The hammer blade is the most important and easily worn working component of the crusher. Its shape, size, arrangement method, manufacturing quality, etc. have a significant impact on crushing efficiency and product quality.

Experiments have shown that,hammerAppropriate length is beneficial for increasing the yield of electricity per kilowatt hour, but if it is too long, the metal consumption will increase and the yield of electricity per kilowatt hour will decrease. According to the China Agricultural Mechanization Research Institute1.6mm、3.0mm、5.0mm、6.25mmFour kinds of thickness hammers were used for corn crushing test,1.6mmcompare6.25mmImproved hammer crushing effect45%, compared to5mmimprove25.4%The efficiency of crushing with thin hammer blades is high, but the service life is relatively shortened. The thickness of the hammer used should vary depending on the size of the crushing object and the machine model.

The hammer blades of feed mills in our country have been standardized. The Ministry of Machinery IndustryⅠ、Ⅱ、ⅢThree types of standard hammer plates (all rectangular double hole hammer plates), their specifications and dimensions are shown in the figure5-7And table5-1.

　　(two)Hammer manufacturing quality

　　1.Material and Heat Treatment of Hammer PlatesAt present, the hammer plate materials mainly used in China include low carbon steel, medium carbon steel, special cast iron, etc. Heat treatment and surface hardening (including surface carburizing quenching and surface welding with tungsten carbide, etc.) can effectively improve the wear resistance and prolong the service life of hammer plates. Briefly describe as follows.

（1）Low carbon steel[Q235(New standards, quite originalA3steel)、15#、20#]Solid carburizing quenching, the carburizing depth is generally0.8~1.2mmThe thickness of the hammer blade is2mmAt that time, for0.3~0.5mm）The surface hardness is generallyHRC56~62, Running hole circumference4mmThe hardness within the range does not exceedHRC28Its characteristics are simple process, low cost, hard surface and soft inner layer of the hammer, and certain wear resistance. But after the wear of the carburized layer, the inner layer wears out quickly.

（2）Medium carbon steel（45#、65#、65SiMn）The hardness of the quenched zone after heat treatment isHRC50~57The hardness of the non quenched area shall not exceedHRC28, generally used60~100hNeed to change the angle. If quenched as a whole, cracks are prone to occur.

（3）Special cast iron: available“Chilled white cast iron”、“Equal temperature quenching of white cast iron”、“Zhongmeng ductile iron”and“malleable iron”Wait. Cast iron is easy to obtain, with high wear resistance and low cost after quenching; But it is necessary to strictly control the material composition and production process of the hammer to ensure quality and prevent fracture accidents during use.

（4）Surface hardening treatment: tungsten carbide alloy is deposited on the working edges and corners of the hammer plate, with a thick weld layer1~3mmAccording to the test results, the ratio of tungsten carbide alloy hammer plates for surfacing welding is65MnThe service life of the overall quenching hammer is improved7~8But the manufacturing cost of the former is more than twice as high. Through crushing corn experiment, the service life of the hammer blade is improved compared to the general hammer blade6.9The consumption of steel is only equivalent to that of ordinary hammer blades1/7The cost of processing one ton of feed with hammer blades is only equivalent to that of ordinary hammer blades1/3Jiangsu Muyang Group took the lead in introducing American technology and built a semi-automatic production line for welding carbide black hammer pieces.

　　2.Processing accuracy of hammer bladesHammer blade is a high-speed rotating component, and its manufacturing accuracy has a significant impact on the balance of the crusher rotor. Generally, it is required that the quality difference between any two sets of hammer plates on the rotor should not exceed5gTherefore, the precision of the hammer piece must be strictly controlled during the processing, especially for tungsten carbide hammer pieces that require strict quality assurance in the welding process. Hammer blades should be shipped in sets. When installing hammer blades, a complete set of hammer blades should be installed every day, and it is not allowed to exchange them between sleeves at will.

Hammer blades are the working parts that directly strike materials in crushers, and therefore are also the fastest worn and most frequently replaced vulnerable parts. The wear of the hammer blade refers to the wear of the working angle of the hammer blade. If the four working angles of the hammer blade are worn, the hammer blade will be scrapped. picture5-8The wear condition of ordinary hammer pieces and surface hardening treated hammer pieces.

Figure5-8Wear condition of two types of hammer blades

　　A. Ordinary hammer bladeBSurface hardening treatment hammer

　　a.New hammer bladeb.Partial wear and tearc.Completely worn out

The arrangement of hammer blades refers to the relative positional relationship between each group of hammer blades on the rotor and between the same group of hammer blades. The arrangement of hammer blades should ideally meet the following requirements: when the rotor rotates, the motion trajectory of each hammer blade should not be repeated; The material will not deviate to one side in the crushing chamber under the movement of the hammer (except for special requirements); The rotor is balanced in force and does not produce vibration during high-speed operation. picture5-9It is a plan view of several common arrangements of hammer blades, which represents the relative positions of four sets of hammer blades on the rotor.

Figure5-9Hammer arrangement method

　　aSpiral line arrangementbSymmetric arrangementcStaggered arrangementdSymmetric staggered arrangement

　　1.Spiral Line Arrangement (Figure)5-9a）This is the simplest arrangement, divided into single helix and double helix. Its hammer blades are evenly distributed and the trajectory is not repeated. But when the rotor rotates, the force is extremely uneven, and the entire equipment vibrates greatly. The motion trajectory of all the hammer pieces forms a spiral line, pushing the material towards one side of the crushing chamber, causing uneven force on the hammer pieces and exacerbating the wear of the hammer pieces on the side with more material displacement. Therefore, this arrangement is only applicable to small crushers with low power and low speed, as well as crushers required by the process.

　　2.Symmetric arrangement (Figure)5-9b）The two sets of hammer blades are symmetrically installed, so that the centrifugal forces acting on the symmetrical two pin shafts on the rotor can be balanced with each other, the rotor operates in a balanced manner, the material distribution in the crushing chamber is uniform, and all hammer blades wear synchronously. At the same time, this arrangement requires very few types of spacers, and the installation of hammer plates is simple and convenient. The most commonly used in domestic feed production nowFSPSeries andSFSPThe series hammer crusher adopts this method. However, the trajectories of symmetrical hammer blades are repeated, so to maintain the same density of hammer blades, the number of required hammer blades needs to be doubled.

　　3.Staggered arrangement (Figure)5-9c）There are two types: single piece and double piece. The staggered trajectory of the hammer blades is uniform and not repeated, and the centrifugal forces acting on the symmetrical pin axis are balanced with each other. However, the material is slightly offset during operation, and there are many types of spacers required for the positioning of the hammer blades, making the installation of the combined hammer blades inconvenient.

　　4.Symmetric staggered arrangement (Figure)5-9d）In theory, this is the best arrangement method, which not only has a uniform and non repetitive trajectory, but also prevents material displacement. Moreover, the four pin shafts are on the same plane, and the symmetry axes are balanced with each other, resulting in good balance performance of the rotor.

The linear velocity at the end of the hammer blade during rotor operation has a significant impact on the performance of the crusher. The hammer crusher mainly relies on the impact of the hammer on the feed raw materials. The higher the linear velocity of the hammer, the greater the impact force of the hammer on the feed particles, and the stronger the crushing ability. Therefore, increasing the linear velocity of the hammer within a certain range can improve the crushing capacity of the crusher——Reduce energy consumption and product granularity. However, if the speed is too high, it will increase the no-load power consumption of the crusher and make the crushing particle size too fine, increasing power consumption. Moreover, excessively high speed will place higher demands on the balance performance of the rotor and even the manufacturing quality of the entire crusher. So, the optimal linear velocity of the hammer should be determined according to specific circumstances. At present, the linear speed of the hammer blades in domestic crushers is generally taken as80~90m/s.