The Effects of Microalloying Elements and Temperaging Treatments Parameters on Nb-V Containing Cast Microalloyed Steels

Abstract

Electrically conductive composite material PANIZr(IV) molybdophosphate (PZMP) was synthesized, via treatment of Zr(IV) molybdophosphate with PANI (polyaniline) gel. The membrane of this material is fabricated for detection of mercury in waste samples. By using 4-in-line-probe the conducting behaviour of the material was determined, and it was found that conductivity of the nanocomposite lies in the range of semiconductors. The composite showed In this study, base composition without alloying elements and three microalloyed steels containing 0.08% wt V, 0.06% wt Nb and 0.06% wt Nb-0.1% wt V in induction furnace, in controlled condition, were casted. Temperaging were carried out on all of specimens for precipitation strengthening. For studying the influence of temperaging time and temperature, specimens with different chemical compositions were temperaged at 400,500,600 and 700 °C for 1,3 and 5 h. All of specimens in as-cast condition were studied using optical microscope and hardness tester. Results showed that as-cast specimens having ferrito-pearlitic microstructures. Nb-bearing specimens shows acicular microstructures. The heat treated samples were studied using Electron Microscope Analysis and hardness tester. Studying of mechanical properties of heat treated specimens, showed that because of precipitation strengthening, hardness of samples increased. By increasing of temperaging temperature in a constant time, hardness has an optimum value. Material To study the effects of microalloying additions and cooling rate on the microstructural and mechanical properties, three heats were produced in the form of 8Cm ×8Cm ×20Cm and 8Cm ×3Cm ×20Cm blocks. The chemical composition of these heats is shown in Table 1. Samle C Mn Si P S V Nb N Base 0.15 1.5 0.3 0.01 0.015 0.01 V 0.15 1.5 0.3 0.01 0.015 0.1 0.01 Nb 0.15 1.5 0.3 0.009 0.011 0.04 0.01 Nb-V 0.15 1.5 0.3 0.009 0.012 0.1 0.04 0.01 Table 1: Chemical compositions of alloys studied (weight %). The alloy designations in Table 1 show the main alloying elements in the heats. The base composition for all heats is 0.15 wt% carbon and 1.5 wt% Mn. Ferroniobium was added to some heats to raise the Nb level to 0.04 wt%. Furthermore, sulfur plus phosphorus levels ranged from 0.02 to 0.035 for all heats. Experimental results To assess the effects of microalloying additions on the mechanical properties, tensile, hardness and Charpy impact tests were conducted for each composition. In order to avoid scattering, three samples were prepared for each test. Optical microscopy and scanning electron microscopy were used for justifying the variation in the mechanical properties. Samples of each heat were optically examined at magnifications ranging from 100 to 1000 times in order to observe major phases and their distributions. Moreover, pearlite volume fraction was determined quantitatively using an image analyzer. Scanning electron microscopy was used for more detailed study of pearlite. Optical microscopy The optical microscopy micrographs of different alloys revealed that all microstructures consisted of pearlite and ferrite. Considerable microstructural changes were not observed after the addition of microalloying elements. Figures 1-6 are the 100×