On determining the sharpening angle of knife blades used in feed grinders operating under conditions of abrasive wear

Enhancing blade durability and determining optimal sharpening angles are critical for extending the service life and increasing the efficiency of feed choppers and industrial processing machinery. This study aims to determine the optimal sharpening angle for feed chopper blades subjected to through-hardening (volumetric quenching) followed by low-temperature tempering under abrasive wear conditions. Experimental samples were fabricated from U7 steel (GOST 1435-99) with sharpening angles of 10°, 20°, and 30°. Heat treatment produced a uniform fine-needle martensite structure across the entire cross-section. The resulting hardness was 740 HV, a 2.96-fold increase over the initial microhardness of 250 HV. Microstructural analysis revealed decarburizationinduced iron oxides at depths of up to 0.079 mm; consequently, suggesting that controlled-atmosphere furnaces should be used during quenching. Wear resistance was tested over a 100-hour period using a custom-made laboratory installation with quartz sand as the abrasive medium. The initial cutting-edge radius ranged from 20 to 35 μm. Under abrasive wear, the smallest increase in edge radius (blunting) was observed in the 10° blades (120 μm), while the 30° blades showed the greatest increase (185 μm). Conversely, the 30° sharpening angle exhibited the lowest overall width wear, while the 10° angle showed the highest. For cutting root crops without impact loads, the 10° sharpening angle is optimal. Furthermore, increasing the cutting speed from 5 to 7 m/s accelerated the dulling rate by 81.5%. These findings provide a technical basis for the design and maintenance of high-efficiency feed choppers and processing equipment