Showing papers in "Metal Science and Heat Treatment in 1970"
26 citations
TL;DR: The main reason for the increase in the red hardness and cutting properties of cobalt high-speed steel is that cobalt, in the α solid solution, changes the properties of the solid solution and as a result the rate of softening of martensite is slowed down as mentioned in this paper.
Abstract: The main reason for the increase in the red hardness and cutting properties of cobalt high-speed steel is that cobalt, in the α solid solution, changes the properties of the solid solution—increases the binding strength, reduces the grain boundary energy and the diffusion mobility of tungsten and carbon-and as the result the rate of softening of martensite is slowed down (the red hardness increases).
17 citations
12 citations
TL;DR: The effect of intercritical quenching is observed only with an original crystallographically ordered structure, ensuring fine-acicular uniformly oriented ferrite precipitates as mentioned in this paper, and an original divorced or lamellar misoriented structure does not result in a high impact toughness after intercritical Quenching.
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.
12 citations
TL;DR: In this paper, the authors 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.
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.
9 citations
TL;DR: The formation of very hard martensite during cooling from temperatures slightly exceeding Ac1 substantially reduces the plasticity and impact toughness ("brittle recrystallization") for alloy steels as discussed by the authors.
Abstract: 1.
The formation of very hard martensite during cooling from temperatures slightly exceeding Ac1 substantially reduces the plasticity and impact toughness ("brittle recrystallization"). For alloy steels "brittle recrystallization" is observed not only in quenching but also in slow cooling from temperatures in the critical range.
2.
The properties of structures of incomplete recrystallization are unusual and depend on the character and distribution of the austenite decomposition products and also the condition of the unrecrystallized ferrite.
3.
Ferrite, not recrystallizing in the critical temperature range, is softened because of recrystallization and causes a general reduction of the properties of the steel undergoing incomplete recrystallization. The degree of weakening of ferrite depends on the original level of the properties and the heating rate, which determines the intensity of the development of recrystallization processes.
4.
In steel heated in the critical temperature range there are two sections with unfavorable properties — sections with low plasticity near Ac1 and sections with low strength between Ac1 and Ac3. This must be taken into account in calculating the service life of machine parts.
8 citations
TL;DR: Additions of lanthanum, yttrium, nickel, palladium, and platinum are the most effective in refining the grains of cast titanium as compared with other transition metals investigated as discussed by the authors.
Abstract: Additions of lanthanum, yttrium, nickel, palladium, and platinum are the most effective in refining the grains of cast titanium as compared with other transition metals investigated.
8 citations
TL;DR: The alloying of beryllium bronzes B2 and BNT1.9 with magnesium substantially improves their strength characteristics as the result of suppression of the discontinuous decomposition mechanism and the uniform strengthening of both the bulk and grain boundary areas as mentioned in this paper.
Abstract: 1.
The addition of a surface-active element (magnesium) increases the dispersity and uniformity of the structure, reducing the average grain size of the α-solid solution and the inclusions of excess plases in quenched beryllium bronzes.
2.
Microalloying of beryllium bronzes B2 and BNT1.9 with magnesium substantially improves their strength characteristics (elastic limit, relaxation resistance, cyclic strength) as the result of suppression of the discontinuous decomposition mechanism and the uniform strengthening of both the bulk and grain boundary areas. The best strength characteristics of beryllium bronzes were attained with 0.1$ Mg.
3.
The newly developed compositions, alloyed with Mg, are designated BNT1.9Mg and B2Mg. The optimal heat treatment for these alloys is quenching from 770°C and aging at 320°C for 6h.
4.
Commercial trials of the new beryllium bronzes showed that elastic elements of these bronzes have better combinations of basic properties than those of the standard compositions.
7 citations
TL;DR: The oxides formed are primarily spinels of the types nFeO·Cr2O3 and MnO·Mn2O 3 as mentioned in this paper, while in some cases titanium and molybdenum oxides are encountered together with one of the two main types of oxides.
Abstract: 1.
Microstructural, x-ray structural, and microspectral analyses indicate that internal oxidation occurs in steels 25KhGT, 25KhGM, and 25KhGNM carburized in an endothermic atmosphere.
2.
The addition of 0.6% Mo to the steel does not eliminate or reduce the internal oxidation zone of chromium and manganese.
3.
Internal oxidation to a depth of 0.03 mm is quantitatively observed by x-ray structural analysis in all steels investigated, although it is possible that oxides also occur at greater depths.
4.
The oxides formed are primarily spinels of the types nFeO·Cr2O3 and MnO·Mn2O3.
5.
With increasing cleanness of the surface the number of oxides formed and the depth at which they are formed decrease substantially.
6.
Manganese and chromium do not occur together in spinels, while in some cases titanium and molybdenum oxides are encountered together with one of the two main types of oxides.
7 citations
TL;DR: In this article, the plastic deformation of steel Kh18N10T increases with time even though extrapolation of the data to 10 years of service gives a small value (e=0.1%).
Abstract: 1.
At the design stress (15 kg/mm2) used for structures operating at −196° the plastic deformation of steel Kh18N10T increases with time even though extrapolation of the data to 10 years of service gives a small value (e=0.1%). In addition the steel undergoes intensive stress relaxation (the stress decreases to one-half).
2.
At −196° we observed no plastic deformation of steel Kh21N5AG7 with time.
3.
Steel Kh18N10T can be replaced with steel Kh21N5AG7 in structures operating at negative temperatures.
6 citations
TL;DR: 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 carbon content as mentioned in this paper.
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.
TL;DR: In this paper, hot brittleness of molybdenum alloys TsM-1 and TsM2A was observed in the temperature range of 0.5-0.75 Tm.
Abstract: 1.
In tests of molybdenum alloys TsM-1 and TsM-2A hot brittleness is observed in the temperature range of 0.5–0.75 Tm. The extent of embrittlement depends on the chemical composition of the alloy and the strain rate.
2.
Electron-microscopic examination showed that hot brittleness of alloys TsM-1 and TsM-2A is induced by precipitation of Mo2C in the grain boundaries during the test.
TL;DR: In this article, the authors show that the strength of carburized steel depends on the yield strength of the core and the residual compressive stresses in the case, and there is an optimal carbon concentration ensuring the highest strength of a carburised steel.
Abstract: 1.
Other conditions being equal, the strength of carburized steel depends on the yield strength of the core and the residual compressive stresses in the case.
2.
With increasing carbon concentrations in the steel the yield strength of the core increases, while the compressive stresses in the case decrease. There is an optimal carbon concentration ensuring the highest strength of the carburized steel.
3.
The optimal carbon concentration depends on the al'oying of the steel and the size of the piece. In carburized steels Kh2N4 and KhGT with small sections (8–12 mm in diameter) the bending strength and fatigue limit are highest at carbon concentrations of 0.19–0.24%.
TL;DR: In this paper, the authors investigated 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, and confirmed Baikov's assumption that cementite is a phase of variable composition.
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.
TL;DR: For low-carbon steels of the 20, 20Kh, and 20KhN type, the optimal cyaniding conditions are 570\dg for 1\2-1.5 h; for improved steels, they were 570\Dg for 2/2-2.5h; and for improved high-alloy steels they were 3/2/3.5H as discussed by the authors.
Abstract: 1.
Liquid low-temperature cyaniding substantially increases the wear resistance, fatigue limit, and corrosion resistance of steels.
2.
The optimal cyaniding conditions ensure obtaining a high-quality diffusion coating with the best combination of mechanical properties. For low-carbon steels of the 20, 20Kh, and 20KhN type the optimal cyaniding conditions are 570\dg for 1\2-1.5 h; for improved steels of the 40, 40Kh, and 40KhN type they are 570\dg for 2\2-2.5 h; for improved high-alloy steels they are 570\dg for 3\2-3.5 h.For parts of complex shape with technological stress concentrators we recommend increasing the processing time by 0.5–1 h.
3.
We showed that it is possible to use domestic salts for low-temperature cyaniding.
TL;DR: In this paper, the structure of bainite and pearlite obtained under high pressure is no different from that of ordinary bainites and parsons obtained at atmospheric pressure.
Abstract: 1.
High pressure slows down the transformation of austenite.
2.
The structure of bainite and pearlite obtained under high pressure is no different from that of ordinary bainite and pearlite obtained at atmospheric pressure.
3.
Pearlite obtained under pressure has larger distances between platelets than pearlite obtained at the same temperature under atmospheric pressure.
4.
The pearlitic region broadens under pressure, extending to lower temperatures than under atmospheric pressure, which is probably due to suppression of the bainitic transformation under high pressure. Low-temperature pearlite obtained under pressure is very fine; the cementite platelets are broken up.
5.
The variation of the mechanical properties of pearlite obtained under pressure conform with the changes in its structure — coarse pearlite has a low ductility, the strength and ductility increase with decreasing distance between platelets of pearlite.
TL;DR: In this paper, the ductility of the alloys is satisfactory and changes little in impact tests at low temperature and the strength is retained at elevated temperatures (up to 400°C).
Abstract: 1.
Alloying with 0.2–0.35 wt. % O increases the strength of Ti−V and Ti−V−Al alloys. The strengthening effect of oxygen is retained at elevated temperatures. The ductility of the alloys is satisfactory and changes little in impact tests at low temperature.
2.
Alloying of Ti−V and Ti−V−Al alloys with oxygen substantially increases the strength. The strength is retained at elevated temperatures (up to 400°C).
3.
The mechanical properties at room, elevated, and low temperatures are optimal for Ti−V−O and Ti−V−Al−O alloys with 0.3–0.35 wt.% O (2.5% V and 3% Al).
TL;DR: The modifying effect of calcium is due to its deactivating influence on impurity particles that serve as solidification centers for eutectic silicon in unmodified Silumin this paper.
Abstract: 1.
The modifying effect of calcium is due to its deactivating influence on impurity particles that serve as solidification centers for eutectic silicon in unmodified Silumin.
2.
Along with its possible influence on deactivation of impurities, the modifying effect of sodium is due to its reduction of the solidification rate of the eutectic.
TL;DR: In this paper, the mechanical properties of aluminum alloys heat treated in a fluidized bed meet the specifications, and they can be used for rapid heating of semifinished products and parts of aluminum alloy in place of salt baths.
Abstract: 1.
Fluidized beds are simple to build, safe to operate, and can be used for rapid heating of semifinished products and parts of aluminum alloys in place of salt baths. Heating in the fluidized bed is 9–10 times more rapid than in the ETA-6 furnace.
2.
Quenching of aluminum alloys in a fluidized bed reduces distortion to the minimum.
3.
The mechanical properties of aluminum alloys heat treated in a fluidized bed meet the specifications.
TL;DR: For some steels, there is a specific cooling rate in the martensitic region at which the probability of quench cracks is maximum as discussed by the authors, and a change in the cooling rate reduces the likelihood of crack formation.
Abstract: 1.
For some steels there is a specific cooling rate in the martensitic region at which the probability of quench cracks is maximum. A change in the cooling rate reduces the probability of crack formation.
2.
During the transformation of austenite to martensite there is considerable evolution of heat, i.e., on the temperature curves there are horizontal sections that occur at lower temperatures with increasing cooling rates, these sections disappearing completely during rapid cooling.
TL;DR: In this paper, an increase of the initial recrystallization temperature of electrolytic iron as compared with pyrometallurgical iron is due to the large amount of oxygen and oxygen-containing impurities in the metal.
Abstract: 1.
An increase of the initial recrystallization temperature of electrolytic iron as compared with pyrometallurgical iron is due to the large amount of oxygen and oxygen-containing impurities in the metal, which pin dislocations and inhibit the formation of recrystallization nuclei.
2.
With increasing initial hardness of the coating the initial recrystallization temperature and the grain size increase.
TL;DR: For alloys AL8 and AL19, this paper obtained simple equations permitting fairly precise determination of the optimal holding time from the average thickness of the inclusions of excess phase in castings.
Abstract: 1.
For alloys AL8 and AL19 we obtained simple equations permitting fairly precise determination of the optimal holding time from the average thickness of the inclusions of excess phase in castings.
2.
We found a quantitative relationship between the cooling rate during solidification and the structural characteristics of AL8 castings.
3.
On the basis of data for AL8 alloys, we showed the possibility of obtaining equations relating the optimal holding time with the cooling rate of the casting during solificatin.
TL;DR: In this paper, a linear relationship between the fatigue limits determined under the combined and separate influences of low-frequency and high-frequency loads was found, and the change in the mean stress with time at low frequency (4 cpm) and small amplitude (6 kg/mm2) leads to a reduction of the limit amplitude of the cycle to one third to one-half.
Abstract: 1.
The low-cycle limit amplitudes of steels 0Kh12NDL and 45 decrease substantially (by 85%) in the presence of high-frequency loads of small amplitude (4 kg/mm2).
2.
We found a linear relationship between the fatigue limits determined under the combined and separate influences of low-frequency and high-frequency loads.
3.
The change in the mean stress with time at low frequency (4 cpm) and small amplitude (6 kg/mm2) leads to a reduction of the limit amplitude of the cycle to one-third to one-half.