Hot rolling generally refers to the rolling process carried out above the temperature of the metal re forming product. During hot rolling, the deformed metal undergoes both hardening and softening processes. Due to the influence of deformation speed, as long as the recovery and recrystallization processes are not carried out in time, the metal will undergo certain work hardening as the degree of deformation increases. However, within the hot rolling temperature range, the softening process plays a dominant role. Therefore, at the end of hot rolling, the recrystallization of the metal is often incomplete, and the aluminum alloy plate and strip after hot rolling exhibit a microstructure state where recrystallization and deformation coexist.

Hot rolling has the following characteristics:

(1) Hot rolling can significantly reduce energy consumption and lower costs. During hot rolling, the metal has high plasticity and low deformation resistance, greatly reducing the energy consumption of metal deformation.

(2) Hot rolling can improve the processing performance of metals and alloys by crushing coarse grains in the cast state, healing microcracks, reducing or eliminating casting defects, transforming the cast structure into a deformed structure, and enhancing the processing performance of metals.

(3) Hot rolling usually adopts large ingot and large reduction rolling, which not only improves production efficiency, but also creates conditions for increasing rolling speed, achieving continuous and automated rolling process.

(4) Hot rolling cannot precisely control the required mechanical properties of products, and the microstructure and properties of hot-rolled products are not uniform enough. Its strength index is lower than that of cold work hardened products, higher than that of cold work hardened products, and lower than that of fully annealed products.

(5) The thickness and size of hot-rolled products are difficult to control, and the control accuracy is relatively poor; Compared with cold-rolled products, the surface of hot-rolled products is rougher, and the R value is generally 0.5-1.5um. Product scheme and process flow

Hot rolled products are generally divided into two categories: hot-rolled thick plates and hot-rolled coils.

Hot rolled thick plate refers to aluminum alloy sheet with a thickness of not less than 6.0mm. The main varieties include hot-rolled plate (H112), annealed plate (O), quenched or quenched pre stretched plate, etc. Hot rolled thick plate is usually produced by block method on the hot rolling machine. Its typical process flow is: ingot (homogenization) - milling surface, milling edge - heating - hot rolling - shearing interruption - straightening.

Aluminum alloy sheets with a thickness less than 6.0mm are produced using the coil method, with the main task of providing billets for cold rolling. The process flow is as follows: ingot (homogenization) - milling surface, milling edge - heating - hot rolling (billet opening rolling) - hot precision rolling (coiling rolling) - unwinding.

Preparation before hot rolling

The ingots used for hot rolling are flat ingots produced using continuous, semi continuous, and iron mold casting methods. Modern large-scale production often uses semi continuous casting method to produce flat ingots, and the weight of the ingots can range from a few tons to tens of tons. In order to ensure product quality and meet processing performance requirements, there are strict requirements for the selection of casting specifications, sizes, and shapes, as well as the control of surface and internal quality,

Before hot rolling, the ingot must undergo surface treatment and heat treatment according to the process characteristics of the alloy and the intended use of the final product.

The preparation work before hot rolling includes: selection of ingots, homogenization annealing of ingots, overlay treatment of ingots, heating of ingots, and other processes.

Selection of ingots

The selection of ingots should fully consider the inherent equipment capabilities and process conditions of the factory, the types and quality requirements of the produced alloys, production organization requirements, and other factors, following the principles of high quality, high efficiency, and low cost. Generally speaking, the thicker the ingot, the greater the total deformation, which is beneficial for improving the performance of the final product; For products with larger thickness, it is advisable to choose ingots with larger thickness, otherwise insufficient deformation will affect the structure and performance of the product. The width of the ingot is mainly determined by the finished product width, taking into account different alloy varieties and processing characteristics, and sufficient trimming should be left. The length of the ingot mainly depends on the rolling speed, roller length, and casting equipment.

Article source: Internet