Results of metallographic studies of cutting parts of cultivator sweeps made of the 30MnB5 steel

BACKGROUND: Cultivators are widely used in our country for surface tillage. Moreover, their most common working organ is the duckfoot sweep. In recent years, foreign manufacturers of agricultural machinery have begun to use boron steels in manufacturing working parts of agricultural machinery, which can increase the wear resistance and durability of machine parts. The paper presents the results of metallographic studies of the structure and properties of the cutting parts of duckfoot cultivator sweeps made of the 30MnB5 boron steel.

AIM: Study of the structure and properties of boron steels after Relit surfacing and subsequent hardening.

METHODS: The cutting parts of the sweeps of the KPIR-3.6 and KPU-5.4 cultivators, mass-produced according to the OST 23.2.164-87 at the Buinsky Machine-Building Plant of the Republic of Tatarstan were used to carry out metallographic studies. These working bodies were made of the 30MnB5 steel according to the DIN EN 10083-3. To ensure heterogeneity of the structure, a layer of Relit was fused to one side of the cutting blade of the cultivator sweep, after which the entire working element was hardened. The macro- and microstructure of the metal part was studied in a microspecimen’s section cut out to the cutting edge. For the macrostructural studies, the MEIJI RZ stereoscopic microscope with a resolving power of up to 7 times was used. The microhardness of the part was measured according to the Vickers hardness test (GOST R ISO 6507-1-2007) at different loads using the MicroMet 5104 microhardness tester. Contamination of the base metal of the part with non-metallic inclusions was assessed using the “Sh4” method according to the GOST 1778-70.

RESULTS: The proposed manufacturing technology for cultivator duckfoot sweep, made of the 30MnB5 steel, made it possible to obtain a cutting part that is heterogeneous in structure and hardness, which ensures self-sharpening of the blade during the friction of the cultivator sweep on the soil. The steel base of the cultivator sweep after heat treatment has a troostomartensite structure with a microhardness of ≈564 HV 0.3. The deposited layer of Relit has a dendritic cast structure of tungsten with a microhardness of 900...1020 HV 0.05 and tungsten carbides with a microhardness of 2315...2460 HV 0.05. The wear of sweeps made of the 30MnB5 steel turned out to be 9.5% less than that of the working bodies made of the 65G steel. The cost of manufacturing working parts using the proposed technology was reduced by 14.3%.

CONCLUSION: The practical value of the study lies in the fact that the results of studies of the cutting parts of self-sharpening cultivator paws made of the 30MnB5 steel using the proposed technology are used in the production process of Buinsky Machine-Building Plant LLC in the Republic of Tatarstan. The sweeps manufactured using the proposed technology are installed on the KPIR-3.6 and KPU-5.4 cultivators. The presence of the self-sharpening effect of the sweeps made it possible to increase the quality of products required by consumers and its high competitiveness.