Determination of rational modes of softening heat treatment of flanges made of medium-carbon steels

The modes of high tempering are investigated, making it clear that at temperatures above 500 °C, a whole or partial replacement of lamellar perlite with granular is observed.

Optimization of softening heat treatment for the Pt950Ru jewelry alloy

Platinum is one of the most precious metals in the world: 15 times rarer than gold and it is widely used in jewellery for its characteristic of unicity, incorruptibility, and colour neutrality. The standard grade in the jewellery industry is Platinum 950‰. In fact, pure platinum jewels are easily scratched, due to the poor hardness linked with the high purity. Among all the commercial alloys available, the Pt-Ru system is the one characterized by the highest mechanical properties. Aim of this work is to find an ideal softening heat treatment, in term of operating time and temperature. The heat treatment must be able to satisfy two main needs: it must permit to complete recrystallization of the work piece, preparing the material for further severe deformation by restoring high ductility and an equiaxed grain distribution; and at the same time, the final average grain size must be fine, in order to avoid counter side aesthetic effects that occur when grain size go over the micrometric scale. Due to its rarity, in literature there are few information about the alloy under discussion. To find the optimal parameters, several samples had been heat treated at different times and temperatures. Then they had been analysed by optical microscopy and with micro hardness tests, providing microstructure images and hardness data. By using a combination of three different temperatures and three different times, significant differences were found between the various samples both in terms of mechanical properties and of grain size. The comparison of the collected data permit to better understand the behaviour of the alloy under recrystallization conditions. In the end, it was observed that the dynamics of recrystallization changes significantly with relative small changes of temperature and was found that the optimal treatment to obtain a fine recrystallized microstructure with the desired mechanical properties is at 1000°C for 15 minutes.

EFFECTS OF AUSTENITIZATION ON STRUCTURE FORMATION СHROMO-MOLYBDENUM-VANADIUM STEEL AFTER HIGH TEMPERING

Influence of austenitization temperature of chrome-molybdenum-vanadium steel on structure formation at the softening heat treatment is studied. It is shown that the decline of the austenitization temperature promotes to reduce the micro-hardness values due to the intensification of spheroidizing of pearlite after the overcooling and high tempering. Increasing the austenitization temperature leads to formation of an uneven structure after tempering.

Mechanical and Structural Behavior of Copper Subjected to the Flow Forming Process

This work paper presents the results of HV 0.5 microhardness measurements and structural documentation of copper before and after the concurrent elongating flow forming process. No strain work hardening of products was noted. The cause of this behavior was recognized to be the location of strain strain localization in shear bands compounded by a change of the strain path imposed by the flow forming process. The dominance of this plastic flow mechanism makes it possible to conduct a technological process encompassing thinning of product walls with omission of expensive inter-operational softening heat treatment.