The Influence of Chemical Composition and Tempering Temperature of Metal Teeth of Excavator Buckets on Their Operational Properties

Mining of solid minerals is associated with increased metal consumption of the tool used, which is associated with wear resistance, therefore, in order to reduce the metal consumption of the industry, it is necessary to increase the wear resistance of the tool. The matrix structure for excavator bucket teeth is martensite, but as a rule, not only the hardness determines the metal's ability to resist wear, but also a certain proportion of plasticity and viscosity. An analysis of operational experience provides some information regarding the durability of teeth with various mechanical properties, but there are still no scientifically sound requirements for the choice of material for excavator bucket teeth.

The aim of the work is to determine the optimal chemical composition and final heat treatment to provide the necessary set of mechanical properties of the metal teeth of the excavator buckets, depending on the operating conditions.

Experimental samples were produced in induction furnaces with a capacity of up to 120 kg. The heat treatment of the samples consisted of quenching in oil and high or low tempering for each sample. The wear resistance test was carried out on an installation representing a sample fixed in the spindle of the machine, which makes a transverse movement and simultaneously rotates around its axis.

Steel with 0.4 % C (1720 MPa temporary resistance) has the highest strength indicators compared to

0.3 % C (1680 MPa) at the same level of plastic characteristics. An analysis of the wear resistance test results showed the most severe wear conditions for SiC abrasives with a dimension of 200 microns (66—71 m/g; 82—89 m/g). The high hardness of the steel after quenching and low tempering guarantees better wear resistance of 130—133 m/g, compared with quenching and high tempering of 95—110 m/g. The main mechanisms of wear during wear are micro-cutting and plastic extrusion.

Taking into account the established requirements for steels for excavator bucket teeth, the corresponding 30KHGNMFL (No. 1) steels are recommended for various rock conditions, where high wear resistance and cold resistance are required, and 40KH2GN2MFL (No. 3) steel for a more temperate climate. Low tempering after quenching is recommended for a more temperate climate, quenching and high tempering are necessary to ensure cold resistance.

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