【China Aluminum Net】A process is used to produce the aluminum alloy plate with high yield strength and proper ductility, especially used in the manufacture of automobile panel. This process will cast the aluminum alloy without heat treatment into a slab, and then after a series of rolling, the final specification aluminum sheets will come out , the better choice is the recrystallization after heat treatment. Rolling step includes hot rolling and medium temperature rolling to get the middle thickness products. Cooling the intermediate products, and then medium temperature rolling and cold rolling the intermediate products in the temperature range of 340 degree to get the final specification sheets. This series of rolling process is continuous , with no coil and no full annealing of the intermediate. This invention also involves the sheets of alloy.
This invention relates to a production process of aluminum sheets, in particular, relates to aluminum sheets which is suitable for forming after being processed by rolling but never by heat treatment. For example, 5000 series aluminum alloy that is used for manufacturing automobile panels.
5000 series aluminum alloy (magnesium is the main element) is usually used in automobile panels(guard plate, door plate cover etc) due to its high yield strength and high ductility. The aluminum sheets with appropriate specification and yield strength can be obtained by continuous casting and rolling. In traditional continuous casting process, metal from the casting gets hot rolling and warm rolling, then gets coiled(at the temperature about 300 degree) and then is sent to another rolling machine to be finally cold rolled in the temperature of less than 160 degree.
In order to refine, the point to be mentioned here is that the hot rolling is usually implemented when the temperature is higher than the recrystallization temperature, so that the alloy between the roll seam can anneal by itself and recrystallize. Cold rolling usually means that there are a lot of work roll with a large amount of working hardness rate so that the alloy after rolling or before rolling will not recrystallize or change back. The medium temperature rolling is made between the hot and cold temperature so that there is no recrystallization but yield strength greatly reduced in the recovery process. For aluminum alloy, the hot rolling temperature is beyond 350 degree, cold temperature is less than 150 degree and medium rolling temperature is between 150-350 degree.
Unfortunately, the middle winding mentioned in above conventional method is bulky and expensive, the storage need a product that has a proper microlitic structure in order to produce expected yield strength.
In the United States patent number 5514228, a coaxial continuous casting process is released on 7/May/1996, in which the aluminum sheet was rolled into the final specification without middle winding. However further solution treatment is needed before the final rolling so that the sheet will be completely annealed before the final winding. However, the 5000 series alloy will not be strengthened after solid solution treatment.
One of the purpose of the present invention is to produce the aluminum alloy sheet that has no heat treatment in a convenient and economic way in order to apply to automobile manufacturing.
Another purpose of this invention is to provide a process for production of 5000 series aluminum alloy plate in successive step but with no secondary rolling in the middle procedure to get aluminum alloy products with high yield strength.
On the one hand, the present invention provides a kind of technology in the production of aluminum alloy sheets, including casting aluminum alloy with no heat treatment to form a flat steel ingot, and then rolling the flat steel ingot in order to produce the final specification. The rolling steps are: hot rolling and medium temperature rolling the slab to form intermediate specification plate, cooling the plate, and then hot rolling and cold rolling the intermediate plate when room temperature reaches to the range of 340 degree. A series of continuous rolling steps without intermediate winding or complete anneal.
On the other hand, the present invention provides a kind of aluminum alloy sheets without heat treatment. The process includes: casting aluminum alloy without heat treatment to form a flat steel ingot, and then rolling the flat steel ingot in order to produce the final specification. The rolling steps are: hot rolling and medium temperature rolling the slab to form intermediate specification plate, cooling the plate, and then hot rolling and cold rolling the intermediate plate when room temperature reaches to the range of 340 degree. A series of continuous rolling steps without intermediate winding or complete anneal.
As mentioned above, this invention need hot rolling and medium temperature rolling, and then go through medium temperature rolling and cold rolling without the winding process in the middle or complete anneal. When continuous rolling on flat slab, the hot slab loses heat to air and roll, so that the hot rolling will be finished in the medium temperature rolling (below the crystallization temperature).