PF1010 impact crusher is a hard rock crushing equipment with compact structure, high crushing efficiency, low noise and good safety performance, which is developed on the basis of digesting and absorbing foreign advanced technology. The design power of the machine is 160 kW, the rotor speed is 37 m / s, the productivity is 120 t / h, the blow bars size is 315 mm × 100 mm × 500 mm, and the weight of the blow bar is 107 kg. The machine is required to be able to crush materials with a compressive strength greater than 300 MPa. The crusher blow bar is the main wearing part for crushing materials in the machine. In order to improve the service life of the crusher blow bars, reduce the number of shutdowns and replacements, and save production costs, we have conducted research on the material of the crusher blow bars. After on-site production testing, the material performance of the developed crusher blow bars is good, which is equivalent to the service life of imported crusher blow bars.
Analysis of Wear Mechanism of PF1010 Impact Crusher Blow Bars
During the crushing process, after the material entered from the upper feeding port, it violently collided with the high-speed rotating crusher blow bars. The material was crushed once, and then the crusher blow bars threw the material to the impact plate at a line speed of 37 m / s. After the secondary crushing, the material is finally squeezed again between the crusher blow bars and the liner to reach the required particle size, and the entire crushing process is completed. During the operation of the workpiece, the impact hammer is subject to the combined effects of high-hardness materials, such as impact and extrusion, on the one hand, causing the substrate and carbide to chip and fall; on the other hand, it causes the substrate to roll over, causing plastic deformation, and finally falling off in fatigue. The crusher blow bars have grooves of varying degrees. At the same time, during the entire operation, due to the repeated high-speed collision of the hammer with the material, the surface temperature of the crusher blow bars is as high as 500 ℃. Therefore, the material of the crusher blow bars should have sufficient hardness, certain impact toughness, and High rigidity.
Design of PF1010 Impact Crusher Blow Bars chemical composition
Based on the wear mechanism of the crusher blow bars and the performance indicators that the crusher blow bars should have, based on the investigation and analysis of the use of wear-resistant materials commonly used at home and abroad, and domestic resources, we have initially determined the use of chromium-based alloy wear-resistant cast iron for trial production. In terms of composition control, it is mainly considered in four aspects. One is to control the number of primary carbides and eutectic carbides to improve the morphology and distribution of carbides. The other is to make the matrix structure have sufficient strength to facilitate hard carbides. It can be very firmly embedded in the matrix; the third is to appropriately increase the amount of carbon to ensure that the alloy has a higher hardness; the fourth is to refine the grain. To this end, we conducted a large number of experiments based on the above principles, and finally determined that the mass fractions of C, Si, Gr, Mn, Ni, and Cu in the material were: 2.8% to 3.2%, 0. 6% ～ 1.0%, 15% ～ 17%, 0.6% ～ 1.0%, 0.5% ～ -0.8%, 0.55% ～ 1.0%, 0.5% ～ 0.7%, P, S mass fractions <0.05%, and a small amount of Re, V-Fe was used for compound inoculation in the furnace.
PF1010 Impact Crusher Blow Bars Melting, casting, heat treatment process, and mechanical properties
Alloy raw materials and melting
The cast iron is smelted in the medium frequency inductive electric furnace with acid lining. The test raw materials are high-quality pig iron with low S and P content, low-rust carbon scrap steel, high-carbon ferrochrome, molybdenum iron, manganese iron, nickel plate, graphite electrode, etc. To: add graphite electrode to the bottom of the furnace, then add a small amount of high-carbon ferrochrome, all ferromolybdenum, then add the regrind, pig iron, scrap steel, and finally the remaining ferrochrome, ferromanganese, and electrolytic copper, so that the initial melting time Carbon is carried out with low chromium content. When the temperature of the molten iron is heated to 1500 ～ 1520 ℃, the furnace can be released after deoxidizing with pure aluminum, and the compound inoculation treatment is performed at 1 440 ～ 1 460 ℃. In order to reduce shrinkage and sticky sand and refine the structure, the pouring temperature should be higher than Low, generally controlled between 1380 ～ 1 400 ℃.
The life of the chrome cast iron crusher blow bars is largely related to the casting quality of the casting, and the casting process has a great impact on its quality. The use of a reasonable casting process can reduce or even avoid the occurrence of many casting defects, especially cracked ones. appear. For this reason, in view of the characteristics of high alloy content, good fluidity, large shrinkage, and poor thermal conductivity in cast iron, the following aspects should be noted in the casting process:
(1) Use 2% shrinkage to make patterns.
(2) In order to prevent the casting from shrinking, attention should be paid to improving the concession of the mold.
(3) When designing the casting molding process, the principle of sequential solidification is generally adopted to strive to eliminate shrinkage defects and increase the density. At the same time, the design of the riser must ensure that the filling channel is smooth and easy to clean during the solidification process.
(4) In order to ensure the tightness of the casting structure, slag blocking should be strengthened to ensure that the various metamorphic alloys added can be completely dissolved to prevent slag particles and undissolved alloys from becoming crack sources in the casting.
The heat treatment process of alloy cast iron is actually a process of completely dissolving and precipitating carbon and alloy elements after heat treatment of unstable as-cast structure. Therefore, when determining the quenching temperature and holding time, it is mainly considered from the two aspects of obtaining the best comprehensive properties of the alloy and ensuring that the casting is fully hardened. After repeated tests, the quenching temperature is determined to be 910 ℃, and the holding temperature is 2.5 to 3h. In addition, in order to avoid high stress caused by phase changes or high heating temperature gradients, step heating is adopted, that is, the temperature is kept at 670 ℃ for 2.5 hours and then heated. When heating, the heating speed is generally not higher than 30 ℃/h.Once the casting is heated to a dark red color, that is, the stress is reduced sufficiently by the plastic deformation temperature, the heating can be accelerated.
After the alloy is quenched, due to the volume expansion when the austenite is transformed into martensite, the volume increases by about 6%, which will cause the internal stress of the alloy to increase significantly. Therefore, the alloy after quenching must be tempered at low temperature to eliminate the internal stress, Reduce the sensitivity to fracture and impact, at the same time, after low-temperature tempering, the quenched martensite is transformed into tempered martensite, which improves the toughness of the alloy. We control the tempering temperature to 200 ～ 250 ℃, and the holding time is 6 h.
For anti-wear cast iron, the most important indicators of mechanical properties are hardness and impact toughness, but these two indicators often conflict with each other. To solve this problem, we must find the best combination of material toughness and hardness under specific conditions. We tested the mechanical properties of the heat-treated alloy cast iron in accordance with the standard GB8263-87 “Abrasion-Resistant White Cast Iron”, and the results were: the average hardness was 64. 5 HRC; the average impact toughness was 7.75J / cm2. It can be seen that this material has very high comprehensive mechanical properties.