Papers by Keyword: Ultra High Carbon Steel

Abstract: Ultrahigh carbon steel containing 1.6 wt pct C was processed to create microduplex structure consisting of fine-spheroidized carbides and fine ferrite grains. Elongation-to-failure tests were conducted at strain rates from 10-4s-1 to 15×10-4s-1, and at temperatures from 600 °C to 850 °C. The steel exhibited superplasticity at and above 700 °C when testing at a strain rate of 10-4s-1, and at 800 °C when testing at strain rates of 7×10-4s-1 and slower. The grains retained the equiaxed shape and initial size during deformation; dynamic grain growth was not observed after superplastic deformation, whereas carbide coarsening was observed. It is concluded that the fine ferrite grains or austensite grains are stabilized by the grain boundary carbides, and grain-boundary sliding controlled by grain boundary diffusion is the principal superplastic deformation mechanism at temperatures in the range of 700-850 °C.

Abstract: The effect of hot rolling parameters on graphitization of a spray formed ultra high carbon steels(UHCSs) was described. The number of graphite stringers and graphite area fractions increased with the increase of rolling reduction. Graphite stringers nucleated at small pores and grew by carbon diffusion from adjacent austenite during hot rolling. Alloy contents, pores and hot deformation atγ+Fe3C phase range are the key factors for graphitization.The graphite stringers of UHCSs have little effect on tensile strength, but reduce the ductility at room temperature.

Abstract: The properties of ultrahigh carbon steels (UHCS) are strongly influenced by aluminum additions. Hardness studies of quenched UHCS-Al alloys reveal that the temperature for the start of transformation increases with increases in aluminum content. It is shown that this change is a function of the atomic percent of solute and of the valence state when comparisons are made with UHCSs containing silicon and tin as solutes. The thermal expansion of UHCSs with dilute aluminum additions shows no discontinuity in the vicinity of the ferrite-austenite transformation temperature. This is the result of a three phase region of ferrite, carbides and austenite. The slope of the expansion curve is higher in the austenite range than in the ferrite range as a result of the dissolution of carbon in austenite with temperature. Processing to achieve a fine grain size in UHCS-Al alloys was principally by hot and warm working (HWW) followed by isothermal warm working (IWW). The high temperature mechanical properties of a UHCS-10Al-1.5C material show nearly Newtonian-viscous behavior at 900 to 10000C. Tensile elongations of 1200% without failure were achieved in the 1.5%C material. The high oxidation corrosion resistance of the UHCS-10Al materials is described.

Abstract: Thermomechanical processing allows the attainment of spheroidized microstructures that show improved mechanical properties. In this work, a thermomechanical processing route consisting of two steps was developed for two ultrahigh carbon steels (UHCS) containing 1.3 and 1.5%C. This route develops structures of fine spheroidized cementite particles in a fine-grained ferrite matrix. Spheroidized microstructures are formed by eutectoid carbide particles in the UHCS- 1.3C and by proeutectoid and eutectoid carbide particles in the UHCS-1.5C. In the latter steel, the proeutectoid carbide particle size is larger than the eutectoid carbide particle size. The carbide size distribution remains basically constant with austenitizing temperature for both steels. Plane-strain fracture toughness of spheroidized UHCS-1.3C is higher than for UHCS-1.5C, about 80 vs 40 MPa m1/2. These values do not vary significantly with austenitizing temperature which is attributed to the constancy of the mean proeutectoid and eutectoid carbide size.

Abstract: Superplastic properties of fine-grained ultrahigh carbon steels (UHCS) have been greatly improved through the addition of 3 wt% Si (UHCS-3Si) and through improved processing conditions. This material showed an elongation to failure of 1300% under optimum superplastic conditions. It is also superplastic at very high strain rates, i.e. 10-2 s-1, in the temperature range between 800 and 825°C. An analysis of the effect of silicon additions on the UHCS and the influence of the introduction of temperatures regions in the phase diagram on the superplastic properties is made.

Abstract: The objective of the present work is to study the manufacturing process of steels with high carbon content (1.5–2.1wt%) obtained by powder metallurgy. The reference material was the Damascus steel, which was employed to manufacture swords named after it and has been widely known due to its very good mechanical properties. The main reasons of the success of this product are: the high carbon content of the initial steel and the thermomechanical treatment (forge and quenching) that ancient iron forgers kept secretly during centuries. Different carbon contents (2 to3 wt%) were added to the same Fe powder matrix (ASC 300), and compacted and sintered steels are heat laminated (750°C) with a reduction of 20%. For 2% carbon content, the result is a steel with yield strength of 450 MPa, Young’s Modulus of 14.3 GPa and hardness of 109 HV(30).

Abstract: A ultrahigh carbon steels (UHCS) containing 1.6 wt pct carbon was studied. Through spheroidizing process by divorced-eutectoid transformation (DET), the forged microstructure was spheroidized and the microstructure was fine carbide particles distributed in ferrite matrix. Second-time heat treatment included two kinds of technologies: normalizing and quenching + tempering. Finally, the UHCS obtained ideal mechanical properties. The yield strength and tensile strength of the UHCS were higher than that of 40CrNiMo, moreover plasticity of the UHCS was equal to that of 40CrNiMo. So the UHCS was an excellent structural material.

Abstract: The recent investigations on spray formed ultrahigh-carbon steels (UHCSs) are reviewed. A satisfactory combination of strength and ductility in spray formed UHCSs can be obtained by hot rolling and annealing. The composition and hot rolling have a marked effect on the formation of graphite in UHCSs. The possibility of achieving high strain rate superplasticity in the spray formed UHCS was first revealed by very recent investigations in Shanghai Baosteel Research Institute. The UHCS processed by a combination of spray forming and hot rolling exhibited high strain rate superplasticity.