Spheroidization Of Carbides Research Articles

Effects of Chromium, Molybdenum and Vanadium on Spheroidization of Carbides in 0.8% Carbon Steel

Effects of Chromium, Molybdenum and Vanadium on Spheroidization of Carbides in 0.8% Carbon Steel

0.8%C鋼の炭化物の球状化におよぼすクロム, モリブデンおよびバナジウムの影響

0.8%C鋼の炭化物の球状化におよぼすクロム, モリブデンおよびバナジウムの影響

Effect of preliminary quenching on spheroidization of carbides

1. We investigated the effect of preliminary quenching on spheroidizing of carbides. It was found that preliminary quenching greatly accelerates spheroidizing of carbides and can be made part of the spheroidizing treatment. 2. For previously quenched steel the austenitizing temperature and time must be selected so that a substantial percentage of the granular carbides remains undissolved. The cooling time or isothermal holding temperature below Ac1 after austenitizing of the quenched steel must prevent formation of lamellar carbides. 3. The spheroidizing treatment proposed not only shortens the spheroidizing time but improves the properties of parts after final heat treatment. 4. This new treatment is recommended for use where it is economically expedient.

Effect of the method of spheroidizing carbides on the wear resistance of steel ShKh15

1. The existence of the effect of dynamic spheroidization of carbides observed previously on wedgeshaped samples was observed on massive samples of rectangular cross section in deformed steel at subcritical temperatures, and the effect of the formation of divorced pearlite during cooling in air of steel deformed at supercritical temperatures. 2. Dynamic spheroidization and spheroidization rolling of steel at supercritical temperature ensure a higher wear resistance after quenching and low-temperature tempering as compared with spheroidization annealing. 3. To obtain these effects the original (before warm rolling) preparation of the microstructure and additional tempering at 600° cannot be used.

The structure and properties of warm-rolled steels

Abstract Microstructure, tensile properties and fracture behaviour were examined in both warm-rolled rods (1150°F, 621°C) and in conventionally hot-rolled rods (1950°F, 1065°C) of four carbon grades (1015, 1038, 1060 and 1090). Both spheroidization of carbides and the development of substructure in the ferrite were produced during warm rolling. The fracture facets were more irregular, indicating an increased amount of plastic tearing, than in the conventionally hot-rolled bars. Compared with hot rolling, the warm rolling caused an increase in yield stress (all grades), in reduction of area (all grades except 1015) and in ratio of yield stress to ultimate tensile stress. The total elongation, with the exception of 1090 steel, was decreased. In the1090-grade rods, the shelf energy for the tear fracture was significantly increased, although the transition temperature was affected very little by warm rolling. In contrast, warm rolling has produced a marked decrease in shelf energy and a 30°C increase in trans...

焼戻マルテンサイト鋼に対する多重焼入熱サイクルの効果

Study is continued on the effect of multi-quenching thermal cycles similar to refined weld heat-affected zone on the mechanical properties of Ni-Cr-Mo and Ni-Cr-Mo-V-B high tensile steel.Results indicate that those steels have as good mechanical properties as ferritic steels when subjected to multi-quenching thermal cycles with incresaingly lower heating temperatures and tempering in furnace.Most suitable initial heating temperature locates around Ac3 temperature; however, quenching from Ac3 below makes the strength lower. Subsequent most suitable quenching temperature is between Ac3-Ac1 temperature range. In those cases a slight decrease in tensile strength appears, but notch toughness is much improved, when tempered in furnace.Multi-quenching from just above Ac3 slightly lowered vTr15 transition temperature; however, it didn't give such superior impact properties as given by quenching from Ac3 above, then Ac3-Ac1 temperature range.Multi-quenching from just above Ac1 retained large ferrite grains and impact properties of those steel were not so good as suitably treated steel.From the results of microstructural studies it was presumed that those superior mechanical properties were developed as a result of refining of γ grains, agglomeration and spheroidization of carbides and sink effect with locally produced r when steel was reheated in later cycles.

The Creep Curve and Stability of Steels at Constant Stress and Temperature

Abstract The creep rate for steels at constant stress and elevated temperature is composed of (1) the strain hardening with a rate which varies inversely with time, and (2) an asymptotic constant creep rate. The sum gives the creep rate at any time, and the formula for the total creep-extension curve. For steels with a physical or structural change during creep, a third quantity must be added to the creep-extension formula, the test value of the quantity indicating the degree of instability of the test metal. To illustrate four of the principal types of instability, the author presents four sets of long-time creep tests extending from 5500 hr to 5 yr. They represent changes due to (1) carbide spheroidization, (2) ferritic banding, (3) dendrites, and (4) alloy segregations.