[China Aluminum Network] A process for producing aluminum alloy sheets with high yield strength and suitable ductility, especially for use in the manufacture of automotive panels. This process involves the casting of an unheated aluminum alloy into a slab. The slab is then subjected to a series of rolling steps to obtain a final gauge sheet. A better choice is the subsequent retreat of the heat treatment to produce recrystallization. The rolling step includes hot rolling and intermediate temperature rolling of the cast slab to obtain an intermediate thickness intermediate product, followed by cooling of the intermediate product, followed by intermediate temperature rolling and cold rolling of the intermediate product at room temperature to a temperature of 340 degrees Celsius to obtain a final gauge sheet. This series of rolling processes is continuous without intermediate winding and complete annealing of the intermediate sheet. The invention also relates to thin sheets of alloy products.
The present invention relates to the production of a process for producing aluminum sheet. In particular, the present invention relates to a plate suitable for forming from a non-heat-treated alloy by rolling. For example, the 5000 series aluminum alloy in the manufacture of automotive panels.
The 5000 series aluminum alloy (ie, magnesium as the main alloying element) is commonly used in automotive panels (panels, door panels, hoods, etc.), and for such applications, it is desirable to provide high yield point and high ductility for the alloy sheet. To be achieved. Aluminum alloy pieces of suitable specifications and yield strength can be obtained by rolling after continuous casting. In the conventional continuous casting process, the metal obtained from the casting is hot-rolled and tempered, then coiled (at a temperature of about 300 degrees Celsius) and then sent to another rolling mill for colder temperatures not exceeding 160 degrees Celsius. Rolling.
For refining, it is mentioned here that what is commonly referred to as "hot rolling" is performed when the temperature is higher than the recrystallization temperature of the alloy. The alloy is annealed and recrystallized by itself in the coils between the roll seams or after rolling. The "cold rolling" described above usually means a work roll having a large work hardening rate such that the alloy neither recrystallizes nor recovers during or after rolling. "Medium temperature rolling" is performed between the two so that no recrystallization effect is obtained but the yield strength is greatly reduced due to the recovery process. For aluminum alloys, the hot rolling temperature exceeds 350 degrees Celsius, the cold rolling temperature is less than 150 degrees Celsius, and the medium temperature rolling is performed between 150 and 350 degrees Celsius.
Unfortunately, the intermediate winding of the conventional method described above is bulky and expensive. The storage and transportation needs to obtain a product with a suitable microcrystalline structure to produce the desired yield strength.
In U.S. Patent No. 5,514,228, a coaxial continuous casting process was disclosed on May 7, 1996, in which the plates were rolled into the later required gauge without passing through the intermediate winding. However, further solution treatment is required before the final rolling, so that the sheet is continuously completely annealed before the subsequent coiling. However, the 5000 series alloys will not be strengthened after solution treatment.
It is an object of the present invention to produce aluminum alloy sheets that are not heat-treated in a convenient and economical manner for use in the manufacture of automobile panels.
Another object of the present invention is to provide a process that produces 5000 series aluminum alloy sheets in continuous steps without intermediate secondary rolling to obtain high yield point aluminum alloy products.
In one aspect of the present invention, there is provided a process for producing an aluminum alloy sheet, which includes casting a non-heat-treated aluminum alloy to form a flat steel ingot, and then flattening the ingot through a series of rolling steps to produce a later specification product. The rolling steps include: hot rolling and intermediate temperature rolling of slabs to form mid-size intermediate plates and cooling of the intermediate plates; intermediate temperature rolling and cold rolling of intermediate plates at room temperature to 340 degrees Celsius; The continuous rolling step has no intermediate sheet winding or complete annealing.
The above process is an alloy in the so-called H2 tempering. The further annealing recrystallization production is suitable for the plates used in automobiles.
In another aspect of the present invention, an aluminum alloy sheet is made of an aluminum alloy that is not heat-treated. This process includes: casting an aluminum alloy that has not been heat-treated to form a flat steel ingot; the flat steel ingot passes through a series of Rolling to produce products of later specifications; rolling steps include: hot rolling and mid-temperature rolling of slabs to form intermediate-sized intermediate sheets, cooling of intermediate sheets, and then intermediate sheets at room temperature to 340 degrees Celsius Medium temperature rolling and cold rolling are performed; a series of continuous rolling steps does not have intermediate sheet winding or complete annealing.
As described above, the present invention requires hot-rolling and medium-temperature rolling and then intermediate-temperature rolling and cold-rolling without intermediate winding or complete retreat. When the flat steel ingot is continuously rolled, the hot slab loses heat to the air and the rolls so that the hot rolling ends in the intermediate temperature rolling (ie, below the crystallization temperature).
This is the method of hot rolling and medium temperature rolling. During hot rolling, the metal is completely recrystallized to release any strain energy generated during casting. The temperature during this period depends on the amount of simultaneous cold work and the composition of the alloy. During medium temperature rolling, strain energy is established due to gradual rolling, which is what the metal calls "recovery." As with recrystallization, the extent to which exit temperature affects the outside depends on the amount of cold work and the composition of the alloy. The important difference between recrystallization and recovery is that recrystallization causes a rapid decrease in internal tension and occurs during hot rolling, whereas recovery occurs during the entire cycle of medium and cold rolling and the internal tension is stable. Reduced, but most of the pressure is released during "warm" rolling.
The process of the present invention is beneficial to any aluminum alloy that is not heat-treated, and these aluminum alloys are treated in a completely annealed condition. However, it is more important to strengthen grain size in the 5000 series alloys for automotive applications. The process can be used for all 5000 series alloys being shipped in the fully annealed state, but is especially useful for AA5754 alloys, which contain a limited amount of Mg. In order to avoid stress corrosion cracking, strengthening the grain size is particularly important for this alloy. of. Alloys with higher Mg content, such as AA5182 alloys, are susceptible to stress corrosion cracking, but they have higher strength. Of course this is beneficial for such alloys, but it is less obvious.
The process of the present invention, at least in its preferred form, provides a 5000 series aluminum sheet for making a car body structure, which is continuously rolled on a continuous casting machine to obtain good mechanical properties.
An advantage of the present invention is that while self annealing does not produce the preferred microstructure and properties, recrystallization and subsequent annealing after rolling at lower temperatures does produce the desired fine grain size, high strength and favorable Crystal texture.
1. A process for producing an aluminum alloy sheet, comprising: casting an aluminum alloy that has not been heat-treated to form a flat steel ingot, and then passing the flat steel ingot through a series of rolling steps to produce a product of a later specification. The rolling steps include: hot rolling and intermediate temperature rolling of slabs to form mid-size intermediate plates and cooling of the intermediate plates; intermediate temperature rolling and cold rolling of intermediate plates at room temperature to 340 degrees Celsius; The continuous rolling step has no intermediate sheet winding or complete annealing.
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