Papers by Keyword: Tempering Treatment

Abstract: Aim of this study is to investigate the effect of tempering with various heating temperatures (200, 300 and 450°C) and time (2, 4 and 6 hours) on toughness and microstructure of high carbon steel in order to improve its properties. The toughness was measured using the Charpy test and the changes of microstructures were evaluated by Optical Microscope. The analysis was performed for specimens before and after tempering. The results showed the energy of impact and the impact number (toughness) of high carbon steel JIS G4401 were increased by rising tempering temperature. Besides, by addition of the time of tempering, the energy of impact and the toughness were also enlarged. The microstructures of specimens after tempering consisted of ferrite and pearlite phases where the pearlite phase appeared more dominantly during increasing temperature and time of aging.

Abstract: Test bends of L415M hot induction bend of 508 mm OD×14.3 mm WT used in –45°C areas were conducted. The bending and tempering process parameters were designed, the influences of bending and tempering process parameters on impact toughness at –45°C and microstructure of tangent weld and bend weld were investigated. Hot induction bend was produced by the process of local induction heating+fast water quenching. After tempering treatment, the weld contained martensite-austenite (M-A) islands, carbide precipitations, welded column crystal structure and little pearlite (P), and the brittle fracture surface contained S segregation, the temper brittleness of the weld occurred, which lead to impact energy of bend weld to be lower than 40 J at –45°C. Without post-bending tempering treatment, the microstructures of bend weld was a composite of polygonal ferrite (PF) and granular bainite (GB) with small size and uniform distribution, the coarse column structure and acicular ferrite (AF) disappeared in the weld, so the impact energy of bend weld was higher than 70 J at –45°C, but the impact energy of tangent weld was very poor. It suggests that the process of overall induction of heating + fast water quenching + no tempering treatment is more reasonable, the process ensures that the impact toughness at –45°C, strength and other properties of bend meet the requirements of CDP-S-OGP-PL-016-2011-2.

Abstract: Non-isothermal resistance heating in the hot stamping of quenchable steel sheets was developed to produce ultra-high strength steel formed parts with tailored properties. The heating temperature of parts is related with width of samples heated by resistance heating. With the same input energy, the strength in the narrow portions is high owing to the high energy density and that in the wide portions is low owing to the low energy density. Hat-shaped products having a tensile strength arrange from 600 MPA to 1800 MPa were formed. The tempering treatment on the directly hot-stamped boron steel resulted in better mechanical properties and higher formability index. The SEM figures indicates that the nano-carbide formation during the tempering treatment were suggested as the evident reasons for the occurrence of the mentioned robust properties. Finally the combination of temperature 250 ℃ and holding time 45 min can achieve the best comprehensive mechanical properties.

Abstract: This study concerned the influence of the material strength, ductility and impact energy and the relationship of the broken section profile vs. ductile transition brittle where the steel material was treated under different tempering temperature and hardness. Generally after the steel materials, 10B35 coil wire materials which was generally applied to form screws, was treated by quenching and tempering, its hardness ranged from HRC30 to HRC45. The results showed that the elongation rate beyond 20.4% would be proportional to the impact energy with linear relation, but with reverse proportion to the hardness value. The brittle-tough point of the hardness was set around HRC37 after heat treatment in order to balance the strength and the toughness. In addition, the coil wire materials were analyzed from broken section materials showing good toughness; this represented that the area of the cross section radiation layer due to ductile fracture would largely increase. On the contrary, the wire material test fragment with bad toughness represented that the area of the shear layer due to brittle fracture would largely increase as well. As to that material, if its hardness was greater than or equal to HRC37, that material would have an excellent turning danger from transition. At the same time, when the tempering temperature of the wire steel material was set under 4600C and its corresponding central hardness was about HRC37, the distance between two cementite phase layers suddenly increased. This result leaded to the reason why the wire material test fragment was turned into brittleness from ductility. Therefore, when the fastener was manufactured under tempering treatment, avoiding the tempering brittleness temperature range was necessary.

Abstract: Microstructure of 0.63C-12.7Cr martensitic stainless steel during various tempering treatments was investigated in this study. Results demonstrate that finely distributed primary carbides were observed on 0.63C-12.7Cr martensitic stainless steel. The matrix phase of 0.63C-12.7Cr martensitic stainless steel when tempered below 500 °C was identified as martensite. However, the matrix structure when tempered at 500 °C and 600 °C was found containing of both ferrite and martensite. On carbide particles, mixed of M7C3 and M23C6 particles were observed on all specimens when tempered at 200-600 °C. The amount of M7C3 carbides was found decreased as the tempered temperature was increased.

Abstract: In this study, the microstructure and mechanical properties of 0.63C-12.7Cr martensitic stainless steel during various tempering treatments were investigated. Experimental results demonstrate that finely distributed primary carbides can be observed in 0.63C-12.7Cr martensitic stainless steel. It was also found that the measured hardness of 0.63C-12.7Cr martensitic stainless steel after 300°C tempered treatment for 60 minutes can still reach to 677Hv. The variation of measured hardness was found not significant during tempering treatments (200°C-500°C). Moreover, owing to lower concentration of C and Cr, the matensitic transformation temperature Ms can be increased to 96.4°C comparing to -127°C of SUS440C materials.

Abstract: Effects of tempering temperature and shot peening on fatigue behavior of SAE 1045 steel are reported. Tensile and fatigue property measurements are reported for samples tempered and shot peened at 300 and 550°C. Microstructural studies and fracture surface observations were carried out by optical and scanning electron microscopes. The experimental results showed that, fatigue strength increases with decrease of tempering temperature and shot peening treatment. SEM analyses indicated that all three stages of fatigue fracture affected by tempering treatment whilst shot peening treatment only have an effect on the crack initiation stage.