Effect Of Preliminary Heat Treatment Research Articles

Effect of preliminary heat treatment on the impact toughness of welded joints in a high-strength steel

Investigations were carried out into structural changes in preliminary heat treatment which affect the increase of impact toughness of welded joints in the conditions after strengthening by heat treatment. These investigations were made on electron beam welded joints produced in 35KhS2N3M1F steel 15 mm thick

Effect of preliminary heat treatment on the formation of a boronized layer on steel 35

1. Preliminary heat treatment of specimens leading to refinement of the austenite grain helps increase the thickness of the boronized layer on steel 35. The greatest thickness of the boronized layer is attained after HC, and this layer is thicker than the layer obtained without preliminary treatyment. 2. Preliminary normalization and HC affect the formation of the phase components of the boronized layer. Normalization reduces the content of α-phase in the layer by 40%, and HC by 60% in comparison with the initial state of the steel. After pendulum normalization the phase composition of the layer does not change. 3. The microhardness of the boronized layer depends on the quantitative ratio of the phases in the layer; the highest microhardness is attained after HC.

The effect of preliminary heat treatment on the life of cold-heading tools

Heat treatment that includes brief tempering with rapid cooling ensures a noticeable refinement of the structure and helps substantially to increase the life of tools operating at normal temperatures.

Effect of preliminary stabilizing heat treatment on the deformation of gears during gas carburizing and hardening

1. The use of preliminary heat treatment (refinement) has a significant effect on the average deformation of components formed by a sharp tool during gas carburizing and hardening in accordance with a continuous cycle. The effect of preliminary heat treatment on the stability (dispersion) of the deformation of an opening is insignificant in this case. 2. The effect of preliminary heat treatment on the average deformation of components formed by a dull tool is weakened. In this case, strain dispersion is reduced by several factors, and attains values close to the strain dispersion of components formed by a sharp tool. 3. Use of preliminary heat treatment for steel 12Kh2N4A components to be hardened by gas carburizing and hardening in accordance with a continuous cycle is expedient after the opening is formed by a dull cutting tool, when significant work-hardening develops, and also when holes are sized with mandrels.

Nucleation in silicate glasses and effect of preliminary heat treatment on it

Time and temperature dependences of the nucleation rate of Li 2O · 2SiO 2 and 2Na 20 · CaO · 3SiO 2 crystals in glasses of the same composition have been studied by a “development” method. It has been found that nucleation kinetics are satisfactorily described by classical nucleation theory. A new phenomenon observed is the strong influence of preliminary isothermal exposure of a glass on nonstationary nucleation taking place at temperature higher than that of the preliminary heat treatment. The phenomenon is ascribed to heterophase fluctuations during the preliminary heat treatment.

Quantitative treatment of electron micrographs from fracture surfaces of oriented capron monofibres

The step value on the wave relief of the mirror zone, d, has been measured on a series of successive microphotographs from replicas taken from rupture surfaces of oriented capron monofibres and relationships corresponding to the increase in d with an increase in crack length have been obtained. The effect of preliminary heat treatment and rate of extension on the way in which d depends on crack length has been discussed. It is shown that there is a certain minimum displacement of the crack front, which does not depend on the crack speed within the mirror zone and which is therefore related to specific structural formations of the microfibril type. The change in the value of the minimum displacement as a result of annealing correlates with the coarsening of the elements in the internal structure, as is confirmed by X-ray structural analysis.

Effect of preliminary heat treatment on the properties of the nitrided case on aluminum-free structural steels

Preliminary heat treatment affects the properties of the nitrided case on aluminumfree steels containing carbide-forming elements. For annealed and normalized steels with a ferrite-pearlite structure the depth and hardness of the nitrided case are lower than for quenched and tempered steels with a structure of sorbite.

Effect of preliminary heat treatment on phase transformations and properties of steel Kh15N5D2T (VNS-2)

Preliminary heat treatment has a substantial effect on the kinetics of the α→γ transformation, the amount of retained austenite, the grain size, and the work of crack propagation in steel Kh15N2D2T after final heat treatment.

Effect of preliminary heat treatment, cold deformation, and electric heating on the mechanical properties of steel 30KhGSA

Effect of preliminary heat treatment, cold deformation, and electric heating on the mechanical properties of steel 30KhGSA

Surface hardening of precipitation-hardening nonmagnetic steels

1. Precipitation-hardening nonmagnetic steels of the Fe−Mn−Ni system can be surface hardened by nitriding and also by work hardening of the surface. Surface layers with an elevated hardness to a depth of 0.3 mm can be obtained by nitriding of high-strength nonmagnetic steel 40G14N9Kh3YuF2. The results of comparative wear resistance tests showed that nitrided steel 40G14N9Kh3YuF2 is not inferior to steel 38KhMYuA, which has a fairly high wear resistance after nitriding. 2. Studies of the effect of preliminary heat treatment and the conditions and medium of nitriding on the hardness, depth, and condition of the nitride case showed that the best nitride case on steel 40G14N9Kh3YuF2 is obtained after nitriding at 560 and 600° in ammonia diluted with nitrogen when the steel has a fine-grained structure (after forging or after quenching from 1100° and aging), with an austenite grain size not lower than grade 6. 3. Surface hardening of steel 40G14N9F2 by roller burnishing and by shot peening increases the fatigue strength of smooth samples by 25–30% and notched samples by 90–140%. The increase in the fatigue strength is due to the high surface hardness (H 550) and compressive stresses (σcom~50–70 kg/mm2) in the surface layer.

Effect of preliminary heat treatment of alumina on the thermal-shock resistance and strength of corundum ceramics

The firing temperature of the starting alumina is one of the important factors influencing the formation of the microstructure of corundum materials and determines the properties of the ceramics. At low alumina firing temperatures (1400°C) the structure of the specimens is finely crystalline. An increase in the firing temperature (to 1600–1750°C) causes an increase in the crystal sizes.

Effect of preliminary heat treatment on the size of inclusions and the stable austenite grain size

1. Preliminary high-temperature heat treatment can have a substantial effect on the tendency of austenite to grain growth. Rapid cooling of carbon steels with low concentrations of aluminum or titanium from 1200–1300°C leads to stable grains of smaller sizes and widening of the stable temperature range. Slow cooling has the opposite effect. Subsequent heating to 830–850°C does not affect the grain size. 2. It was shown that the tendency of austenite to grain growth and the stable grain size are connected with the size of the carbide and nitride inclusions in the steel. Treatments that reduce the size of the inclusions without changing their weight or volume in the steel lead to refinement of the grains during subsequent austenization. In carbon steel with 0.55% C and 0.03% Ti, in which the size of titanium carbide inclusions is 50–100 A, the stable austenite grain size reaches 5–6 μ.

Effect of preliminary heat treatment and vibro-grinding of magnesium oxide on its state of dispersion, hydrating power and sinterability

Effect of preliminary heat treatment and vibro-grinding of magnesium oxide on its state of dispersion, hydrating power and sinterability

The effect of preliminary heat treatment upon the drying of clays

The effect of preliminary heat treatment upon the drying of clays