What is the difference between hot rolling, cold rolling and cast rolling?

The cost of hot rolling is higher than that of cast rolling. However, the difference between them is not just a matter of production cost. The maturity level of hot rolling technology and equipment control level are far higher than those of cast-rolled products. Moreover, hot rolling is rolled within the recrystallization temperature range of aluminum alloy without alloy composition. Restriction, which means that the product can cover all aluminum alloy series, such as 3000 series, 5000 series, 2000 series, 7000 series, etc.

Cold rolling refers to the rolling of hot-rolled plates at room temperature. Although the aluminum plate is heated during the process, it is mainly the recrystallization temperature (the lowest temperature at which the recrystallization process can be completed within 1 hour of holding time is called recrystallization). Crystallization temperature.) Rolling is performed as follows.

Casting-rolling is a new type of technology developed after the 1970s. Its advantage is that molten aluminum directly passes through the rotating mold to directly produce strip products. It has considerable equipment and investment than hot rolling. However, because it is a new technology, the process defects of crystallization and casting have not been solved in the world. Therefore, the casting-rolling mill can only produce 1000 series pure aluminum and a few 3000 series alloy products, domestic and some countries in the world (For example, Brazil and the United States) want to break the alloy limit of casting and rolling and produce 5000 series alloys, but at least so far, they have not been widely successful.

Hot-rolled material: aluminum ingot--melted and cast into flat ingot--milled face--uniform annealing--hot rolled into strip.

Cast-rolled material: aluminum ingots-smelted-rolled into strips by casting and rolling mills

Cast-rolled material has high production efficiency, but defects such as component segregation and inclusions are not easy to solve, and the quality is not as good as hot-rolled material.

  1. The intermediate layer of the cast-rolled strip is a cast structure with feather-shaped columnar crystals; while hot rolling is a processing structure that has undergone more than 90% thermal deformation and is recrystallized during the hot rolling process, so the grains of the strip are fine , All performances are uniform. The resulting problem is that there is a large gap between the casting-rolling method and the hot-rolling method in the deep processing performance of the product (deep drawing, bending performance, etc.).
  2. Hot-rolled billet can also weld some of the defects of the ingot, such as porosity, shrinkage cavity and intercrystalline micro-cracks, without causing internal structural defects in the subsequent processing; while the cast-rolled strip does not have this advantage. And in the subsequent processing, all casting defects cannot be eliminated. When rolling thinner strip products, defects such as capillary cracks are easy to appear, which affects the quality of product processing.
  3. The casting-rolling method is much lower than the hot-rolling method, which is mainly reflected in that the hot-rolling method requires relatively high investment in heating furnaces and hot rolling mills.

How to differentiate:

  1. Generally, the elongation of the final cast-rolled product is lower than that of the hot-rolled final product.
  2. If it is a cast-rolled or hot-rolled product, the surface of the hot-rolled product is usually brighter.
  3. The electron microscope can’t analyze it, but the crystal image shows the difference
  4. Visual inspection can make a rough judgment. The simple method is to test the elongation

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