Influence of ploughshare design and welding reinforcement on the hardness of its nose part

Abstract

The hardness of working surface of ploughshares is very significant for their abrasive wear resistance. Knowing this mechanical property is especially important for manufacturing and hardening of ploughshares, since their wear is not uniform. In this regard, the research problems include studying of hardness distribution in the most loaded nose part of ploughshare, depending on its design and on welding reinforcement as a hardening method. Ploughshares after reinforcement and ploughshares in as-delivered condition after their taking out of service are submitted as objects of the research. Reinforcement included bead welding in the area of share point perpendicularly to the leading edge with the pitch of 30-40 mm. The validity of results was provided by measurement of four parts on each object of research. The total number of tested ploughshares was eight. Hardness was measured with a mobile hardness gage. Measurement results were recorded on Rockwell hardness scale (HRC) with subsequent conversion to Brinell hardness (HB). It is shown that for ploughshares without hardening, the hardness distribution in considered part has the non-uniform character, that is caused by the non-uniformity of processes of recrystallization because of unequal thickness of walls in separate volumes of a product. The hardness values of ploughshares in as-delivered condition are not high (230 HB maximum) and cannot provide the proper abrasive wear resistance. The lowered value of hardness (175 HB) is noted on the deepening part of a ploughshare. Application of welding reinforcement increases hardness (by 200 HB on the deepening part), that is connected with manifestation of heat hardening due to the formation of hardening structures. Traces of reinforcing beads make positive impact on the increase in hardness, which contributes to the growth of abrasive wear resistance.