Showing papers on "Tempering published in 1970"

The influence of structural parameters on the yield strength of tempered martensite and lower bainite.

Abstract: : The contributions to the yield strength of tempered martensitic and bainitic structures was examined in 4340 steel. The principal factors that contribute to the reduction in yield strength with tempering in the range from 600 to 1000F are carbide coarsening and enlargement of the cellular substructure. The yield strength of both tempered martensitic and bainitic structures can be described in terms of cell size and dispersoid distribution by a single relationship in which the Orowan model is employed for the contribution from dispersion hardening and the Langford-Cohen model for that from cell size. (Author)

Strain tempering of bainite

Abstract: In the present investigation the strain tempering of bainite has been carried out with (EN 24) a medium carbon low alloy steel. The specimens were austenitized at 850°C and isothermally transformed at 300°, 360°, and 400°C to produce bainite, strained and tempered in the range 100° to 400°C. The bainite formed at 360°C has been specifically examined by thermomagnetic analysis to confirm quantitatively the solution of ∈ carbide. Thermomagnetic analysis has shown that the carbide phase in bainite formed even at 360°C is a mixture of ∈ carbide and cementite. It has been found that with lowering of bainite transformation temperature, the strain tempering treatment results in higher strength consistent with good ductility. The present investigation favors the carbon dislocation trapping model for the mechanism of strain tempering of bainite, similar to that proposed for the strain tempering of martensite.

Process for producing tempered glass sheet

Abstract: In a process for producing tempered glass sheet which includes a step of tempering treatment comprising heating a glass sheet to a temperature in the vicinity of its softening point and rapidly cooling the heated glass sheet from its surface, the improvement which comprises maintaining the glass sheet, before or after said tempering treatment, at a temperature in the range of 100* to 380*C. for a total period of time which meets the following formula WHEREIN T is a temperature in degrees centigrade at an optional time, H is a time in minutes which is calculated when T is in the range of 100* to 380*C. and A IS A NUMBER 250 AFTER THE TEMPERING TREATMENT AND 540 BEFORE THE TEMPERING TREATMENT, THEREBY TO IMPART A THERMAL HISTORY TO THE GLASS SHEET, AND REMOVING THOSE GLASS SHEETS WHICH BREAK BY SAID THERMAL HISTORY AND TEMPERING TREATMENT, WHEREBY THE REMAINING TEMPERED GLASS SHEETS DO NOT UNDERGO SPONTANEOUS BREAKAGE.

Hard facing of rollers for hot and cold - rolling of steel and non iron metals

Abstract: After welding-on of applied surface layers, the roller is subjected to full annealing, a cutting treatment of its surface, and a subsequent heat treatment consisting of tempering and annealing. The roller core consists pref. of a weldable fine-grained structural steel containing 0.20%C and housing an initial strength >50 Kp/mm2. Wires or strips welded onto the core for hard-facing are pref. composed of 0.2-0.6%, C, 4-20% Cr, 0.5-5% Si, 0.4-1.5% Mn, 0-2% Mo, 0-0.5% V, 0-4% Ni, rest Fe.

High temperature braze heat treatment for precipitation hardening martensitic stainless steels

Abstract: A brazing and heat treating cycle is described as applied to semiaustenitic stainless steel sheet material. The steps include a brazing operation, solution annealing, trigger annealing, subzero cooling and tempering. The brazed assembly exhibits good mechanical properties and good corrosion resistance.

"Intercritical quenching" of structural steels

Abstract: 1. Intercritical quenching results in a higher impact toughness. The steel is not susceptible to temper brittleness, while the hardness is lower than after quenching from temperatures above Ac3. 2. With tempering resulting in identical hardness the impact toughness is considerably higher after intercritical quenching than after standard quenching. 3. The effect of intercritical quenching is observed only with an original crystallographically ordered structure, ensuring fine-acicular uniformly oriented ferrite precipitates. An original divorced or lamellar misoriented structure does not result in a high impact toughness after intercritical quenching. Quenching after cooling down to the intercritical range from the austenitic range also has no effect on the impact toughness.

How to calculate heating time for quenching

Abstract: 1. The empirical formulas obtained make it possible to calculate the through heating time for solid and hollow cylinders, regular prisms with any number of faces, parallelepipeds, and some symmetrical parts of complex shape in various media at 780–1300°, and also to determine the total time necessary for heating them to quenching temperature with the structure of the steel taken into account. 2. The basic calculations can be made by means of the data given in the tables, which facilitate the calculations and make them fairly reliable. 3. The results of the calculations match the existing experimental data on the time for heating to quenching temperature of total steels ensuring the high mechanical and cutting properties required after tempering. 4. We determined the general principle of introducing a correction in the calculations of the heating time due to the influence of the original microstructure of the steel and change in the quenching temperature and requirements for the parts, especially the red hardness.

High tensile steel having high notch toughness

Abstract: A HIGH TENSILE STEEL COMPRISING 0.12-0.21% OF CARBON, 0.70-1.00% OF MANGANESE, 0.20-0.35% OF SILICON, 0.400.65% OF CHROMIUM, 0.15-0.25% OF MOLYBENUM, 0.030.08% OF VANADIUM 0.01-0.03% OF TITANIUM, 0.00050.0005% OF BORON, 0.020-0.60% OF ALUMINUM, 0.0080.020% OF NITROGEN AND THE BALANCE BEING IRON AND IMPURITIES, TREATED BY HARDENING AND TEMPERING TO PROVIDE THE STEEL WITH A YIELD POINT OF MORE THAN 70 KG./MM.2. A TENSILE STRENGTH OF MORE THAN 80 KG./MM.2. AND AN EXCELLENT NOTCH TOUGHNESS AND WELDABILITY.

The Tempering of Iron–Nitrogen Massive Martensite

Abstract: The first stage of tempering of body-centred cubic iron–nitrogen martensites containing 0·18, 0·35, and 0·51 wt.-%N has been investigated using electrical-resistivity measurements, X-ray and electron diffraction, and thin-film electron microscopy. Transformation of the martensite took place below 200° C (475 K) to ferrite and the body-centred tetragonal nitride, Fe16N2. Thin-film electron-microscopy studies showed that the nitrides form approximately parallel ribbons, which are initially coherent and are distributed more or less uniformly in the lath substructure of the massive martensite. Electron-diffraction and trace-analysis experiments revealed that the nitrides precipitate with {100}α′ habit planes in 〈100〉α′ directions. A dislocation-attraction model due to B.S. Lement and M. Cohen (Acta Met., 1956, 4, 469) has been extended to cover iron–nitrogen alloys and tested using the resistivity data obtained. The expected time exponent of 1/3 was observed for first-stage tempering after nucleation...

Effective debye temperature of precipitated carbides

Abstract: An effective Debye temperature Θ of carbides extracted from a tempered steel was determined through the Mossbauer effect. The f factor and Θ increase with tempering temperature, following a reduction of carbon content of the carbides and changes in the elastic properties. The phase transformation at Tc is followed by a discontinuity in the magnitude of the center shift and in ∂(δE/E)/∂T.

The optimal carbon content of high-speed steels

Abstract: 1. The secondary hardness and red hardness of high-speed steels increase with the carbon content up to a specific concentration close to the "quasieutectoid", which is above that of standard steels, and decrease with further increase of the carbon content. 2. The highest hardness and red hardness occur at carbon concentrations around 1% for steels R18 and R12, around 1.15% for steel R12F3, and 1.05–1.10% for tungsten—molybdenum steels. The hardness reaches HRC 65.5-67 and the red hardness (at HRC 60) 625–635°C, i.e., values reached in high-vanadium steels R9F5 and R14F4, which take a poor polish. 3. In steels with an elevated carbon content, ferrite is absent on heating above the pearlitic transformation range, which ensures more complete solution of the carbides. In these steels the precipitation of carbides during tempering occurs in a narrow temperature range, due to which the carbides are more dispersed and more uniform in composition and size than in steels with a lower carbon content. 4. It is expedient to increase the carbon content to 1.0–1.05% in tungsten-molybdenum steels, particularly in R6M5 for use in place of high-vanadium steels with high productivity, since the mechanical properties are better as well as the surface finish.

Ductile low temp steel - contg nickel, hot-rolled and heat -treated to form ultrafine austenite

Abstract: The steel contg. by wt. =0.2% C, 0.05-0.04% Si, 0.3-5% Mn (where 0.3-0.9% Mn may be replaced by equiv. Cu) and 4-7.5% Ni as main alloying elements and opt. 0.05-1% Mo (replaceable by W), 0.1-2% Cu, 0.1-1.5% Cr, =1% Nb, =1% V, =0.05% acid-soluble Al (replaceable by other nitride-forming elements), bal. Fe and tramp elements is heat-treated by once or repeatedly heating quenching or cooling in air at or from a temp. between the Ac1-transition point and the Ac3-transition point, and then tempering below the Ac1-transition point, so that a mixed structure of ferrite, tempered martensite and ultrafine deposited austenite is formed. Prod. combines strength and ductility at low temps.

Variation of the composition, structure, and hardness of cementite with quenching

Abstract: 1. With quenching of white synthetic cast irons (Fe−C and Fe−C−Cr) from temperatures up to 1000°C the cementite lattice is distorted, the volume of the unit cell decreases, the carbon content decreases, and the microhardness increases considerably. The phenomenon is reversible, and the observed effects of the hardening of cementite are removed by high-temperature tempering. 2. The fact that the results contradict earlier results can be explained by the completing processes — the effect of hardening of the carbide phase and the initial stages of graphitization occurring at high temperatures, particularly in commercial cast irons containing silicon. 3. The investigation confirmed Baikov's assumption that cementite is a phase of variable composition. With increasing temperatures cementite approaches austenite in its carbon concentration and the chains of octahedral cells of the iron sublattice.

MAGNETIC PROPERTIES OF PrCo5–PrCu5 ALLOYS

Abstract: The magnetic properties of some ternary alloys PrCoxCu(5−x) in the range 4.5 ≥ x ≥ 2 have been investigated. The remanence and coercive force of these alloys both directly after annealing at 1020 °C for 5 h and after tempering for 4 h at 390 °C are very low in comparison with similar alloys in the SmCo5–SmCu5 and CeCo5–CeCu5 systems.

High-temperature nitriding of steel 1Kh12VNMF

Abstract: 1. Steel 1Kh12VNMF of the ferritic—martensitic class can be nitrided at 680–1000°. The optimal treatment, ensuring high properties of the core and the case, consists of combining nitriding with tempering at 680°. This treatment produces a case of high hardness (HV 800), which increases the wear resistance. The strength of adhesion of the nitrided case to the core is fairly high. 2. Nitriding of steel 1Kh12VNMF substantially increases its heat resistance; the mechanical properties are quite stable.

Effect of original structure on the depth and hardness of the nitrided case

Abstract: 1. With increasing tempering temperatures the case depth and hardness decrease on steels 38KhMYuA and 40Kh. 2. The use of preliminary decarburizing before nitriding in a mixed atmosphere (70% N2+30% NH3) results in high hardness and case depth without an increase of brittleness in steel 38KhMYuA. 3. Nitriding with over 60% dissociation lowers the hardness and case depth.

Properties of carburized steel 18Kh2N4VA after overheating

Abstract: 1 When steel 18Kh2N4VA is heated to 1300–1350° and cooled in air the structure of the fracture is crystalline or lithoidal In subsequent heat treatment the crystalline fracture becomes lithoidal 2 Quenching and low-temperature tempering of the overheated steel retain the high strength charracteristics, including the fatigue strength, but the plasticity decreases sharply 3 The structure of the case on overheated steel differs greatly from that on steel not overheated In the steel not overheated the carbide network resulting from carburizing is fine and even In the overheated steel the carbide network is coarse and occurs in the boundaries of former austenite grains formed during overheating 4 Overheating after carburizing and heat treatment hardly reduces the resistance to bending or fracture toughness, but substantially reduces the fatigue strength 5 When the lithoidal structure is retained in the carburized and heat treated steel after overheating the resistance of the case to galling decreases

Method of Producing Coil Compression Springs from Hardened Steels

Abstract: 1,185,924. Making coil springs. V. N. SHALIN. 20 June, 1967, No. 28413/67. Heading B3A. In a method of making coil springs from hardened steels, the spring is quenched, then tempered at such a temperature that the material of the spring has a hardness of 53-58 Rockwell C, and the spring surface is then cold worked. The cold working preferably comprises shot blasting. For a steel comprising 0A56- 0A64% C, 1A60-2A00% Si, 0A60-0A90% Mn, 0A30% max. Cr, 0A40% max. Ni, 0A03% max. S and 0A035% max. P, the temperature range for tempering is 360-380‹ C., and for a steel comprising 0A61-0A69% C, 1A50-2A00% Si, 0A70- 1A00% Mn, 0A80-1A20% W, and Cr, Ni, S and P as previously the temperature range is 380- 400‹ C.

Tempering of high-coercivity Alnico alloys

Abstract: 1. The standard and multistage tempering of Alnico alloys (Magnico and Ticonal) ordinarily used is not the optimal treatment for obtaining the highest magnetic properties of permanent magnets. The magnetic properties (coercive force and maximum magnetic energy) are inversely proportional to the temperature of stepped tempering with optimal holding times (particularly at elevated tempering temperatures). 2. From the time of attaining the maximum coercive force at different tempering temperatures it is possible to plot a temperature—time diagram that gives the tempering conditions to ensure the highest magnetic properties for any Alnico alloy.

The relation between the fracture behavior of 4340 bend specimens and the observation of tempered martensite embrittlement

Abstract: V-notched and fatigue precracked Charpy specimens of various sizes, tested in impact and slow bend, were used to study tempered martensite embrittlement in a 4340 steel. When plotted as a function of tempering temperature, the results showed that the magnitude of the toughness decrease caused by embrittlement varied with the type and size of the specimens. Embrittlement was always detected using thin samples but its detection in thick specimens depended on whether or not they contained a precrack. In particular, no embrittlement-associated fall in toughness was observed using standard size precracked samples tested in slow bend. Separation of the shear and flat fracture components of the absorbed energies showed that the variation of shear energy is a major factor contributing to embrittlement. The results are interpreted as indicating that intergranular fracture occurs more as the result of inhibition of plastic flow within the grains rather than directly as the result of the appearance of a low resistance crack path at the grain boundaries.