Showing papers on "Tempering published in 1975"

The Secondary Hardening of Tungsten Steels

Abstract: The tempering characteristics of a steel with 2 at.−%W 1.1 at.−%C in the range 500–700°C have been studied and structural changes related to the secondary-hardening phenomenon. The sequence of carbides found both at grain boundaries and in the matrix has been established,and detailed structural observations have been made on the nucleation of W2C and M6C. The ageing behaviour is contrasted with that of a comparable molybdenum steel in which the carbide reactions occur more rapidly. Trace additions of Nb Ti and Ta improve the basic strengthening reaction by providing a fine secondary carbide dispersion which also inhibits the coarsening of the dislocation network. The main carbide dispersion is also refined.

Design of strong tough Fe/Mo/C martensitic steels and the effects of cobalt

Abstract: The microstructures and mechanical properties of a series of vacuum melted Fe/(2 to 4) Mo/(0.2 to 0.4) C steels with and without cobalt have been investigated in the as-quenched fully martensitic condition and after quenching and tempering for 1 h at 673 K (400°C) and 873 K (600°C); austenitizing was done at 1473 K (1200°C) in argon. Very good strength and toughness properties were obtained with the Fe/2 Mo/0.4 C alloy in the as-quenched martensitic condition and this is attributed mainly to the absence of internal twinning. The slightly inferior toughness properties compared to Fe/Cr/C steels is attributed to the absence of interlath retained austenite. The two 0.4 pct carbon steels having low Mo contents had approximately one-half the amount of transformation twinning associated with the two 0.4 pct carbon steels having high Mo contents. The plane strain fracture toughness of the steels with less twinning was markedly superior to the toughness of those steels with similar alloy chemistry which had more heavily twinned microstructures. Experiments showed that additions of Co to a given Fe/Mo/C steel raisedM S but did not decrease twinning nor improve toughness. Molybdenum carbide particles were found in all specimens tempered at 673 K (400°C). The Fe/Mo/C system exhibits secondary hardening after tempering at 873 K (600°C). The precipitate is probably Mo2C. This secondary hardening is associated with a reduction in toughness. Additions of Co to Fe/Mo/C steels inhibited or eliminated the secondary hardening effect normally observed. Toughness, however, did not improve and in fact decreased with Co additions.

The effect of quench rate on the properties and morphology of ferrous martensite

Abstract: The effect of high quench rate on theMs temperature, percent transformed, martensite morphology and austenite hardness has been studied for several Fe-Ni-C steels. For these steels the quench rate was varied only in the austenite region. TheMs temperature was found to increase with increased quench rate for both high- and low carbon steels while the percent transformation increased or decreased depending upon the morphology of the steel. No variations in martensite hardness were found in the as-quenched condition, but a difference in tempering rate was found between fast and slow quenched specimens. Austenite hardness decreased slightly with increasing quench rate while the martensite morphology changed from lath to plate. Parallel aligned plate structures were observed which resemble a twinned lath morphology. It was demonstrated that the actual difference between this morphology and a true lath morphology is the self-accommodating nature of the lath structure. The morphology changes were compared to the measured changes in martensite properties in order to identify the mechanism of the morphology shift. It was concluded that for these alloys the morphology was controlled by the austenite shear mode.

Fatigue crack propagation in 4140 steel

Abstract: The fatigue crack propagation rates, da/dN, of 4140 steel were measured in dry argonvs tempering temperature. In specimens 3.2 mm thick at a given ΔK between 15 and 30 MN/ m3/2, da/dN decreases with increasing tempering temperature, reaches a shallow minimum for tempering at 400°C. The rate for as-quenched specimens increases withR ratio; this is not the case for the 400, 550 and 650°C tempers. Reducing the specimen thickness to 1.3 mm has little effect on the 650°C temper but causes a large decrease in da/dN for the asquenched condition and 200°C temper. Edge notch specimens tempered at 550 and 650°C are subject to crack arrest from cycling prior to crack initiation. The results are discussed in terms of the metallurgical structures and various fatigue crack propagation equations which have been proposed. The results cannot be explained on the basis of da/dN being determined only by Young’s modulus andK c.

Effect of additional alloying elements on the properties of sintered manganese steels

Abstract: Sintered alloys based on the Fe-Mn system have been investigated by using single-pressing and double-pressing techniques. Fe-Mn (Mn up to 8 wt.-%) and Fe-Mn-C (C up to 1·4 wt.-%) alloys were prepared both with manganese as an electrolytic powder and with a Fe-Mn master alloy. The influence of sintering temperature and sintering time on mechanical properties and homogenization is discussed. The effect of the additional alloying elements Cr, Mo, eu, and of their combinations on mechanical properties has been determined. Further investigations were carried out with a Fe-Mn-Cr-Mo-C master alloy. The optimum single-pressed and double-pressed alloy (Fe with Mn 0·8, Cr 0·8, Mo 0·8, and total C 0·6%) has a tensile strength (σB) of >700 N/mm2. Optimum alloys of all investigated systems were hot-forged and their mechanical properties are compared with those of single- and double-pressing techniques. The alloys were heat-treated and their tempering behaviour determined. Jominy standard tests were carried out...

Process for the manufacture of strong tough steel plates

Abstract: Strong and tough steel is prepared by heating to a temperature of 800° - 1000° C., preferably from 800° to 950° C., before the rolling step, finish rolling at temperatures within the range of from 680° to 850° C., preferably from 680° to 800° C. and with a reduction ratio in thickness of not less than 30% based on the plate thickness of the steel when the finish rolling is started. It is advantageous to provide for a pretreatment of the steel, said pretreatment including the steps of initially heating the steel to a temperature higher than 1000° C., rolling the heated steel to a suitable intermediate thickness and cooling the rolled steel to a temperature lower than 650° C. Tempering may also be carried out at a temperature of 500° - 650° C. for 20 minutes -- 2 hours.

Surface defects: Their origin, characterization and effects on strength

Abstract: The usefulness of scanning electron microscopy (SEM) in characterizing surface flaws and in establishing the relationship between such flaws and fracture origins was demonstrated. Effects on strength of surface treatments which produced different average flaw sizes, of hydrofluoric acid etching, and of tempering were investigated. Measurements of fracture origins using the SEM allowed the determination of a fracture-origin constant whose value is independent of strength, as in the fracture-mirror constant. It was shown that tempering leads to higher values of these constants, and that the compressive stresses on the surface act to reduce the size of flaws produced under a given condition.

Tempering glass sheets

Abstract: A multiple stage process for tempering a glass sheet in which a glass sheet, heated to the vicinity of its softening point, is cooled sufficiently rapidly to impart a temper in multiple stages of cooling without marring its softened surfaces to an extent sufficient to impart annoying optical properties.

Strength and Ductility of Cr-Mo-V Steels in Creep at Elevated Temperatures

Abstract: A state-of-the-art survey of literature pertaining to low alloy Cr-Mo-V steels has been completed with a view to elucidate the effects of composition, heat treatment, and microstructure on the creep strength and ductility of the steels. It appears that minor amounts of alloy additions such as boron, titanium, and cerium and impurity elements phosphorus, sulfur, tin, antimony, aluminum, and copper may affect the creep strength or ductility or both of the steels. Higher austenitizing and lower tempering temperatures lead to improved strength at the expense of rupture ductility. An upper bainite microstructure is associated with the highest creep strength and the lowest ductility, for temperatures up to 1050°F (565°C) and for times of at least up to 10,000 h. In bainite-ferrite aggregates, creep and rupture strengths increase in proportion to the amount of bainite, and the difference in strength between the various structures is maintained at least up to 10,000 h at 1070°F (575°C). Stress rupture strengths in general increase linearly with room temperature tensile strength for temperatures up to 1000°F (538°C) and times up to 10,000 h. Variation of rupture strength and minimum creep rate with temperature and time can be adequately described by the Orr-Sherby-Dorn parameter. Activation energies for both creep and for rupture are determined to be about 90 kcal/mole (375 kJ/mole). Further, it is observed that ˙e × tr ⋍ 3.3 and that tt ⋍ 0.3 tr, where ˙ϵ tt, and tr are the minimum creep rate, time for transition from second- to third-stage creep, and time to rupture, respectively.

Apparatus for press bending relatively thin glass sheets

Abstract: A method of and apparatus for bending and tempering a relatively thin glass sheet comprising heating the glass sheet to its softening point, advancing the sheet toward and between a pair of opposed press members, reheating the sheet during movement thereof between said press members, bending the sheet into the desired curvature between the press members and finally, chilling the sheet rapidly below the annealing temperature range of the glass.

200, 020, and 002 X-ray peaks in tempered Fe-18 Ni-C martensites

Abstract: Separate 200, 020, and 002 X-ray peaks were recorded for 0.0, 0.4, and 0.8 wt pct carbon (18 pct Ni) martensites after tempering between 25 and 500°C. The carbon bearing martensites studied here have been tempered initially enough to eliminate the “high tetragonality” 002 peak usually recorded for as-quenched martensite and the present results apply to tempered martensite only. The peak maximum is taken to determine the lattice parameter and the peak shape is recorded. At all carbon levels and after all tempering treatments, the “crd parameter is larger than or equal to the “a” or “b”. The relative enlargement is very small (0.08 pct) for the lowest carbon level and for any carbon level after severe tempering (500°C for 15 min). For the two higher carbon alloys tempered at temperatures below 400°C (for 15 min) the “c” parameter is significantly larger than the “a” and “b” and for the 0.4 wt pct C alloy the “b” is significantly smaller than the“a” whereas in the 0.8 pct C alloy the “b” is slightly larger than the “a”. Within experimental error the mean volume of the unit cell does not change during the tempering studied here and is nearly unaffected by the initial carbon content. This indicates that little (at most 0.1 wt pct) carbon is dissolved in tempered martensite. In the low carbon alloy the peaks are symmetric and sharpen symmetrically during tempering. In the higher carbon alloys the peaks are nearly symmetric and sharp after severe tempering. After less severe tempering the 002 peak is asymmetrically broadened toward lower9 values (higher lattice parameters) whereas the 200 and 020 peaks are asymmetrically broadened toward higher 0 values corresponding to lower lattice parameters. This collection of results is tentatively interpreted as being due to strains in martensite due to transformation induced substructure and precipitated carbides.

Steel abrasives and method for producing same

Abstract: Disclosed is a method of producing a versatile as-cast steel shot having a substantially fully martensitic structure and corresponding full hardness which permits eliminating intermediate steps of heat treating to harden and subsequent drying in producing steel shot having a tempered martensitic structure or in producing steel grit. The method includes steps of charging, melting, refining, and pouring. The pouring step is accomplished by directing a stream of the refined molten steel through a stream of water under pressure and into a fluid quenching bath. The refined steel comprises: carbon in about the range of from 0.6 to 1.20 per cent by weight; manganese in about the range of from 0.50 to 2.26 per cent by weight; silicon in about the range of from 0.3 to 1.80 per cent by weight; sulphur in about the range of from 0.0 to 0.1 per cent by weight; phosphorous in about the range of from 0.0 to 0.1 per cent by weight; boron in about the range of from 0.0 to 0.01 per cent by weight; with the remainder of the metal being substantially all iron and trace elements and impurities commonly found therein. The boron, when present, is the result of an alloy-adding step which includes the addition of ferro-boron to the melted metal. The method yields an as-cast shot hardness in the full hard Rockwell C (Rc) range of 65+ to 67+ in a significantly increased per cent of heats over what is normal in as-cast steel shot having comparable carbon per cent by weight and having generally the same chemistry. The control of carbon in the preferred range and/or the use of boron as an alloying element to produce substantially fully martensitic or full hard as-cast shot permits elimination of both the hardening furnace and drying operation following hardening. The as-cast product goes directly into a tempering operation to make tempered martensitic shot or to a crushing operation to make grit.

Tempered-Martensite Embrittlement in a 12%Cr Steel

Abstract: The influence of tempering on the mechanical properties of an En 56C steel has been studied. The plane-strain fracture toughness was found to be sensitive to tempered-martensite embrittlement; under these conditions, the embrittlement was associated with the replacement of micro-void coalescence either by quasi-cleavage (450–500°C temper), or in the most brittle condition (540°C temper), by intergranular fracture. It is proposed that the apparent degree of embrittlement in plane-strain, and the related fracture mode, depends on the plastic-zone size at the crack tip and on the grain-boundary microstructure. These factors could account for the inconsistencies to be found between previous studies of tempered-martensite embrittlement.

High elastic-limit, weldable low alloy steel

Abstract: This invention provides a manganese steel having a high elastic limit and at the same time a good weldability, its composition comprising, in percentage by weight: Carbon, 0.09 to 0.15; manganese, 1.30 to 1.80; molybdenum, 0.15 to 0.35; silicon, 0.10 to 0.40; vanadium, 0.03 to 0.06; niobium or tantalum 0.005 to 0.05; aluminum, 0.015 to 0.050; titanium, 0.002 to 0.040; nickel, 0.10 to 0.30; chromium, 0.10 to 0.25; sulfur ≦ 0.020 and phosphorus ≦ 0.030, the balance to make 100 % consisting essentially of iron; furthermore, this steel has undergone a cycle of heat treatments including a homogenization at high temperature, a water quenching and a tempering, and has a very fine grained micro-structure consisting of bainite and ferrite; the steel thus obtained has a satisfactory weldability and an elastic limit ≦ 550 N/mm 2 , an elastic-limit to tensile strength ration higher than 0.85 and a breaking energy at -50° C measured on a V-notched test bar which is greater than or equal to 20 Joules. This steel is suitable for manufacturing one-piece articles or parts assembled by welding, notably for the manufacture of automatic one-piece or welded couplings for railway cars and wagons.

Low alloy band saw steel and method of making the same

Abstract: A low alloy temper resistant saw blade steel containing about 0.90-1.4% carbon, 0.8-2% silicon, 0.5-1.5% vanadium, 1-3% tungsten plus twice the percent molybdenum, and the balance iron plus incidental impurities having a minimum hardness of Rc 60 in its hardness and tempered condition and which is not softened by exposure to temperatures of about 600° F. A process for preparing the steel is also disclosed in which the alloy is hot worked to strip which is then austenitized, isothermally transformed at least in part to bainite, and subjected to a subcritical anneal to form a pinpoint carbide structure with hardness reduced sufficiently to facilitate fabrication of the saw teeth. After the saw teeth are formed and set, the heat treatment is completed by flame hardening the teeth and tempering so that the teeth are at a minimum hardness of about Rc 60 and do not soften when exposed to temperatures of about 600° F.

Coherent precipitation and age hardening mechanisms in ferritic and martensitic alloys

Abstract: In the course of tempering ferritic and martensitic structures obtained after quenching with water, an isomorphous, ordered, metastable and transient phase of Fe3Si was observed in the form of spherical particles coherent with the matrix. Coarsening of the precipitate is controlled by bulk diffusion as in the model of Lifshitz and Wagner. If the temper is prolonged, the transient phase is reduced, to the benefit of an isomorphous phase in equilibrium with Laves’ Fe2Ti phase. A study was carried out on this precipitation in an iron-chromium ferritic matrix, an iron-manganese martensitic matrix and a two phased ferrite-martensite matrix of iron-chromium-manganese. The different cases were considered and the mechanical properties of the hardened alloys were examined. Observation by transmission electron microscopy showed that the variations can be explained by an interaction mechanism between the precipitate and the dislocations. It has been seen that at diameters less than a critical value, a shear mechanism exists in the ordered precipitate, followed, when the average diameter is greater, by an Orowan bypass mechanism. The type of fracture observed by scanning electron microscopy has been interpreted in terms of the mechanism.

Influence of heat treatment on the fatigue crack growth rates of a secondary hardening steel

Abstract: The relationships between microstructure and fatigue crack propagation behavior were studied in a 5Mo-0.3C steel. Microstructural differences were achieved by varying the tempering treatment. The amounts, distribution, and types of carbides present were influenced by the tempering temperature. Optical metallography and transmission electron microscopy were used to characterize the microstructures. Fatigue fracture surfaces were studied by scanning electron microscopy. For each heat treatment the fatigue crack growth properties were measured under plane strain conditions using a compact tension fracture toughness specimen. The properties were reported using the empirical relation of Paris [da/dN = CoΔKm]. It was found that secondary hardening did influence the fatigue crack growth rates. In particular, intergranular modes of fracture during fatigue led to exaggerated fatigue crack growth rates for the tempering treatment producing peak hardness. Limited testing in a dry argon atmosphere showed that the sensitivity of fatigue crack growth rates to environment changed with heat treatment.

Method for producing a high tensile strength and high toughness bend pipe

Abstract: S P E C I F I C A T I O N Title of Invention: A METHOD FOR PRODUCING A HIGH TENSILE STRENGTH AND HIGH TOUGHNESS BEND PIPE Abstract of the Disclosure: A method for producing a high tensile strength and toughness bend pipe in which a heat treatment is done as a pretreatment prior to bending, and a tempering treatment is done, if necessary, after the bending, and the bend pipe produced by the present invention is useful for pipe line construction and shows excellent properties at low temperatures.

Method of producing soft thin steel sheet by continuous annealing

Abstract: A continuous annealing process for producing a soft tin plate and black plate with T - 21/2 or T - 3 tempering properties is attained in a conventional continuous annealing furnace for black plate by the use of a novel steel strip composition.

Effect of heat treatment on conditions of formation, shape, and stability of vanadium carbides in vanadium steels

Abstract: 1. It was found that the structure of steels 22F1B, 27F1B, and 35F2B resulting from isothermal transformation of supercooled austenite at 680–720°C consists of evenly distributed high-strength, oriented, dispersed vanadium carbide in a ferrite matrix. Such vanadium carbides impart high strength at normal and elevated temperatures, while ferrite provides fairly high ductility. 2. The structure of the steels after the double heat treatment (normalization at 1130°C for 5 min, tempering at 720°C for 3 h) consists of ferrite and unevenly distributed vanadium carbides. The strength characteristics at normal and elevated temperatures are lower than after the isothermal treatment at 680–720°C for 30 min. 3. The original structure of the steel after quenching or after isothermal treatment has different effects on the hardness during subsequent tempering. Tempering at 400–450°C after quenching or incomplete decomposition of supercooled austenite leads to reduction of the hardness due to coalescence of cementite, while complete decomposition of austenite, with formation of a ferrite-carbide structure, leads to an increase in hardness beginning at very low temperatures.

Red hardness of high-speed steels

Abstract: 1. The red hardness of high-speed steels can be determined from the hardness retained after additional heating at 675°C for 20 or 30 min directly after quenching — criteria RH20675 and RH30675, which give numerically the same values as RH4620 but require less time. These values can be used together with others (austenite grain size, hardness) to judge the quality. 2. In increasing order of red hardness the steels investigated are arranged in the same order in which the alloying of the solid solution changes due to the chemical composition, original structure, and quenching temperature.

Effect of alloying on hardening of martensitic stainless steels of the Fe-Cr-Ni and Fe-Cr-Co systems

Abstract: 1. In maraging steels of the Fe+10\2-14% Cr system the addition of Co, Cu, W, Ni, Mo, Si, and Cr lowers Ms; Si, Mo, and Cu raise As, while Cr, Ni, and Co lower it. 2. Tempering does not increase the hardness of martensitic Fe\t-Cr\t-Ni or Fe\t-Cr\t-Co steels with 10\2-14% Cr, 4\2-9% Ni, and 7\2-12% Co. Considerable hardening occurs after tempering of the steel with 20% Co. 3. Alloying of Fe\t-Cr\t-Ni, Fe\t-Cr\t-Co, and Fe\t-Cr\t-Ni\t-Co steels with molybdenum, tungsten, silicon, or copper separately leads to hardening after tempering, the effect increasing with the nickel content, and especially the cobalt content. Increasing the concentration of molybdenum or silicon has a similar effect to increasing the concentration of cobalt. 4. In Fe\t-Cr\t-Co or Fe\t-Cr\t-Ni\t-Co steels alloyed with molybdenum or silicon there are two temperature ranges of aging, the nature of hardening evidently differing. 5. The compositions investigated can be used as the basis for developing stainless maraging steels with different combinations of properties.