Mastering of production of lead-free ecologically clean free-machining steels

Both in the domestic and world steel industry alternative ecologically clean free-cutting steels, having cutting machinability characteristics and mechanicalproperties, comparable with lead-containing steels, but voided of their drawbacks,are actively searched. First ofall the alternative steels should not be not so ecologically harmful. Scientific and technological aspects of lead-free free-machining steels production, alloyed by bismuth, calcium, tin, boron and nitrogen presented. Solubility of bismuth in iron and iron alloys with chromium, manganese, nickel, tungsten, vanadium, cobalt,phosphor, sulphur, aluminum, carbon and other elements at the temperature of 1550–1650 ºСdetermined. Parameters of interaction of the first and second order calculated. Study of bismuth behavior and tin spherical samples in 40X steel melt accomplished. The study done at the high temperature facility with controlled atmosphere and X-ray TV observation system. Simulation of phase compositions multicomponent alloys of steel АВЦ40ХГНМaccomplished by application of a program package FactSage. Within the study,a production technology of lead-free, ecologically clean free-machining, steels elaborated and masteredat OJSC “Zlatoust electro-metallurgical works”. Free-machining corrosion-resistant steels (АВЦ19ХГН,  АВЦ40Х,  АВЦ40ХГНМ,  АВЦ12Х18Н10, АВЦ40Х13, АВЦ14Х17Н2) alloyed by bismuth and calcium, steels (АО40Х, АО30ХМ) alloyed by tin, and steels (А38ХГМАРand А30ХМАР) containing BN were the objects of the study. The steels samples were in the form of forged billet of 10, 20 and 80 mm diameter and ingots of 18 and 500 kg (round 345 mm). Steel quality characteristics determined such as mechanicalproperties in longitudinal and cross directions of ingots, uniformity of distribution of fusible elements, carbon and Sulphur along the axis zone and in billet transverse sections. Pictures of ingots macrostructure by height and section obtained. Estimation of hardenability and steel contamination by non-metallic inclusions, austenitic grain size, steel machinability by cutting, surfacequality of re-worked billet and steel macrostructure accomplished. Comparable ecological studies of atmosphere contamination during the steel alloying also accomplished.