graphite does not enter when squeezed Instead of pressure, the high temperature and high pressure metal flows into the superficial layer of the product to form graphite.
11.2 Solution 1 Use a good quality lubricant. 2 Lubricant should be applied at a distance away from the orifice or hole. Use as little or no lubricant as possible.
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