Showing papers on "Pearlite published in 1974"

Carbide refining heat treatments for 52100 bearing steel

Abstract: The life of through-hardened 52100 anti-friction bearing components is improved if the excess carbides, undissolved during austenitization, are small and uniformly dispersed. One kind of carbide-refining heat treatment consists of 1) dissolving all carbides, 2) isothermally transforming the austenite to pearlite or bainite, and 3) austenitizing, quenching and tempering in the usual manner. Each step in this sequence of treatments was investigated, and the behavior of pearlitic and bainitic microstructures during subsequent austenitization was contrasted with the behavior of ferrite/spheroidized-carbide microstructures. It was shown that: 1) The usual hardening treatments given spheroidize-annealed bearing components result in an inhomogeneous microstructure, possibly due to the faster dissolution of carbides near austenite grain boundaries. 2) Austenitization of pearlite or bainite produces very uniform dispersions of ultra-fine carbides on the order of 0.1 µm diameter or less. 3) Specimens with ultra-fine carbides tend to have more retained austenite. 4) The rate of coarsening of ultra-fine carbides at austenitizing temperatures of 840°C and below, is slow enough so that conventional furnace heat treatments are satisfactory for producing this microstructure.

The high-temperature hardness of various phases in steel

Abstract: Apparatus constructed in the Department of Metallurgy and Materials Science, University of Cambridge, has enabled the hot hardness of the individual steel phases, ferrite, austenite, cementite, pearlite, Type I MnS, Mn–MnS eutectic, and silicates to be measured in situ with a high degree of accuracy. The work was undertaken in the context of studies of the deformation behaviour of non-metallic inclusions in steel, where the relative yield behaviour of inclusions and matrix is clearly a significant factor. Because of their wider interest the hot hardness results are presented separately. The high-temperature hardness of pearlite, of significance in its behaviour in ‘warm’ working, has been explained in terms of the hardness of its constituent phases.

Thermal treatment of steel

Abstract: A method of hardening hypereutectoid steels having less than about 10 percent total alloy content is described which results in a structure with an ultra-fine grain size (finer than ASTM No. 10) and a natural dispersion of very small excess carbides. The process includes high temperature solid solution of the carbide phase present in the material, controlled cooling through a selected area of the time-temperature-transformation for the material to form pearlite (a ferrite and carbide lamellar structure) and cementite, reheating to austenitize the material, and finally, quenching to produce a structure with an ultra-fine grain and a natural dispersion of very small excess carbides that results in an improvement of fatigue life and an increase in compressive yield strength.

Bainitic ferrous alloy and method

Abstract: This invention relates to an as-worked bainitic ferrous alloy and to a novel method of processing same to obtain optimum strength and toughness. More particularly, this invention is directed to the hot working cycle of a ferrous alloy characterized by an I-T Diagram or "S" Curve having a double nose or a pearlite transformation knee of the beginning curve above a broad bainitic bay region. Such an alloys is heated to an austenitizing temperature of about 1,500 DEG to 2,200 DEG F., and subjected to a plurality of working operations at successively lower temperatures, where the final working operation is conducted after the beginning of the austenite transformation to bainite and before the complete transformation thereof.

The Unidirectional Growth of Copper–Indium Eutectoid Alloy

Abstract: Copper–indium eutectoid alloys have been unidirectionally transformed to produce pearlite that was aligned within ∼ 15° of the pulling direction. The relationship between unidirectional growth velocity V and interlamellar spacing λ was determined. At low growth velocities a growth law of Vλ1·8±0·2 = constant existed that was consistent with the theoretical analyses for a volume diffusion controlled reaction. As the growth velocity increased, the exponent in the growth law continuously changed from 1·8 ± 0·2 to 3·35 ± 0·25. Kinetic factors were considered to be responsible for the exponent being greater than the value of 3 predicted for an interfacial diffusion-controlled reaction. A wide range of interlamellar spacings was found at each given growth velocity.

High toughness spheroidal graphite cast iron and method for producing the same

Abstract: According to this invention, 0.0035 - 0.02 % of N is contained in a spheroidal graphite cast iron to result in ferrite and pearlite structures. This spheroidal graphite cast iron is markedly improved in toughness. This invention further provides a method for producing a high toughness spheroidal graphite cast iron which comprises adding N to a melt of a cast iron during or after spheroidizing treatment to contain 0.0035 - 0.02 % of N in compositions of said cast iron.

Influence of manganese on the impact transition temperature of as-rolled plain carbon–manganese steels

Abstract: The influence of manganese on the 50% fibre Charpy impact transition temperature of as-rolled low-silicon and silicon-killed steels has been examined. The steels were found to have similar grain-boundary carbide thicknesses so that the changes in the transition temperature could be related almost entirely to changes occurring in the ferrite. Whereas manganese had only a small influence on the transition temperature of silicon-killed steels, a very significant improvement occurred with low-silicon steels, a rise of 1% manganese causing an approximate 40°C lowering of the impact transition temperature after correcting to constant grain size and pearlite volume fraction. The decrease in transition temperature is believed to be due predominantly to the prevention of grain-boundary segregation of nitrogen by manganese, as is shown by the accompanying fall in ky value and the lack of any increase in the hardness of ferrite grains close to their grain boundaries.

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

Abstract: 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 Use of Hot-Stage Microscopy in the Study of Phase Transformations

Abstract: This paper summarizes the experimental techniques used in hot-stage light microscopy and the application of these techniques to ferrous transformations. In the hot-stage microscopy examples, particular emphasis is given on results of the martensite, pearlite, and ferrite transformations studied in this laboratory. Reference is also made to the results of many other investigators who have used the hot-stage microscope as a tool to study kinetics and morphology of ferrous transformations during both heating and cooling conditions.

Chilled cast iron with thin walls - contg. aluminium to prevent formation of hard spots

Abstract: The formation of hard spots (e.g. cementite) in cast iron produced in metal moulds is avoided by using a compsn. of 2.80-3.80% C, is not >0.90% Si, is not >0.90% Mn, 0.01-1.0% S, 2.50-4.00% Al and 0.10-1.00% P. The iron has excellent castability and the metal moulds may be water-cooled immediately after casting. Machining is possible even with the addn. of 4% each Cu and Ni, is not >0.25% Cr, is not >0.3% Mo, and is not >0.20% V. Depending on the pre-heating of the mould and the cooling rate, the structure may vary from ferrite/pearlite to pearlite/bainite/austenite, with flake graphite uniformly distributed or in inter dendritic form. The tensile strength and hardness, depending on compsn. and section thickness, are 25-50 kg/mm2, and 180-360 kg/mm2 HB respectively.

Properties of low-pearlite steel with manganese

Abstract: Alloying of low-pearlite steel with 1.5% Mn results in the highest resistance to crack propagation (a p∼14 kg-m/cm2).

Properties of low-pearlitic steels with vanadium and niobium after controlled rolling

Abstract: 1. Raising the initial rolling temperature from 1050–1100 to 1200–1250° increases the strength characteristics due to the solution of carbonitrides; therefore, the effect of the increase in strength is stronger in the steel alloyed with vanadium and niobium, and is hardly manifest in the steel not containing these elements. 2. Lowering the final rolling temperature from 950 to 700° leads to higher strength characteristics, particularly final rolling at 700°. 3. Lowering the final rolling temperature lowers the ductile-brittle transition temperature (T50), i.e., increases the resistance to brittle fracture. However, the work of crack propagation decreases in this case, i.e., the resistance to ductile fracture. 4. The increase in strength and lower ductile-brittle transition temperature when the final rolling temperature is lowered are due to grain refining. However, the work of crack propagation decreases in this case (ap) and also the notch toughness at −40°. A final rolling temperature of 800° produces the best combination of mechanical properties. 5. The high values of the strength, ductility, and toughness in combination with a very low carbon equivalent lead us to consider low-pearlitic steels as promising materials for welded structures and materials requiring good weldability and resistance to fracture. Controlled rolling makes it possible to control the properties of these steels within wide limits by changes in the strength, ductility, and toughness, depending on the requirements.