Failure analysis of high chromium cast steel liner of ball mill

Ball mill is the key equipment for grinding materials. It is widely used in silicate products, such as new building materials, refractories, chemical fertilizers, black non-ferrous metal beneficiation, glass ceramics and other production industries, mainly used for dry or wet grinding of various ores and other grindable materials. The liner of ball mill is the protective plate for the barrel and the end cover of the ball mill, Its working condition is very bad, it must bear the impact and wear of grinding ball and materials. According to statistics, the time of forced shutdown due to the wear of lining plate of ball mill accounts for 50% ~ 55% of the total shutdown time. With the rapid development of material grinding technology, the ball mill tends to be large-scale, which also puts forward higher requirements for the performance of lining plate materials. Because high chromium cast steel is a kind of wear-resistant and corrosion-resistant material, therefore, The high chromium cast steel liner is widely used, but the carbides in this kind of cast steel are mostly distributed in a continuous and large mesh, which is brittle, which is easy to cause the lack of toughness of the high chromium cast steel liner, and easy to crack in the process of use, so that the high chromium cast steel liner of the ball mill fails. Therefore, the liner materials of the ball mill are selected correctly to prevent the liner from failure, It is very important to improve the service life of liner

The failure forms of high chromium cast steel lining plate are: wear, crack, fracture or breakage. Under normal circumstances, the main failure form of lining plate is wear. There are many reasons for lining plate fracture. For high chromium cast steel lining plate, there are the following aspects: improper material selection, improper smelting, casting and heat treatment process control, poor quality of lining plate, unreasonable shape and structure design of lining plate, During the installation, the liner plate does not match the mill barrel, the liner plate fastening screw and screw hole are not properly installed, the liner plate fastening screw torque is too large or too small, when the mill is running, the grinding ball smashes the liner plate empty, during the installation, the cracked liner plate is not replaced, and when the mill is running, the cracked liner plate falls down and smashes other liners.

In the test, the liner plate cracked. After the inspection of chemical composition, mechanical properties, metallographic structure and manufacturing process, the reasons for the cracking are as follows: (1) the liner plate structure is unreasonable. The stepped liner plate is large and thin, the small end is only 20 mm, too thin, and the thickness of the liner plate is calculated to be at least 40 mm. The fastening screw hole of the corrugated liner plate is at the wave peak, and the liner plate is lifting the grinding ball and materials, The hole part bears tensile stress along the direction of motion and produces cracks. Not only cracks are produced in the hole part of the high chromium lining plate, but also cracks are produced in the hole part of the high manganese steel lining plate in the same bin test. (2) the installation of the high chromium cast steel lining plate has a low degree of coincidence with the barrel of the ball mill, because the installation process is not strictly implemented, the lining plate is cracked due to overhead, 2 mm rubber asbestos pad should be added between the high chromium cast steel lining plate and the ball mill barrel to ensure good contact. (3) if carbon steel ball is used, the wear of the ball is large, and the ball needs to be thrown once in about 30-40 days, and the grinding time is long. When the ball is put into the ball and thrown, the ball smashes the lining plate in the air, resulting in cracking of the high chromium lining plate. If high chromium ball is used, the wear of the ball is small, The ball is thrown once every two years. Usually, only a small amount of big balls need to be added, so there is less chance for the grinding ball to hit the lining plate empty. Therefore, the high chromium grinding ball must be used at the same time when using the high chromium cast steel lining plate. Only by keeping the matching of the wear pairs can the high chromium lining plate be prevented from cracking.