Showing papers on "Tempering published in 1971"

Carbides in M-50 high speed steel

Abstract: The carbides in M-50 high speed tool steel were studied in detail. The dissolution of carbides as a function of austenitizing temperature, and their precipitation as a function of tempering temperature were characterized by X-ray diffraction and microchemical analysis. The carbides in the annealed steel are M23C6, M6C, M2C, and MC. Upon austenitizing, with increasing temperatures, the carbides dissolve in the order: M23C6, metastable M2C, M6C, and MC. The residual carbides in the heat treated steel are MC and stable M2C. The solvus temperatures of M23C6 and M6C were determined. Upon tempering the hardened steel, with increasing tempering temperatures, carbides precipitate in the order: M23C6, metastable M2C, MC, and M6C. It is shown that the composition of the precipitated metastable M2C is different from that of the residual stable M2C and it varies with the tempering temperature.

Mössbauer Characteristics of ε, χ, and θ Iron Carbides

Abstract: The Mossbauer effect in 57Fe has been used to study carbide phases appearing during the tempering process of an alloy steel containing 1.33 wt.% Si, 1.13% wt. Mn, and 0.38 Wt.% C. Carbides were chemically extracted from the samples which had been isothermally tempered for 2 h at various temperatures. Carbides obtained from samples tempered at 300° and 400°C were identified as e and χ phases, respectively. The e carbide has an isomer shift (I.S.) of 0.18 mm/sec relative to α iron and an effective hyperfine field (Hn) of 162 kOe at 300°K. The χ carbide has an I.S. of 0.28 mm/sec relative to α iron and Hn of 179 kOe at 300°K. Carbides precipitated at and above 500°C were found to have the orthormbic cementite structure, with a composition of (Fe1−xMnx)3C. As the tempering temperature increases from 500° to 700°C the Curie temperature changes from 440° to 270°K, and x increases from 0.02 to 0.10. Curie points and extrapolated values of Hn(0) were found for all the carbides in question. The early stages of tem...

Structure and mechanical properties of tempered martensite and lower bainite in Fe−Ni−Mn−C steels

Abstract: The structure and mechanical properties of tempered martensite and lower bainite were investigated in a series of high purity 0.25 pct C steels with varying amounts of nickel and manganese. The martensites in 0.25 C-5 Ni−Fe and 0.25 C-3 Mn−Fe alloys were mainly untwinned, while those in 0.25 C-5 Ni-7 Mn−Fe and 0.25 C-7 Mn−Fe alloys were heavily twinned. Manganese appears to promote carbide precipitation along the lath boundaries in tempered martensite. At equivalent yield and ultimate tensile strength levels, the tempered martensite of lower manganese steels showed better impact toughness than the tempered martensite of higher manganese steels. The impact toughness (compared at similar strength levels) of untwinned tempered martensite of 0.25 pct C steel with Widmanstatten precipitation of carbide was higher than that of lower bainite, which showed unidirectional carbides. The reasons for the difference in impact toughness between the alloys, and also between the structures are rationalized in terms of internal twinning, grain boundary precipitation and carbide morphology together with other microstructural features.

Development of a high strength stainless steel with improved toughness and ductility

Abstract: Compositional modifications have been made to the existing Cr−Mo−Co stainless steels to produce a steel (alloy B) which combines the high strength of AFC 77 with the toughness of AFC 260. This has been achieved by utilizing both the strengthening effect of grain refinement and the crack stopping ability of retained austenite. After tempering at 800° to 900°F alloy B possesses higher elongation than other high strength stainless steels due to the ease with which its retained austenite transforms under stress to martensite to delay necking. An explanation has been advanced for the anomalously low tensile yield strength that occurs in both alloy B and AFC 77 after tempering at 1000°F.

High-strength low alloy ferritic steel small-gauge wire

Abstract: THE PROCESS FOR PRODUCING HIGH-STRENGTH FERRITIC STEEL SMALL-GAUGE WIRE HAVING A DIAMETER UP TO 1 MILLIMETER COMPRISING REDUCING THE DIAMETER OF A KILLED LOW ALLOY STEEL ROLLED STARTING WIRE, SAID STEEL CONTAINING BETWEEN ABOUT 0.01 AND 0.06 CARBON, BETWEEN ABOUT 0.05 AND 1% SILICON, BETWEEN ABOUT 0.25 ND 6% MANGANESE, BETWEEN ABOUT 0.01 AND 0.30% NIOBIUM, UP TO 0.03% NITROGEN, UP TO 0.2% ALUMINUM, UP TO 0.5% ZICRTONIUM, UP TO 0.30% VANADIUM, AND UP TO 0.5% TITANIUM, BY SEQUENTIAL PASSES THROUGH DRAWING DIES CONSTITUTING A DRAWING CYCLE, FOLLOWED BY TEMPERING AT A TEMPERATURE BETWEEN ABOUT 400*C. AND 670*C., AND FURTHER REDUCTIION WITH AT LEAST ONE ADDITIONAL DRAWING CYCLE, WITH TEMPERING AT A TEMPERATURE BETWEEN ABOUT 400*C AND 670*C. BETWEEN EACH SAID DRAWING CYCLE, UNTIL THE PRODUCT WIRE DIMENSION IS OBTAINED. THE INVENTION ALSO INCLUDES THE TOUGH HIGH-STRENGTH KILLED LOW ALLOY FERRITIC STEEL WIRE PRODUCE BY SAID PROCESS.

Heat treatment in a fluidized bed furnace

Abstract: 1 The controlled atmospheres obtained during the combustion of natural gas in the prototype furnace with fluidized bed at α≤045 sharply reduce oxidation and decarburization during the heating of alloy steels to 900–1000°C In a carefully controlled furnace no decarburization of the surface layer takes place 2 The heating of steels takes place in a fluidized bed at a considerably higher rate than in an electric furnace so that the heating time for hardening decreases in a ratio of 12∶1 and for tempering in the ratios 8∶1 3 The hardening ability of a fluidized bed is the same as that of oil 4 Mechanical properties and hardness of 18Kh2N4VA and 40KhNVA steels heat treated in a fluidized bed are stable and meet the specified requirements 5 High-speed heat treatment in a fluidized bed without oxidation or decarburization of parts is recommended for use in industry

Structure and properties of high-strength stainless steel 1Kh15N4AM3

Abstract: 1. Tempering of steel 1Kh15N4AM3 at 200° leads to high mechanical properties: σb ≈ 160 kg/mm2,δ5 ∼ 16%, ψ ∼ 60%, an=15 kg-m/cm2, af.cr.=7 kg-m/cm2. The high strength results from the high dislocation density, the presence of twins, and also from the fairly large amount of carbon and nitrogen (total ∼0.23%) retained in the solid solution. The high ductility is due to the presence of 15–20% evenly distributed austenite. 2. Tempering at 300−350° results in some lowering of the strength (σb ∼ 145 kg/mm2) and increase of the plasticity and ductility. The change in the properties is due to the smaller amount of carbon and nitrogen in the solid solution, while the high dislocation density and substantial second-order distortion are retained. With decreasing numbers of interstitial atoms in the solid solution no precipitates are formed. 3. The secondary hardening in tempering at 450−500° concludes with the formation of highly dispersed M2X (detected after overaging), the strength reaching \t}155 kg/mm2 with some decrease of the fracture toughness and substantial reduction of the work of crack propagation. The structure is characterized by some reduction of the dislocation density and considerably smaller second-order distortion. 4. Raising the temperature to 650−700° lowers the strength, since M23C6 forms in the grains and grain boundaries. 5. The reverse α→γ transformation begins at 575−600° and the largest amount of stable austenite is formed after heating at 625−650° for 1−2 h.

The influence of plastic strain upon the aging characteristics of alloys

Abstract: The conditions under which dislocations can influence the decomposition of supersaturated solid solutions with different degrees of supersaturation are discussed. It is shown that the major effects are associated with the formation of intermediate precipitates and with low degrees of super saturation. Examples are then given of the effects of prior plastic strain upon aging reactions in aluminum, nickel and copper based alloys. The changes in mechanical properties are related to the observed changes in microstructure. It is argued that with martensitic steels the tempering reactions are not influenced by prior plastic strain, since the dislocation density is already high as a result of the martensitic reaction; however plastic strain after initial temper, followed by a further temper can produce marked changes in structure and properties. It is shown that in general prior plastic strain can considerably shorten the time cycle for heat treatment and it may at the same time induce improved mechanical properties.

Thermal tempering of glass having short strain point-to-softening point interval

Abstract: Thermal tempering propensity of alkali-alkaline earth-silica glass can be enhanced by changing the chemical composition such that the temperature interval between the softening point and the strain point is decreased. Addition of B2O3 and/or TiO2 in commercial alkali-alkaline earth-silica glass yields the above-mentioned result.

Glass heating and tempering apparatus

Abstract: A tunnel system is provided which heats glass plates horizontally for tempering, delivers them to tempering apparatus with more even temperature, in a shorter time, controls temperature between the heating and blowing sections, controls air turbulence at the discharge port of the heating unit, and applies the blowing air on novel principles, producing a more perfectly tempered plate.

Effect of boron on the cold brittleness of medium-carbon steel

Abstract: 1. When alloyed with ∼0.003% B, steel 40GR with a section as large as 40 mm has a higher fracture toughness and lower cold brittleness threshold than steel 40G after quenching and tempering to a hardness of HB 290. 2. After quenching and low-temperature tempering, medium-carbon steel with boron may have a fairly high fracture toughness along with high hardness. 3. To eliminate the high susceptibility of the steel to brittle fracture the boron content should be ∼0.001–0.004%.

The influence of austenisation on the kinetics of tempering—Mössbauer effect study

Abstract: The Mossbauer effect in 57Fe is used to investigate the kinetics of carbide precipitation in plain carbon steel. The investigated carbides were extracted chemically after the steel had been treated at various austenisation and tempering temperatures. The relative amount of cementite precipitated after a certain heat treatment was determined from the spectral area. The activation energy of the process is found to be 0.3 eV. A formula is suggested for the dependence of carbide formation rate on the austenisation temperature. It is found that in the process of the chemical extraction, amorphous iron gel or oxyhydroxide isomers form, rather than iron oxides. The effective internal field Hn and the isomer shift of the extracted carbides depend on the tempering temperature, while the carbide formation rate depends on the austenisation temperature as well.

Method of liquid quenching of glass sheets

Abstract: AN IMPROVED METHOD FOR THERMALLY TEMPERING GLASS SHEET BY LIQUID QUENCHING IS DISCLOSED. THE IMPROVEMENT COMPRISES A PRELIMINARY STRENGTHING OF THE MARGINAL EDGES OF THE GLASS SHEET SUCH THAT THE GLASS SHEET IS BETTER ABLE TO WITHSTAND THE SUBSEQUENT THERMAL SHOCK OF LIQUID QUENCHING. THE PRELIMINARY STRENGTHENING IS ACCOMPLISHED BY COOLING THE BODY OF THE GLASS SHEET BETWEEN MARGINAL EDGES AT A RATE GREATER THAN THE RATE AT WHICH THE EDGES ARE COOLED. THIS MINIMIZES THE TENSILE STRESSES THAT ARE NORMALLY ASSOCIATED WITH THE EDGES DURING LIQUID QUENCHING. IN A PREFERRED EMBODIMENT, THE INVENTION IS DIRECTED TO AN IMPROVEMENT IN THE DIP-QUENCHING PROCESS FOR THERMALLY TEMPERING GLASS IN WHICH THE EDGE WHICH INITIALLY CONTACTS THE QUENCHING LIQUID IS PUT IN COMPRESSION PRIOR TO IMMERSING THE GLASS IN THE QUENCHING LIQUID.

Decomposition of martensite and formation of carbide phases during tempering of chromium steels

Abstract: 1. The presence of weakly tetragonal α solid solution (decomposed martensite) in naturally aged samples of chromium steels is due not to selftempering of martensite during quenching but to processes occurring during warming of the samples from the temperature of liquid nitrogen to room temperature and rest at room temperature. 2. Aging of martensite at temperatures below 120° is not accompanied by precipitation of carbide phase. At these temperatures the x-ray diffraction patterns show diffuse scattering effects, indicating sections with an elevated carbon concentration in the matrix. With increasing aging temperatures the carbon atoms in the enriched sections are redistributed, their concentration increasing, and then (at 120°) these sections are rebuilt into carbide phase with hexagonal symmetry. 3. An increase of the chromium content of the steel weakens the intensity of diffuse effects from the enriched sections. Reflections of ɛ carbide are correspond'ngly weakened, indicating a smaller amount of it, and it disappears completely in the steel with 7% Cr. With increasing chromium concentrations the carbide phase with the orthorhombic lattice of cementite is formed at a lower temperature.

The Elevated Temperature Properties of Two 81mm Mortar Tube Alloys 4337M and 4140

Abstract: : An evaluation was made of the effect of room and elevated temperatures (800 to 1200F) and times at these temperatures (0 to 30 hours) on the mechanical properties of two mortar tube alloys, AISI 4140 and AISI 4337 modified, quenched and tempered to four strength levels. The elevated temperature yield strength and ductility after exposure to the various temperatures for various times are discussed. The room temperature yield strength and -40F impact energy after exposure to various temperatures for various times are also discussed. Results of the elevated temperature tensile testing of the two alloys showed that the yield strength decreases rapidly with high temperatures. The ductility (%RA) increases with increasing temperature and remains fairly constant with time at temperature. The room temperature yield strength decreases with time after exposure at temperatures above the tempering temperature of the alloy. The -40F Charpy V-notch impact strength increases after exposure at temperatures higher than the tempering temperature of the alloy. Increasing the room temperature yield strength (by lowering the tempering temperature) does not significantly increase the elevated temperature yield strength of the alloy.

Tempering behavior of iron-carbon sputter deposits with 0 to 5 wt pct C

Abstract: Iron-carbon sputter deposits with 006, 018, 066, 2, 3, and 5 wt pct C were tempered at temperatures from 100° to 550°C The 006, 018, and 066 wt pct C sputter deposits were similar to severely cold-worked martensite, both as-deposited and in tempering response Specifically, these three deposits were much harder than water quenched steels of the same composition, and the deposit hardnesses decreased less than martensite hardnesses on tempering below 400°C The hardnesses of the 2 and 3 wt pct C deposits increased 40 to 50 Dph units upon tempering at low temperatures (150° to 250°C) and decreased for higher tempering temperatures The hardness of the 5 wt pct C deposit remained constant (920 Dph) after tempering at 150°C, but increased to 1170 Dph upon tempering at 250°C when monoclinic Hagg carbide (Fe5C2) formed Cementite (Fe3C) was the only other carbide detected in the tempered deposits, and it formed only at 475°C and above The columnar grains of the sputter deposits transformed to equiaxed grains upon tempering above 250°C This change in grain structure was due to recovery and not recrystallization Some grain growth occurred in the 006, 018, 066, and 2 wt pct C deposits above 300°C, but the grain size of the 3 and 5 wt pct C deposits remained submicron The hardnesses of the deposits after tempering at 550°C increased with carbon content, the 5 wt pct C deposit having the highest hardness (960 Dph) and the 006 wt pct C deposit the lowest (360 Dph)

Effect of Mean Stress on Fatigue Strength of Carburized Steel

Abstract: Although it is known that the fatigue strength of carburized steel is greatly influenced by the residual stress on the surface, it is very difficult to assess the effect quantitatively. In this report, the effect of mean stress on the fatigue strength of carburized steel is studied, and therefrom the effect of residual stress can be estimated. Following results are obtained. (1) The fatigue strength of a high hardness and brittle steel, is more sensitive to mean stress, as compared to those of medium and low hardness steels. (2) As the Tempering temperature of carburized steel is increased, the effect of mean stress on the fatigue strength decreases. (3) During the fatigue test little change was observed in the residual stress and half value breadth of X-ray diffraction line of carburized steel. On the basis of these results, the mechanism of fatigue failure of carburized steel was discussed.

Carburizing of heat resistant steels in a controlled endothermic atmosphere

Abstract: 1. The optimal bending strength of high-alloy heat resistant steels 18Kh2N4VA, 14KhGSN2MF, 20Kh3MVF, and 20KhNV4MF after carburizing and heat treatment results from a carbon concentration of 0.9–1.1%; the optimal concentration is 0.8–0.9% for steels of the 18-25KhGT and 25KhGM types. 2. The highest contact fatigue strength of these steels is attained at a higher carbon concentration (1.3–1.4%) than for steels of the 12KhN3A type. 3. The highest heat resistance of the carburized steels investigated can be attained by increasing the surface carbon concentration to 1.4–1.5%. The heat resistance is highest for steel 20KhNV4MF, with a surface hardness of HRC 59–60 after tempering at 375–400°C. 4. In carburizing steels with a large amount of carbide-forming elements (chromium, tungsten, molybdenum, and vanadium) in a controlled endothermic atmosphere it should be kept in mind that these elements substantially increase the carbon concentration in γ-iron. With prolonged processing at elevated carbon potentials the amount of carbide phase in the surface increases greatly. Intensive carbide formation can be prevented by lowering the equilibrium concentration of carbon in γ-iron by 0.1–0.2%.

A Metallurgical Study on Postheat Treatment of Overlaid Austenitic Weld Metals

Abstract: Overlaid weld metals of austenitic stainless steel in a pressure vessel of power reactor are usually postheated for a long period of time after welding. The heat treatment is considered a kind of sensitizing and it is important to check the soundness of the weld metal after heat treatment, especially about the precipitation of carbides.Investigation was made about the distribution of delta ferrite and its change by reheating, precipitation of carbides and their identifications, and sigma phase. The main conclusions reached from this study are as follows:(1) Precipitation of delta ferrite from molten weld metal depends on solidification phenomenon. There was a small amount of ferrite near the bond or toe in which the local solidification time was short, comparing with other parts of weld metal. At no specific location ferrite was found due to macrosegregation or extremely rapid solidification.(2) Shape and amount of ferrite were changed by reheating after solidification. Ferrite was extremely grown after heating at 1350°C for 15 sec. It was spheroidized by heating at 1200°C.(3) There were five types of carbides developed after postheating: a) dot-shaped carbide, b) massive carbide, c) precipitated carbide mostly due to diffusion of carbon from base metal, d) lamellar carbide by eutectic reaction, and e) precipitated carbide due to tempering of martensite.(4) The first two types of carbides were M23C6 type except for a relatively intense postheating of 700°C. A M6C carbide was detected with M23C6 carbide after postheating at 700°C. It should be noticed that dot-shaped carbides were linked to each other on an austenite grain boundary when there was no ferrite, and massive carbides co-existed sometimes with sigma phase.(5) The fourth one, lamellar carbide, which had not been pointed out in previous study, precipitated on an austenite grain boundary near base metal after a fairly large extent of carbon diffusion from base metal. The eutectic phase was very soft and it would be a cause of trouble in a side bend test which is required as part of the procedure test of power reactor.

Thermal stability of the bauschinger effect in quench-hardened and tempered steel

Abstract: 70S2KhA steel strip specimens were plastically deformed in bending and the effect on their behavior of heating them (in an unloaded state) during subsequent reverse bending was studied. It was shown that 1.0 hr at 200° C is almost completely sufficient to suppress the manifestation of the Bauschinger effect during reverse loading.

The Properties of Spot Welds in Anti-Corrosive High Tensile Steels

Abstract: This paper, following the previous report that dealt with the method of selecting the heat-treatment conditions of spot welds in anti-corrosive high tensile steels, gives details of the weldability assessment of these steels.The ductility ratio of these steels is about 50% as welded. But it can be improved by tempering to about 70%. Under combinations of these steels and low carbon steels, it can be improved to about 80% by tempering.The objective of this study was to check the reliability of the welded joint of these steels in SHIN KANSEN electric railcars structures. Therefore, a strict test had to be carried out on the joint.A new machine has been developed to test the fatigue strength of spot welds in these steels. The testing data show that the efiect of heat-treatment on the improvement of ductility of spot welds and the relationships between the fatigue strength of spot welds and the welding conditions can be easily analyzed.Meanwhile, the crack initiating mechanism of spot welds in fatigue failure has been clarified.The experimental work has shown that a clean scale-free surface and high electrode force are essential for the uniform tempering of spot welds.

Thermomechanical processing of the nickel-base alloy U-700

Abstract: Thermomechanical processing of nickel alloy in relation to yield and creep rupture strength