5.0mm thickness 5052-H32 aluminum plate/coil production process

5052-H32 aluminum plate/coil Production process

The production process of 5052 aluminum alloy is: melting and casting → ingot sawing and milling → billet heating → hot rolling → cold rolling → finished product annealing → cross cutting → packaging.

Ingot preparation

On-line double rotor degassing, then use Al5TiB in the chute to refine the grain, and finally filter through the ceramic filter plate, enter the crystallizer and cast into a flat ingot of 630mm×1400mm×8000mm.

Ingot sawing and heating

The ingot is cut off by a sawing machine, and then enters the milling machine for peeling, removing the surface segregation layer and oxide scale, and then transfers to the heating furnace for heating. Heating process system: 480 ° C for 3 hours, after the heat preservation is completed, it is taken out of the furnace and rolled.

Hot rolled

The high-temperature ingot undergoes 19 passes of hot rough rolling to become an intermediate billet. After cutting the material head, it enters the 4-stand hot finish rolling mill. After continuous rolling and thinning, high-temperature coiling begins to control the hot-rolled coil The thickness is 6.7mm, the final rolling temperature is 325°C±5°C, and the coil is naturally cooled after it is off the machine.

Cold rolling hardening

The cooled hot-rolled coils are rolled out of the finished products one by one on the cold rolling mill, and the total processing rate of cold rolling is 25%. In addition, the cold rolling mill must control the angle and air pressure of the edge purge to prevent oil and splash on the surface of the coil, so as to reduce the risk of oil spot defects.

Finished annealing

For direct annealing without cleaning, it is first necessary to ensure that there are no oil spots on the surface of the coil, and it is also necessary to ensure that the residual oil can be completely volatilized, and the process window is very narrow. If the temperature is too low, there will be no oil spots, but there will be residual oil; if the temperature is too high, there will be no residual oil, but there will be oil spots.
The special annealing process system adopted:
In the first stage, the furnace gas is set to 180°C, the heating rate is set to 35°C/h, and the negative pressure and purging are turned on to play the role of pre-drying in the air environment;

In the second stage, when the furnace gas reaches 180°C, start filling N2 gas to control the oxygen content in the furnace below 0.1%, and then keep it warm for 6 hours to play the role of pre-drying in an oxygen-free environment. Will cause oil spots due to oxidation;

In the third stage, the furnace gas is changed to 235°C, and the heating rate is set to 30°C/h. When the temperature of the coil reaches 230°C, it is kept for 3 hours, and the quenching and tempering of the coil is completed, and the expected mechanical properties are achieved. At this time, the residual oil is also volatilized, but it has not entered the dangerous temperature range of oil spots (245 ° C ~ 400 ° C);

In the fourth stage, the furnace gas is set to 0°C, and the side cooling fan is started to quickly cool down. When the metal temperature drops below 150°C, it is out of the furnace and exposed to air.

5052 aluminum alloy chemical composition

Chemical Composition Analysis

1) Si in the alloy is an impurity element. During casting and solidification, it can form complex ternary compounds with Fe and Al. The primary phase has a large size and is distributed on the dendrite boundary. It is an insoluble phase during the melting process, which is harmful to the plasticity of the alloy . Strict control of w(Si)≤0.10% in the test can reduce the overall amount of AlFeSi complex ternary compounds, thereby improving the plasticity of the alloy.

2) Fe in the alloy is not all impurity elements, and its mass fraction is controlled at 0.2% to 0.3%, which can avoid its harmful effects and play its beneficial role. Part of the Fe element in the alloy exists in a supersaturated form. During the homogenization process at high temperature, the AlFeSi dispersed phase can be precipitated inside the grain, and its size is very small, which can refine the recrystallized grain and contribute to the strength and plasticity.

3) In the alloy, w(Fe)/w(Si)>2.0 is controlled, and the α phase (AlFeSi) and a small amount of β phase (AlFeSi) are mainly formed during solidification, and the morphology of the α phase is bone-like. It can be fully broken during the rolling process and is harmless to plasticity. The β phase (AlFeSi) is a needle-like hard and brittle phase, which is difficult to break during hot rolling and is harmful to plasticity.

4) Cu in the alloy is an impurity element, which has an impact on the corrosion resistance of the alloy. The w(Cu) is controlled to be no more than 0.05%.

5) Mn in the alloy is an impurity element. For 5052 aluminum alloy, Cr is used to refine the recrystallized grains, not Mn, so w(Mn) should be controlled within 0.08%.

6) Mg in the alloy is an alloying element, and Mg is dissolved in the aluminum matrix, which can hinder the movement of dislocations and play a role in work hardening. Controlling w(Mg) at 2.5% to 2.7% can ensure a faster work hardening effect, and sufficient tensile strength can be guaranteed without a large cold working rate.

7) Cr in the alloy is an alloying element. It exists in a supersaturated form when the ingot is solidified, and it precipitates during the subsequent heating process to form a dispersed phase CrAl7. The particles have good thermal stability and can refine the recrystallized grains. It can improve the strength and plasticity of the alloy. Control w(Cr) at 0.18% to 0.24%. If the chromium content is too high, a harmful coarse phase will be formed; if the chromium content is too low, the dispersed phase will be insufficient and the beneficial effect will be weakened.

8) Ti in the alloy can form TiAl3 and AlTi5B1, which can refine the grains of the ingot, thereby improving the mechanical properties of the ingot.

Finished 5052-H32 analysis

1) The coil produced by the new process has good surface quality, no oil spots and residual oil, and meets the requirements of the standard. Internal structure observation: the crystal grains are fine and uniform, without fibrous structure. The anisotropy of this organizational state is small, and it is not easy to crack when bent. However, the conventional hot-rolled low-temperature directly off-line products are fibrous structures with large anisotropy, and the plates are prone to cracking when they are bent transversely.

2) The mechanical properties and bending test results of the 5.0mm thick 5052-H32 aluminum alloy plate produced by the new process are shown in Table 4. The plates were sent to the end users for trial use. The results were good, and the 90°0t bending did not crack. The new craft products reached the predetermined target requirements.

The core process in the production of 5052-h32

• 1) The 5052-H32 aluminum alloy national standard medium-thick plate produced by conventional hot-rolling direct low-temperature off-line process has serious fibrous structure and is prone to cracking in transverse bending.
• 2) The newly developed 1+4 hot continuous rolling mill is used for blanking, and the final rolling temperature is precisely controlled at 325°C±5°C, which can achieve a complete recrystallization state, which is the same as the production effect of cold rolling-intermediate annealing.
• 3) The cold-rolled finished plate is directly annealed without cleaning, and the special finished annealing process can ensure that there is no oil spot and residual oil on the surface, and the bending performance is excellent.