Aluminum extrusion die plays an important role in the aluminum extrusion process, and it is the basic tool to ensure that the product is formed and has the correct shape, size and accuracy. In the actual production, in view of several problems that may occur in extrusion of hollow aluminum profiles, we give the corresponding repair methods one by one.
First, there is a seam Angle or poor welding
The hollow aluminum alloy profile is extruded by the planar shunt combination die, and the metal passes through the process of shunt and welding, so the hollow profile is welded, and if the metal welding is not good, there is a gap, it is a defect.
There are two reasons for the gap, one is the shunt hole, the welding chamber is small, the metal flow is insufficient, the metal does not form enough hydrostatic pressure in the welding chamber, the product is not well welded and flows out of the mold hole, resulting in the welding gap of the product; The second is excessive lubrication and poor lubrication caused by poor welding of hollow profiles. The former can be expanded by grinding or milling to expand the area of the shunt hole and the welding chamber, increase the flow of the metal, so that the metal can form enough hydrostatic pressure in the welding chamber to be solved, and the latter can be solved by non-lubricating extrusion process.
Second, the aluminum alloy profile wall appears concave or convex bow surface
1. The reason for the concave bow surface of the hollow aluminum alloy profile wall is that the working belt of the mold core is lower than the working belt of the lower mold hole, and the effective length of the working belt of the mold core is too short.
Correction method: A spacer ring is placed between the die core and the lower die, so that the working belt of the die core is equal to the caliper belt of the lower die hole under stress. At the same time, the exit part of the lower mold is reduced by the same thickness.
2, hollow aluminum alloy profile wall convex causes: mold use time is too long, mold core work belt serious wear, grooves appear, increase the friction resistance, slow metal flow caused hollow profile wall convex.
Correction method: If the wall thickness tolerance of the profile allows, the working belt surface of the mold core can be filed or polished to reduce the friction resistance; If the wear degree of the mold core working belt is very serious, and the wall thickness of the profile has reached the upper deviation, the mold can be preheated to about 300℃, the shape of the mold core can be repaired, and then filed to the required size and polished after use; If the core working belt is not worn out, file the outer obstruction and the inner retention of the core working belt.
Third, the surface stripes of aluminum alloy profiles
Streaks appear on the outer surface of extruded profiles, which are more obvious after anodizing. The defects are more common in the parts with large wall thickness difference, the welding parts of the metal under the shunt bridge, and the back parts with “branches” and threaded holes on the inside.
Cause:
1. The “branches” and threaded holes on the inside of profiles cause surface streaks due to insufficient or excessive metal flow;
2, mold distribution bridge under the welding area caused by the profile surface stripes;
3. The problems existing in the profile design, due to the large wall thickness difference of profiles, the parts at which the length of the working belt changes will produce striped color difference after anodizing;
4, because the cooling capacity of the machine is not enough, resulting in black spots after anodizing;
5, the texture of the casting billet itself is not good, affecting the stripe color difference after anodizing the extruded material.
Correction method:
1. Check whether there is a large difference in wall thickness, branches and threaded holes on the profile decoration surface on the customer’s drawings;
2, the shunt bridge should be designed on the non-decorative surface of the profile, while ensuring the strength of the mold, the welding chamber should be as large as possible, so that the metal can form enough hydrostatic pressure;
3, large diameter pipe or large size hollow profile mold, the upper welding chamber can be provided on the positive mold;
4, the inside of the profile “branches” or thread holes at the stripe, the repair method is to polish the mold of these parts of the hole working belt, grinding smooth, or modify or reduce the connection of these parts of the transition radius;
5, sometimes the streaks are formed by the casting billet itself, requiring the heating temperature of the billet to be uniform and the homogenization annealing to be thorough;
6, after the extrusion material out of the die hole, its grain size depends on the temperature into the quenching zone and the cooling rate of the quenching zone. If the cooling temperature is too low and the cooling speed is not uniform, the grain size will be too large or uneven, and the color difference will be more obvious after anodizing, requiring the operator to adjust the wind pressure and cooling water pressure of the cooling system in time.
Fourth, aluminum alloy profile bending and twisting
Cause:
1. The working belt of the die core and the lower die hole is unreasonable, causing uneven metal flow rate in various parts of the profile;
2, the size and position of the shunt hole of the symmetrical hollow profile die are not symmetrical, and the metal flow is not balanced, causing the metal flow rate to be uneven;
3, the shunt hole processing is irregular or there are obstructions on the mold core to hinder the metal flow.
Correction method:
1. Polish the exit part of the mold core or the shunt hole with the appropriate method, and expand these shunt holes appropriately if necessary to balance the supply.
2. Remove obstructions by grinding.
