Effect of Chills on the Microstructure and Mechanical Properties of Carbidic Austempered Ductile Iron

Carbidic Austempered Ductile Iron (CADI) is a recent addition to the Austempered Ductile Iron (ADI) family. The effect of chills on the microstructure and mechanical properties of CADI was investigated after Austempering. Three samples of chromium alloyed CADI, the first sample without chill, the second sample with bottom chill and the third sample with bottom and side chills were produced in order to evaluate the effect of chills on its mechanical properties. The samples were austenised for 2 hours at 925° C and then austempered at 325° C for 2 hours in a salt bath furnace. The microstructural features of the as-cast and the austempered CADI samples were analysed using Optical Microscope and Scanning Electron Microscope (SEM). The mechanical properties of the CADI samples (as-cast and austempered) were evaluated for hardness, impact and wear. By austempering at 325° C for 2 hours a typical microstructure of bainite was produced in all the three samples. Hardness and wear resistance of austempered samples produced using bottom and side chills were considerably higher than the corresponding values in samples produced without using any chill and also by using only bottom chill. This enhanced mechanical property in the bottom and side chill sample is attributed to the presence of bainite, carbides and more of uniform fine graphite nodules.

Effect of Partitioning Time on the Microstructure and Mechanical Properties of Q&P Steels

The microstructure and properties of Q&P steel were studied by means of tensile test, OM and SEM after simulating heat treatment process in salt bath furnace. The results showed that the main microstructure of Q&P steel was lath martensite and retained film austenite. With the increase of partitioning time, the morphology of the parallel martensite lath became clear and ordered. With the trivialness and disorder with massive martensite appearing, the yield strengths and tensile strength decreased initially and then increased. On the other hand, the elongation increased initially and then decreased. This was because of that the retained austenite is unstable at the beginning for low carbon content, and the carbide precipitated after a long partitioning time. Therefore, there was an optimum partitioning time to obtain the best properties combination. Under 250 quenching temperature and 350 partitioning temperature, partitioning time was 60s, the tensile strength and elongation were 1027MPa and 27%, respectively. The product of strength and elongation was up to 27729MPa·%.

XRD Evidence for Phase Structures of Niobium Alloyed Austempered Ductile Iron

This paper presents the changes on phase structures of niobium alloyed ductile iron after austempering process which started by austenitizing process at 900°C and held at 350°C for 1 hour, 2 hours and 3 hours in salt bath furnace. The phase structure were observed by light microscope, and then verified through X-Ray diffraction (XRD). The phase structure of as cast niobium alloyed ductile iron mainly consists of graphite nodules embedded in ferrite and pearlite phases with presence of niobium carbide. Austempering process resulted in the structure of graphite nodules embedded in ferrite platelets and bainitic structures. Increasing the austempering holding times had resulted in coarsening of the ferrite platelets structures and transformation from lower bainite to upper bainite structures.

Tensile Strength Properties of Niobium Alloyed Austempered Ductile Iron on Different Austempering Time

This study focused on tensile strength properties inclusive of ultimate tensile strength and elongation values of niobium alloyed ductile iron in as cast and austempered conditions. The tensile specimens were machined according to TS 138 EN 10002-1 standard. Austempering heat treatment was conducted by first undergoing austenitizing process at 900°C before rapidly quenched in salt bath furnace and held at 350°C for 1 hour, 2 hours and 3 hours subsequently. The findings indicated that austempering the samples for 1 hour had resulted in improvement of almost twice of the tensile strength in niobium alloyed ductile iron. Improvement of elongations values were also noted after 1 hour austempering times. Increasing the austempering holding times to 2 hour and 3 hours had resulted in decrement in both tensile strength and elongations values.

Phase Transformations and XRD Analysis of Austempered Ductile Iron

This research penetrated on the transformation of phases in the microstructures of austempered ductile iron with respect to different austempering holding times. Ductile iron samples were constituted in form of Y block double cylinder with dimension of 300m x Ø25mm through CO2 sand casting process in 60 kg capacity furnace. Austempering process were conducted by first austenitizing the samples at temperature of 900°C for 1 hour. The process continues by rapidly quenched the samples inside salt bath furnace at 350°C for three different holding times of 1 hour, 2 hours and 3 hour. Samples were then taken out and cooled at room temperature. Samples were then prepared in accordance to standard metallographic process and observed using Tabletop Scanning Electron Microscopy (SEM) model Hitachi TM3000. Phases were then verified through X-Ray Diffraction analysis (XRD) test by Rigaku diffractometer. The phase structures of as cast ductile iron mainly consisted of graphite nodules embedded in ferrite and pearlite phases Austempering the samples for 1 hour holding time promoted the structures of ferrite platelets and bainitic structures surrounding the graphite. Longer austempering holding times resulted in coarsening of the ferrite platelets structures and transformation from lower bainite to upper bainite structures.

Evolution of Micro-Orientations on Non-Oriented Silicon Steels during the Annealing Process Based on the CSP

In this paper, studied was the low carbon and low silicon (0.003%C,0.3%Si) cold-rolling steel sheet whose reduction ratio was 81% annealed at 870 °C in the laboratory salt-bath furnace and heated for 180s.The evolution of micro-orientations of grain coarsening at 1050°C and 1150°C on cold-rolling samples that were annealed at temperature 870°C and heated for 180s was studied by EBSD technology.

Effects of Heating Methods on Recrystallization Texture of an Al-Mg-Si Alloy

The cold-rolled sheets of the Al-Mg-Si Alloy were annealed for recrystallization in the box furnace and the bath furnace respectively, then the microstructures were observed and the recrystallization textures were investigated with the orientation distribution functions (ODFs). The results show that after recrystallization annealing at slow heating rate the coarse a-Al grains and the strong recrystallization texture composed of Cube+nd25 components and the {011}<323> components were formed in the sheets of the Al-Mg-Si alloy, and after recrystallization annealing at rapid heating rate the fine a-Al grains and the weak or almost random recrystallization textures were formed.

The Effects of Ausforming on the Precipitating Process and Mechanical Properties of 17-4PH Stainless Steel

In this study, the effects of ausforming on the precipitating process and mechanical properties of 17-4PH stainless steel were investigated. For doing ausforming, samples were solution treated at 1050°C for an hour, and then quenched into a salt bath furnace at 400°C. Rolling at 400°C in different percents was done for achieving different mechanical works. After finishing ausforming process, samples were tempered for precipitating at 300,400,500 and 600°C for 1, 2, 4, 8, 16 and 32h. Microstructural studies were done for finding the changes on precipitating process and tensile and hardness test done to study mechanical properties. Scanning electron microscope was used to show precipitates and other phases. Also EDS method used to analyze the elements in each phases.

Recrystallisation Texture of Cold Rolled and Annealed IF Steel Produced from Ferritic Rolled Hot Strip

The ferritic rolling strategy allows for the production of two different hot strip grades, a "soft" and a "hard" hot strip. The "soft" hot strip is rolled in the upper ferrite region and a sufficiently high coiling temperature ensures direct recrystallisation in the coil. The "hard" hot strip is rolled at relatively lower temperatures in the ferrite temperature region and exhibits a strained microstructure with a desirable rolling texture. Furthermore, these ferritic rolled hot strips can be used as initial strip for subsequent cold rolling. The current investigation focuses on the development of the recrystallisation texture of cold rolled and annealed ferritic rolled hot strip for different cold reductions. For this purpose "soft" and "hard" hot strips were produced on a laboratory hot rolling mill. These strips were cold rolled with a total reduction of 40 to 80% to a final thickness of 0.5mm. Subsequently the strips were subjected to simulated continuous annealing, using a salt bath furnace. The macro texture of both types of specimens was measured and correlated to the mechanical properties, including the Lankford values. A very different development of the recrystallisation texture and hence mechanical properties has been observed. However, both grades yielded improved deep-drawing properties.