With the rapid development of technology and industry, the wear rate of large mechanical equipment parts has increased significantly, which has seriously affected the grinding efficiency. According to statistics, 1/3 of the world's energy is consumed by friction and wear, and 80% of parts fail due to wear. As a common form of wear failure, abrasive wear accounts for up to 50%. The mining industry is a high-consumption industry of wear-resistant parts. With the continuous expansion of the scale of mining enterprises and the decline of ore grades year by year, the production capacity of crushing and grinding equipment has become a key factor in increasing production capacity. The energy consumption and steel consumption in the material crushing process are also problems. Become more prominent.
1 Principles of selection
At present, there are many kinds of wear-resistant materials on the market, and each has its advantages and limitations. It is necessary to select materials reasonably according to actual working conditions and give full play to the material characteristics in order to improve the service life of wear-resistant parts. For mining equipment, the selection of wear-resistant materials generally follows the following principles.
1.1 Process flow
Due to the different geographical locations and rock forming mechanisms, the mechanical properties of the mineral composition are also different, which makes the degree of difficulty of crushing and grinding of the ore different. Affected by factors such as the scale of the mine, mining methods, and investment and operation costs, the crushing and grinding process is diversified. Concentrators often design and select technological processes according to their own characteristics. The distribution of technological processes is different, and there are production methods of dry and wet grinding at the same time. Different wear-resistant materials need to be selected according to specific working conditions.
1.2 Crushing equipment
The ore crushing process mainly includes crushing operations and grinding operations. Crushing equipment is the key to the stable operation of crushing operations, mainly including cone crushers, jaw crushers, gyratory crushers, high-pressure roller mills, and spiral crushers. The crushing operation is in the upstream link of the crushing and grinding process, and its main function is to crush the large ore mined and provide materials that meet the particle size requirements for the grinding operation. Therefore, the crusher liner is subjected to strong impact and high contact stress, and wear-resistant materials with hard outside and tough inside are required to resist strong impact and strong pressure.
Grinding equipment mainly includes semi-automatic mills, self-mills, ball mills and mixing mills. The working principle of the self-mill, semi-self-mill and ball mill is basically the same, except that the self-mill uses the material itself as the grinding medium to achieve the effect of ore crushing.
The self-grinding machine liner suffers from the grinding of large pieces of material and less impact. The wear-resistant material with high hardness, high wear resistance and certain toughness is a good choice. The high-chromium cast iron liner has been tried in large-scale self-grinding Application on the machine.
The semi-automatic mill uses a certain proportion of abrasive as the grinding medium, and uses the collision, impact and friction between the abrasive, material and liner to form effective pulverization. The semi-automatic mill liner suffers from the strong impact and grinding of abrasives and materials, and the impact wear is more serious. Therefore, material selection pays more attention to the strength and toughness of the material to ensure the safety, reliability and service life of the liner during the operation of the mill, and prevent the liner from early fracture. Generally, high-toughness low-alloy steel and new high-manganese steel can be selected. Steel and composite materials.
The ball mill has a small size and high material filling rate. The impact of the grinding body on the lining board is weak after being lifted. The lining board is mainly grinding. It is advisable to choose materials with high hardness, good wear resistance and a certain degree of toughness, such as Martensite. Body wear-resistant steel, high chromium cast iron or composite materials, etc.
As a fine grinding and ultra-fine grinding equipment, the stirring mill uses an internal agitator to drive the grinding medium to rotate to achieve the purpose of effectively crushing materials and effectively screening complex minerals. The basic grinding effect of the stirring mill is grinding and peeling instead of impact. The surface of the liner is subjected to high stress grinding under the action of the grinding medium and materials. The wear-resistant material is generally chromium-based anti-wear white iron.
With the development of grinding technology and grinding technology, the specifications of crushing and grinding equipment have become larger and larger, the size of the processed materials has increased, the specific crushing rate of the equipment has increased, and the processing capacity has increased. Therefore, the wear-resistant liner for the crushing and grinding equipment The geometric shape becomes larger, the cross-section is thicker, and the quality is increased. It withstands quite strong collision, extrusion, impact and friction, and puts forward higher requirements for the toughness, strength, hardenability and other properties of wear-resistant materials.
1.3 Law of wear
Abrasion refers to objects that are in contact with each other, and the surface material is lost or transferred due to relative movement. According to the mechanism of wear, wear is generally divided into four types: adhesive wear, surface fatigue wear, abrasive wear and chemical wear. Among them, abrasive wear is more serious, especially in wet conditions, due to the presence of corrosive media, the wear rate of the same material is several times that in dry conditions (especially serious in acid media). Therefore, the liner material should have high hardness and yield strength to resist abrasive wear while inhibiting the acceleration of corrosion on wear.
Due to the difference in ore properties, the diversification of the grinding process and the working principle of the grinding equipment, the wear pattern of the liner is also different. Even under the same working conditions, the degree of wear of different parts of the same grinding equipment is different, and there are high-wear areas, high-impact areas, and low-wear and low-impact areas. In the high-impact zone, alloy steel with good strength and toughness is a good choice; in the high-wear zone, wear-resistant materials such as martensitic wear-resistant steel and bainitic steel can be selected; in the low-wear and low-impact zone, rubber is generally used Or steel-rubber composite material, which has the effect of grinding and weight reduction. Therefore, only by grasping the type of wear and the law of wear, can we perform differentiated material selection, realize the replacement of the liner, save costs, and improve the efficiency of grinding.
1.4 Lining board structure
The structural design of the liner is a key factor in the performance of the mill, which determines the trajectory of the material falling in the mill and affects the grinding effect.
The structure of the lining board is various, and it can be roughly divided into smooth lining board and non-smooth lining board. Smooth liner has a small lifting effect, strong abrasive rolling and sliding action, strong grinding effect, and is mostly used for fine grinding; uneven liner has a large lifting effect, reducing the sliding of abrasives, increasing the impact of abrasives on materials, and is beneficial to crushing ore , Mostly used for rough grinding. Modern grinding equipment mostly uses non-smooth liners, mainly including corrugated liners, bead liners, L-shaped and trapezoidal liners. Wave liner is mostly used in ball mills. It is a relatively simple uneven liner. A certain thickness of the wave can increase the height of the abrasive to hit the bottom material. At the same time, its surface is arc-shaped. The abrasive produces sliding grinding on the material, taking into account both rough grinding and rough grinding. Fine grinding effect. Therefore, combined with the specifications of the mill, the material of the corrugated liner can be selected from martensitic alloy steel with excellent hardness and wear resistance, high chromium cast iron and composite materials. Rib structure liners are mostly used in self-mills and semi-automatic mills. The liner has a strong lifting effect, high-energy multi-frequency collisions, and has obvious impact crushing and coarse grinding effects, especially in large-scale mills. It is recommended to use high toughness, High hardness alloy steel, modified high manganese steel, bainite steel or wear-resistant steel composite material. The structural design of the lining board needs to consider the process requirements, so that the material characteristics can be maximized to meet the production and use performance requirements.
1.5 Material properties
Under wet grinding conditions, the ore slurry is generally acidic or neutral, and the hardness of the ore is high. As the specifications of mining mills gradually increase, the diameter of grinding media such as abrasives becomes larger, and the wear-resistant liner bears severe stress during service. Impact and abrasive wear, wear intensified in the middle and late stages of use, and even fracture failure occurs, and its safety and reliability have become particularly important. Therefore, the following performance indicators should be considered when designing large-scale wear-resistant liner materials.
(1) The large-scale grinding equipment with high hardenability and high hardenability, the wear-resistant liner section becomes thicker and larger, and the high hardenability and hardenability can ensure the depth of the hardened layer of the wear-resistant parts and ensure that the material is large in size. Uniformity of organization and performance within the size range.
(2) Good comprehensive mechanical properties and good plastic toughness can better absorb the impact energy under strong impact conditions, effectively prevent the initiation and propagation of cracks, and help resist fracture failure and peeling wear; higher hardness can resist high Hard ore cutting wear; higher yield strength can prevent macroscopic plastic deformation of materials under heavy load impact conditions.
(3) High corrosion resistance High corrosion resistance ensures that the mill liner in a corrosive medium can resist corrosion, which is beneficial to improve the wear resistance of the liner.
(4) High abrasion resistance. Corrosion and wear are not simply superimposed under wet grinding conditions. Their interactive acceleration promotes the rapid failure of the liner. High abrasion resistance is important for the wear-resistant liner under wet grinding conditions. Technical indicators.
Therefore, the wear-resistant liner cannot solely pursue a certain material characteristic. The wear-resistant material should have better comprehensive mechanical properties, high hardenability, hardenability, high corrosion resistance and high wear resistance.
1.6 Production costs
In the service environment, under the premise of satisfying safety and reliability, the alloying elements of the selected wear-resistant materials should be alloyed with rich and inexpensive iron alloys as much as possible, and the appropriate manufacturing process should be implemented. This can not only reduce production costs, but also make reasonable use of existing resources, and at the same time can ensure that the product has a higher service life. This kind of cost-effective wear-resistant product is more favored by customers and improves economic and social benefits.