Wear principle and cause of mill liner
mill liner Wear principle
When the mill is rotating, the grinding media (steel balls, segments, rods, etc.) and materials inside the mill are brought to a certain height by the lining plate and dropped or splattered, which impacts the lining plate during the dropping of the grinding medium and materials. And wear. Due to the requirements of fineness control in the cement industry, the mill length-diameter ratio is generally greater than 2.5, and the full grinding is divided into 2 to 3 silos (up to 5 silos). Generally, a two-bin mill, the function of a bin is fine crushing and coarse grinding, and its particle size is generally P80≤25mm (if equipped with a fine crusher and a roller press, it is about P80≤5mm and P80≤1.0mm, respectively). Different operating conditions and conditions will vary. Due to the large granularity of the materials to be ground, the maximum ball diameter in a warehouse is 90-100mm, and the average ball diameter is 70-75mm. Large-diameter steel balls hit the liner with a large impact force, and the materials are punched and squeezed by the steel balls. , Its sharp corners penetrate the liner, at this time the wear mechanism of the liner is mainly high-stress impact chisel wear, supplemented by extrusion chiseling.
Main forms of mill liner damage
The main forms of mill liner damage are fracture and wear, which are related to unreasonable assembly and output.
First, let’s talk about the problem of breaks. Fracture is the most serious problem in the production and application of mill liners. In addition to the use-related problems, this type of problems generally include the following reasons:
Irrational chemical composition design or inaccurate chemical composition control;
There are serious metallurgical quality problems, such as excessive inclusions, component segregation, etc .;
There are serious casting defects, such as shrinkage, looseness, porosity, and poor metallographic structure of the casting;
Irrational heat treatment process design or inaccurate heat treatment process control;
Unreasonable stress control and elimination during the production process, such as unreasonable casting process design, unreasonable box loosening and unboxing time after casting, improper grinding and welding repair methods, and failure to temper in time after heat treatment and quenching.
Due to the different characteristics of the materials produced by manufacturers, mainly refers to HRC hardness and toughness.
The material selection of the liner does not match the structural design (of course, high manganese steel is no longer used)
This generally refers to two issues. On the one hand, it refers to the fact that in the past, the lining boards were mostly made of high manganese steel. Due to the high brittleness of qualified high manganese steel, the toughness was poor. On the other hand, it means that in the past, the lining board often had two bolt holes, and they were square holes. This is easy to cause internal and sharp corner stress concentration during casting. , The square hole is changed to an oval hole. In this way, the problem of casting stress is solved. At present, the grinding heads and compartment plates of Φ4.2×14.5m and other mills are designed with square holes. It is recommended to change them into ordinary oval holes. Yingde Conch and Yingde Longshan have been transformed with good results. Not only is it convenient to purchase bolts, but it is also possible to use the grinding head liner to a thickness of 1cm to 2cm, which reduces the scrap rate.
Eternal Bliss Alloy Casting And Forging Co.,Limited