Results of metallographic studies of cutting parts of cultivator paws made of 30MnB5 steel

Abstract

Rationale. Cultivators are widely used in our country for surface tillage. Moreover, their most common working organ is the pointed paw. In recent years, foreign manufacturers of agricultural machinery have begun to use boron-containing steels in the manufacture of working parts of agricultural machinery, which can increase the wear resistance and durability of machine parts. The article presents the results of metallographic studies of the structure and properties of the cutting parts of pointed cultivator paws made of boron-containing steel 30MnB5. The purpose of the work is to study the structure and properties of boron-containing steels after surfacing relit and subsequent hardening. Materials and methods. When carrying out metallographic studies, we used the cutting parts of the paws of the KPIR-3.6 and KPU-5.4 cultivators, mass-produced according to OST 23.2.164-87 at the Buinsky Machine-Building Plant of the Republic of Tatarstan. These working bodies were made of steel grade 30MnB5 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 paw, after which the entire working element was hardened. The macro- and microstructure of the metal part was studied using a microsection cut out to the cutting edge. For macrostructural studies, a stereoscopic microscope from MEIJI RZ with a magnification of up to 7 times was used. The microhardness of the part was measured using the Vickers method (GOST R ISO 6507-1-2007) at different loads on a MicroMet 5104 microhardness tester. Contamination of the base metal of the part with non-metallic inclusions was assessed using the “Ш4” method according to GOST 1778-70. Results. The proposed manufacturing technology for cultivator blades made of 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 blade on the soil. The steel base of the cultivator paw 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 paws made of 30MnB5 steel turned out to be 9.5% less than that of working bodies made of 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 30MnB5 steel using the proposed technology, are used in the production process of Buinsky Machine-Building Plant OOO in the Republic of Tatarstan. The paws manufactured using the proposed technology are installed on cultivators KPIR-3.6 and KPU-5.4. The presence of the self-sharpening effect of the paws made it possible to increase the quality of products required by consumers and its high competitiveness.