Aluminum extrusion process planning

3.1 ingot heating

For extrusion, the extrusion temperature is the most basic and most critical process elements. Extrusion Temperature of product quality, production efficiency, the die life, and so have a significant impact on energy consumption.

The most important issue is extruded metal temperature control, from the start of heating the extrusion ingot quenched must ensure that the soluble phase structure is not precipitated from the solution or dispersion of small particles of precipitate present.

6063 ingot heating temperature is generally set at M Anhui University of Technology School g2Si precipitation temperature range, the heating time for the precipitation of Mg2Si have a significant impact, the use of rapid heating may be precipitated can greatly reduce the time. Generally, the heating temperature of 6063 alloy ingots can be set to:

Not homogenized ingot :460-520 ℃; homogenized ingot :430-480 ℃.

Its extrusion temperature during operation depending on the products and unit pressure to adjust the size. In the extrusion process, the temperature of the ingot in the deformation zone is varied, with the completion of the extrusion process, the temperature gradually increased deformation zone, and with the extrusion rate increased and improved. Therefore, in order to prevent extrusion cracks, and the process proceeds with the extrusion deformation zone temperature, the extrusion rate should be decreased.

3.2 extrusion speed

Extrusion process must be carefully controlled extrusion rate. Extrusion speed thermal effects on the deformation, deformation uniformity, recrystallization and solution processes, products, mechanical properties and surface quality of products have an important impact.

Extrusion speed is too fast, the product surface will appear pitting, cracks and other tendencies. Squeeze the metal too fast increases the deformation uniformity. The flow rate of extrusion and profiles depending on the alloy type of geometry, size and surface condition.

6063 Extrusion speed (flow speed of the metal) optionally 20 to 100 m / min.

Modern technology, extrusion speed can achieve process control or analog process control, but also the development of isothermal extrusion process and CADEX other new technologies. By automatically adjusting the extrusion rate to make the deformation zone maintained at a constant temperature range, can achieve rapid extrusion purposes without cracks.

In order to improve production efficiency, in the process, many measures can be taken. When using induction heating, the ingot length direction along the temperature gradient exists 40-60 ℃ (gradient heating), the extrusion temperature side toward the extrusion die, extrusion temperature side toward the pad portion to balance the thermal deformation; there is also an cooled die extrusion, that the rear end of the mold with water forced cooling, the test proved the extrusion speed can be increased by 30% -50%.

In recent years abroad with nitrogen or liquid nitrogen cooled mold (extrusion die) to increase the extrusion speed, improve tool life and improved surface quality profiles. During the extrusion of nitrogen leads to the extrusion die at the discharge outlet, the product can be cooled rapidly shrinking and cooling metal extrusion die and the deformation zone, the deformation of heat is taken away, and the mold by the nitrogen gas at the outlet of the aluminum 1800 t press profiles controlled atmosphere, reducing the oxidation of aluminum, reducing adhesion and accumulation of alumina, the nitrogen cooling improves surface quality of products, can greatly improve the extrusion speed. CADEX is a recent development of a new extrusion process, which during extrusion of the extrusion temperature, extrusion speed and the extrusion pressure to form a closed loop system, to maximize the extrusion speed and efficiency, while ensuring the best performance.

3.3 Online quenching

6063-T5 is quenched at a high temperature for the solid solution in the matrix metal in the mold holes Mg2Si rapidly cooled to room temperature after it has been retained. Cooling rate constant and proportional to the amount of strengthening phase. 6063 can enhance the minimum cooling rate of 38 ℃ / min, and therefore suitable for air quenching. Number of revolutions of fan and fan cooling intensity can be changed, so that products in front of the tension leveler temperature dropped below 60 ℃.

3.4 Tension leveler

Profiles of the die hole, generally are used tractor traction. Tractor work for extruded products in a certain tension traction, while outflow speed synchronization with the product movement. The purpose of using the tractor to reduce multi-line extrusion choppy and wiping injury, but also prevent the mold hole profiles after twisting, bending, tension leveler to cause trouble.

In addition to the tension straightening products eliminate the vertical shape is not the whole, but also can reduce the residual stress, improve strength properties and can maintain its good surface. 3.5 artificial aging

Aging treatment required temperature uniformity, temperature does not exceed ± 3-5 ℃. 6063 artificial aging temperature is generally 200 ℃. Aging holding time of 1-2 hours. In order to improve the mechanical properties, there is also aging 180-190 ℃ for 3-4 hours, but this time the production efficiency will be reduced.

3.6 Optimization and calculation of the ingot length

Method of calculating the length of the ingot volume method and Quality Act. By establishing mathematical relationships, it is easy to select the optimum specification ingot, greatly improving the yield of the profile geometry.

(A) volume method

Vo = V1 ten Vn

AoLo = A1 · L1 ten A · Ln

Lo / Ko = L1 / λ ten Ln

Lo = (L1 / λ + Ln) · K & helli aluminum price p; ...................................................... (1)

Where: Vo - ingot volume (mm3);

V1 - Profile volume (mm3);

Vn - pressure I volume (mm3);

Ao - ingot area (mm2);

Lo - ingot length (mm);

A1 - profile cross-sectional area (mm2);

L1 - Profile Length (mm);

A - extrusion cylinder area (mm2);

Ln - pressure I Length (mm);

K = A / Ao filling factor;

λ = A/A1 squeeze factor.

In accordance with the volume constant truth, after finishing as the simplified formula (1), K and Ln can be considered constant, only requires λ, determine Lmax, can be easily obtained Lo, the ingot length.

(2) Quality Act

mo = m1 ten mn

ρLoLo = L1 · ρL1 + mn

Lo = (L1 · ρL1 + mn) · PLo ......................................................... (2)

Where: Lo ingot length;

L1 profile extrusion length (m);

ρL1 linear density profiles (Kg / m);

mn pressure I Weight (Kg);

mo ingot weight (kg)

m1 extrudate Weight (kg)

ρLo ingot line density (Kg / m);

(2) it can be changed, namely: L1 = n · L + L12 fixed

Lo = · ρLo-1

...................................................... (3)

Where: n length count;

L will be determined Dimensions Length (m); L12 cutting head cut tail length (m).

(3) more intuitive and convenient formula calculates the actual work ρL1 Lo is changing with the thickness profile and increasing. To facilitate the process for ingots, large equipment ingot length can be set to 30mm for a file, a small device set at 20mm to a file. We can according to the formula (3) formulate ρL1, Lo, n, L1 table. General civil sections of length delivery 6m. This table technicians and planners of the process is very convenient to use.

Equation (3) and can be simplified to the following formula:

Lo = KnL1 + C ................................................ (4)

Kn is a coefficient related to n;

C is a constant related with the model;

ρL1 Lo is a function of the input can be programmed computer, more accurately calculate the Lo.

3.7 Measures to improve the yield of extruded

Impact extrusion yield many factors calculated geometry we can waste generated in the extrusion scrap waste is generally divided into geometrical and technical waste, waste in the production process geometry is only related to the production process and product waste. I pressed, cut head, cut tail, etc. are geometric waste. Technology waste in the production process, due process procedures are not performed correctly, caused by human waste (including waste tryout, casting defects caused by waste, etc.). Technology can be avoided and reduced waste, waste is unavoidable geometry, but can be accurately calculated optimal extrusion process and other measures to reduce the length of the ingot.

Extrusion scrap geometric size can be expressed as:

N = Nn ten N12 ................................................ (5)

N several servers waste (%)

Nn pressure I waste (%)

N12 cutting head waste (%)

Hn = K / Lo · Ln

N12 = K / Lo · L12 / λ

N = K / Lo · (Ln + L12 / λ) ......................................................... (6)

N = K / Lo · (Ln + L12 / λ)

K filling factor;

Lo ingot length (mm);

I length Ln pressure (mm, with aluminum prices extrusion cylinder straight path and change, Guangdong);

L12 cut the head and tail (mm, with product specifications and change);

squeeze factor λ.

From (6) it is evident that, the longer ingot length Lo, extrusion greater the coefficient, the geometric scrap N smaller, the geometry of the finished product rate. Some of which influenced the ingot length. However, you can not increase indefinitely Lo and λ, because they are subject to the extruder capacity, pressure and other factors limit the length.

4 Summary

In summary, to improve extrusion yield main ways:

(1) develop a scientific and reasonable production process (process optimization);

(2) to improve the theoretical level technical staff, and constantly sum up experience in the production;

(3) advanced mold design and mold reasonable and strengthen management, improve time pass rate on the plane;

(4) optimize the chemical composition of alloys 6063, improve quality and make ingot or semi-uniform homogenization homogenization;

(5) the use of advanced technologies, such as long ingot hot shear furnace technology and CADEX other new technologies.