Failure cases of Ball Mill liner, Analysis of three causes and four improvement measuresDate: 2019-07-09 Views:
During the operation of ball mill, liner wear and fracture failure often occur. In order to solve the problem of short service life of ball mill liner, this paper analyzes the working conditions of overflow ball mill and the structure of ball mill liner and puts forward some improvement measures.
Three φ 5.03 m × 8.5 m overflow ball mills are used in a copper mine, and the planned annual treatment capacity is 6 million t. After 6 months of operation, the liner will fail to remove. Through the analysis of the actual working conditions and the failure causes of the liner, the material and structure of the liner are improved, and some results are obtained. at present, the service life of the liner is increased to more than 10 months.
1. The use of the original liner
The copper mine overflow ball mill uses liner material to detect the hardness of ZG42Cr2MnSi2MoRe;. The diameter of steel ball added to HRC48-52; is φ 80mm, the grain size of raw ore is 10mm, and the hardness f is 13 ≤ 14. the hardness material belongs to medium hard ore. After the liner is removed, the failure form is observed and analyzed.
The main results are as follows: 1) the wear of the lifting side of the wave peak is serious, while the thickness of the other side is close to 40mm, and the wear is uneven.
2) the wear pattern of liner is serious furrow wear.
2. Analysis of wear causes of liner
1)The main function of ball mill lining plate is to protect the cylinder of the mill and drive the grinding ball inside the mill to fall and fall to punch and crush the materials in the grinding mill.
For this reason, it is required that the mill liner shall have sufficient lifting and disturbance capability for grinding ball. The results show that in the overflow mill, when the height difference between the peak and the wave valley of the cylinder liner reaches about 60%of the maximum grinding ball diameter, the ball movement intensity in the mill is moderate, and the mill is in the best working state. In the φ5.03m×8.5m overflow mill used, the maximum grinding ball diameter is 80mm, and the height difference between the peak and the wave valley of the mill cylinder is only 40mm.
In this case, it is difficult for the liner to improve the grinding ball effectively in the process of mill operation. At this time, the movement intensity of the steel ball in the mill decreases, which leads to the decrease of the crushing efficiency of the mill to the material. At the same time, because the peak of liner and the difference of valley height are not up to standard, the relative slip movement of grinding ball and cylinder liner is violent, which leads to the occurrence of ploughing wear phenomenon of mill liner. The existence of this problem not only aggravates the rapid wear of mill liner, but also causes the liner to be scrapped ahead of time because the bottom of plough will be worn through first.
2)In the design process of the cylinder lining plate of the mill, the designer simply thinks that the wear of the mill liner plate is uniform, so the empty slot on the back of the lining plate is designed as the circular arc space. This is not true.
During the operation of the mill, the reaction force on the top of the wave peak of the liner is particularly strong in the process of lifting the grinding ball, so this part will bear strong cutting wear, so the wear is the most serious. The design scheme of the circular arc vacancy slot on the back of the liner makes the thickness of the liner basically uniform. The rapid wear of the top of the wave peak will make the part be worn through first and cause the liner to be scrapped ahead of time.
3) The traditional mill lining plate is selected from high manganese steel, and its wear resistance is achieved by its specific work hardening characteristics. And under the grinding condition, the high-manganese steel can not be fully hardened, and the high-strength and toughness wear-resistant cast steel is generally selected, the general hardness is between HRC45-60, and the hardness of the lining plate is moderate, so the wear resistance is normal. If the hardness of the lining board body is improved, the wear resistance of the lining plate is improved, and the service life can be greatly improved.
3. Improvement measures
1)Improve the lining plate material.
And the ZG60SiMnCr2Mo material is used for smelting, and is detected by three heat treatment processes of annealing, quenching and tempering.
2) improve the height difference of the wave peak and wave valley of the liner.
The wave peak of the original liner is 100mm, the wave valley is 60mm, the height difference is 40mm, the wave peak is 110mm, the wave valley is 55mm, the height difference is 55mm, the lifting ability of the liner is increased, and the furrow wear of the grinding ball to the liner is reduced.
3) improve the structure of the contact surface between the liner and the cylinder.
The structure of the back vacancy groove of the original liner is with the shape wave peak, the wave valley structure, the thickness of the liner plate is uniform, and the circular arc structure of the cylinder body is changed to increase the thickness of the easy wear part, so as to increase the service life of the liner.
4) Improve the lining direction of the lining plate bolt.
The original liner bolt is closed horizontally, the width of the bolt hole is 120 mm, the current bolt hole is rotated 90 °, and the width is reduced to 100 mm. The length of the liner is 840mm, and the area of the ball increases (640 ≤ 600) / 840 × 100% ≤ 4.76%.
4. Improvement effect
When the improved lining machine is stopped and inspected after 6 months, it is found that the abrasion loss is only about 15 mm, and the wear is even, and it can continue to be used for more than 6 months. The material and structure of the lining plate are improved, and the use effect is obvious, and the same lining plate is also prefabricated for the other two ball mills.