Technology for the production of sickles and knives of the Petrovka Culture of the Southern Trans-Urals (by the results of metallographic analysis)

The data of the metallographic study of sickles and knives (37 pcs) of the Petrovka Culture from the Southern Trans-Urals and the Middle Tobol River basin of the 19th–18th centuries BC are reported. The implements originate from settlements (Ustye 1, Kulevchi 3, Starokumlyak, Kamyshnoe 2, Ubagan 2, Nizhneingaly 3) and burial complexes (Ozernoe 1, Krivoye Ozero, Verkhnyaya Alabuga). The reconstruction of the manufacturing technology of the Petrovka Culture tools from the Southern Trans-Urals was carried out by both taking into account the results of the surface visual inspection, as well as by the data of the microstructural study of the metal. The metallographic analysis was conducted at the Tyumen Scientific Center of the Siberian Branch of the RAS (microscope Axio Observer D1m from Zeiss; microhardness tester PMT-3M from LOMO). A certain correlation was revealed between the functional purpose of the product, type of the raw material, and the tool manufacturing flowchart. The sickles and knives with handles are produced primarily from pure copper (including oxidised) both in the process of casting in mould with subsequent finishing, as well as in the result of the forming forging. The tools obtained in the casting process often had casting defects, accompanied by the phenomenon of shrinking warpage of the metal. The finishing of the copper tools was taking place in most cases either in the regime of incomplete hot forging at 300–500 C, or hot forging at 600–800 C and at near-melting temperatures of 900–1000 C. Most of the sickles in the forging process were purposefully hardened by forging on the cold metal. Unlike the sickles and knives with handles, shank knives are made mainly of low-alloyed tin bronze. Apparently, this category of tools was given a special ritual significance, especially considering the fact that about a third of the tools came from burial complexes with a specific selection of the related implements. The use of tin bronze in the production of knives significantly contributed to the fabrication of high-quality castings with the smooth surface without metal warping defects. The finishing of the knives after casting was carried out with heating up to 600–800 C or 900–1000 C (44 % of the tools) or in the regime of incomplete hot forging (25 %). The forging on the cold metal with annealing was rarely used. Thus, at the basis of the choice of the technological traditions of the metal production lies the availability of a certain raw material base, the type of the metal obtained from this ore, as well as the inheritance of the technologies from the preceding cultural communities. Technological innovations in the processing of non-ferrous metal, associated with the supply of Sn-bronzes in the form of ingots or finished products from Central Kazakhstan to the Southern Trans-Urals, led to the significant increase in the quality of the produce.